Reactive Power Compensation Technology Using Electric Vehicles Off-board Charger

With the seriousness of environment and the shortage of energy,electric vehicles(EVs)with clean electric energy power have got the world's attention and been greatly developed in the past years.The chargers are widespread in public places now,especially EVs off-board charger.And as we all know,reactive power has a bad impact on power grid.So we studied on the reactive power compensation using EVs off-board chargers based on V2G(vehicle to grid).In this paper,EVs can not only meet the charging requirement,but also compensate the reactive power to power grid using off-board chargers,while there aren't bad effects on battery during this operation.The main research contents are as follows:First of all,a new kind of EVs off-board charger is designed and EVs can complete the reactive power compensation using the off-board charger.The simplified model of EVs off-board charger is given and the model consists of AC side and DC side.We calculate the range of resistance,inductance and capacitance on both sides based on the rated power of EVs off-board charger in this part.We design the controller by PI method on both sides based on instantaneous reactive power theory and decoupling control.Components are chosen based on the value range and the simulation is studied in PSCAD/EMTDC.The results shows that EVs can compensate reactive power to power grid using off-board chargers designed above and work well.Secondly,we research on the control strategy of reactive power compensation considering large-scale EVs,so that the EV can get the command reactive power.We analyze the operation characters of off-board charger when EVs compensate reactive power to power grid using off-board chargers.The relationship between node voltage and reactive power that EVs compensate to power grid using off-board charger in three models of power grid is also analyzed,the results show that conclusions about relationship between node voltage and reactive power are same in different models.In order to get the range of reactive power that each EV compensates to power grid using off-board charger,we analyze the range of reactive power in detail.The control strategy of reactive power compensation considering large-scale EVs is studied based on the above works and the control strategy proposed can not only meet the charging requirement,but also compensate the reactive power to power grid.Finally,the scene that EVs compensate reactive power to power grid using the off-board charger is simulated which is based on the above works.The results show that EVs will increase the node voltage fluctuation and deviation between real voltage and rated voltage when they just work as load.But when EVs compensate reactive power to power grid using the off-board charger by control strategy studied in this paper,voltage fluctuation and deviation between real voltage and rated voltage will decline.The more the number of EVs is,the better the effects are.