JP2006220520A - Dielectric resistance measuring device of floating d.c. power supply and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply compose a small measuring device for measuring dielectric resistance of a floating high-voltage D.C. power supply at a low cost. <P>SOLUTION: Resistance value changeover circuits 62 and 162 capable of changing over a high resistance value (Rpa+Rpb=Rp1) to a low resistance value (Rpa=Rp2) and vice versa are connected between a positive terminal 41 of the floating high-voltage D.C. power supply 40 and a ground potential 43 through a protective resistor 51 (resistance value R1). Voltages Vp (Vp1 and Vp2) generated between both ends of the resistance value changeover circuits 62 and 162 before and after the resistance value changeover are measured by voltage measuring instruments 64 and 164; and dielectric resistance Rg is calculated by a controller 66 by using an equation of Rg=[(Vp2-Vp1)/ä(Vp1/Rp1)-(Vp2/Rp2)}]-R1. The need of measuring a voltage between positive and negative terminals of the high-voltage D.C. power supply 40 by a voltage measuring instrument having a special structure with input and output insulated from each other like a conventional technique is obviated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a DC power source in which a positive terminal and a negative terminal are insulated from a ground potential, a so-called non-grounded DC power source insulation resistance measuring apparatus and method, and a power source for a non-grounded DC power source such as an electric vehicle, a train, and a trolley bus. The present invention relates to an insulation resistance measuring device for a non-grounded DC power source suitable for application to an electric vehicle and the like and a method therefor.

  Conventionally, a DC power source such as a high voltage battery mounted on an electric vehicle is used as a so-called non-grounded DC power source in which the positive and negative terminals of the DC power source are electrically insulated from a ground potential (floating or floating). Has been.

  In order to detect a ground fault due to leakage or the like of this ungrounded DC power supply, an insulation resistance measuring device is arranged in the electric vehicle (Patent Document 1).

  FIG. 6 shows a circuit diagram of the insulation resistance measuring apparatus 2 described in Patent Document 1. The insulation resistance measuring device 2 includes a pair of protective resistors 10 and 14 and a leakage detection resistor 12 connected in series to the positive terminal 6 and the negative terminal 8 of the high-voltage DC power source 4 insulated from the ground potential. 16, a changeover switch 18 that selectively connects one end of each leakage detection resistor 12, 16 to the ground potential, and a voltage measuring device 20 that measures the voltage between the positive and negative terminals of the high-voltage DC power supply 4 while being insulated from the ground. And voltmeters 22 and 24 for measuring a voltage when one end of each of the leakage detection resistors 12 and 16 is set to the ground potential through the changeover switch 18, and a leakage determination unit 26.

  And the leakage determination part 26 is positive terminal based on the measured voltage by the voltage measuring device 20 and the voltmeters 22 and 24, the resistance value of each leakage detection resistor 12 and 16, and the resistance value of the protection resistors 10 and 14. It is described that the insulation resistances 27 and 28 on the side or the negative terminal side can be measured.

JP-A-6-153303 (FIG. 1)

  However, in the insulation resistance measuring apparatus 2 according to the above-described prior art, the voltage measuring instrument 20 that measures the voltage between the positive and negative terminals of the high-voltage DC power supply 4 while being insulated from the ground is included as an essential configuration.

  Here, since the voltage measuring instrument 20 is floating on the input side and the output side is the ground potential reference, it is necessary to insulate the input side from the output side. A photocoupler or a Hall element is used as an insulating element, and an amplifier or the like is used. Therefore, there is a problem in that the circuit configuration becomes complicated. Furthermore, since the input terminal side of the voltage measuring device 20 is directly connected between the positive and negative terminals of the high-voltage DC power supply 4, a predetermined creepage distance is required or high-voltage parts are required, resulting in an increase in size. There is also a problem. From such a situation, there is a problem that the voltage measuring device that needs to insulate the input side from the output side is more expensive.

  The present invention has been made in consideration of such problems, and it is possible to measure the insulation resistance of a non-grounded DC power supply that can measure the insulation resistance of a small and inexpensive non-grounded DC power supply with a simple circuit configuration. An object is to provide an apparatus.

  Another object of the present invention is to provide a method for measuring the insulation resistance of a non-grounded DC power supply that makes it possible to easily measure the insulation resistance of the non-grounded DC power supply.

