An efficient SoC-balancing based power management strategy for interconnected subgrids of DC microgrid

Abstract

In this paper, a coordinated power management strategy is proposed for voltage restoration, SoC balancing, and distributed power sharing among the interconnected subgrids of a dc microgrid (DC-MG). In the proposed strategy, coordinated secondary controllers are implemented on the upper layer of generalized primary controls of distributed generators (DGs) and interlinking bidirectional converter (IBC). The primary controllers can be implemented in a decentralized power management strategy using the dc bus voltage deviation of each subgrid. However, to eliminate the voltage deviations and to restore the dc bus voltage at their nominal value, secondary controllers are implemented to all distributed sources. The secondary controller may hamper the effectiveness of the decentralized power management technique. Hence, to resolve this issue, a coordinated secondary IBC controller based on SoC and charging/discharging power of energy storage system (ESS) is proposed. The proposed secondary IBC controller re-establishes a distributed power sharing strategy among the subgrids with limited information through low bandwidth communication (LBC). Further, a dc bus-signaling-based state transition strategy for PV, battery, and IBC controllers is proposed to optimize the performance of the battery and efficiently utilize the PV generations. The feasibility of the proposed strategy is verified by MATLAB simulation and OPAL-RT real-time digital simulator.