Filters for filtering electromagnetic interference in a DC voltage system and drive unit

Abstract

The invention relates to a filter for filtering electromagnetic interference in a DC network. The filter comprises a first DC terminal and a second DC terminal, which are connected by means of two potential lines, a reference ground terminal, a first filter unit, and a second filter unit, which are configured to reduce AC voltage components on a DC voltage applied between each of the two potential lines and a reference ground terminal. The first filter unit comprises a first common-mode choke with a first magnetic core, a first winding that is electrically connected to a first of the two potential lines, and a second winding that is electrically connected to a second of the two potential lines.The second filter unit comprises a sensor stage configured to detect the AC voltage components in the DC voltage applied between each of the two potential lines and the reference ground connection, an electronic stage configured to determine a compensation signal for reducing the AC voltage components, and a coupling stage with a third winding configured to couple the compensation signal determined by the electronic stage into the two potential lines. The third winding of the coupling stage is arranged on the magnetic core of the first common-mode choke such that the first winding of the common-mode choke and the third winding of the coupling stage are inductively coupled to each other.

Description

[0001] The present invention relates to a filter for filtering electromagnetic interference in a DC voltage system and a drive unit. Background of the invention

[0002] Electromagnetic interference (EMI), for example generated by an alternating magnetic field, can affect the DC voltage of a DC power supply, resulting in an AC voltage superimposed on the DC voltage. For example, if a battery is used as a DC voltage source to operate an electric machine, the DC voltage output by the battery can be disturbed by the operation of the electric machine.

[0003] To remove such electromagnetic interference from the DC power grid and improve electromagnetic compatibility (EMC), a passive and / or active filter unit can be used in power electronic systems.

[0004] Conventional passive filter units contain windings or coils and capacitors, and due to the size of the components, they can occupy a significant portion of the volume of a DC power system. In contrast, active filter units offer a solution that reduces the space required.

[0005] Active filter units, unlike passive filter units, utilize active electronic components to dynamically respond to EMI interference. This is achieved by measuring the interference signal and coupling a compensation signal into the DC voltage output by the DC power supply. This compensation signal counteracts the EMI interference, thus reducing its impact. This approach is particularly advantageous in high-power-density applications that employ higher switching frequencies, as it allows for a reduction in the size of the filter unit without compromising performance. Disclosure of the invention

[0006] According to the invention, a filter and a drive unit with the features of the independent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

[0007] The invention relates to a filter for filtering electromagnetic interference in a DC network, for example in the drive unit of an electric vehicle. The filter has a first DC connection and a second DC connection, which are connected by means of two potential lines, a reference ground connection, a first filter unit, and a second filter unit. A DC voltage source, for example, a battery of an electric vehicle, and a DC voltage sink, for example, a load such as a power converter circuit or electric machine, can be connected to the first and second DC connections. The first and second filter units are configured to reduce AC voltage components, particularly those due to common-mode noise, to a DC voltage applied between each of the two potential lines and the reference ground connection.In an electric vehicle, the direct current (DC) voltage can be output to a power converter circuit, such as an inverter, which converts the DC voltage into alternating current (AC) voltage. This AC voltage is then used to drive an electric machine, such as the vehicle's motor. Conversely, AC voltage generated by an electric machine operating as a generator and rectified by a power converter circuit can be fed into the vehicle's electrical system and / or a battery.

[0008] The first filter unit is a passive filter unit and comprises a first common-mode choke with a first magnetic core, a first winding electrically connected to one of the two potential leads, and a second winding electrically connected to the second of the two potential leads. The first and second windings are inductively and magnetically coupled to each other via the first magnetic core. The second filter unit comprises a sensor stage, an electronic stage, and a coupling stage. The sensor stage is configured to detect the AC voltage components of the DC voltage applied between each of the two potential leads and the reference ground connection. The sensor stage can detect either a voltage signal or a current signal representing the AC voltage components.The electronic stage is configured to determine a compensation signal for reducing the AC voltage components. This compensation signal is determined by inverting and amplifying the AC voltage components. For this purpose, the electronic stage uses the current or voltage signal detected by the sensor stage. In particular, amplifying the AC voltage components prevents the compensation signal from being insufficiently counteracting the AC voltage components due to losses in the filter unit and / or the coupling stage. The coupling stage has a third winding, which is part of a transformer and is configured to couple the compensation signal determined by the electronic stage into the two potential lines via this third winding. The compensation signal is coupled in as a voltage from the third winding.

