Power conversion device remaining life estimation device

Abstract

To enable remaining life information on individual life components constituting a power conversion device to be appropriately estimated.SOLUTION: The remaining life estimation device is a remaining life estimation device for a power conversion device having life components housed in a case. The remaining life estimation device is provided with a processor for calculating remaining life information on the life components. The processor calculates cumulative exposure times being cumulative values of times when the life components are exposed to the same temperature while the power conversion device operates, at each life component temperature of the life components. The processor converts each of the cumulative exposure times into a conversion cumulative exposure time being a cumulative exposure time under a reference value of the life component temperature by reflecting a life conversion factor in each of the cumulative exposure times calculated at each life component temperature. Then, the processor calculates remaining life information on the basis of a life reduction time being a sum of conversion cumulative exposure times at each life component temperature, and a reference life time being a life time of the life components under the reference value.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a remaining life estimation device for a power conversion device.

Background Art

[0002] Patent Document 1 discloses a motor drive system. In order to be able to grasp the life of a motor or an inverter outside a vehicle, in the motor drive system, a life prediction value, which is life prediction information, is calculated based on at least any one or a combination of a carrier frequency, a motor current value, a motor voltage value, and component characteristics of an inverter.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technique described in Patent Document 1 mentioned above, it is not possible to estimate the remaining life of each component constituting the inverter. Therefore, there is a possibility of misjudging the timing of repair or replacement of the power conversion device.

[0005] The present disclosure has been made in view of the above problems, and an object thereof is to provide a remaining life estimation device capable of appropriately estimating the remaining life information of each life component constituting a power conversion device.

Means for Solving the Problems

[0006] The remaining life estimation device according to this disclosure is a remaining life estimation device for a power converter having a life-limited component housed in a case. The remaining life estimation device includes a processor that calculates remaining life information for the life-limited component. The processor calculates the cumulative exposure time, which is the cumulative value of the time the life-limited component is exposed to the same temperature while the power converter is operating, for each life-limited component temperature. The processor converts each of the cumulative exposure times calculated for each life-limited component temperature into a converted cumulative exposure time, which is the cumulative exposure time under a reference value for the life-limited component temperature, by applying a life conversion coefficient to each of the cumulative exposure times calculated for each life-limited component temperature. The processor then calculates the remaining life information based on the life reduction time, which is the sum of the converted cumulative exposure times for each life-limited component temperature, and the reference life time, which is the life time of the life-limited component under the reference value. [Effects of the Invention]

[0007] According to this disclosure, it becomes possible to appropriately estimate the remaining lifespan information of individual life components constituting a power converter. As a result, it becomes possible to accurately determine the timing of repair or replacement of the power converter from the remaining lifespan information of each individual life component thus estimated. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram schematically shows the configuration of a power converter to which the remaining life estimation device according to the embodiment is applied. [Figure 2] This flowchart shows an example of the process for calculating remaining life information according to the embodiment. [Figure 3] This table shows examples of the various data used to calculate remaining lifespan information. [Figure 4] This diagram conceptually illustrates the relationship between the ambient temperature Ta and the refrigerant temperature Tw, and the lifespan of the component temperature Tc. [Figure 5] This graph shows an example of the characteristics of the lifespan of a component with respect to its temperature Tc, specifically its lifespan tL. [Modes for carrying out the invention]

[0009] Embodiments of this disclosure will be described with reference to the attached drawings.

[0010] 1.Device configuration Figure 1 is a schematic diagram showing the configuration of a power converter 1 to which the remaining life estimation device 10 according to the embodiment is applied. The power converter 1 is installed in a vehicle such as a hybrid electric vehicle (HEV) or a battery electric vehicle (BEV). The power converter 1 is interposed between the battery and the electric motor for vehicle operation. Hereinafter, the power converter 1 will also be referred to as a PCU (power control unit) 1.

