WO2023041220A1

WO2023041220A1 - Device and method for operating an electric machine

Info

Publication number: WO2023041220A1
Application number: PCT/EP2022/069093
Authority: WO
Inventors: Uwe Rauscher
Original assignee: Robert Bosch Gmbh
Priority date: 2021-09-17
Filing date: 2022-07-08
Publication date: 2023-03-23
Also published as: DE102021210336A1

Abstract

The invention relates to a device (100) and a method (400) for operating an electric machine (190). The device (100) comprises a power module (110) of an inverter (120). The power module (110) comprises a plurality of switching elements (112Px, 112Nx) and a gate-driver ASIC (114). The gate-driver ASIC (114) is designed to control the switching elements (112Px, 112Nx) according to a predetermined sequence during a transition from a controlled operation to a short-circuit mode.

Description

title

Device and method for operating an electrical machine

The invention relates to a device and a method for operating an electrical machine. Furthermore, the invention relates to a drive train with a device and a vehicle with a drive train.

State of the art

Electromobility is playing an increasingly important role in the current generation of automobiles. Electric drives are used either completely as an alternative to the well-known combustion engine or as support for the combustion engine (hybrid). The concept behind these drives is currently a traction battery with battery cells connected in series, a corresponding intermediate circuit and an inverter. By means of an inverter, the DC voltage of the traction battery present at the intermediate circuit is converted into a multi-phase AC voltage for supplying the electrical machine of the electrical drive train. This drive concept can also be used as a generator to convert kinetic energy back into electrical energy. Defects can occur in the electronics used for this purpose due to use, wear and tear and aging. In the event of a defect, this must be detected and the drive system must be placed in a safe state so that the electric drive train does not pose a risk to users or bystanders in the area surrounding the electric drive train. The so-called active short circuit (ACS) of an electrical machine is known to be a safe state. The individual windings of the electrical machine are short-circuited with one another. In the event of a fault, no energy can be fed back into the electronics as a generator, and a braking torque occurs on the rotor of the electrical machine. For the Setting the active short circuit, the individual windings of the electrical machine are short-circuited with one another by permanently closing all high- or low-side switching elements in an inverter. A distinction is currently made between a "hard" active short circuit and a "safe turn off" (STO). With the "hard" active short circuit, a discretely constructed hardware is used to switch to the active short circuit once and permanently immediately after the occurrence of an error. The windings of the electrical machine are connected to one another by closing the switching elements and short circuited. However, since the current flow wants to be maintained due to the inductances in the system, considerable voltage increases occur at the opposite switching elements or power switches in the respective half-bridges in the first moment after the short circuit has been switched, which again leads to a brief current peak in the system. In order to minimize this effect, instead of a hard and one-time switching into the short circuit, a controlled switching into the short circuit takes place. This is called a safe turn off. A corresponding method is known from publication EP 3 083 320 B1, in which no relevant voltage or current overshoots occur when switching to the active short circuit. Depending on the current operating mode of the vehicle and the corresponding current, switching to the active short circuit can be done individually. This is controlled by the software within a control logic of the inverter or inverter. The control logic outputs signals that are transmitted to a gate driver via an interface. The safe turn off is controlled by the inverter software. For this purpose, a gate driver is controlled via an interface, which in turn controls the power module. The switching elements are controlled in a clocked manner and gently clocked into the upper (high-side switching elements closed) or lower (low-side switching elements closed) active short circuit. Due to the gentle triggering in the active short circuit, only slight voltage and thus current overshoots occur at the switching elements or power semiconductors. Therefore, no design reservations need to be taken into account. Safe turn off is preferably controlled via the central pC of the inverter and via the software. Therefore, this method cannot be used for certain types of errors. This includes errors such as software errors, software resets, hardware errors in the PC and peripherals and errors in the transmission from the PC to the gate driver. At If these types of errors occur, the "hard" active short circuit must be activated, since this works without the PC software. In order to be able to take all possible faults into account, both options for switching to the active short circuit are provided. In all cases where the inverter logic and software still work, the safe turn off procedure is preferably used. In all other cases, hard switching to the active short circuit is required. Even if the "hard" active short-circuit method is only used very rarely, the device must be able to withstand the effects of the very high voltages and currents that occur for a short time. This means correspondingly more work in the system design, for example the selection of materials and substances, as well as in the chip design, which in turn leads to increased product costs. There is therefore a need for alternative control solutions that still enable a safe turn off even if the inverter logic and/or software fails.

