Six-pulse converter atypical harmonics caused by second harmonic voltage

This paper reports the orders and levels of atypical harmonics caused by the second harmonic voltage. Two basic types of 6-pulse converters are discussed: The L-filter (current source rectifier) and the C-filter (voltage source rectifier). The response of these converters to symmetrical nonsinusoidal voltage distorted by positive- and negative-sequence 2nd harmonic voltage are summarized. The most significant finding reported in this study is the fact that C-filter converters supplied with traces of positive-sequence 2nd harmonic voltage are prone to inject excessive amount of dc and even harmonic currents into the ac lines.