JP7633775B2 - Gas flow rate control device and method, and fuel cell system - Google Patents

Description

Embodiments of the present invention relate to a gas flow control device and method, and a fuel cell system.

A typical solid polymer fuel cell has a cell stack in which multiple fuel cells are stacked. Such a fuel cell generates electrical energy from the chemical energy of the fuel gas by chemically reacting a fuel gas containing hydrogen with an oxygen-containing gas containing oxygen within each cell stack.

The fuel cell has a polymer electrolyte membrane and an anode and a cathode arranged to sandwich the polymer electrolyte membrane. When generating electricity, the fuel gas is supplied to the anode and the oxygen-containing gas is supplied to the cathode.

The fuel gas discharged from the anode is generally called anode off-gas. This anode off-gas usually contains unreacted hydrogen, so it may be fed back into the fuel cell to make more efficient use of the fuel gas.

On the other hand, if the anode off-gas is reused for a long period of time, the concentration of nitrogen contained in the anode off-gas increases, which can result in a drop in the voltage of the fuel cell. For this reason, when circulating the anode off-gas, a degassing pipe is connected to the recycle pipe, and a portion of the anode off-gas can be discharged as necessary by opening the degassing switch valve of the degassing pipe.

In a fuel cell system equipped with a recycle pipe and a degassing pipe as described above, when switching between a normal operation state in which degassing is not performed and a degassing operation state in which degassing is performed, the flow rates of the fuel gas and anode off-gas supplied to the fuel cell change. As a result, the pressure at the anode electrode fluctuates. When such a change in pressure occurs, normally the flow rate of the fuel gas is adjusted to return the changed pressure to the original pressure.

However, because the operating conditions, such as the pressure and flow rate within the flow path, differ between normal operation and degassing operation, it may not be possible to smoothly control the pressure back to the original level.

In addition, when a fuel cell is operated for a long period of time, for some reason it may no longer be possible to smoothly control the pressure to the desired level, even if it was previously able to control the pressure appropriately. This phenomenon tends to be more noticeable during degassing operation.

JP 2020-95800 A

The problem that the present invention aims to solve is to provide a gas flow control device and method, and a fuel cell system, that can quickly and accurately control the gas supply state to the fuel cell to the desired state, even when anode off-gas degassing is switched on.

The gas flow control device according to one embodiment is a gas flow control device in a fuel cell system that supplies fuel gas whose flow rate has been adjusted by a flow rate adjustment unit to a fuel cell and circulates anode off-gas flowing out from the fuel cell between the flow rate adjustment unit and the fuel cell through a recycle pipe. This gas flow control device includes a detection unit that detects the state of a degassing pipe that branches off from the recycle pipe and is capable of discharging a portion of the anode off-gas to the outside, and a flow rate adjustment operation control unit that selects one map from a plurality of maps used to control the flow rate adjustment unit according to the state of the degassing pipe detected by the detection unit, and adjusts the flow rate of the fuel gas by controlling the operation of the flow rate adjustment unit based on the selected map.

A gas flow rate control method according to one embodiment is a gas flow rate control method in a fuel cell system in which fuel gas whose flow rate has been adjusted by a flow rate adjustment unit is supplied to a fuel cell, and anode off-gas flowing out from the fuel cell is circulated between the flow rate adjustment unit and the fuel cell through a recycle pipe. This method includes a detection step for detecting the state of a degassing pipe that branches off from the recycle pipe and is capable of discharging a portion of the anode off-gas to the outside, and a flow rate adjustment operation control step for selecting one map from among a plurality of maps used to control the flow rate adjustment unit according to the state of the degassing pipe detected in the detection step, and adjusting the flow rate of the fuel gas by controlling the operation of the flow rate adjustment unit based on the selected map.

The fuel cell system according to one embodiment is a fuel cell system that supplies fuel gas whose flow rate is adjusted by a flow rate adjustment unit to a fuel cell, circulates anode off-gas flowing out from the fuel cell between the flow rate adjustment unit and the fuel cell through a recycle pipe, and controls the flow rate adjustment unit using the gas flow control device.

According to the present invention, even when the degassing of anode off-gas is switched, the gas supply state to the fuel cell can be controlled quickly and accurately to the desired state.

1 is a diagram showing a schematic configuration of a fuel cell system including a gas flow rate control device according to an embodiment; 1 is a block diagram showing a functional configuration of a gas flow rate control device according to an embodiment; FIG. 2 is a diagram showing an example of a map stored in the gas flow rate control device according to the embodiment. FIG. 2 is a block diagram showing an example of a control model of a gas flow rate control device according to an embodiment. 4 is a flowchart showing an example of an operation of the gas flow rate control device according to the embodiment. FIG. 4 is a diagram illustrating an operation of updating a map by the gas flow rate control device according to the embodiment.

One embodiment will be described in detail below with reference to the attached drawings.

Figure 1 is a diagram showing the schematic configuration of a fuel cell system 1 equipped with a gas flow control device 200 according to one embodiment.

<Overall composition>
1 is a system capable of reusing anode off-gas flowing out from the fuel electrode of a fuel cell 100 during power generation. This fuel cell system 1 includes a hydrogen gas supply pipe 2, an oxygen gas supply pipe 4, a hydrogen recycle pipe 6, a degassing pipe 8, a fuel cell 100, a hydrogen gas supply device 102, a flow rate adjustment injector 104, a recycle blower 106, a degassing switching valve 108, a pressure sensor 110, a flow rate detection unit 112, and a gas flow rate control device 200.

