Inverter unit

Abstract

The invention relates to an inverter unit (10) having a switch (12), an intermediate circuit (14), and a component (16), the inverter unit (10) being provided for switching the switch (12) in accordance with a predetermined switching sequence in order to empty the intermediate circuit (14), the component (16) being provided for switching the switch (12) in accordance with a predetermined switching sequence in order to empty the intermediate circuit (14). According to the invention, the predetermined switching sequence is provided for generating a current drop with a substantially constant change in the intermediate circuit (14) in order to introduce thermal energy generated by a short circuit into the inverter unit (10) in order to determine the aging of the component (16).

Description

Technical Field

[0001] The invention relates to an inverter unit and a vehicle. Background Art

[0002] There are currently a large number of different inverter unit solutions and methods for disconnecting the battery protection in electrically driven vehicles. Due to the increase in the number of electrically driven vehicles and the increase in efficiency, the demand for innovative and robust inverter units is increasing.

[0003] The continuous reduction of weight in order to reduce consumption and increasing competition in the automotive sector lead to cost pressures, which intensify the demand for more economical and efficient components for vehicles. Summary of the invention

[0004] The inverter unit according to the invention has the following advantages over known inverter units: the energy present in the intermediate circuit to be discharged is used to determine the aging of the inverter unit, in particular the aging of components of the inverter unit. In this case, the inverter unit generates a targeted temperature rise due to the constant discharge, which can be compared with previous temperature rises in order to determine the aging of the thermal path. It is advantageous here that the introduced thermal energy can be derived from the exact knowledge of the energy converted by the intermediate circuit.

[0005] This is achieved according to the invention in that the inverter unit has switches, an intermediate circuit and components. The inverter unit is configured to switch the switches according to a predetermined switching sequence in order to empty the intermediate circuit, wherein the predetermined switching sequence is configured to generate a substantially constantly varying current drop in the intermediate circuit in order to introduce heat energy generated by the short circuit into the inverter unit for determining aging of the components.

[0006] In other words, the switch forms a short circuit with the intermediate circuit in order to generate heat energy as a result. In this case, the short circuit is formed in particular such that a plurality of short circuits introduce a constant heat flow into the inverter unit by opening and closing the switch. In this case, the heat introduced into the inverter unit can be quantified based on the current drop caused by switching the short circuit by means of the switch on the intermediate circuit. The heating of the components of the inverter unit can be calculated based on the introduced heat. Further preferably, the difference between the heating at the first time point and the second time point is determined by comparing the heating of the components of the inverter unit at the first time point with the heating of the components at the second time point when the same heat energy is generated, so that the aging of the components can be determined based on the difference. Thus, the aging of the components of the inverter unit can be tracked in the case of a plurality of discharges caused by the intermediate circuit through the short circuit and the correspondingly introduced heat energy. In this context, the substantially constant change can be in particular a current drop change of + / -50%. Further preferably, the predetermined switching sequence is designed so that the switch is switched for such a long time to form a short circuit that the intermediate circuit is substantially completely discharged, so that a safe state of the inverter unit can be achieved. In this case, the components of the inverter unit can also include switches. Further preferably, at least some of the switches can be heated by means of a predetermined switching sequence and / or a short circuit.

[0007] Preferred embodiments of the invention are described below.

[0008] Preferably, the predetermined switching sequence is provided for at least temporarily generating a short circuit in the inverter unit.

[0009] The advantage of this embodiment is that the inverter unit can have a plurality of switches or similar switches, wherein the inverter unit or a predetermined switching sequence is configured to be able to produce a short circuit by means of at least one switch, wherein all other switches can be switched accordingly in order to thus be able to discharge the intermediate circuit by means of a constant change.

[0010] Further preferably, the short circuit is a high-impedance half-bridge short circuit.

[0011] The advantage of this embodiment is that damage to the inverter unit or other components due to accidental conduction of the switch can be avoided.

[0012] Preferably, the inverter unit is configured to adjust a predetermined switching sequence when the voltage across the switch reaches a reference voltage to eliminate the short circuit.

[0013] The advantage of this embodiment is that the switch can be opened again when the limit voltage as the desired voltage is reached. Therefore, the closing time of the switch and the opening time of the switch can be defined in a predetermined switching sequence and adjusted according to the reference voltage or the voltage measured on the switch.

