WO2012120683A1 - Insulation resistance detection circuit - Google Patents

Insulation resistance detection circuit Download PDF

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Publication number
WO2012120683A1
WO2012120683A1 PCT/JP2011/055673 JP2011055673W WO2012120683A1 WO 2012120683 A1 WO2012120683 A1 WO 2012120683A1 JP 2011055673 W JP2011055673 W JP 2011055673W WO 2012120683 A1 WO2012120683 A1 WO 2012120683A1
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WO
WIPO (PCT)
Prior art keywords
voltage
current
value
measured
voltage dividing
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PCT/JP2011/055673
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French (fr)
Japanese (ja)
Inventor
義人 今井
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三菱電機株式会社
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Application filed by 三菱電機株式会社 filed Critical 三菱電機株式会社
Priority to JP2013503304A priority Critical patent/JPWO2012120683A1/en
Priority to PCT/JP2011/055673 priority patent/WO2012120683A1/en
Publication of WO2012120683A1 publication Critical patent/WO2012120683A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/16—Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line
    • G01R27/18—Measuring resistance to earth, i.e. line to ground
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S50/00—Monitoring or testing of PV systems, e.g. load balancing or fault identification
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S50/00—Monitoring or testing of PV systems, e.g. load balancing or fault identification
    • H02S50/10—Testing of PV devices, e.g. of PV modules or single PV cells
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/40—Testing power supplies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy

Definitions

  • the present invention relates to an insulation resistance detection circuit for measuring an insulation resistance of a DC power supply configured by connecting a plurality of power supply units in series and parallel.
  • a solar cell, a fuel cell, and the like are known as a DC power source configured by connecting a plurality of power source units in series and parallel. Since a system that generates AC power using such a DC power supply is configured by combining a DC power supply and a power converter (power conditioner), in the insulation resistance standard that should be satisfied as a system from the viewpoint of ensuring safety, The insulation resistance value to be satisfied by each component is determined.
  • the non-insulated power conditioner that supplies the converted AC power directly to the load without an insulating transformer is widely used because it has a feature that can improve the power conversion efficiency at low cost.
  • the insulation resistance deterioration at the input DC power supply is caused to the load. It is required to take measures to prevent the impact.
  • a solar power generation system will be described as an example.
  • a solar cell used in a photovoltaic power generation system is configured by connecting a plurality of solar cell modules in series and parallel.
  • the ground insulation resistance value of each solar cell module is very high (for example, 1000 M ⁇ ), but when the 100 solar cell modules are connected in series, for example, the ground insulation resistance value is reduced to 10 M ⁇ . Since the leakage current of the solar cell module is proportional to the area, the total insulation resistance of the solar cell having a large capacity by greatly increasing the number of solar cell modules is greatly reduced.
  • the insulation resistance of the solar cell that is the DC power supply It is necessary to provide a function of self-diagnosis whether or not is equal to or greater than a predetermined value required by the system.
  • the insulation resistance detection circuit targeted by the present invention is a non-insulated power conditioner for converting a DC power source configured by connecting a plurality of power supply units in series and parallel. It is a circuit for measuring the insulation resistance of the DC power supply.
  • the ground fault location occurs at an arbitrary voltage point. Therefore, for the insulation resistance detection circuit, the ground fault resistance regardless of the ground fault voltage point. Is required to be measured.
  • Patent Document 1 As a method for measuring the ground fault resistance, for example, the method proposed in Patent Document 1 is helpful. That is, in Patent Document 1, if the unknown point is supplemented, the unknowns in the ground fault resistance measurement are the ground fault voltage point where the insulation resistance has deteriorated and the insulation resistance value. It can be said that the example of a structure which measures by 2 voltages and calculates
  • the purpose of the insulation resistance detection circuit is to measure the ground fault resistance regardless of the ground fault voltage point, but in order to ensure and improve its measurement accuracy, the measurement time is determined and the circuit configuration is devised. It is necessary to consider from both sides.
  • the method of determining the measurement time is not shown in Patent Document 1.
  • the measurement time is set to be long, so even in normal operation in fine weather, even if the voltage generated by the solar cells reaches a voltage that can be connected, The power generation efficiency of the power generation system has been reduced.
  • the measurement circuit uses a voltage dividing ratio of a voltage dividing circuit that generates an intermediate potential of the output voltage of the DC power supply (the voltage dividing output terminal is connected to the circuit ground).
  • the first current flowing from the voltage dividing output terminal of the voltage dividing circuit to the earth ground when the voltage dividing ratio is the first value and the voltage dividing ratio being the second value are changed to the first value and the second value.
  • This measurement circuit has the following problems. First, if there is a part of the leakage current that changes in temperature or aging (for example, an aluminum electrolytic capacitor) in parallel with the voltage divider circuit, the accuracy of the voltage division ratio as the equivalent impedance of the voltage divider circuit decreases, and the possibility of linkage is determined. The accuracy of the determination level to be determined decreases. Further, the voltage division ratio is switched using a semiconductor switch such as an FET, but a leakage current in the semiconductor switch portion also causes a decrease in the accuracy of the determination level.
  • a semiconductor switch such as an FET
  • the present invention has been made in view of the above, and the insulation resistance of a DC power supply configured by connecting a plurality of power supply units in series and parallel is used to change the ground floating capacitance of the DC power supply or the output voltage of the DC power supply. It is an object of the present invention to obtain an insulation resistance detection circuit that can easily measure and accurately measure changes in electrical resistance, variations in insulation resistance measurement system elements, changes in leakage current, and the like.
  • the present invention provides a voltage dividing circuit that generates an intermediate potential of an output voltage of a DC power supply configured by connecting a plurality of power supply units in series and parallel.
  • a voltage dividing circuit whose intermediate potential generating terminal is connected to circuit ground; a voltage dividing ratio changing means for changing a voltage dividing ratio of the voltage dividing circuit between a first value and a second value; and the voltage dividing circuit.
  • a voltage dividing voltage measuring means for measuring a voltage output from the intermediate potential generation terminal of the circuit, and a ground fault protection resistor arranged in a path from the ground terminal connected to the ground to the intermediate potential generation terminal of the voltage dividing circuit
  • Current measuring means for measuring a ground fault current flowing through the voltage dividing circuit, and a first ground fault current measured by the current measuring means when the voltage dividing ratio changing means is caused to set the voltage dividing ratio of the voltage dividing circuit to a first value.
  • the first current value measured from the above and the divided voltage measuring means are A first measurement voltage output from the intermediate potential generation terminal set, and a first measurement voltage measured by the current measurement unit when the voltage division ratio changing unit is caused to set the voltage division ratio of the voltage dividing circuit to a second value.
  • Insulation resistance calculation control means for calculating a value of a ground fault resistance component formed between the ground terminal and a ground fault voltage point in the DC power supply, wherein the insulation resistance calculation control means comprises the first and The current measuring means measures the time interval for changing the voltage dividing ratio of the voltage dividing circuit between the first value and the second value in the voltage dividing ratio changing means, which is the measurement time for measuring the second current value. Variable setting according to the amount of change in the first and second ground fault currents And wherein the Rukoto.
  • the measurement time is variably set according to the amount of change in the ground fault current, and the insulation resistance value can be calculated so as not to include measurement errors due to variations in the voltage dividing ratio of the voltage dividing circuit. Therefore, the installation area of a DC power source such as a solar cell constituted by connecting a plurality of power supply units in series and parallel, the change in ground floating capacitance due to rain, etc., the change in the output voltage of the DC power source, the insulation resistance measurement system There is an effect that it is possible to easily measure the insulation resistance with high accuracy in response to changes in element variations, leakage current, and the like.
  • FIG. 1 is a conceptual circuit diagram showing a configuration of an insulation resistance detection circuit according to an embodiment of the present invention.
  • FIG. 2 is a circuit diagram in which a ground stray capacitance or the like is added to the insulation resistance detection circuit shown in FIG.
  • FIG. 3 is a specific circuit diagram of the insulation resistance detection circuit shown in FIG.
  • FIG. 4 is a waveform diagram showing a measurement example of a change in the measured current due to the ground floating capacitance used in the saturation time measurement.
  • FIG. 5 is an equivalent circuit diagram of the insulation resistance measurement system for explaining the procedure in the case of performing measurement calculation of insulation resistance using the voltage measured by the divided voltage measurement circuit at the saturation point when the measurement current is stable. A) shows the case where the switch S1 is open, and (B) shows the case where the switch S1 is closed.
  • FIG. 1 is a conceptual circuit diagram showing a configuration of an insulation resistance detection circuit according to an embodiment of the present invention.
  • FIG. 2 is a circuit diagram in which a ground stray capacitance or the like is added to the insulation resistance detection circuit shown in FIG.
  • FIG. 3 is a circuit diagram showing a specific configuration example of the insulation resistance detection circuit shown in FIG.
  • an insulation resistance detection circuit 1 includes a power supply voltage measuring circuit 3 and voltage dividing resistors R1, R2 connected in parallel between a positive terminal (+) and a negative terminal ( ⁇ ) of a DC power source 2. And a voltage dividing circuit.
  • the common connection end 5 of the voltage dividing resistors R1 and R2 is an intermediate potential generation end that generates an intermediate potential of the output voltage of the DC power supply 2, and is connected to the circuit ground GND.
  • a series circuit of a voltage changing resistor R3 and a switch S1 is connected between the positive terminal (+) of the DC power source 2 and the common connection terminal 5, that is, in parallel with the voltage dividing resistor R1.
  • the switch S1 is controlled to open and close by a control circuit (CPU) 4.
  • the voltage dividing ratio of the voltage dividing circuit becomes different between when the switch S1 is open and when the switch S1 is closed. That is, the series circuit of the voltage changing resistor R3 and the switch S1 constitutes a voltage dividing ratio changing means for changing the voltage dividing ratio of the voltage dividing circuit.
  • the potential of the common connection terminal 5 is the circuit S1 is open. It changes between the potential at the time (first potential of the DC power supply 2) and the potential when the switch S1 is closed (second potential of the DC power supply 2).
  • the power supply voltage measurement circuit 3 converts the output voltage value of the DC power supply 2 and outputs it to the CPU 4 as the voltage Vm1.
  • a divided voltage measuring circuit 6 is provided between the negative terminal ( ⁇ ) of the DC power supply 2 and the common connection terminal 5, that is, in parallel with the voltage dividing resistor R2.
  • the divided voltage measuring circuit 6 measures the voltage output from the common connection end 5 of the voltage dividing circuit and outputs it to the CPU 4 as the voltage Vm2.
  • a ground fault protection resistor Rsafe, a voltage conversion resistor Rsense, and a zero adjustment resistor Rbias are inserted in this order between the ground terminal 7 connected to the ground Earth and the common connection end 5.
  • the ground fault protection resistor Rsafe is for securing the insulation performance required between the electronic circuit and the earth, and is generally set to a high resistance of about 10 M ⁇ .
  • the voltage conversion resistor Rsense converts the current flowing from the insulation resistance detection circuit 1 toward the ground Earth through the ground terminal 7 (that is, the ground fault current flowing through the ground fault protection resistor Rsafe).
  • the voltage across the voltage conversion resistor Rsense is amplified by the operational amplifier AMP and input to the CPU 4 as the measurement current Isense.
  • the resistor Rbias and the reference power supply Vbias connected in parallel are provided for adjusting the zero point for current measurement in the operational amplifier AMP. That is, the operational amplifier AMP, the voltage conversion resistor Rsense, the zero adjustment resistor Rbias, and the reference power source Vbias as a whole constitute a current measurement circuit 8.
  • DC power supply 2 is configured by connecting a plurality of power supply units in series and parallel.
  • a solar cell is shown as an example.
  • the solar cell is a series connection body of a plurality of solar cell modules Vy1, Vy2, and Vx.
  • a ground fault resistance component Rx is generated in the path of the ground fault current flowing between the ground fault voltage point 9 where the ground fault has occurred and the ground terminal 7, and the output voltage Vx of the solar cell module Vx is the ground fault voltage.
  • Vx is assumed.
  • FIG. 3 shows that the voltage measurement circuits 3 and 6 can be configured by operational amplifiers OP3 and OP4 having a negative feedback amplifier configuration, and the switch S1 can be configured by a transistor.
  • a specific configuration example of the current measurement circuit 8 is shown in FIG. It is shown.
  • the DC power source (solar cell) 2 the solar cell modules Vy1 and Vy2 are combined with the solar cell module Vy, and a ground fault occurs at the ground fault voltage point 9 between the solar cell module Vx and the solar cell module Vy. It is said.
  • the operational amplifier OP3 outputs the output voltage of the DC power source (solar cell) 2 during the insulation resistance measurement to the CPU 4 as the voltage Vm1.
  • the operational amplifier OP4 outputs the divided output voltage of the voltage dividing circuit during the insulation resistance measurement to the CPU 4 as the voltage Vm2.
  • an operational amplifier AMP for current measurement is configured by an operational amplifier OP1 having a voltage follower configuration and an operational amplifier OP2 having a negative feedback amplifier configuration, and a zero adjustment resistor Rbias is configured by resistors RB1 to RB4.
  • the reference power supply Vbias is connected to them.
  • ground fault resistance component Rx which is the insulation resistance of the DC power supply 2 by measuring the current Isense flowing through the ground fault protection resistor Rsafe.
  • the “value” used in the derivation of the expression uses the identification code of each element.
  • the output voltage (Vx + Vy1 + Vy2) of the DC power source 2 is an input DC voltage of the insulation resistance detection circuit 1.
  • the output voltage of the DC power supply 2 is measured by the power supply voltage measuring circuit 3 as the voltage Vm1 and input to the CPU 4.
  • the current Isense flowing through the ground fault protection resistor Rsafe is measured by the current measuring circuit 8 and input to the CPU 4.
  • the voltage output from the common connection end 5 of the voltage dividing circuit is measured by the divided voltage measuring circuit 6 and input to the CPU 4 as the voltage Vm2.
  • the CPU 4 samples and digitizes the voltages Vm1 and Vm2 and the current Isense input when the switch S1 is opened and closed, and calculates the ground fault resistance value Rx and the ground fault voltage Vx based on them.
  • the time interval for opening and closing the switch S1 is the measurement time. Since the impedance of the current measuring circuit 8 is extremely smaller than the resistance value Rsafe of the ground fault protection resistor Rsafe, it becomes a negligible value in the calculation of the ground fault resistance value Rx.
  • Isense2 (Vm1-Vx) / ⁇ Rx + Rsafe + R1 ⁇ R2 ⁇ R3 / (R1R3 + R1R2 + R2R3) ⁇ (2)
  • the CPU 4 opens and closes the switch S1 at a predetermined time interval, and measures the current Isense1 when the switch S1 is opened and the current Isense2 when the switch S1 is closed, which are input from the current measurement circuit 8.
  • the ground fault resistance value Rx is obtained by applying the equation (6) and the obtained ground fault resistance value Rx is compared with the insulation resistance determination level defined for the insulation resistance standard. This makes it possible to determine whether the insulation resistance is good or not regardless of the DC power supply output voltage and the ground fault potential.
  • the measurement of the ground fault resistance value Rx is affected by the accuracy of measuring the current Isense input by the CPU 4.
  • the current Isense is measured as a charge / discharge current. Is done. That is, if the value of the current Isense before the charge is saturated is measured, the measurement accuracy of the ground fault resistance value Rx is not good.
  • the ground-floating capacitances Cy and Cx are not constant values, and differ depending on the time of fine weather or rain. Further, the insulation resistance of the solar cell is not a constant value, but varies depending on the scale of the solar cell. Therefore, the CPU 4 does not set the time interval for opening and closing the switch S1, that is, the measurement time for determining and taking in the value of the current Isense to be a fixed time, but varies the measurement time according to the amount of change in the current Isense. It has become.
  • the measurement error due to the stray capacitance component of the solar cell module can be reduced, so that the measurement accuracy of the ground fault resistance value Rx can be improved.
  • the voltage Vm1 generated by the voltage dividing circuit is divided. Measurement errors due to variations are not taken into account. That is, in addition, components (such as voltage dividing resistors R1 and R2, voltage changing resistor R3, switch S1, and an aluminum electrolytic capacitor (not shown) arranged in the vicinity) that affect the accuracy of the voltage dividing ratio of the voltage dividing circuit. It is necessary to be able to calculate the insulation resistance value so as not to include measurement errors due to variations in the value of the voltage Vm1 caused by temperature variations and aging of the leakage current.
  • a second calculation method capable of solving this problem will be described.
  • the CPU 4 measures the amount of change in the input current Isense, determines the current value when the current change is stable (when it can be regarded as saturated), and inputs the current value at that time.
  • the voltage Vm2 is measured, and the ground fault resistance value Rx is calculated.
  • an accurate ground fault resistance value Rx can be measured and calculated without being affected by variations in the voltage Vm1. Since the open / close time interval (measurement time) of the switch S1 is a charging standby time, an optimal measurement time can be set. Since the saturation time is measured, the change waveform of the input current Isense is, for example, as shown in FIG. In FIG. 4, the vertical axis indicates the converted voltage by the voltage conversion resistor Rsense, but an example of measuring the measurement current change due to the ground floating capacitance when the switch S1 is opened and closed at intervals of 6 seconds is shown.
  • the second calculation method since the optimum measurement time can be set, the measurement accuracy is increased.
  • the insulation resistance determination level prepared for the power conditioner is not required to have a margin for the required standard value. Therefore, more stable operation is possible against a decrease in the overall insulation resistance value that occurs when the solar cell area increases. Further, since the saturation point at which the current Isense is stabilized is monitored, even when the ground capacity of the solar cell increases in rainy weather or the like, the measurement time is automatically extended, and erroneous determination can be prevented.
  • FIG. 5 is an equivalent circuit diagram of the insulation resistance measurement system for explaining the procedure in the case of performing measurement calculation of insulation resistance using the voltage measured by the divided voltage measurement circuit at the saturation point when the measurement current is stable.
  • A) shows the case where the switch S1 is open, and (B) shows the case where the switch S1 is closed.
  • the divided voltage measuring circuit 6 measures the divided voltage generation voltage Vs output from the common connection end 5 of the voltage dividing circuit through the resistor Rs.
  • the divided voltage generation voltage Vs is the value Vs1 when the switch S1 is open, and the value Vs2 when the switch S1 is closed.
  • the resistance value of the resistor Rs is the value Rs1 when the switch S1 is open, and the value Rs2 when the switch S1 is closed.
  • the voltage Vm2 measured by the divided voltage measuring circuit 6 is the value Vm21 when the switch S1 is open, and the value Vm22 when the switch S1 is closed.
  • the resistor Ramp has a combined resistance value of the voltage conversion resistor Rsense and the resistor Rbias in the current measurement circuit 8 shown in FIG. Further, the DC power source 2 has a configuration in which the positive electrode end (+) and the negative electrode end ( ⁇ ) are connected.
  • the difference between the measurement voltage Vm21 and the measurement voltage Vm22 is a main parameter. Therefore, the current measurement circuit is configured to measure the difference between the measurement voltages Vm21 and Vm22. 8 can reduce the offset error of the amplifier circuit used. That is, more accurate insulation resistance detection can be realized.
  • the second calculation method can be a method of performing measurement a plurality of times as follows. The procedure is the same for each time, but the peak value of the current Isense1 input when the switch S1 is opened is memorized, the current value is continuously measured, and the rate of change of the current reaches a predetermined value (saturated) Current value at a time point that can be regarded as having been measured), and at the same time, the measured voltage Vm21 at that time is stored. Subsequently, the switch S1 is closed, the peak current of the current Isense2 is stored in the same saturation standby time as when the switch S1 is opened, the current value is continuously measured, and the current value and the measured voltage Vm22 at the same elapsed time are stored. . By this measurement, insulation resistance detection (calculation) is performed. In the power conditioner, the quality of the insulation resistance is judged based on the detection result.
  • the rate of change used in the first round is set to a level that passes with high accuracy if the capacitance and the normal insulation resistance value are fine in order to allow the insulation resistance detection to be determined in the shortest time.
  • the current value and the measured voltage at a stable time point are applied to the equation (12) and used for pass / fail judgment of the insulation resistance value, but the difference between the peak current of the current Isense1 and the peak current of the current Isense2 Is not greater than or equal to a predetermined value, it is determined that the insulation resistance detection circuit 1 is in failure, and the process proceeds to failure processing mode.
  • the power conditioner starts system interconnection and starts sending the converted AC power to the distribution system.
  • the process proceeds to the second insulation resistance detection measurement again without immediately determining that the insulation resistance is defective.
  • the current change rate judgment value is set to a smaller value than the first measurement, and in addition to the maximum number of installed solar cell modules in the system specifications, the stray capacitance in rainy weather exceeds the system required insulation resistance value. If so, set the current change rate to pass.
  • the input voltage Vm2 changes during measurement, a voltage fluctuation determination value indicating whether or not the measurement error is within an allowable level is prepared in advance as a simulation result. The insulation resistance detection can be repeated until it is settled.
  • the second calculation method is not limited to the saturation point at which the current Isense is stable. If the switch S1 is inverted before the amount of change in the current Isense1 is stabilized and the current Isense2 is measured in the same manner, the charging current to the ground capacitance is added, so that the ground fault current increases and the estimated insulation resistance value Is smaller than actual. However, since the DC power supply (solar cell) 2 in a normal state has a margin with respect to the insulation resistance determination level, even when the switch S1 is inverted in a short time when determining the ground fault resistance, the insulation is determined. If the resistance value satisfies the judgment standard, the required insulation resistance value can be guaranteed.
  • the measurement result only needs to be an insulation resistance exceeding the required standard, so that the shortest time can be obtained without measuring an accurate insulation resistance. System linkage becomes possible. In this case, if it is determined that there is an abnormality, a method of sequentially extending the determination time may be performed.
  • the measurement time is variably set according to the change amount of the ground fault current, and the insulation resistance is not included so as not to include a measurement error due to variation in the voltage dividing ratio of the voltage dividing circuit. Since the value can be calculated, the installation area of a DC power source such as a solar cell configured by connecting multiple power supply units in series and parallel, the change in ground floating capacity, such as during rain, and the output voltage of the DC power source Insulation resistance can be measured with high accuracy by easily responding to changes in the resistance, variation in insulation resistance measurement system elements, changes in leakage current, and the like.
  • the measurement time is automatically shortened, so that the generated power can be used in a short time.
  • the insulation resistance detection circuit includes the insulation resistance of a DC power supply configured by connecting a plurality of power supply units in series and parallel, the change in the floating capacitance of the DC power supply, and the output of the DC power supply. It is useful as an insulation resistance detection circuit that can easily and accurately measure changes in voltage, variations in insulation resistance measurement system elements, leakage currents, etc., especially non-insulated power in solar power generation systems It is suitable as an insulation resistance detection circuit equipped in the conditioner.
