JP2010268645A - Abnormal insulation detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abnormal insulation detector which can reduce incorrect detection of abnormal insulation in an AC motor or a feeder, even if the current flowing through the neutral point of an AC motor is varied due to external factors. <P>SOLUTION: The abnormal insulation detector includes: a plurality of AC motors which are driven by an inverter to output a driving force or to generate electric power; a neutral point current detection means for detecting the state of currents flowing through the neutral point of the AC motors respectively; a comparison means for comparing the state of a current detected for each AC motor by the neutral point current detection means; and an abnormality decision means for deciding abnormal insulation in the winding of the AC motor, based on the comparison results from the comparison means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an insulation abnormality detection device that detects an insulation abnormality such as leakage from an AC motor winding or the like.

  Conventionally, an insulation abnormality detection device for an electric vehicle equipped with an AC motor is used for an electric vehicle equipped with an AC motor, and includes a capacitor and a current detector connected between the AC power output side of the inverter and the vehicle body. There is known a circuit that includes a series circuit that detects leakage of a current-carrying unit (a winding of an AC motor) including a power supply line from a current value flowing through a current detector (see, for example, Patent Document 1).

JP 2005-20848 A

  However, in the above-described conventional insulation abnormality detection device, a virtual neutral point of the star connection of the capacitor is grounded to the vehicle body, and the leakage is detected using the current flowing through the neutral point. The current flowing through the sex point fluctuates due to external factors such as temperature and humidity, and depending on the amount of fluctuation, it may be judged that there is a leakage even though the winding and power supply line are normal, and false detection may occur. There is a problem that there is.

  The present invention has been made paying attention to the above problems, and the purpose of the present invention is that even if the current flowing through the neutral point of the AC motor fluctuates due to an external factor, the winding of the AC motor is normal. An object of the present invention is to provide a motor insulation abnormality detection device capable of reducing erroneous detections that are considered to be insulation abnormality despite being present.

  For this purpose, the insulation abnormality detection device of the present invention includes a neutral point detection means for detecting the state of a current flowing through a neutral point of each of a plurality of AC motors, and a current state detected by the neutral point detection means. Comparing means for comparing each AC motor, and abnormality determining means for determining an insulation abnormality such as a winding of the AC motor based on the comparison result.

  In the insulation abnormality detection device of the present invention, when the winding of the AC motor is normal, even if the current flowing through the neutral point of the AC motor fluctuates due to an external factor, it is not between the plurality of motors. Since they have the same tendency, the difference between the neutral point currents on the left and right sides hardly changes, so that the fluctuations in the neutral point currents can be removed, and as a result, false detection of insulation abnormality can be reduced.

It is a figure which shows the structure of the electric vehicle carrying the insulation abnormality detection apparatus of Example 1 which concerns on this invention. It is a figure which shows the two alternating current motors and the electric power feeding circuit to which the insulation abnormality detection apparatus of Example 1 was applied. It is a block diagram which shows the structure of the insulation abnormality detection apparatus of Example 1. FIG. (A) is a figure which shows the waveform of the neutral point current input into the frequency classification part of an insulation abnormality detection apparatus, (b) is a figure which shows the waveform of the current signal output from the frequency discrimination part, (c) is rectification The figure which shows the waveform of the current signal rectified by the part, (d) is a figure which shows the waveform of the current signal smoothed by the smoothing part. It is a figure which shows the flow of the earth-leakage current at the time of insulation abnormality having arisen in the winding of the right side AC motor. It is a figure explaining the method of determining an insulation abnormality based on the difference of the neutral point current value of right and left. It is a figure explaining the method of determining the insulation abnormality at the time of applying the insulation abnormality detection apparatus of Example 1 to two or more AC motors. It is a figure explaining the method of determining the insulation abnormality by the insulation abnormality detection apparatus of Example 2 which concerns on this invention. It is the block diagram which showed the structure for performing determination of FIG. Section used when the magnitude of the voltage command value to each phase is U phase> V phase> W phase, which is used in the method for determining an insulation abnormality by the insulation abnormality detection device according to the third embodiment of the present invention. It is a figure explaining the relationship with the voltage of each phase. The section in the case where the magnitude of the voltage command value to each phase is U phase> W phase> V phase, used in the method for determining the insulation abnormality by the insulation abnormality detection device according to the third embodiment of the present invention. It is a figure explaining the relationship with the voltage of each phase. It is a figure which shows the relationship between the magnitude of the voltage command value in U phase, V phase, and W phase, and the voltage which appears in each phase at that time. It is a figure which shows the relationship between the electrical angle in a three-phase alternating current motor, and each phase voltage. It is a figure explaining the influence of the parasitic capacitor of a motor, and parasitic resistance.

  Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.

