METHOD OF CONTROLLING HYBRID DC POWER SUPPLY SYSTEM

• US 20090160252A1
• Filed: 12/18/2008
• Published: 06/25/2009
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: ASANO, Yutaka, MURASHIGE, Seigo, KOJIMA, Yasushi
• Granted Patent: US 7,923,861 B2
• Time in Patent Office: Days
• US Class Current: 307/24
• CPC Class Codes: B60L 2210/10 DC to DC converters
• CPC Class Codes: B60L 3/0046 relating to electric energy storage systems, e.g. batteries or capacitors
• CPC Class Codes: B60L 3/0053 relating to fuel cells
• CPC Class Codes: B60L 58/10 for monitoring or controlling batteries
• CPC Class Codes: B60L 58/30 for monitoring or controlling fuel cells
• CPC Class Codes: B60L 58/40 for controlling a combination of batteries and fuel cells
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• CPC Class Codes: B60W 10/28 including control of fuel cells
• CPC Class Codes: B60W 2710/086 Power
• 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
• CPC Class Codes: Y02T 90/40 Application of hydrogen technology to transportation, e.g. using fuel cells

Abstract

A fuel cell vehicle has a motor driven by an inverter and hybrid DC power supplies including a battery and a fuel cell for supplying electric power to the motor. For preventing a fuse connected to the battery from being blown out, when a motor current Im increases, a first source current flowing from the battery is limited to a range for not blowing out the fuse, and a generated current is increased as much as the first source current is limited.

Claims

1. A method of controlling a hybrid DC power supply system including a first DC power supply device for generating a first output voltage and delivering a first source current or receiving a first sink current;

a second DC power supply device connected to a load, for delivering a second source current which increases as a second output voltage generated thereby decreases and which decreases as the second output voltage increases; and

a voltage increasing/reducing DC/DC converter connected between the first DC power supply device and a junction between the load and the second DC power supply device, for controlling the second output voltage by increasing or reducing duty ratios for driving switching devices thereof, the method comprising the steps of;

controlling the hybrid DC power supply system such that a load sink current demanded by the load is the sum of a current converted from the first source current by the DC/DC converter and the second source current; and

controlling the second output voltage of the second DC power supply device such that a value of a current flowing from an output point of the first DC power supply device through the DC/DC converter to the junction does not exceed a predetermined threshold value.

2. A method according to claim 1, further comprising the steps of

when the value of the current flowing through the DC/DC converter is smaller than the threshold value, performing a first mode for controlling the second source current by controlling the second output voltage, and

when the value of the current flowing through the DC/DC converter is greater than the threshold value, interrupting the first mode and performing a second mode for reducing the second output voltage and increasing the second source current such that the value of the current flowing through the DC/DC converter does not exceed the threshold value.

3. A method according to claim 2, further comprising the step of returning from the second mode to the first mode by monitoring the second output voltage of the second DC power supply device.

4. A method according to claim 3, further comprising the steps of monitoring the second output voltage, and returning the second mode to the first mode when the second output voltage increases up to a voltage at which the first mode is interrupted.

5. A method according to claim 3, wherein the hybrid DC power supply system further includes a higher-level controller for supplying a command voltage, further comprising the steps of

performing a process for controlling the second output voltage so as to be in conformity with the command voltage in the first mode,

interrupting the process for controlling the second output voltage when in the second mode, and

returning the second mode to the first mode when the second output voltage, which is being monitored, exceeds the command voltage.

6. A method according to claim 2, further comprising the step of performing a feedback control process including an integrating process for increasing or reducing the duty ratios with the threshold value being used as a target current for the value of the current flowing through the DC/DC converter in the second mode.

7. A method according to claim 1, wherein the first DC power supply device comprises an electricity storage device, and the second DC power supply device comprises a fuel cell.

8. A method according to claim 1, wherein the load of the hybrid DC power supply system comprises a motor driven by an inverter.

