Leakage current detection device, vehicle power system

Abstract

To quickly and accurately diagnose faults in the coupling capacitor of the leakage current detection device, the voltage output unit (11a, OP1) generates a periodically varying periodic voltage and applies this periodic voltage to the other end of the coupling capacitor (Cc) via a first resistor (R1). A second resistor (R2) and a third resistor (R3) are connected in series between the connection point of the coupling capacitor (Cc) and the first resistor (R1) and a predetermined fixed potential. The voltage measuring unit (11b) measures the voltage at the voltage divider point between the second resistor (R2) and the third resistor (R3). With a fixed voltage output from the voltage output unit (11a, OP1), the diagnostic unit (11d) determines whether the coupling capacitor (Cc) is functioning correctly based on the voltage measured when the switches (MRp, MRm, MRpp) are turned on.

Description

Technical Field

[0001] This invention relates to a leakage current detection device for detecting leakage current in a load insulated from the ground wire, and a power supply system for vehicles. Background Technology

[0002] In recent years, hybrid vehicles (HV), plug-in hybrid vehicles (PHV), and electric vehicles (EV) have become increasingly popular. In these electric vehicles, a high-voltage drive battery (traction battery) is installed separately from the auxiliary battery (usually a 12V lead-acid battery). To prevent electric shock, the high-voltage drive battery, inverter, and high-voltage circuitry of the drive motor are insulated from the vehicle body (chassis ground wire).

[0003] Y capacitors are inserted between the positive terminal wiring on the vehicle side of the high-voltage circuit and the chassis ground wire, and between the negative terminal wiring on the vehicle side of the high-voltage circuit and the chassis ground wire, respectively, to stabilize the power supplied from the high-voltage drive battery to the load on the vehicle side. A leakage detection device is included to monitor the insulation resistance between the high-voltage circuit and the chassis ground wire to detect leakage current.

[0004] In an AC-type leakage detection device, a pulse voltage is applied to the positive or negative terminal of the driving battery via a resistor and a coupling capacitor, and the voltage at the connection point of the resistor and the coupling capacitor is measured to detect whether there is leakage.

[0005] In AC-type leakage current detection devices, one method for diagnosing coupling capacitor faults is based on the variation in waveform height when a relay (contactor) between the battery side and the vehicle side is opened and closed. If the waveform height variation is below a predetermined value, the coupling capacitor is determined to be faulty (see, for example, Patent Document 1).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2004-53367 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] In the aforementioned fault diagnosis method for coupling capacitors, since it is necessary to measure the variation in wave height, it is also necessary to determine the voltages of the upper and lower peak values ​​of the wave height. If the timing of the measurement of either the upper or lower peak value is off, an accurate wave height cannot be measured. Furthermore, if both the upper and lower peak values ​​are not measured, the wave height cannot be determined, thus creating a time constraint in the wave height measurement cycle. This is time-consuming when multiple determinations are performed. The same applies to diagnosing coupling capacitor faults based on variations in either the upper or lower peak value of the wave height.

[0011] This disclosure was made in view of the following circumstances, and its purpose is to provide a technique for rapidly and accurately diagnosing faults in the coupling capacitors of a leakage current detection device.

[0012] Solution for solving the problem

[0013] To address the aforementioned issues, a leakage current detection device according to one aspect of this disclosure is mounted on a vehicle, the vehicle comprising: a power storage unit mounted insulated from the vehicle's chassis ground wire for supplying power to a load within the vehicle; and a switch inserted into wiring connecting the power storage unit to the load. The leakage current detection device comprises: a coupling capacitor, one end of which is connected to the current path of the power storage unit connected to the load insulated from the ground wire; a voltage output unit that generates a periodically varying periodic voltage and applies this periodic voltage to the other end of the coupling capacitor via a first resistor; a second resistor and a third resistor, the second resistor and the... The third resistor is connected in series between the connection point between the coupling capacitor and the first resistor and a predetermined fixed potential; a voltage measuring unit measures the voltage at the voltage divider point between the second resistor and the third resistor; a leakage current determination unit, when the periodic voltage is output from the voltage output unit, determines whether there is leakage current between the current path of the energy storage unit and the ground wire based on the voltage measured by the voltage measuring unit; and a diagnostic unit, when the fixed voltage is output from the voltage output unit, determines whether the coupling capacitor is normal based on the voltage measured by the voltage measuring unit when the switch is turned on.

[0014] The effects of the invention

[0015] According to this disclosure, fault diagnosis of the coupling capacitor of a leakage current detection device can be performed quickly and with high accuracy. Attached Figure Description

[0016] Figure 1 This is a diagram illustrating the structure of a power supply system with a leakage current detection device involved in the comparative example.

[0017] Figure 2This is a diagram illustrating an example of applying a pulse waveform and measuring a voltage waveform.

