JP2018128440A - Ground fault detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an increase in cost attributable to switching elements in a ground fault detector.SOLUTION: The ground fault detector comprises: a control unit; a capacitor; a positive side power supply line connected to the positive side of a high voltage battery; a negative side power supply line connected to a negative side; a positive secondary side resistor, with one end grounded to earth and a voltage at the other end measured; a negative secondary side resistor, with one end grounded to earth; a positive side C contact switch for alternatively switching the destination for one end of the capacitor between a route that includes the positive side power supply line and a route that includes the positive secondary side resistor; and a negative side C contact switch for alternatively switching the destination for the other end between a route that includes the negative side power supply line and a route that includes the negative secondary side resistor. The control unit exercises switching control of C contact switching by switching the measurement of a high voltage battery voltage, the measurement of a voltage affected by a positive side insulation resistor, and the measurement of a voltage affected by a negative side insulation resistor between a measurement mode included in a measurement cycle and a measurement mode in which one of the measurements is omitted.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a ground fault detection apparatus using a flying capacitor.

  In a vehicle such as a hybrid vehicle including an engine and an electric motor as a drive source, or a vehicle such as an electric vehicle, a battery mounted on the vehicle body is charged, and propulsive force is generated using electric energy supplied from the battery. In general, a battery-related power supply circuit is configured as a high-voltage circuit that handles a high voltage of 200 V or higher. To ensure safety, the high-voltage circuit including the battery is electrically isolated from the vehicle body serving as a ground reference potential point. It is a non-grounded configuration.

  In a vehicle equipped with an ungrounded high-voltage battery, a system provided with the high-voltage battery, specifically, an insulation state (ground fault) between the main power supply system from the high-voltage battery to the motor and the vehicle body is monitored. For this purpose, a ground fault detection device is provided. As the ground fault detection device, a method using a capacitor called a flying capacitor is widely used.

  FIG. 11 is a diagram illustrating a circuit example of a conventional grounding fault detection apparatus of a flying capacitor system. As shown in the figure, the ground fault detection device 400 is a device that is connected to an ungrounded high voltage battery 300 and detects a ground fault of a system in which the high voltage battery 300 is provided. Here, the insulation resistance between the positive electrode side and the ground of the high-voltage battery 300 is represented as RLp, and the insulation resistance between the negative electrode side and the ground is represented as RLn.

  As shown in the figure, the ground fault detection apparatus 400 includes a detection capacitor C1 that operates as a flying capacitor. Further, four switching elements S1 to S4 are provided around the detection capacitor C1 in order to switch the measurement path and control charging and discharging of the detection capacitor C1. Further, a switching element Sa for sampling a measurement voltage corresponding to the charging voltage of the detection capacitor C1 is provided.

  In the ground fault detection device 400, in order to grasp the insulation resistances RLp and RLn, the measurement operation is repeated with one cycle of V0 measurement period → Vc1n measurement period → V0 measurement period → Vc1p measurement period. In any measurement period, after the detection capacitor C1 is charged with the voltage to be measured, the charging voltage of the detection capacitor C1 is measured. Then, the detection capacitor C1 is discharged for the next measurement.

  In the V0 measurement period, a voltage corresponding to the voltage Vb of the high voltage battery 300 is measured. Therefore, the switching elements S1 and S2 are turned on, the switching elements S3 and S4 are turned off, and the detection capacitor C1 is charged. That is, as shown in FIG. 12A, the high-voltage battery 300, the resistor R1, and the detection capacitor C1 are measurement paths.

  At the time of measuring the charging voltage of the detection capacitor C1, as shown in FIG. 12B, the switching elements S1 and S2 are turned off, the switching elements S3 and S4 are turned on, and the switching element Sa is turned on. At 420, sampling is performed. Thereafter, as shown in FIG. 12C, the switching element Sa is turned off, and the detection capacitor C1 is discharged for the next measurement. The operation during the measurement of the charging voltage of the detection capacitor C1 and the discharge of the detection capacitor C1 is the same in other measurement periods.

