Control device and control method

Abstract

A control device according to one embodiment of the present invention is a control device for a power conversion device provided with a semiconductor switching element that generates heat by power conversion, a heat sink for the semiconductor switching element, and a cooling mechanism that cools the heat sink. The control device includes an element temperature estimation unit and a control unit. The element temperature estimation unit derives an estimated value of the temperature of the semiconductor switching element using either a drive amount of the semiconductor switching element or a temperature at a predetermined position within a predetermined range from the position of the semiconductor switching element. The control unit identifies an abnormal state of the cooling mechanism when a temperature difference between an estimated temperature value of the semiconductor switching element and a temperature of a predetermined position in the power conversion device exceeds a predetermined threshold temperature. The threshold temperature is determined to be lower than an upper limit temperature in an allowable range of the temperature difference and to be higher than a reference temperature predetermined in accordance with a heat generation amount of the semiconductor switching element.

Description

Technical Field

[0001] Embodiments of the present invention relate to a control device and a control method. Background Art

[0002] When a semiconductor switching element used for power conversion switches on and off, losses occur, causing the semiconductor switching element to heat up. Sometimes, a heat sink, cooling device, or the like is provided to cool the semiconductor switching element, thereby preventing the temperature of the semiconductor switching element from rising excessively. Further improvements in the reliability of temperature management of semiconductor switching elements used for power conversion are desired.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-14329 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] An object of the present invention is to provide a control device and a control method capable of further improving the reliability of temperature management in a semiconductor switching element for power conversion.

[0008] Means for solving problems

[0009] A control device according to one embodiment is a control device for a power conversion device including a semiconductor switching element that generates heat through power conversion, a heat sink for the semiconductor switching element, and a cooling mechanism for cooling the heat sink. The control device includes an element temperature estimating unit and a control unit. The element temperature estimating unit derives an estimated value of the temperature of the semiconductor switching element using either the drive amount of the semiconductor switching element or the temperature at a predetermined location within a predetermined range from the position of the semiconductor switching element. The control unit identifies an abnormal state of the cooling mechanism when the temperature difference between the estimated value of the temperature of the semiconductor switching element and the temperature at a predetermined location within the power conversion device exceeds a predetermined threshold temperature. The threshold temperature is determined to be lower than the upper limit temperature of the allowable range of the temperature difference and higher than a predetermined reference temperature corresponding to the amount of heat generated by the semiconductor switching element. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a configuration diagram of a power conversion device including a control device according to an embodiment.

[0011] Figure 2 This is a flowchart showing the procedure for recognizing the state of the power conversion device according to the embodiment.

[0012] Figure 3A It is a diagram for explaining the arrangement of temperature sensors according to the embodiment.

[0013] Figure 3B This is a diagram for explaining the output capacity limitation based on the disk temperature Ta according to the embodiment.

[0014] Figure 3C This is a diagram for explaining output capacity limitation based on element temperature Tj according to the embodiment.

[0015] Figure 4A This is a flowchart of a process for adjusting the output capacity limit value according to an embodiment.

[0016] Figure 4B This is a flowchart of a process for adjusting the output capacity limit value according to an embodiment.

[0017] Figure 5 This is an elevation view for explaining a first example of arrangement of the temperature sensors according to the embodiment.

[0018] Figure 6A It is a plan view for explaining a second example of arrangement of the temperature sensors according to the embodiment.

[0019] Figure 6B It is an elevation view for explaining a second example of arrangement of the temperature sensors according to the embodiment.

[0020] Figure 7 This is a diagram for explaining the relationship between output capacity and temperature in the embodiment.

[0021] Figure 8 This is a diagram for explaining average heat generation according to the embodiment.

[0022] Figure 9 This is a diagram for explaining the transient thermal impedance of the heat sink according to the embodiment.

[0023] Figure 10 This is a flowchart of the element temperature estimation process according to the embodiment.

[0024] Figure 11 This is a diagram for explaining the performance diagnosis of the cooling device 9 according to the embodiment. DETAILED DESCRIPTION

[0025] The following describes a control device and control method according to an embodiment with reference to the accompanying drawings. In the following description, components with identical or similar functions are denoted by the same reference numerals. Repeated descriptions of these components may be omitted. Furthermore, electrical connection may be simply referred to as "connection." References to "equal in size" in the following description also include cases of approximately equal size.

[0026] Figure 1 1 is a diagram showing the configuration of a power conversion device 1 including a control device 10 according to the embodiment.

[0027] In this Figure 1 1 , which describes a power conversion device 1 , a three-phase AC power supply 2 connected to the power conversion device 1 , and an AC motor 3 .

[0028] The three-phase AC power source 2 supplies, for example, three-phase AC power. For example, the three-phase AC power source 2 includes a power grid of a power company, a generator, etc. The three-phase AC power source 2 supplies the three-phase AC power to the DC converter 4 of the power converter 1 .

[0029] The AC motor 3 is, for example, a three-phase AC motor. AC power is supplied to the AC motor 3 from the power conversion device 1 .

[0030] exist Figure 1 In FIG, the power conversion device 1 includes a DC converter 4 , a smoothing capacitor 5 , an AC converter 6 , a current detector 7 , temperature sensors 8A and 8B, a cooling device 9 , and a control device 10 .

[0031] The DC converter 4 is, for example, a rectifier composed of a diode or a DC converter circuit including a semiconductor switching element. The semiconductor switching element can be an IGBT, a MOSFET, or the like. A freewheeling diode can also be provided in the semiconductor switching element. The DC converter 4 converts the AC power input from the three-phase AC power supply 2 into DC power and outputs it. Figure 1 , as an example, a DC converter 4 composed of a diode is shown. The DC converter 4 may be provided with a heat sink for dissipating heat generated by loss in the diode and the like.

[0032] The smoothing capacitor 5 stores the electric power supplied from the DC converter 4 and smoothes the voltage output from the DC converter 4 .

[0033] The AC converter 6 is an AC converter circuit including a semiconductor switch element 6SW. The semiconductor switch element 6SW can be an IGBT, a MOSFET, or the like. A freewheeling diode can also be provided in the semiconductor switch element 6SW. The AC converter 6 converts DC power into three-phase AC power and outputs it. Figure 1 Figure 6 shows an example of a configuration combining an IGBT and a freewheeling diode. The number of semiconductor switching elements 6SW and the like within the AC converter 6 is not limited to the number shown in the figure; multiple elements may be provided. A heat sink 6HS is provided within the AC converter 6 to dissipate heat generated by losses in the semiconductor switching elements 6SW. The heat sink 6HS dissipates heat generated by losses in the semiconductor switching elements 6SW.

