JP2000207662A - Apparatus and method for detecting power generation abnormality of solar cell, current collector box and solar power generation system equipped with the same - Google Patents

Abstract

(57) [Summary] [Problem] A power generation amount of a solar cell string that is inexpensive and space-saving design, and that can accurately detect and report defects of a plurality of solar cell strings regardless of the installation location of the solar cell. An abnormality detection device and method are provided. further,
A current collection box and a photovoltaic power generation system provided with the device are provided. SOLUTION: A means 4 for detecting a difference in current amount between a plurality of solar cell strings 11 to 14 at one time and an abnormality in the amount of power generation of the solar cell string by comparing the detected current amount difference with a predetermined reference value. And means 5 for detecting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to detection of power generation abnormality of a photovoltaic string (also referred to as "sub-array").
More specifically, the present invention relates to detecting an abnormality in the energization state of a plurality of solar cell strings arranged on the roof of a building and each including a plurality of solar cell modules.

[0002]

2. Description of the Related Art In recent years, interest in the global environment and energy has been increasing due to global warming due to the emission of carbon dioxide and the like accompanying the use of fossil fuels, accidents at nuclear power plants and radioactive contamination by radioactive waste. Under such circumstances, a solar cell, which is a photoelectric conversion element using the incident light of the sun, is expected from all over the world as an inexhaustible and clean energy source.

There are various types of solar power generation systems using solar cells, ranging from several Watts to several thousand kW. For example, there are many systems, such as a system that uses a battery to store the power generation energy of a solar cell, and a system that uses a DC-AC converter to flow the output energy of a solar cell into a commercial system. One example of such a system is shown in FIG. 8 as a comparative example of the present invention. In this solar power generation system, four solar cell strings 1 each configured by connecting a plurality of solar cell modules in series
1 to 14 are connected in parallel to form the solar cell array 1. The output of the solar cell 1 is guided to a power conversion unit 2 including a control device for performing maximum output control and the like, and is supplied to a load 3. Here, the load 3 may be a power system, and such a system that reversely flows the power of the solar cell to the power system is particularly referred to as a system linking system. This is one of various system forms.

[0004] By the way, this type of photovoltaic power generation system is generally equipped with various protection devices in order to prevent an electric shock accident or the like, but a method for detecting a failure of the solar cell module has not been devised much. is the current situation. Conventionally, such a failure detection method includes, for example, calculating the photoelectric conversion efficiency of a solar cell array using an expensive pyranometer and a power measuring device, and when the conversion efficiency falls below a certain standard, the solar cell array is used. Is determined to be abnormal.

Japanese Patent Application Laid-Open No. 07-334767 discloses a power generation system having a solar cell array or the like in which a plurality of solar cell strings in which a plurality of solar cell modules are connected in series are connected in parallel. A power generation system has been devised in which a detection means for an electric parameter (current or the like) is provided for each string, the outputs of the strings are compared, and an abnormality is reported. FIG. 9 shows an example of this system.
Current sensors 141 to 144 are attached to each of the photovoltaic strings 11 to 14 similar to the photovoltaic power generation system of FIG. 8, the respective outputs are compared by a comparison means 105, and an alarm is issued by an alarm means 6 when an abnormality is detected. It is.

[0006]

However, in the case of the above-mentioned conventional method for detecting a failure of a solar cell module, the reference value of the photoelectric conversion efficiency is fixed, and the climate and the installation state of the solar cell installation location are fixed. There is a problem in that it is not possible to determine an appropriate standard according to the situation. That is, since the solar cell has a dependence on the spectrum and the temperature, the conversion efficiency varies considerably. In particular, in an amorphous silicon-based solar cell, the photoelectric conversion element itself has photodegradation. The state of this deterioration largely depends on environmental factors such as the amount of solar radiation and temperature. Therefore, it has been extremely difficult to obtain accurate reference values individually in consideration of these factors and the characteristics of the solar cell itself.

[0007] To determine the reference value accurately,
There has been only a means of providing a measurement site at the installation location and examining the power generation performance in the area or the installation location. However, this has a problem that it requires enormous cost and time. As a means for avoiding this problem, there is a means for providing a reference module in addition to the solar cell array at the installation location, but it is uneconomical to provide a solar cell that does not contribute to power generation. Further, when the reference module is broken due to the influence of a system failure or the like, there is a problem that there is no means for obtaining an accurate reference value. Further, a measurement deviation may occur between the solar cell array for power generation and the reference value module due to a difference in adhesion of dirt due to a difference in surface treatment.

In the case of the method disclosed in Japanese Patent Application Laid-Open No. 07-334767, the above problem can be solved, but the current detection means is required for the number of solar cell strings, which is very expensive. And increased space.

