Methods for monitoring filter function and filter arrangement

Abstract

Method for functional testing of a filter (2), preferably a high-frequency filter or an EMC filter, in particular a common-mode filter and / or a differential-mode filter, and wherein the filter (2) comprises an active filter and / or a passive filter and / or a digital filter, and wherein the filter (2) is arranged in or on a power supply line, preferably installed in a DC network and / or a traction network of a motor vehicle, in order to filter out disturbances, characterized by that a functional detector (3) is arranged at the input and / or output of the filter (2), and that an averaging is carried out with the function detector (3), and that a voltage value is determined by averaging and the determined voltage value is used to assess the functionality of the filter (2) by comparing the voltage value with a threshold value.

Description

[0001] The invention relates to a method for functional testing of a filter with the features of the preamble of claim 1 and a filter arrangement with the features of the preamble of claim 14.

[0002] In practice, filters are used to suppress interference, especially electromagnetic interference. Due to the aging of individual components or defective components, the filters can degrade or fail completely. Often, such a failure or deterioration of the filter goes unnoticed or is only noticed very late.

[0003] DE 10 2009 056 395 A1 describes a method for functional testing of a passive or active filter with a function detector at the filter's output. For this purpose, a signal is introduced at the filter input and output at the filter output, and compared with an expected signal.

[0004] German patent DE 692 01 578 T2 describes a system for evaluating the performance of an electrical filter in electrical power grids. For this purpose, the filter's input is fed with a pulse signal whose frequency lies outside the grid frequency. At the filter's output, the signal is passed through a filter and evaluated based on its rise time, amplitude, and frequency.

[0005] The invention is based on the objective of providing a simplified method for functional testing of a filter and a filter arrangement. In particular, the functional test should be able to be carried out during operation, preferably without interrupting the normal function of the filter.

[0006] This problem is solved according to the invention by the method for functional testing of a filter with the features of claim 1 and a filter arrangement with the features of claim 14.

[0007] According to the invention, a method for functionally testing a filter is provided, preferably for functionally testing a high-frequency filter or an EMC filter, in particular a common-mode filter and / or a differential-mode filter, wherein the filter comprises an active filter and / or a passive filter and / or a digital filter. The filter is arranged in or on a power supply line, preferably integrated into a DC power supply network and / or a traction network of a motor vehicle, in order to filter interference. Essentially, a functional detector is arranged at the input and / or output of the filter, and an averaging process is performed using the functional detector. A voltage value is determined by this averaging process, and the determined voltage value is used to assess the functionality of the filter by comparing the voltage value with a threshold value.

[0008] The advantage of this filter functional testing procedure is that the filter's quality and functionality can be checked during operation, essentially inline. The filter does not need to be removed for testing, nor is any circuit modification or interruption of normal operation required.

[0009] The filter's functionality can be continuously tested. This allows for the timely detection of a fault or a deterioration in filter performance, virtually immediately upon the occurrence of the fault.

[0010] The filter's functional test includes averaging or rectification. This averaging is performed primarily on the interference signals present on a line in the input or output section of the filter under test. This provides a measure of the intensity or amplitude of the interference signals.

[0011] Preferably, the averaging is performed after the desired signal has been separated from the noise. This can be done, for example, using a high-pass filter. If the desired signal is a DC voltage, a capacitor can be used to isolate the noise. If the desired signal contains AC voltages, the noise can be isolated using a high-pass filter.

[0012] It may be stipulated that the averaging is carried out continuously, or over a predetermined period, in particular periodically.

[0013] It can be provided that the voltage value obtained by averaging is determined by a detector or rectifier, preferably a diode rectifier. This enables a cost-effective implementation of the method and simple integration into existing filter topologies. A further advantage is that a diode rectifier functions independently of a supply voltage or auxiliary power supply. This increases reliability and reduces the required circuit complexity.

[0014] By averaging or rectifying the signals, a voltage value is determined that represents a measure of the disturbances. To assess whether the disturbances are above or below a certain limit, the determined voltage value can be compared with a predefined or predefined threshold or target value.

[0015] It may be provided that in one embodiment the comparison of the voltage value with a threshold value is carried out by a discriminator and / or a control unit.

[0016] It can be provided that the voltage value obtained by averaging is monitored, preferably by a control unit, by comparing the obtained voltage value with a target value. For this purpose, the voltage value obtained by averaging can be directly fed to the control unit. Amplification of the voltage value obtained by averaging using an intermediate amplifier can also be provided. The voltage value obtained by averaging can also be converted into a digital signal via an analog-to-digital converter, which is then transmitted to the control unit via a digital bus.

