Method and control unit for functional testing of a differential current sensor

Abstract

Method for functionally testing a differential current sensor (10) of an on-board charger of a motor vehicle or a charging station for a motor vehicle, wherein the differential current sensor (10) is configured to measure a differential current or fault current and to trigger a fault current detection function dependent on the measurement of the differential current or fault current within a triggering time of the differential current sensor (10) dependent on a triggering threshold, comprising the following steps: applying a test current (14) to the differential current sensor (10) during a differential current measuring operation or fault current measuring operation of the differential current sensor (10). Detecting a mixed signal (15) from the test current (14) and any differential current or fault current (17) that may be present.Evaluating the detected mixed signal (15) in such a way that the known test current (14) is subtracted from the mixed signal (15) to determine an evaluation current (16), wherein if it is determined that the evaluation current (16) does not contain any characteristic signal features of the test current (14), it is concluded that the differential current sensor (10) is functioning properly, and if it is determined that the evaluation current (16) contains at least one characteristic signal feature of the test current (14), it is concluded that the differential current sensor (10) is not functioning properly.

Description

[0001] The invention relates to a method and control device for functional testing of a differential current sensor of an on-board charger of a motor vehicle or a charging station for a motor vehicle, wherein the differential current sensor is configured to measure a differential current or fault current and to trigger a fault current detection function dependent on the measurement of the differential current or fault current within a triggering time of the differential current sensor dependent on a triggering threshold.

[0002] As a result of insulation faults, for example, so-called differential currents or fault currents can develop when charging a motor vehicle. A differential current or fault current is that portion of an electrical current that does not flow back to the power source via the intended current path. Differential currents or fault currents can be measured using a so-called differential current sensor. If an impermissibly high differential current or fault current is measured, a fault current detector must be triggered. In this context, it is known that a differential current sensor can have different trigger thresholds. A trigger threshold corresponds to an amplitude of the differential current or fault current; when this amplitude is reached or exceeded compared to a measured differential current or fault current, the fault current detector is triggered. The fault current detector is triggered within a trigger time that depends on the trigger threshold.The higher the tripping threshold of the residual current detection, the shorter the tripping time is typically.

[0003] If a residual current detection is triggered, various measures can be taken to ensure functional reliability, such as galvanic isolation of the vehicle's on-board charger from the energy source used for charging.

[0004] Residual current detection must meet safety-relevant criteria. Currently, residual current sensors do not meet safety-relevant criteria, or only meet them to a limited extent, particularly the so-called ASIL level. There is a need to verify the functionality of a residual current sensor in order to provide residual current detection that meets safety-relevant criteria, particularly ASIL requirements.

[0005] DE 10 2020 131 522 A1 relates to a method for determining a differential current in an electrical system, wherein a first differential current is measured using a first differential current sensor and a second differential current is measured using a second differential current sensor. An additional current is fed into an electrical connection of the electrical system between the two differential current sensors.

[0006] DE 10 2020 209 241 A1 discloses a method for operating a charging device by determining the functionality of a fault current sensor and thus a differential current sensor.

[0007] DE 10 2019 101 636 A1 discloses an electrical circuit device with a differential current sensor and a differential current monitoring module.

[0008] The object of the invention is to provide a novel method and control device for functional testing of a differential current sensor of an on-board charger of a motor vehicle or a charging station for a motor vehicle.

[0009] This object is achieved by a method according to claim 1 and a control device according to claim 9.

[0010] The method according to the invention comprises at least the following steps: Applying a test current to the differential current sensor during a differential current measuring operation or fault current measuring operation of the differential current sensor.

[0011] Detection of a mixed signal from the test current and any differential current or fault current that may be present.

[0012] Evaluating the detected mixed signal in such a way that the known test current is subtracted from the mixed signal to determine an evaluation current, wherein if it is determined that the evaluation current does not contain any characteristic signal features of the test current, it is concluded that the differential current sensor is functioning properly, and if it is determined that the evaluation current contains at least one characteristic signal feature of the test current, it is concluded that the differential current sensor is not functioning properly.

