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Electric vehicles (EVs) are experiencing explosive growth in public adoption, causing a major shift in research and development priorities by OEMs toward electrified powertrains. To verify EV drivetrain platforms and software models in the design phase, testbeds with specific capabilities are essential. Full-scale vehicle testbeds are expensive, bulky, dissipative, and not easily reconfigurable or movable, making scaled testbeds more attractive, especially for education and research institutes. To support this cause, this paper reports on the development of a small-scale, modular, hardware-in-the-loop (HIL) testbed platform for the drivetrain of EVs that is cost-effective, efficient, and easily movable and reconfigurable and allows integration of a battery pack. The testbed is comprised of two directly coupled electric machines. The first machine emulates the traction motor and is used to control vehicle speed according to a specified drive cycle. The second machine is used to impose a torque profile on the first machine's shaft—based on the vehicle's parameters and driving environment—and emulates a gearbox (if necessary). A systematic two-way scaling approach is adopted to downscale the parameters and driving environment of full-size EVs to a level that can be handled by the testbed and to upscale the test results obtained from the testbed to the full-size vehicle level. The power consumption of the testbed is limited to system losses. A case study involving a full-size EV was performed and the HIL simulation results were compared to the computer simulation results to verify the performance of the testbed. [ABSTRACT FROM AUTHOR]

In the event of a DC side fault in modular multilevel converters (MMCs), the fault current contributions are initially made by submodule (SM) capacitor discharge, which occurs before the fault is detected, followed by the AC side contribution to the DC side fault. While the AC side currents can be regulated using fault blocking SMs, the initial discharge of the SM capacitors results in high DC fault currents, which can take several milliseconds to be brought under control. This paper presents a method to actively control the rate of rise of the DC fault current by regulating the discharge of SM capacitors and accelerating the suppression of fault current oscillations during fault ride-through (FRT) in a full-bridge (FB)-MMC system. In the proposed method, the discharge direction of the FBSM capacitors is reversed following the detection of a DC side fault, which leads to a reversal in the fault current direction and a fast drop-off towards the zero-crossing. Immediately after the zero-crossing of the DC fault current, the DC fault is cleared by adjusting the arm voltage references and operating the MMC as a static synchronous compensator (STATCOM) to provide voltage support to the AC grid. The proposed control scheme provides faster fault current suppression, more effective SM capacitor voltage regulation, low AC side and MMC arm current transient peaks, and an overall superior DC-FRT performance compared to methods in which the conventional fault ride-through operation is initiated immediately upon DC fault detection. [ABSTRACT FROM AUTHOR]

Modular multilevel converters (MMCs) based on half-bridge submodules (HBSMs) are unable to prevent the AC side contribution to DC side fault currents, thus necessitating circuit breakers (CBs) for protection. A solution to this problem is using submodules (SMs) that are capable of blocking the flow of current from the AC grid to feed the DC side fault. The full-bridge submodule (FBSM) is one type of fault blocking SM where the presence of two extra switches ensures that in the event of a DC fault, the reverse voltage from the FBSM capacitor is placed in the path of the AC side current feeding the DC side fault through the antiparallel diodes. However, the additional semiconductor switches in the FBSMs increase the converter cost, complexity, and losses. Several SM configurations have been proposed in recent years that provide DC fault blocking capability with lower losses and device counts than those of FBSMs. Besides, many of the proposed hybrid converter configurations that combine different topologies to optimize converter performance are also capable of providing DC fault blocking. Furthermore, certain SM topologies are capable of riding through DC faults by remaining deblocked and operating in static synchronous compensator (STATCOM) mode to provide reactive power support to the AC grid. In this paper, noteworthy SM and MMC configurations capable of DC fault blocking and ride-through are reviewed and compared in terms of component requirements, semiconductor losses, and DC fault handing capability. The review also includes a discussion on control strategies for MMC arm/leg energy balancing during STATCOM operation. [ABSTRACT FROM AUTHOR]

Harmonic pollution is considered to be one of the major power-quality problems in electric power systems. Correct identification of the dominant source of harmonic pollution is an essential step towards solving this problem. The total harmonic power (THP) method is one of the methods proposed in the literature for this purpose. However, the method is still debatable as its complete success has been questioned by some researchers. This paper tries to answer some concerns regarding the success of the THP method in radial systems by using several comprehensive case studies. Then, a modification to the method is proposed to generalize its application to nonradial systems. Moreover, to increase the reliability and applicability of the method, a new time-domain algorithm is proposed for measuring the harmonic, subharmonic and interharmonic powers for single-phase and three-phase four-wire systems. Index Terms--Harmonics, harmonic pollution, harmonic powers, point of common coupling (PCC).

