JP2019045422A - Arc detector - Google Patents

Abstract

To provide an arc detector capable of locating a place of generation of an arc without stopping power generation by a solar cell module even in solar power generation systems in various configurations.SOLUTION: An arc detector 40 includes: measurement means 410 for measuring a noise level for each output cable of each string of solar cell modules; first determination means 420 for determining generation of an arc by comparing a noise level from the measurement means 410 with a first threshold for indicating generation of an arc; and second determination means 430 for determining whether an arc is generated in a string in which the noise level becomes the maximum level or an arc is generated in a place other than each string, based on a second threshold for identifying a relationship between the maximum value of the noise level of a string and a noise level of another string when the first determination means 420 detects generation of an arc.SELECTED DRAWING: Figure 2

Description

  According to the present invention, it is possible to specify an arc generation point generated in each portion of each string of a solar cell module and a power conditioning subsystem (hereinafter abbreviated as PCS) for converting direct current from the solar cell module into alternating current. The present invention relates to an arc detection device that can

In the solar power generation system whose spread is expanding, the solar cell modules to the PCS are direct current circuits. In this DC circuit, higher voltage is achieved to increase the efficiency.
With the increase in voltage, arcs may occur due to component deterioration, vibration due to an earthquake, impact, breakage, etc. in the solar cell module, in the connection connector, in the connection box, and in each part such as the output cable. The occurrence of an arc can cause various problems because the arc is at a high temperature.

  As a conventional apparatus for detecting arc generation, one described in Patent Document 1 is known. The arc detection and protection device described in Patent Document 1 executes the first step of opening the switch when receiving the detection signal from the detector, and the detection signal from the detector is obtained by the execution of the first step. If it has stopped, the second step of maintaining the opening of the switch and notifying the power conditioner that the arc has occurred at the switch is executed, and even if the first step is executed, the sensor When the detection signal continues, the third step of notifying the power conditioner that the abnormality has occurred in the upper part than the switch is performed. In this patent document 1, as a detector, it is described that it is an optical sensor that senses the occurrence of an arc during power generation by detecting light, or an antenna that senses an electromagnetic wave signal that occurs when an arc occurs. .

JP 2014-42364

  However, although the arc detection and protection device described in Patent Document 1 can identify the location where the arc occurs, the location of the occurrence can be determined by sequentially opening the switch installed for each string and repeating the presence or absence of the signal. To identify. Therefore, a switch is required for each string, and in order to open the switch in order to identify an arc generation point, the open string stops generating power. Further, since the switch is necessary, the technique of the arc detection and protection device described in Patent Document 1 can not be applied when only detection of arc generation is performed.

In a solar power generation system, a configuration (centralized PCS-PV system) in which the output cables of each string of solar cell modules are connected to a junction box and the wiring is aggregated and connected to PCS, and the output cables of each string are each There is a configuration directly connected to the PCS (multi-string PCS-PV system) or the like.
In such various configurations, arcs may be generated between solar cell modules of each string, between each string and junction box, or between each string and PCS directly connected, between junction box and PCS, etc. Can occur. Therefore, it is important to be able to identify the location of arcing in various configurations.

  Then, an object of this invention is to provide the arc detection apparatus which can pinpoint an arc generation location, without stopping the electric power generation by a solar cell module also by the solar power generation system of various structures.

  The arc detection apparatus according to the present invention comprises: measuring means for measuring the noise level of each output cable of each string of the solar cell module; and comparing the noise level from the measuring means with a first threshold value indicating arc generation. First determining means for determining occurrence, and second for identifying a relationship between the maximum value of the noise level of each string and the noise level of another string when the first determination means detects the occurrence of arcing A second determination unit that determines whether arcs occur in a string at which the noise level is maximum or arcs occur at other locations than the respective strings based on a threshold value I assume.

  According to the arc detection device of the present invention, first, the first determination means determines whether the arc has occurred by comparing the noise level from the measurement means with the first threshold value indicating the occurrence of the arc. If an arc has occurred, the second determination means makes a determination based on a second threshold value for identifying the relationship between the maximum value of the noise level and the noise level of another string. If the difference between the maximum value of the noise level and the noise level of the other string is small, it can be determined that an arc has occurred at another location other than each string by the second threshold. Also, if the difference between the maximum noise level and the noise level of another string is large, it can be determined that an arc has occurred in the string with the maximum noise level.

