Evaluation of BESS Management Strategies for Grid Primary and Enhanced Frequency Response

Maintaining the electrical power system frequency is becoming a severe challenge due to the increasing penetration of renewable generation schemes, which are highly dynamic and intermittent. System operators are investigating ways of solving this problem. The battery energy storage system (BESS) with a proper control strategy can be a suitable candidate to assist in regulating frequency. However, there are only a few reported specifications and management strategies for the use of BESS to assist the grid. This paper investigates the feasibility of two published frequency reserve strategies, and Primary Frequency Response (PFR) and Enhanced Frequency Response (EFR). A Lithium-ion (Li-ion) battery model is developed for this study. The battery cell model has been previously experimentally tested and dynamically assessed. The cell model is then expanded to a representative BESS of suitable size for future distributed power systems using published data for larger scale battery systems. This paper investigates the performance of BESS when battery terminal voltage variation, current, internal resistance and SoC when subject to PFR and EFR power demands. Four different energy management strategies are compared and alternative battery size and configuration analyzed. In addition, battery performance following existing strategies in real running conditions is examined and discussed in the paper.