Ground fault detection device, control method therefor, and control program

Abstract

[Problem] The purpose of the present invention is to accurately detect a reduction in insulation resistance. [Solution] A decrease in insulation resistances (RLp, RLn) is detected in a measurement period in which a fluctuation in a second charging voltage, which is a charging voltage of a first capacitor (110) charged in a second charging path in which the first capacitor (110) is connected between a positive electrode of a battery (200) and ground, is determined to be less than a second threshold value, and a decrease in insulation resistances (RLp, RLn) is detected in the measurement period in which the fluctuation in the second charging voltage is determined to be less than a second threshold value. The fluctuation of a third charging voltage, which is the charging voltage of the first capacitor (110) charged in a third charging path between the ground and the negative electrode where the first capacitor (110) is connected to the battery (200), is determined to be less than a third threshold value.

Description

Technical Field

[0001] The invention relates to a ground fault detection device, a control method and a control program thereof. Background Art

[0002] Recently, hybrid vehicles and electric vehicles are becoming more and more popular. Hybrid vehicles and electric vehicles are equipped with an electric motor and a battery for powering the electric motor. The battery installed in the hybrid vehicle and the electric vehicle is a high-voltage battery with a voltage equal to or greater than 200V, and in order to ensure its safety, it is necessary to electrically insulate the battery from the vehicle body which is a reference potential for grounding. Therefore, vehicles such as hybrid vehicles and electric vehicles are also equipped with a ground fault detection device that detects a decrease in insulation resistance between a system including an ungrounded battery and the vehicle body.

[0003] As a ground fault detection device, there is a flying capacitor type ground fault detection device (for example, Patent Document 1). A flying capacitor type ground fault detection device has a capacitor used as a flying capacitor, and the ground fault detection device switches between a first charging path, a second charging path, a third charging path, and a measurement path. In the first charging path, the capacitor is connected between the positive and negative electrodes of a battery without being grounded; in the second charging path, the capacitor is connected between the positive electrode of the battery and the ground; in the third charging path, the capacitor is connected between the negative electrode of the battery and the ground; and the measurement path is used to measure the charging voltage of the first capacitor to perform capacitor charging and capacitor charging voltage measurement, and detect a decrease in insulation resistance based on the measured capacitor charging voltage.

[0004] [Citation List]

[0005] [Patent Document]

[0006] [Patent Document 1] JP 2004-170103A Summary of the invention

[0007] [Technical issues]

[0008] In the case where the charging voltage of the battery fluctuates sharply, a decrease in insulation resistance may be erroneously detected even though the insulation resistance has not decreased, or a decrease in insulation resistance may not be detected even though the insulation resistance has decreased.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to accurately detect a decrease in insulation resistance.

[0010] [Solution to the problem]

[0011] In order to solve the above technical problems, according to an embodiment, a ground fault detection device of the present application is a ground fault detection device for detecting a reduction in insulation resistance of a system including an ungrounded battery, wherein the ground fault detection device includes: a first capacitor; a switching unit, the switching unit is configured to switch between a first charging path, a second charging path, a third charging path and a measurement path, in which the first charging path, the first capacitor is connected between the positive electrode and the negative electrode of the battery without being connected to the ground, in the second charging path, the first capacitor is connected between the positive electrode of the battery and the ground, in the third charging path, the first capacitor is connected between the negative electrode of the battery and the ground, and the measurement path is used to measure the charging voltage of the first capacitor; and a control unit configured to control the switching unit to measure the charging voltage of the first capacitor, wherein the control unit is configured to determine whether a fluctuation of a second charging voltage, which is a charging voltage of the first capacitor charged through the second charging path, is less than a second threshold value, and determine whether a fluctuation of a third charging voltage, which is a charging voltage of the first capacitor charged through the third charging path, is less than a third threshold value for each measurement cycle, and detect a decrease in the insulation resistance in a measurement cycle in which the fluctuation of the second charging voltage is determined to be less than the second threshold value and the fluctuation of the third charging voltage is determined to be less than the third threshold value.

[0012] A control method according to an embodiment of the present invention is a control method of a ground fault detection device for detecting a decrease in insulation resistance of a system including an ungrounded battery, the control method being executed by a computer, wherein the ground fault detection device comprises: a first capacitor; and a switching unit configured to switch between a first charging path, a second charging path, a third charging path, and a measurement path. In the first charging path, the first capacitor is connected between a positive electrode and a negative electrode of a battery without being connected to the ground, in the second charging path, the first capacitor is connected between a positive electrode of the battery and the ground, in the third charging path, the first capacitor is connected between a negative electrode of the battery and the ground, and the measurement path is connected between the first charging path and the third charging path. a path for measuring a charging voltage of the first capacitor; and the control method comprises: a measuring step of controlling the switching section to measure the charging voltage of the first capacitor; a step of determining, for each measurement cycle, whether a fluctuation of a second charging voltage, which is a charging voltage of the first capacitor charged through the second charging path, is less than a second threshold value, and a step of determining whether a fluctuation of a third charging voltage, which is a charging voltage of the first capacitor charged through the third charging path, is less than a third threshold value; and a step of detecting a decrease in the insulation resistance in a measurement cycle in which a fluctuation of the second charging voltage is determined to be less than the second threshold value and a fluctuation of the third charging voltage is determined to be less than the third threshold value.