The second determination means compares the noise level of each string with the number of strings exceeding the second threshold value being one, with the second threshold being a predetermined ratio from the maximum value of the noise level of each string as the second threshold. For example, it is determined that an arc occurs in a string having the maximum noise level, and if the number of strings exceeding the second threshold is more than one, an arc occurs in another portion other than the respective strings. It can be determined that there is.
The second determination means compares the noise level of each string with the predetermined value from the maximum value of the noise level of each string as a second threshold.
As a result, if the number of strings exceeding the second threshold is 1, it indicates that the noise level of the maximum string is higher than the noise level of the other strings, and thus the string with the maximum noise level It can be determined that an arc has occurred.
In addition, if the number of strings exceeding the second threshold is more than one, the difference between the noise level of the maximum string and the noise level of the other strings is small, and noise leaks into each string from other than each string It can be determined that an arc has occurred at another location other than each string.

The second determination means may use a threshold value for determining the degree of the level difference between the maximum value of the noise level of each string and the second one as the second threshold value, and the level difference is not less than the second threshold value. If the noise level is determined to be an arc at a string having the maximum value and is less than the second threshold value, it can be determined that an arc is generated at another portion other than each string .
Second determination means compares the difference between the maximum and second noise levels of each string with a second threshold.
As a result, if the level difference is greater than or equal to the second threshold value, it indicates that the noise level of the maximum string is higher than the noise level of the other strings, so that arcs are generated in the string with the maximum noise level. It can be determined that it has occurred.
In addition, if the level difference is less than the second threshold, the difference between the noise level of the maximum string and the noise level of the other strings is small, and it can be estimated that the noise leaks into each string from other than each string. Therefore, it can be determined that an arc has occurred at another place other than each string.

The first determination means may determine that an arc has occurred when the arc detection based on the comparison between the noise level from the measurement means and a first threshold indicating arc occurrence has continuously reached a number based on a third threshold it can.
When the number of noise levels exceeding the first threshold continuously exceeds the third threshold, the first determination means determines that the arc is generated, thereby causing the noise generated accidentally as an arc noise due to the arc generation. It is possible to prevent detection.

A current measuring device for measuring a circuit current from the solar cell module, comparing the circuit current with a fourth threshold and increasing the third threshold when the circuit current is small, and when the circuit current is large It may be provided with a threshold setting means for reducing the third threshold.
The threshold value setting means can increase or decrease the setting value of the number of consecutive times indicated by the third threshold value used for the first determination means to determine the occurrence of arc based on the fourth threshold value of the circuit current measured by the current measuring device .

The fifth threshold is compared with the level difference between the noise level from the measuring means and the first threshold, and the third threshold is decreased when the level difference is small, and the third level difference is large. It can be provided with threshold setting means for increasing the threshold.
The threshold setting means may increase or decrease the setting value of the number of consecutive times indicated by the third threshold used by the first determination means to determine the occurrence of an arc based on the level difference between the noise level from the measurement means and the first threshold. it can.

Of the noise levels from the measuring means, the noise level exceeding the first threshold is excluded and accumulated to calculate the average value, and the level difference between the average value and the first threshold deviates from the sixth threshold Further, threshold value setting means may be provided to increase or decrease the first threshold value so that the level difference becomes the sixth threshold value.
When the level difference between the average value of the noise level and the first threshold deviates from the sixth threshold, the threshold setting means increases or decreases the first threshold so that the level difference becomes the sixth threshold. You can get the threshold for

  According to the arc detection device of the present invention, the measuring means measures the noise level of each output cable of each string, thereby generating an arc in the string whose noise level is the maximum value or not Since it can be determined whether or not an arc has occurred at another location, even for photovoltaic power generation systems with various configurations, to detect the location of the arc occurrence, identify the location where the arc occurs without stopping power generation by the solar cell module. Can.

It is a figure for demonstrating the structure of the solar energy power generation system which concerns on Embodiment 1 of this invention. It is a figure for demonstrating the structure of the arc detection apparatus of the solar energy power generation system shown in FIG. It is a flowchart for demonstrating the operation | movement of the arc detection apparatus shown in FIG. It is a table | surface for demonstrating the relationship of the arc noise which generate | occur | produced in the trunk line, and the arc noise at the time of generate | occur | producing in each string. It is a figure for demonstrating the structure of the 1st modification of the arc detection apparatus which concerns on this Embodiment 1. FIG. It is a flowchart for demonstrating the operation | movement of the 1st modification of the arc detection apparatus shown in FIG. It is a figure for demonstrating the structure of the 2nd modification of the arc detection apparatus which concerns on this Embodiment 1. FIG. It is a figure for demonstrating the structure of the 3rd modification of the arc detection apparatus which concerns on this Embodiment 1. FIG. It is a figure for demonstrating the structure of the 4th modification of the arc detection apparatus which concerns on this Embodiment 1. FIG. FIG. 18 is a diagram for describing an operation of the fourth modification of the arc detection device shown in FIG. 9, and a diagram for describing a case where the level difference between the noise level and the first threshold is large. FIG. 18 is a diagram for describing an operation of the fourth modification of the arc detection device shown in FIG. 9, and a diagram for describing a case where the level difference between the noise level and the first threshold is small. It is a figure for demonstrating the structure of the arc detection apparatus which concerns on Embodiment 2 of this invention. It is a figure for demonstrating the operation | movement of the arc detection apparatus shown in FIG.

First Embodiment
A solar power generation system using an arc detection device according to Embodiment 1 of the present invention will be described based on FIGS. 1 to 4.
The solar power generation system 10 shown in FIG. 1 is an integrated PCS-PV system provided with an arc detection device 40 for identifying an arc generation point.
In the centralized PCS-PV system, each string S (S1 to S4) in which the solar cell modules M are connected in series, the junction box 20 to which the output cables C1 to C4 from the string S are connected, and the junction box 20 And the PCS 30 to which the connected wiring is connected.

  Since the solar cell modules M are connected in series, the strings S (S1 to S4) increase the DC voltage output from the solar cell module M to about 300 V to 1500 V and output the DC voltage.

The connection box 20 is connected to the positive side of the output cables C1 to C4 from the strings S (S1 to S4), and the negative side is connected via the rectifying element to be a main line and connected to the PCS 30.
The PCS 30 supplies the output from the string S (S1 to S4) as a regulated power to a load (not shown). As the function of the PCS 30, in addition to converting the DC output from the string S (S1 to S4) into AC, maximum output operating point control (MPPT: Maxi
The mum Power Point Tracking) outputs the maximum power of the ever-changing environmental change to the load.

As shown in FIG. 2, the arc detection apparatus 40 includes a measurement unit 410, a first determination unit 420, a second determination unit 430, a display unit 440, and a contact output unit 450.
The measuring unit 410 has a function of measuring the noise level of each of the output cables C1 to C4 of each string S of the solar cell module M. The measurement unit 410 includes detectors 411 (411 a to 411 d), a switching unit 412, an A / D conversion unit 413, and a frequency analysis unit 414.

The detectors 411 (411a to 411d) are clamped and disposed for each of the output cables C1 to C4 from each string S.
The detector 411 can make the current change superimposed on the direct current flowing from the solar cell module M to the output cables C1 to C be a CT that outputs a current according to the magnetic change.

The switching means 412, A / D conversion means 413, frequency analysis means 414, first determination means 420, second determination means 430, display means 440, and contact output means 450 of the measurement means 410 Is stored in
The frequency analysis means 414, the first determination means 420, and the second determination means 430 may be microcomputers that execute an arc detection program.

The switching unit 412 illustrated in FIG. 2 can be a selector that selects the detectors 411a to 411d in order per unit time and outputs the signals input from the detectors 411a to 411d.
The A / D conversion means 413 converts the analog signals from the detectors 411a to 411d into digital signals.

  The frequency analysis means 414 takes in a digital signal indicating the voltage converted by the A / D conversion means 413 for a fixed time, and analyzes frequency components as a continuous waveform. The frequency analysis means 414 performs spectrum analysis of a band of several hundred Hz to 100 kHz by FFT (Fast Fourier Transform).

  The first determination means 420 has a function of determining arc generation in any of the strings S based on the noise level from the measurement means 410 by comparing it with the arc detection threshold (first threshold) set as an absolute value. Is equipped.

  The second determination means 430 sets a second threshold value set as a relative value according to the maximum value of the noise level of each string S1 to S4 when the first determination means 420 detects an arc occurrence, and each string S1 to S4. If the number of strings exceeding the second threshold is 1, it is determined that an arc has occurred in the corresponding string S, and the number of strings exceeding the second threshold is more than one. For example, it is determined that an arc has occurred at a point other than the strings S1 to S4.

The display means 440 is for displaying the arc generation location from the second determination means 430. The display means 440 can be an LCD, an LED lamp or the like. In the first embodiment, as shown in FIG. 1, the display means 440 is an LED lamp, and blinks the LED lamp corresponding to the strings S1 to S4 exceeding the second threshold.
The contact output means 450 reports an arc occurrence by opening or shorting the contact point corresponding to the arc generation location from the second determination means 430. The contact output means 450 can be, for example, a relay.

The operation of the arc detection apparatus according to the first embodiment of the present invention configured as described above will be described based on FIGS. 1 to 4.
As shown in FIG. 3, the noise level of the arc noise of each string is measured (step S10). In this measurement, first, signals are sequentially input from the detectors 411a to 411d disposed in the output cables C1 to C4 illustrated in FIG. 1 by the switching unit 412 illustrated in FIG. For example, the switching unit 412 selects a signal from the detectors 411a to 411d every 10 ms and outputs the signal to the A / D conversion unit 413.

