Frequency Safety Control Strategy Based on Multistage Coordination Following Disturbance

After power disturbances occur in power systems, the frequency response presents significant spatial-temporal characteristics. The current situation of asynchronous frequency response in different areas determines that there is room for improvement in the frequency regulation capability of interconnected power systems. Due to the optimal operation of power systems through multi-stage coordinated operation, this paper proposes a multi-stage coordinated active frequency response (CAFR) control strategy based on three lines of defense for frequency stability of power systems, aiming at safety and economic coordination. In the prevention control stage, the regulation capacity is reserved by purchasing the frequency regulation capacity in advance; In the emergency control stage, the frequency response spatial-temporal characteristics are utilized to enhance the frequency regulation capability of the system through feedforward active control; In the correction control stage, penalty items are set to avoid affecting system safety and triggering under frequency load shedding (UFLS). Both numerical example analysis and simulation verification show that the proposed active frequency response (AFR) control strategy for AC/DC hybrid power systems based on three lines of defense coordination is superior to the passive frequency response (PFR) mode in terms of security, and is more superior to the single stage operation control in terms of economy, with significant improvement in overall control effectiveness.