ALBERT

Description: This paper presents a novel energy management strategy for a hybridized power source small urban electric vehicle (EV). First, an analysis of load requirements for typical urban driving cycles is presented. Thereafter, the energy and power management issues are addressed for a multisource EV to define an improved management architecture. A dynamically restricted search space strategy coupled with a simulated annealing technique is exploited to accomplish the global optimization of the energy management system (EMS). The control of the dc/dc converter operations based on this EMS is also presented. The multiple sources have been simulated using an overall model implemented in Matlab/Simulink. A reduced-scale prototype has been built to analyze the performance of the energy management strategy. The results obtained show that energy management has been enhanced leading to an increase of the vehicle performance with reduced size embarked sources.

Description: Prediction intervals (PIs) are a promising tool for quantification of uncertainties associated with point forecasts of wind power. However, construction of PIs using parametric methods is questionable, as forecast errors do not follow a standard distribution. This paper proposes a nonparametric method for construction of reliable PIs for neural network (NN) forecasts. A lower upper bound estimation (LUBE) method is adapted for construction of PIs for wind power generation. A new framework is proposed for synthesizing PIs generated using an ensemble of NN models in the LUBE method. This is done to guard against NN performance instability in generating reliable and informative PIs. A validation set is applied for short listing NNs based on the quality of PIs. Then, PIs constructed using filtered NNs are aggregated to obtain combined PIs. Performance of the proposed method is examined using data sets taken from two wind farms in Australia. Simulation results indicate that the quality of combined PIs is significantly superior to the quality of PIs constructed using NN models ranked and filtered by the validation set.

Description: This paper presents a supervisory control unit (SCU) combined with short-term ahead wind speed prediction for proper and effective management of the stored energy in a small capacity flywheel energy storage system (FESS) which is used to mitigate the output power fluctuations of an aggregated wind farm. Wind speed prediction is critical for a wind energy conversion system since it may greatly influence the issues related to effective energy management, dynamic control of wind turbine, and improvement of the overall efficiency of the power generation system. In this study, a wind speed prediction model is developed by artificial neural network (ANN) which has advantages over the conventional prediction schemes including data error tolerance and ease in adaptability. The proposed SCU-based control would help to reduce the size of the energy storage system for minimizing wind power fluctuation taking the advantage of prediction scheme. The model for prediction using ANN is developed in MATLAB/Simulink and interfaced with PSCAD/EMTDC. Effectiveness of the proposed control system is illustrated using real wind speed data in various operating conditions.

Description: Due to its reduced communication overhead and robustness to failures, distributed energy management is of paramount importance in smart grids, especially in microgrids, which feature distributed generation (DG) and distributed storage (DS). Distributed economic dispatch for a microgrid with high renewable energy penetration and demand-side management operating in grid-connected mode is considered in this paper. To address the intrinsically stochastic availability of renewable energy sources (RES), a novel power scheduling approach is introduced. The approach involves the actual renewable energy as well as the energy traded with the main grid, so that the supply–demand balance is maintained. The optimal scheduling strategy minimizes the microgrid net cost, which includes DG and DS costs, utility of dispatchable loads, and worst-case transaction cost stemming from the uncertainty in RES. Leveraging the dual decomposition, the optimization problem formulated is solved in a distributed fashion by the local controllers of DG, DS, and dispatchable loads. Numerical results are reported to corroborate the effectiveness of the novel approach.

Description: The present paper investigates the effect of high penetration of photovoltaic (PV) systems on the small signal stability of a large power system. Reduced system inertia and altered power flow patterns as a result of the addition of the utility scale and residential rooftop PVs that replace a portion of conventional generation resources, may lead to decreased damping of the critical modes of the system. To identify the critical modes of the system and the effect of the high PV penetration on these modes, eigenvalue analysis is carried out on the aforementioned system under various PV penetration levels. To substantiate the results observed from the small signal analysis, transient analysis is carried out on the system under various PV penetration levels. The simulation results effectively identify the impact of high PV penetration on small signal stability of the studied system.

Description: A speed exclusion zone algorithm to prevent the rotor rotational frequency from exciting the side-side tower mode in a variable-speed wind turbine was designed. The algorithm was first tested on a simple wind turbine model developed in Simulink and then implemented and tested on an experimental test rig. Different speed exclusion zone widths were tested to observe how the performance of the wind turbine is affected. Results obtained from both simulations and experiments showed the effectiveness of the speed exclusion zone algorithm in preventing excitation of tower resonance. Results from different speed exclusion zone widths showed that with a wider exclusion zone, the tower mode is excited less at the expense of a larger power loss.

Description: A control strategy for the quasi-Z-source inverter (qZSI) with a battery-based photovoltaic (PV) power conversion system is proposed. A battery-assisted qZSI can buck/boost PV panel voltage by introducing shoot-through states, and make full use of PV power by the energy-stored battery paralleled to the quasi-Z-source capacitor. A dynamic small-signal model of the battery-assisted qZSI is established to design a closed-loop controller for regulating shoot-through duty ratio and managing the battery's energy storage. A modified space vector modulation (SVM) technique for the qZSI is applied to achieve low harmonics, high voltage utilization, and high efficiency. A P-Q decoupled grid-tie power injection is fulfilled with the maximum power capture from PV panels and the unity power factor. The validity of the proposed PV system is proved by experimental results, showing an efficient method for the energy-stored PV power generation.

Description: Doubly-fed induction generator (DFIG)-based wind turbines (WTs) are reported to suffer reliability problems due to the presence of slip-rings, brushes, and the gearbox. These disadvantages encouraged several research groups to investigate the viability of employing single or double-frame brushless cascade DFIGs (BCDFIGs) in grid-connected multimegawatt WTs especially offshore and in solar chimney power plants. In this regard, this paper tackles three main issues. Initially, the expected reduction in gear ratio when BCDFIGs are used instead of DFIGs is examined from a steady state perspective. A reduction would lead to less frequent maintenance and an improved return on investment. Next, a detailed comparison between DFIG-WTs and BCDFIG-WTs under unbalanced grid voltage is presented. Finally, the extent to which a multimegawatt BCDFIG-WT is grid code compliant in terms of fault ride-through capability is studied. This is illustrated by comparing and quantifying the response of a DFIG-WT and a BCDFIG-WT to a severe three-phase voltage dip. Simulation and experimental results indicate promising behavior for BCDFIGs during disturbances.

Description: We analyze the potential benefits of colocating wind and concentrating solar power (CSP) plants in the southwestern U.S. Using a location in western Texas as a case study, we demonstrate that such a deployment strategy can improve the capacity factor of the combined plant and the associated transmission investment. This is because of two synergies between wind and CSP: 1) the negative correlation between real-time wind and solar resource availability and 2) the use of low-cost high-efficiency thermal energy storage in CSP. The economic tradeoff between transmission and system performance is highly sensitive to CSP and transmission costs. We demonstrate that a number of deployment configurations, which include up to 67% CSP, yield a positive net return on investment.

Description: Renewable energy resources, especially wind power, are expected to provide a considerable portion of the world energy requirements in the near future. Large-scale wind power penetration impacts the electricity industry in many aspects and raises a number of technical challenges for the electricity network. A day-ahead network-constrained market clearing formulation is proposed which considers demand side resources. The proposed approach can provide flexible load profile and reduce the need for ramp up/down services by the conventional generators. This method can potentially facilitate a large penetration of wind power by shifting the wind power generation from the off-peak periods to the high-peak hours. The validity of the proposed approach has been verified using the IEEE 30 bus and 57 bus test systems.

Description: The small generation units including cogeneration units and renewables have been widely spread during the last decades. These units raise several questions regarding the power system, e.g., their integration into power system control or their role on the supply-side of smart grids. A multiagent model was established in order to facilitate the investigations of the emerged questions. Several viewpoints are taken into account and built into the model considering technical specifications, proper wind-speed and temperature simulations, constraints of heating service, fuel consumption, legal regulation, outages, and services. A state-based method is elaborated in order to generalize different technologies. The different aspects of operation control are represented by agent strategies. Applying these methods resulted in an easy-to-follow and flexible model. This paper is dealing with the developed multiagent-based model applied to study the distributed generation system from many viewpoints like power system balance, virtual power plant, or smart grid scheduling.

