Device for monitoring a high-voltage electrical system of an electrically powered vehicle for the presence of an overload

Abstract

Device for monitoring a high-voltage electrical system (1) of an electrically operable vehicle for the presence of an overload, wherein the high-voltage electrical system (1) comprises as components (10) one or more energy sources and / or one or more energy sinks, each of which is connected via a conductor strand arrangement (15) to a first supply potential line (8) and to a second supply potential line (9), in which each of the components (10) is assigned a current sensor (41, 42, 43, 44) which is designed to detect a current flowing through the relevant component (10) and to transmit information representing the level of the current to an evaluation unit (45) for evaluation, characterized in that the evaluation unit (45) is designed to compare the current with a first current threshold, which corresponds to the permitted current in the normal case, and a second current threshold, which corresponds to the tripping current of a fuse element, and to output a switch-off signal at least for the component (10) assigned to the current sensor (41, 42, 43, 44) if, as a first criterion, the level of the current and the duration of the level of the current lie between the first and the second current threshold, and the evaluation unit (45) is further designed to additionally compare the current with a third current threshold and to output a switch-off signal at least for the component (10) assigned to the current sensor (41, 42, 43, 44) if, as a second criterion, the level of the current lies between the second and the third current threshold.

Description

[0001] The invention relates to a device for monitoring a high-voltage electrical system of an electrically operated vehicle for the presence of an overload. The high-voltage electrical system comprises one or more energy sources and / or one or more energy sinks, each of which is connected to a first supply potential line and a second supply potential line via a conductor strand arrangement.

[0002] To protect individual conductor strands in a high-voltage electrical system, fuses adapted to the different current strengths and cable cross-sections are used. The fuses are used to trigger a very high current flow caused by a low-resistance connection of the live conductors, in order to protect the component or components connected to the relevant conductor strand from destruction or damage. Due to the limited space in a vehicle, the fuses are not arranged in a separate fuse distributor, as is the case with fuses in a low-voltage electrical system (12 V electrical system). Instead, additional power connections are attached to existing components, such as a charging device or power electronics, and fuses are installed in these components.

[0003] Fuses exhibit a relatively high degree of variation in the current at which they trip. Furthermore, the current referred to as the tripping current depends on the ambient temperature. If the tripping current of the fuse is greater than the continuous current rating of the conductor strand to be protected, an overload may occur, leading to damage to the conductor strand and possibly to the components connected to it. To reliably rule out such an overload, the cables of each conductor strand must be oversized to such an extent that the tripping current of the fuse is ideally lower than the permitted continuous current through the conductor strand. However, this results in an increased weight of the vehicle, which in turn impairs energy efficiency.

[0004] DE 10 2011 086 495 A1 discloses an energy storage system for a vehicle. A monitoring / control device is configured to monitor for overcurrent. If an overcurrent is detected, an energy storage device is disconnected from the vehicle electrical system by opening main contactors via a control device.

[0005] US Pat. No. 8,432,657 B2 discloses a protective device for an electrical load. To this end, the protective device sets a threshold temperature lower than a permissible temperature of an electrical wire for use in the load circuit and estimates a temperature of the electrical wire based on an ambient temperature, a load current, and a time during which the load current flows through the electrical wire. The protective device simulates the behavior of a fuse.

[0006] US Pat. No. 8,432,657 B2 discloses a device for monitoring a vehicle power supply in which the behavior of a fuse is simulated by an electronic protection circuit. A control signal is output to centrally shut off the loads if a threshold is exceeded for a predefined period of time.

[0007] US 6,369,460 B1 discloses simulating the behavior of a fuse by an electronic protection circuit, whereby a comparison is made with a single threshold value corresponding to the tripping current of a fuse element. A control signal is then output when an overcurrent is present for a specific time in order to simulate the characteristic curve of a fuse.

[0008] It is the object of the present invention to provide a device for monitoring a high-voltage electrical system of an electrically operated vehicle for the presence of an overload, in which no over-dimensioning of the lines of a conductor strand arrangement of the high-voltage electrical system is required.

