KR20230044122A - Apparatus for monitoring a plurality of solar cells using common circuit and controlling method thereof - Google Patents

Abstract

Embodiments relate to a device for monitoring a plurality of solar cells by using a common circuit and a method thereof. According to an embodiment, the device for monitoring a plurality of solar cells comprises: a common circuit connected to a plurality of solar cells; and a processor for controlling the common circuit, measuring the voltage and current of each of the plurality of solar cells, and comparing preset threshold values based on the measured voltage and current to determine whether each of the plurality of solar cells is deteriorated or malfunctions.

Description

Apparatus for monitoring a plurality of solar cells using common circuit and controlling method thereof}

Embodiments relate to a device for monitoring a plurality of solar cells using a common circuit and a control method thereof.

A photovoltaic power generation system is composed of a plurality of strings connecting a plurality of solar cell modules in series, and these strings are connected in parallel in a connection board, and the connection board is configured to be connected to an inverter. Although the efficiency of the system having this structure is excellent, a loss rate of generation amount occurs due to a voltage mismatch between cells, modules, and strings constituting the power generation system. Voltage inconsistency is caused by various causes such as clouds and shadows of buildings, contamination, cell deterioration and burnout, and so causes many problems in the lifespan and safety of power generation.

As solar power generation systems are diversifying and being installed and operated on a large scale, the need for efficient maintenance and monitoring of power generation facilities has emerged. The situation is. However, a problem with existing photovoltaic power generation facility monitoring technology is that since all measurements are performed centering on the inverter, there is a problem in that individual state information of the solar cell module, which accounts for the largest portion of the power generation facility, cannot be known in detail.

In the conventional junction box, a bypass diode is installed in each solar cell module to allow current to flow by bypassing a cell or cell group with reduced output in order to prevent loss due to clouds or shadows. It is difficult to accurately grasp the status information of each solar cell module because there is no function to measure status information such as power generation, abnormalities, and temperature.

Conventional techniques for identifying individual states of solar cells are as follows. There are a voltage and current curve measuring method using a variable resistor (electronic load) and a voltage and current curve measuring method using a capacitor load.

The former is a typical method of measuring a voltage-current curve (hereinafter referred to as an I-V curve) of a solar cell (string) and is a method using a variable resistor. By adjusting the impedance of the variable load connected to the solar output terminal, the voltage/current waveform for the range from the open-circuit voltage to the short-circuit current of the solar cell output is analyzed. This is difficult to apply to the field because the photovoltaic power generation must be stopped during the measurement time and the capacity of the variable load must increase as the capacity of the solar cell array increases.

The latter voltage and current measurement method using a capacitor is a method of analyzing voltage/current characteristics that change as the solar cell output is charged to a capacitor in a 0 V potential state (discharge) by using the charge/discharge characteristics of the capacitor. Two switches are required to control the charge/discharge of the capacitor. In addition, it is measured by connecting the capacitor load for each solar cell (array) in a multi-channel measurement method. In the case of the conventional technology using the charge/discharge characteristics of a capacitor, the output of the solar cell is temporarily connected to analyze the voltage/current characteristics of the solar cell that change when the capacitor is charged, and the solar cell is connected to the capacitor at 0V potential. In this case, it is a method of analyzing the voltage current curve from the point at which the capacitor starts charging to the point at which it is fully charged.

According to the prior art, when configuring multiple channels, that is, a plurality of solar cells, there is a problem in that a capacitor load and a current detection sensor are required for each channel.

An apparatus for monitoring a plurality of solar cells using a common circuit and a method for controlling the same according to an embodiment employs a common circuit to diagnose the status and failure of solar cells, and thus the number of sensors and measurement circuit for multi-channel measurement. can be minimized. Therefore, in a photovoltaic power generation system that operates a plurality of solar cells, it is possible to reduce costs and minimize the size of a monitoring system in determining the deterioration state of each solar cell.

