Leakage detection device, vehicle power supply system

Abstract

In order to accurately perform failure diagnosis of this earth leakage detecting device, a first voltage output unit (11a, OP1) generates a periodic voltage which changes periodically, and applies the same to an other terminal 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 second voltage output unit (11e, OP3) and a connection point which is between the coupling capacitor (Cc) and the first resistor (R1). A voltage measurement unit (11b) measures the voltage at a voltage dividing point between the second resistor (R2) and the third resistor (R3). During a period in which two types of fixed voltages are applied in sequence to the voltage dividing point, a diagnostic unit (11d) determines whether or not the earth leakage detecting device (10) is normal on the basis of the voltage measured by the voltage measurement unit (11b).

Description

[Technical field]

[0001] The present invention relates to an electric leakage detection device for detecting an electric leakage in a load insulated from earth, and to a vehicle power supply system. [Background technology]

[0002] In recent years, hybrid vehicles (HVs), plug-in hybrid vehicles (PHVs), and electric vehicles (EVs) have become popular. These electric vehicles are equipped with a high-voltage drive battery (traction battery) in addition to an auxiliary battery (typically a lead battery with a 12V output). To prevent electric shock, the high-voltage circuit, which includes the high-voltage drive battery, inverter, and driving motor, is insulated from the vehicle body (chassis earth).

[0003] A Y capacitor is inserted between the positive wiring on the vehicle side of the high-voltage circuit and the chassis earth, and between the negative wiring on the vehicle side of the high-voltage circuit and the chassis earth, respectively, to stabilize the power supplied from the high-voltage drive battery to the load on the vehicle side.A leakage detection device is installed to detect leakage by monitoring the insulation resistance between the high-voltage circuit and the chassis earth.

[0004] In an AC type leakage current 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 between the resistor and the coupling capacitor is measured to detect the presence or absence of a leakage current.

[0005] In an AC type leakage current detection device, one method for diagnosing a fault in the leakage current detection device itself is to apply a pulse voltage with a frequency sufficiently lower than the frequency at which leakage current is detected, compare the applied voltage with the measured voltage, and determine that the device is normal if the two are close to each other (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2010 / 058855 Summary of the Invention [Problem to be solved by the invention]

[0007] When the leakage current of the coupling capacitor increases due to deterioration of the coupling capacitor, the leakage current flowing from the leakage detection device to the chassis earth via the coupling capacitor and the high-voltage circuit of the vehicle increases. In the fault diagnosis method for the leakage detection device described above, when this leakage current increases, the applied pulse voltage decreases, and a large discrepancy occurs between the applied voltage and the measured voltage. This increases the possibility of erroneously determining that a normal leakage detection device is abnormal. In order to suppress this erroneous determination, it is necessary to relax the determination criteria for the approximation between the two, but in that case, the possibility of erroneously determining that an abnormal leakage detection device is normal increases.

[0008] The present disclosure has been made in consideration of these circumstances, and has an object to provide a technique for performing fault diagnosis of an earth leakage detection device with high accuracy. [Means for solving the problem]

[0009] In order to solve the above problems, a leakage detection device according to an embodiment of the present disclosure includes a coupling capacitor having one end connected to a current path of a storage unit connected to a load in a state insulated from earth, a first voltage output unit generating a periodically changing periodic voltage and applying the periodic voltage to the other end of the coupling capacitor via a first resistor, a second voltage output unit outputting a fixed voltage, a second resistor and a third resistor connected in series between a connection point between the coupling capacitor and the first resistor and the second voltage output unit, a voltage measurement unit measuring a voltage at a voltage division point between the second resistor and the third resistor, a leakage determination unit determining whether or not there is a leakage current between the current path of the storage unit and the earth based on the voltage measured by the voltage measurement unit while the periodic voltage is output from the first voltage output unit, and a diagnosis unit determining whether or not the leakage detection device is normal based on the voltage measured by the voltage measurement unit during a period during which two types of fixed voltages are applied in sequence to the voltage division point. Effect of the Invention

[0010] According to the present disclosure, fault diagnosis of an earth leakage detection device can be performed with high accuracy. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram for explaining the configuration of a power supply system including a leakage detection device according to a comparative example. [Diagram 2] 4A and 4B are diagrams illustrating an example of an applied pulse waveform and a measured voltage waveform. [Diagram 3] 3(a) to 3(d) are diagrams showing examples of measured waveforms during failure diagnosis of the earth leakage detection device according to the comparative example. [Figure 4] 1 is a diagram showing an example of a leakage path of a power supply system including a leakage detection device according to a comparative example; [Diagram 5] 1 is a diagram for explaining a configuration of a power supply system including a leakage current detection device according to an embodiment; [Figure 6] 6(a) to 6(d) are diagrams showing examples of measured waveforms during failure diagnosis of the earth leakage detection device according to the embodiment. [Figure 7] 1 is a diagram showing an example of a leakage path of a power supply system including a leakage detection device according to an embodiment; [Figure 8] 8(a) to 8(d) are diagrams showing examples of measured waveforms during failure diagnosis of the earth leakage detection device according to the first modification. [Figure 9] 9(a) to 9(d) are diagrams showing examples of measured waveforms during failure diagnosis of the earth leakage detection device according to the second modification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (Comparative Example) FIG. 1 is a diagram for explaining the configuration of a power supply system 5 including a leakage detection device 10 according to a comparative example. The power supply system 5 is mounted on an electric vehicle. The power supply system 5 is provided in the electric vehicle separately from an auxiliary battery (usually a lead battery with an output of 12 V is used). The power supply system 5 includes a high-voltage power storage unit 20 and the leakage detection device 10. The power storage unit 20 includes a plurality of cells E1-En connected in series. The cells may be lithium-ion battery cells, nickel-metal hydride battery cells, lead battery cells, electric double layer capacitor cells, lithium-ion capacitor cells, etc. In the following description, an example using a lithium-ion battery cell (nominal voltage: 3.6-3.7 V) is assumed.

