Capacitor temperature estimation device, capacitor temperature estimation method, and power conversion control device

Abstract

In a capacitor temperature estimation device 10 for estimating the temperature of a capacitor 24 of an inverter 23 in a motor drive system 1, a pre-filter processing estimation unit 11 calculates a temperature rise estimation value of the capacitor 24 on the basis of a data table 15 having a motor rotation speed, a torque command value, and a DC voltage of the motor drive system 1 as parameters. A filter processing part 12 corrects the temperature rise estimation value via low-pass filter processing based on a thermal time constant of the capacitor. A disturbance correction unit 13 further corrects the temperature rise estimation value after the low-pass filter processing via disturbance correction based on a refrigerant flow rate, the ambient temperature of the capacitor 24, and a refrigerant temperature. A temperature estimation unit 14 calculates a temperature estimation value of the capacitor 24 by adding the temperature rise estimation value after the disturbance correction to the refrigerant temperature detection value.

Description

Capacitor temperature estimation device, capacitor temperature estimation method, and power conversion control device

[0001] The present invention relates to a temperature protection technology for a DC smoothing capacitor in a motor drive system.

[0002] DC smoothing capacitors (hereinafter referred to as "capacitors") used in inverter devices for driving motors in applications such as electric vehicles (EVs) generate heat due to the flow of ripple current caused by the switching operation of the inverter device. If this heat generation exceeds the maximum allowable temperature of the capacitor, it may result in a shortened lifespan of the capacitor. Therefore, a temperature sensor is typically used to monitor the capacitor temperature, and control is performed to prevent the temperature from exceeding the maximum allowable temperature. For example, if the capacitor temperature exceeds the maximum allowable temperature, control such as reducing the torque command of the inverter is performed to reduce the current flowing through the capacitor and lower the capacitor temperature.

[0003] The above-mentioned control method requires the temperature sensor, which is not preferable from the viewpoint of reducing the cost and size of the inverter. Furthermore, a temperature sensorless system has advantages in terms of cost, but since it is not possible to monitor the temperature, there is a risk of overheating due to the maximum allowable temperature being exceeded.

[0004] To solve the above problems, a prior art capacitor temperature estimation method is disclosed in Patent Document 1, which estimates the capacitor temperature without a temperature sensor. This estimation method first calculates the ripple current of the capacitor based on the DC voltage of the inverter. Next, the temperature increase of the capacitor per predetermined time is estimated based on the square of this ripple current. This temperature increase is then added to the refrigerant temperature to calculate the capacitor temperature after the predetermined time has elapsed.

[0005] Patent No. 5928260

[0006] However, the above-described conventional capacitor temperature estimation method does not take into consideration the thermal time constant of the capacitor or the influence of external disturbances, and therefore cannot estimate the capacitor temperature with high accuracy.

[0007] In view of the above circumstances, an object of the present invention is to accurately estimate the temperature of a capacitor in a motor drive system without using a capacitor temperature sensor.

[0008] Therefore, one aspect of the present invention is a capacitor temperature estimation device that estimates the temperature of a DC smoothing capacitor of an inverter in a motor drive system, and includes: a pre-filtering estimation unit that calculates an estimated temperature rise value of the DC smoothing capacitor based on a data table having parameters of a motor rotation speed, a torque command value, and a DC voltage of the motor drive system; a filtering processing unit that corrects the estimated temperature rise value by low-pass filtering based on a thermal time constant of the DC smoothing capacitor; a disturbance correction unit that further corrects the estimated temperature rise value after the low-pass filtering by disturbance correction based on a refrigerant flow rate, an ambient temperature of the DC smoothing capacitor, and a refrigerant temperature; and a temperature estimator that calculates the estimated temperature value of the DC smoothing capacitor by adding the disturbance-corrected estimated temperature rise value to a detected refrigerant temperature value.

[0009] In one aspect of the present invention, in the capacitor temperature estimation device, disturbance correction based on the ambient temperature of the DC smoothing capacitor is performed by adding a correction value based on the maximum ambient temperature of the DC smoothing capacitor obtained during trial operation of the inverter to the temperature rise estimate value that has been disturbance-corrected based on the refrigerant flow rate.