[0009] The advantages of voltage coupling lie in the reduced size and lower cost of the active first filter unit, as well as in the improved performance through a low-impedance path available to a noise current, thereby reducing the noise voltage, i.e., the AC voltage component.

[0010] In filters not according to the invention, the compensation signal can be inductively coupled into one of the two potential lines via a transformer, whereby the third winding can be part of the transformer. This transformer can be arranged in the second filter unit between the first common-mode choke and in one of the two potential lines. Using the transformer to couple the compensation signal has the disadvantage that the entire DC current flows through this transformer, which therefore must be correspondingly large. This leads to increased space requirements and high costs. Furthermore, cooling the transformer presents a problem.

[0011] The core of the invention consists in replacing the transformer for voltage coupling or in proposing a circuit in which the transformer is no longer needed for coupling the compensation signal. For this purpose, the third winding of the coupling stage, which is used for coupling the compensation signal and is conventionally part of the transformer, is arranged on the first magnetic core of the first filter unit in such a way that the first winding of the common-mode choke and the third winding of the coupling stage are inductively or magnetically coupled to each other.

[0012] This eliminates the need for the transformer in the coupling stage, thereby reducing the cost and space requirements of the second active filter unit, and consequently the entire filter.

[0013] Specifically, the invention relates to a filter for filtering electromagnetic interference in a DC power network, in particular in a drive unit of an electric vehicle, comprising a first DC voltage connection and a second DC voltage connection, which are connected by means of two potential lines, a reference ground connection, as well as a first, passive filter unit and a second, active filter unit, as described above. The first active filter unit comprises, as described above, a common-mode choke with a first magnetic core, a first winding and a second winding, each of which is connected to one of the potential lines.The second filter unit has a sensor stage, an electronic stage and a coupling stage as described above, wherein the third winding of the coupling stage is arranged on the magnetic core of the first common-mode choke such that the first winding of the common-mode choke and the third winding of the coupling stage are inductively coupled to each other.

[0014] As described above, this eliminates the need for a transformer in the coupling stage, thus reducing the space requirements and costs of the filter while maintaining the same filtering effect.

[0015] In one embodiment, the first filter unit further comprises a first capacitor arranged between the two potential lines. This first capacitor is, in particular, a capacitor, and the filtering effect of the first filter unit can be improved in a simple and cost-effective manner by using this first capacitor.

[0016] In one embodiment, the filter further comprises a third filter unit, which includes a second common-mode choke with a second magnetic core and is electrically connected to the two potential leads. Specifically, the second common-mode choke has a fourth winding and a fifth winding, which are inductively coupled to each other via the second magnetic core. The fourth winding is electrically connected to the first of the two potential leads, and the fifth winding is electrically connected to the second of the two potential leads.

[0017] The third filter unit increases the impedance that counteracts EMI interference, thus ensuring that the EMI interference has been removed from the DC voltage as completely as possible.

[0018] In one embodiment, the sensor stage has a sixth winding arranged on the second magnetic core such that the fourth winding of the second common-mode choke and the sixth winding of the sensor stage are inductively coupled. The sensor stage is configured to inductively detect the AC voltage components on the DC voltage applied between each of the two potential lines and the reference ground connection. With inductive detection of the AC voltage components, these components are detected as a current signal. By implementing inductive detection in a common-mode choke, two purposes are synergistically combined, and a conventionally required transformer can be omitted.

[0019] In an alternative embodiment, the sensor stage has a second capacitor that is electrically connected to one of the two potential lines. The sensor stage is configured to capacitively detect the AC voltage components on the DC voltage applied between each of the two potential lines and the reference ground connection. Through this capacitive detection of the AC voltage components, the AC voltage components are measured as voltage.

[0020] The two above embodiments therefore make it possible in a simple way for the filter to detect the AC voltage components as a voltage or current signal, thus enabling flexible detection of the AC voltage components.

