Inverter, drive unit and method for operating an inverter

Abstract

The invention relates to an inverter (12), to a drive unit (10) comprising an electric machine (14) and an inverter (12), and to a method for operating an inverter (12). The inverter (12) has power electronics (15), a control (35) for operating the power electronics (15), a derating module (38), and a life counter (37) for monitoring at least one component of the inverter (12).

Description

[0001] The present invention relates to an inverter, a drive unit including a motor and an inverter, and a method for operating the inverter.

[0002] An inverter comprises several individual components, such as power electronics, which need to operate under specific conditions, for example, considering their respective temperature limits. If a component's temperature approaches its temperature limit, its electrical losses are typically reduced by derating operating parameters to prevent exceeding the temperature limit. For example, the current amplitude can be reduced or torque can be decreased to reduce the thermal load on the component. In this regard, it is typically assumed that the component's temperature limit is a fixed value, and that severe damage to the component will occur immediately once it is exceeded. Therefore, the parameter space upon which the operation of components is based, according to existing techniques, is limited. Furthermore, considering the temperature limit, the basic control program used to operate the corresponding inverter includes abrupt and drastic control mechanisms, making it impossible to achieve smooth changes in operating conditions.

[0003] Therefore, there is a need for an inverter that provides an expanded parameter space during operation and allows for the implementation of customized control programs.

[0004] The subject matter of the independent claims satisfies this need. Preferred embodiments and aspects are disclosed in consideration of the dependent claims, each of which may represent aspects of the invention, and the following description.

[0005] An inverter is provided. The inverter includes power electronics, control components for operating the power electronics, a derating module, and a lifetime counter for monitoring at least one component of the inverter.

[0006] In short, this invention is based on the discovery that a lifespan counter can be used to more accurately assess the consumed lifespan (aging condition) of inverter components. Therefore, an objective value regarding the extent to which a specific component has aged can be obtained. In other words, it is possible to assess how much of the component's lifespan has been consumed. Consequently, the lifespan counter can also determine the remaining lifespan of the corresponding component. Therefore, it is possible to more accurately determine when maintenance or replacement procedures are needed, rendering predetermined maintenance and replacement procedures obsolete. Resources can be used more efficiently. Furthermore, based on the value determined by the lifespan counter, adaptive control strategies can be applied, allowing at least the abrupt changes in control procedures to be postponed or even avoided. For example, instead of an immediate and drastic derating procedure, a smooth transition to a reduced performance value of the inverter can be considered.

[0007] Preferably, the inverter is configured for use in an electric vehicle. For this purpose, the inverter may be a high-voltage inverter.

[0008] An inverter can be connected to a motor and can be operated to output phase current to the motor.

[0009] In some embodiments, the inverter and motor may be part of a drive unit for an electric vehicle.

[0010] In some embodiments, the inverter may be software-controlled, such as by a controller.

[0011] According to one aspect, a lifetime counter can be adapted to monitor the operating time of at least one monitored component of an inverter within at least two different temperature ranges. Therefore, the lifetime counter takes into account different lifetime loads by distinguishing the time periods during which the component operates within a specific temperature range. This yields a more accurate value for the component's consumed lifetime.

[0012] Preferably, the life counter is configured to determine a cumulative value of the component's consumed life. The cumulative value includes partial contributions. Each partial contribution is related to a specific operating time of the component operating within a specific temperature range.

[0013] Optionally, the at least one monitored component is at least one of the following: DC link capacitor, Cx capacitor, Cy capacitor, bus, power switch, motor, and accessories at least indirectly connected to the inverter. All these component types typically do not immediately fail or even break down when their temperature exceeds the corresponding temperature limit. Therefore, a favorable lifespan assessment of the inverter is applicable, taking into account the wide variety of components.

[0014] Clearly, the lifetime counter can be configured to simultaneously monitor the lifetime of several components of the inverter, taking into account their consumed lifetimes, and the corresponding values ​​of the consumed lifetimes of several components can be determined independently of each other.

[0015] Preferably, the busbar can be a sheathed busbar.

[0016] According to some embodiments, the derating module may include a late-life derating switch. Therefore, the derating module can be configured to apply different derating strategies as needed. For example, the late-life derating switch may be selected based on a lifetime value determined by a lifetime counter.

