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Showing papers on "Electric power system published in 2013"


Journal ArticleDOI
TL;DR: In this paper, a two-stage adaptive robust unit commitment model for the security constrained unit commitment problem in the presence of nodal net injection uncertainty is proposed, which only requires a deterministic uncertainty set, rather than a hard-to-obtain probability distribution on the uncertain data.
Abstract: Unit commitment, one of the most critical tasks in electric power system operations, faces new challenges as the supply and demand uncertainty increases dramatically due to the integration of variable generation resources such as wind power and price responsive demand. To meet these challenges, we propose a two-stage adaptive robust unit commitment model for the security constrained unit commitment problem in the presence of nodal net injection uncertainty. Compared to the conventional stochastic programming approach, the proposed model is more practical in that it only requires a deterministic uncertainty set, rather than a hard-to-obtain probability distribution on the uncertain data. The unit commitment solutions of the proposed model are robust against all possible realizations of the modeled uncertainty. We develop a practical solution methodology based on a combination of Benders decomposition type algorithm and the outer approximation technique. We present an extensive numerical study on the real-world large scale power system operated by the ISO New England. Computational results demonstrate the economic and operational advantages of our model over the traditional reserve adjustment approach.

1,454 citations


Book
01 May 2013
TL;DR: P.P. Anderson, a noted expert on power systems, presents an analytical and technical approach to power system protection, showing how abnormal system behavior can be detected before damage occurs, and points to effective control action to limit system outages.
Abstract: "In a world of huge, interconnected networks that can be completely blacked out by disturbances, POWER SYSTEM PROTECTION offers you an improved understanding of the requirements necessary for prompt and accurate corrective action.P. M. Anderson, a noted expert on power systems, presents an analytical and technical approach to power system protection. His discussion shows how abnormal system behavior can be detected before damage occurs, and points to effective control action to limit system outages.Advance your knowledge of power system protection through a better understanding of:Protective devices and controlsProtection conceptsTransmission protectionApparatus protectionSystem aspects of protective systemsReliability analysis of protective systemsPOWER SYSTEM PROTECTION is expressly written for practicing engineers and advanced graduate-level student engineers who need a comprehensive resource on the principles of power system behavior. This essential reference work provides new and advanced concepts for understanding system performance."

758 citations


Journal ArticleDOI
TL;DR: In this paper, the impact of increased penetration of photovoltaic (PV) systems on static performance as well as transient stability of a large power system, in particular the transmission system, is examined.
Abstract: Present renewable portfolio standards are changing power systems by replacing conventional generation with alternate energy resources such as photovoltaic (PV) systems. With the increase in penetration of PV resources, power systems are expected to experience a change in dynamic and operational characteristics. This paper studies the impact of increased penetration of PV systems on static performance as well as transient stability of a large power system, in particular the transmission system. Utility scale and residential rooftop PVs are added to the aforementioned system to replace a portion of conventional generation resources. While steady state voltages are observed under various PV penetration levels, the impact of reduced inertia on transient stability performance is also examined. The studied system is a large test system representing a portion of the Western U.S. interconnection. The simulation results obtained effectively identify both detrimental and beneficial impacts of increased PV penetration both for steady state stability and transient stability performance.

687 citations


Journal ArticleDOI
TL;DR: In this paper, a look-ahead proportional controller broadcasts control signals to all TCLs, which always remain in their temperature deadband, and achieves power tracking RMS errors in the range of 0.26-9.3% of steady state aggregated power consumption.
Abstract: This paper explores methods to coordinate aggregations of thermostatically controlled loads (TCLs; including air conditioners and refrigerators) to manage frequency and energy imbalances in power systems. We focus on opportunities to centrally control loads with high accuracy but low requirements for sensing and communications infrastructure. We compare cases when measured load state information (e.g., power consumption and temperature) is 1) available in real time; 2) available, but not in real time; and 3) not available. We use Markov chain models to describe the temperature state evolution of populations of TCLs, and Kalman filtering for both state and joint parameter/state estimation. A look-ahead proportional controller broadcasts control signals to all TCLs, which always remain in their temperature dead-band. Simulations indicate that it is possible to achieve power tracking RMS errors in the range of 0.26%-9.3% of steady state aggregated power consumption. We also report results in terms of the generator compliance threshold which is commonly used in industry. Results depend upon the information available for system identification, state estimation, and control. Depending upon the performance required, TCLs may not need to provide state information to the central controller in real time or at all.

