Impact of dead-time on inverter input current, DC-link dynamics and light-load instability in rectifier-inverter-fed induction motor drives

The effect of inverter dead-time on the inverter output voltage is well studied in literature. This paper studies the effect of the dead-time on the inverter input current, and includes this effect in the dc link dynamic model of a diode-bridge-rectifier (DBR) fed voltage source inverter (VSI). Based on this study, this paper proposes a dynamic model of a rectifier-inverter-fed induction motor, that includes the effect of dead-time on both the ac output voltage output and dc input current of the VSI. Simulations based on the proposed model demonstrate oscillatory behaviour of a 100-kW drive over certain flux levels and speed ranges under light-load conditions. These are validated experimentally. Compared to an existing model which ignores dead-time effect on inverter input current, the simulation results based on the proposed model are much closer to the experimental results, and also predict the region of oscillatory behaviour with greater accuracy.