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  • Articles  (2,343)
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  • 1
    Electronic Resource
    Electronic Resource
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 2.2005, 1, art1021 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Power systems optimization problems are very difficult to solve because power systems are very large, complex, geographically widely distributed and are influenced by many unexpected events. It is therefore necessary to employ most efficient optimization methods to take full advantages in simplifying the formulation and implementation of the problem. This article presents an overview of important mathematical optimization and artificial intelligence (AI) techniques used in power optimization problems. Applications of hybrid AI techniques have also been discussed in this article.
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  • 2
    Electronic Resource
    Electronic Resource
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 3.2005, 1, art1031 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: As large load disturbances with changing frequency in the vicinity of the inter-area oscillations mode occur in an interconnected power system, a system frequency may be heavily perturbed and oscillatory. To stabilise frequency oscillations, the active power controlled by a superconducting magnetic energy storage (SMES) unit placed in a power system, can be utilised. However, it may not be feasible to locate a SMES unit in every area of a multi-area interconnected power system due to the economic reason. Therefore, it should be advantageous if a SMES unit located in an area is available for frequency stabilisation of other interconnected areas. To implement this concept, a static synchronous series compensator (SSSC), can be applied to coordinate with a SMES unit to stabilise frequency oscillations. On the other hand, variations of system parameters, several load changes etc., cause system uncertainties. To enhance the robustness of frequency stabilisers against uncertainties, this paper focuses on a robust frequency stabilisation by SMES in co-ordination with SSSC. To take system uncertainties into account, the multiplicative uncertainty is included in system modeling. As a result, the system robust stability can be easily guaranteed in terms of the multiplicative stability margin (MSM). The structure of frequency stabiliser equipped with SMES and SSSC is a second-order lead/lag compensator. Based on the proposed optimisation technique, control parameters of frequency stabilisers can be automatically tuned by a tabu search. Consequently, the desired damping ratio of the target inter-area mode and the best MSM are achieved. Simulation studies in a two-area interconnected power system confirm the high robustness of the coordinated SMES with SSSC against several uncertainties.
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  • 3
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 2.2005, 2, art1032 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents a novel wavelet-based travelling wave fault location algorithm for aged underground cables in transmission systems. Such transmission systems consist of overhead lines combined with underground power cables. Applying the singularity detection feature of wavelets as a powerful signal processing tool, the first and second initial arrival of the voltage travelling waves at the first end of the overhead as well as at the terminal end of the aged cable line can be identified reliably without the need for detection the sign of these waves. In this paper modal signals, rather than the phase signals, are the inputs to the relay. The proposed algorithm is capable of eliminating the effect of the change in the propagation velocity of the travelling waves over the age of the cable. It can be used on-line following the operation of digital relays or off-line using the data stored in the digital transient recording apparatus. Extensive simulation studies carried out using ATP/EMTP show that the proposed algorithm provides an accepted degree of accuracy in fault location under different fault conditions.
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  • 4
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 2.2005, 1, art1035 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Availability Based Tariff (ABT) has been implemented in all the regional grids of India for improving grid discipline by frequency dependent pricing. Currently it is limited to short-term energy transactions between the beneficiary States and Central generating stations without the need for negotiations on price or quantum in real time. In the present scenario, Independent Power Producers (IPP), Captive Power Plants (CPP), small Distributed Generation (DG) like mini-turbine, fuel cell, etc., are not considered under ABT. DG units are normally modular in size and they can be placed close to consumers so as to reduce the T&D costs and losses. Hence, they need to be encouraged so as to meet the ever-increasing electricity demands of Indian power sector within the financial constraints. In this paper, impact of IPPs, CPPs and DGs on intra-State ABT is studied. This paper also proposes to study the impact of grid connected DG on network availability and reliability. The improvement in system reliability is studied after evaluating reliability indices like SAIFI, SAIDI, etc., with the inclusion of DG.
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  • 5
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 2.2005, 2, art1 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The paper deals with an optimized Unified Power Quality Conditioner (UPQC), which aims at the integration of series active and shunt active power filters with minimum VA loading of the UPQC. The series active filter is a Dynamic Voltage Restorer (DVR), which is operated in twofold functioning mode. During the unbalanced voltage sag, the DVR compensates the unbalance in the voltage sag. It also regulates the voltage at the load end with minimum VA loading of the overall UPQC by optimum angle voltage injection. Validity of the proposed scheme is proved through extensive simulation results.
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  • 6
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 3.2005, 1, art1045 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Concentration of greenhouse gases in the atmosphere is steadily increasing leading to global warming. India is expected to be one of the major contributors to Green House Gases (GHGs) due to increased share of thermal power generation, which is a major contributor to carbon dioxide (CO2) emission. One way to limit these emissions is by implementing some economic instruments like carbon tax or energy tax. This study has been carried out to analyze the impact of carbon tax on the complete Indian power sector network. An Integrated Resource Planning and Analysis (IRPA) model and CPLEX software has been used to carry out the present study.
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  • 7
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 2.2005, 1, art1048 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A multi-level dc voltage reinjection concept is described that multiplies the pulse number of the twelve-pulse dual parallel converter. The ideal reinjection waveform for complete elimination of the harmonic content is first derived, and a practical approximation is proposed which converts the standard dual converter into a sixty-pulse scheme, thus meeting the strictest harmonic standards without the assistance of filters or Pulse Width Modulation.
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  • 8
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 4.2005, 1, art1085 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The goal of this paper is to evaluate performances of a new hysteresis current control strategy for autonomous three phase parallel active filter in harmonic currents elimination (by simulation an experiment) as well as the reactive power compensation (by simulation). This strategy, called the Optimized Hysteresis Control Strategy, is based on currents errors and their derivatives calculation each time the zero voltage vector is set at the AC side of the inverter of the active filter. The harmonic currents are identified using the method of the instantaneous real and imaginary powers. A voltage regulation loop is used to regulate the condenser DC voltage which ensure a constant DC voltage to the inverter. A digital software C++ simulation program was developed and implemented via the data acquisition board (AT-MIO-16X DAQ from National Instruments). Simulation and experimental results are presented.
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  • 9
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 3.2005, 2, art1092 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Currently, evolution of energy sector is being characterized by liberalization, increase of energy needs and technological advances. This evolution has eliminated the scale economy on which the generation, transmission and distribution systems are based. So, tendency of generation systems is oriented to integrated devices, which will supply the customers demand, either in medium voltage or low voltage networks. The interconnection of small modular generation sources to the low voltage distribution network establishes a new concept, the electrical micro-grid. These micro-grids can be connected to the electrical distribution network or work in an autonomous way and can include different technologies, such as: micro-turbines, wind mills, fuel cells, photovoltaic cells, etc., together with energy storage devices, such as: batteries, condensers, fly-wheels, etc. The content of this paper cover different aspects related with generation and distribution of electrical power in a small scale, and horizontal technologies for industrial, commercial and domestic energy systems. So, this paper presents a revision of current developed technologies, which can be used for electrical microgeneration installations.
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  • 10
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 4.2005, 1, art1113 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The aim of this paper is to present a novel method for the optimal placement of capacitor and reactor banks, with the objective of maximizing network capacity to absorb new generation. The method is an extension of the Optimal Power Flow used as a tool for network capacity analysis. It can be used to a) plot graphs of the bank investment cost with respect to the increase in network capacity and b) find the optimum investment for the network operator in order to maximize his revenue. A 12-bus low voltage network was used as a test case. The results demonstrate the efficiency of the method to allocate new banks. At a small investment cost, network capacity could nearly double.
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  • 11
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 8.2007, 2, art1 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In recent years, renewable energy generation has been coming up for effective use of natural energy, such as wind energy. Induction generators consisting squirrel-cage rotors are widely used as wind generators because of their salient features like robust rotor design, simplicity in the construction, maintenance free operation, etc. In this paper, it is derived that the transient current, electromechanical torque, and active power taking into account rotor speed change of induction generators at three-phase fault conditions. The output equations of the induction generator has nonlinearity, and the speed-time characteristic in a fault period is also expressed by the nonlinear equation. The approximation to derive analytical formulas for transient conditions is proposed, and the transient behavior of the induction generator is analyzed by the developed equations. The simulation block diagram in MATLAB/SIMULINK is constituted using the system equation in consideration of the nonlinearity of the induction generator. The simulation results obtained from each theoretical analysis are in close agreement with that of results obtained using MATLAB/SIMULINK simulation. Furthermore, theoretical discussion also developed to determine the fault phase angle and the time at which maximum transient currents flow in the system.
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  • 12
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 8.2007, 5, art3 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The tariff is the best incentive factor for the industrial customer today to reduce the peak load. This paper describes different methods of pricing electricity. It is important to study the influence of the tariff on the industrial loads and the costs of electricity before ILM can be implemented. This paper is interested in studying the economic aspects of fixed and operating cost, other factors affecting the generation economy, distribution of power, etc. Costs of supplying electricity to consumers are also considered. A utility can influence its customers' load by providing financial incentives through the prices charged for electricity at different times of use. By designing discriminatory time of use tariffs in which the prices of electricity corresponds to the marginal cost of supply, a utility provides appropriate signals to the customer to increase consumption of electricity at off peak periods. The proposed algorithm is implemented to a real system in operation.
