A photovoltaic module dust occlusion detection system

Abstract

The present invention discloses a photovoltaic module dust shielding detection system, comprising a photovoltaic module group to be tested, a control module, a data acquisition module and a central processing module; the photovoltaic module group to be tested comprises a group of standard photovoltaic modules that are regularly cleaned and a group of comparison photovoltaic modules that are not cleaned; the standard photovoltaic module comprises a first closed loop that can short-circuit a first current source of the standard photovoltaic module, and the comparison photovoltaic module comprises a second closed loop that can short-circuit a second current source of the comparison photovoltaic module; the control module is electrically connected to the photovoltaic module group to be tested; the data acquisition module is respectively connected to the first closed loop and the second closed loop; the central processing module is used to send a control instruction to the control module, and calculate the difference percentage between the first current source and the second current source within a set time. The present invention determines the influence of dust on the power generation efficiency of the photovoltaic module, compromises the cleaning fee and the power generation efficiency, and makes the cleaning fee and the power generation efficiency reach the best economic point.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of photovoltaic power generation technology, and in particular to a photovoltaic module dust occlusion detection system. Background Art

[0002] As a common way to utilize solar energy resources, solar photovoltaic power generation systems have been widely used in life and production. The efficiency of a photovoltaic power generation system is the core factor in measuring the performance of a photovoltaic power station. There are many factors that affect the efficiency of a photovoltaic power generation system, among which dust blocking is one of the most important factors. Dust adheres to the surface of photovoltaic modules, which will block the light, affect the absorption of sunlight by photovoltaic modules, and reduce the power generation efficiency.

[0003] In order to reduce the impact of dust on the efficiency of photovoltaic power generation systems, it is necessary to regularly clean the dust on the surface of photovoltaic modules, but cleaning will incur certain costs. If the cleaning interval is too long, dust will be generated on the surface of photovoltaic modules, affecting the power generation efficiency of the photovoltaic power generation system; frequent cleaning will cause waste of water resources and increase the cost of power generation. In addition, since photovoltaic power generation systems are located outdoors, they are affected by multiple factors such as geography, climate, wind and sand, rain, and atmospheric humidity, making it difficult to formulate effective and reasonable cleaning intervals. Summary of the invention

[0004] The present invention provides a photovoltaic module dust shielding detection system, which can quantitatively calculate the influence of dust shielding on the power generation efficiency of the photovoltaic module, so that the cleaning cost and the power generation efficiency reach the best economic point.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] The embodiment of the present invention provides a photovoltaic module dust shielding detection system, including a photovoltaic module group to be tested, a control module, a data acquisition module and a central processing module;

[0007] The photovoltaic assembly group to be tested includes a group of standard photovoltaic assembly groups that are regularly cleaned and a group of comparison photovoltaic assembly groups that are not cleaned, the standard photovoltaic assembly group includes at least one standard photovoltaic assembly, and the comparison photovoltaic assembly group includes at least one comparison photovoltaic assembly; the standard photovoltaic assembly includes a first closed loop of a first current source that can short-circuit the standard photovoltaic assembly, and the comparison photovoltaic assembly includes a second closed loop of a second current source that can short-circuit the comparison photovoltaic assembly;

[0008] The control module is electrically connected to the photovoltaic assembly group to be tested, and is used to control the on and off of each of the first closed loop and the second closed loop according to the control instruction sent by the central processing module;

[0009] The data acquisition module is connected to the first closed loop and the second closed loop respectively, and is used to collect data of the first current source and the second current source when the first closed loop and the second closed loop are turned on, and send data of the first current source and the second current source to the central processing module;

[0010] The central processing module is used to send a control instruction to the control module, and calculate the difference percentage between the first current source and the second current source within a set time according to the data of the first current source and the second current source sent by the data acquisition module.

