JP2001338671A - Controller for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control pressure flow rate characteristics of a fuel supplied to a fuel cell with sufficient accuracy. SOLUTION: A control equipment 10 of a fuel cell is constituted with a fuel cell 11, a fuel supply section 12, a steam generating section 13, a combustion section 14, a reforming section 15, a CO reduction section 16, an oxidizer supply section 17, a control section 18, a discharge fuel flow rate control section 19, a reforming fuel pressure detecting device 21, a reforming fuel flow rate detecting device 22, a discharge fuel pressure detecting device 23, and a power generation current detecting device 24. The discharge fuel flow rate control section 19 is composed of a plurality of for example, two small flow rate bulbs 27 and a large flow rate bulb 28 with different pressure flow-rate characteristics arranged in parallel. A signal from the reforming fuel pressure detecting element 21 which detects a pressure P1 of the reforming fuel, a signal from the reforming fuel flow rate detecting element 22 which detects a flow rate Q of the reforming fuel, a signal from the discharge fuel pressure detecting element 23 which detects a pressure P2 of the discharge fuel, and a signal from the power generation current detecting element 24 which detects power generation current 1 are inputted into the control section 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a fuel cell, for example, for controlling a pressure flow characteristic of a reaction gas supplied to a fuel cell having a reformer.

[0002]

2. Description of the Related Art Conventionally, a solid polymer membrane fuel cell has a stack (stacked) in which a plurality of cells are stacked on a cell formed by sandwiching a solid polymer electrolyte membrane between an anode and a cathode from both sides. (Hereinafter referred to as a fuel cell), hydrogen is supplied to the anode as fuel, air is supplied to the cathode as an oxidant, and hydrogen ions generated by a catalytic reaction at the anode pass through the solid polymer electrolyte membrane. Then, it moves to the cathode and causes an electrochemical reaction with oxygen at the cathode to generate power. Here, for example, using an alcohol compound such as methanol or a hydrocarbon compound such as gasoline as a raw fuel,
As a fuel cell device provided with a reformer that reforms these raw fuels to generate a hydrogen-rich reformed fuel, for example, a fuel cell device disclosed in Japanese Patent Application Laid-Open No. H11-329472 is known. In such a fuel cell device, a pressure flow rate control valve is provided for the fuel discharged from the fuel cell, and the pressure on the anode side with respect to the cathode side of the fuel cell is set to a predetermined pressure to achieve a predetermined power generation efficiency. And a predetermined output is obtained by controlling the flow rate of the fuel supplied to the fuel cell.

[0003]

By the way, in the fuel cell device according to an example of the above-mentioned prior art, when the pressure flow control valve for the discharged fuel is controlled, for example, by analog control, the valve opening is continuously changed. However, there is a problem that it is difficult to control stably and responsiveness cannot be improved. Also, for example, when only one pressure flow control valve is provided, for example, when digital control is performed by driving with a stepping motor or the like,
Since the valve opening width per step is fixed, there is a problem that it is difficult to accurately control the pressure flow characteristics over the entire flow range from the low output side to the high output side of the fuel cell. The present invention has been made in view of the above circumstances, and provides a fuel cell control device capable of accurately controlling a pressure flow characteristic of a reaction gas supplied to a fuel cell over a wide output range. The purpose is to:

[0004]

In order to solve the above-mentioned problems and achieve the above object, a fuel cell control device according to the present invention according to a first aspect of the present invention includes a fuel cell (for example, an embodiment described below). A reaction gas supply unit (for example, a fuel supply unit 12 or an oxidant supply unit 17 in an embodiment described later) that supplies a reaction gas (for example, a fuel or an oxidant in an embodiment described below) to the fuel cell 11); At the outlets of the exhaust reactant gas (for example, exhaust fuel or exhaust oxidant in an embodiment described later) discharged from the fuel cell, they are arranged in parallel with each other, and are stepwise formed by a predetermined number of valve opening steps. A first control valve (for example, a large flow valve 28 in an embodiment to be described later) that changes a valve opening (for example, a valve opening in an embodiment to be described later) and a second control valve A control valve, and controls the second control valve (for example, a small flow valve 27 in an embodiment described later) until the flow rate of the discharged reactant gas reaches a predetermined value. When the predetermined value is exceeded, the first control valve is set to a target value of the pressure flow characteristic of the reactant gas or the exhaust reactant gas (for example, a target operating pressure and an off gas flow rate in an embodiment described later). Q1)
, And controls the second control valve with the detected value of the pressure flow characteristic of the reaction gas or the discharged reaction gas (for example, the pressure P1, the pressure P2, and the flow Q, Or, the pressure PA, the flow rate QA, the generated current I, and the temperature T
It is characterized by performing feedback control based on A).