  The signal input to the A / D conversion means 413 is converted from an analog signal to a digital signal. Then, by analyzing frequency components as continuous waveforms by the frequency analysis means 414, the noise level of each of the output cables C1 to C4 of each string S shown in FIG. 1 is measured.

Next, the first determination means 420 shown in FIG. 2 compares the noise level with the first threshold (step S20).
Since the PCS 30 is a device for converting direct current generated by the solar cell module M into alternating current, switching noise (PCS noise) is regularly generated also in the direct current circuit (string side circuit). The PCS noise contains many frequency components in the vicinity of several kHz to 100 kHz, and the PCS 30 operates to perform maximum power conversion according to the power generation state of the solar cell module M, so the noise level changes.
The arc noise is a frequency band overlapping with the PCS noise, but occurs at a higher level than the PCS noise, so the first threshold is set to a value higher than the PCS noise and lower than the arc noise level.

  Next, the first determination means 420 determines whether the noise level exceeds the first threshold (step S30). If the noise level is equal to or less than the first threshold, the process proceeds to step S10. When the noise level is larger than the first threshold, the process proceeds to the determination by the second determination unit 430.

  The second determination means 430 searches for the maximum value of the noise level (step S40). Next, the second determination unit 430 calculates a predetermined ratio from the maximum value and sets it as a second threshold (step S50).

Here, the predetermined ratio for determining the second threshold that identifies the relationship between the maximum value of the noise level of each string and the noise level of the other strings will be described in detail.
(When arc occurs in string)
First, when an arc occurs in any of the strings S1 to S4, most of the arc noise flows in the PCS 30 and the string S in which the arc occurred, but in reality, a portion of the arc noise does not occur in the string S It also wraps around.
Although the rate of wraparound varies depending on the type of solar cell module M and the system circuit configuration, it can be expressed as a rate when “noise level of non-generated string” is divided by “arc-generated string noise level”. A (%)

(When arc occurs on the main line)
The arc noise level of each string S1 to S4 when an arc occurs on the main line (hereinafter referred to as a main line arc) is the same as the configuration of the solar cell module M constituting each string S. The generated power and impedance of S are also almost equal.
Therefore, since the arc noise passes through the PCS and uniformly flows into all the strings, theoretically, the noise level due to the arc of each string S is the noise level of the main arc divided by the number of strings.
However, in practice, the wraparound of arc noise into each string has variations. Although the ratio of variation varies depending on the circuit configuration, the characteristics of the solar cell module M, and the like, it can be represented by the ratio of the minimum value to the maximum value, and is defined as a ratio B (%).

(2nd threshold decision)
In consideration of the above two proportions A and B, the second threshold needs to be defined as a proportion larger than the proportion A of the maximum noise level and smaller than the proportion B.
For example, if the ratio A is 10% and the ratio B is 70%, 40% is appropriate on average, so the second threshold can be set to the noise level maximum value × 0.4.
In this way, a second threshold can be determined to identify the relationship between the maximum noise level of each string and the noise level of the other strings.

(Detection of arc)
As shown in FIG. 4 (A) and FIG. 4 (B), in the case of a trunk arc, assuming that the noise level of the trunk arc is 100, the strings S1 to S4 flow around all the strings in the trunk. Generation of 24 to 26 noise levels is assumed.
In the case where an arc occurs in the string S1 (hereinafter referred to as a string arc), assuming that the noise level of the string arc in the string S1 is 100, the trunk lines and strings S2 to S4 wrap around from the string S1 By flowing, it is assumed that the noise level at the trunk line is 70, and that the other strings S2 to S4 have 10 occurrences.

In the table shown in FIG. 4A, since the first threshold is set to 20, in the case of the trunk arc, any of the strings S1 to S4 is larger than the first threshold, so the determination based on the second threshold is made .
Further, as shown in FIG. 4A and FIG. 4C, in the case of a string arc, since the string S1 is larger than the first threshold, the process shifts to the determination based on the second threshold.

In the determination based on the second threshold, in the case of the trunk arc shown in FIG. 4B, the maximum value of the noise level is 26 that the noise level of the string S1 is larger than the other strings S2 to S4. Therefore, the second threshold with the predetermined proportion of the maximum value being 40% is 26 × 0.4 = 10.
Therefore, when the second determination means 430 compares the second threshold with the noise levels of the strings S1 to S4 in step S60, the noise level of the string S1 is larger than the second threshold, but Each noise level is also determined to be greater than the second threshold.