[0017] Optionally, the derating module is configured to initiate different derating procedures based on the late-life derating switch, such as the standard derating procedure (also known as early-life derating) and the adapted derating procedure (also known as late-life derating).

[0018] Early derating reduces inverter performance. To address this, torque demands can be met or current amplitude can be adjusted. Furthermore, the switching speed of the inverter's power electronics can be reduced. Alternatively, the modulation mode and / or pulse width modulation frequency used to control the power electronics can be adjusted. Early derating typically reduces component electrical losses, which in turn reduces thermal load. Therefore, the temperature of the monitored components can be efficiently reduced or at least affected.

[0019] Late-life derating reduces the thermal load of a specific monitored component, typically at the expense of increased electrical losses. In other words, it adjusts the inverter's operation to reduce the thermal load of a particular component, while allowing for increased thermal loads on other components. This can be beneficial if the monitored component has aged beyond that of other components, given its consumed lifetime. Late-life derating can also depend on the appropriate torque demand or adjusted current amplitude. Furthermore, it can depend on the switching speed of the inverter's power electronics, the appropriate modulation mode, and / or pulse width modulation frequency. Late-life derating typically results in increased electrical losses in at least one component of the inverter (but not necessarily the monitored component), leading to less efficient inverter operation. This, in turn, achieves the benefit of reducing the thermal load on the monitored component.

[0020] In one aspect, the lifetime counter may include an input for receiving at least one additional signal related to the lifetime of the at least one monitored component. The additional signal may include information about at least one of current, voltage (DC or AC), electrical power, modulation mode, pulse width modulation frequency, and switching speed. These parameters may also affect the consumed lifetime of the monitored component. Therefore, the consumed lifetime value of the monitored component can be determined more accurately, allowing for the application of customized control strategies.

[0021] Preferably, the lifespan counter receives a measurement signal indicating the temperature of the at least one monitored component. For this purpose, the inverter may include at least one temperature sensor configured to detect the temperature of the monitored component. Alternatively, the temperature sensor may be separate from but assigned to the inverter. Therefore, the value of the consumed lifespan can be determined with greater accuracy.

[0022] According to one aspect, the lifespan counter can receive a calculated signal indicating the temperature of the at least one monitored component. For this purpose, the control unit may include a temperature estimation module configured to estimate the temperature of the monitored component. For example, the temperature estimation module may consider temperatures measured for different components. Furthermore, the temperature estimation module may consider inverter parameters such as current amplitude, voltage (DC or AC) amplitude, electrical power, modulation mode, pulse width modulation frequency, and switching speed. Based on these parameters, the electrical load on a particular component can be accurately estimated, allowing the component's temperature to be determined.

[0023] According to one aspect, the life counter is configured to transmit the determined consumed life value of the component to the control element.

[0024] Preferably, the control unit can be adapted to the control program for controlling the inverter based on a determined lifetime value received by the monitored component and / or based on a trigger signal received from the derating module. For example, the trigger signal can depend on the switching state of the late-life derating switch.

[0025] According to another aspect, a drive unit is provided that includes a motor and an inverter as described earlier herein. The inverter is coupled to the motor and configured to output phase current to the motor.

[0026] This drive unit can also achieve the advantages that can be achieved through the aforementioned inverter.

[0027] According to another approach, a method for operating an inverter is provided. The inverter can be configured as described earlier herein. The method includes at least the following steps: - The life counter monitors the temperature of at least one monitored component while it is in operation.

[0028] - The life counter determines a value indicating the remaining life of at least one monitored component in real time based on operating temperature and operating time.

[0029] - The derating module considers the remaining lifetime value determined by the lifetime counter and the temperature of the monitored components to determine whether the inverter must operate in derating mode.

[0030] This method also achieves the advantages described above with the inverter. An objective value of the consumed lifetime can be determined, which in turn allows for the estimation of the remaining lifespan of the components. This provides the possibility of adapting the control strategy used to control the inverter to meet specific needs. In particular, the derating module can determine which derating procedure to apply in order to optimize the inverter's operating efficiency without damaging the monitored components.

