Showing papers on "Electric power published in 2014"
TL;DR: Electrical and practical designs of the inverter, power lines, pickup, rectifier, and regulator as well as an optimized core structure design for a large air gap for electromotive force shielding for the electric vehicle are described.
Abstract: In this paper, the design and implementation of a wireless power transfer system for moving electric vehicles along with an example of an online electric vehicle system are presented. Electric vehicles are charged on roadway by wireless power transfer technology. Electrical and practical designs of the inverter, power lines, pickup, rectifier, and regulator as well as an optimized core structure design for a large air gap are described. Also, electromotive force shielding for the electric vehicle is suggested. The overall system was implemented and tested. The experimental results showed that 100-kW power with 80% power transfer efficiency under 26-cm air gap was acquired.
725 citations
TL;DR: In this article, an extensive review on various issues related to Integrated Renewable Energy System (IRES) based power generation is presented, including integration configurations, storage options, sizing methodologies and system control for energy flow management.
Abstract: Uneconomical extension of the grid has led to generation of electric power at the end user facility and has been proved to be cost effective and to an extent efficient. With augmented significance on eco-friendly technologies the use of renewable energy sources such as micro-hydro, wind, solar, biomass and biogas is being explored. This paper presents an extensive review on various issues related to Integrated Renewable Energy System (IRES) based power generation. Issues related to integration configurations, storage options, sizing methodologies and system control for energy flow management are discussed in detail. For stand-alone applications integration of renewable energy sources, performed through DC coupled, AC coupled or hybrid DC–AC coupled configurations, are studied in detail. Based on the requirement of storage duration in isolated areas, storage technology options can be selected for integrated systems. Uncertainties involved in designing an effective IRES based power generation system for isolated areas is accounted due to highly dynamic nature of availability of sources and the demand at site. Different methodologies adopted and reported in literature for sizing of the system components are presented. Distributed control, centralized and hybrid control schemes for energy flow management in IRES have also been discussed.
611 citations
TL;DR: In this paper, the pyroelectric effect and potential thermal and electric field cycles for energy harvesting are explored, as well as pyro-electric architectures and systems that can be employed to improve device performance.
Abstract: This review covers energy harvesting technologies associated with pyroelectric materials and systems. Such materials have the potential to generate electrical power from thermal fluctuations and is a less well explored form of thermal energy harvesting than thermoelectric systems. The pyroelectric effect and potential thermal and electric field cycles for energy harvesting are explored. Materials of interest are discussed and pyroelectric architectures and systems that can be employed to improve device performance, such as frequency and power level, are described. In addition to the solid materials employed, the appropriate pyroelectric harvesting circuits to condition and store the electrical power are discussed.
589 citations
TL;DR: In this article, a combined analysis was developed to investigate the performance of electricity and heat networks as an integrated whole, based on a model of electrical power flow and hydraulic and thermal circuits together with their coupling components (CHP units, heat pumps, electric boilers and circulation pumps).
576 citations
TL;DR: In this paper, a comprehensive review of energy storage technologies that are currently engaged for power applications, including pumped hydro, compressed-air, battery, flywheel, capacitor, supercapacitor, superconducting magnetic and thermal systems, is presented.
521 citations
TL;DR: A comprehensive review of existing technological solutions for wireless power transfer used in electric vehicle battery chargers is given in this article, where the concept of each solution is thoroughly reviewed and the feasibility is evaluated considering the present limitations in power electronics technology, cost and consumer acceptance.
Abstract: In this study, a comprehensive review of existing technological solutions for wireless power transfer used in electric vehicle battery chargers is given. The concept of each solution is thoroughly reviewed and the feasibility is evaluated considering the present limitations in power electronics technology, cost and consumer acceptance. In addition, the challenges and advantages of each technology are discussed. Finally, a thorough comparison is made and a proposed mixed conductive/wireless charging system solution is suggested to solve the inherent existing problems.
370 citations
TL;DR: In this paper, the authors examined and compared some machine learning regression methods to develop a predictive model, which can predict hourly full load electrical power output of a combined cycle power plant.
352 citations
TL;DR: In this paper, the authors proposed a dc-DC-DC converter to realize power quality independence from the utility mains by merging renewable energy sources (RESs) into dedicated dc distribution architectures through corresponding dc-dc converters.
