A review on the economic dispatch and risk management of the large-scale plug-in electric vehicles (PHEVs)-penetrated power systems

Nowadays, the deterioration of ecological environment and the ever rising gas price make green transportation our relentless pursuit. Energy-saving, low-emission even zero-emission electric vehicles (EVs) have been considered as one solution to the problem. With the rapid development of plug-in electric vehicle (PHEV) and forceful support and incentives from the government, PHEV and its supporting facilities are being gradually popularized. When randomly being connected to the power grid in large scale, PHEVs will bring new challenges to power grid in operation and management. This paper presents an overall review on historical research on power system integrated with electric vehicles and especially focuses on economic dispatch of PHEV in the electricity market. The paper also discusses the joint scheduling problem considering other renewable energy resources and risk management of PHEV-penetrated power systems.     

A review on the features and technologies for energy efficiency of smart grid

In today's world striving for efficiency in every sector, especially power generation and distribution, smart grids emerge as the solution for efficiently meeting the increasing demand. They adjust themselves to optimally deliver energy at the lowest cost and highest quality possible. The grid successfully makes use of renewable energy resources, electric vehicles, and smart pricing techniques in its attempt to achieve energy efficiency. It also promotes a greener environment by striving to reduce greenhouse gas emissions. Information communication technology (ICT) helps the grid in collecting consumption data from the consumers and in sharing tariff information. ICT also helps to gather information about the status of the grid with regard to aspects like power quality, faults etc. The purpose of this paper is to review recent literature with a view to comprehensively present the technologies employed in the smart grid for achieving energy efficiency and the challenges involved therein.     

Risk-based optimal operation of power,heat and hydrogen-based microgrid considering a plug-in electric vehicle

The growing interest in integrating variable renewable energy resources (RES), besides global concerns about greenhouse pollution, brings multiple challenges for eco and environmentally-friendly operation of systems. Meanwhile, the simultaneous energy supply can improve energy efficiency and mitigate the fluctuation of RES compared with a single-energy system. Therefore, this paper seeks to investigate the optimal scheduling of heating, power, and hydrogen-based microgrid incorporated with RES and plug-in electric vehicles (PEV). The fuel-cell-based hydrogen and electrolyzer facilities are integrated into the multi-energy system to investigate the power-to-hydrogen and hydrogen-to-power technologies in the model. Besides typical electric and thermal loads, the proposed system can directly sell hydrogen to hydrogen-based industrial applications. The PEV as a flexible resource is employed to facilitate the integration of solar energy. Due to the substantial uncertainty from solar energy, price, load, and EVs' arriving and departing times, the risk management of the model based on the conditional value-at-risk is developed to show the operator's behavior against the random inputs and their risk. Results show that integrating the hydrogen storage and plug-in electric vehicle in the model results in a daily cost reduction of up to 9.28%.     

Impact evaluation of large scale integration of electric vehicles on power grid

As the world witnesses a continual increase in the global energy demand, the task of meeting this demand is becoming more difficult due to the limitation in fuel resources as well as the greenhouse gases emitted which accelerate the climate change. As a result, introducing a policy that promotes renewable energy (RE) generation and integration is inevitable for sustainable development. In this endeavor, electrification of the transport sector rises as key point in reducing the accelerating environment degradation, by the deployment of new type of vehicles referred to as PHEV (plug-in hybrid electric vehicle). Besides being able to use two kinds of drives (the conventional internal combustion engine and the electric one) to increase the total efficiency, they come with a grid connection and interaction capability known as the vehicle-to-grid (V2G) that can play a supporting role for the whole power system by providing many ancillary services such as energy storage mean and power quality enhancer. Unfortunately, all these advantages do not come alone. The uncontrolled large scale EV integration may present a real challenge and source of possible failure and instability for the grid. In this work the large scale integration impact of EVs will be investigated in details. The results of power flow analysis and the dynamic response of the grid parameters variation are presented, taking the IEEE 14 bus system as a test grid system.     