[0011] Furthermore, it also includes a first wireless communication module and a second wireless communication module, the first wireless communication module is electrically connected to the control module and the data acquisition module respectively, the second wireless communication module is electrically connected to the central processing module, and the central processing module is wirelessly connected to the control module and the data acquisition module respectively through the second wireless communication module and the first wireless communication module.

[0012] Further, the control module includes a remote terminal control unit and at least two groups of switch control units, and a first input end of the remote terminal control unit is electrically connected to the first wireless communication module for receiving the control instruction;

[0013] The switch control unit includes a relay and a contactor; the first output end of the remote terminal control unit is electrically connected to the control end of each relay, so as to control the closing of the normally open end of each relay; the normally open end of each relay is connected in series with the coil power supply circuit of the contactor in the group, so as to close the contactor when the normally open end is closed; each contactor is connected in series with the corresponding first closed circuit and the second closed circuit, so as to conduct the corresponding first closed circuit and the second closed circuit when the contactor is closed.

[0014] Furthermore, the data acquisition module includes at least two Hall current sensors, each of which is connected in series to the corresponding first closed loop and second closed loop through two current measuring ends, and the current output end of each Hall current sensor is electrically connected to the second input end of the remote terminal control unit to output the data of the first current source and the second current source through the second output end of the remote terminal control unit.

[0015] Furthermore, each of the Hall current sensors is also used to convert the detected first current source and the second current source into corresponding standard currents, wherein the standard current is 4-20 mA.

[0016] Furthermore, the remote terminal control unit includes an analog-to-digital converter, and the analog-to-digital converter is used to convert the received standard current into a digital current signal.

[0017] Further, the central processing module includes a host computer and a background computing unit, the host computer is electrically connected to the second wireless communication module, and is used to send the control instruction to the control module according to a preset period, display, store and analyze the received data of the first current source and the second current source, and transmit the analyzed data of the first current source and the second current source to the background computing unit via the Internet;

[0018] The background calculation unit is used to calculate the difference percentage between the first current source and the second current source within a set time according to the analyzed data of the first current source and the second current source.

[0019] Furthermore, the preset period is 5 minutes and the set time is 1 day.

[0020] Further, the standard photovoltaic component group includes three standard photovoltaic components, and the comparison photovoltaic component group includes three comparison photovoltaic components.

[0021] Furthermore, the control module, the data acquisition module and the first wireless communication module are arranged in a control box at the photovoltaic component group to be tested.

[0022] Furthermore, it also includes a power supply module for supplying power to the control module and the data acquisition module.

[0023] The control module of the present invention controls the first closed loop and the second closed loop to be turned on according to the control instruction of the central processing module, and realizes the measurement of the first current source of the standard photovoltaic module and the second current source of the comparison photovoltaic module through the data acquisition module. The central processing module calculates the difference percentage between the first current source and the second current source according to the data of the first current source and the second current source, determines the influence of dust on the power generation efficiency of the photovoltaic module, and then compromises the cleaning fee of cleaning the photovoltaic module and the power generation efficiency of the photovoltaic module, so that the cleaning fee and the power generation efficiency reach the best economic point, that is, under the premise of ensuring the power generation efficiency, the best dust cleaning effect is achieved with the least cleaning fee. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a structural block diagram of a photovoltaic module dust occlusion detection system provided by an embodiment of the present invention;

[0025] Figure 2 is a schematic diagram of the structure of a photovoltaic module to be tested provided by an embodiment of the present invention;

[0026] Figure 3is a structural block diagram of a first wireless communication module and a second wireless communication module provided by an embodiment of the present invention;

[0027] Figure 4 is a structural block diagram of a control module provided by an embodiment of the present invention;

[0028] Figure 5 is a circuit diagram of a first closed loop provided by an embodiment of the present invention;

[0029] Figure 6 It is a structural block diagram of a Hall current sensor, a remote terminal control unit and a photovoltaic module to be tested provided by an embodiment of the present invention;