In addition, as a method for diagnosing deterioration/failure of multi-channel photovoltaic modules, online conditions in providing information for detecting the degree of deterioration and failure through analysis of the changing current/voltage output waveform of the photovoltaic module under temporary transient conditions In other words, real-time measurement is possible under the condition that photovoltaic power generation is connected to the grid to produce power, enabling uninterrupted operation.

In order to solve the problems of the prior art, a plurality of solar cell monitoring device according to an embodiment of the present invention includes a common circuit connected to a plurality of solar cells; and measuring the voltage and current of each of the plurality of solar cells by controlling the common circuit, and comparing an internal resistance estimated based on the measured voltage and current with a preset threshold value, so that each of the plurality of solar cells Includes a processor for determining whether the deterioration and failure of

In an embodiment, the common circuit may include a plurality of switches connected to one end of each of the plurality of solar cells; a capacitor connected in common with each of the plurality of switches in series; a first discharge control switch connected in parallel with the capacitor; a resistor connected in series with the first discharge control switch; and a second discharge control switch connected in parallel with the capacitor.

In an embodiment, the processor turns off all of the plurality of switches, turns on the first discharge control switch, discharges the voltage of the capacitor through the resistor, and turns on a first switch of the plurality of switches. Turning on the power of the first solar cell to charge the capacitor, measuring the voltage and current until the current of the first solar cell becomes 0, and based on the measured voltage and current, the first solar cell Deterioration and failure conditions of solar cells can be estimated.

In an embodiment, the processor turns on the second discharge control switch when the discharge voltage of the capacitor is less than the first threshold voltage, and the discharge voltage of the capacitor is less than the first threshold voltage. If it is less than, the first and second discharge control switches may be turned off and the first switch may be turned on.

In an embodiment, the processor turns on the first discharge control switch to discharge the voltage of the capacitor through the resistor in order to estimate a deterioration and failure state of a second solar cell among the plurality of solar cells. , Turn on a second switch among a plurality of switches connected to the second solar cell to charge the capacitor with the output of the second solar cell, and when the voltage of the capacitor and the output voltage of the solar cell are the same, the second solar cell The voltage and current are measured until the current of the battery reaches 0 A, and based on the measured voltage and current, it is possible to estimate whether or not the second solar cell has a failure and a deterioration state.

A control method of a plurality of solar cell monitoring apparatus using a common circuit connected to a plurality of solar cells according to another embodiment includes controlling the common circuit to measure voltage and current of each of the plurality of solar cells; and determining deterioration of each of the plurality of solar cells by comparing the measured voltage/current measurement information of each solar cell with a preset threshold value.

In an embodiment, the common circuit may include a plurality of switches connected to one end of each of the plurality of solar cells; a capacitor connected in common with each of the plurality of switches in series; a first discharge control switch connected in parallel with the capacitor; a resistor connected in series with the first discharge control switch; and a second discharge control switch connected in parallel with the capacitor.

In an embodiment, the measuring step turns off all of the plurality of switches, turns on the first discharge control switch, discharges the voltage of the capacitor through the resistor, and discharges the first switch of the plurality of switches. may be turned on to charge the capacitor with power of the first solar cell, and the voltage and current may be measured until the current of the first solar cell becomes zero, and the estimating step may include the measured voltage and a failure and deterioration state of the first solar cell may be estimated based on the current.

In an embodiment, the measuring step may include turning on the second discharge control switch when the discharge voltage of the capacitor is less than the first threshold voltage, and the discharge voltage of the capacitor is less than the first threshold voltage. When the voltage is lower than the voltage, the first and second discharge control switches may be turned off and the first switch may be turned on.

In an embodiment, the measuring step may include turning on the first discharge control switch to discharge the voltage of the capacitor through the resistor in order to estimate a failure and deterioration state of a second solar cell among the plurality of solar cells. and turns on a second switch among a plurality of switches connected to the second solar cell to charge the capacitor with power of the second solar cell, and until the current of the second solar cell becomes zero, the voltage and Current may be measured, and in the estimating step, internal resistance of the second solar cell may be estimated based on the measured voltage and current.

