JP2024066034A - Fuel Cell Control System - Google Patents

Abstract

A fuel cell control system is provided that can control the power generated by a fuel cell in accordance with the composition of fuel gas while reducing costs.
[Solution] A fuel cell control system 10 includes a plurality of fuel cell systems 11 which are supplied with fuel gas of the same composition and can communicate with each other, and each of the plurality of fuel cell systems 11 includes one parent unit 101 equipped with a fuel gas composition estimation unit 87 that estimates the composition of the fuel gas, and at least one child unit 102 which does not include the fuel gas composition estimation unit 87, and the parent unit 101 controls the power generated by the fuel cell 21 based on the fuel gas composition estimated by the fuel gas composition estimation unit 87 and transmits the fuel gas composition estimated by the fuel gas composition estimation unit 87 to the child unit 102, and the child unit 102 controls the power generated by the fuel cell 21 based on the fuel gas composition received from the parent unit 101.
[Selected Figure] Figure 1

Description

The present invention relates to a fuel cell control system.

Conventionally, fuel cell systems that use city gas as fuel gas (sometimes called raw fuel gas) are known. Such fuel cell systems are configured to generate power by generating reformed gas in a reformer from city gas, which is the fuel gas, and water, and supplying the generated reformed gas to a fuel cell. Since the power generated by a fuel cell (generated power) varies depending on the composition and supply amount (flow rate per unit time) of the fuel gas, in order to obtain the desired generated power from the fuel cell, it is necessary to control the supply amount according to the composition of the fuel gas.

City gas, which is a commercial gas, is generally managed so that its composition is constant, and there is little variation in its components. However, there can be regional differences (differences due to the supplier) in the composition of city gas. Also, in recent years, there has been a trend toward relaxing regulations on the calorific value of fuel gas, and as a result, there is also a trend toward relaxing controls on the composition of fuel gas. Furthermore, from the perspective of carbon neutrality, there have been proposals to reduce the amount of hydrocarbon gas mixed into the fuel gas by mixing it with hydrogen gas. In this way, it is expected that the composition of fuel gas used in fuel cell systems will become increasingly diverse.

As fuel gas compositions become more diverse, in order to obtain the desired power generation from a fuel cell system, it is necessary to control the fuel cell according to the composition of the fuel gas supplied. In this case, the fuel cell cogeneration system needs to be configured so that it can estimate (detect) the composition of the fuel gas. For example, Patent Document 1 discloses a fuel cell cogeneration system that is equipped with a thermal flow meter and a composition-independent flow meter and estimates the composition of the fuel gas by utilizing the difference between the outputs of these meters.

International Publication No. 2013/111777

(Problem to be solved by the invention)
However, in order to estimate the composition of the fuel gas, sensors and devices such as a thermal flow meter and a composition-independent flow meter are required, as in the fuel cell cogeneration system described in Patent Document 1. Therefore, such a configuration increases the number of parts of the fuel cell cogeneration system and the number of manufacturing steps, resulting in an increase in price.

The present invention has been made in consideration of the above-mentioned circumstances. One of the objects of the present invention is to provide a fuel cell control system that can control a fuel cell according to the composition of the fuel gas while suppressing the increase in material costs and manufacturing costs that would be caused by adding a mechanism for estimating the composition of the fuel gas.

(Means for solving the problem)
In order to achieve the above object, a fuel cell control system according to the present invention comprises:
A fuel cell system is provided with a plurality of fuel cell systems that are supplied with fuel gas having the same composition and can communicate with each other;
the plurality of fuel cell systems each include one parent unit having a fuel gas composition estimation unit configured to estimate a composition of the fuel gas to be supplied, and one or more child units not having the fuel gas composition estimation unit;
the parent unit includes a fuel cell that generates power from the supplied fuel gas, and is configured to control the power generated by the fuel cell based on the composition of the fuel gas estimated by the fuel gas composition estimation unit, and to transmit the composition of the fuel gas estimated by the fuel gas composition estimation unit to the child unit;
The slave unit includes a fuel cell that generates power using the supplied fuel gas, and is configured to control the power generated by the fuel cell based on the composition of the fuel gas received from the master unit.

According to the present invention, the slave unit can control the power generated by the fuel cell (hereinafter, sometimes referred to as "generated power") based on the composition of the fuel gas received from the master unit. Therefore, the slave unit can appropriately control the generated power of the fuel cell according to the composition of the fuel gas even without having a fuel gas composition estimation unit. And because the slave unit does not have a fuel gas composition estimation unit, it is possible to reduce the number of parts and manufacturing man-hours of the slave unit. This makes it possible to reduce the cost of the slave unit. And by reducing the cost of the slave unit, it is possible to reduce the cost of multiple fuel cell systems included in the fuel cell control system.

the parent unit and the child unit each include a fuel gas blower that supplies the fuel gas to the fuel cell, and a power generation map that defines a relationship between the power generated by the fuel cell and an output of the fuel gas blower for each composition of the fuel gas,
the parent unit controls an output of the fuel gas blower using the power generation map corresponding to the composition of the fuel gas estimated by the fuel gas composition estimation unit;
the slave unit controls the output of the fuel gas blower using the power generation map corresponding to the composition of the fuel gas received from the master unit.
The following configuration can be applied.

With this configuration, the power generation of the fuel cell can be controlled by controlling the output of the fuel gas blower according to the composition of the fuel gas using a power generation map that specifies the relationship between the power generation and the output of the fuel gas blower for each fuel gas composition. Furthermore, by providing each fuel cell system with its own power generation map, the power generation of the fuel cell can be appropriately controlled according to the performance and composition of the fuel cell provided in each fuel cell system.

when the composition of the fuel gas estimated by the fuel gas composition estimation unit changes, the parent unit changes the power generation map in accordance with the changed composition of the fuel gas and transmits the changed composition of the fuel gas to the child unit;
when the slave unit receives the composition of the fuel gas from the master unit, the slave unit changes the power generation map based on the received composition of the fuel gas.
The following configuration can be applied.

With this configuration, if the composition of the fuel gas changes, the parent and child units can control the output of the fuel gas blower (i.e., the power generated by the fuel cell) according to the changed composition of the fuel gas.

when the composition of the fuel gas estimated by the fuel gas composition estimation unit changes, the parent unit calculates a parent unit difference which is a difference between an output of the fuel gas blower for obtaining a predetermined generated power from the fuel gas before the composition changes and an output of the fuel gas blower for obtaining the predetermined generated power from the fuel gas after the composition changes, and transmits the calculated parent unit difference to the child unit;
The slave unit calculates a slave unit difference, which is the difference between the output of the fuel gas blower for obtaining a specified generated power from the fuel gas of a composition before receiving the parent unit difference from the parent unit and the output of the fuel gas blower for obtaining the specified generated power from the fuel gas of a composition after receiving the parent unit difference from the parent unit, and determines that there is a possibility that an abnormality has occurred in the slave unit if a ratio of the slave unit difference to the parent unit difference is equal to or greater than a specified threshold value.
The following configuration can be applied.

With this configuration, the slave unit can determine whether or not an abnormality has occurred in the fuel cell. In this case, there is no need for a device or sensor to detect the abnormality.

the parent unit has a specific operation mode in which the power generated by the fuel cell is equal to or greater than a predetermined threshold and the power generated by the fuel cell is not changed, and when in the specific operation mode, calculates the parent unit difference and transmits the calculated parent unit difference to the child unit;
The following configuration can be applied.

