System and method for operating a fuel cell

Abstract

Disclosed is a system for operating a fuel cell, including a controller configured to derive an output limit value of the fuel cell by an interval average value and a cumulative average value, wherein the interval average value corresponds to an average value of output values of the fuel cell for a specified time, the cumulative average value corresponds to an average value of the output values of the fuel cell from a start of operation of the fuel cell to a current time point, and operation of the fuel cell is controlled based on the derived output limit value.

Description

Technical Field

[0001] The present invention relates to systems and methods for operating fuel cells, wherein when operating the fuel cell system, the output limits of the fuel cell are used variably, taking into account not only real-time output data, but also cumulative usage time and the degree of power generation in each time period, in order to understand the fuel cell state that cannot be detected by real-time data, and to improve the durability of the fuel cell due to more stable operation of the fuel cell. Background Technology

[0002] Generally, fuel cell system output limiting technology is implemented using real-time vehicle conditions such as coolant temperature, ambient temperature, and battery charge limit. In this type of output limiting technology, the limiting values ​​are effective during the early stage (BOL) of the fuel cell system's lifespan, but due to the deterioration of the fuel cell system's durability, it is difficult to apply the same limiting values ​​during the end-of-life (EOL) stage.

[0003] Furthermore, because fuel cell systems are used in various applications, such as commercial vehicles, aircraft, and ships, the durability requirements for fuel cell systems used in these applications are higher than those for applications such as passenger cars. Therefore, compared to the output and durability of fuel cell systems in passenger cars, efforts are still needed to improve the durability of fuel cell systems in commercial vehicles and other applications, despite the output losses.

[0004] To meet the requirements in this situation, the fuel cell system needs to limit its output functionality in consideration of durability, and a technology is needed to operate the fuel cell system under evaluation conditions with the durability of the fuel cell system in advance without limiting the output of the fuel cell system through real-time system parameters.

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of the present invention and should not be construed as conventional technology known to those skilled in the art. Summary of the Invention

[0006] Therefore, the present invention provides a system and method for operating a fuel cell, wherein when operating the fuel cell system, the output limits of the fuel cell are variably used not only with real-time output data, but also with consideration of cumulative usage time and the degree of power generation in each time period, in order to understand the fuel cell state that cannot be detected by real-time data, and thus improve the durability of the fuel cell due to more stable operation of the fuel cell.

[0007] According to one aspect of the invention, the above and other objectives can be achieved by providing a system for operating a fuel cell, the system including a controller configured to derive an output limit value for the fuel cell by means of an interval average and a cumulative average, wherein the interval average corresponds to the average value of the fuel cell's output value over a specified time period, and the cumulative average corresponds to the average value of the fuel cell's output value from the start of operation of the fuel cell to the current time point, and to control the operation of the fuel cell based on the derived output limit value.

[0008] The interval average can be a moving average of the fuel cell's output value.

[0009] The controller can be configured to execute multiple output limiting modes, and the output limiting value can be set differently based on each of the output limiting modes.

[0010] The output limiting modes may include a first mode, a second mode, and a third mode, and the controller can select the first mode or the second mode by means of an interval average and calculate the output limiting value based on the selected mode.

[0011] The output limiting modes may include a first mode, a second mode, and a third mode, and the controller may switch the fuel cell to the second mode when the interval average value in the first mode is equal to or greater than the first reference value.

[0012] When the reference time after switching to the second mode is equal to or greater than the first reference time, the controller can switch the fuel cell back to the first mode.

[0013] The output limiting modes may include a first mode, a second mode, and a third mode, and the controller may switch the fuel cell to the third mode when the cumulative average value in the first mode or the second mode is equal to or greater than the second reference value.

[0014] When, in the first or second mode, the reference time from the start of fuel cell operation to the current time is equal to or greater than the second reference time and the cumulative average value is equal to or greater than the second reference value, the controller can switch the fuel cell to the third mode.

[0015] When the accumulated average value in the third mode decreases to the third reference value or less, the controller can return the fuel cell to the first or second mode.

[0016] The controller can variably derive the output limit value of the fuel cell by accumulating parameters based on the use of the fuel cell.

[0017] As the parameters accumulated based on the use of the fuel cell increase, the output limit of the fuel cell can be reduced.

[0018] The controller can be configured to provide multiple cycle segments divided by parameters accumulated through fuel cell use, and output limit values ​​can be set differently for each cycle segment.

[0019] The parameter could be the cumulative hydrogen consumption of the fuel cell.

[0020] The parameter can be any one of the following: the cumulative power generation of the fuel cell, the cumulative water production of the fuel cell, or the cumulative air consumption of the fuel cell.

