Power conversion device and abnormality determination method

Abstract

To provide a power conversion device capable of surely discriminating abnormality by simple processing.SOLUTION: Temperature detection units (32 and 52) discretely detect temperatures of predetermined portions (33 and 53) of a power conversion device (100), and an abnormality determination unit (72) determines presence or absence of an abnormality of the temperature detection unit (32 and 52) based on comparison between a temperature variation range (ΔT1) between different time points in temperature detection values (T1 and T2) and a temperature change threshold (Tth) set based on characteristics of the power conversion device (100).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power conversion device and an abnormality determination method. [Background technology]

[0002] Hybrid and electric vehicles are equipped with power conversion devices that control the vehicle drive motors. As is well known, these power conversion devices are composed of multiple semiconductor switching elements, through which large currents flow. In particular, in recent years, there has been a demand for even higher output from power conversion devices, and there is a tendency for even larger currents to flow through the semiconductor switching elements.

[0003] When a large current flows through a semiconductor switching element, the semiconductor switching element generates a large amount of heat, and in the worst case, the semiconductor switching element may be damaged. For this reason, conventionally, a temperature sensor or the like is used to monitor the internal temperature of a power conversion device in order to protect the semiconductor switching element and, ultimately, the power conversion device.

[0004] A typical protection measure for a power conversion device is to first suppress the output of the power conversion device when a temperature detection value detected by a temperature sensor or the like becomes high, and then shut down the power conversion device for protection if the temperature detection value does not decrease. However, even if the temperature detection value mistakenly becomes high due to an abnormality such as a temperature sensor failure, the power conversion device will still be shut down. Therefore, it is necessary to determine as much as possible whether the cause of the high temperature detection value is an abnormality in the temperature sensor or an abnormality in the power conversion device and take appropriate action.

[0005] For example, a conventional abnormality determination device for a vehicle drive circuit disclosed in Patent Document 1 is configured to include a change estimation means that estimates the difference between the temperature of an element included in the vehicle drive circuit and a temperature reference value as a temperature change estimated value based on the current flowing through the element, an element temperature detection means that detects the temperature of the element, a change measurement means that obtains the difference between the element's temperature detection value and the temperature reference value as a change measurement value, a measurement value deviation calculation means that obtains the difference between the change measurement value and the change estimated value as a measurement value deviation, and a determination means that determines whether the element is abnormal based on the change over time in the measurement value deviation.

[0006] Patent document 1 states that the abnormality determination device configured as described above can determine abnormalities in elements included in a vehicle drive circuit, or detect abnormal elements from multiple elements for a vehicle drive circuit, while distinguishing them from other abnormality factors. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-170211 Summary of the Invention [Problem to be solved by the invention]

[0008] As described above, the conventional abnormality determination device disclosed in Patent Document 1 requires the provision of dedicated hardware such as a change estimation means, a change measurement means, and a measurement value deviation calculation means, and even if these means are configured using a CPU (Central Processing Unit), there are problems such as an increased load on the CPU.

[0009] The present disclosure discloses a technique for solving the above-described problems, and aims to provide a power conversion device that realizes reliable abnormality detection through simple processing.

[0010] The present disclosure also discloses a technique for solving the above-mentioned problems, and aims to provide an abnormality determination method that reliably determines abnormalities using simple processing. [Means for solving the problem]

[0011] The power conversion device according to the present disclosure comprises: A power conversion device that performs power conversion between a DC voltage source and a load, a temperature detection unit that discretely detects the temperature of a predetermined portion of the power conversion device; an abnormality determination unit that determines whether or not an abnormality exists in the temperature detection unit based on a comparison between a temperature change width between different points in time in the temperature detection value detected by the temperature detection unit and a temperature change width threshold that is set based on characteristics of the power conversion device; The present invention is characterized by the following.

[0012] Further, the power conversion device according to the present disclosure includes: A power conversion device that performs power conversion between a DC voltage source and a load, a temperature detection unit that discretely detects the temperature of a predetermined portion of the power conversion device; an abnormality determination unit that determines that the temperature detection unit is abnormal when a temperature change width between different points in time in a temperature detection value detected by the temperature detection unit exceeds a temperature change width threshold set based on characteristics of the power conversion device, and that the power conversion device is abnormal when the temperature detection value exceeds a predetermined temperature threshold; The present invention is characterized by the following.

[0013] Furthermore, the power conversion device according to the present disclosure includes: A power conversion device that performs power conversion between a DC voltage source and a load, a first temperature detection unit that discretely detects the temperature of a first portion of the power conversion device; a second temperature detection unit that discretely detects the temperature of a second portion of the power conversion device; an abnormality determination unit that compares a difference between a first temperature detection value detected by the first temperature detection unit at a first time point and a second temperature detection value detected by the second temperature detection unit at a second time point with a temperature change width threshold that is set based on characteristics of the power conversion device, and determines whether or not an abnormality exists in the first temperature detection unit or the second temperature detection unit based on the comparison; The present invention is characterized by the following.

[0014] Further, the power conversion device according to the present disclosure includes: A power conversion device that performs power conversion between a DC voltage source and a load, a first temperature detection unit that discretely detects the temperature of a first portion of the power conversion device; a second temperature detection unit that discretely detects the temperature of a second portion of the power conversion device; an abnormality determination unit that determines that the first temperature detection unit or the second temperature detection unit is abnormal when a difference between a first temperature detection value detected by the first temperature detection unit at a first time point and a second temperature detection value detected by the second temperature detection unit at a second time point exceeds a temperature change width threshold set based on characteristics of the power conversion device, and that the power conversion device is abnormal when the first temperature detection value or the second temperature detection value exceeds a predetermined temperature threshold; The present invention is characterized by the following.

[0015] Furthermore, the abnormality determination method according to the present disclosure includes: 1. A method for determining whether or not an abnormality exists in a power conversion device that performs power conversion between a DC voltage source and a load, comprising: discretely detecting a temperature of a predetermined portion of the power conversion device using a temperature detection unit; determining whether or not an abnormality exists in the temperature detection unit based on a comparison between a temperature change value between different points in time of the temperature detection value detected by the temperature detection unit and a temperature change width threshold value set based on the characteristics of the power conversion device; It is characterized by:

[0016] Furthermore, the power conversion method according to the present disclosure includes: 1. A method for determining whether or not an abnormality exists in a power conversion device that performs power conversion between a DC voltage source and a load, comprising: discretely detecting a temperature of a first portion of the power conversion device using a first temperature detection unit; discretely detecting a temperature of a second portion of the power conversion device using a second temperature detection unit; a difference value between a first temperature detection value detected by the first temperature detection unit at a first time point and a second temperature detection value detected by the second temperature detection unit at a second time point is compared with a temperature change width threshold set based on characteristics of the power conversion device, thereby determining whether or not there is an abnormality in the first temperature detection unit or the second temperature detection unit; It is characterized by: [Effects of the Invention]

[0017] According to the power conversion device of the present disclosure, a power conversion device that can reliably determine an abnormality through simple processing can be obtained.

