| The rapid development of DC microgrid has been of great concern in recent years, and has been a good way to accept distributed renewable energy such as photovoltaic (PV) generation.Energy storage device is an essential component and key supporting technology in DC microgrid, how to effectively use and efficient management has an important role to restrain renewable energy generation and load fluctuations, stabilize DC bus voltage and improve the power quality and power supply reliability of DC microgrid.In order to solve the problem of unequal power allocation due to the difference of State of Charge (SOC) and converter for centralized battery energy storage devices in DC microgrid, a power sharing control strategy based on SOC unbalanced degree is proposed. In this method,the SOC unbalanced degree algorithm is introduced and the diagonal matrix of SOC unbalanced degree is constructed, the equilibrium state of the battery energy storage devices are determined by the SOC unbalanced degree threshold to obtain the reasonable power allocation instruction. The simulation and experimental results show that the proposed method can effectively control the centralized battery energy storage devices to achieve the power sharing.The power dynamic sharing control strategy of distributed battery energy storage device for DC microgrid is studied, and an improved droop control method based on SOC is proposed.The proposed method is able to dynamically adjust the droop coefficient through the SOC unbalanced degree algorithm, can control the SOC and output power of battery energy storage devices to achieve dynamic equilibrium. The traditional bus voltage secondary control is adopted to compensate the DC bus voltage drop caused by droop control and to maintain the stability of DC bus voltage. Simulation and experimental results verify the correctness and effectiveness of the proposed control method.Aiming at the problem of DC bus voltage fluctuation caused by renewable energy sources such as photovoltaic and loads, the virtual DC machine (VDCM) control strategy of energy storage interface converter is adopted. The working mechanism of VDCM and its improved control strategy and the principle of stable DC bus voltage are studied, and the small signal model of VDCM control system is established to analyze the influence of control parameters on the stability of the system. Compared with the traditional double closed loop constant voltage control, this paper discusses the effect of VDCM control strategy on the improvement of the bus voltage stability of DC microgrid with photovoltaic, energy storage devices and loads.The simulation and experimental results show that the VDCM control strategy has the characteristics of inertia and damping, which can enhance the inertia and damping of the DC microgrid, effectively buffer and suppress the influence of power fluctuation on the DC bus voltage, and improve the stability of the DC bus voltage. |
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