JP6081119B2 - PV panel diagnostic apparatus, diagnostic method, diagnostic program, and impedance adjustment circuit - Google Patents

Description

  The embodiment of the present invention relates to a technique for diagnosing deterioration of a PV panel in a power generation system in which a plurality of solar cell panels (PV panels) are connected in series, parallel, or series-parallel, for example.

Photovoltaic power generation using a solar cell panel (hereinafter referred to as a PV panel) has attracted attention as a power generation method that generates less CO ₂ . However, the output per general PV panel is as small as several hundred W or less. For this reason, a practical power generation system using PV panels usually has a plurality of PV panels connected in series or in parallel.

  Such a power generation system is configured such that desired power can be obtained by connecting the PV panel to a device called a PCS (Power Conditioning System). This PCS basically has an inverter function for orthogonal transform. The PCS also has a function (MPPТ: Maximum power point Tracker) that follows an operating point (MPP: Maximum power point) at which the output power becomes maximum.

  Further, in a large-scale power generation system, a string in which a plurality of PV panels are connected in series is configured, and a plurality of strings are connected in parallel. By connecting these strings to one PCS, a power generation system capable of obtaining a large amount of power can be formed.

  By the way, the PV panel is used for many years, and the output is reduced and a failure occurs. However, the degree of output decrease and the occurrence timing of failure for each PV panel differ depending on variations in the quality of PV panels, differences in installation positions, and the like.

  On the other hand, in a power generation system composed of a plurality of PV panels, even if one or two PV panels fail or the output is reduced, the overall output may be greatly reduced.

  For example, consider a string composed of a series circuit of 18 PV panels. It is assumed that there are two deteriorated panels (84% output reduction of the normal panel) in this string. Then, the reduction rate when all the outputs of each panel (16 normal panels + 2 deteriorated panels) are simply summed is 97%. However, the output in an actual power generation system may be greatly reduced to 88%.

JP 2011-170835 A

  From the above, finding a degraded panel in the system is very important for maintaining the overall output. For example, the operating voltage of each PV panel is measured, and the PV panel whose operating voltage, that is, the output is greatly reduced as compared with other PV panels, can be identified as a deteriorated panel.

  On the other hand, during the MPPТ operation by the PCS, the output is controlled so as to compensate for a decrease in the operating voltage of the deteriorated panel. For this reason, compared with other normal PV panels, the output does not decrease much, but the output of other normal PV panels may be reduced due to the PV panel.

  Such a degraded panel (hereinafter referred to as “potentially degraded panel”) has an output decrease of only a few percent compared to other normal panels when operating as an MPPТ system. It is difficult to correctly identify a deteriorated panel only by measuring the voltage of the panel. In other words, the PV panel diagnostic techniques proposed so far have not been able to accurately find a deteriorated panel in a series / parallel circuit.

  Embodiments of the present invention have been proposed to solve the above-described problems of the prior art, and provide a PV panel diagnostic technique that can reliably find a deteriorated panel in a photovoltaic power generation system. The purpose is to do.

In order to achieve the above object, the PV panel diagnostic apparatus of the embodiment has the following technical features.
(1) A PV panel circuit including one or more strings in which a plurality of PV panels are connected in series is connected to a PCS that performs MPPT control.
(2) Impedance adjustment circuit having an impedance variable operation unit that performs an impedance variable operation that changes the impedance of the strings, and a through operation unit that performs a through operation that outputs the output of the PV panel as it is without performing the variable impedance operation
(3) An impedance control unit that causes the variable impedance operation unit to perform variable impedance operation of at least one string.
(4) A measurement value storage unit that stores a voltage or current measured in each PV panel circuit as a measurement value in response to a change in impedance in an impedance variable operation.
(5) A specific unit that identifies a deteriorated PV panel or a string including a deteriorated PV panel based on a comparison between a measured value according to a change in impedance or a change amount thereof and a predetermined threshold value.
(6) Recovery predicted value calculation unit for calculating a recovery predicted value when the PV panel specified by the specifying unit is replaced

  In addition, as another aspect, it can also be grasped as a method for executing the functions of the above-described units by a computer or an electronic circuit and a program to be executed by the computer. The impedance adjustment circuit is also an aspect of the embodiment.

1 is a schematic configuration diagram of a power generation system to which an embodiment is applied. It is a functional block diagram which shows the structure of embodiment. It is a schematic block diagram which shows PCS. It is a figure which shows the IV characteristic of strings. It is a figure which shows the impedance adjustment circuit of embodiment. It is a figure which shows the IV characteristic of a normal panel and the deterioration panels D1 and D2. It is a figure which shows the IV characteristic of the string containing a deterioration panel. It is the figure which compared the string comprised with the normal panel, and the output of the strings containing a deterioration panel. It is a figure which shows the operating voltage of each PV panel at the time of MPPT operation | movement. It is a figure which shows the recovery predicted value of the operating voltage of each PV panel at the time of changing the electric current which flows through a string, and a strings output. It is a flowchart which shows the process sequence of embodiment. It is a figure which shows the change of the capacitor voltage at the time of a measurement, and a strings voltage. It is a figure which shows the other aspect of an impedance adjustment circuit. It is a figure which shows the other aspect of an impedance adjustment circuit. It is a figure which shows an example of the impedance adjustment circuit which used the semiconductor switch and the relay for the switch. It is a figure which shows an example of the impedance adjustment circuit which connected the diode for backflow prevention. It is a figure which shows an example of the impedance adjustment circuit which shared the capacitor | condenser with multiple strings. It is a figure which shows the other aspect of the impedance adjustment circuit which shared the capacitor | condenser with multiple strings. It is a figure which shows the other aspect of the impedance adjustment circuit which shared the capacitor | condenser with multiple strings. It is a figure which shows the other aspect of the impedance adjustment circuit which shared the capacitor | condenser with multiple strings.

