Method and apparatus for thermal management of a vehicle fuel cell system

Abstract

A novel method and apparatus for thermal management of a vehicle fuel cell system is provided. The present invention relates to a method for thermal management of a fuel cell system of a vehicle, which estimates the heat output of the entire cooling system of the vehicle based on a physical model that takes into account the current operating status of the vehicle and the existing ambient conditions, and calculates the heat output (Q) in ECO mode that can be dissipated without activating one or more auxiliary consumers, including at least one fan (4). · ECO ) and the total heat output (Q) of the cooling system in Power mode that can be dissipated when one or more auxiliary consumers, including at least one fan (4), are activated. · POWER ) and the thermal output (Q · ECO , Q · POWER ), the target output (P S ) is determined, a determination is made as to whether the fuel cell system is to operate in ECO mode or Power mode, and a heuristic logic is used to determine how much energy the auxiliary consumers need for cooling in order to determine a characteristic value (KW) indicating how much power must currently be used to dissipate a particular heat output, and if the value exceeds 1 kW of power per 1 kW of heat output that can be dissipated, the output of the fuel cell system is not increased.

Description

[Technical Field]

[0001] The invention relates to a method for thermal management of a fuel cell system of a vehicle according to the preamble of claim 1 and to a device for thermal management of a fuel cell system of a vehicle according to claim 10 . [Background technology]

[0002] Fuel cell systems generate waste heat during operation, which must be dissipated by a cooling system. However, when the outside temperature is low or during warm-up, the fuel cell system must first be warmed up. Therefore, fuel cell systems require a thermal management system to ensure that they always operate within the appropriate temperature range.

[0003] Thermal management systems have limited cooling capacity. However, they can release different amounts of heat into the environment depending on the ambient conditions (outside temperature) and driving conditions (driving speed, traffic conditions). The fuel cell itself becomes less efficient over its lifetime, resulting in more waste heat being generated while producing roughly the same amount of electrical energy. If the thermal management system of a fuel cell system were designed to dissipate the maximum possible amount of waste heat from the fuel cell system under all conditions and all aging states of the fuel cell, the system would be extremely large, heavy, expensive, and therefore inefficient. Therefore, a moderately designed thermal management system may not be able to maximize the fuel cell output in all conditions. This could cause the fuel cell system to overheat and shorten its service life. Furthermore, while it may be possible to dissipate the waste heat in most conditions, it would not make sense from an energy perspective because the energy demands of the auxiliary equipment used would be so high. Therefore, the output of the fuel cell system must be reduced in such conditions.

[0004] The following Patent Document 1 describes a system and method for determining battery heating conditions and a preheating lead time of at least one minute based on input parameters and a set of input parameters, and for proactively and dynamically heating a secondary battery so that the battery has a specific power output and a specific output level when used in an electric vehicle or hybrid vehicle. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 10 369 899 (B2) Summary of the Invention [Problem to be solved by the invention]

[0006] SUMMARY OF THE INVENTION It is an object of the present invention to provide a novel method and a novel device for the thermal management of a fuel cell system in a vehicle. [Means for solving the problem]

[0007] According to the invention, this problem is solved by a method for thermal management of a fuel cell system of a vehicle having the features of claim 1 and by a device for thermal management of a fuel cell system of a vehicle having the features of claim 10 .

[0008] Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0009] The thermal management method for a vehicle fuel cell system according to the present invention estimates the thermal output of the entire vehicle cooling system based on a physical model, taking into account the vehicle's current operating situation and available ambient conditions. According to the present invention, the thermal power that can be dissipated in ECO mode without activating at least one fan and one or more auxiliary consumers, including, for example, at least one valve, and the thermal power of the entire cooling system in Power mode that can be dissipated when at least one fan and one or more auxiliary consumers, including, for example, at least one valve, are determined; the energy management system calculates a target power output for the fuel cell regardless of the thermal power output, for example using the current battery state of charge (SOC) and the current running resistance, which is the sum of air resistance, rolling resistance, and gradient resistance; and based on these thermal power outputs, determines one or more target power outputs that can currently be drawn by the fuel cell system, limited by the thermal power if necessary; determines whether the fuel cell system is operating in ECO mode or Power mode; and uses heuristic logic to determine how much energy the auxiliary consumers required for cooling currently require in order to determine a characteristic value that indicates how much power must currently be used to dissipate a certain thermal power. If this value exceeds 1 kW of power per 1 kW of dissipable thermal power, the power output of the fuel cell system is not increased.

