Hybrid Harmonic Suppression at DC Side for Parallel-Connected 12-Pulse Rectifier

In order to simultaneously reduce the input line current harmonic and the output voltage ripple of the 12-pulse rectifier, a hybrid harmonic suppression method (HHSM) with high harmonic suppression performance and low harmonic suppression cost based on the active-tapped inter-phase reactor (AT-IPR) is proposed in this paper. The AT-IPR is connected in series with the load to generate a passive circulating current (PCC) directly modulating the output current of the 12-pulse star diode-bridge rectifier (SDBR); the compensation circuit (CC) connected in parallel with the load is used to inject the active compensation circulating current (ACC) into the AT-IPR to indirectly modulate the output current of the SDBR. The optimally designed compound circulating current consisting of PCC and ACC first modulates the output current of the SDBR. Based on the current relationship between the ac and dc sides and the voltage relationship between the dc sides, the input line current of the SDBR is further shaped nearly the sinusoidal current and the pulse number of output voltage is doubled to 24. Moreover, the kVA ratings of AT-IPR and CC are only about 1.8% and 1% of the output power of the proposed rectifier using HHSM, respectively. Therefore, the proposed method is suitable for high-power rectification where the requirements for power quality and reliability are relatively high. The detailed analysis and relevant simulation results are given to validate the proposed method.