JP2018206744A - Fuel cell system, control arrangement and control method of fuel cell system - Google Patents

Abstract

To solve such a problem that when the capacity of a load is increased for maintaining the generated power required for continuing operation of a fuel cell, the system may become larger or the cost may be increased.SOLUTION: A fuel cell system includes a power generation section for generating power by reaction of fuel gas and oxidant gas, and discharging fuel exhaust gas containing steam produced in a fuel electrode, a modification section supplied with fuel exhaust gas and raw fuel gas, a control section for controlling the quantity of fuel exhaust gas recirculated to the modification section, and a steam production section for producing steam supplied to the modification section by consuming power. When the fuel cell system is disconnected from an external power supply capable of supplying power in parallel with the fuel cell system, the control section controls to supply at least a part of surplus power to the steam production section, and reduces the quantity of the fuel exhaust gas recirculated to the modification section, according to the quantity of the steam produced in the steam production section by consuming at least a part of surplus power.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system, a control device for the fuel cell system, and a control method.

When power is lost to the grid power supply, the power generated by the fuel cell is supplied independently by supplying surplus power other than idling power to the heater and storage battery without supplying power to the external load during the standby time until the start of autonomous operation. A fuel cell system that maintains generated power is known (see, for example, Patent Document 1).
Patent Document 1 Japanese Patent Application Laid-Open No. 2015-186408

  In some cases, a load such as a heater or a storage battery cannot consume surplus power, and the generated power necessary for continuing the operation of the fuel cell may not be maintained. Therefore, if the capacity of the load is increased in order to maintain the generated power necessary to continue the operation, for example, the system may be increased in size and cost.

  In a first aspect of the present invention, a fuel cell system is provided. The fuel cell system may include a power generation unit that generates power by a reaction between the fuel gas and the oxidant gas and discharges fuel exhaust gas containing water vapor generated at the fuel electrode. The fuel cell system may include a reforming unit to which raw fuel gas and recirculated fuel exhaust gas are supplied. The fuel cell system may include a control unit that controls the amount of fuel exhaust gas recirculated to the reforming unit. The fuel cell system may include a steam generating unit that consumes electric power and generates steam supplied to the reforming unit. When the fuel cell system is disconnected from an external power source capable of supplying power in parallel with the fuel cell system, the control unit supplies at least a part of the surplus power to the water vapor generation unit, and at least a part of the surplus power is supplied. The amount of fuel exhaust gas recirculated to the reforming unit may be reduced in accordance with the amount of water vapor generated in the water vapor generating unit by consumption of the water vapor generating unit.

  The external power supply may be a system power supply. When the fuel cell system is disconnected from the system power supply, the control unit supplies at least a part of the surplus power to the steam generation unit, and recycles it to the reforming unit according to the amount of steam generated by the steam generation unit. The amount of fuel exhaust gas circulated may be reduced.

  The control unit may control the power generation unit so that the output of the fuel cell system becomes a rated output while the fuel cell system supplies power in parallel with the external power source. The control unit is configured to reduce the generated power of the power generation unit when the fuel cell system is disconnected from the external power source, and maintain the output of the fuel cell system in order to operate the fuel cell system independently. While reducing the output to stand-alone, supply at least part of the surplus power to the steam generation unit, and reduce the amount of fuel exhaust gas recirculated to the reforming unit according to the amount of steam generated in the steam generation unit It's okay.

  An internal load that consumes power may be further provided. When the fuel cell system is disconnected from the external power source, the control unit further supplies a part of the surplus power to the internal load, and generates the generated power of the power generation unit in the fuel cell module including the reforming unit and the power generation unit You may maintain the electric power which can maintain thermal independence.

  When the generated power of the power generation unit exceeds the load power, the control unit supplies at least a part of surplus power exceeding the load power to the steam generation unit, and reforms according to the amount of steam generated by the steam generation unit. The amount of fuel exhaust gas recirculated to the section may be reduced.

  In order to maintain the steam carbon ratio in the gas containing the fuel exhaust gas and the raw fuel gas recirculated to the reforming unit at a predetermined value, the control unit, according to the amount of steam generated in the steam generating unit, The amount of fuel exhaust gas recirculated to the reforming section may be reduced.

  In the second embodiment, a control device for a fuel cell system is provided. A fuel cell system includes a power generation unit that generates power by reaction of a fuel gas and an oxidant gas and discharges fuel exhaust gas containing water vapor generated at a fuel electrode, and a reforming unit to which fuel exhaust gas and raw fuel gas are supplied. A steam generation unit that consumes electric power and generates steam supplied to the reforming unit may be provided. When the fuel cell system is disconnected from the external power source, the control device supplies at least a part of the surplus power to the steam generating unit, and at least a part of the surplus power is consumed by the steam generating unit. A control unit that reduces the amount of fuel exhaust gas recirculated to the reforming unit according to the amount of water vapor generated may be provided.

