Leakage detection device, vehicle power supply system

Abstract

A leakage detection device (10) detects leakage of a high-voltage section in which a power storage section (20) and a load are connected by a power line while being insulated from a ground line. A Y capacitor (CY) is connected between a current path between the power storage section (20) and the load and the ground line. A driving section (11) of the leakage detection device (10) outputs a rectangular-wave voltage to the current path between the power storage section (20) and the load via a driving coupling capacitor (Cd1) to charge or discharge the Y capacitor (CY). A leakage detection section (12) determines whether there is leakage between the current path and the ground line based on the transition of the voltage at the measurement point of the current path that changes corresponding to the charging or discharging of the Y capacitor (CY) converging to the original voltage.

Description

Technical Field

[0001] The present disclosure relates to a leakage detection device for detecting leakage of a load insulated from a ground wire, and a vehicle power supply system. Background Art

[0002] In recent years, hybrid vehicles (HV), plug-in hybrid vehicles (PHV), and electric vehicles (EV) have become popular. In these electric vehicles, a high-voltage drive battery (traction battery) is mounted separately from an auxiliary battery (generally a lead battery with a 12V output). A high-voltage power circuit including the drive battery, an inverter, and a driving motor is insulated from the vehicle body (chassis ground wire) to prevent electric shock.

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

[0004] In an AC type leakage detection device, a pulse voltage is applied to the positive terminal or negative terminal of the drive 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 leakage. When a ground fault occurs, the impedance at the measurement point decreases, and thus the voltage at the measurement point decreases. Therefore, when the voltage at the measurement point is below a threshold value, it can be determined that leakage has occurred (for example, refer to Patent Document 1).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Laid-Open No. 8-70503 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] In this method, when the capacitance of the Y capacitor is large, the measurement accuracy of the insulation resistance in a parallel connection relationship with the Y capacitor decreases. Since the impedance of the Y capacitor decreases when the capacitance of the Y capacitor is large, the influence of the variation of the Y capacitor on the calculated value of the insulation resistance is large.

[0010] In order to maintain the measurement accuracy of the insulation resistance even when the capacitance of the Y capacitor is large, it is considered to reduce the driving frequency of the applied pulse. In this case, the impedance of the coupling capacitor becomes large, and the influence of the error of the coupling capacitor on the calculated value of the insulation resistance becomes large. In order to reduce the influence of the error of the coupling capacitor, it is considered to increase the capacitance of the coupling capacitor. Since the coupling capacitor is a capacitor that connects between the high-voltage part and the low-voltage part, a capacitor with high withstand voltage is required. If a capacitor with high capacitance and high withstand voltage is used, the cost increases.

[0011] The present disclosure has been made in view of such a situation, and an object thereof is to provide a technique capable of detecting leakage current with low cost and high accuracy even when the capacitance of the Y capacitor is large.

[0012] Solution to the problem

[0013] In order to solve the above problems, a leakage current detection device according to an aspect of the present disclosure detects leakage current of a high-voltage part in which a power storage part and a load are connected by a power supply line in a state insulated from a ground line. A Y capacitor is connected between a current path between the power storage part and the load and the ground line. The leakage current detection device includes: a driving unit that outputs a rectangular wave voltage to the current path between the power storage part and the load via a driving coupling capacitor to charge or discharge the Y capacitor; and a leakage current detection unit that determines whether there is leakage current between the current path and the ground line based on the transition of the voltage at a measurement point of the current path that changes corresponding to the charging or discharging of the Y capacitor converging to the original voltage.

[0014] Effect of the invention

[0015] According to the present disclosure, even when the capacitance of the Y capacitor is large, it is possible to detect leakage current with low cost and high accuracy. Description of the drawings

[0016] Figure 1 It is a diagram for explaining the structure of a power supply system including the leakage current detection device according to Embodiment 1.

[0017] Figure 2 It is a diagram showing an example of voltage waveforms at various points when leakage current is detected by the leakage current detection device according to Embodiment 1.

