SWITCHED BATTERY AND CAPACITOR ARRANGEMENT AND RELATED OPERATING METHODS

• US 20120133203A1
• Filed: 08/05/2011
• Published: 05/31/2012
• Est. Priority Date: 08/24/2010
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: LIENKAMP, SEBASTIAN, KILIAN, PETER, RAISER, STEPHEN
• Granted Patent: US 8,981,589 B2
• Time in Patent Office: Days
• US Class Current: 307/9.1
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2240/549 Current
• CPC Class Codes: B60L 50/40 using propulsion power supplied by capacitors
• CPC Class Codes: B60L 50/51 characterised by AC-motors
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: B60L 58/40 for controlling a combination of batteries and fuel cells
• CPC Class Codes: B60L 7/14 for vehicles propelled by ac motors
• CPC Class Codes: G05F 5/00 Systems for regulating electric variables by detecting deviations in the electric input to the system and thereby controlling a device within the system to obtain a regulated output
• CPC Class Codes: H02J 2310/48 for electric vehicles [EV] or hybrid vehicles [HEV]
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 90/40 Application of hydrogen technology to transportation, e.g. using fuel cells

Abstract

Systems and methods are provided for regulating the state of charge of a battery. An exemplary electrical system includes a fuel cell coupled to a bus and a battery coupled to the bus via a switching arrangement coupled to a capacitor. An exemplary method for operating the electrical system involves operating the switching arrangement such that a voltage of the battery is substantially equal to a voltage of the fuel cell when a state of charge of the battery is greater than a lower threshold value and less than an upper threshold value, and operating the switching arrangement to couple the capacitor electrically in series between the battery and the bus when the state of charge of the battery is not between the lower threshold value and the upper threshold value.

Claims

1. An electrical system for a vehicle, the electrical system comprising:

a capacitive element;

a switching arrangement coupled to the capacitive element, the switching arrangement being configured to be coupled between a rail of a bus and an energy storage element; and

a control module coupled to the switching arrangement and the energy storage element, wherein the control module is configured to;

operate the switching arrangement such that a voltage of the energy storage element is substantially equal to a voltage of the rail of the bus when a state of charge of the energy source is greater than a lower threshold value and less than an upper threshold value;

operate the switching arrangement to add a voltage of the capacitive element to the voltage of the energy storage element when the state of charge of the energy storage element is greater than the upper threshold value; and

operate the switching arrangement to subtract the voltage of the capacitive element from the voltage of the energy storage element when the state of charge of the energy storage element is less than the lower threshold value.

2. The electrical system of claim 1, wherein:

the capacitive element has a first terminal and a second terminal; and

the switching arrangement comprises;

a first node coupled to the first terminal of the capacitive element;

a second node coupled to the second terminal of the capacitive element;

a third node coupled to the rail of the bus;

a fourth node coupled to the energy storage element;

a first switch coupled between the first node and the third node, the first switch being configured to allow current from the first node to the third node when the first switch is closed;

a first diode coupled between the first node and the third node, the first diode being configured antiparallel to the first switch;

a second switch coupled between the second node and the third node, the second switch being configured to allow current from the third node to the second node when the second switch is closed;

a second diode coupled between the second node and the third node, the second diode being configured antiparallel to the second switch;

a third switch coupled between the first node and the fourth node, the third switch being configured to allow current from the first node to the fourth node when the third switch is closed;

a third diode coupled between the first node and the fourth node, the third diode being configured antiparallel to the third switch;

a fourth switch coupled between the second node and the fourth node, the fourth switch being configured to allow current from the fourth node to the second node when the fourth switch is closed; and

a fourth diode coupled between the second node and the fourth node, the fourth diode being configured antiparallel to the fourth switch.

3. The electrical system of claim 2, wherein the control module is configured to:

open the first switch, the second switch, the third switch, and the fourth switch when the state of charge of the energy storage element is less than or equal to the lower threshold value; and

open the first switch, the second switch, the third switch, and the fourth switch when the state of charge of the energy storage element is greater than or equal to the upper threshold value.

4. The electrical system of claim 2, wherein the control module is configured to:

close the first switch and the fourth switch when the voltage of the capacitive element is greater than zero and the state of charge of the energy storage element is greater than or equal to the lower threshold value in a first operating mode; and

close the second switch and the third switch when the voltage of the capacitive element is greater than zero and the state of charge of the energy storage element is less than or equal to the upper threshold value in a second operating mode.

5. The electrical system of claim 1, wherein:

the capacitive element comprises a non-polarized capacitor having a first terminal and a second terminal; and

the switching arrangement comprises;

a first node coupled to the first terminal of the capacitive element and the rail of the bus;

a second node coupled to the second terminal of the capacitive element and the energy storage element;

a third node;

a first switch coupled between the first node and the third node, the first switch being configured to allow current from the first node to the third node when the first switch is closed;

a first diode coupled between the first node and the third node, the first diode being configured antiparallel to the first switch;

a second switch coupled between the second node and the third node, the second switch being configured to allow current from the second node to the third node when the second switch is closed; and

a second diode coupled between the second node and the third node, the second diode being configured antiparallel to the second switch.

6. The electrical system of claim 1, wherein:

the capacitive element comprises a non-polarized capacitor having a first terminal and a second terminal; and

the switching arrangement comprises;

a first node coupled to the first terminal of the capacitive element and the rail of the bus;

a second node coupled to the second terminal of the capacitive element and the energy storage element;

a relay coupled between the first node and the second node, the relay being configured to allow bidirectional current between the first node and the second node.

