Filter device and method for filtering an electromagnetic interference signal, electrical energy converter and drive system

Abstract

A filter device (30) for filtering an electromagnetic interference signal for an electrical energy converter comprises: a sensor unit (36, 44, 40, 48) configured to detect a voltage and / or a current in a DC and / or AC section (18, 20) of the energy converter (8); a feed-in unit (38, 46, 42, 50) configured to feed a voltage and / or a current into the DC and / or AC section (18, 20) of the electrical energy converter (8); a control unit (36, 40) which is configured to determine the electromagnetic interference signal in the detected voltage and / or current and an interference counter-signal corresponding to the electromagnetic interference signal and to instruct the feed-in unit (38, 46, 42, 50) to feed a voltage and / or a current corresponding to the interference counter-signal into the DC and / or AC section (18, 20).The control unit (36, 40) is designed in such a way that it pre-controls the interference counter-signal on the basis of a control signal (S) to control the electric machine (12).

Description

[0001] The invention relates to a filter device and a method for filtering an electromagnetic interference signal. The invention also relates to an electrical energy converter comprising the filter device and a drive system comprising the electrical energy converter.

[0002] In a vehicle, especially an electric vehicle, the number of power electronic components, such as electrical energy converters, is increasing. Due to the switching behavior of switching elements, such as transistors, in these power electronic components, electromagnetic interference (EMI) is increasingly occurring in the vehicle's electrical system, potentially impairing the performance of high-frequency communication. This is further exacerbated by the use of gallium nitride and silicon carbide-based switching elements, which exhibit steep switching edges.

[0003] To reduce electromagnetic interference, a passive filter device is currently used. This is typically bulky, heavy, and expensive, and its increased weight leads to higher energy consumption and thus a reduced range. This contradicts the desired increase in the efficiency of the electric vehicle.

[0004] An active filter device typically uses an analog circuit in a forward or feedback topology to detect an electromagnetic interference signal in a power electronics component, determine a suitable counter-signal, and inject or feed this counter-signal into the power electronics component. However, such an active filter device exhibits a systemic error due to hardware limitations, finite bandwidths, and delay times, resulting in reduced performance at higher frequencies. Therefore, the article "Active Cancellation of the Electromagnetic Emissions at the Input of a Periodically Operating Motor Inverter by Injecting Synthesized and Synchronized Signals" by Gerten et al. addresses the reduction of an electromagnetic interference signal by injecting a synthesized and synchronized counter-signal.

[0005] However, despite the use of the active filter device, a significant hardware limitation remains. Due to the limited number of logic elements or the limited processing capacity of the active filter device's control unit, only a limited number of blocking filters can be implemented by injecting corresponding frequency components into the interference signal.

[0006] It is therefore the object of the present invention to eliminate or at least reduce the disadvantages of the prior art.

[0007] The problem is solved by the items having the features according to the independent claims. Advantageous embodiments are the subject of the dependent claims.

[0008] A filter device according to the invention can be used for filtering, in particular actively filtering, an electromagnetic interference signal in an electrical energy converter. The energy converter has an energy converter unit with at least one switching element to convert direct current energy into alternating current energy. The alternating current energy can, in particular, be three-phase current energy. The electrical energy converter or its energy converter unit can preferably convert the energy bidirectionally. The electrical energy converter is configured to drive an electric motor of an electric vehicle. That is, a corresponding control algorithm is stored and executable in an energy converter control unit to operate the electric motor according to a control signal, such as a required target torque.The filter device includes a sensor unit configured to detect voltage and / or current in a DC and / or AC section, particularly a three-phase section, of the energy converter. Therefore, only voltage or only current can be detected. However, current and voltage can also be detected simultaneously. Detection can occur in the DC section only, in the AC section only, in the three-phase section only, or in both sections.

[0009] Furthermore, the filter device according to the invention comprises a feed-in unit configured to feed a voltage and / or a current, which in particular includes a plurality of frequency components, into the DC and / or AC section or the three-phase section of the energy converter. Again, only a voltage or only a current can be fed in. However, both a voltage and a current can be fed in. Feed-in can occur only into the DC section, only into the AC section or the three-phase section, or into both sections. Particularly preferably, the current and / or voltage is also fed into the section in which the current and / or voltage was previously measured.

[0010] Furthermore, the filter device according to the invention comprises a control unit configured to detect the electromagnetic interference signal in the voltage and / or current detected by the sensor unit and a corresponding counter-signal. The control unit is then configured to instruct the power supply unit to inject a voltage and / or current corresponding to the counter-signal into the DC and / or AC section of the energy converter. Accordingly, the control unit extracts the electromagnetic interference signal from the measured signal, i.e., in the current and / or voltage, and then determines a counter-signal by regulation or control with the aim of eliminating or reducing the detected electromagnetic interference signal. The control unit may include an analog-to-digital converter to digitize the detected analog signal.The feed-in unit can then digitally output the interference counter-signal, and the digital interference counter-signal can be converted by a digital-to-analog converter into an analog interference counter-signal that can be fed into the DC section and / or the AC section or the three-phase section.

[0011] The control unit is designed to pre-control the electric motor by means of a control signal to counter the interference signal. This control signal can correspond to a target torque that is requested and must be supplied by the electric motor. Consequently, the interference signal can be accurately approximated even before the actual regulation or control process, thus reducing the reaction time of the filter device.

[0012] Preferably, the control unit can feed the interference signal back into the circuit using a lookup table or a function equation. The lookup table or function equation specifically links the control signal for controlling the electric machine with the frequency components of the interference signal. The lookup table or function equation can be generated beforehand through experiments and / or simulations. Consequently, a simple feedforward control system can be implemented.

[0013] Advantageously, the control signal can correspond to a command from an accelerator pedal and / or a driver assistance system, such as adaptive cruise control or a (semi-)autonomous driving system. The control signal thus corresponds to a required target torque, and the interference signal can be pre-controlled according to the switching behavior of at least one switching element used to set the target torque.

[0014] The control unit can be designed to determine the electromagnetic interference signal using a Fast Fourier Transform (FFT) of the voltage and / or current detected by the sensor unit. This allows for rapid detection of the electromagnetic interference signal.

[0015] Advantageously, the control unit can be designed to synchronize the interference counter-signal with the control of the energy converter. For this purpose, the control unit can receive a clock signal from the energy converter's control unit. Consequently, the interference counter-signal can be fed in synchronously with the electromagnetic interference signal, thus achieving efficient elimination or reduction of the electromagnetic interference signal.

[0016] An electrical energy converter according to the invention comprises an energy converter unit with at least one switching element for converting direct current energy into alternating current energy, in particular three-phase energy, preferably bidirectionally. The electrical energy converter is designed to drive an electric motor of an electric vehicle, in particular by executing a control algorithm. Furthermore, the electrical energy converter according to the invention comprises a filter device according to one of the preceding aspects, so that the electromagnetic interference signal can be effectively filtered in the electrical energy converter. Consequently, the propagation of electromagnetic interference in the electrical system of an electric vehicle can be reliably prevented.

[0017] Preferably, the at least one switching element can be a switching element based on gallium nitride and silicon carbide. Such switching elements can provide steep switching edges, but also cause a high proportion of electromagnetic interference.

[0018] Advantageously, the sensor unit and / or the power supply unit can be capacitively coupled to the DC section and / or the AC section.

[0019] A drive system according to the invention is applicable to an electric vehicle and comprises a high-voltage direct current (DC) energy source, in particular a high-voltage DC battery, a DC link connected to the high-voltage DC energy source, in particular via a DC-DC converter, an AC circuit, in particular a three-phase circuit, and an electric machine connected to the AC circuit. Furthermore, the drive system according to the invention comprises an electrical energy converter according to one of the preceding aspects, which is connected between the DC link and the AC circuit or the three-phase circuit.

[0020] A method according to the invention can be used for filtering, in particular actively filtering, an electromagnetic interference signal in an electrical energy converter. The electrical energy converter comprises an energy converter unit with at least one switching element for converting direct current energy into alternating current energy, in particular three-phase energy, preferably bidirectionally. The electrical energy converter is configured to drive an electric motor of an electric vehicle. The method initially comprises a step for detecting a voltage and / or a current in a direct current and / or an alternating current section, in particular a three-phase section, of the energy converter.

[0021] The next step involves determining the electromagnetic interference signal in the voltage and / or current detected by the sensor unit. This is followed by a step to determine a corresponding counter-signal, particularly through regulation or control. Finally, a step is performed to inject a voltage and / or current, which comprises, in particular, a plurality of frequency components and corresponds to the counter-signal, into the DC and / or AC section.

[0022] In the step of determining the interference counter-signal, the interference counter-signal is pre-controlled using a control signal for the electric machine. This control signal can correspond to a target torque that is requested and must be supplied by the electric machine. Consequently, the interference counter-signal can be accurately approximated before the actual measurement, thus reducing reaction time.

[0023] The invention is described in detail below with reference to the figure. It shows: Fig. 1 a schematic block diagram of a drive system comprising an electrical energy converter with the filter device according to the invention.

[0024] Fig. Figure 1 schematically shows a drive system 1. The drive system 1 comprises a high-voltage direct current (HVDC) energy source 2, which in this case is configured as a high-voltage battery. The HVDC energy source 2 is preferably connected to a DC link 6 via a DC-DC converter 4, which is configured to convert the voltage supplied by the HVDC energy source 2 into a DC voltage at a higher or lower level. An electrical energy converter 8 is connected to the DC link 6, which is configured to convert the DC energy supplied via the DC link 6 into AC energy, in this case three-phase AC energy, and to output it via an AC circuit 10, in this case a three-phase AC circuit, to an electric motor 12 for driving the wheels of the electric vehicle.

[0025] To convert direct current energy into alternating current energy, the electrical energy converter 8 comprises an energy converter unit 14 with at least one switching element 16, which in this case is designed as a transistor based on gallium nitride and silicon carbide. Various energy converter topologies, as known from the prior art, can be used. The energy converter 8 is designed such that, in the case of recuperation, it can also convert the alternating current energy provided by the electric machine 12 into direct current energy for charging the high-voltage direct current energy source 2. As in Fig. As can be seen in Figure 1, the energy converter unit 14 in the electrical energy converter 8 is connected to the DC link 6 via a DC section 18. A DC link capacitor may be connected in the DC section 18. To supply the AC energy to the electric machine 12, an output side of the energy converter unit 14 is connected to the AC circuit 10 via an AC section 20, in this case a three-phase section.

[0026] The operation of the energy converter unit 14, i.e., the switching behavior of the at least one switching element 16, is controlled by an energy converter control unit 22. The energy converter control unit 22 receives a corresponding control signal from an accelerator pedal control unit 24, which corresponds to a required target torque, and then controls or regulates the currents in the stator windings of the electric machine 12 using a suitable control method known from the prior art. The currents in the stator windings of the electric machine 12 are adjusted by applying a pulse-width modulated voltage. The control signal S, i.e., the target torque, corresponds to a command from an accelerator pedal 26 of the electric vehicle and / or a command from a driver assistance system 28, such as an adaptive cruise control system or a system for (partially) autonomous driving.

[0027] As mentioned at the outset, the proportion of electromagnetic interference, particularly harmonics, increases in a power electronic system. This is further exacerbated by the use of switching elements based on gallium nitride and silicon carbide, which enable steep switching edges. The electrical energy converter 8 therefore incorporates a filter device 30.

[0028] The filter device 30 comprises a DC filter unit 32 and an AC filter unit 34, in this case a three-phase filter unit. However, it is also conceivable that the filter device 30 comprises only one of the two filter units 32 or 34.

[0029] The DC filter unit 32 comprises a control unit 36 ​​and a signal generator 38, also known as an arbitrary waveform generator (AWG). Similarly, the AC filter unit 34 comprises a control unit 40 and a signal generator 42, also known as an arbitrary waveform generator (AWG). Since the processing in the AC filter unit 34 is similar to that in the DC filter unit 32, only the processing in the DC filter unit 32 will be described below as representative of the processing in the AC filter unit 34.

[0030] The control unit 36 ​​of the DC filter unit 32 is connected to a sensor element 44, which in this case is configured as a voltage sensor, for detecting a voltage in the DC section 18. To process an analog signal provided by the sensor element 44, the control unit 36 ​​can include an analog-to-digital converter (not shown). The control unit 36 ​​and the sensor element 44 together thus constitute a sensor unit. The same applies to the control unit 40 and the sensor element 48. However, it is also conceivable that a current is detected instead of a voltage. Furthermore, both a voltage and a current can be detected.

[0031] The control unit 36 ​​then processes the digitized voltage signal to detect electromagnetic interference in the DC voltage of the DC section 18. The control unit 36 ​​detects the electromagnetic interference, in particular, by applying a Fast Fourier Transform (FFT) to the digital DC voltage signal. Subsequently, the control unit 36 ​​generates a counter-signal for the electromagnetic interference in order to eliminate or at least reduce its contribution to the DC voltage of the DC section 18. The control unit 36 ​​then instructs the signal generator 38 to feed the detected counter-signal 38 into the DC section 18 via a feed-in element 46. The signal generator 38 and the feed-in element 46 together thus constitute a feed-in unit. The same applies to the signal generator 42 and the feed-in element 50.Consequently, a portion of the electromagnetic interference signal in the DC section 18 and / or in the AC section 20 can be eliminated or at least reduced.

[0032] To counteract a limitation of the computing power of the control units 36 and 40, the interference counter-signal according to the present invention, as described in Fig.1 is generated and pre-controlled according to the control signal S from the accelerator pedal control unit 24. For this purpose, a look-up table can be stored in the control units 36 and 40, respectively, which links the individual frequency components or the amplitudes of the different frequency components of the interference signal with the control signal S, i.e., the desired target torque. In this way, the interference signal can be accurately approximated before actual regulation or control, since the du / dt of the system and the impedance of the electric machine 12 are known. This reduces the reaction time when filtering the electromagnetic interference signal. The look-up table can be created beforehand based on experiments and / or simulations. Similarly, it is also conceivable that the relationship between the interference signal and the control signal S is defined by a functional equation in the control units 36 and 40, respectively. Reference symbol list 1 Drive system 2 High-voltage direct current power source 4 DC-DC converters 6 DC intermediate circuit 8 electrical energy converters 10 alternating current circuit 12 Electric machine 14 Energy converter unit 16 switching element 18 DC section 20 AC section 22 Energy converter control unit 24 Accelerator pedal control unit 26 Accelerator pedal 28 Driver assistance systems 30 filter device 32 DC filter unit 34 AC filter unit 36 Control unit 38 Signal generator 40 Control unit 42 Signal generator 44 Sensor element 46 Feed-in element 48 sensor elements 50 feed element QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] Active Cancellation of the Electromagnetic Emissions at the Input of a Periodically Operating Motor Inverter by Injecting Synthesized and Synchronized Signals” by Gerten

[0004]

Claims

[1] Filter device (30) for filtering, in particular active filtering, an electromagnetic interference signal for an electrical energy converter (8), which has an energy converter unit (14) with at least one switching element (16) in order to convert direct current energy into alternating current energy, in particular three-phase energy, preferably bidirectionally, and is designed to drive an electric machine (12) of an electric vehicle, wherein the filter device (30) has: a sensor unit (36, 44, 40, 48) which is designed to detect a voltage and / or a current in a direct current and / or an alternating current section (18 20), in particular a three-phase current section, of the energy converter (8); a feed unit (38, 46, 42, 50) which is designed to feed a voltage and / or a current, which in particular comprises a plurality of frequency components, into the direct current and / or the alternating current section (18, 20) of the energy converter (30); and a control unit (36, 38) configured to determine the electromagnetic interference signal in the voltage and / or current detected by the sensor unit (36, 44, 40, 48) and a counter-interference signal corresponding to the electromagnetic interference signal, and to instruct the feed unit (38, 46, 42, 50) to feed a voltage and / or current corresponding to the counter-interference signal into the direct current and / or alternating current section (18, 20) of the energy converter (30); characterized by , that the control unit (36, 40) is designed to pre-control the counter-interference signal based on a control signal (S), in particular a target torque, for controlling the electric machine (12). [2] Filter device (30) according to claim 1, characterized by that the control unit (36, 38) pre-controls the interference counter signal using a look-up table or a functional equation. [3] Filter device (30) according to claim 1 or 2, characterized by that the control signal (S) corresponds to a command from an accelerator pedal (26) and / or from a driver assistance system (28). [4] Filter device (30) according to one of claims 1 to 3, characterized by that the control unit (36, 38) is designed to determine the electromagnetic interference signal based on a Fast Fourier Transformation (FFT) of the voltage and / or current detected by the sensor unit (36, 44, 40, 48). [5] Filter device (30) according to one of claims 1 to 4, characterized by that the control unit (36, 38) is designed to synchronize the interference counter signal with a control of the electrical energy converter (8). [6] Electrical energy converter (8) having an energy converter unit (14) with at least one switching element (16) for converting direct current energy into alternating current energy, in particular three-phase energy, preferably bidirectionally, and designed to drive an electric machine (12) of an electric vehicle, characterized by a filter device (30) according to one of claims 1 to 5. [7] Electrical energy converter (8) according to claim 6, characterized by that the at least one switching element (16) is a switching element based on gallium nitride and silicon carbide. [8] Electrical energy converter (8) according to one of claims 6 or 7, characterized by that the sensor unit (36, 44, 40, 48) and / or the feed unit (38, 46, 42, 50) are capacitively coupled to the direct current and / or the alternating current section (18, 20), in particular the three-phase current section. [9] Drive system (1) for an electric vehicle comprising: a high-voltage direct current power source (2); a DC intermediate circuit (6) which is connected to the high-voltage DC energy source (2), in particular via a DC-DC converter (4); an alternating current circuit (10), in particular a three-phase circuit; and an electric machine (12) connected to the alternating current circuit (10); characterized by an electrical energy converter (8) according to one of claims 6 to 8, which is connected between the DC intermediate circuit (6) and the AC circuit (10). [10] Method for filtering, in particular active filtering, an electromagnetic interference signal for an electrical energy converter (8) which has an energy converter unit (14) with at least one switching element (16) to convert direct current energy into alternating current energy, in particular three-phase energy, preferably bidirectionally, and is designed to drive an electric machine (12) of an electric vehicle, the method comprising the following steps: Detecting a voltage and / or a current in a direct current and / or an alternating current section (18, 20), in particular a three-phase current section, of the energy converter (8); Determining the electromagnetic interference signal in the detected voltage and / or current; Determining a counter-interference signal corresponding to the electromagnetic interference signal; and feeding a voltage and / or a current, which in particular comprises a plurality of frequency components and corresponds to the counter-interference signal, into the direct current and / or alternating current section (18, 20); characterized by , that in the step of determining the counter interference signal, the counter interference signal is pre-controlled using a control signal (S) for controlling the electric machine (12).

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