fuel cell device

Abstract

To provide a fuel cell system that can supply the largest possible amount of power. [Solution] A fuel cell device 10 comprising a fuel cell unit 12 connected to a power grid 1, wherein in a normal state where power is supplied normally from the power grid 1, a first operation is performed to adjust the output power in a manner that does not allow the state value indicating the operating state of the fuel cell unit 12 to deviate from a predetermined first limit range, and when predetermined operating environment conditions are met, including an abnormal state where power is not supplied normally from the power grid 1, a second operation is performed to adjust the output power in a manner that allows the state value indicating the operating state of the fuel cell unit 12 to deviate from the first limit range.

Description

Technical Field

[0001] The present invention relates to a fuel cell device.

Background Art

[0002] Household fuel cell systems, referred to as Ene-Farm, are equipped with a function to generate power during power outages, and have been gaining increasing attention partly due to the recent impact of natural disasters. In addition, even in an emergency such as a power outage, there is a need to maintain a life as close to normal as possible, so it is considered that the demand for the amount of power supplied from the fuel cell is particularly higher during power outages than in normal times.

[0003] As described in Patent Document 1 (Japanese Patent No. 5791070), in solid oxide fuel cells, degradation of the power generation performance of the cell stack (such as an increase in internal resistance) is a problem, and it is known that an approach of limiting the output current is effective as a method for suppressing the degradation.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0005] When a long service life as a product is desired, it is a general idea to impose a certain limit on the output in accordance with the degradation of the fuel cell device to suppress the progress of degradation as much as possible, but the convenience of users in an emergency such as a power outage is not taken into consideration. In the limited situation of a power outage, operating the device safely while taking degradation into account may conversely present a disadvantage from the user's perspective. During a power outage, the fuel cell will serve as part of the living infrastructure, so it is considered that supplying as much power as possible within a range that does not cause failure is a desirable specification for users.

[0006] This invention has been made in view of the above-mentioned problems, and its objective is to provide a fuel cell device that can supply as much power as possible. [Means for solving the problem]

[0007] A characteristic configuration of the fuel cell device according to the present invention for achieving the above objective is a fuel cell device comprising a fuel cell section connected to a power grid, In the case of a normal state where power is supplied normally from the power system, a first operation is performed to adjust the output power in such a way that the state value indicating the operating state of the fuel cell unit does not deviate from a predetermined first limit range. The key point is that, when predetermined operating environment conditions are met, including an abnormal state in which power supply from the power system is not functioning normally, a second operation is performed to adjust the output power while allowing the state value indicating the operating state of the fuel cell unit to deviate from the first limit range. Here, the state value may be the temperature, output current, output voltage, or output power of the fuel cell unit.

[0008] According to the above characteristic configuration, when a user expects the fuel cell system to supply a large output power, such as when a predetermined operating environment condition is met, including an abnormal state in which power supply from the power grid is not functioning normally, a second operation is performed to adjust the output power while allowing the state value indicating the operating state of the fuel cell section to deviate from the first limit range. Therefore, a fuel cell system that can supply the largest possible amount of power can be provided.

[0009] Another characteristic feature of the fuel cell device according to the present invention is that the operating environment conditions are the abnormal conditions and are authorized by the user.

[0010] According to the above characteristic configuration, in the event of an abnormal state where power supply from the power grid is not functioning normally, and with the user's permission, a second operation is performed to adjust the output power while allowing the state value indicating the operating status of the fuel cell unit to deviate from the first limit range. As a result, it is possible to prevent the second operation from being performed when the user does not want it.

[0011] Another characteristic configuration of the fuel cell device according to the present invention is that the operating environment conditions are the abnormal state, and the cumulative deviation time, which is the cumulative value of the time during which the state value deviates from the first limit range, is less than or equal to a predetermined upper limit time.

[0012] According to the above characteristic configuration, if there is an abnormal state in which power supply from the power grid is not functioning normally, and the cumulative deviation time, which is the cumulative value of the time during which the state value deviates from the first limit range, is less than or equal to a predetermined upper limit time, a second operation is performed to adjust the output power while allowing the state value indicating the operating state of the fuel cell unit to deviate from the first limit range. As a result, it is possible to prevent the second operation from being performed even in cases where the fuel cell device has previously performed the second operation for a long period of time (i.e., when the fuel cell device has deteriorated significantly).