According to the fuel cell control device having the above structure,
For example, in a low flow rate region of the exhausted reaction gas, control can be performed using only the second control valve having a relatively small maximum flow rate, and when the flow rate of the exhausted reaction gas increases,
By switching to the first control valve having the largest maximum flow rate, pressure flow rate control can be accurately performed over the entire wide output range, and responsiveness can be improved. In this case, for example, when a stepping motor having a predetermined number of steps is used as a drive source for both control valves, the first control valve having a large valve opening per step performs feedforward control and performs valve opening per step. The second control valve having a small degree is feedback-controlled. Then, in the low flow rate region of the discharged reaction gas, the first control valve is fully closed,
By changing the pressure flow characteristics only with the second control valve, the accuracy with respect to the response can be improved. On the other hand, in the high flow rate region of the discharged reactant gas, the pressure flow characteristic is changed relatively largely by the feedforward control of the first control valve. Correction is made by combining feedback control with valves. Thus, it is possible to prevent the accuracy of the response from deteriorating even in the high flow rate region of the discharged reaction gas.

Further, in the fuel cell control apparatus according to the present invention, the control means may include a valve opening of the first control valve according to a target value of the pressure-flow characteristic of the exhaust gas. (For example, the opening SPLBS of the large flow valve 28 in the embodiment described later) is changed to a predetermined opening (for example, the opening of the small flow valve 27 in the embodiment described later). Selection from the pressure flow characteristic (for example, a map MAP1 in an embodiment to be described later) that changes in accordance with the valve opening of the first control valve in a state of an opening of 1/2 of the maximum opening). The number of valve opening steps for the first control valve is an integer value that satisfies a predetermined approximate value for the valve opening of the first control valve, and the valve opening of the first control valve, A difference from a predetermined approximate value (for example, an embodiment described later) Oite is characterized in that corrected by feedback control of the decimal section), the second control valve.

According to the fuel cell control device having the above configuration,
For example, in a high flow rate region of the exhaust gas, the valve opening of the second control valve is set to an intermediate opening with respect to the maximum opening, so that the increase or decrease of the valve opening can be adjusted,
The control by the first control valve having a large valve opening per step can be corrected by the second control valve. In this case, according to the valve opening obtained when an integer number of steps are set with respect to the first control valve having a large valve opening per step, and the target value of the pressure flow characteristic of the discharged reaction gas. In some cases, a difference may occur between the valve opening selected by the map search and the like, and this difference can be corrected by the second control valve having a relatively small valve opening per step. , High-precision control can be performed while maintaining high responsiveness.

Further, in the fuel cell control device according to the present invention, the reaction gas supplied to the cathode side of the fuel cell is supplied to a pressurizing means (for example, an air compressor in an embodiment described later). ), And is characterized by being pressurized air. According to the fuel cell control device having the above configuration, the pressure flow characteristics of the air supplied to the cathode side of the fuel cell can be accurately controlled over the entire wide flow range from the low output side to the high output side of the fuel cell. can do.