[0018] Furthermore, the abnormality determination method according to the present disclosure provides an abnormality determination method that realizes reliable abnormality determination with simple processing. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a functional block diagram showing a configuration of a power conversion device according to a first embodiment, a second embodiment, and a third embodiment. [Figure 2] 4 is an explanatory diagram illustrating the operation of an abnormality determination unit in the power conversion device according to the first embodiment. FIG. [Figure 3] 5 is a flowchart showing the operation of an abnormality determination unit in the power conversion device according to the first embodiment. [Figure 4] FIG. 3 is an explanatory diagram showing setting of operating conditions of the power conversion device according to the first embodiment. [Figure 5] 10 is a flowchart showing the operation of an abnormality determination unit in the power conversion device according to the second embodiment. [Figure 6] FIG. 10 is an explanatory diagram showing the setting of a temperature change width threshold in the power conversion device according to the second embodiment. [Figure 7] 11 is a flowchart showing the operation of an abnormality determination unit in the power conversion device according to the third embodiment. [Figure 8] FIG. 11 is an explanatory diagram illustrating the operation of an abnormality determination unit in the power conversion device according to the third embodiment. [Figure 9] 1 is a block diagram showing an example of a hardware configuration of an ECU constituting a control device in a power conversion device according to a first embodiment, a second embodiment, and a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Embodiment 1 A power conversion device and an abnormality determination method according to a first embodiment will be described below. Fig. 1 is a functional block diagram showing the configuration of power conversion devices according to the first, second, and third embodiments, which are the same as the power conversion devices according to the second and third embodiments described below. In Fig. 1, a power conversion device 100 mounted on a vehicle or the like is connected between a DC voltage source 1 and a load 2. The DC voltage source 1 is, for example, a battery mounted on the vehicle, and the load 2 is, for example, an AC motor that drives the vehicle.

[0021] The power conversion device 100 is composed of a converter 3, a smoothing capacitor 4 connected between a DC voltage source 1 and the converter 3, an inverter 5, a smoothing capacitor 6 connected between the converter 3 and the inverter 5, and a control device 7. The converter 3 includes a plurality of semiconductor switching elements 31, and by the switching operation of the semiconductor switching elements 31, converts the output of the DC voltage source 1 into a predetermined DC voltage and supplies it to the inverter 5. The inverter 5 includes a plurality of semiconductor switching elements 51, and by the switching operation of the semiconductor switching elements 51, converts the DC output of the converter 3 into AC power and supplies it to the load 2.

[0022] The semiconductor switching element 31 of the converter 3 and the semiconductor switching element 51 of the inverter 5 are configured, for example, by an IGBT (Insulated Gate Bipolar Transistor) with a freewheel diode connected in anti-parallel. Note that, instead of an IGBT, the semiconductor switching elements 31 and 51 may also be FETs (Field Effect Transistors) with a parasitic diode connected in anti-parallel, or may be ordinary bipolar transistors with a diode connected in anti-parallel.

[0023] The first temperature detection unit 32, which is configured using a thermistor or the like, is provided in a first portion 33 of the power conversion device 100. The first portion 33 is a portion where the semiconductor switching element 31 of the converter 3 is mounted. The first temperature detection unit 32 discretely detects the temperature of the semiconductor switching element 31, which is a temperature protection target, via the first portion 33 as described below, and inputs the detected first temperature detection value T1 to the control device 7.

[0024] The second temperature detection unit 52, which is configured using a thermistor or the like, is provided in a second portion 53 of the power conversion device 100. The second portion 53 is a portion where the semiconductor switching element 51 of the inverter 5 is mounted. The second temperature detection unit 52 discretely detects the temperature of the semiconductor switching element 51, which is a temperature protection target, via the second portion 53 as described below, and inputs the detected second temperature detection value T2 to the control device 7.

[0025] At least one of the first temperature detection unit 32 and the second temperature detection unit 52 may be configured to detect the temperature of a reactor, a smoothing capacitor, or other electronic components provided in the power conversion device 100, or the internal atmosphere of the power conversion device 100, or may be configured to detect the temperature of something other than a semiconductor switching element.

[0026] The control device 7 includes a gate control unit 71 and an abnormality determination unit 72. The gate control unit 71 generates a first gate signal G1 and provides the generated first gate signal G1 to the gates of the plurality of semiconductor switching elements 31 of the converter 3 to control the on / off of these semiconductor switching elements 31. The gate control unit 71 also generates a second gate signal G2 and provides the generated second gate signal G2 to the gates of the plurality of semiconductor switching elements 51 of the inverter 5 to control the on / off of these semiconductor switching elements 51.

[0027] As will be described later, when the first temperature detection value T1 becomes an abnormal value, the abnormality determination unit 72 determines whether the abnormality is in the power conversion device 100 or the first temperature detection unit 32. Furthermore, when the second temperature detection value T2 becomes an abnormal value, the abnormality determination unit 72 determines whether the abnormality is in the power conversion device 100 or the second temperature detection unit 52.

[0028] Furthermore, when the internal temperature of the power conversion device 100 rises and exceeds a predetermined temperature threshold, the abnormality judgment unit 72 turns off the semiconductor switching elements 31 and 51 to protect the power conversion device 100.

[0029] The control device 7 is configured with an ECU (Electronic Control Unit) as a part including at least the abnormality determination unit 72. Fig. 9 is a block diagram showing an example of the hardware configuration of the ECU constituting the control device in the power conversion device according to the first embodiment and the second and third embodiments described later.

[0030] As shown in FIG. 9, the ECU 112, which constitutes at least a part of the control device 7, is composed of a processor 1001 and a storage device 1002. Although not shown, the storage device 1002 includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory. Alternatively, an auxiliary storage device such as a hard disk may be used instead of the flash memory. The processor 1001 executes a program input from the storage device 1002. In this case, the program is input to the processor 1001 from the auxiliary storage device via the volatile storage device. The processor 1001 may output data such as calculation results to the volatile storage device of the storage device 1002, or may store the data in the auxiliary storage device via the volatile storage device.

