Method and device for voltage stabilization in a motor vehicle electrical system

Abstract

A method for voltage stabilization in an electrical network, namely in a motor vehicle electrical system, to which several consumers (V1 - V4) are connected, wherein the voltage (U3) applied to at least one consumer (V3, V4) is monitored by means of a consumer-side monitoring unit (UD3, UD4), and wherein, upon detection of a consumer-side voltage drop, this consumer (V3, V4) is put into a power-reduced operating mode or deactivated, wherein the at least one consumer (V3, V4) is assigned a switching control unit (SS3, SS4) which has the consumer-side monitoring unit (UD3, UD4) for monitoring the voltage (U3) applied to the consumer (V3, V4), wherein the switching control unit (SS3, SS4) is integrated into a control unit of the consumer (V3, V4), and wherein a consumer-side voltage drop is detected when the voltage applied to the consumer (V3,V4) applied voltage (U3) is less than a predetermined first threshold (UGr), where the first threshold (UGr) is at least high enough that a reset of the control unit, which would otherwise be feared due to the voltage drop, does not occur.

Description

[0001] The invention relates to a method and device for voltage stabilization in a motor vehicle electrical system.

[0002] The basic structure of a motor vehicle's power system consists of a wiring harness, an energy storage device, an energy source, and the electrical consumers. In principle, multiple energy storage devices or energy sources can be used. While a conventional motor vehicle with a 12V power system uses a generator as the energy source, in hybrid or battery-powered vehicles the supply is provided by a DC / DC converter, which in turn is connected to a high-voltage on-board network. The peak power of these energy sources is usually dimensioned to cover the average power of all installed systems in the vehicle. However, the peak power of the installed systems can be many times greater than the average power. While DC / DC converters have a high dynamic range, the generator in a motor vehicle is limited in its dynamic range due to structural reasons.

[0003] Currently, more and more chassis components in motor vehicles are being electrified for energy efficiency reasons, which significantly increases the load on the 12V on-board power supply. Dynamic peak power consumers in the chassis control systems, such as electric steering or an electronic stability program, exhibit greater dynamic response than the generator. This creates the problem that the generator cannot supply the desired current under dynamic load, and the battery or another energy storage device must serve as an energy storage device. Due to the internal resistance of the battery, voltage drops also occur at the battery terminals when current is delivered. Dynamic peak power consumers, such as electric steering or an electronic stability program, can therefore lead to drastic voltage drops.This problem can also occur in on-board electrical systems that use a DC / DC converter as the power source. However, when the on-board electrical system is subjected to dynamic loads, the battery only needs to act as an energy buffer when the DC / DC converter reaches its performance limit.

[0004] If additional power-hungry heating systems are activated as a customer function, they cause a permanent additional load when the vehicle's power supply is loaded by chassis control systems, leading to more severe drops in the vehicle's voltage. In critical cases, the voltage can drop so sharply that control units reset due to the voltage drop and thus no longer function reliably. Ultimately, these voltage drops can lead to safety-critical conditions and are therefore dangerous for vehicle occupants.

[0005] Currently, there are systems that make predictive decisions about the active conditions of certain systems based on environmental sensor data. Predictive systems have the fundamental disadvantage that they do not have a 100% detection rate, and therefore, false detections must be assumed during system design.

[0006] Furthermore, DE 10 2006 026 404 A1 describes an energy coordinator for an electrical grid that centrally manages the available energy. Since voltage dips often represent a local problem due to the topology of the on-board power grid, such a method may not be effective.

[0007] DE 10 2005 047 011 A1 shows an energy control device for a motor vehicle, which has an on-board network with at least one battery and a number of electrical consumers, with a supply control unit for controlling a plurality of system parameters influencing the current energy production of the motor vehicle based on at least one variable that indicates the total electrical energy required by the consumers, and a distribution control unit for controlling the distribution of the total electrical energy provided by the supply control unit to the individual consumers, wherein the distribution control unit transmits a first variable to the supply control unit, which contains information about the total electrical energy required currently and in the future, and wherein the supply control unit transmits a second variable to the distribution control unit,which contains information about the current total available electrical energy.

[0008] Further researched state of the art regarding motor vehicles shows: DE 103 20 187 B4, DE 101 55 670 A1, DE 199 31 144 A1, DE 197 45 849 A1, DE 102 11 970 A1 and DE 103 11 396 A1.

[0009] Furthermore, DE 10 2006 028 823 A1 shows a power supply network with integrated undervoltage protection in a passenger aircraft.

