JP2021163728A - Fuel cell system and fuel shortage determination method - Google Patents

Abstract

To detect shortage of anode gas to be supplied to a fuel cell stack with good responsiveness while suppressing cost increase.SOLUTION: A fuel cell system includes: a resistance acquisition unit for acquiring internal resistance of a fuel cell stack from output voltage and output current of the fuel cell stack; a moving average calculation unit that on the basis of the internal resistance acquired by the resistance acquisition unit, calculates at every predetermined time a first moving average value, an average of internal resistance in a predetermined first time, and a second moving average value, an average of internal resistance in a second time longer than the first time; and a determination unit that on the basis of a difference between the first moving average value and the second moving average value calculated by the moving average calculation unit, determines whether anode gas to be supplied from a reformer to the fuel cell stack is insufficient.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a fuel cell system including a fuel cell stack that generates power by an electrochemical reaction between an anode gas and a cathode gas, and a fuel shortage determination method.

Conventionally, a fuel cell (fuel cell stack), a power storage means, a first DC / DC converter connected to the electric load and the fuel cell, and a bidirectional second DC connected to the electric load and the power storage means. A fuel cell power supply including a / DC converter is known (see, for example, Patent Document 1). In this fuel cell power supply device, power is supplied from the power storage means to the electric load via the second DC / DC converter, and the current output of the fuel cell is stopped by controlling the first DC / DC converter. The voltage between terminals of the fuel cell in the above, the voltage between terminals of the fuel cell in a state where the output current of the fuel cell is set to the first predetermined current value by controlling the first DC / DC converter, and the first predetermined current. The internal resistance value of the fuel cell is calculated based on the value. Then, the deterioration level of the fuel cell is determined from the change in the internal resistance value of the fuel cell.

Further, conventionally, a cell stack (fuel cell stack) including a plurality of fuel cell cells, a current detecting means for detecting the output current of the cell stack, an output voltage of the cell stack, and one or a plurality of the output voltage of the cell stack at a specific part of the cell stack. A voltage detecting means capable of detecting the output voltage of the fuel cell, a control means capable of controlling the supply amount of the fuel gas, the supply amount of the oxidant gas, and the output current of the cell stack, and a predetermined portion of the cell stack. A fuel cell system including a temperature detecting means for detecting a temperature is known (see, for example, Patent Document 2). In this fuel cell system, the control means is when the output current, the supply amount of the fuel gas, and the supply amount of the oxidant gas are changed at a constant ratio while the temperature of the cell stack is stable, or when the fuel gas is used. The deterioration state of a specific part of the cell stack is determined based on the detection result by the voltage detecting means when the output current of the cell stack is changed while the supply amount and the supply amount of the oxidant gas are kept constant.

JP-A-2009-176491 Japanese Unexamined Patent Publication No. 2010-027580

By the way, in a fuel cell system including a solid oxide type fuel cell stack, in order to prevent a failure of the fuel cell stack due to a shortage of the anode gas (fuel gas) supplied to the fuel cell stack, the anode gas is used. It is necessary to accurately detect the shortage. However, although the above-mentioned patent document describes a method for determining the deterioration of the fuel cell stack, no method for determining the shortage of the anode gas is disclosed. On the other hand, if a high-precision flow meter is used to measure the flow rate of the anode gas, the cost of the fuel cell system will increase. In addition, when the anode gas is insufficient, the off-gas burned in the combustion part around the fuel cell stack decreases and the temperature in the combustion part decreases. Therefore, by detecting the temperature decrease in the combustion part, the anode gas is insufficient. Will be able to detect. However, the time constant of the temperature drop of the combustion part is long, and it takes time to detect the shortage of the anode gas from the temperature of the combustion part.

Therefore, the main object of the present disclosure is to detect the shortage of the anode gas supplied to the fuel cell stack with good responsiveness while suppressing the cost increase.

The fuel cell system of the present disclosure is a fuel cell system including a fuel cell stack that generates power by an electrochemical reaction between an anode gas and a cathode gas, and a reformer that reforms a raw fuel gas to generate the anode gas. , A resistance acquisition unit that acquires the internal resistance of the fuel cell stack from the output voltage and output current of the fuel cell stack, and a predetermined first time based on the internal resistance acquired by the resistance acquisition unit. A moving average calculation unit that calculates the first moving average value, which is the average of the internal resistance, and the second moving average value, which is the average of the internal resistance in the second time longer than the first time, at predetermined time intervals. Is the anode gas supplied from the reformer to the fuel cell stack insufficient based on the difference between the first moving average value and the second moving average value calculated by the moving average calculation unit? It includes a determination unit for determining whether or not to use it.

