Method for adaptive prediction of stack voltage in automotive fuel cell systems
First Claim
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1. A fuel cell system comprising:
- a fuel cell stack providing output power at a particular current density; and
a power controller for controlling the output power of the fuel cell stack, said power controller storing a reference polarization curve that defines the current/voltage relationship of the fuel cell stack, said power controller revising the reference polarization curve to match an actual polarization curve of the stack over time when the stack current density is below a predetermined threshold by changing a first adaptation value and revising the reference polarization curve to match the actual polarization curve of the stack when the stack current density is above a predetermined threshold by changing a second adaptation value;
wherein the first adaptation value defines an absolute voltage difference between the predicted average cell voltage of fuel cells in the stack and the average cell voltage of the reference polarization curve for a particular stack current density, and the second adaptation value defines a current dependent voltage difference between the predicted average cell voltage of fuel cells in the stack and the average cell voltage of the reference polarization curve for a articular stack current density.
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Abstract
A method for revising a reference polarization curve of a fuel cell stack that identifies the relationship between the voltage and the current of the stack over time. When the stack is operating at a low load where kinetic voltage losses of the stack dominate, a first adaptation value is revised as the difference between the actual stack voltage and the stack voltage of the reference polarization curve. When the stack is operating at higher loads where ohmic voltage losses of the stack dominate, a second adaptation value is revised as the difference between the actual stack voltage and the stack voltage of the reference polarization curve.
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Citations
23 Claims
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1. A fuel cell system comprising:
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a fuel cell stack providing output power at a particular current density; and a power controller for controlling the output power of the fuel cell stack, said power controller storing a reference polarization curve that defines the current/voltage relationship of the fuel cell stack, said power controller revising the reference polarization curve to match an actual polarization curve of the stack over time when the stack current density is below a predetermined threshold by changing a first adaptation value and revising the reference polarization curve to match the actual polarization curve of the stack when the stack current density is above a predetermined threshold by changing a second adaptation value; wherein the first adaptation value defines an absolute voltage difference between the predicted average cell voltage of fuel cells in the stack and the average cell voltage of the reference polarization curve for a particular stack current density, and the second adaptation value defines a current dependent voltage difference between the predicted average cell voltage of fuel cells in the stack and the average cell voltage of the reference polarization curve for a articular stack current density. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A fuel cell system comprising:
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a fuel cell stack providing output power at a particular current density; and a power controller for controlling the output power of the fuel cell stack, said power controller storing a reference polarization curve that defines the current/voltage relationship of a new fuel cell stack, said power controller revising the reference polarization curve to match an actual polarization curve of the stack over time when the stack current density is either below or above a predetermined threshold and wherein the predetermined threshold defines a transition between where kinetic voltage losses are dominant and where ohmic voltage losses are dominant, where the kinetic voltage losses are dominant below the threshold and the ohmic voltage losses are dominant above the threshold. - View Dependent Claims (13)
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14. A fuel cell system comprising:
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a fuel cell stack providing output power at a particular current density; and a power controller for controlling the output power of the fuel cell stack, said power controller storing a reference polarization curve that defines the current/voltage relationship of the fuel cell stack, said power controller revising the reference polarization curve to match an actual polarization curve of the stack over time when the stack current density is below a predetermined threshold by changing a first adaptation value and revising the reference polarization curve to match the actual polarization curve of the stack when the stack current density is above a predetermined threshold by changing a second adaptation value; wherein the predetermined threshold defines a transition between where kinetic voltage losses are dominant and where ohmic voltage losses are dominant, where the kinetic voltage losses are dominant below the threshold and the ohmic voltage losses are dominant above the threshold. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification