Design and experimental implementation of a robust DLQR for three-phase grid-connected converters

This paper deals with the design of robust discrete linear quadratic regulators applied to three-phase inverters connected to the grid by means of LCL filters. The system is modeled in the state space in abc coordinates and changed to aβ coordinates, allowing a simple control design and implementation. Resonant controllers are used to ensure the tracking of sinusoidal references for grid current. The control gains are computed by means of a convex optimization problem and ensure that the closed-loop system is robustly stable when operating under conditions of uncertain grid inductance. The controller is experimentally validated with a 5.4 kW prototype, showing good results for three-phase grid current control.