JPH053041A - Controlling method for fuel cell device - Google Patents

Abstract

PURPOSE:To provide a stable electrical output by computing and controlling incremental opening of respective regulating valves for a primary fuel, a cathode air, and a steam from the deviation between the initial cell voltage and the present cell voltage corresponding to the present output power value. CONSTITUTION:The present power value is computed from a cell output voltage and a cell output current, the corresponding initial cell voltage is computed in a function generator FG4, the deviation between the initial cell voltage and the present cell voltage is input into function generators FG'1, FD'2, and FG'3. The generators FG'1, FG'2, and FG'3 compute the valve opening increment, namely flow increment, corresponding to voltage deviations of a primary fuel regulating valve 9, a cathode air regulating valve 10, and a steam regulating valve 11, and are subsequently added to respective regulating valves to control them. Whereby, the deterioration in battery cell characteristics can automatically be detected and increase the quantity of hydrogen being supplied to a hydrogen electrode in the cell main body so as to stably provide an electrical output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling a fuel cell device, and more particularly, to detecting a cell deterioration of a fuel cell body and a catalyst deterioration of a fuel reforming system and controlling a process flow rate so as to compensate for them. By doing so, the present invention relates to a method for controlling a fuel cell device suitable for obtaining a stable electric output.

[0002]

2. Description of the Related Art A configuration example of a conventional general fuel cell system will be described with reference to FIG. FIG. 1 is a system diagram showing the configuration of a general fuel cell system. Thick solid arrows indicate paths of natural gas and reaction gas, one-dot chain arrows indicate paths for combustion air, and two-dot chain arrows indicate exhaust gas paths. , The broken line arrow indicates the steam path, and the thin solid line indicates the cooling water path. In addition, a dotted arrow indicates a control signal system. In FIG. 1, 1 is a fuel cell main body, which is a hydrogen electrode 1a, an oxygen electrode 1b,
And a battery cooling device 1c. A fuel reforming system 2 is a system for generating hydrogen from a hydrocarbon compound such as natural gas and steam by a steam reforming reaction. Three
Is connected to the cell cooling device 1c of the fuel cell main body 1 by the circulation pump 7 in the cell cooling system, and has a role of removing heat generated by the cell reaction, and at the same time generates steam by the heat, thereby the fuel reforming system 2 The steam required for the steam reforming reaction is supplied. 4 is an ejector (or mixer)
Then, it has a role of mixing fuel such as natural gas and water vapor generated from the cell cooling system 3 and supplying it to the fuel reforming system 2.

Reference numeral 5 is an inverter for converting the DC electric output from the fuel cell main body 1 into AC and supplying it to a load. Reference numeral 6 denotes a control device having an arithmetic control unit such as a central control unit (CPU) of a computer. The control device 6 judges the load state from the direct current voltage and direct current value from the fuel cell main body 1, It has a function of controlling the fuel control valve 9, the cathode air control valve 10, and the water vapor control valve 11 (or the variable ejector). Here, the main fuel control valve 9 is provided in the natural gas supply passage, the cathode air control valve 10 is provided in the air supply passage, and the steam control valve 11 is provided.
Is provided in the water vapor supply path indicated by the broken line. Besides, 8 is a feed water pump, and 12 is a burner air control valve for burning the anode exhaust gas discharged from the hydrogen electrode 1a of the fuel cell body 1 as a heat source necessary for the steam reforming reaction.

A conventional method for controlling a fuel cell system having the above-described structure is shown in FIGS.
Will be described with reference to. FIG. 9 is a control system diagram of a conventional fuel cell system, and FIG. 10 is a diagram of valve opening (or flow rate) corresponding to load in the control system of FIG. As shown in FIG. 9, the load amount is calculated by the product of the DC cell output voltage from the fuel cell main body 1 and the cell output current, and the main fuel control valve 9, the cathode air control valve 10 and the steam corresponding to this load amount are calculated. The required valve opening degree (or each flow rate) of each control valve of the control valve 11 is determined by each function generator FG ₁ , FG ₂ , F in the control device 6.
The control valves are controlled by calculation by G ₃ . In each of the function generators FG _{1 to} FG ₃ , as shown in FIG. 10, the valve opening degree (or flow rate) corresponding to the load amount is set by the initial characteristics of the fuel cell body 1 and the fuel reforming system 2. .

