Method for operating a power converter device for controlling an electrical machine and power converter device

Abstract

The invention relates to a method for operating a power converter device (200) for controlling an electrical machine (500), wherein the power converter device (200) has a power converter circuit (115), a control device (123) and a power supply circuit (100) for supplying the power converter circuit (115) and the control device (123), wherein the power supply circuit (100) has a high-voltage branch (110) with a high-voltage level, a low-voltage branch (120) with a low-voltage level and a DC-DC converter (10), wherein the high-voltage branch (110) is connected to the low-voltage branch (120) via the DC-DC converter (10), wherein the high-voltage branch (110) has an intermediate circuit capacitance (111), the method comprising, in a normal operating mode, operating the power converter circuit (115) in a motor operating mode,in which an electrical machine (500) connected to the power converter device (200) is operated as a motor, and in a fault operating mode, operating the power converter circuit (115) in a generator operating mode, in which the electrical machine (500) connected to the power converter device (200) is operated as a generator, and operating the DC-DC converter (10) such that it transfers energy from the high-voltage branch (110) to the low-voltage branch (120). The invention also relates to such a power converter device (200).

Description

[0001] The present invention relates to a method for operating a power converter device for controlling an electrical machine and to such a power converter device, an arrangement and an on-board electrical system. Background of the invention

[0002] In modern electric vehicle applications, a power supply circuit in a power converter device (so-called inverter) is also referred to as a PDN or PDTN (Power Distribution Network or Power Distribution Network Tree). The task of this power distribution network is, among other things, to distribute power to the various loads within the power converter device, such as sensors, communication circuits (e.g., CAN, LIN transceivers), and in particular, the gate driver circuits for high-side (HS) and low-side (LS) switches, and functional safety circuits or MCUs (microcontroller units), etc.

[0003] Today, due to functional safety requirements, two main power sources can be used for the PDN. A common power source in electric vehicles (EVs) is low-voltage batteries (e.g., 12 V), also known as the Class 30 network or low-voltage network. A second source can be a high-voltage DC battery or the high-voltage DC bus (high-voltage network) with a nominal voltage of, for example, 800 V or 400 V. Such high-voltage or high-voltage systems can, in particular, serve as the power supply for an electric traction drive, such as a permanent magnet synchronous motor (PMSM), which is connected to the high-voltage network via the inverter.

[0004] However, the use of an HV powertrain increases the risk of electric shock, especially in the event of an accident. Therefore, the ECC R94 standard requires that the voltage in the high-voltage network, particularly the intermediate circuit voltage (the so-called DC link), drops to a safe voltage (maximum 60 V) in less than five seconds.

[0005] DE 10 2013 224 884 A1, US 7 768 237 B2 and US 9 637 009 B2 each describe a discharge circuit with a series connection of a switch and a resistor.

[0006] DE 10 2007 022 515 A1 describes the discharging of an intermediate circuit capacitor via an inverter.

[0007] DE 10 2004 057 693 A1 shows a device for the rapid discharge of a capacitor, in particular an intermediate circuit capacitor, via a DC-DC converter in an on-board electrical system with a starter generator as an electrical machine and an associated voltage converter, in which a controlled or regulated DC-DC converter is used as the DC-DC converter, the on-board electrical system-side output voltage of which is increased compared to the normal state after the electrical machines and the inverter have been switched off, whereby the charges to be discharged are supplied to the battery connected to the voltage converter.

[0008] DE 10 2023 108 645.6 shows a method for operating a power supply circuit of an inverter for controlling an electrical machine, wherein the power supply circuit has a high-voltage branch with a high-voltage level, a low-voltage branch with a low-voltage level, and a discharge branch with a discharge voltage level, wherein the high-voltage level is higher than the low-voltage level and the discharge voltage level, wherein the high-voltage branch is connectable to the low-voltage branch via an operating DC-DC converter, wherein the high-voltage branch is connectable to the discharge branch via a discharging DC-DC converter, wherein the discharge branch is different from the low-voltage branch, wherein a low-voltage energy storage device is connected in the discharge branch, wherein the method comprises, in a first operating mode, conducting current from the high-voltage branch via the operating DC-DC converter into the low-voltage branch, in a second operating mode,conducting current from the high-voltage branch via the discharge DC-DC converter into the discharge branch, whereby the discharge voltage level is not more than 60 V.

