JP6005775B2 - Solar power system - Google Patents

Description

  The present invention belongs to a technical field related to a string converter that easily detects an abnormality of a solar cell string in a photovoltaic power generation system.

  In recent years, there has been an increasing interest in the safety of nuclear power generation and the environmental destruction of carbon dioxide emissions from thermal power generation. Under such circumstances, attention is focused on solar power generation. Even in general homes, there are some places where a plurality of solar cell panels are connected in series or in parallel or both so that a desired power can be obtained.

  Check whether the solar cell string is in a normal state or in a fault / failure state by checking the current-voltage characteristics or power-voltage characteristics of the solar cell string and confirming that it is not different from the normal characteristics. If they are different from each other, a method for determining that a failure has occurred is known. For example, consider the current-voltage characteristics as shown in FIG. The characteristic indicated by the broken line is the current-voltage characteristic of a normal solar cell string with no abnormality. On the other hand, the current-voltage characteristic of the solar cell string including the solar cell in which a failure or malfunction has occurred is greatly different from the normal characteristic as shown by the solid line in FIG. In addition, a solar cell string means what connected the several solar cell module in series.

  Moreover, in patent document 1, the solar cell which has a failure and a malfunction is detected and reported in the electric power generation system provided with the solar cell array which connected the several solar cell string which connected the several solar cell module in series. Techniques to do this are disclosed.

JP-A-7-334767

However, in the conventional method described above, there is a method in which a dedicated device for measuring the current-voltage characteristic and power-voltage characteristic of the solar cell is actually connected to the solar cell and inspected at the time of solar cell installation or periodic maintenance. Since it uses, there is a problem that it takes time and effort.
Moreover, since the system disclosed in Patent Document 1 is a technique for comparing a plurality of solar cell strings with each other, a large number of solar cell strings are required to operate accurately, and a small number of solar cell strings However, there are difficulties in applying it.
An object of the present invention is to provide a string converter that solves the above-described problems and that can easily detect a failure or malfunction of a solar cell without using the dedicated device and with a small number of solar cell strings. .

  The string converter that performs maximum power point tracking control to which a solar cell is connected according to the present invention has a function of dynamically changing an input voltage position by communication from the outside.

  By the function of changing the input voltage position, it is possible to detect a failure / failure of the solar cell in the state where it is installed in the string converter, not immediately after the production of the solar cell. The presence or absence of defects can be inspected by an easy method.

  In the above string converter, the input voltage and the input current when the input voltage position is dynamically changed by communication from the outside are measured, and the current-voltage characteristic of the solar cell or the power-voltage is stored in the operation control computer. Characteristics can be displayed.

  The characteristic curve of the current-voltage characteristic or power-voltage characteristic of the solar battery displayed on the control computer changes in the shape of the characteristic curve when a failure occurs, as compared with the characteristic curve at normal time. By utilizing this change and comparing the image information of the characteristic curve, it is possible to easily determine the deterioration of the solar cell. Comparison of image information is an effective means for visual confirmation in addition to a method using image processing using a computer. Note that the image processing refers to processing for finding measurement data as a shape and finding a difference between the shape and the shape of the characteristic curve when the solar cell is normal.

  In the string converter for performing the maximum power point tracking control of the connected solar cells according to the present invention, the input voltage and the input current at the input voltage position specified at the specified time every day are measured, and the past fixed period When the maximum measured value of the unit is a representative value, the current measured value is abnormal for the solar cell when the input power has changed more than a certain amount in a decreasing direction from the representative value for a certain period in the past. Judge that there is.

  Thereby, in a state where the solar cell is connected to the string converter, it can be automatically determined whether or not the solar cell is out of order. Note that the measurement period of the representative value to be compared is preferably changed according to the usage such as the surrounding environment and detection sensitivity.

  In the string converter that performs the maximum power point tracking control of the connected solar cells according to the present invention, the current value on the output side of the string converter is measured at a designated time every day, and the measured value of the other string converter In comparison, if the difference is greater than a certain level, it is determined that the solar cell is abnormal.

  Thus, by comparing the output current values from the string converters connected to other solar cell strings, it is possible to perform failure / failure determination with a small number of solar cell strings. .

  In addition, when it is determined that there is an abnormality in the solar battery, it is preferable to transmit information indicating the abnormality to the operation control computer by communication.

  Thereby, when abnormality occurs in the solar cell in the string converter to which the solar cell is connected, the information can be transmitted to the operation control computer by communication to notify the user.

  As described above, according to the present invention, it is possible to provide a string converter that can check whether or not there is a failure or malfunction of a connected solar cell by an easy method without using a dedicated device.

