Interference suppression in a vehicle's power supply network using a controllable resistor

Abstract

Device (8) for suppressing disturbances in a power supply network comprising at least two lines (10) of a vehicle, in particular an electric vehicle, with a filter (81) connected to a first line of the power supply network to tap off unwanted oscillations, and with a controllable resistor (82) connected via a capacitor (21) or an inductive transformer between the first line (10) of the power supply network and either another line (10) of the power supply network or a ground potential or a negative or positive reference potential, and that the filter (81) is designed and connected to the controllable resistor (82) in such a way that the filter (81) reduces the ohmic resistance of the controllable resistor (82) when unwanted oscillations occur, characterized by that the capacitor (21) or the inductive transformer for connecting the controllable ohmic resistance (82) to a line (10) of the power supply network is dimensioned such that in the frequency range to be suppressed of the unwanted oscillations the imaginary part of the impedance resulting from the series connection of the controllable ohmic resistance (82) with the capacitor (21) or the inductive transformer is less than 10% of its real part or its resistance.

Description

[0001] The invention relates to a device for suppressing disturbances in a power supply network of a vehicle according to the features of the preamble of claim 1.

[0002] Such a device is known from DE 10 2017 102 608 B3. This patent describes an active filter for suppressing interference signals, comprising a pre-stage and a final stage. The active filter taps an interference signal from a supply line, inverts this interference signal in the pre-stage, amplifies the signal in the final stage, and feeds the inverted and amplified correction signal back into the supply line.

[0003] From DE 11 2017 007 773 T5, an active filter with a filter circuit is known. The filter circuit comprises a low-pass filter and a connecting circuit, which is controlled by a connecting circuit controller, which in turn is controlled by a measuring circuit 13.

[0004] DE 197 41 430 A1 describes a circuit arrangement for suppressing interference signals from a converter.

[0005] US 4 594 648 A describes an active filter for interference signals.

[0006] US patent 2017 / 0110986A1 discloses an electrical circuit for interference suppression in a vehicle with a motor, an inverter, and a battery. To reduce ripple current, the circuit incorporates an LC filter circuit comprising two capacitors and an inductor. A MOSFET switches one of the capacitors to vary the frequency of the LC filter circuit.

[0007] An electrical circuit for interference suppression using an LC filter circuit is also known from JP 2014-050 230 A. The resonant frequency of the LC filter circuit is shifted by switching elements on and off.

[0008] The documents DE 10 2007 021 978 A1, DE 10 2013 209 185 A1 and KR 10 2019 0 033 386 A each describe a high-pass filter.

[0009] From DE 10 2014 015 309 A1, a device for supplying a consumer with a constant current is known. For this purpose, a transistor is connected as a constant current source. To decouple interfering modulation signals, the transistor is operated in the form of a virtual inductor. The virtual inductor increases the resistance to the AC voltage components of the modulated interference, resulting in modulation voltage decoupling in the vehicle.

[0010] German patent DE 10 2011 079 082 A1 discloses a voltage converter circuit for electric vehicles. This voltage converter supplies, for example, a drive system for electric vehicles with a traction motor with electrical energy. To prevent an excessive drop in output voltage under high loads, it is proposed that a controlled switch be provided to connect the output of the circuit directly to the input, i.e., the power source.

[0011] In practice, electric vehicles employ complex power distribution systems. These systems utilize various circuits for different electrical loads. Due to the inductances and capacitances that inevitably arise when installing such power distribution systems in a real-world environment, these networks exhibit a certain natural resonance. This natural resonance changes when individual control circuits are switched on or off, or when the power distribution system is connected to external power sources. Switching operations within the power distribution system can induce undesired damped oscillations, which, if these oscillations occur near the network's natural resonance, can lead to very high overvoltages. Suppressing such voltage spikes requires the use of correspondingly fast-acting surge protection devices.

[0012] Voltage regulation circuits. Such oscillations in power distribution systems can also be suppressed using active filters. However, these solutions are very complex from a circuit engineering perspective and become ineffective at the latest when the self-resonant frequency of the power supply system changes due to switching circuits on or off.

[0013] The object of the present invention is to suppress such interference in a vehicle's power supply network in a structurally simple manner. In particular, the interference suppression should be cost-effective and preferably achievable in a relatively small installation space. Effective interference suppression should also be achieved even under changing installation conditions or with resonant frequencies of the power supply system.

[0014] This problem is solved according to the invention by a device for suppressing disturbances with the features of claim 1 and by a method for suppressing vibrations excited by switching operations or load changes in a power supply network according to the features of claim 14.

