Power conversion device and control method

Abstract

This power conversion device comprises a semiconductor switching element and a preheating means. The semiconductor switching element is used for power conversion. The preheating means raises the temperature of the semiconductor switching element at the time of cold starting.

Description

Power Conversion Device and Control Method

[0001] An embodiment of the present invention relates to a power conversion device and a control method.

[0002] The semiconductor switching element used in the power conversion device may be affected by its temperature (referred to as the element temperature) in terms of the magnitude of the surge voltage generated when the semiconductor switching element is turned off. For example, the surge voltage at the element temperature (room temperature) during cold start may increase compared to the surge voltage expected at the element temperature during steady operation.

[0003] Japanese Patent Laid-Open No. 2013-242110

[0004] An object of the present invention is to provide a power conversion device and a control method capable of reducing an increase in the surge voltage of a semiconductor switching element during cold start. <00ffff9>

[0005] A power conversion device according to an aspect of the embodiment includes a semiconductor switching element and preheating means. The semiconductor switching element is used for power conversion. The preheating means raises the temperature of the semiconductor switching element during cold start.

[0006] Configuration diagram of a power conversion device including a control device according to an embodiment. Elevation view for explaining a first example of the arrangement of temperature sensors according to an embodiment. Elevation view for explaining a second example of the arrangement of temperature sensors according to an embodiment. Plan view for explaining a second example of the arrangement of temperature sensors according to an embodiment. Diagram for explaining the relationship between the output capacity and temperature according to an embodiment. Flowchart showing the procedure of the warm-up operation control of the power conversion device according to an embodiment. Diagram for explaining the temperature dependence of the surge characteristics of the semiconductor switching element 6SW according to an embodiment. Configuration diagram of a power conversion device including a control device according to an embodiment. Flowchart showing the procedure of the warm-up operation control of the power conversion device according to an embodiment.

[0007] The control device and control method of the embodiment will be described below with reference to the drawings. In the following description, components having the same or similar functions will be denoted by the same reference numerals. Duplication of these components may be omitted. Electrical connection may simply be referred to as "connected." The term "equal in size" in the following description also includes cases where the sizes are approximately equal.

[0008] Figure 1 is a configuration diagram of a power converter 1 including a control device 10 of an embodiment. Figure 1 shows the power converter 1, a three-phase AC power supply 2 connected to the power converter 1, and an AC motor 3. The three-phase AC power supply 2 supplies, for example, three-phase AC power. For example, the three-phase AC power supply 2 includes the power grid of a power company, a generator, etc. The three-phase AC power supply 2 supplies three-phase AC power to the DC conversion unit 4 of the power converter 1. The AC motor 3 is, for example, a motor for three-phase AC. The AC motor 3 is supplied with AC power from the power converter 1.

[0009] In Figure 1, the power conversion device 1 comprises a DC conversion unit 4, a smoothing capacitor 5, an AC conversion unit 6, a current detector 7, temperature sensors 8A and 8B, a preheating unit 9, and a control device 10.

[0010] The DC conversion unit 4 is a DC conversion circuit including a rectifier composed of, for example, diodes, or a semiconductor switching element. IGBTs, MOSFETs, etc., can be used as the semiconductor switching element. A flywheel diode may also be provided as this semiconductor switching element. The DC conversion unit 4 converts the AC power input from the three-phase AC power supply 2 into DC power and outputs it. Figure 1 shows an example of a DC conversion unit 4 composed of diodes. The DC conversion unit 4 may be provided with a heat sink to dissipate the heat generated by losses in the diodes, etc.

[0011] The smoothing capacitor 5 stores the power supplied from the DC conversion unit 4 and smooths the voltage output by the DC conversion unit 4.