[0031] Preferably, the life counter monitors the time the monitored component operates above a predetermined temperature threshold. Based on the temperature threshold, different thermal loads on the monitored component can be distinguished, allowing for a more accurate estimation of the consumed lifespan.

[0032] Of course, a lifetime counter can consider multiple different temperature thresholds, allowing for a more accurate determination of the consumed lifespan of the monitored component. Therefore, the information provided to the derating module more appropriately corresponds to the relevant scenario.

[0033] According to one aspect, when a predefined operating time exceeding a time threshold has been consumed by at least one monitored component, the lifetime counter can change the state of the late-life derating switch. In other words, the value of the cumulative consumed lifetime or remaining lifetime determined by the lifetime counter can trigger the switching state of the late-life derating switch of the derating module. For example, the switching state of the late-life derating switch can depend on whether the value of the cumulative consumed lifetime or remaining lifetime of the monitored component exceeds or falls below the lifetime threshold.

[0034] Optionally, a lifetime counter monitors the temperature of the at least one monitored component while it is operating and determines the consumed lifetime value based on temperature and time. Therefore, partial lifetime consumption contributions can be identified and considered, where each partial lifetime consumption contribution is related to a specific operating time within a specific temperature range. These partial lifetime consumption contributions generate a cumulative value of the total consumed lifetime for the corresponding monitored component.

[0035] In some embodiments, the derating module can consider the difference between the design life of the at least one monitored component and the determined value of its consumed life and / or determined value of its remaining life when determining whether the inverter can operate on demand or must operate in derating mode. Therefore, appropriate control procedures can be applied to maximize the inverter's operational functionality. For example, based on late-life derating procedures, the thermal load on a particular monitored component can be reduced so that the inverter does not fail solely due to the consumption of the design life of a single monitored component, even when the remaining life of other monitored components still allows for significant additional operating time. In other words, based on the derating module, the operating procedures applied to the inverter can be customized according to specific lifespan scenarios, enabling the extension, and particularly optimization, of the inverter's operating efficiency.

[0036] Preferably, adaptation to the inverter's operating mode can be triggered by the difference between the design life of at least one monitored component and the determined value of its consumed life or determined value of its remaining life exceeding or falling below a difference threshold, thereby exposing the specific monitored component to a lower thermal load. Therefore, reliable conditions are defined if adaptation to the operating procedure is required.

[0037] The invention and other advantageous embodiments thereof are described and explained in more detail below with reference to the examples shown in the accompanying drawings.

[0038] - Figure 1 A schematic diagram of a drive unit according to an embodiment of the present invention is shown. - Figure 2 A schematic diagram of a method for operating an inverter according to an embodiment of the present invention is shown, and - Figure 3 and Figure 4 A schematic diagram of the control program applied by the inverter's control components is shown.

[0039] All features mentioned below with reference to the embodiments and / or drawings may be combined individually or in any sub-combination with the features of the present invention, including those of the preferred embodiments.

[0040] Figure 1 A schematic diagram of a drive unit 10 according to an embodiment of the present invention is shown.

[0041] The drive unit 10 can be configured for use in an electric vehicle. The drive unit 10 includes an inverter 12 and a motor 14 coupled to the inverter 12. The inverter 12 can be configured as a high-voltage inverter. The inverter 12 is configured to provide a power supply signal to the motor 14, such that the motor 14 can output torque to components of the vehicle, for example, for driving.

[0042] In the illustrated embodiment, inverter 12 includes power electronics 15, which, according to this embodiment, has a B6 bridge. The B6 bridge has three half-bridges 16. The following functionality is illustrated with reference to only one half-bridge 16, but applies accordingly to all half-bridges 16 of the B6 bridge.

[0043] Each half-bridge 16 includes a first power switch 18 (e.g., a transistor) that acts as a high-side power switch and a second power switch 20 (e.g., a transistor) that acts as a low-side power switch.

[0044] The transistor can be a metal-oxide-semiconductor field-effect transistor (MOSFET), an insulated-gate bipolar transistor (IGBT), or a silicon carbide or gallium nitride field-effect transistor (SiC or GaN FET).

[0045] Between the first power switch 18 and the second power switch 20, each half-bridge 16 includes a central node 22 for outputting phase current (L2 in this case) to the motor 14.

