JP2008165994A - Fuel cell system control device and fuel cell system - Google Patents

Abstract

The present invention provides a control device for a fuel cell system that can more reliably avoid the occurrence of a high potential state of an oxidizer electrode during startup.
Control is provided in a fuel cell system including valves 24 and 25 for opening and closing flow paths 22 and 23 connected to an oxidant electrode 12 of a fuel cell 10 and closing the valves 24 and 25 when the fuel cell 10 is stopped. The apparatus 50 determines whether or not an oxidant gas is present in the oxidant electrode 12 when the fuel cell 10 is started up. If it is determined that the oxidant gas is present, the device 50 sets the output voltage of the fuel cell 10 to a predetermined value. The control is performed to reduce the value to a predetermined target value while limiting the value to the upper limit value or less.
[Selection] Figure 1

Description

  The present invention relates to a control device for a fuel cell system and a fuel cell system.

  There is a fuel cell system that generates power using a fuel gas (for example, hydrogen) and an oxidant gas (for example, oxygen) (see, for example, Patent Documents 1 to 5).

  Patent Document 1 discloses a technique for avoiding a high potential of the oxidizer electrode due to a no-load state at the time of starting the fuel cell system. Specifically, the technique described in Patent Document 1 is a method for starting a fuel cell system in a state where the oxidant gas supply to the oxidant electrode is cut off and the connection between the fuel cell body and the load device is cut off. When supply of the fuel gas to the fuel electrode is started and the voltage of the fuel cell body becomes equal to or higher than the first predetermined value, the fuel cell body and the load device are connected, and the voltage of the fuel cell body is set to the first predetermined value. The supply of the oxidant gas to the oxidant electrode is started when the value becomes equal to or smaller than a second predetermined value smaller than the value.

JP 2005-116402 A JP 2004-179072 A JP 2006-179335 A JP 2004-342406 A JP 2006-128016 A

  However, in the technique described in Patent Document 1, there is a possibility that a high potential state of the oxidizer electrode may occur at the time of start-up, for example, when a valve that opens and closes the flow path connected to the oxidizer electrode fails. .

  Therefore, the present invention provides a control device for a fuel cell system that can more reliably avoid the occurrence of a high potential state of the oxidizer electrode during startup.

  A control apparatus for a fuel cell system according to the present invention is a control apparatus for a fuel cell system that includes a valve that opens and closes a flow path connected to an oxidant electrode of the fuel cell and closes the valve when the fuel cell is stopped. When the fuel cell is started, it is determined whether or not oxidant gas is present in the oxidant electrode. If it is determined that oxidant gas is present, the output voltage of the fuel cell is set to a predetermined upper limit value. Control is performed to reduce to a predetermined target value while limiting to the following.

  In one aspect of the present invention, when the fuel cell is started, control is performed so that fuel gas is supplied to the fuel electrode of the fuel cell with the valve closed, and the output voltage of the fuel cell is a predetermined threshold value. When it becomes above, it determines with oxidizing agent gas existing.

  The fuel cell system according to the present invention opens and closes a fuel cell that generates power using a fuel gas supplied to the fuel electrode and an oxidant gas supplied to the oxidant electrode, and a flow path connected to the oxidant electrode. A valve that is controlled to be closed when the fuel cell is stopped, and whether or not an oxidant gas is present in the oxidant electrode when the fuel cell is started, and the oxidant gas is And a control device that controls to reduce the output voltage of the fuel cell to a predetermined target value while limiting the output voltage of the fuel cell to a predetermined upper limit value or less.

  ADVANTAGE OF THE INVENTION According to this invention, the control apparatus of the fuel cell system which can avoid more reliably generation | occurrence | production of the high electric potential state of an oxidizer electrode at the time of starting can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a fuel cell system 1 according to the present embodiment. The fuel cell system 1 is a system that generates power by receiving supply of a fuel gas and an oxidant gas. In this embodiment, the fuel cell system 1 is mounted on a fuel cell vehicle. However, the fuel cell system 1 may be applied to other than fuel cell vehicles.

  In FIG. 1, the fuel cell system 1 includes a fuel cell 10. The fuel cell 10 includes an electrolyte membrane 11 and an oxidant electrode (cathode) 12 and a fuel electrode (anode) 13 provided on both sides thereof. The fuel cell 10 generates power using the oxidant gas supplied to the oxidant electrode 12 and the fuel gas supplied to the fuel electrode 13.

  In the present embodiment, the fuel cell 10 is a solid polymer electrolyte type. The fuel cell 10 has a stack structure in which a large number (in this case, 400) of single cells are stacked. The fuel cell 10 uses air containing oxygen as the oxidant gas and hydrogen as the fuel gas.