[0012] The AC conversion unit 6 is an AC conversion circuit including a semiconductor switching element 6SW. The semiconductor switching element 6SW can be an IGBT, MOSFET, or the like. A flywheel diode may also be provided in the semiconductor switching element 6SW. The AC conversion unit 6 converts DC power into three-phase AC power and outputs it. Figure 1 shows an example of a configuration combining an IGBT and a flywheel diode. The number of semiconductor switching elements 6SW etc. in the AC conversion unit 6 is not limited to those shown in the figure and may be multiple. The AC conversion unit 6 is provided with a heat sink 6HS for dissipating the heat generated by the losses of the semiconductor switching element 6SW. The heat sink 6HS dissipates the heat generated by the losses of the semiconductor switching element 6SW.

[0013] The current detector 7 is an example of a current transformer including a Hall CT or a shunt resistor. The current detector 7 detects the current output to the AC motor 3 and outputs the detected current value to the current detection unit 101. Furthermore, the location of the current detector 7 is not limited to the AC bus of two or more of the three phases, but may be any location where the current waveform of the current flowing through the AC conversion unit 6 can be reproduced, for example, inside the AC conversion unit 6, or between the DC conversion unit 4 and the AC conversion unit 6.

[0014] The temperature sensors 8A and 8B include, for example, thermistors, resistance thermometers, etc. The temperature sensors 8A and 8B detect the temperature at their respective locations and generate signals that change according to the temperature. For example, temperature sensor 8A is placed at a point in the power conversion device 1, such as the AC converter 6, where the temperature is relatively high. Temperature sensor 8B is placed at a point in the panel of the power conversion device 1 where the temperature is relatively close to the ambient temperature. Note that the positions of temperature sensors 8A and 8B are not limited to those shown in Figure 1. For example, the position of temperature sensor 8A can be anywhere where a temperature rise due to the output power of the power conversion device 1 can be detected.

[0015] The preheating section 9 is an example of a preheating means used to raise the temperature of a semiconductor switching element during a cold start. The preheating section 9 comprises a heating element 9R and a switch 9S. The heating element 9R is a resistor or the like that generates heat when current is applied. The heating element 9R is provided, for example, to raise the temperature of the semiconductor switching element by generating heat. Such a heating element 9R is arranged to indirectly raise the temperature of the semiconductor switching element by increasing the temperature of the heat sink of the semiconductor switching element through the heat generated when current is applied by opening the switch 9S.

[0016] Switch 9S is used to control the supply and disconnection of power to the heating element 9R. Switch 9S is controlled by the warm air control unit 109, which will be described later.

[0017] The control device 10 includes an arithmetic unit such as an MCU or FPGA, and its peripheral circuits. The arithmetic unit of the control device 10 includes a processor that executes processing by software (programs), or hardware arithmetic circuits, etc.

[0018] For example, the control device 10 includes a current detection unit 101, a current calculation unit 102, a heat sink temperature detection unit 103, a heat sink temperature calculation unit 104, an element temperature estimation unit 105, a panel temperature detection unit 106, a panel temperature calculation unit 107, an external command receiving unit 108, a warm air control unit 109, a storage unit 110, a control unit 120, and a PWM output unit 130.

[0019] The current detection unit 101 includes a conversion unit such as an AD converter, takes the signal output by the current detector 7 as input, converts that signal into current data for calculation, and outputs it to the current calculation unit 102.

[0020] The current calculation unit 102 takes the current data output by the current detection unit 101 as input, calculates, for example, the effective value of the current based on the current data, and outputs it to the control unit 120.

[0021] The heat sink temperature detection unit 103 is a conversion unit such as an AD converter, which takes 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.

[0022] The heat sink temperature calculation unit 104 takes the temperature data output by the heat sink temperature detection unit 103 as input, calculates, for example, the temperature in Celsius based on the temperature data, and outputs it to the element temperature estimation unit 105.

[0023] The element temperature estimation unit 105 takes the temperature data from the heat sink temperature calculation unit 104 as input, calculates the junction temperature of the semiconductor switching element 6SW based on the temperature data, and outputs the estimated value of the junction temperature of the semiconductor switching element 6SW to the control unit 120. For example, the element temperature estimation unit 105 derives an estimated value (first estimated value) of the temperature of the semiconductor switching element 6SW using the temperature detection value of a predetermined position within a predetermined range from the position of the semiconductor switching element 6SW.

