Research On Dynamic Power Management And Control Strategy Of AC/DC Hybrid Microgrid

In the past decades,with the popularization of renewable energy sources(RESS)and the promotion of policies to reduce fossil fuel resources,the concept of microgrid has become more and more popular.AC/DC hybrid microgrid is a new type of microgrid which has the advantages of both AC microgrid and DC microgrid in recent years.It has the advantages of cooperating with the large grid to receive distributed energy efficiently and at the same time,it can give full play to the potential of distributed generation(DG).It is the research frontier in the field of power system in order to ensure the safe and reliable operation of microgrid The research of rate management control strategy is an important part of further exploring the key technologies of microgrid,and the research of bidirectional AC/DC power converter control strategy,which coordinates the power of two microgrids,is the basis of realizing the power management control strategy.Firstly,the paper introduces the structure of AC/DC hybrid microgrid system,and explains the mathematical model of photovoltaic,battery and super capacitor(SC),the operation principle of electric vehicle charging station,the basic structure and mathematical model of bidirectional AC/DC power converter,and analyzes the basic control strategy of battery,super capacitor and electric vehicle charging station.In view of the lack of a mature power management and control strategy for islanding microgrid,the power distribution of hybrid energy storage system and electric vehicle charging station can be adjusted by adjusting the current distribution coefficient λ while keeping the DC bus voltage constant,a power management and control strategy for islanding microgrid based on hybrid energy storage and electric vehicle charging station is proposed.According to the state of charge of hybrid energy storage and electric vehicle charging station,nine mode switching conditions are set in the control strategy.When the state of charge of hybrid energy storage system and electric vehicle charging station is reasonably controlled,the purpose of power sharing between hybrid energy storage and electric vehicle charging station is realized.In order to solve the problem that the DC voltage droop control method based on the traditional DC voltage droop control method will generate the circulating power in the AC-DC hybrid microgrid due to the influence of the line resistance,a droop control method is proposed by superimposing a small AC voltage signal on the DC voltage of the DC sub microgrid to distribute the power between the DC and AC sub microgrid.Among them,the frequency of the AC signal is directly proportional to the corresponding output power.Therefore,the transmission and distribution of power can run without any communication network,which improves the accuracy of power distribution.In addition,since the added signal frequency has the same value for all bidirectional AC/DC power converters,the power distribution will not be affected by the line resistance,so the method can also solve the problem of circulating power between the two power grids.Finally,based on MATLAB/Simulink,an hybrid AC/DC microgrid based on hybrid energy storage and electric vehicle charging station is built to verify the feasibility and effectiveness of the proposed control strategy.