An Auxiliary Supply Assisted Input Current Harmonic Reduction for 12-pulse Diode Rectifiers

Abstract

Diode rectifiers have been widely used for an ac-to-dc converter. One of their problems is that they include large lower-order harmonics in the input current. A 12-pulse diode rectifier is useful for reducing them but it still includes the (12m ± 1)^th (m: integer) harmonics. In order to further reduce the input current harmonics a single-phase square wave auxiliary voltage supply is inserted in the middle dc bus of a 12-pulse diode rectifier. The purpose is to obtain a 12-pulse diode rectifier whose harmonic contents are equivalent to those of a 24-pulse diode rectifier. Theoretical analysis of the auxiliary supply assisted 12-pulse diode rectifier is presented and a control method of the auxiliary supply in relation to the dc load current is proposed. Effectiveness of an auxiliary supply is verified by simulation and experimental results.