[0017] Preferably, if the predefined target value is exceeded, an error message is triggered or a fault is reported. For example, in the case of a vehicle, the driver can be instructed to take it to a workshop.

[0018] In one embodiment, the functional detector may include a pre-filter, wherein the pre-filter may be designed as a high-pass filter and / or as a band-pass filter and / or as a low-pass filter.

[0019] It can be advantageous to provide a pre-filter that is adjustable, particularly with regard to its cutoff and / or transmission frequency and / or its quality factor and / or its bandwidth. This allows the averaging process, or the voltage value obtained through averaging, to be optimally adapted to an existing or anticipated interference signal.

[0020] It can be provided that the supply line comprises at least two conductors, preferably each having a different potential, and the pre-filter performs a superposition of signals from the at least two conductors of the supply line additively and / or subtractively in order to filter out common-mode signals and / or differential-mode signals.

[0021] The function detector may be provided with a switching unit to switch between the filter output and filter input, so that averaging can be selectively performed from either the input signal of the filter or the output signal of the filter.

[0022] It can be implemented that during a measurement, the function detector switches between the filter's input and output, and the voltage value obtained by averaging is compared between the filter's input and output, particularly by subtraction, and used as a measure of the filter's functionality. By comparing the levels of the interference signals between the filter's input and output, the current or actual attenuation of the filter can be directly determined. If the attenuation is too low, i.e., insufficient, an error message can be generated.

[0023] For example, it may be possible to specify a target value for the difference between the average input signal of the filter and the average output signal of the filter, and the filter is considered functional if the difference between the input and output signals is equal to or greater than the specified target value. This means that the filter is considered functional if the attenuation of the interference signals by the filter is above a certain value. The interference signal can be weighted via the pre-filter if desired, for example, to give greater weight to individual interference frequencies when calculating the average.

[0024] It can be configured that an error signal is output if the difference between the voltage value determined by averaging between the filter input and the filter output falls below a predefined value. This means that the error signal is generated as soon as the filter's effectiveness is no longer sufficient.

[0025] It can be provided that an error signal is output if the voltage value determined at the filter input by averaging exceeds a second threshold. This second threshold can represent a measure of a permissible maximum level of interference signals on the line. This level can be exceeded if a component of the line, for example, a converter or inverter, is defective and generates an unacceptably high interference signal. In such a case, despite sufficient filtering effectiveness, an unacceptably high level of EMC interference could still result. To address this scenario, the interference signal level present upstream of the filter can be determined and evaluated using the method according to the invention.

[0026] Furthermore, according to the invention, a filter arrangement comprising a filter and a functional detector is provided, preferably for implementing an embodiment of the method described above, wherein the filter is preferably designed as a high-frequency filter or as an EMC filter, in particular as a common-mode filter and / or as a differential-mode filter, and wherein the filter comprises an active filter and / or a passive filter and / or a digital filter, and wherein the filter is arranged in or on a supply line to filter interference, preferably installed in a DC power network and / or a traction network of a motor vehicle.Essentially, the function detector includes a pre-filter and a circuit for averaging, and the function detector includes a discriminator to compare the voltage value obtained by averaging with a predefinable threshold, or the function detector includes an A / D converter to convert the voltage value obtained by averaging into a digital signal and forward it to a control unit via a BUS.

[0027] The BUS can be a standard digital BUS, e.g. a fieldbus or a CAN bus.

[0028] The discriminator threshold can be adjustable and / or programmable, preferably as a voltage value via a D / A converter. This allows different switching thresholds to be achieved with one and the same filter arrangement.

[0029] It may be provided that the function detector and / or the pre-filter is connected to a control unit, preferably that the function detector and / or the pre-filter can be controlled by the control unit. The control unit can, on the one hand, control the filter arrangement and, on the other hand, handle communication with higher-level systems, e.g., a vehicle network or an operating and display device. For this purpose, the control unit can comprise a microprocessor, a memory containing executable program code readable by the microprocessor, and at least one digital interface.

[0030] The discriminator and / or the control unit may be provided with an electrically writable memory to store several of the voltage values ​​measured by averaging, in particular to store them continuously, preferably periodically over the entire service life of the filter. This enables long-term monitoring of the functionality of the filter assembly.

[0031] It may be possible to compare the stored values ​​with each other, for example to detect filter aging.

[0032] It may be possible to read out the values ​​stored in the memory, preferably using a measuring station, to create a quality assurance report for the filter's functionality. For example, in the case of an electric vehicle, routine inspections can be used to verify that the EMC suppression of the filter assembly is functioning correctly. This functional verification can be carried out using the stored values ​​for the entire period since the vehicle's registration or since the last routine inspection.