[0031] Next, the operation of the power conversion device 100 according to the first embodiment will be described. In Fig. 1, a plurality of semiconductor switching elements 31 constituting the converter 3 are controlled to be turned on and off in response to a first gate signal G1 from a gate control unit 71 of a control device 7. As a result, the converter 3 converts the DC voltage supplied from the DC voltage source 1 via a smoothing capacitor 4 into a DC voltage higher than that supplied, and supplies the converted DC voltage to the inverter 5 via a smoothing capacitor 6.

[0032] The plurality of semiconductor switching elements 51 constituting the inverter 5 are controlled to be turned on and off in response to a second gate signal G2 from a gate control unit 71 of the control device 7. As a result, the inverter 5 converts the DC power supplied from the converter 3 via the smoothing capacitor 6 into AC power and supplies it to an AC motor serving as the load 2. The AC motor serving as the load 2 is, for example, a three-phase synchronous motor, which is energized by the AC power supplied from the inverter 5 to rotate and drive the vehicle.

[0033] When the converter 3 and the inverter 5 are operating, the first temperature detection unit 32 detects the temperature of the first portion 33 in the converter 3 where the semiconductor switching element 31 is mounted at predetermined time intervals Ts [ms], for example, 10 [ms], and inputs the detected first temperature detection value T1 [°C] to the abnormality determination unit 72 of the control device 7. The first temperature detection value T1 substantially corresponds to the temperature of the semiconductor switching element 31 in the converter 3.

[0034] Similarly, the second temperature detection unit 52 detects the temperature of the second portion 53 in the inverter 5 where the semiconductor switching element 51 is mounted at predetermined time intervals Ts [ms], for example, 10 [ms], and inputs the detected second temperature detection value T2 [°C] to the abnormality determination unit 72 of the control device 7. The second temperature detection value T2 substantially corresponds to the temperature of the semiconductor switching element 51 in the inverter 5.

[0035] FIG. 2 is an explanatory diagram illustrating the operation of the abnormality determination unit in the power conversion device according to the first embodiment, showing an example of a change in the first temperature detection value T1 when the first temperature detection unit 32 is normal and when it is abnormal. The vertical axis of FIG. 2 represents the first temperature detection value T1 [°C], and the horizontal axis represents time [ms]. The change in the first temperature detection value T1 shown in FIG. 2 is a curve that schematically shows the change in temperature that is detected discretely. Note that in the following description, the units of temperature and time may be omitted.

[0036] The change in the second detected temperature value T2 when the second temperature detector 52 is normal and when it is abnormal is similar to that of the first detected temperature value, and therefore a description thereof will be omitted here.

[0037] 2, a first temperature detection value T1 is detected at predetermined time intervals Ts, for example, 10 ms, by the first temperature detection unit 32. Normally, the temperature inside the power conversion device 100 rises based on the thermal time constant of the power conversion device 100, and if the first temperature detection unit 32 is normal, the first temperature detection value T1 changes over time as shown by the normal temperature change characteristic X1.

[0038] On the other hand, if an abnormality occurs in the first temperature detection unit 32, such as a sticking of the internal circuit of the first temperature detection unit 32, the first temperature detection value T1 will change, for example, as shown by the temperature change characteristic Xa1, even if the power conversion device 100 is normal. Here, the temperature change characteristic Xa1 indicates the case where the above-mentioned abnormality occurs in the first temperature detection unit 32 immediately after time t(n-1).

[0039] As shown in the temperature change characteristic Xa1 of the first temperature detection unit 32 during an abnormality, at time t(n-1) immediately before the occurrence of an abnormality, a first temperature detection value T1(n-1) that is substantially the same as the value of the temperature change characteristic X1 during normal operation is input to the abnormality determination unit 72. However, at time tn after a time interval Ts, a first temperature detection value T1n that has risen sharply is input to the abnormality determination unit 72. The temperature change width ΔT1, which is the difference between the first temperature detection value T1n and the first temperature detection value T1(n-1), exceeds the temperature change width threshold Tth that is set based on the characteristics of the power conversion device 100.

[0040] Here, the temperature change range threshold Tth is the temperature change range obtained from the temperature change characteristic X1 formed by the power conversion device 100 during normal operation based on the thermal time constant of the power conversion device 100. For example, as shown in Figure 2, the temperature change range of the part with the highest temperature increase rate is set as the temperature change range threshold Tth.

[0041] The greater the current flowing through the power conversion device 100, the greater the temperature rise inside the power conversion device 100. Therefore, to prevent the abnormality determination unit 72 from erroneously determining an abnormality in the first temperature detection unit 32 and the second temperature detection unit 52, it is desirable to set the temperature change range threshold Tth based on the temperature rise range under conditions that result in the greatest temperature rise.

[0042] The temperature change width ΔT1 of the first temperature detection value T1 when the first temperature detection unit 32 is abnormal corresponds to the difference between the first temperature detection value T1n at time tn, which is the current temperature detection time, and the first temperature detection value T1(n-1) at time t(n-1), which is the previous temperature detection time, and is the temperature change width of the first temperature detection value T1 over a predetermined time interval Ts. Note that the temperature change width ΔT1 may be a temperature change width over a time interval spanning multiple time intervals Ts.

[0043] 3 is a flowchart showing the operation of the abnormality determination unit 72 in the power conversion device according to the first embodiment, and shows the operation of the abnormality determination unit 72 to determine whether or not there is an abnormality in the first temperature detection unit 32. The determination process by the abnormality determination unit 72 shown in FIG. 3 is performed at each time interval Ts at which the first temperature detection value T1 is input to the abnormality determination unit 72.

[0044] In FIG. 3, in step S101, the abnormality determination unit 72 calculates the temperature change width ΔT1 of the first temperature detection value T1 from the first temperature detection value T1n input this time and the first temperature detection value T1(n-1) input last time, using [ΔT1=|T1n-T1(n-1)|].

[0045] Next, in step S102, the abnormality determination unit 72 compares the temperature change width ΔT1 (=[|T1n-T1(n-1)|]) of the first temperature detection value T1 calculated in step S101 with the aforementioned temperature change width threshold Tth, and determines whether the temperature change width ΔT1 of the first temperature detection value T1 exceeds the temperature change width threshold Tth.

