Method and device for efficiency-related voltage adaptation in a vehicle electrical system

Abstract

A method (300) for reducing the energy consumption of a plurality of electrical consumers (106) of a vehicle, wherein the method (300) comprises - Determining (303) the power consumption of the multitude of electrical consumers (106) at a multitude of different on-board voltages; - Determining (304) an energy-efficient on-board voltage as the on-board voltage from the multitude of different on-board voltages by which the determined power consumption is reduced; and - Operating (305) the multitude of electrical consumers (106) with the determined energy-efficient on-board voltage.

Description

[0001] The invention relates to energy management in a vehicle. In particular, the invention relates to a method and a device for energy-efficient adjustment of the vehicle's electrical system voltage.

[0002] Vehicles (e.g., motor vehicles such as automobiles) contain a variety of electrical consumers. Examples of such electrical consumers include headlights, seat heating, rear window defroster, air conditioning, infotainment system, etc. To supply these electrical consumers, vehicles with internal combustion engines include a generator, which is designed to generate electrical energy from the mechanical energy of the combustion engine. Vehicles also include a battery (e.g., a lead-acid battery or a lithium-ion battery) to store the electrical energy generated by the generator and make it available when needed (e.g., when the combustion engine is not running). Furthermore, vehicles include an electrical system to distribute the electrical energy generated by the generator and / or stored in the battery to the various electrical consumers.

[0003] The numerous electrical components in a vehicle are usually designed to operate with vehicle electrical system voltages that fall within a predefined, standardized range (e.g., a range of 9V to 16V). The vehicle electrical system voltage is therefore typically selected to fall within this predefined, standardized range.

[0004] DE 10 2007 033 720 A1 relates to the recharging of the non-drive battery of a hybrid vehicle and in particular to a method and a device for recharging the battery in order to improve the battery life, the headlight life and the fuel economy of the hybrid vehicle.

[0005] This document describes a method and a device that enable the determination of an on-board voltage that ensures the most energy-efficient operation of a vehicle's electrical consumers. In particular, it proposes linking the selection of the on-board voltage to the different power consumption characteristics of the vehicle's electrical consumers. The aim is to thereby reduce the electrical power loss of the vehicle's electrical consumers and thus the vehicle's fuel consumption.

[0006] According to one aspect, a method for reducing the energy consumption of a large number of electrical consumers in a vehicle is described. These consumers in a vehicle can be, for example, the aforementioned consumers. The electrical consumers can typically be divided into two groups: a first group with a resistive consumption characteristic and a second group with a power-controlled consumption characteristic. The electrical consumers are usually connected via cables (e.g., copper cables) to a generator and / or a battery, which are designed to supply the electrical consumers with electrical energy.

[0007] The method involves determining the power consumption of numerous electrical loads at a variety of different vehicle electrical system voltages. Specifically, the corresponding power consumption of these loads can be determined for each of these voltages. Determining the power consumption can involve varying the vehicle electrical system voltage between a minimum and a maximum voltage. For example, the voltage can be varied from the minimum to the maximum (and / or vice versa), and the power consumption of the electrical loads can be measured. The aforementioned range of voltages lies between the minimum and maximum voltages. The voltage is typically varied within a single measurement period, which can be, for example, 10 seconds.

[0008] The procedure may further include determining the minimum on-board voltage. The minimum on-board voltage may depend on one or more of the following: a minimum charging voltage of the vehicle battery, whereby an on-board voltage above the minimum charging voltage prevents battery discharge; and / or a minimum required operating voltage of the numerous electrical consumers (the latter can be obtained, for example, from a consumer specification). The procedure may further include determining the maximum on-board voltage. The maximum on-board voltage may depend on a maximum possible operating voltage of the numerous electrical consumers (which can be obtained, for example, from a consumer specification) and / or on a maximum possible charging voltage of the battery.

[0009] Determining the power consumption of numerous electrical consumers at a specific vehicle electrical system voltage can involve the following steps. First, the total current supplied by the vehicle's generator or voltage converter at that voltage can be determined (e.g., using suitable measuring devices). Additionally, the charging current of the vehicle's battery at that voltage can be determined (e.g., using suitable measuring devices). The power consumption of the numerous electrical consumers (and their associated wiring) can then be calculated based on the difference between the total current and the charging current.

