JP2012105540A - Electric vehicle equipped with ground fault detecting system - Google Patents

Abstract

An object of the present invention is to improve the detection accuracy of insulation resistance in the presence of first and second ungrounded power supplies.
A first insulation resistance detector 51 for detecting a first insulation resistance RL1 for a ground portion of a first non-grounded power supply 14 and a second insulation resistance RL2 for a ground portion of a second non-grounded power supply 12 are detected. The second insulation resistance detection unit 52 is provided separately, and the first insulation resistances RL1 and R2 are measured at different timings.
[Selection] Figure 1

Description

  The present invention relates to an electric vehicle including a ground fault detection system that detects a ground fault and an insulation state with respect to a ground portion (ground) of an ungrounded power source.

  Generally, in an electric vehicle, a high-voltage power supply (for example, 200 [V] or higher) is insulated from the vehicle body and handled as an ungrounded power supply.

  As described above, there has been proposed a technique for detecting a ground fault of a high-voltage ungrounded power supply (including a state in which an insulation resistance is lowered due to leakage or insulation deterioration) (Patent Document 1).

  In the technique according to Patent Document 1, a ground fault of a single non-grounded power source is determined.

JP-A-8-226950

  By the way, recently, an electric vehicle that drives a load by using a first non-grounded power source, for example, a fuel cell, and a second non-grounded power source, for example, a power storage device (battery or the like) has been proposed. And, the configuration of the ground fault detection system for an electric vehicle having the second ungrounded power source has not been clarified.

  The present invention solves this type of problem, and is suitable for an electric vehicle having first and second ungrounded power supplies, and provides an electric vehicle including a ground fault detection system having high insulation resistance measurement accuracy (detection accuracy). The purpose is to do.

  An electric vehicle equipped with a ground fault detection system according to the present invention includes a load, a first non-grounded power source of a voltage (E1) for supplying power to the load, and one between the load and the first non-grounded power source. And a second non-grounded power source connected to the other input / output terminal of the converter and having a lower voltage (E2 (E2 <E1)) than the first non-grounded power source. The automobile has the following features (1) to (4).

  (1) A first insulation resistance detection unit that detects a first insulation resistance with respect to a grounding part of the first non-grounded power supply, and a second insulation resistance detection that detects a second insulation resistance with respect to the grounding part of the second non-grounded power supply. And the first insulation resistance or the second insulation resistance are compared with an abnormality detection threshold value, and either the first insulation resistance or the second insulation resistance is smaller than the abnormality detection threshold value. A ground fault determination unit for determining a ground fault.

  According to the invention having this feature (1), the first and second insulation resistance detectors are provided in the first and second non-grounded power supplies, respectively, so that the insulation resistance detection accuracy can be improved. .

  (2) In the invention having the above feature (1), the abnormality detection threshold is different from each other in the first abnormality detection threshold and the second abnormality detection value that have the same leakage current value for each of the first insulation resistance and the second insulation resistance. The abnormality detection threshold value is set. With this setting, it is possible to determine the presence or absence of a ground fault with the same leakage current in both the first and second ungrounded power supplies.

  (3) In the invention having the above feature (1) or (2), each of the first insulation resistance detector and the second insulation resistance detector is a circuit having the same connection configuration, and the first insulation The resistance detector obtains a charging voltage (V01) by charging the first capacitor toward the voltage (E1) of the first non-grounded power source for a first predetermined time, discharges the voltage, and then passes through the first insulation resistance. And charging the first capacitor toward the voltage (E1) of the first non-grounded power source for a second predetermined time to obtain a charging voltage (V11), based on the ratio of the charging voltages (V01) and (V11) The first insulation resistance is calculated, and the second insulation resistance detection unit charges the second capacitor for a third predetermined time toward the voltage (E2) of the second non-grounded power source to obtain a charging voltage (V02). And after discharging, through the second insulation resistance, A charge voltage (V12) is obtained by charging the second capacitor toward a ground power supply voltage (E2) for a fourth predetermined time, and based on a ratio between the charge voltage (V02) and (V12), the second insulation The resistance is calculated.

  According to the invention having the feature (3), each of the first and second insulation resistance detectors can be configured by a so-called flying capacitor system.

  (4) In the invention having the above feature (3), the first insulation resistance detection unit and the second insulation resistance detection unit detect the first insulation resistance and the second insulation resistance, respectively, at different timings. It is characterized by that. If comprised in this way, the 1st insulation resistance of a 1st non-grounded power supply and the 2nd insulation resistance of a 2nd non-grounded power supply can be detected reliably and correctly.

