Output Power Analysis of Grid-connected Battery Energy Storage Systems Providing Different Frequency Modulation Services

The fast response and stable power tracking ability of battery energy storage system (BESS) make it potential in providing frequency modulation (FM) services to power grid. The output power characteristics of BESS when providing FM services are important for the state of health of battery. However, the current studies mainly focus on BESS output characteristic at smaller timescale when providing FM service to power grid, and the long-term analysis is lacked. This paper focuses on the long-term output power characteristics of BESS when providing different FM services, where the real frequency data of the UK power grid is adopted for analysis. Firstly, the frequency is converted to load power increment based on the power-frequency relationship. Then, the control systems of BESS and frequency dynamic models for two different scenarios, i.e., primary FM (PFM) and primary & secondary frequency modulation (PFM&SFM) are developed. By inputting the transformed load increment data to the frequency dynamic model with FM services, the dynamics of grid frequency, active power of synchronous generator (SG), and output power of BESS are obtained. The BESS output power in different FM scenarios is compared, and the indexes of battery during FM are analyzed.