Life diagnostic device for passive components

Abstract

The present invention provides a passive component life diagnostic device that can estimate the lifespan of passive components in a circuit being diagnosed, while suppressing increased complexity of the configuration and rising costs. [Solution] The life diagnostic device 70 includes power supplies 72 and 73 and is connected to a circuit to be diagnosed, which includes passive components, so that an energized circuit is formed from the power supplies through the passive components. The circuit impedance is measured when the energized circuit is energized, and the characteristic value of the passive component is calculated based on the measured circuit impedance. The life of the passive component is estimated based on the initial value of the characteristic value of the passive component and the calculated characteristic value.

Description

[Technical Field]

[0001] This disclosure relates to a life diagnostic device for passive components such as capacitors, reactors, and resistors. [Background technology]

[0002] For example, Patent Document 1 discloses a power conversion system for diagnosing the state of an energy storage device. This power conversion system includes an AC-DC converter that converts AC power supplied from an AC power source into first DC power, and a DC-AC converter that converts the first DC power into AC power and outputs it to an AC motor. Furthermore, the power conversion system includes a DC-DC converter that converts the first DC power into second DC power and outputs it to an energy storage device, and also converts the second DC power supplied from the energy storage device into first DC power and outputs it to the DC-AC converter. The DC-DC converter has a function for diagnosing the state of the energy storage device.

[0003] Specifically, the DC-DC converter superimposes an AC voltage onto the DC voltage in the second DC power source, and superimposes an AC current onto the DC current in the second DC power source. The DC-DC converter then detects at least one of the DC voltage detection value with the AC voltage superimposed and the DC current detection value with the AC current superimposed, and diagnoses the state of the energy storage device based on the detection results. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2015 / 125279 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] As mentioned above, the power conversion system described in Patent Document 1 has a DC-DC converter that has a function to diagnose the state of the energy storage device. This leads to problems such as increased complexity of the power conversion system configuration and increased costs.

[0006] This disclosure is made in view of the above-mentioned points, and aims to provide a passive component life diagnostic device that can estimate the lifespan of passive components in a circuit to be diagnosed while suppressing increased complexity of the configuration and rising costs. [Means for solving the problem]

[0007] To achieve the above objective, the lifetime diagnostic device according to this disclosure is a lifetime diagnostic device for passive components including at least one of a capacitor, a reactor, and a resistor, The life diagnostic device includes a power supply (72, 73) and is connected to a circuit to be diagnosed, which includes passive components, such that an energizing circuit is formed from the power supply via the passive components. The lifespan diagnostic device is A measuring unit (75) for measuring the circuit impedance when power is applied to the energized circuit, A calculation unit (76) calculates the characteristic values ​​of passive components based on the circuit impedance measured by the measurement unit, The system includes an estimation unit (77) that estimates the lifespan of a passive component based on the initial values ​​of the passive component's characteristics and the characteristics calculated by the calculation unit.

[0008] The life diagnostic device according to this disclosure includes a power supply and is connected to a circuit to be diagnosed, which includes passive components, so that a current supply circuit is formed from the power supply through the passive components. The circuit impedance is measured when current is supplied to the current supply circuit, and the characteristic value of the passive components is calculated based on the measured circuit impedance. The life of the passive components is estimated based on the initial value of the characteristic value of the passive components and the calculated characteristic value.

[0009] Thus, by simply connecting the life diagnosis device according to the present disclosure to the circuit to be diagnosed, the life of the passive components included in the circuit to be diagnosed can be estimated. Therefore, it is possible to estimate the life of the passive components of the circuit to be diagnosed while suppressing the complication of the configuration of the circuit to be diagnosed and the increase in cost.

[0010] The reference numbers in the above parentheses are merely examples of the correspondence with the specific configurations in the embodiments described later for the purpose of facilitating the understanding of the present disclosure, and are not intended to limit the scope of the present disclosure in any way.

[0011] In addition, regarding the technical features described in each claim of the claims other than the features of the present disclosure described above, they will become clear from the description of the embodiments described later and the accompanying drawings.

Brief Description of Drawings

[0012] [Figure 1] It is a configuration diagram showing an example of the configuration of a power conversion circuit to which the life diagnosis device according to the first embodiment is applied. [Figure 2] It is a configuration diagram showing an example of the configuration of the life diagnosis device according to the present embodiment. [Figure 3] It is a flowchart showing the processes executed by the measurement unit, calculation unit, and estimation unit in the control device of the life diagnosis device. [Figure 4] It is a graph showing an example of the measured value and selected value of the frequency characteristics of the circuit impedance. [Figure 5] It is a diagram showing an equivalent circuit of a circuit to be diagnosed that is the object of diagnosis by the life diagnosis device. [Figure 6] It is a diagram showing examples of the target parameters, target frequency bands, and calculation formulas of the characteristic values, which are the characteristic values of each passive component. [Figure 7] It is a diagram showing a modified example of the life diagnosis device of the first embodiment. [Figure 8] It is a diagram showing another modified example of the life diagnosis device of the first embodiment. [Figure 9] It is a diagram showing yet another modified example of the life diagnosis device of the first embodiment. [Figure 10] This is a configuration diagram showing an example of the configuration of a voltage generation circuit to which the life diagnostic device according to the second embodiment is applied. [Figure 11] This flowchart shows an example of a process performed in the lifespan diagnostic device according to the second embodiment. [Figure 12] This graph shows an example of the life curves for the first and second capacitors. [Figure 13] This graph shows an example of the temperature stress correlation coefficient between the first and second capacitors. [Modes for carrying out the invention]

[0013] Preferred embodiments of this disclosure will be described below with reference to the drawings. Note that identical or similar configurations may be given the same reference numeral across multiple drawings, and their descriptions may be omitted. If only a portion of a configuration is described in each embodiment, the other parts of that configuration can be replaced with configurations from other embodiments described earlier. Furthermore, configurations from multiple embodiments may be partially combined, even if not explicitly stated, as long as there are no particular problems with the combination.

