JP6428448B2 - Insulation resistance drop detector - Google Patents

Description

  The present invention relates to an insulation resistance decrease detection device, and more particularly to an apparatus for detecting a decrease in insulation resistance of an electric system mounted on a vehicle.

  2. Description of the Related Art In recent years, as an environmentally friendly vehicle, a vehicle that is mounted with a power storage device (for example, a secondary battery or a capacitor) and that travels by driving force generated by a motor using electric power stored in the power storage device has attracted attention. . Such vehicles include, for example, electric vehicles, hybrid vehicles, fuel cell vehicles, and the like.

  Such a vehicle is equipped with electric devices of relatively high voltage such as a power storage device, a motor for traveling, and an inverter for driving the vehicle. It is configured to be electrically insulated from the ground potential.

  Japanese Patent Laying-Open No. 2014-155329 (Patent Document 1) discloses a configuration for determining a decrease in insulation of an electric system mounted on a vehicle in such an electric vehicle. In Japanese Patent Application Laid-Open No. 2014-155329 (Patent Document 1), an AC signal is applied to an electric system, and a peak value of the AC signal is detected to determine whether or not insulation is reduced.

JP 2014-155329 A JP 2007-147391 A JP 2002-323526 A

  In the vehicle configured as described above, the stray capacitance of the high-voltage circuit in the common mode changes depending on what kind of electric equipment is connected to the electric system, thereby changing the impedance of the electric system to be detected. . When the stray capacitance increases, the insulation resistance is apparently lowered. Therefore, even if the insulation state of the electric system is actually normal, it may be erroneously determined that the insulation state is lowered.

  In Japanese Patent Application Laid-Open No. 2014-155329 (Patent Document 1), the frequency of the AC signal applied to the electric system is switched, and the stray capacitance in the common mode is estimated from the peak value when each frequency is used. Based on this, by changing the threshold value for determining the insulation decrease, the erroneous detection due to the impedance change as described above is prevented.

  However, in the method proposed in Japanese Patent Application Laid-Open No. 2014-155329 (Patent Document 1), a mechanism for switching the frequency of the AC signal is necessary, or the processing may be complicated to realize the estimation function. Therefore, there is room for further improvement from the viewpoint of cost and miniaturization.

  The present invention has been made to solve such a problem, and an object of the present invention is to accurately detect a decrease in insulation resistance of an electric system mounted on a vehicle using a relatively simple configuration. That is.

  The insulation resistance detection apparatus according to the present invention is an insulation resistance decrease detection apparatus for detecting a decrease in insulation resistance of an electric system mounted on a vehicle. The insulation resistance lowering detection apparatus includes a signal generation unit, a detection unit, a setting unit, and a determination unit. The signal generator applies an AC signal to a signal line that is electrically connected to the electrical system. The detection unit detects the peak value of the AC signal in the signal line. The setting unit changes the threshold value for determining the insulation deterioration according to the electrical device connected to the electrical system. The determination unit detects a decrease in insulation resistance based on the fact that the peak value detected by the detection unit is below the threshold value set by the setting unit.

  By adopting such a configuration, it is possible to set a threshold value for determining an insulation decrease in consideration of a change in stray capacitance caused by an electrical device connected to the electrical system. It is possible to accurately detect a decrease in insulation resistance.

  ADVANTAGE OF THE INVENTION According to this invention, the detection accuracy of the fall of the insulation resistance of the electric system mounted in the vehicle can be improved.

It is a whole block diagram of a vehicle provided with the insulation resistance fall detection apparatus according to this Embodiment. It is an example of the block diagram which shows the detail of the insulation detection part in FIG. It is a figure for demonstrating the relationship between the crest value detected by a detection part, and insulation resistance. It is a figure which shows an example of the common capacity | capacitance and insulation determination threshold value of the electric equipment contained in an electric system. In this Embodiment, it is a flowchart for demonstrating the insulation resistance detection control performed by the insulation detection part.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Basic configuration of vehicle]
FIG. 1 is an overall block diagram of a vehicle 100 including an insulation resistance lowering detection apparatus (hereinafter also referred to as “insulation detection unit”) 600 according to the present embodiment.

  Referring to FIG. 1, vehicle 100 includes a power storage device 110, a system main relay SMR 115, a PCU (Power Control Unit) 120 that is a drive device, a motor generator 130, drive wheels 140, and an auxiliary device 150. And an ECU (Electronic Control Unit) 300 that is a control device and an insulation detection unit 600 that is an insulation decrease detection device.