Description: The trend towards multimegawatt (multi-MW) wind turbines and the increasing interest in direct-drive variable-speed wind energy systems have made multilevel converters a promising candidate for large wind energy conversion systems. This paper presents a new hybrid modular multilevel converter for interfacing a full-scale, permanent magnet synchronous generator (PMSG)-based direct-drive variable-speed wind energy conversion system (WECS). The proposed hybrid converter, which is used on the grid side of the system, consists of a three-level modular multilevel converter (MMC) in series connection with three H-bridge modules. The generator-side converter is based on a conventional three-level neutral-point-clamped converter. The proposed hybrid converter, as opposed to the existing full-scale multilevel converter-based wind energy systems, provides structural modularity and a higher dc-bus voltage utilization. This paper formulates and analyzes the internal dynamics of the proposed hybrid converter including the circulating currents and the capacitor voltage ripples. The ac components of the circulating currents, if not properly reduced, increase the amplitude of the capacitor voltage ripples, rating values of the converter components, and losses. Based on the analysis, closed-loop circulating current and capacitor voltage ripple reduction techniques are developed. The reduction of capacitor voltage ripples help reduce the capacitor value. A mathematical model is also developed for the overall WECS. Performance of the overall WECS, under the proposed multilevel converter-based topology and controls, is evaluated based on time domain simulations in the PSCAD/EMTDC environment.

Description: Electric vehicles (EVs) are likely to have a continued presence in the light-vehicle market in the next few decades. As a result, EV charging will put an extra burden on the distribution grid and adjustments need to be made in some cases. On the other hand, EVs have the potential to support the grid as well. This paper presents a single-phase bidirectional charger topology which pairs up a photovoltaic (PV) source with an EV charger resulting in production cost reduction. The presented topology is then used for vehicle-to-grid (V2G) services. The main focus of this paper is on power quality services which only slightly discharge the battery. Among these services, it studies the possibility of local reactive injection of EVs connected to the grid through a single-phase charger to compensate for voltage drops caused by motor startup or inductive loads. It also studies the possibility of active power injection of EVs for short time periods during PV transients in cloudy weather to keep the system stable. It also studies the potential of EVs to help during low voltage ride-through of the PV sources. The studies are performed using Simulink simulations and a real-time implementation in Real Time Digital Simulator (RTDS). The results demonstrate the effectiveness of power quality V2G services with small wear on the EV battery.

Description: The short-term wind power scenarios have a significant impact on the operation cost and power system reliability due to the stochastic generation scheduling of wind-integrated power systems. In order to obtain the scenarios containing the information of forecast error distribution and fluctuation distribution for short-term wind power, a scenario generation method is proposed. This paper characterizes forecast error via empirical distributions of a set of forecast bins and assumes that wind power fluctuations over unit interval follow $t$ location-scale distribution. An inverse transform sampling from a multivariate normal distribution is adopted to generate a large number of wind power scenarios. The covariance matrix of the multivariate normal distribution is estimated to fit the distribution of historical wind power fluctuations. The proposed scenario generation method is applied to the actual aggregate wind power data in the whole regions of Ireland's Power System. The results indicate that the variability of wind power scenarios can be adjusted by estimating the key range parameter in the exponential covariance structure of a multivariate normal distribution.

Description: Nanofiltration for water and wastewater treatment – a mini review Drinking Water Engineering and Science, 6, 47-53, 2013 Author(s): H. K. Shon, S. Phuntsho, D. S. Chaudhary, S. Vigneswaran, and J. Cho The application of membrane technology in water and wastewater treatment is increasing due to stringent water quality standards. Nanofiltration (NF) is one of the widely used membrane processes for water and wastewater treatment in addition to other applications such as desalination. NF has replaced reverse osmosis (RO) membranes in many applications due to lower energy consumption and higher flux rates. This paper briefly reviews the application of NF for water and wastewater treatment including fundamentals, mechanisms, fouling challenges and their controls.

Description: Application of DVC-FISH method in tracking Escherichia coli in drinking water distribution networks Drinking Water Engineering and Science, 6, 25-31, 2013 Author(s): L. Mezule, S. Larsson, and T. Juhna Sporadic detection of live (viable) Escherichia coli in drinking water and biofilm with molecular methods but not with standard plate counts has raised concerns about the reliability of this indicator in the surveillance of drinking water safety. The aim of this study was to determine spatial distribution of different viability forms of E. coli in a drinking water distribution system which complies with European Drinking Water Directive (98/83/EC). For two years coupons (two week old) and pre-concentrated (100 times with ultrafilters) water samples were collected after treatment plants and from four sites in the distribution network at several distances. The samples were analyzed for total, viable (able to divide as DVC-FISH positive) and cultivable E. coli . The results showed that low numbers of E. coli enters the distribution sytem from the treatment plants and tend to accumulate in the biofilm of water distribution system. Almost all of the samples contained metabolically active E. coli in the range of 1 to 50 cells per litre or cm 2 which represented approximately 53% of all E. coli detected. The amount of viable E. coli significantly increased into the network irrespective of the season. The study has shown that DVC-FISH method in combination with water pre-concentration and biofilm sampling allows to better understand the behaviour of E. coli in water distribution networks, thus, it provides new evidences for water safety control.

Description: A fuzzy fault-tolerant control (FFTC) framework is proposed for wind-diesel-hybrid systems (WDHS) with time-varying bounded sensor faults. The algorithm utilizes fuzzy systems based on “Takagi–Sugeno” (TS) fuzzy models to represent nonlinear systems. A fuzzy proportional-integral estimation observer (FPIEO) design is proposed to achieve fault estimation of TS models with abrupt sensor faults. Sufficient conditions are derived for robust stabilization in the sense of Lyapunov asymptotic stability and are formulated in the format of linear matrix inequalities (LMIs) to obtain controller gains and observer gains. The proposed algorithm maximizes the produced power, minimizes the voltage ripple, and is able to maintain the system's stability during the sensor faults. A physical model of the WDHS is presented and transformed into a TS model. Then, an FFTC algorithm is developed and applied to a WDHS to demonstrate the effectiveness of this method.

Description: Modeling wind speed time series (WSTS) is an essential part of network planning studies in order to generate synthetic wind power time series (WPTS). Hence, this paper proposes a methodology to equip planners with accurate simulation of wind speed and power variations as well as complete temporal dependence structure based on the copula theory. Unlike traditional autoregressive and Markov chain methods, the suggested technique is well-prepared to deal with “nonlinear long-memory temporal dependence” and “non-Gaussian empirical probability distributions” of the WSTS. Meanwhile, the proposed statistical modeling framework is compatible with the scenario-based analysis of active networks as well. Furthermore, a case study for optimal sizing of an autonomous wind/photovoltaic/battery system is presented. The purpose of the presented study is to fully examine the accuracy and effectiveness of the copula-based model of wind generation for planning nonmemoryless power systems. Among a list of commercially available system devices, the optimal number and type of units are calculated ensuring both a minimum 20-year round total system cost and a perfect reliability. The genetic algorithm is used in four wind generation scenarios consisting of real and simulated WPTS. Then, considering the corresponding optimal solutions, the autoregressive moving average (ARMA), nonparametric Markov and proposed copula-based simulations are compared against real data.

Description: This paper presents series grid interface topologies for enhancing the fault ride-through (FRT) performance of doubly-fed induction generator (DFIG)-based wind turbines (WTs). Two voltage booster schemes, 1) dynamic voltage restorer (DVR) and 2) resistive type high temperature superconducting fault current limiter (HTS-FCL), are designed and implemented. The test system represents a WT connected to an electric grid with alternatively employing DVR and HTS-FCL. Both schemes provide fast mitigation of voltage dip that maintains the nominal operating conditions for DFIG-WT. To achieve a flexible control solution for balanced and unbalanced fault conditions, the DVR employs positive and negative sequence controllers while the HTS-FCL is designed to perform fast quenching for each phase individually. The potential of the two booster schemes is evaluated and analyzed in positive and negative sequence reference frames. Comprehensive simulation studies are presented to verify the capability of the series grid interface schemes for ensuring the normal operation and smooth wind power evacuation with effective isolation from grid faults. Furthermore, the grid code requirements of reactive current support are evaluated for both schemes at various fault scenarios.

Description: This paper presents a real-time mechanism to tolerate faults occurring in a wind turbine (WT) system. This system is a FAST coded simulator designed by the U.S. National Renewable Energy Laboratory's (NREL's) National Wind Turbine Center. The demonstrated mechanism lies under the taxonomy of active fault-tolerant control (AFTC) systems, namely the projection-based approach. In the proposed approach, we do not use any a priori information about the model of the turbine in real-time. In fact, we use the online measurements generated by WT. Based on the given control objectives, and the observed measurements, an occurring fault is accommodated by reconfiguring the controller such that the turbine generates the rated power even under faulty conditions. Second, no use of an explicit fault-diagnosis module is seen in this approach. Therefore, the fault accommodation delay in the proposed AFTC structure is smaller than the delay as experienced in the traditional structure of AFTC systems.

