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

Abstract

To accurately estimate the temperature of a capacitor in a motor drive system without using a capacitor temperature sensor. [Solution] In a capacitor temperature estimation device 10 that estimates the temperature of a capacitor 24 of an inverter 23 in a motor drive system 1, a pre-filter processing estimation unit 11 calculates an estimated temperature rise value of the capacitor 24 based on a data table 15 having parameters of the motor rotation speed, torque command value, and DC voltage of the motor drive system 1. A filter processing unit 12 corrects the estimated temperature rise value by low-pass filter processing based on the thermal time constant of the capacitor. A disturbance correction unit 13 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 condenser 24, and the refrigerant temperature. A temperature estimation unit 14 adds the estimated temperature rise value after the disturbance correction to a detected refrigerant temperature value to calculate an estimated temperature value of the capacitor 24.

Description

[Technical field]

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

[0002] A DC smoothing capacitor (hereinafter, "capacitor") used in an inverter device for driving a motor in an EV (electric vehicle) or the like generates 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. For this reason, a temperature sensor is usually used to monitor the capacitor temperature, and control is performed so that the temperature does not exceed the maximum allowable temperature. For example, when the capacitor temperature exceeds the maximum allowable temperature, control is performed to reduce the current flowing through the capacitor by reducing the torque command of the inverter, etc., thereby reducing 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. Although there is an advantage in terms of cost, etc. in making the inverter temperature sensorless, the inability to monitor the temperature may lead to overheating due to the maximum allowable temperature being exceeded.

[0004] To solve the above problems, a capacitor temperature estimation method described in Patent Document 1 is a prior art that estimates the capacitor temperature without a temperature sensor. In this estimation method, first, the ripple current of the capacitor is calculated based on the DC voltage of the inverter. Next, the temperature increase of the capacitor per given 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 given time has elapsed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5928260 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the above-mentioned conventional capacitor temperature estimation method does not take into account the thermal time constant of the capacitor or the influence of 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. [Means for solving the problem]

[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, the device estimating the temperature 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. first a pre-filtering estimation unit for calculating a temperature rise estimation value; first The estimated temperature rise is filtered using a low-pass filter based on the thermal time constant of the DC smoothing capacitor. Second temperature rise estimate A filter processing unit for performing correction; The second Estimated temperature rise A first disturbance correction value obtained by multiplying the above by a flow rate correction coefficient, Based on the ambient temperature of the DC smoothing capacitor A second disturbance correction value; Coolant temperature and a third disturbance correction value based on the third temperature rise estimate value. a disturbance correction unit for correcting the third Estimated temperature rise The refrigerant temperature a temperature estimator that calculates an estimated temperature value of the DC smoothing capacitor by adding The flow rate correction coefficient is a value based on the refrigerant flow rate, the ambient temperature of the DC smoothing capacitor is the maximum ambient temperature measured during a test run of the inverter, and the refrigerant temperature is a value detected by a sensor. .

[0010] In one aspect of the present invention, the data table is created based on a test run result of the inverter for creating the data table, and the thermal time constant is set based on a test run result of the inverter for setting the thermal time constant, The above The flow rate correction coefficient is set based on the test run results of the inverter for setting the flow rate correction coefficient, Second disturbance compensationA positive value is the above-mentioned at the initial ambient temperature of the DC smoothing capacitor. second The estimated temperature rise and the maximum ambient temperature of the DC smoothing capacitor second It is set based on the difference with the estimated temperature rise value, The third disturbance correction value is A correction value based on the maximum ambient temperature of the DC smoothing capacitor at the refrigerant temperature is set based on the test run results of the inverter. Will be .

[0011] In one aspect of the present invention, in the capacitor temperature estimation device, an initial temperature estimate of the DC smoothing capacitor when the operation of the inverter is resumed is calculated based on the temperature estimate value when the inverter is stopped, the stop time of the inverter, and the refrigerant temperature, and a difference between this initial temperature estimate value and the refrigerant temperature is calculated. second The device further includes an initial estimation processor that adds to the temperature rise estimate.

