JP2001021606A - Grounding detecting device and method therefor, and power supply device, and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make accurately detectable the grounded part of a power supply by detecting the voltage or current between the voltage dividing point of a voltage dividing means and the grounding potential and at the same time, adjusting the voltage division ratio so that the detection value can be nearly zero or minimized. SOLUTION: The output voltage of a solar battery or the like is divided by a variable resistor 3, the voltage between a voltage dividing point (d) and grounding potential is detected by a voltmeter 4, and the voltage division ration of the variable resistor 3 is adjusted so that the voltage value reaches zero. Then, as information for a grounded position, the voltage division ration or a voltage being measured by the voltmeters 4 and 5 is displayed. In the variable resistor 3, an arbitrary voltage division ration can be obtained by changing a resistance ratio by a slider that travels on the resistor. Resistance and allowed power across the variable resistor 3 are set to resistance and power suited for the output voltage of a solar battery string 1. The voltmeter 4 detects the voltage between the voltage dividing point (d) and a negative electrode line, and the voltmeter 5 detects the voltage between the voltage dividing point (d) and a positive electrode line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault detecting apparatus and method, and a power supply apparatus and a control method therefor. For example, a ground fault detecting apparatus and method for detecting a ground fault of a DC power supply such as a solar cell. And a power supply device and a control method thereof.

[0002]

2. Description of the Related Art In a photovoltaic power generation system, a string is formed by connecting a plurality of solar cells or modules in series in order to obtain a desired output voltage. further,
To obtain a desired output power, an array in which a plurality of strings are connected in parallel is formed.

[0003] In a solar cell array, the insulation at a certain location may be destroyed for some reason, and a ground fault may occur.
When a ground fault occurs, it is necessary to specify the ground fault location in order to repair the location where the insulation is broken (ground fault location). Insulation confirmation is generally performed by measuring insulation resistance with an insulation resistance meter. However, it is difficult to identify the ground fault location by this measurement.

Japanese Patent Application Laid-Open No. Hei 7-177646 discloses that a potential (ground voltage) at two points on a solar cell array is measured in order, and a ground fault is calculated from the measured two potentials and the output voltage of the solar cell array. Is disclosed.

[0005]

In the above technique for identifying a ground fault, the potential at the two locations and the output voltage of the solar cell array are measured in order, in other words, the three voltages are measured at different times. Things. On the other hand, since the output voltage of the solar cell array fluctuates depending on the intensity of solar radiation and the load state, the output voltage of the solar cell array may fluctuate while three voltages are sequentially measured. That is, when the ground fault location is calculated based on the measurement results in the state where the output voltages of the solar cell arrays are different, an error occurs in the detection of the ground fault location.

[0006] The above problems are not limited to solar power generation systems. A similar problem occurs in a power generation system using hydropower, wind power, a fuel cell, or the like. If a ground fault is detected based on a measurement result in a state where output voltages are different, a detection error is highly likely to occur.

An object of the present invention is to solve the above-described problem, and an object of the present invention is to provide a ground fault detecting device and a ground fault detecting method capable of accurately detecting a ground fault location of a power supply.

It is another object of the present invention to provide a power supply device capable of accurately detecting the ground fault of the power supply and appropriately controlling the operation of the device, and a control method thereof.

[0009]

The present invention has the following configuration as one means for achieving the above object.

A ground fault detecting device according to the present invention is a ground fault detecting device for detecting a ground fault of a power supply, wherein the voltage dividing means divides an output voltage of the power supply at an arbitrary voltage dividing ratio, and the voltage dividing means. Detecting means for detecting a voltage or current between the voltage dividing point and the ground potential, and adjusting means for adjusting the voltage dividing ratio such that a detection value of the detecting means is substantially zero or minimum. It is characterized by.

Preferably, the apparatus further comprises display means for displaying or acquiring the voltage division ratio or the voltage ratio divided by the voltage division means as information corresponding to the ground fault position.

A ground fault detecting method according to the present invention is a ground fault detecting method for detecting a ground fault of a power supply, wherein the output voltage of the power supply is divided by an arbitrary voltage dividing ratio, and the voltage dividing point and the ground potential are divided. And the voltage division ratio is adjusted so that the detected value becomes substantially zero or minimum.

Preferably, the information processing apparatus further comprises displaying or acquiring the divided voltage ratio or the divided voltage ratio as information corresponding to the ground fault position.

[0014] A power supply device according to the present invention is a power supply device comprising a power supply, supply means for supplying output power of the power supply to a load, and control means for controlling the supply means, wherein the control means comprises: And a ground fault detecting unit for detecting a ground fault of the power supply, wherein an operation of the supply unit is controlled based on a detection result by the ground fault detecting unit.