A topology and switching algorithm are presented for producing split-phase output voltages using a current-sourced inverter (CSI). Split-phase generation has previously been accomplished using voltage-sourced inverters (VSIs). There are some advantages to instead using CSIs, such as improved output voltage waveform quality and built-in overcurrent protection; however, two issues have prevented their adoption to date. First, while a CSI does not require the input boost converter used by a VSI when fed from a low-voltage source, it may require a preconditioning circuit to provide the required dc current. Second, no algorithm for producing split-phase outputs with a CSI presently exists. This paper's two major contributions aim to solve these problems. A simple preconditioning circuit is presented to provide the necessary dc current and store energy in a capacitor bank for use during load transients. A switching algorithm is written to produce balanced split-phase output voltages under a variety of unbalanced loading conditions. It is demonstrated using simulation and experimental results on a 400-W prototype that the proposed system is able to successfully generate balanced output voltages under unbalanced, inductive, nonlinear, and transient loading conditions, while equalizing switch utilization and minimizing output voltage ripple. Index Terms--Current supplies, inverters, pulsewidth modulated inverters, pulsewidth modulation.

Although many researchers have investigated the use of different powertrain topologies, component sizes, and control strategies in fuel-cell vehicles, a detailed parametric study of the vehicle types must be conducted before a fair comparison of fuel-cell vehicle types can be performed. This paper compares the near-optimal configurations for three topologies of vehicles: fuel-cell-battery, fuel-cell-ultracapacitor, and fuel-cell-batteryultracapacitor. The objective function includes performance, fuel economy, and powertrain cost. The vehicle models, including detailed dc/dc converter models, are programmed in MATLAB/Simulink for the customized parametric study. A controller variable for each vehicle type is varied in the optimization. Index Terms--Batteries, dc-dc power conversion, fuel cells, optimization methods, vehicles.

In this paper, a MOSFET-based pulsed power supply capable of supplying square pulses of up to 3000 V and widths from nanoseconds to milliseconds is presented and used for an investigation into electroporation-mediated delivery of a plasmid DNA molecule into the pathogenic bacterium Escherichia coli O157:H7. It was concluded that increasing the electric field strength and pulse amplitude resulted in an increase in the number of transformants. However, increasing the number of pulses had the effect of reducing the number of transformants. In all the experiments, the number of calls that were inactivated by the exposure to the pulsed electric field were also measured. Index Terms--Bacterial transformation, DNA transfusion, electroporation, Escherichia coli.

The use of fuzzy logic controllers to improve the performance of HVDC systems under various faults and operating point changes has been well-documented. Recent research has shown that the optimal membership function width in a fuzzy controller is different for different system events (such as current order change or fault). This paper proposes an adaptive approach to designing a fuzzy logic controller for HVDC systems. Simulation data are used to create a look-up table for the fuzzy control system. Based on the operating point and the type and location of fault, the output of the table indicates the membership function width to be used in the fuzzy controller to obtain the best results (i.e., the lowest number of commutation failures). This paper presents the best controllers for nine faults at 27 operating points for the CIGRE benchmark HVDC system, but more importantly, uses trends to develop a method for finding these optimal controllers for other systems without the need for exhaustive simulation of each possibility. Index Terms--Adaptive control, fuzzy logic, HVDC transmission control.

In this paper, the control of an ac-dc-ac converter with a front-end diode rectifier and reduced dc-link capacitor based on the space vector modulation strategy is investigated. The modulation index is time-varying and determined by the instantaneous value of the dc voltage measured by a voltage sensor. Using a small bipolar capacitor, instead of a large electrolytic capacitor on the dc-link, increases the lifetime of the converter and reduces its size. The input current quality of this converter has been shown to be superior to that of the conventional ac-dc-ac converter with front-end diode rectifier. The perfectly sinusoidal local average output voltage can still be achieved under unbalanced input voltage condition by implementing a time-varying modulation index. The rule for determining the dc capacitance has also been studied in this paper. The simulation results obtained from PSIM simulation software and experimental results obtained from the lab prototype are used to verify the theoretical expectations. Index Terms--AC-DC-AC converter, front-end diode rectifier, reduced dc capacitor, space vector modulation, unbalanced input voltage.

STATCOM is a FACTS controller that is used in power systems to regulate the line voltage, enhance the power transmission capacity and extend the transient stability margin. STATCOM is conventionally realized by a voltage-source converter; however, being a current injection device, its performance can be improved when realized by a current-source converter (CSC) that can generate a controllable current directly at its output terminals. In this paper, a STATCOM based on the current-source converter topology is proposed. The nonlinear model of the current-source converter, which is the source of the difficulties in the controller design, has been modified to a linear model through a novel modeling technique. The proposed modeling technique is not based on the linearization of a set of nonlinear equations around an operating point. Instead, the power balance equation and a nonlinear input transformation are used to derive a linear model independent of the operating point. This model acts as the basis for the design of a decoupled state-feedback controller. The proposed STATCOM has been simulated using the PSCAD/EMTDC package. The simulation results show that a CSC-based STATCOM can result in excellent current and voltage waveforms as well as very short response time while operating at a low switching frequency. This makes the proposed scheme suitable for high power applications. Index Terms--CSC, decoupled state-feedback control, FACTS, linear model, STATCOM, VSC.