[0046] The three corresponding phase currents L1, L2, and L3 are applied to the motor 14 via the three half-bridges 16. However, other topologies are also possible, which would require corresponding modifications to the inverter 12, for example, for a six-phase motor 14.

[0047] The corresponding half-bridge 16 is connected to bus 24 of drive unit 10. Bus 24 may be overmolded. Inverter 12 is connected to DC power supply 26, such as a high-voltage storage device. DC power supply 26 includes terminals 28, 30, between which a high voltage (HV) with a voltage amplitude of, for example, 100 V or greater, particularly 400 V or 800 V is provided.

[0048] Additionally, inverter 12 includes a DC link capacitor 34, which acts as a connection element between the DC power supply 26 and the motor 14. The DC link capacitor 34 ensures that the power supply signal is designed to be more uniform in terms of current and / or voltage amplitude, for example, under varying load conditions.

[0049] To control the switching states of power switches 18 and 20, drive unit 10 includes or is coupled to a control element 35 assigned to drive unit 10 and motor 14. According to this embodiment, control element 35 is part of inverter 12. Control element 35 includes at least one data processing unit 36.

[0050] The control unit 35 includes at least a life counter 37 and a derating module 38. According to this embodiment, the control unit 35 also includes a temperature estimation module 39.

[0051] The control unit 35 is configured to provide corresponding control signals G1 and G2 to the power switches 18 and 20, such that the switching positions of the power switches 18 and 20 are affected by these control signals. The control signals G1 and G2 depend on a modulation signal, which is determined by means of the data processing unit 36. For example, the control unit 35 has a pulse width modulator 40 for generating a basic modulation signal.

[0052] Control signals G1 and G2 are output to gate driver circuits 42, which are connected to the gate electrodes of power switches 18 and 20. Based on control signals G1 and G2, gate driver circuits 42 generate corresponding gate signals to affect the switching state of power switches 18 and 20.

[0053] Control signals G1 and G2 can be specifically influenced by the modulation signal of pulse width modulator 40. Consequently, the switching speed and / or switching frequency of power switches 18 and 20 can be affected. Alternatively, pulse width modulator 40 can be adapted to take into account the pulse width modulation frequency applied by pulse width modulator 40. According to another alternative, the modulation pattern based on the modulation signal can be modified, for example, by data processing unit 36 ​​according to corresponding requirements.

[0054] The control unit 35 is typically connected to the drive unit 10 and / or other components of the inverter 12, such as the motor 14, the DC power supply 26, or a corresponding sensor.

[0055] According to this embodiment, the inverter 12 includes a phase current sensor 44 disposed between the center node 22 and the motor 14. The phase current sensor 44 is configured to detect the phase current output by the inverter 12 and transmit the phase current to the control unit 35.

[0056] In addition, according to this embodiment, the inverter 12 and / or drive unit 10 also includes filter capacitors, such as Cx filter 46, Cy filter 48, EMC filter 50, coolant pump 52 connected to the cooling system of the inverter 12 and / or drive unit 10 and / or motor 14, temperature sensor 54, and accessory 56 connected to the inverter 12.

[0057] According to this embodiment, the control element 35 is connected to all these components. However, these connections are optional and may be omitted in other examples.

[0058] According to this embodiment, the temperature sensor 54 is connected to the inverter 12, so that the temperature sensor detects the temperature of the inverter 12 and transmits the detected temperature to the control unit 35.

[0059] Based on the received sensor data (such as the sensor data from phase current sensor 44), the controller 35 can output corresponding control signals G1, G2 via a current control circuit. These control signals vary, for example, with the rotor position, i.e., depending on the rotor's position relative to the stator of motor 14. Therefore, the windings of motor 14 are supplied with corresponding phase currents L1, L2, L3. The precise control of motor 14, and thus the characteristics of these control signals G1, G2, largely depend on the torque request 58 received by the controller 35 from a higher-level component of the vehicle. The torque request 58 indicates which output torque motor 14 will provide. The torque request 58 represents the required performance of the drive unit 10 and inverter 12 in their operation.

[0060] For example, torque request 58 can depend on the position of the vehicle's pedals.

