$H_{\infty}$ Robustness for Distributed Control in Autonomous Microgrids Considering Cyber Disturbances

The physical connections and logical relationships between microgrids and communication networks allow microgrids to develop into typical cyber-physical systems (CPSs). With the extensive use of open communication mechanisms, the impact of cyber disturbances in public communication networks cannot be diminshed. In this paper, a parameter optimal method for a distributed secondary controller based on the robust control theory and consensus algorithm is presented to enhance the robustness of a secondary control system under data disturbance, parameter perturbation, and time delay. First, a distributed secondary control strategy of microgrids is demonstrated that coordinates frequency and voltage restoration and power sharing. Then, considering the impact of cyber events on the secondary control, a distributed robust controller gain design method is proposed to satisfy the $\boldsymbol{H}_{\infty}$ performance index. The solution of the distributed robust control is transformed into a linear matrix in equation problem and latency margin is simultaneously obtained. Finally, a test microgrid CPS is simulated with and without time delay to investigate the impact of cyber events on system operational states and the effectiveness and robustness of the proposed method.