[0014] Preferably, the inverter unit is configured to generate a first current drop in the intermediate circuit at a first point in time and a second current drop in the intermediate circuit at a second point in time, wherein the inverter unit is configured to detect the temperature of the component, wherein the inverter unit is configured to detect a first temperature trend of the component for the first current drop and to detect a second temperature trend of the component for the second current drop, wherein the inverter unit is configured to determine aging of the component based on a comparison between the first temperature trend and the second temperature trend.

[0015] The advantage of this embodiment is that the aging of the components can be deduced by comparing the temperature profiles. Preferably, a plurality of temperature profiles are generated during the operating period of the inverter unit, so that the aging of the components can be determined continuously during the operating period. In this case, the aging can be determined in particular by a continuous decrease in the electrical conductivity of the inverter unit and / or its components during the operating period.

[0016] It is further preferred that the predetermined switching sequence is provided for placing the switch in a first state, wherein in the first state the gate voltage is equal to or less than a higher-order voltage.

[0017] The advantage of this embodiment is that at the current voltage the switch does not conduct with low resistance, which would lead to high short-circuit currents that could damage components of the inverter unit and other components. Thus, despite the short circuit being switched by the switch, the inverter unit remains in a safe state.

[0018] Further preferably, the inverter unit is configured to determine and / or adjust the switching duration of the switches in the predetermined switching sequence. This embodiment has the advantage that the switching duration of the switches can be determined and / or adjusted for each switching cycle in the predetermined switching sequence, so that a current drop that is as constant as possible can be generated in the intermediate circuit. The switching duration depends on a number of factors, which should be taken into account when determining and / or adjusting the switching duration.

[0019] Further preferably, the inverter unit is configured to adjust the switching duration as a function of the energy stored in the intermediate circuit.

[0020] The advantage of this embodiment is that the intermediate circuit can have different charge states and the switching duration or the predetermined switching sequence can be adjusted as a function of the energy in the intermediate circuit in order to be able to achieve a constant variation of the current drop.

[0021] Further preferably, the inverter unit is configured to ascertain an energy quantity for introduction into at least a part of the inverter unit as a function of the switching duration and the stored energy.

[0022] The advantage of this embodiment is that the amount of energy for each switching cycle of the switch can be determined with the help of the switch and the temperature thus formed on the switch can be calculated. In this case, in particular, the energy in the intermediate circuit when discharge begins or the current drops in the intermediate circuit can be determined. With the help of the energy and power loss of the discharge duration of the determined switching frequency, an array of the required energy and intermediate circuit voltage for each switching process can be determined during each switching process in a predetermined switching sequence. Here, the energy array with the required thermal impedance can be expanded so that the temperature during each switching process can be determined. Based on the correlation between the gate voltage and the turn-on time, the temperature correlation (i.e., the K value) of the temperature, the intermediate circuit voltage and the threshold voltage can be advantageously used to calculate the current for the current drop in the intermediate circuit. Further preferably, the following formula can be used:

[0023] I_Dsat=K / 2*(V_GS-V_Th) 2

[0024] Here, I_Dsat is preferably at least a part of the current drop, K is the K value, V_GS is the gate voltage, and V_Th is the threshold voltage.

[0025] From the current, the energy value per switching cycle can be determined in dependence on the switch-on duration by integration with the voltage. The switch-on time can thus advantageously be determined by comparison of the actual energy with the desired value for each cycle.

[0026] Preferably, the inverter unit is designed to adjust the predetermined switching sequence as a function of the determined energy quantity value, so that the intermediate circuit is discharged during a constant change.

[0027] The advantage of this embodiment is that the constant change in the current drop can be further quantified on the basis of the energy quantity determined per switching cycle and the thermal energy can thus be precisely determined.

[0028] It is further preferred that the constant variation has a linear profile and / or a logarithmic profile.

[0029] This embodiment has the advantage that energy can also be withdrawn from the intermediate circuit in a logarithmic manner in order to thereby improve the determination of the aging of the components.

[0030] The inverter unit is preferably configured to determine a voltage change at the intermediate circuit, wherein the inverter unit is configured to adjust the determined energy quantity value as a function of the voltage change.

[0031] This embodiment has the advantage that the voltage change between two or more switching cycles in a predetermined switching sequence can be ascertained and the desired energy can therefore be compared with the actual energy in order to adjust the switching sequence accordingly and thus correct the current drop.

[0032] The inverter unit preferably has a comparator, wherein the inverter unit is provided to adjust a current drop across the intermediate circuit by means of the comparator.

