Electric vehicle operation method

Abstract

The invention relates to a method for operating an electric vehicle (1) equipped with a fuel cell system (2) and a traction battery (3). The method according to the invention is characterized in that a target state of charge of the traction battery (3) is specified on the basis of the terrain around the vehicle (1), for which purpose the position of the vehicle (1) is determined and height information within a specified circumference centered on the vehicle (1) is acquired from a digital map, from which the probability of occurrence of an uphill and / or downhill section is deduced, the target state of charge is then preset as a function of the probability of the uphill and / or downhill road segments.

Description

Technical Field

[0001] The invention relates to a method for operating an electric vehicle equipped with a fuel cell system and a traction battery. Background Art

[0002] A typical problem for hybrid vehicles with a main drive and a traction battery (also called HV battery or high-voltage battery) is how to distribute the power between the battery and the other drive units. A prerequisite for optimal battery utilization is the ability to reliably assess sections where the battery power consumption increases and sections where a large amount of recuperation energy is generated and needs to be stored in the battery.

[0003] For hybrid vehicles equipped with an internal combustion engine and an additional battery, EP 3 124 302 A1 describes a control device that can adjust the battery's state of charge accordingly before going uphill or downhill according to the route pre-planned by the navigation system, thereby achieving energy optimization. The problem with the structure described is that it can only work when driving along the route planned by the navigation device. The prerequisite is that the navigation system is used and the user actively enters the route destination. In addition, the vehicle driver is required to strictly follow the route and not deviate from the planned route. Once deviated, complex recalculations are required, which may no longer achieve the optimal adjustment of the battery's state of charge when the route is changed. If the navigation system is not used, the method cannot be used.

[0004] Reference can also be made to DE 10 2020 128 221 A1 for the prior art. It describes a fuel cell vehicle, i.e. an electric vehicle equipped with a fuel cell. In order to prevent a reduction in vehicle speed due to a power reduction when the fuel cell reaches its maximum power, a route optimization can be performed here so that steep uphill slopes that could lead to power limitations can be avoided, depending on the load of the trailer towed by the vehicle. Summary of the invention

[0005] The object of the present invention is now to specify an improved operating method for an electric vehicle equipped with a fuel cell system and a traction battery in order to reduce the risk of deceleration and to optimize the energy utilization.

[0006] This object is achieved according to the invention by a method having the features of claim 1, in particular the characterizing part of claim 1. Advantageous refinements and developments are derived from the dependent claims.

[0007] The method according to the present invention provides for presetting a target state of charge / target state of charge of the battery according to the terrain around the vehicle. For this purpose, the vehicle position is determined, for example, by a satellite navigation system, and altitude information within a preset circumference with the vehicle as the center is obtained from a digital map. The probability of occurrence of uphill and / or downhill sections is then inferred based on this altitude information, and the target state of charge is subsequently preset based on the probability of uphill and / or downhill sections.

[0008] Unlike planning energy distribution for a main route that has been entered into the navigation system, the method according to the invention is able to make a reasonable assessment and adjust the target state of charge accordingly, without relying on the use of navigation and without being restricted to whether the vehicle maintains the planned main route. This allows both optimal storage of the generated energy and the ability to draw the required power from the battery when necessary, which exceeds the maximum power of the fuel cell system. This optimizes the overall energy consumption on the one hand and reduces the risk of slowing down, for example when driving uphill.

[0009] According to a particularly advantageous embodiment of the method according to the invention, provision can be made for the target state of charge to be preset to a range of above 50% to 60% of the battery capacity when the probability of an uphill section is higher than that of a downhill section. According to a preferred development, the preset value can reach above 80% of the battery capacity. Thus, energy generated during recuperation (e.g. during braking) can be stored in the battery. However, since the probability of an uphill section is higher than that of a downhill section, it can be inferred that the vehicle is now traveling on a relatively flat area and at most may encounter an uphill section, for example when leaving a large valley or the like. Therefore, a relatively high state of charge of preferably about 80% or in particular above 80% of the battery capacity is reasonable, since a large amount of energy generated by recuperation does not have to be taken into account. Instead, it must be taken into account that power needs to be drawn from the traction battery so that when an uphill section, which is much more likely to be encountered than a downhill section, can be driven with the additional power provided by the traction battery, thereby avoiding a reduction in speed.

[0010] According to another very advantageous design of the method of the invention, it can also be provided that, when the probability of a downhill section is higher than that of an uphill section, the target state of charge is preset to a battery capacity range below 50% to 60%, and according to an advantageous improvement, it can be preset to a battery capacity below 30%. If the probability of a downhill section is higher than that of an uphill section, the vehicle is on a certain high ground (such as a plateau), and the probability of driving down a downhill section is significantly higher than that of climbing up an uphill section. In this case, it is very likely that a large amount of recuperation energy will be generated during braking. In this case, a lower battery state of charge (below 30%) will ensure that all or at least most of the energy generated can be stored for subsequent driving.

