Study and application of an innovating topology of converter: SPARC serial and parallel auto regulated configuration

Gerard Kalvelage and Philippe Aubin (patentees of the SPARC patent) of the Faiveley transport company propose a new topology of insulated converter. Two converters, one on the primary side (input) and a second one on the secondary side (output), allow to combine several transformers in series (for high voltage) and/or in parallel (for high current). Mixed combinations are also possible (voltage and current of middle magnitude). The converters used have a "ladder" structure, thus distributing the voltage and/or the current in the switches. A particular control mode ensures an alternating voltage at the transformer terminals. Indeed a circular shift of the instructions sent to the switches leads to various kinds of commutations, such as a hard-switching with voltage and current divided by two: the commutation losses will therefore be reduced by a factor of 4. The interlacing of the switches\´ orders removes the discontinuities in the input and output electric signals, which present a weak ripple signal at high frequency, reducing the size of the associated filters. The principle of operation is illustrated together with steady state analysis. Moreover, the effectiveness of the proposed converter topology is verified by implementing a 5 kW-20 kHz prototype using IGBTs and fast recovery diodes.