[0013] The electric vehicle includes an inverter 2 and a motor 3 as a high-voltage load. The positive electrode of the power storage unit 20 and one end of the inverter 2 are connected by a positive wiring Lp, and the negative electrode of the power storage unit 20 and the other end of the inverter 2 are connected by a negative wiring Lm. A positive-side main relay MRp is inserted in the positive wiring Lp, and a negative-side main relay MRm is inserted in the negative wiring Lm. The positive-side main relay MRp and the negative-side main relay MRm function as contactors that control the conduction / cutoff between the power storage unit 20 and the high-voltage load in the electric vehicle. Note that it is also possible to use a high-voltage and high-insulation semiconductor switch instead of a relay.

[0014] The inverter 2 is a bidirectional inverter connected between the power storage unit 20 and the motor 3. During power running, the inverter 2 converts DC power supplied from the power storage unit 20 into AC power and supplies it to the motor 3. During regeneration, the inverter 2 converts AC power supplied from the motor 3 into DC power and supplies it to the power storage unit 20. For example, a three-phase AC motor is used as the motor 3. During power running, the motor 3 rotates according to the AC power supplied from the inverter 2. During regeneration, the rotational energy generated by deceleration is converted into AC power and supplied to the inverter 2.

[0015] The power storage unit 20 is mounted on the electric vehicle in a state insulated from the chassis earth of the electric vehicle. The auxiliary battery is mounted on the electric vehicle with its negative electrode conductive to the chassis earth. The positive wiring Lp on the inverter 2 side of the positive main relay MRp is connected to the chassis earth via a positive side Y capacitor Cp. The negative wiring Lm on the inverter 2 side of the negative main relay MRm is connected to the chassis earth via a negative side Y capacitor Cm. The positive side Y capacitor Cp and the negative side Y capacitor Cm provide DC insulation between the positive wiring Lp and the chassis earth, and between the negative wiring Lm and the chassis earth, respectively, and have the effect of stabilizing the voltage of the positive wiring Lp and the negative wiring Lm.

[0016] When the power storage unit 20 is ideally insulated from the chassis earth, the intermediate potential of the power storage unit 20 is maintained near the potential of the chassis earth. For example, when the voltage across the power storage unit 20 is 250V, the positive electrode potential of the power storage unit 20 is maintained near +125V, and the negative electrode potential is maintained near -125V. When the high-voltage power storage unit 20 and the chassis earth are in a conductive state, there is a risk of electric shock if a person touches an exposed conductive part of the electric vehicle. Therefore, an electric vehicle equipped with a high-voltage power storage unit 20 needs to be equipped with a leakage detection device 10 to monitor the insulation state between the current path of the power storage unit 20 connected to a high-voltage vehicle load and the chassis earth. In FIG. 1, the insulation state between the positive wiring Lp and the chassis earth is represented as a positive-side leakage resistance Rlp, and the insulation state between the negative wiring Lm and the chassis earth is represented as a negative-side leakage resistance Rlm.

[0017] In the 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 diagnosis unit 11d. The control unit 11 can be configured, for example, by a microcomputer and a non-volatile memory (for example, an EEPROM or a flash memory).

[0018] The coupling capacitor Cc has one end connected to the current path of the power storage unit 20. In the example shown in FIG. 1, one end of the coupling capacitor Cc is connected to the negative electrode of the power storage unit 20. The one end of the coupling capacitor Cc may be connected to the positive electrode of the power storage unit 20, or may be connected to any node of the multiple cells E1-En in the power storage unit 20. The other end of the coupling capacitor Cc is connected to the output end of the voltage output unit via a 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. The first resistor R1 may be replaced with another impedance element.

[0019] In Fig. 1, an aluminum electrolytic capacitor that can be made large-capacity at a relatively low cost is used for the coupling capacitor Cc. The aluminum electrolytic capacitor has polarity, and in Fig. 1, the positive electrode of the aluminum electrolytic capacitor is connected to measurement point A, and the negative electrode of the aluminum electrolytic capacitor is connected to the negative electrode of the power storage unit 20. The coupling capacitor Cc may be configured by connecting multiple aluminum electrolytic capacitors in series. In this case, even if one capacitor shorts out, the remaining capacitors can maintain DC insulation.

[0020] The voltage output unit generates a periodic voltage that changes periodically and applies the generated periodic voltage to the other end of the coupling capacitor Cc via the first resistor R1. In the following, in this specification, an example is assumed in which a square wave voltage is used as the periodic voltage.