  • Insulation resistance detection circuit DC power supply (solar cell) 3 Power supply voltage measurement circuit 4 Control circuit (CPU) 5 Common connection end (intermediate potential generation end) of voltage dividing resistors R1 and R2 constituting the voltage dividing circuit 6 Divided voltage measurement circuit 7 Ground terminal connected to ground 8 Current measurement circuit 9 Ground fault voltage point Vx, Vy (Vy1, Vy2) Solar cell module Rx Ground fault resistance component R3 Voltage change resistor S1 Switch OP3 Power supply voltage Operational amplifier constituting the measurement circuit OP4 Operational amplifier constituting the divided voltage measurement circuit Rsafe Ground fault protection resistor Rsense Voltage conversion resistor constituting the current measurement circuit AMP, OP1, OP2 Operational amplifier constituting the current measurement circuit Rbias, RB1 to RB4 Zero adjustment resistors for current measurement Vbias Reference power supply for current measurement

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Resistance Or Impedance (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)

Abstract

A CPU (4) calculates an insulation resistance value of a direct current power supply (2) using: a first current value, which is measured on the basis of a voltage (Vm21) (first measured voltage) measured by means of a divided voltage measuring circuit (6), and on a current (Isence1) (first grounding current) measured by means of a current measuring circuit (8), said voltage and said current having been measured when a switch (S1) is opened; and a second current value, which is measured on the basis of a voltage (Vm22) (second measured voltage) measured by means of the divided voltage measuring circuit (6), and a current (Isence2) (second grounding current) measured by means of the current measuring circuit (8), said voltage and said current having been measured when the switch (S1) is closed. Time intervals, at which the switch (S1) is opened and closed, said time intervals determining measuring times for measuring the first and the second current values, are variably set, corresponding to a change quantity between the first and the second grounding currents measured by means of the current measuring circuit (8).

Description

絶縁抵抗検知回路Insulation resistance detection circuit
　本発明は、複数の電源ユニットが直並列接続されて構成される直流電源の絶縁抵抗を測定する絶縁抵抗検知回路に関するものである。 The present invention relates to an insulation resistance detection circuit for measuring an insulation resistance of a DC power supply configured by connecting a plurality of power supply units in series and parallel.
　複数の電源ユニットが直並列接続されて構成される直流電源としては、太陽電池や燃料電池などが知られている。そのような直流電源を用いて交流電力を発生するシステムは、直流電源と電力変換装置（パワーコンディショナー）とを組み合わせて構成されるので、安全性確保の観点からシステムとして満たすべき絶縁抵抗規格において、個々の構成要素が満たすべき絶縁抵抗値が定められている。 A solar cell, a fuel cell, and the like are known as a DC power source configured by connecting a plurality of power source units in series and parallel. Since a system that generates AC power using such a DC power supply is configured by combining a DC power supply and a power converter (power conditioner), in the insulation resistance standard that should be satisfied as a system from the viewpoint of ensuring safety, The insulation resistance value to be satisfied by each component is determined.
　パワーコンディショナーとしては、変換した交流電力を、絶縁変圧器を介在させず、直接負荷へ供給する非絶縁型パワーコンディショナーが、安価に電力変換効率を向上できる特徴を有していることから、広く利用されている。この非絶縁型パワーコンディショナーを用いるシステムでは、電力発生側と負荷側との間に絶縁手段である絶縁変圧器がないので、非絶縁型パワーコンディショナーにおいて、入力直流電源での絶縁抵抗劣化が負荷に影響を与えないようにする措置を講ずることが要求されている。以下、理解を容易にするため、太陽光発電システムを例に挙げて説明する。 As a power conditioner, the non-insulated power conditioner that supplies the converted AC power directly to the load without an insulating transformer is widely used because it has a feature that can improve the power conversion efficiency at low cost. Has been. In the system using this non-insulated power conditioner, there is no insulation transformer as an insulating means between the power generation side and the load side, so in the non-insulated power conditioner, the insulation resistance deterioration at the input DC power supply is caused to the load. It is required to take measures to prevent the impact. Hereinafter, in order to facilitate understanding, a solar power generation system will be described as an example.
　太陽光発電システムで使用される太陽電池は、複数の太陽電池モジュールを直並列に接続して構成される。個々の太陽電池モジュールの対地絶縁抵抗値は、非常に高抵抗（例えば１０００ＭΩ）であるが、その太陽電池モジュールが例えば１００枚直並列接続された場合の対地絶縁抵抗値は１０ＭΩに低下する。太陽電池モジュールの漏れ電流は面積に比例するので、太陽電池モジュールの個数を大幅に増やして大容量化した太陽電池の総合絶縁抵抗は大きく低下する。そのため、大容量化した太陽光発電システムでは、正常な太陽電池モジュールであっても、総合絶縁抵抗が低下し、太陽光発電システムに要求される絶縁抵抗規格と正常な太陽電池モジュール群の絶縁抵抗との差が少なくなり、問題になっている。しかし、個々の太陽電池モジュールの絶縁抵抗を更に高抵抗化することは高価となるので、対応が困難である。 A solar cell used in a photovoltaic power generation system is configured by connecting a plurality of solar cell modules in series and parallel. The ground insulation resistance value of each solar cell module is very high (for example, 1000 MΩ), but when the 100 solar cell modules are connected in series, for example, the ground insulation resistance value is reduced to 10 MΩ. Since the leakage current of the solar cell module is proportional to the area, the total insulation resistance of the solar cell having a large capacity by greatly increasing the number of solar cell modules is greatly reduced. Therefore, in a photovoltaic power generation system with a large capacity, even if it is a normal solar cell module, the overall insulation resistance decreases, and the insulation resistance standard required for the photovoltaic power generation system and the insulation resistance of the normal solar cell module group And the difference is becoming a problem. However, since it is expensive to further increase the insulation resistance of each solar cell module, it is difficult to cope with it.
　そのため、太陽光発電システムでは、配電系統への系統連系機器として使用される非絶縁型パワーコンディショナーにおいて、変換した交流電力を配電系統へ連系する前に、直流電源である太陽電池の絶縁抵抗がシステムとして要求される所定値以上であるか否かを自己診断する機能を備える必要がある。 Therefore, in a solar power generation system, in a non-insulated power conditioner used as a grid-connected device to the distribution system, before connecting the converted AC power to the distribution system, the insulation resistance of the solar cell that is the DC power supply It is necessary to provide a function of self-diagnosis whether or not is equal to or greater than a predetermined value required by the system.
　本発明が対象とする絶縁抵抗検知回路は、複数の電源ユニットが直並列に接続されて構成される直流電源を変換対象とする非絶縁型パワーコンディショナーにおいて、上記した自己診断を実行する際に、該直流電源の絶縁抵抗を測定する回路である。複数の電源ユニットが直並列に接続されている直流電源においては、地絡する箇所は任意の電圧点で生ずるので、絶縁抵抗検知回路に対しては、地絡する電圧点に関わらず地絡抵抗を測定できることが要求される。 The insulation resistance detection circuit targeted by the present invention is a non-insulated power conditioner for converting a DC power source configured by connecting a plurality of power supply units in series and parallel. It is a circuit for measuring the insulation resistance of the DC power supply. In a DC power supply in which multiple power supply units are connected in series and parallel, the ground fault location occurs at an arbitrary voltage point. Therefore, for the insulation resistance detection circuit, the ground fault resistance regardless of the ground fault voltage point. Is required to be measured.
　この地絡抵抗を測定する方法としては、例えば特許文献１に提案されている方法が参考になる。すなわち、特許文献１では、不明点を補足すれば、地絡抵抗測定での未知数は、絶縁抵抗が劣化した地絡電圧点と絶縁抵抗値との２つであることから、絶縁抵抗測定電圧を２電圧で測定し、地絡抵抗の未知数を求める構成例が提案されていると言える。 As a method for measuring the ground fault resistance, for example, the method proposed in Patent Document 1 is helpful. That is, in Patent Document 1, if the unknown point is supplemented, the unknowns in the ground fault resistance measurement are the ground fault voltage point where the insulation resistance has deteriorated and the insulation resistance value. It can be said that the example of a structure which measures by 2 voltages and calculates | requires the unknown number of ground fault resistance is proposed.
国際公開第２００４／０９３２８４号International Publication No. 2004/093284
　絶縁抵抗検知回路は、地絡する電圧点に関わらず地絡抵抗を測定することを目的としているが、その測定精度を確保し高めるためには、測定時間の定め方と、回路構成の工夫との両面から検討する必要がある。この測定時間の定め方については、特許文献１では示されていない。 The purpose of the insulation resistance detection circuit is to measure the ground fault resistance regardless of the ground fault voltage point, but in order to ensure and improve its measurement accuracy, the measurement time is determined and the circuit configuration is devised. It is necessary to consider from both sides. The method of determining the measurement time is not shown in Patent Document 1.
　まず、特許文献１では配慮されていないが、太陽電池モジュールは、モジュールフレームを一般には大地にアースするので、大地アースに対し太陽電池電源は浮遊容量が生じている。また、その対地浮遊容量が降雨時においては、太陽電池表面の水膜が導電性の大地電極化する事により大きく増加する。その結果として太陽電池の対地総合容量値は、接続する太陽電池モジュールの枚数や降雨により大きく増加することになる。したがって、太陽電池の絶縁抵抗を正確に測定するには、対地浮遊容量への最大充電時間を考慮した測定時間を設定する必要がある。 First, although not taken into account in Patent Document 1, since a solar cell module generally grounds a module frame to the ground, the solar cell power supply has a stray capacitance with respect to the ground. In addition, when the ground floating capacity is raining, the water film on the surface of the solar cell is greatly increased by forming a conductive ground electrode. As a result, the total ground capacity value of the solar cell greatly increases due to the number of connected solar cell modules and rainfall. Therefore, in order to accurately measure the insulation resistance of the solar cell, it is necessary to set a measurement time in consideration of the maximum charging time for the floating capacitance to the ground.
　また、太陽電池においては、一般的な起動となるのは、日の出の時間帯であるが、その日の出の時間帯においては発生電圧が大きく変化することから、発生電圧が安定するまでの待ち時間が必要となる。 In solar cells, the general start-up is during the sunrise time, but the generated voltage changes greatly during the sunrise time, so there is a waiting time until the generated voltage stabilizes. Necessary.
　従来では、正確な測定を行うために、測定時間を長めに設定していたので、晴天での正常運転において、太陽電池の発生電圧が連系可能な電圧に達していても、速やかに系統連系することができず、発電システムとしての発電効率の低下を招来していた。 Conventionally, in order to perform accurate measurement, the measurement time is set to be long, so even in normal operation in fine weather, even if the voltage generated by the solar cells reaches a voltage that can be connected, The power generation efficiency of the power generation system has been reduced.
　一方、測定回路は、特許文献１に示されるように、直流電源の出力電圧の中間電位を分圧生成する分圧回路（分圧出力端は回路グランドに接続されている）の分圧比を第１の値と第２の値とに変化させ、分圧比が第１の値のときに分圧回路の分圧出力端から大地アースに流れる第１の電流と、分圧比が第２の値のときに分圧回路の分圧出力端から大地アースに流れる第２の電流とを取り込み地絡抵抗を測定するように構成される。 On the other hand, as shown in Patent Document 1, the measurement circuit uses a voltage dividing ratio of a voltage dividing circuit that generates an intermediate potential of the output voltage of the DC power supply (the voltage dividing output terminal is connected to the circuit ground). The first current flowing from the voltage dividing output terminal of the voltage dividing circuit to the earth ground when the voltage dividing ratio is the first value and the voltage dividing ratio being the second value are changed to the first value and the second value. Sometimes configured to take a second current flowing from the voltage divider output end of the voltage divider circuit to earth ground and measure the ground fault resistance.
　この測定回路では、次のような問題がある。まず、分圧回路と並列に漏れ電流の温度変化や経年変化の部品（例えばアルミ電解コンデンサなど）が配置されていると、分圧回路の等価インピーダンスとしての分圧比精度が低下し、連係可否を決める判定レベルの精度が低下する。また、分圧比の切り替えは、ＦＥＴなどの半導体スイッチを用いて行うが、この半導体スイッチの部分での漏れ電流も判定レベルの精度を低下させる要因となる。 This measurement circuit has the following problems. First, if there is a part of the leakage current that changes in temperature or aging (for example, an aluminum electrolytic capacitor) in parallel with the voltage divider circuit, the accuracy of the voltage division ratio as the equivalent impedance of the voltage divider circuit decreases, and the possibility of linkage is determined. The accuracy of the determination level to be determined decreases. Further, the voltage division ratio is switched using a semiconductor switch such as an FET, but a leakage current in the semiconductor switch portion also causes a decrease in the accuracy of the determination level.
