Research On Three-phase Voltage Source PWM Rectifier

Voltage Source Pulse-Width Modulation Rectifier(refer to as VSR) has become a hotspot in power electronics research area recently, due to its special characteristics of controllable power factor, ideality for non-low harmonics and bidirectional flow of energy, etc. It effectively solves the harmonics problem in rectifier system, By studying on the three-phase VSR, this paper expounds the characteristics analysis and implement of VSR system, and provides a more comprehensive design approach. It includes the establishment of system model, the design of main circuit parameters, the design of control system and simulation results.Based on studying the topology of three-phase VSR, this paper particularly analyzes the switching process of main circuit; and establishes the mathematical models using switching function in abc coordinate system and dq coordinate system, respectively. Furthermore, the selection principle of main circuit parameters is determined by considering the steady-state and transient state in which VSR system works in normal conditions, then, the calculation formula is given.Considering that the current control method determines the input performances of whole three-phase VSR system, this paper discusses the direct and indirect current control methods, as well as a detailed comparison of abc coordinate system and dq coordinate system fixed switching frequency direct current control scheme, and come to conclusion that the scheme in dq coordinate system satisfies better static and dynamic performance. Because of fluctuation of power system and the coupling of mathematical model in dq coordinate system, this paper presents a current feedforward decoupling control method. Through this method, the current control model can be represented by a first order link, so the active or reactive current can be controlled independently to simplify the system control structure. After a reasonable approximation, engineering method of the double-loop control is applied to design the PI regulators.Finally,this paper designs a practical three-phase VSR system. Through the MATLAB/Simulink simulation platform, a system dynamic model and circuit model are established. Dynamic model simulation and circuit model simulation verify the effectiveness of the PI regulator design and feedforward decoupling control scheme, respectively.