JP3962993B2 - Insulation detector for ungrounded power supply - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an insulation detection device for a non-grounded power supply, and more particularly to an insulation detection device suitable for a non-grounded DC power supply mounted on a vehicle that uses electric propulsion.
[0002]
[Prior art]
The insulation detection device for the non-grounded power supply is connected to the positive and negative terminals of the non-grounded DC power supply, and is insulated from the ground potential portion. By detecting this, the insulation with respect to the ground potential portion and the ground fault state are detected (for example, see Patent Document 1). In such an insulating detecting device, between the switching means, the negative terminal and the ground potential portion of the ungrounded power supply connected set scheduled period of the capacitor between the positive terminal and the ground potential portion of the DC power source ungrounded blocking of the switching means detected by the switching means, the switching means for detecting which connects the detection means for detecting a voltage between both terminals of the capacitor after interruption of the switching means, detection means for connecting set scheduled period of the capacitor Computation means for computing the insulation resistance, that is, the ground fault resistance for the ground potential portion of the power supply based on the voltage between both terminals of the later capacitor and the power supply voltage calculated in advance by fully charging the capacitor The insulation state is detected and determined from the ground fault resistance calculated by the calculation means.
[0003]
In the insulation detection device as described above, when calculating the ground fault resistance, an equation including the capacitance of the capacitor as a constant is used. However, the capacitance of the capacitor used as the constant includes a variation in capacitance between products and a temperature change. There is a case where there is a variation in capacity due to, and a change with time of the capacity or the like may occur. If the values used as constants vary or change in this way, the measurement error between the calculated ground fault resistance value and the actual ground fault resistance value increases, so the detection accuracy of the insulation state decreases. End up. Therefore, it is hoped that the measurement error of the ground fault resistance will be reduced as much as possible and the detection accuracy of the insulation state will be improved even if there are variations or changes in the constant value when calculating the ground fault resistance such as the capacitance of the capacitor. It is rare.
[0004]
On the other hand, a first switching means for connecting a capacitor in series for a first set time to a DC power source whose positive terminal side and negative terminal side wires are insulated from the ground potential portion, and a positive terminal of the power source Second switching means for connecting a capacitor in series with the ground potential portion for a second set time, and a capacitor in series between the ground potential portion and the negative terminal of the power source for the second set time A third switching means to be connected; a fourth switching means for connecting a detection means for detecting a voltage between both terminals of the capacitor after the first, second and third switching means are cut off; and a first switching means. The power supply voltage is estimated based on the detection voltage at the detection means after the means is shut off, and the power supply is based on the estimated power supply voltage and each detection voltage at the detection means after the second and third switching means are shut off. Grounding power Insulation detecting device has been considered that a structure in which an arithmetic means for calculating the insulation resistance to parts.
[0005]
In such an insulation detection device, if the first set time is set to a time shorter than the time required to fully charge the capacitor, the DC power is supplied by the first switching means during the first set time. The capacitor is connected to a direct current between the ground potential portion and charged, and the voltage between both terminals of the capacitor at this time is detected by the detecting means connected by the fourth switching means. The calculation means can estimate the power supply voltage. And by calculating the insulation resistance based on the estimated power supply voltage and each detection voltage at the detection means after the second and third switching means are cut off, the measurement error of the insulation resistance is reduced, and the insulation state Detection accuracy can be improved.
[0006]
[Patent Document 1]
JP-A-8-226950 (page 4-7, FIG. 1)
[0007]
[Problems to be solved by the invention]
By the way, when the power supply voltage fluctuates, in the insulation detection device that calculates the insulation resistance using the estimated power supply voltage as described above, the first switching means is connected to charge the capacitor in order to estimate the power supply voltage. In some cases, the power supply voltage for charging the capacitor differs from the power supply voltage for charging the capacitor by connecting the second or third switching means. For this reason, when the power supply voltage fluctuates, if the insulation resistance is calculated based on the estimated power supply voltage and each detection voltage at the detection means after the second and third switching means are cut off, the calculated insulation resistance Whether the change in the value reflects the change in the insulation state or the change in the power supply voltage is unknown, and the reliability of detection of the insulation state is lowered.