[0018] Figure 3 This is a diagram illustrating an example of the measured waveform during fault diagnosis of the coupling capacitor Cc involved in the comparative example.

[0019] Figure 4 This is a diagram illustrating the structure of a power supply system equipped with a leakage current detection device according to the embodiments.

[0020] Figure 5 This is a diagram illustrating an example of the measured waveform during fault diagnosis of the coupling capacitor Cc according to the embodiment. Detailed Implementation

[0021] (Comparative Example)

[0022] Figure 1 This diagram illustrates the structure of the power system 5 equipped with the leakage detection device 10, as described in the comparative example. The power system 5 is mounted in an electric vehicle. The power system 5 is installed separately from the auxiliary battery (typically a 12V lead-acid battery) within the electric vehicle. The power system 5 includes the leakage detection device 10 and a high-voltage energy storage unit 20. The energy storage unit 20 includes multiple cells E1-En connected in series. For each cell, lithium-ion battery cells, nickel-metal hydride battery cells, lead-acid battery cells, double-layer capacitor cells, lithium-ion capacitor cells, etc., can be used. In the following specification, an example using a lithium-ion battery cell (nominal voltage: 3.6V-3.7V) is assumed.

[0023] The electric vehicle includes an inverter 2 and a motor 3, which serve as high-voltage loads. The positive terminal of the energy storage unit 20 is connected to one end of the inverter 2 via a positive wiring Lp, and the negative terminal of the energy storage unit 20 is connected to the other end of the inverter 2 via a negative wiring Lm. A large-capacity capacitor 4 is connected in parallel with the inverter 2. A positive-side main relay MRp is inserted into the positive wiring Lp, and a negative-side main relay MRm is inserted into the negative wiring Lm.

[0024] A pre-charge relay MRpp and a pre-charge resistor Rp are connected in series in parallel with the positive main relay MRp. The pre-charge relay MRpp is turned on (closed) before the positive main relay MRp is turned on (closed), thereby pre-charging the capacitor 4 with a limited current, thus suppressing inrush current. Alternatively, the pre-charge relay and pre-charge resistor connected in series can be connected in parallel with the negative main relay MRm.

[0025] The positive-side main relay MRp, the pre-charge relay MRpp, and the negative-side main relay MRm function as contactors to control the switching on / off of the battery storage unit 20 with the high-voltage load within the electric vehicle. Alternatively, high-voltage and highly insulated semiconductor switches can be used instead of relays.

[0026] Inverter 2 is a bidirectional inverter connected between the energy storage unit 20 and the motor 3. During power operation, inverter 2 converts the DC power supplied from the energy storage unit 20 into AC power and supplies it to the motor 3. During regeneration, it converts the AC power supplied from the motor 3 into DC power and supplies it to the energy storage unit 20. Motor 3 is, for example, a three-phase AC motor. During power operation, motor 3 rotates in response to the AC power supplied by inverter 2. During regeneration, the rotational energy generated by deceleration is converted into AC power and supplied to inverter 2.

[0027] The energy storage unit 20 is mounted in the electric vehicle in a state of insulation from the chassis ground wire. The auxiliary battery is mounted in the electric vehicle with its negative terminal connected to the chassis ground wire. Furthermore, the positive terminal wiring Lp, which is closer to the inverter 2 side than the positive main relay MRp, is connected to the chassis ground wire via a positive Y capacitor Cp. Similarly, the negative terminal wiring Lm, which is closer to the inverter 2 side than the negative main relay MRm, is connected to the chassis ground wire via a negative Y capacitor Cm. The positive Y capacitor Cp and the negative Y capacitor Cm serve the following functions: to provide DC insulation between the positive terminal wiring Lp and the chassis ground wire, and between the negative terminal wiring Lm and the chassis ground wire, respectively, and to stabilize the voltage of the positive terminal wiring Lp and the negative terminal wiring Lm.

[0028] When the energy storage unit 20 is ideally insulated from the chassis ground wire, the intermediate potential of the energy storage unit 20 is maintained near the potential of the chassis ground wire. For example, when the voltage across the energy storage unit 20 is 250V, the positive terminal potential of the energy storage unit 20 is maintained near +125V, and the negative terminal potential is maintained near -125V. In a state where the high-voltage energy storage unit 20 is conductive to the chassis ground wire, there is a risk of electric shock if a person touches an exposed conductive part of the electric vehicle. Therefore, in electric vehicles equipped with a high-voltage energy storage unit 20, a leakage current detection device 10 is required to monitor the insulation status between the current path of the energy storage unit 20 connected to the high-voltage vehicle load and the chassis ground wire. Figure 1 In this paper, the insulation state between the positive terminal wiring Lp and the chassis ground wire is represented by the positive side leakage resistance Rlp, and the insulation state between the negative terminal wiring Lm and the chassis ground wire is represented by the negative side leakage resistance Rlm.

