Method for operating a motor vehicle with a fuel cell system and with at least one energy storage device

Abstract

Method for operating a motor vehicle with a fuel cell system and with at least one energy storage device, wherein the fuel cell system and the energy storage device are configured to provide electrical power to at least one electric drive motor, comprising the steps of: - Detecting an impending traffic jam; and - Adjusting the hybridization ratio of energy storage device and fuel cell system depending on the impending traffic congestion, and a) furthermore encompassing the steps: - Determining at least one parameter that represents the amount of energy required by at least one drive motor until the traffic jam; - Adjusting the hybridization ratio based on at least one parameter, and / or b) furthermore, the following steps are included: - Determining the extent of the traffic jam; - Adjusting the hybridization ratio depending on the extent of the traffic congestion, and / or c) furthermore, the following steps are included: - Determining the amount of electrical energy to be provided by the fuel cell system in the traffic jam, which is to be temporarily stored in the energy storage device during the traffic jam; and - Adjusting the hybridization ratio, whereby the hybridization ratio is adjusted so that the amount of electrical energy provided by the fuel cell system in traffic congestion can be temporarily stored in the energy storage device, and / or d) furthermore, the following step: - Adjusting the hybridization ratio, wherein the hybridization ratio is adjusted so that the energy storage device has a charge state that is below a stagnation limit charge state.

Description

[0001] The technology disclosed herein relates to a method for operating a motor vehicle with a fuel cell system and with at least one energy storage device.

[0002] Motor vehicles with a fuel cell system and at least one energy storage device are known as such. The power output of the fuel cell system can be calculated, for example, from the current driver demand and the current on-board electrical system load. To avoid overloading the fuel cell system with power peaks from short-term accelerations, the power demands on the fuel cell system can be filtered, and these short power peaks can be drawn from a high-voltage battery.

[0003] German patent application DE 10 2014 217 780 A1 discloses a method for the predictive operation of a fuel cell in which a high-voltage storage device provides the energy to power the motor vehicle during a traffic jam.

[0004] A preferred function of the technology disclosed herein is to reduce or eliminate at least one disadvantage of previously known solutions. It may also be a preferred function of the technology disclosed herein to provide a method for operating a motor vehicle that exhibits good or better efficiency than previously known systems.

[0005] Further preferred applications may arise from the advantageous effects of the technology disclosed herein. The application(s) is / are solved by the subject matter of claim 1. The dependent claims represent preferred embodiments.

[0006] The technology disclosed herein relates to a method for operating a motor vehicle with a fuel cell system and with at least one energy storage device.

[0007] The technology disclosed here relates, among other things, to a fuel cell system with at least one fuel cell. The fuel cell system is intended, for example, for mobile applications such as motor vehicles, in particular for providing energy to at least one drive motor for propelling the vehicle. In its simplest form, a fuel cell is an electrochemical energy converter that converts fuel (e.g., hydrogen) and oxidizing agents (e.g., air, oxygen, and peroxides) into reaction products, thereby producing electricity and heat.

[0008] An energy storage device is a device for storing electrical energy. For example, the energy storage device can be a high-voltage storage system. The energy storage device can expediently be designed as a battery, particularly a high-voltage battery. Alternatively or additionally, supercapacitors (SCs) can also serve as energy storage devices.

[0009] The energy storage device and the fuel cell system are designed to provide electrical power to at least one drive motor, preferably to all electrical consumers of the motor vehicle.

[0010] The at least one electric drive motor can be an electric motor that contributes to the propulsion of the vehicle. Preferably, the drive motor is an electric motor that can feed electrical energy back to the energy storage device via recuperation. Likewise, the vehicle disclosed herein can comprise several electric drive motors. In the technology disclosed herein, the term "at least one drive motor" encompasses embodiments with "one drive motor," with "several drive motors," and with "one or more drive motor(s) together with at least one or even all auxiliary consumers" of the vehicle. The auxiliary consumers can be auxiliary consumers of the fuel cell system (e.g., oxidizer feeder) or of the vehicle (e.g., air conditioning).

[0011] The electric drive motor, the energy storage device, and the fuel cell system are interconnected via appropriate power electronics. The energy storage device and the fuel cell system are specifically designed to supply the electric current necessary for propelling the vehicle to the electric drive motor via appropriate lines.

