Distributed Frequency Control of Heterogeneous Energy Storage Systems Considering Short-Term Ability and Long-Term Flexibility

Renewable energy sources introduce more fluctuations into the power system and bring challenges to maintain the system stability. Conventional generation units are gradually replaced and may soon become inadequate to meet the frequency regulation (FR) requirements. Consequently, demand-side resources for FR have received increasing attention. Among demand-side sources, inverter air conditioners (IACs) have huge regulation capacity and account for nearly 40% of the total power consumption in summer, while energy storage systems (ESSs) excel in rapid response and powerful ramp rate. However, the inadequate ramp speed of IACs and the insufficient regulation capacity of ESSs render them incapable of providing FR independently. To tackle this problem, this paper proposes a distributed coordinated control algorithm that allows the effective utilization of ESSs and IACs to provide FR considering the respective advantages. Firstly, an equivalent thermal energy storage model of IAC in alignment with ESS is introduced considering heterogeneous parameters. Subsequently, a coordinated control framework is proposed for heterogeneous ESSs (hetero-ESSs), which are composed of ESSs and IACs. Based on the framework, a distributed consensus algorithm is devised for hetero-ESSs, and its stability is demonstrated through the application of the Lyapunov theorem. Finally, numerical studies verify that the proposed framework can promote ESSs’ short-term ability and IACs’ long-term flexibility.