[0029] In a comparative example, the leakage current detection device 10 includes a coupling capacitor Cc, a first resistor R1, a first operational amplifier OP1, a second resistor R2, a smoothing capacitor C1, a second operational amplifier OP2, and a control unit 11. The control unit 11 includes an oscillation unit 11a, a voltage measurement unit 11b, a leakage current determination unit 11c, and a diagnostic unit 11d. The control unit 11 can be, for example, composed of a microcomputer and a non-volatile memory (e.g., EEPROM, flash memory).

[0030] One end of the coupling capacitor Cc is connected to the current path of the energy storage unit 20. Figure 1 In the example shown, one end of the coupling capacitor Cc is connected to the negative terminal of the energy storage unit 20. Alternatively, one end of the coupling capacitor Cc can be connected to the positive terminal of the energy storage unit 20, or to any node of the plurality of individual cells E1-En within the energy storage unit 20. The other end of the coupling capacitor Cc is connected to the output terminal of the voltage output unit via the first resistor R1. The connection point between the other end of the coupling capacitor Cc and the first resistor R1 is the measurement point A. Alternatively, other impedance elements can be used instead of the first resistor R1.

[0031] exist Figure 1 In this configuration, the coupling capacitor Cc utilizes an aluminum electrolytic capacitor, which allows for relatively inexpensive and high-capacity applications. Aluminum electrolytic capacitors are polarized. Figure 1 In this configuration, the positive terminal of the aluminum electrolytic capacitor is connected to the measuring point A, and the negative terminal of the aluminum electrolytic capacitor is connected to the negative terminal of the energy storage section 20. The coupling capacitor Cc can also be constructed by connecting multiple aluminum electrolytic capacitors in series. In this case, even if one capacitor experiences a short-circuit fault, DC insulation can be maintained through the remaining capacitors.

[0032] The voltage output section described above generates a periodically varying periodic voltage and applies the generated periodic voltage to the other end of the coupling capacitor Cc via the first resistor R1. Hereinafter, this specification assumes that a rectangular wave voltage is used as an example of a periodic voltage.

[0033] The voltage output section includes an oscillation section 11a and a first operational amplifier OP1. The oscillation section 11a includes a multivibrator or a local oscillator for generating a rectangular wave of a preset frequency. The rectangular wave voltage generated by the oscillation section 11a is input to the non-inverting input terminal of the first operational amplifier OP1. The output terminal of the first operational amplifier OP1 is connected to a first resistor R1. The inverting input terminal of the first operational amplifier OP1 is connected to the output terminal. The positive power supply terminal of the first operational amplifier OP1 is connected to a first fixed potential (power supply potential Vcc), and the negative power supply terminal of the first operational amplifier OP1 is connected to a second fixed potential (ground potential GND). In the following example, we assume a power supply potential Vcc of 5V and a ground potential GND of 0V.

[0034] The first operational amplifier OP1 functions as a voltage follower with a gain of 1, performing only impedance transformation. Alternatively, an AND gate with one input terminal connected to a first fixed potential, or an OR gate with one input terminal connected to a second fixed potential, can be used instead of the first operational amplifier OP1. Any component that functions as a buffer to impedance-isolate the control unit 11 from the measurement point A can replace the first operational amplifier OP1.

[0035] Measurement point A is connected to the non-inverting input terminal of the second operational amplifier OP2 via the second resistor R2. The inverting input terminal of the second operational amplifier OP2 is connected to the output terminal. The second operational amplifier OP2 also functions as a voltage follower with a gain of 1, performing only impedance transformation. A smoothing capacitor C1 is connected between the non-inverting input terminal of the second operational amplifier OP2 and the second fixed potential (ground potential GND). The smoothing capacitor C1 is used to remove noise from the voltage input to the non-inverting input terminal of the second operational amplifier OP2.

[0036] The second operational amplifier OP2 outputs the voltage at measurement point A to the voltage measurement unit 11b. The voltage measurement unit 11b measures the voltage at measurement point A. The voltage measurement unit 11b includes an A / D converter that samples the analog voltage at measurement point A at a timing synchronized with the rising and falling edges of the rectangular wave voltage generated by the oscillation unit 11a, and converts the sampled analog voltage into a digital value. The voltage sampled at the rising edge of the rectangular wave voltage corresponds to the lower peak value of the measured voltage waveform, and the voltage sampled at the falling edge of the rectangular wave voltage corresponds to the upper peak value of the measured voltage waveform. Furthermore, the rounding of the rectangular wave voltage can be considered, and the timing for sampling the lower peak value and the timing for sampling the upper peak value can be adjusted accordingly. The voltage measurement unit 11b outputs the voltage at measurement point A to the leakage current determination unit 11c and the diagnostic unit 11d.