[0009] This object is achieved by a device according to the features of patent claim 1. Advantageous embodiments emerge from the dependent patent claims.

[0010] To achieve this objective, a device for monitoring a high-voltage electrical system of an electrically operable vehicle for the presence of an overload is proposed. The high-voltage electrical system comprises one or more energy sources and / or one or more energy sinks as components, each of which is connected to a first supply potential line and to a supply potential line via a conductor strand arrangement. It is understood that a component also includes a component that represents both an energy source and an energy sink.

[0011] Each of the components is assigned a current sensor which is designed to detect a current flowing through the respective component and to transmit information representing the magnitude of the current to an evaluation unit for evaluation, wherein the evaluation unit is designed to compare the current with a first current threshold, which corresponds to the permitted current under normal circumstances, and a second current threshold, which corresponds to the tripping current of a fuse element, and to output a shutdown signal at least for the component assigned to the current sensor if, as a first criterion, the magnitude of the current and the duration of the magnitude of the current lie between the first and second current thresholds, and wherein the evaluation unit is designed to additionally compare the current with a third current threshold and to output a shutdown signal at least for the component assigned to the current sensor,if, as a second criterion, the level of the current lies between the second and third current thresholds.

[0012] A current sensor can be implemented, for example, in the form of a shunt or a Hall sensor. However, in principle, any sensor that allows measuring the current flowing through one or more components of a conductor strand can be used.

[0013] The evaluation unit can be, for example, a separate control unit or a specific microcontroller in a control unit already present in the vehicle. Alternatively, the evaluation unit can be implemented in software and run on a control unit already present in the vehicle. Such a control unit could, for example, be a shutdown device that ensures that the high-voltage electrical system disconnects energy sources from the rest of the high-voltage electrical system in the event of an accident. For this purpose, a corresponding shutdown device is typically connected to the relevant components to be shut down via dedicated hardware lines.

[0014] The shutdown signal can, for example, be used by a device processing the shutdown signal to at least shut down the components associated with the current sensor or simply to reduce their power. The shutdown signal can also be used to disconnect all energy sources from the high-voltage electrical system.

[0015] The device makes it possible to detect an overload caused by a current between the permissible current under normal conditions (first current threshold) and the tripping current of a safety element, such as a high-voltage fuse. The device makes it possible to dispense with large cross-sections in the conductor strand arrangement and the resulting requirements for corresponding connector systems. Furthermore, the device meets high integrity requirements. The overload protection can be designed very precisely by selecting appropriate values ​​for the first and second current thresholds. The device is cost-effective to provide, as the only additional costs incurred are for the provision of the current sensors.

[0016] The device can be implemented either using hardware circuits and / or software, enabling high levels of integrity (Automotive Security Integrity Level, ASIL). Furthermore, the device allows for resetting the shutdown of a component in the event of an overload by appropriately controlling the evaluation unit. This makes resetting easier and faster than replacing a fuse. Short-circuit protection using fuse elements can be designed exclusively for short-circuit situations and does not need to consider overload situations. This prevents false triggering at high operating currents, while ensuring isolation capability at high currents.

[0017] According to one embodiment, the first current threshold is represented by a predetermined first characteristic curve in a current-time diagram, which has a first section in which the current has a first, high current value from a first point in time to a second point in time and which has a second section in which the current has a second, comparatively lower current value from the second point in time. The first characteristic curve therefore corresponds, for example, to the permitted current in the conductor strand arrangement under normal circumstances. The permitted current under normal circumstances makes it possible to draw an increased inrush current for a specific period of time. In contrast, a reduced continuous current is provided under normal circumstances.

[0018] The first current threshold can also be chosen arbitrarily, for example, to tolerate a certain degree of overload beyond the normal case. The first characteristic curve then lies to the right of the permissible current in the conductor string arrangement under normal conditions.

