A Simple 24-Pulse Rectifier Employing an Auxiliary Pulse-Doubling Circuit

A simple 24-pulse rectifier that provides low-harmonic utility power interface is proposed in this article. The proposed 24-pulse rectifier consists of a 12-pulse rectifier using a zigzag phase-shifting transformer and an auxiliary pulse-doubling circuit (APDC). Two auxiliary diodes in the APDC extract specific rectangular currents from the dc side of the rectifier to modulate and increase the output states of three-phase rectification bridges first, and then the 12-pulse rectifier is extended to a 24-pulse rectifier in accordance with the current relationship between ac and dc sides. The main low-order harmonics, such as 11th and 13th, are reduced markedly from the input line current and the proposed rectifier draws near-sinusoidal input line currents with less than 5% THD from the utility. The maximum current flowing through the two auxiliary diodes in APDC is only 3.4% of the load current and the capacity of APDC is only 3.06% of the output power. Thus, the proposed scheme is inexpensive and easy to implement and has a simple circuit configuration. Theoretical analyses were experimentally verified using a 1.7-kW experimental prototype.