[0014] (First Embodiment) The life diagnostic device according to this embodiment can be used, for example, to diagnose the life of passive components (e.g., resistors, reactors, and / or capacitors) of a power converter for driving an electric motor. The electric motor can be used, for example, as a power source for a mobile body. Examples of mobile bodies include electric vehicles such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs), electric aircraft such as drones and electric vertical take-off and landing aircraft (eVTOLs), ships, construction machinery, and agricultural machinery. However, the electric motor is not limited to being used as a power source for a mobile body; for example, it may be used to drive a compressor in an air conditioning system.

[0015] In Figure 1, the first and second motor generators (hereinafter referred to as MGs) 50 and 60, which function as electric motors, are, for example, three-phase AC rotating electric machines. Figure 1 shows an example in which the U-phase coils, V-phase coils, and W-phase coils of the first and second MGs 50 and 60 are connected in a Y configuration. The U-phase coils, V-phase coils, and W-phase coils may also be connected in a delta configuration. The first and second MGs 50 and 60 function as drive sources, i.e., electric motors, to drive the front and rear wheels of a vehicle, respectively. In this case, the first and second MGs 50 and 60 generate torque to drive the front and rear wheels, respectively. Furthermore, the first and second MGs 50 and 60 can function as generators that generate regenerative power during vehicle braking. Thus, the power conversion circuit 10 shown in Figure 1 can be used to drive multiple MGs. However, the number of MGs may be as few as one.

[0016] Figure 1 shows an example of the configuration of a power conversion circuit 10. As shown in Figure 1, the power conversion circuit 10 comprises a converter 16, first and second inverters 30 and 31, and a control device 40. The converter 16 has the function of boosting and stepping down the voltage level of DC power. The first and second inverters 30 and 31 have the function of converting DC power to AC power and AC power to DC power. The control device 40 controls the operation of the converter 16 and the first and second inverters 30 and 31.

[0017] Converter 16 boosts the DC power from the high-voltage battery 1 to a voltage level suitable for torque generation by the first and second MG50 and 60. The first and second inverters 30 and 31 convert the DC power boosted by Converter 16 into AC power and supply it to the first and second MG50 and 60. In addition, the first and second inverters 30 and 31 convert the AC power generated by the first and second MG50 and 60 into DC power when the vehicle is braking. Converter 16 then steps down the DC power converted by the first and second inverters 30 and 31 to a voltage level suitable for charging the high-voltage battery 1.

[0018] As shown in Figure 1, the converter 16 is electrically connected to the high-voltage battery 1 via positive terminal 11 and negative terminal 12 provided on the power conversion circuit 10. The positive terminal 11 and negative terminal 12 correspond to existing external connection terminals in this disclosure. Furthermore, the converter 16 is electrically connected to the first and second inverters 30 and 31 via a high-potential power line 22 and a low-potential power line 23.

[0019] The converter 16 includes a filter capacitor 13, a reactor 14, and upper arm switching elements 15H and lower arm switching elements 15L that constitute the upper and lower arm circuits. Upper arm diodes 15DH and 15DL are connected in parallel to the upper arm switching elements 15H and 15L, respectively.

[0020] The filter capacitor 13 removes power supply noise from the high-voltage battery 1. Current is supplied to the reactor 14 when the converter 16 operates as a boost and buck circuit. The reactor 14 converts the electrical energy supplied during operation into magnetic energy and stores it. The upper arm switching element 15H and the lower arm switching element 15L may be composed of, for example, IGBTs or MOSFETs.

[0021] The lower arm switching element 15L is switched on and off when the converter 16 operates as a boost circuit. When the lower arm switching element 15L is switched on, energy is stored in the reactor 14 by the current supplied from the high-voltage battery 1. When the lower arm switching element 15L is switched off, the stored energy is released from the reactor 14. By adjusting the on / off ratio of the lower arm switching element 15L, the energy stored in the reactor 14 changes. As a result, the converter 16 can boost the DC voltage of the high-voltage battery 1 to a desired voltage value.

[0022] The upper arm switching element 15H operates in the opposite direction to the lower arm switching element 15L when the converter 16 is operating as a boost circuit. As a result, when the lower arm switching element 15L is turned off, the energy released from the reactor 14 can be supplied to the smoothing capacitor 18 of the first inverter 30 via the upper arm switching element 15H instead of the upper arm diode 15DH.

[0023] Furthermore, the upper arm switching element 15H is switched on and off when the converter 16 operates as a step-down circuit. When the upper arm switching element 15H is switched on, energy is stored in the reactor 14 by the current supplied from the smoothing capacitor 18 to the reactor 14. When the upper arm switching element 15H is switched off, the stored energy is released from the reactor 14, and the high-voltage battery 1 is charged. By adjusting the on / off ratio of the upper arm switching element 15H, the amount of current flowing from the smoothing capacitor 18 to the reactor 14 changes. As a result, the converter 16 can step down the DC voltage of the smoothing capacitor 18 to a desired voltage value.

[0024] The lower arm switching element 15L operates in the opposite direction to the upper arm switching element 15H when the converter 16 is operating as a step-down circuit. This allows the energy released from the reactor 14 to flow through the lower arm switching element 15L instead of the lower arm diode 15DL when the upper arm switching element 15H is turned off.

[0025] Furthermore, if the converter 16 does not operate as a boost circuit and also does not operate as a buck circuit, the upper arm switching element 15H can be turned on. Also, if the first and second MG50 and 60 do not generate regenerative power, the converter 16 may operate only as a boost circuit.