[0018] Figure 3 It is a diagram for explaining the structure of a power supply system including the leakage current detection device according to the comparative example.

[0019] Figure 4 (a)-(b) thereof are diagrams showing an example of the voltage waveform at point A before the occurrence of a ground fault and the voltage waveform at point A after the occurrence of the ground fault.

[0020] Figure 5 This is a diagram for explaining the structure of the power supply system of the leakage detection device according to Embodiment 2.

[0021] Figure 6 This is a diagram for explaining the structure of the power supply system of the leakage detection device according to Embodiment 3.

[0022] Figure 7 This is a diagram showing an example of the voltage waveforms at various locations during leakage detection by the leakage detection device according to Embodiment 3. Detailed Embodiments

[0023] (Embodiment 1)

[0024] Figure 1 This is a diagram for explaining the structure of the power supply system 5 of the leakage detection device 10 according to Embodiment 1. The power supply system 5 is mounted on an electric vehicle. The power supply system 5 is provided separately from the auxiliary battery (usually a lead battery with a 12V output) inside the electric vehicle. The power supply system 5 includes a power storage unit 20 of the high-voltage system and a leakage detection device 10 of the low-voltage system. The power storage unit 20 includes a plurality of single cells E1 - En connected in series. For the single cells, lithium-ion battery single cells, nickel-metal hydride battery single cells, lead battery single cells, electric double-layer capacitor single cells, lithium-ion capacitor single cells, etc. can be used. Hereinafter, in this specification, an example of using lithium-ion battery single cells (nominal voltage: 3.6V - 3.7V) is assumed.

[0025] The electric vehicle is equipped with an inverter 2 and a motor 3 as loads of the high-voltage system. The positive electrode of the power storage unit 20 is connected to one end of the inverter 2 through a positive power line Lp, and the negative electrode of the power storage unit 20 is connected to the other end of the inverter 2 through a negative power line Lm. A positive-side main relay MRp is inserted into the positive power line Lp, and a negative-side main relay MRm is inserted into the negative power line Lm. The positive-side main relay MRp and the negative-side main relay MRm function as contactors for controlling the conduction / cutoff between the power storage unit 20 and the loads of the high-voltage system inside the electric vehicle. In addition, a semiconductor switch with high withstand voltage and high insulation can also be used instead of the relay.

[0026] 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 the DC power supplied from the power storage unit 20 into AC power and then supplies it to the motor 3. During regeneration, the AC power supplied from the motor 3 is converted into DC power and then supplied to the power storage unit 20. The motor 3 uses, for example, a three-phase AC motor. During power running, the motor 3 rotates in response to the AC power supplied by the inverter 2. During regeneration, the rotational energy generated by deceleration is converted into AC power and then supplied to the inverter 2.

[0027] The power storage unit 20 is mounted on the electric vehicle in a state insulated from the chassis ground wire of the electric vehicle. The auxiliary battery is mounted on the electric vehicle with its negative electrode electrically connected to the chassis ground wire. A first Y capacitor CY1 is connected between the positive power supply line Lp on the inverter 2 side and the chassis ground wire, which is closer to the inverter 2 than the positive-side main relay MRp. In addition, a second Y capacitor CY2 is connected between the negative power supply line Lm on the inverter 2 side and the chassis ground wire, which is closer to the inverter 2 than the negative-side main relay MRm. The first Y capacitor CY1 and the second Y capacitor CY2 have the following functions: they insulate the positive power supply line Lp from the chassis ground wire and the negative power supply line Lm from the chassis ground wire respectively, and stabilize the voltages of the positive power supply line Lp and the negative power supply line Lm. In addition, a structure in which one of the first Y capacitor CY1 and the second Y capacitor CY2 is omitted is also possible.