[0021] According to another aspect of the present invention, a method for operating a fuel cell is provided, the method comprising the steps of: deriving an interval average value by a controller, wherein the interval average value corresponds to the average value of the fuel cell output value at each specified time; deriving a cumulative average value by the controller, wherein the cumulative average value corresponds to the average value of the fuel cell output value from the start of operation of the fuel cell to the current time point; deriving an output limit value of the fuel cell by the controller using the interval average value and the cumulative average value; and controlling the operation of the fuel cell by the controller based on the derived output limit value. Attached Figure Description

[0022] The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, wherein:

[0023] Figure 1 This is a block diagram of a system for operating a fuel cell according to an embodiment of the present invention;

[0024] Figure 2 This is a flowchart illustrating a method for operating a fuel cell according to an embodiment of the present invention;

[0025] Figure 3 and Figure 4 This is a view illustrating a corresponding mode of a system according to an embodiment of the present invention; and

[0026] Figure 5 and Figure 6 This is a graph representing the output of a fuel cell using the system according to an embodiment of the present invention. Detailed Implementation

[0027] It is understood that the terms "vehicle" or "of a vehicle" or other similar terms as used herein include motor vehicles in general, such as passenger vehicles including SUVs, buses, trucks, and various commercial vehicles, watercraft including various boats and vessels, and aircraft, and include hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As mentioned herein, a hybrid vehicle is a vehicle with two or more power sources, such as a vehicle that combines gasoline and electric power.

[0028] The terminology used herein is for illustrative purposes only and is not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should be further understood that when “comprising” and / or “including” are used in this specification, they refer to the presence of stated features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or combinations thereof. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. Throughout this specification, unless expressly stated otherwise, the word “comprising” and variations thereof such as “comprising” or “including” are to be understood as implying inclusion of the stated elements but not excluding any other elements. Furthermore, the terms “unit,” “machine,” “device,” and “module” described in the specification refer to a unit that performs at least one function and operation and can be implemented by hardware or software and combinations thereof.

[0029] Furthermore, the control logic of this invention can be embodied on a non-transitory computer-readable medium containing executable program instructions that are executed by a processor, controller, or the like. Examples of computer-readable media include, but are not limited to, ROM, RAM, optical disc (CD)-ROM, magnetic tape, floppy disk, flash drive, smart card, and optical data storage device. The computer-readable medium can also be distributed across a network-connected computer system, enabling it to be stored and executed in a distributed manner, for example, via a telematics server or a controller area network (CAN).

[0030] The following description will exemplarily illustrate specific structures or functions in embodiments of the invention set forth in the description to describe embodiments of the invention. However, the invention may be embodied in many alternative forms and should not be construed as limited to the embodiments set forth herein. Hereinafter, reference will now be made in detail to preferred embodiments of the invention, examples of which are shown in the accompanying drawings.

[0031] Figure 1This is a block diagram of a system for operating a fuel cell according to an embodiment of the present invention. Figure 2 This is a flowchart illustrating a method for operating a fuel cell according to an embodiment of the present invention. Figure 3 and Figure 4 This is a view illustrating a corresponding mode of a system according to an embodiment of the present invention, and Figure 5 and Figure 6 This is a graph representing the output of a fuel cell using the system according to an embodiment of the present invention.

[0032] Figure 1 This is a block diagram of a system for operating a fuel cell according to an embodiment of the present invention. When the system is used to limit the output of the fuel cell, the system includes: a controller C configured to control the operation of the fuel cell based on an output limit value derived from information processing data transmitted from an input unit; and a fuel cell system F configured to transmit information about the fuel cell to the controller C, such as the current output of the fuel cell and the accumulated hydrogen consumption. The fuel cell system F receives information about the fuel cell from sensors and transmits signals to the controller C, and the controller C performs calculations based on the received signals to derive the logic of the output limit value and transmits the output limit value to the fuel cell DC-DC converter (FDC) to control the output of the fuel cell.

[0033] Such systems for operating fuel cells are higher-level systems that receive information about the fuel cell and issue commands to dynamically or statically limit its output, thereby overcoming performance and durability degradation caused by its use. For example, in the case of controller C dynamically limiting the fuel cell output, controller C changes the maximum output of the fuel cell whenever each condition is met (i.e., the fuel cell's dynamically changing output, its state of charge (SOC) or state of health (SOH), or the coolant temperature is excessively below or above a specified reference value). In other words, dynamic output limiting controls the maximum output limit of the fuel cell under conditions of 1:1 parameter variation or interlocking with parameter variation. On the other hand, in the case of static output limiting, the maximum output limit of the fuel cell can be limited while maintaining a constant output when each condition is met. Systems used to operate fuel cells so that the maximum output dynamically matches real-time parameters or is interlocked with real-time parameters through dynamic output limiting methods may not adequately account for fuel cell durability degradation caused by continuous exposure to high output ranges. Specifically, such systems are not suitable for applications requiring long fuel cell operating times (e.g., commercial vehicles, aircraft, or ships).

[0034] Therefore, in order to apply the system to vehicles or applications where the durability degradation of the fuel cell must be further considered, output limit values ​​can be derived in vehicles and applications equipped with fuel cells by using parameters evaluated with consideration of fuel cell durability. Therefore, the present invention is configured to control the output of the fuel cell using parameters evaluated with consideration of fuel cell durability.

