DE102019118308A1 - Powertrain degradation system for vehicles with multiple power sources - Google Patents

Abstract

The invention describes a drive degradation system for a vehicle with at least one electric motor, which drives the vehicle by generating an electromotive power, with at least two power sources for generating the electromotive power, a first power source in the form of a high-voltage battery and a second power source in the form of a Fuel cells are provided, which can be used alternatively or jointly to generate the electromotive power, with a degradation module that calculates a maximum fuel cell power-related vehicle speed for stationary operation depending on the current maximum possible power of the fuel cell, and with a torque coordinator that sets the electromotive target -Power limited in such a way that the maximum fuel cell power-related vehicle speed is not exceeded in stationary operation, at least the high-voltage battery as the power source est is not used to drive the vehicle until a dynamic demand is made.

Description

State of the art:

In fuel cell vehicles, hydrogen is used as an energy carrier for propulsion. The energy bound in the hydrogen is converted into electrical energy via a fuel cell and is used by one or more so-called e-machines as an energy source for the electric motor drive of the vehicle.

In addition, fuel cell vehicles contain electrical energy storage devices, e.g. lithium-ion batteries - also known as HV batteries or high-voltage storage devices (HVS). These are used to absorb and store kinetic energy during deceleration or braking processes (recuperation), to support the fuel cell during acceleration processes (boosting) and to cover dynamic performance differences (excess and insufficient coverage) between the fuel cell as an energy source and the electric machines and Secondary consumers needed as energy sinks.

Depending on the driver's acceleration and deceleration requirements, the electric machines and fuel cells are controlled via software functionality. Due to the typically significantly lower energy content of the electrical energy store compared to the hydrogen store, the power requirement necessary for the vehicle movement is covered (at least in the long term) by the fuel cell.

Both the fuel cell and the electrical energy storage device are more or less (statically) limited in terms of their power output, depending on the design, layout and operating point.

During operation, certain driving profiles, environmental influences and / or error states may necessitate additional degradation of the fuel cell with regard to the power output.

In the prior art, the limitation of the fuel cell output leads to a greater discharge of the HV battery and, moreover, to a limitation of the available drive output that can be called up by the driver using the accelerator pedal (electric machine output). It is the object of the invention to solve this problem.

This object is achieved by the features of claim 1. Advantageous further developments of the invention are contained in the dependent claims.

The invention describes a drive degradation system for a vehicle with at least one electric motor, which drives the vehicle by generating an electromotive power, with at least two power sources for generating the electromotive power, a first power source in the form of a high-voltage battery and a second power source in the form of a Fuel cells are provided, which can be used alternatively or jointly to generate the electromotive power, with a degradation module that calculates a maximum fuel cell power-related vehicle speed for stationary operation depending on the current maximum possible power of the fuel cell, and with a torque coordinator that sets the electromotive target -Power limited in such a way that the maximum fuel cell power-related vehicle speed is not exceeded in stationary operation, at least the high-voltage battery as the power source est is not used to drive the vehicle until a dynamic demand is made.

In summary, the invention represents a drive degradation concept for vehicles with multiple power sources without any loss of dynamics.

• Die Besonderheit bei einem Brennstoffzellenfahrzeug liegt darin, dass in den bekannten Konzepten die Brennstoffzelle im Vergleich zu einem Hybridfahrzeug mit Verbrennungsmotor nur einen geringen Anteil an der Gesamtantriebsleistung hat (siehe Stand der Technik). Gleichzeitig ist der Energieinhalt der HV-Batterie nicht darauf ausgelegt, die Hauptantriebsleistung langfristig zur Verfügung zu stellen, sie soll lediglich für die Dynamik des Fahrzeuges sorgen.

The invention is based on the following findings:

• The special feature of a fuel cell vehicle is that in the known concepts, the fuel cell has only a small share in the total drive power compared to a hybrid vehicle with an internal combustion engine (see prior art). At the same time, the energy content of the HV battery is not designed to provide the main drive power over the long term, it is only intended to ensure the dynamics of the vehicle.

As a result of this distribution of the drive power, operating the vehicle above the fuel cell power leads to a strong discharge of the HV battery and, as a result, quickly to the elimination of the HV store as an energy source.
This operating state occurs increasingly with degraded fuel cell power, in particular after a long journey uphill and / or after driving at high speed.
The driver perceives this as a very strong limitation of the drive power / acceleration dynamics that can be called up.