[1. Configuration of Embodiment]
[Configuration of power generation system]
A configuration example of a power generation system to which the present embodiment is applied will be described with reference to a schematic configuration diagram in FIG. 1 and block diagrams in FIGS. 2 and 3. In this power generation system, current flows between strings S, voltage monitor 2, current measurement terminal 3, controller 4, impedance adjustment circuit 6, repeater 8, gateway 9, PCS 12, and strings S connected in parallel. It has a backflow prevention diode 15 for preventing, a diagnostic device 100, and a server device 21. Hereinafter, these configurations will be described in detail.

[Strings]
The strings S are PV panel circuits in which a plurality of PV panels 1 are connected in series as described above. The PV panel 1 is a panel that outputs electric power generated by sunlight, and includes any solar cell panel that can be used now or in the future. The number of PV panels 1 in one string S is free. The number of strings S in parallel is also free.

[Voltage monitor]
The voltage monitor 2 is a measuring unit that is connected in parallel to the circuit of each PV panel 1 and detects the operating voltage of each PV panel 1 as a measured value.

[Current measurement terminal]
The current measuring terminal 3 is a measuring unit that detects a current value flowing through the series circuit of the strings S as a measured value. It is conceivable to use a CT (current transformer) as the current measuring terminal 3. However, the current value may be obtained by calculation by inserting a resistor in series with the circuit and measuring the voltage at both ends thereof. It is also possible to obtain a current value from an impedance adjustment circuit 6 described later.

[controller]
The controller 4 is a processing unit that is connected to the current measurement terminal 3 and receives measurement values from the current measurement terminal 3. The controller 4 receives a measurement value from the voltage monitor 2 and controls the voltage monitor 2. The control of the voltage monitor 2 and the transmission / reception of the measurement value sent from the voltage monitor 2 can utilize the power line indicated by reference numeral 11 in the figure.

  The power line 11 is a wiring for supplying electric power via the PCS 12 described later. In addition to the communication using the power line 11, a data transmission / reception line may be separately provided between the voltage monitor 2 and the controller 4, or data may be transmitted / received via a wireless LAN.

[Repeater]
The repeater 8 is a device that collects the data of the controller 4 in each string S and connects them to a gateway 9 described later. The connection between the repeater 8 and the controller 4 and the gateway 9 may be via a communication cable using Ethernet (registered trademark) or USB, or a wireless LAN may be used. Further, the relay device 8 may control each of the lower controllers 4 instead of the gateway 9.

[gateway]
The gateway 9 is a device that performs control of the lower controllers 4, transmission / reception of data with the lower and upper (server device 21, etc.), data communication with the PCS 12, and the like.

[PCS]
The PCS 12 is a power control device connected to the power line 11. As shown in FIG. 3, the PCS 12 includes a converter unit 12a, an inverter unit 12b, an MPP control unit 12c, and a CPU 12d. The converter unit 12 a is a processing unit that boosts the direct current from the PV panel 1. The inverter unit 12b is a processing unit that converts direct current of the PV panel 1 into alternating current.

  The MPP control unit 12c is a processing unit that performs MPPТ on a PV panel circuit including a plurality of strings S. The CPU 12d is a processing unit that controls each unit of the PCS 12. FIG. 4 shows an example in which the voltage and current of the strings S are balanced by MPPT to follow MPP.

[Impactance adjustment circuit]
The impedance adjustment circuit 6 is a circuit that is connected to the power line 11 and adjusts the impedance of the strings S. As shown in FIG. 2, the impedance adjustment circuit 6 according to the present embodiment includes an impedance variable operation unit 61 and a through operation unit 62, and is a circuit that performs switching between an impedance variable operation and a through operation.

  The impedance variable operation is an operation in which the impedance is changed by changing the voltage. The through operation is an operation for outputting the output of the PV panel 1 as it is without performing the impedance variable operation.

  FIG. 5 shows a specific configuration example of the impedance adjustment circuit 6 that realizes such variable impedance operation and through operation. The impedance adjustment circuit 6 is a circuit that changes the current of the strings S by changing the voltage of the strings S.

  First, the capacitor 80 and the switch 81 connected in series are connected to the strings S in parallel. That is, the switch 81 and the capacitor 80 are connected between the high-voltage power line 11a and the low-voltage power line 11b. A discharge resistor 84 and a voltage measuring element 88 are both connected in parallel with the capacitor 80 between the switch 81 and the power line 11b.

  A switch 83 and a charging resistor 85 connected in series with each other are connected in parallel with the switch 81 between the capacitor 80 and the power line 11a. A portion including the capacitor 80, the switch 81, the discharge resistor 84, the voltage measuring element 88, the switch 83, and the charging resistor 85 is the impedance variable operation unit 61. The variable impedance operation unit 61 can also be referred to as a capacitor charging unit because the capacitor 80 is used for charging as described later.

  A switch 82 is connected in series to the high-voltage power line 11a. A portion including the switch 82 is a through operation unit 62. Further, a current measuring element 86 is connected in series to the low-voltage power line 11b.

  As the current measuring element 86, any resistor or CT may be used as long as the current can be measured. The current measurement terminal 3 can also be used as the current measurement element 86. Further, a voltage measuring element 87 is connected between the power line 11a and the power line 11b. Any voltage measuring elements 87 and 88 may be used as long as they can measure voltage.

  The switches 81, 82, 83, the current measuring element 86, and the voltage measuring elements 87, 88 are connected to an impedance control unit 110 described later, and are configured to be able to transmit and receive signals such as measured values and opening / closing instructions. ing.