550 citations


Posted Content
TL;DR: The impact of low rotational inertia on power system stability and operation is investigated, new analysis insights are contributed and impact mitigation options are offered.
Abstract: Large-scale deployment of RES has led to significant generation shares of variable RES in power systems worldwide. RES units, notably inverter-connected wind turbines and PV that as such do not provide rotational inertia, are effectively displacing conventional generators and their rotating machinery. The traditional assumption that grid inertia is sufficiently high with only small variations over time is thus not valid for power systems with high RES shares. This has implications for frequency dynamics and power system stability and operation. Frequency dynamics are faster in power systems with low rotational inertia, making frequency control and power system operation more challenging. This paper investigates the impact of low rotational inertia on power system stability and operation, contributes new analysis insights and offers mitigation options for low inertia impacts.

508 citations


Journal ArticleDOI
TL;DR: An extensive literature review on load-frequency control (LFC) problem in power system has been highlighted in this article, where various configuration of power system models and control techniques/strategies that concerns to LFC issues have been addressed in conventional as well as distribution generation-based power systems.
Abstract: In this paper an extensive literature review on load–frequency control (LFC) problem in power system has been highlighted. The various configuration of power system models and control techniques/strategies that concerns to LFC issues have been addressed in conventional as well as distribution generation-based power systems. Further, investigations on LFC challenges incorporating storage devices BESS/SMES, FACTS devices, wind–diesel and PV systems etc have been discussed too.

485 citations


Proceedings ArticleDOI
21 Jul 2013
TL;DR: In this article, the authors present a novel average value model (AVM) for efficient and accurate representation of a detailed MMC-HVDC system and also develop a detailed 401-level MMC HVDC model for validating the AVM and studies the performance of both models when integrated into a large 400 kV transmission system in Europe.
Abstract: Summary form only given. Voltage Source Converter (VSC) technologies present a bright opportunity in a variety of fields within the power system industry. New Modular Multilevel Converters (MMCs) are expected to supersede two- and three-level VSC-based technologies for HVDC applications due to their recognized advantages in terms of scalability, performance and efficiency. Computational burden introduced by detailed modeling of MMC-HVDC systems in EMT-type programs complicates the study of transients especially when such systems are integrated into a large network. This paper presents a novel average-value model (AVM) for efficient and accurate representation of a detailed MMC-HVDC system. It also develops a detailed 401-level MMC-HVDC model for validating the AVM and studies the performance of both models when integrated into a large 400 kV transmission system in Europe. The results show that the AVM is significantly more efficient while maintaining its accuracy for the dynamic response of the overall system.

425 citations


Journal ArticleDOI
TL;DR: In this article, a decentralized V2G control (DVC) method is proposed for EVs to participate in primary frequency control considering charging demands from EV customers, and a smart charging method, called charging with frequency regulation (CFR), is developed to achieve scheduled charging and provide frequency regulation at the same time.
Abstract: Vehicle-to-grid (V2G) control has the potential to provide frequency regulation service for power system operation from electric vehicles (EVs). In this paper, a decentralized V2G control (DVC) method is proposed for EVs to participate in primary frequency control considering charging demands from EV customers. When an EV customer wants to maintain the residual state of charge (SOC) of the EV battery, a V2G control strategy, called battery SOC holder (BSH), is performed to maintain the battery energy around the residual SOC along with adaptive frequency droop control. If the residual battery energy is not enough for next trip, the customer needs to charge the EV to higher SOC level. Then, a smart charging method, called charging with frequency regulation (CFR), is developed to achieve scheduled charging and provide frequency regulation at the same time. Simulations on a two-area interconnected power system with wind power integration have shown the effectiveness of the proposed method.

