Control of grid-connected voltage source converters with LCL filter using a Linear Quadratic servocontroller with state estimator

The aim of this paper is to propose a multivariable current controller of voltage source converters (VSC) connected to the grid through an LCL filter. The proposal is a linear quadratic (LQ) servocontroller, which uses a fullorder estimator to obtain the full state vector. Two kinds of estimators are proposed and compared: prediction estimator and Luenberger estimator. The behavior and robustness of the controller is tested in presence of grid disturbances and mismatches in the model parameters.