JP5382813B2 - Earth leakage detector - Google Patents

Description

  The present invention relates to a leakage detection device, and more particularly to a leakage detection device that detects leakage by applying an AC signal to a detection target.

  In electric vehicles such as EVs (Electric Vehicles), HEVs (Hybrid Electric Vehicles, hybrid cars), and PHEVs (Plug-in Hybrid Electric Vehicles, plug-in hybrid cars), high-voltage power supplies and high-voltage loads (for example, driving) In order to prevent an electric shock, a high voltage circuit composed of a motor control inverter for a motor is insulated from the body ground of the electric vehicle. However, there is a risk that the user may get an electric shock if the insulation resistance between the high-voltage circuit and the body ground decreases due to an accident or the attachment of battery fluid from a high-voltage battery used with a high-voltage power supply, resulting in a leakage. Therefore, an electric leakage detection device that detects the presence or absence of electric leakage is provided in the electric vehicle. Then, when the insulation resistance falls below a predetermined threshold (for example, 100 kΩ), the leakage detection device determines that a leakage has occurred, and for example, to stop electric power supply, Measures such as stopping the charging operation are taken.

  Therefore, conventionally, a method has been proposed in which an AC signal is applied to a high voltage circuit via a coupling capacitor, and leakage is detected from the amplitude fluctuation amount of the AC signal (see, for example, Patent Document 1).

  Conventionally, an AC signal is applied between the vehicle body and the high-voltage battery, and the resistance component of the admittance between the body and the high-voltage battery is obtained from the phase relationship between the voltage and current of the AC signal, and the obtained resistance component It has been proposed to detect electric leakage from (see, for example, Patent Document 2).

  Further, conventionally, an AC voltage is applied between a vehicle body and a high voltage battery via a series circuit of a resistor and a capacitor, and a voltage across the resistor is measured. Based on the measured voltage, the body and the high voltage battery are measured. Calculate stray capacitance between batteries. And by setting the reference data of the output voltage Vout of the resistor from the calculated value of the stray capacitance, the input voltage Vin of the resistor, and the resistance value of the insulation resistance to be detected, and comparing it with the actual output voltage Vout It has been proposed to detect electric leakage (see, for example, Patent Document 3).

  However, since the leakage detection method described in Patent Document 1 can only detect the combined impedance including the capacitive component on the vehicle side, it is affected by the stray capacitance due to the wiring of the high voltage circuit and the capacitor mounted on the high voltage load. End up. In addition, since the stray capacitance changes with time, even if the insulation resistance does not deteriorate, there is a possibility that the leakage is erroneously detected due to the fluctuation of the stray capacitance.

  In addition, in the leakage detection method described in Patent Document 2, it is necessary to provide a highly accurate current measurement circuit in order to measure a minute current necessary for detecting a resistance component of admittance. On the other hand, when the accuracy of the current measurement circuit is low, there is a possibility that leakage is erroneously detected.

  Furthermore, since the leakage detection method described in Patent Document 3 assumes that the stray capacitance hardly changes, there is a possibility that the leakage is erroneously detected when the stray capacitance changes.

JP-A-8-70503 Japanese Patent Laid-Open No. 11-218554 JP 2002-323526 A

  The present invention makes it possible to detect the leakage more accurately without the influence of the stray capacitance to be detected.

  A leakage detection device according to one aspect of the present invention is a leakage detection device that detects a leakage of a detection target, and is connected in series between an oscillation circuit that oscillates an AC signal, and the detection target and the oscillation circuit. A capacitor, a resistor connected in series between the capacitor and the oscillation circuit, a voltage ratio detecting means for detecting a voltage ratio at both ends of the resistor, and a position for detecting a phase difference between the voltages at both ends of the resistor. Phase difference detection means, and leakage detecting means for detecting the presence or absence of leakage based on the voltage ratio and phase difference of the voltage across the resistor.

  In the leakage detection device of one aspect of the present invention, an AC signal is applied to a detection target via a resistor and a capacitor, a voltage ratio between both ends of the resistor, and a phase difference between voltages at both ends of the resistor are detected. Based on a voltage ratio and a phase difference between voltages at both ends of the resistor, presence / absence of leakage is detected.

  Therefore, the leakage can be detected more accurately without the influence of the stray capacitance to be detected.

  This detection target is constituted by, for example, a high voltage circuit of an electric vehicle. This voltage ratio detection means, phase difference detection means, and leakage detection means are constituted by, for example, a microcomputer or a processor.

  The leakage detection means calculates a DC resistance component between the detection target and the ground based on a voltage ratio and a phase difference between voltages at both ends of the resistor, and compares the calculated DC resistance component with a predetermined threshold value. Based on the result, it is possible to detect the presence or absence of electric leakage.

  Thereby, the reference | standard which detects electric leakage can be set to a desired value.

