Assembly with inverter

Abstract

The invention discloses an assembly with an inverter for an electric drive of a vehicle, wherein at the direct current input of the inverter a direct current sensor is provided for acquiring the direct current flowing into the inverter, wherein the direct current sensor is connected to a processor for acquiring a quantity representing the direct current, wherein the processor determines a short circuit in the inverter depending on the quantity and at least one further parameter on the inverter or an electric motor connected to the inverter and sends a message depending on the first determination.

Description

Technical Field

[0001] According to the type of independent patent claim, the present invention relates to a component having an inverter and a method for operating such a component. Background Technology

[0002] For example, it is known from DE 10 2018 105 505 A1 that short circuits in traction battery assemblies can be identified by means of current balancing.

[0003] Accordingly, components with inverters having the features of the independent claims of the patent, or methods for operating such components, have the advantage of reliably identifying short circuits in the inverter in general by determining the short circuit based on the DC current flowing into the inverter and another parameter obtained from the inverter or the electric motor connected to the inverter. Here, the components according to the invention are particularly suited to slowly developing and progressively larger short circuits. In this case, it is difficult to reliably identify the short circuit based solely on the parameter (the DC current necessarily flowing into the inverter), because such a slowly developing short circuit is similar to normal operation. Therefore, a second test condition is introduced by the parameter to ensure reliable identification of the short circuit. If such a slowly developing short circuit cannot be reliably identified, there is a risk of the inverter catching fire. Summary of the Invention

[0004] Therefore, an assembly for an inverter with an electric drive unit for a vehicle is proposed, wherein a DC current sensor for acquiring the DC current flowing into the inverter is provided at the DC current input terminal of the inverter, wherein the DC current sensor is connected to a processor for acquiring a parameter representing the DC current, wherein the processor determines a short circuit in the inverter based on the parameter and at least one other parameter on the inverter or an electric motor connected to the inverter, and sends a message based on this first determination. Correspondingly, a method for operating such an assembly is proposed.

[0005] The component is understood as an inverter having connected parts (e.g., a DC current sensor, at least one processor, and at least one electric motor). An inverter is also understood herein as a power electronic device.

[0006] An inverter is a component that converts direct current (DC) to alternating current (AC). DC current is supplied via a so-called intermediate circuit and intermediate circuit capacitors, and then converted to AC current by a circuit with power switches. This is done by chopping the DC current. The AC current is then used to control or drive, for example, an electric motor. Here, the AC current consists of three phases, and for this purpose, three sets of power switches (i.e., those used to generate the corresponding phases) are provided.

[0007] Electric drive units should be understood as electric drive units of vehicles (e.g., passenger motor vehicles) or so-called hybrid drive units of vehicles, i.e., drive units having at least one electric motor and a combustion engine.

[0008] The DC current input terminal should be understood as supplying power to the inverter; DC current reaches the inverter through this DC current input terminal. Here, this serves as the intermediate circuit feed.

[0009] A DC current sensor measures the DC current flowing into the inverter. All possible measurement principles for detecting DC current can be used. This DC current sensor is connected to a processor that receives the measured value as a parameter and can also perform the final determination of the DC current.

[0010] A parameter is understood as a measured value of the DC current itself or a parameter derived therefrom (e.g., power input to an inverter), but it can also be understood as any other parameter derived from the measured value.

[0011] The processor is, for example, a microcontroller, a microprocessor, or any other suitable arithmetic architecture, which is suitable for processing parameters and the at least one parameter and for implementing the first determination.

[0012] The at least one parameter is obtained on the inverter and / or the electric motor. Here, the at least one parameter is preferably a parameter derived from the alternating current (e.g., the alternating current itself, or the output power of the inverter, or the mechanical power of the electric motor). As implemented in the dependent claims, the basic concept of the invention is to ensure, in its sense, the parameter with respect to the first determination. This can be used, for example, to re-determine the direct current (which is ultimately the intermediate circuit current) by means of the parameter, so as to determine whether the parameter is based on a correctly measured value.