  In a third aspect of the present invention, a method for controlling a fuel cell system is provided. A fuel cell system includes a power generation unit that generates power by reaction of a fuel gas and an oxidant gas and discharges fuel exhaust gas containing water vapor generated at a fuel electrode, and a reforming unit to which fuel exhaust gas and raw fuel gas are supplied. A steam generation unit that consumes electric power and generates steam supplied to the reforming unit may be provided. The control method may include a step of supplying at least a part of surplus power exceeding the load power to the steam generation unit when the fuel cell system is disconnected from the external power source. The control method includes a step of reducing the amount of fuel exhaust gas recirculated to the reforming unit according to the amount of water vapor generated in the water vapor generating unit by consuming at least part of the surplus power by the water vapor generating unit. It's okay.

  The above summary of the present invention does not enumerate all of the features of the present invention. A sub-combination of these feature groups can also be an invention.

1 schematically shows an external power supply 80, an external load 90, and an external power supply line 20 including functional blocks of the fuel cell system 10 in one embodiment. It is a figure for demonstrating the time change of the operation parameter when the fuel cell system 10 is disconnected during the interconnection operation. It is a figure for demonstrating the time change of the operating parameter in the fuel cell system of the comparative example 1. FIG. 3 is a flowchart illustrating a control method of the fuel cell system 10 by a control unit 100. 2 schematically shows an external power supply 80, an external load 90, and an external power supply line 20 including functional blocks of a fuel cell system 500 according to another embodiment.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 schematically shows an external power supply 80, an external load 90, and an external power supply line 20 including functional blocks of the fuel cell system 10 according to an embodiment.

  In FIG. 1, thick lines indicate flows of electricity, current, and power. A solid line shows the flow of fluids, such as gas and water, for example. Broken lines indicate the flow of various signals such as control signals and detection signals.

  The fuel cell system 10 is connected to the external power supply line 20 and supplies power to the external power supply line 20. An external power supply 80 and an external load 90 are connected to the external power supply line 20. The external power supply 80 supplies power to the external power supply line 20. The external load 90 operates with power supplied from the external power supply line 20.

  The fuel cell system 10 can supply power in parallel with the external power supply 80. For example, the fuel cell system 10 performs rated operation when supplying power in parallel with the external power supply 80. Thereby, the rated output of the fuel cell system 10 can be supplied to the external power supply line 20. The external load 90 receives, from the external power supply 80, a portion of the power consumed by the external load 90 that cannot be covered by the rated output of the fuel cell system 10.

  In the present embodiment, the external power source 80 is a commercial grid power source, and the fuel cell system 10 can perform a linked operation. In other embodiments, the external power source 80 may be a generator such as an internal combustion power generator.

  The fuel cell system 10 includes a relay 22, an internal power line 24, an internal load 30, a water vapor generation unit 40, a heating unit 50, a DC-AC conversion unit 60, a desulfurization unit 70, a control unit 100, Fuel cell module 110, flow sensor 150, blower 160, raw fuel flow path 180, water vapor supply flow path 181, fuel exhaust gas flow path 182, fuel exhaust gas recirculation flow path 183, and fuel exhaust gas discharge flow path 184, an oxidant gas channel 186, an oxidant exhaust gas channel 188, and an exhaust energy utilization unit 190. The fuel cell module 110 includes a reforming unit 120 and a power generation unit 130. The fuel cell module 110 is a solid oxide fuel cell (SOFC).

  In the fuel cell system 10, the heating unit 50 supplies heat necessary for starting the fuel cell system 10. For example, the heating unit 50 consumes external power or the like and heats at least one of the reforming unit 120 and the power generation unit 130. For example, the heating unit 50 is an electric heater. The heating unit 50 may heat a heat medium such as air with heat generated by electric power supplied from the external power supply 80 and supply the heated medium to at least one of the reforming unit 120 and the power generation unit 130.

  The water vapor generating unit 40 consumes external electric power or the like when the fuel cell system 10 is activated to generate water vapor. For example, the water vapor generating unit 40 generates water vapor by heating water with heat using electric power supplied from the external power supply 80. The water vapor generated by the water vapor generation unit 40 is supplied to the raw fuel flow path 180 through the water vapor supply flow path 181 and is supplied to the fuel cell module 110 together with the raw fuel gas. In addition, when the fuel cell system 10 is connected to the external power source 80, the heating unit 50 and the water vapor generating unit 40 are stopped.

  A desulfurization unit 70 is connected to the raw fuel flow path 180. Raw fuel gas is supplied to the desulfurization unit 70. Raw fuel gas is produced | generated from city gas, LP gas, kerosene etc., for example. The desulfurization unit 70 substantially removes sulfur components contained in the raw fuel gas. The raw fuel gas desulfurized by the desulfurization unit 70 is supplied to the raw fuel flow path 180.