  An oxidant supply flow path 22 that guides air supplied from the compressor 21 to the oxidant electrode 12 is connected to the inlet of the oxidant electrode 12, and an outlet from the oxidant electrode 12 is connected to the outlet of the oxidant electrode 12. An oxidant discharge flow path 23 is connected to guide the discharged gas (called cathode off gas) to the outside. The oxidant supply flow path 22 is provided with a valve (hereinafter referred to as “air shut valve”) 24 for opening and closing the flow path, and the oxidant discharge flow path 23 is opened and closed. A valve (hereinafter referred to as “air shut valve”) 25 is provided. Further, a bypass flow path 26 that bypasses the air from the compressor 21 from the oxidant electrode 12 is connected between the oxidant supply flow path 22 and the oxidant discharge flow path 23. Is provided with a valve (hereinafter referred to as “air bypass valve”) 27 for opening and closing the flow path. Although not shown in FIG. 1, the flow paths 22 and 23 connected to the oxidizer electrode 12 are appropriately equipped with a pressure sensor for measuring the pressure of the gas in the flow path, and the gas in the flow path. A pressure regulating valve for regulating the pressure is provided.

  On the other hand, a fuel supply flow path 32 that leads hydrogen supplied from a hydrogen tank 31 that stores high-pressure hydrogen gas to the fuel electrode 13 is connected to the inlet of the fuel electrode 13. A circulation passage 33 is connected to return gas discharged from the fuel electrode 13 (referred to as anode off gas) to the fuel supply passage 32. The fuel supply channel 32 includes a valve (hereinafter referred to as “hydrogen supply shut valve”) 37 that opens and closes the flow channel, and a pressure adjustment valve (hereinafter referred to as “pressure regulation”) that adjusts the pressure of gas in the channel. 34) (referred to as "valve"). The circulation channel 33 is provided with a hydrogen pump 38 for circulating hydrogen. The circulation channel 33 is connected to a fuel discharge channel 35 that guides the gas discharged from the fuel electrode 13 to the outside. The fuel discharge channel 35 has a valve (hereinafter referred to as a valve) that opens and closes the channel. , Referred to as “purge valve”) 36. Although not shown in FIG. 1, the flow paths 32 and 33 connected to the fuel electrode 13 are appropriately provided with a pressure sensor for measuring the pressure in the flow path.

  An external load 41 is electrically connected to the fuel cell 10. In the present embodiment, the external load 41 includes a DC / DC converter connected to the fuel cell 10 and a load (for example, a secondary battery, a capacitor, an auxiliary battery) connected to the fuel cell 10 via the DC / DC converter. Machine, resistor, etc.). A switch 42 is provided between the fuel cell 10 and the external load 41 to open / close (shut off / connect) the electrical connection therebetween.

  The fuel cell system 1 further includes a voltage sensor 43 that detects an output voltage (here, a stack voltage) of the fuel cell 10 and a control device 50 that controls the entire fuel cell system 1. Specifically, the control device 50 controls the controlled devices (compressor 21, various valves, external load 41, switch 42, etc.) based on the outputs of various sensors (voltage sensor 43, etc.).

  The control device 50 can be realized by an appropriate configuration, but in the present embodiment, the control device 50 is configured to include a CPU (Central Processing Unit), a ROM (Read Only Memory), a main memory, and the like, and the function thereof is a ROM or the like. The control program stored in the storage medium is executed by the CPU.

  In the above configuration, when the air shut valve 24 or 25 fails to open, or when the air shut valve 24 or 25 cannot be kept airtight after being left for a long time, the air enters the oxidizer electrode 12 and the fuel When the battery 10 is stopped, the oxidant gas is present at the oxidant electrode 12. When this state continues, the oxidant gas also exists in the fuel electrode 13. If the start control of the fuel cell 10 is executed as in the case where the oxidant gas does not exist in the oxidant electrode 12, the potential of the oxidant electrode 12 becomes higher than that during normal start-up (for example, 1.0 V or more). A phenomenon, that is, an abnormal cathode potential occurs, which may oxidize the carbon carrying the catalyst of the oxidant electrode 12 and cause the oxidant electrode 12 to deteriorate.

  Therefore, from the viewpoint of avoiding deterioration of the oxidizer electrode 12 due to the abnormal cathode potential, the control device 50 performs the following control. That is, the control device 50 controls the air shut valves 24 and 25 to be closed when the fuel cell 10 is stopped, and determines whether or not oxidant gas is present in the oxidant electrode 12 when the fuel cell 10 is started. When it is determined that oxidant gas is present, control is performed to reduce the output voltage of the fuel cell 10 to a predetermined target value while limiting the output voltage to a predetermined upper limit value or less. Here, the conditions for determining whether or not the oxidant gas is present, and the predetermined upper limit value and target value are set from the viewpoint of avoiding deterioration of the oxidant electrode 12 due to the abnormal cathode potential.