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  • 13
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 8.2007, 2, art5 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Accurate electricity load and pool-price forecasting can provide a set of vital predicted information that helps generation, transmission and retailer participating companies to bid strategically into a deregulated electricity market in order to maximize their profits and increase returns to their stakeholders. Although a number of forecasting methods have been proposed to solve the short-term and long-term electricity load forecast, pool-price forecasting is a relatively new research area. In this article, we propose an autoregressive approach, based on a wavelet multiscale decomposition, for the prediction of one-hour ahead load and pool price based respectively on historical electricity load, and pool-price data. This approach is based on a multiple resolution decomposition of the signal using the redundant Haar à trous wavelet transform whose advantage is taking into account the asymmetric nature of the time-varying data. There is an additional computational advantage in that there is no need to re-compute the wavelet transform (wavelet coefficients) of the full signal if the electricity and pool price data (time series) is regularly updated. We assess results produced by this multiscale autoregressive method, in both linear and nonlinear variants, with single resolution autoregressive, multilayer perceptron, Elman recurrent neural network and the general regression neural network models. The input data consists of historical load and pool price data, which is collected over a period of 3 years (1999-2001), used for training, and 1 year (2002) used for testing. Experimental results are based on the New South Wales (Australia) electricity load and pool price data that is provided by the National Electricity Market Management Company.
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  • 14
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 8.2007, 1, art4 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper investigates the use of trajectory sensitivity analysis (TSA) technique for assessing the transient stability of a power system at various operating conditions. The effect of placement of a thyristor controlled series compensator (TCSC) as well as the influence of the change in firing angle is also discussed. The TCSC is modeled by a variable capacitor, the value of which changes with the firing angle. The systems studied are the WSCC 3-machine, 9-bus system and IEEE 16 machine 68 bus system. The results using TSA are validated by PSCAD/EMTDC simulation.
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  • 15
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 8.2007, 2, art7 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A range of techniques has been proposed to define the optimal locations and capacities of distributed generation (DG) as a means of ensuring that the maximum amount of DG can be connected to existing and future networks. However, there are limitations inherent in these methods, not least in finding the best combination of sites for connecting a predefined number of DGs. Here, a method combining optimal power flow and genetic algorithms aims to meet this requirement. Its use would be in enabling Distribution Network Operators to search a network for the best sites and capacities available to strategically connect a defined number of DGs among a large number of potential combinations. Some applications of the proposed methodology confirmed its effectiveness in sitting and sizing an assigned number of DG units.
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  • 16
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 8.2007, 4, art3 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents an approach for identifying the faulted line section and fault location on transmission systems using support vector machines (SVMs) for diagnosis/post-fault analysis purpose. Power system disturbances are often caused by faults on transmission lines. When fault occurs on a transmission system, the protective relay detects the fault and initiates the tripping operation, which isolates the affected part from the rest of the power system. Based on the fault section identified, rapid and corrective restoration procedures can thus be taken to minimize the power interruption and limit the impact of outage on the system. The approach is particularly important for post-fault diagnosis of any mal-operation of relays following a disturbance in the neighboring line connected to the same substation. This may help in improving the fault monitoring/diagnosis process, thus assuring secure operation of the power systems. In this paper we compare SVMs with radial basis function neural networks (RBFNN) in data sets corresponding to different faults on a transmission system. Classification and regression accuracy is reported for both strategies. Studies on a practical 24-Bus equivalent EHV transmission system of the Indian Southern region is presented for indicating the improved generalization with the large margin classifiers in enhancing the efficacy of the chosen model.
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  • 17
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 8.2007, 4, art7 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents a new decision tree (DT) based approach for fast voltage contingency screening and ranking for on-line applications in energy management systems. The hybrid decision tree model is developed to learn all the selected contingencies simultaneously, therefore fewer DTs are required. To reduce the size and improve the accuracy of the decision tree, the K-class problem is converted into the set of K two-class problems, and separate decision tree modules are trained for each of the two class problems. All the selected contingencies are presented to the filter module, which is trained to separate them in critical and non-critical contingency classes, which reduces the burden on ranking modular DT. The critical contingencies screened out by the filter module are presented to the ranking modular decision tree for their further ranking. To measure the severity of contingencies, bus voltage violation based scalar performance index is used. Full AC load flow is performed to generate the training and testing patterns for the proposed hybrid decision tree, under each contingency. The effectiveness of the proposed approach is tested on IEEE test systems. Once trained, a hybrid decision tree method gives fast and accurate screening and ranking of contingencies for unknown load patterns.
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  • 18
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 8.2007, 5, art1 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In this paper, a novel control algorithm is proposed to compensate the unbalanced and non-linear loads in a three-phase four-wire system using active power filters. The algorithm results in balanced and sinusoidal source currents under unbalanced and distorted three-phase supply voltages. The algorithm makes use of the positive sequence extraction of the supply voltage and the theory of instantaneous symmetrical components. To illustrate the concept, a three-phase four-wire system with unbalanced and non-linear load is considered for compensation. The detailed simulation and experimental results are presented to validate the proposed method.
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  • 19
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 8.2007, 5, art6 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The necessity of dynamic equivalents for power system analysis has been well known since the expansion of large interconnected power networks, and has been discussed during the last decades. The present paper proposes a new method for constructing dynamic equivalents of power systems. In this method, at the first step the ``study system" is modeled completely via a single machine-infinite bus modeling procedure. Then the ``external system" is identified as a MIMO feedback block of this model in such a manner that can include dynamic effects of the latter on the behavior of the former. The method is successfully experimented on a part of the Iranian southern network.
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  • 20
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 8.2007, 5, art4 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In this paper a comprehensive dynamical assessment of a high order synchronous generator plant is carried out using the Individual Channel Analysis and Design (ICAD) framework -a multivariable control engineering tool that allows robustness and system performance evaluations. The great benefits of ICAD are elucidated and contrasted to those provided by the long-time honored block diagram representations. Several models used for the small signal stability analysis of synchronous generators are evaluated under the framework of ICAD. The study, which builds on pioneering work, reveals the great advantages of carrying out control system analysis and design with higher order generator models. Moreover, careful analysis of the ICAD's Multivariable Structure Function (MSF) helps to explain, formally, why some operating conditions of the control system are more critical than others. Furthermore, correct interpretations of MSFs are amenable to robust and stable control system designs. Two kinds of studies are considered in the paper; one assesses operation under various power factor conditions and the other under a varying tie-line reactance. The control system design and stability and structural robustness assessment of the system are presented in the second part of this paper. Moreover, results obtained under the ICAD framework are compared with those arising from conventional controllers.
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  • 21
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 8.2007, 6, art3 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: For high-frequency (HF) interference in an HVDC converter station, the modeling of the noise source which causes interference with the power line carrier (PLC) remains a problem. Based on the profound analysis of the basic principles on which HF noise in PLC band is produced during the commutation process, the equivalent model of the HVDC valve with a snubber circuit is applied to the simulation of the GUI-GUANG HVDC project in PSCAD/EMTDC. Then spectrum plots of the noise source in the frequency domain are obtained by FFT analysis of the voltage waveforms gained from the simulation. Through analyzing the spectrum characteristics of the noise source in various operating modes, the main factors influencing the level of HF noise are found. Furthermore, a modified empirical model used to calculate the level of the noise source is introduced, with particular explanation of the physical quantities used in the model. The spectra of the noise source gained from the modified empirical model and from the simulation are compared with an actual spectrum based on the GUI-GUANG HVDC project. The results show that the modified empirical model can meet the requirement of HF interference calculation.
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  • 22
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 2.2005, 1, art1033 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In India, apart from state owned generators, a central sector power pool has been created consisting of central sector power stations. The Central Transmission Utility (CTU) has built an EHV network to transfer this power to the constituents of the regional network. To recover the costs incurred, the CTU levies the Transmission Service Charges (TSC) over the constituents. The constituents are billed for network usage charges which are proportional to their allocated share in the central sector power generation. An ideal pricing mechanism would have been to find out the usage of the network by the constituents and charge accordingly. In this paper, a real power tracing based method for recovery of Transmission Service Charge (TSC) from the constituents of Western regional grid in India is proposed. The method uses proportionality based real power tracing to find out the network usage by various constituents. Loss allocation on EHV network to the various constituents is also done. Actual data of power flows over the EHV network of Western regional grid for one day is considered.
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  • 23
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 3.2005, 1, art1066 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In this paper we explain how to design intelligent agents able to process the information acquired from interaction with a system to learn a good control policy and show how the methodology can be applied to control some devices aimed to damp electrical power oscillations. The control problem is formalized as a discrete-time optimal control problem and the information acquired from interaction with the system is a set of samples, where each sample is composed of four elements: a state, the action taken while being in this state, the instantaneous reward observed and the successor state of the system. To process this information we consider reinforcement learning algorithms that determine an approximation of the so-called Q-function by mimicking the behavior of the value iteration algorithm. Simulations are first carried on a benchmark power system modeled with two state variables. Then we present a more complex case study on a four-machine power system where the reinforcement learning algorithm controls a Thyristor Controlled Series Capacitor (TCSC) aimed to damp power system oscillations.
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  • 24
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 3.2005, 2, art1070 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Design and successful operation of wind energy conversion systems (WECs) is a very complex task and requires the skills of many interdisciplinary skills, e.g., civil, mechanical, electrical and electronics, geography, aerospace, environmental etc. Performance of WECs depends upon subsystems like wind turbine (aerodynamic), gears (mechanical), generator (electrical); whereas the availability of wind resources are governed by the climatic conditions of the region concerned for which wind survey is extremely important to exploit wind energy. This paper presents a number of issues related to the power generation from WECs e.g. factors affecting wind power, their classification, choice of generators, main design considerations in wind turbine design, problems related with grid connections, wind-diesel autonomous hybrid power systems, reactive power control of wind system, environmental aspects of power generation, economics of wind power generation, and latest trend of wind power generation from off shore sites.