[0010] In one embodiment, it is contemplated that the energy management system will increase the required target power output of the fuel cell for values ​​significantly lower than 1 kW of power per kW of dissipated thermal power, particularly for values ​​of 0.2 kW or less of power per kW of thermal power.

[0011] In one embodiment, the current driving conditions are considered, including road speed and / or coolant temperature.

[0012] In one embodiment, ambient temperature is considered an ambient condition.

[0013] In one embodiment, the energy management system calculates the possible power of the fuel cell based on a characteristic map that takes into account the currently existing aging of the fuel cell system, and requests this power from the fuel cell.

[0014] In one embodiment, the mass flow rate of the coolant supplied by one or more pumps is estimated from the current waste heat of the fuel cell system, and this mass flow rate is taken into account in addition to the current operating conditions and available ambient conditions by one or more coolers in estimating the heat that can be dissipated.

[0015] In one embodiment, if the fuel cell system has low waste heat, one or more valves can be used to adjust the desired target temperature at the fuel cell system inlet.

[0016] In one embodiment, the current waste heat of the fuel cell system and the heat that can be dissipated by one or more coolers are considered when determining the additional waste heat required for the at least one fan.

[0017] In one embodiment, the mass flow rate that can be provided by the at least one fan is estimated from the waste heat required by the at least one fan, and from that estimation, an energy-optimal allocation of the mass flow rate to the fans and control of the fans accordingly is determined.

[0018] In one embodiment, a prediction is made for the driving route ahead, and based on the planned driving route, the web-based traffic service and / or the prediction module determines the vehicle's expected driving speed profile and expected ambient temperature profile, and using a thermal model of the cooling system, based on these data, determines how the convertible cooling capacity and corresponding characteristic values ​​of the cooling system will occur in ECO mode and Power mode for the driving route ahead, and based on this, an optimal power trajectory for the fuel cell system is planned, taking into account the driving route and the influence of the external environment.

[0019] According to one aspect of the present invention, a thermal management device for a fuel cell system of a vehicle is proposed, comprising an energy management system of the fuel cell system and a vehicle control device configured to perform a method according to any one of the preceding claims. -Thermal management estimates the current available cooling capacity of the cooling system in two power stages (ECO and Power). -Using an interface to the energy management system, the central control unit is informed of the currently available cooling capacity, - The characteristic value relating to the currently required power input (power consumption) per kilowatt of cooling capacity consumed provides information indicating whether or not an additional energy input would necessarily result in an improvement in the cooling of the system.

[0020] The thermal management of fuel cell commercial vehicles determines the currently available cooling capacity of the cooling system, taking into account the current driving situation and the ambient conditions. Therefore, information can be provided about the cooling capacity without additional energy demand (ECO mode) and with additional energy demand, for example through fan ventilation (Power mode). This information is provided to the energy management system via an interface, which can determine the most energy-efficient operating point of the fuel cell system. The specific value of the power currently obtained by the auxiliary unit per kW of excess heat removed is used to determine whether it would be beneficial to increase the cooling capacity.

[0021] The service life of a fuel cell system depends heavily on good and consistent temperature control within the fuel cell's optimal comfort range. The more frequently overheating is avoided, the longer the service life of the fuel cell. The interface of the present invention makes it possible to more reliably operate the fuel cell within its optimal temperature range. The use of hydrogen as fuel should be as efficient as possible. Operating conditions in which unnecessary amounts of hydrogen are consumed without providing any benefit to driving performance or the onboard network should be avoided. Therefore, the power requirements of the fuel cell must be adjusted so that the energy requirements of the auxiliary equipment are as optimal as possible. The present invention improves both of these points by providing the energy management system with the current or future state of the thermal management system, thereby preventing overheating and inefficient operating states of the fuel cell, and allowing it to be optimally designed. The present invention minimizes the required design margin of the thermal management system and allows the design of the most efficient thermal management, so that the thermal management system is always used nearly optimally.

