Power conversion device and power conversion method

Abstract

When the measured temperature measured by the temperature sensor for the switching element on the one arm side is higher than the estimated temperature based on the amount of temperature increase estimated by the first temperature estimation unit, the second temperature estimation unit estimates the refrigerant temperature on the basis of the ratio obtained by dividing the difference between the measured temperature and the refrigerant temperature by the amount of temperature increase. The predicted temperature of the other switching element on the other arm side is estimated by correcting the amount of temperature increase estimated by the first temperature estimation unit for the other switching element on the other arm side.

Description

TECHNICAL FIELD

[0001] The present application relates to a power conversion device and a power conversion method, and is particularly suitable for a power conversion device relating to, for example, a technique of measuring the temperature of a switching element of a U-phase, a V-phase, and a W-phase. BACKGROUND

[0002] In recent years, in a power conversion device mounted on a vehicle, a configuration is adopted in which a temperature sensor is provided only on one switching element of a plurality of switching elements of each phase. In such a conventional power conversion device, the temperature of another switching element is estimated from the measured temperature of the temperature sensor provided on the one switching element, taking into account the heat transfer impedance. The heat transfer impedance varies depending on the refrigerant flow rate, on the assumption that the cooling system of the switching element is normal, regardless of whether the cooling system is air cooling or water cooling.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-097812 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] However, in the technology described in Patent Document 1, particularly in the case where so-called water shortage (water emptying) occurs in the water-cooled cooling system, the temperature of the switching element can be significantly different from that at the time of normality. That is, the actual temperature of the switching element at the time of cooling system abnormality easily becomes a curve extending upward in the vertical axis direction, as compared with the curve representing the characteristic of the temperature rise with respect to the current at the time of normality, because the cooling system does not operate normally. However, the calculated value of the temperature of the other switching element estimated from the temperature of the one switching element of the above-described arm (hereinafter also referred to as "estimated temperature") is on the assumption that the cooling system remains normal, and thus the actual temperature of the other switching element deviates from the estimated temperature.

[0008] The present application is made in consideration of the above points, and aims to provide a power conversion device and a power conversion method in which, even if an abnormality occurs in the cooling system of the switching element, the predicted temperature of the other switching element can be correctly estimated from the measured temperature of the temperature sensor provided on the one switching element.

[0009] MEANS FOR SOLVING THE PROBLEMS

[0010] To solve the problem, in the present application, there are provided: a refrigerant temperature acquisition unit that acquires a temperature of a refrigerant that cools a plurality of switching elements corresponding to upper arms and lower arms of each phase of a power conversion device; a temperature sensor that measures a temperature of a switching element on one arm side among the plurality of switching elements; a first temperature estimation unit that estimates an estimated temperature based on a temperature rise amount of each of the switching elements when operating according to a driving condition of the switching element; and a second temperature estimation unit that, in a case where a measured temperature measured by the temperature sensor of the switching element on the one arm side is higher than an estimated temperature based on the temperature rise amount estimated by the first temperature estimation unit, corrects the temperature rise amount estimated by the first temperature estimation unit of the switching element on the other arm side according to a ratio obtained by dividing a difference between the measured temperature and the temperature of the refrigerant by the temperature rise amount, thereby estimating a predicted temperature of the other switching element on the other arm side.

[0011] In addition, in the present application, there are provided: a refrigerant temperature acquisition step in which a refrigerant temperature acquisition unit acquires a temperature of a refrigerant that cools a plurality of switching elements corresponding to upper arms and lower arms of each phase of a power conversion device; a switching element temperature measurement step in which a temperature sensor measures a temperature of a switching element on one arm side among the plurality of switching elements; a first temperature estimation step in which a first temperature estimation unit estimates an estimated temperature based on a temperature rise amount of each of the switching elements when operating according to a driving condition of the switching element; and a second temperature estimation step in which a second temperature estimation unit, in a case where a measured temperature measured by the temperature sensor of the switching element on the one arm side is higher than an estimated temperature based on the temperature rise amount estimated by the first temperature estimation unit, corrects the temperature rise amount estimated by the first temperature estimation unit of the switching element on the other arm side according to a ratio obtained by dividing a difference between the measured temperature and the temperature of the refrigerant by the temperature rise amount, thereby estimating a predicted temperature of the other switching element on the other arm side.

