Enhanced Linear Quadratic Regulator‐Based Strategy for Seamless Transition Between Microgrid Operation Modes

ABSTRACT Ensuring a seamless transition between grid‐connected and islanded modes of operation in microgrids is a critical challenge due to transient disturbances during the transition between the corresponding control strategies (grid‐forming and grid‐following control strategies), affecting system stability and reliability. This paper presents an advanced control strategy that relies on a linear quadratic regulator‐based smooth transition regulator (LQR‐STR) to enhance the smoothness and reliability of microgrid mode transitions. Unlike previous LQR‐based approaches, the proposed method integrates the full control loops in the smooth regulator design, including the virtual impedance loop, and voltage and current feedforward coefficients for the grid‐forming controller, and active/reactive power control loops for the grid‐following controller. The impact of imperfect islanding detection and premature reconnection is analysed, demonstrating the robustness of the proposed method under varying transition conditions. The effectiveness of the proposed approach is validated through detailed simulations in MATLAB/Simulink and through a real‐time embedded system using the NI sbRIO GPIC Evaluation Kit. The simulation and experimental results show significant improvements in reducing transient overshoots, enhancing voltage and frequency stability and ensuring reliable mode transitions.