Method for detecting arc faults in a circuit arrangement and motor vehicle

Abstract

A method for detecting arc faults in a circuit arrangement, the circuit arrangement comprising a control device, an energy accumulator, and a plurality of loads each connected to the energy accumulator via a load line, a current measuring device being assigned to the energy accumulator and a voltage measuring device being assigned to each load, the current measurement values ​​and the voltage measurement values ​​being continuously transmitted to the control device, a parallel arc being detected by comparing the current measurement values ​​and / or a temporal change in the energy accumulator current described by the current measurement values ​​with at least one current threshold value, a series arc being detected in one of the load lines by comparing the voltage measurement values ​​and / or a temporal change in the load voltage of the loads of the load line described by the voltage measurement values ​​with at least one voltage threshold value, the energy accumulator being disconnected from the load when a parallel arc is detected, and the load of the load line being disconnected when a series arc is detected in one of the load lines.

Description

Technical Field

[0001] The invention relates to a method for detecting an arc fault in a circuit arrangement, wherein the circuit arrangement comprises a control device, an energy store, and a plurality of loads each connected to the energy store via a load line. The invention also relates to a motor vehicle. Background Art

[0002] In circuit arrangements, for example, if there is damage to the insulation of conductors and / or other components of the circuit arrangement, arcs can occur starting at a voltage level of approximately 24 V. Such arcs represent a fault state that can damage components of the circuit arrangement and / or components in the environment surrounding the circuit arrangement.

[0003] In motor vehicles with an onboard electrical system with a voltage of 24 V or higher, for example 48 V, individual line sections of the onboard electrical system, where there is a risk of arcing, are usually located in a safe area. This results in passive protection, as this prevents arcing or at least makes it more difficult, and / or, in the event of an arc, prevents further damage to the motor vehicle, in particular a vehicle fire.

[0004] In addition to or as an alternative to passive protective measures, active protective measures can also be used. These typically consist of additional hardware that must be integrated into the vehicle electrical system and that shuts down the vehicle electrical system in the event of a fault, such as an arc. This hardware requires additional installation space in the vehicle and incurs additional costs during vehicle production. Various methods for detecting arcs in electrical circuits are known from the prior art.

[0005] DE 10 2014 222 878 A1 describes a motor vehicle power supply network comprising a current source, a power distributor connected to the current source via a feed current path, and at least one load connected to the power distributor via a load current path using an integrated semiconductor switch. The power distributor includes a current measuring unit, a voltage measuring unit, and a monitoring unit, wherein the monitoring unit detects an impending fault based on measurement data determined by the measuring units. When an overcurrent fault or an arc fault is detected, at least one load is disconnected using the semiconductor switch.

[0006] DE 10 2015 209 588 B3 discloses a device for detecting faults in an onboard electrical system of a vehicle. The device includes a receiving device that receives a first time series of current or voltage measurement values ​​and a second time series of current or voltage measurement values. The first time series of measurement values ​​is measured at a first measurement point in the onboard electrical system, and the second time series of measurement values ​​is measured at a second measurement point in the onboard electrical system that is different from the first measurement point. An evaluation device of the device determines a fault based on a comparison of the dispersion of the first time series of measurement values ​​with the dispersion of the second time series of measurement values.

[0007] US 2018 / 0083434 A1 discloses an interruption circuit having multiple arc detection blocks that can emit multiple signatures corresponding to arcs. The circuit also includes a processor that receives the signatures and compares them with measured values ​​to detect the occurrence of a fault. Summary of the Invention

[0008] The object of the present invention is to provide an improved method for detecting arc faults in a circuit arrangement.

[0009] According to the invention, this object is achieved in a method of the type mentioned at the outset in that a current measuring device for determining a current measurement value describing the energy store current is assigned to the energy store, and a voltage measuring device for determining a voltage measurement value describing the load voltage at the respective load is assigned to each load, wherein the current measurement value and the voltage measurement value are continuously transmitted to the control device via at least one communication connection, wherein a parallel arc in the circuit arrangement is determined by comparing the current measurement value and / or the temporal change of the energy store current described by the current measurement value with at least one current threshold value, and a series arc in one of the load lines is determined by comparing the voltage measurement value and / or the temporal change of the load voltage of the load of the load line described by the voltage measurement value with at least one voltage threshold value associated with the respective load, wherein either the energy store is disconnected from the load when the occurrence of a parallel arc is determined, or the load of one of the load lines is disconnected when the occurrence of a series arc is determined in the load line.

[0010] The control device of the circuit arrangement receives a current measurement value that describes the energy storage current and is detected by a current measuring device associated with the energy storage device. For each load that is connected to the energy storage device via a load line and thus forms part of the circuit arrangement, a voltage measurement value that describes the voltage drop at the respective load is determined by a voltage measuring device associated with the load and transmitted to the control device.

[0011] The control device determines the occurrence of a parallel arc in the circuit arrangement based on a comparison of current measurements describing the battery current and / or the temporal variation of the energy storage current described by the current measurements with at least one current threshold value. Depending on the definition of the at least one current threshold value, this may occur, for example, when the value of the energy storage current and / or the temporal variation of the energy storage current exceeds or falls below the current threshold value. The current measurements may be compared directly with the current measurement values, or a variable determined from at least one of the current measurement values, optionally taking into account other measurement values, may be compared with the current threshold value. The temporal variation of the energy storage current may be determined using current measurement values ​​determined at different times. A parallel arc fault—i.e., the occurrence of a parallel arc in the circuit arrangement—is typically characterized by a sudden increase in current. Current is typically initially supplied from a capacitor present in the circuit arrangement and then withdrawn from the energy storage as part of the energy storage current.