[0010] In one aspect of the present invention, in the capacitor temperature estimation device, the data table is created based on the results of a trial run of the inverter for creating the data table, the thermal time constant is set based on the results of a trial run of the inverter for setting the thermal time constant, a flow rate correction coefficient for the refrigerant flow rate-based disturbance correction is set based on the results of the trial run of the inverter for setting the flow rate correction coefficient, a correction value based on a maximum ambient temperature of the DC smoothing capacitor is set based on the difference between the temperature rise estimated value after the low-pass filter processing at the initial ambient temperature of the DC smoothing capacitor and the temperature rise estimated value after the low-pass filter processing at the maximum ambient temperature of the DC smoothing capacitor, and the refrigerant temperature-based disturbance correction is performed by adding the correction value, which is set based on the results of a trial run of the inverter for setting the correction value based on the maximum ambient temperature of the DC smoothing capacitor at that refrigerant temperature, to the temperature rise estimated value after the low-pass filter processing.

[0011] In one aspect of the present invention, the capacitor temperature estimation device further includes an initial estimation processing unit that calculates an initial temperature estimate of the DC smoothing capacitor when operation of the inverter is resumed based on the temperature estimate value when the inverter is stopped, the stop time of the inverter, and the refrigerant temperature, and adds the difference between this initial temperature estimate and the refrigerant temperature to the temperature rise estimate value after the low-pass filter processing.

[0012] In one aspect of the present invention, the capacitor temperature estimation device further includes an initial estimation processing unit that adds a difference between a peripheral component temperature of the DC smoothing capacitor and the refrigerant temperature to the temperature rise estimated value after the low-pass filter processing.

[0013] One aspect of the present invention is a capacitor temperature estimation method for estimating the temperature of a DC smoothing capacitor of an inverter in a motor drive system, comprising the steps of: calculating an estimated temperature rise value of the DC smoothing capacitor based on a data table having parameters of a motor rotation speed, a torque command value, and a DC voltage of the inverter in the motor drive system; correcting the estimated temperature rise value by low-pass filtering based on a thermal time constant of the DC smoothing capacitor; further correcting the estimated temperature rise value after the low-pass filtering by disturbance correction based on a refrigerant flow rate, an ambient temperature of the DC smoothing capacitor, and a refrigerant temperature; and calculating the estimated temperature value of the DC smoothing capacitor by adding the disturbance-corrected estimated temperature rise value to a detected refrigerant temperature value.

[0014] One aspect of the present invention is a power conversion control device including the capacitor temperature estimation device described above.

[0015] According to the present invention as described above, the temperature of the capacitor in the motor drive system can be estimated with high accuracy without a capacitor temperature sensor.

[0016] 1 is a block diagram of a power conversion control device to which a capacitor temperature estimation device according to a first embodiment of the present invention is applied; FIG. 2 is a control block diagram of capacitor temperature estimation according to the first embodiment; FIG. 3 is a block diagram of a capacitor temperature estimation device according to a second embodiment of the present invention; and FIG. 4 is a control block diagram of capacitor temperature estimation according to the second embodiment.

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0018] First Embodiment A capacitor temperature estimation device 10 according to a first embodiment of the present invention shown in FIG. 1 is applied to a motor drive system 1 for use in an EV, for example.

[0019] The motor drive system 1 includes a drive circuit 2 that drives the motor M, and a power conversion control device 3 that controls the drive circuit 2 .

[0020] The drive circuit 2 includes a battery 21, a converter 22, an inverter 23, a capacitor 24, a cooling unit 25, a flow rate / temperature sensor 26, and a voltage sensor 27. The battery 21 supplies power to the motor M via the converter 22 and the inverter 23. The converter 22 boosts DC power from the battery 21 to a desired voltage. The inverter 23 converts the boosted DC power to AC power and supplies it to the motor M. The capacitor 24 is a DC smoothing capacitor connected between the positive and negative electrodes on the input side of the inverter 23 and smoothes DC ripple voltage generated by the switching operation of the inverter 23. The cooling unit 25 cools the inverter 23 and the capacitor 24. The cooling unit 25 includes a refrigerant flow path 28 disposed in heat-generating portions of the inverter 23 and the capacitor 24, a radiator R that cools the refrigerant (e.g., coolant or cooling oil) flowing through the refrigerant flow path 28, and a pump P that pumps the refrigerant. The flow rate and temperature sensor 26 detects the flow rate and temperature of the refrigerant in the refrigerant flow path 28 and outputs the results to the power conversion control device 3. The voltage sensor 27 measures the DC voltage input from the converter 22 to the inverter 23 and outputs the results to the power conversion control device 3. The power conversion control device 3 outputs a PWM signal to the converter 22 and the inverter 23 based on the DC voltage, the motor current of the motor M, the motor rotation speed, etc.