[0005]

In the conventional fuel cell system control method as described above, the battery of the fuel cell main body 1 serving as the basis for setting the valve opening (or flow rate) corresponding to the load amount shown in FIG. The initial characteristics of the cell characteristics are shown in FIG. FIG. 11 is an initial characteristic diagram of a battery cell, and FIG. 12 is a characteristic diagram showing a case where the battery cell characteristic is deteriorated. FIG. 11 shows
The horizontal axis represents the battery current density Ai (mA / cm ² ) and the vertical axis represents the battery cell voltage Vc (V), showing the initial characteristics. If a certain load amount is determined, the operation on the characteristic curve is performed. The point a is set. The area A indicated by hatching is the electric power (= load) per cell.

Consider the case where the battery cell characteristics are deteriorated in the above fuel cell system control method. Figure 1
2 shows the case where the battery cell characteristics deteriorated, and the characteristics shown by the broken line are the characteristics at the time of deterioration. When the same electric power (= load) as that in the initial characteristic is required for the deteriorated battery cell characteristic, the area A'in the hatching of the broken line should be the same as A shown in FIG. The process moves to the operating point a'on the characteristic curve. That is, in order to obtain the same electric power, the decrease in the battery cell voltage is compensated by increasing the battery current value. This means that the amount of hydrogen consumed at the hydrogen electrode 1a of the fuel cell body 1 increases.

In this case, the conventional control method based on the initial performance of the battery cell characteristics cannot cope with an increase in the consumption of hydrogen, and battery damage due to lack of hydrogen in the hydrogen electrode 1a, Further, there are problems such as deterioration of reforming performance and burner misfire due to insufficient burner fuel supplied to the fuel reforming system 2. Further, in the conventional control method of the fuel cell system, the decrease in the amount of hydrogen in the reformed gas due to the catalyst deterioration of the fuel reforming system is not taken into consideration, and there is a problem of hydrogen shortage in the fuel cell main body.

The present invention has been made to solve the above-mentioned problems of the prior art. In response to deterioration of battery cell characteristics, the amount of hydrogen supplied to the hydrogen electrode of the fuel cell body at the time of deterioration is increased. Accordingly, it is a first object of the present invention to provide a method for controlling a fuel cell device that can obtain a stable electric output. A second object of the present invention is to provide a fuel cell device capable of obtaining stable electric output by increasing the main fuel flow rate and steam flow rate to the fuel reforming system in response to catalyst deterioration of the fuel reforming system. It is to provide a control method of.

[0009]

In order to achieve the above-mentioned first object, a first method according to a control method of a fuel cell device of the present invention is provided.
According to another aspect of the present invention, there is provided a fuel cell main body, a fuel reforming system for the fuel cell main body, an air supply system, a cell cooling system, an exhaust gas system, and a control system for controlling these. In a control method of a fuel cell device having a control function of a main fuel control valve for controlling the supply amount of hydrogen and oxygen required for a reaction, a cathode air control valve, and a steam control means, an initial cell voltage with respect to a current output power value The main fuel control valve, the cathode air control valve, and the steam are controlled by a control system that has a function of calculating the necessary increase amounts of the main fuel flow rate, the cathode air flow rate, and the steam flow rate from the deviation between the current value and the current cell voltage value. The adjusting means is controlled.