The hydrogen gas supply pipe 2 is a pipe that connects the inlet J1 of the fuel electrode flow path 100a (the "anode" electrode flow path in the figure) of the fuel cell 100 to the hydrogen gas supply device 102. The hydrogen gas supply device 102 is a device that supplies hydrogen-containing gas, which is stored fuel gas, and may be, for example, a hydrogen cylinder. In this embodiment, the fuel source pressure, which is the original pressure of the hydrogen-containing gas supplied from the hydrogen gas supply device 102, is maintained at a constant value.

The hydrogen gas supply pipe 2 is provided with a flow rate adjustment injector 104, which adjusts the flow rate of the hydrogen-containing gas from the hydrogen gas supply device 102 and supplies it to the fuel cell 100. In this embodiment, the flow rate adjustment injector 104 is used as a means for adjusting the supply flow rate of the hydrogen-containing gas, but other means may be used, such as a flow rate adjustment valve.

The flow rate adjustment injector 104 can adjust the flow rate of the hydrogen-containing gas supplied to the fuel cell 100, and can adjust the flow rate of the hydrogen-containing gas according to the amount of power generated by the fuel cell 100. A shutoff valve may be provided upstream of the flow rate adjustment injector 104 in the hydrogen gas supply pipe 2.

The oxygen gas supply pipe 4 is a pipe connected to the inlet of the oxidizer electrode flow passage 100b (the "cathode" electrode flow passage in the figure) in the fuel cell 100, and supplies oxygen-containing gas to the oxidizer electrode flow passage 100b of the fuel cell 100.

The hydrogen recycle pipe 6 is a pipe that connects the outlet J2 of the fuel electrode flow path 100a in the fuel cell 100 to the junction J3 set between the flow rate adjustment injector 104 in the hydrogen gas supply pipe 2 and the fuel cell 100. This hydrogen recycle pipe 6 circulates the anode off-gas flowing out from the fuel electrode flow path 100a through the junction J3 of the hydrogen gas supply pipe 2, making it possible to reuse the anode off-gas.

The hydrogen recycle pipe 6 is provided with a recycle blower 106, which draws the anode off-gas from the fuel cell 100 into the hydrogen recycle pipe 6, circulating the anode off-gas to the hydrogen gas supply pipe 2. The recycle blower 106 may be, for example, a diaphragm pump, a Roots pump, or a scroll pump.

The degassing pipe 8 is a pipe branching off from a branching point J4 that is set between the recycle blower 106 and the junction J3 in the hydrogen recycle pipe 6. A degassing switch valve 108 is provided in the degassing pipe 8, and by switching the degassing switch valve 108 from a closed state to an open state, a portion of the anode off-gas can be discharged from the degassing pipe 8 to the outside.

The fuel cell 100 connected to the hydrogen gas supply pipe 2 and oxygen gas supply pipe 4 has a fuel electrode flow path 100a that supplies hydrogen-containing gas to the fuel electrode (anode electrode) and an oxidizer electrode flow path 100b that supplies oxygen-containing gas to the oxidizer electrode (cathode electrode), and generates power using the hydrogen-containing gas supplied to the fuel electrode and the oxygen-containing gas supplied to the oxidizer electrode. The oxygen-containing gas is, for example, air. In this embodiment, a load 300 is connected to the fuel cell 100, and the electric energy generated by the fuel cell 100 can be supplied to the load 300. The load 300 may be, for example, a motor or a storage battery.

Here, the above-mentioned anode off-gas is a gas discharged from the fuel electrode flow path 100a during power generation of the fuel cell 100, and usually contains unreacted hydrogen gas. On the other hand, nitrogen _N2 in the oxygen-containing gas supplied to the oxidizer electrode is mixed into the anode off-gas. Therefore, the nitrogen concentration of the circulating anode off-gas (hydrogen _H2 + nitrogen _N2 ) increases over time, and conversely, the hydrogen concentration in the anode off-gas decreases. The above-mentioned degassing pipe 8 is provided to restore the hydrogen concentration of the hydrogen-containing gas supplied to the fuel cell 100 by discharging the anode off-gas with an increased impurity concentration.

The pressure sensor 110 detects the pressure in the flow path between the flow rate adjustment injector 104 and the fuel cell 100 in the hydrogen gas supply pipe 2. The pressure sensor 110 detects the pressure of the hydrogen-containing gas in the flow path of the hydrogen gas supply pipe 2 and transmits the detected information to the gas flow control device 200.

The flow rate detection unit 112 detects the flow rate of the hydrogen-containing gas flowing through the hydrogen gas supply pipe 2. More specifically, the flow rate detection unit 112 detects the flow rate of the hydrogen-containing gas flowing through the portion of the hydrogen gas supply pipe 2 between the flow rate adjustment injector 104 and the junction J3. The flow rate detection unit 112 then transmits information on the detected flow rate of the hydrogen-containing gas to the gas flow control device 200. In this embodiment, the flow rate detection unit 112 is, for example, a mechanical flow meter such as an impeller type, but the flow rate detection unit 112 may be configured by software. In this case, for example, the flow rate detection unit 112 may be configured to predict the flow rate based on the operating status (opening degree and opening/closing frequency) of the flow rate adjustment injector 104, or may be configured to predict the flow rate based on the indication value of the pressure sensor 110.