Abstract: Current trends indicate that worldwide electricity distribution networks are experiencing a transformation toward direct current (dc) at both the generation and consumption level. This tendency is powered by the outburst of various electronic loads and, at the same time, the struggle to meet the lofty goals for the sharing of renewable energy sources (RESs) in satisfying total demand. RESs operate either natively at dc or have a dc link in the heart of their power electronic interface, whereas the end-point connection of electronic loads, batteries, and fuel cells is exclusively dc. Therefore, merging these devices into dedicated dc distribution architectures through corresponding dc?dc converters is an attractive option not only in terms of enhancing efficiency because of reduction of conversion steps but also for realizing power quality independence from the utility mains. These kinds of systems generally provide improved reliability in comparison to their alternating current (ac) counterparts since the number of active elements in dc?dc power electronic devices is smaller than in dc-ac converters. Control design in dc systems is also significantly simpler since there are no reactive and harmonic power flows or problems with synchronization.
294 citations
TL;DR: Reactive power support operation using offboard PEV charging stations while charging a PEV battery is investigated and a control system for the PQ command following of a bidirectional offboard charger is presented.
Abstract: The number of offboard fast charging stations is increasing as plug-in electric vehicles (PEVs) are more widespread in the world. Additional features on the operation of chargers will result in more benefits for investors, utility companies, and PEV owners. This paper investigates reactive power support operation using offboard PEV charging stations while charging a PEV battery. The topology consists of a three-phase ac-dc boost rectifier that is capable of operating in all four quadrants. The operation modes that are of interest are power-factor-corrected charging operation, and charging and capacitive/inductive reactive power operation. This paper also presents a control system for the PQ command following of a bidirectional offboard charger. The controller only receives the charging power command from a user and the reactive power command (when needed) from a utility, and it adjusts the line current and the battery charging current correspondingly. The vehicle's battery is not affected during the reactive power operation. A simulation study is developed utilizing PSIM, and the control system is experimentally tested using a 12.5-kVA charging station design.
265 citations
TL;DR: Load profiles of selected major household appliances in the U.S., including two clothes washers, two clothes dryers, two air conditioners, an electric water heater, anelectric oven, a dishwasher, and two refrigerators, are discussed.
Abstract: Electrical power consumption data and load profiles of major household appliances are crucial elements for demand response studies. This paper discusses load profiles of selected major household appliances in the U.S., including two clothes washers, two clothes dryers, two air conditioners, an electric water heater, an electric oven, a dishwasher, and two refrigerators. Their electrical power consumption data measured in one-second intervals, together with one-minute data (averaged over 60 one-second readings), are provided in an online data repository (URL: www.ari.vt.edu/research-data/). The data were gathered from two homes in Virginia and Maryland during July-October 2012. In this paper, demand response opportunities provided by these appliances are also discussed.
256 citations
Patent•
17 Mar 2014TL;DR: In this paper, a system and method to provide fast charge and discharge of electrical power without wires between two elements configured to have resonant tuned coils and circuits is presented, where the coils are energized by a power source that includes super capacitors, fast charging batteries and oscillating power management system.
Abstract: A system and method to provide fast charge and discharge of electrical power without wires between two elements configured to have resonant tuned coils and circuits. The coils are energized by a power source that includes super capacitors, fast charging batteries and oscillating power management system.
TL;DR: It is found that electric vehicles (EVs) powered by electricity from natural gas or wind, water, or solar power are best for improving air quality, whereas vehicles powered by corn ethanol and EVs powered by coal are the worst.
Abstract: Commonly considered strategies for reducing the environmental impact of light-duty transportation include using alternative fuels and improving vehicle fuel economy. We evaluate the air quality-related human health impacts of 10 such options, including the use of liquid biofuels, diesel, and compressed natural gas (CNG) in internal combustion engines; the use of electricity from a range of conventional and renewable sources to power electric vehicles (EVs); and the use of hybrid EV technology. Our approach combines spatially, temporally, and chemically detailed life cycle emission inventories; comprehensive, fine-scale state-of-the-science chemical transport modeling; and exposure, concentration–response, and economic health impact modeling for ozone (O3) and fine particulate matter (PM2.5). We find that powering vehicles with corn ethanol or with coal-based or “grid average” electricity increases monetized environmental health impacts by 80% or more relative to using conventional gasoline. Conversely, EVs powered by low-emitting electricity from natural gas, wind, water, or solar power reduce environmental health impacts by 50% or more. Consideration of potential climate change impacts alongside the human health outcomes described here further reinforces the environmental preferability of EVs powered by low-emitting electricity relative to gasoline vehicles.