  In the insulation resistance measuring apparatus for a non-grounded DC power source according to the present invention, between the positive terminal and the negative terminal of the DC power source in which the positive terminal and the negative terminal are insulated from the ground potential, between at least one terminal and the ground potential. A resistance value switching circuit connected to the voltage sensor, a voltage measuring device for measuring a voltage generated in the resistance value switching circuit before and after the resistance value switching, and an insulation resistance calculator. The insulation resistance calculator calculates an insulation resistance between the other terminal of the at least one terminal and the ground potential based on a resistance value before and after switching of the resistance value switching circuit and a measured voltage before and after switching. it can.

  Note that a resistance value switching circuit may be connected in series with a protective resistor between at least one of the positive terminal and the negative terminal of the DC power supply and the ground potential. In this case, the resistance value of the protective resistor may be taken into account when calculating the insulation resistance by the insulation resistance calculator.

  Further, in the method for measuring the insulation resistance of a non-grounded DC power supply according to the present invention, in the method for measuring the insulation resistance of a DC power supply in which the positive terminal and the negative terminal are insulated from the ground potential, the positive terminal and the negative terminal of the DC power supply are measured. A connection step of connecting a resistance value switching circuit between at least one of the terminals and the ground potential, a measurement step of measuring a voltage before and after the resistance value switching generated in the resistance value switching circuit, and an insulation resistance A calculation step. In the calculation step of the insulation resistance, the insulation resistance between the other terminal of the at least one terminal and the ground potential may be calculated based on the resistance value before and after the switching of the resistance value switching circuit and the measured voltage before and after the switching. it can.

  Also in this case, when the resistance value switching circuit is connected in series with a protective resistor between at least one of the positive terminal and the negative terminal of the DC power source and the ground potential in the connection step. In the step of calculating the insulation resistance, the resistance value of the protective resistor may be taken into consideration.

  According to the present invention, when calculating the insulation resistance, the voltage value before and after switching of the resistance value switching circuit is measured, so it is not necessary to measure the voltage between the positive and negative terminals of the DC power supply, and as a result, A voltage measuring instrument that measures the voltage between the positive and negative terminals of the DC power supply as described in the prior art while being insulated from the ground is not required.

  Since the resistance value switching circuit can be composed of only passive elements as compared with the voltage measuring device according to the prior art, the circuit configuration is simple, inexpensive, and miniaturized.

  As a result, the insulation resistance measuring device itself of the non-grounded DC power supply can be configured simply, inexpensively and compactly.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a schematic configuration diagram of an electric vehicle 30 to which an embodiment of the present invention is applied.

  The electric vehicle 30 basically has a high-voltage DC power supply 40 of about several hundred volts in which the positive terminal 41 and the negative terminal 42 are insulated from the ground potential 43, and the insulation between the positive terminal 41 of the high-voltage DC power supply 40 and the ground potential 43. An insulation resistance measuring device 32 that measures resistance (resistance value) Rg and / or an insulation resistance (resistance value) Rg ′ between the negative terminal 42 and the ground potential 43, and a high-voltage DC power supply 40 as a power source through a motor drive circuit 36. And a motor 34 to be driven.

  The insulation resistance measuring device 32 includes a protective resistor (resistance value R1) 51, a resistance value switching circuit 62, a high resistance value and a low resistance connected in series between the positive terminal 41 of the high-voltage DC power supply 40 and the ground potential 43. A voltage measuring device 64 that measures a voltage Vp before and after the resistance value switching of the resistance value switching circuit 62 that can be switched to a resistance value (a voltage before switching is Vp1, and a voltage after switching is Vp2), and a protective resistor 51 A controller (insulation resistance calculator) that calculates an insulation resistance Rg (Rg ′) based on the resistance value R1, the resistance values before and after the resistance value switching (Rpa + Rpb, Rpa), and the voltages Vp (Vp1, Vp2) before and after the resistance value switching. 66).

  The resistance value switching circuit 62 includes a resistor (resistance value Rpa) 67, a resistor (resistance value Rpb) 68, and a switch K2 that short-circuits the resistor 68.

  The resistance value switching circuit 62 is connected between the common contact side of the switch K 1 and the ground potential 43. The fixed contact side of the switch K1 is connected to the positive terminal 41 of the high-voltage DC power supply 40 via the protective resistor 51.

  The resistance value Rp of the resistance value switching circuit 62 is the resistance value Rp = Rpa when the switch K2 is closed, and the resistance value Rp = Rpa + Rpb when the switch K2 is opened. The switches K1 and K2 are closed and opened (open / close) by the controller 66 switching the potentials of the switching control terminals of the switches K1 and K2.