  According to this invention, the detection accuracy of the insulation resistance of the electric vehicle having the first and second ungrounded power supplies can be improved.

1 is an overall configuration diagram of an electric vehicle including a ground fault detection system according to an embodiment of the present invention. It is a circuit diagram of a DC / DC converter. It is a circuit diagram of an inverter. It is a circuit diagram of a 1st insulation resistance detection part. It is a circuit diagram of a 2nd insulation resistance detection part. It is a time chart used for the principle operation | movement description of the measurement of an insulation resistance. It is explanatory drawing of a power supply voltage measurement period (charging period). It is explanatory drawing of a capacitor voltage reading and discharge period. It is explanatory drawing of + side ground fault measurement period (charge period). It is explanatory drawing corresponding to the magnitude of an insulation resistance, and the change of the charging voltage within predetermined time. It is a characteristic explanatory view of the relationship between the voltage ratio and the insulation resistance value. It is explanatory drawing of the example which has a ground fault in the middle of the 1st ungrounded power supply. It is explanatory drawing of the example which has a ground fault in the middle of the 2nd non-grounded power supply. It is correspondence explanatory drawing of the charge time by the difference in the power supply which has a ground fault. It is explanatory drawing of the read value of the insulation resistance by the difference in the power supply which has a ground fault. It is explanatory drawing of the extent of detection of ground fault resistance by the voltage difference of a 1st non-grounded power supply and a 2nd non-grounded power supply. It is explanatory drawing of the example which cannot detect ground fault resistance, when the voltage difference of a 1st non-grounded power supply and a 2nd non-grounded power supply is large. It is a time chart used for operation | movement description of one Example of this invention. FIG. 6 is an explanatory diagram of a correspondence relationship between a voltage ratio and a first insulation resistance. FIG. 6 is an explanatory diagram of a correspondence relationship between a voltage ratio and a second insulation resistance. It is a whole block diagram of an electric vehicle provided with the ground fault system which concerns on other embodiment of this invention.

  Hereinafter, an embodiment of an electric vehicle including a ground fault detection system according to the present invention will be described with reference to the drawings.

  FIG. 1 shows an overall configuration diagram of an electric vehicle 10 according to an embodiment.

  The electric vehicle 10 basically has a fuel cell 14 (first non-power source) as a first ungrounded power source (first DC power source) that generates a voltage E1 between the first main circuit wirings 1P and 1N. And a battery 12 (a power storage device and a second power source) that generates a voltage E2 (E1> E2) between the second main circuit wirings 2P and 2N. 2 also referred to as a non-grounded power supply 12) and a travel drive motor 16 that is a load to which electric power is supplied from the hybrid DC power supply device through the inverter 22. A diode 15 is inserted between the fuel cell 14 and the inverter 22 to prevent current from flowing into the fuel cell 14.

  The fuel cell 14 has, for example, a stack structure in which cells formed by sandwiching a solid polymer electrolyte membrane between an anode electrode and a cathode electrode from both sides are stacked. A reaction gas supply unit 18 is connected to the fuel cell 14 through a pipe. The reaction gas supply unit 18 includes a hydrogen tank (not shown) that stores hydrogen (fuel gas) as one reaction gas, and a compressor (not shown) that compresses air (oxidant gas) as the other reaction gas. I have. A power generation current generated by an electrochemical reaction in the fuel cell 14 of hydrogen and air supplied from the reaction gas supply unit 18 to the fuel cell 14 is supplied to the motor 16 and the battery 12.

  The fuel cell system 11 includes an ECU (Electronic Control Unit) 40 (control unit) that controls the entire electric vehicle 10 including control of the fuel cell 14 and the reaction gas supply unit 18.

  The DC / DC converter 20 has one side connected to the battery 12 through the second main circuit wires 2P and 2N and the switch 42, and the other side connected to the fuel cell 14 and the motor 16 side through the first main circuit wires 1P and 1N. This is a chopper type voltage converter.

  FIG. 2 shows a circuit diagram of the DC / DC converter 20.

  The DC / DC converter 20 converts the voltage E2 of the battery 12 into a voltage E1 (E2 <E1) on the fuel cell 14 side, and converts the voltage E1 on the fuel cell 14 side to a voltage E2 on the battery 12 side. This is a step-up / step-down voltage converter that performs voltage conversion (step-down conversion).

