JP5672639B2 - Fuel cell system and operation method thereof - Google Patents

Description

  The present invention relates to a fuel cell system and an operation method thereof.

  2. Description of the Related Art Conventionally, a fuel cell system including a fuel cell that generates power by receiving a supply of reaction gas (fuel gas and oxidizing gas) has been put into practical use. At present, intermittent operation of a fuel cell is performed for the purpose of improving the fuel consumption rate in the fuel cell system. In the intermittent operation, when the output required for the fuel cell system is less than or equal to a predetermined threshold value, the power generation in the fuel cell is temporarily stopped and the power is supplied from the secondary battery to the load device. Is an operation mode for intermittently supplying the reaction gas to the extent that the open-circuit voltage can be maintained.

  In recent years, a technique for suppressing the deterioration of the electrode catalyst due to voltage fluctuation accompanying intermittent operation has been proposed. For example, a technique has been proposed in which the lower limit voltage value and the upper limit voltage value of a fuel cell during intermittent operation of the fuel cell system are set in consideration of the progress of deterioration of the carbon support accompanying voltage fluctuation (see Patent Document 1). ). If such a technique is adopted, the lower limit (upper limit) voltage value can be set while balancing the improvement in fuel consumption rate and carbon degradation.

JP 2010-021072 A

  In the technique described in Patent Document 1, the lower limit (upper limit) voltage setting value is gradually changed according to the travel distance by using a curve (deterioration characteristic) indicating the correlation between the travel distance and the carbon carrier deterioration amount. The technique of letting it be adopted. However, when such a method is adopted, it is necessary to measure voltage fluctuations a great number of times (for example, about 30,000 km) for obtaining deterioration characteristics, which requires labor and labor.

  In addition, the conventional technique described in Patent Document 1 considers only the carbon carrier deterioration amount due to the travel distance (total number of potential fluctuations), and the upper and lower limit voltage values (voltage fluctuation amount during intermittent operation). Therefore, there is a possibility that the deterioration of the electrode catalyst cannot be effectively suppressed depending on the duration of the intermittent operation.

  The present invention has been made in view of such circumstances, and in a fuel cell system, the amount of electrode catalyst deterioration caused by the number of voltage fluctuations of the fuel cell during intermittent operation and the amount of voltage fluctuation of the fuel cell during intermittent operation. An object is to effectively suppress the deterioration of the electrode catalyst in consideration of both the corresponding amount of electrode catalyst deterioration.

  In order to achieve the above object, a fuel cell system according to the present invention includes a fuel cell, an air supply device that supplies air to the fuel cell, and an air supply when an output required from a load device is equal to or less than a predetermined threshold value. A fuel cell system comprising: a control device that performs intermittent operation for intermittently supplying air from the device and is capable of setting a plurality of upper and lower limit voltage values of voltage fluctuations of the fuel cell during intermittent operation. The upper and lower limits according to the intermittent operation duration time by using a deterioration characteristic map having a deterioration characteristic curve representing a correlation between the intermittent operation duration time and the amount of electrode catalyst deterioration of the fuel cell for each of the upper and lower limit voltage values. While changing and setting a voltage value, intermittent operation is implemented by the set upper-lower limit voltage value. Here, the deterioration characteristic curve is based on the amount of electrode catalyst deterioration per voltage fluctuation for each upper and lower limit voltage value of the fuel cell and the number of voltage fluctuations during intermittent operation at each upper and lower limit voltage value of the fuel cell. Generated.

  In addition, an operating method according to the present invention includes a fuel cell and an air supply device that supplies air to the fuel cell, and the output from the air supply device when the output required from the load device is a predetermined threshold value or less. An operation method of a fuel cell system in which intermittent operation in which air supply is intermittently performed and a plurality of upper and lower limit voltage values of the fuel cell voltage fluctuation during intermittent operation can be set, each upper and lower limit voltage value of the fuel cell Between the duration of intermittent operation and the amount of electrode catalyst deterioration of the fuel cell based on the amount of electrode catalyst deterioration per time of voltage fluctuation for each and the number of voltage fluctuations during intermittent operation at each upper and lower limit voltage value of the fuel cell A map generation process for generating a deterioration characteristic map having a deterioration characteristic curve representing a relationship for each of a plurality of upper and lower limit voltage values, and using the deterioration characteristic map, the upper and lower limit voltage values are changed according to the intermittent operation duration time. A lower limit voltage setting step on allowed to set, in which and a intermittent operation step of performing the intermittent operation with upper and lower limit voltage setting upper and lower limit voltage value set in step.