[0010] The object of the invention is to provide a simple and cost-effective method and a corresponding device for voltage stabilization that is improved compared to the prior art.

[0011] This object is achieved by a method according to claim 1 and a device according to claim 4. Advantageous further developments emerge from the dependent claims.

[0012] The method for voltage stabilization according to the invention is intended for a motor vehicle electrical system to which several consumers are connected.

[0013] The basic idea of ​​the invention is to provide an autonomous mechanism for the consumers connected to an electrical grid or their control units, which can locally and quickly trigger a reduction in energy consumption from the electrical grid. The decision as to whether a reduction in energy consumption from the electrical grid is necessary should be made solely based on the terminal voltage applied to the consumer or the control unit.

[0014] The voltage stabilization method according to the invention is designed such that the voltage applied to at least one load is monitored by a load-side monitoring unit. Upon detection of a load-side voltage drop, this load is extremely quickly switched to a reduced-power operating mode or completely deactivated. Advantageously, in the reduced-power operating mode, the load is controlled in such a way that less energy is drawn from the electrical grid.

[0015] The device according to the invention for voltage stabilization in an electrical network, namely in a motor vehicle electrical system to which several consumers are connected, is designed such that, with at least one switching control unit assigned to a consumer, which has a voltage detector arranged on the consumer side for monitoring the voltage applied to the consumer, the switching control unit switches this consumer to a reduced-power operating mode or deactivates it upon detecting a voltage drop on the consumer side. Advantageously, an electronic switch on the consumer side is provided for deactivating the consumer assigned to this switch, which is controlled by the switching control unit upon detection of a voltage drop on the consumer side such that the consumer assigned to this switch is deactivated.Ideally, the switch is designed as a MOS-FET switch, which enables the consumer to be deactivated quickly.

[0016] Advantageously, those consumers, control units, and customer functions in a motor vehicle electrical system are monitored and, in the event of a corresponding voltage drop, partially or completely deactivated that are particularly power-hungry and / or that can be briefly switched off without being noticed by the vehicle occupants. This particularly applies to any type of heating provided in the vehicle, since a brief shutdown of just a few seconds remains unnoticed by the vehicle occupants due to the large thermal time constants of the heating systems. Additional local energy reserves can also be released by monitoring and initiating reduced operation of other consumers, such as when braking a fan.

[0017] In the event of a drop in the vehicle electrical system voltage due to dynamic chassis control systems, a critical vehicle electrical system condition can be detected directly at the monitored loads, and the monitored load can be partially or completely shut down. The partial or complete shutdown of power-hungry systems or loads has a stabilizing effect on the vehicle electrical system, as the released power reserves can be used directly by the dynamic loads at the time of shutdown. As a result, the entire vehicle electrical system behaves as if there was no additional load on the vehicle electrical system at the time the dynamic chassis control systems were activated.

[0018] To detect a voltage drop on the consumer side, the voltage applied to the consumer or the corresponding control unit is evaluated according to the invention in such a way that a voltage drop on the consumer side is detected if the voltage applied to the consumer is lower than a predetermined first threshold. The threshold is at least high enough to prevent a reset of the control unit, which would be feared due to the voltage drop. The threshold can also be variable depending on various parameters and / or can be specified individually for each monitored consumer.

[0019] If a voltage drop on the load side is detected and the corresponding load is operated in a reduced-power mode or completely deactivated, in an advantageous embodiment of the invention, the load operated in the reduced-power mode or deactivated is returned to its original operating mode after a predetermined time interval or when a predetermined return condition is met. In particular, the load can also be slowly ramped back to normal operation after the predetermined time interval has elapsed, with the speed or type of ramp-up of the load being oriented towards the dynamics of the generator.

[0020] The invention will now be explained in more detail with reference to the following exemplary embodiments. Fig. 1 a device for voltage stabilization in a motor vehicle electrical system, and Fig. 2 a method for voltage stabilization in a motor vehicle electrical system.

[0021] In the Fig. Figure 1 shows a motor vehicle electrical system with at least one energy supplier E, to which various consumers V1 - V4 are connected. The energy supplier E consists, as is well known, of a 12V battery and an alternator. Consumers V1 and V2 are dynamic peak-power consumers in the chassis control systems, such as an electric steering system or an electronic stability program. In contrast, consumers V3 and V4 are power-hungry consumers, such as the vehicle heater and seat heater.

[0022] Since the power-hungry consumers V3 and V4 in particular lead to an enormous additional load on the vehicle electrical system during operation, which can lead to a considerable voltage drop in the vehicle electrical system in the event of an overlap with the dynamic peak power consumers V1 and V2, it is sensible to provide the device according to the invention for voltage stabilization for the power-hungry consumers V3 and V4.

