Method and system for fuel cell control

• US 6,794,844 B2
• Filed: 08/31/2001
• Issued: 09/21/2004
• Est. Priority Date: 08/31/2001
• Status: Expired due to Fees

• Current Assignee: Ford Motor Company, Daimler AG (Mercedes-Benz Group AG)
• Original Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Inventors: Singh, Prabhakar, Hochgraf, Clark
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/945,047
• Publication Number:
  US 20030044658A1
• Time in Patent Office: 1,117 Days
• Field of Search: 320/101, 320/103, 320/132, 320/167, 429/12, 429/13
• US Class Current: 320/101
• CPC Class Codes: H01M 16/006 of fuel cells with rechargeable batteries
• CPC Class Codes: H01M 8/04089 of gaseous reactants
• CPC Class Codes: H01M 8/04119 with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying
• CPC Class Codes: H01M 8/04305 Modeling, demonstration models of fuel cells, e.g. for training purposes
• CPC Class Codes: H01M 8/04574 Current
• CPC Class Codes: H01M 8/04626 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/0488 of fuel cell stacks
• CPC Class Codes: H01M 8/0491 of fuel cell stacks
• CPC Class Codes: H01M 8/04917 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/04992 characterised by the implementation of mathematical or computational algorithms, e.g. feedback control loops, fuzzy logic, neural networks or artificial intelligence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A control system (20) for controlling the state of charge in an energy storage device (28) by manipulating the voltage of a fuel cell (24) through dynamic system modeling of predetermined parameters (21) for the fuel cell (24) as well as the energy storage device (28). According to the method (100) of the present invention, manipulation (108) of predetermined parameters related to the fuel cell and the energy storage device control the energy storage device to a desired state of charge or divides the load current between the two devices.

Claims

1. A system for controlling an output of a fuel cell, said system comprising:

a fuel cell having an output voltage;

an energy storage device directly paralleled to said fuel cell;

a controller in communication with said fuel cell, said controller for controlling an output voltage of said fuel cell and an output voltage of said energy storage device, said controller having logic for controlling said fuel cell voltage as a function of predetermined parameters and said energy storage device state of charge as a function of said predetermined parameters; and

wherein said controller models, measures and controls a subset of said predetermined parameters for said fuel cell and said predetermined parameters of said energy storage device to control a state-of-charge of said energy storage device.

2. The system as claimed in claim 1 wherein said predetermined parameters for said fuel cell voltage further comprise at least one of a mass flow rate of fuel, a mass flow rate of air, a pressure of fuel, a pressure of air, a humidity of air, a humidity of hydrogen, a temperature of said fuel cell and a current drawn from said fuel cell;

and

said predetermined parameters for said energy storage device voltage further comprise at least one of a state-of-charge for said energy storage device, a current of said energy storage device and an age of said energy storage device.

3. The system as claimed in claim 1 wherein said controller uses a load current to determine a demand load.

4. The system as claimed in claim 3 wherein said controller further comprises logic to modify a fuel cell voltage for dividing said load current into a first portion related to said energy storage device and a second portion related to said fuel cell.

5. The system as claimed in claim 1 wherein said energy storage device is a battery.

6. The system as claimed in claim 1 wherein said energy storage device is an ultracapacitor.

7. A method for controlling an output of a fuel cell system having, a controller, a fuel cell in communication with the controller, an energy storage device directly paralleled to the fuel cell, and an external load, said method comprising the steps of:

determining a desired state of charge for said energy storage device;

measuring a load current;

modeling predetermined parameters of the fuel cell and the energy storage device based on said desired state of charge;

controlling a state-of-charge for the energy storage device based on said predetermined parameter models; and

coordinating voltage-current characteristics for the energy storage device with voltage-current characteristics for the fuel cell.

8. The method as claimed in claim 7 wherein said step of modeling predetermined parameters further comprises:

modeling at least one of a mass flow rate of air, a mass flow rate of fuel, a pressure of air, a pressure of fuel, a temperature of said fuel cell, a humidity of air, a humidity of hydrogen, arid a fuel cell current for the fuel cell; and

modeling at least one of a state of charge, a current, a temperature and an age of the energy storage device.

9. The method as claimed in claim 7 wherein said step of coordinating voltage-current characteristics for the energy storage device and the fuel cell further comprises the steps of:

determining a first operating point for a detected state of charge defined by the intersection of the voltage-current characteristic for the fuel cell and the voltage-current characteristic of the energy storage device;

determining a final operating point for a desired state of charge; and

modifying the predetermined parameters to adjust the detected state of charge to the desired state of charge.

10. The method as claimed in claim 9 further comprising the step of dividing said load current to define a first portion relative to said fuel cell and a second portion relative to said energy storage device, wherein the load current is being served by both the energy storage device and the fuel cell and wherein at a 100% state of charge for said energy storage device, the load current is supplied entirely by the fuel cell.

11. A method of controlling the state of charge for an energy storage device in a system having a fuel cell in communication with a controller and directly paralleled to an energy storage device and an external load, said method comprising the steps of:

determining a current state of charge for the energy storage device;

determining a desired state of charge for the energy storage device;

modeling a subset of predetermined parameters of the fuel cell and the energy storage device based on the measured value of a load current;

controlling a voltage of the fuel cell based on the predetermined parameter models; and

coordinating a voltage-current characteristic of the storage device with a voltage-current characteristic of the fuel cell to adjust the current state of charge to the desired state of charge for the energy storage device.

12. The method as claimed in claim 11 wherein said step of modeling predetermined parameters of the fuel cell further comprises modeling at least one of a mass flow rate of air, a mass flow rate of fuel, a pressure of air, a pressure of fuel, a temperature of said fuel cell, a humidity of air, a humidity of hydrogen, and a fuel cell current;

and

said step of modeling predetermined parameters of the energy storage device further comprises modeling at least one of a state of charge, a current, a temperature and an age.

13. The method as claimed in claim 12 further comprising the step of dividing the load current between the fuel cell and the energy storage device based on the state of charge for the energy storage device.

14. The method as claimed in claim 13 wherein said step of dividing the load current further comprises, at 100% state of charge, the load current is supplied entirely by the fuel cell.