Three-phase regenerative front-ends for induction motor drives

There has been considerable interest in regenerative front ends for supplying the DC link in induction motor drives. An AC/DC converter comprising a three-phase inverter circuit with line inductors can achieve fully regenerative operation with near-sinusoidal line currents and near-unity power factor. This paper provides an overview of the topology, and outlines the most important design criteria. An attractive benefit of this kind of converter is the possibility of compensating for harmonics present on the supply voltage. In principle it is possible to “clean up” the local supply by drawing specific harmonics of input current, at a phase such as to cancel out these harmonics on the supply. A method for generating a 7th harmonic component in the input currents is described, and preliminary results are presented. The remaining obstacles to full implementation of this technique are outlined