3-level t-type inverter with 3-phase electric machine as an ac or DC charging device

Abstract

The invention relates to an assembly (100) comprising a 3-level inverter (200) having an inverter DC voltage terminal (210) and an inverter AC voltage terminal (220); an electric machine (300) having a plurality of phase windings (310), which are connected to the inverter AC voltage terminal (220), wherein at least one of the phase windings (310) is each connected to a phase contact element (410) of a connector (400) for connecting a charging cable or an AC voltage source; a star point switching unit, which electrically connects the plurality of phase windings (310) to a star point (322) on a side facing away from the 3-level inverter (200) in a first star point switching unit circuit configuration, and electrically disconnects the plurality of phase windings (310) from the star point (322) in a second star point switching unit circuit configuration; a DC-to-DC converter (500) having a first converter DC voltage terminal (510) and a second converter DC voltage terminal (520), wherein the first converter DC voltage terminal (510) is connected to the inverter DC voltage terminal (210); a DC voltage source (600), which is connected to the second converter DC voltage terminal (520); and a DC-to-DC converter switching unit (800) that bridges the DC-to-DC converter (500) in a first DC-to-DC converter switching unit circuit configuration and does not bridge the DC-DC converter (500) in a second DC-to-DC converter switching unit circuit configuration.

Description

[0001] R.417110IP1

[0002] - 1 -

[0003] Description

[0004] title

[0005] Arrangement comprising a 3-level inverter and an electrical machine and method for operating such an arrangement

[0006] The present invention relates to an arrangement comprising a 3-level inverter and an electric machine and a method for operating such an arrangement, in particular as a charger replacement.

[0007] Background of the invention

[0008] Reusing electrification components for different applications within a vehicle is beneficial for reducing volume and costs. For example, in an electric vehicle, the electric motor and inverter can be used as AC chargers (i.e., the onboard charger is completely replaced as a component). Such a solution is used, for example, in the

[0009] WO 2010 / 103063 A1 shows that the inverter and the electric machine are used as a boost converter and upstream power factor correction (PFC) stage, which shapes the current drawn from the grid in such a way that the grid quality requirements are met.

[0010] Disclosure of the invention

[0011] According to the invention, an arrangement comprising a 3-level inverter and an electric machine, and a method for operating such an arrangement with the features of the independent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description. R.417110IP1

[0012] - 2 -

[0013] The invention relates to a 3-level inverter, in particular a so-called "3-level T-type neutral-point-clamped inverter" (TNPC inverter). Compared to conventional 2-level inverters with regular half-bridges, 3-level inverters offer advantages in terms of switching losses and ripple currents.

[0014] Unlike a 2-level inverter, in a TNPC inverter the center tap of each half-bridge is connected to a DC voltage center point on the DC side via a bidirectional switching element, thus generating an additional (third) voltage level (zero level) at the center tap. This additional number of voltage levels allows for a more precise approximation of the desired phase voltage waveform.

[0015] In addition to improved output voltage quality, the 3-level inverter also offers more switching combinations than the 2-level inverter. This allows the same voltage to be achieved using other switching combinations if one semiconductor switch fails. This increases system redundancy and makes the inverter more resilient to statistically significant semiconductor defects.

[0016] One aspect of the invention relates to an arrangement consisting of a 3-level, in particular TNPC, inverter and an electrical machine with multiple phase windings.

[0017] The inverter has a DC inverter connection with, in particular, at least two DC lines and an AC inverter connection with, in particular, at least two, for example, three AC lines.

[0018] Furthermore, at least one, preferably each of the several phase windings, is connected, in particular via a charging terminal switching unit, to a phase contact element (e.g. a male or female contact element)R.417110IP1

[0019] - 3 -

[0020] a connector for connecting a charging cable or an AC power source. This connector can be, in particular, a so-called Type 1 plug (single-phase), Type 2 plug (three-phase), CCS plug, GB / T plug, or similar (depending on the country and / or region). When the term "plug" is used here or in the following, it should be understood generally and specifically includes a socket. For example, a connector may also be designed to be equipped with different adapters, so that the assembly can be connected to different power sources, such as adapters with CCS or Type 2 plugs for charging stations or wallboxes, or adapters with Schuko plugs or country-specific plug types for household sockets, etc.The connector can, in particular, have (exactly) one phase contact element, which is then usually designated "P", or three phase contact elements, which are then usually designated "L1", "L2", "L3".