  The DC / DC converter 20 includes three-phase phase arms PA, QA, RA driven by the ECU 40, and a reactor 90.

  P-phase arm PA is composed of an upper arm element (upper arm switching element 81p and diode 83p) and a lower arm element (lower arm switching element 82p and diode 84p).

  Q-phase arm QA includes an upper arm element (upper arm switching element 81q and diode 83q) and a lower arm element (lower arm switching element 82q and diode 84q).

  R-phase arm RA is composed of an upper arm element (upper arm switching element 81r and diode 83r) and a lower arm element (lower arm switching element 82r and diode 84r).

  As the upper arm switching elements 81p, 81q, 81r and the lower arm switching elements 82p, 82q, 82r, for example, MOSFETs or IGBTs are employed.

  Reactor 90 is inserted between the midpoint (common connection point) of each phase arm PA, QA, RA and the positive electrode of battery 12, and DC / DC converter 20 converts the voltage between voltage E2 and voltage E1. In doing so, it has the function of releasing and storing energy.

  Smoothing capacitors 94 and 96 are inserted between the second main circuit wirings 2P and 2N and the first main circuit wirings 1P and 1N, respectively.

  The arm switching elements 81p, 81q, 81r, 82p, 82q, and 82r are switched on and off according to the level of the gate drive signal (drive voltage) supplied from the ECU 40. In this case, the DC / DC converter 20 operates in a three-phase arm replacement driving operation or an all-phase simultaneous driving operation.

  FIG. 3 shows a circuit diagram of the inverter 22. The inverter 22 has a three-phase full-bridge configuration, performs DC / AC conversion, converts DC to three-phase AC, and supplies it to the U-phase coil, V-phase coil, and W-phase coil of the motor 16. The direct current after the alternating current / direct current conversion accompanying the regenerative operation is supplied from the first main circuit wiring 1P, 1N side to the second main circuit wiring 2P, 2N side through the DC / DC converter 20, and the battery 12 is charged.

  The inverter 22 includes switching elements 51u, 51v, 51w, 52u, 52v, 52w such as MOSFETs or IGBTs driven by the ECU 40, and diodes 53u, 53v, 53w, 54u, 54v, 54w connected in the reverse direction. The

  Again in FIG. 1, motor 16 rotates wheels 26 through transmission 24. In practice, the inverter 22 and the motor 16 are collectively referred to as a load 23.

  The high voltage battery 12 connected between the second main circuit wirings 2P and 2N via the switch 42 is a power storage device (energy storage), and uses, for example, a lithium ion secondary battery or a capacitor. be able to. In this embodiment, a lithium ion secondary battery is used.

  As described above, the ECU 40 controls the entire electric vehicle 10 including the fuel cell system 11, the switch 42, the DC / DC converter 20, the load 23, and first and second insulation resistance detectors 51 and 52 described later. And a microcomputer to be controlled. A main switch 35 (power switch) is connected to the ECU 40, and the main switch 35 has a function as an ignition switch for turning on (starting or starting) and turning off (stopping) the electric vehicle 10 and the fuel cell system 11. .

  Further, a first insulation resistance detection unit 51 that detects a ground fault of the fuel cell 14, the inverter 22 and the motor 16 connected to the first main circuit wirings 1P and 1N based on the value of the insulation resistance RL1 includes a first main circuit wiring 1P, A second insulation resistance detection unit 52 is provided between 1N and detects the ground fault of the battery 12 connected to the second main circuit wirings 2P and 2N based on the value of the insulation resistance RL2. Provided.

  The ground fault detection system is configured by the ECU 40 having the first and second insulation resistance detection units 51 and 52 and the ground fault determination unit 39 (comparison unit) as a functional unit.

  FIG. 4 shows a circuit diagram of the first insulation resistance detector 51. FIG. 5 shows a circuit diagram of the second insulation resistance detector 52. The first and second insulation resistance detectors 51 and 52 have the same circuit connection configuration.

  In FIG. 4 (FIG. 5), one ends of a switch SW1 (SW11) and a switch SW2 (SW21) are connected between the first main circuit wirings 1P and 1N (second main circuit wirings 2P and 2N), and the switch SW1 (SW11 ) Is connected to one end of a resistor 101 (111) having a resistance value R1 (R11). The other end of the resistor 101 (111) is connected to one end of a resistor 104 (114) having a resistance value R4 (R41), one end of a switch SW3 (SW13), and one end of a capacitor 106 (116) of a capacitor C1 (C11). Is done.