[0021] The power conversion control device 3 also includes a capacitor temperature estimation device 10. The capacitor temperature estimation device 10 performs low-pass filtering and disturbance correction on an estimated temperature rise value of the capacitor 24, which is based on the motor rotation speed, torque command value, and DC voltage of the inverter 23, and then adds the estimated temperature value to the refrigerant temperature detected by the flow rate temperature sensor 26 to calculate an estimated temperature value of the capacitor 24. This estimated temperature value is used for PWM control of the inverter 23 to control the motor current of the motor M (see Patent Document 1).

[0022] The capacitor temperature estimation device 10 includes a pre-filtering estimation unit 11, a filtering unit 12, a disturbance correction unit 13, and a temperature estimation unit 14.

[0023] When the pre-filtering estimation unit 11 receives the motor rotation speed, torque command value, and DC voltage of the motor drive system 1 as input, it calculates an estimated temperature rise value of the capacitor 24 based on a data table 15 that uses the motor rotation speed, torque command value, and DC voltage as parameters. The data table 15 stores the relationship between the motor rotation speed, torque command value, and DC voltage and the estimated temperature rise value based on a test run of the inverter 23.

[0024] The filter processing unit 12 corrects the estimated temperature rise value by low-pass filtering (hereinafter referred to as LPF processing) based on the thermal time constant of the capacitor 24. The thermal time constant is set based on the results of a trial run of the inverter 23 for setting this thermal time constant.

[0025] The disturbance correction unit 13 further corrects the temperature rise estimated value after the low-pass filtering process using disturbance correction based on the refrigerant flow rate, the ambient temperature of the condenser 24, and the refrigerant temperature. A flow rate correction coefficient for the disturbance correction based on the refrigerant flow rate is set based on the results of a trial run of the inverter 23 for setting this flow rate correction coefficient. The disturbance correction based on the ambient temperature of the condenser 24 is performed by adding a correction value based on the maximum ambient temperature of the condenser 24 obtained during the trial run of the inverter 23 (i.e., the maximum capacitor ambient temperature that can be expected during actual operation of the inverter 23) to the temperature rise estimated value that has been disturbance-corrected based on the refrigerant flow rate. The correction value based on the maximum ambient temperature of the condenser 24 is set based on the difference between the temperature rise estimated value after the low-pass filtering process at the initial ambient temperature of the condenser 24 and the temperature rise estimated value after the low-pass filtering process at the maximum ambient temperature of the condenser 24. The disturbance correction based on the refrigerant temperature is performed by adding a correction value set based on the test run results of the inverter 23 to the estimated temperature rise value after the low-pass filter processing in order to set a correction value based on the maximum ambient temperature of the capacitor 24 at that refrigerant temperature.

[0026] The temperature estimator 14 calculates an estimated temperature value of the condenser 24 by adding the estimated temperature rise value after the disturbance correction to the detected refrigerant temperature value.

[0027] The process of estimating the temperature of the capacitor 24 in this embodiment will be described with reference to FIG.

[0028] S1: Upon receiving the motor rotation speed, torque command value, and DC voltage of the motor drive system 1, the pre-filtering estimation unit 11 calculates an estimated temperature rise value of the capacitor 24 by referring to the data table 15.

