Constant torque control method for permanent magnet synchronous motor

Patent metadata

Field	Value
Publication number	US-10868485-B2
Application number	US-201916584915-A
Country	US
Kind code	B2
Filing date	Sep 26, 2019
Priority date	Nov 10, 2018
Publication date	Dec 15, 2020
Grant date	Dec 15, 2020

Abstract

A constant torque control method for a permanent magnet synchronous motor. The method includes: 1) starting a motor; setting a torque T of the motor; calculating a given current iq_limit on a q-axis based on the torque T; setting a target current iq_A on the q-axis to be equal to the given current iq_limit; and allowing the motor to operate in a constant torque control mode by a current-based proportional integral (PI) controller on the q-axis; 2) presetting a reference speed Vref1 of the motor; measuring a real-time speed V of the motor; when the real-time speed V is less than the reference speed Vref1, increasing an extra current delta_iq to the given current iq_limit to intervene the real-time speed V of the motor; and 3) measuring the real-time speed V of the motor; and calculating a speed difference Err=V−Vref2.

First claim

What is claimed is:

1. A method, comprising:
1) starting a motor; setting a torque T of the motor; calculating a given current iq_limit on a q-axis based on the torque T; setting a target current iq_A on the q-axis to be equal to the given current iq_limit; and allowing the motor to operate in a constant torque control mode by a current-based proportional integral (PI) controller on the q-axis;
2) presetting a reference speed Vref1 of the motor; measuring a real-time speed V of the motor; when the real-time speed V is less than the reference speed Vref1, increasing an extra current delta_iq to the given current iq_limit to intervene the real-time speed V of the motor, so that the motor withdraws from the constant torque control mode and enters a constant speed control mode with a target speed Vref2; and
3) measuring the real-time speed V of the motor; calculating a speed difference Err=V−Vref2; when the speed difference Err is greater than a given value E 0 , allowing the motor to withdraw from the constant speed control mode and return to the constant torque control mode in 1).

2. The method of claim 1 , wherein the reference speed Vref1=the target speed Vref2 or Vref1<Vref2.

3. The method of claim 2 , wherein the given current iq_limit on the q-axis is calculated according to a formula T=K×iq_limit, where T is the preset torque of the motor, and K is a coefficient.

4. The method of claim 3 , wherein the constant speed control mode is maintained by a speed-based PI controller disposed outside the current-based PI controller on the q-axis.

5. The method of claim 4 , wherein when the speed difference Err is negative, the speed-based PI controller constantly acquires the extra current delta_iq of the q-axis; in the constant speed control mode, the target current iq_A is a sum of the given current iq_limit and a plurality of extra currents delta_iq of the q-axis.

6. The method of claim 5 , wherein whether or not the speed-based PI controller quits a working mode is determined by the speed difference Err; when the speed difference Err is larger than a preset value E 0 which is greater than 0, the speed-based PI controller quits the working mode.

7. The method of claim 6 , wherein the real-time speed V is measured by a speed observer; a signal corresponding to the real-time speed V is processed by average filtering and recursive filtering to inhibit a speed fluctuation.

8. The method of claim 7 , wherein the reference speed Vref1 is acquired by a plurality of experiments.

9. The method of claim 7 , wherein a response time t1 of the speed-based proportional integral controller is less than a response time t2 of the current-based proportional integral controller; the response time t1 of the speed-based proportional integral controller is determined by a rotational inertia of a load connected to the motor, and the response time t1 of the speed-based proportional integral controller is proportional to the rotational inertia of the load.

Assignees

• Zhongshan Broad Ocean Motor Co

Inventors

• Lan Jinghao
• Bian Wenqing

Classifications

• H02P2207/05

  Synchronous machines, e.g. with permanent magnets or DC excitation · CPC title

• H02P25/024

  controlled by supply frequency · CPC title

• H02P21/24 Primary

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

• H02P21/0021

  using different modes of control depending on a parameter, e.g. the speed · CPC title

• H02P21/13 Primary

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