Controller for combined peak-load shaving and capacity firming utilizing multiple energy storage units in a microgrid

In this paper, a controller capable of simultaneously providing both peak-load shaving and capacity firming required by renewable energy sources is proposed. This controller is designed to combine power/energy from multiple energy storage systems, including unidirectional systems such as fuel cells. Quick response energy storage systems such as ultracapacitors meet the requirements of initial fluctuations in power, and slower response systems provide the power for extended periods of activity. The rate of response of each energy storage system is a parameter known to the control system. The proposed algorithm improves the overall system's performance in terms of fast response, smart energy management, and ability to manage different energy storage and unidirectional/bidirectional sources. Simulations verify the operation of the control strategy in peak shaving mode and in steady state mode that can extend for a longer duration. Results show preferential power allocation to the quick response energy storage system, and limited power fluctuations on other sources.