In order to achieve the above second object,
The configuration of the second invention relating to the control method of the fuel cell device of the present invention is to control a fuel cell main body, a fuel reforming system, an air supply system, a cell cooling system, and an exhaust gas system for the fuel cell main body. A control system for a fuel cell device, comprising at least a main fuel control valve for controlling a supply amount of hydrogen required for a cell reaction in the fuel cell main body, and a control function of a steam control means. The main fuel control valve and steam control are controlled by a control system that adds a function to calculate the required increase in each of the main fuel flow rate and steam flow rate from the deviation between the initial value and the current value of the hydrogen concentration at the combustion gas outlet of the system. The means is controlled.

[0011]

The characteristic of the cell voltage with respect to the initial load of the fuel cell body is stored as a function in the control device. Further, from the above function, from the deviation between the initial battery voltage and the current battery voltage value with respect to the current output power value, the main fuel control valve,
The increased opening degree (or increased flow rate) of the cathode air control valve and the steam control valve is stored as a function in the control device in advance. As a result, it is possible to automatically perform the optimum opening degree control (or flow rate control) of each of the control valves based on the current power value and the voltage obtained from the battery output voltage and the output current. As a result, problems such as lack of hydrogen in the hydrogen electrode of the fuel cell body, deterioration of reforming performance in the fuel reforming system, burner misfire, etc. do not occur.

The characteristic of the hydrogen concentration at the reformed gas outlet with respect to the initial load of the fuel reforming system is stored in the control device as a function, and from this function, the deviation between the present reformed gas hydrogen concentration and the initial value is stored. Therefore, the increased opening degree (or increased flow rate) of the main fuel control valve and the steam control valve is stored in advance in the control device as a function. As a result, it is possible to automatically perform optimum opening accuracy (or flow rate control) of the main fuel control valve and the steam control valve from the hydrogen concentration at the reformed gas outlet of the fuel reforming system.

[0013]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a system diagram showing the configuration of a general fuel cell system as described above, and the device configuration and system of the fuel cell system of this embodiment are basically the same as those shown in FIG. Therefore, the description of the configuration is omitted. First, an embodiment of the first invention will be described with reference to FIGS. 2 to 5 in addition to FIG. 2 is a control system diagram of a fuel cell system according to an embodiment of the present invention, and FIG.
A diagram of the valve opening (or flow rate) corresponding to the load in the control system in the figure, FIG. 4 is an initial characteristic diagram of the function generator FG ₄ in FIG. 2, and FIG. 5 is a function generator FG in FIG. ₁ 'to FG ₃
It is a diagram showing a setting example of '.

In FIG. 2, the same reference numerals and symbols as those in FIG. 9 are equivalent to those in the conventional control system, and therefore their explanations are omitted. The function generator FG ₄ shown in FIG. 2 is a function of the relationship between the load and the battery voltage at the initial characteristic of the battery cell characteristic, and the function as shown in FIG. 4 is set.
Here, FIG. 4 shows the function (curve) of the initial performance with the load (%) on the horizontal axis and the battery total voltage (V) on the vertical axis. As shown in FIG. 2, the current output power value is calculated from the product of the battery output voltage and the battery output current value, and the initial battery voltage corresponding to the power value (load) is calculated as the function generator FG.
Calculate with ₄ . The calculation result, that is, the difference between the initial battery voltage and the current battery output voltage is calculated and input to the function generators FG ₁ ′, FG ₂ ′, FG ₃ ′.

FG ₁ ′ is a function generator for calculating the valve opening increase corresponding to the voltage deviation of the main fuel control valve 9, that is, the flow rate increase amount, and FG ₂ ′ is the cathode air control valve 10. The function generator for calculating the increase in valve opening corresponding to the voltage deviation, that is, the flow rate increase amount, FG ₃ ′, is the increase in valve opening corresponding to the voltage deviation of the control valve 11, that is, the increase in flow rate. It is a function generator for calculating a quantity.
These function generators are set as shown in FIG. Here, FIG. 5 shows that the horizontal axis indicates the voltage deviation (ΔV) and the vertical axis indicates the valve opening or the flow rate increase (%), and the set function changes linearly. It goes without saying that the function setting differs depending on the type of valve and fluid conditions.