[0010] The procedure can further include determining an energy-efficient on-board voltage. The energy-efficient on-board voltage can be identified as the voltage from a multitude of different on-board voltages that reduces the measured power consumption. In particular, the on-board voltage can be determined as the energy-efficient voltage at which the measured power consumption is below an absolute or relative (in relation to all measured power consumptions) power threshold. For example, the on-board voltage can be used as the energy-efficient voltage at which the minimum power consumption of the electrical consumers is achieved.

[0011] The procedure can further include operating the numerous electrical consumers with the determined energy-efficient on-board voltage. Operating the electrical consumers with the determined energy-efficient on-board voltage takes place over an operating period that is typically significantly longer than the measurement period.

[0012] The procedure can further include determining whether a condition exists that triggers an update of the energy-efficient on-board voltage. This condition can, for example, include one or more of the following: the expiration of a timer; and / or a change in actual power consumption at the determined energy-efficient on-board voltage compared to the determined power consumption at the determined energy-efficient on-board voltage by more than a predetermined value; and / or the switching on / off of an electrical load.

[0013] The described method ensures that the vehicle electrical system and the connected electrical consumers are operated with an energy-optimized vehicle electrical system voltage, thereby reducing the consumption of the electrical consumers (and the lines) of the vehicle electrical system.

[0014] According to another aspect, a control unit for the energy management of numerous electrical consumers in a vehicle's electrical system is described. The control unit can be configured to determine the total power consumption of the numerous electrical consumers at a variety of different electrical system voltages. Furthermore, the control unit can be configured to determine an energy-efficient electrical system voltage from among the various different voltages, thereby reducing the determined total power consumption. Additionally, the control unit can be configured to instruct an energy converter to supply the determined energy-efficient electrical system voltage to the electrical system. The energy converter could be, for example, a power supply unit.This refers to a system designed to convert mechanical energy into electrical energy and to supply the electrical energy at different vehicle electrical system voltages. For example, the system may include a generator that converts the mechanical energy of an internal combustion engine into electrical energy, and a voltage regulator designed to supply the electrical energy generated by the vehicle's generator at different vehicle electrical system voltages.

[0015] The energy converter can also be a voltage converter (e.g., a DC-to-DC converter) designed to convert electrical energy from a first voltage range into electrical energy with different vehicle electrical system voltages. Such voltage converters can be used, for example, in connection with electric or hybrid vehicles.

[0016] Upon instruction from the control unit, the energy converter can provide the determined energy-efficient on-board voltage.

[0017] The numerous electrical loads are typically connected to the energy converter via a corresponding number of electrical lines. Furthermore, the multitude of electrical loads can include at least one electrical load with a resistive load characteristic and / or at least one electrical load with a power-controlled load characteristic.

[0018] The control unit can be configured to determine the energy-efficient vehicle electrical system voltage during the measurement period and to operate the electrical system at this determined voltage during the operating period. The measurement period is typically shorter than the operating period, ensuring the electrical system operates in an energy-optimized manner for as long as possible. Typically, the measurement period is approximately 10 seconds, while the operating period is usually several minutes or hours.

[0019] According to another aspect, a vehicle (e.g., a motor vehicle) is described. The vehicle includes, for example, an internal combustion engine and a generator configured to produce electrical energy from the mechanical energy of the internal combustion engine. Furthermore, the vehicle may include a voltage regulator configured to supply the electrical energy generated by the generator to the vehicle's electrical system at a specific voltage. Alternatively or additionally, the vehicle may include a battery configured to provide electrical energy at a specific voltage (e.g., to power an electric motor). In this case, the vehicle may include a voltage converter configured to supply the battery's electrical energy at the vehicle's electrical system voltage.The generator with voltage regulator and the voltage converter can generally be referred to as an energy converter, designed to provide electrical energy at the vehicle's electrical system voltage. The vehicle's electrical system serves to supply a variety of electrical consumers, which are connected to the energy converter via numerous wires, with electrical energy. Furthermore, the vehicle includes a control unit designed to control or regulate the energy converter so that it maintains an energy-efficient electrical system voltage.

[0020] Another aspect described is a software (SW) program. The SW program can be configured to run on a processor and thereby execute the procedure described in this document.