[0035] Figure 1 This is a block diagram of a system for operating a fuel cell according to an embodiment of the present invention, and specifically the system according to the present invention includes a controller C configured to derive an output limit value for the fuel cell by means of an interval average value and a cumulative average value, the interval average value being the average value of the fuel cell's output value over a specified time period, and the cumulative average value being the average value of the fuel cell's output value from the start of fuel cell operation to the current time point, and to control the operation of the fuel cell based on the derived output limit value.

[0036] In this invention, the interval average value and the cumulative average value of the fuel cell output are used as criteria for determining the output limit of the fuel cell. Fuel cells have various parameters, and since excessive output can increase the risk of degradation, fuel cell durability assessments can be performed based on the fuel cell output. However, when assessing fuel cell durability based solely on either a temporary increase in output or an average output over a long period, it is not easy to simultaneously determine the degree of degradation under specific conditions and the overall degree of degradation. Therefore, the interval average value is used when the fuel cell output temporarily increases, and the cumulative average value is used when the fuel cell deteriorates due to its use over a long period.

[0037] Specifically, interval average and cumulative average refer to the average value of the fuel cell output over a specified time period, obtained using output values ​​and time values ​​(considered variables measured from the fuel cell), and are different parameters in terms of the time range for calculating the respective average values. The reason for using the concept of time average of the fuel cell output is that, by excluding conventional parameters (SOC, SOH, and coolant temperature) measured by devices other than the fuel cell, the system can be universally applied to a specific vehicle or specific applications designed for other devices and their control systems (e.g., passenger cars, commercial vehicles, trams, aircraft, ships, etc.).

[0038] Specifically, the interval average and cumulative average, as time-based averages, are used to more accurately assess the parameters used to determine fuel cell durability degradation, i.e., whether the fuel cell output deviates from the high-output range. Typically, fuel cell durability degradation is determined when the fuel cell operates at a specified high output or higher for a specified period. However, in this case, it is unclear whether any time the fuel cell output is lower than a specific output is considered an interruption, or whether the specified time from when the fuel cell output decreases to below a specified high output to when the fuel cell output reaches the specified high output again is considered an interruption. Furthermore, due to this ambiguity, output limits are over-tuned due to the characteristics of parameters such as time and output that dynamically and significantly change according to user needs. This means that a significant amount of time and effort is required to extract meaningful data to limit the fuel cell output. Therefore, the interval average and cumulative average used in this invention address the ambiguity of dynamically changing criteria for limiting fuel cell output and thereby minimize resource input variables.

[0039] Figure 5 This is a graph representing the output of a fuel cell using a system according to an embodiment of the present invention. The graph represents the output of a fuel cell using a system according to the present invention, which includes a controller C configured to derive an output limit value for the fuel cell using an interval average and a cumulative average. The interval average is the average output value of the fuel cell over a specified time period, and the cumulative average is the average output value of the fuel cell from the start of operation to the current time point. The controller C then controls the operation of the fuel cell based on the derived output limit value. Specifically, the interval average can be a moving average of the fuel cell's output value. In other words, the interval average corresponds to the average output value of the fuel cell over a specified time period, traced back from the current time point, and is continuously updated.

[0040] In addition, Figure 5 In the graph, the horizontal axis indicates time and the vertical axis indicates output value. The interval average refers to the average output value of the fuel cell over a specified time period and is used as a moving average. When the average output value of the fuel cell (i.e., the moving average) over a first reference time period from the current time point B to a specified time point A is equal to or greater than the first reference value, the controller C controls the operation of the fuel cell based on an output limit value derived from a different value than the previous output limit value. In other words, Figure 5 The time-output curve is represented as follows: when the moving average of a first reference time is equal to or greater than a first reference value, the operation of the fuel cell is controlled based on a second output value, which is derived to be different from the first output value, which is a threshold output value used to limit the previous maximum output.

[0041] Here, the moving average refers to the average of data from the current point in time up to a specified point in time. In other words, the moving average is a variable that takes previous output values ​​into account over time, and it fully reflects the time the fuel cell has been exposed to a high output range based on its current state. For example, if a user intends to accelerate the vehicle, causing the fuel cell output to change dramatically only over a very short period of time, when only considering the current output of the fuel cell, the operation of the fuel cell should be controlled by decreasing or increasing the output limit value. However, conversely, when only considering time, the output limit value should not be set.

[0042] Conversely, in the opposite scenario, for example, a user continuously operates a fuel cell to produce high output, and then operates the fuel cell to maintain an output equal to or less than the output limit value for a long period, taking into account the fuel cell's output limit. In this case, contrary to the previous situation, the output limit value can be adjusted when only the current instantaneous output or the fuel cell's long-term exposure to the high output segment is considered, but it may not be possible to adjust the output limit value when only the current state of the fuel cell entering the low output segment is considered. In the moving average-based fuel cell output limiting, even if the output value suddenly decreases or remains at a high output value equal to or less than the output limit value, the fuel cell output limiting is not executed in response to sudden output fluctuations, and the output limit value is only adjusted when a specified interruption segment in the fuel cell's deviation from the high output segment is determined. Therefore, the moving average-based fuel cell output limiting eliminates the noise or excessive delay generated when determining the time the fuel cell was previously exposed to the high output segment based on conventional variables, thereby enabling accurate and rapid determination and therefore continuous monitoring and management of fuel cell durability degradation.