[0021] In one embodiment, the electronic stage of the second filter unit comprises an operational amplifier with an inverting and a non-inverting input terminal and an output terminal, wherein the non-inverting input terminal of the operational amplifier is electrically connected to the sensor stage, the inverting input terminal of the operational amplifier is electrically connected to the reference ground terminal, and an output terminal of the operational amplifier is electrically connected, in particular via a first resistor, to the coupling stage, in particular to a first terminal of the first winding of the coupling stage. A supply voltage can also be applied to the operational amplifier. The non-inverting input terminal of the operational amplifier is electrically connected, in particular via a second resistor, to the reference ground terminal.

[0022] By using an operational amplifier, the compensation signal can be determined in a simple way and largely optimal gain and phase characteristics can be ensured.

[0023] In the embodiment in which the AC voltage components in the sensor stage are determined capacitively, the inverting input terminal of the operational amplifier is electrically connected to a second terminal of the third winding.

[0024] In the embodiment in which the AC voltage components in the sensor stage are determined inductively, the non-inverting input terminal of the operational amplifier is connected to a first terminal of the sixth winding and the inverting input terminal of the operational amplifier is connected to a second terminal of the sixth winding.

[0025] The two configurations described enable the simple and efficient detection of the AC voltage components via both current and voltage.

[0026] The depicted electronic stage is just one example of various possible configurations. For instance, a different forward or reverse control structure could be used. Furthermore, other types of amplifiers that process the input signal inverted or non-inverted can be employed.

[0027] The invention further relates to a drive unit comprising an electric machine, a power converter circuit, and a filter according to the invention, which is configured to filter a DC voltage applied to the drive unit. The power converter circuit has a DC voltage converter connection, which is electrically connected to the first DC voltage connection or the second DC voltage connection of the filter, and an AC voltage converter connection, which is electrically connected to the electric machine.

[0028] This allows the DC voltage of a DC voltage source, in particular the vehicle's battery, or of the electric machine operated as a generator in an electric vehicle, which is disturbed by the operation of the electric machine, to be efficiently filtered in a drive unit, thus improving the operation of the drive unit, in particular making it more efficient.

[0029] The converter circuit, for example, has at least one half-bridge, in particular one half-bridge per phase winding of the electric machine. Each half-bridge contains a first controllable semiconductor switching element and a second controllable semiconductor switching element, with each phase winding of the electric machine being supplied with electrical power via a center terminal of a half-bridge. Furthermore, a smoothing capacitor can be arranged in parallel with the converter's DC voltage terminal in the converter circuit, which further smooths the DC voltage applied to the converter circuit, thereby enabling more efficient operation of the electric machine and, consequently, the entire drive unit.

[0030] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawing.

[0031] The invention is schematically illustrated in the drawing using exemplary embodiments and is described below with reference to the drawing. Brief description of the drawings Fig. Figure 1 shows a block diagram of a filter according to an embodiment of the invention, Fig. 2 shows a block diagram of a filter according to a further embodiment of the invention, Fig. Figure 3 shows a block diagram of a filter according to a further embodiment of the invention, and Fig. Figure 4 shows a block diagram of a drive unit according to an embodiment of the invention. Detailed description of the drawing

[0032] Fig. Figure 1 shows a block diagram of a filter 100 according to an embodiment of the invention. The filter 100 is designed to filter electromagnetic interference in a DC power network, for example in a drive unit of a partially or fully electric vehicle.

[0033] The filter 100 has a first DC voltage connection 51, 52 and a second DC voltage connection 56, 57, which are connected by means of two potential lines P1, P2, as well as a reference ground connection M1, M2, M3, M4. For example, a DC voltage to be filtered is applied to the first DC voltage connection 51, 52, and the filtered DC voltage is output at the second DC voltage connection 56, 57. For this purpose, the filter 100 has a first filter unit 10 and a second filter unit 20, which are configured to reduce AC voltage components in the DC voltage applied between each of the two potential lines P1, P2 and the reference ground connection M1, M2, M3, M4.

[0034] The first filter unit 10 is a passive filter unit and comprises a first common-mode choke 11 with a first magnetic core 11a, a first winding 11b electrically connected to a first potential line P1 of the two potential lines, and a second winding 11c electrically connected to a second potential line P2 of the two potential lines. The first winding 11b and the second winding 11c are inductively coupled to each other via the first magnetic core 11a. The first filter unit 10 also comprises a first capacitor 12 arranged between the two potential lines P1 and P2.