[0012] To detect a series arc, the control device compares a voltage measurement value and / or the temporal variation of the load voltage described by the voltage measurement value with at least one voltage threshold value for each load. Depending on the definition of the at least one voltage threshold value, a series arc in the load and / or in the load circuit of the load can be detected, for example, when the value of the load voltage and / or the value of the temporal variation of the load voltage exceeds or falls below the voltage threshold value. The voltage measurement values ​​can be compared directly with the voltage threshold value, or a variable determined from one or more of the voltage measurement values, optionally taking into account other measurement values, can be compared with the voltage threshold value. It is possible to determine a variable that describes the load voltage at one of the loads from one or more voltage measurement values. It is also possible to determine a variable that describes the load voltage at different loads within the load. The temporal variation of the load voltage can be determined using voltage measurement values ​​of the load voltage of a load determined at different times.

[0013] If a parallel arc is detected in the circuit, the energy store is disconnected from the loads. For example, a switching device associated with the energy store, such as a battery junction box (BJB), can be actuated in such a way that the electrical connection from the energy store to the multiple loads is interrupted. This disconnects the energy store from the other components of the circuit arrangement, in particular all loads, thereby eliminating the parallel arc generated in the circuit arrangement.

[0014] When detecting a series arc, the load or load line in which the series arc occurred can be determined based on the voltage measurement values ​​evaluated for each load. Disconnecting the corresponding load extinguishes the series arc in the load or the corresponding load line due to the interruption of the current loop in the load line. Other loads—in which no series arc occurred—remain connected to the energy storage device and can therefore advantageously continue to operate after disconnecting one of the loads due to a series arc.

[0015] The method according to the present invention also has the following advantages: In particular, in circuit arrangements designed as onboard electrical systems for motor vehicles, parallel and series arcs can be detected based on measured values ​​that have already been determined in the vehicle for use in other functions. The ability to transmit these measured values ​​to a control unit allows arc fault detection by the control unit, which can also be aware of other tasks within the vehicle. Because motor vehicle onboard electrical systems typically include both switching devices for disconnecting energy stores from connected loads and switching devices for connecting or disconnecting individual loads in the onboard electrical system, the method according to the present invention allows for the detection of occurring arc faults without additional hardware complexity. This advantageously eliminates the need for additional hardware modules, such as additional sensors, switches, or the like.

[0016] When a parallel arc occurs, the control device can be used to actuate the switching device associated with the energy store to disconnect the energy store from the load. When a series arc occurs, the load or the switching device associated with the load can be actuated to disconnect the load. In the event of both parallel and series arcs, only disconnection of the energy store from the load is possible, as this also extinguishes the series arc in the power path. However, it is possible to disconnect the load or disconnect the switching device associated with the load in this case.

[0017] The current measurement values ​​and / or the temporal variation of the energy accumulator current described by the current measurement values ​​can be compared with one or more current threshold values. In this way, different criteria can be used to detect a parallel arc, each of which includes exceeding or falling below a current threshold value. Each comparison with a current threshold value is a criterion or condition, which can be a necessary or sufficient condition for disconnecting the energy accumulator. Thus, if deviations from multiple current threshold values ​​are used as sufficient conditions, multiple different current threshold values ​​can be used, which, if exceeded or fallen below, respectively, indicate the occurrence of a parallel arc and, therefore, lead to disconnection of the energy accumulator from the load. When using one or more current threshold values ​​as necessary conditions, a plausibility test can be performed, so that the energy accumulator is disconnected from the load only when multiple current threshold values ​​are exceeded or fallen below.

[0018] This also applies to voltage measurement values ​​that describe the load voltage or the temporal behavior of the load voltage of the corresponding load. Under these conditions, the criteria or conditions represented by exceeding or falling below a voltage threshold can also be sufficient or necessary conditions, respectively. In this way, multiple voltage thresholds can be defined that each indicate the occurrence of a series arc and thus cause the load to be disconnected.

[0019] In the case of multiple voltage thresholds, these voltage thresholds, or at least some of them, can also be necessary conditions, so that a series arc is detected only when all of the voltage thresholds are exceeded or fallen below. In this way, it is possible to generate a plausibility test, whereby a plurality of voltage thresholds are predetermined, which the voltage measurement values ​​and / or the load voltage must exceed or fall below over time in order to indicate the presence of a series arc and thus trigger a shutdown of the load. This enables plausibility testing of the individual measured values ​​and increases the robustness of the method by avoiding erroneous shutdowns caused by temporary exceeding or falling below one of the voltage thresholds due to the effect that no arc has occurred.

[0020] The current and voltage thresholds used in the respective comparisons can be determined, for example, based on known load curves for the electrical consumers. For example, the maximum energy storage current, load voltage, and / or their temporal variation occurring during normal circuit operation can be determined by calculation and / or measurement, respectively, so that the respective thresholds can be selected such that they are not exceeded during normal operation. The current and / or voltage thresholds used can be determined based on the type of circuit arrangement or the type of energy storage device and the load of the circuit arrangement and stored, for example, in the control device.

