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

Abstract

To accurately detect a decrease in insulating resistance.SOLUTION: A ground fault detection device detects a decrease in insulating resistance RLp, RLn in a measurement cycle in which a change in second charging voltage that represents the charging voltage of a first capacitor 110 charged by a second charging path where the first capacitor 110 is connected between the cathode of a battery 200 and the ground, is determined to be smaller than a second threshold, and a change in third charging voltage that represents the charging voltage of the first capacitor 110 charged by the second charging path where the first capacitor 110 is connected between the anode of the battery 200 and the ground, is determined to be smaller than a third threshold.SELECTED DRAWING: Figure 8

Description

[Technical field]

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

[0002] 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 that supplies power to the electric motor. The battery installed in hybrid vehicles and electric vehicles is a high-voltage battery of 200V or more, and in order to ensure safety, it needs to be electrically insulated from the vehicle body, which is the ground reference potential point. 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 the system including the battery, which is ungrounded, and the vehicle body.

[0003] One example of a ground fault detection device is a flying capacitor type ground fault detection device (for example, Patent Document 1). The flying capacitor type ground fault detection device has a capacitor that operates as a flying capacitor, and switches between a first charging path in which the capacitor is connected between the positive and negative electrodes of a battery without going through ground, a second charging path in which the capacitor is connected between the positive and negative electrodes of the battery and ground, a third charging path in which the capacitor is connected between the negative and negative electrodes of the battery and ground, and a measurement path for measuring the charging voltage of the first capacitor, to charge the capacitor and measure the charging voltage of the capacitor, and detect a decrease in insulation resistance based on the measured charging voltage of the capacitor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-170103 A Summary of the Invention [Problem to be solved by the invention]

[0005] If a sudden fluctuation occurs in the charging voltage of a battery, a decrease in insulation resistance may be erroneously detected even though there is no decrease in insulation resistance, or a decrease in insulation resistance may not be detected even though there is a decrease in insulation resistance.

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to accurately detect a decrease in insulation resistance. [Means for solving the problem]

[0007] In order to solve the above problem, a ground fault detection device according to one embodiment of the present invention is a ground fault detection device that detects a decrease in insulation resistance of a system including an ungrounded battery, and includes a first capacitor, a first charging path in which the first capacitor is connected between a positive electrode and a negative electrode of the battery without going through ground, a second charging path in which the first capacitor is connected between the positive electrode of the battery and ground, a third charging path in which the first capacitor is connected between the negative electrode of the battery and ground, and a measurement path for measuring a charging voltage of the first capacitor, and a switching unit that controls the switching unit to switch between the first charging path, and a control unit that measures the charging voltage of the capacitor, wherein the control unit determines, for each measurement cycle, whether a fluctuation in a second charging voltage, which is the charging voltage of the first capacitor charged through the second charging path, is smaller than a second threshold value, and whether a fluctuation in a third charging voltage, which is the charging voltage of the first capacitor charged through the third charging path, is smaller than a third threshold value, and detects a decrease in the insulation resistance in a measurement cycle in which it is determined that the fluctuation in the second charging voltage is smaller than the second threshold value and that the fluctuation in the third charging voltage is smaller than the third threshold value.

[0008] A control method according to one embodiment of the present invention is a control method for a ground fault detection device that detects a decrease in insulation resistance of a system including an ungrounded battery, the control method being executed by a computer, the ground fault detection device having a first capacitor, a first charging path in which the first capacitor is connected between a positive electrode and a negative electrode of the battery without going through ground, a second charging path in which the first capacitor is connected between the positive electrode of the battery and ground, a third charging path in which the first capacitor is connected between the negative electrode of the battery and ground, and a measurement path for measuring a charging voltage of the first capacitor, the control method comprising: the step of controlling a switching unit to measure a charging voltage of the first capacitor; the step of determining, for each measurement cycle, whether a fluctuation in a second charging voltage, which is a charging voltage of the first capacitor charged through the second charging path, is smaller than a second threshold value and whether a fluctuation in a third charging voltage, which is a charging voltage of the first capacitor charged through the third charging path, is smaller than a third threshold value; and the step of detecting a decrease in the insulation resistance in a measurement cycle in which it is determined that the fluctuation in the second charging voltage is smaller than the second threshold value and that the fluctuation in the third charging voltage is smaller than the third threshold value.