Description: Conventionally operated full power converter wind plants show high short-term power output variability caused by variable winds, and does not contribute to the power system inertia due to the decoupled generator speed and grid frequency. There is, however, abundant inertial resources in wind plant rotors for both smoothing of output power and for synthetic inertia contribution. Together with added frequency controlling functionality, this could facilitate inclusion of wind power in islanding systems, enabling greater system loads and enhancing power system stability. This paper describes modeling of power smoothing and frequency controlling wind plants and assesses different control strategies as well as the grid frequency performance gains achievable over hydro powered islanding systems and over islanding systems incorporating both hydro power and conventional wind plants. The results show that wind plant power output could be smoothed in the short time frame, and support frequency in both primary and secondary frequency control timescales including droop functionality.

Description: This paper deals principally with the grid connection problem of a kite-based system, named the “Kite Generator System (KGS).” It presents a control scheme of a closed-orbit KGS, which is a wind power system with a relaxation cycle. Such a system consists of a kite with its orientation mechanism and a power transformation system that connects the previous part to the electric grid. Starting from a given closed orbit, the optimal tether's length rate variation (the kite's tether radial velocity) and the optimal orbit's period are found. The trajectory-tracking problem is not considered in this paper; only the kite's tether radial velocity is controlled via the electric machine rotation velocity. The power transformation system transforms the mechanical energy generated by the kite into electrical energy that can be transferred to the grid. A Matlab/simulink model of the KGS is employed to observe its behavior, and to insure the control of its mechanical and electrical variables. In order to improve the KGS's efficiency in case of slow changes of wind speed, a maximum power point tracking (MPPT) algorithm is proposed.

Description: To maximize the revenue from selling energy, photovoltaic systems (PVs) in general operate in the so-called maximum power point tracking mode. However, the increasing penetration of renewable energy sources in power systems has motivated the design of innovative control to provide ancillary services. The focus of this paper is to develop a new control strategy that enables PVs to adjust the active power outputs and provide frequency regulation to power systems. In this strategy, two different modes are designed: 1) the frequency droop control mode for PVs to provide primary frequency support to power systems, and 2) the emergency control mode to prevent system frequency collapse and, therefore, to prevent too much generation tripping after fault. Based on a detailed PV dynamic model, simulation results show the effectiveness of the proposed control strategy in improving the frequency stability.

Description: Standalone microgrids with renewable sources and battery storage play an important role in solving power supply problems in remote areas such as islands. To achieve reliable and economic operations of a standalone microgrid, in addition to the consideration of utilization of renewable resources, the lifetime characteristics of a battery energy storage system also need to be fully investigated. In this paper, in order to realize the economic operation of a recently developed standalone microgrid on Dongfushan Island in China, an optimization model including battery life loss cost, operation and maintenance cost, fuel cost, and environmental cost is established to obtain a set of optimal parameters of operation strategy. Considering the lifetime characteristics of lead–acid batteries, a multiobjective optimization to minimize power generation cost and to maximize the useful life of lead–acid batteries has been achieved via the nondominated sorting genetic algorithm (NSGA-II). The results show that the proposed method can optimize the system operations under different scenarios and help users obtain the optimal operation schemes of the actual microgrid system.

Description: Plug-in electric vehicles in the future will possibly emerge widely in city areas. Fleets of such vehicles in large numbers could be regarded as considerable stochastic loads in view of the electrical grid. Moreover, they are not stabled in unique positions to define their impact on the grid. Municipal parking lots could be considered as important aggregators letting these vehicles interact with the utility grid in certain positions. A bidirectional power interface in a parking lot could link electric vehicles with the utility grid or any storage and dispersed generation. Such vehicles, depending on their need, could transact power with parking lots. Considering parking lots equipped with power interfaces, in more general terms, parking-to-vehicle and vehicle-to-parking are propose here instead of conventional grid-to-vehicle and vehicle-to-grid concepts. Based on statistical data and adopting general regulations on vehicles (dis)charging, a novel stochastic methodology is presented to estimate total daily impact of vehicles aggregated in parking lots on the grid. Different scenarios of plug-in vehicles' penetration are suggested in this paper and finally, the scenarios are simulated on standard grids that include several parking lots. The results show acceptable penetration level margins in terms of bus voltages and grid power loss.

Description: It is demonstrated that a physical-based equivalent electrical circuit could be developed based on electrochemical impedance spectroscopy (EIS) to describe electrochemical performance of a commercial $hbox{Li}_{1-{x}}hbox{PO}_{4}$ -cathode, Li-ion cell. This model uses only EIS modeling and Fourier transform techniques to provide reasonably accurate voltage performance characteristics while providing insight into the physical processes at work in the cell.

Description: The demand for reducing fossil fuel consumption and carbon emissions has stimulated the development and deployment of electric vehicles (EVs). The reliability of power systems will be significantly influenced by the increasing penetration of EVs. Currently, there are mainly two potential modes for EVs charging: 1) plug-in mode and 2) battery exchange (BE) mode. There have been many papers studying the impact of EVs using plug-in mode. However, research on BE mode is still only limited. This paper aims at estimating the reliability impact caused by EVs using BE mode. First, the behavior of EV users under BE mode are extracted from two reliable databases. The behavior extraction method is developed specifically for BE mode, which is modified based on a method originally designed for plug-in mode. Afterwards, power system reliability is studied from the viewpoint of both the power system and the EV users by introducing a new reliability index named User Demand Not Satisfied (UDNS). The algorithm for reliability assessment is developed based on an algorithm designed for energy storage system (ESS) integration. The numerical results demonstrate the integration of EVs using BE mode can greatly benefit the reliability performances of power systems.

Description: As increasing number of nations, industries, and individuals are involved in the carbon mitigation initiative, it becomes significant to answer what amount of carbon emissions social entities are responsible for, especially from electricity service. In this paper, a carbon flow tracing method is presented to determine carbon emissions obligation from electricity consumption. The method traces energy sources of electricity consumption across the electricity network to determine the indirect carbon emissions caused. From a “generation-to-consumption” perspective, the transmission characteristic of electricity supply and locational energy mix are reflected. The method is employed to address two important issues uniformly, i.e., carbon accounting at the regional level and locational carbon intensity assessment at the user level, respectively. Test results from two examples show that the method is a preferable choice to solve the two problems. Additionally, the method may contribute to carbon reduction cooperation and end user participation in carbon mitigation.

Description: This paper presents an intelligent economic operation of smart grid environment facilitating an advanced quantum evolutionary method. The proposed method models the wind generation (WG) and photovoltaic (PV) generation as renewable power generation sources as a measure of global warming effect. Thermal generators (TGs) are included in this model to provide the maximum amount of energy to meet consumers' demand. On the other hand, plug-in hybrid electric vehicles (PHEVs) are capable of reducing CO $_2$ , NO $_x$ , and gradually becoming an integral part of smart-grid infrastructure. Such integration introduces uncertainties into the system that are addressed by fuzzy-logic-based formulations. Demanded load, wind speed, solar radiation, and number of involved PHEVs are taken under fuzzy formulations. An intelligent quantum inspired evolutionary algorithm (IQEA) is proposed and applied in this model to perform the intelligent economic scheduling operation concerning scheduling and dispatching TG, WG, PV, and PHEV. IQEA features intelligent operators such as sophisticated rotation operator, differential operator, etc. The method is tested on a hypothetical power system with 10 thermal units, equivalent number of PHEVs, equivalent solar and wind farm. The simulation results will show the effectiveness of IQEA that provides excellent operational resource scheduling while reducing the production cost and emission.

Description: Often voltage rise along low voltage (LV) networks limits their capacity to accommodate more renewable energy (RE) sources. This paper proposes a robust and effective approach to coordinate customers' resources and control voltage rise in LV networks, where photovoltaics (PVs) are considered as the RE sources. The proposed coordination algorithm includes both localized and distributed control strategies. The localized strategy determines the value of PV inverter active and reactive power, while the distributed strategy coordinates customers' energy storage units (ESUs). To verify the effectiveness of proposed approach, a typical residential LV network is used and simulated in the PSCAD-EMTC platform.

Description: It is well known that control systems, which can modulate the power takeoff force of a wave energy device, have the capability of extending the effective device bandwidth and thereby improve energy capture. For an array of wave energy devices, there is the additional complication that each device is subject to radiated waves from other devices, which are a function of the device motion and, hence, an indirect function of each of the device controllers. This gives the possibility of enhancing the energy harvesting properties of the wave farm as a whole, by giving each controller information about the motion of other devices and employing a global performance function which allows coordinated control for the overall benefit of the farm. This paper examines the possibilities of using such coordinated control and makes conclusions on the types of devices, and types of arrays, that might benefit from such coordinated control. In addition, the overall benefit of a global array control strategy, compared to independent control of each device, is assessed against the added complexity of a coordinated control strategy.

