A novel 3-phase, transformerless H-8 topology with low variation in CMV to reduce leakage current

Abstract

A novel 3-phase transformerless H-8 topology is proposed in this paper, which aims to limit the leakage current as per the standards by reducing the variation in common mode voltage (CMV). The proposed topology utilizes the advantages of both DC bypass and AC bypass circuit configurations. Thus, it is actually a hybrid bypass circuit configuration. Proposed topology has eight power devices, controlled in such a way that the variation in CMV during powering and freewheeling modes is significantly reduced. Thus, the leakage current is maintained within the limits as per the standards by reducing the variation in the magnitude of CMV. The modulation strategy for the proposed topology is based on simple SPWM followed by specifically derived logic functions, which enables it to use the full range of modulation index. Simulation and experimental results are presented to validate the theoretical analysis of the proposed topology, which shows low leakage current and THD.