A novel resilient state of charge balancing method for distributed storage systems based autonomous microgrids

Abstract

In order to reduce the number of charge/discharge cycles of distributed energy storage systems (DESSs) to extend their lifespan, a State-of-Charge (SoC) balancing control is used. In conventional SoC balancing strategies, a local integral control is generally introduced in each DESS to ensure SoC equalization and Distributed Generators (DGs) frequency restoration. These strategies increase the system order and have a constraining bandwidth that may lead to stability issues. The few methods in which a local integrator is not added generally result in poor performance of the SoC synchronization strategy and frequency restoration, with the inability to eliminate static error. In this proposal, a novel resilient distributed control is proposed to ensure an effective SoC balancing of DESSs and frequency restoration with high performance without increasing the system order with a local integral control. The dynamic average consensus is modified to evaluate the participation level of each DESS in order to determine the active power references to synchronize the SoCs of the DESSs. These active power references are chosen to regulate the DG frequency to the nominal frequency of the MG. Therefore, the proposed method ensures SoC balancing with automatic frequency regulation and accurate output power sharing performance. Only voltage restoration control is added for DGs voltage regulation. In this distributed control architecture, SoC equalization as well as voltage/frequency restoration are performed only with local DG information and information from their neighbors. Simulations and then experimental results are performed to verify the effectiveness of the proposed method in discharging mode, in charging mode, in the presence of intermittent renewable energy sources, in the case of communication failure, in the case of communication delay, in the case of load variation, and in the case of “plug and play”. Comparisons were also made with two SoC balancing strategies from the literature.