[0029] The heat generated by the capacitor 24 is divided into a self-heating component due to the ripple current flowing through the capacitor 24 and a disturbance component. Since the heat generated by the ripple current Irip flowing through the capacitor 24 depends on the square of the effective value of the ripple current Irip, the self-heating component is calculated as an estimated temperature rise ΔT by the calculation of the following equation (1):

[0030] ΔT: Estimated temperature rise value ΔTc: Heat generation temperature of the capacitor 24 Irip: Ripple current flowing through the capacitor 24 Irip ｃ : Ripple current flowing through capacitor 24 when heat is generated at heat temperature ΔTc

[0031] Heat generation temperature ΔTc and ripple current Irip ｃ is a value given in the catalogue of the capacitor 24. The catalogue also gives the values ​​of the heat generation temperature ΔTc and the ripple current Irip ｃ If there is no description, the ripple current Irip ｃ The actual measured temperature rise value of the capacitor 24 when the test run of the inverter 23 is performed under the condition that the current flows is set as the heat generation temperature ΔTc.

[0032] Since the ripple current Irip varies depending on the motor rotation speed, the torque command value of the motor M input to the inverter 23, and the DC voltage input to the inverter 23, an estimated temperature rise value ΔT, which is the self-heating component corresponding to this ripple current Irip, is stored in the data table 15.

[0033] A method for creating the data table 15 will be described below.

[0034] First, a trial run of the inverter 23 is performed to create the data table 15. In this trial run, the inverter 23 is operated for each of the parameters (detected motor rotation speed value, torque command value, and detected DC voltage value), the current of the capacitor 24 is measured, and an estimated temperature rise ΔT is calculated offline using equation (1). Then, this estimated temperature rise ΔT is stored in the data table 15 in association with the parameter.

[0035] S2: The filter processing unit 12 corrects the estimated temperature rise ΔT obtained in step S1 by LPF processing based on the thermal time constant of the capacitor 24.

[0036] The temperature of the capacitor 24 has a thermal time constant, but the estimated temperature rise ΔT calculated by equation (1) is a temperature rise value at temperature saturation that does not take the thermal time constant into consideration.

[0037] Therefore, in the LPF processing, the estimated temperature rise value ΔT output from the data table 15 is corrected by calculating the following equation (2) taking into account the thermal time constant, thereby improving the accuracy of the estimated temperature rise value ΔT.

[0038]

[0039] T is a thermal time constant, which is set based on a trial run of the inverter 23. In this trial run, a temperature sensor (not shown) is attached to the capacitor 24, and the temperature change of the capacitor 24 after the inverter 23 starts operating under each combination of parameters (motor rotation speed, torque command value, and DC voltage) is recorded, and the thermal time constant is calculated from the waveform of this temperature change.

[0040] 1 (trigger signal for starting current flow to the capacitor 24) is received (hereinafter referred to as the calculation sampling time). If the thermal time constant T is listed in the catalog for the capacitor 24, the thermal time constant T listed in the catalog may be used instead of the calculated value of the thermal time constant obtained through the trial run.

[0041] Furthermore, there may be cases where each parameter fluctuates during the correction calculation of equation (2). Therefore, equation (2) is calculated at each calculation sampling time (e.g., 5 ms), and the result is added to ΔT (after thermal time constant correction) at the previous sampling time. In this calculation, ΔT (before thermal time constant correction) is input at each calculation sampling. The calculation sampling time (e.g., 5 ms) is input each time.

[0042] S3: The disturbance corrector 13 further corrects the post-LPF temperature rise estimate ΔT (after thermal time constant correction) obtained in step S2 by performing disturbance correction based on the refrigerant flow rate, the ambient temperature of the condenser 24, and the refrigerant temperature.

[0043] (Disturbance Correction [1] Based on Refrigerant Flow Rate) The value of the estimated temperature rise ΔT (after thermal time constant correction) depends on the refrigerant flow rate. Therefore, in disturbance correction [1], the value of ΔT (after thermal time constant correction) in equation (2) obtained in step S2 is multiplied by a flow rate correction coefficient C, as shown in the following equation (3). The flow rate correction coefficient C is set according to the refrigerant flow rate shown in Table 1.

[0044]

[0045]

[0046] The flow rate correction coefficient C is calculated by performing a test run of the inverter 23 to set the flow rate correction coefficient. In this test, a temperature sensor (not shown) is attached to the capacitor 24, and the temperature change value (at temperature saturation) of the capacitor 24 is measured under conditions of a combination of parameters (e.g., motor rotation speed, torque command value, and DC voltage) and the refrigerant flow rate measured by the flow rate temperature sensor 26. Then, the ratio of the measured temperature change value to the temperature change value of the condenser 24 at a reference refrigerant flow rate (e.g., 9 L / min) is calculated as the flow rate correction coefficient C.