[0013] A control program according to an embodiment of the present invention causes a computer to execute the above-mentioned information processing method.

[0014] [Effects of the invention]

[0015] According to the present invention, it is possible to accurately detect a decrease in insulation resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a view showing a ground fault detection device 100 according to an embodiment of the present invention.

[0017] Figure 2 2 is a diagram showing a configuration example of the ground fault detection device 100 .

[0018] Figure 3 is a diagram describing a first charging path.

[0019] Figure 4 is a diagram describing a second charging path.

[0020] Figure 5 is a diagram describing a third charging path.

[0021] Figure 6 is a view that describes the measurement path.

[0022] Figure 7 is a view describing the discharge path.

[0023] Figure 8 is an example of a processing operation performed for each measurement cycle in the ground fault detection device 100 .

[0024] Fig. 9 3 is a diagram describing the notification of the reduction of the insulation resistances RLp, RLn.

[0025] Fig.10 1 is a diagram describing the notification of the reduction of the insulation resistances RLp, RLn.

[0026] Reference Mark List

[0027] 100 Ground fault detection device

[0028] 110 First capacitor

[0029] 120 Switching Department

[0030] 130 Control Department

[0031] 200 Batteries

[0032] 210 Positive side power cable

[0033] 220 Negative power line DETAILED DESCRIPTION

[0034] <Ground Fault Detection Device 100>

[0035] Figure 1 is a view showing a ground fault detection device 100 according to an embodiment of the present invention. The ground fault detection device 100 is a flying capacitor type ground fault detection device, which is connected to a non-grounded battery 200 to detect a decrease in insulation resistance of a system including the battery 200. Here, the insulation resistance between the positive electrode side of the battery 200 and the ground is referred to as a positive electrode side insulation resistance RLp, and the insulation resistance between the negative electrode side of the battery 200 and the ground is referred to as a negative electrode side insulation resistance RLn.

[0036] The battery 200 is, for example, a battery for supplying power to the motor of the vehicle, and is a high voltage (for example, 200 V or more) battery. The battery 200 includes, for example, a plurality of rechargeable batteries (for example, lithium ion batteries). The positive side of the battery 200 is connected to the positive side power line 210, and the negative side of the battery 200 is connected to the negative side power line 220.

[0037] The system including the battery 200 is connected with a Y capacitor for reducing the noise caused by the common mode. Figure 1In the example shown, the positive side Y capacitor CYp is connected between the positive side power line 210 and the ground, and the negative side Y capacitor CYn is connected between the negative side power line 220 and the ground. The positive side Y capacitor CYp includes stray capacitance between the positive side power line 210 and the ground, and the negative side Y capacitor CYn includes stray capacitance between the negative side power line 220 and the ground.

[0038] The ground fault detection device 100 is connected to the positive electrode of the battery 200 via the positive electrode side power line 210 and is connected to the negative electrode of the battery 200 via the negative electrode side power line 220. The ground fault detection device 100 includes a first capacitor 110, a switch 120, and a control unit 130.

[0039] The first capacitor 110 is a capacitor having a first electrode plate and a second electrode plate and configured to operate as a flying capacitor.

[0040] The switching unit 120 is configured to switch between a first charging path, a second charging path, a third charging path and a measurement path, in which in the first charging path, the first capacitor 110 is connected between the positive electrode and the negative electrode of the battery 200 without being grounded, in the second charging path, the first capacitor 110 is connected between the positive electrode of the battery 200 and the ground, in the third charging path, the first capacitor 110 is connected between the negative electrode of the battery 200 and the ground, and the measurement path is used to measure the charging voltage of the first capacitor 110.

[0041] Regarding the first charging path, the first capacitor 110 is charged by a current flowing through a closed circuit in which the positive electrode of the battery 200, the first capacitor 110, and the negative electrode of the battery 200 are sequentially connected in series without being grounded. Thus, in the first charging path, a first charging voltage V0 corresponding to the charging voltage of the battery 200 is charged to the first capacitor 110.

[0042] Regarding the second charging path, the first capacitor 110 is charged by the current flowing through the closed circuit in which the positive electrode of the battery 200, the first capacitor 110, the negative electrode side insulation resistor RLn, and the negative electrode of the battery 200 are sequentially connected in series. Thus, in the second charging path, the second charging voltage VC1n reflecting the influence of the negative electrode side insulation resistor RLn is charged to the first capacitor 110.