[Server device]
The server device 21 is a computer capable of transmitting and receiving information by being connected to the controller 4 and the impedance adjustment circuit 6 via the network cable 22. Information on the power generation system can be used in a host monitoring device or the like via the server device 21.

[Diagnostic equipment]
The diagnostic device 100 is a device that diagnoses the PV panel 1 by operating together with the impedance adjustment circuit 6. The diagnostic device 100 is connected to the controller 4 via a cable (not shown) and is provided so as to be able to transmit and receive information.

  As illustrated in FIG. 2, the diagnostic device 100 includes an impedance control unit 110, a diagnostic processing unit 200, a storage unit 300, an input unit 400, an output unit 500, and the like. The impedance control unit 110 is a processing unit that controls the impedance adjustment circuit 6.

  The impedance control unit 110 includes a switching control unit 112 and an adjustment unit 111. The switching control unit 112 is a processing unit that instructs the impedance adjustment circuit 6 to switch between the impedance variable operation and the through operation.

  More specifically, the switching control unit 112 performs operation selection to perform the impedance variable operation or the through operation by controlling the opening and closing of the switch 81 and the switch 82.

  The adjustment unit 111 is a processing unit that adjusts the impedance value when the impedance variable operation is performed. For example, the adjustment unit 111 controls the switch 83 so that the charging voltage of the capacitor 80 becomes a desired value. This control is performed by controlling the voltage measured by the voltage measuring element 88 to be a preset charging voltage.

  This control may be controlled based on the charging time determined by the charging time constant CR, based on whether or not the time when the desired charging voltage has elapsed from the start of charging. The charging time constant CR is determined by the capacitance C of the capacitor 80 and the resistance value R of the charging resistor 85. The impedance control unit 110 can also be configured in the controller 4. In this case, the controller 4 controls the operation of the impedance adjustment circuit 6.

  The diagnosis processing unit 200 is a processing unit that diagnoses the PV panel 1 and the strings S based on various measurement values. The diagnosis processing unit 200 includes a measurement value receiving unit 210, a calculation unit 211, a measurement value comparison unit 212, an abnormality determination unit 213, a change instruction unit 220, a change amount determination unit 221, a specifying unit 222, a recovery predicted value calculation unit 223, A display control unit 231 and the like are included.

  The measurement value receiving unit 210 is a processing unit that receives measurement values from the controller 4. The measurement value received by the measurement value receiving unit 210 is stored in the storage unit 300 described later.

  The calculation unit 211 is a processing unit that performs various calculations based on measurement values. For example, the calculation unit 211 obtains the PV panel output and the strings output based on the PV panel voltage and the strings current. Moreover, the calculation part 211 calculates | requires a strings voltage based on PV panel voltage. The calculation unit 211 can also obtain a threshold value to be described later.

  The controller 4 may include the calculation unit 211 and the measurement value reception unit 210 may receive the calculation result. In the present embodiment, the above calculation result is also included in the measured value. The measured value that is the calculation result is also stored in the storage unit 300 described later.

  The measurement value comparison unit 212 is a processing unit that compares the output of the PV panel 1 and the strings S with a normal value serving as a reference. This normal value can be set in advance, or the normal PV panel 1 and strings S are determined based on the majority rule in consideration of changes in sunshine conditions and the like, and the measured value is normal. It can also be used as a value. The abnormality determination unit 213 is a processing unit that determines abnormality of the PV panel 1 and the strings S based on the comparison result by the measurement value comparison unit 212.

  The change instruction unit 220 is a processing unit that instructs the impedance control unit 110 to change the load impedance of the PV panel circuit.

  The change amount determination unit 221 is a processing unit that determines the change amount of the measurement value of each PV panel 1 when the load impedance of the strings S is changed. The change amount determination unit 221 of the present embodiment determines the amount of change in the voltage of the PV panel 1. The specifying unit 222 is a processing unit that specifies a deteriorated panel or the strings S including the deteriorated panel based on the determination result by the change amount determining unit 221. The specifying unit 222 can also specify the deteriorated panel or the strings S including the deteriorated panel based on the measured value instead of the change amount.

  The recovery predicted value calculation unit 223 is a processing unit that calculates a recovery predicted value that is an output value of the PV panel circuit that is predicted to recover when the deteriorated panel is replaced. The recovery predicted value calculation unit 223 of this embodiment calculates a recovery predicted value of the output value of the strings S.

  The display control unit 231 is a processing unit that causes the output unit 500 described later to display the processing results of the above-described units such as a measured value, a deteriorated panel, and a recovery predicted value.

  The storage unit 300 includes a measurement value storage unit 311, an adjustment value storage unit 312, a setting storage unit 313, and the like. The measurement value storage unit 311 is a storage unit that stores measurement values such as a PV panel voltage, a strings current, a PV panel output, a strings voltage, and a strings output.

  As the measurement value, information received by the measurement value reception unit 210, information calculated by the calculation unit 211, or information input from the input unit 400 described later is used. The storage area for each information can also be regarded as a storage unit for each information.

  The adjustment value storage unit 312 is a storage unit that stores an adjustment value serving as a reference for an impedance change instruction by the change instruction unit 220. For example, it is conceivable to set the voltage value as an adjustment value so that the charging voltage of the capacitor 80 before the measurement becomes a desired value. For example, the set voltage is set to a desired ratio (such as 1/2) with respect to the MPPT voltage. It is also conceivable to set the charging time at which a desired voltage value is obtained as an adjustment value. With such a set value, the minimum voltage of the measurement range can be determined.

  The setting storage unit 313 is a storage unit that stores information related to various settings necessary for the processing of the diagnosis processing unit 200, such as arithmetic expressions, parameters, and determination threshold values. This information includes a voltage / current / output power value for determining deterioration, a voltage / current / output power value at normal time, an MPP operating point, a product specification, and the like. These pieces of information are input by the user using the input unit 400. It is also possible to input from the controller 4 or the PCS 12.