In step S70, when the second determination unit 430 determines that the number of strings of noise levels larger than the second threshold is more than one, the noise level of the string S1 having the maximum value and the noise levels of the other strings S are determined. It can be estimated that the difference is small and the noise is looped into each of the strings S1 to S4.
Therefore, in step S80, notification means such as the display means 440 and the contact point output means 450 output that it is a trunk arc.

When calculating the second threshold from the maximum value of the noise level in step S50, in the case of a string arc, as shown in FIG. 4C, the maximum value of the noise level corresponds to another string of the noise level of the string S1. It is 100 greater than S2 to S4. Therefore, the second threshold, which is 40% of the maximum value, is 100 × 0.4 = 40.
Therefore, when the second determination means 430 compares the second threshold with the noise levels of the strings S1 to S4 in step S60, the noise level of the string S1 is larger than the second threshold, but Each noise level is less than the second threshold.

In step S70, when the second determination means 430 determines that the number of strings of noise levels greater than the second threshold is 1, the noise level of the string having the maximum value is greater than the noise levels of other strings. Therefore, it can be determined that an arc has occurred in a string whose noise level is the maximum value.
In step S90, the notification means such as the display means 440 and the contact point output means 450 outputs that the generated string is the string S1.

In this manner, the noise level of each string is measured by the measuring means 410, and these noise levels are compared with the first threshold value indicating the occurrence of arcing to determine whether an arc has occurred or not. If it does occur, the second determination means 430 compares it with the second threshold to identify the relationship between the maximum value of the noise level and the noise level of another string S.
Thus, when the number of strings exceeding the second threshold is 1, it can be determined that an arc has occurred in the string S1 of which the noise level is the maximum value.
In addition, when the number of strings exceeding the second threshold is more than one, it can be determined that an arc has occurred at another location other than each string.

In this way, the second threshold for identifying whether the noise level generated in one string is prominent or the noise level is generated in the entire string on average is By identifying the relationship between the maximum noise level and the noise level of other strings, it is possible to determine whether it is a string arc or a trunk arc.
At this time, since the output cables of the strings S1 to S4 are not cut off, the solar cell modules M of the strings S1 to S4 can continue the power generation to the PCS 30.

  In the first embodiment, although the photovoltaic power generation system 10 is the centralized PCS-PV system having the connection box 20, in the case where each string S1 to S4 is a multi-string PCS-PV system directly connected to the PCS. Can also be applied.

  Therefore, since the arc detection device 40 only measures the noise level for each output cable of each string, it can measure even solar power generation systems of various configurations, and does not stop power generation by the solar cell module. , Where the arc occurs can be identified.

First Modification of First Embodiment
A first modified example according to the first embodiment of the present invention will be described based on FIG. 5 and FIG. In addition, in FIG. 5, the thing of the same structure as FIG. 2 attaches | subjects a same sign, and abbreviate | omits description.
As described above, the PCS noise level changes from operating to perform maximum power conversion according to the power generation status of the solar cell module M. In addition, the noise level fluctuates depending on the type of PCS, the configuration of the photovoltaic system, and the discharge state of the arc. From this, when the first threshold value for detecting an arc is too low, PCS noise is also detected, and when it is too high, arc generation can not be detected.

  In the arc detection device 41 shown in FIG. 5, as shown in FIG. 6, if the noise level does not exceed the first threshold in step S130, the first determination means 421 determines the counter of the corresponding string S in step S140. After resetting, the process proceeds to step S110, but if it is determined in step S130 that the noise level has exceeded the first threshold, the counter of the corresponding string S of the noise level exceeding the first threshold is incremented by 1 in step S150. I assume.

Then, in step S160, the first determination unit 421 determines whether the counter value has reached a predetermined number (third threshold) indicating the number of consecutive times (the number of consecutive arc detections) exceeding the first threshold. Do. The third threshold can be, for example, five times.
If the counter value has reached the predetermined number of times, it is determined that an arc has occurred, and the process proceeds to the processing by the second determination unit 430 (processing from step S170). If the counter value has not reached the predetermined number of times, the process proceeds to step S110 to continuously detect arc noise.

  As described above, when the number of noise levels exceeding the first threshold continuously exceeds the predetermined number of times (third threshold), it is determined that arcing has occurred, and noise generated randomly is arc noise due to arcing. And false detection can be prevented.

  In the flowchart shown in FIG. 6, step S110 to step S120 are the same as step S10 to step S20 shown in FIG. 3, and step S170 to step S220 shown in FIG. Since the process from step S90 to step S90 is the same, the description is omitted.

