KR101350184B1 - Method for controlling operation temperature of fuel cell stack - Google Patents

Abstract

The present invention relates to a method for controlling the operating temperature of a fuel cell stack, and to estimate the residual water content or membrane moisture content in the stack and to control the operating temperature of the fuel cell stack based on the estimate, thereby flooding and drying out the stack. The main purpose is to provide a method for controlling the operating temperature of a fuel cell stack that can effectively improve the efficiency of the fuel cell stack. In order to achieve the above object, the process of estimating the residual amount or membrane moisture content in the fuel cell stack of the fuel cell system in real time; Detecting flooding or dry-out occurrence in the stack based on an estimate of remaining water content or a membrane moisture content estimated in the stack; And controlling an operating temperature of the fuel cell stack such that the flooding or dry-out state is eliminated by increasing or decreasing the temperature of the coolant supplied to the fuel cell stack when the flooding or dry-out occurs. A method of controlling the operating temperature of a stack is disclosed.

Description

Method for controlling operation temperature of fuel cell stack}

The present invention relates to a method for controlling the operating temperature of a fuel cell stack, and more particularly, to estimate the residual water content or membrane moisture content in the stack, and then to control the operating temperature of the fuel cell stack based on the estimated value. The present invention relates to a method for controlling an operating temperature of a fuel cell stack that can effectively improve out.

A fuel cell system applied to a hydrogen fuel cell vehicle, which is one of environmentally friendly vehicles of the future, includes a fuel cell stack that generates electricity from electrochemical reactions by supplying air containing hydrogen and oxygen, A fuel processing system (FPS) responsible for recirculation and hydrogen purging, an air processing system (APS) for air supply and humidification, and an operating temperature control of the fuel cell stack And a thermal management system (TMS).

In this configuration, the fuel cell discharges heat together with water to the reaction by-product while generating electrical energy from an electrochemical reaction between hydrogen and oxygen, which are reaction gases, so that the thermal management system emits heat as a reaction by-product to the outside. Cooling system is included as standard to prevent stack temperature rise.

In general, in a vehicle fuel cell system, a cooling system for discharging heat of a fuel cell stack to the outside is applied with a water cooling system in which cooling water is supplied to a cooling water channel in the stack and circulated.

In the water cooling system, the cooling water is a medium for dissipating heat from the stack to the outside through the radiator, and is also used as a medium for raising the temperature of the stack by heating the cooling water by a heater as needed. It is an important factor in determining temperature.

For example, the operating temperature of the stack can be controlled by varying the temperature of the coolant flowing into the inlet of the stack.

The configuration of a water-cooled system that controls the operating temperature of the fuel cell stack, as is known, connects the coolant between the radiator and the radiator fan, and the fuel cell stack and the radiator to dissipate the heat of the coolant to the outside. Coolant line, bypass line for bypassing the coolant so as not to pass through the radiator, thermostat for adjusting the flow rate of coolant through the radiator and bypass line, and pump pumping the coolant from the coolant line It includes.

On the other hand, the fuel cell is theoretically a simple power generation system that generates electricity and water from the outside by receiving hydrogen and air (or oxygen) from the outside, but in reality, water, which is a byproduct of the electrochemical reaction, Since the quantity and state vary depending on the real-time operating conditions, it is difficult to estimate the internal phenomenon of the fuel cell.

This is because water varies in the form of water vapor, saturated liquid, and ice according to the operating conditions. Therefore, the water transfer characteristics change, and the change of water state passes through the separator channel, gas diffusion layer, catalyst layer, and membrane of the stack. This also affects the transport properties of gases and electrons.

In particular, the Proton Exchange Membrane (PEM) fuel cell, known as the fight against water, combines the so-called "floating" overflow with water and the "dry-out" lack of water, resulting in a change in stack performance. It is more difficult to estimate the internal phenomena of a fuel cell because it is a system with very high nonlinearity.

The most effective way to improve the flooding and dry-out is to change the operating temperature of the fuel cell stack according to the operating conditions. To this end, the thermal management system (TMS) is optimized according to various operating conditions such as the remaining amount of the stack. Development of controllable technology is essential.

Techniques for using passive thermostats (waxes) and heaters to control the operating temperature of fuel cell stacks have been proposed (US 2006/0216554, US 2011/0159393). It is not possible to precisely control the temperature by controlling the flow direction of the coolant in a passive manner, and it is impossible to perform control for improving the in-stack flooding and dry-out according to various operation conditions of the stack. In addition, there is a problem that energy consumption occurs when using the heater.

In order to precisely control the operating temperature according to the operation status of the stack, it is possible to use a 3-way valve with electronic control, and to operate the remaining amount in the stack to improve the flooding and dry-out in the stack. Depending on the state, it is necessary to actively control the opening of the three-way valve.

Currently, the AC impedance method using a separate measurement system is known to indirectly estimate the remaining amount in the stack. However, when the existing AC impedance method is applied, the use of a high voltage battery is inevitable (not available in the fuel cell alone mode). There is also a certain amount of energy loss.

In addition, when using a separate sensor to determine the remaining amount in the stack, there is a problem of an increase in the cost of using the sensor, an increase in sensor maintenance costs, and a decrease in control reliability due to frequent failure of the sensor.

Therefore, the present invention was invented to solve the above problems, and after estimating the operation state such as the residual quantity in the stack using various sensor signals existing in the fuel cell system without adding a separate sensor, By using the fuel cell stack to control the operating temperature of the fuel cell stack, it is possible to use the residual amount estimate in the stack based on the conventional AC impedance method (using a separate measuring system), and to use the residual amount estimate in the stack through a separate sensor. It is an object of the present invention to provide a method for controlling an operating temperature of a fuel cell stack that can solve various problems.

In addition, the present invention can effectively improve the internal flooding and dry-out by varying the operating temperature in accordance with the various operating conditions of the fuel cell stack, stack voltage drop phenomenon due to flooding, stack degradation due to high temperature in advance It is an object of the present invention to provide a method for controlling an operating temperature of a fuel cell stack that can be prevented.

In order to achieve the above object, the present invention, the process of estimating the residual water content or membrane moisture content in the fuel cell stack of the fuel cell system in real time; Detecting flooding or dry-out occurrence in the stack based on an estimate of remaining water content or a membrane moisture content estimated in the stack; And controlling an operating temperature of the fuel cell stack such that the flooding or dry-out state is eliminated by increasing or decreasing the temperature of the coolant supplied to the fuel cell stack when the flooding or dry-out occurs. Provides a method of controlling the operating temperature of the stack.

In the control method of the present invention, when the occurrence of the flooding or dry-out is to increase or decrease the temperature of the cooling water by controlling the opening degree of the 3-way valve for adjusting the cooling water passage flow rate of the radiator and bypass line It features.

Here, the opening degree of the 3-way valve is controlled so that the stack inlet coolant temperature follows the target value based on the stack inlet coolant temperature and the stack inlet coolant temperature target value detected by the stack inlet water temperature sensor.

In addition, in the process of controlling the opening degree of the three-way valve, the stack inlet coolant temperature target value corresponding to the outside air temperature detected by the outside air temperature sensor is calculated, and the target value corresponding to the outside air temperature is increased by the set value or by the set value. And lowering the final target value to control the stack inlet cooling water temperature to follow the calculated final target value.

In addition, the stack inlet coolant temperature target value calculated from the outside air temperature is set to be lower as the outside air temperature is higher.