[0012] In one aspect of the present invention, in the capacitor temperature estimation device, a difference between the peripheral component temperature of the DC smoothing capacitor and the refrigerant temperature is second The device further includes an initial estimation processor that adds to the temperature rise estimate.

[0013] One aspect of the present invention is a capacitor temperature estimation method for estimating a temperature of a DC smoothing capacitor of an inverter in a motor drive system, the method comprising: determining a temperature 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; first calculating an estimated temperature rise; first The estimated temperature rise is filtered using a low-pass filter based on the thermal time constant of the DC smoothing capacitor. Second temperature rise estimate The correction process, The second Estimated temperature rise A first disturbance correction value obtained by multiplying the above by a flow rate correction coefficient, Based on the ambient temperature of the DC smoothing capacitor A second disturbance correction value; Refrigerant temperature A third temperature rise estimated value is calculated by adding a third disturbance correction value based on and third Estimated temperature rise The refrigerant temperature and calculating a temperature estimate of the DC smoothing capacitor by adding the calculated temperature estimate to the DC smoothing capacitor. The flow rate correction coefficient is a value based on the refrigerant flow rate, the ambient temperature of the DC smoothing capacitor is the maximum ambient temperature measured during a test run of the inverter, and the refrigerant temperature is a value detected by a sensor. .

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

[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. [Brief description of the drawings]

[0016] [Figure 1] 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. [Diagram 2] FIG. 2 is a control block diagram of the condenser temperature estimation according to the first embodiment. [Diagram 3] FIG. 4 is a block diagram of a capacitor temperature estimation device according to a second embodiment of the present invention. [Figure 4] FIG. 11 is a control block diagram of a condenser temperature estimation according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0018] [Embodiment 1] A capacitor temperature estimation device 10 according to a first embodiment, which is an aspect 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 a 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 the DC power from the battery 21 to a desired voltage. The inverter 23 converts the boosted DC power into 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 a heat generating portion of the inverter 23 and the capacitor 24, a radiator R that cools the refrigerant (e.g., cooling water 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 based on the DC voltage, the motor current of the motor M, the motor rotation speed, etc. to the converter 22 and the inverter 23.

[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 further disturbance correction on an estimated temperature rise value of the capacitor 24, which is based on the motor speed, torque command value, and DC voltage of the inverter 23, and then adds the estimated temperature rise value of the capacitor 24 to the refrigerant temperature detection value from the flow rate temperature sensor 26 to calculate an estimated temperature value of the capacitor 24. This estimated temperature value is provided to the PWM control of the inverter 23 to control the motor current of the motor M (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, it estimates the capacitance of the capacitor 24 based on a data table 15 having the motor rotation speed, torque command value, and DC voltage as parameters. first The data table 15 stores the motor speed, the torque command value, the DC voltage, and the first The relationship with the estimated temperature rise value is stored.

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

[0025] The disturbance correction unit 13 is The second signal from the filter processing unit 12 The temperature rise estimate is based on the refrigerant flow rate, the ambient temperature of the condenser 24, and the refrigerant temperature. Third temperature rise estimate Correct the amount of refrigerant based on the flow rate. Used to calculate the first disturbance correction value The flow rate correction coefficient is set based on the test run results of the inverter 23 for setting the flow rate correction coefficient. correction is based on the maximum ambient temperature of the capacitor 24 obtained during the test run of the inverter 23 (i.e., the maximum ambient temperature of the capacitor that can be assumed during the actual operation of the inverter 23). The second disturbance The correction value is determined based on the refrigerant flow rate. correction The above First disturbance correction value Based on the maximum ambient temperature of the capacitor 24 The second disturbance The correction value is the initial ambient temperature of the capacitor 24. The second Estimated temperature rise and maximum ambient temperature of capacitor 24 The second The temperature rise is set based on the difference between the estimated temperature rise and the coolant temperature. correction is a correction value set based on the test run results of the inverter 23 for setting a correction value based on the maximum ambient temperature of the condenser 24 at the refrigerant temperature. (Third disturbance correction value) of, A value obtained by adding the second disturbance correction value to the first disturbance correction value Add to.