　この場合、判定レベルを法規制により要求される絶縁抵抗値を満足するように判定精度低下分を加算した判定規格に設定すると、太陽電池モジュールに要求される絶縁抵抗値が増加するので、高価な太陽電池モジュールが必要となり大容量化が困難となる。また、分圧抵抗器を低抵抗化すれば測定精度の向上が図れるが、特許文献１に示される構成では、分圧抵抗器の消費電力上昇や抵抗発熱の問題があり、精度向上の手段として容易に用いることができない。 In this case, since the insulation resistance value required for the solar cell module increases when the judgment level is set to the judgment standard obtained by adding a reduction in judgment accuracy so as to satisfy the insulation resistance value required by law and regulation, it is expensive. A solar cell module is required, making it difficult to increase the capacity. In addition, the measurement accuracy can be improved by reducing the resistance of the voltage dividing resistor. However, in the configuration shown in Patent Document 1, there is a problem of an increase in power consumption of the voltage dividing resistor and resistance heat generation. It cannot be used easily.
　本発明は、上記に鑑みてなされたものであり、複数の電源ユニットが直並列接続されて構成される直流電源の絶縁抵抗を、該直流電源の対地浮遊容量の変化や該直流電源の出力電圧の変化、絶縁抵抗測定系素子のバラツキや漏れ電流等の変化に対し、容易に対応して正確に測定することができる絶縁抵抗検知回路を得ることを目的とする。 The present invention has been made in view of the above, and the insulation resistance of a DC power supply configured by connecting a plurality of power supply units in series and parallel is used to change the ground floating capacitance of the DC power supply or the output voltage of the DC power supply. It is an object of the present invention to obtain an insulation resistance detection circuit that can easily measure and accurately measure changes in electrical resistance, variations in insulation resistance measurement system elements, changes in leakage current, and the like.
　上述した課題を解決し、目的を達成するために、本発明は、複数の電源ユニットが直並列接続されて構成される直流電源の出力電圧の中間電位を分圧生成する分圧回路であって該中間電位生成端が回路グランドに接続される分圧回路と、前記分圧回路の分圧比を第１の値と第２の値とに変化させるための分圧比変化手段と、前記分圧回路の中間電位生成端から出力される電圧を測定する分圧電圧測定手段と、大地に接続されるアース端子から前記分圧回路の中間電位生成端に至る経路に配置される地絡保護用抵抗器を流れる地絡電流を測定する電流測定手段と、前記分圧比変化手段に前記分圧回路の分圧比を第１の値に設定させたときに前記電流測定手段が測定した第１の地絡電流から測定した第１の電流値および前記分圧電圧測定手段が測定した前記中間電位生成端から出力される第１の測定電圧と、前記分圧比変化手段に前記分圧回路の分圧比を第２の値に設定させたときに前記電流測定手段が測定した第２の地絡電流から測定した第２の電流値および前記分圧電圧測定手段が測定した前記中間電位生成端から出力される第２の測定電圧とを用いて前記直流電源の絶縁抵抗値である前記アース端子と前記直流電源内の地絡電圧点との間に形成される地絡抵抗成分の値を算出する絶縁抵抗算出制御手段とを備え、前記絶縁抵抗算出制御手段は、前記第１および第２の電流値を測定する測定時間である前記分圧比変化手段に前記分圧回路の分圧比を第１の値と第２の値とに変化させる時間間隔を、前記電流測定手段が測定した第１および第２の地絡電流の変化量に応じて可変設定することを特徴とする。 In order to solve the above-described problems and achieve the object, the present invention provides a voltage dividing circuit that generates an intermediate potential of an output voltage of a DC power supply configured by connecting a plurality of power supply units in series and parallel. A voltage dividing circuit whose intermediate potential generating terminal is connected to circuit ground; a voltage dividing ratio changing means for changing a voltage dividing ratio of the voltage dividing circuit between a first value and a second value; and the voltage dividing circuit. A voltage dividing voltage measuring means for measuring a voltage output from the intermediate potential generation terminal of the circuit, and a ground fault protection resistor arranged in a path from the ground terminal connected to the ground to the intermediate potential generation terminal of the voltage dividing circuit Current measuring means for measuring a ground fault current flowing through the voltage dividing circuit, and a first ground fault current measured by the current measuring means when the voltage dividing ratio changing means is caused to set the voltage dividing ratio of the voltage dividing circuit to a first value. The first current value measured from the above and the divided voltage measuring means are A first measurement voltage output from the intermediate potential generation terminal set, and a first measurement voltage measured by the current measurement unit when the voltage division ratio changing unit is caused to set the voltage division ratio of the voltage dividing circuit to a second value. The insulation resistance value of the DC power source using the second current value measured from the ground fault current of 2 and the second measured voltage output from the intermediate potential generation terminal measured by the divided voltage measuring means. Insulation resistance calculation control means for calculating a value of a ground fault resistance component formed between the ground terminal and a ground fault voltage point in the DC power supply, wherein the insulation resistance calculation control means comprises the first and The current measuring means measures the time interval for changing the voltage dividing ratio of the voltage dividing circuit between the first value and the second value in the voltage dividing ratio changing means, which is the measurement time for measuring the second current value. Variable setting according to the amount of change in the first and second ground fault currents And wherein the Rukoto.
　本発明によれば、地絡電流の変化量に応じて測定時間を可変設定する構成とするとともに、分圧回路の分圧比のバラツキによる測定誤差を含まないように絶縁抵抗値を算出できる構成としたので、複数の電源ユニットを直並列接続して構成される太陽電池等の直流電源の設置面積や降雨時等による対地浮遊容量の変化や、該直流電源の出力電圧の変化、絶縁抵抗測定系素子のバラツキや漏れ電流等の変化に対し、容易に対応して精度よく絶縁抵抗を測定することができるという効果を奏する。 According to the present invention, the measurement time is variably set according to the amount of change in the ground fault current, and the insulation resistance value can be calculated so as not to include measurement errors due to variations in the voltage dividing ratio of the voltage dividing circuit. Therefore, the installation area of a DC power source such as a solar cell constituted by connecting a plurality of power supply units in series and parallel, the change in ground floating capacitance due to rain, etc., the change in the output voltage of the DC power source, the insulation resistance measurement system There is an effect that it is possible to easily measure the insulation resistance with high accuracy in response to changes in element variations, leakage current, and the like.
図１は、本発明の一実施例による絶縁抵抗検知回路の構成を示す概念回路図である。FIG. 1 is a conceptual circuit diagram showing a configuration of an insulation resistance detection circuit according to an embodiment of the present invention. 図２は、図１に示す絶縁抵抗検知回路に対地浮遊容量等を追加した回路図である。FIG. 2 is a circuit diagram in which a ground stray capacitance or the like is added to the insulation resistance detection circuit shown in FIG. 図３は、図１に示す絶縁抵抗検知回路の具体的な回路図である。FIG. 3 is a specific circuit diagram of the insulation resistance detection circuit shown in FIG. 図４は、飽和時点測定で用いる対地浮遊容量による測定電流変化の測定例を示す波形図である。FIG. 4 is a waveform diagram showing a measurement example of a change in the measured current due to the ground floating capacitance used in the saturation time measurement. 図５は、測定電流が安定した飽和時点での分圧電圧測定回路が測定した電圧を用いて絶縁抵抗の測定算出を行う場合の手順を説明する絶縁抵抗測定系の等価回路図であり、（Ａ）はスイッチＳ１が開路している場合を示し、（Ｂ）はスイッチＳ１が閉路している場合を示す。FIG. 5 is an equivalent circuit diagram of the insulation resistance measurement system for explaining the procedure in the case of performing measurement calculation of insulation resistance using the voltage measured by the divided voltage measurement circuit at the saturation point when the measurement current is stable. A) shows the case where the switch S1 is open, and (B) shows the case where the switch S1 is closed.
　以下に、本発明にかかる絶縁抵抗検知回路の実施例を図面に基づいて詳細に説明する。なお、この実施例によりこの発明が限定されるものではない。 Hereinafter, an embodiment of an insulation resistance detection circuit according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.
　図１は、本発明の一実施例による絶縁抵抗検知回路の構成を示す概念回路図である。図２は、図１に示す絶縁抵抗検知回路に対地浮遊容量等を追加した回路図である。図３は、図１に示す絶縁抵抗検知回路の具体的な構成例を示す回路図である。 FIG. 1 is a conceptual circuit diagram showing a configuration of an insulation resistance detection circuit according to an embodiment of the present invention. FIG. 2 is a circuit diagram in which a ground stray capacitance or the like is added to the insulation resistance detection circuit shown in FIG. FIG. 3 is a circuit diagram showing a specific configuration example of the insulation resistance detection circuit shown in FIG.
　図１において、絶縁抵抗検知回路１は、直流電源２の正極端（＋）と負極端（－）との間に並列に接続された、電源電圧測定回路３と、分圧用抵抗器Ｒ１，Ｒ２による分圧回路とを備えている。分圧用抵抗器Ｒ１，Ｒ２の共通接続端５は、直流電源２の出力電圧の中間電位を分圧生成する中間電位生成端であり、回路グランドＧＮＤに接続されている。 In FIG. 1, an insulation resistance detection circuit 1 includes a power supply voltage measuring circuit 3 and voltage dividing resistors R1, R2 connected in parallel between a positive terminal (+) and a negative terminal (−) of a DC power source 2. And a voltage dividing circuit. The common connection end 5 of the voltage dividing resistors R1 and R2 is an intermediate potential generation end that generates an intermediate potential of the output voltage of the DC power supply 2, and is connected to the circuit ground GND.
　そして、図１では、直流電源２の正極端（＋）と共通接続端５との間に、つまり分圧用抵抗器Ｒ１に並列に，電圧変更用抵抗器Ｒ３とスイッチＳ１との直列回路が接続されている。スイッチＳ１は、制御回路（ＣＰＵ）４により開閉制御される。これによって、分圧回路の分圧比が、スイッチＳ１が開路している時と閉路している時とで異なる値となる。すなわち、電圧変更用抵抗器Ｒ３とスイッチＳ１の直列回路は、分圧回路の分圧比を変化させる分圧比変化手段を構成している。 In FIG. 1, a series circuit of a voltage changing resistor R3 and a switch S1 is connected between the positive terminal (+) of the DC power source 2 and the common connection terminal 5, that is, in parallel with the voltage dividing resistor R1. Has been. The switch S1 is controlled to open and close by a control circuit (CPU) 4. As a result, the voltage dividing ratio of the voltage dividing circuit becomes different between when the switch S1 is open and when the switch S1 is closed. That is, the series circuit of the voltage changing resistor R3 and the switch S1 constitutes a voltage dividing ratio changing means for changing the voltage dividing ratio of the voltage dividing circuit.
　スイッチＳ１が開路している時の分圧比を第１の値とし、閉路している時の分圧比を第２の値とすれば、共通接続端５の電位は、スイッチＳ１が開路している時の電位（直流電源２の第１の電位）とスイッチＳ１が閉路している時の電位（直流電源２の第２の電位）との間で変化する。電源電圧測定回路３は、直流電源２の出力電圧値を変換し電圧Ｖｍ１としてＣＰＵ４へ出力する。 If the voltage dividing ratio when the switch S1 is open is the first value and the voltage dividing ratio when the switch S1 is closed is the second value, the potential of the common connection terminal 5 is the circuit S1 is open. It changes between the potential at the time (first potential of the DC power supply 2) and the potential when the switch S1 is closed (second potential of the DC power supply 2). The power supply voltage measurement circuit 3 converts the output voltage value of the DC power supply 2 and outputs it to the CPU 4 as the voltage Vm1.