[0019] According to a further embodiment, the second current threshold is represented by a temperature-dependent, non-linear set of characteristics in a current-time diagram, which has a substantially exponentially decreasing profile. The higher the temperature (e.g., the ambient temperature), the smaller the difference between a current value of the first current threshold and a current value of the second current threshold at a given point in time. The profile of the set of characteristics in the current-time diagram, and in particular the distance between a current value of the first current threshold and a current value of the second current threshold at a given point in time, can be selected by designing and dimensioning a fuse.In principle, it is advisable if each current value of the second current threshold is at any time greater than the current value of the first current threshold at the same time in order to avoid unwanted triggering of the fuse in a non-critical operating case.

[0020] According to the invention, the evaluation unit is configured to additionally compare the current with a third current threshold and to output a shutdown signal at least for the component associated with the current sensor if, as a second criterion, the current level lies between the second and third current thresholds. The third current threshold corresponds to the line characteristic determined by the thickness and cross-section of a line.

[0021] The third current threshold is represented by a temperature-dependent, non-linear characteristic curve in a current-time diagram, which essentially exhibits an exponentially declining curve and corresponds to the conduction characteristic. The lower the ambient temperature of the vehicle, the greater the difference between a current value of the third current threshold and a current value of the second current threshold at the same time.

[0022] The high-voltage electrical system can comprise a disconnection device that disconnects power sources from the first and second supply potential lines using a trigger signal. The disconnection device is configured to generate the trigger signal in the event of a sensor-determined acceleration that exceeds a predetermined limit value. The disconnection signal output by the evaluation unit can be fed to the energy sources as a trigger signal. This makes it possible to disconnect the component or components connected to a conductor strand from the high-voltage electrical system in the event of an overload using components present in a vehicle.

[0023] The evaluation unit can be designed to only output the shutdown signal when a third criterion, a predetermined period of time since the occurrence of the first, and optionally also the second, criterion, has been met. The length of the predetermined period of time can depend on the level of the measured current. This embodiment enables a distinction to be made between an uncritical and an unprotected overload case. The uncritical overload case occurs when the current detected by the current sensor lies between the permissible current through a conductor phase under normal conditions (first current threshold) and the current characteristic of the continuous current design (third current threshold). There is no immediate danger to the cable or the component connected to the cable.In contrast, an immediate shutdown occurs if a critical overload occurs in which the measured current lies between the current characteristic of the continuous current design of the line (third current threshold) and the tripping characteristic of the high-voltage fuse.

[0024] In order to inform the driver or a workshop that a (non-critical) overload has occurred, the evaluation unit can be designed to output a diagnostic or error signal if the first and / or the second criterion is met.

[0025] The evaluation unit can further be configured to store one or more of the following information in a memory upon the occurrence of the first and / or second criterion: an identifier of the current sensor that detected the increased current exceeding the first current threshold; the magnitude of the measured current; and the duration of the increased current occurrence. This makes it possible, for example, to determine during a workshop visit by reading the corresponding information that a fault is occurring and even in which conductor strand. This facilitates troubleshooting and rectification.

[0026] According to a further embodiment, one or more fuses are provided in the conductor strand arrangement, each fuse being triggered when a predetermined current which is greater than the second threshold value is exceeded in the conductor sub-strand in which the respective fuse is arranged, in order to protect the components connected to the conductor strand.

[0027] Each component can be assigned a fuse. Alternatively, multiple components can be assigned a common fuse.

[0028] In a further embodiment, each component can be assigned a current sensor. Alternatively, a common current sensor can be assigned to several components.

[0029] The invention is explained in more detail below using exemplary embodiments in the drawings. They show: Fig. 1 a schematic representation of a high-voltage electrical system of an electrically operated vehicle according to the prior art; Fig. 2 a current-time diagram showing the characteristics of the tripping current, the continuous current rating of a conductor phase and the nominal current through a Fig. 1 shows the conductor strand; Fig. 3 a schematic representation of a high-voltage electrical system according to the invention of an electrically operated vehicle according to a first embodiment variant; Fig. 4 is a current-time diagram illustrating the operation of the device according to the invention; Fig. 5 a current-time diagram supplemented by a warning area within an overload range; Fig. 6 a schematic representation of a high-voltage electrical system of an electrically powered vehicle according to a second embodiment; and Fig. 7 a schematic representation of a process for monitoring a high-voltage electrical system of an electrically powered vehicle for the presence of an overload.

