Electric leakage detection device, vehicle power supply system

Abstract

In order to perform failure diagnosis of the electric leakage detection device with high precision, a first voltage output section (11a, OP1) generates a periodic voltage that periodically changes, and applies the periodic voltage to the other end of a coupling capacitor (Cc) via a first resistor (R1). A second resistor (R2) and a third resistor (R3) are connected in series between a connection point between the coupling capacitor (Cc) and the first resistor (R1) and a second voltage output section (11e, OP3). A voltage measurement section (11b) measures the voltage of a voltage division point between the second resistor (R2) and the third resistor (R3). During a period in which two fixed voltages are alternately applied to the voltage division point, a diagnosis section (11d) determines whether or not the electric leakage detection device (10) is normal based on the voltage measured by the voltage measurement section (11b).

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 faults in the leakage current detection device itself is to apply a pulse voltage with a frequency sufficiently lower than the frequency during leakage current detection, and compare the applied voltage with the measured voltage. If the two are similar, the device is considered normal (see, for example, Patent Document 1).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2010 / 058855 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] When the leakage current of the coupling capacitor increases due to capacitor deterioration, the leakage current flowing from the leakage current detection device through the coupling capacitor and the vehicle's high-voltage circuit to the chassis ground wire also increases. In the aforementioned fault diagnosis method for the leakage current detection device, when this leakage current increases, the applied pulse voltage decreases, resulting in a large discrepancy between the applied voltage and the measured voltage. This increases the likelihood of misjudging a normal leakage current detection device as abnormal. To suppress this misjudgment, it is necessary to relax the judgment criteria for approximation between the two, but in this case, the likelihood of misjudging an abnormal leakage current detection device as normal increases.

[0011] This disclosure was made in view of the following circumstances, and its purpose is to provide a technique for high-precision fault diagnosis of leakage current detection devices.

[0012] Solution for solving the problem

[0013] To address the aforementioned problems, a leakage current detection device according to one aspect of this disclosure comprises: a coupling capacitor, one end of which is connected to a current path of an energy storage unit connected to a load in a state of insulation from ground; a first voltage output unit that 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 voltage output unit that outputs a fixed voltage; a second resistor and a third resistor connected in series between the connection point between the coupling capacitor and the first resistor and the second voltage output unit; a voltage measuring unit that measures the voltage at a voltage divider point between the second resistor and the third resistor; a leakage current determination unit that, when the periodic voltage is output from the first 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 that, during the alternating application of two fixed voltages to the voltage divider point, determines whether the leakage current detection device is functioning properly based on the voltage measured by the voltage measuring unit.

[0014] The effects of the invention

[0015] According to this disclosure, fault diagnosis of leakage current detection devices can be performed with high precision. 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 2 This is a diagram illustrating an example of applying a pulse waveform and measuring a voltage waveform.

[0018] Figure 3Figures (a)-(d) are examples of measured waveforms during fault diagnosis of the leakage current detection device involved in the comparative example.

[0019] Figure 4 This is a diagram illustrating an example of the leakage current path in a power supply system equipped with a leakage current detection device involved in the comparative example.

[0020] Figure 5 This is a diagram illustrating the structure of a power supply system equipped with a leakage current detection device according to the embodiments.

[0021] Figure 6 Figures (a)-(d) are examples of measured waveforms during fault diagnosis of the leakage current detection device according to the embodiment.

[0022] Figure 7 This is a diagram illustrating an example of a leakage current path in a power supply system equipped with a leakage current detection device according to an embodiment.

[0023] Figure 8 Figures (a)-(d) are examples of the measured waveforms during fault diagnosis of the leakage current detection device involved in Modification 1.

[0024] Figure 9 Figures (a)-(d) are examples of the measured waveforms during fault diagnosis of the leakage current detection device involved in Modification 2. Detailed Implementation

[0025] (Comparative Example)

[0026] 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 this specification, an example using a lithium-ion battery cell (nominal voltage: 3.6V-3.7V) will be assumed.

