HYBRID SYSTEM OF A MOTOR VEHICLE AND ASSOCIATED CONTROL METHOD

Abstract

The present development relates to a method for controlling a hybrid system (10) of a motor vehicle (1), which has a buffer battery (11), a power generation unit (12) electrically coupled to the buffer battery (11) and at least one electrical consumer (15, 16, 17) fed by the buffer battery (11) and coupled to the buffer battery (11) via an electrical supply line (20) (wherein the electrical supply line (20) is provided with a current limiting unit (21)). - wherein the power generation unit (12) is controlled to maintain a predetermined initial charge state of the buffer battery (11), at which charge state an output supply voltage for the at least one electrical consumer (15, 16, 17, 18) can be tapped from the buffer battery (11), - wherein at the latest at a time at which the at least one electrical consumer (15, 16, 17, 18) has an increased electrical power consumption which, while maintaining the output supply voltage, would lead to a current in the electrical supply line (20) which is above a permissible limit value, the charge state of the buffer battery (11) is increased in order to at least temporarily increase the supply voltage which can be tapped from the buffer battery (11).

Description

Technical area

[0001] The present development relates to a method for controlling a hybrid system of a motor vehicle and a corresponding hybrid system of a motor vehicle. background

[0002] Hybrid systems for motor vehicles typically have a battery that can be charged by a power generation unit. The hybrid system also has several electrical consumers that are powered by the backup battery.

[0003] During motor vehicle operation, a supply line connecting the electrical consumers to the buffer battery or the power generation unit may have different electrical power requirements depending on the respective driving situation. High-voltage (HV) electrical consumers, such as an air conditioning compressor or an air compressor intended for a fuel cell, have a significant power consumption in certain operating states of the motor vehicle, which can potentially result in the maximum permissible current on the supply line being exceeded. Therefore, the electrical supply line of a motor vehicle hybrid system is typically equipped with a current-limiting unit, such as one or more fuses, which protects the hybrid system, in particular the supply line, against damage caused by excessive currents.

[0004] However, limiting the current on or in the supply line also leads to a corresponding reduction or limitation of the maximum electrical power available to the electrical consumers.

[0005] For example, DE 102 22 422 B4 discloses a fuel cell control / regulating device comprising a compressor for supplying air as a reaction gas to a fuel cell and an atmospheric pressure detection device for detecting the atmospheric pressure. Furthermore, a current control / regulating device is provided for controlling and / or regulating an electric current generated by the fuel cell and applied to a load in response to the atmospheric pressure detected by the atmospheric pressure detection device. The current control / regulating device includes a current limiting device for limiting the current output by the fuel cell.

[0006] Against this background, the objective of this further development is to provide an improved hybrid system and an associated method for controlling a hybrid system of a motor vehicle, by means of which the consumers connected to the supply line can be supplied with the highest possible electrical power while adhering to a maximum permissible current intensity on the supply line. Furthermore, the objective is to limit the maximum electrical current flowing through the supply line and, in particular, to design the electrically conductive components of the supply line as cost-effectively and space-savingly as possible. In this respect, the objective is to minimize the cable cross-sections of a supply line and / or the dimensioning of fuses in the supply line to reduce costs and weight.

[0007] Early design of fuses on the supply train is often not possible because interfaces are inherited and reused across projects. For example, the interface of a high-voltage buffer battery. This has multiple feeders with limited current. The limitation can be achieved via the electrical fuses. However, if a demand for increased current arises at certain operating points of fed consumers, the current level is often limited and cannot be increased any further. This is then artificially restricted using calibration parameters to avoid damaging the fuse. In a fuel cell-fed power train, this behavior manifests itself in a reduction in performance, and the vehicle's traction system may not receive sufficient drive power. Advantageous designs

[0008] The described disadvantages and deficiencies of existing hybrid systems for motor vehicles are solved by means of a method for controlling a hybrid system, by means of a hybrid system, and by means of a motor vehicle according to the features of the independent patent claims. Advantageous embodiments are the subject of dependent patent claims.

[0009] In this respect and in a first aspect, a method for controlling a hybrid system of a motor vehicle is provided. The hybrid system comprises a buffer battery, a power generation unit electrically coupled to the buffer battery, and at least one electrical consumer powered by the buffer battery. The at least one electrical consumer, such as a high-voltage consumer, is coupled to the buffer battery via an electrical supply line. It is provided that the power generation unit is regulated or operated to maintain a predetermined initial charge state of the buffer battery, at which charge state an output supply voltage for the at least one electrical consumer can be tapped from the buffer battery.In particular, the power generation unit is operated in such a way that a predetermined state of charge (SOC) is maintained in the buffer battery in order to be able to supply the electrical consumers connected to it with electrical energy as required.