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  • 25
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 3.2005, 1, art1067 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In bilateral transaction market, the congestion relief cost should be allocated in an equitable manner among all the market participants contributing to the congestion. Unfortunately in the allocation of the congestion relief cost to the congested lines, which is the first step of cost allocation, the previously proposed shadow price method and the aggregated allocation method both have some shortcomings. To overcome these shortcomings, a cost allocation method based on the Aumann-Shapley value is proposed. By means of the Aumann-Shapley value, a solution concept in the cooperative game with infinitely many players, the proposed method takes all orders of relieving congestion on the lines into consideration and satisfies the consistency of the allocation, thus guarantees equitable allocation of the congestion relief cost to the congested lines. In addition, the calculating procedure is both simple and accurate due to the use of the Gauss Integration method. Test results show that this method can lead to better allocation than do the shadow price method and the aggregated allocation method.
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  • 26
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 4.2005, 2, art2 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In this paper, a novel neural network controlled Hybrid Parallel Active Power Filter has been presented. The neural network controller comprises two similar adaptive linear neurons (ADALINE), and it has been designed to extract fundamental frequency components from non-sinusoidal and unbalanced currents. It has been shown that the proposed neural controller is simple, fast and accurate. The proposed system is implemented using Digital Signal Processor (DSP). Experimental results with different nonlinear loads are presented to confirm the validity of the proposed technique.
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    International journal of emerging electric power systems 3.2005, 2, art1072 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A dynamic voltage restorer is a power quality (custom power) device used to correct the voltage disturbances by injecting voltage as well as power into the system. The compensation capability of a dynamic voltage restorer (DVR) depends primarily on the maximum voltage injection ability and the amount of stored energy available within the restorer. In this paper a new phase advance compensation (PAC) strategy for the DVR is proposed in order to enhance the voltage restoration property of the device. Also a method of determining the exact amount of voltage injection required to systematically correct a specific voltage drop with minimum active power injection is proposed. Using the proposed method it can be shown that a particular disturbance can be corrected with less amount of storage energy compared to that of existing in-phase boosting method. Analytical expressions for both the magnitude and angle of the injected voltage are also derived. A closed-loop controller that consists of an inner current loop and an outer voltage loop is also incorporated into the DVR system.
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    International journal of emerging electric power systems 3.2005, 2, art1077 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper proposes a new bid based redispatching method to relieve congestion in a pool type market, based on bilateral generation exchanges between generation units. Sensitivity analysis is used to find and implement the cheapest consecutive bilateral exchanges that would remove congestion in an iterative process. Congestion cost is calculated as exchange cost during congestion removal and is divided between congested parts using load flow results in each iteration. Divided cost is recovered from consumers, based on their relative contributions on congested parts using generalized load distribution factors. IEEE 39 and 118 bus test systems are used for case study to evaluate the merits of proposed method and the results are discussed in comparison with other conventional methods.
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    International journal of emerging electric power systems 3.2005, 2, art1080 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents two mathematical models based on graph theory, and a fuzzy logic approach for the steady state analysis of three phase self excited induction generator with and without series compensation. The first model is developed using nodal admittance method and the second model is developed using loop impedance method. Both models results in simple matrix form which are convenient for computer solutions. Since these models are more generalized the steady state performance of the three phase self excited induction generator can be easily obtained with and without series compensation along with fuzzy logic algorithm. These models are so flexible, wherein an element like core loss component can be included or eliminated if required and also the leakage reactance of the stator (Xls) and rotor (Xlr) can be handled separately, by avoiding the assumptions Xls=Xlr without any modifications in the models. Next to carry out the steady state analysis, a fuzzy logic approach is used first time to find any combinations of unknown variables using above models. The analysis presented is validated by experimental results.
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    International journal of emerging electric power systems 4.2005, 1, art1082 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Reactive Power Dispatch (RPD) is one of the important tasks in the operation and control of power system. The objective is to apply Particle Swarm Optimization (PSO) algorithm for arriving optimal settings of RPD problem control variables. Incorporation of PSO as a derivative free optimization technique in solving RPD problem significantly relieves the assumptions imposed on the optimized objective functions. The proposed algorithm has been applied to find the optimal reactive power control variables in IEEE 30-bus system and in a practical Indian power system with different objectives that reflect loss minimization, voltage profile improvement and voltage stability enhancement. The results of this approach have been compared with the results of Genetic Algorithm (GA). The results are promising and show the effectiveness and robustness of the proposed approach.
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    International journal of emerging electric power systems 4.2005, 1, art1084 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In this paper, an adaptive fuzzy PI-sliding mode control (AFPISMC) is proposed for induction motor (IM) speed control. First, an adaptive sliding-mode controller (APISMC) with a proportional plus integral equivalent control action is investigated, in which a simple adaptive algorithm is utilized for generalised soft-switching parameters. The proposed control design uses the fuzzy logic techniques to dynamically control parameter settings of the SMC equivalent control action. The theoretical analyses for the proposed fuzzy PI-sliding-mode controller are described in detail. Simulated results show that the proposed controller provides high-performance dynamic characteristics and is robust with regard to plant parameter variations and external load disturbance.
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    International journal of emerging electric power systems 3.2005, 2, art1088 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Most tracing algorithms have used variants of proportionality based tracing algorithm. However, proportional sharing is not an inherent characteristic of the system. It is a rule enforced to arrive at a solution in a simple and fair manner. We propose a multi-commodity network flow optimization approach for optimal tracing of power flows. The resulting optimization formulation is shown to be sparse linear programming (LP) problem. The paper is devoted to the constraint modeling of this optimization approach. A unified formulation that models lossy MW flow network and provides consistent results for generation and load tracing is presented. Optimal tracing provides complete power audit information like share of loads in generation, generators' contribution in loads, loss allocation to generators and loads, and decomposition of branch flows into generation and load components. Illustrative examples and results on IEEE 30 bus system show the workability of the proposed approach.
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    International journal of emerging electric power systems 8.2007, 4, art1 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Dynamic economic emission dispatch is an extension of the conventional economic emission dispatch problem that takes into consideration the ramp rate limits of the generators. Evolutionary programming based fuzzy satisfying method has been proposed to determine the optimal noninferior generation schedule. This paper treats economy and emission as competing objectives for optimal dispatch, which requires some form of conflict resolution to arrive at a solution. The multi-objective problem is configured as a minimax problem under the assumption that the decision-maker has fuzzy goals for each of the objective functions. The present algorithm employs evolutionary programming technique in solving this problem. The solution methodology can offer a global or near-global noninferior solution for the decision-maker. Numerical results of a sample test system have been presented to demonstrate the performance and applicability of the proposed method. Results obtained from the proposed method are compared to those obtained by fuzzy satisfying method based on simulated annealing technique.
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    International journal of emerging electric power systems 4.2005, 2, art5 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Flicker is an important power quality disturbance and has received an increasing concern from power system researchers. Interharmonics are the non-integral frequencies other than harmonic frequencies. Nowadays, research has shown that interharmonics and flicker seem to be closely related. To clarify this relationship, flicker is characterized in the frequency domain. The traditional Fourier-based methods have shown some drawbacks in representing non-stationary, non-periodic power signals and therefore other methods should be investigated for accomplishing this task. This paper introduces the most common signal processing approaches to assess the problem, power spectrum estimation methods and linear transforms. The wavelet transform has shown superior performance comparing to other methods and circumventing the problem time-frequency resolution.
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    International journal of emerging electric power systems 8.2007, 1, art1 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Brushless doubly-fed machines (BDFMs) allow the use of a partially rated inverter and therefore offer reliable, maintenance-free operation at low cost, especially in large power variable speed applications with limited speed ranges such as off-shore wind turbines, pumps etc. However, with a special cage rotor design, the machine has substantial rotor losses, poor efficiency and complicated control being difficult to implement.The BDFM reluctance type, the brushless doubly-fed reluctance machine (BDFRM), can overcome most of the above BDFM deficiencies while retaining all its merits. It has a "cold" reluctance rotor, which makes it more efficient and much easier to model/control than the BDFM.A theoretical study of the BDFRM is very important to gain proper understanding of its unusual operation, the main control features and compromises between optimal performance and the size of the inverter and machine required. This paper will attempt to develop, and provide a comprehensive comparative analysis of, different control strategies for the machine that are suitable for digital implementation.
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    International journal of emerging electric power systems 8.2007, 3, art4 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Very Fast Transient Overvoltages (VFTO) and the associated Very Fast Transient Currents (VFTC) generated during switching operations in a Gas Insulated Substation (GIS) couple conductively and inductively to the secondary equipment connected to the GIS. The frequency spectrum of the VFTC gives the dominant frequencies present but cannot provide the time varying current amplitude w.r.t. any particular frequency. Since the transient response of the control circuits is a function of the frequency content of the VFTC, it becomes necessary to segregate the VFTC waveform both in time and frequency scale simultaneously. This has been achieved by employing the GABOR wavelet function and the time-frequency spectrum of the VFTC waveform has been calculated at various locations for a 245 kV GIS during a switching event. The validity of the wavelet model is confirmed by reconstructing the VFTC signal at the GIS-cable termination as well as at the switching point using the time varying current waveforms obtained for different frequencies. Finally, the transient current vs frequency as well as the current vs distance charts are developed for the 245 kV GIS under study during various switching operations.