[0012] Effects of the Invention

[0013] According to the present application, even if an abnormality occurs in the cooling system of the switching element, it is possible to correctly estimate the predicted temperature of the other switching element according to the measured temperature of the temperature sensor provided on one switching element. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a block diagram showing a configuration example of the power conversion device of the present embodiment.

[0015] Figure 2 is a graph showing an example of the characteristics of the current versus the temperature rise of the switching element of the present embodiment.

[0016] Figure 3is a diagram showing an example of a path of a current flowing through a switching element.

[0017] Figure 4A is a diagram showing an example of a temperature change of a switching element.

[0018] Figure 4B is a diagram showing an example of a temperature change of a switching element.

[0019] Figure 4C is a diagram showing an example of a temperature change of a switching element.

[0020] Figure 4D is a diagram showing an example of a temperature change of each switching element of an upper arm and a lower arm of 3 phases.

[0021] Figure 5 is a diagram showing an example of a relationship between a current phase and a current of each switching element.

[0022] Figure 6 is a diagram showing an example of a current versus temperature rise characteristic of each switching element at a low frequency when temperatures are different.

[0023] Figure 7 is a diagram showing an example of a temperature change of a switching element of a lower arm at a low frequency.

[0024] Figure 8 is a diagram showing an example of a current versus temperature rise characteristic. DETAILED DESCRIPTION

[0025] Hereinafter, one embodiment of the present application will be explained in detail with reference to the drawings.

[0026] Figure 1 is a block diagram showing an example of a configuration of a power conversion device of the present embodiment. Figure 2 is a diagram showing an example of a characteristic of a current versus temperature rise with respect to a switching element of the present embodiment. As an example, the power conversion device of the present embodiment is applied to an electric vehicle.

[0027] As Figure 1As shown, the power conversion device of the present embodiment includes a direct-current voltage source 1, a smoothing capacitor 2, a direct-current voltage sensor 3, a switching element Sup of an upper arm of a U-phase, a freewheeling diode Dup of the upper arm of the U-phase, a switching element Sun of a lower arm of the U-phase, a freewheeling diode Dun of the lower arm of the U-phase, a temperature sensor Tu of the U-phase, a switching element Svp of an upper arm of a V-phase, a freewheeling diode Dvp of the upper arm of the V-phase, a switching element Svn of a lower arm of the V-phase, a freewheeling diode Dvn of the lower arm of the V-phase, a temperature sensor Tv of the V-phase, a switching element Swp of an upper arm of a W-phase, a freewheeling diode Dwp of the upper arm of the W-phase, a switching element Swn of a lower arm of the W-phase, a freewheeling diode Dwn of the lower arm of the W-phase, a temperature sensor Tw of the W-phase, an alternating-current current sensor 4, a motor 5, an angle sensor 6, a control device 7, a gate drive circuit 8, a refrigerant temperature sensor 24, a temperature detection circuit 9, a motor control section 10, a first temperature estimation section 11, a second temperature estimation section 12, and a current control section 13.

[0028] A torque command value 14 of the motor 5 is input to the control device 7 from an unillustrated ECU (Electronic Control Unit) or the like for controlling the above-described electric vehicle.

[0029] The direct-current voltage source 1 is a power source that supplies a direct-current voltage, and supplies the direct-current voltage to the switching elements Sup, Svp, Swp of the upper arms of the respective phases of the motor 5 and the switching elements Sun, Svn, Swn of the lower arms of the respective phases. The smoothing capacitor 2 is connected in parallel to the direct-current voltage source 1.

[0030] The direct-current voltage sensor 3, which outputs a direct-current voltage detection value 15 indicating a value of the measured direct-current voltage of the direct-current voltage source 1 to the motor control section 10, is connected in parallel to the smoothing capacitor 2.

[0031] In the upper arms, the freewheeling diodes Dup, Dvp, Dwp are connected in parallel to the collector and emitter of the switching elements Sup, Svp, Swp. On the other hand, in the lower arms, the freewheeling diodes Dun, Dvn, Dwn are connected in parallel to the collector and emitter of the switching elements Sun, Svn, Swn.

