A Distributed Control Strategy for State-of-Charge Balance of Energy Storage Without Continuous Communication in AC Microgrids

With the high penetration of renewable energy sources (RES), the energy storage system (ESS) units have been employed as critical components to compensate for the power fluctuation generated by RESs in an ac microgrid. However, it's a major challenge to achieve the state-of-charge (SoC) balance of ESS units due to the difference of initial SoC values and varied capacities. To deal with this issue, a distributed event-triggered control strategy has been proposed to realize the SoC balance among ESS units by regulating the virtual resistances. Compared with existing methods, only the local SoC of each energy storage is exchanged with the neighboring ESS units. Furthermore, by employing the proposed event-triggered mechanism, the data sampling and signal transmission are only conducted when the predefined triggering condition is satisfied, which effectively saves the usage of communication resources. Moreover, the stability and inter-event interval with the proposed control strategy is analyzed in this paper. Finally, several case studies are presented in the experiment where the presented approach shows its robustness against dynamic load and unexpected single-point communication failure.