  In the Vc1n measurement period, a voltage reflecting the influence of the insulation resistance RLn is measured. Therefore, the switching elements S1 and S4 are turned on, the switching elements S2 and S3 are turned off, and the detection capacitor C1 is charged. That is, as shown in FIG. 13A, the high-voltage battery 300, the resistor R1, the detection capacitor C1, the resistor R4, the ground, and the insulation resistance RLn are measurement paths.

  In the Vc1p measurement period, a voltage reflecting the influence of the insulation resistance RLp is measured. Therefore, the switching elements S2 and S3 are turned on, the switching elements S1 and S4 are turned off, and the detection capacitor C1 is charged. That is, as shown in FIG. 13B, the high-voltage battery 300, the insulation resistance RLp, the ground, the resistance R3, the resistance R1, and the detection capacitor C1 are measurement paths.

  It is known that (RLp × RLn) / (RLp + RLn) can be obtained based on (Vc1p + Vc1n) / V0 calculated from V0, Vc1n, and Vc1p obtained in these measurement periods. For this reason, the control device 420 in the ground fault detection device 400 can grasp the insulation resistances RLp and RLn by measuring V0, Vc1n, and Vc1p. When the insulation resistances RLp and RLn are equal to or lower than a predetermined determination reference level, it is determined that a ground fault has occurred, and an alarm is output.

  Patent Document 1 proposes a ground fault detection device 440 having a circuit configuration as shown in FIG. Also in the ground fault detection device 440, the switching switching state in each measurement period is the same as that of the ground fault detection device 400.

JP 2009-281986 A

  In the conventional ground fault detection device, the switching elements S1 to S4 are configured by using four optical MOS-FETs that are insulating switching elements. However, since the optical MOS-FET is expensive, the cost of the ground fault detection device is increased.

  Accordingly, an object of the present invention is to suppress an increase in cost caused by a switching element in a ground fault detection device using a flying capacitor.

In order to solve the above-described problem, a ground fault detection device of the present invention is a ground fault detection device that is connected to an ungrounded high voltage battery and detects a ground fault of a system provided with the high voltage battery. Part, a detection capacitor that operates as a flying capacitor, a positive power line connected to the positive side of the high voltage battery, a negative power line connected to the negative side of the high voltage battery, one end is grounded, Based on a positive secondary resistance whose voltage at the other end is measured by the control unit, a negative secondary resistance whose one end is grounded, and an instruction from the control unit, the connection destination of the one end of the detection capacitor is A positive-side C contact switch that selectively switches between a path including the positive-side power line and a path including the positive-side secondary resistance, and the other end of the detection capacitor based on an instruction from the control unit Connect to the negative electrode A negative-side C contact switch that selectively switches between a path including a power supply line and a path including the negative-electrode secondary-side resistance, and the control unit measures the high-voltage battery equivalent voltage, and positive-side insulation Switching between the measurement of the voltage affected by the resistance, the first measurement mode including the measurement of the voltage affected by the negative-side insulation resistance in the measurement cycle, and the second measurement mode without any measurement, Switching control of the positive side C contact switch and the negative side C contact switch is performed.
Here, the control unit shifts to the first measurement mode when the measurement result of the voltage affected by the positive-side insulation resistance or the measurement result of the voltage affected by the negative-side insulation resistance satisfies a predetermined condition. be able to.
The control unit may switch the measurement mode in accordance with an instruction from an external control device, and the second measurement mode may further include a measurement mode in which all measurements are omitted.
In the second measurement mode, the measurement of the voltage equivalent to the high-voltage battery is omitted, the measurement of the voltage affected by the positive-side insulation resistance, and the measurement of the voltage affected by the negative-side insulation resistance are included in the measurement cycle. The control unit includes a voltage value obtained from the measurement result of the voltage affected by the positive-side insulation resistance and a voltage value obtained from the measurement result of the voltage affected by the negative-side insulation resistance in this measurement mode. When either exceeds a predetermined threshold, the first measurement mode may be entered.
Alternatively, in the second measurement mode, the measurement of the voltage that is affected by the positive-side insulation resistance and the measurement of the voltage that is affected by the negative-side insulation resistance are omitted in the measurement cycle, without measuring the high-voltage battery equivalent voltage. In this measurement mode, the control unit, when either the voltage change rate affected by the positive-side insulation resistance or the voltage change rate affected by the positive-side insulation resistance satisfies a predetermined condition The first measurement mode may be entered.