[0030] Figure 7 is a structural block diagram of a central processing module provided by an embodiment of the present invention;

[0031] Figure 8 It is a specific structural block diagram of the photovoltaic module dust occlusion detection system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0033] Figure 1 This is a structural block diagram of a photovoltaic module dust occlusion detection system provided by an embodiment of the present invention. Figure 1 , the structural block diagram includes a photovoltaic module group 2 to be tested, a control module 3, a data acquisition module 4 and a central processing module 1;

[0034] Figure 2 This is a schematic diagram of the structure of the photovoltaic module to be tested provided by an embodiment of the present invention. Figure 1 and Figure 2 The photovoltaic assembly group 2 to be tested includes a group of standard photovoltaic assembly groups that are regularly cleaned and a group of comparison photovoltaic assembly groups that are not cleaned, the standard photovoltaic assembly group includes at least one standard photovoltaic assembly 21, and the comparison photovoltaic assembly group includes at least one comparison photovoltaic assembly 23; the standard photovoltaic assembly 21 includes a first closed loop 22 of a first current source that can short-circuit the standard photovoltaic assembly 21, and the comparison photovoltaic assembly 23 includes a second closed loop 24 of a second current source that can short-circuit the comparison photovoltaic assembly 23; the control module 3 is electrically connected to the photovoltaic assembly group 2 to be tested, and is used to control the on-off of each first closed loop 22 and the second closed loop 24 according to the control instruction sent by the central processing module 1;

[0035] The data acquisition module 4 is connected to the first closed loop 22 and the second closed loop 24 respectively, and is used to collect data of the first current source and the second current source when the first closed loop 22 and the second closed loop 24 are turned on, and send data of the first current source and the second current source to the central processing module 1;

[0036] The central processing module 1 is used to send a control instruction to the control module 3, and calculate the difference percentage between the first current source and the second current source within a set time according to the data of the first current source and the second current source sent by the data acquisition module 4.

[0037] Optionally, the number of standard photovoltaic modules 21 and comparison photovoltaic modules 23 may be the same or different. Exemplarily, if the number of standard photovoltaic modules 21 is less than the comparison photovoltaic modules 23, all the comparison photovoltaic modules 23 may be selected for calculation, or the comparison photovoltaic modules 23 having the same number as the standard photovoltaic modules 21 may be selected for calculation. Exemplarily, if the central processing module 1 analyzes that there are obviously erroneous data in the standard photovoltaic modules 21 or the comparison photovoltaic modules 23, the abnormal data may be filtered out before calculation.

[0038] The control module of the embodiment of the present invention controls the first closed loop and the second closed loop to be turned on according to the control instruction of the central processing module, and realizes the measurement of the first current source of the standard photovoltaic module and the second current source of the comparison photovoltaic module through the data acquisition module. The central processing module calculates the difference percentage between the first current source and the second current source based on the data of the first current source and the second current source, determines the influence of dust on the power generation efficiency of the photovoltaic module, and then compromises the cleaning fee of cleaning the photovoltaic module and the power generation efficiency of the photovoltaic module, so that the cleaning fee and the power generation efficiency reach the best economic point, that is, under the premise of ensuring the power generation efficiency, the best dust cleaning effect is achieved with the least cleaning fee.

[0039] The photovoltaic module dust obstruction detection system provided in the embodiment of the present invention directly collects the short-circuit current of two groups of photovoltaic modules as the basis for comparison, rather than comparing by power generation. This avoids the superimposed influence of other factors such as current loss in cables, photovoltaic array series-parallel mismatch, inverter efficiency, etc., and the calculated power generation efficiency value of the photovoltaic module to be tested is more reliable.

