Energy management of a fuel cell vehicle

Abstract

Method for operating an electric drive system of a motor vehicle, which has at least one fuel cell fed from a fuel tank of the motor vehicle and at least one traction battery, comprising Reading in and processing navigation data (11) comprising a current location of the motor vehicle, a destination of the motor vehicle, at least one route between the current location and the destination, and route information; Dividing (100) the at least one route into route sections (segments) within which at least one type of route information remains the same or varies only slightly; Determining (200) predicted consumption data (210) comprising an expected energy consumption and a possible charging power for each segment of the at least one route; Optimizing (400) the operating mode of the fuel cell for the operation of the fuel cell along the at least one route based on the predicted consumption data (210) taking into account a current state of charge (41) of the at least one traction battery and a current tank content (42) of the motor vehicle, wherein during the optimization (400) a modeling of the state of charge profile of the traction battery on the route and a determination of optimal sections for the operation of the fuel cell takes place.

Description

[0001] The invention relates to a method for operating a purely electrically powered motor vehicle with fuel cells (FC vehicle), as well as to an energy supply system for the motor vehicle designed to carry out the method.

[0002] In fuel cell-powered vehicles, a traction battery is used to absorb braking energy and maximize system performance during high power demands. The traction battery also enables the fuel cell to deliver a constant power output, which is necessary for its efficient operation, eliminating the need for a direct coupling between driving tasks and the fuel cell's power. In addition, such a battery buffers the fuel cell's power while it ramps up or down its power.

[0003] Due to the currently poor refueling infrastructure for fuel cell propulsion, the traction battery may have to ensure driving operation if hydrogen cannot be refueled. Therefore, such vehicles can also be equipped with an interface to charge the traction battery using an external charging option (e.g., a home power outlet or a charging station).

[0004] A relatively large amount of energy must always be left in the traction battery during driving to ensure its buffer function and system performance. This reduces the maximum range without hydrogen and impairs the efficiency of the traction battery.

[0005] It also happens that hydrogen is used unnecessarily to charge the traction battery, even though, taking into account the brake energy recovery, fuel cell operation would not have been necessary until the next destination with a charging station.

[0006] On the other hand, it may also happen that a hydrogen filling station is available on a route, but due to increased use of the traction battery, the hydrogen tank has not been emptied significantly when the filling station is reached.

[0007] Against this background, the object of the invention is to provide a method for operating a purely electrically powered motor vehicle with a fuel cell system and a traction battery and a system for carrying out the method, with which the efficiency of the drive system of the motor vehicle is increased and the range of the motor vehicle is optimized.

[0008] For plug-in hybrid vehicles (PHEVs), various methods for optimizing the interaction between electric and combustion engine drive have already been developed. These serve, for example, to avoid poor combustion engine efficiency at low loads and unnecessary engine starts, or to enable emission-free driving in urban areas.

[0009] EP 1 297 982 A2 discloses a hybrid vehicle with a navigation system which, based on route information from the navigation system, identifies restricted zones for vehicles emitting exhaust gases along the route and ensures that, before reaching such a zone, the vehicle's traction battery is sufficiently charged to drive through the zone without using the combustion engine.

[0010] DE 101 45 514 A1 describes a method for operating a vehicle with an energy source that feeds a DC voltage intermediate circuit connected to an electric motor.

[0011] US 2015 / 0 276 420 A1 describes a method for determining the anticipated energy use of the selected route based on energy consumption estimates of different segments.

[0012] DE 10 2013 000 367 A1 describes a method for operating a navigation device for a motor vehicle by specifying a destination, determining a route, the energy consumption, determining a speed profile and determining the energy consumption of the energy supply device.

[0013] DE 10 2017 006 158 A1 describes a method for operating an electrically powered vehicle with an electronic traction battery and a power generation unit.

[0014] DE 10 2010 062 866 A1 describes a method for generating an operating strategy for an electric vehicle with a range extender unit.

[0015] DE 10 2013 003 608 A1 describes a method for operating a fuel cell vehicle in a fleet, each fuel cell vehicle being equipped with a navigation device.

[0016] DE 10 2012 011 996 A1 describes a method and a device for optimizing the operation of a vehicle with at least one electric motor and at least one energy storage device.

[0017] DE 10 2011 018 182 A1 describes a self-learning assisted hybrid vehicle system which has a main power source, a supplementary power source and an electric motor or other mechanical system for driving the vehicle.

[0018] EP 1 932 740 A1 discloses a hybrid vehicle and a method for controlling it. A control unit determines the distance of the vehicle to a target charging station, sets upper and lower limits for the state of charge (SoC) of the vehicle's traction battery, and regulates the state of charge to maintain it within the range between the limits.