  Here, the controller 66 has an input / output interface such as a CPU, an EEPROM (or flash ROM) such as a ROM, a RAM, and an A / D converter, and is insulated based on data and programs described later stored in the ROM. The resistance value Rg (Rg ′) is calculated, and a state signal (a signal indicating whether or not there is a ground fault) St based on the calculation result is transmitted to the motor drive circuit 36. In this case, the warning information based on the calculation result is displayed on the meter panel, displayed on the navigation display, or the sound from the speaker is notified to the driver of the electric vehicle 30 to call attention.

  Note that the voltage measuring devices 64 and 164 may be integrated into the controller 66.

  The motor drive circuit 36 is an ECU, and determines whether to drive or not drive the motor 34 based on the state signal St.

  In this embodiment, the circuit including the protective resistor 51 and the resistance value switching circuit 62 connected between the positive terminal 41 of the high-voltage DC power supply 40 and the ground potential 43 is connected to the negative terminal 42 of the high-voltage DC power supply 40 and the ground. It is possible to measure the insulation resistance Rg between the potential 43. On the other hand, the positive terminal 41 and the ground potential 43 of the high-voltage DC power supply 40 are provided by a circuit including the protective resistor 151 and the resistance value switching circuit 162 connected between the negative terminal 42 of the high-voltage DC power supply 40 and the ground potential 43. It is possible to measure the insulation resistance Rg ′ between the two.

  However, since they have the same circuit configuration, the operation when measuring the insulation resistance Rg will be mainly described below.

  Here, a simple description will be given of a configuration for measuring the insulation resistance Rg ′. A protective resistor 151, a switch K11, and a resistance value switching circuit 162 are connected in series between the negative terminal 42 of the high-voltage DC power supply 40 and the ground potential 43, and a series resistor 167 constituting the resistance value switching circuit 162, 168, the switching control terminal of the switch K12 that short-circuits or opens the resistor 168, the switching control terminal of the switch K11 that connects the protective resistor 151, the resistance value switching circuit 162, and the negative terminal 42 of the high-voltage DC power supply 40 in series. Is connected to the controller 66, and the output terminal of the voltage measuring device 164 that measures the voltage Vp ′ before and after the resistance value switching of the resistance value switching circuit 162 is connected to the controller 66.

  Needless to say, the resistance value switching circuits 62 and 162 described above are not limited to a series circuit of two resistors, as long as they can be switched to at least two different resistance values.

  In addition, in order to calculate the insulation resistances Rg and Rg ′, the ROM of the controller 66 stores in advance the resistance value R1 of the protection resistor 51, the resistance value Rpa of the resistor 67, the resistance value Rpb of the resistor 68, and the protection resistance. The resistance value of the resistor 151, the resistance value of the resistor 167, and the resistance value of the resistor 68 are stored.

  Next, an example of a method for measuring insulation resistance will be described with reference to the flowchart of FIG. 2 is a content of the method of measuring the insulation resistance Rg between the negative terminal 42 of the ungrounded high-voltage DC power supply 40 and the ground potential 43, but the insulation resistance Rg ′ between the positive terminal 41 and the ground potential 43. Those skilled in the art can easily make a measurement with reference to the flowchart of FIG.

  First, the connection process of the insulation resistance measuring device 32 in step S1 will be described. At least one of the positive terminal 41 and the negative terminal 42 of the high-voltage DC power source 40 in which the positive terminal 41 and the negative terminal 42 are insulated from the ground potential 43. For example, a resistance value switching circuit 62 is connected between the positive terminal 41 and the ground potential 43 via the protective resistor 51 and the switch K1. The voltage measuring device 64 is connected between both terminals of the resistance value switching circuit 62, and the switching control terminals of the switches K 1 and K 2 and the output terminal of the voltage measuring device 64 are connected to the controller 66.

  Next, in the initial setting in step S2, the switches K1 and K2 are opened by the controller 66. Note that the switch K2 may be closed. When the closed state is set, steps S3a and S3b described later may be interchanged with steps S3c and S3d.

  Next, in the measurement process of step S3 (S3a to S3d), the voltage Vp before and after the resistance value switching generated in the resistance value switching circuit 62 is measured.

  In this case, first, in step S3a, the switch K1 is closed and the switch K2 is opened.

