Decentralized Control Coordination of PV-BSS Systems in Islanded DC Nanogrids

Solar photovoltaics (PV s) and battery storage systems (BSSs) are two important distributed energy resources that can bring measurable environmental and economic benefits to the power grids. In this paper, a decentralized strategy is presented for coordinating the control of PV sand BSSs in islanded DC nanogrids. Depending on the measured DC bus voltages, PVs can adaptively switch between the V-P droop mode and the maximum power point tracking (MPPT) mode, thus reducing the impact of transient disturbances on the system operation. In addition, the dual active bridge (DAB) DC-DC converters are employed to interface BSSs to the nanogrid due to the converter's high-performance power conversion capabilities. To prevent overcharging/ discharging of batteries, a state of charge (SoC)-based adaptive droop control method is proposed. The control of PVs and BSSs is coordinated in a communication-less fashion to maintain the nanogrid load balancing, as well as to regulate the common DC bus voltage. The proposed control strategy is easy to implement with reduced complexity, while its satisfactory dynamic performance is demonstrated via numerical simulations using MATLAB/Simulink.