[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 speed, torque command value and DC voltage of the motor drive system 1, the pre-filtering estimation unit 11 calculates an estimated value of the temperature rise 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 calculating the following equation (1).

[0030]

number

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

[0032] Since the ripple current Irip changes 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 test run of the inverter 23 is performed to create the data table 15. In this test run, the inverter 23 is operated for each of the parameters (detected motor speed value, torque command value, detected DC voltage value), the current of the capacitor 24 is measured, and an estimated temperature rise value ΔT is calculated offline using equation (1). Then, this estimated temperature rise value ΔT is stored in the data table 15 in association with the parameter.

[0035] S2: The filter processing unit 12 corrects the temperature rise estimated value 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 value ΔT calculated by the formula (1) is a temperature rise value at temperature saturation that does not take into account the thermal time constant.

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

[0038]

number

[0039] T is a thermal time constant, which is set based on a trial run of the inverter 23 to set this thermal time constant. 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 a combination of each parameter (motor speed, torque command value, 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 capacitor 24) (hereinafter, referred to as calculation sampling time). If the thermal time constant T is listed in the catalog for 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 by the trial run.

[0041] There may also be cases where the parameters fluctuate during the correction calculation of formula (2). Therefore, formula (2) is calculated at every calculation sampling time (e.g., 5 ms), and the result is added to ΔT (after thermal time constant correction) from the previous sampling. For this calculation, ΔT (before thermal time constant correction) is input for each calculation sampling. The calculation sampling time (e.g., 5 ms) is input each time.

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

[0043] (Disturbance compensation based on refrigerant flow rate [1]) The estimated temperature rise value 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 first disturbance correction value is calculated. The flow rate correction coefficient C is set according to the refrigerant flow rate shown in Table 1.

[0044]

number

[0045] [Table 1]

[0046] The flow rate correction coefficient C is calculated by performing a trial 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 condenser 24 is measured under the conditions of a combination of parameters (e.g., motor rotation speed, torque command value, 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 compensation based on the ambient temperature of the capacitor 24 [2]) The temperature rise of the capacitor 24 depends not only on the above-mentioned parameters (motor speed, torque command value, and 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 this sensor is undesirable in terms of reducing the cost and size of inverter 23.

[0049] Therefore, in the disturbance correction [2], a 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 condenser 24 is calculated under the conditions of a combination of each parameter (e.g., motor speed, torque command value, DC voltage) and a specified refrigerant flow rate, based on the initial ambient temperature of condenser 24 (e.g., 25°C) due to trial operation of inverter 23 up to disturbance correction [1]. Next, condenser 24 is heated from the initial ambient temperature to the maximum ambient temperature by an external heater or the like, and further, an estimated temperature rise value (ΔT value in equation (3)) of condenser 24 is calculated under the condition that the temperature of the refrigerant (e.g., cooling water) reaches the maximum temperature (e.g., 60°C) due to the trial operation. Then, the difference between these two estimated temperature rise values ​​(ΔT value in equation (3)) is The second disturbance This is calculated as a correction value (fixed value). The second disturbance The correction value is added to the temperature rise value of the capacitor 24 (the value of ΔT in equation (3)) obtained in 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 capacitor 24 is lower than its maximum temperature. However, this is not a problem since the purpose of the present invention is to reliably prevent the temperature of capacitor 24 from exceeding the allowable temperature (reducing cost and size by reducing the number of temperature sensors rather than improving the accuracy of the correction amount).

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

[0053] (Disturbance compensation based on coolant temperature [3]) The temperature rise of the capacitor 24 depends not only on the above-mentioned parameters (motor rotation speed, torque command value, and 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 is further considered in the disturbance correction [2]. That is, based on the result of the test run of the inverter 23 for setting a correction value based on the ambient maximum temperature of the capacitor 24 at the refrigerant temperature from the flow rate temperature sensor 26, the said correction value (Third disturbance correction value) is added to the estimated temperature rise value after the low-pass filter processing (The value obtained by adding the second disturbance correction value to the first disturbance correction value) .