In the fuel cell system of the present disclosure, the moving average calculation unit has a first moving average value, which is the average of the internal resistances of the fuel cell stack in the predetermined first time, and the inside in the second time, which is longer than the first time. The second moving average value, which is the average of the resistances, is calculated at predetermined time intervals. Then, the determination unit determines whether or not the anode gas supplied from the reformer to the fuel cell stack is insufficient based on the difference between the first moving average value and the second moving average value. That is, if the anode gas supplied from the reformer to the fuel cell stack decreases (insufficient) during power generation of the fuel cell stack, the internal resistance of the fuel cell stack increases, and the first moving average value becomes the second moving average. It increases early compared to the value. Therefore, by monitoring the difference between the first and second moving average values, the anode gas supplied from the reformer to the fuel cell stack is insufficient without using a flow meter that can accurately detect the flow rate of the anode gas. It is possible to quickly determine whether or not the fuel cell is used. As a result, in the fuel cell system of the present disclosure, it is possible to detect a shortage of the anode gas supplied to the fuel cell stack with good responsiveness while suppressing an increase in cost.

Further, the determination unit determines whether or not the difference between the first moving average value and the second moving average value is equal to or greater than a predetermined threshold value, and if the difference is equal to or greater than the threshold value, It may be considered that the anode gas supplied from the reformer to the fuel cell stack is insufficient.

Further, the fuel cell system either increases the amount of the raw fuel gas to the reformer, reduces the output of the fuel cell stack, or reduces the output of the fuel cell stack when the difference is greater than or equal to the threshold. It may be the one that stops the power generation by.

The fuel shortage determination method of the present disclosure is a fuel cell system including a fuel cell stack that generates power by an electrochemical reaction between an anode gas and a cathode gas, and a reformer that reforms the raw fuel gas to generate the anode gas. The first moving average value, which is the average of the internal resistances in the predetermined first time, and the average of the internal resistances in the second time, which is longer than the first time. The two moving average values are calculated at predetermined time intervals, and the anode gas supplied from the reformer to the fuel cell stack is insufficient based on the difference between the first moving average value and the second moving average value. It determines whether or not it is done.

According to this method, it is possible to detect the shortage of the anode gas supplied to the fuel cell stack with good responsiveness while suppressing the cost increase.

It is a schematic block diagram which shows the fuel cell system of this disclosure. It is a flowchart which shows an example of the fuel shortage determination routine executed in the fuel cell system of this disclosure. It is a time chart which illustrates the time change of the fuel utilization rate, the output voltage of a combustion battery stack, and the 1st and 2nd moving average values while the fuel shortage determination routine of FIG. 2 is executed.

Next, a mode for carrying out the invention of the present disclosure will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing the fuel cell system 10 of the present disclosure. The fuel cell system 10 shown in the figure includes a power generation unit 20 having a fuel cell stack FCS that generates power by an electrochemical reaction between hydrogen in an anode gas (fuel gas) and oxygen in a cathode gas (oxidant gas), and hot water. It is a cogeneration system including a hot water supply unit 100 having a hot water storage tank 101 for storing the hot water, and a control device 80 for controlling the entire system. Further, the power generation unit 20 includes a fuel cell stack FCS, a box-shaped module case 31 formed of a heat insulating material, a vaporizer (evaporator) 33, a power generation module 30 including two reformers 34, and the like, and power generation. A raw fuel gas supply system 40 for supplying a raw fuel gas (raw fuel) such as city gas (natural gas) or LP gas to the vaporizer 33 of the module 30 and a fuel cell stack FCS of the power generation module 30 as cathode gas. To recover the exhaust heat generated by the cathode gas supply system 50 for supplying the air, the reformed water supply system 55 for supplying the reformed water to the vaporizer 33 of the power generation module 30, and the power generation module 30. The exhaust heat recovery system 60, the power conditioner 71 connected to the output terminal of the fuel cell stack FCS, and the housing 22 accommodating these are included.

In the present embodiment, the power generation module 30 includes two fuel cell stack FCSs, and the two fuel cell stack FCSs are installed on a manifold 32 arranged in the module case 31 so as to face each other at a distance. NS. Each fuel cell stack FCS has, for example, an electrolyte such as zirconium oxide, and an anode electrode and a cathode electrode that sandwich the electrolyte, and a plurality of solid oxide fuel cells arranged in the left-right direction (horizontal direction) in FIG. Includes cell SC. In the anode electrode of each single cell SC, an anode gas passage (not shown) is formed so as to extend in a direction orthogonal to the arrangement direction of the single cell SC, that is, in the vertical direction. Further, around the cathode electrode of each single cell SC, a cathode gas passage (not shown) through which the cathode gas flows is formed so as to extend in a direction orthogonal to the arrangement direction of the single cell SC, that is, in a vertical direction. The anode gas passage of each single cell SC is connected to an anode gas passage (not shown) formed in the manifold 32, and the cathode gas passage of each single cell SC is connected to a cathode gas passage (not shown) in the module case 31.

