Bi-Level Optimal Scheduling of Peak Shaving and Frequency Regulation Resources for Combined Thermal Generators and BESSs

Abstract

With the development of China electricity ancillary services market (EASM) and battery energy storage technologies, more integrated battery energy storage systems (BESSs) participate in the ancillary services market. Capable of providing ancillary services individually, thermal units can further improve the ancillary services quality with the help of BESSs. In order to study the optimal scheduling of peak shaving and frequency regulation resources for the combined thermal generators and BESSs (CTGB), a bi-level optimal model is established based on the rules of China EASM. The upper-level model optimally schedules all the peak shaving and frequency regulation resources from the ISO perspective. The lower-level model minimizes the operation costs of the CTGB with its frequency regulation performance considered. The linearized version of constraints in the lower-level model is formulated through the binary expansion method and the exact relaxation method. Additionally, by introducing the Karush-Kuhn-Tucker (KKT) condition, the proposed bi-level optimal model is transformed into a single-level optimal model. Numerical case studies show the validity of the proposed model and the importance of appropriately allocating BESSs to improve frequency regulation performance of thermal units.