[0022] An embodiment of the invention will now be described in more detail with reference to the drawings. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic diagram of a method for estimating dissipatable heat power with and without fan activation in a fuel cell vehicle; [Figure 2] 1 is a schematic diagram of a reactive method for thermal management of a fuel cell vehicle. [Figure 3] FIG. 1 is a schematic diagram of a method for predicting thermal management of a fuel cell vehicle. [Figure 4] FIG. 1 is a schematic diagram of a simplified model for estimating the cooling capacity dissipated by a vehicle cooler. [Figure 5] FIG. 1 is a schematic diagram of a method for estimating air mass flow. [Figure 6] 10 is a schematic profile of the driving performance range FLH during predictive control. DETAILED DESCRIPTION OF THE INVENTION

[0024] Corresponding parts are labeled with the same reference numbers in all figures.

[0025] FIG. 1 is a schematic diagram of a method for estimating the dissipable heat output (heat amount) with and without fan activation in a fuel cell vehicle.

[0026] FIG. 2 is a schematic diagram of a reactive method for thermal management of a fuel cell vehicle.

[0027] The fuel cell vehicle includes a vehicle control device 1 configured to control the thermal management system. The vehicle control device 1 determines the current driving conditions, such as the driving speed v and the temperature T of the coolant. KM and the available ambient conditions, e.g., ambient temperature T U Based on a physical model that takes into account the heat output that can currently be dissipated (radiated) by the entire cooling system, for example, the heat Q that can be dissipated by one or more coolers 5, · K1 , Q · K2 Estimate.

[0028] The module 12 for driving performance-oriented energy allocation and SOC-based energy allocation of the high-voltage battery determines the target output of the fuel cell without thermal limitations, taking into account the current state of charge SOC of the battery and the current running resistance AFW, which is composed of the sum of air resistance, rolling resistance, and gradient resistance.

[0029] The cooling water mass flow rate can be determined based on the current pump speed, while the air mass flow rate is known from simulation calculations, measurements, and experience. Any inaccuracies may be corrected using downstream correction factors or functions.

[0030] For this estimation, the model considers the amount of heat Q that can be dissipated when passing through the cooler at a constant given air mass flow rate, which can be assumed to have different magnitudes for ECO and Power modes, for example. ·K1 , Q · K2 4 shows a schematic diagram of a simplified model for estimating the cooling capacity dissipated by the cooler 5. In that case, to determine the correction value KoW, the cooling water inlet temperature T W and the air inlet temperature T L The difference between these values ​​is calculated and multiplied by the thermal conductivity value WLW, which is determined by the characteristic map KF, which is based on the cooling water mass flow rate m · W and air mass flow rate m · L The thermal conductivity value WLW is determined based on the above.

[0031] Using the following formula, calculate the mass flow rate of cooling water m from the pump speed n. · W can be estimated.

[0032]

number

[0033] P Drive output (kW) p Pump outlet operating pressure (bar) Q Volumetric flow rate (dm 3 / min) η ges Overall efficiency (-) M Torque (Nm) n Pump rotation speed (1 / min)

[0034] For example, the mass flow rate of cooling water m · W has a known relationship to the volumetric flow rate via the density of the cooling water.

[0035] Pump mass flow rate m · W is determined from the input drive power and the generated working pressure as in the previous equation, or from the pump speed and mass flow rate m ·W In this case, the current mass flow rate m is related to the maximum pump speed in the same way that the current pump speed is related to the maximum pump speed. · W is related to the maximum mass flow rate.

