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Research on Control Strategy of Hybrid Energy Storage System in Islanded AC Microgrid Based on Virtual Impedance
According to To realize the distributed control of the hybrid energy storage system (HESS) in an island AC microgrid (AC-MG), a dynamic HESS power sharing strategy based on the virtual impedance for the supercapacitor (SC) and the storage battery (Battery) is proposed. Dynamic power sharing of two kinds of energy storage devices can be realized without real-time measuring of load power. The theoretical principle of dynamic power sharing of HESS is derived based on the establishment of HESS equivalent circuit model. By analyzing the influence of the voltage and current double loop control parameters on the output impedance and the virtual impedance of the DC-AC converter, the method of setting the control parameters for power distribution is given. On this basis, a simulation model of HESS is established. Two typical equivalent power fluctuation conditions are designed, and the operation characteristics of HESS under various operating conditions are analyzed. The simulation results show that, under various working conditions, HESS can compensates the high frequency part of the equivalent power fluctuation by controlling the supercapacitor series virtual capacitor (VC), while the battery series virtual resistor (VR) absorbs the low frequency part of the power fluctuation, the dynamic power sharing is realized effectively, and the robustness and reliability of the system are improved.