Lower order harmonic cancellation: impact of low-voltage network topology

Cancellation due to phase-angle diversity between dispersed single-phase nonlinear loads is insignificant for the 3rd and 5th harmonics, but becomes increasingly significant for higher harmonics. Since the transformer connection has a significant effect on the propagation of 3rd harmonic current, most of the focus by international standard organizations such as the IEC for harmonic limits is primarily based on the concern for 5th and 7th harmonic components. However, depending on the low-voltage customer network topology, there may be significant cancellation of 5th and 7th harmonic currents of nonlinear loads. This paper demonstrates the extent of this cancellation based on realistic load harmonic current spectrum and shows how the difference in mainly European and North American low voltage customer network topology greatly impacts this cancellation.