Method of protecting electricity storage device in hybrid DC power supply system

• US 8,174,241 B2
• Filed: 03/06/2009
• Issued: 05/08/2012
• Est. Priority Date: 03/14/2008
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Kojima, Yasushi, Asano, Yutaka, Murashige, Seigo
• Primary Examiner(s): Tso, Edward
• Assistant Examiner(s): Berhanu, Samuel
• Application Number:
  US12/399,354
• Publication Number:
  US 20090230917A1
• Time in Patent Office: 1,159 Days
• Field of Search: 320/134, 320/104
• US Class Current: 320/134
• CPC Class Codes: B60L 2210/10 DC to DC converters
• CPC Class Codes: B60L 58/10 for monitoring or controlling batteries
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

A method protects a battery in a fuel cell vehicle, in which an inverter-driven motor is supplied with electric power from the battery and a fuel cell. If a battery voltage of the battery falls outside of a prescribed range, a primary current and a secondary current that flow through the DC/DC converter, or currents in branch paths that correspond to the primary current and the secondary current, are reduced in order to limit a charging current flowing into the battery or a discharging current flowing from the battery.

Claims

1. A method of protecting an electricity storage device in a hybrid DC power supply system, which includes an electric power generating device and a DC/DC converter, the electricity storage device being connected to the electric power generating device through the DC/DC converter, comprising the steps of:

controlling a voltage of the electric power generating device through the DC/DC converter so that the voltage tracks a command voltage;

monitoring whether a voltage of the electricity storage device falls outside of a prescribed range or not while the voltage of the electric power generating device is being controlled to track the command voltage;

if the voltage of the electricity storage device falls outside of the prescribed range, interrupting the step of controlling the voltage of the electric power generating device to track the command voltage, and controlling a current passing through the DC/DC converter to track a passing current limit value as a target current for protecting the electricity storage device; and

monitoring the voltage of the electric power generating device and returning to the step, which has been interrupted, of controlling the voltage of the electric power generating device, depending on the monitored voltage.

2. A method according to claim 1, wherein the step of returning to the step of controlling the voltage of the electric power generating device to track the command voltage further comprises the step of:

returning to the step of controlling the voltage of the electric power generating device when the monitored voltage of the electric power generating device returns to a voltage level existing at the time the step of controlling the voltage of the electric power generating device to track the command voltage is interrupted in the step of controlling the current passing through the DC/DC converter to track the passing current limit value.

3. A method according to claim 1, wherein the step of returning to the step of controlling the voltage of the electric power generating device to track the command voltage further comprises the step of:

returning to the step of controlling the voltage of the electric power generating device to track the command voltage when the monitored voltage of the electric power generating device is of a value close to the command voltage for controlling the voltage of the electric power generating device.

4. A method according to claim 1, wherein the step of controlling the current passing through the DC/DC converter to track the passing current limit value for protecting the electricity storage device further comprises the step of:

if the voltage of the electricity storage device falls outside of the prescribed range, setting the passing current limit value to a smaller value depending on the voltage of the electricity storage device that falls outside of the prescribed range.

5. A method according to claim 1, wherein the step of controlling the current passing through the DC/DC converter to track the passing current limit value for protecting the electricity storage device further comprises the step of:

controlling the passing current limit value so as not to exceed a current value at which a fuse connected in series to the electricity storage device is blown.

6. A method according to claim 1, wherein the step of controlling the current passing through the DC/DC converter to track the passing current limit value for protecting the electricity storage device further comprises the step of:

if the voltage of the electricity storage device exceeds an upper limit setting value of the prescribed range, limiting a current passing through the DC/DC converter in a direction to charge the electricity storage device to the passing current limit value.

7. A method according to claim 6, wherein, when the current passing through the DC/DC converter in the direction to charge the electricity storage device is limited to the passing current limit value, the voltage of the electric power generating device is increased through the DC/DC converter.

8. A method according to claim 7, wherein the electric power generating device comprises a fuel cell.

9. A method according to claim 1, wherein the step of controlling the current passing through the DC/DC converter to track the passing current limit value for protecting the electricity storage device further comprises the step of:

if the voltage of the electricity storage device becomes lower than a lower limit setting value of the prescribed range, limiting a current passing through the DC/DC converter in a direction to discharge the electricity storage device to the passing current limit value.

10. A method according to claim 9, wherein, when the current passing through the DC/DC converter in the direction to discharge the electricity storage device is limited to the passing current limit value, the voltage of the electric power generating device is lowered through the DC/DC converter.

11. A method according to claim 10, wherein the electric power generating device comprises a fuel cell.

12. A method according to claim 1, which is applied to a fuel cell vehicle in which a load of the hybrid DC power supply system comprises an inverter-driven motor.