[0008]
An object of the present invention is to improve the reliability of detection of an insulation state.
[0009]
[Means for Solving the Problems]
In the insulation detection device of the present invention, a series connection body of a capacitor and a resistor is connected in parallel to a DC power source in which the wiring on the positive terminal side and the negative terminal side is insulated from the ground potential portion, and the time for which the capacitor is fully charged is exceeded. First switching means for connecting for a short first set time; second switching means for connecting the series connection body for a second set time between the positive terminal of the power supply and the ground potential portion; A third switching means for connecting the series connection body between the ground potential portion and the negative terminal of the power source for a second set time; and a capacitor after the first, second and third switching means are shut off. A fourth switching means for connecting a detection means for detecting a voltage between the two terminals; and an arithmetic means for calculating an insulation resistance with respect to the ground potential portion of the power source. The arithmetic means is configured to shut off the first switching means. With detection means The power supply voltage of the power supply is estimated based on the output voltage, and among the two consecutive insulation detection cycles, the power supply voltage estimated in the previous insulation detection cycle, the power supply voltage estimated in the subsequent insulation detection cycle, and each estimation The fluctuation of the power supply voltage during the time when the voltage between both terminals of the capacitor was detected to calculate each estimated power supply voltage based on the time interval at which the voltage between the two terminals of the capacitor for calculating the power supply voltage was detected A ratio is calculated, and each detection voltage at the detection means after the second and third switching means is cut off in the previous insulation detection cycle is corrected based on the calculated fluctuation ratio of the power supply voltage. The above problem is solved by calculating the insulation resistance for the ground potential portion of the power supply from the voltage and the power supply voltage estimated in the previous insulation detection cycle.
[0010]
By adopting such a configuration, the fluctuation ratio of the power supply voltage is calculated, and the detection voltage at the detection means after the second switching means and the third switching means are shut off based on the calculated fluctuation ratio of the power supply voltage. , And the corrected detection voltage is used to detect the insulation state. Therefore, the influence of the fluctuation of the power supply voltage on the calculated insulation resistance value for the ground potential of the power supply is reduced, and the reliability of detection of the insulation state is improved. it can.
[0011]
Moreover, as said insulation detection apparatus, a 1st switching means contains the 1st switch part connected to the positive terminal of the power supply, and the 2nd switch part connected to the negative terminal of the power supply, 3rd The switching means includes a second switch section and a third switch section connected in series to the first switch, and the second switching means includes the first switch section and the second switch section. A fourth switch unit connected in series to the first switch unit and between the first switch unit and the third switch unit and between the second switch unit and the fourth switch unit. A first diode, a first resistor, and a capacitor that rectify in the direction from the negative side to the negative side are connected in series, and in parallel with the first diode and the first resistor, the first diode that rectifies in the direction opposite to the first diode. Two diodes and a second resistor connected in series And the detection means is connected between the third switch part and the fourth switch unit, between the detecting means and the fourth switching unit is a circuit configuration which is grounded to the ground potential portion.
[0012]
Furthermore, if the configuration includes a bypass means including a fifth switch portion that forms a path that bypasses the second resistor when the circuit is closed, the bypass means can be connected with the fourth switching means closed. It is preferable to close the switch unit 5 because the discharge time of the capacitor can be shortened and the time required for detecting the insulation state can be shortened.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of an insulation detection device to which the present invention is applied will be described with reference to FIGS. 1 to 5. FIG. 1 is a diagram showing a schematic configuration of an insulation detection apparatus to which the present invention is applied. FIG. 2 is a flowchart showing the calculation operation of the insulation resistance of the insulation detection device to which the present invention is applied. FIG. 3 is a time chart showing the charge / discharge state of the capacitor and the voltage reading timing for the operation of each switch unit. FIG. 4 is a flowchart showing the process of calculating the insulation resistance of the insulation detection device to which the present invention is applied. FIG. 5 is a diagram showing fluctuations in the power supply voltage and voltage detection timing by the microcomputer.
