Method and apparatus for vehicle fuel cell system thermal management

Abstract

The invention relates to a method for thermal management of a fuel cell system of a vehicle, in which the thermal output of the entire cooling system of the vehicle is estimated on the basis of a physical model, taking into account the current driving situation and the existing environmental conditions of the vehicle, in an energy management system (ENM), a heat output # imgabs0 #, which can dissipate in an ECO mode without switching on one or more auxiliary electrical appliances comprising at least one fan (4), and a heat output # imgabs1 #, which can dissipate in a Power mode with one or more auxiliary electrical appliances comprising at least one fan (4), are determined, according to the invention, a target power (PS) which can be currently invoked from the fuel cell system is determined on the basis of the heat output # imgabs2, and whether the fuel cell system is operating in an ECO mode or a Power mode is determined, in which how much energy is currently required by the auxiliary electrical equipment required for cooling is determined by means of a heuristic logic system, in order to determine a characteristic value (KW), and the characteristic value (KW) is determined on the basis of the heat output # imgabs2. The characteristic value represents how much electric power must be introduced currently to dissipate a specific thermal output, where the power of the fuel cell system does not increase when the value represents that more than 1 kilowatt electric power is required to dissipate per kilowatt thermal output.

Description

Field of the Invention

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

[0002] During operation, a fuel cell system generates waste heat that must be dissipated through a cooling system. On the other hand, at low ambient temperatures or during a warm-up phase, the fuel cell system must first be heated. Therefore, a fuel cell system requires a thermal management system to always be able to operate within an appropriate temperature range.

[0003] The cooling capacity of the thermal management system is limited. However, depending on the environmental conditions (ambient temperature) and driving conditions (driving speed, traffic conditions), the thermal management system can dissipate different amounts of heat to the environment. The fuel cell itself gradually loses efficiency during its service life, so that with almost constant electrical power generation, it generates increasing amounts of waste heat. If the thermal management system for the fuel cell system is designed to be able to dissipate the maximum waste heat that the fuel cell system may generate in all usage cases and all aging states of the fuel cell, then the system will be very large, heavy, and expensive, and thus inefficient. An appropriately designed thermal management system may also result in not being able to utilize the full power of the fuel cell in all battery usage cases. This may cause the fuel cell system to overheat and shorten its service life. In addition, in some cases, although the waste heat can be discharged, the energy requirement of the auxiliary equipment used in this process will be very high, making it unreasonable from an energy perspective. Therefore, in these cases, the power of the fuel cell system must be reduced.

[0004] US10 369 899 B2 describes a system and method for determining battery heating conditions and a preheating lead time of at least one minute or longer based on input parameters and a set of input parameters for prospectively and dynamically heating a secondary battery such that the battery has a specific power output and a specific performance level when used in an electric or hybrid vehicle application. Summary of the Invention

[0005] The object of the present invention is to provide a novel method and device for thermal management of a vehicle fuel cell system.

[0006] According to the present invention, the object is achieved by a method for thermal management of a vehicle fuel cell system having the features of claim 1 and a device for thermal management of a vehicle fuel cell system having the features of claim 10.

[0007] Advantageous designs of the present invention are the subject matter of the dependent claims.

[0008] In the method for thermal management of a vehicle fuel cell system according to the present invention, based on a physical model, considering the current driving condition of the vehicle and the existing environmental conditions, the heat output of the entire vehicle cooling system is estimated. According to the present invention, the heat output that can be dissipated in the ECO mode without turning on one or more auxiliary electrical devices including at least one fan and for example at least one valve is determined; the heat output of the entire cooling system that can be dissipated in the Power mode when turning on one or more auxiliary electrical devices including at least one fan and for example at least one valve is determined, wherein, in the energy management system, for example, based on the current state of charge (SOC) of the battery and the current driving resistance composed of the sum of air resistance, rolling resistance and gradient resistance, a fuel cell target power independent of the heat output is calculated. Based on these heat outputs, one or the current target power that can be currently invoked from the fuel cell system and may be limited by the heat output is determined, and it is judged whether the fuel cell system is operating in the ECO mode or the Power mode, wherein, by means of heuristic logic, it is determined how much energy is currently required for the auxiliary electrical devices required for cooling, so as to determine a characteristic value, which represents how much electrical power must be used to currently dissipate a specific heat output. When the value is more than 1 kilowatt of electrical power required to dissipate each kilowatt of heat output, the power of the fuel cell system does not increase.