408 citations


Journal ArticleDOI
TL;DR: In this article, the levels of inertia in power systems may decrease in the future, due to increased levels of energy being provided from renewable sources, which typically have little or no inertia.
Abstract: There is concern that the levels of inertia in power systems may decrease in the future, due to increased levels of energy being provided from renewable sources, which typically have little or no inertia. Voltage source converters (VSC) used in high voltage direct current (HVDC) transmission applications are often deliberately controlled in order to de-couple transients to prevent propagation of instability between interconnected systems. However, this can deny much needed support during transients that would otherwise be available from system inertia provided by rotating plant.

372 citations


Journal ArticleDOI
TL;DR: In this paper, a low-voltage bipolar-type dc microgrid with two energy storage units and a dc/dc converter was proposed to achieve both power sharing and energy management.
Abstract: Installation of many distributed generations (DGs) could be detrimental to the power quality of utility grids. Microgrids facilitate effortless installation of DGs in conventional power systems. In recent years, dc microgrids have gained popularity because dc output sources such as photovoltaic systems, fuel cells, and batteries can be interconnected without ac/dc conversion, which contributes to total system efficiency. Moreover, high-quality power can be supplied continuously when voltage sags or blackouts occur in utility grids. We had already proposed a “low-voltage bipolar-type dc microgrid” and described its configuration, operation, and control scheme, through experiments. In the experiments, we used one energy storage unit with a dc/dc converter to maintain the dc-bus voltage under intentional islanding operation. However, dc microgrids should have two or more energy storage units for system redundancy. Therefore, we modified the system by adding another energy storage unit to our experimental system. Several kinds of droop controls have been proposed for parallel operations, some of which were applied for ac or dc microgrids. If a gain-scheduling control scheme is adopted to share the storage unit outputs, the storage energy would become unbalanced. This paper therefore presents a new voltage control that combines fuzzy control with gain-scheduling techniques to accomplish both power sharing and energy management. The experimental results show that the dc distribution voltages were within 340 V ± 5%, and the ratios of the stored energy were approximately equal, which implies that dc voltage regulation and stored energy balancing control can be realized simultaneously.

364 citations


Journal ArticleDOI
04 Apr 2013
TL;DR: This paper traces the history of wireless power transmission starting with Nikola Tesla, continuing on to experiments with beaming power using microwaves, and explaining why near-field technique is more suitable for consumer electronic devices and exploring the near- field transmission of power via the magnetic field.
Abstract: Wireless power has been a topic of interest from the early 20th century until today. This paper traces the history of wireless power transmission starting with Nikola Tesla, continuing on to experiments with beaming power using microwaves. Examining the difference between near-field and far-field techniques, this paper continues into modern times explaining why near-field technique is more suitable for consumer electronic devices and exploring the near-field transmission of power via the magnetic field. Examples of short-range and midrange wireless power systems are explored.

Proceedings ArticleDOI
Salvatore D'Arco1, Jon Are Suul1
16 Jun 2013
TL;DR: In this article, a comprehensive literature review on VSM and a possible classification of the different schemes is provided, and the small-signal response of the inertia emulation characteristics of VSM-based control is proved to be equivalent to conventional droop-based controller for standalone and microgrid operation of converters.
Abstract: The concept of Virtual Synchronous Machines (VSM) is emerging as an alternative approach for control of power electronic converters operating in the power system. One main motivation for applying VSM-based control is to achieve a simple approach for emulating the inertia effect of traditional synchronous machines. This paper provides a comprehensive literature review on VSM and a possible classification of the different schemes. In addition, the small-signal response of the inertia emulation characteristics of VSM-based control is proved to be equivalent to conventional droop-based control for standalone and microgrid operation of converters. Thus, the droop gain and the filter time constant of the power feedback in a droop controller can be directly related to the damping factor and the inertia constant of a Virtual Synchronous Machine. The derived results are providing additional physics-based insight into the operation and tuning of both types of controllers.