Further, in the fuel cell control device according to the present invention, the reaction gas supplied to the anode side of the fuel cell reforms the fuel to generate a hydrogen-rich reformed fuel. The reformed fuel is generated by a fuel reforming means (for example, a reforming unit 15 in an embodiment described later). According to the control device for a fuel cell having the above configuration, the pressure flow characteristic of the reformed fuel supplied to the anode side of the fuel cell can be accurately measured over a wide flow range from the low output side to the high output side of the fuel cell. You can control well.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a fuel cell control device according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a configuration diagram of a control device 10 for a fuel cell according to an embodiment of the present invention. The fuel cell control device 10 according to the present embodiment includes a fuel cell 11, a fuel supply unit 12 that supplies a liquid fuel composed of, for example, a mixed solution of methanol and water, and a fuel vapor that is generated by evaporating the liquid fuel. A steam generator 13, a combustion unit 14 that generates combustion gas used for warming up the steam generator 13 and evaporating the liquid fuel, and a reforming unit 15 that generates hydrogen-rich reformed fuel from the fuel vapor.
A CO reduction unit 16 that selectively oxidizes and removes carbon monoxide in the reformed fuel, an oxidant supply unit 17 that supplies an oxidant such as air to the fuel cell 11, a control unit 18, An exhaust fuel flow control unit 19, a reformed fuel pressure detector 21,
Reformed fuel flow rate detector 22 and exhaust fuel pressure detector 23
A power generation current detector 24, an auxiliary fuel supply unit 25, an output control unit 26, a small flow valve 27 and a large flow valve 28 provided in the exhaust fuel flow control unit 19, and a target power generation amount input unit 29. It is provided with.

The fuel cell 11 has a structure in which a solid polymer electrolyte membrane made of, for example, a solid polymer ion exchange membrane is sandwiched between an anode and a cathode from both sides.
The fuel cell stack includes a stack formed by stacking a plurality of cells, and includes a hydrogen electrode to which, for example, hydrogen is supplied as a fuel, and an air electrode to which air containing, for example, oxygen is supplied as an oxidant. The air electrode and the fuel electrode are provided with outlets for discharging unreacted fuel and oxidizer out of the supplied fuel and oxidant, and each outlet is provided with a combustion unit 14. There is a pipe leading to

The fuel supply unit 12 is a liquid fuel such as a mixed liquid obtained by mixing a fuel composed of an alcohol compound such as methanol or a hydrocarbon compound such as methane, ethane or gasoline with water at a predetermined ratio. Is supplied to the steam generator 13. The steam generating unit 13 includes, for example, a nozzle or the like for supplying liquid fuel to the inside, and the liquid fuel sprayed from the nozzle is evaporated by the heat of the combustion gas supplied from the combustion unit 14.

The combustion unit 14 is, for example, a nozzle for introducing discharged fuel containing unreacted hydrogen discharged from the fuel electrode of the fuel cell 11 and discharged oxidant containing unreacted oxygen discharged from the air electrode. And a combustion catalyst for maintaining the combustion state of the exhausted fuel and the exhausted oxidant, and an ignition source, for example, an electric heater. Then, the combustion gas generated by the combustion of the exhaust fuel and the exhaust oxidant is supplied to the steam generating section 1.
Supply to 3. Further, the combustion unit 14 is provided with an auxiliary fuel supply unit 25. By burning auxiliary fuel supplied from the auxiliary fuel supply unit 25, the combustion unit 1
4 is warmed up, and the vapor generation unit 13 generates combustion gas used for evaporating the liquid fuel.

The reforming section 15 is provided with, for example, a reforming catalyst, and the reforming catalyst generates a reformed fuel having a high hydrogen content (hydrogen-rich) from fuel vapor. For example, in the case of fuel vapor comprising a mixture of methanol and water, a reformed fuel containing hydrogen, water, and carbon monoxide is generated by the following reaction formulas (1) to (3). CH ₃ OH + H ₂ O → 3H ₂ + CO ₂ (1) CH ₃ OH + 2O ₂ → 2H ₂ O + CO ₂ (2) CH ₃ OH → 2H ₂ + CO (3) The reaction formula (1) is modified with methanol and water. Reaction, and hydrogen as fuel is produced. The reaction formula (2) is an oxidation reaction of methanol, and replenishes the amount of heat required in the reaction formula (1), which is an endothermic reaction. The reaction formula (3) is a decomposition reaction of methanol inevitably generated, and carbon monoxide is generated. This carbon monoxide is removed by the CO reduction unit 16 in order to poison a Pt catalyst or the like included in the fuel cell 11 to lower the power generation efficiency and shorten the life of the fuel cell 11.

The CO reduction unit 16 includes a selective oxidation catalyst made of, for example, Pt or Ru, and selectively oxidizes carbon monoxide contained in the reformed fuel according to the following reaction formula (4). Remove. 2CO ₂ + O ₂ → 2CO ₂ (4) Then, the reformed fuel having a reduced carbon monoxide content is
The fuel is supplied to the fuel electrode of the fuel cell 11.