  When such a configuration and method are employed, a plurality of deterioration characteristic curves generated based on the amount of deterioration per voltage fluctuation for each upper and lower limit voltage value and the number of voltage fluctuations during intermittent operation at each upper and lower limit voltage value are obtained. Using the deterioration characteristic map for each upper and lower limit voltage value, intermittent operation can be performed while changing the upper and lower limit voltage values according to the intermittent operation duration time. Therefore, the electrode catalyst deterioration amount is considered in consideration of both the amount of electrode catalyst deterioration caused by the number of voltage fluctuations of the fuel cell during intermittent operation and the amount of electrode catalyst deterioration corresponding to the amount of voltage fluctuation of the fuel cell during intermittent operation. It is possible to perform intermittent operation control that effectively suppresses the amount.

  In the fuel cell system (operation method) according to the present invention, the map deterioration characteristic curve can be corrected (comprising a map correction step) based on the dryness of the electrolyte membrane of the fuel cell.

  By adopting such a configuration (method), the deterioration characteristic curve can be corrected based on the dryness of the electrolyte membrane, so that accurate intermittent operation control can be performed even when the dryness of the electrolyte membrane changes. For example, when the dryness of the electrolyte membrane increases, the amount of gas that permeates through the electrolyte membrane decreases, so the frequency of air supply required during intermittent operation also decreases. In consideration of such a phenomenon, it is possible to perform correction such that the slope of the deterioration characteristic curve gradually becomes gentle as the dryness of the electrolyte membrane increases.

  Further, in the fuel cell system (operation method) according to the present invention, the map deterioration characteristic curve can be corrected based on the air supply amount from the air supply device (including a map correction step).

  When such a configuration (method) is employed, the deterioration characteristic curve can be corrected based on the air supply amount from the air supply device, so that accurate intermittent operation control can be performed even when the air supply amount changes. . For example, when the amount of air supplied from the air supply device increases, the dryness of the electrolyte membrane increases, thereby reducing the amount of gas that permeates the electrolyte membrane, so the frequency of air supply required during intermittent operation is also increased. Decrease. In consideration of such a phenomenon, it is possible to perform correction such that the slope of the deterioration characteristic curve gradually becomes gentle as the air supply amount from the air supply device increases.

  In the fuel cell system (operating method) according to the present invention, the map deterioration characteristic curve can be corrected based on the deterioration over time of the electrolyte membrane of the fuel cell (comprising a map correction step).

  By adopting such a configuration (method), the deterioration characteristic curve can be corrected based on the aging deterioration of the electrolyte membrane, so that accurate intermittent operation control can be performed even when the electrolyte membrane has deteriorated over time. For example, when the amount of cross leak increases due to aging deterioration (thinning of the electrolyte membrane), the frequency of air supply required during intermittent operation also increases. In consideration of such a phenomenon, it is possible to perform correction such that the slope of the deterioration characteristic curve gradually becomes steeper according to the aging of the electrolyte membrane (elapsed years of use).

  Further, in the fuel cell system (operation method) according to the present invention, the map deterioration characteristic curve can be corrected based on the fuel cell temperature (cell temperature) or the outside air temperature (including a map correction step).

  When such a configuration (method) is employed, the deterioration characteristic curve can be corrected based on the cell temperature (or the outside air temperature), so that accurate intermittent operation control can be performed even when the cell temperature changes. For example, when the amount of cross leak increases due to an increase in cell temperature, the frequency of air supply required during intermittent operation also increases. In consideration of such a phenomenon, it is possible to perform correction such that the slope of the deterioration characteristic curve gradually becomes steep as the cell temperature increases.

  According to the present invention, in the fuel cell system, the amount of electrode catalyst deterioration caused by the number of voltage fluctuations of the fuel cell during intermittent operation and the amount of electrode catalyst deterioration corresponding to the amount of voltage fluctuation of the fuel cell during intermittent operation are: Considering both, it is possible to effectively suppress the deterioration of the electrode catalyst.