[0021] According to the present invention, it may be provided that the average value of the accumulator current corresponding to each time interval is used as the current measurement value, the average value being a measure of the total current flowing during the time interval, wherein the change in the average value over time is compared with a mean value threshold value serving as a current threshold value. The time interval may have a length between 1 ms and 100 ms, in particular between 5 ms and 50 ms, preferably 10 ms. The average value of the accumulator current during this time interval may be used as the current measurement value, wherein the average value is compared with the mean value threshold value serving as the current threshold value. The average value may be determined, for example, by summing and / or filtering a plurality of individual measurement values ​​of the current measuring device. The average value may be transmitted, for example, as a current measurement value, from the current measuring device associated with the accumulator to the control device via a communication connection. The control device may then compare the transmitted average value with a mean value threshold value, for example stored in the control device, wherein a parallel arc is detected when the average value of the accumulator current exceeds the mean value threshold value.

[0022] In a preferred embodiment of the present invention, it can be provided that the maximum value of the energy storage current corresponding to each time interval is used as the current measurement value, the maximum value describing the absolute maximum value of the energy storage current within the time interval, wherein the temporal variation of the maximum value is compared with a maximum value threshold value as the current threshold value. The time interval in which the maximum value of the energy storage current is described can, in particular, correspond to the time interval for which the average value as the current measurement value is compared. The maximum value corresponding to each time interval is compared with a maximum threshold value, for example, stored in the control device, wherein the presence of a parallel arc can be inferred if the absolute maximum value of the energy storage current in this time interval exceeds the maximum threshold value.

[0023] According to the present invention, it can be provided that the average value of the energy storage current corresponding to each time interval and the maximum value of the energy storage current corresponding to the time interval are used as current measurement values. The average value is a measure of the total current flowing through the time interval, and the maximum value describes the absolute maximum value of the energy storage current within the time interval. The difference between the average value and the maximum value of the time interval is compared with a difference threshold value as a current threshold value. This makes it possible to determine the deviation of the absolute maximum value of the energy storage current from the temporal average value of the energy storage current in the time interval for which the average value or the absolute maximum value was determined. This difference can be compared with a difference threshold value, for example, stored in the control device, in order to detect the presence of a parallel arc.

[0024] In a preferred embodiment of the present invention, the energy store is disconnected from the load if at least one of the current threshold values ​​is exceeded. In particular, the aforementioned average value threshold, the aforementioned maximum threshold, and the aforementioned difference threshold can be used as current thresholds. If at least one of the current threshold values ​​is exceeded, a parallel arc is detected or the energy store is disconnected from the load. This advantageously allows the energy store to be disconnected from the load as soon as the criteria for determining a parallel arc or the conditions for determining the occurrence of a parallel arc, i.e., the exceeding of at least one of the current threshold values, are met.

[0025] According to the present invention, the communication connection can be a data bus, wherein the time interval corresponds to the time between two transmission time windows in which the current measuring device sends at least one current measurement value to the control device. The communication connection configured as a data bus can transmit voltage measurement values ​​of the load to the control device in addition to the current measurement values. When the communication connection is configured as a data bus, the measurement values ​​can be transmitted to the control device individually or in batches within the corresponding transmission time windows. A series arc occurs in the load circuit of the load, where the control device determines upon receiving the current and / or voltage measurement values ​​whether a parallel arc and / or a series arc is present and, if necessary, disconnects the energy storage device if a parallel arc is present or disconnects the corresponding load if a series arc is present. In particular, multiple current or voltage measurement values ​​can be transmitted in batches within the transmission time window if the determined frequency or sampling rate of the current or voltage measurement values ​​is higher than the frequency at which the current or voltage measurement device transmits the corresponding measurement values ​​to the control device via the communication connection.

[0026] According to the invention, provision can be made for each load to determine a reference voltage difference between a measured voltage value of the load and a reference voltage value of a reference voltage source, in particular a reference voltage value of the energy storage device, wherein the reference voltage difference is compared with a reference difference threshold value as a voltage threshold value assigned to the respective load. For each load connected to the energy storage device, a reference voltage difference can be determined, wherein the reference voltage difference can be the difference between the load voltage described by the voltage value of the load and the reference voltage value.

[0027] The voltage of a reference voltage source can be used as the reference voltage value, wherein an energy storage device can be used in particular as the reference voltage source. A reference voltage difference determined in this manner, for example by measurement, can be compared with a reference difference threshold value, which serves as a voltage threshold value, corresponding to the respective load. In this case, a reference voltage exceeding or falling below the reference difference threshold value can be a necessary or sufficient condition for determining the occurrence of a series arc in the load circuit of the respective load for which the reference voltage value is determined. The comparison with the reference voltage source allows inferences about a fault mode that can be attributed to the occurrence of a fault, such as a series arc, in the load circuit of the load.

[0028] In a preferred embodiment of the present invention, provision can be made for each load to determine at least one load voltage difference between a voltage measurement value and at least one voltage measurement value of at least one other of the loads, wherein the at least one load voltage difference is compared with a load difference threshold value, serving as a voltage threshold value, assigned to the respective load. The load voltage difference is the difference between the load voltage described by the voltage value of the load and the voltage value of another of the loads, which describes the load voltage at the other of the loads. The load voltage difference is compared with a voltage threshold value, for example, stored in a control device, wherein a necessary or sufficient condition for determining a series arc is considered satisfied when the voltage threshold value is exceeded or fallen below. Each load of the circuit arrangement can be assigned its own load difference threshold value. Alternatively, a load can be assigned multiple load difference threshold values, each corresponding to different other loads, and used to determine the load voltage difference for the respective other loads.