  FIG. 1 is a schematic diagram of an electric vehicle equipped with an insulation abnormality detection device of the present invention. In the figure, in the case of an electric vehicle, the vehicle body 1 has a left front wheel side suspension device 5FL, a right front wheel side suspension device 5FR, a left rear wheel side suspension device 5RL, and a right rear wheel side suspension device 5RR. Front wheel 2FL, right front wheel 2FR, left rear wheel 2RL, right rear wheel 2RR are attached.

  The left front wheel 2FL and the right front wheel 2FR are steerable by the steering operation of the steering wheel 7. On the other hand, an AC motor 3RL and an AC motor 3RR are connected to the left rear wheel 2RL and the right rear wheel 2RR, respectively, so that the left rear wheel 2RL and the right rear wheel 2RR can be driven. The same AC motor is used for the AC motor 3RL for driving the left rear wheel 2RL and the AC motor 3RR for driving the right rear wheel 2RR. In the first embodiment, a three-phase AC in-wheel motor is used.

  The AC motor 3RL for driving the left rear wheel 2RL and the AC motor 3RR for driving the right rear wheel 2RR are electrically connected to the left rear wheel side inverter 24L and the right rear wheel side inverter 24R, respectively, and are supplied with driving power. Like that. The left rear wheel side inverter 24L and the right rear wheel side inverter 24R are connected to the power supply unit 12 made of a battery or the like and are supplied with electric power. A control unit 6 is connected to the power supply unit 12, the left rear wheel side inverter 24L, and the right rear wheel side inverter 24R. With this control unit 6, the AC motor 3RL for driving the left rear wheel 2RL and the right rear wheel 2RR drive The drive power supplied to the AC motor 3RR and the regenerative power from these AC motors 3RL and 3RR are controlled.

  The control unit 6 comprises a microcomputer, a steering operation amount sensor 8 that detects the operation amount of the steering wheel 7, an accelerator pedal depression amount sensor 13 that detects the depression amount of the accelerator pedal 9, and a brake A brake operation sensor 14 that detects the operation of the pedal 10 and a vehicle motion state detection sensor 11 that detects acceleration in the front / rear and left / right directions of the vehicle are connected.

  The control unit 6 receives the detection signals from each of the above sensors, and controls the left rear wheel side inverter 24L, the right rear wheel side inverter 24R, etc. to drive the rear wheels 2RL, 2RR by the AC motors 3RL, 3RR and regenerative power. In addition to controlling the recovery of the battery to the battery, the insulation abnormality detection device of the present invention is also configured. Needless to say, these units may be separated and configured as respective units.

  FIG. 2 shows an AC motor 3RL for driving the left rear wheel side, an AC motor 3RR for driving the right rear wheel side, and a power feeding circuit thereof. In the figure, the first fuse 22A is connected to the positive side of the battery of the power supply unit 12, and the second fuse 22B is connected to the negative side thereof. Further, a DC contactor 23 for turning on / off direct current is connected between the fuses 22A and 22B.

  The DC contactor 23 is connected to a voltage type inverter 24L on the left rear wheel side and a voltage type inverter 24R on the left rear wheel side so that they are in parallel. Each of these voltage type inverters 24L, 24R includes a semiconductor switch unit 24a and an input capacitor 24b for current smoothing, so that the output voltage is a rectangular wave and the average voltage value is determined by the duty of PMW, The output amount of AC motors 3RL and 3RR is controlled by the voltage and output frequency. The output current is a sine wave.

  The voltage type inverter 24L and the voltage type inverter 24R on the left rear wheel side are star-connected to the AC motor 3RL for driving the left rear wheel 2RL and the AC motor 3RR for driving the right rear wheel 2RR, respectively. It is connected to the AC contactors 25L and 25R to be operated, and the AC motors 3RL and 2RR can be driven.

  AC motors 3RL and 2RR have stator windings (coils) 3La and 3Ra and motor cases 3La and 3Lb, respectively. Parasitic resistances 3Lc and 3Rc and parasitic capacitors 3Ld and 3Rd are respectively provided between the stator windings 3La and 3Ra and the motor cases 3Lb and 3Rb.

  Similarly, the voltage type inverters 24L and 24R or the power supply unit 12 side thereof also have parasitic capacitors between the high voltage circuit and the casing. Here, in the present invention, the remaining life of the insulation of the stator windings of the AC motors 3RL and 2RR, particularly the AC motors 3RL and 2RR, is monitored from the voltage type inverters 24L and 24R. Therefore, here, only the above three parasitic elements are considered, and the voltage-type inverters 24L and 24R and the ground insulation resistance on the power supply unit 12 side are assumed to be infinite or do not vary.

  Here, in order to measure the neutral point current value, the position where the neutral point current sensor is provided is indicated by circle 1, circle 2 and circle 3 in FIG. 2 (circle 1 etc. is indicated by a number in a circle in the drawing). Show. That is, in the present embodiment, the magnitude of the neutral point current at three locations is detected.