[0043] Regarding the third charging path, the first capacitor 110 is charged by the current flowing through the closed circuit in which the positive electrode of the battery 200, the positive electrode side insulation resistor RLp, the first capacitor 110, and the negative electrode of the battery 200 are sequentially connected in series. Thus, in the third charging path, the third charging voltage VC1p reflecting the influence of the positive electrode side insulation resistor RLp is charged to the first capacitor 110.

[0044] The control section 130 is configured to measure the charging voltage of the first capacitor 110. For example, the control section 130 controls the switching section 120 to measure a first charging voltage V0 as the charging voltage of the first capacitor 110 charged through the first charging path, a second charging voltage VC1n as the charging voltage of the first capacitor 110 charged through the second charging path, and a third charging voltage VC1p as the charging voltage of the first capacitor 110 charged through the third charging path in the measurement path.

[0045] Then, the control unit 130 detects the decrease of the insulation resistance RLp, RLn (detects the ground fault) based on the measured charging voltage of the first capacitor 110. For example, the control unit 130 detects the decrease of the insulation resistance RLp, RLn based on the first charging voltage V0, the second charging voltage VC1n, and the third charging voltage VC1p. At this time, the control unit 130 measures the values ​​of the insulation resistance RLp, RLn based on the charging voltage of the first capacitor 110, and then detects the decrease of the insulation resistance RLp, RLn based on the measured values ​​of the insulation resistance RLp, RLn. For example, the control unit 130 is composed of a computer.

[0046] The control unit 130 detects the reduction of the insulation resistance RLp, RLn in each measurement cycle. That is, the control unit 130 repeats the measurement cycle for detecting the reduction of the insulation resistance RLp, RLn. At this time, for example, the control unit 130 measures the value of the insulation resistance RLp, RLn in each measurement cycle, and then detects the reduction of the insulation resistance RLp, RLn by comparing the insulation resistance RLp, RLn measured in the current measurement cycle with the insulation resistance RLp, RLn measured in the measurement cycle before the current measurement cycle (for example, the measurement cycle immediately before the current measurement cycle).

[0047] The measurement cycle includes a first measurement period (V0 measurement period), a second measurement period (VC1n measurement period), and a third measurement period (VC1p measurement period). In the first measurement period, the first capacitor 110 is charged through the first charging path, and then the first charging voltage V0 as the charging voltage of the first capacitor 110 charged through the first charging path is measured while the first capacitor 110 is discharged through the measurement path. In the second measurement period, the first capacitor 110 is charged through the second charging path, and then the second charging voltage VC1n as the charging voltage of the first capacitor 110 charged through the second charging path is measured while the first capacitor 110 is discharged through the measurement path. In the third measurement period, the first capacitor 110 is charged through the third charging path, and then the third charging voltage VC1p as the charging voltage of the first capacitor 110 charged through the third charging path is measured while the first capacitor 110 is discharged through the measurement path. In other words, for each measurement cycle, the control unit 130 measures the first charging voltage V0, the second charging voltage VC1n, and the third charging voltage VC1p, and then detects the reduction of the insulation resistance based on the measured first charging voltage V0, the second charging voltage VC1n, and the third charging voltage VC1p. Within the measurement cycle, for example, the above measurement periods are implemented in the order of the first measurement period, the second measurement period, the first measurement period, and the third measurement period.

[0048] When an abnormality occurs (for example, the moment when the reduction of the insulation resistance RLp, RLn is detected), the control unit 130 notifies the occurrence of the abnormality (for example, the reduction of the insulation resistance RLp, RLn). At this time, the control unit 130 may be configured to display information indicating the occurrence of the abnormality by using an indication device for displaying information (for example, a display and a lamp), thereby notifying the occurrence of the abnormality, or may be configured to output a sound indicating the occurrence of the abnormality by using an indication device for outputting a sound for displaying information (for example, a speaker), thereby notifying the occurrence of the abnormality, or may be configured to send information indicating the occurrence of the abnormality to another device (for example, a superior ECU (electronic control unit)) by using a communication device for sending information to another device, thereby notifying the occurrence of the abnormality.

[0049] The control unit 130 may be configured to notify the measured insulation resistance RLp, RLn values. In this way, not the control unit 130, but a person or other device that obtains information through the notification can detect a decrease in the insulation resistance RLp, RLn.

[0050] <Configuration Example of Ground Fault Detection Device 100>

[0051] For example, Figure 2As shown, the switching unit 120 may be configured to include four switches (a first switch S1, a second switch S2, a third switch S3, and a fourth switch S4). The four switches are insulating switch elements (eg, optical MOSFETs).

