Power Regulation of Islanded PV-Battery DC Microgrid With Seamless Transition

In this article, a power regulation for islanded PV-battery DC microgrid with seamless transition is proposed under sudden load changes. In the power regulation, there are two modes, mode 1 for normal operation and mode 2 for the case where the load power is greater than the PV output, using droop control of PV to maintain the bus voltage and constant voltage control of energy storage to maintain the bus voltage, respectively. Mode 1 ensures that the battery is in a stable charging state and avoids frequent charging/discharging of battery. Mode 2 can maximize the use of PV energy. A seamless switching strategy without communication between the two modes is also established to suppress the fluctuation of bus voltage through the cooperation of PV and energy storage units, and a suitable switching timing is selected to avoid the sudden change of power during the switching process. Finally, the effectiveness and feasibility of the proposed control strategy is verified by the OPAL-5700 hardware-in-loop simulation platform.