[0019] DE 10 2008 017 556 A1 proposes a charging and discharging control device for a hybrid vehicle and a control program device therefor. A navigation system calculates a route for the hybrid vehicle based on charging stations along the route and adapts a drive strategy to the route. If the charging station is a destination on an optimal route, the navigation system determines the one continuous section where EV travel to the charging station is possible and switches from HV travel to EV travel at the beginning of the section.

[0020] The latter two patent applications use a predictive operating strategy that uses map data and a route entered by the driver into the navigation device.

[0021] The present invention is based on the finding that a predictive operating strategy can also optimize the efficiency of a purely electric drive system with fuel cell and traction battery.

[0022] The invention relates to a method for operating an electric drive system of a motor vehicle, which has at least one fuel cell fed from a fuel tank of the motor vehicle and at least one traction battery.

[0023] In one embodiment, the at least one traction battery is also configured to be charged from an external power source, e.g., a charging column, a charging station, or a power outlet. In another embodiment, the at least one fuel cell is configured to deliver electrical energy to the at least one traction battery. In another embodiment, the at least one fuel cell is also configured to deliver electrical energy directly to the electric drive of the motor vehicle.

[0024] The method according to the invention comprises the following steps: Reading in and processing navigation data comprising a current location of the motor vehicle, a destination of the motor vehicle, at least one route between the current location and the destination, and route information; Dividing the at least one route into segments within which at least one type of route information remains the same or varies only slightly; Determining predicted consumption data comprising an expected energy consumption and a possible charging power for each segment of the at least one route; Optimizing the operating mode of the fuel cell along the at least one route based on the predicted consumption data, taking into account a current state of charge of the at least one traction battery and a current tank content of the motor vehicle. In one embodiment, the optimization additionally takes into account location data of charging stations for the at least one traction battery and / or filling stations for the fuel of the at least one fuel cell along the at least one route.

[0025] In a further embodiment, the optimization is preceded by a prioritization in which segments along the at least one route are identified within which the at least one fuel cell is preferably active and generates electrical energy.

[0026] In a first step of the method according to the invention, also referred to as "route segmentation," navigation data is read in and evaluated. In one embodiment of the method, the navigation data is provided by a navigation device.

[0027] The navigation data comprises a current location of the motor vehicle, a destination of the motor vehicle, at least one route between the current location and the destination, and route information. In one embodiment, the route information comprises an elevation profile of the at least one route or the gradient along the at least one route. In another embodiment, the route information comprises the route type (highway, country road, urban road, field path, etc.). In another embodiment, the route information comprises information about speed limits along the at least one route. In another embodiment, the route information comprises information about the locations or number of stop signs and / or traffic lights along the at least one route.In a further embodiment, the route information includes information about current traffic volume along the at least one route ("online traffic jam information"). In a further embodiment, the route information includes information about the locations of filling stations for the fuel of the at least one fuel cell, e.g., hydrogen filling stations, or charging columns or stations along the at least one route.

[0028] Based on the navigation data, the at least one route is divided into route sections (segments) based on the expected energy consumption. These segments have similar route information, i.e., within which at least one type of route information remains the same or varies only slightly. Two adjacent segments each have significantly different expected energy consumption.

[0029] In a second step of the method according to the invention, also referred to as "consumption prediction," an expected energy consumption and a possible charging power are determined for each segment of the at least one route. In one embodiment, the driving energy required for each route section is determined using a characteristic value determined by a measurement for the motor vehicle. When determining the expected energy consumption, "negative consumption" on downhill segments is also taken into account in order to plan for braking recuperation. In one embodiment, segments with maximum power requirements are identified and marked.

[0030] Then, for each segment, the possible charging power P(Charge) is determined from the power of the fuel cell at the most efficient operating point P(FC) and the power P(Drive) required for the driving task, where P(Charge)=P(FC) - P(Drive).

[0031] In an optional third step of the method according to the invention, also referred to as “prioritization,” the drive type is prioritized for each segment, i.e., a determination is made as to whether the at least one fuel cell should preferably be active or inactive. The at least one fuel cell is preferably used on longer stretches of road with constant power demand so that it does not have to be switched on and off frequently. Furthermore, the at least one fuel cell is preferably used when the remaining distance is very long, so that it is clear that the range achievable with the traction battery alone will not be sufficient. The at least one fuel cell is also preferably used when the electric driving mode has a rather low level of efficiency, such as when driving on the motorway or uphill, where high power demand and only low brake recuperation are to be expected.

