For the problem of large-scale battery energy storage(BES) system participating in the secondary frequency regulation

a hierarchical coordinated control strategy considering the state of charge(SOC) of the BES is proposed. At the area control center level

a power allocation strategy for the secondary frequency regulation considering the area regulation requirement(ARR) and the SOC of the BES is presented. The power allocation strategy makes the SOC of the BES maintain in the normal interval as much as possible to enable the BES to participate in the secondary frequency regulation continuously. At the BES station level

a distributed cooperative control algorithm is adopted to realize the power command tracking of the secondary frequency regulation

and ensure that the SOC of all the energy storage units reach a consensus to improve the comprehensive operation performances of the BES. Finally

the effectiveness of the proposed control strategy for the large-scale BES participating in the secondary frequency regulation is verified through the simulation on a two-area interconnected power system.