  The other end of the resistor 104 (114) is connected through a switch SW4 (SW41) to a voltage sensor (voltmeter) 50a (50b) that measures a voltage value (voltage) V between the resistor 104 (114) and the ground (vehicle body, vehicle body ground). At the same time, the detected voltage value V is stored in the memory (storage unit) of the ECU 40. The other end of the switch SW3 (SW31) is grounded through a resistor 103 (113) having a resistance value RS1 (RS11).

  The other end of the capacitor 106 (116) is connected to the other end of the switch SW2 (SW21) and grounded through the resistor 105 (115) having a resistance value R5 (R51) via the switch SW5 (SW51).

  The opening / closing timing of the switches SW1 to SW4 (SW11 to SW51) is controlled by the ECU 40 (switch opening / closing timing control unit).

  Basically, the ground fault detection operation of the electric vehicle 10 including the ground fault detection system configured as described above will be described in the following order of A, B, and C.

A. B. Description of operation principle of insulation resistance measurement (detection) by the first and second insulation resistance detectors 51 and 52 Explanation of problems (problems) when only the first insulation resistance detection unit 51 exists and the second insulation resistance detection unit 52 does not exist, which is a premise of the present invention. Explanation of operation when both the first and second insulation resistance detectors 51 and 52 according to the embodiment of the present invention exist

  First, A. The operation principle of the insulation resistance measurement (detection) by the first and second insulation resistance detectors 51 and 52 will be described by taking the first insulation resistance detector 51 as an example.

FIG. 6 is a time chart used to explain the operation of measuring the insulation resistance RL. At the first rise time (first predetermined time) T1r at time points t0 to t1 of “I: power supply voltage measurement period”, the switches SW1 and SW2 are closed as shown in FIG. The charging shown by the following equation (1) is performed toward the voltage E1 [V] of 14.
V0 = E1 [1-exp {− (T1r / R1 × C1)}] (1)

  As shown in FIG. 8, the voltage V0 is measured by the voltage sensor 50a and stored in the memory of the ECU 40 at the time t1 when the switches SW1 and SW2 are opened and the switches SW4 and SW5 are closed. The ECU 40 and the voltage sensor 50a operate as a peak hold circuit from time t1 to time t2. Time t1 to t2 is “II. Capacitor voltage reading / discharging period”. The discharge is performed through the internal resistance of the voltage sensor 50a as shown by the path of the arrow in FIG.

  In addition, between time t0 and t2, with respect to charging of the capacitor 106, an insulation resistance RL between the vehicle body (ground) and the positive side of the first non-grounded power supply 14 (the resistance value is also RL [Ω]). It can be seen that the circuit connection is free from the influence of.

Next, at a second rise time (second predetermined time) T2r between time points t2 and t3 of “III. + Side ground fault measurement period”, as shown in FIG. 9, the switches SW2 and SW3 are closed, and the first From the positive side of the non-grounded power supply 14, the insulation resistance RL (here, the first insulation resistance RL 1 is described as RL), the resistor 103, the switch SW 3, the capacitor 106, the switch SW 2, and the first non-grounded power supply 14. The current flows along the path to the negative side, and the capacitor 106 is charged by the following equation (2) toward the voltage E1 [V] of the first non-grounded power supply 14.
V1 = E1 [1-exp {-(T2r / (RL + RS1) × C1)}]
... (2)

  This voltage V1 is measured by the voltage sensor 50a in a connection circuit similar to that shown in FIG. 8 (the switches SW1 and SW2 are opened and the switches SW4 and SW5 are closed) and stored in the memory of the ECU 40. . The ECU 40 and the voltage sensor 50a operate as a peak hold circuit from time t3 to time t4. Times t3 to t4 are “IV. Capacitor voltage reading / discharging period”. As described above, the capacitor 106 functions as a flying capacitor.

  In this case, as shown in FIG. 10, which is a diagram for explaining the correspondence between the magnitude of the insulation resistance and the change in the charging voltage within a predetermined time, the voltage V1 can be understood from the equation (2) that the current limiting resistance is RL + RS1. As the insulation resistance RL increases, the time constant increases, and the voltage V1 at the second predetermined time T2r decreases. As the insulation resistance RL decreases, the charging voltage V1 becomes the voltage of the first ungrounded power supply 14 (power supply). It can be seen that the voltage approaches E1.

