Single-phase high power hybrid front-end rectifier with soft-commutation

This paper presents the development and the experimental analysis of a new single-phase hybrid rectifier with high power factor (FP) and low harmonic distortion of current (DHT_I), suitable for application in Trolleybus electrical traction systems. This front-end rectifier structure is capable to operate in AC or DC distribution network platforms, providing significant improvements in trolleybuses systems and in the costs and efficiency of urban distribution networks. The proposed structure is composed by an ordinary single-phase diode rectifier with parallel connection of a switched converter. It is outlined that the switched converter is capable of composing the input line current waveform assuring high PF and low DHT_I, however, the power rating of the switched converter is lesser than 50% of the total output power, assuring robustness and reliability for the proposed hybrid rectifier. A PWM control strategy was implemented imposing quasi-sinusoidal input line current waveform and limiting the switched converter power contribution. It was found that the input line current harmonic spectrum is in accordance with the harmonic limits imposed by IEC61000-3-4. The principle of operation, the mathematical analysis, and experimental results from a 10 kW prototype are also presented herein. Additionally, it is proposed the insertion of a soft-commutation cell in order to improve the overall efficiency of the proposed front-end converter.