[0010] The method is designed so that at the latest at a time at which the at least one electrical consumer has an increased electrical power consumption which, while maintaining the output supply voltage of the buffer battery, would lead to a current in the electrical supply line that is above a permissible limit value, the charge state of the buffer battery is increased in order to at least temporarily increase the supply voltage that can be tapped from the buffer battery.

[0011] In this regard, it is particularly intended to increase the charge level of the buffer battery to increase the supply voltage available from the buffer battery. In this way, increased electrical power can be made available to at least one electrical consumer without increasing the current or while maintaining a maximum permissible current on the supply line. This is achieved by at least temporarily increasing the supply voltage available from the buffer battery.

[0012] In this way, the at least one electrical consumer can be supplied at least temporarily with an increased electrical power without exceeding a maximum permissible current on the electrical supply line.

[0013] According to a further embodiment of the method, the electrical supply line has one or more current-limiting units, by means of which the current in the supply line is kept below the permissible limit. The current-limiting unit can have one or more electrical fuses, which can be placed at predetermined or arbitrary locations in the supply line. Individual electrical consumers, distributors, or converters connected to the electrical supply line can also be equipped with one or more current-limiting units, for example in the form of electrical fuses.

[0014] By means of such current limiting units, the current intensity present in the supply line area can be limited within the permissible limit value.

[0015] According to a further embodiment of the method, the charge level of the buffer battery is at least temporarily increased before the time at which the at least one electrical consumer has an increased electrical power consumption. In this respect, the method can be implemented predictively and, for example, estimate or forecast an expected or imminent increase in electrical power consumption of the at least one electrical consumer in advance using one or more sensors.

[0016] This makes it possible to control the power generation unit accordingly and increase the charge level of the buffer battery to a higher level, so that the output supply voltage tapped via the supply line from the buffer battery increases by a specified amount. In this way, an increased electrical power can be provided that meets the requirements of at least one electrical consumer without significantly increasing the current or exceeding the permissible upper limit for the current on the supply line.

[0017] According to a further embodiment, the charge state of the buffer battery is increased by an amount of increase depending on an amount of the increased electrical power consumption of the at least one electrical consumer.

[0018] In other words, the degree of increased electrical power consumption of the at least one electrical consumer is quantitatively determined, estimated, or predicted. Based on the measured or predicted increase in electrical power consumption, the charge level of the buffer battery is then increased. The higher the electrical power consumption of the at least one electrical consumer, the higher the charge level of the buffer battery is increased. In this way, the method can respond particularly well to increased power requirements of the at least one electrical consumer.

[0019] According to a further embodiment, the power generation unit is a fuel cell, and the at least one electrical consumer is an air compressor coupled to the fuel cell. The charge level of the buffer battery is regulated as a function of the ambient air pressure. When the ambient air pressure drops, the air compressor must provide increased compression power in order to be able to consistently supply the fuel cell with a reaction gas. When the air pressure drops, the air compressor therefore has an increased electrical power consumption.

[0020] By means of the method provided here, the increased electrical power consumption is provided by an at least temporary increase in the supply voltage from the buffer battery, so that the current on the supply line does not exceed the specified limit.

[0021] The ambient air pressure can be measured, predicted, or estimated using one or more sensors. On the one hand, the ambient air pressure can be determined using appropriate pressure sensors. On the other hand, it can also be derived, for example, from a vehicle navigation system, which contains altitude information that can be used to determine the vehicle's position above sea level.

[0022] In this respect, a further embodiment of the method provides for the ambient air pressure to be determined based on the vehicle's position above sea level. As the altitude above sea level increases, for example when the motor vehicle is in a mountainous region, on a high plateau, or traveling over a mountain pass, the motor vehicle is typically exposed to lower air pressure than at sea level. From the navigation data, for example from a navigation system, changes in air pressure can be determined, estimated, or predicted before they occur. Early detection of a change in ambient air pressure enables early adaptation and modification, in particular an increase in the output supply voltage of the buffer battery.