  According to the present invention, since the ground fault detection device using the flying capacitor does not use the optical MOS-FET that causes the increase in cost, the increase in cost due to the switching element can be suppressed.

It is a block diagram which shows the structure of the ground fault detection apparatus which concerns on embodiment of this invention. It is a figure which shows the state of the C contact switch in each measurement period. It is a figure which shows another example of the positive electrode side C contact switch arrangement | positioning location. It is a figure which shows the example of measurement mode. It is a flowchart explaining the switching determination of the measurement mode which a ground fault detection apparatus performs. It is a flowchart explaining the switching determination of the measurement mode which an external control apparatus performs. It is a figure explaining the control which switches a measurement mode when measured value Vc1 is larger than a determination threshold value. It is a figure explaining the time change at the time of the rise of the charging voltage of the capacitor | condenser C. FIG. It is a flowchart explaining the operation | movement in the case of performing determination based on the magnitude | size of the change rate of a charging voltage. It is a figure which shows the example of measurement mode B1. It is a figure which shows the circuit example of the conventional ground fault detection apparatus of a flying capacitor system. It is a figure which shows the measurement path | route of V0 measurement period. It is a figure which shows the measurement path | route of a Vc1n measurement period and a Vc1p measurement period. It is a figure which shows another example of the circuit of the conventional ground fault detection apparatus of a flying capacitor system.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a ground fault detection apparatus 100 according to an embodiment of the present invention. As shown in the figure, the ground fault detection apparatus 100 is a flying capacitor type apparatus that is connected to an ungrounded high voltage battery 300 and detects a ground fault of a system provided with the high voltage battery 300. Here, the insulation resistance between the positive electrode side and the ground of the high-voltage battery 300 is represented as RLp, and the insulation resistance between the negative electrode side and the ground is represented as RLn. The high voltage means a voltage higher than a low voltage battery (generally 12V) for driving various devices (lamps, wipers, etc.) in the vehicle, and the high voltage battery 300 is used for driving the vehicle. A battery used for driving.

  The high voltage battery 300 is configured by a rechargeable battery such as a lithium ion battery, and discharges via a high voltage bus bar (not shown) to drive an electric motor connected via an inverter or the like. In addition, during regeneration or when charging equipment is connected, charging is performed via a high-pressure bus bar.

  In order to remove high frequency noise from the power source and stabilize the operation, a Y capacitor is provided between the positive power line 301 and the ground electrode and between the negative power line 302 and the ground electrode of the high voltage battery 300, respectively. Capacitors CYp and CYn called (line bypass capacitors) are connected. However, the Y capacitor may be omitted.

  As shown in the figure, the ground fault detection apparatus 100 includes a detection capacitor C1 that operates as a flying capacitor, and includes a switching element Sa for sampling a measurement voltage corresponding to the charging voltage of the detection capacitor C1. I have. However, the switching element Sa can be omitted. Moreover, the control apparatus 120 comprised with the microcomputer etc. is provided. The control device 120 executes various programs required for the ground fault detection device 100 such as a switch switching process described later by executing a program incorporated in advance. The control device 120 communicates with the external control device 200, which is a higher-level device, and outputs measurement values and ground fault detection results obtained during the measurement period, and inputs operation instructions and the like.

  As described with reference to FIGS. 12 and 13, in the measurement path of each measurement period, the switching element S1 and the switching element S3 of the positive power supply line 301 system are not simultaneously turned on, and the negative power supply line The 302 series switching element S2 and the switching element S4 are not simultaneously turned on. That is, the switching element S1 and the switching element S3 are exclusively switched, and the switching element S2 and the switching element S4 are exclusively switched.

  Therefore, in the ground fault detection device 100, the positive side C contact switch 111 is used as the switching element of the positive side power supply line 301 system, and the negative side C contact switch 112 is used as the switching element of the negative side power line 302 system. Yes. The positive-side C contact switch 111 and the negative-side C contact switch 112 can be configured by, for example, a high voltage-small signal mechanical relay or a reed relay.

