Compensation of Second Harmonic Current Based on Bus Voltage Ripple Limitation in Single-Phase Photovoltaic Grid-Connected Inverter

In the two-stage single-phase photovoltaic (PV) grid-connected inverter, the flying-capacitor-clamped boost three-level converter is adopted to achieve maximum power point tracking of the PV panel. To restrain the second harmonic current (SHC) in the PV panel and remove the undesired electrolytic capacitors, the flying capacitor is employed to compensate the SHC. To achieve this goal, the flying capacitor average voltage control incorporated bus voltage ripple limitation scheme is proposed in this letter. The closed-loop parameters design for the bus voltage ripple limitation loop is given. Finally, a prototype of 3-kVA PV grid-connected inverter is fabricated and tested in the lab, and the experimental results verify the validity of the proposed scheme.