[0034] Current detector 7 is an example of a current transformer including a Hall effect CT or a shunt resistor. Current detector 7 detects the current output to AC motor 3 and outputs the detected current value to current detection unit 101. Furthermore, the location of current detector 7 is not limited to the AC bus of two or more of the three phases; it may also be located in a location where the current waveform of the current flowing through AC converter 6 can be reproduced, such as within AC converter 6 or between DC converter 4 and AC converter 6.

[0035] The temperature sensors 8A and 8B include, for example, thermistors and temperature measuring resistors. The temperature sensors 8A and 8B detect the temperature of the locations where they are located and generate signals that vary according to the temperature. For example, the temperature sensor 8A is located at a location in the power conversion device 1 such as the AC converter 6 where the temperature is relatively high. The temperature sensor 8B is located at a location within the power conversion device 1 that is relatively close to the outside temperature. The locations of the temperature sensors 8A and 8B are not limited to the locations where the temperature sensor 8A and 8B is located. Figure 1 For example, the temperature sensor 8A may be positioned at any location as long as it can detect a temperature rise caused by the output power of the power conversion device 1 .

[0036] The cooling device 9 cools the radiator 6HS and the like of the AC converter 6. For example, the cooling device 9 includes a fan for air cooling of the radiator 6HS, a heat exchange system for water cooling of the radiator 6HS, and the like.

[0037] The control device 10 includes a computing unit such as an MCU or FPGA and its peripheral circuits. The computing unit of the control device 10 includes a processor that executes processing based on software (program) or a hardware computing circuit.

[0038] For example, the control device 10 includes a current detection unit 101, a current calculation unit 102, a radiator temperature detection unit 103, a radiator temperature calculation unit 104, an element temperature estimation unit 105, an in-disk temperature detection unit 106, an in-disk temperature calculation unit 107, an external command receiving unit 108, a storage unit 110, a control unit 120, and a PWM output unit 130.

[0039] The current detection unit 101 includes a conversion unit such as an AD converter, receives a signal output from the current detector 7 as input, converts the signal into current data for calculation, and outputs the data to the current calculation unit 102 .

[0040] The current calculation unit 102 receives the current data output by the current detection unit 101 as input, calculates, for example, an effective value of the current based on the current data, and outputs the calculated value to the control unit 120 .

[0041] The heat sink temperature detection unit 103 is a conversion unit such as an AD converter, which receives the signal output by the temperature sensor 8 as input, converts it into temperature data for calculation, and outputs it to the heat sink temperature calculation unit 104 .

[0042] The heat sink temperature calculation unit 104 receives the temperature data output from the heat sink temperature detection unit 103 as input, calculates, for example, a Celsius temperature based on the temperature data, and outputs the calculated value to the element temperature estimation unit 105 .

[0043] The element temperature estimating unit 105 receives the temperature data from the heat sink temperature calculating unit 104 , calculates the junction temperature of the semiconductor switching element 6SW based on the temperature data, and outputs an estimated value of the junction temperature of the semiconductor switching element 6SW to the control unit 120 .

[0044] For example, the element temperature estimating unit 105 derives an estimated value (first estimated value) of the temperature of the semiconductor switching element 6SW using a detected value of the temperature at a predetermined position within a predetermined range from the position of the semiconductor switching element 6SW.

[0045] The disk temperature detection unit 106 is a conversion unit such as an AD converter, which receives the signal output by the temperature sensor 8B as input, converts it into temperature data for calculation, and outputs it to the disk temperature calculation unit 107 .

[0046] The disk temperature calculation unit 107 receives the temperature data output from the disk temperature detection unit 106 , calculates, for example, Celsius temperature based on the temperature data, and outputs the detected value of the disk temperature (referred to as disk temperature Ta) to the control unit 120 .

[0047] The external command receiving unit 108 receives an external command value used for controlling the AC motor 3 from, for example, a host device, and outputs the value to the control unit 120 .

[0048] The storage unit 110 includes a storage medium such as a semiconductor memory or a magnetic storage device. The storage unit 110 writes new data to the storage unit 110 through a write operation from the control unit 120 and stores the data. The storage unit 110 outputs the stored data through a read operation from the control unit 120. Instead of writing data from the control unit 120, a dedicated controller may be used to write data to the storage unit 110.

[0049] The control unit 120 performs various processes related to collection and management of various data, control of the AC converter 6 , recognition of the state of the power conversion device 1 , and the like.

[0050] The control unit 120 collects and manages various data and performs the following processing. The control unit 120 acquires the component temperature data calculated by the component temperature estimation unit 105, the disk temperature data calculated by the disk temperature calculation unit 107, and the current data calculated by the current calculation unit 102. The control unit 120 monitors the acquired data. The control unit 120 writes and stores the monitoring results and the aforementioned data as time history data in the storage unit 110.

[0051] The control unit 120 controls the AC converter 6 and performs the following processing. Using various data stored in the storage unit 110 or collected data, the control unit 120 calculates a control variable (e.g., a voltage reference) for PWM control of the AC motor 3 in each control cycle and outputs it to the PWM output unit 130.

[0052] Furthermore, the control unit 120 performs processing related to recognition of the state of the power conversion device 1. Details will be described later.

[0053] The PWM output unit 130 generates a PWM signal based on the control variable (voltage reference) supplied from the control unit 120 , and outputs the PWM signal to the AC converter 6 .

[0054] Figure 2 This is a flowchart showing the procedure of recognizing the state of the power conversion device 1 according to the embodiment.

[0055] The control device 10 performs an estimation process (element temperature estimation) of the element temperature Tj using the element temperature estimation unit 105 and the like (SA11). For example, the element temperature estimation unit 105 estimates the junction temperature of the semiconductor switching element 6SW based on the temperature data output by the heat sink temperature detection unit 103. The details of the estimation process of the element temperature Tj will be described later.

[0056] Furthermore, the disk temperature calculation unit 107 may also perform an estimation process (disk temperature estimation) of the disk temperature Ta accordingly to generate the disk temperature (disk temperature data), and update the disk temperature Ta to the latest estimated value. For simplicity of explanation, the disk temperature Ta may be assumed to be constant. In practice, if an environment in which the disk temperature Ta is assumed to be constant exists, the estimation process of the disk temperature Ta may be omitted.

[0057] The control unit 120 calculates an estimated value of the element temperature rise (Tj-Ta) based on the temperature difference between the element temperature Tj and the disk temperature Ta (SA12). The element temperature rise (Tj-Ta) is, for example, the amount of temperature increase of the element temperature Tj from the reference disk temperature Ta.

[0058] The control unit 120 determines whether the element temperature rise (Tj-Ta) is smaller than a predetermined determination value (SA13).

