WO2018131817A1 - Fuel cell system - Google Patents

Abstract

The present application provides a fuel cell system comprising: a fuel cell stack; a calculation unit for calculating a current density-voltage performance curve of the fuel cell stack and a slope thereof; and a control unit capable of determining and/or controlling an operation condition of a fuel cell on the basis of the performance curve or a value of the slope.

Description

Fuel cell system

Cross Citation with Related Applications

This application claims the benefit of priority based on Korean Patent Application No. 10-2017-0005963, filed Jan. 13, 2017, and all contents disclosed in the literature of that Korean patent application are incorporated as part of this specification.

Technical Field

The present application relates to a fuel cell system.

The fuel cell is provided as a stack in which several tens to hundreds of unit cells are stacked, and the unit cell is a gas diffusion layer that delivers an electrode-membrane assembly (MEA) and a reactor body in which an electrochemical reaction occurs. (Gas Diffusion Layer, GDL), a separator for forming a flow path for supplying fuel and discharging water generated by the reaction, and a gasket for preventing leakage of the reactor body and cooling water. The electrode membrane assembly is configured to include an anode, a cathode, and a polymer electrolyte membrane provided between the two electrodes.

The fuel cell of the above configuration can generate electrical energy together with water. Specifically, electrons and hydrogen ions generated by the oxidation reaction of hydrogen generated in the anode move through the electrolyte membrane and the separator, respectively, to the cathode, and electrochemical reactions with oxygen generate electrical energy together with water. At this time, since sufficient humidification condition contributes to smooth movement of hydrogen ions to the cathode, it is necessary to operate the fuel cell stack in a sufficient humidification state, or to control the fuel cell to be operated at the next optimal condition even if it is not sufficiently humidified. It is one of the factors to consider in order to prevent the reduction.

On the other hand, during the initial operation of the fuel cell, since it is often placed in low humidification conditions, such as when the relative humidity of the gas supplied to the stack is less than 80%, the voltage of the electrode-membrane assembly or the resulting degradation of the fuel cell or Long term durability deterioration is a problem.

One object of the present application is to solve the voltage drop phenomenon of the fuel cell stack due to insufficient humidification state during the initial operation of the fuel cell, and thereby the durability degradation problem.

The above and other objects of the present application can all be solved by the present application described in detail below.

In one example of the present application, the system of the present application comprises a fuel cell stack; A calculator for calling the current density-voltage performance curve of the fuel cell stack and calculating the slope of the called current density-voltage performance curve; And a controller configured to control operating conditions of the fuel cell based on the current density-voltage performance curve and its slope.

In another example of the present application, the control unit lowers or minimizes the flow rate of the reaction gas supplied to the cathode and the anode when the current density-voltage performance curve has a voltage value less than the set voltage value in a predetermined current density section. When the reference current density is lowered and the current density-voltage performance curve has a voltage value equal to or higher than the voltage value set in the predetermined current density section, the calculator may be provided to calculate the slope of the current density-voltage performance curve.

In yet another example of the present application, the calculation unit may be provided to call the current density-voltage performance curve under the condition that a current density of 1 A / cm ² or less is applied.

In yet another example of the present application, the calculation unit may be arranged to call the current density-voltage performance curve under the condition that the relative humidity of air and hydrogen supplied to the fuel cell stack is 80% or less.

In another example of the present application, the predetermined current density section may mean a section in which a current density of 1 A / cm ² or less is applied or a section of a minimum flow rate reference current density or less.

In yet another example of the present application, the set voltage value may be 0.4V.

In another example of the present application, when the slope of the current density-voltage performance curve calculated by the calculation unit is −0.1 V · cm ² / A or more, the controller lowers or minimizes the flow rate of the gas supplied to the cathode and the anode. The flow reference current density can be lowered.

In yet another example of the present application, when the slope of the current density-voltage performance curve calculated by the calculator is less than −0.1 V · cm ² / A, the controller may not change the operating condition.

In yet another example of the present application, the fuel cell stack may be controlled by the controller to operate in consideration of the stoichiometric ratio.

In yet another example of the present application, one or more of a temperature sensor, a humidity sensor, a pressure sensor, a flow sensor, a current sensor, or a voltage sensor may be further included.

In another example of the present application, the fuel cell system may measure in real time the operating conditions of any one or more of the inlet concentration, flow rate, pressure, humidity, or temperature of the reaction gas, or the current density or voltage applied to the fuel cell. have.