• Die Auslegung der Energieinhalte von H2-Tank und HV-Batterie, als auch die Leistungsdaten dieser Energiequellen führen dazu, dass dynamische Fahranteile verstärkt aus der HV-Batterie abgedeckt werden. Dagegen müssen die stationären Antriebsleistungsbedarfe (stationäre Fahrwiderstände, Leistungsbedarf für Bergfahrt und höhere Geschwindigkeiten) von der Brennstoffzelle abgedeckt werden.

The present invention is intended to prevent this:

• The design of the energy content of the H2 tank and HV battery, as well as the performance data of these energy sources mean that dynamic driving components are increasingly covered by the HV battery. In contrast, the stationary drive power requirements (stationary driving resistances, power requirements for uphill travel and higher speeds) must be covered by the fuel cell.

In order to counteract the greater discharge of the HV battery when the performance of the fuel cell is degraded, operating the vehicle in areas with higher stationary drive power requirements must be avoided.

If the stationary drive power requirement (stationary driving resistances) exceeds the maximum available fuel cell power, the HV battery is discharged. The invention is intended to prevent this.

The stationary driving resistances result from influencing variables such as rolling resistance, air resistance and gradient resistance. These influencing variables in turn result from constant, unchangeable parameters such as vehicle mass, aerodynamic drag coefficient and road inclination as well as the variable vehicle speed.

From this consideration it follows that the only (meaningfully) influenceable variable for reducing the steady-state drive power requirement is the vehicle speed.

A model is therefore used to calculate a maximum fuel cell power-related vehicle speed from the available fuel cell power and the drive is limited to this. This procedure prevents the HV battery from discharging when the maximum vehicle speed is usually only slightly reduced. This means that the full acceleration dynamics are retained. The drivability is significantly improved.

The discharge of the HV battery cannot be completely prevented in all driving situations simply by limiting it to a maximum fuel cell power-related vehicle speed. For example, repeated acceleration maneuvers can lead to the HV battery discharging. Errors or inaccuracies in the calculation model can also lead to a gradual discharge of the battery.

• - Vorhalt einer Mindest-Ladeleistung im Rahmen der Bestimmung der maximale brennstoffzellenleistungsbezogene Fahrzeuggeschwindigkeit zum Laden der HV-Batterie abhängig vom Batterieladezustand SOC.
• - Begrenzung auf eine maximale Gesamtantriebsleistung abhängig vom Verhältnis der Brennstoffzellenleistung zur Gesamtantriebsleistung.
• - Bestimmung der maximalen Gesamtantriebsleistung abhängig vom Batterieladezustand (SOC).
• - Bestimmte temporär wirkende Fahrwiderstände können über vorausschauende Datenerfassung (z.B. Navigationsdaten) erkannt und gezielt in der Berechnung der maximalen brennstoffzellenleistungsbezogenen Fahrzeuggeschwindigkeit berücksichtigt oder ausgeblendet werden (z.B. Vorausschau blendet einen „kleinen Berg“ über Manipulation des Neigungswinkels aus. Analog führt ein Gefälle zu einem Anstieg der maximalen brennstoffzellenleistungsbezogenen Fahrzeuggeschwindigkeit.
• - Ein „Überdrücken“ der Geschwindigkeitsbegrenzung auf die maximale brennstoffzellenleistungsbezogene Fahrzeuggeschwindigkeit über Fahrpedal (z.B. Kickdown) kann in der Funktion enthalten sein.
• - Die Begrenzung auf eine maximale brennstoffzellenleistungsbezogene Fahrzeuggeschwindigkeit kann auch unabhängig von einer Degradation des Brennstoffzellensystems immer aktiv oder aktivierbar sein (Anwendungsbeispiel Bergfahrt oder manuelle Auswählbarkeit dieser Funktion durch den Fahrer über ein entsprechendes Bedienelement).
• - Übergänge von nicht degradiertem System zu den verschiedenen Degradationsniveaus sollen keine Sprünge in der Fahrzeuggeschwindigkeit zur Folge haben, sondern verschliffen ausgeführt werden. Gleiches gilt für die Begrenzung der Antriebsleistung. Dies führt zur Verbesserung der Fahrbarkeit.