Journal ArticleDOI
TL;DR: In this article, a model that determines the theoretical maximum of flexibility of a combined heat and power system coupled with a thermal energy storage solution that can be either centralized or decentralized is presented.

Journal ArticleDOI
TL;DR: In this paper, the authors present different applications of electrical energy storage technologies in power systems emphasizing on the collaboration of such entities with renewable energy systems (RESs), where the role of ESSs in intelligent micropower grids is also discussed where the stochastic nature of renewable energy sources may affect the power quality.
Abstract: The ever increasing penetration of renewable energy systems (RESs) in today deregulated intelligent power grids, necessitates the use of electrical storage systems. Energy storage systems (ESSs) are helpful to make balance between generation and demand improving the performance of whole power grid. In collaboration with RESs, energy storage devices can be integrated into the power networks to bring ancillary service for the power system and hence enable an increased penetration of distributed generation (DG) units. This paper presents different applications of electrical energy storage technologies in power systems emphasizing on the collaboration of such entities with RESs. The role of ESSs in intelligent micropower grids is also discussed where the stochastic nature of renewable energy sources may affect the power quality. Particular attention is paid to flywheel storage, electrochemical storage, pumped hydroelectric storage, and compressed air storage and their operating principle are discussed as well. The application of each type in the area of power system is investigated and compared to others.

Journal ArticleDOI
TL;DR: This paper presents a unit commitment model for studying the impact of large-scale wind integration in power systems with transmission constraints and system component failures, and presents a scenario selection algorithm for selecting and weighing wind power production scenarios and composite element failures.
Abstract: In this paper we present a unit commitment model for studying the impact of large-scale wind integration in power systems with transmission constraints and system component failures. The model is formulated as a two-stage stochastic program with uncertain wind production in various locations of the network as well as generator and transmission line failures. We present a scenario selection algorithm for selecting and weighing wind power production scenarios and composite element failures, and we provide a parallel dual decomposition algorithm for solving the resulting mixed-integer program. We validate the proposed scenario selection algorithm by demonstrating that it outperforms alternative reserve commitment approaches in a 225 bus model of California with 130 generators and 375 transmission lines. We use our model to quantify day-ahead generator capacity commitment, operating cost impacts, and renewable energy utilization levels for various degrees of wind power integration. We then demonstrate that failing to account for transmission constraints and contingencies can result in significant errors in assessing the economic impacts of renewable energy integration. Subject classifications: unit commitment; stochastic programming; wind power; transmission constraints. Area of review: Environment, Energy, and Sustainability.

Journal ArticleDOI
TL;DR: This work describes and implements a methodology to construct detailed temporal and spatial representations of demand response resources and to incorporate those resources into power system models and demonstrates how the combination of these three analyses can be used to assess economic value of the realizable potential ofDemand response for ancillary services.
Abstract: Many demand response resources are technically capable of providing ancillary services. In some cases, they can provide superior response to generators, as the curtailment of load is typically much faster than ramping thermal and hydropower plants. Analysis and quantification of demand response resources providing ancillary services is necessary to understand the resources' economic value and impact on the power system. Methodologies used to study grid integration of variable generation can be adapted to the study of demand response. In the present work, we describe and implement a methodology to construct detailed temporal and spatial representations of demand response resources and to incorporate those resources into power system models. In addition, the paper outlines ways to evaluate barriers to implementation. We demonstrate how the combination of these three analyses can be used to assess economic value of the realizable potential of demand response for ancillary services.