  As the storage unit 300, for example, any storage medium that can be used at present or in the future, such as a memory, a hard disk, or an optical disk, can be used. A mode in which a storage medium in which information has already been stored is mounted on a reading device so that the stored content can be used for various processes.

  Furthermore, the storage unit 300 includes a register, a memory, and the like used as a temporary storage area. Therefore, even a storage area temporarily stored for the processing of each unit described above can be regarded as the storage unit 300. Queues, stacks, and the like can also be realized using the storage unit 300.

  The input unit 400 is a component that inputs information necessary for processing of the diagnosis processing unit 200, selection of processing, and instructions. As this input unit 400, for example, a keyboard, a mouse, a touch panel (including one configured in a display device), a switch, and the like are conceivable. The input unit 400 includes a terminal configured as an operation terminal and a terminal configured as an operation panel. However, all input devices available now or in the future are included.

  The output unit 500 is a component that outputs various processing results and the like by the diagnostic processing unit 200 so that the operator can recognize them. Examples of the output unit 500 include a display device, a printer, a meter, a lamp, a speaker, and a buzzer. Further, the output unit 500 includes those configured as a display terminal and those configured as an operation panel. However, any output device available now or in the future is included.

  Note that all or part of the diagnostic apparatus 100 can be realized by controlling the computer with a predetermined program. The program in this case realizes the processing of each unit as described above by physically utilizing computer hardware. A method, a program, and a recording medium that records the program for executing the processing of each unit described above are also one aspect of the embodiment.

  Moreover, how to set the range processed by hardware and the range processed by software including a program is not limited to a specific mode. For example, any one of the above-described units can be configured as a circuit that realizes each process.

  The server device 21 or the relay device 8 may have any of the functions of the storage unit 300, the diagnosis processing unit 200, the input unit 400, and the output unit 500.

[2. Operation of the embodiment]
[Identification method of deteriorated panel]
First, according to the present embodiment, a method for easily finding a potentially deteriorated panel by actively changing the impedance of the PV panel circuit and measuring the voltage / current will be described.

  First, as an example, consider a string S which is a circuit in which 18 PV panels 1 are connected in series. Assume that in the 18 PV panels 1 in the string S, there are two types of deterioration panels D1 and D2, each having two different deterioration patterns, for a total of four.

  FIG. 6 shows the IV characteristics of the normal panel, the deteriorated panel D1, and the deteriorated panel D2 in this case. FIG. 6 also shows the MPP operating point of each PV panel 1. The output after the deterioration of each of the deteriorated panels D1 and D2 at the MPP operating point is 84% and 89%, respectively, with respect to the normal panel.

  Further, FIG. 7 shows IV characteristics of the strings S including the normal panel and the deteriorated panels D1 and D2. The MPP operating point of strings S is shown in the figure. The MPP operating point of the strings S is an operating point that is out of the MPP operating point of each PV panel.

  What should be noted here is the following. First, in one string S, a value obtained by summing up the outputs on the specifications of all PV panels 1, that is, a value in which one string S is composed of all normal panels is considered as a reference value of 100%. .

  In one string S, it is assumed that four deteriorated panels D1 and D2 as shown in FIG. It is considered that all the PV panels 1 in this string S have operated at their MPP operating points. Then, the output of the strings S at this time is 97% with respect to the reference value. However, in actual operation, as shown in FIG. 8, the output of the string S is reduced to 88%.

  Next, the measurement result of the operating voltage of each PV panel during the MPPT operation is shown in FIG. From this measurement result, both the deteriorated panels D1 and D2 output 90% or more of the normal panel. Therefore, it can be considered that neither of the deteriorated panels D1 and D2 is deteriorated so much.

  Further, even when the deteriorated panel D1 and the deteriorated panel D2 are compared, the deterioration can be considered to be the same degree. When the numerical values are strictly compared, it can be said that the deterioration of the output of the deteriorated panel D2 is larger than that of the deteriorated panel D1.

  Here, when the impedance adjustment circuit 6 connected to the strings S changes the voltage of the strings S to change the current for each string S, the operating point of the strings S changes. Then, the operating point of each PV panel 1 also changes correspondingly.

  For example, when the current flowing through the string S is increased, the operating voltage of the normal panel hardly changes. However, the operating voltage of some deteriorated panels drops rapidly.

  Such a change is shown in FIG. According to FIG. 10, the operating voltage of the deteriorated panel D1 is greatly reduced only by increasing the current during the MPPT operation from 4.06 A to 4.20 A by about 3.5%.

  On the other hand, even if the current increases in the same manner, the voltages of the normal panel and the deteriorated panel D2 hardly change. This shows that the outputs of the normal panel and the deteriorated panel D2 increase with the current. That is, it can be seen that the output of the normal panel and the deteriorated panel D2 was lowered by being pulled by the deteriorated panel D1.

  From the above, it can be seen that it is the deteriorated panel D1 that changes the overall output of the strings S. Such a deteriorated panel D1 will be referred to as a potential deteriorated panel.

[Determining the need for replacement of deteriorated panels]
Next, a method for determining whether or not to replace a deteriorated panel as described above will be described. First, when the current of the strings S is changed while changing the voltage of the strings S, each of the PV panels passes through the respective MPP points. Therefore, by recording the output of each PV panel at that time and performing arithmetic processing, it is possible to predict the output recovery value when the deteriorated panel is replaced.

  That is, the output of the strings S is calculated on the assumption that the operating currents of the deteriorated panels D1 and D2 in FIG. Thereby, it is possible to obtain the output recovery value when only the deteriorated panel D1, only the deteriorated panel D2, and both the deteriorated panels D1 and D2 are replaced.

