JP7139630B2 - SOLAR BATTERY ARRAY INSPECTION SYSTEM, POWER CONDITIONER AND SOLAR BATTERY ARRAY INSPECTION METHOD - Google Patents

Description

The present invention relates to a solar cell array inspection system, a power conditioner, and a solar cell array inspection method.

As a power conditioner (PCS) for photovoltaic power generation, there is known a PCS (see, for example, Patent Document 1) that incorporates a connection unit having the same function as a connection box. The connection unit is a unit (electric circuit) that connects the outputs of a plurality of strings in parallel via a plurality of blocking diodes so that the current from each string does not flow into the other strings.

Each string of the solar cell array should be directly connected to such a PCS. However, due to construction errors or lack of knowledge of the installer, the solar cell array may be connected to the PCS containing the connection unit via the connection box. If a solar cell array is connected to a PCS containing a connection unit via a connection box, power generation loss will occur in both the blocking diode in the connection unit and the blocking diode in the connection box.

The presence of extra blocking diodes increases power generation losses by as much as 40 W (ie, as much as 0.7% of 6 kW) if the PCS is, for example, of 6 kW (300 V, 20 A). Considering that the power generation efficiency of recent PCS is about 95% to 98%, this increase in power generation loss cannot be ignored. The problem of increased power generation loss due to extra blocking diodes can also occur in a PCS that does not have a built-in connection unit.

JP 2016-100990 A

SUMMARY OF THE INVENTION It is an object of the present invention to provide a technique capable of determining whether or not a plurality of blocking diodes exist on a current path from a solar cell array.

In order to achieve the above object, a solar cell array inspection system according to one aspect of the present invention includes: a measuring unit for measuring an IV curve of a solar cell array including a plurality of strings; Based on the IV curve, the open-circuit voltage of the solar cell array and the voltage at the inflection point located on the highest voltage side of the IV curve are specified, and the specified open-circuit voltage and the inflection a determination unit that determines whether or not a plurality of blocking diodes are present on a current path between the solar cell array and the measurement unit, based on the voltage difference between the voltages of the points.

That is, if one or more blocking diodes exist on the current path between the solar cell array and the measurement unit that measures the IV curve of the solar cell array, the IV curve measured by the measurement unit A portion with a gentle slope appears in the vicinity of the open-circuit voltage of the V curve. The length of this portion in the voltage axis direction (the voltage difference between the open-circuit voltage of the solar cell array and the voltage at the inflection point located on the highest voltage side of the IV curve) It changes according to the number of blocking diodes existing on the current path between the measurement unit. Therefore, according to the solar cell array inspection system having the above configuration, it is determined whether or not there are a plurality of blocking diodes (in other words, redundant blocking diodes) on the current path between the solar cell array. be able to.

The solar cell array inspection system according to the above aspects of the present invention can be implemented in various forms with different specific configurations. For example, in a solar cell array inspection system, ``the measurement unit connects inputs from each of a plurality of connection terminals in parallel via a blocking diode provided for each connection terminal, and outputs them based on the output of a connection unit, By measuring the IV curve of the solar cell array and comparing the voltage difference with the voltage predetermined according to the forward voltage of the blocking diode in the connection unit, determining whether or not there is a blocking diode different from the blocking diode in the connection unit on the current path between the solar cell array and the measurement unit.

Further, a power conditioner according to an aspect of the present invention includes a plurality of connection terminals for connecting strings, and a blocking diode provided for each connection terminal for input from each of the plurality of connection terminals. a connection unit for outputting by connecting in parallel via a connection unit; and a measurement unit for measuring the IV curve of a solar cell array configured by a plurality of strings connected to the plurality of connection terminals based on the output of the connection unit. Based on the IV curve measured by the measuring unit, the open-circuit voltage of the solar cell array and the voltage at the inflection point located on the highest voltage side of the IV curve are specified, and specified. Based on the voltage difference between the open-circuit voltage and the voltage at the inflection point, it is determined whether or not a plurality of blocking diodes are present on the current path between the solar cell array and the measurement unit. and a determination unit.

