DE102021205851A1 - Method for operating an on-board network - Google Patents

Abstract

Method for operating an on-board electrical system (202) in which consumers (208) and at least one energy source (206) are provided, wherein energy is predicted to be fed back by at least one of the consumers (208) and, if a feed back is detected, at least one countermeasure is initiated, which affects the level of an overvoltage caused by the feedback in the vehicle electrical system (202).

Description

The invention relates to a method for operating a vehicle electrical system and an arrangement for carrying out the method. The invention further relates to a computer program and a machine-readable storage medium.

State of the art

In automotive use, an on-board network is to be understood as the entirety of all electrical components in a motor vehicle. This includes both electrical consumers and supply sources, such as batteries. A distinction is made between the on-board power supply and the on-board communication supply.

A vehicle electrical system, which is also referred to as a vehicle electrical system, has a nominal voltage range of z. B. 9 to 16 volts, in which all components are fully functional. Leaving this range for a certain period of time causes functional degradation or component failure. For this reason, different control algorithms, such as load management, are used to maintain this range.

Current predictive load management systems have the aim of downgrading the low-priority consumers in order to prevent a voltage drop when highly dynamic consumers are activated, such as e.g. B. the steering and the brakes, and not to violate the lower voltage limit. For this purpose, the power reserves of the energy sources and the power requirements of the consumers are predicted, compared and the power balance is determined. In the event of a power deficit, consumers are degraded or switched off. Otherwise, the loads are operated based on the switch-on requests.

The pamphlet WO 2018/077518 A1 describes a method for operating a vehicle electrical system, in which an operating strategy for the vehicle electrical system is developed, with at least one criterion being taken into account. Values are stored for each criterion in an order according to their priority, with it being at least checked whether selected values for the at least one criterion must be complied with by comparing an energy requirement for a further journey according to the selected criterion with the available energy resources. In the event that the energy requirement exceeds the energy resources, the value of at least one of the at least one criterion is downgraded at least once according to the assigned order. This process is repeated until the energy requirements are covered by the resources.

Some electrical system consumers, such as the steering or the fan, are required to feed current back into the electrical system depending on the situation. In these situations, the consumers act as sources and work in generator mode. If the current fed back cannot be absorbed by other consumers or energy storage devices, the voltage level in the vehicle electrical system increases, which can lead to the upper voltage limit being violated, e.g. B. 16 V and functional degradation or component failure.

The pamphlet DE 10 2014 210 283 A1 describes a method for operating a vehicle electrical system with at least two voltage levels, which have different nominal voltages, and with at least one voltage converter, which is arranged between the voltage levels. The method comprises the following steps: detecting the electrical power in the at least one voltage converter and/or the voltage levels, calculating an optimal operating point for the at least one voltage converter based at least on the calculated electrical power, controlling the at least one voltage converter in such a way that it is in the optimal Operating point is operated, with operation of the at least one voltage converter in the optimal operating point, the electrical losses in the vehicle electrical system are minimized.

Disclosure of Invention

Against this background, a method with the features of claim 1 and an arrangement according to claim 8 are presented. A computer program according to claim 9 and a machine-readable storage medium according to claim 10 are also presented. Embodiments emerge from the dependent claims and from the description.

The method presented is used to operate an on-board electrical system in which consumers and at least one energy source are provided. In this case, energy is predicted to be fed back by at least one of the consumers. If a typically imminent or impending feedback is detected, at least one countermeasure is initiated which affects the magnitude of an overvoltage in the vehicle electrical system caused by the feedback. This means that the overvoltage is reduced or even avoided.

The vehicle electrical system is thus coordinated with a higher-level function in such a way that an overvoltage in the vehicle electrical system is avoided or minimized by ensuring a situation-oriented load in the vehicle electrical system.

The method provides for predicting regenerative energy, for example, the regenerative energy of an electric drive machine (recuperation) can be predicted in order to take this into account, for example, when controlling a DC-DC converter and the limits of a battery. There is no concentration on the recuperation phases, but also the prediction of other feedback situations in which additional consumers or loads, such as the steering or the fan, can feed back.

When countermeasures are initiated, the battery can be discharged prematurely, for example, in order to provide space for the regenerative energy as soon as an imminent regenerative phase is detected. This can be achieved, for example, by lowering the output power of a DC/DC converter. In addition, the consumer power, for example an air conditioning consumer or a seat heater, can be increased, in particular for the duration of the feedback phase if the battery is not able to absorb all of the feedback energy. This case can occur, for example, if the reduction in the output power of the DC/DC converter is not sufficient. In this way, the regenerative energy can be dissipated quickly in order to avoid overvoltage in the vehicle electrical system.

