Bidirectional switches for matrix converter in contactless energy transmission systems

For an increasing number of applications in mechanical engineering, production technology, transportation, process engineering and medical engineering there are promising application prospects for contactless inductive energy transmission systems in the power range of several kilowatts. In particular the dimensions of the primary and secondary system, the existence of ferrite cores on the primary or secondary side and the air gap length determine the transmission behaviour. The transferable electric power and the efficiency of contactless magnetic systems can be considerably increased by using higher transmission frequencies, greater than 100 kHz. At conventional systems the main losses of the complete system are caused by the primary inverter. Therefore novel power electronic topologies for direct energy conversion are necessary for this special application. The use of a matrix converter for contactless energy transmission reduces the number of energy conversion steps, avoids voluminous and expensive electrolytic DC link capacitors, increases the reliability especially at high temperatures, reduces conduction losses in power semiconductors and enables four-quadrant operation with sinusoidal line currents. The paper investigates special aspects of the matrix converter with high output frequencies in combination with contactless energy transmission, for instance commutation strategies, control concepts for three-phase line connection and sinusoidal line currents and the conduction and switching losses in the bidirectional power semiconductors