[0032] A gate drive circuit 8 is connected to the gates of the switching elements Sup, Svp, Swp of the upper arm and the switching elements Sun, Svn, Swn of the lower arm. The gate drive circuit 8 controls the switching elements Sup, Svp, Swp of the upper arm and the switching elements Sun, Svn, Swn of the lower arm to apply an alternating-current voltage to the motor 5 from the output line of the U phase connected to the emitter of the switching element Sup (and the collector of the switching element Sun) of the lower arm, the output line of the V phase connected to the emitter of the switching element Svp (and the collector of the switching element Svn) of the lower arm, and the output line of the W phase connected to the emitter of the switching element Swp (and the collector of the switching element Swn) of the lower arm, respectively.

[0033] An alternating-current current sensor 4 is provided on each of the output lines of the U phase, the V phase, and the W phase, and each of the alternating-current current sensors 4 measures an alternating-current current applied to each of the output lines of the U phase, the V phase, and the W phase, and outputs an alternating-current current detection value 16 as a result of the detection to the motor control section 10. The alternating-current current detection value 16 indicates a value of the alternating-current current input to the motor 5.

[0034] An angle sensor 6 detects a rotation angle of the motor 5 driven by the alternating-current current applied to each of the input lines of the U phase, the V phase, and the W phase, and outputs an angle detection value 17 to the motor control section 10.

[0035] The motor control section 10 generates a current command value 22 based on the direct-current voltage detection value 15, the alternating-current current detection value 16, and the angle detection value 17 of the motor 5, and outputs the current command value 22 to the current control section 13. The current control section 13 generates a gate drive signal 23 for generating an alternating-current voltage for driving the motor 5 based on the current command value 22, the alternating-current current detection value 16, and the angle detection value 17 of the motor.

[0036] The motor control section 10 also calculates a driving condition 19 of the switching elements in the process of generating the current command value 22, and the first temperature estimation section 11 operates based on the driving condition 19.

[0037] The refrigerant temperature sensor 24 is an example of a refrigerant temperature acquisition section, and is capable of acquiring a temperature of a refrigerant that cools a plurality of switching elements Sup, Svp, Swp, Sun, Svn, Swn corresponding to the upper arm and the lower arm of each of the U phase, the V phase, and the W phase of the power conversion device (or the motor).

[0038] The temperature detection circuit 9 is an example of a refrigerant temperature acquisition section, and outputs a temperature detection value 18 indicating the temperature of the refrigerant acquired by the refrigerant temperature sensor 24 to the motor control section 10 and the second temperature estimation section 12.

[0039] The temperature sensors Tu, Tv, Tw are provided on the lower-arm-side switching elements Sun, Svn, Swn, not on the upper-arm-side switching elements Sup, Svp, Swp. The temperature sensors Tu, Tv, Tw measure the temperatures of the lower-arm-side switching elements Sun, Svn, Swn.

[0040] The first temperature estimation unit 11 estimates a temperature (hereinafter also referred to as "estimated temperature") based on the temperature rise amount (ΔTestl, ΔTest2) of each of the switching elements Sup, Svp, Swp, Sun, Svn, Swn when the switching element operates according to the drive condition 19 (refer to FIG. 6). Figure 2 ).

[0041] The second temperature estimation unit 12 corrects the temperature rise amount ΔTestl, ΔTest2 of the upper-arm-side switching elements estimated by the first temperature estimation unit 11 according to the ratio ((Tact-Tc) / ΔTestl) of the difference (Tact-Tc) between the actual temperature Tact measured by the temperature sensors Tu, Tv, Tw for the lower-arm-side switching elements Sun, Svn, Swn and the temperature Tc of the refrigerant divided by the temperature rise amount ΔTestl, and thereby estimates the predicted temperature Test2c of the other switching element on the other arm (upper arm) side (refer to "corrected estimated temperature" of FIG. 6). Figure 2

[0042] That is, the second temperature estimation unit 12 corrects the temperature estimation values of the switching elements Sup, Svp, Swp estimated by the first temperature estimation unit 11, for example, according to the temperature detection values 18 of the temperature sensors Tu, Tv, Tw of the lower-arm-side switching elements Sun, Svn, Swn and the refrigerant temperature sensor 24 and the alternating-current current detection value 16, and calculates the predicted temperature Test2c.