[0052] The first switch S1 is connected between the positive electrode of the battery 200 and the first electrode plate of the first capacitor 110. Figure 2 As shown, the first switch S1 is connected to the first electrode plate of the first capacitor 110 through the first resistor R1. In addition, the first diode D1 can be connected between the first switch S1 and the first resistor R1, or between the first resistor R1 and the first capacitor 110. The forward direction of the first diode D1 is from the positive electrode of the battery 200 toward the first electrode plate of the first capacitor 110. Figure 2 In the configuration example shown, the first diode D1 is connected between the first switch S1 and the first resistor R1.

[0053] The second switch S2 is connected between the negative electrode of the battery 200 and the second electrode plate of the first capacitor 110. The second resistor R2 can be configured to be connected between the second switch S2 and the second electrode plate of the first capacitor 110, or between the second switch S2 and the negative electrode of the battery 200. Figure 2 In the configuration example shown, the second resistor R2 is connected between the second switch S2 and the second electrode plate of the first capacitor 110 .

[0054] The third switch S3 is connected between the first electrode plate of the first capacitor 110 and the ground. Figure 2 As shown, the third switch S3 is grounded through the third resistor R3. In addition, the second diode D2 and the third diode D3 can be connected in parallel between the third switch S3 and the first electrode plate of the first capacitor 110. The forward direction of the second diode D2 is the direction from the first electrode plate of the first capacitor 110 toward the third switch S3. The forward direction of the third diode D3 is the direction from the third switch S3 toward the first electrode plate of the first capacitor 110. Between the third switch S3 and the first electrode plate of the first capacitor 110, a fifth resistor R5 can be connected in series with the second diode D2. Figure 2 In the illustrated configuration example, the fifth resistor R5 is connected to the cathode side of the second diode D2.

[0055] The fourth switch S4 is connected between the second electrode plate of the first capacitor 110 and the ground. Figure 2 As shown, the fourth switch S4 is grounded via a fourth resistor R4.

[0056] Therefore, in Figure 2 In the configuration example shown in FIG. 1 , when the first switch S1 and the second switch S2 are turned on, and the third switch S3 and the fourth switch S4 are turned off, as shown in FIG. Figure 3 As shown, a first charging path is formed, in which the first capacitor 110 is connected between the positive electrode and the negative electrode of the battery 200 without being grounded. Figure 2 In the configuration example shown, according to the first charging path, the first capacitor 110 is charged due to a closed circuit in which the positive electrode of the battery 200, the first switch S1, the first diode D1, the first resistor R1, the first capacitor 110, the second resistor R2, the second switch S2, and the negative electrode of the battery 200 are sequentially connected in series. Thus, with respect to the first charging path, the first charging voltage V0 corresponding to the charging voltage of the battery 200 is charged to the first capacitor 110.

[0057] In addition, Figure 2 In the configuration example shown in FIG. 1 , when the first switch S1 and the fourth switch S4 are turned on, and the second switch S2 and the third switch S3 are turned off, Figure 4 As shown, a second charging path is formed, in which the first capacitor 110 is connected between the positive electrode of the battery 200 and the ground. Figure 2 In the configuration example shown, according to the second charging path, the first capacitor 110 is charged due to a closed circuit in which the positive electrode of the battery 200, the first switch S1, the first diode D1, the first resistor R1, the first capacitor 110, the fourth switch S4, the fourth resistor R4, the negative electrode side insulation resistor RLn, and the negative electrode side of the battery 200 are sequentially connected in series. Thus, in the second charging path, the second charging voltage VC1n reflecting the influence of the negative electrode side insulation resistor RLn of the battery 200 is charged to the first capacitor 110.

[0058] exist Figure 2 In the configuration example shown in FIG. 1 , when the second switch S2 and the third switch S3 are turned on, and the first switch S1 and the fourth switch S4 are turned off, Figure 5 As shown, a third charging path is formed, in which the first capacitor 110 is connected between the negative electrode of the battery 200 and the ground. Figure 2 In the illustrated configuration example, in the third charging path, the first capacitor 110 is charged due to a closed circuit in which the positive electrode of the battery 200, the positive electrode side insulation resistance RLp, the third resistor R3, the third switch S3, the third diode D3, the first capacitor 110, the second resistor R2, the second switch S2, and the negative electrode of the battery 200 are sequentially connected in series. Thus, in the third charging path, the third charging voltage VC1p reflecting the influence of the positive electrode side insulation resistance RLp of the battery 200 is charged to the first capacitor 110.

[0059] like Figure 2As shown, the control unit 130 is connected to the first electrode plate of the first capacitor 110 through the third switch S3. Thus, when the third switch S3 and the fourth switch S4 are turned on, and the first switch S1 and the second switch S2 are turned off, as shown in FIG. Figure 6 As shown, the current flows from the first electrode plate of the first capacitor 110 to the control unit 130. Thus, the control unit 130 can measure the charging voltage of the detection capacitor C1. That is, when the third switch S3 and the fourth switch S4 are turned on and the first switch S1 and the second switch S2 are turned off, a measurement path for measuring the charging voltage of the first capacitor 110 is formed. Figure 2 As shown, the line connecting the third switch S3 and the control unit 130 may be grounded through the second capacitor C2.