[0015] According to the invention, a device for suppressing disturbances in a power supply network of a vehicle, in particular an electric vehicle or hybrid vehicle, comprising at least two conductors, is provided. The device includes a filter connected to a first conductor of the power supply network to capture unwanted oscillations, and a controllable resistor connected via a capacitor or an inductive transformer between the first conductor of the power supply network and either another conductor of the power supply network, a ground potential, or a negative or positive reference potential. Crucially, the filter is designed and connected to the controllable resistor in such a way that, when unwanted oscillations occur, the filter reduces the ohmic resistance of the controllable resistor.

[0016] An advantage is that the controllable resistor effectively dampens any unwanted oscillations that may occur in the power supply network. It is advantageously designed that, by using a controllable resistor whose characteristics are defined by a filter, the resistor is not effective in the frequency range required for power transmission, but only in a frequency range where interference is typically expected. In particular, the controllable resistor does not impair power transmission in the power supply network.

[0017] Another advantage is that the controllable resistor reduces the quality of any natural resonances in the power supply network, thereby also reducing voltage spikes. This effect of the controllable resistor extends over a very wide frequency range and is therefore not limited to a specific frequency, as is the case with an active filter. This means that even if the resonant frequency of the power supply network shifts due to the switching on or off of individual circuits, this frequency shift does not impair the interference suppression effect.

[0018] The power supply network can be a direct current (DC) network, an alternating current (AC) network, or a multi-phase network. The minimum two conductors of the power supply network can, for example, be the positive and negative conductors of a DC network. However, they can also be a phase and neutral conductor of an AC network, or conductors of a multi-phase network.

[0019] An advantage is that the controllable resistor is galvanically isolated from the power supply network via a capacitor or transformer. This allows the power loss occurring in the controllable resistor to be kept very low. The device and method can also be used in high-voltage networks. Preferably, the power supply network can be a high-voltage network, meaning it has voltages of more than 60 V, 120 V, or 400 V.

[0020] Preferably, a frequency-dependent and / or oscillation-dependent ohmic resistance is formed across the controllable resistor. The controllable resistor creates an ohmic resistance for the corresponding disturbance oscillations by pulling the relevant lines of the power supply network through the ohmic resistor to a ground potential, another line of the power supply network, or a negative or positive reference potential. That is, when oscillations occur, an additional ohmic resistance acts on the power supply network via the controllable resistor in order to dampen these oscillations, in particular to convert them into heat energy. The negative or positive reference potential in this context can be another voltage level, which is, for example, + / - 12 volts or + / - 24 volts above or below the average potential of the power supply network line.

[0021] In particular, the filter is designed such that, under normal operating conditions (i.e., without disturbances on the power supply network), the controllable ohmic resistance has a high resistance value. Specifically, this high resistance value is normally dimensioned so that it does not affect the power supply network.

[0022] In one embodiment, the filter can be configured as a high-pass filter or a band-pass filter. It can also be designed to include an impedance converter function, meaning that the filter has a high input impedance and minimizes interference with the power supply network. The high-pass or band-pass filter can detect oscillations occurring on the power supply line. When such oscillations occur, the filter adjusts the controllable resistor to reduce its ohmic value. The frequency range of the high-pass or band-pass filter is specifically defined such that the frequency of the expected disturbances or oscillations falls within this range.

[0023] In one embodiment, it may be provided that the filter is designed such that the controllable resistance is configured as a frequency-dependent controllable ohmic resistance.

[0024] According to the invention, a method for suppressing oscillations excited by switching operations or load changes in a vehicle's power supply network, particularly an electric vehicle, is provided. The power supply network comprises a power source and at least one switchable or switching electrical load, and is connected via a controllable resistor, which is galvanically isolated, either to two conductors of the power supply network or to one conductor of the power supply network and either a ground potential or a negative or positive reference potential. Crucially, the controllable resistor is designed as a frequency-dependent ohmic resistor. Frequency-dependent oscillations are detected by a filter connected to a conductor of the power supply network, and the ohmic resistance of the controllable resistor is reduced accordingly.

[0025] To achieve good interference suppression, the filter may be designed to reduce the ohmic resistance of the controllable resistor by at least a factor of 10, 100, 1,000, or 10,000 when unwanted oscillations occur.

[0026] In a structurally simple embodiment, it can be provided that the controllable resistance is designed as a controllable ohmic resistance, preferably by the controllable ohmic resistance being a controlled semiconductor, in particular a transistor or a field-effect transistor.