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    International journal of emerging electric power systems 8.2007, 3, art6 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: During the last two decades, renewable wind energy has become increasingly popular as a consequence of strong ecological concerns and appealing advantages with regard to economical energy solutions in remote communities. Furthermore, with very large wind farms emerging, the dispersed renewable wind energy is required to be fully connected to the electrical distribution networks. However, the integration of dispersed renewable wind energy will pose a great challenge to the power quality in the distribution networks when the weak nature of the grid in remote areas and the uncertainty of wind are taken into consideration.This paper presents a novel Modulated Power Filter Compensator (MPFC) for the distribution networks with dispersed renewable wind energy interfaced. A tri-loop error driven controller is used to adjust the PWM switching of the modulated power filter compensator. Full power factor correction and power quality improvement is validated under different operation conditions, like load switching and wind velocity excursions. The MPFC device is a member of novel FACTS based compensators developed by the first author.
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    International journal of emerging electric power systems 8.2007, 2, art2 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The importance and conduct of necessary studies on grid reliability evaluation have become increasingly important in recent years due to the number of blackout events occurring throughout the world. Additionally, quantitative evaluation of transmission system reliability is very important in a competitive electricity environment. The reason is that successful operation of an electric power under a deregulated electricity market depends on transmission system reliability management. This paper suggests that the important input parameters of a probabilistic reliability evaluation tool for the KEPCO-system by sensitivity analysis of high reliability level operation. Simultaneously, it also presents sensitivity analysis probabilistic reliability evaluation of practical KEPCO-system long-term transmission system expansion planning (2006-2010). The tool utilized a Transmission Reliability Evaluation for Large-Scale Systems (TRELSS) which was developed by EPRI and Southern Company Services Inc.
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    International journal of emerging electric power systems 8.2007, 1, art5 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The electric power industry in the United States and in other countries is undergoing profound regulatory and operational changes. The underlying rationale behind these transformations is to move once highly monopolized vertically-integrated industry from a centralized operation approach to a competitive one. The emerging competitive markets and an increase in the number of market participants have, in turn, fundamentally changed not only electricity trading patterns but also the structure of the electric power supply chains. This new framework requires new mathematical and engineering models and associated algorithmic tools. Moreover, the availability of fuels for electric power generation is a topic of both economic importance and national security. This paper uses the model developed by Nagurney and Matsypura (2004, 2006) as the foundation for the introduction of explicit fuel suppliers, in the case of nonrenewable and/or renewable fuels, and their optimizing behavior, into a general electric power supply chain network model along with "direct-supply" generation. We derive the optimality conditions for the various decision-makers, including fuel suppliers, power generators, suppliers, as well as the transmission service providers and the consumers at the demand markets. We establish that the governing equilibrium conditions satisfy a finite-dimensional variational inequality problem. We provide qualitative properties of the equilibrium flow pattern; in particular, existence of a solution and uniqueness under suitable assumptions. Finally, we discuss how the equilibrium fuel supply and electric power flow pattern can be computed.
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    International journal of emerging electric power systems 8.2007, 4, art4 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The steady state thermal rating of overhead transmission lines is limited by the conductor`s maximum design temperature, which is related to the maximum sag and the loss of tensile strength of the conductors. Traditionally, this overhead transmission lines rating is computed using a deterministic approach, with reference to severe weather conditions. Thus, the application of this method leads to conservative results resulting in under-utilization of conductors. In this paper, a new method based on an hourly probabilistic index is proposed to predict the line thermal rating for each hour of the day; this index is evaluated using the conductor current limit probability density function (pdf). The method uses Bayesian time series models for the weather parameters (ambient temperature, wind speed and wind direction) and calculates the conductor current limit pdf using a Monte Carlo simulation. The probabilistic index is applied by considering measured weather data of both hot and cold seasons; the corresponding lines ratings are reported and analyzed.
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    International journal of emerging electric power systems 2.2005, 1, art1034 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The framework of transformer condition assessment system is proposed in this paper through mainly using data warehouse techniques, data mining techniques, and Open Agent Architecture. In this system, a data warehouse is used to collect transformers' testing data, a multi-agent system is used to design the framework of the software, and data mining techniques are used to evaluate transformers' conditions. The present framework is open and flexible, so the objective system is easy to be developed and maintained. The system can support transformers' condition-based maintenance to reduce electric utility's cost. Because the condition of a transformer depends on its design, present and historical operating data, and relates to its installation environment, load amounts, and so on, it is necessary to integrate all above information to evaluate transformer's condition. However, the off-line testing results, operational data, fault records and weather conditions have been stored in different systems, so finding an effective method to utilize all this information for condition assessment is difficult. Therefore, a data warehouse has been set up to integrate all of the above data, and some data mining techniques have been used to find the pattern and trend of the condition of a transformer. Then whether it is healthy can be determined. In order to make the system open and flexible, Open Agent Architecture (OAA) is employed to compose the multi-agent system. Seven application agents are designed to evaluate transformers' conditions synthetically. The Grey correlation method, grey theory prediction model GM(1,1), Bayesian network classifier and Bayesian network are employed in the agents.
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    International journal of emerging electric power systems 3.2005, 1, art1037 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The objective of this paper is to optimize maintenance scheduling of generating units of a captive thermal plant using intelligent optimization techniques such as genetic algorithm (GA) and simulated annealing (SA). A multi-class maintenance scheduling has been considered to incorporate statutory safety regulations for maintenance of boilers, turbines and generators. Such multi-class maintenance scheduling in terms of mathematical formulations necessitates a planning horizon of five years compared to the conventional one to two year horizon. As the utilities catered by captive power plants are very sensitive to power failure, the reliability of power supply has been evaluated by loss of load probability (LOLP) index. The significant contribution of this paper is to evaluate confidence intervals of LOLP instead of conventional point estimate of LOLP. A point-estimate of LOLP uses expected values and provides no information about the range of values over which LOLP may vary. Some variations from optimum schedules are anticipated while executing maintenance schedules due to different real-life unforeseen exigencies. Such exigencies are considered in terms of near-optimum schedules obtained from SA during the final stages of convergence. LOLP evaluated from such sub-optimum schedules forms the basis to treat LOLP as a random variable for subsequent evaluation of confidence intervals. Case studies pertaining to a captive power plant for an aluminium smelter corroborate that the schedules obtained from two optimization techniques yield the same optimum schedule and thus the efficacy of the proposed algorithm is validated. Also the interval of confidence for LOLP denotes the possible risk in a quantified manner and it is of immense use from perspective of captive power plants intended for quality power.
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    International journal of emerging electric power systems 2.2005, 2, art1044 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents the design of a Linear Quadratic Gaussian (LQG) regulator for the frequency control of a multi-area power system in a restructured competitive electricity market environment. A general model of the LQG regulator has been developed for multi-area system (with hydro and thermal generators) having Poolco and bilateral transactions. To account for the modeling uncertainties and non-measurable states, a Kalman filter has been designed to estimate the state variables. The controller uses these estimates, optimizes a given performance index, and reschedules the generators' outputs according to their bids for the frequency regulation. The functioning of the proposed LQG regulator has been demonstrated on a four area test system and the results have been compared with those obtained by using an optimal PID controller.
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    International journal of emerging electric power systems 2.2005, 2, art1047 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Many analytical solution methods are incapable of dealing with modern power system planning, operation and control problems due to various uncertainties involved in the system. Generation output from most of renewable energy (RE) sources is uncertain which varies with time. Therefore, appropriate solution methods need to be considered in light of the uncertainty of RE generation. In this paper, a generation duration curve approach has been presented in order to handle the uncertainty of RE generation output while solving a combined dispatch problem of fossil fuel (FF) units and RE sources. A cost minimisation scheduling problem of FF units along with forecasted quantities of RE sources is formulated and solved considering the probability of meeting or exceeding anticipated shortfalls of RE outputs. Due to the complexity of the problem a genetic algorithm (GA) based solution approach is considered for solving the problem. A test problem with five FF units and three RE sources is formulated and solved under various considerations. It is demonstrated that the combined operation of FF units with RE sources gives better results, which can also manage uncertainty associated with RE generation outputs.
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    International journal of emerging electric power systems 3.2005, 1, art1054 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This article presents a solution model for the unit commitment problem (UCP) using fuzzy logic to address uncertainties in the problem. Hybrid simulated annealing (SA), particle swarm optimization (PSO) and sequential quadratic programming (SQP) technique (hybrid SA-PSO-SQP) is used to schedule the generating units based on the fuzzy logic decisions. The fitness function for the hybrid SA-PSO-SQP is formulated by combining the objective function of UCP and a penalty calculated from the fuzzy logic decisions. Fuzzy decisions are made based on the statistics of the load demand error and spinning reserve maintained at each hour. SA is used to solve the combinatorial sub-problem of the UCP. An improved random perturbation scheme and a simple method for generating initial feasible commitment schedule are proposed for the SA method. The non-linear programming sub-problem of the UCP is solved using the hybrid PSO-SQP technique. Simulation results on a practical Neyveli Thermal Power Station system (NTPS) in India and several example systems validate, the presented UCP model is reasonable by ensuring quality solution with sufficient level of spinning reserve throughout the scheduling horizon for secure operation of the system.
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    International journal of emerging electric power systems 3.2005, 1, art1055 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents novel, simple and efficient method for ranking line outage contingencies from network loadability limit considerations. The method follows conventional optimal multiplier based Newton Raphson power flow. The simulation of line outage contingencies is carried out near pre-contingency critical loading using the above power flow. A salient feature of the method is the use of the pre-contingency power flow Jacobian factors for simulation of all contingencies. Results for two sample test systems have been obtained with the new method and continuation power flow method in order to verify the potential of the former method for practical use.