[0027] 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 positive main relay MRp is inserted into the positive wiring Lp, and a negative main relay MRm is inserted into the negative wiring Lm. The positive and negative main relays MRp and MRm function as contactors to control the switching on / off of the energy storage unit 20 with the high-voltage load within the electric vehicle. Alternatively, a high-voltage, high-insulation semiconductor switch can be used instead of the relays.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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).

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] Return to Figure 1 The diagnostic unit 11d determines whether the leakage current detection device 10 is functioning properly based on the voltage measured by the voltage measuring unit 11b. That is, it diagnoses whether the leakage current detection device 10 itself is faulty. During fault diagnosis of the leakage current detection device 10, a pulse voltage with a frequency sufficiently lower than that used during leakage current detection is applied to the measurement point A. For example, a 10Hz pulse voltage can be applied during leakage current detection, while a 1Hz pulse voltage can be applied during fault diagnosis of the leakage current detection device 10.

[0042] Figure 3 Figures (a)-(d) are examples of measured waveforms during fault diagnosis of the leakage current detection device 10 involved in the comparative example. Figure 3(a) shows an example of the measured waveform when the leakage current detection device 10 is functioning normally. If the path of the oscillation unit 11a, the first operational amplifier OP1, the first resistor R1, the second resistor R2, the second operational amplifier OP2, and the voltage measuring unit 11b is normal, the pulse voltage output from the oscillation unit 11a is measured by the voltage measuring unit 11b as is. In addition, due to the influence of the smoothing capacitor C1, the measured waveform becomes rounded. When the voltage measured during the high level of the applied pulse voltage is near the first reference voltage (5V in this comparative example), and the voltage measured during the low level is near the second reference voltage (0V in this comparative example), the diagnostic unit 11d determines that the leakage current detection device 10 is normal.

[0043] Furthermore, leakage current increases when the coupling capacitor Cc deteriorates. When aluminum electrolytic capacitors are used for the coupling capacitor Cc, leakage current tends to increase when the capacitor is left unloaded for extended periods.

[0044] Figure 4 This diagram illustrates an example of the leakage current path in the power supply system 5 equipped with the leakage detection device 10, as described in the comparative example. Even under normal conditions, a small leakage current flows between the current path of the energy storage unit 20 and the chassis ground wire with a leakage resistance of tens of MΩ to 100 MΩ. Even when the positive main relay MRp and the negative main relay MRm are disconnected (open circuit), a small leakage current flows between the current path on the energy storage unit 20 side and the chassis ground wire (refer to the leakage resistance Rlb). When the insulation resistance of the coupling capacitor Cc decreases, a small leakage current flows through the path of the first operational amplifier OP1, the first resistor R1, the coupling capacitor Cc, the energy storage unit 20, and the leakage resistance Rlb. For example, when the resistance value of the first resistor R1 is set to 200 kΩ, when the insulation resistance of the coupling capacitor Cc drops to about 20 MΩ, the measured waveform of the pulse voltage generated by the 5V power supply decreases by about 1V due to the influence of this leakage current.

[0045] Figure 3 (b) shows an example of a measured waveform when a small leakage current flows from the first operational amplifier OP1 to the chassis ground. Furthermore, the circuitry of the leakage current detection device 10 itself is in a normal state. Figure 3 In (b), the overall measured waveform decreases due to the influence of this leakage current. Furthermore, in Figure 3 In the examples shown in (a)-(d), the measured voltage is clamped at 0V for most of the low-side period of the applied pulse voltage because a measuring circuit that cannot detect voltages less than 0V is used.

[0046] Figure 3 (c) shows an example of the measured waveform when the leakage current detection device 10 malfunctions. Figure 3 In (c), a voltage near 0V is measured during either the high-level or low-level period of the applied pulse voltage. When the voltage measured during the high-level period of the applied pulse voltage deviates from the specified value of the first reference voltage (5V in this comparative example), the diagnostic unit 11d determines the leakage current detection device 10 to be abnormal. For example, if a break occurs somewhere in the path of the oscillation unit 11a, the first operational amplifier OP1, the first resistor R1, the second resistor R2, the second operational amplifier OP2, and the voltage measuring unit 11b, a voltage near 0V is also measured during the high-level period of the applied pulse voltage. Furthermore, if a short-circuit fault or open-circuit fault occurs in any circuit element, the voltage measured during the high-level period also deviates significantly from the first reference voltage.