[0027] To achieve symmetrical or amplitude-independent suppression of interference, the controllable resistor can be designed as a controllable ohmic resistor by comprising a push-pull circuit with transistors or field-effect transistors.

[0028] An advantage is that the controllable resistor can be designed as a passive two-terminal network, in particular a controllable passive two-terminal network.

[0029] Preferably, the controllable resistor can operate in a purely two-quadrant mode, thereby only dissipating electrical energy. This contrasts with an active filter, which operates in a four-quadrant mode and requires the input of correction signals to suppress interference.

[0030] In one embodiment, it can be provided in particular that the capacitor or the inductive transformer for connecting the controllable resistance to a line of the power supply network is connected in series with the controllable resistance, preferably that the capacitor or the inductive transformer is arranged in a collector circuit or in an emitter circuit of a transistor of the controllable ohmic resistance, or that the capacitor or the inductive transformer for connecting the controllable ohmic resistance to a line of the power supply network is arranged in a drain circuit or a source circuit of a field-effect transistor of the controllable ohmic resistance.

[0031] According to the invention, the capacitor or inductive transformer for connecting the controllable ohmic resistance to a line of the power supply network is dimensioned such that, in the frequency range of the unwanted oscillations to be suppressed, the imaginary part of the impedance resulting from the series connection of the controllable ohmic resistance with the capacitor or inductive transformer is less than 10% of its real part or its resistance, preferably less than 1% of its real part or its resistance.

[0032] The degree of interference suppression depends primarily on the value of the ohmic resistance, or rather the ratio between the ohmic resistance without interference and the ohmic resistance when interference is present. This can be achieved by connecting a controllable ohmic resistor in series with a capacitor or an inductive load.

[0033] An impedance is generated in the transformer. This impedance is determined by the formula: Z=R+i*X. The following applies: Z: Impedance R: Real part X: Imaginary part

[0034] For the controllable ohmic resistor to function effectively, the capacitor or inductive transformer is dimensioned such that the imaginary part X, which is active in the relevant frequency range, is as small as possible. This allows the phase shift or energy storage caused by the imaginary part to be neglected compared to the effect of the controllable ohmic resistor. Preferably, the relevant frequency range is the one in which the unwanted interference is to be suppressed.

[0035] An application of the invention can be made, for example, in a power supply network for a vehicle with at least one power source and at least one switchable or switching electrical consumer, wherein the electrical consumer is supplied with electrical energy from the power source via at least two lines and a device for suppressing disturbances according to one of the preceding claims is connected between two lines of the power supply network or between a line of the power supply network and either a ground potential or a negative or positive reference potential.

[0036] In particular, the power supply network may include a wiring harness with several branch lines for supplying multiple consumers and / or for feeding power from one or more sources. The branch lines may, for example, represent individual switchable or switchable circuits. These branch lines may each have a different length and connect consumers located at different points within a vehicle to the power supply network. For example, the power supply network may include switches to control individual circuits. The switches may be single-pole or multi-pole.

[0037] The power supply may consist of a battery and / or a generator and / or an external power supply and / or a fuel cell. The power supply network may, for example, include a single power source or multiple power sources. In particular, the power supply network may include a plug connection for connecting an external power source, such as a charger.

[0038] In particular, the electrical consumer may be either one or more of the following: an electric motor, in particular a traction motor, and / or an electric heater, in particular a seat heater, and / or a voltage converter, and / or a lighting device, and / or a control unit.

[0039] The described design of a device according to the invention naturally also achieves the implementation of a method for suppressing vibrations in a power supply network.

[0040] Preferably, the disturbances or vibrations to be suppressed are vibrations of the power supply network caused by switching operations or load changes, in particular damped vibrations.

[0041] In one embodiment, it is preferably provided that a semiconductor, preferably a transistor or field-effect transistor, is used as the controllable ohmic resistor, which is connected to a line of the power supply network via a capacitor or inductive transformer connected in series for galvanic isolation, wherein the capacitor or inductive transformer is dimensioned such that the imaginary part of the impedance resulting from the series connection in the frequency range to be suppressed is less than 10% of the real ohmic part or the resistance, preferably less than 1% of the real ohmic part or the resistance.

[0042] Preferably, it can be provided that the ohmic resistance of the controllable resistor is controlled by varying a base current or a gate voltage or by periodically switching a semiconductor.

