JP6476972B2 - Leakage determination device - Google Patents

Description

  The present invention relates to a leakage determination device that determines the presence or absence of leakage between a high-voltage circuit and a vehicle body.

  Although the high voltage circuit mounted on the vehicle and the vehicle body are electrically insulated, the insulation performance may be reduced. Therefore, it has been conventionally determined whether or not there is a leakage between the high voltage circuit and the vehicle body.

  For example, in Patent Literature 1, an alternating-current signal having a first frequency and an alternating-current signal having a second frequency different from the first frequency are output from the oscillating unit at different timings. A plurality of AC signals having different frequencies are applied. The electrical characteristics of the high voltage circuit (electric system) specified by detecting the peak value of the first AC signal corresponding to the first frequency and the second peak value corresponding to the second frequency. Based on the above, the common capacity of the high-voltage circuit is estimated. Then, a threshold value for leakage detection is set based on the estimated value of the common capacity, and when the peak value of the AC signal is lower than the threshold value, it is determined that the insulation resistance is reduced.

JP 2014-155329 A

  When performing leakage check using an AC signal, it is preferable to use a low-frequency AC signal in order to avoid a decrease in the peak value of the AC signal due to the influence of the common capacitance. However, making a leakage determination using a low-frequency AC signal is a limitation when reducing the leakage determination time.

  This invention is made | formed in view of the above, and makes it a main objective to provide the leak determination apparatus which can implement a leak determination more appropriately.

  The present invention is a leakage determination device (20) for determining whether or not there is a leakage between a high voltage circuit (100) and a vehicle body, and outputs an AC signal to the high voltage circuit via a resistor (26). With the AC signal output means (24) and the AC signal output means outputting the AC signal, the peak value of the AC signal divided by the resistor and the insulation resistance component of the high voltage circuit is obtained. Leakage determination for determining the presence or absence of leakage based on whether or not the peak value acquisition means (51) to be acquired, frequency setting means (54) for setting the frequency of the AC signal, and whether the peak value is less than a threshold value Means (50b), wherein the frequency setting means can switch the frequency of the AC signal between a first frequency and a second frequency lower than the first frequency, and the leakage determination means The AC signal in the setting means In a state where the frequency is set to the first frequency, a first determination is made as to whether or not the peak value is less than the threshold value, and it is determined in the first determination that the peak value is less than the threshold value In the state where the frequency of the AC signal is set to the second frequency, a second determination is made as to whether or not the peak value is less than the threshold, and based on the determination result of the second determination, It is characterized by determining the presence or absence of electric leakage.

  According to the present invention, in the state where it is determined that there is no possibility of electric leakage in the first determination, since the first determination is continued, the time required for the electric leakage determination can be shortened. On the other hand, when it is determined that there is a possibility of electric leakage in the first determination, the second determination is performed at the second frequency lower than the first frequency, so the electric leakage determination is performed at a low frequency with little influence of the common capacity. Can be implemented, and the accuracy of the leakage determination can be improved. As described above, leakage determination can be performed with high accuracy while speeding up leakage determination.

1 is an overall configuration diagram including a leakage determination device. The figure which shows an electrical leakage determination apparatus. The flowchart of an electrical leakage determination process. The timing chart of a leak determination process.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The leakage determination device of the present embodiment is applicable to a vehicle such as a hybrid vehicle or an electric vehicle that can travel using the power of the DC power source as a travel drive source and can charge the DC power source with external power. .

  In FIG. 1, the high voltage circuit 100 includes a DC power supply 11 and a power conversion circuit 10. DC power supply 11 and power conversion circuit 10 are connected via a system main relay (hereinafter referred to as SMR 12). In addition, a leakage determination device 20 is connected to the high voltage circuit 100.

  The DC power supply 11 is a battery group configured by connecting a plurality of secondary batteries such as rechargeable lithium ion batteries in series. The SMR 12 is connected when power is supplied from the DC power supply 11 to the power conversion circuit 10 or when power is supplied from the power conversion circuit 10 to the DC power supply 11.