[0009] DE 10 2024 105 223.6 discloses a power converter device for controlling an electrical machine. The power converter device comprises a power converter circuit, a control device, and a power supply circuit for supplying the power converter circuit and the control device. The power supply circuit comprises a high-voltage branch with a high-voltage level and a low-voltage branch with a low-voltage level. The high-voltage branch is connected to the low-voltage branch via a DC-DC converter, the high-voltage branch having an intermediate circuit capacitance, and the power converter circuit and the control device are supplied with power from the low-voltage branch. A discharge circuit is provided in the low-voltage branch, which has at least one semiconductor switch connected between two low-voltage potential lines of the low-voltage branch in order to electrically connect them in accordance with a control signal.

[0010] The invention aims to improve these concepts in order to discharge an intermediate circuit as quickly as possible. Disclosure of the invention

[0011] According to the invention, a method for operating a power converter device for controlling an electrical machine, as well as such a power converter device, an arrangement, and an on-board electrical system are proposed with the features of the independent patent claims. Advantageous embodiments are the subject of the subclaims and the following description. It should be emphasized that the features and advantages described below apply equally to the power converter device and the method for operating the power converter device.

[0012] In detail, the power converter device comprises a power converter circuit, a control device and a power supply circuit for supplying the power converter circuit and the control device.

[0013] The power converter circuit is used, as usual, to connect the AC voltage terminals (machine terminals) of the electric machine with DC voltage terminals (high-voltage terminals) or to generate an AC voltage for the electric machine from a DC voltage, in particular from the high-voltage network or high-voltage branch. For this purpose, the power converter circuit has a number of semiconductor switches, for example as a number of half-bridge circuits, which can each be opened (non-conductive) and closed (conductive) in accordance with a control signal. The semiconductor switches can comprise MOSFETs or IGBTs, for example gallium nitride (GaN) or silicon carbide (SiC) FETs. For example, the power converter circuit has a half-bridge comprising two series-connected "switches" for each AC voltage terminal (or stator winding / phase winding) of the electric machine, with the AC voltage terminal located between the two "switches."Such a “switch” can comprise one or more semiconductor switches connected in parallel.

[0014] The power supply circuit, in turn, has a high-voltage branch with a high-voltage level and a low-voltage branch with a low-voltage level, with the high-voltage branch being connected to the low-voltage branch via a DC-DC converter. The power converter circuit and the control device are supplied with power from the low-voltage branch. The high-voltage branch has an intermediate circuit capacitance, in particular to store and / or smooth the DC voltage in the high-voltage branch. It should be emphasized that the power supply circuit is part of the power converter circuit (i.e., the inverter) and is not distributed across the entire vehicle electrical system.

[0015] The high-voltage branch is configured to be connected to a high-voltage network (in particular in the vehicle), and the low-voltage branch is configured to be connected to a low-voltage network (in particular in the vehicle), wherein a nominal voltage level of the high-voltage network (referred to as high-voltage level in this disclosure) is higher than a nominal voltage level of the low-voltage network (referred to as low-voltage level in this disclosure). The high-voltage branch and the low-voltage branch have corresponding terminals for connecting to the high-voltage network and the low-voltage network, respectively.

[0016] In particular, in embodiments of the invention, the power converter device has (in particular two) low-voltage connections which are designed to be connected to the low-voltage network of the vehicle, and (in particular two) high-voltage connections which are designed to be connected to the high-voltage network of the vehicle.

[0017] The high-voltage level can, for example, be significantly higher than a permissible contact voltage of, in particular, 60 V, e.g., up to several hundred volts. The low-voltage level can, for example, correspond to conventional vehicle low voltages of, for example, 12 V, 24 V, or 48 V. The low-voltage branch serves or is designed to distribute power to the components or consumers of the power converter device, such as sensors, communication circuits (e.g., CAN, LIN transceivers), and in particular the gate driver circuits for high-side (HS) and low-side (LS) switches, logic circuits (such as discrete or integrated circuits (e.g., ICs, ASICs) or so-called MCUs (microcontroller units)), and functional safety circuits, etc.

[0018] In particular, the low-voltage branch is not intended to distribute power to any consumers in the vehicle outside the power converter device (inverter).