[0021] Another aspect describes a storage medium. This storage medium can include a software program configured to run on a processor and thereby execute the procedure described in this document.

[0022] It should be noted that the methods, devices, and systems described in this document can be used both alone and in combination with other methods, devices, and systems described in this document. Furthermore, any aspect of the methods, devices, and systems described in this document can be combined with one another in a variety of ways. In particular, the features of the claims can be combined with one another in a variety of ways.

[0023] The invention will now be described in more detail using exemplary embodiments. Fig. 1 a block diagram of an exemplary electrical system of a vehicle; Fig. 2 exemplary consumption characteristics of electrical consumers in a vehicle; and Fig. 3 a flowchart of an exemplary procedure for adjusting the on-board power supply voltage.

[0024] Fig. Figure 1 shows a block diagram of an example vehicle electrical system 100. The electrical system 100 includes a generator 101, which is configured to convert the mechanical energy of an internal combustion engine into electrical energy. The generator 101 is usually coupled to a voltage regulator 102, which is configured to set a specific electrical system voltage and to supply the electrical energy generated by the generator 101 at the set voltage. The voltage regulator 102 can be controlled by an energy management control unit 103. The control unit 103 can be configured to change the electrical system voltage based on the voltage regulator 102. In other words, the control unit 103 can be configured to control the voltage regulator 102 so that it sets a specific electrical system voltage.

[0025] Fig. Figure 1 shows an example of a vehicle with an internal combustion engine. The invention is also applicable to vehicles with electric motors or to vehicles with hybrid drives. In this case, the vehicle electrical system 100 can include a voltage converter configured to convert electrical energy from a first voltage (e.g., 300 V) into electrical energy with the set vehicle electrical system voltage. The electrical energy can be supplied, for example, by a high-voltage battery. The control unit 103 can be configured to change the vehicle electrical system voltage based on the voltage converter.

[0026] The vehicle electrical system 100 can include a battery 104 (e.g., a lead-acid battery or a lithium-ion battery) designed to store electrical energy and supply it to the electrical consumers 106 in the vehicle as needed (e.g., when the combustion engine is off). The battery 104 typically receives a charging current from the generator 101 when the vehicle electrical system voltage exceeds a certain charging voltage threshold U_L_min. Conversely, the battery 104 is typically discharged when the vehicle electrical system voltage falls below the charging voltage threshold. The charging voltage threshold typically depends on the state of charge of the battery 104 and is, for example, 12.5 V + / - 0.5 V (depending on the state of charge of the battery 104). Furthermore, the charging voltage threshold U_L_min may depend on the temperature of the battery 104. The control unit 103 can be configured to determine the current charging voltage threshold U_L_min of the battery 104 (e.g.(using suitable sensors on the battery 104). The control unit 103 can further be configured to adjust the on-board voltage in such a way that the charging voltage threshold U_L_min is not undercut, in order to prevent the battery 104 from discharging.

[0027] Typically, the charging current I_L of battery 104 increases with increasing vehicle electrical system voltage (above the charging voltage threshold U_L_min). Battery 104 can be designed for a maximum possible charging current I_L_max and / or a maximum possible charging voltage U_L_max. The control unit 103 can be configured to adjust the vehicle electrical system voltage so that the maximum charging voltage U_L_max of battery 104 is not exceeded, thus preventing damage to battery 104.

[0028] Furthermore, the vehicle electrical system 100 comprises one or more distribution boards 105, which are configured to distribute the electrical energy from the generator 101 and / or the battery 104 to a multitude of electrical consumers 106 in the vehicle. The individual consumers 106 are connected via electrical cables 107 to a distribution board 105 and / or to the energy sources generator 101 / battery 104. Both the individual consumers 106 and the cables 107 result in the consumption of electrical energy in the vehicle.

[0029] As outlined at the beginning, this document proposes that the operating strategy of a vehicle's energy management system determines an optimal on-board voltage from an efficiency perspective and sets it, taking into account any further boundary conditions. To determine an energy-efficient on-board voltage, the energy management system (which is implemented, for example, on the control unit 103) can use a search process in which the on-board voltage is varied. The voltage variation can be performed by increasing the on-board voltage from a first voltage (e.g., 12 V) to a second voltage (e.g., 15 V) within a predefined time interval (e.g., approximately 10 seconds) and then decreasing it again (or vice versa). Parallel to the variation of the on-board voltage, the power consumption of the consumers 106 and the lines 107 in the vehicle is calculated and recorded.