In addition, when the flooding is detected, the stack inlet coolant temperature is increased by a set value, and when the dry-out is detected, the stack inlet coolant temperature is reduced by the set value.

In addition, it is characterized in that it is determined that the flooding occurs when the residual water amount estimate or the membrane moisture content estimate in the stack exceeds the set flooding detection threshold value for a predetermined duration.

In addition, it is characterized in that it is determined that the dry-out occurs when the remaining water content estimate or the membrane moisture content estimate in the stack exceeds the set dry-out detection threshold for a predetermined duration.

The membrane moisture content estimate may be an output value of an estimator for estimating the membrane moisture content in the fuel cell system based on flow rate dynamics and mass balance equations of oxygen, nitrogen, hydrogen, and water of the fuel cell system.

In addition, the remaining amount in the stack is an output value of an estimator for estimating the remaining amount of each layer of the stack in the fuel cell system based on the flow dynamics and mass balance equations of oxygen, nitrogen, hydrogen, and water of the fuel cell system. The sum of the remaining amount of each layer of the stack is characterized by being calculated by multiplying the number of cells in the stack.

Here, the sum of the residual amount of each layer is the residual amount of the cathode gas channel (CGC), the residual amount of the cathode gas diffusion layer (CGDL), the residual amount of cathode gas diffusion layer (CGDL), the residual amount of cathode catalyst layer (CCL), the membrane (MEM A) the sum of the residual amount, the residual amount of the anode catalyst layer (ACL), the residual amount of the anode gas diffusion layer (AGDL), the residual amount of the anode gas diffusion layer (AGDL), and the residual amount of the anode gas channel (AGC).

Accordingly, in the method for controlling the operating temperature of the fuel cell stack according to the present invention, the operating temperature of the stack is estimated by estimating the residual amount or membrane moisture content in the stack using an estimator and variably controlling the stack inlet coolant temperature target value according to the estimated value. Can be effectively controlled according to the current stack state, thereby effectively eliminating the flooding and dry-out phenomenon in the stack, and preventing the stack voltage drop due to flooding and the stack deterioration due to high temperature in advance. There is an advantage to this.

In addition, the present invention estimates the residual water content and membrane moisture content in the stack using various sensor signals in the fuel cell system without adding a separate sensor, and controls the thermal management system based on the estimated value, thereby controlling the in-stack based on the AC impedance method. It is possible to solve various problems in the conventional method using the residual amount estimation method and the method using the residual amount estimation in the stack using a separate sensor.

In particular, there is a cost reduction effect by dynamically estimating the residual amount and membrane moisture content in the stack using the existing sensor signal without the addition of a separate sensor.

1 is a block diagram showing an exemplary input signal and output signal of the fuel cell relative humidity and condensate estimator used in the present invention;
2 is an internal configuration of the fuel cell relative humidity and condensate estimator used in the present invention,
3 is a block diagram illustrating an air blow controller of a fuel cell relative humidity and condensate estimator used in the present invention;
4A and 4B are block diagrams illustrating a humidifier controller of a fuel cell relative humidity and condensate estimator used in the present invention;
5A and 5G are block diagrams illustrating a stack controller of a fuel cell relative humidity and condensate estimator used in the present invention;
6 is a block diagram illustrating a fuel processing system (FPS) controller of a fuel cell relative humidity and condensate estimator used in the present invention;
7 is a block diagram showing the configuration of a thermal management system for performing a control process according to the present invention;
8 and 9 are flowcharts illustrating a control process according to the present invention;
10 is a diagram illustrating an example of a map for calculating a stack inlet coolant temperature target value according to an outside air temperature in a control process of the present invention;
11 and 12 are diagrams showing an example of a state in which the stack inlet coolant temperature target value is changed in real time according to the control procedures shown in FIGS. 8 and 9.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains.

The present invention relates to a method of variably controlling the operating temperature of a fuel cell stack using a relative humidity and a condensate estimator for a fuel cell, and using the estimator to dynamically estimate the residual amount or membrane moisture content in the stack, If a flooding or dry-out condition of the stack is detected from the residual water content or membrane moisture content value, it is configured to perform cooling water temperature and operating temperature control of the fuel cell stack to resolve it.

Applicants and inventors of the present application patented an estimator capable of dynamically estimating the relative humidity and condensate of a fuel cell system, and a method for controlling the drain of condensate present on the anode side (hydrogen side) using the estimator. [Korean Patent Application No. 10-2010-0125324, 2010.12.09 application].

The relative humidity and condensate estimator for the fuel cell is configured to estimate the relative humidity and the condensate using various sensor signals in the fuel cell system without the addition of a separate sensor. After estimating the residual water content or membrane moisture content in the stack, the process of controlling the operating temperature of the fuel cell stack is performed according to the residual water content estimate or membrane moisture content estimate and the outside temperature.

In other words, it detects the occurrence of flooding or dry-out in the stack from the residual water quantity estimate or the membrane moisture content estimate obtained through the estimator, and the coolant temperature target value of the stack inlet calculated according to the outside temperature at the time of flooding or dry-out detection. (Controlling the target value variable), the opening degree of the 3-way valve is controlled so that the coolant temperature at the stack inlet follows the final target value, thereby flooding or drying by controlling the coolant temperature and the operating temperature of the fuel cell stack. The out is to be resolved.

The relative humidity and condensate estimator dynamically estimates relative humidity and condensate in the fuel cell system based on pre-installed air / hydrogen / coolant side temperature / flow / pressure sensor signals for overall control of the fuel cell system. As a kind of controller, the output signal is air side / hydrogen side relative humidity, air side / hydrogen side / humidifier instantaneous and cumulative condensate ratio, membrane moisture content, catalyst layer oxygen / hydrogen partial pressure, stack voltage, air side / hydrogen catalyst layer relative humidity , Oxygen / hydrogen supercharge ratio, residual amount in stack, residual amount in humidifier and the like.

Hereinafter, the relative humidity and the condensate estimator used in the present invention will be described in detail.

As shown in Figure 1, the relative humidity and condensate estimator according to the present invention, air temperature, atmospheric pressure, atmospheric relative humidity (RH), the stack current, the air flow rate supplied to the cathode of the stack, humidifier inlet / outlet and stack Air temperature at inlet / outlet, air pressure at humidifier inlet / outlet and stack inlet / outlet, coolant temperature at stack inlet / outlet, hydrogen flow rate to anode of stack, hydrogen supply line and stack inlet / outlet An actuator signal including a hydrogen temperature, a hydrogen pressure at the stack inlet / outlet, a hydrogen recycle blow rate, and a hydrogen purge / drain valve on / off state is received as an input signal.

The relative humidity and condensate estimator, which receives the input signal, has a cathode (= air) relative humidity (= air side) at the stack inlet / outlet and the humidifier inlet / outlet and an anode at the stack inlet / outlet according to the logic described below. Hydrogen side) relative humidity (Anode RH), instantaneous and cumulative condensate ratio of cathode / anode / humidifier (CWT, AWT, SWT based), membrane (Membrane, electrolyte membrane) moisture content, oxygen / hydrogen partial pressure of cathode and anode catalyst layers, Outputs stack (or cell) voltage, relative humidity of cathode / anode catalyst layer, oxygen / hydrogen supercharge ratio, stack residue (by layer), humidifier residue (by tube / shell), etc. do.

