Multi-source PV-battery DC microgrid operation mode and power allocation strategy based on two layer fuzzy controller

Abstract

The conventional DC bus signaling (DBS) coordination control strategy for islanded DC microgrids (IDCMGs) faces challenges in coordinating multiple distributed generators (DGs) and fails to effectively incorporate the state of charge (SOC) information of the energy storage system, reducing system flexibility. In this article, a two-layer fuzzy control-based coordination strategy is proposed for multi-PV islanded DC microgrids. The first layer fuzzy logic controller (FLC) quantifies and selects the optimal system operating mode, adaptively adjusting the number of PV units operating in maximum power point tracking (MPPT) mode to manage system power surplus or deficit, thereby simplifying system design and enhancing flexibility. The second layer FLC adaptively adjusts the output of distributed energy sources based on SOC and current system conditions to better align the energy storage system's output with overall system operation, resulting in at least a 4% improvement in SOC level and effectively preventing overcharging or over-discharging issues seen in traditional control. Additionally, for PV units operating in droop mode, the droop coefficient is recalculated based on their maximum generation capacity under changing external conditions, thereby achieving more efficient power distribution and preventing system instability caused by power exceeding the limits of individual PV units. Finally, the effectiveness of the proposed control strategy is validated through RT-lab hardware-in-the-loop (HIL) simulations.