  First, the first neutral point current sensors 15L and 15R are provided in positions (circle 1) in the loop, that is, in the feeders connecting the voltage type inverters 24L and 24R and the AC contactors 25L and 25R, respectively. The first neutral point current sensors 15L and 15R detect a total current value obtained by collecting all phases (here, three phases) of AC coupling wires from the voltage type inverters 24L and 24R to the AC motors 3RL and 2RR, respectively. One current sensor may be provided, or a current sensor may be provided for each AC coupling line, and the detected values may be summed to calculate the magnitude of the driving frequency neutral point current. The first neutral point current sensors 15L and 51R are connected to the control unit 6 and send a current signal representing the drive frequency neutral point current value measured at the position (circle 1) to the control unit 6.

  On the other hand, the voltage-type inverters 24L and 24R are grounded to the vehicle body 1 having an equipotential through bonding. The position (circle 2) is set in the middle of this bonding, and the second neutral point current sensors 16L and 16R are provided here. These second neutral point current sensors 16L and 16R are connected to the control unit 6 and send a current signal representing the neutral point current value measured at the position (circle 2) to the control unit 6. In addition, as said bonding, you may make it comprise with the fasteners, such as a volt | bolt which attaches the housing | casing of voltage type inverters 24L and 24R to the vehicle body 1, or it replaces with the vehicle body 1 and installs in common with AC motor M1 and M2. It is also possible to provide a current detector in the device being implemented. Alternatively, high frequency grounding may be performed with a capacitor as a noise countermeasure.

  The motor cases 3Lb and 3Rb of the AC motors 3RL and 2RR are also grounded to the vehicle body 1 through bonding. The position (circle 3) is set in the middle of this bonding, and third neutral point current sensors 17L and 17R are provided here, respectively. These third neutral point current sensors 17L and 17R are connected to the control unit 6 and send a current signal representing the neutral point current value measured at the position (circle 3) to the control unit 6. In addition, as these bonding, you may make it comprise with fasteners, such as a volt | bolt which attaches motor case 3Lb, 3Rb to the vehicle body 1, and you may make it make high frequency grounding with a capacitor | condenser as a noise countermeasure. Also in this case, it is possible to provide a current detector in a device installed in common with the AC motors M1 and M2 instead of the vehicle body 1.

  FIG. 3 is a block diagram showing the configuration of the insulation abnormality detection device. As described above, the insulation abnormality detection device is constituted by a part of the control unit 6 in this embodiment.

  The insulation abnormality detection device, and thus the control unit 6, includes a first neutral point current sensor 15L on the left rear wheel drive AC motor 3RL side and a first neutral point on the right rear wheel drive AC motor 3RR side. A neutral point current signal is input from each of the current sensors 15R. The insulation abnormality detection device includes frequency discriminating units 61L and 61R that extract a signal of a necessary band by frequency discrimination from these input neutral point currents, and rectification units 62L and 62R that rectify the frequency discriminated current signals, respectively. And smoothing units 63L and 63R that smooth the rectified current signals, respectively, and a comparison determination unit 64 that receives these smoothed current signals and makes a comparison determination.

  The frequency discriminating units 61L and 61R are configured by filters. As this filter, a low-pass filter for removing measurement noise or a high-pass filter for removing an offset of a current signal or the like is used. When comparing and evaluating the driving frequency of the neutral point current by the comparison / determination unit 64, the band pass filter that covers the fluctuation range of the driving frequency or the frequency corresponding to the driving frequency that changes instantaneously can be changed. A band-pass filter may be used.

  Here, FIG. 4A shows an example of time-series measured values of the neutral point current signals input from the first neutral point current sensors 15L and 15R. In this way, the neutral point current signal including high frequency noise is subjected to high frequency noise removal by the low pass filters of the frequency discriminators 61L and 61R, and becomes a current signal as shown in FIG. 4B. Output from the frequency discriminators 61L and 61R.

  In the rectifying units 62L and 62R, the minus side signals of the current signals input from the frequency discriminating units 61L and 61R are folded back to the plus side as shown in FIG. The electric signal rectified in this way is input to the smoothing units 63L and 63R.

  In the smoothing units 63L and 63R, the rectified electric signals output from the rectifying units 62L and 62R are converted into the rectified electric signals output from the rectifying units 62L and 62R using a low pass filter having a longer time constant than the frequency discriminating units 61L and 61R. ) And smoothing each as shown by a thick solid line to signal the magnitude of the neutral point current.

  The comparison / determination unit 64 determines the insulation abnormality based on the difference in the waveform of the driving frequency neutral point current. In this embodiment, as the difference in waveform, the magnitude of the driving frequency neutral point current on the AC motor 3RL side that drives the left rear wheel 2RL and the driving frequency neutral point current on the AC motor 3RR side that drives the right rear wheel 2RR are shown. A difference from the magnitude (subtraction value), a ratio thereof, or both of the difference and the ratio are used, and when these absolute values are equal to or larger than a predetermined value, it is determined that an abnormality is present. In other words, when the absolute value of the difference in resistance component of the driving frequency neutral point current is greater than a predetermined value, if the absolute value of the difference in resistance component tends to increase above a predetermined value, a winding insulation abnormality occurs. Judge that you are doing.