  This ground is constituted by, for example, a ground of an electronic device or an electric circuit, a body ground of an electric vehicle, or the like.

  According to one aspect of the present invention, it is possible to detect a leakage current to be detected. In particular, according to one aspect of the present invention, it is possible to more accurately detect a leakage current without the influence of the stray capacitance to be detected.

It is a block diagram which shows one Embodiment of the leak detection apparatus to which this invention is applied. It is a block diagram which shows the structural example of the function of the calculating part of an electrical leakage detection apparatus. It is a graph which shows the simulation result of the alternating voltage detected when a stray capacitance does not exist. It is a graph which shows the simulation result of the alternating voltage detected when a stray capacitance exists.

Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described. The description will be given in the following order.
1. Embodiment 2. FIG. Modified example

<1. Embodiment>
[Example of configuration of leakage detection device]
FIG. 1 is a block diagram showing an embodiment of a leakage detection apparatus to which the present invention is applied. For example, the leakage detection device 101 is provided in an electric vehicle including the high voltage circuit 102 and detects the presence or absence of electric leakage between the high voltage circuit 102 and the body ground of the electric vehicle. The leakage detection device 101 is configured to include an oscillation circuit 111, a resistor 112, a coupling capacitor 113, voltage detection units 114 and 115, and a calculation unit 116.

  A resistor 112 and a coupling capacitor 113 are connected in series between the oscillation circuit 111 and the high voltage circuit 102, and an AC signal output from the oscillation circuit 111 passes through the resistor 112 and the coupling capacitor 113. Applied to the high voltage circuit 102. One end different from the one connected to the resistor 112 of the oscillation circuit 111 is connected to the body ground. Further, one end different from the one connected to the resistor 112 of the coupling capacitor 113 is connected to the negative terminal of the battery 121 of the high voltage circuit 102.

The voltage detection unit 114 detects the AC voltage V ₁ between the oscillation circuit 111 and the resistor 112 and supplies a signal indicating the detection result to the calculation unit 116. The voltage detector 115 detects the AC voltage V ₂ between the resistor 112 and the coupling capacitor 113 and supplies a signal indicating the detection result to the calculator 116. That is, the AC voltages V ₁ and V ₂ across the resistor 112 are detected by the voltage detectors 114 and 115.

The calculation unit 116 is configured by, for example, a microcomputer or a processor. As will be described later, the calculation unit 116 determines that the high voltage circuit 102 and the body are based on the amplitude ratio | V _S | (= | V ₂ / V ₁ |) of the AC voltage V ₁ and the AC voltage V ₂ and the phase difference φ. Detects whether there is a leakage between the earth and outputs the detection result to the outside.

  The high voltage circuit 102 is configured to include a battery 121 and a high voltage load 122. The high voltage load 122 includes, for example, a drive motor control inverter for an electric vehicle, a compressor motor for an air conditioner, and the like, and is driven by the power of the battery 121.

  Further, the high voltage circuit 102 and the body ground are insulated. Therefore, as shown in FIG. 1, it can be regarded equivalently that both are connected by the insulation resistance 131. A stray capacitance 132 exists between the high voltage circuit 102 and the body ground.

Hereinafter, the resistance value of the resistor 112 is represented by R _S , the capacitance of the coupling capacitor 113 is represented by C _I , the resistance value of the insulation resistor 131 is represented by R _L , and the capacitance of the stray capacitance 132 is represented by C _f . Further, the frequency of the AC signal of the oscillation circuit 111 is represented by f, and the angular frequency is represented by ω (= 2πf).

[Configuration Example of Calculation Unit 116]
The calculation unit 116 is configured to include an amplitude ratio detection unit 151, a phase difference detection unit 152, and a leakage detection unit 153.

The amplitude ratio detection unit 151 detects the amplitude ratio | V _S | of the AC voltage V ₁ and the AC voltage V ₂ and outputs the amplitude ratio | V _S | to the DC resistance calculation unit 161 of the leakage detection unit 153.

The phase difference detection unit 152 detects the phase difference φ between the AC voltage V ₁ and the AC voltage V ₂ , and outputs the phase difference φ to the DC resistance calculation unit 161 of the leakage detection unit 153.

  The leakage detection unit 153 includes a DC resistance calculation unit 161, a comparison unit 162, and a memory 163, and detects the presence or absence of leakage between the high voltage circuit 102 and the body ground by the method described below.

The DC resistance calculation unit 161 calculates the resistance value R _L of the insulation resistance 131 from the amplitude ratio | V _S | of the AC voltage V ₁ and the AC voltage V ₂ and the phase difference φ.

[Calculation Method of Resistance Value _RL of Insulation Resistance 131]
Here, a method of calculating the resistance value _RL of the insulation resistor 131 will be described.

Combined impedance Z _L between the high-voltage circuit 102 and body ground is represented by the following formula (1).