[0013] For the first determination, the presence of a short circuit in the inverter is determined based on parameters and specifications. This can be done through threshold lookup or comparison with stored values ​​(e.g., from a lookup table), where one or more models are stored, such as how the time curves of DC current behave relative to typical short-circuit behavior. That is, whether the curve corresponds to this short circuit.

[0014] Typically, a message (sent by the processor) is sent in the event of a short circuit, causing, for example, a battery control unit to disconnect a DC current contactor to minimize damage. However, messages can also be sent periodically, reporting that everything is normal even if no short circuit is detected. For this transmission, the processor is connected to an interface that enables data transmission of the message. This could be, for example, a CAN bus interface or other wired data transmission interfaces. Radio transmission is also possible.

[0015] Advantageous improvements to the current converter for at least partially electrically driven vehicles, as given in the independent patent claims, are provided by means of the measures and improvements listed in the dependent claims.

[0016] It is proposed here that the DC current sensor is designed as a magnetoresistive DC current sensor. This type of sensor can achieve current decoupling between the current to be measured and the measured current, and the sensor is based on the anisotropic magnetoresistive effect (AMR). Furthermore, the sensor may have a first signal processing device.

[0017] Furthermore, it is proposed that the processor is adapted to perform a reliability test on the parameter using the at least one additional parameter and to determine the short circuit based on the parameter and the reliability test. Accordingly, the reliability test here means that the parameter is judged to be correct and the short circuit is reliably determined using the parameter.

[0018] Furthermore, it is proposed that the processor performs the reliability test by determining the DC current or a parameter representing the DC current, which depends on at least one parameter. Thus, the DC current or parameter is determined again using the parameter to perform a reliability test on the parameter.

[0019] Furthermore, it is proposed that the processor implements the second determination using power balancing, in that, for input power, the processor sets the first power loss from the input wire to the inverter, the second power loss of the inverter, the third power loss of the AC current wire between the inverter and the electric motor, the fourth power loss of the electric motor, and the mechanical output power of the electric motor into the inverter. By analyzing the power balancing, where the power applied to the inverter is compared with the power loss and output power of the inverter due to heat generation, and further compared with the power loss and mechanical output power of the electric motor, the DC current can be deduced. Here, the power loss of the current-guiding wires entering and leaving the inverter is also considered. It can be proposed that the first and / or third power loss be set to zero, as they do not play a decisive role.

[0020] Furthermore, it is proposed that the processor determines the mechanical output power using the torque and speed of the electric motor. These values ​​can be obtained through corresponding sensors.

[0021] Furthermore, it is proposed that the processor determines the fourth power loss using the copper losses of the electric motor. Here, the current flowing into the electric motor is considered, and ohmic resistance is taken into account using a model; that is, the ohmic resistance is stored and changes, for example, using one or more parameters, such as stored characteristic curves. Here, the resistance depends on temperature and rotor speed. The skin effect is also considered.

[0022] Furthermore, it is proposed that the processor determines the second power loss based on the alternating current. A model is then used. A feature map is stored in the processor, which determines the second power loss based on the switching frequency, voltage, and current magnitude.

[0023] Furthermore, it is proposed that the processor implements the second determination by means of current balancing, wherein the processor determines an additional DC current by means of the inverter DC current and the machine DC current, wherein the inverter DC current is determined by the second power loss and the input DC voltage on the inverter, and wherein the machine DC current is determined by the AC current and the duty cycle value of the power switch in the inverter.

[0024] Furthermore, it is proposed that the processor determines the second power loss based on the AC current, and / or the switching frequency of the power switch, and / or the temperature.

[0025] Furthermore, it is proposed that when the power switch is not operated and the electric motor has no speed, the processor sets the second DC current to zero. This achieves calibration.

[0026] Furthermore, it is proposed that the processor identifies the short circuit based on the duration of the short circuit within a predetermined time period and / or by determining the number of short circuits that occur. This ensures that a brief event indicating the occurrence of a short circuit does not trigger action against that short circuit, but only when the short circuit itself is confirmed over a period of time. The magnitude of the DC current can also affect the judgment. A high current can lead to a rapid identification of a short circuit; a low current can lead to a slower identification. Attached Figure Description

[0027] Embodiments of the invention are illustrated in the accompanying drawings and will be described in more detail in the following description.