1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. 2 is a deterioration characteristic map used in intermittent operation control of the fuel cell system shown in FIG. 1. It is a map which shows the amount of electrode catalyst degradation per voltage change with respect to each upper and lower limit voltage value during intermittent operation of the fuel cell. It is a time chart which shows the time history of the voltage fluctuation during intermittent operation of a fuel cell. 2 is a flowchart for explaining a method of operating the fuel cell system shown in FIG. It is a deterioration characteristic map corrected based on the dryness etc. of the electrolyte membrane.

  Hereinafter, a fuel cell system 1 according to an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, an example in which the present invention is applied to an on-vehicle power generation system of a fuel cell vehicle will be described.

  First, the configuration of the fuel cell system 1 according to the embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 1, the fuel cell system 1 according to the present embodiment supplies electric power generated by the fuel cell 2 and the battery 52 to the traction motor M3 via the traction inverter 53, whereby the traction motor M3 is It is rotationally driven. A fuel cell system 1 includes a fuel cell 2 that generates electric power upon receiving supply of reaction gases (oxidizing gas and fuel gas), an oxidizing gas piping system 3 that supplies air as oxidizing gas to the fuel cell 2, and fuel gas A fuel gas piping system 4 for supplying hydrogen gas to the fuel cell 2, a power system 5 for charging / discharging system power, a control device 6 for controlling the entire system, and the like are provided.

  The fuel cell 2 is formed of, for example, a solid polymer electrolyte type and has a stack structure in which a large number of single cells are stacked. The unit cell constituting the fuel cell 2 is a separator for supplying a fuel gas and an oxidizing gas to a membrane / electrode assembly (MEA) formed by sandwiching a polymer electrolyte membrane between two electrodes, an anode electrode and a cathode electrode. And a pair of separators so as to sandwich the cathode electrode and the anode electrode from both sides. The fuel gas is supplied to the fuel gas flow path of one separator and the oxidizing gas is supplied to the oxidizing gas flow path of the other separator, and the fuel cell 2 generates electric power by this gas supply. That is, in the fuel cell 2, an oxidation reaction of the following formula (1) occurs in the anode electrode, a reduction reaction of the following formula (2) occurs in the cathode electrode, and the fuel cell 2 as a whole has the following formula (3). The electromotive reaction occurs.

H ₂ → 2H ⁺ + 2e ⁻ (1)
(1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
H ₂ + (1/2) O ₂ → H ₂ O (3)

  The fuel cell 2 is provided with a current sensor 2a and a voltage sensor 2b that detect current and voltage (output current and output voltage) during power generation. In addition to the solid polymer electrolyte type, various types of fuel cells 2 such as a phosphoric acid type and a molten carbonate type can be adopted as the fuel cell 2. In addition, cooling water for cooling the fuel cell 2 circulates inside the fuel cell 2, and the temperature (cell temperature) of the fuel cell 2 is indirectly measured by detecting the temperature of the cooling water. It has come to be.

  The oxidizing gas piping system 3 includes an air compressor 31, an oxidizing gas supply path 32, a humidification module 33, a cathode offgas flow path 34, a diluter 35, a motor M <b> 1 that drives the air compressor 31, and the like.

  The air compressor 31 is driven by the driving force of the motor M <b> 1 that operates according to the control command of the control device 6, and air (oxidized gas) taken from outside air via an air filter (not shown) is supplied to the cathode electrode of the fuel cell 2. It supplies and corresponds to the air supply apparatus in the present invention. The oxidizing gas supply path 32 is a gas flow path for guiding the air supplied from the air compressor 31 to the cathode electrode of the fuel cell 2. Cathode off-gas is discharged from the cathode electrode of the fuel cell 2. This cathode off gas is in a highly moist state because it contains moisture generated by the cell reaction of the fuel cell 2.

  The humidification module 33 exchanges moisture between the low-humidity oxidizing gas flowing through the oxidizing gas supply path 32 and the high-humidity cathode offgas flowing through the cathode offgas flow path 34 and is supplied to the fuel cell 2. Appropriately humidify the oxidizing gas. The cathode off-gas channel 34 is a gas channel for exhausting the cathode off-gas outside the system, and an air pressure regulating valve A1 is disposed in the vicinity of the cathode electrode outlet of the gas channel. The back pressure of the oxidizing gas supplied to the fuel cell 2 is regulated by the air pressure regulating valve A1. The diluter 35 dilutes the hydrogen gas discharge concentration so that it falls within a preset concentration range (such as a range determined based on environmental standards). The diluter 35 communicates with the downstream side of the cathode offgas channel 34 and the downstream side of the anode offgas channel 44 described later, and the hydrogen offgas and the oxygen offgas are mixed and diluted and exhausted outside the system.