[0013] Another characteristic configuration of the fuel cell device according to the present invention is that the operating environment conditions are the abnormal state, authorized by the user, and the cumulative deviation time, which is the cumulative value of the time during which the state value deviates from the first limit range, is less than or equal to a predetermined upper limit time.

[0014] According to the above characteristic configuration, if there is an abnormal state in which power supply from the power grid is not functioning normally, and the user has given permission, and the cumulative deviation time, which is the cumulative value of the time during which the state value deviates from the first limit range, is less than or equal to a predetermined upper limit time, then a second operation is performed to adjust the output power while allowing the state value indicating the operating state of the fuel cell unit to deviate from the first limit range. As a result, it is possible to prevent the second operation from being performed when the user does not want it, and when the fuel cell device has previously performed the second operation for a long period of time (i.e., when the fuel cell device has deteriorated significantly).

[0015] Another characteristic configuration of the fuel cell device according to the present invention is that the operating environment conditions are the abnormal state, and the performance of the fuel cell unit is on the higher end of a predetermined limit value.

[0016] According to the above characteristic configuration, in the event of an abnormal state where power supply from the power grid is not functioning properly, and the performance of the fuel cell unit is above a predetermined limit, a second operation is performed to adjust the output power while allowing the state value indicating the operating state of the fuel cell unit to deviate from the first limit range. As a result, it is possible to prevent the second operation from being performed when the user does not want it, and when the performance of the fuel cell unit is not above a predetermined limit (i.e., when the fuel cell device is considered to be deteriorating).

[0017] Another characteristic configuration of the fuel cell device according to the present invention is that it includes an information output unit that outputs information to the user, The information output unit outputs to the user the remaining time until the cumulative deviation time, which is the cumulative value of the time the status value has deviated from the first limit range, reaches the upper limit time.

[0018] According to the above feature configuration, users who check the remaining time can find out how much time remains for the fuel cell system to perform second-stage operation.

[0019] Another characteristic configuration of the fuel cell device according to the present invention includes an information output unit that outputs information to a user, The information output unit is configured to output the upper limit power of the output power during execution of the second operation to the user.

[0020] According to the above characteristic configuration, the user can know how much power is available when the fuel cell device performs the second operation in an abnormal state where power supply from the power system is not normally performed. Brief Description of the Drawings

[0021] [Figure 1] It is a diagram showing the configuration of a facility provided with a fuel cell device. [Figure 2] It is a diagram showing changes in output current, output voltage and temperature of the fuel cell unit with respect to the cumulative power generation time of the fuel cell unit when the output power of the fuel cell unit is kept constant. [Figure 3] It is a diagram showing changes in output current, output voltage and output power of the fuel cell unit with respect to the cumulative power generation time of the fuel cell unit when control is performed to maximize the output power while keeping the temperature of the fuel cell unit constant. [Figure 4] It is a diagram showing changes in output voltage, output power and temperature of the fuel cell unit with respect to the cumulative power generation time of the fuel cell unit when control is performed to maximize the output power while keeping the output current of the fuel cell unit constant. [Figure 5] It is a diagram showing the relationship between the cumulative power generation time of the fuel cell unit, and the first limit range and the second limit range of the output power as a state value. [Figure 6] It is a diagram showing the relationship between the cumulative power generation time of the fuel cell unit, and the first limit range and the second limit range of the temperature of the fuel cell unit. [Figure 7] It is a diagram showing the relationship between the cumulative power generation time of the fuel cell unit, and the output voltage when the output current and the output power of the fuel cell unit are kept constant. Modes for Carrying Out the Invention

[0022] A fuel cell device 10 according to an embodiment of the present invention will be described below with reference to the drawings. Figure 1 shows the configuration of a facility 4 in which a fuel cell device 10 is installed. As shown in the figure, the fuel cell device 10 and power load 3 are installed in a facility 4 such as a dwelling or business office. The fuel cell device 10 and power load 3 are connected to a power line 2 which is connected to a power system 1. A circuit breaker 7 is installed on the power line 2. The circuit breaker 7 closes when power is being supplied normally from the power system 1, connecting the fuel cell device 10 and power load 3 to the power system 1. Conversely, the circuit breaker 7 opens when power is not being supplied normally from the power system 1, disconnecting the fuel cell device 10 and power load 3 from the power system 1.

