A Leakage-Current Reduction Technique for Two-Stage Transformerless PV Inverters with Consideration of Resonant Phenomenon

This paper presents a leakage-current reduction technique for commercial transformerless grid-connected 2-stage PV inverters. The switching-frequency component of common-mode voltage is examined by Fourier series, and it is reduced by the selection of the optimal zero-sequence voltages among the 2-arm modulation schemes. In addition, the resonant phenomenon in PV system is investigated. By insertion of a bypass capacitor in the common-mode model, the obstacle from this phenomenon can be alleviated by relocating the resonant frequency of the PV system to be lower than that of the switching frequency. Both simulation and experimental results show that the proposed method can significantly reduce the leakage current to comply with VDE-0126-1-1 standard, and also successfully avoid the drawback from resonant phenomenon.