Discontinuous pulse width modulation

• US 9,369,071 B2
• Filed: 02/20/2014
• Issued: 06/14/2016
• Est. Priority Date: 02/20/2014
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Wang, Chang-Jiang, Degner, Michael W., Reynolds, William
• Primary Examiner(s): Ismail, Shawki S
• Assistant Examiner(s): BROWN, BRADLEY R
• Application Number:
  US14/185,274
• Publication Number:
  US 20150236628A1
• Time in Patent Office: 845 Days
• Field of Search: 318/139
• US Class Current: 1/1
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: H02M 7/53876 based on synthesising a desired voltage vector via the selection of appropriate fundamental voltage vectors, and corresponding dwelling times
• CPC Class Codes: H02M 7/5395 by pulse-width modulation
• CPC Class Codes: H02P 27/08 with pulse width modulation
• CPC Class Codes: H02P 6/182 using back-emf in windings
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors

Abstract

A discontinuous pulse width modulation technique is used in a controller to control an inverter that converts DC battery power to AC power to operate an electric motor, e.g., in a hybrid electric vehicle. The discontinuous pulse width modulation technique uses only one of the two zero state voltage vectors in its calculations whereas traditional pulse width modulation uses both zero state voltage vectors. The use of a single zero state voltage vector can result in one of a group of switches in the inverter remaining in a constant state during a complete duty cycle while still providing the commanded voltage vector to the electrical motor. As a result losses due to switching can be reduced.

Claims

1. A vehicle discontinuous PWM method comprising:

outputting a voltage-command to control an electric motor using two adjacent active vectors and a single zero-vector associated with the two active vectors, and to include a vector angle that is proportional to a sum of rotor position and an output of a commanded vector angle and a sector dependent parameter; and

alternating the single zero-vector for calculating the voltage-command for subsequent adjacent active vectors of an adjacent sector.

2. The method of claim 1, wherein outputting includes calculating a first active vector duty cycle for a first of the two adjacent active vectors, calculating a second active vector duty cycle for a second of the two adjacent active vectors, calculating a single zero vector duty cycle for the single zero-vector, and converting the first active vector duty cycle, the second active vector duty cycle and the zero vector duty cycle to control duty cycles of three upper switches of an inverter, respectively.

3. The method of claim 2, wherein outputting includes calculating a third active vector duty cycle for the first adjacent active vector, calculating a fourth active vector duty cycle for the second active vector, calculating a single, second zero-vector duty cycle for a second single zero vector, and converting the third active vector duty cycle, the fourth active vector duty cycle and the second zero vector duty cycle to control duty cycles of three lower switches of the inverter, respectively.

16. The method of claim 1, wherein outputting includes:

outputting first duty cycles based on two active vectors and a single zero-vector in a sector, and control signals for an upper group of inverter switches and a lower group of inverter switches using the first duty cycles,

holding one of the control signals for the upper group of inverter switches constant,

holding one of the control signals for the lower group of inverter switches constant, and

wherein the single zero-vector alternates on a sector basis.

17. The method of claim 16, wherein the single zero-vector is selected from two zero-vectors and wherein a first vector of the two zero-vectors is used with calculating in a first sector for the upper group of inverter switches and a second vector of the two zero-vectors is used with calculating in the first sector for the lower group of inverter switches;

and

wherein outputting includes holding constant one of the control signals for the upper group of inverter switches and wherein outputting includes holding constant one of the control signals for the lower group of inverter switches such that one switch of both the upper group and the lower group do not switch during one duty cycle.

18. The method of claim 1, wherein outputting includes calculating and internal duty cycle variables using

19. The method of claim 18, wherein outputting includes calculating inverter switch control signals from σ

₁, σ

₂, and σ

₀; and

outputting a control signal to the switches of the inverter and wherein at least one control signal is equal to one of σ

₁, σ

₂, and σ

₀.

20. The method of claim 1, wherein vector angle (θ

_a) is computed using

4. A discontinuous pulse width modulation method for a vehicle, the method comprising:

receiving an angle of a motor-drive commanded vector to drive an electric motor; and

outputting first duty cycles based on two active vectors and a single zero vector in a sector, and control signals for an upper group of inverter switches and a lower group of inverter switches using the first duty cycles, wherein at least one of the control signals for the sector is held constant,

wherein outputting calculates a command voltage vector angle θ

_a relative to the active voltage vector of a sector of a voltage vector plane using

5. The method of claim 4, wherein outputting includes holding one of the control signals for the upper group of inverter switches constant.

6. The method of claim 5, wherein outputting includes holding one of the control signals for the lower group of inverter switches constant.

7. The method of claim 4, wherein the single zero vector alternates on a sector basis.

8. The method of claim 7, wherein the single zero vector is selected from two zero vectors and wherein a first vector of the two zero vectors is used with calculating in a first sector for the upper group of inverter switches and a second vector of the two zero vectors is used with calculating in the first sector for the lower group of inverter switches.

9. The method of claim 8, wherein outputting includes holding constant one of the control signals for the upper group of inverter switches and wherein outputting includes holding constant one of the control signals for the lower group of inverter switches such that one switch of both the upper group and the lower group do not switch during one duty cycle.

10. A vehicle comprising:

a battery;

an electrical motor to be powered by the battery;

inverter circuitry to convert a DC signal of the battery to an AC signal of the electric motor, the inverter circuitry including three legs that include two series connected switches and a node intermediate the two switches connected to the electrical motor; and

a controller to output a state signal for the inverter circuitry in response to a target command voltage for the electric motor, wherein the inverter circuitry in response to the state signal holds at least one switch in a constant state throughout a duty cycle,

wherein the controller calculates an angle of a command voltage vector θ

_a relative to the active voltage vector of a sector of the voltage vector plane using

11. The vehicle of claim 10, wherein the inverter circuitry defines a six sector voltage vector plane with six active voltage vectors ({right arrow over (V)}₁, {right arrow over (V)}₂, {right arrow over (V)}₃, {right arrow over (V)}₄, {right arrow over (V)}₅, {right arrow over (V)}₆) defining the six sectors and two zero voltage vectors ({right arrow over (V)}₀, {right arrow over (V)}₇) for use in the controller to control state of the inverter circuitry and electrical signals from the battery to the electrical motor.

12. The vehicle of claim 11, wherein at least one switch in each leg is held at a constant state for a duty cycle to reduce switching losses.

13. The vehicle of claim 10, wherein the controller calculates internal duty cycle variables using

14. The vehicle of claim 13, wherein the controller calculates inverter switch control signals from

σ

₁,σ

₂, and σ

₀.

15. The vehicle of claim 14, wherein the controller outputs a control signal to the switches of the inverter and wherein at least one control signal is equal to one of σ

₁, σ

₂, and σ

₀.