[0030] Fig. 1 shows a schematic representation of a high-voltage electrical system 1 of an electrically operated vehicle. The electrically operated vehicle can be a hybrid vehicle or an electric vehicle. The high-voltage electrical system 1 comprises, as essential components, a drive motor 2, an electronic control unit 3, an electrochemical storage unit 4 (accumulator), and a conductor strand arrangement 15. The drive motor 2 is supplied with electrical energy to drive the drive motor 2 via the electronic control unit 3, which is connected to the storage unit 4 via a first supply line 8 and a second supply line 9. For energy recovery, energy can be stored again in the storage unit 4 by appropriately controlling the drive motor 2 and the electronic control unit 3.

[0031] In a manner known to those skilled in the art, the storage device 4 comprises the actual electrochemical storage cells 5, of which only one is shown schematically for the sake of clarity. The storage cells 5 are connected to the supply lines 8, 9 via a controllable switching element 6, e.g., a contactor or relay, and a fuse 7 connected in series therewith. In practice, the fuse 7 is connected to only one of the supply lines 8 or 9. The fuse 7 is designed for a maximum permissible current via the supply lines 8, 9, with the triggering current being above the maximum permissible current.

[0032] In addition, the high-voltage electrical system 1 comprises a number of components 10, which represent either an energy source and / or an energy sink. For example, component 10 represents an energy source 11 in the form of a charger. Reference numerals 12, 13, and 14 denote energy sinks, with energy sink 12 being, for example, a compressor of an air conditioning system, energy sink 13 being a heater, and energy sink 14 being a DC / DC converter for a 12 V electrical system of the vehicle (not shown in the figure for the sake of simplicity).

[0033] The components 10 are connected to the first and second supply lines 8, 9 via respective lines or, more generally, conductor sections. For example, the energy source 11 is connected to the second supply line 9 via a line 16 (also referred to as a conductor section), the energy sink 12 via a line 18, the energy sink 13 via a line 20, and the energy sink 14 via a line 22. The energy source 11 is connected to the first supply line 8 via a line 17 (also referred to as a conductor section), the energy sink 12 via a line 19, the energy sink 13 via a line 21, and the energy sink 14 via a line 23. Respective fuses 24, 25, 26, 27 are arranged in the lines 17, 19, 21, 23.

[0034] The cross-section of lines 16 to 23 and the dimensioning of fuses 24 to 27 depend on the nominal data of the respective components and lines. This means, for example, that lines 16 and 17 may have different dimensions than lines 18 to 23 of energy sinks 12 to 14. Likewise, lines assigned to a component 10 may have a different cross-section than the lines of another component. The dimensioning is determined according to the requirements of the component to be supplied or the energy-supplying component 10.

[0035] In Fig. 1 also shows a shutdown device 30 which, via trigger signal paths 31, 32, 33, is capable of shutting off the energy sources of the high-voltage vehicle electrical system 1 or disconnecting them from the supply lines 8, 9 when a predetermined criterion is met. The trigger signal paths can be implemented, for example, using communication lines, i.e. lines via which communication signals can be transmitted. One such criterion is, for example, that a predetermined acceleration is exceeded, which indicates a crash of the vehicle. The energy sources controlled by the shutdown device 30 are the control electronics 3, the storage device 4, and the energy source 11 in the form of a charger.While the storage device 4 is disconnected from the supply lines 8, 9 by controlling a dedicated switching element 6, the drive motor 2 is disconnected by controlling the control electronics 3 and the energy source 11 by controlling the switching elements contained in these components. In the case of the control electronics 3 and the energy source 11 in the form of a charger, these switching elements are switching elements of the respective inverters.