[0024] The internal temperature detection unit 106 is a conversion unit such as an AD converter, which takes the signal output by the temperature sensor 8B as input, converts it into temperature data for calculation, and outputs it to the internal temperature calculation unit 107.

[0025] The internal temperature calculation unit 107 takes the temperature data output by the internal temperature detection unit 106 as input, calculates, for example, the temperature in Celsius based on the temperature data, and outputs the detected internal temperature value (referred to as internal temperature Ta) to the control unit 120.

[0026] The external command receiving unit 108 receives, for example, an external command value used for controlling the AC motor 3 from a higher-level device and outputs it to the control unit 120.

[0027] The warm air control unit 109 controls the state of the switch 9S to control the supply of power to the heating element 9R.

[0028] The storage unit 110 includes, for example, a storage medium such as a semiconductor memory or a magnetic storage device. The storage unit 110 receives new data written to it by a write process from the control unit 120 and holds this data. The storage unit 110 outputs the data it holds through a read process from the control unit 120. Instead of being written to by the control unit 120, each piece of data to the storage unit 110 may be written by a dedicated controller.

[0029] The control unit 120 performs various processes, including the collection and management of various data, the control of the AC conversion unit 6, and the identification of the state of the power converter 1.

[0030] The control unit 120 is responsible for collecting and managing various data and performs the following processes. The control unit 120 acquires element temperature data calculated by the element temperature estimation unit 105, panel temperature data calculated by the panel temperature calculation unit 107, and current data calculated by the current calculation unit 102. The control unit 120 monitors the acquired various data. The control unit 120 writes the monitoring results and the above various data as time history data to the storage unit 110 for storage.

[0031] The control unit 120 controls the AC converter 6 and performs the following processes. The control unit 120 uses various data stored in the memory unit 110 or collected data to calculate a control amount (for example, a voltage reference) for PWM control of the AC motor 3 for each control cycle and outputs it to the PWM output unit 130.

[0032] Furthermore, the control unit 120 performs processing related to the identification of the state of the power converter 1. Details of this will be described later.

[0033] The PWM output unit 130 generates a PWM signal based on a control variable (voltage reference) supplied from the control unit 120 and outputs it to the AC conversion unit 6.

[0034] Referring to Figure 2A, a first example of the arrangement of the temperature sensors in the embodiment will be described. Figure 2A is an elevation view illustrating a first example of the arrangement of the temperature sensors in the embodiment.

[0035] The heat sink 6HS is, for example, a metal plate. A module 6M, which is thermally coupled to the heat sink 6HS, is placed on the first surface of the heat sink 6HS.

[0036] A preheating section 9 is positioned adjacent to the heat sink 6HS. For example, the preheating section 9 comprises a heat transfer section 9HS and a heating element 9R. The heat transfer section 9HS is made of the same type of metal as the heat sink 6HS. The heat transfer section 9HS is positioned adjacent to the heat sink 6HS in the direction of extension. It is preferable that the heat transfer section 9HS and the heat sink 6HS are thermally coupled. For example, a heating element 9R, which is thermally coupled to the heat transfer section 9HS, is positioned on the first surface of the heat transfer section 9HS.

[0037] This module 6M includes, for example, a substrate 6BS, a semiconductor switching element 6SW, and a temperature sensor 8A. The substrate 6BS includes an insulating core material such as ceramic or glass fiber resin. The semiconductor switching element 6SW of module 6M is arranged on the first surface 6F1 of the substrate 6BS. The temperature sensor 8A is located in module 6M. For example, the temperature sensor 8A may be located inside module 6M. The inside of module 6M is filled with air or resin.

