Research On Bidirectional AC/DC Converter Of Isolated Electric Vehicle Based On V2G Technology

With the rapid development of electric vehicle technology,the interaction between electric vehicles and power grid becomes more and more frequent,so V2G(vehicle to grid)technology has attracted wide attention.At present,electric vehicles can be used as both power consumers and power providers in the power system.However,with the increasing penetration rate of electric vehicles as an important part of distributed new energy in the power system,the safe and stable operation of the power grid has been greatly challenged.Therefore,the application of V2 G technology can guarantee the two-way flow of power between the electric vehicle and the power grid and achieve friendly interaction at the same time.In addition,improving the two-way charging and discharging efficiency of electric vehicles has become the top priority in the development of electric vehicles,and new requirements are put forward for electric equipment.As the hub of realizing the two-way interaction between electric vehicles and power grid,the interface converter connecting ac and dc busbars has attracted more and more attention from domestic and foreign scholars.Aimed at the requirement of electric vehicle in the process of charging and discharging the interface converter,this paper puts forward a applicable to the isolation of the electric vehicle charging and discharging machine bidirectional AC/DC converter,the converter by former three-phase voltage source inverter type and level after the CLC dual active bridge resonance of two parts,a former three-phase full bridge circuit adopts virtual synchronous motor control,level of dual active bridge after the control strategy based on PWM control,in the realization of two-way efficient transfer of power at the same time to provide DC voltage dynamic response process of inertia.First of all,in order to improve the charging and discharging efficiency and solve the problem of low inertia in the traditional droop control,the traditional droop control strategy adopted by the front-stage three-phase voltage source inverter is improved to Virtual Synchronous Machine(VSM).The mathematical model of three-phase voltage source inverter is established,and the control strategy of ac interface based on virtual synchronous motor is designed according to the power exchange characteristics between power grid and ev power battery and the charging and discharging requirements of ev.It consists of three parts: active power control,virtual excitation control and voltage-current double closed-loop control.At the same time,the control strategy can provide inertia and damping for the dynamic response process in the interaction between the ev and the power grid,improve the dynamic response of the output dc voltage,and thus improve the dc voltage anti-disturbance performance of the ev power battery.Secondly,the topology of the isolated bidirectional power converter based on the biactive full-bridge structure is studied and improved,and the CLC resonance module is added on the basis of the biactive full-bridge structure.According to the characteristics of the electric vehicle power battery,the dual active bridge control model based on PWM control,the design of the control strategy of dc interface in different charging and discharging mode,the control strategy can achieve zero in the process of charging and discharging voltage conduction and zero current turn off,greatly improve the efficiency of the electric car charge and discharge,and analyses the level after the CLC resonant dual active bridge module switch tube conduction of zero voltage and zero current turn off.In order to further verify the effectiveness and correctness of the proposed control strategy,a simulation control model of three-phase isolated bidirectional power converter based on CLC resonant converter was established by using MATLAB Simulink.The simulation results proved the effectiveness and superiority of the control strategy.Finally,former level is developed using virtual synchronous machine control,level control strategy based on PWM control after the isolation of bidirectional power converter prototype,and the converter in the power grid voltage response of transient fault response,mesh side power changes,the effect of charging and discharging soft switch and charging and discharging mode conversion,verified the correctness and feasibility of the proposed control strategy.