[0029] According to the present invention, provision can be made for each load to compare the temporal change in the load voltage with a load voltage threshold value assigned to the respective load, wherein the load is disconnected if the reference difference threshold value, the load difference threshold value, and the load voltage threshold value are each exceeded. In this way, exceeding or falling below the load voltage threshold value, the load difference threshold value, and the reference difference threshold value are each considered as necessary conditions for determining the occurrence of a series arc or for disconnecting the respective load. This makes it possible to plausibly check the individual voltage measurements, or the values ​​for the reference voltage difference or the load voltage difference derived from the voltage measurements, and / or the change in the load voltage derived from the voltage measurements, against one another. This advantageously prevents the disconnection of a load due to a single exceeding of one of the used voltage threshold values. The evaluation of the temporal change in the load voltage can be used as a criterion for the occurrence of an arc, since arc faults always result in large voltage changes, particularly large changes in the value of the load voltage.

[0030] According to the invention, it can be provided that a series arc is detected if the at least one voltage threshold value is exceeded for a predetermined duration and / or a predetermined number of temporally consecutive voltage measurements exceeds the at least one voltage threshold value. In this way, it is possible to prevent the occurrence of a series arc from being determined due to voltage peaks in one of the load voltages that occur only briefly and are not caused by a series arc.

[0031] In a preferred embodiment of the present invention, it can be provided that the current measuring device determines the current measured value and / or the voltage measuring device determines the voltage measured value at a frequency between 50 Hz and 20 kHz, in particular between 100 Hz and 10 kHz. The frequency at which the current measuring device determines the current measured value and / or the voltage measuring device determines the corresponding voltage measured value can be, for example, 1 kHz. This frequency can in particular be higher than the transmission frequency at which the current measuring device or the voltage measuring device transmits the corresponding measured value to the control device via the communication connection. In this case, it can be provided that in a message transmitted via the communication connection, the communication connection transmits a plurality of measured values ​​determined at time intervals corresponding to the transmission time interval on the communication connection. In particular, after receiving the corresponding current measured value and / or voltage measured value, the control device can perform a corresponding comparison with a current threshold value and / or a voltage threshold value. For this purpose, for example, the control device can also determine variables derived or calculated from the current measured value and the voltage measured value, such as the difference between the average value and the maximum value of the energy storage current, a reference voltage difference, and / or a load voltage difference. It is also possible for the current measuring device or the voltage measuring device to adapt its transmission frequency, with which it transmits the corresponding measured values ​​to the control device via the communication connection, to the sampling rate or measurement frequency of the current measuring device and / or the voltage measuring device.

[0032] According to the present invention, it can be provided that the voltage measurement values ​​are transmitted via the communication connection at at least partially different times, with the voltage measurement values ​​being synchronized by the control device. In a communication connection that enables data transmission using transmission time windows that can be provided sequentially over time, it may be necessary to synchronize the voltage measurement values ​​transmitted by different components, in particular different loads and / or reference voltage sources, for example, in order to achieve, as described above, a load voltage difference between a voltage measurement value of a load and a voltage measurement value of another load corresponding to the time at which the load voltage measurement value was determined. This can also occur when determining a reference voltage difference, wherein the reference voltage difference is formed by comparing the voltage measurement value of the load with a reference voltage value determined at the corresponding time.

[0033] In a preferred embodiment of the present invention, provision can be made for using a control device that is also designed to control the energy flow between the energy store and at least one of the loads. This advantageously allows for a method for detecting arc faults in the control device, which generally receives and processes measured values ​​for detecting arcs. In particular, even in control devices designed for central energy management and therefore referred to as energy management coordinators, measured values ​​for detecting arc faults are present, as these are necessary for controlling the power flow in the circuit arrangement or in the onboard electrical system of the motor vehicle. This advantageously allows the existing structure of the motor vehicle to be utilized, thereby advantageously eliminating the need for additional hardware for detecting arc faults.

[0034] According to the present invention, it can be provided that the motor vehicle's onboard power supply, in particular an onboard power supply with a voltage of 48 V, is used as the circuit arrangement, and / or that at least one of the loads is an electrical consumer of the motor vehicle, in particular an inverter, a drive train generator, a starter generator, an electrically operated catalytic converter, an electrically driven compressor, and / or an electric refrigerant compressor. The load can in particular be a load that is operated via the motor vehicle's onboard power supply, in particular an onboard power supply with a voltage of 48 V.

[0035] Provision is made for a motor vehicle according to the invention that the motor vehicle comprises a circuit arrangement having a control device, an energy store and a plurality of loads each connected to the energy store via load lines, wherein a current measuring device for determining a current measurement value describing the energy store current is assigned to the energy store, and a voltage measuring device for determining a voltage measurement value describing the load voltage at the respective load is assigned to each load, wherein the current measuring device and the voltage measuring device are connected to the control device via a communication connection in order to continuously transmit the current measurement values ​​and the voltage measurement values, wherein the control device is configured to carry out the method according to the invention.

