Common Mode Voltage Elimination in Induction Motor Drive by Space Vector based Pulse Density Modulation Scheme

Common mode voltage is responsible for the flow of bearing current through the motor bearings, leading to motor bearing damage, electromagnetic interference and motor winding insulation breakdown in induction motor drives. Common mode voltage elimination by space vector based pulse density modulation scheme is proposed in this paper. In the proposed scheme, the inverter switching vectors having zero common mode voltage among the nearest three switching vectors of integrated error vector is selected as the code vector. The scheme embeds the benefits of space vector based pulse density modulation such as avoidance of minimum pulse width problem and non-requirement of complex timing calculations along with better harmonic performance. The proposed scheme is experimentally implemented for a five level dual fed induction motor and the results obtained confirms the elimination of common mode voltage.