System and procedure for controlling a vehicle's fuel cell

Abstract

Method for controlling a fuel cell (100) of a vehicle, comprising: Determine by means of a control whether pressure regulation is required to exert pressure on air being discharged from an air supply device (200), based on whether additional power output from the fuel cell (100) is required or whether the fuel cell (100) is in a drying-out state; In response to the determination that pressure control is required, deriving an opening degree of a valve on one side of an air outlet of the fuel cell (100) required for pressure control, by controlling and adjusting the valve based on the derived opening degree of the valve; Calculating a pressure ratio by the controller, which is obtained by calculating the following: (current degree of opening - first degree of opening) / (second degree of opening - first degree of opening), wherein the current degree of opening is a valve opening degree at the present time, the first degree of opening is an opening degree required when an air pressure is atmospheric pressure, and the second degree of opening is an opening degree at a time when the pressure regulation is complete; and Increasing a target hydrogen pressure based on an increase in the calculated pressure ratio or an increase in the flow rate of the air discharged from the air supply device (200).

Description

BACKGROUND Area of ​​the invention

[0001] Exemplary embodiments of the present invention relate to a system and method for controlling a fuel cell of a vehicle, wherein the reliability of a variable pressure control is ensured by preventing fuel cell performance degradation and system malfunction. Description of the related technique

[0002] To prevent performance degradation of a fuel cell stack, humidity control is essential. In particular, in areas with high temperature / power output, the stack is susceptible to drying out due to the fuel cell's humidity-dependent performance limit. Consequently, a power-limiting method is used to reduce the vehicle's output to prevent stack degradation, but this can be frustrating for the driver. Therefore, the present invention proposes a method for improving humidity control by operating a fuel cell system without using the power-limiting method.

[0003] As in Fig. As illustrated in Figure 3, the fuel cell system experiences a performance degradation due to the humidity limit in situations with high output / high temperature, thus degrading or reducing the output from state 1 to state 2. To prevent such performance degradation, a method for limiting the power output in advance has also been proposed. However, this method results in a reduction of the operating power and is therefore not capable of providing a fundamental solution. Furthermore, many methods for increasing the operating pressure have been proposed to improve the humidity state of the system.

[0004] To increase the operating pressure, an air compressor and an opening adjustment valve can be used. However, this can increase the power consumption of an auxiliary drive and cause noise in the air compressor. A related technology proposes a method for operating under pressure only under a specific condition: that a drying-out situation is detected by measuring or estimating the moisture content of the stack. Similar to the present invention, this technology employs variable pressure control. However, in implementing variable pressure control, the present invention proposes an improved technology to ensure reliability in controlling the flow rate / pressure.

[0005] From DE 10 2007 026 331 A1, a method for controlling a vehicle fuel cell is known, comprising: determining by a control system whether pressure regulation is required to exert pressure on air that is discharged from an air supply device, based on whether an additional fuel cell output is required or whether the fuel cell is in a drying-out state; and in response to determining that pressure regulation is required, deriving a degree of opening of a valve required for pressure regulation by controlling and adjusting the valve based on the derived degree of opening of the valve.

[0006] JP 2007-172971A further discloses a fuel cell system comprising a fuel cell with a fuel electrode and an oxidant electrode for clamping an electrolyte and for generating current by supplying fuel gas and oxidant gas to the fuel electrode and the oxidant electrode, respectively; a humidifier for humidifying at least one of the two gases, namely the fuel gas or the oxidant; an exhaust duct for venting exhaust gas from the fuel cell; and a pressure regulating valve arranged in the exhaust duct for regulating the operating pressure of the fuel cell. The fuel cell system includes an exhaust gas flow rate estimator for estimating the exhaust gas flow rate from the fuel cell outlet, and the humidification quantity of the humidification device is adjusted according to the exhaust gas flow rate estimated by the exhaust gas flow rate estimator at the time of load transition.

[0007] The terms described as a background technology of the present invention are used only to improve the understanding of the background of the present invention and should not be assumed to imply that the terms correspond to related technology already known to someone with ordinary technical skills.

[0008] The object of the present invention is to provide a system and method for controlling or regulating a fuel cell of a vehicle in order to ensure the reliability of a variable pressure control by preventing fuel cell performance degradation and system malfunction.

[0009] The problem is solved by a method having the features of claim 1 and a system having the features of claim 25. Advantageous further developments are found in the dependent claims.

[0010] Other problems and advantages of the present invention can be understood from the following description and will become apparent with regard to the exemplary embodiments of the present invention. It is also obvious to someone with technical expertise in the field to which the present invention belongs that the problems and advantages of the present invention can be achieved by the means claimed and combinations thereof.

[0011] According to an exemplary embodiment of the present invention, a method for controlling a vehicle fuel cell comprises the following: determining whether pressure control is required for the compressed air supplied by an air supply device, starting from whether additional power output is requested from the fuel cell or whether the fuel cell is in a drying-out state; and in response to determining that pressure control is required, deriving a degree of opening of a valve on one side of an air outlet of the fuel cell that is required for pressure control, and adjusting the valve based on the derived degree of opening of the valve.Furthermore, the system includes calculating a pressure ratio by the controller, obtained by calculating the following: (current opening degree - first opening degree) / (second opening degree - first opening degree), where the current opening degree is a valve opening degree at the present time, the first opening degree is an opening degree required when air pressure is atmospheric pressure, and the second opening degree is an opening degree at a time when pressure regulation is complete; and increasing a set hydrogen pressure based on an increase in the calculated pressure ratio or an increase in the flow rate of air discharged from the air supply device.

