JP3829767B2 - Fuel cell control system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell control system including an exhaust fuel combustor that combusts exhaust fuel gas, and in particular, a fuel that can supply an amount of oxidizing gas required for combustion of exhaust fuel gas in the exhaust fuel combustor. The present invention relates to a battery control system.
[0002]
[Prior art]
Conventionally, as a fuel cell control system in which exhaust fuel gas of a fuel cell is burned by a combustor, for example, there is one described in Japanese Patent Application Laid-Open No. 2001-023669.
[0003]
In order to control the temperature of the combustor, excess air is always supplied from the compressor, and when the temperature of the combustor is too low, surplus air as oxidizing gas is discharged to the atmosphere, and the temperature of the combustor is high. In this case, the gas is supplied to the combustor without being released into the atmosphere.
[0004]
[Problems to be solved by the invention]
However, in the above conventional example, an excess amount of air is always supplied in anticipation of an increase in exhaust fuel gas at the time of purging, etc., so excess air unnecessary for controlling the temperature of the combustor is always discharged to the atmosphere. However, there is a problem that power is continuously consumed by the compressor.
[0005]
Accordingly, the present invention has been made in view of the above problems, and a fuel cell control system in which an exhaust fuel combustor can supply an amount of oxidizing gas required for combustion of exhaust fuel gas without being discharged to the atmosphere. The purpose is to provide.
[0006]
[Means for Solving the Problems]
The present invention relates to a fuel cell control system including an exhaust fuel combustor that reacts exhaust fuel gas discharged by a purge unit and exhaust oxidant gas discharged from the fuel cell stack. The exhaust fuel gas flow rate estimating means for estimating the exhaust fuel gas flow rate from the output of the exhaust gas, and the exhaust oxidation for setting the target value of the flow rate of the exhaust oxidizing gas supplied to the exhaust fuel combustor based on the output of the exhaust fuel gas flow rate estimating means A gas target flow rate setting means, and the oxidizing gas flow rate control means controls the oxidizing gas flow rate based on the exhaust oxidizing gas target flow rate.
[0007]
【The invention's effect】
Therefore, in the present invention, the exhaust fuel gas flow rate estimation means estimates the exhaust fuel gas flow rate when the purge means is operated from the output of the operating state detection means of the fuel cell stack, and the exhaust oxidation gas target flow rate setting means estimates the exhaust fuel gas. A target value of the flow rate of exhaust oxidant gas supplied to the exhaust fuel combustor is set in accordance with the flow rate, and the oxidant gas flow rate is controlled by the oxidant gas flow rate control means so as to become the exhaust gas target flow rate. For this reason, it is possible to prevent thermal deterioration due to an excessive temperature rise of the exhaust fuel combustor due to a shortage of oxidizing gas supplied to the exhaust fuel combustor, and to minimize energy consumption of the oxidizing gas supply means.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the fuel cell control system of the present invention will be described based on each embodiment.
[0009]
(First embodiment)
1 and 2 show a fuel cell control system according to a first embodiment to which the present invention is applied. FIG. 1 is a schematic configuration diagram of the fuel cell control system, and FIG. 2 is a configuration diagram of a controller.
[0010]
In FIG. 1, a fuel cell control system receives a supply of hydrogen gas as a fuel gas and air as an oxidant gas, generates a fuel cell stack 1 that generates electrical energy through an electrochemical reaction, and supplies hydrogen gas to the fuel cell stack 1. A circulation path 2 that supplies and recirculates the exhaust hydrogen gas from the fuel cell stack 1 and supplies it again to the fuel cell stack 1; a purge means 3 that exhausts the hydrogen gas in the circulation path 1; An exhaust hydrogen combustor 4 as an exhaust fuel combustor for combusting gas, an air (oxidizing gas) supply means 5 for supplying air as an oxidizing gas to the fuel cell stack 1, and a controller 6 are provided.
