Sampled-Data-Based Load Frequency Control for Islanded Microgrids via a Virtual Inertia Control Mechanism

This paper presents a robust load frequency control (LFC) scheme for an islanded microgrid (IMG) based on sampled-data control. First, a novel LFC system model for an IMG is proposed by incorporating a virtual inertia control (VIC) mechanism with a sampled-data-based auxiliary controller. Then, through applying Lyapunov theory and introducing an exponential decay rate (EDR) as a performance indicator, a novel stability criterion is established for the LFC of the IMG. Based on the stability criteria, the controller design is presented by utilizing $H_{\infty }$ performance index $\mu $ and EDR as conditions, resulting in a fast and robust LFC scheme. Finally, simulation results and comparison analysis show that the proposed method is superior, and the introduced VIC mechanism with a sampled-data-based auxiliary controller can effectively improve the dynamic performance of the system. Note to Practitioners—The high penetration of renewable energy sources (RESs) reduces the inertia of the IMG, leading to a fast and large frequency deviation after a contingency, and desiring fast and robust LFC. This paper focuses on designing a robust LFC scheme to address issues like these rapid and significant frequency deviations after contingencies. Specifically, we propose a novel LFC system model for IMGs by incorporating a VIC mechanism with a sampled-data-based auxiliary controller into the LFC system to supply virtual inertia power to the system under high RES penetration. To achieve rapid frequency stabilization, we introduce the EDR as a performance index to guide the controller design. To meet various requirements within the LFC design, a comprehensive design methodology is outlined, integrating the sampling period, $H_{\infty }$ performance index $\mu $ , and EDR. Simulation results and comparative analysis validate that the proposed LFC scheme effectively compensates for the adverse effects of low inertia in IMGs and achieves the desired stability.