Description: Providing information about the leak flow rate caused by a loss-of-coolant accident (LOCA) to nuclear power plant (NPP) operation personnel is a key to the management and mitigation of severe post-LOCA circumstances at NPPs where active safety injection systems do not actuate. The leak flow rate is a function of break size, differential pressure (i.e., difference between internal and external reactor vessel pressure), temperature, and so on. In this study, the break position and size were first identified and predicted, and then, the leak flow rate was predicted using a fuzzy neural network (FNN). The FNN was developed using training data and validated using independent test data. The data were generated from simulations of the optimized power reactor 1000 (OPR1000) using MAAP4 code. The data for training the FNN model were selected among the acquired data using the subtractive clustering method, and FNN performance was improved. The developed FNN model was sufficiently accurate to be used for predicting leak flow rate, which is useful information for managing severe post-LOCA situations.

Description: The gigabit laser driver (GBLD) and low-power GBLD (LpGBLD) are two radiation-tolerant laser drivers designed to drive laser diodes at data rates up to 4.8 Gb/s. They have been designed in the framework of the gigabit-transceiver (GBT) and versatile-link projects to provide fast optical links capable of operation in the radiation environment of future high-luminosity high-energy physics experiments. The GBLD provides laser bias and modulation currents up to 43 mA and 24 mA, respectively. It can thus be used to drive vertical cavity surface emitting laser (VCSEL) and edge-emitting laser diodes. A pre-emphasis circuit, which can provide up to 12 mA in 70 ps pulses, has also been implemented to compensate for high external capacitive loads. The current driving capabilities of the LpGBLD are 2 times smaller that those of the GBLD as it has been optimized to drive VCSELs in order to minimize the power consumption. Both application-specific integrated circuits are designed in 0.13 $~mu$ m commercial complementary metal–oxide semiconductor technology and are powered by a single 2.5 V supply. The power consumption of the core circuit is 89 mW for the GBLD and 55 mW for the LpGBLD.

Description: This paper presents a new SEU-tolerant latch design based on Quatro and NMOS feedback transistors. By using these feedback transistors, the SEU susceptibility is decreased because of the cutoff feedback loop. Simulation results demonstrate that the proposed design is immune to static single node upsets. The proposed latch and the reference Quatro were designed and fabricated on a 130 nm process. The test chip was exposed to heavy ions at the TAMU Cyclotron facility. The testing results show that the proposed design has a higher upset LET threshold and lower cross-section when compared to the reference latch. Its lower SEU vulnerability comes with small area penalty.

Description: This paper provides a detailed description of the Energetic Particle Telescope (EPT) accommodated on board the PROBA-V satellite launched on May 7th, 2013 on a LEO, 820 km altitude, 98.7 $^circ $ inclination and a 10:30–11:30 Local Time at Descending Node. The EPT is an ionizing particle spectrometer that was designed based on a new concept and the most advanced signal processing technologies: it performs in-flight electron and ion discrimination and classifies each detected particle in its corresponding physical channels from which the incident spectrum can be readily reconstructed. The detector measures electron fluxes in the energy range 0.5–20 MeV, proton fluxes in the energy range 9.5–300 MeV and He-ion fluxes between 38 and 1200 MeV. The EPT is a modular configurable instrument with customizable maximum energy, field of view angle, geometrical factor and angular resolution. Therefore, the features of the currently flying instrument may slightly differ from those described in past or future configurations. After a description of the instrument along with the data acquisition and analysis procedures, the first particle fluxes measured by the EPT will be shown and discussed. The web-site located at http://web.csr.ucl.ac.be/csr_web/probav/ which daily displays measured fluxes and other related studies will also be briefly described.

Description: Dynamic random access memory (DRAM) data retention time degradation induced by radiation exposure is investigated in this paper. We present the experimental setup and the results of total ionizing dose (TID) test on a COTS SDRAM device. We observed a significant retention time reduction related to the absorbed dose and we assume radiation induced interface trap generation as the origin of the retention time reduction. By measuring individual cells retention time before and after radiation exposures, we found out that the reduction is not homogeneous among cells: the amount of leakage current increase depends on the position and the energy level of the generated trap, leading to a wide distribution of retention time reduction. Of particular interest is the fact that device was unbiased during irradiation and that no post-irradiation recovery was observed.

Description: A serpentine transmission-line in a microstrip configuration is used to enable fine position sensing in semiconductor radiation detectors. Specifically demonstrated with silicon substrates coupled to standard charge-sensitive preamplifiers, a meandering electrode is used to enable lateral position sensing to within an approximately 1 cm length along the electrode. Configured in a rectilinear shape, the lateral resolution is therefore equivalent to the strip pitch, which we have made as small as $4 ~muhbox{m}$ . The position-of-interaction is extracted using either timing or amplitude techniques, both enabled by the slow-wave propagation structure inherent to the standard metal-semiconductor-insulator configuration of the bounding electrodes, the analysis of which is summarized and compared experimentally.

Description: We developed a field-programmable gate array (FPGA) TDC module for the tracking detectors of the Fermilab SeaQuest (E906) experiment, including drift chambers, proportional tubes, and hodoscopes. This 64-channel TDC module had a 6U VMEbus form factor and was equipped with a low-power, radiation-hardened Microsemi ProASIC3 Flash-based FPGA. The design of the new FPGA firmware (Run2-TDC) aimed to reduce the data volume and data acquisition (DAQ) deadtime. The firmware digitized multiple input hits of both polarities while allowing users to turn on a multiple-hit elimination logic to remove after-pulses in the wire chambers and proportional tubes. A scaler was implemented in the firmware to allow for recording the number of hits in each channel. The TDC resolution was determined by an internal cell delay of 450 ps. A measurement precision of 200 ps was achieved. We used five kinds of tests to ensure the qualification of 93 TDCs in mass production. We utilized the external wave union launcher in our test to improve the TDC’s measurement precision and also to illustrate how to construct the Wave Union TDC using an existing multi-hit TDC without modifying its firmware. Measurement precision was improved by a factor of about two (108 ps) based on the four-edge wave union. Better measurement precision (69 ps) was achieved by combining the approaches of Wave Union TDC and multiple-channel ganging.

Description: By measuring the time of flight of scattered X-ray photons, the point of interaction, assuming a single scatter, can be determined, providing 3-D information about an object under inspection. This paper describes experimental ToF Compton scatter measurements conducted at the versatile electron linear accelerator (VELA), a picosecond pulsewidth electron source situated in Daresbury, U.K. The ToF of scattered X-ray photons was measured using a CeBr3 detector, and a full width at half maximum (FWHM) of between 29  and 36 cm was achieved with a 5-cm-thick plastic test object. By implementing a low-energy cutoff, the FWHM was reduced to between 12 and 26 cm. Two test objects placed in series with a 50-cm space between were separable in the data after applying the low energy cutoff.

Description: This work describes in detail the Radiation Hardness Assurance methodology applied to the development of new radiation tolerant power converter control system for the Large Hadron Collider at the European Organization for Nuclear Research (CERN). This system is based primarily on commercial-off-the-shelf components for which the extensive testing scheme is applied to decrease the probability of radiation failures during the operation of the LHC machine in the high-luminosity operating conditions era.

Description: As it is planned to switch the heavy-ion synchrotron SIS18 from single- to dual-harmonic cavity operation after construction of the new Facility for Antiproton and Ion Research (FAIR), its closed-loop control system for the damping of coherent longitudinal oscillations needs an appropriate adjustment. To damp dipole oscillations, the phase shift, applied by the control system to the first cavity voltage (running with harmonic number ${h_1}$ ) has to be doubled for the second cavity (running with double frequency and harmonic number ${h_2} = 2 cdot {h_1}$ ). Furthermore, the dipole oscillation frequency can no longer be estimated by linearization of the applied voltage like it is done in a single-harmonic cavity setting. In a dual-harmonic cavity setting as it is presented here, the dipole oscillation frequency depends nonlinearly on the bunch length. The control loop is closed by a digital signal processor, an optical splitter, and direct digital synthesizers. This paper describes the control loop and its theoretical background, and presents measurement results. In addition, simulation results and theoretical predictions are given, which are all in good agreement. Furthermore, optimal filter parameter settings are derived.

Description: In this paper, we describe the whole process of designing and manufacturing an 83.2 MHz, three-stage radio frequency (RF) amplifier for a SKKUCY-9 cyclotron. It consisted of a preamplifier, intermediate power amplifier (IPA), and power amplifier (PA) stage. The maximum power value for each stage is 0.05 kW, 1.5 kW, then 20 kW RF power. Formula calculation, circuit design, and electromagnetic analysis were implemented in the RF amplifier design. Along with the power stage and anode power supply, an RF amplifier control system for the RF amplifier was developed. After design and manufacturing, we conducted impedance matching measurements with a network analyzer to achieve $50Omega $ for the IPA and PA. Finally, we analyzed the RF amplifier characteristics by implementing RF testing with both a dummy load and a RF coupler. The expected and measured RF characteristics were in agreement, and a detailed analysis is described.