[0028] When the power storage unit 20 is ideally insulated from the chassis ground wire, the intermediate potential of the power storage unit 20 is maintained near the potential of the chassis ground wire. For example, when the voltage across the power storage unit 20 is 250V, the positive potential of the power storage unit 20 is maintained near +125V, and the negative potential is maintained near -125V. When the power storage unit 20 of the high-voltage system is electrically connected to the chassis ground wire, there is a risk of electric shock when a person touches the exposed conductive part of the electric vehicle. Therefore, in an electric vehicle equipped with the power storage unit 20 of the high-voltage system, a leakage detection device 10 needs to be mounted to monitor the insulation state between the current path of the power storage unit 20 of the vehicle load connected to the high-voltage system and the chassis ground wire. In Figure 1 the insulation state between the positive power supply line Lp and the chassis ground wire is represented as the first leakage resistance RL1, and the insulation state between the negative power supply line Lm and the chassis ground wire is represented as the second leakage resistance RL2.

[0029] The leakage detection device 10 includes a drive unit 11 and a leakage detection unit 12. The drive unit 11 includes a drive coupling capacitor Cd1, an output resistor Ro, an operational amplifier OP1, an oscillation unit 11a, a first protection diode D1, and a second protection diode D2.

[0030] One end of the drive coupling capacitor Cd1 is connected to the current path between the power storage unit 20 and the vehicle load. In Figure 1 the example shown, one end of the drive coupling capacitor Cd1 is connected to the positive power supply line Lp. In addition, as long as one end of the drive coupling capacitor Cd1 is connected to this current path, it can be connected to any position. For example, it can also be connected to the negative power supply line Lm. The other end of the drive coupling capacitor Cd1 is connected to the output resistor Ro. A first protection diode D1 is connected between the wiring between the other end of the drive coupling capacitor Cd1 and the output resistor Ro and the power supply potential Vcc of the low-voltage system, and a second protection diode D2 is connected between this wiring and the ground potential.

[0031] The oscillation unit 11a includes a multivibrator or a local oscillator for generating a rectangular wave (pulse) with a preset frequency. The rectangular wave voltage generated by the oscillation unit 11a is input to the non-inverting input terminal of the operational amplifier OP1. The output terminal of the operational amplifier OP1 is connected to the output resistor Ro. The inverting input terminal of the operational amplifier OP1 is connected to the output terminal. The operational amplifier OP1 functions as a voltage follower with a gain of 1 for impedance transformation only.

[0032] The oscillation unit 11a outputs a rectangular wave voltage to point A via the operational amplifier OP1 and the output resistor Ro. The rectangular wave voltage output to point A is applied to point B on the current path between the power storage unit 20 and the vehicle load via the driving coupling capacitor Cd1. Thereby, the first Y capacitor CY1 and the second Y capacitor CY2 are charged or discharged.

[0033] The leakage detection unit 12 includes a measurement coupling capacitor Cd2, a resistor Rf, a capacitor Cf, an A / D converter 12a, a voltage measurement unit 12b, a leakage determination unit 12c, a third protection diode D3, and a fourth protection diode D4.

[0034] One end of the measurement coupling capacitor Cd2 is connected to the current path between the power storage unit 20 and the vehicle load. In Figure 1 , one end of the measurement coupling capacitor Cd2 is connected to point B on this current path where the driving coupling capacitor Cd1 is connected, but as long as it is connected to this current path, it can be connected to any position. The other end of the measurement coupling capacitor Cd2 is connected to a low-pass filter composed of the resistor Rf and the capacitor Cf. A third protection diode D3 is connected between the wiring between the other end of the measurement coupling capacitor Cd2 and the resistor Rf and the power supply potential Vcc of the low-voltage system, and a fourth protection diode D4 is connected between this wiring and the ground potential.

[0035] This low-pass filter removes noise from the voltage at point C input by the measurement coupling capacitor Cd2 and outputs the voltage at point D after noise removal. The A / D converter 12a converts the analog voltage at point D input from this low-pass filter into a digital value voltage and outputs it to the voltage measurement unit 12b. The voltage measurement unit 12b measures the digital value voltage input from the A / D converter 12a. The leakage determination unit 12c determines whether there is a leakage between the current path between the power storage unit 20 and the vehicle load and the chassis ground wire based on the voltage measured by the voltage measurement unit 12b.