[0033] The filter can be arranged in a high-voltage direct current (HVDC) line of a vehicle's traction network between an energy source, preferably a battery, and an energy sink, preferably an electric motor. In particular, the HVDC line can have a voltage greater than or equal to 200 volts, preferably greater than or equal to 400 volts, and most preferably greater than or equal to 600 volts.

[0034] The filter may be designed for a frequency range of 1 kHz to 1,000 MHz, or for a frequency range of 10 kHz to 100 MHz, preferably for a frequency range of 50 kHz to 50 MHz.

[0035] The invention can be applied in the field of electromobility or stationary electrical machines or other industrial applications.

[0036] Further examples and embodiments of the invention are shown in the figures and described below. These show: Fig. 1: Filter between a source of interference and a sink of interference; Fig. 2: Interference spectrum with a functioning filter Fig. 1 measured at the filter outlet; Fig. 3: Interference spectrum with defective filter Fig. 1 measured at the filter outlet; Fig. 4: first embodiment of a filter arrangement according to the invention; Fig. 5: Second embodiment of a filter arrangement according to the invention with a switching unit to switch between filter input and filter output; Fig. 6: First embodiment of a functional detector made of Fig. 4 or Fig. 5; Fig. 7: Second embodiment of a functional detector made of Fig. 4 or Fig. 5; Fig. 8: Third embodiment of a functional detector made of Fig. 4 or Fig. 5; Fig. 9a: Rating level with functioning filter for positive supply line measured at the filter output; Fig. 9b: Rating level with functioning filter for negative supply line measured at the filter output; Fig. 9c: Rating level with a functioning common-mode filter, measured at the filter output; Fig. 9d: Rating level with a functioning differential mode filter measured at the filter output; Fig. 10a: Rating level with defective filter for positive supply line measured at the filter output; Fig. 10b: Rating level with defective filter for negative supply line measured at the filter output; Fig. 10c: Rating level with defective filter for common-mode disturbances measured at the filter output; Fig. 10d: Rating level with defective differential-mode interference filter measured at the filter output; Fig. 11: Third embodiment of filter arrangements according to the invention from the Fig. 6 to 8 in the positive and negative supply lines.

[0037] The figures show various exemplary embodiments of the invention, which are neither exhaustive nor limiting. A person skilled in the art can modify or combine the illustrated embodiments of the invention based on their technical expertise within the scope of the claims, without departing from the scope of the invention.

[0038] Fig. Figure 1 shows a filter 2 between a source of interference 4, for example a converter 4 or inverter 4, and a sink of interference 5, for example a vehicle battery 5 or a rechargeable battery 5, which are connected to each other via a positive supply line 6 and a negative supply line 7. Further details are shown in the Fig. Figure 1 schematically shows the areas of the input signal measurement points 8 and the output signal measurement points 9, where the voltage of the positive supply line 6 and / or the negative supply line 7, or between the supply lines, or a ground potential, or a negative or positive reference potential, can be measured. The area of ​​the input signal measurement points 8 is located between the interference source 4 and the filter 2. The area of ​​the output signal measurement points 9 is located between the filter 2 and the interference sink 5.

[0039] Fig. Figure 2 shows an example of the interference spectrum measured in the area of ​​output signal measurement points 9 with a functioning filter. For comparison, the interference spectrum with a defective filter is shown below. Fig. 3 measured in the area of ​​output signal measurement points 9.

[0040] The Fig. Figure 3 shows a filter arrangement 1 with a filter 2 and a functional detector 3. The filter 2 is as shown in Fig. The function detector 3 is positioned between a source of interference 4 and a sink of interference 5. In the area of ​​the output signal measurement points 9, the function detector 3 is connected to the positive supply line 6 and the negative supply line 7. It is also possible for the function detector 3 to be connected to only one supply line. The function detector 3 can also be connected to the supply lines, or only one supply line, in the area of ​​the input signal measurement points 8.

[0041] The functional detector 3 indicates in Fig. Figure 4 comprises a pre-filter 30, a rectifier 31, and a discriminator 32. A control unit 43 can control the pre-filter 30 and the discriminator 32, or exchange and compare signals. The control unit 43 transmits a threshold value to the discriminator. When the threshold value is exceeded or fallen below, the discriminator transmits a signal to the control unit 43. The control unit 43 has a memory 44 and is connected to a measuring station 45. The connection to a measuring station 45 is not necessary for the function of the filter arrangement but serves for monitoring purposes. The connection to the measuring station 45 is temporary, for example, via a diagnostic connector (not shown). For instance, the connection to a measuring station 45 can be made briefly for routine checks to read or create measurement logs.It is also possible that the values ​​of the discriminator 32 are read via the control unit 43 and stored in the memory 44.