  As will be described later, when the fuel cell module 110 is interconnected with the external power source 80, fuel exhaust gas containing water vapor discharged from the fuel cell module 110 is circulated and supplied to the raw fuel flow path 180.

  The raw fuel gas and water vapor are supplied to the reforming unit 120 through the raw fuel channel 180. The reforming unit 120 reforms the raw fuel gas to generate fuel gas. Specifically, the reforming unit 120 reforms the raw fuel contained in the raw fuel gas using water vapor contained in the fuel exhaust gas to generate fuel gas. The fuel gas is, for example, reformed hydrogen containing water vapor. The fuel gas generated by the reforming unit 120 is supplied to the power generation unit 130. The power generation unit 130 is further supplied with an oxidant gas through the oxidant gas flow path 186. The oxidant gas may be generated from air, for example. The reforming unit 120 may be provided inside the power generation unit, or may be provided as a reformer outside the power generation unit.

  The power generation unit 130 generates power by a reaction between the fuel gas and the oxidant gas. Specifically, the power generation unit 130 has a cell stack configured by stacking or assembling a plurality of power generation cells. Each power generation cell has a configuration in which an electrolyte is sandwiched between an oxidant electrode and a fuel electrode. A separator is provided between the power generation cells, and the power generation cells are electrically connected in series. In each power generation cell of the power generation unit 130, oxide ions generated at the oxidizer electrode permeate the electrolyte and move to the fuel electrode, and the oxide ions electrochemically react with hydrogen or carbon monoxide at the fuel electrode. To generate electrical energy. For example, in the fuel electrode of the power generation unit 130, oxygen ions react with hydrogen to generate electrical energy.

  In the fuel electrode of the power generation unit 130, water is generated by oxygen ions reacting with hydrogen. The water produced at the fuel electrode is discharged from the power generation cell as fuel exhaust gas together with the fuel gas component that has not contributed to the electrochemical reaction in the power generation cell. As described above, the power generation unit 130 discharges the fuel exhaust gas containing the water vapor generated at the fuel electrode. The fuel exhaust gas is discharged outside the fuel cell module 110 through the fuel exhaust gas flow path 182. Further, the oxidant exhaust gas containing the oxidant component that has not contributed to the electrochemical reaction with hydrogen and carbon monoxide at the oxidant electrode is discharged to the outside of the fuel cell module 110 through the oxidant exhaust gas channel 188. .

  At least a part of the fuel exhaust gas discharged from the fuel cell module 110 through the fuel exhaust gas channel 182 is supplied to the exhaust energy utilization unit 190 through the fuel exhaust gas channel 184. The oxidant exhaust gas discharged from the fuel cell module 110 through the oxidant exhaust gas channel 188 is supplied to the exhaust energy utilization unit 190 through the oxidant exhaust gas channel 188.

  The exhaust energy utilization unit 190 collects at least one of thermal energy and chemical energy contained in the fuel exhaust gas and the oxidant exhaust gas and discharges it as exhaust gas. For example, the exhaust energy utilization unit 190 generates warm water by heating water with thermal energy obtained by burning fuel exhaust gas and oxidant exhaust gas. The exhaust gas generated by the combustion is discharged to the outside air.

  At least a part of the fuel exhaust gas discharged from the fuel cell module 110 through the fuel exhaust gas passage 182 is recirculated to the raw fuel passage 180 through the fuel exhaust gas recirculation passage 183. Therefore, the fuel exhaust gas and the raw fuel gas are supplied to the reforming unit 120 as described above. Thereby, the reforming unit 120 can reform the raw fuel contained in the raw fuel gas using the water vapor contained in the recirculated fuel exhaust gas to generate a hydrogen-rich fuel gas.

  The direct current obtained by the power generation of the power generation unit 130 of the fuel cell module 110 is supplied to the DC-AC conversion unit 60. The DC-AC converter 60 converts the direct current from the power generation unit 130 into an alternating current. When the relay 22 is on, the alternating current output from the DC-AC conversion unit 60 is supplied to the external power supply line 20. As described above, the fuel cell system 10 is connected to the external power source 80 when the relay 22 is on. When the relay 22 is in the off state, it is in a disconnected state.

  The control of the control unit 100 when the fuel cell system 10 is in the connected state will be described. Here, it is assumed that the fuel cell system 10 is performing a rated operation. The control unit 100 controls the flow rate of the raw fuel gas from the desulfurization unit 70 to a predetermined value for the fuel cell system 10 to perform rated operation. Further, the control unit 100 controls the blower 160 to set the flow rate of the fuel exhaust gas recirculated from the fuel cell module 110 to a predetermined value for rated operation of the fuel cell system 10. For example, the control unit 100 controls the blower 160 so that the flow rate of the fuel exhaust gas detected by the flow sensor 150 becomes a specified value. In addition, during the rated operation of the fuel cell system 10, the control unit 100 stops the heating unit 50 and the water vapor generation unit 40.

