V2G Service Research Articles

Optimal Frequency Regulation V2G Control with DOD of EV Battery

As the proportion of electric vehicles increases, interest in Vehicle to Grid (V2G) service is increasing. Many studies are underway to use V2G for peak shaving and frequency regulation in power system. However, V2G can shorten battery cycle life for electric vehicle (EV) which is the most variable part in EV. Hence battery cycle life should be considered in V2G service. As well as the number of discharges, depth of discharge (DOD) also highly affects battery cycle life. High depth of discharge reduces the cycle life of the EV battery exponentially. However, conventional droop control, which has been used for frequency regulation, controls the active power linearly without regard to the DOD. This paper proposes an optimal frequency regulation V2G control which considers the DOD of EV. Proposed method uniformly distributes the discharge for V2G. Therefore battery cycle life is preserved and inconvenience of EV owner from discharge is reduced. The case study result demonstrates the advantages of the proposed method over the conventional droop method. Battery cycle life of entire EV is preserved and energy consumption under V2G is uniformly distributed.

Synergistic optimization scheduling of a wind–thermal power system considering V2G technology based on probability model

Large‐scale grid‐connected electric vehicles (EVs) and wind power generation have brought new challenges to economical optimal scheduling of power system because of their uncertainties. It is essential to establish accurate scheduling models and arrive at the economical optimal scheduling strategy. This paper develops a probability model of wind power output, which adopts the normal distribution to depict the randomness of wind speed, considering turbulence. The probability model of vehicle‐to‐grid (V2G) is also established, and the corresponding probability distribution is used to describe the initial charge/discharge time, daily mileage, and charge state of the EV. A collaborative scheduling model is built for the grid and consumers, taking account of the fuel cost of thermal power unit, the uncertainty cost of wind power output, and the cost of V2G service. The scheduling model is solved by an improved particle swarm optimization algorithm, which applies the inertia weight obeying the standard normal distribution and the nonlinear anticosine learning factors to avoid premature convergence and the loss of population space diversity. Finally, the validity and practicability of the proposed method are verified by the simulation of a ten‐machine power system integrated with wind power and EVs. Simulation results show that V2G can optimize the output of thermal power units and eliminate the surplus output of wind power. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Distributed control for large-scale plug-in electric vehicle charging with a consensus algorithm

As the development of plug-in-electric vehicles (PEVs) accelerates, the effective integration of large-scale PEVs with power grid becomes an urgent problem for utilities and PEV users. Mainly considering grid side preference, this paper proposes a distributed control method with a consensus algorithm to deal with large-scale PEV charging coordination. The objectives of the proposed coordination strategy are: minimizing the charging power loss and maximizing the available PEV power for vehicle-to-grid (V2G) services. The incremental cost functions are formulated for these objectives. The graph theory is applied to specify the communication network for PEVs. An interaction rule, the consensus algorithm is applied to realize the local information updating and external information exchanging among neighboring PEVs. A variable-size stochastic matrix is defined to specify the communication topology among PEVs, as well as guarantee the convergence of the consensus targets. The simulation results show that, with limited communication, the large-scale PEV charging/discharging can be efficiently coordinated to reduce total charging power loss or provide V2G service with maximum available PEV power. Meanwhile the PEV charging requirements specified by drivers can be satisfied. In addition, the convergence of the proposed distributed consensus algorithm can always be guaranteed upon random PEV departures.

Vehicle-to-grid service development logic and management formulation

Vehicle-to-grid (V2G) is regarded as the effective way to reconcile contradictions between an electric power system and electric vehicles (EVs). A lot of research has been carried out to affect this, often based on different technical and trading model assumptions. The value of the research is dependent on how reasonable the assumptions it makes are. This paper presents a framework for analyzing V2G service development from a coevolutionary perspective in which the interactive relation between the diffusion of EVs and the upgrade of the distribution grid system is considered. A V2G service development logic and its management formulation are put forward. First, the motivations and contradictions of developing V2G services are analyzed. Then a development phase division of the V2G services is proposed in view of the coevolution relation between the grid upgrade and the development of the EV. Next, taking into account the characteristics of each phase, the physical trade structures and corresponding management hierarchies, management relations as well as management measures, are proposed. This paper provides a new perspective of V2G service development, answers the core question on how to make the V2G vision come true in synergy with the development of EVs, and gives some advice on future V2G management paradigms.