  The power conversion circuit 10 includes various electric devices (not shown) such as a converter, an inverter, and an MG. The voltage of the DC power source 11 is boosted by the converter, and the AC power generated by the MG is converted by the inverter. The DC power is converted into DC power, and the converted DC power is stepped down by a converter and supplied to the DC power supply 11.

  The high voltage circuit 100 having the above configuration is electrically insulated from the vehicle body. Therefore, a ground insulation resistance (hereinafter referred to as an insulation resistance Rg) is generated between the DC power source 11 and the vehicle body, and between the power conversion circuit 10 and the vehicle body.

  Further, since the high voltage circuit 100 is insulated from the vehicle body, a common capacitance Cg is generated between the DC power source 11 and the vehicle body, and between the power conversion circuit 10 and the vehicle body. The common capacitance Cg is an electrostatic capacitance of the high voltage circuit 100 with respect to the vehicle body, and is also referred to as a stray capacitance. FIG. 1 shows an equivalent circuit of these insulation resistance Rg and common capacitor Cg for convenience of explanation.

  When this insulation resistance Rg is lowered, an electric leakage in which an unintended current flows through the vehicle body may occur. Therefore, the leakage determination by the leakage determination device 20 is performed.

  In FIG. 2, the leakage determination device 20 includes a capacitor 22, an oscillator 24, a resistor 26, a signal input unit 28, and a microcomputer 50. In FIG. 2, the high voltage circuit 100 is shown as an equivalent circuit of an insulation resistance Rg and a common capacitor Cg.

  The capacitor 22 insulates the high voltage circuit 100 and the leakage determination device 20 in a DC manner, and has one end connected to the high voltage circuit 100 and the other end connected to the resistor 26.

  The oscillator 24 generates and outputs an AC signal. Specifically, the oscillator 24 generates a rectangular wave voltage signal and outputs the voltage signal to the wiring path (common path) of the high voltage circuit 100 connected to the capacitor 22 via the resistor 26. The common path is a wiring path that connects the DC power supply 11 and the resistor 26, and more specifically, a wiring that connects the other end of the capacitor 22 and the resistor 26. The oscillator 24 of this embodiment can variably set the frequency of the AC signal. For example, the frequency of the AC signal can be variably set in the range of 2 to 100 Hz.

  The signal input unit 28 inputs a voltage applied to a connection point D between the resistor 26 and the capacitor 22 in the common path as a detection signal, and outputs the detection signal to an A / D converter (not shown). The A / D converter converts the detection signal detected by the signal input unit 28 into a digital signal and outputs it to the microcomputer 50. In the present embodiment, the microcomputer 50 and the A / D converter are configured separately, but the microcomputer 50 may include an A / D converter.

  The microcomputer 50 is mainly configured by a microcomputer including a CPU, RAM, ROM, flash memory, and the like, and the CPU executes various processes relating to leakage determination according to a program stored in the ROM.

  The microcomputer 50 of the present embodiment temporarily determines whether or not there is a possibility of electric leakage by setting the frequency f of the AC signal output from the oscillator 24 to a predetermined first frequency f1 when the electric leakage determination condition is satisfied. To implement. If it is determined that there is a possibility of electric leakage in the tentative determination, the frequency f of the AC signal output from the oscillator 24 is set to a second frequency f2 that is lower than the first frequency f1, and a high voltage is set. This determination is performed to determine that the circuit 100 has a leakage.

  More specifically, the microcomputer 50 includes a digital filter processing unit 50a and an electric leakage determination processing unit 50b. The digital filter processing unit 50a extracts the frequency band of the AC signal output from the oscillator 24 and its surrounding band components from the digital AC signal after A / D conversion by, for example, a finite impulse response. By doing so, the noise component contained in the AC signal is removed.

  The digital filter processing unit 50a extracts a signal in the frequency band of the AC signal output from the oscillator 24. That is, the filter characteristics of the digital filter processing unit 50a are variably set in accordance with the frequency band of the AC signal output from the oscillator 24.

  The leakage determination processing unit 50 b includes an AC signal frequency setting unit 54, a common capacity estimation unit 55, and a leakage determination unit 56.

