Bidirectional power converter for balancing state of charge among series connected electrical energy storage units

• US 7,378,818 B2
• Filed: 11/19/2003
• Issued: 05/27/2008
• Est. Priority Date: 11/25/2002
• Status: Active Grant

• Current Assignee: Tiax, LLC
• Original Assignee: Tiax, LLC
• Inventors: Fowler, J. Thomas, King, Darrell J., Chertok, Allan, Larocque, Gerald R., Shi, Jay J., Onnerud, Per
• Primary Examiner(s): Laxton; Gary L
• Assistant Examiner(s): PIGGUSH, AARON C
• Application Number:
  US10/717,207
• Publication Number:
  US 20040135545A1
• Time in Patent Office: 1,651 Days
• Field of Search: 320/119, 320/108, 320/118, 320/121, 320/125
• US Class Current: 320/119
• CPC Class Codes: B60L 2260/56 Temperature prediction, e.g. for pre-cooling
• CPC Class Codes: B60L 53/11 DC charging controlled by the charging station, e.g. mode 4
• CPC Class Codes: B60L 58/15 Preventing overcharging
• CPC Class Codes: B60L 58/18 of two or more battery modules
• CPC Class Codes: B60L 58/22 Balancing the charge of battery modules
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/0018 using separate charge circuits
• CPC Class Codes: H02J 7/0019 using switched or multiplexed charge circuits
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• 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 10/92 Energy efficient charging or discharging systems for batteries, ultracapacitors, supercapacitors or double-layer capacitors specially adapted for vehicles
• CPC Class Codes: Y02T 90/12 Electric charging stations
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles

Abstract

A system is provided for balancing state of charge among plural series connected electrical energy storage units that includes a power converter that selectively couples to an individual storage unit of the a string of electrical energy storage units and bidirectionally transfers energy between the individual storage unit and the string of storage units.

Claims

1. A system, comprising:

a string of electrical energy storage units; and

a power converter selectively coupled to an individual storage unit of the string of storage units, the power converter being configured to transfer energy bidirectionally between the individual storage unit and the string of storage units, and to balance state of charge of the individual storage unit to a target state of charge, the state of charge of the individual storage unit being determined from an impedance of the individual storage unit, a current of the individual storage unit, and the terminal voltage of the individual storage unit,

wherein the power converter comprises;

a primary inductor;

a first secondary inductor magnetically coupled to the primary inductor;

a first switch selectively coupling the individual storage unit to the primary inductor; and

the first secondary inductor coupling to an output capacitor;

the output capacitor coupled in parallel to the string of storage units;

the system further comprises;

a first pulse generator configured to provide first enable signals to the first switch;

the first switch being configured to couple the individual storage unit to the primary inductor in response to the first enable signals, and to transfer energy from the individual storage unit to the string of storage units, and

a second pulse generator configured to provide second enable signals to the first pulse generator;

the first pulse generator being configured to provide first enable signals in response to the second enable signals, the second enable signals being capable of controlling a transfer of energy from the individual storage unit to the string of storage units at a controllable rate.

2. The system of claim 1 wherein the power converter is configured to transfer energy at a controllable rate of transfer.

3. The system of claim 1, wherein the power converter is configured to monitor voltage and current data of the individual storage unit resulting from a transfer of energy.

4. The system of claim 1, wherein the power converter is configured to transfer units of energy between the individual storage unit and the string of storage units.

5. The system of claim 1, wherein:

the power converter is further configured to transfer energy from the individual storage unit to charge the primary inductor when the first switch is on, and to discharge energy into the first secondary inductor to charge the output capacitor when the first switch is off, the output capacitor discharging energy to the string of storage units.

6. The system of claim 1, further comprising:

a second secondary inductor coupled to the individual storage unit, the second secondary inductor having a secondary voltage;

a voltage comparator;

a reference voltage and the secondary voltage being inputs of the voltage comparator.

7. The system of claim 6, wherein the second pulse generator is configured to activate when the secondary voltage is greater than the reference voltage.

8. The system of claim 6, wherein the second pulse generator is configured to deactivate when the secondary voltage reaches the reference voltage.

13. The system of claim 1, wherein the power converter comprises:

an up-converter configured to transfer energy from the individual storage unit to the string of storage units; and

a down-converter configured to transfer energy from the string of storage units to the individual storage unit.

14. The system of claim 13, wherein a common transformer is configured to serve as the up-converter and the down converter.

