Design And Optimization Of Interleaved Boost PFC System For On Board Chargers

The On-Board Charger provides a direct connection between the power grid and the electric vehicle power battery.The former stage of the OBC——Power Factor Correction(PFC)circuit,can effectively suppress the harmonic pollution of the power grid.The PFC circuit of traditional vehicle charger mostly adopts average current control.Because of the low bandwidth of the outer voltage loop,the dynamic response of the system is slow and the stability is poor,which reduces the lifetime of the output capacitance and affects the reliability of the converter.Therefore,a new control strategy is needed to solve this problem.In this paper,the optimal control theory of discrete time system is introduced into the converter,aiming at the dynamic response problem in the traditional average current control of interleaved Boost PFC.Based on the discrete state space model of the converter,the discrete energy function of the converter is established and the controller is designed.The feasibility of the discrete energy function control method of interleaving parallel Boost PFC is verified by theoretical analysis and simulation.In the realization of discrete energy function control,the peak power detector has delay problem and potential positive feedback problem.In this paper,the discrete energy function control system is optimized for these two problems,and the control stability of the system is improved by improving the selection of system reference value.On the basis of simulation and hardware design,an interleaved Boost PFC prototype is built,and the working performance of digital average current control and discrete energy function control under a wide range of input and multiple load conditions is compared.The advantages of the improved discrete energy function control in the dynamic response and stability of the lifting system are verified.