  Next, in step S3b, the voltage drop generated in the series resistance of the resistor 67 and the resistor 68 is measured by the voltage measuring device 64 as the voltage Vp = Vp1, and supplied to the controller 66. The controller 66 stores this voltage Vp1 in the RAM.

  Next, in step S3c, both the switches K1 and K2 are closed.

  In this case, since the resistor 68 is short-circuited, the voltage drop generated in the resistor 67 is measured by the voltage measuring device 64 as Vp = Vp2 and supplied to the controller 66 in step S3d. The controller 66 stores this voltage Vp2 in the RAM.

  Next, in step S4, the switches K1 and K2 are opened.

  Next, in step S5, the controller 66 calculates the insulation resistance Rg based on the measurement result in step S3.

  A method of calculating the insulation resistance Rg will be described below.

  FIG. 3 shows the configuration of the measurement circuit when the switch K1 is closed and the switch K2 is open in step S3a. At this time, when Kirchhoff's law is applied with the loop current set to ip1, the following equation (1) is obtained.

  Vbatt-R1.ip1-Vp1-Rg.Ip1 = 0 (1)

  FIG. 4 shows the configuration of the measurement circuit when the switch K1 is closed and the switch K2 is open in step S3c. At this time, when Kirchhoff's law is applied with the loop current set to ip2, the following equation (2) is obtained.

  Vbatt-R1.ip2-Vp2-Rg.ip2 = 0 (2)

  Further, according to Ohm's law, ip1 and ip2 are expressed by the following equations (3) and (4), respectively.

  ip1 = Vp1 / (Rpa + Rpb) (3)

  ip2 = Vp2 / Rpa (4)

  When Vbatt is eliminated from the above equations (1) to (4) and the insulation resistance Rg is obtained, the following equation (5) is obtained.

Rg = {(Vp2-Vp1) / (ip1-ip2)}-R1
= [(Vp2-Vp1) / [[Vp1 / (Rpa + Rpb)]-(Vp2 / Rpa)]]-R1 (5)

  Here, for the sake of easy understanding, if Rpa + Rpb = Rp1 and Rpa = Rp2 are set, equation (5) is expressed by the following equation (6).

Rg = [(Vp2-Vp1) / {(Vp1 / Rp1)-(Vp2 / Rp2)}]
-R1 (6)

  Here, since the resistance value Rp1 = Rpa + Rpb and the resistance value Rp2 = Rpa are known, the insulation between the negative terminal 42 of the high-voltage DC power supply 40 and the ground potential 43 is obtained by measuring the voltage VP2 and the voltage Vp1. The resistance Rg can be calculated (measured).

  The ground resistance Rg ′ between the positive terminal 41 of the high-voltage DC power supply 40 and the ground potential 43 can be similarly measured using the resistance value switching circuit 162.

  In addition, as shown in FIG. 5, it can also be set as the structure of 30 A of electric vehicles carrying the insulation resistance measuring apparatus 32A which abbreviate | omitted the protective resistors 51 and 151. FIG.

  In this case, the insulation resistance Rg can be obtained by the following equation (7) in which R1 = 0 in the above equation (6).

Rg = [(Vp2-Vp1) / {(Vp1 / Rp1)-(Vp2 / Rp2)}]
... (7)

  Thereafter, the controller 66 compares the obtained insulation resistance Rg and the insulation resistance Rg ′ with the threshold value, and if the insulation resistances Rg and Rg ′ exceed the threshold value, the insulation resistance Rg, If a state signal indicating that Rg ′ is normal is sent and the insulation resistances Rg and Rg ′ are below the threshold values, the insulation resistances Rg and Rg ′ are abnormal with respect to the motor drive circuit 36, and a ground fault occurs. A status signal St indicating that the

  The motor drive circuit 36 continues to drive the motor 34 when the state signal St is a signal indicating a normal state, and stops driving the motor 34 when the signal is an signal indicating an abnormal state.

  Note that the current terminal voltage Vbatt of the high-voltage DC power supply 40 can be obtained by substituting the obtained insulation resistance Rg into the equations (1) to (4).

  As described above, according to the above-described embodiment, the protective terminals 51 and 151 are connected between the positive terminal 41 and the negative terminal 42 of the high-voltage DC power source 40 insulated from the ground potential 43 and the ground potential 43, or The resistance value switching circuits 62 and 162 that can switch the resistance value between a high resistance value (Rp1 = Rpa + Rpb) and a low resistance value (Rp2 = Rpa) are directly connected.