Disclosure of Invention

A device for operating an electrical machine is provided. The device includes a power module of an inverter. The power module includes a plurality of switching elements and a gate driver ASIC. The gate driver ASIC is designed to provide an AC voltage at the terminals of the electrical machine by driving the switching elements in controlled operation and to electrically connect the terminals of the electrical machine to one another in short-circuit operation. Furthermore, the gate driver ASIC is designed to drive the switching elements according to a predetermined sequence when there is a transition from controlled operation to short-circuit operation.

An apparatus is provided that includes a power module. A power module includes multiple switching elements or power semiconductors. For example, a power module for supplying a three-phase electrical machine includes a B6 bridge circuit. These are three half-bridges connected in parallel. A half bridge comprises a series connection of two switching elements mente and is connected between the DC voltage potentials or input terminals of an inverter. A center tap between the two switching elements is electrically connected to one of the phase connections for connection to a multi-phase electrical machine. By closing one of the upper or lower switching elements of a half-bridge, an electrical connection is established between the upper or the lower DC voltage potential and a phase connection. The power module further includes a gate driver ASIC. To control the switching elements, these include a control contact or a gate. If a switching signal with a high level or voltage is applied to this control contact, the switching element closes. As soon as a low level or voltage is present at the control contact or at the gate, the switching element opens again. A gate driver is an electronic circuit that provides the appropriate level at the gate or drive contact depending on a drive signal. An ASIC is an application-specific integrated circuit (English application-specific integrated circuit, ASIC, also custom chip). It is an electronic circuit realized as an integrated circuit. The function of an ASIC can no longer be changed. In the case of large quantities, the lower production costs amortize the one-time high development costs. The power module with the integrated switching elements includes a gate driver ASIC, i.e. an integrated circuit for controlling the control contacts. Both the switching elements and the integrated circuit are cast together in one component. In controlled operation, the power module, i.e. the gate driver ASIC and the controlled switching elements together, provide an AC voltage at the phase connections of the inverter. In short-circuit operation, the power module, and thus the gate driver ASIC and the activated switching elements together, electrically connect the phase connections for connecting an electrical machine to one another according to a predetermined sequence. A sequence for controlling the switching elements is preferably specified in the gate driver ASIC, which sequence controls the switching elements in such a way that switching to a safe turn off is performed gently. This can preferably be adjusted individually, preferably using a characteristic field within the gate driver ASICS depending on the operating point, determined current speed and/or voltages or currents of the electrical machine or the DC voltage potential at the input of the inverter. A device is advantageously provided which independently sets a safe turn off. This means that when designing an inverter, the special operating case of "hard" switching of an active short circuit does not have to be taken into account and significant savings are possible in chip areas of the power semiconductors or materials in the assembly and connection technology.

In another embodiment of the invention, the actuation of the switching elements according to a predetermined sequence includes setting the amplitude of the AC voltage provided at the phase terminals for connecting the electrical machine to a predetermined value.

The gate driver ASIC is designed to lower the amplitude of the AC voltage provided at the phase connections for connecting the electrical machine to 0 volts during a transition from controlled operation to short-circuit operation and then preferably closes the switching elements for a lower or upper active short circuit permanently close. Alternatively, the amplitude of the AC voltage provided at the phase connections for connecting the electrical machine can be lowered to a value during a transition from controlled operation to short-circuit operation, which is lower than the phase voltage at the phase connections for connecting the electrical machine during controlled operating. Such a reduction in the electrical voltage at the phase connections for connecting the electrical machine before the transition to the active short circuit can ensure that no dangerous overcurrents occur that would lead to damage or premature aging of the components used.

In another embodiment of the invention, the power module includes an error pin. The control of the switching elements is activated according to a specified sequence by means of the error pin.

An error pin is arranged on the power module. If a level at this error pin exceeds a predetermined voltage, the gate driver ASIC is driven directly and the gate driver ASIC is directly driving the Switching elements activated after a predetermined sequence. This means that the device changes from controlled operation to short-circuit operation. Advantageously, no further PC or inverter logic or another functioning circuit/control unit is necessary in the event of a fault in order to transfer the device, and preferably an electrical machine connected to it, to a safe state.