[0036] In Figure 1In this case, the oscillation unit 11a, the voltage measurement unit 12b, and the leakage determination unit 12c may also be configured by one IC.

[0037] In Embodiment 1, a rectangular wave voltage is applied from the drive unit 11 to point B to charge the first Y capacitor CY1 and the second Y capacitor CY2. Leakage is detected based on the voltage change (specifically, the rate of change of the voltage) when the electric charges charged in the first Y capacitor CY1 and the second Y capacitor CY2 are discharged via the first leakage resistance RL1 and the second leakage resistance RL2.

[0038] Figure 2 FIG. is an example of voltage waveforms at respective locations when leakage is detected by the leakage detection device 10 according to Embodiment 1. When the voltage waveform at point A rises, electric charges are charged into the first Y capacitor CY1 and the second Y capacitor CY2, and the voltage at B rises due to the increase in the capacitance of the first Y capacitor CY1 and the second Y capacitor CY2 (see W1). The voltage change amount at point B is transmitted to point C via the measurement coupling capacitor Cd2. The voltage waveform at point D is a waveform obtained by removing noise from the voltage waveform at point C by the above-described low-pass filter (see W2). From the perspective of the leakage detection device 10, the voltage at point A is the output voltage Vout for driving, and the voltage at point D is the input voltage Vin for measurement.

[0039] As the electric charges charged in the first Y capacitor CY1 and the second Y capacitor CY2 escape via the first leakage resistance RL1 and the second leakage resistance RL2, the voltage at point B gradually decreases and converges to the original voltage. In Embodiment 1, the leakage resistance value is calculated by measuring the recovery time of the voltage at point B.

[0040] In the following calculation formulas, the parallel resistance value of the first leakage resistance RL1 and the second leakage resistance RL2 is simply denoted as RL. The parallel capacitance value of the first Y capacitor CY1 and the second Y capacitor CY2 is simply denoted as CY. The capacitance value of the drive coupling capacitor Cd1 is simply denoted as Cd. Figure 1 The time constant τ at point B of the shown circuit is defined as follows in Equation (1). The input voltage Vin at point D is defined as follows in Equation (2). E is the voltage applied from the drive unit 11 to point B.

[0041] τ = RL × (CY + Cd) ··· (Equation 1)

[0042] Vin = E × Cd / (Cd + CY) × e -t / τ ··· (Equation 2)

[0043] The leakage determination unit 12c determines that Vin = E × Cd / (Cd + CY) × e -aIt is measured at time t. Since the relationship of t = aτ = a×(RL×CY) holds, the insulation resistance RL is defined as shown in the following (Equation 3).

[0044] RL = t / (a×CY) ··· (Equation 3)

[0045] The smaller the leakage resistance RL, the shorter the time for the voltage at point D to converge to the original voltage. The leakage determination unit 12c measures the time t when the voltage Vin at point D becomes E×Cd / (Cd + CY)×e -α to calculate the value of the leakage resistance RL. The leakage determination unit 12c compares the calculated value of the leakage resistance RL with a resistance threshold value. When the calculated value of the leakage resistance RL is less than or equal to the resistance threshold value, it is determined that a leakage has occurred. Alternatively, the leakage determination unit 12c compares the value of the voltage Vin at point D measured after a set time has elapsed since the application of the drive voltage Vout with a voltage threshold value. When the measured value of the voltage Vin at point D is less than or equal to the voltage threshold value, the leakage determination unit 12c determines that a leakage has occurred. The above-mentioned resistance threshold value, set time, and voltage threshold value are preset based on the leakage resistance value determined to be a leakage.

