Research On Control Strategy Of Three Phase PWM Rectifier Based On Decoupling Unit Of Positive And Negative Sequence Component Seperation

Three phase voltage source PWM rectifier is a kind of widely used powerconverters, and the power quality transformed by the rectifier has always beenone of the properties of attention. Taking three phase voltage source PWMrectifier as the research object, the paper studies the grid vo ltage oriented vectorcontrol based on the two phase synchronization rotating coordinates in theconventional circumstances of balanced grid voltage, and also the quasi directpower control based on the two phase stationary coordinates. The nonlinear SMCalgorithm is applied to the outer voltage loop. According to the unbalanced casesof the grid voltage, this paper puts forward a method of extracting the positiveand negative sequence components based on the decoupling unit in theapplication of unbalanced control strategies. The good performance of thecontrol has been verified through simulation. The hardware platform has beenbuild, and the parameters of the main circuits and the controll er’s compensationhave been designed. The software design of the grid voltage oriented vectorcontrol algorithm has been done with the use of modular idea programming, andsome preliminary PWM rectifier experiments have been done at the moment.First of all, the operation states of three phase voltage source PWM rectifierhave been analyzed. The switch function models of PWM rectifier in threecoordinate have been constructed according to the circuit theory, and alsoincluding the models in the circumstances of unbalanced grid voltage.Secondly, the grid voltage oriented vector control algorithm has beenresearched, realizing the sinusoidal waveform of ac current and in phase with thegrid voltage operating in the unit power factor. The quasi direct power co ntrol isrealized with the use of calculation of reference current consideringinstantaneous power in the two phase stationary coordinate without using thecomplex link for detecting the phase angle of grid voltage. The SMC algorithm isused to the outer voltage loop to improve the robustness of the system,strengthening the perturbation of DC side voltage.Thirdly, according to the special case of unbalanced grid voltage, this paperuses the independent control strategy of two sets of positive and nega tivesequence synchronization rotating coordinate, bringing a method based ondecoupling unit different from the conventional notch method into detectingpositive and negative sequence components, eliminating the interacts betweenpositive and negative sequence components well. And the feasibility of thealgorithm is verified with the simulation. At last, the hardware platform is build and the parameters of ac inductanceand dc capacitor in the main circuit are designed, including the controller’scompensation network. The TMS320F283335of TI Company has been adoptedas the control chip, and the software design is completed for the system usingmodular programming, including the overall process. Some preliminaryexperiments of the three phase voltage source PWM rectifier composed with IPMpower devices have been done.