Robust control design for integration of energy storage into frequency regulation

An H_∞-based decentralized robust control approach is proposed in this paper to integrate energy storage into primary frequency control and to address increased frequency deviations introduced by renewable energy sources (RESs). The proposed new primary frequency control design is formulated as an H_∞ minimization problem with decentralized static output feedback. The three objectives are: 1) to minimize frequency deviations; 2) to minimize the use of energy storage devices; 3) to minimize the ramp rates required from conventional generators. A so-called frequency separation objective is achieved, i.e. low frequency variations of the RES power fluctuations are balanced by the conventional generators while the high frequency variations are compensated by the storage device. The detailed derivation of an interconnected power system model based on component-level models is provided to facilitate the control design. In order to evaluate the performance loss due to controller decentralization, a centralized counterpart of the proposed approach is presented and tested as well. Simulation results on the WECC 9-bus test system illustrate the performance of the proposed control.