Impact of time delay on performance and stability of inverter-fed islanded MG utilizing internal model controller

Abstract

The wide integration of power electronics-fed systems presents new challenges to modern grids in terms of stability and power-quality. The various time constants associated with power electronic devices and their corresponding feedback control loop leads to dynamic frequency-couplings in a wide range of time-scale. This paper presents a comprehensive state-space model to examine the stability of an inverter-fed microgrids (IFMGs) using internal model controller (IMC) considering the digital time delay into account. The impact of control parameters along with power-droop coefficients and digital time-delay on system stability for analysing the cause of low-and-high-frequency instability phenomenon is evaluated through eigenvalue analysis. The delay effect on the significant parameters of the considered microgrid (MG) model is established and corresponding stability margins are investigated. Moreover, the states contributing to the oscillation modes are revealed through participation factor analysis. Finally, the real-time simulation results using OPAL-RT OP4510 are presented for validating the theoretical analysis and the efficacy of the proposed model is compared with well established traditional PI-based controller.