[0009] A control program according to an embodiment of the present invention causes a computer to execute the above-described information processing method. Effect of the Invention

[0010] According to the present invention, a decrease in insulation resistance can be accurately detected. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram showing a ground fault detection device 100 according to an embodiment of the present invention. [Diagram 2] 1 is a diagram illustrating an example of the configuration of a ground fault detection device 100. FIG. [Diagram 3] FIG. 4 is a diagram illustrating a first charging path. [Figure 4] FIG. 11 is a diagram illustrating a second charging path. [Diagram 5] FIG. 13 is a diagram illustrating a third charging path. [Figure 6] FIG. 2 is a diagram illustrating a measurement path. [Figure 7] FIG. 2 is a diagram illustrating a discharge path. [Figure 8] 13 is an example of a processing operation executed in the ground fault detection device 100 for each measurement cycle. [Figure 9] FIG. 11 is a diagram for explaining notification of a decrease in insulation resistances RLp and RLn. [Figure 10] FIG. 11 is a diagram for explaining notification of a decrease in insulation resistances RLp and RLn. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] <Ground fault detection device 100> 1 is a diagram showing a ground fault detection device 100 according to one embodiment of the present invention. The ground fault detection device 100 is a flying capacitor type ground fault detection device that is connected to an ungrounded battery 200 and detects 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 taken 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 taken as a negative electrode side insulation resistance RLn.

[0013] Battery 200 is, for example, a battery for supplying power to an electric motor of a vehicle, and is a high-voltage battery (for example, 200 V or higher). Battery 200 is, for example, composed of a plurality of rechargeable batteries (for example, lithium ion batteries). The positive electrode side of battery 200 is connected to positive electrode side power supply line 210, and the negative electrode side of battery 200 is connected to negative electrode side power supply line 220.

[0014] A Y capacitor is connected to the system including the battery 200 to reduce common mode noise. In the example shown in Fig. 1, a positive Y capacitor CYp is connected between the positive power supply line 210 and the ground, and a negative Y capacitor CYn is connected between the negative power supply line 220 and the ground. The positive Y capacitor CYp includes a stray capacitance between the positive power supply line 210 and the ground, and the negative Y capacitor CYn includes a stray capacitance between the negative power supply line 220 and the ground.

[0015] The ground fault detection device 100 is connected to the positive electrode of the battery 200 via a positive power supply line 210, and is connected to the positive electrode of the battery 200 via a negative power supply line 220. The ground fault detection device 100 has a first capacitor 110, a switching unit 120, and a control unit 130.

[0016] The first capacitor 110 is a capacitor having a first plate and a second plate, and operates as a flying capacitor.

[0017] The switching unit 120 switches between a first charging path in which the first capacitor 110 is connected between the positive electrode and the negative electrode of the battery 200 without grounding, a second charging path in which the first capacitor 110 is connected between the positive electrode of the battery 200 and ground, a third charging path in which the first capacitor 110 is connected between the negative electrode of the battery 200 and ground, and a measurement path for measuring the charging voltage of the first capacitor 110.

[0018] In 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 connected in series in this order without being grounded. Therefore, in the first charging path, the first capacitor 110 is charged with a first charging voltage V0 corresponding to the charging voltage of the battery 200.

[0019] In the second 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, the negative electrode side insulation resistance RLn, and the negative electrode of the battery 200 are connected in series in this order. Therefore, in the second charging path, the first capacitor 110 is charged with a second charging voltage VC1n that reflects the influence of the negative electrode side insulation resistance RLn.

[0020] In the third 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 positive electrode side insulation resistance RLp, the first capacitor 110, and the negative electrode of the battery 200 are connected in series in this order. Therefore, in the third charging path, the first capacitor 110 is charged with a third charging voltage VC1p that reflects the influence of the positive electrode side insulation resistance RLp.