[0009] In one embodiment, it is stipulated that when the value is significantly less than 1 kilowatt of electrical power required to dissipate each kilowatt of heat output, especially when at most 0.2 kilowatt of electrical power is required for each kilowatt of heat output, the energy management system increases the target power requested for the fuel cell.

[0010] In one embodiment, for the current driving condition, the driving speed and / or the temperature of the cooling medium are considered.

[0011] In one embodiment, the ambient temperature is taken into account as an environmental condition.

[0012] In one embodiment, it is stipulated that the energy management system inversely calculates the possible electrical power of the fuel cell according to a characteristic curve considering the current aging state of the fuel cell system, and requests the fuel cell for the electrical power.

[0013] In one embodiment, based on the current waste heat of the fuel cell system, the mass flow rate of the cooling medium that one or more pumps need to provide is estimated, and this mass flow rate is considered together with the current driving condition and the existing environmental conditions when estimating the heat that one or more coolers can dissipate.

[0014] In one embodiment, when the waste heat of the fuel cell system is less, the target temperature required at the inlet of the fuel cell system can be adjusted by means of one or more valves.

[0015] In one embodiment, when determining the additional waste heat required by at least one fan, the current waste heat of the fuel cell system and the heat that can be dissipated through one or more coolers are considered.

[0016] In one embodiment, according to the waste heat required by at least one fan, the mass flow rate that the at least one fan must provide is estimated, thereby determining the energy-optimal distribution of the mass flow rate on the fan and the corresponding fan control.

[0017] In one embodiment, a forward driving route is predicted. Among them, according to the planned driving route, the change curve of the expected vehicle driving speed and the change curve of the expected ambient temperature are determined through a network-based traffic service and / or a prediction module. Then, using the thermal model of the cooling system, based on this data for the forward driving route, it is determined how the achievable cooling power of the cooling system and the corresponding characteristic values will develop in the ECO mode and the Power mode. On this basis, considering the driving route and external environmental impacts, the optimal power trajectory of the fuel cell system is planned.

[0018] According to one aspect of the present invention, a device for thermal management of a vehicle fuel cell system is proposed, including an energy management system of the fuel cell system and a vehicle controller, which are configured to execute the method according to one of the foregoing claims.

[0019] - The thermal management system estimates the currently possible cooling power of the cooling system at two power levels (ECO and Power).

[0020] - Through an interface with the energy management system, the central control unit is informed of the currently available cooling power.

[0021] - The characteristic value of the current power input required to dissipate each kilowatt of cooling power indicates whether investing more energy can also improve the system cooling effect.

[0022] The thermal management system of a fuel cell commercial vehicle considers the current driving conditions and environmental conditions to determine the currently available cooling power of the cooling system. Therefore, it can provide information on the cooling potential under no additional energy requirement (ECO mode) and with additional energy requirement (Power mode), for example, achieved through a fan. This information is provided to the energy management system through an interface, so that the most energy-efficient operating point of the fuel cell system can be determined. The specific value of the power consumed by auxiliary equipment for dissipating each kilowatt of excess heat currently is used to determine whether it is beneficial to increase the cooling power.