[0015] A control method according to the present invention is a control method for a power supply apparatus comprising: a power supply; supply means for supplying output power of the power supply to a load; and control means for controlling the supply means. Divide the output voltage at an arbitrary division ratio, detect the voltage or current between the division point and the ground potential, adjust the division ratio based on the detected value, and adjust the division ratio based on the adjustment result of the division ratio. A ground fault of the power supply is detected, and an operation of the supply unit is controlled based on a detection result of the ground fault.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A ground fault detecting device according to an embodiment of the present invention will be described below in detail with reference to the drawings. In the present invention, the power supply may be either DC or AC, or both may be used. In the following description, a form in which a plurality of DC power supplies are connected in series will be particularly exemplified.

[0017]

First Embodiment FIGS. 1 and 2 are circuit diagrams showing a configuration example of a ground fault detecting device according to a first embodiment.

Reference numeral 1 denotes a solar cell string in which a plurality of solar cell modules (DC power supplies) are connected in series.
In other words, it is a group of modules. In the following description, it is assumed that a ground fault has occurred at point a inside solar cell string 1. The solar cell module connected to the positive electrode side from point a is 1A, and the solar cell module connected to the negative electrode side is 1B.

In this embodiment, the types of the photovoltaic elements constituting the solar cell module, in other words, the types of the solar cell and the solar cell module, and the combination method and installation form thereof can be appropriately changed. .
In addition, what is indicated by reference numeral 1A in FIG. 1 is a solar cell string,
In other words, it may be a module group, and in that case, what is indicated by reference numeral 1 is a strings group. In the present embodiment, a plurality of solar cell modules may be connected in parallel. Further, a plurality of solar cell strings may be connected in parallel. The power supply group connected in parallel is called an array. That is, what is indicated by reference numeral 1 in FIG. 1 may be a solar cell array.

Reference numeral 2 denotes a ground fault detecting device having the following configuration. Reference numeral 3 denotes a variable resistor, and an arbitrary voltage dividing ratio can be obtained by changing a resistance ratio by a slider moving on the resistor. Note that the resistance value and the allowable power at both ends of the variable resistor 3 are set to the resistance value and the power corresponding to the output voltage of the solar cell string 1.

The means for dividing the voltage is not limited to a variable resistor such as a potentiometer, but may be a connection of a plurality of fixed resistors connected in series as shown in FIG.
Alternatively, it can be realized by various means such as a voltage divider 3 'that changes the voltage division ratio by a short circuit, or a combination of a fixed resistor and a variable resistor. In the configuration shown in Fig. 3, the voltage division ratio can be set with higher precision as the number of series fixed resistors increases, but the voltage division ratio can be set more precisely than the series number of fixed resistors by combining the opening and closing of the switch RY. And high accuracy can be obtained.

Reference numerals 4 and 5 denote voltmeters, and reference numerals 6 to 8 denote switches. A relay, a semiconductor switch, or the like can be applied to the switch.

FIG. 4 is a diagram showing an appearance of the ground fault detecting device 2. As shown in FIG.

9 is an electrode connected to the positive electrode line of the solar cell string 1, 10 is an electrode connected to the negative electrode line of the solar cell string 1, and 11 is an electrode connected to the ground potential. It is desirable that each electrode can be securely and easily connected to an object, and a crimp terminal, an alligator clip, or the like is used, but is not limited thereto.

Reference numeral 12 denotes an operation mode switching switch for switching the operation mode of the ground fault detecting device 2. The open / close states of the switches 6 to 8 change as shown in Table 1 depending on the switch state of the operation mode changeover switch 12.

The adjustment mode is a mode for adjusting the voltage dividing ratio of the variable resistor 3, and FIG.
8 shows the open / closed state. The measurement mode is a mode for measuring the partial pressure ratio set in the adjustment mode,
FIG. 2 shows the switching state of the switches 6 to 8 in the measurement mode.

In the adjustment mode, the voltmeter 4 detects the voltage between the voltage dividing point d and the ground potential, and the voltmeter 5 is open. In the measurement mode, the voltmeter 4 detects the voltage between the voltage dividing point d and the negative electrode line, and the voltmeter 5 detects the voltage between the voltage dividing point d and the positive electrode line.

Reference numerals 14 and 15 shown in FIG. 4 denote display units for displaying the voltage values detected by the voltmeter 5 and the voltmeter 4, respectively. The display units 14 and 15 can be realized by various display devices such as an LED and a liquid crystal panel.

Reference numeral 13 denotes a hold switch. When the hold switch 13 is pressed, the measured voltage is held at the pressed timing, and the display units 14 and 15 display a voltage value corresponding to the held voltage. When the hold switch 13 is pressed again, the hold of the measured voltage is released, and the display units 14 and 15 are released.
Displays the measured voltage value in real time.

