A Comparative Study of Robust Optimal Controllers for Grid Voltage Control in Islanded Microgrids

Abstract

This paper presents several optimized control methods for voltage control of an islanded microgrid connected through an inverter system. The control methodology of the microgrid is based on converter control using the PWM. Optimal controllers such as Linear Quadratic Regulator (LQR), Linear Quadratic Integrator (LQI) and Linear Quadratic Gaussian (LQG) are developed to control the voltage of converters. A robust optimal controller provides fast dynamic response and is capable of resisting voltage fluctuations from instantaneous reference grid voltage; to control the inverter voltage that can be utilized in a microgrid (MG). The proposed control strategies basically allow the MG to be controlled with minimum control input while impeding voltage deviation from a reference voltage during disturbances in the power system, such as sudden load change. The performance of designed controllers has been compared against linear and non-linear loads with several conditions. The studied systems are modeled and simulated in the MATLAB/SIMULINK environment and the comparison results show that both LQI and LQG controllers provide good tracking and reasonable performance.