The vaporizer 33 and the reformer 34 of the power generation module 30 are arranged above the two fuel cell stack FCSs in the module case 31 at intervals from each other. In this embodiment, the vaporizer 33 and one reformer 34 are arranged above one fuel cell stack FCS, and the other reformer 34 is arranged above the other fuel cell stack FCS. Further, between one fuel cell stack FCS and the vaporizer 33 and one reformer 34, and between the other fuel cell stack FCS and the other reformer 34 in the vertical direction, the fuel cell stack FCS The combustion unit 35 that generates the heat required for the operation of the fuel cell 33 and the reaction in the vaporizer 33 and the reformer 34 is defined. An ignition heater 36 is installed in each combustion unit 35, and a temperature sensor 37 is installed in at least one of the combustion units 35 so as to be close to the fuel cell stack FCS.

The vaporizer 33 heats the raw fuel gas from the raw material fuel gas supply system 40 and the reformed water from the reformed water supply system 55 by the heat from the combustion unit 35 to preheat the raw material fuel gas and reformed water. To generate water vapor. The raw material fuel gas preheated by the vaporizer 33 mixes with water vapor, and the mixed gas of the preheated raw material fuel gas and water vapor flows from the vaporizer 33 into the reformer 34. The reformer 34 has, for example, a Ru-based or Ni-based reforming catalyst filled therein, and the reaction of the mixed gas from the vaporizer 33 by the reforming catalyst in the presence of heat from the combustion unit 35. Hydrogen gas and carbon monoxide are produced by (steam reforming reaction). Further, the reformer 34 produces hydrogen gas and carbon dioxide by the reaction between carbon monoxide generated by the steam reforming reaction and steam (carbon monoxide shift reaction). As a result, the reformer 34 produces an anode gas containing hydrogen, carbon monoxide, carbon dioxide, steam, unreformed raw material fuel gas, and the like. The anode gas generated by the reformer 34 is supplied to the anode electrodes of each single cell SC via a pipe (not shown) or an anode gas passage of the manifold 32.

Further, air as a cathode gas containing oxygen is supplied to the cathode electrodes of each single cell SC of the fuel cell stack FCS through the cathode gas passage in the module case 31. Each at the cathode electrode of the single cell SC, oxide ions (O ₂ ^-) is generated, the electric energy can be obtained by the oxide ions react with the hydrogen and carbon monoxide at the anode electrode through the electrolyte. The anode gas (hereinafter referred to as "anode off gas") and the cathode gas (hereinafter referred to as "cathode off gas") not used for the electrochemical reaction (power generation) in each single cell SC are used in the anode gas passage of each single cell SC. It flows out from the cathode gas passage to the upper combustion part 35.

The anode off gas that has flowed into the combustion section 35 from each single cell SC is a flammable gas that contains fuel components such as hydrogen and carbon monoxide, and is mixed with the cathode off gas that contains oxygen that has flowed into the combustion section 35 from each single cell SC. Fit. Hereinafter, the mixed gas of the anode off gas and the cathode off gas is referred to as "off gas". Then, when the ignition heater 36 ignites and the off-gas (anode off-gas) is ignited in the combustion unit 35, the combustion of the off-gas causes the operation of the fuel cell stack FCS, the preheating of the raw fuel gas in the vaporizer 33, and the steam. The heat required for the generation, the steam reforming reaction in the reformer 34, and the like will be generated. Further, with the combustion of off-gas, the combustion unit 35 generates combustion exhaust gas containing water vapor.

As shown in FIG. 1, the raw material fuel gas supply system 40 includes a raw material fuel gas supply pipe 41 connecting a raw material fuel supply source 1 for supplying city gas or LP gas and a vaporizer 33, and the raw material fuel gas supply pipe 41. The raw material fuel gas supply valve (electromagnetic on-off valve) 42 and the raw material fuel gas pump 44 incorporated in, and the raw material fuel gas supply pipe 41 incorporated in the raw material fuel gas supply pipe 41 so as to be located between the vaporizer 33 and the raw material fuel gas pump 44, for example, at room temperature. Includes a desulfurization type desulfurizer 45. Further, a pressure sensor 46 and first and second flow meters 47 and 48 are incorporated between the raw fuel gas supply valve 42 of the raw fuel gas supply pipe 41 and the raw fuel gas pump 44. The pressure sensor 46 is incorporated in the raw material fuel gas supply pipe 41 so as to be located near the discharge port of the raw material fuel gas pump 44, and detects the pressure of the raw material fuel gas flowing through the raw material fuel gas supply pipe 41. The first and second flow meters 47 and 48 are thermal flow meters including a temperature sensor and a heater (not shown), and the raw fuel supply source 1 is based on the temperature change of the raw fuel gas to which heat is applied from the heater. The flow rate per unit time of the raw material fuel gas flowing through the raw material fuel gas supply pipe 41 toward the reformer 34 (vaporizer 33) is detected.