FIG. 5 is a flowchart for explaining the ground fault detection procedure.

In step S 1, from the electrode 9 of the ground fault detecting device 2
11 is the positive and negative electrode lines of solar cell string 1,
And connected to ground potential. Next, in step S2,
The operation mode of the ground fault detection device 2 is set to the adjustment mode. Then, in step S3, the slider of the variable resistor 3 is moved so that the voltage value detected by the voltmeter 4 and displayed on the display unit 15 becomes zero (or the absolute value becomes minimum).
Adjust the partial pressure ratio. In addition, regardless of the voltage dividing ratio of the variable resistor 3, when the voltage measured by the voltmeter 4 is zero,
No ground fault has occurred in solar cell string 1.

Subsequently, in step S4, the operation mode of the ground fault detecting device 2 is switched to the measurement mode. The display unit 14 displays the voltage value between the voltage dividing point d detected by the voltmeter 5 and the positive electrode line, and the display unit 15 displays the voltage measured between the voltage dividing point d detected by the voltmeter 4 and the negative electrode line. The voltage value is displayed.
When the hold switch 13 is pressed in step S5, the measured voltage is held, and the value is displayed on the display units 14 and 15. In step S6, the voltage V1 displayed on the display unit 14 and the voltage V2 displayed on the display unit 15 are read by the operator. Then, in step S7, the obtained voltage V1 and
The ground fault point a is specified by V2. The voltage ratio between the solar cell modules (groups) 1A and 1B is the measured voltage V1
Since V1 and V2 are equal to each other, it is possible to easily specify from V1 / V2 the ground fault point a, that is, at what position of the series-connected solar cell module a ground fault occurs.

As described above, according to the present embodiment, the partial pressure point
By adjusting the voltage dividing ratio of the variable resistor 3 so that the voltage between d and the ground potential becomes zero, the voltage ratio V1 / V2 indicating the ground fault point a of the solar cell string 1 can be obtained. Therefore,
Even if the output voltage of the solar cell string 1 fluctuates, the voltage ratio V1 /
Since V2 is not affected, it is possible to detect a ground fault location with high accuracy.

Furthermore, the ground fault location is detected by utilizing the fact that the voltage ratio between the solar cell modules (groups) 1A and 1B and the voltage ratio V1 / V2 measured by the ground fault detector 2 match. Solar cell string 1 due to fluctuations in solar radiation
Can be accurately detected without being affected by the fluctuation of the output voltage.

Further, in the adjustment mode, a ground fault is detected by balancing the voltage ratio between the solar cell modules (groups) 1A and 1B and the voltage ratio V1 / V2 divided by the variable resistor 3. There are no undetectable ground faults. In addition, in the adjustment mode, if the voltage value that is constantly measured regardless of the voltage division ratio is zero, it can be determined that a ground fault has not occurred, and erroneous detection of a ground fault can be prevented.

In particular, by connecting the ground fault detecting device 2 to a current collecting box or the like to which the output of the solar cell string 1 is connected, a ground fault location can be detected, and each module of the solar cell string 1 can be detected individually. Can be specified very easily and in a short time as compared with a case where a ground fault location is searched by visually observing. For example, when the solar cell string 1 is installed on a roof, a ground fault location can be specified without climbing the roof.

When measuring the voltage ratio V1 / V2, if the internal impedance of the voltmeters 4 and 5 is sufficiently large with respect to the resistance value of the variable resistor 3, it can be said that there is no influence on the detection accuracy. If the internal impedance of the voltmeters 4 and 5 is not sufficiently large compared to the resistance value of the variable resistor 3, the ground impedance is determined based on the resistance value of the variable resistor 3 and the internal impedance of the voltmeters 4 and 5. Voltage ratio V1 that indicates the point of connection
By correcting / V2, a more accurate ground fault location may be calculated.

Also, an example in which the voltage division ratio is set manually has been described. However, if means such as a buzzer or an LED for notifying that the voltage measured in the adjustment mode has fallen below a predetermined value close to zero is provided, The partial pressure ratio can be adjusted more easily.
Further, if a scale of the voltage division ratio is provided on the variable resistor 3, the approximate voltage division ratio (= V1 / V2) can be directly known. Although it has a simple configuration and can be roughly detected, when the number of solar cell modules in series is small, it is possible to specify a short-circuited portion by such a method. That is, in the case of a solar cell string, it is sufficient that the ground fault location can be specified for each solar cell module constituting the solar cell string, and the detection accuracy of the voltage ratio (division ratio) is sufficient to match the accuracy. For example, if the same number of partial pressure ratios as the number of solar cell modules in series can be set, it is possible to identify the short-circuited portion most simply and in the shortest time.

