Ground fault detection device, control method thereof, 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. [Background technology]

[0002] Hybrid and electric vehicles are becoming increasingly popular. Hybrid and electric vehicles are equipped with an electric motor and a battery that supplies power to the electric motor. The batteries installed in hybrid and electric vehicles are high-voltage batteries of 200V or more, and to ensure safety, they must be electrically isolated from the vehicle body, which serves as the ground reference potential point. Therefore, vehicles such as hybrid and electric vehicles are also equipped with a ground fault detection device that detects a decrease in insulation resistance between the vehicle body and the system, including the battery, which is not grounded.

[0003] One example of a ground fault detection device is a flying capacitor type ground fault detection device (see, for example, Patent Document 1). A 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 electrode of the battery and ground, a third charging path in which the capacitor is connected between the negative electrode 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] Japanese Patent Application Laid-Open No. 2004-170103 Summary of the Invention [Problem to be solved by the invention]

[0005] When a sudden change occurs in the charging voltage of a battery, a decrease in insulation resistance may be falsely 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] Therefore, 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 switching unit that switches between a first charging path in which the first capacitor is connected between a positive electrode and a negative electrode of the battery without being grounded, a second charging path in which the first capacitor is connected between a positive electrode of the battery and ground, a third charging path in which the first capacitor is connected between a negative electrode of the battery and ground, and a measurement path for measuring a charging voltage of the first capacitor, and a control unit that controls the switching unit to switch between the first charging path and the negative electrode of the battery without being grounded. 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 executed by a computer for a ground fault detection device that detects a decrease in insulation resistance of a system including an ungrounded battery, 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 being grounded, 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 the control method includes: a measuring step of controlling a switching unit to measure a charging voltage of the first capacitor; a 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 a 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 information processing method. [Effects of the Invention]

[0010] According to the present invention, it is possible to accurately detect a decrease in insulation resistance. [Brief explanation 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. [Figure 2] 1 is a diagram illustrating an example of the configuration of a ground fault detection device 100. FIG. [Figure 3] FIG. 4 is a diagram illustrating a first charging path. [Figure 4] FIG. 10 is a diagram illustrating a second charging path. [Figure 5] FIG. 10 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] 10 is an example of a processing operation executed in the ground fault detection device 100 for each measurement cycle. [Figure 9] 10A and 10B are diagrams illustrating notification of a decrease in insulation resistances RLp and RLn. [Figure 10] 10A and 10B are diagrams illustrating notification of a decrease in insulation resistances RLp and RLn. DETAILED DESCRIPTION OF THE INVENTION

[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 in 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 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 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 a system including battery 200 to reduce common-mode noise. In the example shown in Fig. 1, a positive-side Y capacitor CYp is connected between positive-side power supply line 210 and ground, and a negative-side Y capacitor CYn is connected between negative-side power supply line 220 and ground. The positive-side Y capacitor CYp includes a stray capacitance between positive-side power supply line 210 and ground, and the negative-side Y capacitor CYn includes a stray capacitance between negative-side power supply line 220 and 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 and negative electrodes of the battery 200 without going through ground, 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 controls, for example, the switching unit 120 to measure, in the measurement paths, 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 a 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 a 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 a 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 a decrease in the insulation resistances RLp and RLn for each measurement cycle. That is, the control unit 130 repeats a measurement cycle in which the control unit 130 detects a decrease in the insulation resistances RLp and RLn. At this time, the control unit 130 detects a decrease in the insulation resistances RLp and RLn, for example, by measuring the values ​​of the insulation resistances RLp and RLn for each measurement cycle and comparing the values ​​of the insulation resistances RLp and 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 discharged via a measurement path while measuring a first charging voltage V0, which is the charging voltage of the first capacitor 110 charged via this first charging path; a second measurement period (VC1n measurement period) in which the first capacitor 110 is charged via a second charging path and discharged via the measurement path while measuring a second charging voltage VC1n, which is the charging voltage of the first capacitor 110 charged via this second charging path; and a third measurement period (VC1p measurement period) in which the first capacitor 110 is charged via a third charging path and discharged via the measurement path while measuring a third charging voltage VC1p, which is the charging voltage of the first capacitor 110 charged via this third charging 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 a decrease in insulation resistance based on the measured first charging voltage V0, the second charging voltage VC1n, and the third charging voltage VC1p. In a 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 insulation resistances RLp, RLn is detected), control unit 130 notifies the occurrence of the abnormality (for example, a decrease in insulation resistances RLp, RLn). At this time, control unit 130 may notify the occurrence of the abnormality by displaying information indicating the occurrence of the abnormality using a display device that displays information (for example, a display or a lamp), or may notify the occurrence of the abnormality by outputting a sound indicating the occurrence of the abnormality using a display device that outputs sound indicating the information (for example, a speaker), 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 and RLn. In this way, a decrease in the insulation resistances RLp and RLn can be detected not by the control unit 130 but by a person who receives information from the notification or by another device that receives information from the information.

