Research And Implementation Of Digital One Cycle Control Three - Phase VIENNA Rectifier

With the increasing requirement of power factor in power electronic equipment,PWM rectifier with high power factor and low current harmonic component is widely used in medium and high power equipment.As a typical three-level rectifier topology,VIENNA rectifier has the advantages of low harmonic component of input current and low voltage stress of power devices compared with two-level rectifier.On the other hand,compared with other types of three-level rectifier,VIENNA rectifier also has the advantages of fewer power devices,fewer control signals and no risk of voltage through.However,three-level rectifier has the inherent problem of unbalanced neutral-point potential under traditional control strategy.Therefore,the research on VIENNA rectifier control strategy and performance optimization has important theoretical significance and practical value.Firstly,this paper briefly describes the background and significance of power factor correction and introduces the current development status of power factor correction topology and control strategy.It analyses the working principle of three-phase VIENNA rectifier,it furthert introduces one cycle control strategy technology and analyses the modified modulation mode.It obtains the core control function under one cycle control strategy with establishing the mathematical model of one cycle control VIEENA rectifier through state space averaging method.Secondly,in order to solve the problem of the inherent unbalance of neutral-point potential of three-level rectifier,the fundamental reason of unbalance of neutral-point potential was analyzed,and a three-harmonic injection method was adopted to balance the neutral point potential.On the basis of this method,an modified neutral-point balance control method that the equalizing vlotage ring is introduced.Based on PSIM simulation software,the simulation model of three-phase one cycle control VIENNA rectifier with neutral-point potential balance control is built.The simulation results verify the feasibility of the theory.Then,the VIENNA rectifier system structure with digital chip TMS320F28035 as the control core is designed.The hardware part introduces the calculation of three-phaseboost inductance,the selection of main circuit power devices,the design of sampling circuit,driving circuit and auxiliary power supply circuit of digital control module,and the software part introduces the implementation plan of system design and resource allocation,digital one-cycle control algorithm and the neutral-point potential balance control method.Finally,a 6 kW experimental prototype of three phase VIENNA rectifier is built.Based on the traditional one cycle control strategy,a modified neutral-point potential balance control method with third harmonic zero sequence component and equalizing voltage ring was tested.The experimental results show that the DC bus neutral-point potential of the VIENNA rectifier is effectively controlled after adding the neutral-point potential balance control method,and verifies the effectiveness of this control method.