| Early rectifier circuits were constituted by uncontrolled diode and half-controlled thyristor,which had simple structure to achieve the circuit easily.But the early rectifier circuit had higher harmonic component and absorb reactive power to the grid,which had a certain amount of pollution on the grid.PWM rectifier has replaced the early rectifier circuits due to the input current harmonic distortion rate is low;grid side current is sinusoidal;electricity two-way transmission;high power factor and other advantages.At first,this article analyzes the topology and four quadrant operation principle of three-phase voltage PWM rectifier.Establishing the mathematical model in threephase static coordinate abc and two-phase static coordinate ?? by coordinate transformation theory.Secondly,introduces the traditional direct power control strategy,aim at the unfixed switching frequency and grid side current harmonic component is high and other disadvantages,proposing the control strategy of three-phase voltage PWM rectifier direct power control is based on model predictive,which achieve double closed-loop control,by using SVPWM technology to achieve fixed switching frequency.In order to reduce the cost of the system,proposing the control strategy of three-phase voltage PWM rectifier model predictive direct power control is based on virtual flux,through designing the virtual flux observer to observe the flux,which can eliminate the AD side voltage transformers to improve the efficiency of the system.Thirdly,setting up the simulation models in the MATLAB/Simulink for the two strategies,which to verify the superiority of the two strategies by simulation and comparison analysis.Finally,on the basis of theroretical analysis,in view of the two PWM rectifier control strategies has carried on the overall design of system.Design the hardware circuit of system,such as main circuit,control circuit,detection circuit,drive circuit and so on,and design the software process for the system. |
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