In another example of the present application, the controller may lower the temperature of the fuel cell stack instead of lowering the flow rate of the gas supplied to the cathode and the anode or lowering the minimum flow reference current density.

In yet another example of the present application, the present application relates to a method of controlling the operation of a fuel cell based on a current density-voltage performance curve of a fuel cell stack.

According to an example of the present application, a fuel cell system and a control method thereof capable of preventing a voltage drop of a fuel cell appearing at low humidification conditions during initial driving, and thus deterioration of an electrode-membrane assembly or deterioration of long-term durability of the fuel cell Can be provided.

FIG. 1 is a graph showing a current density-voltage curve of a fuel cell stack measured when a reaction gas, that is, hydrogen and air (oxygen) is supplied at a relative humidity of 32%.

FIG. 2 is a graph showing current density-voltage curves and slopes of a fuel cell stack measured when a reaction gas is supplied at a relative humidity of 50%.

3 schematically illustrates a concept of a fuel cell system according to an example of the present application.

4 illustrates operation condition control and results according to one embodiment of the present application.

5 illustrates operation condition control and results according to another embodiment of the present application.

Hereinafter, a fuel cell system and a control method of a fuel cell system according to an embodiment of the present application will be described in detail with reference to the accompanying drawings. The conditions of the experiments performed in connection with the following figures were controlled the same unless otherwise noted.

1 is a graph showing a current density-voltage curve of a fuel cell stack measured when a reaction gas is supplied at a relative humidity of 32%. Specifically, FIG. 1 shows that the stoichiometric ratio of hydrogen supplied to the cathode and oxygen supplied to the anode is 1.5: 2.0, and the current applied to the fuel cell is gradually increased at a predetermined ratio (about 50 mA / cm ² per hour). The current density-voltage curve observed when increasing is shown. In general, when the fuel cell is operated in conjunction with the gas flow rate supplied to the electrode and the current density (operation considering the stoichiometric ratio mentioned below), an increase in the current density may mean an increase in the reaction. This may mean that more reactants, ie more oxygen and hydrogen, are required. However, when the applied current density is too low to reduce the flow rate of both hydrogen and oxygen supplied, sufficient chemical reaction for driving the fuel cell cannot be guaranteed. Thus, when the current density is below a certain value, the fuel cell system can be controlled so that a chemical reaction can occur or the fuel cell can be driven normally, so that a constant (minimum) flow rate can be supplied to the fuel cell stack. In other words, a gas with a constant flow rate can be supplied to the fuel cell stack when a current of less than the set current density value is applied, and when the current exceeds a set current density value, the gas flow increases. The fuel cell can be controlled to supply gas at a corresponding flow rate. In this case, the set current density value may be referred to as a minimum flow reference current density. In this regard, Figure 1, if the minimum flow rate based on the current density is set to 800 mA / cm ^2, to which the current density of 800 mA / cm ² or less is a certain amount of gas, i.e., 212 cc / min hydrogen and This is measured with the fuel cell system controlled to supply 672 cc / min of air (oxygen).

As shown in FIG. 1, when the current (density) applied to the fuel cell is gradually increased at a predetermined rate, current loss occurs due to individual components of the fuel cell or other resistive elements, thereby reducing the voltage. May show a trend. In some cases, the stoichiometric ratio is considered during operation, and the operating state of the fuel cell reaches a steady-state while supplying the reaction gas flow rate corresponding to the increasing current density, and is reduced by the loss. The voltage may be restored. In this regard, referring to FIG. 1, an inflection point (point of zero tilt) for the slope of the IV curve is observed around 200 mA / cm ² . Specifically, the voltage is rapidly reduced in the section below about 200 mA / cm ² , 200 mA / cm ² After passing through the voltage is increasing rapidly again. 800 mA / cm ² 800 mA / cm ² when compared to the following sections In the excess period, the change (decrease or increase) of the voltage decreases (stabilizes). This is because the flow rate of hydrogen and oxygen set to be supplied in a certain amount in a section below the minimum flow reference current density (800 mA / cm ² ) is excessive, so that the rate at which the electrolyte membrane is dried is faster than the rate at which the electrolyte membrane is humidified. This is because the voltage change (drop) sharpens as the conductivity decreases.