Journal ArticleDOI
TL;DR: A new PID controller for resistant differential control against load disturbance is introduced that can be used for load frequency control (LFC) application and a comparison between this controller and two other prevalent PI controllers, optimized by GA and Neural Networks, has been done which represents advantages of this controller over others.
Abstract: A new PID controller for resistant differential control against load disturbance is introduced that can be used for load frequency control (LFC) application. Parameters of the controller have been specified by using imperialist competitive algorithm (ICA). Load disturbance, which is due to continuous and rapid changes of small loads, is always a problem for load frequency control of power systems. This paper introduces a new method to overcome this problem that is based on filtering technique which eliminates the effect of this kind of disturbance. The object is frequency regulation in each area of the power system and decreasing of power transfer between control areas, so the parameters of the proposed controller have been specified in a wide range of load changes by means of ICA to achieve the best dynamic response of frequency. To evaluate the effectiveness of the proposed controller, a three-area power system is simulated in MATLAB/SIMULINK. Each area has different generation units, so utilizes controllers with different parameters. Finally a comparison between the proposed controller and two other prevalent PI controllers, optimized by GA and Neural Networks, has been done which represents advantages of this controller over others.

Journal ArticleDOI
TL;DR: In this article, the authors propose an architecture for voltage regulation in distribution networks that relies on controlling reactive power injections provided by distributed energy resources (DERs), where a local controller on each bus monitors the bus voltage and, whenever there is a voltage violation, it uses locally available information to estimate the amount of reactive power that needs to be injected into the bus in order to correct the violation.
Abstract: In this paper, we propose an architecture for voltage regulation in distribution networks that relies on controlling reactive power injections provided by distributed energy resources (DERs). A local controller on each bus of the network monitors the bus voltage and, whenever there is a voltage violation, it uses locally available information to estimate the amount of reactive power that needs to be injected into the bus in order to correct the violation. If the DERs connected to the bus can collectively provide the reactive power estimated by the local controller, they are instructed to do so. Otherwise, the local controller initiates a request for additional reactive power support from other controllers at neighboring buses through a distributed algorithm that relies on a local exchange of information among neighboring controllers. We show that the proposed architecture helps prevent voltage violations and shapes the voltage profile in radial distribution networks, even in the presence of considerable penetration of variable generation and loads. We present several case studies involving 8-, 13-, and 123-bus distribution systems to illustrate the operation of the architecture.

Patent
03 May 2013
TL;DR: In this paper, a selection unit of the electric power supply apparatus selects, from the total plurality of electric power devices, a plurality of devices whose locations correspond to a position where the reception apparatus is placed, and a control unit controls the supply of electricity to the reception device.
Abstract: An electric power supply system includes an electric power reception apparatus and an electric power supply apparatus adapted to supply electric power to the electric power reception apparatus when the electric power reception apparatus is placed on the electric power supply apparatus. The electric power supply apparatus includes a plurality of electric power supply units adapted to supply electric power by electromagnetic induction to the electric power reception apparatus. A selection unit of the electric power supply apparatus selects, from the total plurality of electric power supply units, a plurality of electric power supply units whose location corresponds to a position where the electric power reception apparatus is placed, and a control unit controls the supply of electric power such that electric power is supplied to the electric power reception apparatus from the selected plurality of electric power supply units.

Journal ArticleDOI
TL;DR: In this article, a two area thermal system with governor dead-band nonlinearity is considered for the design and analysis purpose and differential evolution (DE) algorithm based on parallel 2-Degree Freedom of Proportional-Integral-Derivative (2-DOF PID) controller for Load Frequency Control (LFC) of interconnected power system is presented.