[0026] The first inverter 30 includes a discharge resistor 17, a smoothing capacitor 18, a U-phase up / down arm circuit, a V-phase up / down arm circuit, and a W-phase up / down arm circuit.

[0027] The smoothing capacitor 18 is connected between the high-potential power line 22 and the low-potential power line 23. The smoothing capacitor 18 smooths the DC voltage supplied by the high-voltage battery 1 and / or the DC voltage boosted by the converter 16. The DC voltage supplied by the smoothing capacitor 18 becomes the high DC voltage for driving the first and second MG50 and 60. The discharge resistor 17 is for quickly discharging the high voltage charged in the smoothing capacitor 18 when the driving of the first and second MG50 and 60 is stopped.

[0028] The first inverter 30 uses U-phase up / down arm circuits, V-phase up / down arm circuits, and W-phase up / down arm circuits to convert DC voltage to three-phase AC voltage and output it to the first MG 50. In addition, the first inverter 30 uses U-phase up / down arm circuits, V-phase up / down arm circuits, and W-phase up / down arm circuits to convert the three-phase AC voltage generated by the first MG 50 to DC voltage during regenerative braking of the vehicle.

[0029] The U-phase upper and lower arm circuits, V-phase upper and lower arm circuits, and W-phase upper and lower arm circuits each have an upper arm and a lower arm. The upper and lower arms are connected in series between the high-potential power line 22 and the low-potential power line 23, with the upper arm on the high-potential power line 22 side. The connection points of the upper and lower arms are connected to the windings of the corresponding phases in the first MG50 via output lines 19, 20, 21 and motor connection terminals 24, 25, 26.

[0030] The upper arm of the U-phase upper arm circuit has a U-phase upper arm switching element 19UH. The lower arm of the U-phase upper arm circuit has a U-phase lower arm switching element 19UL. The U-phase upper arm switching element 19UH and the U-phase lower arm switching element 19UL are connected in parallel to a U-phase upper arm diode 19DH and a U-phase lower arm diode 19DL for recirculation, respectively.

[0031] The upper arm of the V-phase upper arm circuit has a V-phase upper arm switching element 20VH. The lower arm of the V-phase upper arm circuit has a V-phase lower arm switching element 20VL. The V-phase upper arm switching element 20VH and the V-phase lower arm switching element 20VL are connected in parallel to a V-phase upper arm diode 20DH and a V-phase lower arm diode 20DL, respectively.

[0032] The upper arm of the W-phase upper arm circuit has a W-phase upper arm switching element 21WH. The lower arm of the W-phase upper arm circuit has a W-phase lower arm switching element 21WL. The W-phase upper arm switching element 21WH and the W-phase lower arm switching element 21WL are connected in parallel to a W-phase upper arm diode 21DH and a W-phase lower arm diode 21DL for recirculation, respectively.

[0033] The number of switching elements 19UH, 19UL, 20VH, 20VL, 21WH, and 21WL in each arm is not particularly limited. There may be one or more. In the case of multiple switching elements, the multiple switching elements are connected in parallel and are turned on or off at the same timing by a common gate drive signal (drive voltage). Furthermore, the switching elements 19UH, 19UL, 20VH, 20VL, 21WH, and 21WL exemplified in Figure 1 may be composed of, for example, IGBTs or MOSFETs.

[0034] The second inverter 31 shares a discharge resistor 17 and a smoothing capacitor 18 with the first inverter 30. The second inverter 31, like the first inverter 30, has a U-phase up / down arm circuit, a V-phase up / down arm circuit, and a W-phase up / down arm circuit. The second inverter 31 uses the U-phase up / down arm circuit, the V-phase up / down arm circuit, and the W-phase up / down arm circuit to convert a DC voltage into a three-phase AC voltage and output it to the second MG 60. Furthermore, the second inverter 31 uses the U-phase up / down arm circuit, the V-phase up / down arm circuit, and the W-phase up / down arm circuit to convert the three-phase AC voltage generated by the second MG 60 into a DC voltage during regenerative braking of the vehicle. Since the U-phase up / down arm circuit, the V-phase up / down arm circuit, and the W-phase up / down arm circuit of the second inverter 31 are configured similarly to the U-phase up / down arm circuit, the V-phase up / down arm circuit, and the W-phase up / down arm circuit of the first inverter 30, further explanation is omitted.

[0035] As described above, the converter 16 drives the two first and second MGs 50 and 60 by boosting the DC voltage of the high-voltage battery 1 and stepping down the high voltage regenerated by the first and second MGs 50 and 60. Furthermore, the discharge resistor 17 and smoothing capacitor 18 are shared by the first and second inverters 30 and 31. Therefore, compared to a power conversion device for driving a single MG, the power conversion circuit 10 shown in Figure 1 tends to be more susceptible to degradation of passive components such as resistors, reactors, and capacitors. For this reason, it is highly meaningful to apply this embodiment as a circuit to be diagnosed in the life diagnostic device.

[0036] The control device 40 generates drive commands (e.g., PWM signals) to drive the switching elements 15H, 15L of the converter, and the switching elements 19UH, 19UL, 20VH, 20VL, 21WH, 21WL of the first and second inverters 30, 31. The generated drive commands are output to a driver circuit (not shown). Based on the drive commands, the driver circuit supplies drive signals (drive voltages) to the gates of the corresponding switching elements 15H, 15L, 19UH, 19UL, 20VH, 20VL, 21WH, 21WL. These drive signals either turn the corresponding switching elements 15H, 15L, 19UH, 19UL, 20VH, 20VL, 21WH, 21WL on or off.

[0037] The control device 40 generates a drive command based on, for example, a torque request input from a higher-level ECU (not shown) and signals detected by various sensors. Examples of various sensors include a current sensor, a rotation angle sensor, and a voltage sensor. The current sensor detects the phase current flowing through the windings of each phase of the first and second MG50 and 60. The rotation angle sensor detects the rotation angle of the rotors of the first and second MG50 and 60. The voltage sensor detects the voltage across the smoothing capacitor 18. The control device 40 outputs, for example, a PWM signal as a drive command.

