JP6229586B2 - Ground fault judgment device - Google Patents

Description

  The present invention relates to a ground fault determination device that determines the presence or absence of a ground fault.

  Conventionally, in a vehicle equipped with a high voltage battery system (high voltage circuit) such as a hybrid vehicle or an electric vehicle, a ground insulation resistance exists between the high voltage portion and the vehicle, and the ground insulation resistance due to a ground fault or the like exists. In order to protect an occupant and the like from leakage due to a decrease, a ground fault determination device that determines a ground fault is provided.

  For example, in Patent Document 1, the ground fault determination device has a predetermined frequency via a resistor with respect to the high voltage portion in a state where the ground fault determination device and the high voltage portion are galvanically insulated via a coupling capacitor. An AC signal (pulse signal) is applied. And the presence or absence of a ground fault is determined from the fluctuation | variation of the voltage (crest value) of the alternating current signal determined by the partial pressure of resistance and ground insulation resistance. Note that the ground fault determination device is provided with a filter that removes noise by filtering the frequency band of the AC signal, so that the detection accuracy of the voltage of the AC signal is improved (see Patent Document 1).

JP 2003-274504 A

  However, when the frequency of the noise superimposed on the AC signal is close to or overlaps with the frequency band of the AC signal, if the filter circuit is used to filter the noise, the AC signal used for ground fault determination The component is also removed, and there is a possibility that the detection accuracy of the AC signal is lowered.

  In view of the above circumstances, it is an object of the present invention to provide a ground fault determination device capable of improving the accuracy of ground fault determination.

  In the present invention, AC signal output means for outputting an AC signal having a predetermined oscillation frequency applied to the ground insulation resistance of the high voltage portion, a coupling capacitor provided between the AC signal output means and the ground insulation resistance, A filter means for taking in an AC signal between the AC signal output means and the coupling capacitor and removing high-frequency noise contained in the AC signal, and an AC signal after passing through the filter means after being input, A ground fault determination device comprising a ground fault determination means for performing a ground fault determination of the high voltage portion based on a peak value of an AC signal, wherein the low frequency noise is higher than the oscillation frequency and cannot be removed by the filter means Is determined to be superimposed on the AC signal after passing through the filter. Characterized in that it comprises a and disabling means for disabling the ground fault determination by means.

  In the above invention, when low-frequency noise that is higher than the oscillation frequency of the AC signal output from the stream signal output means but is not removed by the filter means is superimposed on the AC signal, it is based on the AC signal. Disable ground fault determination. Thereby, the precision of ground fault determination can be improved.

The circuit diagram of the ground fault determination apparatus concerning this embodiment. Explanatory drawing of the learning process of a ground fault determination value. Explanatory drawing of the correction process of a ground fault determination parameter. Explanatory drawing of the correction process of a ground fault determination parameter. Explanatory drawing of the invalidation process at the time of low frequency noise superimposition. The flowchart of a ground fault determination process. The timing chart of a ground fault determination process.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The ground fault determination device shown in FIG. 1 is a device that determines a ground fault (leakage) of a high voltage battery (hereinafter referred to as a battery) mounted on a vehicle such as a hybrid vehicle or an electric vehicle. In the present embodiment, a circuit including the battery 11, the electric load 10, and the SMR 15 is referred to as a high voltage circuit 1.

  The battery 11 is a power source that supplies electric power to the electric load 10 of the vehicle, and is configured as a battery group in which a plurality of lithium ion batteries or the like are connected in series, for example. The battery 11 and the electrical load 10 are connected via a system main relay (hereinafter referred to as SMR 15).

  The SMR 15 is connected to each of the negative electrode terminal and the positive electrode terminal of the battery 11, and the connection (ON) / interruption (OFF) of the SMR 15 is switched, whereby the electrical connection (ON) between the battery 11 and the electric load 10 is performed. ) / Blocking (off).

  The electrical load 10 includes, for example, an MG 12 (motor generator), an inverter 13, and a converter 14. When the SMR 15 is on, the power of the battery 11 is converted by the inverter 13 and the converter 14 and supplied to the MG 12. Further, the battery 11 is charged with the regenerative energy of the MG 12.