[0033] The advantage of this embodiment is that the current drop for a switching cycle can be quantified in a predetermined switching sequence and the current drop on the intermediate circuit can thus be further linearized. In particular, it is possible to switch from a controlled operation of the inverter unit to a regulated operation, since the inverter unit can quantify the current drop accordingly by means of a comparator.

[0034] Preferably, the inverter unit is configured to determine the temperature of the component, wherein the inverter unit is configured to form a difference between the thermal energy generated by the short circuit and the heating of the component, wherein the inverter unit is configured to determine aging of the component from the difference.

[0035] This embodiment has the advantage that the difference increases continuously during the operating period of the inverter unit. Further preferably, the difference over a period of the operating period of the inverter unit can be compared with individual discharges or discharges of the intermediate circuit in order to be able to draw conclusions about aging of the components.

[0036] Another aspect of the present invention relates to a vehicle having the above-mentioned inverter unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Embodiments of the present invention are described in detail below with reference to the accompanying drawings. In the accompanying drawings:

[0038] Figure 1 : An inverter unit according to one embodiment.

[0039] Figure 2 : A graph for illustrating the operation of an inverter unit according to one embodiment.

[0040] Figure 3 : A graph for illustrating the operation of an inverter unit according to one embodiment.

[0041] Figure 4 : A graph for illustrating the operation of an inverter unit according to one embodiment.

[0042] Figure 5 :vehicle.

[0043] Preferably, all identical components, units and / or elements are provided with the same reference symbols in all figures. DETAILED DESCRIPTION

[0044] Figure 1An inverter unit 10 according to one embodiment is shown. The inverter unit 10 has a switch 12, an intermediate circuit 14 and a component 16. The inverter unit 10 is configured to switch the switch 12 according to a predetermined switching sequence in order to discharge the intermediate circuit 14. Further preferably, the predetermined switching sequence is configured to generate a current drop with a substantially constant change in the intermediate circuit 14 in order to introduce the heat energy generated by the short circuit into the inverter unit 10 in order to determine the aging of the component 16. Further preferably, the inverter unit 10 can have a plurality of switches 12. Further preferably, the inverter unit 10 has a comparator 22.

[0045] Figure 2 A graph 50 is shown for illustrating the operation of an inverter unit 10 according to one embodiment. The graph 50 has a first sub-axis 52 representing the current on the switch 12. A second sub-axis 54 represents the voltage on the switch 12. A third sub-axis 56 shows the power. A fourth sub-axis 58 shows the electric field strength. A fifth sub-axis 60 shows the temperature. A sixth sub-axis 64 shows the measured temperature. In addition, the graph 50 has a time axis 62 for each sub-axis. Further preferably, Figure 2 The trend of the measured temperature 63 is shown. Further preferably, Figure 2 The trend of the calculated temperature 69 is shown. Further preferably, Figure 2 The trend of the electric field strength 68 is shown. Further preferably, Figure 2 The trend of power 67 is shown. Figure 2 In the embodiment, the trend of the power 67 is linearly configured so that a linear profile 18 is achieved. Further preferably, Figure 2 66. Further preferably, Figure 2 The trend of the current 65 is plotted in FIG.

[0046] Figure 3 A second graph 70 is shown for illustrating the working mode of the inverter unit 10 according to one embodiment. The second graph 70 has a first sub-axis 72 showing the current. Further preferably, the second graph 70 has a second sub-axis 74 showing the voltage. Further preferably, the second graph 70 has a third sub-axis 76 showing the power. Further preferably, the second graph 70 has a fourth sub-axis 78 showing the electric field strength. Further preferably, the second graph 70 has a fifth sub-axis 80 showing the theoretical temperature. Further preferably, the second graph 70 has a sixth sub-axis 82 representing the measured temperature. All sub-axes of the second graph 70 have a time axis 84. In Figure 386 of the current is shown. Further preferably, a voltage curve 88 is shown. Further preferably, a power curve 90 from the intermediate circuit 14 is shown. The power curve 90 increases logarithmically, so that this represents a logarithmic profile 20. Further preferably, in Figure 3 The trend of the electric field strength is shown in FIG92. Further preferably, Figure 3 The trend of the theoretical temperature is shown in 94. Further preferably, Figure 3 The measured temperature 96 is shown in FIG.