[0013] The method according to the invention allows self-diagnosis of a residual current sensor during the operation of the residual current sensor, i.e., during the residual current measurement mode or fault current measurement mode. The method can be used for the measurement or detection of residual currents or fault currents in the form of alternating current or direct current. The self-diagnosis is performed while the residual current sensor is running by applying a test current to the residual current sensor during the residual current or fault current measurement. The resulting mixed signal consisting of the test current and any residual current or fault current present is recorded and evaluated to determine whether the residual current sensor is functioning properly or improperly, thus enabling the sensor to perform its self-diagnosis.

[0014] To perform a functional test and thus self-diagnosis of the residual current sensor, it is not necessary to interrupt its operation. The triggering of a residual current detection signal within a defined trigger threshold and a trigger time dependent on the trigger threshold is not affected by the method according to the invention.

[0015] The invention can provide a fault current detection system that meets safety-relevant criteria, in particular ASIL requirements.

[0016] Preferably, the test current is applied to the differential current sensor, particularly periodically, during the continuous measurement of the differential current or fault current, with an amplitude of the test current and / or a frequency of the test current being adapted to the trigger threshold of the differential current sensor and / or to the trigger time of the differential current sensor. This is particularly preferred for functional testing and thus self-diagnosis of the differential current sensor during its runtime, i.e., parallel to the differential current measurement operation or fault current measurement operation and thus parallel to the actual fault current detection.

[0017] Preferably, the amplitude of the test current is or lies on the order of magnitude of the lowest trigger threshold of the residual current sensor. Preferably, the frequency-dependent period of the test current is shorter than the trigger time of the highest trigger threshold of the residual current sensor. This makes it particularly advantageous to perform the functional test and thus the self-diagnosis of the residual current sensor during runtime while the residual current sensor remains fully available for fault current detection.

[0018] For example, a test current is applied to the differential current sensor that has a pulse-like or abruptly changing amplitude and / or a pulse-like or abruptly changing frequency. Such a test current differs from potentially occurring differential currents or fault currents and thus allows for a particularly advantageous functional test and thus self-diagnosis of the differential current sensor.

[0019] Preferred developments of the invention will become apparent from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail, without being limited thereto, with reference to the drawings. Herein: Fig. 1 a highly schematic representation of a differential current sensor of an on-board charger of a preferably battery-electric motor vehicle or a charging station for a preferably battery-electric motor vehicle for detecting an alternating current as a differential current or fault current, Fig. 2a temporal signal curves to illustrate the invention when detecting an evaluation current without an existing alternating fault current, Fig. 2b further temporal signal curves to illustrate the invention when detecting an evaluation current superimposed with an alternating fault current, Fig. 2c further temporal signal curves to illustrate the invention when detecting an evaluation current in the case of a defective differential current sensor, Fig. 3a temporal signal curves to illustrate the invention when detecting an evaluation current without any DC fault current, Fig. 3b further temporal signal curves to illustrate the invention when detecting an evaluation current superimposed with a DC fault current, Fig. 3c further temporal signal curves to illustrate the invention when detecting an evaluation current in the case of a defective differential current sensor.

[0020] The invention relates to a method and a control unit for functionally testing a differential current sensor. The differential current sensor can be a component of an on-board charger of a preferably battery-electric motor vehicle or of a charging station for such a preferably battery-electric motor vehicle. The differential current sensor is configured to measure a differential current or fault current and, dependent on the measurement of the differential current or fault current, to trigger a fault current detection function within a triggering time of the differential current sensor that depends on a triggering threshold of the differential current sensor.

[0021] Fig. Figure 1 shows a highly schematic diagram of a differential current sensor 10, wherein the phase conductors L1, L2 and L3 of an alternating current network and a neutral conductor N of the same extend through a core 11 of the differential current sensor 10. A protective conductor PE is provided in Fig. 1, which, however, does not extend through the core 11 of the differential current sensor 10.