An updated review of energy storage systems: Classification and applications in distributed generation power systems incorporating renewable energy resources

The demand of electric energy is increasing globally, and the fact remains that the major share of this energy is still being produced from the traditional generation technologies. However, the recent trends, for obvious reasons of environmental concerns, are indicating a paradigm shift towards distributed generation (DG) incorporating renewable energy resources (RERs). But there are associated challenges with high penetration of RERs as these resources are unpredictable and stochastic in nature, and as a result, it becomes difficult to provide immediate response to demand variations. This is where energy storage systems (ESSs) come to the rescue, and they not only can compensate the stochastic nature and sudden deficiencies of RERs but can also enhance the grid stability, reliability, and efficiency by providing services in power quality, bridging power, and energy management. This paper provides an extensive review of different ESSs, which have been in use and also the ones that are currently in developing stage, describing their working principles and giving a comparative analysis of important features and technical as well as economic characteristics. The wide range of storage technologies, with each ESS being different in terms of the scale of power, response time, energy/power density, discharge duration, and cost coupled with the complex characteristics matrices, makes it difficult to select a particular ESS for a specific application. The comparative analysis presented in this paper helps in this regard and provides a clear picture of the suitability of ESSs for different power system applications, categorized appropriately. The paper also brings out the associated challenges and suggests the future research directions.     

Review of design considerations and technological challenges for successful development and deployment of plug-in hybrid electric vehicles

Automobile drivetrain hybridization is considered as an important step in reducing greenhouse gases and related automotive emissions. However, current hybrid electric vehicles are a temporary solution on the way to zero emission road vehicles. Recently there has been a lot of interest in the concept of plug-in hybrid electric vehicles, which have great potential to attain higher fuel economy and efficiency, with a longer range in pure electric propulsion mode. PHEVs represent the next generation of hybrid vehicles that bridges the gap between present hybrid electric vehicles and battery operated electric vehicles. In this paper a brief review of design considerations and selection of major components for plug-in hybrid electric vehicles is provided. This paper also focuses on the technological challenges ahead of plug-in hybrid electric vehicles in relation to its major components, which are reviewed in detail. The importance of economics and government support for the successful deployment of this plug-in hybrid technology in the near future to achieve national energy security is also discussed in the paper.     

Optimal redundant placement of PMUs in Indian power grid — northern,eastern and north-eastern regions

Effective utilization of renewable energy sources and efficient management of electric energy are essential for any developing countries like India. This can be envisioned through the implementation of concepts of smart grid (SG). One of the key requisites for SG implementation is that the grid should be completely observable. Renovation of conventional Indian power grid to a SG necessitates incorporation of the phasor measurement units (PMUs) in the present power grid measurement and monitoring system. Since the cost of PMU is high and any bus containing a PMU makes the neighboring connected buses observable, optimal placement of PMUs is very important for complete observability of the grid. This paper proposes optimal redundant geographical locations in the northern, eastern and north-eastern regions of Indian power grid for PMU placement. The PMUs installed in these geographical locations will make the grid completely observable and maintain the observability under the conditions of failure of some PMUs or branch outages. Integer linear programming has been used for finding the optimal PMU locations. The results proposed in this paper can be a stepping stone for revamping the Indian power grid to a SG ensuring complete observability during different contingency conditions.     

Changing the electricity game

The U.S. power system will face many challenges in the next several decades. The arrival of plug-in hybrid vehicles, exponential growth in customer-controlled generation, growth of nondispatchable and intermittent renewable sources of energy, increasing demand for higher service reliability and power quality, microgrids---these are just some of the challenges that our system faces now and will continue to confront into the future. While the nature of these challenges is somewhat known, the extent of their impact is not fully understood. American Electric Power (AEP) views distributed energy storage as a key piece of its future grid. By strategically locating and controlling distributed energy storage systems (DESSs) on a large scale, AEP can potentially reduce adverse impacts on the grid by creating a controllable buffer between utility and nonutility-controlled assets (Figure 1).     

Managing peak loads in energy grids: Comparative economic analysis

One of the key issues in modern energy technology is managing the imbalance between the generated power and the load, particularly during times of peak demand. The increasing use of renewable energy sources makes this problem even more acute. Various existing technologies, including stationary battery energy storage systems (BESS), can be employed to provide additional power during peak demand times. In the future, integration of on-board batteries of the growing fleet of electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV) into the grid can provide power during peak demand hours (vehicle-to-grid, or V2G technology).This work provides cost estimates of managing peak energy demands using traditional technologies, such as maneuverable power plants, conventional hydroelectric, pumped storage plants and peaker generators, as well as BESS and V2G technologies. The derived estimates provide both per kWh and kW year of energy supplied to the grid. The analysis demonstrates that the use of battery storage is economically justified for short peak demand periods of <1 h. For longer durations, the most suitable technology remains the use of maneuverable steam gas power plants, gas turbine,reciprocating gas engine peaker generators, conventional hydroelectric, pumped storage plants.     