TL;DR: A novel cascaded boost-buck dc-dc converter is designed to provide the optimal impedance matching in WPT system for various loads including resistive load, ultracapacitors, and batteries.
Abstract: Wireless power transfer (WPT) has attracted an ever increasing interest from both industry and academics over the past few years. Its applications vary from small power devices such as mobile phones and tablets to high power electric vehicles and from small transfer distance of centimeters to large distance of tens of centimeters. In order to achieve a high-efficiency WPT system, each circuit should function at a high efficiency along with the proper impedance matching techniques to minimize the power reflection due to the impedance mismatch. This paper proposes an analysis on the system efficiency to determine the optimal impedance requirement for coils, rectifier, and dc-dc converter. A novel cascaded boost-buck dc-dc converter is designed to provide the optimal impedance matching in WPT system for various loads including resistive load, ultracapacitors, and batteries. The proposed 13.56-MHz WPT system can achieve a total system efficiency over 70% in experiment.
TL;DR: This study proposes a DR energy management scheme for industrial facilities based on the state task network (STN) and mixed integer linear programming (MILP) and takes advantage of distributed energy resources (DERs) to implement DR.
Abstract: Demand response (DR) smart grid technology provides an opportunity for electricity consumers to actively participate in the management of power systems. Industry is one of the major consumers of electric power. In this study, we propose a DR energy management scheme for industrial facilities based on the state task network (STN) and mixed integer linear programming (MILP). The scheme divides the processing tasks in industrial facilities into nonschedulable tasks (NSTs) and schedulable tasks (STs), and takes advantage of distributed energy resources (DERs) to implement DR. Based on day-ahead hourly electricity prices, the scheme determines the scheduling of STs and DERs in order to shift the demand from peak periods (with high electricity prices) to off-peak periods (with low electricity prices), which not only improves the reliability of the electric power system, but also reduces energy costs for industrial facilities.
TL;DR: In this article, the authors examined the effect of size control policy on the energy and carbon efficiency for Chinese fossil fuel power industry and proposed two non-radial directional distance functions for energy/carbon efficiency analysis of fossil fuel electricity generation.
TL;DR: In this article, the authors developed optimal control strategies regarding various optimization goals for the management of PV batteries charge control strategies to reach the goals of both the distribution system operators and the local power producer.
TL;DR: In this paper, the authors investigate the key features of micro-grids and provide a comprehensive literature survey on the stochastic modeling and optimization tools for a microgrid, and identify future research directions.
Abstract: The future smart grid is expected to be an interconnected network of small-scale and self-contained microgrids, in addition to a large-scale electric power backbone. By utilizing microsources, such as renewable energy sources and combined heat and power plants, microgrids can supply electrical and heat loads in local areas in an economic and environment friendly way. To better adopt the intermittent and weather-dependent renewable power generation, energy storage devices, such as batteries, heat buffers and plug-in electric vehicles (PEVs) with vehicle-to-grid systems can be integrated in microgrids. However, significant technical challenges arise in the planning, operation and control of microgrids, due to the randomness in renewable power generation, the buffering effect of energy storage devices and the high mobility of PEVs. The two-way communication functionalities of the future smart grid provide an opportunity to address these challenges, by offering the communication links for microgrid status information collection. However, how to utilize stochastic modeling and optimization tools for efficient, reliable and economic planning, operation and control of microgrids remains an open issue. In this paper, we investigate the key features of microgrids and provide a comprehensive literature survey on the stochastic modeling and optimization tools for a microgrid. Future research directions are also identified.
Book•
06 Jan 2014
TL;DR: In this paper, the authors present an overview of the main components used in distribution system design, including lines, Transformers, and Underground Cables, as well as the per-unit system.