[0022] Fig. 1 further shows two controllers 12, 13 of a control unit 18, wherein a first controller 12 receives a measurement signal from the differential current sensor 10 and provides the same to a second controller 13 for functional testing of the differential current sensor 10. Although in Fig. While two controllers 12, 13 are shown in Figure 1, only a single controller may be present. In this case, the function of controller 13 is integrated into controller 12.

[0023] The controllers 12, 13 can also be distributed across two different control units of a control system.

[0024] The controller 12 and in particular the controller 13 can also be an integral part of the differential current sensor 10.

[0025] The differential current sensor 10 is used to measure or detect a differential current or fault current in the form of an alternating current or a direct current. Fig. 1, the differential current sensor 10, through whose core 11 the phase conductors L1, L2 and L3 of an alternating current network as well as a neutral conductor N extend, is used to detect a differential current or fault current in the form of an alternating current.

[0026] To trigger a residual current detection, it is provided that, depending on the measurement signal provided by the residual current sensor 10, a residual current detection is carried out or triggered within a triggering time dependent on a triggering threshold. The higher the triggering threshold, the shorter the triggering time. The triggering threshold and the triggering time dependent on the triggering threshold, within which a residual current detection is to be triggered in the presence of a residual current or fault current, are preferably implemented or stored in the controller 12.

[0027] In order to provide a functional test for such a differential current sensor 10 and thus a self-diagnosis for the same, a test current is impressed on the differential current sensor 10, namely the core 11 thereof, while a differential current or fault current is being measured using the differential current sensor 10, i.e. during runtime and thus during the differential current measuring operation or fault current measuring operation of the differential current sensor 10. Fig. 1 shows that in the Fig. 1, the controller 13 applies a test current 14 to the core 11 of the differential current sensor 10 during its running time and thus during the differential current measuring operation or fault current measuring operation, preferably via an interface 19 of the control unit 18 having the controller 13.

[0028] During the application of the test current 14 as a measurement signal, a mixed signal 15 comprising the test current 14 and any differential current or fault current that may be present is then detected via the core 11 of the differential current sensor 10 and is provided to the controller 12 via an interface 20 thereof, wherein the controller 12 provides the detected mixed signal 15 to the controller 13.

[0029] The detected mixed signal 15 is evaluated in the controller 13 in such a way that the known test current 14 is subtracted from the mixed signal 15 to determine an evaluation current 16. The controller 13 checks whether the evaluation current 16 contains at least one characteristic signal feature of the test current 14. If it is determined that the evaluation current 16 does not contain a characteristic signal feature of the test current 14, it is concluded that the residual current sensor 10 is functioning properly, and the evaluation current 16 can be provided to the controller 12 for actual fault current detection. If, on the other hand, it is determined that the evaluation current 16 contains at least one characteristic signal feature of the test current 14, it is concluded that the residual current sensor 10 is functioning improperly, and further use of the evaluation current 16 for fault current detection is prevented.

[0030] Fig. 2a and Fig. 2b each show signal curves over time t, which can develop when the differential current sensor 10 is functioning properly. Fig. 2a, Fig. 2b shows possible differential currents or fault currents 17 that can develop during operation, where Fig. 2a there is no differential current or fault current 17 and in Fig. 2b a differential current or fault current 17 in the form of an alternating current is present. Furthermore, Fig. 2a and Fig. 2b shows the time course of an embodiment of the test current 14, which is impressed on the differential current sensor 10 in connection with the method according to the invention.

[0031] Furthermore, Fig. 2a and Fig. 2b temporal courses of the recorded mixed signal 15. Furthermore, Fig. 2a and Fig. 2b temporal courses of the evaluation current 16, which results from a subtraction of the detected mixed signal 15 and the test current 14 known on the control side.

[0032] The test current 14, which is impressed on the core 11 of the differential current sensor 10, has, according to Fig. 2a, Fig. 2b has as a characteristic signal feature a pulse-like or abruptly changing amplitude and thus a temporal progression that differs from the progression of possibly occurring differential currents or fault currents 17. In Fig. 2a, Fig. 2b, the evaluation currents 16 shown there do not contain any characteristic signal feature of the test current 14, i.e. no pulse-like or sudden change in amplitude. In this respect, Fig. 2a, Fig. 2b indicates that the differential current sensor 10 is functioning properly.