[0021] The control unit 130 measures the charging voltage of the first capacitor 110. The control unit 130, for example, controls the switching unit 120 to measure, in the measurement path, a first charging voltage V0 which is the charging voltage of the first capacitor 110 charged via the first charging path, a second charging voltage VC1n which is the charging voltage of the first capacitor 110 charged via the second charging path, and a third charging voltage VC1p which is the charging voltage of the first capacitor 110 charged via the third charging path.

[0022] Then, the control unit 130 detects the decrease in the insulation resistances RLp, RLn (detects a ground fault) based on this measured charging voltage of the first capacitor 110. The control unit 130 detects the decrease in the insulation resistances RLp, RLn, for example, 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 resistances RLp, RLn, for example, based on the charging voltage of the first capacitor 110, and detects the decrease in the insulation resistances RLp, RLn, based on the measured values ​​of the insulation resistances RLp, RLn. The control unit 130 is, for example, configured by a computer.

[0023] The control unit 130 detects the decrease in the insulation resistances RLp, RLn for each measurement cycle. That is, the control unit 130 repeats the measurement cycle for detecting the decrease in the insulation resistances RLp, RLn. At this time, the control unit 130 detects the decrease in the insulation resistances RLp, RLn by, for example, measuring the values ​​of the insulation resistances RLp, RLn for each measurement cycle and comparing the values ​​of the insulation resistances RLp, RLn measured in the measurement cycle with the values ​​of the insulation resistances RLp, RLn measured in the measurement cycle before the measurement cycle (for example, the measurement cycle immediately before the measurement cycle).

[0024] The measurement cycle includes a first measurement period (V0 measurement period) in which the first capacitor 110 is charged via a first charging path, and a first charging voltage V0 is measured, which is the charging voltage of the first capacitor 110 charged via the first charging path, while discharging the first capacitor 110 via a measurement path; a second measurement period (VC1n measurement period) in which the first capacitor 110 is charged via a second charging path, and a second charging voltage VC1n is measured, which is the charging voltage of the first capacitor 110 charged via the second charging path, while discharging the first capacitor 110 via the measurement path; and a third measurement period (VC1p measurement period) in which the first capacitor 110 is charged via a third charging path, and a third charging voltage VC1p is measured, which is the charging voltage of the first capacitor 110 charged via the third charging path, while discharging the first capacitor 110 via the measurement path. That is, the control unit 130 measures the first charging voltage V0, the second charging voltage VC1n, and the third charging voltage VC1p for each measurement cycle, and detects the decrease in insulation resistance based on the measured first charging voltage V0, the second charging voltage VC1n, and the third charging voltage VC1p. In the measurement cycle, the measurement periods are performed in the order of, for example, the first measurement period, the second measurement period, the first measurement period, and the third measurement period.

[0025] When an abnormality occurs (for example, when a decrease in the insulation resistances RLp and RLn is detected), the control unit 130 notifies the occurrence of the abnormality (for example, a decrease in the insulation resistances RLp and RLn). At this time, the control unit 130 may notify the occurrence of the abnormality by displaying information indicating the occurrence of the abnormality using a display device (for example, a display or a lamp) that displays information, may notify the occurrence of the abnormality by outputting a sound indicating the occurrence of the abnormality using a display device (for example, a speaker) that outputs a sound indicating the occurrence of the abnormality, or may notify the occurrence of the abnormality by transmitting information indicating the occurrence of the abnormality to another device (for example, a higher-level ECU (Electronic Control Unit)) using a communication device that transmits information to another device.

[0026] The control unit 130 may be configured to notify the measured values ​​of the insulation resistances RLp, RLn. In this manner, a person who receives information from the notification or another device that receives information from the information can detect the decrease in the insulation resistances RLp, RLn, instead of the control unit 130.

[0027] <Configuration example of ground fault detection device 100> The switching unit 120 may have, for example, four switches (a first switch S1, a second switch S2, a third switch S3, and a fourth switch S4) as shown in Fig. 2. These four switches are, for example, insulating switching elements (for example, optical MOSFETs).