Description: A transmission particle detector based on a super-thin diamond membrane film which can also be used simultaneously as a vacuum window for ion beam extraction has been developed. Charge collection characteristics of a $6.8~mu{hbox{m}}$ -thick diamond membrane detector for high-energy heavy ions including 75 MeV Ne, 150 MeV Ar, 322 MeV Kr, and 454 MeV Xe have been investigated for the first time. Charge collection signals under single particle flux from the thin part are stable and are well distinguishable from background signals. This behavior suggests that the diamond membrane detector could be used for counting single ions. On the other hand, charge collection efficiency is found to decrease with increasing of charge generated in the diamond membrane detector. This suggests that the pulse height defect, which has been previously reported for Si and SiC detectors, also occurs in the diamond membrane detector.

Description: A novel, multi-point contact high-purity germanium detector has been developed for applications in high-rate gamma environments. The planar detector was fabricated with seven point contacts, a high-voltage steering grid and bias electrode using amorphous germanium technology. We have characterized this detector and report herein on the depletion profile, leakage current, energy resolution, and charge-sharing behavior.

Description: Stored-heat assessments: a review in the light of field experience Geothermal Energy Science, 2, 49-54, 2014 Author(s): M. A. Grant Stored-heat or volumetric assessments of geothermal resources are appealingly simple: the resource being exploited is heat. A stored-heat calculation simply computes the amount of heat in the resource, similarly to computing the amount of ore in an ore body. The method has theoretical support in numerical simulations of resource production. While there are significant unknowns in any resource, some of these can be covered by probabilistic approaches, notably a Monte Carlo method. The Australian Geothermal Reporting Code represents one specification of such stored-heat assessments. However the experience of recent decades, with the development of significant numbers of geothermal resources, has shown that the method is highly unreliable and usually biased high. The tendency to overestimates, in particular, has led to the reduced credibility of the method. An example is quoted where simple application of the apparently simple rules gives a ridiculous result. Much of the problem lies in the "recovery factor", the proportion of the resource that can actually be exploited, where comparison with actual performance shows past values have been in all cases too high, as is the current version of the Australian code. There are further problems, usually overlooked, in the way that the reservoir volume and "cutoff temperature" are defined. Differing approaches mean that results between different reports are not comparable. The different approaches also imply unrecognised assumptions about the physical processes controlling reservoir depletion. The failure of Monte Carlo methods is similarly due to unrecognised violation of logical consistency in the use of probabilities. The net effect of these problems is that the method is not a simple means to generate a rough resource estimate, and it often generates faulty results. Usually, such results are overestimates. Monte Carlo methods do not provide a protection against these errors. The Australian Geothermal Reporting Code should be used for hydrothermal systems with an average recovery factor of 10%. With this average, results are subject to an error of ±70%. For enhanced geothermal systems (EGS), the recovery factor should be a few percent.

Description: Airborne wind energy harvesting offers an alternative to traditional wind turbines by flying crosswind cycles with a tethered airfoil. By reeling in and out the tether periodically, net electrical power can be generated. When looking for the optimal cycle to fly, one should optimize for maximal electrical power generation. However, the conversion from mechanical to electrical power was not yet included in the models. In this paper, it is shown that by including an electrical energy conversion model into cycle optimization, the electrical output of the system increases and the acquired system can be used in a broader range of wind speeds. The approach is illustrated with experimentally verified models.

Description: The vital problems of the grid-connected doubly fed induction generator (DFIG) wind turbine are the fault ride through (FRT) capability and the output power fluctuation. To tackle these problems, this paper focuses on the optimization of the superconducting coil (SC) integrated into a dc link of the DFIG wind turbine for an enhancement of the FRT capability and a suppression of the output power fluctuation. The dcdc converter, which is used to control the exchanged energy between the SC and the system, is additionally connected between the grid side converter (GSC) and the rotor side converter. During normal operation, the SC acts as an energy storage device to exchange energy with the system so that the power fluctuation of the DFIG wind turbine can be alleviated. On the other hand, when severe faults occur in the system, the SC is used as the current limiting inductor to suppress both overcurrent in the rotor and stator, and overvoltage in the dc link of the DFIG. In the optimization, the inductance of the SC, the initial necessary stored energy in the SC, and the proportional integral (PI) parameters of the dcdc converter are tuned simultaneously so that both objectives can be achieved. Simulation study elucidates the control effect of the DFIG wind turbine with the optimal SC.

Description: This paper formulates and solves the economic power dispatch (ED) problem with practical operation constraints using potential games. Each generator operates as an independent player in a self-optimizing manner with marginal contribution utility functions to minimize the total generation cost. The proposed distributed formulation converts inequality constraints into feasible action sets, incorporates equality constraints by penalty functions, and extends to practical cases that exhibit non-convex or non-smooth objective functions. Two learning algorithms with guaranteed convergence to Nash equilibria and/or optima are applied to solve the proposed formulation. How generators react as best responses to others is analyzed to capture the reasoning of operations. As a numerical example, the solutions obtained using the proposed ED method in a benchmark system are analyzed. Examples are provided to emphasize how priority for renewable sources are incorporated.

Description: This paper presents control algorithms and sizing strategies for using energy storage to manage energy imbalance for variable generation resources. The control objective is to minimize the hourly generation imbalance between the actual and the scheduled generation of wind farms. Three control algorithms are compared: 1)tracking minute-by-minute power imbalance; 2)postcompensation; and 3)precompensation. Measured data from a wind farm are used in the study. The results show that tracking minute-by-minute power imbalance achieves the best performance by keeping hourly energy imbalance zero. However, the energy storage system (ESS) will be significantly oversized. Postcompensation reduces the power rating of the ESS but the hourly energy imbalance may not be reduced to zero when a large and long-lasting power imbalance occurs. A linear regression forecasting algorithm is developed for a two-stage precompensation algorithm to precharge or predischarge the ESS based on the predicted energy imbalance. An equivalent charge cycle estimation method is proposed to evaluate the effect of providing the energy balancing service on battery life. The performance comparison shows that the precompensation method reduces the size of the ESS by 30% with satisfactory performance.

Description: The presence of high levels of renewable energy resources (RES) and especially wind power production poses technical and economic challenges to system operators, which under this fact have to procure more ancillary services (AS) through various balancing mechanisms, in order to maintain the generation-consumption balance and to guarantee the security of the grid. Traditionally, these critical services had been procured only from the generation side, yet the current perception has begun to recognize the demand side as an important asset that can improve the reliability of a power system, offering notable advantages. In this study, a two-stage stochastic programming model, representing the day-ahead market clearing procedure on an hourly basis and the actual minute-to-minute operation of the power system, is developed comprising different services that specifically address various disturbance sources of the normal operation of a power system, namely intra-hour load variation, intra-hour wind variation, as well as generating unit and transmission line outages.

Description: Ever increasing penetration of wind power generation along with the integration of energy storage systems (ESSs) makes the successive states of the power system interdependent and more stochastic. Appropriate stochastic modeling of wind power is required to deal with the existence of uncertainty either in observations of the data (spatial) or in the characteristics that drive the evolution of the data (temporal). Particularly, for capturing spatiotemporal interdependencies and determining energy storage requirements, this paper proposes a versatile model using advanced statistical modeling based on the vine-copula theory. To tackle the complexity and computational burden of modeling high-dimensional wind data, a systematic truncation method is utilized that significantly reduces computational burden of the method while preserving the required accuracy. By constructing a graphical dependency model, unlike existing autoregressive and Markov chain models, the proposed method can replicate the exact autocorrelation function (ACF) and cross-correlation function (CCF), while retaining the correct distribution of the original data as well as the effective dependence between different sites under study. The practical importance of the proposed model is demonstrated through an example of ESS sizing for wind power.

Description: In this paper, islanding detection in a hybrid distributed generation (DG) system is analyzed by the use of hyperbolic S-transform (HST), timetime transform, and mathematical morphology methods. The merits of these methods are thoroughly compared against commonly adopted wavelet transform (WT) and S-transform (ST) techniques, as a new contribution to earlier studies. The hybrid DG system consists of photovoltaic and wind energy systems connected to the grid within the IEEE 30-bus system. Negative sequence component of the voltage signal is extracted at the point of common coupling and passed through the above-mentioned techniques. The efficacy of the proposed methods is also compared by an energy-based technique with proper threshold selection to accurately detect the islanding phenomena. Further, to augment the accuracy of the result, the classification is done using support vector machine (SVM) to distinguish islanding from other power quality (PQ) disturbances. The results demonstrate effective performance and feasibility of the proposed techniques for islanding detection under both noise-free and noisy environments, and also in the presence of harmonics.