As shown in FIG. 1, the inflection point observed in the region below the minimum flow reference current density (= 800 mA / cm ² ) may mean that the electrolyte membrane's drying rate is predominant, thereby deteriorating the ion conductivity of the electrolyte membrane and deteriorating fuel cell performance. Can be. In addition, the inflection point observed in the region below the minimum flow reference current density may mean that the same voltage may appear at different current densities (repetition of voltage drop and voltage rise). Since the change in performance is large, it can be directly linked to the problem of deterioration in durability of the fuel cell.

FIG. 2 is a graph showing current density-voltage curves and slopes of a fuel cell stack measured when a reaction gas is supplied at a relative humidity of 50%. Specifically, FIG. 2 (a) shows that the stoichiometric ratio of hydrogen supplied to the cathode and oxygen supplied to the anode is set to 1.5: 2.0, and the minimum flow reference current density is set to 800 mA / cm ² and applied to the fuel cell. It shows the current density-voltage curve observed when the current to be gradually increased at a predetermined rate. At this time, 212 cc / min of hydrogen and 672 cc / min of air (oxygen) were supplied in the section below 800 mA / cm ² which is the minimum flow reference current density. Since the relative humidity of the reaction gas is higher than that of FIG. 1, it can be seen that the change in voltage is gentler than that of FIG. 1. However, referring to FIG. 2 (a) in detail, in the region of about 700 mA / cm ² and in the range of 200 mA / cm ² to 300 mA / cm ² , the degree of decrease of the voltage (tilt) according to the current density may be close to the inflection point. It is observed that it is gentle enough. In fact, in FIG. 2 (b) showing the change in slope of the curve of FIG. 2 (a), a slope of 0 V · cm ² / A is observed around 700 mA / cm ² , and 200 mA / cm ² to 300 mA A slope very close to the 0 V · cm ² / A slope was observed in the / cm ² interval.

2 (a) and 2 (b), in a region where a current lower than the minimum flow reference current density (= 800 mA / cm ² ) is applied, a point where the slope of the IV curve is zero, that is, an inflection point appears, The point where the slope approximates 0 indicates that the fuel cell is operating in a state in which the rate at which the electrolyte membrane is dried is faster than the rate at which the electrolyte membrane is humidified, or in a condition similar to that condition. It is. As mentioned above, under operating conditions in which the electrolyte membrane is predominantly dry, there is a risk that the tendency of a moderate voltage drop normally predicted in the fuel cell stack in operation is broken, or the durability of the fuel cell is degraded as the voltage change rapidly increases. . In view of this, measures to prevent the durability of the fuel cell due to a large voltage change by avoiding a condition in which the electrolyte membrane loses sufficient humidification state during operation of the fuel cell, that is, an operation condition in which the drying speed is predominant are required. do.

In one example, a fuel cell system of the present application includes a fuel cell stack; A calculator for calculating a current density-voltage performance curve and a slope of the fuel cell stack; And a controller configured to determine and / or control an operating condition of a fuel cell based on the performance curve or its slope value. 3 conceptually illustrates a fuel cell system according to an example of the present application.

The fuel cell stack used in the system of the present application may have the same configuration as that of a general fuel cell. For example, the fuel cell stack of the present application includes an electrode-membrane assembly (MEA) in which an electrochemical reaction takes place, a gas diffusion layer (GDL) for delivering a reactor, a flow path for supplying fuel and discharging water generated by the reaction. It may have a structure in which a plurality of unit cells including a separator plate is formed, and a gasket for preventing leakage of the reactor body and cooling water. In this case, the electrode-membrane assembly may include an anode, a cathode, and a polymer electrolyte membrane provided therebetween, similarly to the structure of the electrode-membrane assembly used in a conventional fuel cell. In addition, specific components of the fuel cell stack are not particularly limited, but a fuel cell configured to exhibit a commercially required level of performance may be used. A fuel cell having a commercially required level of performance is, for example, 0.4 V or more, or 0.6 V at a current density of 1 A / cm ^2, even if a voltage drop occurs after application of current, based on a current density-voltage performance curve. It may mean a fuel cell configured to exhibit the above performance.

In the present application, the determination of the operating conditions of the fuel cell stack and / or the control of the operating conditions may be made based on the current density-voltage curve of the fuel cell stack. The operating conditions in the present application are not particularly limited, and may be, for example, an inflow concentration, a flow rate, a pressure, a humidity, a temperature associated with a reaction gas, or may be such as a current (density) or a voltage applied to the fuel cell. .

In order to determine the driving conditions, that is, to measure the conditions under which the fuel cell operates, the system of the present application may further include an operating condition measuring unit. For example, the measuring unit may include one or more of a temperature sensor, a humidity sensor, a pressure sensor, a flow sensor, a current sensor, or a voltage sensor, and the sensors may measure each operating condition in real time.

