Power converter assembly and method for operating a drive unit

Abstract

The invention relates to a power converter assembly (20) for supplying an electric machine (1) with electric power. For this purpose, the power converter assembly (20) has a first DC voltage connection (22a) and a second DC voltage connection (22b), which are designed to be connected to a DC voltage source. Furthermore, the power converter assembly (20) has at least one half-bridge (21U, 21V, 21W) having at least one first controllable semiconductor switch (21Ua, 21Va, 21Wa), which is provided between the first DC voltage connection (22a) and a central connection (21Uc, 21Vc, 21Wc) of the half-bridge (21U, 21V, 21W), and at least one second controllable semiconductor switch (21Ub, 21Vb, 21Wb), which is provided between the second DC voltage connection (22b) and the central connection (21Uc, 21Vc, 21Wc) of the half-bridge (21U, 21V, 21W). Each first semiconductor switch (21Ua, 21Va, 21Wa) and / or each second semiconductor switch (21Ub, 21Vb, 21Wb) is a normally-on semiconductor switch. The power converter assembly (20) additionally has an actuatable disconnecting circuit (24) which is designed to disconnect an electric connection between one of the DC voltage connections (22a, 22b) and the central connection (21Uc, 21Vc, 21Wc) of the at least one half-bridge (21U, 21V, 21W) when the actuatable disconnecting circuit (24) is not actuated. The invention further relates to a drive unit.

Description

[0001] Description

[0002] title

[0003] Power converter arrangement and method for operating a drive unit

[0004] The present invention relates to a power converter arrangement and a method for operating a drive unit, as well as a drive unit, a computing unit and a computer program for carrying it out.

[0005] Background of the invention

[0006] In fully or partially electric vehicles, electric machines, such as permanent magnet synchronous machines (PSMs), are frequently used. The three-phase alternating current required to operate these electric machines can be generated from battery voltage by a power converter arrangement, often three-phase, such as a pulse inverter or inverter. The power converter arrangement can, for example, be configured as a DC link converter in a B6 configuration.

[0007] Examples of switching elements used in the power converter arrangement include silicon (Si) metal oxide semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), or silicon carbide (SiC) MOSFETs. The use of other switching elements, such as gallium nitride (GaN) FETs, is also conceivable.

[0008] For an electric drive unit using a permanent magnet synchronous machine, the active short circuit (ACC) is often chosen as the safe state, in which all high-side switching elements or all low-side switching elements of the half-bridges are conductive. This safe state must exhibit high availability and therefore requires additional effort in the electrical control of the power semiconductors used as switching elements.

[0009] Disclosure of the invention

[0010] According to the invention, a power converter arrangement, a method for operating a drive unit, a drive unit, and a computer program for carrying out the method, comprising the features of the independent claims, are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

[0011] The invention relates to a power converter arrangement for supplying an electric machine with electrical power. For this purpose, the power converter arrangement has a first DC voltage terminal (e.g., a positive or negative terminal) and a second DC voltage terminal (e.g., a negative or positive terminal) configured to be connected to a DC voltage source. Furthermore, the power converter arrangement comprises at least one half-bridge, wherein, in particular, one half-bridge is provided for each phase winding of the electric machine. The half-bridge has at least one first controllable semiconductor switch arranged between the first DC voltage terminal and a center terminal of the half-bridge, and at least one second controllable semiconductor switch arranged between the second DC voltage terminal and the center terminal of the half-bridge.The half-bridge can be divided into a high-side, comprising at least one first controllable semiconductor switch, and a low-side, comprising at least one second controllable semiconductor switch. Each phase winding of the electrical machine is connected to one of the center terminals.

[0012] As explained above, conventional semiconductor switches used are MOSFETs, which are normally off; that is, if no voltage is applied between the gate and source of the MOSFET, no current can flow between the source and drain of the MOSFET. However, this also means that to create an active short circuit, which is conventionally used as a safe state, at least one semiconductor switch per half-bridge must be continuously supplied with a gate-source voltage to activate and maintain the active short circuit.