[0021] The voltage output unit includes an oscillator 11a and a first operational amplifier OP1. The oscillator 11a includes a multivibrator and a local oscillator, and generates a square wave of a preset frequency. The square wave voltage generated by the oscillator 11a is input to a 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 and output terminal of the first operational amplifier OP1 are connected. 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 description, an example in which the power supply potential Vcc is 5V and the ground potential GND is 0V is assumed.

[0022] The first operational amplifier OP1 functions as a voltage follower that has an amplification factor of 1 and performs only impedance conversion. Note that, instead of the first operational amplifier OP1, 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 may be used. Any element that functions as a buffer that separates the impedance of the control unit 11 and the measurement point A can be used to replace the first operational amplifier OP1.

[0023] Measurement point A is connected to the non-inverting input terminal of the second operational amplifier OP2 via a second resistor R2. The inverting input terminal and output terminal of the second operational amplifier OP2 are connected. The second operational amplifier OP2 also functions as a voltage follower with an amplification factor of 1 and only performs impedance conversion. A smoothing capacitor C1 is connected between the non-inverting input terminal of the second operational amplifier OP2 and a second fixed potential (ground potential GND). The smoothing capacitor C1 removes noise from the voltage input to the non-inverting input terminal of the second operational amplifier OP2.

[0024] The second operational amplifier OP2 outputs the voltage at the measurement point A to the voltage measurement unit 11b. The voltage measurement unit 11b measures the voltage at the measurement point A. The voltage measurement unit 11b includes an A / D converter, which samples the analog voltage at the measurement point A at timings synchronized with the timings of the rising edge and falling edge of the square wave voltage generated by the oscillation unit 11a, and converts the sampled analog voltage into a digital value. The voltage sampled at the timing of the rising edge of the square wave voltage corresponds to the lower peak value of the measured voltage waveform, and the voltage sampled at the timing of the falling edge of the square wave voltage corresponds to the upper peak value of the measured voltage waveform. Note that the timings at which the lower peak value should be sampled and the upper peak value should be sampled may be adjusted in consideration of the blunting of the square wave voltage. The voltage measurement unit 11b outputs the voltage at the measurement point A to the leakage current determination unit 11c and the diagnosis unit 11d.

[0025] The leakage current determination unit 11c determines the presence or absence of leakage current between the current path of the storage unit 20 and the chassis earth based on the voltage at the measurement point A measured by the voltage measurement unit 11b. When a peak-to-peak value indicated by the difference between the upper peak value and the lower peak value is smaller than a set value, the leakage current determination unit 11c determines that leakage current occurs between the current path of the storage unit 20 and the chassis earth. The set value is determined based on a peak-to-peak value of a measured voltage waveform at the time of leakage current occurrence, which is derived in advance by a designer through experiments or simulations. When leakage current occurs between the current path of the storage unit 20 and the chassis earth, an AC current flows from the first operational amplifier OP1 to the coupling capacitor Cc via the first resistor R1 acting as a detection resistor. When a current flows through the first resistor R1, the voltage amplitude at the measurement point A is reduced due to a voltage drop.

[0026] 2 is a diagram showing an example of an applied pulse waveform and a measured voltage waveform. The pulse waveform applied from the voltage output unit to measurement point A has a high-side potential of 5 V and a low-side potential of 0 V. The leakage current determination unit 11c identifies an upper peak value Vp1 and a lower peak value Vp2 of the voltage waveform measured during the period when the pulse voltage is applied to measurement point A, and determines the presence or absence of leakage based on a peak-to-peak value defined as the difference between the upper peak value Vp1 and the lower peak value Vp2.

[0027] Returning to FIG. 1, the diagnosis unit 11d judges whether the earth leakage detection device 10 is normal or not based on the voltage measured by the voltage measurement unit 11b. That is, it diagnoses whether the earth leakage detection device 10 itself has a malfunction. When diagnosing a malfunction of the earth leakage detection device 10, a pulse voltage of a sufficiently lower frequency is applied to the measurement point A compared to when earth leakage is detected. For example, a pulse voltage of 10 Hz may be applied when earth leakage is detected, and a pulse voltage of 1 Hz may be applied when diagnosing a malfunction of the earth leakage detection device 10.

[0028] 3(a)-(d) are diagrams showing an example of a measured waveform during a fault diagnosis of the leakage detection device 10 according to the comparative example. FIG. 3(a) shows an example of a measured waveform when the leakage detection device 10 is normal. If the path of the oscillator 11a, the first operational amplifier OP1, the first resistor R1, the second resistor R2, the second operational amplifier OP2, and the voltage measurement unit 11b is normal, the pulse voltage output from the oscillator 11a is measured by the voltage measurement unit 11b as it is. Note that the measured waveform is blunted due to the influence of the smoothing capacitor C1. The diagnosis unit 11d judges the leakage detection device 10 to be normal when the voltage measured during the high-level period of the applied pulse voltage is close to the first reference voltage (5V in this comparative example) and the voltage measured during the low-level period is close to the second reference voltage (0V in this comparative example).

[0029] By the way, as the coupling capacitor Cc deteriorates, the leakage current increases. When an aluminum electrolytic capacitor is used as the coupling capacitor Cc, the leakage current is likely to increase if it is left unloaded for a long period of time.