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    International journal of emerging electric power systems 4.2005, 1, art1052 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper deals with a model to simulate the operating of an autonomous induction generator. The model used is a diphase one obtained by the application of the Park transform. This model permits, when adopting some simplifying hypothesis, to take account of the saturation effect. This is achieved using a variable inductance function of the magnetising current. The non linearity is then based on the approximation of the magnetising inductance with regards to the current. In our case, we use a polynomial function, of 12th degree to perform it. This approach is simple and very accurate. The developed model has been used to study the operating of an induction machine when a capacitive bank is connected to the stator windings. The simulation calculation was achieved using MATLAB®-SIMULINK® package. This paper presents transient analysis of the self-excited induction generator. In order to simulate the voltage build-up process and the dynamic behaviour of the machine, we first establish the machine's model based on a d-q axis considering the machine's saturation effect. Secondly, effect of excitation capacitors or load imbalances on voltage build-up process is investigated. Simulations results for a 5.5 kW induction generator are presented and discussed. Several experimentations are presented to validate simulations and verify the effectiveness of the developed model.
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    International journal of emerging electric power systems 4.2005, 1, art1064 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Specially connected transformers can reduce the voltage unbalance in a High Speed Railway (HSR) power supply system. Differently connected transformers reduce unbalance differently. Traditionally, a two-dimensional figure is used to represent the degree of unbalance associated with specially connected transformers. However, such a figure cannot completely express the conditions under which the voltage unbalance factor (VUF) is maximized. This work proposes a new approach to creating figures that represent the VUF of specially connected transformers under different dispatch schedules. Besides helping engineers to estimate voltage unbalance associated with various connected transformers, the analytical results can also provide a valuable reference for train dispatchers of HSR to plan dispatching.
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    International journal of emerging electric power systems 3.2005, 2, art1116 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: To achieve a sustainable power generation industry it is necessary to study the environmental impacts and economic costs of all aspects of a power generation plants' lifecycle - from mining to electricity distribution, and, ultimately, decommission (from cradle to grave). One key component in improving and maintaining quality of life for consumers is the application of the Green Productivity Index (GPI) in order to evaluate the related factors of Life Cycle Assessment (LCA) and Life Cycle Costing (LCC). The goal of this research is to appraise the efficacy of decision-making tools in accurately assessing the potential results of 'green' improvements to coal-fired and natural gas-fired power plants in both ecological and economic terms. The recently developed Numerical Eco-load Total Standardization (LCA-NETS) evaluates environmental impacts by identifying and quantifying input energy and output waste released to the environment throughout the life cycle of a power plant. Environmental impacts caused by global and regional environmental issues are numerically calculated in the units of NETS. Environmental assessment tools such as LCA, LCC and GPI can be used to improve the 'environmental friendliness' of electricity generation by demonstrating the future sustainability of 'green' power generation plants and their contribution to the quality of life of consumer.
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    International journal of emerging electric power systems 8.2007, 2, art6 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents a Digital Signal Processor (DSP) based implementation of Hybrid of Fuzzy Logic Controller (FLC) and Proportional-Integral (PI) speed controller for Direct Torque Controlled (DTC) Permanent Magnet Synchronous Motor (PMSM) drive. The fuzzy membership function is used for hybrid control of these two FLC and PI speed controllers in such a way that at the time of dynamic conditions such as starting, the degree of belonging for FLC speed controller is higher than the PI speed controller and near set point the degree of belonging of PI controller is having higher weightage. The simulation model of the drive system is developed in MATLAB environment with simulink, PSB and FLC toolboxes to analyze the performance of the PMSM drive system. This hybrid speed controller is found suitable for DTC based PMSM drive to maintain the high level of performance while maintaining the excellent response at the time of starting, speed reversal, load perturbation and steady-state operating condition of the drive.
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    International journal of emerging electric power systems 8.2007, 1, art2 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The operating cost of a radial distribution system may be minimized by reducing the amount of real power and reactive power drawn from the transmission system. Presently, real power is being priced through a market clearing scheme all over North America. Reactive power is an ancillary service and its supply would be priced appropriately in the near future through a clearing market structure. A recent US Federal Energy Regulatory Commission staff report [1] has initiated a discussion on the formulation of a reactive power market. When such a market is designed and operated, large customers (distribution corporations) will have to purchase reactive power along with real power from the transmission corporation through an independent system operator. Envisaging such a prospect, this paper proposes a new method of reconfiguring radial systems considering costs of real and reactive power while maintaining an appropriate voltage profile and level of reliable power supply. The proposed method is tested on sample test systems and reported.
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    International journal of emerging electric power systems 8.2007, 2, art4 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The benefit to end-users of electricity, mainly in terms of low prices, is strictly related to the interaction among the consumers themselves and retailers. The literature on retail competition has highlighted possible distortions in market outcomes due to unresponsive demand and boundedly rational consumers. Hence, a model appropriate to represent this aspect of the market is needed. The paper proposes a general model of the interaction among retailers and consumers in the electricity market based on the theory of multi-agent systems. The model incorporates different assumptions concerning the behavior of the players that corresponds to different levels of interaction in determining the market outcomes. The model is validated interpretively by the results provided in terms of Game Theory equilibrium. The results of an extensive set of simulations on a population of 1,000 consumers is presented and discussed.
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 8.2007, 1, art3 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Deregulation of the power industry, increases in consumer demand of electricity and mandates to reduce greenhouse gases has significantly heightened the interest in distributed generation (DG). Typical DG sources include wind turbines, fuel cells, micro gas/diesel turbines, small hydro generators and photovoltaics. Currently most of these generation sources are optimized for local operation and thus the potential of DG that is both dispatchable and cost-effective has yet to be fully realized. One key technical challenge is the development of low-cost communications for remote telemetry and control of individual DG sources. Along with cost, other key communication system requirements are modularity, range and reliability. This paper presents a distributed generation communication system (DGCS) that is based on a wide area network (WAN) and local area network (LAN) topology and utilizes two variants of low-cost radio modems (RM) to satisfy the desired connectivity between the DG sites and a centralized control center. For the LAN, low-cost RMs operating in the industrial, scientific, and medical (ISM) frequency band offers point-to-multipoint scalability to multiple DG sites within a limited range. Integration of the ISM RMs with a cellular RM provides connectivity to a WAN or Internet thus providing long-range access to DG sites from any facility that has internet-access. Given the LAN scalability requirement, an ISM field programmable gate array (FPGA) channel simulator was developed to assess DGCS performance using channel impairments such as free-space path loss, multipath reflections, additive white Gaussian noise (AWGN), multiple access interference, and narrowband interference. This study provides the evaluation of two commercially available ISM radio modems and recommendations are made based on LAN requirements such as cost and performance given difficult channel conditions.
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 8.2007, 1, art7 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A stochastic multi-objective line security constrained problem is formulated to minimize non-commensurable objectives viz. operating cost, polluting gaseous emission and variance of active power generation and reactive power generation, with explicit recognition of statistical uncertainties in the thermal power generation cost coefficients, gaseous emission coefficients, power demands and hence power generations and bus voltages, which are considered random variables. Specific technique is put forth to convert the stochastic models into their respective deterministic equivalents. Fuzzy set theory has been exploited to evaluate the different objectives that are quantified by defining their membership functions. Security of transmission lines with respect to expected active power flow is considered in the form of fuzzy objective function. The solution set of such formulated problems is non-inferior due to contradictions among the objectives undertaken. The weighting method is used to simulate the trade-off relationship between the conflicting objectives in the non-inferior domain. Generally, the weights are either simulated or searched in the non-inferior domain. In the paper Evolutionary search technique is implemented to search the 'preferred' weightage pattern in the non-inferior domain, which corresponds to the 'best' compromised solution. Among the non-inferior solutions, the system operator selects the 'preferred' optimal operating point that provides maximum satisfaction level of the most under achieved objective in terms of membership function and is termed as fitness function. The validity of the proposed method has been demonstrated on an IEEE system comprising of 11-nodes, 17-lines and 5-generators.
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 8.2007, 1, art6 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The security of the transmission system is dependent on the relays' performance after various disturbances. Undesirable relay operation will trip the lines and lead to cascading events. In this paper the operation margin of mho relays is equivalently redefined as function of bus voltages instead of line impedance. The sensitivities of the operation margin to bus voltage and bus power is applied to quantify the vulnerability of transmission system. The contribution of the shunt compensation by SVC is analyzed based on the sensitivities (control factors) of the operation margin to the shunt susceptance. It is found that the control effect of SVC is approximately linear when the mho relay has relative smaller operation margin. In this range the linear model based on the control factors is accurate enough to simulate the control effect. It is also found that the shunt compensations at different locations may yield opposite effect to the operation margin of the mho relays, which can be easily judged by the value of the control factors.
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 8.2007, 5, art5 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents the design and analysis of a multi-phase ac-dc converter system for harmonic reduction at the point of common coupling (PCC) in vector controlled induction motor drives (VCIMD's). The design of the proposed 3-phase to 15-phase autotransformer is presented along with the VCIMD. The proposed 15-phase ac-dc converter is found capable of suppressing up to the 29th harmonic in the supply current, along with the power factor improvement close to unity in the wide operating range of the drive. The effect of load variation on VCIMD is also studied to demonstrate the effectiveness of the proposed ac-dc converter. A set of power quality indices on input ac mains and on dc bus for a VCIMD fed from existing 6-pulse and proposed 15-phase ac-dc converters are also given to compare their performance.