[0037] The leakage current determination unit 11c determines whether there is leakage between the current path of the energy storage unit 20 and the chassis ground wire based on the voltage at measurement point A measured by the voltage measurement unit 11b. If the peak-to-peak value, expressed as the difference between the upper and lower peak values, is less than a set value, the leakage current determination unit 11c determines that leakage has occurred between the current path of the energy storage unit 20 and the chassis ground wire. This set value is determined based on the peak-to-peak value of the measured voltage waveform when leakage occurs, which is pre-derived by the designer through experiments or simulations. In the event of leakage between the current path of the energy storage unit 20 and the chassis ground wire, an alternating current flows from the first operational amplifier OP1 through the first resistor R1, which acts as a detection resistor, to the coupling capacitor Cc. When current flows through the first resistor R1, the voltage amplitude at measurement point A decreases due to the voltage drop.

[0038] Figure 2 This diagram illustrates an example of an applied pulse waveform and a measured voltage waveform. The high-side potential of the pulse waveform applied to measurement point A from the voltage output unit is set to 5V, and the low-side potential is set to 0V. The leakage current determination unit 11c determines the upper peak value Vp1 and the lower peak value Vp2 of the voltage waveform measured during the application of the pulse voltage to measurement point A, and determines whether leakage current exists based on the peak-to-peak value defined by the difference between the upper peak value Vp1 and the lower peak value Vp2.

[0039] Return to Figure 1 The diagnostic unit 11d performs fault diagnosis on whether the coupling capacitor Cc is functioning properly based on the voltage at measurement point A measured by the voltage measurement unit 11b. Specifically, when a pulse voltage is applied from the voltage output unit to measurement point A, the diagnostic unit 11d diagnoses the coupling capacitor Cc based on the changes in the measured voltage before and after the positive main relay MRp is turned on (closed), before and after the positive main relay MRp is turned off (open), before and after the negative main relay MRm is turned on, or before and after the negative main relay MRm is turned off.

[0040] Figure 3 This is a diagram illustrating an example of the measured waveform during fault diagnosis of the coupling capacitor Cc involved in the comparative example. Figure 3 An example is shown of diagnosing coupling capacitor Cc based on the change in measured voltage before and after the positive main relay MRp is turned on and after the positive main relay MRp is turned off.

[0041] When the peak-to-peak value Vppc of the measured voltage immediately after the positive main relay MRp is turned on, relative to the peak-to-peak value Vppr (specified value) of the measured voltage immediately before the positive main relay MRp is turned on, the diagnostic unit 11d determines that the coupling capacitor Cc is normal. When the decrease is not below the specified value, the diagnostic unit 11d determines that the coupling capacitor Cc is abnormal. If the coupling capacitor Cc is normally connected to the vehicle side, the change in the leakage current state on the vehicle side with the turn-on of the positive main relay MRp is manifested as a decrease in the measured waveform. In the case of an abnormal coupling capacitor Cc, this decrease in the measured waveform will not occur.

[0042] Alternatively, the diagnostic unit 11d can diagnose the coupling capacitor Cc when the positive main relay MRp is disconnected. If the increase in the peak-to-peak value Vppo of the measured voltage immediately after the positive main relay MRp disconnects relative to the peak-to-peak value Vppr (reference value) of the measured voltage immediately before the positive main relay MRp disconnects is greater than or equal to a predetermined value, the diagnostic unit 11d determines the coupling capacitor Cc to be normal. If the increase is not greater than the predetermined value, the diagnostic unit 11d determines the coupling capacitor Cc to be abnormal. If the coupling capacitor Cc is normally connected to the vehicle side, the change in leakage current state on the vehicle side with the disconnection of the positive main relay MRp is manifested as an increase in the measured waveform. In the case of an abnormal coupling capacitor Cc, this increase in the measured waveform will not occur.

[0043] Furthermore, if the diagnostic unit 11d detects a change exceeding its specified value both when the positive main relay MRp is turned on and off, it will determine that the coupling capacitor Cc is normal. Additionally, in Figure 3 In this method, the coupling capacitor Cc can be diagnosed based on the variation of the measured peak-to-peak voltage when the positive-side main relay MRp is turned on or off. Alternatively, the coupling capacitor Cc can be diagnosed based on the variation of the measured peak-to-peak voltage when the negative-side main relay MRm is turned on or off.

[0044] (Implementation Method)

[0045] Figure 4 This is a diagram illustrating the structure of the power supply system 5 equipped with the leakage current detection device 10 according to the embodiment. The following will describe the structure of the power supply system 5. Figure 1 The differences in the structure of the power supply system 5 involved in the comparative example shown are as follows. In this embodiment, a third resistor R3 and a third operational amplifier OP3 are added. The control unit 11 also includes a constant voltage output unit 11e. The constant voltage output unit 11e is capable of outputting a fixed voltage of at least one of a first reference voltage (5V in this embodiment) and a second reference voltage (0V in this embodiment).