The control methodology of the active power-line filter is the key element for its successful performance in mitigating the line current harmonics. The control system processes the distorted line current signal and forces the converter to inject the proper compensating current. At the same time, it regulates the dc term, i.e., the dc current in the current source converter topology and the dc voltage in the voltage source converter topology. in this paper, a new intelligent control scheme for a modular single-phase active power filter based on the current source converter (CSC) topology is proposed. The intelligent controller utilizes two adaptive linear neurons (ADALINEs) to process the signals obtained from the power-line. The first ADALINE (the Current ADALINE) extracts the harmonic components of the distorted line current signal and the second ADALINE (the Voltage ADALINE) estimates the fundamental component of the line voltage signal. The outputs of the two ADALINEs are used to construct the modulating signals of a number of CSC modules, each dedicated to eliminate a specific harmonic. The proposed controller is also responsible for activating selected CSC filter module(s) to the electric grid. The automated activation of the corresponding filter module(s) is based on the decision-making rules in accordance with the current total harmonic distortion (TH[D.sub.i]) and the harmonic factor (HF) levels set by the IEEE 519-1992 standard. A special 3-level PWM switching strategy is proposed for the filter modules which results in a 50% reduction in the overall switching losses compared with the 2-level method. The proposed controller adjusts the [I.sub.dc] in each CSC module based on the present magnitude of the corresponding harmonic current which results in optimum dc-side current value and minimal converter losses. The high speed, accuracy, efficiency and flexibility offered by the proposed controller, combined with the fast response and low dc energy storage requirement of CSC topology, are the main advantages of the proposed active filter system. The analytical expectations are verified by digital simulation using EMTDC simulation package. Index Terms--Harmonic mitigation, ADALINE, active power filter, 3-level PWM technique, CSC, EMTDC.

The research on direct ac/ac conversion in the past twenty years has been following two major directions: 1) improving the performance of the original nine-bidirectional-switch matrix converter topology; 2) using converter topologies composed of unidirectional switches only. In this paper, a direct ac/ac converter topology based on current-source converter modules is proposed. It is shown, through analysis and simulation, that the proposed topology is free of any switching difficulties and gives high-quality sinusoidal waveforms on both sides. Furthermore, with the same number of semiconductor devices as in the original nine-bidirectional-switch matrix converter topology, it is able to perform all aspects of frequency changing, real power flow control, and independent reactive power flow control on both sides. The proposed topology finds applications in electric drive industry, as an ac motor drive, and power system industry, as an asynchronous link. Index Terms--AC/AC converter, CSC, frequency changer, high-quality sinusoidal waveforms, independent reactive power flow control, L-C filter, nine-bidirectional-switch, NPT IGBT, real power flow control, semiconductor devices, SVC, THDs, topology.

Three-phase voltage- and current-source converters are the building blocks of a great number of power electronic systems. The origin of difficulties in the control of the above converters is in their nonlinear nature. In this paper, a novel modeling technique is introduced to derive the linear models of the converters from the nonlinear transformations of the conventional nonlinear models. Then, based on the derived linear models, a high-performance linear controller with satisfactory performances is designed. The bold feature of the new model is the independence of the controller design from the operating point. A DSP-based control system has been built in the lab to verify the performance of the new models and the control algorithm. The simulation and experimental results are in close agreement. The results show that the dc term and the ac-side reactive power can be controlled independently in less than one cycle. Index Terms--Control algorithm, converter, DSP, nonlinear, PWM, reactive power.

Wind farms featuring a series-connected dc collection system have been shown to offer advantages in terms of total conversion efficiency and amount of offshore-deployed equipment. To ensure proper exploitation of these benefits, it is necessary to determine the ratings of wind turbine converters. These ratings must be sufficient to cover the expected operating conditions over the life of the wind farm, without unnecessarily oversizing the equipment. As shown in this article, the variable string current results in an interdependence of operating points among wind turbines that has to be considered for sizing these converters. This article proposes a generic sizing framework for such single-string, series-connected dc wind farms. This framework is applied to three wind farm configurations featuring differential power processing, voltage-source converters, and diode-bridge rectifiers and buck converters. Finally, a case study for a 450 MW offshore wind farm demonstrates the implementation of this sizing methodology and quantifies the design tradeoffs between converter ratings and energy production enabled from those converters. In two of the studied wind farm configurations, significant rating reductions are achievable while still avoiding energy curtailment for >99.7% of the energy production of an equivalent ac wind farm. [ABSTRACT FROM AUTHOR]

This paper shows that the voltage-source matrix converter has all the features of an asynchronous intertie, namely: (1) frequency changing capability, (2) 360 [degrees] phase shift range, and (3) bi-directional real power transfer. In addition, it has the capabilities for: (4) series line reactance compensation using a complex conjugate property, and (5) static VAR compensation. Series reactance compensation gives rise to high synchronization power which improves transient stability. The matrix converter also has the flexibility to control both the transmitted real power and, independently, the reactive power flows at the sending-end and receiving-end of the transmission line. Keywords: AC transmission, FACTS, power flow controller, line compensation, phase shifter, asynchronous link, GTO, matrix converter.