Second Modification of First Embodiment
A second modification of the arc detection device according to the first embodiment of the present invention will be described based on FIG. In FIG. 7, the same components as those in FIG. 2 have the same reference numerals, and the description thereof is omitted.
In the first modification of the first embodiment, the occurrence of arcing is determined by the fact that the counter value indicating the number of times the noise level has continuously exceeded the first threshold has exceeded the third threshold. In the second modification, the third threshold is changed according to the measured value of the circuit current.

  As shown in FIG. 7, the arc detection device 42 includes an amperometer 411 e clamped to a main line in addition to the detectors 411 a to 411 d installed in each of the strings S1 to S4 (see FIG. 1) for arc detection. ing. The arc detection device 42 further includes an A / D conversion unit 460 and a threshold setting unit 470.

  The current measuring instrument 411e can be a Hall element type current sensor including a magnetic core to be clamped to a main line and a Hall element inserted in the gap portion of the magnetic core. When the magnetic flux in the magnetic core due to the current flowing through the trunk passes through the Hall element, the current measuring instrument 411e outputs the Hall voltage according to the magnetic flux as the current flowing through the trunk due to the Hall effect of the Hall element.

  The A / D conversion means 460 converts the analog signal from the current measuring device 411 e into a digital signal. When the digital value corresponding to the circuit current value flowing in the trunk line converted by the A / D conversion means 460 is smaller than a predetermined value (fourth threshold value), the threshold setting means 470 determines that the first judgment means 421 has generated an arc. The set value of the number of consecutive times indicated by the third threshold used in the above is a value obtained by increasing from the initial value. For example, the third threshold may be five to seven or ten.

  In addition, when the circuit current measured by the current measuring device 411e is larger than a predetermined value, the threshold setting unit 470 sets the setting value of the number of consecutive times indicated by the third threshold to a value reduced from the initial value. For example, the third threshold may be five to three times.

When the circuit current is small, the arc current is small and the heat quantity of the arc is small. Therefore, even if the counter value indicated by the third threshold value is greatly increased, the influence on the cable and the equipment is small.
Therefore, the arc noise due to arc generation can be firmly detected by increasing the third threshold until arc generation is determined and taking a long time until arc generation is determined.

On the other hand, when the circuit current is large, the arc current is large and the heat quantity of the arc is large, so the influence on the cable and the equipment is large.
Therefore, arc occurrence can be detected in a short time by reducing the third threshold until arc occurrence is determined and shortening the time to arc determination.

  In the second modification, the third threshold is the number of times of continuous arc detection, but the third threshold may be the measurement time for arc detection. When the third threshold is the measurement time, the first determination means 421 performs arc detection the number of times that can be performed during the measurement time indicated by the third threshold, and when the arc is detected continuously, to determine the arc occurrence. do it.

  Further, in the second modification, the current measuring instrument 411e is installed on the main line, but in order to accurately measure the circuit current from each of the strings S1 to S4, the strings S1 to S4 are similarly to the detectors 411a to 411d. It is desirable to install the current measuring instrument 411e in the output cables C1 to C4 of S2.

Third Modification of First Embodiment
A third modification of the arc detection device according to the first embodiment of the present invention will be described based on FIG. In FIG. 8, the same components as those in FIG. 2 have the same reference numerals, and the description thereof will be omitted.
In the second modification of the first embodiment shown in FIG. 7, threshold value setting means 470 indicates a predetermined number of times the number of consecutive times exceeds the first threshold value depending on whether the circuit current is larger than the predetermined value (the fourth threshold value). (The third threshold) was increased or decreased, but in the third modification shown in FIG. 8, the threshold setting means 471 of the arc detection device 43 sets the level difference between the noise level from the measuring means 410 and the first threshold. On the basis of this, the setting value of the number of consecutive times indicated by the third threshold used by the first determination means 421 for determination of arc occurrence is increased or decreased.

  When the level difference between the noise level from the measuring means 410 and the first threshold is smaller than a predetermined value (fifth threshold), the threshold setting means 471 sets the setting value of the number of consecutive times indicated by the third threshold from the initial value. It is a reduced value. For example, the third threshold may be five to three times.

  Further, when the level difference between the noise level from the measuring means 410 and the first threshold is larger than a predetermined value (fifth threshold), the threshold setting means 471 initially sets the setting value of the number of consecutive times indicated by the third threshold. The value is increased from the value. For example, the third threshold may be five to seven or ten.

When the circuit current is large, arc noise including high frequency components propagates through the output cables C1 to C4 and the arc noise detected by the frequency analysis means 414 tends to decrease in level. Therefore, the level difference between the noise level of the arc noise and the first threshold is reduced.
On the other hand, since the circuit current is large, the arc current is large, and the heat quantity of the arc is large, so the influence on the cable and the equipment is large.
Therefore, if the level difference between the noise level of the arc noise and the first threshold is smaller than the fifth threshold, the third threshold until the arc occurrence is determined is decreased to shorten the time until the arc determination. Arc generation can be detected in a short time.