  When the fuel cell system 10 is in a disconnected state, the fuel cell system 10 performs a self-supporting operation. During the autonomous operation, the control unit 100 reduces the output of the fuel cell system 10 to an autonomous output that is lower than the rated output. For example, the rated output is 100 kW and the self-sustained output is 50 kW. During the self-sustained operation, a part of the generated power of the power generation unit 130 is used by auxiliary equipment such as the blower 160. Of the power generated by the power generation unit 130, 50 kW, excluding the power used by the auxiliary equipment, is the output during the self-sustained operation. When the fuel cell system 10 operates independently, this 50 kW can be surplus power.

  During the self-sustaining operation of the fuel cell system 10, the control unit 100 drives at least the water vapor generation unit 40 with surplus power. The control unit 100 supplies a part of surplus power to the internal load 30 during the independent operation. The internal load 30 may be an electric heater, for example. The heat generated by the electric heater may be released around the fuel cell system 10.

  By consuming surplus power during the self-sustaining operation with the steam generation unit 40 and the internal load 30, the power generation amount of the power generation unit 130 can be maintained at a power generation amount that allows the fuel cell module 110 to be thermally independent. Therefore, when the fuel cell system 10 restarts the connection with the external power source 80, the output of the fuel cell system 10 can be returned to the rated output in a short time. The fuel cell module 110 is in a state where the temperature of the power generation unit 130 and the temperature of the reforming unit 120 can be maintained at specified values by heat generated by power generation of the power generation unit 130, for example. It may be.

  Thus, according to the fuel cell system 10, since the surplus power during the self-sustaining operation is consumed by the steam generation unit 40, an increase in the capacity of the internal load 30 necessary for maintaining the self-sustaining operation can be suppressed. . As a result, the enlargement and cost increase of the fuel cell system 10 can be suppressed.

  Note that the amount of water vapor supplied to the raw fuel flow path 180 is increased by driving the water vapor generating unit 40. Therefore, the steam carbon ratio (S / C) of the gas supplied to the reforming unit 120 is increased. Therefore, the control unit 100 controls the blower 160 to reduce the recirculation flow rate of the fuel exhaust gas. Thereby, a raise of a steam carbon ratio (S / C) can be suppressed and the output fall of the electric power generation part 130 can be suppressed. Therefore, it becomes easy to make the fuel cell system 10 thermally independent during the self-sustaining operation.

  Thus, in the fuel cell system 10, when the fuel cell system 10 is disconnected from the system power supply, the control unit 100 supplies at least a part of the surplus power to the water vapor generation unit 40, and the water vapor generation unit 40. The amount of fuel exhaust gas recirculated to the reforming unit 120 is reduced according to the amount of water vapor generated in step (b). Specifically, the control unit 100 generates the S / C in the gas including the fuel exhaust gas and the raw fuel gas recirculated to the reforming unit 120 at a predetermined value in order to maintain the S / C in a predetermined value. The amount of the fuel exhaust gas recirculated to the reforming unit 120 is reduced according to the amount of steam that has been made.

  Specifically, the control unit 100 controls the power generation unit 130 so that the output of the fuel cell system 10 becomes the rated output while the fuel cell system 10 is connected to the grid power supply. When the fuel cell system 10 is disconnected from the system power supply, the control unit 100 reduces the generated power of the power generation unit 130 so that the output of the fuel cell system 10 can be operated independently. To a predetermined self-sustained output to be maintained at the same time, supply at least part of the surplus power to the steam generation unit 40, and in accordance with the amount of steam generated by the steam generation unit 40, the reforming unit 120 Reduce the amount of fuel exhaust gas recirculated.

  Further, the control unit 100 further supplies a part of the surplus power to the internal load 30 when the fuel cell system 10 is disconnected from the system power supply. As a result, the power generated by the power generation unit 130 is maintained at a power level that can maintain the heat self-sustaining in the reforming unit 120 and the power generation unit 130.

  In the present embodiment, the case where the external power source 80 is a commercial power source will be mainly described. However, the same control as the control described in the present embodiment can also be applied to the case where the fuel cell system 10 is disconnected from the external power source 80 when the external power source 80 is a power source other than the commercial power source. That is, when the fuel cell system 10 is disconnected from the external power supply 80, the control unit 100 supplies at least part of the surplus power to the water vapor generation unit 40, and according to the amount of water vapor generated by the water vapor generation unit 40. The amount of fuel exhaust gas recirculated to the reforming unit 120 may be reduced.

  FIG. 2 is a diagram for explaining the change over time in the operating parameters when the fuel cell system 10 is disconnected during the interconnected operation. The horizontal axis in FIG. 2 indicates time, and the vertical axis indicates operation parameters. In FIG. 2, the system output, the power consumption of the internal load 30, the power consumption of the water vapor generation unit 40, the recirculation flow rate of the fuel exhaust gas, and the S / C are shown as operation parameters.