  The battery 11 and the electric load 10 are insulated from the vehicle body 100 of the vehicle, respectively. However, between the battery 11 and the vehicle body 100, a ground insulation resistance 30 including an insulation resistance Rg0 and a stray capacitance Cg0 exists. Similarly, a ground insulation resistance 31 including an insulation resistance Rg1 and a stray capacitance Cg1 exists between the electric load 10 and the vehicle body 100. In FIG. 1, the insulation resistance Rg0 is connected to the battery 11 and the vehicle body 100, and the floating resistance Cg0 is connected in parallel to the insulation resistance Rg0, and the insulation resistance Rg1 is connected to the electric load 10 and the vehicle body 100. For convenience of explanation, a state where the stray capacitance Cg1 is connected in parallel to the insulation resistance Rg1 is shown.

  When the ground fault does not occur in the battery 11, the insulation resistance Rg0 of the ground insulation resistance 30 is maintained at a predetermined value or more (for example, several MΩ or more). On the other hand, when the ground fault occurs in the battery 11, the insulation resistance Rg0 of the ground insulation resistance 30 decreases.

  The ground fault determination device 2 includes an oscillation circuit 21, a resistor 22, a coupling capacitor 23, a filter 24, a differential amplifier 25, and a control device 26.

  The oscillation circuit 21 is a circuit that outputs an AC signal having a predetermined oscillation frequency. For example, the oscillation circuit 21 outputs a rectangular wave AC signal having a center frequency fc = 2 Hz and a peak value of 5V.

  The resistor 22 divides an AC signal from the ground insulation resistor 30, and one end is connected to the oscillation circuit 21 and the other end is connected to a connection point B between the coupling capacitor 23 and the filter 24.

  The coupling capacitor 23 is an element for blocking a direct current component and allowing an alternating current signal to pass between the ground fault determination device 2 and the battery 11, one end of which is connected to the resistor 22, and the other end of the battery 11. Connected to the negative electrode side.

  The filter 24 is an analog filter including a resistor R and a capacitor C. For example, the filter 24 is provided as an antialiasing filter for suppressing aliasing when an AC signal is A / D converted by the control device 26 described later. It has been. The filter 24 is configured to remove frequency components that are more than half of the sampling frequency (reciprocal of the A / D conversion period) of the control device 26.

  The differential amplifier 25 adjusts the amplitude level of the AC signal after passing through the filter 24, and the reference voltage is determined so that the maximum value of the amplitude of the AC signal after passing through the differential amplifier 25 becomes a predetermined value. It has been. For example, in the present embodiment, when the amplitude of the AC signal output from the oscillation circuit 21 is 5 V, the differential amplifier is set so that the maximum value of the amplitude of the AC signal after passing through the filter 24 is 4.5 V. 25 reduces the amplitude of the AC signal.

  The control device 26 is configured to include a RAM, a ROM, a flash memory, and the like in addition to the A / D conversion unit 28 and the CPU 29, and performs various processes when the CPU executes various programs stored in the ROM.

  Specifically, in the control device 26, the CPU 29 performs digital filter processing of the AC signal input via the A / D conversion unit 28, and the ground fault of the battery 11 is performed based on the AC signal after the filter processing. Perform the judgment process. In the digital filter processing, noise having a frequency away from the frequency band of the AC signal is removed from noise included in the digital AC signal after A / D conversion. For example, the frequency band of the AC signal output from the oscillation circuit 21 and the surrounding band components are filtered by a finite impulse response, and signals in other frequency bands are blocked.

  In the ground fault determination process, the peak value (amplitude) of the AC signal is calculated in the disconnected state of the SMR 15, and the presence / absence of a ground fault is determined by comparing the peak value with a predetermined ground fault determination value. That is, the control device 26 determines that no ground fault has occurred when the peak value of the AC signal is equal to or greater than the ground fault determination value, that is, when the voltage dividing ratio of the resistor 22 to the ground insulation resistance 30 is low. . On the other hand, when the peak value of the AC signal is lower than the ground fault determination value, that is, when the voltage dividing ratio of the resistor 22 to the ground insulation resistance 30 increases as the ground insulation resistance 30 decreases, the ground fault occurs. It is determined that it has occurred.

