Research On Micro-source And Energy Storage Control Strategy Of Hybrid Microgrid

With the continuous development of renewable energy,more and more distributed power sources are assembled to form micro-grid.AC/DC hybrid micro-grid has become a research hotspot because it combines the advantages of AC micro-grid and DC micro-grid to improve the utilization efficiency of new energy.The interconnection converter and energy storage equipment are important devices to coordinate the power balance of AC/ DC hybrid microgrid,which have important research value and practical significance.This paper first studies the DC constant voltage control strategy of the hybrid microgrid interconnected converter in the grid-connected mode.By analyzing the droop characteristics of the microgrids on both sides in the islanding mode,an equivalent range control strategy of the interconnected converter is proposed to realize the autonomous control of the interconnected converter.Then,the threshold method is used to realize the power self-coordination between the interconnected converter and the energy storage device,which can avoid unnecessary action of power electronic devices and reduce harmonic interference.In this paper,a control strategy of interconnected converter based on mode switching and comprehensive droop control is proposed to solve the problem of unnecessary power flow caused by the use of existing control strategies for interconnected converter.This paper points out the operation rules,mode selection method and application scope of the control strategy,gives the calculation method of the comprehensive droop coefficient,and designs the current compensation link in the smooth mode switching.The Simulink simulation results show that the frequent power flow can be reduced and the phenomenon of sub-microgrid operation crossing the boundary can be avoided.Finally,in view of the problem that the coordinated control of photovoltaic energy storage in island mode increases the complexity of the system,this paper proposes a comprehensive control strategy without complex programming to realize the power coordinated control of microgrid system.Considering the charging state of energy storage and the reference voltage deviation of DC bus,a multi-loop power control strategy is constructed in the front stage structure,which can effectively prevent the charging state of energy storage and the sudden change of DC bus voltage and realize the power balance of the front stage.In addition,the virtual synchronous generator control strategy is adopted for the main inverter of the latter stage of the microgrid to realize the voltage frequency control and load following of the microgrid,and the constant power control strategy is adopted for the secondary inverter to provide constant power to the microgrid.