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 <inline-formula> <tex-math notation="LaTeX">$R_{\textrm {droop}}$ </tex-math></inline-formula>, which allows the PV converter to operate at MPP or load sharing mode. By fine-tuning <inline-formula> <tex-math notation="LaTeX">$R_{\textrm {droop}}$ </tex-math></inline-formula> 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.