[0036] Figure 5 shows the air mass flow rate m · L Schematic diagram of a method for estimating the air mass flow rate m passing through the cooler 6. · L is the air mass flow rate m passing through the fan 4 in particular. · LL Simulation results for determining SE and, in particular, the air mass flow rate m · LFW characteristic map KF with empirical values ​​for determining EW , the running speed v and the ambient temperature T U The total air mass flow rate m · ges is the mass flow rate of air passing through fan 4 m · LL and the air mass flow rate m from the air stream · LFW It can be calculated as the sum of

[0037] In that case, on the one hand, there is the heat power Q that can be dissipated without additional measures such as starting one or more fans 4. · ECO The so-called dissipable heat output Q resulting from the wind alone is determined. · ECO This results in a heat output value representing the minimum energy consumption of the auxiliary consumers (ECO mode). On the other hand, the heat output Q that can be dissipated by further measures such as the activation of one or more fans 4 is determined. · POWER This results in a thermal power value that allows an increase in the power output of the fuel cell (Power mode), although it certainly means an increase in the energy consumption of the auxiliary consumers.

[0038] The vehicle control device 1 for carrying out thermal management has an interface 2 to the energy management system ENM of the fuel cell, which interface 2 informs the energy management system ENM of the two currently possible thermal cooling capacities.

[0039] From this information, the energy management system ENM can further determine the power that can currently be obtained from the fuel cell. The energy management system ENM can back-calculate the fuel cell's possible electrical output from a characteristic map that also takes into account the fuel cell system's current service life, and request this electrical output from the fuel cell. Depending on the current situation, the energy management system ENM can decide whether to operate the fuel cell at an operating point that requires the least energy for the auxiliary equipment (thermal management in ECO mode) or whether a more energy-consuming Power mode is required.

[0040] Additionally, the vehicle control device 1 determines via heuristic logic how much energy is currently required by auxiliary consumers required for cooling, such as the pump 6 and the fan 4. This allows a characteristic value in KW to be determined that indicates how much power currently needs to be used to dissipate a certain heat output.

[0041] In particular, the current waste heat Q of the fuel cell system · BZ from the mass flow rate m of the refrigerant supplied by one or more pumps 6 · P is estimated, and this mass flow rate m · P is the current driving situation, e.g., the driving speed v and the refrigerant temperature T KM , as well as the existing ambient conditions, e.g., ambient temperature T U In addition to the heat Q that can be dissipated by one or more coolers 5 · K1 , Q · K2 This can be taken into account when estimating

[0042] Additional waste heat Q required for at least one fan 4· L When determining the current waste heat Q of the fuel cell system, · BZ and heat Q that can be dissipated by one or more coolers 5. · K1 , Q · K2 and can be considered.

[0043] Waste heat Q required for at least one fan 4 · L from the mass flow m supplied by at least one fan 4 · L1 , m · L2 This allows us to estimate the mass flow rate m · L1 , m · L2 The optimal energy allocation 9 and the corresponding control 3 of the fans 4 can be determined.

[0044] In certain circumstances, the cooling system may use a large number of auxiliary devices, such as fans 4, to generate high cooling capacity, which may result in very high electrical energy consumption that may completely consume or even exceed the additional fuel cell output that is generated thereby.

[0045] In this case, only the hydrogen consumption would increase without any positive effect on the high-voltage electrical system in terms of a charging effect. The additional power generated would be consumed directly by auxiliary consumers. This situation should be avoided. This is possible with the characteristic value KW of the thermal management mentioned above. If this characteristic value KW is, for example, a value that exceeds 1 kW of power per 1 kW of dissipated heat power, this characteristic value KW indicates that operation is not appropriate. In this case, the energy management system ENM, taking into account the thermal management limitations 10, limits the target power P of the fuel cell system. SIf the characteristic value KW is significantly lower, i.e., for example, 0.2 kW of power per kW of thermal power, the energy management system ENM will not further increase the required target power P S can be increased.

[0046] FIG. 3 is a schematic diagram of a predictive method for thermal management of a fuel cell vehicle.