[0047] (Disturbance Correction Based on Ambient Temperature of Capacitor 24 [2]) The temperature rise of the capacitor 24 depends not only on the above-mentioned parameters (motor rotation speed, torque command value, DC voltage) and the amount of cooling water, but also on the ambient temperature of the capacitor 24.

[0048] In order to accurately correct the estimated temperature rise of capacitor 24 taking into account the ambient temperature of capacitor 24, a sensor is required to detect the ambient temperature of capacitor 24. However, installing such a sensor is undesirable in terms of reducing the cost and size of inverter 23.

[0049] Therefore, in the disturbance correction [2], correction is performed assuming that the ambient temperature is the maximum ambient temperature (e.g., 105°C) measured during a test run of the inverter 23. The correction value based on this disturbance correction [2] is calculated, for example, by the following test run.

[0050] First, an estimated temperature rise value (ΔT value in equation (3)) of the capacitor 24 is calculated under the conditions of a combination of various parameters (e.g., motor rotation speed, torque command value, and DC voltage) and a predetermined refrigerant flow rate, based on the initial ambient temperature of the capacitor 24 (e.g., 25°C) during the test run of the inverter 23 up to the disturbance correction [1]. Next, the condenser 24 is heated from the initial ambient temperature to the maximum ambient temperature using an external heater or the like, and the estimated temperature rise value (ΔT value in equation (3)) of the capacitor 24 is calculated under the condition that the temperature of the refrigerant (e.g., cooling water) reaches the maximum temperature (e.g., 60°C) during the test run. The difference between these two estimated temperature rise values ​​(ΔT value in equation (3)) is then calculated as a correction value (fixed value). This correction value is added to the temperature rise value (ΔT value in equation (3)) of the capacitor 24 obtained during the disturbance correction [1].

[0051] The above disturbance correction [2] does not have good accuracy in estimating the temperature rise when the ambient temperature of the capacitor 24 is lower than its maximum temperature. However, this is not a problem because the purpose of the present invention is to reliably avoid an abnormality in which the temperature of the capacitor 24 exceeds the allowable temperature (reducing costs and size by reducing the number of temperature sensors rather than improving the accuracy of the correction amount).

[0052] Furthermore, since the correction value of disturbance correction [2] is not large compared to the temperature rise value of capacitor 24 after disturbance correction [1] (the value of ΔT in equation (3)), the error in the correction amount in disturbance correction [2] has almost no effect on the overall estimated temperature value of capacitor 24.

[0053] (Disturbance Correction Based on Refrigerant Temperature [3]) The temperature rise of the capacitor 24 depends not only on the parameters (motor rotation speed, torque command value, DC voltage) and the refrigerant flow rate, but also on the refrigerant temperature.

[0054] Therefore, in the disturbance correction [3], the detected value of the refrigerant temperature in the disturbance correction [2] is further taken into consideration. That is, a correction value based on the maximum ambient temperature of the condenser 24 at the refrigerant temperature from the flow rate temperature sensor 26 is set based on the results of a trial run of the inverter 23, and the correction value is added to the estimated temperature rise value after the low-pass filter process.

[0055] In the trial operation, the temperature of condenser 24 (at temperature saturation) is measured under a plurality of refrigerant temperature conditions, which are variably set by cooling unit 25, based on a combination of parameters (e.g., motor rotation speed, torque command value, and DC voltage), a reference refrigerant flow rate, and a maximum ambient temperature of condenser 24. The correction value is set based on the measurement results.

[0056] S4: The temperature estimator 14 calculates an estimated temperature value of the condenser 24 by adding the estimated temperature rise value after the disturbance correction [1] [2] [3] obtained in step S3 to the detected refrigerant temperature value.

[0057] The detected refrigerant temperature value is input to the temperature estimation unit 14 from the flow rate temperature sensor 26. The flow rate temperature sensor 26 is provided in the refrigerant flow path 28 of the cooling unit 25 outside the inverter 23, so there is no need to provide it inside the inverter 23.