[0043] ​In the following description, the switching elements Sup, Svp, Swp of the upper arms Sp of the respective phases are collectively referred to as switching elements SP without the need to particularly distinguish the switching elements, and the switching elements Sun, Svn, Swn of the lower arms Sn of the respective phases are collectively referred to as switching elements SN without the need to particularly distinguish the switching elements. In addition, the freewheeling diodes Dup, Dvp, Dwp of the upper arms Sp of the respective phases are collectively referred to as freewheeling diodes DP without the need to particularly distinguish the diodes, and the freewheeling diodes Dun, Dvn, Dwn of the lower arms Sn of the respective phases are collectively referred to as freewheeling diodes DN without the need to particularly distinguish the diodes.

[0044] Reference will be made primarily to Figure 2 An outline of the power conversion method of the present embodiment will be described, in which there are provided: a refrigerant temperature acquisition step in which the refrigerant temperature sensor 24, which is an example of a refrigerant temperature acquisition section, acquires the temperature of the refrigerant that cools a plurality of switching elements corresponding to the upper arms Sp and the lower arms Sn of the respective phases of the power conversion device; a switching element temperature measurement step in which the temperature sensors Tu, Tv, Tw measure the temperature of the switching element on the side of one arm (lower arm) Sn of the plurality of switching elements; a first temperature estimation step in which the first temperature estimation section 11 estimates the temperature rise amount (ΔTestl, ΔTest2) of each of the switching elements (estimated temperature) when the switching element operates according to the drive condition 19 of the switching element; and a second temperature estimation step in which, in the case where the temperature (hereinafter also referred to as "measured temperature") of the switching element on the side of one arm (lower arm) Sn measured by the temperature sensors Tu, Tv, Tw (actual temperature Tact) is higher than the estimated temperature based on the temperature rise amount estimated by the first temperature estimation section 11, the second temperature estimation section 12 corrects the temperature rise amount (ΔTestl, ΔTest2) of the switching element on the side of the other arm (upper arm) Sxp estimated by the first temperature estimation section 11 according to the ratio ((Tact-Tc) / ΔTestl) of the difference (Tact-Tc) between the measured temperature (actual temperature Tact) and the temperature Tc of the refrigerant divided by the temperature rise amount estimation value (ΔTestl) of the switching element, thereby estimating the predicted temperature of the other switching element on the side of the other arm (upper arm) (refer to the "corrected estimated temperature" of the second temperature estimation characteristic curve 25).

[0045] The motor control section 10 described above is an example of a drive control section that changes the drive condition 19 of the switching element. In the case where at least one of the measured temperature of the temperature sensors Tu, Tv, Tw and the predicted temperature (corrected estimated temperature) estimated by the second temperature estimation section 12 exceeds a prescribed threshold temperature, the motor control section 10 restricts the drive condition 19 of the switching element.

[0046] Specifically, in a case where at least one of the temperature detection value 18 of the switching elements Sun, Svn, Swn and the second temperature estimation value 21 exceeds a prescribed value, the motor control section 10 changes the drive conditions 19 of the switching elements by limiting the torque of the motor 5, to control in a manner that the temperature of the final switching elements Sup, Svp, Swp, Sun, Svn, Swn does not further increase.

[0047] In a case where the rotation speed of the motor 5 is less than a prescribed value (for example, in a case of extremely low speed), the motor control section 10 changes the drive conditions 19 of the switching elements, for example, to be within a threshold temperature or to stop the motor 5, based on the temperature (the "corrected estimation temperature") estimated by the second temperature estimation section 12. Figure 2

[0048] Figure 3 An example of a path of a current flowing through each switching element in the power conversion device is shown. The illustrated example takes the switching elements of the upper arm Sp and the lower arm Sn of one phase as an example, and indicates which switching element the current flows through by the polarity of the current and the ON / OFF state of the switching element.