  A common contact c is arranged on the detection capacitor C1 side for both the positive side C contact switch 111 and the negative side C contact switch 112. Specifically, the common contact c of the positive side C contact switch 111 is connected to the detection capacitor C1 via a parallel circuit of a path of the diode D1 and the resistor R1 and a path of the resistor R2 and the diode D2. The common contact c of the negative side C contact switch 112 is connected to the other end of the detection capacitor C1. The diode D1 serving as a charging path is connected in a direction in which the detection capacitor C1 is in the forward direction from the positive-side C contact switch 111, and the diode D2 serving as a discharging path is connected in the reverse direction. The resistor R2 functions as a discharging resistor.

  The contact a of the positive side C contact switch 111 is connected to the positive power line 301 via the resistor Ra, and the contact a of the negative side C contact switch 112 is connected to the negative side power line 302 via the resistor Rb. Yes. That is, in any C contact switch, the high voltage battery 300 side is set as the contact a. However, the resistor Ra and the resistor Rb may be omitted.

  The contact b of the positive side C contact switch 111 is connected to the switching element Sa and is connected to a resistor R3 which is a positive side secondary resistance whose other end is grounded. The contact b of the negative side C contact switch 112 is connected to a resistor R4, which is a negative secondary side resistor whose other end is grounded. That is, in any C contact point switch, the control device 120 side (ground side) is set as the contact point b.

  As shown in FIG. 1, the positive side C contact switch 111 and the negative side C contact switch 112 are switched and controlled independently by the control device 120. The control device 120 switches the measurement path by independently controlling the positive side C contact switch 111, the negative side C contact switch 112, and the switching element Sa to charge and discharge the detection capacitor C1 and measure the charging voltage. To do.

  Specifically, in the V0 measurement period, as shown in FIG. 2A, both the positive side C contact switch 111 and the negative side C contact switch 112 are switched to the contact a side, and the high voltage battery 300, resistor Ra, resistor R1 are switched. , A measurement path of the detection capacitor C1 and the resistor Rb is formed.

  At the time of measuring the charging voltage of the detection capacitor C1, as shown in FIG. 2D, both the positive side C contact switch 111 and the negative side C contact switch 112 are switched to the contact b side, and the switching element Sa is turned on. Thereafter, the switching element Sa is turned off, and the detection capacitor C1 is discharged mainly using the resistor R2 for the next measurement. The operation at the time of measuring the charging voltage of the detection capacitor C1 and discharging is the same in other measurement periods.

  In the Vc1n measurement period, as shown in FIG. 2 (b), the positive side C contact switch 111 is switched to the contact a side and the negative side C contact switch 112 is switched to the contact b side, and the high voltage battery 300, resistor Ra, resistor R1, A measurement path including a detection capacitor C1, a resistor R4, a ground, and an insulation resistance RLn is formed.

  In the Vc1p measurement period, as shown in FIG. 2 (c), the positive side C contact switch 111 is switched to the contact b side, and the negative side C contact switch 112 is switched to the contact a side, and the high voltage battery 300, insulation resistance RLp, ground, A measurement path including a resistor R3, a resistor R1, a detection capacitor C1, and a resistor Rb is formed.

  In the ground fault detection device 100, the resistor Ra, the resistor Rb, and the resistor R1 are, for example, high resistance of about several hundred kΩ, and the resistor R2, the resistor R3, and the resistor R4 are, for example, low resistance of about several kΩ.

  Aside from the resistor R1, the resistor Ra is arranged on the positive electrode side, the resistor Rb is arranged on the negative electrode side, and the positive electrode side C contact switch 111 and the negative electrode C contact switch 112 are constituted by C contact relays. Even if the contact switch is stuck, either the high-resistance resistor Ra or the resistor Rb is interposed between the high-voltage battery 300 and the control device 120 to limit the current. For this reason, the control device 120 and the energization circuit can be protected.

  Further, even if the contact a and the contact b are short-circuited by any one of the C contact switches, either the high-resistance resistor Ra or the resistance Rb is interposed between the high-voltage battery 300 and the control device 120. Since the current is limited, the control device 120 can be protected.