[0036] All advantages and configurations described above with respect to the method according to the invention apply correspondingly to the motor vehicle according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Further advantages and details of the invention are apparent from the exemplary embodiments described below and from the accompanying drawings. These drawings are schematic illustrations and show:

[0038] Figure 1 An embodiment of a motor vehicle according to the invention is shown,

[0039] Figure 2 A first block diagram is shown for illustrating an exemplary embodiment of the method according to the present invention.

[0040] Figure 3 A schematic diagram showing battery current versus time,

[0041] Figure 4 shows a second block diagram for illustrating an embodiment of the method according to the present invention, and

[0042] Figure 5 A diagram is shown for explaining the determination of the current threshold value. DETAILED DESCRIPTION

[0043] exist Figure 1 FIGURE 1 shows an exemplary embodiment of a motor vehicle 1 according to the present invention. Motor vehicle 1 includes a circuit arrangement 2 designed as an onboard electrical system of motor vehicle 1, comprising a control device 3, an energy storage device 4, and two loads 5 and 6 connected to energy storage device 4. Loads 5 and 6 are connected in parallel to one another and to energy storage device 4. During normal operation of circuit arrangement 2, loads 5 and 6 are operated via energy storage device 4.

[0044] A load 5 is connected to the energy accumulator 4 via a load line 7 including a switch 8 for disconnecting the load 5. Correspondingly, another load 6 is connected to the energy accumulator 4 via a load line 9 including a switch 10 for disconnecting the load 6 from the energy accumulator 4. The energy accumulator 4 is connected to the loads 5 and 6 via a switching device 11, which enables disconnection of the energy accumulator 4 from the loads 5 and 6.

[0045] In addition to the loads 5 and 6 shown, the circuit arrangement 2 may also include further loads, each of which is connected to the energy storage device 4 via a load line, in particular by means of a switching element, corresponding to the load 5 or 6. The loads 5 and 6 and / or any further loads present are in particular electrical consumers of the motor vehicle 1, which can be operated by the energy storage device 4. The voltage of the energy storage device 4 or the circuit arrangement 2 may be, for example, 48 V. The loads 5 and 6 and / or any further loads present may each be, for example, an inverter, a drive train generator, a starter generator, an electrically operated catalytic converter, an electrically driven compressor, and / or an electric refrigerant compressor of the motor vehicle 1.

[0046] A current measuring device 12 is assigned to the energy store 4, by means of which a current measurement value describing the energy store current can be determined. A voltage measuring device 13 and a voltage measuring device 14 are assigned to the load 5 and the load 6, respectively, wherein a voltage measurement value describing the load voltage of the load 5 is determined by the voltage measuring device 13, and a voltage measurement value describing the load voltage of the load 6 is determined by the voltage measuring device 14.

[0047] The current measuring device 12 and the voltage measuring devices 13 and 14 are connected to a communication connection 15 designed as a data bus. The control device 3 of the circuit arrangement 2 is also connected to the communication connection 15. The current measurement values ​​measured by the current measuring device 12 and the voltage measurement values ​​measured by the voltage measuring devices 13 and 14 are continuously transmitted to the control device 3 via the communication connection 15.

[0048] The control device 3 is configured to determine the occurrence of a parallel arc in the circuit arrangement 2 by comparing current measurement values ​​and / or the temporal profile of the energy storage current described by the current measurement values ​​with at least one current threshold value. Furthermore, the control device 3 is configured to determine the occurrence of a series arc in the load 5 or the load line 7 by comparing voltage measurement values ​​and / or the temporal profile of the load voltage of the load 5 described by the voltage measurement values ​​with at least one voltage threshold value assigned to the load 5, and to determine the occurrence of a series arc in the load 6 or the load line 9 by comparing voltage measurement values ​​and / or the temporal profile of the load voltage of the load 6 described by the voltage measurement values ​​with at least one voltage threshold value assigned to the load 6.

[0049] If a parallel arc is detected in circuit arrangement 2, for example, as indicated by arrow 15, energy store 4 is disconnected from loads 5 and 6. Disconnection of energy store 4 from loads 5 and 6 occurs via a switching device 11, which is designed, for example, as a battery junction box (BJB). If a series arc occurs in load line 7, for example, as indicated by arrow 16, load 5 is disconnected by opening switch 8 in load line 7. Similarly, if a series arc occurs in load line 9, load 6 is disconnected by opening switch 10 in load line 9.

[0050] In this way, when a parallel arc occurs in circuit arrangement 2, it can be extinguished due to the isolated energy storage device. If a series arc occurs, the arc can be extinguished accordingly by disconnecting load 5 or opening switch 8. To actuate switches 8, 10, and switching device 11, control device 3 is connected to these switches and switching device 11, although the connections between control device 3 and switches 8, 10, and switching device 11 are not shown for the sake of clarity.

[0051] exist Figure 2 1 shows a schematic block diagram 17 which shows the detection of the occurrence of a parallel arc in the circuit arrangement 2 by the control device 3. The block diagram 17 comprises a first part 18, a second part 19 and a third part 20. The average value I of the energy storage current corresponding to the time interval is used as an input variable. BAT and the absolute maximum value I of the accumulator current corresponding to the time interval BAT_MIN / MAX .