Of course, the measured voltage is zero, or
A servo mechanism that adjusts the absolute value of the voltage value to be the minimum value or less than the minute voltage can be easily realized. When a servo mechanism is used, there are a configuration in which the variable resistor 3 is driven by a motor and a method in which fixed resistors connected in series as shown in FIG. 3 are connected and / or short-circuited. In the former case, the partial pressure ratio (= V1 / V2) can be obtained directly from the rotation amount of the stepping motor, and in the latter case, it can be directly obtained. Therefore, a configuration in which at least one of the voltmeter and the display unit is not required can be adopted. Further, the measurement procedure can be simplified, steps S2 to S5 shown in FIG. 5 are simplified, and the partial pressure ratio (= V1 / V2) displayed on the display unit in step S6 may be read.

[0040]

[Second Embodiment] Next, as a second embodiment, a ground fault detecting device 2 capable of detecting a ground fault location even when the solar cell string 1 is in a non-power generation state such as at night will be described. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIGS. 6 and 7 are circuit diagrams showing examples of the configuration of the ground fault detecting device 2 of the second embodiment. The difference from the configuration shown in FIG. 1 is that the ground fault detecting device 2 has a power supply 20 and a switch. 21 and a backflow prevention diode 22 are provided. Various switches can be applied to the switch 21, as in the first embodiment. The switch 21 is normally open.

The backflow prevention diode 22 prevents the power output from the solar cell string 1 from flowing into the power supply 20 and protects the power supply 20. As the backflow prevention diode 22, a diode having a reverse withstand voltage that can withstand the power generation voltage of the solar cell string 1 and a forward current and an allowable junction temperature that can withstand the current supplied from the power supply 20 to the solar cell string 1 can be used. Silicon junction diodes and Schottky barrier diodes can be used.

The power supply 20 is, for example, an insulated DC power supply having a variable output voltage with a commercial AC power supply as an input. The positive electrode of the power supply 20 is connected via a backflow prevention diode 22 and a switch 21,
Connected to the positive line of solar cell string 1 and power supply 20
Is connected to the negative electrode line of the solar cell string 1. The power supply 20 may be any power supply that can supply power to the solar cell string 1 and is insulated from the ground potential, and may be a combination of a storage battery and an inverter or a generator.

It is preferable to use the DC output power supply 20 because the configuration and the detection procedure of the short-circuit detecting device 2 are simpler, but the AC output power supply can be used depending on the device. That is, an appropriate voltage setting, current limit, and a voltmeter that measures the effective value voltage are used.

Further, the voltage of the power supply 20 may not be variable. This is because if the configuration of the solar cell string 1 is determined, an appropriate applied voltage can be determined in advance. The applied voltage may be determined based on the characteristics of the solar cell string 1, but a short-circuited portion can be sufficiently detected with a voltage lower than the standard output voltage of the solar cell string 1. When the applied voltage is increased, the heat generation of the solar cell string 1 increases. Therefore, the applied voltage is carefully determined according to the characteristics of the solar cell string 1.

Further, the applied voltage is
When the voltage is set lower than the standard output voltage value, the power supply 20 can be made small (small capacity). The standard output voltage value is
This is a voltage value at which the current suddenly increases when the applied voltage is gradually increased.

The direction of voltage application from the power supply 20 to the solar cell string 1 is a so-called forward bias direction in which the positive electrode of the power supply 20 is connected to the positive electrode side of the solar cell string 1, but a voltage is applied in the reverse bias direction. Can also detect a ground fault location. If the solar cell module constituting the solar cell string 1 has a reverse flow bypass element, the applied voltage at the time of reverse bias is determined by the characteristics of the bypass element.

FIG. 8 is a flowchart for explaining the ground fault detection procedure.

The ground fault detecting procedure shown in FIG. 8 differs from the ground fault detecting procedure shown in FIG. 5 in that steps S10 and S12 are added between steps S1 and S2. Steps
According to the judgment of the power generation state of the solar cell string 1 in S10, in step S11 or S12, the switch 2
Open and close 1.

That is, when the solar cell string 1 is in a power generating state such as in the daytime, the switch 21 is opened in the adjustment mode, and the ground fault location is specified as in the first embodiment.

On the other hand, when the solar cell string 1 is in a non-power generation state, such as at night, the switch 21 is closed in the measurement mode, and a voltage is applied from the power supply 20 to the solar cell string 1 to identify a ground fault location. I do. The voltage applied from the power supply 20 to the solar cell string 1 is divided into voltages proportional to the respective impedances of the solar cell module (group) 1A and the module (group) 1B. Normally, since the solar cell modules constituting the solar cell string 1 have the same characteristics, the above partial pressure is not applied to the solar cell module (group).
It is proportional to the ratio of the serial number of 1A to the serial number of module (group) 1B. Therefore, the short-circuit point a can be detected by adjusting the voltage division ratio of the variable resistor 3 as in the first embodiment.