When the reference value for determining the ground fault for the insulation resistance RLp and the insulation resistance RLn is RLs, when the insulation resistance RLp and the insulation resistance RLn are the reference value RLs, the V0 measurement period, the Vc1n measurement period, and the Vc1p measurement period are on the path. So that the resistance values of
R1 + Ra + Rb = R1 + R4 + Ra + RLs = R1 + R3 + Rb + RLs
By determining the respective resistance values in such a relationship, even when a ceramic capacitor is used as the detection capacitor C1, it is possible to prevent the ground fault detection accuracy from being lowered due to the influence of the DC bias characteristic.

In the positive side C contact switch 111 and the negative side C contact switch 112, which of the contact a on the high voltage battery 300 side and the contact b on the control device 120 side (grounding side) is the normally closed side has the following characteristics. It can be determined as appropriate in consideration.
1) When both the positive side C contact switch 111 and the negative side C contact switch 112 have the contact a on the high voltage battery 300 side as the normally closed side, the high voltage is already charged in the detection capacitor C1 when the ground fault detection device 100 is started. Therefore, the charging process in the first V0 measurement period can be omitted. For this reason, it is possible to meet the functional need to make the ground fault determination earlier than usual for ensuring safety at the time of startup.
2) If both the positive side C contact switch 111 and the negative side C contact switch 112 are set to the normally closed contact b on the control device 120 side (ground side), the detection capacitor C1 is discharged when the operation is stopped. For this reason, the risk of electric shock when removing the ground fault detection device 100 is reduced.
3) When one of the positive side C contact switch 111 and the negative side C contact switch 112 is set to the normally closed side, the voltage between one of the electrodes and the ground is charged in the detection capacitor C1 at the time of startup. Will be. By measuring this voltage and comparing it with the normal state, it is possible to quickly grasp the situation where the insulation resistance of one of the poles is reduced, although it is simple.

  As described above, the ground fault detection apparatus 100 according to the present embodiment does not use the optical MOS-FET that causes an increase in cost as the measurement path changeover switch for ground fault detection, and thus is caused by the switching element. Increase in cost can be suppressed.

  Further, since the four switching elements conventionally used are constituted by two C contact switches, the number of parts can be reduced and the control lines can be reduced as compared with the conventional one. Furthermore, since the C contact switch can be easily miniaturized, space saving is also possible.

  In the above example, the positive side C contact switch 111 has the common contact c connected to the detection capacitor C1 via a parallel circuit of the path of the diode D1 and the resistor R1 and the path of the resistor R2 and the diode D2. However, as shown in FIG. 3, the common contact c of the positive side C contact switch 111 may be directly connected to the detection capacitor C1. In this case, the contact a is connected to the resistor Ra via the diode D1 and the resistor R1, and the contact b is connected to the switching element Sa via the diode D2 and the resistor R2, and the diode D2 in parallel with the path of the diode D2. What is necessary is just to connect the path | route of the diode D11 and resistance R11 of the reverse direction.

  By the way, since the C contact switch has a mechanical contact configuration, there is a limit on the number of times of opening and closing. In particular, the greater the energization current and applied voltage, the greater the effect on the number of opening / closing durability. Therefore, in order to improve the number of times of opening and closing, the number of times of opening and closing may be reduced by performing control as described below.

  Conventionally, as shown in FIG. 4A, the measurement for detecting a ground fault repeats the measurement operation with one cycle of V0 measurement period → Vc1n measurement period → V0 measurement period → Vc1p measurement period. This cycle is referred to as measurement mode A. In this case, since the respective states shown in FIG. 2 are frequently switched, the number of times the C contact switch is opened and closed increases.

  Therefore, as shown in FIGS. 4B to 4D, a measurement mode B that omits the V0 measurement period, a measurement mode C that omits the Vc1 measurement period, and a measurement mode D that does not perform all measurements are prepared as appropriate. The number of times the C contact switch is opened and closed is reduced by switching the mode.