When the circuit current is small, the arc noise detected by the frequency analysis means 414 tends to increase in level. Therefore, the level difference between the noise level of the arc noise and the first threshold becomes large.
Since the circuit current is small, the arc current is small and the amount of heat of the arc is small, so the influence on the cable and the equipment is small.
Therefore, if the level difference between the noise level of the arc noise and the first threshold is greater than the fifth threshold, increase the third threshold until arcing is determined and take longer time to determine arcing. Thus, arc noise due to arc generation can be detected firmly.

Fourth Modification of First Embodiment
The 4th modification of the arc detection apparatus concerning Embodiment 1 to this invention is demonstrated based on FIGS. 9-11. In FIG. 9, the same components as those in FIG.
In the fourth modification, the first threshold is increased or decreased based on the difference between the noise level of the PCS noise periodically measured and the first threshold.

  In the fourth modification, the threshold setting unit 472 shown in FIG. 9 first accumulates the noise level (PCS noise level) periodically input from the measuring unit 410 except for the noise level exceeding the first threshold. Calculate the average value. Next, the threshold setting unit 472 increases or decreases the first threshold so as to become the specified value when the level difference between the average value and the first threshold deviates from the specified value (sixth threshold).

For example, the case where the noise level of the PCS noise is low will be described based on FIG.
When the threshold setting unit 472 periodically acquires the noise level of the PCS noise from the measurement unit 410 in step S210, the threshold setting unit 472 accumulates the noise level in step S220 and calculates an average value, and the average value is calculated. Since the level difference is larger than the specified value as a result of comparing the level difference between and the first threshold with the specified value, the first threshold is decreased so that the level difference between the average value and the first threshold becomes the specified value.
Thereafter, the arc generation by the first determination means 420 is detected with the new first threshold value lowered in level (step S230).

Next, the case where the noise level of the PCS noise is low will be described based on FIG.
In step S310, the threshold setting unit 470 periodically acquires the noise level of the PCS noise from the measurement unit 410. Next, in step S320, the threshold setting unit 472 accumulates the noise level and calculates the average value, and as a result of comparing the level difference between the average value and the first threshold with the specified value, the level difference is smaller than the specified value. Therefore, the first threshold value is increased so that the level difference between the average value and the first threshold value becomes a specified value.
Thereafter, the arc generation by the first determination means 420 is detected by the new first threshold whose level is increased (step S330).

  As described above, the noise level of the PCS noise level is also changed by MPPT (Maximum Power Point Tracking) control that performs maximum power conversion according to the type of PCS and the power generation status of the solar cell. However, by constantly monitoring the level of PSC noise in the steady state and increasing or decreasing the first threshold, it is possible to obtain a threshold for optimal determination, and achieve both prevention of false detection and certainty of detection. Can.

Second Embodiment
A solar power generation system using an arc detection device according to a second embodiment of the present invention will be described based on FIGS. 12 and 13. In FIG. 12, the same components as those in FIG. 2 have the same reference numerals and the description thereof will be omitted.

  The arc detection device 45 according to the second embodiment shown in FIG. 12 is installed in a centralized PCS-PV system, similarly to the arc detection device 40 according to the first embodiment (see FIG. 2).

In the arc detection device 45, the second determination means 431 determines whether the occurrence of the arc is a main line or each string S.
Next, the determination by the second determination means 431 will be described based on FIG. In FIG. 13, since the determination based on the first threshold value in steps S410 to S430 is the same as that in steps S10 to S30 shown in FIG. 3, the description will be omitted.

The second determination means 431 identifies the string S that is the maximum value from the noise level of each string S and the string S of the second largest value (step S440).
Next, the second determination means 431 calculates the level difference between the maximum value of the noise level and the second value, and compares it with the second threshold (step S450).
The second threshold is a threshold for determining the degree of the second level difference between the maximum value of the noise level of the string and can be, for example, the maximum value of the noise level × 0.6.

If the level difference between the maximum value and the second value is greater than or equal to the second threshold value, the second determination unit 431 determines in step S460 that an arc has occurred in the string S whose maximum value has been measured. Do. This is because if the arc occurs in any of the strings S, as can be seen from the table shown in FIG. 4, the level difference between the arc generation string S and the other strings S becomes large. Therefore, it can be determined that an arc has occurred in the string S whose maximum value has been measured.
In that case, notification means such as the display means 440 and the contact point output means 450 output that it is a string arc (step S470).

