On the reduction of vibration caused by DTC strategies in automotive drives: An attempt to guarantee passenger comfort

It is well known that DTC strategies are penalized by the uncontrolled switching frequency of the inverter yielding high torque ripple, which in the case of electric and hybrid propulsion applications, induces vibration and therefore compromises passenger comfort. Although in DTC strategies the hysteresis band widths of both torque and flux regulators greatly influence the drive performance, these are generally chosen arbitrary. The paper deals with the influence of these bands on the inverter average switching frequency, which is the result of the one due to the torque regulator and of the one due to the flux regulator. Of particular interest are the so-called focal speeds for which the inverter average switching frequency due to the torque regulator is null. A special attention is focused upon such particular speeds which are derived in the case of a constant load torque characterizing electric and hybrid propulsion applications.