[0033] In contrast, Fig. 2c shows the time course of the electrical currents 14, 15, 16 and 17, which can develop if, during operation or during the running time of the differential current sensor 10, a malfunction of the differential current sensor 10 or a defective differential current sensor 10 is detected during a functional test. In this case, according to Fig. 2c the evaluation current 16 has at least one characteristic signal feature of the test current 14, namely in Fig. 2c a sudden or pulse-like change in the amplitude of the evaluation current 16.

[0034] According to Fig. 2a, Fig. 2b, Fig. 2c, the test current 14 is superimposed on the potentially present differential current or fault current 17, with the differential current sensor 10 detecting or measuring the mixed signal 15, which corresponds to a geometric addition of the test current 14 and the potentially present differential current or fault current 17. During the evaluation of the mixed signal 15, the known test current 14 is subtracted from the mixed signal 15 to obtain the evaluation current 16. This evaluation current 16 is evaluated for functional testing and thus for self-diagnosis of the differential current sensor 10. The test current 14 can have almost any profile, but differs from an expected differential current or fault current at least with regard to one characteristic property, in particular by at least one, for example, pulse-like or sudden amplitude change.Alternatively or additionally, the frequency of the test current 14 can also be changed in a pulse-like or step-like manner.

[0035] The test current 14 is impressed on the core 11 of the differential current sensor 10 during the continuous detection of any differential current or fault current 17 that may be present and thus parallel to the differential current measuring operation or fault current measuring operation of the differential current sensor 10, wherein an amplitude of the test current 14 and / or a frequency of the test current 14 is adapted to the triggering threshold of the differential current sensor 10 and / or to the triggering time of the differential current sensor 10.

[0036] Preferably, the test current 14 is periodically applied to the differential current sensor 10 during the detection of any residual current or fault current 17, with the amplitude of the test current 14 being in the order of magnitude of the lowest trigger threshold of the differential current sensor 10. The period duration of the test current 14, which depends on the frequency of the test current 14, is smaller, preferably at least 75%, at least 50%, or at least 25% smaller, than the trigger time of a highest trigger threshold of the differential current sensor 10.

[0037] While Fig. 2a, Fig. 2b and Fig. 2c show the method according to the invention in connection with the detection or measurement of a differential current or fault current in the form of an alternating current, Fig. 3, Fig. 3b and Fig. 3c shows the signal curves 14, 15, 16 and 17 when a possibly existing direct current is detected or measured as the differential current or fault current 17. In addition to the possibly existing differential current or fault current 17, Fig. 3a, Fig. 3b and Fig. 3c again the test current 14, which is impressed on the differential current sensor 10, the mixed signal 15 detected by the differential current sensor 10 during the impression of the test current and the evaluation current 16 determined during the evaluation of the mixed signal 15, which in Fig. 3a, Fig. 3b does not contain any characteristic signal feature of the test current 14, which, however, Fig. 3c contains a characteristic signal feature of the test current, so that in Fig. 3a, Fig. 3b on proper functioning of the differential current sensor 10 and in Fig. 3c indicates a malfunction of the differential current sensor 10 or a defective differential current sensor 10.

[0038] Test current 14 is used in Fig. 3a, Fig. 3b, Fig. 3c preferably a DC-free rectangular current is impressed on the core 11 of the differential current sensor 10, preferably with an amplitude in the range of the smallest or lowest trigger threshold of the differential current sensor 10. If according to Fig. 3b a differential current or fault current 17 deviating from zero is present, the mixed signal 15 of the Fig. 3b, which corresponds to the geometric addition of differential current or fault current 17 and test current 14. As already explained, the frequency and thus period of the test signal 14 is dimensioned such that the frequency-dependent period of the test current 14 is shorter than the triggering time of a highest triggering threshold of the differential current sensor 10. This does not impair fault detection by the functional test.

