Fractional order harmonic disturbance observer control for three-phase LCL-type inverter

Abstract The quality of output current of L C L -type voltage source inverter (VSI) is degraded by the grid voltage distortion, the dead time effect, and the parameter mismatches. This paper proposes a novel fractional order harmonic disturbance observer-based control (FOHDO) for the three-phase L C L -type inverter to suppress all the dc- and ac-component periodic disturbances. Firstly, a harmonic disturbance observer based control for L C L -type inverter is proposed with the internal model knowledge of the periodic disturbances signals. Subsequently, the FOHDO based on Lagrange interpolating polynomial fractional order delay approximation is put forward to enhance the adaptability of the grid frequency. Then, the stability and robustness performance of the proposed FOHDO for L C L -type inverter are evaluated, which also involves a detailed parameter design process. Finally, the effectiveness and performance of the proposed FOHDO method are verified by both experimental and simulation results.