Power Factor Correction and Harmonic Elimination for LCL-Filtered Three-Level Photovoltaic Inverter with Inverter-Side Current Control

LCL-filtered three-level inverters have been widely used in PV applications because of their high efficiency, high power density, and low cost. In practice, the inverter-side current feedback (ICF) control has dominated the PV market due to its low-cost property. However, the grid-side current becomes more sensitive to the grid distortion owing to its indirect regulation in an ICF controlled system. To address this issue, this paper proposes a new control structure to improve the power factor and eliminate the low-order harmonics of the grid-side current simultaneously. By combining the feedforward and proportional feedback of the capacitor current, this method can effectively eliminate the reactive power induced by the capacitor of an LCL-filter. In addition, the low-order harmonics can also be eliminated if the capacitor current is sent back to the resonant controller. Effectiveness of the proposed method has finally been verified with a 5kW LCL-filtered three-phase T-type PV inverter.