[0032] In a fourth step of the method according to the invention, also called "optimization," the charge level curve of the traction battery along the route is modeled, taking into account the current charge level of the traction battery and the current tank content, and optimal sections for fuel cell operation are determined. In one embodiment of the method, optimization is carried out to maximize the overall range of the motor vehicle. In another embodiment of the method, optimization is carried out to maximize the available driving performance of the motor vehicle. To ensure maximum driving performance, a higher charge level of the traction battery can be planned, for example, before motorway sections.

[0033] In one embodiment, the optimization also takes into account the availability of filling stations for the fuel of the at least one fuel cell, e.g. hydrogen filling stations, and / or the availability of external charging options such as charging stations or charging columns along the route. In this way, the “perceived total range” can be increased by reducing the number of necessary stops for refueling or by avoiding detours to filling stations. If, for example, an intermediate destination is located at a hydrogen filling station, fuel cell operation can be prioritized on the section before the route. If there is a charging column at the destination but no hydrogen filling station, fuel cell operation can be dispensed with on the section before the route. In one embodiment of the method, the driver is provided with information on how to plan his filling station stops.In one embodiment, the driver is notified that they should approach a specific hydrogen refueling or charging station along their route. For example, if there is insufficient hydrogen available for an upcoming section of the route at maximum speed, a refueling stop can be brought forward and the traction battery can be charged to maximum until that point.

[0034] The result of the method according to the invention is a recommendation for the operating mode of the at least one fuel cell, which is incorporated into the control of the electric drive system of the motor vehicle, in particular the control of the activity and the power output of the at least one fuel cell.

[0035] The invention further relates to an energy supply system for an electrically powered motor vehicle, which is configured to carry out the method according to the invention. In addition to at least one traction battery, which is configured to deliver energy to an electric drive of a motor vehicle and to absorb brake recuperation energy, and at least one fuel cell, which is configured to deliver electrical energy to the traction battery, the system comprises a control unit, which is configured to receive and process navigation data and to provide a recommendation for the operating mode of the at least one fuel cell. In one embodiment, the control unit is also configured to control the energy generation of the at least one fuel cell and to regulate its power output.In a further embodiment of the system, the at least one fuel cell is also configured to supply energy to the electric drive of the motor vehicle. In a further embodiment, the at least one traction battery is also configured to be charged from an external power source, e.g., a charging column, a charging station, or a power outlet.

[0036] The advantages of the present invention include optimizing the vehicle's range and increasing the efficiency of the fuel cell system through maximum, situation-specific use of the traction battery. Furthermore, driver comfort is increased by assisting in planning refueling stops and avoiding unnecessary refueling stops. Further advantages will become apparent from the description and the drawing.

[0037] An embodiment of the invention is schematically illustrated in the drawing and will be further described with reference to the drawing. It shows: Fig. 1 a schematic representation of an embodiment of the method according to the invention.

[0038] Fig. Figure 1 schematically shows the sequence of one embodiment of the method according to the invention. First, navigation data 11 is read in, for example, from a navigation system. The navigation data 11 includes, for example, a current position of the vehicle, a route to a destination, a remaining distance to the destination, speed limits along the route, a road gradient along the route, online traffic jam information along the route, the number of stop signs and traffic lights along the route, and the locations of hydrogen filling stations / charging stations along the route.

[0039] Based on the navigation data 11, the route is segmented 100. The route is divided into sections with significantly different energy consumption. For example, the route can be divided into segments of the following types: 0 traffic jam 1 city 2 motorway, downhill 3 Motorway 4 Highway, uphill 5 Country road, downhill 6 Country Road 7 Country road, uphill 8 City, downhill 9 City, uphill 10 City, high stop density 11 Motorway, open (no speed limit) 12 Third-party transport or segment type unknown (e.g. route guidance from a backend)

[0040] As a result, segment data 110 is obtained which contains information about the segments of the route, e.g. number of segments, start and end or position and length of each individual segment as well as its segment type (0-12).

[0041] A consumption prediction 200 is derived from the segment data 110 using consumption indicators 21. The consumption indicators 21 include, for example, typical consumption values ​​for the different segment types and typical charging power values. The results of the consumption prediction 200 include expected consumption data 210 for the individual route sections according to drive type, e.g., the purely electric energy consumption for each route section and the possible charging power of the fuel cell for each route section. Segments with maximum power requirements can also be marked.