[0043] Furthermore, moving averages can be more than just the simple moving average (SMA) as described above; they can also be weighted moving averages (WMA) calculated by assigning higher weighting factors to times closer to the current time, endpoint moving averages (EPMA), or exponential moving averages (EMA) calculated by assigning higher weighting multipliers to times closer to the current time. Compared to SMA, these variables can be selectively used depending on whether the vehicle (or application) responds more sensitively to recent output changes rather than output changes prior to a specified time. For example, in the case of a vehicle with WMA, EPMA, or EMA applied, the output limit may change more sensitively when the user suddenly increases or decreases the fuel cell output compared to a typical vehicle using SMA. Therefore, when these variables are applied, systems optimized for vehicles requiring higher acceleration performance than those using SMA can be provided.

[0044] Figure 3This is a view illustrating a corresponding mode of a system according to an embodiment of the present invention. The controller C can be configured to execute multiple output limiting modes, and the output limiting value can be set differently depending on each output limiting mode. In other words, the output limiting value is set in stages, and when it is determined that the fuel cell is exposed to a high output segment for a long time, the fuel cell can continuously maintain a constant output while deviating from the high output segment. Thus, logic that improves durability compared to conventional methods while simultaneously reducing acceleration performance for a short period of time can be implemented for vehicles or applications optimized for this logic. Furthermore, through... Figure 3 The illustrated mode allows the user to easily identify the difference in output limitation levels between segments requiring acceleration performance (especially at the beginning of a driving cycle) and segments where acceleration performance is not required. For example, assuming no system according to the invention, a user might excessively and continuously demand acceleration performance without recognizing high-output infeasibility segments where acceleration is not possible. Therefore, when continuously turning the output limitation mode on and off, detrimental effects such as performance and durability degradation and errors, which occur in conventional systems, cannot be avoided. However, the advantage of the system according to embodiments of the invention is that the user can fully predict segments where high-output acceleration is feasible and segments where it is not feasible. In other words, the user can demand acceleration performance only in segments where high-output acceleration is feasible and can recognize that excessive demand for acceleration performance should not be made in segments where high-output acceleration is not feasible, and adjust the fuel cell output accordingly, thereby preventing detrimental effects (such as errors encountered in conventional systems).

[0045] Figure 3 This is a view illustrating corresponding modes of a system according to an embodiment of the present invention. Specifically, the output limiting modes may include a first mode, a second mode, and a third mode, and the controller C can select the first mode or the second mode by means of an interval average value and calculate the output limiting value depending on the selected mode. The output limiting modes may include the first mode, the second mode, and the third mode, and the controller C may switch from the first mode to the second mode when the interval average value in the first mode is equal to or greater than a first reference value.

[0046] In other words, when the average value of the interval is equal to or greater than the specified value, controller C can choose the mode with the lower output limit or switch the current mode to that mode, and when the average value of the interval is equal to or less than the specified value, controller C can choose the mode with the higher output limit or switch the current mode to that mode. Figure 3Exemplary examples illustrate a maximum output limiting mode as a first mode and a constant output limiting mode as a second mode. Here, the maximum output limiting mode is the output limiting mode prior to the application of the system according to the invention, and in response to real-time fluctuations in parameters, the maximum output of the fuel cell is limited in real-time to a first output value or less. Furthermore, the constant output limiting mode is a mode in which, when the fuel cell is exposed to maximum output for a specified time, the maximum output of the fuel cell is limited to a smaller second output value for a specified time compared to the maximum output limiting mode. Specifically, when the output limiting value is set in the constant output limiting mode instead of the maximum output limiting mode, sufficient cooling time can be ensured for the fuel cell after it rises to high temperature and dries out after entering the high output range, thereby preventing degradation of the fuel cell's durability.

[0047] Furthermore, when the reference time after switching to the second mode is equal to or greater than the first reference time, the controller C can switch back to the first mode from the second mode. In other words, the constant output limiting mode can be a mode that ensures a specified recovery time for the fuel cell based on its exposure to maximum output. Therefore, after determining the specified recovery time at a time point where the interval average is equal to or greater than a specified value, the maximum output limiting mode is switched to a constant output limiting mode where the output limit value is lower than the output limit value in the maximum output limiting mode, and the fuel cell can re-enter the first mode to ensure acceleration performance. Otherwise, when the user increases the interval average to the first reference value or greater, the first mode can be switched back to the second mode. Therefore, the system according to an embodiment of the present invention can simultaneously meet the acceleration performance and durability performance required for a specified time for a specific vehicle according to the user's needs. Furthermore, after the switch between the first mode and the second mode, the user receives feedback to consider the output limit to reduce the acceleration performance in the first mode.