In another embodiment of the invention, the specified sequence is permanently implemented within the gate driver ASIC.

A device is provided in which the predetermined sequence is permanently implemented in the gate driver ASIC. This means that the specified sequence is stored hard via logic in the gate driver ASIC or is immutably implemented as an integrated circuit within the gate driver ASIC. A variant for integration within the gate driver ASIC is advantageously provided.

In another embodiment of the invention, the specified sequence is implemented via a programmable ROM/EPROM within the gate driver ASIC.

A device is provided, with the specified sequence being implemented in the gate driver ASIC via a programmable memory component within the gate driver ASIC. This means that the specified sequence can be set in the gate driver ASIC via a programmable memory module, preferably a ROM or EPROM. The setting of the specified sequence as a function of the inverter and its power is thus preferably carried out by means of programming, preferably in an end-of-line test of the inverter. A variant for integration within the gate driver ASIC is advantageously provided.

Furthermore, the invention includes an electric drive train of a vehicle. The electric drive train includes a device described and an inverter. The drive train preferably includes a traction battery. A drive train of a vehicle is used to convert electrical energy from an energy source into mechanical energy, which is used to propel the vehicle. In an electric drive train, for example, the electric energy from an energy source is converted into an AC voltage by means of an inverter, with which an electric machine is operated. The device provides a way of effectively converting the drive train into a safe state.

Furthermore, the invention relates to a vehicle with a drive train as previously described. A vehicle is advantageously provided which is effectively transferred to a safe state.

Furthermore, the invention relates to a method for operating an electrical machine. The method is carried out using a device. The device includes a power module of an inverter. The power module includes a plurality of switching elements and a gate driver ASIC. The method comprises the steps: Driving the switching elements using the gate driver ASIC in a controlled operation to provide an AC voltage at the terminals of the electrical machine and driving the switching elements using the gate driver ASIC according to a predetermined sequence at a transition from the controlled operation to the short-circuit operation.

A method is provided for controlling an electric machine. In open-loop operation, the electric machine is activated as a function of a specified torque. The rotor of the electrical machine rotates accordingly and delivers a corresponding torque. In the event of an error, the power module within the inverter is switched to a safe state. For this purpose, a predetermined sequence is activated in the gate driver ASIC, with which the upper or lower switching elements of the power module are controlled or clocked and closed. A safe turn off is carried out. The electrical phases of the connected electrical machine are thus short-circuited and the entire drive train or the vehicle is brought into a safe state. A method is advantageously provided which effectively transfers the device, the inverter, the drive train or the vehicle to a safe state. It goes without saying that the features, properties and advantages of the device apply or can be applied accordingly to the method or the drive train and the vehicle and vice versa.

Further features and advantages of embodiments of the invention result from the following description with reference to the accompanying drawings.

Brief description of the drawing

In the following, the invention will be explained in more detail with reference to some figures, showing:

Figure 1 is a schematic representation of the device,

Figure 2 shows a vehicle shown schematically with a drive train with the device,

FIG. 7 shows a diagrammatically illustrated method for operating an electrical machine