In this embodiment, information on the amount of power generated by the fuel cell 100 during power generation is also transmitted to the gas flow control device 200. The information on the amount of power generated may be the output current of the fuel cell 100.

<Gas flow rate control device>
2 is a block diagram showing the functional configuration of the gas flow rate control device 200. The gas flow rate control device 200 is configured to adjust the flow rate of the hydrogen-containing gas supplied to the fuel cell 100, and to control the pressure of the fuel gas supplied to the fuel cell 100 to a desired pressure.

The gas flow control device 200 includes a processor, and realizes various functions by reading and executing necessary programs from the storage unit 202. The storage unit 202 is realized, for example, by a semiconductor memory element such as a random access memory (RAM), a flash memory, a hard disk, an optical disk, etc. The term "processor" refers to a circuit such as a central processing unit (CPU), an application specific integrated circuit (ASIC), a programmable logic device (SPLD, CPLD), or a field programmable gate array (FPGA). Instead of storing a program in the storage unit 202, the program may be directly incorporated into the processor circuit.

As shown in FIG. 2, the gas flow control device 200 has the above-mentioned memory unit 202, state detection unit 204, flow rate acquisition unit 205, power generation detection unit 206, pressure detection unit 208, flow rate adjustment operation control unit 210, anode off-gas discharge amount control unit 212, pressure control unit 214, and tuning unit 216. Of these, the functional units other than the memory unit 202 are realized by executing a program called from the memory unit 202.

The memory unit 202 stores various programs and has a map storage unit 202a that stores multiple maps used for controlling the flow rate adjustment injector 104, etc.

Figure 3 shows examples of maps stored in the map storage unit 202a, specifically, examples of normal maps Nfm, Nufm and reference degassing maps Dfm, Dufm used to control the flow rate adjustment injector 104. The normal maps Nfm, Nufm are maps used in normal operation in which anode off-gas is not discharged from the degassing pipe 8, and the reference degassing maps Dfm, Dufm are maps used in degassing operation in which anode off-gas is discharged from the degassing pipe 8.

The normal map Nfm and the reference degassing map Dfm shown in the upper part of Figure 3 define the relationship between the amount of power that can be generated by the fuel cell 100 and the flow rate of the hydrogen-containing gas supplied by the flow rate adjustment injector 104 to obtain a predetermined amount of power generation by the fuel cell 100 (for example, a specified amount of power generation or an amount of power generation determined as a design value).

The normal map Nufm and the reference degassing map Dufm shown in the lower part of FIG. 3 define the relationship between the amount of power that can be generated by the fuel cell 100 and the fuel utilization rate of the hydrogen-containing gas supplied by the flow rate adjustment injector 104 to obtain a predetermined amount of power generation by the fuel cell 100. Here, the fuel utilization rate means the proportion of the hydrogen-containing gas supplied by the flow rate adjustment injector 104 that is used for power generation by the fuel cell 100. The fuel utilization rate is determined by the amount of hydrogen consumed divided by the flow rate of the hydrogen-containing gas supplied. The amount of hydrogen consumed can be calculated from the actual amount of power generation by the fuel cell 100.

In this embodiment, the flow rate adjustment injector 104 is controlled using the normal map Nfm and the reference degassing map Dfm shown in the upper part of FIG. 3, which define the relationship between the amount of power generation and the flow rate of the hydrogen-containing gas. That is, the fuel cell system 1 controls the flow rate of the hydrogen-containing gas supplied from the flow rate adjustment injector 104 to obtain a certain amount of power generation from the fuel cell 100. At this time, the normal map Nfm and the reference degassing map Dfm are referenced. Specifically, when performing degassing operation using the reference degassing map Dfm, if the amount of power generation X is specified as shown in FIG. 3, the normal map Nfm is referenced to determine the flow rate Y.

As is clear from the illustration of the normal map Nfm and the map Dfm for reference degassing, the larger the specified amount of power generation (in other words, the target amount of power generation), the larger the flow rate of the hydrogen-containing gas supplied from the flow rate adjustment injector 104 is set. On the other hand, in the normal map Nufm and the map Dufm for reference degassing shown in the lower part of FIG. 3, which define the relationship between the amount of power generation and the fuel utilization rate of the hydrogen-containing gas, when the normal map Nufm is used, the fuel utilization rate of the hydrogen-containing gas is approximately constant, and when the map Dufm for reference degassing is used, the larger the specified amount of power generation, the larger the fuel utilization rate of the hydrogen-containing gas supplied from the flow rate adjustment injector 104 is set, and the flow rate adjustment injector 104 is controlled so that the fuel utilization rate becomes larger.

Returning to FIG. 2, the state detection unit 204 detects the state of the degassing pipe 8, and specifically detects the state of the degassing pipe 8 as a state in which anode off-gas is not discharged from the degassing pipe 8 (normal operation) or a state in which anode off-gas is discharged from the degassing pipe 8 (degassing operation). The state detection unit 204 may detect the state of the degassing pipe 8 as described above based on the state of the degassing switching valve 108 that opens and closes the degassing pipe 8.

The flow rate acquisition unit 205 acquires information on the flow rate of the hydrogen-containing gas from the flow rate detection unit 112. Note that, when the flow rate detection unit 112 is configured by software as described above, the flow rate detection unit 112 may be integrated with the flow rate acquisition unit 205.

