Observer-based state feedback controller for LCL filter used in PV applications with grid current measurement only

This paper proposes a observer-based state feedback controller for the PWM inverter output LCL filter used in PV applications. The controller is comprised of an inner pole-placement loop and its poles are placed following the state-apace control theory. An additional outer current loop is responsible for making sure the grid inductor output current is as clean as possible of harmonic components. Its gains are adjusted following the well-know concepts of phase and gain margins of the classical control theory. Simulation results validate the proposed controller.