  The power storage device 110 is a power storage element configured to be chargeable / dischargeable. The power storage device 110 includes, for example, a secondary battery such as a lithium ion battery, a nickel metal hydride battery, or a lead storage battery, and a power storage element such as an electric double layer capacitor.

  Power storage device 110 is connected to PCU 120 via power lines PL1 and NL1. Then, power storage device 110 supplies power for generating driving force of vehicle 100 to PCU 120. The power storage device 110 stores the electric power generated by the motor generator 130. The output of power storage device 110 is, for example, about 200V.

  Although not shown, power storage device 110 is provided with a voltage sensor and a current sensor for detecting the voltage and input / output current of power storage device 110. The detected voltage VB and current IB are output to ECU 300. ECU 300 calculates a state of charge (SOC) of power storage device 110 based on these detected values.

  SMR 115 includes a relay connected to the positive terminal of power storage device 110 and power line PL1, and a relay connected to the negative terminal of power storage device 110 and power line NL1. SMR 115 switches between supply and interruption of power between power storage device 110 and PCU 120 based on control signal SE <b> 1 from ECU 300.

  Although not shown, the PCU 120 includes a converter, an inverter, and the like. The converter is controlled by a control signal PWC from ECU 300 to convert the voltage from power storage device 110. The inverter is controlled by a control signal PWI from ECU 300 and drives motor generator 130 using electric power converted by the converter.

  Motor generator 130 is an AC rotating electric machine, for example, a permanent magnet type synchronous motor including a rotor in which permanent magnets are embedded.

  The output torque of motor generator 130 is transmitted to drive wheels 140 via a speed reducer, a power split mechanism, etc., and causes vehicle 100 to travel. The motor generator 130 can generate electric power by the rotational force of the drive wheels 140 during the regenerative braking operation of the vehicle 100. Then, the generated power is converted into charging power for power storage device 110 by PCU 120.

  Although FIG. 1 shows a configuration in which one motor generator and inverter pair is provided, the number of motor generators and inverters is not limited to this. A configuration in which more than two motor generator and inverter pairs are provided may be employed.

  Moreover, in this Embodiment, although an electric vehicle is demonstrated as an example as the vehicle 100, the vehicle 100 is not limited to this. That is, vehicle 100 represents a vehicle equipped with an electric motor for generating vehicle driving force, and includes, in addition to an electric vehicle, a fuel cell vehicle, a hybrid vehicle that generates vehicle driving force by an engine and an electric motor, and the like.

  The auxiliary machine device 150 is a generic term for air conditioners and low-voltage devices in the vehicle 100. Auxiliary device 150 includes, for example, a DC / DC converter for stepping down the voltage from power storage device 110, an auxiliary battery, and an auxiliary load such as audio, in addition to the above air conditioner.

  Vehicle 100 further includes a charging device 200, a charging relay CHR 210, and an inlet 220 as a configuration for external charging that charges power storage device 110 with electric power supplied from external power supply 500.

  Inlet 220 is provided on the outer surface of vehicle 100. A connector 410 of the charging cable 400 is connected to the inlet 220. Then, electric power from external power supply 500 is transmitted to vehicle 100 via charging cable 400.

  In addition to connector 410, charging cable 400 includes a plug 420 for connecting to outlet 510 of external power supply 500, and a wire portion 430 that electrically connects connector 410 and plug 420. In addition, the electric wire unit 430 may optionally include a charging circuit interrupt device (CCID) 440 for switching between supply and interruption of power from the external power supply 500.

  Charging device 200 is connected to inlet 220 through power lines ACL1 and ACL2. Charging device 200 is connected to power storage device 110 via charging relay CHR210 by power lines PL2 and NL2. Charging device 200 is controlled by control signal PWD from ECU 300, and converts AC power supplied from inlet 220 into charging power for power storage device 110.

  CHR 210 includes a relay connected to the positive terminal of power storage device 110 and power line PL2, and a relay connected to the negative terminal of power storage device 110 and power line NL2. Each relay included in CHR 210 is controlled by a control signal SE <b> 2 from ECU 300, and switches between supply and interruption of power from charging device 200 to power storage device 110.