Further, in the solar cell array inspection method according to one aspect of the present invention, one or more computers determine the open-circuit voltage of the solar cell array, the I -Specifying step of specifying the voltage of the inflection point located on the highest voltage side of the V curve, and the voltage between the specified open circuit voltage and the voltage of the inflection point specified by the specifying step and determining, based on the difference, whether or not there are a plurality of blocking diodes on a current path between the solar cell array and the IV curve measurement system.

Therefore, even with these techniques (power conditioner, solar cell array inspection method), it is possible to determine whether or not there are a plurality of blocking diodes on the current path to the solar cell array.

According to the present invention, it is possible to determine whether or not a plurality of blocking diodes exist on the current path to the solar cell array.

FIG. 1 is an explanatory diagram of a schematic configuration and usage of a solar cell array inspection system according to one embodiment of the present invention. FIG. 2 is a flowchart of overlapping blocking diode inspection processing performed by the inspection device of the solar cell array inspection system according to the embodiment. FIG. 3 is an explanatory diagram of forward characteristics of a diode. FIG. 4 is an explanatory diagram of the IV curve measured by the IV curve measurement system of the PCS. FIG. 5 is an explanatory diagram of an erroneous connection example of a solar cell array.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below based on the drawings.

FIG. 1 shows a schematic configuration and usage of a solar cell array inspection system according to one embodiment of the present invention.

A solar cell array inspection system according to this embodiment is a system configured by a power conditioner (PCS) 10 and an inspection device 20 .

The PCS 10 has a plurality of (four in the drawing) connection terminals for connecting the strings 31, and the power from the plurality of strings 31 (that is, the solar cell arrays 30) connected to these connection terminals is supplied to the grid 40. and/or a device that supplies the load 45 . Note that the string 31 is a unit in which a plurality of (plurality of) solar panels 32 are connected in series.

As shown in FIG. 1, the PCS 10 comprises a connection unit 16, a power conversion section 11 and a control section 12. FIG. The connection unit 16 is a circuit that connects inputs from each connection terminal in parallel via a blocking diode (backflow prevention diode) 15 provided for each connection terminal and outputs the same. That is, the PCS 10 includes a connection unit 16 having the same function as the connection box.

The power converter 11 is a unit for converting the DC power from the connection unit 16 (that is, the power generated by the solar cell array 30) into AC power. The power converter 11 is composed of a DC/DC converter and a DC/AC inverter, and the PCS 10 includes a current sensor 21 for detecting the input current DCI of the power converter 11 and the power converter 11 A voltage sensor 22 is provided for detecting the input voltage DCV of the . Inside the PCS 10, sensors (not shown) other than the sensors 21 and 22 are also provided.

The control unit 12 is a unit including a processor (CPU, microcontroller, etc.), a gate driver, a communication interface circuit for communicating with an inspection device 20 (details will be described later), and the like. Outputs of various sensors including the current sensor 21 and the voltage sensor 22 are input to the control unit 12, and the control unit 12 performs normal processing and IV curve measurement processing based on information from the various sensors.

The normal processing performed by the control unit 12 is processing for controlling the power conversion unit 11 so that the maximum power is extracted from the solar cell array 30 and converted to desired alternating current.

The IV curve measurement process is a process executed by the control unit 12 when the inspection apparatus 20 instructs to measure the IV curve. During this IV curve measurement process, the control unit 12 controls the power conversion unit 11 to change the operating point voltage (the input voltage DCV of the power conversion unit 11) while changing the input voltage DCV and the input current of the power conversion unit 11. By measuring the DCI, the IV curve of the solar cell array 30 is measured. After providing the measured IV curve (DCV and DCI measurement results) to the inspection apparatus 20, the control unit 12 terminates the IV curve measurement process. In the following, the parts in the PCS 10 that function during the IV curve measurement process (the parts that mainly consist of the control unit 12, the DC/DC converter in the power conversion unit 11, the current sensor 21, and the voltage sensor 22) are described below. , IV curve measurement system 17 .