[0038] The control device 40 may consist of, for example, a processor, memory, and storage. The processor performs various processes by accessing the memory. The processor may include at least one of the following: a CPU, GPU, RISC-CPU, DFP, GSP, etc. The memory is a volatile storage medium, such as RAM. The storage is a non-transitional tangible recording medium that stores the program executed by the processor. The storage is a rewritable, non-volatile storage medium, such as ROM or flash memory.

[0039] The processing performed by the control device 40 can be implemented by software processing, where the processor executes the program described above. Alternatively, the processing performed by the control device 40 may be implemented by hardware processing using dedicated electronic circuits such as ASICs or FPGAs. Furthermore, the processing performed by the control device 40 may be implemented by a combination of software processing and hardware processing.

[0040] Next, the configuration of the life diagnostic device 70 according to this embodiment will be described with reference to Figure 2. In Figure 2, the various functions of the control device 74 of the life diagnostic device 70 are shown by blocks.

[0041] As shown in Figure 2, the life diagnostic device 70 is connected to the existing external connection terminals of the power conversion circuit 10: the positive terminal 11, the negative terminal 12, and the motor connection terminal 24. The motor connection terminal to which the life diagnostic device 70 is connected may be any of the motor connection terminals 24, 25, or 26.

[0042] The life diagnostic device 70 is equipped with a DC power supply 72 and an AC power supply 73 as power sources. The DC power supply 72 is connected between the motor connection terminal 24 and the positive terminal 11 so that a DC current flows from the motor connection terminal 24 towards the positive terminal 11 and the negative terminal 12. The AC power supply 73 is connected between the positive terminal 11 and the negative terminal 12. The AC power supply 73 is capable of generating an AC voltage with a swept frequency. In this way, in the power conversion circuit 10, which is the circuit to be diagnosed, an energizing circuit is formed that is energized via passive components by the power supply of the life diagnostic device 70. Figure 2 shows an example of an energizing circuit.

[0043] The life diagnostic device 70 has a control device 74. The control device 74 may consist of, for example, a processor, memory, and storage. The processor performs various processes by accessing the memory. The processor may include at least one of the following: a CPU, GPU, RISC-CPU, DFP, GSP, etc. The memory is a volatile storage medium such as RAM. The storage is a non-transitional tangible recording medium that stores the program executed by the processor. The storage is a rewritable non-volatile storage medium such as ROM or flash memory.

[0044] The various functions of the control device 74 can be realized through software processing by the processor executing the program described above. Alternatively, the various functions of the control device 74 may be realized through hardware processing using dedicated electronic circuits such as ASICs or FPGAs. Furthermore, the various functions of the control device 74 may be realized through a combination of software and hardware processing.

[0045] The control device 74 has various functions, including a measurement unit 75, a calculation unit 76, an estimation unit 77, and a storage unit 78. The measurement unit 75 measures the voltage value between the external input terminals and the current value flowing through the external input terminals as a circuit impedance measurement when a DC voltage is applied from the DC power supply 72, and when a superimposed voltage is applied, which is the DC voltage of the DC power supply 72 superimposed with the AC voltage of the AC power supply 73. The calculation unit 76 calculates the characteristic value (e.g., resistance value, inductance value, capacitance value) of at least one passive component based on the circuit impedance (voltage value and current value) measured by the measurement unit 75. The estimation unit 77 estimates the lifespan of the passive component based on the initial value (design value) of the passive component's characteristic value and the characteristic value calculated by the calculation unit 76. The storage unit 78 stores the program described above, as well as the initial value of the passive component's characteristic value and the characteristic equation of the circuit to be diagnosed, which will be explained later.

[0046] The processes performed by the measurement unit 75, the calculation unit 76, and the estimation unit 77 will be explained in detail below with reference to the flowchart in Figure 3. The flowchart in Figure 3 shows the lifespan diagnosis process performed by the control device 74 of the lifespan diagnosis device 70.

[0047] In step S100, the control device 74 applies a DC voltage from the DC power supply 72 between the motor connection terminal 24 and the positive terminal 11. At this time, the upper arm switching element 15H of the converter 16 is turned off. Therefore, in response to the DC voltage applied by the DC power supply 72, a DC current flows through the U-phase upper arm diode 19DH and the discharge resistor 17 in Figure 2.

[0048] In step S110, the measurement unit 75 of the control device 74 measures the voltage value V and current value I when a DC current flows through the U-phase upper arm diode 19DH and the discharge resistor 17 as a measurement of the circuit impedance. In this case, the circuit impedance is the resistance value R of the discharge resistor 17, but the measured voltage value is the voltage drop (V) across the U-phase upper arm diode 19DH. F This includes the effect of ). Therefore, in step S120, the calculation unit 76 of the control device 74 calculates the resistance value R of the discharge resistance 17 according to the following formula 1.

number

[0049] In step S130, the control device 74 commands the control device 40 to turn on the upper arm switching element 15H of the converter 16. Based on this command, the control device 40 turns on the upper arm switching element 15H. As described above, the upper arm switching element 15H can be turned on when the converter 16 is neither operating as a boost circuit nor as a buck circuit.

[0050] In step S140, the control device 74 applies an AC voltage between the positive connection terminal 11 and the negative connection terminal 12 while sweeping the frequency of the AC voltage of the AC power supply 73. At this time, a superimposed voltage in which the AC voltage of the AC power supply 73 is superimposed on the DC voltage of the DC power supply 72 is applied to the circuit to be diagnosed. As a result, a sufficient current can be made to flow through the upper arm switching element 15H. As a result, while reducing the influence of the voltage drop by the upper arm switching element 15H, the voltage value V AC and the current value I AC can be measured accurately.