[0028] The first switch S1 is connected between the positive electrode of the battery 200 and the first plate of the first capacitor 110. At this time, the first switch S1 is connected to the first plate of the first capacitor 110 via a first resistor R1 as shown in FIG. 2. A first diode D1 may 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 to the first plate of the first capacitor 110. In the configuration example shown in FIG. 2, the first diode D1 is connected between the first switch S1 and the first resistor R1.

[0029] The second switch S2 is connected between the negative electrode of the battery 200 and the second plate of the first capacitor 110. A second resistor R2 may be connected between the second switch S2 and the second plate of the first capacitor 110 or between the second switch S2 and the negative electrode of the battery 200. In the configuration example shown in FIG. 2, the second resistor R2 is connected between the second switch S2 and the second plate of the first capacitor 110.

[0030] The third switch S3 is connected between the first plate of the first capacitor 110 and the ground. At this time, the third switch S3 is connected to the ground via the third resistor R3 as shown in FIG. 2. In addition, the second diode D2 and the third diode D3 may be connected in parallel between the third switch S3 and the first plate of the first capacitor 110. The forward direction of the second diode D2 is from the first plate of the first capacitor 110 to the third switch S3. The forward direction of the third diode D3 is from the third switch S3 to the first plate of the first capacitor 110. Between the third switch S3 and the first plate of the first capacitor 110, the fifth resistor R5 may be connected in series with the second diode D2. In the configuration example shown in FIG. 2, the fifth resistor R5 is connected to the cathode side of the second diode D2.

[0031] The fourth switch S4 is connected between the second plate of the first capacitor 110 and ground. The fourth switch S4 is connected to ground through a fourth resistor R4 as shown in FIG.

[0032] Therefore, in the configuration example shown in Fig. 2, when the first switch S1 and the second switch S2 are on and the third switch S3 and the fourth switch S4 are off, as shown in Fig. 3, the first capacitor 110 is connected between the positive and negative electrodes of the battery 200 without being grounded, forming a first charging path. In the configuration example shown in Fig. 2, the first capacitor 110 is charged by a closed circuit connected in series in the following order: 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. Therefore, in 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.

[0033] In the configuration example shown in Fig. 2, when the first switch S1 and the fourth switch S4 are on and the second switch S2 and the third switch S3 are off, the first capacitor 110 becomes a second charging path connected between the positive electrode of the battery 200 and the ground as shown in Fig. 4. In the configuration example shown in Fig. 2, in the second charging path, the first capacitor 110 is charged by a closed circuit connected in series in the following order: 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 insulation resistor RLn, and the negative electrode of the battery 200. Therefore, in the second charging path, the second charging voltage VC1n reflecting the influence of the negative electrode insulation resistor RLn of the battery 200 is charged to the first capacitor 110.

[0034] In the configuration example shown in Fig. 2, when the second switch S2 and the third switch S3 are on and the first switch S1 and the fourth switch S4 are off, the first capacitor 110 is connected between the negative electrode of the battery 200 and the ground as a third charging path as shown in Fig. 5. In the configuration example shown in Fig. 2, in the third charging path, the first capacitor 110 is charged by a closed circuit connected in series in the following order: 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. Therefore, 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.

[0035] The control unit 130 is connected to the first plate of the first capacitor 110 via the third switch, as shown in FIG. 2. Therefore, when the third switch S3 and the fourth switch S4 are on and the first switch S1 and the second switch S2 are off, a current flows from the first plate of the first capacitor 110 to the control unit 130, as shown in FIG. 6. Therefore, 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 on and the first switch S1 and the second switch S2 are off, the measurement path is used to measure the charging voltage of the first capacitor 110. The line connecting the third switch S3 and the control unit 130 may be grounded via the second capacitor C2, as shown in FIG. 2.

[0036] 6, in the measurement path, a current flows from the first plate to the second plate of the first capacitor 110. Therefore, in the measurement path, the first capacitor 110 is discharged.

[0037] The switching unit 120 may further include a measurement switch Sa as shown in FIG. 2. In this way, when the third switch S3, the fourth switch S4, and the measurement switch Sa are on and the first switch S1 and the second switch S2 are off, the path becomes a measurement path for measuring the charging voltage of the first capacitor 110 as shown in FIG. 6. When the third switch S3 and the fourth switch S4 are on and the first switch S1, the second switch S2, and the measurement switch Sa are off, the control unit 130 is separated from the first capacitor 110 as shown in FIG. 7, and the path becomes a discharge path for discharging the first capacitor 110. In the first charging path, the second charging path, and the third charging path, the measurement switch Sa is turned off as shown in FIG. 3-5.