[0019] The invention describes a possibility for reducing a high and dangerous voltage of the high-voltage network (particularly in the form of energy stored in the intermediate circuit capacitance) in the vehicle as quickly as possible to a permissible contact voltage value of no more than 60 V in the event of a fault, e.g., in the event of a vehicle accident or a fault or failure of the power converter device. The invention requires only very few, standard components and is thus very simple and cost-effective to implement, also with regard to the control. The invention is implemented in the power converter device for controlling the electrical machine in the vehicle and is thus very easy to implement in a vehicle.

[0020] To this end, the invention utilizes the measure of dissipating the energy stored in the high-voltage branch into both the low-voltage branch and the electric machine in the event of a fault or fault operating mode. In the low-voltage branch, this energy can be converted into heat, for example, in a resistor or a power circuit (semiconductor), or stored in a battery. It is converted into heat in the electric machine, in particular without generating any driving torque.

[0021] The proposed hybrid discharge concept represents a significant improvement over conventional discharge methods. One advantage is that the simultaneous discharge of the intermediate circuit capacitance into the low-voltage branch and the electric machine provides two discharge paths, which both accelerates the discharge in the normal case and provides redundancy in the event of a fault in one of the discharge branches.

[0022] The discharge into the low-voltage branch takes place via the DC-DC converter, so that after the conversion only a voltage at low voltage level needs to be treated, which is significantly less complex than, for example, short-circuiting the high-voltage connections using a bleeder resistor.

[0023] The DC-DC converter is preferably operated in both normal operating mode and fault operating mode, so that the power transferred from the high-voltage branch to the low-voltage branch remains essentially constant and does not exhibit peaks; the DC-DC converter can be operated in voltage regulation mode.

[0024] Discharging into the electrical machine preferably takes place in such a way that a braking torque is generated. Although this means that the electrical machine operates in a generator mode, i.e., generates current, this allows adjustment of the reactive power and thus improved discharge of the intermediate circuit capacitance. Discharging into the electrical machine can preferably take place using a negative iq current (q component of the stator current in the d / q system (rotor-fixed coordinate system); torque-relevant component, quadrature component), i.e., with a braking torque. This prevents excessive voltage overshoot and, at the same time, allows a higher iq current to be fed in, which enables a reduction in the id current and thus reduces the risk of damaging the machine magnets.

[0025] The invention provides a way to limit or reduce overshoot of the intermediate circuit voltage and shorten the discharge time. It can also be used, in particular, for extremely fast operation, including field weakening.

[0026] Embodiments of the invention include operating the DC-DC converter in the normal operating mode so that it transfers energy from the high-voltage branch to the low-voltage branch. Thus, the DC-DC converter can advantageously serve to supply energy to the components of the power converter device. The DC-DC converter can be operated at a constant low-voltage level.

[0027] In embodiments of the invention, in fault operating mode, a high-voltage battery is first disconnected from the high-voltage network. In particular, a torque coupling between the electric machine and a drive train of the vehicle, for example a transmission, is also disconnected so that the electric machine can rotate freely. In this case, the semiconductor switches or their freewheeling diodes / body diodes in the power converter arrangement operate as uncontrolled rectifiers (a voltage drop across these diodes can be neglected here for the sake of simplicity). The machine operates in generator mode and charges the intermediate circuit capacitor. The DC-DC converter is connected as a load in the intermediate circuit. The voltage surge generated by applying the negative iq current setpoint is suppressed by discharging into the low-voltage branch, with the DC-DC converter dissipating the energy from the high-voltage branch or the intermediate circuit capacitance.

[0028] In embodiments of the invention, in fault operating mode, the magnitude of the q-component of the stator current is increased with decreasing speed of the electric machine, i.e. the q-component of the stator current becomes smaller or more negative with decreasing speed. In particular, the electric machine is operated with a negative iq current setpoint, the magnitude of which is increased when the speed of the electric machine decreases. For example, for permanent magnet synchronous machines (PMSM), as a typical example of an electric machine in this field of application, there is a critical speed at which the generated counter voltage is so large that it keeps the voltage of the intermediate circuit capacitor below the desired threshold of, for example, 60 V during freewheeling or when applying a braking torque. This speed depends, among other things, on the number of pole pairs (P) and the flux density of the permanent magnet arrangement in the rotor (ψ PM ) away.