The procedure after step S2 is different from that in the first embodiment in that the detection of the ground fault is performed by the voltage generated by the solar cell string 1 or by the voltage applied from the power supply 20 to the solar cell string. Since it is the same as the embodiment, the detailed description is omitted.

As described above, according to the present embodiment, the same effects as those of the first embodiment can be obtained, and even when the solar cell string 1 is in a non-power generation state such as at night, a voltage is applied from the power supply 20 to the solar cell string 1. By doing so, a ground fault location can be detected.

FIGS. 6 and 7 show an example in which two voltmeters are provided to detect voltages V1 and V2, respectively. However, the solar cell string 1 is in a non-power generation state and is stabilized by the power supply 20. If the voltage can be applied, the voltages V1 and V2 can be
Is detected, the short-circuited portion can be accurately specified.

Further, as shown in FIG. 9, a voltage is applied to the solar cell string 1 by power supplies 31 and 32, which are connected in series and whose output voltage is variable, and a connection point (middle point) d between the power supplies 31 and 32 is The voltmeter 4 may be connected between the ground potentials, and the output voltages of the power supplies 31 and 32 may be adjusted so that the measured voltage value is zero (or the absolute value is minimum). If the solar cell string 1 is in a non-power generation state, a ground fault location can be specified by the output voltage ratio of the power supplies 31 and 32.

Also, an execution command means such as a one-chip microprocessor is incorporated in the ground fault detecting device 2, and some steps in the ground fault detecting procedure shown in FIG. 5 or FIG. 8, for example, steps S10 to S5 in FIG. It is possible to execute the procedure. Therefore, the present invention includes a medium such as a ROM or a magnetic disk in which the program described in the first or second embodiment, specifically, the program of the ground fault detection procedure as shown in FIGS. 5 and 8 is recorded. .

[0057]

Third Embodiment FIG. 10 is a block diagram showing a configuration example of a photovoltaic power generation system according to a third embodiment of the present invention. Hereinafter, a solar power generation system according to a third embodiment having a ground fault detection function will be described. In the third embodiment,
The same components as those in the first or second embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 10, reference numeral 41 denotes a solar cell string having the same configuration as the solar cell string according to the first or second embodiment, and a plurality of solar cell modules are connected in series and in parallel. An inverter 42 converts DC power output from the solar cell string 41 into AC power. An AC switchboard 43 interconnects an inverter 42 and an AC power system 44 such as a commercial AC power supply. This system is a so-called grid-connected solar power generation system.

FIG. 11 is a block diagram showing a configuration example of the inverter 42.

Reference numeral 51 denotes an input terminal for inputting DC power from the solar cell string 41, and reference numeral 52 denotes AC power.
Output terminal for output to 44 or AC load. 53 is a ground terminal connected to the ground potential.

Reference numeral 54 denotes an input-side noise filter constituted by a capacitor or the like. Reference numeral 55 denotes a cross-current conversion circuit including a smoothing capacitor, a reactor, a diode, a switching element, and the like, which is a so-called transformerless inverter circuit (hereinafter, referred to as an “inverter circuit”). 56
Is an output switch for opening and closing the AC output, and 57 is an output-side noise filter.

Reference numeral 61 denotes a controller for the inverter 42 composed of a microprocessor or the like. Based on detection signals from detectors such as a DC voltage detector 58, an AC voltage detector 59, and an AC current detector 60, the controller 61
It controls 55 operations and protection. Reference numeral 66 denotes a nonvolatile memory which can be read / written by the controller 61. The memory 66 only needs to retain its memory when the supply of power to the controller 61 is stopped, and various configurations such as a combination of an SRAM and a backup power supply and a flash memory are possible.

Reference numeral 62 denotes a ground fault detection circuit for detecting a ground fault in the DC circuit. The ground fault detection circuit 62 includes a variable voltage divider 63, a ground voltage detector 64, a ground switch 65, and the like. The voltage dividing ratio of the variable voltage divider 63 that divides the DC voltage output from the solar cell string 41 can be controlled by the controller 61. The ground voltage detector 64 detects a voltage between the voltage dividing point of the variable voltage divider 63 and the ground terminal 53, and outputs the voltage to the controller 61. The open / close state of the ground switch 65 can be controlled by the controller 61.

FIG. 12 is a flowchart illustrating a control procedure executed by the controller 61.