[0058] If there is a risk that the estimated temperature value will exceed the maximum allowable temperature, the power conversion control device 3 issues an alarm and takes action such as changing the operating conditions of the inverter 23 (such as reducing the torque command) or shutting down the inverter 23 due to a fault. This prevents the capacitor 24 from being degraded in life due to high temperatures.

[0059] As described above, according to the capacitor temperature estimation device 10 of this embodiment, by adding disturbance correction [1] [2] [3] to the output of the LPF processing, highly accurate monitoring of the temperature of the capacitor 24 can be achieved without a capacitor temperature sensor.

[0060] Furthermore, the estimated temperature rise ΔT calculated offline using equation (1) is tabulated. This means that there is no need to perform the complex equation (1) online, which requires a square calculation, and the calculation load can be reduced. This is also an advantage over the prior art (Patent Document 1), which requires a square calculation online.

[0061] Furthermore, when mass-producing inverters of the same type, it is possible to arbitrarily select either 1) to perform a test run on only one representative inverter and use the test run results for the other inverters, or 2) to perform a test run on all inverters. Because there are individual differences in the temperature characteristics of capacitor 24 (variations in thermal time constants, etc.), selecting 2) enables more accurate temperature estimation of capacitor 24.

[0062] [Embodiment 2] The capacitor temperature estimation in embodiment 1 enables temperature protection in a cold start state of the inverter 23, but depending on the operating conditions of the inverter 23, temperature protection may also be necessary in a hot start state in which components such as the capacitor 24 in the inverter 23 are warm.

[0063] That is, if the inverter 23 is stopped while the capacitor 24 is heated due to a long period of operation of the motor drive system 1, the power supply to the control circuit of the inverter 23 is also cut off, and then the operation of the inverter 23 is restarted while the capacitor 24 is warmed up (hereinafter referred to as a hot start). In this case, the power supply to the microcomputer in the control circuit of the power conversion control device 3 is reset once, so that the temperature estimation in embodiment 1 starts assuming that the initial value of the temperature of the capacitor 24 is the same as the refrigerant temperature. As a result, a discrepancy occurs between the actual temperature of the capacitor 24 and the estimated temperature, which may prevent appropriate temperature protection by torque suppression or the like.

[0064] Therefore, the capacitor temperature estimation device 10 of the second embodiment shown in FIG. 3 is configured to estimate the temperature rise estimated value ΔT (after thermal time constant correction) (hereinafter referred to as the temperature rise estimated value ΔT) provided from the filter processing unit 12 to the disturbance correction unit 13 when the inverter 23 resumes operation. ＬＰＦBy providing an initial estimation processing unit 16 that corrects the temperature difference θ, temperature protection is possible even in the case of a hot start.

[0065] The temperature rise estimated value ΔT by the initial estimation processing unit 16 ＬＰＦ The following methods (1) and (2) can be used as a method for correcting the above.

[0066] The method (1) uses the estimated temperature T of the capacitor 24 stored when the inverter 23 is stopped. ＲＯＭ and the stop time Δt of the inverter 23 Ｓ Based on this, the estimated temperature rise value ΔT ＬＰＦ Correction is performed.

[0067] Method (2) is to calculate the temperature T ｔｈ Based on the estimated temperature rise ΔT ＬＰＦ Correction is performed.

[0068] The processing steps S201 and S202 of the method (1) will be described with reference to FIG.

[0069] S201: When the operation of the inverter 23 is terminated (the power supply to the inverter 23 is cut off), the estimated temperature value of the capacitor 24 calculated by the temperature estimator 14 in S4 becomes the estimated temperature value T ＲＯＭ The data is stored in an EEPROM, which is a nonvolatile memory in the control circuit of the power conversion control device 3, as the power conversion control signal.

[0070] S202: The estimated temperature value T of the capacitor 24 is read from the EEPROM. ＲＯＭ is derived. This temperature estimate T ＲＯＭ and the refrigerant temperature T from the flow rate temperature sensor 26 ｃｏｏｌ and the stop time Δt of the inverter 23 Ｓ and the thermal time constant T of the capacitor 24, the estimated initial temperature value T1 of the capacitor 24 when the operation of the inverter 23 is restarted is calculated by the following equation (4): Ｓ For example, time information received from outside the inverter 23 is used as the time information.