[0029] In embodiments of the invention, a negative iq current setpoint iq is applied, which depends on the electrical resistance R S the stator winding, a maximum permissible current I max, the number of pole pairs P, the mechanical angular frequency ω and the flux density ψ PM the permanent magnet arrangement in the rotor, in particular according to. iq=−Rs×Imax2P×ω×ΨPM

[0030] In embodiments of the invention, at least one negative id current setpoint id (d-component of the stator current in the d / q system; torque-free component, direct component) is applied, which is greater than a lower current limit value id min , which is the quotient of the flux density of the permanent magnet arrangement in the rotor ψ PM and the d-component of the inductance of the stator winding L d results. id>idmin=−ΨPMLd

[0031] This can prevent demagnetization of the rotor or reduce the risk of demagnetization.

[0032] In embodiments of the invention, the power converter device has a discharge circuit in the low-voltage branch. In the fault operating mode, the discharge circuit is operated such that electrical energy is converted into heat. Since the low-voltage level is significantly lower than the high-voltage level, a very simple, compact discharge circuit can be used.

[0033] In embodiments of the invention, the discharge circuit comprises at least one semiconductor switch connected between two low-voltage potential lines of the low-voltage branch and configured to electrically connect these low-voltage potential lines in accordance with a control signal. Energy transferred from the high-voltage branch or the intermediate circuit capacitance therein to the low-voltage branch is converted into heat in the at least one semiconductor switch.

[0034] In embodiments of the invention, the discharge circuit is operated in the normal operating mode such that the at least one semiconductor switch is in a blocking state, so that the two low-voltage potential lines of the low-voltage branch are not electrically connected to one another, and in the fault operating mode is in a conducting state, so that the two low-voltage potential lines of the low-voltage branch are electrically connected to one another.

[0035] In embodiments of the invention, the power converter device has a blocking circuit that blocks a current flow from the low-voltage terminals into the discharge circuit, or the low-voltage terminals and the discharge circuit are not electrically conductively connected.

[0036] In embodiments of the invention, the discharge circuit is electrically separated from the low-voltage terminals in the fault operating mode.

[0037] In this way, undesirable feedback from the low-voltage network (to which the power converter device is connected at the low-voltage terminals) on the discharge circuit can be prevented.

[0038] In embodiments of the invention, the power converter device has a bypass circuit in the low-voltage branch, wherein the bypass circuit is operated in the fault mode such that current from the DC-DC converter is directed into a low-voltage network connected to the low-voltage branch. Such a bypass circuit can also be implemented very simply with just a few switches and is very compact. When energy is transferred from the high-voltage network to the low-voltage network, it does not harm people in terms of the voltage level. The energy can be used there to supply consumers or stored in a low-voltage energy storage device (e.g., battery).

[0039] In embodiments of the invention, the low-voltage branch comprises a DC-DC converter branch and a grid branch, wherein the grid branch serves to connect to the low-voltage grid, and the DC-DC converter branch serves to distribute power to the components or consumers of the inverter. The method then comprises, in the normal operating mode, conducting power from the high-voltage branch via the DC-DC converter into the DC-DC converter branch, and, in the fault operating mode, conducting power from the high-voltage branch via the DC-DC converter into the grid branch (and there, if applicable, into the discharge circuit and / or the bypass circuit).

[0040] In the normal operating mode, in particular, no current is passed from the high-voltage branch via the DC-DC converter into the grid branch, whereas in the fault operating mode, current from the high-voltage branch may or may not continue to be passed via the DC-DC converter into the DC-DC converter branch.

[0041] In one embodiment, the DC-DC converter branch, the grid branch, and the DC-DC converter are electrically connected via a blocking circuit such that a current flow from the DC-DC converter branch into the DC-DC converter is blocked, a current flow from the DC-DC converter branch into the grid branch is blocked, and a current flow from the grid branch into the DC-DC converter is blocked. This prevents mutual negative influences.

[0042] In one embodiment, the diversion circuit comprises a network branch disconnector for connecting and disconnecting the network branch from the DC-DC converter, and / or a DC-DC converter branch disconnector for connecting and disconnecting the DC-DC converter branch from the DC-DC converter. This is a very simple measure, both in terms of design and circuitry, for implementing the aforementioned different operating modes. The switches can comprise semiconductor switches or mechanical switches (relays). If the aforementioned switches are implemented as semiconductor switches, the current flowing through the switches can also be regulated in conjunction with a current measurement.

[0043] In embodiments of the invention, the converter arrangement is operated in fault mode until a voltage drop across the intermediate circuit capacitance and / or a voltage present between the two low-voltage potential lines of the low-voltage branch corresponds at most to a safety threshold. A suitable safety threshold at the intermediate circuit capacitance can be at most 60 V or be lower by a safety margin. This allows a safe touch voltage level to be achieved. A suitable safety threshold in the low-voltage branch can be specified depending on a nominal voltage level of the low-voltage branch, e.g., 75% of the nominal voltage level.