[0013] As a result, for example if the power supply to the converter arrangement or to the gate drivers of the converter arrangement, which are set up to control the semiconductor switches, fails, the active short circuit may not be activated and / or maintained, which may lead to hazardous situations and / or damage to the electrical machine and / or the converter arrangement.

[0014] Based on this, the invention proposes using self-conducting semiconductor switches (e.g., junction field-effect transistors, JFETs) as first and / or second controllable semiconductor switches. These are in a conducting state without an applied gate-source voltage, i.e., without being controlled. This allows the active short circuit to be activated and maintained even without a gate-source voltage and therefore also in the event of a failure of the power converter's supply voltage.

[0015] Specifically, the invention relates to a power converter arrangement as described above, in which each first semiconductor switch and / or each second semiconductor switch is a self-conducting semiconductor switch. Furthermore, the power converter arrangement includes a controllable disconnect circuit configured to disconnect an electrical connection between one of the first DC voltage terminals and the second DC voltage terminal and the center terminal of at least one half-bridge when the controllable disconnect circuit is not activated.

[0016] This reduces the effort, especially the control effort, required to bring the power converter arrangement into the safe state, since it is not necessary to control the first and second controllable semiconductor switching elements to activate the safe state.

[0017] Furthermore, the availability of the safe state is increased, since the safe state can also be activated in the event of a failure of the power supply to the converter arrangement or the gate drivers, which are set up to control the controllable first and / or second semiconductor switches.

[0018] This further leads to a reduction in the cost of the power converter arrangement, as additional components, such as a redundant power supply for the power converter arrangement or the gate drivers, or additional fault logic, can be dispensed with.

[0019] Furthermore, in the case of no control, for example if the power supply to the converter arrangement has failed and the gate driver circuit can no longer control the semiconductor switches, no current can flow from or to the voltage source connected to the current directional arrangement, for example a battery of an electric vehicle, thus preventing discharge and / or damage to the battery.

[0020] In one embodiment, each first controllable semiconductor switch is a self-blocking semiconductor switch, and each second controllable semiconductor switch is a self-conducting semiconductor switch. The controllable disconnect circuit comprises at least one or the self-blocking semiconductor switches, i.e., at least one of the second controllable semiconductor switches. Each of the self-blocking semiconductor switches is, in particular, a metal oxide semiconductor field-effect transistor (MOSFET).

[0021] By using self-blocking and self-conducting semiconductor switches, the aforementioned advantages can be achieved simply and without additional components. In the event of a power supply failure to the converter assembly, all semiconductor switches automatically return to their "ground state" without any control input; that is, the self-conducting semiconductor switches are conducting and the self-blocking semiconductor switches are blocking. This creates an active short circuit in the converter assembly via the self-conducting semiconductor switches, without causing a short circuit in the battery.

[0022] In one embodiment, each first controllable semiconductor switch and each second controllable semiconductor switch is a self-conducting semiconductor switch, and the controllable disconnecting circuit has a first controllable disconnecting switch arranged between the first DC terminal and the at least one half-bridge and configured to disconnect an electrical connection between the first DC terminal and the at least one half-bridge when the first controllable disconnecting switch is not controlled.

[0023] By using self-conducting semiconductor switches for all controllable semiconductor switches of the half-bridges, the current-carrying capacity of the converter arrangement can be increased, while still enabling an active short circuit as a safe state without controlling the semiconductor switches of the half-bridges or the isolating circuit. This is because self-conducting semiconductor switches typically have a lower on-resistance than self-blocking semiconductor switches.

[0024] In the safe state, all first and second semiconductor switches can conduct current, thus distributing the current flowing in the safe state across more semiconductor switches. Therefore, when designing the converter assembly, semiconductor switching elements with a lower maximum current can be selected, thereby reducing the cost of the converter assembly.