  The frequency setting unit 54 sets the frequency f of the AC signal output from the oscillator 24. Specifically, the frequency f of the AC signal is set to the first frequency f1 in the provisional determination. In this determination, the frequency f of the AC signal is set to the second frequency f2. In the present embodiment, the second frequency f2 is set by gradually reducing the frequency in the range from the first frequency f1 to the lower limit value of the predetermined frequency (hereinafter referred to as the lower limit frequency fa). That is, when this determination is started, the second frequency f2 is set by subtracting the predetermined frequency Δf from the first frequency f1. Then, it is determined whether or not the peak value at the second frequency is less than the threshold value. Thereafter, every time this determination is made, a predetermined frequency Δf is subtracted from the previous frequency to set the current second frequency f2.

  The common capacity estimation unit 55 calculates an estimated value of the common capacity Cg at the time of this determination. Specifically, a difference ΔV between the peak value of the AC signal acquired in the provisional determination and the peak value of the AC signal acquired in the main determination is calculated. Then, an estimated value of the common capacitance Cg is calculated using an arithmetic expression or a map that defines the relationship between the difference ΔV of the peak values and the common capacitance Cg. In the provisional determination, since the frequency of the AC signal is not basically changed, the estimated value of the common capacitance Cg is not calculated. In this case, the speed of temporary determination can be further increased.

  The leakage determination unit 56 determines the presence or absence of leakage using the peak value of the AC signal detected by the digital filter processing unit 50a. Specifically, in the provisional determination, it is determined whether the detected value of the peak value of the AC signal is less than a predetermined threshold Th. If it is determined in the tentative determination that the peak value of the AC signal is equal to or greater than the threshold Th, the tentative determination is continued. If the peak value is determined to be less than the threshold Th in the tentative determination, this determination is performed. In this determination, the detected value of the peak value of the AC signal acquired in this determination is corrected using the estimated value of the common capacity Cg calculated by the common capacity estimation unit 55, and the peak value of the corrected AC signal is a predetermined value. Based on whether or not it is less than the threshold value Th, the presence or absence of electric leakage is determined. When it is determined that there is a leak in this determination, it is determined that there is a leak in the high voltage circuit 100.

  In the present embodiment, the threshold Th used in the temporary determination and the main determination is the same, but the threshold Th used in the temporary determination and the main determination may be different. For example, in consideration of the influence of the common capacitance Cg, the threshold value in the main determination may be set lower than the threshold value in the temporary determination.

  As described above, in the temporary determination, the time required for the leakage determination can be shortened by using the first frequency f1. In this determination, the presence or absence of electric leakage can be accurately determined in a state in which the decrease in the peak value of the AC signal due to the influence of the common capacitance Cg is suppressed.

  By the way, it is assumed that the peak value of the AC signal decreases due to the influence of the common capacitance Cg in the temporary determination. In this case, if the second frequency f2 lower than the first frequency f1 is used in this determination, the influence of the common capacitor Cg can be suppressed, and the peak value of the AC signal can be recovered to the threshold Th or higher. In this case, it is preferable that the temporary determination is performed after the main determination that requires a relatively long time to determine the leakage is completed. In addition, when the high voltage circuit 100 is temporarily in a leakage state, the peak value of the AC signal may be restored to the threshold value Th or more when the cause is eliminated. Also in this case, it is preferable that the final determination is performed after the final determination.

  Therefore, in the present embodiment, when the peak value of the AC signal is recovered to be equal to or greater than the threshold Th during the main determination, the main determination is terminated and the provisional determination state is restored. Thereby, the time taken for the leakage determination when there is no possibility of leakage is shortened.

  Note that when the peak value decreases due to the influence of the common capacitance Cg during the temporary determination and the peak value of the AC signal recovers to a threshold value or more in this determination, the temporary determination is performed using the frequency at that time. Accordingly, it is possible to avoid a decrease in the peak value due to the influence of the common capacitance Cg. Therefore, in the present embodiment, when the peak value of the AC signal is recovered to the threshold value Th or more in the main determination and returned to the temporary determination state, the frequency of the AC signal at the time when the main determination is finished is the first frequency f1. Are updated and provisional determination is performed.