[0030] FIG. 4 is a diagram showing an example of a leakage path of a power supply system 5 including a leakage detection device 10 according to a comparative example. Even in a normal state, a minute leakage current flows between the current path of the power storage unit 20 and the chassis ground due to a leakage resistance of several tens of MΩ to 100 MΩ. Even when the positive side main relay MRp and the negative side main relay MRm are in an off (open) state, a minute leakage current flows between the current path on the power storage unit 20 side and the chassis ground (see leakage resistance Rlb). When the insulation resistance of the coupling capacitor Cc decreases, a minute leakage current flows through the path of the first operational amplifier OP1, the first resistor R1, the coupling capacitor Cc, the power 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 decreases to about 20 MΩ, the measured waveform of the pulse voltage generated by the 5 V power supply decreases by about 1 V due to the influence of the leakage current.

[0031] Fig. 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. The circuit of the leakage detection device 10 itself is in a normal state. In Fig. 3(b), the entire measured waveform is lowered due to the influence of the leakage current. Note that in the examples shown in Figs. 3(a)-(d), a measurement circuit that cannot detect voltages below 0V is used, so the measured voltage is clamped to 0V for most of the low-side period of the applied pulse voltage.

[0032] FIG. 3(c) shows an example of a measured waveform when the leakage detection device 10 is abnormal. In FIG. 3(c), a voltage near 0V is measured during both the high-level period and the low-level period of the applied pulse voltage. The diagnosis unit 11d judges the leakage detection device 10 to be abnormal when the voltage measured during the high-level period of the applied pulse voltage deviates from the first reference voltage (5V in this comparative example) by a specified value or more. For example, if there is a break in any of the paths of the oscillator 11a, the first operational amplifier OP1, the first resistor R1, the second resistor R2, the second operational amplifier OP2, and the voltage measurement unit 11b, a voltage near 0V is measured during the high-level period of the applied pulse voltage. In addition, if a short circuit or an open circuit occurs in any of the circuit elements, the voltage measured during the high-level period also deviates significantly from the first reference voltage.

[0033] 3(d) shows an example of a measured waveform when the constants of the circuit elements used in the earth leakage detection device 10 are changed. In the comparative example, even if the constants of the circuit elements are changed, 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 is reduced from 200 kΩ to 100 kΩ due to degradation, the measured waveform of the pulse voltage hardly changes.

[0034] As shown in FIG. 3(b), the method for diagnosing the leakage detection device 10 according to the comparative example is greatly affected by the minute leakage current flowing from the first operational amplifier OP1 to the chassis earth. In the example shown in FIG. 3(b), since the circuit of the leakage detection device 10 itself is in a normal state, it is expected that the diagnostic unit 11d will determine that the leakage detection device 10 is normal. However, the measured voltage during the high side period of the applied pulse voltage is around 4V, which is significantly different from the original theoretical value of 5V. In order to determine this state as normal, it is necessary to provide a margin of about 1V in the specified value for determination, and it is necessary to significantly relax the determination standard. In this case, a small failure of the circuit element will be overlooked. Also, as shown in FIG. 3(d), the method for diagnosing the leakage detection device 10 according to the comparative example has difficulty in detecting changes in the constants of the circuit elements. Specifically, it is difficult to detect deterioration of the first resistor R1.

[0035] (Embodiment) FIG. 5 is a diagram for explaining the configuration of a power supply system 5 including a leakage current detection device 10 according to an embodiment. Below, differences from the configuration of the power supply system 5 according to the comparative example shown in FIG. 1 will be explained. In the embodiment, a third resistor R3 and a third operational amplifier OP3 are added. The control unit 11 further includes a constant voltage output unit 11e. The constant voltage output unit 11e can output two types of fixed voltages, a first reference voltage (5V in this embodiment) and a second reference voltage (0V in this embodiment).

[0036] In this embodiment, the oscillator 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 also configured to be able to output two types of fixed voltages, a first reference voltage and a second reference voltage.

[0037] A second resistor R2 and a third resistor R3 are connected in series between a connection point A between the coupling capacitor Cc and the first resistor R1 and the second voltage output unit. More specifically, the constant voltage output from the constant voltage output unit 11e is input to a non-inverting input terminal of a third operational amplifier OP3. The output terminal of the third operational amplifier OP3 is connected to the third resistor R3. The inverting input terminal and the output terminal of the third operational amplifier OP3 are connected. The third operational amplifier OP3 also functions as a voltage follower with an amplification factor of 1 and performing only impedance conversion.

[0038] In this embodiment, the voltage at the voltage dividing point between 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 the voltage dividing point between the second resistor R2 and the third resistor R3, thereby measuring the voltage at the measurement point A as a compressed voltage. The leakage current determining unit 11c calculates a leakage current resistance value by referring to a leakage current resistance conversion table based on the amplitude value of the voltage measured by the voltage measuring unit 11b, and determines the presence or absence of leakage current between the current path of the storage unit 20 and the chassis earth. In this embodiment, the voltage at the measurement point A is divided and measured, thereby making it possible to reduce the period during which the voltage at the measurement point A falls outside the measurement range (0 to 5V in this embodiment). That is, it is possible to reduce the period during which leakage current determination cannot be performed.