Based on the current density and the voltage measured by the measuring unit, a current density-voltage performance curve is called, and the slope of the performance curve can be calculated based on the called performance curve. The performance curve and its slope may be called and calculated by the calculation unit, respectively.

In one example, the calculator may call the current density-voltage performance curve in a section where a current density of 2 A / cm ² or less, 1.5 A / cm ² or less or 1 A / cm ² or less is applied. In consideration of the fact that the current applied gradually increases at a predetermined rate during driving of the fuel cell, a section in which a current density of 1 A / cm ² or less is applied may be referred to as the initial stage of driving of the fuel cell. As such, the system of the present application may check the operating state or operating condition for the initial fuel cell driving through the current density-voltage performance curve, and reflect this in the operating condition control.

In one example, the calculator may call the current density-voltage performance curve under low humidification where the relative humidity of the gas, ie air (oxygen) and / or hydrogen, supplied to the fuel cell stack is 80% or less. When the relative humidity of these gases is 80% or less, the decrease in the ionic conductivity in the electrolyte membrane may be accelerated depending on the fuel cell operating conditions, and thus the fuel cell durability may be particularly concerned. As such, the system of the present application may check the operating state or the operating condition in the low-humidity state through the current density-voltage performance curve and reflect it in the operating condition control.

The controller may determine differently the operating condition (state) of the fuel cell according to the aspect of the called current density-voltage performance curve. In the following description, the predetermined current density section used for the operation state determination means a section to which a current density of 2 A / cm ² or less, 1.5 A / cm ² or less, or 1 A / cm ² or less is applied, or a minimum flow rate. It may mean a section in which a current density of less than or equal to the reference current density is applied. In this case, the minimum flow reference current density may be set by the controller.

Specifically, when the voltage value appearing in the called performance curve in the predetermined current density section is observed only above the predetermined predetermined voltage value, the controller may determine that the fuel cell is normally driven (operated). . When the controller makes such a determination, the calculator may additionally calculate the slope of the performance curve. In this case, the predetermined predetermined voltage value is a value determined in consideration of the use or configuration of the fuel cell, and may be set by the controller. In one example, the predetermined predetermined voltage value may mean a voltage value enough to confirm whether the commercially required level of performance is achieved, and may be 0.4 V or 0.6 V, for example.

Conversely, if a voltage less than a predetermined predetermined voltage value is observed in a predetermined current density section of the called current density-voltage performance curve, the controller may determine that the fuel cell is not normally driven. In a predetermined section, the voltage less than the preset value is observed when the drying speed of the electrolyte membrane is predominantly higher than the humidification speed, so that the ion conductivity of the electrolyte membrane is accelerated and the voltage drop of the fuel cell is accelerated. Because it can. If the controller determines in this way, the controller can immediately control the operating conditions as described below without calculating the performance curve slope by the calculator.

After the determination is made as described above, the controller may proceed with the additional operation condition determination and control as follows. Examples of operating conditions controlled based on the determination of the controller include inflow concentration, flow rate, pressure, humidity, and temperature associated with the reaction gas, or examples of current (density) and voltage applied to the fuel cell. . In this case, the controller may simultaneously adjust the current density and the supply flow rate of the reaction gas. Specifically, it is possible to control the flow rate of hydrogen and oxygen supplied so as to satisfy the stoichiometric ratio such that a chemical reaction corresponding to the applied current density can occur. The reverse is also possible. In the present application, such operation may be referred to as operation in which the stoichiometric ratio is considered.

If it is determined that the fuel cell is normally operated by the controller, and the calculator calculates the slope of the performance curve IV curve, the controller re-determines whether the slope is -0.1 V · cm ² / A or more. Upon application of a certain current density which increases at a constant rate, voltage drops are inevitable in the current density-voltage performance curve due to various resistance elements. In consideration of this point, the inclination of more than -0.1 V · cm ² / A may mean that the inclination of the IV curve is close to 0 (= zero), that is, the inflection point. At this time, the control unit may lower the flow rate of the gas supplied to the cathode and the anode in order to avoid operating conditions in which the drying rate is faster than the humidification rate of the electrolyte membrane. When the predetermined section is a section in which a current density of less than or equal to the minimum flow reference current density is applied, the controller lowers the minimum flow reference current density to reduce the flow rate of the gas supplied at a constant flow rate at a low current density value than before. You can. The latter measure presupposes the operation taking into account the current density and stoichiometric ratio between the fluids to be supplied, and in operation considering the stoichiometric ratio, lowering the minimum flow reference current density and directly adjusting the flow rate of the gas supplied to the cathode and the anode. Lowering can be treated with the same prescription. In contrast, when the calculated slope is less than −0.1 V · cm ² / A, the controller may not change the operating conditions because it may be determined that the inclination of the IV curve is relatively low to reach the inflection point.

