METHOD FOR OPERATING A DRIVE UNIT, POWER DIRECTOR ARRANGEMENT AND DRIVE UNIT

Abstract

The invention relates to a method for operating a drive unit comprising a power converter arrangement and an electric machine connected to the power converter arrangement. The power converter arrangement (1000) comprises a power converter circuit (100) with at least one half-bridge (20U, 20V, 20W) having a low side and a high side, the latter having a first and second controllable semiconductor switching element (21U, 21V, 21W), respectively, arranged between a first and second DC voltage terminal (B+, B-) and a center terminal (24U, 24V, 24W). The low side has a current sensor (23U, 23V, 23W) arranged in series with the first controllable semiconductor switching element (21U, 21V, 21W). The power converter circuit further comprises at least one gate driver circuit (25) which is configured to drive at least some of the first and / or the second controllable semiconductor switching elements (22U, 22V, 22W).The converter arrangement (1000) further comprises a machine control unit (10) configured to control the converter circuit (100). In this process, the currents detected by the current sensors (23U, 23V, 23W), a variety of temperature values, and a variety of fault signals are received, and, depending on the received values, it is determined whether a fault exists in the converter arrangement. If a fault is determined in the converter arrangement, a type of safe state is determined based on a rotational speed of the electric machine, and the high-speed and / or low-speed side on which the safe state should be set is specified. The converter circuit is then switched to the specified safe state.

Description

[0001] The present invention relates to a method for operating a drive unit, a power converter arrangement and a drive unit. Background of the invention

[0002] Power converter circuits, such as DC or AC converters, are electrical circuits used to convert one type of electrical current into another, for example, from direct current to alternating current or vice versa. These circuits can utilize, for instance, one or more half-bridges connected in parallel. A half-bridge consists of two switches connected in series to a voltage source, with the center terminal between the two switches providing the AC voltage connection.

[0003] Traditionally, three-phase converter circuits have three half-bridges (one for each phase), each comprising a high-side and a low-side. The high-side contains one or more parallel high-side switching elements, and the low-side contains one or more parallel low-side switching elements. The number of switching elements used is determined by the maximum load current that will flow through the converter circuit. The number of half-bridges is conveniently determined by the number of phase windings of the electrical machine that is supplied with electrical power by the converter circuit. For example, converter circuits for a six-phase electrical machine have six half-bridges.

[0004] In the event of a fault in the converter circuit, the converter circuit should be switched to a safe state. For example, the safe state consists of actively short-circuiting the phases of the electrical machine by either closing all low-side switches or all high-side switches, i.e., switching them to the conducting state, in order to prevent high overvoltages on the DC link and the switches. Alternatively, the converter circuit can also be operated as a passive rectifier. In this case, all switching elements are switched to the non-conducting state.

[0005] Power converter circuits can have protective functions to safeguard against faults such as overcurrent, overvoltage, internal gate driver circuit errors, etc. If these protective functions detect a fault, all relevant components of the power converter circuit, and possibly a higher-level machine control unit (MCU), should be informed of the fault, for example, by activating a shutdown path unit. There are various ways to implement such a shutdown path unit, for example, by using logic within the MCU and / or an external circuit. A signal command can be sent to the gate driver circuit to initiate the safe state. Disclosure of the invention

[0006] According to the invention, a method for operating a drive unit, a power converter arrangement, and a drive unit with the features of the independent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

[0007] The invention relates to a drive unit comprising a power converter arrangement and an electric machine connected to the power converter arrangement. The power converter arrangement includes a power converter circuit and a machine control unit configured to control the power converter circuit. The power converter arrangement thus represents, in particular, the entire device (so-called inverter), including the housing and connections to which the electric machine and a DC power supply are to be connected.

[0008] The converter circuit comprises at least one half-bridge, which has a low-side and a high-side, with a center terminal between them. The converter circuit is specifically designed to supply phase windings of the electric machine with an output current via the center terminals. The number of half-bridges expediently corresponds to the number of phase windings of the electric machine.

[0009] The low side features a first controllable semiconductor switching element arranged between a first DC voltage terminal and the center terminal of the converter circuit. Furthermore, the low side features a current sensor connected in series with the first controllable semiconductor switching element and configured to measure the current flowing through the first controllable semiconductor switching element. For example, the current sensor may include a shunt resistor across which a voltage drop is detected, from which the current can be determined. The high side features a second controllable semiconductor switching element arranged between a second DC voltage terminal and the center terminal.While in this context and in the following sections, one first and one second controllable semiconductor switching element per half-bridge are described, the number of first and / or second controllable semiconductor switching elements is not limited to a single first and second controllable semiconductor switching element. Rather, the number of (then parallel) semiconductor switching elements depends on the maximum load current that is to flow through each half-bridge. If a half-bridge has several first and / or second controllable semiconductor switching elements, these are connected in parallel to each other between the corresponding DC voltage terminal and the center terminal. Each low side can still only have one current sensor, which detects the total current flowing through all first controllable semiconductor switching elements, i.e., is connected in series with the parallel connection of all first controllable semiconductor switching elements.

[0010] Furthermore, the power converter circuit includes at least one gate driver circuit configured to control at least some of the first and / or second controllable semiconductor switching elements, i.e., to switch between a conducting and a non-conducting state. The gate driver circuits can be designed, for example, as circuits with individual semiconductor switching element drivers, i.e., with individual gate drivers for each semiconductor switching element. In multiphase power converter circuits, the semiconductor switching elements can also be controlled by multiple 3-phase gate driver circuits. For example, in a six-phase electric machine with its associated six half-bridges, three half-bridges can be controlled by a single 3-phase gate driver circuit.Each 3-phase driver circuit can still be implemented with auxiliary transistors such as level shifters in combination with amplifiers or a conventional integrated circuit.

[0011] The core of the invention consists in combining a multitude of quantities, such as the current flowing through the first controllable semiconductor switching elements and the temperature values ​​of various components of the drive unit, as well as a multitude of error signals, and in using these quantities and error signals to determine whether a fault is present in the drive unit, and, if a fault is present, to determine what type of safe state should be set on which side (high and / or low side) of the converter circuit.

[0012] By combining the multitude of parameters and error signals, a single sum error signal for the entire drive unit can be determined and output to all relevant points, thereby enabling the drive unit to be brought into a safe state efficiently in the event of a fault.

[0013] By positioning the current sensors on the low side of the converter circuit, the current flowing in the converter arrangement can be determined more cost-effectively, in contrast to phase current sensors located between the center terminal and the electrical machine.

[0014] Furthermore, the use of a current sensor in each half-bridge makes it possible to estimate the current flowing through the half-bridges based on the currents detected by the remaining current sensors, even if one or two current sensors fail.

