A Nonclamped H10 Topology to Achieve Leakage Current Reduction for Transformerless Grid-Connected Converter

Due to the advantages of smaller size and lower cost, transformerless grid-connected converter (GCC) has been widely used in photovoltaic (PV) power generation system. But this may incur obviously leakage current, which is related to the common-mode voltage (CMV) of the GCC. Topology improvement by adding additional switches is an effective way to reduce CMV, i.e., H7, H8, and H10 topologies. However, some topologies suffer from high leakage current and low-power quality of the grid current. To solve those problems, based on the existing H8 topology, this article proposed a nonclamped H10 (NCH10) topology. First, the large variation in CMV of H8 topology is analyzed using complex frequency-domain model. Second, a NCH10 topology which could achieve a 66.7% reduction in CMV is proposed. Finally, the PWM control signals based on novel logic functions are established. Compared to H10 topology, the proposed NCH10 topology which has special arrangement of additional switches owns better loss performance. Moreover, its isolated operation between grid and PV array during zero-voltage vectors (ZVVs) greatly reduces the leakage current. The effectiveness in terms of CMV limitation and leakage current reduction is demonstrated by numerous simulation and experiment results.