[0011]
The circulation path 2 supplies hydrogen gas as a fuel gas supplied from a hydrogen supply source (not shown) to the fuel cell stack 1 via the hydrogen pressure control valve 7 and the ejector 8, and exhaust hydrogen gas from the fuel cell stack 1. Is recirculated to the ejector 8, mixed with the hydrogen gas supplied by the ejector 8, circulated and supplied to the fuel cell stack 1. The hydrogen pressure control valve 7 adjusts the operating pressure of the fuel cell stack 1 by adjusting the pressure of hydrogen gas supplied to the fuel cell stack 1 in accordance with a command from the controller 6. The operating pressure is variable, and the operation pressure is increased when the power generation output taken out from the fuel cell stack 1 is high, and the operation pressure is decreased when the power generation output is low. The control of the hydrogen pressure control valve 7 is measured by the hydrogen inlet pressure sensor 9 and fed back to the controller 6 together with the hydrogen temperature at the fuel cell stack 1 inlet by the hydrogen inlet temperature sensor 10.
[0012]
The purge means 3 (hereinafter referred to as the hydrogen purge valve 3) normally returns the exhausted hydrogen gas discharged from the fuel cell stack 1 to the ejector 8 to cause overflow of the fuel cell stack 1 (hereinafter referred to as flooding). In this case or when the operating pressure of the fuel cell stack 1 is lowered, the hydrogen purge valve 3 is operated by the controller 6 to discharge the hydrogen gas existing in the circulation path 2 and the fuel cell stack 1 to the exhaust hydrogen combustor 4.
[0013]
The air supply means 5 supplies air, which is an oxidizing gas, to the fuel cell stack 1 via the air flow rate sensor 12 by the compressor 11. The compressor 11 is driven according to the target rotational speed by the controller 6, the supply flow rate is measured by the air flow sensor 12, and the measured value is input to the controller 6. Air discharged from the fuel cell stack 1 to the exhaust air passage 13 (hereinafter referred to as exhaust air) is throttled by an air pressure control valve 14 to control the upstream air pressure. The control target value is a target value corresponding to the hydrogen gas pressure at that time. The air pressure is measured by an air inlet pressure sensor 15 disposed at the inlet of the fuel cell stack 1 and input to the controller 6. The air that has passed through the air pressure control valve 14 is released into the atmosphere via the exhaust hydrogen combustor 4.
[0014]
The exhaust hydrogen combustor 4 generates exhaust hydrogen gas discharged from the hydrogen purge valve 3 when water overflow (flooding) or the like occurs in the fuel cell stack 1 or when the operating pressure of the fuel cell stack 1 is reduced. The exhaust gas supplied from the air pressure control valve 14 is combusted and processed. The temperature of the exhaust hydrogen combustor 4 during processing is measured by the combustor temperature sensor 16 and input to the controller 6.
[0015]
In order to detect the operating state of the fuel cell stack 1, its output current and output voltage are measured by a current sensor 17 and a voltage sensor 18 and input to the controller 6.
[0016]
In FIG. 2, a controller 6 receives signals of a target output, a hydrogen inlet temperature, a hydrogen inlet pressure, and a combustor temperature that are input from a fuel cell stack output command unit (not shown), and based on these signals, The target rotational speed of the pressure control valve 7, the air pressure control valve 14, the hydrogen purge valve 3, and the compressor 11 is controlled.
[0017]
The controller 6 calculates a target operating pressure setting unit 21 that calculates a target operating pressure based on the target output, a first air target flow rate setting unit 22 that calculates a first air target flow rate based on the target output, and calculates a purge air target flow rate. A purge air target flow rate setting unit 23; an air target flow rate selection unit 24 that selects either the first air target flow rate or the purge air target flow rate; and a target rotation speed setting unit 25 that calculates a compressor target rotation speed; It consists of
[0018]
The first air target flow rate setting unit 22 calculates a first air target flow rate Qair1 corresponding to the target output with reference to the control map shown in FIG. 3 from the target output, and outputs it to the air target flow rate selection unit 24. The control map shown in FIG. 3 has the fuel cell stack output serving as the target output as the horizontal axis and the first target air flow rate Qair1 as the vertical axis, and the first target air flow rate increases as the target output increases. Qair1 is increased.
