| Three-phase Voltage-Source PWM Rectifier (VSR) has been widely used in recent yearsbecause of its superior performance, such as unity power factor, high quality DC voltage ofoutput, low distortion input current. And in the actual operation of the three-phase voltagesource PWM rectifier, there will be irregular phenomenons such as critical collapse of voltage,control system intermittent instability, unknown electromagnetic noise. So from theperspective of the nature of that three-phase voltage source PWM rectifier belongs to thenonlinear system, using the nonlinear dynamics to research irregular phenomena ofthree-phase voltage source PWM rectifier helps to understand the operation of the three-phasevoltage source PWM rectifier and has practical significance to the application of three-phasevoltage source PWM rectifier.To elaborate the mechanism of the dc voltage collapse phenomenon of three-phasevoltage source PWM rectifier, this paper establishes the closed loop model of three-phasevoltage source PWM rectifier. And then according to different types of load, the influence ofload parameters on voltage is analysed on the basis of the theory of nonlinear dynamics.Finally the results are verified by the simulation and experimental.The main work of this paper includes following fields:1. Takes voltage loop and current loop to control the three-phase VSR, and then analyze thedc voltage collapse phenomenon from the two perspective of which the the system’sconservation of energy and over-modulation analysis of PWM, and establish the closedloop model of three-phase voltage source PWM rectifier.2. Use Jacobi matrix method to analyze the changes of locus diagram of characteristic rootload resistance R and filter capacitors C in dc side changes of three-phase voltage sourcePWM rectifier with pure resistive load. And the critical value of R and C when the dc sidevoltage collapse is concluded.3. For the close loop model of three-phase voltage source PWM rectifier withresistance-inductance load, the area of stable operation is obtained through calculationcharacteristic root value of Jacobi matrix under different load resistance R. Then based onthe closed loop model of system, draw the local trajectories of motion of each state valuewhen changing the load resistance R. Therefore the critical value of R is concluded whendc side voltage collapses.4. Similar to the analysis of three-phase voltage source PWM rectifier withresistance-inductance load, three-phase voltage source PWM rectifier with reverse EMF (Electromotive Force) load is analysed, and the critical value of R and reverse EMF E areobtained.5. All of the above analytical solution are verified by Matlab/Simulink simulation. Moreover,based on the RT-LAB semi-physical simulation platform structures, experimental circuitof three-phase voltage source PWM rectifier is established and the related experimentverifies the voltage collapse phenomenon. |
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