Abstract: Preface Acknowledgments Author Distribution System Planning and Automation Load Characteristics Application of Distribution Transformers Design of Subtransmission Lines and Distribution Substations Design Considerations of Primary Systems Design Considerations of Secondary Systems Voltage-Drop and Power-Loss Calculations Application of Capacitors to Distribution Systems Distribution System Voltage Regulation Distribution System Protection Distribution System Reliability Electric Power Quality Distributed Generation and Renewable Energy Energy Storage Systems for Electric Power Utility Systems Concept of Smart Grid and Its Applications Appendix A: Impedance Tables for Lines, Transformers, and Underground Cables Appendix B: Graphic Symbols Used in Distribution System Design Appendix C: Standard Device Numbers Used in Protection Systems Appendix D: The Per-Unit System Appendix E: Glossary for Distribution System Terminology Notation Answers to Selected Problems Index
TL;DR: In this paper, the reliability aspects of power electronic techniques are discussed in the context of high-efficiency power conversion for adjustable-speed drives, power quality correction, renewable energy systems, energy storage systems, and electric vehicles.
Abstract: Power electronic systems play an increasingly important role in providing high-efficiency power conversion for adjustable-speed drives, power-quality correction, renewable-energy systems, energy-storage systems, and electric vehicles. However, they are often presented with demanding operating environments that challenge the reliability aspects of power electronic techniques. For example, increasingly thermally stressful environments are seen in applications such as electric vehicles, where ambient temperatures under the hood exceed 150 °C, while some wind turbine applications can place large temperature cycling conditions on the system. On the other hand, safety requirements in the aerospace and automotive industries place rigorous demands on reliability.
TL;DR: An integrated control scheme for vehicle-to-grid (V2G) operation in the distribution grid with renewable energy sources and an experimental platform is incorporated into the proposed integrated energy management to demonstrate the instantaneous response of EV battery storage.
Abstract: This paper presents an integrated control scheme for vehicle-to-grid (V2G) operation in the distribution grid with renewable energy sources. A hierarchical framework is proposed for V2G applications, and the mathematical models are built for both smart charging and V2G operation with distribution grid constraints. V2G power is regulated to minimize the total operating cost (TOC) while providing frequency regulation. The simulation results verify the control algorithm in coordinating distributed electric vehicle (EV) aggregations with the varying wind power and daily load. For V2G dynamic regulation, EVs connected in close proximity to wind power generators can locally compensate for the wind fluctuation with fast response and, hence, smooth out the power fluctuation at the bus having wind power generators and EVs. Each individual EV is strategically assigned to implement the simulated control algorithm through a bidirectional converter. An experimental platform is incorporated into the proposed integrated energy management to demonstrate the instantaneous response of EV battery storage.
TL;DR: In this article, the authors reviewed primary issues regarding the drivers and specific benefits of hybrid renewable energy systems (HRES) and discussed the various renewable energy sources which can be explored for HRES implementation.
Abstract: A hybrid power system is an emerging power generation technique which involves a combination of different energy systems, mostly renewables for optimal output configuration. In modern pursuit for renewable energy (RE) development, optimum conditions for the production and utilization of energy system are considered to be an indispensable feature for economic load dispatch. This is a rationalizing fact taking into consideration the rising price of energy for socio-economic development. Therefore, this paper reviews primary issues regarding the drivers and specific benefits of hybrid renewable energy systems (HRES). Moreover, this paper presents discussions on the various renewable energy sources which can be explored for HRES implementation. Finally, the framework unfolds a vivid review on factors to be considered for designing and implementation of HRES in general including simulation and optimization software packages for making such analyses.
TL;DR: In this paper, some features of the smart grid have been discussed such as communications, demand response, and security, and microgrids and issues with integration of distributed energy sources are also considered.
Abstract: The smart grid is expected to revolutionize existing electrical grid by allowing two-way communications to improve efficiency, reliability, economics, and sustainability of the generation, transmission, and distribution of electrical power. However, issues associated with communication and management must be addressed before full benefits of the smart grid can be achieved. Furthermore, how to maximize the use of network resources and available power, how to ensure reliability and security, and how to provide self-healing capability need to be considered in the design of smart grids. In this paper, some features of the smart grid have been discussed such as communications, demand response, and security. Microgrids and issues with integration of distributed energy sources are also considered.
TL;DR: In this article, the authors proposed an intelligent workplace parking garage for plug-in hybrid electric vehicles (PHEVs) with a developed smart power charging controller, a 75kW photovoltaic (PV) panel, a dc distribution bus, and an ac utility grid.