[0046] (Comparative example)

[0047] Figure 3 is a diagram for explaining the structure of the power supply system 5 including the leakage detection device 10 according to the comparative example. Next, the differences from Figure 1 the leakage detection device 10 according to the first embodiment shown are described. In the comparative example, the measurement coupling capacitor Cd2 is not provided, and the leakage detection unit 12 measures the voltage at point A between the drive coupling capacitor Cd1 and the output resistor Ro. The leakage detection unit 12 detects leakage based on the impedance ratio of the output resistor Ro, the drive coupling capacitor Cd1, and the leakage resistance RL.

[0048] Figure 4 Figs. (a)-(b) are diagrams showing an example of the voltage waveform at point A before the occurrence of a ground fault and the voltage waveform at point A after the occurrence of a ground fault. Figure 4 Fig. (a) shows the voltage waveform at point A before the occurrence of a ground fault, Figure 4 Fig. (b) shows the voltage waveform at point A after the occurrence of a ground fault. When a ground fault occurs, the impedance at point A decreases, and thus the voltage at point A decreases. When the measured voltage value at point A is less than or equal to the voltage threshold value Vth, the leakage determination unit 12c determines that a leakage has occurred.

[0049] However, in practice, a Y capacitor CY is connected in parallel with the leakage resistance RL. When the capacitance of the Y capacitor CY is large (i.e., the impedance is small), the degree of influence of the change in the leakage resistance RL on the combined impedance becomes small. As a result, it is difficult to detect the leakage resistance RL with high precision.

[0050] In order to maintain the detection accuracy of the insulation resistance RL even when the capacitance of the Y capacitor is large, it is considered to reduce the frequency of the driving voltage. In this case, as described above, the driving coupling capacitor Cd1 needs to use a capacitor with a high capacitance and a high withstand voltage, increasing the cost.

[0051] Regarding this point, in Embodiment 1, as shown in the above (Equation 3), the capacitance of the driving coupling capacitor Cd1 has no effect on the detection accuracy of the leakage resistance RL. Therefore, even when the capacitance of the Y capacitor CY is large, the driving coupling capacitor Cd1 can reduce the frequency of the driving voltage without using a high-specification capacitor. In this way, according to Embodiment 1, even when the capacitance of the Y capacitor CY is large, leakage can be detected with high accuracy at low cost.

[0052] (Embodiment 2)

[0053] Figure 5 FIG. is a diagram for explaining the structure of the power supply system 5 including the leakage detection device 10 according to Embodiment 2. Hereinafter, the differences from Figure 1 the leakage detection device 10 according to Embodiment 1 shown will be described. In Embodiment 2, a series-connected adjustment resistor Rc and an adjustment switch Rc are connected in parallel with the first Y capacitor CY1 between the positive power supply line Lp and the chassis ground wire. Alternatively, the adjustment resistor Rc and the adjustment switch Rc may be connected between the negative power supply line Lm and the chassis ground wire.

[0054] In the following calculation formulas, the parallel resistance value of the first leakage resistance RL1, the second leakage resistance RL2, and the adjustment resistor Rc is denoted as RL'. In Figure 5 the circuit shown, the time constant τ1 of point B when the adjustment switch SWc is off is defined as follows in the following (Equation 4). The input voltage Vin at point D when the adjustment switch SWc is off is defined as follows in the following (Equation 5). The time constant τ2 of point B when the adjustment switch SWc is on is defined as follows in the following (Equation 6). The input voltage Vin at point D when the adjustment switch SWc is on is defined as follows in the following (Equation 7).

[0055] τ1 = RL×(CY + Cd)”·(Equation 4)

[0056] Vin = E×Cd / (Cd + CY)×e -t / τ1 ···(Equation 5)

[0057] τ2 = RL’ × (CY + Cd) ··· (Equation 6)

[0058] Vin = E × Cd / (Cd + CY) × e -t / τ2 ··· (Equation 7)

[0059] The leakage determination unit 12c measures the time t when Vin = E × Cd / (Cd + CY) × e -α The time t1 when the adjustment switch SWc is off is defined as follows (Equation 8), and the time t2 when the adjustment switch SWc is on is defined as follows (Equation 9).