[0012] The provision may include a stipulation that pressure control is required if the operating temperature of the fuel cell is equal to or greater than a reference temperature, if the output of the fuel cell is equal to or greater than a reference output, or if the fuel cell is in a state of drying out.

[0013] The method for controlling a fuel cell may further include determining whether atmospheric pressure control is required to change the pressure of air discharged from the air supply device to atmospheric pressure if flooding occurs during pressure operation; adjusting the valve to the degree of opening required for pressure control; and deriving the degree of opening required for pressure control and adjusting the valve based on the derived degree of opening in response to the determination that pressure control is required.

[0014] Control can include selecting a target air pressure and deriving a valve opening command to follow the selected target air pressure. The flow rate of the air discharged from the air supply device and the target air pressure can each have values ​​within preset limits with respect to the air flow rate and air pressure. Deriving a valve opening command can include deriving the valve opening command using an opening map in which the target air pressure and the valve opening degree to follow the target air pressure are predefined.

[0015] In the valve opening characteristic map, the target air pressure and the valve opening degree required to maintain that target air pressure can be predefined differently based on the flow rate of the air supplied by the air delivery system and the fuel cell operating temperature. The valve opening characteristic map can be predefined where the opening degree during pressure control is lower than during atmospheric pressure control. Furthermore, the valve opening characteristic map can be predefined where the required valve opening degree is reduced while the fuel cell operating temperature is increased, provided the target air pressure is approximately equal to the air flow rate.

[0016] The target air pressure can include a first air pressure in an atmospheric pressure state and a second air pressure in a pressure state, and the opening degree characteristic map can be mapped in advance, where a required valve opening degree becomes a first opening degree when the target air pressure is the first air pressure, and the required valve opening degree becomes a second opening degree when the target air pressure is the second air pressure.

[0017] Furthermore, the opening degree map can be pre-mapped to reduce the required valve opening degree between the first and second opening degrees when the target air pressure is in a section where it increases from the first to the second air pressure. The opening degree map can also be pre-mapped to change a required valve opening degree with a hysteresis band based on a change in the air flow rate. Finally, the opening degree map can be pre-mapped to change a required valve opening degree over time when a maximum rate of increase is limited.

[0018] The method for controlling a fuel cell may further include setting a maximum stoichiometric ratio (SR) to a minimum value once pressure control is complete. Additionally, the method may include increasing a maximum stoichiometric ratio (SR) based on an increase in the valve opening degree during atmospheric pressure control. This setting process may involve gradually decreasing the maximum SR value before pressure control is complete, using a slope or gradient, to reach the minimum value upon completion of pressure control.

[0019] Determining a pressure control closing time can be based on calculating a pressure ratio obtained by calculating (current opening degree - first opening degree) / (second opening degree - first opening degree). The current opening degree can be the valve opening degree at the present time, the first opening degree can be the opening degree required when the air pressure is at atmospheric pressure, and the second opening degree can be the opening degree at a time when the pressure control is complete. The pressure ratio can have a value between 0 and 1. The maximum value of the closing time can be inversely proportional to an increase in the pressure ratio, and the maximum value of the closing time can be equal to the minimum value of the closing time when the pressure ratio is 1.

[0020] The target hydrogen pressure level, which is increased based on the increase in the air flow rate, can differ based on the pressure ratio. Furthermore, the method for controlling a fuel cell can include comparing the derived valve opening degree with a detected actual valve opening degree; and limiting the fuel cell power output if the derived valve opening degree is greater than the actual valve opening degree. The method for controlling a fuel cell can also include comparing the derived valve opening degree with a detected actual valve opening degree; and maximizing the valve opening degree if the derived valve opening degree is greater than the actual valve opening degree.

[0021] Furthermore, the method for controlling a fuel cell may include comparing the derived valve opening with a detected actual valve opening; and limiting a maximum rotational speed (RPM; revolutions per minute) of the air supply device if the derived valve opening is greater than the actual valve opening. The method for controlling a fuel cell may also include comparing the derived valve opening with a detected actual valve opening; and setting a maximum value for a stoichiometric ratio (SR) if the derived valve opening is greater than the actual valve opening.The method for controlling a fuel cell may further include increasing the maximum opening degree of the valve when the deviation of the fuel cell voltages becomes equal to or greater than a predetermined value.