[0051] In step S150, the measurement unit 75 of the control device 74 measures the voltage value V AC and the current value I AC when a superimposed voltage in which an AC voltage with a swept frequency is superimposed on the DC voltage of the DC power supply 72 is applied as the measurement of the circuit impedance Z. The circuit impedance Z(=V AC / I AC ) changes according to the frequency of the AC voltage. Fig. 4 shows the measured values of the circuit impedance Z for each frequency. Hereinafter, the collection of the measured values of the circuit impedance Z that changes according to the frequency is called the frequency characteristic of the circuit impedance Z. In step S150, the measurement unit 75 measures the frequency characteristic of the circuit impedance Z.

[0052] Here, the equivalent circuit of the circuit to be diagnosed shown in Fig. 2, which the life diagnosis device 70 diagnoses, can be represented as shown in Fig. 5. In Fig. 5, l CF is the equivalent series inductance (ESL) of the filter capacitor 13, r CF is the equivalent series resistance (ESR) of the filter capacitor 13. r L is the equivalent series resistance of the reactor 14. l CS is the equivalent series inductance of the smoothing capacitor 18, r CS is the equivalent series resistance of the smoothing capacitor 18.

[0053] With respect to the equivalent circuit shown in Figure 5, the absolute value of the circuit impedance Z can be expressed by the characteristic equation shown in Equation 2 below. Therefore, it can be said that the characteristic equation in Equation 2 represents the impedance frequency characteristics corresponding to the initial characteristic values ​​of passive components such as the filter capacitor 13, reactor 14, discharge resistor 17, and smoothing capacitor 18.

number

[0054] In step S160, the calculation unit 76 of the control device 74 calculates multiple impedance frequency characteristics by substituting values ​​that have been varied from their initial values ​​(design values) for the resistance, inductance, and capacitance in the characteristic equation shown in Equation 2. Then, by applying, for example, the least squares method to the multiple calculated impedance frequency characteristics and the frequency characteristics of the measured circuit impedance Z, the calculation unit 76 selects the impedance frequency characteristic that best approximates the frequency characteristics of the measured circuit impedance Z. By using this analysis method, the calculation unit 76 determines the capacitance value C of the filter capacitor 13 based on the resistance, inductance, and capacitance values ​​used to obtain the selected impedance frequency characteristic. F L is the inductance value of the reactor 14, and C is the capacitance value of the smoothing capacitor 18. S This can be calculated. Figure 4 shows an example of the impedance frequency characteristics selected using the analysis method described above, indicated by a dotted line.

[0055] Furthermore, when setting the characteristic formula described above, the inductance of the connector terminals and the wiring impedance may be taken into consideration. This will result in the capacitance value C of the filter capacitor 13. F L is the inductance value of the reactor 14, and C is the capacitance value of the smoothing capacitor 18. S This can improve the accuracy of the calculation.

[0056] Furthermore, to further improve accuracy, the calculation unit 76 of the control device 74 may calculate the characteristic values ​​of passive components based on the measured impedance frequency characteristics in a specific frequency range corresponding to the connection position and type of passive components such as the filter capacitor 13, reactor 14, discharge resistor 17, and smoothing capacitor 18, and the initial impedance frequency characteristics corresponding to the initial characteristic values ​​of the passive components.

[0057] For example, in the circuit being diagnosed, the filter capacitor 13 is connected near the positive terminal 11 and the negative terminal 12 to which the AC power supply 73 is connected. Furthermore, a reactor 14 exists between the filter capacitor 13 and the smoothing capacitor 18. Therefore, as the frequency of the AC voltage of the AC power supply 73 increases, the AC current is obstructed by the reactor 14 and flows mainly through the filter capacitor 13. Consequently, as shown in Figures 4 and 6, the capacitance value C of the filter capacitor 13... F This strongly affects the impedance frequency characteristics in the relatively high frequency range f3 to f4. Conversely, in the relatively high frequency range f3 to f4, by using the analysis method described above, the capacitance value C of the filter capacitor 13 can be determined. F This can be determined with high precision. Note that the capacitance value C of the filter capacitor 13 is... F When determining this, the specific values ​​of other passive components should be treated as constant values ​​such as initial values, and the above analysis method should be executed.

[0058] Capacitance value C of filter capacitor 13 F As shown in Figure 6, this can also be calculated using the following formula 3.

number

[0059] Furthermore, in the circuit being diagnosed, the smoothing capacitor 18 is connected to the AC power supply 73 via the reactor 14. Therefore, when the frequency of the AC voltage of the AC power supply 73 decreases, the AC current passes more easily through the reactor 14, and the smoothing capacitor 18 also becomes energized. Consequently, as shown in Figures 4 and 6, the capacitance value C of the smoothing capacitor 18 S This affects the impedance frequency characteristics in the relatively low frequency range f1 to f2. Therefore, by using the analysis method described above in the relatively low frequency range f1 to f2, the capacitance value C of the smoothing capacitor 18 can be determined. S This can be determined with high precision. Note that the capacitance value C of the smoothing capacitor 18 is... S When calculating this, the capacitance value C of the filter capacitor 13, which has already been determined, is used. S The above analysis method can be performed using [this method].

[0060] Capacitance value C of smoothing capacitor 18 S As shown in Figure 6, this can also be calculated using the following formula 4.

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[0061] Furthermore, in the circuit under diagnosis, the reactor 14 forms a resonant circuit with the smoothing capacitor 18, so as shown in Figures 4 and 6, the resonant frequency f of the resonant circuit C1 In this case, by using the analysis method described above, the inductance value L of the reactor 14 can be determined with high accuracy. Note that when determining the inductance value L of the reactor 14, the capacitance value C of the filter capacitor 13, which has already been determined, is used. S and the capacitance value C of the smoothing capacitor 18 F The above analysis method can be performed using [this method].

