Research On V2G Reactive Power Compensation Method

Over the past decade,the energy imbalance between supply and demand and the integration of renewable energy have attracted wide attention.In the field of transportation dominated by internal combustion engines,electric vehicles have developed rapidly,bringing environmental and economic benefits to society.As long as electric vehicles are charged with renewable energy,they will produce almost zero carbon emissions.Electric cars reduce our dependence on foreign oil and provide additional benefits,such as Vehicle-to-grid?V2G?.V2G is a technology that allows energy stored in batteries of electric vehicles to return to the grid at peak demand.V2G can also provide voltage regulation,frequency modulation,reactive power compensation and distributed generation.Vehicle-to-grid?V2G?is a way to perform grid-friendly services through an electric vehicle?EV?with a bidirectional battery charger?BBC?.Active power switching V2G service for load balancing has attracted a lot of attention.Less attention has been paid to so-called auxiliary V2G services,such as reactive power compensation.However,reactive power compensation technology has been widely used in distribution systems to improve voltage support,transient stability and power oscillation damping.This service is very attractive because it does not involve any active power switching,so EV batteries are charged without exposing them to additional discharge-charge cycles.The purpose of this paper is to explore the ability of V2G-enabled EV to perform reactive power compensation.Considering the design of a bi-directional battery charger for a given EV battery charge,the compensation is based on the battery specifications of the electric vehicle.The theoretical calculation of rated voltage and current of AC-DC during battery charging is analyzed.The maximum current and minimum voltage of AC-DC during battery discharging do not affect battery life.The topology selection conditions of bi-directional battery charger are determined quantitatively,and the operation area of bi-directional battery charger is studied.Then,according to the maximum reactive power absorbed by the BBC,as a function of the actual battery charging status and the BBC task,that is whether the BBC performs reactive power compensation alone or simultaneously battery charging or battery power supply.The maximum active power and reactive power absorbed by the BBC during battery charging and discharging were tested by simulation.The F-G-A'study of single-stage BBC during CC charging was carried out.The AC-DC input current was adjusted to keep the battery charging current constant at 11A and meet the AC-DC input voltage limitation conditions.In the CV stage of battery charging,the trajectory A'-G-D is explored.By keeping the AC-DC input current at the rated value and adjusting its phase angle,the battery current is gradually reduced to 0.1I_CC.The results show that the obtained power values are in agreement with the theoretical results.