  In the present embodiment, in particular, the following three processes are performed when the ground fault is determined by the control device 26. By performing these processes, the accuracy of the ground fault determination is improved.

(1) Ground fault determination value learning process (2) Ground fault determination parameter correction process (3) Invalidation process at the time of low frequency noise superimposition Each process will be described below.

<Learning detection process for ground fault judgment value>
In the ground fault determination of the battery 11, a ground fault determination value generally determined when the vehicle is shipped from the factory is used, and the presence or absence of a ground fault is determined based on the ground fault determination value and the peak value of the AC signal. However, in consideration of individual differences and aging of the batteries 11, it is considered that the resistance value of the ground insulation resistance 30 varies. Further, it is considered that the AC signal input to the control device 26 also varies due to individual differences or deterioration of each element of the ground fault determination device 2. Therefore, there is a concern that the accuracy of the ground fault determination is affected due to such variation.

  Therefore, in the present embodiment, the peak value of the AC signal corresponding to the actual resistance value of the ground insulation resistance 30 is detected in time series, and the ground fault determination value is learned based on the time series peak value. That is, the peak value of the AC signal is detected under a predetermined condition when the vehicle is used, and the ground fault determination value is sequentially set based on a plurality of time-series peak values.

  More specifically, as shown in FIG. 2, the control device 26 detects the peak value p of the alternating current signal each time the operation of the vehicle starts (that is, every trip), and time-series n waves. The average value is calculated for the high values p1 to pn. For example, the peak value p of the AC signal detected every time the vehicle is used is stored in a flash memory or the like, and the average value of the peak values for the current and past n times is calculated. Further, the ground fault determination value A is calculated by subtracting the predetermined value α from the average value of the peak values. In the present embodiment, the ground fault determination value A is stored as a learning value and set for each trip. However, it is also possible to memorize | store the average value of a crest value as a learning value. And the control apparatus 26 determines the presence or absence of a ground fault based on the comparison with the peak value of an alternating current signal using the ground fault determination value which is a learning value.

  Further, there is a difference in the peak value of the AC signal detected by the partial pressure of the resistor 22 between the closed state and the opened state of the SMR 15 that connects the battery 11 and the electric load 10, and the ground fault of the battery 11 occurs. The accuracy of the judgment is affected. Therefore, in the present embodiment, the presence or absence of a ground fault is determined based on the peak value of the AC signal each time while the SMR 15 is open. Also in the ground fault determination value learning process, the ground fault determination value is learned based on a plurality of time-series peak values with the SMR 15 open.

  Here, there is a possibility that the SMR 15 may be turned on, such as being welded by heat of a transient current generated when the connection state is switched. In this case, if the on-failure of the SMR 15 occurs, the battery 11 and the electrical load 10 remain unintentionally connected, which also affects the accuracy of ground fault determination.

  Therefore, in the present embodiment, the control device 26 determines whether or not the SMR 15 is on-failed when performing the ground fault determination. That is, the control device 26 sets an abnormality determination value for SMR abnormality determination based on the average value of the above-described peak values, and based on a comparison between the abnormality determination value and the peak value of each AC signal, the on-failure of the SMR 15 The presence or absence of is determined. The ground fault determination value and the SMR abnormality determination value can be the same value. When the ground fault determination value and the SMR abnormality determination value are set as a common abnormality determination value, either the ground fault or the SMR on failure occurs because the peak value of the AC signal is equal to or lower than the abnormality determination value. It is determined that In such a case, the SMR 15 is opened / closed (ON / OFF) to specify whether a ground fault or an SMR ON failure has occurred. That is, it can be determined that a ground fault has occurred if the peak value of the AC signal changes by turning on / off the SMR 15, and it can be determined that an SMR on failure has occurred if it does not change. By properly determining the on-failure of the SMR 15, an improvement in the accuracy of ground fault determination can be expected.