Description: The focus of our work is the use of an energy storage system (ESS) to integrate solar energy generators into the electrical grid. Although, in theory, an ESS allows intermittent solar power to be shaped to meet any desired load profile, in practice, parsimonious ESS dimensioning is challenging due to the stochastic nature of generation and load and the diversity and high cost of storage technologies. Existing methods for ESS sizing are based either on simulation or on analysis, both of which have shortcomings. Simulation methods are computationally expensive and depend on the availability of extensive data traces. Existing analytical methods tend to be conservative, overestimating expensive storage requirements. Our key insight is that solar power fluctuations arise at a few distinct time scales. We separately model fluctuations in each time scale, which allows us to accurately estimate ESS performance and efficiently size an ESS. Numerical examples with real data traces show that our model and analysis are tight.

Description: The real-time control of wave energy converters (WECs) requires the prediction of the wave elevation at the location of the device in order to maximize the power extracted from the waves. One possibility is to predict the future wave elevation by combining its past history with the spatial information coming from a sensor which measures the free surface elevation up-wave of the WEC. As an application example, this paper focuses on the prediction of the wave elevation inside the chamber of the oscillating water column (OWC) for the Pico OWC plant in the Azores, and two different sensors for the measurement of the free surface elevation up-wave of the OWC were tested. The study showed that the use of the additional information coming from the up-wave sensor does not significantly improve the linear prediction of the chamber wave elevation given by a forecasting model based only on the past values of the chamber wave elevation.

Description: In this paper, a combination of a fuzzy multiobjective approach and ant colony optimization (ACO) as a metaheuristic algorithm is used to solve the simultaneous reconfiguration and optimal allocation (size and location) of photovoltaic (PV) arrays as a distributed generation (DG) and distribution static compensator (DSTATCOM) as a distribution flexible ac transmission system (DFACT) device in a distribution system. The purpose of this research includes loss reduction, voltage profile (VP) improvement, and increase in the feeder load balancing (LB). The proposed method is validated using the IEEE 33-bus test system and a Tai-Power 11.4-kV distribution system as a real distribution network. The results proved that simultaneous reconfiguration and optimal allocation of PV array and DSTATCOM unit leads to significantly reduced losses, improved VP, and increased LB. Obtained results have been compared with the base value and found that simultaneous placement of PV and DSTATCOM along with reconfiguration is more beneficial than separate single-objective optimization. Also, the proposed fuzzy-ACO approach is more accurate as compared to ACO and other intelligent techniques like fuzzy-genetic algorithm (GA) and fuzzy-particle swarm optimization (PSO).

Description: This paper numerically investigates the effect of the trailing edge profile on the performance of the straight-blade vertical axis wind turbine (SB-VAWT). In a 2-D cross-section of the SB-VAWT model, four trailing edge profiles are investigated, namely sharp, rounded, S-blunt, and R-blunt. The numerical investigation is based on the unsteady Reynolds averaged Navier-Stokes (URANS) equations combined with the transition shear stress transport (SST) model in order to account for the transition in the boundary layer in the vicinity of the airfoils. It has been found that the trailing edge profile may play a significant role in improving the turbine performance and should be accurately accounted for in the design process of the SB-VAWT.

Description: This paper employs impedance model-based frequency domain analysis to detect subsynchronous resonances (SSRs) in Type-3 wind farms with thyristor-controlled series capacitor (TCSC). The contributions of this paper are 1)the derivation of dynamic phasor-based TCSC impedance model and 2)the application of such an impedance model in Type-3 wind energy systems for SSR analysis. Impedance models for TCSC with constant firing angle control and impedance control are derived in this paper. With the derived impedance models, Nyquist stability criterion is applied to compare SSR stability in Type-3 wind farm with TCSC or with fixed capacitor compensation. This paper employs analytical models to demonstrate TCSCs capability in avoiding SSR in Type-3 wind generator interconnection systems. The analytical results obtained through impedance models are validated by detail model-based (with thyristor switch-modeled) time-domain simulation in MATLAB/SimPowerSystems.

Description: Environmental concerns caused by burning fossil fuel and the safety concerns associated with nuclear power plants have led to increased interest and investment in wind power. Wind penetration in power systems has been rapidly increasing worldwide and has resulted in increased variability and uncertainty in power generation. Proper modeling of the wind resource has, therefore, become increasingly important in modern wind-integrated power systems. The correlation between wind speeds at multiple wind farms considerably affects the overall variability of wind power generation. Many power utilities are considering expansion to multiple wind farms. Analysis of wind power at different sites requires sufficient time-synchronized wind data in order to incorporate their cross-correlations in the evaluation model. Such data are usually not available or very limited for many prospective wind sites that may be considered in energy planning or policy making. This paper proposes a simple analytical method to develop approximate wind models when time-synchronized wind data for two wind sites are not available and further extends the method to incorporate more than two wind sites.

Description: Application of optical tomography in the study of discolouration in drinking water distribution systems Drinking Water Engineering and Science Discussions, 4, 39-59, 2011 Author(s): P. van Thienen, R. Floris, and S. Meijering Theories describing the turbulent deposition of particles from aerosols have recently been applied to drinking water distribution. In order to allow the study of these processes in a quantitative way and internally observe a cloud of suspended particles in a pipe, we have developed an optical tomography technique and measuring device using low cost electronic components specifically for this application. The mathematical methodology and the electronic device are described in this paper, and tests of both the mathematical approach and the actual device are presented. We conclude that the described methodology may provide a valuable tool for the study of processes related to drinking water discolouration in the lab.

Description: Status of organochlorine pesticides in the drinking water well-field located in the Delhi region of the flood plains of river Yamuna Drinking Water Engineering and Science, 4, 51-60, 2011 Author(s): P. K. Mutiyar, A. K. Mittal, and A. Pekdeger This study presents the occurrence of pesticides in a well-field located in Yamuna flood plain of Delhi region. Ground water sampling campaigns were carried out during pre-monsoon and post-monsoon periods covering 21 borewells and 5 Ranney wells. Major 17 organochlorine pesticides (OCP's) along with other water quality parameters were monitored during this period. Pesticide concentrations were determined using GC-ECD, while GC-MS was used for confirmatory purposes. OCP's groups like ∑HCH, ∑DDT, endosulfan and aldrin were observed in this well-field. Concentration of OCPs from Ranney well exceeded the limit (1 μg l −1 ) prescribed by the Bureau of Indian Standards (BIS) in pre-monsoon season, though OCP levels in borewells were within BIS limits. However, these levels were very close to the World Health Organisation (WHO) and European Union (EU) limit of for pesticides (0.5 μg l −1 ) in many samples. Borewell produced better quality water compared to the water from Ranney wells. Although, the level of OCP's was slightly lower than prescribed limit of national regulatory agency but such low doses may cause long-term damage to human populations if such water is consumed for longer durations. At low doses OCP's acts as endocrine disrupting agent and cause metabolic disorders in local population.

Description: Application of optical tomography in the study of discolouration in drinking water distribution systems Drinking Water Engineering and Science, 4, 61-69, 2011 Author(s): P. van Thienen, R. Floris, and S. Meijering Theories describing the turbulent deposition of particles from aerosols have recently been applied to drinking water distribution. In order to allow the study of these processes in a quantitative way and internally observe a cloud of suspended particles in a pipe, we have developed an optical tomography technique and measuring device using low cost electronic components specifically for this application. The mathematical methodology and the electronic device are described in this paper, and tests of both the mathematical approach and the actual device are presented. We conclude that the mathematical framework presented is suitable and that the technical implementation works in a test setting. The described methodology may provide a valuable tool for the study of processes related to drinking water discolouration in the lab.

Description: A new model for the simplification of particle counting data Drinking Water Engineering and Science Discussions, 4, 151-172, 2011 Author(s): M. F. Fadal, J. Haarhoff, and S. Marais This paper proposes a three-parameter mathematical model to describe the particle size distribution in a water sample. The proposed model offers some conceptual advantages over two other models reported on previously, and also provides a better fit to the particle counting data obtained from 321 water samples taken over three years at a large South Africa water utility. By using the data from raw water samples taken from a moderately turbid, large surface impoundment, as well as samples from the same water after treatment, typical ranges of the model parameters are presented for both raw and treated water. Once calibrated, the model allows the calculation of total particle number and volumes over any randomly selected size interval of interest.