An optimization scheduling method of electric vehicle virtual energy storage to track planned output based on multiobjective optimization

Electric vehicle virtual energy storage technology can effectively improve the utilization of renewable energy. Aiming at the impact of the uncertainty of electric vehicle on the power grid, an optimized dispatching method of hybrid energy storage systems based on multiobjective optimization in the scenario of tracking plan output is proposed in this paper. The predicted value of the photovoltaic power obtained by the particle swarm optimization (PSO)-back propagation (BP) neural network is used to formulate the planned output of photovoltaic power generation, and the principle component analysis algorithm is used to extract the main features affecting photovoltaic power generation to further improve the prediction accuracy of photovoltaic output power. From the perspective of the service life of electric vehicles, a two-stage optimal control method of hybrid energy storage systems based on the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) is used to achieve energy distributions between electric vehicles and supercapacitors. Fully consider the benefits of electric vehicle users and the capacity of tracking plans, a multiobjective optimization model of hybrid energy storage systems to track planned output is established, and the nondominated sorted genetic algorithm-III is adopted to solve the model. The validity of the model is verified by a simulation test of actual operating data of a business park in China. The simulation results show that after the optimized control, the average absolute error of the deviation power reduces from 1.092 to 0.0528 MW, power fluctuating times of electric vehicles decreases from 151 to 80, and the daily income benefit increases from $404.468 to $483.116 in the cloudy day. The method proposed in this paper can effectively improve the controllability of renewable energy, and provide a theoretical basis for the application of electric vehicle virtual energy storage technology.     

Is the concept of ‘grid parity’ defined appropriately to evaluate the cost-competitiveness of renewable energy technologies?

The concept of ‘grid parity’ has emerged as a key indicator of the competitiveness of renewable electricity generation technologies. In this study, we firstly summarize the definition of the current levelized cost of electricity (LCOE) based methodology for the concept and address its limitation in not taking into account the systematic changes in an electric power system. Secondly, we introduce a bottom-up energy system model based methodology to overcome the limitation. Lastly, we apply the methodology to a case study, the grid parity analysis of solar photovoltaic and onshore wind technologies in the Korean electric power system, to highlight the differences between the results obtained using both methodologies. The results of the study show three implications. First, even if the LCOE of onshore wind is already lower than that of natural gas technologies and the average price of grid electricity, the LCOE is required to be much lower to achieve cost-competitiveness in the electric power system. Second, different technologies might be required to have different LCOE levels to be cost-competitive in the same power system. Third, a policy or plan for the deployment of renewable energy technologies must be harmonized with other policies and plans within the same system.     

A hybrid optimization technique for proficient energy management in smart grid environment

Electrical energy is one of the key components for the development and sustainability of any nation. India is a developing country and blessed with a huge amount of renewable energy resources still there are various remote areas where the grid supply is rarely available. As electrical energy is the basic requirement, therefore it must be taken up on priority to exploit the available renewable energy resources integrated with storage devices like fuel cells and batteries for power generation and help the planners in providing the energy-efficient and alternative solution. This solution will not only meet electricity demand but also helps reduce greenhouse gas emissions as a result the efficient, sustainable and eco-friendly solution can be achieved which would contribute a lot to the smart grid environment. In this paper, a modified grey wolf optimizer approach is utilized to develop a hybrid microgrid based on available renewable energy resources considering modern power grid interactions. The proposed approach would be able to provide a robust and efficient microgrid that utilizes solar photovoltaic technology and wind energy conversion system. This approach integrates renewable resources with the meta-heuristic optimization algorithm for optimal dispatch of energy in grid-connected hybrid microgrid system. The proposed approach is mainly aimed to provide the optimal sizing of renewable energy-based microgrids based on the load profile according to time of use. To validate the proposed approach, a comparative study is also conducted through a case study and shows a significant savings of 30.88% and 49.99% of the rolling cost in comparison with fuzzy logic and mixed integer linear programming-based energy management system respectively.     

