DC/DC POWER CONVERTER CONTROL STRATEGY FOR SOURCE PROTECTION

• US 20150229202A1
• Filed: 05/21/2012
• Published: 08/13/2015
• Est. Priority Date: 05/21/2012
• Status: Active Grant

• Current Assignee: Audi AG (Volkswagen AG)
• Original Assignee: Ballard Power Systems Corporation (Superior Plus Corporation)
• Inventors: Varigonda, Subbarao, Orlowski, Daniel F.
• Granted Patent: US 9,680,366 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01M 8/04559 of fuel cell stacks
• CPC Class Codes: H01M 8/0494 of fuel cell stacks
• CPC Class Codes: H01M 8/04947 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A controller (11a) of a DC/DC converter (10a) responsive to power output of a fuel cell power plant (13) operates under a control strategy which determines if fuel cell voltage exceeds a limit, and if so, provided neither fuel cell output current nor DC/DC converter output current is excessive, causes an increase in DC/DC converter duty cycle to thereby increase power demanded from the fuel cell stack. This eliminates the need for conventional voltage limiting to protect fuel cells from corrosion. Digital control loops and state machines are illustrated.

Claims

1. A method characterized by:

preventing a critical parameter of a DC power source, that is operating a DC/DC converter, from exceeding a safe limiting value, by operating said DC/DC converter in a manner to alter power output of the DC source to retain the value of the critical parameter below the safe limiting value.

2. The method according to claim 1 further characterized in that:

altering power output of the DC source from that which is being demanded by the load attached to the DC/DC converter occurs only when the load of the DC/DC converter changes in a manner tending to render it more likely that the value of said critical parameter will be in excess of said limiting value.

3. The method according to claim 1 further characterized in that:

altering power output of the DC source from that which is being demanded by the load attached to the DC/DC converter is conditioned upon there not being an excess in either the value of an additional critical parameter of the DC source or in the value of a critical parameter of the DC/DC converter.

4. A method according to claim 1 further characterized in that:

the DC power source is a fuel cell power plant.

5. The method of claim 4 further characterized in that:

the critical parameter of the DC power source is cell voltage in the fuel cell stack of said fuel cell power plant.

6. The method according to claim 5 further characterized in that:

altering of power output from that demanded by the load attached to the DC/DC converter comprises increasing the power output.

7. The method according to claim 4 further characterized in that:

altering of power output from that demanded by the load attached to the DC/DC converter is conditioned upon there not being an excess above a corresponding limit of the value either of fuel cell stack output current or DC/DC converter output current.

8. Apparatus comprising:

a DC power source (13) having a critical parameter with a limiting value which should not be exceeded;

a DC/DC converter (10a), in which power conversion is controlled by a control strategy, to convert the output power of said DC power source to provide a desired output of the DC/DC converter;

characterized by;

the control strategy of said DC/DC converter including—

a) determining if the limiting value of said critical parameter has been exceeded, and if so,

b) causing a first change in the output of the DC/DC converter in a direction which will make it less likely said critical parameter will exceed said limiting value.

9. Apparatus according to claim 8 further characterized in that:

said control strategy includes determining if the value of a second critical parameter, of the DC/DC converter, is in excess of a second limiting value and if so,

changing control of the DC/DC converter to cause, instead of said first change, a second change in the output of the DC/DC converter which will make it less likely that said second critical parameter will exceed said second limiting value.

10. Apparatus according to claim 8 further characterized in that:

said control strategy includes determining if the value of a third critical parameter, of the DC source, is in excess of a third limiting value and if so,

changing control of the DC/DC converter to cause, instead of either said first change or said second change, a third change in the output of the DC/DC converter which will make it less likely that said third critical parameter will exceed said third limiting value.

12. A method according to claim 8 further characterized by:

determining if the value of a second critical parameter, of the DC/DC converter, is in excess of a second limiting value and if so,

changing control of the DC/DC converter to cause, instead of said first change, a second change in the output of the DC/DC converter which will make it less likely that said second critical parameter will exceed said second limiting value.

13. A method according to claim 8 further characterized by:

said control strategy includes determining if the value of a third critical parameter, of the DC source, is in excess of a third limiting value and if so,

changing control of the DC/DC converter to cause, instead of either said first change or said second change, a third change in the output of the DC/DC converter which will make it less likely that said third critical parameter will exceed said third limiting value.

11. A method of controlling a DC power source (13), having a critical parameter with a limiting value which should not be exceeded, and providing power to a DC/DC converter (10a), in which power conversion is controlled by a control strategy, to convert the output power of said DC power source to provide a desired output of the DC/DC converter;

characterized by;

a) determining if the limiting value of said critical parameter has been exceeded, and if so,

b) causing a first change in the output of the DC/DC converter in a direction which will make it less likely said critical parameter will exceed said limiting values.