Active Common Mode Filter

Abstract

An active common-mode filter (2) comprising a processing unit (6) configured to detect AC disturbances (AC_Int) in a potential (HV+, HV-) applied to the common-mode filter (2) relative to a reference potential (PA) and to determine an AC target value (AC_ZG) based on the detected AC disturbances (AC_Int), and active electronics (7) configured to inject a compensation current (I) into the potential (HV+, HV-) or to apply a compensation voltage to the potential (HV+, HV-) based on the AC target value (AC_ZG) to compensate for the AC disturbances (AC_Int), wherein the processing unit (6) is further configured to determine, based on a potential distribution between the applied potential (HV+) and another potential (HV-) relative to the reference potential (PA) and based on at least one predefined target value (ZW) that exhibits maximum asymmetry of the potential distribution or a maximum voltage of one of the potentials (HV+,HV-) to the reference potential (PA) describes determining, in particular calculating and / or controlling and / or regulating, a DC target quantity (DC_ZG) which can be supplied to the active electronics (7) together with the AC target quantity (AC_ZG) to change the potential distribution according to the target value (ZW) by injecting the compensation current (I) or applying the compensation voltage, wherein the processing unit (6) is configured to , - to determine the potential distribution by measuring a voltage (V_P) between the applied potential (HV+) and the reference potential (PA) and a voltage (V_N) between another potential (HV-) and the reference potential (PA), or by measuring a voltage (V_P) between the applied potential (HV+) and the reference potential (PA) and a voltage between the applied potential (HV+) and another potential (HV-) with subsequent difference calculation, or - to use voltages (V_P, V_N) or a potential distribution determined in a high-voltage system (1) to which the common-mode filter (2) is connected, wherein a capacitor (EMC_ln_P) for detecting the AC disturbance (AC_Int) is connected to the applied potential (HV+, HV-) and the processing unit (6) is configured for inductive detection of the AC disturbance (AC_Int) or for digital detection of the AC disturbance (AC_Int) by sampling the applied potential (HV+, HV-) and software-based filtering and / or calculation.

Description

[0001] The invention relates to an active common-mode filter according to the preamble of claim 1.

[0002] The use of an active filter in an electric vehicle generally aims to improve the filtering characteristics of the EMC filter and / or reduce the required installation volume for the desired filtering effect. This is usually limited to a specific maximum frequency range by the components used (e.g., operational amplifiers, transistors). Therefore, it is advantageous to use a combination of passive and active filters to cover a wider frequency range. In this case, the filter serves to compensate for AC interference.

[0003] Requirements such as those in the IEC 60479-2 standard describe a maximum current, depending on its dwell time, that may flow through a human body when touching a high-voltage potential due to faulty insulation. Compliance with this standard becomes increasingly difficult with higher high-voltage system voltages because, on the one hand, the filter capacitances used necessitate Y-capacitances to meet EMC requirements between the high-voltage potentials and the protective earth (PA), and on the other hand, the stored charge also increases with rising high-voltage voltage. Compliance with these requirements is based on a worst-case scenario. This scenario occurs when the high-voltage potentials are distributed as asymmetrically as possible relative to the PA, without an insulation fault having occurred (i.e., when it has just barely not yet occurred).If the vehicle's high-voltage system is connected to a high-voltage system of a lower insulation class (for example, when DC charging an 800 V vehicle via a galvanically coupled boost function), the high-voltage potential asymmetry in the vehicle can lead to an overload of the insulation of the DC charging station.

[0004] DE 10 2017 105 839 A1 describes a power supply system for a vehicle, comprising a battery, a charging interface for receiving external power supply for charging the battery; a network connecting the battery and the charging interface, wherein at least part of the network is a DC network; and an active EMI filter between the battery and the charging interface in the DC network.

[0005] The subsequently published document EP 4 439 962 A1 describes a battery energy storage system comprising a battery and at least two capacitors connected in series, forming a DC center point between the two capacitors and connected in parallel to the battery. A three-level converter is connected in parallel to the battery with a positive and a negative DC input. A controller measures the respective differential voltages between the positive and a negative DC input and the DC center point and determines the difference between the two differential voltages, so that the output current can be corrected accordingly.

[0006] From the conference publications and presentations of - MA Mulla, R. Chudamani and A. Chowdhury, “Series Hybrid Active Power Filter for mitigating voltage unbalance and harmonics under unbalanced non-sinusoidal supply conditions.” 2012 IEEE International Conference on Power and Enërgy (PECon), Kota Kinabalu, Malaysia, 2012. pp. 671-676, doi: IO.1109 / PECon.2012.6450300 and - A. Hamadi, S. Rahmani and K. Al-Haddad, “A new hybrid series active filter configuration to compensate voltage sag, swell, voltage and current harmonics and reactive power,” 2009 IEEE International Symposium on Industrial Electronics, Seoul, Korea (South), 2009, pp. 286-291, doi: IO.1109 / ISLE.2009.5218895 suggests transferring the active filtering of an AC voltage to a DC voltage and using a known common-mode filter for this purpose.

[0007] The invention is based on the objective of providing a novel active common-mode filter.

[0008] The problem is solved according to the invention by an active common-mode filter with the features of claim 1.

[0009] Advantageous embodiments of the invention are the subject of the dependent claims.

[0010] An active common-mode filter is proposed, comprising a processing unit configured to detect AC disturbances in a potential applied to the common-mode filter, for example a high-voltage potential, relative to a reference potential, for example a potential equalization conductor, and to determine an AC target quantity based on the detected AC disturbances, and active electronics configured to inject a compensation current into the potential or to apply a compensation voltage to the potential based on the AC target quantity to compensate for the AC disturbances.According to the invention, the processing unit is further configured to determine, in particular to calculate and / or control and / or regulate, a DC target quantity based on a potential distribution between the applied potential and another potential relative to the reference potential, and based on at least one predetermined target value that describes a maximum asymmetry of the potential distribution or a maximum voltage of one of the potentials relative to the reference potential. This DC target quantity can be supplied to the active electronics together with the AC target quantity to change the potential distribution (in particular so that it becomes more symmetrical) according to the target value by injecting the compensation current or applying the compensation voltage.

[0011] According to the invention, the processing unit is configured to determine the potential distribution by measuring a voltage between the applied potential and the reference potential and a voltage between a further potential and the reference potential, or by measuring a voltage between the applied potential and the reference potential and a voltage between the applied potential and a further potential, followed by calculating the difference.

[0012] Alternatively, according to the invention, the processing unit is configured to use voltages or potential distributions determined in a high-voltage system to which the common-mode filter is connected.

[0013] According to the invention, a capacitor for detecting the AC disturbance is connected to the applied potential and the processing unit.

[0014] According to the invention, the processing unit is configured for inductive detection of the AC disturbance or for digital detection of the AC disturbance by sampling the applied potential and software-based filtering and / or calculation.

[0015] In one embodiment, the processing unit is constructed as an analog circuit (for example, comprising at least one transistor and / or operational amplifier) ​​and / or as a digital circuit and / or as a hybrid circuit consisting of analog and digital components.

[0016] In one embodiment, the active electronics include an amplifier configured to generate the compensation current or compensation voltage depending on an AC+DC target obtained by summing the AC target quantity and the DC target quantity, and to feed it into the potential via an output capacitor or inductively.

[0017] In one embodiment, a voltage source is arranged to supply the active electronics with an operating voltage.

[0018] The active common-mode filter can be used, for example, in an on-board electrical system, especially a high-voltage on-board electrical system, of an electrically powered vehicle, such as a passenger car, a commercial vehicle or a bus, or in a DC charging station for charging a high-voltage battery of an electrically powered vehicle.

[0019] According to the invention, the active EMC filter is extended to include the function of controlling or regulating the high-voltage potential distribution. The original injection of a compensating AC current from the (classic) active EMC filter is supplemented by a second target variable, namely a voltage from a high-voltage potential to a potential equalization conductor. This can be used (to comply with CY requirements) to influence the maximum high-voltage potential asymmetry or to prevent a maximum voltage value between a high-voltage potential and the potential equalization conductor from being exceeded, for example, to protect the insulation in a 500V DC charging station.

[0020] This prevents overloading of a less well-insulated high-voltage system during galvanic coupling, for example, when charging an 800V vehicle at a 500V DC charging station. The maximum limits of the high-voltage potential distribution are maintained to meet the requirements of the C1 characteristic curve. Furthermore, the advantages of an active common-mode filter, such as a smaller, lighter EMC filter design, are retained. The active common-mode filter regulates and / or controls the high-voltage potential distribution to a specific target value.

[0021] The solution according to the invention can be used, for example, in electrically powered vehicles with a galvanically coupled boost charging method for charging a high-voltage battery whose nominal voltage (e.g., 800 V) is higher than the voltage provided by a charging station (e.g., 500 V DC). Furthermore, the solution according to the invention can be used in electrically powered vehicles, particularly those with an 800 V high-voltage battery, whose Y-capacitances have a total value that, with complete potential asymmetry at a DC charging station, would not meet the values ​​of the C1 characteristic curve.

[0022] The solution according to the invention serves to prevent overloading a less well-insulated high-voltage system during galvanic coupling, for example, during galvanically coupled charging of an 800V vehicle at a 500V DC charging station. The maximum limits of the high-voltage potential distribution are maintained to meet the requirements of the C1 characteristic curve. Furthermore, the advantages of an active common-mode filter, such as a smaller, lighter design of the EMC filter, are retained.

[0023] Exemplary embodiments of the invention are explained in more detail below with reference to a drawing.

[0024] This shows: Fig. 1 A schematic view of a high-voltage system and an active common-mode filter.

[0025] The only Fig.Figure 1 is a schematic view of a high-voltage system 1 and an active common-mode filter 2, which may be arranged between a source of interference 3 (for example, an inverter) and a sink of interference 4 (for example, an on-board electrical system).

[0026] High-voltage system 1 can be, for example, an electrically powered vehicle and / or a DC charging station, or a part thereof. High-voltage system 1 is represented by, • Insulation resistances R_iso_P, R_iso_N between a positive high-voltage potential HV+ and a reference potential PA, for example an equipotential bonding conductor PA, as well as between a negative high-voltage potential HV- and the equipotential bonding conductor PA, • Y-capacitances CY_P, CY_N between the positive high-voltage potential HV+ and the equipotential bonding conductor PA, and between the negative high-voltage potential HV- and the equipotential bonding conductor PA, • at least one intermediate circuit capacitor C between the positive high-voltage potential HV+ and the negative high-voltage potential HV-, • an isolation monitor 5.

[0027] The active common-mode filter 2 can be designed as an AC filter with additional control and / or regulation of the high-voltage potential distribution, comprising: - two voltage meters V1, V2 for measuring the voltage V_P, V_N between the positive high-voltage potential HV+ and the equipotential bonding conductor PA, and between the negative high-voltage potential HV- and the equipotential bonding conductor PA, - a processing unit 6 for recording disturbances as well as for control and / or regulation, - an active electronics 7 for generating the determined current and / or voltage.

[0028] The processing unit 6 is configured to detect the high-voltage potential distribution by measuring a voltage V_P from the positive high-voltage potential HV+ to the equipotential bonding conductor PA and a voltage V_N between the negative high-voltage potential HV- to the equipotential bonding conductor PA, or by measuring a high-voltage DC voltage between the positive high-voltage potential HV+ and the negative high-voltage potential HV- and measuring a potential voltage of one of the high-voltage potentials HV+, HV- to the equipotential bonding conductor PA with subsequent difference calculation (not shown).

[0029] The processing unit 6 can also have a sensor input for detecting an AC disturbance AC_Int. The AC disturbance AC_Int can be detected capacitively, as shown, using a capacitor EMC_ln_P connected to one of the high-voltage potentials HV+ or HV-. Alternatively, the AC disturbance AC_Int can be detected inductively or digitally by sampling the high-voltage potentials HV+ or HV-, including software filtering and / or software calculation (not shown).

[0030] Furthermore, processing unit 6 can be configured to determine (calculate and / or regulate and / or control) a DC target variable DC_ZG for high-voltage potential distribution and an AC target variable AC_ZG for compensating AC disturbances AC_Int. For this purpose, a target value ZW is specified, for example, a maximum potential asymmetry or a maximum negative voltage of one of the high-voltage potentials HV+, HV- to the equipotential bonding conductor PA. The determination of the AC target variable AC_ZG and / or DC target variable DC_ZG can be performed by an analog circuit (for example, comprising operational amplifiers, transistors including circuitry), by digital processing of the input variables (V_P, V_N, AC_Int), or by a combination of both.

[0031] The active electronics 7, or output stage, is configured to convert an AC+DC input V_AC_DC, obtained by summing the AC target variable AC_ZG and the DC target variable DC_ZG, into a compensation current I via a semiconductor output stage. This current is then fed into an output capacitor EMC_In_P1 (injection unit) to compensate for the AC disturbance AC_Int and the potential asymmetry. The EMC_In_P1 is connected to one of the high-voltage potentials HV+ or HV-. An inductive input can also be selected (not shown). The active electronics 7 can be supplied with operating voltage by its own voltage source 8.

[0032] According to the present invention, an active common-mode filter 2 is obtained by extending an EMC filter to include the function of controlling and / or regulating the high-voltage potential distribution. The original injection of a compensating current I from the (classic) active EMC filter is supplemented by a DC target variable DC_ZG, namely a voltage from a high-voltage potential HV+, HV- to the equipotential bonding conductor PA. This can be used to influence the maximum high-voltage potential asymmetry (to comply with CY requirements) or to prevent exceeding a maximum voltage value between a high-voltage potential HV+, HV- and the equipotential bonding conductor PA, for example, to protect the insulation in a 500V DC charging station.

[0033] In addition to detecting the AC interference AC_Int and injecting a compensation current I (classic function of an active EMC filter), detection of the high-voltage potential distribution is also required.

[0034] Suitable implementation options include analog circuits (e.g., using operational amplifiers and / or transistors) and / or digital methods such as sampling the high-voltage voltage distribution and the AC disturbance AC_Int for regulation and / or control, and injecting the compensation current I and influencing the high-voltage potential distribution. If a digital variant is chosen, it is sometimes possible to use values ​​already acquired elsewhere in the vehicle, such as the high-voltage system voltage or high-voltage potential distribution.

[0035] A combination of analog solutions such as AC EMC compensation and a digital method for (slower) influencing the high-voltage potential distribution is also possible.

[0036] In a purely digital solution, the AC fault AC_Int can be detected solely from the high-voltage potential voltage measurement and fast sampling. The capacitor EMC_In_P shown in the diagram can be omitted in this case. Reference symbol list 1 High-voltage system 2 active common-mode filters 3. Source of interference 4. Disturbance sink 5 Insulation monitor 6 processing units 7 active electronics 8 Voltage source AC_ZG AC target variable AC_Int AC fault C Intermediate circuit capacitor CY_P, CY_N Y-capacity DC_ZG DC target size EMC_In_P Capacitor EMC_In_P1 output capacitor HV+, HV potential, high voltage potential I Compensation current PA potential equalization conductor, reference potential R_iso_P, R_iso_N insulation resistance V1, V2 voltage meter V_AC_DC AC+DC specification V_P, V_N Input variable, voltage ZW target value

Claims

[1] Active common-mode filter (2) comprising a processing unit (6) configured to detect AC disturbances (AC_Int) in a potential (HV+, HV-) applied to the common-mode filter (2) relative to a reference potential (PA) and to determine an AC target quantity (AC_ZG) based on the detected AC disturbances (AC_Int), and active electronics (7) configured to inject a compensation current (I) into the potential (HV+, HV-) or to apply a compensation voltage to the potential (HV+, HV-) based on the AC target quantity (AC_ZG) to compensate for the AC disturbances (AC_Int), wherein the processing unit (6) is further configured to determine, based on a potential distribution between the applied potential (HV+) and another potential (HV-) relative to the reference potential (PA) and based on at least one predefined target value (ZW) that exhibits maximum asymmetry the potential distribution or a maximum voltage of one of the potentials (HV+,HV-) to the reference potential (PA) describes determining a DC target quantity (DC_ZG), in particular calculating and / or controlling and / or regulating it, which can be supplied to the active electronics (7) together with the AC target quantity (AC_ZG) to change the potential distribution according to the target value (ZW) by injecting the compensation current (I) or applying the compensation voltage, wherein the processing unit (6) is configured to - to determine the potential distribution by measuring a voltage (V_P) between the applied potential (HV+) and the reference potential (PA) and a voltage (V_N) between another potential (HV-) and the reference potential (PA), or by measuring a voltage (V_P) between the applied potential (HV+) and the reference potential (PA) and a voltage between the applied potential (HV+) and another potential (HV-) with subsequent difference calculation, or - to use voltages (V_P, V_N) or a potential distribution determined in a high-voltage system (1) to which the common-mode filter (2) is connected, wherein a capacitor (EMC_ln_P) for detecting the AC disturbance (AC_Int) is connected to the applied potential (HV+, HV-) and the processing unit (6) is configured for inductive detection of the AC disturbance (AC_Int) or for digital detection of the AC disturbance (AC_Int) by sampling the applied potential (HV+, HV-) and software-based filtering and / or calculation. [2] Active common-mode filter (2) according to claim 1, characterized by , that the processing unit (6) is constructed as an analog circuit and / or as a digital circuit and / or as a hybrid circuit consisting of analog and digital components. [3] Active common-mode filter (2) according to claim 1 or 2, characterized by, that the active electronics (7) has an amplifier configured to generate the compensation current (I) or the compensation voltage depending on an AC+DC target value (V_AC_DC) obtained by summing the AC target quantity (AC_ZG) and the DC target quantity (DC_ZG) and to feed it into the potential (HV+, HV-) via an output capacitor (EMC_ln_P1) or inductively. [4] Active common-mode filter (2) according to any one of the preceding claims, characterized by a voltage source (8) to supply the active electronics (7) with an operating voltage.

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