A review of fault ride through of PV and wind renewable energies in grid codes

This paper presents a comprehensive review of fault ride through (FRT) in the grid code of 38 selected countries with an emphasis on renewable energy (REN) sources–related rules. Grid codes are the rules legislated usually by the transmission system operators (TSOs) to determine the grid integration requirements of electrical power generators. Each country establishes its grid code for satisfying the minimum required technical criteria and revises it frequently to cope with new modifications of the utility. Growing the penetration of REN sources have influenced many operational aspects of the power system such as protection, power quality, reliability, and stability. Thereupon, regulations must ensure the power system's secure and controllable operation of REN sources. FRT is one of the main parts of the grid code, and its characteristics affect the performance and rating of power system apparatus. FRT defines the performance of electric power generators during and in postfault conditions. FRT of solar photovoltaic (PV) and wind turbines (WTs) as the main REN sources of energy has great importance in the grid codes. In this paper, a comparison of FRTs in the grid code of 38 countries, including low‐voltage ride through (LVRT), zero‐voltage ride through (ZVRT), and high‐voltage ride through (HVRT) are provided and surveyed.     

Application and development trends of energy storage technology in the field of traffic

纵观当前全球电力系统发展规划,智能电网,可再生能源和分布式发电,微电网以及电动汽车都列入了各国电力系统发展的重点方向,而储能技术正是实现上述领域发展必不可少的技术支撑.目前,储能技术较高的成本阻碍了其在电力系统中的应用.若将电动汽车动力电池作为电力系统的储能元件,便可使其作为传统交通工具的同时,充当电力系统的一种潜在的备用电源.通过电动汽车V2G模式和动力电池的梯次使用,将帮助电网调峰调频,促进电动汽车动力电池的产业化和多种应用,降低电动汽车的生产和使用成本,最终实现交通能源消费的电力化.本文在对电动汽车储能相关技术,基础设施建设及与之匹配的商业模式进行梳理和分析的基础上,展望电动汽车储能的发展潜力并提出相应的政策建议.     

Review on health-conscious energy management strategies for fuel cell hybrid electric vehicles: Degradation models and strategies

Considering the overwhelming pressure on worldwide demand of fossil fuels and the climate change caused by air pollution, hybrid electric vehicles have seen a promising future thanks to the development of renewable energy sources. Among various kinds of energy sources that have been used in hybrid electric vehicles, lithium-ion battery and proton exchange membrane (PEM) fuel cell exist to be the most favorable ones owing to their high energy density and power density. However, the degradation issues of the energy sources tend to be neglected when designing the energy management strategies for the hybrid electric vehicles. Concerning existing literature, degradation modelling methods of lithium-ion batteries and PEM fuel cells are reviewed and the possibility of integrating them into health-conscious energy management is discussed. Besides, a variety of energy management strategies that have taken the influence of degradations into consideration are reviewed and classified. The contribution of this paper is to investigate the possibility of developing a health-conscious energy management strategy based on accurate estimation of degradation to improve the durability of the system.     

Impact of electric vehicles on a future renewable energy‐based power system in Europe with a focus on Germany

Electric mobility is expected to play a key role in the decarbonisation of the energy system. Continued development of battery electric vehicles is fundamental to achieving major reductions in the consumption of fossil fuels and of CO₂ emissions in the transport sector. Hydrogen can become an important complementary synthetic fuel providing electric vehicles with longer ranges. However, the environmental benefit of electric vehicles is significant only if their additional electricity consumption is covered by power production from renewable energy sources. Analysing the implications of different scenarios of electric vehicles and renewable power generation considering their spatial and temporal characteristics, we investigate possible effects of electric mobility on the future power system in Germany and Europe. The time horizon of the scenario study is 2050. The approach is based on power system modelling that includes interchange of electricity between European regions, which allows assessing long‐term structural effects in energy systems with over 80% of renewable power generation. The study exhibits strong potential of controlled charging and flexible hydrogen production infrastructure to avoid peak demand increases and to reduce the curtailment of renewable power resulting in reduced system operation, generation, and network expansion costs. A charging strategy that is optimised from a systems perspective avoids in our scenarios 3.5 to 4.5 GW of the residual peak load in Germany and leads to efficiency gains of 10% of the electricity demand of plug‐in electric vehicles compared with uncontrolled loading.     