[0048] Furthermore, the combination of the acceleration and recovery phases can more aggressively prevent durability degradation. For example, in the acceleration phase corresponding to the first mode, in vehicles such as commercial vehicles or applications requiring durability, the dynamics of the motor output can be accommodated in the battery with sufficient state of charge (SOC), and the fuel cell can produce a constant output as the remaining required power, thereby reducing the fuel cell's exposure to the high-output phase. In the recovery phase corresponding to the second mode, the fuel cell can maintain a constant output lower than that in the first mode to ensure durability performance, and the battery can be pre-charged to adequately prepare for the anticipated durability degradation when the fuel cell enters the high-output phase. Figure 3 The first reference time is shown as the recovery time.

[0049] When the cumulative average value in the first or second mode is equal to or greater than the second reference value, controller C can switch from the first or second mode to the third mode. Furthermore, when the reference time from the start of fuel cell operation to the current time point is equal to or greater than the second reference time and the cumulative average value is equal to or greater than the second reference value, controller C can switch from the first or second mode to the third mode. Additionally, when the cumulative average value decreases to or less than the third reference value, controller C can return from the third mode to the first or second mode.

[0050] Here, the third mode can be an average output limiting mode. The average output limiting mode can be a mode where the fuel cell output is further limited or released through a cumulative average value, which corresponds to the average output value of the fuel cell from the start of fuel cell operation to the current time point. Here, compared to the interval average value, the cumulative average value is a parameter reflecting the degradation of durability performance across all segments of the entire driving cycle; it is the average output value of the fuel cell from the start of fuel cell operation to the current time point. In other words, the interval average value is an indicator that determines the extent to which the fuel cell has been exposed to high output segments from the current time point up to a specified time, while the cumulative average value is an indicator that reflects the degradation of the system's temperature regulation capability due to long-term operation of the fuel cell, even if the fuel cell has not maintained high output recently.

[0051] When a fuel cell operates for extended periods, the coolant performance deteriorates, and the entire system, including the fuel cell, remains at consistently high temperatures. When the fuel cell returns to its normal high-output range under these conditions, the already dried fuel cell's durability deteriorates further. This cannot be prevented solely by short recovery times assessed using interval averages, but rather by increasing the output limit and using longer recovery times assessed using cumulative averages. Therefore, the average output limit mode using cumulative averages is used to more accurately warn of the danger of overall system durability deterioration due to prolonged fuel cell operation. Specifically, this durability improvement can be maximized when the system is applied to vehicles, such as commercial vehicles, or applications requiring longer driving times or lifespans compared to general passenger vehicles. Figure 3 The cumulative average value is shown as a second reference value.

[0052] Therefore, the system according to this embodiment of the invention can control the operation of the fuel cell in such a way that it simultaneously reflects the degree to which the fuel cell is temporarily exposed to a high output segment between a first mode and a second mode, and reflects the degree to which the fuel cell is cumulatively exposed to a high output segment between the first mode (or the second mode) and a third mode. This system can prevent durability degradation primarily by rapidly providing recovery time in response to temporary entry into a high output segment, and can also provide secondary protection against durability degradation, considering that fuel cells are more susceptible to durability degradation due to prolonged high-output operation.

[0053] In addition, such as Figure 3 As shown, the system can be configured so that the fuel cell cannot be switched to a third mode before the second reference time. In other words, an output limit can be set in a first or second mode that requires acceleration performance while having a recovery time, and after the second reference time, the fuel cell can be switched to a third mode that further limits the output limit. Figure 3 As shown, user acceleration performance requests are guaranteed only for the first reference time prior to the second reference time, and are completely excluded until the entire system has been sufficiently cooled after the second reference time. Therefore, durability requirements can be further met for applications such as commercial vehicles or those requiring long-term driving or long lifespan rather than acceleration performance. Furthermore, users receive feedback regarding these short-term and long-term output limitations, thus minimizing wasteful acceleration that degrades durability performance during long-term operation, and thereby further stabilizing the system.

[0054] Here, the third reference value corresponding to the tuning point from the third mode back to the first or second mode can be set as the cumulative average value of the fuel cell's output value. Of course, the third reference value can be set as the recovery time of the third reference time (which is equal to or greater than the first and second reference times), or it can be set as an interval average value serving as an output limit (which is equal to or less than the first reference value). Therefore, the degree of output limitation can be set to suit the needs of a specific vehicle or application. In other words, in addition to the recovery time, either a recoverable cumulative average value or a moving average value, or a combination of these variables, can be used to satisfy the optimal point between lifespan and acceleration performance for a specific vehicle. Figure 3 The third reference value is shown as the cumulative average of the fuel cell's output value.

[0055] Figure 3 and Figure 4 This is a view illustrating a corresponding mode of a system according to an embodiment of the present invention. For example... Figure 3 and Figure 4As shown, controller C can variably derive the output limit value of the fuel cell based on parameters accumulated from fuel cell usage. Specifically, as the parameters accumulated from fuel cell usage increase, the output limit value of the fuel cell can decrease.