The valve opening (flow rate) increments of the main fuel control valve 9, the cathode air control valve 10 and the steam control valve 11 obtained by the function generators FG ₁ ′, FG ₂ ′ and FG ₃ ′, respectively, By controlling the control valves by adding them to the valve opening (flow rate) of each control valve obtained by the function generators FG ₁ , FG ₂ , and FG ₃ , the control shown by the broken line in FIG. 3 is performed. The value is obtained.

According to this embodiment, with respect to the deterioration of the battery performance, that is, the deterioration of the battery cell characteristics, which is deteriorated over time, the deterioration is automatically detected and the hydrogen supplied to the hydrogen electrode of the fuel cell body is supplied. Since the amount can be increased, it is possible to provide a control method for a fuel cell system that solves problems such as hydrogen shortage due to cell performance deterioration, reforming performance deterioration, burner misfire, and the like, and a stable electric output can be obtained. In the above embodiment, the steam supply flow rate is controlled by adjusting the valve opening of the steam control valve 11. However, steam control means such as a variable ejector may be controlled.

Next, an embodiment of the second invention will be described with reference to FIGS. 6 to 8 in combination with FIG. FIG. 6 is a control system diagram of a fuel cell system according to another embodiment of the present invention, FIG. 7 is an initial characteristic diagram of the function generator FG ₅ of FIG. 6, and FIG.
Is a function generator FG ₁ ″ to F in the control system of FIG.
9 is a diagram showing a setting example of G ₃ ″. In FIG. 6, the same reference numerals and symbols as those in FIG. 9 are the same as those in the control system of the conventional art, and thus the description thereof will be omitted.
Is a hydrogen concentration detector, and this hydrogen concentration detector 13 detects the hydrogen concentration at the combustion gas outlet of the fuel reforming system 2 and sends the detected value to the control device 6.

The function generator FG ₅ shown in FIG. 6 sets the relationship between the load and the hydrogen concentration at the initial characteristic of the hydrogen concentration at the combustion gas outlet of the fuel reforming system 2 to the function shown in FIG. . In FIG. 7, the load (%) is plotted on the horizontal axis and the hydrogen concentration is plotted on the vertical axis, and the function of the initial performance is shown by a solid line, and the present value of the hydrogen concentration having a deviation of ΔH ₂ is shown by a broken line. Figure 6
As shown in, the current output power value is calculated from the product of the battery power voltage and the battery output current value, and the initial hydrogen concentration corresponding to the power value (load) is calculated by the function generator FG ₅ . The difference between this calculation result, that is, the initial value of the hydrogen concentration and the present value of the hydrogen concentration at the combustion gas outlet of the fuel reforming system 2 detected by the hydrogen concentration detector 13 is calculated, and the function generator FG ₁ ″, Input to FG ₂ ″ and FG ₃ ″.

FG ₁ ″ is a function generator for calculating the valve opening increase corresponding to the hydrogen concentration deviation of the main fuel control valve 9, that is, the flow rate increase amount, and FG ₂ ″ is the cathode air control valve 10. Function generator for calculating the valve opening increase corresponding to the hydrogen concentration deviation of
G ₃ ″ is a function generator for calculating the valve opening increase corresponding to the hydrogen concentration deviation of the steam control valve 11, that is, the flow rate increase.

These function generators are set as shown in FIG. Here, FIG. 8 shows that the abscissa represents the hydrogen concentration deviation and the ordinate represents the valve opening or the flow rate increase (%), and the set function changes linearly. The function generators FG ₁ ″, FG ₂ ″, and FG ₃ ″ are used to calculate the valve opening (flow rate) increments of the main fuel control valve 9, the cathode air control valve 10, and the steam control valve 11, respectively. F
By adding to the valve opening (flow rate) of each control valve obtained in G ₁ , FG ₂ , and FG ₃ to control each control valve,
A proper control value can be obtained.

