Variable voltage convert system with reduced bypass diode conduction

• US 9,931,944 B2
• Filed: 03/22/2016
• Issued: 04/03/2018
• Est. Priority Date: 03/22/2016
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Alam, Mohammed Khorshed, Chen, Lihua, Zhou, Yan, Xu, Fan
• Primary Examiner(s): HOUSTON, ADAM D
• Application Number:
  US15/077,495
• Publication Number:
  US 20170274777A1
• Time in Patent Office: 742 Days
• Field of Search: 307 101, 307 45, 307 46
• CPC Class Codes: B60L 15/007 Physical arrangements or structures of drive train converters specially adapted for the propulsion motors of electric vehicles
• CPC Class Codes: B60L 15/2009 for braking
• CPC Class Codes: B60L 2210/10 DC to DC converters
• CPC Class Codes: B60L 2240/526 Operating parameters
• CPC Class Codes: B60L 2240/527 Voltage
• CPC Class Codes: B60L 2240/529 Current
• CPC Class Codes: B60L 50/10 using propulsion power supplied by engine-driven generators, e.g. generators driven by combustion engines
• CPC Class Codes: B60L 50/16 with provision for separate direct mechanical propulsion
• CPC Class Codes: B60L 50/61 by batteries charged by engine-driven generators, e.g. series hybrid electric vehicles
• CPC Class Codes: B60L 7/18 Controlling the braking effect B60L7/12, B60L7/14, B60L7/16 take precedence
• CPC Class Codes: H02J 7/1492 by means of controlling devices between the generator output and the battery
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 7/533 using discharge tubes only
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• 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
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility
• CPC Class Codes: Y02T 10/92 Energy efficient charging or discharging systems for batteries, ultracapacitors, supercapacitors or double-layer capacitors specially adapted for vehicles

Abstract

A vehicle powertrain includes a bypass diode and a controller. The bypass diode is configured to clamp an inverter DC terminal voltage to a battery voltage. The controller is configured to, while the terminal voltage is within a predetermined range of the battery voltage, maintain off a lower IGBT of a DC-DC converter while in a propulsion mode, and modulate the lower IGBT to increase the terminal voltage to maintain the bypass diode reverse biased while in a regenerative mode.

Claims

1. A vehicle powertrain comprising:

a bypass diode configured to clamp an inverter DC terminal voltage to a battery voltage; and

a controller configured to, while the terminal voltage is within a predetermined range of the battery voltage, maintain off a lower IGBT of a DC-DC converter while in a propulsion mode, and modulate the lower IGBT to increase the terminal voltage to maintain the bypass diode reverse biased while in a regenerative mode.

2. The vehicle powertrain of claim 1, wherein the controller is further configured to modulate the lower IGBT and an upper IGBT of the DC-DC converter at a regenerative frequency that is less than an operating frequency.

3. The vehicle powertrain of claim 2, wherein the operating frequency of the converter is at least 5 kHz, and the regenerative frequency is no more than 2.5 kHz.

4. The vehicle powertrain of claim 3, wherein the IGBTs are modulated such that an on-time percentage of the lower IGBT is greater than a 2% PWM duty cycle.

5. The vehicle powertrain of claim 3, wherein the IGBTs are modulated at a PWM duty cycle in which the lower IGBT on-time percentage increases as the regenerative frequency decreases.

6. The vehicle powertrain of claim 1 further comprising an electric machine, and wherein the controller is further configured to, in response to a rotational speed of the electric machine decreasing below a minimum speed limit, while operating in the regenerative mode, modulate the lower IGBT and an upper IGBT of the DC-DC converter to boost the terminal voltage to at least the battery voltage.

7. The vehicle powertrain of claim 1, wherein the modulation of the lower IGBT increases a current fluctuation magnitude through an inductor of the converter to increase the inverter DC terminal voltage to reverse bias the bypass diode.

8. A method of operating a DC-DC converter of a vehicle powertrain comprising:

while a bus voltage is within a predetermined range of a battery voltage, by a controller

maintaining in an on state an upper IGBT to enhance a channel from a battery to a load while in a propulsion mode; and

modulating the upper IGBT to increase a current fluctuation magnitude through an inductor of the converter to reverse bias a converter bypass diode.

9. The method of claim 8 further comprising modulating a lower IGBT inversely to the upper IGBT such that the lower IGBT on-time percentage is greater than 2%.

10. The method of claim 8, wherein the upper IGBT is modulated such that the upper IGBT off-time percentage is greater than 2%.

11. The method of claim 8, wherein the predetermined range is within 25 volts.

12. The method of claim 8, wherein the modulation is at a regenerative frequency that is less than an operating frequency.

13. The method of claim 12, wherein the regenerative frequency is less than half of the operating frequency.

14. A vehicle powertrain comprising:

a boost converter coupling a battery with an inverter;

a bypass diode configured to clamp an inverter DC terminal voltage to a battery voltage; and

a controller configured to, while operating the powertrain in a regenerative mode, modulate IGBTs of the boost converter to increase a current fluctuation magnitude through an inductor of the boost converter to shutoff the bypass diode by increasing an average of the inverter DC terminal voltage.

15. The vehicle powertrain of claim 14, wherein the controller is further configured to modulate the IGBTs of the boost converter to decrease a voltage fluctuation across an input capacitor of the boost converter to shutoff the bypass diode by increasing an average of the inverter DC terminal voltage.

16. The vehicle powertrain of claim 14, wherein the controller is configured to, when the DC terminal voltage is within a predetermined range of the battery voltage, turn on an upper IGBT and turn off a lower IGBT when the powertrain is in a propulsion mode, and modulate the upper IGBT and lower IGBT when the powertrain is in a regeneration mode.

17. The vehicle powertrain of claim 16, wherein the predetermined range is within 25 volts.

18. The vehicle powertrain of claim 14, wherein the controller is further configured to modulate the lower IGBT and an upper IGBT of the boost converter at a regenerative frequency that is less than an operating frequency.

19. The vehicle powertrain of claim 18, wherein the operating frequency of the boost converter is at least 5 kHz, and the regenerative frequency is no more than 2.5 kHz.

20. The vehicle powertrain of claim 19, wherein the IGBTs are modulated such that an on-time percentage of the lower IGBT is greater than a 2% PWM duty cycle.