The inspection apparatus 20 is a computer configured (programmed) so as to perform overlapping blocking diode inspection processing (hereinafter also referred to as overlapping BLD inspection processing) of the procedure shown in FIG. This inspection apparatus 20 can be used as a component of a solar cell array inspection system even if a general computer (laptop computer, desktop computer, etc.) is programmed to be capable of executing redundant BLD inspection processing. It may be a device manufactured in Also, the inspection device 20 may be connected to the PCS 10 via a cable such as a USB cable, or may be connected to the PCS 10 via a communication network (such as the Internet).

The duplicate BLD inspection process is a process executed by the inspection device 20 (the processor within the inspection device 20) when a predetermined operation is performed on an input device (keyboard, etc.) included in the inspection device 20. FIG. Note that this overlap BLD inspection process is a process for inspecting whether or not there is an extra blocking diode between the solar cell array 30 and the PCS 10 . Therefore, the redundant BLD inspection process is normally performed after changing the configuration of the solar cell array 30 or after replacing the power conditioner with the PCS 10 .

The contents of the overlap BLD inspection process (FIG. 2) will be described below in order of the procedure of the overlap BLD inspection process and the principle of the overlap BLD inspection process.

Processing Procedure of Duplicate BLD Inspection Processing As shown in the figure, the inspection apparatus 20 that has started the duplicate BLD inspection processing first instructs the PCS 10 (control unit 12) to measure the IV curve (step S101). Then, according to the instruction, the inspection device 20 acquires the processing result of the IV curve measurement process executed by the control unit 12 (that is, the measurement result of the IV curve) from the PCS 10 (step S101).

The inspection device 20, which has acquired the IV curve of the solar cell array 30 from the PCS 10, determines the open-circuit voltage Voc of the solar cell array 30 and the IV curve located on the highest voltage side based on the IV curve. A voltage Vbld at an inflection point is specified (step S102). Also, the inspection device 20 calculates Vref (=Voc-Vbld), which is the voltage difference between those voltages (step S102).

After that, the inspection device 20 determines whether or not the voltage difference Vref is higher than the threshold voltage (step S103). Here, the threshold voltage is larger than the forward voltage Vf of the blocking diode 15 used in the connection unit 16, and is the order of Vf and a general blocking diode (or a blocking diode with the smallest forward voltage). It is a value (voltage value) predetermined to be smaller than the sum of the direction voltage Vf.

If Vref is equal to or lower than the threshold voltage (step S103; NO), inspection device 20 outputs inspection result information indicating that there is no excess blocking diode between solar cell array 30 and PCS 10. (step S104). The process performed by the inspection apparatus 20 according to the present embodiment in step S104 is a process of displaying inspection result information on the screen of the display. However, the processing of step S104 may be other processing capable of notifying the user of the inspection result information, for example, processing of outputting the inspection result information by voice, or processing of printing the inspection result information.

On the other hand, if Vref exceeds the threshold voltage (step S103; YES), inspection device 20 outputs inspection result information indicating that there is no extra blocking diode between solar cell array 30 and PCS 10. (step S105).

After finishing the process of step S104 or S105, the inspection apparatus 20 ends this double BLD inspection process.

- Principle of redundant BLD inspection process The redundant BLD inspection process described above inspects whether or not an extra blocking diode exists between the solar cell array 30 and the PCS 10 based on the following principle.

General diodes have forward characteristics as shown in FIG. It has a forward characteristic that a large current flows. The output of the solar cell array 30 is input to the IV curve measurement system 17 via the connection unit 16 (blocking diode 15). Therefore, due to the influence of the forward characteristics of the blocking diode 15, the IV curve of the solar cell array 30 measured by the IV curve measurement system 17 has an open-circuit voltage Voc A portion with a gentle slope appears in the vicinity.