[0036] Fig. 2 shows a current-time diagram (It diagram) that shows the design of the high-voltage electrical system from Fig. 1. Both the current I and the time t are plotted logarithmically across the axes. Reference numeral 100 represents a first characteristic curve, which represents the permissible current of a conductor strand with the component (or components) connected to it under normal circumstances. In the following, the conductor strands are considered to be, for example, the lines 16, 17 and the energy source 11 connected to them. The first characteristic curve 100 comprises a first section 101, which extends from a time t0 to a time t1. The first section 101 indicates the permissible inrush current of the component 11. In the exemplary embodiment, this is 30 A. From the time t1, the first characteristic curve 100 abruptly changes into a second section 102, which represents the continuous current of the component 11. For example, the continuous current of the component 11 under consideration should be 10 A. In the Fig. In the embodiment selected in Figure 1, the switch-on time lasts approximately 1 second (t1 = 1 sec.). From this point on, i.e., t > t1, continuous or normal operation of component 10 occurs.

[0037] Reference numerals 200 and 210 designate a second characteristic curve, which designates a tripping characteristic of the high-voltage fuse 24 in line 17. For the sake of simplicity, only two tripping characteristics for two different temperatures T1 and T2 are shown. In practice, the tripping characteristic curve is formed by a family of characteristics, for example between characteristics 200 and 210, wherein the respective characteristic curve depends on the ambient temperature of the vehicle. Characteristic curve 200 applies, for example, to a temperature T1 which corresponds to the specified minimum ambient temperature, e.g., -40°C. Characteristic curve 210 applies to a second temperature T2, which represents a maximum specification temperature of the vehicle's environment, e.g., +85°C.

[0038] Reference numeral 300 represents a third characteristic curve of the line to be protected, in this embodiment, lines 16, 17. The third characteristic curve 300 represents the maximum permissible operating current of the lines protected by the fuse.

[0039] A critical case, a so-called overload case, is marked with D. The range D is formed between the second characteristic curve valid for a temperature T (in the exemplary embodiment, characteristic curve 200) and the third characteristic curve 300. 402 represents the fluctuation range of the second characteristic curve between the maximum limit temperatures T1 and T2. It is immediately apparent that if the current supplied, for example, by the energy sink 11, lies in range D, the current is not sufficiently large to trigger the fuse. On the other hand, the current exceeds the maximum tolerable continuous current rating of the lines 16, 17. This results in the insulation surrounding the lines 16, 17 melting, which can cause further faults or damage to the vehicle.

[0040] A non-critical case, because it is protected by the fuse, is marked with B. In this area B, which is located to the right of a second characteristic curve 200, 210 valid for a specific temperature and above the third characteristic curve 300, the current supplied by component 11 is greater than the tripping current of the fuse. This protects both lines 16, 17 and the component.

[0041] The area marked A, located to the left of the first characteristic curve 100, is the valid operating range of the component and the associated cable. There is no danger here.

[0042] C indicates an overload range located between the first characteristic curve 100 and the second characteristic curve 200. Here, too, a problem already exists, but it does not pose an immediate danger to the cables or the component(s) connected to them.

[0043] The embodiments described below are capable of monitoring areas C and D with little effort, in which the fuse has not yet tripped, but the current flowing through a component is greater than the permissible current under normal circumstances.

[0044] One in Fig. The first embodiment variant of the device according to the invention shown in Figure 3 is based on the Fig. 1, so that only the differences will be described. As is readily apparent, current sensors 41, 42, 43, 44 are arranged in the lines 17, 19, 21, 23 (i.e., conductor sections) in series with the high-voltage fuses 24, 25, 26, 27. The current sensors can be formed, for example, by shunts or a Hall sensor. Each of the current sensors assigned to a component is designed to detect a current flowing through the relevant component 10 and to transmit information representing the level of the current to an evaluation unit 45. The signal paths required for this purpose are shown with dashed lines and provided with the reference numerals 46, 47, 48, 49.