The oxidizing agent supply unit 17 is provided with, for example, an air compressor (not shown), and pressurizes air or the like containing oxygen as an oxidizing agent based on a control signal from the control unit 18 so as to pressurize the fuel cell 11. To the air electrode. In the fuel cell 11, hydrogen (fuel) and oxidant (oxygen) in the reformed fuel cause an electrochemical reaction to generate power.

The control unit 18 controls the flow rate of the discharged fuel in the discharged fuel flow control unit 19 in response to a power generation request based on, for example, the operation of an accelerator pedal in a vehicle such as an electric vehicle. For this reason, the control unit 18 includes the CO reduction unit 1
6, a signal from a reformed fuel pressure detector 21 for detecting the pressure P1 of the reformed fuel supplied to the fuel cell 11, and a reformed fuel flow rate for detecting the flow rate Q of the reformed fuel supplied to the fuel cell 11. A signal from the detector 22, a signal from a discharged fuel pressure detector 23 for detecting a pressure P2 of the discharged fuel discharged from the fuel cell 11, and a generated current detection for detecting a generated current I generated in the fuel cell 11. The signal from the heater 24 and the signal of the target power generation amount from the target power generation amount input unit 29 are input. Then, for example, the fuel injection command value is output from the control unit 18 to the fuel supply unit 12 and the auxiliary fuel supply unit 25, and the generated current command value is output to the output control unit 26 including, for example, a DC-DC converter and an inverter. And is used for output control for the load.

The discharged fuel flow control section 19 has a plurality of, for example, two small flow valves 27 and two large flow valves 28 having different pressure flow characteristics arranged in parallel. The two valves 27 and 28 are driven by, for example, a stepping motor or the like to adjust the valve opening in steps of a predetermined opening. For example, the valve opening per one step of the large flow valve 28 is a small flow valve. 27 is set to be smaller than the maximum valve opening. The coarse adjustment pressure flow control valve having a large valve opening per step (that is, the large flow valve 28) is feedforward controlled, and the fine adjustment pressure flow control valve having a small valve opening per step (that is, a small flow valve). 27) performs feedback control such as PID control. Here, in the low flow rate range of the discharged fuel, the large flow valve 28 is fully closed, and the pressure flow characteristic is changed only by the small flow valve 27. On the other hand, in the high flow rate region of the discharged fuel, the pressure flow characteristic is relatively largely changed by the feedforward control of the large flow valve 28.
The small flow valve 27 is feedback-controlled so as to compensate for a large change caused by the control of the small flow valve 8.

Control device 1 for a fuel cell according to the present embodiment
0 has the above-described configuration. Next, the operation of the control device 10 for a fuel cell will be described with reference to the accompanying drawings. FIG. 2 is a flowchart showing a process of calculating a pressure flow control command to the exhaust fuel flow control unit 19,
FIG. 3 is a flowchart showing a process of controlling the small flow valve 27 and the large flow valve 28 of the discharged fuel flow control unit 19, and FIG.
FIG. 5 is a graph showing a change in the anode operating pressure, that is, a change in pressure loss. FIG. FIG.

First, in step S01 shown in FIG. 2, a fuel injection amount is calculated from a target power generation current value (that is, a target power generation amount) corresponding to, for example, an operation amount of an accelerator pedal, and the fuel injection amount is calculated. Is output to the fuel supply unit 12 and the auxiliary fuel supply unit 25, for example. Also,
In step S02, a generated current command is calculated from the fuel injection command and output to, for example, a DC-DC converter or an inverter (not shown) to control the generated current output from the fuel cell 11.

Then, in step S03, the target anode operating pressure (see FIG.
(Target pressure). The target anode operating pressure is
A predetermined pressure loss set according to the reaction efficiency of the fuel cell 11, that is, a value related to a difference between the pressure of the reformed fuel supplied to the fuel cell 11 and the pressure of the discharged fuel discharged from the fuel cell 11, For example, as shown in FIG. 4, a predetermined target anode operating pressure is set for a generated current output from the fuel cell 11. In step S04, the flow rate of the discharged fuel, that is, the off-gas, is calculated based on the fuel injection command and the generated current command.