[0011] The PCU1 comprises a PCU case 2. The PCU case 2 houses several limited-life components that constitute the PCU1. These limited-life components include, for example, a capacitor 3, a reactor 4, a control board 5, a DC / DC converter 6, and a current sensor 7. A refrigerant channel 9 through which a refrigerant 8 flows is also formed within the PCU case 2. The refrigerant 8 is, for example, cooling water (coolant) or oil. More specifically, the capacitor 3, reactor 4, DC / DC converter 6, and current sensor 7 are cooled by the refrigerant 8 flowing through the refrigerant channel 9.

[0012] The remaining life estimation device 10 includes an ambient temperature sensor 12, a refrigerant temperature sensor 14, and an electronic control unit (ECU) 16. The ambient temperature sensor 12 detects the ambient temperature Ta inside the PCU case 2. The refrigerant temperature sensor 14 detects the temperature Tw of the refrigerant 8.

[0013] The ECU16 is a computer that calculates the remaining lifespan information for each of the above-mentioned components with a limited lifespan, such as the capacitor 3. The ECU16 includes a processor 18 and a storage device 20. The processor 18 performs various processes. These processes include the calculation of remaining lifespan information, which will be described later. The storage device 20 stores various information necessary for the processing performed by the processor 18. The various processes performed by the ECU16 are realized when the processor 18 executes a computer program. The computer program is stored in the storage device 20. Alternatively, the computer program may be recorded on a computer-readable recording medium. Note that the ECU16 may be configured by combining multiple ECUs.

[0014] 2. Calculation of remaining lifespan information In this embodiment, in order to estimate the remaining lifespan of each major lifespan component in the PCU1, the ECU16 calculates remaining lifespan information for each individual lifespan component.

[0015] Figure 2 is a flowchart showing an example of the process for calculating remaining life information according to the embodiment. The process in this flowchart starts when the vehicle system is started. This process is executed for each individual life component. That is, the process is executed for each of the above-mentioned components, such as the capacitor 3, reactor 4, control board 5, DC / DC converter 6, and current sensor 7. Figure 3 is a table showing an example of the various data used to calculate the remaining life information. More specifically, the various data shown in Figure 3 are stored in the storage device 20 for each life component.

[0016] In step S100, the ECU 16 (processor 18) acquires the ambient temperature Ta and refrigerant temperature Tw using the ambient temperature sensor 12 and the refrigerant temperature sensor 14, respectively. The process then proceeds to step S102.

[0017] In step S102, the ECU 16 calculates (estimates) the component temperature Tc of the life component, which is the temperature of the life component for which the remaining life information is to be calculated this time (or simply the component temperature). The component temperature Tc is calculated based on the ambient temperature Ta, the refrigerant temperature Tw, and the temperature calculation coefficient K1. More specifically, for example, as expressed by the following formula (1), the component temperature Tc is calculated by multiplying the sum of the ambient temperature Ta and the refrigerant temperature Tw by the temperature calculation coefficient K1. The temperature calculation coefficient K1 is determined in advance for each life component as a coefficient corresponding to the sensitivity of the life component to each of the ambient temperature Ta and the refrigerant temperature Tw. Tc = (Ta + Tw) × K1 ···(1)

[0018] Specifically, FIG. 4 is a diagram conceptually showing the relationship between the life component temperature Tc with respect to the ambient temperature Ta and the refrigerant temperature Tw. The component temperature Tc is expressed as shown in FIG. 4 using the thermal resistance R1 between the ambient temperature Ta and the component temperature Tc and the thermal resistance R2 between the refrigerant temperature Tw and the component temperature Tc. These thermal resistances R1 and R2 can be specified as design values based on, for example, analysis by CAE (Computer Aided Engineering), or experimental values with the ambient temperature Ta and the refrigerant temperature Tw as parameters. The temperature calculation coefficient K1 for each life component is determined in advance as a value corresponding to such thermal resistances R1 and R2 and is stored in the storage device 20. Additionally, in the example shown in FIG. 1, although the control board 5 is not a component actively cooled by the refrigerant 8, it is arranged inside the PCU case 2 and thus is affected by the refrigerant temperature Tw.