[0015] Furthermore, by determining the appropriate safe state for the respective situation, the thermal stress of the semiconductor switching elements can be reduced, thereby improving the service life of the semiconductor switching elements or the entire power converter assembly.

[0016] Specifically, the process involves receiving the current values ​​recorded by the current sensors, the numerous temperature readings, and the numerous error signals indicating whether a fault exists in one or more parts of the drive unit. Based on these readings, the system determines whether a fault exists in the drive unit. If a fault is determined to exist in the drive unit, the system then determines, based on the rotational speed of an electric machine, whether the safe state should be an active short circuit or a state in which the converter circuit operates as a passive rectifier.Subsequently, if it is determined that the safe state is an active short circuit, it is determined on which of the high and / or low sides the safe state should be set, and the converter circuit is switched to the determined safe state.

[0017] The procedure allows a cumulative "cumulative error" to be determined and, furthermore, the "correct", i.e., the safe state most suitable for the respective situation, to be determined and set.

[0018] The invention further relates to a power converter arrangement comprising a power converter circuit with at least one half-bridge having a high side and a low side. The low side has a first controllable semiconductor switching element arranged between a first DC voltage terminal and a center terminal of the power converter circuit, and a current sensor connected in series with the first controllable semiconductor switching element and configured to detect the current flowing through the first controllable semiconductor switching element. The high side has a second controllable semiconductor switching element arranged between a second DC voltage terminal and the center terminal.The power converter circuit further comprises at least one gate driver circuit configured to control at least a portion of the first controllable semiconductor switching elements and / or the second controllable semiconductor switching elements. The power converter arrangement further comprises a machine control unit configured, particularly in terms of programming, to perform all process steps of a method according to the invention.

[0019] The invention further relates to a drive unit comprising an electric machine and the power converter arrangement.

[0020] In one embodiment, the plurality of temperature values ​​comprises temperature values ​​from one or more, in particular all, of the first controllable semiconductor switching elements and / or the second controllable semiconductor switching elements, one or more windings of the electric machine, a printed circuit board on which the at least gate driver circuit is mounted, and / or an ambient temperature. The temperature values ​​can be detected, in particular, by several temperature sensors installed in the drive unit.

[0021] In one embodiment, the plurality of error signals includes error signals that indicate a fault in one or more components of the machine control unit software, the machine control unit memory, a power supply and / or the power converter circuit.

[0022] This allows the temperature and fault signals to be used to precisely determine in which part of the drive unit a fault exists, and thus the most suitable safe state can be determined.

[0023] In one embodiment, the fault signal indicating a fault in the power converter circuit is output by the gate driver circuit when, in particular by the gate driver circuit, it is determined that there is an overvoltage in the power converter circuit, a fault in one or more of the first controllable semiconductor switching elements and / or the second controllable semiconductor switching elements and / or a fault in the gate driver circuit.

[0024] This makes it possible, in particular, to determine directly in the at least one gate driver circuit that a fault exists in a part of the power converter circuit.

[0025] In one embodiment, when determining whether a fault exists in the power converter arrangement, a fault is determined to exist in the drive unit if one or more of the received currents exceed a current threshold value, and / or one or more of the multiple temperature values ​​exceed a temperature threshold associated with the temperature value, and / or one or more of the multiple fault signals indicate a fault. The current threshold value depends in particular on the semiconductor switching elements used and can, for example, be the same for all semiconductor switching elements.The temperature thresholds are different temperature thresholds for the temperature values, since, for example, a threshold for the semiconductor switching element temperature may be 170°C, while the temperature of the circuit board on which the gate driver circuit and microcontroller are mounted, or the ambient temperature, may be significantly lower.

[0026] This allows a fault in the drive unit to be identified in a simple and effective way.

[0027] In one embodiment, determining on which high side and / or low side the safe state is to be set includes determining whether one or more of the first controllable semiconductor switching elements and / or one or more of the second controllable semiconductor switching elements and / or one or more of the gate driver circuits have a fault. If it is determined that neither of the first nor the second controllable semiconductor switching elements has a fault, it is determined that the active short circuit is to be set alternately on the low side and the high side. If it is determined that one or more of the first controllable semiconductor switching elements or a gate driver circuit has a fault that causes the first controllable semiconductor switching element to be permanently in a non-conducting state, it is determined that the active short circuit is to be set on the high side. If, however, it is determined thatIf it is determined that one or more of the second controllable semiconductor elements or a gate driver circuit have a fault that causes the second controllable semiconductor element to be permanently in a non-conducting state, it is determined that the active short circuit should be set in the low side. If it is determined that a first controllable semiconductor element and / or a gate driver circuit has a fault that causes the first controllable semiconductor element to be permanently in a conducting state, it is determined that the active short circuit should be set in the low side without driving the first controllable semiconductor element and the second controllable semiconductor element of the half-bridge containing the faulty first controllable semiconductor element.If a second controllable semiconductor switching element and / or a gate driver circuit has a fault that causes the second controllable semiconductor switching element to be permanently in a conducting state, it is determined that the active short circuit without controlling the first controllable semiconductor switching element and the second controllable semiconductor switching element of the half-bridge containing the faulty second controllable semiconductor switching element should be set on the high side.

[0028] This allows the most suitable safe state for the given situation to be determined if a fault occurs in one or more of the controllable semiconductor switching elements.

[0029] In one embodiment, transitioning the converter circuit to the specified safe state comprises switching each of the first controllable semiconductor switching elements of the converter circuit and each of the second controllable semiconductor switching elements of the converter circuit to the non-conducting state, if the safe state is defined as a state in which the converter circuit operates as a passive rectifier. If the safe state is defined as an active low-side short circuit, each of the first controllable semiconductor switching elements is switched to the conducting state and each of the second controllable semiconductor switching elements is switched to the non-conducting state.If an active short circuit on the high side is defined as the safe state, each of the first controllable semiconductor switching elements is switched to the non-conducting state and each of the second controllable semiconductor switching elements is switched to the conducting state. If an active short circuit on both the low and high sides is defined as the safe state, each of the first controllable semiconductor switching elements and each of the second controllable semiconductor switching elements is switched back and forth between the conducting and non-conducting states at a predetermined frequency such that at any given time either each of the first controllable semiconductor switching elements or each of the second controllable semiconductor switching elements is in the conducting state.

[0030] This allows the power converter circuit to be switched to the most suitable safe state in any situation. By alternately switching the first and second controllable semiconductor switching elements, the electrical and thermal load can be distributed across more semiconductor switching elements, allowing them to be designed for lower loads and increasing their service life.