[0059] When the element temperature rise (Tj-Ta) is above the specified judgment value, the control unit 120 issues a temperature abnormality alarm (temperature abnormality alarm) (SA14) indicating a reduction in cooling capacity, controls the device to a protection action mode (SA15), and then ends a series of processing.

[0060] If the element temperature rise (Tj-Ta) is less than a predetermined determination value, the control unit 120 determines whether the element temperature rise (Tj-Ta) is less than a determination value obtained by adding a predetermined value α to the value of the initial data (SA16). If the element temperature rise (Tj-Ta) is less than the determination value obtained by adding the predetermined value α to the value of the initial data, the control unit 120 terminates the series of processes.

[0061] If the element temperature rise (Tj-Ta) is not less than the determination value obtained by adding a predetermined value α to the value of the initial data, the control unit 120 issues an alarm indicating a reduction in cooling capacity (cooling capacity reduction alarm) (SA17) and ends a series of processes.

[0062] Through the above-described processing, the state of the power conversion device 1 can be recognized.

[0063] The threshold temperature used for the above identification may also be associated with initial data obtained by operating the semiconductor switching element 6SW in the power conversion device 1. In this case, the control unit 120 can identify that an abnormality has occurred in the state of the cooling device 9 based on the initial data and the estimated temperature value of the semiconductor switching element 6SW.

[0064] Figure 3A It is a diagram for explaining the arrangement of the temperature sensor 8A according to the embodiment. Figure 3B This is a diagram for explaining the output capacity limitation based on the disk temperature Ta according to the embodiment. Figure 3C This is a diagram for explaining output capacity limitation based on element temperature Tj according to the embodiment.

[0065] exist Figure 3A The power converter 1 shown has a panel (casing) provided with a DC converter 4, a smoothing capacitor 5, an AC converter 6, a cooling device 9, etc. Furthermore, a temperature sensor 8B, etc., is provided within the panel (casing) of the power converter 1.

[0066] Figure 3A The cooling device 9 shown includes a fan unit for air cooling. The cooling device 9 in this case can be configured as follows.

[0067] The case where the cooling device 9 includes an exhaust type fan unit will be described. In this case, the cooling device 9 is arranged to match the opening portion of the upper surface of the disk (casing) of the power conversion device 1 ( Figure 3A The power converter 1 has an air intake port on the door or other portion of the panel (housing). This port is equipped with a filter for dust removal and insect protection. Cool air drawn in through the air intake port absorbs heat while passing through the panel (housing) and is then exhausted to the outside of the panel via the fan unit of the cooling device 9.

[0068] Alternatively, the cooling device 9 may include a blower-type fan unit. In this case, the cooling device 9 may be arranged upstream of the radiator so that cool air flows around the radiator.

[0069] In addition, a water-cooling heat exchanger may be included as the cooling device 9. In this case, the cooling device 9 may be arranged so that the heat exchanger is thermally coupled to the radiator of the heat exchange unit 6.

[0070] As described above, the cooling device 9 can adopt various forms.

[0071] In any of the above cases, the temperature sensor 8A may be disposed in a path through which cool air taken in from the vicinity of the air intake port or from the air intake port passes within the panel (casing) of the power conversion device 1 .

[0072] like Figure 3B As shown, the output capacity of the semiconductor switch element 6SW is defined by the current value within the range below the upper limit (TaMAX) of the internal disk temperature Ta. If the internal disk temperature Ta exceeds the upper limit (TaMAX), the control unit 120 limits the output of the semiconductor switch element 6SW.

[0073] For example, within the range where the disk temperature Ta is below the first temperature (Ta1), the semiconductor switching element 6SW is permitted to operate at its rated output capacity (100%). Within the range where the disk temperature Ta exceeds the first temperature (Ta1) but is below the upper limit (TaMAX) of the disk temperature Ta, the semiconductor switching element 6SW is permitted to operate with its output capacity limited to a value greater than the rated output capacity (100%). For example, when the disk temperature Ta is at the upper limit (TaMAX) of the disk temperature Ta, the control unit 120 derates the output capacity of the semiconductor switching element 6SW to 80%.

[0074] Furthermore, within the range where the disk temperature Ta is below the first temperature (Ta1), if predetermined conditions are satisfied, the drive is permitted if the rated output capacity (100%) of the semiconductor switching element 6SW is exceeded and falls within the range of 120%.

[0075] For example, if the temperature Ta in the panel is within the range from the lower limit value (TaMIN) to the upper limit value (TaMAX), the limit value of the output capacity can be derated at the same reduction rate.

[0076] In this case, the predetermined upper limit value for limiting the output capacity (driving amount) of the semiconductor switching element 6SW may be determined to be a value exceeding the rated output capacity (100%) of the semiconductor switching element.

[0077] like Figure 3C As shown, the output capacity of semiconductor switch element 6SW is defined by the current value when the junction temperature (referred to as element temperature Tj) of semiconductor switch element 6SW is within a range below an upper limit value (TjMAX). When element temperature Tj exceeds the upper limit value (TjMAX) of element temperature Tj, control unit 120 limits the output of semiconductor switch element 6SW.

[0078] For example, within the range where the element temperature Tj is below the first temperature (Tj1), the semiconductor switch element 6SW is permitted to be driven at its rated output capacity (100%). Within the range where the element temperature Tj exceeds the first temperature (Tj1) and is below the upper limit value (TjMAX) of the element temperature Tj, the semiconductor switch element 6SW is permitted to be driven with its output capacity limited. For example, when the element temperature Tj is at the upper limit value (TjMAX) of the element temperature Tj, the output capacity of the semiconductor switch element 6SW is derated (80%).

[0079] Furthermore, when the element temperature Tj is within the range of the first temperature ( Tj1 ) or lower and predetermined conditions are satisfied, the control unit 120 permits the driving within a range exceeding the rated output capacity (100%) to 120% of the semiconductor switching element 6SW.

[0080] For example, the control unit 120 may derate the output capacity limit value at the same reduction rate within the range of the element temperature Tj from the lower limit value (TjMIN) to the upper limit value (TjMAX).

[0081] Reference Figure 4A and Figure 4B , the process of adjusting the output capacity limit value of the implementation method is explained.

[0082] Figure 4A and Figure 4B This is a flowchart of a process for adjusting the output capacity limit value according to an embodiment.

[0083] Figure 4A and Figure 4B The processes shown can be implemented independently of each other.

[0084] For example, Figure 4AAs shown, the control device 10 performs an estimation process (element temperature estimation) of the element temperature Tj (SB11) by the element temperature estimation unit 105 etc. The process of SB11 may be the same as the process of SA11 described above, or may be performed as a common process.