The power generation amount detection unit 206 detects the actual power generation amount of the fuel cell 100 based on the information on the power generation amount transmitted from the fuel cell 100 during power generation. When calculating the fuel utilization rate, for example, the fuel consumption amount may be determined from the actual power generation amount of the fuel cell 100 and divided by the flow rate of the hydrogen-containing gas acquired by the flow rate acquisition unit 205. However, the method of calculating the fuel utilization rate is not limited to this.

The pressure detection unit 208 detects the pressure in the flow path between the flow rate adjustment injector 104 and the fuel cell 100 in the hydrogen gas supply pipe 2 based on information from the pressure sensor 110.

Then, the flow rate adjustment operation control unit 210 selects one map from among multiple maps (normal map Nfm and reference degassing map Dfm) used to control the flow rate adjustment injector 104 according to the state of the degassing pipe 8 detected by the state detection unit 204, and adjusts the flow rate of the hydrogen-containing gas by controlling the operation of the flow rate adjustment injector 104 based on the selected map.

In more detail, the flow rate adjustment operation control unit 210 selects the normal map Nfm in normal operation, in which anode off-gas is not discharged from the degassing pipe 8, and selects the reference degassing map Dfm in degassing operation, in which anode off-gas is discharged from the degassing pipe 8. The flow rate adjustment operation control unit 210 then determines the flow rate of the hydrogen-containing gas based on the selected normal map Nfm or reference degassing map Dfm and, for example, the specified power generation amount of the fuel cell 100, and controls the flow rate adjustment injector 104.

Next, the anode off-gas discharge amount control unit 212 controls the amount of anode off-gas discharged from the fuel cell 100 by controlling the recycle blower 106. In detail, the anode off-gas discharge amount control unit 212 adjusts the control amount of the recycle blower 106 based on the blower control map stored in the map holding unit 202a of the memory unit 202.

The blower control map defines, for example, the relationship between the air volume (rotation speed) of the recycle blower 106 and a certain amount of power generation by the fuel cell 100. In this embodiment, the anode off-gas emission control unit 212 controls the recycle blower 106 using map control, but it may also be controlled using PID control or the like.

The pressure control unit 214 also controls the operation of the flow rate adjustment injector 104 based on the difference between the pressure detected by the pressure detection unit 208 and the target pressure, in this example PID control, so that the pressure detected by the pressure detection unit 208 matches the target pressure. The target pressure is determined according to the power generation amount of the fuel cell 100, and the relationship between the target pressure and the power generation amount may be stored in advance in the memory unit 202.

Here, in this embodiment, the flow rate of the flow rate adjustment injector 104 is adjusted by map control by the flow rate adjustment operation control unit 210 and PID control by the pressure control unit 214. Figure 4 is a block diagram showing an example of a control model of the gas flow control device 200 for the flow rate adjustment injector 104.

As shown in FIG. 4, when controlling the flow rate adjustment injector 104, information on the power generation amount of the fuel cell 100 and the state of the degassing tube 8 is input to the flow rate adjustment operation control unit 210. Meanwhile, information on the target pressure based on the power generation amount of the fuel cell 100 is input to the pressure control unit 214. The flow rate adjustment operation control unit 210 then performs feedforward control based on the selected map for the flow rate adjustment operation control unit 210. The pressure control unit 214 also performs feedback control by PID based on the difference between the target pressure and the detected pressure for the flow rate adjustment operation control unit 210. That is, in this embodiment, the responsiveness of the control is improved by performing feedforward control corresponding to the change in the state of the degassing tube 8.

The tuning unit 216 will be described below. The tuning unit 216 tunes the characteristics of the map Dfm (or Dufm) for reference degassing. During degassing operation, the tuning unit 216 starts tuning operation when the difference between the flow rate (or fuel utilization rate) of hydrogen-containing gas determined from the map Dfm for reference degassing with respect to the actual power generation amount of the fuel cell 100 detected by the power generation amount detection unit 206 and the actual flow rate (or fuel utilization rate) of hydrogen-containing gas obtained by the flow rate detection unit 112 becomes equal to or greater than a predetermined tuning start reference value.

The tuning procedures for the reference degassing map Dfm and the reference degassing map Dufm are similar, so the following describes the tuning operation for the reference degassing map Dfm used in this embodiment.

When the tuning operation starts, the tuning unit 216 stops the control operation for the currently specified power generation amount of the fuel cell 100, but maintains the degassing operation. After that, the tuning unit 216 specifies multiple power generation amounts, and causes the flow rate adjustment operation control unit 210 to perform flow rate control based on the reference degassing map Dfm corresponding to each power generation amount.

Then, the tuning unit 216 obtains the difference between the flow rate of the hydrogen-containing gas determined from the reference degassing map Dfm and the actual flow rate of the hydrogen-containing gas for each specified power generation amount, relative to the actual power generation amount of the fuel cell 100 detected by the power generation amount detection unit 206. After that, the tuning unit 216 generates a new degassing map by changing the reference degassing map Dfm based on the obtained differences between the multiple flow rates.

As a tuning operation, while performing a control operation for the power generation amount of the fuel cell 100 required by the load 300, only at the timing when the degassing operation is performed, the difference between the flow rate of the hydrogen-containing gas determined from the reference degassing map Dfm and the actual flow rate of the hydrogen-containing gas is obtained for the actual power generation amount of the fuel cell 100 detected by the power generation amount detection unit 206, and after obtaining the difference at each specified power generation amount, the tuning unit 216 generates a new degassing map by changing the reference degassing map Dfm based on the obtained difference between the multiple flow rates.