[0031] In one embodiment, the converter circuit comprises a first half-bridge group with three half-bridges, a second half-bridge group with three half-bridges, a first gate driver circuit configured to drive the semiconductor switching elements of the first half-bridge group, and a second gate driver circuit configured to drive the semiconductor switching elements of the second half-bridge. Determining whether a fault exists in the converter arrangement includes determining whether the fault is located in the first half-bridge group and / or the second half-bridge group and / or the machine control unit. When transitioning the converter circuit to the specified safe state, the first half-bridge group is transitioned to the safe state if the fault is located only in the first half-bridge group. If the fault is located only in the second half-bridge group, only the second half-bridge group is transitioned to the safe state.The half-bridge group that is not faulty can continue to be controlled to operate the electric machine at reduced power. Alternatively, both half-bridge groups can be brought to a safe state. If the fault is located in the first half-bridge group and / or the second half-bridge group and / or the machine control unit and / or in one or more other parts of the drive unit, both the first and second half-bridge groups are brought to a safe state. The other parts of the drive unit could be, for example, the connection to the machine control unit or the electronic control unit of the vehicle in which the drive unit is installed, which, if interrupted, would result in a fault.Furthermore, the safe state can be set in the high or low side if one of the gate drivers of the power converter circuit or an integrated power management circuit (PMIC) is defective.

[0032] This allows the electric machine to continue operating at a reduced power level if only part of the drive unit is faulty.

[0033] In one embodiment, the power converter circuit comprises a first half-bridge group with three half-bridges, a second half-bridge group with three half-bridges, a first gate driver circuit configured to drive the semiconductor switching elements of the first half-bridge group, and a second gate driver circuit configured to drive the semiconductor switching elements of the second half-bridge.

[0034] The method according to the invention can also be implemented as a computer program or computer program product on which a program code is stored which, when executed by the machine control unit, causes the machine control unit to carry out all steps of the method according to the invention.

[0035] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawing.

[0036] The invention is schematically illustrated in the drawing using exemplary embodiments and is described below with reference to the drawing. Brief description of the drawings Fig. Figure 1 shows a block diagram of an embodiment of a drive unit that is set up to carry out the method according to the invention. Fig. Figure 2 shows a block diagram of a further embodiment of a drive unit which is set up to carry out the method according to the invention, Fig. Figure 3 shows a block diagram of a machine control unit and two gate driver circuits according to one embodiment in detail. Fig. Figure 4 shows a block diagram of a safe-state aggregator of a machine control unit of one embodiment in detail, and Fig. Figure 5 shows a flowchart of an embodiment of the method according to the invention. Detailed description of the drawing

[0037] Fig. Figure 1 shows a block diagram of an embodiment of a drive unit configured to carry out the method according to the invention. The drive unit comprises an electric machine 1 and a converter arrangement 1000. The converter arrangement 1000 comprises a converter circuit 100 and a machine control unit 10, which is configured to control the converter circuit 100.

[0038] The converter circuit 100 is connected on one input side to a first DC voltage terminal B-, which is in particular a ground terminal, and a second DC voltage terminal B+. On one output side, the converter circuit 100 is connected to the electric machine 1. In the illustrated embodiment, the electric machine 1 is a three-phase electric machine with phase windings U, V, and W. The converter circuit 100 is configured to convert the DC voltage applied to the first DC voltage terminal B- and the second DC voltage terminal B+ into a three-phase AC voltage, which is supplied to the electric machine 1, and vice versa. In particular, the converter arrangement 1000 represents a device (so-called inverter) that may have a housing (not shown) from which the DC voltage terminals and the terminals for connecting the electric machine are brought out.

[0039] The power converter circuit 100 has a half-bridge 20U, 20V, 20W with a low side and a high side for each phase. Each of the low sides has a first controllable semiconductor switching element 21U, 21V, 21W. The first controllable semiconductor switching element 21U, 21V, 21W is arranged between the first DC voltage terminal B- and a center terminal 24U, 24V, 24W of the power converter circuit 100. The power converter circuit 100 is connected to the electric machine 1 via the center terminal 24U, 24V, 24W. Each first controllable semiconductor switching element 21U, 21V, 21W is connected in series with a current sensor 23U, 23V, 23W, which is configured to detect a current flowing through the first controllable semiconductor switching element 21U, 21V, 21W. For example, the current sensor 23U, 23V, 23W can have a shunt resistor, whereby a voltage drop across the shunt resistor can be measured and converted into a current.On the high side, a second controllable semiconductor switching element 22U, 22V, 22W is arranged between the second DC voltage terminal B+ and the center terminal 24U, 24V, 24W.

[0040] Furthermore, the power converter circuit 100 includes a gate driver circuit 25, which is configured to control the first and second controllable semiconductor switching elements 21U, 21V, 21W, 22U, 22V, 22W. The gate driver circuit 25 is specifically configured to control the first and second controllable semiconductor switching elements 21U, 21V, 21W, 22U, 22V, 22W individually. For this purpose, the gate driver circuit 25 includes, for example, a gate driver for each controllable semiconductor switching element that is to be controlled by the gate driver circuit 25. The connections of the gate driver circuit 25 to the first and second controllable semiconductor switching elements 21U, 21V, 21W, 22U, 22V, 22W are labeled S1. The currents detected by the current sensors 23U, 23V, 23W are transmitted to the gate driver circuit 25 via connections S2.The gate driver circuit 25 transmits the detected current strengths to the machine control unit 10 via connections S3.

[0041] The power converter circuit 100 also has a capacitor 30, which is arranged between the first DC voltage terminal B- and the second DC voltage terminal B+ and through which the DC voltage is buffered and smoothed.

[0042] The machine control unit 10 outputs a control signal, in particular a pulse width modulation (PWM) signal, at connection S4. Based on this signal, the gate driver circuit 25 controls the first and second controllable semiconductor switching elements 21U, 21V, 21W, 22U, 22V, 22W via connections S1. Furthermore, the machine control unit 10 receives from the gate driver circuit 25, via connection S5, a multitude of error signals concerning the gate driver circuit 25 and / or the first and second controllable semiconductor switching elements 21U, 21V, 21W, 22U, 22V, 22W, and a multitude of temperature values ​​via connection S6, as well as a multitude of other error messages from other parts of the drive unit via connection S7.Depending on the detected currents, the multitude of fault signals, and the multitude of temperature values, the machine control unit determines whether a fault exists in the drive unit and, if a fault is determined, which type of safe state—active short circuit or operation as a passive rectifier—should be set, and on which side of the converter circuit (high and low). For this purpose, the machine control unit 10 outputs a request signal via connection S8 to the gate driver circuit 25, requesting a safe state and indicating the type of safe state. Via connection S9, the gate driver circuit 25 also receives information from the machine control unit 10 regarding whether the safe state should be set on the high and / or low side.

[0043] Fig. Figure 2 shows a block diagram of a further embodiment of a drive unit configured to carry out the method according to the invention. The structure of the drive unit essentially corresponds to that shown in Figure 2. Fig. The drive unit shown in point 1 will be discussed here, so only the differences will be addressed.