On the contrary, in the case where it is determined by the control unit that the fuel cell is not normally operated, that is, when a voltage less than the predetermined voltage value is observed in the predetermined current density section, the calculation of the slope of the performance curve by the calculation unit is performed. Without, the control unit may lower the flow rate of the gas supplied to the cathode and the anode to avoid the condition in which the drying rate of the electrolyte membrane is significantly superior to the humidification rate and to increase the degree of humidification. When the predetermined section is a section in which a current density of less than or equal to the minimum flow reference current density is applied, the controller lowers the minimum flow reference current density to reduce the flow rate of the gas supplied at a constant flow rate at a low current density value than before. You can. Similarly, the latter formulation is based on the operation considering the current density and the stoichiometric ratio between the fluids supplied, and in operation considering the stoichiometric ratio, lowering the minimum flow reference current density and the flow rate of the gas supplied to the cathode and the anode. Directly lowering can be treated with the same prescription.

In another example, when it is determined that the fuel cell is not normally operated or when the slope is determined to be -0.1 V · cm ² / A or more even when the fuel cell is normally operated, the controller may control temperature or humidity. For example, the controller may lower the temperature of the fuel cell stack. Lowering the temperature of the fuel cell stack can have an effect similar to increasing the relative humidity of the gas supplied to the stack, rather than lowering the temperature of the stack, even if other process conditions do not change. The temperature drop of the stack may be achieved by lowering the coolant temperature by the controller or by operating a cooler fan.

In one example, the calculator may call or calculate the current density-voltage performance curve and its slope in real time, and the controller may determine whether to control and determine the operating conditions as mentioned above based on the performance curve and the slope. Can be done in real time.

4 is a graph of a current density-voltage performance curve and its slope measured using the same sample as the fuel cell used in the graph of FIG. 2 but with a relative humidity lowered to 32%, according to one embodiment of the present application. The driving condition control and the result thereof are shown. Specifically, FIG. 4 (a) sets the minimum flow reference current density to 800 mA / cm ² and supplies 212 cc / min of hydrogen and 672 cc / min of air (oxygen) in a section of 800 mA / cm ² or less. The result is a graph. In addition, Figure 4 (b) is set to the minimum flow rate reference current density to 200 mA / cm ² , supplying 57 cc / min hydrogen and 180 cc / min air (oxygen) in the section below 200 mA / cm ² The result is a graph shown. At this time, the minimum flow rate reference current density and the flow rate of the supplied gas was set to the control unit to be adjusted according to the stoichiometric ratio.

4 (a) and 4 (b), the voltage rapidly drops below 0.4 V, but in FIG. 4 (b) where the minimum flow reference current density is lowered, it is 0.4. All voltages above V (2 A / cm ²⁾ It can be confirmed that it is observed in the following section, or section below the minimum flow rate reference current density set in each). From this, it can be confirmed that lowering the minimum flow reference current density is suitable for maintaining the humidified state of the electrolyte membrane.

5 illustrates operation condition control and results according to another embodiment of the present application. Specifically, unlike in the case of FIG. 2, the minimum flow reference current density was reduced to 200 mA / cm ² , and 57 cc / min of hydrogen and 180 cc / min of air (oxygen) in a section of 200 mA / cm ² or less. The result of supply is a graph shown. At this time, the minimum flow rate reference current density and the flow rate of the supplied gas was set to the control unit to be adjusted according to the stoichiometric ratio.

Looking at the current density-voltage performance curve of Figure 5 (a), it can be seen that the voltage drops slowly. In fact, also in FIG. 5 (b) which shows the slope of the performance curve shown in FIG. 5 (a), in the section below the minimum flow reference current density of 200 mA / cm ^{2, the} section having the slope of −0.1 V · cm ² / A or more Not observed. From this, it can be confirmed that lowering the minimum flow reference current density is suitable for maintaining the humidified state of the electrolyte membrane.

In yet another example of the present application, the present application relates to a method of controlling a fuel cell.

