Robust Control of a Microgrid System Under Real Parameter Variations

Abstract

The importance of microgrids in power systems is increasing rapidly due to their advantages. In a microgrid system, voltage source converters are used to integrate renewable energy sources that have intermittent nature. These systems require better control methods to improve performance when the parameters of the system change. This paper presents a robust control method for the voltage source converter connected in a microgrid in continuous-time system model by using the linear quadratic regulator method. Robust stability bound measures based on the Lyapunov stability and time-invariant methods are introduced to ensure the stability of the converter based microgrid system if parameter uncertainties occur. These robust stability measures are used to design robust controller for the microgrid system. It is previously shown that the time-invariant robust stability methods give better results than the Lyapunov stability method. However, the Lyapunov stability method for a dependent uncertainty is found to give better results in this paper than the time-invariant method for the microgrid system. The eigenvalues of the closed-loop system designed by using the linear quadratic regulator, with perturbations that meet the stability conditions, have negative real parts making the system stable. MATLAB implementation of the proposed robust control method for microgrid system provided effective results by giving stable initial condition responses for the closed-loop system with perturbations.