Design of a back-to-back multilevel induction motor drive for traction systems

This paper deals with the design of a single phase AC/DC/AC converter feeding an induction motor for traction applications. A cascade of H-bridge cells has been used to obtain a multilevel conversion structure. The front-end rectifier should absorb current with low harmonic content to eliminate disturbances on the communication equipments and, more in general, to reduce electromagnetic pollution. Additional specification is the elimination of the transformer such as to reduce encumbrance and cost. A similar H-bridge cascade has been used in the motor side. In fact, supplying the motor by multilevel voltages greatly reduce the current harmonic distortion, enhancing induction motor performance, and the switching frequency, improving efficiency and extending component life. In this paper the design of the converter has been described with the help of theoretical analysis and simulations, moreover some first partial experimental results are also shown.