  The voltages Vp (Vp1, Vp2) and Vp ′ (Vp1 ′, Vp2 ′) generated at both ends of the resistance value switching circuits 62, 162 before and after the resistance value switching are measured by the voltage measuring devices 64, 164, and the insulation resistance is calculated. Insulation resistances Rg and Rg ′ are calculated by the above-described equation (6) or (7) by a controller 66 as a device.

  According to this embodiment, as in the prior art, the insulation resistances Rg and Rg ′ are measured without measuring the voltage between the positive and negative terminals of the high-voltage DC power supply 40 with a voltage measuring device having a special structure in which the input and output are insulated. can do.

  Since the resistance value switching circuit 62 can be composed of only resistors 67, 167, 68, 168 and passive elements of the switches K2, K12 as compared with the voltage measuring device having such a special structure, the circuit configuration is It is simple, inexpensive and can be downsized. As a result, the insulation resistance measuring devices 32 and 32A themselves of the ungrounded high-voltage DC power supply 40 can be configured simply, inexpensively, and compactly.

1 is a configuration diagram of an electric vehicle to which an insulation resistance measuring device according to an embodiment of the present invention is applied. It is a flowchart with which operation | movement description of an insulation resistance measuring apparatus is provided. It is a circuit schematic diagram when a resistance value switching circuit is in a relatively high resistance state. It is a circuit schematic diagram when a resistance value switching circuit is in a relatively low resistance body. It is a block diagram of the electric vehicle to which the insulation resistance measuring apparatus which concerns on other embodiment of this invention was applied. It is a block diagram of the insulation resistance measuring apparatus which concerns on a prior art.

Explanation of symbols

30, 30A ... Electric vehicle 32, 32A ... Insulation resistance measuring device 34 ... Motor 36 ... Motor drive circuit 40 ... High voltage DC power supply 41 ... Positive terminal 42 ... Negative terminal 43 ... Ground potential 51, 151 ... Protection resistor 62, 162 ... Resistance value switching circuit 64, 164 ... Voltage measuring device 66 ... Controller (insulation resistance calculator)
67, 68, 167, 168 ... resistors

Claims (4)

A resistance value switching circuit connected between at least one of the positive terminal and the negative terminal of the DC power source in which the positive terminal and the negative terminal are insulated from the ground potential, and the ground potential;
A voltage measuring device for measuring a voltage before and after the resistance value switching generated in the resistance value switching circuit;
An insulation resistance calculator that calculates an insulation resistance between the other terminal of the at least one terminal and the ground potential based on a resistance value before and after switching of the resistance value switching circuit and a measured voltage before and after switching. An insulation resistance measuring device for a non-grounded DC power supply. A resistance value switching circuit connected via a protective resistor between at least one of the positive terminal and the negative terminal of the DC power source, the positive terminal and the negative terminal of which are insulated from the ground potential, and the ground potential; ,
A voltage measuring device for measuring a voltage before and after the resistance value switching generated in the resistance value switching circuit;
Insulation resistance between the other terminal of the at least one terminal and the ground potential based on the resistance value of the protective resistor, the resistance value before and after switching of the resistance value switching circuit, and the measured voltage before and after switching An insulation resistance measuring device for an ungrounded DC power supply, comprising: an insulation resistance calculator for calculating In the method of measuring the insulation resistance of a DC power source in which the positive terminal and the negative terminal are insulated from the ground potential,
A connecting step of connecting a resistance value switching circuit between at least one of the positive terminal and the negative terminal of the DC power source and the ground potential;
A measurement step of measuring a voltage before and after resistance value switching generated in the resistance value switching circuit;
A calculation step of calculating an insulation resistance between the other terminal of the at least one terminal and the ground potential based on a resistance value before and after switching of the resistance value switching circuit and a measured voltage before and after switching. Measurement method for insulation resistance of ungrounded DC power supplies. In the method of measuring the insulation resistance of a DC power source in which the positive terminal and the negative terminal are insulated from the ground potential,
A connection step of connecting a resistance value switching circuit via a protective resistor between at least one of the positive terminal and the negative terminal of the DC power source and the ground potential;
A measurement step of measuring a voltage before and after resistance value switching generated in the resistance value switching circuit;
Based on the resistance value of the protective resistor, the resistance value before and after switching of the resistance value switching circuit, and the measured voltage before and after switching, the insulation resistance between the other terminal of the at least one terminal and the ground potential is calculated. A method for measuring an insulation resistance of a non-grounded DC power supply comprising the steps of:

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