[0055] In the test run, the temperature (at temperature saturation) of the capacitor 24 is measured under a plurality of refrigerant temperature conditions that can be variably set by the cooling unit 25 based on combinations of each parameter (for example, motor rotation speed, torque command value, DC voltage), the reference refrigerant flow rate, and the ambient maximum temperature of the capacitor 24. Based on this measurement result, the said correction value is set

[0056] S4: The temperature estimation unit 14 adds the estimated temperature rise value after the disturbance corrections [1][2][3] obtained in step S3 to the detected refrigerant temperature value to calculate the estimated temperature value of the capacitor 24

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

[0058] And when there is a possibility that the said estimated temperature value exceeds the allowable maximum temperature, the power conversion control device 3 issues an alarm and performs processes such as changing the operating conditions of the inverter 23 (reducing the torque command, etc.) and the failure stop of the inverter 23. Therefore, the life deterioration due to the high temperature of the capacitor 24 is suppressed

[0059] As described above, according to the capacitor temperature estimation device 10 of the present embodiment, by adding the disturbance corrections [1][2][3] to the output of the LPF processing, high-precision monitoring of the temperature of the capacitor 24 without a temperature sensor for the capacitor is realized

[0060] In addition, the temperature rise estimated value ΔT calculated offline using equation (1) is tabulated. In other words, there is no need to perform the complex equation (1) online, which requires squaring, and the calculation load can be reduced. This is also an advantage over the conventional technology (Patent Document 1), which requires squaring 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. Since there are individual differences in the temperature characteristics of the capacitor 24 (variations in thermal time constants, etc.), selecting 2) enables more accurate temperature estimation of the 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, when the inverter 23 is stopped in a state where the capacitor 24 has generated heat due to a long-term 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 resumed in a state where the capacitor 24 has 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 of the first embodiment starts with the initial value of the temperature of the capacitor 24 regarded as being equal to the refrigerant temperature. As a result, a discrepancy occurs between the actual temperature of the capacitor 24 and the estimated temperature value, and appropriate temperature protection by torque suppression or the like may not be performed.

[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) provided from the filter processing unit 12 to the disturbance correction unit 13 when the operation of the inverter 23 is restarted (hereinafter, the temperature rise estimated value ΔT LPF By providing an initial estimation processing unit 16 that corrects the temperature, it is possible to protect the temperature even in the case of a hot start.

[0065] Temperature rise estimated value ΔT by the initial estimation processing unit 16 LPF The following methods (1) and (2) can be used to correct this.

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

[0067] In the method (2), the peripheral component temperature T th Based on the estimated temperature rise ΔT LPF Correction is performed.

[0068] The process 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 of the inverter 23 is cut off), the temperature estimation value of the capacitor 24 calculated by the temperature estimation unit 14 in S4 is the temperature estimation value T ROM The calculated value is stored in the EEPROM, which is a non-volatile memory in the control circuit of the power conversion control device 3.

[0070] S202: The temperature estimate T of the capacitor 24 is read from the EEPROM. ROM 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 Sand the thermal time constant T of the capacitor 24, the initial temperature estimate T1 of the capacitor 24 when the operation of the inverter 23 is resumed 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]

number

[0072] Next, the temperature rise estimate ΔT from S2 (LPF processing) LPF The initial temperature estimate T1 of the condenser 24 and the refrigerant temperature T from the flow temperature sensor 26 are cool The corrected temperature rise estimate (1) ΔT is calculated by the following formula (5) HOSEI(1) Calculate.

[0073]

number

[0074] And 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), S2(L PFEstimated temperature rise ΔT through LPF The stop time of the inverter 23 is Δt S 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, it becomes possible to estimate the temperature of the capacitor 24 with high accuracy without using a temperature sensor for the capacitor 24.

[0076] In the method (2), the peripheral component temperature T th The capacitor 24 and the control board are disposed relatively close to each other, so the difference in ambient temperature between them is not large. The thermistor is provided as standard on the control board, so method (2) can avoid the inverter 23 from becoming larger.