With this configuration, the parent unit can calculate the parent unit difference when the power generated by the parent unit's fuel cell is large and stable, which improves the accuracy of the calculation of the parent unit difference. This improves the accuracy of detecting abnormalities in the child unit.

the slave unit has a specific operation mode in which the power generated by the fuel cell is equal to or greater than a predetermined threshold and the power generated by the fuel cell is not changed, and calculates the slave unit difference when the slave unit is in the specific operation mode;
The following configuration can be applied.

With this configuration, the child unit difference can be calculated when the power generated by the child unit's fuel cell is large and stable, improving the accuracy of the calculation of the child unit difference. This improves the accuracy of detecting abnormalities in the child unit.

FIG. 1 is a schematic diagram showing the configuration of a fuel cell control system. FIG. 2 is a diagram showing the configuration of the parent device. FIG. 3 is a diagram showing the configuration of the slave unit. FIG. 4 is a flowchart showing the control executed by the control device of the parent unit. FIG. 5A is a flowchart showing the control executed by the control device of the child device. FIG. 5B is a flowchart showing the control executed by the control device of the child device.

(Overall configuration of fuel cell control system)
FIG. 1 is a diagram showing the overall configuration of a fuel cell control system 10. As shown in FIG. 1, the fuel cell control system 10 includes a fuel cell cogeneration system 11 as a plurality of fuel cell systems. The plurality of fuel cell cogeneration systems 11 include one parent unit 101 and other child units 102. The plurality of fuel cell cogeneration systems 11 included in one fuel cell control system 10 are configured to be able to transmit and receive data via a network 12. In particular, the parent unit 101 is configured to be able to transmit predetermined data to the child units 102, which will be described later, and the child units 102 are configured to be able to receive the predetermined data transmitted by the parent unit 101. The network 12 is a communication network that allows data to be transmitted and received between the plurality of fuel cell cogeneration systems 11. For example, a WAN or a LAN can be applied to the network 12. However, the specific form of the network 12 is not particularly limited. The network 12 may be wired or wireless. The network 12 may utilize the Internet.

Each fuel cell cogeneration system 11 is configured to receive fuel gas from a commercial fuel gas supply source 13. The fuel gas supplied from the commercial fuel gas supply source 13 may be, for example, city gas. All fuel cell cogeneration systems 11 included in one fuel cell control system 10 are configured to receive fuel gas of the same composition. For example, the fuel cell cogeneration system 11 included in the fuel cell control system 10 according to this embodiment may be configured as follows.
A plurality of fuel cell cogeneration systems 11 installed in each block (each unit) of a single apartment building (an apartment building receiving fuel gas from a single fuel gas supply source 13).
A plurality of fuel cell cogeneration systems 11 installed in an area receiving fuel gas from a single same fuel gas supply source 13

The number of fuel cell cogeneration systems 11 included in one fuel cell control system 10 is not particularly limited. The number of child units 102 may be one or two or more. Furthermore, the geographical or physical range of one fuel cell control system 10 is not particularly limited. In short, the multiple fuel cell cogeneration systems 11 included in one fuel cell control system 10 need only be configured to be able to send and receive data to each other via the network 12 and to be supplied with fuel gas of the same composition.

(Configuration of fuel cell cogeneration system)
Next, a description will be given of the configuration of the fuel cell cogeneration system 11 included in the fuel cell control system 10. Fig. 2 is a diagram showing the configuration of a parent unit 101 of the multiple fuel cell cogeneration systems 11 included in the fuel cell control system 10, and Fig. 3 is a diagram showing the configuration of a child unit 102.

As shown in Figures 2 and 3, the fuel cell cogeneration system 11 includes a power generation module 20, a fuel gas supply system 30, a reflux system 40, a reforming water supply system 50, an air supply system 60, an exhaust heat recovery system 70 (sometimes referred to as a hot water supply system), a power conditioner 83, a power supply unit 84, a control device 85, and a hot water tank 86. Furthermore, the parent unit 101 includes a fuel gas composition estimation unit 87. On the other hand, the child unit 102 does not include a fuel gas composition estimation unit 87.

The power generation module 20 includes a fuel cell 21, a carburetor 22, a reformer 23, and an ignition plug 24. The fuel cell 21, the carburetor 22, the reformer 23, and the ignition plug 24 are disposed inside a module case 25 formed from a thermal insulating material.

The fuel cell 21 of the power generation module 20 is a solid oxide fuel cell in this embodiment, but may be another type of fuel cell, such as a solid polymer fuel cell. The fuel cell 21 has a cell stack composed of a plurality of stacked cells. Each cell constituting the cell stack has an anode electrode, a cathode electrode, and a solid electrolyte such as zirconium oxide sandwiched between the anode electrode and the cathode electrode. An anode gas path for circulating anode gas is provided on the anode electrode side of each cell so as to extend in a direction perpendicular to the stacking direction of each cell. An air path for circulating air, which is a cathode gas, is provided on the cathode electrode side of each cell so as to extend in a direction perpendicular to the stacking direction of each cell. When anode gas is supplied to the anode gas path of each cell and air, which is a cathode gas, is supplied to the air path of each cell, the anode gas reacts with oxygen in the cathode gas. This reaction causes the fuel cell 21 to generate electricity and output DC power.

The cell stack of the fuel cell 21 is placed on the manifold 26. The manifold 26 has an anode gas path and an air path (not shown). The anode gas path of the manifold 26 is connected to the anode gas supply path 28 and the anode gas path of each cell. The anode gas path of the manifold 26 is configured so that the anode gas supplied from the reformer 23 through the anode gas supply path 28 can be supplied to the anode gas path of each cell. The air path of the manifold 26 is connected to the air path of each cell of the cell stack and the air supply path 61 of the air supply system 60. The air path of the manifold 26 is configured so that the air supplied through the air supply path 61 can be supplied to the air path of each cell.

The vaporizer 22 and the reformer 23 are disposed above the cell stack of the fuel cell 21 and spaced apart from the cell stack. A combustion section 27 is provided between the cell stack and the vaporizer 22 and the reformer 23. The combustion section 27 is an area for burning anode gas (hereinafter referred to as "anode off-gas") that has not been used in power generation (electrochemical reaction) in the cell stack. An ignition plug 24 for igniting the anode off-gas is disposed in the combustion section 27.

The inlet of the vaporizer 22 is connected to the fuel gas supply path 31 of the fuel gas supply system 30 and the reforming water supply path 53 of the reforming water supply system 50. The outlet of the vaporizer 22 is connected to the inlet of the reformer 23. The vaporizer 22 is configured to preheat the fuel gas supplied thereto with heat generated by combustion of the anode off-gas in the combustion section 27, and to heat the reforming water supplied thereto through the reforming water supply path 53 to generate water vapor.

The reformer 23 is configured to generate an anode gas containing hydrogen from the fuel gas and water vapor. In this embodiment, the anode gas refers to the gas generated in the reformer 23. The reformer 23 has, for example, a Ru-based or Ni-based reforming catalyst. When the fuel gas and water vapor are supplied from the vaporizer 22 to the inside of the reformer 23, hydrogen gas and carbon monoxide are generated by a water vapor reforming reaction between the fuel gas and the water vapor. Furthermore, hydrogen gas and carbon dioxide are generated by a carbon monoxide shift reaction between the generated carbon monoxide and the water vapor. Therefore, the anode gas generated in the reformer 23 contains hydrogen, carbon monoxide, and carbon dioxide. In addition to the anode gas, the gas discharged from the reformer 23 contains water vapor and fuel gas that did not contribute to the reforming reaction. The outlet of the reformer 23 is connected to an anode gas supply path 28 for supplying the generated anode gas containing hydrogen to the fuel cell 21. Therefore, the anode gas containing hydrogen produced in the reformer 23 can be supplied to the anode gas path on the anode electrode side of the fuel cell 21 through the anode gas supply path 28.

