Secondary Frequency Control of Decoupled Trigonometric Saturated Droop Controller for Islanded Low-Voltage Mesh Microgrid with Linear Load

Abstract

This paper presents a robust secondary frequency control integrated with decoupled trigonometric saturated droop controller (DTSDC). The primary frequency controller may induce an error in frequency regulation, which affects the load sharing accuracy among microgrid distributed generators (DGs). Therefore, a centralized secondary controller is designed to converge the frequency to its nominal value for grid-forming inverters. Using an advanced communication channel, the proposed primary and secondary controller can primarily restore the frequency during disturbances, such as DG on/off switching and loading system variation. The practicality and performance of the proposed controller have been demonstrated with MATLAB simulation environment on a mesh microgrid system consisting of four parallel DGs-based inverters. Simulation results show the proposed controller’s robustness in the microgrid frequency stability. Hence, it achieves accurate active power sharing with a linear load. Moreover, the impact of resistive and inductive line impedance is discussed in this study. A comparison between the microgrid centralized controller (MGCC) and the decoupled trigonometric saturated droop controller (DTSDC) only is conducted to show the robustness of the presented controller performance.