Research On Operation Control Of Wind-solar-storage-AC-DC Hybrid Microgrid

In recent years,the problems of environmental pollution and energy crisis have become increasingly serious,which has aroused widespread concern.In order to solve these problems,many scientific research organizations pay attention to the development and utilization of clean and renewable energy,such as wind energy and solar energy,thus the wind photovoltaic storage AC and DC hybrid microgrid arises at the historic moment.The microgrid includes not only wind power,photovoltaic and energy storage systems,but also AC bus and DC bus,which has all the advantages of AC microgrid and DC microgrid.However,because of its many microsources and complex structure,it is prone to appear voltage and frequency fluctuations and power imbalance in the process of operation and control.In view of the above problems,this thesis studies the operation control of the wind photovoltaic storage AC and DC hybrid microgrid.The main work done is as follows:(1)The structure of wind photovoltaic storage AC and DC hybrid microgrid is established.The working principles of wind power generation,photovoltaic power generation and energy storage system are introduced,and their mathematical model and MATLAB / Simulink simulation model are given.At the same time,the basic principles of several commonly used microgrid control methods are analyzed and introduced.(2)Based on the research of work(1),the working principle and model of bidirectional interconnected converter in AC / DC hybrid microgrid system are analyzed and studied.A robust droop control method for grid connected photovoltaic system is proposed.In this method,an integral sliding mode controller is designed in the double closed-loop control current inner loop control structure of the bi-directional interconnected converter,which is used to suppress the voltage and frequency fluctuation of photovoltaic power generation system in the process of grid connection.Finally,the effectiveness and superiority of the method are verified by simulation examples.(3)Based on the research of work(1),a double-layer master-slave control system for wind thermal storage microgrid is designed,and its structure and three main operation modes are given.An improved droop control method is proposed for the operation of the double-layer master-slave control system of wind thermal storage microgrid under the condition of lowvoltage island,and its working principle is introduced.Finally,the feasibility and superiority of the system and its control method are verified by simulation examples.(4)Based on the research of work(2)and(3),the simulation model of wind photovoltaic storage AC and DC hybrid microgrid is established.Through the analysis of its working conditions in several different operating states,such as grid connected operation,off grid operation,grid connected and off grid switching operation,the effectiveness and stability of the control strategy proposed in this thesis are verified.