15. The system of claim 1, wherein each storage unit is a storage cell.

16. The system of claim 1, wherein each storage unit is a battery module having a string of storage units.

17. The system of claim 1, wherein a battery pack comprises a string of one or more storage units.

9. A system, comprising:

a string of electrical energy storage units; and

a power converter selectively coupled to an individual storage unit of the string of storage units, the power converter being configured to transfer energy bidirectionally between the individual storage unit and the string of storage units, and to balance state of charge of the individual storage unit to a target state of charge, the state of charge of the individual storage unit being determined from an impedance of the individual storage unit, a current of the individual storage unit, and the terminal voltage of the individual storage unit,

a primary inductor;

a first secondary inductor magnetically coupled to the primary inductor;

a switch selectively coupling the first secondary inductor to the string of storage units, and configured to transfer energy from the string of storage units to charge the first secondary inductor when the switch is on, and to discharge energy into the primary inductor and charging the individual storage unit when the switch is off,

a first pulse generator configured to provide first enable signals to the switch;

the switch being configured to couple the string of storage units to the first secondary inductor in response to the first enable signals, and to transfer energy from the string of storage units to the individual storage unit,

a second pulse generator configured to provide second enable signals to the first pulse generator;

the first pulse generator being configured to provide first enable signals in response to the second enable signals, the second enable signals being configured to control a transfer of energy from the string of storage units to the individual storage unit at a controllable rate.

10. The system of claim 9, further comprising:

a second secondary inductor coupled to the individual storage unit, the second secondary inductor having a secondary voltage;

a voltage comparator;

a reference voltage and the secondary voltage being inputs of the voltage comparator.

11. The system of claim 10, wherein the second pulse generator is configured to activate when the secondary voltage is less than the reference voltage.

12. The system of claim 10, wherein the second pulse generator is configured to deactivate when the secondary voltage reaches the reference voltage.

18. A system, comprising:

a string of electrical energy storage units; and

a power converter selectively coupled to an individual storage unit of the string of storage units, the power converter being configured to transfer energy bidirectionally between the individual storage unit and the string of storage units, wherein the power converter comprises;

a primary inductor;

a first secondary inductor magnetically coupled to the primary inductor;

a first switch selectively coupling the individual storage unit to the primary inductor; and

the first secondary inductor coupling to an output capacitor;

the output capacitor coupled in parallel to the string of storage units;

a first pulse generator configured to provide first enable signals to the first switch;

the first switch being configured to couple the individual storage unit to the primary inductor in response to the first enable signals, and to transfer energy from the individual storage unit to the string of storage units; and

a second pulse generator configured to provide second enable signals to the first pulse generator;

the first pulse generator being configured to provide first enable signals in response to the second enable signals, the second enable signals being capable of controlling a transfer of energy from the individual storage unit to the string of storage units at a controllable rate.

19. The system of claim 18, further comprising:

a second secondary inductor coupled to the individual storage unit, the second secondary inductor having a secondary voltage;

a voltage comparator;

a reference voltage and the secondary voltage being inputs of the voltage comparator.

20. The system of claim 19, wherein the second pulse generator is configured to activate when the secondary voltage is greater than the reference voltage.

21. The system of claim 19, wherein the second pulse generator is configured to deactivate when the secondary voltage reaches the reference voltage.

22. A system, comprising:

a string of electrical energy storage units; and

a power converter selectively coupled to an individual storage unit of the string of storage units, the power converter being configured to transfer energy bidirectionally between the individual storage unit and the string of storage units;

a primary inductor;

a first secondary inductor magnetically coupled to the primary inductor;

a switch selectively coupling the first secondary inductor to the string of storage units, and configured to transfer energy from the string of storage units to charge the first secondary inductor when the second switch is on, and to discharge energy into the primary inductor and charging the individual storage unit when the second switch is off;

a first pulse generator configured to provide first enable signals to the second switch;

the switch being configured to couple the string of storage units to the first secondary inductor in response to the first enable signals, and to transfer energy from the string of storage units to the individual storage unit; and

a second pulse generator configured to provide second enable signals to the first pulse generator;

the first pulse generator being configured to provide first enable signals in response to the second enable signals, the second enable signals being configured to control a transfer of energy from the string of storage units to the individual storage unit at a controllable rate.

23. The system of claim 22, further comprising:

a second secondary inductor coupled to the individual storage unit, the second secondary inductor having a secondary voltage;

a voltage comparator;

a reference voltage and the secondary voltage being inputs of the voltage comparator.

24. The system of claim 22, wherein the second pulse generator is configured to activate when the secondary voltage is less than the reference voltage.

25. The system of claim 22, wherein the second pulse generator is configured to deactivate when the secondary voltage reaches the reference voltage.