[0085] The control unit 120 identifies whether the element temperature Tj is lower than the threshold value Tj1 (SB12).

[0086] When the element temperature Tj is equal to or higher than the threshold value Tj1, the control unit 120 determines whether the element temperature Tj is lower than the upper limit element temperature TjMAX (SB13).

[0087] When the element temperature Tj is equal to or higher than the upper limit element temperature TjMAX, the control unit 120 issues a temperature abnormality alarm (SB14), shifts to "device protection operation" of the protection device (SB15), and then ends a series of processes.

[0088] When the element temperature Tj is lower than the upper limit element temperature TjMAX, the control unit 120 determines the output capacity limit F_Tj to be within a range of 100% to 80% of the rated value (SB16), and proceeds to the process SB30.

[0089] If the element temperature Tj is lower than the threshold value Tj1, the control unit 120 determines whether to release the output capacity limit (SB17). If not, the control unit 120 sets the output capacity limit F_Tj to 100% of the rated value (SB17) and proceeds to SB30.

[0090] When the output capacity limit is released, the control unit 120 determines the output capacity limit F_Tj to be within the range of 120% to 100% of the rated value (SB18), and proceeds to SB30.

[0091] Through the above-described processing, the control device 10 recognizes the state of the element junction temperature of the power conversion device 1 and can adjust the output capacity limitation based on the element junction temperature.

[0092] In addition, the control device 10 can also be used with Figure 4A The identification process of the "element junction temperature state" shown is performed in association with Figure 4B The identification process of the "state of the temperature inside the pan" is shown.

[0093] For example, Figure 4B As shown, the control device 10 performs estimation processing of the internal disk temperature Ta (internal disk temperature estimation) by the internal disk temperature calculation unit 107 and the like (SB21).

[0094] The control unit 120 determines whether the disk temperature Ta is lower than a threshold value Ta1 (SB22).

[0095] When the internal disk temperature Ta is equal to or higher than the threshold value Ta1, the control unit 120 determines whether the internal disk temperature Ta is lower than the upper limit internal disk temperature Ta2 (SB23).

[0096] When the plate temperature Ta is equal to or higher than the upper limit plate temperature Ta2, the control unit 120 causes the process to proceed to the aforementioned Figure 4A SB14 issues a temperature anomaly alarm and moves to the "device protection action" of the protection device, ending a series of processing.

[0097] When the internal temperature Ta is lower than the upper limit internal temperature Ta2, the control unit 120 determines the output capacity limit F_Ta to be within the range of 100% to 80% of the rated value (SB26), and the process proceeds to the aforementioned step Figure 4A SB30.

[0098] When the temperature Ta inside the disk is lower than the threshold value Ta1, the control unit 120 determines whether to release the output capacity limit (SB27). If the output capacity limit is not released, the control unit 120 determines the output capacity limit F_Ta to be 100% of the rated value (SB27), and the process enters the aforementioned Figure 4A SB30.

[0099] When the output capacity limit is released, the control unit 120 determines the output capacity limit F_Ta from 120% to the rated value 100% (SB28), and the process enters the aforementioned Figure 4A SB30.

[0100] By the above-described process, the state of the temperature inside the panel of the power conversion device 1 is recognized, and thus the output capacity limitation based on the temperature inside the panel can be adjusted.

[0101] For example, the control unit 120 changes the upper limit value for limiting the drive amount of the power conversion device 1 based on whether the estimated temperature value of the semiconductor switching element 6SW has reached the upper limit temperature of the allowable range. In this case, if the upper limit temperature is reached, the upper limit value is maintained to limit the drive amount. If the upper limit temperature is not reached, the upper limit value for limiting the drive amount is relaxed.

[0102] Reference Figure 5 , a first example of the configuration of the temperature sensor according to the embodiment is described.

[0103] Figure 5 This is an elevation view for explaining a first example of arrangement of the temperature sensors according to the embodiment.

[0104] The module 6M is arranged on the heat sink 6HS.

[0105] The module 6M includes, for example, a substrate 6BS, a semiconductor switching element 6SW, and a temperature sensor 8A. The substrate 6BS comprises a core material such as ceramic, fiberglass, or resin. The semiconductor switching element 6SW of the module 6M is disposed on the first surface 6F1 of the substrate 6BS. The temperature sensor 8A is disposed within the module 6M. For example, the temperature sensor 8A may be disposed within the module 6M. The interior of the module 6M is filled with air, resin, or the like.

[0106] The second surface 6F2 of the substrate 6BS of the module 6M is configured to be thermally coupled to the heat sink 6HS. For example, a screen (e.g., a screen made of silicon or polyester film) to improve thermal conductivity may be provided between the second surface 6F2 of the substrate 6BS of the module 6M and the heat sink 6HS, or oil may be applied. This thermal coupling method can be a conventional method.

[0107] If the Figure 5 As shown, a temperature sensor 8A is provided in the module 6M itself.

[0108] In this case, the thermal resistance Rth between the location where the temperature sensor 8A is installed and the representative position of the semiconductor switch element 6SW is preset. For example, the control unit 120 uses the thermal resistance Rth to calculate the element temperature Tj of the semiconductor switch element 6SW based on the temperature measured by the temperature sensor 8A (referred to as the sensor measured temperature). This calculation can be performed using the following equation (1).

[0109] Component temperature Tj = sensor measurement temperature + Rth × average heat generation [W] (1)

[0110] In addition, the average value of the heat amount of the module 6M estimated from the average output current of the module 6M can be used as the "average heat amount [W]" in the formula (1).

[0111] Reference Figure 6A and Figure 6B , a second example of the arrangement of the temperature sensor 8A according to the embodiment will be described.

[0112] Figure 6A It is a plan view for explaining a second example of the arrangement of the temperature sensor 8A according to the embodiment.

[0113] Figure 6B It is an elevation view for explaining a second example of the arrangement of the temperature sensor 8A according to the embodiment.

[0114] With Figure 5 The explanation focuses on the differences between the examples.

[0115] The module 6MA does not include the temperature sensor 8A inside its housing. Instead, the temperature sensor 8A is disposed on the heat sink 6HS. Therefore, the heat conduction characteristics between the location where the temperature sensor 8A is disposed and the semiconductor switch element 6SW are replaced.

[0116] The Figure 6A and Figure 6B The thermal resistance of the example shown is expressed by the following formula (2).