When generating a new degassing map as described above, in this embodiment, if the flow rate of hydrogen-containing gas determined from the reference degassing map Dfm for the actual power generation tends to be smaller than the actual flow rate of hydrogen-containing gas, the reference degassing map Dfm is changed, for example, in the direction of increasing the flow rate. On the other hand, if the flow rate of hydrogen-containing gas determined from the reference degassing map Dfm for the actual power generation tends to be larger than the actual flow rate of hydrogen-containing gas, the reference degassing map Dfm is changed, for example, in the direction of decreasing the flow rate.

After generating a new degassing map in the above manner, the tuning unit 216 determines whether the amount of change between the reference degassing map Dfm and the new degassing map exceeds a first standard, whether it exceeds a second standard that is greater than the first standard, and whether it exceeds a third standard that is greater than the second standard. The amount of change may be compared to the standard, for example, by comparing the average value of the flow rate differences for multiple amounts of power generation with the corresponding standard, or by comparing the cumulative value of the flow rate differences for multiple amounts of power generation with the corresponding standard.

If the amount of change between the reference deaeration map Dfm and the new deaeration map does not exceed the first standard, the tuning unit 216 maintains the existing reference deaeration map Dfm. On the other hand, if the amount of change exceeds the first standard but does not exceed the second standard, the tuning unit 216 sets the new deaeration map as the new reference deaeration map Dfm.

In addition, if the amount of change between the reference degassing map Dfm and the new degassing map exceeds the second standard but does not exceed the third standard, the tuning unit 216 tunes the control amount of the anode off-gas emission control unit 212 while maintaining the existing reference degassing map Dfm. At this time, the tuning unit 216 tunes the control amount of the anode off-gas emission control unit 212 by tuning the blower control map described above.

Tuning of the blower control map is performed, for example, by gradually changing the blower control map while maintaining the degassing operation, and is completed when a predetermined condition is met. This predetermined condition may be, for example, a condition that the difference between the flow rate of the hydrogen-containing gas determined from the reference degassing map Dfm for the actual power generation amount of the fuel cell 100 and the actual flow rate of the hydrogen-containing gas is less than a predetermined value that is smaller than the tuning start reference value.

When tuning of the blower control map is completed as described above, the tuned blower control map is stored in the memory unit 202 as a new blower control map. The new stored blower control map is used by the anode off-gas discharge amount control unit 212 during subsequent degassing operations. This new blower control map may also be used during normal operation. Then, in this embodiment, the tuning unit 216 performs the above-described tuning operation on the reference degassing map Dfm again in a state in which the anode off-gas discharge amount control unit 212 performs control using the new blower control map and the flow rate adjustment operation control unit 210 performs control using the existing reference degassing map Dfm.

That is, after tuning the blower control map, the tuning unit 216 again obtains the difference between the flow rate of hydrogen-containing gas determined from the reference degassing map Dfm and the actual flow rate of hydrogen-containing gas for each specified power generation amount relative to the actual power generation amount of the fuel cell 100 detected by the power generation amount detection unit 206. The tuning unit 216 then generates a new degassing map by changing the reference degassing map Dfm based on the obtained differences in the multiple flow rates, and again compares the amount of change between the reference degassing map Dfm and the new degassing map with the first to third standards.

On the other hand, if the amount of change between the reference deaeration map Dfm and the new deaeration map exceeds the third standard, the tuning unit 216 displays a warning and/or stops the fuel cell system 1. In this embodiment, a warning is displayed.

The tuning unit 216 starts the tuning operation described above when the difference in flow rates becomes equal to or greater than the tuning start reference value, as described above, but also has a tuning function that fine-tunes the map even when the difference in flow rates does not exceed the tuning start reference value.

Specifically, even if the difference in flow rates is less than the tuning start reference value, the tuning unit 216 records the difference between the flow rate of the hydrogen-containing gas determined from the reference degassing map Dfm for the actual power generation amount of the fuel cell 100 detected by the power generation amount detection unit 206 and the actual flow rate of the hydrogen-containing gas. Then, when the number of the recorded differences reaches or exceeds a predetermined number, the tuning unit 216 generates a new degassing map by changing the reference degassing map Dfm based on the recorded differences, and sets the new degassing map as the new reference degassing map Dfm.

The above-described tuning unit 216 is provided to restore the fuel cell system 1 to a state where proper control can be performed when the responsiveness and accuracy of controlling the anode pressure to the desired pressure during degassing operation decreases. Such a tuning unit 216 makes it possible to improve the reliability of the fuel cell system 1.

<Operation>
Next, an example of the operation of the gas flow rate control device 200 will be described. Fig. 5 is a flowchart showing an example of the operation of the gas flow rate control device 200. Here, an example of the operation of the gas flow rate control device 200 after switching from normal operation to degassing operation will be described.

When the operation is switched from normal operation to degassing operation, information indicating that the operation has been switched to degassing operation is sent from the state detection unit 204 to the flow rate adjustment operation control unit 210. As a result, in step S101, the flow rate adjustment operation control unit 210 first selects the map Dfm for reference degassing from the normal map Nfm.

Then, in step S102, the flow rate adjustment operation control unit 210 determines the flow rate of the hydrogen-containing gas based on the reference degassing map Dfm and information on the amount of power generated by the fuel cell 100.