[0019] In step S104 following step S102, the ECU 16 counts the component temperature Tc calculated in step S102. As a result of this count, that is, the count number (see FIG. 3) is stored in the storage device 20. Next, in step S106, the ECU 16 determines whether the vehicle system is in operation.

[0020] If the vehicle system is in the startup state in step S106, that is, if the PCU1 is operating, the process returns to step S100. That is, the calculation and counting of the component temperature Tc are repeatedly executed during the operation of the PCU1. Here, the component temperature Tc changes during the startup of the vehicle system. Therefore, by repeatedly calculating and counting the component temperature Tc in this way, the counting of the component temperature Tc is performed separately for each component temperature Tc (for example, every 1°C). In FIG. 3, an example of the cumulative value of the count number, which is the result of the counting performed in this way, is shown for each component temperature Tc. More specifically, this cumulative value of the count number includes not only the count number during the current startup of the vehicle system but also the count numbers during the past startups of the vehicle system.

[0021] In addition, the period (sampling period) ts of the calculation and counting of the component temperature Tc is, for example, 1 second. The sampling period ts may be constant regardless of the life components, or may be changed according to the characteristics of individual life components. Specifically, the way in which the component temperature Tc changes during the operation of the PCU1 differs depending on the life components. For example, if the heat capacity of the life component is large, the component temperature Tc is less likely to change. Therefore, the sampling period ts used for the life component with a large heat capacity may be set longer than the sampling period ts used for the life component with a small heat capacity. Thereby, while appropriately suppressing the calculation load of the ECU16 in consideration of the characteristics of the life components, the counting of the component temperature Tc can be performed.

[0022] On the other hand, if the vehicle system is no longer running (step S106; No), the process proceeds to step S108. In step S108, the ECU 16 calculates the cumulative exposure time t1 for each lifespan component temperature Tc. The cumulative exposure time t1 is the cumulative value of the exposure time, which is the time that the lifespan component is exposed to the same temperature. In step S108, the ECU 16 calculates the cumulative exposure time t1 for each component temperature Tc by multiplying the latest cumulative value of the above count stored in the memory device 20 by the sampling period ts. That is, the cumulative exposure time t1 is calculated to include not only the exposure time during the most recent vehicle system startup, but also the exposure time during past vehicle system startups.

[0023] The process in step S108 updates the cumulative exposure time t1 at each component temperature Tc and stores it in the storage device 20. Figure 3 shows an example of the cumulative exposure time t1 that is updated in this way for each component temperature Tc.

[0024] In step S110, following step S108, the ECU16 calculates (updates) the converted cumulative exposure time t2 for each component temperature Tc. The converted cumulative exposure time t2 corresponds to the cumulative exposure time t1 under a reference value Tcr for the component temperature Tc. An example of a reference value Tcr is the maximum operating temperature (design value) of the component's lifespan. The converted cumulative exposure time t2 is calculated by reflecting the lifespan conversion factor K2 in the cumulative exposure time t1.

[0025] Figure 5 is a graph showing an example of the characteristics of the lifetime time tL for a component with respect to its temperature Tc. The characteristics shown in Figure 5 correspond to the data in the second left column of the table shown in Figure 3. This data for the characteristics of lifetime time tL for component temperature Tc is pre-designed for each component whose remaining lifetime information is to be calculated and is pre-stored in the storage device 20. In the example characteristics shown in Figure 5, the reference value Tcr for component temperature Tc is 100°C, which corresponds to the maximum operating temperature. More specifically, the characteristics (linear line) shown in Figure 5 are identified using two component temperatures Tc (e.g., 25°C and 100°C) and pre-measured lifetime times tL for these two component temperatures Tc.

