Rectifier unit is typical non-linear harmonic sources and injection of its generated harmonic current into the power network causes distortion of busbar voltage and leads other equipment in the system not operate safely and stably. The amount of harmonic generation of the multi-pulsation rectifier unit is related closely to the operation mode of the unit and the harmonic current of the multi-pulsation rectifier unit can be offset each other at symmetrical operation condition. In this paper

the unified analysis and the calculation method on harmonics of the multi-pulsation rectifier unit are introduced and the calculation formula on the harmonic current of multi-pulsation rectifier circuit at symmetrical and asymmetrical operation condition is obtained by the theoretical calculation. The unit combination with minimum harmonic generation amount is obtained by the theoretical analysis

which is sued to instruct production operation. At the same time

the harmonic improvement result of the filtering devices installed at different locations is compared

showing that the result of filtering device installed on the high voltage side is more superior to that on the tertiary winding side.