Preferably, the relative humidity and condensate estimator is configured to dynamically estimate the relative humidity and condensate in the fuel cell system based on the flow dynamics and mass balance equations of oxygen, nitrogen, hydrogen, water, (1) Air-side relative humidity, (2) hydrogen-side relative humidity, (3) air-side instantaneous or cumulative condensate, (4) hydrogen-side instantaneous or cumulative condensate, (5) humidifier instantaneous or cumulative condensate, (6) membrane moisture content, ( 7) catalyst bed oxygen partial pressure, (8) catalyst bed hydrogen partial pressure, (9) stack or cell voltage, (10) catalyst bed relative humidity on air side, (11) catalyst bed relative humidity on hydrogen side, (12) oxygen supercharge ratio, (13 ) Outputs two or more output signals, including hydrogen supercharge ratio, (14) residual volume in stack, and (15) humidifier residual volume.

For reference, the portions indicated by ellipses in each drawing represent the relative humidity and the output signal of the condensate estimator.

The configuration of the estimator 10 for receiving the input signal as described above and outputting the output signal, as illustrated in FIG. 2, includes an internal air blower controller 20, a tube control unit 32, and a shell control unit 34. An estimator internal humidifier controller 30, an estimator fuel processing system (FPS) controller 40, and an estimator internal stack controller 50 are included.

The air blower controller 20 calculates the supply flow rate and the relative humidity, and as shown in FIG. 3, the cathode relative humidity of the humidifier inlet (assuming that a vapor flow supplied through the air blower is preserved). Calculate Cathode RH).

That is, receiving the atmospheric temperature, atmospheric pressure, atmospheric relative humidity (using a sensor signal or an experimental map), calculates the cathode relative humidity at the inlet of the humidifier, and sends the calculated relative humidity signal to the humidifier controller 30.

The humidifier consists of a shell that receives the wet air discharged from the cathode of the stack, and a tube (hollow fiber membrane) that humidifies the air by receiving the wet air from the shell while simultaneously flowing the dry air supplied from the air blower to the cathode of the stack. The humidifier controller 30 for overall control of the fluid flowing through the humidifier calculates the tube outlet flow rate of the humidifier through PI control following the target pressure P1, and then balances air and water. and a shell controller 34 for calculating the air and water balance after calculating the shell outlet flow rate of the humidifier through PI control following the target pressure P2. .

The tube control unit 32 of the humidifier controller 30, as shown in Figure 4a, the dry air supply flow rate of the humidifier inlet, the air temperature of the cathode inlet of the stack, the dry air passed through the humidifier tube without humidification A dry air balance calculation unit 32-1 including an integrator to receive the discharge flow rate and calculate a partial pressure of the dry air of the humidifier tube; The steam supply flow at the humidifier inlet, the steam discharge at the stack inlet delivered from the humidifier shell, the air temperature at the stack inlet, the partial pressure of the steam at the humidifier tube, the cathode relative humidity at the stack inlet, and the humidifier tube A water balance calculator 32-2 including an integrator to calculate a residual amount of water; An outlet flow rate calculation unit 32-3 which calculates a flow rate of dry air at the stack inlet and a steam discharge flow rate at the stack inlet is based on the air pressure and the target pressure P1 of the stack inlet.

In this case, the flow rate of steam discharged from the humidifier shell is calculated in a diffusion manner based on the difference in water activity between the humidifier tube and the shell, and the outlet flow rate, that is, the dry air discharge flow rate at the stack inlet, and The steam discharge flow rate at the stack inlet is calculated by applying proportional-integral control to follow the air pressure (stack inlet) to the target pressure P1, and the target pressure P1 is the air pressure (stack inlet). Use sensor data or air flow based map data.

As shown in FIG. 4B, the shell controller 34 of the humidifier controller 30 receives a dry air inflow flow rate at the stack outlet, a dry air discharge flow rate at the humidifier outlet, and an air temperature at the humidifier outlet. A dry air balance calculator 34-1 including an integrator to calculate a dry air partial pressure of the shell; The steam inlet flow rate at the stack outlet, the steam discharge flow rate at the humidifier outlet, the steam transfer flow rate delivered to the humidifier tube, the liquid inflow flow rate at the stack outlet, the liquid discharge flow rate at the humidifier outlet, and the air temperature at the humidifier outlet. A water balance calculator 34-2 including an integrator to receive the steam partial pressure of the humidifier shell, the cathode relative humidity of the humidifier outlet, and the residual amount of the humidifier shell; It consists of an outlet flow rate (Out Flow) calculation unit 34-3 for calculating the dry air discharge flow rate and the steam discharge flow rate of the humidifier outlet based on the air pressure and the target pressure (P2) of the humidifier outlet.

At this time, the steam delivery flow rate delivered to the humidifier tube is the same as the steam delivery flow rate from the humidifier shell, and the outlet flow rate, that is, the dry air discharge flow rate at the humidifier outlet and the steam discharge flow rate at the humidifier outlet, is the air pressure (humidifier outlet). ) Is calculated by applying PI (Proportional-Integral) control to follow the target pressure (P2), and the target pressure (P2) is the air pressure (humidifier outlet) sensor data or air flow-based map data The air temperature (humidifier outlet) is a sensor data or a humidifier inlet and stack inlet / outlet air temperature sensor values that are calculated based on an energy balance equation.

Meanwhile, the liquid inflow flow rate at the outlet of the stack is an amount trapped in the cathode water trap (CWT), and the liquid discharge flow rate at the outlet of the humidifier is an amount trapped in the humidifier shell water trap (SWT). If the cathode relative humidity at the outlet is less than 100%, shell water trap (SWT) = cathode water trap (CWT) x α is established, and α = 0 to 1 range.

On the other hand, if the cathode relative humidity at the outlet of the humidifier is more than 100%, shell water trap (SWT) = cathode water trap (CWT) × α + humidifier shell net water flow × β, where α = 0 to 1, β = 0 to 1 range.

Here, the stack controller 50 calculates the outlet flow rate of the cathode gas channel of the stack through the PI control for estimating the target pressure P3, as shown in FIG. A CGC: Cathode Gas Channel (51) controller 51; A cathode gas diffusion layer (CGDL) control unit 52 for calculating an air and water movement amount due to diffusion and capillary action of a gas diffusion layer (GDL) by calculating concentrations of air and water; A cathode catalyst layer (CCL) controller 53 for calculating generation water, voltage (variable: current, temperature, partial pressure of oxygen, partial pressure of hydrogen) and residual amount through electrochemical reaction; Electrolyte membrane (MEM: Membrane Layer), which calculates the water concentration of the membrane by osmotic drag, back diffusion, and heat pipe, and calculates the amount of water transferred to the cathode and anode catalyst layers. Control unit 54; An anode catalyst layer (ACL) control unit 55 for calculating a residual amount of the anode catalyst layer; An anode gas diffusion layer (AGDL) control unit 56 for calculating air and water movement due to diffusion and capillary phenomenon of the gas diffusion layer by calculating hydrogen and water concentrations; And an anode gas channel (AGC) controller 57 for calculating the air and water balance after calculating the outlet flow rate of the anode gas channel of the stack through the PI control for estimating the target pressure P5. .