  Therefore, the insulation resistance RL can be obtained from the ratio V0 / V1 of the voltage V1 to the voltage V0 as shown in the example of the characteristic 110 in FIG. 11 showing the relationship between the voltage ratio V0 / V1 and the insulation resistance (insulation resistance value) RL. .

  Note that the ground fault occurs from the positive side (positive electrode) of the first non-grounded power source 14 and the middle of the first non-grounded power source 14 {the fuel cell 14 is a stack configuration in which fuel cells are stacked (connected in series). May occur at any cell position}, but in this case, as shown in Patent Document 1, by detecting the insulation resistance on the negative side (negative electrode), , The error can be offset. That is, if the voltage from the negative electrode to the ground fault location is E1L and the voltage from the ground fault location to the positive electrode is E1H, E1L + E1H = E1, and thus the error can be offset.

For example, as shown in FIG. 12, the voltage V1 when the switch SW2 and the switch SW3 are closed can be obtained by the following equation (3).
V1 = E1L [1-exp {-(T2r / (RL + RS1) × C1)}]
... (3)

  Next, the ground fault determination unit 39 of the ECU 40 compares the abnormality detection threshold value Rx [Ω] (reference value), which is an insulation resistance threshold value that is equal to or less than a predetermined leakage current considering safety, with the measured insulation resistance RL, When the insulation resistance RL is smaller than the abnormality detection threshold Rx (RL <Rx), it is determined that there is a ground fault, and a warning is given.

  Next, B. A problem (problem) when only the first insulation resistance detection unit 51 exists and the second insulation resistance detection unit 52 does not exist will be described.

  As shown in FIG. 13, consider a case where only the first insulation resistance detection unit 51 exists and the second non-grounded power supply 12 is grounded (insulation resistance is lowered) on the way. In this case, when the time chart shown in FIG. 6 is applied and the insulation resistance RL of the first ungrounded power supply 14 is to be detected, the connection is made as shown in FIG. 7, and the voltage V0 is expressed by the above equation (1). It is measured.

Next, in order to detect the insulation resistance RL of the first non-grounded power supply 14, it is the second non-grounded power supply 12 that is actually grounded when connected as shown in FIG. 9 (FIG. 13). Since the current flows through the path of FIG. 13, the voltage V1 is obtained by the following equation (4).
V1 = E2L [1-exp {-(T2r / (RL + RS1) × C1)}]
... (4)

  However, if the voltage from the ground fault point to the positive electrode of the first non-grounded power supply 14 is E2H, E2H + E2L = E1, and therefore the error cannot be eliminated even by using the method according to Patent Document 1.

  That is, with reference to the charging characteristic diagram of FIG. 14, even when the insulation resistance RL has the same value, there is a case where a ground (earth fault) exists on the first ungrounded power supply 14 side of the voltage E1, and the voltage E2 ( When the (E2 <E1) side exists (ground fault), the measurement result of the voltage V1 is different. In other words, when only the first insulation resistance detection unit 51 is present, measurement is performed based on the voltage E1, and therefore when there is a ground fault (insulation resistance RL) on the second non-grounded power supply 12 side of the voltage E2. The reached voltage V1 during the charging time of the second predetermined time T2r is lower than V1b and the reached voltage V1fc when there is a ground fault (insulation resistance RL) on the first non-grounded power supply 14 side. In other words, when there is a ground fault (insulation resistance RL) on the second non-grounded power supply 12 side of the voltage E2, there is a problem that the rise time becomes longer and the insulation resistance RL is read higher.

  Referring to the characteristic 111 of the insulation resistance with respect to the voltage ratio shown in FIG. 15, when the insulation resistance RL is measured on the basis of the voltage E1 only by the first insulation resistance detection unit 51, the ground fault (insulation resistance RL) becomes the voltage E2. In the case of the second ungrounded power supply 12 side, the ratio V0 / V1 = V0 / V1b becomes high, and the insulation resistance RL is read higher. When the ground fault (insulation resistance RL) is on the first ungrounded power supply 14 side of the voltage E1, the ratio V0 / V1 = V0 / V1fc becomes small, and the insulation resistance RL can be read accurately and accurately.