<Correction processing for ground fault determination parameter>
The ground fault determination of the battery 11 is performed using the peak value of the AC signal as a determination parameter. In this case, the presence or absence of a ground fault is determined according to the magnitude of the insulation resistance Rg0 of the ground insulation resistance 30, but when the ground fault determination is performed using an AC signal, the capacitance due to the stray capacitance Cg0 The peak value of the AC signal fluctuates due to the reactance. In this case, the ground fault may be erroneously determined due to the influence of the capacitive reactance due to the stray capacitance Cg0 even though the insulation resistance Rg0 is not lowered and the ground fault is not generated.

  Therefore, in the present embodiment, the ground fault determination is performed in a state where the voltage error due to the capacitive reactance of the stray capacitance Cg0 is removed. That is, using the fact that the capacitive reactance of the stray capacitance Cg0 changes according to the frequency of the AC signal, the detected value of the peak value of the AC signal, which is a ground fault determination parameter, is corrected.

  The insulation resistance value and the peak value of the AC signal are in the relationship shown in FIG. 3, and the peak value increases as the insulation resistance value increases. In FIG. 3, the first peak value V1 indicates an amplitude component generated by the insulation resistance Rg0 and the stray capacitance Cg0 when the center frequency fc of the oscillation circuit 21 is the first frequency f1 for ground fault determination. The second peak value V2 indicates an amplitude generated by the insulation resistance Rg0 and the stray capacitance Cg0 when the center frequency fc of the oscillation circuit 21 is the second frequency f2 different from the first frequency f1. In this case, the control device 26 calculates the difference ΔV (= V1−V2) between the first peak value V1 and the second peak value V2, and performs the ground fault determination using the difference ΔV as the ground fault determination parameter. . Regarding the SMR abnormality determination, the SMR abnormality determination is performed using the difference ΔV as the SMR abnormality determination parameter.

  Specifically, as shown in FIG. 4, when the center frequency fc of the AC signal is changed from the first frequency f1 to the second frequency f2, the AC voltage is changed according to the change in the capacitive reactance of the stray capacitance Cg0. Utilizing the change from the peak value V1 to the second peak value V2, the stray capacitance Cg0 is estimated from the difference ΔV between the first peak value V1 and the second peak value V2. Then, the first peak value V1 is corrected using the estimated stray capacitance Cg0.

  For example, information such as an arithmetic expression and a map for calculating the stray capacitance Cg0 from the difference ΔV is stored in the ROM, and the CPU 29 calculates an estimated value of the stray capacitance Cg0 using these calculations. Then, using the estimated value of the stray capacitance Cg0, the capacitance impedance Zc at the first frequency f1 is calculated, and the corrected peak value V11 is obtained by subtracting the voltage error caused by the capacitance impedance Zc from the first peak value V1. obtain. The first frequency f1 of the AC signal is set in the range of 2 to 10 Hz, for example. The second frequency f2 is a frequency higher than the first frequency f1, and is set in the range of 4 Hz to 100 Hz, for example.

<Disabling process when low frequency noise is superimposed>
Since stray capacitance Cg0 exists between the vehicle body 100 and the battery 11, common mode noise generated due to a change in the state of the electric load 10 can enter the ground fault determination device 2 via the stray capacitance Cg0. There is sex. When the frequency of the common mode noise is close to or superimposed on the frequency band of the AC signal output from the oscillation circuit 21, the noise cannot be removed by the digital filter processing of the control device 26, and ground fault determination Will affect the accuracy of.

  Therefore, in the present embodiment, the control device 26 determines whether or not low frequency noise that is higher than the oscillation frequency of the oscillation circuit 21 and cannot be removed by the filter 24 is superimposed on the AC signal after passing through the filter 24. When the noise is superimposed, the ground fault determination based on the peak value of the AC signal is invalidated. That is, when noise having a frequency that cannot be separated from the AC signal is superimposed on the AC signal, the AC signal is not used for the ground fault determination. This suppresses the occurrence of erroneous ground fault determination and increases the accuracy of ground fault determination.

  That is, in FIG. 1, the control device 26 includes an A / D conversion unit 28 and a CPU 29, and the CPU 29 includes a digital filter 27. The analog AC signal input to the control device 26 is A / D converted by the A / D converter 28 and converted into a digital AC signal. The digital AC signal after A / D conversion is input to the digital filter 27. The digital filter 27 passes an AC signal having the oscillation frequency of the oscillation circuit 21.