[0038] The second surface 6F2 of the substrate 6BS of module 6M is positioned to be thermally coupled to the heat sink 6HS. For example, a film that enhances thermal conductivity (e.g., a film made of silicon, mylar, etc.) or an oil can be applied between the second surface 6F2 of the substrate 6BS of module 6M and the heat sink 6HS. A general method may be selected for this thermal coupling.

[0039] As shown in Figure 2A, a temperature sensor 8A is installed on the module 6M itself. In this case, the thermal resistance Rth between the installation location of the temperature sensor 8A and a representative location of the semiconductor switching element 6SW is set in advance. For example, the control unit 120 uses the thermal resistance Rth to calculate the element temperature Tj of the semiconductor switching element 6SW from the temperature measured by the temperature sensor 8A (referred to as the sensor measurement temperature). This calculation may be performed using the following equation (1).

[0040] Element temperature Tj = Sensor measurement temperature + Rth × Average heat generation [W] (1)

[0041] Note that, for the "average heat generation [W]" in Equation (1), the average value of the heat generation amount of the module 6M estimated from the average of the output current of the module 6M may be applied.

[0042] Referring to FIGS. 2B and 3, a second example of the arrangement of the temperature sensor 8A according to the embodiment will be described. FIG. 2B is an elevation view for explaining a second example of the arrangement of the temperature sensor 8A according to the embodiment. FIG. 3 is a plan view for explaining a second example of the arrangement of the temperature sensor 8A according to the embodiment.

[0043] The description will focus on the differences from the case of FIG. 2A. This module 6MA does not include the temperature sensor 8A inside its case. Instead, the temperature sensor 8A is arranged on the heat sink 6HS. Therefore, the heat conduction characteristics between the installation location of the temperature sensor 8A and the semiconductor switching element 6SW change.

[0044] The thermal resistance of the case shown in FIGS. 2B and 3 is shown in the following Equation (2).

[0045] Thermal resistance Rth = Rth(h) + Rth(j - c) (2)

[0046] "Rth(h)" in Equation (2) is the thermal resistance between the installation location of the temperature sensor 8A and the representative position of the module 6M. "Rth(j - c)" is the thermal resistance between the representative position of the module 6M and the representative position of the semiconductor switching element 6SW. The representative position of this module 6M may be determined, for example, within the range of the image obtained by projecting the semiconductor switching element 6SW onto the surface of the heat sink 6HS. A dot is provided at the representative position of the module 6M. Thus, due to the difference in the position of the temperature sensor 8A, the definition of the thermal resistance from the heat generation location changes. Accordingly, the above Equation (1) is replaced with the following Equation (3).

[0047] Element temperature Tj = Sensor measured temperature + (Rth(h) + Rth(j - c)) × Average heat generation [W] (3)

[0048] As shown in FIGS. 2A to 3 described above, the temperature sensor 8A is provided within a predetermined range from the position of the semiconductor switching element 6SW. This predetermined range may be within the module 6M including the semiconductor switching element 6SW, or within a range (on the surface or in the vicinity of the surface) predetermined based on the surface of the heat sink 6HS. The predetermined position in the former case is the position (referred to as the first position) of the temperature sensor 8A (first sensor) disposed in the module 6M including the semiconductor switching element 6SW, as shown in FIG. 2A. The predetermined position in the latter case is the position (referred to as the second position) of the temperature sensor 8A (second sensor) disposed within a range (on the surface or in the vicinity of the surface) predetermined based on the surface of the heat sink 6HS, as shown in FIG. 2B. Thus, depending on the difference between the modules 6M and 6MA to be used, any one of the above may be selected.

[0049] Referring to FIG. 4, the relationship between the estimated temperature and the output capacity in the embodiment will be described. FIG. 4 is a diagram for explaining the relationship between the output capacity and the temperature in the embodiment. The graph shown in FIG. 4 shows the relationship between the measured temperature (vertical axis) 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 as well. The range of the output capacity shown in this graph indicates a range from 0 to 150% when the rated output is 100%. Over the entire range of the output capacity shown in FIG. 4, the measured temperature (vertical axis) by the temperature sensor 8A and the estimated temperature of the semiconductor switching element 6SW increase monotonically with an upward slope to the right. Comparing the measured temperature (vertical axis) by the temperature sensor 8A and the estimated temperature of the semiconductor switching element 6SW, as shown in the aforementioned equations (1) and (3), the estimated temperature of the semiconductor switching element 6SW is higher.