[0049] In a case where the switching elements of the upper arm Sp are collectively referred to as Sp and the freewheeling diodes are collectively referred to as Dp, and the switching elements of the lower arm Sn are collectively referred to as Sn and the freewheeling diodes are collectively referred to as Dn, the upper arm Sp and the lower arm Sn are in a state where the switching element of either arm is ON and the switching element of the other arm is OFF, and the ON / OFF alternately switches every certain period. As shown in FIG. 6, in a case where the polarity of the current is +, the current alternately flows through the switching element SP and the freewheeling diode Dn, and in a case where the polarity of the current is -, the current alternately flows through the freewheeling diode Dp and the switching element SN. Figure 3

[0050] In a case where the rotation speed of the motor 5 is high, that is, in a case where the frequency of the alternating current is high, since the current uniformly flows in the switching element SP, the freewheeling diode Dp, the switching element SN, and the freewheeling diode Dn, respectively, the heat generation of each switching element of the upper arm Sp and the lower arm Sn is equal to each other. In the illustrated example, the explanation is given for one phase, but the same explanation can be given for three phases.

[0051] Here, as an example of an extreme case of the low rotation speed region, in a case where the motor 5 is stopped, the current flowing through the motor 5 becomes direct current. Assuming that in a case where the motor 5 is stopped in a state where the polarity of the current of a certain phase is + without using the present embodiment, since the current flows only in the switching element SP and the freewheeling diode Dn, the amount of heat generation is excessively large, and, on the contrary, since the current does not flow in the freewheeling diode Dp and the switching element SN, no heat is generated.

[0052] Figure 4A - Figure 4C ​​indicate an example of temperature change of the switching elements SP, SN, respectively. The illustrated example indicates the temperature change of the switching elements SP, SN when the frequency of the alternating current is low.

[0053] Figure 4A Figure 4B and Figure 4C indicate the temperature change of the upper arm Sp and the lower arm Sn of the phase 1, respectively. For example, in the Figure 4A , there is a temperature amplitude of about 4°C at 10 Hz, in the Figure 4B , there is a temperature amplitude of about 30°C at 1 Hz, and in the Figure 4C , there is a temperature amplitude of about 120°C at 0.1 Hz.

[0054] Figure 4D An example of the temperature change of each of the switching elements Sup, Sun, Svp, Svn, Swp, and Swn of all the arms of the three phases is shown. Since the temperature peak points of each arm are different, in the case where the present embodiment is not applied, in order to protect each of the switching elements Sup, Sun, Svp, Svn, Swp, and Swn from over temperature, it is necessary to detect or estimate the temperature of each of the switching elements Sup, Sun, Svp, Svn, Swp, and Swn of each arm.

[0055] Figure 5 indicates an example of the relationship between the current phase and the current of each of the switching elements in the present embodiment. In the present embodiment, it is assumed that the state where the motor 5 is stopped in the current phase shown on the right side of the upper side of Figure 5 , the frequency of the current is 0 Hz, the U phase (corresponding to "U" of the illustration) is a peak point of + polarity, the V phase (corresponding to "V" of the illustration) and the W phase (corresponding to "W" of the illustration) are - polarity, and the current of half of the peak continues to flow.

[0056] Therefore, as explained in the above Figure 3 , which one of the switching elements SP, SN and the freewheeling diodes Dp, Dn through which the current flows depends on the current polarity. In the present embodiment, the current flows through the switching element Sup of the upper arm Sp in the U phase, and flows through the switching elements Svn, Swn of the lower arm Sn in the V phase and the W phase.

[0057] Therefore, although these three switching elements Sup, Svn, Swn generate heat, as already explained, in the present embodiment, the temperature of the switching elements Sup, Svn, Swn can be detected by only these two temperature sensors Tv, Tw provided on the lower arm Sn, and the temperature cannot be detected since no temperature sensor is provided on the switching element Sup of the upper arm Sp.

[0058] Figure 6 indicates an example of the relationship between the current phase and the current of each of the switching elements in the present embodiment. In the present embodiment, it is assumed that the state where the motor 5 is stopped in the current phase shown on the right side of the upper side of Figure 5 ​An example of the current versus temperature characteristic in the case where the temperature of each switching element at the time of low frequency is assumed to be different. In the driving conditions 19 of the switching elements described above, the direct current voltage, the switching frequency, and the switching duty cycle indicating the ratio of the ON / OFF period of the switching element, the flow rate of the cooling refrigerant, and the like are included. These are common in each arm. At the time of low frequency, the temperature also increases and decreases according to the increase and decrease of the current, and the characteristic becomes the first temperature estimation characteristic curve 27.

