Balance Control Of Microgrid Based On Soft Normally Open Switch

Under the development concept of low-carbon and environmental protection,distributed photovoltaic power generation,electric vehicles and energy storage have been widely concerned with the advantages of energy saving and low pollution.Because the photovoltaic power supply and electric vehicle charging pile have the characteristics of large output and load fluctuation,and the control ability of independent micro grid is limited,its large number of applications put forward higher requirements for the stable operation of the superior distribution network.Therefore,based on the soft normally open point,two or more microgrids are connected to each other to realize the flexible interconnection between microgrids.Through the coordinated control of each part of the microgrid,it is very important to maintain the normal balance state of transformer load,load balance,power quality and the normal state of charge of the energy storage system in the microgrid,and reduce the impact on the superior distribution network Righteousness.Firstly,this paper describes the research status of distributed photovoltaic power generation,electric vehicles and micro grid flexible interconnection.The basic structure of microgrid is analyzed from three parts:photovoltaic power generation system,energy storage system and electric vehicle charging pile.Then,the simulation model of microgrid based on interconnection of interconnection switches is established in MATLAB/Simulink.Simulation results show that the power flow cannot be controlled artificially based on interconnection of interconnection switches,and there is circulating current.For the soft normally open point,the paper first analyzes the working principle and performance characteristics of various hardware topologies,compares the advantages and disadvantages,and finally selects the back-to-back converter as the topology of the soft normally open point in this paper according to the actual situation.Then,the control algorithm of soft normally open point is analyzed.Build simulation model in MATLAB/Simulink.The simulation results show that compared with the interconnection switch,the soft normally open point can control the transmitted power quantitatively without circulating current.In case of short circuit of one side microgrid,it can play the role of fault isolation and voltage support.Aiming at the balance control of micro grid system based on soft normally open point,this paper divides it into several working states based on the idea of finite state machine,analyzes the control objectives under each state,and then considers the objectives of load balance,power quality assurance,photovoltaic absorption and energy storage system protection under each condition,which are soft normally open point,photovoltaic power generation system,energy storage system.The corresponding control strategy is designed.In MATLAB/Simulink,the simulation under various conditions is carried out.The results show that after the proposed control strategy is adopted,the power balance between microgrids is distributed,the quality of load power supply is normal,the important load power supply can be maintained in case of failure.There is no overload of transformer and over charging and discharging of energy storage system,and the microgrid can be maintained in a balanced state.The feasibility of the control strategy is verified.Figure[73],table[5],reference[80]...