[0014]
As shown in FIG. 1, the insulation detection device 1 according to the present embodiment is applied to a DC power source 3 serving as a power source of an electric propulsion vehicle or the like that obtains a propulsive force by using electric power, for example. The power supply 3 is a fuel cell or the like in which a plurality of storage batteries are connected in series, and the positive main circuit wiring 5a on the positive terminal side and the negative main circuit wiring 5b on the negative terminal side of the power supply 3 are respectively connected to the ground potential. It is insulated from the part 7, for example, the vehicle body, and the power source 3 is an ungrounded power source. The insulation detection device 1 is configured with a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a capacitor 9, a microcomputer 11 that doubles as a detection unit and a calculation unit and determines an insulation state, and sets each switch. The switching control circuit (not shown) that performs opening / closing control according to the set time is configured. Note that the detection unit, the calculation unit, the switching control circuit, and the like can be appropriately formed separately or integrally, for example, by including a switching control circuit (not shown) integrally in the microcomputer 11. In addition, the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 shown in FIG. 1 are schematically illustrated with a switch unit made of a part having various switch functions such as a relay or a semiconductor switch as a contact. It is shown in.
[0015]
The first switch S1 and the third switch S3 are sequentially connected in series from the positive terminal to the positive terminal of the power source 3, and the second switch S2 and the second switch S2 from the negative terminal side to the negative terminal of the power source 3. A four switch S4 and a fourth resistor R4 are sequentially connected in series. A first diode D1, a first resistor R1, and a capacitor 9 are sequentially connected in series between the first switch S1 and the third switch S3 and between the second switch S2 and the fourth switch S4. A second diode D2 and a second resistor R2 are sequentially connected in series between the first resistor R1 and the capacitor 9 and between the first switch S1 and the third switch S3. That is, the first diode D1 and the first resistor R1, and the second diode D2 and the second resistor R2 are connected in parallel. A fifth switch S5 is connected in parallel with the second resistor R2 between both terminals of the second resistor R2. The first diode D1 is rectified in the direction from the positive side to the negative side, and the second diode D2 is rectified in the opposite direction to the first diode D1.
[0016]
A third resistor R3 is connected in series with the third switch S3 and the fourth resistor R4 between the third switch S3 and the fourth resistor R4, and between the third switch S3 and the third resistor R3. The microcomputer 11 that serves as both detection means and calculation means is connected via an analog / digital conversion port, that is, an A / D port of the microcomputer 11. Further, a portion between the third resistor R3 and the fourth resistor R4 is grounded to the ground potential portion 7.
[0017]
Therefore, the first switching means for connecting the capacitor 9 in series with the power source 3 for the first set time is the first switch S1, the second switch S2, a switching control circuit (not shown), and the like. The second switching means for connecting the capacitor 9 in series between the terminal and the ground potential unit 7 for the second set time is the first switch S1, the fourth switch S4, a switching control circuit (not shown), and the like. The third switching means for connecting the capacitor 9 in series between the ground potential unit 7 and the negative terminal of the power source 3 for the second set time is the second switch S2, the third switch S3, and not shown. In the switching control circuit or the like, the fourth switching means is formed by the third switch S3, the fourth switch S4, a switching control circuit (not shown), and the like. The capacitor 9 has a relatively high capacity, for example, several μF, and the first resistor R1 and the second resistor R2 have a relatively high resistance value, for example, several hundred kΩ. .