[0012] The procedure disclosed here includes the following step: - Detecting an impending traffic jam.

[0013] A traffic jam, as defined by the technology disclosed here, can also be called a congestion and generally refers to a severely slowed or completely stopped flow of traffic on a roadway. This means, in particular, that the number of vehicles per unit of time or per distance exceeds a predetermined threshold. Specifically, a traffic jam exists when the traffic, i.e., the vehicles, is moving at a speed of less than 40 km / h, especially less than 20 km / h, and preferably less than 12 km / h. In such a traffic jam, the total power requirement of the vehicle for propulsion and all auxiliary consumers can be less than 20%, less than 10%, or less than 5% of the rated power of the fuel cell system. A future or imminent traffic jam is a traffic jam that already exists but in which the vehicle is not yet located.An impending traffic jam, as defined by the technology disclosed here, can also, in one configuration, be a predicted traffic jam in front of a red light, provided that it is accompanied, for example, by a waiting time of more than 2 minutes.

[0014] Methods for detecting impending traffic jams are known from the state of the art. For example, traffic jams can be detected using Floating Car Data (FCD) or Floating Phone Data (FPD) and / or stationary detection systems. Information about such a jam can be transmitted to the vehicle via various communication channels and formats. For instance, traffic jam information can be generated and transmitted to the vehicle via the Traffic Message Channel (TMC) or other traffic telematics systems. Vehicle-to-vehicle communication that provides information about a traffic jam is also conceivable. Navigation systems already installed in vehicles use such methods for detecting traffic jams. However, other methods for detecting impending traffic jams are also conceivable.

[0015] Preferably, the detection of a traffic jam includes the detection or determination of the exact location and extent of the traffic jam. The extent of the traffic jam, as defined by the technology disclosed herein, can be characterized, among other things, by the following parameters: length and / or duration of the traffic jam, average speed of traffic flow within the traffic jam, number of motor vehicles per lane, etc. Preferably, the extent of the traffic jam is defined by the length of the jam and the average speed of traffic flow within it.

[0016] The procedure disclosed herein further includes the step: - Adjusting the hybridization ratio of energy storage device and fuel cell system depending on the impending traffic jam before arriving at the traffic jam afterwards.

[0017] The hybridization ratio indicates how much power is supplied to the at least one electric drive motor (preferably all electrical consumers of the vehicle) by the at least one energy storage device and how much power is supplied to the at least one electric drive motor (preferably all electrical consumers of the vehicle) by the fuel cell system. Thus, the hybridization ratio denotes the proportion of electrical power that the fuel cell system and the energy storage device, respectively, provide to the at least one electric drive motor, preferably relative to the total electrical energy consumption of the vehicle. The hybridization ratio H can, for example, be defined as H=PbatPFC where Pbat, the power supplied to the at least one electric drive motor by the energy storage device; and PFC is the power supplied by the fuel cell to at least one electric drive motor.

[0018] However, other definitions are also conceivable.

[0019] Adjusting the hybridization ratio can, in particular, include the steps of increasing the electrical power supplied to the at least one drive motor by the energy storage device before arriving at the traffic jam, and / or reducing the electrical power supplied to the at least one drive motor by the fuel cell system before arriving at the traffic jam. For example, the electrical power supplied by the fuel cell system can be reduced so that the fuel cell system provides no or only a small portion of the power to the vehicle's electrical consumers. Preferably, the fuel cell system does not charge the energy storage device at this time.In other words, it may be provided that at this time the fuel cell system produces less than 100% of the vehicle's electric load and that electrical energy for the vehicle's electrical consumers, in particular for the at least one drive motor, is taken from the at least one energy storage device.

[0020] The technology revealed here may further include the following steps: - Determining at least one parameter representing the amount of energy required by at least one drive motor, preferably by all electrical consumers, from the current position of the motor vehicle until the impending traffic jam; and - Adjusting the hybridization ratio before arriving at the traffic jam based on at least one parameter.

[0021] The at least one parameter representing the required amount of energy can, for example, be the distance and / or the time until the impending traffic jam. However, other parameters are also conceivable. Preferably, the method disclosed here includes the step of determining, based on the at least one parameter, the amount of energy required to operate the motor vehicle until the impending traffic jam. The calculations to be performed for this purpose are familiar to those skilled in the art and can, in addition to the aforementioned parameters, also include further information such as the exact route (e.g., uphill, downhill, etc.), the predicted consumption of auxiliary consumers, the efficiencies of the various components, etc.

