Three-phase Voltage Source PWM Rectifier And Its Sliding Mode Control Strategy

Three phase voltage source PWM rectifier has been widely studied by scholars at home and abroad because of its two-way flow of energy,stable output DC voltage,unit power factor operation,sinusoidal input current and fundamentally reducing the impact of harmonics on the power grid.This paper takes the three-phase voltage source PWM rectifier as the research object.In order to make it have good dynamic and static performance,the sliding mode control strategy is adopted,and the control strategy is improved according to the problems of sliding mode control.Firstly,the principle of three-phase PWM rectifier is introduced,and the mathematical model in two-phase rotating coordinate system is derived based on the analysis of three-phase bridge topology.The traditional sliding mode controller based on exponential reaching rate is designed.It is found that the output voltage of three-phase PWM rectifier using sliding mode controller has chattering problem,and then a variable speed reaching rate is proposed to suppress chattering;At the same time,in order to improve the tracking accuracy of output voltage,a modified sliding function is added in the controller.Then,aiming at the problem that the improved sliding mode controller is not sensitive to the lumped disturbance,the extended state observer is introduced,and the observer is applied to the voltage outer loop sliding mode controller.Its characteristics are used to quickly estimate the lumped disturbance and compensate the control quantity,so as to improve the dynamic performance of the DC side output voltage of the rectifier and ensure that the system can converge quickly in the effective time.The sliding mode controller based on exponential reaching rate,the sliding mode controller with improved reaching rate and additional modified sliding function and the sliding mode controller with extended state observer are simulated.The simulation results show that the proposed control strategy can improve the chattering problem of the traditional sliding mode controller and has good dynamic response ability.Finally,the experimental platform of three-phase voltage source PWM rectifier is built.Through the experimental platform,the steady-state experimental verification and dynamic experimental verification such as voltage command mutation and load mutation are carried out.The experimental results show that the proposed sliding mode control strategy has stronger dynamic response ability than the traditional sliding mode control strategy based on exponential approach rate,the output voltage of DC side is more stable,the sinusoidal degree of AC side current is higher,and the harmonic content is less.