[0061] Additionally, the control unit 35 is connected to a memory device 60, which can store the history of operating parameters of the inverter 12 and drive unit 10, motor 14 and / or components connected to one of these components.

[0062] Figure 2 A schematic diagram of a method for operating an inverter 12 according to an embodiment of the present invention is shown. Optional steps are shown in dashed lines.

[0063] In optional step S2, the temperature of at least one monitored component is detected. The detected temperature is transmitted to the control unit 35. For example, a temperature sensor 54 coupled to the inverter 12 can be used in this regard.

[0064] In optional step S4, the temperature of at least one monitored component is estimated. Step S4 may be applied, for example, considering components for which a temperature sensor 54 is not provided or for which a temperature sensor is not applicable. This could be due to space constraints or cost savings. The temperature of the monitored component can be estimated, for example, by the temperature estimation module 39 of the control unit 35. In this regard, the temperature estimation module 39 may consider information about the current operating mode of the inverter 12, such as current amplitude, voltage amplitude, switching speed, modulation mode of the pulse width modulator 40, pulse width modulation frequency, or various operating parameters that affect the temperature of the monitored component.

[0065] Optional step S4 can be further modified by optional step S6. According to optional step S6, the temperature of at least one monitored component is estimated by considering the temperature cycles performed by the corresponding component during operation. During use, some monitored components may perform predetermined temperature cycles based on the operating procedure of inverter 12. A temperature cycle can be considered as a specific temperature distribution (curve) during a specific time period. This temperature cycle caused by the operating parameters of inverter 12 can be repeated. Therefore, based on the number of temperature cycles, the consumed lifespan of the corresponding monitored component can be determined more accurately. Therefore, in step S6, the temperature cycles can be counted, or corresponding time points during the temperature cycles can be considered to estimate the temperature of the component in question.

[0066] The method includes step S8, in which the life counter 37 monitors the temperature of at least one monitored component during operation. In this regard, the life counter 37 may incorporate optional steps S2 through S6. For example, the temperature detected by the temperature sensor 54 may be considered by the life counter 37.

[0067] In the subsequent step S10, the lifetime counter 37 determines the operating time of the monitored component within a corresponding temperature range. This determination yields a cumulative value of the operating time within a specific temperature range, enabling the achievement of characteristic parameters for the specific monitored component. To differentiate between different temperature ranges, the lifetime counter 37 may consider temperature thresholds.

[0068] In a subsequent optional step S12 of the method, the lifetime counter 37 determines the cumulative value of the consumed lifetime of the monitored component. The cumulative value may include portions of the value that depend on the contribution of operating time when the monitored component operates within a specific temperature range. In other words, the control 35, and specifically the lifetime counter 37, determines how much aging has occurred in a particular monitored component. In optional step S12, the number of temperature cycles determined in optional step S6 may also be considered.

[0069] In a subsequent optional step S14, the control element 35 (e.g., its life counter 37) compares the cumulative value of the consumed life of the monitored component with the design life of the corresponding component. The design life can be considered a predetermined parameter set by the manufacturer.

[0070] The method proceeds to the next step S16, in which the lifetime counter 37 determines in real time a value indicating the remaining lifetime of the monitored component. In this regard, the lifetime counter 37 takes into account the operating time, i.e., the value determined in step S10, during which the monitored component has a temperature within a specific temperature range.

[0071] Subsequently, in step S18 of the method, the derating module 38 determines whether the inverter 12 can operate according to requested performance (e.g., according to torque request 58), or whether the inverter 12 must operate in derating mode. In step S18, the derating module 38 may consider different derating modes. The derating module 38 considers the remaining lifetime value determined by the lifetime counter 37. In other words, the derating module 38 determines whether it is necessary to adapt the operating mode of the inverter 12; otherwise, the monitored components will significantly limit the overall lifetime of the inverter 12.

[0072] The method can be modified by optional steps S20 and S22, which can include these optional steps to adapt steps S14 to S18.

[0073] According to optional step S20, derating module 38 can determine the difference between the design life of the monitored component and the cumulative value of the consumed life, or the difference between the design life of the monitored component and the remaining life of the monitored component.