[0040] Figure 3 is a structural block diagram of a first wireless communication module and a second wireless communication module provided by an embodiment of the present invention. Figure 3The photovoltaic module dust shielding detection system provided by the embodiment of the present invention further includes a first wireless communication module 51 and a second wireless communication module 52. The first wireless communication module 51 is electrically connected to the control module 3 and the data acquisition module 4 respectively, and the second wireless communication module 52 is electrically connected to the central processing module 1. The central processing module 1 is wirelessly connected to the control module 3 and the data acquisition module 4 respectively through the second wireless communication module 52 and the first wireless communication module 51. It should be noted that the data acquisition module is not directly connected to the first wireless communication module 51, but is first connected to the control module 4 by wire, and then connected to the central processing module 1 through the control module 4.

[0041] Normally, in order to ensure the photoelectric conversion efficiency of the photovoltaic module, the photovoltaic module needs to be placed outdoors under conditions with good sunlight, while the central processing module 1 is generally composed of a single-chip microcomputer or a computer, etc., and is usually placed in an indoor environment. The photovoltaic module works under various complex geological conditions. The use of wired communication will limit the scope of use of the photovoltaic module dust occlusion detection system provided by the embodiment of the present invention. In order to ensure that the central processing module 1 can normally send instructions to the control module 3 and receive data fed back by the data acquisition module 4, it is necessary to use a first wireless communication module 51 and a second wireless communication module 52 to connect the central processing module 1 and the control module 3 and the data acquisition module 4.

[0042] Optionally, the first wireless communication module 51 and the second wireless communication module 52 can use Lora (Long Range, long-range) wireless communication technology. Compared with other industrial wireless technologies, this technology is suitable for the long-distance transmission of small amounts of data in complex environments. The present invention also uses efficient cyclic interleaving error correction coding, which has good anti-interference and sensitivity and strong penetration. Since the distance between the photovoltaic module and the central processing module is relatively far, it is necessary to select a reliable, anti-interference, and stable wireless communication technology, which does not require on-site wiring and is convenient for construction and later operation and maintenance.

[0043] Figure 4 This is a structural block diagram of a control module provided by an embodiment of the present invention. Figure 4 The control module 3 includes a remote terminal control unit (RTU) 31 and at least two switch control units 32. The first input terminal 311 of the remote terminal control unit 31 is electrically connected to the first wireless communication module 51 for receiving control instructions.

[0044] Among them, the switch control unit 32 includes a relay 32 and a contactor 33; the first output end of the remote terminal control unit 31 is electrically connected to the control end of each relay 32, so as to control the closing of the normally open end of each relay 32; the normally open end of each relay 32 is connected in series with the coil power supply circuit of the contactor 33 in the group, so as to close the contactor 33 when the normally open end is closed; each contactor 33 is respectively connected in series to the corresponding first closed loop 22 and the second closed loop 24, so as to conduct the corresponding first closed loop 22 and the second closed loop 24 when the contactor 33 is closed.

[0045] The control command transmitted from the first wireless communication module 51 enters the remote terminal control unit 31 through the input end of the remote terminal control unit 31, and is transmitted from the first output end of the remote terminal control unit 31 to each relay 32, and finally realizes the control of the standard photovoltaic module 21 or the comparison photovoltaic module 23. Exemplarily, taking the standard photovoltaic module as an example, the control signal output from the first output end of the remote terminal control unit 31 can control the normally open end of the relay 32 to close, and then the contactor 33 is attracted, the first closed loop 22 is turned on, and the control of the standard photovoltaic module 21 is realized. The principle of the control module 3 controlling the conduction of the second closed loop 24 is the same as this, and it will not be repeated.

[0046] Since the signals outputted from the first input end of the remote terminal control unit 31 to each relay are the same, the first input end of the remote terminal control unit 31 can be a plurality of ports corresponding one-to-one to the relays 32, or it can be a single port. After the control instruction is outputted from the first input end of the remote terminal control unit 31, it is outputted to each relay 32 respectively.

[0047] It should be noted that the photovoltaic module dust occlusion detection system provided in the embodiment of the present invention can also use wired communication to send the control instructions of the central processing module 1 to the control module 3, and transmit the data of the photovoltaic module 2 to be tested back to the central processing module 1.

