A robustness-enhanced frequency regulation scheme for power system against multiple cyber and physical emergency events

Abstract

Emergency events, e.g., accidental generator outages and abrupt steeps in electric load in physical layer, and unexpected communication time delays in cyber layer, are raising increasing concerns in modern power systems, and can cause system frequency deterioration, thus threatening power energy security. However, currently there is few discussions on dealing with multiple emergency events in power system comprehensively and simultaneously. In order to counter the adverse effects caused by these various emergency events and maintain the system frequency, a robustness-enhanced frequency regulation scheme is proposed in this article based on the coordinate transformation technique and Lyapunov theorem. First, to analyze the dynamic process of the power system in contingency conditions, the model of the power system frequency regulation is reconstructed considering multiple emergency events. Furthermore, to guarantee the power system frequency stability, a virtual auxiliary surface is constructed based on the coordinate transformation technique, which can provide the control reference for frequency regulation. On this basis, a robust controller is developed to drive the system’s trajectory to the proposed virtual auxiliary surface, thus guaranteeing the robustness of power system frequency, e.g., minor frequency deviation and faster recovery speed, even with emergency events. In addition, the stability of the system with the proposed controller is rigorously proved by Lyapunov theorem. Finally, the effectiveness of the proposed scheme is verified by case studies. The results show that by using the proposed scheme, the maximum frequency deviation and recovery time can be improved to about 61.11% and 46.40% of the original value under multiple emergency events, respectively. Therefore, the proposed scheme can counter well against emergency events and contribute to the power system’s frequency regulation and energy security.