  Next, the procedure of the leakage determination process performed by the microcomputer 50 will be described with reference to FIG. This process is repeatedly performed by the microcomputer 50 at a predetermined cycle.

  First, it is determined whether or not a leakage determination condition is satisfied (S11). In this process, for example, an affirmative determination is made before the SMR 12 is connected, after the SMR 12 is opened, or when power conversion by the power conversion circuit 10 is not performed.

  If the leakage determination condition is satisfied, it is determined whether or not the determination flag is off (S12). This determination flag is turned on when it is determined in S16 described later that the peak value is less than the threshold value Th.

  When this determination flag is off, provisional determination is performed in S13 to S18. First, it is determined whether this determination is not performed (S13). This process makes an affirmative determination when the determination flag has never been turned on after the leakage determination condition is satisfied. When this determination is not performed in S13, the frequency of the AC signal is set to the first frequency f1 (S14). Next, it is determined whether or not the peak value of the AC signal is less than the threshold value Th (S16). If the peak value of the AC signal is greater than or equal to the threshold Th, the determination flag is turned off (S17). When the peak value of the AC signal is less than the threshold value Th, this determination flag is turned on (S18).

  If it is determined in S12 that the main determination flag is on, the main determination is performed in S19 to S25. First, it is determined whether or not the frequency f of the previous AC signal is equal to or higher than a predetermined lower limit frequency fa (S19). If an affirmative determination is made, the second frequency f2 is set by subtracting the predetermined frequency Δf from the frequency f of the previous AC signal (S20). If a negative determination is made in S19, the lower limit frequency fa is set to the second frequency f2 (S21).

  Thereafter, an estimated value of the common capacity Cg is calculated (S22). Next, it is determined whether or not the peak value of the AC signal after correction based on the estimated value of the common capacitance Cg is less than a predetermined threshold Th (S23). If an affirmative determination is made, it is determined that a leakage has occurred in the high voltage circuit 100 (S24). If a negative determination is made, this determination flag is turned off (S25).

  In addition, a process is complete | finished when the leak determination conditions are not satisfied in S11. In this case, all conditions are once reset. If it is determined in S13 that the main determination is performed, the first frequency f1 is updated (S15). That is, when the previous determination is the final determination, the second frequency f2 at the end of the final determination (switching to the temporary determination) is set to the first frequency f1. When the previous preliminary determination is made, the first frequency f1 is set to be the same as the previous temporary determination. Then, the process of S16-S18 is implemented.

  Next, an execution example of the above process will be described with reference to FIG. In the following process, the leakage determination process in the case where it is determined in this determination that no leakage has occurred after it is determined that there is a possibility of leakage in the tentative determination is illustrated.

  When the leakage determination condition is satisfied at time t1, an AC signal having the first frequency f1 is output. At this time, since the peak value of the AC signal is equal to or greater than the threshold value Th, the determination flag is turned off, and the provisional determination at the first frequency f1 is continued.

  When the peak value of the AC signal becomes less than the threshold Th at time t2, the main determination flag is turned on, and the main determination is performed at the second frequency f2. In this determination, it is determined that a leakage has occurred by determining that the peak value of the AC signal is less than the threshold Th. Thereafter, this determination is continued while the second frequency f2 is gradually decreased. When the peak value of the AC signal becomes equal to or greater than the threshold Th at time t3 during the actual determination, the determination flag is turned off, and the first frequency f1 is updated using the second frequency f2 at that time. The provisional determination is performed at the later first frequency f1. Here, it is determined that the peak value of the AC signal is equal to or greater than the threshold value Th.

  In FIG. 4, when the peak value of the AC signal does not recover above the threshold Th after time t3, the second frequency f2 is lowered to the lower limit frequency fa as indicated by the broken line in the figure. Then, after time t4 when the lower limit frequency fa is reached, the main determination at the lower limit frequency fa is continued.