[0026] The life conversion factor K2 is calculated for each component temperature Tc based on the characteristics shown in Figure 5. More specifically, the life conversion factor K2 is calculated according to the following equation (2). In equation (2), tLr is the reference life time corresponding to the life time tL at the reference value Tcr. For example, in the case of a life component having the characteristics shown in Figure 5, the life conversion factor K2 when the component temperature Tc is 50°C is calculated as 0.1 by dividing the reference life time tLr, which is 1000 hours, by the life time at 50°C, which is 10000 hours. Figure 3 shows an example of the life conversion factor K2 calculated in this way for each component temperature Tc. The life conversion factor K2 is calculated in advance using the component temperature Tc and life time tL data shown in Figure 3 and stored in the memory device 20. K2 = tLr / tL ... (2)

[0027] When the life conversion factor K2 expressed as in equation (2) is used, the converted cumulative exposure time t2 at each component temperature Tc is calculated by multiplying the cumulative exposure time t1 at each component temperature Tc by the life conversion factor K2 at each component temperature Tc, as shown in equation (3). Figure 3 shows an example of the converted cumulative exposure time t2 calculated in this way for each component temperature Tc. t² = t⁻¹ × K² ... (3)

[0028] In step S112, following step S110, the ECU16 calculates the life reduction time t3. The life reduction time t3 corresponds to the sum of the converted cumulative exposure times t2 at each component temperature Tc. In the example table shown in Figure 3, the sum of the converted cumulative exposure times t2 at each component temperature Tc within the temperature range from 25°C to 100°C is calculated as the life reduction time t3, which is 2.28 hours. The process then proceeds to step S114.

[0029] In step S114, the ECU 16 calculates the remaining lifespan information. The remaining lifespan information is calculated based on the lifespan reduction time t3 calculated in step S112 and the reference lifespan time tLr, which is the lifespan under the reference value Tcr. The calculated remaining lifespan information is stored in the storage device 20.

[0030] The remaining life information is calculated as the remaining life rate X [%] according to, for example, the following formula (4). In the example table shown in Figure 3, the life reduction time t3 is 2.28 and the reference life time tLr is 1000. Therefore, the remaining life rate X is calculated as 99.7% by subtracting 2.28 / 1000 from 1 and multiplying the result by 100. X = (1 - t³ / tLr) × 100 ... (4)

[0031] Furthermore, the remaining life information may be calculated using, for example, remaining life years, remaining life hours, or remaining mileage instead of the remaining life rate X. Specifically, the standard remaining life years (e.g., 15 years), which is the number of years a part can be used from when it is new (i.e., when the remaining life rate X is 100%), is predetermined in the design. Therefore, the remaining life years may be calculated by multiplying this standard remaining life years by the remaining life rate X / 100. The remaining life hours may also be calculated by subtracting the life depreciation time t3 from the standard life hours tLr. Furthermore, similar to the example of remaining life years, the remaining mileage may be calculated by using the design value of the standard remaining mileage from when the part is new and multiplying this standard remaining mileage by the remaining life rate X / 100.

[0032] 3. Effects As described above, according to the remaining life estimation device of this embodiment, the cumulative exposure time t1 is calculated for each life component temperature Tc during the operation of the PCU1. Each of the cumulative exposure times t1 calculated for each life component temperature is converted to a converted cumulative exposure time t2, which is the cumulative exposure time under a reference value Tcr for the component temperature Tc. Then, the remaining life information is calculated based on the life reduction time t3, which is the sum of the converted cumulative exposure times t2 for each component temperature Tc, and the life time tL of the life component under the reference value Tcr. This makes it possible to appropriately estimate the remaining life information of each life component constituting the PCU1. Therefore, it becomes possible to accurately determine the timing of repair or replacement of the PCU1 from the remaining life information of each life component stored in the storage device 20. Furthermore, the remaining life information stored in the storage device 20 can be suitably used, for example, to determine whether to reuse a PCU1 recovered from a scrapped vehicle.