  If low frequency noise having a frequency close to or overlapping with the oscillation frequency of the oscillation circuit 21 is included in the AC signal, the low frequency noise also passes through the digital filter 27, so that the low frequency noise is not removed from the AC signal. . In this case, since the ground fault determination is performed based on the AC signal whose peak value fluctuates due to the low frequency noise, the accuracy of the ground fault determination is lowered.

  Therefore, in this embodiment, the peak value (amplitude) of the AC signal output from the oscillation circuit 21 is set to an amplitude that is the same as or larger than the input voltage range of the A / D converter 28, and the amplitude of the AC signal is different. Reduction is performed by the dynamic amplifier 25. Thereby, in the A / D converter 28 having a predetermined input voltage range (for example, 0 to 5 V), the AC signal after passing through the A / D converter 28 exceeds the input voltage range on the upper limit side of the input voltage range. An excess determination region (4.5 V to 5 V) for determining the presence is formed. When the peak value of the AC signal is included in the excess determination region, the AC signal is not used for the ground fault determination on the assumption that the low-frequency noise that cannot be removed by the digital filter 27 is superimposed on the AC signal. To.

  Specifically, as shown in FIG. 5, the CPU 29 compares the peak value of the AC signal after passing through the digital filter 27 with the upper limit value (4.5 V) of the excess determination region, and the peak value of the AC voltage. Exceeds the upper limit value and is included in the excess determination region a plurality of times within a unit time, it is determined that the AC signal is not used (deactivated) for ground fault determination. Alternatively, when the rising edge of the voltage of the AC signal is included in the excess determination region a plurality of times within the unit time, it may be determined that the AC signal is not used for the ground fault determination.

  Next, the process of a ground fault determination apparatus provided with the above structure is demonstrated. The following processing is performed by the CPU 29 of the control device 26 in a state where an ignition switch of a vehicle (not shown) is turned on. As an initial setting, it is assumed that the frequency of the AC signal output from the oscillation circuit 21 is set to the first frequency f1 = 2 Hz, and the frequency band through which the digital filter 27 passes is set accordingly.

  In FIG. 6, it is determined in step S10 whether or not the SMR 15 is off. For example, an affirmative determination is made when the SMR 15 is turned off, such as when the vehicle is started. If the determination is affirmative, the A / D value of the AC signal is acquired in step S11. That is, an analog AC signal is converted into a digital AC signal. In step S12, digital filter processing is performed. That is, it passes the frequency component of the oscillation frequency of the AC signal after A / D conversion. Thus, the first peak value V1 at the first frequency f1 is acquired.

  In step S13, it is determined whether or not the AC signal is used for ground fault determination. Here, when the number of times the peak value of the AC signal after passing through the digital filter 27 is included in the excess determination region is less than a predetermined value within the unit time, an affirmative determination is made when the AC signal is used for ground fault determination.

  If an affirmative determination is made in step S13, the second peak value V2 of the AC signal at the second frequency f2 different from the first frequency f1 has been acquired in step S14 in order to correct the voltage error due to the stray capacitance Cg0. It is determined whether or not.

  If a negative determination is made in step S14, the process proceeds to step S18 to change to the second frequency f2 of the oscillation circuit 21. For example, the second frequency f2 = 20 Hz is set. Further, the frequency band through which the digital filter 27 passes is set in accordance with the frequency change of the oscillation circuit 21. In step S19, the second peak value V2 of the AC signal at the second frequency f2 is detected.

  If an affirmative determination is made in step S14, in step S15, the first peak value V1 at the first frequency f1 is corrected, and the corrected peak value V11 is calculated. That is, the stray capacitance Cg0 is estimated from the difference ΔV, and the capacitance impedance Zc at the first frequency f1 is calculated using the estimated value of the stray capacitance Cg0. Then, a corrected peak value V11 is obtained by subtracting a voltage error caused by the capacitive impedance Zc at the first frequency f1.