[0050] FIG. 5 is a flowchart showing the procedure of the heating operation control of the power conversion device 1 in the embodiment.

[0051] The control device 10 performs an estimation process for the element temperature Tj (element temperature estimation) using the element temperature estimation unit 105, etc. (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. Details of this element temperature Tj estimation process will be described later.

[0052] The panel temperature calculation unit 107 may also perform panel temperature estimation processing (panel temperature estimation) to generate panel temperature (panel temperature data) and update panel temperature Ta as the latest estimated value. For the sake of simplicity, the explanation may sometimes assume that panel temperature Ta is constant. In fact, if an environment is provided in which panel temperature Ta can be considered constant, this panel temperature Ta estimation processing may be omitted.

[0053] 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 panel temperature Ta (SA12). The above element temperature rise (Tj - Ta) is taken as, for example, the temperature rise of the element temperature Tj from the reference panel temperature Ta.

[0054] The control unit 120 identifies whether the element temperature rise (Tj - Ta) is less than a predetermined determination value (SA13).

[0055] If the element temperature rise (Tj - Ta) exceeds a predetermined threshold, the control unit 120 starts a warm-up operation (SA14) and returns the process to SA11.

[0056] The above procedure can reduce the increase in surge voltage of the semiconductor switching element during a cold start. The determination value used to determine the element temperature rise (Tj-Ta) should preferably be predetermined in relation to the initial data value. This determination value may be the initial data value itself, or it may be the initial data value plus a predetermined value. The initial data value may be a value determined in the design, or it may be a value adjusted based on the temperature change obtained by actually operating the power converter 1. The control unit 120 may use the initial data value to mitigate the effects of individual variations and the influence of the field environment.

[0057] Referring to Figure 6, the temperature dependence of the surge characteristics of the semiconductor switching element 6SW of the embodiment will be explained. Figure 6 is a diagram illustrating the temperature dependence of the surge characteristics of the semiconductor switching element 6SW of the embodiment.

[0058] The graphs in Figures 6(a) to 6(d) show the relationship between the observed temperature of the semiconductor switching element 6SW and the surge voltage generated when it is cut off. Figures 6(a) and 6(b) show examples of the characteristics of the semiconductor switching element 6SW at high temperatures, and Figures 6(c) and 6(d) show examples of the characteristics of the semiconductor switching element 6SW at low temperatures.

[0059] (Example of electrical characteristics at high temperatures) The difference in conditions between Figure 6(a) and (b) is due to the difference in the magnitude of the current flowing before the semiconductor switching element 6SW was shut off. The current value in Figure 6(a) is 492A, and the current value in Figure 6(b) is 542A. Comparing Figures 6(a) and (b), Figure 6(b) has a larger current value. Therefore, the peak value of the surge voltage generated when the semiconductor switching element 6SW is shut off is 1376V in Figure 6(a), while it is 1384V in Figure 6(b).

[0060] (Example of electrical characteristics at low temperature (room temperature)) The difference in conditions between Figure 6(c) and (d) is due to the difference in the magnitude of the current flowing before the semiconductor switching element 6SW was shut off. Similar to the case at high temperature described above, the current value in Figure 6(c) is 492A, and the current value in Figure 6(d) is 542A. Comparing Figures 6(c) and (d), the current value in Figure 6(d) is larger. Therefore, the peak value of the surge voltage generated when the semiconductor switching element 6SW is shut off is 1440V in Figure 6(c), while it is 1472V in Figure 6(d).

