Method and system for controlling output of fuel cell power generator

• US 5,637,414 A
• Filed: 05/20/1996
• Issued: 06/10/1997
• Est. Priority Date: 05/22/1995
• Status: Expired due to Term

• Current Assignee: Fuji Electric Company Limited (Fuji Electric Systems Company Limited)
• Original Assignee: Fuji Electric Company Limited (Fuji Electric Systems Company Limited)
• Inventors: Mogi, Hiroshi, Komatsu, Tadashi, Wakatsuki, Shigeru, Inoue, Shinichiro, Nagai, Tetsuya
• Primary Examiner(s): SKAPARS, ANTHONY
• Application Number:
  US08/650,516
• Time in Patent Office: 386 Days
• Field of Search: 429/13, 429/12, 429/22, 429/23, 429/24, 429/25, 320/30, 320/31, 320/32, 320/39
• US Class Current: 429/431
• CPC Class Codes: H01M 8/04089 of gaseous reactants
• CPC Class Codes: H01M 8/04388 of anode reactants at the inlet or inside the fuel cell
• CPC Class Codes: H01M 8/04402 of anode exhausts
• CPC Class Codes: H01M 8/04447 of anode reactants at the inlet or inside the fuel cell
• CPC Class Codes: H01M 8/04589 of fuel cell stacks
• CPC Class Codes: H01M 8/04619 of fuel cell stacks
• 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 8/04992 characterised by the implementation of mathematical or computational algorithms, e.g. feedback control loops, fuzzy logic, neural networks or artificial intelligence
• CPC Class Codes: H01M 8/0612 from carbon-containing material
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y10S 429/90 Fuel cell including means for power conditioning, e.g. Conversion to ac

Abstract

A fuel cell power generator having an output controlling system for preventing the deterioration of the fuel cell performance caused by fuel gas shortages. The fuel cell power generator includes a fuel reformer, a fuel cell, an inverter, and an output controlling system. The output controlling system includes an output control regulator for controlling the output power of the inverter as close to the current value corresponding to the output power set value as possible, a current command computing unit, an inverter controller, and an output correction section. The output correction section includes an available output computing unit for computing the maximum available output power value of the fuel cell on the basis of the detected flow rate of fuel gas flowing into the fuel cell or fuel exhaust gas flowing out of the fuel cell; a low level selector for selecting either the computed maximum available output power value or the output power set value, whichever is the lower; and an output correction regulator for supplying the output control regulator with a signal for correcting the output power set value so as to control the detected output current from the fuel cell as close to the current value corresponding to the output current value of the low level selector as possible.

Claims

1. An output controlling system for controlling the output of a fuel cell power generator having a fuel cell which generates a direct-current output when supplied with fuel gas from a fuel reformer, the direct-current output being converted by inverting means into an alternating-current output to be fed to a power system, the output controlling system including:

an output control regulator for controlling the output current of said inverter as close to the current value corresponding to the output power set value of said inverting means as possible;

a current command value computing unit for updating a current command value on the basis of the output signal of said output control regulator;

inverting means controller for controlling the output current of said inverting means as close to said current set value as possible; and

output correction means, provided on the upstream side of said output control regulator, for correcting said output current set value of said inverting means so that the output power of said fuel cell is kept at a maximum available output power value of said fuel cell in accordance with either the state of the supply of said fuel gas to said fuel cell and/or the state of the consumption of said fuel gas by said fuel cell.

2. The output controlling system as claimed in claim 1, wherein said output correction means comprises:

a fuel gas flow rate detector, provided on the upstream side of said fuel cell, for detecting the fuel gas flow rate flowing into said fuel cell;

an output setting unit for setting an output power set value of said fuel cell;

an available output computing unit for computing a current value corresponding to the maximum available output value of said fuel cell on the basis of the detected flow rate;

a low level selector for selecting and outputting either the computed current value corresponding to the maximum available output power value or a current value corresponding to said output power set value, whichever is the lower; and

an output correction regulator for outputting to said output control regulator a signal for correcting the current value corresponding to said output power set value so that the detected output current value of said fuel cell is controlled as close to the output current value of said low level selector as possible.