  The detected current values between the second neutral point current sensors 16L and 16R on the left rear wheel 2RL side and the right rear wheel 2RR, and the detected current values between the third neutral point current sensors 17L and 17R. In the same manner as described above, a comparative judgment is also made.

  FIG. 6 shows a state of judgment by the comparison judgment unit 64 at the time of the abnormality. FIG. 6 shows the coordinates of the neutral point current on the right side on the horizontal axis and the neutral point current on the left side on the vertical axis. Plotting the differences in the parts (circle 1), (circle 2), and (circle 3) detected by the first to third current detectors, the left and right of the first neutral point current sensors 15L and 15R The neutral point current difference (or ratio) of the second and the neutral point current difference (or ratio) of the second neutral point current sensors 16L and 16R are such that their absolute values are smaller than a predetermined value. Although the difference (or ratio) at the position (circle 1) and position (circle 2) is within the “normal range of difference”, the difference in neutral point current between the third neutral point current sensors 17L and 17R ( (Or ratio), because there is an insulation abnormality in the right winding 3La, the absolute value becomes a predetermined value or more, and the difference (or ratio) at the position (circle 3) deviates from the “normal range of difference”. It will be located in the lower abnormal area. Also, if there is an insulation abnormality in the left winding 3Ra, the neutral point current difference (or ratio) of the third neutral point current sensors 17L and 17R is outside the “normal range of difference” and above it. It will be located in the abnormal area.

  That is, since the current value flowing through the neutral point varies depending on external factors such as outside temperature and humidity, the windings 3La and 3Ra of the AC motors 3RL and 3RR are individually individually based on the current value flowing through each neutral point. If an attempt is made to determine an insulation abnormality, the windings 3La and 3Ra are determined to be abnormal and erroneously detected depending on the amount of fluctuation. However, in the above configuration, based on the difference between the neutral point currents on the left and right, canceling and removing the fluctuations in the neutral point current due to external factors, the presence or absence of insulation abnormality in the windings 3La and 3Ra I try to detect it.

  The neutral point current fluctuation due to external factors can be canceled in the AC motors 3RL and 3RR and the first to third neutral point current sensors 15L, 15R, 16L, 16R, 17L, and 17R. When the windings 3La and 3Ra of AC motors 3RL and 3RR are normal, even if the neutral point current value measured due to external factors fluctuates, these tend to be the same on the left and right This is because the difference and the ratio of the neutral point current value on the left and right hardly change. On the other hand, if an insulation abnormality occurs in any of the windings 3La and 3Ra of the AC motors 3RL and 3RR, the absolute value of the difference between the right and left neutral point current values and the absolute value of the ratio will increase. The difference becomes large and insulation abnormality can be detected.

  For example, if leakage occurs due to insulation abnormality only in the winding 3Ra of the AC motor 3RR for driving the right rear wheel, it is driven from the winding 3Ra to the vehicle body 1 through bonding between the motor case 3Rb and the vehicle body 1. As a result of the current flowing as shown by the thick arrows in FIG. 5, the current detection value of the third neutral point current sensor 17R on the right rear wheel 2RL side increases. However, since there is no insulation abnormality in the winding 3La of the AC motor 3RL for driving the left rear wheel, the current detection value of the third neutral point current sensor 17L on the left rear wheel 2RL side is larger than that on the right side. The absolute value of the difference between the two is large.

    In this case, the current flows from the vehicle body 1 to both the left and right rear wheel side voltage type inverters 24L and 24R through bonding, but neutrality at the position between the left and right (circle 2). It can be determined that the difference between the point currents does not become larger than a predetermined value, and the position (circle 2) is normal. On the other hand, since the neutral current value applied from the inverters 24L and 24R does not change significantly at the position (circle 1), it can be determined that the position (circle 2) is normal.

  For example, in the case of weather as one of the external factors, the neutral point current value varies considerably between fine weather and rainy weather. That is, when the windings 3La and 3Ra of the AC motors 3RL and 3RR are normal, the neutral point current value of the AC motor 3RR on the right rear wheel side is 5 and the AC motor current value on the left rear wheel side in fine weather However, the neutral point current value tends to increase during rainy weather, so the neutral point current value of the AC motor 3RR on the right rear wheel side is 10 and the AC motor current on the left rear wheel side. Assume that the value is 9. In this case, the absolute value of the difference between the neutral point current values in fine weather obtained by the comparison judgment unit 64 is 5-4 = 1, while the neutral point current value in the rainy weather obtained by the comparison judgment unit 64 is The absolute value of the difference is also 9-8 = 1. Therefore, when the absolute value of the difference between right and left in fine weather and rainy weather is smaller than a predetermined value (for example, 4), the windings 3La and 3Ra are normal even if the neutral point current value increases due to an external factor. It can be determined that there is no insulation error.