[0056] The output limit values ​​described herein may include those derived through a conventional maximum output limit mode or through a constant output limit mode or average output limit mode as described in this invention. Furthermore, parameters accumulated based on fuel cell usage may include parameters that increase or decrease through accumulation. For example, driving cycles, cumulative hydrogen consumption, cumulative air consumption, and cumulative water generation, generated based on fuel cell usage, are parameters that increase through accumulation. On the other hand, the ratio of the current voltage of the fuel cell system to the voltage of the fuel cell system relative to a specific output in the early life (BOL), the rate of maximum hydrogen storage, and the current density based on the cycle voltage are parameters that decrease through accumulation based on fuel cell usage. Here, fuel cell usage includes not only generating energy by consuming hydrogen in the fuel cell, but also work for maintaining the existing functions of a general fuel cell (such as fuel cell repair, replacement, and regeneration) or work that degrades the existing output performance of the fuel cell (such as fuel cell failure, malfunction, over-operation (or under-operation), and abuse).

[0057] Most importantly, the system according to this embodiment of the invention can set the output limit value of the fuel cell in consideration of output reduction or increase due to cumulative use and repair of the fuel cell. This is particularly important in the end-of-life (EOL) state where energy depletion occurs. For example, even using the same fuel cell system, the fuel cell system may produce a certain level of maximum output in the BOL state, but may produce a lower maximum output in the EOL state. Furthermore, the fuel cell can produce improved output through repair. However, when a fixed output limit value is applied without considering these aspects, the fuel cell is exposed to the high output range for a longer period and therefore its durability deteriorates rapidly, or the fuel cell is limited to the low output range and therefore may not exhibit acceleration performance. Therefore, the output limit value varies in a state interlocked with parameters that take into account the changes in the fuel cell output due to use or repair of the fuel cell, and thus the output limit value can be redesigned to more aggressively prevent durability degradation and suit improved acceleration performance than a fixed output limit value. In other words, this embodiment of the invention provides a system for operating a fuel cell that ensures fuel cell durability and is optimized for fuel cell conditions compared to conventional output limits.

[0058] Figure 3 and Figure 4This represents a first reference value, which is the average value of the interval, multiplied by a deceleration factor less than 1; a second reference value, which is the cumulative average value, multiplied by a deceleration factor less than 1; and a third reference value, which is the cumulative average value, multiplied by a deceleration factor less than 1. However, from the above perspective, the first or second reference time (not shown) can be extended, i.e., the recovery time (not shown) when the fuel cell switches to the second or third mode in a state interlocked with the parameters accumulated using the fuel cell. In this case, by setting a new output limit value that takes into account the state of the fuel cell that has developed due to durability degradation or the recovery state of the fuel cell, the user can ensure the fuel cell's operational time required for a specific vehicle or application and simultaneously predict the fuel cell's operational time.

[0059] Figure 3 and Figure 4 This is a view illustrating a corresponding mode of a system according to an embodiment of the present invention, and specifically, the degree to which the output limit value increases or decreases in the corresponding mode of the system can be discrete or continuous. In other words, when the ratio of the new output limit value to the regular output limit value is defined as a deceleration coefficient, the same deceleration coefficient can be applied to each specific loop segment in a plurality of loop segments divided by parameters, or a deceleration coefficient that increases or decreases proportionally to the parameters or based on other mathematical expressions can be applied.

[0060] For example, Figure 3 The parameters can be applied to the first loop segment. Figure 4 The parameters can be applied to the second cycle segment, and can be applied discretely by multiplying the parameters by the deceleration coefficient set for each segment. Otherwise, Figure 3 The parameter can be a first specific value. Figure 4 The parameter can be a second specific value, and can be derived and applied sequentially with... Figure 3 The output limit value is reduced compared to a second specific value or based on other mathematical expressions. The former case sets the same output limit due to durability degradation in a specific cycle segment (especially a long-term use segment), thus allowing the user to fully identify and predict that segment. The latter case allows for a more comprehensive reflection of the degree of durability degradation in the vehicle or application through real-time increases or decreases in parameters, thereby extending the fuel cell's operational life.

[0061] Figure 6This is a graph representing the output of a fuel cell using the system according to an embodiment of the present invention. Specifically, the controller C can execute multiple cycle segments divided by parameters accumulated according to the use of the fuel cell, and the output limit value of the fuel cell can be set differently in the respective cycle segments. Specifically, the parameter can be the cumulative hydrogen consumption of the fuel cell. In addition, the parameter can be the cumulative power generation of the fuel cell, the cumulative water production of the fuel cell, or the cumulative air consumption of the fuel cell.

[0062] Here, Figure 6 A graph is shown where the horizontal axis indicates the cumulative hydrogen consumption of the fuel cell, and the vertical axis indicates the output of the fuel cell. Specifically, Figure 6 This indicates that a new output limit value, reduced compared to the existing output limit value, is derived for a specific cycle segment. Therefore, when the same output limit is discretely set for a specific cycle segment (especially a long-term use segment) due to durability degradation in that cycle segment, the user can effectively identify and predict this lifespan reduction in the corresponding segment. Furthermore, when the starting point of a specific cycle segment is set before the expected lifespan reduction time point, durability degradation of a particular vehicle can be prevented in advance by strengthening the output limit to a constant value.