With the method described, overvoltages in the low-voltage vehicle electrical system of a motor vehicle can be avoided. It is provided that the feedback energy is reused and not minimized or avoided. This creates the prerequisite for the fact that central energy storage can be omitted. These energy stores are used in today's vehicle electrical systems to buffer excess energy.

By using the method described, a large central energy store is no longer required from the point of view of buffering, since the feedback energy is used sensibly through the coordination of the consumers and does not have to be temporarily stored. In addition, the method can be implemented with the currently available vehicle electrical system components. There are no additional requirements for the components, at least in some versions of the method.

If the aim is to minimize the feedback currents of individual loads, this has an impact on the component design, e.g. B. by additional circuit elements and new control strategies to be expected. This can lead to an increase in costs.

In a conventional vehicle electrical system with a lead-acid battery, an attempt is made to keep its state of charge at a certain level, for example at 80%, in order to reserve space for the recuperation energy by feeding back the generator. Operating a lead-acid battery at a certain state of charge for recuperation purposes without countermeasures, such as providing a refresh charge at certain time intervals, leads to a loss of capacity due to sulphation. However, with the proposed method, a targeted lead is only required depending on the situation. Only if a recuperation phase is predicted is a lead attempted. Otherwise the full upper charge level range of the lead-acid battery can be used.

• eine Leistungserhöhung von insbesondere nicht sicherheitsrelevanten Lasten bzw. Verbrauchern und/oder ein Zuschalten von deaktivierten nicht sicherheitsrelevanten Lasten,
• eine Koordination der Energiequellen, um die Ausgangsleistung zu reduzieren oder im Falle einer zu hohen Rückspeiseleistung diese in ein anderes Teilnetz zu transportieren.

For this purpose, the vehicle electrical system is coordinated via a higher-level function in such a way that overvoltage in the vehicle electrical system is avoided or minimized by ensuring a situation-oriented load in the vehicle electrical system. The feedback from consumers is predicted and various countermeasures can be initiated. These possible countermeasures include:

• an increase in output of, in particular, non-safety-related loads or consumers and/or switching on deactivated non-safety-related loads,
• a coordination of the energy sources in order to reduce the output power or, in the event that the feedback power is too high, to transport it to another sub-grid.

The arrangement presented is used to carry out the method and is implemented, for example, in hardware and/or software or a computer program. In addition, the arrangement can be integrated in a control unit of a motor vehicle or designed as such. The computer program for carrying out the method can be stored on a machine-readable storage medium.

Further advantages and refinements of the invention result from the description and the accompanying drawings.

It goes without saying that the features mentioned above and those still to be explained below are not only in the respectively specified Combination, but also in other combinations or alone can be used without departing from the scope of the present invention.

character list

• 1 shows in a flowchart a sequence of an embodiment of the presented method.
• 2 shows in a flowchart a sequence of a further embodiment of the method presented.
• 3 shows a schematic representation of a vehicle with an on-board network for carrying out the method.

Embodiments of the invention

The invention is shown schematically on the basis of embodiments in the drawings and is described in detail below with reference to the drawings.

T0

Prädiktionszeitpunkt

delT

Prädiktionshorizont

Takt

aktueller Zeitpunkt

Taus

Zeitpunkt zum Einleiten des Notbetriebs

1 shows an embodiment of the presented method in a flowchart. The normal case is shown with arrows with solid lines. Arrows with dashed lines indicate emergency operation. The following applies:

T0

prediction time

delT

prediction horizon

tact

current time

dew

Time to initiate emergency operation

The method starts with a start step 5 . In a step 1 (reference number 10), a feedback is predicted at the time T0+delT.

In order to be able to initiate countermeasures "in good time", the phases in which consumers can feed electricity back into the vehicle electrical system must be predicted. These phases can be derived from the driving situations ahead. Here, the time T0 is the prediction time and delT is the prediction horizon. The prediction horizon delT is chosen so that it is longer than the time required for evaluating and initiating countermeasures.

If a vehicle has a system for predicted driving situation detection, it should provide the relevant information to the presented method about the type and time of occurrence of a driving situation. Accordingly, the task of step 1 would be to derive the driving situation relevant for regeneration from the driving situations identified.
Otherwise, the task of step 1 is to predict the relevant driving situations. For this z. B. the data from driver assistance systems, navigation and GPS are used. For example, an imminent descent can be derived from the altitude profile of the route ahead. On a steep descent with the corresponding environmental conditions, the engine cooler fan can tend to feed back and lead to overvoltage in the vehicle electrical system. If the information required for the prediction is not available for a certain period of time, emergency operation can be initiated in this case in order to reserve a certain residual capacity of the energy store.