[0047] Figure 3 (d) shows an example of the measured waveform when the constants of the circuit elements used in the leakage current detection device 10 change. In the comparative example, even if the constants of the circuit elements change, the measured waveform of the applied pulse voltage hardly changes compared to the normal state. For example, even if the resistance value of the first resistor R1 decreases from 200kΩ to 100kΩ due to deterioration, the measured waveform of the pulse voltage hardly changes.

[0048] like Figure 3 As shown in (b), in the diagnostic method of the leakage current detection device 10 involved in the comparative example, it is significantly affected by the small leakage current flowing from the first operational amplifier OP1 to the chassis ground wire. Figure 3 In the example shown in (b), since the circuit of the leakage current detection device 10 is in a normal state, the diagnostic unit 11d was expected to determine that the leakage current detection device 10 is normal. However, the measured voltage during the high-side period of the applied pulse voltage is around 4V, which deviates significantly from the theoretical value of 5V. In order to determine that this state is normal, a margin of about 1V needs to be set for the specified value used for determination, and the determination criteria need to be greatly relaxed. In this case, small faults in circuit components may be missed. In addition, as Figure 3 As shown in (d), in the diagnostic method of the leakage current detection device 10 involved in the comparative example, it is difficult to detect changes in the constants of the circuit elements. Specifically, it is difficult to detect the deterioration of the first resistor R1.

[0049] (Implementation Method)

[0050] Figure 5 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 1The 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 two fixed voltages: a first reference voltage (5V in this embodiment) and a second reference voltage (0V in this embodiment).

[0051] 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 both a first reference voltage and a second reference voltage, both fixed voltages.

[0052] 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.

[0053] 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.

[0054] During the period when two fixed voltages are alternately output from the first voltage output unit, the diagnostic unit 11d diagnoses whether the leakage current detection device 10 is functioning properly based on the voltage measured by the voltage measuring unit 11b. Specifically, the diagnostic unit 11d calculates the difference between the voltage measured in the first state and the voltage measured in the second state during this period, and determines that the leakage current detection device 10 is functioning properly when the difference is within a set range. The first state and the second state each last for a few seconds (e.g., 4 seconds).

[0055] Figure 6Figures (a)-(d) are diagrams illustrating an example of the measured waveforms during fault diagnosis of the leakage current detection device 10 according to the embodiment. In the examples shown below, the resistance value of the first resistor R1 is set to 200kΩ, the resistance value of the second resistor R2 is set to 1000kΩ, and the resistance value of the third resistor R3 is set to 1000kΩ. Furthermore, the following conditions apply: in the first state, the first voltage output unit outputs a first reference voltage (5V in this embodiment), and the second voltage output unit outputs a second reference voltage (0V in this embodiment); in the second state, the first voltage output unit outputs the second reference voltage, and the second voltage output unit outputs the first reference voltage.

[0056] Figure 6 Figure (a) shows an example of the measured waveform when the leakage current detection device 10 is functioning normally. If the first voltage output section, the first resistor R1, the second resistor R2, the third resistor R3, the second voltage output section, the second operational amplifier OP2, and the voltage measuring section 11b are functioning normally, approximately 2.27V is measured in the first state and approximately 2.73V is measured in the second state. The theoretical values ​​of the measured voltage in the first state and the second state are calculated using the following equations (1) and (2).

[0057] 5×(1000 / (200+1000+1000))≈2.27…(Equation 1)

[0058] 5×((200+1000) / (200+1000+1000))≈2.73…(Equation 2)

[0059] The diagnostic unit 11d calculates the voltage difference ΔV between the two. In this example, it is 0.46V. If the voltage difference ΔV is within the set range, the diagnostic unit 11d determines that the leakage current detection device 10 is normal. Based on data obtained by the designer through experiments or simulations, the set range is set to obtain the most suitable accuracy.

[0060] In this embodiment, similar to the comparative example, the leakage current also increases when the coupling capacitor Cc deteriorates. Figure 7 This is a diagram illustrating an example of the leakage current path of a power supply system 5 equipped with a leakage current detection device 10 according to an embodiment.

