Direct Torque Control of Induction Machines Drives for the Minimization of the Common Mode Emissions

This paper presents a new DTC algorithm for induction machine drives capable of reducing the common mode conducted emissions of the drive. It is based on the application of only odd or only even voltage vectors in each sector in which the stator flux lies. In the work, after an overview of the problem of common mode emissions of inverter fed drives and the most employed techniques for their minimisation, a simplified equivalent circuit of the common mode path is developed on the basis of experimental measurements. Then the new DTC technique is described and applied to an induction machine drive. Finally results are presented and compared to those obtained with a traditional DTC technique. During numerical simulations this methodology succeeded in reducing the common mode voltage variation and therefore the resulting common mode currents in comparison with the classic DTC up to the frequency of about 20 kHz.