New 24-Pulse Rectifier With Passive Current Injection Circuit Based on Dual Auxiliary Transformers

To enhance the harmonic mitigation capacity of the 12-pulse rectifier, a series-connected 24-pulse rectifier with a passive current injection circuit based on dual auxiliary transformers (PCIC-DAT) is proposed. The proposed PCIC-DAT is installed on the dc side of the proposed rectifier in parallel. The PCIC-DAT generates a specific square-wave current first, then the square-wave current is injected into the connection point of the two three-phase bridge rectifiers (TPBRs) so that the working modes of two TPBRs can be increased, and the series-connected 12-pulse rectifier is converted into a new 24-pulse rectifier subsequently. The resulting rectifier draws an approximately sinusoidal input current (THD < 5%) and has a smaller ripple output voltage. The PCIC-DAT contains only a pair of low KVA rating (0.985%
$P_{d}$
) auxiliary transformers with identical construction. The maximum current through the diodes in PCIC-DAT is only 3.4% of the load current. The proposed scheme has the merits of simple circuit configuration, small kVA rating, and low conduction loss, and thus, it has better application potential in industrial occasions. A 1.5 kW output power experimental prototype is established for testing to verify the harmonic reduction performance and the theory analysis.