[0045] The evaluation unit 45, which can be implemented, for example, as a separate control unit or as additional software of an existing control unit of the vehicle, is designed to compare the information representing the current with current thresholds stored in the evaluation unit. The comparison is made for each conductor sub-strand to be monitored against a first current threshold, which is represented by the aforementioned first characteristic curve 100 in the current-time diagram. This makes it possible to determine whether the current flowing through a component 10 is greater than the permitted current in the normal case defined by the first characteristic curve 100. A comparison is also made with a second current threshold. The second current threshold is represented by the temperature-dependent non-linear second characteristic curve 200 or 210 in the current-time diagram, which is valid for a current temperature.If the current is less than the current specified by the second current threshold, the component is operated either in overload range C or in overload range D.

[0046] If exceeding the current permitted under normal conditions is intended to result in shutdown, the evaluation unit 45 can output a shutdown signal 50. In the present embodiment, this shutdown signal is treated like a trigger signal output by the shutdown device 30 and transmitted to the energy sources 3, 4, 11 via the trigger signal paths 31, 32, 33. This opens the corresponding switching elements, disconnecting the high-voltage vehicle electrical system from all energy sources.

[0047] In a design variant not shown, the shutdown signal could also be used to disconnect only the component 10 that has an increased operating current from the high-voltage vehicle electrical system 1.

[0048] The output of the shutdown signal 50 can also be based on a fifth characteristic curve 500 (cf. Fig. 4), which is located between the first characteristic curve 100 and the third characteristic curve 300. For example, the fifth characteristic curve 500 can be configured such that it has a horizontal profile at a time t2 which is greater than the time t1 and, beyond the time t2, has a predetermined current which is greater than the predetermined current in the second section 102 of the first characteristic curve 100. This has the consequence that the shutdown signal 50 is only output when the operating current of the component is to the right of or above the fifth characteristic curve.

[0049] The area C lying between the first characteristic curve 100 and the fifth characteristic curve 500 can be interpreted as an overload area with further possible use. The characteristic curve can be modified by further grading so that other areas lying in area C are also defined as overload areas with further possible use, ie if the operating current lies between the characteristic curve 100 and a correspondingly stepped course of the fifth characteristic curve 500, no shutdown signal is output. This situation is exemplified in Fig. 5 shown.

[0050] Fig. Figure 6 shows a second embodiment of a high-voltage electrical system according to the invention of an electrically powered vehicle for monitoring the presence of an overload. The second embodiment differs from that shown in Fig. 4 in that the components 10 are connected via a common node to the line 21 and thus to the first supply line 8 via only a single high-voltage fuse 70. The line 21 is, in comparison to the line 21 in the embodiment according to Fig. 4 must be dimensioned more strongly if it is intended that the energy sinks 12, 13, 14 are operated simultaneously. The fuse 70 must also be dimensioned differently accordingly. The energy source 11 is connected to the line 21 via a line 71, the energy sink 12 is connected to the line 21 via a line 72, the energy sink 13 is connected to the line 21 via a line 73, and the energy sink 14 is connected to the line 21 via a line 74.

[0051] In a first variant, represented by a solid line, each of the components 10 is assigned its own current sensor 41, 42, 43, 44. In an alternative embodiment, represented by a dashed line with the reference numeral 75, the current sensor 42 can be omitted if the energy sink 12 is connected to the current sensor in the line 73 via the line 75. In this case, the current sensor 43 monitors the energy sinks 12 and 13. The detection of the current flowing through the relevant conductor sub-strand and the transmission of information representing the current to the shutdown device 30 takes place as described above.

[0052] Fig. Figure 7 shows a schematic representation of the monitoring process for the presence of an overload in a flowchart. In a first step S1, the current sensors 41, 42, 43, 44 each detect a current through the associated conductor strand 17, 19, 21, 23 ( Fig. 4) or 71, 72, 73, 74 ( Fig. 6 in the variant with a solid line) and transmit information representing the current I to the evaluation unit 45. In a step S2, the evaluation unit 45 checks whether the measured current I is less than the current threshold value I defined by the first characteristic curve 100 100 If this is the case ("YES"), operating range A is present (S3). The method continues in this branch with step S1.