[0042] It may be provided that instead of a discriminator, 32 is used in the Fig. 4 an A / D converter is configured. In contrast to the discriminator 32, a signal is then passed to the control unit 43 and this signal is compared with a threshold value in the control unit 43.

[0043] In Fig. 5 shows a further embodiment, which differs from the embodiment of the Fig. 4 differs only in that a switching unit 36 ​​is arranged in front of the pre-filter 30 in the function detector 3, so that it is possible to switch between a measurement in the area of ​​the input signal measuring points and a measurement in the area of ​​the output signal measuring points.

[0044] Fig. Figure 6 shows a first embodiment of a functional detector 3 with pre-filter 20, rectifier 31 and discriminator 32 for measuring the function of the filter 2 in the positive or negative supply line 6, 7.

[0045] Fig. Figure 7 shows a second embodiment of a functional detector 3 with pre-filter 20, rectifier 31 and discriminator 32 for measuring the function of the filter 2 for common-mode disturbances in the positive or negative supply line 6, 7.

[0046] Fig. Figure 8 shows a third embodiment of a functional detector 3 with pre-filter 20, rectifier 31 and discriminator 32 for measuring the function of the filter 2 for differential mode disturbances in the positive or negative supply line 6, 7.

[0047] It may be provided that the function detector 3 is derived from the circuits of the Fig. 6 to 8 is designed. It can also be provided that the function detector 3 can switch between different pre-filters 30 in order to select the function detectors 3 from the Fig. 6 to 8 in a circuit. For this purpose, the pre-filter 30 can be used from the Fig. 4 and Fig. 5 can be controlled via control unit 43.

[0048] In the Fig. 9a to 9d represent rating levels with a functioning filter, which are used, for example, in discriminator 32 in the Fig. 4 or Fig. 5 can be measured. Fig. Figure 9a shows the evaluation level in the positive supply line 6 measured in the area of ​​the output signal measurement points 9. Fig. Figure 9b shows the evaluation level in the negative supply line 7 measured in the area of ​​the output signal measurement points 9. Fig. Figure 9c shows the evaluation level for a common-mode disturbance measured in the area of ​​output signal measurement points 9. Fig. Figure 9d shows the evaluation level for a differential mode disturbance measured in the area of ​​output signal measurement points 9.

[0049] To compare the rating levels in the Fig. 9 are in the Fig. 10 rating levels for a defective filter according to the Fig. 9 shown.

[0050] Fig. Figure 11 shows a filter arrangement in which the function detectors 3 are formed separately between the filter 2 and the disturbance sink 5 in the positive supply line 6, the negative supply line 7, as well as for common-mode disturbances and differential-mode disturbances between the positive supply line 6 and the negative supply line 7. Reference symbol list 1 Filter arrangement 2 filters 3 Function detector 4. Source of interference, inverter 5. Disturbance sink, battery 6 positive supply lines 7 negative supply line 8 measuring points input signal 9 measuring points output signal 30 pre-filters 31 rectifiers 32 Discriminator 43 Control unit 44 storage 45 measuring station 36 switching unit