An apparatus for monitoring a plurality of solar cells using a common circuit and a method for controlling the same according to an embodiment employs a common circuit to diagnose the status and failure of solar cells, and thus the number of sensors and measurement circuit for multi-channel measurement. can be minimized.

In addition, in a photovoltaic power generation system that operates a plurality of solar cells, it is possible to reduce costs and minimize the size of a monitoring system to determine the deterioration state of each solar cell.

In addition, as a method for diagnosing deterioration/failure of multi-channel photovoltaic modules, online conditions in providing information for detecting the degree of deterioration and failure through analysis of the changing current/voltage output waveform of the photovoltaic module under temporary transient conditions In other words, real-time measurement is possible under the condition that photovoltaic power generation is connected to the grid to produce power, enabling uninterrupted operation.

1 is a schematic diagram of an apparatus for monitoring a plurality of solar cells using a common circuit according to an embodiment.
FIG. 2 is a schematic diagram of a plurality of solar cell monitoring devices shown in FIG. 1 .
FIG. 3 is a detailed schematic diagram of the control unit 110 shown in FIG. 2 .
FIG. 4 is a circuit diagram for explaining the common circuit 120 shown in FIG. 2 .
5 to 7 are flowcharts for explaining a control method of a plurality of solar cell monitoring devices using a common circuit according to another embodiment.

The terms used in this specification will be briefly described, and the present invention will be described in detail.

The terms used in the present invention have been selected from general terms that are currently widely used as much as possible while considering the functions in the present invention, but they may vary depending on the intention or precedent of a person skilled in the field, the emergence of new technologies, and the like. In addition, in a specific case, there is also a term arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the description of the invention. Therefore, the term used in the present invention should be defined based on the meaning of the term and the overall content of the present invention, not simply the name of the term.

When it is said that a certain part "includes" a certain component throughout the specification, it means that it may further include other components without excluding other components unless otherwise stated. In addition, terms such as "...unit" and "module" described in the specification mean a unit that processes at least one function or operation, which may be implemented as hardware or software or a combination of hardware and software. .

A solar cell is a device that converts solar light energy into electrical energy, and is usually made of a junction of a p-type semiconductor and an n-type semiconductor.

In solar cells using semiconductors, when electrons in atoms absorb energy that can go to the conduction band, positive holes (+) and electrons (-) are created in p-type semiconductors and n-type semiconductors. Due to the electric field created at the p-n junction, electrons (-) move toward the n-type semiconductor and holes (+) move toward the p-type semiconductor. At this time, when electrons flow to an external circuit by forming electrodes on the surfaces of the p-type semiconductor and the n-type semiconductor, electrical energy is obtained.

The basic unit of a solar cell is called a cell, and a module for obtaining necessary power is formed by connecting these cells. When the modules are connected and installed, it becomes a solar power array. A solar cell in an embodiment may be a cell as a basic unit, a module connecting the cells, or an array connecting the modules.

FIG. 1 is a schematic diagram of an apparatus for monitoring a plurality of solar cells using a common circuit according to an embodiment, and FIG. 2 is a schematic diagram of the apparatus for monitoring a plurality of solar cells shown in FIG. 1 .

Referring to FIGS. 1 and 2 , solar cells 1 to N (200 to 220) are connected to the solar cell monitoring device 100. The solar cell monitoring device 100 is commonly connected to solar cells 1 to N (200 to 220). The solar cell monitoring device 100 includes a common circuit 120 and a controller 110 . The control unit 110 controls the common circuit 120 to measure the voltage and current of each of the solar cells 1 to N (200 to 220), and the solar cells 1 to N (200 to 220) based on the measured voltage and current. ) estimate the internal resistance of each. The solar cell monitoring device 100 may determine the deterioration state of each of the solar cells 1 to N (200 to 220) by comparing the estimated internal resistance with a preset threshold.