Description: Assessing variable speed pump efficiency in water distribution systems Drinking Water Engineering and Science Discussions, 5, 47-65, 2012 Author(s): A. Marchi, A. R. Simpson, and N. Ertugrul Energy savings and greenhouse gas emission reductions are increasingly becoming important design targets in many industrial systems where fossil fuel based electrical energy is heavily utilised. In water distribution systems (WDSs) a significant portion of operational cost is related to pumping. Recent studies have considered variable speed pumps (VSPs) which aim to vary the operating point of the pump to match demand to pumping rate. Depending on the system characteristics, this approach can lead to considerable savings in operational costs. In particular, cost reductions can take advantage of the demand variability and can decrease energy consumption significantly. One of the issues in using variable speed pumping systems, however, is the total efficiency of the electric motor/pump arrangement under a given operating condition. This paper aims to provide a comprehensive discussion about the components of WDS that incorporate variable speed pumps (including electric motors, inverters and the pumps themselves) to provide an insight of ways of increasing the system efficiency and hence to reduce energy consumption. In addition, specific attention is given to selection of motor types, sizing, duty cycle of pump (ratio of on-time and time period), losses due to installation and motor faults. All these factors affect the efficiency of motor drive/pump system.

Description: Fluoride in the drinking water of Pakistan and the possible risk of crippling fluorosis Drinking Water Engineering and Science, 6, 17-23, 2013 Author(s): M. A. Tahir and H. Rasheed To explore the possibility of fluoride toxicity, 747 water samples were collected from surface water and groundwater sources of 16 major cities of Pakistan, adopting a uniform sampling design with distribution of samples: Lahore (79), Kasur (46), Faisalabad (30), Khushab (50), Chakwal (51), Mianwali (30), Jhelum (53), Bahawalpur (60), Karachi (60), Mirpur Khas (55), Peshawar (38), Risalpur (35), Quetta (81), Ziarat (21), Loralai (21), and Mastung (37). Comparison of analytical findings with WHO Guidelines of Drinking Water for Fluoride (i.e., 1.5 ppm) has concluded that 16% of the monitored water sources have fluoride concentration beyond the permissible safe limit of 1.5 mg L −1 falling in the concentration range of 1.6–25 mg L −1 . The highest fluoride contamination (22%) is detected in the Balochistan province followed by 19% in Punjab province. Comparatively higher fluoride levels of 〉 20% in the groundwater sources like hand pumps supported the possibility of increased groundwater contamination as excessive fluoride concentrations are expected to come from calcium-poor aquifers and in areas where fluoride-bearing minerals are common or where cation exchange of sodium for calcium occurs. Field observations have also indicated the prevalence of fluoride-associated health implications in the study areas with excessive fluoride in water sources. Findings of this study have provided bidirectional vision for the epidemiological investigations as well as to mitigate the issues in the affected vicinities of fluoride-rich areas.

Description: We present the design and fabrication of a 2D monolithic pixelated detector array using metalorganic vapor-phase epitaxy grown thick CdTe epitaxial layers on Si substrates. Each pixel in the array consists of a ${rm p-CdTe/n-CdTe/n}^{+}-{rm Si}$ heterojunction diode structure, and pixels were patterned by cutting deep vertical grooves using a dicing saw. We also developed a low-temperature conductive-epoxy based bonding technique to bond the array to the read out electronic circuit via an interface board. Preliminary evaluation shows that the fabricated array is capable of discriminating energies of the incident radiation and can be applied for the energy discriminating imaging purpose. Moreover, this fabrication technique is useful in developing larger imaging arrays.

Description: The time over threshold (TOT) method has several advantages over direct pulse height analysis based on analog to digital converters (ADCs). A key advantage is the simplicity of the conversion circuit which leads to a high level of integration and a low power consumption. The TOT technique is well suited to build multi-channel readout systems for pixelated detectors as described in our previous work that also exploits the Pulse Width Modulation (PWM) method. The main limitation of the TOT technique is that the relation between the input charge to be measured and the width of the encoded pulse is strongly non-linear. Dynamic range limitation is also an issue. To address these aspects, we propose a new time over threshold conversion circuit where the threshold of the comparator is dynamically changed instead of being constant. We call this scheme the “dynamic TOT method”. We show that it improves linearity and dynamic range. It also shortens the duration of measured pulses leading to higher counting rates. We present a short analysis that explains how the ideal linear input charge to TOT transfer function can theoretically be obtained. We describe the results obtained with a test circuit built from discrete components and present several of the spectrums obtained with crystal detectors and a radioactive source. The proposed method can be used for applications like Positron Emission Tomography (PET) that require moderate energy resolution.

Description: The objective of this paper is to describe a Switcher ASIC with 64 high voltage output channels. Each channel provides two high voltage control pulses with maximum amplitudes of 32 V. The high voltage level shifter was designed with a current mirror switching circuit that has a readily adjustable switching speed, unlike conventional switching circuits. The logic control circuit uses a forward and reverse chain of Flip-Flops along with other combinational logic gates to generate bidirection sequential control pulses with adjustable pulsewidth and polarity. The layout was carefully designed to achieve a 14 $mu$ m width for the last stage transistors' drain path based on the 50 $mu$ m output channel pitch set up. At least a 200 mA current driving capability was obtained for each channel. The design was fabricated using TSMC's 180 nm CMOS HV technology. The paper further discusses the critical design steps including chip architecture, layout, simulation and bench test. The final experimental results demonstrate that the Switcher ASIC meets requirements and the rising time could reach 480 ns with a 1 nF capacitive load at 15 V pulse amplitude. With this load, the total power consumption of the chip was measured to be approximately 4 mW when the input clock period was 42.2 $mu$ s. In addition to use in a charge-pump detector, the ASIC can be used to control the charge accumulation and readout in other detectors, such as X-ray pump probe detectors (XPP).

Description: Online nuclear measurements inside experimental channels of material testing reactors (MTRs) are needed for experimental works (to design mock-ups) and for numerical works (input data) in order to better understanding complex phenomena occurring during the accelerated ageing of materials and the irradiation of nuclear fuels. In this paper, we focus only on one kind of measurements: nuclear heating performed by means of a radiometric calorimeter. The aims of numerical and experimental works are firstly to optimize the sensor response: in particular the sensitivity for new energy deposit ranges (new lower nuclear heating level in the reflector), and then to miniaturize and adapt this sensor for irradiation conditions in the Jules Horowitz Reactor (JHR). A calorimeter, developed previously by the CEA, is studied. It corresponds to a graphite differential calorimeter. It is used with a nonadiabatic mode called heat flow mode too. Experimental calibration of the sample cell is presented. In that case, energy deposit is simulated by Joule effect and the sample cell is inserted into a bath at a regulated temperature and controlled flow. The response of the sensor is discussed versus electrical power imposed for two flow rates. Numerical works show the influence of the gas conductivity and of specific dimensions on the cell sensitivity.

Description: This paper deals with the effects of $^{60}$ Co gamma irradiation on punch-through commercial insulated gate bipolar transistors turn-off switching behavior. The response of the threshold voltage, the gate-emitter leakage current, the collector leakage current, the collector-emitter breakdown voltage and the turn-off switching parameters under three different in situ gate biases are described. Charge trapping in the gate oxide causes the decrease of the threshold voltage. It is shown that the decrease of this parameter and the modifications in the Miller plateau level and width result in an increase of the turn-off delay time, the collector current fall-time, the collector-emitter voltage rise-time, and consequently an increase of the turn-off switching losses and a decrease of the turn-off overshoot collector-emitter voltage.

Description: The GUINEVERE (Generation of Uninterrupted Intense NEutron pulses at the lead VEnus REactor) project was launched in 2006 within the framework of FP6 EUROTRANS in order to validate online reactivity monitoring and subcriticality level determination in accelerator driven systems (ADS). Therefore, the VENUS reactor at SCK•CEN in Mol, Belgium, was modified towards a fast core (VENUS-F) and coupled to the GENEPI-3C accelerator built by CNRS. The accelerator can operate in both continuous and pulsed mode. The VENUS-F core is loaded with enriched Uranium and reflected with solid lead.

Description: Novel techniques to measure induced fissions in spent fuel after re-irradiation at low power have been developed and tested at the Proteus zero-power research reactor. The two techniques are based on the detection of high energy gamma-rays emitted by short-lived fission products and delayed neutrons.

Description: Increased production flexibility will be needed for the operation of a future power system with more uncertainty due to an increased share of uncontrollable generation from renewable sources. Wind energy is expected to cover a large portion of the future renewable generation. In this paper, a comparison is carried out between two balancing market models, simulating a non- and fully-integrated northern European market in a future 2030 scenario. Wind power is modelled based on high resolution numerical weather prediction models and wind speed measurement for actual and forecasted wind power production. The day-ahead dispatch and balancing energy markets are settled separately. First, the day-ahead market is modelled with simultaneous reserve procurement for northern continental Europe. Available transmission capacity is taken into account in the reserve procurement phase. In a second step, the balancing energy market is modelled as a real-time power dispatch on the basis of the day-ahead market clearing results. The results show the benefit of balancing market integration for the handling of variable production. Cost savings are obtained from balancing market integration due to less activation of reserves resulting from imbalance netting and increased availability of cheaper balancing resources when integrating larger geographical areas.