  Here, the “recovery predicted value (kW) when the deteriorated panel is replaced” in FIG. 10 is a value obtained by such a method. In FIG. 10, the predicted recovery value (2.76 kW) when only the deteriorated panel D1 is replaced is almost the same as the predicted value (2.8 kW) when all the deteriorated panels are replaced.

  On the other hand, the recovery predicted value (2.49 kW) when only the deteriorated panel D2 is replaced is substantially the same as the current output (2.46 kW). For this reason, it can be seen that sufficient recovery cannot be expected even if only the deteriorated panel D2 is replaced.

[Diagnosis Processing of Embodiment]
The diagnosis processing of this embodiment based on the above principle will be described. In the following description, the deterioration panel determined by the normal measurement process is referred to as “deterioration panel”, the deterioration panel specified by the diagnosis process of the present embodiment is referred to as “potential deterioration panel”, and “deterioration panel”. Those other than the “potentially deteriorated panel” are designated as “normally deteriorated panels”.

[Normal measurement processing]
First, measurement processing in normal MPPT operation will be described. That is, during power generation by the PV panel 1, the PCS 12 performs the MPPT operation. The measurement value storage unit 311 stores the measurement value received by the measurement value reception unit 210. The measurement value storage unit 311 also stores the measurement value calculated by the calculation unit 211.

  Under this condition, the measurement value comparison unit 212 compares the PV panel voltage and the strings current with the threshold values stored in the setting storage unit 313 in advance. Note that the threshold value here may be a threshold value created by an operation stored in advance in the setting storage unit 313 using a normal panel voltage determined from a measured value based on the majority rule as a reference. The abnormality determination unit 213 determines that the PV panel voltage and the string current are lower than the threshold value and that the PV panel voltage 1 and the strings S that include the deteriorated PV panel 1 are included.

  However, as described above, since there is a case where the change is slight, it is not always possible to identify a potential deteriorated panel by such normal measurement processing. Therefore, in the present embodiment, the following diagnosis processing is performed.

[Diagnostic processing]
The diagnosis processing according to this embodiment will be described with reference to the flowchart of FIG. This diagnosis process can be performed when the power generation system is activated, or can be performed periodically. Further, as described above, when an abnormality is determined, a diagnostic process can be executed.

  As shown in FIG. 1, the present embodiment is a power generation system in which two or more strings S are connected in parallel. Each string S is connected in parallel to one PCS 12. The basic configuration of the PCS 12 is as shown in FIG. 3, and MPPT control is performed so that the output of the entire string S is maximized. The PCS 12 continues the MPPT control even during the diagnosis process.

  First, based on a program stored in the server device 21, the repeater 8, or the diagnostic device 100, it is determined whether each string S is operated by a variable impedance operation or a through operation (step 01). According to the determination, the impedance control unit 110 of each string S controls the impedance adjustment circuit 6.

  As described above, the impedance adjustment circuit 6 changes the current of the strings S by changing the voltage of the strings S to change the impedance (step 02). That is, by connecting the capacitor 80 and the switch 81 connected in series to the strings S in parallel and closing the switch 81, the voltage of the strings S can be reduced and the equivalent impedance can be changed.

  The operation of the impedance adjustment circuit 6 will be described in detail. FIG. 12 shows how the voltage of the capacitor 80 changes before and after the measurement and how the voltage of the strings S changes. In FIG. 12, the time on the horizontal axis is greatly expanded in order to make the waveform easy to understand.

  First, the impedance adjustment circuit 6 of the strings S that performs the through operation maintains the normal operation state in which the switch 81 and the switch 83 are open and the switch 82 is closed.

  On the other hand, when the variable impedance operation is performed, the impedance adjustment circuit 6 of the strings S first closes the switch 83. Then, charging of the capacitor 80 starts (charging phase in FIG. 12). The adjusting unit 111 instructs the switching control unit 112 to switch to the impedance variable operation when the charging voltage of the capacitor 80 measured by the voltage measuring terminal 88 becomes a preset value.

  For example, the charging resistor 85 is set so that the charging current at this time is a very small value of 1% or less compared to the string current. Therefore, the current taken out to the outside is almost the same as in the through operation. As a result, the power is almost the same as that in the through operation. The charging time constant CR at this time is set from several seconds to several minutes.

  As described above, when the voltage of the capacitor 80 reaches a set voltage (for example, 1/2 of the MPPT voltage), the switching control unit 113 controls switching of the switches 81 to 83 of the impedance adjustment circuit 6.

  That is, after the switch 81 is closed, the switch 82 is opened. This is because since a large current flows through the power line 11a, the current is passed to the capacitor 80 side by opening the switch 81 first to prevent damage when the switch 82 is opened. The switch 83 is also opened, but this may be before the switch 81 is closed or after the switch 81 is closed.

  When the switch 81 is closed, the voltage of the strings S becomes the same as the voltage across the capacitor 80, the current from the PV panel 1 flows to the capacitor 80, the capacitor 80 is charged, and the voltage of the capacitor 80 increases (FIG. 12). Measurement phase).

  When the switch 82 is opened after the switch 81 is closed, the output of the strings S to the PCS 12 is interrupted for a moment, and the strings voltage becomes equal to or higher than the MPPT voltage. By this operation, the string voltage can be changed, and the string current also changes accordingly, so that the load impedance of the strings changes.

  Thus, when the load impedance of the strings changes, the current / voltage measurement of the strings S is performed by the controller 4 using the current measuring element 86 (or the current measuring terminal 3) and the voltage measuring element 87. Further, the voltage of the PV panel 1 is measured by the voltage monitor 2 connected to each PV panel 1.

