Research On High Frequency Performance Of Three Phase Vienna Rectifier

Three phase PWM rectifiers have been much more widely used because of increasing demand of large power applications.Vienna rectifier is a hotspot with advantages of low swicth voltage stress,high power density,high efficiency and low THD.This paper focuses on three phase three line topology for small current ripple and traditional double loop control strategy for low complexity.Firstly,this paper analyses topology structure and operation modes of Vienna rectifier.Mathematical model is derived in abc natural coordinates.Harmonic analysis of the voltage across inductor is obtained based on equivalent simplified circuit.Then the inductor current ripple characteristic can be achieved.From the theoretical analysis results,the switching frequency component in current ripple is reduced markedly in three phase three line Vienna.As a result,amplitude of current ripple in three line Vienna than four line topology.When it comes parallel structure,two channel interleaving topology can cancel switching frequency component in input bus current.However,interleaving can result in drastically increasing of switching frequency component in inductor current ripple.Theoretical conclusions are verified by simulation in PLECS and experimental results.Secondly,this paper presents digital control strategy based on load feedforward to optimize output dynamic response of Vienna rectifier.Load step detection algorithm is adopted to determine the moment that feedforward calculation works.PI compensator works alone during stable state.Therefore the line frequency sinusoidal current waveforms are not disturbed by feedforward compensation.Frequency response characteristic is achieved with the modelling of voltage loop.Simulations in Saber and experimental results both verified the feasibility of control strategy.Finally,discreteness and delay of digital control are analysed in this paper.Achievable control frequency of several typical DSP products is given with consideration of performance parameters.Then the selection suggestions of digital controller for Vienna are given.In the end,this paper builds 3kW Vienna rectifier prototypes.Efficiency curves and loss analysis are presented.At last,GaN transistor is used in Vienna to further optimize efficiency.