7. A method for operating an electrical system in a vehicle, the electrical system comprising a fuel cell coupled to a bus and a battery coupled to the bus via a switching arrangement coupled to a capacitor, the method comprising:

operating the switching arrangement such that a battery voltage of the battery is substantially equal to a fuel cell voltage of the fuel cell when a state of charge of the battery is greater than a lower threshold value and less than an upper threshold value;

operating the switching arrangement to couple the capacitor electrically in series between the battery and the bus when the state of charge of the battery is less than or equal to the lower threshold value; and

operating the switching arrangement to couple the capacitor electrically in series between the battery and the bus when the state of charge of the battery is greater than or equal to the upper threshold value.

8. The method of claim 7, wherein operating the switching arrangement such that the battery voltage is substantially equal to the fuel cell voltage comprises short circuiting the capacitor when the state of charge of the battery is between the lower threshold value and the upper threshold value.

9. The method of claim 8, wherein operating the switching arrangement such that the battery voltage is substantially equal to the fuel cell voltage further comprises:

when a voltage of the capacitor is greater than zero and the state of charge of the battery is between the lower threshold value and the upper threshold value, discharging the capacitor prior to short circuiting the capacitor.

10. The method of claim 7, wherein:

operating the switching arrangement to couple the capacitor electrically in series between the battery and the bus when the state of charge of the battery is less than or equal to the lower threshold value comprises subtracting a voltage of the capacitor from the battery voltage; and

operating the switching arrangement to couple the capacitor electrically in series between the battery and the bus when the state of charge of the battery is greater than or equal to the upper threshold value comprises adding a voltage of the capacitor to the battery voltage.

11. An electrical system comprising:

a bus comprising a positive rail and a negative rail;

a battery having a positive battery terminal, and having a negative battery terminal coupled to the negative rail;

a capacitive element having a positive capacitor terminal and a negative capacitor terminal;

a first switching element coupled between the positive capacitor terminal and the positive rail, the first switching element being configured to allow current from the positive capacitor terminal to the positive rail when closed;

a second switching element coupled between the negative capacitor terminal and the positive rail, the second switching element being configured to allow current from the positive rail to the negative capacitor terminal when closed;

a third switching element coupled between the positive capacitor terminal and the positive battery terminal, the third switching element being configured to allow current from the positive capacitor terminal to the positive battery terminal when closed; and

a fourth switching element coupled between the negative capacitor terminal and the positive battery terminal, the fourth switching element being configured to allow current from the positive battery terminal to the negative capacitor terminal when closed.

12. The electrical system of claim 11, further comprising:

a first diode coupled between the positive capacitor terminal and the positive rail, the first diode being configured to allow current from the positive rail to the positive capacitor terminal;

a second diode coupled between the negative capacitor terminal and the positive rail, the second diode being configured to allow current from the negative capacitor terminal to the positive rail;

a third diode coupled between the positive capacitor terminal and the positive battery terminal, the third diode being configured to allow current from the positive battery terminal to the positive capacitor terminal; and

a fourth diode coupled between the negative capacitor terminal and the positive battery terminal, the fourth diode being configured to allow current from the negative capacitor terminal to the positive battery terminal.

13. The electrical system of claim 11, further comprising a fuel cell having a positive fuel cell terminal coupled to the positive rail of the bus and a negative fuel cell terminal coupled to the negative rail of the bus.

14. The electrical system of claim 13, the capacitive element having a capacitor voltage between the positive capacitor terminal and the negative capacitor terminal, wherein the electrical system further comprises a control module coupled to the battery and the capacitive element, wherein the control module is configured to short circuit the capacitive element using at least one of the first switching element, the second switching element, the third switching element, and the fourth switching element when the capacitive element voltage is equal to zero and a state of charge of the battery is within a predefined range.

15. The electrical system of claim 14, further comprising:

a first diode coupled between the positive capacitor terminal and the positive rail of the bus, the first diode being configured to allow current from the positive rail to the positive capacitor terminal;

a second diode coupled between the negative capacitor terminal and the positive rail of the bus, the second diode being configured to allow current from the negative capacitor terminal to the positive rail;

a third diode coupled between the positive capacitor terminal and the positive battery terminal, the third diode being configured to allow current from the positive battery terminal to the positive capacitor terminal; and

a fourth diode coupled between the negative capacitor terminal and the positive battery terminal, the fourth diode being configured to allow current from the negative capacitor terminal to the positive battery terminal.

16. The electrical system of claim 15, wherein the control module is coupled to the first switching element, the second switching element, the third switching element, and the fourth switching element, and the control module is configured to open the first switching element, the second switching element, the third switching element, and the fourth switching element when the state of charge of the battery is not within the predefined range.

17. The electrical system of claim 14, the control module being coupled to the first switching element, the second switching element, the third switching element, and the fourth switching element, wherein in response to a change in operating mode, the control module is configured to:

discharge the capacitive element by closing the first switching element and the fourth switching element when the state of charge of the battery is greater than a lower threshold value; and

discharge the capacitive element by closing the second switching element and the third switching element when the state of charge of the battery is less than an upper threshold value.

18. The electrical system of claim 13, wherein an open circuit voltage of the battery is less than an open circuit voltage of the fuel cell, and greater than a voltage of the fuel cell under full load.

19. The electrical system of claim 13, wherein the capacitive element comprises an ultracapacitor.

20. The electrical system of claim 13, further comprising an electric drive unit coupled to the bus, the electric drive unit being configured to:

receive current from the bus in a first operating mode; and

provide current to the bus in a second operating mode.