[0039] During a period in which the first voltage output unit sequentially outputs two types of fixed voltages, the diagnosis unit 11d diagnoses whether the earth leakage detection device 10 is normal or not based on the voltage measured by the voltage measurement unit 11b. Specifically, the diagnosis unit 11d calculates the difference between the voltage measured in the first state during that period and the voltage measured in the second state, and determines that the earth leakage detection device 10 is normal when the difference is within a set range. The first state and the second state each continue for several seconds (for example, 4 seconds).

[0040] 6(a)-(d) are diagrams showing an example of measured waveforms during fault diagnosis of the earth leakage detection device 10 according to the embodiment. In the example shown below, it is assumed that the resistance value of the first resistor R1 is set to 200 kΩ, the resistance value of the second resistor R2 is set to 1000 kΩ, and the resistance value of the third resistor R3 is set to 1000 kΩ. It is also assumed that in the first state, the first voltage output unit outputs a first reference voltage (5V in this embodiment), the second voltage output unit outputs a second reference voltage (0V in this embodiment), and 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.

[0041] 6(a) shows an example of a measured waveform when the earth leakage detection device 10 is normal. If the first voltage output unit, the first resistor R1, the second resistor R2, the third resistor R3, the second voltage output unit, the second operational amplifier OP2, and the voltage measurement unit 11b are normal, approximately 2.27 V is measured in the first state, and approximately 2.73 V is measured in the second state. The theoretical values ​​of the measured voltage in the first state and the theoretical values ​​of the measured voltage in the second state are calculated by the following (Equation 1) and (Equation 2).

[0042] 5×(1000 / (200+1000+1000))≒2.27 (Formula 1) 5 × ((200 + 1000) / (200 + 1000 + 1000)) ≒ 2.73 (Formula 2)

[0043] The diagnosis unit 11d calculates the differential voltage ΔV between the two. In this example, it is 0.46 V. If the differential voltage ΔV is within a set range, the diagnosis unit 11d determines that the earth leakage detection device 10 is normal. The set range is set to a range that provides optimal accuracy based on data obtained by experiments and simulations by the designer.

[0044] In the present embodiment, as in the comparative example, when the coupling capacitor Cc deteriorates, the leakage current increases. Fig. 7 is a diagram showing an example of a leakage path in a power supply system 5 including a leakage detection device 10 according to an embodiment.

[0045] FIG. 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. Note that the circuitry of the leakage detection device 10 itself is in a normal state. In FIG. 6(b), the entire measured waveform drops by 1 V due to the effect of the leakage current. Approximately 1.27 V is measured in the first state, and approximately 1.72 V is measured in the second state. The difference voltage ΔV between the two is 0.46 V.

[0046] Fig. 6(c) shows an example of a measured waveform when the earth leakage detection device 10 is abnormal. In Fig. 6(c), a voltage close to 0V is measured in both the first and second states. The differential voltage ΔV between the two is 0V. Since the differential voltage ΔV falls outside a predetermined set range (center value is 0.46V), the diagnosis unit 11d determines that the earth leakage detection device 10 is abnormal.

[0047] Fig. 6(d) shows an example of a measured waveform when the constants of the circuit elements used in the earth leakage detection device 10 are changed. The example shown in Fig. 6(d) shows a measured waveform when the resistance value of the first resistor R1 is reduced from 200 kΩ to 100 kΩ due to degradation. Approximately 2.38 V is measured in the first state, and approximately 2.62 V is measured in the second state. When the resistance value of the first resistor R1 is 100 kΩ, the theoretical values ​​of the measured voltage in the first state and the second state are calculated by the following (Equation 3) and (Equation 4).

[0048] 5×(1000 / (100+1000+1000))≒2.38 (Formula 3) 5 × ((100 + 1000) / (100 + 1000 + 1000)) ≒ 2.62 (Formula 4)

[0049] The differential voltage ΔV between the two is 0.24 V. The diagnosing unit 11d determines that the earth leakage detection device 10 is abnormal because the differential voltage ΔV falls outside a predetermined set range (the center value is 0.46 V).

[0050] As described above, according to this embodiment, during the period in which two types of fixed voltages are applied to the voltage dividing point in sequence, it is possible to perform a fault diagnosis of the leakage detection device 10 with high accuracy by determining whether or not the differential voltage ΔV between the first state and the second state falls within the set range. Specifically, even if a minute leakage current flows from the first operational amplifier OP1 to the chassis earth, as shown in FIG. 6(b), the differential voltage ΔV has almost the same value as in the normal state. Therefore, it is possible to perform a fault diagnosis of the leakage detection device 10 with almost no influence of the minute leakage current. In this respect, the comparative example is greatly influenced by the minute leakage current as shown in FIG. 3(b). In this embodiment, it is not necessary to take a large margin for the set range, and it is possible to reduce overlooking minor defects of circuit elements.

[0051] In addition, as shown in FIG. 6(d), in this embodiment, it is also possible to detect changes in the constants of the circuit elements. Specifically, it is possible to detect the deterioration of the first resistor R1 that functions as a detection resistor. In this regard, as shown in FIG. 3(d), in the comparative example, it is difficult to detect changes in the constants of the circuit elements.