[0022] Following the procedure for controlling a fuel cell in a vehicle with the configuration described above, fuel cell performance degradation and system malfunctions can be prevented, thus ensuring the reliability of the variable pressure control. The air pressure can be adjusted by setting the opening degree control valve on the air outlet side to prevent abrupt changes in air pressure caused by sudden changes in the opening degree. Consequently, operation can be carried out without deviating from the operating limits. Furthermore, the hydrogen supply pressure and the air supply pressure (SR) can be optimally adjusted, and even a fail-safe operating strategy can be implemented when setting the air opening degree to ensure the reliability of the opening degree control. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above-mentioned and other features and advantages of the present disclosure will become more apparent from the following detailed description in conjunction with the accompanying drawings. Fig. Figure 1 is a representation illustrating the configuration of a vehicle's fuel cell system according to the related technique. Fig. Figure 2 is a flowchart illustrating a method for controlling a fuel cell of a vehicle according to an exemplary embodiment of the present invention. Fig. Figure 3 is a graph illustrating the performance degradation of a vehicle's fuel cell according to the related technology. Fig. Figure 4 is a representation illustrating a data characteristic map in a method for controlling a fuel cell of a vehicle according to an exemplary embodiment of the present invention. Fig. Figure 5 is a graph illustrating a relationship between an airflow rate and a valve opening degree of an air outlet in a method for controlling a fuel cell of a vehicle according to an exemplary embodiment of the present invention. The Fig. 6 and Fig. Figure 7 are graphs illustrating a valve opening degree of an air outlet in a method for controlling a fuel cell of a vehicle according to an exemplary embodiment of the present invention. The Fig. Figures 8 to 10 are graphs illustrating an SR, a pressure ratio and a hydrogen pressure in a method for controlling a fuel cell of a vehicle according to an exemplary embodiment of the present invention. The Fig. Figures 11 to 13 are flowcharts that schematically illustrate a fail-safe control system in conjunction with a variable opening degree control system according to an exemplary embodiment of the present invention. Fig. Figure 14 is a graph illustrating changes in airflow rates and valve opening degrees according to temperatures according to an exemplary embodiment of the present invention. Fig. Figure 15 is a representation illustrating variable control of an SR based on an estimate of the relative humidity according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0024] It is clear that the term "vehicle" or "vehicle-" or any other similar term used herein includes motor vehicles in general, such as passenger cars, including all-terrain vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft, including a variety of boats and ships, aircraft and the like, and hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and vehicles using other alternative fuels (e.g., fuels derived from raw materials other than petroleum). As defined herein, a hybrid vehicle is a vehicle that has two or more power sources, such as both gasoline-powered and electric-powered vehicles.

[0025] Although an exemplary embodiment is described using a plurality of units to carry out the exemplary process, it is clear that the exemplary processes can also be carried out by a single module or a plurality of modules. Furthermore, it is clear that the term controller / control unit refers to a hardware device containing memory and a processor. The memory is intended for storing the modules, and the processor is specifically intended for executing the modules to carry out one or more processes, which are described below.

[0026] Furthermore, the control logic of the present invention can be implemented as non-transient computer-readable media on a computer-readable storage medium containing executable program instructions that are executed by a processor, a controller / control unit, or the like. Examples of computer-readable storage media include, but are not limited to, read-only memory, random-access memory, compact disc read-only memory (CD-ROMs), magnetic tapes, floppy disks, flash drives, smart cards, and optical data storage devices. The computer-readable storage medium can also be distributed across networked computer systems, allowing the computer-readable medium to be stored and executed in a distributed manner, for example, by a telematics server or a controller area network (CAN).

[0027] The terminology used herein serves only to describe certain embodiments and is not intended to limit the invention. As used herein, the singular forms "a" and "the" shall also include the plural forms unless the context otherwise makes clear. It shall also be clear that the expressions "has" and / or "having" when used in this description specify the presence of the aforementioned features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the expression "and / or" includes any and all combinations of one or more of the associated listed elements.

[0028] Exemplary embodiments of the present invention are described in more detail below with reference to the accompanying drawings. However, the present invention can be implemented in various forms and is not intended to be limited to the exemplary embodiments set forth herein. These exemplary embodiments are provided instead so that this disclosure will be comprehensive and complete and will fully convey the scope of the present invention to someone with technical expertise. Throughout the disclosure, similar reference numbers refer to similar parts throughout the various figures and exemplary embodiments of the present invention.

[0029] Fig. Figure 1 is a diagram illustrating the configuration of a vehicle's fuel cell system. A fuel cell system includes a hydrogen supply system, an air supply system, a cooling system, and a separate fuel cell load device. The air supply system includes an air blower 200 for air supply, a humidification device 300 for humidification, and a separate outlet opening degree control valve 400 for air pressure regulation. The hydrogen supply system includes a hydrogen supply valve 500, a hydrogen outlet condensate valve, a hydrogen purge valve, and a hydrogen recirculation device 600. The cooling system includes a water pump configured to supply cooling water, a radiator, and a radiator fan configured to cool a water outlet.Water drainage is configured, and a thermostat 700 is configured to set a water flow rate in a cooler loop and a bypass loop. The fuel cell load device can be used to prevent a build-up of stack voltage during fuel cell 100 warm-up or start / stop operation. The fuel cell load device can be a resistor, a rechargeable high-voltage battery, or other load devices.

[0030] In the present invention, the temperature of a fuel cell 100 can be measured by a cooling water thermostat 700, and a control unit can be configured to adjust the opening degree of an air supply device 200 or a fuel cell air outlet valve 400. Furthermore, the control unit can be configured to adjust the air and hydrogen pressure and a setpoint by actuating the hydrogen supply valve 500 or a hydrogen recirculation device 600.