The cathode gas supply system 50 is incorporated into the cathode gas supply pipe 51 connected to the cathode gas passage in the module case 31, the air filter 52 installed at the gas inlet of the cathode gas supply pipe 51, and the cathode gas supply pipe 51. Includes the blower 53 and the blower 53. By operating the blower 53, air as the cathode gas sucked through the air filter 52 is pumped (supplied) by the blower 53 to each fuel cell stack FCS via the cathode gas passage. Further, the cathode gas supply pipe 51 is provided with a flow rate switch 54 that turns on when the flow rate of the cathode gas flowing through the cathode gas supply pipe 51 per unit time reaches a predetermined value.

The reformed water supply system 55 includes a reformed water supply pipe 56 connected to the vaporizer 33, a reformed water tank 57 connected to the reformed water supply pipe 56 and storing the reformed water, and the reformed water. It includes a reforming water pump 58 incorporated in the supply pipe 56. By operating the reforming water pump 58, the reforming water in the reforming water tank 57 is pumped (supplied) to the vaporizer 33 by the reforming water pump 58. Further, in the reformed water tank 57, a water purifier (not shown) for purifying the stored reformed water is installed.

The exhaust heat recovery system 60 is a heat exchanger that exchanges heat between the circulation pipe 61 connected to the hot water storage tank 101 of the hot water supply unit 100, the hot water flowing through the circulation pipe 61, and the combustion exhaust gas from the combustion unit 35 of the power generation module 30. 62 and a circulation pump 63 incorporated in the circulation pipe 61. By operating the circulation pump 63, the hot water stored in the hot water storage tank 101 by the circulation pump 63 is introduced into the heat exchanger 62, and the heat exchanger 62 removes heat from the combustion exhaust gas to heat the hot water. It can be returned to the hot water storage tank 101.

Further, the exhaust heat recovery system 60 consumes power from the radiator 64 incorporated in the circulation pipe 61, the radiator fan (electric fan) 65 for sending air to the radiator 64, and the power generation module 30, and is contained in the circulation pipe 61. It includes an electric heater (for example, a ceramic heater) 66 for heating hot water and a thermistor (temperature sensor) 67 for detecting the temperature of hot water in the circulation pipe 61. The radiator 64 is incorporated in the circulation pipe 61 so as to be located between the heat exchanger 62 and the circulation pump 63, and the electric heater 66 is installed in the circulation pipe 61 so as to be located between the circulation pump 63 and the radiator 64. Be incorporated. Further, the thermistor 67 is installed on the downstream side of the electric heater 66 so as to be close to the electric heater 66.

The electric heater 66 is operated so as to consume surplus power when the output required for the power generation module 30 (fuel cell stack FCS) is lower than the normal rated output. At this time, the circulation pump 63 is duty-controlled so that the temperature detected by the temperature sensor 67 reaches the set temperature, and the radiator fan 65 is operated as necessary. As a result, even when the output required for the power generation module 30 is low, the heat exchanger 62 recovers the exhaust heat of each fuel cell stack FCS, or the electric heater 66 consumes the surplus power of the power generation module 30. While doing so, it becomes possible to continue the operation of the power generation module 30. Further, by appropriately operating the radiator fan 65 to send air to the radiator 64, the hot water flowing through the circulation pipe 61 is cooled (radiated), and the temperature of the hot water in the hot water storage tank 101 is suppressed from rising more than necessary. can do.

Further, the heat exchanger 62 (combustion exhaust gas passage) of the exhaust heat recovery system 60 is connected to the reforming water tank 57 via a pipe, and the steam in the combustion exhaust gas is the heat of the hot water from the hot water storage tank 101. The condensed water obtained by condensing by exchange is introduced into the reforming water tank 57 via the pipe. Further, the passage of the combustion exhaust gas of the heat exchanger 62 is connected to the exhaust pipe 68. As a result, the exhaust gas discharged from the combustion unit 35 of the power generation module 30 and from which the water has been removed by the heat exchanger 62 is discharged to the atmosphere through the exhaust pipe 68.

