Research On Active Disturbance Rejection Control Strategy Of Bidirectional DC-DC Converter In Independent Photovoltaic Power Generation System

In an independent photovoltaic energy storage system,the bidirectional DC-DC converter is used as an interface device between the DC bus and the energy storage unit,which can adjust the bidirectional flow of energy between the energy storage unit and the DC bus,thereby maintaining the stability of the DC bus voltage under the action of disturbance.If the DC bus voltage is not properly controlled,it will seriously affect the energy transmission between the photovoltaic power source and the load,and even trigger the related protection equipment.Therefore,the research on robust control of bidirectional DC-DC converters has always been a research hotspot.In order to effectively solve the problem of stable control of DC bus voltage under multi-source disturbance,this thesis proposes to design linear active disturbance rejection control（LADRC）in the voltage outer ring structure of bidirectional DC-DC converter to improve the immunity of DC bus voltage.This thesis takes the independent photovoltaic energy storage system as the research object and LADRC as the starting point.The main work is as follows:（1）In this thesis,the background and significance of the topic are introduced.For Buck/Boost bi-directional DC-DC converter,the linearized small signal model is constructed by using state space averaging method,and the principle analysis of common double closed-loop PI control method is carried out.（2）In order to solve the inadaptability of DC bus voltage to multi-source disturbance,LADRC is proposed to replace the traditional PI control.The structure and control principle of LADRC are analyzed.The potential problems of traditional linear extended state observer（LESO）are pointed out,and an improved LESO with error proportional feedback is proposed.Finally,through theoretical analysis and simulation verification,it shows the new control strategy can improve the tracking performance and disturbance suppression performance of DC bus voltage,and reduce the fluctuation range of DC bus voltage under multi-source disturbance.（3）In order to solve the problem of difficult parameter setting of traditional LADRC and further improve the immunity of outer loop voltage control system,a control method combining fuzzy control and LADRC is proposed.The strategy consists of a fuzzy proportional controller and LESO,and the fuzzy rules can select better control parameters.Finally,based on MATLAB/SIMULINK,the improved LADRC is verified under different operating conditions.