In order to take these cases into account, the following additional functions are preferably provided:

• - Provision of a minimum charging power as part of the determination of the maximum fuel cell power-related vehicle speed for charging the HV battery depending on the battery state of charge SOC.
• - Limitation to a maximum total drive power depending on the ratio of the fuel cell power to the total drive power.
• - Determination of the maximum total drive power depending on the battery state of charge (SOC).
• - Certain temporarily acting driving resistances can be recognized via predictive data acquisition (e.g. navigation data) and specifically taken into account or hidden in the calculation of the maximum fuel cell performance-related vehicle speed (e.g. Prediction hides a "small mountain" by manipulating the angle of inclination. Similarly, a gradient leads to an increase in the maximum fuel cell performance related vehicle speed.
• - "Overpressing" the speed limit to the maximum fuel cell power-related vehicle speed using the accelerator pedal (eg kickdown) can be included in the function.
• The limitation to a maximum fuel cell power-related vehicle speed can also always be active or can be activated independently of a degradation of the fuel cell system (Application example uphill travel or manual selection of this function by the driver via a corresponding control element).
• - Transitions from the non-degraded system to the various degradation levels should not result in jumps in the vehicle speed, but should be smoothed out. The same applies to the limitation of the drive power. This leads to an improvement in drivability.

• 1 einen schematischen Überblick über eine erfindungsgemäße Funktionsstruktur mit entsprechenden Signalflüssen und
• 2 ein Fahrprofil-Beispiel unter Anwendung der erfindungsgemäßen Funktionsstruktur.

An exemplary embodiment of the invention is shown in the drawing. It shows

• 1 a schematic overview of a functional structure according to the invention with corresponding signal flows and
• 2 a driving profile example using the functional structure according to the invention.

P_EM

Leistung E-Maschine (Fahrerwunsch; nicht durch Betriebsstrategie beeinflusst)

P_BNNV

Leistung Bordnetz- und Nebenverbraucher (Speicherheizung oder -kühlung, Innraumheizung oder -kühlung, 12 V Verbraucher; teilweise durch Betriebsstrategie beeinflusst)

P_FCS

Leistung Brennstoffzelle (kann variiert werden, muss mittelfristig P_EM + P_BNNV abdecken; durch Betriebsstrategie beeinflusst)

P_HVS

Leistung HV-Speicher (= „Resultierende“, ergibt sich aus der Leistungsbilanz; durch Betriebsstrategie beeinflusst)

As an introduction, there is an overview of the power distribution in a concept with an e-machine (electric motor), an on-board network with auxiliary consumers (BNNV), a fuel cell (FCS) and a high-voltage storage device (HVS): $${\text{P}}_{\text{EM}}+{\text{P}}_{\text{BNNV}}={\text{P}}_{\text{FCS}}+{\text{P}}_{\text{HVS}}$$

P _EM

E-machine performance (driver request; not influenced by operating strategy)

P _BNNV

Power on board electrical system and auxiliary consumers (storage heating or cooling, interior heating or cooling, 12 V consumers; partly influenced by operating strategy)

P _FCS

Fuel cell performance (can be varied, must cover P _EM + P _{BNNV in the} medium term; influenced by operating _strategy )

P _HVS

HV storage capacity (= "resultant", results from the power balance; influenced by operating strategy)

• → P_FCS ≠ PEM + P_BNNV
• → Laden / Entladen HV-Speicher
• → Erhöhung HV-Speichertemperatur

P _FCS => P _HVS through FCS power increase or decrease:

• → P _FCS ≠ PEM + P _BNNV
• → Charge / discharge HV storage
• → Increase in the HV storage tank temperature

An advantageous functional structure according to the invention is illustrated below with reference to FIG 1 explained in more detail. In 1 is operated by a brake pedal 1 a brake pedal pressure p_B (or a brake pedal force or a brake pedal travel) to an electronically controlled brake control system 2 directed. The brake control system 2 divides the deceleration request requested by the brake pedal pressure p_B into a wheel brake pressure p_R and a brake recuperation request REKU_soll. The brake recuperation request REKU_soll is the input signal of a torque coordinator 4th . The accelerator pedal angle FW of an accelerator pedal 5 actuated by the driver is also the input signal of the torque coordinator 4th and reflects the driver's request. The moment coordinator 4th determines a target torque or a target drive power P _{EM_soll} from these two input _signals , which is sent to a power _coordinator 7th is issued. The performance coordinator 7th is preferably dependent on the maximum power P _{HVS_max of} the high-voltage _battery 9 which is determined in particular by the battery state of charge SOC and other storage _limits , depending on the requested power P _{BNNV of} the secondary consumers 10 and possibly dependent on the current power P _{FCS_ist of} the fuel cell 8th a target power P _{FCS_soll} to the fuel cell 8th out.