[0052] Assigned an average value of IBAT and the absolute maximum value I BAT_MIN / MAX The time interval corresponds to the time interval at which the current measuring device 12 transmits the current measurement value to the control device 3 via the communication connection 15. The current measurement value determination by the current measuring device 12 can be performed, for example, at a frequency between 50 Hz and 20 kHz, in particular between 100 Hz and 10 kHz. The time interval at which the current measuring device 12 transmits the current measurement value to the control device 3 via the communication connection 15 can deviate from the frequency at which the current measurement value is determined by the current measuring device 12. For example, the current measurement value can be transmitted from the current measuring device 12 to the control device 3 every 10 ms. In this case, the average value I of the energy storage current is determined by the current measuring device 12. BAT and the absolute maximum value I BAT_MIN / MAX The time interval is likewise 10 ms. When using another time interval for data transmission via the communication connection 15, the average value I is determined. BAT and the absolute maximum value I BAT MIN / MAX The time intervals of φi can also correspond to the time intervals of the transmission of the current measurement values ​​via the communication connection 15 .

[0053] exist Figure 3 , a diagram is shown in which the energy storage current I is shown by way of example over time t. Furthermore, the measured values ​​of the energy storage current I determined by the current measuring device 12 at a sampling frequency of 1 kHz and the absolute maximum value I obtained within a time interval of 10 ms are plotted. BAT MIN / MAX And the average current I BAT For example, since the sampling frequency of the current measuring device 12 is higher than the transmission frequency from the current measuring device 12 to the control device 3, the absolute maximum value I is taken as the current measurement value. BAT MIN / MAX and the average value I BAT Transmission to the control device 3, such as Figure 2 As shown in block diagram 17.

[0054] It is also possible to transmit individual measured values ​​describing the energy storage current at the measuring time as current measured values ​​from the current measuring device 12 to the control device 3, wherein the control device 3 determines the average value I in particular independently of the transmission frequency of the communication connection 15. BAT and the absolute maximum value I BAT MIN / MAXThis can be the case, for example, if the current measuring device 12 transmits the current measurement values ​​via the communication connection 15 to the control device 3 at a transmission frequency that is equal to or higher than the sampling rate or measurement frequency of the current measuring device 12 and / or if the current measuring device 12 transmits a plurality of current measurement values ​​in packets via the communication connection 15 to the control device 3 .

[0055] In a first part 18 of block diagram 17, the mean values ​​I determined for different time intervals of 10 ms each are determined. BAT Changes over time. Average value I BAT For example, it can be the arithmetic mean of the measured values ​​recorded within the time interval at the sampling rate of the current measuring device 12 and / or the values ​​obtained by filtering from the measured values ​​recorded within the time interval. In a first block 18, the mean value I determined for two consecutive time intervals k or k-1 is calculated. BAT Determine the average value I BAT Here, the value of the difference between the average values ​​of these time intervals and the current threshold value I TH，1 For comparison, the current threshold represents the average value threshold.

[0056] In the second part 19 of the block 17, the absolute maximum value I is determined accordingly. BAT_MIN / MAX Time variation, from two absolute maximum values ​​I determined for successive time intervals k or k-1 BAT_MIN / MAX The time variation is determined. Here, the value of the difference between the two absolute maximum values ​​is compared with the second current threshold value I TH，2 By comparison, the second current threshold value represents the maximum threshold value.

[0057] In the third part 20 of the block 17, the average value I corresponding to the time interval k is BAT and the absolute maximum value I corresponding to the time interval k BAT_MIN / MAX are subtracted from each other, wherein the value of the difference is compared with a third current threshold value ITH,3 representing a difference threshold value. As indicated by block 21, the current threshold value I TH，1 , I TH，2 and I TH，3 The corresponding comparisons are associated with a logical "OR". TH，1 , I TH，2 or I TH，3 When at least one of the three threshold values ​​is exceeded, the occurrence of a parallel arc fault is determined by the control device 3, so that when one of the three threshold values ​​is exceeded, a disconnection request is transmitted by the control device 3 to the energy accumulator 4 or the switching device 11 in box 22 and / or the switching device 11 is controlled by the control unit 3 and the energy accumulator 4 is thus disconnected from the loads 5, 6.

[0058] It is possible to use another current threshold value as an additional or alternative to the mean value threshold value, the maximum threshold value and / or the difference threshold value. Here, for example, another current threshold value can be compared with the current measurement value or with another variable determined or derived from at least one current measurement value.

[0059] exist Figure 4 , which describes the determination of the occurrence of a series arc in load 5 or load line 7. The determination of the occurrence of a series arc in load 6 or load line 9 of circuit arrangement 2 or in a further load or load line of a further load is implemented analogously.

[0060] The block diagram 23 comprises a first part 24, a second part 25 and a third part 26. The input variable of the block diagram 23 is the voltage U of the energy storage device 4. BAT , the load voltage U on the load 5 described by the voltage value transmitted to the control device 3 via the voltage measuring device 13 V1 , and the load voltage U across the further load 6 described by the voltage measurement value detected by the current measuring device 14 V2 .

[0061] In the first part 24 of the block diagram 23 , it is determined for the load 5 that the load voltage U V1 The voltage measurement value of the energy storage device 4 and the voltage U BAT The reference voltage difference can be determined both at the time k and for one or more previous voltage measurement values. This is represented in section 24 by determining the value of the difference between the voltage measurement value of the load 5 at the time k and the reference measurement value and by determining the corresponding value of the difference between the voltage measurement value of the load 5 at the time kn and the reference voltage value of the energy storage 4. The determined reference voltage values ​​are respectively compared with the voltage threshold value U TH，1 The voltage threshold represents the reference difference threshold. Both the comparison with the reference difference threshold for the measured value at time k and the measured value at time kn are logically ANDed in block 27 at the output of the first part 24 .