[0044] In embodiments of the invention, the power converter device comprises a housing in which the power converter circuit, the control device, and the power supply circuit are arranged. In other words, as already described above, the power converter device (or inverter) is a device with a number of components in a housing.

[0045] In embodiments of the invention, the DC-DC converter is an isolating DC-DC converter, such as a flyback converter, forward converter, push-pull converter, etc. In isolating DC-DC converters, there is galvanic isolation between the input and output networks, which is usually achieved by means of a transformer. These offer increased safety. In the high-voltage range (>60 V), the use of an isolating DC-DC converter is advantageous or may even be required for safety reasons. Consequently, no signal isolation or independent isolated power supply is required for the discharge circuit.

[0046] The control device of the power converter device, e.g. an integrated circuit (e.g. IC, ASIC or FPGA), is designed, in particular in terms of programming and / or circuitry, to carry out a method according to the invention.

[0047] The invention offers particular advantages because the discharge capability is integrated directly into the power converter device. Necessary components such as switches, coils, capacitors, etc., are already present there. This allows the invention to be advantageously implemented directly in the power converter device, which in turn is advantageously structurally connected to the electric machine and serves to connect the AC voltage terminals of the electric machine to the DC voltage terminals of the vehicle electrical system, particularly the high-voltage branch.

[0048] An HV discharge resistor and HV discharge switch are not required. An existing DC-DC converter, including its control system, can be used unchanged. Discharge can be performed at any speed of the electric motor and is independent of the voltage at the electric motor. The invention can also be easily retrofitted to existing inverter concepts.

[0049] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0050] The invention is illustrated schematically in the drawing using exemplary embodiments and is described below with reference to the drawing. Short description of the drawings Fig. 1 schematically shows an embodiment of a power converter device according to the invention. Fig. 2 shows temporal courses of different signals as they can occur in an exemplary sequence of an embodiment of a method according to the invention. Embodiment(s) of the invention

[0051] In the following, an embodiment of the invention is described with reference to the figures. In order to reduce the complexity of the Fig. 1, not all connections and signal flows are shown. Return lines, ground lines, and negative lines are also not always fully depicted.

[0052] Fig. 1 schematically shows an embodiment of a power converter device 200 (so-called inverter) according to the invention for controlling an electrical machine 500. In vehicles, a power converter device or inverter typically refers to a component or device that controls an electrical machine. The power converter device 200 can, in particular, implement torque and speed control and convert the on-board electrical system's DC voltage into the machine's AC voltage and—during recuperation—conversely convert the machine's AC voltage into the on-board electrical system's DC voltage and feed it into the on-board electrical system.

[0053] The power converter device 200 has a power converter circuit 115, a control device 123 and a power supply circuit 100 for supplying the power converter circuit 115 and the control device 123 and possibly further components 121.

[0054] The power supply circuit 100 has a high-voltage branch 110 with two high-voltage potential lines and two high-voltage connections HV+, HV- for connecting a high-voltage network 1 with a high-voltage level, and a low-voltage branch 120 with two low-voltage potential lines and two low-voltage connections B+, B- for connecting a low-voltage network (so-called Kl.30 network) 2 with a low-voltage level. The high-voltage level is, for example, in the range from 300 V to 1,000 V and can be provided by a high-voltage battery 1a. The low-voltage level can be, for example, 12 V, 24 V, or 48 V and can be provided by a low-voltage battery. One of the low-voltage potential lines or the low-voltage connection B- simultaneously represents a ground potential.

[0055] The high-voltage branch 110 has an intermediate circuit capacitance 111, for example in the form of one or more capacitors, which serves in particular to store and / or smooth the direct voltage in the high-voltage branch. The use of intermediate circuit capacitances in the high-voltage network in a vehicle increases the risk of electric shock, particularly in the event of an accident. Therefore, the invention presents a possibility of quickly reducing the voltage applied to the intermediate circuit capacitance 111 or, generally, the energy stored in intermediate circuit capacitances in the high-voltage network to a touch-safe level or a safety threshold value of, in particular, no more than 60 V in the event of a fault.

[0056] For this purpose, a discharge circuit 31 and / or a diversion circuit 32 is provided in the low-voltage branch 120.