[0059] For example, in the case where the flow rate of the refrigerant decreases due to an abnormality of the cooling system or the like, it can be expected that the actual temperature is higher than the first temperature estimation characteristic curve 27. This expected temperature characteristic is set as the second temperature estimation characteristic curve 25.

[0060] With respect to Figure 5 The current of the U phase is assumed to be the largest among the three phases, and the temperatures of the V phase and the W phase, which can be detected as described above, are used. The temperature rise of the switching element Svn of the lower arm Sn of the V phase estimated by the first temperature estimation characteristic curve 27 is set as ΔTv_mdl, the actually detected temperature is set as Tv, and the temperature of the refrigerant is set as Tc, and the second temperature estimation characteristic curve 25 is obtained by enlarging the first temperature estimation characteristic curve 27 in the vertical axis direction by the following coefficient.

[0061] ΔTv_act / ΔTv_mdl, where ΔTv_act = Tv - Tc

[0062] In the first temperature estimation characteristic curve 27, if the temperature rise corresponding to the current value of the U phase is set as ΔTu_mdl, the temperature of the switching element Sup of the upper arm Sp of the U phase can be estimated by the following equation.

[0063] ΔTu_est = ΔTu_mdl x (ΔTv_act / ΔTv_mdl)

[0064] Figure 7 An example of the temperature change of the switching elements Sun, Svn, Swn of the lower arm Sn at the time of low frequency is shown. The example shown in the drawing shows the temperature change of the switching elements Sun, Svn, Swn of the lower arm Sn of each phase from the time when the temperature of the switching element Sun of the lower arm Sn of the V phase is 20°C to the time when the temperature of the switching element Sun of the lower arm Sn of the V phase is 40°C. Figure 4D An example of the temperature change of the switching elements Sun, Svn, Swn of the lower arm Sn of each phase is extracted from the example of the time versus temperature characteristic shown in the drawing.

[0065] As shown in the drawing, since the temperature of the switching elements Sun, Svn, Swn of a certain phase can be detected, by applying the present embodiment, the temperature of the switching element of the upper arm Sp can be estimated. Therefore, it is not necessary to provide a temperature sensor on the switching element of the upper arm Sp.

[0066] Figure 8 An example of the temperature change of the switching elements Sun, Svn, Swn of the lower arm Sn at the time of low frequency is shown. The example shown in the drawing shows the temperature change of the switching elements Sun, Svn, Swn of the lower arm Sn of each phase from the time when the temperature of the switching element Sun of the lower arm Sn of the V phase is 20°C to the time when the temperature of the switching element Sun of the lower arm Sn of the V phase is 40°C. Figure 6The illustrated current versus temperature characteristic is an example of a current versus temperature characteristic at low frequencies and when the cooling refrigerant is stopped.

[0067] Generally, the refrigerant temperature sensor 24 is provided on the upstream side of the refrigerant flow path. Therefore, as shown in the illustrated example, the detected value of the refrigerant temperature remains at Tc, but if the refrigerant temperature around the switching element rises to a temperature Tc' due to heat generation by the element, the relationship between the current and the temperature rise is as shown by the curve 26.

[0068] On the other hand, since the 2nd temperature estimation section 12 recognizes the refrigerant temperature as Tc, the 2nd temperature estimation characteristic curve 25 is output with the temperature Tvl of the switching element Svn as the intersection point. Therefore, according to the present embodiment, the estimated temperature rise ΔTu_est of the U phase is estimated to be higher than the actual temperature, thereby exerting a protective effect on the switching element earlier than the overtemperature.