Claims

[1] Method for functional testing of a filter (2), preferably a high-frequency filter or an EMC filter, in particular a common-mode filter and / or a differential-mode filter, and wherein the filter (2) comprises an active filter and / or a passive filter and / or a digital filter, and wherein the filter (2) is arranged in or on a power supply line, preferably installed in a DC network and / or a traction network of a motor vehicle, in order to filter out disturbances, characterized by , that a functional detector (3) is arranged at the input and / or output of the filter (2), and that an averaging is carried out with the function detector (3), and that a voltage value is determined by averaging and the determined voltage value is used to assess the functionality of the filter (2) by comparing the voltage value with a threshold value. [2] Method for functional testing of a filter (2) according to claim 1, characterized by that the averaging is carried out over a predetermined period. [3] Method for functional testing of a filter (2) according to one of claims 1 or 2, characterized by , that the voltage value obtained by averaging is determined by a detector or rectifier (31), preferably by a diode rectifier. [4] Method for functional testing of a filter (2) according to any one of claims 1 to 3, characterized by , that the comparison of the voltage value with a threshold value is carried out by a discriminator (32) and / or a control unit (43). [5] Method for functional testing of a filter (2) according to any one of claims 1 to 4, characterized by , that the voltage value obtained by averaging is monitored, preferably by a control unit (43) by comparing the obtained voltage value with a target value and, if the predefinable target value is exceeded, an error message is displayed or an error is reported. [6] Method for functional testing of a filter (2) according to any one of claims 1 to 5, characterized by , that the functional detector (3) comprises a pre-filter (30), wherein the pre-filter (30) is configured as a high-pass filter and / or as a band-pass filter; [7] Method for functional testing of a filter (2) according to claim 6, characterized by , that the pre-filter (30) is adjustable, in particular with regard to its cutoff and / or transmission frequency and / or its quality and / or its bandwidth. [8] Method for functional testing of a filter (2) according to one of claims 6 or 7, characterized by , that the supply line comprises at least two conductors, preferably having different potentials, and the pre-filter (30) performs an additive and / or subtractive superposition of signals from the at least two conductors of the supply line in order to filter out common-mode signals and / or differential-mode signals. [9] Method for functional testing of a filter (2) according to any one of claims 1 to 8, characterized by , that the function detector (3) has a switching unit to switch between the filter output and filter input, so that averaging is optionally possible from the input signal of the filter (2) or from the output signal of the filter (2). [10] Method for functional testing of a filter (2) according to any one of claims 1 to 9, characterized by, that during a measurement the function detector (3) is switched between the input of the filter (2) and the output of the filter (2) and the voltage value obtained by averaging is compared between the input of the filter (2) and the output of the filter (2), in particular by subtraction and is used as a measure of the functionality of the filter (2). [11] Method for functional testing of a filter (2) according to any one of claims 1 to 10, characterized by , that a setpoint for the difference between the mean signal of the input of the filter (2) and the mean signal of the output of the filter (2) can be specified and the functionality of the filter (2) is given if the difference between the input signal and the output signal is equal to or greater than the specified setpoint for the difference. [12] Method for functional testing of a filter (2) according to any one of claims 1 to 11, characterized by, that an error signal is output if the difference between the voltage value determined by averaging between the input of the filter (2) and the output of the filter (2) is below the specified value. [13] Method for functional testing of a filter (2) according to any one of claims 1 to 12, characterized by , that an error signal is output if the voltage value determined at the input of the filter (2) by averaging is above a second threshold. [14] Filter arrangement (1) comprising a filter (2) and a functional detector (3), wherein the filter (2) is preferably designed as a high-frequency filter or as an EMC filter, in particular a common-mode filter and / or a differential-mode filter, and wherein the filter (2) comprises an active filter and / or a passive filter and / or a digital filter, and wherein the filter (2) is arranged in or on a supply line, preferably installed in a DC power network and / or a traction network of a motor vehicle, in order to filter out disturbances, characterized by , that the function detector (3) comprises a pre-filter (30) and a circuit for averaging (31), and the functional detector (3) includes a discriminator (32) to compare the voltage value obtained by averaging with a predefinable threshold, or The function detector (3) includes an A / D converter to convert the voltage value obtained by averaging into a digital signal and to transmit it to a control unit via a BUS. [15] Filter arrangement (1) according to claim 14, characterized by that the discriminator threshold is adjustable and / or programmable, preferably that the discriminator threshold is adjustable as a voltage value via a D / A converter. [16] Filter arrangement (1) according to claim 14 or 15, characterized by , that the function detector (3) and / or the pre-filter (30) is connected to a control unit (43), preferably the function detector (3) and / or the pre-filter (30) is controllable by the control unit (43). [17] Filter arrangement (1) according to any one of claims 14 to 16, characterized by , that the discriminator (32) and / or the control unit (43) has an electrically writable memory (44) to store several of the voltage values ​​measured by averaging, in particular to store continuously, preferably periodically over the entire lifetime of the filter. [18] Filter arrangement (1) according to claim 17, characterized by , that the stored values ​​are compared with each other in order to detect aging of the filter component. [19] Filter arrangement (1) according to one of claims 17 or 18, characterized by, that the values ​​stored in the memory (44) are read out, preferably by a measuring station (45) in order to create a quality verification for the functionality of the filter (2). [20] Filter arrangement (1) according to any one of claims 14 to 19, characterized by , that the filter (2) is arranged in a high-voltage direct current line of a traction network of a vehicle between an energy source, preferably a battery, and an energy sink, preferably an electric motor. [21] Filter arrangement (1) according to any one of claims 14 to 20, characterized by that the filter is designed for a frequency range of 1 kHz to 1,000 MHz, or for a frequency range of 10 kHz to 100 MHz, preferably for a frequency range of 50 kHz to 50 MHz.

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