Research On Sliding Mode Control Strategy Of Three-Phase Voltage Source PWM Rectifier

Because of its sinusoidal input current,unit power factor,bidirectional power flow and constant output voltage,the PWM rectifier can control the grid harmonics and reactive power "pollution" caused by rectifiers from the source,which is of great significance to ensure safe and economic operation of power grid and electrical equipments.Therefore,the research of PWM rectifier has gained wide attention.This paper takes three-phase voltage source PWM rectifier(VSR)as research object,designs and improves sliding mode control strategy to ensure excellent robustness,dynamic performance and static performance of the system.Firstly,this paper briefly introduces the commonly used control strategies of PWM rectifier and analyzes their advantages and disadvantages,then compares them with the sliding mode control strategy to show the superiority of the sliding mode control strategy.Secondly,the topology and working principle of PWM rectifier are introduced,then the mathematical models of three-phase voltage source PWM rectifier in abc static coordinate system and dq rotating coordinate system are established.On this basis,according to the sliding mode control theory and the design method of the sliding mode controller,the constant speed reaching law sliding mode controllers of three-phase voltage source PWM rectifier are designed,combined with space vector pulse width modulation(SVPWM)technology,the constant speed reaching law sliding mode control strategy with fixed switching frequency is obtained,then the control strategy is simulated and analyzed.Through analysis,it is concluded that there is a contradiction between the anti-disturbance ability and chattering of the constant speed reaching law sliding mode control system.It is necessary to introduce a disturbance observer to observe the disturbance and compensate it.Therefore,the extended state observer(ESO)is introduced into the design of the controllers to solve the contradiction above,and a reaching law with excellent performance is designed,then an improved approaching law sliding mode control strategy based on ESO is obtained,which suppresses the chattering while ensuring the robustness of the system.The corresponding model is built for simulation,and the simulation results verify the superiority of the proposed control strategy.Finally,the hardware system is designed according to the topology and control strategy of three-phase voltage source PWM rectifier.By selecting appropriate control chips and components,designing relevant hardware circuits,and programming in CCS,a complete experimental platform is finally established,then the proposed control strategy is experimentally verified.