Small-signal stability and robustness analysis for microgrids under time-constrained DoS attacks and a mitigation adaptive secondary control method

Abstract

With the close integration of cyber and power systems, the consensus-based secondary frequency control in a microgrid is increasingly vulnerable to communication failures such as transmission delays and denial-of-service (DoS) attacks, which can affect the efficiency of frequency recovery in the secondary frequency control. Leveraging the small-signal model, this paper develops a novel cyber-physical system model to analyze the cross-layer effect of DoS attacks on microgrids. In this way, the cross-layer impact on the microgrid from the cyber system to the physical system can be convincingly analyzed. Based on the root approximation method, the tolerant saving time is designed for the microgrid as the index to evaluate the tolerance margin of the time-constrained DoS attack, and then the relationship between the margin and secondary control coefficients is found. A mitigation adaptive secondary control technique is proposed so that the attacked microgrid can dynamically tune the secondary control gain according to the saving time and tolerant saving time (TST). The simulation results show that although the microgrid with high secondary control gain has good dynamic robustness, its TST is low. In addition, the proposed adaptive secondary control system is significantly better than the traditional control system in terms of the stability performance of the microgrid under a DoS attack.