[0023] According to a further embodiment, the at least one electrical consumer is an air conditioning compressor, by means of which the temperature in the vehicle interior can be tempered, for example cooled. In this case, the charge level of the buffer battery can be regulated as a function of an ambient temperature and / or as a function of the intensity of solar radiation into the vehicle interior of the motor vehicle. Typically, the air conditioning compressor has an increased electrical power consumption when the temperature in the vehicle interior rises and / or when the solar radiation into the vehicle interior intensifies. In order to serve the increased electrical power consumption of the air conditioning compressor, the initial charge level of the buffer battery can be increased at least temporarily in order to enable an increased electrical power consumption in the air conditioning compressor while maintaining or complying with the permissible limit value of the current on the electrical supply line.

[0024] According to a further embodiment, the charge level of the buffer battery is temporarily increased by means of the power generation unit. In particular, the operation of the power generation unit can be variably adapted to the power requirements of individual electrical consumers of the hybrid system. For example, if it is estimated at a time that an increased power demand from individual electrical consumers will soon arise, the power generation unit can be regulated not only to maintain a predetermined initial charge level of the buffer battery, but the charge level of the buffer battery can also be increased beyond what is actually required in order to at least temporarily provide an increased output supply voltage to the buffer battery.

[0025] Finally, a further aspect provides a hybrid system for a motor vehicle. This system comprises a buffer battery, a power generation unit electrically coupled to the buffer battery, and at least one electrical consumer. The hybrid system further comprises an electrical supply line, via which the at least one electrical consumer is electrically coupled to the buffer battery. The at least one electrical consumer can be supplied with electrical power via the electrical supply line. The hybrid system further comprises a controller, by means of which the power generation unit can be regulated to maintain a predetermined initial charge state of the buffer battery. At this initial charge state, an output supply voltage can be tapped or provided for the at least one electrical consumer.

[0026] The controller is designed to increase the charge level of the buffer battery to at least temporarily increase the supply voltage tapped from the buffer battery at the latest at a time at which the at least one electrical consumer has an increased electrical power consumption, which, while maintaining the output supply voltage, would lead to a current in the electrical supply line above a permissible limit. In other words, an increased power requirement on the part of the at least one electrical consumer can be responded to by at least temporarily increasing the output supply voltage of the buffer battery, thus enabling an increased power consumption for the at least one electrical consumer without having to increase the current in the supply line or without exceeding a permissible limit of the current in the supply line.

[0027] The hybrid system is designed and implemented specifically to carry out the method described above. Therefore, all advantages, features, and characteristics previously described with regard to the method for controlling the hybrid system also apply equally to the hybrid system; and vice versa.

[0028] In particular, the hybrid system comprises a current-limiting unit, such as a fuse, by means of which the current in the supply line can be kept below a permissible limit. The hybrid system can, in particular, comprise multiple current-limiting units, such as fuses, in the area of ​​individual electrical consumers, electrical distributors, or converters.

[0029] Finally, in a further aspect, the present development relates to a motor vehicle equipped with a previously described hybrid system. The motor vehicle, in particular its hybrid system, is implemented and configured to carry out the previously described method for controlling a hybrid system. In this respect, all of the previously described features, advantages, and possible applications of the method for controlling the hybrid system also apply equally to the motor vehicle; and vice versa. Short description of the characters

[0030] Further objects, features, and advantageous applications of the present method and the hybrid system are explained in the following description with reference to the drawings. Fig. 1 a schematic representation of a motor vehicle with a hybrid system, Fig. 2 Block diagram of a hybrid system of a motor vehicle, Fig. 3 a diagram of the operation or power output of the power generation unit as a function of the charge level of the buffer battery and Fig. 4 a flowchart of the method for controlling a hybrid system. Detailed description

[0031] The Fig. 1 schematically shown motor vehicle 1 has a motor vehicle body 2 and an interior 3 functioning as a passenger compartment. The motor vehicle is equipped as a hybrid motor vehicle. It has a hybrid system 10 according to Fig. 2. The hybrid system 10 comprises a buffer battery 11 and a power generation unit 12, which is configured, for example, as a fuel cell 13. Furthermore, the hybrid system 10 comprises various electrical consumers 15, 16, 17, 18. The electrical consumer 15 is configured, for example, as an air compressor 14, by means of which a reaction gas can be supplied to the fuel cell 13 while maintaining a predetermined elevated pressure.

[0032] Another electrical load 16 is configured, for example, as a heater for the buffer battery 11. The electrical load 17 is implemented, for example, as a heater for the fuel cell 13, and the electrical load 18 has an air conditioning compressor 19 for controlling the temperature of the vehicle interior 3. The hybrid system 10 can further comprise a charging system 26, by means of which externally supplied electrical power can be fed into the buffer battery 11. The electrical loads 17, 18 are electrically coupled to the buffer battery 11 via a distributor 29, such as a junction box.