[0044] In contrast to the in Fig. In the embodiment of the drive unit shown in 1, the electric machine 1' is the one shown in Fig. In the embodiment shown in Figure 2, a six-phase electric machine 1' is used. The converter circuit 100' further comprises six half-bridges 20U, 20V, 20W, 20X, 20Y, 20Z to supply the electric machine 1' with a six-phase alternating voltage. The half-bridges 20U, 20V, 20W, 20X, 20Y, 20Z are divided into a first half-bridge group 20a and a second half-bridge group 20b, each comprising three of the six half-bridges 20U, 20V, 20W, 20X, 20Y, 20Z. Each of the half-bridges 20U, 20V, 20W, 20X, 20Y, 20Z has a low side and a high side. Each lower side again has a first controllable semiconductor switching element 21U, 21V, 21W, 21X, 21Y, 21Z and a current sensor 23U, 23V, 23W, 23X, 23Y, 23Z, which, as in the embodiment of the Fig. 1 are interconnected. Each high side has a second controllable semiconductor switching element 22U, 22V, 22W, 22X, 22Y, 22Z.

[0045] To control the first and second semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z, 22U, 22V, 22W, 22X, 22Y, 22Z, the power converter circuit 100' comprises a first gate driver circuit 25a and a second gate driver circuit 25b. The first gate driver circuit 25a is configured to control the first and second semiconductor switching elements 21U, 21V, 21W, 22U, 22V, 22W of the first half-bridge group 20a, and the second gate driver circuit 25b is configured to control the first and second semiconductor switching elements 21X, 21Y, 21Z, 22X, 22Y, 22Z of the second half-bridge group 20b. As in the embodiment of the Fig. 1. The currents detected by the current sensors 23U, 23V, 23W, 23X, 23Y, 23Z are output to the respective gate driver circuit 25a, 25b via the connections S2 of the corresponding half-bridge group 20a, 20b, which then pass them on to the machine control unit 10 via the connections S3.

[0046] Fig. Figure 3 shows a block diagram of a machine control unit 10 and two gate driver circuits 25a, 25b according to one embodiment in detail.

[0047] The machine control unit 10 comprises a power converter control unit 11, a safe-state aggregator 12, an analog-to-digital converter 13 (A / D converter), and a digital input / output (DIP) port 14. The power converter control unit 11 is configured to generate a control signal and output it to the gate driver circuits 25a and 25b via connection S4. These gate driver circuits individually control the first and second semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z, 22U, 22V, 22W, 22X, 22Y, and 22Z based on the control signal received via connection S1. Furthermore, the power converter control unit 11 can receive register data from the gate driver circuits 25, 25a, 25b via a connection S10, indicating which of the first and second controllable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z, 22U, 22V, 22W, 22X, 22Y, 22Z has a fault and, if applicable, which fault.The converter control unit 11 can transmit this information to the safe-state aggregator 12 via connection S11. Furthermore, the converter control unit 11 is configured to receive and analyze warning signals from the gate driver circuits 25, 25a, and 25b, and to implement load reduction if necessary. The A / D converter 13 also receives numerous temperature values ​​via connection S19 and, if an overtemperature is detected, outputs them to the safe-state aggregator 12.

[0048] In the first and second gate driver circuits 25a, 25b, a determination is made, based on a multitude of signals received via connections S12, as to whether a fault exists in the power converter circuit 100', i.e., in the first or second gate driver circuits 25a, 25b, or in one of the first or second controllable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z, 22U, 22V, 22W, 22X, 22Y, 22Z, which are controlled by the first or second gate driver circuits 25a, 25b. For this purpose, fault detection units 251a, 251b of the gate driver circuits 25a, 25b receive, for example, a signal indicating whether an overvoltage is present. Furthermore, the fault detection units 251a, 251b each receive a gate driver fault signal, which indicates whether there is an internal fault in the first and / or second gate driver circuit 25a, 25b.The fault detection units 251a, 251b continue to receive semiconductor switching element fault signals via connections S12, indicating whether one or more of the first and second semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z, 22U, 22V, 22W, 22X, 22Y, 22Z are stuck in a conductive or non-conductive state, i.e., can no longer be switched, or whether a current is flowing through one of the first semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z which is outside a normal range. If one of the fault detection units 251a, 251b detects that a fault is indicated by one or more of the semiconductor switching element fault signals received via connections S12, the fault detection unit 251a, 251b in question outputs a gate driver sum fault signal to the digital input / output terminal 14 of the machine control unit 10, in particular connection S5.The gate driver sum error signal is output to the power converter control unit 11 and via a connection S17 to the safe-state aggregator 12.

[0049] The currents measured by the current sensors 23U, 23V, 23W in the first half-bridge 20a, which are present primarily as voltage drops across the shunt resistors, are output via connections S2 to the first gate driver circuit 25a. This circuit amplifies the currents in an amplifier 252a and outputs them as analog current signals via connections S3 to the A / D converter 13 of the machine control unit 10. The currents measured by the current sensors 23X, 23Y, 23Z in the second half-bridge 20b are again output via connections S2 to the second gate driver circuit 25b. This circuit amplifies the currents in an amplifier 252b and outputs them as analog current signals via connections S3 to the A / D converter 13 of the machine control unit 10. The currents received by the A / D converter 13 are passed on to the power converter control unit 11 via a connection S14 and to the safe-state aggregator 12 via a connection S15.Alternatively, the received current values ​​can also be transmitted directly from the A / D converter 13 to the safe-state aggregator 12, i.e., from the A / D converter 13 to the power converter control unit 11 and the safe-state aggregator 12.

[0050] Each of the first and second gate driver circuits 25a, 25b can also output a warning signal to the machine control unit 10 via a connection S13, for example, if the temperature of the gate driver circuit 25a, 25b exceeds a gate driver circuit temperature threshold. Based on the warning signal, the machine control unit 10 can determine, for example, whether the power in the converter circuit 100' should be reduced.

[0051] The machine control unit 10 receives the measured currents from the gate driver circuits 25a and 25b via connections S3 at the A / D converter 13, and furthermore the gate driver sum error signal via connection S5, a multitude of temperature values ​​via connection S6, and a multitude of error signals from other parts of the drive unit via connection S7. Based on the received values, the safe-state aggregator 12 determines whether a fault exists in the drive unit and whether the converter circuit 100' should be switched to a safe state. If it is determined that the converter circuit 100' should be switched to a safe state, it determines which safe state the converter circuit 100' should be switched to and, if applicable, on which side (high or low) the safe state should be set.

[0052] In particular, the safe-state aggregator 12 can determine that a fault exists only in one of the first and second half-bridge groups 20a, 20b, and transfer only this half-bridge group to the safe state, while the other half-bridge group continues to operate in normal operation.