[0048] In addition, since the difference percentage between the first current source and the second current source requires the current data of the standard photovoltaic module 21 and the comparison photovoltaic module 22 at the same time, it is meaningless to measure the current data of the standard photovoltaic module 21 or the comparison photovoltaic module 22 alone, so the control signals output by each first output terminal 312 of the remote terminal control unit 31 at any time are the same. The number of ports of the first output terminal 312 of the remote terminal control unit 31 corresponds to the number of relays 321 and the number of contactors 322.

[0049] Figure 5 is a circuit diagram of a first closed loop provided by an embodiment of the present invention, Figure 6is a structural block diagram of the Hall current sensor, the remote terminal control unit and the photovoltaic module to be tested provided by the embodiment of the present invention. Figure 5 and 6 The data acquisition module 4 includes at least two Hall current sensors 41, each Hall current sensor 41 is connected in series to the corresponding first closed loop 22 and second closed loop 24 through two current measuring ends, and the current output end of each Hall current sensor 41 is electrically connected to the second input end of the remote terminal control unit 31 to output the data of the first current source and the second current source through the second output end of the remote terminal control unit 31.

[0050] It can be understood that the difference between the standard photovoltaic module group and the comparison photovoltaic module group is only the different dust deposition time on the surface, and their internal circuit structures are exactly the same.

[0051] The Hall current sensor measures the current in the conductor based on the magnitude of the magnetic field generated around the current-carrying conductor. It is a non-contact current measurement method, has little effect on the current of the measured circuit, and the measurement result is reliable. The Hall current sensor also has the advantages of accurate and reliable measurement results, fast response speed, and wide measurement range. Therefore, the Hall current sensor is selected to measure the current of the first closed loop 22 and the second closed loop 24. In practical applications, each of the first closed loop 22 or the second closed loop 24 includes a Hall current sensor 41.

[0052] The Hall current sensor 41 sends the collected data of the first current source and the second current source to the remote terminal control unit 31 , and further transmits the collected data to the central processing module 1 through the first wireless communication unit 51 and the second wireless communication module 52 .

[0053] Optionally, the second input end of the remote terminal control unit 31 includes a plurality of input ports corresponding one-to-one to the Hall current sensors 41 , and is used to receive the standard current collected by each Hall current sensor.

[0054] Furthermore, each Hall current sensor 41 is also used to convert the detected first current source and second current source into corresponding standard currents, wherein the standard current is 4-20 mA. The advantage of using industrial standard currents is that it can avoid problems such as voltage drop and noise interference caused by long-distance signal transmission, and it is also convenient for the central processing module 1 to store and analyze.

[0055] Furthermore, the remote terminal control unit 31 includes an analog-to-digital converter, which is used to convert the received standard current into a digital current signal. The current output from the current output end of the Hall current sensor 41 is a standard current corresponding to the current in the first closed loop 21 or the second closed loop 22, which is an analog current. In order to facilitate transmission and subsequent data processing and calculation, the standard current needs to be converted into a digital current signal.

[0056] Figure 7 is a structural block diagram of the central processing module provided by an embodiment of the present invention. Figure 7 The central processing module 1 includes a host computer 11 and a background computing unit 12. The host computer 11 is electrically connected to the second wireless communication module 52, and is used to send control instructions to the control module 3 according to a preset period, display, store and analyze the received data of the first current source and the second current source, and transmit the analyzed data of the first current source and the second current source to the background computing unit 12 via the Internet; the background computing unit 12 is used to calculate the difference percentage between the first current source and the second current source within a set time according to the analyzed data of the first current source and the second current source.