[0060] In addition, if Figure 6 As shown, in the measurement path, current flows from the first electrode plate to the second electrode plate of the first capacitor 110. Thus, in the measurement path, the first capacitor 110 is discharged.

[0061] like Figure 2 As shown, Figure 6 As shown, the switching unit 120 may also be configured to include a measuring switch Sa. Thus, when the third switch S3, the fourth switch S4, and the measuring switch Sa are turned on, and the first switch S1 and the second switch S2 are turned off, a measuring path for measuring the charging voltage of the first capacitor 110 is formed. Then, as shown in FIG. Figure 7 As shown, when the third switch S3 and the fourth switch S4 are turned on, and the first switch S1, the second switch S2, and the measuring switch Sa are turned off, a discharge path is formed in which the control unit 130 is disconnected from the first capacitor 110 to discharge the first capacitor 110. Figure 3-5 As shown, in the first charging path, the second charging path and the third charging path, the measuring switch Sa is set to be open.

[0062] <Rapid Fluctuation of Charging Voltage of Battery 200>

[0063] When the charging voltage of the battery 200 fluctuates sharply, there is a case where a decrease in the insulation resistances RLp and RLn is erroneously detected even if they have not decreased, or a case where a decrease in the insulation resistances RLp and RLn is not detected even if they have decreased.

[0064] Therefore, the control unit 130 detects the reduction in insulation resistance of the battery 200 based on the charging voltage of the first capacitor 110 measured when the fluctuation of the charging voltage of the battery 200 is small. That is, according to the present embodiment, when detecting the reduction in insulation resistance RLp, RLn, the charging voltage of the first capacitor 110 measured when the fluctuation of the charging voltage of the battery 200 is large is not used.

[0065] The control unit 130 detects the reduction of the insulation resistance RLp and RLn in each measurement cycle. Then, the measurement cycle includes a first measurement period (V0 measurement period) for measuring the first charging voltage V0 corresponding to the charging voltage of the battery 200. Thus, for example, the control unit 130 can make a determination as to whether the fluctuation of the first charging voltage V0 (for example, the fluctuation from the last measured first charging voltage V0 to the current measured first charging voltage V0) is less than the first threshold value in each first measurement period. Then, the control unit 130 can detect the reduction of the insulation resistance RLp and RLn in the measurement cycle that does not include the first measurement period in which the fluctuation of the first charging voltage V0 is equal to or greater than the first threshold value. That is, in the measurement cycle that includes only the first measurement period in which the fluctuation of the first charging voltage is determined to be less than the first threshold value, the control unit 130 detects the reduction of the insulation resistance RLp and RLn, and in the measurement cycle that includes the first measurement period in which the fluctuation of the first charging voltage is determined to be equal to or greater than the first threshold value, the control unit 130 does not detect the reduction of the insulation resistance RLp and RLn.

[0066] Thus, the reduction in the insulation resistance RLp, RLn can be detected without being affected by a sharp fluctuation in the charging voltage of the battery 200. As a result, according to the present embodiment, it is possible to prevent erroneous detection and non-detection of the reduction in the insulation resistance RLp, RLn.

[0067] There is a case where the charging voltage of the battery 200 fluctuates sharply during the second measurement period (VC1n measurement period) and the third measurement period (VCIp measurement period). In the case where the charging voltage of the battery 200 fluctuates sharply during the second measurement period and the third measurement period, due to the sharp fluctuation of the charging voltage of the battery 200, there is a case where the second charging voltage VC1n and the third charging voltage VC1p, which respectively reflect the influence of the insulation resistances RLp and RLn of the battery 200, fluctuate sharply.

[0068] Therefore, according to this embodiment, in each measurement cycle, the control unit 130 determines whether the fluctuation of the second charging voltage VC1n (for example, the fluctuation from the second charging voltage VC1n measured in the previous second measurement period to the second charging voltage VC1n measured in the current second measurement period) is less than the second threshold value within the second measurement period, and determines whether the fluctuation of the third charging voltage VC1p (for example, the fluctuation from the third charging voltage VC1p measured in the previous third measurement period to the third charging voltage VC1p measured in the current third measurement period) is less than the third threshold value within the third measurement period.

[0069] Then, in the measurement period in which it is determined that the fluctuation of the second charging voltage VC1n is less than the second threshold value and the fluctuation of the third charging voltage VC1p is lower than the third threshold value, the control section 130 may detect the decrease in the insulation resistances RLp and RLn. That is, in the measurement period including the second measurement period in which the fluctuation of the second charging voltage VC1n is equal to or greater than the second threshold value or the third measurement period in which the fluctuation of the third charging voltage VC1p is equal to or greater than the third threshold value, the control section 130 may be prevented from detecting the decrease in the insulation resistances RLp and RLn.