[0019]
The target operating pressure setting unit 21 calculates the target operating pressure of the hydrogen inlet pressure of the fuel cell stack 1 from the target output according to the control map shown in FIG. 4, and the hydrogen pressure control valve 7 so that the hydrogen inlet pressure becomes the target operating pressure. To control. The air pressure control valve 14 is controlled by a target value of air pressure control corresponding to the hydrogen inlet pressure.
[0020]
The purge air target flow rate setting unit 23 includes a waste hydrogen flow rate estimation unit 26 serving as an exhaust fuel gas flow rate estimation means during purge, a second air target flow rate setting unit 27 that calculates an air amount corresponding to the exhaust hydrogen flow rate, and The air system delay correction unit 28 that corrects the air system delay of the second air target flow rate, and the second air target flow rate that has been corrected for delay are corrected based on the fed-back combustor temperature to set the supply air amount. 3 air target flow rate setting unit 29. The exhaust oxidant gas target target flow rate setting means corresponds to each part obtained by removing the exhaust hydrogen flow rate estimation unit 26 from the purge air target flow rate setting unit 23.
[0021]
The exhaust hydrogen flow rate estimation unit 26 of the purge air target flow rate setting unit 23 estimates the exhaust hydrogen flow rate supplied from the purge valve 3 to the exhaust hydrogen combustor 4 according to the procedure described below.
(1) The total gas flow rate passing through the hydrogen purge valve 3 is estimated.
(2) The water vapor partial pressure of the gas passing through the hydrogen purge valve 3 is obtained.
(3) The hydrogen flow rate in all gases passing through the hydrogen purge valve 3 is obtained.
[0022]
First, (1) the total gas flow rate passing through the hydrogen purge valve 3 is estimated. The total gas flow rate Q1 is calculated by the following equation (1-1):
Q1 = A1 × (2 × ρc × (Pc−Pa)) ^1/2 ... (1-1)
presume. The symbol in the above formula is
Q1: the total gas flow rate passing through the hydrogen purge valve 3,
A1: Aperture opening area of the hydrogen purge valve 3
ρc: density of hydrogen gas in the hydrogen circulation passage 2 and the fuel cell stack 1,
Pc: internal pressure of the hydrogen circulation passage 2 and the fuel cell stack 1,
Pa: Pressure downstream of the hydrogen purge valve 3 (can be regarded as almost atmospheric pressure),
It is. However, when the purge valve 3 is closed, the total gas flow rate Q1 is zero.
[0023]
Next, (2) the water vapor partial pressure Ph20 of the gas passing through the hydrogen purge valve 3 is obtained. The water vapor partial pressure Ph20 is a partial pressure of water vapor contained in the gas passing through the purge valve 3, and a hydrogen vapor inlet using a saturated vapor pressure diagram (Cox diagram or the like) showing a change in saturated vapor pressure with respect to a temperature change. It is determined according to the temperature detected by the temperature sensor 10.
[0024]
Next, (3) the hydrogen flow rate Qh in all gases passing through the hydrogen purge valve 3 is estimated. The hydrogen flow rate Qh can be obtained by subtracting the water vapor content from the total gas flow rate Q1. That is, the exhaust gas flow rate estimated value Qh from the total gas flow rate Q1 obtained in (1), the water vapor partial pressure Ph20 obtained in (2), and the pressure in the hydrogen circulation passage 2 detected by the hydrogen inlet pressure sensor 9. According to the following formula (1-2):
Qh = Q1 × (1- (Ph20 / Pc)) (1-2)
calculate. The estimated value (Qh) of the exhaust hydrogen flow rate is zero during normal operation when the purge valve 3 is closed.
[0025]
The second air target flow rate setting unit 27 of the purge air target flow rate setting unit 23 calculates an air amount corresponding to the exhaust hydrogen flow rate Qh obtained by the exhaust hydrogen flow rate estimation unit 26. Specifically, the input exhaust hydrogen flow rate estimated value Qh is multiplied by a desired coefficient Ki to obtain the second air target flow rate Qair2 by the following equation (1-3):
Qair2 = Qh × Ki (1-3)
calculate. The coefficient Ki may be set so that the temperature of the exhaust hydrogen combustor 4 becomes a desired value or less.