The fuel gas supply system 30 is configured to supply fuel gas (sometimes referred to as raw fuel gas) supplied from a fuel gas supply source 13 (a commercial gas supply source in this embodiment, more specifically, a city gas pipe) external to the fuel cell cogeneration system 11 to the vaporizer 22 of the power generation module 20. The fuel gas supply system 30 has a fuel gas supply path 31. One end of the fuel gas supply path 31 is connected to the vaporizer 22 of the power generation module 20, and the other end is configured to be connectable to an external fuel gas supply source 13. The fuel gas supply path 31 is provided with an inlet solenoid valve 32, an adjustment valve 33, a fuel gas blower 34, and a desulfurizer 35, in that order from the end configured to be connectable to the fuel gas supply source 13.

The inlet solenoid valve 32 is a valve (two-valve) that can open and close the fuel gas supply path 31. The inlet solenoid valve 32 is controlled to open and close by a control device 85 described later. The adjustment valve 33 is a valve for adjusting the internal pressure of the fuel gas supply path 31, and is configured to adjust the pressure of the fuel gas that flows from the fuel gas supply source 13 into the fuel gas supply path 31 and allow it to flow downstream (the side where the desulfurizer 35 and the fuel gas blower 34 are located). Specifically, the adjustment valve 33 is configured to open when the pressure downstream becomes equal to or lower than a predetermined negative pressure, and to close when the pressure becomes higher than the predetermined negative pressure.

The fuel gas blower 34 is controlled by a control device 85, which will be described later. The fuel gas blower 34 is configured to supply (pressure-feed) fuel gas (raw fuel gas) to the vaporizer 22 when it operates. The fuel gas blower 34 is configured to be able to change its output, and by changing the output, the amount of fuel gas supplied to the vaporizer 22 (amount supplied per unit time) can be changed.

The desulfurizer 35 is configured to remove sulfur compounds (i.e., sulfur components contained in the fuel gas) from the fuel gas. For example, a hydrodesulfurization type desulfurizer is applied to the desulfurizer 35. In this case, a catalyst and an ultra-high order desulfurizing agent are housed inside the desulfurizer 35. Hydrogen sulfide is generated by the reaction of hydrogen with the sulfur compounds contained in the fuel gas inside the desulfurizer 35 (i.e., in the presence of a catalyst). The ultra-high order desulfurizing agent captures the generated hydrogen sulfide. This removes the sulfur components from the fuel gas. For the catalyst, a nickel-molybdenum catalyst, a cobalt-molybdenum catalyst, or the like is used. For the ultra-high order desulfurizing agent, for example, a copper-zinc desulfurizing agent, a copper-zinc-aluminum desulfurizing agent, or the like is used.

Furthermore, a flow sensor 36, a pressure sensor 37, and a temperature sensor 38 are arranged between the desulfurizer 35 and the module case 25 of the fuel gas supply path 31. The flow sensor 36 is configured to detect the flow rate per unit time of the fuel gas flowing through the fuel gas supply path 31. The flow sensor 36 is a flow meter (mass flow meter) that has a dependency on the composition of the fluid to be detected, and for example, a thermal mass flow meter is used. The thermal mass flow meter utilizes the fact that the amount of heat that the fluid takes away from the thermal flow meter (heating element) is proportional to the mass flow rate of the fluid, and since the detection value is proportional to the mass flow rate of the fuel gas, the mass flow rate of the fuel gas can be measured based on the detection value. The pressure sensor 37 is configured to detect the pressure of the fuel gas (the internal pressure of the fuel gas supply path 31). The temperature sensor 38 is configured to detect the temperature of the fuel gas (the internal temperature of the fuel gas supply path 31). The configurations of the pressure sensor 37 and the temperature sensor 38 are not particularly limited, and known configurations can be applied. The detection results of the fuel gas flow rate by the flow sensor 36, the detection results of the fuel gas pressure by the pressure sensor 37, and the detection results of the fuel gas temperature by the temperature sensor 38 are continuously transmitted to the control device 85.

The reflux system 40 is configured to introduce a portion of the anode gas generated in the reformer 23 into the desulfurizer 35. Specifically, the reflux system 40 includes a reflux path 41. The reflux path 41 is a path for introducing the anode gas containing hydrogen generated in the reformer 23 into the desulfurizer 35. One end of the reflux path 41 is connected to the outlet side of the reformer 23. The other end of the reflux path 41 is connected to a portion between the fuel gas blower 34 and the adjustment valve 33 in the fuel gas supply path 31.

The air supply system 60 is configured to supply air, which is a cathode gas, to the fuel cell 21 (more precisely, to supply air to the air path of the manifold 26). The air supply system 60 has an air supply path 61, an air filter 62, an air blower 63, and an air flow meter 64. One end of the air supply path 61 is connected to the air path of the manifold 26. The other end of the air supply path 61 is connected to the outside air. The air filter 62 is provided at the other end of the air supply path 61. The air blower 63 and the air flow meter 64 are disposed on the air supply path 61. The air blower 63 is configured to operate under the control of the control device 85. The air blower 63 is configured to operate to draw air (outside air) into the air supply path 61 through the air filter 62 and supply (pressure-feed) the drawn air to the air path of the manifold 26. The air flow meter 64 is configured to measure the flow rate per unit time of air flowing through the air supply path 61 and transmit the measurement result to the control device 85.

The reforming water supply system 50 is configured to supply reforming water to the vaporizer 22. The reforming water supply system 50 includes a reforming water tank 51, a condensed water path 52, a reforming water supply path 53, and a reforming water pump 54. The condensed water path 52 is connected to the exhaust gas path of the heat exchanger 73 at one end, and to the reforming water tank 51 at the other end. As a result, the condensed water generated in the heat exchanger 73 flows into the reforming water tank 51 through the condensed water path 52. The reforming water tank 51 is configured to store the condensed water that flows in through the condensed water path 52 as reforming water. Note that a water purifier (not shown) for purifying the stored reforming water is disposed inside the reforming water tank 51. The reforming water supply path 53 is connected to the reforming water tank 51 at one end, and to the vaporizer 22 at the other end. The reforming water pump 54 is disposed on the reforming water supply path 53. When the reforming water pump 54 operates, it supplies (pressure-feeds) the reforming water stored inside the reforming water tank 51 to the vaporizer 22 through the reforming water supply path 53.

The exhaust heat recovery system 70 has a circulation path 71, a circulation pump 72, and a heat exchanger 73. The circulation path 71 is connected to the hot water storage tank 86 and the heat exchanger 73, and is configured to circulate hot water between the hot water storage tank 86 and the heat exchanger 73. The circulation pump 72 is configured to operate under the control of the control device 85 to supply hot water in the hot water storage tank 86 to the heat exchanger 73, and to return hot water that has been heat exchanged with the combustion exhaust gas in the heat exchanger 73 (i.e., heated hot water) to the hot water storage tank 86. The heat exchanger 73 has a path (exhaust gas path) for the combustion exhaust gas discharged from the module case 25, and is configured to exchange heat between the hot water flowing through the circulation path 71 and the combustion exhaust gas discharged from the module case 25. The hot water storage tank 86 is configured to store hot water. In addition to the circulation path 71, a water supply path for receiving a supply of water from the outside and a hot water supply path for supplying hot water to the outside are connected to the hot water storage tank 86. In addition, a combustion catalyst 74 (also called a purification catalyst) is arranged on the path of the combustion exhaust gas from the module case 25 to the heat exchanger 73. Unburned combustible components contained in the combustion exhaust gas are removed by catalytic combustion in the combustion catalyst 74. Furthermore, the exhaust gas path of the heat exchanger 73 is connected to a chimney 82 via an exhaust path 81.