[0061] Figure 6 (b) shows an example of a measured waveform when a small leakage current flows from the first operational amplifier OP1 to the chassis ground. Furthermore, the circuitry of the leakage current detection device 10 itself is in a normal state. Figure 6In (b), due to the leakage current, the measured waveform drops by 1V overall. Approximately 1.27V was measured in the first state and approximately 1.72V in the second state. The voltage difference ΔV between the two is 0.46V.

[0062] Figure 6 (c) shows an example of the measured waveform when the leakage current detection device 10 malfunctions. Figure 6 In (c), a voltage near 0V is measured in either the first or second state. The voltage difference ΔV between the two is 0V. Since the voltage difference ΔV deviates from the specified setting range (center value 0.46V), the diagnostic unit 11d determines that the leakage current detection device 10 is abnormal.

[0063] Figure 6 (d) shows an example of a measured waveform when the constants of the circuit elements used in the leakage current detection device 10 change. Figure 6 Example (d) shows the measured waveform when the resistance of the first resistor R1 decreases from 200kΩ to 100kΩ due to degradation. Approximately 2.38V was measured in the first state and approximately 2.62V in the second state. With the resistance of the first resistor R1 at 100kΩ, the theoretical values ​​of the measured voltage in the first state and the second state are calculated using Equations (3) and (4) below.

[0064] 5×(1000 / (100+1000+1000))≈2.38…(Equation 3)

[0065] 5×((100+1000) / (100+1000+1000))≈2.62…(Equation 4)

[0066] The voltage difference ΔV between the two is 0.24V. Since the voltage difference ΔV deviates from the specified setting range (center value is 0.46V), the diagnostic unit 11d determines that the leakage current detection device 10 is abnormal.

[0067] As explained above, according to this embodiment, during the alternating application of two fixed voltages to the voltage divider point, fault diagnosis of the leakage current detection device 10 can be performed with high precision by determining whether the voltage difference ΔV between the first state and the second state converges to a set range. Specifically, even in the case of a small leakage current flowing from the first operational amplifier OP1 to the chassis ground wire, such as Figure 6 As shown in (b), the differential voltage ΔV is also approximately the same as in the normal state. Therefore, fault diagnosis of the leakage current detection device 10 can be performed with almost no effect from minute leakage currents. Regarding this, in the comparative example, as... Figure 3As shown in (b), it is significantly affected by minute leakage currents. In this embodiment, there is no need to increase the margin of the setting range, thereby reducing the omission of minor defects in circuit elements.

[0068] In addition, such as Figure 6 As shown in (d), in this embodiment, changes in the constants of circuit elements can also be detected. Specifically, it is possible to detect the deterioration of the first resistor R1, which functions as a sensing resistor. Regarding this, in the comparative example, as... Figure 3 As shown in (d), it is difficult to detect changes in the constants of circuit elements.

[0069] (Variation Example 1)

[0070] Figure 8 Figures (a)-(d) are illustrations showing an example of the measured waveforms during fault diagnosis of the leakage current detection device 10 according to Modification 1. The structure of the leakage current detection device 10 is similar to... Figure 5 The structure shown is the same. In Modification 1, the resistance values ​​of the first resistor R1 are also set to 200kΩ, the second resistor R2 is set to 1000kΩ, and the third resistor R3 is set to 1000kΩ. Furthermore, the following conditions apply: in the first state, the first voltage output unit outputs a first reference voltage (5V in Modification 1), and the second voltage output unit outputs the first reference voltage; in the second state, the first voltage output unit outputs the first reference voltage, and the second voltage output unit outputs a second reference voltage (0V in Modification 1).

[0071] Figure 8 Figure (a) shows an example of the measured waveform when the leakage current detection device 10 is functioning normally. If the first voltage output section, the first resistor R1, the second resistor R2, the third resistor R3, the second voltage output section, the second operational amplifier OP2, and the voltage measuring section 11b are functioning normally, approximately 5V is measured in the first state and approximately 2.27V is measured in the second state. In the first state, since 5V is applied across the first resistor R1, the second resistor R2, and the third resistor R3 connected in series, the theoretical value of the measured voltage in the first state is also 5V. The theoretical value of the measured voltage in the second state is calculated using the above-described (Equation 1).