This paper shows that by transforming both sides of the matrix converter to the d-q-o frames of their respective frequencies, there is significant simplification in the transformation matrix which enables the network of one side to be integrated to the other. Thus, it is possible to design for operation with field vector control on the motor side and unity displacement factor on the supply side. Laboratory experimental and digital simulation results are presented to substantiate the theory. The matrix converter used in the test is based on three modules of voltage-source SPWM converters to implement the nine switches and it has the innovative feature that the SVC voltages (for displacement factor improvement) can be derived from the zero-sequence voltages.

The peak line-to-line inverter ac voltage, in general, cannot exceed the supply dc voltage and transformers have to be used when voltage step-up is required. This paper describes how the necessity of using a Tri-Level PWM strategy in the Current Source Inverter can be turned into an advantage by producing a voltage boost so that transformers are no longer required. During the frequent occurrence of the 'shoot-through' states, which is the characteristic of the Tri-Level PWM-controlled inverter, magnetic energy builds up in the dc link inductor. At the end of these periods, the [L.sub.dc]d[I.sub.dc]/dt voltage across the inductor augments the inverter output voltage in the same way as in the basic boost type dc/dc converter. The paper describes the circuitry required to ensure linear control. Analytical, simulation, and experimental results are given. Applications are found in all instances where the ac voltage is higher than the available supply dc voltage.

Secondary control strategies in hybrid ac/dc microgrids have been conventionally designed independently for each side of the microgrid, neglecting the interaction between the ac and dc sides due to the power transferred through the interlinking converter. This has a negative effect on the power sharing and dynamic response of the system. In this article, a novel distributed secondary control strategy for hybrid ac/dc-microgrids is presented which coordinates the control actions of the ac and dc sides. The proposed control scheme simultaneously regulates ac-voltage magnitude and frequency, as well as the dc-voltage magnitude, by including the interlinking converters in the control strategy via a distributed consensus approach. This improves the power-sharing accuracy and secondary control restoration of the variables in both ac and dc sides of the microgrid. Moreover, the proposed methodology avoids the circulating currents which are typically produced in systems with multiple interlinking converters. Several simulation and experimental tests, such as load impacts and plug-and-play capability, are presented to validate the performance of the proposed control strategy using a 24-kW hybrid ac/dc-microgrid laboratory prototype. [ABSTRACT FROM AUTHOR]

The analysis of wind turbine output power measurements from the offshore wind farm Horns Rev 1 demonstrates a significant likelihood of wind turbine output powers to be very similar at a given time within offshore wind farms. This paper exploits this observation by proposing a new offshore wind farm configuration with DC collection system and series-connected wind turbines based on partial power processing converters (PPPCs) and diode-bridge rectifiers. In the proposed wind farm configuration, PPPCs are only required to process output power differences among wind turbines in a wind farm to achieve maximum power point (MPP) operation, yielding a potential for efficiency and sizing improvements. This paper addresses major design considerations at wind farm, wind turbine, and PPPC levels. System operation of the wind turbine design is derived, alongside with a matching control system and HVDC-link current scheduling algorithm. The proposed wind farm is successfully tested for low voltage ride through, power curtailment, inertia response, and communication system outage scenarios. Time-transient simulations of a 30-turbine series string using measured and artificial wind speed profiles demonstrate that wind turbines can achieve MPP operation while only a fraction of power needs to be processed by the PPPCs. [ABSTRACT FROM AUTHOR]

This paper presents a novel distributed control strategy for frequency control, congestion management, and optimal dispatch (OD) in isolated microgrids. The proposed strategy drives the distributed generators (DGs) within the microgrid to a dispatch that complies with the Karush–Kuhn–Tucker (KKT) conditions of a linear optimal power flow (OPF) formulation. The controller relies on local power and frequency measurements, information from neighboring DGs, and line-flow measurements transmitted through a communications network. Extensive simulations show a good performance of the controller against sudden changes in the load, congested lines and availability of DGs in the microgrid, and the ability to successfully drive the system to an optimal economic operation. [ABSTRACT FROM AUTHOR]