  According to the above, the following excellent effects can be achieved.

  (1) When the AC signal used for the leakage determination is set to a low frequency, the influence on the leakage determination by the common capacitance Cg included in the high voltage circuit 100 can be suppressed, but when the time required for the leakage determination is to be shortened It becomes a restriction of. On the other hand, if the AC signal used for leakage detection is set to a high frequency, the time required for leakage determination can be shortened. However, the detected value of the peak value of the AC signal changes due to the influence of the common capacitance Cg, and the accuracy of the leakage determination is improved. May fall.

  Therefore, first, it is determined whether or not the peak value is less than the threshold using the AC signal having the first frequency f1 (first determination). If the peak value is less than the threshold in this state, the frequency of the AC signal is subsequently lowered. It changes to the 2nd frequency f2 by the side of a frequency, and it is determined whether a crest value is less than a threshold value (2nd determination). That is, in the first determination, it is temporarily determined whether or not there is a possibility of electric leakage at the first frequency f1, and when it is determined that there is a possibility of electric leakage, the second frequency f2 that is lower than the first frequency f1. In this case, it is determined that there is a leak.

  In this case, in the state where it is determined that there is no possibility of electric leakage in the first determination, since the first determination is continued, the time required for the electric leakage determination can be shortened. On the other hand, when it is determined that there is a possibility of electric leakage in the first determination, the second determination is performed at the second frequency f2 lower than the first frequency f1, so that the low frequency with less influence of the common capacitance Cg With this, it is possible to carry out leakage determination and improve the accuracy of leakage determination. As described above, leakage determination can be performed with high accuracy while speeding up leakage determination.

  (2) When a temporary determination is performed using a high-frequency AC signal, it is assumed that the peak value of the AC signal is lowered due to the influence of the common capacitance Cg, so that it is determined that there is a possibility of electric leakage. In this case, when this determination is performed at the second frequency f2, the influence of the common capacitor Cg is suppressed, and the peak value of the AC signal can be recovered to a threshold value or more. In addition, even when a short circuit has occurred temporarily, the peak value of the AC signal can be restored to a threshold value or more when the cause is eliminated.

  Therefore, when the peak value of the AC signal is equal to or greater than the threshold value during execution of the main determination and it is determined that there is no leakage, the main determination is terminated and the state is returned to the state in which the temporary determination is performed. In this case, it is possible to shorten the time for determining leakage in a situation where leakage does not occur.

  (3) When the peak value of the AC signal decreases due to the influence of the common capacitor Cg, the influence of the common capacitor Cg is suppressed by lowering the frequency f of the AC signal to the second frequency f2 in this determination. The peak value of the AC signal can recover to a threshold value or more. In this case, if the provisional determination is performed at the frequency f when the peak value of the AC signal is restored to the threshold value or more, the provisional determination can be performed in a state where the decrease of the peak value due to the influence of the common capacitance Cg is avoided. .

  Therefore, when it is determined that there is no electric leakage in this determination and the state of the temporary determination is returned, the temporary determination is performed in a state where the frequency f of the AC signal when the determination is finished is updated as the first frequency f1. In this case, it is possible to reduce the time required for the leakage determination by performing the temporary determination while suppressing the influence of the common capacitance Cg.

  (4) In this determination, since the first frequency f1 is lowered stepwise and the second frequency f2 is set, after it is determined in this determination that there is no leakage, the updated second used in the temporary determination One frequency f1 can be set as high as possible.

  (5) Using the change of the frequency f of the AC signal between the temporary determination and the final determination, the first peak value acquired at the temporary determination and the second peak value acquired at the final determination. An estimated value of the common capacity Cg is calculated from the difference. In this determination, the first peak value or the second peak value is corrected using the estimated value of the common capacitance Cg, and the leakage determination is performed using the corrected peak value. The accuracy of determination can be further increased.

