JP3446465B2 - Raw fuel flow control device for fuel cell power plant - Google Patents

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 controlling a raw fuel flow rate to a fuel reformer in a fuel cell power generator.

[0002]

2. Description of the Related Art FIG. 5 is a conventional raw fuel for a fuel cell power generator.
It is a system block diagram which simplifies and shows a flow control device.
In the figure, the fuel reformer 3 is a raw fuel such as natural gas.
The mixed gas with the reforming steam is hydrogen reformed by steam reforming.
The reformed fuel gas is supplied to the fuel cell 4. Fuel cell
Pond 4 supplies fuel gas to its fuel electrode and air electrode
Power generation based on an electrochemical reaction with the reaction air
Outputs a flowing current. Fuel cell power generation configured in this way
The raw fuel flow rate control device of the apparatus is provided in the raw fuel supply system 8.
On the output side of the fuel cell 4 and the flow meter 1 and control valve 2.
The current detector 5 provided and the fuel cell detected by the current detector 5
Pond output current I_DFlow rate set value Q of raw fuel corresponding to_SPlayed
The flow rate calculation unit 7 that calculates and outputs the raw fuel detected by the flow meter
Flow rate Q_FIs the raw fuel flow rate setting value Q_SControl to follow
It is composed of a valve control unit 6 that controls the opening degree of the control valve 2.
Output current I of the fuel cell 4_DSupply of raw fuel following
Quantity Q _FIs configured to control.

The control of the output current I _D of the fuel cell 4 uses a method of controlling a power converter (not shown) by an external load command, but the output current I _D is controlled by an external load command.
_When a rapid increase in _D is commanded, the fuel cell 1 tries to increase the output current I _D rapidly without delay, whereas the fuel reformer 3 that involves mass transfer and chemical reaction has a slow response, so The supply is delayed, and the fuel cell 4 transiently has a fuel gas shortage state (gas shortage state). Further, when the fuel cell is operated in this state, a deterioration phenomenon such as coarsening of the electrode catalyst particles occurs, which causes a problem that the power generation performance and the life characteristic of the fuel cell are deteriorated.

In order to prevent such a deterioration phenomenon, in the conventional raw fuel flow rate control device, a linear equation is used for the flow rate calculation unit 7,
By changing the flow rate set value Q _S of the raw fuel in response to the change in the fuel cell output current I _D , the fuel cell output current I
It is configured so that the raw fuel flow rate Q _F changes in accordance with the rapid increase in _D. Also, in order not to run short of fuel gas when the fuel cell output current I _D suddenly increases, the raw fuel flow rate set value Q _S
Or adding a pre-increased by previously correcting, proposals or providing a means for reducing quickly the fuel cell output current I _D has been proposed by the present of the same Applicants (Japanese Patent Application No. 6-99
397).

[0005]

FIG. 6 is a characteristic diagram schematically showing the operation of the conventional raw fuel flow rate control device shown in FIG. 5 when the output current suddenly decreases. In the figure, when the fuel cell output current I _D suddenly decreases from the A level to the B level, the flow rate set value Q _S of the raw fuel output by the flow rate calculation unit 7 also decreases in proportion to this, and the valve control detecting this change The section 6 issues a command for controlling the opening of the control valve 2 so that the detected flow rate Q _F of the flow meter follows the flow rate set value Q _S of the raw fuel.
However, since the operation of the control valve 2 cannot follow the rapid decrease in the flow rate set value Q _S, an undershoot occurs in the raw fuel flow rate Q _F , which causes a transient gas shortage state in the fuel cell 4, It has been found that there is a problem that the prior art does not notice, such as deterioration phenomena such as coarsening of the electrode catalyst particles and deterioration of the life characteristics of the fuel cell cannot be completely avoided.

An object of the present invention is to provide a raw fuel flow rate control device capable of preventing an undershoot of the raw fuel flow rate when the output current of the fuel cell suddenly decreases and avoiding the occurrence of a gas shortage condition.

[0007]

In order to solve the above-mentioned problems, the invention according to claim 1 is a fuel reformer for reforming a raw fuel supplied from a raw fuel supply system into a hydrogen-rich fuel gas. Quality device and a flow meter and a control valve provided in the raw fuel supply system of a fuel cell power generation device having a fuel cell that receives the fuel gas to generate power, and a current detector provided on the output side of the fuel cell. A flow rate calculation unit for calculating and outputting a flow rate set value of the raw fuel corresponding to the detected value of the current detector; and the control valve so that the detected flow rate of the flow meter matches the flow rate set value of the raw fuel. In the raw fuel flow rate control device for controlling the supply amount of the raw fuel according to the output current of the fuel cell, the output flow rate set value of the flow rate calculation unit is increased or decreased. Determine the flow rate setting value Outputs the correction flow setting value alleviate the reduction rate during the reduced, when an increase of the flow rate set value comprises a change speed limiting means for output as the flow rate set value which is not decelerating.