[0030] The power consumption of the electrical consumers 106 and lines 107 in the vehicle can be calculated, for example, using the equation P_Load = U_BN * I_BN, where U_BN is the vehicle electrical system voltage and I_BN is the effective vehicle electrical system current I_BN. The effective vehicle electrical system current I_BN includes the current drawn by the numerous electrical consumers 106 and the lines 107 in the vehicle. However, the effective vehicle electrical system current does not include the battery charging current I_L, which is used to charge the vehicle's battery 104. The effective vehicle electrical system current I_BN can be determined, for example, from the difference between the total current I_G supplied by the generator 101 and the battery charging current I_L, i.e., I_BN = I_G - I_L. Alternatively or additionally, the consumer currents I_V could also be measured individually or collectively. The effective vehicle electrical system current I_BN is the sum of the consumer currents I_V to the consumers 106 in the vehicle.

[0031] The vehicle electrical system current I_BN is measured for different vehicle electrical system voltages U_BN, and thus the power consumption P_Load of the numerous electrical consumers 106 and the lines 107 in the vehicle is determined for different vehicle electrical system voltages. From an efficiency perspective, the optimal vehicle electrical system voltage U_BN is the voltage U_BN with the lowest power consumption P_Load of the numerous consumers 106 and lines 107.

[0032] Due to the ohmic characteristic of the wiring 107, i.e., the resistance of the copper conductors 107 to the electrical loads 106, the power loss in the wiring 107 increases with increasing current I_V to a load 106. If a load 106 also has an ohmic characteristic (such as a seat heater or a rear window defroster), the power consumption of the ohmic load 106 will also increase with increasing current I_V. Thus, the ratio of P_loss (power in the conductors 107) to P_load (power at the load 106) remains constant for an ohmic load 106. However, the power P_consumer of the consumer 106 and also the power loss P_loss in the cabling 107 increase quadratically with the operating network voltage U_BN, since for resistive consumers P_load=P_loss+ V_consumer=U_BN* U_BN / R, where R is the total resistance of the line 107 and the resistive consumer 106.

[0033] For a consumer 106 with constant power consumption (e.g., a power-regulated consumer such as a controlled pump), the required current I_V decreases as the on-board voltage U_BN increases in order to achieve the power P_consumer in this power-regulated consumer 106 (P_consumer = U_BN * I_V). Consequently, the current I_V through the wiring 107 to the power-regulated consumer 106 also decreases, and thus the power loss P_loss in the wiring 107 decreases.

[0034] Fig. Figure 2 shows the power loss in the vehicle electrical system 100 from various consumers 106 and their wiring 107 up to the battery 104 or to the generator 101. In the example shown, the consumers 106 have a power-controlled consumption characteristic with a constant power input of 1000 W (curve 204) or a resistive consumption characteristic with a power input of 1000 W at U_BN = 12 V (curve 203). On the x-axis of the Fig. Figure 2 shows the on-board voltage U_BN 202, measured at the positive terminal of battery 104. The y-axis shows the total power consumption P_Last 201, where P_Last = P_Loss (due to wiring 107) + P_Consumer (due to the consumer 106).

[0035] Out of Fig. Figure 2 shows that for resistive loads 106, the total power consumption P_Load 201 increases with increasing on-board voltage 202 (curve 203). Conversely, for power-controlled loads 106, the total power consumption P_Load 201 decreases with increasing on-board voltage 202 (curve 204). Since the on-board network 100 comprises a large number of loads 106, varying the on-board voltage 202 will typically result in a curve for the total power consumption 201 of all loads 106 (and their wiring 107) that lies between the curves 203 and 204 for purely resistive and purely power-controlled loads, respectively.