Embodiments of the invention

FIG. 1 shows a device 100 for operating an electrical machine 190. The device 100 includes a power module 110 of an inverter 120, pulse-controlled inverter or inverter. The power module 110 includes a plurality of switching elements 112P1, 112P2, 112P3, 112N1, 112N2, 112N3 and a gate driver ASIC 114. A power module 110 is shown as an example with a B6 bridge, which includes the six switching elements 112Px, 112Nx for conversion a DC voltage into a multi-phase, in this case three-phase, AC voltage. Depending on the application, required power and/or number of phases for supplying a load, fewer or more switching elements 112Px, 112Nx can be connected in parallel as half-bridges. The gate driver AS IC 114, preferably within the power module 110, is designed to provide an AC voltage at the phase connections 118 for the connection of an electrical machine 190 by driving the switching elements 112Px, 112Nx in a controlled operation and the phase connections in a short-circuit operation 118 for the connection of an electrical machine 190 to be electrically connected to one another. The direct driving of the switching elements by means of the gate driver ASICS 114 is shown in the drawing by means of the arrow pointing to the switching elements. The gate driver ASIC 114 is designed to drive the switching elements 112Px, 112Nx according to a predefined sequence when there is a transition from controlled operation to short-circuit operation and then preferably to permanently set an upper or lower active short circuit. For this purpose, the power module preferably includes an error pin 116, via which the actuation of the switching elements 112Px, 112Nx by means of the gate driver AS IC 114 is activated according to a predetermined sequence. The error pin 116 is preferably actuated via a PC, a control unit or switching logic 130 of the inverter, which is preferably arranged outside the power module. Outside of the power module can be inside the inverter 120 or also outside of the inverter 120, for example in another control device in a vehicle. In the event of a fault, such a switching logic preferably provides an increased voltage level at the fault pin 116 in order to activate the actuation of the switching elements 112Px, 112Nx by means of the gate driver ASIC 114 according to a predetermined sequence. An intermediate circuit capacitor for smoothing the input DC voltage is preferably connected on the input side of the inverter 120 or the power module 110 to the input connections or the DC voltage potentials 119 . A traction battery 150 for supplying the electrical machine is preferably also connected to these direct voltage potentials 119 .

Figure 2 shows a schematically illustrated vehicle 300 with four wheels 302 and a drive train 200. The vehicle 300 is shown here only as an example with four wheels 302, the invention being equally applicable in any vehicle with any number of wheels on land, on water and in the air can be used. The drive train 200 shown as an example includes at least one device 100. The drive train 200 also includes an inverter 120, within which the device 100 is arranged and in particular a traction battery 150. The drive train 200 preferably includes an electric machine 190 for driving a drive axle of the vehicle 300 .

FIG. 3 shows a schematically illustrated flowchart for a method 400 for operating an electrical machine 190. The method begins with step 405. In step 410, switching elements 112 Px,

112Nx provided by the gate driver ASIC 114 in a controlled operation, an AC voltage at the terminals of the electrical machine 190. In the event of a transition to short-circuit operation, in a step 420 the switching elements 112Px, 112Nx are driven by the gate driver ASIC 114 according to a predetermined sequence. With step 425 the method ends.

Claims

Expectations

1. Device (100) for operating an electrical machine (190), the device (100) comprising a power module (110) of an inverter (120), the power module (110) having a plurality of switching elements (112 Px, 112Nx) and a gate driver ASIC (114), wherein the gate driver ASIC (114) is designed to drive the switching elements (112Px, 112Nx) in a controlled operation, an AC voltage at the phase terminals (118) for connecting a to provide an electrical machine (190) and to electrically connect the phase connections (118) for the connection of an electrical machine (190) to one another in a short-circuit mode, characterized in that the gate driver ASIC (114) is designed to, during a transition from to drive the switching elements (112 Px, 112Nx) according to a predetermined sequence from the controlled operation to the short-circuit operation.

2. Device according to claim 1, wherein the actuation of the switching elements according to a predetermined sequence comprises the setting of the amplitude of the AC voltage provided at the phase terminals (118) for the connection of the electrical machine (190) to a predetermined value.

3. Device according to one of the preceding claims, wherein the power module comprises an error pin (116) via which the driving of the switching elements (112Px, 112Nx) is activated according to a predetermined sequence.

4. Device according to one of the preceding claims, wherein the predetermined sequence is permanently implemented within the gate driver ASIC (114).

5. Device according to one of claims 1 to 3, wherein the predetermined sequence is implemented via a programmable memory component within the gate driver ASICS (114).

6. Electrical drive train (200) for a vehicle, wherein the drive train comprises a device (100) according to any one of claims 1 to 5 and an inverter (120) and in particular a traction battery (150).

7. Vehicle (300) with a drive train (200) according to claim 6.

8. Method (400) for operating an electrical machine (190), with a device (100), wherein the device (100) comprises a power module (110) of an inverter (120), and the power module (110) comprises a plurality of switching elements (112Px, 112Nx) and a gate driver ASIC (114), comprising the steps:

Driving (410) the switching elements (112Px, 112Nx) by means of the gate driver ASIC (114) in a controlled operation to provide an AC voltage at the terminals of the electrical machine (190);

Driving (420) the switching elements (112Px, 112Nx) by means of the gate driver ASIC (114) according to a predetermined sequence during a transition from the controlled operation to the short-circuit operation.