Design And Research Of Three Phase Voltage Source PWM Rectifier On Double Loop Control

The traditional uncontrolled rectification and phased rectification methods have the disadvantages of low power factor and large harmonics,which cause pollution to the power system and arouse the attention of the academic community.The PWM rectifier overcomes the shortcomings of traditional uncontrolled rectifiers and phased-controlled rectifiers.It has a power factor controllable,can achieve bidirectional(rectifier/inverter)unit power factor operation,AC side current waveform sinusoidal,the system has a fast dynamic response,Direct current control is easy to control system design,etc.Therefore,in high-performance power electronics applications and devices that have higher technical requirements,they are favored by academic circles and have been increasingly used.This paper takes the three-phase voltage-type PWM rectifier as the research object,and focuses on the application and realization of the nonlinear control method in the power electronic system.This paper is based on the topological structure of three-phase voltage type PWM rectifier,and analyzes its working principle.It establishes the mathematical model under three-phase stationary coordinate system and two-phase synchronous rotating coordinate system.The range of the inductance and capacitance of the main circuit was analyzed and calculated.The realization of the traditional SVPWM control algorithm is studied.In view of the complexity of the implementation of this method and the low execution efficiency of the controller,a novel differential SVPWM method is proposed.This method starts with the voltage and uses the voltage relationship to determine the sectors.It greatly simplifies the SVPWM algorithm process and has a small amount of calculation.It is suitable for real-time and high-precision control.Based on the double closed-loop controller structure,the traditional current closedloop PI linear control method is analyzed,the limitations of the nonlinear system are pointed out,the nonlinear control theory is applied,and a sliding mode variable structure voltage loop based on load current feedforward is proposed.Variable-structure current loop double closed-loop optimization design scheme for input and output linearization.In order to verify the superiority of the hybrid nonlinear control scheme proposed in this paper to the disturbance of dynamic response,traditional PWM closedloop PI vector control and nonlinear hybrid control PWM rectifier system simulation models were established respectively in Simulink.The scheme can improve the system steady-state characteristics,and can effectively reduce the voltage fluctuations caused by external disturbances,and accelerate the response speed of the grid-side current.In order to achieve the hybrid nonlinear control strategy of the three-phase voltagetype PWM rectifier system proposed in this paper,an experimental prototype with a power level of 33 k W was designed.The main hardware part and DSP program structure were introduced in detail.The dynamic steady-state experiments were conducted under resistive linear load and non-linear load of the inverter.The results show that the nonlinear control method based on the double closed-loop control structure can be used.The three-phase voltage source PWM rectifier can operate with unit power factor and has input current.Harmonic distortion is low,the advantages of fast dynamic response.