[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 electrode plate of the first capacitor 110. At this time, the first switch S1 is connected to the first electrode plate of the first capacitor 110 via a first resistor R1, as shown in FIG. 2. Furthermore, 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 electrode 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 electrode plate of the first capacitor 110. A second resistor R2 may 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. In the configuration example shown in FIG. 2, the second resistor R2 is connected between the second switch S2 and the second electrode plate of the first capacitor 110.

[0030] The third switch S3 is connected between the first plate of the first capacitor 110 and ground. In this case, the third switch S3 is connected to ground via a third resistor R3, as shown in FIG. 2 . Alternatively, a second diode D2 and a 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. A fifth resistor R5 may be connected in series with the second diode D2 between the third switch S3 and the first plate of the first capacitor 110. 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] 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, a first charging path is established in which the first capacitor 110 is connected between the positive and negative electrodes of the battery 200 without being grounded, as shown in FIG. 3. In the configuration example shown in FIG. 2, the first capacitor 110 is charged through 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, a first charging voltage V0 corresponding to the charging voltage of the battery 200 is charged to the first capacitor 110.

[0033] 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, a second charging path is established in which the first capacitor 110 is connected between the positive electrode of the battery 200 and ground, as shown in FIG. 4. In the configuration example shown in FIG. 2, the second charging path charges the first capacitor 110 through 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 resistance RLn, and the negative electrode of the battery 200. Therefore, in the second charging path, a second charging voltage VC1n that reflects the influence of the negative electrode insulation resistance RLn of the battery 200 is charged to the first capacitor 110.

[0034] 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, a third charging path is established in which the first capacitor 110 is connected between the negative electrode of the battery 200 and ground, as shown in FIG. 5. In the configuration example shown in FIG. 2, the first capacitor 110 is charged through 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, a third charging voltage VC1p that reflects the influence of the positive electrode-side insulation resistance RLp of the battery 200 is charged to the first capacitor 110.

[0035] As shown in FIG. 2, the control unit 130 is connected to the first electrode plate of the first capacitor 110 via a third switch. 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, current flows from the first electrode plate of the first capacitor 110 to the control unit 130, as shown in FIG. 6. This allows the control unit 130 to measure the charging voltage of the detection capacitor C1. In other words, when the third switch S3 and the fourth switch S4 are on and the first switch S1 and the second switch S2 are off, this becomes a measurement path for measuring 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, a current flows from the first electrode plate to the second electrode plate of the first capacitor 110. Therefore, the first capacitor 110 is discharged in the measurement path.

[0037] The switching unit 120 may further include a measurement switch Sa as shown in FIG. 2. In this configuration, 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 serves as 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 disconnected from the first capacitor 110 as shown in FIG. 7, and the path serves as 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 FIGS. 3-5.

[0038] <Sudden fluctuations in the charging voltage of battery 200> When a sudden change occurs in the charging voltage of the battery 200, a decrease in the insulation resistances RLp and RLn may be erroneously detected even though the insulation resistances RLp and RLn have not decreased, or a decrease in the insulation resistances RLp and RLn may not be detected even though the insulation resistances RLp and RLn have decreased.

[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 fluctuations in the charging voltage of the battery 200 are small. In other words, in this embodiment, the charging voltage of the first capacitor 110 measured when fluctuations in the charging voltage of the battery 200 are large is not used to detect a decrease in the insulation resistances RLp and RLn.

[0040] The control unit 130 detects a 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 a fluctuation in the first charging voltage V0 (e.g., a fluctuation from the first charging voltage V0 measured previously to the first charging voltage V0 measured currently) is smaller than a first threshold value for each first measurement period. The control unit 130 may detect a 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 and RLn in a measurement cycle that includes only the first measurement period in which it is determined that the fluctuation in the first charging voltage is smaller than the first threshold, and does not detect a decrease in the insulation resistances RLp and RLn in a measurement cycle that includes the 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.