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    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    International journal of emerging electric power systems 8.2007, 3, art7 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper addresses the problem of curtailing the number of control actions using fuzzy expert approach for voltage/reactive power dispatch. It presents an approach using fuzzy set theory for reactive power control with the purpose of improving the voltage profile of a power system. To minimize the voltage deviations from pre-desired values of all the load buses, using the sensitivities with respect to reactive power control variables form the basis of the proposed Fuzzy Logic Control (FLC). Control variables considered are switchable VAR compensators, On Load Tap Changing (OLTC) transformers and generator excitations. Voltage deviations and controlling variables are translated into fuzzy set notations to formulate the relation between voltage deviations and controlling ability of controlling devices. The developed fuzzy system is tested on a few simulated practical Indian power systems and modified IEEE-30 bus system. The performance of the fuzzy system is compared with conventional optimization technique and results obtained are encouraging. Results obtained for a modified IEEE-30 bus test system and a 205-node equivalent EHV system a part of Indian southern grid are presented for illustration purposes. The proposed fuzzy-expert technique is found suitable for on-line applications in energy control centre as the solution is obtained fast with significant speedups with few number of controllers.
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    International journal of emerging electric power systems 8.2007, 4, art6 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents a novel concept of Static Var Compensator (SVC) damping control using a weighted sum of bus voltage angles of remote generators that are responsible for causing inter-area oscillations in power systems. These remote bus voltage angle signals are acquired through Phasor Measurement Units (PMUs). A time domain simulation study on a 39-bus New England multi-machine system is utilized to show that an SVC auxiliary damping control, based on the derivative of these remote bus voltage angles, is superior to the conventionally employed local signals in damping inter-area oscillations. The effect of transmission delay in the acquisition of remote signals is also presented and a simple mechanism to compensate this delay is proposed and validated. The robustness of the delay compensator is finally shown for a wide range of signal transmission delays. The designed SVC controller shows a superior performance in damping the inter-area oscillations despite the signal transmission delays.
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    International journal of emerging electric power systems 8.2007, 6, art1 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Series compensation at the midpoint of a transmission line creates problems to conventional protection approaches. A new fault classification technique has been developed for a transmission line with a series capacitor at the midpoint, having different percentages of compensation varying from 25% to 75%. The proposed technique requires three line currents and voltages at each end and computes fundamental phasors of these quantities using a modified version of Full Cycle Discrete Fourier Transform. Using these phasors, the absolute values of three phase impedances are calculated for faulted phase identification. Moreover, the involvement of the ground in the fault is identified using a zero sequence component of the fault current. Using a PSCAD/EMTDC software package, a large test data (28,800) set has been generated with different types of faults and system variables, which includes fault resistances, fault inception angles, fault positions (before and after series capacitor) and variable loading conditions along with wide variations in the source impedances at both ends of a transmission line. The proposed scheme is tested on the said data set and the results are found to be promising. The results indicate that the proposed technique is fast, accurate and robust for a wide variation in system and fault conditions.
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    International journal of emerging electric power systems 8.2007, 6, art4 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents an assessment of the vulnerability of the power grid to blackout using graph topological indexes. Based on a FERC 715 report and the outage reports, the cascading faults of summer WSCC 1996 are reconstructed, and the graphical property of the grid is compared between two cases: when the blackout triggering lines are removed simulating the actual sequence of cascading outages and when the same number of randomly selected lines are removed. The investigation finds that the critical path lengths of the triggering events of the July and August outages of 1996 WSCC blackout are higher than those of no-outage and arbitrary events. In addition, the small world-ness index for each of the outage triggering events is much smaller than that of normal or any no-outage scenario, indicating that events of shifting a network from small world to a random network would be more likely cascaded to wide area outage.
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    International journal of emerging electric power systems 2.2005, 1, art1 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: An asynchronous parallel electromagnetic simulation method for large scale power system is developed, in which the original system is divided into two subsystems, A and B. Subsystem A is the local system including the disturbance source and any devices that should be simulated in details. Subsystem B is the external system consisting of all the other part of the system. The time domain digital simulation of subsystem A and B are executed by two independent processes with different time-steps. Signal transmission between A and B is implemented at each time step by a series of time varying Norton equivalent circuits and equivalent voltage sources. Because the digital simulation for subsystem A and B are processed in parallel, and simulation time of process B lags that of process A, so it's called asynchronous parallel electromagnetic simulation method. The basic principle, implementation procedure and error analysis of this new method are discussed, computer coding is also implemented in one version of EMTP program. Practical power system simulation and other application with the new method are also presented.
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    International journal of emerging electric power systems 2.2005, 2, art1051 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This study aims to present a new approach to detecting high impedance faults (HIFs) in the distribution feeder. Discrete wavelet transformations (DWT) and neural networks (NN) have been widely applied in power system research. Consequently, this study developed a novel technique to discriminate effectively between the HIFs and the switch operations by combining DWT with NN. The proposed approach has three distinct features. First, the input signal of this algorithm is neutral line current, rather than the conventional currents based on three individual phases. Second, HIFs identification uses the details at levels 3, 4 and 5 and the approximations at level 5 of the neutral line current are utilized for. Third, the input signals of the three-phase voltages classify the faulty and healthy phases. The results of simulation and field staged fault clearly show that the proposed technique can accurately identify the HIFs in the distribution feeder.
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    International journal of emerging electric power systems 2.2005, 1, art1038 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Fixed shunt reactors are traditionally used in long distance EHV and UHV lines to reduce Ferranti over voltages and over voltages that arise due to load rejection. A new equipment called Controlled shunt reactor (CSR) has been developed [3] and [4]. Detailed load flow and voltage stability analysis on a typical 400KV interconnected network prove that replacement of fixed shunt reactors with CSR is beneficial. This study report is an attempt to justify and quantify the economic and technical benefits of CSR in a 400KV system
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    International journal of emerging electric power systems 2.2005, 2, art1039 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: When two protective apparatus installed in series have characteristics, which provide a specified operating sequence, they are said to be coordinated or selective. The coordination of directional overcurrent relays poses serious problems in the modern complex power system networks, which are interconnected. Researchers have looked upon the problem of coordination from different considerations by making use of computer aids. Many efforts have been made to the automation of the coordination process in the area of relay coordination. This paper compiles the most of the significant developments in the area of time-overcurrent relay coordination using different techniques and methodologies. It is hoped that this work will be useful for future generation researchers to find the relevant references to advance the research work in future.
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    International journal of emerging electric power systems 4.2005, 2, art1 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents a new approach to detection of high impedance faults in distribution systems using artificial neural networks. The proposed neural network, was trained by data from simulation of a distribution system under different faults conditions, and tested by data with different system conditions. The proposed neural network has been implemented on a digital signal processor board and its behavior is investigated on a computer power system model. Details of the design procedure, implementation and the results of performance studies with the proposed relay are given in this paper. Performance studies results show that the proposed algorithm performs very well in detecting a high impedance fault with nonlinear arcing resistance. It is clearly shown that with this integrated approach, the accuracy in fault detection is significantly improved compared to other techniques based on conventional algorithms.
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    International journal of emerging electric power systems 2.2005, 2, art1050 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents a sensitivity based approach to determine optimal location of Static VAR Compensator (SVC) for voltage security enhancement. The proposed approach of SVC placement computes sensitivity of system loading factor with respect to reactive power generation, derived from reactive power balance equation. This sensitivity factor has been termed as Bus Static Participation Factor (BSPF). The sensitivity of the most critical eigen value with respect to bus voltage magnitude has been considered as Bus Dynamic Participation Factor (BDPF). BSPF and BDPF have been combined to obtain Bus Hybrid Participation Factor (BHPF), which have been computed for the system intact case and critical contingency cases and used for selecting the optimal site for the SVC installation. The effectiveness of the proposed approach of SVC placement has been validated on a practical 75-bus Indian system with respect to enhancement of the static as well as dynamic voltage stability margins.
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    International journal of emerging electric power systems 4.2005, 2, art3 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The preset work tested a freely domain software for solving index zero and one systems of differential-algebraic equations, named as DASSL. The code encompasses an efficient variable step size and variable order based on BDF methods to solve a system of DAEs or ODEs. The code was applied in power systems time domain studies, i.e., synchronous machine angular transient stability and long-term voltage stability, using the Brazilian South-Southeast Equivalent Power System. Using this real power system model including fast and slow response control devices, it was possible to investigate the code capability in simulating different stability phenomena in the same run. The variable step size and variable order algorithm implemented in DASSL results in a very powerful tool for power system time domain computer simulation.
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    International journal of emerging electric power systems 4.2005, 2, art4 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In this paper a novel control strategy for a real synchronous generator is presented. It is based on linear, diagonal, low order, minimum-phase, fixed, and stable controllers. The controller was obtained via individual channel design (ICD), a framework that allows analysis and synthesis of multivariable control systems by means of classical techniques based on the Bode and Nyquist plots. The generator is part of a one machine - infinite bus system. A linearised model around an operating point in a rotating coordinate frame is used. The theoretical principles behind this control strategy are summarised for completeness. The results using this novel control strategy are obtained throughout simulations in MATLAB®.
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    International journal of emerging electric power systems 4.2005, 1, art1172 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Transient stability is recognized as a critical problem for modern electrical power systems, since the deregulation could involve more and more restricted margins. Continuous improvements in power electronics technology gives the possibility to improve significantly the dynamic behaviour. Recently, a great attention in the relevant literature has been paid to Superconducting Magnetic Energy Storage (SMES) devices, showing their intrinsic ability to improve power transmission capability. In the paper, a control strategy for these devices is derived starting from a Control Lyapunov function, thus determining reference values for SMES active and reactive powers injections, able to counteract the effects of large disturbances. Hence, a new topology of the power conditioning system for interfacing SMES device with a power system is proposed. Finally, a control law based upon quasi-sliding technique is employed for tracking the required active and reactive powers. In the last part of the paper an application is presented, with reference to a test system, allowing to outline the flexibility and the goodness of the proposed control strategy.