  The fuel gas piping system 4 includes a fuel supply source 41, a fuel gas supply path 42, a fuel gas circulation path 43, an anode off-gas flow path 44, a hydrogen circulation pump 45, a check valve 46, and a motor for driving the hydrogen circulation pump 45. M2 etc.

  The fuel supply source 41 is means for supplying a fuel gas such as hydrogen gas to the fuel cell 2 and is constituted by, for example, a high-pressure hydrogen tank or a hydrogen storage tank. The fuel gas supply path 42 is a gas flow path for guiding the fuel gas discharged from the fuel gas supply source 41 to the anode electrode of the fuel cell 2, and the gas flow path includes a tank valve H1, hydrogen gas from upstream to downstream. Valves such as a supply valve H2 and an FC inlet valve H3 are provided. The tank valve H1, the hydrogen supply valve H2, and the FC inlet valve H3 are shut valves for supplying (or shutting off) the fuel gas to the fuel cell 2, and are constituted by, for example, electromagnetic valves.

  The fuel gas circulation path 43 is a return gas flow path for recirculating unreacted fuel gas to the fuel cell 2, and the gas flow path includes an FC outlet valve H4, a hydrogen circulation pump 45, and a check valve from upstream to downstream. 46 are respectively arranged. The low-pressure unreacted fuel gas discharged from the fuel cell 2 is moderately pressurized by the hydrogen circulation pump 45 driven by the driving force of the motor M <b> 2 that operates according to the control command of the control device 6, and is supplied to the fuel gas supply path 42. Led. The backflow of the fuel gas from the fuel gas supply path 42 to the fuel gas circulation path 43 is suppressed by the check valve 46. The anode off gas passage 44 is a gas passage for exhausting the anode off gas containing the hydrogen off gas discharged from the fuel cell 2 to the outside of the system, and a purge valve H5 is disposed in the gas passage.

  The power system 5 includes a high voltage DC / DC converter 51, a battery 52, a traction inverter 53, an auxiliary inverter 54, a traction motor M3, an auxiliary motor M4, and the like.

  The high-voltage DC / DC converter 51 is a direct-current voltage converter that adjusts the direct-current voltage input from the battery 52 and outputs it to the traction inverter 53 side, and the direct-current input from the fuel cell 2 or the traction motor M3. And a function of adjusting the voltage and outputting it to the battery 52. The charge / discharge of the battery 52 is realized by these functions of the high-voltage DC / DC converter 51. Further, the output voltage of the fuel cell 2 is controlled by the high voltage DC / DC converter 51.

  The battery 52 is connected in parallel to the fuel cell 2 with respect to the traction motor M3, and has a function of storing surplus power and regenerative energy during regenerative braking, and at the time of load fluctuation accompanying acceleration or deceleration of the fuel cell vehicle. It functions as an energy buffer. The battery 52 is a chargeable / dischargeable secondary battery, and is composed of various types of secondary batteries (for example, nickel-cadmium storage battery, nickel-hydrogen storage battery, lithium secondary battery, etc.). The battery 52 can be charged with surplus power or supplementarily supplied with power by control of a battery computer (not shown). Part of the direct-current power generated by the fuel cell 2 is stepped up and down by the high-voltage DC / DC converter 51 and charged in the battery 52. Instead of the battery 52, a chargeable / dischargeable battery (for example, a capacitor) other than the secondary battery may be employed.

  The traction inverter 53 and the auxiliary inverter 54 are pulse width modulation type PWM inverters, and convert DC power output from the fuel cell 2 or the battery 52 into three-phase AC power in accordance with a given control command, thereby obtaining a traction motor. Supply to M3 and auxiliary motor M4. The traction motor M3 is a motor for driving the wheels 7L and 7R. The traction motor M3 is provided with a rotation speed detection sensor 5a for detecting the rotation speed. The auxiliary motor M4 is a motor for driving various auxiliary machines, and is a generic term for the motor M1 that drives the air compressor 31, the motor M2 that drives the hydrogen circulation pump 45, and the like. In the present embodiment, all devices that operate by receiving power supplied from the fuel cell 2 are collectively referred to as load devices.