[0041] This makes it possible to detect the decrease in the insulation resistances RLp and RLn without being affected by sudden fluctuations in the charging voltage of the battery 200. As a result, in this embodiment, it is possible to prevent erroneous detection or non-detection of the decrease in the insulation resistances RLp and 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 second charging voltage VC1n and third charging voltage VC1p, which reflect the influence of insulation resistances RLn and RLp of battery 200.

[0043] Therefore, in this embodiment, the control unit 130 determines, for each measurement cycle, whether 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 the second threshold value during the second measurement period, and whether 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 the third threshold value during the third measurement period.

[0044] The control unit 130 may then detect a decrease in the insulation resistances RLp, RLn in a measurement cycle in which it is determined that the fluctuation in the second charging voltage VC1n is smaller than the second threshold and that the fluctuation in the third charging voltage VC1p is smaller than the third threshold. In other words, the control unit 130 may not detect a decrease in the insulation resistances RLp, RLn in a measurement cycle that includes a 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, or a 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.

[0045] This makes it possible to detect a decrease in the insulation resistances RLp and RLn without being affected by sudden fluctuations in the charging voltage of the battery 200. As a result, in this embodiment, it is possible to further prevent erroneous detection or non-detection of a decrease in the insulation resistances RLp and RLn.

[0046] When a decrease in the insulation resistances RLp and RLn is detected by another device (e.g., a higher-level ECU) or a person, the control unit 130 may notify the values ​​of the insulation resistances RLp and RLn measured in a measurement cycle including a 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 or a 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, and may also notify the user that a sudden fluctuation in the charging voltage of the battery 200 may have occurred in that measurement cycle. This makes it possible to detect the insulation resistances RLp and RLn without using the values ​​of the insulation resistances RLp and RLn measured in a measurement cycle in which a sudden fluctuation in the charging voltage of the battery 200 may have occurred. 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 a 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 (step S802), and if the fluctuation of the first charging voltage V0 is not smaller than the first threshold (step S802, NO), sets a first error flag (step S803).

[0049] The control unit 130 measures the second charging voltage VC1n during the second measurement period (step S804). The control unit 130 determines whether the fluctuation of the second charging voltage VC1n (the fluctuation 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 fluctuation of 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 during the third measurement period (step S810). The control unit 130 determines whether the fluctuation of the third charging voltage VC1p (the fluctuation 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 fluctuation of the third charging voltage VC1p is not smaller than the third threshold (step S811, NO), 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 a 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 is 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 be configured to notify the decrease in the insulation resistances RLp and RLn when a predetermined number (e.g., three) of consecutive measurement cycles have been detected in which a decrease in the insulation resistances RLp and RLn has been detected (i.e., measurement cycles in which values ​​of the insulation resistances RLp and RLn that are lower than the normal values ​​of the insulation resistances RLp and RLn have been measured). In such a case, if the values ​​of the insulation resistances RLp and RLn measured in a measurement cycle (measurement cycle with fluctuations) that includes 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 are not used to detect the decrease in the insulation resistances RLp and RLn, the notification of the decrease in the insulation resistances RLp and RLn may be delayed.

[0054] For example, as shown in FIG. 9, if a decrease in insulation resistances RLp and 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 fluctuations (measurement cycle 2), it is highly likely that a decrease in insulation resistances RLp and RLn also occurred in measurement cycle 2. If a decrease in insulation resistances RLp and RLn occurs in measurement cycle 2, and the values ​​of insulation resistances RLp and RLn measured in measurement cycle 2 are not used to detect a decrease in insulation resistances RLp and RLn, notification of the decrease in insulation resistances RLp and RLn will be delayed by one measurement cycle compared to when the values ​​of insulation resistances RLp and RLn measured in measurement cycle 2 are used to detect a decrease in insulation resistances RLp and RLn (FIG. 10).

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

[0056] Therefore, when notifying the decrease in insulation resistances RLp and RLn after a predetermined number of consecutive measurement cycles in which a decrease in insulation resistances RLp and RLn has been detected, the control unit 130 may use the values ​​of insulation resistances RLp and RLn measured in a measurement cycle (measurement cycle with fluctuations) that includes 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, to detect the decrease in insulation resistances RLp and RLn. This prevents delays in notifying the decrease in insulation resistances RLp and RLn.