When the level difference is less than the second threshold, the second determination unit 431 determines in step S460 that an arc has occurred on the trunk line. This is because, if arcs are generated on the main line, arc noise from the main line wraps around each of the strings S1 to S4, as can be understood from the table shown in FIG. 4A. The level difference is smaller. Therefore, it can be determined that an arc has occurred on the trunk line.
In that case, notification means such as the display means 440 and the contact point output means 450 output that it is a trunk arc (step S480).

Thus, using the second threshold to identify the relationship between the maximum noise level of each string and the noise level of the other strings, the level difference between the maximum noise level and the second value is If the threshold value is equal to or higher than the second threshold value, it indicates that the noise level of the maximum string S is higher than the noise level of the other strings S. It can be determined that an arc has occurred.
Also, if the level difference is less than the second threshold, it can be estimated that the noise level of the maximum string S has a small noise level difference of the other strings S, and the noise level is embedded in each string S Therefore, it can be determined that an arc has occurred at another portion other than each string S, for example, the trunk line.
Therefore, the arc detection device 45 can identify the generation point without stopping the power generation by the solar cell module even in the solar power generation system with various configurations.

In addition, when the arc detection device 45 is installed in a multi-string PCS-PV system in which each string S1 to S4 is directly connected to the PCS, the maximum value of the noise level and the second level difference are at least the second threshold. For example, the string whose maximum value was the measured noise level.
However, if the maximum value of the noise level and the second level difference are less than the second threshold, the occurrence of an arc can be determined not as each string S1 to S4, but as another place such as in the PCS.

  Also in the arc detection device 45 according to the second embodiment, the same effects can be obtained by applying the configurations of the first to fourth modifications of the first embodiment.

  The arc detection apparatus according to the present invention can identify the location of the arc generation only by installing a measurement means for measuring the noise level for each output cable of each string, so that the centralized PCS-PV system or the multi-string PCS-PV system Either method is suitable.

10 solar power system 20 connection box 30 PCS
40, 41, 42, 43, 44, 45 Arc detection device 400 Device main body 410 Measuring means 411, 411a to 411d Detector 411e Current measuring device 412 Switching means 413, 460 A / D conversion means 414 Frequency analysis means 420, 421 1 Judgment means 430, 431 Second judgment means 440 Display means 450 Contact output means 470, 471, 472 Threshold setting means M Solar cell module S, S1 to S4 String C1 to C4 output cable

Claims (7)

Measuring means for measuring the noise level from the current waveform for each output cable of each string of the solar cell module;
First determining means for determining arc occurrence by comparing the noise level from the measuring means with a first threshold value indicating arc occurrence;
The noise level is maximum based on a second threshold value for identifying the relationship between the maximum value of the noise level of each string and the noise level of another string when the first determination means detects an arc occurrence. An arc detection device comprising: second determination means for determining whether an arc has occurred in a string and an arc has occurred in another location other than each of the strings.   The second determination means compares the noise level of each string with the noise level of each string as the second threshold value by using a predetermined ratio from the maximum value of the noise level of the string, and the number of strings exceeding the second threshold value is one. If the number of strings exceeding the second threshold is more than one, it is determined that an arc has occurred at a location other than each of the strings. The arc detection device according to claim 1, wherein it is determined that   The second determination means may use a threshold for determining the degree of the level difference between the maximum value of the noise level of the string and the second one as the second threshold, and the level difference is not less than the second threshold, The noise level is determined to be an arc occurring in the string of the maximum value, and if it is less than the second threshold value, it is determined that an arc occurs in another portion other than the respective strings. Arc detection device.   The first determination means determines that an arc is generated when arc detection based on a comparison between the noise level from the measurement means and a first threshold indicating arc generation has continuously reached a number based on a third threshold. The arc detection device according to any one of 1 to 3. A current measuring device for measuring a circuit current from the solar cell module;
The circuit is provided with threshold setting means for comparing the circuit current with a fourth threshold and increasing the third threshold when the circuit current is small and decreasing the third threshold when the circuit current is large. Arc detection device as described.   The level difference between the noise level from the measurement means and the first threshold is compared with the fifth threshold, and the third threshold is decreased when the level difference is small, and the third level difference is large. 5. The arc detection apparatus according to claim 4, further comprising: threshold setting means for increasing the threshold.   Of the noise levels from the measuring means, the noise level exceeding the first threshold is excluded and accumulated to calculate the average value, and the level difference between the average value and the first threshold deviates from the sixth threshold The arc detection apparatus according to any one of claims 1 to 6, further comprising threshold setting means for increasing or decreasing the first threshold so that a level difference becomes the sixth threshold.