Coordinated control of heterogeneous grid-connected energy storage systems

In this paper, it is demonstrated how the coordinated control of heterogeneous grid-connected Energy Storage Systems (ESSs) can result in increased profits compared to operating the ESSs independently when participating in the UK frequency market. A heterogeneous set of ESSs is made up of varying storage technology types, such as batteries, compressed air, and flywheels. The future mix of grid connected ESS technologies is likely to be increasingly heterogeneous and so effective coordination becomes increasingly important. For an example case where five ESSs have operating costs that vary over a range of 2.3:1, costs are reduced by 17% through coordination compared to operating the ESSs independently. The proposed algorithm is practical, has low computational overhead, and importantly, meets all frequency response rules in the event of communication failure. A heartbeat mechanism, which requires round trip communication times of less than 150ms, is used to handle communication failure. Experimental results are presented, demonstrating that this round trip time is feasible with modern communication systems. The practicality of the novel algorithm, combined with the heartbeat based fault handling, makes it readily implementable in real-world distributed ESSs.