  In step S16, it is determined whether or not the corrected peak value V11 is equal to or greater than the ground fault determination value A. If the determination is affirmative, the ground fault determination value A is learned in step S16. That is, as shown in FIG. 2, an average value of n peak values including the peak value of the AC signal acquired in step S12 is calculated, and the ground fault determination value A is set. The ground fault determination value A set this time is used as a determination criterion for the next ground fault determination.

  When a negative determination is made in step S16, the process proceeds to step S20, where the SMR 15 is opened and closed (on / off), and a change in the peak value of the AC signal at that time is detected. In step S21, it is determined whether the SMR 15 is normal. That is, when the peak value of the AC signal changes as SMR 15 is turned on / off, it is determined that SMR 15 is normal. On the other hand, when the peak value of the AC signal does not change as SMR 25 is turned on / off, it is determined that SMR 15 is abnormal.

  If SMR 15 is normal in step S21, it is determined in step S22 that the ground fault is abnormal. In this case, information indicating that a ground fault abnormality has occurred is output. If the SMR 15 is abnormal in step S21, it is determined in step S23 that the SMR 15 is on. In this case, information indicating that an on failure has occurred in the SMR 15 is output. If a negative determination is made in steps S10 and S13, the process ends.

  Next, an example of execution of the above process will be described using the timing chart of FIG. The following processing is repeatedly performed at a predetermined cycle when the IG switch is on. In the initial state, the SMR 15 is off, and the oscillation circuit 21 outputs an AC signal having the first frequency f1.

  When the IG switch is turned on at time t1, the oscillation circuit 21 outputs an AC signal having the first frequency f1 (= 2 Hz). Moreover, the process of the control apparatus 26 is started, A / D conversion of an alternating current signal and the noise removal by the digital filter 27 are implemented, and the 1st peak value V1 is detected.

  At this time, if the frequency at which the first peak value V1 is included in the excess determination region is greater than or equal to a predetermined value, noise is superimposed and invalidation processing that does not perform processing using the AC signal is performed. . At this time, a signal indicating that the first peak value V1 is in a noise superimposed state may be output. When the frequency at which the first peak value V1 is included in the excess determination region is less than a predetermined value, it is determined that the AC signal is used for ground fault determination.

  When it is determined that the AC signal is used for ground fault determination, the first frequency f1 of the oscillation circuit 21 is temporarily changed from f1 to f2, and the second peak value V2 of the AC signal at that time is detected. The stray capacitance Cg0 is estimated from the peak value difference ΔV of the AC signal, and the corrected peak value V11 is calculated using the estimated value of the stray capacitance Cg0.

  When it is determined that the corrected peak value V11 is greater than or equal to the ground fault determination value A, that is, when it is determined that a ground fault has not occurred, the waves for n times including the peak value of the AC signal acquired this time The average of the high values is calculated. In this case, the updated ground fault determination value A is used in the next ground fault determination.

  On the other hand, when it is determined that the peak value V11 is less than the ground fault determination value A, the SMR 15 is opened and closed, and a change in the peak value of the AC signal is detected. At this time, if it is detected that the peak value of the AC signal does not fluctuate even when the SMR 15 is moved, it is determined that the SMR 15 has an on failure. On the other hand, when the peak value of the AC signal varies, it is determined that the ground fault is abnormal.

  When it is determined that the SMR 15 is normal, the SMR 15 is switched on in response to a command signal from a host ECU (not shown) at time t2. The connection / disconnection of the SMR 15 may be switched simultaneously between the positive side and the negative side SMR 15, or may be switched in order one by one.

  When both the IG switch and the SMR 15 are turned on, the battery 11 and the electric load 10 are electrically connected to enable vehicle travel. At this time, the driving of the MG is controlled based on a detection signal from an accelerator sensor (not shown), and the vehicle travels.

  Then, after the IG is switched off at time t3, the SMR 15 is switched off at time t4.