[0117] Thermal resistance Rth=Rth(h)+Rth(jc)(2)

[0118] In equation (2), "Rth(h)" is the thermal resistance between the location where the temperature sensor 8A is installed and the representative position of the module 6M. "Rth(jc)" is the thermal resistance between the representative position of the module 6M and the representative position of the semiconductor switch element 6SW. The representative position of the module 6M can be set, for example, within the range of the image of the semiconductor switch element 6SW projected onto the surface of the heat sink 6HS. A point is set at the representative position of the module 6M.

[0119] Thus, the definition of the thermal resistance from the heat generating portion changes depending on the position of the temperature sensor 8A. Therefore, the above-mentioned formula (1) is replaced by the following formula (3).

[0120] Element temperature Tj = sensor measurement temperature + (Rth(h) + Rth(jc)) × average heat generation [W] (3)

[0121] As mentioned above Figures 5 to 6B As shown, the temperature sensor 8A is provided within a predetermined range from the semiconductor switch element 6SW. The predetermined range may be within the module 6M including the semiconductor switch element 6SW, or within a predetermined range based on the surface of the heat sink 6HS (on or near the surface).

[0122] like Figure 5 As shown, the predetermined position in the former case is the position (referred to as a first position) of the temperature sensor 8A (first sensor) arranged in the module 6M including the semiconductor switch element 6SW.

[0123] In the latter case, the predetermined position is as follows Figure 6A 、 Figure 6B 1 , which is a position (referred to as a second position) of the temperature sensor 8A (second sensor) disposed within a predetermined range (on the surface or near the surface) with respect to the surface of the heat sink 6HS.

[0124] In this way, any one of the above can be selected depending on the difference between the module 6M and the module 6MA to be used.

[0125] Reference Figure 7 , the relationship between the estimated temperature and the output capacity of the embodiment will be described.

[0126] Figure 7 This is a diagram for explaining the relationship between output capacity and temperature in the embodiment. Figure 7 The graph shown shows the relationship between the temperature (vertical axis) measured by the temperature sensor 8A with respect to the output capacity (horizontal axis) and the estimated temperature (vertical axis) of the semiconductor switching element 6SW.

[0127] The output capacity range shown in this graph represents the range of 0 to 150% when the rated output is set to 100%. Figure 7 Throughout the entire output capacity range shown, the temperature measured by temperature sensor 8A (vertical axis) and the estimated temperature of semiconductor switch element 6SW increase monotonically toward the upper right. Comparing the temperature measured by temperature sensor 8A (vertical axis) with the estimated temperature of semiconductor switch element 6SW, as shown in equations (1) and (3), the estimated temperature of semiconductor switch element 6SW is higher.

[0128] Reference Figure 8 and Figure 9 , the average heat generation of the embodiment is described.

[0129] Figure 8 This is a diagram for explaining average heat generation according to the embodiment.

[0130] Figure 8 Indicates the result of simulated heating. Figure 8 The upper layer represents the AC output current (one-phase quantity) of the AC converter unit 6, the middle layer represents the instantaneous heat generation of the semiconductor switch element 6SW, and the lower layer represents the average heat generation resulting from a moving average of the instantaneous heat generation of the semiconductor switch element 6SW within the AC cycle. Furthermore, the analysis assumes that the instantaneous heat generation of the semiconductor switch element 6SW shown in the middle layer is caused by the sum of the conduction loss and switching loss of the semiconductor switch element 6SW.

[0131] During each AC cycle, semiconductor switching element 6SW switches on and off multiple times. The results in the middle panel indicate the instantaneous heat generated at this switching timing. Furthermore, calculating the moving average of this instantaneous heat generation while maintaining the AC cycle and output current constant reveals that the resulting average heat generation also remains constant (lower panel).

[0132] Depending on the application, the AC cycle and the magnitude of the output current may be sequentially changed. In such applications, it is required to estimate the element temperature Tj more accurately in real time.

[0133] Utilizing information from the control signal representing the most recent control of the semiconductor switching element 6SW makes it easier to analyze the element temperature Tj in real time. In this embodiment, it is recommended to pattern the control signal representing the most recent control of the semiconductor switching element 6SW. For example, the operating mode of the AC converter 6 may be specified in the control signal pattern. These operating modes include power running mode and regeneration mode. Alternatively, the modulation rate of the PWM control may be used to distinguish between these modes.

[0134] As mentioned above, the average value of the heat output (average heat output) is used for analysis. To make this average heat output more stable, the data for one or more cycles of the AC output frequency can be used to calculate the average heat output data within that period.

[0135] Assuming the average heat generation is calculated using data from a period shorter than one cycle of the AC output frequency, the total heat generation during the average calculation period varies depending on whether the semiconductor switching element 6SW switches on and off once, and whether the period for calculating the average includes a single switching event. Therefore, if a relatively short period is selected, the average heat generation value obtained will vary depending on whether or not switching actually occurs. Thus, using an analysis process with a relatively short period can be used when responsiveness is prioritized over accurately estimating the element temperature Tj.

[0136] Furthermore, when calculating the average value of the element temperature Tj in a relatively short period, the following conditions must also be considered: The "relatively short period" described below is, for example, a period shorter than 1 second.

[0137] First, the transient thermal impedance will be described.

[0138] Figure 9 : is a diagram for explaining the transient thermal impedance of the heat sink according to the embodiment. Figure 9 The transient thermal impedance characteristics of the heat sink shown are modeled for ease of explanation.

[0139] Should Figure 9 The graph shown shows an example of the relationship between averaging time (LOG scale) and transient thermal impedance (LOG scale). The averaging time refers to the width of the time window that defines the target period for applying the averaging process.

[0140] If the averaging time is greater than 1 second, the transient thermal impedance becomes a constant value (e.g., 1). If the averaging time is shorter than 1 second, the shorter the time, the smaller the transient thermal impedance value. The averaging time may be a fixed value.

[0141] Furthermore, when the averaging time is changed, the influence of the transient thermal impedance can be included in the estimation conditions. If this value is not included, the error in the estimated value may become large.

[0142] Furthermore, it takes time for actual devices and detection systems to dissipate the received heat, so it is sometimes difficult to accurately reproduce the time range of 1 second or more.

[0143] In this way, when considering the average heat generation in the embodiment, the average time may be set to be longer than 1 second, for example.

[0144] Reference Figure 10 , the element temperature estimation process of the embodiment is described.

[0145] Figure 10 This is a flowchart of the element temperature estimation process according to the embodiment.

[0146] The heat sink temperature detection unit 103 and the heat sink temperature calculation unit 104 detect the temperature of the heat sink 6HS by detecting the temperature using the temperature sensor 8A ( SC11 ).

[0147] The element temperature estimation unit 105 obtains temperature data corresponding to the temperature Th of the measurement result. The element temperature estimation unit 105 uses the temperature Th and the aforementioned Figure 7 The output capacity with respect to the temperature Th and the temperature Tj with respect to the output capacity are estimated based on the information in the table of characteristics of the graph shown (SC12).

