A Series-Connected 24-Pulse AC–DC Converter With Double-Diode Harmonic Suppression Circuit

A series-connected 24-pulse ac–dc converter with a double-diode harmonic suppression circuit (DDHSC) is presented in this article. The DDHSC is installed at the dc side of the ac–dc converter, and it consists of several passive devices. The DDHSC generates a specific current at the dc link to modulate and increase the operating modes of this ac–dc converter. Then, the series-connected 12-pulse ac–dc converter is extended to a novel 24-pulse ac–dc converter, and total harmonic distortion of the input line current is reduced to the acceptable levels (less than 5%). The maximum current through the auxiliary diodes in the DDHSC is only 6.8% of the load current, which means the current rating and conduction losses of the auxiliary diodes are low. The proposed DDHSC scheme is more suitable for high-current occasions. Given that only a low capacity (2.06% of the output power) DDHSC is sufficient to double the number of pulse of the 12-pulse ac–dc converter, the proposed scheme is simple and cost effective. The detailed theoretical analysis is provided, and an experimental prototype is established to demonstrate the performance of the proposed converter.