Next, in step S05, as described later, a predetermined map relating to the pressure and the flow rate is searched based on the target anode operating pressure and the flow rate of the off-gas, so that the small flow rate valve of the exhaust fuel flow rate control unit 19 is searched. The valve openings of the large flow valve 27 and the large flow valve 28 are calculated. In step S06, as described later, the reforming fuel pressure P1 detected by the reforming fuel pressure detector 21 (actual pressure output from the anode inlet pressure gauge in FIG. 2).
And the target anode operating pressure, especially the small flow valve 2
The feedback coefficient relating to the valve opening of No. 7 is calculated. Then, in step S07, as described later, in the low flow rate region of the discharged fuel, the large flow valve 28
Is output as the valve opening of the small flow valve 27.
The value calculated by the feedback control is output as the valve opening degree. On the other hand, in the high flow rate range of the discharged fuel, the small flow rate valve 27 calculated by the feedback control by correcting the valve opening degree in the feed forward control of the large flow rate valve 28 and the valve opening degree of the large flow rate valve 28 is corrected. Is output as a valve opening command.

The processing for controlling the valve opening of the small flow valve 27 and the large flow valve 28 of the exhaust fuel flow control unit 19 will be described below. First, step S shown in FIG.
At 11, a target operating pressure (for example, a target anode operating pressure) is calculated, and then, at step S12, a flow rate Q1 of off gas (for example, a flow rate Q1 of exhaust fuel on the anode side) is calculated.

Then, in step S13, based on the target operating pressure and the flow rate Q1 of the off-gas, a map search for the opening degree SPLBS of the large flow valve 28 is performed from a map MAP1 of the valve opening degree which changes according to the flow rate and the pressure. Next, in step S14, it is determined whether or not the opening SPLBS of the large flow valve 28 is smaller than a predetermined threshold. If the result of this determination is “NO”, that is, if it is determined that the region is in the high flow rate region of the discharged fuel, the processing from step S17 described below is performed. On the other hand, the determination result is “YES”
In the case of, that is, when it is determined that the range is the low flow rate range of the discharged fuel, the process proceeds to step S15, and the valve opening of the large flow rate valve 28 is fully closed. Then, in step S16, the map MAP of the valve opening that changes according to the flow rate and the pressure based on the target operating pressure and the flow rate Q1 of the off-gas.
From 2, a map search is performed for the opening degree SPSBS of the small flow valve 27, and the process proceeds to step S18. On the other hand, step S17
In step S18, the opening of the small flow valve 27 is set to a predetermined opening, for example, 開 of the maximum opening.
Proceed to.

In step S18, a feedback coefficient relating to the valve opening is calculated from the reformed fuel pressure P1 (actual pressure) detected by the reformed fuel pressure detector 21 and the target operating pressure. Then, in step S19, the valve opening degree of the small flow valve 27 is
Feedback control is performed by control. The map MA
P1 is the small flow valve 27 set in step S17.
Shows the change in the pressure flow characteristic of the large flow valve 28 according to the valve opening at the predetermined opening of the map MAP.
2 shows a change in the pressure flow characteristic of the small flow valve 27 in accordance with the valve opening degree when the large flow valve 28 is fully closed.

That is, for example, as shown in FIG. 5, in a low flow rate region until the flow rate of the exhaust fuel passing through the exhaust fuel flow rate control unit 19 reaches a predetermined flow rate F (the flow rate F shown in FIG. 5), the large flow rate The valve opening of the valve 28 (solid line L shown in FIG. 5) is fully closed, and the valve opening of the small flow valve 27 (FIG.
Is changed stepwise by feedback control, and the flow rate and back pressure of the discharged fuel, that is, the fuel cell 1 is changed.
Adjust the pressure of the discharged fuel on one side.