[0053] While the embodiment with two gate driver circuits 25a, 25b is shown here, the described elements can also be transferred to the power converter arrangement 1000, which has only one gate driver circuit 25.

[0054] Fig. Figure 4 shows a block diagram of a safe-state aggregator 12 of a machine control unit 10 of an embodiment in detail, and Fig. Figure 5 shows a flowchart of an embodiment of the method according to the invention. Both figures will be described together in the following.

[0055] In step S100, the machine control unit 10, in particular the safe-state aggregator 12 of the machine control unit 10, receives the current intensities detected by the current sensors 23U, 23V, 23W, 23X, 23Y, 23Z, a variety of temperature values ​​and a variety of error signals.

[0056] The currents detected by the current sensors 23U, 23V, 23W, 23X, 23Y, 23Z are fed via connection S15 to an overcurrent detection unit 125 of the safe-state aggregator 12.

[0057] The multitude of temperature values ​​includes, for example, one or more temperature values ​​of one or more of the first controllable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z and / or the second controllable semiconductor switching elements 22U, 22V, 22W, 22X, 22Y, 22Z, temperature values ​​of one or more of the phase windings of the electric machine 1, 1', temperature values ​​of a circuit carrier (such as a printed circuit board) on which the gate driver circuit 25, 25a, 25b is mounted, and / or an ambient temperature. The multitude of temperature values ​​is supplied via connection S19 to a temperature fault detection unit 126 of the safe-state aggregator 12.

[0058] The numerous error signals from other parts of the drive unit include, for example, one or more error signals indicating a fault in the software of the machine control unit 10, an error signal indicating a fault in a memory of the machine control unit 10, an error signal indicating a fault in a power supply, and / or an error signal indicating a fault in the converter circuit 100, 100'. These error signals are fed via connection S7 to a summation error determination unit 121 of the safe-state aggregator 12.

[0059] The gate driver sum fault signal is fed to a gate driver circuit fault detection unit 124 via connection S17. Furthermore, modern gate driver circuits can report the status of registers containing protection functions to the machine control unit 10 or the power converter control unit 11 via SPI communication (Serial Peripheral Interface). For example, if a gate driver signal fault, a semiconductor switching element fault, or an overvoltage fault occurs, the register bit corresponding to this function is changed, and the machine control unit 10 can read the updated register status map and determine which protection has been triggered. The semiconductor switching element fault detection unit 123a is connected (connection S11) to the registers and can determine from the register data in which or whichwhich of the first and / or second semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z, 22U, 22V, 22W, 22X, 22Y, 22Z has a fault.

[0060] Subsequently, in step S110, depending on the received currents, the multitude of temperature values ​​and the multitude of error signals, it is determined whether a fault exists in the drive unit, whereby it is determined that a fault exists in the drive unit if one or more of the received currents are above a current threshold value and / or one or more of the multitude of temperature values ​​are above a temperature threshold value and / or one or more of the multitude of error signals indicate a fault.

[0061] The process determines whether one or more of the received currents exceed a current threshold. To do this, the received currents are compared with the current threshold in the overcurrent detection unit 125. The current threshold is, in particular, a predetermined threshold for all of the first addressable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z. It is also possible to use an individual current threshold for each of the first addressable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z. If it is determined that one or more of the detected currents exceeds the corresponding current threshold, the overcurrent detection unit 125 outputs an overcurrent error signal to the sum error determination unit 121, indicating that an overcurrent error has occurred, i.e., that one or more of the received currents exceed a current threshold.To avoid unwanted transient phenomena, the signal can be sent with a predetermined time delay, i.e., if the overcurrent only exists for a short period and the current falls below the current threshold again within the time delay period, the signal indicating that one or more of the detected currents show an overcurrent is not sent to the safe-state aggregator 12.

[0062] Furthermore, it is determined whether one or more of the numerous temperature values ​​exceed a temperature threshold. Since the temperature values ​​are from various components of the drive unit, it is expedient to have an individual temperature threshold for each component. In the temperature fault detection unit 126, for example, the temperature values ​​of the first and second controllable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z, 22U, 22V, 22W, 22X, 22Y, 22Z are compared with a semiconductor switching element temperature threshold.Furthermore, the temperature of the phase windings of the electric machine 1, 1' is compared to a winding temperature threshold, the temperature of the circuit carrier on which the gate driver circuit 25, 25a, 25b and microcontroller are mounted is compared to a gate driver circuit temperature threshold, and the ambient temperature is compared to an ambient temperature threshold. The ambient temperature can also be used to adjust the thresholds. If it is determined that one or more of the multiple temperature values ​​exceeds the corresponding temperature threshold, the temperature fault detection unit 126 outputs a temperature fault signal to the total fault determination unit 121, indicating that a temperature fault is present in one or more components of the drive unit.Like the overcurrent fault signal, the temperature fault signal can be transmitted with a time delay. This prevents the converter circuit 100, 100' from being switched directly to a safe state even by brief temperature spikes in one or more components. The time delay can be the same as that used for the overcurrent fault signal. Alternatively, separate time delays can be used for the overcurrent fault signal and the temperature fault signal.

[0063] Furthermore, the converter circuit fault detection unit 124 determines whether one or more of the converter circuit fault signals output by the gate driver circuits 25, 25a, 25b indicate that a fault exists in the converter circuit 100, 100'. If it is determined that one or more of the converter circuit fault signals indicate that a fault exists in the converter circuit 100, 100', the converter circuit fault detection unit 124 outputs a summation drive unit fault signal to the summation fault determination unit 121 and the converter control unit 10. If the converter control unit 10 receives the summation drive unit fault signal, it stops sending control signals to the gate driver circuits 25, 25a, 25b.

[0064] The summation fault determination unit 121 then determines that a fault exists in the drive unit if the overcurrent fault signal, the temperature fault signal, the overall converter circuit fault signal, or any of the other received fault signals indicates that a fault is present. If the summation fault determination unit 121 determines that a fault exists in the drive unit, it outputs a summation fault signal indicating that a fault exists in the drive unit to the safe state determination unit 122 via connection S16. Furthermore, the summation fault signal is also sent to the converter control unit 11 (see...). Fig.3) outputs signals which, if the sum error signal indicates that there is a fault in the drive unit, interrupt or stop the transmission of the pulse width modulation signals to the gate driver circuits 25, 25a, 25b or, if operation as a rectifier is to be set as a safe state, output signals to the gate driver circuits 25, 25a, 25b so that these control the first and second controllable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z, 22U, 22V, 22W, 22X, 22Y, 22Z accordingly.

[0065] The sum fault determination unit 121, the power converter circuit fault detection unit 124, the overcurrent detection unit 125 and the temperature fault detection unit 126 can be designed as software-based OR logic or as a hardware-based OR gate.