[0021] A neutral conductor contact element of the connector, which is usually designated "N", can in particular be connected to the DC voltage center point (zero level) of the 3-level inverter.

[0022] Furthermore, the arrangement includes a neutral switching unit which, in a first neutral switching unit circuit configuration, electrically connects the multiple phase windings on a side facing away from the 3-level inverter to a neutral point, and in a second neutral switching unit circuit configuration, electrically disconnects the multiple phase windings from the neutral point. In other words, the phase windings are connected at one end to the inverter AC voltage terminal and at the other end to the neutral switching unit.

[0023] For example, in a motor or generator operating mode of the arrangement, the neutral point switching unit is located in the first neutral point switching unit circuit configuration (i.e., connected to the neutral point), and in a charging operating mode of the arrangement in the second R.417110IP1

[0024] - 4 -

[0025] Star point switching unit circuit configuration (i.e., not connected to the star point).

[0026] The arrangement comprises a DC-DC converter with a first and a second converter DC terminal, wherein the first converter DC terminal is connected to the inverter DC terminal and the second converter DC terminal is connected to a DC voltage source. The DC voltage source can be, in particular, a battery, and more specifically, a high-voltage battery. In this context, "high voltage" means a voltage above a permissible touch voltage of, in particular, 60 V, and can be in the range of several hundred volts or more. In other words, the DC-DC converter is arranged between the inverter and the DC voltage source, and the DC-DC converter is configured, in particular, to convert an input voltage supplied to the inverter into an output voltage applied to the DC voltage source, or vice versa.

[0027] The DC-DC converter can be designed as an isolating or non-isolating DC-DC converter, depending on safety requirements.

[0028] The DC / DC converter can be designed as a step-up converter, a step-down converter, or a combined step-down / step-up converter (so-called buck / boost converter), depending on the requirements of the voltage conditions.

[0029] The arrangement includes a DC-DC converter switching unit which, in a first DC-DC converter switching unit circuit configuration, bridges the DC-DC converter and, in a second DC-DC converter switching unit circuit configuration, does not bridge the DC-DC converter.

[0030] For example, in a motor or generator operating mode of the arrangement, the DC-DC converter switching unit is located in the first DC-DC converter switching unit circuit configuration (dhR417110IP1).

[0031] - 5 -

[0032] the DC-DC converter is bypassed and non-functional), and in a charging operating mode of the arrangement in the second DC-DC converter switching unit circuit configuration (i.e. the DC-DC converter converts the charging voltage applied to the connector into a voltage suitable for the DC voltage source).

[0033] This arrangement advantageously fulfills the functions of a converter stage, in particular a boost converter, and a power factor correction (PFC) stage to shape the current drawn from the grid in such a way as to meet the grid quality requirements. In particular, the invention makes it possible to utilize the inverter and the inductors of the electric machine to perform the function of the PFC stage of a conventional charger within the vehicle. This results in significant cost savings. The arrangement can, for example, be used in the drive system of a vehicle, especially an electric vehicle.

[0034] Unless otherwise noted, the terms "connect", "connected", "connectable" or similar are to be understood in the sense of electrically conductive connections.

[0035] According to at least one embodiment, the at least one phase winding, each connected to a phase contact element of the connector, is connected to the phase contact element of the connector via a charging port switching unit. In a second charging port switching unit circuit configuration, the charging port switching unit connects the at least one phase winding to the phase contact element, and in a first charging port switching unit circuit configuration, it either does not connect the at least one phase winding to the phase contact element or disconnects it. This allows the phase contact elements to be disconnected from the phase windings when the connection is not required, thus increasing operational safety. In particular, it prevents an accidental voltage from being present on a phase contact element and endangering people. R.417110IP1

[0036] - 6 -

[0037] For example, in a motor or generator operating mode of the arrangement, the charging terminal switching unit is in the first charging terminal switching unit circuit configuration (i.e., the phase windings are not connected to the connector), and in a charging operating mode of the arrangement, it is in the second charging terminal switching unit circuit configuration (i.e., the phase windings are connected to the connector).