[0023] Upstream of the circuit breaker 7 (i.e., on the side of power system 1), the power line 2 is equipped with a current meter 5 for measuring the current of the power supplied from power system 1, and a voltage meter 6 for measuring the voltage of the power supplied from power system 1. The measurement results from the current meter 5 and the voltage meter 6 are transmitted to the fuel cell device 10. In the fuel cell device 10, the power received from power system 1, or the power flowing in the reverse direction to power system 1, can be determined by multiplying the current measured by the current meter 5 and the voltage measured by the voltage meter 6. In addition, by monitoring the voltage measured by the voltage meter 6, the fuel cell device 10 can determine whether the power supply from power system 1 is functioning normally or whether it is functioning abnormally.

[0024] The fuel cell device 10 includes a fuel cell unit 12 that generates electricity using fuel gas, a power conversion unit 11 that converts the electricity generated by the fuel cell unit 12 to a predetermined voltage, frequency, and phase and supplies it to the power line 2, and an operation control unit 13 that controls the operation of the fuel cell device 10. The fuel cell device 10 may also include a fuel reformer that generates hydrogen, which is the fuel gas for the fuel cell unit 12. In addition, the fuel cell device 10 includes a state value determination unit 14, a storage unit 15, an input reception unit 16, and an information output unit 17.

[0025] The operation control unit 13 can adjust the output power from the fuel cell device 10 to the power line 2 within a limit range bounded by predetermined upper and lower limits. For example, the operation control unit 13 can maintain the output power of the fuel cell device 10 at the rated output power (upper limit of the limit range) for continuous operation. The operation control unit 13 can also operate the fuel cell device 10 so that its output power follows the load power of the power load 3. For example, the operation control unit 13 can operate the fuel cell device 10 so that the power derived based on the measurement results of the current meter 5 and the voltage meter 6 (i.e., the power supplied from the power system 1) is zero or close to zero, thereby causing it to follow the load power of the power load 3. Alternatively, the operation control unit 13 can adjust the output power of the fuel cell device 10 so that the power derived based on the measurement results of the current meter 5 and the voltage meter 6 is a predetermined negative power (i.e., a predetermined reverse power flow).

[0026] Even when the fuel cell unit 12 is operating at or below its rated output power (i.e., below the upper limit of the limit range), its performance deteriorates as the cumulative power generation time increases. For example, the deterioration of the fuel cell unit 12 occurs when the electrical resistance of the fuel cell cells constituting the fuel cell unit 12 increases.

[0027] Figure 2 illustrates the degradation of the fuel cell unit 12. Figure 2 shows the changes in output current, output voltage, and temperature of the fuel cell unit 12 with respect to the cumulative power generation time of the fuel cell unit 12, when the output power of the fuel cell unit 12 is kept constant. As described above, as the cumulative power generation time of the fuel cell unit 12 increases, the electrical resistance of the fuel cell cells increases. Therefore, if the power conversion unit 11 tries to extract the same output power from the fuel cell unit 12, the output current must be increased as the cumulative power generation time increases. And as the output current increases, the output voltage decreases as the cumulative power generation time increases. Furthermore, since Joule heating increases as the output current increases, the temperature of the fuel cell unit 12 rises as the cumulative power generation time increases.

[0028] Figure 3 shows the changes in output current, output voltage, and output power of the fuel cell unit 12 with respect to the cumulative power generation time of the fuel cell unit 12 when the temperature of the fuel cell unit 12 is kept constant and controlled to maximize the output power. As shown in the figure, the output current and output voltage are determined so that the output power (i.e., the product of output current and output voltage) is maximized, and the unit operates to keep the output current constant for a while as the cumulative power generation time progresses. However, when the increase in heat dissipation due to degradation becomes significant, it becomes necessary to reduce the output current.

[0029] Figure 4 shows the changes in output voltage, output power, and temperature of the fuel cell unit 12 with respect to the cumulative power generation time of the fuel cell unit 12 when the output current of the fuel cell unit 12 is kept constant and controlled to maximize output power. As shown in the figure, the output power decreases in line with the decrease in output voltage due to degradation, and it is necessary to raise the temperature in order to increase the output current.

