Analysis of abnormal harmonics in converters applications

Equipment supplied by static converters require a careful examination of the harmonic distortion, which affects the power supply system. The conventional frequency domain approach for investigating the harmonic pollution often produces results which may be inaccurate to some extent due to the simplified approximations used. In this paper, a simulation of some selected case of typical converters used in industrial applications is carried on by using the Pspice program. Abnormal harmonic sources are examined; in particular, the asymmetry of the control pulses, the unbalance in the supply voltages and the asymmetry in converter transformer are considered. The results provided by the simulation are discussed to point out the relevance of the abnormal harmonics and their penetration into the linefeed busbar system.