[0046] In this embodiment, the oscillation unit 11a and the first operational amplifier OP1 constitute a first voltage output unit, and the constant voltage output unit 11e and the third operational amplifier OP3 constitute a second voltage output unit. In this embodiment, the first voltage output unit is configured to output a fixed voltage, which is at least one of the first reference voltage and the second reference voltage.

[0047] The second resistor R2 and the third resistor R3 are connected in series between the connection point A between the coupling capacitor Cc and the first resistor R1 and the second voltage output section. More specifically, the constant voltage output from the constant voltage output section 11e is input to the non-inverting input terminal of the third operational amplifier OP3. The output terminal of the third operational amplifier OP3 is connected to the third resistor R3. The inverting input terminal of the third operational amplifier OP3 is connected to the output terminal. The third operational amplifier OP3 also functions as a voltage follower with a gain of 1, which only performs impedance transformation.

[0048] In this embodiment, the voltage at the voltage divider point of the second resistor R2 and the third resistor R3 is input to the non-inverting input terminal of the second operational amplifier OP2. That is, the voltage measuring unit 11b measures the voltage at measuring point A as a compressed voltage by measuring the voltage at the voltage divider point of the second resistor R2 and the third resistor R3. The leakage current determination unit 11c determines whether there is leakage current between the current path of the energy storage unit 20 and the chassis ground wire based on the amplitude value of the voltage measured by the voltage measuring unit 11b and the leakage resistance value by referring to the leakage resistance transformation table. In this embodiment, by dividing the voltage at measuring point A before measurement, the period during which the voltage at measuring point A deviates from the measurement range (0V to 5V in this embodiment) can be reduced. That is, the period during which leakage current determination cannot be performed can be reduced.

[0049] When a fixed voltage is output from the first voltage output unit, the diagnostic unit 11d diagnoses whether the coupling capacitor Cc is normal based on the voltage measured by the voltage measuring unit 11b during the on sequence of the positive main relay MRp, the negative main relay MR, and the pre-charge relay MRpp. Specifically, if the voltage fluctuation measured during the on sequence exceeds a predetermined value, the diagnostic unit 11d determines that the coupling capacitor Cc is normal; if the fluctuation is below the predetermined value, the diagnostic unit 11d determines that the coupling capacitor Cc is abnormal.

[0050] The specified value is set based on data obtained by the designer through experiments or simulations.

[0051] Alternatively, the diagnostic unit 11d performs diagnostics on the coupling capacitor Cc after the vehicle is started (key on) and the positive main relay MRp, negative main relay MRm, and pre-charge relay MRpp are initially activated. In this case, the first voltage output unit outputs a fixed voltage after the vehicle is started. After a predetermined time has elapsed since the vehicle started, the ECU (Electronic Control Unit) (not shown) on the vehicle side initiates the energizing sequence of the positive main relay MRp, negative main relay MRm, and pre-charge relay MRpp. The diagnostic unit 11d performs diagnostics on the coupling capacitor Cc during this energizing sequence. After the energizing sequence ends, the first voltage output unit switches the output voltage from a fixed voltage to a pulse voltage, and the leakage current detection unit 11c begins monitoring for leakage current.

[0052] Figure 5 This is a diagram illustrating an example of the measured waveform during fault diagnosis of the coupling capacitor Cc according to the embodiment. The first voltage output unit outputs a fixed voltage after the vehicle is started. For example, when the resistance value of the first resistor R1 is 200kΩ, the resistance value of the second resistor R2 is 1000kΩ, and the resistance value of the third resistor R3 is 1000kΩ, and 5V is output from the first voltage output unit and 0V is output from the second voltage output unit, the fixed voltage measured by the voltage measuring unit 11b is approximately 2.27V, as shown in Equation 1 below. When 0V is output from the first voltage output unit and 5V is output from the second voltage output unit under the same circuit constants, the fixed voltage measured by the voltage measuring unit 11b is approximately 2.73V, as shown in Equation 2 below.

[0053] 5×(1000 / (200+1000+1000))≈2.27…(Equation 1)

[0054] 5×((200+1000) / (200+1000+1000))≈2.73…(Equation 2)

[0055] exist Figure 5 In the example shown, the vehicle-side ECU initiates the activation sequence of the positive main relay MRp, the negative main relay MR, and the pre-charge relay MRpp several hundred milliseconds after the vehicle starts. This elapsed time t1 is the time used to eliminate the rounding effect of the measured waveform caused by the smoothing capacitor C1, and is the time until the measured waveform stabilizes.

[0056] exist Figure 5In the example shown, the turn-on sequence period t2 is set to several hundred ms. During the turn-on sequence period t2, the vehicle-side ECU turns on the negative main relay MRm, the pre-charge relay MRpp, and the positive main relay MRp in that order. Furthermore, when the pre-charge relay is connected to the negative side, the ECU turns on the positive main relay MRp, the pre-charge relay, and the negative main relay MRm in that order.