The combined impedance of the capacitor _{C I} and a synthetic impedance _{Z L} of the coupling capacitor 113 and _{Z h,} when the _{V 2 / V 1 = V S} , V S is represented by the following formula (2).

Therefore, the amplitude ratio | V _S | of the AC voltage V ₁ and the AC voltage V ₂ is expressed by the following equation (3).

Also, -Tanfai based on the phase difference φ of the AC voltages V ₁ and an AC voltage V ₂ is represented by the following formula (4).

From the equations (3) and (4), the resistance value _RL of the insulation resistor 131 is expressed by the following equation (5).

Since the resistance value R _S of the resistor 112 and the capacitance C _I of the coupling capacitor 113 are known, the detected amplitude ratio | V _S | of the AC voltage V ₁ and AC voltage V ₂ and the phase difference φ are expressed by Equation (5). by applying to a DC resistance component of the combined impedance Z _L can be determined resistance value R _L of the insulation resistance 131.

The direct current resistance calculation unit 161 outputs the resistance value _RL calculated as described above to the comparison unit 162.

The comparison unit 162 compares the resistance value _RL with the leakage detection resistance threshold value stored in advance in the memory 163, and detects the presence or absence of leakage based on the comparison result. That is, when the resistance value R _L is greater than or equal to the leakage detection resistance threshold value, the comparison unit 162 determines that no leakage has occurred, and when the resistance value R _L is less than the leakage detection resistance threshold value, Is determined to have occurred. The comparison unit 162 outputs the detection result of the presence or absence of leakage to the outside.

[Simulation results of AC voltages V ₁ and V ₂ ]
3 and 4 show the simulation results of the AC voltages V ₁ and V ₂ when the stray capacitance 132 does not exist and when it exists in the circuit of FIG. The simulation conditions in both figures are the same except for the capacitance C _f of the stray capacitance 132. Specifically, in the simulation of FIG. 3, the capacitance C _f = 0 μF is set, and in the simulation of FIG. 4, the capacitance C _f = 0.5 μF is set. In both simulations, the resistance value R _S = 100 kΩ of the resistor 112, the capacitance C _I of the coupling capacitor 113 = 1 μF, the resistance value R _L of the insulation resistor 131 = 100 kΩ, and the frequency f of the AC signal of the oscillation circuit 111 = It is set to 10 Hz.

Comparing the simulation result of FIG. 4 with the simulation result of FIG. 3, it can be seen that a phase difference φ occurs between the AC voltage V ₁ and the AC voltage V ₂ and the amplitude of the AC voltage V ₂ is small. That is, it can be seen that the amplitude ratio | V _S | and the phase difference φ between the AC voltage V ₁ and the AC voltage V ₂ vary depending on the capacitance C _f of the stray capacitance 132.

  Therefore, in Patent Document 1 described above, since the leakage detection is performed by simply comparing the peak value of the AC signal and the peak value of the detection voltage, for example, as shown in FIG. If it drops, there is a possibility of false detection of leakage.

As described above, according to the leakage detection device 101, it is possible to detect the presence / absence of leakage based only on the resistance value R _L of the insulation resistance 131 without the influence of the stray capacitance 132, and as a result, Detection accuracy is improved.

Further, as in the invention described in Patent Document 2 described above, only the amplitude ratio | V _S | and the phase difference φ between the AC voltage V ₁ and the AC voltage V ₂ are detected without detecting a minute current. The detection accuracy of leakage can be improved.

<2. Modification>
In the above description, the example in which the leakage detection device 101 is applied to an electric vehicle has been shown. However, the present invention can be applied to leakage detection of devices other than the electric vehicle.

  The embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 101 Leakage detection apparatus 102 High voltage circuit 111 Oscillation circuit 112 Resistance 113 Coupling capacitor 114,115 Voltage detection part 116 Operation part 121 Battery 122 High voltage load 131 Insulation resistance 132 Stray capacity 151 Amplitude ratio detection part 152 Phase difference detection part 153 Leakage Detection unit 161 DC resistance calculation unit 162 Comparison unit

Claims (2)

In the leakage detection device that detects the leakage of the detection target,
An oscillation circuit for oscillating an AC signal;
A capacitor connected in series between the detection object and the oscillation circuit;
A resistor connected in series between the capacitor and the oscillation circuit;
Voltage ratio detecting means for detecting a voltage ratio between both ends of the resistor;
Phase difference detecting means for detecting a phase difference between voltages at both ends of the resistor;
A leakage detecting device comprising: a leakage detecting means for detecting the presence or absence of leakage based on a voltage ratio and a phase difference between voltages at both ends of the resistor. The leakage detection means calculates a DC resistance component between the detection target and the ground based on a voltage ratio and a phase difference between voltages at both ends of the resistor, and compares the calculated DC resistance component with a predetermined threshold value. The leakage detection device according to claim 1, wherein the presence / absence of leakage is detected based on the following.

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