Byline: Afshin Majd, Mehrdad Kazerani Almost all of the commercial microturbine-based dispersed generation systems today are composed of a high-speed permanent-magnet alternator and a diode rectifier-PWM inverter pair. A dispersed generation scheme - made up of a microturbine, an induction generator, and a diode rectifier-PWM inverter pair - is introduced in this paper. A complete model for the self-excited squirrel-cage induction generator is developed and used to study the steady-state and transient behaviours of the overall system. The power delivered to the grid is controlled by an injected current control loop. The input/output power balance is maintained by regulating the DC-bus voltage using a new method based on the torque control of microturbine. Analysis shows that the Simulink simulation results of induction generator is a viable substitute for permanent magnet alternator in microturbine-based dispersed generation systems due to its low cost, low maintenance, rugged structure, and slack between rotor speed and terminal frequency, which isolates the transients of the grid from the generator system when the DC-bus capacitor size is reduced. Both schemes have been simulated and the simulation results are presented to compare the proposed scheme based on induction generator with the present microturbine-based dispersed generation scheme based on synchronous machine.

Battery energy storage systems (BESSs) can be very beneficial to power systems and microgrids for various applications. With increasing sales of electric vehicles (EV), the availability of used electric vehicle batteries (EVBs) is on the rise, which has received significant attention in recent years. The retired EVBs, after repurposing, can serve as an alternative option to new batteries in a BESS. In addition, when a microgrid operator desires to install a BESS, the optimal decisions such as installation year, energy and power size, replacement year, and the number of cycles to failure, that are normally overlooked, have to be determined. Therefore, this paper proposes a comprehensive and novel framework for planning and operation of the BESS based on repurposed EVBs. A novel linearized BESS sizing model is proposed that obtains the BESS optimal decisions regarding design and operation. Various new, modified, and linearized relationships for the BESS have been included in the planning model to ensure that the replacement year of the BESS is optimally determined. Several classes of EVs with multiple drive cycles are clustered and integrated within the proposed framework. [ABSTRACT FROM AUTHOR]

This paper proposes a generalized and efficient power-flow algorithm for islanded hybrid ac/dc microgrids. The algorithm considers the microgrid operational aspects, i.e., absence of a slack bus, unbalanced ac subgrid, droop-controlled ac and dc voltages and ac frequency, and coupling between the ac frequency and dc voltage through interlinking converters. To attain high computational efficiency, the algorithm adopts three features. First, it models the ac subgrid elements in sequence components, thereby dividing the subgrid's set of equations into three smaller sets for faster parallel solution. This approach also accurately represents the different types of ac distributed generators. Second, the algorithm sequentially solves for the power-flow variables of the ac and dc subgrids, thus reducing the number of equations to be solved simultaneously, once again for further computational cost alleviation. Third, the algorithm implements the quadratically convergent Newton–Raphson technique to solve the decoupled sets of equations. The proposed algorithm is validated through comparisons with time-domain simulations, in MATLAB/Simulink, for test hybrid ac/dc microgrids of different configurations. Moreover, three case studies are introduced to examine the proposed algorithm's effectiveness in solving large-scale microgrids, to investigate its limits-enforcement capabilities, and to evaluate its performance as compared to conventional methods. [ABSTRACT FROM AUTHOR]

Given the expected impact of electric vehicle (EV) charging on power grids, this paper presents a novel two-step approach for the smart operation of EVs with four-quadrant chargers in a primary distribution feeder, accounting for the uncertainties associated with EVs, and considering the perspectives of both the utility and the EV owners. In the first step of the proposed approach, the mean daily feeder peak demand and corresponding hourly feeder control schedules, such as taps and switched capacitor setpoints, considering the bidirectional active and reactive power transactions between EVs and the grid, are determined. A nonparametric bootstrap technique is used, in conjunction with a genetic algorithm-based optimization model, to account for EV uncertainties and discrete variables. In the second step, the maximum possible power that can be given to connected EVs at each node, while providing active and/or reactive power to maintain the peak demand value and corresponding feeder dispatch schedules defined in the first step, is computed every few minutes in a way which is fair to the EVs. The proposed approach is validated using the distribution feeder model of a real primary feeder in Ontario, Canada, considering significant EV penetration levels. The results show that the proposed approach could be implemented in practice to properly operate EVs, satisfying feeder, and peak demand constraints, which would be better than the business-as-usual practice or a popular heuristic method in terms of number of tap operations, system peak demand, and voltage regulation. [ABSTRACT FROM AUTHOR]