Next, in step S103, the flow rate adjustment operation control unit 210 controls the operation of the flow rate adjustment injector 104 so that the flow rate adjustment injector 104 supplies hydrogen-containing gas at the flow rate of the hydrogen-containing gas determined in step S102.

In addition, in step S104, the pressure control unit 214 controls the operation of the flow rate adjustment injector 104 so that the pressure detected by the pressure detection unit 208 matches the target pressure.

Then, in step S105, the power generation amount detection unit 206 detects the current power generation amount of the fuel cell 100 during power generation, and the flow rate acquisition unit 205 acquires the flow rate of the hydrogen-containing gas from the flow rate detection unit 112.

Next, in step S106, the tuning unit 216 calculates the difference between the flow rate of the hydrogen-containing gas determined from the reference degassing map Dfm for the actual power generation amount of the fuel cell 100 detected by the power generation amount detection unit 206 and the actual flow rate of the hydrogen-containing gas.

Then, in step S107, the tuning unit 216 determines whether the difference calculated in step S106 is equal to or greater than the tuning start reference value. If the determination in step S107 is that the difference is less than the tuning start reference value (NO), it is determined that there is no abnormality in the reference deaeration map Dfm, and the process proceeds to step S108.

Then, in step S108, the tuning unit 216 records the difference between the flow rate of the hydrogen-containing gas determined from the reference degassing map Dfm for the actual power generation amount of the fuel cell 100 detected by the power generation amount detection unit 206 and the actual flow rate of the hydrogen-containing gas.

Next, in step S109, the tuning unit 216 determines whether the number of differences recorded in step S108 is equal to or greater than a predetermined number. If the determination in step S109 is that the number of differences recorded in step S108 is less than the predetermined number (NO), the process proceeds to step S110.

Then, in step S110, switching to normal operation is monitored, and if switching to normal operation has not occurred, the process returns to step S101. If switching to normal operation is detected, the degassing operation is stopped (end).

Also, if the determination in step S109 is that the number of differences recorded in step S108 is equal to or greater than a predetermined number (YES), the process proceeds to step S111.

In step S111, the tuning unit 216 generates a new deaeration map by changing the reference deaeration map Dfm based on the difference recorded in step S108, and sets (updates) the new deaeration map as the new reference deaeration map Dfm. Then, in step S110, a switch to normal operation is monitored, and if there is no switch to normal operation, the process returns to step S101. At this time, in step S101, the new reference deaeration map Dfm is used.

On the other hand, if it is determined in step S107 that the difference is equal to or greater than the tuning start reference value, it is determined that there is an abnormality in the reference deaeration map Dfm, and the process proceeds from step S108 to step S112. Then, active tuning operation by the tuning unit 216 begins.

During the tuning operation, first, in step S112, the tuning unit 216 obtains the difference between the flow rate of the hydrogen-containing gas determined from the reference degassing map Dfm and the actual flow rate of the hydrogen-containing gas for the actual power generation amount of the fuel cell 100 detected by the power generation amount detection unit 206 for multiple specified power generation amounts. In other words, the fuel cell 100 is controlled to multiple power generation amounts, and the state (flow rate difference) at each power generation amount is obtained.

Next, in step S113, the tuning unit 216 generates a new degassing map by changing the reference degassing map Dfm based on the difference between the multiple flow rates obtained in step S112.

Then, in step S114, the tuning unit 216 determines whether the amount of change between the reference deaeration map Dfm and the new deaeration map exceeds a first criterion. If the amount of change does not exceed the first criterion (NO) in the determination in step S114, it is determined that there is no abnormality in the reference deaeration map Dfm, and the process proceeds to step S110, returning to the state before the tuning operation.

On the other hand, if the determination in step S114 is that the amount of change exceeds the first criterion (YES), the process proceeds to step S115, where the tuning unit 216 determines whether the amount of change exceeds the second criterion.

If the determination in step S115 is that the amount of change does not exceed the second reference (NO), the tuning unit 216 sets the new deaeration map as the new reference deaeration map Dfm in step S116. Then, the process proceeds to step S110, and the state is returned to before the tuning operation.

On the other hand, if the determination in step S115 indicates that the amount of change exceeds the second criterion (YES), the tuning unit 216 determines in step S117 whether the amount of change exceeds the third criterion.

If the amount of change does not exceed the third standard (NO) in the determination in step S117, the tuning unit 216 tunes the control amount (blower control map) of the anode off-gas emission control unit 212 in step S118. Thereafter, the tuning unit 216 returns to step S112 and performs the operation to generate a new deaeration map again.

On the other hand, if the amount of change is found to exceed the third standard in step S117 (YES), the tuning unit 216 displays a warning in step S119, and then proceeds to step S110, returning to the state before the tuning operation. If the amount of change is found to exceed the third standard in step S117, it is determined that there is a significant abnormality in the current reference deaeration map Dfm. Therefore, the warning display in step S119 is performed, for example, to prompt the user to stop the system.

Here, FIG. 6 is a diagram conceptually explaining an example of the operation of the gas flow control device 200 to update the map. Specifically, FIG. 6 conceptually shows an example of the operation performed in steps S112 to S116 in FIG. 5.

As shown in FIG. 6(A), the gas flow control device 200 stores in advance a normal map Nfm and a reference degassing map Dfm.

