Method of duty cycle generation for extending the linear modulation range in a pulse width modulated voltage source inverter

Patent metadata

Field	Value
Publication number	US-11239787-B2
Application number	US-202017011223-A
Country	US
Kind code	B2
Filing date	Sep 3, 2020
Priority date	Oct 4, 2019
Publication date	Feb 1, 2022
Grant date	Feb 1, 2022

Abstract

A control system and method of controlling a multi-phase electric machine for controlling the flow of electrical current between a voltage source and the multi-phase electric machine or other application/load. The control system includes, between each phase of the multi-phase electric machine and the voltage source: a high side diode and a high side switch positioned in parallel between a positive terminal of the voltage source and the electric machine with the high side diode being reverse biased with regard to the positive terminal; and a low side diode and a low side switch positioned in parallel between a negative terminal of the voltage source and the electric machine with the low side diode being reverse biased with regard to the electric machine. The control system operates the high side and low side switches to provide efficient operation of the electric machine.

First claim

What is claimed is:

1. A control system for a multi-phase electric machine for controlling the flow of electrical current between a voltage source and the multi-phase electric machine to operate the electric machine as a motor, the control system comprising:
wherein, between each phase of the multi-phase electric machine and the voltage source, the control system includes:
a high side diode and a high side switch positioned in parallel between a positive terminal of the voltage source and the electric machine with the high side diode being reverse biased with regard to the positive terminal; and
a low side diode and a low side switch positioned in parallel between a negative terminal of the voltage source and the electric machine with the low side diode being reverse biased with regard to the electric machine;

wherein the control system is a pulse width modulated control system with a pulse cycle duration and wherein the physical components of the control system define a minimum duty cycle (Dmin), the control system further defining a deadtime duty cycle (Ddead) and being operable to define a variable duty cycle (D*) from zero to one:
wherein Dmin is the minimum non-zero duty cycle defined by the control system during operation of the electric machine as a motor; and
wherein the maximum non-unity duty cycle (Dmax) defined by the control system during operation of the electric machine is equivalent to (1−Dmin).

2. The control system of claim 1 wherein the variable duty cycle defined by the control system is determined using a carrier signal wherein the carrier signal linearly falls from 1.0 at a start of the pulse cycle to 0.0 at a mid-point of the pulse cycle and linearly rises from 0.0 at the midpoint of the pulse cycle to 1.0 at an end point of the pulse cycle and wherein commands for controlling the high side switch and the low side switch are determined as a function of the carrier signal.

3. The control system of claim 2 wherein, when the variable duty cycle is between Dmin and (Dmax−2(Ddead)) and the electrical current is positive, the control system commands:
the high side switch to be open when the carrier signal is greater than D* and closed when the carrier signal is less than D*; and
the low side switch to be closed when the carrier signal is greater than (D*+2(Ddead)) and open when the carrier signal is less than (D*+2(Ddead)).

4. The control system of claim 2 wherein, when the electrical current is positive and (D*+2(Ddead)) is greater than Dmax and D* is at or below Dmax, the control system commands:
the high side switch to be closed when the carrier signal is less than D* and open when the carrier signal is greater than D*; and
the low side switch to be open for the entire pulse cycle duration (PWM period).

5. The control system of claim 2 wherein, when the electrical current is positive and D* is greater than Dmax and D* is also at or below (1−Dmin/2), the control system commands:
the high side switch to be closed when the carrier signal is less than Dmax and open when the carrier signal is greater than Dmax; and
the low side switch to be open for the entire pulse cycle duration (PWM period).

6. The control system of claim 2 wherein, when the electrical current is positive and D* is greater than (1−Dmin/2), the control system commands:
the high side switch to be closed for the entire pulse cycle duration (PWM period); and
the low side switch to be open for the entire pulse cycle duration (PWM period).