[0060] t1 = aτ1 = a × (RL × CY) ··· (Equation 8)

[0061] t2 = aτ2 = a × (RL’ × CY) ··· (Equation 9)

[0062] The combined resistance RL’ of the leakage resistance RL and the adjustment resistance Rc is defined as follows (Equation 10).

[0063] RL’ = RL × Rc / (RL + Rc) ··· (Equation 10)

[0064] According to the above (Equation 8), (Equation 9), and (Equation 10), t2 can be rewritten as follows (Equation 11).

[0065] t2 = a × RL’ × t1 / (a × RL) = t1 × RL’ / RL = t1 × Rc / (RL + Rc) ··· (Equation 11)

[0066] When solving the above (Equation 11) for RL, RL can be defined as follows (Equation 12).

[0067] RL = t1 × Rc / t2 - Rc ··· (Equation 12)

[0068] In this way, in Embodiment 2, the leakage determination unit 12c measures the time t1 when Vin = E × Cd / (Cd + CY) × e when the adjustment switch SWc is off -α and the time t2 when Vin = E × Cd / (Cd + CY) × e when the adjustment switch SWc is on -α to calculate the value of the leakage resistance RL. The leakage determination unit 12c compares the calculated value of the leakage resistance RL with a resistance threshold, and when the calculated value of the leakage resistance RL is less than or equal to the resistance threshold, it determines that leakage has occurred.

[0069] As shown in the above (Equation 12), according to Embodiment 2, in addition to being able to remove the influence of the deviation of the driving coupling capacitor Cd1 from the calculated leakage resistance RL, the influence of the deviation of the Y capacitor CY can also be removed. Thus, the detection accuracy of leakage can be further improved.

[0070] (Embodiment 3)

[0071] Figure 6 FIG. is a diagram for explaining the structure of the power supply system 5 including the leakage detection device 10 according to Embodiment 3. Hereinafter, the differences from Figure 1 the leakage detection device 10 according to Embodiment 1 shown will be described. In Embodiment 3, a switch SW1 is inserted between the output resistance Ro and the driving coupling capacitor Cd1. The measurement coupling capacitor Cd2 is not provided, and the leakage detection unit 12 measures the voltage at point B via the driving coupling capacitor Cd1 during the period when the switch SW1 is off.

[0072] Figure 7 FIG. is a diagram showing an example of the voltage waveforms at various points when the leakage detection device 10 according to Embodiment 3 performs leakage detection. In the state where the switch SW1 is on, when the voltage waveform at point A rises, charge is stored in the Y capacitor CY, and since the capacitance of the Y capacitor CY increases, the voltage at B rises (see W1). After that, the leakage detection unit 12 turns off the switch SW1.

[0073] When the switch SW1 becomes off, the voltage change amount at point B is transmitted to point C via the measurement coupling capacitor Cd2. The voltage waveform at point D is the waveform obtained by removing noise from the voltage waveform at point C through the above low-pass filter (see W2). As the charge stored in the Y capacitor CY leaks out through the leakage resistance RL, the voltage at point B gradually decreases and converges to the original voltage. In Embodiment 3, the value of the leakage resistance RL can be calculated in the same manner as in Embodiment 1.

[0074] As described above, according to Embodiment 3, the measurement coupling capacitor Cd2 can be omitted, so that the cost and the circuit area can be reduced.

[0075] The present disclosure has been described based on the embodiments. Those skilled in the art can understand that the embodiments are illustrative, and various modifications can be made to the combinations of their respective structural elements and respective processing procedures, and such modification examples are also within the scope of the present disclosure.