[0011] According to another embodiment of the method according to the invention, it can now be provided that the target state of charge is preset to a range of 50% to 60% of the battery capacity when the probability of an uphill section is approximately the same as the probability of a downhill section. This medium state of charge of the traction battery can therefore be advantageous when the probability of an uphill section and a downhill section is judged to be similar based on the determined terrain. This situation usually occurs in hilly or mountainous terrain, where uphill sections and downhill sections usually alternate on most possible routes. Keeping the traction battery in a medium state of charge can then provide both power support and energy storage, where the probability of these two situations being expected to occur is similar.

[0012] A particularly advantageous embodiment of the method according to the invention can provide that the radius of the circumference of the terrain determination is approximately 50 kilometers. The terrain is thus determined within this circumference centered on the vehicle in order to prepare for possible uphill and downhill sections that may occur there (preferably in the manner described above). Here, according to an advantageous embodiment of the method according to the invention, the coverage angle of this circumference can be preset to 360° centered on the vehicle, i.e. the terrain is evaluated in all directions from the vehicle. This can be particularly useful when no navigation system is used and no other information about the potential travel destination is available.

[0013] An advantageous design of the method according to the invention can be applied to the following situations: routes planned by a navigation system, known destinations without a planned route, or routes that have been frequently traveled in the past when the vehicle was in a similar position. In this case, the coverage angle of the circular range can be limited to a certain angle interval along the potentially expected direction of travel. Therefore, this is not limited to planning the battery charge state that provides ideal conditions as accurately as possible according to a specific main route. Instead, the circular range for determining the terrain is correspondingly reduced according to the approximate direction of travel. This reduction can be preset, for example, according to other parameters in the following way, that is, the angle interval is reduced to 90° to 270° along the direction of travel. 90° means that, starting from the vehicle, according to the direction of travel, a sector area of ​​45° is taken on the left and right sides of the direction of travel; 270° means that 135° is taken on both sides. As a result, on the one hand, the workload of the terrain assessment is reduced, and on the other hand, large height differences in the area behind the direction of travel (which may lead to steeper downhill or uphill sections) can be ignored, thereby improving the assessment quality.

[0014] Depending on whether the driving direction is a planned route from the navigation device, past estimated data, or a destination location obtained from a calendar entry, for example, the angle may be restricted to different degrees. For a relatively accurate route preset by the navigation device, a smaller angle interval, i.e., a range of 90° to 120°, may be selected; for a relatively uncertain preferred driving direction assumption based on past trips, for example, a larger angle interval, e.g., 200° to 270°, may be selected accordingly to ensure the rationality of the operation strategy.

[0015] In summary, the hydrogen consumption can be reduced by optimizing the utilization of the traction battery. Furthermore, in particular when an uphill section is expected, the optimized utilization of the traction battery can ensure a higher vehicle performance, i.e., for example, prevent a reduction in vehicle speed. In addition to this, any of the above-described embodiments of the method according to the invention ultimately also allows for a protective use of the traction battery and the fuel cell system, thereby achieving an extension of the service life through efficiency-optimized use. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Further advantageous designs of the method according to the invention also result from the following detailed description of the embodiments with reference to the accompanying drawings, in which:

[0017] Figure 1 A schematic vehicle for performing the method of the present invention is shown;

[0018] Figure 2 A first example situation is shown where the vehicle is in a flat area;

[0019] Figure 3 Another example situation where the vehicle is at a plateau is shown;

[0020] Figure 4 A third situation is shown where the vehicle is in a hilly or mountainous area. DETAILED DESCRIPTION

[0021] Figure 1 The illustration of is very schematically a vehicle 1 which may be equipped with a fuel cell system 2 and a traction battery 3. The vehicle is a commercial vehicle, here a truck consisting of a tractor 4 and a semitrailer 5. However, other types of vehicles are also conceivable, with or without a trailer, and may be commercial vehicles or passenger cars.

[0022] The vehicle 1 is equipped with a GPS sensor 6, which is schematically shown here, in the area of ​​its tractor 4. This allows the vehicle 1 to determine its own position. The terrain around the vehicle 1 can now be determined based on the position of the vehicle 1 determined by the GPS sensor 6, by means of an onboard control unit and / or an offboard server (not shown here) (e.g., in the cloud). For this purpose, altitude information is read from a digital map stored in the vehicle 1 or on an offboard server, and if no specific information about potential driving sections or driving directions is available, this altitude information is evaluated within a predefined circumference (e.g., 50 kilometers) centered on the vehicle 1. By comparing the altitude difference between the current position of the vehicle 1 and the potential driving area, uphill and / or downhill sections can be inferred, so that the probability of uphill sections and downhill sections within this predefined circumference can be determined. The target state of charge of the traction battery 3 is now predefined based on the probability of uphill and downhill sections.