When the inverter 42 is started, a step S2
Initialization processing is performed in step 1, and the inverter circuit 55 is started. The output switch 56 and the ground switch 65 are open when the inverter 42 is stopped and immediately after the inverter 42 is started.

Next, in step S22, the ground switch 65 is closed to detect a ground fault, and in step S23, the detected value of the ground voltage detector 64 is zero, the absolute value is minimum, or becomes equal to or less than a predetermined value. Adjust the variable voltage divider 63 as follows. However, in order to prevent erroneous detection, adjustment starting from a different partial pressure ratio is performed twice. If the partial pressure ratios of the two adjustment results are equal or approximate, a ground fault is determined in step S24, and the
Proceed to. If the voltage division ratios of the two adjustment results are different, an erroneous detection is conceivable, so the process returns to step S23 to adjust the variable voltage divider 63 again. If the voltage of the ground voltage detector 64 does not become zero even if the division ratio is changed, it is determined that the greenery is maintained, and the process proceeds to step S25.

In the case of a large-scale solar power generation system, the ground capacitance of the solar cell string 41 and the ground capacitance of the input side of the inverter 42 may be large. In this case, the resistance value of the variable voltage divider 63 and the ground voltage detector 64
Charge / discharge the ground capacitance via the internal impedance of the device, it is necessary to consider the measurement time corresponding to the time constant determined by the charge / discharge. For example, after setting the voltage division ratio of the variable voltage divider 63, it is necessary to take measures such as measuring the voltage after the fluctuation of the ground voltage detector 64 stops.

In step S25, it is determined whether or not other conditions for starting the system interconnection operation are satisfied.
It is determined whether or not the output voltage and frequency in 55 are appropriate. If the conditions are not satisfied, the process returns to step S23. If the conditions are satisfied, step S26 is executed to start the grid interconnection operation.
To open the ground switch 65, and in step S27, close the output switch 56 to start the interconnection operation. In this state, the switching operation of the inverter circuit 55 is controlled, and power is supplied to the AC power system 44.

Then, in step S28, it is monitored whether or not a condition for stopping the system interconnection operation has occurred. If such a condition has occurred, the process proceeds to step S29, where the inverter circuit 55
Is stopped, the output switch 56 is opened, and the system interconnection is released, and the process returns to step S22 to detect a ground fault.

On the other hand, if a ground fault is detected in step S24, the grounding switch 65 is opened in step S30, and the voltage dividing ratio of the variable voltage divider 63 is recorded in the memory 66 in step S31.
In step S32, the operation of the inverter circuit 55 and the like is stopped,
The stopped state of the inverter 42 is maintained. That is, since an abnormal state called a ground fault is detected, the stopped state is maintained for safety.

Since a ground fault may be detected due to dew condensation inside the inverter 42, it is desirable to detect the ground fault at a predetermined cycle even after the ground fault is detected and the stopped state is maintained. If the dew condensation inside the inverter 42 is the cause, the operation can be started after the dew condensation has been eliminated, and if such data is recorded in the memory 66, it is needless to say that it is useful for a later investigation.

Further, when a ground fault is detected, a buzzer or
The ground fault may be notified by an LED or the like, so that prompt action can be taken against the occurrence of the ground fault.

As described above, in the transformerless inverter of the system interconnection type of the present embodiment, the AC power system 44 is always grounded, so that the ground fault is detected when the output switch 56 is open and not connected. After the ground fault is detected, the ground switch 65 of the ground fault detection circuit 62 is opened, and if there is no abnormality, the system interconnection operation is started. As a result, the ground fault detection can be accurately performed, and the occurrence of the ground fault current via the ground fault detection circuit 62 can be prevented.

Furthermore, when a ground fault occurs, the voltage division ratio of the variable voltage divider 63 corresponding to the ground fault location is recorded in the non-volatile memory 66, so that the voltage division ratio recorded in the memory 66 can be easily checked. You can know the ground fault location. For example, a ground fault that occurs only in rainy weather may be difficult to reproduce during a survey. In such a case, if the partial pressure ratio corresponding to the ground fault location is recorded as in the present embodiment, the ground fault location can be specified without reproducing the ground fault. When recording the partial pressure ratio corresponding to the ground fault location, data indicating the date and time when the ground fault occurs, the time after the inverter 42 is started, and the like may be recorded together.

Of course, in the case of an inverter having an independent operation function, ground fault detection may be performed during the independent operation. In addition, in the case of an inverter whose input / output is green through a transformer, ground fault detection can be performed during system interconnection operation. Further, the present invention is not limited to the grid-connected inverter, and is applicable to a DC / DC converter.