[0061] As described above, if the temperature of the semiconductor switching element 6SW increases due to warm-up operation, the peak value of the surge voltage generated when the semiconductor switching element 6SW is shut off can be reduced.

[0062] According to the above embodiment, the power converter 1 comprises a semiconductor switching element 6SW and a preheating unit 9. The semiconductor switching element 6SW is used for power conversion. The preheating unit 9 raises the temperature of the semiconductor switching element 6SW during a cold start. This reduces the increase in surge voltage of the semiconductor switching element during a cold start.

[0063] More specifically, the preheating section 9 of the power converter 1 includes a heating element 9R that generates heat when energized and is provided to raise the temperature of the semiconductor switching element by the heat generated, and a warm air control unit 109 that controls the supply of power to the heating element 9R. By controlling the supply of power to the heating element 9R by the warm air control unit 109, the temperature of the semiconductor switching element 6SW can be increased during a cold start.

[0064] (Second Embodiment) A second embodiment will be described with reference to Figures 7 and 8.

[0065] Figure 7 is a configuration diagram of the power converter 1A including the control device 10A of the embodiment. The power converter 1A shown in Figure 7 is equipped with a control device 10A in place of the control device 10A of the power converter 1. The power converter 1A does not have the preheating unit 9 of the power converter 1. The differences described above will be explained below.

[0066] The control device 10A is configured without the warm air control unit 109 of the control device 10, and instead of the control unit 120, it is equipped with a control unit 120A.

[0067] The control unit 120A controls the semiconductor switching element 6SW to increase its temperature during a cold start, thereby promoting self-heating.

[0068] The control unit 120A is an example of a preheating means. The control unit 120A (warm air control unit) energizes the semiconductor switching element 6SW during a cold start, thereby increasing the temperature of the semiconductor switching element 6SW due to the power loss of the semiconductor switching element 6SW.

[0069] The power converter 1A of this embodiment does not have a preheating unit 9, but by conducting a DC current (output frequency 0 Hz) through the semiconductor switching element 6SW for a predetermined period of time, the semiconductor switching element 6SW is heated by internal losses. As a result, the temperature of the semiconductor switching element 6SW begins to rise from the initial temperature (room temperature). By pre-determining the energizing period to account for the temperature rise of the semiconductor switching element 6SW, the temperature of the semiconductor switching element 6SW can be raised to a desired temperature range when that energizing period is completed.

[0070] Figure 8 is a flowchart showing the procedure for controlling the warm-up operation of the power converter 1A in the embodiment.

[0071] The control device 10 performs an estimation process for the element temperature Tj (element temperature estimation) using the element temperature estimation unit 105, etc. (SA11).

[0072] The control unit 120A calculates an estimated value of the element temperature rise (Tj - Ta) based on the temperature difference between the element temperature Tj and the panel temperature Ta (SA12). The above element temperature rise (Tj - Ta) is taken as, for example, the temperature rise of the element temperature Tj from the reference panel temperature Ta.

[0073] The control unit 120A identifies whether the element temperature rise (Tj - Ta) is less than a predetermined determination value (SA13).

[0074] If the result of SA13 indicates that the element temperature rise (Tj-Ta) is greater than or equal to a predetermined value, the control unit 120A starts a warm-up operation (SA14) and performs a warm-up operation for a predetermined period. When the warm-up operation period of SA14 ends, the temperatures of the semiconductor switching element 6SW and the heat sink 6HS are higher than before the warm-up operation started. When the predetermined period has expired, the control unit 120A proceeds to process SA17.

[0075] Based on the determination result of SA13, if the element temperature rise (Tj-Ta) is less than a predetermined determination value, or after the warm-up operation (SA14) is completed, the control unit 120A starts normal operation (SA17).

[0076] The above procedure can reduce the increase in surge voltage of the semiconductor switching element during a cold start. The determination value used to determine the element temperature rise (Tj-Ta) should preferably be predetermined in relation to the initial data value. This determination value may be the initial data value itself, or it may be the initial data value plus a predetermined value. The initial data value may be a value determined in the design, or it may be a value adjusted based on the temperature change obtained by actually operating the power converter 1. The control unit 120A should use the initial data value to mitigate the effects of individual variations and the influence of the field environment.