[0076] For example, Embodiment 2 and Embodiment 3 can also be combined. Specifically, in Figure 6In the circuit structure, an adjustment resistor Rc and an adjustment switch SWc connected in series may also be connected between the positive power supply line Lp and the chassis ground wire in parallel with the first Y capacitor CY1. Additionally, the adjustment resistor Rc and the adjustment switch SWc may be connected between the negative power supply line Lm and the chassis ground wire.

[0077] In the above-described embodiment, a rectangular wave voltage for charging is applied from the drive unit 11 to point B to charge the Y capacitor CY, and leakage is detected based on the voltage change (specifically, the rate of change of the voltage) when the charge stored in the Y capacitor CY is discharged through the leakage resistor RL. In this regard, a rectangular wave voltage for discharging may also be applied from the drive unit 11 to point B to discharge the charge from the Y capacitor CY, and leakage may be detected based on the voltage change when the charge discharged from the Y capacitor CY is charged through the leakage resistor RL.

[0078] In the above-described embodiment, an example of using the leakage detection device 10 mounted on an electric vehicle has been described. In this regard, the leakage detection device 10 according to the embodiment can also be applied to uses other than in-vehicle uses. As long as the structure is such that the power storage unit 20 and the load receiving power supply from the power storage unit 20 are insulated from the ground wire, the load can be any load. For example, it can also be a load used inside a railway vehicle.

[0079] In addition, the embodiment can be determined by the following items.

[0080] [Item 1]

[0081] A leakage detection device (10) that detects leakage in a high-voltage section in which a power storage unit (20) and a load (2) are connected by power supply lines (Lp, Lm) in a state insulated from the ground wire, the leakage detection device (10) being characterized in that

[0082] A Y capacitor (CY) is connected between the current path between the power storage unit (20) and the load (2) and the ground wire,

[0083] The leakage detection device (10) includes:

[0084] A drive unit (11) that outputs a rectangular wave voltage to the current path between the power storage unit (20) and the load (2) via a drive coupling capacitor (Cd1) to charge or discharge the Y capacitor (CY); and

[0085] A leakage detection unit (12) that determines whether there is leakage between the current path and the ground wire based on the voltage at the measurement point of the current path converging to the original voltage in response to the charging or discharging of the Y capacitor (CY).

[0086] Accordingly, even when the capacitance of the Y capacitor (CY) is large, it is possible to detect leakage current with low cost and high precision.

[0087] [Item 2]

[0088] The leakage current detection device (10) according to Item 1, wherein

[0089] the leakage current detection unit (12) calculates a leakage resistance value between the current path and the ground wire based on the change in the voltage at the measurement point from when the Y capacitor (CY) is charged or discharged, and determines that leakage has occurred between the current path and the ground wire when the calculated leakage resistance value is equal to or less than a threshold value.

[0090] Accordingly, the influence of the driving coupling capacitor (Cd1) can be removed from the calculated leakage resistance value.

[0091] [Item 3]

[0092] The leakage current detection device (10) according to Item 1 or 2, wherein

[0093] the leakage current detection unit (12) measures the voltage at the measurement point of the current path via a measurement coupling capacitor (Cd2).

[0094] Accordingly, it is possible to measure the change in the voltage of the current path.

[0095] [Item 4]

[0096] The leakage current detection device (10) according to Item 1 or 2, wherein

[0097] the drive unit (11) includes:

[0098] an oscillation unit (11a) for outputting the rectangular wave voltage;

[0099] an output resistor (Ro) connected to the output of the oscillation unit (11a); and

[0100] a switch (SW1) inserted between the output resistor (Ro) and the driving coupling capacitor (Cd1),

[0101] the leakage current detection unit (12) includes a voltage measurement unit (12b) that measures the voltage at the measurement point of the current path via the driving coupling capacitor (Cd1) while the switch (SW1) is open.

[0102] Accordingly, the measurement coupling capacitor (Cd2) can be omitted.

[0103] [Item 5]

[0104] The leakage detection device (10) according to any one of Items 1 to 4, characterized in that:

[0105] A series-connected adjustment resistor (Rc) and an adjustment switch (SWc) are connected in parallel with a Y capacitor (CY) between the current path and the ground wire.