Further, in the above-described embodiment, an example in which the voltage dividing ratio is set (detected) based on the voltage between the voltage dividing point and the ground potential has been described. A partial pressure ratio to be zero may be set (detected). At this time, by setting the voltage dividing point of the voltage dividing means in advance to a middle level, it is possible to prevent a large ground fault current from flowing. If a current limiting resistor is connected in series with the current detector, there is an effect that a large ground fault current does not flow at any voltage dividing point.

In addition, various modifications are possible within the scope of the present invention.

According to each of the embodiments described above, the voltage divider is connected between the output lines of the DC power supply, and the voltage or current detector is connected between the voltage dividing point of the voltage divider and the ground potential. And the detection value of the detector is zero, the absolute value is the minimum, or
By adjusting the voltage division ratio of the voltage divider so as to be equal to or less than the predetermined value, it is possible to detect (identify) a ground fault location of the DC power supply from the voltage division ratio (or voltage ratio). Therefore, according to each embodiment, the following effects can be obtained. (1) Even if the output voltage of the DC power supply fluctuates, a ground fault location can be accurately detected. In particular, the effect is large in a solar cell in which the voltage is apt to fluctuate due to the fluctuation of solar radiation or load. (2) Even when the DC power supply is not generating power, such as a solar cell that does not generate power at night, a ground fault can be detected by applying a voltage from outside. (3) At least when the ground voltage is zero at two different voltage division ratios, it can be determined that no ground fault has occurred, and erroneous detection of the ground fault can be prevented. (4) When a current detector is used, an excessive ground fault current can be prevented by connecting a current limiter in series with the current detector. (5) Even when the inverter has a non-insulated input / output, by properly controlling the connection between the load and the grounding battery, a ground fault can be detected accurately, and the ground can be detected even when power is supplied to the load. Unnecessary generation of ground fault current through the fault detection circuit can be prevented. (6) If a ground fault is detected, the partial pressure ratio corresponding to the ground fault location is recorded in the memory, so that the ground fault location can be easily known even later.

[0079]

As described above, according to the present invention,
It is possible to provide a ground fault detecting device and a method thereof that accurately detect a ground fault location of a power supply.

Further, it is possible to provide a power supply device and a control method thereof that accurately detect the ground fault of the power supply and appropriately control the operation of the device.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration example of a ground fault detecting device according to a first embodiment;

FIG. 2 is a circuit diagram illustrating a configuration example of a ground fault detecting device according to the first embodiment;

FIG. 3 is a circuit diagram showing a second configuration example of the ground fault detecting device according to the first embodiment;

FIG. 4 is a diagram showing an appearance of a ground fault detecting device;

FIG. 5 is a flowchart illustrating a ground fault detection procedure according to the first embodiment;

FIG. 6 is a circuit diagram illustrating a configuration example of a ground fault detection device 2 according to a second embodiment;

FIG. 7 is a circuit diagram illustrating a configuration example of a ground fault detection device 2 according to a second embodiment;

FIG. 8 is a flowchart illustrating a ground fault detection procedure according to the second embodiment;

FIG. 9 is a circuit diagram showing a second configuration example of the ground fault detecting device according to the second embodiment;

FIG. 10 is a block diagram illustrating a configuration example of a solar power generation system according to a third embodiment;

11 is a block diagram illustrating a configuration example of the inverter illustrated in FIG.

12 is a flowchart illustrating a control procedure executed by the controller shown in FIG.

[Explanation of symbols]

 1 Solar cell string 2 Ground fault detector 3 Variable resistor 4,5 Voltmeter 6-8 Switch 9 Electrode connected to positive line 10 Electrode connected to negative line 11 Electrode connected to ground potential 12 Operating mode Selector switch 13 Measurement hold switch 14, 15 Display

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Naoki Manabe 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2G014 AA04 AB61 AB62 AC18 2G033 AA00 AB01 AC02 AD21 AG12 AG14

Claims (30)