[0038] According to at least one embodiment, the charging port switching unit has a fault current sensor, wherein the fault current sensor is configured to monitor the connection between the at least one phase winding and the phase contact element for a fault current. A fault current can be defined, for example, as a current difference between at least two conductors (here, phase contact elements and neutral conductor contact element). In an electrical circuit, particularly one that is not defective, the sum of the incoming and outgoing currents is zero. If a fault current occurs, this means a (particularly undesirable) short circuit in the circuit or the occurrence of undesired leakage currents.

[0039] According to at least one embodiment, the arrangement is configured to disconnect at least one phase winding from the phase contact element, in particular by switching the charging port switching unit into the first charging port switching unit circuit configuration when the fault current sensor detects a fault current. In particular, the connection between the neutral conductor contact element and the DC voltage center point is also disconnected.

[0040] According to at least one embodiment, the arrangement includes an AC filter unit between the connector and the at least one phase winding, for example, between the connector and the charging terminal switching unit. The AC filter unit can reduce emissions from the DC-DC converter into the AC voltage source and act as an EMI filter (electromagnetic interference). R.417110IP1

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[0042] According to at least one embodiment, the arrangement includes a leakage current compensation unit connected on the DC side of the 3-level inverter between the positive and negative DC potentials. The leakage current compensation unit can be signal-connected to the AC filter unit to control it. Leakage current compensation is useful for reducing unwanted leakage currents due to Y-capacitances in the high-voltage network. Without an isolation barrier, these currents can cause charging interruptions and problems with sensitive residual current devices (RCDs). The compensation also minimizes electromagnetic interference and meets regulatory requirements.

[0043] According to at least one embodiment, the charging port switching unit has a number of charging port disconnect switches corresponding to the number of at least one phase winding, with each of the at least one phase winding being connected to the phase contact element via a charging port disconnect switch. Each neutral point disconnect switch can be switched in a conductive or non-conductive manner. This allows for the simple provision of a suitable charging port switching unit.

[0044] According to at least one embodiment, the neutral switching unit has a number of neutral switching unit connections at least corresponding to the number of phase windings, each of which is connected to the neutral point via a neutral disconnect switch. Each neutral disconnect switch can be switched in a conductive or non-conductive manner. This allows for the simple provision of a suitable neutral switching unit.

[0045] According to at least one embodiment, the arrangement further comprises a DC charging circuit which includes a DC charging terminal for connecting a DC charging source, a DC charging R.417110IP1

[0046] - 8 -

[0047] The inverter connection (352), which is connected to the star point, has a DC charging capacitor and a DC charging disconnect switch. This advantageously allows for DC charging operation as well.

[0048] According to at least one embodiment, the DC charging inverter connection is connected to the DC charging terminal and, via the DC charging capacitor, to a ground potential. This allows different charging voltages to be used and converted appropriately by controlling the inverter accordingly.

[0049] Another aspect of the invention relates to a method for operating an arrangement as described above. In this method, the neutral switching unit and the DC-DC converter switching unit are switched into specific combinations of first and second neutral switching unit circuit configurations and DC-DC converter switching unit circuit configurations, depending on the operating mode.

[0050] According to at least one embodiment, in a motor or generator operating mode of the arrangement, the neutral point switching unit is switched to the first neutral point switching unit circuit configuration, the DC voltage converter switching unit is switched to the first DC voltage converter switching unit circuit configuration, and in particular the DC voltage charging disconnect switch is opened.

[0051] According to at least one embodiment, in the motor or generator operating mode of the arrangement, the charging port switching unit is switched to the first charging port switching unit circuit configuration.

[0052] According to at least one embodiment, in a charging mode of the arrangement, the star point switching unit is switched to the second star point switching unit circuit configuration and the R.417110IP1

[0053] - 9 -

[0054] DC-DC converter switching unit switched into the second DC-DC converter switching unit circuit configuration.

[0055] According to at least one embodiment, in the charging mode of the arrangement, the charging port switching unit is switched to the second charging port switching unit circuit configuration.

[0056] According to at least one embodiment, the charging mode comprises an AC charging mode in which, in particular, the DC charging disconnect switch is open, and a DC charging mode in which, in particular, the DC charging disconnect switch is closed.

[0057] In this way, the aforementioned operating modes can be generated safely and reliably.