The power conditioner 83 is configured to convert the DC power output from the fuel cell 21 into an AC voltage of a predetermined voltage and output it. The power conditioner 83 is controlled by a control device 85. The power conditioner 83 has a DC/DC converter and an inverter (not shown). The DC/DC converter is electrically connected to the fuel cell 21 and boosts the DC power output from the fuel cell 21 to a predetermined voltage. The inverter converts the DC power output from the DC/DC converter into AC power. The output terminal of the power conditioner 83 is configured to be connectable to a power wiring connected to a system power source 91 (a power source supplied from a commercial power distribution network). Then, when the power conditioner 83 is connected to the system power source 91, the fuel cell cogeneration system 11 can convert the DC power generated in the fuel cell 21 into AC power and supply it to a power load 92 such as a home appliance.

The power supply device 84 converts the AC power supplied from the system power supply 91 and the power conditioner 83 into DC power and supplies it to each part (each auxiliary device) of the fuel cell cogeneration system 11, such as the control device 85, the inlet solenoid valve 32, the fuel gas blower 34, and the air blower 63. The power supply device 84 has an AC/DC converter that converts the AC power supplied from the system power supply 91 into DC power.

The control device 85 has a computer having a CPU, a ROM, a RAM, a storage medium other than the ROM, and an I/F. The control device 85 is connected to the inlet solenoid valve 32, the flow sensor 36, the pressure sensor 37, the temperature sensor 38, the fuel gas blower 34, the air flow meter 64, the air blower 63, the ignition plug 24, the reforming water pump 54, the circulation pump 72, and the power conditioner 83 via the I/F. The control device 85 acquires the detection result of the fuel gas flow rate by the flow sensor 36, the detection result of the fuel gas pressure by the pressure sensor 37, the detection result of the fuel gas temperature by the temperature sensor 38, and the detection result of the air flow rate by the air flow meter 64, and controls the inlet solenoid valve 32, the fuel gas blower 34, the air blower 63, the ignition plug 24, the reforming water pump 54, the circulation pump 72, and the power conditioner 83. The control device 85 is also connected to the network 12 via the I/F. The control device 85 can then transmit and receive specific data to and from the control devices 85 of other fuel cell cogeneration systems 11 via the network 12.

The ROM of the computer of the control device 85 stores in advance a computer program and predetermined data for controlling each part of the fuel cell cogeneration system 11. The CPU of the computer of the control device 85 reads this computer program from the ROM, expands it into the RAM (using the RAM as a work area) and executes it. At this time, the CPU reads and references the predetermined data stored in the ROM and the storage medium as appropriate. This controls the fuel cell cogeneration system 11 and realizes the operations described below.

Now, we will explain how to estimate the composition of the fuel gas. In this embodiment, the control device 85, the flow sensor 36, the pressure sensor 37, and the temperature sensor 38 function as a fuel gas composition estimation unit 87 that estimates the composition of the fuel gas. Also, in this embodiment, the fuel gas composition estimation unit 87 estimates the valence V and carbon number C of the fuel gas as the composition of the fuel gas.

The control device 85 continuously acquires the flow rate of the fuel gas detected by the flow rate sensor 36, and calculates a flow rate moving average Vf, which is a moving average of the acquired flow rate of the fuel gas. The control device 85 also continuously acquires the pressure of the fuel gas detected by the pressure sensor 37, and calculates a pressure moving average P, which is a moving average based on the acquired pressure of the fuel gas. The control device 85 continuously acquires the temperature of the fuel gas detected by the temperature sensor 38, converts the pressure detected by the pressure sensor 37 to 0°C (0°C correction) using the temperature detected by the temperature sensor 38, calculates the square root of the 0°C converted pressure, and calculates the moving average of the square root, thereby calculating the pressure moving average P. The control device 85 then calculates the actual mass flow rate F of the fuel gas using the following formula (1) based on the flow rate moving average Vf, the pressure moving average P, and the temperature sensor 38 average value T.

F = Vf x [a x (P / 1013.25) + b x (T / 273.15) + c] Formula (1)

In formula (1), "a" and "b" are coefficients, and "c" is a constant. The control device 85 calculates the hydrogen valence n corresponding to the composition of the fuel gas using the following formulas (2) to (4) based on the calculated actual mass flow rate F, flow rate moving average Vf, and pressure moving average P, and calculates the carbon number m corresponding to the composition of the fuel gas based on the actual mass flow rate F, flow rate moving average Vf, and pressure moving average P. In formulas (2), (3), and (4), "d", "e", "f", "g", "h", and "i" are coefficients.

CmHn + d × _H2O → e × _CH4 + f × _H2 + g × CO + h × _CO2 + i × _H2O Formula (2)
m = e + g + h Equation (3)
n = 4 × e + 2 × f - 2 × (d - i) Equation (4)

Since the flow sensor 36 is dependent on the composition of the fluid to be detected, the calculated actual mass flow rate F contains a component corresponding to the mass flow rate of the fuel gas and a component corresponding to the composition of the fuel gas (valence, carbon number), and the actual mass flow rate F is expressed as the product of both components. Therefore, by dividing the flow rate moving average Vf and pressure moving average P corresponding to the mass flow rate of the fuel gas by the actual mass flow rate F, the influence of the mass flow rate of the fuel gas can be removed from the obtained divided values Vf/F and P/F, and the composition of the fuel gas (hydrogen valence, carbon number) can be estimated based on the divided values Vf/F and P/F.

The configuration of the fuel gas composition estimation unit 87 that estimates the fuel gas composition and the method of estimating the fuel gas composition are not limited to the above configuration and method. For example, as configurations and methods for estimating the fuel gas composition, the configurations and methods described in International Publication No. 2013/11777, Japanese Patent Application Publication No. 2013-20705, and Japanese Patent Application Publication No. 2006-140103 can be applied. In short, it is sufficient for the fuel gas composition estimation unit 87 to be able to estimate the fuel gas composition (in this embodiment, the valence V and the carbon number C).

(Outline of operation of each fuel cell cogeneration system)
Next, an overview of the operation of the fuel cell cogeneration system 11 will be described. When the control device 85 controls the fuel gas blower 34 to operate the fuel gas blower 34, a portion of the fuel gas supply path 31 between the regulating valve 33 and the fuel gas blower 34 becomes negative pressure. This causes the regulating valve 33 to open, and fuel gas is supplied from the external fuel gas supply source 13 to the desulfurizer 35 through the fuel gas supply path 31. Furthermore, due to the operation of the fuel gas blower 34, anode gas containing hydrogen is supplied to the desulfurizer 35 through the return path 41 and the fuel gas supply path 31.

The fuel gas desulfurized in the desulfurizer 35 flows into the vaporizer 22. In addition, reforming water stored in the reforming water tank 51 is supplied to the vaporizer 22 by the operation of the reforming water pump 54. The fuel gas preheated in the vaporizer 22 and the generated water vapor are mixed together to form a mixed gas, which flows into the reformer 23. Then, in the reformer 23, the mixed gas of the fuel gas and the water vapor reacts to generate anode gas containing hydrogen.