[0025] In one embodiment, the controllable disconnect switch further comprises a second controllable disconnect switch, which is arranged between the second DC voltage terminal and the at least one half-bridge and is configured to disconnect an electrical connection between the second DC voltage terminal and the at least one half-bridge when the second controllable disconnect switch is not activated. Providing the first or second controllable disconnect switch between a DC voltage terminal and the half-bridges is advantageous because it means that only one switch is required, and the total current between a DC voltage terminal and the half-bridges is significantly lower than the sum of the currents through the first or second semiconductor switches. This allows the single disconnect switch to be implemented with a significantly smaller chip area than would be required for three disconnect switches in the half-bridges.Furthermore, only a control unit with a corresponding power supply is necessary.

[0026] In one embodiment, the first controllable disconnect switch and / or the second controllable disconnect switch comprises a self-blocking semiconductor switch, which is in particular a metal-oxide-semiconductor field-effect transistor. The first and / or second disconnect switch can also be configured as a cascode, i.e., a series connection of a self-blocking and a conducting semiconductor switch. This allows the aforementioned embodiments and their advantages to be implemented in a particularly simple and cost-effective manner. By using a cascode, the flowing current can be distributed across multiple semiconductor switches without increasing the control complexity, thereby improving the service life of the semiconductor switches and saving costs due to a lower current limit for the semiconductor switches.

[0027] In one embodiment, each of the self-conducting semiconductor switches is a junction field-effect transistor, in particular a silicon carbide (SiC) junction field-effect transistor. Junction field-effect transistors have a particularly low on-resistance and low manufacturing costs, which allows the drive unit to be operated very efficiently and the power converter circuit to be manufactured cost-effectively.

[0028] In one embodiment, a smoothing capacitor is arranged in the power converter assembly between the first DC voltage terminal and the second DC voltage terminal. The smoothing capacitor allows the voltage between the first and second DC voltage terminals to be smoothed, thereby enabling particularly efficient operation of the power converter assembly and the drive unit.

[0029] The invention further relates to a method for operating a drive unit comprising an electric machine and a power converter arrangement according to the invention. In the method, it is determined whether a safe state is to be activated, and if it is determined that the safe state is to be activated, the drive unit is brought into the safe state. The safe state is an active short circuit in the power converter arrangement in which all first controllable semiconductor switches and / or all second controllable semiconductor switches are conductive and the controllable disconnect circuit is non-conductive, and in which the first controllable semiconductor switches, the second controllable semiconductor switches, and the disconnect circuit are not controlled.

[0030] This prevents a short circuit between the first DC terminal and the second DC terminal, and thus avoids corresponding damage, if a supply voltage failure occurs in the power converter arrangement and the active short circuit is activated as a safe state.

[0031] In one embodiment, the method further includes checking whether at least one first controllable semiconductor switch or a second controllable semiconductor switch, which is a self-blocking semiconductor, has a fault that prevents the at least one self-blocking semiconductor switch from being switched to the non-conducting state. Such a fault occurs, for example, when a self-blocking semiconductor switch is "short-circuited," i.e., when, due to the influence of heat, the drain and source of the self-blocking semiconductor switch are permanently electrically connected and therefore permanently conduct current without a gate-source voltage being applied. When checking the self-blocking semiconductor switches, all of the self-blocking semiconductor switches are specifically checked to see if they have the fault.If it is determined that at least one of the self-blocking semiconductor switches cannot be switched to the non-conductive state, the drive unit is brought into the safe state by switching each self-blocking semiconductor switch of the first controllable semiconductor switches and second controllable semiconductor switches to the conductive state, and each self-conductive semiconductor switch of the first controllable semiconductor switches and second controllable semiconductor switches to the non-conductive state.

[0032] Whenever the terms "connect" or "connected" are used within the scope of this invention, they always refer to an electrical connection, unless otherwise specified.