7. The control system of claim 2 wherein, when the electrical current is positive and D* is below Dmin and D* is also greater than or equal to (Dmin/2), the control system commands:
the high side switch to be closed when the carrier signal is less than Dmin and open when the carrier signal is greater than Dmin; and
the low side switch to be open when the carrier signal is less than (Dmin+2(Ddead)) and closed when the carrier signal is greater than (Dmin+2(Ddead)).

8. The control system of claim 2 wherein, when the electrical current is positive and the D* is below (Dmin/2), the control system commands:
the high side switch to be open for the entire pulse cycle duration (PWM period); and
the low side switch to be closed for the entire pulse cycle duration (PWM period).

9. The control system of claim 2 wherein, when the variable duty cycle (D*) is between (Dmin+2(Ddead)) and Dmax and the electrical current is negative, the control system commands:
the high side switch to be open when the carrier signal is greater than (D*−2(Ddead)) and closed when the carrier signal is less than (D*−2(Ddead)); and
the low side switch to be closed when the carrier signal is greater than D* and open when the carrier signal is less than D*.

10. The control system of claim 2 wherein, when the electrical current is negative and D* is greater than Dmax and D* is also less than or equal to (1−Dmin/2), the control system commands:
the high side switch to be closed when the carrier signal is less than (Dmax−2(Ddead)) and open when the carrier signal is greater than (Dmax−2(Ddead)); and
the low side switch to be closed when the carrier signal is greater than Dmax and open when the carrier signal is less than Dmax.

11. The control system of claim 2 wherein, when the electrical current is negative and D* is greater than (1−Dmin/2), the control system commands:
the high side switch to be closed for the entire pulse cycle duration (PWM period); and
the low side switch to be open for the entire pulse cycle duration (PWM period).

12. The control system of claim 2 wherein, when the electrical current is negative and (D*−2(Ddead)) is less than Dmin and D* is greater than or equal to Dmin, the control system commands:
the high side switch to be open for the entire pulse cycle duration (PWM period); and
the low side switch to be closed when the carrier signal is greater than D* and open when the carrier signal is less than D*.

13. The control system of claim 2 wherein, when the electrical current is negative and D* is less than Dmin and D* is also greater than or equal to (1−Dmin/2), the control system commands:
the high side switch to be open for the entire pulse cycle duration (PWM period); and
the low side switch to be closed when the carrier signal is greater than Dmin and open when the carrier signal is less than Dmin.

14. The control system of claim 2 wherein, when the electrical current is negative and D* is less than (Dmin/2), the control system commands:
the high side switch to be open for the entire pulse cycle duration (PWM period); and
the low side switch to closed for the entire pulse cycle duration (PWM period).

15. The control system of claim 2 wherein, when the variable duty cycle is between Dmin and (Dmax−2(Ddead)) and the electrical current is positive, the control system commands:
the high side switch to be open when the carrier signal is greater than D* and closed when the carrier signal is less than D*; and
the low side switch to be closed when the carrier signal is greater than (D*+2(Ddead)) and open when the carrier signal is less than (D*+2(Ddead)); and
wherein, when the variable duty cycle (D*) is between (Dmin+2(Ddead)) and Dmax and the electrical current is negative, the control system commands:
the high side switch to be open when the carrier signal is greater than (D*−2(Ddead)) and closed when the carrier signal is less than (D*−2(Ddead)); and
the low side switch to be closed when the carrier signal is greater than D* and open when the carrier signal is less than D*.

16. The control system of claim 15 wherein, when the elect

Assignees

• Borgwarner Inc

Inventors

• Secrest Caleb W

Classifications

• H02P27/085

  wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency · CPC title

• H02M7/53871

  with automatic control of output voltage or current · CPC title

• H02M7/48 Primary

  using discharge tubes with control electrode or semiconductor devices with control electrode · CPC title

• H02M1/38

  Means for preventing simultaneous conduction of switches · CPC title

• H02M7/5395 Primary

  by pulse-width modulation · CPC title