The anode gas generated in the reformer 23 is supplied to the anode gas supply path 28, the anode gas path of the manifold 26, and the anode gas path provided on the anode electrode side of each cell of the fuel cell 21. Meanwhile, air (cathode gas) is supplied to the air path provided on the cathode electrode side of each cell of the fuel cell 21 via the air supply path 61 and the air path of the manifold 26 by operation of the air blower 63 of the air supply system 60. Then, oxide ions (O ₂ ⁻ ) are generated at the cathode electrode of each cell, and the generated oxide ions permeate the solid electrolyte and react with hydrogen and carbon monoxide in the anode gas at the anode electrode to generate DC power. The obtained DC power is output to the power conditioner 83.

The anode gas (hereinafter referred to as "anode off-gas") and air (hereinafter referred to as "cathode off-gas") that are not used for power generation (electrochemical reaction) in the cell stack of the fuel cell 21 flow out of the fuel cell 21 through the anode gas path and air path of each cell. The anode off-gas that flows out of the fuel cell 21 through the anode gas path of each cell and the cathode gas that flows out of the fuel cell 21 through the air path of each cell are mixed in the combustion section 27. The anode off-gas is then combusted in the combustion section 27. The combustion of the anode off-gas generates heat required for the operation of the fuel cell 21, the preheating of the fuel gas and the generation of steam in the vaporizer 22, and the steam reforming reaction in the reformer 23.

As the anode off-gas is burned, combustion exhaust gas containing water vapor is generated in the combustion section 27. The moisture in the generated combustion exhaust gas is removed by the heat exchanger 73. The fuel exhaust gas from which the moisture has been removed is discharged into the atmosphere via the exhaust path 81 and the chimney 82.

A portion of the anode gas generated in the reformer 23 flows into the fuel gas supply path 31 through the reflux path 41 and is introduced into the desulfurizer 35 together with the fuel gas. Specifically, the reflux path 41 is connected to a portion of the fuel gas supply path 31 between the fuel gas blower 34 and the adjustment valve 33. Therefore, when the fuel gas blower 34 operates to create a negative pressure in the fuel gas supply path 31, a portion of the anode gas generated in the reformer 23 is sucked into the reflux path 41 and flows into the fuel gas supply path 31. The anode gas that flows into the fuel gas supply path 31 is mixed with the fuel gas and supplied to the desulfurizer 35. Then, in the desulfurizer 35, the sulfur compounds contained in the fuel gas react with the hydrogen contained in the anode gas to generate hydrogen sulfide, and the generated hydrogen sulfide is removed by the ultra-high-order desulfurizing agent. Therefore, the fuel gas desulfurized in the desulfurizer 35 is supplied to the vaporizer 22 and the reformer 23.

Each fuel cell cogeneration system 11 has two operating modes: a rated mode and a load following mode. The rated mode is an operating mode in which a predetermined constant power (rated power) is continuously generated. For example, when operating in the rated mode, each fuel cell cogeneration system 11 continuously generates 0.7 kW of power regardless of the amount of power consumed by the power load 92. In this case, if the power consumed by the power load 92 is greater than the rated power, the control device 85 receives power from the system power source 91 to make up for the shortage.

The load following mode is an operating mode in which the power generated by the power generation module 20 is controlled to follow the power consumption by the power load 92. Specifically, in a range in which the power consumption by the power load 92 does not exceed the maximum power generated by the power generation module 20, the control device 85 controls the power generated by the power generation module 20 so that the power generated by the power generation module 20 follows the power consumption by the power load 92. On the other hand, when the power consumption by the power load 92 exceeds the maximum power generated by the power generation module 20, the control device 85 controls the power generated by the power generation module 20 so that the power generated by the power generation module 20 is maximized, and receives power from the system power source 91 to make up for the shortage of power.

The load following mode includes a normal mode and a high efficiency mode. The normal mode is an operation mode in which the power consumption of the power load 92 does not exceed the maximum power generated by the power generation module 20. In the normal mode, the control device 85 controls the power generated by the power generation module 20 so that the power generated by the power generation module 20 follows the power consumption by the power load 92. For this reason, in the normal mode, the power generated by the power generation module 20 is likely to change over time. The high efficiency mode is an operation mode in which a constant power generation is continuously generated at or above a predetermined threshold, for example, when the power consumption of the power load 92 exceeds the maximum power generation (rated power) by the power generation module 20. In the high efficiency mode, the power generation is larger and the change in the power generation over time is smaller (or there is no change) than in the normal mode. In other words, the high efficiency mode is an operation mode in which the power generation is equal to or above a predetermined threshold and is almost constant.

The power generated by the power generation module 20 is determined by the composition of the fuel gas and the amount (flow rate) of fuel gas supplied to the power generation module 20 per unit time. The control device 85 of the parent unit 101 estimates the composition of the fuel gas using the fuel gas composition estimation unit 87 so as to obtain the required power generation, and controls the flow rate (amount supplied per unit time) of the fuel gas supplied to the power generation module 20 according to the estimated fuel gas composition.

The composition of city gas, which is a commercial gas, is generally managed to be constant, and there is little variation in the composition. However, there may be regional differences (differences depending on the supplier) in the composition of city gas. In addition, in recent years, there has been a trend toward easing regulations on the calorific value of fuel gas, and therefore, management of the composition of fuel gas is also likely to be relaxed. Furthermore, from the perspective of carbon neutrality, there has been a proposal to reduce the amount of hydrocarbon gas mixed by mixing hydrogen gas into the fuel gas. Thus, it is expected that the composition of the fuel gas used in the fuel cell cogeneration system 11 will become more diverse. For this reason, the composition of the fuel gas is continuously estimated (in other words, the composition of the fuel gas is continuously monitored), and when the composition of the fuel gas changes, the power generated by the power generation module 20 is controlled according to the changed composition of the fuel gas.

Specifically, the storage medium of the computer of the control device 85 stores in advance a power generation map in which the output of the fuel blower for obtaining a predetermined power generation is specified for each fuel gas composition (in other words, according to the fuel gas composition). It can also be said that this power generation map is a map in which the relationship between the power generation and the output of the fuel blower is specified according to the fuel gas composition. In this embodiment, the power generation map specifies the output ratio (ratio of output to maximum output) of the fuel gas blower 34 as a parameter for controlling the fuel blower. Hereinafter, this ratio may be referred to as the duty ratio. Furthermore, the storage medium of the computer of the control device 85 stores a predetermined fuel gas composition. Then, both the parent unit 101 and the child unit 102 of the fuel cell cogeneration system 11 control the power generation by the power generation module 20 using the fuel gas composition and the power generation map stored in advance immediately after being put into use (for example, immediately after being installed and starting operation for the first time). In this way, in this embodiment, the control device 85 controls the power generation by the power generation module 20 by controlling the output of the fuel gas blower 34.

When the control device 85 of the parent unit 101 starts operation, it continuously estimates the fuel gas composition (in other words, it constantly monitors the fuel gas composition), and if the fuel gas composition changes, it changes the power generation map used to control the fuel gas blower 34 to a power generation map corresponding to the changed fuel gas composition. Furthermore, if the fuel gas composition estimation unit 87 of the parent unit 101 detects that the fuel gas composition has changed, it transmits the changed fuel gas composition to each child unit 102 via the network 12.

On the other hand, the child unit 102 does not have a fuel gas composition estimation unit 87, and therefore cannot estimate the composition of the fuel gas. Therefore, the control device 85 of the child unit 102 controls the output of the fuel gas blower 34 based on the composition of the fuel gas received from the parent unit 101. Specifically, when the control device 85 of the child unit 102 receives the composition of the fuel gas from the parent unit 101 (i.e., when the composition of the fuel gas has changed), it changes the power generation map to one that corresponds to the composition of the received fuel gas. Then, the control device 85 of the child unit 102 controls the output of the fuel gas blower 34 using the selected power generation map, thereby controlling the power generated by the power generation module 20. With this configuration, even the child unit 102 that does not have a fuel gas composition estimation unit 87 can control the output of the fuel gas blower 34 according to the composition of the fuel gas.