[0030] In such a fuel cell device 10, the operation control unit 13 performs a first operation in which, in a normal state where power is supplied normally from the power system 1, the state value indicating the operating state of the fuel cell unit 12 does not deviate from a predetermined first limit range, in order to slow down the progression of deterioration of the fuel cell unit 12 as much as possible.

[0031] The status values ​​indicating the operating state of the fuel cell unit 12 are, for example, the temperature, output current, output voltage, or output power of the fuel cell unit 12, and are determined by the status value determination unit 14.

[0032] When the state value is the temperature of the fuel cell unit 12, the state value determination unit 14 can be implemented using a temperature sensor (not shown) provided in the fuel cell power unit. The operation control unit 13 can then adjust the output power from the fuel cell device 10 to the power line 2 so that the temperature (state value) of the fuel cell unit 12 measured by the state value determination unit 14 does not deviate from a predetermined temperature range (limit range).

[0033] When the state value is the output current of the fuel cell unit 12, the state value determination unit 14 can be implemented using the power conversion unit 11. The operation control unit 13 can then adjust the output power from the fuel cell device 10 to the power line 2 so that the output current (state value) of the fuel cell unit 12 measured by the state value determination unit 14 does not deviate from a predetermined current range (limit range).

[0034] When the state value is the output voltage of the fuel cell unit 12, the state value determination unit 14 can be implemented using the power conversion unit 11. The operation control unit 13 can then adjust the output power from the fuel cell device 10 to the power line 2 so that the output voltage (state value) of the fuel cell unit 12 measured by the state value determination unit 14 does not deviate from a predetermined voltage range (limit range).

[0035] When the state value is the output power of the fuel cell unit 12, the state value determination unit 14 can be implemented using the power conversion unit 11. The operation control unit 13 can then adjust the output power from the fuel cell device 10 to the power line 2 so that the output power (state value) of the fuel cell unit 12 measured by the state value determination unit 14 does not deviate from a predetermined power range (limit range).

[0036] In the event of an abnormal situation where power supply from power grid 1 is not functioning properly, the fuel cell device 10 will be the only device capable of supplying power to the power load 3 of facility 4. Therefore, in the event of an abnormal situation, it is desirable to increase the output power of the fuel cell device 10 as much as possible. However, outputting power greater than the set rated output power would place a heavy load on the fuel cell unit 12, rapidly accelerating its deterioration.

[0037] Therefore, in the fuel cell device 10 of this embodiment, the operation control unit 13 performs a first operation in which, when power is supplied normally from the power system 1, the state value indicating the operating state of the fuel cell unit 12 does not deviate from a predetermined first limit range. When predetermined operating environment conditions are met, including an abnormal state in which power is not supplied normally from the power system 1, the operation control unit 13 performs a second operation in which the state value indicating the operating state of the fuel cell unit 12 deviates from the first limit range. Furthermore, in this embodiment, a second limit range separate from the first limit range is set, and in the second operation, the operation control unit 13 adjusts the output power in a state that allows deviation from the first limit range but does not allow deviation from the second limit range. The first limit range, which is bounded by predetermined upper and lower limits, is included in the second limit range, which is bounded by predetermined upper and lower limits. Information indicating these first and second limit ranges is stored in the storage unit 15.

[0038] Figure 5 shows the relationship between the cumulative power generation time of the fuel cell unit 12 and the first and second limit ranges of output power as state values. Figure 5 shows the upper limit of the first limit range in a normal state and the upper limit of the second limit range in an abnormal state, while the lower limit of the first limit range in a normal state and the lower limit of the second limit range in an abnormal state are omitted. As shown in the figure, for both the first and second limit ranges, the upper limit of output power as a state value decreases as the cumulative power generation time increases.

[0039] Furthermore, if a second operation is performed in which the state value indicating the operating state of the fuel cell unit 12 deviates from the first limit range, a large load will be placed on the fuel cell unit 12, rapidly accelerating its deterioration. Therefore, in the example shown in Figure 5, if a second operation is performed in which the state value indicating the operating state of the fuel cell unit 12 deviates from the first limit range, the operation control unit 13 performs a range change process to change the upper limit of both the first limit range and the upper limit of the second limit range in a direction that reduces the upper limit.