According to a second aspect of the present invention, in the raw fuel flow rate control device for a fuel cell power generator according to the first aspect, the change speed limiting means determines whether the flow rate set value is increased or decreased. Section, the increase / decrease determination section operates when it detects a sudden increase in the flow rate set value, and outputs the flow rate set value that does not decelerate, and the increase / decrease determination section detects a sudden decrease in the flow rate set value. It is convenient to configure so as to include a decreasing speed reducing unit that operates at that time and outputs a corrected flow rate set value that reduces the decreasing speed.

According to the first aspect of the present invention, when the change speed limiting means outputs the corrected flow rate set value which is relaxed when the output flow rate set value of the flow rate calculation unit suddenly decreases, for example, the decrease rate is controlled. By mitigating the valve operation to such an extent that it can follow, it becomes possible to prevent an undershoot of the raw fuel flow rate, and to avoid a gas shortage condition which occurs in the fuel cell due to the undershoot of the raw fuel flow rate. Further, since the change speed limiting means outputs the flow rate set value that does not decelerate when the flow rate set value increases, it is possible to rapidly increase the raw fuel flow rate in proportion to the flow rate set value, and to prevent gas shortage. To be

According to the second aspect of the present invention, when the increase / decrease determination unit detects a rapid increase in the flow rate set value, the flow rate increase set value output unit operates to output the flow rate set value that does not decelerate as it is and increases / decreases. When the determination unit detects a sudden decrease in the flow rate set value, the decrease speed reduction unit operates and outputs a corrected flow rate set value that relaxes the decrease speed, so the action to prevent undershoot of the raw fuel flow rate and the raw fuel flow rate are The function of rapidly increasing the flow rate setting value can be easily obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on embodiments. Since the members having the same reference numerals as those of the conventional example have the same functions as those of the conventional example, the description thereof will be omitted. FIG. 1 is a simplified system configuration diagram of a raw fuel flow rate control device of a fuel cell power generator showing an embodiment of the invention described in claim 1. In the figure, the raw fuel flow rate control device calculates a raw fuel flow rate setting value Q _S corresponding to the fuel cell output current I _D detected by the current detector 5 and outputs the flow rate setting value Q _S to the output side of the flow rate calculation unit 7 to limit the changing speed. comprising means 10, when rapid reduction of the flow rate set point Q _S and outputs the corrected flow setpoint Q _St that alleviate the reduced speed is output as the flow setpoint Q _S is not decelerated during an increase of the flow rate set point Q _S. Therefore, for example, the undershoot of the raw fuel flow rate Q _F , which has been a problem in the conventional technique, can be prevented by relaxing the rate of decrease of the corrected flow rate set value Q _{St to such} an extent that the operation of the control valve 2 can follow. This makes it possible to avoid the gas shortage state that occurs in the fuel cell 4 due to the undershoot of the raw fuel flow rate. Further, since the changing speed limiting means 10 outputs the flow rate setting value Q _S that does not decelerate when the flow rate setting value Q _S increases, the raw fuel flow rate Q _F changes to the flow rate setting value Q _S and the fuel cell output current _ID . It is possible to control the opening degree of the control valve 2 to rapidly increase in proportion, and it is also possible to prevent a gas shortage state when the output current rapidly increases.

FIG. 2 is a simplified block diagram of the changing speed limiting means showing an embodiment of the invention described in claim 2. In the figure, the change speed limiting means includes an increase / decrease determination unit 11 that determines whether the flow rate setting value Q _S output by the flow rate calculation unit 7 is increased or decreased, and the increase / decrease determination unit 11 detects a sudden increase in the flow rate set value and outputs it. Flow rate setting value output section 12 that outputs the flow rate setting value Q _S that does not decelerate by operating
And an increase / decrease determination unit 11 that operates according to a signal output by detecting a sudden decrease in the flow rate set value and outputs a corrected flow rate set value Q _St that relaxes the decrease rate, and a decrease rate reduction unit 13.

FIG. 3 is a characteristic diagram schematically showing the operation of the decreasing speed reducing section in the embodiment shown in FIG. In the figure, it is assumed that the flow rate calculation unit 7 detects a sudden decrease in the fuel cell output current I _{D and} outputs a flow rate set value Q _{S (AB)} that rapidly decreases from Q _SA to Q _SB . At this time, the decreasing speed reducing unit 13 outputs the corrected flow rate setting value Q _St that decreases at the decreasing speed obtained by dividing the flow rate setting value Q _{S (AB)} by the relaxation time T _D determined by the followable speed of the control valve 2. Since the valve control unit 6 which receives the control the opening of the control valve 2 so that raw fuel flow rate Q _F detected by the flow meter to follow the correction flow setting value Q _St of the raw fuel, the raw fuel flow rate Q _F The undershoot is eliminated, the out-of-gas state of the fuel cell 4 caused by this is avoided, and the adverse effects such as the occurrence of a deterioration phenomenon such as coarsening of the electrode catalyst particles and the deterioration of the life characteristic of the fuel cell are eliminated. .

