Induction electric motor with flux injection in multiple reference frames

A method of suppressing tonal noises in a propulsion system having an induction electric motor with a rotor and a stator, a pulse width modulated (PWM) inverter, and a controller with a processor and tangible, non-transitory memory, the method comprising:

• generating torque for propulsion via the induction electric motor;
• injecting flux harmonics through a respective voltage injection simultaneously in a plurality of reference frames, including a rotor reference frame, a first flux reference frame and a second flux reference frame;
• generate a PWM signal based in part on the flux harmonics;
• controlling operation of the electric vehicle based on the PWM signal, including applying the PWM signal to the PWM inverter;
• selecting the rotor reference frame based in part on a rotor bar order and a rotor position of the rotor;
• selecting the first flux reference frame based in part on a first induction order, the rotor position and a slip position;
• selecting the second flux reference frame based in part on a second induction order, the rotor position and the slip position, wherein the first induction order and the second induction order are respective electrical harmonic orders associated with stator-induced electromagnetic excitations in the induction electric motor, the first induction order and the second induction order being selected based in part on a number of phases, stator slots and pole pairs in the induction electric motor;
• obtaining a respective angular position of the rotor reference frame (θ1) as θ1=(H1*θr), where H1 is the rotor bar order and θr is the rotor position, the rotor bar order being defined as a ratio of a number of rotor bars in the rotor to the number of pole pairs, via the controller;
• and
• obtaining the respective angular position of the first flux reference frame (θ2) as θ2=H2*(θr+θs), where H2 is the first induction order, θs is the slip position and θr is the rotor position, via the controller.

An electric vehicle comprising:

• an induction electric motor configured to generate torque for propulsion, the electric motor having a rotor and a stator;
• a controller in communication with the induction electric motor and having a processor and tangible, non-transitory memory on which instructions are recorded for a method of suppressing tonal noises;
• a pulse width modulated (PWM) inverter operatively connected to the controller;
• wherein the controller is adapted to simultaneously inject flux harmonics through a respective voltage injection in a plurality of reference frames, including a rotor reference frame, a first flux reference frame and a second flux reference frame;
• wherein the controller is adapted to generate a PWM signal based in part on the flux harmonics, the controller being adapted to control operation of the electric vehicle based on the PWM signal, including applying the PWM signal to the PWM inverter;
• wherein the rotor reference frame is based in part on a rotor bar order and a rotor position of the rotor, the rotor bar order being defined as the ratio of a number of rotor bars in the rotor to the number of pole pairs;
• wherein the controller is configured to obtain a respective angular position of the rotor reference frame (θ1) as θ1=(H1*θr), where H1 is the rotor bar order and θr is the rotor position;
• wherein the first flux reference frame is based in part on a first induction order, the rotor position and a slip position;
• wherein the second flux reference frame is based in part on a second induction order, the rotor position and the slip position;
• wherein the first induction order and the second induction order are respective electrical harmonic orders associated with stator-induced electromagnetic excitations in the induction electric motor, the first induction order and the second induction order being selected based in part on a number of phases, stator slots and pole pairs in the induction electric motor;
• and
• wherein the controller is configured to obtain the respective angular position of the first flux reference frame (θ2) as θ2=H2*(θr+θs), where H2 is the first induction order, θs is the slip position and θr is the rotor position.