[0039] The test current 14 can be different in each test cycle of the differential current sensor 10, both in Fig. 2a, Fig. 2b, Fig. 2c as well as in Fig. 3a, Fig. 3b, Fig. 3c. Thus, the test current 14 can have an individual amplitude and / or frequency in each test cycle.

[0040] The invention further relates to a control device 18 which is configured to automatically execute the method described above during the running time of the differential current sensor 10, i.e. parallel to the actual differential current measuring operation or fault current measuring operation.

[0041] The control unit 18 has an interface 19 with which it applies the test current 14 to the core 11 of the differential current sensor 10 during the detection of the differential current or fault current 17.

[0042] As a further interface, the control unit 18 has an interface 20, via which it receives the detected mixed signal 15. Furthermore, the control unit 18 has at least one controller 12, 13 for evaluating the mixed signal 15 and for triggering the fault current detection in the manner described above. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 131 522 A1

[0005] DE 10 2020 209 241 A1

[0006] DE 10 2019 101 636 A1

[0007]

Claims

[1] Method for functional testing of a differential current sensor (10) of an on-board charger of a motor vehicle or a charging station for a motor vehicle, wherein the differential current sensor (10) is designed to measure a differential current or fault current and to trigger a fault current detection function dependent on the measurement of the differential current or fault current within a triggering time of the differential current sensor (10) dependent on a triggering threshold, comprising the following steps: Imposing a test current (14) on the differential current sensor (10) during a differential current measuring operation or fault current measuring operation of the differential current sensor (10), detecting a mixed signal (15) from the test current (14) and any differential current or fault current (17) that may be present, Evaluating the detected mixed signal (15) such that the known test current (14) is subtracted from the mixed signal (15) to determine an evaluation current (16), if it is determined that the evaluation current (16) does not contain any characteristic signal features of the test current (14), it is concluded that the differential current sensor (10) is functioning properly, if it is determined that the evaluation current (16) contains at least one characteristic signal feature of the test current (14), it is concluded that the differential current sensor (10) is not functioning properly. [2] Method according to claim 1, characterized by that the test current (14) is impressed on the differential current sensor (10) during the continuous measurement of the differential current or fault current (17), wherein an amplitude and / or a frequency of the test current (14) is adapted to the triggering threshold of the differential current sensor (10) and / or to the triggering time of the differential current sensor (10). [3] Method according to claim 1 or 2, characterized by that the test current (14) is periodically impressed on the differential current sensor (10) during the detection of the differential current or fault current (17). [4] Method according to claim 2 or 3, characterized by that the amplitude of the test current (14) is in the order of magnitude of a lowest trigger threshold of the differential current sensor (10). [5] Method according to claim 2, 3 or 4, characterized by that the period duration of the test current (14), which depends on the frequency of the test current (14), is smaller than the tripping time of a highest tripping threshold of the differential current sensor (10). [6] Method according to one of claims 1 to 5, characterized by that a test current (14) is impressed on the differential current sensor (10) which has a pulse-like changing amplitude and / or frequency or a step-like changing amplitude and / or frequency. [7] Method according to one of claims 1 to 6, characterized by that an alternating current is detected as the differential current or fault current (17). [8] Method according to one of claims 1 to 6, characterized by that a direct current is detected as the differential current or fault current (17). [9] Control unit (18) for functional testing of a differential current sensor (10) of an on-board charger of a motor vehicle or a charger of a charging station for a motor vehicle, characterized by that the control device (18) is set up to automatically carry out the method according to one of claims 1 to 8 during a differential current measuring operation or fault current measuring operation of the differential current sensor (10) and thus during the running time of the differential current sensor (10). [10] Control device (18) according to claim 9, characterized by , that the same has an interface (19) via which the test current (14) is applied to the differential current sensor (10) during the detection of the differential current or fault current, the same has an interface (20) via which it receives the detected mixed signal (15) from the differential current sensor (10), the same has at least one controller (12, 13) for evaluating the mixed signal (15).

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