A DC Droop-Based Optimal Dispatch Control and Power Management of Hybrid Photovoltaic-Battery and Diesel Generator Standalone AC/DC System

This article deals with the parallel operation of photovoltaic (PV), battery energy storage (BES), and diesel generator (DG) for standalone ac/dc system. It is known that the maximum penetration of PV systems in DG-based power system is limited in the range of 40%-60%. When the PV capacity becomes comparable to DG capacity, the system suffers from stability and synchronization issues. Hence, this article proposes a dc droop-based hierarchical control of the PV-BES-DG system based on dc integration at a common dc bus. The dc integration alleviates the scalability limit on PV and facilitates better control of the hybrid system than ac counterpart. Moreover, an optimal regulator-based secondary control is proposed to ensure optimal load sharing among DG and BES. Further, a power management scheme (PMS) is designed to ensure reliable operation of the standalone system during source and load power imbalances and operation under critical state of charge limit condition of BES. Also, the PMS constraints the operation of DG below a defined low-level loading. Further, small signal stability analysis is presented to analyze the effects of droop and optimal regulator gain on the system's stability. The laboratory-scale prototype is developed to evaluate the performance of proposed PMS and dc droop-based hierarchical control of the PV-BES-DG system.