[0057] The upper computer 11 and the background calculation unit 12 can calculate the difference percentage between the first current source and the second current source, and decide whether to clean the comparison photovoltaic assembly group according to the relationship between the difference percentage and the cleaning cost. For example, when the difference percentage between the first current source and the second current source is small, it indicates that the dust has little effect on the power generation efficiency of the comparison photovoltaic assembly group, and the cleaning cost is high at this time, so it can be chosen not to clean the comparison photovoltaic assembly group; but when the difference percentage between the first current source and the second current source is large, it indicates that the dust has seriously affected the power generation efficiency of the comparison photovoltaic assembly group, so it is necessary to clean the comparison photovoltaic assembly group in time to avoid the photovoltaic assembly group from having too low power generation efficiency due to the presence of dust.

[0058] Optionally, the host computer 11 may be a single chip microcomputer, an industrial computer or a computer, and the background computing unit 12 may be a computer. Alternatively, the host computer 11 and the background computing unit 12 may also be the same computer.

[0059] Optionally, the host computer 11 can adopt an IPC-610H industrial computer, and monitor and control the photovoltaic module 2 under test by using Scada software to realize the automatic closing and opening of the short-circuit current loop contactor of the photovoltaic module 2 under test. It can not only obtain the short-circuit current of the photovoltaic module, but also avoid the overheating problem of the short-circuit current loop of the photovoltaic module caused by the photovoltaic module being in a short-circuit state for a long time, thereby ensuring the safety of system use.

[0060] Furthermore, the preset period and setting time can be set according to actual conditions. If the photovoltaic module is installed in a desert or other environment with strong wind and sand, the preset period and setting time can be shortened; if the amount of dust in the environment where the photovoltaic module is located is relatively small, the preset period and setting time can be extended. For example, the preset period is 5 minutes and the setting time is 1 day.

[0061] Furthermore, the standard photovoltaic module group includes three standard photovoltaic modules 21, and the comparison photovoltaic module group includes three comparison photovoltaic modules 23. It should be noted that the selected three standard photovoltaic modules and three comparison photovoltaic modules are six modules of the same specification produced by the same manufacturer. Optionally, generally speaking, the number of standard photovoltaic module groups and comparison photovoltaic module groups does not need to be too large. In actual operation, it is only necessary to select a few photovoltaic modules from the same photovoltaic power plant as the standard combination comparison group. By testing the difference percentage of the power supply of the standard group and the comparison group, the dust shielding degree of the photovoltaic modules of the entire electric field can be known. Optionally, the comparison group can also select more groups of photovoltaic modules.

[0062] Exemplarily, the embodiment of the present invention takes three groups of standard photovoltaic modules and three groups of comparative modules as examples to further illustrate the calculation method of the difference percentage between the first current source and the second current source. i It represents the short-circuit current of the second current source of the ith PV module at a certain moment, IB i represents the short-circuit current of the first current source of the i-th standard photovoltaic module at the same time, and α represents the difference percentage between the first current source and the second current source, where i is 1, 2, or 3.

[0063] Furthermore, assuming that n sets of data are collected in a certain day, where n is a positive integer, and θ represents the average value of the difference percentage of the short-circuit current at all sampling moments in this day, then When calculating the power generation efficiency of standard PV modules and comparison PV modules, you can choose data collected at a certain moment as the basis for calculation, or you can choose average data within a certain period of time as the basis for calculation.

[0064] Furthermore, the control module 3, the data acquisition module 4 and the first wireless communication module 51 are arranged in a control box at the photovoltaic assembly group 2 to be tested. Such an arrangement is convenient for installation and construction by the staff, and the control box can also protect the control module 3, the data acquisition module 4 and the first wireless communication module 51. Optionally, the control box is located near the photovoltaic assembly to be tested.