[0058] A computing unit according to the invention, e.g. a control unit of a drive system, is, in particular in terms of programming, equipped to carry out a method according to the invention.

[0059] Implementing a method according to the invention in the form of a computer program or computer program product with program code for carrying out all method steps is also advantageous, as this incurs particularly low costs, especially if an executing control unit is already available for other tasks. Finally, a machine-readable storage medium is provided with a computer program stored on it as described above. Suitable storage media or data carriers for providing the computer program are, in particular, magnetic, optical, and electrical storage media, such as hard drives, flash memory, EEPROMs, DVDs, etc. Downloading a program via computer networks (Internet, intranet, etc.) is also possible. Such a download can be wired or wireless (e.g., via a WLAN network, a 3G, 4G, 5G, or 6G connection, etc.). R.417110IP1

[0060] - 10 -

[0061] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawing.

[0062] The invention is schematically illustrated in the drawing using exemplary embodiments and is described below with reference to the drawing.

[0063] Brief description of the drawings

[0064] Figure 1 shows schematically and in circuit diagram form an embodiment of an arrangement comprising a 3-level inverter and an electric machine.

[0065] Figure 2 shows an embodiment of a method for operating the arrangement from Fig. 1 or 3.

[0066] Figure 3 shows schematically and in circuit diagram form an embodiment of another arrangement comprising a 3-level inverter and an electric machine.

[0067] Detailed description

[0068] Figure 1 shows a schematic and circuit-diagram representation of an arrangement according to one embodiment, comprising a 3-level inverter 200 and an electric machine 300, and is collectively designated 100. For example, the arrangement 100 can be used as an AC charger in an electric vehicle.

[0069] The arrangement 100 includes the 3-level inverter 200 with an inverter DC voltage connection 210 and an inverter AC voltage connection 220. In the example shown, the 3-level inverter 200 is designed as a so-called 3-level T-type neutral-point-clamped inverter (TN PC inverter). The inverter 200 forms a transition between R.417110IP1

[0070] - 11 -

[0071] The arrangement 100 comprises a DC voltage side and an AC voltage side. The inverter DC connection 210 can have a first (e.g., positive) DC voltage contact 211 and a second (e.g., negative) DC voltage contact 212. DC voltage potentials "+" and ground, respectively, are present at the DC voltage contacts 211 and 212. These potentials are supplied by a DC voltage source 600, for example, a high-voltage battery, in a motor operating mode of the arrangement 100, and are supplied to the DC voltage source 600 in a generator or charging operating mode of the arrangement 100.

[0072] In the example shown, the TN-PC inverter 200 and the electric machine 300 are three-phase, so that the TN-PC inverter has three half-bridges 230, each with a high-side switch 231 and a low-side switch 232. The high-side switches 231 and / or low-side switches 232 can be designed as semiconductor switches, in particular MOSFETs. A respective center tap U, V, W of the half-bridges 230 is connected on one side to an AC voltage contact 221, 222, or 223 of the AC voltage terminal 220 and on the other side to a DC voltage center point 213 via a bidirectional switch 233. The bidirectional switch 233 is implemented here as an anti-series circuit of two MOSFETs, so that current conduction and interruption are possible in both directions. On the DC side, an intermediate circuit capacitor 214 is connected between the first DC contact 211 and the DC contact 214.The second DC voltage contact 212 and the DC voltage center point 213 are arranged. Half the supply DC voltage or DC circuit voltage Vs / 2 is applied to each intermediate circuit capacitor 214.

[0073] The DC voltage center point 213 represents a third potential (zero level) and serves as the neutral conductor N in arrangement 100. The DC voltage center point 213 is connected to a neutral conductor contact 224. R.417110IP1

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[0075] The arrangement 100 further comprises the electric machine 300 with three phase windings 310, which are connected at one end to the inverter AC voltage connection 220 or the AC voltage contacts 221, 222, 223. Each of the phase windings 310 is connected at its other end to a star point 322 via a star point switching unit 320.