Abstract: This paper proposes an intelligent workplace parking garage for plug-in hybrid electric vehicles (PHEVs). The system involves a developed smart power charging controller, a 75-kW photovoltaic (PV) panel, a dc distribution bus, and an ac utility grid. Stochastic models of the power that is demanded by PHEVs in the parking garage and the output power of the PV panel are presented. In order to limit the impact of the PHEVs' charging on the utility ac grid, a fuzzy logic power-flow controller was designed. Based on their power requirements, the PHEVs were classified into five charging priorities with different rates according to the developed controller. The charging rates depend on the predicted PV output power, the power demand by the PHEVs, and the price of the energy from the utility grid. The developed system can dramatically limit the impact of PHEVs on the utility grid and reduce the charging cost. The system structure and the developed PHEV smart charging algorithm are described. Moreover, a comparison between the impact of the charging process of the PHEVs on the grid with and without the developed smart charging technique is presented and analyzed.
Book•
17 Jan 2014
TL;DR: Wireless Power Transfer: A New Paradigm for Green CommunicationsWireless Information and Power Transfer for Electric Vehicles and Mobile DevicesWireless power transfer algorithms, technologies and applications in Ad Hoc Communication NetworksWireless-Powered Communication NetworksSmart Adaptive Systems on SiliconOpportunities for High-Power, High-Frequency Transmitters to Advance Ionospheric/Thermospheric Research as discussed by the authors.
Abstract: Wireless Power TransferExperiments with Alternate Currents of High Potential and High FrequencyWireless Power TransferCurrent Understanding of ApoptosisInductive PoweringWireless Information and Power TransferResonant Power ConvertersAssessment of the Possible Health Effects of Ground Wave Emergency NetworkWireless Power TransferRecent Wireless Power Transfer Technologies via Radio WavesImplantable BioelectronicsTechnological Innovation for Cyber-Physical SystemsHistory of WirelessRenewable EnergyNext-Generation NetworksElectromagnetic Fields and WavesWireless Power Transmission for Sustainable ElectronicsTour of the Electromagnetic SpectrumICT Energy Concepts for Energy Efficiency and SustainabilityOptical Communication TechnologyWireless Power TransferEnergy HarvestingApplications of Electromagnetic Waves2021 IEEE 18th Annual Consumer Communications and Networking Conference (CCNC)Wireless Power Transfer via RadiowavesHybrid Electric VehiclesWireless Infrared CommunicationsDigital Radio System DesignExperimental RoboticsSurface WavesPlug In Electric Vehicles in Smart GridsShort-range Wireless CommunicationWireless Information and Power Transfer: A New Paradigm for Green CommunicationsWireless Power Transfer for Electric Vehicles and Mobile DevicesWireless Power Transfer Algorithms, Technologies and Applications in Ad Hoc Communication NetworksWireless-Powered Communication NetworksSmart Adaptive Systems on SiliconOpportunities for High-Power, High-Frequency Transmitters to Advance Ionospheric/Thermospheric ResearchRecent Wireless Power Transfer TechnologiesWireless Power Transfer
01 Jan 2014
TL;DR: In this paper, the contribution of wind power providing active power control (APC) can benefit the total power system economics, increase revenue streams, improve the reliability and security of the power system, and provide superior and efficient response while reducing any structural and loading impacts that may reduce the life of the wind turbine or its components.
Abstract: This paper details a comprehensive study undertaken by the National Renewable Energy Laboratory, Electric Power Research Institute, and the University of Colorado to understand how the contribution of wind power providing active power control (APC) can benefit the total power system economics, increase revenue streams, improve the reliability and security of the power system, and provide superior and efficient response while reducing any structural and loading impacts that may reduce the life of the wind turbine or its components. The study includes power system simulations, control simulations, and actual field tests using turbines at NREL's National Wind Technology Center (NWTC). The study focuses on synthetic inertial control, primary frequency control, and automatic generation control, and analyzes timeframes ranging from milliseconds to minutes to the lifetime of wind turbines, locational scope ranging from components of turbines to large wind plants to entire synchronous interconnections, and additional topics ranging from economics to power system engineering to control design.
TL;DR: In this article, the electric vehicle demand/supply model was formulated as a queuing theory problem, exhibiting stochastic characteristics, to address the impacts of battery charger efficiency on the amount of power demand during battery charging and also how the latter is effected by inverter efficiency during discharging.
