Speed sensorless hybrid vector controlled induction motor with zero speed operation

The method of operating a three phase AC motor, having a stator with stator windings and a rotor, from a source of electric power, comprising the steps:

• generating orthogonal, two phase stator current and voltage component signals in the stationary reference frame from sensed motor parameters, the means comprising a signal harmonic reducing low pass filter that introduces a harmonic reducing filter phase lag;
• transforming the orthogonal, two phase stator current component signals in the stationary reference frame into orthogonal, two phase stator current component signals in the synchronous reference frame;
• generating orthogonal, two phase commanded stator voltage component signals in the synchronous reference frame from the orthogonal, two phase stator current component signals in the synchronous reference frame and input commanded torque and flux signals;
• transforming the orthogonal, two phase commanded stator voltage component signals in the synchronous reference frame into orthogonal, two phase commanded stator voltage component signals in the stationary reference frame;
• generating stator voltages in the motor in response to the orthogonal, two phase commanded stator voltage component signals in the stationary reference frame;
• deriving a set of phase compensated unit vectors from the orthogonal, two phase, stator current and voltage component signals in the stationary reference frame, the set of phase compensated unit vectors being compensated for the harmonic reducing phase lag;
• and
• providing the set of phase compensated unit vectors to the vector rotation means.

Motor apparatus comprising a three phase AC motor having a stator with stator windings and a rotor, a source of electric power and a control, with no rotor speed sensor, for applying power from the source of electric power to the stator windings, the control comprising, in combination:

• means for generating orthogonal, two phase stator current and voltage component signals in the stationary reference frame from sensed motor parameters;
• means for deriving a first set of unit vectors from predetermined starting values of input commanded torque and flux signals,
• means for deriving a second set of unit vectors and a third set of unit vectors from the orthogonal, two phase, stator current and voltage component signals in the stationary reference frame;
• inverse vector rotation means responsive to a selected one of the first and second sets of unit vectors for transforming the orthogonal, two phase stator current component signals in the stationary reference frame into orthogonal, two phase stator current component signals in the synchronous reference frame;
• means for deriving orthogonal, two phase, commanded stator voltage component signals in the synchronous reference frame from the orthogonal, two phase stator current signals in the synchronous reference frame and the input commanded torque and flux signals;
• vector rotation means responsive to one of the first and third sets of unit vectors for transforming the orthogonal, two phase, commanded stator voltage component signals in the synchronous reference frame into orthogonal, two phase, commanded stator voltage component signals in the stationary reference frame;
• means for deriving the motor control signals from the orthogonal, two phase, commanded stator voltage component signals in the stationary reference frame;
• means for generating stator voltages in the motor in response to the motor control signals;
• and
• selection means for starting the motor in an indirect vector control mode with no rotor speed sensor using the first set of unit vectors with the inverse vector rotation means and vector rotation means and changing, after the motor is started, to a direct vector control mode alternatively using the second set of unit vectors with the inverse vector rotation means and the third set of unit vectors in the vector rotation means.

The method of operating a three phase AC motor, having a stator with stator windings and a rotor, from a source of electric power, with no rotor speed sensor, comprising the steps:

• generating orthogonal, two phase stator current and voltage component signals in the stationary reference frame from sensed motor parameters;
• deriving a first set of unit vectors from predetermined starting values of input commanded torque and flux signals,
• deriving a second set of unit vectors and a third set of unit vectors from the orthogonal, two phase, stator current and voltage component signals in the stationary reference frame;
• transforming the orthogonal, two phase stator current component signals in the stationary reference frame into orthogonal, two phase stator current component signals in the synchronous reference frame in an inverse vector rotator using one of the first and second sets of unit vectors;
• deriving orthogonal, two phase, commanded stator voltage component signals in the synchronous reference frame from the orthogonal, two phase stator current signals in the synchronous reference frame and the input commanded torque and flux signals;
• transforming the orthogonal, two phase, commanded stator voltage component signals in the synchronous reference frame into orthogonal, two phase, commanded stator voltage component signals in the stationary reference frame using one of the first and third sets of unit vectors;
• deriving the motor control signals from the orthogonal, two phase, commanded stator voltage component signals in the stationary reference frame;
• generating stator voltages in the motor in response to the motor control signals;
• starting the motor in an indirect vector control mode with no rotor speed sensor using the first set of unit vectors in the inverse vector rotator and the vector rotator;
• and
• changing, after the motor is started, to a direct vector control mode alternatively using the second set of unit vectors in the inverse vector rotator and the third set of unit vectors in the vector rotator.