On the other hand, in the high flow rate region after exceeding the predetermined flow rate F, the valve opening degree (solid line L shown in FIG. 5) of the large flow rate valve 28 is changed stepwise by feedforward control, and the flow rate of the discharged fuel is changed. And the back pressure, that is, the pressure of the discharged fuel on the fuel cell 11 side, is changed relatively large. However, the valve opening of the small flow valve 27 is set to an intermediate opening, for example, 開 of the maximum opening, and according to the change of the valve opening of the large flow valve 28 for each step, For example, as shown in a region α shown in FIG. 5, the valve opening of the small flow valve 27 is feedback-controlled for fine adjustment so that the target anode operating pressure and the off-gas flow rate Q1 can be accurately satisfied. That is, when searching the map for the opening degree SPLBS of the large flow rate valve 28 that changes stepwise, the number of steps obtained as an integer value is
For example, terms after the decimal point approximated by rounding
The correction is made by adjusting the opening of the small flow valve 27. Note that, by performing the feedforward control on the large flow valve 28, it is possible to prevent a change due to disturbance from becoming large as compared with, for example, a case where the large flow valve 28 is feedback controlled.

As described above, according to the fuel cell control apparatus 10 of the present embodiment, the pressure flow characteristics differ from each other.
The two small flow valves 27 and the large flow valve 28 are arranged in parallel, the large flow valve 28 is feed-forward controlled, and the small flow valve 27 is feedback-controlled. Control can be performed.

In the above-described embodiment,
Two small flow valves 27 and two large flow valves 28 having different pressure flow characteristics are arranged in parallel on the discharge fuel discharge side for discharging unreacted fuel from the fuel cell 11, but the present invention is not limited to this. For example, as in a control device 30 for a fuel cell according to a modification of the present embodiment shown in FIG. 6, two small flow valves 27 and large flow valves 28 having different pressure flow characteristics are unreacted from the fuel cell 11. It may be arranged in parallel on the discharge oxidant discharge port side for discharging the oxidant. less than,
A control device 30 for a fuel cell according to a modification of the present embodiment will be described with reference to the accompanying drawings. FIG. 6 is a configuration diagram showing in detail the configuration of the control device 30 of the fuel cell according to the modification of the present embodiment, particularly the configuration of the oxidant supply system.
9 is a flowchart showing a process for calculating a pressure flow control command to the discharged oxidant flow control unit 34. In addition,
The same portions as those of the control device 10 of the fuel cell according to the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified.

The control device 30 for the fuel cell detects the flow rate QA of the oxidant (for example, air containing oxygen) supplied from the oxidant supply unit 17 to the air electrode of the fuel cell 11. Detector 31, an oxidizer pressure detector 32 for detecting the pressure PA of the oxidizer supplied to the air electrode of the fuel cell 11, and an exhaust oxidizer for detecting the temperature TA of the exhaust oxidizer discharged from the fuel cell 11. It comprises a temperature detector 33 and a discharged oxidant flow control unit 34 in which a plurality of, for example, two small flow valves 27 and a large flow valve 28 having different pressure flow characteristics are arranged in parallel.

Here, the control unit 18 has a signal of the flow rate QA of the oxidant supplied to the air electrode of the fuel cell 11 detected by the oxidant flow rate detector 31 and a signal of the oxidant pressure detector 32. The signal of the pressure PA of the oxidant supplied to the air electrode of the fuel cell 11, the signal of the temperature TA of the exhaust oxidant discharged from the fuel cell 11 detected by the exhaust oxidant temperature detector 33, and the power generation current Detected by the detector 24, the fuel cell 1
The signal of the power generation current I that changes according to the amount of the oxidant consumed in step 1 and the signal of the target power generation amount from the target power generation amount input unit 29 are input. Then, as described later, the control unit 18 calculates a target pressure of the oxidant on the inlet side of the air electrode based on the target power generation amount.

Further, as will be described later, the control unit 18
The flow rate QA of the oxidant supplied to the air electrode and the fuel cell 11
Based on the generated current I related to the amount of the oxidizing agent consumed at the temperature and the temperature TA of the discharged oxidizing agent, the flow rate of the off-gas discharged to the outside via the discharged oxidizing agent flow control unit 34 (that is, the discharged oxidizing agent) Flow). That is, the amount of the oxidant consumed in the fuel cell 11 is calculated based on the power generation current I, and this oxidant consumption is subtracted from the flow rate QA of the oxidant supplied to the air electrode, whereby When calculating the flow rate, volume correction relating to temperature is performed based on the temperature TA of the discharged oxidant.