[0026]
The air system delay correction unit 28 of the purge air target flow rate setting unit 23 performs advance compensation of the second air target flow rate Qair2 in consideration of the delay of the air supply system. For example, the advance compensation second air target flow rate Q′air2 is expressed by the following equation (1-4).
Q′air2 = Qair2 × (1 + τ1 × s) / (1 + τ2 × s) (1-4)
Perform the operation. Note that τ1 and τ2 are desired constants and have a relationship of τ1> τ2.
[0027]
The third air target flow rate setting unit 29 of the purge air target flow rate setting unit 23 calculates the third from the advance compensation second air target flow rate Q′air2 and the difference between the output Tr of the combustor temperature sensor 16 and the desired temperature Tt. The air target flow rate Qair3 is calculated. For example, in IP control, the following formula (1-5) and formula (1-6):
Qairfb = Kp (Tt−Tr) + Ki∫ (Tt−Tr) dt (1-5)
Qair3 = Q'air2-Qairfb (1-6)
A third air target flow rate Qair3 is calculated.
[0028]
The air target flow rate selector 24 selects either the first air target flow rate Qair1 or the third air target flow rate (purge air target flow rate) Qair3 as the target air flow rate Qair. As a selection criterion, the first air target flow rate Qair1 and the third air target flow rate Qair3 are compared, and the higher value is selected and selected.
[0029]
The target rotational speed setting unit 25 obtains a target rotational speed of the compressor 11 for obtaining an input target air flow rate Qair. Specifically, the target rotational speed of the compressor 11 is obtained based on the map shown in FIG. 5 in which the rotational speed of the compressor 11 with respect to the target air flow rate Qair is stored.
[0030]
In the fuel cell control system configured as described above, when the purge valve 3 is closed, the fuel cell stack 1 includes the hydrogen pressure set by the hydrogen pressure control valve 7 and the air pressure control valve corresponding to the hydrogen pressure. The power generation operation is performed by the operation pressure due to the air pressure by 14.
[0031]
The exhausted hydrogen discharged from the fuel cell stack 1 is returned to the ejector 8 via the purge valve 3, mixed with the supplied hydrogen, and supplied to the fuel cell stack 1. Exhaust air discharged from the fuel cell stack 1 is supplied to the exhaust hydrogen combustor 4 via the air pressure control valve 14 and is exhausted from the exhaust hydrogen combustor 4.
[0032]
The controller 6 controls the hydrogen pressure control valve 7 and the air pressure control valve 14 so that the operating pressure set by the target operating pressure setting unit 21 is obtained. The first air target flow rate setting unit 22 calculates the first air target flow rate Qair1.
[0033]
Since the purge valve 3 is closed, the purge air target flow rate setting unit 23 has a zero exhaust hydrogen flow rate in the exhaust hydrogen flow rate estimation unit 26, the second air target flow rate Qair2, and the advance correction second air target flow rate Q. 'air2 and the third air target flow rate Qair3 are zero. For this reason, the air target flow rate selection unit 24 selects the first air target flow rate Qair1, and the target rotation speed setting unit 25 outputs the target rotation speed of the compressor 11 corresponding to the first air target flow rate Qair1.
[0034]
FIG. 6 is a simulation result of the exhaust hydrogen flow rate H and the exhaust air flow rate A when the present invention is applied, and FIG. 7 is a temperature simulation result of the exhaust hydrogen combustor 4 when the present invention is applied. 6 and 7, the state in which the purge valve 3 is closed is shown from time t0 to time t1. At time t0 to t1, the exhaust hydrogen gas H from the purge valve 3 to the exhaust hydrogen combustor 4 is zero, and only the exhaust air A exhausted from the air pressure control valve 14 is supplied to the exhaust hydrogen combustor 4. Yes.
[0035]
When the overflow of water (flooding) or the like in the fuel cell stack 1 occurs or the operating pressure of the fuel cell stack 1 needs to be reduced, and the controller 6 opens the hydrogen purge valve 3 at time t1, the hydrogen circulation passage 2 and Hydrogen gas present in the fuel cell stack 1 is discharged to the exhaust hydrogen combustor 4 via the purge valve 3.