[0047] Figure 4 A circuit diagram 200 is shown for illustrating the mode of operation of the inverter unit 10. In this case, the energy stored in the intermediate circuit 14 can be calculated 206. The calculation 206 is based on the charge 202 and the voltage 204. Based on the stored energy of the intermediate circuit 14 calculated 206, a switching sequence 212 can be determined. Here, the inputs of the switching sequence calculation 212 are the charging duration 208, the switching frequency 210 of the switch 12, and the power loss 214. Further preferably, the temperature can be quantified 220 when determining 212 the switching sequence. The temperature determination 220 is based on the starting temperature 216 and the switching number 218 of the intermediate circuit 14. Based on the determination 212 of the switching sequence and the thermal energy 220, a current can be estimated 232. Here, the current estimation 233 is based in particular on the voltage 228 and the K value 230. Further preferably, the determination 232 of the current is based on the time constant 226 of the voltage at the gate 222 and the resistance at the gate 224 detected. Further preferably, energy 234 can be ascertained based on ascertaining switching sequence 212 and current 232. Based on ascertaining energy 234, switching duration 236 of a switching cycle of switch 12 for a constant current drop can be ascertained.

[0048] Figure 5 A vehicle 100 is shown which has the inverter unit 10 described above.

Claims

1. An inverter unit (10), comprising: - a switch (12), - an intermediate circuit (14), - component (16), -in, The inverter unit (10) is configured to switch the switch (12) according to a predetermined switching sequence in order to discharge the intermediate circuit (14). - wherein the predetermined switching sequence is arranged to generate a current drop with a substantially constant variation in the intermediate circuit (14) in order to introduce heat energy generated by the short circuit into the inverter unit (10) for determining the aging of the component (16).

2. The inverter unit (10) according to claim 1, wherein: The predetermined switching sequence is configured to at least temporarily generate a short circuit in the inverter unit (10).

3. The inverter unit (10) according to claim 1 or 2, wherein: The inverter unit (10) is configured to adjust the predetermined switching sequence to eliminate the short circuit when the voltage on the switch (12) reaches a reference voltage.

4. The inverter unit (10) according to any one of the preceding claims, wherein: The inverter unit (10) is configured to generate a first current drop in the intermediate circuit (14) at a first time point and to generate a second current drop in the intermediate circuit (14) at a second time point, wherein the inverter unit (10) is configured to detect the temperature of the component (16), wherein the inverter unit (10) is configured to detect a first temperature trend of the component (16) for the first current drop and to detect a second temperature trend of the component (16) for the second current drop, wherein the inverter unit (10) is configured to determine aging of the component (16) based on a comparison between the first temperature trend and the second temperature trend.

5. The inverter unit (10) according to any one of the preceding claims, wherein: The predetermined switching sequence is arranged to place the switch (12) in a first state, wherein in the first state the gate voltage is equal to and / or less than a high-order voltage.

6. The inverter unit (10) according to any one of the preceding claims, wherein: The inverter unit (10) is configured to determine and / or adjust a switching duration of the switches (12) in the predetermined switching sequence.

7. The inverter unit (10) according to claim 6, wherein: The inverter unit (10) is configured to adjust the switching duration as a function of the energy stored in the intermediate circuit (14).

8. The inverter unit (10) according to claim 7, wherein: The inverter unit (10) is configured to determine an energy quantity for introduction into at least a part of the inverter unit (10) as a function of the switching duration and the stored energy.

9. The inverter unit (10) according to claim 8, wherein: The inverter unit (10) is designed to adjust the predetermined switching sequence as a function of the determined energy quantity value, so that the intermediate circuit is discharged with a constant change.

10. The inverter unit (10) according to claim 9, wherein: The constant variation has a linear profile (18) and / or a logarithmic profile (20).

11. The inverter unit (10) according to any one of claims 9 to 10, wherein: The inverter unit (10) is configured to determine a voltage change across the intermediate circuit (14), wherein the inverter unit (10) is configured to adjust the determined energy quantity as a function of the voltage change.

12. The inverter unit (10) according to any one of claims 9 to 11, wherein: The inverter unit (10) has a comparator (22), wherein the inverter unit (10) is provided to adjust a current drop across the intermediate circuit (14) by means of the comparator (22).

13. The inverter unit (10) according to any one of the preceding claims, wherein: The inverter unit (10) is configured to determine the temperature of the component (16), wherein the inverter unit (10) is configured to form a difference between the thermal energy generated by the short circuit and the heating of the component (16), wherein the inverter unit (10) is configured to determine the aging of the component (16) based on the difference.

14. A vehicle (100) having an inverter unit (10) according to any one of the preceding claims.

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