This paper proposes a generic steady-state modeling and power-flow analysis approach for droop- and isochronously controlled microgrids. The proposed framework adopts symmetrical sequence component models, rather than phase-coordinate models, of microgrid elements. Such approach immensely reduces the power-flow execution time, as it breaks down the system model into independent equation sets with considerably reduced sizes. To render the proposed approach practical and generic, it integrates different types and control schemes of distributed generation (DG), including synchronous generator-based DG (SGDG) and electronically interfaced DG units. Furthermore, it incorporates unbalanced loads and feeders, transformer connections, different load characteristics, and configurations, as well as microgrid droop features. A novel power-flow algorithm based on a modified Newton–Raphson method is proposed to solve for the microgrid steady-state voltage magnitudes, angles, and frequency. The accuracy of the models and algorithm is verified through comparison with detailed time-domain simulations in MATALB/Simulink. Additionally, the proposed approach is shown to outperform the reported Newton-Trust Region approach in generality, accuracy, and performance. Two case studies, incorporating IEEE 123-node test microgrid, are further performed to examine the effectiveness of the proposed approach in solving complicated droop-controlled microgrids, and to examine the behavior of droop-controlled DGs in isochronous microgrids. [ABSTRACT FROM AUTHOR]

Active power filtering is performed by detecting the line current and voltage signals, generating a current equal-but-opposite to the distortion current using a power converter and injecting the compensating current into the power line. In such applications, it is desirable to combine high power and high switching frequency while minimizing the losses. This asks for special converter topologies and control techniques. In this paper, a multi-converter active power-line filter, based on current-source converter (CSC) modules, is proposed. The power rating and switching frequency of each CSC module is equal to those required for the filtering job divided by the number of modules. The control system utilizes two linear adaptive neurons (ADALINE's) to process the signals obtained from the line. The first ADALINE (the Current ADALINE) extracts the harmonic components of the distorted line current signal and the second ADALINE (the Voltage ADALINE) estimates the fundamental component of the line voltage signal. The outputs of both ADALINE's are used to construct the modulating signals of the filter modules. The proposed modular active filter offers the following advantage: 1) high efficiency due to low conduction and switching losses; 2) high reliability and 3) high serviceability. The proposed active power-line filter treats the ac system on a per-phase basis, has fast response and adapts to the load variations. Theoretical expectations are verified by digital simulation using EMTDC simulation package. Index Terms--Active filter, ADALINE, modular, PWM converter.

With the increased penetration of electric vehicle (EV) chargers in distribution systems, there is a need to understand and minimize their impact on medium-voltage (MV) and low-voltage (LV) networks. Thus, this paper proposes a three-stage algorithm to coordinate the operation of four-quadrant EV chargers with other volt/var control devices in MV and LV distribution feeders. The first stage operates on a day-ahead basis and defines the load tap changer and capacitor schedules while minimizing the peak load associated with EVs in the distribution system. The second and third stages update their operation every five minutes, to fairly allocate the aggregated and individual EV loads in the MV an LV feeders, respectively, while minimizing active power losses and voltage deviations. The proposed technique is applied to CIGRE’s North-American MV and LV benchmark systems to demonstrate its ability to properly allocate EV loads, and improve distribution system performance in terms of losses and voltage deviations. [ABSTRACT FROM AUTHOR]

This paper proposes a model of a single-phase bidirectional electric vehicle (EV) charger with capability of operating in all four quadrants of the P – Q plane. The steady-state and step responses of the proposed model are used to validate it based on the actual responses of a bidirectional charger prototype for different P – Q requests. The model can be used efficiently in time-domain simulations that require models of a number of EV chargers, such as EV integration studies in low-voltage (LV) distribution networks. A practical case study is presented to demonstrate and test the proposed smart charger and model, investigating the provision of vehicle-to-grid (V2G) for active and reactive power in an LV residential distribution network. These results demonstrate the advantages of the presented charger model for developing V2G strategies in distribution networks. [ABSTRACT FROM PUBLISHER]

This paper presents the mathematical formulation and control architecture of a stochastic-predictive energy management system for isolated microgrids. The proposed strategy addresses uncertainty using a two-stage decision process combined with a receding horizon approach. The first stage decision variables (unit commitment) are determined using a stochastic mixed-integer linear programming formulation, whereas the second stage variables (optimal power flow) are refined using a nonlinear programming formulation. This novel approach was tested on a modified CIGRE test system under different configurations comparing the results with respect to a deterministic approach. The results show the appropriateness of the method to account for uncertainty in the power forecast. [ABSTRACT FROM PUBLISHER]

This paper provides a detailed comparative analysis of optimal sizing of battery-only, ultracapacitor-only, and battery–ultracapacitor hybrid energy storage systems (ESSs) for a plug-in electric city bus (PECB). It is shown how the configuration affects the optimal size of the ESS. The problem of optimal sizing of the storage system for the PECB is formulated and solved for a specific set of vehicle parameters, battery, and ultracapacitor cell data, as well as a specific daily drive cycle. A modified particle swarm optimization algorithm is used to solve the optimal sizing problem. The optimization platform developed by the authors and used for this study is highly flexible and accepts different component data, vehicle parameters, and drive cycles as the input for determining the optimal sizes of the storage system. [ABSTRACT FROM PUBLISHER]