  Insulation detection unit 600 is connected to the negative electrode of power storage device 110 and ground node GND (vehicle chassis), and detects a decrease in the insulation resistance of the power path in the vehicle system shown in FIG. Insulation detection unit 600 outputs a signal LDP indicating the presence or absence of leakage to ECU 300. Details of the insulation detection unit 600 will be described later with reference to FIG.

  ECU 300 includes a CPU (Central Processing Unit), a storage device, and an input / output buffer, all of which are not shown in FIG. 1, and inputs signals from each sensor and the like, and outputs control signals to each device. 100 and each device are controlled. Note that these controls are not limited to processing by software, and can be processed by dedicated hardware (electronic circuit).

  ECU 300 receives signal LDP indicating the presence or absence of electric leakage from insulation detection unit 600. The ECU 300 drives the PCU 120 and the auxiliary device 150 when a decrease in the insulation resistance of the vehicle system is detected by the signal LDP from the insulation detection unit 600 during traveling or when the auxiliary device 150 is driven. Is stopped and SMR1 is opened. If a decrease in insulation resistance is detected during external charging, driving of the charging device 200 is stopped and the CHR 210 is opened.

  In FIG. 1, one control device is provided as the ECU 300, but for example, a separate control device may be provided for each control target device or for each function. Further, the function of the insulation detection unit 600 may be included in the ECU 300.

  In the vehicle system of FIG. 1, a device excluding power storage device 110, ECU 300, and insulation detection unit 600 is collectively referred to as “electric system 105”.

[Configuration of insulation detector]
FIG. 2 is a diagram for explaining an example of a detailed configuration of the insulation detection unit 600 shown in FIG. Referring to FIG. 2, insulation detection unit 600 includes AC power supply 610 that is a signal generation unit, detection resistor 620, coupling capacitor 630, detection unit 640, threshold setting unit 650, and determination unit 660. Including. Detection unit 640 includes a bandpass filter (BPF) 642 and a peak hold circuit 644.

  AC power supply 610 and detection resistor 620 are connected in series between node N1 and ground node GND. The AC power source 610 outputs an AC signal SIG that changes at a predetermined frequency.

  Coupling capacitor 630 is connected between the negative terminal of power storage device 110 and node N1. Coupling capacitor 630 insulates electrical system 105 of vehicle 100 from ground node GND.

  Band-pass filter 642 receives AC signal SIG on node N 1, extracts only a component of a predetermined frequency from the received AC signal SIG, and outputs it to peak hold circuit 644. Peak hold circuit 644 holds the peak of the signal received from bandpass filter 642 and outputs the held signal VA to determination unit 660. That is, the signal VA is a signal representing the peak value of the AC signal received from the bandpass filter 642.

  Threshold setting unit 650 receives information INF relating to the electrical equipment connected to electrical system 105 from ECU 300. Based on information INF from ECU 300, threshold setting unit 650 determines threshold value Vth for determining the insulation decrease, and outputs determined threshold value Vth to determination unit 660.

  Determination unit 660 receives signal VA from peak hold circuit 644 and threshold value Vth for determination set by threshold setting unit 650. Determination unit 660 detects a decrease in insulation resistance Ri of the vehicle system by comparing signal VA with threshold value Vth, and outputs a signal LDP indicating a decrease (leakage) in insulation resistance Ri to ECU 300.

Next, an operation for detecting a decrease in the insulation resistance Ri will be described.
The AC signal SIG output from the AC power supply 610 is applied to a series circuit including a detection resistor 620, a coupling capacitor 630, and an insulation resistor Ri. As a result, the node N1 corresponding to the connection point of the detection resistor 620 and the coupling capacitor 630 has a voltage dividing ratio of the insulation resistance Ri and the detection resistor 620 (resistance value Rd): Ri / (Rd + Ri) and the AC from the AC power source 610. An AC voltage having a peak value that is a product of the amplitude (V0) of the signal SIG is generated.

  In the AC voltage generated at the node N1, components other than the frequency of the AC signal SIG are attenuated by the band-pass filter 642. The peak hold circuit 644 outputs the peak voltage VA of the AC voltage that has passed through the band pass filter 642 to the determination unit 660.

  The resistance value of the insulation resistance Ri is Ri >> Rd when normal. As Ri increases, the peak voltage VA becomes substantially equal to the voltage V0 of the AC power supply. On the other hand, when the insulation resistance Ri decreases, the voltage division ratio: Ri / (Rd + Ri) decreases, and the peak voltage VA decreases accordingly.