[0036]
The purge air target flow rate setting unit 23 estimates the exhaust hydrogen flow rate Qh discharged from the purge valve 3 based on the target output, the hydrogen inlet temperature, and the hydrogen inlet pressure in the exhaust hydrogen flow rate estimation unit 26, and the second air target The flow rate setting unit 27 calculates the second air target flow rate Qair2, and the air system delay correction unit 28 calculates the second air target flow rate Q'air2 for advance correction. Further, the third air target flow rate setting unit 29 calculates the third air target flow rate Qair3 by correction based on the temperature signal from the combustor temperature sensor 16. Since the third air target flow rate Qair3 is based on the second air target flow rate Q'air2 which is compensated in view of the operation delay of the air system, as shown in FIG. 6, the waste water whose flow rate suddenly rises from time t1. Prior to the elementary flow rate HQh, the first air target flow rate Qair1 is exceeded at the time t1, the third air target flow rate Qair3 is selected by the air target flow rate selection unit 24, and the target of the compressor 11 is based on the third air target flow rate Qair3. The compressor target rotational speed is set by the rotational speed setting unit 25.
[0037]
Therefore, in anticipation of an increase in the exhaust hydrogen flow rate H (Qh), the compressor 11 is driven by the target compressor speed based on the increased third air target flow rate Qair3 at time t1 in FIG. And the increased amount of exhaust air A is supplied to the exhaust hydrogen combustor 4. As shown in FIG. 7, the temperature T in the exhaust hydrogen combustor 4 has a portion that temporarily rises at the time point t <b> 1, but a sudden temperature increase occurs due to the supply of the increased exhaust air amount A. Suppressed and rises to equilibrium temperature with increasing waste hydrogen.
[0038]
6 and 7, lines (A) and (T) indicated by dotted lines are obtained when the lead compensation in the air system delay correction unit is not performed, that is, when the rise of the compressor 11 to the target rotational speed has a delay. The change of exhaust air flow rate ((A) of FIG. 6) and combustor temperature ((T) of FIG. 7) is shown. As shown in FIG. 6, when the rise is delayed as in the exhaust air flow rate (A), the exhaust hydrogen combustor 4 is overheated as in the temperature (T) immediately after the purge as shown in FIG. Absent.
[0039]
In the above embodiment, the air target flow rate Qair supplied at the time of purging has been described with advance compensation. However, although not shown, instead of performing advance compensation to the supplied air target flow rate, a hydrogen purge valve 3 may be delayed so as to suppress a rapid temperature rise of the exhaust hydrogen combustor 4. In this case, before opening the hydrogen purge valve 3, first, the rotational speed of the compressor 11 is increased and air is supplied to the exhaust hydrogen combustor 4.
[0040]
In the present embodiment, the following effects can be achieved.
[0041]
(A) The exhaust hydrogen gas flow rate estimation unit 26 as the exhaust fuel gas flow rate estimation means calculates the exhaust fuel gas (exhaust hydrogen) when the purge valve 3 is operated from the hydrogen inlet pressure and the hydrogen inlet temperature as the operation state detection means of the fuel cell stack 1. The exhaust gas oxidation is supplied to the exhaust hydrogen combustor 4 serving as the exhaust fuel combustor in accordance with the estimated exhaust hydrogen gas flow rate by the purge air target flow rate setting unit 23 as the exhaust oxidizing gas target flow rate setting means. A target value Qair of the gas (exhaust air) flow rate is set, and the air flow rate is controlled by the target rotation number setting unit 25 of the compressor 11 as the oxidizing gas flow rate control means so as to become the air target flow rate Qair. For this reason, an excessive temperature rise of the exhaust hydrogen combustor 4 due to a shortage of air supplied to the exhaust hydrogen combustor 4 can be prevented, and energy consumption of the compressor 11 as the oxidizing gas supply means can be minimized.