[0052] (Variation 1) 8(a)-(d) are diagrams showing an example of measured waveforms during fault diagnosis of the leakage detection device 10 according to the first modification. The configuration of the leakage detection device 10 is the same as that shown in FIG. 5. In the first modification, it is also assumed that the resistance value of the first resistor R1 is set to 200 kΩ, the resistance value of the second resistor R2 is set to 1000 kΩ, and the resistance value of the third resistor R3 is set to 1000 kΩ. It is also assumed that in the first state, the first voltage output unit outputs the first reference voltage (5V in the first modification), the second voltage output unit outputs the first reference voltage, and in the second state, the first voltage output unit outputs the first reference voltage, and the second voltage output unit outputs the second reference voltage (0V in the first modification).

[0053] FIG. 8(a) shows an example of a measured waveform when the earth leakage detection device 10 is normal. If the first voltage output unit, the first resistor R1, the second resistor R2, the third resistor R3, the second voltage output unit, the second operational amplifier OP2, and the voltage measurement unit 11b are normal, about 5V is measured in the first state, and about 2.27V is measured in the second state. In the first state, 5V is applied across the first resistor R1, the second resistor R2, and the third resistor R3 connected in series, so that 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 by the above (Equation 1).

[0054] The diagnostic unit 11d calculates the difference voltage ΔV between the two, which in this example is 2.73 V. If the difference voltage ΔV is within a set range, the diagnostic unit 11d determines that the earth leakage detection device 10 is normal.

[0055] FIG. 8(b) shows an example of a measured waveform when a small leakage current flows from the first operational amplifier OP1 to the chassis earth. Note that the circuitry of the earth leakage detection device 10 itself is in a normal state. In FIG. 8(b), the entire measured waveform drops by 1 V due to the influence of the leakage current. Approximately 4 V is measured in the first state, and approximately 1.27 V is measured in the second state. The differential voltage ΔV between the two is 2.73 V. Since the differential voltage ΔV falls within a predetermined set range (with a center value of 2.73 V), the diagnosis unit 11d determines that the earth leakage detection device 10 is normal.

[0056] Fig. 8(c) shows an example of a measured waveform when the earth leakage detection device 10 is abnormal. In Fig. 8(c), a voltage close to 0V is measured in both the first state and the second state. The differential voltage ΔV between the two is 0V. Since the differential voltage ΔV falls outside a predetermined set range (the center value is 2.73V), the diagnosis unit 11d determines that the earth leakage detection device 10 is abnormal.

[0057] FIG. 8(d) shows an example of a measured waveform when the constant of the circuit element used in the leakage detection device 10 changes. The example shown in FIG. 8(d) shows a measured waveform when the resistance value of the first resistor R1 drops from 200 kΩ to 100 kΩ due to degradation. Approximately 5 V is measured in the first state, and approximately 2.38 V is measured in the second state. In the first state, 5 V is applied to both ends of the first resistor R1, the second resistor R2, and the third resistor R3 connected in series, so that the theoretical value of the measured voltage in the first state is also 5 V regardless of the resistance value of the first resistor. The theoretical value of the measured voltage in the second state is calculated by the above (Equation 3). The difference voltage ΔV between the two is 2.62 V. The diagnosis unit 11d determines that the leakage detection device 10 is abnormal because the difference voltage ΔV is outside a predetermined setting range (the center value is 2.73 V).

[0058] As described above, according to the first modification, even if the first voltage output unit continuously outputs the same voltage in the first state and the second state, the output voltage of the second voltage output unit is switched to achieve the same effect as the above embodiment. Note that the first voltage output unit may continuously output the second reference voltage instead of the first reference voltage.

[0059] (Variation 2) 9(a)-(d) are diagrams showing an example of measured waveforms during fault diagnosis of the leakage detection device 10 according to the second modification. The configuration of the leakage detection device 10 is the same as that shown in FIG. 5. In the second modification, it is also assumed that the resistance value of the first resistor R1 is set to 200 kΩ, the resistance value of the second resistor R2 is set to 1000 kΩ, and the resistance value of the third resistor R3 is set to 1000 kΩ. It is also assumed that in the first state, the first voltage output unit outputs the first reference voltage (5V in the second modification), the second voltage output unit outputs the first reference voltage, and in the second state, the first voltage output unit outputs the second reference voltage (0V in the second modification), and the second voltage output unit outputs the first reference voltage.

[0060] 9(a) shows an example of a measured waveform when the earth leakage detection device 10 is normal. If the first voltage output unit, the first resistor R1, the second resistor R2, the third resistor R3, the second voltage output unit, the second operational amplifier OP2, and the voltage measurement unit 11b are normal, about 5V is measured in the first state, and about 2.73V is measured in the second state. In the first state, 5V is applied across the first resistor R1, the second resistor R2, and the third resistor R3 connected in series, so that 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 by the above (Equation 2).

[0061] The diagnostic unit 11d calculates the difference voltage ΔV between the two, which in this example is 2.27 V. If the difference voltage ΔV is within a set range, the diagnostic unit 11d determines that the earth leakage detection device 10 is normal.