[0076] The neutral point switching unit 320 is configured to electrically connect the three phase windings 310 on the side facing away from the TNPC inverter 200 to the neutral point 322 in a first neutral point switching unit circuit configuration, and to disconnect the three phase windings 310 from the neutral point 322 in a second neutral point switching unit circuit configuration. For this purpose, the neutral point switching unit 320 has three neutral point switching unit terminals 321 (one for each phase winding 310), each of the three neutral point switching unit terminals being connected to the neutral point 322 via a neutral point disconnect switch S1, S2, S3.

[0077] At the same time, each of the phase windings 310 is also connected at the end facing away from the inverter 200 via a charging connection switching unit 700 to a phase contact element 410 of a connector 400 for connecting a charging cable or an AC voltage source.

[0078] The connector can be, for example, a three-phase plug, such as a Type 2 plug, which is connected directly to a single-phase or three-phase (household) socket (e.g., Schuko® socket or CEE socket) via a charging cable. In the example shown, the connector 400 has three phase contact elements 410, labeled "L1", "L2", and "L3". Furthermore, the connector 400 has a neutral conductor contact element 420, labeled "N". The connector typically also has a protective earth (PE) contact element, which is not shown.

[0079] The charging port switching unit 700 has four charging port disconnect switches 720 (three for the phase lines L1, L2, L3 and one for the neutral conductor N)R.417110IP1

[0080] - 13 -

[0081] on, wherein each of the phase windings 310 and the neutral conductor N is connected via a charging connection disconnect switch 720 to one of the phase contact elements 410 or the neutral conductor contact element 420 respectively.

[0082] The charging port switching unit 700 is configured to connect the three phase windings 310 to the phase contact elements 410 and the neutral conductor N to the neutral conductor contact element 420 in a second charging port switching unit circuit configuration (i.e., to close or switch the charging port disconnect switches 720 in a conductive state), and in a first charging port switching unit circuit configuration, to not connect or disconnect the three phase windings 310 to the phase contact elements 410 and the neutral conductor N to the neutral conductor contact element 420 (i.e., to open or switch the charging port disconnect switches 720 in a non-conductive state).

[0083] Furthermore, the charging port switching unit 700 includes a residual current sensor 710, which is configured to monitor the phase lines L1, L2, L3 and the neutral conductor N for a residual current. The arrangement 100 is configured to disconnect the three phase windings 310 and the neutral conductor N from the phase contact elements 410 and the neutral conductor contact element 420, respectively, when the residual current sensor 710 detects a residual current. For this purpose, the charging port disconnect switches 720 are opened or switched to non-conductive operation.

[0084] Furthermore, the arrangement 100 has on the DC side a DC voltage converter 500 with a first converter DC voltage connection 510 and a second converter DC voltage connection 520, wherein the first converter DC voltage connection 510 is connected to the inverter DC voltage connection 210 and the second converter DC voltage connection 520 is connected to the DC voltage source 600.

[0085] The DC-DC converter 500 can be used as a boost converter, a buck converter, or a combined buck / boost converter (so-called R.417110IP1).

[0086] - 14 -

[0087] Buck / boost converters), depending on the requirements for the voltage conditions.

[0088] In the illustrated embodiment, the DC-DC converter 500 is designed as an interleaved buck converter. The DC-DC converter 500 has two half-bridges 530, each with a high-side switch 531 and a low-side switch 532, the center tap of which is connected via an inductor 533 to a DC-DC converter output 522 of the second converter DC input 520.

[0089] The DC potentials "+" and

[0090]

[0091] The DC and ground connections are routed through the DC converter 500 at the DC converter contacts 521 and 523 of the second DC converter connection 520.

[0092] The DC voltage converter output 522 is connected via a capacitor 534 to the converter DC voltage contact 523 of the negative DC voltage potential or ground potential.

[0093] The arrangement 100 includes a DC voltage converter switching unit 800 which, in a first DC voltage converter switching unit circuit configuration, bridges the DC voltage converter 500 and, in a second DC voltage converter switching unit circuit configuration, does not bridge the DC voltage converter 500.

[0094] The DC-DC converter switching unit 800 has two switchable paths, each with a switch S4, S5. Switches S4, S5 can be designed as semiconductor switches, e.g., MOSFETs. The two paths are connected at the end furthest from the DC voltage source 600 to the converter DC voltage contact 521 and the DC-DC converter output 522, and at the end furthest from the DC voltage source 600 to the positive terminal (+) of the DC voltage source 600. R.417110IP1

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[0096] In the first DC-DC converter switching unit circuit configuration, the upper switch S4 is closed (conducting) and the lower switch S5 is open (non-conducting). In the second DC-DC converter switching unit circuit configuration, the upper switch S4 is open (non-conducting) and the lower switch S5 is closed (conducting).

