Control of single-phase inverter connected to the grid through an LCL filter

This paper presents a method to control a single-phase grid-connected LCL filter based power converter. The controller design is made in two steps, first, an active damping injection (ADI) mechanism is introduced to damp the resonance of the LCL filter and thus guarantee stability, and second, a harmonics compensation mechanism (HCM) is included, to cope with the harmonic distortion present in the grid voltage. Implementation of the ADI mechanism requires the design of a reduced-order observer (R-OBS), to estimate the non available states based on the measurable output. Simulation and experimental results are presented to assess the performance of the proposed controller.