[0018]
The operation of the insulation detection device having such a configuration and the features of the present invention will be described. As shown in FIGS. 2 and 3, when the insulation detection device 1 starts detecting the insulation state, the switching control circuit (not shown) sets the first switch S1 and the second switch S2 to the first set time. The circuit is closed for one circuit closing time T1 (step 101). That is, the first switching means forms a circuit in which the capacitor 9 is connected in series to the power source 3 without going through the ground potential portion 7, and the capacitor 9 is charged during the first closing time T1. The voltage VC between the 9 terminals increases. The first closing time T1 is set to a time shorter than the time required to fully charge the capacitor 9, for example, 1/5 to 1 of the time required to fully charge the capacitor 9. The first closing time T1 is selected according to the required measurement error range of the insulation resistance.
[0019]
When the first closing time T1 elapses in step 101, the first switch S1 and the second switch S2 are opened, that is, shut off, and after the elapse of a predetermined time tw1 shorter than the first closing time T1, the third switch S3 and the fourth switch S4. Is closed (step 103). That is, the fourth switching means forms a circuit connected to the microcomputer 11 for detecting the voltage between both terminals of the capacitor 9, and includes the second resistor R2, the third resistor R3, and the fourth resistor R4. A discharge circuit from the capacitor 9 is formed, and the voltage VC between both terminals of the capacitor 9 drops. After a lapse of a predetermined time tw2 shorter than the first closing time T1 after the third switch S3 and the fourth switch S4 are closed, the microcomputer 11 sends A / D conversion data, that is, both ends of the capacitor 9 via the A / D port. The voltage VC between the children is read (step 105). Based on the value of the voltage VC between both terminals of the capacitor 9 at this time, that is, the detected voltage V0, an estimated power supply voltage V0s is calculated from the following equation (1) (step 107).
V0 = V0s (1-EXP (-T1 / C.R1)) (1)
In Equation (1), T1 is the closing time of the first switch S1 and the second switch S2, C is the capacitance of the capacitor 9, and R1 is the resistance value of the first resistor R1.
[0020]
On the other hand, the switching control circuit (not shown) detects the voltage VC between both terminals of the capacitor 9 in step 105, and then closes the fifth switch S5 with the third switch S3 and the fourth switch S4 closed. By bypassing the second resistor R2, the resistance value of the second resistor R2 is lowered, and the time required for discharging from the capacitor 9 is shortened. After the fifth switch S5 is closed and a predetermined time td1 shorter than the first closing time T1 has elapsed, the fifth switch S5 is opened, that is, shut off, and then the microcomputer 11 sends A / D conversion data via the A / D port. That is, the voltage VC between both terminals of the capacitor 9 is read (step 109).
[0021]
When it is confirmed in step 109 that the voltage VC is 0 V, the switching control circuit (not shown) opens the third switch S3 and closes the first switch S1 after a predetermined time tw1 has elapsed. Then, the first switch S1 and the fourth switch S4 are closed for a second closing time T2, which is a second set time (step 111). That is, a circuit in which a capacitor 9 is connected in series between the positive terminal of the power source 3 and the ground potential portion 7 by the second switching means, that is, as shown in FIG. 1, the positive-side main circuit wiring 5a, the first The switch S1, the first diode D1, the first resistor R1, the capacitor 9, the fourth switch S4, the fourth resistor R4, the ground potential unit 7, and the ground on the negative terminal side assumed at the position shown by the dotted line in FIG. A circuit is formed in which the resistance Rn and the negative main circuit wiring 5b are sequentially connected to the power source 3 in series. Thereby, the capacitor 9 is charged during the second closing time T2, and the voltage VC between both terminals of the capacitor 9 increases according to the value of the ground fault resistance Rn as shown in FIG. Note that the second closing time T2, which is the second setting time, is also shorter than the time necessary to fully charge the capacitor 9, similarly to the first closing time T1, and is shorter than the predetermined times tw1, tw2, td1. It is set for a long time.