Note that there may be individual differences in the performance (characteristics) of the power generation module 20. In addition, the performance of the power generation module 20 may change over time due to aging and the like. For this reason, the control device 85 of each fuel cell cogeneration system 11 in both the parent unit 101 and the child unit 102 continuously monitors the actual power generated by the power generation module 20 and the actual output of the fuel gas blower 34. Then, when the relationship between the actual power generation and the actual output of the fuel gas blower 34 deviates from the relationship between the power generation and the duty ratio specified in the power generation map, the control device 85 of each fuel cell cogeneration system 11 corrects the contents of the power generation map. For this reason, the contents of the power generation map of each fuel cell cogeneration system 11 change with continued use. Therefore, the contents of the power generation map (specific values of the duty ratio) provided by the computer of the control device 85 of each fuel cell cogeneration system 11 included in one fuel cell control system 10 may differ for each fuel cell cogeneration system 11.

When the control device 85 of the parent unit 101 detects a change in the composition of the fuel gas, it calculates the difference Δτp between the duty ratio for obtaining a specified generated power before the change in the composition of the fuel gas and the duty ratio for obtaining the same specified generated power after the change in the composition of the fuel gas. Hereinafter, this difference may be referred to as the parent unit difference Δτp.

Then, the control device 85 of the parent unit 101 transmits the calculated parent unit difference Δτp together with the changed fuel gas composition to each child unit 102 via the network 12. When the control device 85 of each child unit 102 receives the changed fuel gas composition and the parent unit difference Δτp from the parent unit 101, it calculates the difference Δτc between the duty ratio of the child unit for obtaining a specified generated power before reception and the duty ratio of the child unit for obtaining a specified generated power in accordance with the received fuel gas composition. This difference may be referred to as the child unit difference Δτc below. Furthermore, the control device 85 of the child unit 102 calculates the degree of deviation between the received parent unit difference Δτp and the calculated child unit difference Δτc. For example, the control device 85 of the child unit 102 calculates the following deviation rate E

Deviation rate E = (child unit difference Δτc) / (parent unit difference Δτp) × 100 (%)

Calculate the following.

As described above, the parent unit 101 and the child unit 102 are supplied with fuel gas of the same composition, so if the composition of the fuel gas changes, it is expected that the parent unit difference Δτp and the child unit difference Δτc will be close to each other. For this reason, if the child unit 102 is normal, it is expected that the deviation rate E will be close to 100%. On the other hand, if an abnormality has occurred in the child unit 102, it is expected that this deviation rate E will be a value far from 100%. Therefore, if the deviation rate E is not within a predetermined range that has been specified in advance, the control device 85 of the child unit 102 determines that there is a possibility that an abnormality has occurred in the child unit 102.

In this embodiment, the control device 85 of the child device 102 calculates the deviation rate E each time the composition of the fuel gas changes (i.e., each time the composition of the fuel gas and the parent device difference Δτp are received from the parent device 101). Then, the control device 85 of the child device 102 determines that an abnormality has occurred in the child device 102 if the calculated deviation rate E is not within a predetermined range for a predetermined number of consecutive occurrences. Then, when the control device 85 of the child device 102 determines that an abnormality has occurred, it executes a predetermined control. In this embodiment, the control device 85 of the child device 102 stops power generation by the power generation module 20. With this configuration, an abnormality in the child device 102 can be detected without adding a separate device for detecting the abnormality.

The relationship between the generated power and the duty ratio is more stable as the generated power is larger and the temporal fluctuation of the generated power is smaller. Therefore, in this embodiment, the control device 85 of the parent unit 101 calculates the parent unit difference Δτp when the operation mode is the high efficiency mode of the load following mode. Similarly, the control device 85 of the child unit 102 calculates the child unit difference Δτc when the operation mode is the high efficiency mode of the load following mode. Then, the control device 85 of the child unit 102 uses the parent unit difference Δτp and the child unit difference Δτc to determine whether an abnormality has occurred in the child unit 102. This configuration can improve the accuracy of abnormality determination.

According to this embodiment, the child unit 102 controls the generated power based on the composition of the fuel gas received from the parent unit 101 (controls the output of the fuel gas blower 34), so the child unit 102 does not need to be equipped with a fuel gas composition estimation unit 87. This allows the number of parts and manufacturing man-hours of the child unit 102 to be reduced, thereby reducing the cost of the child unit 102. In addition, since each fuel cell control system 10 only needs to include one parent unit 101, the number of parent units 101 manufactured can be reduced compared to the number of child units 102 manufactured. This allows the overall price of the multiple fuel cell cogeneration systems 11 included in the fuel cell control system 10 to be reduced (in other words, the price per unit of the multiple fuel cell cogeneration systems 11 included in one fuel cell control system 10 can be reduced).

Furthermore, according to this embodiment, the control device 85 of the child unit 102 determines whether or not an abnormality has occurred in the child unit 102 based on the ratio between the parent unit difference Δτp and the child unit difference Δτc. With this configuration, the occurrence of an abnormality can be detected even if each child unit 102 does not have a device or sensor for detecting the abnormality. Therefore, it is possible to provide a highly reliable fuel cell cogeneration system 11 while reducing the price (or preventing or suppressing price increases).

(Parent unit operation)
Next, a specific operation of the control device 85 of the parent unit 101 will be described. Fig. 4 is a flow chart showing a series of processes executed by the control device 85 of the parent unit 101. A computer program and a power generation map for executing this series of processes are stored in advance in a storage medium of the computer of the control device 85 of the parent unit 101. The control device 85 of the parent unit 101 repeatedly executes the series of processes shown in Fig. 4 at a predetermined short cycle.

In step S101, the control device 85 of the parent unit 101 acquires the detection result of the fuel gas flow rate by the flow rate sensor 36, the detection result of the fuel gas pressure by the pressure sensor 37, and the detection result of the fuel gas temperature by the temperature sensor 38, and estimates the fuel gas composition using the acquired detection results (the fuel gas composition estimation unit 87 estimates the current fuel gas composition). Then, the control device 85 of the parent unit 101 advances the process to step S102.

In step S102, the control device 85 of the parent unit 101 determines whether the composition of the fuel gas has changed. Specifically, the control device 85 compares the composition of the fuel gas stored in the storage medium (described later) with the composition of the fuel gas acquired in step S101. If the control device 85 of the parent unit 101 determines that the composition of the fuel gas has changed (if it determines that the composition of the fuel gas stored in the storage medium is different from the composition of the fuel gas acquired in step S101), it advances the process to step S103. On the other hand, if the control device 85 of the parent unit 101 determines that the composition of the fuel gas has not changed (if it determines that the composition of the fuel gas stored in the storage medium is the same as the composition of the fuel gas acquired in step S101), it advances the process to step S109.

In step S103, the control device 85 of the parent unit 101 sets the first flag value, which is a "variable indicating whether the composition of the combustion gas after the composition change and the parent unit difference Δτp have been transmitted or not transmitted to the child unit 102," to a value indicating that the "composition of the combustion gas after the composition change and the parent unit difference Δτp have not been transmitted" ("false" in this embodiment). Then, the control device 85 of the parent unit 101 proceeds to step S104.