Journal ArticleDOI
01 Dec 2013
TL;DR: The effectiveness of the hBFOA-PSO algorithm has been tested for automatic generation control (AGC) of an interconnected power system and the superiority of the proposed approach is shown by comparing the results of craziness based particle swarm optimization (CRAZYPSO) approach.
Abstract: In the bacteria foraging optimization algorithm (BFAO), the chemotactic process is randomly set, imposing that the bacteria swarm together and keep a safe distance from each other. In hybrid bacteria foraging optimization algorithm and particle swarm optimization (hBFOA-PSO) algorithm the principle of swarming is introduced in the framework of BFAO. The hBFOA-PSO algorithm is based on the adjustment of each bacterium position according to the neighborhood environment. In this paper, the effectiveness of the hBFOA-PSO algorithm has been tested for automatic generation control (AGC) of an interconnected power system. A widely used linear model of two area non-reheat thermal system equipped with proportional-integral (PI) controller is considered initially for the design and analysis purpose. At first, a conventional integral time multiply absolute error (ITAE) based objective function is considered and the performance of hBFOA-PSO algorithm is compared with PSO, BFOA and GA. Further a modified objective function using ITAE, damping ratio of dominant eigenvalues and settling time with appropriate weight coefficients is proposed to increase the performance of the controller. Further, robustness analysis is carried out by varying the operating load condition and time constants of speed governor, turbine, tie-line power in the range of +50% to -50% as well as size and position of step load perturbation to demonstrate the robustness of the proposed hBFOA-PSO optimized PI controller. The proposed approach is also extended to a non-linear power system model by considering the effect of governor dead band non-linearity and the superiority of the proposed approach is shown by comparing the results of craziness based particle swarm optimization (CRAZYPSO) approach for the identical interconnected power system. Finally, the study is extended to a three area system considering both thermal and hydro units with different PI coefficients and comparison between ANFIS and proposed approach has been provided.

Journal ArticleDOI
TL;DR: In this paper, the role of electric vehicles (EVs) contributes to primary frequency response in the Great Britain (GB) power system, and a tool was developed to estimate the EV charging load based on statistical analysis of EV type, battery capacity, maximum travel range and battery state of charge.
Abstract: With the increasing use of renewable energy in the Great Britain (GB) power system, the role of electric vehicles (EVs) contributes to primary frequency response was investigated. A tool was developed to estimate the EV charging load based on statistical analysis of EV type, battery capacity, maximum travel range and battery state of charge. A simplified GB power system model was used to investigate the contribution of EVs to primary frequency response. Two control modes were considered: disconnection of charging load (case I) and discharge of stored battery energy (case II). For case II, the characteristic of the EV charger was also considered. A case study shows results for the year 2020. Three EV charging strategies: “dumb” charging, “off-peak” charging, and “smart” charging, were compared. Simulation results show that utilizing EVs to stabilize the grid frequency in the GB system can significantly reduce frequency deviations. However the requirement to schedule frequency response from conventional generators is dynamic throughout the day.

Journal ArticleDOI
TL;DR: In this paper, a simple approach to load frequency control (LFC) design for the power systems having parameter uncertainty and load disturbance is proposed, which is based on two-degree-of-freedom, internal model control (IMC) scheme, which unifies the concept of model-order reduction like Routh and Pade approximations.
Abstract: The large-scale power systems are liable to performance deterioration due to the presence of sudden small load perturbations, parameter uncertainties, structural variations, etc. Due to this, modern control aspects are extremely important in load frequency control (LFC) design of power systems. In this paper, the LFC problem is illustrated as a typical disturbance rejection as well as large-scale system control problem. For this purpose, simple approach to LFC design for the power systems having parameter uncertainty and load disturbance is proposed. The approach is based on two-degree-of-freedom, internal model control (IMC) scheme, which unifies the concept of model-order reduction like Routh and Pade approximations, and modified IMC filter design, recently developed by Liu and Gao [24]. The beauty of this paper is that in place of taking the full-order system for internal-model of IMC, a lower-order, i.e., second-order reduced system model, has been considered. This scheme achieves improved closed-loop system performance to counteract load disturbances. The proposed approach is simulated in MATLAB environment for a single-area power system consisting of single generating unit with a non-reheated turbine to highlight the efficiency and efficacy in terms of robustness and optimality.