  Specifically, in the present embodiment, the control device 50 causes the fuel gas to be supplied to the fuel electrode 13 of the fuel cell 10 with the air shut valves 24 and 25 closed when the fuel cell 10 is started. When the output voltage of the fuel cell 10 is equal to or higher than a predetermined threshold value, it is determined that oxidant gas is present in the oxidant electrode 12. Here, the predetermined threshold is set from the viewpoint of avoiding deterioration of the oxidizer electrode 12 due to the abnormal cathode potential. Further, when it is determined that the oxidant gas is present, the control device 50 controls the external load 41 so that the output voltage of the fuel cell 10 is reduced to a predetermined target value while being limited to a predetermined upper limit value or less. . For example, the control device 50 performs switching control of the DC / DC converter as control of the external load 41. Then, the control device 50 opens the air shut valves 24 and 25 after the oxidant gas of the oxidant electrode 12 is consumed, for example, after both the oxidant electrode 12 and the fuel electrode 13 are filled with the fuel gas, Supply of the oxidant gas to the oxidant electrode 12 is started. For example, the control device 50 opens the air shut valves 24 and 25 after the output voltage of the fuel cell 10 reaches the predetermined target value.

  Hereinafter, the operation of the fuel cell system 1 having the above-described configuration will be described separately during normal operation and during startup.

(During normal operation)
During normal operation, the hydrogen supply shut valve 37 and the air shut valves 24 and 25 are opened, hydrogen is supplied from the hydrogen tank 31 to the fuel electrode 13 via the fuel supply flow path 32, and the oxidant supply flow from the compressor 21. Air is supplied to the oxidizer electrode 12 through the path 22. The fuel cell 10 generates power using air supplied to the oxidant electrode 12 and hydrogen supplied to the fuel electrode 13. Specifically, due to the catalytic action of platinum, the reaction represented by the following formula (1) occurs on the fuel electrode 13 side, and the reaction represented by the following formula (2) occurs on the oxidant electrode 12 side. An electromotive reaction represented by the following formula (3) occurs.

H ₂ → 2H ⁺ + 2e ⁻ (1)
2H ⁺ + (1/2) O ₂ + 2e ⁻ → H ₂ O (2)
H ₂ + (1/2) O ₂ → H ₂ O (3)

  The anode offgas containing hydrogen that has not contributed to the reaction is discharged from the fuel electrode 13, and the anode offgas is supplied to the fuel electrode 13 again through the circulation channel 33. At this time, since the anode off gas contains impurities other than hydrogen, the concentration of hydrogen in the anode off gas decreases while circulating. Therefore, the purge valve 36 is opened at an appropriate timing, and the anode off gas having a reduced hydrogen concentration is exhausted to the outside through the fuel discharge passage 35.

  On the other hand, the cathode offgas containing the oxidant gas that has not contributed to the reaction is discharged from the oxidant electrode 12, and the cathode offgas is discharged to the outside through the oxidant discharge passage 23.

(At startup)
FIG. 2 is a flowchart showing an operation procedure when the fuel cell system 1 according to the present embodiment is started. Hereinafter, the operation at the start of the fuel cell system 1 will be described with reference to FIG.

  In the initial state before the start of startup, the compressor 21 is in a stopped state, the air shut valves 24 and 25 are in a closed state, the pressure regulating valve 34 is in a closed state, and the switch 42 is in an open (shut off) state.

  First, the control device 50 starts supplying hydrogen to the fuel electrode 13 by opening the pressure regulating valve 34 (S1). At this time, if the air shut valves 24 and 25 are functioning normally and oxygen is not present in the oxidizer electrode 12, the output voltage of the fuel cell 10 does not rise. On the other hand, if the air shut valve 24 or 25 is not functioning normally due to an open failure or left standing for a long time and oxygen is present in the oxidizer electrode 12, the output voltage of the fuel cell 10 rises.

  Therefore, after starting the supply of hydrogen, the control device 50 determines whether or not the output voltage of the fuel cell 10 is equal to or higher than a predetermined threshold (100 V in this case) based on the detection signal of the voltage sensor 43 (S2). .

  When it is determined that the output voltage of the fuel cell 10 is equal to or higher than the predetermined threshold (S2: YES), it is considered that oxygen is present in the oxidizer electrode 12, and therefore the control device 50 closes the switch 42 and closes the fuel cell 10 Is connected to the external load 41, and the external load 41 is controlled so that the output voltage of the fuel cell 10 is reduced to a predetermined target value (here 40V) while being limited to a predetermined upper limit value (here 100V) or less. (S3). By this control, hydrogen moves from the fuel electrode 13 to the oxidant electrode 12 due to the hydrogen pumping phenomenon, the amount of oxygen in the oxidant electrode 12 decreases due to reaction with the hydrogen, and the oxidant electrode 12 is filled with hydrogen. When the oxygen amount of the oxidant electrode 12 is sufficiently reduced (or when the oxidant electrode 12 is sufficiently filled with hydrogen), for example, when the output voltage of the fuel cell 10 reaches a predetermined target value, the control device 50 The process proceeds to step S4.