[0046] If the result of the determination in step S102 is [|T1n-T1(n-1)|]>Tth (YES), the process proceeds to step S103, and if not (NO), the process proceeds to step S104. When proceeding to step S103, the process determines that the first temperature detection unit 32 is abnormal and ends the abnormality determination process, and when proceeding to step S104, the process determines that the first temperature detection unit 32 is normal and ends the abnormality determination process.

[0047] The determination operation by the abnormality determination unit 72 for the second temperature detection unit 52 is substantially the same as the operation according to the flowchart of FIG.

[0048] When the first temperature detection value T1 or the second temperature detection value T2 rises instantaneously as described above and the abnormality determination unit 72 determines that the first temperature detection unit 32 or the second temperature detection unit 52 is abnormal, there is a possibility that the first temperature detection value T1 or the second temperature detection value T2 may simultaneously exceed the temperature threshold value Tth1 [°C] shown in FIG. 3, and the power conversion device 100 may be determined to be abnormal.

[0049] 3, the temperature threshold Tth1 is set to be greater than the maximum temperature value that can be assumed by the temperature change characteristic X1 of the first temperature detection value T1 detected by the power conversion device 100 in a normal state. The temperature threshold (not shown) for detecting an abnormality in the power conversion device 100 using the second temperature detection value T2 is also the same as the temperature threshold Tth1.

[0050] When the first temperature detection value T1 exceeds the temperature threshold value Tth1, the abnormality determination unit 72 determines that an abnormality has occurred in the power conversion device 100. When the abnormality determination unit 72 determines that an abnormality has occurred in the power conversion device 100, the control device 7 operates to turn off the semiconductor switching elements 31 and 51 in order to protect the power conversion device 100 and the semiconductor switching elements 31 and 51. The same applies when the second temperature detection value T2 exceeds a temperature threshold value corresponding to the temperature threshold value Tth1.

[0051] However, if the first temperature detection unit 32 or the second temperature detection unit 52 is abnormal but the power conversion device 100 is normal, there is no need to turn off the semiconductor switching elements 31, 51 to stop the power conversion device 100. Therefore, if the abnormality determination unit 72 determines that the first temperature detection unit 32 or the second temperature detection unit 52 is abnormal but the power conversion device 100 is normal, the protection function that stops the power conversion device may be disabled, and the operation of the power conversion device 100 may be continued as is.

[0052] Furthermore, if the abnormality determination unit 72 determines that the first temperature detection unit 32 or the second temperature detection unit 52 is abnormal but the power conversion device 100 is normal, the operating conditions of the power conversion device 100 may be set according to the first temperature detection value T1 or the second temperature detection value T2 immediately before the abnormality determination unit 72 determines that the first temperature detection unit 32 or the second temperature detection unit 52 is abnormal, as will be explained next in FIG. 4.

[0053] 4 is an explanatory diagram showing the setting of the operating conditions of the power conversion device according to the first embodiment, and is an explanatory diagram showing a case where the operating conditions of the power conversion device 100 are set in accordance with the first temperature detection value T1 or the second temperature detection value T2 immediately before it is determined that the first temperature detection unit 32 or the second temperature detection unit 52 is abnormal. In FIG. 4, the vertical axis represents temperature [°C] and the horizontal axis represents time [msc].

[0054] 4, if the first temperature detection value T1 or the second temperature detection value T2 immediately before it is determined that the first temperature detection unit 32 or the second temperature detection unit 52 is abnormal is less than Ta, the operating conditions of the power conversion device 100 are set to "low-level suppression operation," if it is equal to or greater than Ta but less than Tb, the operating conditions of the power conversion device 100 are set to "medium-level suppression operation," and if it is equal to or greater than Tb but less than Tc, the operating conditions of the power conversion device 100 are set to "high-level suppression operation," and operation of the power conversion device 100 is continued, where Tc>Tb>Ta.

[0055] The suppression operation of the power conversion device 100 is, for example, to reduce the on-duty of the semiconductor switching elements 31, 51 compared to the on-duty during normal operation, and when the on-duty is reduced to a small extent, it is a "low-level suppression operation," when the on-duty is reduced to a medium extent, it is a "medium-level suppression operation," and when the on-duty is reduced to a large extent, it is a "high-level suppression operation." These on-duty values ​​may be set as appropriate.

[0056] The above-described abnormality judgment operation in the power conversion device according to embodiment 1 includes an abnormality judgment method for judging whether or not there is an abnormality in a power conversion device that performs power conversion between a DC voltage source and a load, in which the temperature of a predetermined portion of the power conversion device is discretely detected using a temperature detection unit, and the presence or absence of an abnormality in the temperature detection unit is judged based on a comparison between the temperature change range between different points in time of the temperature detection value detected by the temperature detection unit and a temperature change range threshold value set based on the characteristics of the power conversion device.

[0057] As described above, according to the power conversion device and the abnormality determination method of embodiment 1, it is possible to determine whether there is an abnormality in the temperature detection unit and whether the temperature inside the power conversion device is actually high, using only simple processing, without adding any dedicated hardware, and to prevent the power conversion device from being stopped unnecessarily.

[0058] Embodiment 2 Next, a power conversion device and an abnormality determination method according to embodiment 2 will be described. Fig. 1 is a functional block diagram showing the configuration of the power conversion devices according to embodiment 1, embodiment 2, and embodiment 3, which is the same as the power conversion device according to embodiment 1 described above and embodiment 3 described below. The power conversion device 100 according to embodiment 2 has the same abnormality detection logic as the functional block diagram of the power conversion device 100 according to embodiment 1, but the processing flow for abnormality detection is different from that of the power conversion device according to embodiment 1.

[0059] 5 is a flowchart showing the operation of the abnormality determination unit in the power conversion device according to the second embodiment, and shows the operation of the abnormality determination unit 72 to determine whether or not there is an abnormality in the first temperature detection unit 32. The determination process by the abnormality determination unit 72 shown in FIG. 5 is performed at each time interval Ts at which the first temperature detection value T1 is input to the abnormality determination unit 72.

[0060] 5, in step S201, as a preliminary step to the subsequent abnormality determination process, the abnormality determination unit 72 performs a process of setting a temperature change width threshold Tth in accordance with the current value of the power conversion device 100. The current value of the power conversion device 100 is detected, for example, by a current sensor (not shown) that detects the current supplied from the power conversion device 100 to the load 2. The abnormality determination unit 72 sets the temperature change width threshold Tth in accordance with the detected current value.