[0070] Thus, the reduction in the insulation resistance RLp, RLn can be detected without being affected by a sharp fluctuation in the charging voltage of the battery 200. As a result, according to the present embodiment, it is possible to prevent erroneous detection and non-detection of the reduction in the insulation resistance RLp, RLn.

[0071] In the case where the reduction of the insulation resistance RLp and RLn is detected by other devices (for example, a superior ECU) and personnel, the control unit 130 can notify the values ​​of the insulation resistance RLp and RLn measured in the measurement cycle in the measurement cycle including the second measurement period in which the fluctuation of the second charging voltage VC1n is determined to be equal to or greater than the second threshold value or the third measurement period in which the fluctuation of the third charging voltage VC1p is determined to be equal to or greater than the third threshold value, and notify that the charging voltage of the battery 200 may fluctuate sharply in the measurement cycle. In this way, when the charging voltage of the battery 200 may fluctuate sharply in the measurement cycle in which the reduction of the insulation resistance RLp and RLn is detected, the values ​​of the insulation resistance RLp and RLn can be detected without using the values ​​of the insulation resistance RLp and RLn measured in the measurement cycle. As a result, the insulation resistance RLp and RLn can be detected without being affected by the sharp fluctuation of the charging voltage of the battery 200.

[0072] Figure 8 is an example of a processing operation performed in the ground fault detection device 100 in each measurement cycle.

[0073] The control section 130 measures the first charging voltage V0 in the first measurement period (step S801). The control section 130 determines whether the fluctuation of the first charging voltage V0 (the fluctuation from the first charging voltage V0 measured last time to the first charging voltage V0 measured currently) is less than the first threshold value (step S802), and if the fluctuation of the first charging voltage V0 is not less than the first threshold value (step S802, no), the control section 130 sets the first error flag (step S803).

[0074] The control section 130 measures the second charging voltage VC1n in the second measurement period (step S804). The control section 130 determines whether the fluctuation of the second charging voltage VC1n (the fluctuation from the second charging signal VC1n measured last time to the second charging voltage VC1n measured currently) is less than the second threshold value (step S805), and if the fluctuation of the second charging voltage VC1n is not less than the second threshold value (step S803, no), the control section 130 sets the second error flag (step S806).

[0075] The control section 130 measures the first charging voltage V0 in the first measurement period (step S807). The control section 130 determines whether the fluctuation of the first charging voltage V0 is less than the first threshold value (step S808), and if the fluctuation of the first charging voltage V0 is not less than the first threshold value (step S808, no), the control section 130 sets the third error flag (step S809).

[0076] The control section 130 measures the third charging voltage VC1p in the third measurement period (step S810). The control section 130 determines whether the fluctuation of the third charging voltage VC1p (the fluctuation from the third charging voltage VC1p measured last time to the third charging voltage VC1p measured currently) is less than the third threshold value (step S811), and if the fluctuation of the third charging voltage VC1p is not less than the third threshold value (step S811, no), the control section 130 sets the fourth error flag (step S812).

[0077] If none of the first to fourth error flags are set (step S813, yes), the control unit 130 detects the decrease of the insulation resistances RLp and RLn based on the first charging voltage V0, the second charging voltage VC1n, and the third charging voltage VC1p (step S814). If any one of the first to fourth error flags is set (step S813, no), the control unit 130 clears the set error flag and ends the process (step S815).

[0078] <Notice of Reduction of Insulation Resistance RLp and RLn>

[0079] In the case where the number of measurement cycles in which a decrease in the insulation resistance RLp, RLn is detected (i.e., measurement cycles in which the values ​​of the insulation resistance RLp, RLn decrease to less than the normal value of the insulation resistance RLp, RLn) is a predetermined number of consecutive times (e.g., three), the control section 130 may be configured to notify the decrease in the insulation resistance RLp, RLn. At this time, in the case where the values ​​of the insulation resistance RLp, RLn measured in the measurement cycle (measurement cycle with fluctuation) including the first measurement period in which the fluctuation of the first charging voltage is equal to or greater than the first threshold, the second measurement period in which the fluctuation of the second charging voltage VC1n is equal to or greater than the second threshold, or the third measurement period in which the fluctuation of the third charging voltage VC1p is equal to or greater than the third threshold are not used for the detection of the decrease in the insulation resistance RLp, RLn, there may be a case where the notification of the decrease in the insulation resistance RLp, RLn is delayed.

[0080] For example, Fig. 9 As shown, in a predetermined number of measurement cycles (in Fig. 9 In the example shown, in the three measurement cycles, i.e., measurement cycle 3, measurement cycle 4, and measurement cycle 5), when a decrease in the insulation resistance RLp, RLn is detected, the insulation resistance RLp, RLn in measurement cycle 2 is also likely to decrease. In the case where a decrease in the insulation resistance RLp, RLn occurs in measurement cycle 2, the values ​​of the insulation resistance RLp, RLn measured in measurement cycle 2 are used to detect a decrease in the insulation resistance RLp, RLn (see Fig.10 ), if the values ​​of the insulation resistances RLp, RLn measured in the measurement cycle 2 are not used to detect a decrease in the insulation resistances RLp, RLn, the notification of the decrease in the insulation resistances RLp, RLn is delayed by only one measurement cycle.