Menu-Based Pricing for Charging of Electric Vehicles With Vehicle-to-Grid Service

The paper considers a bidirectional power flow model of the electric vehicles (EVs) in a charging station. The EVs can inject energy by discharging via a vehicle-to-grid (V2G) service, which can enhance the profits of the charging station. However, frequent charging and discharging degrade battery life. We propose a menu-based pricing scheme, where the charging station selects a price for each arriving user (EV owner) for the amount of battery utilization, the total energy, and the time (deadline) that the EV will stay. The user can accept one of the menus or rejects all. The user reaches its decision based on the utilities. The charging utilizes its own limited renewable energy, and the conventional energy bought from the grid to serve the users. We show that there exists a prior-free pricing mechanism, which maximizes the ex-post social welfare for a myopic scenario. It selects a lower price for the menu containing a higher V2G service. However, the prior free pricing mechanism does not necessarily maximizes the expected profit. We show that the pricing strategy, which sets the price for a menu at a fixed value greater than the marginal cost of serving the menu, maximizes the expected profit for a wide class of utility functions. In the menu-based pricing, when the harvested renewable energy is small the users have higher incentives for the V2G service. We, numerically, show that the charging station's profit and the user's surplus both increase as V2G service is efficiently utilized by the pricing mechanism.

Range anxiety of electric vehicles in energy management of microgrids with controllable loads

Abstract Recently-developed smart grids have a diverse range of load types that makes their energy scheduling different from conventional power systems. In this paper, an energy scheduling is proposed for smart grids to minimize operational cost and energy losses taking into account flexible (adjustable and shiftable) loads, which are used here as network resources. Special attention is paid to Electric Vehicles (EVs) as a sort of flexible loads. It is shown that the Vehicle-to-Grid (V2G) service may intensify power losses by charging and discharging EVs for multiple times and consequently, it is necessary to observe and optimize energy losses while using V2G. Range anxiety, which is one of main barriers to promote EVs, is formulated and optimized in order to address the concern of EV owners in depletion of battery energy and to encourage them to more actively participate in V2G service. Under the proposed scheme, EVs act as distributed energy storage systems to more employ renewables and also to make it possible to take the advantage of lower tariff electric energy from upstream networks. Results from examining the proposed method on a standard test system are presented and discussed.

A fast and efficient coordinated vehicle-to-grid discharging control scheme for peak shaving in power distribution system

This study focuses on the potential role of plug-in electric vehicles (PEVs) as a distributed energy storage unit to provide peak demand minimization in power distribution systems. Vehicle-to-grid (V2G) power and currently available information transfer technology enables utility companies to use this stored energy. The V2G process is first formulated as an optimal control problem. Then, a two-stage V2G discharging control scheme is proposed. In the first stage, a desired level for peak shaving and duration for V2G service are determined off-line based on forecasted loading profile and PEV mobility model. In the second stage, the discharging rates of PEVs are dynamically adjusted in real time by considering the actual grid load and the characteristics of PEVs connected to the grid. The optimal and proposed V2G algorithms are tested using a real residential distribution transformer and PEV mobility data collected from field with different battery and charger ratings for heuristic user case scenarios. The peak shaving performance is assessed in terms of peak shaving index and peak load reduction. Proposed solution is shown to be competitive with the optimal solution while avoiding high computational loads. The impact of the V2G management strategy on the system loading at night is also analyzed by implementing an off-line charging scheduling algorithm.