In view of the above-mentioned problems, the present invention is an inexpensive and space-saving design, and is capable of accurately detecting and reporting a failure in a solar cell array regardless of the installation location. It is intended to provide a device.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to detect a current difference between strings across a plurality of solar cell strings at one time and compare the detected current difference with a reference value to detect an abnormality. Achieved.

That is, the solar cell string power generation abnormality detection device of the present invention is a device for detecting that the power generation amount of a solar cell string formed by connecting a plurality of solar cell modules in series is abnormal. A means for detecting a difference between the current amounts of the plurality of solar cell strings at one time, and a means for detecting an abnormality in the amount of power generation of the solar cell string by comparing the detected current amount difference with a predetermined reference value. It is characterized by having.

[0012] It is preferable that the solar cell string power generation abnormality detecting apparatus of the present invention further comprises abnormality notification means for notifying that the power generation is abnormal.

The present invention also relates to a current collection box provided with the solar cell string power generation amount abnormality detecting device of the present invention for collecting power generated by a plurality of solar cell strings.

Further, the present invention provides a solar cell string power generation amount abnormality detecting apparatus of the present invention, a plurality of solar cell strings, power conversion means for converting the power of the solar cell strings, and power conversion means. The invention also relates to a photovoltaic power system having a connected load.

[0015] Still further, the present invention is a method for detecting that the power generation amount of a solar cell string constituted by connecting a plurality of solar cell modules in series is abnormal. A step of detecting a difference in the amount of current at a time, and a step of detecting an abnormality in the amount of power generation of the solar cell string by comparing the detected current amount difference with a predetermined reference value. The present invention also relates to a method for detecting a power generation abnormality.

In the present invention, the current difference between the solar cell strings or the sub-arrays of a plurality of solar cell arrays during operation of the system is collectively detected for each block of an arbitrary amount and detected by a single current sensor. If the value exceeds the reference value, it is determined to be abnormal and an alarm is issued. This makes it possible to perform a relative comparison between strings with a simple configuration, thereby achieving cost reduction and space saving.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings. FIG. 7 is a schematic diagram illustrating an example of a power generation system using the abnormality detection device of the present invention. Hereinafter, this system will be described in detail for each unit.

Solar Cell Array 1 The solar cell array 1 has a plurality of solar cell modules connected in series, and solar cell strings 11, 12, 1
3, 14 are connected in parallel. As the solar cell module, a module using an amorphous silicon-based photoelectric conversion unit, a module using polycrystalline silicon, or a crystal silicon are preferably used. Here, the number of series solar cell modules may be appropriately set so as to obtain a voltage required for a solar power generation system.
It is preferable that the system is set so that a voltage of about 200 V can be output in a kW output system. As for the number of parallel strings, at least two parallel circuits are required to achieve the object of the present invention.

Current Collection Box 7 Each solar cell string constituting the solar cell array 1 is collected in the current collection box 7. In the current collection box, a backflow prevention diode for preventing current backflow between strings is connected for each string. The current collection box 7 is installed at a place where a user or an inspector can inspect.

The current collecting box 7 is provided with a single or a small number of means (current sensors) 4 for detecting a current difference between the solar cell strings, a comparing means 5 and an alarming means 6 so as to be in a normal state. If the detecting means 4 detects a current difference equal to or more than a certain value between the respective solar cell strings that should generate power equally, the comparing means 5 determines that the power generation amount is abnormal and notifies the warning means 6. As the current detecting means 4,
For example, a standard resistor for current measurement, a current sensor using a Hall element, or the like can be used.

Power Conversion Means 2 In the power generation system of FIG. 7, the output of the solar cell array 1 is collected in the current collection box 7 and then guided to the power conversion means 2. The power conversion unit 2 converts DC power of the solar cell into AC power, and adjusts DC voltage and DC current.
Others have a control system that keeps the operating point of the solar cell at the maximum power. Although this control system is not an essential component of the present invention, a system of several kW class is generally used to effectively use the solar cell output. In addition, a system configuration in which a storage battery is connected via a charge controller in addition to or instead of the power conversion means may be adopted. Then, the output of the power conversion means 2 is consumed by the load 3.

Load 3 The load 3 is a power device such as a motor, a light source such as a light, or a heat source such as a heater, and specifically includes an air conditioner with an indoor load. Alternatively, the load 3 can be a storage battery such as a nickel hydrogen battery, a lithium secondary battery, or a lithium ion secondary battery, or a commercial system or a combination thereof.

