Simulation Research On Three-Phase Isolated Energy Storage Converter For Electric Vehicle

Indicators such as the capacity,energy density and voltage level of electric vehicle batteries are the basic conditions for ensuring cruise,acceleration,and endurance performance.The increase of battery pack voltage level can effectively solve the electric vehicle efficiency problem during high-power charge and discharge.Meanwhile,batteries naturally can be energy storage nodes in the active distribution grid.So a three-phase isolated electric vehicle energy storage converter suitable for different battery voltage levels is researched.It can realize electric vehicle high-power charge and controllable discharge as large-capacity energy storage.According to the requirements of AC side power factor and harmonics,output voltage,power grade,and bidirectional energy flow of electric vehicle energy storage converters,the system topology is proposed.A three-level neutral point clamp converter(NPC)is selected as the three phase grid side high power factor front end,which provides a stable DC voltage for the last stage.An isolated bidirectional dual active full bridge(DAB)is selected as the last stage converter to realize battery charge-discharge power control.The mathematical model and their power transmission modes of NPC and DAB are analyzed respectively.By simulation and comparison,the modulation strategies of the two power stages,the space vector modulation(SVM)and the optimized duty cycle triple phase shift(TPS)are determined.The dual-loop d-q control structure of the NPC is designed to realize the DC side voltage regulation control under AC side input current follow-up.On the premise of optimizing the duty cycle of the two stages,a PI controller is used to adjust the phase shift angle of the last stage DAB circuit,which realizes the control of charge-discharge power flow under the condition of wide voltage battery voltage.The NPC and DAB circuit models are built in MATLAB/Simulink respectively.to verify the feasibility of the topology structure,the optimized modulation strategies,the control methods and setting parameters are verified,and the two-stage topology cascade system simulation is achieved.Meanwhile,the efficiency under different charging currents,battery pack voltages and transmission power are compared through simulation.The current,wide voltage and power range suitable of the bidirectional converter device are determined.The simulation results of the high power dual power transmission electric vehicle battery show that the electric vehicle energy storage system can perform high power factor energy interaction with the power grid according to the instructions,verifying the bidirectional energy flow this design goal of the system.