[0097] Furthermore, arrangement 100 includes, by way of example, an AC filter unit 900 between connector 400 and charging connection switching unit 700. The AC filter unit 900 can be used to reduce emissions from the DC-DC converter 500 into the AC voltage source. In the case of a non-insulating or galvanically non-isolated arrangement 100, the AC filter unit 900 can, by way of example, be connected via signaling to a leakage current compensation unit 910, which is connected on the DC side of the inverter 200 between the first DC contact 211 and the second DC contact 212. Leakage current compensation is useful for reducing unwanted leakage currents through Y-capacitances in the high-voltage network. Without an isolation barrier, these currents can cause charging interruptions and problems with sensitive residual current devices (RCDs).The compensation also minimizes electromagnetic interference and meets regulatory requirements.

[0098] Furthermore, the arrangement 100 can include a DC charging circuit 350, which serves to receive or apply a DC voltage at a DC charging port 351 for connecting a charging cable or a DC charging source. The DC charging circuit 350 can be operated as a so-called DC boost circuit. The DC charging port 351 can be routed into the connector 400, for example, if it is designed as a CCS connector, and connected there to a DC contact.

[0099] The DC charging circuit 350 has a DC charging inverter connection 352, which is connected to the star point 322. Further R.417110IP1

[0100] - 16 -

[0101] The DC charging inverter connection 352 is connected to the DC charging connection 351 via a branch 355. Furthermore, the DC charging inverter connection 352 is connected via the branch 355 to a DC charging capacitor 353, which in turn is connected to the DC potential or ground. At least one DC charging disconnect switch S6 is arranged either between the branch 355 and the DC charging inverter connection 352 and / or between the DC charging capacitor 353 and the branch 355. Preferably, the DC charging disconnect switch S6 is arranged before or after the branch 355 to the DC charging connection 351.

[0102] The DC charging circuit 350 allows the DC voltage source 600 (battery) to be charged from a DC charging source connected to the DC charging terminal 351.

[0103] Furthermore, the arrangement 100 has a computing unit 110 which is configured to carry out a method for operating the arrangement 100, wherein the neutral switching unit 320 and the DC-DC converter switching unit 800 are switched in predetermined combinations of first and second neutral switching unit circuit configuration and DC-DC converter switching unit circuit configuration depending on an operating mode of the arrangement 100, as shown in Figure 2.

[0104] In step 1000, a distinction is made as to whether the arrangement should be operated in a motor or generator operating mode (branch 1) or in an AC charging operating mode (branch 2). Another advantageously possible (optional) operating mode is a DC charging operating mode (branch 3).

[0105] Additional functions such as V2X operation ("vehicle-to-everything"; e.g., V2L "vehicle-to-load", V2V "vehicle-to-vehicle", V2G "vehicle-to-grid", etc.) or an R.417110IP1

[0106] - 17 -

[0107] AC heating is also possible and simply corresponds to a reversal of the charging modes.

[0108] In step 1100, the arrangement is operated in motor or generator mode.

[0109] The neutral point switching unit 320 is switched into the first neutral point switching unit circuit configuration, i.e., the neutral point disconnect switches S1, S2, S3 are closed or switched to conducting, and the DC voltage converter switching unit 800 is switched into the first DC voltage converter switching unit circuit configuration, i.e., the upper switch S4 is closed or switched to conducting and the lower switch S5 is open or switched to non-conducting.

[0110] Furthermore, the charging port switching unit 700 is switched into the first charging port switching unit circuit configuration, i.e. the four charging port disconnect switches 720 are opened or switched to non-conductive operation.

[0111] If a DC charging circuit 350 is present, the DC charging disconnect switch S6 is opened.

[0112] In step 1200, the arrangement is operated in AC charging mode.