  The control device 6 is a computer system for controlling each part of the fuel cell system 1 in an integrated manner, and has a CPU and various memories (ROM, RAM, etc.). The control device 6 receives input of signals supplied from various sensors (for example, each sensor signal sent from the rotational speed detection sensor 5a, the accelerator pedal sensor 6a for detecting the accelerator pedal opening degree, etc.), and the load device. Calculate the load (requested output). Then, the control device 6 controls the output voltage and output current of the fuel cell 2 so as to generate output power corresponding to this load. The control device 6 controls the traction motor M3 and the auxiliary motor M4 by controlling the output pulse widths of the traction inverter 53 and the auxiliary inverter 54, and the like.

  The load of the load device is, for example, the total value of the vehicle running power and the auxiliary machine power. Auxiliary power is consumed by various auxiliary equipment (air compressor 31, hydrogen circulation pump 45, etc.) and equipment required for vehicle travel (transmission, wheel control device, steering device, suspension device, etc.). Power, power consumed by a device (air conditioner, lighting equipment, audio, etc.) disposed in the passenger space.

  In addition, the control device 6 switches between the normal operation mode and the intermittent operation mode. The normal operation mode means an operation mode in which the fuel cell 2 continuously generates power for supplying power to a load device such as the traction motor M3. In the intermittent operation mode, for example, the power generation of the fuel cell 2 is temporarily performed during low-load operation (operation in a region where the load of the load device is equal to or less than a predetermined threshold) such as idling, low-speed traveling, and regenerative braking. This means an operation mode in which power is supplied from the battery 52 to the load device, and hydrogen gas and air are supplied intermittently to the fuel cell 2 so that the open-end voltage can be maintained.

  The control device 6 is configured to be able to set a plurality of upper and lower limit voltage values of voltage fluctuation of the fuel cell 2 when performing intermittent operation, and suppresses deterioration of the electrode catalyst constituting the fuel cell 2. Control (deterioration suppression type intermittent operation control) is performed. Here, the degradation suppression type intermittent operation control will be described.

As shown in FIG. 2, a deterioration characteristic map including a plurality of deterioration characteristic curves C _{1 to} C ₃ is recorded in the memory of the control device 6. The deterioration characteristic curve represents the correlation between the intermittent operation continuation time (horizontal axis) and the electrode catalyst deterioration amount (vertical axis) of the fuel cell 2. In this embodiment, the deterioration characteristic curve at the upper and lower limit voltage value “V ₃ −V ₁ ” (upper limit voltage value: V ₃ (V), lower limit voltage value: V ₁ (V)) is referred to as “first deterioration characteristic curve C”. ₁ ”, upper and lower limit voltage value“ V ₂ −0 ”(upper limit voltage value: V ₂ (V), lower limit voltage value: 0 (V)), the deterioration characteristic curve is“ second deterioration characteristic curve C ₂ ”, The deterioration characteristic curve at the voltage value “V ₂ −V ₁ ” (upper limit voltage value: V ₂ (V), lower limit voltage value: V ₁ (V)) is referred to as “third deterioration characteristic curve C ₃ ”, respectively. I decided to. Note that a relationship of “V ₃ > V ₂ > V ₁ > 0” is established.

As shown in FIG. 2, when the intermittent operation duration time is t _C or less, the deterioration amount when the upper and lower limit voltage value “V ₂ −V ₁ ” corresponding to the third deterioration characteristic curve C ₃ is adopted. However, the amount of deterioration is smaller than that when the upper and lower limit voltage values “V ₃ −V ₁ ” and “V ₂ −0” corresponding to the first deterioration characteristic curve C ₁ and the second deterioration characteristic curve C ₂ are employed. I understand that. On the other hand, when the intermittent operation continuation time is equal to or longer than t _C , the deterioration amount when the upper and lower limit voltage value “V ₂ −0” corresponding to the second deterioration characteristic curve C ₂ is adopted is the first deterioration characteristic curve. It can be seen from FIG. 2 that the amount of deterioration is smaller than when the upper and lower limit voltage values “V ₃ −V ₁ ” and “V ₂ −V ₁ ” corresponding to C ₁ and the third deterioration characteristic curve C ₃ are adopted. I can read.