[Claims] 1. A ground fault detecting device for detecting a ground fault of a power supply, comprising: a voltage dividing means for dividing an output voltage of the power supply at an arbitrary voltage dividing ratio; a voltage dividing point of the voltage dividing means; Detecting means for detecting the voltage or current between the two, and adjusting means for adjusting the voltage dividing ratio so that the detection value of the detecting means becomes substantially zero or minimum. . 2. The apparatus according to claim 1, further comprising display means for displaying or acquiring the voltage division ratio or the voltage ratio divided by the voltage division means as information corresponding to a ground fault position. A ground fault detecting device described in the above. 3. The ground fault detecting device according to claim 1, wherein the power source is a solar cell. 4. The ground fault detecting device according to claim 1, further comprising a power supply unit for applying a voltage to the power supply when the power supply is not generating power. . 5. In any of the cases where at least two partial pressure ratios of the partial pressure means are set, if the detected value is substantially zero, it can be determined that no ground fault has occurred. 5. The ground fault detection device according to claim 1, wherein: 6. The ground fault detecting device according to claim 1, further comprising a current limiting means connected in series to said detecting means. 7. The ground fault detecting device according to claim 1, wherein the power source is a DC power source. 8. The ground fault detecting device according to claim 1, wherein the power source is a plurality of power sources connected in series. 9. A ground fault detection method for detecting a ground fault of a power supply, wherein the output voltage of the power supply is divided at an arbitrary voltage dividing ratio, and a voltage or current between the voltage dividing point and a ground potential is detected. And adjusting the partial pressure ratio so that the detected value becomes substantially zero or minimum. 10. The ground fault detecting method according to claim 9, further comprising displaying or acquiring the divided voltage ratio or the divided voltage ratio as information corresponding to a ground fault position. 11. The ground fault detection method according to claim 9, wherein the power supply is a DC power supply. 12. The ground fault detecting method according to claim 9, wherein the power supply is a plurality of power supplies connected in series. 13. A power supply device comprising: a power supply; supply means for supplying output power of the power supply to a load; and control means for controlling the supply means, wherein the control means detects a ground fault of the power supply. A power supply device comprising: a ground fault detecting unit for detecting, and controlling an operation of the supply unit based on a detection result by the ground fault detecting unit. 14. The ground fault detecting means, at least, a voltage dividing means for dividing an output voltage of the power supply at an arbitrary voltage dividing ratio,
Detecting means for detecting a voltage or current between a voltage dividing point of the voltage dividing means and a ground potential, and adjusting means for adjusting the voltage dividing ratio based on a detection value of the detecting means, 14. The power supply device according to claim 13, wherein: 15. The power supply according to claim 14, wherein the control unit determines that a ground fault has occurred in the power supply when there is a voltage division ratio that makes the detection value of the detection unit substantially zero or minimum. Power supply as described. 16. The power supply device according to claim 14, wherein said control means records a voltage dividing ratio of said voltage dividing means in a memory when a ground fault is detected. 17. In any case where at least two voltage division ratios are set in the voltage dividing means, the control means determines that a ground fault has not occurred if the value detected by the detecting means is substantially zero. 17. The power supply device according to claim 14, wherein: 18. The power supply device according to claim 14, wherein said ground fault detecting means further includes a current limiting means connected in series to said detecting means. 19. The power supply device according to claim 13, wherein the supply unit converts the output power of the power supply into a form corresponding to the load and supplies the power. 20. The input and output of said supply means is non-green,
A switch is provided on the power output side, and when the load is grounded, the control means operates the ground fault detection means when the switch is open.
The power supply according to item 19. 21. The power supply device according to claim 13, wherein the power supply is a solar cell. 22. The power supply according to claim 13, wherein the power supply is a DC power supply. 23. The power supply device according to claim 13, wherein the power supply is a plurality of power supplies connected in series. 24. A control method for a power supply device, comprising: a power supply, a supply unit that supplies output power of the power supply to a load, and a control unit that controls the supply unit, wherein the output voltage of the power supply is set to an arbitrary value. Divide by the division ratio, detect the voltage or current between the division point and the ground potential, adjust the division ratio based on the detected value, and ground-fault the power supply based on the adjustment result of the division ratio. A control method, comprising: detecting an operation of the supply unit based on a detection result of the ground fault. 25. The control method according to claim 24, wherein the power supply is a DC power supply. 26. The control method according to claim 24, wherein the power supply is a plurality of power supplies connected in series. 27. A recording medium on which a program code for detecting a ground fault of a power supply is recorded, wherein the program code includes at least a code for a step of dividing an output voltage of the power supply at an arbitrary voltage division ratio, A code for detecting a voltage or a current between a voltage point and a ground potential; and a code for adjusting the voltage division ratio so that the detected value becomes substantially zero or a minimum. Medium. 28. A recording medium storing a program code for controlling a power supply device comprising: a power supply; a supply unit for supplying output power of the power supply to a load; and a control unit for controlling the supply unit. The program code includes at least a code of a step of dividing an output voltage of the power supply at an arbitrary division ratio, a code of a step of detecting a voltage or a current between the division point and a ground potential, and a detection value of the code. Controlling the operation of the supply unit based on the code of the step of adjusting the voltage dividing ratio based on the result of the adjustment of the voltage dividing ratio, the code of the step of detecting the ground fault of the power supply based on the result of the adjustment of the voltage dividing ratio, and the detection result of the ground fault. And a step code. 29. The recording medium according to claim 27, wherein the power supply is a DC power supply. 30. The recording medium according to claim 27, wherein the power supply is a plurality of power supplies connected in series.