[0065] Furthermore, the photovoltaic module dust shielding detection system provided by the embodiment of the present invention also includes a power module for supplying power to the control module 3 and the data acquisition module 4. Optionally, the power module can output a 24V power supply, and the power module needs to continuously supply power to the control module 3 and the data acquisition module 4, so as to ensure that the control module 3 and the data acquisition module 4 can always be in a standby state, and ensure that the control module 3 and the data acquisition module 4 can work according to the received control instructions. Exemplarily, the AC22V power supply can be converted into a 24V DC power supply through a small transformer to supply power to the photovoltaic module dust shielding detection system.

[0066] Figure 8 This is a specific structural block diagram of the photovoltaic module dust occlusion detection system provided by the embodiment of the present invention. Figure 8 , the control instruction sent from the host computer 11 is sent to the first wireless communication module 51 in a wireless manner through the second wireless communication module 52, the remote terminal control unit 31 receives the control instruction from the first wireless communication module 51 and sends it to the relay 32, the relay 32 controls the contactor 33 to attract, so as to control the first closed loop and the second closed loop to be turned on; the Hall current sensor 41 converts the collected data of the first current source of the first closed loop and the second current source of the second closed loop into a standard current, and then converts the standard current into a digital current signal through the analog-to-digital converter of the remote terminal control unit 31, and then transmits it back to the host computer 11 through the first wireless communication module 51 and the second wireless communication module 52 in turn for display, storage and analysis, and transmits the analyzed data of the first current source and the second current source to the background calculation unit 12 through the Internet. The background calculation unit 12 can calculate the difference percentage between the first current source and the second current source.

[0067] For example, Table 1 gives a set of current difference percentages between standard photovoltaic modules and comparison photovoltaic modules, and the data is from a 100MW large-scale ground photovoltaic power station. As can be seen from Table 1, as the number of statistical days increases, the percentage of the power generation efficiency of the standard photovoltaic modules higher than that of the comparison photovoltaic modules gradually increases, indicating that as the dust on the comparison photovoltaic modules increases, the power generation efficiency of the comparison photovoltaic modules gradually decreases; when the number of statistical days is 25, the power generation efficiency of the standard photovoltaic modules is 16.03% higher than that of the comparison photovoltaic modules.

[0068] It should be noted that the results in Table 1 are calculated based on the average values ​​of all data of the standard PV modules and the comparison PV modules on the same day.

[0069] It should be noted that when the statistical day in Table 1 is 0, it does not mean that the standard PV modules and the comparison PV modules were cleaned at the same time on the same day. In fact, on September 26, 2017, the staff cleaned the standard PV modules and the comparison PV modules at the same time. After that, only the standard PV modules were cleaned every day, and the comparison PV modules were not cleaned.

[0070] Furthermore, taking October 7 and October 8, 2017 as examples, analyzing the data of these two days, it can be found that the percentage difference on October 8 is smaller than that on October 7, which means that the amount of dust on the comparison photovoltaic module on October 8 is less than that on October 7. This may be due to a small amount of rainfall on October 7. The amount of dust on the surface of the photovoltaic module in the outdoor state is not only related to the length of the deposition time, but also related to the weather conditions in a certain period of time. However, by analyzing the entire Table 1, it can be found that compared with the standard photovoltaic module, as the number of statistical days increases, the power generation efficiency of the comparison photovoltaic module shows a downward trend, which indicates that the amount of dust on the surface of the comparison photovoltaic module is gradually increasing.

[0071] Decide when to clean the PV panels based on the loss of power generation due to dust and the cost of cleaning the panels: when the loss of power generation is less than the cost of cleaning the PV panels, you can choose not to clean the PV panels for the time being; when the loss of power generation is greater than the cost of cleaning the PV panels, you can choose to clean the PV panels as soon as possible to improve power generation efficiency.

