Sensorless control of AC induction motor method and apparatus

A sensorless alternating current induction motor (ACIM) controller, comprising:

• a driver power stage hardware circuit comprising a plurality of power transistors for selectively connecting first and second reference voltages to generate a plurality of phase shifted voltages under control of a plurality of PWM gate control signals, where the plurality of phase shifted voltages are connected to a corresponding plurality of stator windings in an alternating current induction motor such that a plurality of energized stator windings are energized to cause rotation of the rotor relative to the stator while at least one stator winding is disconnected and floating;
• a processor coupled to receive the plurality of phase shifted voltages and a DC bus current measurement and to calculate:
• an estimated slip based on a DC bus current value measured from the DC bus current measurement;
• a plurality of commutation events based on integration of an inducted voltage from the alternating current induction motor while the at least one stator winding is disconnected and floating;
• and
• a rotor speed based on at least the estimated slip and stator speed derived from the plurality of calculated commutation events;
• and
• a pulse width modulator (PWM) hardware circuit for generating the PWM gate control signals so that the driver power stage hardware circuit energizes only the plurality of energized stator windings concurrently while leaving the at least one stator winding unpowered.

A system for controlling a sensorless alternating current induction motor (ACIM) comprising a rotor and a stator comprising a plurality of stator windings, comprising:

• a full bridge inverter circuit for generating a plurality of phase shifted voltages under control of a plurality of PWM control signals, where the plurality of phase shifted voltages are connected to a corresponding plurality of stator windings in an alternating current induction motor such that a plurality of energized stator windings are energized in a connected phase to cause rotation of the rotor relative to the stator while at least one stator winding is floating in a disconnected phase;
• a phase voltage observer coupled to receive the plurality of phase shifted voltages from the full bridge inverter circuit for generating a plurality of commutation events for each of the plurality of phase shifted voltages by integrating an inducted phase voltage during the disconnected phase and producing a stator period measure based on the plurality of commutation events;
• a slip compensation block coupled to receive a DC bus current measurement value from the full bridge inverter circuit for computing an estimated slip as function of the DC bus current measurement value;
• a speed measurement hardware circuit for producing an estimated rotor speed based on the estimated slip and stator period measure;
• a pulse width modulator (PWM) hardware circuit for generating the PWM control signals in response to the estimated rotor speed so that the full bridge inverter circuit energizes only the plurality of energized stator windings concurrently while leaving the at least one stator winding unpowered.