[0071] T1: initial temperature estimate of capacitor 24 ＲＯＭ : Estimated temperature of the capacitor 24 stored when the inverter 23 is stopped Tｃｏｏｌ : Refrigerant temperature Δt Ｓ : Stop time of inverter 23 T: Thermal time constant of capacitor 24

[0072] Next, the temperature rise estimated value ΔT from S2 (LPF processing) ＬＰＦ The initial temperature estimate T1 of the condenser 24 and the refrigerant temperature T ｃｏｏｌ The corrected temperature rise estimate value (1) ΔT is calculated by the following equation (5) ＨＯＳＥＩ（１） Calculate.

[0073] ΔT ＨＯＳＥＩ（１） : Corrected temperature rise estimate (1) ΔT ＬＰＦ : Estimated temperature rise value T1: Estimated initial temperature value of the capacitor 24 T ｃｏｏｌ : Refrigerant temperature

[0074] Then, this corrected temperature rise estimate (1) ΔT ＨＯＳＥＩ（１） is output to the disturbance correction unit 13 and is provided to S3 (disturbance correction).

[0075] According to the above method (1), the estimated temperature rise value ΔT via S2 (LPF processing) ＬＰＦ The stop time Δt of the inverter 23 Ｓ The corrected temperature rise estimate ΔT ＨＯＳＥＩ（１） This increases the accuracy of S3 (disturbance correction) and S4 (temperature estimation). Therefore, even in a hot start state, the temperature of the capacitor 24 can be estimated with high accuracy without a temperature sensor for the capacitor 24.

[0076] The method (2) is to measure the temperature T of the peripheral components of the capacitor 24 (for example, the control board on which the control circuit of the inverter 23 is mounted) detected by a thermistor used for temperature protection. ｔｈ Since the capacitor 24 and the control board are located relatively close to each other, the difference in ambient temperature between them is not large. Since the thermistor is provided as standard on the control board, method (2) can avoid increasing the size of the inverter 23.

[0077] The processing steps S203 and S204 of the method (2) will be described with reference to FIG.

[0078] S203: The temperature T of the peripheral parts of the capacitor 24 from the thermistor ｔｈ and the refrigerant temperature T from the flow rate temperature sensor 26 ｃｏｏｌ If the difference is less than a threshold, it is determined to be a "cold start," and if the difference is equal to or greater than the threshold, it is determined to be a "hot start."

[0079] S204: If it is determined that the start is a hot start, the estimated temperature rise ΔT from S2 (LPF processing) ＬＰＦ The surrounding component temperature T ｔｈ and refrigerant temperature T ｃｏｏｌ The corrected temperature rise estimate value (2) ΔT is calculated by the following equation (6) ＨＯＳＥＩ（２） Calculate.

[0080] ΔT ＨＯＳＥＩ（２） : Corrected temperature rise estimate (2) ΔT ＬＰＦ : Estimated temperature rise T ｔｈ : Surrounding parts temperature T ｃｏｏｌ : Refrigerant temperature

[0081] Then, this corrected temperature rise estimate ΔT ＨＯＳＥＩ（２） is output to the disturbance correction unit 13 and is provided to S3 (disturbance correction).

[0082] In addition, if it is determined in step S203 that the start is a cold start, the estimated temperature rise ΔT from S2 (LPF processing) is ＬＰＦ is supplied to S3 (disturbance correction) and S4 (temperature estimation) of the first embodiment without going through S204.

[0083] The above method (2) is less accurate than the method (1), but does not require complex processing. Ｓ When the time is long, the difference between the ambient temperature of the capacitor 24 and the ambient temperature of the control board is small, so method (2) is effective because it reduces the error in the estimated temperature.

[0084] Therefore, the stop time Δt of the inverter 23 Ｓ If the time is shorter than the predetermined time, the method (1) is executed, and the stop time Δt ＳIf the time is equal to or longer than the predetermined time, the method may be switched to method (2) to estimate the initial temperature of the capacitor 24 .