Journal ArticleDOI
TL;DR: This paper presents a graphical user interface (GUI) based on a genetic algorithm (GA) which is shown able to find the optimal locations and sizing parameters of multi-type FACTS devices in large power systems.
Abstract: Flexible AC transmission systems, so-called FACTS devices, can help reduce power flow on overloaded lines, which would result in an increased loadability of the power system, fewer transmission line losses, improved stability and security and, ultimately, a more energy-efficient transmission system. In order to find suitable FACTS locations more easily and with more flexibility, this paper presents a graphical user interface (GUI) based on a genetic algorithm (GA) which is shown able to find the optimal locations and sizing parameters of multi-type FACTS devices in large power systems. This user-friendly tool, called the FACTS Placement Toolbox, allows the user to pick a power system network, determine the GA settings and select the number and types of FACTS devices to be allocated in the network. The GA-based optimization process is then applied to obtain optimal locations and ratings of the selected FACTS to maximize the system static loadability. Five different FACTS devices are implemented: SVC, TCSC, TCVR, TCPST and UPFC. The simulation results on IEEE test networks with up to 300 buses show that the FACTS placement toolbox is effective and flexible enough for analyzing a large number of scenarios with mixed types of FACTS to be optimally sited at multiple locations simultaneously.

Journal ArticleDOI
TL;DR: In this paper, a three-port dc-dc converter integrating photovoltaic (PV) and battery power for high step-up applications is proposed, which includes five power switches, two coupled inductors, and two active-clamp circuits.
Abstract: A three-port dc–dc converter integrating photovoltaic (PV) and battery power for high step-up applications is proposed in this paper. The topology includes five power switches, two coupled inductors, and two active-clamp circuits. The coupled inductors are used to achieve high step-up voltage gain and to reduce the voltage stress of input side switches. Two sets of active-clamp circuits are used to recycle the energy stored in the leakage inductors and to improve the system efficiency. The operation mode does not need to be changed when a transition between charging and discharging occurs. Moreover, tracking maximum power point of the PV source and regulating the output voltage can be operated simultaneously during charging/discharging transitions. As long as the sun irradiation level is not too low, the maximum power point tracking (MPPT) algorithm will be disabled only when the battery charging voltage is too high. Therefore, the control scheme of the proposed converter provides maximum utilization of PV power most of the time. As a result, the proposed converter has merits of high boosting level, reduced number of devices, and simple control strategy. Experimental results of a 200-W laboratory prototype are presented to verify the performance of the proposed three-port converter.

Journal ArticleDOI
TL;DR: In this paper, the authors show that the war of currents started in 1888 and George Westinghouse and Nikolai Tesla with the alternating current (ac) system were on one side and Thomas Edison and his dc distribution system on the other side.
Abstract: It has been over 100 years since Thomas Edison built the first direct current (dc) electricity supply system on 4 September 1882, at Pearl Street in New York City. Many prominent events occurred in the electricity supply industry after that. The first one, ?the war of currents,? started in 1888. Thomas Edison and his dc distribution system were on one side, and George Westinghouse and Nikolai Tesla with the alternating current (ac) system were on other side. The war ?ended? in about 1891 when ac won as the dominant power supply medium. The key behind the ac win was the invention of the transformer that could easily step up medium voltage to high and extra-high voltage for long-distance power transfer from a remote ac generation station to load centers hundreds of kilometers away with lower transmission losses. Transformers can also step down high voltage back to low voltage at load stations to supply the low-voltage equipment. Since the end of the war, ac power systems have been developed and expanded at a tremendous speed from the initial small isolated networks, with each supplying only lighting and motor loads with a few hundreds of customers, to its current scale of super interconnected networks each supplying billions of customers over large geographic areas in one or several countries. The voltage levels and capacities of transmission networks have increased from the first commercialized three-phase ac system with only 2.4 kV, 250 kW in the town of Redlands, California, United States, to the first commercial long-distance, ultra-high-voltage, ac transmission line in China with 1,000 kV, 2,000 MW. Transmission distance has been increased from several miles to over thousands of kilometers (miles). With such major achievements, it is little wonder that the ac power system became the top engineering achievement of the 20th century. Does this mean that dc is gone? The answer is an unambiguous no. What has happened in the past 50 years, such as applications of advanced control technologies in conventional power system loads, the power electronics based high-voltage dc (HVdc) transmission, and the additional renewable power sources in low-voltage distribution system, calls for a rethink about dc and ac in electricity supply systems.