The power conditioner 71 includes a DC / DC converter that boosts DC power from each fuel cell stack FCS, an inverter that converts DC power from the DC / DC converter into AC power, and the like (all not shown). The output terminal of the power conditioner 71 (inverter) is connected to the power line 3 connected to the system power supply 2. As a result, at least one of the electric power from the grid power source 2 and the electric power from each fuel cell stack FCS (AC power converted by the above inverter) can be supplied to a plurality of loads 4 such as home appliances. It becomes. Further, the fuel cell system 10 includes a power supply board 72 connected to the power conditioner 71. The power supply board 72 converts the DC power from each fuel cell stack FCS and the AC power from the grid power supply 2 into low-pressure DC power, and converts the raw material fuel gas supply valve 42, the raw material fuel gas pump 44, the blower 53, and the reformed water pump. The DC power is supplied to 58, auxiliary equipment such as a circulation pump 63 and a radiator fan 65, sensors such as a temperature sensor 37, and a control device 80 and the like.

Further, in the auxiliary equipment room where the power conditioner 71, the power supply board 72, etc. are arranged, a cooling fan (not shown) for cooling the power conditioner 71, the power supply board 72, etc., and a ventilation fan 24 are arranged. Has been done. A cooling fan (not shown) sends air to the heat generating portion of the power conditioner 71 or the power supply board 72, and the air heated by cooling the heat generating portion is discharged to the atmosphere by the ventilation fan 24.

The control device 80 is a computer including a CPU 81, a ROM 82 for storing various programs, a RAM 83 for temporarily storing data, an input port, an output port, and the like (all not shown). The control device 80 includes detection values of the temperature sensor 37, the pressure sensor 46, the first and second flow meters 47 and 48, the thermista 67, etc., a signal from the flow switch 54, and a power generation module 30 (fuel) detected by the voltage sensor 88. The output voltage (stack voltage) Vs of the battery stack FCS), the output current (stack current) Is of the power generation module 30 (fuel cell stack FCS) detected by the current sensor 89, and the like are input via the input port. The control device 80 includes a ventilation fan 24, an ignition heater 36, a solenoid of a raw fuel gas supply valve 42, a raw fuel gas pump 44, a blower 53, a reforming water pump 58, a circulation pump 63, a radiator fan 65, and an electric heater 66. , A control signal to a power conditioner 71 (DC / DC converter and an inverter), a power supply board 72, a display unit (not shown), etc. is output via an output port to control these devices. Further, a remote controller (not shown) is connected to the control device 80 via a wireless or wired communication line. The control device 80 executes various controls based on a signal from the remote controller operated by the user of the fuel cell system 10.

Here, in the fuel cell system 10 as described above, when the flow rate of the anode gas actually supplied from the reformer 34 to each fuel cell stack FCS is insufficient with respect to the flow rate required for power generation, oxygen is excessive. As a result, the anode electrode and the like are oxidized and expanded, which may lead to failure of the fuel cell stack FCS. Therefore, the fuel cell system 10 detects a shortage of the flow rate of the anode gas supplied from the reformer 34 to each fuel cell stack FCS with respect to the flow rate required for power generation, and prevents the failure of each fuel cell stack FCS. Therefore, the control device 80 executes the fuel shortage determination routine shown in FIG.

The fuel shortage determination routine of FIG. 2 is repeatedly executed at predetermined time (for example, 1 second) while the operating state of the power generation module 30 is the rated operating state. At the start of the fuel shortage determination routine, the control device 80 (CPU81) acquires the values of the internal resistance (stack resistance) R and the flag F of each fuel cell stack FCS (power generation module 30) (step S100). The internal resistance R is obtained by dividing the output voltage Vs of the power generation module 30 (fuel cell stack FCS) detected by the voltage sensor 88 by the output current Is of the power generation module 30 (fuel cell stack FCS) detected by the current sensor 89. It is calculated separately by. The flag F is set to a value 0 when the flow rate of the anode gas actually supplied to each fuel cell stack FCS during the rated operation of the power generation module 30 is not insufficient with respect to the flow rate required for power generation. Is.

After the processing of step S100, the control device 80 determines the short-term moving average resistance which is the average of the internal resistance R of each fuel cell stack FCS in the predetermined first time of 30 seconds based on the acquired internal resistance R. The value (first moving average value) Rs and the long-term moving average resistance value (second moving average value) Rl, which is the average of the internal resistance R in 180 seconds, which is the second time longer than the first time, are calculated ( Step S110). In step S110, when the control device 80 first calculates the short-term moving average resistance value Rs (first time, k = 1) after the operating state of the power generation module 30 shifts to the rated operation, the control device 80 follows the following equation (1). The internal resistance R acquired in step S100 is used as it is as the short-term moving average resistance value Rs. Further, when the control device 80 calculates the short-term moving average resistance value Rs at the 2nd to 30th times (2 ≦ k ≦ 30) during the rated operation of the power generation module 30, the short-term moving average resistance value Rs according to the following equation (2). When calculating the short-term moving average resistance value Rs from the 31st time onward (k ≧ 31), the short-term moving average resistance value Rs is calculated according to the following equation (3).