[0033] The diagnosis of whether a fault exists in a self-locking semiconductor switch is performed, in particular, before the voltage source is disconnected from the converter assembly, for example, by opening a contactor of a battery. Therefore, it can usually only be carried out if the fault that induces the activation of the safe state is not a failure of the converter assembly's supply voltage. Alternatively, the diagnosis can also be performed during normal operation of the drive unit or electric machine. If a fault is detected during operation, the active short circuit on the side of the half-bridge containing the self-locking semiconductor switches can be activated.

[0034] The invention further relates to a method for operating a drive unit comprising an electric machine and a power converter arrangement according to the invention in an embodiment with at least the first disconnect switch. In the method, when all first semiconductor switches are conductive, the first controllable disconnect switch is opened.

[0035] This prevents the phase potentials from being pulled against the potential of the connected first DC voltage terminal during normal PWM operation of the power converter arrangement in the freewheeling state (i.e., all first semiconductor switches closed). This has a positive effect on common-mode interference in the DC power supply, allowing for a more advantageous, and especially smaller, design of the common-mode filter to ensure electromagnetic compatibility.

[0036] The invention further relates to a method for operating a drive unit comprising an electric machine and a power converter arrangement according to the invention with the first and the second controllable disconnect switch. In the method, when all first semiconductor switches are conductive, the first controllable disconnect switch is opened, and when all second semiconductor switches are conductive, the second controllable disconnect switch is opened.

[0037] This prevents the phase potentials from being pulled against the potential of the connected first or second DC voltage terminal during normal PWM operation of the power converter assembly in the freewheeling state (i.e., all first semiconductor switches closed and / or all second semiconductor switches closed). This has a positive effect on common-mode interference in the DC power supply, allowing for a more advantageous, and especially smaller, design of a common-mode filter to ensure electromagnetic compatibility.

[0038] The invention further relates to a drive unit comprising an electric machine, a power converter arrangement according to one of the preceding embodiments, and a computing unit configured to perform all process steps of a method according to one of the preceding embodiments. The computing unit, e.g., a control unit of a motor vehicle, is configured, particularly in terms of programming, to perform a method according to the invention.

[0039] 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.).

[0040] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawing.

[0041] The invention further relates to a drive unit comprising an electric machine, a power converter arrangement and a computing unit, which are set up to carry out the method according to one of the preceding embodiments.

[0042] The invention is schematically illustrated in the drawing using exemplary embodiments and is described below with reference to the drawing.

[0043] Brief description of the drawings

[0044] Figure 1 shows a block diagram of a drive unit according to an embodiment of the invention,

[0045] Figure 2 shows a flowchart of a process according to an embodiment of the invention,

[0046] Figure 3 shows a block diagram of a drive unit according to a further embodiment of the invention,

[0047] Figure 4 shows a block diagram of a drive unit according to a further embodiment of the invention, and Figure 5 shows a flow diagram of a method according to a further embodiment of the invention.

[0048] Embodiments of the invention

[0049] Figure 1 shows a block diagram of a drive unit 100 according to an embodiment of the invention, and Figure 2 shows a flowchart of a method according to an embodiment of the invention that can be carried out with the drive unit 100 of Figure 1. Both figures will be described together below.

[0050] The drive unit 100 comprises an electric machine 1 and a power converter arrangement 20. In the example shown, the electric machine 1 is a three-phase electric machine with three phase windings U, V, W. To supply the electric machine 1 with electrical power, the power converter arrangement 20 is connected via a first and a second DC voltage connection 22a, 22b to a DC voltage source 30, for example a battery, in particular a high-voltage battery, which provides, for example, a voltage of more than 60 V, e.g. 400 V or more. The battery can, for example, be installed in a vehicle in which the drive unit 100 is also installed and supply the entire vehicle with electrical energy.

[0051] The power converter arrangement 20 has three half-bridges 21 II, 21V, 21 W, wherein in each half-bridge 21 II, 21V, 21 W a first controllable semiconductor switch 21 lla, 21 Va, 21 Wa is arranged in a high side of the half-bridge 21 II, 21V, 21 W between the first DC voltage terminal 22a and a mid-terminal 21 Uc, 21 Vc, 21 Wc of the half-bridge 21 II, 21V, 21 W and in a low side of the half-bridge 21 II, 21V, 21 W a second controllable semiconductor switch 21 llb, 21 Vb, 21 Wb is arranged between the second DC voltage terminal 22b and the mid-terminal 21 Uc, 21 Vc, 21 Wc of the half-bridge 21 U, 21V, 21 W. Each phase winding U, V, W of the electrical machine 1 is supplied with electrical power via a center connection 21 Uc, 21 Vc, 21 Wc.The first semiconductor switches 21Ua, 21Va, 21Wa are normally off semiconductor switches, for example MOSFETs, and the second semiconductor switches 21Ilb, 21Vb, 21Wb are normally on semiconductor switches, for example junction field-effect transistors. The first and second semiconductor switches 21Ila, 21Va, 21Wa, 21Ilb, 21Vb, 21Wb are controlled, for example, by a gate driver circuit (not shown). The normally off semiconductor switches can alternatively be arranged on the lower side.

[0052] The power converter arrangement 20 includes a disconnect circuit 24 configured to disconnect the electrical connection between the first DC voltage terminal 22a and each of the center terminals 21Uc, 21Vc, 21Wc when the disconnect circuit 24 is not activated. In the embodiment shown in Figure 1, the disconnect circuit 24 includes the first semiconductor switches 21I1a, 21Va, 21Wa, which are self-blocking semiconductor switches.

[0053] In the converter arrangement 20, a smoothing capacitor 23 is arranged between the first DC voltage terminal 22a and the second DC voltage terminal 22b. The smoothing capacitor 23 serves to smooth the DC voltage and thus improve the operation of the converter arrangement 20 and the electric machine 1.

[0054] The DC voltage source 30 also has a contactor 31 with which the connection between the DC voltage source 30 and, in this case, the first DC voltage terminal 22a can be interrupted, for example, if there is a fault in the drive unit 100 or if the drive unit 100 is to be switched off.

[0055] In step S100 of the procedure, it is determined whether the drive unit 100 should be brought into a safe state, for example, because a fault exists in the converter arrangement 20 or the electric machine 1. The fault could, for example, be an overcurrent fault, which is determined by measurements of the current flowing through the electric machine 1.

[0056] If it is determined that the drive unit 100 is to be brought into a safe state, the drive unit 100 is brought into a safe state in step S110. In this case, the safe state is an active short circuit in the converter arrangement 20, in which all semiconductor switches on either the high-side or the low-side, i.e., either each of the first controllable semiconductor switches 2111a, 21Va, 21Wa or each of the second controllable semiconductor switches 2111b, 21Vb, 21Wb, are switched to a conducting state and all semiconductor switches on the other side are switched to a non-conducting state. In the safe state, none of the first and second semiconductor switches 21 lla, 21 Va, 21 Wa, 21 llb, 21 Vb, 21 Wb are driven, i.e., the gate driver circuits do not apply any voltages between the gate and source of the first and second semiconductor switches 21 lla, 21 Va, 21 Wa, 21 llb, 21Vb, 21Wb.

[0057] Since the first semiconductor switches 2111a, 21Va, 21Wa are normally closed (NC) semiconductor switches, they do not conduct current when no gate-source voltage is applied. The second semiconductor switches 2111b, 21Vb, 21Wb, however, are normally open (DO) semiconductor switches, meaning they conduct current when no gate-source voltage is applied. This creates an active short circuit on the low-side of the converter assembly 20 without causing a short circuit in the DC voltage source 30.