[0042]
(A) Since the exhaust hydrogen gas flow rate Qh as the exhaust fuel gas flow rate is estimated based on the temperature and pressure of the hydrogen gas at the inlet of the fuel cell stack 1, the fuel cell control system can be configured very inexpensively.
[0043]
(C) The purge target air flow rate setting means 23 as the exhaust gas target flow rate setting means expects a delay time until the air from the compressor 11 as the oxidation gas supply means reaches the exhaust hydrogen combustor 4. Since the compressor 11 is operated with advance compensation, it is possible to prevent the exhaust hydrogen combustor 4 from being overheated immediately after purging.
[0044]
(D) When the purge means 4 is operated after a delay time in which the air from the compressor 11 as the oxidizing gas supply means arrives at the exhaust hydrogen combustor 4, the supply delay is very large. Even in this case, prevention of overheating of the exhaust hydrogen combustor 4 and prevention of discharge of unburned components of the exhaust hydrogen gas can be easily achieved.
[0045]
(E) The temperature of the exhaust hydrogen combustor 4 is measured by the combustor temperature sensor 16, and the purge target air flow rate setting means 23 corrects the air flow rate supplied to the exhaust hydrogen combustor 4 based on the detected temperature. Thus, even if a deviation occurs in the estimated value of the exhaust hydrogen gas flow rate, overheating of the exhaust hydrogen combustor 4 can be prevented.
[0046]
(Second Embodiment)
8 to 10 show a fuel cell control system according to a second embodiment to which the present invention is applied. When the purge valve 3 is operated, the fuel cell stack 1 is bypassed and air is supplied to the exhaust hydrogen combustor 4 while the waste water is discharged. When the element is excessive, the exhaust hydrogen is discharged without being burned by the exhaust hydrogen combustor 4. FIG. 8 is a schematic configuration diagram of the fuel cell control system, and FIGS. 9 and 10 are control flowcharts of control executed on a regular basis by the controller.
[0047]
In FIG. 8, in order to bypass the fuel cell stack 1 and supply air to the exhaust hydrogen combustor 4 when the purge valve 3 operates, an air bypass passage 30 that bypasses the fuel cell stack 1 and the air pressure control valve 14, and air An air bypass valve 31 disposed in the bypass passage 30 and controlled by the controller 6 is provided. In addition, in order to discharge the exhausted hydrogen without burning when the exhausted hydrogen is excessive, the controller is provided in the exhausted hydrogen bypass passage 32 that opens the inlet of the exhausted hydrogen combustor 4 to the atmosphere, and the exhausted hydrogen bypass passage 32. 6 is provided with an exhaust hydrogen bypass valve 33 controlled by 6. Other components are the same as those in the first embodiment, and a detailed description thereof will be omitted.
[0048]
First, the air bypass valve 31 will be described. The air bypass valve 31 is periodically controlled by the control flowchart shown in FIG. 9 while the purge valve 3 is operating. Hereinafter, the operation of the air bypass valve 31 will be described with reference to FIG.
[0049]
That is, in step 110, the air target flow rate Qair described in the first embodiment is calculated.
[0050]
In step 120, it is determined whether the calculated air target flow rate Qair is equal to or greater than the open flow rate Qt of the air bypass valve 31. The open flow rate Qt is set to, for example, about 1.5 times the air flow rate when the fuel cell stack 1 generates power at the maximum load. If the air target flow rate Qair is equal to or greater than the open flow rate Qt (air target flow rate Qair ≧ open flow rate Qt), the routine proceeds to step 130. If it is less than (target air flow rate Qair <open flow rate QT), the routine proceeds to step 140.
In step 130, a valve opening command is output to the air bypass valve 31, and the process ends.
[0051]
In step 140, a valve closing command is output to the air bypass valve 31, and the process ends.