When the tuning operation is started, as shown in FIG. 6(B), the difference between the flow rate of the hydrogen-containing gas determined from the map Dfm for reference degassing and the actual flow rate of the hydrogen-containing gas is obtained for the actual power generation amount of the fuel cell 100 detected by the power generation amount detection unit 206 for multiple power generation amounts. In FIG. 6(B), the relationship between the actual power generation amount of the fuel cell 100 detected by the power generation amount detection unit 206 and the flow rate of the hydrogen-containing gas determined from the map Dfm for reference degassing is connected by a solid line. Meanwhile, the circle in FIG. 6(B) indicates the actual flow rate of the hydrogen-containing gas, and the Δ in FIG. 6(B) indicates an image of the difference in flow rate.

Figure 6 (C) shows a new deaeration map generated by changing the reference deaeration map Dfm based on the difference between the multiple flow rates acquired by the tuning unit 216. When the amount of change between the reference deaeration map Dfm and the new deaeration map exceeds the first standard and is less than the second standard, the new deaeration map is set as the new reference deaeration map Dfm, as shown in Figure 6 (D).

As described above, the gas flow control device 200 according to this embodiment selects between the normal operation map Nfm and the reference degassing map Dfm used to control the flow rate adjustment injector 104 depending on the state of the degassing pipe 8, and controls the operation of the flow rate adjustment injector 104 based on the selected map. This allows the gas supply state to the fuel cell 100 to be quickly and accurately controlled to the desired state even when the degassing of the anode off-gas is switched.

In addition, the tuning unit 216 can appropriately tune the map Dfm for reference degassing, so that when the responsiveness and accuracy of pressure control during degassing operation deteriorates, it is possible to restore a state in which proper control can be performed. This improves the reliability of the fuel cell system 1.

Although one embodiment has been described above, the above embodiment is presented as an example and is not intended to limit the scope of the invention. This new embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. The above-mentioned embodiment and other modifications are included within the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

1...Fuel cell system, 2...Hydrogen gas supply pipe, 4...Oxygen gas supply pipe, 6...Hydrogen recycle pipe, 8...Deaeration pipe, 100...Fuel cell, 100a...Anode flow path, 100b...Oxidizer electrode flow path, 102...Hydrogen gas supply device, 104...Flow rate adjustment injector, 106...Recycle blower, 108...Deaeration switching valve, 110...Pressure sensor, 112...Flow rate detection unit, 200...Gas flow rate control device, 202...Memory unit, 202a...Map storage unit, 204...Status detection unit, 205...Flow rate acquisition unit, 206...Power generation detection unit, 208...Pressure detection unit, 210...Flow rate adjustment operation control unit, 212...Anode off-gas discharge amount control unit, 214...Pressure control unit, 216...Tuning unit

Claims (15)

