Hybrid space vector modulation for low‐order common‐mode voltage reduction in current‐source rectifier for transformerless medium voltage drives

Abstract

AbstractFor transformerless current‐fed medium voltage drives, low‐order harmonics of common‐mode voltages (CMVs) are more concerned with than peak values. To mitigate low‐order harmonics, the average values of CMVs should be suppressed. A hybrid space vector modulation (SVM) is proposed in this study to further reduce CMV average values generated by a current‐source rectifier (CSR) compared to existing zero‐state vector selection modulation. The proposed SVM is a combination of zero‐state vector selection and active zero‐state modulations. The transition points between two modulations are defined based on various modulating index. Power losses and efficiency of the proposed hybrid SVM are analysed in detail. Simulation on a medium‐voltage CSR (1 MW/4160 V/139 A) and experiments on a scale‐down CSR (2.5 kW/208 V/6.94 A) are conducted under various working conditions, which validates the effectiveness of the proposed SVM to further mitigate 180 Hz and other low‐order harmonics in CMVs in contrast to that by conventional zero‐state vector selection modulation.