Inductance-emulation-based active damping of dead-time-induced oscillations in a 100-kW induction motor drive

Volts-per-hertz (V/f) controlled induction motor drives could exhibit small-signal instability in the low and medium speed ranges, and particularly under light-load conditions. This results in sustained sub-harmonic oscillations in motor current, torque and speed. This instability is accentuated on account of inverter dead-time. This paper examines improving the stability by connecting an external inductor in series with the stator winding. Further, to avoid an actual external three-phase inductor which could be expensive in the case of high-power drives, a simple control scheme which emulates this series inductor is proposed. The emulation scheme also has the advantage that the value of series inductor could be programmable. This inductive emulation scheme, along with V/f control, is implemented on a TMS320F2812 DSP processor platform to control a 100-kW induction motor drive. Simulation and experimental results show that the proposed control scheme is effective in mitigating the oscillations in the 100-kW induction motor drive.