[0028] In the attached diagram:

[0029] Figure 1 A first schematic diagram of the components according to the present invention is shown;

[0030] Figure 2 A second schematic diagram of the components according to the invention is shown;

[0031] Figure 3 A schematic diagram of power balance is shown;

[0032] Figure 4 A schematic diagram showing current balance, and

[0033] Figure 5 A block diagram of the method according to the present invention is shown. Detailed Implementation

[0034] Figure 1 A first schematic diagram of the component according to the invention is shown. The component is powered by a high-voltage direct current (HVDC) grid (e.g., a high-voltage battery connected to the HVDC grid). For this purpose, leads ZLW are provided from the connection terminal of the HVDC grid to the inverter WR. These leads ZLW typically have ohmic losses. A DC current sensor GSS is also provided in the leads ZLW to measure the DC current I flowing into the inverter WR. DC A DC voltage U is applied to the input terminal of the inverter WR. DC Therefore, the power P input to the inverter is... DC =I DC *U DC The DC current sensor GSS is connected to a microcontroller μC (as a processor) via a data cable. The current I is transmitted through this data cable. DC The parameter is then processed by the microcontroller μC. This parameter is particularly used to determine whether a short circuit is currently present. Signal analysis or pattern recognition can be used for this purpose. To ensure this, or for reliability testing, this parameter is compared with a DC current determined based on the AC current parameters of the inverter WR or the electric motor EM, or the mechanical parameters of the electric motor EM. Ideally, the measured DC current should match the determined DC current. An interval is set around the measured DC current to infer the consistency between the measured and determined DC currents. If it is determined that a short circuit exists and persists for a predetermined time, a message is sent from the microcontroller μC, via the CAN bus, to other control devices or only one device: a short circuit exists. These controllers will then implement measures to prevent or minimize damage caused by the short circuit.

[0035] The microcontroller μC is connected to the inverter WR to detect measured values ​​of the inverter (such as current, voltage, and temperature). Control of the inverter WR is also performed through this connection to convert DC current into AC current.

[0036] At the inverter WR, a connecting wire VLM leading to the electric motor EM is provided on the output side, through which three-phase alternating current is conducted. The microcontroller μC obtains the value i representing the alternating current, for example, using a current sensor.WR In order to improve control and to determine the DC current flowing into the inverter WR according to the present invention.

[0037] Furthermore, the microcontroller μC is connected to the electric motor EM to detect measurements, such as those from speed and torque sensors. The microcontroller μC can also be replaced by multiple processors, which are then interconnected.

[0038] exist Figure 2 A second illustration of the component according to the invention is shown. Here, the power applied to or output to the component and the potential power loss are shown on the component. The component is then connected to the high-voltage DC grid HVN via a connection terminal ZLW. The connection terminal ZLW and its conductors have a power loss P due to ohmic losses. ldc-cable In which power P is applied to the inverter WR eldc =I dc *U dc According to the present invention, the DC current I is checked. dc To what extent does it indicate a short circuit, especially a slowly worsening one? If the voltage Udc is not measured directly at the inverter WR, but at the connection between the HVDC grid HVN and the lead ZLW, then the power loss P on the lead must be subtracted from the power balance. ldc-cable .

[0039] In an inverter WR, power losses P due to heat generation in power electronics must be considered during power balance. linv Similarly, the wires used to guide the alternating current phase from the inverter WR to the electric motor EM generate ohmic loss power P. lac-cable At the same time, with P elac This indicates the output power generated by the inverter WR through alternating current.

[0040] Electric motor EM has power loss P lem and mechanical output power P mech This power loss P lem This is particularly due to ohmic losses in the coil.

[0041] Therefore, a power balance can now be established, and the DC current I can thus be deduced from the AC power or mechanical power. DS And therefore, a credibility test was conducted: the measured I DS Is this correct? Individual power loss can be predetermined or obtained through measured and stored values.