In step S104, the control device 85 of the parent unit 101 changes the power generation map used to control the output of the fuel gas blower 34 from the power generation map used up until then to the power generation map corresponding to the fuel gas composition acquired in the immediately preceding step S101. The control device 85 of the parent unit 101 also stores the fuel gas composition acquired in the immediately preceding step S101 (i.e., the changed fuel gas composition) in the storage medium as the "currently supplied fuel gas composition". The control device 85 of the parent unit 101 then proceeds to step S105. The "currently supplied fuel gas composition" stored in the storage medium is used to determine whether the fuel gas composition has changed in the aforementioned step S102. The control device 85 of the parent unit 101 also controls the output of the fuel gas blower 34 using the changed power generation map until it is determined again in step S102 that the fuel gas composition has changed.

In step S105, the control device 85 of the parent unit 101 determines whether the current operation mode is the high efficiency mode of the load following mode. If the control device 85 of the parent unit 101 determines that the current operation mode is the high efficiency mode of the load following mode, the process proceeds to step S106. On the other hand, if the control device 85 of the parent unit 101 determines that the current operation mode is not the high efficiency mode of the load following mode, the control device 85 of the parent unit 101 ends this series of processes.

In step S106, the control device 85 of the parent unit 101 acquires the current duty ratio. This current duty ratio can also be said to be "the duty ratio when operating to generate a specified power in high efficiency mode of load following mode using the changed power generation map." The control device 85 of the parent unit 101 then calculates the parent unit difference Δτp, which is the difference between "the duty ratio when operating to generate a specified power in high efficiency mode of load following mode using the power generation map before the change" and this current duty ratio. The control device 85 of the parent unit 101 also stores the acquired current duty ratio in a storage medium. The control device 85 of the parent unit 101 then proceeds to step S107.

In step S107, the control device 85 of the parent unit 101 transmits the fuel gas composition acquired in step S101 and the parent unit difference Δτp calculated in step S107 to the control device 85 of the child unit 102 via the network 12. Then, the control device 85 of the parent unit 101 advances the process to step S108.

In step S108, the control device 85 of the parent unit 101 changes the first flag value to a value indicating that "the composition of the combustion gas after the composition change and the parent unit difference Δτp have been transmitted" ("True" in this embodiment). Then, the control device 85 of the parent unit 101 temporarily ends this series of processes.

When the control device 85 of the parent unit 101 determines in step S102 that the composition of the fuel gas has not changed, the process proceeds to step S109. In step S109, the control device 85 of the parent unit 101 determines whether the first flag value is a value indicating that "the composition of the combustion gas after the composition change and the parent unit difference Δτp have been transmitted." If the first flag value is a value indicating that "the composition of the combustion gas after the composition change and the parent unit difference Δτp have not been transmitted," the control device 85 of the parent unit 101 proceeds to step S105. On the other hand, if the first flag value is a value indicating that "the composition of the combustion gas after the composition change and the parent unit difference Δτp have been transmitted," the control device 85 of the parent unit 101 ends this series of processes.

In this way, the control device 85 of the parent unit 101 continuously acquires the composition of the fuel gas being supplied (step S101), and when it is determined that the composition of the fuel gas has changed ("Y" in step S102), it changes the power generation map used to control the output of the fuel blower to the power generation map corresponding to the fuel gas after the composition change (step S104). Furthermore, in this case, the control device 85 of the parent unit 101 determines whether the current operation mode is the high efficiency mode of the load following mode (step S105). Then, when the current operation mode is the high efficiency mode of the load following mode, the control device 85 of the parent unit 101 calculates the parent unit difference Δτp (step S106). Then, the control device 85 of the parent unit 101 transmits the changed composition of the fuel gas and the parent unit difference Δτp to the control device 85 of the child unit 102 via the network 12 (step S107).

Note that, after determining that the composition of the fuel gas has changed ("Y" in step S102), if the control device 85 of the parent unit 101 determines that the current operation mode is not the high-efficiency mode of the load following mode ("N" in step S105), it does not calculate the parent unit difference Δτp. In this case, after the composition of the fuel gas has changed ("Y" in step S102), the control device 85 of the parent unit 101 continues to determine whether the current operation mode is the high-efficiency mode of the load following mode ("Y" in step S102, and then "N" in step S102 and "N" in step S109) until it determines that the current operation mode is the high-efficiency mode of the load following mode ("Y" in step S105).

In addition, if the control device 85 of the parent unit 101 determines that the composition of the fuel gas has not changed ("N" in step S102 and "Y" in step S109), it does not change the power generation map used to control the fuel gas blower 34 and does not calculate the parent unit difference Δτp (does not transmit the power generation map and parent unit difference Δτp).

(Operation of child unit)
Next, a specific operation of the control device 85 of the slave unit 102 will be described. Figures 5A and 5B are flowcharts showing a series of processes executed by the control device 85 of the slave unit 102. A computer program and a power generation map for executing this series of processes are stored in advance in a computer storage medium of the control device 85 of the slave unit 102. The control device 85 of the slave unit 102 repeatedly executes the series of processes shown in Figures 5A and 5B at a predetermined short period.

In step S201, the control device 85 of the slave unit 102 determines whether or not it has received the fuel gas composition and master unit difference Δτp from the master unit 101. If the control device 85 of the slave unit 102 determines that it has received these, it proceeds to step S202. If the control device 85 of the slave unit 102 determines that it has not received these, it proceeds to step S213.

In step S202, the control device 85 of the child device 102 sets the second flag value, which is a "variable indicating whether or not it has been determined that an abnormality has occurred in the child device 102 based on the deviation rate E," to a value indicating that "the occurrence of an abnormality has not been determined" ("False" in this embodiment). Note that the initial value of this determined flag value is "True." The control device 85 of the child device 102 then proceeds to step S203.

In step S203, the control device 85 of the child device 102 changes the power generation map used to control the output of the fuel gas blower 34 from the power generation map currently being used to the power generation map received in step S201. The control device 85 of the child device 102 also stores the fuel gas composition received in step S201 in a storage medium as the "current (changed) fuel gas composition". The control device 85 of the child device 102 then advances the process to step S204. Note that from this point on, the control device 85 of the child device 102 continues to control the fuel gas blower 34 using the power generation map corresponding to the fuel gas of the received composition until the fuel gas composition is received again from the parent device 101 in step S201.

In step S204, the control device 85 of the child device 102 determines whether the current operation mode is the high efficiency mode of the load following mode. If the control device 85 of the child device 102 determines that the current operation mode is not the high efficiency mode of the load following mode, it ends this series of processes. If the control device 85 of the child device 102 determines that the current operation mode is the high efficiency mode of the load following mode, it advances the process to step S205.

In step S205, the control device 85 of the child device 102 acquires the current duty ratio. This current duty ratio can also be said to be "the duty ratio when operating to generate a predetermined power in high efficiency mode of load following mode using the changed power generation map". The control device 85 of the child device 102 then calculates the child device difference Δτc, which is the difference between "the duty ratio when operating to generate a predetermined power in high efficiency mode of load following mode using the power generation map before the change" and this current duty ratio. This child device difference Δτc can be said to be "the difference in duty ratio to obtain the same generated power before and after the change in the composition of the fuel gas". The control device 85 of the child device 102 also stores the acquired current duty ratio in a storage medium. The control device 85 of the child device 102 then proceeds to step S206.

In step S206, the control device 85 of the child unit 102 determines whether the deviation rate E (=(child unit difference Δτc)/(parent unit difference Δτp))×100), which is the ratio of the child unit difference Δτc calculated in step S205 to the parent unit difference Δτp received in step S201, is within a predetermined range. If the control device 85 of the child unit 102 determines that the deviation rate E is not within the predetermined range, it proceeds to step S207, and if it determines that the deviation rate E is within the predetermined range, it proceeds to step S210.