[0069] As described above, the power conversion device of the present embodiment is provided with a refrigerant temperature sensor 24 that acquires the temperature of the refrigerant that cools a plurality of switching elements Sup, Sun, Svp, Svn, Swp, Swn corresponding to the upper and lower arms of each phase of the motor 5, temperature sensors Tu, Tv, Tw that measure the temperature of the switching elements Sun, Svn, Swn on one arm (lower arm) side among the plurality of switching elements Sup, Sun, Svp, Svn, Swp, Swn, a 1st temperature estimation section 11 that estimates an estimated temperature based on the temperature rise amount ΔTest1, ΔTest2 of each switching element when the switching element operates according to the drive condition 19 of the switching element, and a 2nd temperature estimation section 12 that, in the case where the measured temperature (actual temperature Tnmax) measured by the temperature sensors Tu, Tv, Tw of the switching elements Sun, Svn, Swn on one arm (lower arm) side is higher than the estimated temperature based on the temperature rise amount estimated by the 1st temperature estimation section 11, corrects the temperature rise amount (ΔTest1, ΔTest2) estimated by the 1st temperature estimation section 11 for the switching elements on the other arm (upper arm) side according to the ratio ((Tact-Tc) / ΔTest1) of the difference (Tact-Tc) between the measured temperature (actual temperature Tact) and the refrigerant temperature Tc divided by the temperature rise amount (ΔTest1), thereby estimating the predicted temperature Test2c of the other switching elements Sup, Svp, Swp on the other arm (upper arm) side (corresponding to the "corrected estimated temperature" illustrated). Figure 2

[0070] ​Thus, even when the cooling system of the switching element is abnormal, the predicted temperature of the other switching element can be correctly estimated from the measured temperature of the temperature sensor Tu, Tv, Tw provided only on one switching element Sun, Svn, Swn. Thus, even when the cooling system of the switching element is abnormal, the actual temperature of the other switching element Sup, Svp, Swp does not become excessively high.

[0071] The power conversion device of the embodiment has the motor control section 10 as an example of the drive control section that changes the drive condition 19 of the switching element, and in a case where either the measured temperature of the temperature sensor Tu, Tv, Tw or the predicted temperature (the corrected predicted temperature) estimated by the 2nd temperature estimation section 12 exceeds a prescribed threshold temperature, the motor control section 10 limits the drive condition of the switching element. Here, limiting the drive condition of the switching element means, for example, stopping the motor or making it within the threshold temperature. Thus, failure of the switching element due to over-temperature can be prevented.

[0072] In the embodiment, in a case where the rotational speed of the motor 5 is less than a prescribed value (for example, in a case of extremely low speed), the motor control section 10 changes the drive condition 19 of the switching element in accordance with the predicted temperature (corresponding to the "corrected predicted temperature" of the above-described "predicted temperature") estimated by the 2nd temperature estimation section 12. Thus, in a case where the rotational speed of the motor 5 is less than a prescribed value (for example, in a case of extremely low speed), the switching element of the upper arm can excessively heat, but by changing the drive condition 19 of the switching element in accordance with the predicted temperature, excessive heating can actually be avoided. Figure 2

[0073] The motor control section 10 generates the current command value 22 in accordance with the direct-current voltage detection value 15 that indicates the value of the direct-current voltage of the direct-current voltage source 1, the alternating-current current detection value 16 that indicates the value of the alternating-current current input to the motor 5, and the angle detection value 17 of the motor 5, and also calculates the drive condition 19 of the switching element in the process of generating the current command value 22. Thus, the motor control section 10 can prevent the switching elements Sup, Svp, Swp, Sun, Svn, Swn from being excessively heated due to the driving of the motor 5, and thus can prevent failure of the switching elements Sup, Svp, Swp, Sun, Svn, Swn.

[0074] The motor control section 10 outputs the drive condition 19 of the switching element calculated as described above to the 1st temperature estimation section 11. Thus, since the 1st temperature estimation section 11 can take the drive condition 19 into consideration to estimate the temperature, the 1st temperature estimation section 11 can more correctly estimate the temperature of the switching elements Sup, Svp, Swp.

[0075] ​In addition, the present application is not limited to the above-described embodiments, and various modifications and equivalent configurations within the spirit of the appended claims are included. For example, the above-described embodiments are described in detail in order to easily understand the present application, and the present application is not necessarily limited to having all the configurations described.

[0076] In the above-described embodiments, a 3-phase power conversion device is described as an example, but the present embodiment is not necessarily limited to 3-phase, and can be applied to a multi-phase or more.

[0077] Industrial Applicability

[0078] The present application can be applied to a power conversion device related to a technology of measuring temperatures of U-phase, V-phase, and W-phase switching elements.