[0036] In particular, a mixture of resistive and power-controlled loads in the vehicle can result in a minimum total power consumption 201 at an on-board voltage 202, which lies between a minimum possible on-board voltage U_min and a maximum possible on-board voltage U_max. The minimum possible on-board voltage U_min can, for example, be the lower limit of the predefined, standardized voltage range for which the electrical loads 106 of a vehicle must be designed. Alternatively or additionally, the minimum possible on-board voltage U_min can, for example, be the current charging voltage threshold U_L_min of the battery 104, to ensure that the battery 104 is not under load. The maximum possible on-board voltage U_max can, for example, be the upper limit of the predefined, standardized voltage range for which the electrical loads 106 of a vehicle must be designed.Alternatively or additionally, the maximum possible on-board voltage U_max can be, for example, the maximum possible charging voltage U_L_max of battery 104, to ensure that battery 104 is not damaged.

[0037] Consequently, according to the further boundary conditions in the vehicle electrical system 100, which allow a voltage range between a minimum possible and a maximum possible voltage [U_min, U_max], the vehicle electrical system voltage can be determined and set by taking into account the optimally efficient voltage determined above.

[0038] It is to be expected that if the vehicle electrical system 100 includes a high proportion of power-controlled loads 106, a vehicle electrical system voltage 202 will be set close to the maximum possible voltage U_max, while in the case of a vehicle electrical system 100 with a high proportion of resistive loads 106, a voltage close to the minimum possible voltage U_min will be set.

[0039] Since the characteristics of the consumers 106 can change depending on operating points, and / or since switching consumers 106 on and off by the user changes the composition of the active consumers 106 in the vehicle, it can be useful to repeatedly determine an energy-optimized on-board voltage 202. For example, after starting the combustion engine, an initial energy-optimized on-board voltage 202 can be determined in a first search. This search can then be repeated periodically (at a predefined time interval of, for example, 10 minutes or 1 hour). Alternatively or additionally, the search can be repeated situation-specifically, for example, if the on-board load (i.e., P_Last) changes significantly.For example, a search process to determine an energy-optimized on-board network voltage 202 can be initiated if the total power consumption P_Last has increased or decreased by more than a predefined value since the last search process.

[0040] The type and extent of consumers 106 typically depend on the respective vehicle class and its equipment. The periodicity of search processes to determine an energy-optimized on-board voltage 202 and / or the aforementioned predefined value that triggers a new search process can depend on the respective vehicle class or the specific vehicle and the consumers 106 contained therein.

[0041] Fig.Figure 3 shows a flowchart of an exemplary procedure 300 for determining an energy-efficient on-board voltage 202 in a vehicle. The vehicle comprises a multitude of electrical consumers 106, which are connected via electrical lines 107 to a generator 101 and / or a battery 104. The procedure 300 includes determining 301 a minimum possible operating voltage U_min and / or determining 302 a maximum possible operating voltage U_max. Furthermore, the procedure 300 includes determining 303 the power consumption P_load of the multitude of electrical consumers 106 and the multitude of electrical lines 107 for different operating voltages between U_min and U_max. Subsequently, the operating voltage 202 is determined (step 304) for which the power consumption P_load is reduced (e.g., minimized in the interval [U_min, U_max]).Finally, the on-board network 100 is operated with the determined operating network voltage 202 305.

[0042] Procedure 300 can be repeated periodically. Alternatively or additionally, procedure 300 can further include determining whether a trigger condition exists (306). If a trigger condition exists, procedure 300 is executed repeatedly to determine and provide an updated, energy-optimized on-board voltage (202). The trigger condition could be, for example, that the power consumption P_Last has changed by at least one predefined value since the last determined on-board voltage (202). Another example of a trigger condition is that a timer for the periodic repetition of procedure 300 has expired. The timer enables the periodic repetition of procedure 300.

[0043] The procedure 300 can be implemented as software within the framework of a vehicle's energy management system (e.g. on the control unit 103) and can therefore be implemented cost-effectively.

[0044] The procedure described in this document allows the energy management system to adapt to the specifically equipped vehicle, its operating point, and its user operation in order to set an efficiency-optimized on-board voltage. This reduces electrical power loss in the vehicle and thus also fuel consumption. For example, if the power loss is reduced by 100 W by selecting the appropriate on-board voltage, fuel savings of approximately 0.1 liters / 100 km can be expected. Furthermore, determining an energy-optimized on-board voltage reduces the load on the consumers 106 and the lines 107 in the vehicle, leading to a reduced failure rate of the consumers 106.

[0045] The present invention is not limited to the embodiments shown. In particular, it should be noted that the description and the figures are intended only to illustrate the principle of the proposed methods, devices, and systems.