[0053] If the condition in step S2 is not fulfilled (“NO”), a check is carried out in step S4 to determine whether the measured current I is greater than the first current value I 100, represented by the first characteristic curve 100, and smaller than a second current value I 200 / 210 , represented by the second, temperature-dependent characteristic curve 200 or 210. If this is not the case, operating range B applies. In this case, the fuse located in the relevant cable harness trips (S5).

[0054] If the condition in step S4 is met ("YES"), it is determined in step S6 that operation is in the overload range. The overload range is defined by the ranges C or D. In step S7, it is checked whether the current is greater than the first current threshold I 100 , represented by the first characteristic curve 100, and smaller than a defined current threshold I 500, represented by the characteristic curve 500. The characteristic curve 500 largely replicates the course of the line characteristic curve (third characteristic curve 300), the course of which is not known in detail to the evaluation unit. If this is not the case ("NO"), then in step S8 it is determined that an overload case in operating range D exists. If the condition in step S7 is fulfilled ("YES"), then it is checked whether a predefined time criterion is met. If this is not met, i.e. a predefined time limit has not yet been reached, then no shutdown signal is output, since operation takes place in range C. This is an overload range with further possible use, as in Fig. 5 is shown hatched as an example. The check to determine whether the time criterion is met in step S9 is performed iteratively, which is why step S9 is repeated. As soon as the time criterion is met ("YES"), the shutdown signal 50 is output. This assumes a permanent fault, which is why an overload case due to a timeout occurs.

[0055] The invention thus proposes providing a current sensor in the current paths of a high-voltage vehicle electrical system, which are to be protected against overload. Existing shutdown mechanisms, such as a crash shutdown device, can be used to shut down the high-voltage vehicle electrical system.

[0056] The shutdown can be coordinated. Since an overload event usually requires a certain response time to be addressed, it is possible to delay the system shutdown and create a manageable situation in the vehicle. This, for example, makes it possible to park the vehicle.

[0057] The short-circuit protection is implemented with known safety devices, such as fuses. It is possible to reduce the number of fuses by providing appropriate current sensors in different conductor sections, as is the case in the exemplary embodiment of the Fig. 6 is shown.

[0058] The current sensors also enable fault localization. For this purpose, the evaluation unit can store an identifier of a current sensor that delivers an increased current. Based on this identifier, it is possible to identify the conductor or conductor segment and thus a potentially defective component. The magnitude of an overcurrent allows the severity of the fault to be determined in the event of an overload. Furthermore, the information provided by the current sensors can be used to check the plausibility of the high-voltage electrical system.

[0059] Since fuses or similar protective devices now need only be designed for short-circuit situations, they can be consistently designed for short-circuit situations. This prevents, in particular, false triggering at high operating currents, since these are now detected by the inventive method. List of reference symbols 1 high-voltage electrical system 2 drive motor 3 Control electronics 4 electro-chemical storage (battery) 5 memory cells 6 Switching element (contactor or relay) 7 Fuse 8 first supply line 9 second supply line 10 components 11 Energy source 12 Energy sink (e.g. compressor of an air conditioning system) 13 Energy sink (e.g. heater) 14 Energy sink (e.g. DC / DC converter for 12V vehicle electrical system) 15 Conductor strand arrangement 16 Line 17 Line 18 Line 19 Line 20 Line 21 Line 22 Line 23 Line 24 fuse 25 fuse 26 Fuse 27 Fuse 30 shutdown device 31 Trigger signal path 32 trigger signal path 33 Trigger signal path 41 Current sensor 42 Current sensor 43 Current sensor 44 Current sensor 45 Evaluation unit 46 shutdown path 47 shutdown path 48 shutdown path 49 Shutdown path 50 shutdown signal path 70 fuse 71 Line 72 Line 73 Line 74 cable as an alternative to cable 72 and current sensor 42 t time t1 first time point t2 second time point I Current 100 first characteristic curve in the It diagram 101 first section 102 second section 200 second characteristic curve in the It diagram at temperature T1 210 second characteristic curve in the It diagram at temperature T2 (where T2 > T1) 300 third characteristic curve of the line to be protected (line characteristic curve) 400 unprotected temperature range 402 Fluctuation range of the second characteristic curve between T1 and T2 500 characteristic curve generated by evaluation unit 500 for the output of a shutdown signal A operating area B Triggering of a fuse C Overload area with further possible use D Overload range