[0047] The vehicle control device 1 can be configured to predict the driving route ahead in addition to the currently available conditions. Based on the planned driving route, the expected driving speed profile v(t) of the vehicle can be determined by a web-based traffic service and / or a separate prediction module 7.

[0048] Furthermore, the gradient profile and curvature profile of the route can be determined, for example, from a digital map. From this information, the actually drivable speed profile over the forecast period or driving performance range FLH and the corresponding power requirements for drive torque and / or brake torque can be determined using the longitudinal dynamics model (see FIG. 3). Based on the resulting energy requirements, the energy management ENM, in particular the module 13 for determining the driving performance-oriented energy allocation range and the SOC-based energy allocation range of the high-voltage battery as part of the energy management ENM, then determines the fuel cell power P required over the forecast period. S (t) and the waste heat from the fuel cell efficiency characteristic map can be determined. Additionally, taking into account the waste heat from auxiliary consumers, the battery, and possibly auxiliary braking, the overall cooling requirement can be calculated, which can be plotted over a forecast range.

[0049] Figure 6 shows the road conditions for the available forward travel route s, including the travel speed v (e.g., from speed prediction), road gradient FBS (e.g., from a map), and ambient temperature T U1 shows a schematic profile of the driving performance range FLH in predictive control using a trajectory (e.g., from a web service). Variables that can be calculated from this include the estimated drive power ATL, the estimated fuel cell power BZL, the battery state of charge SOC, and the waste heat Q of the fuel cell system. · BZ , available cooling capacity Q · K1 , Q · K2 (e.g., due to wind when driving) and the necessary fan start-up BLZ.

[0050] Similarly, a web-based weather forecast service might provide a forecast of the expected ambient temperature, T U The profile of (t) as well as other weather data, e.g., rain, can be retrieved, for example, from cloud 8. Using a thermal model of the cooling system, it is possible to calculate, based on these data, how the convertible cooling capacity of the cooling system and the corresponding characteristic value of the energy consumption in KW will be for the driving route ahead, not only in ECO mode but also in Power mode. For this purpose, based on the driving performance expected for the driving route ahead s, it is calculated whether the resulting expected fuel cell waste heat can be dissipated with the help of all actuators, for example, one or more pumps 6, one or more coolers 5, one or more coolers 4, and one or more valves 11. If the waste heat cannot be dissipated, a limit violation LV is determined and the expected fuel cell target power is corrected in the energy management ENM.

[0051] Using this information, the energy management system ENM calculates the optimal power trajectory P for the fuel cell system, taking into account the driving route s and the influence of the external environment. S It is possible to plan (t): for example, if it is already known in the planning stage that the fuel cell output BZL needs to be reduced on an uphill route for thermal management reasons (thermal system limit violation LV within the range), the fuel cell can be started earlier, when the cooling situation is easier, to provide a corresponding energy buffer in the high-voltage battery.

[0052] The apparatus and method may be used in fuel cell vehicles, particularly commercial vehicles, for example heavy commercial vehicles. [Explanation of symbols]

[0053] 1 Vehicle control device 2. Interface 3 Fan Control 4 Fans 5 Cooler 6. Pump 7 Prediction Module 8. Cloud 9 Mass flow distribution 10 Considering Thermal Management Limits 11 Valve 12 modules 13 modules AFW Current running wind resistance ATL drive output BLZ Fan Start Required BZL fuel cell output ENM Energy Management FBS Road Gradient FLH driving performance range KF characteristic map KF EW Experience Map KW characteristic value KoW correction value LV limit violation m · ges Total Air Mass Flow m · L Air Mass Flow Rate m · LFW Air mass flow rate due to road wind m · LL Air mass flow rate through the fan m · L1 , m · L2 Mass flow rate for the fan m · PPump Mass Flow Rate m · W Cooling water mass flow rate n Pump rotation speed P S Target Output P S (t) Expected profile of target output, output profile (output trajectory) Q · BZ Waste heat from fuel cell systems Q · ECO Heat output in ECO mode Q · K1 , Q · K2 Heat that can be dissipated by a cooler Q · L Heat dissipation to the fan Q · POWER Heat output in Power mode s Driving route SE simulation results SOC State of Charge T KM Coolant temperature T L Air inlet temperature T U Ambient temperature T U (t) Expected ambient temperature profile T W Cooling water inlet temperature v Traveling speed v(t) Expected driving speed profile WLW thermal conductivity value