[0043] Exemplary embodiments of the invention are shown in the figures and explained in the following figure description. These show: Fig. 1a: A schematic diagram of a high-voltage system with filter and controllable resistor according to an application example of the invention; Fig. 1b: Frequency response of the voltage measurement at the first and second measuring points in the high-voltage system of the Fig. 1; Fig. 2a: A first embodiment of a filter with controllable resistance according to the invention; Fig. 2b: Voltage measurement with filter switched on and off with controllable resistor from Fig. 2a; Fig. 3: Principle Circuit diagram of a second embodiment of a filter with controllable resistance according to the invention;

[0044] The Fig. Figure 1a shows a schematic diagram of a power distribution system, such as that used in an electric vehicle. The circuit arrangement includes a battery 1, which is connected via lines 10 and a high-voltage wiring harness 2 to several loads, for example, power electronics with an electric motor 3, in particular a traction motor, an electric heater 4, in particular a seat heater, a voltage converter 5, integrated charging electronics 6, and a control unit 7. It is possible to include additional, fewer, or different loads in the circuit arrangement.

[0045] In the Fig. 1a A device for interference suppression 8 is arranged between the battery 1, or the wiring harness 2 and the electric motor 3; preferably the interference suppression 8 can be equipped with a filter 81 (not shown in Fig. 1a) and with a controllable resistor 82 (not shown in Fig. 1a) be designed. It is also possible to use the interference suppression 8, preferably with filter 81 (not shown in Fig. 1a) and with controllable resistor 82 (not shown in Fig. 1a) Alternatively or additionally, to arrange a filter with a controllable resistor 82 upstream of each other consumer, or to assign a separate filter with a controllable resistor 82 to each consumer, so that a filter with a controllable resistor 82 is connected upstream of each consumer or some of the consumers. The filter with a controllable resistor 82 is connected between the first line of the power supply network and either another line of the power supply network, or a ground potential, or a negative or positive reference potential.

[0046] Furthermore, in the Fig. 1a The areas of the first measuring points 30 and second measuring points 31 are shown schematically, where the voltage between a first line of the power supply network and either another line of the power supply network or a ground potential or a negative or positive reference potential can be measured. The first measuring points 30 are located at a point between the interference suppression device 8, or the filter 81 with controllable resistor 82, and a load, in Fig. 1a and Fig. 1b, for example, the power electronics with electric motor 3. The second measuring points 31 are located between the battery 1, or the wiring harness 2, and a consumer, in Fig. 1a and Fig. 1b for example the integrated charging electronics 6, in which no filter 81 with controllable resistance 82 is arranged between the consumer and the battery.

[0047] In Fig. Figure 1b shows voltage measurements at the first measuring points 30 and the second measuring points 31 as a function of the frequency that can occur in a power distribution system. Firstly, the cables 10, or of the cable harness 2, exhibit... Fig. 1a. Cables reach a certain length and therefore possess a specific inductance, which results from the cable length and also the cable routing. Secondly, power distribution networks exhibit a certain natural resonance due to the inductances and parasitic capacitances that inevitably occur when such power distribution systems are installed in a real environment. This natural resonance can change when individual control circuits or loads are switched on or off, or when the power distribution system is connected to external power sources. Switching operations in the power distribution system can excite undesired damped oscillations, which, if these oscillations occur in the region of the power distribution network's natural resonance, can lead to very high overvoltages. Such a frequency-dependent overvoltage is in Fig. 1b between the second measurement points 31 with a natural resonance at approximately 19 kHz. In Fig. Figure 1b further illustrates the voltage behavior of the power distribution network at the first measuring points 30, which is suppressed by the switchable resistor 82. Crucially, the interference suppression device 8 is designed such that the filter 81 is connected to the controllable resistor 82 in such a way that, when unwanted oscillations occur, the filter 81 reduces the ohmic resistance of the controllable resistor 82.

[0048] A frequency-dependent, amplitude-dependent, and / or oscillation-dependent ohmic resistance is generated via the controllable resistor 82. The controllable resistor 82 creates an ohmic resistance for the corresponding disturbance oscillations by drawing the relevant power supply line conductors through the resistor to a ground potential, another conductor of the power supply network, or a negative or positive reference potential. This means that when oscillations occur, the controllable resistor 82 exerts an additional ohmic resistance on the power supply network to dampen these oscillations, particularly by converting them into heat energy. The negative or positive reference potential in this context can be another voltage level, for example, + / - 12 volts or + / - 24 volts above or below the average potential of the power supply line.