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

  The ground fault determination device 2 applies the AC signal output from the oscillation circuit 21 to the ground insulation resistance 30 and determines the ground fault using the peak value of the AC signal that changes according to the actual resistance value of the ground insulation resistance 30. Has been implemented. At this time, the high frequency noise included in the AC signal is removed by the filter 24. However, when low frequency noise that is higher than the oscillation frequency but cannot be removed by the filter 24 is included in the AC signal, the ground fault determination is performed based on the peak value of the AC signal that has fluctuated due to the low frequency noise. It affects the accuracy of ground fault determination. Therefore, when a low-frequency noise that is higher than the oscillation frequency of the AC signal output from the oscillation circuit 21 but is not removed by the filter 24 is superimposed on the AC signal, the ground fault determination based on the AC signal is performed. Disable. Thereby, the precision of ground fault determination can be improved.

  In the A / D converter 28 having a predetermined input voltage range, it is determined that the AC signal after passing through the filter 24 exceeds the input voltage range on at least one of the upper limit side and the lower limit side of the input voltage range When the excess determination area to be provided is provided, it is possible to determine whether the AC signal is in a noise superimposed state using the A / D conversion unit 28.

  The amplitude of the AC signal after passing through the filter 24 is reduced to form an excess determination area in the A / D converter 28. Thereby, the excess determination area can be formed in the A / D conversion unit 28 without changing the AC characteristics of the A / D conversion unit 28.

  When low frequency noise having a frequency close to or overlapping the oscillation frequency of the AC signal output from the oscillation circuit 21 is included in the AC signal, the digital filter 27 passes the AC signal having the oscillation frequency in the oscillation circuit 21. When trying to do so, the low frequency noise is also passed through, and the low frequency noise cannot be removed from the AC signal. In this case, the ground fault determination may be erroneously determined. Therefore, when the peak value after the filter processing by the digital filter 27 is in the excess determination region, the ground fault determination by the ground fault determination device 2 is invalidated. Thereby, the precision of ground fault determination is raised.

  The present embodiment is not limited to the above, and may be implemented as follows.

  In the above description, when the peak value V11 becomes less than the ground fault determination value A, the SMR 15 is opened and closed to determine whether it is a ground fault or an SMR 15 on failure. In addition, a ground fault determination criterion and an SMR 15 on-failure determination criterion are individually provided, and a ground fault or an SMR 15 on-failure is determined by comparing the peak value V11 with each criterion. May be.

  When an on failure such as welding occurs in the SMR 15, the ground insulation resistance 30 of the battery 11 and the ground insulation resistance 31 of the electric load 10 are connected in parallel, and the ground fault determination is performed by the ground fault determination device 2. In this case, the capacitance impedance varies depending on the stray capacitance Cg1. Therefore, the presence / absence of an on failure of the SMR 15 may be determined using the fact that the capacitance impedance changes according to the frequency of the oscillation circuit 21. That is, the oscillation frequency of the oscillation circuit 21 is changed when the SMR 15 is off. At this time, if an on-failure has occurred in the SMR 15, the change in the peak value of the AC signal is increased by the amount of variation in the capacitance impedance due to the stray capacitance Cg 1, compared to the case where no on-failure has occurred in the SMR 15. Therefore, the on-failure of the SMR 15 may be determined using the magnitude of fluctuation of the peak value of the AC signal when the SMR 15 is turned on / off.

  In the above description, the ground fault determination value A is calculated for n time-series peak values, but the ground fault determination value A may be calculated for all peak values acquired from the start of use of the vehicle.

  In FIG. 6, for example, after step S <b> 10, it may be determined whether or not the electrical load 10 such as the inverter 13 is operating. In this case, it can be avoided that the ground fault determination is performed in the operating state of the electric load 10.

  In the above description, the SMR 15 is switched off after the IG is turned off. However, the IG may be switched off after the MR 15 is turned off.

  In the above, an example in which the corrected peak value V11 is calculated using the estimated value of the stray capacitance Cg0 is shown. In addition to this, the corrected peak value V11 may be directly calculated using the difference ΔV. In this case, the ROM stores an arithmetic expression, a map, and the like for calculating the corrected peak value V11 from the difference ΔV.

  In the above description, the peak value p of the AC signal is detected every time the operation of the vehicle starts. However, the peak value p of the AC signal may be detected every time the operation of the vehicle ends. Alternatively, the peak value p of the AC signal may be detected both at the start and end of the operation of the vehicle, and the ground fault determination value may be set using these.