  On the other hand, if an insulation abnormality occurs in the winding 3Ra of the AC motor 3RR on the right rear wheel side, the neutral point current value on the AC motor 3RR side for driving the right rear wheel is 9 and the left rear wheel in clear weather. The neutral point current value on the AC motor 3RL side for driving is 2, whereas the neutral point current value on the AC motor 3RR side for driving the right rear wheel is 16 in the rain, and the alternating current for driving the left rear wheel is It is assumed that the neutral point current value on the motor 3RL side is 10. In this case, the absolute value of the difference between the neutral point current values at the time of fine weather obtained by the comparison judgment unit 64 is 9-2 = 7, whereas the neutral point current value at the time of rain obtained by the comparison judgment unit 64 is The absolute value of the difference is also 16-10 = 6. Therefore, as a result of the absolute value of the difference between the left and right in fine weather and rainy weather becoming larger than a predetermined value (for example, 4), it can be determined that the winding Ra is an insulation abnormality.

  In the above description, two AC motors are used and the left and right neutral point currents are compared. However, the present invention can be applied to a case where more AC motors are used. As shown in FIG. 7, the signals of the neutral point current magnitudes are input from the four AC motors # 1 to # 4, and the average value, standard deviation, and each deviation are calculated as a set of these signals. If each deviation is a predetermined value or more, for example, 1.5 times or more than the standard deviation, an abnormality flag may be set to indicate that the AC motor has an insulation abnormality.

  As described above, in the insulation abnormality device of the first embodiment, the following effects can be obtained.

  Based on the difference, ratio, deviation, standard deviation, etc., on the left and right of the neutral point current, the neutral point current fluctuation due to external factors is canceled and eliminated, and the insulation abnormality of the windings 3La and 3Ra of the AC motor 3RL and 3RR is eliminated. Since it can be detected, erroneous detection of insulation abnormality can be reduced.

  In addition, because the neutral point current is compared using the low frequency drive frequency neutral point current, measurement and comparison of the insulation resistance can be performed with high accuracy without degrading the measurement accuracy due to current measurement noise. be able to.

  Since the insulation abnormality is detected when the difference in the resistance component of the driving frequency neutral point current is greater than the predetermined value, only the current component that is sensitive to the insulation resistance is extracted from the neutral point current for comparison. Thus, measurement and comparison of insulation resistance can be performed with high accuracy.

  Since an increase in the resistance component of the drive frequency neutral point current, which indicates that the insulation resistance is reduced, is detected and compared, it is possible to extract an AC motor in which the insulation resistance is particularly low. Furthermore, more accurate detection can be performed by removing the neutral point current fluctuation that does not mean a decrease in insulation performance, which is common to normal AC motors.

  Next, an insulation abnormality detection apparatus according to Embodiment 2 of the present invention will be described with reference to the accompanying drawings. In the second embodiment, a neutral point current sensor is provided for each high-frequency neutral point current at the position (circle 1) in the first embodiment for each feeder line, and each neutral point voltage application state or each fluctuation state thereof is provided. The characteristic value of the neutral point current is compared to detect the insulation abnormality of the windings 3La and 3Ra. Since the other parts are the same as those in the first embodiment, the same portions are denoted by the same reference numerals as those in the first embodiment.

  Here, since the three-phase AC motor is used for the AC motor 3RL that drives the left rear wheel 2RL and the AC motor 3RR that drives the right rear wheel 2RR, the voltage-type inverters 24L and 24R are replaced with the AC motors 3RL and 3RR. The voltages output via the three power supply lines are respectively at the same potential as the DC positive side voltage Vp or the negative side voltage Vn. Therefore, there are 8 combinations of 2 to the third power, but when classified according to the difference in neutral point potential, the combinations are divided into the following four types.

  That is, (1) when all three wires are at the positive side voltage Vp, in this case, the neutral point potential is also Vp. (2) When two lines are positive potential Vp and the remaining one line is negative potential Vn, the neutral point potential is (2Vp + Vn) / 3 in this case. (3) When one line is the positive potential Vp and the second line is the negative potential Vn, in this case, the neutral point potential is (Vp + 2Vn) / 3. (4) If all three wires are at negative potential Vn, the neutral point potential is Vn in this case.

  A neutral point current process for determining a winding insulation abnormality according to the above four differences depending on the neutral point potential will be described with reference to FIG. This process is the same in the above eight cases.

  FIG. 8 shows the motor virtual neutral point potential Vmn at the top stage, the neutral point current at the second stage, and the neutral point current cut out at section A by section discrimination at the third stage. The average value (indicated by a thick solid line) of the intermediate current cut out in the section A is shown in the time series, and the attenuation coefficient (indicated by the thick attenuation envelope) of the intermediate current cut out in the section A is shown in time series in the lowermost stage.

