The Study Of PWM Rectifier With Soft-switching Function

Three-phase voltage source PWM rectifier has been widely used because of its high power factor and low harmonic content of grid current.However,with the increase of switching frequency and power level of the rectifier,the switching loss of semiconductor devices also increases,which not only reduces the efficiency of the rectifier,but also easily leads to overheating or even burning of the switch devices.Compared with traditional hard-switching rectifiers,soft-switching rectifiers have lower switching losses,making it possible to achieve higher efficiency,higher power density and lower cost.Firstly,this paper describes the industry background and research significance of soft-switching three-phase PWM rectifier,compares and introduces the topology structure of various soft-switching rectifiers,and analyses their advantages and disadvantages.A soft-switching three-phase PWM rectifier with simple topology,low cost and easy realization of control algorithm is selected for this paper and the position of resonant element is adjusted to solve the problem of high turn-off voltage stress of the topology.Subsequently,the working principle of the topology and the realization process of soft switch are deeply analyzed.The phase-locked loop scheme and double-loop control strategy of soft-switching three-phase PWM rectifier are expounded.After analyzing their advantages and disadvantages,an improved modulation strategy is proposed to solve the current distortion problem caused by the original modulation strategy in small sector switching.In addition,the hardware circuit design of soft-switching three-phase PWM rectifier is introduced,including the selection of main devices,the sampling and protection circuits of each power quantity,and the design steps of resonance parameter group.Finally,the simulation model based on MATLAB/Simulink platform and the experimental platform based on the simulation model are built.The simulation results correspond to the experimental data one by one,which verifies the basic principle of the soft switch and the feasibility of the improved scheme.