On Beneficial Vehicle-to-Grid (V2G) Services

A number of studies have investigated the possibility of extending Electric Vehicle (EV) Lithium-ion battery life by deliberately choosing to store the battery at a low to moderate state of charge. Recently, there has been considerable interest shown in the scheme of a deliberate discharge and subsequent recharge of a battery to yield an overall reduction in battery degradation whilst carrying out Vehicle-to-Grid (V2G) services (so-called `beneficial V2G'). This paper presents an investigation of the conditions permitting successful operation of this method by examining incremental time variation of the relevant parameters for two types of cells from results of the same physical size and chemistry, and similar capacity. These two types of cells are found in this present analysis to offer differing degrees of suitability for beneficial V2G

Vehicle to Grid: An Economic and Technological Key to California\u27s Renewable Future

This paper explores how the concept of Vehicle to Grid (V2G) could bring benefits to California\u27s electric grid, transportation sector, and environmental goals

Bidirectional AC-DC Converter for Vehicle-to-Grid (V2G) Applications

Electric vehicles are growing at a rapid pace in the internal combustion engine dominated transportation sector, and bring environmental and economic benefits to society. Electric vehicles produce nearly zero carbon emission, provided that they are charged through renewable energy sources. Electric vehicles reduce our dependency on foreign oil and also offer additional benefits like Vehicle-to-grid (V2G). V2G is a technology that allows electric energy stored in the electric vehicle batteries to be returned to the grid during peak demand. V2G can also provide voltage regulation, voltage shaving, reactive power compensation and distributed generation. This necessitates that an electric vehicle battery charger be bi-directional, capable of sinking or sourcing real and reactive power. The state of the art battery charging converter is unidirectional and has multiple stages of power conversion. In this thesis, a single phase, single stage, isolated, bi-directional Silicon Carbide (SiC) AC-DC converter based on Dual Active Bridge (DAB) topology is proposed and analyzed. Direct-quadrature axis (DQ) current control of the DABbased topology is implemented with phase shift modulation. Simulation results are presented with various operating conditions showing the converter’s ability to sink or source real and reactive power in the AC grid. Hardware and firmware implementation of a single phase bi-directional AC-DC converter operating at 100 kHz utilizing Silicon Carbide (SiC) MOSFETs are discussed in detail. Experimental results are shown confirming simulation results. A single phase bi-directional AC-DC converter uses large electrolytic capacitors to filter ripple currents in the DC bus. Electrolytic capacitors are bulky and are prone to failure. These electrolytic capacitors can be eliminated by rejecting the ripple current in the DC bus. The ripple current is rejected by injecting a current of same magnitude and opposite phase to the ripple current. A rigorous analysis is performed on the ripple rejection technique used in single phase bi-directional AC-DC converters. Simulation results are presented to verify the analysis. A three phase bi-directional AC-DC converter improves the charging time of the electric vehicles by charging the batteries at a higher power level. A three phase, single stage, isolated, bi-directional AC-DC converter is analyzed. DQ current control of the three phase AC-DC converter is implemented in simulation to verify the analysis

Business Models for Vehicle to Grid (V2G)

The variable nature of renewable energy has consequences for electricity supply control and management. The control of the electricity grid in most European countries is premised on the ready availability of high energy density fossil fuels, use of which for electricity production (including for electrified transport) leads to adverse environmental impacts. There is progress in using renewable energy sources for electricity generation but they are low density and variable with implications for grid control and management. A projected rise in the use of Electric Vehicles (EVs) produces considerable interest in the impact on grid control, and using the energy storage capacity of EVs as a means for helping with grid management. The EV battery can provide a important service to the grid by providing storage to enable both import and export of power from/to the grid, termed Vehicle to Grid (V2G). Other methods of regulating the intermittent nature of renewables are to use (in addition) stationary batteries. V2G means that the EV battery can be used for peak lopping and frequency stabilisation. Technologies for such power sharing are developing with commercial demonstrators under test. There need to be business models ensuring that EV owners are rewarded for allowing the vehicles to be used for V2G as the EVs cannot then simultaneously be used for transport use and EV batteries may experience additional degradation. There also needs to be a system for ensuring that EVs used for grid management are sufficiently re-charged to meet user needs

On Beneficial Vehicle-to-Grid (V2G) Services

A number of studies have investigated the possibility of extending Electric Vehicle (EV) Lithium-ion battery life by deliberately choosing to store the battery at a low to moderate state of charge. Recently, there has been considerable interest shown in the scheme of a deliberate discharge and subsequent recharge of a battery to yield an overall reduction in battery degradation whilst carrying out Vehicle-to-Grid (V2G) services (so-called ‘beneficial V2G’). This paper presents an investigation of the conditions permitting successful operation of this method by examining incremental time variation of the relevant parameters for two types of cells from results of the same physical size and chemistry, and similar capacity. These two types of cells are found in this present analysis to offer differing degrees of suitability for beneficial V2G

Bi-directional coordination of plug-in electric vehicles with economic model predictive control