[0040] As shown in Figure 5, in the example, a first limit range and a second limit range for the output power of the fuel cell unit 12 are set as state values ​​indicating the operating state of the fuel cell unit 12. The operation control unit 13 performs a first operation in which, when power is supplied normally from the power system 1, the output power of the fuel cell unit 12 is adjusted in a manner that does not allow it to deviate from the preset first limit range. When predetermined operating environment conditions are met, including an abnormal state in which power is not supplied normally from the power system 1, the operation control unit 13 performs a second operation in which the output power of the fuel cell unit 12 is adjusted in a manner that allows it to deviate from the first limit range but does not allow it to deviate from the second limit range. For example, when performing the second operation, the operation control unit 13 controls the operation of the power conversion unit 11 so that it outputs power equal to the load power of the power load 3 from the fuel cell unit 12 (i.e., outputs from the power conversion unit 11 to the power line 2). However, the operation control unit 13 ensures that the upper limit of the power output from the fuel cell unit 12 (i.e., output from the power conversion unit 11 to the power line 2) during the second operation is less than or equal to the upper limit of the second limit range.

[0041] Furthermore, the operation control unit 13 may output the upper limit power of the output power during the second operation (i.e., the upper limit of the second limit range) to the user via the information output unit 17. In this case, the user can find out how much power (upper limit power) is available when the fuel cell device 10 performs the second operation in an abnormal state where power supply from the power system 1 is not functioning normally.

[0042] Figure 6 shows the relationship between the cumulative power generation time of the fuel cell unit 12 and the first and second temperature limit ranges of the fuel cell unit 12. Figure 6 shows the upper limit of the first limit range under normal conditions and the upper limit of the second limit range under abnormal conditions. As shown in the figure, the upper limit of the first temperature limit range of the fuel cell unit 12 is set to increase as the cumulative power generation time increases. The upper limit of the second temperature limit range of the fuel cell unit 12 is set to remain constant regardless of the length of the cumulative power generation time.

[0043] Next, we will explain some examples of operating environment conditions.

[0044] [Example of operating environment conditions 1] In Example 1, when the fuel cell device 10 performs a second operation to adjust the output power while allowing the state value indicating the operating state of the fuel cell unit 12 to deviate from the first limit range, the above operating environment conditions are that the power supply from the power system 1 is not functioning normally and that the user has given permission. The user's permission can be received from the user by the input receiving unit 16. For example, if the operation control unit 13 enters an abnormal state where the power supply from the power system 1 is not functioning normally, it will use the information output unit 17 to request permission from the user to allow the output power, which is an example of a state value indicating the operating state of the fuel cell unit 12, to deviate from the first limit range. Then, if the input receiving unit 16 has received permission from the user, the operation control unit 13 will determine that the condition "the user has given permission" included in the above operating environment conditions has been met. Alternatively, the operation control unit 13 may use the information output unit 17 to request permission from the user to allow the output power to deviate from the first limit range at a stage before an abnormal state has occurred. Furthermore, if the input receiving unit 16 receives permission from the user, the operation control unit 13 may determine that the condition "the user has given permission" included in the above operating environment conditions has been met and store it in the storage unit 15.

[0045] Furthermore, the user may configure the system to allow the output power to deviate from the first limit range, by switching this setting via an input to the input receiving unit 16.

[0046] Alternatively, if the load power of power load 3 is equal to or greater than the set power, it can be considered that the user is requesting an increase in the output power of the fuel cell device 10. Therefore, the operation control unit 13 may determine that the condition "the user has given permission" included in the above operating environment conditions is met when the load power of power load 3 is equal to or greater than the set power. Whether or not the load power of power load 3 is equal to or greater than the set power can be detected, for example, by the power conversion unit 11.