[0031] Fig. Figure 2 is a flowchart illustrating a method for controlling a vehicle fuel cell according to an exemplary embodiment of the present invention. In the flowchart, the subject of the control method can be the controller configured to execute the method. A method for controlling a vehicle fuel cell according to an exemplary embodiment of the present invention can involve detecting a time at which pressure control is required (S200) by scanning whether a power or pressure control is required.an additional output power of the fuel cell is required or whether the fuel cell is in a drying-out state; in response to the detection that pressure control is required, deriving a required valve opening degree of an air outlet (S300) by replacing a target air pressure with a data map; and setting a fuel cell air outlet valve 400 based on the derived valve opening degree of the air outlet (S400).

[0032] In other words, the controller can be configured to determine, based on whether additional fuel cell power is required or whether the fuel cell is in a drying-out state, whether pressure control is needed to apply pressure to air drawn from an air supply unit 200. In response to determining that pressure control is needed, the controller can be configured to derive the valve opening degree required for pressure control and adjust the valve based on this derived opening degree. If the target air pressure for pressure control is selected first, a valve opening degree command can be derived to follow the selected target air pressure, and thus the valve can be adjusted based on the derived valve opening degree.

[0033] The controller can be configured to further determine that pressure control is required when the operating temperature of the fuel cell 100 is equal to or greater than a reference temperature, when the power output of the fuel cell 100 is equal to or greater than a reference power output, or when the fuel cell 100 is in a drying-out state. The flow rate of the air discharged by the air supply unit 200 and the target air pressure can each have values ​​within preset limit ranges with respect to the air flow rate and the air pressure. Fig. Section 4, indicated by a dashed line, specifies an operating limit range as a preset limit. If operation is carried out in a range that deviates from the operating limit range, the air supply unit 200 may be damaged, and therefore it is necessary to increase the pressure to the operating limit range.

[0034] A valve opening degree command can be derived from an opening degree map, in which the target air pressure and the valve opening degree to maintain that pressure can be predefined. In the opening degree map, the target air pressure and the valve opening degree to maintain that pressure can be predefined differently based on the flow rate of the air supplied by the air supply unit 200 and the operating temperature of the fuel cell. Furthermore, the opening degree map can be predefined to reduce the opening degree during pressure control, making it lower than the opening degree during atmospheric pressure control. If the operating temperature is lower than the preset reference temperature, atmospheric pressure control can be used, and consequently, the predefined opening degree map corresponding to atmospheric pressure control can be applied.

[0035] The target air pressure can be divided into a first air pressure at one atmospheric pressure state and a second air pressure at another pressure state. Specifically, the valve opening characteristic can be mapped in advance to represent the valve opening degree as a first opening degree when the target air pressure is the first air pressure, and as a second opening degree when the target air pressure is the second air pressure. Furthermore, the valve opening characteristic can be mapped in advance to decrease the required valve opening degree between the first and second opening degrees when the target air pressure is in a section where it increases from the first to the second air pressure.

[0036] In particular, the opening degree map can be pre-mapped to change a required valve opening degree with a hysteresis band based on a change in the airflow rate. Furthermore, the opening degree map can be pre-mapped to change the required valve opening degree over time when a maximum rate of increase is limited. Even if the target air pressure is substantially high, the opening degree values ​​can remain the same when the flow rate is increased, and the target air pressure can be increased based on the increase in airflow rate. The valve opening degree can be maintained equally based on the increase in airflow rate, but when the control is changed from atmospheric pressure control to pressure control, the opening degree value can be decreased.

[0037] If flooding occurs in the fuel cell 100, when pressure control is required and the valve is set with the opening degree of the valve 400 required for pressure control, the opening degree of the valve 400 required for atmospheric pressure control to change the pressure of the air discharged from the air supply device 200 to atmospheric pressure can also be derived and the valve 400 can be set based on the derived opening degree of the valve.

[0038] In the case of fuel cell 100, the fuel cell's atmospheric pressure can be adjusted by setting valve 400 on the side of the air outlet, which discharges air to the outside. The fuel cell can operate at atmospheric pressure under normal conditions, and under pressure conditions requiring high power output, it can operate at a pressure higher than atmospheric pressure. Generally, atmospheric pressure control can be performed first to operate the fuel cell at atmospheric pressure (S100). The point at which pressure control is required can then be determined by monitoring whether additional power from the fuel cell is needed or whether the fuel cell is in a drying-out state (S200).

[0039] If the fuel cell output is equal to or greater than a reference output and the temperature is equal to or greater than a reference temperature, the control system can be configured to detect that pressure control is required (S200). In other words, high output may be required, or fuel cell drying may be anticipated. Conversely, if low output is required, or flooding may occur, atmospheric pressure control may be necessary. In response to the detection that pressure control is required, the required air outlet valve opening can be derived by replacing the target atmospheric pressure with a data map (S300).