Journal ArticleDOI
TL;DR: This paper deals with day-ahead security management with respect to a postulated set of contingencies, while taking into account uncertainties about the next day generation/load scenario, using a DC grid model and a mixed integer linear programming (MILP) solver.
Abstract: This paper deals with day-ahead security management with respect to a postulated set of contingencies, while taking into account uncertainties about the next day generation/load scenario In order to help the system operator in decision making under uncertainty, we aim at ranking these contingencies into four clusters according to the type of control actions needed to cover the worst uncertainty pattern of each contingency with respect to branch overload To this end we use a fixed point algorithm that loops over two main modules: a discrete bi-level program (BLV) that computes the worst-case scenario, and a special kind of security constrained optimal power flow (SCOPF) which computes optimal preventive/corrective actions to cover the worst-case We rely on a DC grid model, as the large number of binary variables, the large size of the problem, and the stringent computational requirements preclude the use of existing mixed integer nonlinear programming (MINLP) solvers Consequently we solve the SCOPF using a mixed integer linear programming (MILP) solver while the BLV is decomposed into a series of MILPs We provide numerical results with our approach on a very large European system model with 9241 buses and 5126 contingencies

Journal ArticleDOI
TL;DR: In this article, the CIGRE Working Group C4.605 (Modeling and aggregation of loads in flexible power networks) established a working group to identify current international industry practice on load modeling for static and dynamic power system studies.
Abstract: Power system load modeling is a mature and generally well researched area which, as many other in electrical power engineering at the present time, is going through a period of renewed interest in both industry and academia. This interest is fueled by the appearance of new non-conventional types of loads (power electronic-based, or interfaced through power electronics) and requirements to operate modern electric power systems with increased penetration of non-conventional and mostly intermittent types of generation in a safe and secure manner. As a response to this renewed interest, in February 2010 CIGRE established working group C4.605: “Modelling and aggregation of loads in flexible power networks”. One of the first tasks of the working group was to identify current international industry practice on load modeling for static and dynamic power system studies. For that purpose, a questionnaire was developed and distributed during the summer/autumn of 2010 to more than 160 utilities and system operators in over 50 countries on five continents. This paper summarizes some of the key findings from about 100 responses to the questionnaire received by September 2011 and identifies prevalent types of load models used as well as typical values of their parameters.

Journal ArticleDOI
TL;DR: Based on the decentralized sliding mode control, a load frequency controller is designed in this article for multi-area interconnected power systems with matching and unmatched uncertainties, and a proportional and integral switching surface is constructed for each area to improve system dynamic performance in reaching intervals.
Abstract: Based on the decentralized sliding mode control, a load frequency controller is designed in this paper for multi-area interconnected power systems with matching and unmatched uncertainties. The proportional and integral switching surface is constructed for each area to improve system dynamic performance in reaching intervals. The robust controller is proposed by the reaching law method to assure that frequency fluctuation converges to zero after a load and operation point variation. A three-area interconnected power system is studied to illustrate the effectiveness of the proposed decentralized sliding mode control scheme.

BookDOI
01 Jan 2013
TL;DR: In this paper, the authors discuss the impact of large-scale deployment of electric vehicles in the electric power system and the regulatory framework and business models for integrating EVs in power systems.
Abstract: State of the Art on Different Types of Electric Vehicles.- Electric Vehicle Battery Technologies.- The Impact of EV Charging on the System Demand.- Business Models and Control and Management Architectures for EV Electrical Grid Integration.- ICT Solutions to Support EV Deployment.- Advanced Models and Simulation Tools to Address Electric Vehicle Power System Integration (Steady State and Dynamic Behavior).- Impacts of Large Scale Deployment of Electric Vehicles in the Electric Power System.- Regulatory Framework and Business Models Integrating EVs in Power Systems.- Electrical Vehicles Activities Around the World.