[0061] Figure 6 is an explanatory diagram showing the calculation of the temperature change range threshold in the power conversion device according to embodiment 2, where the vertical axis represents the temperature change range threshold Tth [°C] of the power conversion device 100 and the horizontal axis represents the current value [A] of the power conversion device 100.

[0062] The larger the current value flowing through the power conversion device 100, the greater the temperature rise inside the power conversion device 100. Therefore, if the current value flowing through the power conversion device 100 is small, the temperature change range threshold Tth is set relatively small, and the larger the current value flowing through the power conversion device 100, the larger the temperature change range threshold Tth is set.

[0063] 6 increases quadratically as the current value of the power conversion device 100 increases, as indicated by curve Y. For example, if the current value of the power conversion device 100 is I_0 [A], the temperature change range threshold is calculated as Tth_0. The temperature change range threshold Tth is calculated based on the current value of the power conversion device 100 at each abnormality determination process performed at time intervals Ts.

[0064] Next, in step S202 shown in FIG. 5, the abnormality determination unit 72 calculates the temperature change width ΔT1 of the first temperature detection value T1 from the first temperature detection value T1n input this time and the first temperature detection value T1(n-1) input last time, using [ΔT1=|T1n-T1(n-1)|], and proceeds to step S203.

[0065] In step S203, the abnormality determination unit 72 compares the temperature change width ΔT1 (=[|T1n-T1(n-1)|]) of the first temperature detection value T1 calculated in step S202 with the temperature change width threshold Tth calculated in step S201, and determines whether the temperature change width ΔT1 of the first temperature detection value T1 exceeds the temperature change width threshold Tth.

[0066] If the result of the determination in step S203 is [|T1n-T1(n-1)|]>Tth (YES), the process proceeds to step S204, and if not (NO), the process proceeds to step S205. When proceeding to step S204, the first temperature detection unit 32 is determined to be abnormal and the abnormality determination process is terminated, and when proceeding to step S205, the first temperature detection unit 32 is determined to be normal and the abnormality determination process is terminated.

[0067] As described above, by calculating and setting the temperature change range threshold Tth according to the current value of the power conversion device 100, it is possible to expand the range in which abnormalities in the first temperature detection unit 32 and the second temperature detection unit 52 can be detected, compared to when the temperature change range threshold Tth is a fixed value.

[0068] Other operations are the same as those of the power conversion device according to the first embodiment.

[0069] The above-described operation of the abnormality determination in the power conversion device according to the second embodiment includes an abnormality determination method for determining whether or not an abnormality exists in a power conversion device that performs power conversion between a DC voltage source and a load, in which the temperature of a predetermined portion of the power conversion device is discretely detected by a temperature detection unit, and the presence or absence of an abnormality in the temperature detection unit is determined based on a comparison between a temperature change width between different points in time of the temperature detection value detected by the temperature detection unit and a temperature change width threshold value set based on the characteristics of the power conversion device. Furthermore, the abnormality determination method includes a step of calculating and setting a temperature change width threshold value Tth according to the current value of the power conversion device 100 as a preliminary step of the abnormality determination process.

[0070] As described above, the power conversion device and the abnormality determination method according to the second embodiment can achieve the same effects as the power conversion device according to the first embodiment. Furthermore, simply by monitoring the value of the current flowing through the power conversion device, it becomes possible to set a more appropriate temperature change width threshold, and it becomes possible to expand the range in which abnormalities in the temperature detection unit can be detected.

[0071] Embodiment 3 Next, a power conversion device and an abnormality determination method according to embodiment 3 will be described. Fig. 1 is a functional block diagram showing the configuration of the power conversion devices according to embodiments 1, 2, and 3, which is the same as the power conversion devices according to the above-mentioned embodiments 1 and 2. A power conversion device 100 according to embodiment 3 has the same functional block diagram as the power conversion device 100 according to embodiments 1 and 2, but the processing logic and processing flow for abnormality detection differ from those of the power conversion devices according to embodiments 1 and 2.

[0072] In embodiment 3, if the difference between the current first temperature detection value T1n by the first temperature detection unit 32 and the previous second temperature detection value T2(n-1) by the second temperature detection unit 52 having a thermal time constant equivalent to that of the first temperature detection unit 32 exceeds the temperature change width threshold Tth, it is determined that there is some abnormality in the first temperature detection unit 32 or the second temperature detection unit 52.

[0073] 7 is a flowchart showing the operation of the abnormality determination unit in the power conversion device according to the third embodiment, and shows the operation of the abnormality determination unit 72 to determine whether or not there is an abnormality in the first temperature detection unit 32. The determination process by the abnormality determination unit 72 shown in FIG. 3 is performed at each time interval Ts at which the first temperature detection value T1 is input to the abnormality determination unit 72.

[0074] In FIG. 7, in step S301, the abnormality determination unit 72 calculates the temperature change width ΔT12 from the first temperature detection value T1n input this time and the second temperature detection value T2(n-1) input last time, using [ΔT12=|T1n-T2(n-1)|].

[0075] Here, we will explain the abnormality determination logic in the power conversion device and the abnormality determination method according to embodiment 3. Fig. 8 is an explanatory diagram explaining the operation of the abnormality determination unit in the power conversion device according to embodiment 3, and shows an example of changes in the first temperature detection value T1 and the second temperature detection value when the first temperature detection unit 32 and the second temperature detection unit 52 are normal and when they are abnormal.

[0076] The vertical axis of Fig. 8 represents the first detected temperature value T1 [°C] and the second detected temperature value T2 [°C], and the horizontal axis represents time [ms]. The changes in the first detected temperature value T1 and the second detected temperature value T2 shown in Fig. 8 are shown as curves that schematically represent the changes in temperature that are detected discretely. Note that in the following explanation, the units of temperature and time may be omitted.

[0077] 8, the first temperature detection value T1 is detected at predetermined time intervals Ts, for example, 10 ms, by the first temperature detection unit 32. Normally, the temperature inside the power conversion device 100 rises based on the thermal time constant of the power conversion device 100, and if the first temperature detection unit 32 is normal, the first temperature detection value T1 changes over time as shown by the normal temperature change characteristic X1.