[0113] The neutral point switching unit 320 is switched to the second neutral point switching unit circuit configuration, i.e., the neutral point disconnect switches S1, S2, S3 are opened (non-conducting), and the DC-DC converter switching unit 800 is switched to the second DC-DC converter switching unit circuit configuration, i.e., the upper switch S4 is open (non-conducting) and the lower switch S5 is closed (conducting). R.417110IP1

[0114] - 18 -

[0115] Furthermore, the charging port switching unit 700 is switched to the second charging port switching unit circuit configuration, i.e. the four charging port disconnect switches 720 are closed or switched to conduction.

[0116] If a DC charging circuit 350 is present, the DC charging disconnect switch S6 is opened.

[0117] In step 1300, the arrangement is operated in DC charging mode. For this, the DC charging circuit 350 is required, with one positive terminal of the DC charging source connected to the DC charging terminal 351.

[0118] The neutral point switching unit 320 is switched into the first neutral point switching unit circuit configuration, i.e., the neutral point disconnect switches S1, S2, S3 are closed or switched to conducting, and the DC voltage converter switching unit 800 is switched into the first DC voltage converter switching unit circuit configuration, i.e., the upper switch S4 is closed or switched to conducting and the lower switch S5 is open or switched to non-conducting.

[0119] The DC charging disconnect switch S6 is closed, at least when it is located between the inverter terminal 352 and the DC charging terminal 351.

[0120] When the DC charging source and the DC voltage source (battery) 600 have the same voltage, the high-side switches 231 in the TN PC inverter 200 are closed (conducting) and the low-side switches 232 and the bidirectional switches 233 are opened (non-conducting). This establishes a connection between the positive terminal of the battery 600 and the DC charging terminal 351.

[0121] If the DC charging source and the DC voltage source (battery) have different voltages, the high-side switches 231 and the low-side switches 232 in the TN PC inverter 200 are alternately opened and closed. R.417110IP1

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[0123] The switches open and close in opposite directions, with the duty cycle depending on the ratio of the charging voltage to the battery voltage. The bidirectional switches 233 are open or non-conductive. This achieves a voltage conversion between the positive terminal of the DC voltage source (battery) 600 and the DC voltage charging terminal 351.

[0124] To mitigate plating effects during DC charging at high battery charge levels (SOG > 80%), the TN PC-Inverter 200 can generate pulses through brief discharges via an active short circuit. This mode is made possible by the addition of a capacitor at the machine's star point. Since significant voltage fluctuations to the charging station occur in this mode, capacitor 353 effectively dampens them.

[0125] The operating modes mentioned can be generated safely and reliably in the ways described.

[0126] Figure 3 shows a schematic and circuit-diagram representation of an arrangement according to another (simpler) embodiment, comprising the 3-level inverter 200 and the electric machine 300, and is designated collectively by 1. For example, arrangement 1 can be used as a DC charger in an electric vehicle. Unlike arrangement 100 in Figure 1, arrangement 1 does not have a star point switching unit 320, as this is only required for AC charging. For the same reason, the charging connection switching unit 700, the AC filter unit 900, the leakage current compensation unit 910, and—depending on the configuration—possibly an (AC) connector 400 are also omitted. In the simplest case, the DC-DC converter 500 and the DC-DC converter switching unit 800 can also be omitted.

[0127] The arrangement 1 can be operated in the motor or generator operating mode (branch 1) and in the DC charging operating mode (branch 3) as shown in Fig. 2.

Claims

R.417110IP1 - 20 - Claims 1. Arrangement (100) showing: -- a 3-level inverter (200) with an inverter DC voltage connection (210) and an inverter AC voltage connection (220), -- an electric machine (300) with multiple phase windings (310) connected to the inverter AC voltage terminal (220), wherein at least one of the phase windings (310) is connected to a phase contact element (410) of a connector (400) for connecting a charging cable or an AC voltage source, -- a neutral point switching unit which, in a first neutral point switching unit circuit configuration, electrically connects the multiple phase windings (310) on a side facing away from the 3-level inverter (200) to a neutral point (322), and, in a second neutral point switching unit circuit configuration, electrically disconnects the multiple phase windings (310) from the neutral point (322), -- a DC-DC converter (500) with a first converter DC voltage terminal (510) and a second converter DC voltage terminal (520), wherein the first converter DC voltage terminal (510) is connected to the inverter DC voltage terminal (210), -- a DC voltage source (600) connected to the second converter DC voltage terminal (520), -- a DC-DC converter switching unit (800) which, in a first DC-DC converter switching unit circuit configuration, bypasses the DC-DC converter (500) and, in a second DC-DC converter switching unit circuit configuration, does not bypass the DC-DC converter (500). R.417110IP1 - 21 - 2. Arrangement (100) according to claim 1, wherein the at least one phase winding (310), which is connected to a phase contact element (410) of the connector (400), is connected to the phase contact element (410) of the connector (400) via a charging port switching unit (700), wherein the charging port switching unit (700) in a first charging port switching unit circuit configuration does not connect the at least one phase winding (310) to the phase contact element (410) and in a second charging port switching unit circuit configuration connects the at least one phase winding (310) to the phase contact element (410).