[0022]
When the second closing time T2 elapses in step 111, as shown in FIGS. 2 and 3, the first switch S1 is opened, that is, shut off, and after the predetermined time tw1 has elapsed, the third switch S3 is closed, and the third switch S3 And the fourth switch S4 is closed. That is, the fourth switching means forms a circuit connected to the microcomputer 11 for detecting the voltage between both terminals of the capacitor 9, and includes the second resistor R2, the third resistor R3, and the fourth resistor R4. A discharge circuit from the capacitor 9 is formed, and the voltage VC between both terminals of the capacitor 9 drops. Then, after a predetermined time tw2 has elapsed since the third switch S3 was closed, the microcomputer 11 reads A / D conversion data, that is, the voltage VCN between both terminals of the capacitor 9 via the A / D port (step 113). .
[0023]
On the other hand, the switching control circuit (not shown) detects the voltage VC between both terminals of the capacitor 9 in step 113 and then closes the fifth switch S5 with the third switch S3 and the fourth switch S4 closed. By bypassing the second resistor R2, the resistance value of the second resistor R2 is lowered, and the time required for discharging from the capacitor 9 is shortened. After the fifth switch S5 is closed and a predetermined time td2 shorter than the second closing time T2 has elapsed, the fifth switch S5 is opened, that is, shut off, and then the microcomputer 11 performs A / D conversion data via the A / D port. That is, the voltage VC between both terminals of the capacitor 9 is read (step 115).
[0024]
When it is confirmed in step 115 that the voltage VC is 0 V, the switching control circuit (not shown) opens the fourth switch S4 and closes the second switch S2 after a predetermined time tw1 has elapsed. Then, the second switch S2 and the third switch S3 are closed during a second closing time T2 that is a second set time (step 117). That is, a circuit in which a capacitor 9 is connected in series between the ground potential portion 7 and the negative terminal of the power source 3 by the third switching means, that is, as shown in FIG. 1, the positive main circuit wiring 5a, FIG. , The grounding resistance Rp on the positive terminal side assumed at the position shown by the dotted line, the ground potential section 7, the third resistance R3, the third switch S3, the first diode D1, the first resistance R1, the capacitor 9, the second A circuit is formed in which the switch S2 and the negative main circuit wiring 5b are sequentially connected to the power source 3 in series. Thereby, the capacitor 9 is charged during the second closing time T2, and the voltage VC between both terminals of the capacitor 9 rises according to the value of the ground fault resistance Rp as shown in FIG.
[0025]
When the second closing time T2 elapses in step 117, as shown in FIGS. 2 and 3, the second switch S2 is opened, that is, shut off, and after the predetermined time tw1 has elapsed, the fourth switch S4 is closed, and the third switch S3 And the fourth switch S4 is closed. That is, the fourth switching means forms a circuit connected to the microcomputer 11 for detecting the voltage between both terminals of the capacitor 9, and includes the second resistor R2, the third resistor R3, and the fourth resistor R4. A discharge circuit from the capacitor 9 is formed, and the voltage VC between both terminals of the capacitor 9 drops. Then, after a predetermined time tw2 has elapsed since the fourth switch S4 was closed, the microcomputer 11 reads A / D conversion data, that is, the voltage VCP between both terminals of the capacitor 9 via the A / D port (step 119). .
[0026]
On the other hand, the switching control circuit (not shown) detects the voltage VC between both terminals of the capacitor 9 in step 119, and then closes the fifth switch S5 with the third switch S3 and the fourth switch S4 closed. By bypassing the second resistor R2, the resistance value of the second resistor R2 is lowered, and the time required for discharging from the capacitor 9 is shortened. After the fifth switch S5 is closed and the predetermined time td2 has elapsed, the fifth switch S5 is opened, that is, shut off, and then the microcomputer 11 passes A / D conversion data between the two terminals of the capacitor 9 via the A / D port. The voltage VC is read (step 121). Then, when it is confirmed in step 121 that the voltage VC is 0 V, one insulation state detection cycle is completed.