The discharged oxidant flow rate control section 34 is constituted by arranging a plurality of, for example, two small flow rate valves 27 and two large flow rate valves 28 having different pressure flow rate characteristics in parallel. The two valves 27 and 28 are driven by, for example, a stepping motor or the like to adjust the valve opening in steps of a predetermined opening. For example, the valve opening per one step of the large flow valve 28 is a small flow valve. 27 is set to be smaller than the maximum valve opening. And 1
The coarse adjustment pressure flow control valve having a large valve opening per step (that is, the large flow valve 28) is feedforward controlled, and the fine adjustment pressure flow control valve having a small valve opening per step (that is, the small flow valve 27) is provided. For example, feedback control such as PID control is performed. Here, in the low flow rate region of the discharged oxidant, the large flow valve 28 is fully closed, and the pressure flow characteristic is changed only by the small flow valve 27. On the other hand, in the high flow rate region of the discharged oxidizing agent, the pressure flow characteristic is relatively largely changed by the feedforward control of the large flow valve 28, and further, the small flow is corrected by correcting the large change by the large flow valve 28. The valve 27 is feedback-controlled.

Next, a process for calculating a pressure flow control command to the exhaust oxidant flow control unit 34 will be described.
First, in step S21 shown in FIG. 7, for example, a required value between the fuel electrode and the air electrode of the fuel cell 11 is obtained from a target power generation current value (that is, a target power generation amount) corresponding to, for example, an operation amount of an accelerator pedal. The target pressure of the oxidant at the inlet of the air electrode (the target pressure at the cathode inlet in FIG. 7) required to secure a predetermined inter-electrode pressure is calculated. In step S22, the flow rate QA of the oxidant supplied to the air electrode detected by the oxidant flow rate detector 31 (actual flow rate output from the cathode inlet flowmeter in FIG. 7) and the generation current detection The generated current I detected by the heater 24 (the current output from the ammeter in FIG. 7) and the temperature TA detected by the discharged oxidant temperature detector 33 (output from the cathode outlet thermometer in FIG. 7) The flow rate of the off-gas (that is, the discharged oxidant) is calculated based on

Next, in step S23, a predetermined map relating to the pressure and the flow rate is searched based on the target operating pressure of the cathode inlet portion and the flow rate of the off-gas. The valve opening of the large flow valve 28 is calculated. Step S24
In FIG. 7, the pressure PA of the oxidant supplied to the air electrode detected by the oxidant pressure detector 32 (actual pressure output from the cathode inlet pressure gauge in FIG. 7), the cathode inlet target operating pressure, and In particular, a feedback coefficient relating to the valve opening of the small flow valve 27 is calculated.

In step S25, in the low flow rate region of the exhaust oxidant, zero is output as the valve opening of the large flow valve 28, and the value calculated by feedback control as the valve opening of the small flow valve 27 is obtained. Is output. On the other hand, in the high flow rate region of the exhaust oxidant, the small flow rate valve calculated by the feedback control by correcting the valve opening degree in the feed forward control of the large flow rate valve 28 and the valve opening degree of the large flow rate valve 28 27 is output as a valve opening command.

As described above, according to the fuel cell control device 30 according to the modification of the present embodiment, the two small flow rate valves 27 having different pressure flow rate characteristics with respect to the oxidant discharged from the fuel cell 11. And the large flow valve 28 are arranged in parallel, the large flow valve 28 is feedforward controlled, and the small flow valve 27 is feedback controlled, so that high precision control can be performed while maintaining high responsiveness. it can.

In the above-described control device 10 for the fuel cell according to the present embodiment and the control device 30 for the fuel cell according to the modification of the present embodiment, the discharged fuel or discharged oxidant discharged from the fuel cell 11 is used. The two small flow valves 27 and the large flow valves 28 having different pressure flow characteristics are arranged in parallel for either one of the above. However, the present invention is not limited to this. For both oxidants, small flow valves 27
And the large flow valve 28 are arranged in parallel, that is, the fuel cell 1
1 may include both the discharged fuel flow control unit 19 and the discharged oxidant flow control unit 34.

[0039]

As described above, according to the fuel cell control apparatus of the present invention, the first control valve is subjected to feedforward control, and the second control valve is subjected to feedback control. Thus, the responsiveness and accuracy of the pressure flow control can be improved over the entire wide output range from the low flow rate range to the high flow rate range. For example, in the low flow rate region of the exhaust fuel, the first control valve is fully closed, and the pressure flow characteristic is changed only by the second control valve, so that the response accuracy can be improved. On the other hand, in the high flow rate region of the exhaust fuel, the response and the accuracy with respect to the response are improved by changing the pressure flow characteristic relatively large by the first control valve and further by adding the correction by the second control valve. Can be improved.