By using such a deterioration characteristic map, the control device 6 changes and sets the upper and lower limit voltage values according to the intermittent operation duration so that the deterioration amount of the electrode catalyst is minimized. Specifically, in the time region where the intermittent operation time is equal to or shorter than t _C , the control device 6 determines the upper and lower limit voltage values “V” corresponding to the third deterioration characteristic curve C ₃ with the least amount of deterioration of the electrode catalyst in this region. setting the ₂ -V ₁ ". On the other hand, in the time region where the intermittent operation time is equal to or longer than t _C , the control device 6 has an upper and lower limit voltage value “V ₂ −0” corresponding to the second deterioration characteristic curve C ₂ with the least amount of deterioration of the electrode catalyst in this region. "Is set. Then, the control device 6 performs intermittent operation at the set upper and lower limit voltage values.

The deterioration characteristic curves C _{1 to} C ₃ constituting the deterioration characteristic map indicate the amount of deterioration of the electrode catalyst per voltage change for each upper and lower limit voltage value during intermittent operation of the fuel cell 2 and the intermittent of the fuel cell 2. It is generated based on the number of voltage fluctuations at each upper and lower limit voltage value during operation. Here, a procedure for generating a deterioration characteristic map will be described with reference to FIGS. 3 and 4.

FIG. 3 is a map showing the amount of electrode catalyst deterioration per voltage change for each upper and lower limit voltage value during intermittent operation of the fuel cell 2. This map shows a voltage-deterioration curve representing the correlation between the lower limit voltage (horizontal axis) during intermittent operation of the fuel cell 2 and the amount of degradation of the electrode catalyst per vertical voltage variation (vertical axis). For each of the two types of upper limit voltages (V ₂ , V ₃ ). As shown in the two types of voltage-deterioration curves in FIG. 3, when compared at the same lower limit voltage (for example, V ₁ ), the lower the upper limit voltage, the smaller the amount of electrode catalyst deterioration per voltage change. I understand that. Note that the amount of degradation of the electrode catalyst per voltage change also varies depending on the cell temperature (the amount of degradation decreases as the cell temperature decreases). The amount of deterioration changes for each cell temperature, and the gas permeation amount changes accordingly, and the frequency of air supply required during intermittent operation also changes, so the deterioration characteristic curve also changes for each cell temperature. .

FIG. 4 is a time chart showing a time history of voltage fluctuation during intermittent operation of the fuel cell. FIG. 4 shows a time chart T ₁ of the voltage fluctuation of the fuel cell 2 when the upper and lower limit voltage value “V ₃ −V ₁ ” is adopted, and the fuel when the upper and lower limit voltage value “V ₂ −0” is adopted. and the time chart T ₂ of the voltage fluctuation of the battery 2, and the time chart T ₃ of the voltage variation of the fuel cell 2 in the case of adopting upper and lower limit voltage value "V ₂ -V _1", and is shown.

As shown in the three types of time charts T _{1 to} T ₃ in FIG. 4, for example, in the case of returning to normal operation (output voltage V ₂ ) when t ₁ seconds have elapsed from the start of intermittent operation, the upper and lower limit voltages When the value “V ₃ −V ₁ ” is adopted, the voltage rise occurs once (V ₂ → V ₃ ), and the upper and lower limit voltage values “V ₂ −0” and “V ₂ −V ₁ ” are adopted. The voltage rise that occurs in this case is also once (V ₄ → V ₂ ) (V ₄ <V ₂ ). On the other hand, in the case of returning to normal operation when t ₂ (> t ₁ ) seconds have elapsed from the start of intermittent operation, the voltage rise that occurs when the upper and lower limit voltage value “V ₃ −V ₁ ” is adopted is 2 Times (V ₂ → V ₃ , V ₅ → V ₂ ), when the upper / lower limit voltage value “V ₂ −0” is adopted, the voltage rise that occurs once (V ₆ → V ₂ ), the upper and lower voltage value “V _The voltage rise that occurs when “ _2- V ₁ ” is adopted is three times (V ₁ → V ₂ , V ₁ → V ₂ , V ₄ → V ₂ ) (V ₆ <V ₂ , V ₅ <V _2). ). Thus, it can be seen that the number of times of voltage increase during intermittent operation changes depending on the setting of the upper and lower limit voltage values. In addition, since it is known that the electrode catalyst is greatly deteriorated when the voltage rises, in this embodiment, the “voltage rise count” is counted as the voltage fluctuation count.