[0023] The service life of a fuel cell system depends to a large extent on good and stable temperature control within the optimal temperature range suitable for the fuel cell. The more overheating can be avoided, the longer the service life of the fuel cell. Through the interface of the present invention, the fuel cell can operate more reliably within the optimal temperature range. The use of hydrogen as fuel must be as efficient as possible. Operating states that consume an unnecessary large amount of hydrogen without contributing to driving performance or on-vehicle power supply should be avoided. Therefore, the power demand for the fuel cell must be adjusted so that the energy demand of auxiliary devices is optimized as much as possible. The above two points can be improved and optimized design can be achieved through the present invention, because by transmitting the current or expected state of the thermal management system to the energy management system, overheating and inefficient operating states of the fuel cell can be avoided. Through the present invention, the design redundancy required for the thermal management system can be minimized, and the most efficient thermal management system can be designed; therefore, it can always obtain near-optimal use. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein:

[0025] Figure 1 A schematic diagram showing a method for estimating the heat dissipation output of a fuel cell vehicle in the fan-on and fan-off states;

[0026] Figure 2 A schematic diagram showing a responsive method for thermal management of a fuel cell vehicle;

[0027] Figure 3 A schematic diagram showing a predictive method for thermal management of a fuel cell vehicle;

[0028] Figure 4 A simplified model schematic diagram showing a method for estimating the cooling power dissipated through a vehicle cooler;

[0029] Figure 5 A schematic diagram showing a method for estimating the air mass flow rate; and

[0030] Figure 6 A schematic variation curve showing the driving power range (FLH) under anticipatory control. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] Corresponding components have the same reference numerals in all the drawings.

[0032] Figure 1 A schematic diagram showing a method for estimating the heat dissipation output of a fuel cell vehicle in the fan-on and fan-off states.

[0033] Figure 2 A schematic diagram showing a responsive method for thermal management of a fuel cell vehicle.

[0034] A fuel cell vehicle has a vehicle controller 1, which is configured to execute control of a thermal management system. The vehicle controller, based on a physical model, takes into account the current driving conditions, such as the driving speed v and the temperature T of the cooling medium KM , as well as the existing environmental conditions, such as the ambient temperature T U , and estimates the current heat output that can be dissipated by the entire cooling system, such as the heat that can be dissipated by one or more coolers 5

[0035] In module 12 for power-oriented and SOC-based energy distribution of a high-voltage battery, in order to determine the fuel cell target power without thermal limitation, the current state of charge SOC of the battery and the current driving resistance AFW are taken into account, where the resistance consists of the sum of air resistance, rolling resistance, and gradient resistance

[0036] The mass flow rate of the cooling water can be determined according to the current pump speed, while the air mass flow rate can be known through simulation calculations, measurements, and empirical values. Possible errors can be compensated by a subsequent correction factor or correction function

[0037] For this estimation, in the model, characteristic curves of thermal conductivity provided by the cooler manufacturer (these characteristic curves are obtained under a constant set air mass flow rate - different assumptions can be made for the ECO mode and the Power mode) are used, for example, to determine the heat that can be dissipated by the cooler Figure 4 A simplified model schematic for estimating the cooling power dissipated by cooler 5 is shown. In this process, to determine the correction value KoW, the inlet temperature T of the cooling water of cooler 5 is calculated W and the difference from the air inlet temperature T L is multiplied by the heat transfer coefficient WLW determined according to the mass flow rate of the cooling water and the air mass flow rate of the cooler through the characteristic curve KF

[0038] To estimate the mass flow rate of the cooling water according to the pump speed n the following formula can be used

[0039]

[0040] P Driving power (kilowatts)

[0041] p Pump outlet working pressure (bar)

[0042] Q Volume flow rate (dm 3 / min)

[0043] η gesOverall efficiency (-)

[0044] M Torque (Nm)

[0045] n Pump speed (1 / min)

[0046] Through the density of the cooling water, the mass flow rate of the cooling water For example, it has a known relationship with the volume flow rate.

[0047] The mass flow rate of the pump Can be determined by the input drive power and the generated working pressure in the formula as above, or can also be determined by the linear relationship between the pump speed and the mass flow rate The linear relationship has been determined in advance through tests of the existing system. In this case, the current mass flow rate Has the same relationship with the maximum mass flow rate as the current pump speed has with the maximum pump speed.