[0049] Fig. Figure 2a shows a schematic representation of a first embodiment of the interference suppression device 8 according to the invention, comprising a filter 81 and a controllable resistor 82. The circuit includes a high-pass filter 81 consisting of a capacitor 21 and a resistor 22, and a controllable resistor 82 consisting of a voltage source 24, a differential amplifier 25, and a variable semiconductor 23, which operates in the linear range. The galvanic isolation of the switchable resistor 82 from the high-voltage line 10 is achieved via a capacitor 21 (in Fig. 2a right capacitor 21). This capacitor 21 acts as a decoupling capacitor so that no DC current is present in the interference suppression device 8. The embodiment according to the invention of the Fig. 2a represents a single-pole smoothing of the overvoltage, since the filter 81 with controllable resistor 82 acts against ground. This smoothing of the overvoltage is implemented in the Fig. 2b is shown in a time-voltage diagram, where the measurement with the interference suppression device 8 switched off, or with the filter 81 with controllable resistor 82 switched off, shows large voltage fluctuations, and with the measurement with the interference suppression device 8 switched on, or with the filter 81 with controllable resistor 82 switched on, the significantly smaller voltage fluctuations are measured.

[0050] In the Fig. Figure 3 shows a schematic diagram of a second embodiment of the interference suppression device 8, or of the filter 81 with controllable resistor 82, according to the invention. Fig.In this embodiment, filter 81 is configured as a high-pass filter comprising capacitor 21 and the emitter resistor 22 of transistor T1. Controllable resistor 82 is configured as a controlled semiconductor comprising transistors T2 and T3. Controllable resistor 82 is configured as a push-pull circuit with transistors or field-effect transistors. In this embodiment, controllable resistor 82 affects both the positive and negative half-waves of an interference oscillation by diverting both positive and negative half-waves of the interference via the positive or negative supply line, respectively, through the push-pull circuit.

[0051] The galvanic isolation to line 10 is achieved via the capacitors 21.

[0052] A voltage of ±12V is applied to transistors T1 to T1 by a symmetrical low-voltage source U1 to U4.

[0053] The symmetrical low-voltage source U1, U2 or U3, U4 can be supplied from the high-voltage source via a voltage converter. Alternatively, the low-voltage source U1, U2 or U3, U4 can be supplied from a separate network, for example, a 12V or 24V vehicle electrical system. Reference symbol list 1 battery 2 HV cable harness 3 Power electronics with electric motor 4 electric heaters 5 voltage converters 6 integrated charging electronics 7 Control unit 8. Interference suppression device 81 filters 82 controllable resistor 10 Management 20 coils 21 Capacitor 22 Resistance 23 Semiconductors 24 Voltage source 25 Differential amplifiers 30 first measuring points 31 second measuring points T1 Transistor 1 T2 Transistor 2 T3 Transistor 3 U1 first low-voltage source U2 second low-voltage source U3 third low-voltage source U4 fourth low-voltage source