[0148] Furthermore, the control unit 120 estimates the loss Ploss generated in the semiconductor switching element 6SW based on the output capacity (current capacity) of the AC supplied to the AC motor 3 and the frequency of the AC (SC13). A general method can be applied to the estimation calculation method of the loss Ploss.

[0149] The control unit 120 estimates the temperature Tj (SC14) using the aforementioned equation (3) containing the temperature Th, a predetermined thermal resistance, and the average heat generation of the semiconductor switch element 6SW as variables. The average heat generation of the semiconductor switch element 6SW varies depending on the magnitude of the loss Ploss in the semiconductor switch element 6SW.

[0150] The control unit 120 obtains the temperature Tj obtained in step SC12 and the temperature Tj obtained in step SC14. The control unit 120 selects the larger value from the two temperatures Tj and determines it as the estimated value of the element temperature Tj.

[0151] The control unit 120 obtains an estimated value of the element temperature Tj through the above-mentioned processing.

[0152] In this manner, the element temperature estimating unit 105 derives an estimated value (first estimated value) of the temperature of the semiconductor switching element 6SW using the detected value of the temperature at a predetermined position within a predetermined range from the position of the semiconductor switching element 6SW.

[0153] Furthermore, the control unit 120 derives the element temperature Tj, which is an estimated value (second estimated value) of the temperature of the semiconductor switching element 6SW, using the drive amount of the semiconductor switching element 6SW.

[0154] The control unit 120 may use any one of the first estimated value and the second estimated value to identify an abnormal state of the cooling device 9 (cooling mechanism).

[0155] (Diagnostic processing of cooling system)

[0156] Next, the diagnostic process of the cooling device 9 will be described.

[0157] If the cooling fan of the cooling device 9 fails or the filter becomes clogged, the performance of the cooling device 9 may be reduced from the standard performance. In the comparative example, this may cause the temperature of the semiconductor switching element 6SW to rise, resulting in the inability to continue the operation of the power conversion device 1.

[0158] Therefore, in this embodiment, the estimated result of the element temperature Tj of the semiconductor switching element 6SW is used to diagnose the performance of the cooling device 9. For example, by detecting that the temperature rise trend of the semiconductor switching element 6SW is different from the normal trend, the occurrence of the above-mentioned factor can be detected in advance.

[0159] Regarding this case, refer to the above Figure 3A and the following Figure 11 Provide explanation. Figure 11 This is a diagram for explaining the performance diagnosis of the cooling device 9 according to the embodiment. Figure 11 The graph shows normal temperature relative to output (horizontal axis). The temperatures shown here represent the relationship between the detection results of temperature sensor 8A, the device temperature Tj of semiconductor switch element 6SW, and the maximum junction temperature (device temperature Tj). The detection results of temperature sensor 8A and the device temperature Tj of semiconductor switch element 6SW tend to increase as the output increases. Furthermore, the maximum junction temperature (device temperature Tj) remains constant regardless of the output.

[0160] As mentioned above Figure 3A As shown, the cooling device 9 includes a cooling fan in its configuration.

[0161] For example, the cooling fan blows cool air around the heat sink 6HS of the semiconductor switching element 6SW. This ventilation improves the heat dissipation efficiency of the heat sink 6HS.

[0162] Regarding temperature sensor 8A and the ventilation direction, when temperature sensor 8A is located upstream of semiconductor switch element 6SW in the ventilation direction of the cooling fan, the temperature detected by temperature sensor 8A is lower than the temperature of semiconductor switch element 6SW.

[0163] Conversely, when the temperature sensor 8A is located downstream of the semiconductor switch element 6SW, the temperature detected by the temperature sensor 8A is higher than the temperature when the temperature sensor 8A is located upstream of the semiconductor switch element 6SW.

[0164] In order to make the temperature Ta inside the dish equivalent to the temperature outside the dish, the former is required.

[0165] However, in this embodiment, initialization data based on the detection results of temperature sensor 8A can be used. This initialization data is based on test results that also take into account the ventilation direction condition. Similarly, the thermal resistance in the calculation formula is also determined by taking into account the ventilation direction condition. Therefore, the placement of temperature sensor 8A can also be adapted to the latter position.

[0166] For example, if there are no cooling fan failures or filter clogging, the ventilation direction and air volume can be considered to remain essentially unchanged. Even if the in-disk temperature Ta, detected by temperature sensor 8A, remains unchanged during operation, the air volume may decrease if a cooling fan failure or filter clogging occurs. This decreases the heat dissipation efficiency of radiator 6HS, increasing the value detected by temperature sensor 8B and the estimated value of element temperature Tj based on this value. The cooling device 9 including such a cooling fan and filter is an example of a cooling mechanism.

[0167] By detecting such a temperature change (temperature rise), the state of the cooling device 9 and the like can be diagnosed.

[0168] For example, Figure 11 As shown, a threshold value for detecting failure of the cooling device 9 and a threshold value for detecting clogging of the filter and the wind tunnel can be set to a temperature higher than the line of the estimated value of the element temperature Tj, and based on this, an abnormal temperature rise of the estimated value of the element temperature Tj can be detected.

[0169] According to the above embodiment, the control device 10 is a control device for the power conversion device 1. The power conversion device 1 includes a semiconductor switching element 6SW that generates heat during power conversion, a heat sink 6HS for the semiconductor switching element 6SW, and a cooling mechanism for cooling the heat sink 6HS. The control device 10 includes an element temperature estimator 105 and a control unit 120. The element temperature estimator 105 derives an estimated value for the temperature (element junction temperature) of the semiconductor switching element 6SW using either the amount of drive of the semiconductor switching element 6SW or the temperature at a predetermined location within a predetermined range from the location of the semiconductor switching element 6SW. The control unit 120 identifies an abnormal state of the cooling device 9 when the temperature difference between the estimated element temperature Tj (element junction temperature) and the temperature at a predetermined location within the power conversion device 1 (disc internal temperature Ta) exceeds a predetermined threshold temperature, and outputs the identification result. The threshold temperature is set to be lower than the upper limit of the allowable temperature difference range and higher than a predetermined reference temperature corresponding to the amount of heat generated by the semiconductor switching element 6SW. This makes it possible to further improve the reliability of temperature management of the semiconductor switching element for power conversion.