[0074] In the subsequent optional step S22, the derating module 38 can then compare the difference determined in optional step S20 with the difference threshold. Based on appropriate conditions, such as if the determined difference exceeds the difference threshold or if the determined difference drops below the difference threshold, the conclusion of step S18 can be triggered, that is, the inverter 12 will operate according to the adapted operating mode.

[0075] Following step S18, the method includes an optional step S24, in which the control unit 35 operates the inverter 12, including the monitored component, such that the inverter 12 operates in a specific operating mode, which includes a potential derating mode determined by the derating module 38. Therefore, the inverter 12 is specifically operated to take into account the thermal load of the monitored component, which has aged to a certain extent.

[0076] Optionally, if it is determined in step S18 that a derating mode should be applied, the control unit 35 may consider the corresponding temperature limit, which the detected or estimated temperature of the monitored component needs to exceed if the derating mode is to be actually applied.

[0077] Step S24 can be modified by optional step S26, whereby the control unit 35 applies a late-life derating mode, resulting in increased electrical losses. This allows for a reduction in the thermal load on a specific monitored component compared to different components of the inverter 12 or different operating modes of the inverter 12. Therefore, the aging of the monitored component can be slowed. In other words, the inverter 12 is intentionally operated at lower efficiency, resulting in additional electrical losses, but this is beneficial for reducing the thermal load on at least one monitored component. This can be exemplarily achieved by modifying at least one of the modulation mode considered by the pulse width modulator 40, the pulse width modulation frequency of the pulse width modulator 40, and the switching speeds of the power switches 18 and 20.

[0078] Figure 3 and Figure 4 A schematic diagram of the control program applied by the inverter 12, and in particular by the control unit 35, is shown.

[0079] according to Figure 3 In the control program shown, at module 62, the lifespan counter 37 exemplarily accumulates the operating time and corresponding temperature range of a specific monitored component. The selected temperature range depends on the detected or estimated temperature of the monitored component. For example, the temperature of the monitored component can be estimated based on the temperature estimation module 39. After comparing the accumulated value of the consumed lifespan of the monitored component with the design lifespan, the remaining lifespan of the monitored component is estimated by the lifespan counter 37.

[0080] In this regard, the lifespan counter 37 receives information about the current operating mode of the inverter 12, such as inverter parameters and the detected or estimated temperature of the corresponding components. The detected temperature can be provided by the temperature sensor 54. The estimated temperature can be achieved by the control unit 35 or the temperature estimation module 39, for example, based on the received parameters of the inverter 12.

[0081] The control unit 35 includes a first operating mode module 64 relating to a standard derating procedure (early life derating) and a second operating mode module 66 relating to a modified derating procedure (late life derating). Both the first operating mode module 64 and the second operating mode module 66 also take into account the detected or estimated temperature of the respective monitored component.

[0082] The control unit 35 also includes a late-life derating switch 70 as part of the derating module 38, which determines the specific operating mode modules 64, 66 to be applied to the operation of the inverter 12. The late-life derating switch 70 relies on a threshold 68 that takes into account the determined remaining lifespan of the monitored components in module 62.

[0083] If the cumulative value of the consumed life of the corresponding monitored component is determined to be less than the threshold 68, the late life derating switch 70 is triggered, so that the application operates the inverter 12 according to the early life derating of the first operating mode module 64.

[0084] In contrast, if the late-life derating switch of the corresponding monitored component is determined to be greater than the threshold 68, the late-life derating switch 70 is triggered, causing the application to operate the inverter 12 according to the late-life derating of the second operating mode module 64.

[0085] While for late-life derating, the operating mode of inverter 12 is modified to reduce the thermal load on the monitored component compared to other operating modes (potentially at the cost of increased electrical losses), this is not the case for early-life derating. Therefore, based on threshold 68, a trigger event is provided to modify the operating mode only when the determined remaining lifespan of the monitored component necessitates a reduction in the thermal load on that component in order to extend the overall operating life of inverter 12.

[0086] Control component 35 can also be applied Figure 4 The control procedure is shown. In this case, according to module 72, the life counter 37 accumulates the operating time and corresponding temperature range of a specific monitored component. The remaining life of the monitored component is determined by taking into account the design life of the specific component. Similarly, the detected or estimated temperature of the corresponding monitored component is taken into account for this assessment.

