Fuel cell system and method for voltage monitoring for a fuel cell system

• US 20030228503A1
• Filed: 04/25/2003
• Published: 12/11/2003
• Est. Priority Date: 04/26/2002
• Status: Active Grant

• Current Assignee: Daimler AG (Mercedes-Benz Group AG)
• Original Assignee: Daimler AG (Mercedes-Benz Group AG)
• Inventors: Georgii, Martin
• Granted Patent: US 7,211,343 B2
• Time in Patent Office: Days
• US Class Current: 429/13
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: H01M 8/04559 of fuel cell stacks
• CPC Class Codes: H01M 8/04567 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A fuel cell system having a redundant voltage monitoring system for monitoring the voltage which is present on a fuel cell unit, and a method for voltage monitoring.

Claims

1. A method for voltage monitoring for a fuel cell system having a fuel cell unit, with the fuel cell unit being connected via cables to an electrical component, said method comprising the steps:

determining a voltage on the electrical component;

producing a first actual value and a second, redundant actual value from the determined voltage which is present on the electrical component; and

comparing at least one of the first actual value with a first limit value, and the second actual value with a second limit value.

2. The method according to claim 1, wherein the first actual value is compared with the second actual value, and a comparison value is formed.

3. The method according to claim 1, wherein at least one of a fault signal is produced and the electrical component is switched off if the first limit value is exceeded.

4. The method according to claim 1, wherein at least one of a fault signal is produced and the electrical component is switched off if the second limit value is exceeded.

5. The method according to claim 2, wherein at least one of a fault signal is produced and the electrical component is switched off if at least one of the comparison value and the magnitude of the comparison value exceeds a third limit value.

6. The method according to claim 1, wherein at least one of the first and the second limit value is equal to the no-load voltage of the fuel cell unit.

7. The method according to claim 1, wherein the second limit value is higher than the first limit value.

8. The method according to claim 1, wherein an additional voltage signal is produced when a voltage is present on the cables.

9. The method according to claim 8, wherein the additional voltage signal is compared with at least one of the first and the second actual value.

10. A fuel cell system comprising

a fuel cell unit;

and

an electrical component connected via cables to outputs of the fuel cell unit with the electrical component having a redundant associated voltage monitoring system.

11. The fuel cell system according to claim 10, wherein the voltage monitoring system contains a first and a second voltage monitoring unit.

12. The fuel cell system according to claim 11, wherein the first voltage monitoring unit has at least one of first measurement electronics and a first converter.

13. The fuel cell system according to claim 12, wherein the first voltage monitoring unit has first and second measurement electronics and a first and a second converter.

14. The fuel cell system according to claim 11, wherein the second voltage monitoring unit has means which produce a voltage signal when a voltage is present on the cables.

15. The fuel cell system according to claim 13, wherein the first and second measurement electronics are connected to a control and evaluation unit.

16. The fuel cell system according to claim 10, wherein the electrical component is a bidirectional converter.

17. The fuel cell system according to claim 10, wherein the electrical component is at least one of a converter and an electrical machine.