[0048] Figure 5 Shows a schematic diagram of a method for estimating the air mass flow rate The air mass flow rate flowing through the cooler 6 Can be determined by the simulation result SE (especially for determining the air mass flow rate flowing through the fan 4 ), the characteristic curve KF with empirical values EW (Especially for determining the air mass flow rate generated by the driving wind ) and the combination of the current environmental conditions (such as the driving speed v and the environmental temperature T U ). Then, the total air mass flow rate Can be calculated as the sum of the air mass flow rate flowing through the fan 4 And the air mass flow rate generated by the driving wind .

[0049] On the one hand, determine the heat output This is the heat output that can be dissipated without taking additional measures such as turning on one or more fans 4. That is to say, determine the heat output that can be dissipated only by the driving wind The obtained heat output value represents the minimum energy consumption of the auxiliary electrical equipment (ECO mode). On the other hand, the heat output can also be determined This is the heat output that includes the heat output that can be dissipated by taking additional measures such as turning on one or more fans 4. Although the obtained heat output value means an increase in the energy consumption of the auxiliary electrical equipment, it allows the fuel cell to output higher power (Power mode / power mode).

[0050] The vehicle controller 1 for performing thermal management has an interface 2 connected to the fuel cell energy management system ENM, and the interface provides the energy management system ENM with information about these two currently possible thermal cooling capabilities.

[0051] The energy management system ENM can in turn determine how much electrical power can currently be called from the fuel cell based on this information. Based on a characteristic curve that also takes into account the current aging degree of the fuel cell system, the energy management system ENM can reverse-calculate the possible electrical power of the fuel cell and request said power from the fuel cell. According to the current situation, the energy management system ENM can then determine whether the fuel cell is operating at the operating point with the lowest energy consumption of auxiliary equipment (i.e., the thermal management is in the ECO mode), or whether the Power mode with higher energy consumption needs to be adopted.

[0052] In addition, the vehicle controller 1 determines how much energy is currently required for the auxiliary electrical equipment (such as pumps 6 and fans 4) for cooling through heuristic logic. From this, a characteristic value KW can be determined, indicating how much electrical power must be invested to dissipate a specific heat output currently.

[0053] In particular, based on the current waste heat of the fuel cell system the mass flow rate of the cooling medium provided by one or more pumps 6 can be estimated This mass flow rate is considered together with the current driving conditions (such as driving speed v and cooling medium temperature T ) and the existing environmental conditions (such as ambient temperature T KM ) when estimating the heat that can be dissipated through one or more coolers 5. U )

[0054] When determining the additional waste heat required by at least one fan 4 the current waste heat of the fuel cell system can be considered as well as the heat that can be dissipated through one or more coolers 5

[0055] According to the waste heat required by the at least one fan 4 the mass flow rate that the at least one fan 4 must provide can be estimated From this, the determined mass flow rate the optimal energy distribution 9 on the fan 4 and the corresponding control 3 of the fan 4 can be determined.

[0056] In some cases, the cooling system may generate high cooling power when a large number of auxiliary equipment (such as fans 4) are used, but at this time the power consumption of the electrical energy will be very high, such that the additional fuel cell power obtained overall will be completely consumed or even exceeded.

[0057] In this case, it will only result in an increase in hydrogen consumption and will not have a positive impact on the charging effect of the high-voltage vehicle power supply. The additionally generated electric power will be directly consumed by the auxiliary electrical devices. These situations should be avoided. This can be achieved through the characteristic value KW of the above-mentioned thermal management system. If the value of the characteristic value KW is such that more than 1 kW of electric power is required to dissipate 1 kW of heat output, it indicates unreasonable operation. In this case, when considering the limitations 10 of the thermal management, the energy management system ENM will not further increase the target power P of the fuel cell system S . If the value is significantly lower than this, for example, 0.2 kW of electric power corresponds to 1 kW of heat output, the energy management system ENM can increase the requested fuel cell target power P S .