  During the interconnected operation, the control unit 100 controls the output of the fuel cell system 10 to be a rated output of 100 kW. Specifically, the control unit 100 controls the desulfurization unit 70 so that the amount of the raw fuel gas supplied to the raw fuel flow path 180 becomes a specified amount associated with the rated output. In addition, the control unit 100 controls the blower 160 so that the flow rate of the fuel exhaust gas in the fuel exhaust gas recirculation flow path 183 becomes a specified amount associated with the rated output. As a result, the control unit 100 controls the S / C of the gas supplied to the reforming unit 120 to be the specified value 3.5.

  As shown in the figure, during rated operation of the fuel cell system 10, power is not supplied to the internal load 30 and the water vapor generation unit 40. The output of the fuel cell system 10 is the power obtained by subtracting the power supplied to the auxiliary machine included in the fuel cell system 10 from the power that can be output by the DC-AC conversion unit 60.

  When the fuel cell system 10 is disconnected, the control unit 100 performs control so that the output of the fuel cell system 10 is 50 kW, which is the output during the self-sustained operation. For example, the control unit 100 controls the desulfurization unit 70 so that the flow rate of the raw fuel gas in the raw fuel flow path 180 becomes a specified amount associated with the output at the time of self-supporting. Specifically, the control unit 100 halves the flow rate of the raw fuel gas from the flow rate during rated operation.

  Then, the control unit 100 supplies the electric power from the DC-AC conversion unit 60 to the internal load 30 through the internal power supply line 24 and consumes it. The electric power supplied to the internal load 30 during the independent operation is 25 kW. Moreover, the control part 100 supplies the output electric power from the DC-AC conversion part 60 to the water vapor | steam production | generation part 40 through the internal power supply line 24, and produces | generates water vapor | steam. The electric power supplied to the water vapor generation unit 40 is 25 kW. The self-sustained heat in the fuel cell module 110 is maintained by consuming electric power in the internal load 30 and the water vapor generating unit 40.

  As indicated by a line 210 in the S / C graph of FIG. 2, the water vapor generation unit 40 consumes 25 kW of electric power, so that the water vapor amount contributes 3.0 in terms of S / C. Therefore, the control unit 100 reduces the recirculation amount of the fuel exhaust gas until it becomes 0.5 in S / C conversion as indicated by a line 200 in the S / C graph of FIG. The S / C of the supply gas to 120 is maintained at a default value of 3.5. Specifically, the control unit 100 reduces the recirculation flow rate of the fuel exhaust gas to 1/7 of the recirculation flow rate during the rated operation. By reducing the recirculation flow rate of the fuel exhaust gas, it is possible to suppress a decrease in the output of the control unit 100. Note that the surplus fuel exhaust gas by reducing the recirculation flow rate of the fuel exhaust gas is supplied to the exhaust energy utilization unit 190 through the fuel exhaust gas exhaust passage 184.

  In this way, the control unit 100 supplies and consumes the 50 kW power of the self-sustained output to the water vapor generation unit 40. Thereby, it is not necessary to increase the capacity of the internal load 30 excessively.

Table 1 shows the specifications of the fuel cell system 10 of the present embodiment and the specifications of the fuel cell systems in Comparative Example 1, Comparative Example 2, and Comparative Example 3.

  In the fuel cell system in Comparative Example 1, the capacity of the internal load is set to 50 kW, and the control for consuming all of the self-sustained output by the internal load is performed.

  FIG. 3 is a diagram for explaining temporal changes in operating parameters in the fuel cell system of Comparative Example 1. The operation parameters in FIG. 3 are the same as the operation parameters in FIG.

  As shown in FIG. 3, when the fuel cell system is disconnected, the output of the fuel cell module is reduced to 50 kW. The 50 kW self-sustained output is all consumed by the internal load. In order to maintain the S / C at 3.5, the recirculation flow rate of the fuel exhaust gas is controlled to 50% of the rated operation.

  The fuel cell system of Comparative Example 1 can also maintain a self-sustaining operation. However, it is necessary to provide the fuel cell system with an internal load having a capacity of 50 kW. Therefore, as shown in Table 1, the size of the internal load is increased, and the fuel cell system is increased in size. In addition, the cost of the entire fuel cell system increases.

  Next, Comparative Example 2 will be described. The fuel cell system in Comparative Example 2 is the same as the fuel cell system in Comparative Example 1, except that the internal load capacity is 25 kW and the self-sustained output of the fuel cell is 25 kW. According to the fuel cell system of Comparative Example 2, an increase in size of the fuel cell system can be suppressed. However, since the output when the fuel cell is self-supporting is 25 kW, the amount of heat generated in the power generation unit of the fuel cell module is small. Therefore, it is not easy to maintain the heat self-supporting of the fuel cell module 110.