[0022] The technology revealed here may further include the following steps: - Determining the extent of the traffic jam; - Adjusting the hybridization ratio before arriving at the traffic jam, depending on the extent of the traffic jam.

[0023] In particular, the amount of electrical energy that the fuel cell system will supply to the energy storage device during the traffic jam can be determined (preferably based on parameters indicative of the extent of the traffic jam). This energy is to be temporarily stored in the energy storage device during the traffic jam. If the amount of energy to be supplied to the energy storage device during the traffic jam is known so that the fuel cell system can operate at an energy-efficient point, the hybridization ratio can be adjusted before arriving at the traffic jam so that the energy storage device can absorb this amount of energy even while the traffic jam is in progress. The current storage capacity of the energy storage device can also be determined for this purpose.The difference between the current storage capacity and the storage capacity required during the traffic jam results in a delta by which the energy storage device should be discharged before reaching the traffic jam. The hybridization strategy can then increase the proportion of electrical power drawn from the energy storage device so that it has the required storage capacity at the time of the traffic jam. Preferably, the hybridization ratio can be adjusted before arriving at the traffic jam so that the amount of electrical energy provided by the fuel cell system in the traffic jam can be temporarily stored in the energy storage device during the traffic jam. However, it is also possible that the current storage capacity is already sufficient for the charging process during the traffic jam, in which case the hybridization ratio can remain unchanged.

[0024] The technology revealed here may also include the following steps: - Adjusting the hybridization ratio before arriving at the traffic jam, wherein the hybridization ratio is adjusted so that the energy storage device has a charge state below a congestion limit charge state before arriving at the traffic jam.

[0025] The stagnation limit state of charge (SoC) can be a state of charge (also called state of charge or SoC) of at least one energy storage device that can absorb enough energy from the fuel cell system during traffic jams so that the fuel cell system itself can operate predominantly at an energy-efficient operating point. For example, the stagnation limit state of charge (SoC) STAU 5% or 10% or 20% or 30% of the maximum storage capacity.

[0026] The method disclosed here may include the step of calculating the electrical power (P) produced by the fuel cell system in the traffic jam. BZ,jThe operating point is limited to 1% to 40% of the rated power of the fuel cell system, preferably to 3% to 20% of the rated power of the fuel cell system, and particularly preferably to 6% to 10% of the rated power of the fuel cell system. Preferably, the fuel cell system is operated at an operating point or load point where it can provide electrical power with high efficiency. Preferably, the electrical power provided by the fuel cell system during a traffic jam is supplied to the at least one drive motor. Typically, at such a high-efficiency load point, the fuel cell system produces more electrical power than the at least one drive motor requires during a traffic jam. This additional electrical power can be temporarily stored in the energy storage device using the technology disclosed herein.This usually improves the overall efficiency of the motor vehicle.

[0027] The method disclosed herein may include the step whereby the electrical power provided by the energy storage device before arrival at the traffic jam is increased only if the state of charge of the energy storage device is above a lower state of charge limit.

[0028] In other words, the technology disclosed herein relates to a method for the efficient operation of a motor vehicle with a fuel cell system and at least one energy storage device. During a journey, the navigation system (e.g., via GPS) receives information that a traffic jam is located approximately 10 km from the current position. The motor vehicle will be stationary for most of the time in the traffic jam. According to the technology disclosed herein, the motor vehicle can be supplied with electrical power from the fuel cell system while in the traffic jam. Advantageously, the fuel cell system is operated at a load point where it exhibits high efficiency. Typically, at this optimized load point, the fuel cell system produces more electrical power than the motor vehicle (e.g., all drive motors and auxiliary consumers) requires in the traffic jam.The portion of electrical power that the vehicle does not require while stuck in traffic can be temporarily stored in the energy storage device according to the technology disclosed herein. For this purpose, the energy storage device is preconditioned accordingly before arriving at the traffic jam. A further advantage of the technology disclosed herein is that, compared to previously known solutions, the fuel cell system exhibits comparatively high current densities at the optimized load point, allowing the fuel cell system to be operated at lower cell voltages. This reduces degradation.

