Dynamic fuel cell system management controller

• US 7,362,073 B2
• Filed: 11/21/2003
• Issued: 04/22/2008
• Est. Priority Date: 11/21/2003
• Status: Expired due to Fees

• Current Assignee: MTI MicroFuel Cells, Inc. (Soluna Holdings, Inc.)
• Original Assignee: MTI MicroFuel Cells, Inc. (Soluna Holdings, Inc.)
• Inventors: Lecky, John Edward
• Primary Examiner(s): Tso; Edward H
• Application Number:
  US10/719,456
• Publication Number:
  US 20050110453A1
• Time in Patent Office: 1,614 Days
• Field of Search: 320/101, 320/132, 429/22, 429/23
• US Class Current: 320/132
• CPC Class Codes: H01M 8/04186 of liquid-charged or electrolyte-charged reactants
• CPC Class Codes: H01M 8/04246 Short circuiting means for defective fuel cells detection of defective fuel cells H01M8/04664, methods for shunting fuel cells H01M8/04955
• CPC Class Codes: H01M 8/04447 of anode reactants at the inlet or inside the fuel cell
• CPC Class Codes: H01M 8/04552 of the individual fuel cell
• CPC Class Codes: H01M 8/04559 of fuel cell stacks
• CPC Class Codes: H01M 8/04589 of fuel cell stacks
• CPC Class Codes: H01M 8/04597 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/04798 of fuel cell reactants
• CPC Class Codes: H01M 8/04873 of the individual fuel cell
• CPC Class Codes: H01M 8/0488 of fuel cell stacks
• CPC Class Codes: H01M 8/0491 of fuel cell stacks
• CPC Class Codes: H01M 8/0494 of fuel cell stacks
• CPC Class Codes: H01M 8/1009 with one of the reactants being liquid, solid or liquid-charged H01M8/12 takes precedence
• CPC Class Codes: H01M 8/1011 Direct alcohol fuel cells [DAFC], e.g. direct methanol fuel cells [DMFC]
• CPC Class Codes: H02J 2300/30 The power source being a fuel cell
• CPC Class Codes: H02J 7/34 Parallel operation in networks using both storage and other dc sources, e.g. providing buffering H02J7/14 takes precedence
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A method and system for dynamically controlling and managing a fuel cell system is provided. The method and system ensures that predetermined operating parameters and conditions are met. This is achieved using programmable on-board hardware that is already available in the fuel cell system and does not require additional components. More specifically, operating characteristics are measured such as the voltage of the weakest cell, the stack output voltage, the stack output current, the current of a battery being charged by the stack and/or the power of the stack. When each of these measurements is taken, a determination is made to find the load change that should be made in order to adjust the stack voltage to achieve a desired goal. In particular, the load on the fuel cell system can be varied by adjusting the duty cycle of the switches within a DC-DC converter that is being operated by an associated microcontroller. Measurements can also be used to measure methanol concentration and to predict optimal points at which a dosing of additional fuel should be delivered to the fuel cell system.

Claims

1. A method of dynamically controlling and managing operating characteristics of a fuel cell system, comprising:

(A) providing a DC-DC converter circuit having an input connection to receive the output of a fuel cell, and connected to place a load across the fuel cell, said DC-DC converter circuit having internal switches that are operated at a duty cycle that is adjustable;

(B) providing a programmable controller that receives as an input, present and stored values of one or more operating characteristics, said programmable controller also being programmed to signal said DC-DC converter switches to adjust its duty cycle;

(C) identifying a weakest cell in a fuel cell stack;

(D) measuring the output voltage of the weakest cell;

(E) dynamically determining a desired value for said output voltage;

(F) comparing a present value of said weakest cell output voltage with a desired value;

(G) calculating a new duty cycle for the associated DC-DC converter within the fuel cell system required to substantially achieve said desired value for the output voltage of the weakest cell; and

(H) signaling said DC-DC converter to adjust its duty cycle to said new duty cycle.

2. A method of dynamically controlling and managing operating characteristics of a fuel cell system used to power a battery or an application device, comprising:

(A) providing a DC-DC converter circuit having an input connection to receive the output of a fuel cell, and connected to place a load across the fuel cell, said DC-DC converter circuit having internal switches that are operated at a duty cycle that is adjustable;

(B) providing a programmable controller that receives as an input, present and stored values of one or more operating characteristics, said programmable controller also being programmed to signal said DC-DC converter switches to adjust its duty cycle;

(C) dynamically determining a desired value for a plurality of operating characteristics of the fuel cell system, depending upon the operating conditions of the fuel cell system;

(D) measuring said plurality of operating characteristics;

(E) dynamically determining an output power of the fuel cell stack that does not exceed a maximum power needed by at least one of the battery or the application device being powered by the system, but maintains said desired values of said operating characteristics;

(F) comparing a present value of said output power with a desired value;

(G) calculating a new duty cycle for the associated DC-DC converter within the fuel cell system required to substantially achieve said desired value for the output power; and

(H) signaling the DC-DC converter to adjust its duty cycle to said new duty cycle.

3. A method of controlling a fuel cell system, comprising:

(A) dynamically determining desired values for a plurality of operating characteristics being monitored in a current mode of operation of a fuel cell system;

(B) measuring each of said selected operating characteristics;

(C) determining a duty cycle required to substantially achieve each individual desired value and storing each duty cycle;

(D) comparing stored values and selecting the minimum duty cycle; and

(E) using this duty cycle as the new duty cycle of the DC-DC converter circuit switches within said fuel cell system.

4. The method as defined in claim 3 further comprising:

periodically repeating determining the desired values and the measurements and updating the duty cycle.

5. A method of dynamically controlling and managing temperature in a fuel cell system, comprising:

(A) measuring the stack output voltage of the fuel cell system;

(B) determining whether the stack output voltage is at a desired value depending upon the present desired temperature range of the fuel cell system, for the present operating conditions, and

(C) adjusting the duty cycle of an associated DC-DC converter to change the output stack voltage to substantially the desired value.