Reduced switch count multi-level unidirectional rectifiers

The research in this paper will focus on performance evaluation of reduced switch count diode clamped multilevel unidirectional rectifiers with levels more than three. Such rectifiers are favored in more electric aircraft applications mainly due to their improved voltage harmonic spectrum, lower stress on components in comparison to conventional two level rectifiers. The rectifier will be analyzed considering it´s a) pulse width modulation (PWM), b) terminal voltage distortion, c) capacitor voltage balancing circuit, d) common-mode (CM) voltage and e) semiconductor losses. From the analysis it is seen that the phase voltage distortion is considerably lower in certain operating regions. Due to presence of capacitor voltage balancing circuit, the common mode voltage amplitude as well as the semiconductor losses are higher in comparison to three-level rectifier. Simulation results of a six-switch/four-level unidirectional rectifier are presented as a case study. Preliminary open loop experimental results for the same are also presented validating the converter´s switching operation.