Research On Control Strategy And Hardware Design Of Three-phase Voltage Type PWM Rectifier

The traditional converter method has been gradually replaced by pulse width modulation(PWM)rectification technology due to the disadvantages of large harmonics and low power factor.The PWM rectifier has the advantages of unit power factor,grid-side current without distortion,four-quadrant operation and DC bus voltage stability,etc.It meets the country's demand for the development of a green energy-saving society and is widely used in high-performance AC drives and flexible AC transmission Variable field.At present,the research of PWM rectifier control technology still focuses on the traditional control strategy,and there are still limitations in the research of the voltage and current measurement errors in the sampling process of the PWM rectifier.In this paper,based on a detailed study of the working principle and topological junction of the PWM rectifier,the mathematical models of the switching function description and the duty cycle description are built respectively.After analyzing the advantages and disadvantages of the two mathematical models,the PWM rectifier is established in dq.The mathematical model of the two-phase rotating coordinate system,and analyzes the mathematical principle of the space pulse width vector modulation(SVPWM)adopted by the system and the derivation process of the output switching signal.The double closed-loop control of the rectifier is briefly introduced,and the design process and parameter design of the voltage outer loop and current inner loop are given respectively.In the actual operation of the PWM rectifier,after the voltage and current pass through the sampling conditioning link,the non-linearity of the sensor,the drift of the conditioning circuit,the quantization error of the AD converter,and the imbalance of the three-phase power voltage will cause the current and voltage measurement values to exist Gain-error and offset-error.Obviously,the traditional control method cannot realize the non-static error tracking of the sinusoidal input,nor can it suppress the voltage ripple on the DC bus side,which causes the grid-side current distortion and seriously affects the quality of the power grid.Aiming at the problems of AC side current distortion harmonics and DC bus voltage ripple caused by voltage and current measurement errors,this article presents a simple and effective solution to deal with the voltage and current measurement errors of three-phase voltage PWM rectifiers.Band-pass filter and low-pass filter to estimate the offset error and gain error in current measurement;the current inner loop connects the PI controller in parallel with two quasi-resonant filters to reduce the DC offset and gain error in voltage measurement.This method does not require additional hardware configuration,is not affected by sensors and system parameters,and can effectively suppress DC ripple and grid-side current distortion caused by measurement errors.Finally,on the Matlab / Simulink simulation experiment platform,a three-phase voltage-type PWM rectifier simulation model is constructed.The traditional PI control strategy and the voltage and current strategy error compensation strategy designed in this paper are simulated and experimentally studied,and the PI control is compared and analyzed.In combination with PI-QR control,the effect of voltage ripple suppression on the grid side is also studied and analyzed in detail in the case of sudden load changes and DC given voltage sudden changes.The experimental results and simulation waveforms verify the proposed control strategy Effectiveness and correctness.