　また、直流電源２の負極端（－）と共通接続端５との間に、つまり分圧用抵抗器Ｒ２に並列に、分圧電圧測定回路６が設けられている。分圧電圧測定回路６は、分圧回路の共通接続端５から出力される電圧を測定し電圧Ｖｍ２としてＣＰＵ４へ出力する。 Also, a divided voltage measuring circuit 6 is provided between the negative terminal (−) of the DC power supply 2 and the common connection terminal 5, that is, in parallel with the voltage dividing resistor R2. The divided voltage measuring circuit 6 measures the voltage output from the common connection end 5 of the voltage dividing circuit and outputs it to the CPU 4 as the voltage Vm2.
　大地Ｅａｒｔｈに接続されるアース端子７と共通接続端５との間に、地絡保護用抵抗器Ｒｓａｆｅ、電圧変換用抵抗器Ｒｓｅｎｃｅ、零点調整用抵抗器Ｒｂｉａｓがこの順に挿入されている。地絡保護用抵抗器Ｒｓａｆｅは、電子回路と大地Ｅａｒｔｈとの間に要求される絶縁性能を確保するためのもので、一般に１０ＭΩ程度の高抵抗に設定される。 A ground fault protection resistor Rsafe, a voltage conversion resistor Rsense, and a zero adjustment resistor Rbias are inserted in this order between the ground terminal 7 connected to the ground Earth and the common connection end 5. The ground fault protection resistor Rsafe is for securing the insulation performance required between the electronic circuit and the earth, and is generally set to a high resistance of about 10 MΩ.
　電圧変換用抵抗器Ｒｓｅｎｃｅは、当該絶縁抵抗検知回路１からアース端子７を介して大地Ｅａｒｔｈに向かって流れる電流（つまり、地絡保護用抵抗器Ｒｓａｆｅを流れる地絡電流）を電圧変換する。電圧変換用抵抗器Ｒｓｅｎｃｅの両端電圧は、演算増幅器ＡＭＰにて増幅され、測定電流ＩｓｅｎｃｅとしてＣＰＵ４に入力される。抵抗器Ｒｂｉａｓおよび並列に接続される基準電源Ｖｂｉａｓは、演算増幅器ＡＭＰにおいて電流測定用の零点を調節するために設けられている。すなわち、演算増幅器ＡＭＰ、電圧変換用抵抗器Ｒｓｅｎｃｅ、零点調整用抵抗器Ｒｂｉａｓおよび基準電源Ｖｂｉａｓの全体は、電流測定回路８を構成している。 The voltage conversion resistor Rsense converts the current flowing from the insulation resistance detection circuit 1 toward the ground Earth through the ground terminal 7 (that is, the ground fault current flowing through the ground fault protection resistor Rsafe). The voltage across the voltage conversion resistor Rsense is amplified by the operational amplifier AMP and input to the CPU 4 as the measurement current Isense. The resistor Rbias and the reference power supply Vbias connected in parallel are provided for adjusting the zero point for current measurement in the operational amplifier AMP. That is, the operational amplifier AMP, the voltage conversion resistor Rsense, the zero adjustment resistor Rbias, and the reference power source Vbias as a whole constitute a current measurement circuit 8.
　直流電源２は、複数の電源ユニットを直並列接続して構成される。図１では、その一例として太陽電池を示してある。太陽電池は、複数の太陽電池モジュールＶｙ１，Ｖｙ２、Ｖｘの直列接続体である。図１では、地絡が生じた地絡電圧点９とアース端子７との間を流れる地絡電流の経路に地絡抵抗成分Ｒｘが生成され、太陽電池モジュールＶｘの出力電圧Ｖｘが地絡電圧Ｖｘとなるとしている。 DC power supply 2 is configured by connecting a plurality of power supply units in series and parallel. In FIG. 1, a solar cell is shown as an example. The solar cell is a series connection body of a plurality of solar cell modules Vy1, Vy2, and Vx. In FIG. 1, a ground fault resistance component Rx is generated in the path of the ground fault current flowing between the ground fault voltage point 9 where the ground fault has occurred and the ground terminal 7, and the output voltage Vx of the solar cell module Vx is the ground fault voltage. Vx is assumed.
　次に、図２では、図１に示した構成において、電流測定回路８を簡潔に示してあるが、直流電源（太陽電池）２の対地浮遊容量Ｃｘ，Ｃｙが追加され、また、回路の雑音防止コンデンサＣｅｍｃが追加されている。対地浮遊容量Ｃｘ，Ｃｙや雑音防止コンデンサＣｅｍｃの静電容量は非常に大きい。 Next, in FIG. 2, although the current measurement circuit 8 is simply shown in the configuration shown in FIG. 1, the ground stray capacitances Cx and Cy of the DC power source (solar cell) 2 are added, and the noise of the circuit A prevention capacitor Cemc is added. The electrostatic capacitances of the ground floating capacitances Cx and Cy and the noise prevention capacitor Cemc are very large.
　次に、図３では、電圧測定回路３，６が負帰還増幅器構成の演算増幅器ＯＰ３，ＯＰ４で構成でき、スイッチＳ１がトランジスタで構成できることが示され、電流測定回路８の具体的な構成例が示されている。また、直流電源（太陽電池）２は、太陽電池モジュールＶｙ１，Ｖｙ２が太陽電池モジュールＶｙとまとめられ、太陽電池モジュールＶｘと太陽電池モジュールＶｙとの間の地絡電圧点９で地絡が生じたとしている。 Next, FIG. 3 shows that the voltage measurement circuits 3 and 6 can be configured by operational amplifiers OP3 and OP4 having a negative feedback amplifier configuration, and the switch S1 can be configured by a transistor. A specific configuration example of the current measurement circuit 8 is shown in FIG. It is shown. Further, in the DC power source (solar cell) 2, the solar cell modules Vy1 and Vy2 are combined with the solar cell module Vy, and a ground fault occurs at the ground fault voltage point 9 between the solar cell module Vx and the solar cell module Vy. It is said.
　演算増幅器ＯＰ３は、絶縁抵抗測定中の直流電源（太陽電池）２の出力電圧を電圧Ｖｍ１としてＣＰＵ４へ出力する。演算増幅器ＯＰ４は、絶縁抵抗測定中の分圧回路の分圧出力電圧を電圧Ｖｍ２としてＣＰＵ４へ出力する。 The operational amplifier OP3 outputs the output voltage of the DC power source (solar cell) 2 during the insulation resistance measurement to the CPU 4 as the voltage Vm1. The operational amplifier OP4 outputs the divided output voltage of the voltage dividing circuit during the insulation resistance measurement to the CPU 4 as the voltage Vm2.
　電流測定回路８では、電流測定用の演算増幅器ＡＭＰが電圧フォロワ構成の演算増幅器ＯＰ１と負帰還増幅器構成の演算増幅器ＯＰ２とにより構成され、零点調整用抵抗器Ｒｂｉａｓが抵抗器ＲＢ１～ＲＢ４により構成され、それらに基準電源Ｖｂｉａｓが接続されている。 In the current measurement circuit 8, an operational amplifier AMP for current measurement is configured by an operational amplifier OP1 having a voltage follower configuration and an operational amplifier OP2 having a negative feedback amplifier configuration, and a zero adjustment resistor Rbias is configured by resistors RB1 to RB4. The reference power supply Vbias is connected to them.
　以下、地絡保護用抵抗器Ｒｓａｆｅを流れる電流Ｉｓｅｎｃｅを測定して直流電源２の絶縁抵抗である地絡抵抗成分Ｒｘを測定算出する方法について説明する。ここでは、２つの算出方法を示す。なお、式の導出で用いる「値」には、各要素の識別符号を用いる。 Hereinafter, a method of measuring and calculating the ground fault resistance component Rx which is the insulation resistance of the DC power supply 2 by measuring the current Isense flowing through the ground fault protection resistor Rsafe will be described. Here, two calculation methods are shown. The “value” used in the derivation of the expression uses the identification code of each element.
　図１において、直流電源２の出力電圧（Ｖｘ＋Ｖｙ１＋Ｖｙ２）は、当該絶縁抵抗検知回路１の入力直流電圧である。直流電源２の出力電圧は、電圧Ｖｍ１として電源電圧測定回路３にて測定されＣＰＵ４へ入力される。また、地絡保護用抵抗器Ｒｓａｆｅを流れる電流Ｉｓｅｎｃｅは、電流測定回路８にて測定されＣＰＵ４へ入力される。さらに、分圧回路の共通接続端５から出力される電圧は、分圧電圧測定回路６にて測定され電圧Ｖｍ２としてＣＰＵ４に入力される。 1, the output voltage (Vx + Vy1 + Vy2) of the DC power source 2 is an input DC voltage of the insulation resistance detection circuit 1. The output voltage of the DC power supply 2 is measured by the power supply voltage measuring circuit 3 as the voltage Vm1 and input to the CPU 4. The current Isense flowing through the ground fault protection resistor Rsafe is measured by the current measuring circuit 8 and input to the CPU 4. Further, the voltage output from the common connection end 5 of the voltage dividing circuit is measured by the divided voltage measuring circuit 6 and input to the CPU 4 as the voltage Vm2.
　ＣＰＵ４は、スイッチＳ１を開路した時および閉路した時に入力される電圧Ｖｍ１，Ｖｍ２および電流Ｉｓｅｎｃｅをそれぞれサンプリングしてデジタル化し、それらに基づき地絡抵抗値Ｒｘおよび地絡電圧Ｖｘを算出する。スイッチＳ１を開閉する時間間隔が測定時間である。なお、電流測定回路８のインピーダンスは、地絡保護用抵抗器Ｒｓａｆｅの抵抗値Ｒｓａｆｅよりも極めて小さいので、地絡抵抗値Ｒｘの算出においては、無視できる値となる。 The CPU 4 samples and digitizes the voltages Vm1 and Vm2 and the current Isense input when the switch S1 is opened and closed, and calculates the ground fault resistance value Rx and the ground fault voltage Vx based on them. The time interval for opening and closing the switch S1 is the measurement time. Since the impedance of the current measuring circuit 8 is extremely smaller than the resistance value Rsafe of the ground fault protection resistor Rsafe, it becomes a negligible value in the calculation of the ground fault resistance value Rx.
＜第１の算出方法＞
　まず、図１と図２を参照して、電圧Ｖｍ１と電流Ｉｓｅｎｃｅとを用いて地絡抵抗値Ｒｘおよび地絡電圧Ｖｘを算出する場合について説明する。スイッチＳ１を開路して電圧変更用抵抗器Ｒ３を開放した時の電流Ｉｓｅｎｃｅ１は、式（１）で示される。
　Ｉｓｅｎｃｅ１＝（Ｖｍ１－Ｖｘ）
　　　　　　　　　　／｛Ｒｘ＋Ｒｓａｆｅ＋Ｒ１×Ｒ２／（Ｒ１＋Ｒ２）｝　…（１） <First calculation method>
First, a case where the ground fault resistance value Rx and the ground fault voltage Vx are calculated using the voltage Vm1 and the current Isense will be described with reference to FIGS. The current Isense1 when the switch S1 is opened and the voltage changing resistor R3 is opened is expressed by Expression (1).