[0078] The second temperature detection value T2 is detected at predetermined time intervals Ts, for example, 10 ms, by the second temperature detection unit 52. Normally, the temperature inside the power conversion device 100 rises based on the thermal time constant of the power conversion device 100, and if the second temperature detection unit 52 is normal, the second temperature detection value T2 changes over time as shown by the normal temperature change characteristic X2.

[0079] On the other hand, if an abnormality occurs in the first temperature detection unit 32, such as a sticking of the internal circuit of the first temperature detection unit 32, the first temperature detection value T1 will change, for example, as shown by the temperature change characteristic Xa1, even if the power conversion device 100 is normal. Here, the temperature change characteristic Xa1 indicates the case where the above-mentioned abnormality occurs in the first temperature detection unit 32 immediately after time t(n-1).

[0080] As shown in the temperature change characteristic Xa1 of the first temperature detection unit 32 during an abnormality, at time t(n-1) immediately before the occurrence of the abnormality, a first temperature detection value T1(n-1) that is substantially identical to the value in the temperature change characteristic X1 during normal times is input to the abnormality judgment unit 72, but at time tn after a time interval Ts, a first temperature detection value T1n that has risen sharply is input to the abnormality judgment unit 72.

[0081] On the other hand, the second temperature detection unit 52 is normal, and as shown in the temperature change characteristic X2, there is no sudden temperature change between the second temperature detection value at the current time tn and the second temperature detection value T2(n-1) at the previous time t(n-1).

[0082] The temperature change width ΔT12, which is the difference between the current first temperature detection value T1n and the previous second temperature detection value T2(n−1), exceeds the temperature change width threshold Tth set based on the characteristics of the power conversion device 100. Here, the temperature change width threshold Tth is the temperature change width obtained from the temperature change characteristic X1 of the first temperature detection value T1 formed based on the thermal time constant of the power conversion device 100 when the power conversion device 100 is operating normally, or the temperature change characteristic X2 of the second temperature detection value T2 formed based on the thermal time constant of the power conversion device 100. For example, as shown in FIG. 8, the temperature change width of the part with the highest temperature increase rate is set as the temperature change width threshold Tth.

[0083] The temperature change width threshold Tth is set to be larger than the difference between the first temperature detection value T1 and the second temperature detection value T2, which is based on the variation in temperature characteristics between the first temperature detection unit 32 and the second temperature detection unit 52. Note that the temperature change width threshold Tth may be set to a different value depending on the operating state of the power conversion device, as in the second embodiment described above.

[0084] The greater the current flowing through the power conversion device 100, the greater the temperature rise inside the power conversion device 100. Therefore, to prevent the abnormality determination unit 72 from erroneously determining an abnormality in the first temperature detection unit 32 and the second temperature detection unit 52, it is desirable to set the temperature change range threshold Tth based on the temperature rise range under conditions that result in the greatest temperature rise.

[0085] The temperature change width ΔT12 of the first temperature detection value T1 when the first temperature detection unit 32 is abnormal corresponds to the difference between the first temperature detection value T1n at time tn, which is the current temperature detection time, and the second temperature detection value T2(n-1) at time t(n-1), which is the previous temperature detection time, and is the temperature change width over a predetermined time interval Ts. Note that the temperature change width ΔT12 may be the temperature change width over a time interval spanning multiple time intervals Ts.

[0086] In FIG. 7 mentioned above, when the process proceeds from step S301 to step S302, the abnormality determination unit 72 compares the temperature change range ΔT12 (=[|T1n-T2(n-1)|]) calculated in step S301 with the temperature change range threshold Tth mentioned above, and determines whether the temperature change range ΔT12 exceeds the temperature change range threshold Tth.

[0087] If the result of the determination in step S302 is [|T1n-T2(n-1)|]>Tth (YES), the process proceeds to step S303, and if not (NO), the process proceeds to step S304. When proceeding to step S303, the process determines that the first temperature detection unit 32 is abnormal and ends the abnormality determination process, and when proceeding to step S304, the process determines that the first temperature detection unit 32 is normal and ends the abnormality determination process.

[0088] The above has explained the abnormality determination operation when an abnormality occurs in the first temperature detection unit 32, but even if an abnormality occurs in the second temperature detection unit 52, the presence or absence of an abnormality in the second temperature detection unit 52 can be determined using the same logic as above.

[0089] When the first temperature detection value T1 or the second temperature detection value T2 rises instantaneously as described above and the abnormality determination unit 72 determines that the first temperature detection unit 32 or the second temperature detection unit 52 is abnormal, there is a possibility that the first temperature detection value T1 or the second temperature detection value T2 may simultaneously exceed the temperature threshold value Tth1 [°C] shown in FIG. 8, and the power conversion device 100 may be determined to be abnormal.

[0090] Here, the temperature threshold value Tth1 is a temperature threshold value for determining whether or not the power conversion device 100 is abnormal, and as shown in FIG. 8, is set to be greater than the maximum temperature value that can be taken by the temperature change characteristic X1 of the first temperature detection value T1 and the temperature change characteristic X2 of the second temperature detection value T2 detected by the power conversion device 100 under normal conditions.

[0091] The above-mentioned abnormality judgment operation in the power conversion device according to embodiment 3 includes an abnormality judgment method for judging whether or not there is an abnormality in a power conversion device that performs power conversion between a DC voltage source and a load, in which the temperature of a first portion of the power conversion device is discretely detected using a first temperature detection unit, the temperature of a second portion of the power conversion device is discretely detected using a second temperature detection unit, and the difference value between the first temperature detection value detected by the first temperature detection unit at a first point in time and the second temperature detection value detected by the second temperature detection unit at a second point in time is compared with a temperature change width threshold value set based on the characteristics of the power conversion device, thereby judging whether or not there is an abnormality in the first temperature detection unit or the second temperature detection unit.

[0092] As described above, the power conversion device and abnormality determination method according to embodiment 3 can achieve the same effects as those of the power conversion device according to embodiment 1, and further, by simply changing the temperature detection value to be compared from the temperature detection value according to embodiment 1, it is possible to expand the range in which it is possible to determine whether or not there is an abnormality in the temperature detection unit.

[0093] Although exemplary embodiments are described in this disclosure, the various features, aspects, and functions described in these embodiments are not limited to the application of a particular embodiment, but can be applied to the embodiments alone or in various combinations. Therefore, countless modifications not illustrated are anticipated within the scope of the technology disclosed in this application. For example, this includes cases where at least one component is modified, added, or omitted, and even cases where at least one component is extracted and combined with components of another embodiment.