[0085] 1...motor drive system 2...drive circuit, 21...battery, 22...converter, 23...inverter, 24...capacitor, 25...cooling section, 26...flow rate temperature sensor, 27...voltage sensor 3...power conversion control device, 10...capacitor temperature estimation device, 11...pre-filtering estimation section, 12...filtering processing section, 13...disturbance correction section, 14...temperature estimation section, 15...data table, 16...initial estimation processing section

Claims

1. A capacitor temperature estimation device for estimating the temperature of a DC smoothing capacitor in a motor drive system, comprising: A pre-filter processing unit that calculates an estimated value of the temperature rise of the DC smoothing capacitor based on a data table using the motor speed, torque command value, and DC voltage of the motor drive system as parameters; A filter processing unit that corrects the estimated temperature rise value by low-pass filter processing based on the thermal time constant of the DC smoothing capacitor; A disturbance correction unit that further corrects the estimated temperature rise value after the low-pass filter processing by disturbance correction based on the refrigerant flow rate, the ambient temperature of the DC smoothing capacitor, and the refrigerant temperature; A temperature estimation unit that adds the estimated temperature rise value after the disturbance correction to the refrigerant temperature detection value to calculate the estimated temperature of the DC smoothing capacitor. A capacitor temperature estimation device characterized by comprising the above components.

2. The disturbance correction based on the ambient temperature of the DC smoothing capacitor is characterized in that a correction value based on the highest ambient temperature of the DC smoothing capacitor obtained during the trial operation of the inverter is added to the estimated temperature rise value that has been disturbance-corrected based on the refrigerant flow rate. The capacitor temperature estimation device according to claim 1.

3. The data table is created based on the trial operation results of the inverter for creating this data table. The thermal time constant is set based on the trial operation results of the inverter for setting this thermal time constant. The flow rate correction coefficient for disturbance correction based on the refrigerant flow rate is set based on the trial operation results of the inverter for setting this flow rate correction coefficient. The correction value based on the highest ambient temperature of the DC smoothing capacitor is set based on the difference between the estimated temperature rise value after the low-pass filter processing at the initial ambient temperature of the DC smoothing capacitor and the estimated temperature rise value after the low-pass filter processing at the highest ambient temperature of the DC smoothing capacitor. The disturbance correction based on the refrigerant temperature is characterized in that the correction value set based on the trial operation results of the inverter for setting the correction value based on the highest ambient temperature of the DC smoothing capacitor at the refrigerant temperature is added to the estimated temperature rise value after the low-pass filter processing. The capacitor temperature estimation device according to claim 2.

4. An initial estimation processing unit is further provided which calculates an initial temperature estimation value of the DC smoothing capacitor when the operation of the inverter resumes based on the temperature estimation value at the time of stopping of the inverter, the stop time of the inverter, and the refrigerant temperature, and adds the difference between this initial temperature estimation value and the refrigerant temperature to the temperature rise estimation value after the low-pass filter processing. The capacitor temperature estimation device according to claim 1, characterized in that it has this.

5. An initial estimation processing unit is further provided which adds the difference between the temperature of the peripheral components of the DC smoothing capacitor and the refrigerant temperature to the temperature rise estimation value after the low-pass filter processing. The capacitor temperature estimation device according to claim 1, characterized in that it has this.

6. A capacitor temperature estimation method for estimating the temperature of a DC smoothing capacitor of an inverter in a motor drive system, comprising: a process of calculating a temperature rise estimation value of the DC smoothing capacitor based on a data table using the motor speed, torque command value, and DC voltage of the motor drive system as parameters; a process of correcting the temperature rise estimation value by low-pass filter processing based on the thermal time constant of the DC smoothing capacitor; a process of further correcting the temperature rise estimation value after the low-pass filter processing by disturbance correction based on the refrigerant flow rate, the ambient temperature of the DC smoothing capacitor, and the refrigerant temperature; and a process of calculating the temperature estimation value of the DC smoothing capacitor by adding the temperature rise estimation value after the disturbance correction to the refrigerant temperature detection value. The capacitor temperature estimation method is characterized by having these processes.

7. A power conversion control device, characterized in that it includes the capacitor temperature estimation device according to claim 1.

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