[0066] If it is determined that there is a fault in the drive unit, in step S120, depending on a rotational speed of the electric machine 1, 1', which is received from the electric machine 1, 1' via a connection S18, it is determined whether the safe state should be an active short circuit or a state in which the converter circuit 100, 100' is operated as a passive rectifier.

[0067] The safe state determination unit 122 receives the rotational speed of the electric machine 1, 1' and compares it to a speed threshold. If the rotational speed is above or equal to the speed threshold, an active short circuit is determined as the safe state. In this case, the safe state determination unit 122 outputs a side determination signal to the side determination unit 123, indicating that an active short circuit has been determined as the safe state and that it is to be determined on which side of the half-bridge the safe state should be set. Furthermore, the safe state determination unit 122 outputs a safe state signal to the gate driver circuits 25, 25a, 25b via connection S8, indicating that an active short circuit should be set as the safe state.

[0068] If the rotational speed is below the speed threshold, the safe state is determined to be the operation of the converter circuit 100, 100' as a passive rectifier. In this case, the safe state determination unit 122 outputs a safe state signal to the gate driver circuits 25, 25a, 25b, indicating that the safe state should be set to operation as a passive rectifier. This can be achieved, for example, by terminating the transmission of the pulse width modulation signals, i.e., by no longer transmitting a control signal.

[0069] Furthermore, if the power converter circuit 100' has a first half-bridge group 20a and a second half-bridge group 20b, or even more than two half-bridge groups, step S121 determines in which of the half-bridge groups 20a, 20b a fault exists. For this purpose, the safe-state determination unit 122 receives a signal from the first and second gate driver circuits 25a, 25b, indicating whether one or more of the first and / or second controllable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z, 22U, 22V, 22W, 22X, 22Y, 22Z, which are controlled by the respective gate driver circuits 25a, 25b, have a fault. Based on this signal, the safe state determination unit 122 can determine whether the safe state should be set only in one of the two half-bridge groups 20a, 20b, or in both half-bridge groups 20a, 20b.

[0070] In step S130, if it is determined that the safe state is an active short circuit, it is determined on which of the high and / or low sides the safe state should be set.

[0071] First, in step S131, it is determined whether a first controllable semiconductor switching element 21U, 21V, 21W, 21X, 21Y, 21Z or a second controllable semiconductor switching element 22U, 22V, 22W, 22X, 22Y, 22Z and / or a gate driver circuit 25, 25a, 25b has a fault. For this purpose, the semiconductor switching element fault detection unit 123a receives the status of all first and second addressable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z, 22U, 22V, 22W, 22X, 22Y, 22Z from the gate driver circuits 25, 25a, 25b via connection S11 and determines whether a fault exists in one or more of the first and / or second addressable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z, 22U, 22V, 22W, 22X, 22Y, 22Z. The semiconductor switching element fault detection unit 123a then outputs a semiconductor switching element fault signal to the side determination unit 123, indicating which of the semiconductor switching elements has which fault, i.e.,in particular, whether the semiconductor switching elements have a defect that causes them to be permanently in a conductive or non-conductive state.

[0072] Subsequently, in step S132, the side determination unit 123 determines that the active short circuit should be set alternately in the low side and the high side if none of the first controllable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z and the second controllable semiconductor switching elements 22U, 22V, 22W, 22X, 22Y, 22Z has a fault.

[0073] If it is determined that a first controllable semiconductor switching element 21U, 21V, 21W, 21X, 21Y, 21Z or a gate driver circuit 25, 25a, 25b has a fault that causes the first controllable semiconductor switching element 21U, 21V, 21W, 21X, 21Y, 21Z to be permanently in a non-conducting state, step S132 determines that the active short circuit should be set on the high side.

[0074] If it is determined that a second controllable semiconductor switching element 22U, 22V, 22W, 22X, 22Y, 22Z or a gate driver circuit 25, 25a, 25b has a fault that causes the second controllable semiconductor switching element 22U, 22V, 22W, 22X, 22Y, 22Z to be permanently in a non-conducting state, it is determined in step S132 that the active short circuit should be set in the low side.

[0075] If it is determined that a first controllable semiconductor switching element 21U, 21V, 21W, 21X, 21Y, 21Z or a second controllable semiconductor switching element 22U, 22V, 22W, 22X, 22Y, 22Z and / or a gate driver circuit 25, 25a, 25b has a fault that causes the first controllable semiconductor switching element 21U, 21V, 21W, 21X, 21Y, 21Z or the second controllable semiconductor switching element 22U, 22V, 22W, 22X, 22Y, 22Z to be permanently in a conducting state, it is determined in step S132 that the active short circuit without control of the first controllable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z and the second controllable semiconductor switching elements 22U, 22V, 22W, 22X, 22Y, 22Z of the half-bridge 20U, 20V, 20W, 20X, 20Y, 20Z, which has the faulty first or second controllable semiconductor switching element 21U, 21V, 21W, 21X, 21Y, 21Z, 22U, 22V, 22W, 22X, 22Y, 22Z, is to be set in the high side or in the low side.

[0076] The side determination unit 123 then outputs the side determination signal via connection S9 to the gate driver circuits 25, 25a, 25b.

[0077] Subsequently, in step S140, the power converter circuit 100, 100' is switched to the specified safe state. For this purpose, the first and second controllable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z, 22U, 22V, 22W, 22X, 22Y, 22Z are controlled by the gate driver circuit 25 or by the first and second gate driver circuits 25a, 25b such that the specified safe state is established.

[0078] The transition of the power converter circuit 100, 100' takes place in different ways depending on the specific safe state.

[0079] In step S141, if the safe state is determined to be one in which the converter circuit 100, 100' operates as a passive rectifier, each of the first controllable semiconductor elements 21U, 21V, 21W, 21X, 21Y, 21Z and each of the second controllable semiconductor elements 22U, 22V, 22W, 22X, 22Y, 22Z are switched to the non-conducting state. If the safe state is determined to be an active short circuit on the low side, in step S141 each of the first controllable semiconductor elements 21U, 21V, 21W, 21X, 21Y, 21Z is switched to the conducting state and each of the second controllable semiconductor elements 22U, 22V, 22W, 22X, 22Y, 22Z is ​​switched to the non-conducting state.If an active short circuit on the high side is determined to be the safe state, in step S141 each of the first controllable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z is switched to the non-conducting state and each of the second controllable semiconductor switching elements 22U, 22V, 22W, 22X, 22Y, 22Z is ​​switched to the conducting state.If an active short circuit on both the low and high sides is defined as the safe state, then in step S141, each of the first controllable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z and each of the second controllable semiconductor switching elements 22U, 22V, 22W, 22X, 22Y, 22Z is ​​switched back and forth between the conducting and non-conducting states at a predetermined frequency such that at any given time either each of the first controllable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z or each of the second controllable semiconductor switching elements 22U, 22V, 22W, 22X, 22Y, 22Z is ​​in the conducting state. This means that the active short circuit between the high and low sides is switched back and forth.It is particularly important to ensure that at no time is each of the first controllable semiconductor switching elements 21U, 21V, 21W, 21X, 21Y, 21Z and each of the second controllable semiconductor switching elements 22U, 22V, 22W, 22X, 22Y, 22Z in a conducting state, as otherwise a short circuit of the voltage source 30 may occur if it is not switched off.