[0040] Fig. Figure 4 illustrates a data map for a method of controlling a vehicle fuel cell according to an exemplary embodiment of the present invention and shows the relationship between the target air pressure and the airflow rate. The target air pressure can be increased under high-performance conditions, and pressure control can be performed. The lower curve of the graph, positioned below, is curve b under atmospheric pressure conditions, and when the pressure is equal to or greater than a preset pressure, the curve behaves as if under pressure conditions. A boundary line outside the graph indicates an operating limit. Consequently, even when pressure operation is performed, the graphs should generally be positioned within the operating limit c.

[0041] In general, the discharge rate of an air blower can be reduced while the system pressure is increased at approximately the same blower speed, and the blower can be damaged if operation deviates from its operating limits. Consequently, the pressure can be increased to the operating limits. In the case of pressure operation, operating outside the operating limits at low power can cause problems. When applying pressure at low power, the amount of pressure increase may be negligible, and thus the pressure effect may be minimal. Therefore, variable pressure operation at high power can be carried out with consideration for stability and efficiency.

[0042] To maximize the pressure effect, the target air pressure can be set during pressure application to operate up to a range just below the operating limit (it is necessary to ensure a safety margin), and pressure application can be performed during medium / high power output as needed. The opening rate to follow the target pressure can be preset and stored in the controller as a characteristic map.

[0043] While opening degree control can be achieved by feeding back the pressure at the air outlet in real time without the opening degree map, a more accurate pressure sensor and a highly responsible opening degree control actuator may be required, and unstable actuators or control elements can be affected by disturbances that influence the pressure. Therefore, the opening degree map corresponding to the target pressure (e.g., following it) can be determined through preliminary tests and stored in the controller's memory, and an actual angle can be set to follow the opening degree control map (e.g., data map).

[0044] Furthermore, the degree of opening can be reduced in the data map to increase the pressure based on the flow rate increase, and the degree of opening can be made to vary based on the fuel cell's operating temperature (e.g., the degree of opening to maintain the target pressure can vary based on the operating temperature). Additionally, according to the change reference to pressure or atmospheric pressure, pressure operation can be performed in a situation with a substantially high temperature at medium / high power, and atmospheric pressure operation can be performed at a substantially low temperature or at low power.Furthermore, if the drying situation is detected, pressure operation can be carried out without any conditions regardless of the operating temperature, and if a deviation in cell voltage occurs due to flooding or the like during pressure operation, atmospheric pressure operation can be immediately resumed or returned to immediately.

[0045] Fig. Figure 5 is a graph illustrating the relationship between an airflow rate and the valve opening degree of an air outlet in a method for controlling a vehicle fuel cell according to an exemplary embodiment of the present invention. When the airflow rate and the temperature of the fuel cell are determined, the valve opening degree of the air outlet can be determined using the illustrated graph. The graph of the valve opening degree of the air outlet approaches a predetermined convergence value d. In particular, the airflow rate can be derived using the target air pressure, as shown in Figure 5. Fig. Figure 4 shows that the valve opening degree of the air outlet can be derived using the airflow rate and the temperature of the fuel cell. During this derivation, the graph can be positioned within the operating limit range with respect to the target air pressure and airflow rate.

[0046] During the derivation, as in Fig. As shown in Figure 6, the valve opening degree of the air outlet can be adjusted inversely proportional to the airflow rate using a slope. As shown in Fig. As shown in Figure 7, the convergence value of the air outlet valve opening degree can also be set inversely proportional to the fuel cell temperature using a slope. In other words, when defining the data map of the opening degree control, the opening degree map can be set based on the airflow rate, and a predetermined slope can be applied to a transition section of the opening degree map change based on the airflow rate to eliminate unstable controls due to an abrupt opening degree change (see Figure 7). Fig. 14) To prevent the degree of opening from changing too sensitively with respect to changes in airflow rate and temperature, a hysteresis band, as illustrated, can also be used. In particular, the maximum rate of increase with respect to the change in the degree of opening over time can also be limited, thus limiting abrupt changes over time.

[0047] The fuel cell control procedure can further include controlling the SR to adjust the maximum value of a stoichiometric ratio (SR) of the fuel cell to the minimum value SR_Lo upon completion of pressure regulation. Furthermore, during SR control, as described in Fig. Figure 8 shows that the maximum value of the SR can be set to gradually decrease with a slope and reach the minimum value SR_Lo. In other words, the maximum value of the SR can be set to gradually decrease with a slope before the pressure regulation is complete and reach the minimum value SR_Lo when the pressure regulation is complete.

[0048] The determination of a pressure control closing time can be based on a calculation of a pressure ratio obtained by calculating (current opening degree - first opening degree) / (second opening degree - first opening degree), where the current opening degree is a valve opening degree at the present time, the first opening degree is an opening degree required when air pressure is atmospheric pressure, and the second opening degree is an opening degree at a time when the pressure control is complete. Fig. Figure 8 shows that the maximum SR value can be decreased with the slope from the maximum SR value SR_Hi to the minimum SR value SR_Lo. During atmospheric pressure control, the maximum SR value can be increased based on increasing the valve opening degree.