[0057] If the variation amplitude ΔV of the measured voltage during the turn-on sequence t2 exceeds a specified value, the diagnostic unit 11d determines that the coupling capacitor Cc is normal; if the variation amplitude ΔV is below the specified value, the diagnostic unit 11d determines that the coupling capacitor Cc is abnormal. The variation amplitude ΔV is defined by the difference between the maximum and minimum values ​​of the measured voltage during the turn-on sequence t2.

[0058] As explained above, according to this embodiment, under a fixed voltage applied state, fault diagnosis of the coupling capacitor Cc is performed based on the measured voltage variation amplitude ΔV during the turn-on sequence period t2. Therefore, fault diagnosis of the coupling capacitor Cc can be performed quickly and with high accuracy.

[0059] In this embodiment, since the voltage at the voltage divider point of the second resistor R2 and the third resistor R3 is measured, a fixed voltage can be measured near the middle of the measurement range when a fixed voltage is applied. Therefore, regardless of whether the measured voltage increases or decreases, its variation can be measured with high accuracy. In contrast, in Figure 1 In the circuit structure involved in the comparative example shown, it is difficult to detect the decrease in the measurement voltage when a fixed voltage of 0V is applied, and it is difficult to detect the increase in the measurement voltage when a fixed voltage of 5V is applied.

[0060] In addition, fault diagnosis of coupling capacitor Cc based on the variation of the upper or lower peak value measured under the applied pulse voltage is also considered. However, the peak value usually varies with a period of several hundred ms or more, so the upper or lower peak value can only be detected with a period of several hundred ms or more, which consumes time in sampling the peak value at multiple points.

[0061] Regarding this, if the voltage is constant, the value can be measured in periods of less than tens of milliseconds, thus quickly determining whether there is a voltage fluctuation exceeding the specified value. Even including the initial stabilization time t1, the diagnosis of the coupling capacitor Cc can be completed in less than 1 second.

[0062] The present disclosure has been described above based on the embodiments. It will be understood by those skilled in the art that the embodiments are illustrative and various modifications can be made to the combination of these structural elements and processing procedures, and such modifications are also within the scope of the present disclosure.

[0063] It could also be, in Figure 1 In the circuit structure shown, the voltage output unit outputs a fixed voltage set to a value near the center of the measurement range of the voltage measuring unit 11b. The diagnostic unit 11d determines whether the coupling capacitor Cc is functioning correctly based on the voltage measured during the contactor's on-time sequence. The value near the center of the measurement range of the voltage measuring unit 11b can be a value set within ±1V of the center voltage of the measurement range. For example, when the measurement range is 0V to 5V, the fixed voltage is set to a value within the range of 1.5V to 3.5V. Furthermore, the fixed voltage value can be set to a value outside the ±1V range of the center voltage of the measurement range, as long as it prevents the measured voltage from fluctuating due to vertical changes and remains fixed at the upper or lower limit of the measurement range. By using the above method, the same effect as the above embodiment can be obtained.

[0064] In the above embodiment, an example of fault diagnosis of coupling capacitor Cc was described when the vehicle was started. Alternatively, fault diagnosis of coupling capacitor Cc could be performed after the vehicle has been parked. In this case, since there is ample time, the contactor can be repeatedly switched on and off, and the final diagnosis can be based on the results of these multiple checks.

[0065] In the above embodiment, a pre-charge relay MRpp and a pre-charge resistor Rp are connected in parallel with the positive main relay MRp. However, in the case of a small load, the structure of the pre-charge relay MRpp and the pre-charge resistor Rp can be omitted.

[0066] In the above embodiment, an example was described where a rectangular wave voltage was applied to the coupling capacitor Cc from the first voltage output unit via the first resistor R1. Alternatively, a sinusoidal voltage could be applied to the coupling capacitor Cc. In this case, the leakage current determination unit 11c also determines the peak-to-peak value from the voltage waveform at measurement point A, and can determine whether leakage current exists in the same way as in the above embodiment.

[0067] In the above embodiments, an example of using the leakage current detection device 10 mounted on an electric vehicle was described. In this regard, the leakage current detection device 10 described in the above embodiments can also be applied to applications other than vehicle-mounted use. As long as the energy storage unit 20 and the load receiving power from the energy storage unit 20 are insulated from the ground wire, the load can be any type of load. For example, it can also be a load used inside a railway vehicle.

[0068] In addition, the implementation method can be determined through the following items.