Isense1 = (Vm1-Vx)
/ {Rx + Rsafe + R1 × R2 / (R1 + R2)} (1)
　また、スイッチＳ１を閉路して電圧変更用抵抗器Ｒ３を分圧用抵抗器Ｒ１に並列接続した時の電流Ｉｓｅｎｃｅ２は、同様に式（２）で示される。
　Ｉｓｅｎｃｅ２＝（Ｖｍ１－Ｖｘ）
　　　／｛Ｒｘ＋Ｒｓａｆｅ＋Ｒ１×Ｒ２×Ｒ３／（Ｒ１Ｒ３＋Ｒ１Ｒ２＋Ｒ２Ｒ３）｝　　…（２） Similarly, the current Isense2 when the switch S1 is closed and the voltage changing resistor R3 is connected in parallel to the voltage dividing resistor R1 is expressed by Expression (2).
Isense2 = (Vm1-Vx)
/ {Rx + Rsafe + R1 × R2 × R3 / (R1R3 + R1R2 + R2R3)} (2)
　式（１）における固定値「Ｒｓａｆｅ＋Ｒ１×Ｒ２／（Ｒ１＋Ｒ２）」をＣ１とし、式（２）における固定値「Ｒ１×Ｒ２×Ｒ３／（Ｒ１Ｒ３＋Ｒ１Ｒ２＋Ｒ２Ｒ３）」をＣ２とすると、式（１）、式（２）は、
　Ｉｓｅｎｃｅ１＝（Ｖｍ－Ｖｘ）／（Ｒｘ＋Ｃ１）　…（３）
　Ｉｓｅｎｃｅ２＝（Ｖｍ－Ｖｘ）／（Ｒｘ＋Ｃ２）　…（４）
となる。 When the fixed value “Rsafe + R1 × R2 / (R1 + R2)” in Formula (1) is C1, and the fixed value “R1 × R2 × R3 / (R1R3 + R1R2 + R2R3)” in Formula (2) is C2, Formula (1), Formula ( 2)
Isense1 = (Vm−Vx) / (Rx + C1) (3)
Isense2 = (Vm−Vx) / (Rx + C2) (4)
It becomes.
　式（３）、式（４）から、
　Ｉｓｅｎｃｅ１×（Ｒｘ＋Ｃ１）＝Ｉｓｅｎｃｅ２×（Ｒｘ＋Ｃ２）　…（５）
であるので、地絡抵抗値Ｒｘは、
　Ｒｘ＝（Ｉｓｅｎｃｅ２×Ｃ２－Ｉｓｅｎｃｅ１×Ｃ１）
　　　　　　　　　　　　　　　　／（Ｉｓｅｎｃｅ１－Ｉｓｅｎｃｅ２）　…（６）
と求められる。 From Equation (3) and Equation (4),
Isense1 × (Rx + C1) = Isense2 × (Rx + C2) (5)
Therefore, the ground fault resistance value Rx is
Rx = (Isense2 × C2-Isense1 × C1)
/ (Isense1-Isense2) (6)
Is required.
　すなわち、ＣＰＵ４は、スイッチＳ１を所定の時間間隔で開閉し、電流測定回路８から入力される、スイッチＳ１を開路した時の電流Ｉｓｅｎｃｅ１と、スイッチＳ１を閉路した時の電流Ｉｓｅｎｃｅ２とをそれぞれ測定して取り込み、式（６）に適用して地絡抵抗値Ｒｘを求め、求めた地絡抵抗値Ｒｘと絶縁抵抗規格に対して定められた絶縁抵抗判定レベルとを比較する。これによって、直流電源出力電圧および地絡電位に関わらずに絶縁抵抗の良否を判定することが可能となる。 That is, the CPU 4 opens and closes the switch S1 at a predetermined time interval, and measures the current Isense1 when the switch S1 is opened and the current Isense2 when the switch S1 is closed, which are input from the current measurement circuit 8. The ground fault resistance value Rx is obtained by applying the equation (6) and the obtained ground fault resistance value Rx is compared with the insulation resistance determination level defined for the insulation resistance standard. This makes it possible to determine whether the insulation resistance is good or not regardless of the DC power supply output voltage and the ground fault potential.
　ここで、地絡抵抗値Ｒｘの測定では、ＣＰＵ４が入力される電流Ｉｓｅｎｃｅを測定する精度の影響を受ける。実際には図２に示すように、対地浮遊容量Ｃｙ，Ｃｘや回路の雑音防止コンデンサＣｅｍｃが存在し、高抵抗の地絡保護用抵抗器Ｒｓａｆｅが存在するので、電流Ｉｓｅｎｃｅは充放電電流として測定される。つまり、充電が飽和する前の電流Ｉｓｅｎｃｅの値を測定したのでは、地絡抵抗値Ｒｘの測定精度はよくない。 Here, the measurement of the ground fault resistance value Rx is affected by the accuracy of measuring the current Isense input by the CPU 4. Actually, as shown in FIG. 2, since there are ground stray capacitances Cy and Cx and a circuit noise prevention capacitor Cemc, and a high resistance ground fault protection resistor Rsafe exists, the current Isense is measured as a charge / discharge current. Is done. That is, if the value of the current Isense before the charge is saturated is measured, the measurement accuracy of the ground fault resistance value Rx is not good.
　しかし、対地浮遊容量Ｃｙ，Ｃｘは、一定値ではなく、晴天時や降雨時などによって異なる。また、太陽電池の絶縁抵抗は、一定値ではなく、太陽電池の規模によって異なる。そこで、ＣＰＵ４は、スイッチＳ１を開閉する時間間隔、つまり電流Ｉｓｅｎｃｅの値を確定して取り込む測定時間を一定の固定時間とするのではなく、電流Ｉｓｅｎｃｅの変化量に応じて測定時間を可変するようになっている。 However, the ground-floating capacitances Cy and Cx are not constant values, and differ depending on the time of fine weather or rain. Further, the insulation resistance of the solar cell is not a constant value, but varies depending on the scale of the solar cell. Therefore, the CPU 4 does not set the time interval for opening and closing the switch S1, that is, the measurement time for determining and taking in the value of the current Isense to be a fixed time, but varies the measurement time according to the amount of change in the current Isense. It has become.
　上記した第１の算出方法でも、太陽電池モジュールの浮遊容量成分による測定誤差を少なくできるので、一応地絡抵抗値Ｒｘの測定精度を向上させ得るが、分圧回路が分圧生成する電圧Ｖｍ１のバラツキによる測定誤差が考慮されていない。すなわち、さらに、分圧回路の分圧比の精度に影響を与える部品（分圧用抵抗器Ｒ１，Ｒ２、電圧変更用抵抗器Ｒ３、スイッチＳ１、周辺に配置される図示しないアルミ電解コンデンサなど）での値のバラツキ、漏れ電流の温度変化や経年変化によって生ずる電圧Ｖｍ１のバラツキによる測定誤差を含まないように絶縁抵抗値を算出できることが必要である。以下、この問題を解決できる第２の算出方法を説明する。 Even in the first calculation method described above, the measurement error due to the stray capacitance component of the solar cell module can be reduced, so that the measurement accuracy of the ground fault resistance value Rx can be improved. However, the voltage Vm1 generated by the voltage dividing circuit is divided. Measurement errors due to variations are not taken into account. That is, in addition, components (such as voltage dividing resistors R1 and R2, voltage changing resistor R3, switch S1, and an aluminum electrolytic capacitor (not shown) arranged in the vicinity) that affect the accuracy of the voltage dividing ratio of the voltage dividing circuit. It is necessary to be able to calculate the insulation resistance value so as not to include measurement errors due to variations in the value of the voltage Vm1 caused by temperature variations and aging of the leakage current. Hereinafter, a second calculation method capable of solving this problem will be described.
＜第２の算出方法＞
　第２の算出方法では、ＣＰＵ４は、入力される電流Ｉｓｅｎｃｅの変化量を測定し、電流変化が安定した時点（飽和したと見なせる時点）にて電流値を確定し、その確定時点において入力される電圧Ｖｍ２を測定し、地絡抵抗値Ｒｘを算出する。この第２の算出方法によれば、電圧Ｖｍ１のバラツキに影響されず、正確な地絡抵抗値Ｒｘを測定算出することができる。スイッチＳ１の開閉時間間隔（測定時間）は、充電待機時間となるので、最適な測定時間を設定することができる。飽和時間測定となるので、入力される電流Ｉｓｅｎｃｅの変化波形は例えば図４に示すようになる。図４では、縦軸を電圧変換用抵抗器Ｒｓｅｎｃｅによる変換電圧で示してあるが、スイッチＳ１を６秒の間隔で開閉した場合の対地浮遊容量による測定電流変化の測定例が示されている。 <Second calculation method>
In the second calculation method, the CPU 4 measures the amount of change in the input current Isense, determines the current value when the current change is stable (when it can be regarded as saturated), and inputs the current value at that time. The voltage Vm2 is measured, and the ground fault resistance value Rx is calculated. According to the second calculation method, an accurate ground fault resistance value Rx can be measured and calculated without being affected by variations in the voltage Vm1. Since the open / close time interval (measurement time) of the switch S1 is a charging standby time, an optimal measurement time can be set. Since the saturation time is measured, the change waveform of the input current Isense is, for example, as shown in FIG. In FIG. 4, the vertical axis indicates the converted voltage by the voltage conversion resistor Rsense, but an example of measuring the measurement current change due to the ground floating capacitance when the switch S1 is opened and closed at intervals of 6 seconds is shown.
　この第２の算出方法によれば、最適な測定時間を設定できるので測定精度が高くなる。測定精度が向上することにより、パワーコンディショナーに用意する絶縁抵抗判定レベルは、必要とされる規格値に余裕をとる必要性がなくなる。したがって、太陽電池面積が増加した場合において生じる総合絶縁抵抗値の低下に対し、より安定な動作が可能となる。また、電流Ｉｓｅｎｃｅが安定した飽和時点を監視するので、雨天等において太陽電池の対地容量が増加した場合においても、自動的に測定時間が延長され、誤判定を防ぐことが可能となる。 According to the second calculation method, since the optimum measurement time can be set, the measurement accuracy is increased. By improving the measurement accuracy, the insulation resistance determination level prepared for the power conditioner is not required to have a margin for the required standard value. Therefore, more stable operation is possible against a decrease in the overall insulation resistance value that occurs when the solar cell area increases. Further, since the saturation point at which the current Isense is stabilized is monitored, even when the ground capacity of the solar cell increases in rainy weather or the like, the measurement time is automatically extended, and erroneous determination can be prevented.
　図５を参照して、第２の算出方法（分圧電圧測定回路６が測定した電圧Ｖｍ２を用いて算出する方法）を説明する。図５は、測定電流が安定した飽和時点での分圧電圧測定回路が測定した電圧を用いて絶縁抵抗の測定算出を行う場合の手順を説明する絶縁抵抗測定系の等価回路図であり、（Ａ）はスイッチＳ１が開路している場合を示し、（Ｂ）はスイッチＳ１が閉路している場合を示す。 A second calculation method (a method of calculating using the voltage Vm2 measured by the divided voltage measurement circuit 6) will be described with reference to FIG. FIG. 5 is an equivalent circuit diagram of the insulation resistance measurement system for explaining the procedure in the case of performing measurement calculation of insulation resistance using the voltage measured by the divided voltage measurement circuit at the saturation point when the measurement current is stable. A) shows the case where the switch S1 is open, and (B) shows the case where the switch S1 is closed.