As shown in FIG. 5A, the cathode gas channel (CGC) controller 51 of the stack controller 50 includes a dry air supply flow rate at a stack inlet, a dry air discharge flow rate at a stack outlet, and a cathode. Oxygen supercharge ratio, oxygen concentration of cathode gas channel, dry air portion of cathode gas channel by inputting oxygen discharge flow rate to gas diffusion layer (CGDL), air temperature of stack outlet, dry air discharge flow rate of stack outlet A dry air balance calculation unit 51-1 including an integrator to calculate a pressure; Steam supply flow rate at the stack inlet, steam discharge flow rate at the stack outlet, steam flow rate from the cathode gas diffusion layer (CGDL), liquid discharge flow rate at the stack outlet, liquid flow rate from the cathode gas diffusion layer, and air temperature at the stack outlet The partial pressure of the cathode gas channel, the relative humidity of the cathode at the stack outlet, the residual volume of the cathode gas channel (CGC), the vapor concentration of the cathode gas channel, and the liquid S (CGC Liquid S = (s-s_im) A water balance calculator 51-2 including an integrator to calculate / (1-s_im); It consists of an outlet flow calculation part 51-3 which calculates the dry air discharge flow volume of a stack outlet and the steam discharge flow volume of a stack outlet based on the air pressure and target pressure P3 of the cathode gas channel CGC. do.

At this time, the outlet flow rate, that is, the dry air discharge flow rate of the stack outlet and the steam discharge flow rate of the stack outlet, is applied to the PI (Proportional-Integral) control for following the air pressure (stack outlet) to the target pressure P3. The target pressure P3 is based on air pressure (stack outlet) sensor data or air flow based map data, and the air temperature (stack outlet) is based on sensor data or stack coolant inlet / outlet temperature. Leverage map data from

On the other hand, the liquid discharge flow rate at the stack outlet is the amount trapped in the cathode water trap (CWT), and if the cathode relative humidity at the stack outlet is less than 100%, the cathode water trap (CWT) = liquid from the cathode gas diffusion layer The flow rate x α holds, and α = 0 ranges from 0 to 1.

On the other hand, if the cathode relative humidity at the stack exit is more than 100%, then cathode water trap (CWT) = liquid flow from the cathode gas diffusion layer x α + cathode gas channel (CGC) net water flow (x) At this time, α = 0 ~ 1, β = 0 ~ 1 range.

If s> s_im, the cathode gas channel liquid S (CGC Liquid S) = (s-s_im) / (1-s_im) holds, and if s ≤ s_im, then S (CGC Liquid S) = 0, where s = residual liquid volume of the cathode gas channel ÷ cathode gas channel volume, and s_im means fixed saturation (Immobile Saturation), which is a reference condition in which liquid flow rate occurs in capillary action.

The cathode gas diffusion layer (CGDL) control unit 52 of the stack controller 50 includes an oxygen inflow flow rate from the cathode gas channel and a cathode catalyst layer (CCL) as illustrated in FIG. 5B. An oxygen balance control unit 52-1 including an integrator to calculate an oxygen concentration of the cathode gas diffusion layer CGDL based on the oxygen discharge flow rate for the; A steam balance control unit comprising an integrator to calculate the amount of residual vapor in the cathode gas diffusion layer CGDL based on the vapor inflow flow rate from the cathode catalyst layer CCL and the vapor discharge flow rate for the cathode gas channel CGC. 52-2); A liquid balance control unit 52-3 including an integrator to calculate a residual amount of liquid in the cathode gas diffusion layer CGDL based on the cathode gas diffusion layer condensation rate and the liquid flow rate to the cathode gas channel; A condensation rate calculator 52-4 calculating a condensation rate of the cathode gas diffusion layer CGDL based on the temperature and the vapor concentration of the cathode gas diffusion layer CGDL; A liquid that calculates the liquid flow rate of the cathode gas channel based on the temperature of the cathode gas diffusion layer and the liquid S (CGDL Liquid S = (s-s_im) / (1-s_im)) and the cathode gas channel liquid S (CGC Liquid S) A flow rate calculator 52-5; An oxygen diffusion calculator 52-6 which calculates an oxygen inflow flow from the cathode gas channel based on the oxygen concentration of the cathode gas diffusion layer, the oxygen concentration of the cathode gas channel, and the oxygen diffusion coefficient of the cathode gas diffusion layer; ; The vapor diffusion calculation unit 52-7 calculates a vapor discharge flow rate for the cathode gas channel based on the vapor concentration of the cathode gas diffusion layer, the vapor concentration of the cathode gas channel, and the vapor diffusion coefficient of the cathode gas diffusion layer. It is configured to include.

At this time, the cathode gas diffusion layer (CGDL) temperature is utilized by the stack cooling water inlet / outlet temperature based map data.

If s> s_im, cathode gas diffusion layer liquid S (CGDL Liquid S) = (s-s_im) / (1-s_im) is established, and if s ≤ s_im, then S (CGDL Liquid S) = 0, where s = cathode gas diffusion layer (CGDL) residual liquid volume ÷ cathode gas diffusion layer (CGDL) void volume, s_im means fixed saturation, which is a reference condition in which liquid flow occurs in capillary action, In the capillary phenomenon, under the condition of s> s_im, the liquid flow rate is generated by the difference of the liquid S (Liquid S) of the adjacent layers.

Meanwhile, the cathode gas diffusion layer (CGDL) condensation rate is generated in proportion to the difference between the saturation pressure according to the cathode gas diffusion layer temperature and the vapor pressure according to the concentration of the cathode gas diffusion layer vapor (CGDL Vapor), and also the cathode gas diffusion layer (CGDL). ), It is desirable to configure the equation so that the diffusion coefficient of oxygen and vapor decreases as the amount of liquid (ie, the larger the CGDL Liguid s) becomes.

The cathode catalyst layer (CCL) controller 53 of the stack controller 50 may be configured based on the oxygen concentration of the cathode gas diffusion layer CGDL and the temperature of the cathode catalyst layer CCL, as shown in FIG. 5C. An oxygen partial pressure calculator 53-1 for calculating an oxygen partial pressure of the cathode catalyst layer CCL; A relative humidity calculator 53-2 that calculates a relative humidity of the cathode catalyst layer CCL based on the vapor concentration of the cathode gas diffusion layer CGDL and the temperature of the cathode catalyst layer CCL; A residual vapor amount calculation unit 53-3 that calculates a residual vapor amount of the cathode catalyst layer CCL based on the vapor concentration of the cathode gas diffusion layer CGDL; A steam flow rate calculator 53-4 for calculating a flow rate of the water flowing into the cathode gas diffusion layer based on the flow rate of the generated water by the electrochemical reaction of the stack and the steam flow rate to the membrane; And a voltage calculator 53-5 that calculates a voltage by an electrochemical reaction of the stack based on the stack current, the cathode catalyst layer temperature, the membrane electrical resistance, the oxygen partial pressure of the cathode catalyst layer, and the hydrogen partial pressure of the anode catalyst layer. do.

Electrolyte membrane (MEM: Membrane Layer) control unit 54 of the stack controller 50, as shown in Figure 5d, the electroosmotic drag (Electro-) of the cathode catalyst layer and the anode catalyst layer based on the use current and the water content of the membrane an osmotic drag detection unit 54-1 for outputting an osmotic drag; A despread detector 54-2 that detects back diffusion of the cathode catalyst layer and the anode catalyst layer based on the cathode catalyst layer relative humidity, the anode catalyst layer relative humidity, the membrane temperature, and the water content; A heat pipe detector 54-3 which detects a state of water movement by the heat pipe mechanism based on the membrane temperature, the temperature difference between the cathode catalyst layer and the cathode gas diffusion layer, and the temperature difference between the cathode catalyst layer and the anode gas diffusion layer; The electroosmotic force output signal of the electroosmotic force detector 54-1, the despread output signal of the despreading detector 54-2, the output signal of the heat pipe detector 54-3, and the membrane temperature, etc. It is configured to include a water balance calculation unit 54-4 including an integrator to receive the input, the moisture content, the residual amount, the electrical resistance of the membrane (MEM).