For each upper and lower limit voltage value, it is shown in FIG. 2 by multiplying the electrode catalyst deterioration amount per voltage fluctuation shown in FIG. 3 by the number of voltage rises per hour during intermittent operation shown in FIG. A plurality of deterioration characteristic curves C _{1 to} C ₃ (for each upper and lower limit voltage values) representing the correlation between the intermittent operation continuation time and the amount of electrode catalyst deterioration are obtained.

  Next, an operation method of the fuel cell system 1 according to the present embodiment will be described.

  First, according to the above-described procedure, a deterioration characteristic map as shown in FIG. 2 is generated (map generation step: S1), and the generated deterioration characteristic map is recorded in the memory of the control device 6. In the map generation step S1, the user himself / herself may generate a deterioration characteristic map, or the control device 6 may generate a deterioration characteristic map. When the control device 6 generates the deterioration characteristic map, data relating to the map of FIG. 3 and the time chart of FIG. 4 is recorded in the memory of the control device 6, and the deterioration characteristic is determined using a specific program based on this data. A map can be generated.

Next, the control device 6 uses the deterioration characteristic map recorded in the memory to change and set the upper and lower limit voltage values according to the intermittent operation duration so that the deterioration of the electrode catalyst is minimized (upper and lower limits). Voltage setting step: S2). For example, as shown by a thick solid line in FIG. 2, the control device 6 sets “V ₂ −V ₁ ” as the upper and lower limit voltage values in the time region where the intermittent operation time is t _C or less, while the intermittent operation time t _In the time region of _C or more, “V ₂ −0” can be set as the upper and lower limit voltage values.

  Subsequently, the control device 6 performs intermittent operation with the upper and lower limit voltage values set in the upper and lower limit voltage setting step S2 (intermittent operation step: S3).

In the fuel cell system 1 according to the embodiment described above, the fuel cell system 1 is generated based on the amount of deterioration per voltage fluctuation for each upper and lower limit voltage value and the number of voltage fluctuations during intermittent operation at each upper and lower limit voltage value. In addition, using the deterioration characteristic map having a plurality of deterioration characteristic curves C _{1 to} C ₃ (for each upper and lower limit voltage values), intermittent operation can be performed while changing the upper and lower limit voltage values according to the intermittent operation duration time. it can. Therefore, the electrode catalyst deterioration amount due to the number of voltage fluctuations of the fuel cell 2 during the intermittent operation and the electrode catalyst deterioration amount corresponding to the voltage fluctuation amount of the fuel cell 2 during the intermittent operation are considered. It is possible to perform intermittent operation control that effectively suppresses the catalyst deterioration amount.

  In the above embodiment, an example in which one type of deterioration characteristic map is used has been described. However, the deterioration characteristic map can be corrected according to various situations (map correction step).

<Correction based on dryness and air supply>
For example, if the dryness of the electrolyte membrane of the fuel cell 2 increases due to an increase in the amount of air supplied from the air compressor 31, the amount of gas that permeates through the electrolyte membrane decreases, which is necessary during intermittent operation. The frequency of air supply is also reduced. Considering such a phenomenon, the slope of the third deterioration characteristic curve C ₃ in the deterioration characteristic map is gradually increased in accordance with an increase in the dryness of the electrolyte membrane of the fuel cell 2 (an increase in the amount of air supplied from the air compressor 31). It is possible to make corrections that make the camera shake. C ₃ ′ indicated by a broken line in FIG. 6 indicates a third deterioration characteristic curve corrected in accordance with an increase in the dryness of the electrolyte membrane of the fuel cell 2 (an increase in the amount of air supplied from the air compressor 31). is there.

The control device 6 can correct the initially set upper and lower limit voltage values by using the thus corrected deterioration characteristic map, and can perform intermittent operation with the corrected upper and lower limit voltage values. Specifically, as shown in FIG. 6, it is possible to change the timing of switching the upper and lower limit voltage value "V ₂ -V _1" to "V ₂ -0" to t _C 'from t _C. In this way, accurate intermittent operation control can be performed even when the dryness of the electrolyte membrane (the amount of air supplied from the air compressor 31) changes.

<Correction based on aging and cell temperature>
On the other hand, if the amount of cross leak increases due to aging (thinning) of the electrolyte membrane of the fuel cell 2, cell temperature (temperature of cooling water for cooling the fuel cell 2), or increase in outside air temperature, intermittent operation is in progress. The frequency of air supply required for the increase also increases. In consideration of such a phenomenon, correction is made so that the slope of the third deterioration characteristic curve C ₃ in the deterioration characteristic map gradually becomes steeper according to the years of use of the electrolyte membrane or the increase in the cell temperature (or outside air temperature). It can be carried out.