FIG. 4 is a flow chart showing a different embodiment of the invention described in claim 2, and shows an example in which the changing speed limiting means is configured as an arithmetic processing circuit. In the figure, if the flow rate set value Q _S output by the flow rate calculation unit 7 in step 21 does not indicate a sharp decrease in flow rate, step 22
Thus, the corrected flow rate set value Q _St that does not decelerate and is equal to the flow rate set value Q _S is output. If the flow rate set value Q _S instructs the rapid decrease of the flow rate, the timer starts counting, decreasing speed Q _{S (AB)} / T decreases at _D correction flow setpoint Q _St is output at step 25 at step 23, Corrected flow rate set value Q until the condition of Q _St ≧ Q _SB or timer ≦ T _D is reached
_St is updated.

[0015]

As described above, according to the present invention, when the flow rate set value output by the flow rate calculation unit of the raw fuel suddenly decreases, the changing speed limiting means for relaxing and outputting the decrease rate is provided. As a result, the undershoot of the raw fuel flow rate, which has been a problem in the conventional raw fuel flow rate control device, is eliminated, and the out-of-gas state that occurs in the fuel cell due to this undershoot is avoided. It is possible to provide a fuel cell power generation device provided with a raw fuel flow rate control device that can eliminate a decrease in power generation performance and life characteristic caused in a fuel cell.

[Brief description of drawings]

FIG. 1 is a simplified system configuration diagram of a raw fuel flow rate control device for a fuel cell power generator showing an embodiment of the invention as set forth in claim 1;

FIG. 2 is a configuration diagram of a change speed limiting means showing an embodiment of the invention described in claim 2;

FIG. 3 is a characteristic diagram schematically showing the operation of a reduction speed reduction unit in the embodiment shown in FIG.

FIG. 4 is a flowchart showing a different embodiment of the invention described in claim 2;

FIG. 5 is a system configuration diagram schematically showing a conventional raw fuel flow rate control device of a fuel cell power generator.

FIG. 6 is a characteristic diagram schematically showing the operation of the conventional raw fuel flow rate control device shown in FIG. 5 when the output current suddenly decreases.

[Explanation of symbols]

1 ... Flowmeter, 2 ... Control valve, 3 ... Fuel reformer, 4 ... Fuel cell, 5 ... Current detector, 6 ...
..Valve control unit, 7 ... Flow rate calculation unit, 8 ... Raw fuel supply system, 10 ... Change speed limiting unit, 11 ... Increase / decrease determination unit, 12 ... Output of flow rate increase set value Department, 13
.. Decreasing speed reducing section, Q _S ... Flow rate setting value, Q _F
・ Raw fuel flow rate (actual value), Q _St ...
I _D ... Fuel cell output current, T _D ... Relaxation time.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01M 8/04

Claims (2)

(57) [Claims] 1. A fuel cell power generator having a fuel reformer for reforming a raw fuel supplied from a raw fuel supply system into a hydrogen-rich fuel gas, and a fuel cell power generator for receiving the fuel gas to generate electricity. A flow meter and a control valve provided in the raw fuel supply system, a current detector provided on the output side of the fuel cell, and a flow rate set value of the raw fuel corresponding to the detection value of the current detector are calculated. It comprises a flow rate calculation section for outputting and a valve control section for controlling the opening degree of the control valve so that the detected flow rate of the flow meter matches the flow rate setting value of the raw fuel, depending on the output current of the fuel cell. In the raw fuel flow rate control device for controlling the supply amount of the raw fuel, the increase / decrease in the output flow rate set value of the flow rate calculation unit is discriminated, and when the flow rate set value sharply decreases, the corrected flow rate set value with a reduced rate is output. The flow rate setting Raw fuel flow control device of the fuel cell power generation apparatus characterized by comprising a change speed limiting means for output as the flow rate set value which is not decelerated during the increase. 2. The raw fuel flow rate control device for a fuel cell power generator according to claim 1, wherein the change speed limiting means determines whether the flow rate set value is increased or decreased, and the increase / decrease determination section sets the flow rate. When the increase in the value is detected, it does not decelerate and outputs the flow rate set value as it is, and the output unit for the flow rate increase set value, and when the increase / decrease determination unit detects a sudden decrease in the flow rate set value, it operates to reduce the decrease rate. A raw fuel flow rate control device for a fuel cell power generator, comprising: a reduction speed reduction unit that outputs a corrected flow rate set value.