The control method includes calling a current density-voltage performance curve of a fuel cell stack and comparing a voltage value of a performance curve observed in a predetermined current density section with a preset voltage value; And calculating a slope of the performance curve when the voltage value of the performance curve has a voltage value greater than or equal to a preset voltage value. Specifically, in the control method, when the slope of the calculated performance curve is -0.1 V · cm ² / A or more, the flow rate of the gas supplied to the cathode and the anode may be lowered or the minimum flow rate reference current density may be lowered.

In one example, the control method, by comparing the voltage value of the performance curve and the predetermined voltage value, when the voltage value of the performance curve has a voltage value less than the predetermined voltage value, the flow rate of the gas supplied to the cathode and the anode Can be lowered or the minimum flow reference current density can be lowered.

In addition, the control method of the present application can be made so that it is possible to execute operation condition determination and control performed by each component described in connection with the above-described fuel cell system.

The examples of the present application described above are only disclosed for illustrative purposes. Those skilled in the art having ordinary knowledge in the technical field to which the present application belongs may make various modifications, changes, and / or additions to the examples of the present application within the spirit and scope of the present application. Such modifications, changes, and additions should be considered to be within the scope of the claims of the present application.

Claims (13)

Fuel cell stacks; A calculator for calling the current density-voltage performance curve of the fuel cell stack and calculating the slope of the called current density-voltage performance curve; And A control unit controlling an operating condition of a fuel cell based on the current density-voltage performance curve and its slope; To include, wherein the control unit, in a predetermined current density interval, When the current density-voltage performance curve has a voltage value less than the set voltage value, the flow rate of the reaction gas supplied to the cathode and the anode is lowered or the minimum flow rate reference current density is lowered, and the voltage at which the current density-voltage performance curve is set is set. And having a voltage value greater than or equal to the value to cause the calculator to calculate the slope of the current density-voltage performance curve. The fuel cell system as claimed in claim 1, wherein the calculator calls a current density-voltage performance curve under a condition where a current density of 2 A / cm ² or less is applied. The fuel cell system as claimed in claim 1, wherein the calculation unit calls a current density-voltage performance curve under a condition that a relative humidity of a reactor body supplied to a fuel cell stack is 80% or less. The fuel cell system of claim 1, wherein the predetermined current density section means a section in which a current density of 2 A / cm ² or less is applied or a section in which a current density of less than or equal to a minimum flow rate reference current density is applied. . The fuel cell system of claim 1, wherein the set voltage has a value of at least 0.4V. The method of claim 1, wherein when the slope of the current density-voltage performance curve calculated by the calculation unit is -0.1 V · cm ² / A or more, the controller lowers the flow rate of the gas supplied to the cathode and the anode or is based on the minimum flow rate. A fuel cell system, characterized by lowering current density. The fuel cell system according to claim 1, wherein the control unit does not change the operating condition when the slope of the current density-voltage performance curve calculated by the calculating unit is less than -0.1 V · cm ² / A. The fuel cell system of claim 1, wherein the fuel cell stack is controlled by a controller to operate in consideration of stoichiometric ratios. The fuel cell system of claim 1, further comprising at least one of a temperature sensor, a humidity sensor, a pressure sensor, a flow sensor, a current sensor, or a voltage sensor. The fuel cell system of claim 9, wherein the operating conditions of at least one of inflow concentration, flow rate, pressure, humidity, or temperature of the reaction gas, and current density or voltage applied to the fuel cell are measured in real time. The fuel cell system of claim 9, wherein the controller lowers the temperature of the fuel cell stack instead of lowering the flow rate of the gas supplied to the cathode and the anode or lowering the minimum flow reference current density. Calling a current density-voltage performance curve of the fuel cell stack and comparing the voltage value of the performance curve observed in the predetermined current density section with a preset voltage value; Calculating a slope of the performance curve when the voltage value of the performance curve has a voltage value equal to or greater than a preset voltage value; When the slope of the calculated performance curve is -0.1 V · cm ² / A or more, the control method of the fuel cell is provided to lower the flow rate of the gas supplied to the cathode and anode or lower the minimum flow rate reference current density. The method of claim 12, wherein when the voltage value of the performance curve is compared with a preset voltage value and the voltage value of the performance curve has a voltage value less than the preset voltage value, the flow rate of the gas supplied to the cathode and the anode is reduced or minimized. A control method of a fuel cell provided to lower the flow reference current density.

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