Control of AC electric machine using average synchronous frame currents

Patent metadata

Field	Value
Publication number	US-10889285-B2
Application number	US-201916266799-A
Country	US
Kind code	B2
Filing date	Feb 4, 2019
Priority date	Feb 4, 2019
Publication date	Jan 12, 2021
Grant date	Jan 12, 2021

Abstract

A method for controlling an electric machine in a powertrain system in which a driven load is connected to a rotor of the electric machine includes measuring phase currents at a starting point of a sample period using current sensors connected to phase windings of the electric machine. The individual phase currents also are determined at a midpoint of the previous sample period. An angular position of the rotor is determined at the starting point and previous midpoint before calculating synchronous reference frame currents of the electric machine at the starting and previous midpoint using the phase currents and angular position. The method includes calculating average synchronous reference frame currents over the sample period and regulating operation of the electric machine using the average. An electrical system includes the electric machine, a power inverter module, and a controller that executes the method.

First claim

What is claimed is:

1. A method for controlling a polyphase electric machine, the method comprising:
measuring phase currents of the polyphase electric machine at a starting point of a present sample period using a set of current sensors;
determining the phase currents at a midpoint of a prior sample period, wherein the prior sample period occurs immediately prior to the present sample period;
determining, via a controller, an angular position of a rotor of the polyphase electric machine at the starting point and at the midpoint;
calculating synchronous reference frame currents of the polyphase electric machine at the starting point and the midpoint, via the controller, using the phase currents and the angular position determined at the starting point and at the midpoint;
calculating average synchronous reference frame currents over a duration of the present sample period using the synchronous reference frame currents at the starting point and at the midpoint; and
regulating torque and/or speed of the polyphase electric machine via the controller using the average synchronous reference frame currents.

2. The method of claim 1 , wherein determining the phase currents at the midpoint of the prior sample period includes measuring the phase currents via the set of current sensors.

3. The method of claim 1 , wherein determining the phase currents at the midpoint of the prior sample period includes extrapolating the phase currents via the controller.

4. The method of claim 1 , wherein calculating average synchronous reference frame currents over a duration of the present sample period includes determining the average synchronous reference frame currents at a present or a future instant in time using a current observer of the controller.

5. The method of claim 4 , wherein calculating average synchronous reference frame currents over the duration of the prior sample period includes extrapolating the average synchronous reference frame currents at the future instant in time using the average synchronous reference frame currents at the present and/or a past instant in time, wherein the average synchronous reference frame currents at the present and/or the past instant in time are provided by the current observer.

6. The method of claim 5 , wherein extrapolating the average synchronous reference frame currents at the future instant in time is accomplished by the controller using linear extrapolation.

7. The method of claim 5 , wherein extrapolating the average synchronous reference frame currents at the future instant in time is accomplished by the controller using second order or higher-order extrapolation.

8. The method of claim 1 , the method further comprising:
determining a difference between the average synchronous reference frame currents and the synchronous reference frame currents for the present sample period or the prior sample period;
processing the difference through a low-pass filter to produce a filtered difference; and
adjusting a set of synchronous reference frame current commands to the polyphase electric machine, via the controller in real-time, using the filtered difference.

9. The method of claim 1 , wherein the polyphase electric machine includes a rotor coupled to a set of road wheels of a motor vehicle, and wherein regulating torque or speed of the polyphase electric machine includes controlling a corresponding torque or speed of the set of road wheels.

10. The method of claim 1 , further comprising:
registering, in logic of the controller, that the synchronous reference frame currents are shaped as a rectified sine wave between concurrent samples; and
deriving the average synchronous reference frame currents over a duration of the present sample period by solving the following equations:

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Assignees

• Gm Global Tech Operations Llc

Inventors

• Secrest Caleb W

Classifications

• Y02T10/64

  Electric machine technologies in electromobility · CPC title

• Y02T10/62

  Hybrid vehicles · CPC title

• Y02T10/7072

  Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors · CPC title

• B60W20/10 Primary

  Controlling the power contribution of each of the prime movers to meet required power demand · CPC title

• B60L2240/429

  Current · CPC title