[0033] For example, a current-limiting unit 21, such as a fuse, can be provided in the area of ​​the distributor 29. Additional current-limiting units 21 can also be provided in the area of ​​the buffer battery 11 or in the area of ​​a converter 28. The hybrid system 10 has a supply line 20, which, for example, comprises several sub-lines by means of which the electrical consumers 15, 16, 17, 18, the power generation unit 12, and the buffer battery 11 are electrically connected or coupled to one another.

[0034] The motor vehicle 1, or the hybrid system 10, further comprises a traction system 25, for example in the form of one or more electric motors, by means of which the motor vehicle 1 can be propelled. The traction system 25 is also supplied with electrical power by the buffer battery 11.

[0035] The hybrid system 10 further comprises a controller 30, by means of which in particular the power generation unit 12 can be controlled or regulated in order to keep the buffer battery 11 at a predetermined state of charge and / or to provide an output supply voltage sufficient for the electrical consumers 15, 16, 17, 18 by means of the buffer battery.

[0036] The buffer battery 11 is coupled to the power generation unit 12 via a converter 27, typically a DC-DC converter. In this way, the electrical power provided by the power generation unit 12, or a power generation voltage, can be adjusted to a voltage level corresponding to the buffer battery 11. Furthermore, the electrical load 15 can also be coupled to the buffer battery 11 via a converter 28, for example in the form of a DC / AC converter.

[0037] The controller 30 is coupled in particular to sensors 32, 34, wherein the sensor 32 can be implemented, for example, as an air pressure sensor and the sensor 34 can be configured as a temperature sensor. Additionally or alternatively, the controller 30 can also be connected to or integrated into a central control system of the motor vehicle 1.

[0038] Diagram 50 according to Fig. 3 shows the electrical power P provided by the power generation unit 12 as a function of the state of charge SOC of the buffer battery 11. The illustration shown here is highly simplified and is intended only to illustrate the changed or modified operation of the power generation unit 12, or rather the buffer battery 11, according to the present method. If the state of charge of the buffer battery 11 is approximately below 50%, the power generation unit 12 is operated at maximum power. If the state of charge increases further, approximately to the range of 75% of a maximum charge, the power of the power generation unit 12 is successively throttled, as illustrated in diagram 51. When the buffer battery 11 is almost fully charged, the power of the power generation unit 12 can be minimal. The power generation unit 12 can, for example, also be temporarily deactivated in such situations.

[0039] However, if the hybrid system 10, in particular the controller 30 according to the present method, detects an increased power consumption of at least one of the consumers, such as the air compressor 14 or the air conditioning compressor 19, the method can be operated according to graph 52, according to which the power generation unit 12 is throttled or successively deactivated only when a much higher charge level of the buffer battery 11 is reached, with a further increasing battery charge level. This results in situations in which individual electrical consumers 15, 16, 17, 18 have an increased electrical power consumption, the charge level of the buffer battery 11 being increased by a predetermined amount, so that an increased amount of electrical power can now be made available to the individual consumers 15, 16, 17, 18 even without increasing the current and / or while adhering to the current limit on the supply line 20.

[0040] This control method also has the effect that the permissible limit of the current intensity on the supply line can sometimes be reduced compared to conventional hybrid systems, so that the corresponding current-carrying components can be designed to carry lower electrical currents. This allows the cable cross-sections of individual sub-lines or of the entire electrical supply line to be reduced, which can lead to a reduction in weight and cost. Furthermore, the current-limiting units provided to comply with a permissible limit can also be reduced with regard to the permissible limit, which enables the use of correspondingly smaller current-limiting units. In this respect, smaller fuses can be used as current-limiting units, as well as thinner cables for the supply line.

[0041] The flowchart according to Fig.4 again shows individual method steps for controlling the hybrid system 10. Beginning with a step 100, the power generation unit 12 generates a certain predetermined amount of electrical power during operation of the motor vehicle 1, which is supplied to the buffer battery 11. In step 102, an increased power consumption of individual electrical consumers 15, 16, 17, 18 can be determined, estimated, or predicted for the future, for example by evaluating sensors 32, 34. In step 104, the controller 30 of the hybrid system 10 can intervene to regulate this or operate the power generation unit 12 in a modified manner such that the buffer battery 11 is, so to speak, artificially transferred to an increased state of charge, in which an increased electrical output supply voltage can be tapped from the buffer battery 11.