[0081] according to Fig. 9 In the example shown, the notification of the decrease in the insulation resistance RLp, RLn is performed after three consecutive measurement cycles (after measurement cycle 5) in which the values ​​of the insulation resistance RLp, RLn measured are lower than the normal insulation resistance RLp, RLn values ​​without fluctuation; on the other hand, according to Fig.10 In the example shown, regardless of whether there is fluctuation, notification of a decrease in the insulation resistance RLp, RLn is made after three consecutive measurement cycles without fluctuation in which the insulation resistance RLp, RLn values ​​are lower than the normal insulation resistance RLp, RLn values ​​(after measurement cycle 4).

[0082] Therefore, in the case where the reduction of the insulation resistance RLp, RLn is notified when there are a predetermined number of consecutive measurement cycles in which the reduction of the insulation resistance RLp, RLn is detected, the control section 13 can use the values ​​of the insulation resistance RLp, RLn measured in the measurement cycle (measurement cycle with fluctuation) including the first measurement period in which the fluctuation of the first charging voltage is equal to or greater than the first threshold, the second measurement period in which the fluctuation of the second charging voltage VC1n is equal to or greater than the second threshold, or the third measurement period in which the fluctuation of the third charging voltage VC1p is equal to or greater than the third threshold in the detection of the reduction of the insulation resistance RLp, RLn. In this way, it is possible to prevent the delay in the notification of the reduction of the insulation resistance RLp, RLn.

[0083] The present invention has been described above using the preferred embodiments of the present invention. Although the present invention has been described by referring to specific examples, various modifications and changes can be made to these examples without departing from the spirit and scope of the present invention as described in the claims.

Claims

1. A ground fault detection device (100) for detecting a decrease in insulation resistance (RLp, RLn) of a system including an ungrounded battery (200), the ground fault detection device (100) comprising: A first capacitor (110); a switching unit (120), the switching unit (120) being configured to switch between a first charging path, a second charging path, a third charging path and a measuring path, In the first charging path, the first capacitor (110) is connected between the positive electrode and the negative electrode of the battery (200) but is not connected to the ground. In the second charging path, the first capacitor (110) is connected between the positive electrode of the battery (200) and the ground. In the third charging path, the first capacitor (110) is connected between the negative electrode of the battery (200) and the ground. The measurement path is used to measure the charging voltage of the first capacitor (110); and a control unit (130) configured to control the switch unit (120) to measure a charging voltage of the first capacitor (110), Wherein, the control unit (130) is configured as follows: for each measurement cycle, determining whether the fluctuation of the second charging voltage (VC1n) is less than a second threshold, and determining whether the fluctuation of the third charging voltage (VC1p) is less than a third threshold, wherein the second charging voltage (VC1n) is the charging voltage of the first capacitor (110) charged through the second charging path, and the third charging voltage (VC1p) is the charging voltage of the first capacitor (110) charged through the third charging path, and The detection of the decrease in the insulation resistance is performed in a measurement period in which the fluctuation of the second charging voltage is determined to be smaller than the second threshold value and the fluctuation of the third charging voltage is determined to be smaller than the third threshold value.

2. The ground fault detection device (100) according to claim 1, wherein: The measurement cycle includes: a first measurement period, in which the first capacitor (110) is charged in the first charging path and a first charging voltage (V0) is measured in the measurement path, the first charging voltage (V0) being a charging voltage of the first capacitor (110) charged by the first charging path; a second measurement period, in which the first capacitor (110) is charged in the second charging path and the second charging voltage (VC1n) is measured in the measurement path; and A third measurement period is used to charge the first capacitor (110) in the third charging path and measure the third charging voltage (VC1p) in the measurement path.

3. The ground fault detection device (100) according to claim 2, wherein: The control unit (130) is configured to: When the number of consecutive measurement cycles during which the measured value of the insulation resistance (RLp, RLn) is lower than the normal value of the insulation resistance (RLp, RLn) reaches a predetermined value, notifying the decrease of the insulation resistance (RLp, RLn), and The reduction in the insulation resistance (RLp, RLn) is detected using the value of the insulation resistance (RLp, RLn) measured in the measurement period including the second measurement period in which the fluctuation of the second charging voltage (VC1n) is equal to or greater than the second threshold or the third measurement period in which the fluctuation of the third charging voltage (VC1p) is equal to or greater than the third threshold.

