Impact of Under-Compensation and Over-Compensation of Dead-Time Effect on Small-Signal Stability of Induction Motor Drive

Inverter dead-time is known to make open-loop induction motor drives oscillatory, while operating at light-loads in particular. While dead-time compensation schemes exist, precise compensation of the same is often challenging as it involves factors such as device and driver delays and switching transition times, which are difficult to be quantified accurately. Hence, the effect of dead-time could be under-or over-compensated. A theoretical and experimental study on the impact of such under-compensation and over-compensation on the stability of a 100-kW induction motor drive is presented here. Small-signal models are proposed for an open-loop drive, when it is under-compensated and over-compensated. Stability analysis of the above motor drive is reported, which predicts the fundamental frequency range of oscillatory behaviour for both these cases. Further, different types of oscillatory behaviour are observed for the two cases. The analyses are supported by simulation and experimental results