Abstract: Vehicle-to-grid (V2G) units are gaining prominence and may dominate the auto-market in the near future. The V2G batteries require corporate parking lots for charging and discharging operations. The electric power capacity of an existing parking lot can be increased by the installation of photovoltaic (PV) rooftops. This paper describes mathematical models for estimating the electric power capacity of a V2G parking lot (VPL) system with PV canopy. The electric vehicle (EV) demand/supply model was formulated as a queuing theory problem, exhibiting stochastic characteristics. New formulae were developed to address the impacts of battery charger efficiency on the amount of power demand during battery charging, and also how the latter is effected by inverter efficiency during discharging. Mathematical models for grid gain factor were developed. The proposed models were tested using Tesla Roadster EV and Nissan leaf EV. Promising simulation results are gained leading to a conclusion that vehicle parking lots with PV facilities can potentially relieve and enhance the grid capacity. Results show that 60% gain factor is possible. The effect of weather uncertainties and energy market price were studied. The study could be useful in battery-charger control studies.
TL;DR: Simulation results carried out on MATLAB show that the magnitude/variation of battery power and power loss can be concurrently reduced in real time by the proposed framework.
Abstract: Batteries mounted on electric vehicles (EVs) are often damaged by high peak power and rapid charging/discharging cycles, which are originated from repetitive acceleration/deceleration of vehicles particularly in urban situations. To reduce battery damage, the battery/supercapacitor (SC) hybrid energy storage system (HESS) has been considered as a solution because the SC can act as a buffer against large magnitudes and rapid fluctuations in power. While the traditional purpose of employing the HESS in EVs is to minimize the magnitude/variation of battery power or power loss, the previous approaches proposed for controlling the HESS have some drawbacks; they neither consider these objectives simultaneously nor reflect real-time load dynamics for computing the SC reference voltage. In this paper, we present a power control framework consisting of two stages: one for computing the SC reference voltage and another for optimizing the power flowing through the HESS. In the presented framework, we propose a methodology for calculating the SC reference voltage considering the real-time load dynamics without given future operation profiles. In addition, we formulate the HESS power control problem as a convex optimization problem that minimizes the magnitude/fluctuation of battery power and power loss at the same time. The optimization problem is formulated so that it can be repeatedly solved by general solvers in polynomial time. Simulation results carried out on MATLAB show that the magnitude/variation of battery power and power loss can be concurrently reduced in real time by the proposed framework.
TL;DR: In this article, the authors describe the capabilities of the PROCESS this article code, which is used to assess the engineering and economic viability of a hypothetical fusion power station using simple models of all parts of a reactor system, from the basic plasma physics to the generator.
TL;DR: The development of a hurricane power outage prediction model applicable along the full U.S. coastline is described, the use of the model is demonstrated for Hurricane Sandy, and what the impacts of a number of historic storms, including Typhoon Haiyan, would be on current U.s. energy infrastructure are estimated.
Abstract: Hurricanes regularly cause widespread and prolonged power outages along the U.S. coastline. These power outages have significant impacts on other infrastructure dependent on electric power and on the population living in the impacted area. Efficient and effective emergency response planning within power utilities, other utilities dependent on electric power, private companies, and local, state, and federal government agencies benefit from accurate estimates of the extent and spatial distribution of power outages in advance of an approaching hurricane. A number of models have been developed for predicting power outages in advance of a hurricane, but these have been specific to a given utility service area, limiting their use to support wider emergency response planning. In this paper, we describe the development of a hurricane power outage prediction model applicable along the full U.S. coastline using only publicly available data, we demonstrate the use of the model for Hurricane Sandy, and we use the model to estimate what the impacts of a number of historic storms, including Typhoon Haiyan, would be on current U.S. energy infrastructure.
09 Jun 2014
TL;DR: In this article, the main factors and modeling methods of EV charging load are analyzed; the literature reviews are carried out on EV integration and impacts on power grids, including grid access capability, power quality, power economy and environment.
Abstract: Electric vehicle (EV) industry gets into fast growth period in China, so that charging of large scale of EV will pose inevitable impacts on power grid in the future. In this article, the main factors and modeling methods of EV charging load are analyzed; The literature reviews are carried out on EV integration and impacts on power grids, including grid access capability, power quality, power economy and environment; Additionally, the benefits and realization methods of smart charging strategy are discussed. The current research on V2G (vehicle to grid) operation are summarized as well. Finally, the unresolved problems and possible future research areas are presented.