[0058] Before activating the active short circuit, and in particular before the contactor 31 is switched to disconnect the connection between the DC voltage source 30 and the first DC voltage terminal 22a, step S120 checks whether one of the self-blocking semiconductor switches, in the converter arrangement 20 of the embodiment shown in Figure 1, has a fault that prevents the self-blocking semiconductor switch from being switched to the non-conducting state. This can occur, for example, if the semiconductor switch is shorted, i.e., if there is a faulty, permanent conductive connection between the source and drain. Each self-blocking first semiconductor switch 211a, 21Va, 21Wa is expediently checked.

[0059] If it is determined that at least one self-blocking semiconductor switch cannot be switched to the non-conductive state, the drive unit 100 is brought into the safe state in step S111 by switching each self-blocking semiconductor switch (first semiconductor switches 21 lla, 21 Va, 21 Wa) to the conductive state and each self-conductive semiconductor switch (second semiconductor switches 21 llb, 21 Vb, 21 Wb) to the non-conductive state.

[0060] However, this requires a voltage from the DC voltage source 30 or another voltage source, for example a starter or 12V battery of a vehicle in which the drive unit 100 is installed, because the first and second controllable semiconductor switches 21 lla, 21 Va, 21 Wa, 21 llb, 21 Vb, 21 Wb must be controlled, i.e. a voltage must be applied between the gate and source of each of the first and second controllable semiconductor switches 21 lla, 21 Va, 21 Wa, 21 llb, 21 Vb, 21 Wb.

[0061] Figures 3 and 4 each show a block diagram of a drive unit 100 according to a further embodiment of the invention, and Figure 5 shows a flowchart of a method according to a further embodiment of the invention. Both figures will be described together below.

[0062] In contrast to the embodiment of the drive unit 100 shown in Figure 1, in the embodiments shown in Figures 3 and 4 each first and second semiconductor switch 21 lla, 21 Va, 21 Wa, 21 llb, 21 Vb, 21 Wb is a self-conducting semiconductor switch, e.g. a junction field-effect transistor, and therefore conducts current when it is not driven, i.e. no voltage is applied between gate and source.

[0063] To enable a safe state without a battery short circuit, the power converter arrangement 20 of the embodiment shown in Figure 3 includes a disconnect circuit 24 with a first disconnect switch 24a between the first DC voltage terminal 22a and the half-bridges 21 U, 21 V, 21 W. The first disconnect switch 24a is configured to disconnect the electrical connection between the first DC voltage terminal 22a, 22b and the half-bridges 21 U, 21 V, 21 W when the first disconnect switch 24a is not activated. For this purpose, the first disconnect switch is designed as a self-blocking semiconductor switch.

[0064] In a method for operating the drive unit 100, when all of the first controllable semiconductor switches 21 lla, 21 Va, 21 Wa are conductive, the first disconnect switch 24a is opened.

[0065] In the embodiment of the method shown in Figure 5, as in the previous embodiment of Figure 2, in step S100 it is detected whether a safe state is to be activated, and if it is detected that the safe state is to be activated, in step S110 the drive unit 100 is brought into the safe state, which is an active short circuit.

[0066] In this process, the first and second controllable semiconductor switches 2111a, 21Va, 21Wa, 211lb, 21Vb, 21Wb are not activated, i.e., no voltage is applied between gate and source, leaving the first and second controllable semiconductor switches 2111a, 21Va, 21Wa, 211lb, 21Vb, 21Wb in the conducting state. Furthermore, the first disconnect switch 24a is also not activated.

[0067] In contrast to the embodiment shown in Figure 3, the isolating circuit 24 in the embodiment shown in Figure 4 comprises a first isolating switch 24a and a second isolating switch 24b, which is arranged between the second DC voltage terminal 22b and each of the half-bridges 21 II, 21 V, 21 W. Both isolating switches 24a and 24b are again configured to disconnect the electrical connection between the first and second DC voltage terminals 22a and 22b, respectively, when they are not activated. For this purpose, the first isolating switch 24a and the second isolating switch 24b are designed as self-blocking semiconductor switches. It should be noted in this context that one or both of the isolating switches 24a and 24b are sufficient.