  Here, “no measurement” in each measurement mode means that the positive side C contact switch 111 and the negative side C contact switch 112 are set to the contact b side as shown in FIG. No need to switch. For this reason, the more the period of “no measurement” is, the more the number of times of opening and closing the C contact switch can be suppressed.

  Note that the measurement modes to be prepared are not limited to the measurement modes A to D. For example, a measurement mode in which the entire measurement period is a V0 measurement period or two V0 measurement periods in one cycle in the measurement mode A may be prepared.

  Moreover, you may prepare the measurement mode which combined multiple different measurement modes. For example, by preparing a measurement mode in which a pattern in which the measurement mode D is repeated a plurality of times after the measurement mode A is prepared as one cycle, ground fault determination is performed intermittently, and during that time, switching of the C contact switch is unnecessary. Can be done.

  The measurement mode switching determination is performed by, for example, the ground fault detection device 100 or the external control device 200. FIG. 5 is a flowchart showing an example of control when the ground fault detection device 100 makes a measurement mode switching determination.

  At the time of start-up, a measurement operation in measurement mode A is performed to accurately determine the ground fault (S101). Thereafter, in order to reduce the number of times the C contact switch is opened and closed, the process proceeds to the measurement mode B measurement operation (S102). In measurement mode B, since only Vc1 measurement is performed, the current load and voltage load of the C contact switch can be suppressed.

  In the measurement operation in measurement mode B, V0 measurement is not performed, so accurate insulation resistance measurement cannot be performed. However, an approximate measurement based on measurement values (collectively referred to as measurement value Vc1) obtained in the Vc1n measurement period and the Vc1p measurement period is not possible. The ground fault situation can be grasped. That is, when the insulation resistances RLp and RLn are small, the current flowing in the measurement circuit increases, and thus the measured value Vc1 increases from the normal time.

  For this reason, when the measured value Vc1 is larger than the predetermined determination threshold value (S103: Yes), the process shifts to the measurement mode A in order to accurately measure the insulation resistance (S104). After the transition to the measurement mode A, for example, if it is determined that there is no abnormality in the accurate insulation resistance measurement, the measurement mode B may be returned.

  FIG. 6 is a flowchart showing an example of control when the external control device 200 makes a measurement mode switching determination and instructs the ground fault detection device 100 to switch the measurement mode. In addition, the external control device 200 can acquire the voltage Vb of the high-voltage battery 300 through another measurement path separately from the V0 measurement of the ground fault detection device 100.

  At the time of start-up, the measurement mode A measurement operation is performed in order to accurately determine the ground fault (S201). Thereafter, in order to suppress the number of times of opening and closing the C contact switch, the measurement mode B is shifted to the measurement operation (S202).

  During the measurement operation in the measurement mode B, the voltage Vb of the high voltage battery 300 is acquired from a measurement path different from the ground fault detection device 100 (S203), and the voltage Vc1 that is the measurement result of the ground fault detection device 100 is obtained. Obtain (S204).

  Then, an insulation resistance is calculated based on the acquired voltage Vb and voltage Vc1 (S206). Since the acquisition path is different between the voltage Vb and the voltage Vc1, the voltage Vb and the voltage Vc1 are not limited to being synchronized, and the measurement conditions and the like may be different. For this reason, the calculated insulation resistance is not necessarily an accurate value.

  Therefore, when the insulation resistance is lower than the predetermined reference value (S206: Yes), the measurement mode A measurement operation is performed to accurately determine the ground fault (S207).

  On the other hand, even if the insulation resistance is not lower than the predetermined reference value (S206: No), if the predetermined mode change condition is satisfied (S208: Yes), the ground fault detection device 100 is set to the measurement mode according to the condition. May be changed (S209).

  For example, when there is a measurement value necessary for the operation of the external control device 200, a measurement mode in which the measurement value can be obtained can be performed. Further, when a measurement value is unnecessary, it is possible to shift to a measurement mode D that does not require opening / closing of the C contact switch. The changed measurement mode can be appropriately changed to another measurement mode based on each condition.

  The measurement mode switching determination may be performed by both the ground fault detection device 100 and the external control device 200. In this case, for example, when the ground fault detection device 100 receives a measurement mode switching instruction from the external control device 200 while performing the switching determination as shown in FIG. The measurement mode is switched with priority given to the instruction.