[0062] FIG. 9(b) shows an example of a measured waveform when a small leakage current flows from the first operational amplifier OP1 to the chassis earth. Note that the circuitry of the earth leakage detection device 10 itself is in a normal state. In FIG. 9(b), the entire measured waveform drops by 1 V due to the influence of the leakage current. Approximately 4 V is measured in the first state, and approximately 1.73 V is measured in the second state. The differential voltage ΔV between the two is 2.27 V. The diagnostic unit 11d determines that the earth leakage detection device 10 is normal because the differential voltage ΔV falls within a predetermined set range (with a center value of 2.27 V).

[0063] Fig. 9(c) shows an example of a measured waveform when the earth leakage detection device 10 is abnormal. In Fig. 9(c), a voltage close to 0V is measured in both the first state and the second state. The differential voltage ΔV between the two is 0V. Since the differential voltage ΔV falls outside a predetermined set range (center value is 2.27V), the diagnosis unit 11d determines that the earth leakage detection device 10 is abnormal.

[0064] FIG. 9(d) shows an example of a measured waveform when the constant of the circuit element used in the leakage detection device 10 changes. The example shown in FIG. 9(d) shows a measured waveform when the resistance value of the first resistor R1 drops from 200 kΩ to 100 kΩ due to degradation. Approximately 5 V is measured in the first state, and approximately 2.62 V is measured in the second state. In the first state, 5 V is applied to both ends of the first resistor R1, the second resistor R2, and the third resistor R3 connected in series, so that the theoretical value of the measured voltage in the first state is also 5 V regardless of the resistance value of the first resistor. The theoretical value of the measured voltage in the second state is calculated by the above (Equation 4). The difference voltage ΔV between the two is 2.38 V. The diagnosis unit 11d determines that the leakage detection device 10 is abnormal because the difference voltage ΔV is outside a predetermined setting range (the center value is 2.27 V).

[0065] As described above, according to the second modification, even if the second voltage output unit continuously outputs the same voltage in the first state and the second state, the output voltage of the first voltage output unit can be switched to achieve the same effect as the above embodiment. Furthermore, according to the second modification, the theoretical value of the measured voltage in the second state is higher than that of the first modification, so that the resistance to the decrease of the entire measured waveform is higher. Note that the second voltage output unit may continuously output the second reference voltage instead of the first reference voltage.

[0066] The present disclosure has been described above based on the embodiments. The embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each processing step, and that such modifications are also within the scope of the present disclosure.

[0067] In the above embodiment, an example has been described in which the power supply voltage of 5 V is used as the first reference voltage and the ground voltage of 0 V is used as the second reference voltage. In this regard, the first reference voltage and the second reference voltage are not limited to 5 V and 0 V, and any two different voltages can be used.

[0068] In the above embodiment, an example has been described in which a square wave voltage is applied from the first voltage output unit to the coupling capacitor Cc via the first resistor R1. However, a sine wave voltage may be applied to the coupling capacitor Cc. In this case, the leakage determination unit 11c can also identify the peak-to-peak value from the voltage waveform at the measurement point A and determine the presence or absence of leakage in the same manner as in the above embodiment.

[0069] In the above embodiment, an example has been described in which the earth leakage detection device 10 is mounted on an electric vehicle and used. In this regard, the earth leakage detection device 10 according to the embodiment can be used for purposes other than mounting on a vehicle. As long as the power storage unit 20 and the load that receives power from the power storage unit 20 are configured to be insulated from earth, the load may be any type of load. For example, the load may be a load used in a railway vehicle.

[0070] The embodiment may be specified by the following items.

[0071] [Item 1] a coupling capacitor (Cc) having one end connected to a current path of a storage unit (20) connected to a load (2) in a state insulated from earth; a first voltage output section (11a, OP1) that generates a periodically changing periodic voltage and applies the periodic voltage to the other end of the coupling capacitor (Cc) via a first resistor (R1); a second voltage output unit (11e, OP3) that outputs a fixed voltage; a second resistor (R2) and a third resistor (R3) connected in series between a connection point between the coupling capacitor (Cc) and the first resistor (R1) and the second voltage output section (11e, OP3); a voltage measuring unit (11b) that measures a voltage at a voltage dividing point between the second resistor (R2) and the third resistor (R3); a leakage current determination unit (11c) that determines the presence or absence of leakage current between the current path of the storage unit (20) and the earth based on a voltage measured by the voltage measurement unit (11b) in a state in which the periodic voltage is output from the first voltage output unit (11a, OP1); a diagnosis unit (11d) for determining whether or not the earth leakage detection device (10) is normal based on the voltage measured by the voltage measurement unit (11b) during a period in which two types of fixed voltages are applied to the voltage division point in sequence; A leakage current detection device (10) comprising: This makes it possible to perform fault diagnosis of the earth leakage detection device (10) with high accuracy. [Item 2] the diagnosing unit (11d) determines that the earth leakage detection device (10) is abnormal when a difference between a voltage measured in a first state during the period and a voltage measured in a second state during the period is outside a set range; The leakage current detection device (10) described in item 1, characterized in that the second state is different from the first state in output voltage of at least one of the first voltage output unit (11a, OP1) and the second voltage output unit (11e, OP3). This makes it possible to perform fault diagnosis of the earth leakage detection device (10) with high accuracy. [Item 3] 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; 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; 3. The earth leakage detection device (10) according to item 2, This makes it possible to measure a suitable differential voltage for determination. [Item 4] the first voltage output unit (11a, OP1) continuously outputs the first reference voltage or the second reference voltage in the first state and the second state; 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; 3. The earth leakage detection device (10) according to item 2, This makes it possible to measure a suitable differential voltage for determination. [Item 5] 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; 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. 3. The earth leakage detection device (10) according to item 2, This makes it possible to measure a suitable differential voltage for determination. [Item 6] the first reference voltage is a high-side reference voltage; The second reference voltage is a low-side reference voltage. 6. The earth leakage detection device (10) according to any one of items 3 to 5. This makes it possible to easily generate the first reference voltage and the second reference voltage. [Item 7] an electricity storage unit (20) mounted in a state insulated from a chassis earth of a vehicle and supplying electric power to a load (2) within the vehicle; A leakage current detection device (10) according to any one of items 1 to 6, A vehicle power supply system (5). This makes it possible to realize a vehicle power supply system (5) including an earth leakage detection device (10) capable of performing fault diagnosis of the vehicle power supply system (5) with high accuracy. [Explanation of symbols]