In a step 2 (reference number 20), the feedback energy is estimated.

The amount of regenerative energy varies depending on the driving situation. Accordingly, feedback cannot always lead to a critical situation. In this regard, in this step, the feedback energy is estimated based on the detected driving situation in order to evaluate the effect of the feedback on the vehicle electrical system behavior and to check whether countermeasures need to be initiated. The estimation can be implemented with a database, for example.

In a step 3 (reference number 30), the charging acceptance and the cyclization of the energy store are evaluated.

An overvoltage usually only occurs when the charging acceptance of the battery is "poor" and the energy storage device cannot, or only slowly, absorb the excess regenerative energy. Charge acceptance is influenced by various factors such as state of charge, temperature and previous use of the energy storage device. In this regard, the current charging acceptance is determined in this step in order to evaluate the effect of the feedback on the behavior of the vehicle electrical system and to check whether countermeasures need to be initiated. In addition, the cyclization of the energy storage is evaluated. This makes it possible to prioritize whether the regenerative energy should be absorbed by the consumers or by the energy storage itself with regard to the current energy storage status.

In a step 4 (reference number 40), the utilization of the consumers is evaluated.

In this step, the extent to which the performance of non-safety-related consumers can be increased is evaluated. For this purpose, the information from analyzes certain consumers and determines how many degrees of freedom are currently available. The most suitable devices are the air conditioning consumers, since they have a high power requirement. In addition, the momentary manipulations in component behavior may not be immediately noticed by the driver. For example, the level of the heating can be evaluated and, if this is possible, increased by one or more levels for the duration of the feedback without the driver having to intervene. In addition, it is possible to reduce the heating level by 2 for the same period of time after the feedback phase in order to ensure a balanced interior temperature and save additional energy.

In a step 5 (reference number 50), the consumer power is increased.

In this step, the selected consumers are coordinated. For this, consumers are asked to draw more power in order to generate a higher on-board network load. This can happen via communication messages or through a direct signal line. The prerequisite for this is the connectivity of the selected consumers with a target control device that can be used in the presented method.

The increase in performance includes both the coordination of the active consumers and the connection of inactive consumers.

In a step 6 (reference number 60) the coordination of energy sources takes place.

If the consumers in the vehicle electrical system are fully utilized and/or there is no possibility of increasing the consumer load, the energy store is discharged in a targeted manner. This causes the charging acceptance of the energy store to be increased. For this purpose, the output power of the energy sources, such as the generator and direct-current converter (DC/DC), is reduced, as a result of which the energy store is loaded and discharged by an additional load. This is intended to reduce the state of charge and improve charging acceptance.

If a vehicle electrical system does not have a central energy store and the feedback power is greater than the consumer power, the DC/DC converter can be switched to boost mode in order to transport the excess energy to another sub-network.

In step 70 it is checked whether there is a failure of the input data for Toff. If this is the case, a jump follows (dashed arrow 72). In step 74, a check is made as to whether feedback is detected at time T0+delT. If this is the case, the method continues with step 2 20 (arrow 76). If this is not the case, there is a jump (arrow 78) to the beginning. In step 80 it is checked whether the cyclization is tolerable. If this is the case, there is a jump (arrow 82) to step 6 60. If this is not the case, there is a jump (arrow 84) to jump 4 40. In step 86 it is checked whether the energy consumption is limited. If this is the case, there is a jump (arrow 88) to step 660 in emergency operation or to step 80 in normal operation. If this is not the case, there is a jump (arrow 90) to step 110. Step 92 is checked whether an increase in performance is possible. If this is the case, there is a jump (arrow 94) to step 5 50. If this is not the case, there is a jump (arrow 96) to step 6 60.

In step 110 it is checked whether clock <T0 + delT. If this is the case, there is a jump (arrow 112) to step 3 30. If this is not the case, there is a jump (arrow 114) to the beginning. In step 120 it is checked whether input data is present. If this is the case, there is a jump (arrow 122) to step 110. If this is not the case, there is a jump (arrow 124) to step 3 30.