[0094] Next, aspects of the power conversion device and the abnormality determination method disclosed in the present application will be described below as supplementary notes. (Appendix 1) A power conversion device that performs power conversion between a DC voltage source and a load, a temperature detection unit that discretely detects the temperature of a predetermined portion of the power conversion device; an abnormality determination unit that determines whether or not an abnormality exists in the temperature detection unit based on a comparison between a temperature change width between different points in time in the temperature detection value detected by the temperature detection unit and a temperature change width threshold that is set based on characteristics of the power conversion device; A power conversion device comprising: (Appendix 2) The temperature change width of the temperature detection value is a difference value between the current temperature detection value and the previous temperature detection value. 2. The power conversion device according to claim 1, (Appendix 3) the temperature change width threshold is set to be larger than a temperature change width based on a thermal time constant of the power conversion device. 3. The power conversion device according to claim 1 or 2. (Appendix 4) the power conversion is performed by a switching operation of a semiconductor switching element mounted in a power conversion device, the portion is a portion on which the semiconductor switching element is mounted, 4. The power conversion device according to claim 1, wherein: (Appendix 5) the temperature change width threshold is set to a different value depending on the operating state of the power conversion device. 5. The power conversion device according to claim 1, wherein: (Appendix 6) A power conversion device that performs power conversion between a DC voltage source and a load, a temperature detection unit that discretely detects the temperature of a predetermined portion of the power conversion device; an abnormality determination unit that determines that the temperature detection unit is abnormal when a temperature change width between different points in time in a temperature detection value detected by the temperature detection unit exceeds a temperature change width threshold set based on characteristics of the power conversion device, and that the power conversion device is abnormal when the temperature detection value exceeds a predetermined temperature threshold; A power conversion device comprising: (Appendix 7) When the abnormality determination unit determines that the temperature detection unit is abnormal, and controlling an operating condition of the power conversion device in accordance with the temperature detection value immediately before the determination. 7. The power conversion device according to claim 1, wherein: (Appendix 8) A power conversion device that performs power conversion between a DC voltage source and a load, a first temperature detection unit that discretely detects the temperature of a first portion of the power conversion device; a second temperature detection unit that discretely detects the temperature of a second portion of the power conversion device; an abnormality determination unit that compares a difference between a first temperature detection value detected by the first temperature detection unit at a first time point and a second temperature detection value detected by the second temperature detection unit at a second time point with a temperature change width threshold that is set based on characteristics of the power conversion device, and determines whether or not an abnormality exists in the first temperature detection unit or the second temperature detection unit based on the comparison; A power conversion device comprising: (Appendix 9) the temperature change width threshold is set to a value greater than a difference between the first temperature detection value and the second temperature detection value due to a variation in characteristics between the first temperature detection unit and the second temperature detection unit. 9. The power conversion device according to claim 8, (Appendix 10) the power conversion is performed by a switching operation of a semiconductor switching element mounted in a power conversion device, the first portion and the second portion are portions on which the semiconductor switching elements are mounted, respectively. 10. The power conversion device according to claim 8 or 9, (Appendix 11) A power conversion device that performs power conversion between a DC voltage source and a load, a first temperature detection unit that discretely detects the temperature of a first portion of the power conversion device; a second temperature detection unit that discretely detects the temperature of a second portion of the power conversion device; an abnormality determination unit that determines that the first temperature detection unit or the second temperature detection unit is abnormal when a difference between a first temperature detection value detected by the first temperature detection unit at a first time point and a second temperature detection value detected by the second temperature detection unit at a second time point exceeds a temperature change width threshold set based on characteristics of the power conversion device, and that the power conversion device is abnormal when the first temperature detection value or the second temperature detection value exceeds a predetermined temperature threshold; A power conversion device comprising: (Appendix 12) the first time point is a time point at which the temperature is detected by the first temperature detection unit this time, the second time point is the time point at which the temperature was detected by the second temperature detection unit the previous time; The difference value between the first temperature detection value and the second temperature detection value is the difference value between the current first temperature detection value and the previous second temperature detection value. 12. The power conversion device according to claim 11, (Appendix 13) When the abnormality determination unit determines that the first temperature detection unit or the second temperature detection unit is abnormal, and controlling an operating condition of the power conversion device in accordance with at least one of the first temperature detection value and the second temperature detection value immediately before the determination. 13. The power conversion device according to claim 11 or 12. (Appendix 14) the temperature change width threshold is set to a different value depending on the operating state of the power conversion device. 14. The power conversion device according to any one of claims 11 to 13, (Appendix 15) the temperature change width threshold is set to a value greater than a difference between the first temperature detection value and the second temperature detection value due to a variation in characteristics between the first temperature detection unit and the second temperature detection unit. 15. The power conversion device according to any one of claims 11 to 14, (Appendix 16) When it is determined that the first temperature detection unit or the second temperature detection unit is abnormal, and controlling an operating condition of the power conversion device in accordance with at least one of the first temperature detection value and the second temperature detection value immediately before the determination. 16. The power conversion device according to any one of appendices 11 to 15, (Appendix 17) 1. A method for determining whether or not an abnormality exists in a power conversion device that performs power conversion between a DC voltage source and a load, comprising: discretely detecting a temperature of a predetermined portion of the power conversion device using a temperature detection unit; determining whether or not an abnormality exists in the temperature detection unit based on a comparison between a temperature change width between different points in time of the temperature detection value detected by the temperature detection unit and a temperature change width threshold value set based on the characteristics of the power conversion device; An abnormality determination method comprising: (Appendix 18) 1. A method for determining whether or not an abnormality exists in a power conversion device that performs power conversion between a DC voltage source and a load, comprising: discretely detecting a temperature of a first portion of the power conversion device using a first temperature detection unit; discretely detecting a temperature of a second portion of the power conversion device using a second temperature detection unit; a difference value between a first temperature detection value detected by the first temperature detection unit at a first time point and a second temperature detection value detected by the second temperature detection unit at a second time point is compared with a temperature change width threshold set based on characteristics of the power conversion device, thereby determining whether or not there is an abnormality in the first temperature detection unit or the second temperature detection unit; An abnormality determination method comprising: (Appendix 19) the temperature change width threshold is set to a different value depending on the operating state of the power conversion device. 19. The abnormality determination method according to claim 17 or 18, [Explanation of symbols]