[0038] <Sudden fluctuation in charging voltage of battery 200> When a sudden fluctuation occurs in the charging voltage of battery 200, a decrease in insulation resistances RLp, RLn may be erroneously detected even though there has been no decrease in insulation resistances RLp, RLn, or a decrease in insulation resistances RLp, RLn may not be detected even though there has been a decrease in insulation resistances RLp, RLn.

[0039] Therefore, the control unit 130 detects a decrease in the insulation resistance of the battery 200 based on the charging voltage of the first capacitor 110 measured when the fluctuation in the charging voltage of the battery 200 is small. That is, in this embodiment, the charging voltage of the first capacitor 110 measured when the fluctuation in the charging voltage of the battery 200 is large is not used to detect a decrease in the insulation resistances RLp, RLn.

[0040] The control unit 130 detects the decrease in the insulation resistances RLp and RLn for each measurement cycle. The measurement cycle includes a first measurement period (V0 measurement period) for measuring a first charging voltage V0 corresponding to the charging voltage of the battery 200. For this reason, for example, the control unit 130 may determine whether or not the fluctuation in the first charging voltage V0 (for example, the fluctuation from the first charging voltage V0 measured previously to the first charging voltage V0 measured this time) is smaller than a first threshold value for each first measurement period. The control unit 130 may detect the decrease in the insulation resistances RLp and RLn in a measurement cycle that does not include a first measurement period in which it is determined that the fluctuation in the first charging voltage V0 is equal to or greater than the first threshold value. In other words, the control unit 130 detects a decrease in the insulation resistances RLp, RLn in a measurement cycle including only a first measurement period in which it is determined that the fluctuation in the first charging voltage is smaller than the first threshold value, and does not detect a decrease in the insulation resistances RLp, RLn in a measurement cycle including a first measurement period in which it is determined that the fluctuation in the first charging voltage is greater than or equal to the first threshold value.

[0041] In this manner, it becomes possible to detect the decrease in the insulation resistances RLp, RLn without being affected by abrupt fluctuations in the charging voltage of the battery 200. As a result, in this embodiment, it becomes possible to prevent erroneous detection or non-detection of the decrease in the insulation resistances RLp, RLn.

[0042] During the second measurement period (VC1n measurement period) or the third measurement period (VC1p measurement period), a sudden change may occur in the charging voltage of battery 200. If a sudden change occurs in the charging voltage of battery 200 during the second measurement period or the third measurement period, the sudden change in the charging voltage of battery 200 may cause a sudden change in the second charging voltage VC1n and the third charging voltage VC1p, which reflect the influence of the insulation resistances RLn and RLp of battery 200.

[0043] Therefore, in this embodiment, the control unit 130 determines, for each measurement cycle, whether or not the fluctuation in the second charging voltage VC1n (e.g., 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 smaller than a second threshold value during the second measurement period, and determines whether or not the fluctuation in the third charging voltage VC1p (e.g., 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 smaller than a third threshold value during the third measurement period.

[0044] The control unit 130 may detect the decrease in the insulation resistances RLp, RLn in a measurement cycle in which the fluctuation of the second charging voltage VC1n is determined to be smaller than the second threshold and the fluctuation of the third charging voltage VC1p is determined to be smaller than the third threshold. In other words, the control unit 130 may not detect the decrease in the insulation resistances RLp, RLn in a measurement cycle including a second measurement period in which the fluctuation of the second charging voltage VC1n is determined to be equal to or larger than the second threshold or a third measurement period in which the fluctuation of the third charging voltage VC1p is determined to be equal to or larger than the third threshold.

[0045] In this manner, it becomes possible to detect the decrease in the insulation resistances RLp, RLn without being affected by abrupt fluctuations in the charging voltage of the battery 200. As a result, in this embodiment, it becomes possible to more effectively prevent erroneous detection or non-detection of the decrease in the insulation resistances RLp, RLn.