[0069] [Project 1]

[0070] A leakage current detection device (10) is mounted on a vehicle, the vehicle comprising: an energy storage unit (20) mounted insulated from the chassis ground wire of the vehicle for supplying power to a load (2) within the vehicle; and switches (MRp, MRm, MRpp) inserted into wiring connecting the energy storage unit (20) to the load (2), the leakage current detection device (10) being characterized in that it comprises:

[0071] A coupling capacitor (Cc) is connected at one end to the current path of the energy storage unit (20) connected to the load (2) in a state of insulation from the ground wire;

[0072] The voltage output section (11a, OP1) generates a periodically changing periodic voltage and applies the periodic voltage to the other end of the coupling capacitor (Cc) via the first resistor (R1);

[0073] The second resistor (R2) and the third resistor (R3) are connected in series between the connection point between the coupling capacitor (Cc) and the first resistor (R1) and a predetermined fixed potential;

[0074] The voltage measuring unit (11b) measures the voltage at the voltage divider point between the second resistor (R2) and the third resistor (R3);

[0075] The leakage current determination unit (11c), when the periodic voltage is output from the voltage output unit (11a, OP1), determines whether there is leakage current between the current path of the energy storage unit (20) and the ground wire based on the voltage measured by the voltage measuring unit (11b); and

[0076] The diagnostic unit (11d) determines whether the coupling capacitor (Cc) is normal based on the voltage measured by the voltage measuring unit (11b) when the switch (MRp, MRm, MRpp) is turned on, while the voltage output from the voltage output unit (11a, OP1) is at a fixed voltage.

[0077] Therefore, fault diagnosis of coupling capacitors (Cc) can be performed quickly and with high accuracy.

[0078] [Project 2]

[0079] A leakage current detection device (10) is mounted on a vehicle, the vehicle comprising: an energy storage unit (20) mounted insulated from the chassis ground wire of the vehicle for supplying power to a load (2) within the vehicle; and switches (MRp, MRm, MRpp) inserted into wiring connecting the energy storage unit (20) to the load (2), the leakage current detection device (10) being characterized in that it comprises:

[0080] The voltage output section (11a, OP1) generates a periodically changing periodic voltage and applies the periodic voltage to the other end of the coupling capacitor (Cc) via a resistor (R1);

[0081] The voltage measuring unit (11b) measures the voltage at the connection point between the coupling capacitor (Cc) and the resistor (R1);

[0082] The leakage current determination unit (11c), when the periodic voltage is output from the voltage output unit (11a, OP1), determines whether there is leakage current between the current path of the energy storage unit (20) and the ground wire based on the voltage measured by the voltage measuring unit (11b); and

[0083] The diagnostic unit (11d) determines whether the coupling capacitor (Cc) is normal when the voltage output unit (11a, OP1) outputs a fixed voltage that is set to be near the center of the measurement range of the voltage measuring unit (11b). This voltage is based on the voltage measured by the voltage measuring unit (11b) when the switch (MRp, MRm, MRpp) is turned on.

[0084] Therefore, fault diagnosis of coupling capacitors (Cc) can be performed quickly and with high accuracy.

[0085] [Project 3]

[0086] The leakage current detection device (10) according to item 1 or 2 is characterized in that,

[0087] If the voltage fluctuation measured by the voltage measuring unit (11b) is below a predetermined value when the switches (MRp, MRm, MRpp) are turned on, the diagnostic unit (11d) determines that the coupling capacitor (Cc) is abnormal.

[0088] Therefore, fault diagnosis of coupling capacitors (Cc) can be performed quickly and with high accuracy.

[0089] [Project 4]

[0090] According to the leakage current detection device (10) described in Project 3, the characteristic is that,

[0091] The switches (MRp, MRm, MRpp) include:

[0092] A positive relay (MRp) is inserted into the positive wiring that connects the positive terminal of the energy storage unit (20) to one end of the load (2);

[0093] A negative relay (MRm) is inserted into the negative wiring that connects the negative terminal of the energy storage unit (20) to the other end of the load (2); and

[0094] A pre-charge relay (MRpp) is connected in parallel with either the positive relay (MRp) or the negative relay (MRm).

[0095] If the measured voltage fluctuation during the period from the activation of one of the three relays (MRp, MRm, MRpp) – the positive relay, the negative relay, and the pre-charge relay – until all three relays are in the ON state is below the specified value, the diagnostic unit (11d) determines that the coupling capacitor (Cc) is abnormal.

[0096] Therefore, in a structure that uses a contactor including a pre-charge relay to connect to the load (2) on the vehicle side, fault diagnosis of the coupling capacitor (Cc) can be performed quickly and with high accuracy.

[0097] [Project 5]

[0098] A vehicle power supply system (5), characterized in that it comprises:

[0099] An energy storage unit (20), which is mounted insulated from the vehicle's chassis ground wire, is used to supply power to the load (2) within the vehicle; and

[0100] The leakage current detection device (10) according to any one of items 1 to 4.

[0101] Thus, a vehicle power supply system (5) can be realized that has a leakage current detection device (10) capable of rapidly and accurately diagnosing faults in coupling capacitors (Cc).

[0102] [Project 6]

[0103] According to the vehicle power supply system (5) described in Project 5, it is characterized in that,

[0104] The diagnostic unit (11d) determines whether the coupling capacitor (Cc) is normal when the switches (MRp, MRm, MRpp) are initially turned on after the vehicle is started.