[0033] Furthermore, according to this embodiment, the component temperature Tc used to calculate the remaining lifespan information is calculated during the operation of the PCU1 based on the ambient temperature Ta, the refrigerant temperature Tw, and a temperature calculation coefficient K1 corresponding to the sensitivity of the component to the ambient temperature Ta and refrigerant temperature Tw. With this method, by acquiring only two temperatures, the ambient temperature Ta and the refrigerant temperature Tw, during the operation of the PCU1, the temperature Tc of each component can be easily estimated regardless of the number of components. Therefore, compared to an example where a dedicated temperature sensor is provided for each component to acquire the component temperature Tc, it is possible to increase the number of components for which remaining lifespan information can be obtained while suppressing the increase in the cost required to acquire the component temperature Tc of each component.

[0034] Furthermore, according to this embodiment, the reference life time tLr for calculating remaining life information is a value that has been measured in advance as the life time tL of a component at the maximum operating temperature, which is the reference value Tcr. In this regard, the measured value of the life time tL at any temperature other than the maximum operating temperature may be used as the reference life time tLr. However, the relationship between component temperature Tc and life time tL is not strictly linear as schematically shown in Figure 5. That is, the rate of change of life time tL with respect to component temperature Tc may change, for example, around the maximum operating temperature. Therefore, when using the life time tL at a temperature other than the maximum operating temperature as the reference life time tLr, it becomes necessary to consider a safety factor in order to estimate the life time tL at the maximum operating temperature. In contrast, by using the measured value of the life time tL at the maximum operating temperature as the reference life time tLr, it becomes possible to accurately determine the life time tL at the maximum operating temperature and accurately calculate the remaining life information. [Explanation of Symbols]

[0035] 1 Power Conversion Unit (PCU), 2 PCU Case, 3 Capacitor, 4 Reactor, 5 Control Board, 6 DC / DC Converter, 7 Current Sensor, 8 Refrigerant, 9 Refrigerant Flow Path, 10 Remaining Life Estimation Device, 12 Ambient Temperature Sensor, 14 Refrigerant Temperature Sensor, 16 Electronic Control Unit (ECU), 18 Processor, 20 Memory Device

Claims

1. A remaining life estimation device for a power converter having life-limited components housed in a case, A processor that calculates the remaining lifespan information of the aforementioned lifespan component, A storage device that stores various information necessary for processing by the aforementioned processor, An ambient temperature sensor for detecting the ambient temperature inside the case, A refrigerant temperature sensor for detecting the refrigerant temperature of the refrigerant flowing through the flow path in the case, Equipped with, The aforementioned processor, During the operation of the power converter, the calculation of the lifespan component temperature of the lifespan component based on the ambient temperature, the refrigerant temperature, and a temperature calculation coefficient corresponding to the sensitivity of the lifespan component to the ambient temperature and the refrigerant temperature, and the counting of the calculated lifespan component temperature are performed at the sampling period. By multiplying the latest cumulative value of the count stored in the memory device by the sampling period, the cumulative exposure time, which is the cumulative value of the time the life-sustaining component is exposed to the same temperature during the operation of the power converter, is calculated for each life-sustaining component temperature. By applying a life conversion factor to each of the cumulative exposure times calculated for each life component temperature, each of the cumulative exposure times is converted into a converted cumulative exposure time, which is the cumulative exposure time under a reference value for the life component temperature. Based on the life reduction time, which is the sum of the converted cumulative exposure times for each life component temperature, and the reference life time, which is the life time of the life component under the reference value, the remaining life information is calculated. The aforementioned lifetime components are multiple, and the sampling period is changed according to the characteristics of each lifetime component. A device for estimating the remaining lifespan of a power converter.

2. The sampling period used for a life component with a large heat capacity is set to be longer than the sampling period used for a life component with a small heat capacity. A device for estimating the remaining lifespan of a power converter according to claim 1.

3. The aforementioned standard life time is a value that has been measured in advance as the life time of the life component under the maximum operating temperature, which is the standard value. A device for estimating the remaining lifespan of a power converter according to claim 1 or 2.

4. The aforementioned lifespan components include capacitors, reactors, control boards, DC / DC converters, and current sensors. A device for estimating the remaining lifespan of a power converter according to claim 1 or 2.

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