Research On Intelligent Control Strategy Of Three-phase Voltage PWM Rectifier

Due to the advantages of low distortion rate of current on the grid side,constant output voltage on the DC side,bidirectional flow of possible quantity and unit power factor operation,the Pulse Width Modulation(PWM)rectifier is widely used in power electronics technology,industrial production,transportation and other fields.It is the key part to realize the "green transformation" of energy saving and electricity.Three-phase PWM rectifier is a strong coupling nonlinear time-varying system with multi-input and multi-output.The system often encounters uncertain conditions such as load mutation,system parameter change and external disturbance in the actual operation process.It is difficult to obtain ideal control effect by using traditional linear control.For three-phase PWM rectifier,it is still the core issue of current PWM rectifier research to explore the multi-input multi-output nonlinear control strategy with strong robustness,strong adaptability and strong disturbance rejection ability.The active disturbance rejection control method has the characteristics of nonlinear function with variable combination,which does not depend on or does not completely depend on the precise mathematical model of the system,and has the characteristics of high control precision and strong disturbance rejection ability.Fuzzy control can use mathematical means to imitate people’s thinking process to a certain extent,fuzzy recognition and fuzzy decision for complex things,and is good at making use of imprecise and incomplete information.These characteristics of active disturbance rejection control and fuzzy control provide substantial help for the control of multi-input and multi-output strongly coupled nonlinear systems such as PWM rectifier.In this paper,the three-phase voltage-type PWM rectifier is taken as the research object,and a new fuzzy active disturbance rejection controller is designed to provide support for the control of multi-input multi-output strongly coupled nonlinear system such as PWM rectifier.The specific research content is as follows.Firstly,the working principle of three-phase voltage type PWM rectifier is summarized.Further,based on Kirchhoff’s voltage and current law,the mathematical model of the rectifier in three-phase static coordinate system,two-phase static coordinate system and two-phase synchronous rotation coordinate system is derived,which lays the foundation for the subsequent control strategy design of the rectifier system.Secondly,for three-phase voltage PWM rectifier,nonlinear active disturbance rejection control strategy is used to replace the traditional PI control strategy.The principle,structure and parameter setting of active disturbance rejection controller are analyzed,and continuous and smooth qin function is constructed to design the expanded state observer and nonlinear error state feedback law.In this way,the phenomenon of high frequency tremor in the operation of the traditional extended state observer can be improved.Thirdly,when the internal parameters of three-phase voltage-type PWM rectifier change and external interference,the traditional double closed-loop PI control strategy has the problem of poor dynamic and disturbance resistance.The active disturbance rejection controller is adopted to replace the voltage outer loop control,and the disturbances inside and outside the system are estimated and compensated by the extended state observer,so as to realize the linearization of the rectifier system.In order to solve the problem of difficult parameter setting and bandwidth limitation of active disturbance rejection controller,fuzzy controller is introduced into the nonlinear state error feedback law of active disturbance rejection controller for parameter self-tuning.Combining the advantages of the two controllers,the simulation results show that,Compared with traditional PI controller and active disturbance rejection controller,fuzzy active disturbance rejection controller effectively improves the dynamic response performance and robustness of the rectifier system.Finally,by building the experimental prototype of three-phase voltage PWM rectifier,the hardware design and software design of the experimental prototype are introduced,and the designed fuzzy active disturbance rejection controller is verified experimentally.The experimental results show that compared with the traditional PI control method,The fuzzy active disturbance rejection control method designed in this paper can improve the dynamic response performance and anti-interference ability of three-phase voltage type PWM rectifier,which proves the feasibility and superiority of the algorithm.