In the electrolyte membrane (MEM: Membrane Layer) control unit 54, the membrane (MEM) temperature utilizes the stack cooling water inlet / outlet temperature based map data, and the temperature difference between the cathode catalyst layer (CCL) and the cathode gas diffusion layer (CGDL), The temperature difference between the cathode catalyst layer (CCL) and the anode gas diffusion layer (AGDL) utilizes map data based on the current used and the stack coolant inlet / outlet temperature, and the vapor flow rate from the cathode catalyst layer and the vapor flow rate to the anode catalyst layer are respectively the cathode catalyst layer side. And the electroosmotic drag, the back diffusion rate, the heat pipe output value, and the like on the anode catalyst layer side.

Meanwhile, the electro-osmotic drag water movement mechanism refers to the water movement that occurs when hydrogen ions (H +) pass through the membrane depending on the current used, and the back diffusion water movement mechanism is a membrane ( MEM) refers to the water movement according to the water activity of the cathode catalyst layer and the anode catalyst layer at both ends, and the heat-pipe water movement mechanism is used to change the temperature between layers in the saturated state of the membrane. By water movement (hot layer → cold layer).

In addition, the membrane moisture content is a representative factor that can determine the membrane dry-out (MEM Dry-out), water flood (Flooding), a dimensionless factor between 0 ~ 16.8, the smaller the value is dry- out).

An anode catalyst layer (ACL) control unit 55 for calculating the residual amount of the anode catalyst layer of the stack controller 50 may include a hydrogen concentration and an anode catalyst layer of the anode gas diffusion layer (AGDL), as shown in FIG. 5E. A hydrogen partial pressure calculator 55-1 that calculates a hydrogen partial pressure of the anode catalyst layer ACL based on the temperature of the ACL; A relative humidity calculator 55-2 that calculates a relative humidity of the anode catalyst layer ACL based on the vapor concentration of the anode gas diffusion layer AGDL and the temperature of the anode catalyst layer ACL; A residual vapor amount calculation unit 55-3 calculating a residual vapor amount of the anode catalyst layer ACL based on the vapor concentration of the anode gas diffusion layer AGDL; And a steam flow rate calculator 55-4 that calculates a steam flow rate flowing to the anode gas diffusion layer based on the steam flow rate from the membrane.

In this case, the temperature of the anode catalyst layer utilizes map data based on the stack cooling water inlet / outlet temperature.

The anode gas diffusion layer (AGDL) control unit 56 of the stack controller 50 includes a hydrogen inflow flow rate from the anode gas channel AGC and an anode catalyst layer (ACL) as illustrated in FIG. 5F. A hydrogen balance controller 56-1 including an integrator to calculate a hydrogen concentration of the anode gas diffusion layer AGDL based on the hydrogen discharge flow rate for the anode catalyst layer; A vapor balance control unit 56 comprising an integrator to calculate the residual vapor amount and the vapor concentration of the anode gas diffusion layer AGDL based on the vapor inflow flow rate from the anode catalyst layer ALC and the vapor discharge flow rate for the anode gas channel AGC. -2) and; A liquid balance controller 56-3 including an integrator to calculate a residual liquid amount of the anode gas diffusion layer AGDL based on the anode gas diffusion layer AGDL condensation rate and the liquid flow rate to the anode gas channel AGC; A condensation rate calculator 56-4 calculating a condensation rate of the anode gas diffusion layer AGDL based on the temperature and the vapor concentration of the anode gas diffusion layer AGDL; Based on the temperature of the anode gas diffusion layer and the liquid S (AGDL Liquid S = (s-s_im) / (1-s_im)), and the anode gas channel liquid S (AGC Liquid S) to calculate the liquid flow rate to the anode gas channel A liquid flow rate calculation unit 56-5; A hydrogen diffusion calculation unit 56-6 that calculates a hydrogen inflow rate from the anode gas channel based on the hydrogen concentration of the anode gas diffusion layer, the hydrogen concentration of the anode gas channel, and the hydrogen diffusion coefficient of the anode gas diffusion layer; ; A vapor diffusion calculation unit 56-7 for calculating a vapor discharge flow rate for the anode gas channel based on the vapor concentration of the anode gas diffusion layer, the vapor concentration of the anode gas channel, and the vapor diffusion coefficient of the anode gas diffusion layer is provided. It is configured to include.

In this case, the temperature of the anode gas diffusion layer (AGDL) utilizes a stack cooling water inlet / outlet temperature based map data.

Where s> s_im, the anode gas diffusion layer liquid S (AGDL Liquid S) = (s-s_im) / (1-s_im) is established, and when s ≤ s_im, AGDL Liquid S = 0, where s (AGDL Liquid s) = anode gas diffusion layer (AGDL) residual liquid volume ÷ anode gas diffusion layer (AGDL) void volume, and s_im stands for fixed saturation, a reference condition in which liquid flow occurs in capillary action. In the capillary phenomenon, the liquid flow rate is generated by the difference of the liquid S (Liquid S) of the adjacent layers under the condition of s> s_im.

Meanwhile, the condensation rate of the anode gas diffusion layer (AGDL) is generated in proportion to the difference between the saturation pressure according to the anode gas diffusion layer temperature and the vapor pressure according to the concentration of the anode gas diffusion layer vapor (AGDL Vapor), and also the anode gas diffusion layer (AGDL). It is desirable to configure the formula so that the diffusion coefficient of hydrogen and vapor decreases as the amount of liquid (ie, the larger the AGDL Liquid s) becomes.

The anode gas channel (AGC) control unit 57 of the stack controller 50 includes a hydrogen supply flow rate at the stack inlet, a hydrogen discharge flow rate at the stack outlet, and an anode gas diffusion layer, as shown in FIG. 5G. The hydrogen supercharge ratio, the hydrogen concentration of the anode gas channel, and the hydrogen in the anode gas channel by inputting the hydrogen discharge flow rate to the (AGDL), the anode gas channel (AGC) temperature at the stack outlet, and the hydrogen discharge flow rate at the stack outlet. A hydrogen balance calculator 57-1 including an integrator to calculate the partial pressure; Steam supply flow rate at the stack inlet, steam discharge flow rate at the stack outlet, steam flow rate from the anode gas diffusion layer (AGDL), liquid discharge flow rate at the stack outlet, liquid flow rate from the anode gas diffusion layer, and anode gas at the stack outlet The temperature of the channel (AGC) is input to the vapor partial pressure of the anode gas channel, the anode relative humidity of the stack outlet, the residual volume of the anode gas channel, the vapor concentration of the anode gas channel and the liquid S (AGC Liquid S = (s- a water balance calculator 57-2 including an integrator to calculate s_im) / (1-s_im)); It consists of an outlet flow calculation unit 57-3 which calculates the hydrogen discharge flow rate of the stack outlet and the steam discharge flow rate of the stack outlet based on the anode gas channel (AGC) pressure of the stack outlet and the target pressure P5. do.