[0062] The inductance value L of reactor 14 can also be determined by the following equation 5, as shown in Figure 6.

number

[0063] In step S170, the estimation unit 77 of the control device 74 calculates the resistance value R calculated in step S120 and the capacitance value C calculated in step S160. S , C F Based on the inductance value L, the lifetimes of the discharge resistor 17, filter capacitor 13, smoothing capacitor 18, and reactor 14 are estimated.

[0064] Regarding the discharge resistor 17, its resistance value may decrease or increase due to degradation of the resistor. Therefore, the estimation unit 77 can estimate the lifespan of the discharge resistor 17 based on the degree of deviation of the calculated resistance value R from the initial resistance value R0. For example, if the degree of deviation between the resistance value R and the initial resistance value R0 is small, the estimation unit 77 can estimate that there is still sufficient lifespan remaining. The estimation unit 77 can then estimate the lifespan of the discharge resistor 17 such that the lifespan decreases as the degree of deviation increases.

[0065] With respect to the filter capacitor 13, smoothing capacitor 18, and reactor 14, the capacitance and inductance values ​​tend to decrease as degradation progresses. Therefore, the estimation unit 77 can estimate the lifespan of the filter capacitor 13, smoothing capacitor 18, and reactor 14 based on the degree of decrease in capacitance and inductance values ​​from their respective initial values.

[0066] However, the capacitance value of a capacitor and the inductance value of a reactor do not decrease at a constant rate as degradation progresses. The degree of degradation can be rephrased as the degree of damage. Specifically, as will be explained later, as degradation progresses, the decrease in capacitance and inductance values ​​is initially small. However, as the degree of damage increases, the capacitance and inductance values ​​decrease significantly in proportion to the progression of degradation. And once the degree of damage reaches a certain level, the magnitude of the decrease in capacitance and inductance values ​​in proportion to the progression of degradation becomes smaller.

[0067] The memory unit 78 may store the above-described characteristics (referred to as lifetime curves) for each passive element. The estimation unit 77 may then refer to the lifetime curves to determine the degree of damage from the calculated capacitance and inductance values, and estimate the lifetime of the capacitors and reactors from that degree of damage.

[0068] (Modification of the first embodiment) In the first embodiment described above, an example was described in which the life diagnostic device 70 is connected to the positive electrode connection terminal 11, the negative electrode connection terminal 12, and the motor connection terminal 24. However, the connection configuration of the life diagnostic device 70 is not limited to the example described above.

[0069] For example, as shown in Figure 7, the power conversion circuit 10, which is the circuit to be diagnosed, is provided with a high-voltage DC terminal 27 connected to the positive side of the smoothing capacitor 18 as an external connection terminal. In this case, the life diagnosis device 70 may be connected to the positive connection terminal 11, the negative connection terminal 12, and the high-voltage DC terminal 27.

[0070] More specifically, the DC power supply 72 of the life diagnostic device 70 is connected between the positive terminal 11 and the high-voltage DC terminal 27 so that the DC current flows from the positive terminal 11 to the high-voltage DC terminal 27. The AC power supply 73 of the life diagnostic device 70 is connected between the positive terminal 11 and the negative terminal 12.

[0071] In the connection configuration shown in Figure 7, as described above, the DC current flows from the positive terminal 11 to the high-voltage DC terminal 27. In this case, the DC current flows through the upper arm diode 15DH, not the upper arm switching element 15H. Therefore, the control device 74 of the life diagnosis device 70 does not need to instruct the control device 40 of the power conversion circuit 10 to turn on the upper arm switching element 15H.

[0072] Furthermore, in the connection configuration shown in Figure 7, the energizing circuit formed by the life diagnostic device 70 in the power conversion circuit 10 does not include the U-phase upper arm diode 19DH. This reduces the circuit resistance in the energizing circuit. Moreover, even in the connection configuration shown in Figure 7, when a superimposed voltage is applied, which is the DC voltage of the DC power supply 72 superimposed with the AC voltage of the AC power supply 73, the DC current (DC bias current) does not flow through the discharge resistor 17, so no overvoltage is applied to the discharge resistor 17.

[0073] The connection configuration of the life diagnostic device 70 is not limited to the example shown in Figure 7. For example, as shown in Figure 8, the life diagnostic device 70 may have both a DC power supply 72 and an AC power supply 73 connected between the positive terminal 11 and the high-voltage DC terminal 27. Furthermore, as shown in Figure 9, the life diagnostic device 70 may have only the AC power supply 73 connected between the positive terminal 11 and the negative terminal 12, and the DC power supply 72 may be omitted. In this case, as shown in Figure 9, one terminal of the AC power supply 73 is connected to the positive terminal 11 via the diagnostic changeover switch 28. Furthermore, the other terminal of the AC power supply 73 is connected to the high-voltage DC terminal 27 via the diagnostic changeover switch 29.

[0074] (Second Embodiment) Next, a life diagnostic device according to the second embodiment of this disclosure will be described with reference to the drawings. In the first embodiment described above, an example was described in which the life diagnostic device 70 is used for diagnosing the life of passive components of a power converter. In this embodiment, an example will be described in which the life diagnostic device diagnoses the life of passive components included in the internal circuit of an electronic control device, with the internal circuit of the electronic control device as the circuit to be diagnosed.

[0075] For example, Figure 10 shows a voltage generation circuit as an example of the internal circuitry of an electronic control device, which generates a high voltage for the drive circuit that drives each switching element constituting the inverter in the power conversion circuit described above. The drive circuit uses the high voltage generated by the voltage generation circuit to output a drive signal for each switching element constituting the inverter.