Batteries are the most commonly used electrical energy storage devices. The cost and performance of an electric vehicle (EV) are strongly affected by the proper selection of technology, number, and arrangement of the battery cells used. This paper formulates the problem of optimal sizing of the battery unit (BU) for a plug-in EV (PEV), given the specifications of the vehicle, battery cell data, and drive cycle. This paper employs a metaheuristic optimization algorithm to find the optimal size of the BU with the objective of minimizing the overall cost. Feasibility of the optimization results in terms of respecting the constraints is verified via simulation. The developed optimization platform is highly flexible and allows use of different vehicle designs, component data, and drive cycles. [ABSTRACT FROM PUBLISHER]

Active power-line filtering is conventionally performed by injecting equal-but-opposite of the distortion into the line. The power converter used for this purpose is rated based on the magnitude of the distortion current and operated at the switching frequency dictated by the desired filter bandwidth. Fast switching at high power, even if technically possible, causes high switching losses. In this paper, a new modular approach to active harmonic filtering is proposed. The method utilizes two linear adaptive neurons (ADALINEs) to process the signals obtained from the line. The first ADALINE (the Current ADALINE) extracts the harmonic components of the distorted line current signal and the second ADALINE (the Voltage ADALINE) estimates the fundamental component of the line voltage signal. The outputs of both ADALINEs are used to construct the modulating signals of a number of current-source inverter (CSI) modules, each dedicated to eliminate a specific harmonic. The power rating of the modules will decrease and their switching frequency will increase as the order of the harmonic to be filtered is increased. The overall switching losses are minimized due to the selected harmonic elimination and balanced 'power rating'-'switching frequency' product. Power losses are also reduced by adjusting the [I.sub.dc] in each CSI module according to the present magnitudes of the individual harmonics to be filtered. Speed and accuracy of ADALINE, self-synchronizing harmonic tracking, optimum [I.sub.dc] value and minimal converter losses, high reliability and flexibility and speed and low dc energy requirement of the CSI, result in superb performance of the proposed active conditioner. The theoretical expectations are verified by digital simulation using EMTDC simulation package. Index Terms--Active power filter, ADALINE, CSI, EMTDC.

Access to energy in many of the world?s remote communities is still restricted; these locations only have access to simple and inexpensive local energy sources, such as biomass for cooking and kerosene lamps or candles for lighting. The World Bank and the International Energy Agency (IEA) perceive this energy deficit as a major obstacle to achieving community economic development as well as to obtaining adequate access to health services and clean water. Electricity is a flexible, modern source of energy that is considered to be one of the principal driving forces that stimulate community development and access to basic services in remote locations. Governments, private institutions, and nongovernmental organizations have gradually recognized these energy needs and have established electrification programs at the national and regional levels that aim at the gradual electrification of remote locations. [ABSTRACT FROM PUBLISHER]

The increasing interest in integrating intermittent renewable energy sources into microgrids presents major challenges from the viewpoints of reliable operation and control. In this paper, the major issues and challenges in microgrid control are discussed, and a review of state-of-the-art control strategies and trends is presented; a general overview of the main control principles (e.g., droop control, model predictive control, multi-agent systems) is also included. The paper classifies microgrid control strategies into three levels: primary, secondary, and tertiary, where primary and secondary levels are associated with the operation of the microgrid itself, and tertiary level pertains to the coordinated operation of the microgrid and the host grid. Each control level is discussed in detail in view of the relevant existing technical literature. [ABSTRACT FROM PUBLISHER]

This paper presents the mathematical formulation of the microgrid's energy management problem and its implementation in a centralized Energy Management System (EMS) for isolated microgrids. Using the model predictive control technique, the optimal operation of the microgrid is determined using an extended horizon of evaluation and recourse, which allows a proper dispatch of the energy storage units. The energy management problem is decomposed into Unit Commitment (UC) and Optimal Power Flow (OPF) problems in order to avoid a mixed-integer non-linear formulation. The microgrid is modeled as a three-phase unbalanced system with presence of both dispatchable and non-dispatchable distributed generation. The proposed EMS is tested in an isolated microgrid based on a CIGRE medium-voltage benchmark system. Results justify the need for detailed three-phase models of the microgrid in order to properly account for voltage limits and procure reactive power support. [ABSTRACT FROM PUBLISHER]