It is _{essential to} the invention that the currently maximum possible power P _{FCS_max of} the fuel cell 8th determined and to a degradation module 12th is output, which calculates a maximum fuel cell power-related vehicle speed v_max for stationary operation as a function thereof. Stationary operation is understood to mean driving at an essentially constant vehicle speed v, that is to say without a dynamic demand, in particular without a positive acceleration demand via the accelerator pedal 5 or the accelerator pedal angle FW.

The vehicle is in stationary operation with at least one electronically controllable electric motor 6th driven, the electromotive power P _EM for this purpose by means of the torque coordinator 4th preferably exclusively through the fuel cell 8th is generated as a power source. The maximum fuel cell power-related vehicle speed v_max for stationary operation is the input signal of the Moment coordinator 4th which is controlled by a v_max limiting module 11 the electromotive target power P _{EM is} limited in such a way that the maximum fuel cell power-related vehicle speed v_max is not exceeded in stationary operation. The high-voltage battery 9 not used as a power source to drive the vehicle, at least up to a dynamic requirement.

The moment coordinator 4th with the v_max limitation module 11 , the performance coordinator 7th and the degradation module 12th are function modules that can be contained in at least one electronic control unit.

The maximum fuel cell power-related vehicle speed v_max can also be determined by other vehicle parameters, such as B. the current driving resistance S1 , the angle of inclination S2 the roadway, navigation data S3 and / or the provision of a minimum charging capacity S4 of the high-voltage storage system 9 .

Preferably, a limitation to the maximum fuel cell power-related vehicle speed v_max is only made up to a predetermined, comparatively low amount of speed reduction below the driver's request-related target power P _{EM_soll} so that the driver does not perceive an excessive power limitation.

The vehicle speed v is further limited, for example, by connecting the high-voltage battery 9 avoided.

The maximum fuel cell power-related vehicle speed v_max can also be dependent on the maximum possible power P _{HVS_max} or the state of charge HVS_SOC of the high-voltage battery 9 to be determined.

The limitation to the maximum fuel cell power-related vehicle speed v_max can only be activated if the maximum possible power P _{FCS_max of} the fuel cell 8th has _fallen below a defined degradation _{threshold value} P _{FCS_deg} . This limitation can, however, also be configured so that it can be switched on and off manually by the driver using an operating element.

• - Die obere Kurve beschreibt die Fahrzeuggeschwindigkeit v über der Zeit t.
• - Die mittlere Kurve beschreibt den Ladezustand der Hochvoltbatterie HVS_SOC über der Zeit t.
• - Die untere Kurve beschreibt den Fahrerwunsch bzw. den Fahrpedalwinkel FW über der Zeit t.

Phase ohne Erfindung mit Erfindung P1 Beschleunigung auf eine (etwas) höhere Geschwindigkeit als mit Erfindung. Beschleunigung, bis die Fahrzeuggeschwindigkeit vom Geschwindigkeitsregler auf das gemäß der Erfindung berechnete Geschwindigkeitslimit v_max eingeregelt wird. P2 Der HV-Speicher (Batterie) wird entladen, da der stationäre Leistungsbedarf für die Fahraufgabe nicht von der Der HV-Speicher (Batterie) wird nachgeladen, da noch eine Leistungsreserve der Brennstoffzelle für das Nachladen vorhanden ist. Brennstoffzelle abgedeckt werden kann. Ist der HV-Speicher vollständig entladen, fällt die Fahrzeuggeschwindigkeit ab. Die Fahrzeuggeschwindigkeit kann dauerhaft gehalten werden. P3 Während der Fahrzeugverzögerung wird der HV-Speicher durch Rekuperation und die Brennstoffzelle auf relativ niedrigem Niveaus nachgeladen. Während der Fahrzeugverzögerung wird der HV-Speicher durch Rekuperation und die Brennstoffzelle auf relativ hohem Niveau nachgeladen. P4 Der Energieinhalt des HV-Speichers reicht nicht aus, um die vom Fahrer gewünschte Fahrzeugbeschleunigung (Dynamikanforderung) während des gesamten Beschleunigungsvorganges aufrecht zu erhalten. Die Fahrzeugbeschleunigung fällt deutlich unter den Fahrerwunsch ab. Der Energieinhalt des HV-Speichers reicht aus, um die vom Fahrer gewünschte Fahrzeugbeschleunigung während des gesamten Beschleunigungsvorganges aufrecht zu erhalten. Sofort nach Erreichen der Konstantfahrtphase oder eines niedrigeren Beschleunigungswunsches erfolgt das Nachladen des HV-Speichers. P5 Erst nach Ablauf des deutlich trägeren / längeren Beschleunigungsvorgangs kann der HV-Speicher nachgeladen werden. Der HV-Speicher hat frühzeitig hohen Ladezustand, um weitere Zwischenbeschleunigungen mit hoher Dynamik abdecken zu können. Finally, the invention is based on 5 phases P1 to P5 a driving profile example according to 2 explained in more detail:

• - The upper curve describes the vehicle speed v over time t.
• - The middle curve describes the state of charge of the high-voltage battery HVS_SOC over time t.
• - The lower curve describes the driver's request or the accelerator pedal angle FW over time t.

phase without invention with invention P1 Acceleration to a (slightly) higher speed than with the invention. Acceleration until the vehicle speed is regulated by the speed controller to the speed limit v_max calculated according to the invention. P2 The HV storage (battery) is being discharged because the stationary power requirement for the driving task is not dependent on the The HV storage (battery) is being recharged because the fuel cell still has a power reserve for recharging. Fuel cell can be covered. If the HV storage unit is completely discharged, the vehicle speed drops. The vehicle speed can be maintained permanently. P3 During vehicle deceleration, the HV storage system is recharged through recuperation and the fuel cell is recharged at a relatively low level. During vehicle deceleration, the HV storage system is recharged at a relatively high level through recuperation and the fuel cell. P4 The energy content of the HV storage tank is not sufficient to maintain the vehicle acceleration desired by the driver (dynamic requirement) during the entire acceleration process. The vehicle acceleration falls well below the driver's request. The energy content of the HV storage system is sufficient to maintain the vehicle acceleration desired by the driver during the entire acceleration process. Immediately after reaching the constant travel phase or a lower acceleration requirement, the HV storage is reloaded. P5 The HV storage unit can only be recharged after the significantly slower / longer acceleration process has expired. The HV storage has a high state of charge early on in order to be able to cover further intermediate accelerations with high dynamics.

Claims (5)

Drive degradation system for a vehicle with at least one electronically controllable electric motor (6) which drives the vehicle by generating an electric motor power (P _EM ), with at least two power sources for generating the electric motor power (P _EM ), a first power source in the form a high-voltage battery (9; HVS) and a second power source in the form of a fuel cell (8; FCS) are provided, which can be used alternatively or jointly to generate the electromotive power (P _EM ), with a degradation module (12), which is dependent on the current maximum possible power (P _{FCS_max} ) of the fuel cell (8; FCS) calculates a maximum fuel cell power-related vehicle speed (v_max) for stationary operation, and with a torque coordinator (4) which limits the electromotive target power (P _EM ) that the maximum fuel cell power-related vehicle speed (v_max) in the st ationary operation is not exceeded, the high-voltage battery (9; HVS) as a power source in stationary operation is not used to drive the vehicle, at least up to a dynamic requirement. Drive degradation system according to Claim 1 , characterized in that the maximum fuel cell power-related vehicle speed (v_max) is limited only up to a predetermined amount of speed reduction depending on the desired power (P _{EM_soll} ) _{related to the driver's request} . Drive degradation system according to one of the preceding claims, characterized in that the maximum fuel cell power-related vehicle speed (v_max) is limited only up to a predetermined amount of speed reduction depending on the target power (P _{EM_soll} ) _{related to the driver's request} and that the vehicle speed is further limited (v) is avoided by connecting the high-voltage battery (9; HVS). Drive degradation system according to one of the preceding claims, characterized in that the maximum fuel cell power-related vehicle speed (v_max) is determined depending on the maximum possible power (P _{HVS_max} ) and / or the state of charge (HVS_SOC) of the high-voltage battery (9; HVS). Drive degradation system according to one of the preceding claims, characterized in that the limitation to the maximum fuel cell power-related vehicle speed (v_max) is only activated if the maximum possible power (P _{FCS_max} ) of the fuel cell (8; FCS) _exceeds a defined degradation _{threshold value} (P _{FCS_deg} ) has fallen below.

Images