[0047] [Example of operating environment conditions 2] In Example 2, when the fuel cell device 10 performs a second operation to adjust the output power while allowing the state value indicating the operating state of the fuel cell unit 12 to deviate from the first limit range, the above operating environment conditions are that the state is abnormal and the cumulative deviation time, which is the cumulative value of the time the state value deviates from the first limit range, is less than or equal to a predetermined upper limit time. For example, when the second operation is performed in which the state value indicating the operating state of the fuel cell unit 12 actually deviates from the first limit range, the operation control unit 13 measures and accumulates the length of time the state value deviates from the first limit range and stores the accumulated deviation time in the storage unit 15. Then, if the cumulative deviation time is less than or equal to a predetermined upper limit time, the operation control unit 13 determines that the condition "the cumulative deviation time, which is the cumulative value of the time the state value deviates from the first limit range, is less than or equal to a predetermined upper limit time" included in the above operating environment conditions is satisfied.

[0048] Furthermore, the operation control unit 13 may output to the user from the information output unit 17 the remaining time until the cumulative deviation time stored in the memory unit 15 reaches the upper limit. In that case, the user who checks the remaining time can find out how much time remains for the fuel cell device 10 to perform the second operation.

[0049] [Example 3 of operating environment conditions] In Example 3, when the fuel cell device 10 performs a second operation to adjust the output power while allowing the state value indicating the operating state of the fuel cell unit 12 to deviate from the first limit range, the above operating environment conditions are that the state is abnormal, the user has given permission, and the cumulative deviation time, which is the cumulative value of the time the state value has deviated from the first limit range, is less than or equal to a predetermined upper limit time. Similar to Example 1, when the input receiving unit 16 receives permission from the user, the operation control unit 13 determines that the condition "the user has given permission" included in the above operating environment conditions has been met. Also, similar to Example 2, when the cumulative deviation time is less than or equal to a predetermined upper limit time, the operation control unit 13 determines that the condition "the cumulative deviation time, which is the cumulative value of the time the state value has deviated from the first limit range, is less than or equal to a predetermined upper limit time" included in the above operating environment conditions has been met.

[0050] This upper limit time can be set to, for example, 0.5% to 1% of the design life of the fuel cell device 10, and can be stored in advance in the memory unit 15.

[0051] [Example of operating environment conditions 4] In Example 4, the operating environment conditions when performing the second operation with the fuel cell device 10 are an abnormal state, and the performance of the fuel cell unit 12 is on the higher end of a predetermined limit value. Because there are individual differences in the performance of the fuel cell unit 12, if the performance of the fuel cell unit 12 is high, it may be permissible to perform a second operation in which the state value indicating the operating state of the fuel cell unit 12 deviates from the first limit range. Therefore, in Example 4, the operation control unit 13 determines whether the measured performance value of the fuel cell unit 12 is on the higher end of the performance limit value of the fuel cell unit 12, which is set according to its cumulative power generation time.

[0052] Figure 7 shows the relationship between the cumulative power generation time of the fuel cell unit 12 and the output voltage when the output current and output power of the fuel cell unit 12 are kept constant. In Figure 7, the higher the output voltage shown on the vertical axis, the higher the performance of the fuel cell unit 12, and the lower the output voltage, the lower the performance of the fuel cell unit 12. As the deterioration of the fuel cell unit 12 progresses, the electrical resistance of the fuel cell cells constituting the fuel cell unit 12 increases. As shown in the figure, the output voltage when the output current and output power of the fuel cell unit 12 are kept constant decreases monotonically as the cumulative power generation time of the fuel cell unit 12 increases.

[0053] The performance limit of the fuel cell unit 12, which is set according to the cumulative power generation time shown in Figure 7, is, for example, the lowest acceptable performance limit of the fuel cell unit 12. The operation control unit 13 then measures the output voltage when the output current and output power of the fuel cell unit 12 are kept constant at predetermined values ​​while the fuel cell unit 12 is actually performing power generation, and stores this measurement in the storage unit 15 along with the cumulative power generation time at that point. As a result, if the measured performance of the fuel cell unit 12 is higher than the performance limit of the fuel cell unit 12 corresponding to the cumulative power generation time at that point, the operation control unit 13 determines that the condition "the performance of the fuel cell unit 12 is higher than the predetermined limit" included in the above operating environment conditions has been met.

[0054] This prevents the second operation from being performed when the user does not want it and when the performance of the fuel cell unit 12 is not above a predetermined limit (i.e., when the fuel cell device 10 is considered to be deteriorating).

[0055] <Another Embodiment> In the above embodiment, the configuration of the fuel cell device 10 was specifically described, but its configuration can be changed as appropriate.