© 2017 by the authors. Licensee MDPI, Basel, Switzerland. The emergence of plug-in electric vehicles (PEVs) is unveiling new opportunities to de-carbonise the vehicle parcs and promote sustainability in different parts of the globe. As battery technologies and PEV efficiency continue to improve, the use of electric cars as distributed energy resources is fast becoming a reality. While the distribution network operators (DNOs) strive to ensure grid balancing and reliability, the PEV owners primarily aim at maximising their economic benefits. However, given that the PEV batteries have limited capacities and the distribution network is constrained, smart techniques are required to coordinate the charging/discharging of the PEVs. Using the economic model predictive control (EMPC) technique, this paper proposes a decentralised optimisation algorithm for PEVs during the grid-To-vehicle (G2V) and vehicle-To-grid (V2G) operations. To capture the operational dynamics of the batteries, it considers the state-of-charge (SoC) at a given time as a discrete state space and investigates PEVs performance in V2G and G2V operations. In particular, this study exploits the variability in the energy tariff across different periods of the day to schedule V2G/G2V cycles using real data from the university's PEV infrastructure. The results show that by charging/discharging the vehicles during optimal time partitions, prosumers can take advantage of the price elasticity of supply to achieve net savings of about 63%

Vehicle-to-grid (V2G) and grid conditioning systems

The term Vehicle-to-Grid (V2G) refers to the technology that enables a bidirectional power exchange between the electric grid and the batteries of plug-in electric vehicles (PEV). V2G technology can be a key element of the intelligent network, which may use the batteries of the vehicle as a system of local storage. The vehicle battery may contribute to the stability of the grid and to meeting the energy demand, especially in peak hours. A PEV needs a bidirectional charger to implement V2G, and, consequently, the studies regarding their design, functionality and efficiency are of the utmost interest. This thesis describes the state of art of these chargers and discusses some aspects of a bi-directional converter and some case studies related to this topic. The main objective of this work is to develop the design and the control algorithms of a bidirectional battery charger with capability to charge the battery of a PEV and simultaneously to act as an active filter for the supply line. After the first introductory chapter, the second chapter reports the terminology used in this field of research. Several smart strategies for charging, approaches for the implementation of the battery chargers for PEVs and the recharging standards are briefly described. The analysis of different types of charger is detailed in chapter three. The conventional battery chargers (CBC) with front-end formed by a diode rectifier, battery chargers with power factor correction (PFC), bi-directional battery chargers (BBC), and integral battery chargers (IBC) are considered. In chapter four, definitions are given of the electrical power in non-sinusoidal conditions, together with some examples of the inadequacies of the classical power theory in describing non-linear phenomena that occur during the operation of a power system. The fifth chapter presents the basic concepts of the theory of instantaneous active and reactive power (also known as p-q theory) applied to the compensation of non-sinusoidal systems. Definition of real, imaginary and zero sequence power are introduced and it is shown how this theory makes it easier to understand the phenomena caused by non-sinusoidal voltages or currents. The theory is particularly suitable for the design of a battery charger when it is seen as a power conditioner. Chapter six is devoted to the basic concepts of shunt active filters. They can perform different types of functions, such as the compensation of current harmonics generated by nonlinear loads to prevent their propagation in the network. The compensation algorithm based on powers defined in reference is very flexible and therefore the theory of instantaneous power has been considered as the basis for the development of the control system of active filters. Some examples of compensation described in the previous chapter were simulated and the results have been included. In chapter seven, sizing of the power devices that constitute the battery charger is considered in relation to the various auxiliary services that it can provide. The power electronic switches, the coupling inductors and the other passive components have been sized in voltage and current. In chapter eight it is considered a charger that supplies its load and simultaneously compensates for non-linear loads connected nearby. These additional features in terms of power conditioning were quantified in order to determine the capacity of a battery charger that is formed by given active and passive components to support the network acting as an active filter. In the ninth chapter the filter inductances of a battery charger are sized for a specific case study in which it is required the capability to recharge the battery and to inject active power in the network, both in the case of single-phase and three-phase connection. Evaluation of the ripple current is an important requirement for the design of inductors. Therefore a precise calculation was made of this magnitude both in the case of a battery charger connected to the single phase grid and operating according to the PWM technique, and, in the case of connection to the three-phase grid, operating according to the technique SVM. In chapter ten a case study is considered regarding the design of an LCL filter. Chapter eleven contains a theoretical study of resonant controllers. They solve the problem posed by the conventional PI controllers that, when used for the control of alternate quantities as it occurs for the currents of a DC/AC converter, are not able to cancel the steady state error due to the finite gain at the operating frequency. Instead, a resonant controller has a gain ideally infinite at the operating frequency and thus ensures a zero steady-state error. The effectiveness of the resonant regulators has been verified by means of simulations. Chapter twelve deals with the regulations regarding connectors, charging modes and ways of connecting the PEV chargers to the grid. They are intended to define a charging procedure common to all the PEVs and to all the charging infrastructures, whether public or private

SEEV4City INTERIM 'Summary of the State of the Art' report

This report summarizes the state-of-the-art on plug-in and full battery electric vehicles (EVs), smart charging and vehicle to grid (V2G) charging. This is in relation to the technology development, the role of EVs in CO2 reduction, their impact on the energy system as a whole, plus potential business models, services and policies to further promote the use of EV smart charging and V2G, relevant to the SEEV4-City project