[0063] Furthermore, cumulative hydrogen consumption is an indicator reflecting the actual cumulative use of fuel cells. In contrast, conventional vehicles that use only fuel (including composite fuels such as gasoline, diesel, LPG, and CNG) as energy sources use driving time as a parameter to measure the amount of fuel used in the fuel system. However, in vehicles that use both fuel and battery (electricity) as energy sources (hybrid vehicles, hydrogen-powered vehicles, etc.), driving time cannot adequately reflect the state of durability degradation, such as when the vehicle is idling and operating solely on battery power. Therefore, the cumulative hydrogen consumption of fuel cells can more positively reflect the actual degree of output degradation, and the output limit value of the fuel cell system, which is interlocked with the cumulative hydrogen consumption, can more steadily improve the durability performance of the fuel cell.

[0064] Furthermore, compared to other metrics, the cumulative hydrogen consumption of a fuel cell is a clear indicator of the reduction in the average lifespan of the fuel cell. A fuel cell has a life cycle in which its durability decreases due to internal system degradation, as the fuel cell changes from the beginning of its life (BOL) to the end of its life (EOL) based on cumulative use. Here, the boundary between BOL and EOL is not clear, and the fuel cell's durability decreases linearly or non-linearly throughout its life cycle. The variable indicative of this linear or non-linear decrease in fuel cell durability can be a parameter accumulated through the use of the fuel cell. Other parameters, such as the voltage drop at the BOL of the fuel cell, may be variables that change slightly more sensitively or non-linearly depending on their relationship with other variables. On the other hand, the cumulative hydrogen consumption of a fuel cell is an average indicator that can fully predict the reduction in lifespan due to the cumulative use of the fuel cell and increases linearly. Therefore, the cumulative hydrogen consumption of a fuel cell clearly indicates the degree of foreseeable lifespan reduction for the user, and the output limit value derived from the cumulative hydrogen consumption of the fuel cell can more stably prevent the degradation of fuel cell durability.

[0065] Furthermore, although not shown, parameters that accumulate based on fuel cell usage could include the cumulative power generation of the fuel cell, the cumulative water production, or the cumulative air consumption of the fuel cell. These parameters can be easily and accurately measured using various sensors widely used in industry and general consumer applications. This allows for a more stable control system operation by more accurately reflecting the current durability degradation state of the fuel cell.

[0066] Figure 2 This is a flowchart illustrating a method for operating a fuel cell according to an embodiment of the present invention, and the method according to the present invention includes the following steps: deriving an interval average value, which is the average value of the fuel cell output value for each specified time (S200); deriving a cumulative average value, which is the average value of the fuel cell output value from the start of fuel cell operation to the current time point (S400); deriving an output limit value of the fuel cell from the interval average value and the cumulative average value (S300 and S500); and controlling the operation of the fuel cell based on the derived output limit value.

[0067] Specifically, in a method according to an embodiment of the present invention, the controller executes output limiting logic applied to a conventional vehicle (or application), as shown in reference... Figure 3 and Figure 4The maximum output limit mode described is the first mode (S100). Thereafter, the controller receives information about a specified time of the fuel cell and the fuel cell output for that specified time, and performs calculations based on that information to derive an interval average, which is the average of the fuel cell output values ​​for each specified time (S200). Here, the interval average can be as follows: Figure 3 and Figure 4 The moving average is shown. Furthermore, the interval average can be WMA, EPMA, or EMA. The controller then derives the output limit value from the interval average. In this case, the controller can derive an output limit value that differs from the output limit value derived through conventional output limit logic, such as... Figure 3 and Figure 4 The second output value shown corresponds to the output limit value in the second mode, which is different from the first output value corresponding to the output limit value in the first mode. Then, the constant output limit mode corresponding to the second mode (S300) can be executed. Furthermore, as in... Figure 3 and Figure 4 As shown, after the first reference time has elapsed, the method can return to executing the normal constraint logic.

[0068] Subsequently (or simultaneously with or before this), the controller receives information about the time from the start of fuel cell operation to the current time point and the fuel cell output at that time, and performs calculations based on this information to derive a cumulative average value, which is the average of the fuel cell output values ​​from the start of fuel cell operation to the current time point (S400). This operation can be performed after a specified time delay, such as... Figure 3 and Figure 4 The case shown is after the second reference time.

[0069] In this scenario, the controller can derive an output limit value that differs from the output limit value derived through conventional output limit logic, such as a third output value corresponding to the output limit value in the third mode (which differs from the output limit value in the first or second mode). Figure 3 and Figure 4 As shown, the average output limiting mode corresponding to the third mode (S500) can then be executed. Afterward, the controller can terminate control of the fuel cell operation. Therefore, the method may also include returning to the first mode or the second mode when the cumulative average value decreases to or is less than a third reference value, or when the reference time from the start of fuel cell operation to the current time point is equal to or greater than a third reference time (not shown) as a recovery time.

[0070] The present invention relates to systems and methods for operating fuel cells, and more specifically, to techniques for limiting the output of a fuel cell in consideration of durability degradation in order to improve the durability of the fuel cell during operation of the fuel cell system.