  After the measurement, the switch 82 is quickly closed and the switch 81 is opened to return to normal operation. When the switch 82 is closed and the switch 81 is opened, the capacitor 80 is discharged through the discharge resistor 84, so that the voltage of the capacitor 80 gradually decreases (discharge phase in FIG. 12).

  In addition, since measurement time is completed in 100 milliseconds or less, it does not affect the PCS 12 or the like. Further, the measurement is performed for each string S while shifting the time, so that the overall output is not affected.

  Moreover, when repeating the same measurement, the charge amount of the capacitor | condenser 80 is maintained without discharging all, and the time to recharge from zero can be saved. That is, the adjusting unit 111 determines that the voltage measured by the voltage measuring element 88 has dropped to a predetermined voltage during the discharge of the capacitor 80.

  At this time, the switching control unit 112 can perform the same measurement as described above by controlling the switch 81 to be closed and the switch 82 to be opened. The predetermined voltage here may be the same as the set voltage when charging in advance, or may be another value. Further, the switch 81 may be closed and the switch 82 may be opened when the time when the desired charging voltage has elapsed from the start of discharging based on the discharging time determined by the charging time constant CR.

  In response to the change in impedance as described above, the measurement value receiving unit 210 receives the PV panel voltage and the strings current from the controller 4 (step 03). The PV panel output can be calculated by the calculation unit 211. These PV panel voltage and string current are stored in the measured value storage unit 311 as measured values.

  The change amount determination unit 221 determines the change amount of the voltage of each PV panel 1 (step 04). And the specific | specification part 222 specifies PV panel 1 in which the voltage is falling based on the threshold value previously memorize | stored in the setting memory | storage part 313 (step 05). Note that the threshold value here may be a threshold value created by an operation stored in advance in the setting storage unit 313 using a normal panel voltage determined from a measured value based on the majority rule as a reference.

  Further, the specifying unit 222 may specify the PV panel 1 in which the voltage is lowered by comparing the measured value with the threshold value instead of the change amount. Since the voltage drop when there is a deterioration is significant as described above, this determination is simpler than the determination by the abnormality determination unit 213.

  When the specifying unit 222 specifies the PV panel 1 whose voltage is significantly reduced (YES in Step 06), the PV panel 1 becomes a potentially deteriorated panel. When the identifying unit 222 cannot identify the PV panel 1 whose voltage is significantly reduced (NO in Step 06), the diagnosis process is terminated.

  Further, the predicted recovery value calculation unit 223 calculates the recovery predicted value of the string S based on each PV panel output stored in the measurement value storage unit 311 or the normal PV panel output stored in the setting storage unit 313. Calculate (step 07). The recovery predicted value calculation unit 223 calculates a recovery predicted value for the case where a normal deteriorated panel, a potential deteriorated panel, and all deteriorated panels including both are replaced.

  The display control unit 231 causes the output unit 500 to compare and display the recovery predicted value and the actually measured output value (step 08). Note that the display control unit 231 may cause the output unit 500 to display a measurement value, a normal deterioration panel, a voltage change accompanying a change in impedance, a potential deterioration panel, and the like (see FIG. 10).

  In this case, a display that can identify a normal deterioration panel and a potential deterioration panel (for example, highlighting of color, size, thickness, font, brightness, blinking, etc.) may be performed. A simple mode such as lighting the lamp of the corresponding PV panel 1 on the operation panel may be used. It is also possible to output sound by a speaker or buzzer.

[3. Effects of the embodiment]
According to the present embodiment, when the voltage is measured by actively changing the impedance of each string S, the operating voltage of the deteriorated panel is greatly reduced. For this reason, it is possible to easily find a potential deteriorated panel that is difficult to specify by measurement only during the MPPT operation.

  In addition, since the operating voltage of the potentially deteriorated panel is greatly reduced as compared with the normal panel, it is not necessary to increase the accuracy of the measuring instrument, the monitor, the determination process, etc., and the cost can be reduced.

  In addition, the recovery value of the system when the deteriorated panel is replaced can be predicted. For this reason, it becomes possible to know how much the entire output is recovered by replacing which panel. Therefore, a suitable guideline for panel replacement is obtained.

  Further, since the impedance can be changed by using charging / discharging of the capacitor 80, the impedance adjustment circuit can be simply configured. Prior to the measurement, the minimum voltage in the measurement range can be determined by closing the switch 83 and charging the capacitor 80 to the minimum voltage in the range to be measured in advance. Thereby, the time required for measurement can be shortened. Note that the minimum voltage in the measurement range can be set to zero. In this case, the switch 83 and the charging resistor 85 can be omitted.

  Further, by stopping the discharging of the capacitor 80 and maintaining the charged state, the time required for charging can be shortened when the same measurement is repeated.

[4. Other Embodiments]
This embodiment is not limited to the above aspects.
(1) In said embodiment, the aspect which performs the exchange determination according to a recovery prediction value is also configurable. For example, the diagnosis processing unit 200 is provided with a predicted value comparison unit and an exchange determination unit. The predicted value comparison unit is a processing unit that compares the predicted recovery value and the current output of the strings S based on the output of each PV panel 1 when the current of the strings S is changed. The replacement determination unit is a processing unit that determines whether or not replacement is necessary based on the comparison result in the predicted value comparison unit.

  The replacement determination unit has a recovery predicted value when a certain deteriorated panel (deteriorated panel here refers to both a normal deteriorated panel and a potential deteriorated panel) is replaced by a predetermined recovery value or higher. If it exceeds, it is determined that the deteriorated panel needs to be replaced. The replacement determination unit determines that the replacement is unnecessary when the predicted recovery value when a certain deteriorated panel is replaced is less than or less than a preset recovery value. The determination result is displayed on the output unit by the display control unit. Thereby, the user can easily determine whether or not replacement is necessary. The replacement of the PV panel may be effective only when a plurality of deteriorated panels are replaced at the same time. Various display modes can be applied depending on the PV panel 1 and the strings S that need to be replaced, as in the case of the identification display of the above-described deteriorated panel or the like.

