Research On Cooperative Control Strategy Of AC/DC Hybrid Microgrid

With the increasingly serious energy problems,the application of renewable energy has attracted global attention.compared with traditional thermal power,characterized by heavy pollution,high energy consumption and insufficient resources,renewable energy has the advantages of efficiency and convenience as well as energy saving and emission reduction.However,in order to minimize the impact of renewable energy on the power grid because of its uncertainty and intermittent generation,it usually is first connected in the form of distributed power into the microgrid and then the large power grid.Combining the advantages of AC and DC microgrid,AC/DC hybrid microgrid has flexible topological structure and diversified operation modes,and can incorporate more distributed power supply.It can also be directly connected to DC load,which enhances the efficiency,flexibility and reliability of power supply of the distributed power grid.However,the connection of a large number of random distributed power of high permeability presents challenges to the stable operation control of AC/DC hybrid microgrid.This paper intends to study the distributed power control strategy in AC/DC hybrid microgrid in depth.Firstly,the distributed power supply(photovoltaic panel and battery)model and control strategy are introduced.The distributed power supply is connected to the microgrid through DC/DC converter.The DC/DC converter is modeled by using the state averaging method and the small signal model method,and the transfer function of the converter is deduced.And the microgrid system with photovoltaic and energy storage is simulated.Secondly,as the core device connecting AC microgrid and DC microgrid,Interlinking Converter(ILC)is responsible for power bidirectional flow.In this paper,the three-phase topology structure model of ILC in different coordinate systems is established,and four operating modes of hybrid microgrid are analyzed.Two common operating modes are studied for ILC control strategy respectively,and the AC/DC hybrid microgrid system under islandmode is simulated.Finally,in view of the frequent switching working mode of ILC and the unbalanced State of Charge(SOC)of multiple energy storage units in the microgrid,starting from the underlying control of the AC/DC hybrid microgrid,the power adaptive control is proposed for the photovoltaic system respectively,and the improved droop control of SOC value is proposed for the energy storage system.Then the photovoltaic system and the energy storage system are connected through the DC bus voltage signal.The photovoltaic system can adjust the photovoltaic working mode according to the load demand and the feedback of the energy storage SOC value,so as to realize the coordinated operation of the source,storage and charge,coordinate the balance of multiple energy storage SOC,and ensure the power balance and stable operation of the microgrid.The proposed cooperative control strategy is simulated on the Matlab/Simulink platform,and the simulation results that the proposed control strategy has a good control effect.