[0058] Figure 3 A schematic diagram showing a predictive method for the thermal management of a fuel cell vehicle

[0059] In addition to the currently existing situations, the vehicle controller 1 can also be configured to predict the forward driving route. According to the planned driving route, the curve of the expected driving speed v(t) of the vehicle can be determined through network-based traffic services and / or through another prediction module 7

[0060] Furthermore, the slope and curvature curves of the driving route can be determined, for example, obtained from a digital map. Based on this information, the actual drivable speed curve and the corresponding driving and / or braking torque power requirements within the forward-looking range or driving performance range FLH can be determined with the aid of a longitudinal dynamics model (see Figure 3 ). Then, based on the resulting energy demand, in the energy management system ENM, especially in the module 13 that is part of the energy management system ENM and is used to determine the energy distribution range of the high-voltage battery based on the driving power and SOC, the fuel cell power Ps(t) required within the forward-looking range can be determined, and the waste heat can be determined according to the efficiency characteristic curve of the fuel cell. If the waste heat of the auxiliary electrical devices, the battery, and possibly the continuous brake is calculated, the total cooling demand that can be plotted regarding the forward-looking range can be obtained

[0061] Figure 6 A schematic change curve of the driving performance range (FLH) under predictive control is shown, where the driving speed v (e.g., from speed prediction), the road slope FBS (e.g., from the map), and the ambient temperature T U (e.g., from network services) along the forward driving route s are shown. The parameters that can be calculated therefrom include: the estimated driving power ATL, the estimated fuel cell power BZL, the state of charge SOC of the battery, the waste heat of the fuel cell system The available cooling power (e.g., generated by driving wind) and the required fan turns on the BLZ.

[0062] Similarly, the change curve T of the expected ambient temperature can be obtained through a web-based weather service (e.g., from the cloud 8) U (t) and other weather data (e.g., rainfall). Using the thermal model of the cooling system, based on this data for the forward driving route, it can be calculated how the achievable cooling power of the cooling system will develop, and how the corresponding energy consumption characteristic values KW in ECO mode and Power mode will develop. For this purpose, according to the expected driving power of the forward driving route s, it is calculated whether the resulting expected fuel cell waste heat can be dissipated by means of all actuators (e.g., one or more pumps 6, one or more coolers 5, one or more fans 4, and one or more valves 11). If this cannot be achieved, it is determined that there is a limit value violation LV, and the expected fuel cell target power is corrected in the energy management system ENM.

[0063] With the help of the said information, the energy management system ENM can plan the optimal power trajectory P for the fuel cell system considering the driving route s and external environmental influencing factors S (t). For example, if the planning system already knows in advance that due to thermal management reasons, the fuel cell power BZL must be reduced on an uphill route (limit value violation LV of the thermal system within the forward-looking range), it can start the fuel cell earlier under conditions with a simpler cooling situation and provide the corresponding energy buffer in the high-voltage battery.

[0064] The said device and method can be applied to fuel cell vehicles, especially commercial vehicles, such as heavy commercial vehicles.