[0062] In the second part 25 of block diagram 23, a load voltage difference is determined between the voltage measurement value of load 5 and the voltage measurement value of another load in the load of circuit arrangement 2. Here, another load 6 is used for this purpose. Similar to the determination of the reference voltage difference, even if the voltage threshold U representing the load difference threshold is TH In the case of a comparative load voltage difference, measurements are also performed for the measured value at time k and for the measured value kn recorded at the previous time. The measured values ​​determined at different times are linked in a block 28 by a logical AND at the output of the second part 25 .

[0063] In the third part 26 of the block diagram 23, the load voltage U V1 The time variation of the load voltage is determined from the voltage measurement values ​​of k and k-1. The time variation is determined from the voltage measurement values ​​measured at two consecutive times k and k-1. The time variation of the load voltage is compared with the voltage threshold U representing the load voltage threshold. TH，3 Make a comparison.

[0064] In block 29, the outputs of the first part 24 and the second part 25 and the third part 26 are linked logically "AND". If for the instant k and for one or more instants kn, the voltage threshold U as the reference difference threshold TH，1 The reference voltage difference determined for the first part 24 exceeds the voltage threshold U , which serves as the load difference threshold. TH，2 In the second part 25 , the load voltage difference determined for the times k and kn is exceeded, and if the voltage threshold value U 2 as the load voltage threshold value is exceeded. TH，3 If the load voltage at load 5 changes over time in third section 26, load 5 is disconnected in block 30 by a logical AND operation in block 29. For this purpose, control device 3 actuates switch 8, for example, so that it is opened.

[0065] Therefore, exceeding the reference difference threshold, the load difference threshold, and the load voltage threshold is a necessary condition for disconnecting the load 5. This allows the individual voltage measurement values ​​transmitted by the voltage measuring device 13 to the control device 3 to be plausible with respect to one another. In this way, a three-stage plausibility test cycle is formed, which is represented by block diagram 23. This improves the detection of series arcs because multiple conditions that characterize the presence of an arc are checked.

[0066] It is possible to use another voltage threshold as an additional or alternative to the reference difference threshold, the load difference threshold and / or the load voltage threshold. Here, for example, the other voltage threshold can be compared with the voltage measurement value or with another variable determined or derived from at least one voltage measurement value.

[0067] Since the voltage measurement values ​​are received by the control device 3 at different times, in particular by means of transmission via the communication connection 15 , in block 31 , the voltage threshold value U TH，1 、U TH，2 and U TH，3 Before the respective comparison of the voltage values ​​received, a synchronization is performed, which synchronizes the respective voltage measurement values ​​received in time. In this way, the reference voltage difference or load voltage difference determined in the first part 24 and the second part 25 respectively refers to the measured values ​​determined at the same time k, k-1 or kn. The voltage U of the energy storage device 4 used as a reference voltage BATThe voltage can be measured by a voltage measuring device (not shown) assigned to the energy store 4 , which likewise communicates with the control device 3 via the communication connection 15 .

[0068] The current threshold value used and the voltage threshold value used are determined by calculation and / or measurement for normal operation of the circuit arrangement 2, so that the current values, voltage values, and / or their temporal variations occurring through the energy storage device 4 during fault-free operation of the loads 5, 6 do not result in exceeding the corresponding threshold value. For example, the threshold values ​​stored in the control device 3 can be selected based on the time intervals used to determine the voltage and / or current measurement values. In particular, the voltage threshold values ​​can be at least partially different for each of the loads 5, 6 and / or other loads.

[0069] exist Figure 5 The determination of the current threshold value is schematically shown in a diagram 32, wherein for the duration t i Different time intervals of 10 ms, 20 ms, 30 ms and 40 ms respectively give different maximum threshold values ​​di / dt for the change in the energy storage current over time. _max The maximum threshold value can be as follows: Figure 2 As shown in the first part 19 of the block diagram 17, the current threshold I TH，1 and the time interval t for the respectively given duration i The absolute maximum value I BAT_MIN / MAX Make a comparison.

[0070] The area below curve 33 represents the normal operating range, which contains the maximum permissible current change for different time intervals, which occurs during normal operation of circuit arrangement 2, that is, without the occurrence of a parallel arc. The triggering range is located in the area above curve 34, wherein curve 34 specifies the corresponding value for the maximum threshold value, which is compared with the maximum value of the energy storage current determined in the corresponding time interval.

[0071] A tolerance range is provided between the curves 33 and 34 in order to avoid false triggering due to slight violations of the operating range.

[0072] The corresponding curves 33 and 34 can be determined based on the transmission time window respectively realized by the communication connection device, as well as for further current threshold values ​​and further voltage threshold values ​​for the respective loads 5, 6. This makes it possible to determine the load curves of the loads 5, 6 during normal operation of the circuit arrangement 2 and to determine corresponding threshold values, which are stored in the control device 3 and can be used as criteria or conditions for determining parallel arcs and / or series arcs in the circuit arrangement 2.