3. The output controlling system as claimed in claim 1, wherein said output correction means includes:

a fuel gas flow rate detector, provided on the downstream side of said fuel cell, for detecting the fuel exhaust gas flow rate flowing out of said fuel cell;

an output setting unit for setting an output power set value of said fuel cell;

an available output computing unit for computing a current value corresponding to the maximum available output value of said fuel cell on the basis of the detected flow rate;

a low level selector for selecting and outputting either the computed current value corresponding to the maximum available output power value or a current value corresponding to said output set power value, whichever is the lower; and

an output correction regulator for outputting to said output control regulator a signal for correcting the current value corresponding to said output power set value so that the detected output current value of said fuel cell is controlled as close to the output current value of said low level selector as possible.

4. The output controlling system as claimed in claim 1, wherein said output correction means includes:

two fuel gas flow rate detectors, provided both on the upstream side and the downstream side of said fuel cell, for detecting the fuel gas flow rate flowing into said fuel cell and the fuel exhaust gas flow rate flowing out of said fuel cell, respectively;

a fuel utilization factor computing unit for computing a fuel utilization factor on the basis of said detected two flow rates;

an output setting unit for setting an output power set value of said fuel cell;

an available output computing unit, provided on the upstream side of said fuel utilization factor computing unit, for computing a current value corresponding to the maximum available output power value of said fuel cell on the basis of the computed fuel utilization factor;

a low level selector for selecting and outputting either the computed current value corresponding to the maximum available output power value or a current value corresponding to said output power set value, whichever is the lower; and

an output correction regulator for outputting to said output control regulator a signal for correcting the current value corresponding to said output power set value so that the detected output current value of said fuel cell is controlled as close to the output current value of said low level selector as possible.

5. A method for controlling the output of a fuel cell power generator having a fuel cell which generates a direct-current output when supplied with fuel gas from a fuel reformer, said direct-current output being converted by inverting means into an alternating-current output to be fed to a power system, by using an output controlling system having:

an output control regulator for controlling the output current of said inverting means as close to the current value corresponding to the output power set value of said inverting means as possible;

a current command value computing unit for updating a current command value on the basis of the output signal of said output control regulator; and

an inverting means controller for controlling the output current of said inverting means as close to said current set value as possible;

the method comprising the steps of;

setting an output power set value of said fuel cell;

detecting the fuel gas flow rate flowing into said fuel cell or the fuel exhaust gas flow rate flowing out of said fuel cell;

computing a current value corresponding to the maximum available output power value of said fuel cell on the basis of the detected flow rate;

selecting and outputting either the computed current value corresponding to the maximum available output power value or a current value corresponding to said output power set value, whichever is the lower; and

outputting to said output control regulator a signal for correcting the current value corresponding to said output power set value so that the detected output current value of said fuel cell is controlled as close to the output current value of said low level selector as possible.

6. A method for controlling the output of a fuel cell power generator having a fuel cell which generates a direct-current output when supplied with fuel gas from a fuel reformer, said direct-current output being converted by inverting means into an alternating-current output to be fed to a power system, by using an output controlling system having:

an output control regulator for controlling the output current of said inverting means as close to the current value corresponding to the output power set value of said inverting means as possible;

a current command value computing unit for updating a current command value on the basis of the output signal of said output control regulator; and

an inverting means controller for controlling the output current of said inverting means as close to said current set value as possible;

the method comprising the steps of;

setting an output power set value of said fuel cell;

detecting both the fuel gas flow rate flowing into said fuel cell and the fuel exhaust gas flow rate flowing out of said fuel cell;

computing the fuel utilization factor on the basis of said flow rate of the fuel gas flowing into said fuel cell and the flow rate of the fuel exhaust gas flowing out of said fuel cell;

computing a current value corresponding to the maximum available output power value of said fuel cell on the basis of the computed fuel utilization factor;

selecting and outputting either the computed current value corresponding to the maximum available output power value or a current value corresponding to said output power set value, whichever is the lower; and

outputting to said output control regulator a signal for correcting the current value corresponding to said output power set value so that the detected output current value of said fuel cell is controlled as close to the output current value of said low level selector as possible.