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    International journal of emerging electric power systems 8.2007, 3, art1 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper focuses on dispatching of mixed generation portfolio of renewable energy (RE) and non-RE (firm) units. A genetic algorithm (GA) based rolling window approach is developed for solving economic dispatch (ED) problem. Profit maximisation ED problem is formulated and solved which also considers New Electricity Trading Arrangements for England and Wales (NETA) market features. In this problem, a penalty approach is used in order to consider intermittency problem of RE generation output. A single GA technique is also applied for solving the formulated problem. Of these, GA based rolling window approach achieved promising results for a Generator Company, which holds both renewable and fossil fuel units and participates in the short-term market trading. It is also shown that a Generator Company can get more profit by using the possibility of increase in generation output of RE sources from their forecast positions by combining both RE and non-RE units and participating in a NETA-like market trading. This approach allows to some extent the management of uncertainty problem of RE generation output, which also accounts risk associated with power non-delivery.
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    International journal of emerging electric power systems 8.2007, 3, art3 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Unit commitment (UC), originally employed to minimize the generating cost of a vertically integrated utility, has become a basic tool for revenue adequacy evaluation by GENeration COmpanies (GENCOs). The strategic role of UC is apparent in those market environments where GENCOs are asked to internalize all costs and the relevant UC decisions within their day-ahead market bids. In this paper, a parametric UC method is presented to assess the convenience of making energy bids for marginal or nearly marginal generation units. The convenience is gauged by the basis of revenue adequacy that is on each unit's ability to cover all expenses and generate profits. Beside UC choices, the parametric UC procedure provides a market price behavior that would make it profitable to commit a certain unit for generation. A Monte Carlo simulation program is employed to find the probability that actual market prices will fulfill the revenue adequacy requirements. Market prices are handled as random variables with multivariate normal distribution, taking into account the correlation between prices at successive time periods. The parametric UC procedure and the Monte Carlo simulation are carried out by using reasonable data of generation units available to some Italian GENCOs.
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    International journal of emerging electric power systems 8.2007, 3, art2 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The present paper reports the results of a study of dielectric ageing of Ethylene Propylene Diene Monomer (EPDM) by gamma radiation. EPDM flat specimens were aged under gamma radiation with three different doses. Samples were irradiated in air up to 300 kRad with a dose rate of 51 kRad/h using a 60Co gamma source. The resistance to tracking on applying DC and AC voltage was examined. We found that the DC resistance to tracking is lower than the AC resistance. The tracking resistance under -ve DC voltages are lower than +ve DC values. With the increase in radiation dose, the DC and AC tracking resistances change in a non-linear way. The erosion depth and contact angle affected by radiation have been studied. In addition, Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) analyses were done, to analyze the morphological changes.
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    International journal of emerging electric power systems 8.2007, 2, art3 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In recent developments wind power has been gaining rapid usage as an alternative source of electrical power and there is need to formulate optimized control schemes for power generation. This paper presents a sensorless maximum power point tracking control methodology for a wind power generation system. For the sensorless vector control a sliding mode observer is utilized in the estimation of the rotor speed while the rotor position is estimated based on the flux linkage. The Powell method is introduced to improve the efficiency of the permanent magnet synchronous generator (PMSG) d-axis current optimization. To ensure robustness of the proposed paradigm to parameter variations, the windmill loss coefficients determining the optimal rotor speed are identified online. Results of simulations confirm the effectiveness of the proposed method.
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    International journal of emerging electric power systems 8.2007, 3, art5 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents the steady-state and transient behavior of a single-phase self-excited induction generator (SEIG) using a three-phase machine with one shunt and one series excitation capacitors for resistive and inductive loads. The generation scheme consists of one three-phase delta connected induction machine and two capacitors - one connected in parallel with one winding and the other in series with a single-phase load. The dynamic model of the system has been developed as a hybrid model considering the stator phase currents in abc reference frame and the rotor currents in stationary d-q axes reference frame as state variables. The simulated and experimental results are presented for different dynamic conditions such as initiation of self-excitation, load perturbation and short-circuit. The simulated results of the steady-state analysis have been compared with the transient and experimental results and a close agreement between them indicates the accuracy and effectiveness of the approach.
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    International journal of emerging electric power systems 8.2007, 4, art2 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The present work proposes an extended model representing part of a huge aluminum industry load for short-term voltage stability investigations in time domain. The efforts were concentrated in the expansion of the industrial power distribution system model including explicit representation of the main transformers, capacitors, feeders and induction motors. The extended model is validated through a comparison between computer simulation results and the industry/power system utility recordings. A real sequence of events which took place in the Brazilian North Power System in the year of 2002 causing a complete industry breakdown (loss of bulk supply) was considered here for this purpose.
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    International journal of emerging electric power systems 8.2007, 4, art5 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper proposes a new approach for solving the state estimation problem. The approach is aimed at producing a robust estimator that rejects bad data, even if they are associated with leverage-point measurements. This is achieved by solving a sequence of Linear Programming (LP) problems. Optimization is carried via a new algorithm which is a combination of ``upper bound optimization technique" and ``an improved algorithm for discrete linear approximation". In this formulation of the LP problem, in addition to the constraints corresponding to the measurement set, constraints corresponding to bounds of state variables are also involved, which enables the LP problem more efficient in rejecting bad data, even if they are associated with leverage-point measurements. Results of the proposed estimator on IEEE 39-bus system and a 24-bus EHV equivalent system of the southern Indian grid are presented for illustrative purpose.
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    International journal of emerging electric power systems 8.2007, 5, art2 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Large power systems are highly complex systems that defy predictions with any degree of certainty. In this paper, an analytical framework for the assessment of small signal stability under operating uncertainty is presented. A rigorous analysis framework for the description of uncertainty in operating conditions is suggested. Using structured singular value theory and optimization tools, techniques for robust stability analysis of complex power systems are then derived and a method to quantify the effect of parametric uncertainties on the stability of critical inter-area modes is presented. A computationally-efficient method for modeling parametric uncertainty based on linear fractional transformation (LFT) theory is investigated and tested. With this approach, it becomes possible to estimate the effects of variations in the parameters of major transmission resources on the nominal stability of critical inter-area modes.The use of the analysis methods is demonstrated on two systems: i) a two-machine test system, and ii) a two-area, 11-bus, 4-machine test system.
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    International journal of emerging electric power systems 8.2007, 5, art7 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The proposed voltage source converter is composed of a series double bridge converter with an auxiliary circuit. The auxiliary circuit injects DC voltage via the mid point of the double bridge converter. The injection ratio and frequency are chosen to convert the standard 12-pulse into 60-pulse configuration without PWM or increasing the number of bridges, thus the voltage and current harmonic can fulfill the THD limit without a conventional filter. The converter is operated under fundamental frequency for the main bridges, thus its switching lose is low. The converter can be widely used in the STATCOM and HVDC system. The paper describes the principles and control strategies of the proposed converter. The operational feasibility of the proposed converter is verified by computer simulation using the PSCAD/EMTDC package.
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    International journal of emerging electric power systems 8.2007, 6, art2 
    ISSN: 1553-779X
    Source: Berkeley Electronic Press Academic Journals
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper describes a new iterative method to locate fault on a single transmission line. The method uses synchronized voltage and current measurements from both line terminals. Using the positive sequence components of the pre-fault and the post-fault phasors, positive sequence source impedances at both terminals are first estimated. Using these source impedances and the line data, the positive sequence bus impedance matrix (Zbus) is formed. Using the properties of Zbus, an iterative algorithm is proposed to locate the fault. This algorithm is tested extensively with data obtained from the EMTP simulation of a long transmission line simulated with distributed parameters in the presence of fault resistance and CT saturation. The simulation results show that the method is very accurate and robust.
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  • 80
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    Circuits, systems and signal processing 6 (1987), S. 363-387 
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract For a broad class of interconnected nonlinear systems, this paper develops a complete design methodology for decentralized variable structure control. Specifically, the paper sets forth design schemes for local switching surfaces and the related local switched feedback gains which together force the original nonlinear interconnected system to behave as a reduced order interconnected equivalent system having a desired response such as stability, tracking, or prespecified eigenvalues. Also developed is a numerical algorithm for constructing the switched local feedback gains. A simple nonlinear example illustrates the control strategy.
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    Circuits, systems and signal processing 6 (1987), S. 391-419 
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A new stabilization method of a large-scale dynamic system, consisting of a set of interconnected subsystems, is presented in this paper. The topology of the interconnected subsystems is given as a network containing nodes with only one ingoing link, and none, one, or more outgoing links. Here, when the notion “node” is used a subsystem is assumed, and the links stand for the subsystem interconnections. The stabilization method is made only by the use of local linear state feedback around each subsystem, in order to satisfy constraints given in the problem. The interconnections among the subsystems are assumed to be nonlinear, time-varying. According to the topology of the large-scale system, the method of stabilization is hierarchic, one proceeds from node to node, and is applicable from a computer standpoint. A design algorithm follows directly, and can be made using the Generate and Test method for each subsystem independently, thus enabling designers to use a computer which has a video terminal as a peripheral unit and providing a possibility for interactive applications.
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    Circuits, systems and signal processing 6 (1987), S. 421-447 
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The estimation of covariance matrices which are structured, for example, of Toeplitz type, from measurement data is considered. The problem is considered in the context of array beamforming, and various methods of estimation are derived and compared, such comparison including consideration of the behavior of the estimate in beamforming applications.