FIG. 3 is a detailed schematic diagram of the control unit 110 shown in FIG. 2, and FIG. 4 is a circuit diagram for explaining the common circuit 120 shown in FIG. The control unit 110 turns off all of the first to N th switches S ₁ to S _N through the switching control unit 111 and turns on the first discharge control switch SD1 so that the capacitor C _L The voltage can be discharged through the resistor (R). The controller 110 may turn on the first switch S1 to charge the capacitor C with the power of the first solar cell. Alternatively, when the discharge voltage of the capacitor C is lower than the first threshold voltage, the controller 110 may turn on the second discharge control switch SD2 to short-circuit it. The controller 110 turns off the first and second discharge control switches SD1 and SD2 when the discharge voltage of the capacitor is smaller than the second threshold voltage, which is smaller than the first threshold voltage, and then turns the first switch S1. can be warmed up

The controller 110 may measure the voltage and current of the battery through the voltage sensing unit 112 and the current sensing unit 113 until the current of the first solar cell becomes zero. The controller 110 may estimate a failure and deterioration state of the first solar cell based on the measured voltage and current. The controller 110 may compare the internal resistance of the first solar cell with a preset threshold through the deterioration determining unit 114 to determine the degree of failure or deterioration of the first solar cell. Here, the threshold value is a value predetermined according to the specifications of the first solar cell, and may be set equal to or different from the threshold values of the second to Nth solar cells.

In order to determine deterioration of the second solar cell, the controller 110 turns off the first switch S1 and turns on the first discharge control switch to transfer the charged power of the capacitor C _L to the resistance Rdsg. discharge through When all power of the capacitance C _L is discharged, the controller 110 turns off the first discharge control switch SD1 and turns on the second switch S ₂ connected to the second solar cell. . In addition, through the above-described process, the output voltage and current of the second solar cell are measured, and failure and deterioration are determined using change pattern information of the voltage-current curve.

The controller 110 may determine all degrees of deterioration of each solar cell up to the Nth solar cell through the above-described process. In an embodiment, as a method for diagnosing deterioration/failure of a channel solar module (string) using a common circuit, degradation through analysis of a changing current/voltage output waveform of a solar module (string) under a temporary transient condition It can provide information for degree and fault detection. In addition, there is an advantage in that photovoltaic power generation is linked to a system (not shown) and real-time measurement is possible without stopping the system under power production conditions.

Referring to FIGS. 3 and 4 , the control unit 110 includes a switching control unit 111 , a voltage detection unit 112 , a current detection unit 113 and a degradation determination unit 114 .

Solar cells 1 to N (200 to 220) are connected to first to Nth switches S1 to N, respectively. One end of each switch, a capacitor C, a first discharge control switch SD1 and a resistor R, and a second discharge control switch SD2 are connected in common.

The switching controller 111 controls turn on/off of the first to Nth switches S1 to SN and the first and second discharge control switches SD1 and SD2.

The voltage detector 112 senses the voltage across the capacitor C and detects the discharge voltage or the voltage of the solar cell.

The current sensing unit 113 is connected between the first to Nth switches S1 to SN and the capacitor C, and senses the current of the solar cells 1 to N.

5 to 7 are flowcharts illustrating a control method of a plurality of solar cell monitoring devices using a common circuit according to another embodiment.

Referring to FIG. 5 , in step 500, first through Nth switches connected to each of a plurality of solar cells are all turned off.

In steps 502 and 504, the first discharge control switch is turned on and the discharge voltage is monitored. By turning on the first discharge control switch, the electric power charged in the capacitor is discharged through the resistor.

In step 506, when the first discharge voltage is less than the first threshold voltage, in step 508, the second discharge control switch is turned on to short the circuit.

In step 510, when the second discharge voltage or the capacitor voltage is less than the second threshold value, in step 512, both the first and second discharge control switches are turned off.

In an embodiment, after a common circuit initialization process is performed to determine deterioration of the solar cell through steps 500 to 512, a process for measuring voltage and current of the solar cell connected to the common circuit is performed.

Referring to FIG. 6 , in step 600, a first switch connected to a first solar cell is turned on.

In step 602, the output voltage and current of the first solar cell are measured through the voltage sensing unit and the current sensing unit connected to the common circuit.