Thus, according to the embodiment of the second invention,
Since the shortage of hydrogen amount due to catalyst deterioration of the fuel reforming system can be automatically detected and the required amount of hydrogen can be supplied to the fuel cell main body, the same effect as that of the first embodiment of the invention is expected, A stable electric output can be obtained. In the above embodiment, an example in which the main fuel control valve 9, the cathode air control valve 10, and the steam control valve 11 are controlled based on the deviation between the initial value and the current value of the hydrogen concentration has been described. Control valve,
The purpose can be achieved by controlling the water vapor control means.

[0023]

As described in detail above, according to the present invention, in response to the deterioration of battery cell characteristics, by increasing the amount of hydrogen supplied to the hydrogen electrode of the fuel cell main body at the time of deterioration, stable operation is achieved. It is possible to provide a method for controlling a fuel cell device that can obtain an electric output. Further, it is possible to provide a method of controlling a fuel cell device that can obtain a stable electric output by increasing the main fuel flow rate and the steam flow rate to the fuel reforming system in response to catalyst deterioration of the fuel reforming system. .

[Brief description of drawings]

FIG. 1 is a system diagram showing a configuration of a general fuel cell system.

FIG. 2 is a control system diagram of a fuel cell system according to an embodiment of the present invention.

3 is a diagram of a valve opening (or flow rate) corresponding to a load in the control system of FIG.

FIG. 4 is an initial characteristic diagram of the function generator FG ₄ of FIG.

5 is a diagram showing a setting example of the function generators FG ₁ ′ to FG ₃ ′ of FIG.

FIG. 6 is a control system diagram of a fuel cell system according to another embodiment of the present invention.

7 is an initial characteristic diagram of the function generator FG ₅ of FIG.

8 is a diagram showing a setting example of function generators FG ₁ ″ to FG ₃ ″ in the control system of FIG.

FIG. 9 is a control system diagram of a conventional fuel cell system.

10 is a diagram of a valve opening (or flow rate) corresponding to a load in the control system of FIG.

FIG. 11 is an initial characteristic diagram of a battery cell.

FIG. 12 is a characteristic diagram showing when the battery cell characteristics are deteriorated.

[Explanation of symbols]

1 Fuel cell body 2 Fuel reforming system 3 Battery cooling system 4 ejectors 6 control device 9 Main fuel control valve 10 Cathode air control valve 11 Water vapor control valve 13 Hydrogen concentration detector

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Susumu Horiuchi             603 Jinmachi-cho, Tsuchiura-shi, Ibaraki Japan Co., Ltd.             Tachiura Tsuchiura Factory (72) Inventor Genichi Ikeda             6-9 Hisagi, Zushi City, Kanagawa Prefecture B-9 (72) Inventor Makoto Okuda             3-2 Takasago 3-72, Katsushika-ku, Tokyo

Claims (2)

[Claims] 1. A cell reaction in the fuel cell body, comprising a fuel cell body, a fuel reforming system for the fuel cell body, an air supply system, a cell cooling system, an exhaust gas system, and a control system for controlling these. In the control method of the fuel cell device having the control functions of the main fuel control valve for controlling the supply amount of hydrogen and oxygen required for the fuel cell, the cathode air control valve, and the steam control means, the initial cell voltage value with respect to the current output power value Of the main fuel flow rate, cathode air flow rate, and steam flow rate based on the deviation between the current fuel cell voltage value and the current cell voltage A method for controlling a fuel cell device, comprising controlling the means. 2. A fuel cell main body, a fuel reforming system for the fuel cell main body, an air supply system, a cell cooling system, an exhaust gas system, and a control system for controlling these, at least in the fuel cell main body. In a control method of a fuel cell device having a control function of a main fuel control valve and a steam control means for controlling a hydrogen supply amount required for a cell reaction, an initial value and a current value of hydrogen concentration at a combustion gas outlet of a fuel reforming system. Of the main fuel flow rate and the steam flow rate, the control system having a function of calculating the required increase amounts of the main fuel flow rate and the steam flow rate controls the main fuel control valve and the steam control means. Control method.