4. The ground fault detection device (100) according to claim 2, wherein: The control unit (130) is configured to: For each first measurement period, a determination is made as to whether the fluctuation of the first charging voltage (V0) is less than a first threshold value, and The detection of the decrease in the insulation resistance (RLp, RLn) is performed in a measurement cycle that does not include the first measurement period in which the fluctuation of the first charging voltage (V0) is determined to be equal to or greater than the first threshold value.

5. The ground fault detection device (100) according to claim 4, wherein: The control section (130) is configured to use a fluctuation from the first charging voltage (V0) measured last time to the first charging voltage (V0) measured currently as the fluctuation of the first charging voltage (V0).

6. A ground fault detection device (100) for measuring the insulation resistance (RLp, RLn) of a system including an ungrounded battery (200), the ground fault detection device (100) comprising: A first capacitor (110); a switching unit (120), the switching unit (120) being configured to switch between a first charging path, a second charging path, a third charging path and a measuring path, In the first charging path, the first capacitor (110) is connected between the positive electrode and the negative electrode of the battery (200) but is not connected to the ground. In the second charging path, the first capacitor (110) is connected between the positive electrode of the battery (200) and the ground. In the third charging path, the first capacitor (110) is connected between the negative electrode of the battery (200) and the ground. The measurement path is used to measure the charging voltage of the first capacitor (110); and a control unit (130) configured to control the switching unit (120), measure the charging voltage of the first capacitor (110), and measure the value of the insulation resistance (RLp, RLn) for each measurement cycle based on the measured charging voltage of the first capacitor (110), Wherein, the measurement cycle includes: a first measurement period, in which the first capacitor (110) is charged in the first charging path and a first charging voltage (V0) is measured in the measurement path, the first charging voltage (V0) being a charging voltage of the first capacitor (110) charged by the first charging path; a second measurement period, in which the first capacitor (110) is charged in the second charging path and a second charging voltage (VC1n) is measured in the measurement path, the second charging voltage (VC1n) being a charging voltage of the first capacitor (110) charged by the second charging path; and a third measurement period, in which the first capacitor (110) is charged in the third charging path and a third charging voltage (VC1p) is measured in the measurement path, the third charging voltage (VC1p) being the charging voltage of the first capacitor charged by the second charging path, and The control unit is configured to: For each measurement cycle, a determination is made as to whether the fluctuation of the second charging voltage (VC1n) is less than a second threshold value, and a determination is made as to whether the fluctuation of the third charging voltage (VC1p) is less than a third threshold value, and Notification that there is a possibility that the charging voltage of the battery (200) has suddenly fluctuated in the measurement cycle including the second measurement period in which the fluctuation of the second charging voltage (VC1n) is determined to be equal to or greater than the second threshold or the third measurement period in which the fluctuation of the third charging voltage (VC1p) is determined to be equal to or greater than the third threshold.

7. The ground fault detection device (100) according to any one of claims 2 to 6, wherein: The control unit (130) is configured to: in the second measurement period, using a fluctuation from the second charging voltage (VC1n) measured in the previous second measurement period to the second charging voltage (VC1n) measured in the current second measurement period as the fluctuation of the second charging voltage (VC1n), and In the third measurement period, a fluctuation from the third charging voltage (VC1p) measured in the last third measurement period to the third charging voltage (VC1p) measured in the current third measurement period is used as the fluctuation of the third charging voltage (VC1p).

8. A control method for a ground fault detection device (100), the ground fault detection device (100) being used to detect a decrease in insulation resistance (RLp, RLn) of a system including an ungrounded battery (200), the control method being executed by a computer, The ground fault detection device (100) comprises: A first capacitor (110); as well as a switching unit (120), the switching unit (120) being configured to switch between a first charging path, a second charging path, a third charging path and a measuring path, In the first charging path, the first capacitor (110) is connected between the positive electrode and the negative electrode of the battery (200) but is not connected to the ground. In the second charging path, the first capacitor (110) is connected between the positive electrode of the battery (200) and the ground. In the third charging path, the first capacitor (110) is connected between the negative electrode of the battery (200) and the ground. The measurement path is used to measure the charging voltage of the first capacitor (110), The control method comprises: a measuring step of controlling the switching unit (13) to measure the charging voltage of the first capacitor (110); for each measurement cycle, determining whether the fluctuation of the second charging voltage (VC1n) is less than a second threshold value, and determining whether the fluctuation of the third charging voltage (VC1p) is less than a third threshold value, wherein the second charging voltage (VC1n) is the charging voltage of the first capacitor (110) charged through the second charging path, and the third charging voltage (VC1p) is the charging voltage of the first capacitor (110) charged through the third charging path; and A step of detecting a decrease in the insulation resistance (RLp, RLn) in a measurement period in which a fluctuation in the second charging voltage (VC1n) is determined to be smaller than the second threshold and a fluctuation in the third charging voltage (VC1p) is determined to be smaller than the third threshold.

9. An information processing program for causing a computer to execute the control method according to claim 8.

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