[0052]
If an attempt is made to control the air-fuel ratio in the exhaust hydrogen combustor 4 during the purge operation, if the fuel cell stack 1 is generating power at the maximum load, the exhaust hydrogen combustor 4 has a very large amount. It is necessary to supply air. For this purpose, a large amount of air may be supplied to the fuel cell stack 1, but 1) a large amount of air that does not contribute to power generation passes through the fuel cell stack 1 to dry the fuel cell stack 1. ) There is a possibility that the air pressure at the inlet of the fuel cell stack 1 becomes excessive due to the pressure loss of the fuel cell stack 1. However, the use of the air bypass valve 31 and the air bypass passage 30 may cause the above problem. The problem is solved. In addition, although the case where the air bypass valve 31 is an ON / OFF valve has been described, the bypass air amount may be continuously controlled by a flow control valve.
[0053]
Next, the exhaust hydrogen bypass valve will be described. When the temperature of the exhaust hydrogen combustor 4 is monitored and the flow rate of air to be supplied is controlled, it is conceivable that some cause, for example, the air cannot be supplied and the exhaust hydrogen combustor 4 is heated to promote thermal deterioration. . When the temperature of the exhaust hydrogen combustor 4 is too high, the exhaust hydrogen bypass valve 33 opens and discharges exhaust hydrogen to the atmosphere via the exhaust hydrogen bypass passage 32, so that the exhaust hydrogen combustor 4 Prevent excessive temperature rise.
[0054]
The exhaust hydrogen bypass valve 33 is controlled periodically according to the control flowchart shown in FIG. 10 while the purge valve 3 is operating. Hereinafter, the operation of the exhaust hydrogen bypass valve 33 will be described with reference to FIG.
[0055]
That is, in step 210, it is determined whether or not the corrected air amount Qairfb based on the output Tr of the combustor temperature sensor 16 is equal to or greater than the upper limit value Qtfb. Thus, it can be determined whether or not the temperature of the exhaust hydrogen combustor 4 is within the correction range. If the corrected air amount Qairfb is equal to or greater than the upper limit value Qtfb, that is, if the corrected air amount deviates from the correction range (corrected air amount Qairfb ≧ upper limit value Qtfb), the process proceeds to step 220, and if the corrected air amount Qairfb <upper limit value Qtfb. Proceed to 240.
[0056]
In step 220, it is determined whether or not the signal Tr of the combustor temperature sensor 16 is equal to or higher than the upper limit value Ttcm. If the temperature Tr is higher than the upper limit value Ttcm, the exhaust hydrogen combustor 4 may excessively rise in temperature, and the process proceeds to step 230. If the temperature Tr of the combustor 4 is lower than the upper limit value Ttcm, the process proceeds to step 240.
[0057]
In step 230, the exhaust hydrogen bypass valve 33 is opened, and in step 240, the exhaust hydrogen bypass valve 33 is closed, and the control calculation ends.
[0058]
In addition, although the case where the exhaust hydrogen bypass valve 33 is an ON / OFF valve has been described, the bypass hydrogen discharge amount may be continuously controlled by a flow control valve.
[0059]
In the present embodiment, in addition to the effects (a) to (e) according to the first embodiment, the following effects can be achieved.
[0060]
(F) Since air can be supplied to the exhaust hydrogen combustor 4 by bypassing the fuel cell stack 1 by the air bypass passage 30 provided with the air bypass valve 31, a very large amount of air must be supplied to the exhaust hydrogen combustor 4. Even when it is necessary, it is possible to prevent an excessive pressure from acting on the fuel cell stack 1. In addition, the delay in supplying air to the exhaust hydrogen combustor 4 can be reduced, and it is possible to promptly cope with the optimization of the air-fuel ratio at the time of transition and the need for emergency cooling.
[0061]
(G) When the correction amount of the air flow rate due to the temperature of the exhaust hydrogen combustor 4 exceeds the correction range, the exhaust hydrogen is discharged by the exhaust hydrogen bypass valve 33 without being burned. Even when the air cannot be supplied to the exhaust gas 4, overheating of the exhaust hydrogen combustor 4 can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a fuel cell control system showing an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of the controller.
FIG. 3 is a first air target flow rate calculation map.
FIG. 4 is a fuel cell stack target pressure map.
FIG. 5 is a compressor target rotation speed map.
FIG. 6 is a graph showing simulation results of the exhaust hydrogen flow rate and the exhaust air flow rate.