[0035] The first filter unit 10 passively filters out part of the EMI interference from the applied DC voltage.

[0036] The second filter unit 20 is an active filter unit with a sensor stage 21, an electronic stage 22 and a coupling stage 23.

[0037] Sensor stage 21 is configured to detect the AC voltage components on the DC voltage applied between each of the two potential lines P1, P2 and the reference ground connection M1, M2, M3, M4. For this purpose, sensor stage 21 has a second capacitor 21a, which is electrically connected to the first potential line P1. Sensor stage 21 is configured to capacitively detect the AC voltage components on the DC voltage applied between each of the two potential lines P1, P2 and the reference ground connection M1, M2, M3, M4. The capacitively detected AC voltage components are output to electronic stage 22.

[0038] The electronic stage 22 is configured to determine a compensation signal for reducing the AC voltage components, whereby the compensation signal is determined by inverting and amplifying the AC voltage components. For this purpose, the electronic stage 22 has an operational amplifier 22a with an inverting (-) and a non-inverting (+) input terminal and an output terminal, and is supplied with a supply voltage V. CC supplied to enable reinforcement.

[0039] The non-inverting input (+) of operational amplifier 22a is electrically connected to sensor stage 21 and receives the measured voltage present between the two potential lines P1 and P2. Furthermore, the non-inverting input (+) of operational amplifier 22a, as well as the second capacitor 21a, is connected to the reference ground terminal M1 via a second resistor 21b.

[0040] The inverting input terminal (-) of the operational amplifier 22a is electrically connected to a second terminal of a third winding 23a of the coupling stage 23. Furthermore, the inverting input terminal (-) of the operational amplifier 22a and the second terminal of the third winding 23a are electrically connected to the reference ground terminal M2.

[0041] The output terminal of the operational amplifier 22a is electrically connected via a first resistor 22b to a first terminal of the third winding 23a and outputs the specific compensation signal, which is used to compensate the interference signal, to the third winding 23a.

[0042] The coupling stage 23 has a third winding 23a and is configured to couple the compensation signal determined by the electronic stage 22 into the two potential lines via the third winding 23a. For this purpose, the third winding 23a of the coupling stage 23 is arranged on the magnetic core 11a of the first common-mode choke 11 such that the first winding 11b of the common-mode choke 11 and the third winding 23a of the coupling stage 23 are inductively coupled to each other. Furthermore, the second winding 11c of the common-mode choke 11 is also inductively coupled to the third winding 23a of the coupling stage 23.

[0043] By inductively coupling the first and third windings 11b, 23a, a separate transformer can be dispensed with in the coupling stage 23, making the filter 100 cheaper and more space-saving.

[0044] Fig. Figure 2 shows a block diagram of a filter 100' according to a further embodiment of the invention.

[0045] How the embodiment of filter 100 of the Fig. 1 indicates the filter 100' which is in Fig. In the embodiment shown in 2, a first and a second filter unit 10, 20 are provided, which are like the first and second filter units 10, 20 of the embodiment of the filter 100. Fig. 1 are designed. For further details, please refer to the explanations regarding Fig. 1 referred.

[0046] Unlike the Filter 100 which is in Fig. In the embodiment shown in 1, the filter 100' has the following features: Fig. In the embodiment shown in Figure 2, a third filter unit 30 is also provided, which has a second common-mode choke 31.

[0047] The third filter unit 30 has a second common-mode choke 31 with a second magnetic core 31a, which is electrically connected to the two potential lines. Furthermore, the second common-mode choke 31 has a fourth winding 31b and a fifth winding 31c, which are inductively coupled to each other via the second magnetic core 31a, with the fourth winding 31b being electrically connected to the first potential line P1 and the fifth winding 31c being electrically connected to the second potential line P2.

[0048] The third filter unit 30 filters the DC voltage a further time, ensuring that the EMI interference signal, i.e. the AC components of the DC voltage, is compensated as completely as possible.

[0049] Fig. Figure 3 shows a block diagram of a 100" filter according to a further embodiment of the invention. The structure of the 100" filter shown in Figure 3 is as follows: Fig. The embodiment shown in Figure 3 is similar to the construction of filter 100' shown in Figure 3. Fig. 2 embodiment shown and in particular has a third filter unit 30.