In step 604, the voltage and current are measured until the output current of the first solar cell becomes zero. In step 604, when the output current is 0, in step 606, the first switch is turned off.

In steps 608 to 614, the voltage and current of the second solar cell may be measured in the same manner as in steps 600 to 606.

Also, although not shown in FIG. 6 , between steps 606 and 608 , the common circuit initialization process shown in FIG. 5 is performed to discharge all the electric power charged in the capacitor of the common circuit, and then to the second solar cell. Measure the voltage and current for

Referring to FIG. 7 , in step 700, the voltage and current of all solar cells are measured. In step 701, degradation information of each solar cell is determined based on the voltage and current of each solar cell. In the embodiment, it has been described that after measuring the voltage and current of all solar cells and analyzing the change pattern of the voltage-current curve, the deterioration is determined. Of course it can.

Although not shown, the solar cell monitoring device according to the embodiment determines deterioration information of all solar cells, and then outputs an alarm indicating that a specific solar cell has deteriorated or displays a warning on a display panel so that a user or system operator can check. can do

A device according to an embodiment includes a processor, a memory for storing and executing program data, a permanent storage unit such as a disk drive, a communication port for communicating with an external device, a user interface such as a touch panel, a key, and a button. interface devices and the like. Methods implemented as software modules or algorithms may be stored on a computer-readable recording medium as computer-readable codes or program instructions executable on the processor. Here, the computer-readable recording medium includes magnetic storage media (e.g., read-only memory (ROM), random-access memory (RAM), floppy disk, hard disk, etc.) and optical reading media (e.g., CD-ROM) ), and DVD (Digital Versatile Disc). A computer-readable recording medium may be distributed among computer systems connected through a network, and computer-readable codes may be stored and executed in a distributed manner. The medium may be readable by a computer, stored in a memory, and executed by a processor.

Reference numerals have been described in the embodiments shown in the drawings, and specific terms have been used to describe the embodiments, but the present invention is not limited by specific terms, and the embodiments are all configurations commonly conceivable to those skilled in the art. elements may be included.

An embodiment may be presented as functional block structures and various processing steps. These functional blocks may be implemented with any number of hardware or/and software components that perform specific functions. For example, an embodiment is an integrated circuit configuration such as memory, processing, logic, look-up table, etc., which can execute various functions by control of one or more microprocessors or other control devices. can employ them. Similar to components of the present invention that may be implemented as software programming or software elements, embodiments may include various algorithms implemented as data structures, processes, routines, or combinations of other programming constructs, such as C, C++ , Java (Java), can be implemented in a programming or scripting language such as assembler (assembler). Functional aspects may be implemented in an algorithm running on one or more processors. In addition, the embodiment may employ conventional techniques for electronic environment setting, signal processing, and/or data processing. Terms such as “mechanism”, “element”, “means” and “composition” may be used broadly and are not limited to mechanical and physical components. The term may include a meaning of a series of software routines in connection with a processor or the like.

Specific executions described in the embodiments are examples, and do not limit the scope of the embodiments in any way. For brevity of the specification, description of conventional electronic components, control systems, software, and other functional aspects of the systems may be omitted. In addition, the connection of lines or connecting members between the components shown in the drawings are examples of functional connections and / or physical or circuit connections, which can be replaced in actual devices or additional various functional connections, physical connection, or circuit connections. In addition, if there is no specific reference such as “essential” or “important”, it may not be a component necessarily required for the application of the present invention.

In the specification of embodiments (particularly in the claims), the use of the term “above” and similar indicating terms may correspond to both singular and plural. In addition, when a range is described in the examples, it includes the invention to which individual values belonging to the range are applied (unless there is no description to the contrary), and it is as if each individual value constituting the range is described in the detailed description. . Finally, if there is no explicit description or description of the order of steps constituting the method according to the embodiment, the steps may be performed in an appropriate order. Examples are not necessarily limited according to the order of description of the steps. The use of all examples or exemplary terms (eg, etc.) in the embodiments is simply to describe the embodiments in detail, and the scope of the embodiments is limited due to the examples or exemplary terms unless limited by the claims. It is not. In addition, those skilled in the art can appreciate that various modifications, combinations and changes can be made according to design conditions and factors within the scope of the appended claims or equivalents thereof.