　図５において、分圧電圧測定回路６は、分圧回路の共通接続端５から出力される分圧発生電圧Ｖｓを抵抗器Ｒｓを通して測定する。分圧発生電圧Ｖｓは、スイッチＳ１が開路している場合は値Ｖｓ１であり、スイッチＳ１が閉路している場合は値Ｖｓ２である。また、抵抗器Ｒｓの抵抗値は、スイッチＳ１が開路している場合は値Ｒｓ１であり、スイッチＳ１が閉路している場合は値Ｒｓ２である。分圧電圧測定回路６が測定する電圧Ｖｍ２は、スイッチＳ１が開路している場合は値Ｖｍ２１であり、スイッチＳ１が閉路している場合は値Ｖｍ２２である。抵抗器Ｒａｍｐは、図１に示す電流測定回路８における電圧変換用抵抗器Ｒｓｅｎｃｅと抵抗器Ｒｂｉａｓとの合成抵抗値を有する。また、直流電源２は、正極端（＋）と負極端（－）とが接続された構成になる。 In FIG. 5, the divided voltage measuring circuit 6 measures the divided voltage generation voltage Vs output from the common connection end 5 of the voltage dividing circuit through the resistor Rs. The divided voltage generation voltage Vs is the value Vs1 when the switch S1 is open, and the value Vs2 when the switch S1 is closed. The resistance value of the resistor Rs is the value Rs1 when the switch S1 is open, and the value Rs2 when the switch S1 is closed. The voltage Vm2 measured by the divided voltage measuring circuit 6 is the value Vm21 when the switch S1 is open, and the value Vm22 when the switch S1 is closed. The resistor Ramp has a combined resistance value of the voltage conversion resistor Rsense and the resistor Rbias in the current measurement circuit 8 shown in FIG. Further, the DC power source 2 has a configuration in which the positive electrode end (+) and the negative electrode end (−) are connected.
　さて、図５（Ａ）から、スイッチＳ１が閉路している場合の電流Ｉｓｅｎｃｅ１は、
　Ｉｓｅｎｃｅ１＝（Ｖｍ２１－Ｖｘ）／（Ｒｘ＋Ｒｓａｆｅ＋Ｒａｍｐ）　…（７）
と表されるから、
　Ｖｍ２１－Ｖｘ＝Ｉｓｅｎｃｅ１×（Ｒｘ＋Ｒｓａｆｅ＋Ｒａｍｐ）　…（８）
と求まり、地絡電圧Ｒｘは、
　Ｒｘ＝Ｖｍ２１－Ｉｓｅｎｃｅ１×（Ｒｘ＋Ｒｓａｆｅ＋Ｒａｍｐ）　…（９）
となる。 From FIG. 5A, the current Isense1 when the switch S1 is closed is
Isense1 = (Vm21−Vx) / (Rx + Rsafe + Ramp) (7)
Because it is expressed as
Vm21−Vx = Isense1 × (Rx + Rsafe + Ramp) (8)
The ground fault voltage Rx is
Rx = Vm21−Isense1 × (Rx + Rsafe + Ramp) (9)
It becomes.
　同様に、図５（Ｂ）から、スイッチＳ１が閉路している場合の地絡電圧Ｒｘは、
　Ｒｘ＝Ｖｍ２２－Ｉｓｅｎｃｅ２×（Ｒｘ＋Ｒｓａｆｅ＋Ｒａｍｐ）　…（１０）
と求まる。 Similarly, from FIG. 5B, the ground fault voltage Rx when the switch S1 is closed is
Rx = Vm22−Isense2 × (Rx + Rsafe + Ramp) (10)
It is obtained.
　式（９）＝式（１０）から、
　Ｖｍ２１－Ｉｓｅｎｃｅ１×（Ｒｘ＋Ｒｓａｆｅ＋Ｒａｍｐ）
　　　　＝Ｖｍ２２－Ｉｓｅｎｃｅ２×（Ｒｘ＋Ｒｓａｆｅ＋Ｒａｍｐ）　…（１１）
となり、式（１１）から、
　Ｒｘ＋Ｒｓａｆｅ＋Ｒａｍｐ
　　　＝（Ｖｍ２１－Ｖｍ２２）／（Ｉｓｅｎｃｅ１－Ｉｓｅｎｃｅ２）
　　　＝ΔＶｍ２／ΔＩｓｅｎｃｅ　　…（１２）
が導出される。式（１２）において、Ｒｓａｆｅ＋Ｒａｍｐは、回路定数であるから、地絡抵抗値Ｒｘは計算できる。 From equation (9) = equation (10)
Vm21-Isense1 × (Rx + Rsafe + Ramp)
= Vm22−Isense2 × (Rx + Rsafe + Ramp) (11)
From equation (11),
Rx + Rsafe + Ramp
= (Vm21-Vm22) / (Isense1-Isense2)
= ΔVm2 / ΔIsense (12)
Is derived. In Expression (12), Rsafe + Ramp is a circuit constant, and thus the ground fault resistance value Rx can be calculated.
　地絡抵抗値Ｒｘを求める式（１２）においては測定電圧Ｖｍ２１と測定電圧Ｖｍ２２との差分が主要なパラメータであることから、測定電圧Ｖｍ２１，Ｖｍ２２の差分を測定する構成とすることにより電流測定回路８で使用される増幅回路のオフセット誤差を軽減することができる。すなわち、より精度の高い絶縁抵抗検知が実現できる。 In the equation (12) for obtaining the ground fault resistance value Rx, the difference between the measurement voltage Vm21 and the measurement voltage Vm22 is a main parameter. Therefore, the current measurement circuit is configured to measure the difference between the measurement voltages Vm21 and Vm22. 8 can reduce the offset error of the amplifier circuit used. That is, more accurate insulation resistance detection can be realized.
　この第２の算出方法は、具体的には、次のように測定を複数回行う方法が可能である。各回において手順は同じであるが、スイッチＳ１を開路させたときに入力される電流Ｉｓｅｎｃｅ１のピーク電流を記憶し継続して電流値を測定し、電流の変化率が所定以下に達した時点（飽和したと見なせる時点）での電流値を記憶し、同時にその時の測定電圧Ｖｍ２１を記憶する。続いて、スイッチＳ１を閉路させ、スイッチＳ１開路時と同じ飽和待機時間において電流Ｉｓｅｎｃｅ２のピーク電流を記憶し継続して電流値を測定し、同じ経過時間での電流値および測定電圧Ｖｍ２２を記憶する。この測定によって絶縁抵抗検知（算出）を実施する。パワーコンディショナーでは、検知結果に基づき絶縁抵抗の良否判定を実施する。 Specifically, the second calculation method can be a method of performing measurement a plurality of times as follows. The procedure is the same for each time, but the peak value of the current Isense1 input when the switch S1 is opened is memorized, the current value is continuously measured, and the rate of change of the current reaches a predetermined value (saturated) Current value at a time point that can be regarded as having been measured), and at the same time, the measured voltage Vm21 at that time is stored. Subsequently, the switch S1 is closed, the peak current of the current Isense2 is stored in the same saturation standby time as when the switch S1 is opened, the current value is continuously measured, and the current value and the measured voltage Vm22 at the same elapsed time are stored. . By this measurement, insulation resistance detection (calculation) is performed. In the power conditioner, the quality of the insulation resistance is judged based on the detection result.
　この１回目で用いる変化率は、絶縁抵抗検知を最短で判定できるようにするため、晴天時における静電容量並びに正常な絶縁抵抗値ならば高確度で合格するレベルに設定する。安定した時点（飽和したとみなせる時点）での電流値および測定電圧は式（１２）に適用し、絶縁抵抗値の合否判定に用いるが、電流Ｉｓｅｎｃｅ１のピーク電流と電流Ｉｓｅｎｃｅ２のピーク電流との差分が所定値以上でない場合は、当該絶縁抵抗検知回路１の故障と判断し、故障処理モードへ移行する。 The rate of change used in the first round is set to a level that passes with high accuracy if the capacitance and the normal insulation resistance value are fine in order to allow the insulation resistance detection to be determined in the shortest time. The current value and the measured voltage at a stable time point (a time point that can be regarded as saturated) are applied to the equation (12) and used for pass / fail judgment of the insulation resistance value, but the difference between the peak current of the current Isense1 and the peak current of the current Isense2 Is not greater than or equal to a predetermined value, it is determined that the insulation resistance detection circuit 1 is in failure, and the process proceeds to failure processing mode.
　上記の１回目の判定にて絶縁抵抗値合格並びに絶縁抵抗検知回路１が正常であれば、パワーコンディショナーは系統連系を行って変換した交流電力を配電系統へ送出することを開始する。一方、絶縁抵抗値不合格時においては、直ちに絶縁抵抗不良とは判定せずに、再度、２回目の絶縁抵抗検知測定へ移行する。２回目の測定では、電流変化率の判定値を１回目測定よりも小さい値とし、システム仕様での最大設置太陽電池モジュール枚数に加えて、雨天時の浮遊容量においてもシステム要求の絶縁抵抗値以上であれば合格する電流変化率に設定する。なお、測定中に入力電圧Ｖｍ２が変化した場合には、予め測定誤差として許容レベル内であるか否の電圧変動判定値をシミュレーション結果等にて用意しておけば、電圧変動が所定値以下に収まるまで、絶縁抵抗検知を繰り返すこともできる。 If the insulation resistance value passes and the insulation resistance detection circuit 1 is normal in the first determination described above, the power conditioner starts system interconnection and starts sending the converted AC power to the distribution system. On the other hand, when the insulation resistance value is unacceptable, the process proceeds to the second insulation resistance detection measurement again without immediately determining that the insulation resistance is defective. In the second measurement, the current change rate judgment value is set to a smaller value than the first measurement, and in addition to the maximum number of installed solar cell modules in the system specifications, the stray capacitance in rainy weather exceeds the system required insulation resistance value. If so, set the current change rate to pass. If the input voltage Vm2 changes during measurement, a voltage fluctuation determination value indicating whether or not the measurement error is within an allowable level is prepared in advance as a simulation result. The insulation resistance detection can be repeated until it is settled.
　なお、第２の算出方法は、電流Ｉｓｅｎｃｅが安定する飽和時点に限定されるものではない。電流Ｉｓｅｎｃｅ１の変化量が安定する前にスイッチＳ１を反転し、電流Ｉｓｅｎｃｅ２も同様に測定した場合は、対地容量への充電電流が加算されるので、地絡電流は大きくなり、推定する絶縁抵抗値は実際よりも小さくなる。しかし、正常な状態の直流電源（太陽電池）２においては、絶縁抵抗判定レベルに対して余裕があるので、地絡抵抗を判定する場合において、短時間にスイッチＳ１を反転させた場合でも、絶縁抵抗値が判定規格を満足していれば、要求する絶縁抵抗値を保証できる。 Note that the second calculation method is not limited to the saturation point at which the current Isense is stable. If the switch S1 is inverted before the amount of change in the current Isense1 is stabilized and the current Isense2 is measured in the same manner, the charging current to the ground capacitance is added, so that the ground fault current increases and the estimated insulation resistance value Is smaller than actual. However, since the DC power supply (solar cell) 2 in a normal state has a margin with respect to the insulation resistance determination level, even when the switch S1 is inverted in a short time when determining the ground fault resistance, the insulation is determined. If the resistance value satisfies the judgment standard, the required insulation resistance value can be guaranteed.
　すなわち、スイッチＳ１の開閉周期を充電電流が変化している状態時間内に設定しても測定結果が要求規格以上の絶縁抵抗であればよいので、正確な絶縁抵抗を測定せずとも最短時間にて系統連係が可能となる。なお、この場合において、異常と判定した場合においては、順次判定時間を延長する方法へ移行するなどを行えばよい。 That is, even if the switching cycle of the switch S1 is set within the state time in which the charging current is changing, the measurement result only needs to be an insulation resistance exceeding the required standard, so that the shortest time can be obtained without measuring an accurate insulation resistance. System linkage becomes possible. In this case, if it is determined that there is an abnormality, a method of sequentially extending the determination time may be performed.