[0042] Figure 3 A schematic diagram of power balance is shown. In box 34, the mechanical power P is determined according to parameters 35 and 36.mech Parameter 35 is the motor torque, which can be obtained using a torque sensor. Alternatively, in a permanently excited electric motor, the torque can be obtained from the measured alternating current and the measured angle of the rotor. In an asynchronous motor, this can be obtained from the rotational speed and the alternating current. Parameter 36 is the motor speed, which is determined based on the rotational speed. For this purpose, a speed sensor is provided, for example.

[0043] Adder 33 converts the mechanical power P of electric motor EM. mech The power loss P of the electric motor EM lem Add them together. This power loss P lem In box 37, the ohmic losses in the electric motor EM are determined. This is done using the AC currents of the three phases and the stator parameters. As mentioned above, a model is used to determine the copper losses in the electric motor. Additionally, the iron losses of the electric motor can also be considered. Here, the loss torque can then be determined based on the rotational speed. The model or characteristic curve is also stored here. Other parameters that cause power loss are also ignored here. These include eddy currents, harmonics, friction, and magnetic losses.

[0044] The sum P from adder 33 elac This generates the output power of the inverter WR. This power P is then converted using adder 32. elac With the inverter's power loss P linv Add them together to determine the power P input to the inverter WR. eldc Determine the power loss P in box 30. linv This power loss P linv Determined based on the AC current and (if necessary) the switching frequency of the inverter WR.

[0045] According to power P eldc and voltage U dc The current I is calculated in the operator by division. dc Here, the voltage can be used as a fixed value or a measured value. Then, the calculated current I... dc Used to measure the current I dc Conduct a credibility test.

[0046] The determination of power balance shown here is performed in the microcontroller μC using the sensor values ​​mentioned above or the stored values.

[0047] Figure 4 A schematic diagram of current balancing is shown, which is also performed in the microcontroller μC. In block 43, the current is balanced using alternating current I. wr The switching frequency is used to determine the power loss P of the inverter WR. inverterHowever, other input parameters can also be used here, such as the temperature in the inverter WR.

[0048] According to the power loss P inverter and voltage U dc The current loss I is determined by division 42. dcinv The current loss I is converted by adder 41. dcinv With machine current I dcm Add them together to get the calculated value I dc .

[0049] Machine current I dcm It is direct current (DC), which is eventually converted into alternating current (AC). This machine current is represented in box 40 according to the AC current I. WR The duty cycle (DC) is determined by the pulse width modulation used to control the power switches in the inverter WR. Here, the DC current components of the three phases are summed. The duty cycle is the ratio of the number of times the power switch is controlled to the number of times it is not controlled within one cycle.

[0050] Figure 5 A block diagram of the method according to the invention is shown. In block 50, a DC current Idcm is measured, and in block 51, the current is determined based on an AC current parameter or a mechanical parameter of the electric motor, in one of the ways described above. In block 52, the two current values ​​are compared: whether they at least substantially match. A match is then determined in block 53. This can be done by corresponding to an interval around the measured values ​​to suppress minor errors. If no match is found, the process jumps back to blocks 50 and 51. However, if a match is found, a short circuit is checked for in block 54, for example, by means of a pre-stored model. In block 55, it is checked whether this short circuit identification is not a one-off event but rather confirmed over a period of time. In block 56, it is checked whether both points are met; if so, a message is sent in block 57 (e.g., to the battery control unit) so that protective measures can be taken. An instruction may also be given to the driver to take the vehicle to a repair shop in a timely manner. However, if no short circuit is found, the process jumps back to blocks 50 and 51.

[0051] This method is performed on a microcontroller μC.