[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 judged as "hot start", S2(L PF Estimated temperature rise ΔT from LPF The surrounding component temperature T th and the coolant temperature T cool The corrected temperature rise estimate (2) ΔT is calculated by the following formula (6) HOSEI(2) Calculate.

[0080]

number

[0081] And 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", S2(L PF Estimated temperature rise ΔT from 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 inferior in estimation accuracy to the method (1), but does not require complicated 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 S If the time is shorter than the predetermined time, execute method (1) and set the stop time Δt S If 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. [Explanation of symbols]

[0085] 1. Motor drive system 2... drive circuit, 21... battery, 22... converter, 23... inverter, 24... capacitor, 25... cooling unit, 26... flow rate temperature sensor, 27... voltage sensor 3...Power conversion control device, 10: Capacitor temperature estimation device, 11: Pre-filtering estimation section, 12: Filter 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 a temperature of a DC smoothing capacitor of an inverter in a motor drive system, comprising: a pre-filtering estimation unit that calculates a first temperature rise estimate 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 filter processor that corrects the first temperature rise estimated value to a second temperature rise estimated value by low-pass filtering based on a thermal time constant of the DC smoothing capacitor; a disturbance correction unit that calculates a third temperature rise estimated value by adding a second disturbance correction value based on an ambient temperature of the DC smoothing capacitor and a third disturbance correction value based on a refrigerant temperature to a first disturbance correction value obtained by multiplying the second temperature rise estimated value by a flow rate correction coefficient; a temperature estimator that calculates a temperature estimate of the DC smoothing capacitor by adding the third temperature rise estimate to the refrigerant temperature; Equipped with The flow rate correction coefficient is a value based on a refrigerant flow rate, The ambient temperature of the DC smoothing capacitor is a maximum ambient temperature measured during a test run of the inverter, and the refrigerant temperature is a value detected by a sensor.

2. the data table is created based on a test run result of the inverter for creating the data table, the thermal time constant is set based on a test run result of the inverter for setting the thermal time constant; the flow rate correction coefficient is set based on a test run result of the inverter for setting the flow rate correction coefficient; the second disturbance correction value is set based on a difference between the second temperature rise estimated value at an initial ambient temperature of the DC smoothing capacitor and the second temperature rise estimated value at a maximum ambient temperature of the DC smoothing capacitor, 2. The capacitor temperature estimation device according to claim 1, wherein the third disturbance correction value is set based on a test run result of the inverter for setting a correction value based on a maximum ambient temperature of the DC smoothing capacitor at the refrigerant temperature.

3. 2. The capacitor temperature estimation device according to claim 1, further comprising 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 when the inverter is stopped, a stop time of the inverter, and the refrigerant temperature, and adds a difference between this initial temperature estimate and the refrigerant temperature to the second temperature rise estimate.

4. The capacitor temperature estimation device according to claim 1 , further comprising 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 second temperature rise estimated value.

5. A capacitor temperature estimation method for estimating a temperature of a DC smoothing capacitor of an inverter in a motor drive system, comprising: calculating a first temperature rise estimate 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; correcting the first temperature rise estimated value to a second temperature rise estimated value by low-pass filtering based on a thermal time constant of the DC smoothing capacitor; a step of calculating a third temperature rise estimated value by adding a second disturbance correction value based on an ambient temperature of the DC smoothing capacitor and a third disturbance correction value based on a refrigerant temperature to a first disturbance correction value obtained by multiplying the second temperature rise estimated value by a flow rate correction coefficient; calculating a temperature estimate of the DC smoothing capacitor by adding the third temperature rise estimate to the refrigerant temperature; having The flow rate correction coefficient is a value based on a refrigerant flow rate, The capacitor temperature estimation method, wherein the ambient temperature of the DC smoothing capacitor is a maximum ambient temperature measured during a test run of the inverter, and the refrigerant temperature is a value detected by a sensor.

6. A power conversion control device comprising the capacitor temperature estimation device according to claim 1.

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