9. A method of controlling a hybrid DC power supply system including a first DC power supply device for generating a first output voltage and delivering a first source current or receiving a first sink current;

a second DC power supply device connected to a load, for delivering a second source current which increases as a second output voltage generated thereby decreases and which decreases as the second output voltage increases; and

a voltage increasing/reducing DC/DC converter connected between the first DC power supply device and a junction between the load and the second DC power supply device, for controlling the second output voltage by increasing or reducing duty ratios for driving switching devices thereof, the method comprising the steps of;

controlling the hybrid DC power supply system such that the first sink current flows from the DC/DC converter into the first DC power supply device; and

controlling the second output voltage of the second DC power supply device such that a value of a current flowing from the junction through the DC/DC converter to an input point of the first DC power supply device does not exceed a predetermined threshold value.

10. A method according to claim 9, further comprising the steps of

when the value of the current flowing through the DC/DC converter is smaller than the threshold value, performing a first mode for controlling the second source current by controlling the second output voltage, and

when the value of the current flowing through the DC/DC converter is greater than the threshold value, interrupting the first mode and performing a second mode for increasing the output voltage and reducing the second source current such that the value of the current flowing through the DC/DC converter does not exceed the threshold value.

11. A method according to claim 10, further comprising the step of returning from the second mode to the first mode by monitoring the second output voltage of the second DC power supply device.

12. A method according to claim 10, further comprising the steps of monitoring the second output voltage, and returning the second mode to the first mode when the second output voltage decreases to a value at which the first mode is interrupted.

13. A method according to claim 10, wherein the hybrid DC power supply system further includes a higher-level controller for supplying a command voltage, further comprising the steps of

performing a process for controlling the second output voltage so as to be in conformity with the command voltage in the first mode,

interrupting the process for controlling the second output voltage when in the second mode, and

returning the second mode to the first mode when the second output voltage, which is being monitored, becomes lower than the command voltage.

14. A method according to claim 10, further comprising the step of performing a feedback control process including an integrating process for increasing or reducing the duty ratios with the threshold value being used as a target current for the value of the current flowing through the DC/DC converter in the second mode.

15. A method of controlling a hybrid DC power supply system including a first DC power supply device, a second DC power supply device connected to a load, and a chopper DC/DC converter connected between the first DC power supply device and a junction between the load and the second DC power supply device, the method comprising the steps of:

(a) increasing or reducing duty ratios for driving switching devices of the DC/DC converter depending on a value of a current flowing from an output point of the first DC power supply device through the DC/DC converter to the junction;

(b) increasing or reducing a second output voltage of the second DC power supply device when the duty ratios are increased or reduced;

(c) increasing a second source current flowing from the second DC power supply device when the second output voltage of the second DC power supply device is reduced, and reducing the second source current flowing from the second DC power supply device when the second output voltage of the second DC power supply device is increased; and

(d) increasing or reducing the second source current such that the value of the current flowing from the output point of the first DC power supply device through the DC/DC converter to the junction does not exceed a predetermined threshold value.

16. A method according to claim 15, further comprising the steps of

controlling an output of the second DC power supply device by increasing or reducing the duty ratios in an ordinary operation mode in the step (a) if the value of the current flowing through the DC/DC converter is smaller than the threshold value, and

interrupting the ordinary operation mode in the step (a) and controlling a current input to and a current output from the first DC power supply device such that the current input and the current output do not exceed a predetermined threshold value in a monitoring operation mode in the steps (b), (c), (d) if the value of the current flowing through the DC/DC converter is equal to or greater than the threshold value.

17. A method according to claim 16, further comprising the step of returning from the monitoring operation mode to the ordinary operation mode by monitoring the second output voltage of the second DC power supply device.

18. A method according to claim 17, further comprising the steps of monitoring the second output voltage, and returning the monitoring operation mode to the ordinary operation mode when the second output voltage returns to a voltage at which the ordinary operation mode is interrupted.

19. A method according to claim 17, wherein the hybrid DC power supply system further includes a higher-level controller for supplying a command voltage, further comprising the steps of

performing a process for controlling the second output voltage so as to be in conformity with the command voltage in the ordinary operation mode,

interrupting the process for controlling the second output voltage when in the monitoring operation mode, and

returning the monitoring operation mode to the ordinary operation mode when the second output voltage, which is being monitored, returns to the command voltage.

20. A method according to claim 15, wherein the first DC power supply device comprises an electricity storage device, and the second DC power supply device comprises a fuel cell.

21. A method according to claim 15, wherein the load of the hybrid DC power supply system comprises a motor driven by an inverter.