[0072] The diagnostic unit 11d calculates the voltage difference ΔV between the two. In this example, it is 2.73V. If the voltage difference ΔV is within the set range, the diagnostic unit 11d determines that the leakage current detection device 10 is normal.

[0073] Figure 8(b) shows an example of a measured waveform when a small leakage current flows from the first operational amplifier OP1 to the chassis ground. Furthermore, the circuitry of the leakage current detection device 10 itself is in a normal state. Figure 8 In (b), due to the influence of the leakage current, the measured waveform dropped by 1V overall. Approximately 4V was measured in the first state, and approximately 1.27V was measured in the second state. The voltage difference ΔV between the two is 2.73V. Since the voltage difference ΔV converges to the specified set range (center value 2.73V), the diagnostic unit 11d determines the leakage current detection device 10 to be normal.

[0074] Figure 8 (c) shows an example of the measured waveform when the leakage current detection device 10 malfunctions. Figure 8 In (c), a voltage near 0V is measured in either the first or second state. The voltage difference ΔV between the two is 0V. Since the voltage difference ΔV deviates from the specified setting range (center value is 2.73V), the diagnostic unit 11d determines that the leakage current detection device 10 is abnormal.

[0075] Figure 8 (d) shows an example of a measured waveform when the constants of the circuit elements used in the leakage current detection device 10 change. Figure 8 Example (d) shows the measured waveform when the resistance value of the first resistor R1 decreases from 200kΩ to 100kΩ due to degradation. Approximately 5V is measured in the first state, and approximately 2.38V is measured in the second state. In the first state, since 5V is applied across the series-connected first resistor R1, second resistor R2, and third resistor R3, the theoretical value of the measured voltage in the first state is also 5V, regardless of the resistance value of the first resistor. The theoretical value of the measured voltage in the second state is calculated using the above-described (Equation 3). The voltage difference ΔV is 2.62V. Because the voltage difference ΔV deviates from the specified setting range (center value 2.73V), the diagnostic unit 11d determines the leakage current detection device 10 to be abnormal.

[0076] As explained above, according to Modification 1, even if the first voltage output unit continuously outputs the same voltage in both the first and second states, switching the output voltage of the second voltage output unit achieves the same effect as in the above-described embodiment. Alternatively, the first voltage output unit may continuously output a second reference voltage instead of continuously outputting a first reference voltage.

[0077] (Variation Example 2)

[0078] Figure 9 Figures (a)-(d) are illustrations showing an example of the measured waveforms during fault diagnosis of the leakage current detection device 10 according to Modification 2. The structure of the leakage current detection device 10 is similar to... Figure 5 The structure shown is the same. In Modification 2, the resistance values ​​of the first resistor R1 are also set to 200kΩ, the second resistor R2 is set to 1000kΩ, and the third resistor R3 is set to 1000kΩ. Furthermore, the following conditions apply: in the first state, the first voltage output unit outputs a first reference voltage (also 5V in Modification 2), and the second voltage output unit outputs the first reference voltage; in the second state, the first voltage output unit outputs a second reference voltage (also 0V in Modification 2), and the second voltage output unit outputs the first reference voltage.

[0079] Figure 9 Figure (a) shows an example of the measured waveform when the leakage current detection device 10 is functioning normally. If the first voltage output section, the first resistor R1, the second resistor R2, the third resistor R3, the second voltage output section, the second operational amplifier OP2, and the voltage measuring section 11b are functioning normally, approximately 5V is measured in the first state and approximately 2.73V is measured in the second state. In the first state, since 5V is applied across the first resistor R1, the second resistor R2, and the third resistor R3 connected in series, the theoretical value of the measured voltage in the first state is also 5V. The theoretical value of the measured voltage in the second state is calculated using the above-described (Equation 2).

[0080] The diagnostic unit 11d calculates the voltage difference ΔV between the two. In this example, it is 2.27V. If the voltage difference ΔV is within the set range, the diagnostic unit 11d determines that the leakage current detection device 10 is normal.

