Harmonic cancellation by mixing nonlinear single-phase and three-phase loads

The voltage on the distribution line is in most cases distorted even at no load of the transformer. This is due to the "background" distortion on the medium voltage line caused by the large number of single-phase nonlinear loads such as PC\´s, TV, VCR etc. This paper proposes a method to mix single-phase and three-phase nonlinear loads and reduce the harmonic currents significantly. The dependence of the phase angle of the harmonic currents as a function of the short circuit impedance is investigated using SABER for the three-phase and the single-phase diode rectifier both with and without DC-link inductance. The phase angle of the 5/sup th/ and 7/sup th/ harmonic current of a three-phase diode rectifier is often in counter phase with the 5/sup th/ and 7/sup th/ harmonic current of a single-phase diode rectifier. This leads to the conclusion that adding a three-phase rectifier load often lowers the voltage and current distortion at the transformer. This is also validated by a number of measurements.