[0170] For example, the relationship between the output pattern of the operating power conversion device 1 and the temperature rise of the semiconductor switching element 6SW is stored in the storage unit 110. The control unit 120 detects an output pattern that is identical or similar to the output pattern of the power conversion device 1 stored in the storage unit 110. If this situation occurs based on the detection result, the control unit 120 compares the temperature rise of the semiconductor switching element 6SW with the temperature rise based on past data to easily determine whether the same phenomenon as the temperature rise based on the past data has occurred.

[0171] For example, the above-mentioned control device 10 includes a temperature sensor 8A (second sensor) arranged within a predetermined range based on the surface of the radiator 6HS (on the surface or near the surface) and a temperature sensor 8B (third sensor) arranged at a predetermined position within the disk of the power conversion device 1.

[0172] The element temperature estimating unit 105 derives a first estimated value of the temperature of the semiconductor switching element 6SW using the detection value of the temperature sensor 8A.

[0173] The control unit 120 can identify an abnormal state of a cooling mechanism such as the cooling device 9 when the temperature difference between the estimated value of the temperature of the semiconductor switching element 6SW based on the detection value of the temperature sensor 8A and the temperature of a specified position within the disk of the power conversion device 1 based on the detection result of the temperature sensor 8B exceeds a predetermined threshold temperature.

[0174] (Second embodiment)

[0175] A second embodiment will be described.

[0176] In the description of the first embodiment, for simplicity of description, the case where one semiconductor switch element 6SW on the heat sink 6HS is operated is described as an example. Figure 6A and Figure 6B As shown, a plurality of semiconductor switching elements 6SW and one temperature sensor 8A may be arranged on the heat sink 6HS. Figure 6A and Figure 6B The number of semiconductor switch elements 6SW and the number of modules 6MA shown are examples. In this embodiment, an analysis method is described in which a plurality of semiconductor switch elements 6SW are arranged on a heat sink 6HS and each of them is switched at appropriate timing.

[0177] There are several methods for estimating the device temperatures Tj of the plurality of semiconductor switching devices 6SW, as described below. An appropriate method can be selected from these methods for implementation.

[0178] Estimation Method 1: Historical data recording temperature changes of multiple semiconductor switch elements 6SW on the heat sink 6HS when operated in a predetermined pattern is used as initial data. For example, based on the initial data, one semiconductor switch element 6SW reaching the highest temperature is extracted from the multiple semiconductor switch elements 6SW. The element temperature Tj of the extracted semiconductor switch element 6SW is estimated, and the temperatures of other elements are not estimated. This only requires estimating the element temperature Tj of the semiconductor switch element 6SW reaching the highest temperature, and the element temperatures of semiconductor switch elements 6SW other than the semiconductor switch element 6SW reaching the highest temperature can be assumed to be below the aforementioned element temperature Tj. In this way, by selecting the semiconductor switch element 6SW reaching the highest temperature as the analysis target, the analysis target can be narrowed, and the estimation and determination of individual temperatures can be omitted. According to this estimation method 1, the substantially necessary information can be obtained using a simple method.

[0179] Presumption method 2: For example, as mentioned above Figure 7 As shown in the graph, if the "outside the disk (housing), that is, the external air temperature (Ta0) is assumed to be 25 degrees", the disk temperature Ta and the radiator temperature Th when the output is 0% are both 25 degrees.

[0180] For example, the temperature difference ΔT between the panel temperature Ta and the heat sink temperature Th when each semiconductor switching element 6SW is independently operated and the outside air temperature ( Ta0 ) is calculated.

[0181] The temperature differences ΔT of (outside air temperature Ta0−Ta) are added together to obtain ΣTa when the plurality of semiconductor switching elements 6SW are operated.

[0182] Furthermore, by adding the temperature differences ΔT between (outside air temperature Ta0 −Th), ΣTh when the plurality of semiconductor switching elements 6SW are operated is obtained.

[0183] The temperature difference (Tj-Ta) from the disk temperature Ta or the temperature difference (Tj-Th) from the heat sink temperature Th at a certain output uses a predetermined temperature difference. Figure 7 In the graph of , the value at the time of the above output can also be used. The temperature Ta inside the disk at this time can be regarded as 25 degrees.

[0184] The estimated value of the element temperature Tj when a plurality of elements are operating is based on the following calculation formula.

[0185] Element temperature when multiple elements are operating: Tj = (Tj-Ta) + ∑Ta or element temperature when multiple elements are operating: Tj = (Tj-Th) + ∑Th

[0186] Estimation method 3: Similar to the above “Estimation method 2”, based on the above Figure 7 The graph assumes that "when the external air temperature (Ta0) of the housing is 25 degrees, the disk temperature Ta and the radiator temperature Th at 0% output are both 25 degrees."

[0187] Initial data of the disk temperature Ta when the plurality of semiconductor switching elements 6SW operate in a predetermined mode are referred to as ΣTa and ΣTh, and similarly, initial data of the heat sink temperature Th is referred to as ΣTh.

[0188] The temperature difference (Tj-Ta) from the disk temperature Ta or the temperature difference (Tj-Th) from the heat sink temperature Th at the time of output of a certain predetermined pattern is a predetermined temperature difference. Figure 7 The graphs obtained are respectively.

[0189] The estimated value of the element temperature Tj when a plurality of elements are operating is based on the following calculation formula.

[0190] Element temperature when multiple elements are operating: Tj = (Tj-Ta) + ∑Ta or element temperature when multiple elements are operating: Tj = (Tj-Th) + ∑Th

[0191] By using any of the above-described estimation methods, it is possible to perform analysis when the plurality of semiconductor switching elements 6SW are arranged on the heat sink 6HS and each of the semiconductor switching elements 6SW is switched at appropriate timing.

[0192] According to at least one embodiment described above, a control device is a control device for a power conversion device including a semiconductor switching element that generates heat through power conversion, a heat sink for the semiconductor switching element, and a cooling mechanism for cooling the heat sink. The control device includes an element temperature estimating unit and a control unit. The element temperature estimating unit derives an estimated value for the temperature of the semiconductor switching element using either the drive amount of the semiconductor switching element or the temperature at a predetermined location within a predetermined range from the position of the semiconductor switching element. The control unit identifies an abnormal state of the cooling mechanism when the temperature difference between the estimated value for the temperature of the semiconductor switching element and the temperature at a predetermined location within the power conversion device exceeds a predetermined threshold temperature. The threshold temperature is determined to be lower than the upper limit of the allowable range for the temperature difference and higher than a predetermined reference temperature corresponding to the amount of heat generated by the semiconductor switching element.

[0193] In the power conversion device 1 of the embodiment described above, some or all of the functional units of the control device 10 may be implemented as software functional units, for example, by executing a program (computer program, software component) stored in a storage unit (memory, etc.) of the computer by a computer processor (hardware processor). Furthermore, some or all of the functional units of the control device 10 may be implemented as hardware, such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), or an FPGA (Field-Programmable Gate Array), or may be implemented as a combination of software functional units and hardware.