  Next, Comparative Example 3 will be described. The fuel cell system in Comparative Example 3 performs control to make the recirculation flow rate of the fuel exhaust gas 50% in the fuel cell system 10 of the present embodiment. According to the fuel cell system of Comparative Example 3, an increase in size of the fuel cell system can be suppressed. However, if the recirculation flow rate of the fuel exhaust gas is set to 50%, the water vapor partial pressure in the gas supplied to the reforming section is remarkably increased. That is, S / C is remarkably increased. Thereby, since the output of a power generation part falls, it is not easy to maintain the heat self-supporting of a fuel cell module.

  Compared to the fuel cell systems of Comparative Example 1, Comparative Example 2, and Comparative Example 3, according to the fuel cell system 10, the fuel cell module is easy to be thermally independent and provides a smaller fuel cell system. be able to.

  FIG. 4 is a flowchart showing a method for controlling the fuel cell system 10 by the control unit 100. The subject of the operation at each stage in the present control method may be the control unit 100. The control unit 100 may include a processing device such as a CPU or an ASIC, a memory, and the like in order to implement the control method described in this flowchart. Note that the flowchart of FIG. 4 only shows an example of a control method in the fuel cell system 10. Each step of the flowchart of FIG. 4 may be appropriately recombined, some steps of the flowchart of FIG. 4 may be omitted, and other steps may be added to the flowchart of FIG.

  In S400 of this flowchart, the control unit 100 performs a startup process of the fuel cell system 10. Specifically, the control unit 100 supplies power from the external power source 80 to the heating unit 50 to drive the heating unit 50 to heat the reforming unit 120 and the power generation unit 130. Further, the control unit 100 supplies power from the external power source 80 to the water vapor generation unit 40 to drive the water vapor generation unit 40 to supply water vapor to the raw fuel flow path 180 and control the flow rate of the raw fuel gas. Then, the raw fuel flow path 180 is supplied.

  When the output of the fuel cell system 10 reaches the rated output, the interconnection operation with the external power source 80 is performed in S402. During the interconnection operation, the operations of the water vapor generating unit 40 and the heating unit 50 are stopped.

  In S404, it is determined whether or not the fuel cell system 10 is disconnected from the external power source 80. For example, the control unit 100 determines to disconnect from the external power supply 80 when a power failure occurs in the external power supply 80. For example, the control unit 100 may determine that a power failure has occurred when the voltage of the external power supply line 20 falls below a predetermined value. Further, the control unit 100 may determine that the external power supply 80 is disconnected when the difference between the frequency of the external power supply line 20 and the reference frequency exceeds a predetermined value. Further, the control unit 100 may determine to disconnect from the external power supply 80 when a disconnection instruction is received from the outside.

  When disconnecting from the external power source 80, the fuel cell system 10 is disconnected from the external power source 80 in S406. Specifically, the control unit 100 disconnects the fuel cell system 10 from the external power supply 80 by turning off the relay 22.

  In S408, the control unit 100 reduces the output of the fuel cell system 10 from the rated output of 100 kW to the self-sustained output of 50 kW. Specifically, the control unit 100 sets the output of the fuel cell system 10 from the rated output by setting the flow rate of the raw fuel supplied from the desulfurization unit 70 to the raw fuel flow path 180 to 50% during the rated operation. Reduce to self-sustained output.

  In S410, the control unit 100 supplies power from the DC-AC conversion unit 60 to the water vapor generation unit 40 through the internal power supply line 24 to start the water vapor generation unit 40, and generates water vapor in the water vapor generation unit 40. Let

  In step S <b> 412, the control unit 100 supplies the electric power from the DC-AC conversion unit 60 to the internal load 30 through the internal power supply line 24 and causes the internal load 30 to consume it.

  Subsequently, in S414, the control unit 100 controls the blower 160 to control the recirculation flow rate of the fuel exhaust gas so that the S / C of the supply gas to the reforming unit 120 is maintained in the vicinity of 3.5. To do.

  In S416, it is determined whether or not the connection with the external power source 80 is resumed. For example, when disconnecting in response to a power failure of the external power supply 80 in S404, the control unit 100 may determine that the connection with the external power supply 80 is resumed when the power recovery of the external power supply 80 is detected. Further, the control unit 100 may determine that the external power supply 80 is disconnected when the difference between the frequency of the external power supply line 20 and the reference frequency is equal to or less than a predetermined value. In addition, when an interconnection instruction from the outside is received, it may be determined that the interconnection with the external power supply 80 is resumed.