Rs (1) = R ... (1)
Rs (k) = Rs (k-1) x (1-1 / k) + R x 1 / k ... (2)
Rs (k) = Rs (k-1) x (1-1 / 30) + R x 1/30 ... (3)

Further, in step S110, when the control device 80 first calculates the long-term moving average resistance value Rl (first time, k = 1) after the operating state of the power generation module 30 shifts to the rated operation, the following equation (4) Therefore, the internal resistance R acquired in step S100 is used as it is as the long-term moving average resistance value Rl. Further, when the control device 80 calculates the long-term moving average resistance value Rl at the 2-180th time (2 ≦ k ≦ 180) during the rated operation of the power generation module 30, the long-term moving average resistance value Rl is calculated according to the following equation (5). When calculating the long-term moving average resistance value Rl from the 181st time onward (k ≧ 181), the long-term moving average resistance value Rl is calculated according to the following equation (6).

Rl (1) = R ... (4)
Rl (k) = Rl (k-1) × (1-1 / k) + R × 1 / k… (5)
Rl (k) = Rl (k-1) × (1-1 / 180) + R × 1/180 ... (6)

By using the above equations (1)-(3) and (4)-(6), the internal resistance R and the like are stored when calculating the short-term moving average resistance value Rs and the long-term moving average resistance value Rl. It is possible to reduce the storage area such as the RAM 83 for the purpose. However, in step S110, a required number (plurality) of past internal resistances R are stored in the RAM 83 or the like, and the short-term moving average resistance value Rs and the long-term moving average resistance value Rl are set based on the plurality of internal resistances R. It may be calculated.

After calculating the short-term moving average resistance value Rs and the long-term moving average resistance value Rl, the control device 80 determines whether or not the flag F has a value of 0 (step S120). When it is determined that the flag F has a value of 0 (step S120: YES), the control device 80 subtracts the long-term moving average resistance value Rl from the short-term moving average resistance value Rs to obtain the difference ΔR (= Rs−Rl) between the two. Calculate (step S130). Further, the control device 80 determines whether or not the difference ΔR is equal to or greater than a predetermined threshold value ΔRref (step S140).

The threshold value ΔRref is rated by the fuel utilization rate Uf, which is the ratio of the anode gas actually used for power generation to the raw fuel gas supplied from the raw material fuel gas supply system 40 to the power generation module 30 (each fuel cell stack FCS). It is determined based on the difference between the short-term moving average resistance value Rs and the long-term moving average resistance value Rl when the value (for example, 85%) is larger than the target value during operation (for example, 80%). When it is determined that the difference ΔR is less than the threshold value ΔRref (step S140: NO), the control device 80 is insufficient for the flow rate of the anode gas actually supplied to each fuel cell stack FCS with respect to the flow rate required for power generation. It is considered that this has not been done, the fuel shortage determination routine is temporarily terminated, and when the next execution timing arrives, the fuel shortage determination routine is executed again.

On the other hand, when it is determined that the difference ΔR is equal to or greater than the threshold ΔRref (step S140: YES), the flow rate of the anode gas actually supplied to each fuel cell stack FCS is insufficient with respect to the flow rate required for power generation. The control device 80 sets the flag F to a value of 1 (step S150), and then executes a process (step S160) for resolving the shortage of the anode gas. In step S160, the control device 80 increases the amount of raw fuel gas supplied from the raw material fuel gas supply system 40 to the reformer 34, or reduces the output of the power generation module 30 (each fuel cell stack FCS). After executing the process of step S160, the control device 80 temporarily terminates the fuel shortage determination routine, and when the next execution timing arrives, the control device 80 re-executes the fuel shortage determination routine.

Further, if the fuel shortage determination routine is executed after the flag F is set to the value 1 in step S150, a negative determination is made in step S120. In this case, the control device 80 determines whether or not a predetermined time has elapsed since the flag F was set to the value 1 in step S150 (step S170). When it is determined that the predetermined time has not elapsed since the flag F was set to the value 1 (step S170: NO), the control device 80 executes the process of step S170 and temporarily ends the fuel shortage determination routine. Let me. When it is determined that a predetermined time has elapsed since the flag F was set to the value 1 (step S170: YES), the flag F is set to the value 0 and the process for solving the shortage of the anode gas is stopped. (Step S180), the fuel shortage determination routine is temporarily terminated.