Feasibility of renewable energy storage using hydrogen in remote communities in Bhutan

This paper considers the technical and economic feasibility of using renewable energy with hydrogen as the energy storage medium for two remote communities in Bhutan, selected to illustrate two common scenarios presenting different challenges. The Royal Government of Bhutan has published plans to provide electricity to all households in the next 20 years, but the practical problems of extending the grid over long distances and mountainous terrain will make that target difficult and expensive to achieve. Consequently, the possibility of using natural energy and diversified generation is attractive. This paper examines the use of hydro power in one community and photovoltaics with wind power in another. Hydrogen is the proposed energy storage medium in both cases. Analysis suggests that it is technically possible to use renewable energy and hydrogen for diversified power supplies and that where, as here, the costs of grid extension are high, it may also be financially viable. Thus we argue that there is a good case for establishing a test and demonstration system near the capital Thimphu for further investigation prior to use in remote locations.     

Performance analysis of hybrid power configurations: Impact on primary energy intensity,carbon dioxide emissions,and life cycle costs

Utilization of Natural gas and Hydrogen to support current and future building energy needs to offset the total electric demand while improving the grid resiliency and energy efficiency was investigated. Demand side energy management will play an important role in efficiently managing the available energy resources. Performance assessment of different power generation and energy management configurations is presented in this paper. Development of solutions in addressing grid resiliency by providing the ability to design suitable configurations for meeting individual building energy needs is discussed. Primary movers (PM) such as internal combustion engines (ICE) and fuel cells (FC) along with small scale auxiliary renewable energy source such as photovoltaics (PV) were considered. Key attributes of total carbon foot-print, life cycle costs including capital and operational expenditure, electric grid offset or peak shaving capability, thermal energy availability and its further potential to offset total electric demand, and primary energy intensity are analyzed and discussed in detail.     

The effects of vehicle‐to‐grid systems on wind power integration

Renewable energy portfolio standards have created a large increase in the amount of renewable electricity production, and one technology that has benefited greatly from these standards is wind power. The uncertainty inherent in wind electricity production dictates that additional amounts of conventional generation resources be kept in reserve, should wind electricity output suddenly dip. The introduction of plug‐in hybrid electric vehicles into the transportation fleet presents an possible solution to this problem through the concept of vehicle‐to‐grid power. The ability of vehicle‐to‐grid power systems to help solve the variability and uncertainty issuess in systems with large amounts of wind power capacity is examined through a multiparadigm simulation model. The problem is examined from the perspectives of three different stakeholders: policy makers, the electricity system operator and plug‐in hybrid electric vehicle owners. Additionally, a preliminary economic analysis of the technology is performed, and a comparison made with generation technologies that perform similar functions. Copyright © 2011 John Wiley & Sons, Ltd.     

Regulatory framework and business models for charging plug-in electric vehicles: Infrastructure,agents, and commercial relationships

Electric vehicles (EVs) present efficiency and environmental advantages over conventional transportation. It is expected that in the next decade this technology will progressively penetrate the market. The integration of plug-in electric vehicles in electric power systems poses new challenges in terms of regulation and business models. This paper proposes a conceptual regulatory framework for charging EVs. Two new electricity market agents, the EV charging manager and the EV aggregator, in charge of developing charging infrastructure and providing charging services are introduced. According to that, several charging modes such as EV home charging, public charging on streets, and dedicated charging stations are formulated. Involved market agents and their commercial relationships are analysed in detail. The paper elaborates the opportunities to formulate more sophisticated business models for vehicle-to-grid applications under which the storage capability of EV batteries is used for providing peak power or frequency regulation to support the power system operation. Finally penetration phase dependent policy and regulatory recommendations are given concerning time-of-use pricing, smart meter deployment, stable and simple regulation for reselling energy on private property, roll-out of public charging infrastructure as well as reviewing of grid codes and operational system procedures for interactions between network operators and vehicle aggregators.