(2) Various impedance adjustment circuits 6 in the above embodiment can be applied. For example, a circuit system as shown in FIGS. 13 and 14 may be used. FIG. 13 shows an example in which the switches 81 and 83 are connected to the low-voltage power line 11b, contrary to FIG. FIG. 14 shows an example in which the switch 81 is connected to the low-voltage power line 11b.

  When a switch is connected to the high voltage side, it is necessary to prepare an insulation amplifier or the like and perform the switching operation after insulation. However, by connecting at least the switch 81 to the low voltage side, a part of such an insulation configuration can be omitted.

  As shown in FIG. 15, semiconductor switches 91, 92, and 93 that operate at high speed such as IGBTs and FETs can be used as the switches 81, 82, and 83. However, when the semiconductor switch 92 is used as the switch 82, a voltage drop of about 1 to 5 V may occur. In order to prevent such voltage loss from occurring during the through operation, a relay 94 is connected in parallel to the semiconductor switch 92.

  In this case, since the operation speed of the relay 94 is slow, the opening / closing operation is performed in the following procedure. That is, during the through operation, the relay 94 is closed and the semiconductor switch 92 is opened. Thereby, since the current from the PV panel 1 during normal operation is bypassed to the relay 94 side, the voltage loss of the semiconductor switch 92 can be eliminated.

  On the other hand, during the variable impedance operation, after charging the capacitor 80 and before closing the semiconductor switch 91, the semiconductor switch 92 is closed and then the relay 94 is opened. At the start of measurement, the semiconductor switch 91 is closed and the semiconductor switch 92 is opened to start the measurement. After the measurement is completed, the semiconductor switch 92 is quickly closed and the semiconductor switch 91 is opened, and then the relay 94 is closed. After the relay 94 is closed, the semiconductor switch 92 is opened to return to normal operation.

  Depending on the power generation system, the backflow prevention diode 15 connected between the strings S shown in FIG. 1 may not be connected. In this case, a diode 95 is connected in series with the semiconductor switch 92 as shown in FIG. This makes it possible to prevent backflow. Since the current during the through operation is bypassed by the relay 94, a voltage drop due to the diode 95 does not occur.

  In addition, as shown in FIG. 17, a mode in which a capacitor 80 occupying most of the volume capacity of the impedance adjustment circuit 6 is used in common for a plurality of strings S can also be configured. This embodiment is an example in which the capacitor 80, the discharge resistor 84, and the voltage measuring element 88 in each impedance adjustment circuit 6 are separated and shared and accommodated in the capacitor charging box B. That is, both ends of the capacitor 80 connected in parallel with the discharge resistor 84 and the voltage measuring element 88 are connected to the semiconductor switch 91 and the low-voltage power line 11b in each string S through the diode 33 in each string S, respectively. . The diode 33 has a function of preventing backflow from other strings during measurement. For example, when an IGBT is used for the semiconductor switch 91 or 93, it is essential because the IGBT does not have a backflow prevention function. When the semiconductor switches 91 and 93 use an element having a backflow prevention function such as an FET, the diode 33 may not be connected.

  The operation of this aspect is basically the same as the above aspect. However, when the number of strings S is large, the impedance adjustment circuits 6 of all the strings S cannot use the capacitors 80 at the same time. For this reason, only the impedance adjustment circuit 6 of some strings S uses the capacitor 80 simultaneously. Alternatively, the impedance adjustment circuit 6 of each string S uses the capacitors 80 sequentially.

  Further, FIG. 18 is an embodiment in which the capacitor 80 is tried to be used in common as in the embodiment of FIG. However, the aspect of FIG. 18 is an example in which, in the impedance adjustment circuit 6, the semiconductor switch 91 is separated and shared together with the capacitor 80, the discharge resistor 84, and the voltage measuring element 88 and accommodated in the capacitor charging box B. . That is, the semiconductor switch 91 and the charging resistor 85 are connected in parallel between the capacitor 80 and the low-voltage power line 11b in each string S. Other configurations are the same as those in FIG. Further, when an IGBT is used for the semiconductor switch 93, the diode 33 is essential because the IGBT does not have a backflow prevention function. When an element having a backflow prevention function such as an FET is used for the semiconductor switch 93, the diode 33 may not be connected.

  Furthermore, as shown in FIG. 19, the current measuring element 86 may be provided on the power line 11 a of the strings S. That is, the current measuring element 86 may be connected to either side of the power lines 11a and 11b of the strings S as long as the current can be measured correctly.

  Depending on the power generation system, the backflow prevention diode 15 connected between the strings S shown in FIG. 1 may not be connected. Also in the embodiment in which the capacitor 80 shown in FIG. 17 and later is commonly used, backflow can be prevented by connecting the diode 95 in series to the semiconductor switch 92 as in the embodiment of FIG. . FIG. 20 shows an embodiment when applied to FIG. Since the current during the through operation is bypassed by the relay 94, a voltage drop due to the diode 95 does not occur.

(3) The diagnosis processing unit, the storage unit, etc. may be realized by a controller, a relay machine, a CPU in the PCS, a gateway, and other common computers, or by a plurality of computers connected by a communication network. Also good. Furthermore, the impedance control unit can be integrated with the controller.

