Collaborative Control Strategy of Megawatt-Level Zinc–Iron Flow Battery Energy Storage System Based on Source–Grid–Load–Storage Integration

The zinc–iron redox battery (ZIRB) has become one of the hot technologies of electrochemical energy storage due to its safety, stability and low cost of the electrolyte. In this paper, a collaborative control strategy for an MW-level zinc–iron flow battery energy storage system is studied, and the operation control and management of the MW-level zinc–iron flow battery energy storage system are coordinated and optimized to improve the operation efficiency of the whole system. The model of the megawatt zinc–iron flow battery energy storage system is established in this paper. A ZIRB state of charge (SOC) estimation method based on least squares (LS) and an extended Kalman filter (EKF) is proposed. Experiments under constant-current discharge show that the proposed LS-EKF method can achieve accurate SOC estimation for the tested ZIRB system, with a maximum estimation error of approximately 2.3%. Experiments show that the proposed algorithm has good accuracy, rapidity and robustness at different SOC initial values. According to SOC differences between battery cells, the coordination strategy of each cell is designed to meet the requirements of frequency modulation while taking into account the safety of battery operation. On this basis, the optimization problem is designed and solved with the goal of optimal frequency modulation effect and battery energy loss, and the collaborative control of the MW-level ZIRB energy storage system is realized.