  Next, another example of the control when the ground fault detection apparatus 100 described with reference to FIG. 5 performs the switching determination from the measurement mode B in which V0 measurement is not performed to the measurement mode A in which V0 measurement is performed will be described. In the above-described process (S103), when the measured value Vc1 is larger than a predetermined determination threshold value, the mode is shifted to the measurement mode A.

  For example, as shown in FIG. 7A, when both Vc1n and Vc1p are not larger than the determination threshold, the measurement mode B is continued. On the other hand, as shown in FIG. 7B, when at least one of Vc1n and Vc1p becomes larger than the determination threshold value, the mode shifts to the measurement mode A in order to accurately measure the insulation resistance.

  However, Vc1n and Vc1p increase / decrease according to the voltage fluctuation of the high voltage battery 300. For this reason, when the voltage of the high-voltage battery 300 increases for some reason, Vc1n and Vc1p exceed the determination threshold as shown in FIG. 7C even though the insulation resistance does not decrease. There is a time. This may unnecessarily shift to the measurement mode A and increase the number of times the C contact switch is opened and closed.

  Therefore, in order to prevent unnecessary transition to the measurement mode A, instead of determining whether or not the voltage values of Vc1n and Vc1p are larger than the determination threshold value, charging of the detection capacitor C1 as described below is performed. You may make it perform determination based on the magnitude | size of the change rate in the predetermined period of a voltage.

In general, in the RC series circuit, the time change of the charging voltage Vc of the capacitor C when the voltage E is applied is
Vc = E (1-exp (-t / RC))
It becomes.

  At the time of measuring Vc1 of the ground fault detection device 100, E is the voltage of the high voltage battery 300, C is the capacitance of the detection capacitor C1, and R is a composite value of the measurement path resistance value and the insulation resistance value of the ground fault detection device 100. It corresponds to. In order to simplify the explanation, the influence of the Y capacitor is ignored.

  From this equation, as shown in FIG. 8, the Vc1 measurement value is high because the voltage of the high-voltage battery 300 is high even though the insulation resistance is high and normal, and the high voltage When the Vc1 measurement value is high because the voltage of the battery 300 is normal and the insulation resistance is low, even if the Vc1 measurement value is equal, the charging voltage of the capacitor C at the rise time Time changes will be different.

  Specifically, when the insulation resistance is lowered, the rising curve becomes steep. For this reason, the charging voltage when the insulation resistance is low during the charging time tc of Vc1 is Vc1L, the charging voltage when the insulation resistance is high is Vc1H, the charging voltage when the insulation resistance is low during the time ta shorter than tc is VaL, and the insulation resistance. When the charging voltage at the time of high is VaH, (Vc1H / VaH)> (Vc1L / VaL) is established.

  The value of Vc1 / Va is not affected by the voltage of the high voltage battery 300 and depends on the insulation resistance. For this reason, it is possible to determine whether to shift to the measurement mode A based on Vc1 / Va that is a ratio of the charging voltage Vc1 at time tc and the charging voltage Va at time ta. That is, when Vc1 / Va is smaller than a predetermined determination ratio, it can be determined that the measurement mode A is entered because the insulation resistance may be reduced. Of course, the determination may be made based on the inverse number Va / Vc1.

  Here, the measurement of Va may be performed separately from the measurement of Vc1, or Va may be measured during the measurement of Vc1. In the latter case, after the time ta has elapsed since the start of the measurement of Vc1, the measurement path is once switched to measure Va, and then the Vc1 measurement path is switched again to secure the remaining charging time tc. do it. Hereinafter, an example in which the measurement of Va is performed separately from the measurement of Vc1 will be described.

  FIG. 9 is a flowchart for explaining the operation in the case of making a determination based on the magnitude of the change rate of the charging voltage. In the flowchart shown in FIG. 5, processing (S1021) is performed instead of processing (S102), and processing (S1031) is performed instead of processing (S103).

