Method for direct voltage saturation calculation and prevention of inverter voltage saturation

Patent metadata

Field	Value
Publication number	US-11689134-B2
Application number	US-201916560657-A
Country	US
Kind code	B2
Filing date	Sep 4, 2019
Priority date	Apr 14, 2019
Publication date	Jun 27, 2023
Grant date	Jun 27, 2023

Abstract

A voltage saturation prevention algorithm used as at least part of a method of controlling an electric vehicle, wherein the electric vehicle comprises an electric motor, a controller, and an inverter. The controller receives a control signal with an instruction to operate the electric motor, then sends a switching signal corresponding to the control signal to the inverter, wherein the inverter provides a plurality of output signals for operation of the electric motor. The method includes determining the expected amplitude of the plurality of output signals based on the instruction to operate the electric motor, calculating the amount of modification of the plurality of output signals required to prevent the expected amplitude from reaching a saturation value, and modifying, based on the calculation, the instruction to operate the electric motor to prevent the expected amplitude from reaching the saturation value. The method is implemented in software, without any additional hardware.

First claim

What is claimed is:

1. A method of controlling an electric vehicle that comprises an electric motor and an inverter, the method comprising:
receiving a control signal comprising an instruction to operate the electric motor, the instruction comprising a specific command current value;
determining an expected amplitude of a plurality of output signals for the inverter to provide for operating the electric motor;
determining, as a function of the specific command current value without using any measurement systems, a modulation index;
calculating, based on the modulation index and a maximum allowable modulation index determined based on a current modulation strategy of the inverter, a saturated voltage modifier value indicating an amount of modification of the plurality of output signals required to prevent the expected amplitude from reaching a saturation value, the calculated saturated voltage modifier value limited to a maximum allowable value based on an application-specific design parameter; and
modifying, based on the calculation, the specific command current value to operate the electric motor to prevent the expected amplitude from reaching the saturation value;
wherein the specific command current comprises:
a commanded quadratic current component value I q,cmd ; and
a commanded direct current component value I d,cmd ; and

modifying the specific command current value comprises:
determining a modified commanded quadratic current component value, I q,cmd,modified , by calculating:
Iq, cmd, modified=Iq,cmd×Ecompensator;

wherein E compensator is the saturated voltage modifier value;
determining a modified direct current component value, I d,cmd,modified , by calculating:

Id
,
cmd
,

modified
=
Id

,

cmd
-

Iq
,

cmd
2

×
Ecompensator

❘
"\[LeftBracketingBar]"

Id

❘
"\[RightBracketingBar]"

⁢
max

;
and

wherein |Id| max is a maximum potential value of the direct current component for the electric motor.

2. The method of claim 1 , wherein the method is implemented in software.

3. The method of claim 1 , wherein the plurality of output signals is a plurality of voltage components.

4. The method of claim 1 , wherein calculating the amount of modification of the plurality of output signals is based on current angle modification.

5. The method of claim 4 , wherein a modification in the current angle results in a reduction of amplitude of the plurality of output signals.

6. The method of claim 1 , wherein the method automatically corrects errors in a calibration table of the electric motor.

7. An electric vehicle comprising:
an electric motor;
an inverter providing a plurality of output signals for operation of the electric motor; and
a controller in communication with the inverter and performing operations comprising:
receiving a control signal comprising an instruction to operate the electric motor, the instruction comprising a specific command current value;
determining an expected amplitude of a plurality of output signals for the inverter to provide for operating the electric motor;
determining, as a function of the specific command current value-without using any measurement systems, a modulation index;
calculating, based on the modulation index and a maximum allowable modulation index determined based on a current modulation strategy of the inverter, a saturated voltage modifier value indicating an amount of modification of the plurality of output signals required to prevent the expected amplitude from reaching a saturation value, the calculated saturated voltage modifier value limited to a maximum allowable value based on an application-specific design parameter; and
modifying, based on the calculation, the specific command current value to operate the electric motor to prevent the expected amplitude from reaching the saturation value;
wherein the specific command current comprises:
a commanded quadratic current component value I q,cmd ; and
a commanded direct current component value I d,cmd ; and

modifying the specific command current value comprises:
determining a modified commanded quadratic current component value, I q,cmd,modified , by calculating:
Iq,cmd ,modified= Iq,cmd×E compensator;

wherein E compensator is the saturated voltage modifier value;
determining a modified direct current component value, I d,cmd,modified , by calculating:

Id
,
cmd
,

modified
=
Id

,

cmd
-

Iq
,

cmd
2

×
Ecompensator

❘
"\[LeftBracketingBar]"

Id

❘
"\[RightBracketingBar]"

⁢
max

;

 and
wherein |Id| max is a maximum potential value of the direct current component for the electric motor.

8. The electric vehicle of claim 7 , wherein the method is implemented in software.

9. The electric vehicle of claim 7 , wherein the plurality of output signals is a plurality of voltage components.

10. The electric vehicle of claim 7 , wherein calculating the amount of modification of the plurality of output signals is based on current angle modification.

11. The electric vehicle of claim 10 , wherein a modification in the current angle results in a reduction of amplitude of the plurality of output signals.

12. The electric vehicle of claim 7 , wherein the method automatically corrects errors in a calibration table of the electric motor.

Assignees

• Karma Automtoive Llc
• Karma Automotive Llc

Inventors

• Ziaieinejad Saleh
• Niu Geng

Classifications

• H02P27/085

  wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency · CPC title

• H02P23/0077 Primary

  Characterised by the use of a particular software algorithm · CPC title

• B60Y2200/91

  Electric vehicles · CPC title

• B60L15/20

  for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed · CPC title

• H02P23/00 Primary

  Arrangements or methods for the control of AC motors characterised by a control method other than vector control · CPC title