  This tendency becomes more prominent as the difference between the voltage E1 and the voltage E2 increases. Therefore, as shown in FIG. 16, when the difference ΔV (E1−E2) is small, the abnormality detection threshold Rx is compared with the insulation resistance RL (E1 side result, E2 side result) on the E1 side and E2 side. As shown in FIG. 17, when the difference ΔV (E1-E2) is large, the abnormality detection threshold value Rx and the insulation resistance RL (E1 side, E2 side) can be detected. Even if the E1 side result and the E2 side result) are compared, the ground fault cannot be detected.

  C. The operation when both the first and second insulation resistance detectors 51 and 52 according to the embodiment of the present invention are present will be described with reference to FIGS.

  The ECU 40 outputs an operation signal for operating the first insulation resistance detection unit 51 between the time point ta and the time point tb to the first insulation resistance detection unit 51, and then the second operation signal between the time points tc and td at different timings. An operation signal for operating the insulation resistance detection unit 52 is output to the second insulation resistance detection unit 52.

  In this case, the first insulation resistance detector 51 charges the T1r capacitor 106 (capacitance C1) for the first predetermined time toward the voltage E1 of the first non-grounded power supply 14 to obtain the charging voltage V01 (time point t0), and discharges it. (Time t2), the T2r capacitor 106 is charged through the first insulation resistance RL1 (RL in FIG. 7) toward the voltage E1 of the first non-grounded power supply 14 for a second predetermined time to obtain the charging voltage V11. (Simultaneous point t2) Based on the ratio (V01 / V11) between the charging voltages V01 and V11, the first insulation resistance RL1 is calculated using the characteristic 110 shown in FIG. 19 corresponding to FIG.

  Next, the second insulation resistance detector 52 charges the T12r capacitor 106 (capacitance C11) for the third predetermined time toward the voltage E2 of the second non-grounded power supply 12 to obtain the charging voltage V02 (time t11), and discharges it. After that (time t12), the charging voltage V12 is obtained by charging the T22r capacitor 116 for the fourth predetermined time toward the voltage E2 of the second non-grounded power supply 12 via the second insulation resistance RL2, and the charging voltages V02 and V12 are obtained. Based on this ratio (V02 / V12), the second insulation resistance RL2 is calculated using the characteristic 210 shown in FIG.

  In this way, by measuring the first and second insulation resistances RL1 and RL2 while shifting the timing based on the voltage E1 of the first non-grounded power supply 14 and the voltage E2 of the second non-grounded power supply 12, respectively, the insulation resistance RL is measured. The detection accuracy of (RL1, RL2) can be increased.

  Next, the ground fault determination unit 39 compares the measured first insulation resistance RL1 and second insulation resistance RL2 with the abnormality detection thresholds Rx1 (FIG. 19) and Rx2 (FIG. 20), respectively, to determine the first insulation resistance RL1 or If any of the second insulation resistances RL2 has a value smaller than the abnormality detection thresholds Rx1 and Rx2 (RL1 <Rx1 or RL2 <Rx2), it is determined that there is a ground fault and a warning is given.

  Although the abnormality detection thresholds Rx1 and Rx2 may be the same value, it is preferable to set the leakage current to a different value that is not less than a predetermined value (leakage current is the same value), for example, not less than a standard value defined in the power supply standard. .

  Note that the present invention is not limited to the above-described embodiment, and based on the description in this specification, for example, as shown in the overall configuration diagram of another embodiment of FIG. The resistance detection unit 53 is provided, the timings are shifted, the first to third insulation resistance detection units 51 to 53 are operated, and the first to third insulation resistances RL1, RL2, and RL3 are changed to the measurement configuration. Of course, it is possible to adopt the following configuration.

DESCRIPTION OF SYMBOLS 10 ... Electric vehicle provided with a ground fault detection system 12 ... Second ungrounded power source (battery) 14 ... First ungrounded power source (fuel cell)
39 ... Ground fault determination unit 40 ... ECU
51-53 ... 1st-3rd insulation resistance detection part

An electric vehicle including a ground fault detection system according to the present invention includes a load including a drive motor, a first ungrounded power source that supplies power to the load and generates a first voltage (E1), the load, and the load A converter having one input / output terminal connected to the first ungrounded power supply, and a second voltage (E2 (E2 <E2 <) connected to the other input / output terminal of the converter and lower than the first ungrounded power supply. An electric vehicle including a second non-grounded power source that generates E1)) has the following features (1) to ( 2 ).