  In this operation, instead of the measurement mode B, a measurement mode B1 in which measurement of Va is added is performed (S1021). The measurement mode B1 is a mode in which Vna that is Va for Vc1n and Vpa that is Va for Vc1p are measured in addition to Vc1n and Vc1p without performing V0 measurement.

  In the measurement mode B1, for example, as shown in FIG. 10 (a), the Vna measurement period, the Vc1n measurement period, the Vpa measurement period, and the Vc1p measurement period may be one cycle, or as shown in FIG. 10 (b). The Vna measurement period, the Vpa measurement period, the Vc1n measurement period, and the Vc1p measurement period may be one cycle.

  When each measurement value is obtained in the measurement mode B1, Vc1n / Vna and Vc1p / Vpa are calculated, and when at least one is smaller than a predetermined determination ratio (S1031: Yes), accurate insulation resistance measurement is performed. In order to carry out, the measurement mode A is entered (S104).

  As a result, the determination to shift to the measurement mode A is not affected by the voltage fluctuation of the high-voltage battery 300, and therefore an increase in the number of times of opening and closing the C contact switch due to unnecessary shift to the measurement mode A can be prevented.

100 Ground Fault Detection Device 111 Positive Side C Contact Switch 112 Negative Side C Contact Switch 120 Control Device 200 External Control Device 300 High Voltage Battery 301 Positive Side Power Line 302 Negative Side Power Line

Claims (5)

A ground fault detection device connected to a non-grounded high voltage battery and detecting a ground fault of a system provided with the high voltage battery,
A control unit;
A detection capacitor that operates as a flying capacitor;
A positive-side power line connected to the positive-side of the high-voltage battery;
A negative-side power line connected to the negative-side of the high-voltage battery;
One end is grounded, and the other end of the voltage is measured by the controller.
A negative secondary resistance whose one end is grounded;
Based on an instruction from the control unit, a positive-side C contact that selectively switches a connection destination of one end of the detection capacitor between a path including the positive-side power line and a path including the positive-side secondary resistance. A switch,
Based on an instruction from the control unit, a negative electrode side C that selectively switches a connection destination of the other end of the detection capacitor between a path including the negative power supply line and a path including the negative secondary resistance. A contact switch;
With
The controller is
A first measurement mode including measurement of the high-voltage battery equivalent voltage, measurement of the voltage affected by the positive side insulation resistance, measurement of the voltage affected by the negative side insulation resistance in the measurement cycle;
A ground fault detection device, wherein switching between the positive side C contact switch and the negative side C contact switch is performed by switching to a second measurement mode in which any measurement is omitted.   The control unit shifts to the first measurement mode when the measurement result of the voltage affected by the positive-side insulation resistance or the measurement result of the voltage affected by the negative-side insulation resistance satisfies a predetermined condition. The ground fault detection apparatus according to claim 1.   The control unit switches the measurement mode according to an instruction from an external control device, and the second measurement mode further includes a measurement mode in which all measurements are omitted. The ground fault detection apparatus described in 1. The second measurement mode is a measurement mode in which the measurement of the voltage equivalent to the high-voltage battery is omitted, the measurement of the voltage affected by the positive-side insulation resistance, and the measurement of the voltage affected by the negative-side insulation resistance are included in the measurement cycle. Including
In this measurement mode, the control unit determines whether a voltage value obtained from the measurement result of the voltage affected by the positive electrode side insulation resistance or a voltage value obtained from the measurement result of the voltage affected by the negative electrode side insulation resistance is predetermined. The ground fault detection device according to claim 1, wherein the ground fault detection device shifts to the first measurement mode when exceeding the threshold value. The second measurement mode is a measurement mode in which the measurement of the voltage equivalent to the high-voltage battery is omitted, the measurement of the voltage affected by the positive-side insulation resistance, and the measurement of the voltage affected by the negative-side insulation resistance are included in the measurement cycle. Including
In this measurement mode, the control unit performs the first measurement when either the voltage change rate affected by the positive electrode side insulation resistance or the voltage change rate affected by the positive electrode side insulation resistance satisfies a predetermined condition. The ground fault detection apparatus according to claim 1, wherein the ground fault detection apparatus shifts to a mode.

Images