At this time, the outlet flow (Out flow), that is, the hydrogen discharge flow rate of the stack outlet and the steam discharge flow rate of the stack outlet are proportional-integral (PI) control for following the anode gas channel pressure (stack outlet) to the target pressure P5. The target pressure P5 utilizes the anode gas channel pressure (stack outlet) sensor data or the map data based on the anode gas channel flow rate, and the anode gas channel temperature (stack outlet) is the sensor data or Leverage map data based on stack coolant inlet and outlet temperatures.

On the other hand, the liquid discharge flow rate at the stack outlet is an amount trapped in the anode water trap (AWT), and if the anode relative humidity at the stack outlet is less than 100%, the anode water trap (AWT) = liquid from the anode gas diffusion layer The flow rate x α holds, and α = 0 ranges from 0 to 1.

On the other hand, if the anode relative humidity at the stack exit is 100% or more, anode water trap (AWT) = liquid flow rate from the anode gas diffusion layer × α + anode gas channel (AGC) net water flow × β is established. In this case, α = 0 ~ 1, β = 0 ~ 1 range.

Where s> s_im, the anode gas channel liquid S (AGC Liquid S) = (s-s_im) / (1-s_im) holds, and if s ≤ s_im, AGC Liquid S = 0, where s = anode Residual liquid volume ÷ anode gas channel volume of the gas channel, s_im means a fixed saturation (Immobile Saturation) which is a reference condition that the liquid flow rate occurs in the capillary phenomenon.

The fuel processing system (FPS) controller 40 includes: a hydrogen supply control unit 42 for calculating a hydrogen supply flow rate through a PI control following a target pressure P4 as shown in FIG. 6; A hydrogen inlet manifold controller 44 for controlling the mixing ratio between the supplied hydrogen and recycle hydrogen; A hydrogen outlet manifold control section 46 for hydrogen purging and condensate drain control of the hydrogen outlet manifold; And a hydrogen recycle loop controller 48 for ejector and recycle blower control.

More specifically, the fuel processing system controller 40 receives the target pressure P4, the anode gas channel pressure at the stack outlet, the hydrogen supply temperature, the relative humidity of the supply hydrogen, and the hydrogen supply flow rate and hydrogen. A hydrogen supply control section 42 for outputting a supply pressure, a hydrogen supply temperature, and a relative humidity of the supply hydrogen to the hydrogen inlet manifold control section 44; The hydrogen supply flow rate, the hydrogen supply pressure, the hydrogen supply temperature, and the relative humidity of the supply hydrogen are input from the hydrogen supply control unit 42, and the hydrogen recycle flow rate, the steam recycle flow rate, and the hydrogen are supplied from the hydrogen recycle loop control unit 48. The second recycle loop temperature, the hydrogen second recycle loop pressure, the relative humidity of the hydrogen second recycle loop are input, and the hydrogen flow rate at the stack inlet, the vapor flow rate at the stack inlet, the anode gas channel temperature and pressure at the stack inlet, A hydrogen inlet manifold controller 44 which outputs the anode relative humidity of the stack inlet to the anode gas channel (AGC) controller 57; From the anode gas channel (AGC) control unit 57, the hydrogen flow rate at the stack outlet, the vapor flow rate at the stack outlet, the liquid flow rate at the stack outlet, the anode gas channel temperature and pressure at the stack outlet, and the anode relative humidity at the stack outlet are input. A hydrogen outlet manifold that outputs the hydrogen recycle flow rate, the steam recycle flow rate, the hydrogen first recycle loop temperature, the hydrogen first recycle loop pressure, and the relative humidity of the hydrogen first recycle loop to the hydrogen recycle loop controller 48. A fold control section 46; From the hydrogen outlet manifold control section 46, the hydrogen recycle flow rate, the steam recycle flow rate, the hydrogen first recycle loop temperature, the hydrogen first recycle loop pressure, and the relative humidity of the hydrogen first recycle loop are input. And a hydrogen recycle loop controller 48 for outputting a steam recycle flow rate, a hydrogen second recycle loop temperature, a hydrogen second recycle loop pressure, and a relative humidity of the hydrogen second recycle loop.

At this time, in the hydrogen recycle loop, the second recycle loop temperature / pressure / relative humidity is calculated on the basis of the heat map (Heat map) according to the hydrogen recycle blower RPM, the hydrogen + steam purge flow rate when the hydrogen purge valve On It is calculated from the nozzle equation based on the pressure difference, and the condensate drain flow rate is calculated based on the condensate discharge test map for the unit time when the condensate drain valve is on, and the amount of condensate remaining in the condensate drain port is discharged. It is calculated by the Liquid Balance equation considering the anode water trap (AWT) input to the flow rate.

In addition, the hydrogen supply flow rate is calculated by applying PI (Proportional-Integral) control to follow the anode gas channel pressure at the stack inlet (using the anode gas channel pressure-based map at the stack outlet) to the target pressure P4. The target pressure P4 utilizes anode gas channel pressure (stack inlet) sensor data or anode gas channel flow rate based map data, and the hydrogen supply temperature is sensor data or atmospheric temperature, hydrogen tank temperature, and stack coolant. Leverage inlet / outlet temperature based map data.

At this time, the relative humidity of the supply hydrogen is set to 0% in consideration of the pure hydrogen conditions, the anode gas channel temperature (stack inlet) is the energy balance of the supply hydrogen + vapor calories, and the recycle hydrogen + steam calories ), And the anode relative humidity (stack inlet) is calculated based on the Humidity Ratio, which is defined as the ratio of the steam flow rate to the hydrogen flow rate.

As described above, the relative humidity and condensate estimator for the fuel cell has been described. Hereinafter, a method of controlling the operating temperature of the fuel cell stack performed based on the estimated residual water content or the membrane water content estimated using the estimator will be described. .

The method for controlling the operating temperature of a fuel cell stack according to the present invention continuously monitors whether the flooding or dry-out occurs in the stack from an estimate of residual water content or a membrane moisture content estimated in real time using the estimator, and monitors a predetermined condition. When a satisfactory flooding state or a dry-out state is detected, the control process of the thermal management system to solve this problem is characterized.

In the present invention, the flooding state and the dry-out state in the stack are sensed from the residual water amount (the remaining amount of the entire stack) estimate or the membrane moisture content estimate obtained in real time through the relative humidity and condensate estimator for the fuel cell, and the estimated value is When the predetermined flood generation condition or the dry-out occurrence condition is satisfied, it is determined that the flooding generation state or the dry-out generation state in the stack is satisfied.

In addition, the control of the thermal management system for flooding or dry-out elimination in the present invention is made by controlling the operating temperature of the fuel cell stack by controlling the coolant temperature, in particular, so that the coolant temperature of the stack inlet follows a specific target value. While controlling the opening degree of the -way valve, a target variable control method is applied in which the cooling water temperature target value of the stack inlet calculated from the outside temperature is varied so that the flooding or dry-out is eliminated when the flooding or dry-out is sensed.

7 is a block diagram showing a configuration of a thermal management system for performing a control process according to the present invention. As shown, the thermal management system includes a radiator 102 and a cooling fan 102a for dissipating heat of cooling water to the outside. Coolant line 103 connected to circulate the coolant between the fuel cell stack 101 and the radiator 102, bypass line 104 and radiator 102 for bypassing the coolant so as not to pass through the radiator 102. And a three-way valve 105 for adjusting the coolant passage flow rate of the bypass line 104, and a pump 106 for pumping the coolant in the coolant line 103.