[0079] Explanation of Symbols

[0080] 1…DC voltage source, 2…smoothing capacitor, 3…DC voltage sensor, 4…AC current sensor, 5…motor, 6…angle sensor, 7…control device, 8…gate drive circuit, 9…temperature detection circuit, 10…motor control section, 11…1st temperature estimation section, 12…2nd temperature estimation section, 13…current control section, 14…motor control command, 15…DC voltage detection value, 16…AC current detection value, 17…motor angle detection value, 18…temperature detection value, 19…switching element drive condition, 20…1st temperature estimation value, 21…2nd temperature estimation value, 22…current command value, 23…gate drive signal, 24…refrigerant temperature sensor.

Claims

1. A power conversion device, characterized in that, have: The refrigerant temperature acquisition unit acquires the temperature of the refrigerant used to cool multiple switching elements corresponding to the upper and lower arms of each phase of the power conversion device. A temperature sensor that measures the temperature of one arm-side switching element among the plurality of switching elements; The first temperature estimation unit estimates the temperature based on the estimated temperature of each switching element when it operates according to the driving conditions of the switching element. as well as The second temperature estimation unit, when the measured temperature of the switching element on one arm side measured by the temperature sensor is higher than the estimated temperature estimated by the first temperature estimation unit based on the temperature rise, corrects the temperature rise estimated by the first temperature estimation unit for the switching element on the other arm side by dividing the difference between the measured temperature and the refrigerant temperature by the temperature rise, thereby estimating the predicted temperature of the other switching element on the other arm side.

2. The power conversion device according to claim 1, characterized in that, A drive control unit capable of changing the drive conditions of the switching element. If the drive control unit exceeds a predetermined threshold temperature in either the measured temperature of the temperature sensor or the predicted temperature estimated by the second temperature estimation unit, the drive control unit restricts the drive conditions of the switching element.

3. The power conversion device according to claim 1, characterized in that, When the motor speed is less than a predetermined value, the drive control unit changes the drive conditions of the switching element based on the predicted temperature estimated by the second temperature estimation unit.

4. The power conversion device according to claim 2 or 3, characterized in that, The drive control unit generates a current command based on a DC voltage detection value representing the value of the DC voltage source, an AC current detection value representing the value of the AC current input to the motor, and an angle detection value of the motor. During the generation of the current command, the drive conditions of the plurality of switching elements are calculated.

5. The power conversion device according to claim 4, characterized in that, The drive control unit outputs the calculated drive conditions of the plurality of switching elements to the first temperature estimation unit.

6. A power conversion method, which is a power conversion method in a power conversion device. The power conversion method is characterized by having: The refrigerant temperature acquisition step involves the refrigerant temperature acquisition unit acquiring the temperature of the refrigerant used to cool multiple switching elements corresponding to the upper and lower arms of each phase of the power conversion device. The temperature measurement step of the switching element involves a temperature sensor measuring the temperature of one arm-side switching element among the plurality of switching elements. The first temperature estimation step involves the first temperature estimation unit estimating a temperature based on the estimated temperature rise of each switching element when it operates according to the driving conditions of the switching element. as well as In the second temperature estimation step, if the measured temperature of the switching element on one arm side measured by the temperature sensor is higher than the estimated temperature estimated by the first temperature estimation unit based on the temperature rise, the second temperature estimation unit corrects the temperature rise estimated by the first temperature estimation unit for the switching element on the other arm side according to the ratio of the difference between the measured temperature and the temperature of the refrigerant divided by the temperature rise, thereby estimating the predicted temperature of the other switching element on the other arm side.

7. The power conversion method according to claim 6, characterized in that, If the drive control unit that changes the drive conditions of the switching element exceeds a predetermined threshold temperature, the drive control unit restricts the drive conditions of the switching element.

8. The power conversion method according to claim 6, characterized in that, When the motor speed is less than a predetermined value, the drive control unit changes the drive conditions of the switching element based on the predicted temperature estimated by the second temperature estimation unit.

9. The power conversion method according to claim 7 or 8, characterized in that, The drive control unit generates a current command based on a DC voltage detection value representing the value of the DC voltage source, an AC current detection value representing the value of the AC current input to the motor, and an angle detection value of the motor. During the generation of the current command, the drive conditions of the plurality of switching elements are calculated.

10. The power conversion method according to claim 9, characterized in that, The drive control unit outputs the calculated drive conditions of the plurality of switching elements to the first temperature estimation unit.

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