[0056] In the above embodiment, specific examples were given to illustrate the limit ranges (first limit range, second limit range) of the state values. However, these limit ranges are provided for illustrative purposes only and can be changed as appropriate. For example, Figure 5 shows an example where the limit range (upper limit of the limit range) is determined according to the cumulative power generation time, but the limit range may be determined as a value unrelated to the cumulative power generation time.

[0057] In the above embodiment, specific examples were given to illustrate the performance limits of the fuel cell unit 12. However, these performance limits are provided for illustrative purposes only and can be changed as appropriate. For example, Figure 7 illustrates an example where the performance limit of the fuel cell unit 12 is determined according to the cumulative power generation time. However, the performance limit of the fuel cell unit 12 may be determined as a value independent of the cumulative power generation time. In other words, a limit value for the output voltage may be set when the output current and output power of the fuel cell unit 12 are kept constant at predetermined values, and this limit value may be uniformly compared with the current output voltage of the fuel cell unit 12 regardless of the length of the cumulative power generation time. Furthermore, while Figure 7 shows a limit value for the output voltage when the output current and output power of the fuel cell unit 12 are kept constant at predetermined values, it is also possible to set a limit value for the temperature of the fuel cell unit 12 when the output current and output power of the fuel cell unit 12 are kept constant at predetermined values, and compare that limit value with the current temperature of the fuel cell unit 12.

[0058] In the above embodiment, specific examples of operating environment conditions were given, but these operating environment conditions are described for illustrative purposes only and can be changed as appropriate.

[0059] The configurations disclosed in the above embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with configurations disclosed in other embodiments, as long as no inconsistencies arise. Furthermore, the embodiments disclosed herein are illustrative, and the embodiments of the present invention are not limited thereto and can be modified as appropriate without departing from the purpose of the present invention. [Industrial applicability]

[0060] This invention can be used in fuel cell devices that can supply the largest possible amount of power. [Explanation of Symbols]

[0061] 1 Power system 2 Power lines 3 Power load 4 facilities 5 Current measuring device 6. Voltage Measuring Instrument 7 Circuit breaker 10 Fuel cell device 11 Power Conversion Unit 12 Fuel cell section 13 Operation Control Unit 14. State Value Determination Unit 15 Storage section 16 Input Reception Section 17 Information Output Unit

Claims

1. A fuel cell system comprising a fuel cell unit connected to a power grid, In the case of a normal state where power is supplied normally from the power system, a first operation is performed to adjust the output power in such a way that the state value indicating the operating state of the fuel cell unit does not deviate from a predetermined first limit range. A fuel cell device that, when predetermined operating environment conditions are met, including an abnormal state in which power supply from the power system is not functioning normally, performs a second operation in which it adjusts the output power while allowing the state value indicating the operating state of the fuel cell unit to deviate from the first limit range.

2. The fuel cell apparatus according to claim 1, wherein the state value is the temperature of the fuel cell unit, the output current, the output voltage, or the output power.

3. The fuel cell apparatus according to claim 1 or 2, wherein the operating environment conditions are the abnormal conditions and are permitted by the user.

4. The fuel cell apparatus according to claim 1 or 2, wherein the operating environment conditions are the abnormal state, and the cumulative deviation time, which is the cumulative value of the time during which the state value deviates from the first limit range, is less than or equal to a predetermined upper limit time.

5. The fuel cell apparatus according to claim 1 or 2, wherein the operating environment conditions are the abnormal state, the user has given permission, and the cumulative deviation time, which is the cumulative value of the time during which the state value deviates from the first limit range, is less than or equal to a predetermined upper limit time.

6. The fuel cell device according to claim 1 or 2, wherein the operating environment conditions are the abnormal conditions, and the performance of the fuel cell unit is on the higher end than a predetermined limit value.

7. It is equipped with an information output unit that outputs information to the user, The fuel cell apparatus according to claim 4, wherein the information output unit outputs to the user the remaining time until the cumulative deviation time, which is the cumulative value of the time the state value has deviated from the first limit range, reaches the upper limit time.

8. It is equipped with an information output unit that outputs information to the user, The fuel cell apparatus according to claim 1 or 2, wherein the information output unit outputs to the user the upper limit power of the output power during the second operation.

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