[0057] The discharge circuit 31 is designed, for example, to short-circuit the two low-voltage potential lines of the low-voltage branch 120 via an energy dissipation element as needed or in accordance with a control signal. Such an energy dissipation element can comprise one or more resistance components and / or semiconductor switches.

[0058] In a simple embodiment, the diversion circuit 32 may comprise a switch for connecting the DC-DC converter to the B+ terminal. The diversion circuit 32 serves to divert current from the DC-DC converter 10 into the low-voltage network 2 connected to the low-voltage branch.

[0059] It is sufficient if the power converter device 200 has either the discharge circuit 31 or the bypass circuit 32. It can also have both. The high-voltage branch 110 is connected to the low-voltage branch 120 via a DC-DC converter 10. References to "connect," "connection," etc., in the context of this disclosure, always refer to an electrically conductive connection unless otherwise stated. The DC-DC converter 10 can be a galvanically isolating DC-DC converter, particularly for safety reasons. The DC-DC converter 10 can be used to supply energy to components of the power converter device from the high-voltage network 1.

[0060] The low-voltage branch 120 supplies power to the components of the power converter device and has a DC-DC converter branch 120a, which is fed from the DC-DC converter 10, and a grid branch 120b, which is connectable to and fed from the low-voltage grid. The low-voltage branch 120 can also be referred to as PDN (see above). The DC-DC converter branch 120a is connected to the DC-DC converter 10 via a blocking circuit, here comprising a diode 122a. The grid branch 120b is connected to a potential terminal B+ of the low-voltage terminals via a blocking circuit, here also comprising a diode 122b. The DC-DC converter branch 120a and the grid branch 120b can also be connected to one another.The DC-DC converter branch 120a, the network branch 120b, the DC-DC converter 10 and the potential connection B+ are connected via the blocking circuit(s) 122a, 122b in such a way that a current flow from the DC-DC converter branch 120a into the DC-DC converter 10 is blocked, a current flow from the network branch 120b into the low-voltage network 2 is blocked and a current flow from the network branch 120b into the DC-DC converter 10 is blocked.

[0061] Furthermore, one or more low-voltage consumers 121 of the power converter device, indicated only schematically, are arranged in the DC-DC converter branch 120a, e.g. sensors (e.g. speed, angular position, temperature, etc.), communication devices (CAN transceiver, LIN transceiver, etc.).

[0062] The control device 123 is configured to carry out a method according to an embodiment of the invention and can, for this purpose, control the power converter circuit 115, the discharge circuit 31 and / or the bypass circuit 32 in a suitable manner.

[0063] The control device 123 may be configured to initiate the error operating mode when it receives an external error signal F and / or when it detects an error in another way.

[0064] A measured value of the voltage in the high-voltage branch 110 or the voltage drop across the intermediate circuit capacitance 111, which is detected, for example, by means of a voltmeter, can be supplied to the control device 123. This allows the control device 123 to determine, for example, when a fault operating mode can be terminated.

[0065] The power converter circuit 115 is also arranged on the supply or control side in the low-voltage branch 120. The power converter circuit 115 serves to connect the (three in the example shown) AC voltage terminals U, V, W of the electric machine 500, which is not part of the power converter device 200, to the positive DC voltage terminal HV+ and the negative DC voltage terminal HV- of the high-voltage branch 110. For this purpose, the power converter circuit 115 can comprise a logic circuit or gate driver circuit for generating control signals, associated power supplies for the gate driver circuit, and a number of semiconductor switches to be controlled by the control signals. The semiconductor switches can be arranged in particular in the form of half-bridges 15a, 115b, 115c, wherein a half-bridge can be provided for each of the AC voltage terminals U, V, W of the electric machine 500.

[0066] The control device 123, the components 121, the low-voltage branch 120 including 120a, 120b, 122a, 122b, the discharge circuit 31 or the bypass circuit 32 can be implemented as a common circuit 150, in particular on a common circuit carrier such as a printed circuit board (PCB).

[0067] The power converter device 200 also has, in particular, a housing (not shown) in which the power converter circuit 115, the control device 123, the components 121, the energy supply circuit 100, the discharge circuit 31 and the bypass circuit 32 are arranged and in which the terminals B+, B-, HV+, HV-, U, V, W are formed.

[0068] The power converter device 200 (i.e. the entire device) can advantageously be structurally connected to the electrical machine 500, ie in particular be fastened to it.