(4) It is possible to omit the change amount determination unit and the specifying unit. For example, the storage unit stores the voltage or current measured in the PV panel circuit as a measurement value in response to the impedance change by the adjustment unit. And a display control part compares and displays the measured value before an impedance change, and the measured value after a change. Thereby, the user can determine the deterioration of the PV panel and the strings that are remarkably changed.

(5) The specific contents and values of the information used in the embodiment are free and are not limited to specific contents and numerical values. In the embodiment, in the determination of the magnitude of the threshold, the determination of coincidence mismatch, etc., it may be determined that the value is included as follows, or may be determined not to include the value as larger, larger, smaller, or lower. Be free.

(6) Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

S ... Strings 1 ... PV panel 2 ... Voltage monitor 3 ... Current measurement terminal 4 ... Controller 6 ... Impedance adjustment circuit 8 ... Repeater 9 ... Gateway 11, 11a, 11b ... Power line 12 ... PCS
12a ... Converter unit 12b ... Inverter unit 12c ... MPP control unit 12d ... CPU
DESCRIPTION OF SYMBOLS 15, 33, 95 ... Diode 21 ... Server apparatus 22 ... Network cable 61 ... Impedance variable operation part 62 ... Through operation part 80 ... Capacitor 81, 82, 83 ... Switch 84 ... Discharge resistance 85 ... Charge resistance 86 ... Current measurement element 87, 88 ... Voltage measuring elements 91, 92, 93 ... Semiconductor switch 94 ... Relay 100 ... Diagnostic device 110 ... Impedance control unit 111 ... Adjustment unit 112 ... Switching control unit 200 ... Diagnosis processing unit 210 ... Measurement value receiving unit 211 ... Calculation unit 212 ... Measurement value comparison unit 213 ... Abnormality determination unit 220 ... Change instruction unit 221 ... Change amount determination unit 222 ... Specification unit 223 ... Recovery predicted value calculation unit 231 ... Display control unit 300 ... Storage unit 311 ... Measurement value storage unit 312 ... Adjustment value storage unit 313 ... Setting storage unit 400 ... Input unit 500 ... Output unit

Claims (10)

A PV panel circuit including one or more strings in which a plurality of PV panels are connected in series is connected to a PCS that performs MPPT control,
An impedance adjustment circuit having an impedance variable operation unit that performs an impedance variable operation that changes the impedance of the strings, and a through operation unit that performs a through operation of outputting the output of the PV panel as it is without performing the impedance variable operation;
An impedance control unit for causing the impedance variable operation unit to perform an impedance variable operation of at least one string;
In response to a change in impedance in the variable impedance operation, a measured value storage unit that stores a voltage or current measured in each PV panel circuit as a measured value;
A specific unit that identifies a degraded PV panel or a string including a degraded PV panel based on a comparison between a measured value corresponding to a change in impedance or a change amount thereof and a predetermined threshold;
A predicted recovery value calculating unit that calculates a predicted recovery value when the PV panel specified by the specifying unit is replaced;
A PV panel diagnostic apparatus comprising: The PV panel diagnostic apparatus according to claim 1, further comprising an output unit that displays the recovery predicted value calculated by the recovery predicted value calculation unit. The impedance variable operation unit is connected between a pair of power lines in the string, and includes a capacitor and a switch connected in series with each other,
The through operation unit, the capacitor and provided on PCS side of the connection point between the switches at both ends and the power line, according to claim 1 or claim 2, characterized in that a switch for opening and closing at least one power line PV panel diagnostic apparatus according to. Said impedance variable operation unit, which is connected between the power line and the capacitor, the prior measurement, claim 3, characterized in that it comprises a switch and a charging resistor to charge said capacitor to charge amount set beforehand The PV panel diagnostic apparatus of description. The PV panel diagnostic apparatus according to claim 3 or 4, wherein a relay is connected in parallel with a switch for opening and closing the power line. The PV panel diagnostic apparatus according to claim 3 , wherein the capacitor is common among a plurality of strings. A computer or electronic circuit
A PV panel circuit including one or more strings in which a plurality of PV panels are connected in series is connected, and an impedance variable operation for changing the impedance of the strings and an output of the PV panel are directly output without performing the impedance variable operation. An impedance variable process for controlling the impedance adjustment circuit of at least one string by controlling an impedance adjustment circuit that switches between through operations; and
Corresponding to a change in impedance due to the impedance variable operation, a measured value storage process for storing a voltage or current measured in each PV panel circuit as a measured value;
A specific process for identifying a deteriorated PV panel or a string including a deteriorated PV panel based on a comparison between a measured value according to a change in impedance or a change amount thereof and a predetermined threshold value;
A predicted recovery value calculation process for calculating a predicted recovery value when the PV panel specified by the specific process is replaced;
The PV panel diagnostic method characterized by performing. 8. The PV panel diagnosis method according to claim 7, wherein the predicted recovery value calculated by the predicted recovery value calculation process is displayed. On the computer,
A PV panel circuit including one or more strings in which a plurality of PV panels are connected in series is connected, and an impedance variable operation for changing the impedance of the strings and an output of the PV panel are directly output without performing the impedance variable operation. An impedance variable process for controlling the impedance adjustment circuit of at least one string by controlling an impedance adjustment circuit that switches between through operations; and
Corresponding to a change in impedance due to the impedance variable operation, a measured value storage process for storing a voltage or current measured in each PV panel circuit as a measured value;
A specific process for identifying a deteriorated PV panel or a string including a deteriorated PV panel based on a comparison between a measured value according to a change in impedance or a change amount thereof and a predetermined threshold value;
A predicted recovery value calculation process for calculating a predicted recovery value when the PV panel specified by the specific process is replaced;
A PV panel diagnostic program characterized in that The PV panel diagnosis program according to claim 9, wherein the recovery prediction value calculated by the recovery prediction value calculation process is displayed.

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