[0080] Furthermore, depending on which of the half-bridge groups 20a, 20b was identified as having a fault in step S121, only the half-bridge group 20a, 20b for which a fault was identified is brought into the safe state. This means that if a fault was identified only in the first half-bridge group 20a, only the first half-bridge group 20a is brought into the safe state, while the second half-bridge group 20b continues to operate normally. The same applies in the reverse case. If a fault is detected in both half-bridge groups 20a, 20b, both half-bridge groups 20a, 20b are brought into the identified safe state.

Claims

[1] Method for operating a drive unit comprising a converter arrangement (1000, 1000') and an electric machine (1, 1') connected to the converter arrangement (1000, 1000'), wherein the converter arrangement (1000, 1000') comprises a converter circuit (100, 100') and a machine control unit (10) configured to control the converter circuit (100, 100'), wherein the power converter circuit (100, 100') has at least one half-bridge (20U, 20V, 20W, 20X, 20Y, 20Z) which has: - a low-side comprising a first controllable semiconductor switching element (21U, 21V, 21W, 21X, 21Y, 21Z) arranged between a first DC voltage terminal (B-) and a center terminal (24U, 24V, 24W, 24X, 24Y, 24Z) of the converter circuit (100, 100'), and a current sensor (23U, 23V, 23W, 23X, 23Y, 23Z) connected in series with the first controllable semiconductor switching element (21U, 21V, 21W, 21X, 21Y, 21Z) and configured to detect a current flowing through the first controllable semiconductor switching element (21U, 21V, 21W, 21X, 21Y, 21Z). - a high side which has a second controllable semiconductor switching element (22U, 22V, 22W, 22X, 22Y, 22Z) arranged between a second DC voltage terminal (B+) and the center terminal (24U, 24V, 24W, 24X, 24Y, 24Z) and, - at least one gate driver circuit (25, 25a, 25b) configured to drive at least some of the first controllable semiconductor switching elements (21U, 21V, 21W, 21X, 21Y, 21Z) and / or the second controllable semiconductor switching elements (22U, 22V, 22W, 22X, 22Y, 22Z), the method comprising: Receiving (S100) the current intensities detected by the current sensors (23U, 23V, 23W, 23X, 23Y, 23Z), a variety of temperature values ​​and a variety of error signals indicating whether there is a fault in one or more parts of the drive unit, Determine (S110) whether a fault exists in the drive unit depending on the received current intensities, the multitude of temperature values ​​and the multitude of fault signals, If it is determined that a fault exists in the drive unit, determine (S120) whether the safe state should be an active short circuit or a state in which the converter circuit (100, 100') is operated as a passive rectifier, depending on a speed of the electric machine (1, 1'). If it is determined that the safe state is an active short circuit, determine (S130) on which of the high and low sides the safe state should be set, and Transferring (S140) the converter circuit (100, 100') into the specified safe state. [2] Method according to claim 1, wherein the plurality of temperature values ​​comprises temperature values ​​of: one or more, in particular all, of the first controllable semiconductor switching elements (21U, 21V, 21W, 21X, 21Y, 21Z) and / or the second controllable semiconductor switching elements (22U, 22V, 22W, 22X, 22Y, 22Z), one or more windings of the electric machine (1, 1'), a circuit carrier on which the at least gate driver circuit (25, 25a, 25b) is mounted, and / or an ambient temperature. [3] Method according to claim 1 or 2, wherein the plurality of error signals indicate a fault in one or more of: a software of the machine control unit (10), a memory of the machine control unit (10), a power supply and / or the power converter circuit (100, 100'). [4] Method according to claim 3, wherein the fault signal indicating a fault in the converter circuit (100, 100') is output by the gate driver circuit (25, 25a, 25b) when the gate driver circuit (25, 25a, 25b) determines that there is an overvoltage in the converter circuit (100, 100'), a fault in one or more of the first controllable semiconductor switching elements (21U, 21V, 21W, 21X, 21Y, 21Z) and / or the second controllable semiconductor switching elements (22U, 22V, 22W, 22X, 22Y, 22Z), and / or a fault in the gate driver circuit (25, 25a, 25b). [5] Method according to one of the preceding claims, wherein in determining (S110) whether a fault exists in the drive unit, it is determined that a fault exists in the drive unit if one or more of the received current intensities are above a current threshold value and / or one or more of the plurality of temperature values ​​are above a temperature threshold value and / or one or more of the plurality of fault signals indicate a fault. [6] Method according to any of the preceding claims, wherein determining (S130) on which of the high side and / or the low side the safe state is to be set comprises: - Determine (S131) ​​whether one or more of the first addressable semiconductor switching elements (21U, 21V, 21W, 21X, 21Y, 21Z) and / or one or more of the second addressable semiconductor switching elements (22U, 22V, 22W, 22X, 22Y, 22Z) and / or a gate driver circuit (25, 25a, 25b) have a fault, and - Determine (S132) if none of the first controllable semiconductor switching elements (21U, 21V, 21W, 21X, 21Y, 21Z) and the second controllable semiconductor switching elements (22U, 22V, 22W, 22X, 22Y, 22Z) has a fault, that the active short circuit should be set alternately in the low side and the high side, and / or if a first controllable semiconductor switching element (21U, 21V, 21W, 21X, 21Y, 21Z) and / or a gate driver circuit (25, 25a, 25b) has a fault that causes the first controllable semiconductor switching element (21U, 21V, 21W, 21X, 21Y, 21Z) to be permanently in a non-conducting state, that the active short circuit on the high side should be set, and / or, if a second controllable semiconductor switching element (22U, 22V, 22W, 22X, 22Y, 22Z) and / or a gate driver circuit (25, 25a, 25b) has a fault that causes the second controllable semiconductor switching element (22U, 22V, 22W, 22X, 22Y, 22Z) to be permanently in a non-conducting state, that the active short circuit should be set on the low side, and / or, if a first controllable semiconductor switching element (21U, 21V, 21W, 21X, 21Y, 21Z) and / or a gate driver circuit (25, 25a, 25b) has a fault that causes the first controllable semiconductor switching element (21U, 21V, 21W, 21X, 21Y, 21Z) or the second controllable semiconductor switching element (22U, 22V, 22W, 22X, 22Y, 22Z) to be permanently in a conducting state, that the active short circuit occurs without control of the first controllable semiconductor switching