[0068] Furthermore, in all embodiments it is conceivable that the first and / or the second disconnect switch 24a, 24b are designed as a cascode, i.e. as a series connection of a self-conducting and a self-blocking semiconductor switch.

[0069] In a method for operating the drive unit, in order to transfer the drive unit 100 into the active short circuit in step S110, none of the first and second controllable semiconductor switches 21 lla, 21 Va, 21 Wa, 21 Ub, 21Vb, 21Wb or the first and second controllable disconnect switches 24a, 24b are controlled.

[0070] Another method for operating the drive unit 100 according to Figures 3 and 4 involves PWM operation, in which the first and second semiconductor switches are alternately opened and closed to enable the desired motor or generator operation of the electric machine 1. With this type of PWM control, so-called freewheeling phases can occur, in which all first or second semiconductor switches are closed. To improve these freewheeling phases, it is provided that when all first controllable semiconductor switches 21Ua, 21Va, 21Wa are conducting, the first disconnect switch 24a is open, and / or when all second controllable semiconductor switches 21Ub, 21Vb, 21Wb are conducting, the second disconnect switch 24b is open. Opening the respective disconnect switch prevents the potentials of the phase windings of the electric machine from being pulled to the DC potential of the terminal.If both disconnect switches are opened, all first and second semiconductor switches can also be opened during the free-running phase, which reduces the current flow per semiconductor switch.

Claims

Claims 1. Converter arrangement (20) for supplying an electrical machine (1) with electrical power, wherein the converter arrangement (20) comprises: a first DC voltage terminal (22a) and a second DC voltage terminal (22b) which are configured to be connected to a DC voltage source, comprising at least one half-bridge (21 II, 21V, 21 W): -- at least one first controllable semiconductor switch (21 lla, 21 Va, 21 Wa) arranged between the first DC voltage terminal (22a) and a center terminal (21 Uc, 21 Vc, 21 Wc) of the half-bridge (21 II, 21 V, 21 W), and -- at least one second controllable semiconductor switch (2111b, 21Vb, 21Wb) arranged between the second DC terminal (22b) and the center terminal (21Uc, 21Vc, 21Wc) of the half-bridge (21U, 21V, 21W), wherein each first semiconductor switch (21Ua, 21Va, 21Wa) and / or each second semiconductor switch (21Ub, 21Vb, 21Wb) is a self-conducting semiconductor switch, a controllable isolating circuit (24) configured to disconnect an electrical connection between one of the first DC terminals (22a) and the second DC terminal (22b) and the center terminal (21Uc, 21Vc, 21Wc) of the at least one half-bridge (21U, 21V, 21W) when the controllable isolating circuit (24) is not controlled is.

2. Power converter arrangement (20) according to claim 1, wherein each first controllable semiconductor switch (21 Ua, 21 Va, 21 Wa) is a self-blocking semiconductor switch and each second controllable semiconductor switch (21 Ub, 21 Vb, 21 Wb) is a self-conducting semiconductor switch, wherein the controllable disconnecting circuit (24) has at least one or the self-locking semiconductor switches.

3. Power converter arrangement (20) according to claim 2, wherein each of the self-blocking semiconductor switches is a metal oxide semiconductor field-effect transistor.

4. Power converter arrangement (20) according to claim 1, wherein each first controllable semiconductor switch (21 lla, 21 Va, 21 Wa) and each second controllable semiconductor switch (21 llb, 21 Vb, 21 Wb) is a self-conducting semiconductor switch, wherein the controllable disconnect circuit (24) has a first controllable disconnect switch (24a) arranged between the first DC voltage terminal (22a) and the at least one half-bridge (21 II, 21V, 21 W) and configured to disconnect the electrical connection between the first DC voltage terminal (22a) and the at least one half-bridge (21 U, 21V, 21 W) when the first controllable disconnect switch (24a) is not controlled.