Claims

1. A method for detecting an arc fault in a circuit arrangement (2), wherein: The circuit arrangement (2) comprises a control device (3), an energy accumulator (4) and a plurality of loads (5, 6) connected to the energy accumulator (4) via load lines (7, 9), wherein a current measuring device (12) is assigned to the energy accumulator (4) for determining a current measurement value describing the energy accumulator current, and a voltage measuring device (13, 14) is assigned to the loads (5, 6) for determining a voltage measurement value describing the load voltage at the respective load (5, 6), wherein the current measurement values ​​and the voltage measurement values ​​are continuously transmitted to the control device (3) via at least one communication connection (15), wherein a parallel arc in the circuit arrangement (2) is determined by comparing the current measurement values ​​with at least one current threshold value and / or by comparing the change in the energy accumulator current over time described by the current measurement values ​​with at least one current threshold value, and by comparing the voltage measurement values ​​with at least one voltage corresponding to the respective load. A series arc in one of the load lines (7, 9) is determined by comparing the load voltage of the load (5, 6) of the load line (7, 9) with a voltage threshold value and / or by comparing the load voltage of the load (5, 6) of the load line (7, 9) over time, as described by the voltage measurement value, with at least one voltage threshold value corresponding to the corresponding load (5, 6), wherein either the energy storage device (4) is disconnected from the load (5, 6) when a parallel arc is determined, or the load (5, 6) of the load line (7, 9) is disconnected when a series arc is determined in one of the load lines (7, 9), and an average value of the energy storage device current corresponding to each time interval and a maximum value of the energy storage device current corresponding to the time interval are used as current measurement values, wherein the frequency or sampling rate at which the current measurement value or the voltage measurement value is determined is higher than the frequency at which the current measurement device or the voltage measurement device transmits the corresponding measurement value to the control device via the communication connection.

2. The method according to claim 1, characterized in that The mean value is a measure of the total current flowing in the time interval, wherein the change in the mean value over time is compared with a mean value threshold value as a current threshold value.

3. The method according to claim 1 or 2, characterized in that The maximum value describes the absolute maximum value of the energy store current within the time interval, wherein the change in the maximum value over time is compared with a maximum value threshold value as a current threshold value.

4. The method according to claim 1 or 2, characterized in that The mean value is a measure of the total current flowing in the time interval, and the maximum value describes the absolute maximum value of the energy storage current within the time interval, wherein the difference between the mean value and the maximum value of the time interval is respectively compared with a difference threshold value as the current threshold value.

5. The method according to claim 1 or 2, characterized in that If at least one of the current threshold values ​​is exceeded, the energy store (3) is disconnected from the load.

6. The method according to claim 2, characterized in that The communication connection (15) is a data bus, wherein the time interval corresponds to the time between two transmission time windows in which the current measuring device (12) sends at least one current measurement value to the control device (3).

7. The method according to claim 1, characterized in that At least one reference voltage difference between a voltage measurement value of the load (5, 6) and a reference voltage value of a reference voltage source is determined for each load (5, 6), wherein the reference voltage difference is compared with a reference difference threshold value as a voltage threshold value assigned to the respective load (5, 6).

8. The method according to claim 1, characterized in that At least one load voltage difference is determined for each load (5, 6) between a voltage measurement value of the load (5, 6) and at least one voltage measurement value of at least one other of the loads (5, 6), wherein the load voltage difference is compared with a load difference threshold value assigned to the respective load (5, 6) as a voltage threshold value.

9. The method according to claim 7 or 8, characterized in that For each load (5, 6), the change in load voltage over time is compared with a load voltage threshold corresponding to the respective load (5, 6), wherein the load (5, 6) is disconnected if a reference difference threshold, a load difference threshold and a load voltage threshold are exceeded.

10. The method according to claim 1 or 2, characterized in that A series arc is determined if the at least one voltage threshold value is exceeded for a predetermined duration and / or a predetermined number of temporally consecutive voltage measurement values ​​exceeds the at least one voltage threshold value.

11. The method according to claim 1 or 2, characterized in that Current measurement values ​​are determined by the current measuring device (12) and / or voltage measurement values ​​are determined by the voltage measuring devices (13, 14) at a frequency between 50 Hz and 20 kHz.

12. The method according to claim 1 or 2, characterized in that The voltage measured values ​​are transmitted via the communication connection (15) at at least partially different times, wherein the voltage measured values ​​are synchronized by the control device (3).

13. The method according to claim 1 or 2, characterized in that A control device (3) is used, which is also designed to control the energy flow between the energy store (4) and at least one of the loads (5, 6).

14. The method according to claim 1 or 2, characterized in that The onboard electrical system of the motor vehicle (1) is used as the circuit arrangement (2) and / or an electrical consumer of the motor vehicle (1) is used as at least one of the loads (5, 6).

15. The method according to claim 14, characterized in that The electrical consumers of the motor vehicle (1) are an inverter, a drive train generator, a starter generator, an electrically operated catalytic converter, an electrically driven compressor and / or an electric refrigerant compressor.

16. A motor vehicle comprising a circuit arrangement (2) having a control device (3), an energy accumulator (4) and a plurality of loads (5, 6) connected to the energy accumulator (4) via load lines (7, 9), wherein: A current measuring device (12) is assigned to the energy accumulator (4) for determining a current measurement value describing the energy accumulator current, and a voltage measuring device (13, 14) is assigned to each load (5, 6) for determining a voltage measurement value describing the load voltage across the respective load (5, 6), wherein the current measuring device (12) and the voltage measuring device are connected to a control device (3) via a communication connection in order to continuously transmit the current measurement value and the voltage measurement value, wherein the control device (3) is configured to implement a method according to one of the preceding claims.

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