[0076] In Figure 10, 101 is a DC power supply that provides a low voltage to the electronic control unit. The DC power supply 101 is connected to the voltage generation circuit via positive terminal 111 and negative terminal 112. 113 is a filter capacitor. 114 and 115 are coils that constitute a common-mode noise filter. Capacitors 116 and 118 and reactor 117 constitute a π-type differential-mode noise filter.

[0077] MOSFET 119 is a transistor for overcurrent protection. Capacitor 120 stabilizes the DC voltage of the DC power supply 101. MOSFET 121 is a transistor for controlling power transmission from capacitor 120 to capacitor 124. 122 is an isolation transformer. Capacitor 120 is connected to the primary coil of the isolation transformer 122. While MOSFET 121 is on, current flows from capacitor 120 to the primary coil of the isolation coil. Capacitor 124 is connected to the secondary coil of the isolation transformer via a reverse current prevention diode 123. When MOSFET 121 is turned off, the energy stored in the secondary coil of the isolation transformer is released, and capacitor 124 is charged. The drive duty cycle of MOSFET 121 is controlled so that the voltage stored in capacitor 124 becomes the desired voltage. Thus, the voltage generation circuit shown in Figure 10 is configured as a PWM flyback converter.

[0078] Using the circuit illustrated in Figure 10 as the circuit to be diagnosed, the life diagnostic device 70 described in the first embodiment can measure the circuit impedance of the circuit to be diagnosed by applying a frequency-swept AC voltage in addition to the DC power supply 101 between the positive terminal 11 and the negative terminal 12. Based on the measured circuit impedance, the life diagnostic device 70 can calculate the characteristic values ​​of passive components such as the filter capacitor 113, coils 114 and 115, capacitors 116, 118, and 120, and reactor 117 of the circuit shown in Figure 10. Then, based on the calculated characteristic values, the life diagnostic device 70 can estimate the lifespan of each passive component.

[0079] Here, as mentioned above, the electronic control unit may include multiple circuits operating at different voltage levels. Often, a voltage regulator is provided to stabilize the voltage level in each circuit. For example, in the circuit illustrated in Figure 10, the voltage stored in capacitor 120 is different from the voltage stored in capacitor 124. In this case, a voltage regulator may be provided to stabilize the voltage stored in capacitor 124. However, with respect to capacitor 124, it becomes impossible to observe the electrical response due to the frequency-swept AC voltage.

[0080] Therefore, in the life diagnostic device 70 according to this embodiment, the life of the second capacitor, capacitor 124, whose electrical response cannot be observed, is estimated from the capacitance value of the first capacitor, capacitor 120, whose electrical response due to a frequency-swept AC voltage can be observed. The second capacitor, capacitor 124, is connected downstream of the first capacitor, capacitor 120, and their operating states are correlated, so it is possible to estimate the life of capacitor 124 based on the capacitance value of capacitor 120. The specific processing in the life diagnostic device 70 according to this embodiment will be described below with reference to the flowchart in Figure 11.

[0081] In step S200, the life diagnostic device 70 calculates the capacitance value of capacitor 120, whose electrical response to a frequency-swept AC voltage can be observed, according to the method described in the first embodiment above. In step S210, the life diagnostic device 70 calculates the stress amount of capacitor 120 based on the calculated capacitance value, by referring to the life curve stored in the memory unit 78. The stress amount is synonymous with the degree of damage. For example, as shown in Figure 12, the memory unit 78 stores the life curve of capacitor 120 and the life curve of capacitor 124. The life curves show the relationship between the magnitude of the change in the measured capacitance value relative to the initial capacitance value of each capacitor 120 and 124 and the stress amount.

[0082] In step S220, the life diagnostic device 70 refers to the temperature stress correlation coefficient of the first capacitor stored in the memory unit 78 and estimates the stress amount of the second capacitor, capacitor 124, based on the stress amount of capacitor 120 calculated in step S210. As shown in Figure 13, the temperature stress correlation coefficient is a graph showing the relationship between the operating temperature of the first capacitor, capacitor 120, and the operating temperature of the second capacitor, capacitor 124, when the electronic control device is operating normally.

[0083] The stress on capacitors 120 and 124 is primarily caused by temperature. Therefore, the stress on capacitor 124, the second capacitor, can be estimated by multiplying the stress on capacitor 120, the first capacitor, by the temperature stress correlation coefficient.

[0084] In step S230, as shown in Figure 12, the life diagnostic device 70 refers to the temperature stress correlation coefficient of the second capacitor stored in the memory unit 78 and estimates the capacitance value of the capacitor 124 based on the amount of stress of the capacitor 124 estimated in step S220. Then, in step S240, the life diagnostic device 70 estimates the life of the capacitor 124 based on the estimated capacitance value. Alternatively, the life diagnostic device 70 may use the amount of stress of the second capacitor, capacitor 124, estimated in step S220, as the life of the capacitor 124.

[0085] While preferred embodiments of this disclosure have been described above, this disclosure is not limited in any way to the embodiments described above and can be implemented in various modified forms without departing from the spirit of this disclosure.