(1) Connected to both ends of the first non-grounded power source, connected to both ends of the second non-grounded power source, and a first insulation resistance detecting unit for detecting a first insulation resistance with respect to the grounding part of the first non-grounded power source A second insulation resistance detection unit for detecting a second insulation resistance with respect to a ground part of the second non-grounded power source, the first insulation resistance and the second insulation resistance are compared with an abnormality detection threshold, and the first one of the insulation resistance and the second insulation resistance, e Bei and a ground fault and determines the ground determining unit when the an abnormality detection threshold value smaller than the first insulation resistance detector, the first The first capacitor is charged to the first voltage (E1) of the 1 ungrounded power source for a first predetermined time to obtain a first charging voltage (V01), and after discharging, the first capacitor is passed through the first insulation resistance. The second predetermined time toward the first voltage (E1) of the first ungrounded power source 1 capacitor is charged to obtain a second charging voltage (V11), the first insulation resistance is calculated based on a ratio between the first charging voltage (V01) and the second charging voltage (V11), The 2 insulation resistance detector obtains a third charging voltage (V02) by charging the second capacitor toward the second voltage (E2) of the second non-grounded power source for a third predetermined time, and after discharging, The second capacitor is charged through a second insulation resistance toward the second voltage (E2) of the second ungrounded power source for a fourth predetermined time to obtain a fourth charging voltage (V12), and the third based on the ratio of the charge voltage (V02) and the fourth charging voltage (V12), characterized that you calculate the second insulation resistance.

According to the invention having the above feature ( 1 ), each of the first and second insulation resistance detectors can be configured by a so-called flying capacitor system.

( 2 ) In the invention having the above feature ( 1 ), the first insulation resistance detection unit and the second insulation resistance detection unit detect the first insulation resistance and the second insulation resistance, respectively, at different timings. It is characterized by that. If comprised in this way, the 1st insulation resistance of a 1st non-grounded power supply and the 2nd insulation resistance of a 2nd non-grounded power supply can be detected reliably and correctly.

Claims (4)

A load, a first non-grounded power source of voltage (E1) for supplying power to the load, a converter having one input / output terminal connected between the load and the first non-grounded power source, and In an electric vehicle comprising: a second non-grounded power source connected to the other input / output terminal and having a lower voltage (E2 (E2 <E1)) than the first non-grounded power source,
A first insulation resistance detector for detecting a first insulation resistance with respect to a ground part of the first non-grounded power source;
A second insulation resistance detector for detecting a second insulation resistance with respect to a ground part of the second non-grounded power source;
The first insulation resistance or the second insulation resistance is compared with an abnormality detection threshold, and when either the first insulation resistance or the second insulation resistance is smaller than the abnormality detection threshold, A ground fault determination unit for determining;
An electric vehicle equipped with a ground fault detection system. An electric vehicle comprising the ground fault detection system according to claim 1.
The abnormality detection threshold value is set to a first abnormality detection threshold value and a second abnormality detection threshold value which are different from each other in the same leakage current value for each of the first insulation resistance and the second insulation resistance. An electric vehicle equipped with a detection system. In an electric vehicle comprising the ground fault detection system according to claim 1 or 2,
Each of the first insulation resistance detector and the second insulation resistance detector is a circuit having the same connection configuration,
The first insulation resistance detecting unit charges the first capacitor for a first predetermined time toward the voltage (E1) of the first non-grounded power source to obtain a charging voltage (V01), discharges the first insulation, The first capacitor is charged through a resistor toward the voltage (E1) of the first ungrounded power source for a second predetermined time to obtain a charging voltage (V11), and the charging voltages (V01) and (V11) And calculating the first insulation resistance based on the ratio of
The second insulation resistance detection unit charges the second capacitor for a third predetermined time toward the voltage (E2) of the second non-grounded power source to obtain a charging voltage (V02), and discharges the second insulation resistance. Charge the second capacitor through a resistor toward the voltage (E2) of the second non-grounded power source for a fourth predetermined time to obtain a charging voltage (V12), and the charging voltages (V02) and (V12) An electric vehicle comprising a ground fault detection system, wherein the second insulation resistance is calculated on the basis of the ratio. An electric vehicle comprising the ground fault detection system according to claim 3,
An electric vehicle comprising a ground fault detection system, wherein the first insulation resistance detection unit and the second insulation resistance detection unit detect the first insulation resistance and the second insulation resistance, respectively, at different timings.

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