Electric motor in propulsion system with auxiliary power generation

Patent metadata

Field	Value
Publication number	US-11095240-B2
Application number	US-201916515695-A
Country	US
Kind code	B2
Filing date	Jul 18, 2019
Priority date	Jul 18, 2019
Publication date	Aug 17, 2021
Grant date	Aug 17, 2021

Abstract

A propulsion system having an electric motor and corresponding method. A controller is configured to receive a torque request and selectively command the electric motor. The controller has a processor and tangible, non-transitory memory on which instructions are recorded for a method of generating an auxiliary power. The controller is configured to obtain a desired auxiliary power and a delta factor (δ). The delta factor is set as a speed modifier (Δω=δ) when the cosine of an angle (θ), between a constant torque unit vector and a decreasing voltage ellipse unit vector, is less than a predefined threshold. A modified rotor speed is obtained as a sum of an original rotor speed and a speed modifier (Δω). The controller is configured to obtain modified stator current commands based on the modified rotor speed and torque request. The auxiliary power is generated by commanding the modified stator current commands.

First claim

What is claimed is:

1. A propulsion system comprising: an electric motor including a rotor with at least one permanent magnet and a stator;
a controller configured to receive a torque request and selectively command the electric motor based in part on the torque request;
wherein the controller has a processor and tangible, non-transitory memory on which instructions are recorded for a method of generating an auxiliary power, execution of the instructions by the processor causing the controller to:
determine a desired auxiliary power based on the torque request;
obtain a delta factor (δ) based on the desired auxiliary power and an estimated power loss;
set the delta factor (δ) as a speed modifier (Δω) when a cosine of an angle (θ) between a first vector and a second vector is greater than or equal to a predefined threshold;
obtain a modified rotor speed as a sum of an original rotor speed and the speed modifier (Δω);
obtain modified stator current commands based in part on the modified rotor speed and the torque request; and
generate the auxiliary power by commanding the modified stator current commands.

2. The propulsion system of claim 1 , wherein:
the controller is configured to set the speed modifier (Δω) to zero when the cosine of the angle (θ) is less than the predefined threshold.

3. The propulsion system of claim 1 , wherein:
the delta factor (δ) is obtained by a closed-loop control module configured to obtain an error value as a difference between the desired auxiliary power (P desired ) and the estimated power loss (P loss ), limited to a maximum allowable power loss (P loss,max ); and
the closed-loop control module is configured to minimize the error value over time by adjusting the delta factor (δ).

4. The propulsion system of claim 1 , wherein:
the first vector is a constant torque unit vector (T 1 , T 2 ) and the second vector is a decreasing voltage ellipse unit vector (V 1 , V 2 ); and
the cosine of the angle (θ) is obtained as an inner product of the constant torque unit vector (T 1 , T 2 ) and the decreasing voltage ellipse unit vector (V 1 , V 2 ) such that: cos θ=(T 1 ·V 1 +T 2 ·V 2 ).

5. The propulsion system of claim 4 , wherein:
the constant torque unit vector (T 1 , T 2 ) is based in part on a partial derivative of the torque request (T e ) with respect to a measured q-axis current (i q ) and a measured d-axis current (i d ) such that:

(

T
1

,

T
2

)

=



-

∂

T
e

∂

i
q

,

∂

T
e

∂

i
d



.

6. The propulsion system of claim 4 , wherein:
the decreasing voltage ellipse unit vector (V 1 , V 2 ) is based in part on a partial derivative of a voltage cost function (J) with respect to the measured q-axis current (i q ) and the measured d-axis current (i d ) such that:

(

V
1

,

V
2

)

=



-

∂
J

∂

i
d

,

-

∂
J

∂

i
q



;

and
the voltage cost function (J) is based on a d-axis voltage command (v d ) and a q-axis voltage command (v q ) such that: J=½(v d 2 +v q 2 ).

7. The propulsion system of claim 6 , wherein:
the d-axis voltage command (v d ) is obtained as: v d =(i d *R s −i q *ω′L q );
the q-axis voltage command (v q ) is obtained as: v q =(λ f ω′+i q *R s +i d *ω′L d ); and
λ f is a rotor magnet flux magnitude, R s is a stator resistance, i d * is the d-axis stator current command, i q * is the q-axis stator current command, ω′ is the modified rotor speed, L d is a d-axis static inductance and L q is a q-axis static inductance.

8. The propulsion system of claim 1 , further comprising:
an inverter operatively connected to the electric motor;
a cooling loop in thermal communication with the inverter and the electric motor; and
wherein the controller is configured to at least partially direct the auxiliary power, through the cooling loop, to the inverter.

9. The propulsion system of claim 1 , further comprising:
a direct current power source configured to provide a DC link voltage (V dc ) to the electric motor;
a cooling loop in thermal communication with the direct current power source and the electric motor; and
wherein the controller is configured to at least partially direct the auxiliary power, through the cooling loop, to the direct current power source.

10. The propulsion system of claim 1 , further comprising:
a direct current (DC) power source configured to provide a DC link voltage (V dc ) to the electric motor; and
wherein the modified stator current commands include a d-axis stator current command and a q-axis stator current command obtained from a stored data module based on the modified rotor speed, the torque request and the DC link voltage (V dc ).

11. A method of operating an electric motor in a propulsion system, the electric motor having a stator and a rotor with at least one permanent magnet, the propulsion system having a control

Assignees

• Gm Global Tech Operations Llc

Inventors

• Ballal Siddharth
• Yoo Anno

Classifications

• H02P21/28

  Stator flux based control · CPC title

• B60L50/51

  characterised by AC-motors · CPC title

• B60L50/60

  using power supplied by batteries (in combination with fuel cells B60L50/75) · CPC title

• H02P21/06

  Rotor flux based control involving the use of rotor position or rotor speed sensors · CPC title

• B60L2210/44

  Current source inverters · CPC title