Grid Current Control Method Appling Active Damping for Three-level Flying Capacitor Inverter with Small LCL-Filter

This paper proposes an active damping method in the grid current control for a three-level flying capacitor grid-tied inverter with high robustness against the grid impedance variation. The proposed active damping control expands the stability region by adjusting the updating period of the voltage reference in active damping. This paper also introduces the design criteria of the LCL-filter and feedback control design for the stabilization of the inverter system. Experimental results demonstrate the validity of the proposed current control method. The experimental result shows that the proposed control improved the stability of the flying capacitor inverter under grid impedance variations. Finally, a sinusoidal current waveform with a Total Harmonic Distortion (THD) of less than 5% was obtained.