  In addition, as a section of discrimination, it discriminate | determines into 4 sections AD according to the above-mentioned 4 types, These are determined by the switching teaming of the semiconductor switch part 24a of the voltage type inverters 24L and 24R. As shown in the top row, the motor virtual neutral point potential Vmn is the maximum voltage value Vp in the section A, the voltage value (2Vp + Vn) / 3 in the following section B, and the voltage value (Vp + 2Vn) / in the following section C. 3. In the following section D, it gradually decreases to the lowest potential Vn. Thereafter, the potential increases with the interval C, the interval B, and the interval A, and is repeated as the interval B, the interval C, and the interval D again.

  In FIG. 8, the neutral point current measured at the position (circle 1) is obtained by calculating an average value and a damping coefficient as characteristic values of the vibration attenuation waveform of the neutral point current cut out in the section A. However, these are calculated for each section. Note that a frequency spectrum may be calculated as the characteristic amount.

  The characteristic amounts obtained by calculating for each section in this way are compared between the AC motors 3RL and 3RR on the left and right rear wheels for each section, and those having large differences are determined to be abnormal. This comparison determination is performed in the same manner as in the comparison of the magnitude of the driving frequency neutral point current in the first embodiment.

  FIG. 9 shows a configuration for performing the characteristic amount calculation by the cutout. In the figure, the cut-out signal generation unit 30 receives an inverter switching timing signal composed of a rectangular ON signal and an OFF signal that are switched according to time t, and a section A cut-out section 31 and a section B cut-out section according to the respective timings. 39, the section C cutout section 40 and the section D cutout section (not shown) cut out neutral point signals corresponding to the sections from the left and right neutral point currents.

  The neutral point signal cut out by the section A cutout unit 31 is sent to the average value calculation unit 32, the absolute value calculation unit 33, and the FET 34, and the frequency spectrum representing the power value Power at the average value, absolute value, and frequency f, respectively. Is calculated. The output of the absolute value calculator 33 is input to the interval maximum value calculator 38 and the post-predetermined value calculator 36 after the high-frequency noise is removed by the low pass filter 35. The section maximum value calculation unit 38 calculates the maximum value in the section A that has been cut out, and the value calculation unit 36 after the predetermined time calculates a cut-out neutral point current value after a predetermined time after the point when the maximum value is reached. . The attenuation coefficient calculation unit 37 calculates an attenuation coefficient from the maximum value from the section maximum value calculation unit 38 and the value after a predetermined time from the predetermined value subsequent value calculation unit 36.

  In addition, even in the section B cutout section 39, the section C cutout section 40, and the section D cutout section, each section has an average value calculation section 32 to an attenuation coefficient calculation section 37 as in the section A cutout section 31. The average value, the attenuation coefficient, and the frequency spectrum at are calculated, but these are omitted in FIG.

  The characteristic quantity obtained in this way is compared with the high-frequency neutral point current for each applied voltage state of the neutral point voltage of AC motor 3RL, 3RR or the fluctuation state of neutral point voltage in comparison judgment unit 64, When the difference in the waveform of the neutral current between the left and right AC motors 3RL and 3RR is greater than a predetermined value, it is determined that the insulation is abnormal. In the comparison of the difference in waveform, the difference in average value of neutral point currents is compared, and when the difference in these average values is larger than a predetermined value, it is determined that the insulation is abnormal. Further, in the comparison of the waveform difference, the difference in vibration attenuation coefficient between the left and right neutral point currents is compared, and when the difference in these attenuation coefficients is large by a predetermined value, it is determined that the insulation is abnormal. Alternatively, in the comparison of waveform differences, an insulation abnormality is determined when the frequency spectrum of the neutral point current vibration is different.

  Therefore, even in the insulation abnormality detection device of the second embodiment, similarly to the first embodiment, based on the difference between the left and right of the neutral point current, the fluctuation amount of the neutral point current due to the external factor is removed, and the AC motor 3RL. Since the insulation abnormality of the 3RR windings 3La and 3Ra can be detected, erroneous detection of the insulation abnormality can be reduced.

  In addition, since the high-frequency neutral point current is used as the neutral point current, even if the current component of the drive frequency is small, such as when the 3RL and 3RR torque command values are small, the drive frequency Neutral point current can be measured and compared regardless of whether or not the insulation 24L, 24R is always switched as long as the inverters 24L, 24R are switching.

  In addition, since the neutral point current is compared for each applied voltage state of the neutral point applied voltage of AC motors 3RL and 3RR, to parasitic capacitors 3Lc and 3Rc of windings 3La and 3Ra of AC motors 3RL and 3RR Compare the waveform of the neutral point current (charging / discharging current) when the applied voltage step is the same, and erroneously detect the difference in the waveform due to the difference in the high frequency neutral point current due to the difference in the applied voltage step Can be prevented.

