Optimal coordination control strategy of hybrid energy storage systems for tie-line smoothing services in integrated community energy systems

Increasing renewable energy penetration into integrated community energy systems (ICESs) requires more efficient methods to prevent power fluctuations of the tie-line (connection of the ICESs to the main grid). In this paper, centrally-controlled air conditioners are considered as a virtual energy storage system (VESS). The optimal thermostat regulation is used to manage the charging/discharging power of the VESS within the customer comfort level range and the virtual state of charge (VSOC) is used to describe the charging/discharging power of the VESS. On this basis, the model of the hybrid energy storage system is built with a VESS and a battery storage system (BSS). Then, an optimal coordination control strategy (OCCS) for a hybrid energy storage system is developed considering the state-space equation to describe the OCCS, the constraints of the OCCS, and the objective function to express the optimal coordination control performance. Finally, the influence of the outdoor temperature and the deadband of air conditioners on the results of the OCCS is analyzed. Results show that the OCCS can realize optimal allocation of the storage response amount to trace the reference target accurately and guarantee both the state of charge (SOC) of the batteries in a reasonable range to prolong the battery life and ensure the level of comfort experienced by users.