The three-way valve 105 is an electronic valve that is controlled by the opening state by an electrical signal (control signal) applied from the outside, in this case, an electronic thermostat (for example, using a wax) as the electronic valve -0067942, Published Patent 2006-0005750, or a known electronic three-way valve in which the valve body is driven by a solenoid or a motor to control the opening state can be used.

The opening degree control of the three-way valve 105 is controlled by a control signal output from the valve controller 110, the valve controller 110 is the stack inlet coolant target value (T_FC_Target) finally calculated from the fuel cell controller 109 And the stack inlet coolant temperature T_FC (detected by the water temperature sensor of the stack inlet) to control the opening degree of the 3-way valve 105 so that the stack inlet coolant temperature follows the target value.

When the 3-way valve 105 is a valve whose opening degree is controlled by the angular rotation of the valve body by the motor, the valve controller 110 outputs a motor control signal for controlling the rotation angle (opening angle) of the valve body. It is applied to the way valve 105.

When the flow rate of the cooling water passing through the radiator 102 and the bypass line 104 is controlled by the three-way valve 105, the temperature of the cooling water supplied to the fuel cell stack 101, that is, the stack inlet cooling water temperature. Can be controlled, and thus the operating temperature of the fuel cell stack can be controlled.

In addition, the stack inlet coolant temperature T_FC detected in real time by the water temperature sensor 107 is input to the fuel cell controller 109, and the fuel cell controller 109 receives the outside air temperature detection signal of the outside temperature sensor 108. do.

In the above-described system configuration, the fuel cell controller 109 and the valve controller 110 may be provided as separate controllers as illustrated in FIG. 7, but the estimator 10, the water temperature sensor 107, and the outside air temperature sensor 108 are provided. An integrated controller may be used to directly control the 3-way valve 105 by calculating the stack inlet coolant temperature target value T_FC_Target while receiving an output signal (temperature detection signal).

8 and 9 are flowcharts illustrating a control process according to the present invention, and FIG. 8 illustrates an embodiment of detecting flooding or dry-out based on an estimate of residual amount in a stack obtained by the estimator 10. 9 illustrates an embodiment of detecting flooding or dry-out based on the membrane moisture content estimates obtained by estimator 10.

FIG. 10 is a diagram illustrating an example of a map for calculating a stack inlet coolant temperature target value according to an outside temperature in a control process of the present invention. In the present invention, the stack inlet coolant temperature target value (T_FC_Target) is determined when flooding or dry-out is detected. It is variable.

11 and 12 illustrate examples of a state in which the stack inlet coolant temperature target value T_FC_Target is changed in real time according to the control process illustrated in FIGS. 8 and 9.

In the drawing, T_FC_Target is a target value actually used to control the opening degree of the 3-way valve 105, and based on this target value and the stack inlet coolant temperature T_FC detected by the water temperature sensor 107, the 3-way valve ( The opening degree of 105) is controlled.

In the control process of the present invention, an estimate of the residual amount or membrane moisture content in the stack obtained through the relative humidity and the condensate estimator 10 and an outside temperature T_Amb detected by the outside air temperature sensor 108 are used. Estimates and membrane moisture content estimates are used to detect flooding and dry-out occurrences within the stack, and the outside temperature T_Amb is used to calculate the stack inlet coolant temperature target.

In the control process of the present invention, when the occurrence of flooding or dry-out is detected, the temperature of the coolant supplied to the fuel cell stack 101 is increased or lowered so that the flooding or dry-out state is eliminated. In this case, the operating temperature of the fuel cell stack 101 may be controlled by using a variable variable control method for controlling a target temperature of the stack inlet coolant temperature for controlling the thermal management system (opening control of the 3-way valve). Apply.

First, since the relative humidity and condensate estimator 10 estimates and outputs the remaining liquid and vapor phase residual amounts of each layer in the stack (see FIG. 1), the fuel cell controller 109 ) Inputs an estimate of the residual amount in the stack for each layer, which is an output signal of the estimator 10, sums all of them, and multiplies the number of cells to obtain an estimate of the remaining amount in the entire stack.

That is, the residual amount in the entire stack can be expressed by the following equation (1).

Residual amount in stack = number of stack cells × [CGC + Residual Vapor (CGDL) + CGDL Residual Liquid (CGDL) Liquid + CCL Residual Vapor (+) CMEM Residual Vapor (+) MEM Residual (AC) Volume + AGDL residual vapor volume + AGDL residual liquid volume + residual volume (AGC)] (1)

 Here, the residual amount CGC is an estimated value calculated by the water balance calculation unit 51-2 shown in FIG. 5A, and the CGDL residual vapor amount and the CGDL residual liquid amount are the steam balance control unit shown in FIG. 5B. It is the estimated value computed by (52-2) and the liquid balance control part 52-3, respectively.

In addition, the amount of CCL residual vapor (Vopor) in the residual vapor amount calculation unit 53-3 shown in Fig. 5C, the MEM residual amount in the water balance calculation unit 54-4 shown in Fig. 5D, the ACL residual vapor (Vapor) amount Are estimated values respectively calculated by the residual steam amount calculating section 55-3 shown in FIG. 5E.

The AGDL residual vapor amount and the AGDL residual liquid amount are estimated values calculated by the vapor balance control unit 56-2 and the liquid balance control unit 56-3 shown in FIG. 5F, respectively. ) Is an estimated value calculated by the water balance calculator 57-2 shown in FIG. 5G.

As such, the residual amount of the entire stack is estimated by the residual amount of each layer obtained in each component of the estimator 10, that is, the cathode gas channel (CGC), the cathode gas diffusion layer (CGDL), the cathode catalyst layer (CCL), the membrane (MEM), Residual volume calculated and output based on each layer of the stack, including anode catalyst layer (ACL), anode gas diffusion layer (AGDL), anode gas channel (AGC), etc. The number of cells in the stack can be calculated.

The membrane (MEM) moisture content estimate used to detect the flooding or dry-out state inside the stack is an estimate calculated by the water balance calculator 54-4 shown in FIG. 5D.

8 and 9, the fuel cell controller 109 basically calculates the stack inlet coolant temperature target value T_FC_Target1 based on the outside temperature T_Amb1 detected by the outside air temperature sensor 108 ( For example, by using the outside temperature-target calculation map of FIG. 10), at the same time, the occurrence of flooding or dry-out in the stack may be monitored from the residual water content estimate or the membrane moisture content estimate obtained through the estimator 10.

At this time, the stack inlet coolant temperature target value T_FC_Target1 according to the outside temperature may be calculated from the outside temperature-target value calculation map as shown in FIG. 10 stored in the fuel cell controller 109.

In addition, when monitoring the occurrence of flooding or dry-out, the stack inlet coolant temperature target value calculated from the outside temperature (T-Amb1) when the estimated residual water content or the membrane moisture content in the stack exceeds the preset flooding detection threshold value ( It is determined that T_FC_Target1 is in a flooding state which should be compensated by the set value ΔT_FC_H1 so that flooding is eliminated.

On the other hand, when the residual water amount estimate or the membrane moisture content estimate in the stack is less than the preset dry-out detection threshold, the set value of dry-out of the stack inlet coolant temperature target value T_FC_Target1 calculated from the outside temperature T_Amb1 is set to be eliminated. It is determined that there is a dry-out occurrence state that should be compensated by ΔT_FC_L1).