[0023] The following will be combined Figures 2 to 4 Three purely exemplary situations are described.

[0024] according to Figure 2 The example shows that the vehicle 1 is in an area that is essentially flat but with higher surrounding terrain. The potential uphill slope measured within the circumference is therefore 838 meters, while the potential downhill slope is only 45 meters. The example shown here purely schematically shows the section of the A5 motorway from Karlsruhe to Basel. In this area, the probability of encountering uphill slopes is relatively high, while the probability of encountering downhill slopes is very low. Therefore, the target state of charge of the traction battery 3 is preset to a high level, for example above 80% of the battery capacity. This makes it possible to achieve an ideal utilization of the traction battery 3. Since the expected downhill slopes are very limited, a correspondingly fully charged battery can be used without the risk of not being able to store the recovered energy. At the same time, the high state of charge of the traction battery 3 can provide electric drive support for the vehicle 1 on the uphill slopes that are expected to be encountered with great probability.

[0025] The second embodiment (see Figure 3 ) Figure 1The same representation logic shows a driving situation on a plateau, where the vehicle 1 is already at a higher altitude, so that the expected height difference for the uphill section accumulates to approximately 380 meters, while the expected height difference for the downhill section accumulates to nearly three times the value, approximately 1,160 meters. The terrain example in this case is taken from the B500 federal highway (the so-called "Black Forest Viaduct"). In this case, the probability of encountering a downhill section is very high, while the probability of an uphill section is lower. Therefore, the target state of charge of the traction battery 3 can be set relatively low here, for example, about 30% of the battery capacity, and even lower in similar scenarios with a lower probability of uphill sections. In other words, it must be assumed in this case that a downhill section is likely to be encountered. At the same time, wear-free braking in generator mode with the help of the electric motor generates considerable recuperation energy. The very low target state of charge of the traction battery 3 allows the recuperation energy to be stored completely or at least largely, thus achieving energy-saving operation.

[0026] The third example (such as Figure 4 ) shows a situation where a vehicle is driving on a mountainous or hilly road section, and the scene is taken from the "Kassel Mountains" section of the A7 highway. Within the corresponding circumference, the terrain shows that the cumulative height difference of the uphill section is about 800 meters, while the cumulative height difference of the downhill section is similar. Therefore, it can be assumed here that the vehicle will encounter not only downhill sections but also uphill sections. In this case, the target charge state of the traction battery 3 is preset to a medium level, for example in the range of 50% to 60% of the battery capacity. Therefore, this medium charge state can both support driving on the uphill section and store at least most of the recuperation energy on the downhill section so that it can be reused on the subsequent uphill section.

Claims

1. A method for operating an electric vehicle (1), the electric vehicle being equipped with at least one fuel cell system (2) and at least one traction battery (3), It is characterized in that The target state of charge of the at least one traction battery (3) is preset according to the terrain around the vehicle (1). To this end, the position of the vehicle (1) is determined and the altitude information within a preset circumference with the vehicle (1) as the center is obtained from a digital map, and the probability of the occurrence of uphill and / or downhill sections is inferred, and then the target state of charge is preset according to the probability of the uphill and / or downhill sections.

2. The method according to claim 1, characterized in that In the case where the probability of an uphill section is higher than that of a downhill section, the target state of charge is preset to be higher than 50% to 60% of the battery capacity.

3. The method according to claim 2, characterized in that The target state of charge is preset to be higher than 80% of the battery capacity.

4. The method according to claim 1, 2 or 3, characterized in that: In the case where the probability of a downhill section is higher than that of an uphill section, the target state of charge is preset to be lower than 50% to 60% of the battery capacity.

5. The method according to claim 4, characterized in that The target state of charge is preset to be less than 30% of the battery capacity.

6. The method according to any one of claims 1 to 5, characterized in that For a situation where the probabilities of the uphill section and the downhill section are similar, the target state of charge is preset to be about 50% to 60% of the battery capacity.

7. The method according to any one of claims 1 to 6, characterized in that A circular range with a radius of about 50 kilometers and the vehicle (1) as the center is preset.

8. The method according to any one of claims 1 to 7, characterized in that A circular range with the vehicle (1) as the center and a coverage angle of 360° is preset.

9. The method according to any one of claims 1 to 7, characterized in that The coverage angle of the circular range is limited to an angle interval along the expected driving direction in the following situations: a driving route planned by a navigation system, a known destination without a planned driving route, or a driving route that the vehicle (1) has frequently traveled in the past when it was in the same position.

10. The method according to claim 9, characterized in that The limited angle interval is preset to be 90° to 270°.

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