[0050] Unlike the 100" filter which is in Fig. In the embodiment shown in 2, the sensor stage 21' of the Fig. In the embodiment shown in Figure 3, a sixth winding 21c is provided, which is arranged on the second magnetic core 31a such that the fourth winding 31b of the second common-mode choke 31 and the sixth winding 21c of the sensor stage 21' are inductively coupled to each other. The sensor stage 21' is configured to inductively detect the AC voltage components on the DC voltage applied between each of the two potential lines P1, P2 and the reference ground connection M1, M2, M3, M4.

[0051] A first terminal of the sixth winding 21c is electrically connected to the non-inverting input terminal (+) of the operational amplifier 22a of the electronic stage 22, and a second terminal of the sixth winding 21c is electrically connected to the inverting input terminal (-) of the operational amplifier 22a of the electronic stage 22. Furthermore, the first terminal of the sixth winding 21c and the non-inverting input terminal (+) of the operational amplifier 22a are connected via a second resistor 21b of the sensor stage 21' to the third reference ground terminal M3.

[0052] In this embodiment, the second terminal of the third winding 23a of the coupling stage 23 is connected to the reference ground terminal M4 instead of the inverting input terminal (-) of the operational amplifier 22a. [To the inventor: Is this relevant, or can 23a also be connected directly to (-) and M3?]

[0053] Through the in Fig. In the embodiment of the filter shown in Figure 3, the AC voltage components are detected based on the flowing current.

[0054] Fig. Figure 4 shows a block diagram of a drive unit 1000, for example a drive unit 1000 of a partially or fully electric vehicle, according to an embodiment according to the invention.

[0055] The drive unit 1000 comprises an electric machine 1, a power converter circuit 200, and a filter 100, 100', 100". A DC voltage source 300, for example, a battery from a vehicle in which the drive unit 1000 is installed, is connected to the drive unit 1000, in particular to the first DC voltage input terminal 51, 52 of the filter 100, 100', 100", and a DC voltage is applied which is used to operate the drive unit 1000. The applied DC voltage may be affected by EMI interference, for example, from the alternating magnetic field generated by the electric machine 1, which induces AC components in the DC voltage that must be removed to ensure efficient operation of the electric machine 1.

[0056] The filter unit 100, 100', 100" is therefore designed to filter the DC voltage applied to the drive unit 1000.

[0057] The converter circuit 200 has a converter DC voltage connection 241, 242, which is electrically connected to the second DC voltage connection 56, 57 of the filter 100, 100', 100" and a converter AC voltage connection U, V, W, which is electrically connected to the electric machine 1.

[0058] The converter circuit 200 further comprises a smoothing capacitor or DC link capacitor 250, which is arranged in parallel to the converter DC voltage terminal 241, 242 of the converter circuit 200 or between the potential lines P1, P2. Furthermore, the converter circuit 200 has three half-bridges 210, 220, 230 shown, each of which is arranged in parallel to the converter DC voltage terminal 241, 242 of the converter circuit 200 or between the potential lines P1, P2.

[0059] Each of the half-bridges 210, 220, 230 has a first and second controllable semiconductor switching element 201 and supplies one of the phase windings of the electric machine 1 with electrical power via a center connection or the converter AC voltage connection U, V, W.

