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The series-type 12-pulse rectifier generates a large amount of harmonics in the AC side current due to the strong nonlinearity of its rectifying diodes, causing serious harmonic pollution to the power grid. This article proposes a series 36-pulse rectifier based on a DC side dual passive frequency-doubling circuit to suppress the AC side current harmonics of a 12-pulse rectifier. The rectifier uses two symmetrical passive pulse multiplication circuits to regulate the circulation in the DC side circuit, increasing the output voltage and current state of the rectifier bridge, thereby increasing the number of pulses in the rectifier from 12 times to 36 times. Firstly, the working principle of the rectifier and the working mode of the dual passive frequency-doubling circuit were analyzed. Secondly, the harmonic suppression mechanism of the rectifier input current was revealed, and the frequency-doubling characteristics of the load voltage were analyzed. Finally, the correctness of the theoretical analysis was verified through a semi-physical platform. The verification and comparison results show that under the optimal conditions of the injecting transformer turns ratio, the DPPC can not only reduce the THD value of the input current by about 1/3 (from 14.87% to 4.78%) but can also increase the fluctuation frequency of the load voltage by 3 times (from 12 to 36), while improving the power quality of the AC/DC side rectifier and achieving the low harmonic operation of the rectifier. The proposed 36-pulse rectifier can effectively suppress harmonics; it has the advantages of simple structure, strong robustness, and high output voltage gain, and it is suitable for medium-voltage and high-voltage high-power rectification applications. [ABSTRACT FROM AUTHOR]

To reduce the current harmonics on the input side of a multi-pulse rectifier, this paper proposes a low harmonic current source series multi-pulse rectifier based on an auxiliary passive injection circuit at the DC side. The rectifier only needs to add an auxiliary passive injection circuit on the DC side of the series 12-pulse rectifier, which can change its AC input voltage from 12-step waves to 24-step waves. We analyzed the working mode of the rectifier, optimized the optimal turn ratio of the injection transformer from the perspective of minimizing the total harmonic distortion (THD) value of the input voltage on the AC side, and analyzed the diode open circuit fault in the auxiliary passive injection circuit. Test verification shows that, after using the passive harmonic injection circuit, the THD value of the input voltage of the AC side of the rectifier is reduced from 14.03% to 4.86%. The THD value of the input current is reduced from 5.30% to 2.16%. The input power factor has been increased from 98.86% to 99.83%, and the power quality has been improved. [ABSTRACT FROM AUTHOR]