[0194] Several embodiments of the present invention have been described, but these embodiments are provided as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways and can be omitted, replaced, or modified in various ways without departing from the main purpose of the invention. For example, the structures of the various embodiments can be implemented in combination with each other or can be applied to components that have been omitted from the description. These embodiments or their variations are included within the scope or main purpose of the invention and are also included within the scope of the invention described in the claims and their equivalents.

[0195] Description of Reference Numerals

[0196] 1 ...power conversion device, 3 ...AC motor, 6 ...inverter, 6HS ...heat sink, 6SW ...semiconductor switching element, 8A, 8B ...temperature sensors; 10 ...control device; 105 ...element temperature estimating unit; 110 ...storage unit; 120 ...control unit.

Claims

1. A control device for a power conversion device, the power conversion device comprising a semiconductor switching element that generates heat by power conversion, a heat sink for the semiconductor switching element, and a cooling mechanism for cooling the heat sink. The control device includes a control unit configured to recognize an abnormal state of the cooling mechanism when a temperature difference between an estimated temperature value of the semiconductor switching element and a temperature at a predetermined position within the power conversion device exceeds a predetermined threshold temperature. The threshold temperature is determined to be lower than the upper limit temperature of the allowable range of the temperature difference and higher than a reference temperature that is predetermined in accordance with the heat generation amount of the semiconductor switching element.

2. The control device according to claim 1, comprising: An element temperature estimating unit derives a first estimated value of the temperature of the semiconductor switching element using a detected value of a temperature at a predetermined position within a predetermined range from the position of the semiconductor switching element.

3. The control device according to claim 2, The predetermined range is within a module including the semiconductor switching element, or within a range predetermined based on the surface of the heat sink.

4. The control device according to claim 3, The predetermined position includes any one of a first position of a first sensor disposed at a module including the semiconductor switching element and a second position of a second sensor disposed within a predetermined range with respect to the surface of the heat sink.

5. The control device according to any one of claims 2 to 4, The control unit deriving a second estimated value of the temperature of the semiconductor switching element using the drive amount of the semiconductor switching element, Either the first estimated value or the second estimated value is used to identify an abnormal state of the cooling mechanism.

6. The control device according to claim 5, The control unit The predetermined upper limit value for limiting the drive amount is changed based on whether the estimated value of the temperature of the semiconductor switching element reaches an upper limit temperature of an allowable range.

7. The control device according to claim 6, storing the relationship between the output mode of the operating power conversion device and the temperature rise of the semiconductor switching element in a storage unit, The control unit When an output pattern identical to or similar to the output pattern of the power conversion device stored in the storage unit occurs, a temperature increase of the semiconductor switching element in this case is compared with a temperature increase based on past data.

8. The control device according to claim 6, The threshold temperature is associated with initial data obtained by operating the semiconductor switching element in the power conversion device. The control unit Based on the initial data and the estimated value of the temperature of the semiconductor switching element, it is recognized that an abnormality has occurred in the state of the cooling mechanism.

9. The control device according to claim 6, The control device comprises: A second sensor is disposed within a predetermined range based on the surface of the radiator; and A third sensor is arranged at a predetermined position in the power conversion device. The element temperature estimating unit deriving a first estimated value of the temperature of the semiconductor switching element using the detection value of the second sensor, The control unit The abnormal state of the cooling mechanism is identified when the temperature difference between the estimated value of the temperature of the semiconductor switching element based on the detection value of the second sensor and the temperature of a specified position in the power conversion device based on the detection result of the third sensor exceeds a predetermined threshold temperature.

10. The control device according to claim 5, The predetermined upper limit value for limiting the drive amount is determined to be a value exceeding a rated output of the semiconductor switching element.

11. A control method for a power conversion device comprising a semiconductor switching element that generates heat by power conversion, a heat sink for the semiconductor switching element, and a cooling mechanism for cooling the heat sink. The control method includes a process of recognizing an abnormal state of the cooling mechanism when a temperature difference between an estimated temperature value of the semiconductor switching element and a temperature at a predetermined position within the power conversion device exceeds a predetermined threshold temperature. The threshold temperature is determined to be lower than the upper limit temperature of the allowable range of the temperature difference and higher than a reference temperature that is predetermined in accordance with the heat generation amount of the semiconductor switching element.

12. The control method according to claim 11, further comprising: A process of deriving a first estimated value of the temperature of the semiconductor switching element using a detected value of the temperature at a predetermined position within a predetermined range from the position of the semiconductor switching element.

13. The control method according to claim 12, The predetermined range is within a module including the semiconductor switching element, or within a range predetermined based on the surface of the heat sink.

14. The control method according to claim 13, The predetermined position includes any one of a first position of a first sensor disposed at a module including the semiconductor switching element and a second position of a second sensor disposed within a predetermined range with respect to the surface of the heat sink.

15. The control method according to any one of claims 12 to 14, deriving a second estimated value of the temperature of the semiconductor switching element using the drive amount of the semiconductor switching element, Either the first estimated value or the second estimated value is used to identify an abnormal state of the cooling mechanism.

16. The control method according to claim 15, The predetermined upper limit value of the drive amount is changed based on whether the estimated value of the temperature of the semiconductor switching element has reached an upper limit temperature of an allowable range.

17. The control method according to claim 16, storing the relationship between the output mode of the operating power conversion device and the temperature rise of the semiconductor switching element in a storage unit, When an output pattern identical to or similar to the output pattern of the power conversion device stored in the storage unit occurs, a temperature increase of the semiconductor switching element in this case is compared with a temperature increase based on past data.

18. The control method according to claim 16, The threshold temperature is associated with initial data obtained by operating the semiconductor switching element in the power conversion device. Based on the initial data and the estimated value of the temperature of the semiconductor switching element, it is recognized that an abnormality has occurred in the state of the cooling mechanism.

19. The control method according to claim 16, The power conversion device comprises: A second sensor is disposed within a predetermined range based on the surface of the radiator; and A third sensor is arranged at a predetermined position in the power conversion device. deriving a first estimated value of the temperature of the semiconductor switching element using the detection value of the second sensor, The abnormal state of the cooling mechanism is identified when the temperature difference between the estimated value of the temperature of the semiconductor switching element based on the detection value of the second sensor and the temperature of a specified position in the power conversion device based on the detection result of the third sensor exceeds a predetermined threshold temperature.

20. The control method according to claim 15, The predetermined upper limit value for limiting the drive amount is determined to be a value exceeding a rated output of the semiconductor switching element.

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