As a result of executing the fuel shortage determination routine as described above, in the fuel cell system 10, the short-term moving average resistance value which is the average of the internal resistance R of each fuel cell stack FCS in 30 seconds during the rated operation of the power generation module 30. The (first moving average value) Rs and the long-term moving average resistance value (second moving average value) Rl, which is the average of the internal resistance R in 180 seconds, are determined by the control device 80 as the moving average calculation unit. Is calculated every 1 second (predetermined time), which is the execution cycle of (step S110). Then, the control device 80 as the determination unit lacks the anode gas supplied from the reformer 34 to each fuel cell stack FCS based on the difference ΔR between the short-term moving average resistance value Rs and the long-term moving average resistance value Rl. It is determined whether or not this is done (steps S130, S140).

That is, if the anode gas supplied from the reformer 34 to each fuel cell stack FCS decreases (insufficiently) during the power generation of the power generation module 30, the internal resistance R of each fuel cell stack FCS increases and is acquired in step S100. Even if the internal resistance R varies widely, the short-term moving average resistance value Rs (see the solid line in the figure) is earlier than the long-term moving average resistance value Rl (see the broken line in the figure) as shown in FIG. Increases to. Therefore, by monitoring the difference ΔR between the short-term moving average resistance value Rs and the long-term moving average resistance value Rl, each fuel cell can be used from the reformer 34 without using a flow meter capable of accurately detecting the flow rate of the anode gas. It is possible to quickly determine whether or not the anode gas supplied to the stack FCS is insufficient. As a result, in the fuel cell system 10, the process for detecting the shortage of the anode gas supplied to each fuel cell stack FCS with good responsiveness and eliminating the shortage of the anode gas while suppressing the cost increase (step S160). Can be executed.

Here, as shown in FIG. 3, when the fuel utilization rate Uf increases from, for example, 80% to 90% due to fuel shortage, the internal resistance R of each fuel cell FCS increases by about 0.2Ω in about 30 minutes. .. On the other hand, the increase in the internal resistance R due to the deterioration of the fuel cell FCS is about 0.1Ω when the operating time of the fuel cell system 10 reaches about 10,000 hours. Therefore, the increase in the internal resistance R due to the shortage of the anode gas can be clearly separated from the increase in the internal resistance R due to the deterioration of the fuel cell FCS, and even if the usage period of the fuel cell system 10 is prolonged, the short-term moving average resistance From the difference ΔR between the value Rs and the long-term moving average resistance value Rl, the shortage of anode gas can be detected with good responsiveness.

Further, the control device 80 as the determination unit determines whether or not the difference ΔR between the short-term moving average resistance value Rs and the long-term moving average resistance value Rl is equal to or greater than the threshold value ΔRref (steps S130-S150), and the difference ΔR is When it is equal to or more than the threshold value ΔRref, it is considered that the anode gas supplied from the reformer 34 to each fuel cell stack FCS is insufficient. The threshold Rref is based on the difference (= Rs-Rl) between the short-term moving average resistance value Rs and the long-term moving average resistance value Rl when the fuel utilization rate Uf is larger than the target value during rated operation. It is decided. As a result, the threshold value ΔRref can be appropriately determined, and the shortage of the anode gas can be accurately detected by comparing the difference ΔR with the threshold value ΔRref.

In the fuel cell system 10, when the difference ΔR between the short-term moving average resistance value Rs and the long-term moving average resistance value Rl is equal to or greater than the threshold value ΔRref, the source is supplied from the raw material fuel gas supply system 40 to the reformer 34. The amount of fuel gas can be increased, or the output of the power generation module 30 (each fuel cell stack) can be reduced, but the present invention is not limited to this. That is, when it is determined in step S140 of FIG. 2 that the difference ΔR between the short-term moving average resistance value Rs and the long-term moving average resistance value Rl is equal to or greater than the threshold value ΔRref, the power generation module 30 (each fuel cell stack FCS) generates power. The fuel cell system 10 may be stopped so that Further, the first time for calculating the short-term moving average resistance value Rs is not limited to 30 seconds, and a sufficient difference from the long-term moving average resistance value Rl when the anode gas is insufficient is sufficiently secured. The shortage of the anode gas may be set shorter than 30 seconds or longer than 30 seconds within a range in which the shortage of the anode gas can be detected with good responsiveness. Further, the second time for calculating the long-term moving average resistance value Rl is not limited to 180 seconds, and the difference from the short-term moving average resistance value Rs when the anode gas is insufficient is sufficiently secured, and the difference from the short-term moving average resistance value Rs is sufficiently secured. The shortage of the anode gas may be set shorter than 180 seconds or longer than 180 seconds within a range in which the shortage of the anode gas can be detected with good responsiveness.