  DESCRIPTION OF SYMBOLS 11 ... Battery, 21 ... Oscillator circuit, 23 ... Coupling capacitor, 24 ... Filter, 26 ... Control apparatus.

Claims (6)

AC signal output means (21) for outputting an AC signal having a predetermined oscillation frequency applied to the ground insulation resistance (30) of the high voltage section (11);
A coupling capacitor (23) provided between the AC signal output means and the ground insulation resistance;
Filter means (24) for taking in the AC signal between the AC signal output means and the coupling capacitor and removing high frequency noise contained in the AC signal;
An A / D converter (28) for A / D converting the AC signal after passing through the filter means at the sampling frequency after passing through the filter means ;
A digital filter (27) that performs a digital filter process that passes through the frequency band of the AC signal output from the AC signal output means among the AC signals after passing through the filter after the A / D conversion and blocks the others. When,
A ground fault determination means (26) for performing a ground fault determination of the high voltage portion based on the peak value of the post-filter AC signal after the digital filter processing ;
A ground fault determination device comprising:
The filter means removes a frequency component that is half or more of the sampling frequency,
Noise superimposition determination means (26) for determining that a noise component that is not removed by the filter means and that is passed through the digital filter processing is superimposed on the AC signal after passing through the filter;
Invalidation means (26) for invalidating ground fault determination by the ground fault determination means when the noise superimposition determination means is in a noise superimposed state;
A ground fault determination device comprising: AC signal output means (21) for outputting an AC signal having a predetermined oscillation frequency applied to the ground insulation resistance (30) of the high voltage section (11);
A coupling capacitor (23) provided between the AC signal output means and the ground insulation resistance;
Filter means (24) for taking in the AC signal between the AC signal output means and the coupling capacitor and removing high frequency noise contained in the AC signal;
A ground fault determination means (26) for inputting a post-filter AC signal after passing through the filter means, and performing a ground fault determination of the high voltage section based on a peak value of the AC signal;
A ground fault determination device comprising:
Noise superimposition determination means (26) for determining that low frequency noise that is higher than the oscillation frequency and cannot be removed by the filter means is superimposed on the AC signal after passing through the filter;
Invalidating means (26) for invalidating ground fault determination by the ground fault determining means when the noise superimposition determining means is in a noise superimposed state,
The signal input unit (28) for inputting the AC signal after passing through the filter has a predetermined input voltage range,
At least one of the upper limit side and the lower limit side of the input voltage range of the signal input unit is provided with an excess determination region for determining that the AC signal after passing the filter exceeds the input voltage range. And
It said disabling means, as long as the passing through the filter AC signal enters the excess detectable region, the ground determining device you deactivate the grounding determined as a noise superimposed state. Amplitude adjusting means (25) capable of changing the amplitude of the AC signal after passing through the filter,
The alternating current signal output from the alternating current signal output means changes alternating current with an amplitude equal to or larger than the input voltage range,
The ground fault determination device according to claim 2, wherein the amplitude adjustment unit forms an excess determination region in the input voltage range by reducing the amplitude of the AC signal after passing through the filter. A second filter (27) for passing the AC signal output from the AC signal output means;
The ground fault determination means performs ground fault determination based on a peak value of the AC signal that has passed through the second filter,
The said invalidation means invalidates the ground fault determination by the said ground fault determination means when the peak value of the said alternating current signal which passed the said 2nd filter enters into the excess determination area. Ground fault determination device.   The invalidation means invalidates the ground fault by the ground fault determination means when the frequency of the peak value of the AC signal after passing through the filter enters the excess determination range is a predetermined frequency or more. The ground fault determination apparatus according to item 1. A resistor (22) for dividing the AC signal output from the AC signal output means with the ground insulation resistance;
5. The ground fault determination unit according to claim 2, wherein the ground fault determination unit performs ground fault determination of the high voltage unit based on a peak value of an AC signal determined by a partial pressure between the ground insulation resistance and the resistance. The ground fault determination apparatus according to item.

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