[0069] In Fig. Figure 2 shows various signals, such as those that can occur during an exemplary sequence of an embodiment of a method according to the invention, plotted against time t. Diagram a) shows the speed of the electric machine versus time when implementing a method according to the invention. Diagram b) shows the voltage drop across the intermediate circuit capacitance 111, and diagram c) shows the current values ​​id (220) and iq (210). These are simulated curves for an exemplary application.

[0070] The Fig. The example underlying Figure 2 is based on a scenario that is demanding for the invention, in which the high-voltage network is to be discharged as quickly as possible at a time when the electric machine has a speed of approximately 17,000 min -1 which means a very high back voltage or back EMF.

[0071] The machine is started up (not part of the invention) and accelerated to maximum speed in field-weakening mode. The machine is not connected to any load and requires a minimum current to overcome the rotor inertia.

[0072] In the figure, stationary operation (normal operating mode) begins at approximately a time t=0.45 s.

[0073] The fault operating mode is initiated at time t=0.5 s. Currents id and iq are injected according to the relationships explained above. The voltage drop across the DC link capacitance 111 decreases until it reaches the value of the induced counter voltage at approximately t=0.55 s. From this point on, a negative iq injection is performed, causing a slight overshoot of the voltage drop across the DC link capacitance 111 to be observed at a time of approximately t=0.65 s. The negative iq value is gradually changed from -1.74 A at time approximately t=0.51 s to -41.70 A at time approximately t=3.47 s.

[0074] At approximately t=3.5 s the machine comes to a standstill and the voltage drop across the intermediate circuit capacitance 111 is approximately zero.

[0075] In Fig. 3 are diagrams a) and b) from Fig.2 with signals from non-inventive or conventional methods, on the one hand a machine-based method (discharging via the machine windings) with maximum power (ie specification of id and iq current components) and on the other hand a machine-based method with specification of only an id current component.

[0076] A graph 310 in diagram a) again shows the speed of the electric machine against time when carrying out a method according to the invention, a graph 311 when carrying out the machine-based method with maximum power and a graph 312 when carrying out the machine-based method with only the id current component.

[0077] In diagram b), a graph 320 again shows the voltage drop across the intermediate circuit capacitance 111 versus time when carrying out a method according to the invention, a graph 321 when carrying out the machine-based method with maximum power and a graph 322 when carrying out the machine-based method with only the id current component.

[0078] The simulation results show that the discharge time is reduced by approximately 10% (by 2.28 s compared to the machine-based process with only the id current component) and the voltage overshoot is reduced by approximately 56% (by approximately 540 V compared to the machine-based process with maximum power).

[0079] Compared to the machine-based process with maximum power, the voltage overshoot is reduced from approximately 961 V at approximately t=0.9 s to approximately 420 V at approximately t=0.68 s.

[0080] Compared to the machine-based method with only the id current component, the discharge time is shortened from approximately t=5.8 s to approximately t=3.5 s, which can be further reduced if the rated power of the DC-DC converter is further increased and more energy is delivered in the discharge circuit 31 or the bypass circuit 32.

[0081] Although the PMSM electric machine acts as a generator during the discharge phase and charges the intermediate circuit capacitance 111, the rate at which the intermediate circuit capacitance 111 is charged remains below the rate at which the intermediate circuit capacitance 111 is discharged via the DC-DC converter 10. This eliminates the need for discharging via a high-voltage bleeder resistor. The proposed solution significantly reduces the cost and space requirements of the discharge system by eliminating the high-voltage control loop.

[0082] The simulation results of conventional discharge and hybrid discharge according to embodiments of the invention demonstrate the improvements in discharge rate and reduced voltage overshoot achieved by implementing the hybrid discharge technique. This proposed solution can discharge the capacitor within 5 s or even less, regardless of the initial speed of the electric machine, demonstrating the robustness and effectiveness of the proposed solution. In an emergency, for example, when a low-voltage battery (12 V battery) is disconnected, this discharge strategy ensures that the inverter components are supplied with power via the DC-DC converter to ensure a safe shutdown. QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2013 224 884 A1

[0005] US 7 768 237 B2

[0005] US 9 637 009 B2

[0005] DE 10 2007 022 515 A1

[0006] DE 10 2004 057 693 A1

[0007] DE 10 2023 108 645.6

[0008] DE 10 2024 105 223.6

[0009]