[0027]
When this detection cycle, that is, the previous detection cycle is completed in step 121, the process proceeds to the next detection cycle following this detection cycle, that is, the current detection cycle, and the same ground fault resistance detection operation is performed. At this time, when the estimated power supply voltage V0s is calculated in step 107 of the current detection cycle, as shown in FIG. 4, the ground fault resistances Rp and Rn in the previous detection cycle are calculated (steps 123 to 133). ) Is performed. It should be noted that while steps 123 to 133 are being performed, steps after step 109 in the current detection cycle are performed.
[0028]
When entering the calculation process of the ground fault resistances Rp and Rn in the previous detection cycle, as shown in FIG. 4, the power supply voltage V0s estimated in the previous detection cycle, the power supply voltage V0s estimated in the current detection cycle, and the previous In order to calculate the power supply voltage V0s estimated in the detection cycle, the microcomputer 11 detects the voltage between both terminals of the capacitor 9 and in the microcomputer 11 to calculate the power supply voltage V0s estimated in the current detection cycle. The power supply voltage fluctuation ratio of the power supply 3 is calculated by the following equation (2) from the proportional calculation based on the measurement interval with respect to the time when the voltage between the two terminals is detected, that is, the measurement cycle I1 of the detection cycle of the insulation state (step) 123).
Power supply voltage fluctuation ratio = (previous V0s−current V0s) / measurement period I1 (2)
Here, in the insulation detection device of the present embodiment, for example, the time required for closing a switch necessary for voltage detection between both terminals of the capacitor 9 is about 1 second or less, and the time required for one voltage detection is also 1. Less than a second. The time required for one detection cycle, that is, the detection cycle is about several seconds. Therefore, when the power supply voltage fluctuates at intervals of several tens of seconds or hundreds of seconds, the fluctuation of the power supply voltage in one detection cycle time of about several seconds is a straight line or an approximate straight line as shown in FIG. Thus, the fluctuation ratio of the power supply voltage can be obtained by proportional calculation as shown in equation (2) of step 123.
[0029]
After step 123, the power supply voltage fluctuation ratio obtained in step 123 and the time when the microcomputer 11 detects the voltage between both terminals of the capacitor 9 to calculate the estimated power supply voltage V0s and the detected voltage VCN in the microcomputer 11 are obtained. Based on the measurement interval I2 with respect to the detected time, the power supply voltage fluctuation amount ΔV0s (VCN) when the microcomputer 11 detects the detection voltage VCN is calculated from the following equation (3) (step 125).
ΔV0s (VCN) = (power supply voltage fluctuation ratio × measurement interval I2) (3)
Similarly to step 125, the microcomputer 11 detects the voltage between both terminals of the capacitor 9 in order to calculate the power supply voltage fluctuation ratio obtained in step 123 and the estimated power supply voltage V0s, and the detected voltage VCP in the microcomputer 11. The power supply voltage fluctuation amount ΔV0s (VCP) at the time of detection of the detection voltage VCP in the microcomputer 11 is calculated from the following equation (4) based on the measurement interval I3 with respect to the time at which the signal is detected (step 127).
ΔV0s (VCP) = (power supply voltage fluctuation ratio × measurement interval I3) (4)
After step 127, a VCN correction value is calculated from the following equation (5) based on the power supply voltage fluctuation amount ΔV0s (VCN) at the time of detection of the detection voltage VCN obtained in step 125 (step 129).
VCN correction value = VCN × (1−ΔV0s (VCN)) / previous V0s (5)
Similarly, a VCP correction value is calculated from the following equation (6) based on the power supply voltage fluctuation amount ΔV0s (VCP) at the time of detection of the detection voltage VCP obtained in step 127 (step 131).