The comparing means 5 sends the current difference between the photovoltaic strings detected by the current difference detecting means 4 to the comparing means 5. Here, if the current difference is found to be a certain value or more, it is determined that the string has failed. Then, an abnormal signal is sent to the alarm means 6. It is preferable that the comparing means 5 is configured to detect that the current difference is a value equal to or more than a certain value for a certain time. With such a configuration, it is possible to take a countermeasure when a specific string is shaded for a short time. For such applications, a one-chip microcomputer is very suitable, but it can also be constituted simply by an analog circuit. In the case of using only an analog circuit, a configuration may be used in which the reference value is compared with a reference value via a low-pass filter such as a CR.

Warning means 6 The warning means 6 specifically includes a light source such as an LED,
A sound source such as a buzzer can be used.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the photovoltaic power generation system of the present invention will be described below with reference to the drawings. FIG. 2 shows a building in which the solar cell power generation system is installed. The building on which the photovoltaic power generation system shown in the figure is mounted is supplied with electric power from a commercial system, and is also self-supplied by the system and reverse power flows to the commercial system.

The commercial system 21 is connected to the building via an electric line.
2 are installed. Inside it, a power purchase meter that integrates the amount of power supplied to the building from the electric circuit and a power sale meter that integrates the amount of power flowing backward from the solar power generation system to the commercial system are connected in series. I have.

A switchboard 23 is installed in the building, and the electric circuit connected to the building is branched and connected to indoor wiring so as to supply power to general loads such as lighting fixtures and outlets in various parts of the building by the switchboard. I have. The distribution board 23 is provided with a main breaker for the purpose of separating the commercial system from the home circuit,
A branch breaker is installed in each of the branching electric circuits.

The photovoltaic power generation system converts sunlight into electric power using a plurality of solar cell arrays installed on the roof of a building and uses the electric power. Outputs of the respective solar cell modules constituting the solar cell array are collected by a current collection box 7 serving as a wiring connector, converted from DC to AC by the power conversion means 2, and then connected to the switchboard 23.

[0029]

Embodiment 1 FIG. 1 shows a detailed configuration of a solar power generation system according to this embodiment. In this embodiment, an amorphous solar cell module (nominal output 22 W, maximum output operating voltage =
14V) are connected in series, and the output voltage is about 200 V
(Output 308W). Ten solar cell strings were arranged on the same roof surface.

In each of the solar cell strings, the solar cell modules are connected to each other via a + side electric wire (not shown) and a − side electric wire (not shown). Pole connection cable,
The pole connection cables are connected and these connection cables are drawn indoors. The connection cables for these 10 strings are connected in parallel in the current collection box to form a solar cell array 1 of about 3 kW.

In the current collection box 7, the current sensor 4 is mounted on the solar cell side from the current collection point so as to clamp the negative cables of all the strings. The current sensor is a clamp-type current sensor that includes a Hall element or the like and detects the amount of current flowing through a clamped cable by a magnetic field generated from the cable. This current sensor measures the current without cutting the electric wire and converts the current into a voltage. The current sensor used in the present embodiment converts 0.1 A to 1 V.

The direction in which the negative cable of each string is passed through the current sensor will be described with reference to the four-string configuration shown in FIG. 1. Strings 11 and 13 have the same direction, and strings 12 and 14 have the opposite direction. ing. In this case, the detection value of the current sensor is ΔI = (output current of string 11 + output current of string 13) − (output current of string 12 + output current of string 14). Therefore, the output value of the current sensor becomes almost zero when the respective photovoltaic strings pass the generated current almost equally. However, when the generated current of any one of the solar cell strings decreases, the detection current of the current sensor increases. This makes it possible to detect an abnormality in the amount of power generation.

The detection current signal converted into the voltage signal is
It is compared with a reference voltage which can be set by a one-chip microcomputer of a comparison means 5 provided in the current collection box, and when ΔI becomes equal to or more than the reference value, it is determined that there is an abnormality in the string, and an abnormal signal is output. .

In the configuration of this embodiment, an abnormal signal is output when a current difference of 20% of the maximum current occurs in two different strings. That is, since each solar cell string used in the present embodiment generates a maximum current of about 1.5 A, an abnormal signal is generated when a current difference of 0.3 A, which is 20% of the maximum, is generated. Therefore,
In the one-chip microcomputer provided in the current collection box, a reference voltage of 3 V corresponding to a current of 0.3 A is compared with a signal of the detected current, and when ΔI becomes 0.3 A or more, the string is abnormal. Judge that there is.

The reason why the current difference for outputting the abnormal signal in this embodiment is set to 20% of the maximum current is that the solar cell module used in this embodiment has an output variation of about 10% at the time of manufacturing. This is because if the current difference between the strings due to the deterioration is 10% or more, it is determined that a failure has occurred.

