Improved Dual Volts-Per-Hertz Control of Double Inverter-Fed Wound Rotor Induction Machine

Dual volts-per-hertz (dual V/F) control is a simple and cost-effective speed control strategy for double inverter-fed wound rotor induction machine based on the steady-state model of the machine. However, the existing dual V/F control limits the maximum torque developed during acceleration or deceleration of the drive. Furthermore, the existing control can only operate with a limited choice of operating frequency profiles and has no control over magnetizing current sharing between stator and rotor. In this article, these limitations of the otherwise simple and robust dual V/F control are overcome by incorporating a torque control scheme along with a stator and rotor voltage magnitude selection scheme. The improved dual V/F control can operate with any frequency profile, develop torque as commanded, and distribute magnetizing current between stator and rotor. The resulting drive provides more control over the machine and a faster dynamic response compared to the existing dual V/F scheme. A 5-hp, 8-pole wound rotor induction machine drive is used to experimentally validate the proposed control scheme.