[0052] List of reference numerals

[0053] HVN High Voltage Direct Current Grid

[0054] Connection terminals on ZLW inverter

[0055] I dc DC current

[0056] U dc DC voltage

[0057] GSS DC voltage sensor

[0058] WR inverter

[0059] VLM inverter to electric motor connection wires

[0060] I wr Alternating current

[0061] μC micro controller

[0062] CAN bus

[0063] EM electric motor

[0064] P eldc Input power

[0065] P ldc-cable Lead power loss

[0066] P linv Inverter power loss

[0067] P lac-cable Power loss of connecting wires

[0068] P elac Inverter output power

[0069] P lem Power loss of electric motor

[0070] P mech Mechanical output power

[0071] Operators 30-37

[0072] Operators 40-43

[0073] DC duty cycle value, duty cycle

[0074] FS switching frequency

[0075] P inverter Inverter power loss

[0076] Methods and steps (50-57)

Claims

1. An assembly having an inverter (WR) for an electric drive device for a vehicle, wherein a method for acquiring a DC current (I) flowing into the inverter (WR) is provided at the DC current input terminal (ZVL) of the inverter (WR). dc A current sensor (GSS) for obtaining a representation of the direct current (I) dc A processor (µC) is connected to the parameters of the inverter (WR) and at least one other parameter on the inverter (WR) or the electric motor (EM) connected to the inverter (WR) to determine a short circuit in the inverter (WR), and sends a message based on this first determination, wherein, The at least one additional parameter is a DC current determined based on the AC current parameters of the inverter (WR) or the electric motor (EM) or the mechanical parameters of the electric motor (EM), characterized in that the processor (µC) is adapted such that the processor (µC) performs a reliability test on the parameter using the at least one additional parameter and determines the short circuit based on the parameter and the reliability test.

2. The component according to claim 1, characterized in that, The DC current sensor (GSS) is designed as a magnetoresistive DC current sensor.

3. The component according to claim 1, characterized in that, The processor (µC) carries out the plausibility test by taking a second determination of the direct current (I dc ) or of a quantity representing the direct current (I dc ).

4. The component according to claim 3, characterized in that, The processor (µC) implements the second determination using power balancing in the following manner: for input power (P) eldc In this regard, the processor (µC) will convert the first power loss (P) of the inverter (WR) linv The second power loss of the electric motor (P) lem ) and the mechanical output power (P) of the electric motor (EM). mech ) is set in the inverter.

5. The component according to claim 4, characterized in that, The processor (µC) determines the mechanical output power (P) using the torque and speed of the electric motor (EM). mech ).

6. The component according to claim 4, characterized in that, The processor (µC) determines the second power loss (P) using the copper losses of the electric motor. lem ).

7. The component according to claim 4, characterized in that, The processor (µC) determines the first power loss (P) based on the alternating current. linv ).

8. The component according to any one of claims 4 to 7, characterized in that, Additionally, regarding the power balance, with respect to the input power, the processor considers the third power loss (P) from the input conductor (ZVL) to the inverter (WR). ldc-cable The fourth power loss (P) in the AC current conductor (VLM) between the inverter and the electric motor. lac-cable ).

9. The component according to claim 3, characterized in that, The processor (µC) implements the second determination by means of current balancing, wherein the processor determines an additional DC current by means of the inverter DC current and the machine DC current, wherein the inverter DC current is determined by the second power loss and the input DC voltage on the inverter (WR), and wherein the machine DC current is determined by the AC current of each phase and the corresponding duty cycle value of the power switch in the inverter (WR) thereby controlling it.

10. The component according to claim 9, characterized in that, The processor (µC) determines the second power loss based on the AC current, and / or the switching frequency of the power switch, and / or the temperature.

11. The component according to claim 9, characterized in that, When the power switch is not operated and the electric motor (EM) has no rotational speed, the processor (µC) sets the second DC current to zero.

12. The component according to claim 1, characterized in that, The processor (µC) identifies the short circuit based on the duration of the short circuit within a predetermined time, and / or the number of short circuits that occur, and / or the magnitude of the DC current.

13. A method for operating a component according to any one of claims 1 to 12, characterized in that, The method includes the following steps: - By means of at least one additional parameter on the inverter (WR) or the electric motor (EM) connected to the inverter (WR), the DC current (I) flowing into the inverter (WR) is expressed as... dc The parameters of ) are tested for credibility. The short circuit in the inverter (WR) is determined based on the parameters and the reliability test, and - The message is sent based on this first determination.

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