[0071] Generally, fuel cell system output limiting technology is implemented using real-time vehicle conditions, such as coolant and ambient temperatures, and the electrical output used to limit fuel cell charging. This is because conventional output limiting techniques are optimized for vehicle applications. Specifically, these real-time vehicle conditions are defined as values ​​of factors that vary significantly depending on driving conditions, or even small changes can have a significant impact. Therefore, when the same system is applied to other vehicles or applications, the system's durability deteriorates considerably, and it may fail to meet the required fuel cell operating time for the corresponding vehicle or application. Furthermore, to apply a fuel cell system to a specific vehicle or application, the device and system, including the fuel cell system, must be reconfigured.

[0072] However, the system and method for operating a fuel cell according to the present invention not only uses real-time output data, but also takes into account the cumulative usage time when operating the fuel cell system and the power generation in each time period to change the output limit of the fuel cell. This allows for understanding fuel cell states that cannot be detected by real-time data, thereby improving the fuel cell's durability due to more stable operation. Furthermore, the system and method according to the present invention use variables (using the fuel cell's output and time) to control the operation of the fuel cell, thus enabling its wide applicability to all vehicles or applications using fuel cell systems.

[0073] Furthermore, the system and method according to the invention take into account the cumulative usage of the fuel cell based on the current durability degradation state of the fuel cell system, and more actively utilize the output limit value of the fuel cell, thereby enabling an understanding of the durability state of the fuel cell and thus improving the durability of the fuel cell to meet the operating time of the fuel cell required for the corresponding vehicle or application.

[0074] As is evident from the above description, the system and method for operating a fuel cell according to the present invention not only uses real-time output data, but also takes into account the cumulative usage time of the fuel cell system during operation and the power generation in each time period to change the output limit of the fuel cell, thereby enabling the understanding of fuel cell states that cannot be detected by real-time data, thus improving the durability of the fuel cell due to more stable operation of the fuel cell.

[0075] Although preferred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various modifications, additions, and substitutions are possible without departing from the scope and spirit of the invention as disclosed in the appended claims.

Claims

1. A system for operating a fuel cell, the system comprising: The controller is configured to derive the output limit value of the fuel cell by means of an interval average and a cumulative average, and to control the operation of the fuel cell based on the derived output limit value, wherein the interval average corresponds to the average value of the output value of the fuel cell over a specified time period, and the cumulative average corresponds to the average value of the output value of the fuel cell from the start of operation of the fuel cell to the current time point.

2. The system according to claim 1, wherein the interval average value is a moving average value of the output value of the fuel cell.

3. The system of claim 1, wherein the controller is configured to execute a plurality of output limiting modes and to set the output limiting value differently based on each of the output limiting modes.

4. The system according to claim 3, wherein: The output limiting modes include a first mode, a second mode, and a third mode; and The controller selects the first mode or the second mode based on the interval average value and calculates the output limit value based on the selected mode.

5. The system according to claim 3, wherein: The output limiting modes include a first mode, a second mode, and a third mode; and When the average value of the interval in the first mode is equal to or greater than the first reference value, the controller switches the fuel cell to the second mode.

6. The system according to claim 5, wherein: When the reference time after switching to the second mode in the second mode is equal to or greater than the first reference time, the controller switches the fuel cell back to the first mode.

7. The system according to claim 3, wherein: The output limiting modes include a first mode, a second mode, and a third mode; and When the cumulative average value in the first mode or the second mode is equal to or greater than the second reference value, the controller switches the fuel cell to the third mode.

8. The system according to claim 7, wherein: When, in the first mode or the second mode, the reference time from the start of operation of the fuel cell to the current time point is equal to or greater than the second reference time and the cumulative average value is equal to or greater than the second reference value, the controller switches the fuel cell to the third mode.

9. The system according to claim 7, wherein: When the cumulative average value in the third mode decreases to a third reference value or less, the controller returns the fuel cell to the first mode or the second mode.

10. The system according to claim 1, wherein: The controller variably derives the output limit value of the fuel cell by parameters accumulated based on the use of the fuel cell.

11. The system according to claim 1, wherein: As the parameters accumulated from the use of the fuel cell increase, the output limit of the fuel cell decreases.

12. The system according to claim 1, wherein: The controller is configured to provide multiple cycle segments divided by parameters accumulated through the use of the fuel cell, and to set the output limit value differently based on each of the cycle segments.

13. The system of claim 10, wherein the parameter is the cumulative hydrogen consumption of the fuel cell.

14. The system of claim 10, wherein the parameter is any one of the cumulative power generation of the fuel cell, the cumulative water volume generated by the fuel cell, or the cumulative air consumption of the fuel cell.

15. A method for operating a fuel cell, the method comprising the steps of: The controller derives an interval average value, which corresponds to the average value of the fuel cell's output value at each specified time. The controller derives a cumulative average value, which corresponds to the average value of the fuel cell's output value from the start of operation of the fuel cell to the current time point. The controller derives the output limit value of the fuel cell from the interval average value and the cumulative average value; as well as The controller controls the operation of the fuel cell based on the derived output limit values.

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