[0081] Figure 9 (b) shows an example of a measured waveform when a small leakage current flows from the first operational amplifier OP1 to the chassis ground. Furthermore, the circuitry of the leakage current detection device 10 itself is in a normal state. Figure 9 In (b), due to the influence of the leakage current, the measured waveform dropped by 1V overall. Approximately 4V was measured in the first state, and approximately 1.73V was measured in the second state. The voltage difference ΔV between the two is 2.27V. Since the voltage difference ΔV converges to the specified set range (center value 2.27V), the diagnostic unit 11d determines the leakage current detection device 10 to be normal.

[0082] Figure 9 (c) shows an example of the measured waveform when the leakage current detection device 10 malfunctions. Figure 9 In (c), a voltage near 0V is measured in either the first or second state. The voltage difference ΔV between the two is 0V. Since the voltage difference ΔV deviates from the specified setting range (center value 2.27V), the diagnostic unit 11d determines that the leakage current detection device 10 is abnormal.

[0083] Figure 9 (d) shows an example of a measured waveform when the constants of the circuit elements used in the leakage current detection device 10 change. Figure 9 Example (d) shows the measured waveform when the resistance value of the first resistor R1 decreases from 200kΩ to 100kΩ due to degradation. Approximately 5V is measured in the first state, and approximately 2.62V is measured in the second state. In the first state, since 5V is applied across the series-connected first resistor R1, second resistor R2, and third resistor R3, the theoretical value of the measured voltage in the first state is also 5V, regardless of the resistance value of the first resistor. The theoretical value of the measured voltage in the second state is calculated using the above-described (Equation 4). The voltage difference ΔV is 2.38V. Because the voltage difference ΔV deviates from the specified setting range (center value 2.27V), the diagnostic unit 11d determines the leakage current detection device 10 to be abnormal.

[0084] As explained above, according to Modification 2, even if the second voltage output unit continuously outputs the same voltage in both the first and second states, switching the output voltage of the first voltage output unit achieves the same effect as in the above-described embodiment. Furthermore, according to Modification 2, compared to Modification 1, the theoretical value of the measured voltage in the second state is higher, thus increasing the tolerance to overall descent of the measured waveform. Alternatively, the second voltage output unit may continuously output a second reference voltage instead of continuously outputting a first reference voltage.

[0085] 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.

[0086] In the above embodiment, an example was described using a power supply voltage of 5V as the first reference voltage and a ground voltage of 0V as the second reference voltage. However, the first and second reference voltages are not limited to 5V and 0V, and any two different voltages can be used.

[0087] 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.

[0088] 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 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.

[0089] In addition, the implementation method can be determined through the following items.

[0090] [Project 1]

[0091] A leakage current detection device (10), characterized in that it comprises:

[0092] 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;

[0093] The first 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);

[0094] The second voltage output section (11e, OP3) outputs a fixed voltage;

[0095] 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 the second voltage output section (11e, OP3).

[0096] The voltage measuring unit (11b) measures the voltage at the voltage divider point between the second resistor (R2) and the third resistor (R3);

[0097] The leakage current determination unit (11c), when the periodic voltage is output from the first 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

[0098] The diagnostic unit (11d) determines whether the leakage current detection device (10) is normal based on the voltage measured by the voltage measuring unit (11b) during the period when two fixed voltages are applied alternately to the voltage divider point.

[0099] Therefore, it is possible to perform fault diagnosis of the leakage current detection device (10) with high accuracy.

[0100] [Project 2]

[0101] According to the leakage current detection device (10) described in Project 1, the characteristic is that,

[0102] When the difference between the voltage measured in the first state during the period and the voltage measured in the second state during the period deviates from the set range, the diagnostic unit (11d) determines that the leakage current detection device (10) is abnormal.

[0103] Compared with the first state, the second state has a different output voltage for at least one of the first voltage output unit (11a, OP1) and the second voltage output unit (11e, OP3).

[0104] Therefore, it is possible to perform fault diagnosis of the leakage current detection device (10) with high accuracy.

