Research On Bidirectional Converter For Electric Vehicle Charging Pil

In recent years,electric vehicle as a green travel tool,because of its characteristics of energy saving and environmental protection has been rapidly developed.Vehicle to Grid(V2G)technology,as a two-way interactive technology that breaks the boundary between electric vehicles and power grid,is also paid more attention by more people.V2 G technology regards the battery pack of electric vehicles as a mobile energy storage unit,which can charge or discharge the battery pack through a power electronic converter when the electric vehicle is idle,so as to realize the two-way energy flow between electric vehicles and the power grid.As a physical medium of V2 G technology,electric vehicle charging and discharging pile has become a hot topic in the field of electric vehicle research,and its performance directly affects the development of electric vehicle.In this paper,a power converter with two-stage topology is designed.Firstly,the switching state of the former three-phase voltage source converter is analyzed,and the mathematical model of the three-phase voltage source PWM converter in the rotating coordinate system is established.The SPWM and SVPWM modulation strategies are briefly analyzed,and a simplified SVPWM modulation strategy is proposed to solve the complex problems of sector selection and trigonometric function operation in traditional SVPWM modulation methods.The instantaneous value of the three-phase reference voltage is used to judge the vector falling into the sector,and then the voltage vector is decomposed into the switching vector.The action time of the switching vector is obtained by the side length relation of the right triangle and the knowledge of simple trigonometric functions.This algorithm avoids the complicated coordinate transformation and inverse tangent function operation involved in the conventional algorithm,and the implementation process is relatively simple.Simulation and experiment show that this method can effectively simplify the problem of large amount of computation in traditional SVPWM modulation.Then,the basic operating principle,operating mode and operating characteristics of the double-active full-bridge converter under the triple phase shift control strategy are analyzed,and the zero-voltage switching condition and the output power under the triple phase shift control are calculated.In order to optimize the current stress and response speed of DC/DC converter,a TPS compensation power control strategy is proposed.The TPS compensation power control strategy sends the difference between the output voltage and the given reference voltage to the PI controller so that the controller can quickly calculate the new transmission power per unit value when the converter load or input voltage is disturbed.The simulation and experiment verify that the converter can adjust the output voltage quickly and stabilize the output voltage when the load or input voltage is disturbed by introducing power compensation,so that the converter has better dynamic response performance.This method can effectively control the stability of output voltage and current in the charging and discharging process of electric vehicle battery,meet the requirements of electric vehicle battery charging and discharging,and extend the service life of electric vehicle battery.Finally,this paper builds the overall simulation model of electric vehicle charging and discharging pile through Matlab/Simulink,and simulates the electric vehicle battery working in charging state,discharge state,and alternating state of charge and discharge.The simulation results show that the proposed topology structure has little voltage fluctuation on the DC bus side of the three-phase voltage source converter under the simplified SVPWM modulation and TPS control strategy,and the EV charge-discharge control system has good dynamic performance.In addition,a low-power hardware platform was built for experimental verification,including the selection of switching devices,inductance and capacitance design,sampling circuit design,drive circuit design,protection circuit design,and preparation of control system flow charts.Experimental results show that the structure and optimal control strategy proposed in this paper can realize bidirectional power transmission,so as to strengthen the security and dynamic interaction of the charging pile and improve the efficiency of energy.