Common‐Mode Voltage Analysis and Reduction Method for SiC‐Based Four‐Level Hybrid Clampled Converter

ABSTRACT The hybrid clamped converter (HCC) is a novel high‐performance four‐level multilevel converter for medium‐voltage motor drives. However, the high common mode voltage (CMV) in motor drives will cause harmful shaft voltages and bearing currents, which threaten the system's safety. The CMV performance of the HCC is unknown compared with traditional two‐/three‐level converters, as well as its reduction method. This paper studies the HCC's CMV modeling and clarifies the relationship between CMV amplitude and reference voltage. Then, an algorithm is proposed to determine the CMV envelope accurately, and an optimal injected zero‐sequence voltage (ZSV) is obtained to suppress the CMV amplitude based on the proposed algorithm. Finally, a silicon carbide (SiC)‐based HCC prototype is established to verify the proposed method. Results show that the proposed method for HCCs can reduce the CMV from ± 5 V dc /18 to ± V dc /18 at a high modulation index, which is much smaller than existing two‐ or three‐level converters. Compared with the traditional control method of HCCs, the peak‐to‐peak value of CMV can be reduced by more than 70%. In addition, the loss can be reduced at a high modulation index with the proposed method.