　以上のように、この実施例によれば、地絡電流の変化量に応じて測定時間を可変設定する構成とするとともに、分圧回路の分圧比のバラツキによる測定誤差を含まないように絶縁抵抗値を算出できる構成としたので、複数の電源ユニットを直並列接続して構成される太陽電池等の直流電源の設置面積や降雨時等によう対地浮遊容量の変化や、該直流電源の出力電圧の変化、絶縁抵抗測定系素子のバラツキや漏れ電流等の変化に対し、容易に対応して精度よく絶縁抵抗を測定することができる。 As described above, according to this embodiment, the measurement time is variably set according to the change amount of the ground fault current, and the insulation resistance is not included so as not to include a measurement error due to variation in the voltage dividing ratio of the voltage dividing circuit. Since the value can be calculated, the installation area of a DC power source such as a solar cell configured by connecting multiple power supply units in series and parallel, the change in ground floating capacity, such as during rain, and the output voltage of the DC power source Insulation resistance can be measured with high accuracy by easily responding to changes in the resistance, variation in insulation resistance measurement system elements, changes in leakage current, and the like.
　絶縁性能が正常な場合は、自動的に測定時間が短くなるので、発生電力の利用を短時間に開始することが可能となる。 When the insulation performance is normal, the measurement time is automatically shortened, so that the generated power can be used in a short time.
　また、太陽電池を例に挙げて説明すれば、設置面積の増加などで、該太陽電池の電源容量が大きい場合は、各太陽電池パネルが正常にも関わらず総合漏れ電流は増加するので、正確な絶縁抵抗測定が必要となる。この場合、この実施例によれば、自動的に長時間測定での高精度測定を実施することができるので、最適な測定時間を得ることが可能となる。 Further, taking solar cells as an example, if the power capacity of the solar cell is large due to an increase in the installation area, etc., the total leakage current will increase even though each solar cell panel is normal. Insulation resistance measurement is required. In this case, according to this embodiment, it is possible to automatically perform high-accuracy measurement over a long period of time, so that an optimum measurement time can be obtained.
　以上のように、本発明にかかる絶縁抵抗検知回路は、複数の電源ユニットが直並列接続されて構成される直流電源の絶縁抵抗を、該直流電源の対地浮遊容量の変化や該直流電源の出力電圧の変化、絶縁抵抗測定系素子のバラツキや漏れ電流等の変化に容易に対応して正確に測定することができる絶縁抵抗検知回路として有用であり、特に太陽光発電システムでの非絶縁型パワーコンディショナーに装備する絶縁抵抗検知回路として好適である。 As described above, the insulation resistance detection circuit according to the present invention includes the insulation resistance of a DC power supply configured by connecting a plurality of power supply units in series and parallel, the change in the floating capacitance of the DC power supply, and the output of the DC power supply. It is useful as an insulation resistance detection circuit that can easily and accurately measure changes in voltage, variations in insulation resistance measurement system elements, leakage currents, etc., especially non-insulated power in solar power generation systems It is suitable as an insulation resistance detection circuit equipped in the conditioner.
　１　絶縁抵抗検知回路
　２　直流電源（太陽電池）
　３　電源電圧測定回路
　４　制御回路（ＣＰＵ）
　５　分圧回路を構成する分圧用抵抗器Ｒ１，Ｒ２の共通接続端（中間電位生成端）
　６　分圧電圧測定回路
　７　大地に接続されるアース端子
　８　電流測定回路
　９　地絡電圧点
　Ｖｘ，Ｖｙ（Ｖｙ１，Ｖｙ２）　太陽電池モジュール
　Ｒｘ　地絡抵抗成分
　Ｒ３　電圧変更用抵抗器
　Ｓ１　スイッチ
　ＯＰ３　電源電圧測定回路を構成する演算増幅器
　ＯＰ４　分圧電圧測定回路を構成する演算増幅器
　Ｒｓａｆｅ　地絡保護用抵抗器
　Ｒｓｅｎｃｅ　電流測定回路を構成する電圧変換用抵抗器
　ＡＭＰ，ＯＰ１，ＯＰ２　電流測定回路を構成する演算増幅器
　Ｒｂｉａｓ，ＲＢ１～ＲＢ４　電流測定用の零点調整用抵抗器
　Ｖｂｉａｓ　電流測定用の基準電源 1 Insulation resistance detection circuit 2 DC power supply (solar cell)
3 Power supply voltage measurement circuit 4 Control circuit (CPU)
5 Common connection end (intermediate potential generation end) of voltage dividing resistors R1 and R2 constituting the voltage dividing circuit
6 Divided voltage measurement circuit 7 Ground terminal connected to ground 8 Current measurement circuit 9 Ground fault voltage point Vx, Vy (Vy1, Vy2) Solar cell module Rx Ground fault resistance component R3 Voltage change resistor S1 Switch OP3 Power supply voltage Operational amplifier constituting the measurement circuit OP4 Operational amplifier constituting the divided voltage measurement circuit Rsafe Ground fault protection resistor Rsense Voltage conversion resistor constituting the current measurement circuit AMP, OP1, OP2 Operational amplifier constituting the current measurement circuit Rbias, RB1 to RB4 Zero adjustment resistors for current measurement Vbias Reference power supply for current measurement

Claims (4)

  1. 　複数の電源ユニットが直並列接続されて構成される直流電源の出力電圧の中間電位を分圧生成する分圧回路であって該中間電位生成端が回路グランドに接続される分圧回路と、
    　前記分圧回路の分圧比を第１の値と第２の値とに変化させるための分圧比変化手段と、
    　前記分圧回路の中間電位生成端から出力される電圧を測定する分圧電圧測定手段と、
    　大地に接続されるアース端子から前記分圧回路の中間電位生成端に至る経路に配置される地絡保護用抵抗器を流れる地絡電流を測定する電流測定手段と、
    　前記分圧比変化手段に前記分圧回路の分圧比を第１の値に設定させたときに前記電流測定手段が測定した第１の地絡電流から測定した第１の電流値および前記分圧電圧測定手段が測定した前記中間電位生成端から出力される第１の測定電圧と、前記分圧比変化手段に前記分圧回路の分圧比を第２の値に設定させたときに前記電流測定手段が測定した第２の地絡電流から測定した第２の電流値および前記分圧電圧測定手段が測定した前記中間電位生成端から出力される第２の測定電圧とを用いて前記直流電源の絶縁抵抗値である前記アース端子と前記直流電源内の地絡電圧点との間に形成される地絡抵抗成分の値を算出する絶縁抵抗算出制御手段と、
    　を備え、
    　前記絶縁抵抗算出制御手段は、前記第１および第２の電流値を測定する測定時間である前記分圧比変化手段に前記分圧回路の分圧比を第１の値と第２の値とに変化させる時間間隔を、前記電流測定手段が測定した第１および第２の地絡電流の変化量に応じて可変設定することを特徴とする絶縁抵抗検知回路。     A voltage dividing circuit for dividing and generating an intermediate potential of an output voltage of a DC power supply configured by connecting a plurality of power supply units in series and parallel, wherein the intermediate potential generating terminal is connected to a circuit ground;
    A voltage dividing ratio changing means for changing the voltage dividing ratio of the voltage dividing circuit between a first value and a second value;
    A divided voltage measuring means for measuring a voltage output from the intermediate potential generation terminal of the voltage dividing circuit;
    Current measuring means for measuring a ground fault current flowing through a ground fault protection resistor arranged in a path from the ground terminal connected to the ground to the intermediate potential generation end of the voltage dividing circuit;
    A first current value measured from the first ground fault current measured by the current measuring means and the divided voltage when the voltage dividing ratio changing means is made to set the voltage dividing ratio of the voltage dividing circuit to a first value. The current measuring means outputs the first measured voltage output from the intermediate potential generation terminal measured by the measuring means and the voltage dividing ratio changing means to set the voltage dividing ratio of the voltage dividing circuit to the second value. Insulation resistance of the DC power source using the second current value measured from the measured second ground fault current and the second measured voltage output from the intermediate potential generation terminal measured by the divided voltage measuring means Insulation resistance calculation control means for calculating a value of a ground fault resistance component formed between the ground terminal which is a value and a ground fault voltage point in the DC power supply,
    With
    The insulation resistance calculation control means changes the voltage dividing ratio of the voltage dividing circuit from a first value to a second value, to the voltage dividing ratio changing means which is a measurement time for measuring the first and second current values. An insulation resistance detection circuit characterized in that the time interval to be set is variably set according to the amount of change in the first and second ground fault currents measured by the current measuring means.
  2. 　前記絶縁抵抗算出制御手段は、
    　前記分圧比変化手段に前記分圧回路の分圧比を第１の値と第２の値とに変化させる時間間隔を、前記電流測定手段が測定した第１および第２の地絡電流が安定したとみなさせる所定の変化率となる時点で前記第１および第２の電流値を測定できるように設定する
    　ことを特徴とする請求項１に記載の絶縁抵抗検知回路。     The insulation resistance calculation control means includes
    The first and second ground fault currents measured by the current measuring means are stabilized for a time interval during which the voltage dividing ratio changing means changes the voltage dividing ratio of the voltage dividing circuit between the first value and the second value. The insulation resistance detection circuit according to claim 1, wherein the first and second current values are set to be measurable at a time when a predetermined rate of change is considered.
  3. 　前記絶縁抵抗算出制御手段は、
    　前記分圧比変化手段に前記分圧回路の分圧比を第１の値と第２の値とに変化させる時間間隔を、前記電流測定手段が測定した第１および第２の地絡電流が大きな変化率で変化している時間内で前記第１および第２の電流値を測定できるように設定する
    　ことを特徴とする請求項１に記載の絶縁抵抗検知回路。     The insulation resistance calculation control means includes
    The first and second ground fault currents measured by the current measuring means change greatly in the time interval during which the voltage dividing ratio changing means changes the voltage dividing ratio of the voltage dividing circuit between the first value and the second value. The insulation resistance detection circuit according to claim 1, wherein the first resistance value and the second current value are set so as to be measured within a time changing at a rate.
  4. 　前記絶縁抵抗算出制御手段は、
    　前記分圧電圧測定手段が測定した第１の測定電圧と第２の測定電圧値との差分を用いて前記電流測定手段内の増幅回路のオフセット誤差を軽減する処理を行う
    　ことを特徴とする請求項１に記載の絶縁抵抗検知回路。     The insulation resistance calculation control means includes
    The processing for reducing the offset error of the amplifier circuit in the current measuring means is performed using the difference between the first measured voltage and the second measured voltage value measured by the divided voltage measuring means. Item 2. The insulation resistance detection circuit according to Item 1.
PCT/JP2011/055673 2011-03-10 2011-03-10 Insulation resistance detection circuit WO2012120683A1 (en)

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EP2975720A1 (en) * 2014-06-30 2016-01-20 Sungrow Power Supply Co., Ltd. Device and method for detecting insulation of photovoltaic modules against ground and photovoltaic grid-connected power generation system
CN105425048A (en) * 2015-11-04 2016-03-23 武汉精测电子技术股份有限公司 Device and method capable of sampling and detecting multipath impedance
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CN107870298A (en) * 2017-11-29 2018-04-03 深圳市锐能微科技有限公司 Circuit parameter detection circuit, method and the electric energy meter of a kind of bleeder circuit
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CN109521277A (en) * 2018-12-03 2019-03-26 欣旺达电子股份有限公司 Insulating properties detection circuit and detection method
CN109917186A (en) * 2019-03-13 2019-06-21 江苏迈吉易威电动科技有限公司 A kind of vehicle high-voltage Insulation Inspection Device for Direct-Current System and monitoring method
CN111983393A (en) * 2020-07-03 2020-11-24 中广核核电运营有限公司 Method and device for measuring insulation of generator sealing tile by voltage time method
CN112083299A (en) * 2020-09-11 2020-12-15 国网重庆市电力公司北碚供电分公司 Direct current system insulation fault prediction method based on Kalman filtering
WO2021043173A1 (en) * 2019-09-06 2021-03-11 中兴通讯股份有限公司 Distributed insulation detection device for multi-stage dc system
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CN103105537B (en) * 2012-12-26 2015-08-12 深圳创动科技有限公司 Battery panel ground insulation impedance detection circuit and method
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