  When the connection with the external power supply 80 is restarted, a connection restart process is performed in S418. Specifically, the control unit 100 connects the output side of the DC-AC conversion unit 60 to the external power supply line 20 by turning on the relay 22. In addition, the control unit 100 increases the flow rate of the raw fuel supplied to the raw fuel flow path 180 to a specified amount during rated operation. Next, after proceeding to S402 for performing an interconnection operation with the external power source 80, the output of the fuel cell system 10 is increased to the rated output. As described above, according to the fuel cell system 10, since the self-sustaining operation with the output of 50 kW can be maintained in the disconnected state, the time required to start the interconnection operation can be shortened.

  If it is determined in S416 of this flowchart that the connection with the external power supply 80 is not resumed, it is determined whether or not the operation of the fuel cell system 10 is stopped in S420. For example, the control unit 100 determines to stop the operation of the fuel cell system 10 when an instruction to stop the operation of the fuel cell system 10 is received. If the operation of the fuel cell system 10 is not stopped, the process proceeds to S414. When stopping the operation of the fuel cell system 10, the stop process of the fuel cell system 10 is performed in S422, and the process of this flowchart is ended.

  Also, in S404 of this flowchart, when it is determined that the external power supply 80 is disconnected, it is determined whether or not the operation of the fuel cell system 10 is stopped in S430, similarly to S420. When the operation of the fuel cell system 10 is not stopped, the process proceeds to S402. When stopping the operation of the fuel cell system 10, the process proceeds to S422.

  FIG. 5 schematically shows the external power supply 80, the external load 90, and the external power supply line 20 including the functional blocks of the fuel cell system 500 according to another embodiment. The structure of the fuel cell system 10 includes the control valve 510, the control valve 520, and the water vapor discharge channel 580 in addition to the components included in the fuel cell system 10 described above. Is different.

  The water vapor discharge channel 580 is branched from the water vapor supply channel 181. The water vapor discharge channel 580 is connected to the fuel exhaust gas discharge channel 184. The control valve 510 is provided in the water vapor discharge channel 580. The control valve 520 is provided on the downstream side of the branch point of the water vapor supply channel 181 with the water vapor discharge channel 580.

  About the control content of the fuel cell system 500, the difference with the fuel cell system 10 is mainly demonstrated. The control unit 100 closes the control valve 520 and opens the control valve 510 when the fuel cell system 10 is operated at the self-sustained output. As a result, the water vapor generated by the water vapor generation unit 40 is discharged to the fuel exhaust gas discharge flow path 184 through the water vapor discharge flow path 580. According to the fuel cell system 500, it is possible to maintain the output at the time of self-supporting without greatly reducing the recirculation flow rate of the fuel exhaust gas.

  In the above description, the mode in which the internal load 30 consumes a part of the self-sustained output in the fuel cell system 10 has been described. As another embodiment, the control unit 100 may cause the heating unit 50 to consume a part of the output during self-supporting. That is, the internal load is a concept including the heating unit 50 in addition to the internal load 30 described in the present embodiment. The internal load may include various loads that are not substantially driven in the fuel cell system 10 during rated operation.

  The control unit 100 may be realized by a computer. When the computer executes the program, the program may realize the function of the control unit 100 by controlling each unit such as a processor and a memory included in the computer. The program may be stored in a computer-readable recording medium.

  Note that the same control as the control of the control unit 100 described in the present embodiment can be applied to cases other than the case where the fuel cell system 10 is disconnected from the external power supply 80. For example, when the fuel cell system 10 maintains a self-sustained operation after startup, the present invention can also be applied to a case where the power generated by the power generation unit 130 during the self-sustaining operation of the fuel cell system 10 exceeds the load power during the self-sustained operation. Here, the load power during the independent operation may be the power consumed by the auxiliary equipment of the fuel cell system 10. Further, when an emergency load is connected to the internal power supply line 24, the load power during the self-sustaining operation may include the power consumed by the emergency load. Furthermore, the same control as the control of the control unit 100 described in the present embodiment is that power that can be generated by the power generation unit 130 is generated regardless of whether the fuel cell system 10 is connected to the external power source 80 or not. It is applicable when the load power that consumes 130 generated power is exceeded.

  That is, when the generated power of the power generation unit 130 exceeds the load power, the control unit 100 supplies at least a part of the surplus power exceeding the load power to the steam generation unit 40 and at least a part of the surplus power to the steam generation unit. The amount of fuel exhaust gas supplied to the reforming unit 120 may be reduced according to the amount of water vapor generated by the water vapor generating unit 40 as a result of consumption of 40. Thereby, the output required in order to maintain the thermal self-supporting of the fuel cell system 10 can be maintained by suppressing the decrease in the generated power accompanying the increase in the amount of water vapor.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  The order of execution of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior to”. It should be noted that the output can be realized in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for convenience, it means that it is essential to carry out in this order. It is not a thing.

