LQR Based Current Controller for Improved Power Quality of Grid-Tied PV Systems

This paper proposes a new LQR-based feedforward current control scheme for the three-phase inverter of a grid-tied PV system to achieve better power quality. In order to mitigate the THD in the grid current and variation in the grid voltage, the proposed control mechanism combines an LQR-based feedforward current regulator with a disturbance decoupling approach. The feedback gains of the current regulator are obtained using the LQR method and the fluctuation in the grid voltage is modeled as a disturbance to get rid of its effect. In order to mitigate the computational complexity, the control strategy is developed in the synchronous reference frame (SRF) and to verify its effectiveness, the PV system along with the controller is simulated under various operating situations using the Matlab/Simulink platform. The simulation results show that the proposed LQR-based current control scheme has been more successful in improving the power quality of grid-tied PV systems than some of the conventional controllers, particularly in decreasing the Total Harmonic Distortion (THD) in the grid current.