5. Power converter arrangement (20) according to claim 4, wherein the controllable disconnect circuit (24) has a second controllable disconnect switch (24b) arranged between the second DC voltage terminal (22b) and each of the at least one half-bridge (21 II, 21V, 21W) and configured to disconnect an electrical connection between the second DC voltage terminal (22b) and each of the at least one half-bridge (21 II, 21V, 21W) when the second controllable disconnect switch (24b) is not controlled.

6. Power converter arrangement (20) according to claim 4 or 5, wherein the first controllable disconnect switch (24a) and / or the second controllable disconnect switch (24b) comprises a self-blocking semiconductor switch, which is in particular a metal oxide semiconductor field-effect transistor.

7. Power converter arrangement (20) according to one of the preceding claims, wherein each of the self-conducting semiconductor switches has a junction- Field-effect transistor, in particular a silicon carbide, SiC, junction field-effect transistor.

8. Power converter arrangement (20) according to one of the preceding claims, wherein a smoothing capacitor (23) is arranged between the first DC voltage terminal (22a) and the second DC voltage terminal (22b).

9. Method for operating a drive unit (100) comprising an electric machine (1) and a converter arrangement (20) according to one of the preceding claims, the method comprising: Determine (S100) whether a safe state should be activated, if it is determined that the safe state should be activated, transfer (S110) the drive unit (100) into the safe state, wherein the safe state is an active short circuit in the converter arrangement (20) in which all first controllable semiconductor switches (21 lla, 21 Va, 21 Wa) and / or all second controllable semiconductor switches (21 llb, 21 Vb, 21 Wb) are conducting and the controllable disconnecting circuit (24) is non-conducting, and in which the first controllable semiconductor switches (21 lla, 21 Va, 21 Wa), the second controllable semiconductor switches (21 llb, 21 Vb, 21 Wb) and the disconnecting circuit (24) are not controlled.

10. The method of claim 9 with reference to one of claims 2 or 3, the method further comprising: Check (S120) whether at least one of the first controllable semiconductor switches (21 1lla, 21 Va, 21 Wa) or second controllable semiconductor switch (21 1llb, 21 Vb, 21 Wb), which is a self-blocking semiconductor switch, has a fault that prevents the at least one self-blocking semiconductor switch from being switched to the non-conducting state, and, if it is determined that at least one of the self-blocking semiconductor switches cannot be switched to the non-conducting state, transfer (S130) the drive unit (100) to the safe state by transferring each self-blocking semiconductor switch of the first controllable semiconductor switches (21 1lla, 21 Va, 21 Wa) and second controllable Semiconductor switches (21 lib, 21 Vb, 21 Wb) into the conducting state and each self-conducting semiconductor switch of the first controllable semiconductor switches (21 lla, 21 Va, 21 Wa) and second controllable semiconductor switches (21 llb, 21 Vb, 21 Wb) into the non-conducting state.

11. Method for operating a drive unit (100) comprising an electric machine (1) and a converter arrangement (20) according to any one of claims 1 to 8, with reference to at least claim 4, the method comprising: Opening the first controllable disconnect switch (24a) when all first semiconductor switches (24Ua, 24Va, 24Wa) are conductive.

12. Method for operating a drive unit (100) comprising an electric machine (1) and a converter arrangement (20) according to any one of claims 1 to 8, with reference to at least claim 5, the method comprising: Opening the first controllable disconnect switch (24a) when all first semiconductor switches (24Ua, 24Va, 24Wa) are conductive; Opening the second controllable disconnect switch (24b) when all second semiconductor switches (24Ub, 24Vb, 24Wb) are conductive.

13. Drive unit (100) comprising an electric machine (1), a power converter arrangement (20) according to one of claims 1 to 8 and a computing unit configured to perform all process steps of a method according to one of claims 9 to 12.

14. Computer program that causes the computing unit of the drive unit (100) according to claim 13 to perform all process steps of a method according to any one of claims 9 to 12 when executed on the computing unit.

15. Machine-readable storage medium with a computer program stored thereon according to claim 14.

Images