Claims

[1] Device (8) for suppressing disturbances in a power supply network comprising at least two lines (10) of a vehicle, in particular an electric vehicle, with a filter (81) connected to a first line of the power supply network to tap off unwanted oscillations, and with a controllable resistor (82) connected via a capacitor (21) or an inductive transformer between the first line (10) of the power supply network and either another line (10) of the power supply network or a ground potential or a negative or positive reference potential, and that the filter (81) is designed and connected to the controllable resistor (82) in such a way that the filter (81) reduces the ohmic resistance of the controllable resistor (82) when unwanted oscillations occur, characterized by , that the capacitor (21) or the inductive transformer for connecting the controllable ohmic resistance (82) to a line (10) of the power supply network is dimensioned such that in the frequency range to be suppressed of the unwanted oscillations the imaginary part of the impedance resulting from the series connection of the controllable ohmic resistance (82) with the capacitor (21) or the inductive transformer is less than 10% of its real part or its resistance. [2] Device (8) for suppressing disturbances according to claim 1, characterized by , that the filter (81) is designed as a high-pass filter or as a band-pass filter. [3] Device (8) for suppressing disturbances according to claim 1 or 2, characterized by, that the filter (81) reduces the ohmic resistance of the controllable resistor (82) by at least a factor of 10, or a factor of 100, or a factor of 1,000, or a factor of 10,000 when unwanted oscillations occur. [4] Device (8) for suppressing disturbances according to any one of claims 1 to 3, characterized by , that the controllable resistor (82) is designed as a controllable ohmic resistor (82), preferably that the controllable ohmic resistor (82) is a controlled semiconductor (23), in particular a transistor (T2, T3) or a field-effect transistor. [5] Device (8) for suppressing disturbances according to any of the preceding claims, characterized by , that the controllable resistor (82) is designed as a controllable ohmic resistor (82) by comprising a push-pull circuit with transistors (T2, T3) or field-effect transistors. [6] Device (8) for suppressing disturbances according to any of the preceding claims, characterized by , that the capacitor (21) or the inductive transformer for connecting the controllable resistor (82) to a line (10) of the power supply network is connected in series with the controllable resistor (82), preferably that the capacitor (21) or the inductive transformer is arranged in a collector circuit or in an emitter circuit of a transistor (T2, T3) of the controllable ohmic resistor (82), or that the capacitor (21) or the inductive transformer for connecting the controllable ohmic resistor (82) to a line (10) of the power supply network is arranged in a drain circuit or a source circuit of a field-effect transistor of the controllable ohmic resistor (82). [7] Device (8) for suppressing disturbances according to any of the preceding claims, characterized by, that the capacitor (21) or the inductive transformer for connecting the controllable ohmic resistance (82) to a line (10) of the power supply network is dimensioned such that in the frequency range to be suppressed of the unwanted oscillations the imaginary part of the impedance resulting from the series connection of the controllable ohmic resistance (82) with the capacitor (21) or the inductive transformer is less than 1% of its real part or its resistance. [8] Power supply network for a vehicle comprising at least one power source and at least one switchable or switching electrical consumer, wherein the electrical consumer is supplied with electrical energy from the power source via at least two lines (10) and a device (8) for suppressing disturbances according to one of the preceding claims is connected between two lines (10) of the power supply network or between a line (10) of the power supply network and either a ground potential or a negative or positive reference potential. [9] Power supply network according to claim 8, characterized by , that the power supply network includes a cable harness (2) with several branch lines for supplying several consumers and / or for feeding in power from one or more power sources. [10] Power supply network according to claim 8 or 9, characterized by, that the power source comprises a battery (1) and / or a generator and / or an external power supply and / or a fuel cell. [11] Power supply network according to one of claims 8 to 10, characterized by , that the electrical consumer is either a power electronics unit with an electric motor (3), in particular a traction motor, and / or an electric heater (4), in particular a seat heater, and / or a voltage converter (5) and / or an integrated charging electronics unit (6) and / or a control unit (7). [12] Method for suppressing vibrations in a power supply network using a device (8) arrangement according to one of the preceding claims. [13] Method according to claim 12, characterized by that the vibrations are vibrations of the power supply network that are excited, in particular damped, by switching operations or load changes. [14] Methods for suppressing oscillations in a power supply network caused by switching operations or load changes of a vehicle, in particular an electric vehicle, wherein the power supply network comprises a power source and at least one switchable or switching electrical load, wherein a controllable resistor (82) is galvanically isolated and connected either to two lines (10) of the power supply network or to one line (10) of the power supply network and either a ground potential or a negative or positive reference potential, and that the controllable resistor (82) is designed as a frequency-dependent ohmic resistor, in that frequency-dependent oscillations are detected by a filter (81) connected to a line (10) of the power supply network and the ohmic resistance of the controllable resistor (82) is reduced according to the detected oscillations. characterized by , that a semiconductor (23), preferably a transistor (T2, T3) or field-effect transistor, is used as a controllable ohmic resistance (82), which is connected to a line (10) of the power supply network via a capacitor (21) or inductive transformer connected in series for galvanic isolation, wherein the capacitor (21) or inductive transformer is dimensioned such that the imaginary part of the impedance resulting from the series connection in the frequency range to be suppressed is less than 10% of the real ohmic part or the resistance. [15] Method for suppressing vibrations excited by switching operations or load changes according to claim 14, characterized by , that a semiconductor (23), preferably a transistor (T2, T3) or field-effect transistor, is used as a controllable ohmic resistance (82), which is connected to a line (10) of the power supply network via a capacitor (21) or inductive transformer connected in series for galvanic isolation, wherein the capacitor (21) or inductive transformer is dimensioned such that the imaginary part of the impedance resulting from the series connection in the frequency range to be suppressed is less than 1% of the real ohmic part or the resistance. [16] Method for suppressing vibrations excited by switching operations or load changes according to claim 14 or 15, characterized by , that in the controllable resistor (82) the ohmic resistance is controlled by varying a base current or a gate voltage or by periodically switching a semiconductor (23).

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