Claims

1. 1. A method for thermal management of a fuel cell system of a vehicle, comprising: estimating a thermal output of an entire cooling system of the vehicle based on a physical model that takes into account the current operating situation of the vehicle and available ambient conditions, the method comprising: The heat output (Q) in ECO mode can be dissipated without activating one or more auxiliary consumers, including at least one fan (4). ・ ＥＣＯ ) and the heat output (Q ) of the entire cooling system in Power mode that can be dissipated when one or more auxiliary consumers, including at least one fan (4), are activated. ・ ＰＯＷＥＲ ) and the thermal output (Q ・ ＥＣＯ , Q ・ ＰＯＷＥＲ ), a target output (P Ｓ ) is determined, it is determined whether the fuel cell system is to operate in the ECO mode or the Power mode, and using heuristic logic, it is determined how much energy the auxiliary consumers need for cooling currently require in order to determine a characteristic value (KW) indicating how much power must currently be used to dissipate a specific heat output, and if the value exceeds 1 kW of power per 1 kW of heat output that can be dissipated, the power output of the fuel cell system is not increased. A method characterized by:

2. When the power per kW of dissipated heat output is significantly lower than 1 kW, in particular when the power per kW of heat output is 0.2 kW or less, the energy management system (ENM) determines that the required target power output (P Ｓ ) to increase 2. The method according to claim 1, characterized in that

3. The current driving situation is determined by the driving speed (v) and / or the refrigerant temperature (T ＫＭ ) is taken into consideration 3. The method according to claim 1 or claim 2, characterized in that

4. The ambient conditions are ambient temperature (T Ｕ ) is taken into consideration The method according to any one of claims 1 to 3, characterized in that

5. The energy management system (ENM) calculates the available power of the fuel cell based on a characteristic map that takes into account the currently existing aging of the fuel cell system and requests this power from the fuel cell. The method according to any one of claims 1 to 4, characterized in that

6. The current waste heat (Q ・ ＢＺ ) to the mass flow rate (m ・ Ｐ ) is estimated, and the mass flow rate is determined based on the heat available for dissipation by one or more coolers (5) (Q ・ Ｋ１ , Q ・ Ｋ２ ) are taken into account when estimating The method according to any one of claims 1 to 5.

7. The additional waste heat (Q) required by said at least one fan (4) ・ Ｌ ) at the time of determining the current waste heat (Q ・ ＢＺ ) and heat (Q) that can be dissipated by one or more coolers (5). ・ Ｋ１ , Q ・ Ｋ２ ) and are taken into consideration. The method according to any one of claims 1 to 6, characterized in that

8. The waste heat (Q ・ Ｌ ) to the mass flow rate (m ・ Ｌ１ , m ・ Ｌ２ ) and from that estimation, the mass flow rate (m ・ Ｌ１ , m ・ Ｌ２ ) and the corresponding control (3) of said fan (4).

8. The method according to claim 7, characterized in that

9. A prediction of the driving route ahead is made and based on the planned driving route, a profile of the expected driving speed (v(t)) of the vehicle and a profile of the expected ambient temperature (T Ｕ (t)) is determined, and using a thermal model of the cooling system, it is determined based on these data how the convertible cooling capacity and corresponding characteristic value (kW) of the cooling system will be in the ECO mode and the Power mode for the forward driving route, and based on this, an optimal power trajectory (P Ｓ (t)) is planned The method according to any one of claims 1 to 8, characterized in that

10. A thermal management device for a fuel cell system of a vehicle, the thermal management device being configured to perform an energy management system (ENM) of said fuel cell system and a vehicle control device (1) configured to perform the method according to any one of claims 1 to 9. An apparatus comprising:

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