[0095] 100 power conversion device, 1 DC voltage source, 2 load, 3 converter, 31, 51 semiconductor switching element, 32 first temperature detection unit. 33 first part, 4, 6 smoothing capacitor, 5 inverter, 52 second temperature detection unit, 53 second portion, 7 control device, 71 gate control unit, 72 abnormality determination unit, T1 first temperature detection value, T2 second temperature detection value, Ts time interval, Tth temperature change threshold, Tth1 temperature threshold, ΔT1, ΔT12 temperature change range, X1, X2, Xa1 temperature change characteristics, G1: First gate signal, G2: Second gate signal

Claims

1. A power conversion device that performs power conversion between a DC voltage source and a load, a temperature detection unit that discretely detects the temperature of a predetermined portion of the power conversion device; an abnormality determination unit that determines whether or not an abnormality exists in the temperature detection unit based on a comparison between a temperature change width between different points in time in the temperature detection value detected by the temperature detection unit and a temperature change width threshold that is set based on characteristics of the power conversion device; A power conversion device comprising:

2. The temperature change width of the temperature detection value is a difference value between the current temperature detection value and the previous temperature detection value.

2. The power conversion device according to claim 1.

3. the temperature change width threshold is set to be larger than a temperature change width based on a thermal time constant of the power conversion device.

3. The power conversion device according to claim 1 or 2.

4. the power conversion is performed by a switching operation of a semiconductor switching element mounted in a power conversion device, the portion is a portion on which the semiconductor switching element is mounted, 3. The power conversion device according to claim 1 or 2.

5. the temperature change width threshold is set to a different value depending on the operating state of the power conversion device.

3. The power conversion device according to claim 1 or 2.

6. A power conversion device that performs power conversion between a DC voltage source and a load, a temperature detection unit that discretely detects the temperature of a predetermined portion of the power conversion device; an abnormality determination unit that determines that the temperature detection unit is abnormal when a temperature change width between different points in time in a temperature detection value detected by the temperature detection unit exceeds a temperature change width threshold set based on characteristics of the power conversion device, and that the power conversion device is abnormal when the temperature detection value exceeds a predetermined temperature threshold; A power conversion device comprising:

7. When the abnormality determination unit determines that the temperature detection unit is abnormal, and controlling an operating condition of the power conversion device in accordance with the temperature detection value immediately before the determination.

7. The power conversion device according to claim 1, 2, or 6.

8. A power conversion device that performs power conversion between a DC voltage source and a load, a first temperature detection unit that discretely detects a temperature of a first portion of the power conversion device; a second temperature detection unit that discretely detects the temperature of a second portion of the power conversion device; an abnormality determination unit that compares a difference between a first temperature detection value detected by the first temperature detection unit at a first time point and a second temperature detection value detected by the second temperature detection unit at a second time point with a temperature change width threshold that is set based on characteristics of the power conversion device, and determines whether or not an abnormality exists in the first temperature detection unit or the second temperature detection unit based on the comparison; A power conversion device comprising:

9. the temperature change width threshold is set to a value greater than a difference between the first temperature detection value and the second temperature detection value due to a variation in characteristics between the first temperature detection unit and the second temperature detection unit.

9. The power conversion device according to claim 8.

10. the power conversion is performed by a switching operation of a semiconductor switching element mounted in a power conversion device, the first portion and the second portion are portions on which the semiconductor switching elements are mounted, 10. The power conversion device according to claim 8 or 9.

11. A power conversion device that performs power conversion between a DC voltage source and a load, a first temperature detection unit that discretely detects a temperature of a first portion of the power conversion device; a second temperature detection unit that discretely detects the temperature of a second portion of the power conversion device; an abnormality determination unit that determines that the first temperature detection unit or the second temperature detection unit is abnormal when a difference between a first temperature detection value detected by the first temperature detection unit at a first time point and a second temperature detection value detected by the second temperature detection unit at a second time point exceeds a temperature change width threshold set based on characteristics of the power conversion device, and that the power conversion device is abnormal when the first temperature detection value or the second temperature detection value exceeds a predetermined temperature threshold; A power conversion device comprising:

12. the first time point is a time point at which the temperature is detected by the first temperature detection unit this time, the second time point is a time point at which the temperature was detected by the second temperature detection unit the previous time; the difference between the first temperature detection value and the second temperature detection value is the difference between the current first temperature detection value and the previous second temperature detection value; The power conversion device according to claim 11 .

13. When the abnormality determination unit determines that the first temperature detection unit or the second temperature detection unit is abnormal, and controlling an operating condition of the power conversion device in accordance with at least one of the first temperature detection value and the second temperature detection value immediately before the determination.

13. The power conversion device according to claim 11 or 12.

14. the temperature change width threshold is set to a different value depending on the operating state of the power conversion device.

13. The power conversion device according to claim 11 or 12.

15. the temperature change width threshold is set to a value greater than a difference between the first temperature detection value and the second temperature detection value due to a variation in characteristics between the first temperature detection unit and the second temperature detection unit.

13. The power conversion device according to claim 11 or 12.

16. When it is determined that the first temperature detection unit or the second temperature detection unit is abnormal, and controlling an operating condition of the power conversion device in accordance with at least one of the first temperature detection value and the second temperature detection value immediately before the determination.

13. The power conversion device according to claim 11 or 12.

17. 1. A method for determining whether or not an abnormality exists in a power conversion device that performs power conversion between a DC voltage source and a load, comprising: discretely detecting a temperature of a predetermined portion of the power conversion device using a temperature detection unit; determining whether or not there is an abnormality in the temperature detection unit based on a comparison between a temperature change width between different points in time of the temperature detection value detected by the temperature detection unit and a temperature change width threshold value set based on the characteristics of the power conversion device; An abnormality determination method comprising:

18. 1. A method for determining whether or not an abnormality exists in a power conversion device that performs power conversion between a DC voltage source and a load, comprising: discretely detecting a temperature of a first portion of the power conversion device using a first temperature detection unit; discretely detecting a temperature of a second portion of the power conversion device using a second temperature detection unit; a difference value between a first temperature detection value detected by the first temperature detection unit at a first time point and a second temperature detection value detected by the second temperature detection unit at a second time point is compared with a temperature change width threshold value set based on characteristics of the power conversion device, thereby determining whether or not there is an abnormality in the first temperature detection unit or the second temperature detection unit; An abnormality determination method comprising:

19. the temperature change width threshold is set to a different value depending on the operating state of the power conversion device.

19. The method for determining an abnormality according to claim 17 or 18.

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