A Simple 24-Pulse Star Rectifier Combining Two Different Tap Converters

Abstract

To further improve the harmonic mitigation capability of the double-star rectifier, a simple 24-pulse star rectifier using a conventional tap converter (CTC) and an improved tap converter (ITC) is proposed. The proposed rectifier comprises two double-star rectification units, a CTC, an ITC and an interphase reactor (IPR). The CTC and ITC first expand the double-star rectifiers into 12-pulse rectifiers, and provide a phase shift of 15°, then connect through an IPR to achieve the effect of quadrupling the number of pulses. This configuration solves the problem of limited pulse multiplication capability (pulse multiplication number≤3) of the existing passive tap converter, and upgrades the double-star rectifier to a novel 24-pulse star rectifier. The resulting rectifier shows an approximately sinusoidal input current with the absence of the 5th, 7th, 17th and 19th harmonics. The proposed scheme has the advantages of simple structure, small size, and being economically justified because the proposed scheme does not change the structure of the double-star transformer, and the capacity of CTC and ITC is only 3.49% and 6.29% of the output power, respectively. An experimental prototype with an output power of 1 kW is built to verify the correctness of the theoretical analysis.