Reactive Power Compensation Capabilities of V2G-Enabled Electric Vehicles

Vehicle-to-grid (V2G) paradigm is a way of executing services in favor of the grid by electric vehicles (EVs) with bidirectional battery chargers (BBC). The V2G service that has attracted the major interest is the exchange of active power for load leveling purposes. Less attention has received the so-called ancillary V2G services, such as the reactive power compensation. This service is much attractive since it does not involve any exchange of active power and, therefore, leaves the EV batteries charged and does not expose them to additional discharging–charging cycles. The purpose of this paper is to investigate the capabilities of V2G-enabled EVs in executing the reactive power compensation, whether done alone or simultaneously with either battery charging or battery power delivery to the grid. Two topologies of BBC are examined, namely the topologies with the dc side of the charger either directly connected to the battery or through a bidirectional dc–dc converter of buck type. This paper closes by reporting experimental results that corroborate the theoretical findings.

Modeling and Feasibility Analysis of Quasi-Dynamic WPT System for EV Applications

In this paper, a new bidirectional wireless power transfer (WPT) charging and discharging concept is analyzed for its feasibility in integration at traffic signals. Classified as quasi-dynamic WPT (QDWPT), a string of coils are proposed to be installed beneath the road surface to provide grid-to-vehicle and vehicle-to-grid (V2G) services to battery electric vehicles (BEVs) while stopped. An experimentally verified lithium-ion battery array and Bidirectional Wireless Power Transfer system are combined to provide a comprehensive simulation under three proposed scenarios. First, four fixed standardized WPT charging levels are evaluated under a Federal Test Procedure-72 city driving profile. Second, a variable charging scenario autonomously adjusts the charging level based on the BEV state of charge. Third, an algorithm is proposed to toggle between charging and discharging based on the BEV psychological and grid retail price to evaluate V2G service viability. For each scenario, a comparison over the maximum driving range per drive cycle and range gained for each consumed kWh is quantified. Moreover, the effect of WPT coil misalignment over the driving performance is investigated and evaluated. This paper concludes that QDWPT at traffic signals is a promising solution to substantially extend the driving range and operating time for city driving especially at high charging levels.

Solving the Multivariant EV Routing Problem Incorporating V2G and G2V Options

In the near future, gasoline-fueled vehicles are expected to be replaced by electrical vehicles (EVs) to save energy and reduce carbon emissions. A large penetration of EVs threatens the stability of the electric grid but also provides a potential for grid ancillary services, which strengthens the grid, if well managed. This paper incorporates grid-to-vehicle (G2V) and vehicle-to-grid (V2G) options in the travel path of logistics sector EVs. The paper offers a complete solution methodology to the multivariant EV routing problem rather than considering only one or two variants of the problem like in previous research. The variants considered include a stochastic environment, multiple dispatchers, time window constraints, simultaneous and nonsimultaneous pickup and delivery, and G2V and V2G service options. Stochastic demand forecasts of the G2V and V2G services at charging stations are modeled using hidden Markov model. The developed solver is based on a modified custom genetic algorithm incorporated with embedded Markov decision process and trust region optimization methods. An agent-based communication architecture is adopted to ensure peer-to-peer correspondence capability of the EV, customer, charging station, and dispatcher entities. The results indicate that optimal route for EVs can be achieved while satisfying all constraints and providing V2G ancillary grid service.

On the Front Lines of a Sustainable Transportation Fleet: Applications of Vehicle-to-Grid Technology for Transit and School Buses

The electricity generation/supply and transportation sectors are the two largest contributors to greenhouse gas (GHG) emissions in the U.S., and vehicle-to-grid (V2G) technology is a rapidly emerging solution to reduce these emissions with the adoption of battery-electric (BE) vehicles. Deployments of BE transit and school buses are expected to have larger battery capacities than passenger vehicles, making them more feasible candidates for V2G service. Five electricity generation regions are considered for cash flow analysis of BE and diesel transit and school buses over their entire respective lifetimes with the allowance of V2G services’ net revenue. Besides, the environmental benefits of using the V2G system are studied in place of combustion power generation plants for the regulation services of each study region. Air emission externalities are another crucial issue for bus operations because buses are operated near highly populated areas, so these externalities are also studied in this research with the benefits of a V2G emission reduction potential taken into account. The analysis concluded that BE transit and school buses with V2G application have potential to reduce electricity generation related greenhouse-gas emissions by 1067 and 1420 tons of CO2 equivalence (average), and eliminate $13,000 and $18,300 air pollution externalities (average), respectively.