  Therefore, a decrease in the insulation resistance Ri can be detected by comparing the threshold voltage Vth according to the voltage division ratio between the allowable lower limit value of the insulation resistance Ri and the resistance value Rd of the detection resistor 620 with the peak voltage VA. it can.

  When insulation is normal, the peak voltage VA exceeds the threshold voltage Vth and reaches the maximum voltage V0. On the other hand, when insulation is abnormal, the peak voltage VA is smaller than the threshold voltage Vth.

  With the configuration of the insulation detection unit 600 as described above, it is possible to determine whether or not the insulation resistance of the electrical system 105 has decreased.

[Description of insulation resistance detection control]
On the other hand, each electric device connected to the electric system 105 has at least a stray capacitance (hereinafter also referred to as “common capacitance”) with respect to the ground node GND. For this reason, depending on the electrical equipment to be connected, the common capacity between the electric system 105 and the ground node GND may increase, and the impedance between the electric system 105 and the ground node GND may decrease due to the influence. Then, due to the increase in the common capacity, there is a possibility that it is erroneously detected that the insulation resistance of the electric system 105 is lowered although the insulation drop (leakage) has not actually occurred.

  Therefore, in the present embodiment, the electric power connected to the electric system 105 is set by variably setting the threshold value Vth for determining the insulation decrease according to the electric equipment connected to the electric system 105. Insulation resistance detection control is performed to reduce the influence of the common capacitance of the equipment and suppress false detection of insulation resistance drop.

  FIG. 3 is a diagram for explaining the relationship between the peak value (peak voltage VA) detected by the detection unit 640 and the insulation resistance in the present embodiment. In FIG. 3, the horizontal axis indicates the insulation resistance, and the vertical axis indicates the peak value.

  Referring to FIG. 3, in the design specification related to leakage, the upper limit value of the insulation resistance that should be detected as an insulation abnormality (insulation drop) is represented by Z1, and the minimum value of the insulation resistance that can be judged normal is Z2 (> Z1). Represent. That is, if the detected insulation resistance is Z1 or less, it is determined that the insulation of the electrical system is in an abnormal state, and if the detected insulation resistance is Z2 or more, it is determined that the insulation of the electrical system is normal. The The region where the insulation resistance is larger than Z1 and smaller than Z2 (Z1 <insulation resistance <Z2) is a region where normal / abnormal judgment can be different depending on the impedance of the electrical system.

  The curve L1 is a curve showing a relationship when the common capacitance of the electric system is 0 nF, that is, when the impedance of the electric system is the highest, for example, a curve in a state where all electric devices are disconnected.

  In this curve L1, when the peak value (voltage) in the case of the insulation resistance Z1 that is always detected as abnormal is Vth1, when the common capacitance is 0 nF, if the detected peak value is greater than this threshold value Vth1, It can be determined that at least the insulation resistance is not in an abnormal state.

  When the electric equipment is connected to the electric system and the common capacity increases, the peak value detected in the case of the same insulation resistance is lowered as shown by the curves L2, L3, and L4. In other words, as the common capacitance increases, the intersection of the threshold value Vth1 of the peak value and the curve shifts in the right direction of the graph (that is, the direction in which the insulation resistance increases).

  Here, the detected peak value is the threshold voltage until the common capacitance increases (curve L2, common capacitance = C1) until the intersection of the curve and the threshold value Vth1 reaches the position of the insulation resistance Z2. If Vth1 or more, it can be determined that the insulation resistance is not in an abnormal state.

  However, when the common capacitance is further increased, the peak value detected in the case of the insulation resistance Z2 that can be determined to be normal as shown by the curves L3 and L4 becomes lower than the threshold value Vth1. Therefore, in this state, when the insulation state is determined based on the comparison between the detected peak value and the threshold value Vth1, the abnormality is actually abnormal although the insulation resistance is normal (> Z2). There is a possibility of judging.

  Therefore, in the present embodiment, the threshold value Vth for determination is changed according to the common capacity of the electric equipment connected to the electric system. For example, as shown in FIG. 3, when the common capacitance is greater than C1 and less than or equal to C2, the threshold for determination is set to Vth2 (<Vth1), and when the common capacitance is greater than C2 and less than or equal to C3. Sets the threshold for determination to Vth3 (<Vth2). By determining using the threshold value Vth thus changed, it is possible to reduce the possibility of erroneously detecting a decrease in insulation even when the common capacitance is increased.