[0049] Taking into account the transition phase until the actual application of pressure is complete, the pressure ratio concept can also be introduced (e.g., it is considered whether the opening degree command reaches the final target pressure command and whether the actual opening degree reaches the final target pressure opening degree). The pressure ratio can have a value between 0 and 1. If the pressure ratio is 1, the maximum value of the SR can be the minimum SR value SR_Lo, and if the pressure ratio is 0, the maximum value of the SR can be the maximum SR value SR_Hi. The maximum value of the SR can be inversely proportional to the increase in the pressure ratio. If the pressure ratio is 1, the actual opening degree reaches the final target opening degree of the pressure operation, and the maximum value of the SR becomes equal to the minimum value of the SR. Until the pressure reaches 1, the maximum value of the SR can decrease linearly to the minimum SR value SR_Lo.

[0050] Furthermore, SR control (S600) can be implemented to reduce the fuel cell's SR using a slope based on the pressure ratio. The slope in SR control can be a gradient connecting two points: pressure ratio 0 (maximum SR) and pressure ratio 1 (minimum SR). Consequently, during pressure control, the air outlet valve opening and the maximum SR can be adjusted, and the maximum SR can be gradually reduced based on the pressure ratio. When the pressure ratio reaches 1, corresponding to the final pressure, the maximum SR can eventually approach the minimum SR.

[0051] After deriving the ratio, the hydrogen supply pressure can be adjusted to increase the slope as the pressure ratio increases, using the graph that shows the slope increased based on the increase in the airflow rate, as shown in Fig. 10 shown, (S700). Fig. Figure 10 illustrates that as the pressure ratio is increased from 0 to 1, the hydrogen supply pressure and its convergence value can be increased. Once the opening degree is set, the pressure ratio can be calculated as (current opening degree - first opening degree) / (second opening degree - first opening degree), and the target hydrogen pressure can be increased based on the increase in the flow rate of the air discharged from the air supply device.

[0052] The target hydrogen pressure level, which is increased based on the airflow rate, can differ based on the pressure ratio (e.g., the current opening degree is the valve opening degree at the present time, the first opening degree is the opening degree required when the air pressure is atmospheric pressure, and the second opening degree is the opening degree at a time when pressure regulation is complete). For example, increasing the calculated pressure ratio can raise the target hydrogen pressure.

[0053] In a fuel cell system, it is necessary to maintain a sufficiently high pressure on the anode side compared to the cathode side. Consequently, the hydrogen supply pressure must be increased based on the rise in atmospheric pressure. Similarly, as described above, the target hydrogen pressure can be determined using pressure ratio information. During the transition phase, an average of the target hydrogen pressures at pressure ratio 1 and atmospheric pressure (pressure ratio 0) can be used.

[0054] If the fuel cell's air supply system or hydrogen supply system is in a fault condition (e.g., a fault or failure occurs), a safety logic can be executed to open all air outlet valves (S800). If the difference between the setpoint of the air outlet valve opening and the current opening becomes equal to or greater than a predetermined value, or if the fuel cell voltage deviation becomes equal to or greater than a predetermined value, all air outlet valves can be opened.

[0055] Regarding the Fig. In sections 11 to 13, when a cell voltage deviation occurs, it is taken into account that the current situation is a flooding situation, and the control can be carried out in the sequence of additional air supply, additional hydrogen purge, and power limitation based on the level of the cell voltage deviation. If the cell voltage deviation is being sampled with respect to variable pressure operation (e.g., the cell voltage deviation corresponding to the level of additional air supply is being sampled), the control can be carried out separately to avoid operating the pressure system.

[0056] If the cell voltage deviation is detected during pressurized operation, the opening degree may be fully open, and the system may switch to atmospheric pressure operation. Simultaneously, a variable SR operation (e.g., atmospheric pressure operation, in which case the maximum SR value is increased) can be automatically initiated to allow water to drain to the outside, thus managing flooding. Even if the cell voltage deviation decreases, the operating state may not immediately switch back to pressurized operation, but atmospheric pressure operation at low power can be performed before pressurized operation becomes possible again.If the atmospheric pressure / pressure operation is changed immediately based on whether the cell voltage deviation is mitigated, the system operation may become unstable due to the frequent changes in the opening degree control.

[0057] If the opening degree is set to be less than a specified opening degree command, i.e., in a closing direction, operation can occur above the operating limit (pump operation), thus enabling power limitation, limiting of air blower operation, an attempt at full opening, and fixed SR operation. The degree of error and the sampling time can be correctly selected. If the opening degree is set to be greater than the specified opening degree command, i.e., in a closing direction, the humidity situation may be compromised because the desired pressure operation is not carried out. The controller can further be configured to sample whether the humidity situation is compromised (e.g., IV slope characteristic, impedance measurement, and high temperature exposure), and then a recovery control (e.g.,a reduction of the reference temperature, which corresponds to the power limitation at a high temperature, forced cooling, SR minimization, battery charging or fuel cell water generation operation using a fuel cell load) may be carried out.

[0058] Even if a problem or failure occurs in the air / hydrogen supply system (e.g., failure or malfunction of the airflow rate sensor, emergency operation of the air blower, or emergency operation of a hydrogen supply unit), operation can be carried out to fully open the valve. The fail-safe strategy described above minimizes fuel cell performance degradation and system malfunctions, thus ensuring the reliability of the variable pressure control.