[0106] The leakage detection unit (12) calculates a leakage resistance value between the current path and the ground wire based on the voltages at the measurement points of the current path during the period when the adjustment switch (SWc) is turned on and the period when it is turned off.

[0107] Thereby, the influence of the Y capacitor (CY) can be removed from the calculated leakage resistance value.

[0108] [Item 6]

[0109] A vehicle power supply system (5), characterized by comprising:

[0110] A power storage unit (20) mounted in a state insulated from the vehicle's chassis ground wire for supplying power to a load (2) inside the vehicle; and

[0111] The leakage detection device (10) according to any one of Items 1 to 5.

[0112] Thereby, a vehicle power supply system (5) can be realized that includes a leakage detection device (10) capable of detecting leakage with low cost and high accuracy even when the capacitance of the Y capacitor (CY) is large.

[0113] Description of Reference Numerals

[0114] 5: Power supply system; 20: Power storage unit; 2: Inverter; 3: Motor; Lp: Positive power supply line; Lm: Negative power supply line; CY: Y capacitor; Cd1: Driving coupling capacitor; Cd2: Measuring coupling capacitor; Cf: Capacitor; RL: Leakage resistance; Ro: Output resistance; Rf: Resistor; MRp: Positive-side main relay; MRm: Negative-side main relay; E1-En: Cells; 10: Leakage detection device; 11: Driving unit; 11a: Oscillation unit; 12: Leakage detection unit; 12a: A / D converter; 12b: Voltage measurement unit; 12c: Leakage determination unit; OP1: Operational amplifier; SW1: Switch; SWc: Adjustment switch; Rc: Adjustment resistor; D1-D4: Protection diodes.

Claims

1. A leakage detection device for detecting leakage of a high-voltage part that connects a power storage part and a load using a power supply line in a state insulated from a ground wire, wherein the leakage detection device is characterized in that a Y capacitor is connected between a current path between the power storage part and the load and the ground wire, the leakage detection device includes: a driving part including a driving coupling capacitor, the driving part outputs a rectangular wave voltage to the current path between the power storage part and the load via the driving coupling capacitor to charge or discharge the Y capacitor; and a leakage detection part including a measurement coupling capacitor, the leakage detection part measures the voltage at a measurement point of the current path via the measurement coupling capacitor, and determines whether there is leakage between the current path and the ground wire according to the change of the voltage at the measurement point of the current path corresponding to the charging or discharging of the Y capacitor converging to the original voltage, Among them, a node between the driving coupling capacitor and the measurement coupling capacitor is connected to the measurement point of the current path between the power storage part and the load.

2. The leakage detection device according to claim 1, wherein the leakage detection part calculates a leakage resistance value between the current path and the ground wire based on the change of the voltage at the measurement point from when the Y capacitor is charged or discharged, and determines that leakage has occurred between the current path and the ground wire when the calculated leakage resistance value is below a threshold value.

3. The leakage detection device according to claim 1 or 2, wherein the driving part includes: an oscillation part for outputting the rectangular wave voltage; an output resistor connected to the output of the oscillation part; and a switch inserted between the output resistor and the driving coupling capacitor, the leakage detection part includes a voltage measurement part, and the voltage measurement part measures the voltage at the measurement point of the current path via the driving coupling capacitor during the period when the switch is off.

4. The leakage detection device according to claim 1 or 2, wherein a series-connected adjustment resistor and an adjustment switch are connected in parallel with the Y capacitor between the current path and the ground wire, the leakage detection part calculates the leakage resistance value between the current path and the ground wire based on the voltage at the measurement point of the current path during the period when the adjustment switch is on and off.

5. A power supply system for a vehicle, characterized in that, including: a power storage part mounted in a state insulated from the vehicle's chassis ground wire for supplying power to a load in the vehicle; and the leakage detection device according to any one of claims 1 to 4.

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