The length of this portion (hereinafter referred to as the flat portion) in the voltage axis direction, that is, between the open circuit voltage Voc and the voltage Vbld at the inflection point located on the highest voltage side of the IV curve Voltage difference Vref changes according to the number of blocking diodes 15 present on the current path between solar cell array 30 and IV curve measurement system 17 . More specifically, the voltage difference Vref has a value substantially equal to the total sum of the forward voltages Vf of the blocking diodes 15 existing between the solar cell array 30 and the IV curve measuring system 17 . Note that Vf is about 1 V, and Voc of the solar cell array 30 is usually about 200 V to 300 V. Therefore, the flat portion that actually appears in the IV curve of the solar cell array 30 is shown in FIG. It's much smaller than anything else.

The relationship between the voltage difference Vref and the number of blocking diodes 15 between the solar cell array 30 and the IV curve measurement system 17 is as described above. Therefore, when each string 31 of the solar cell array 30 is directly connected to the PCS 10 (see FIG. 1), the voltage difference Vref is approximately the same value as the forward voltage Vf of the blocking diode 15 in the connection unit 16. becomes. On the other hand, when the solar cell array 30 is connected to the PCS 10 via the junction box 18 as shown in FIG. The value is approximately doubled (approximately the sum of the forward voltages Vf of the two blocking diodes 15 in the connection unit 16 and the connection box 18).

Therefore, the voltage difference Vref is greater than the forward voltage Vf of the blocking diode 15 in the connection unit 16, and the forward voltage Vf of the common blocking diode (or the blocking diode with the smallest forward voltage) and Vf (that is, the above-described threshold voltage) makes it possible to check (determine) whether or not an extra blocking diode exists between the solar cell array 30 and the PCS 10 .

As described above, the solar cell array inspection system according to the present embodiment provides the user (such as the installer of the solar cell array 30) with the possibility that an extra blocking diode exists between the solar cell array 30 and the PCS 10. You can let us know if you have it or not. Therefore, according to the solar cell array inspection system according to the present embodiment, it is possible to prevent the solar cell array system from being continuously used in a state where power generation loss is large due to the presence of extra blocking diodes.

<<Modification>>
Various modifications are possible for the solar cell array inspection system according to the embodiment described above. For example, the solar cell array 30 may be connected to a PCS that does not incorporate the connection unit 16 through two or more blocking diodes. Therefore, the PCS 10 of the photovoltaic array inspection system may be changed to a PCS that does not incorporate the connection unit 16 .

The control unit 12 of the PCS 10 may be given the function of the inspection device 20 . Also, it is a matter of course that the specific circuit configuration of the PCS 10 and the specific processing procedure of the duplicate BLD inspection process may be different from those described above.

<<Note>>
(1) a measuring unit (17) for measuring an IV curve of a solar cell array (30) including a plurality of strings (31);
Based on the IV curve measured by the measuring unit (17), the open-circuit voltage of the solar cell array (30) and the voltage at the inflection point located on the highest voltage side of the IV curve and based on the voltage difference between the identified open-circuit voltage and the voltage at the inflection point, a plurality of current paths between the solar cell array (30) and the measurement unit (17) a determination unit (20) for determining whether or not a blocking diode (15) exists;
A solar cell array inspection system comprising:

(2) a plurality of connection terminals, each for connecting a string (31);
a connection unit (18) for connecting inputs from each of the plurality of connection terminals in parallel via a blocking diode (15) provided for each connection terminal and outputting the input;
a measurement unit (17) for measuring an IV curve of a solar cell array composed of a plurality of strings connected to the plurality of connection terminals, based on the output of the connection unit (18);
Based on the IV curve measured by the measuring unit (17), the open-circuit voltage of the solar cell array (30) and the voltage at the inflection point located on the highest voltage side of the IV curve and a plurality of blocking diodes ( 15), a determination unit (12) for determining whether or not there exists;
A power conditioner comprising:

(3) one or more computers
Based on the IV curve of a solar cell array (30) including a plurality of strings (31), the open-circuit voltage of the solar cell array (30) and the variable located on the highest voltage side of the IV curve. an identification step (S102) of identifying the voltage at the bending point;
Current between the solar cell array (30) and the IV curve measurement system based on the voltage difference between the open-circuit voltage and the inflection point voltage specified in the specifying step (S102) a step of determining whether a plurality of blocking diodes (15) are present on the path (S103);
A solar cell array inspection method characterized by:

REFERENCE SIGNS LIST 10 power conditioner 11 power conversion unit 12 control unit 15 blocking diode 16 connection unit 18 junction box 17 IV curve measurement system 20 inspection device 21 current sensor 22 voltage sensor 30 solar cell array 31 string 32 solar cell panel 40 system 45 load

Claims (4)

a measuring unit for measuring an IV curve of a solar cell array including a plurality of strings;
Based on the IV curve measured by the measuring unit, the open-circuit voltage of the solar cell array and the voltage at the inflection point located on the highest voltage side of the IV curve are specified, and specified. Based on the voltage difference between the open-circuit voltage and the voltage at the inflection point, it is determined whether or not a plurality of blocking diodes are present on the current path between the solar cell array and the measurement unit. a determination unit;
with
The determination unit is
The voltage difference is a threshold voltage set based on the forward voltage, which is the voltage at which the ratio of the current increase to the voltage increase switches to a predetermined value or more when the voltage of a predetermined blocking diode is increased from 0V. compared to
A solar cell array inspection system, wherein when the voltage difference is equal to or less than the threshold voltage, it is determined that the plurality of blocking diodes do not exist. The measurement unit measures the IV curve of the solar cell array based on the output of a connection unit that outputs inputs from each of a plurality of connection terminals connected in parallel via a blocking diode provided for each connection terminal. measure and
The determination unit compares the voltage difference with the threshold voltage predetermined according to the forward voltage of the blocking diode in the connection unit, thereby determining the voltage difference between the solar cell array and the measurement unit. determining whether there is a blocking diode different from the blocking diode in the connection unit on the current path of
The solar cell array inspection system according to claim 1, characterized in that: a plurality of connection terminals for connecting strings, respectively;
a connection unit that connects inputs from each of the plurality of connection terminals in parallel via a blocking diode provided for each connection terminal and outputs the input;
a measurement unit that measures an IV curve of a solar cell array configured by a plurality of strings connected to the plurality of connection terminals based on the output of the connection unit;
Based on the IV curve measured by the measuring unit, the open-circuit voltage of the solar cell array and the voltage at the inflection point located on the highest voltage side of the IV curve are specified and specified. Based on the voltage difference between the open-circuit voltage and the voltage at the inflection point, it is determined whether or not a plurality of blocking diodes are present on the current path between the solar cell array and the measurement unit. a determination unit;
with
The determination unit is
The voltage difference is a threshold voltage set based on the forward voltage, which is the voltage at which the ratio of current increase to voltage increase switches to a predetermined value or more when the voltage of a predetermined blocking diode is increased from 0V. compared to
A power conditioner that determines that the plurality of blocking diodes do not exist when the voltage difference is equal to or less than the threshold voltage. one or more computers
Based on an IV curve of a solar cell array including a plurality of strings, identifying the open-circuit voltage of the solar cell array and the voltage at the inflection point located on the highest voltage side of the IV curve. When,
Based on the voltage difference between the specified open-circuit voltage and the voltage at the inflection point, a plurality of blocking diodes exist on the current path between the solar cell array and the IV curve measurement system. a step of determining whether there is
and run
In determining whether the plurality of blocking diodes are present,
The voltage difference is a threshold voltage set based on the forward voltage, which is the voltage at which the ratio of the current increase to the voltage increase switches to a predetermined value or more when the voltage of a predetermined blocking diode is increased from 0V. compared to
A method for inspecting a solar cell array, wherein it is determined that the plurality of blocking diodes do not exist when the voltage difference is equal to or less than the threshold voltage.

Images