수요자원 거래시장을 고려한 전기차 운영기준에 관한 연구

The concept known as Vehicle-to-Grid (V2G) is to provide power to help balance loads by charging at night when demand is low and sending power to the grid when demand is high. Therefore, it is important to model the cost-benefit characteristics of Electric vehicle(EV)'s operation considering the negawatt market in real time. This paper proposes a methodology to formulate the various costs and economic benefits for sending the EV's power back to the grid, including a concept of inconvenience costs caused by operating the EV as a battery. This paper also introduces the general decision-making process based on the cost-benefit analysis in order to simulate the reasonable participation of V2G service. In the case study, it is confirmed by two-case simulations that the proposed approach is useful to help EV owners' decision-making. In the future, it is expected that the proposed methodology can be used as a decision-making guideline to help prepare the EV' power transmission.

총소유비용 분석을 이용한 전기차의 V2G 도입에 대한 연구

Abstract - Increasing concerns on climate change and energy sec urity accelerated policies to reduce green-house gas emission, especially from the transportation sector. Electric vehicle (EV) has been on the spotlight to deal with such environmental issue and V2G (Vehicle-to-Grid) te chnology began to draw attentions as an alternative to reduce ownership costs while contributing to an efficient and decentralized power grid. This study conducts a scenario analysis on total cost of ownership of EV under V2G scheme and compare with non-V2G EV and Internal Combustion Engine (ICE) vehicle. As res ult, V2G service is expected to provide an annual average profit of $210 to EV users willing to reverse fl ow its residual power in the battery. The profit from V2G service leaves a margin of $4,530 over operational lif etime, compared with $2,420 cost of charge for non-V2G EV. In summary, total cost of ownership of V2G-capa ble EV was 6.2% less than non-V2G EV and 10.2% higher than ICE vehicle. The results confirm a compar ative economic advantage of operating EV under V2G scheme. Increased number of EVs with V2G service has shown to provide positive effects to power industry for valley filling in load distribution, thus, f avorably increasing the overall economic feasibility.

Research on the Performance of Electric Vehicles in Peak Load Shifting

Electric vehicles (EVs) are developing remarkably fast these years which makes the technology of vehicle-to-grid (V2G) easier to implement. Peak load shifting (PLS) is an important part of V2G service. A model of EVs’ capacity in V2G service is proposed for the research on PLS in this paper. The capacity is valued in accordance with three types of situations. Based on the model, three different scenarios are suggested in order to evaluate the capacity with MATLAB. The evaluation results indicate that EVs can provide potential energy to participate in PLS. Then, the principle of PLS with EVs is researched through the analysis of the relationship between their power and capacity. The performance of EVs in PLS is also simulated. The comparison of two simulation results shows that EVs can fulfill the request of PLS without intensely lowering their capacity level.

Using vehicle-to-grid technology for frequency regulation and peak-load reduction

This paper explores the potential financial return for using plug-in hybrid electric vehicles as a grid resource. While there is little financial incentive for individuals when the vehicle-to-grid (V2G) service is used exclusively for peak reduction, there is a significant potential for financial return when the V2G service is used for frequency regulation. We propose that these two uses for V2G technology are not mutually exclusive, and that there could exist a “dual-use” program that utilizes V2G for multiple uses simultaneously. In our proposition, V2G could be used for regulation on a daily basis to ensure profits, and be used for peak reduction on days with high electricity demand and poor ambient air quality in order to reap the greatest environmental benefits. The profits for the individual in this type of dual-use program are close to or even higher than the profits experienced in either of the single-use programs. More importantly, we argue that the external benefits of this type of program are much greater as well. At higher V2G participation rates, our analysis shows that the market for regulation capacity could become saturated by V2G-based regulation providers. At the same time, there is plenty of potential for widespread use of V2G technology, especially if the demand for regulation, reserves, and storage grows as more intermittent renewable resources are being incorporated into the power systems.