3. Arrangement (100) according to claim 2, wherein the charging port switching unit (700) has a fault current sensor (710) wherein the fault current sensor (710) is configured to monitor the connection between the at least one phase winding (310) and the phase contact element (410) for a fault current.

4. Arrangement (100) according to claim 3, wherein the arrangement (100) is configured to disconnect at least one phase winding (310) from the phase contact element (410) when the fault current sensor (710) detects a fault current.

5. Arrangement (100) according to one of claims 2 to 4, wherein the charging port switching unit (700) has a number of charging port disconnect switches (720) corresponding to the number of at least one phase winding (310), wherein each of the at least one phase winding (310) is connected to the phase contact element (410) via a charging port disconnect switch (720).

6. Arrangement (100) according to any one of the preceding claims, wherein the neutral point switching unit (320) has a number of neutral point switching unit terminals at least corresponding to the number of phase windings (310), each of which R.417110IP1 - 22 - The star point switching unit connections are each connected to the star point (322) via a star point disconnect switch (S1, S2, S3).

7. Arrangement (100) according to one of the preceding claims, further comprising a DC charging circuit (350), wherein the DC charging circuit (350) comprises a DC charging terminal (351) for connecting a DC charging source, a DC charging inverter terminal (352) connected to the star point (322), a DC charging capacitor (353) and a DC charging disconnect switch (S6).

8. Arrangement (100) according to the preceding claim, wherein the DC charging inverter connection (352) is connected to the DC charging connection (351) and to a ground potential via the DC charging capacitor (353).

9. Method for operating an arrangement (100) according to any one of the preceding claims, wherein the neutral switching unit (320) and the DC-DC converter switching unit (800) are switched in predetermined combinations of first and second neutral switching unit circuit configuration and DC-DC converter switching unit circuit configuration depending on an operating mode of the arrangement (100).

10. Method according to claim 9, wherein in a motor or generator operating mode of the arrangement (100) the neutral point switching unit (320) is switched to the first neutral point switching unit circuit configuration and the DC-DC converter switching unit (800) is switched to the first DC-DC converter switching unit circuit configuration R.417110IP1 - 23 - is, and in particular the DC charging disconnect switch (S6) is opened.

11. Method according to claim 10, wherein in the motor or generator operating mode of the arrangement (100) the charging port switching unit (700) is switched to the first charging port switching unit circuit configuration.

12. Method according to any one of claims 9 to 11, wherein in a charging operating mode of the arrangement (100) the star point switching unit (320) is switched into the second star point switching unit circuit configuration and the DC voltage converter switching unit (800) is switched into the second DC voltage converter switching unit circuit configuration.

13. Method according to claim 12, wherein in the charging mode of the arrangement (100) the charging port switching unit (700) is switched to the second charging port switching unit circuit configuration.

14. Method according to any one of claims 9 to 13 with reference back to at least claim 7, the charging mode includes an AC charging mode and a DC charging mode, wherein the DC charging disconnect switch (S6) is open in the AC charging mode and closed in the DC charging mode.

15. Arrangement (100) according to any one of claims 1 to 8, further comprising a computing unit (10) configured to perform all process steps of a method according to any one of claims 9 to 14. R.417110IP1 - 24 - 16. Computer program that causes the computing unit (10) of the arrangement (100) according to claim 15 to perform all the process steps of a method according to any one of claims 9 to 14 when executed on the computing unit (10).

17. Machine-readable storage medium with a computer program stored thereon according to claim 16.

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