2007 Volume 127 Issue 3 Pages 241-247
This paper describes an auxiliary power supply system of railways (SIV) for 1500-Vdc power line substituting series connection of 1.2-kV rated standard IGBTs as a switching device for 3.3-kV rated IGBTs. The SIV is allowed to operate up to 5-kHz carrier frequency due to considerable small losses of the IGBTs. Voltages across the series connected IGBTs are balanced by magnetically coupling all the gate lines using a simple two-winding transformer without any snubber circuits. In order to investigate advantages of the SIV operated at higher carrier frequencies, a 150-kVA rated SIV system was tested under 1260-Hz and 4980-Hz carrier frequency conditions, and these performances were compared. The results verifies that making the carrier frequency high can play an important role to realize high performances concerning suppression of an undesired sound from the filter reactor, decrease of the filter size, and improvement of the control response to output voltage with any sudden change of load.