[0046] When the decrease in the insulation resistances RLp and RLn is detected by another device (for example, a higher-level ECU) or a person, the control unit 130 may notify the values ​​of the insulation resistances RLp and RLn measured in the measurement cycle including the second measurement period in which it is determined that the fluctuation in the second charging voltage VC1n is equal to or greater than the second threshold value, or the third measurement period in which it is determined that the fluctuation in the third charging voltage VC1p is equal to or greater than the third threshold value, and may notify that a sudden fluctuation in the charging voltage of the battery 200 may have occurred in the measurement cycle. In this way, it is possible to detect the insulation resistances RLp and RLn without using the values ​​of the insulation resistances RLp and RLn measured in the measurement cycle in which a sudden fluctuation in the charging voltage of the battery 200 may have occurred for detecting the decrease in the insulation resistances RLp and RLn. As a result, it is possible to detect the insulation resistances RLp and RLn without being affected by a sudden fluctuation in the charging voltage of the battery 200.

[0047] FIG. 8 shows an example of a processing operation executed in the ground fault detection device 100 for each measurement cycle.

[0048] The control unit 130 measures the first charging voltage V0 during the first measurement period (step S801). The control unit 130 determines whether the fluctuation of the first charging voltage V0 (the fluctuation from the first charging voltage V0 measured previously to the first charging voltage V0 measured this time) is smaller than a first threshold value (step S802), and if the fluctuation of the first charging voltage V0 is not smaller than the first threshold value (step S802, NO), it sets a first error flag (step S803).

[0049] The control unit 130 measures the second charging voltage VC1n in the second measurement period (step S804). The control unit 130 determines whether the change in the second charging voltage VC1n (the change from the second charging voltage VC1n measured previously to the second charging voltage VC1n measured this time) is smaller than a second threshold (step S805), and if the change in the second charging voltage VC1n is not smaller than the second threshold (step S805, NO), sets a second error flag (step S806).

[0050] The control unit 130 measures the first charging voltage V0 during the first measurement period (step S807). The control unit 130 determines whether the fluctuation of the first charging voltage V0 is smaller than the first threshold (step S808), and if the fluctuation of the first charging voltage V0 is not smaller than the first threshold (step S808, NO), sets a third error flag (step S809).

[0051] The control unit 130 measures the third charging voltage VC1p in the third measurement period (step S810). The control unit 130 determines whether the change in the third charging voltage VC1p (the change from the third charging voltage VC1p measured previously to the third charging voltage VC1p measured this time) is smaller than a third threshold (step S811), and if the change in the third charging voltage VC1p is not smaller than the third threshold (step S811, NO), it sets a fourth error flag (step S812).

[0052] If none of the first to fourth error flags are set (step S813, YES), the control unit 130 detects the decrease in 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 of the first to fourth error flags are set (step S813, NO), the control unit 130 clears the set error flag (step S815) and ends the process.

[0053] <Notification of decrease in insulation resistance RLp, RLn> The control unit 130 may notify the decrease in the insulation resistances RLp, RLn when a predetermined number (e.g., three) of measurement cycles in which a decrease in the insulation resistances RLp, RLn was detected (i.e., measurement cycles in which values ​​of the insulation resistances RLp, RLn lower than the values ​​of the insulation resistances RLp, RLn under normal conditions were measured) are consecutive. In this case, if the values ​​of the insulation resistances RLp, RLn measured in a measurement cycle (measurement cycle with fluctuations) including a first measurement period in which it is determined that the fluctuation of the first charging voltage is equal to or greater than the first threshold, a second measurement period in which the fluctuation of the second charging voltage VC1n is equal to or greater than the second threshold, or a 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 to detect the decrease in the insulation resistances RLp, RLn, the notification of the decrease in the insulation resistances RLp, RLn may be delayed.