[0072] 2 inverter, 3 motor, Lp positive wiring, Lm negative wiring, Cp positive Y capacitor, Cm negative Y capacitor, Rlp positive leakage resistor, Rlm negative leakage resistor, Rlb leakage resistor, MRp positive main relay, MRm negative main relay, 5 power supply system, 20 storage unit, E1-En cell, 10 leakage detection device, 11 control unit, 11a oscillation unit, 11b voltage measurement unit, 11c leakage determination unit, 11d diagnosis unit, 11e constant voltage output unit, Cc coupling capacitor, R1 first resistor, R2 second resistor, R3 third resistor, C1 smoothing capacitor, OP1 first op amp, OP2 second op amp, OP3 third op amp.

Claims

1. a coupling capacitor having one end connected to a current path of a storage unit connected to a load while being insulated from a ground; a first voltage output section that generates a periodically changing 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 the first reference voltage or the second reference voltage; a second resistor and a third resistor connected in series between a connection point between the coupling capacitor and the first resistor and the second voltage output section; a voltage measuring unit for measuring a voltage at a voltage dividing point between the second resistor and the third resistor; a leakage current determination unit that determines whether or not there is a leakage current between the current path of the power storage unit and the earth based on a voltage measured by the voltage measurement unit in a state in which the periodic voltage is output from the first voltage output unit; and a diagnosis unit that determines that the leakage current detection device is abnormal when a difference between a voltage measured in a first state during a diagnosis period and a voltage measured in a second state during the diagnosis period is outside a set range; Equipped with the first voltage output unit outputs the first reference voltage in the first state and outputs the 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. A leakage current detection device comprising:

2. a coupling capacitor having one end connected to a current path of a storage unit connected to a load while being insulated from a ground; a first voltage output section that generates a periodically changing 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 the first reference voltage or the second reference voltage; a second resistor and a third resistor connected in series between a connection point between the coupling capacitor and the first resistor and the second voltage output section; a voltage measuring unit for measuring a voltage at a voltage dividing point between the second resistor and the third resistor; a leakage current determination unit that determines whether or not there is a leakage current between the current path of the power storage unit and the earth based on a voltage measured by the voltage measurement unit in a state in which the periodic voltage is output from the first voltage output unit; and a diagnosis unit that determines that the leakage current detection device is abnormal when a difference between a voltage measured in a first state during a diagnosis period and a voltage measured in a second state during the diagnosis period is outside a set range; Equipped with the first voltage output unit continuously outputs the first reference voltage or the second reference voltage in 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. A leakage current detection device comprising:

3. a coupling capacitor having one end connected to a current path of a storage unit connected to a load while being insulated from a ground; a first voltage output section that generates a periodically changing 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 the first reference voltage or the second reference voltage; a second resistor and a third resistor connected in series between a connection point between the coupling capacitor and the first resistor and the second voltage output section; a voltage measuring unit for measuring a voltage at a voltage dividing point between the second resistor and the third resistor; a leakage current determination unit that determines whether or not there is a leakage current between the current path of the power storage unit and the earth based on a voltage measured by the voltage measurement unit in a state in which the periodic voltage is output from the first voltage output unit; and a diagnosis unit that determines that the leakage current detection device is abnormal when a difference between a voltage measured in a first state during a diagnosis period and a voltage measured in a second state during the diagnosis period is outside a set range; Equipped with the first voltage output unit outputs the first reference voltage in the first state and outputs the second reference voltage in the second state; the second voltage output unit continuously outputs the first reference voltage or the second reference voltage in the first state and the second state. A leakage current detection device comprising:

4. the first reference voltage is a high-side reference voltage; the second reference voltage is a low-side reference voltage; 4. The earth leakage detection device according to claim 1, wherein the electric leakage detection device is a leakage current detecting device.

5. a power storage unit mounted in a state insulated from a chassis earth of a vehicle and supplying power to a load in the vehicle; The leakage detection device according to any one of claims 1 to 4, A vehicle power supply system comprising:

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