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    Circuits, systems and signal processing 6 (1987), S. 449-456 
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The planar least-squares inverse (PLSI) polynomials are used for stabilization of two-dimensional unstable recursive filters. In order to obtain the PLSI polynomials, the main work involved consists in forming a set of linear equations and then solving them. In this paper we present an efficient and simple method to form the necessary set of linear equations (i.e., the required coefficient matrix) for a chosen pattern and order of the desired PLSI polynomial, starting from the denominator polynomial of a two-dimensional unstable recursive filter.
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    Circuits, systems and signal processing 6 (1987), S. 347-362 
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper shows how to use orthogonal functions to invert singular (i.e., generalized state-space) systems. The approach is to express the inverse system itself as a singular system, and then to apply the theory of orthogonal functions to convert that differential-algebraic system to a purely algebraicgeneralized Lyapunov equation whose solution yields the input of the original system given its output. Both left and right inversion are treated. Necessary and sufficient conditions for the existence and uniqueness of the generalized Lyapunov equation are derived, and a generalizedQZ algorithm is given for its efficient solution. It is also shown that the coefficients in the Walsh function expansion may be approximately found using an FFT-type butterfly network. These results provide both an extension in theory, by investigating the properties of a new Lyapunov equation, and an extension in the implementation of system inversion, by providing a scheme which applies to generalized state-space systems and uses an unconventional approach which may prove to be a useful contribution.
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    Circuits, systems and signal processing 6 (1987), S. I 
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    Circuits, systems and signal processing 6 (1987), S. 457-470 
    ISSN: 1531-5878
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In digital communication networks, a special class of complex biquad recursive digital filters called orthogonal filters is increasingly being used. The separate effects of the overflow and quantization nonlinearities on these orthogonal filters' responses have been investigated [5], [6]. In this paper we examine the zero-input stability properties of the actual orthogonal filter having both overflow and quantization nonlinearities. The overflow nonlinearities considered include saturation, bit-by-bit inversion, zeroing, and modulo 2 arithmetic. The quantization techniques used may be roundoff, magnitude, or value truncation. An example demonstrates the adverse coupling effect between the overflow and quantization nonlinearities. Two criteria are therefore derived to ensure asymptotic overflowstability of the filter in the presence of quantization. These criteria have been translated to the coefficient plane; various regions corresponding to different minimum wordlengths required to ensure decoupling of the overflow and quantization phenomena have been derived.
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    Circuits, systems and signal processing 6 (1987), S. 471-505 
    ISSN: 1531-5878
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The identification problem for electromagnetic objects excited by transients is discussed. Several classes of models are reviewed, and an output error model is selected. An algorithm for solving the transient identification problem using this model is presented, and some of the issues connected with its use are considered. Examples of the application of this algorithm to electromagnetic data are given.
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    Circuits, systems and signal processing 6 (1987), S. 3-30 
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Conditions are obtained for the cepstrum of anl 1 sequence having arbitrary support on theM-dimensional lattice to exist also as anl 1 sequence with arbitrary support. These conditions are used to show that the cepstrum of a sequence with support on a half-space will, when it exists, also have support on the same half-space. This result is used, in turn, to describe the support of the cepstrum of a sequence with bounded support on a half-space. The relationship between the existence of the cepstrum and bounded-input, bounded-output (BIBO) stability for all three of these cases is considered. Finally, the derivatives of the inversion operator, the homomorphic transform operator, and its inverse are calculated. These results are also useful in the one-dimensional case.
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    Circuits, systems and signal processing 6 (1987), S. 31-43 
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A signal-processing software system is described which allows the simulation of systems described by block diagrams or signal-flow graphs. A high-level data-flow language describes the interconnection of the components. All configurations of interconnections are allowed, including those containing feedback. Component systems (blocks) are allowed to be multi-input, multi-output, and to be programmed in any language. Blocks are implemented as separate processes running under a UNIX2 operating system. Input and output signals are transferred between blocks via the UNIXpipe facility. Thedata type of a signal is arbitrary in the context of the compiler; within a component or system, signals and internal variables can be either floating point or fixed point. The compiler enforces strong or weak type checking of signals according to the characteristics of the blocks generating and receiving the signals. The invariance of the program to implementation data type is accomplished by the use of abstract data types. Fixed-point simulations having differing number of bits per signal and per internal variable in a block are supported. Special display software is used to allow any signal in the system to be displayed on any graphics device.
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    Circuits, systems and signal processing 6 (1987), S. 61-75 
    ISSN: 1531-5878
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Necessary and sufficient conditions are given for the solvability of fully implicit index-one and semiexplicit index-two linear time-varying semistate systems of the formA(t)x′+B(t)x=f(t). Using these solvability criteria, we establish the convergence and stability of backward difference formulas (BDF) for solvable semiexplicit index-two systems. In the algebraic variables, these methods exhibit a boundary layer of instability of length 2k, wherek is the order of the method. Finally, we show that the systems considered in this paper belong to a class of problems, solvable by BDF, which strictly contains the systems safely transformable to standard canonical form.
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    Circuits, systems and signal processing 6 (1987), S. 45-60 
    ISSN: 1531-5878
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The design of two-dimensional IIR digital filters is approached using linear-programming techniques. The problem is formulated as an approximation problem and filter frequency response characteristics are represented via the square of the magnitude of the filter transfer function. An appropriate approximation error is minimized leading to a linear problem formulation. The latter problem does not require differential correction methods for its solution, thus resulting in a computationally efficient algorithm. Stability conditions and symmetry considerations are easily accounted for. The linear programming approach assures convergence of the solution to a global minimum, among other advantages over nonlinear methods. Several examples illustrate the strength and effectiveness of the methodology.
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    Circuits, systems and signal processing 6 (1987), S. 77-93 
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Necessary and sufficient conditions for output and state feedback stabilization are given for single-input/single-output systems. Extensions are also provided for single-input/multi-output and multi-input/single-output systems. A technique for constructing explicitly a stabilizing controller is presented, and the main differences with respect to the one-dimensional case are clarified. Finally, the existence of “intrinsically unstable” transfer functions, i.e., not allowing stabilizable realizations, is discussed.
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    Circuits, systems and signal processing 6 (1987), S. 95-106 
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A single-parameter controlled-variable amplitude change function has been constructed for digital filtering using multiple units of a prototype filter. The limits of variation are discussed. The technique is shown to be useful not only for the reduction of errors in either the pass band or the stop band of the overall filter, but also for varying the cutoff frequency of the overall filter over a wide range. Hardware implementation problems resulting from a wide variation are shown to be overcome by a modular approach.
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    Circuits, systems and signal processing 6 (1987), S. 125-126 
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    Circuits, systems and signal processing 6 (1987), S. 123-123 
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    Topics: Electrical Engineering, Measurement and Control Technology
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    Circuits, systems and signal processing 6 (1987), S. 107-119 
    ISSN: 1531-5878
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper considers the problem of estimating the parameters of continuous-time stationary Gaussian processes with rational spectra, from uniformly sampled measurements. The sampled process is shown to be an autoregressive moving-average process, and explicit relationships between the parameters of the continuous-time and the sampled processes are derived. These relationships are then used to derive a lower bound on the variances of biased estimates of the continuous-time parameters, and on the generalized variance of such estimates. It is shown by some examples that the bound on the generalized variance depends on the sampling interval in a nonmonotonic manner. In particular, for each specific set of parameters there exists a sampling interval for which the lower bound is minimized.
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    Circuits, systems and signal processing 6 (1987), S. 127-137 
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The identification of concurrency is a critical factor in the high-speed calculation of algorithms. This study considers maps onX, a discrete resolution space. We establish a resolution on the space of linear maps onX which exhibit compatibility with array processing. Our results are extended to the partially ordered resolution space setting. While on-line array processing motivates our study, the results also suggest efficient processing procedures for off-line applications.
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    Circuits, systems and signal processing 6 (1987), S. 139-151 
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper describes a method for designing systolic structures with bit-level pipelining. The proposed technique starts with the signal flow graph representation of a given algorithm. A new signal flow graph rule, called the gain transfer rule is introduced to achieve bit-level pipelining. Using this approach, systolic arrays with bit-level pipelining are derived for a general recursive digital filter and a convolver. The proposed technique is quite general and has also been applied to obtain systolic structures for other problems such as vector transformation. In comparison with some previously reported designs, the new architectures are characterized by simpler basic processing cells and faster data throughput rate or smaller chip area requirements.
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    Circuits, systems and signal processing 6 (1987), S. 191-215 
    ISSN: 1531-5878
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract NON-VON is a highly parallel non-von Neumann supercomputer presently under construction at Columbia University. The basis for NON-VON's significant cost/performance advantage lies in a highly unusual application of VLSI technology to the realization of massive computational parallelism. This paper outlines the manner in which the emerging technology of VLSI circuits is employed in NON-VON to achieve this advantage. Particular emphasis is given to novel aspects of the design, layout, and operation of the NON-VON processing element, eight of which are to be embedded within each integrated circuit chip.
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    Circuits, systems and signal processing 6 (1987), S. 153-174 
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Parallel sorting algorithms have been proposed for VLSI implementation. Random defects in the silicon wafer and fabrication errors render processors in the wafer faulty, and may cause these algorithms to fail despite a significant number of nonfaulty processors. This paper presents twofault-tolerant pipelined sorting algorithms that would work on a wafer comprised of faulty and nonfaulty processors. Both the algorithms useO(n) processors and requireO(n) time to sortn elements.
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