  On the other hand, when it is determined that the output voltage of the fuel cell 10 is not equal to or higher than the predetermined threshold value (S2: NO), it is considered that oxygen is not present in the oxidizer electrode 12, and therefore the control device 50 performs the control in step S3. Without performing this, the process proceeds to step S4.

  In step S <b> 4, the control device 50 starts the compressor 21 and gives an opening command to the air shut valves 24 and 25, thereby starting supply of air to the oxidant electrode 12. In this case, in a preferred aspect, the control device 50 keeps the air bypass valve 27 open. As a result, hydrogen discharged from the oxidant electrode 12 is diluted with air from the bypass flow path 26, and high concentration hydrogen is prevented from being discharged to the outside.

  As described above, in the present embodiment, in the fuel cell system that includes a valve that opens and closes the flow path connected to the oxidant electrode of the fuel cell and closes the valve when the fuel cell is stopped, the oxidation is performed when the fuel cell is started. It is determined whether or not oxidant gas is present in the agent electrode, and if it is determined that oxidant gas is present, the output voltage of the fuel cell is reduced to a predetermined target value while being limited to a predetermined upper limit value or less. To control. For this reason, according to the present embodiment, it is possible to more reliably avoid the occurrence of a high potential state of the oxidizer electrode at the time of startup as compared with the technique described in Patent Document 1. Specifically, in the technique described in Patent Document 1, since the load device is simply connected to the fuel cell, when there is no valve for sealing the flow path or when the valve is provided and the valve is open In this embodiment, for example, the output voltage of the fuel cell is positively controlled by controlling an external load. Even in the case of an open failure, the high potential state of the oxidizer electrode at startup can be avoided more reliably. As a result, according to the present embodiment, it is possible to more reliably suppress the oxidation of carbon carrying the catalyst of the oxidant electrode due to the abnormal cathode potential at the time of startup.

  Further, in the present embodiment, when the fuel cell is started, control is performed so that the fuel gas is supplied to the fuel electrode of the fuel cell with the valve closed, and the output voltage of the fuel cell is equal to or higher than a predetermined threshold value. When it becomes, it determines with oxidizing gas existing in an oxidizing agent pole. For this reason, according to this Embodiment, it can be determined by simple structure whether oxidant gas exists.

  In addition, this invention is not limited to the said embodiment, It can change variously within the range which does not deviate from the summary of this invention.

It is a figure which shows the structure of the fuel cell system which concerns on embodiment. It is a flowchart which shows the operation | movement procedure at the time of starting of the fuel cell system which concerns on embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Fuel cell system, 10 Fuel cell, 11 Electrolyte membrane, 12 Oxidant electrode, 13 Fuel electrode, 21 Compressor, 22 Oxidant supply flow path, 23 Oxidant discharge flow path, 24, 25 Valve (air shut valve), 26 Bypass flow path, 27 valve (air bypass valve), 31 Hydrogen tank, 32 Fuel supply flow path, 33 Circulation flow path, 34 Pressure adjustment valve (pressure regulating valve), 35 Fuel discharge flow path, 36 Valve (purge valve), 37 Valve (hydrogen supply shut valve), 38 hydrogen pump, 41 external load, 42 switch, 43 voltage sensor, 50 control device.

Claims (3)

A control device for a fuel cell system comprising a valve for opening and closing a flow path connected to an oxidant electrode of a fuel cell, and closing the valve when the fuel cell is stopped,
When starting the fuel cell, it is determined whether or not oxidant gas is present in the oxidant electrode. If it is determined that oxidant gas is present, the output voltage of the fuel cell is less than or equal to a predetermined upper limit value. A control device for a fuel cell system, wherein the control is performed so as to reduce the target value to a predetermined target value. A control device for a fuel cell system according to claim 1,
When the fuel cell is started, control is performed so that fuel gas is supplied to the fuel electrode of the fuel cell while the valve is closed, and when the output voltage of the fuel cell becomes a predetermined threshold value or more, A control device for a fuel cell system, wherein it is determined that oxidant gas is present. A fuel cell that generates electricity using a fuel gas supplied to the fuel electrode and an oxidant gas supplied to the oxidant electrode;
A valve for opening and closing a flow path connected to the oxidant electrode, the valve being controlled to be closed when the fuel cell is stopped;
When starting the fuel cell, it is determined whether or not oxidant gas is present in the oxidant electrode, and when it is determined that oxidant gas is present, the output voltage of the fuel cell is reduced to a predetermined upper limit value or less. A control device that performs control to reduce to a predetermined target value while limiting;
A fuel cell system comprising:

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