[0054] For example, as shown in FIG. 9, when a decrease in the insulation resistances RLp, RLn is detected in a predetermined number of measurement cycles (three measurement cycles (measurement cycle 3, measurement cycle 4, and measurement cycle 5) in the example shown in FIG. 9) following a measurement cycle with fluctuation (measurement cycle 2), it is highly likely that a decrease in the insulation resistances RLp, RLn has also occurred in measurement cycle 2. If a decrease in the insulation resistances RLp, RLn has occurred in measurement cycle 2, and the values ​​of the insulation resistances RLp, RLn measured in 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 will be delayed by one measurement cycle compared to the case in which the values ​​of the insulation resistances RLp, RLn measured in measurement cycle 2 are used to detect a decrease in the insulation resistances RLp, RLn (FIG. 10).

[0055] In the example shown in FIG. 9, a notification of the decrease in insulation resistances RLp, RLn is made after three consecutive measurement cycles without fluctuation in which insulation resistances RLp, RLn that are lower than the normal insulation resistances RLp, RLn values ​​are measured (after measurement cycle 5), whereas in the example shown in FIG. 10, a notification of the decrease in insulation resistances RLp, RLn is made after three consecutive measurement cycles without fluctuation in which insulation resistances RLp, RLn that are lower than the normal insulation resistances RLp, RLn values ​​are measured (after measurement cycle 4), regardless of the presence or absence of fluctuation.

[0056] Therefore, when notifying the decrease in the insulation resistances RLp, RLn when a predetermined number of consecutive measurement cycles have been detected in which the decrease in the insulation resistances RLp, RLn has been detected, the control unit 130 may use the values ​​of the insulation resistances RLp, RLn measured in a measurement cycle (measurement cycle with fluctuations) including a first measurement period in which it is determined that the fluctuation in the first charging voltage is equal to or greater than the first threshold, a second measurement period in which the fluctuation in the second charging voltage VC1n is equal to or greater than the second threshold, or a third measurement period in which the fluctuation in the third charging voltage VC1p is equal to or greater than the third threshold, for detecting the decrease in the insulation resistances RLp, RLn. In this way, it is possible to prevent delays in notifying the decrease in the insulation resistances RLp, RLn.

[0057] The present invention has been described above in terms of preferred embodiments thereof. Although the present invention has been described herein with reference to specific examples, various modifications and variations can be made to these examples without departing from the spirit and scope of the present invention as set forth in the claims. [Explanation of symbols]

[0058] 100 Earth fault detection device 110 First Capacitor 120 Switching section 130 Control section 200 Battery 210 Positive power line 220 Negative power line

Claims

1. A ground fault detection device that detects a decrease in insulation resistance of a system including an ungrounded battery, A first capacitor; a switching unit that switches among a first charging path in which the first capacitor is connected between the positive electrode and the negative electrode of the battery without being connected to ground, a second charging path in which the first capacitor is connected between the positive electrode and the ground of the battery, a third charging path in which the first capacitor is connected between the negative electrode and the ground of the battery, and a measurement path for measuring a charging voltage of the first capacitor; a control unit that controls the switching unit and measures a charging voltage of the first capacitor, The control unit is determining whether or not a fluctuation in a second charging voltage, which is a charging voltage of the first capacitor charged through the second charging path, is smaller than a second threshold value, and determining whether or not a fluctuation in a third charging voltage, which is a charging voltage of the first capacitor charged through the third charging path, is smaller than a third threshold value, for each measurement cycle; A ground fault detection device that detects a decrease in the insulation resistance in a measurement cycle in which the fluctuation in the second charging voltage is determined to be smaller than the second threshold and the fluctuation in the third charging voltage is determined to be smaller than the third threshold.

2. The measurement cycle comprises: a first measurement period in which the first capacitor is charged in the first charging path and a first charging voltage, which is a charging voltage of the first capacitor charged through the first charging path, is measured in the measurement path; a second measurement period in which the first capacitor is charged in the second charging path and the second charging voltage is measured in the measurement path; The ground fault detection device according to claim 1 , further comprising: a third measurement period in which the first capacitor is charged in the third charging path and the third charging voltage is measured in the measurement path.