Claims

[1] Filter (100, 100', 100") for filtering electromagnetic interference in a DC network, in particular in a drive unit (1000) of an electric vehicle, comprising - a first DC voltage connection (51, 52) and a second DC voltage connection (56, 57) which are connected by means of two potential lines (P1, P2), - a reference ground connection (M1, M2, M3, M4), - a first filter unit (10) and a second filter unit (20) which are configured to reduce AC voltage components on a DC voltage applied between each of the two potential lines (P1, P2) and a reference ground connection (M1, M2, M3, M4), wherein the first filter unit (10) is a passive filter unit and comprises a first common-mode choke (11) with a first magnetic core (11a), a first winding (11b) electrically connected to a first of the two potential lines (P1, P2), and a second winding (11c) electrically connected to a second of the two potential lines (P1, P2), wherein the first winding (11b) and the second winding (11c) are inductively coupled to each other via the first magnetic core (11a), the second filter unit (20) is an active filter unit and has: - a sensor stage (21, 21') designed to detect the AC voltage components on the DC voltage applied between each of the two potential lines (P1, P2) and the reference ground connection (M1, M2, M3, M4), - an electronic stage (22) configured to determine a compensation signal for reducing the AC voltage components, wherein the compensation signal is determined by inverting and amplifying the AC voltage components, and - a coupling stage (23) having a third winding (23a) and configured to couple the compensation signal determined by the electronic stage (22) into the two potential lines (P1, P2) through the third winding (23a), wherein the third winding (23a) of the coupling stage (23) is arranged on the magnetic core (11a) of the first common-mode choke (11) such that the first winding (11b) of the common-mode choke (11) and the third winding (23a) of the coupling stage (23) are inductively coupled to each other. [2] Filter (100, 100', 100") according to claim 1, wherein the first filter unit (10) further comprises a first capacitor (12) arranged between the two potential lines (P1, P2). [3] Filter (100', 100") according to one of the preceding claims, wherein the filter (100') further comprises a third filter unit (30), wherein the third filter unit (30) comprises a second common-mode choke (31) with a second magnetic core (31a), wherein the second common-mode choke (31) is electrically connected to the two potential lines (P1, P2). [4] Filter (100', 100") according to claim 3, wherein the second common-mode choke (31) has a fourth winding (31b) and a fifth winding (31c) which are inductively coupled to each other via the second magnetic core (31a), and wherein the fourth winding (31b) is electrically connected to the first of the two potential lines (P1, P2) and the fifth winding (31c) is electrically connected to the second of the two potential lines (P1, P2). [5] Filter (100") according to one of claims 3 or 4, wherein the sensor stage (21') has a sixth winding (21c) arranged on the second magnetic core (31a) such that the fourth winding (31b) of the second common-mode choke (31) and the sixth winding (21c) of the sensor stage (21') are inductively coupled to each other, and wherein the sensor stage (21') is configured to inductively detect the AC voltage components on the DC voltage applied between each of the two potential lines (P1, P2) and the reference ground connection (M1, M2, M3, M4). [6] Filter (100, 100') according to one of claims 1 to 4, wherein the sensor stage (21) has a second capacitor (21a) which is electrically connected to one of the two potential lines (P1, P2), and wherein the sensor stage (21) is configured to capacitively detect the AC voltage components on the DC voltage applied between each of the two potential lines (P1, P2) and the reference ground connection (M1, M2, M3, M4). [7] Filter (100, 100', 100") according to one of the preceding claims, wherein the electronic stage (22) of the second filter unit (20) comprises an operational amplifier (22a) with an inverting and a non-inverting input terminal and an output terminal, wherein the non-inverting input terminal is electrically connected to the sensor stage (21, 21'), the inverting input terminal is electrically connected to the reference ground terminal (M1, M2, M3, M4), and the output terminal is electrically connected, in particular via a first resistor (22b), to the coupling stage (23), in particular to a first terminal of the first winding (23a) of the coupling stage (23). [8] Filter (100, 100', 100") according to claim 7, wherein the non-inverting input terminal of the operational amplifier (22a) is electrically connected to the reference ground terminal (M1, M2, M3, M4) via a second resistor (21b). [9] Filter (100, 100', 100") according to claim 7 or 8 in reference to claim 6, wherein the inverting input terminal of the operational amplifier (22a) is electrically connected to a second terminal of the first winding (23a). [10] Filter (100") according to claim 7 or 8 in reference to claim 5, wherein the non-inverting input terminal of the operational amplifier (22a) is electrically connected to a first terminal of the sixth winding (21c) and the inverting input terminal of the operational amplifier (22a) is electrically connected to a second terminal of the sixth winding (21c). [11] comprising drive unit (1000) - an electric machine (1), - a power converter circuit (200), and - a filter (100, 100', 100") according to one of the preceding claims, which is configured to filter a DC voltage applied to the drive unit (1000), wherein the converter circuit (200) has a converter DC connection (241, 242) which is electrically connected to the first DC connection or the second DC connection of the filter (100, 100', 100") and a converter AC connection (U, V, W) which is electrically connected to the electric machine (1).

Images