[0059] In other words, the derived valve opening can be compared to the measured actual valve opening. If the derived valve opening is greater than the actual valve opening, the fuel cell's power output can be limited. If the derived valve opening is greater than the actual valve opening, the valve opening can be increased to its maximum. Furthermore, if the derived valve opening is greater than the actual valve opening, the maximum speed of the air supply unit (200 rpm) can be limited and the SR (Seasonal Resistance) can be set. If the deviation of the fuel cell voltages becomes equal to or greater than the predetermined value due to pressure regulation, the valve opening can be increased to its maximum.

[0060] In relation to Fig.15. In a model for estimating relative humidity, as illustrated in the drawing, the relative humidity (RH) on the cathode outlet side can be estimated using the current, airflow rate, and temperature information, and an SR determination device can be configured to determine the target SR based on the estimated relative humidity. Specifically, when determining the SR, as illustrated in the drawing, a map-type controller can be used, and the estimated relative humidity can be fed back based on the target relative humidity to perform PI control.

[0061] Internal parameters of the relative humidity estimation model require pressures at the cathode inlet and outlet, and a pressure-test map for the flow rate can be used without any separate pressure sensor. Specifically, during pressure operation, the pressure can be changed based on the airflow rate and the valve opening degree, and this can influence the calculation of the relative humidity estimate. Even during variable pressure operation, applying a more accurate relative humidity estimation model requires using pressure change data based on the valve opening degree, thus potentially increasing complexity.The conditions during atmospheric pressure operation can therefore be applied to the model for estimating relative humidity, and variable SR control itself cannot be performed during pressure operation.

[0062] Following the procedure for controlling a vehicle's fuel cell with the configuration described above, fuel cell performance degradation and system malfunctions can be prevented, thus ensuring the reliability of the variable pressure control. The air pressure can be adjusted via the opening degree adjustment valve on the air outlet side, and the opening degree can be adjusted to prevent abrupt changes in air pressure caused by sudden changes in the opening degree. Consequently, operation can be carried out without deviating from the operating limits. Furthermore, the hydrogen supply pressure and the air supply pressure (SR) can be optimally adjusted, and even a fail-safe operating strategy can be implemented when adjusting the air opening degree to ensure the reliability of the opening degree control.