[0029] The technology revealed here will now be explained using the schematic figures as examples. They show: Fig. 1. A schematic diagram of the technology disclosed herein; Fig. 2 a schematic representation of the efficiency of the fuel cell system as a function of the electrical power supplied; Fig. 3 a schematic representation of a polarization curve of the fuel cell system; and Fig. 4 a schematic representation of the process steps of the procedure disclosed herein.

[0030] In the Fig. 1. The vehicle detects at time t0 that a traffic jam is beginning at a distance E0. This information can be provided, for example, by the vehicle's integrated navigation system. Until it reaches the traffic jam at time t2, the vehicle can continue to operate at a normal speed, e.g., 100 km / h. For this operation at normal speed, the vehicle can, for example, draw electrical power P. KFZ,nThe system would require 50 kW. If no traffic jam had been detected, this electrical power of 50 kW would be provided entirely by the fuel cell system. Only for short peak loads, for example during period t1, would the energy storage device, such as a high-voltage storage battery, provide additional electrical energy.

[0031] According to the technology disclosed here, the hybridization ratio is now changed by having the fuel cell system deliver only the electrical power P instead of 50 kW. BZ,n provides, for example, 40 kW (see dashed line in Fig. 1) The missing electrical power P HV,n (here, 10 kW) is now supplied to the vehicle by the high-voltage storage battery (see dotted line in Fig. 1) The dashed line shows the state of charge (SOC) of the high-voltage storage battery. Since electrical power P is continuously supplied during the journey until the traffic jam... HV,n As power is drawn from the high-voltage storage battery, the battery gradually discharges until time t2. Any peak loads, such as those occurring during period t1, can still be drawn from the high-voltage storage battery. At time t2, the high-voltage storage battery then has a comparatively low state of charge (SOC).

[0032] In a traffic jam, the motor vehicle, including all drive motors and auxiliary consumers, requires electrical power P. KFZ,j , which is typically significantly lower than the electrical power P KFZ,n , which is required during normal operation. For example, this electrical power consumption P KFZ,j many times lower than the electrical power consumption P KFZ,nDuring normal operation, the amount of electrical energy drawn from the high-voltage storage battery before arriving at the traffic jam can be dimensioned such that the high-voltage storage battery covers the proportion of electrical power P supplied by the fuel cell system at the energy-efficient load point during the traffic jam. BZ,j It can store energy that is not immediately needed by the vehicle. Alternatively, it can be stipulated that such a forecast of power consumption in traffic jams is dispensed with and that a congestion limit charge state of the high-voltage storage battery should always be reached at the beginning of the traffic jam at time t2.

[0033] In traffic jams, the fuel cell system provides all the electrical power required by the vehicle. The fuel cell system is advantageously installed at an energy-efficient load point (see...). Fig. 2) operated. The fuel cell system then produces more electrical power at this load point than the vehicle requires. The excess is stored in the high-voltage storage battery. Accordingly, the state-of-charge (SOC) curve for the energy storage system slowly rises again during the traffic jam. After the traffic jam clears, the vehicle can be operated normally again. Here, for example, it can be provided that the fuel cell system again supplies the entire electrical power P KFZ,n' provides for the motor vehicle.

[0034] The Fig. Figure 2 schematically shows the efficiency of the fuel cell system for different electrical power outputs. The efficiency of the fuel cell system is significantly lower in normal operation (e.g., at 50 kW) than in the range P. BZ,j,in which the fuel cell system is operated during traffic jams. It is readily apparent that the technology disclosed here improves the overall efficiency of the vehicle.

[0035] If the vehicle could not temporarily store electrical energy in the high-voltage storage battery during the traffic jam, the fuel cell system would have to be operated at a load point where even lower electrical power levels than P are available. BZ,j, be handed in. Fig. Figure 3 schematically shows the polarization curve of the fuel cell system disclosed herein. The polarization curve shows that at electrical output powers below P BZ,j, (here is the corresponding current density to P) BZ,j, (entered) very low current densities are set, which are associated with very high cell voltages. These high cell voltages lead to a comparatively high cell degradation.

