Method and apparatus for multiple mode control of voltage from a fuel cell system
First Claim
1. A fuel cell system, comprising:
- a fuel cell stack;
a battery;
a series pass element electrically coupled between at least a portion of the fuel cell stack and a portion of the battery; and
a regulating circuit for regulating current through the series pass element in response to a greater of a battery charging current error, a battery voltage error and a stack current error.
3 Assignments
0 Petitions
Accused Products
Abstract
A fuel cell system determines each of a battery charging current error, a battery voltage error, and a stack current error. The fuel cell system regulates current through a series pass element in response to a greater of the determined errors. Thus, the fuel cell system operates in three modes: battery voltage limiting mode, stack current limiting mode and battery charging current limiting mode. Additionally, there can be a fourth “saturation” mode where the stack voltage VS drops below the battery voltage VB as the load pulls even more current. Individual fuel cell systems can be combined in series and/or parallel to produce a combined fuel cell system having a desired output voltage and current.
99 Citations
51 Claims
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1. A fuel cell system, comprising:
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a fuel cell stack;
a battery;
a series pass element electrically coupled between at least a portion of the fuel cell stack and a portion of the battery; and
a regulating circuit for regulating current through the series pass element in response to a greater of a battery charging current error, a battery voltage error and a stack current error. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A fuel cell system, comprising:
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a number of fuel cells forming a fuel cell stack;
a number of battery cells forming a battery;
a series pass element;
a blocking diode electrically coupled between the fuel cell stack and the series pass element; and
a regulating circuit for regulating current through the series pass element in proportion to at least a greater of a difference between a battery charging current and a battery charging current limit, a difference between a battery voltage and a battery voltage limit, and a difference between a stack current and a stack current limit. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A control circuit for a fuel cell system having a fuel cell stack and a battery, the control circuit comprising:
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a series pass element electrically coupleable between at least a portion of the fuel cell stack and a portion of the battery; and
a regulating circuit for regulating current through the series pass element in response to a greater of a battery charging current error, a battery voltage error and a stack current error. - View Dependent Claims (17, 18, 19)
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20. A control circuit for a fuel cell system, comprising:
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a series pass element;
a blocking diode electrically coupled in series with the series pass element; and
a regulating circuit coupled to the series pass element to regulate a current through the series pass element in proportion to at least a greater of a difference between a battery charging current and a battery charging current limit, a difference between a battery voltage and a battery voltage limit, and a difference between a stack current and a stack current limit. - View Dependent Claims (21, 22, 23, 24)
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25. A control circuit for a fuel cell system, comprising:
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a battery charging current sensor;
a battery charging current error integrator having a first input coupled to the battery charging current sensor to receive a battery charging current signal proportional to a battery charging current, a second input coupled to receive a battery charging current limit signal proportional to a battery charging current limit, and an output to supply a battery current error signal proportional to a difference between the battery charging current and the battery charging current limit;
a battery voltage sensor;
a battery voltage error integrator having a first input coupled to the battery voltage sensor to receive a battery voltage signal proportional to a battery voltage, a second input coupled to receive a battery voltage limit signal proportional to a battery voltage limit, and an output to supply a battery voltage error signal proportional to a difference between the battery voltage and the battery voltage limit;
a stack current sensor;
a stack current error integrator having a first input coupled to the stack current sensor to receive a stack current signal proportional to a stack current, a second input coupled to receive a stack current limit signal proportional to a stack current limit, and an output to supply a stack current error signal proportional to a difference between the stack current and the stack current limit;
an OR circuit coupled to the output of each of the battery current error integrator, the battery voltage error integrator and the stack current error integrator; and
a series pass element having a pair of terminals for selectively providing a current path and a control terminal coupled to the OR circuit for regulating current through the current path in proportion to a greater of the battery current error signal, the battery voltage error signal and the stack current error signal. - View Dependent Claims (26, 27, 28, 29)
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30. A control circuit for a fuel cell system, comprising:
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means for determining a greater of a difference between a battery charging current and a battery charging current limit, a difference between a battery voltage and a battery voltage limit, and a difference between a stack current and a stack current limit; and
series pass regulating means for regulating a flow of stack current through a blocking diode in proportion to the determined greater difference. - View Dependent Claims (31)
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32. A control circuit for a fuel cell system, comprising:
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means for determining a difference between a battery charging current and a battery charging current limit;
means for determining a difference between a battery voltage and a battery voltage limit; and
means for determining a difference between a stack current and a stack current limit; and
series pass regulating means for regulating a flow of stack current through a blocking diode in response to the greater of the determined differences. - View Dependent Claims (33, 34)
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35. A method of operating in a fuel cell system, the method comprising:
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determining a battery charging current error;
determining a battery voltage error;
determining a stack current error; and
regulating current through a series pass element in response to a greater of the battery charging current error, the battery voltage error and the stack current error. - View Dependent Claims (36, 37, 38, 39, 40)
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41. A method of operating in a fuel cell system, the method comprising:
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determining a difference between a battery charging current and a battery charging current limit;
determining a difference between a battery voltage and a battery voltage limit;
determining a difference between a stack current and a stack current limit; and
regulating a current through a series pass element in proportion to at least a greater of the difference between the battery charging current and the battery charging current limit, the difference between the battery voltage and the battery voltage limit, and the difference between the stack current and the stack current limit. - View Dependent Claims (42, 43, 44, 45)
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46. A fuel cell system, comprising:
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a voltage bus;
a first fuel cell stack electrically couplable across the voltage bus;
a first battery electrically couplable across the voltage bus;
a first series pass element electrically coupled in series on the voltage bus between at least a portion of the first fuel cell stack and a portion of the first battery;
a first regulating circuit for regulating current through the first series pass element in response to a greater of a battery charging current error, a battery voltage error and a stack current error;
a second fuel cell stack electrically couplable across the voltage bus;
a second battery electrically couplable across the voltage bus;
a second series pass element electrically coupled in series on the voltage bus between at least a portion of the second fuel cell stack and a portion of the second battery; and
a second regulating circuit for regulating current through the second series pass element in response to a greater of a battery charging current error, a battery voltage error and a stack current error. - View Dependent Claims (47, 48, 49, 50, 51)
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Specification