Size Optimization and Power Allocation Optimization of a Hybrid Energy Storage System for Grid Enhanced Frequency Response Service

Abstract

Aiming at the scenario where the energy storage system participates in the grid enhanced frequency response auxiliary service, this paper first establishes a frequency response model to provide power requirements for the ESS. A two-layer optimization approach is proposed to solve the size optimization problem. On the bottom layer, a mixed-integer linear programming technique is investigated to optimally allocate the power of the HESS. On the top layer, a size optimization framework is proposed to optimize the configuration of the ESS. The size optimization results show that comparing with the BESS, the capacity of the HESS was reduced by 64%, the battery aging cost was reduced by 52.5%, and the total cost was reduced by 35.1%. Based on the feature of the optimal power allocation result, a novel adaptive online power allocation method is proposed. Simulation results show that the adaptive power allocation method can fully utilize the advantages of batteries and supercapacitors. Finally, the case of a HESS participating in long-term enhanced frequency response is studied. Based on the optimal configuration and adaptive power allocation method, each energy storage unit works within the set power and capacity range, and the fluctuation of the battery power is significantly reduced.