As described above, the fuel cell system 10 of the present disclosure includes a fuel cell stack FCS that generates power by an electrochemical reaction between an anode gas and a cathode gas, and a reformer that reforms a raw material fuel gas to generate an anode gas. 34 and a control device 80 are included. Then, the control device 80 is predetermined based on the resistance acquisition unit (step S100) that acquires the internal resistance R of the fuel cell stack FCS from the output voltage Vs and the output current Is of the fuel cell stack FCS, and the internal resistance R. The short-term moving average resistance value (first moving average value) Rs, which is the average of the internal resistance R in 30 seconds, which is the first time, and the average of the internal resistance R in 180 seconds, which is the second time longer than the first time. The difference ΔR between the moving average calculation unit (step S110) that calculates the long-term moving average resistance value (second moving average value) Rl, which is, and the short-term moving average resistance value Rs and the long-term moving average resistance value Rl. It functions as a determination unit (steps S140, S150) for determining whether or not the anode gas supplied from the reformer 34 to the fuel cell stack FCS is insufficient based on the above. As a result, the fuel cell system 10 can detect the shortage of the anode gas supplied to the fuel cell stack FCS with good responsiveness while suppressing the cost increase.

Further, the invention of the present disclosure is not limited to the above-described embodiment, and it goes without saying that various changes can be made within the scope of the extension of the present disclosure. Furthermore, the above-described embodiment is merely a specific embodiment of the invention described in the column of the outline of the invention, and does not limit the elements of the invention described in the column of the outline of the invention.

The invention of the present disclosure can be used in the manufacturing industry of fuel cell systems and the like.

1 Raw fuel supply source, 2 system power supply, 3 power line, 4 load, 10 fuel cell system, 20 power generation unit, 22 housing, 24 ventilation fan, 30 power generation module, 31 module case, 32 manifold, 33 vaporizer, 34 Reformer, 35 combustion unit, 36 ignition heater, 37 temperature sensor, 40 raw fuel gas supply system, 41 raw fuel gas supply pipe, 42 raw fuel gas supply valve, 44 raw fuel gas pump, 45 desulfurizer, 46 pressure sensor, 47 1st flow meter, 48 2nd flow meter, 49 3rd flow meter, 50 cathode gas supply system, 51 cathode gas supply pipe, 52 air filter, 53 blower, 54 flow switch, 55 reformed water supply system, 56 modified Quality water supply pipe, 57 reformed water tank, 58 reformed water pump, 60 exhaust heat recovery system, 61 circulation pipe, 62 heat exchanger, 63 circulation pump, 64 radiator, 65 radiator fan, 66 electric heater, 67 thermista, 68 Exhaust pipe, 71 Power conditioner, 72 Power supply board, 80 Controller, 81 CPU, 82 ROM, 83 RAM, 88 Voltage sensor, 89 Current sensor, 100 Hot water supply unit, 101 Hot water storage tank, FCS fuel cell stack, SC single cell ..

Claims (4)

In a fuel cell system including a fuel cell stack that generates power by an electrochemical reaction between an anode gas and a cathode gas, and a reformer that reforms a raw fuel gas to generate the anode gas.
A resistance acquisition unit that acquires the internal resistance of the fuel cell stack from the output voltage and output current of the fuel cell stack, and
Based on the internal resistance acquired by the resistance acquisition unit, the first moving average value which is the average of the internal resistance in the predetermined first time and the internal in the second time longer than the first time. A moving average calculation unit that calculates the second moving average value, which is the average of resistance, at predetermined time intervals,
Whether or not the anode gas supplied from the reformer to the fuel cell stack is insufficient based on the difference between the first moving average value and the second moving average value calculated by the moving average calculation unit. Judgment unit to determine whether
A fuel cell system equipped. In the fuel cell system according to claim 1,
The determination unit determines whether or not the difference between the first moving average value and the second moving average value is equal to or greater than a predetermined threshold value, and if the difference is equal to or greater than the predetermined threshold value, the modification is performed. A fuel cell system that considers that the anode gas supplied from the pawn to the fuel cell stack is insufficient. In the fuel cell system according to claim 2.
A fuel cell system that increases the amount of raw fuel gas to the reformer, reduces the output of the fuel cell stack, or stops power generation by the fuel cell stack when the difference is equal to or greater than the threshold value. .. A method for determining fuel shortage in a fuel cell system including a fuel cell stack that generates power by an electrochemical reaction between an anode gas and a cathode gas, and a reformer that reforms a raw fuel gas to generate the anode gas.
The first moving average value, which is the average of the internal resistance in the predetermined first time, and the second moving average value, which is the average of the internal resistance in the second time longer than the first time, are set every predetermined time. Calculated to
Based on the difference between the first moving average value and the second moving average value, it is determined whether or not the anode gas supplied from the reformer to the fuel cell stack is insufficient.
Fuel shortage determination method.

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