A Simple 24-Pulse Rectifier Combining Power Electronic Phase-Shifting Transformer and SCIC

To reduce the volume and weight of the phase-shifting transformer while effectively suppressing the input current harmonics of the 12-pulse rectifier, this article proposes a 24-pulse rectifier combining a medium-frequency power electronic phase-shifting transformer and a square-wave current injector circuit (SCIC). The proposed 24-pulse rectifier consists of a dual-switch ac/ac converter, a medium-frequency phaseshifting transformer, a three-phase diode rectifier bridge, and a SCIC. The SCIC modulates the output current and voltage of the rectifier bridge by injecting square-wave current. Subsequently, the step number of the input current is increased to 24 based on the relationship between ac and dc currents, which reduces the THD of the input current to half of its original value. The switches in the ac/ac converter operate in a 50% duty cycle medium-frequency state. As a result, the phase-shifting transformer operates at a medium frequency, which effectively reduces the volume and weight of the transformer. Moreover, the SCIC has a low capacity (1.96% Pd) without the need for active device. The circuit has advantages such as simple structure, high reliability, low cost, and high reliability. A test prototype with an output power of 1.5 kW was constructed to validate the correctness of the theoretical analysis.