3. The control unit is notifying the decrease in insulation resistance when a predetermined number of measurement cycles have been consecutively measured in which the insulation resistance value is lower than the normal insulation resistance value; 3. The ground fault detection device according to claim 2, wherein a value of the insulation resistance measured in a measurement cycle including the second measurement period during which the fluctuation of the second charging voltage is equal to or greater than the second threshold value or the third measurement period during which the fluctuation of the third charging voltage is equal to or greater than the third threshold value is used to detect a decrease in the insulation resistance.

4. The control unit is determining whether or not a fluctuation in the first charging voltage is smaller than a first threshold value during each of the first measurement periods; 3. The ground fault detection device according to claim 2, wherein the decrease in the insulation resistance is detected in a measurement cycle that does not include the first measurement period during which it is determined that the fluctuation in the first charging voltage is equal to or greater than the first threshold value.

5. The ground fault detection device according to claim 4 , wherein the control unit uses a change from the previously measured first charging voltage to the currently measured first charging voltage as the change in the first charging voltage.

6. A ground fault detection device for measuring insulation resistance of a system including an ungrounded battery, A first capacitor; a switching unit that switches among a first charging path in which the first capacitor is connected between the positive electrode and the negative electrode of the battery without being connected to ground, a second charging path in which the first capacitor is connected between the positive electrode and the ground of the battery, a third charging path in which the first capacitor is connected between the negative electrode and the ground of the battery, and a measurement path for measuring a charging voltage of the first capacitor; a control unit that controls the switching unit, measures a charging voltage of the first capacitor, and measures a value of the insulation resistance for each measurement cycle based on the measured charging voltage of the first capacitor, The measurement cycle comprises: a first measurement period in which the first capacitor is charged in the first charging path and a first charging voltage, which is a charging voltage of the first capacitor charged through the first charging path, is measured in the measurement path; a second measurement period in which the first capacitor is charged in the second charging path and a second charging voltage, which is a charging voltage of the first capacitor charged through the second charging path, is measured in the measurement path; a third measurement period in which the first capacitor is charged in the third charging path and a third charging voltage, which is a charging voltage of the first capacitor charged through the third charging path, is measured in the measurement path; The control unit is determining whether the fluctuation of the second charging voltage is smaller than a second threshold value and whether the fluctuation of the third charging voltage is smaller than a third threshold value for each measurement cycle; a ground fault detection device that notifies, in a measurement cycle including the second measurement period in which the fluctuation in the second charging voltage is determined to be equal to or greater than the second threshold, or the third measurement period in which the fluctuation in the third charging voltage is determined to be equal to or greater than the third threshold, that a sudden fluctuation may have occurred in the charging voltage of the battery in the measurement cycle.

7. The control unit is In the second measurement period, a change in the second charging voltage from the second charging voltage measured in the previous second measurement period to the second charging voltage measured in the current second measurement period is used as the change in the second charging voltage; 7. The ground fault detection device according to claim 2, wherein, during the third measurement period, the fluctuation in the third charging voltage is determined as the fluctuation from the third charging voltage measured during a previous third measurement period to the third charging voltage measured during a current third measurement period.

8. A method for controlling a ground fault detection device that detects a decrease in insulation resistance of a system including an ungrounded battery, the method being executed by a computer, comprising: The ground fault detection device includes: A first capacitor; a switching unit that switches among a first charging path in which the first capacitor is connected between a positive electrode and a negative electrode of the battery without a ground, a second charging path in which the first capacitor is connected between a positive electrode of the battery and a ground, a third charging path in which the first capacitor is connected between a negative electrode of the battery and a ground, and a measurement path for measuring a charging voltage of the first capacitor, The control method includes: a measuring step of controlling the switching unit and measuring a charging voltage of the first capacitor; determining whether or not a fluctuation in a second charging voltage, which is a charging voltage of the first capacitor charged through the second charging path, is smaller than a second threshold value, and determining whether or not a fluctuation in a third charging voltage, which is a charging voltage of the first capacitor charged through the third charging path, is smaller than a third threshold value, for each measurement cycle; detecting a decrease in the insulation resistance in a measurement cycle in which the fluctuation in the second charging voltage is determined to be smaller than the second threshold value and the fluctuation in the third charging voltage is determined to be smaller than the third threshold value.

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

Images