In this case, when the residual water amount estimate or the membrane moisture content estimate in the stack exceeds the flooding detection threshold value is maintained for a predetermined duration Δt, it is preferable to set the final flooding state.

Likewise, if the condition in which the residual water content estimate or the membrane moisture content estimate exceeds the dry-out detection threshold is maintained for a predetermined duration Δt, it is preferably set to determine that the dry-out occurs.

After all, in the normal state in which flooding or dry-out has not occurred, as shown in FIG. 10, the stack inlet coolant temperature target value T_FC_Target1 corresponding to the outside temperature T_Amb1 is the final target value according to the outside temperature-target value calculation map. In the flooding or dry-out state, the final target value T_Fc_Target is calculated by compensating the target values T_FC_Target1 corresponding to the outside temperature by the set values ΔT_FC_H1 and ΔT_FC_L1.

8, 9, and 10, when the stack inlet coolant temperature target value is set to T_FC_Target1 at any outside temperature T_Amb1, T_FC_Target1 controls the opening degree of the three-way valve 105 without modification in the normal state. It is used as the final target value (T_FC_Target) (T_FC_Target = T_FC_Target1), but when the flooding or dry-out occurs, the final target value (T_FC_Target = T_FC_Target_T_FC_T_FC_T_T_T_T_T_T_T_T_T_T_T_T_T_T_T_T_T_T_T_T_T_T_T_Tget) can see.

The target value calculation map of FIG. 10 is data obtained experimentally through a preceding test, and is set such that the stack inlet coolant temperature target value T_FC_Target decreases as the outside temperature T_Amb rises (from low temperature to high temperature).

In addition, when the flooding detection is performed even under the same ambient temperature condition, the final target value of increasing the set value ΔT_FC_H1 to the basic target value T_FC_Target1 corresponding to the outside temperature T_Amb1 may be calculated through the target value calculation map. When the out is detected, a final target value obtained by reducing the set target value ΔT_FC_L1 to the basic target value T_FC_Target1 may be calculated.

Referring to Figures 11 and 12, when the residual water content estimate or membrane moisture content estimate in excess of the flooding detection threshold is maintained for a set duration Δt, and the residual water content estimate or membrane moisture content estimate in the stack is dry. When the state below the out-out detection threshold value is maintained for the set duration Δt, it is determined that the stack internal flooding and dry-out have occurred, and the set value ΔT_FC_H1, from the determination point of the stack inlet coolant temperature target value T_FC_Target1 It is shown that the final target values T_FC_Target1 + ΔT_FC_H1 and T_FC_Target1-ΔT_FC_L1 are calculated by compensating ΔT_FC_L1.

In addition, as shown in FIGS. 11 and 12, even when the estimated value is returned to the normal state which is lower than the flooding detection threshold or higher than the dry-out detection threshold, only when the steady state is maintained for the set duration Δt from the return time point. It is finally determined that the flooding and dry-out states are eliminated, and from the determination point, the stack inlet coolant temperature target value is finally determined as the target value T_FC_Target1 corresponding to the outside temperature T_Amb1 of the map without compensation of the set value.

In this way, the present invention optimizes the operating temperature of the stack according to the current stack state by estimating residual water content or membrane moisture content in the stack using an estimator and variably controlling the stack inlet coolant temperature target value according to the estimated value. By controlling, it is possible to effectively eliminate the flooding and dry-out phenomenon in the stack, and further, it is possible to prevent the stack voltage drop due to flooding and the stack degradation problem due to high temperature in advance.

The embodiments of the present invention have been described in detail above, but the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are provided. Also included in the scope of the present invention.

10: relative humidity and condensate estimator
20: air blower controller inside estimator
30: humidifier controller inside the estimator
40: Estimator internal fuel processing system (FPS) controller
50: estimator internal stack controller
101: fuel cell stack 102: radiator
103: cooling water line 104: bypass line
105: 3-way valve 106: pump
107: stack inlet water temperature sensor 108: outside temperature sensor
109: fuel cell controller 110: valve controller

Claims (11)

Obtaining a membrane moisture content estimate of the fuel cell system using an estimator based on flow rate dynamics and mass balance equations of oxygen, nitrogen, hydrogen, and water of the fuel cell system;
The sum of the residual quantities of each layer of the stack is obtained using an estimator for estimating the residual quantity of each layer of the stack in the fuel cell system based on the flow dynamics and mass dynamics equations of oxygen, nitrogen, and hydrogen water of the fuel cell system. Multiplying by the number of cells in the stack to obtain a residual quantity estimate in the stack;
Detecting flooding or dry-out occurrence in the stack based on an estimate of remaining water content or a membrane moisture content estimated in the stack; And
And controlling an operating temperature of the fuel cell stack such that the flooding or dry-out state is eliminated by increasing or decreasing the temperature of the coolant supplied to the fuel cell stack when the flooding or dry-out occurs. Operating temperature control method of the fuel cell stack.
The method according to claim 1,
When the flooding or dry-out occurs, the operating temperature of the fuel cell stack increases or decreases the temperature of the coolant by controlling the opening degree of a 3-way valve for adjusting the flow rate of the coolant through the radiator and the bypass line. Control method.
The method according to claim 2,
An operating temperature of the fuel cell stack, wherein the opening degree of the 3-way valve is controlled so that the stack inlet coolant temperature follows the target value based on the stack inlet coolant temperature and the stack inlet coolant temperature target value detected by the stack inlet water temperature sensor. Control method.
The method according to claim 3,
In the process of controlling the opening degree of the 3-way valve, a target value of the stack inlet coolant temperature corresponding to the outside temperature detected by the outside air temperature sensor is calculated, and the target value corresponding to the outside temperature is increased by the set value or lowered by the set value. And calculating a final target value, then controlling the stack inlet coolant temperature to follow the calculated final target value.
The method of claim 4,
The stack inlet coolant temperature target value calculated from the outside temperature is set lower as the outside temperature is higher.
The method according to claim 1 or 2,
The method of controlling the operating temperature of a fuel cell stack, wherein when the flooding is detected, the stack inlet coolant temperature is increased by a set value, and when the dry-out is detected, the stack inlet coolant temperature is lowered by a set value.
The method according to claim 1,
And determining that the flooding occurs when the remaining water content estimate or the membrane moisture content estimate in the stack exceeds the set flooding detection threshold value for a predetermined duration.
The method according to claim 1,
The method of controlling the operating temperature of a fuel cell stack, characterized in that it is determined that the dry-out occurs when the remaining amount of water in the stack estimate or the membrane moisture content estimate is less than the set dry-out detection threshold for a set duration. .
The method according to claim 1,
The sum of the residual amount of each layer is the residual amount of the cathode gas channel (CGC), the residual amount of cathode gas diffusion layer (CGDL), the residual amount of cathode gas diffusion layer (CGDL), the residual amount of cathode catalyst layer (CCL), the residual amount of membrane (MEM) Operating temperature of the fuel cell stack, characterized in that the sum of the amount, the residual amount of the anode catalyst layer (ACL), the residual amount of the anode gas diffusion layer (AGDL), the residual liquid amount of the anode gas diffusion layer (AGDL), and the residual amount of the anode gas channel (AGC) Control method. delete delete

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