  The control device 6 corrects the initially set upper and lower limit voltage values by using the deterioration characteristic map corrected based on the aging deterioration of the electrolyte membrane and the cell temperature, and intermittently uses the corrected upper and lower limit voltage values. Driving can be carried out. In this way, accurate intermittent operation control can be performed even when the electrolyte membrane deteriorates over time or the cell temperature changes.

  In the above embodiment, an example in which the fuel cell system according to the present invention is mounted on a fuel cell vehicle has been shown. However, various mobile bodies (robots, ships, aircrafts, etc.) other than the fuel cell vehicle are related to the present invention. A fuel cell system can also be installed. Further, the fuel cell system according to the present invention may be applied to a stationary power generation system used as a power generation facility for a building (house, building, etc.). Furthermore, the present invention can be applied to a portable fuel cell system.

1 ... fuel cell system, 2 ... fuel cell, 6 ... control device, 31 ... air compressor (air supply apparatus), C ₁ ... First deterioration characteristic curve, C ₂ ... second degradation characteristic curve, C ₃ ... Third degradation Characteristic curve, S1... Map generation step, S2... Upper / lower limit voltage setting step, S3.

Claims (7)

A fuel cell, an air supply device that supplies air to the fuel cell, and an intermittent operation that intermittently supplies air from the air supply device when the output required from the load device is below a predetermined threshold A control device capable of setting a plurality of upper and lower limit voltage values of voltage fluctuations of the fuel cell during intermittent operation, and a fuel cell system comprising:
The control device responds to the intermittent operation duration by using a degradation characteristic map having a degradation characteristic curve representing a correlation between the intermittent operation duration and the amount of electrode catalyst degradation of the fuel cell for each of a plurality of upper and lower limit voltage values. The upper and lower limit voltage values are changed and set, and intermittent operation is performed with the set upper and lower limit voltage values.
The deterioration characteristic curve is based on the amount of electrode catalyst deterioration per voltage fluctuation for each upper and lower limit voltage value of the fuel cell and the number of voltage fluctuations during intermittent operation at each upper and lower limit voltage value of the fuel cell. Generated,
Fuel cell system. The deterioration characteristic curve is corrected based on the dryness of the electrolyte membrane of the fuel cell.
The fuel cell system according to claim 1. The deterioration characteristic curve is corrected based on an air supply amount from the air supply device.
The fuel cell system according to claim 1. The deterioration characteristic curve is corrected based on aged deterioration of the electrolyte membrane of the fuel cell.
The fuel cell system according to claim 1. The deterioration characteristic curve is corrected based on a temperature of the fuel cell or an outside air temperature.
The fuel cell system according to claim 1. An intermittent air supply device that includes a fuel cell and an air supply device that supplies air to the fuel cell, and that intermittently supplies air from the air supply device when an output required from the load device is below a predetermined threshold An operation method of a fuel cell system that is capable of setting a plurality of upper and lower limit voltage values of voltage fluctuation of the fuel cell during intermittent operation,
Based on the amount of electrode catalyst deterioration per voltage fluctuation for each upper and lower limit voltage value of the fuel cell and the number of voltage fluctuations during intermittent operation at each upper and lower limit voltage value of the fuel cell, the intermittent operation duration time A map generation step of generating a deterioration characteristic map having a deterioration characteristic curve representing a correlation with the amount of electrode catalyst deterioration of the fuel cell for each of a plurality of upper and lower limit voltage values;
By using the deterioration characteristic map, an upper / lower limit voltage setting step for changing and setting an upper / lower limit voltage value according to the intermittent operation duration time;
An intermittent operation step of performing intermittent operation at the upper and lower limit voltage values set in the upper and lower limit voltage setting step,
Operation method of fuel cell system. Based on at least one of the dryness of the electrolyte membrane of the fuel cell, the amount of air supplied from the air supply device, the aging of the electrolyte membrane of the fuel cell, the temperature of the fuel cell, and the outside air temperature, A map correction step of correcting the deterioration characteristic curve of the deterioration characteristic map;
The operation method of the fuel cell system according to claim 6.

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