  More specifically, as shown in FIG. 4, a map showing the relationship between the common capacity corresponding to each electric device measured in advance by experiments or the like and the threshold value for judgment corresponding thereto is set as a threshold value. Stored in unit 650 (FIG. 2), threshold setting unit 650 sets determination threshold value Vth by referring to the map according to the connection state of each electrical device notified from ECU 300. To do.

  Thereafter, as described above with reference to FIG. 2, the determination unit 660 compares the threshold value Vth set by the threshold setting unit 650 with the peak value VA detected by the detection unit 640, Determine if there is insulation loss.

  FIG. 5 is a flowchart for explaining the insulation resistance detection control executed by the insulation detection unit 600 in the present embodiment. In the flowchart shown in FIG. 5, the processing is realized by a program stored in advance in the insulation detection unit 600 being called from the main routine and executed in a predetermined cycle. Alternatively, for some steps, it is also possible to construct dedicated hardware (electronic circuit) and realize processing.

  Referring to FIG. 5, threshold setting unit 650 determines which electrical device (high voltage unit) is currently in electrical system 105 based on information INF from ECU 300 at step (hereinafter abbreviated as S) 100. ) Is connected.

  In S110, threshold value setting unit 650 obtains threshold value Vth for determination according to the common capacity of the connected electrical device, using the map described with reference to FIG.

  In S120, determination unit 660 compares the threshold value currently used for insulation determination with threshold value Vth acquired in S110, and determines whether the threshold value currently in use is appropriate. Determine whether. Specifically, determination unit 660 determines whether or not the currently used threshold value is smaller than acquired threshold value Vth.

  If the currently used threshold value is appropriate (YES in S120), determination unit 660 skips S130 and proceeds to S140 to receive the currently used threshold value from peak hold circuit 644. Comparison with the peak voltage VA is performed to detect insulation drop.

  On the other hand, if the threshold value currently in use is not appropriate (NO in S120), the process proceeds to S130, and determination unit 660 uses threshold value Vth acquired in S110 as the determination threshold value. change. In addition, during the execution of the threshold value change, it is preferable to temporarily interrupt the detection of the insulation decrease in order to prevent erroneous determination.

  When the change of the threshold value for determination is completed, the process proceeds to S140, and the determination unit 660 restarts the insulation decrease detection using the changed threshold value and the peak voltage VA.

  By performing control according to the above processing, it is possible to determine a decrease in insulation resistance in consideration of the common capacity of the electric equipment connected to the electric system. Thereby, the erroneous determination resulting from the common capacity of the electrical equipment can be prevented, and thereby the detection accuracy of the decrease in insulation resistance can be improved. Further, in the control as described above, since no additional mechanism or complicated processing is required, the detection accuracy can be improved with a relatively simple configuration.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  100 vehicle, 105 electrical system, 110 power storage device, 115 SMR, 120 PCU, 130 motor generator, 140 driving wheel, 150 auxiliary device, 200 charging device, 210 CHR, 220 inlet, 300 ECU, 400 charging cable, 410 connector, 420 plug, 430 electric wire section, 440 CCID, 500 external power supply, 510 outlet, 600 insulation detection section, 610 AC power supply, 620 detection resistor, 630 coupling capacitor, 640 detection section, 642 band pass filter, 644 peak hold circuit, 650 Threshold setting unit, 660 determination unit, ACL1, ACL2, NL1, NL2, PL1, PL2 power line, GND ground node, N1 node.

Claims (1)

An insulation resistance decrease detection device for detecting a decrease in insulation resistance of an electrical system mounted on a vehicle,
A signal generating unit that provides an AC signal to a signal line that is electrically connected to the electrical system;
A detection unit for detecting a peak value of the AC signal in the signal line;
A setting unit for setting a threshold value for determining a decrease in insulation according to an electrical device connected to the electrical system;
A determination unit that detects a decrease in the insulation resistance based on the fact that the peak value detected by the detection unit falls below a threshold value set by the setting unit ;
The determination unit is an insulation resistance decrease detection device that temporarily interrupts the detection of a decrease in insulation resistance while the threshold value is changed in the setting unit .

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