Research And Design Of Energy Storage Converter In AC Microgrid

With the rapid development of China's economy,China's power system is facing the problem of continuous growth of power load and unreasonable power supply structure.Combining energy storage with distributed power generation to form a microgrid is an important means to solve energy and environmental problems.The AC microgrid has the advantages of flexible configuration,easy expansion,and easy maintenance,so it has gradually become a research hotspot in the field of microgrid.Structurally,all distributed power and energy storage units are connected in parallel to the AC bus via a converter.When connected to the grid,the energy storage unit can quickly stabilize the system power fluctuation caused by distributed power generation,and can also store the surplus power in the system.When operating off-grid,the energy storage unit maintains the stability of the AC bus voltage and frequency.Based on these,this paper studys the constant power control and constant current/constant voltage control under the grid connection of energy storage converter,and the constant voltage constant frequency control under the off-grid condition,Then the simulation model is established and verified by experiments.Specifically,the main work of the paper includes the following:(1)Explain the overall structure of the AC microgrid and analyze the internal energy flow.Considering the advantages and disadvantages of the energy storage converter structure type,the voltage three-phase bridge topology is selected,and the mathematical model of the topology under the three-phase stationary coordinate system and the two-phase rotating coordinate system is established.(2)According to the operating conditions of the AC microgrid,the constant power control,constant current/constant voltage control and constant voltage constant frequency control of the energy storage converter are proposed.In order to realize the fast and accurate phase locking of the phase-locked loop in the non-ideal grid environment,a decoupling software phase-locked loop based on double dq transform is designed.(3)The system model is built in the MATLAB/Simulink simulation environment,and the constant power control and constant voltage/constant current control under the grid connection of the energy storage converter are realized,and the constant voltage constant frequency control under the off-grid is realized.(4)Complete the hardware and software design of the whole system.The hardware part mainly includes the main circuit,signal conditioning circuit,protection circuit and drive circuit.The software part mainly includes the main program,the interrupt program,each function subroutine,and adopts the modular idea optimization program.(5)Finally,an experimental platform for energy storage converter based on DSP28335 control chip is built.The operation of the energy storage converter under three control strategies is verified experimentally.The experimental results show the feasibility of the design.