[0077] According to at least one embodiment described above, the power conversion device comprises a semiconductor switching element and a preheating means. The semiconductor switching element is used for power conversion. The preheating means raises the temperature of the semiconductor switching element during a cold start. This reduces the increase in surge voltage of the semiconductor switching element during a cold start.

[0078] In the power converter 1 of the embodiment described above, some or all of the functional units of the control device 10 may include a software functional unit that is realized by a program (computer program, software component) stored in the computer's memory (such as a computer's memory) being executed by the computer's processor (hardware processor). Some or all of the functional units of the control device 10 may be realized by hardware such as an LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), or FPGA (Field-Programmable Gate Array), or by a combination of software functional units and hardware.

[0079] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be implemented in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. For example, the configurations of each embodiment may be implemented in combination with each other and can be applied to components that have not been described. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0080] (Note) (1) The power conversion device of the embodiment comprises a semiconductor switching element used for power conversion and a preheating means for raising the temperature of the semiconductor switching element during a cold start. (2) In the power conversion device of (1) above, the preheating means may comprise a heating element that generates heat when energized and raises the temperature of the semiconductor switching element by the heat generated, and a warm air control unit that controls the energization of the heating element. (3) In the power conversion device of (1) above, the heating element may be arranged to raise the temperature of the heat sink of the semiconductor switching element by generating heat when energized, thereby indirectly raising the temperature of the semiconductor switching element. Power conversion device according to claim 2. (4) In the power conversion device of (1) above, the preheating means comprises a warm air control unit that raises the temperature of the semiconductor switching element by power loss of the semiconductor switching element by energizing the semiconductor switching element during a cold start. (5) The control method for the power converter of the embodiment is a control method for a power converter equipped with semiconductor switching elements used for power conversion, and includes preheating to raise the temperature of the semiconductor switching elements during a cold start.

[0081] 1...Power converter, 3...AC motor, 6...AC converter unit, 6HS...Heat sink, 6SW...Semiconductor switching element, 8A, 8B...Temperature sensors, 9...Preheating unit, 10...Control device, 105...Element temperature estimation unit, 110...Storage unit, 120...Control unit

Claims

1. A power conversion device comprising a semiconductor switching element used for power conversion and a preheating means for raising the temperature of the semiconductor switching element during a cold start.

2. The power conversion device according to claim 1, wherein the preheating means comprises a heating element that generates heat when an electric current is applied and raises the temperature of the semiconductor switching element by the heat generated, and a warm air control unit that controls the supply of electric current to the heating element.

3. The power conversion device according to claim 2, wherein the heating element is arranged to indirectly increase the temperature of the semiconductor switching element by increasing the temperature of the heat sink of the semiconductor switching element due to the heat generated when power is supplied.

4. The power conversion device according to claim 1, wherein the preheating means comprises a warm air control unit that energizes the semiconductor switching element during the cold start, thereby increasing the temperature of the semiconductor switching element due to the power loss of the semiconductor switching element.

5. A control method for a power conversion device equipped with semiconductor switching elements used for power conversion, the control method including performing preheating to raise the temperature of the semiconductor switching elements during a cold start.

6. The power conversion device is provided with a heating element that generates heat when energized, and the heat generated raises the temperature of the semiconductor switching element to perform preheating, and the control method according to claim 5 includes controlling the energization of the heating element.

7. The control method according to claim 6, wherein the heating element is arranged such that it increases the temperature of the heat sink of the semiconductor switching element by generating heat when power is supplied, thereby indirectly increasing the temperature of the semiconductor switching element.

8. The control method according to claim 5, further comprising energizing the semiconductor switching element during the cold start to increase the temperature of the semiconductor switching element due to power loss of the semiconductor switching element.

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