  In addition, charge / discharge current (neutral point current) is compared for each state of the applied voltage of neutral point voltage of AC motors 3RL and 3RR, and insulation abnormality is detected by the difference in their average value. It is possible to compare the magnitude of the leakage current under the same voltage step, and to compare the deterioration of the insulation resistance with high accuracy.

  In addition, since the neutral point current is compared for each state of the applied voltage of the neutral point voltage of the AC motors 3RL and 3RR and the insulation abnormality is detected by the difference in their attenuation coefficients, the applied voltage step is the same state The magnitudes of the charge / discharge currents (neutral point currents) of the parasitic capacitors 3Ld and 3Rd can be compared with each other, and the deterioration of the insulation resistance can be compared with high accuracy.

  In addition, since the charge / discharge current (neutral point current) is compared for each state of the applied voltage of the neutral point voltage of the AC motors 3RL and 3RR, the insulation abnormality is detected by the difference in the frequency spectrum of the vibration. Under the same applied voltage step, it is possible to compare the resonance frequency and attenuation of the charge / discharge current (neutral point current) of the parasitic capacitors 3Ld and 3Rd, and to compare the deterioration of insulation resistance with high accuracy. .

  Next, an insulation abnormality detection apparatus according to Embodiment 3 of the present invention will be described with reference to the accompanying drawings. In this embodiment, the neutral point current is processed by a combination of voltages of each phase of the alternating current instead of the four processes divided for each neutral point voltage application state of the motor in the second embodiment. Do. In the third embodiment, the same parts as those in the first and second embodiments will be described with the same numbers.

  In the case of a three-phase AC motor, there are the following eight combinations of the voltage of each phase as the cube of 2 as described above. That is, NNN, NNP, NPN, NPP, PNN, PNP, PPN, PPP. Here, in the above three characters combined with N (representing negative voltage Vn) and P (representing positive voltage Vp), the first character, the middle character, and the last character are all The voltages in the U-phase, V-phase, and W-phase of AC motors 3RL and 3RR are represented as Vn or Vp, respectively.

  The above eight states may not appear for a while due to the magnitude of all UVW voltage commands in AC motors 3RL and 3RR. FIG. 10 shows the case where the magnitude of the applied voltage is U phase> V phase> W phase, and among the above eight patterns, four patterns of PNN, NNN, PPN, and PPP appear. On the other hand, FIG. 11 shows a case where the magnitude of the applied voltage is U phase> W phase> V phase, and further three types of PNN and PNP appear. These appearance situations are summarized in a table as shown in FIG. In FIG. 12, a place corresponding to ◯ appears.

  In normal three-phase alternating current, all combinations of U-phase, V-phase, and W-phase magnitude combinations appear as shown in FIG. 13 depicting the relationship between the electrical angle and each phase voltage. All eight voltage states shown in FIG. 12 can be detected. Therefore, for example, if PNN, NPN, and NNP are distinguished and there is an abnormality in the characteristic amount of PNN, it is said that an insulation abnormality has occurred in the U-phase coil. You can determine whether you are doing. That is, it becomes possible to discriminate.

  Therefore, in the insulation abnormality detection device of the third embodiment, the same effects as those of the second embodiment can be obtained, and the following effects not found in the first and second embodiments can be obtained.

  As shown in FIG. 8, compared with the second embodiment in which the difference is obtained by sorting into four sections divided for each neutral point voltage application state, in the third embodiment, the AC motor 3RL, as shown in FIG. Since the charge / discharge current (neutral point current) is compared for each fluctuation state of the neutral point voltage applied to the 3RR, the waveforms of the neutral point currents on the left and right are compared, and the insulation abnormality is determined based on the difference between them. Although there are many types of sections to be sorted and the processing becomes complicated, it is possible to determine which phase winding has an insulation abnormality.

  As can be seen from the above embodiments, in the present invention, in order to cancel the fluctuation of the neutral point of the day due to external factors, the characteristic values are compared relatively between a plurality of AC motors. The insulation abnormality of the AC motor is detected. This will be described below in more detail with reference to FIG.

  The average voltage or virtual neutral point voltage potential applied to the winding of the AC motor changes stepwise in synchronization with the switching at the semiconductor switch portion of the inverter as shown in FIG. As a result, a weak current flows through the parasitic capacitance and insulation resistance between the motor winding and the motor stator core or the motor case. Among these, the parasitic capacitor is charged in conjunction with the step-like voltage change. At this time, the inverter-side parasitic capacitor and the motor-side parasitic capacitor in series are electrostatically divided by voltage, but the motor-side parasitic capacitor is an insulation coating for insulating the windings from the ground. The capacitance is larger than that of the parasitic capacitor on the inverter side, and as a result, it can be considered that most of the voltage is generated on the motor side.