[0036] The Fig. Figure 4 schematically shows a flowchart of the method disclosed herein. The method begins with step S100. In step S200, a subroutine is executed that can detect a traffic jam. Various technologies familiar to those skilled in the art can be used for this purpose. In step S300, it can be checked whether a traffic jam exists. If no traffic jam exists, the distance to the traffic jam can be determined in step S400. Based on the distance to the traffic jam and other operating parameters of the vehicle, in particular the fuel cell system and / or the energy storage device, the amount of energy required by the vehicle to reach the traffic jam can be determined (see step S500).

[0037] In step S610, it may be stipulated that the amount of energy is determined at time t0. - which is provided by the fuel cell system operating at the energy-efficient load point during traffic jams, - which is not instantly needed by at least one drive motor (preferably by all electrical consumers of the motor vehicle) during the traffic jam, and - which is to be stored in the energy storage device during the traffic jam.

[0038] Alternatively or additionally, step S620 may provide that at time t0 the amount of energy to be drawn from the high-voltage storage battery is determined in order to reach a maximum charge state at time t2.

[0039] In step S700, the hybridization ratio of the fuel cell system and at least one energy storage device can be adjusted. Typically, the hybridization ratio is adjusted so that more energy is drawn from the high-voltage storage battery for the instantaneous supply of the vehicle's electrical consumers, while simultaneously less electrical energy is provided by the fuel cell system for the instantaneous supply of the vehicle's electrical consumers.

[0040] However, this does not have to be the case. If, at time t0, the high-voltage storage battery is already sufficiently discharged that the excess electrical power provided by the fuel cell system during the traffic jam at the energy-efficient load point can be stored in the high-voltage storage battery, then the fuel cell system can continue to operate at the normal load point.

[0041] Step S800 checks whether the vehicle is already in a traffic jam. If not, the preceding steps can be repeated. In other words, the adjustment of the hybridization ratio revealed here can be continuously checked and, if necessary, readjusted based on current traffic data.

[0042] If it is determined in step S800 that the vehicle is in a traffic jam, the fuel cell system is operated in step S900 at a load point with energy-efficient power output (see...). Fig. 3).

[0043] The preceding description of the present invention serves only for illustrative purposes and not to limit the invention. Various changes and modifications are possible within the scope of the invention without departing from the scope of the invention and its equivalents.

Claims

[1] Method for operating a motor vehicle with a fuel cell system and with at least one energy storage device, wherein the fuel cell system and the energy storage device are configured to provide electrical power to at least one electric drive motor, comprising the steps: - Detecting an impending traffic jam; and - Adjusting the hybridization ratio of energy storage device and fuel cell system depending on the impending traffic congestion, and a) furthermore encompassing the steps: - Determining at least one parameter that represents the amount of energy required by at least one drive motor until the traffic jam; - Adjusting the hybridization ratio based on at least one parameter, and / or b) furthermore, the following steps are included: - Determining the extent of the traffic jam; - Adjusting the hybridization ratio depending on the extent of the traffic congestion, and / or c) furthermore, the following steps are included: - Determining the amount of electrical energy to be provided by the fuel cell system in the traffic jam, which is to be temporarily stored in the energy storage device during the traffic jam; and - Adjusting the hybridization ratio, whereby the hybridization ratio is adjusted so that the amount of electrical energy provided by the fuel cell system in traffic congestion can be temporarily stored in the energy storage device, and / or d) furthermore, the following step: - Adjusting the hybridization ratio, wherein the hybridization ratio is adjusted so that the energy storage device has a charge state that is below a stagnation limit charge state. [2] The method of claim 1, wherein the adjustment of the hybridization ratio comprises the steps whereby the electrical power supplied by the energy storage device to the at least one drive motor (P) HV,n ) is increased, and after which the electrical power (P) provided by the fuel cell system is increased BZ,n ) is reduced. [3] Method according to one of the preceding claims, wherein the electrical power provided by the fuel cell system in the traffic jam (P BZ,j ) is limited to 1% to 40% of the nominal power of the fuel cell system, preferably to 3% to 20% of the nominal power of the fuel cell system, and particularly preferably to 6% to 10% of the nominal power of the fuel cell system. [4] Method according to one of the preceding claims, wherein the electrical power provided by the energy storage device before arrival at the traffic jam is increased only if the state of charge of the energy storage device is above a lower state of charge limit.

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