It is the block diagram which showed the structural example of the system provided with the string converter which concerns on 1st Embodiment and 2nd Embodiment of this invention. It is a flowchart explaining the example of 1st Embodiment of this invention. It is a flowchart explaining the example of 2nd Embodiment of this invention. It is the block diagram which showed the structural example of the system provided with the string converter which concerns on 3rd Embodiment of this invention. It is a flowchart explaining the operation example of the output current value measurement means 22 in 3rd Embodiment of this invention. It is a flowchart explaining the operation example of the comparison means 18 in 3rd Embodiment of this invention. It is a figure of the current-voltage characteristic of the solar cell string used in order to explain the background art of the present invention and the first embodiment. It is a figure of the current-voltage characteristic of the solar cell string used for describing 2nd Embodiment of this invention.

  Hereinafter, the form for implementation is demonstrated using drawing. FIG. 1 shows a configuration example of a system including a string converter according to the first and second embodiments of the present invention, and FIG. 4 shows a configuration example of a system including a string converter according to the third embodiment. Yes.

  The string converter main body 11 has a circuit for setting a voltage from the connected solar cell string 17 to a desired voltage. An input voltage conversion DC-DC converter 12, an input voltage control unit 13, and a communication interface 14 are provided.

  As the input voltage conversion DC-DC converter 12, there is a DC-DC converter that can change the input voltage input from the solar cell string 17 by a signal from the input voltage control unit 13. This converter can be realized by using an element such as a field effect transistor that can be switched on and off using an external signal. The input voltage can be controlled by changing the duty ratio of the gate pulse to be applied.

  The input voltage control unit 13 includes an input current value measuring unit 20 and an input voltage measuring unit 21, and based on data from the input current value measuring unit 20, the input voltage measuring unit 21 and the operation control computer 16, a solar cell It has a function of transmitting a signal such as a gate pulse for determining a voltage value from the string 17 to the input voltage conversion DC-DC converter 12. Normally, MPPT control is performed based on the measured values from the input current value measuring means 20 and the input voltage measuring means 21. This can be realized by a control microcomputer composed of a CPU, RAM, ROM, I / O and the like. Examples of the signal such as the gate pulse include a gate pulse applied to a field effect transistor that determines the input voltage position if the input voltage conversion DC-DC converter 12 is a booster circuit.

  The communication interface 14 is an interface mainly composed of serial communication capable of long-distance communication with the outside, and particularly includes a wireless LAN such as Wi-Fi. The input voltage control unit 13 communicates with the operation control computer 16 by wire or wireless using this communication interface.

  Examples of the external load 15 include an inductive load, a lamp load, a resistance load, or a combination thereof, or a commercial power system.

  The operation control computer 16 is a commonly used computer. Data received through communication can be displayed on the display. Further, the duty ratio of the gate pulse that is given to the input voltage conversion DC-DC converter 12 so that the input voltage position from the solar cell string 17 is changed to a specified value to the input voltage control unit 13 in the string converter 11. It is also possible to transmit data to the input voltage control unit 13 so as to change.

  The solar cell string 17 refers to a solar cell string in which a plurality of solar cells are connected in series. Here, the solar cells 30 to 33 are connected in series. In addition, a solar cell is a part which converts a light energy into electric power using a photovoltaic effect. Of course, a single solar cell may be used.

  As the comparison means 18, the current values measured by the two output current value measurement means 22 are compared, and when a difference of a certain level or more appears, one of the string converter main body portions 11 connected to the comparison means 18. It is determined that the solar cell string 17 connected to is abnormal. In addition, data indicating an abnormality is transmitted to the operation control computer 16. This can be realized by a control microcomputer composed of a CPU, RAM, ROM, I / O and the like.

  A first embodiment according to the present invention will be described below with reference to FIG. The string converter 11 in this embodiment includes an input voltage conversion DC-DC converter 12, an input voltage control unit 13, a communication interface 14, and an operation control computer 16.

A control method will be described with reference to FIG. When it is desired to check the failure or malfunction of the solar cell string 17 connected to the string converter main body 11, the position of the input voltage from the solar cell string 17 is sent from the operation control computer 16 to the input voltage control unit 13. To change to a nominal open circuit voltage. The input voltage control unit 13 transmits a signal to the input voltage conversion DC-DC converter 12 so that the designated input voltage position is reached (Step 1_1). The input voltage and input current from the solar cell string 17 at that time are sampled (Step 1_2). Thereafter, the measurement result is transmitted to the operation control computer 16 (Step 1_3). The operation control computer 16 displays the received measurement result. At this time, the graph may be displayed in a graph format with the vertical axis representing current and power and the horizontal axis representing voltage. Using this method, about 100 points are obtained up to 0V in the direction of decreasing input voltage so that the outline of the power-voltage characteristics and current-voltage characteristics of the solar cell string 17 can be understood. This is transmitted to the operation control computer 16. The direction of changing the input voltage position is not limited to the direction of moving from the nominal open circuit voltage to 0V, but any method can be used as long as the characteristics of the connected solar cell string can be understood, such as moving from 0V to the nominal open circuit voltage. Absent.
Based on the displayed information, it is visually determined whether the solar cell string 17 has a failure or a malfunction.
A current-voltage characteristic of a normal solar cell string is shown by a broken line in FIG. 7, and a typical example of a characteristic when a malfunction or failure occurs is shown by a solid line. When the waveform as shown by the solid line is confirmed through the above operation, the solar cell string 17 may be determined to be abnormal.