Therefore, it is desirable to set the reference value of the current difference for each product of the solar cell. Further, although the solar cell strings used in the present embodiment are installed on the same surface of the roof, it is also possible to perform abnormality detection by increasing the current difference limit value for the solar cell strings installed on different surfaces. .

The one-chip microcomputer of the comparison means is as follows:
The configuration is such that an abnormal signal is generated when the current difference ΔI is 0.3 A or more for one minute or more. With such a configuration, it is possible to take a countermeasure when a certain string is shaded for a short time. Therefore,
Depending on the installation environment, for example, in an environment where shadows are likely to occur for a long time, it is desirable to make the current difference detection time longer accordingly. For example, a method of counting the accumulated current amount per day and comparing the difference between different strings with a predetermined value to generate an abnormal signal may be used, or a method of counting the accumulated current amount for one month. Good.

The one-chip microcomputer is connected to an abnormality notifying means 6 for notifying an abnormality in the output of the solar cell. In this embodiment, the abnormality notification means is an alarm buzzer provided in the current collection box. With such a configuration, the user of the system can immediately hear that the current generated in the string is abnormal by hearing the buzzer sound.

In this embodiment, the alarm means is an alarm buzzer provided in the current collection box. However, in an apparatus in which the power conversion means and the current collection box are in the same housing, the notification means is provided in the power conversion means. And a display means such as a light source, a sound source, etc., provided in the display device.

As described above in the present embodiment, in the present invention, the quality of a solar cell string is determined by spreading a current sensor over a plurality of different strings and detecting a current difference between the strings at a time. Therefore, it is possible to accurately detect a defective string and issue an alarm in a small space without being affected by an installation place or a deterioration state.

In the above embodiment, the case where the amorphous solar cell module is used has been described. However, the same effect can be expected when a crystalline solar cell module is used instead of the amorphous solar cell module.

Further, since the means for determining the quality of the solar cell string is provided in a current collection box which can be easily checked by an inspector and a user, it is not necessary to provide a box for detecting an abnormality in particular.
Problems such as an increase in cost and an increase in installation space do not occur. In addition, an effect that inspection of the detection means and the warning means can be easily performed can be expected as compared with providing the detection means and the warning means on the roof surface.

[0043]

[Embodiment 2] In this embodiment, a method of detecting a current difference which is different from that of Embodiment 1 will be described. FIG. 3 shows a detailed configuration of the solar power generation system according to the present embodiment. As in the first embodiment, in each solar cell string, the solar cell modules are connected to each other by a + side electric wire and a − side electric wire (not shown). The + pole connection cable and the-pole connection cable are connected, and these connection cables are drawn indoors. The connection cables for these 10 strings are connected in parallel in the current collection box to form a solar cell array of about 3 kW.

In the current collection box of this embodiment, a current sensor is mounted on the solar cell side from the current collection point in such a manner that one of the cables of all the strings is clamped. Specifically, for the strings 11 and 13, the negative side cable is used,
For the strings 12 and 14, the + side cable is clamped. In this case, the detected value of the current sensor is ΔI = (the output current of the string 11 + the output current of the string 13) − (the output current of the string 12 + the output current of the string 14), which is the same as the configuration of the first embodiment. The effect of can be obtained.

As described above, in this embodiment, the quality of a plurality of different solar cell strings is determined by the relative comparison of each string current by one current sensor, thereby affecting the installation location and the state of deterioration. Instead, a bad string can be detected accurately and an alarm can be issued.

In the structure of this embodiment, the direction in which the cable from the solar cell string passes through the current sensor is as follows.
Since it is unified in the direction from the solar cell array side to the power conversion means, it is effective for saving space in the current collection box.

[0047]

Embodiment 3 In this embodiment, a method of detecting a difference current different from Embodiments 1 and 2 will be described. 4 to 6 show the detailed configuration of the solar power generation system according to the present embodiment.

In the configuration shown in FIG. 4, the strings of the solar cell array are clamped by one current sensor with two strings as one set, and the current difference between the generated currents of the strings is detected. Then, the two minus cables in each set were made to penetrate through the current sensor so that the directions of the two minus cables were opposite to each other, and the current difference was detected.

In the configuration shown in FIG. 5, one of the two solar cell strings in a set is of a type in which a positive cable is inserted into the current sensor and the negative cable is inserted into a single current sensor to detect a current difference. .