Claims

[1] Device for monitoring a high-voltage vehicle electrical system (1) of an electrically operable vehicle for the presence of an overload, wherein the high-voltage vehicle electrical system (1) comprises as components (10) one or more energy sources and / or one or more energy sinks, each of which is connected via a conductor strand arrangement (15) to a first supply potential line (8) and to a second supply potential line (9), in which each of the components (10) is assigned a current sensor (41, 42, 43, 44) which is designed to detect a current flowing through the relevant component (10) and to transmit information representing the level of the current to an evaluation unit (45) for evaluation, characterized by , that the evaluation unit (45) is designed to compare the current with a first current threshold, which corresponds to the permitted current in the normal case, and a second current threshold, which corresponds to the tripping current of a fuse element, and to output a switch-off signal at least for the component (10) assigned to the current sensor (41, 42, 43, 44) if, as a first criterion, the level of the current and the duration of the level of the current lie between the first and the second current threshold, and the evaluation unit (45) is further designed to additionally compare the current with a third current threshold and to output a switch-off signal at least for the component (10) assigned to the current sensor (41, 42, 43, 44) if, as a second criterion, the level of the current lies between the second and the third current threshold. [2] Device according to claim 1, wherein the first current threshold is represented by a predetermined first characteristic curve (100) in a current-time diagram, which has a first section (101) in which the current has a first, high current value from a first time (t0) to a second time (t1) and which has a second section (102) in which the current has a second, comparatively lower current value from the second time (t1). [3] Device according to claim 1 or 2, wherein the second current threshold is represented by a temperature-dependent, non-linear family of characteristics (200, 210) in a current-time diagram, which has a substantially exponentially decreasing course. [4] The apparatus of claim 3, wherein each current value of the second current threshold at any time is greater than the current value of the first current threshold at the same time. [5] Device according to one of the preceding claims, in which the third current threshold is represented by a temperature-dependent, non-linear characteristic curve (300) in a current-time diagram, which has a substantially exponentially decreasing course and corresponds to the conduction characteristic curve. [6] Device according to one of the preceding claims, in which the high-voltage vehicle electrical system (1) comprises a switch-off device (30) which separates current sources from the first and the second supply potential line (9) by means of a trigger signal, wherein the switch-off device (30) is designed to generate the trigger signal in the event of a sensor-determined acceleration which exceeds a predetermined limit value, wherein the switch-off signal output by the evaluation unit (45) can be fed to the energy sources (2, 3, 11) as a trigger signal. [7] Device according to one of the preceding claims, in which the evaluation unit (45) is designed to output the switch-off signal only when, as a third criterion, a predetermined period of time since the time of occurrence of the first and / or second criterion is met. [8] Device according to claim 7, wherein the length of the predetermined time period is dependent on the level of the measured current. [9] Device according to one of the preceding claims, wherein the evaluation unit (45) is designed to output a diagnostic or error signal when the first and / or second criterion is met. [10] Device according to one of the preceding claims, in which the evaluation unit (45) is designed to store one or more of the following information in a memory upon occurrence of the first and / or second criterion: - an identifier of the current sensor (41, 42, 43, 44) which has detected the increased current exceeding the first current threshold, - the level of the measured current, - the duration of the occurrence of the increased current. [11] Device according to one of the preceding claims, in which one or more fuses are provided in the conductor strand arrangement (15), each fuse being triggered when a predetermined current which is greater than the second threshold value is exceeded in the conductor sub-strand in which the respective fuse is arranged, in order to protect the components (10) connected to the conductor strand. [12] Device according to one of claims 1 to 11, in which each component (10) is assigned a fuse. [13] Device according to one of claims 1 to 11, in which a common fuse is assigned to several components (10).

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