[0065] List of reference numerals

[0066] 1 Vehicle controller

[0067] 2 Interface

[0068] 3 Fan control

[0069] 4 Fan

[0070] 5 Cooler

[0071] 6 Pump

[0072] 7 Prediction module

[0073] 8 Cloud

[0074] 9 Mass flow distribution

[0075] 10 Consider the limitations of thermal management

[0076] 11 Valve

[0077] 12 modules

[0078] 13 modules

[0079] AFW Current driving resistance

[0080] ATL Driving power

[0081] BLZ Required fan switch-on

[0082] BZL Fuel cell power

[0083] ENM Energy management

[0084] FBS Road gradient

[0085] FLH Driving performance range

[0086] KF Characteristic curve

[0087] KF EW Characteristic curve with empirical values

[0088] KW Eigenvalue

[0089] KoW Correction value

[0090] LV Limit value violation

[0091] Total air mass flow

[0092] Air mass flow

[0093] Air mass flow generated by driving wind

[0094] Air mass flow through the fan

[0095] Mass flow for the fan

[0096] Pump mass flow

[0097] Cooling water mass flow

[0098] n Pump speed

[0099] P S Target power

[0100] P S (t) Expected curve of the target power, power trajectory

[0101] Waste heat of the fuel cell system

[0102] Heat output under ECO mode

[0103] Heat that can be dissipated through the cooler

[0104] Waste heat of the fan

[0105] Heat output under Power mode

[0106] s Driving route

[0107] SE simulation results

[0108] SOC State of charge

[0109] T KM Temperature of the cooling medium

[0110] T L Air inlet temperature

[0111] T U Ambient temperature

[0112] T U (t) Variation curve of the expected ambient temperature

[0113] T W Cooling water inlet temperature

[0114] v Driving speed

[0115] v(t) Variation curve of the expected driving speed

[0116] WLW Heat transfer coefficient.

Claims

1. A method for thermal management of a vehicle fuel cell system, wherein, Based on a physical model, taking into account the current driving condition of the vehicle and the existing environmental conditions, estimate the heat output of the entire cooling system of the vehicle. Characterized in that, Determine the heat output that can be dissipated in the ECO mode without activating one or more auxiliary electrical devices including at least one fan (4). And determine the heat output of the entire cooling system that can be dissipated in the Power mode with one or more auxiliary electrical devices including at least one fan (4) activated. Wherein, in the energy management system (ENM), based on the heat output Determine the target power (P S ) currently available from the fuel cell system, and determine whether the fuel cell system is operating in the ECO mode or the Power mode. Wherein, the amount of energy currently required by the auxiliary electrical devices required for cooling is determined by means of heuristic logic, thereby determining a characteristic value (KW), which represents how much electrical power must be input to dissipate a specific heat output. When the value is more than 1 kilowatt of electrical power required to dissipate each kilowatt of heat output, the power of the fuel cell system does not increase.

2. The method according to claim 1, characterized in that, When the value is such that significantly less than 1 kW of electrical power is required per kW of heat output, especially in the case of up to 0.2 kW of electrical power per kW of heat output, the energy management system (ENM) increases the requested fuel cell target power (P S ).

3. The method according to claim 1 or 2, characterized in that, For the current driving situation, the driving speed (v) and / or the cooling medium temperature (T KM ) are considered.

4. The method according to one of the preceding claims, characterized in that, The ambient temperature (T U ) is taken into account as the said environmental condition.

5. The method according to any one of the preceding claims, characterized in that According to the characteristic curve considering the current aging state of the fuel cell system, the energy management system (ENM) reversely calculates the possible electric power of the fuel cell and requests the electric power from the fuel cell.

6. The method according to one of the preceding claims, characterized in that, Based on the current waste heat of the fuel cell system Estimate the mass flow rate of the cooling medium provided by one or more pumps (6), which is considered together with the current driving conditions and the existing environmental conditions when estimating the heat that can be dissipated by one or more coolers (5). ​ 7. The method according to one of the preceding claims, characterized in that, When determining the additional waste heat required for the at least one fan (4), the current waste heat of the fuel cell system is taken into account and the heat that can be dissipated by one or more coolers (5).

8. The method according to claim 7, wherein The waste heat required by the at least one fan (4) Estimate the mass flow rate that the at least one fan (4) must provide Thereby determine the mass flow rate The energy-optimal distribution (9) on the fan (4) and the corresponding control (3) of the fan (4).

9. The method according to one of the preceding claims, characterized in that, Predict the forward driving route, wherein, according to the planned driving route, the change curve (v(t)) of the expected driving speed of the vehicle and the change curve (T U (t)) of the expected ambient temperature are determined through network-based traffic services and / or through a prediction module (7), wherein, using the thermodynamic model of the cooling system, based on these data for the forward driving route, it is determined how the cooling power achievable by the cooling system will develop, and how the corresponding characteristic value (KW) will develop in the ECO mode and the Power mode, and on this basis, considering the driving route and external environmental impacts, the optimal power trajectory (P S (t)) of the fuel cell system is planned.

10. A device for thermal management of a vehicle fuel cell system, comprising an energy management system (ENM) of the fuel cell system and a vehicle controller (1), which is configured to execute the method according to one of the foregoing claims.

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