T0

Detektionszeitpunkt

Taus

Zeitpunkt zum Einleiten des Notbetriebs

In 2 an alternative embodiment of the method presented is shown in a flowchart. The normal case is shown with arrows with solid lines. Arrows with dashed lines indicate emergency operation. The following applies:

T0

time of detection

dew

Time to initiate emergency operation

If it is not possible to predict an upcoming driving situation, the feedback can be detected based on the current/voltage behavior of the vehicle electrical system. In this case, the countermeasures will only intervene at the beginning and/or in the course of the feedback. In the alternative embodiment, the functionality of steps 3 to 6 remains unchanged. Steps 1 and 2 are combined into the step explained below.

The method starts with a start step 5 . In a step 1 (reference number 100), a backfeed is detected.

In order to detect feedback, current and/or voltage measurements must be carried out at suitable points in the vehicle electrical system. Both the currents measured directly on the components and the total currents measured from sub-networks can be used for this purpose. The prerequisite for using the summation currents is that there is no energy source in a Sub-grid exists and the sum of the load currents is smaller than the sum of all feed-back currents of a sub-grid.

In step 70 it is checked whether there is a failure of the input data for Toff. If this is the case, a jump follows (dashed arrow 72). In step 75 it is checked whether feedback is detected at time T0. If this is the case, the method continues with step 2 20 (arrow 76). If this is not the case, there is a jump (arrow 78) to the beginning. In step 80 it is checked whether the cyclization is tolerable. If this is the case, there is a jump (arrow 82) to step 6 60. If this is not the case, there is a jump (arrow 84) to jump 4 40. In step 86 it is checked whether the energy consumption is limited. If this is the case, there is a jump (arrow 88) to step 660 in emergency operation or to step 80 in normal operation. If this is not the case, there is a jump (arrow 90) to step 110. Step 92 is checked whether an increase in performance is possible. If this is the case, there is a jump (arrow 94) to step 5 50. If this is not the case, there is a jump (arrow 96) to step 6 60.

In step 111 it is checked whether there is feedback. If this is the case, there is a jump (arrow 112) to step 3 30. If this is not the case, there is a jump (arrow 114) to the beginning. In step 120 it is checked whether input data is present. If this is the case, there is a jump (arrow 122) to step 110. If this is not the case, there is a jump (arrow 124) to step 3 30.

Parallel to the current-based detection, the voltage trend can be derived from voltage measurements in order to initiate countermeasures in the event of a significant voltage increase. If the information required for detection is not available for a certain period of time, emergency operation is initiated in this case in order to reserve a certain residual capacity of the energy store.

The proposed method can be used in both passenger cars and trucks, regardless of the degree of electrification.

Since the method can be implemented in a computer program and thus provided as a software product, it can be used in a control device such as a Body Control Module (BCM), a zone control device or a coupling element such as a DC/DC -Converter or a PowerNet Guardian (PNG: on-board circuit breaker), with a connection to the communication buses.

3 shows a vehicle 200 with a vehicle electrical system 202 and an arrangement 204 for carrying out the method in a schematic, highly simplified representation. Furthermore, two energy sources 206, for example batteries, and a number of loads 208 as well as a DC voltage converter 210 are provided in the vehicle electrical system 202.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• WO 2018077518 A1 [0005]
• DE 102014210283 A1 [0007]

Claims (10)

Method for operating a vehicle electrical system (202) in which consumers (208) and at least one energy source (206) are provided, wherein energy is predicted to be fed back by at least one of the consumers (208) and, if a feed back is detected, at least one countermeasure is initiated, which affects the level of an overvoltage in the vehicle electrical system (202) caused by the feedback. procedure after claim 1 , wherein at least one of the at least one energy source (206) is discharged. procedure after claim 1 or 2 , in which a power increase of at least one of the consumers (208) is made. Procedure according to one of Claims 1 until 3 , in which deactivated non-safety-related consumers (208) are switched on. Procedure according to one of Claims 1 until 4 , in which the at least one energy source (206) is coordinated. Procedure according to one of Claims 1 until 5 , which includes the following steps: - predicting a feedback, - estimating a feedback energy, - evaluating a charging acceptance and a cyclization of the energy storage (206), - evaluating the utilization of the consumers (208), - increasing the consumer power, - coordinating the energy sources (206 ). Procedure according to one of Claims 1 until 5 , which includes the following steps: - detecting a feedback, - evaluating a charging acceptance and a cyclization of the energy storage, - evaluating the utilization of the consumers (208), - increasing the consumer power, - coordinating the energy sources (206). Arrangement for operating a vehicle electrical system (202) for performing a method according to one of Claims 1 until 7 is set up. Computer program with program code means that is set up to implement a method according to one of Claims 1 until 7 execute when the computer program is executed on a computing unit. Machine-readable storage medium with a computer program stored on it claim 9 .

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