A Unified Control Scheme for a Standalone Solar-PV Low Voltage DC Microgrid System With HESS

This paper proposes a combined adaptive droop-based load sharing, maximum power point tracking (MPPT), and energy management of photovoltaic (PV)-based dc microgrid system. A proportional droop index (PDI) algorithm is introduced, which is a function of normalized current sharing difference and voltage deviation at the output side of the converter. The proposed method calculates adaptive virtual resistance Rdroop, which allows the PV converter to operate at MPP or load sharing mode. By fine-tuning Rdroop values, the proposed method eliminates poor voltage regulation issues of the conventional droop method. The control of the hybrid energy storage system (HESS) with a battery and a supercapacitor (SC) is also discussed to stabilize the dc grid voltage and energy management of the dc microgrid. The detailed analysis and the design procedure of low-voltage (LV) dc microgrid systems are explained, and the effectiveness of the proposed method is verified by simulation and experimental studies.