[0023] For this purpose, a switching control unit SS3 and SS4 is assigned to the respective loads V3 and V4, which is integrated into the control unit of the respective load for cost and practical reasons. In addition to a voltage detector UD3 or UD4 for monitoring the terminal voltage applied to the load, the respective switching control unit SS3 or SS4 includes a switch S3 or S4 for deactivating or switching off the respective load V3 or V4 when a corresponding voltage drop is detected on the load side.

[0024] The method according to the invention for voltage stabilization of the vehicle electrical system by monitoring and deactivating the consumer is described with reference to Fig. 2 with reference to consumer V3 from Fig.1. The method begins with method step 10, in which the terminal voltage U3 applied to the load V3 is continuously monitored. If a voltage drop occurs that causes the terminal voltage U3 to drop below a predetermined first threshold UGr, the switch control unit SS3 opens switch S3 in the next method step 20, thus deactivating the load V3 by disconnecting it from the vehicle's electrical system. At the same time, a timer T is started for time monitoring.

[0025] If the specified time interval dT (approx. 1-2 seconds) has elapsed or been exceeded (monitored in step 30), the terminal voltage is monitored again in process step 40. If the terminal voltage exceeds the specified limit UGr, switch S3 is closed again by the switching control unit SS3 in process step 50 and the consumer is reconnected to the vehicle electrical system, allowing it to resume its normal operation.

[0026] A key advantage of the invention is that these autonomous shutdown mechanisms contribute to preventing critical voltage drops in the on-board power system or reducing the magnitude of the voltage drop. This fundamentally ensures better system stability and reduces the risk of a safety-critical state in individual control units. Furthermore, the autonomous mechanism simplifies the design of the entire on-board power system, as fewer critical load cases that can arise from the overlap of various consumers need to be considered during development.

Claims

[1] Method for voltage stabilization in an electrical network, namely in a motor vehicle electrical system to which several consumers (V1 - V4) are connected, wherein the voltage (U3) applied to at least one consumer (V3, V4) is monitored by means of a consumer-side monitoring unit (UD3, UD4), and wherein upon detection of a consumer-side voltage drop, this consumer (V3, V4) is put into a power-reduced operating mode or deactivated, wherein a switching control unit (SS3, SS4) is assigned to the at least one consumer (V3, V4), which switching control unit has the consumer-side monitoring unit (UD3, UD4) for monitoring the voltage (U3) applied to the consumer (V3, V4), wherein the switching control unit (SS3, SS4) is integrated into a control unit of the consumer (V3, V4), and wherein a consumer-side voltage drop is detected when the voltage applied to the consumer (V3,V4) is less than a predetermined first threshold (UGr), wherein the first threshold (UGr) is at least high enough that a reset of the control unit, which is to be feared due to the voltage drop, does not take place. [2] Method according to claim 1, characterized by that in the reduced-power operating mode the consumer is controlled in such a way that less or no energy is drawn from the electrical grid. [3] Method according to one of the preceding claims, characterized by that the consumer (V3) operated in the reduced-power operating mode or deactivated is operated again in the original operating mode after a predetermined time interval (dT) or when a predetermined return condition exists. [4] Device for voltage stabilization in an electrical network, namely in a motor vehicle electrical system to which several consumers (V1 - V4) are connected, with at least one switching control unit (SS3, SS4) assigned to a consumer (V3, V4), which has a voltage detector (UD3, UD4) arranged on the consumer side for monitoring the voltage (U3) applied to the consumer (V3, V4), wherein the switching control unit (SS3, SS4) is integrated into a control unit of the consumer (V3, V4), and wherein the switching control unit (SS3, SS4) switches or deactivates this consumer (V3, V4) in a power-reduced operating mode upon detection of a voltage drop on the consumer side, wherein a voltage drop on the consumer side is detected when the voltage (U3) applied to the consumer (V3, V4) is less than a predetermined first threshold (UGr), wherein the first threshold (UGr) is at least so high,that a reset of the control unit, which is to be feared due to the voltage drop, does not take place. [5] Device according to claim 4, characterized by that a consumer-side electronic switch (S3, S4) is provided for deactivating the consumer (V3, V4) assigned to this switch (S3, S4), which is controlled by the switching control unit (SS3, SS4) upon detection of a consumer-side voltage drop in such a way that the consumer (V3, V4) assigned to this switch (S3, S4) is deactivated.

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