FIG. 7 is a graph showing simulation results of exhaust hydrogen combustor temperature.
FIG. 8 is a schematic configuration diagram of a vehicle fuel cell control system showing a second embodiment of the present invention.
FIG. 9 is a control flowchart of the air bypass valve.
FIG. 10 is a control flowchart of the exhaust bypass valve.
[Explanation of symbols]
1 Fuel cell stack
2 Circulation route
3 Hydrogen purge valve as purge means
4 Exhaust hydrogen combustor as an exhaust fuel combustor
5 Air supply means
6 Controller
7 Hydrogen pressure control valve
8 Ejecta
9 Hydrogen inlet pressure sensor
10 Hydrogen inlet temperature sensor
11 Compressor
12 Air flow sensor
14 Air pressure control valve
16 Combustor temperature sensor
21 Target operating pressure setting section
22 First air target flow rate setting unit
23 Purge air target flow rate setting section
24 Air target flow rate selector
25 Target speed setting part
26 Exhaust hydrogen flow rate setting section
27 Second air target flow rate setting unit
28 Air system delay correction part
29 Third air target flow rate setting section
31 Air bypass valve
33 Exhaust hydrogen bypass valve

Claims (7)

A fuel cell stack formed by stacking a plurality of cells that are supplied with fuel gas and oxidizing gas to generate electric power;
A circulation path for circulating fuel gas to the fuel cell stack;
Oxidizing gas supply means for supplying the oxidizing gas to the fuel cell;
Means for controlling the flow rate of the oxidizing gas;
An operation state detection means for detecting an operation state of the fuel cell stack;
Purge means for discharging fuel gas in the circulation path;
In a fuel cell control system comprising: an exhaust fuel combustor that reacts exhaust fuel gas exhausted by the purge means and exhaust oxidant gas exhausted from the fuel cell stack;
An exhaust fuel gas flow rate estimating means for estimating the exhaust fuel gas flow rate from the output of the operating state detecting means;
Exhaust gas target flow rate setting means for setting a target value of the exhaust gas flow rate supplied to the exhaust fuel combustor based on the output of the exhaust fuel gas flow rate estimation means,
The fuel cell control system, wherein the oxidant gas flow rate control means controls the oxidant gas flow rate based on the exhaust oxidant gas target flow rate. The circulation path includes means for detecting the pressure of the fuel gas in the vicinity of the fuel cell stack inlet, and means for detecting the temperature of the fuel gas in the vicinity of the fuel cell stack inlet,
2. The fuel cell control system according to claim 1, wherein the exhaust fuel gas flow rate estimation means estimates the exhaust fuel gas flow rate based on detection signals from the fuel gas pressure detection means and temperature detection means. The exhaust oxidant gas target flow rate setting means operates the oxidant gas supply means to compensate and operate in anticipation of a delay time until the oxidant gas from the oxidant gas supply means reaches the exhaust fuel combustor. The fuel cell control system according to claim 1 or 2. 3. The purge unit according to claim 1, wherein the purge unit operates after a delay time allowing for a delay time until the oxidizing gas from the oxidizing gas supply unit reaches the exhaust fuel combustor. Fuel cell control system. The oxidizing gas supply means includes a bypass passage capable of directly supplying oxidizing gas to the exhaust fuel combustor,
The fuel cell control system according to any one of claims 1 to 4, wherein a flow rate of the oxidizing gas flowing through the bypass passage is controlled in accordance with an output of the operating state detection means. The exhaust fuel combustor includes combustor temperature detection means for measuring the temperature of the exhaust fuel combustor,
6. The fuel according to claim 1, wherein the exhaust oxidant gas target flow rate setting unit corrects the exhaust oxidant gas target flow rate according to an output of a combustor temperature detection unit. Battery control system. The exhaust fuel combustor can discharge exhaust fuel gas without going through the exhaust fuel combustor,
The exhaust fuel gas is discharged without passing through the exhaust fuel combustor when the correction amount of the exhaust gas target flow rate by the combustor temperature detection means exceeds the upper limit value of the correction range. Item 7. The fuel cell control system according to Item 6.

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