[0042] In the illustrated embodiment, following the consumption prediction 200, a prioritization 300 of the drive type (with / without fuel cell activity) for the individual route sections is performed based on the consumption data 210. This prioritization takes into account, for example, that the fuel cell should be used preferentially on long, constant route sections, or when the remaining distance is still very long, or when pure electric driving has a rather low efficiency.

[0043] Using the prioritized data 310, an optimization 400 is then performed. The current state of charge of the traction battery 41 and the current tank content 42 are taken into account. Furthermore, location data 43 of hydrogen filling stations and charging columns along the route are taken into account. The location data 43 is contained in the navigation data 11. By modeling the state of charge profile, the optimal route section for fuel cell operation can be selected. If, for example, an intermediate destination is located at a hydrogen filling station, fuel cell operation can be preferred on the previous route section. If there is a charging column at the destination but no filling station, fuel cell operation can be dispensed with.

[0044] The result of optimization 400 is an operating recommendation 410 for the fuel cell, which is transmitted to a control unit of the motor vehicle's energy supply system and taken into account by the control unit when controlling the operating state and regulating the power output of the fuel cell. The operating recommendation 410 can include a recommendation for the current operating state of the energy supply system, for example: 0 SoC hold 1 Driving electric (EV) 2 Charge LIST OF REFERENCE SYMBOLS: 11 Navigation data 21 consumption figures 41 current charge level of the traction battery 42 current tank contents 43 Location data of petrol stations / charging stations 100 route segmentation 110 segment data 200 Consumption prediction 210 Consumption data 300 Prioritization 310 prioritized data 400 Optimization 410 Operating recommendation for fuel cells

Claims

[1] Method for operating an electric drive system of a motor vehicle, which has at least one fuel cell fed from a fuel tank of the motor vehicle and at least one traction battery, comprising Reading in and processing navigation data (11) comprising a current location of the motor vehicle, a destination of the motor vehicle, at least one route between the current location and the destination, and route information; Dividing (100) the at least one route into route sections (segments) within which at least one type of route information remains the same or varies only slightly; Determining (200) predicted consumption data (210) comprising an expected energy consumption and a possible charging power for each segment of the at least one route; Optimizing (400) the operating mode of the fuel cell for the operation of the fuel cell along the at least one route based on the predicted consumption data (210) taking into account a current state of charge (41) of the at least one traction battery and a current tank content (42) of the motor vehicle, wherein during the optimization (400) a modeling of the state of charge profile of the traction battery on the route and a determination of optimal sections for the operation of the fuel cell takes place. [2] Method according to claim 1, wherein the optimization (400) additionally takes into account location data (43) of charging stations for the at least one traction battery and / or filling stations for the fuel of the at least one fuel cell along the at least one travel route. [3] Method according to claim 1 or 2, wherein the optimization (400) is preceded by a prioritization (300) in which segments along the at least one route are identified within which the at least one fuel cell is preferably active and generates energy. [4] Method according to one of the preceding claims, wherein the route information comprises an elevation profile of the at least one travel route or a gradient along the at least one travel route. [5] A method according to any one of the preceding claims, wherein the route information comprises the route type along the at least one travel route. [6] A method according to any one of the preceding claims, wherein the route information comprises information about speed limits along the at least one travel route. [7] A method according to any one of the preceding claims, wherein the route information comprises information about locations or numbers of stop signs and / or traffic lights along the at least one travel route. [8] Method according to one of the preceding claims, wherein the route information comprises information about a current traffic volume along the at least one travel route. [9] Method according to one of the preceding claims, wherein the optimization (400) maximizes the total range of the motor vehicle. [10] Method according to one of the preceding claims, wherein the optimization (400) maximizes the power of the motor vehicle available for driving. [11] Method according to one of the preceding claims, wherein the number of refueling stops of the motor vehicle along the at least one route is minimized during the optimization (400). [12] Energy supply system for a purely electrically powered motor vehicle, comprising at least one traction battery configured to deliver energy to an electric drive of the motor vehicle and to absorb brake recuperation energy; at least one fuel cell configured to deliver electrical energy to the traction battery; and a control unit configured to receive and process navigation data (11) and to provide a recommendation (410) according to the method according to one of claims 1 to 11 for the operating mode of the at least one fuel cell. [13] Energy supply system according to claim 12, wherein the control unit is also arranged to control and regulate the energy generation of the at least one fuel cell. [14] Energy supply system according to claim 12 or 13, wherein the at least one fuel cell is also arranged to deliver energy directly to the electric drive of the motor vehicle. [15] Energy supply system according to one of claims 12 to 14, wherein the at least one traction battery is also adapted to be charged from an external power source.

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