element (21U, 21V, 21W, 21X, 21Y, 21Z) and the second controllable semiconductor switching element (22U, 22V, 22W, 22X, 22Y, 22Z) of the half-bridge (20U, 20V, 20W, 20X, 20Y, 20Z), which has the faulty first addressable semiconductor switching element (21U, 21V, 21W, 21X, 21Y, 21Z), is to be set in the low side, and / or if a second controllable semiconductor switching element (22U, 22V, 22W, 22X, 22Y, 22Z) and / or a gate driver circuit (25, 25a, 25b) has a fault that causes the second controllable semiconductor switching element (22U, 22V, 22W, 22X, 22Y, 22Z) to be permanently in a conductive state, that the active short circuit occurs without control of the first controllable semiconductor switching element (21U, 21V, 21W, 21X, 21Y, 21Z) and the second controllable semiconductor switching element (22U, 22V, 22W, 22X, 22Y, 22Z) of the half-bridge (20U, 20V, 20W, 20X, 20Y, 20Z) which contains the faulty second controllable semiconductor switching element (22U, 22V, 22W, 22X, 22Y, 22Z) is to be set on the top side. [7] Method according to the preceding claim, wherein the process (S140) of the converter circuit (100, 100') comprises: - Switching (S141) each of the first controllable semiconductor switching elements (21U, 21V, 21W, 21X, 21Y, 21Z) and each of the second controllable semiconductor switching elements (22U, 22V, 22W, 22X, 22Y, 22Z) to the non-conducting state when a state in which the converter circuit (100, 100') is operated as a passive rectifier is determined as the safe state, and / or - Switching (S141) each of the first addressable semiconductor switching elements (21U, 21V, 21W, 21X, 21Y, 21Z) to the conducting state and each of the second addressable semiconductor switching elements (22U, 22V, 22W, 22X, 22Y, 22Z) to the non-conducting state when an active short circuit in the low side is determined to be the safe state, and / or -Switching (S141) each of the first addressable semiconductor switching elements (21U, 21V, 21W, 21X, 21Y, 21Z) to the non-conducting state and each of the second addressable semiconductor switching elements (22U, 22V, 22W, 22X, 22Y, 22Z) to the conducting state when an active short circuit on the high side is determined to be the safe state, and / or - Switching (S141), at a predetermined frequency, each of the first controllable semiconductor switching elements (21U, 21V, 21W, 21X, 21Y, 21Z) and each of the second controllable semiconductor switching elements (22U, 22V, 22W, 22X, 22Y, 22Z) between the conducting state and the non-conducting state such that at any given time either each of the first controllable semiconductor switching elements (21U, 21V, 21W, 21X, 21Y, 21Z) or each of the second controllable semiconductor switching elements (22U, 22V, 22W, 22X, 22Y, 22Z) is in the conducting state, when an active short circuit in the low side and the high side is defined as the safe state. [8] Method according to any one of the preceding claims, wherein the converter circuit (100') comprises a first half-bridge group (20a) with three half-bridges (20U, 20V, 20W), a second half-bridge group (20b) with three half-bridges (20X, 20Y, 20Z), a first gate driver circuit (25a) configured to drive the semiconductor switching elements (21U, 21V, 21W, 22U, 22V, 22W) of the first half-bridge group (20a), and a second gate driver circuit (25b) configured to drive the semiconductor switching elements (21X, 21Y, 21Z, 22X, 22Y, 22Z) of the second half-bridge (20b), wherein determining (S120) whether a fault exists in the converter arrangement (1000') comprises: - Determine (S121) whether the fault is in the first half-bridge group (20a) and / or the second half-bridge group (20b) and / or the machine control unit (10) and / or in one or more other parts of the drive unit, and, when transitioning (S140) the converter circuit (100') to the determined safe state, the first half-bridge group (20a) is transitioned to the safe state if the fault is only in the first half-bridge group (20a), the second half-bridge group (20b) is transitioned to the safe state if the fault is only in the second half-bridge group (20b), and the first half-bridge group (20a) and the second half-bridge group (20b) are transitioned to the safe state if the fault is in the first half-bridge group (20a) and / or the second half-bridge group (20b) and / or the machine control unit (10) and / or in one or more other parts of the The drive unit is present. [9] Power converter arrangement (1000, 1000') comprising a power converter circuit (100, 100') with at least one half-bridge (20U, 20V, 20W) comprising: - a low-side comprising a first controllable semiconductor switching element (21U, 21V, 21W, 21X, 21Y, 21Z) arranged between a first DC voltage terminal (B-) and a center terminal (24U, 24V, 24W, 24X, 24Y, 24Z) of the converter circuit (100, 100'), and a current sensor (23U, 23V, 23W, 23X, 23Y, 23Z) connected in series with the first controllable semiconductor switching element (21U, 21V, 21W, 21X, 21Y, 21Z) and configured to detect a current flowing through the first controllable semiconductor switching element (21U, 21V, 21W, 21X, 21Y, 21Z), - a high side which has a second controllable semiconductor switching element (22U, 22V, 22W, 22X, 22Y, 22Z) arranged between a second DC voltage terminal (B+) and the center terminal (24U, 24V, 24W, 24X, 24Y, 24Z) and - at least one gate driver circuit (25, 25a, 25b) configured to control at least a part of the first controllable semiconductor switching elements (21U, 21V, 21W, 21X, 21Y, 21Z) and the second controllable semiconductor switching elements (22U, 22V, 22W, 22X, 22Y, 22Z), the converter arrangement (1000, 1000') further comprising a machine control unit (10) configured to carry out a method according to one of the preceding claims. [10] Power converter arrangement (1000, 1000') according to claim 9, wherein the power converter circuit (100') comprises a first half-bridge group (20a) with three half-bridges, a second half-bridge group (20b) with three half-bridges, a first gate driver circuit (25a) configured to drive the semiconductor switching elements (21U, 21V, 21W, 22U, 22V, 22W) of the first half-bridge group (20a), and a second gate driver circuit (25b) configured to drive the semiconductor switching elements (21X, 21Y, 21Z, 22X, 22Y, 22Z) of the second half-bridge (20b). [11] Drive unit comprising an electric machine (1, 1') and a converter arrangement (1000, 1000') according to claim 9 or 10. [12] Computer program which, when executed on the machine control unit (10) of the converter arrangement (1000, 1000') according to claim 9 or 10, causes the machine control unit (10) to perform a method according to any one of claims 1 to 8. [13] Machine-readable storage medium on which the computer program according to claim 12 is stored.

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