Active Disturbance Rejection Control Of Bidirectional AC/DC Converter For DC Microgrid Bus Voltage

Due to the advantages of DC microgrid in distributed energy access,controllability and flexibility,DC microgrid has become a research hotspot in recent years.Bidirectional AC / DC converter is an important component of DC microgrid.Maintaining its voltage stability is the key to ensure the stable operation and energy flow of DC microgrid.Therefore,around the application background of DC bus voltage control,this paper mainly does three parts of work.The details are as follows:(1)The topology structure of bidirectional AC-DC converter in DC microgrid is analyzed,and the mathematical model of three-phase AC-DC bidirectional converter in different coordinate systems is established.The advantages and disadvantages of the model in each coordinate system are pointed out.On this basis,the double closed-loop control strategy of bi-directional AC-DC converter is designed.The specific design methods of current inner loop and voltage outer loop are described.(2)Based on(1),a sliding mode active disturbance rejection control strategy is proposed by combining sliding mode control with active disturbance rejection control.The linear extended state observer is used to observe the state variables of the system,and the observed values are used in the design of feedforward compensation and sliding mode controller.The control strategy can not only reduce the number of sensors,but also ensure the robustness and dynamic performance of the system.(3)The contradiction between the output peak value and the observation accuracy of the traditional linear extended state observer in(2)is analyzed,and a variable gain linear extended state observer is proposed.It can effectively overcome the contradiction between the output peak value and the observation accuracy of the traditional linear extended state observer in the initial stage of operation.Finally,a DC microgrid bidirectional AC / DC system with sliding mode active disturbance rejection controller and variable gain sliding mode active disturbance rejection controller is built in Matlab/Simulink,and the bus voltage waveforms of DC microgrid under load fluctuation,parameter perturbation and photovoltaic grid connected conditions are recorded.The simulation results further verify the correctness and superiority of the proposed control strategy in this paper.