A quasi-passive modulation circuit improving the current waveform of conventional rectifiers

This paper proposes a new auxiliary modulation circuit to be retrofitted to an existing conventional AC/DC converter to improve line current waveform. The auxiliary circuit modulates the rectifier's DC side current at triple line-frequency and injects a calculated amount of third harmonic current back into its AC side. This circuit takes advantage of DC ripple voltage to generate the modulation current. It consists of mainly passive components and can be easily retrofitted to existing rectifiers. Theoretical analysis, digital simulation results and experimental verification on a 12.5 kW prototype have been presented in this paper.