Systems and methods for sensorless control of a motor

A motor controller, comprising:

• a flux observer configured to estimate rotor flux in an induction motor based on a stator voltage and current measurements of the induction motor;
• a low-frequency signal injection (LFSI) module configured to inject a pulsating current along a reference axis of the induction motor to generate a first flux estimation error signal at low speeds of the induction motor;
• a baseline observer configured to generate a second flux estimation error signal at medium-to-high speeds of the induction motor, based on dynamic equations of the induction motor;
• a switching mechanism configured to select between the first flux estimation error signal and the second flux estimation error signal based on a switching signal;
• a Proportional-Integral (PI) regulator configured to:
• receive the selected flux estimation error signal;
• and
• generate a rotor speed derivative estimate based on the selected flux estimation error signal;
• an integrator coupled to the PI regulator, configured to integrate the rotor speed derivative estimate in time to obtain a rotor speed estimate;
• a lead compensator coupled to the integrator, configured to adjust phase of the rotor speed estimate to maintain stability during transitions;
• and
• a switching signal generator configured to monitor a stator frequency of the motor and to activate the LFSI module when the stator frequency falls below a predefined threshold,
• wherein the control system provides estimation of rotor flux and speed across a full range of motor speeds by adaptively switching between the LFSI and baseline observers based on motor operating conditions.

A drive control method for operating an induction machine at torque control mode, the method comprising:

• collecting a temporal profile of a preferred torque for the induction machine, a first estimate of rotor flux angle, and a first estimate of rotor speed of the induction machine;
• determining d-axis current reference and q-axis current reference for the induction machine, based on the first estimate of rotor flux angle and the first estimate of rotor speed;
• generating an injection signal based on the first estimate of rotor speed;
• obtaining d-axis current measurement and q-axis current measurement for the induction machine;
• generating a d-axis error signal based on the d-axis current reference and the d-axis current measurement;
• generating a q-axis error signal based on the q-axis current reference and the q-axis current measurement;
• generating a d-axis reference voltage based on the d-axis error signal and the injection signal;
• generating a q-axis reference voltage based on the q-axis error signal;
• generating a three-phase voltage reference from the d-axis reference voltage and q-axis reference voltage, based on an inverse Clarke/Park transformation;
• and
• controlling the induction machine based on the three-phase voltage reference.