  The present invention is not limited to the embodiment described above, and may be implemented as follows. In the following description, the same components as those described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the processing of FIG. 3 described above, when it is determined in S12 that the main determination flag is ON, the second frequency f2 is gradually decreased with the lower limit frequency fa as the lower limit value. In addition to this, the frequency f of the AC signal in the provisional determination and the main determination may be switched in n stages. For example, the first frequency f1 of the AC signal at the time of provisional determination and the second frequency f2 of the AC signal at the final determination may be switched in two steps.

  In the process of FIG. 3 described above, when the peak value of the AC signal is restored to the threshold value Th and returned to the temporary determination state during the main determination, the threshold value Th for the electric leakage determination is set higher. Also good. In this case, it is possible to more correctly determine whether or not the state is a return state from the leakage state.

  In the process of FIG. 3 described above, when the peak value of the AC signal recovers to the threshold value Th and returns to the tentative determination state during the main determination, switching from the main determination is performed in the subsequent tentative determination. The first frequency f1 is updated with the current frequency f, and the provisional determination is performed with the updated first frequency f1. In addition to this, when switching from the main determination to the provisional determination, the original first frequency f1 may be restored.

  In the processing of FIG. 3 above, in S22, the estimated value of the common capacitance Cg is calculated using the difference ΔV between the peak value of the AC signal acquired in the temporary determination and the peak value of the AC signal acquired in the main determination. doing. In addition to this, in this determination, the estimated value of the common capacitance Cg may be calculated using the difference ΔV in the peak values of the AC signals acquired at different frequencies f.

  DESCRIPTION OF SYMBOLS 20 ... Leakage determination apparatus, 24 ... Oscillator, 26 ... Resistor, 50 ... Microcomputer, 54 ... Frequency setting part, 100 ... High voltage circuit.

Claims (5)

An electric leakage determination device (20) for determining the presence or absence of electric leakage between the high voltage circuit (100) and the vehicle body,
AC signal output means (24) for outputting an AC signal to the high voltage circuit via a resistor (26);
A peak value acquisition means (50a) for acquiring a peak value of the AC signal divided by the resistor and an insulation resistance component of the high voltage circuit in a state where the AC signal is output by the AC signal output means. When,
Frequency setting means (54) for setting the frequency of the AC signal;
A leakage determining means (50b) for determining whether or not there is a leakage based on whether or not the peak value is less than a threshold value,
The frequency setting means can switch the frequency of the AC signal between a first frequency and a second frequency lower than the first frequency,
The leakage determination means includes
In a state where the frequency of the AC signal is set to the first frequency by the frequency setting means, a first determination is made as to whether the peak value is less than the threshold value,
When it is determined in the first determination that the peak value is less than the threshold value, whether or not the peak value is less than the threshold value in a state where the frequency of the AC signal is set to the second frequency. 2 Make a decision,
When it is determined in the second determination that the peak value is less than the threshold value, it is determined that there is a leakage, and in the second determination, it is determined that the peak value is greater than or equal to the threshold value. It is determined that there is no electric leakage.   The said leakage determination means ends said 2nd determination, and returns to the state of said 1st determination, when the said peak value becomes more than the said threshold value in the said 2nd determination, and it determines with there being no leakage. The leakage determination device described. The frequency setting means, when performing the second determination, gradually reduces the second frequency in a range from the first frequency to a predetermined lower limit,
3. The leakage determination device according to claim 1, wherein the leakage determination unit determines whether the peak value is less than the threshold at each frequency as the second frequency as the second determination. 4. The leakage determination means ends the second determination when it is determined that there is no leakage before the second frequency is lowered to the lower limit value when the second determination is performed. To return to the judgment state,
The leakage determination apparatus according to claim 3, wherein the frequency setting means sets the second frequency when it is determined that there is no leakage in the second determination as the first frequency. The leakage determination means includes a first peak value acquired in a state where the frequency of the AC signal is the first frequency, and a second peak value acquired in a state where the frequency of the AC signal is the second frequency. Common capacity calculation means (55) for calculating an estimated value of the common capacity from the difference;
Crest value correcting means (50b) for correcting the second crest value using the estimated value of the common capacity,
5. The leakage determination device according to claim 1, wherein the leakage determination unit performs the second determination using the peak value corrected by the peak value correction unit.

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