[0057] The present invention has been described above in terms of preferred embodiments thereof. While 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 Unit 200 Battery 210 Positive power supply line 220 Negative power supply 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 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; a control unit that controls the switching unit and measures the charging voltage of the first capacitor for each measurement cycle, The measurement cycle comprises: a first measurement period in which the first capacitor is charged through 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 through the measurement path; a second measurement period in which the first capacitor is charged through 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 through 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 determining whether the fluctuation in the second charging voltage is smaller than a second threshold value and whether the fluctuation in the third charging voltage is smaller than a third threshold value for each measurement cycle; 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; In the third measurement period, a change in the third charging voltage from the third charging voltage measured in the previous third measurement period to the third charging voltage measured in the current third measurement period is used as the change in the third charging voltage; detecting a decrease in the insulation resistance based on the first charging voltage, the second charging voltage, and the third charging voltage 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; a ground fault detection device that does not detect a decrease in the insulation resistance in a measurement cycle that includes the second measurement period during which it is determined that the fluctuation in the second charging voltage is equal to or greater than the second threshold, or the third measurement period during which it is determined that the fluctuation in the third charging voltage is equal to or greater than the third threshold.

2. The control unit notifying the decrease in insulation resistance when a predetermined number of consecutive measurement cycles have measured an insulation resistance value lower than the normal insulation resistance value; 2. The ground fault detection device according to claim 1, 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 or the third measurement period during which the fluctuation of the third charging voltage is equal to or greater than the third threshold is used to detect a decrease in the insulation resistance.

3. The control unit determining whether or not a fluctuation in the first charging voltage is smaller than a first threshold value for each first measurement period; In the first measurement period, a change in the first charging voltage from the first charging voltage measured in the previous first measurement period to the first charging voltage measured in the current first measurement period is used as the change in the first charging voltage; 2. The ground fault detection device according to claim 1, wherein even in a measurement cycle in which it is determined that the fluctuation in the second charging voltage is smaller than the second threshold and the fluctuation in the third charging voltage is smaller than the third threshold, if the measurement cycle includes the 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, the decrease in the insulation resistance is not detected in the measurement cycle.

4. 4. The ground fault detection device according to claim 3, wherein the control unit uses a change from the first charging voltage measured last time to the first charging voltage measured this time as the change in the first charging voltage.

5. A ground fault detection device for measuring the 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 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; a control unit that controls the switching unit, measures a charging voltage of the first capacitor, and measures the 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 through 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 through the measurement path; a second measurement period in which the first capacitor is charged through 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 through 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 determining whether the fluctuation in the second charging voltage is smaller than a second threshold value and whether the fluctuation in the third charging voltage is smaller than a third threshold value for each measurement cycle; 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; In the third measurement period, a change in the third charging voltage from the third charging voltage measured in the previous third measurement period to the third charging voltage measured in the current third measurement period is used as the change in the third charging voltage; a ground fault detection device that notifies that a sudden fluctuation may have occurred in the charging voltage of the battery during a measurement cycle including the second measurement period during which it is determined that the fluctuation in the second charging voltage is equal to or greater than the second threshold, or the third measurement period during which it is determined that the fluctuation in the third charging voltage is equal to or greater than the third threshold.

6. A control method for 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 is 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 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 includes: a measuring step of controlling the switching unit to measure a charging voltage of the first capacitor for each measurement cycle; The measurement cycle comprises: a first measurement period in which the first capacitor is charged through 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 through the measurement path; a second measurement period in which the first capacitor is charged through 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 through 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 method includes: a determining step of determining whether a fluctuation in the second charging voltage is smaller than a second threshold value and whether a fluctuation in the third charging voltage is smaller than a third threshold value for each measurement cycle; a detection step of detecting a decrease in the insulation resistance based on the first charging voltage, the second charging voltage, and the third charging voltage 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, The detecting step a measurement cycle including the second measurement period during which it is determined that the fluctuation in the second charging voltage is equal to or greater than the second threshold value, or the third measurement period during which it is determined that the fluctuation in the third charging voltage is equal to or greater than the third threshold value, does not detect a decrease in the insulation resistance; The determination step includes: 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; A control method in which, during the third measurement period, the fluctuation in the third charging voltage is determined by using the fluctuation in the third charging voltage measured during the previous third measurement period to the third charging voltage measured during the current third measurement period.

7. An information processing program that causes a computer to execute the control method according to claim 6.

Images