The paper investigates renewable energy alternatives to reduce diesel fuel dependency on electricity generation in Ontario's remote northern communities; currently, these communities use diesel fuel as the sole energy source to produce electricity. The current operation is complex, involving several stakeholders, high operating costs, and a considerable CO2 footprint. Several of these communities have electric load restrictions that limit further building construction and economic growth. This preliminary work discusses the barriers for renewable energy (RE) projects in northern Ontario communities by analyzing the current economic structure, the high capital costs, the available natural resources, and the installation and operation complexity. Also, a detailed analysis of six scenarios is presented; three scenarios consider a solar and/or wind-diesel system with a low RE penetration of 7% without any excess energy, whereas other three scenarios increase the RE penetration to 18%, requiring a dump load, an additional small diesel engine, or a battery storage system. The proposed systems reduce fuel consumption, operating costs and CO2 emissions, considering the investment, operation and maintenance costs and constraints in remote regions. [ABSTRACT FROM PUBLISHER]

Common-mode voltages (CMVs) can lead to premature failure of the motor insulation system in medium-voltage current-source-fed drives. By analyzing the CMV values at all switching states under different operating conditions of a current-source-inverter (CSI)-based motor drive, this paper first indicates that the CMV peaks are produced by the zero states in most of the cases. The nonzero-state (NZS) modulation techniques employed in voltage-source converters are adapted for use in a space-vector-modulated current-source converter (CSC) to reduce the CMV magnitude. For NZS modulation in CSCs, the nearest three-state (NTS) modulation sequences are designed with good low-order harmonic performances in their linear modulation region of m _a ≥ 0.67 and with no increase in the device switching frequency. A combined active-zero-state (AZS) modulation technique is also proposed as compensation, for a lower modulation index in the range of 0.4–0.67, when a compromise is made between the dc-link current minimization and high input power factor control. The simulation and experimental results are provided to validate the CMV reduction effects and harmonic performances of the NTS and combined AZS modulation methods in CSI-fed drives. [ABSTRACT FROM AUTHOR]

Partial shading of a photovoltaic array is the condition under which different modules in the array experience different irradiance levels due to shading. This difference causes mismatch between the modules, leading to undesirable effects such as reduction in generated power and hot spots. The severity of these effects can be considerably reduced by photovoltaic array reconfiguration. This paper proposes a novel mathematical formulation for the optimal reconfiguration of photovoltaic arrays to minimize partial shading losses. The paper formulates the reconfiguration problem as a mixed integer quadratic programming problem and finds the optimal solution using a branch and bound algorithm. The proposed formulation can be used for an equal or nonequal number of modules per row. Moreover, it can be used for fully reconfigurable or partially reconfigurable arrays. The improvement resulting from the reconfiguration with respect to the existing photovoltaic interconnections is demonstrated by extensive simulation results. [ABSTRACT FROM PUBLISHER]

A mismatch in a photovoltaic array implies differences in the I\–V characteristics of the modules forming the array. This can lead to significant energy losses known as mismatch losses. The mismatch and the resulting losses can be reduced by altering the interconnection of the array. This paper proposes an optimal total cross tied interconnection, based on a thorough mathematical formulation that can significantly reduce mismatch losses. The improvement over existing photovoltaic array interconnections has been demonstrated by extensive simulation results. [ABSTRACT FROM PUBLISHER]

Voltage-source inverter (VSI) topology is widely used for grid interfacing of distributed generation (DG) systems. However, when employed as the power conditioning unit in photovoltaic (PV) systems, VSI normally requires another power electronic converter stage to step up the voltage, thus adding to the cost and complexity of the system. To make the proliferation of grid-connected PV systems a successful business option, the cost, performance, and life expectancy of the power electronic interface need to be improved. The current-source inverter (CSI) offers advantages over VSI in terms of inherent boosting and short-circuit protection capabilities, direct output current controllability, and ac-side simpler filter structure. Research on CSI-based DG is still in its infancy. This paper focuses on modeling, control, and steady-state and transient performances of a PV system based on CSI. It also performs a comparative performance evaluation of VSI-based and CSI-based PV systems under transient and fault conditions. Analytical expectations are verified using simulations in the Power System Computer Aided Design/Electromagnetic Transient Including DC (PSCAD/EMTDC) environment, based on a detailed system model. [ABSTRACT FROM PUBLISHER]

This paper presents modeling guidelines and a benchmark system for power system simulation studies of grid-connected, three-phase, single-stage Photovoltaic (PV) systems that employ a voltage-sourced converter (VSC) as the power processor. The objective of this work is to introduce the main components, operation/protection modes, and control layers/schemes of medium- and high-power PV systems, to assist power engineers in developing circuit-based simulation models for impact assessment studies, analysis, and identification of potential issues with respect to the grid integration of PV systems. Parameter selection, control tuning, and design guidelines are also briefly discussed. The usefulness of the benchmark system is demonstrated through a fairly comprehensive set of test cases, conducted in the PSCAD/EMTDC software environment. However, the models and techniques presented in this paper are independent of any specific circuit simulation software package. Also, they may not fully conform to the methods exercised by all manufacturers, due to the proprietary nature of the industry. [ABSTRACT FROM AUTHOR]