Description: In electrical islands, frequency excursions are sizeable and automatic load shedding is often required in response to disturbances. Moreover, the displacement of conventional generation with wind and solar plants, which usually do not provide inertial response, further weakens these power systems. Fast-acting storage, by injecting power within instants after the loss of a generating unit, can back up conventional generation assets during the activation of their primary reserve. This paper relies on dynamic simulations to study the provision of such a dynamic frequency control support by energy storage systems in the French island of Guadeloupe with large shares of wind or solar generation. The results show that fast-acting storage, by acting as a synthetic inertia, can mitigate the impact of these sources on the dynamic performance of the studied island grid in the case of a major generation outage. The other concerns raised by renewables (e.g., variability, forecast accuracy, low voltage ride-through, etc.) have not been addressed within this project.

Description: The significant expansion of wind power capacity in the Electric Reliability Council of Texas (ERCOT) will increase the amount of ancillary services (AS) necessary to maintain ERCOT system frequency targets. This paper analyzes ERCOT regulation adequacy from a simplified dynamical model of ERCOT validated by empirical data. The model includes a representation of system frequency response characteristics; a stochastic, empirical-based model of wind power expansion; and a model of net load forecast error based on current performances. The simulation uses current ERCOT methodology for determining regulation, and NERC Balancing Authority Standards to examine frequency control performance.

Description: The ongoing development in the electrical system and the transition from a mainly thermal dominated power system into a system widely affected by renewable production resources, requires a revision of future balancing strategies facilitating the secure integration of renewable energy. Especially the increasing wind power penetration with its uncertain production on all time scales will largely affect the system operation, requiring a higher flexibility and thus more reserve capacity providing balancing energy. Based on high resolution numerical weather prediction models and wind speed measurements, the actual and the forecasted wind power production is simulated for five scenarios covering the years 2010 and 2020. These scenarios are taken as an input to a Northern European regulating power market model, analyzing the procurement of reserve capacity and their activation. Further on, the potential benefit of integrating Northern European regulating power markets handling the varying wind power production is investigated. Due to remaining wind forecast errors, more reserve capacity is required in the electrical system. The simulations comprise frequency restoration reserves and replacement reserves. Based on the assumption of an integrated regulating power market, the determined results illustrate that the Nordic power system can provide such reserves at optimal cost. In 2020, an overall cost increase is recognized, concurrently displaying significant saving possibilities by a cross-border procurement of reserve capacity and the exchange of balancing energy.

Description: Increasing levels of wind energy are adding to the uncertainty and variability inherent in electricity grids and are consequently driving changes. Here, some of the possible evolutions in optimal short-term energy balancing to better deal with wind energy uncertainty are investigated. The focus is mainly on managing reserves through changes in scheduling, in particular market structure (more regular and higher resolution scheduling), reserve procurement (dynamic as opposed to static), and improved operational planning (stochastic as opposed to deterministic). Infrastructure changes including flexible plant, increased demand side participation, more interconnection, transmission, larger balancing areas, and critically improved forecasting can also be significant and are dealt with in the discussion. The evolutions are tightly coupled, their impact is system-dependent and so no “best” set is identifiable but experience of system operators will be critical to future developments.

Description: Since the advent of the integration of wind power technologies into power systems, power system operators have developed numerous strategies to accommodate its impacts. At low penetrations, many system operators will treat wind power as negative load, in that it is planned for as a fixed value, not as an option to assist in the optimal dispatch solution. However, a number of system operators have recently seen the benefits of allowing wind power to be part of the optimal dispatch or commitment solution. This paper discusses the potential societal benefits to the energy market by allowing the economic dispatch of wind generation in times when it may enhance reliability and be economically advantageous to do so.

Description: The impact of increased penetration of renewable generation has been the subject of much discussion related to system operations. As the percentage of generation from renewable generation provides us a greener and more sustainable future, it also introduces new challenges in scheduling and dispatching controllable resources to follow the net load and control the power balance in the system. The increased renewable generation tends to introduce more variability that must be met by the traditionally more flexible generation resources. Incentives are needed to encourage the existing generators of all types to maximize the availability of their operational “load following” flexibility and to encourage entry of new flexible suppliers such as energy storage devices or demand response.

Description: A challenge now facing utilities is how to adjust reserves in the operations-planning horizon of 0 to 48 hours ahead to mitigate the effects of wind variability and forecast uncertainties, in addition to those of load uncertainties and unavailability of generation. Reserves are maintained to ensure a high level of reliability and security to the system. They are subdivided into two groups: those responding within an intrahourly time horizon to regulate power imbalances, and those responding over a 1–48 hours ahead time horizon addressing the net forecast uncertainties. In this paper, we present a methodology for calculating reserves in the latter category, referred to as balancing reserves (BRs), following the integration of wind generation in a power system. Their computation is based on maintaining a predefined level of risk. The novelty here is that wind forecast error distributions are adjusted as a function of wind generation forecast levels. Gamma-like distributions with time-varying parameters, estimated from real data, were chosen to approximate the wind generation forecast errors. It is shown that this improved modeling significantly modifies the values of required balancing reserves and associated risk. The methodology developed is based on a clear criterion, namely risk, and it demonstrates the imperativeness of considering dynamic balancing reserves as a function of the imminent wind generation forecast.

Description: This paper describes a study conducted to address the question of how much power transfer capacity should be provided on a meshed transmission system to maintain reliability of supply to consumers in the presence of wind generation. A simulation methodology is presented that includes modeling of the available wind generation in the longer term across a quite large area taking into account correlations in available power between different locations in that area. A description is given of the results obtained in characterization of the relationship between the peak load in an area, the total generation capacity in that area, the proportion of it that is wind generation, and how much transmission import capability— “interconnection reserve” —is required for a given reliability of supply. Finally, a number of issues faced by power system investment planners are discussed and pointers given to further work to enable transmission utilities to meet the challenges presented by policy makers in respect of development of wind power to meet renewable energy targets.

Description: This paper proposes a novel strategy for participation of variable speed wind turbines in primary frequency control. The proposed strategy is based on the deployment of the kinetic energy of the rotating masses to reduce the need for deloaded operation while still being able to provide the required power reserve for the defined time frame. A steady-state deloaded operating point is optimized with respect to the amount of kinetic energy stored in the rotating masses. The parameters of the algorithm are calculated offline and stored in lookup tables. The proposed strategy is tested using a modified Nordic 32-bus test system for various operating scenarios. The results show that part of the primary frequency control power reserve of the thermal units can be replaced by the reserve provided by wind power, while retaining the desired frequency response following a disturbance. A comparison with the conventional deloaded strategy shows that between 1.16% and 2.79% energy savings can be achieved on a yearly basis, depending on the wind regime of the sites analyzed.

Description: This paper represents the first attempt to discuss the use of an artificial single-crystal diamond as a new microdosimeter. The Diamond MicroDosimeter (DMD) detecting region is a thin layer of highly controlled thickness $(〈 5~mu {rm m})$ and high purity intrinsic monocrystalline diamond grown over a backing boron doped monocrystalline diamond. This viable, small, compact and user-friendly device is able to obtain spectra of the energy deposition in sensitive volumes of the order of micrometer. The paper reports the first experimental tests performed to measure the dose distribution in terms of lineal energy and the simulation performed by the Monte Carlo code FLUKA to optimize the design of the new DMD. Advantages and shortcomings of the DMD are discussed.

Description: A prototype 1mm thick CdTe detector bonded to a Timepix chip with 256*256 pixels at 55 $mu$ m pitch was evaluated for use as a photon-counting imaging detector at high energy synchrotron beamlines (energy range 30–100 keV). A complete characterization of the system was performed. Powder diffraction experiments have also been conducted using a monochromatic beam at the ESRF. The expected gain in efficiency at energies above 30 keV with reference to silicon pixel detectors and current CCD systems of similar pixel size was demonstrated, together with an improved spatial resolution. Background-free powder diffraction spectra were obtained using the Timepix energy thresholding feature. The energy-resolved detection capabilities are limited by a strong charge sharing. The major limitations preventing a wider use of these devices at synchrotron X-ray sources are the lack of homogeneity of the CdTe crystal which exhibits numerous defects, and the unavailability of large fields of view.

Description: This paper reports about the performances of single crystal diamond (SCD) detectors operated at high temperature (up to 200 $^{circ}$ C) and irradiated with alpha particles. Two different types of SCD detectors were studied: a) SCD of commercial type; b) SCD produced at Rome “Tor Vergata” University and characterized by a layered structure.

Description: In many modern applications based on detected radiation measurements, high rate and high resolution are more and more features of primary importance. In this scenario, it is well known that high resolution of measurements and high rate of pulses are conflicting issues, which implies a trade-off between live time of the system and precision of measurements. We propose a digital processing technique based on adaptive filters for maximizing both achievable resolution and sustainable rate.