[0042] In step 106, at least one of the electrical consumers 15, 16, 17, 18 can request an increased electrical power consumption from the buffer battery 11 compared to a normal state, which is provided in step 108 by the buffer battery 11 due to the previously increased electrical supply voltage.

[0043] The illustrated embodiments merely show possible configurations of the development, for which numerous further variants are conceivable within the scope of the development. The exemplary embodiments shown are in no way to be interpreted as limiting the scope, applicability, or configuration options of the development. This description merely shows the person skilled in the art one or several possible implementations of an exemplary embodiment. Thus, a wide variety of modifications can be made to the function and arrangement of the described elements without departing from the scope of protection defined by the following claims or their equivalents. LIST OF REFERENCE SYMBOLS 1 motor vehicle 2 Body 3 Interior 10 Hybrid system 11 buffer battery 12 power generation units 13 Fuel cell 14 Air compressor 15 electrical consumers 16 electrical consumers 17 electrical consumers 18 electrical consumers 19 Air conditioning compressor 20 supply line 21 Current limiting unit 25 Traction system 26 Charging system 27 converters 28 converters 29 distributors 30 Control 32 sensors 34 Sensor QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 102 22 422 B4

[0005]

Claims

[1] Method for controlling a hybrid system (10) of a motor vehicle (1), which has a buffer battery (11), a power generation unit (12) electrically coupled to the buffer battery (11) and at least one electrical consumer (15, 16, 17) fed by the buffer battery (11) and coupled to the buffer battery (11) via an electrical supply line (20), - wherein the power generation unit (12) is controlled to maintain a predetermined initial charge state of the buffer battery (11), at which charge state an output supply voltage for the at least one electrical consumer (15, 16, 17, 18) can be tapped from the buffer battery (11), - wherein at the latest at a time at which the at least one electrical consumer (15, 16, 17, 18) has an increased electrical power consumption which, while maintaining the output supply voltage, would lead to a current in the electrical supply line (20) which is above a permissible limit value, the charge state of the buffer battery (11) is increased in order to at least temporarily increase the supply voltage which can be tapped from the buffer battery (11). [2] Method according to claim 1, wherein the electrical supply line (20) has a current limiting unit (21) by means of which the current intensity in the supply line (20) is kept below the permissible limit value. [3] Method according to one of the preceding claims, wherein the charge state of the buffer battery (11) is at least temporarily increased before the time at which the at least one electrical consumer (15, 16, 17, 18) has an increased electrical power consumption. [4] Method according to one of the preceding claims, wherein the state of charge of the buffer battery (11) is increased by an amount of increase depending on an amount of the increased electrical power consumption of the at least one electrical consumer (15, 16, 17, 18). [5] Method according to one of the preceding claims, wherein the power generation unit (12) is a fuel cell (13) and the at least one electrical consumer (15) is an air compressor (14) coupled to the fuel cell (13), and wherein the charge state of the buffer battery (11) is regulated as a function of an ambient air pressure. [6] The method of claim 5, wherein the ambient air pressure is determined based on a position of the vehicle above sea level. [7] Method according to one of the preceding claims, wherein the at least one electrical consumer (18) is an air conditioning compressor (19), and wherein the charge state of the buffer battery (11) is regulated as a function of an ambient temperature and / or as a function of the intensity of solar radiation into a vehicle interior (3) of the motor vehicle. [8] Method according to one of the preceding claims, wherein the charge state of the buffer battery (11) is temporarily increased by means of the power generation unit (11). [9] Hybrid system (10) of a motor vehicle (1) comprising: - a buffer battery (11), - a power generation unit (12) electrically coupled to the buffer battery (11), - at least one electrical consumer (15, 16, 17, 18), - an electrical supply line (20) via which the at least one electrical consumer (15, 16, 17, 18) is electrically coupled to the buffer battery (11), - a controller (30) by means of which the power generation unit (12) can be controlled to maintain a predetermined initial charge state of the buffer battery (11), at which initial charge state an output supply voltage for the at least one electrical consumer (15, 16, 17, 18) can be tapped from the buffer battery (11), - wherein the controller (30) is designed to increase the charge state of the buffer battery (11) in order to at least temporarily increase the supply voltage that can be tapped from the buffer battery (11) at the latest at a time at which the at least one electrical consumer (15, 16, 17, 18) has an increased electrical power consumption which, while maintaining the output supply voltage, would lead to a current in the electrical supply line (20) that is above a permissible limit value. [10] Motor vehicle with a hybrid system according to claim 9.

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