DESCRIPTION OF SYMBOLS 10 Fuel cell system 20 External power supply line 22 Relay 24 Internal power supply line 30 Internal load 40 Steam generation part 50 Heating part 60 DC-AC conversion part 70 Desulfurization part 80 External power supply 90 Load 100 Control part 110 Fuel cell module 120 Reforming part 130 Power generation unit 150 Flow rate sensor 160 Blower 180 Raw fuel flow path 181 Water vapor supply flow path 182 Fuel exhaust gas flow path 183 Fuel exhaust gas recirculation flow path 184 Fuel exhaust gas discharge flow path 186 Oxidant gas flow path 188 Oxidant exhaust gas flow path 190 Exhaust energy Use part 200, 210 Line 500 Fuel cell system 510 Control valve 520 Control valve 580 Water vapor discharge passage

Claims (8)

A fuel cell system,
A power generation unit that generates power by a reaction between the fuel gas and the oxidant gas, and discharges fuel exhaust gas containing water vapor generated at the fuel electrode;
A reforming section to which the fuel exhaust gas and raw fuel gas are supplied;
A control unit for controlling the amount of the fuel exhaust gas recirculated to the reforming unit;
A steam generating unit that consumes electric power and generates steam supplied to the reforming unit;
When the fuel cell system is disconnected from an external power source capable of supplying power in parallel with the fuel cell system, the control unit supplies at least part of the surplus power to the water vapor generation unit, and the surplus power The fuel cell system reduces the amount of the fuel exhaust gas recirculated to the reforming unit according to the amount of water vapor generated by the water vapor generating unit by consuming the at least part of the water vapor generating unit. The external power supply is a system power supply,
When the fuel cell system is disconnected from the system power supply, the control unit supplies at least a part of the surplus power to the water vapor generation unit, and according to the amount of water vapor generated by the water vapor generation unit. The fuel cell system according to claim 1, wherein the amount of the fuel exhaust gas recirculated to the reforming unit is reduced. The controller is
While the fuel cell system supplies power in parallel with the external power supply, the power generation unit is controlled so that the output of the fuel cell system becomes a rated output,
When the fuel cell system is disconnected from the external power source, the power generated by the power generation unit is reduced, and the output of the fuel cell system should be maintained in order to operate the fuel cell system independently. In addition, the output is reduced to a self-sustained output, and at least a part of the surplus power is supplied to the steam generation unit, and is recirculated to the reforming unit according to the amount of steam generated by the steam generation unit. The fuel cell system according to claim 1, wherein the amount of fuel exhaust gas is reduced. An internal load that consumes power,
The control unit further supplies a part of the surplus power to the internal load when the fuel cell system is disconnected from the external power source, and converts the generated power of the power generation unit to the reforming unit and the reforming unit. The fuel cell system according to any one of claims 1 to 3, wherein the fuel cell system is maintained at electric power capable of maintaining thermal independence in the fuel cell module including the power generation unit. When the generated power of the power generation unit exceeds load power, the control unit supplies at least a part of surplus power exceeding the load power to the water vapor generation unit, and the at least part of the surplus power is supplied to the water vapor. The amount of the said fuel exhaust gas recirculated to the said reforming part is reduced according to the amount of water vapor | steam produced | generated by the said water vapor | steam production | generation part by consuming a production | generation part. Fuel cell system. The controller generates the steam generated by the steam generator so as to maintain a steam carbon ratio in a gas including the fuel exhaust gas and the raw fuel gas supplied to the reforming unit at a predetermined value. The fuel cell system according to any one of claims 1 to 5, wherein the amount of the fuel exhaust gas recirculated to the reforming unit is reduced according to the amount. A power generation unit that generates power by a reaction between the fuel gas and the oxidant gas, and discharges fuel exhaust gas containing water vapor generated at the fuel electrode;
A reforming section to which the fuel exhaust gas and raw fuel gas are supplied;
A control device for a fuel cell system comprising a water vapor generating unit that consumes electric power and generates water vapor supplied to the reforming unit,
When the fuel cell system is disconnected from an external power source capable of supplying power in parallel with the fuel cell system, at least a part of surplus power is supplied to the water vapor generating unit, and the at least part of the surplus power is A control device comprising a control unit that reduces the amount of the fuel exhaust gas recirculated to the reforming unit according to the amount of water vapor generated by the water vapor generation unit as a result of consumption of the water vapor generation unit. A power generation unit that generates power by a reaction between the fuel gas and the oxidant gas, and discharges fuel exhaust gas containing water vapor generated at the fuel electrode;
A reforming section to which the fuel exhaust gas and raw fuel gas are supplied;
A method for controlling a fuel cell system, comprising a water vapor generating unit that consumes electric power and generates water vapor supplied to the reforming unit,
When the fuel cell system is disconnected from an external power source capable of supplying power in parallel with the fuel cell system, supplying at least a part of surplus power to the water vapor generating unit;
Reducing the amount of the fuel exhaust gas recirculated to the reforming unit according to the amount of water vapor generated in the water vapor generating unit by consuming at least a part of the surplus power by the water vapor generating unit; A control method comprising:

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