Claims

[1] A method (300) for reducing the energy consumption of a plurality of electrical consumers (106) of a vehicle, the method (300) comprising - determining (303) a power consumption of the plurality of electrical consumers (106) at a plurality of different vehicle electrical system voltages; - determining (304) an energy-efficient vehicle electrical system voltage as the vehicle electrical system voltage from the plurality of different vehicle electrical system voltages by which the determined power consumption is reduced; and - Operating (305) the plurality of electrical consumers (106) with the determined energy-efficient vehicle electrical system voltage. [2] The method (300) of claim 1, wherein determining (303) the power consumption comprises: varying the vehicle electrical system voltage between a minimum vehicle electrical system voltage and a maximum vehicle electrical system voltage; wherein the plurality of different vehicle electrical system voltages are between the minimum and the maximum vehicle electrical system voltage. [3] The method (300) according to claim 2, further comprising - Determining (301) the minimum vehicle electrical system voltage; wherein the minimum vehicle electrical system voltage depends on one or more of: a minimum charging voltage of a battery (104) of the vehicle, wherein a vehicle electrical system voltage above the minimum charging voltage prevents discharging of the battery (104); a minimum required operating voltage of the plurality of consumers (106); and - Determining (302) the maximum vehicle electrical system voltage; wherein the maximum vehicle electrical system voltage depends on a maximum possible operating voltage of the plurality of consumers (106) and / or a maximum possible charging voltage of the battery (104). [4] The method according to any preceding claim, further comprising - determining (306) whether a condition for updating the energy-efficient vehicle electrical system voltage exists; wherein the condition comprises one or more of: Expiry of a timer; and change in an actual power consumption at the determined energy-efficient vehicle electrical system voltage compared to the determined power consumption at the determined energy-efficient vehicle electrical system voltage by more than a predetermined value. [5] The method according to any preceding claim, wherein determining (303) the power consumption of the plurality of electrical loads (106) at a particular vehicle electrical system voltage comprises: - determining the total current supplied by a generator (101) of the vehicle at the determined vehicle electrical system voltage; - determining a charging current of a battery (104) of the vehicle at the determined vehicle electrical system voltage; and - Determining (303) the power consumption of the plurality of electrical consumers (106) based on the difference between the total current and the charging current. [6] A control unit (103) for the energy management of a plurality of electrical consumers (106) in an on-board network (100) of a vehicle, wherein the control unit (103) is configured - to determine the total power consumption of the plurality of electrical consumers (106) at a plurality of different vehicle electrical system voltages; - to determine an energy-efficient vehicle electrical system voltage as the vehicle electrical system voltage from the multitude of different vehicle electrical system voltages by which the determined total power consumption is reduced; and - instructing an energy converter (101, 102) to provide the determined energy-efficient vehicle electrical system voltage in the vehicle electrical system (100). [7] The control unit (103) according to claim 6, wherein the plurality of electrical loads (106) - are coupled to the energy converter (101, 102) via a corresponding plurality of electrical lines (107); and / or - comprise at least one electrical consumer (106) with an ohmic consumption characteristic; and / or - comprise at least one electrical consumer (106) with a power-controlled consumption characteristic. [8] The control unit (103) according to any one of claims 6 to 7, wherein the energy converter (101, 102) - a generator (101) and a voltage regulator (102) which are designed to convert mechanical energy into electrical energy and to provide it with different vehicle electrical system voltages; or - comprises a voltage converter which is configured to convert and provide electrical energy having a first voltage into electrical energy having different vehicle electrical system voltages. [9] The control unit (103) according to any one of claims 6 to 8, wherein the control unit (103) is arranged - to determine the energy-efficient vehicle electrical system voltage in one measurement period; and - in an operating period, to operate the vehicle electrical system (100) with the determined energy-efficient vehicle electrical system voltage; wherein a temporal length of the measuring period is shorter than a temporal length of the operating period. [10] A vehicle which includes - an energy converter (101, 102) which is arranged to provide electrical energy with an on-board network voltage; - a plurality of electrical consumers (106) coupled to the energy converter (101, 102) via a plurality of lines (107); and - a control unit (103) according to any one of claims 6 to 9, which is arranged to instruct the energy converter (101, 102) to provide an energy-efficient vehicle electrical system voltage.

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