[0087] Based on the determined remaining lifetime determined by module 74, it is used to determine at which initiation temperature TS the inverter 12 needs to be derating in order to reduce the risk of heat-induced damage and to maximize the utilization of the lifetime limits of each monitored component. For an increase in the determined cumulative value of the consumed lifetime, i.e., a smaller value for the determined remaining lifetime of a particular monitored component, the initiation temperature TS for derating needs to be lowered to a lower value.

[0088] In module 76, the detected or estimated temperature of the corresponding monitored component is considered and compared with the initial temperature TS. Once the detected or estimated temperature of the monitored component exceeds the initial temperature TS, a derating procedure is applied.

[0089] according to Figure 4 The control program shown is a derating program related to late-life derating. This means that the operating mode of inverter 12 is specifically modified to reduce the thermal load on certain monitored components relative to other operating modes, potentially at the cost of increased electrical losses.

[0090] Therefore, the inverter 12, drive unit 10, and the method of operating the inverter 12 allow the components of the inverter 12 to operate above a certain temperature limit for a limited time, while making better use of the determined cumulative value of the consumed lifespan. For example, the inverter 12 can be operated such that different monitored components have equal or similar cumulative values ​​of consumed lifespan (given the corresponding design lifespan). This increases the parameter space for operating the inverter 12. Furthermore, the lifespan of the inverter 12 is extended. In addition, it is possible to more accurately determine when maintenance or replacement is needed. Moreover, by adapting the operating mode, a smoother control program can be implemented, avoiding abrupt and drastic changes in the control program.

Claims

1. An inverter (12) comprising power electronics (15), a control (35) for operating the power electronics (15), a derating module (38), and a lifetime counter (37) for monitoring at least one component of the inverter (12).

2. The inverter (12) as described in claim 1, wherein, The life counter (37) is adapted to monitor the operating time of at least one monitored component of the inverter (12) in at least two different temperature ranges.

3. The inverter (12) as described in claim 1 or 2, wherein, The at least one monitored component is at least one of the following: DC link capacitor, Cx capacitor, Cy capacitor, bus (24), power switch (18, 20), motor (14), and accessory (56) at least indirectly connected to the inverter (12).

4. The inverter (12) as described in any of the preceding claims, wherein, The derating module (38) includes a late-life derating switch (70).

5. The inverter (12) as described in any of the preceding claims, wherein, The life counter (37) includes an input for receiving at least one additional signal related to the life of the at least one monitored component.

6. The inverter (12) as described in any of the preceding claims, wherein, The life counter (37) receives a measurement signal indicating the temperature of the at least one monitored component.

7. The inverter (12) as claimed in any one of claims 1 to 5, wherein, The life counter (37) receives a calculated signal indicating the temperature of the at least one monitored component.

8. A drive unit (10) comprising a motor (14) and an inverter (12) according to any one of the preceding claims, the inverter (12) being coupled to the motor (14) and configured to output phase current to the motor (14).

9. A method for operating an inverter (12) as described in any of the preceding claims, the method comprising the steps of: -The life counter (37) monitors the temperature of at least one monitored component while it is operating. - The life counter (37) determines in real time a value indicating the remaining life of the at least one monitored component based on the operating temperature and operating time. - The derating module (38) considers the remaining lifetime value determined by the lifetime counter (37) and the temperature of the monitored component to determine whether the inverter (12) must operate in derating mode.

10. The method of claim 9, wherein, The lifetime counter (37) monitors the time during which the monitored component operates above a defined time threshold.

11. The method of claim 10, wherein, When a predefined operating time above the time threshold of the at least one monitored component has been consumed, the lifetime counter (37) changes the state of the late lifetime derating switch (70).

12. The method of claim 9, wherein, The life counter (37) monitors the temperature of the at least one monitored component while it is operating, and determines the consumed life value based on the temperature and time.

13. The method of claim 12, wherein, When determining whether the inverter (12) can operate according to requested performance or must operate in derating mode, the derating module (38) considers the difference between the design life of the at least one monitored component and the determined remaining life value.

Images