Claims

[1] Method for operating a power converter device (200) for controlling an electrical machine (500), wherein the power converter device (200) comprises: - a converter circuit (115), - a control device (123) and - a power supply circuit (100) for supplying the power converter circuit (115) and the control device (123), wherein the power supply circuit (100) has a high-voltage branch (110) with a high-voltage level, a low-voltage branch (120) with a low-voltage level and a DC-DC converter (10), wherein the high-voltage branch (110) is connected to the low-voltage branch (120) via the DC-DC converter (10), wherein the high-voltage branch (110) has an intermediate circuit capacitance (111), the procedure includes: in a normal operating mode, operating the power converter circuit (115) in a motor operating mode in which an electrical machine (500) connected to the power converter device (200) is motor-operated, and in a fault operating mode, operating the power converter circuit (115) in a generator operating mode in which the electrical machine (500) connected to the power converter device (200) is operated as a generator, and operating the DC-DC converter (10) such that it transfers energy from the high-voltage branch (110) to the low-voltage branch (120). [2] The method of claim 1, further comprising: in the normal operating mode, operating the DC-DC converter (10) such that it transfers energy from the high-voltage branch (110) to the low-voltage branch (120). [3] The method of claim 1 or 2, further comprising: in the generator operating mode, operating the converter circuit (115) such that the q component of the stator current is negative and its magnitude increases with decreasing speed of the electric machine. [4] Method according to claim 3, wherein the q-component of the stator current, iq, is predetermined as a function of an electrical resistance, R S , the stator winding, a maximum permissible current, I max, a number of pole pairs, P, of the rotor of the electrical machine, the mechanical angular frequency ω of the electrical machine and the flux density, ψ PM , the permanent magnet arrangement in the rotor of the electrical machine, in particular according to: iq=Rs×Imax2P×ω×ΨPM [5] Method according to one of the preceding claims, further comprising: in the generator operating mode, operating the converter circuit (115) such that the d-component of the stator current, id, is negative and greater than a lower current limit value which is the quotient of the flux density of the permanent magnet arrangement in the rotor, ψ PM , and the d-component of the inductance of the stator winding, L d , erabt. according to: id>−ΨPMLd [6] Method according to one of the preceding claims, wherein the power converter device in the low-voltage branch (120) has a discharge circuit (31), further comprising: in the fault operating mode, operating the discharge circuit (31) so that electrical energy is converted into heat. [7] Method according to one of the preceding claims, wherein the power converter device in the low-voltage branch (120) has a bypass circuit (32), further comprising: in the fault operating mode, operating the bypass circuit (32) such that current from the DC-DC converter (10) is conducted into a low-voltage network (2) connected to the low-voltage branch (120). [8] The method of claim 7, further comprising: in the normal operating mode, operating the bypass circuit (32) such that no current is conducted from the DC-DC converter (10) into the low-voltage network (2) connected to the low-voltage branch (120). [9] Power converter device (200) for controlling an electrical machine (500), the power converter device (200) comprising: - a converter circuit (115), - a control device (123) and - a power supply circuit (100) for supplying the power converter circuit (115) and the control device (123), wherein the power supply circuit (100) has a high-voltage branch (110) with a high-voltage level, a low-voltage branch (120) with a low-voltage level and a DC-DC converter (10), wherein the high-voltage branch (110) is connected to the low-voltage branch (120) via the DC-DC converter (10), wherein the high-voltage branch (110) has an intermediate circuit capacitance (111), wherein the power converter device (200) is configured to carry out the method according to one of the preceding claims. [10] The power converter device (200) according to claim 9, further comprising a housing in which the power converter circuit (115), the control device (123) and the power supply circuit (100) are arranged. [11] Power converter device (200) according to claim 9 or 10, further comprising low-voltage terminals (B+, B-) which are configured to be connected to a low-voltage network (2) of a vehicle, high-voltage terminals (HV+, HV-) which are configured to be connected to a high-voltage network (1) of the vehicle, and machine terminals (U, V, W) which are configured to be connected to stator windings of the electric machine (500). [12] Arrangement comprising a power converter device (200) according to one of claims 9 to 11 and an electrical machine (500) connected to the power converter circuit (115). [13] On-board electrical system, in particular of a vehicle, with a low-voltage network (2) connected to the low-voltage branch (120), a high-voltage network (1) connected to the high-voltage branch (110), and an arrangement according to claim 12.

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