[0086] For example, in the second embodiment, if the stress levels (degree of damage) of the first capacitor, capacitor 120, and the second capacitor, capacitor 124, are different, the life diagnostic device 70 may estimate the stress level of capacitor 124 using different temperature stress correlation coefficients depending on the stress level of capacitor 120. In this case, for example, the life diagnostic device 70 may store a plurality of different temperature stress correlation coefficients in the memory unit 78 in advance, depending on the stress level of capacitor 120. Alternatively, the life diagnostic device 70 may calculate different temperature stress correlation coefficients depending on the stress level of capacitor 120 by multiplying the stored temperature stress correlation coefficient by a correction value corresponding to the stress level of capacitor 120. [Explanation of Symbols]

[0087] 1: High-voltage battery, 10: Power conversion circuit, 11: Positive terminal, 12: Negative terminal, 13: Filter capacitor, 14: Reactor, 15DH: Upper arm diode, 15DL: Lower arm diode, 15H: Upper arm switching element, 15L: Lower arm switching element, 16: Converter, 17: Discharge resistor, 18: Smoothing capacitor, 19: Output line, 19DH: U-phase upper arm diode, 19DL: U-phase lower arm diode, 19UH: U-phase upper arm switching element, 19UL: U-phase lower arm switching element, 20: Output line, 20DH: V-phase upper arm diode, 20DL: V 20VH: V-phase upper arm switching element, 20VL: V-phase lower arm switching element, 21: Output line, 21DH: W-phase upper arm diode, 21DL: W-phase lower arm diode, 21WH: W-phase upper arm switching element, 21WL: W-phase lower arm switching element, 24, 25, 26: Motor connection terminals, 27: High voltage DC terminal, 30: First inverter, 31: Second inverter, 40: Control device, 50: First MG, 60: Second MG, 70: Life diagnostic device, 72: DC power supply, 73: AC power supply, 74: Control device, 75: Measurement unit, 76: Calculation unit, 77: Estimation unit, 78: Memory unit

Claims

1. A life diagnostic device for passive components, comprising at least one of a capacitor, a reactor, and a resistor, The life diagnostic device includes a power supply (72, 73) and is connected to a circuit to be diagnosed, which includes the passive component, such that a power supply circuit is formed from the power supply through the passive component. The lifespan diagnostic device is, A measuring unit (75) for measuring the circuit impedance when the aforementioned power supply circuit is energized, A calculation unit (76) calculates the characteristic value of the passive component based on the circuit impedance measured by the measurement unit, A life diagnostic device comprising: an estimation unit (77) that estimates the lifespan of the passive component based on the initial value of the characteristic value of the passive component and the characteristic value calculated by the calculation unit.

2. The power supply of the life diagnostic device energizes the current supply circuit by applying an AC voltage with a swept frequency. The passive component includes at least one of a capacitor and a reactor, The measurement unit measures the impedance frequency characteristics, which are the circuit impedance of the current-carrying circuit, when an AC voltage with a swept frequency is applied. The life diagnostic device according to claim 1, wherein the calculation unit calculates the characteristic value of the passive component based on the impedance frequency characteristics measured by the measurement unit and the initial impedance frequency characteristics corresponding to the initial characteristic value of the passive component.

3. The life diagnostic device according to claim 2, wherein the calculation unit calculates the characteristic value of the passive component based on the measured impedance frequency characteristics in a specific frequency range corresponding to the connection position and type of the passive component, and the initial impedance frequency characteristics corresponding to the initial characteristic value of the passive component.

4. The lifespan diagnostic device according to claim 1, wherein the lifespan diagnostic device is connected to the existing external connection terminals (11, 12, 24) of the circuit to be diagnosed.

5. If the current supply circuit includes a semiconductor switching element (15H), the life diagnostic device commands a control device (40) that controls the circuit to be diagnosed to make the semiconductor switching element conductive, according to claim 1.

6. The circuit to be diagnosed is a power conversion circuit that includes a boost circuit and an inverter circuit that converts a DC voltage into an AC voltage for driving an AC motor. The life diagnostic device according to claim 5, wherein the passive component is at least one of a filter capacitor (13) connected to the upstream of the boost circuit, a reactor (14) constituting the boost circuit, a smoothing capacitor (17) that stores the voltage boosted by the boost circuit, and a discharge resistor (16) connected in parallel with the smoothing capacitor.

7. The life diagnostic device according to claim 6, wherein the power conversion circuit includes two inverter circuits (30, 31) for driving two AC motors.

8. The semiconductor switching element included in the current supply circuit is provided on the upper arm of the boost circuit, The life diagnostic device according to claim 6, wherein the life diagnostic device commands the control device to make the semiconductor switching element on the upper arm of the boost circuit conductive by giving an instruction signal to the control device so that the control device controls the semiconductor switching element on the upper arm of the boost circuit to be in a conductive state.

9. The semiconductor switching element included in the current supply circuit is provided on the upper arm of the boost circuit, A diode (15DH) is connected in parallel to the semiconductor switching element. The power supply of the life diagnostic device applies a superimposed voltage to the current supply circuit, which is obtained by superimposing a DC voltage with a frequency-swept AC voltage onto the DC voltage. The life diagnostic device according to claim 6, wherein the direction in which the DC current due to the DC voltage is passed is opposite to the forward direction of the diode.

10. The diagnostic circuit includes a first capacitor (120) whose electrical response to a frequency-swept AC voltage can be observed, and a second capacitor (124) connected downstream of the first capacitor whose electrical response cannot be observed. A storage unit (78) stores the relationship between the operating temperatures of the first capacitor and the second capacitor when the diagnostic target circuit is operating as a temperature stress correlation coefficient, and stores the relationship between the magnitude of the change in the measured capacitance value relative to the initial capacitance value of the first capacitor and the amount of stress as a life curve. A first stress amount calculation unit (S210) calculates the stress amount of the first capacitor based on the capacitance value, which is a specific value of the first capacitor, calculated by the calculation unit, The system includes a second stress amount estimation unit (S220) that estimates the stress amount of the second capacitor by referring to the temperature stress correlation coefficient based on the stress amount of the first capacitor calculated by the first stress amount calculation unit, The life diagnostic device according to claim 1 or 2, wherein the estimation unit estimates the lifespan of the second capacitor based on the amount of stress of the second capacitor calculated by the second stress amount estimation unit.

11. The life diagnostic device according to claim 10, wherein the second stress amount estimation unit calculates the stress amount of the second capacitor using different temperature stress correlation coefficients depending on the stress amount of the first capacitor calculated by the first stress amount calculation unit.

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