Research On Control Strategies For Three-Phase Isolated Matrix Rectifier

With the rapid development and wide application of new energy technology,electric vehicles(EVs)have become an important novel transportation.And as the energy supply equipment of EVs,the high-power DC charger is an important way to solve the "range anxiety" problem of the EVs.The traditional DC charger usually adopts a two-stage structure composed of a three-phase AC/DC converter and an isolated DC/DC converter,which has low power density and large equipment volume.The three-phase isolated matrix rectifier(TIMR)does not need the DC bus link of the two-stage charger,so it can achieve single-stage energy conversion and improve the efficiency of system.In addition,in the process of charging,there are strict requirements on both the harmonic pollution brought to the grid side and the response and disturbance rejection ability of the output side.Therefore,the research on the control strategies that can reduce the harmonic pollution on the grid side and improve the performance of the output side are the key to the efficient and reliable operation of the charger.In this paper,the control strategies of the TIMR are studied,and the main achievements are as follows:1.The working principle of the TIMR is analyzed in detail and its mathematical model is established.Based on space vector modulation,the implementation method of bipolar space vector modulation strategy which can adjust the output current and power factor correction function is studied,which lays a foundation for the research of the TIMR control strategies.2.Aiming at the problem of current harmonics on the grid side,a plug-in repetitive control structure with the ability of harmonic compensation is proposed,and the stability of the control system is analyzed.According to the characteristic that the harmonics’order of the TIMR are 6n±1,the core of the repetitive controller is improved to reduce the computation of the controller.A fractional delay compensator was designed to improve the steady-state tracking performance of the TIMR because the non-integer delay link of the improved controller could not be realized in the digital system.3.In order to improve the response speed and disturbance rejection performance of the output side of the TIMR,a second-order linear active disturbance rejection control(LADRC)strategy is designed.A linear extended state observer is designed to estimate the disturbance of the system for the inner and outer current loops,and the disturbance is compensated by feedback law.A parameter tuning method based on bandwidth method is proposed to reduce the number of parameters of the controller while ensuring the dynamic performance of the system.4.Based on Matlab/Simulink and dSPACE 1007 digital control system,a 2kW TIMR simulation and experiment platform were built,and the design and prototype debugging of the double closed-loop control system based on the plug-in repetitive controller and LADRC controller were completed respectively.Simulation and experimental results show that the proposed repetitive controller can suppress the currents harmonics of the gird side well.The system using LADRC controller has the advantages of fast response speed and strong disturbance rejection performance.The effectiveness and feasibility of the proposed controllers are verified by simulation and experimental results.