  Next, a second embodiment according to the present invention will be described with reference to FIG. The configuration of this embodiment is the same as that of the first embodiment.

  The control method will be described with reference to FIG. The input voltage control unit 13 controls the input voltage conversion DC-DC converter 12 so that the input voltage position from the solar cell string 17 becomes a predetermined value at a predetermined time every day by a built-in program. Send a signal (Step 2_1). At this time, it is preferable to designate the vicinity of the point A shown in FIG. 8 where the current value greatly changes when a failure or malfunction occurs. Then, input voltage and input current are measured (Step 2_2).

The maximum measured value in the past month is set as the representative value I_max, and if the measured current value is reduced by 20% or more from the representative value I_max, the dedicated counter Cnt is incremented by 1 (Step 2_3). If it is not in a state where it has decreased by 20% or more from the previous month input current value, the dedicated counter is initialized to 0 (Step 2_4). If the dedicated counter is 3 or more, the input voltage control unit 13 transmits a signal to the operation control computer 16 by communication indicating that a failure or malfunction has occurred in the solar cell array (Step 2_5). FIG. 8 shows current-voltage characteristics when an abnormality occurs in the solar cells in the solar cell string. The current value I_b of this month is lower than the current value I_n of the previous month. Here, if I_b <I_n * 0.8, the dedicated counter is incremented by one.
In addition, you may evaluate not only with input current but with the value which multiplied input voltage to input current, ie, input power.
Further, the value such as the reduction ratio of 20% in the above description is a setting for explaining this operation, and may be an arbitrary value such as 10% or 25%. By changing this value, it is possible to change the sensitivity of defect detection. It is desirable to set an appropriate value according to the surrounding environment and the judgment of the operator. The measurement period of the representative value to be compared is set to one month here, but it is desirable to change it according to the usage such as the surrounding environment and detection sensitivity.

  Next, a third embodiment according to the present invention will be described with reference to FIG. The string converter 11 in this embodiment includes an input voltage conversion DC-DC converter 12, an input voltage control unit 13, a communication interface 14, an operation control computer 16, and a comparison means 18.

  The control method will be described with reference to FIGS. In practicing the present invention, it is preferable that the comparison unit 18 stores the inspection time in the ROM in advance. The current value output from the string converter 11 is measured by the output current value measuring means 22 at a designated time every day (Step 3_1). The comparing means 18 compares the current values measured by the two output current value measuring means 22 (Step 4_1). If the absolute value of the difference is 20% or more of the larger current value, there is an abnormality in the solar cell string 17 connected to one of the string converter main body parts 11 connected to the comparison means 18. Assuming that there is an error, a signal notifying the abnormality to the operation control computer 16 is transmitted (Step 4_2). Receiving the signal, the operation control computer 16 displays that the solar cell string connected to the string converter has a failure or malfunction.

In the inspection method, actual values of current values measured by the output current value measuring means 22 in the string converter main body 11 are compared with each other as shown in FIG.
When a string converter is installed, the case where the number of series connection of the solar cell in a solar cell string is not all equal is considered.
In this case, under the conditions of the third embodiment, since a difference in current value occurs from the beginning, a failure cannot be detected.
In such a case, the ratio of the current values in the initial state from the two solar cell strings 17 in the vicinity measured by the output current value measuring means 22 is stored, and the ratio of the current values measured every day is When the state changes by 20% or more with respect to the ratio of the initial state, it is considered that there is an abnormality in the solar cell string 17 connected to one of the string converter main body portions 11 connected to the comparison means 18. The method is effective.

Further, the value such as 20% in the above description is a setting for explaining this operation, and may be an arbitrary value such as 10% or 25%. It is desirable to set an appropriate value according to the surrounding environment and the judgment of the operator.

DESCRIPTION OF SYMBOLS 11 String converter main body part 12 Input voltage conversion DC-DC converter 13 Input voltage control part 14 Communication interface 15 External load 16 Operation control computer 17 Solar cell string 18 Comparison means 20 Input current value measurement means 21 Input voltage value measurement means 22 Output Current value measuring means 30 to 33 Solar cell

Claims (2)

In a photovoltaic power generation system including two string converters that perform maximum power point tracking control of connected solar cells,
The ratio of the current value of the initial state of the two string converters is stored in advance, the current value on the output side of the two string converters is measured at a designated time every day , and the ratio of the measured two current values but if more than a predetermined difference occurs with respect to the stored ratio in the initial state, the solar power generation system determines that there is an abnormality in the solar cell. The solar power generation system according to claim 1, wherein the solar cells connected to the two string converters are arranged in the vicinity of each other .

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