[0072]

[0073]

[0074] Table 1

[0075] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A photovoltaic module dust occlusion detection system, characterized in that: It includes a photovoltaic module group to be tested, a control module, a data acquisition module and a central processing module; The photovoltaic assembly group to be tested includes a group of standard photovoltaic assembly groups that are regularly cleaned and a group of comparison photovoltaic assembly groups that are not cleaned, the standard photovoltaic assembly group includes at least one standard photovoltaic assembly, and the comparison photovoltaic assembly group includes at least one comparison photovoltaic assembly; the standard photovoltaic assembly includes a first closed loop of a first current source that can short-circuit the standard photovoltaic assembly, and the comparison photovoltaic assembly includes a second closed loop of a second current source that can short-circuit the comparison photovoltaic assembly; The control module is electrically connected to the photovoltaic assembly group to be tested, and is used to control the on and off of each of the first closed loop and the second closed loop according to the control instruction sent by the central processing module; The data acquisition module is connected to the first closed loop and the second closed loop respectively, and is used to collect data of the first current source and the second current source when the first closed loop and the second closed loop are turned on, and send data of the first current source and the second current source to the central processing module; The central processing module is used to send a control instruction to the control module, and calculate the difference percentage between the first current source and the second current source within a set time according to the data of the first current source and the second current source sent by the data acquisition module; It also includes a first wireless communication module and a second wireless communication module, the first wireless communication module is electrically connected to the control module and the data acquisition module respectively, the second wireless communication module is electrically connected to the central processing module, and the central processing module is wirelessly connected to the control module and the data acquisition module respectively through the second wireless communication module and the first wireless communication module; It also includes a power supply module for supplying power to the control module and the data acquisition module.

2. The photovoltaic module dust occlusion detection system according to claim 1, characterized in that: The control module includes a remote terminal control unit and at least two groups of switch control units, wherein a first input end of the remote terminal control unit is electrically connected to the first wireless communication module for receiving the control instruction; The switch control unit includes a relay and a contactor; the first output end of the remote terminal control unit is electrically connected to the control end of each relay, so as to control the closing of the normally open end of each relay; the normally open end of each relay is connected in series with the coil power supply circuit of the contactor in the group, so as to close the contactor when the normally open end is closed; each contactor is connected in series with the corresponding first closed circuit and the second closed circuit, so as to conduct the corresponding first closed circuit and the second closed circuit when the contactor is closed.

3. The photovoltaic module dust occlusion detection system according to claim 2, characterized in that: The data acquisition module includes at least two Hall current sensors, each of which is connected in series to the corresponding first closed loop and second closed loop through two current measurement ends, and the current output end of each Hall current sensor is electrically connected to the second input end of the remote terminal control unit to output the data of the first current source and the second current source through the second output end of the remote terminal control unit.

4. The photovoltaic module dust occlusion detection system according to claim 3, characterized in that: Each of the Hall current sensors is further used to convert the detected first current source and the second current source into corresponding standard currents, wherein the standard current is 4-20 mA.

5. The photovoltaic module dust occlusion detection system according to claim 4, characterized in that: The remote terminal control unit comprises an analog-to-digital converter, which is used to convert the received standard current into a digital current signal.

6. The photovoltaic module dust occlusion detection system according to claim 1, characterized in that: The central processing module includes a host computer and a background computing unit, the host computer is electrically connected to the second wireless communication module, and is used to send the control instruction to the control module according to a preset period, display, store and analyze the received data of the first current source and the second current source, and transmit the analyzed data of the first current source and the second current source to the background computing unit via the Internet; The background calculation unit is used to calculate the difference percentage between the first current source and the second current source within a set time according to the analyzed data of the first current source and the second current source.

7. The photovoltaic module dust shielding detection system according to claim 6, characterized in that: The preset period is 5 minutes and the set time is 1 day.

8. The photovoltaic module dust occlusion detection system according to claim 1, characterized in that: The standard photovoltaic module group includes three standard photovoltaic modules, and the comparative photovoltaic module group includes three comparative photovoltaic modules.

9. The photovoltaic module dust occlusion detection system according to claim 1, characterized in that: The control module, the data acquisition module and the first wireless communication module are arranged in a control box at the photovoltaic component group to be tested.

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