VCP correction value = VCP × (1−ΔV0s (VCP)) / previous V0s (6)
Using the VCN correction value and the VCP correction value obtained in step 129 and step 131, the ground fault resistance Rn on the negative terminal side of the power source 3 and the ground fault on the positive terminal side of the power source 3 by the following equations (7) and (8) The resistance Rp is calculated (step 133).
Rn = −R1−T2 / C · ln (1−VCN correction value / V0s) (7)
Rp = −R1−T2 / C · ln (1−VCP correction value / V0s) (8)
In equations (7) and (8), T2 is the closing time of the second switch S2 and the third switch S3, C is the capacitance of the capacitor 9, R1 is the resistance value of the first resistor R1, and V0s is estimated in step 107. Power supply voltage.
[0030]
After step 133, the microcomputer 11 determines the insulation state from the ground fault resistances Rn and Rp obtained in step 133. For example, the ground fault resistances Rn and Rp obtained in step 133 are compared with a predetermined reference resistance value, and if any one of the ground fault resistances Rn and Rp is equal to or lower than the reference resistance value, It is determined that a defect has occurred. Further, while detecting the insulation state, the insulation state detection cycle from step 101 to step 121 and from step 123 to step 133 is repeated.
[0031]
Thus, in the insulation detection device of the present embodiment, the power supply voltage fluctuation ratio of the power supply 3 is calculated from step 123 to step 133, and the detection voltages VCN and VCP are corrected based on the calculated power supply voltage fluctuation ratio. The grounding resistance is detected by the corrected detection voltages VCN and VCP to determine the insulation state. For this reason, the influence of the fluctuation | variation of the power supply voltage to the change of the value of the detected ground fault resistance can be reduced, and the reliability of detection of an insulation state can be improved.
[0032]
By the way, in the insulation detection device that does not correct the detection voltages VCN and VCP as in the insulation detection device of the present embodiment, when there is a fluctuation in the power supply voltage that affects the detection of the ground fault resistance, the influence of the fluctuation in the power supply voltage is included. In order to eliminate the detection value of the ground fault resistance that may be detected from the determination of the insulation state, if the difference between the previously estimated power supply voltage V0s and the current estimated V0s is equal to or greater than a preset value, It is assumed that the fluctuation affects the detected value of the ground fault resistance, and the current ground fault resistance detection cycle is cancelled. For this reason, depending on the fluctuation state of the power supply voltage, the number of times of detecting the ground fault resistance per unit time decreases, and for example, the detection probability may be about 50%.
[0033]
However, in the insulation detection device of this embodiment, since the influence of the fluctuation of the power supply voltage on the change in the value of the detected ground fault resistance is reduced, the previous estimation for canceling the detection cycle of the ground fault resistance is performed. The set value for the difference between the power supply voltage V0s and the currently estimated V0s can be set to a value larger than that of the insulation detection device that does not correct the detection voltages VCN and VCP. Therefore, the number of detections of the ground fault resistance per unit time is greater than that of the insulation detection device that does not correct the detection voltages VCN and VCP, and the detection probability of the insulation state can be improved. And since the detection probability of an insulation state can be improved, the detection accuracy of an insulation state can be improved.
[0034]
Furthermore, since the insulation detection device 1 according to the present embodiment includes a bypass unit including the fifth switch S5 that forms a path for bypassing the second resistor R2 when the circuit is closed, between the two terminals of the capacitor 9 by the microcomputer 11 The discharge time from the capacitor 9 can be shortened by closing the fifth switch S5 after the detection of this voltage. Therefore, the time required for one cycle for insulation detection can be shortened, the number of insulation detections per unit time can be increased, and the accuracy of insulation detection can be further improved.
[0035]
The bypass means including the fifth switch S5 is not limited to the configuration of the present embodiment, and the bypass means is connected between the second diode D2 and the second resistor R2 to the ground potential portion 7, and the fifth switch S5 and A fifth resistor R5 having a resistance lower than that of the second resistor R2 may be connected in series. In addition, when there is no need to reduce the time required for one cycle for insulation detection, a configuration in which bypass means including the fifth switch S5 is not provided can be employed.