[0105] Therefore, even without setting a specific diagnostic period, fault diagnosis of the coupling capacitor (Cc) can be performed.

[0106] Explanation of reference numerals in the attached figures

[0107] 2: Inverter; 3: Motor; 4: Capacitor; Lp: Positive wiring; Lm: Negative wiring; Cp: Positive Y capacitor; Cm: Negative Y capacitor; Rlp: Positive leakage resistance; Rlm: Negative leakage resistance; MRp: Positive main relay; MRm: Negative main relay; MRpp: Pre-charge relay; Rp: Pre-charge resistor; 5: Power supply system; 20: Energy storage unit; E1-En: Individual cells; 10: Leakage detection device; 11: Control unit; 11a: Oscillation unit; 11b: Voltage measurement unit; 11c: Leakage determination unit; 11d: Diagnostic unit; 11e: Constant voltage output unit; Cc: Coupling capacitor; R1: First resistor; R2: Second resistor; R3: Third resistor; C1: Smoothing capacitor; OP1: First operational amplifier; OP2: Second operational amplifier; OP3: Third operational amplifier.

Claims

1. A leakage current detection device mounted on a vehicle, the vehicle comprising: a power storage unit mounted insulated from the vehicle's chassis ground wire for supplying power to a load within the vehicle; and a switch inserted into wiring connecting the power storage unit to the load, the leakage current detection device characterized in that it comprises: A coupling capacitor, one end of which is connected to the current path of the energy storage unit connected to the load in a state of insulation from the ground wire; The voltage output section generates a periodically varying periodic voltage and applies the periodic voltage to the other end of the coupling capacitor via a first resistor; A second resistor and a third resistor are connected in series between the connection point between the coupling capacitor and the first resistor and a predetermined fixed potential; The voltage measuring unit measures the voltage at the voltage divider point between the second resistor and the third resistor. The leakage current determination unit, when the periodic voltage is output from the voltage output unit, determines whether there is leakage between the current path of the energy storage unit and the ground wire based on the voltage measured by the voltage measuring unit. as well as The diagnostic unit, when outputting a fixed voltage from the voltage output unit, determines whether the coupling capacitor is functioning correctly based on the voltage measured by the voltage measuring unit when the switch is turned on. The switch includes: A positive relay is inserted into the positive wiring that connects the positive terminal of the energy storage unit to one end of the load; A negative relay, which is inserted into the negative wiring connecting the negative terminal of the energy storage unit to the other end of the load; and A pre-charge relay, which is connected in parallel with either the positive or negative relay. If the voltage fluctuation measured during the period from the activation of one of the three relays (positive relay, negative relay, and pre-charge relay) until all three relays are in the ON state is below a predetermined value, the diagnostic unit determines that the coupling capacitor is abnormal.

2. A leakage current detection device mounted on a vehicle, the vehicle comprising: a power storage unit mounted insulated from the vehicle's chassis ground wire for supplying power to a load within the vehicle; and a switch inserted into wiring connecting the power storage unit to the load, the leakage current detection device being characterized in that it comprises: A coupling capacitor, one end of which is connected to the current path of the energy storage unit connected to the load in a state of insulation from the ground wire; The voltage output section generates a periodically varying periodic voltage and applies the periodic voltage to the other end of the coupling capacitor via a resistor; The voltage measuring unit measures the voltage at the connection point between the coupling capacitor and the resistor; The leakage current determination unit, when the periodic voltage is output from the voltage output unit, determines whether there is leakage between the current path of the energy storage unit and the ground wire based on the voltage measured by the voltage measuring unit. as well as The diagnostic unit, when outputting a fixed voltage from the voltage output unit that is set to be near the center of the measurement range of the voltage measuring unit, determines whether the coupling capacitor is functioning correctly based on the voltage measured by the voltage measuring unit when the switch is turned on. The switch includes: A positive relay is inserted into the positive wiring that connects the positive terminal of the energy storage unit to one end of the load; A negative relay, which is inserted into the negative wiring connecting the negative terminal of the energy storage unit to the other end of the load; and A pre-charge relay, which is connected in parallel with either the positive or negative relay. If the voltage fluctuation measured during the period from the activation of one of the three relays (positive relay, negative relay, and pre-charge relay) until all three relays are in the ON state is below a predetermined value, the diagnostic unit determines that the coupling capacitor is abnormal.

3. A power supply system for a vehicle, characterized in that, have: An energy storage unit, which is mounted insulated from the vehicle's chassis ground wire, is used to supply power to loads within the vehicle; and The leakage current detection device according to claim 1 or 2.

4. The vehicle power supply system according to claim 3, characterized in that, The diagnostic unit determines whether the coupling capacitor is functioning properly when the switch is initially turned on after the vehicle is started.

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