Variable speed drive for the sensorless PWM control of an AC motor by exploiting PWM-induced artefacts

Patent metadata

Field	Value
Publication number	US-11264935-B2
Application number	US-202017031223-A
Country	US
Kind code	B2
Filing date	Sep 24, 2020
Priority date	Sep 25, 2019
Publication date	Mar 1, 2022
Grant date	Mar 1, 2022

Abstract

A variable speed drive comprises an output for delivering a drive voltage to an electric motor, power inverter, a drive controller, and a current sensor. The drive controller includes a PWM generator, a control law module, and a state variable estimator for estimating a state variable of the electric motor. The module computes a target voltage signal based on state variable estimates provided by the estimator and outputs the target voltage signal to the PWM generator. The generator approximates the target voltage signal with a PWM control signal, controls the inverter using the control signal, computes, based on the deviation between the control signal and the target voltage signal, an estimation support signal, and outputs the estimation support signal to the estimator. The estimator estimates a state variable of the motor based on the estimation support signal and the drive current, and outputs the estimate to the module.

First claim

The invention claimed is:

1. A variable speed drive for the closed loop control of the operation of an AC electric motor based on a given control law, the variable speed drive comprising:
an output terminal for delivering a controlled alternating drive voltage (upwm) to the controlled AC electric motor;
a solid-state power inverter for generating the drive voltage;
a drive controller for controlling the generation of the drive voltage by the power inverter; and
a drive current sensing device for measuring the instantaneous intensity of the drive current taken up by the controlled AC electric motor and for providing the resulting measurements as a drive current intensity signal to the drive controller,
wherein the drive controller includes:
a pulse-width modulation generator;
a control law module storing the given control law; and
a state variable estimation module for estimating the instantaneous value of at least one state variable of the controlled AC electric motor,
wherein the control law module is adapted to, based on the stored control law and state variable estimates provided by the estimation module, compute a target voltage signal and output the computed target voltage signal to the pulse-width modulation generator,
wherein the pulse-width modulation generator is adapted to:
approximate the received target voltage signal with a pulse-width modulated inverter control signal;
control the operation of the power inverter using the inverter control signal, thereby obtaining the drive voltage;
compute, based on the deviation between the inverter control signal and the target voltage signal, a state variable estimation support signal; and
output the computed state variable estimation support signal to the state variable estimation module, and
wherein the state variable estimation module is adapted to:
estimate the instantaneous value of a state variable of the AC electric motor based on the received state variable estimation support signal and the drive current intensity signal provided by the drive current sensing device; and
output the resulting state variable estimate to the control law module.

2. The variable speed drive of claim 1 , wherein the pulse-width modulation generator is adapted to compute the state variable estimation support signal based on a pulse-width modulation inherent disturbance signal, which is obtained by subtracting the target voltage signal from the inverter control signal.

3. The variable speed drive of claim 2 , wherein the pulse-width modulation generator is adapted to compute the state variable estimation support signal by integrating the disturbance signal to obtain the primitive of the disturbance signal.

4. The variable speed drive of claim 1 , wherein the variable speed drive is adapted to rely on a single feedback to perform closed loop control of the AC electric motor, namely the drive current intensity signal provided by the drive current sensing device.

5. The variable speed drive of claim 1 , wherein the variable speed drive is adapted to control the operation of the AC electric motor without the injection of a dedicated probing signal into the drive voltage.

6. The variable speed drive of claim 1 , wherein the drive controller further includes an analog-to-digital converter for converting the drive current intensity signal into a digital signal prior to its input into the state variable estimation module.

7. The variable speed drive of claim 1 , wherein the state variable estimation module is adapted to estimate the instantaneous value of the rotor position of the electric motor based on the received state variable estimation support signal and the drive current intensity signal provided by the drive current sensing device.

8. The variable speed drive of claim 1 , wherein the pulse-width modulation generator is adapted to apply three-phase pulse-width modulation with single carrier to generate the inverter control signal.

9. The variable speed drive of claim 1 , wherein the pulse-width modulation generator is adapted to apply three-phase pulse-width modulation with interleaved carriers to generate the inverter control signal.

10. An electric drive assembly comprising a synchronous reluctance motor and a variable speed drive of claim 1 for controlling the synchronous reluctance motor.

11. An electric drive assembly comprising a permanent-magnet synchronous motor and a variable speed drive of claim 1 for controlling the permanent-magnet synchronous motor.

12. A method of controlling, in a closed loop, the operation of an AC electric motor based on a given control law, the method comprising the following steps:
a) measuring the instantaneous intensity of the drive current taken up by the controlled AC electric motor;
b) estimating the instantaneous value of a state variable of the AC electric motor using the measured drive current intensity;
c) computing, based on the given control law and the estimated state variable, a target voltage signal;
d) approximating the computed target voltage signal with a pulse-width modulated inverting control signal;
e) computing, based on the deviation between the inverting control signal and the target voltage signal, a state variable estimation support signal;
f) generating, by voltage inversion, a controlled alternating drive voltage using the inverting control signal; and
g) delivering the generated drive voltage to the controlled AC electric motor;
wherein the state variable estimation according to step b) relies on the state variable estimation support signal computed in step e) as an additional input together with the drive current intensity measured in step a).

Assignees

• Schneider Toshiba Inverter Europe Sas

Inventors

• Combes Pascal
• Surroop Dilshad
• Martin Philippe
• Rouchon Pierre

Classifications

• H02P23/03 Primary

  specially adapted for very low speeds · CPC title

• H02P21/18

  Estimation of position or speed · CPC title

• H02P21/04

  specially adapted for very low speeds · CPC title

• H02P21/24

  Vector control not involving the use of rotor position or rotor speed sensors · CPC title

• H02P23/12

  Observer control, e.g. using Luenberger observers or Kalman filters · CPC title