Claims

[1] Method for controlling a fuel cell (100) of a vehicle, comprising: Determine by means of a control whether pressure regulation is required to exert pressure on air being discharged from an air supply device (200), based on whether additional power output from the fuel cell (100) is required or whether the fuel cell (100) is in a drying-out state; In response to the determination that pressure control is required, deriving an opening degree of a valve on one side of an air outlet of the fuel cell (100) required for pressure control, by controlling and adjusting the valve based on the derived opening degree of the valve; Calculating a pressure ratio by the controller, which is obtained by calculating the following: (current degree of opening - first degree of opening) / (second degree of opening - first degree of opening), wherein the current degree of opening is a valve opening degree at the present time, the first degree of opening is an opening degree required when an air pressure is atmospheric pressure, and the second degree of opening is an opening degree at a time when the pressure regulation is complete; and Increasing a target hydrogen pressure based on an increase in the calculated pressure ratio or an increase in the flow rate of the air discharged from the air supply device (200). [2] Method according to claim 1, wherein the determination may include determining that pressure control is required when an operating temperature of the fuel cell (100) is equal to or greater than a reference temperature, when the power output of the fuel cell (100) is equal to or greater than a reference power output, or when the fuel cell (100) is in the drying-out state. [3] Method according to claim 1, further comprising: Determine by the control whether atmospheric pressure regulation is required to change the pressure of air discharged from the air supply device (200) to atmospheric pressure when flooding occurs during pressure operation to adjust the valve to the degree of opening required for pressure regulation; and Deriving the degree of valve opening required for pressure control by controlling and adjusting the valve based on the derived degree of valve opening in response to the determination that pressure control is required. [4] Method according to claim 1, further comprising: Selecting a target air pressure via the controller; and Deriving a valve opening degree command by the controller to follow the selected target air pressure. [5] Method according to claim 4, wherein the air flow rate discharged from the air supply device (200) and the target air pressure each have values ​​within preset limit ranges with respect to the air flow rate and the air pressure. [6] Method according to claim 4, wherein the derivation of a valve opening degree command includes deriving the valve opening degree command using an opening degree map in which the target air pressure and the valve opening degree to follow the target air pressure are mapped in advance. [7] Method according to claim 6, wherein in the opening degree characteristic map the target air pressure and the valve opening degree to follow the target air pressure are mapped differently in advance based on the flow rate of the air that is discharged from the air supply device (200) and an operating temperature of the fuel cell (100). [8] Method according to claim 6, wherein the degree of opening is mapped in advance, wherein the degree of opening during pressure control is less than the degree of opening during atmospheric pressure control. [9] Method according to claim 7, wherein the opening degree characteristic map is mapped in advance to reduce a required valve opening degree while increasing the operating temperature of the fuel cell (100) when the air flow rate is equal to the target air pressure. [10] Method according to claim 6, wherein the target air pressure comprises a first air pressure in an atmospheric pressure state and a second air pressure in a pressure state, and the opening degree characteristic map is mapped in advance to set a required valve opening degree to a first opening degree when the target air pressure is the first air pressure, and to set the required valve opening degree to a second opening degree when the target air pressure is the second air pressure. [11] Method according to claim 10, wherein the opening degree characteristic map is mapped in advance to reduce the required valve opening degree between the first opening degree and the second opening degree when the target air pressure is in a section where the target air pressure is increased from the first air pressure to the second air pressure. [12] Method according to claim 7, wherein the opening degree characteristic map is mapped in advance to change a required valve opening degree with a hysteresis band based on a change in the flow rate of the air. [13] Method according to claim 6, wherein the opening degree characteristic map is mapped in advance to change a required valve opening degree over time when a maximum rate of increase is limited. [14] Method according to claim 1, further comprising: Setting a maximum value of a stoichiometric ratio (SR) to a minimum value by the control system when pressure regulation is complete. [15] Method according to claim 3, further comprising: Increasing the maximum value of a stoichiometric ratio (SR) based on an increase in the valve opening degree during atmospheric pressure control by the controller. [16] Method according to claim 14, wherein the setting comprises adjusting the maximum value of the SR in order to gradually decrease the maximum value of the SR before completing the pressure regulation with a slope and to reach the minimum value when completing the pressure regulation. [17] Method according to claim 16, wherein the determination of a pressure control closure time is based on a calculation of a pressure ratio obtained by calculating the following: (current degree of opening - first degree of opening) / (second degree of opening - first degree of opening), where the present opening degree is a valve opening degree at the present time, the first opening degree is an opening degree required when an air pressure is atmospheric pressure, and the second opening degree is an opening degree at a time when the pressure regulation is complete. [18] Method according to claim 17, wherein the pressure ratio has a value between 0 and 1, the maximum value of the SR is inversely proportional to an increase in the pressure ratio and the maximum value of the SR is equal to the minimum value of the SR when the pressure ratio is 1. [19] Method according to claim 1, wherein the level of the target hydrogen pressure, which is increased based on the increase in the flow rate of the air, differs based on the pressure ratio. [20] Method according to claim 1, further comprising: Comparing the derived valve opening degree with the actual valve opening degree detected by the controller; and Limiting the power output of the fuel cell (100) by the controller when the derived valve opening degree is greater than the actual valve opening degree. [21] Method according to claim 1, further comprising: Comparing the derived valve opening degree with the actual valve opening degree detected by the controller; and Maximum increase of the valve opening degree by the controller when the derived valve opening degree is greater than the actual valve opening degree. [22] Method according to claim 1, further comprising: Comparing the derived valve opening degree with the actual valve opening degree detected by the controller; and Limiting the maximum rotational speed (RPM) of the air supply device (200) by the controller when the derived opening degree of the valve is greater than the actual opening degree of the valve. [23] Method according to claim 1, further comprising: Comparing the derived valve opening degree with the actual valve opening degree detected by the controller; and Setting a maximum value for a stoichiometric ratio (SR) by the controller when the derived opening degree of the valve is greater than the actual opening degree of the valve. [24] Method according to claim 1, further comprising: Maximum increase of the valve opening degree by the controller when the deviation of the fuel cell cell voltages (100) becomes equal to or greater than a predetermined value. [25] System for controlling a fuel cell (100) of a vehicle, comprising: a memory configured to store program instructions; and a processor configured to execute the program instructions, wherein the program instructions, when executed, are configured to do the following: Determine whether pressure control is required to exert pressure on air discharged from an air supply device (200), based on whether additional power output from the fuel cell (100) is required or whether the fuel cell (100) is in a drying-out state; In response to the determination that pressure control is required, deriving an opening degree of a valve on one side of an air outlet of the fuel cell (100) required for pressure control, and adjusting the valve based on the derived opening degree of the valve; Calculating a pressure ratio by the controller, which is obtained by calculating the following: (current degree of opening - first degree of opening) / (second degree of opening - first degree of opening), wherein the current degree of opening is a valve opening degree at the present time, the first degree of opening is an opening degree required when an air pressure is atmospheric pressure, and the second degree of opening is an opening degree at a time when the pressure regulation is complete; and Increasing a target hydrogen pressure based on an increase in the calculated pressure ratio or an increase in the flow rate of the air discharged from the air supply device (200). [26] System according to claim 25, wherein the determination may include program instructions which, when executed, are further configured to determine that pressure control is required when an operating temperature of the fuel cell (100) is equal to or greater than a reference temperature, when the power output of the fuel cell (100) is equal to or greater than a reference power output, or when the fuel cell (100) is in the drying-out state. [27] System according to claim 25, wherein the program commands, when executed, are further configured to do the following: Determine whether atmospheric pressure control is required to change the pressure of air discharged from the air supply device (200) to atmospheric pressure when flooding occurs during pressure operation, in order to adjust the valve to the degree of opening required for pressure control; and Deriving the degree of valve opening required for pressure control and adjusting the valve based on the derived degree of valve opening in response to the determination that pressure control is required. [28] System according to claim 25, wherein the program commands, when executed, are further configured to do the following: Selecting a target air pressure; and Deriving a valve opening degree command to follow the selected target air pressure.

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