Research On Performance Optimization Of High Power Factor Charger

As the market for new energy vehicles continues to expand,the number of chargers in cities has also increased.As a device for charging energy storage devices for vehicles,the performance of the charger will directly affect the service life of the battery and the efficiency of each charge to a large extent.And because the charger is a grid-connected operation device,if its performance is too poor,it will even cause great harmonic pollution to the power grid.Therefore,this article takes the performance optimization of the high power factor charger as an angle to conduct research.Through the analysis of several common topologies of the charger,the performance optimization of the charger with the three-phase voltage PWM rectifier as the main topology structure is selected.Firstly,the working principle of the PWM rectifier is analyzed,its general mathematical model based on the switching function method is deduced,and the coordinate transformation theory required for conversion under different coordinate systems is explained.Then the basic principle and modulation process of space vector pulse width modulation(SVPWM)are introduced.In terms of control strategy,a Bode diagram was used to compare and analyze the PI controller used in the traditional current inner loop and the quasi-proportional resonant controller to be used.The influence of each parameter in the charger on the control performance was analyzed by the control variable method,so that it could finally select the most suitable control parameters for the charger system to achieve the best tracking error-free tracking effect.At the same time,the power grid is not always maintained in a stable state.It is extremely important that the charger can maintain a stable DC side output when the grid voltage is unbalanced.In order to solve this problem,the reason for the power ripple of the rectifier in the case of unbalance is analyzed.On this basis,a direct current command control strategy is proposed,that is,the active power and the DC voltage pulsation are suppressed by injecting an appropriate amount of negative sequence current into the grid.Based on the above analysis,a simulation platform for the charger system is built in Simulink,and an experimental prototype is built on the basis of correct simulation,and the design methods and ideas of the hardware and software are given.Finally,two sets of comparative experiments verify the feasibility and effectiveness of this optimization method.