Claims (10)

a common circuit connected to a plurality of solar cells; and
By controlling the common circuit, the voltage and current of each of the plurality of solar cells are measured, and the measured voltage and current measurement information of each of the solar cells is compared with a preset threshold, so that each of the plurality of solar cells is measured. A plurality of solar cell monitoring devices including a processor that determines deterioration. According to claim 1,
The common circuit,
a plurality of switches connected to one end of each of the plurality of solar cells;
a capacitor connected in common with each of the plurality of switches in series;
a first discharge control switch connected in parallel with the capacitor;
a resistor connected in series with the first discharge control switch; and
A plurality of solar cell monitoring devices including a second discharge control switch connected in parallel with the capacitor. According to claim 2,
the processor,
turn off all the switches,
Turning on the first discharge control switch to discharge the voltage of the capacitor through the resistor;
Turning on a first switch among the plurality of switches to charge the capacitor with power of the first solar cell;
The apparatus for monitoring a plurality of solar cells, measuring the voltage and current until the current of the first solar cell becomes zero. According to claim 3,
the processor,
Turning on the second discharge control switch when the discharge voltage of the capacitor is less than the first threshold voltage;
When the discharge voltage of the capacitor is less than a second threshold voltage that is less than the first threshold voltage, turning off the first and second discharge control switches;
Turning on the first switch, a plurality of solar cell monitoring device. According to claim 3,
the processor,
In order to estimate the internal resistance of a second solar cell among the plurality of solar cells, the first discharge control switch is turned on to discharge the voltage of the capacitor through the resistance;
Turning on a second switch among a plurality of switches connected to the second solar cell to charge the capacitor with power of the second solar cell;
A plurality of solar cell monitoring device measuring the voltage and current until the current of the second solar cell becomes 0A. A method for controlling a plurality of solar cell monitoring devices using a common circuit connected to a plurality of solar cells, comprising:
measuring the voltage and current of each of the plurality of solar cells by controlling the common circuit; and
and determining deterioration of each of the plurality of solar cells by comparing the measured voltage and current measurement information of each of the solar cells with a preset threshold value. According to claim 6,
The common circuit,
a plurality of switches connected to one end of each of the plurality of solar cells; a capacitor connected in common with each of the plurality of switches in series; a first discharge control switch connected in parallel with the capacitor; a resistor connected in series with the first discharge control switch; and a second discharge control switch connected in parallel with the capacitor. According to claim 7,
In the measuring step,
turn off all the switches,
Turning on the first discharge control switch to discharge the voltage of the capacitor through the resistor;
Turning on a first switch among the plurality of switches to charge the capacitor with power of the first solar cell;
Measuring the voltage and current until the current of the first solar cell becomes zero;
The estimation step is
A method for controlling a plurality of solar cell monitoring devices, wherein a failure and deterioration state of the first solar cell is estimated based on the measured voltage and current. According to claim 8,
In the measuring step,
Turning on the second discharge control switch when the discharge voltage of the capacitor is less than the first threshold voltage;
When the discharge voltage of the capacitor is less than a second threshold voltage that is less than the first threshold voltage, turning off the first and second discharge control switches;
A method of controlling a plurality of solar cell monitoring devices, wherein the first switch is turned on. According to claim 8,
In the measuring step,
In order to estimate the internal resistance of a second solar cell among the plurality of solar cells, the first discharge control switch is turned on to discharge the voltage of the capacitor through the resistance;
Turning on a second switch among a plurality of switches connected to the second solar cell to charge the capacitor with power of the second solar cell;
Measuring the voltage and current until the current of the second solar cell reaches 0A;
The estimation step is
A method for controlling a plurality of solar cell monitoring devices, wherein a failure and deterioration state of the second solar cell is estimated based on the measured voltage and current.

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