Electric power system for controlling an electric machine

Patent metadata

Field	Value
Publication number	US-9853589-B2
Application number	US-201615059941-A
Country	US
Kind code	B2
Filing date	Mar 3, 2016
Priority date	Mar 3, 2016
Publication date	Dec 26, 2017
Grant date	Dec 26, 2017

Abstract

An electric power system including a front-end converter that is supplied electric power from a high-voltage DC power source, and an associated motor control system is described. A control method includes monitoring the electric machine and determining a reference current based upon the electric power supplied from the high-voltage DC power source. A motor current is determined based upon the monitoring of the electric machine, and a feed-forward current is determined based upon the motor current and the monitoring of the electric machine. A first duty cycle is determined based upon the reference current, the motor current and the feed-forward current, and a feed-forward duty cycle is determined based upon the monitoring of the electric machine. A second duty cycle is determined based upon the feed-forward duty cycle and the first duty cycle, and the front-end converter is controlled based upon the second duty cycle.

First claim

The invention claimed is:

1. A method for controlling a front-end converter, wherein the front-end converter is electrically connected to an electric inverter electrically connected to an electric machine via a high-voltage DC bus, and wherein a high-voltage DC power source is disposed to supply electric power to the front-end converter, the method comprising:
monitoring, via a controller, the electric machine;
determining a reference current based upon the electric power supplied from the high-voltage DC power source;
determining a motor current based upon the monitoring of the electric machine;
determining a feed-forward current based upon the motor current and the monitoring of the electric machine, including:
determining an average motor current,
determining a rate limiter term associated with a command to operate the front-end converter in one of a linear mode and a six-step mode, and
determining the feed-forward current based upon the motor current, the average motor current and the rate limiter;

determining a first duty cycle based upon the reference current, the motor current and the feed-forward current;
determining a feed-forward duty cycle based upon the monitoring of the electric machine;
determining a second duty cycle based upon the feed-forward duty cycle and the first duty cycle; and
controlling operation of the front-end converter based upon the second duty cycle.

2. The method of claim 1 , wherein determining a reference current based upon the electric power supplied from the high-voltage DC power source comprises determining the reference current based upon a difference between a voltage potential of the high-voltage bus and a commanded voltage for the high-voltage bus.

3. The method of claim 1 , wherein determining the feed-forward current based upon the motor current, the average motor current and the rate limiter comprises determining the feed-forward current based upon only the motor current when the rate limiter term is associated with a command to operate the front-end converter in the linear mode.

4. The method of claim 1 , wherein determining the feed-forward current based upon the motor current, the average motor current and the rate limiter comprises determining the feed-forward current based upon the average motor current when the rate limiter term is associated with a command to operate the front-end converter in the six-step mode.

5. The method of claim 1 , wherein determining a motor current based upon the monitoring of the electric machine comprises:
determining electric current supplied to the electric machine;
determining a motor torque command, motor speed, a battery electrical potential and a bus electrical potential;
determining commanded duty cycles for controlling the front-end converter based upon the motor torque command, the motor speed, the battery electrical potential and the bus electrical potential; and
determining the motor current based upon the electric current and the commanded duty cycles.

6. The method of claim 1 , wherein determining a feed-forward duty cycle based upon the monitoring of the electric machine comprises:
determining a motor current;
determining an average motor current;
determining a ripple current based upon a difference between the motor current and the average motor current;
determining a rate limiter term associated with a command to operate the front-end converter in one of a linear mode and a six-step mode; and
determining the feed-forward duty cycle based upon the ripple current and the rate limiter term.

7. The method of claim 6 , comprising determining the feed-forward duty cycle based upon the ripple current and the rate limiter term only when the command to operate the front-end converter comprises a six-step mode.

8. The method of claim 6 , wherein the feed-forward duty cycle is zero when the command to operate the front-end converter comprises a linear mode.

9. The method of claim 1 , wherein determining a second duty cycle based upon the feed-forward duty cycle and the first duty cycle comprises adding the feed-forward duty cycle and the first duty cycle.

10. An electric power system, comprising:
a front-end converter electrically connected to an electric inverter electrically connected to an electric machine via a high-voltage DC bus;
a capacitor electrically connected between positive and negative conductors of the high-voltage DC bus;
a high-voltage DC power source disposed to supply electric power to the front-end converter;
a controller in communication with the front-end converter, the electric inverter, the electric machine, and the high-voltage DC power source, and operatively connected to the front-end converter and the electric inverter, the controller including an instruction set, the instruction set executable to:
monitor operation of the electric machine;
determine a reference current based upon a magnitude of electric power supplied from the high-voltage DC power source;
determine a motor current based upon the operation of the electric machine;
determine a feed-forward current based upon the motor current and the operation of the electric machine;
determine a first duty cycle based upon the reference current, the motor current and the feed-forward current;
determine a feed-forward duty cycle based upon the monitoring of the electric machine, including the instruction set executable to:
determine an average motor current,
determine a rate limiter term associated with a command to operate the front-end converter in one of a linear mode and a six-step mode, and
determine the feed-forward current based upon the motor current, the average motor current and the rate limiter;

determine a second duty cycle based upon the feed-forward duty cycle and the first duty cycle; and
control operation of the front-end converter based upon the second duty cycle.

11. The electric power system of claim 10 , wherein the instruction set is executable to determine the reference current based upon a difference between a voltage potential of the high-voltage bus and a commanded voltage for the high-voltage bus.

12. The electric power system of claim 10 , wherein the instruction set is executable to determine the feed-forward current based upon only the motor current when the rate limiter term is associated with a command to operate the front-end converter in the linear mode.

13. The electric power system of claim 10 , wherein the instruction set is executable to determine the feed-forward current based upon the average motor current when the rate limiter term is associated with a command to operate the front-end converter in the six-step mode.

14. The electric power system of claim 10 , wherein the instruction set is executable to:
determine electric current supplied to the electric machine;
determine a motor torque command, motor speed, a battery electrical potential and a bus electrical potential;
determine commanded duty cycles for controlling the front-end converter based upon the motor torque command, the motor speed, the battery electrical potential and the bus electrical potential; and
determine the motor current based upon the electric current and the commanded duty cycles.

15. The electric power system of claim 10 , wherein the instruction set is executable to:
determine a motor current;
determine an average motor current;
determine a ripple current based upon a difference between the motor current and the average motor current;
determine a rate limiter term associated with a command to operate the front-end converter in one of a linear mode and a six-step mode; and
determin

Assignees

• Gm Global Tech Operations Llc

Inventors

• Jing Xin
• Stancu Constantin C
• Welchko Brian A

Classifications

• B60L2210/40

  DC to AC converters · CPC title

• B60L2240/429

  Current · CPC title

• H02P27/08 Primary

  with pulse width modulation · CPC title

• B60W10/08

  including control of electric propulsion units, e.g. motors or generators · CPC title

• B60L15/02

  characterised by the form of the current used in the control circuit · CPC title