A gas flow rate control device in a fuel cell system, which supplies a fuel gas whose flow rate has been adjusted by a flow rate adjustment unit to a fuel cell, and circulates an anode off-gas flowing out from the fuel cell between the flow rate adjustment unit and the fuel cell through a recycle pipe,
a detection unit that detects a state of a degassing pipe branched off from the recycle pipe and capable of discharging a portion of the anode off-gas to the outside, the detection unit detecting a state in which the anode off-gas is not discharged from the degassing pipe or a state in which the anode off-gas is discharged from the degassing pipe;
a flow rate adjustment operation control unit that selects one map from a plurality of maps used for controlling the flow rate adjustment unit according to the state of the degassing pipe detected by the detection unit, and adjusts the flow rate of the fuel gas by controlling the operation of the flow rate adjustment unit based on the selected map,
the plurality of maps include at least a first normal map that defines a relationship between an amount of power generated by the fuel cell and a first flow rate of the fuel gas supplied by the flow rate adjustment unit, and a first reference deaeration map that defines a relationship between an amount of power generated by the fuel cell and a second flow rate of the fuel gas supplied by the flow rate adjustment unit, and specifies that for an amount of power generated by the fuel cell that is the same as the normal map, the second flow rate is greater than the first flow rate in at least a portion of the range of the amount of power generated;
The flow rate adjustment operation control unit selects the first normal map when the anode off-gas is not discharged from the degassing pipe, and selects the first reference degassing map when the anode off-gas is discharged from the degassing pipe. the plurality of maps further include a second normal map in which a fuel utilization rate of the fuel gas supplied by the flow rate regulator with respect to an amount of power generation of the fuel cell is defined as a fixed value, and a second reference deaeration map in which a relationship between an amount of power generation of the fuel cell and a fuel utilization rate of the fuel gas supplied by the flow rate regulator is defined as a nonlinear relationship,
2. The gas flow control device according to claim 1, wherein the flow rate adjustment operation control unit selects the second normal map when the anode off-gas is not discharged from the degassing pipe, and selects the second reference degassing map when the anode off-gas is discharged from the degassing pipe. The gas flow control device according to claim 1 or 2, wherein the detection unit detects the state of the degassing tube based on the state of a degassing switching valve that opens and closes the degassing tube. the plurality of maps include a normal map used when the anode off-gas is not discharged from the degassing pipe, and a reference degassing map used when the anode off-gas is discharged from the degassing pipe,
The apparatus further includes a tuning unit that tunes the characteristics of the reference degassing map,
The tuning unit includes:
controlling the flow rate regulator by the flow rate regulation operation control unit using the map for reference degassing when the degassing pipe is in a state in which the anode off-gas is discharged;
A difference between the flow rate or fuel utilization rate of the fuel gas determined from the reference degassing map for an actual amount of power generation of the fuel cell detected during power generation is obtained for a plurality of amounts of power generation, and the actual flow rate or fuel utilization rate of the fuel gas is obtained;
4. The gas flow control device according to claim 3, further comprising: a reference degassing map for generating a new degassing map by changing the reference degassing map based on the acquired multiple differences; and when a change between the reference degassing map and the new degassing map exceeds a first reference, the new degassing map is set as a new reference degassing map. The gas flow control device according to claim 4, wherein the tuning unit tunes the control amount of an anode off-gas emission control unit that controls the emission amount of the anode off-gas flowing out from the fuel cell when the amount of change between the reference degassing map and the new degassing map exceeds a second standard that is greater than the first standard. The gas flow control device according to claim 5, wherein the anode off-gas discharge amount control unit controls the discharge amount of the anode off-gas by controlling a recycle blower that draws the anode off-gas into the recycle pipe. The anode off-gas discharge control unit adjusts a control amount of the recycle blower based on a blower control map,
the tuning unit tunes a control amount of the anode off-gas discharge amount control unit by tuning the blower control map,
The gas flow rate control device according to claim 6 , wherein the blower control map tuned by the tuning unit is held as a new blower control map. The tuning unit tunes the control amount of the anode off-gas discharge control unit, and then
a difference between the flow rate or fuel utilization rate of the fuel gas determined from the reference degassing map for an actual amount of power generation of the fuel cell detected during power generation and the actual flow rate or fuel utilization rate of the fuel gas is again obtained for a plurality of amounts of power generation;
8. The gas flow rate control device according to claim 5, further comprising: a step of generating a new degassing map by changing the reference degassing map based on the acquired differences. A gas flow control device according to any one of claims 4 to 8, wherein the tuning unit starts a tuning operation when, while the fuel cell is generating power with the degassing tube in a state where the anode off-gas is discharged, a difference between the fuel gas flow rate or fuel utilization rate detected during power generation and determined from the map for reference degassing with respect to the actual power generation amount of the fuel cell, and the actual fuel gas flow rate or fuel utilization rate, becomes equal to or greater than a tuning start reference value. The tuning unit performs the tuning start reference value even if a difference between the flow rate or fuel utilization rate of the fuel gas determined from the map for reference deaeration with respect to an actual amount of power generation of the fuel cell detected during power generation and the actual flow rate or fuel utilization rate of the fuel gas is less than the tuning start reference value.
A difference between the flow rate or fuel utilization rate of the fuel gas determined from the map for reference degassing time for an actual amount of power generation of the fuel cell detected during power generation and the actual flow rate or fuel utilization rate of the fuel gas is recorded at a plurality of points;
10. The gas flow control device according to claim 9, wherein when a number of the recorded differences reaches a predetermined number or more, a new degassing map is generated by changing the reference degassing map based on the recorded differences. The gas flow control device according to claim 5, wherein the tuning unit displays a warning and/or stops the fuel cell system when the amount of change between the reference degassing map and the new degassing map exceeds a third standard that is greater than the second standard. a pressure detection unit that detects a pressure in a flow path between the flow rate regulator and the fuel cell;
12. The gas flow control device according to claim 1, further comprising: a pressure control unit that controls an operation of the flow rate adjustment unit by PID control based on a difference between the pressure detected by the pressure detection unit and a target pressure so that the pressure detected by the pressure detection unit coincides with the target pressure. The gas flow control device according to claim 12, wherein the target pressure is determined according to the amount of power generated by the fuel cell. A gas flow rate control method in a fuel cell system, comprising: supplying a fuel gas whose flow rate has been adjusted by a flow rate adjustment unit to a fuel cell; and circulating an anode off-gas flowing out of the fuel cell between the flow rate adjustment unit and the fuel cell through a recycle pipe, the method comprising the steps of:
a detection step of detecting a state of a degassing pipe branched off from the recycle pipe and capable of discharging a portion of the anode off-gas to the outside, the state being a state in which the anode off-gas is not discharged from the degassing pipe, or a state in which the anode off-gas is discharged from the degassing pipe;
a flow rate adjustment operation control step of selecting one map from a plurality of maps used for controlling the flow rate adjustment unit according to the state of the degassing pipe detected in the detection step, and adjusting the flow rate of the fuel gas by controlling the operation of the flow rate adjustment unit based on the selected map,
the plurality of maps include at least a first normal map that defines a relationship between an amount of power generated by the fuel cell and a first flow rate of the fuel gas supplied by the flow rate adjustment unit, and a first reference deaeration map that defines a relationship between an amount of power generated by the fuel cell and a second flow rate of the fuel gas supplied by the flow rate adjustment unit, and specifies that for an amount of power generated by the fuel cell that is the same as the normal map, the second flow rate is greater than the first flow rate in at least a portion of the range of the amount of power generated;
In the flow rate adjustment operation control step, the first normal map is selected when the anode off-gas is not discharged from the degassing pipe, and the first reference degassing map is selected when the anode off-gas is discharged from the degassing pipe.
Gas flow control method. A fuel cell system comprising: a fuel gas whose flow rate is adjusted by a flow rate adjustment unit; and an anode off-gas flowing out from the fuel cell is circulated between the flow rate adjustment unit and the fuel cell through a recycle pipe,
A fuel cell system, comprising: a gas flow rate control device according to claim 1 ; and a flow rate regulator that controls the flow rate regulator.