In step S207, the control device 85 of the child device 102 updates a counter variable that indicates the number of times that the deviation rate E is determined not to be within the predetermined range (by adding "1" to the counter variable). Then, the control device 85 of the child device 102 advances the process to step S208.

In step S208, the control device 85 of the child device 102 determines whether the value of the counter variable is equal to or greater than a predetermined threshold. In other words, the control device 85 of the child device 102 determines whether the "number of times it is determined that the deviation rate E is not within the predetermined range" has reached a predetermined number of times. If the counter variable is less than the predetermined threshold, the control device 85 of the child device 102 ends this series of processes, and if the value of the counter variable is equal to or greater than the predetermined threshold (has reached the predetermined threshold), the process proceeds to step S209.

In step S209, the control device 85 of the child device 102 stops power generation by the power generation module 20. The control device 85 of the child device 102 also executes a notification process to notify the user of the child device 102 that the child device 102 has stopped power generation. The control device 85 of the child device 102 then advances the process to step S210.

If the control device 85 of the child device 102 determines in step S206 that the deviation rate E is within the predetermined range, the process proceeds to step S210. In step S210, the control device 85 of the child device 102 clears the counter variable (sets the value to "0"). Then, the control device 85 of the child device 102 proceeds to step S211.

In step S211, the control device 85 of the child device 102 initializes the second flag value (changes the value to "True"). Then, the control device 85 of the child device 102 ends this series of processes.

In this way, when the control device 85 of the child unit 102 receives the fuel gas composition and difference from the parent unit 101, it changes the power generation map used to control the output of the fuel gas blower 34 to a power generation map corresponding to the fuel gas of the received composition.

Furthermore, after receiving the fuel gas composition and parent unit difference Δτp from the parent unit 101, the control device 85 of the child unit 102 judges whether an abnormality has occurred in the child unit 102 using the deviation rate E calculated from the parent unit difference Δτp and the child unit difference Δτc at the timing when the load following mode becomes high efficiency mode. Specifically, when the control device 85 of the child unit 102 receives the fuel gas composition and parent unit difference Δτp from the parent unit 101 ("Y" in step S201), if the operation mode is the high efficiency mode of the load following mode ("Y" in step S204), it calculates the deviation rate E from the received parent unit difference Δτp and the calculated child unit difference Δτc. If this deviation rate E is not within a predetermined range, it can be considered that there is a possibility that an abnormality has occurred in the child unit 102. The control device 85 of the child device 102 then determines whether or not the deviation rate E is within a predetermined range (step S206), and if the number of consecutive times that it has been determined that the deviation rate E is not within the predetermined range reaches a predetermined number ("Y" in step S208), it determines that an abnormality has occurred in the child device 102.

In addition, even if the control device 85 of the child unit 102 receives the fuel gas composition and the parent unit difference Δτp from the parent unit 101 ("Y" in step S201), if the operation mode is not the high efficiency mode of the load following mode ("N" in step S204), it does not determine whether or not an abnormality has occurred in the child unit 102. In addition, if the control device 85 of the child unit 102 has previously received the fuel gas composition and the parent unit difference Δτp from the parent unit 101 ("Y" in step S201) but has not subsequently determined whether or not the deviation rate E is within a predetermined range ("N" in step S201 and "N" in step S213), it determines whether or not the operation mode is the high efficiency mode of the load following mode (step S204), and if it determines that the operation mode is the high efficiency mode of the load following mode ("Y" in step S204), it determines whether or not the deviation rate E is within a predetermined range (step S206). If the deviation rate E is not within the predetermined range ("N" in step S206), the control device 85 of the slave unit 102 determines whether an abnormality has occurred in the slave unit 102 (step S208).

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. The present invention can be modified in various ways without departing from the spirit of the invention, and these modifications are also included in the technical scope of the present invention. For example, the configuration of the fuel gas composition estimation unit 87 and the method of estimating the fuel gas composition are not limited to the above embodiment.

10...Fuel cell control system, 11...Fuel cell cogeneration system, 12...Network, 13...Fuel gas supply source, 20...Power generation module, 21...Fuel cell, 34...Fuel gas blower, 85...Control device, 87...Fuel gas composition estimation unit, 101...Parent unit of fuel cell cogeneration system, 102...Child unit of fuel cell cogeneration system

Claims (6)

A fuel cell system is provided with a plurality of fuel cell systems that are supplied with fuel gas having the same composition and can communicate with each other;
the plurality of fuel cell systems each include one parent unit having a fuel gas composition estimation unit configured to estimate a composition of the fuel gas to be supplied, and one or more child units not having the fuel gas composition estimation unit;
the parent unit includes a fuel cell that generates power from the supplied fuel gas, and is configured to control the power generated by the fuel cell based on the composition of the fuel gas estimated by the fuel gas composition estimation unit, and to transmit the composition of the fuel gas estimated by the fuel gas composition estimation unit to the child unit;
the slave unit includes a fuel cell that generates power using the supplied fuel gas, and is configured to control the power generated by the fuel cell based on the composition of the fuel gas received from the master unit.
Fuel cell control system. 2. The fuel cell control system according to claim 1,
the parent unit and the child unit each include a fuel gas blower that supplies the fuel gas to the fuel cell, and a power generation map that defines a relationship between the power generated by the fuel cell and an output of the fuel gas blower for each composition of the fuel gas,
the parent unit controls an output of the fuel gas blower using the power generation map corresponding to the composition of the fuel gas estimated by the fuel gas composition estimation unit;
the slave unit controls the output of the fuel gas blower using the power generation map corresponding to the composition of the fuel gas received from the master unit.
Fuel cell control system. 3. The fuel cell control system according to claim 2,
when the composition of the fuel gas estimated by the fuel gas composition estimation unit changes, the parent unit changes the power generation map in accordance with the changed composition of the fuel gas and transmits the changed composition of the fuel gas to the child unit;
when the slave unit receives the composition of the fuel gas from the master unit, the slave unit changes the power generation map based on the received composition of the fuel gas.
Fuel cell control system. 4. The fuel cell control system according to claim 3,
when the composition of the fuel gas estimated by the fuel gas composition estimation unit changes, the parent unit calculates a parent unit difference which is a difference between an output of the fuel gas blower for obtaining a predetermined generated power from the fuel gas before the composition changes and an output of the fuel gas blower for obtaining the predetermined generated power from the fuel gas after the composition changes, and transmits the calculated parent unit difference to the child unit;
The slave unit calculates a slave unit difference, which is the difference between the output of the fuel gas blower for obtaining a specified generated power from the fuel gas having a composition before receiving the fuel gas composition from the master unit, and the output of the fuel gas blower for obtaining the specified generated power from the fuel gas having a composition received from the master unit, and determines that there is a possibility that an abnormality has occurred in the slave unit if the ratio of the slave unit difference to the master unit difference is equal to or greater than a specified threshold value.
Fuel cell control system. 5. The fuel cell control system according to claim 4,
the parent unit has a specific operation mode in which the power generated by the fuel cell is equal to or greater than a predetermined threshold and the power generated by the fuel cell is not changed, and when in the specific operation mode, calculates the parent unit difference and transmits the calculated parent unit difference to the child unit;
Fuel cell control system. 6. A fuel cell control system according to claim 4, further comprising:
the slave unit has a specific operation mode in which the power generated by the fuel cell is equal to or greater than a predetermined threshold and the power generated by the fuel cell is not changed, and calculates the slave unit difference when the slave unit is in the specific operation mode;
Fuel cell control system.

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