Communication delay robustness for multi-agent state of charge balancing between distributed AC microgrid storage systems

This paper presents a communication delay robust multi-agent control strategy for state of charge balancing between energy storage systems in droop controlled AC micro-grids. Under the multi-agent control strategy microgrid energy storage systems communicate over a sparse communication network and adjust their output powers so that they approach a balanced state of charge, while regulating the microgrid frequency and voltage. The proposed control strategy provides a robustness condition for balanced communication topologies with uniform communication delays. The robustness condition depends only on the individual energy storage system dynamics and is thus scalable to microgrids with many ES systems. It is shown that the structure of the proposed control strategy preserves the normal synchronous frequency of the droop controlled microgrid, so frequency regulation is not affected. Simulations are presented demonstrating the performance of the proposed control strategy for an AC microgrid with variable PV generation and energy storage systems connected by a sparse communication network with communication delays.