  Since the resistance of the main circuit in series with the capacitor on the motor side is small, the voltage or charge / discharge current of the capacitor has a waveform oscillating at each frequency ω = √ (CR) determined by small C and small R. On the other hand, since this capacitor has an insulation resistance in parallel, the vibration waveform is gradually discharged to a waveform as shown in FIG.

  If the insulation resistance is reduced, a steady leakage current appears in the current. This can be extracted by taking a section average as in the second and third embodiments. On the other hand, when the insulator is thin (mechanical contraction), the capacitance of the parasitic capacitor increases, and the resonance frequency changes. This resonance frequency can be extracted from the frequency spectrum. Even if the insulation resistance changes such that no steady leakage current is generated, the damping speed of the vibration waveform varies. This can be extracted using the attenuation coefficient.

  Theoretically, these changes should be detected by monitoring the trend of a single motor continuously for a long time, but in reality, the daily fluctuation due to changes in the temperature, humidity, etc. of the insulators. In practice, detection is not easy because it is much larger than the variation of the insulator. However, in the present invention, as described above, since the insulation abnormality is detected by relatively comparing the characteristic values among a plurality of motors, the daily fluctuation due to the external factor can be canceled, and an error is detected. Detection can be reduced.

    As described above, the insulation abnormality detection device of the present invention has been described based on the above embodiments. However, the present invention is not limited to these embodiments, and design changes and Variations are included in the present invention.

  For example, in the above embodiment, the AC motor is provided only on the left and right rear wheels, but it may be provided only on the left and right front wheels or on the four wheels on the left and right sides. By applying the detection device, the same effects as those of the first to third embodiments can be obtained.

  The insulation abnormality detection device of the present invention can be used for a vehicle equipped with a plurality of AC motors.

1 body
2FL, 2fR, 2RL, 2RR wheels
3RL, 3RR AC motor
3La, 3Ra winding
3Lb, 3Rb motor case
3Lc, 3Rc parasitic resistance
3Ld, 3Rd parasitic capacitor
6 Control unit
12 Power supply unit
15L, 15R, 16L, 16R, 17L, 17R Neutral point current sensor
23L, 23R DC contactor
24L, 24R voltage type inverter
24a Semiconductor switch part
25L, 25R AC contactor
30 Cutout signal generator
31, 39, 40 section cutout
32 Average value calculator
33 Absolute value calculator
34 FET
35 Low pass filter
36 After-hours calculation unit
37 Damping coefficient calculator
38 Section maximum value calculator
61L, 61R frequency discriminator
62L, 62R Rectifier
63L, 63RF Smoothing section
64 Comparison judgment section

Claims (10)

A plurality of AC motors driven by an inverter to generate driving force or generate power;
Neutral point current detecting means for detecting the state of neutral point current flowing through the neutral point of the AC motor;
Comparison means for comparing the state of the neutral point current detected for each of the AC motors by the neutral point current detection means;
An abnormality determination means for performing an insulation abnormality determination of the winding of the AC motor based on a comparison result by the comparison means;
An insulation abnormality detection device comprising: In the insulation abnormality detection device according to claim 1,
The neutral point current detection means detects the waveform of the neutral point current, the comparison means compares the waveforms, and the abnormality determination means determines that the insulation abnormality is present when the absolute value of the difference between the waveforms is greater than a predetermined value. An insulation abnormality detection device characterized by determining. In the insulation abnormality detection device according to claim 1 or 2,
An insulation abnormality detection device, wherein the neutral point current is a drive frequency neutral point current. In the insulation abnormality detection device according to claim 3,
An insulation abnormality detection device, wherein an insulation abnormality is determined when an absolute value of a difference between resistance components of the driving frequency neutral point current is larger than a predetermined value. In the insulation abnormality detection device according to claim 3,
An insulation abnormality detection device, wherein an insulation abnormality is determined when an absolute value of a difference between resistance components of the driving frequency neutral point current tends to increase beyond a predetermined value. In the insulation abnormality detection device according to claim 1 or 2,
An insulation abnormality detection device, wherein the neutral point current is a high-frequency neutral point current. In the insulation abnormality detection device according to claim 6,
The neutral point current is compared for each applied voltage state of the neutral point voltage of the plurality of AC motors or the fluctuation state of the neutral point voltage, and the waveform difference of the neutral point current among the plurality of AC motors An insulation abnormality detection device that determines an insulation abnormality when is greater than a predetermined value. In the insulation abnormality detection device according to claim 7,
An insulation abnormality detection device, wherein an insulation abnormality is determined when a difference in an average value of the neutral point currents between the plurality of AC motors is greater than a predetermined value. In the insulation abnormality detection device according to claim 7,
An insulation abnormality detection device, wherein an insulation abnormality is determined when a difference in vibration attenuation of the neutral point current among the plurality of AC motors is greater than a predetermined value. In the insulation abnormality detection device according to claim 7,
An insulation abnormality detection apparatus, wherein an insulation abnormality is determined when a frequency spectrum of the neutral point current vibration differs between the plurality of AC motors.

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