Model reference current control of a unipolar induction motor drive

A control algorithm to yield the required current shaping control of a three active switch, three-phase unipolar drive system for an induction motor is derived in this paper. The method utilizes terminal voltage control through PWM to properly shape the phase currents. Phase voltages are calculated based on both the fundamental frequency and zero sequence steady-state equivalent circuits of an induction machine to achieve the desired speed and load set point. Since this method relies on characterizing the machine parameters, it does not require feedback of the phase currents, and therefore, drive systems using this method for this topology can eliminate three current sensors over traditional hysteretic current control methods. Both simulation and experimental results are included to verify the proposed terminal voltage control method on this potential low cost variable speed topology for integrated motor-inverter products.