[0105] [Project 3]

[0106] According to the leakage current detection device (10) described in Project 2, its characteristic is that,

[0107] The first voltage output unit (11a, OP1) outputs a first reference voltage in the first state and outputs a second reference voltage in the second state.

[0108] The second voltage output unit (11e, OP3) outputs the second reference voltage in the first state and outputs the first reference voltage in the second state.

[0109] Therefore, it is possible to measure the appropriate differential voltage for judgment.

[0110] [Project 4]

[0111] According to the leakage current detection device (10) described in Project 2, its characteristic is that,

[0112] The first voltage output unit (11a, OP1) continuously outputs a first reference voltage or a second reference voltage in the first state and the second state.

[0113] The second voltage output unit (11e, OP3) outputs the first reference voltage in the first state and outputs the second reference voltage in the second state.

[0114] Therefore, it is possible to measure the appropriate differential voltage for judgment.

[0115] [Project 5]

[0116] According to the leakage current detection device (10) described in Project 2, its characteristic is that,

[0117] The first voltage output unit (11a, OP1) outputs a first reference voltage in the first state and outputs a second reference voltage in the second state.

[0118] The second voltage output unit (11e, OP3) continuously outputs the first reference voltage or the second reference voltage in the first state and the second state.

[0119] Therefore, it is possible to measure the appropriate differential voltage for judgment.

[0120] [Project 6]

[0121] The leakage current detection device (10) according to any one of claims 3 to 5 is characterized in that,

[0122] The first reference voltage is the high-side reference voltage.

[0123] The second reference voltage is the low-side reference voltage.

[0124] Therefore, it is possible to easily generate the first reference voltage and the second reference voltage.

[0125] [Project 7]

[0126] A vehicle power supply system (5), characterized in that it comprises:

[0127] 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

[0128] The leakage current detection device (10) according to any one of items 1 to 6.

[0129] Thus, a vehicle power supply system (5) can be realized that has a leakage current detection device (10) capable of performing its own fault diagnosis with high precision.

[0130] Explanation of reference numerals in the attached figures

[0131] 2: Inverter; 3: Motor; Lp: Positive wiring; Lm: Negative wiring; Cp: Positive Y capacitor; Cm: Negative Y capacitor; Rlp: Positive leakage resistance; Rlm: Negative leakage resistance; Rlb: Leakage resistance; MRp: Positive main relay; MRm: Negative main relay; 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, characterized in that, have: 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; A first 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; The second voltage output section outputs a reference voltage; The second resistor and the third resistor are connected in series between the connection point between the coupling capacitor and the first resistor and the second voltage output section; 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 outputting the periodic voltage from the first 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 determines whether the leakage current detection device is functioning properly based on the voltage measured by the voltage measuring unit during the period when the first voltage output unit and the second voltage output unit alternately apply two reference voltages to the voltage divider point.

2. The leakage current detection device according to claim 1, characterized in that, When the difference between the voltage measured in the first state during the period and the voltage measured in the second state during the period deviates from a set range, the diagnostic unit determines that the leakage current detection device is abnormal. Compared with the first state, the second state has a different output voltage for at least one of the first voltage output unit and the second voltage output unit.

3. The leakage current detection device according to claim 2, characterized in that, The first voltage output unit outputs a first reference voltage in the first state and outputs a second reference voltage in the second state. The second voltage output unit outputs the second reference voltage in the first state and outputs the first reference voltage in the second state.

4. The leakage current detection device according to claim 2, characterized in that, The first voltage output unit continuously outputs a first reference voltage or a second reference voltage in both the first state and the second state. The second voltage output unit outputs the first reference voltage in the first state and outputs the second reference voltage in the second state.

5. The leakage current detection device according to claim 2, characterized in that, The first voltage output unit outputs a first reference voltage in the first state and outputs a second reference voltage in the second state. The second voltage output unit continuously outputs the first reference voltage or the second reference voltage in both the first state and the second state.

6. The leakage current detection device according to any one of claims 3 to 5, characterized in that, The first reference voltage is the high-side reference voltage. The second reference voltage is the low-side reference voltage.

7. 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 any one of claims 1 to 6.

Images