Further, according to the fuel cell control device of the present invention, in the high flow rate range of the discharged fuel, the valve opening of the second control valve is set to the intermediate opening with respect to the maximum opening. By setting the degree to the degree, the increase / decrease of the valve opening can be adjusted, and the control by the second control valve can be corrected by the first control valve having a large valve opening per step. And high-accuracy control can be performed while maintaining high responsiveness. Furthermore, according to the fuel cell control device of the present invention, the air supplied to the cathode side of the fuel cell in the entire flow rate range from the low output side to the high output side of the fuel cell. Can be accurately controlled. Furthermore, according to the fuel cell control device of the present invention as set forth in claim 4, over the entire flow rate range from the low output side to the high output side of the fuel cell,
The pressure flow characteristic of the reformed fuel supplied to the anode side of the fuel cell can be accurately controlled.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a control device for a fuel cell according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a process of calculating a pressure flow control command for an exhaust fuel flow control unit illustrated in FIG. 1;

FIG. 3 is a flowchart showing a process of controlling a small flow valve and a large flow valve of the exhaust fuel flow control unit shown in FIG. 1;

FIG. 4 is a graph showing changes in generated current output from the fuel cell shown in FIG. 1 and anode operating pressure, that is, pressure loss.

FIG. 5 is a graph showing changes in the flow rate of exhaust fuel passing through an exhaust fuel flow rate control unit shown in FIG. 1 and the valve opening of a small flow valve and a large flow valve.

FIG. 6 is a configuration diagram showing in detail a configuration of a control device for a fuel cell, particularly a configuration of an oxidant supply system, according to a modification of the present embodiment.

FIG. 7 is a flowchart showing a process of calculating a pressure flow control command to an exhaust oxidant flow control unit shown in FIG. 6;

[Explanation of symbols]

 Reference Signs List 10 control device for fuel cell 11 fuel cell 12 fuel supply unit (reaction gas supply unit) 15 reforming unit (fuel reforming unit) 17 oxidant supply unit (reaction gas supply unit) 27 small flow valve (second control valve) ) 28 Large flow valve (first control valve)

Claims (4)

[Claims] 1. A reactant gas supply means for supplying a reactant gas to a fuel cell, and a reactant gas supply means arranged in parallel at an outlet of a reactant gas exhausted from the fuel cell, wherein the reactant gas supply means has a predetermined valve opening width. A first control valve and a second control valve for changing a valve opening degree in a step-like manner, wherein the second control valve is controlled until a flow rate of the exhaust reactant gas reaches a predetermined value; When the flow rate of the first control valve exceeds the predetermined value, the first control valve is feed-forward controlled based on a target value of the pressure flow characteristic of the reaction gas or the discharged reaction gas, and the second control valve is controlled by the second control valve. A control device for a fuel cell, wherein a valve is feedback-controlled based on a detected value of a pressure flow characteristic of the reaction gas or the discharged reaction gas. 2. The method according to claim 1, wherein the control means determines a valve opening of the first control valve in accordance with a target value of a pressure flow characteristic of the discharged reactant gas, and sets a valve opening of the second control valve to a predetermined opening. In the state of
Selecting from the pressure flow characteristics that change according to the valve opening degree of the first control valve; and setting the number of valve opening steps for the first control valve to a predetermined value for the valve opening degree of the first control valve. 2. An integer value satisfying an approximate value, wherein a difference between the valve opening degree of the first control valve and the predetermined approximate value is corrected by feedback control of the second control valve. 3. The control device for a fuel cell according to claim 1. 3. The fuel according to claim 1, wherein the reactant gas supplied to the cathode side of the fuel cell is air pressurized by pressurizing means. Battery control device. 4. The reaction gas supplied to the anode side of the fuel cell is the reformed fuel generated by a fuel reforming unit that reforms a fuel to generate a hydrogen-rich reformed fuel. The control device for a fuel cell according to any one of claims 1 to 3, wherein: