Electric motor emulator

Abstract

The invention relates to an electric motor emulator (EME) for emulating an electric motor, in particular a three-phase electric motor, comprising at least one emulation converter (12), a galvanically isolated DC / DC converter (11), and at least one common-mode choke (14). The aim of the invention is to allow an emulation of a neutral point. This is achieved in that the electric motor emulator (EME) has at least one switchable bridging device (30) which is designed to bridge the galvanically isolated DC / DC converter (11).

Description

[0001]

[0002] electric motor emulator

[0003] The invention relates to an electric motor emulator for emulating, in particular, a three-phase electric motor, comprising at least one emulation converter, a galvanically isolated DC / DC converter, and at least one common-mode choke. The invention further relates to a test bench, in particular a hardware-in-the-loop test bench, for testing a device under test, in particular formed by a drive inverter, comprising a battery emulator and an electric motor emulator of the type mentioned. The invention further relates to a method for testing a device under test, in particular formed by a drive inverter, with a test bench comprising a battery emulator and an electric motor emulator.

[0004] Fig. 1 shows a known powertrain concept 101 of an electric vehicle in which a neutral point 105 of a three-phase electric motor 102 can be connected to a center point 106 of a vehicle battery 104. This connection enables a controlled zero-current flow i_0 from the neutral point 105 of the electric motor 102 back to the center point 106 of the vehicle battery 104 (or to a DC link center point of the inverter 103). This controlled zero-current flow i_0 from the electric motor 102 can be used for several functions in the powertrain 101, e.g., for warming up the vehicle battery 104 without having to apply any torque to the electric motor 102.

[0005] PHIL test benches (PHIL = Power Hardware in the Loop) with electric motor emulators and battery emulators are used to test drive inverters. Hardware in the Loop (HIL) refers to a method in which an embedded system (e.g., a drive inverter) is connected to a suitable counterpart via its inputs and outputs and tested.

[0006] However, PHIL test benches for drive inverters known from the state of the art do not allow a controlled zero current from emulated electric motors to the center point of an emulated battery, which poses a problem when testing this type of drive inverter function used in the described drive train concepts.

[0007] Fig. 2 shows a block diagram of a known PHIL test bench 110 for drive inverters, in which an electric motor emulator EME0 can emulate an electric motor. Galvanically isolated DC / DC converters 111 are used in the electric motor emulator EME0 to physically simulate the galvanically isolated neutral point of the emulated machine. The emulation converter 112 and the phase chokes 113 with inductances Lph emulate the physical behavior of an electric machine in the d / q coordinate system. The common-mode chokes 114 with inductances L_CMC are used to dampen the high-frequency zero-current that arises from stray capacitances in the test system. The common-mode chokes 114 also act as filters for a zero-current component. A zero-current component is not provided in the known electric motor emulator EME0 and therefore cannot be taken into account.The galvanic isolation of the DC / DC converter 111 prevents zero-current flow, i.e., a current that does not generate torque. Therefore, it is impossible to emulate an electric motor with a connected star point to drive the inverter's intermediate circuit or the battery's center point.

[0008] EP 3 742 601 A1 discloses a motor emulator for an inverter under test (IUT), comprising a voltage-following inverter configured to at least partially cancel an output voltage of the IUT, and an output current control unit configured to control the output current of the IUT based on the output voltage of the IUT and an estimated current of an emulation target motor. The output current control unit includes a circuit electrically connected to an output terminal of the IUT; and a second control unit configured to estimate a current of the emulation target motor based on the output voltage of the IUT and a characteristic of the emulation target motor, and to control the switching of the switching control based on the estimated current.The motor emulator further comprises a filter unit located between an output terminal of the IUT and the voltage-dependent converter, wherein the filter unit includes at least a single-phase choke, a three-phase choke and a zero-impedance filter.

[0009] The object of the invention is to enable the emulation of a star point in an electric motor emulator with a galvanically isolated DC / DC converter.

[0010] Another task is to emulate an electric motor with a star point connection.

[0011] According to the invention, this problem is solved in an electric motor emulator of the type mentioned above by the fact that the electric motor emulator has at least one switchable bridging device which is designed to bridge the galvanically isolated DC / DC converter.

[0012] Preferably, the switchable bridging device has at least one bypass line for bypassing the galvanic isolation of the DC / DC converter, wherein at least one first switching device is arranged in the bypass line.

[0013] The galvanically isolated DC / DC converter in the electric motor emulator can be bypassed by the first switching device to allow zero current flow.

[0014] In one embodiment of the invention, the electric motor emulator further provides for at least one switching device for the common-mode choke. Preferably, the switching device for the common-mode choke has at least one external winding, which is configured to switch off the common-mode choke by generating a magnetic field that opposes the zero-mode current. Advantageously, the external winding can be switched via a second switching device. By closing the second switching device, the external winding can be activated and the common-mode choke deactivated.

[0015] In an alternative embodiment of the invention, it is provided that the shutdown device has at least one switchable bypass line with a contactor switch in each phase.

[0016] The electric motor emulator can thus emulate an electric motor with a connected star point to drive the intermediate circuit center of the inverter or the battery center.

[0017] The zero-current component is taken into account by the machine model and the current control algorithms in the EME.

[0018] The invention is further solved by a test bench for testing a test specimen, with a battery emulator and an electric motor emulator, in that the electric motor emulator has a switchable bridging device which is designed to bridge the galvanically isolated DC / DC converter.

[0019] Preferably, the switchable bridging device has at least one bypass line for bypassing the galvanic isolation of the DC / DC converter, wherein at least one first switching device is arranged in the bypass line.

[0020] In one embodiment of the invention, the battery emulator has at least one center-tap connection for the device under test. Advantageously, a star point of the electric motor emulator and / or a center terminal of the emulation converter can be connected to the center-tap connection of the battery emulator. In one embodiment of the invention, the electric motor emulator in the test rig has at least one disconnect device for the common-mode choke, which advantageously has at least one external winding—preferably switchable via a second switching device—designed to disconnect the common-mode choke by generating a magnetic field that opposes zero current. Alternatively, the disconnect device can have at least one switchable bypass line with a contactor switch in each phase.

[0021] In a further embodiment of the invention, at least one common-mode choke is deactivated, preferably by generating a magnetic field through an external winding that opposes a zero-current current. The external winding prevents a magnetic flux from forming in the common-mode chokes.

[0022] The object of the invention is achieved by a method for testing a test specimen with a test bench comprising a battery emulator and an electric motor emulator, in that a star point of the electric motor emulator and / or a middle terminal of the emulation converter is connected to a center terminal of the battery emulator, and that the galvanically isolated DC / DC converter is bypassed.

[0023] The invention will be explained in more detail below with reference to the exemplary embodiments shown in the figures. These schematically illustrate:

[0024] Fig. 1 shows a drive train of a known electrically powered motor vehicle in a block diagram,

[0025] Fig. 2 shows a test bench for drive inverters with an electric motor emulator according to the state of the art in a block diagram,

[0026] Fig. 3 shows a test bench for drive inverters with an electric motor emulator according to the invention in a block diagram, and

[0027] Fig. 4 shows another test bench for drive inverters with an electric motor emulator according to the invention in a block diagram.

[0028] Fig. 1 shows a drive train 101 of an electrically powered vehicle. The three-phase electric motor 102 is connected via the phase terminals U, V, W to a drive inverter 103 designed as an AC / DC converter. The currents of the phases are denoted by i_U, i_V and i_W. The drive inverter 103 is connected via the lines DC+, DC- to a vehicle battery 104, which has the battery modules BT1, BT2. The neutral point 105 of the electric motor 102 is connected via a neutral conductor 100 to a center point 106 of the vehicle battery 104, with a switch 107 arranged in the line 100. This neutral conductor 100 enables a controlled zero-current flow i_0 from the star point 105 of the electric motor 102 back to the center point 106 of the vehicle battery 104. This controlled zero-current flow i_0 from the electric motor 102 can be used for some functions in the drive train 101, e.g.for warming up the vehicle battery 104 without requiring any torque from the electric motor 102.

[0029] Fig. 2 shows a block diagram of a known PHIL test bench 110 (PHIL = Power Hardware in the Loop) for a device under test, for example, a drive inverter, which is designated here as UUT0 (Unit Under Test). The PHIL test bench 110 has an electric motor emulator EME0, with which an electric motor can be emulated. The test bench 110 also has a battery emulator BE0 for emulating a vehicle battery. The battery emulator BE0 has inputs 115 and 116 as well as the midpoint 117, which are connected via the paths “DCJn+”, “DCJn-” and “DCJn-mid” to the DC / DC converter 111 and to the mains-powered power supply unit PSU0. The outputs 118 and 119 of the battery emulator BE0 are connected via the DC+ and DC- lines to the drive inverter UUT0 under test, whose phase connections U, V, W are connected to the electric motor emulator EME0.In the battery emulator BE0, a midpoint 120 ("DC_mid") on the output side is internally directly connected to the DC midpoint 117 on the input side.

[0030] In the electric motor emulator EME0, galvanically isolated DC / DC converters 111 are used to physically simulate the galvanically isolated neutral point of the emulated machine. The emulation converter 112 and the phase chokes 113 with inductances Lph emulate the physical behavior of the electric machine in the d / q coordinate system. The common-mode chokes 114 with inductances L_CMC are used to dampen the high-frequency zero-current that arises from stray capacitances in the test system. The common-mode chokes 114 also act as filters for a zero-current component. This zero-current component is not present in the conventional electric motor emulator EME0 and therefore cannot be taken into account. The galvanic isolation of the DC / DC converter 111 prevents a zero-current, i.e., a current that does not generate torque, from flowing.There is therefore no possibility of emulating an electric motor with a connected star point to drive the DC link of the inverter or the battery center point. Fig. 3 shows a block diagram of a PHIL test bench 10 according to the invention for test specimens, for example, drive inverters, which is designated here as UUT (Unit Under Test), wherein an electric motor emulator EME can emulate an electric motor of a drive train. The test bench 10 further comprises a battery emulator BE for emulating a vehicle battery. The battery emulator BE has inputs 15 and 16 as well as the center point 17, which are connected via the paths “DCJn+”, “DCJn-” and “DCJn-mid” to the DC / DC converter 11 and to the mains-connected power supply unit PSU.The outputs 18 and 19 of the battery emulator BE are connected via the paths “DC+” and “DC-” to the drive inverter UUT under test, whose output is connected via the phase connections U, V, W to the electric motor emulator EME.

[0031] In the electric motor emulator EME, galvanically isolated DC / DC converters 11 are used – as shown in Fig. 2 – to physically imitate the galvanically isolated neutral point of the emulated machine. The emulation converter 12 and the phase chokes 13 with inductances Lph emulate the physical behavior of an electric machine in the d / q coordinate system. The common-mode chokes

[0032] 14 with the inductances L_CMC are used to dampen the high-frequency zero current caused by stray capacitances in the test system.

[0033] In the battery emulator BE, a center-tap terminal 20 ("DC-mid") on the output side is internally directly connected to the DC center point 17 on the input side. The presence of the center-tap terminal 20 ("DC-mid") of the battery emulator BE is an essential prerequisite for the emulation of the electric motor with this type of connection.

[0034] According to the invention, the galvanically isolated DC / DC converters 11 in the electric motor emulator EME can be bypassed via a bypass device 30, wherein the bypass device 30 has bypass lines 31, 32, 33 with first switches S1 for the paths “DCJn+”, “DCJn-” and “DCJn-mid”. A first bypass line 31 allows the path “DC-in+” of the input to be bypassed.

[0035] 15 of the battery emulator BE can be connected to the positive terminal 21 ("+"), with a second bypass line 32 the path "DCJn-" of input 16 of the battery emulator BE can be connected to the negative terminal 22 ("-"), and with a third bypass line 33 the path "DCJn-mid" of the battery emulator BE can be connected to a middle terminal 23 ("mid") of the emulation converter 12 (or to a star point) of the electric motor emulator EME. This allows zero current flow.

[0036] Furthermore, the electric motor emulator EME has a shutdown device 40 for the common-mode choke 14. The shutdown device 40 has an external winding 41, which is designed to switch off the common-mode choke 14 by generating a magnetic field through the external winding 41 that opposes the zero-mode current. The external winding 41 can be activated or deactivated by a second switch S2.

[0037] The zero-current component is taken into account by the machine model and the current control algorithms in the electric motor emulator EME.

[0038] The invention has the advantage that the drive inverter UUT under test can drive the electric motor simulated by the electric motor emulator EME, which has a connection between its star point and the center point terminal 20 (DC-mid) of the simulated vehicle battery or the center point of the drive inverter UUT under test. The invention enables the complete testing of drive inverters UUT whose drive concept is based on the connection between the star point of the electric motor and the center point of the vehicle battery or the center point of the drive inverter UUT, in order to perform certain functions, such as heating the vehicle battery by utilizing the thermal losses resulting from the zero current regulated in the aforementioned path.

[0039] The battery emulator BE in the PHIL test bench 10 should have an optional center point connection 20 for the device under test UUT, which is only the case if its power electronics have the topology to support this. This allows for asymmetrical loading of the battery modules of the emulated vehicle battery.

[0040] Figure 4 shows another test bench 10 for drive inverters with an electric motor emulator EME according to the invention. The embodiment of the invention shown in Figure 4 corresponds in many features to the embodiment shown in Figure 3; therefore, only the most significant differences are discussed here. The embodiment shown in Figure 3 also applies here to the extent applicable. In contrast to the test bench 10 shown in Figure 3, the shutdown device 40 for the common-mode choke 14 is designed as a common-mode choke bypass device 42. The common-mode choke bypass device 42 has bypass lines 43, 44, 45 for the currents I Uz IV and I w with second switches S2, which can be used to bridge the common-mode chokes 14.

[0041] In comparison to the prior art, the following technical changes to the electric motor emulator EME are provided within the scope of the invention:

[0042] • The galvanic isolation of the DC / DC converters 11 in the electric motor emulator EME, which provides galvanic isolation of the neutral point of the electric machine, is bypassed to allow current flow between the neutral point of the electric motor emulator EME and the battery emulator BE.

[0043] • The common-mode choke 14 for filtering the zero current is deactivated by a switching device 40.

[0044] • New machine models and new zero-current path control algorithms are implemented in the EME electric motor emulator, taking into account the connection of the electric machine's star point to the center point of the vehicle battery or the drive inverter.

Claims

PATENT CLAIMS 1. Electric motor emulator (EME) for emulating a particularly three-phase electric motor, comprising at least one emulation converter (12), a galvanically isolated DC / DC converter (11) and at least one common-mode choke (14), characterized in that the electric motor emulator (EME) has at least one switchable bridging device (30) which is designed to bridge the galvanically isolated DC / DC converter (11).

2. Electric motor emulator (EME) according to claim 1, characterized in that the switchable bypass device (30) has at least one bypass line (31, 32, 33) for bypassing the galvanic isolation of the DC / DC converter (11), wherein at least one first switching device (Sl) is arranged in the bypass line (31, 32, 33).

3. Electric motor emulator (EME) according to claim 1 or 2, characterized in that the electric motor emulator (EME) has at least one shutdown device (40) for the common-mode choke (14).

4. Electric motor emulator (EME) according to claim 3, characterized in that the switching device (40) for the at least one common-mode choke (14) has at least one - preferably switchable via a second switching device (S2) - external winding (41) which is designed to switch off the common-mode choke (14) by generating a magnetic field through the external winding (41) which opposes a zero current.

5. Electric motor emulator (EME) according to claim 3, characterized in that the shutdown device (40) has at least one switchable bypass line with a contactor switch in each phase.

6. Test bench (10), in particular hardware-in-the-loop test bench (10), for testing a test object (UUT) formed in particular by a drive inverter, with a battery emulator (BE) and an electric motor emulator (EME), according to one of claims 1 to 5, characterized in that the electric motor emulator (EME) has a switchable bridging device (30) which is designed to bridge the galvanically isolated DC / DC converter (11).

7. Test bench (10) according to claim 6, characterized in that the switchable bridging device (30) has at least one bypass line (31, 32, 33) for bypassing the galvanic isolation of the DC / DC converter (11) wherein at least one first switching device (Sl) is arranged in the bypass line (31, 32, 33).

8. Test stand (10) according to claim 6 or 7, characterized in that the battery emulator (BE) has at least one center connection (20) for the test specimen (UUT).

9. Test bench (10) according to claim 8, characterized in that a star point of the electric motor emulator (EME) and / or a central terminal (23) of the emulation converter (12) can be connected to the center terminal (20) of the battery emulator (BE).

10. Test bench (10) according to one of claims 6 to 9, characterized in that the electric motor emulator (EME) has at least one shutdown device (40) for the at least one common-mode choke (14).

11. Test bench (10) according to claim 10, characterized in that the switching device (40) for the at least one common-mode choke (14) has at least one - preferably switchable via a second switching device (S2) - external winding (41) which is designed to switch off the common-mode choke (14) by generating a magnetic field through the external winding (41) which opposes a zero current.

12. Test bench (10) according to claim 10, characterized in that the shutdown device (40) has at least one switchable bypass line with a contactor switch in each phase.

13. Method for testing a test object (UUT) formed in particular by a drive inverter with a test bench (10) comprising a battery emulator (BE) and an electric motor emulator (EME) according to one of claims 6 to 12, characterized in that a star point of the electric motor emulator (EME) and / or a middle terminal (23) of the emulation converter (12) is connected to a center terminal (20) of the battery emulator (BE), and that the galvanically isolated DC / DC converter (11) is bypassed.

14. Method according to claim 13, characterized in that at least one common-mode choke (14) is deactivated.

15. Method according to claim 14, characterized in that a magnetic field is generated by an external winding (41) which opposes a zero current. 08.08.2025 / FU

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