[0036]
Further, in the present embodiment, the ground fault resistance Rp on the positive terminal side and the ground fault resistance Rn on the negative terminal side are calculated separately, and thereby, a portion having a poor insulation can be detected. However, in the case of determining only the occurrence of insulation failure without detecting the insulation failure site, the grounding resistance Rp on the positive terminal side and the negative terminal are based on the estimated power supply voltage V0s and the detection voltages VCP, VCN, etc. Another equation for calculating a ground fault resistance value representing the ground fault resistance Rn on the side can also be used.
[0037]
Further, the present invention is not limited to the circuit configuration shown in the present embodiment, and a capacitor is connected in series for a first set time to a DC power source in which the wirings on the positive terminal side and the negative terminal side are insulated from the ground potential portion. First switching means for connecting the capacitor in series between the positive terminal of the power source and the ground potential portion for a second set time, between the negative terminal of the power source and the ground potential portion And a third switching means for connecting a capacitor in series for a second set time, and a detection means for detecting a voltage between both terminals of the capacitor after the first, second and third switching means are shut off. If the fourth switching means is provided, the present invention can be applied to an insulation detection device having various circuit configurations.
[0038]
【The invention's effect】
According to the present invention, the reliability of detection of an insulation state can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an embodiment of an insulation detection device to which the present invention is applied.
FIG. 2 is a flowchart showing an insulation resistance calculation operation in an embodiment of an insulation detection device to which the present invention is applied.
FIG. 3 is a time chart showing a charge / discharge state of a capacitor and a voltage reading timing with respect to the operation of each switch unit;
FIG. 4 is a flowchart showing an insulation resistance calculation process in an embodiment of an insulation detection device to which the present invention is applied.
FIG. 5 is a diagram showing fluctuations in power supply voltage and voltage detection timing by a microcomputer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Insulation detection apparatus 3 Power supply 5a Positive side main circuit wiring 5b Negative side main circuit wiring 7 Grounding potential part 9 Capacitor 11 Microcomputer S1 1st switch S2 2nd switch S3 3rd switch S4 4th switch Rp Positive terminal side ground fault resistance Rn Negative terminal side ground fault resistance

Claims (1)

A series connection of a capacitor and a resistor is connected in parallel to a DC power source in which the positive terminal side and negative terminal side wirings are insulated from the ground potential portion , for a first set time shorter than the time during which the capacitor is fully charged. A first switching means to be connected; a second switching means for connecting the series connection body between a positive terminal of the power supply and the ground potential portion for a second set time; a negative terminal of the power supply; A third switching means for connecting the series connection body to the ground potential portion for a second set time; and both terminals of the capacitor after the first, second and third switching means are shut off. A fourth switching means for connecting a detection means for detecting a voltage between the power supply, and a calculation means for calculating an insulation resistance for the ground potential portion of the power source,
The calculation means estimates the power supply voltage of the power source based on the detection voltage of the detection means after the first switching means is shut off, and the previous insulation detection cycle of two consecutive insulation detection cycles. The estimated power supply based on the power supply voltage estimated in step 4, the power supply voltage estimated in the subsequent insulation detection cycle, and the time interval at which the voltage between both terminals of the capacitor for calculating the estimated power supply voltage is detected. The power supply voltage fluctuation ratio during the time when the voltage between the two terminals of the capacitor for calculating the voltage is detected is calculated, and the power supply voltage fluctuation ratio is calculated based on the calculated power supply voltage fluctuation ratio in the previous insulation detection cycle. Each detection voltage in the detection means after the second and third switching means is cut off is corrected, and the corrected detection voltage and the power supply voltage estimated in the previous insulation detection cycle are used to correct the detection voltage. Wherein calculating the insulation resistance to ground potential portion formed by ungrounded power insulating detecting device source.

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