Operation of Single-Delta Bridge-Cell Converter With Single-Phase Medium-Frequency Transformer Under Low Magnetizing Inductance

Abstract

A single-delta bridge-cell (SDBC) converter with a single-phase transformer operating at 150 Hz can exchange the active power of 37% of the rated reactive power with three-phase ac mains without increasing voltage and current ratings of the SDBC converter. Meanwhile, it is difficult to achieve negative-sequence reactive power control because of high magnetizing inductance of the transformer, which is required under grid fault conditions. To achieve the negative-sequence reactive power control, this article applies a single-phase transformer with low magnetizing inductance to the converter at the cost of exchangeable active and reactive power. The relationship of magnetizing inductance, active power, and reactive power is revealed in this article, and the operation of the converter under low magnetizing inductance is verified experimentally using a downscaled 110-V, 7.0-kVA model.