Granted Patent B2

US 7,880,425 · App. 11/944,793 · Granted Feb 1, 2011

Abstract

Claims (198)

1. An electric motor drive system comprising:

an inverter adapted to generate, based on inverter control inputs, a total number, N, of phase current waveforms, and to provide the N phase current waveforms to a same number, N, of motor input terminals;

a phase current sampling apparatus having the same number, N, of current sensors, wherein each of the N current sensors is adapted to receive one of the N phase current waveforms that are provided to the N motor input terminals, and wherein the N current sensors are adapted simultaneously to sample the N phase current waveforms and to generate N digital values representing amplitudes of the N phase current waveforms; and

a controller adapted to receive the N digital values representing the amplitudes of the N phase current waveforms, to perform an evaluation of the N digital values, and to generate the inverter control inputs based on the evaluation, wherein the controller is adapted to perform the evaluation, at least in part, by determining reference frame currents as a function of all of the N digital values, and wherein the controller is further adapted to measure the phase current waveforms prior to motor operations to produce initial offsets, and to store the initial offsets.

2. The electric motor drive system of claim 1 , wherein the controller is adapted to perform the evaluation by converting the N digital values into synchronous frame currents, and by evaluating the synchronous frame currents.

3. The electric motor drive system of claim 2 , wherein the controller is adapted to convert the N digital values into the synchronous frame currents by performing the steps of:

converting the N digital values into the reference frame currents by applying an equation:

[

i

β

i

α

]

=

2

/

3

⁡

[

0

3

2

-

3

2

1

-

1

2

-

1

2

]

⁡

[

i

a

i

b

i

c

]

 where i α is a first reference frame current, i β is a second reference frame current, i a is a first phase current represented by a first one of the N digital values, i b is a second phase current represented by a second one of the N digital values, and i c is a third phase current represented by a third one of the N digital values; and

converting the reference frame currents into the synchronous frame currents.

4. The electric motor drive system of claim 1 , wherein the controller is further adapted to subtract the initial offsets from the N digital values during the process of performing the evaluation.

5. The electric motor drive system of claim 1 , wherein the plurality of current sensors includes three current sensors.

6. The electric motor drive system of claim 1 , wherein the inverter comprises the same number, N, of phase legs, wherein each of the phase legs generates one of the phase current waveforms and includes a pair of switching elements that includes an upper switching element and a lower switching element.

7. The electric motor drive system of claim 1 , wherein the controller comprises:

a processor adapted to receive the N digital values representing the amplitudes of the phase current waveforms, to perform the evaluation, and to generate regulator control inputs based on the evaluation; and

a regulator adapted to receive the regulator control inputs and to generate the inverter control inputs based on the regulator control inputs.

8. A motor vehicle comprising:

an electric motor adapted to receive a total number, N, of phase current waveforms at a same number, N, of motor input terminals, and to provide torque in response to the N phase current waveforms; and

an electric motor drive system having

an inverter adapted to generate, based on inverter control inputs, a same number, N, of phase current waveforms, and to provide the N phase current waveforms to the N motor input terminals,

a phase current sampling apparatus having the same number, N, of current sensors, wherein each of the N current sensors is adapted to receive one of the N phase current waveforms that are provided to the N motor input terminals, and wherein the N current sensors are adapted simultaneously to sample the N phase current waveforms and to generate N digital values representing amplitudes of the N phase current waveforms, and

a controller adapted to receive the N digital values representing the amplitudes of the N phase current waveforms, to perform an evaluation of the N digital values, and to generate the inverter control inputs based on the evaluation, wherein the controller is adapted to perform the evaluation, at least in part, by determining reference frame currents as a function of all of the N digital values, and wherein the controller is further adapted to measure the phase current waveforms prior to motor operations to produce initial offsets, and to store the initial offsets.

9. The motor vehicle of claim 8 , wherein the controller is adapted to perform the evaluation by converting the N digital values into synchronous frame currents, and by evaluating the synchronous frame currents.

10. The motor vehicle of claim 8 , wherein the electric motor is adapted to receive three phase current waveforms.

11. The motor vehicle of claim 8 , further comprising:

an alternate propulsion system adapted to provide torque alternatively to or simultaneously with the electric motor.

12. A method for regulating phase current waveforms performed by an electric motor drive system, the method comprising the steps of:

an inverter generating, based on inverter control inputs, a total number, N, of phase current waveforms, and providing the N phase current waveforms to a same number, N, of motor input terminals;

generating, by a same number, N, of current sensors, the same number, N, of simultaneous phase current waveform samples at a plurality of sampling instants, resulting in generation of a same number, N, of digital values representing amplitudes of the N phase current waveforms;

performing an evaluation, by a controller, of the N digital values, wherein the controller is adapted to perform the evaluation, at least in part, by determining reference frame currents as a function of all of the N digital values;

generating the inverter control inputs based on the evaluation;

measuring the N phase current waveforms prior to motor operations to produce initial offsets; and

storing the initial offsets.

13. The method of claim 12 , wherein performing the evaluation comprises the steps of:

converting the N digital values into synchronous frame currents; and

performing the evaluation based on the synchronous frame currents.

14. The method of claim 13 , wherein converting the N digital values into the synchronous frame currents comprises the steps of:

converting the N digital values into the reference frame currents by applying an equation:

[

i

β

i

α

]

=

2

⁢

/

⁢

3

⁡

[

0

3

2

-

3

2

1

-

1

2

-

1

2

]

⁡

[

i

a

i

b

i

c

]

where i α is a first reference frame current, i β is a second reference frame current, i a is a first phase current represented by a first one of the N digital values, i b is a second phase current represented by a second one of the N digital values, and i c is a third phase current represented by a third one of the N digital values; and

converting the reference frame currents into the synchronous frame currents.

15. The method of claim 14 , wherein converting the reference frame currents into the synchronous frame currents comprises the step of applying an equation:

[

i

d

i

q

]

=

[

cos

⁢

⁢

θ

e

sin

⁢

⁢

θ

e

-

sin

⁢

⁢

θ

e

cos

⁢

⁢

θ

e

]

⁡

[

i

α

i

β

]

Where i d is a first synchronous frame current, i q is a second synchronous frame current, i α is a first reference frame current, and i β is a second reference frame current.

16. The method of claim 12 ,

wherein the step of performing the evaluation includes subtracting the initial offsets from the N digital values.

17. A method for regulating phase current waveforms performed by an electric motor drive system, the method comprising the steps of:

an inverter generating, based on inverter control inputs, a number, N, of phase current waveforms;

generating, by a same number, N, of current sensors, the same number, N, of simultaneous phase current waveform samples at a plurality of sampling instants, resulting in generation of a plurality of digital values representing amplitudes of the phase current waveforms;

performing an evaluation, by a controller, of the plurality of digital values by:

converting the plurality of digital values into synchronous frame currents by converting the plurality of digital values into reference frame currents by applying an equation:

[

i

β

i

α

]

=

2

⁢

/

⁢

3

⁡

[

0

3

2

-

3

2

1

-

1

2

-

1

2

]

⁡

[

i

a

i

b

i

c

]

10 where i α is a first reference frame current, i β is a second reference frame current, i a is a first phase current, i b is a second phase current, and i c is a third phase current,

converting the reference frame currents into the synchronous frame currents, and

performing the evaluation based on the synchronous frame currents; and

generating the inverter control inputs based on the evaluation.

Assignments (12)