FIG. 6 shows a method of detecting a current difference when the number of strings constituting the solar cell array is an odd number. In the configuration shown in FIG. 6, the difference between the normal state (the state in which each string is generating the same current) is obtained by passing the + side cables of the strings 12 and 13 and the − side cable of the string 11 twice through the current sensor. The current was reduced to zero. Similarly, even in a photovoltaic power generation system using solar cell strings having different sizes and the like and different nominal output currents of the solar cell module, by adjusting the number of electric wires passing through the current sensor, the normal state can be obtained. Various applications are possible, such as making the current difference zero.

As described above, also in this embodiment, the quality of the solar cell string is determined by the relative comparison of each string current by a single or a small number of current sensors, so that the solar cell string is not affected by the installation place or the deterioration state. In this case, a bad string can be detected accurately and an alarm can be issued.

In the structure of the present embodiment, even when the solar cell strings are installed on different roof surfaces, the strings installed on the same surface are paired to detect the current difference of the generated current. It becomes possible to
A bad string can be detected properly and an alarm can be issued.

[0053]

As described above, the present invention has the following effects. (1) The solar cell string power generation abnormality detection device of the present invention is configured such that the current difference detecting means detects the current amount difference at a time across the entire solar cell string or the cable of the solar cell string for each block. It suffices to provide one or a small number of detecting means, so that it is inexpensive and has a space-saving structure.

(2) Since a failure is detected by comparing a plurality of strings relatively, an abnormal amount of power generation can be accurately obtained regardless of the amount of power generation current and deterioration of the strings that vary depending on the installation location, environment, and the like. It is possible to perform detection.

(3) Since the means for judging the quality of the solar cell string is provided in the current collection box which can be easily checked by the inspector and the user, it is not necessary to provide a special box or the like for detecting an abnormality. Problems such as an increase in installation space do not occur.

(4) Since the means for judging the quality of the solar cell string is provided in the current collection box which can be easily checked by the inspector and the user, the detection means and the warning means are provided in comparison with the provision of the detection means and the warning means on the roof surface. It is easy to check the means.

(5) Even when a plurality of solar cell strings are installed on different roof surfaces, each of the strings installed on the same surface is paired to detect a difference in the amount of generated current. Accordingly, a defective string can be accurately detected and an alarm can be issued.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a solar power generation system according to a first embodiment.

FIG. 2 is a building in which a solar power generation system employing the present invention is installed.

FIG. 3 is a configuration diagram of a solar power generation system according to a second embodiment.

FIG. 4 is a configuration diagram of a photovoltaic power generation system according to a third embodiment.

FIG. 5 is a configuration diagram of a photovoltaic power generation system according to a third embodiment.

FIG. 6 is a configuration diagram of a solar power generation system according to a third embodiment.

FIG. 7 is a schematic diagram of a photovoltaic power generation system employing the present invention.

FIG. 8 is a configuration diagram of an example of a conventional solar power generation system.

FIG. 9 is a configuration diagram of an example of a conventional solar power generation system.

[Explanation of symbols]

1: solar cell array, 2: power conversion means, 3: load,
4, 141, 142, 143, 144: current difference detection means, 5, 105: comparison means, 6: alarm means, 7: current collection box, 11, 12, 13, 14: solar cell string, 2
1: System, 22: Power meter, 23: Switchboard.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Naoki Manabe 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 5C087 AA11 AA23 AA32 AA42 DD08 DD24 DD33 EE01 EE03 FF01 FF04 FF11 FF13 GG08 GG30 GG31 GG71

Claims (5)

[Claims] An apparatus for detecting an abnormal amount of power generation of a solar cell string configured by connecting a plurality of solar cell modules in series, wherein a difference between current amounts of the plurality of solar cell strings is detected by one. And a means for detecting a power generation abnormality of the solar cell string by comparing the detected current amount difference with a predetermined reference value. apparatus. 2. The apparatus according to claim 1, further comprising abnormality notification means for notifying that the power generation amount is abnormal.
The solar cell string power generation amount abnormality detection device according to the above. 3. A current collection box, comprising the solar cell string power generation abnormality detection device according to claim 1 or 2, for collecting power generated by a plurality of solar cell strings. 4. The solar cell string power generation amount abnormality detecting device according to claim 1, a plurality of solar cell strings, power conversion means for converting the power of the solar cell strings, and the power conversion means. A photovoltaic system having a connected load. 5. A method for detecting that a power generation amount of a solar cell string formed by connecting a plurality of solar cell modules in series is abnormal, wherein a difference between current amounts of the plurality of solar cell strings is determined by one. Detecting a power generation abnormality of the photovoltaic string by comparing the detected current amount difference with a predetermined reference value to detect a power generation abnormality of the photovoltaic string. Method.