A method for evaluating the dust accumulation level of a photovoltaic module

Abstract

The present invention relates to the technical field of photovoltaic power generation, and particularly to a method for evaluating the dust accumulation level of a photovoltaic module, including: collecting real-time measured values of the output power of the photovoltaic module; calculating a corrected reference value of the output power of the photovoltaic module; calculating the dust accumulation percentage of the photovoltaic module; and evaluating the dust accumulation level of the photovoltaic module according to the dust accumulation percentage of the photovoltaic module. Through this evaluation method, the problems of unstable dust accumulation prediction results and low accuracy can be effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power generation, and particularly to a method for evaluating the dust accumulation level of photovoltaic modules. Background Art

[0002] Photovoltaic power generation mainly relies on the photovoltaic effect of photovoltaic modules to convert light energy into electrical energy. As an important power generation unit of a photovoltaic power generation system, the photoelectric conversion efficiency of photovoltaic modules has an important impact on the power generation of the entire photovoltaic power generation system. Since large-scale photovoltaic power stations are mostly built in harsh environments such as deserts and gobi, adverse weather conditions such as sandstorms and extreme dryness often occur, greatly increasing the dust accumulation degree on the surface of photovoltaic modules, reducing the conversion efficiency of photovoltaic modules, and bringing adverse effects to the efficient operation of the entire photovoltaic power generation system. At present, most photovoltaic power stations adopt a regular cleaning strategy for all power generation units, which is inefficient and has poor economy.

[0003] In the prior art, a Chinese invention patent document with a publication number of CN107665382A and a publication date of February 6, 2018 was proposed to solve the above-mentioned existing technical problems. The technical solution disclosed in the patent document is as follows: A power grayscale prediction algorithm for photovoltaic modules based on historical power data, which successively includes the following steps: Step 1, select one or more groups of photovoltaic module arrays in a photovoltaic power station as a monitoring group; Step 2, set a monitoring subsystem at the photovoltaic module arrays of the monitoring group to collect power generation data and dust accumulation data; Step 3, establish a function model according to the power generation data and the dust accumulation data to obtain the functional relationship between the power generation power data and the dust accumulation data; Step 3, monitor the power generation data and the dust accumulation data for a period of time through the monitoring subsystem and collect the data; Step 4, establish a relationship comparison database between the dust accumulation data and the power data; Step 5, compare and analyze the power data with the currently obtained power data through the comparison database to obtain the dust accumulation data corresponding to the power data of the current photovoltaic module array.

[0004] The above technical solution obtains the relationship between the dust accumulation data and the power data, and predicts the current dust accumulation data through the power data of the current photovoltaic module array. This technical solution completely relies on historical power generation data, has high requirements for historical power generation data, and the historical power generation data cannot fully reflect the dust accumulation situation. The established function also cannot fully and effectively fit the relationship between the power data and the dust accumulation data, resulting in possible instability and low accuracy in the predicted dust accumulation results. Summary of the Invention

[0005] To solve the above technical problems, the present invention proposes a method for evaluating the dust accumulation level of photovoltaic modules, which can effectively solve the problems of unstable dust accumulation prediction results and low accuracy.

[0006] The present invention is realized by adopting the following technical solutions:

[0007] A method for evaluating the dust accumulation level of a photovoltaic module, comprising the following steps:

[0008] Calculate the corrected reference value of the output power of the photovoltaic module :

[0009] ,

[0010] wherein, represents the correction factor of the ideal reference value of the output power of the photovoltaic module, represents the correction factor of the historical reference value of the output power of the photovoltaic module, represents the historical reference value of the output power of the photovoltaic module, represents the ideal reference value of the output power of the photovoltaic module;

[0011] Collect the real-time measured value of the output power of the photovoltaic module ;

[0012] Calculate the dust accumulation percentage of the photovoltaic module :

[0013] ,

[0014] Evaluate the dust accumulation level of the photovoltaic module according to the dust accumulation percentage of the photovoltaic module .

[0015] The calculation method of the ideal reference value of the output power of the photovoltaic module is: Obtain the ideal reference value of the output power of the photovoltaic module by calculating the diode model parameters of the photovoltaic module:

[0016] ,

[0017] wherein, represents the maximum power point operating current of the photovoltaic module under the measured temperature and measured irradiance intensity conditions, represents the maximum power point operating voltage of the photovoltaic module under the measured temperature and measured irradiance intensity conditions, V m represents the maximum power point operating voltage of the photovoltaic module under the standard temperature and standard irradiance intensity conditions.

[0018] The diode model parameters of the photovoltaic module are calculated from the real-time operating parameters of the photovoltaic module and the factory parameters of the photovoltaic module under the standard test conditions.

[0019] The specific calculation method of the diode model parameters of the photovoltaic module is:

[0020] ,

[0021] Among them, T represents the measured temperature of the photovoltaic module, represents the temperature of the photovoltaic module under standard test conditions, represents the difference between the measured temperature of the photovoltaic module and the temperature of the photovoltaic module under standard test conditions, S represents the measured irradiance intensity, represents the irradiance intensity under standard test conditions, represents the difference between the measured irradiance and the irradiance intensity under standard test conditions, represents the operating current at the maximum power point of the photovoltaic module under standard test conditions, a represents the temperature coefficient of the short-circuit current of the photovoltaic module under standard test conditions, represents the operating current at the maximum power point when the photovoltaic module operates under the measured temperature and measured irradiance intensity conditions, b represents the temperature coefficient of the open-circuit voltage of the photovoltaic module under standard test conditions, represents the maximum power temperature coefficient under standard test conditions, e represents the base of the natural logarithm, represents the operating voltage at the maximum power point when the photovoltaic module operates under the measured temperature and measured irradiance intensity conditions, V m represents the operating voltage at the maximum power point when the photovoltaic module operates under standard temperature and standard irradiance intensity conditions.

[0022] When calculating the diode model parameters of the photovoltaic module, it also includes preprocessing the real-time operation parameters and factory parameters of the photovoltaic module; the preprocessing specifically includes: respectively removing the outliers of the weather monitor parameters in the real-time operation parameters and factory parameters of the photovoltaic module, and complementing the missing parameter values based on linear interpolation; extracting the data with solar irradiance greater than 800w / m 2 and module temperature greater than 20°C; respectively performing linear normalization on the real-time operation parameters and factory parameters of the photovoltaic module, and calculating the average value and / or weighted average value of the normalized data.

[0023] The calculation method of the historical reference value of the output power of the photovoltaic module is: establish a historical operation parameter database of the photovoltaic module, and according to the real-time operation parameters of the photovoltaic module, search and match the working conditions similar to the real-time operation parameters of the photovoltaic module in the historical operation parameter database of the photovoltaic module, and calculate the historical reference value of the output power of the photovoltaic module.

[0024] The calculation method of the historical reference value of the output power of the photovoltaic module specifically includes: according to the real-time operation parameters of the photovoltaic module, search and match in the historical operation parameter database for working conditions similar to the real-time operation parameters of the photovoltaic module, and the search and match error does not exceed a preset threshold; extract the DC output current and DC output voltage of the photovoltaic module from the similar working conditions found; calculate the product of the DC output current and DC output voltage of the photovoltaic module, which is the historical reference value of the output power of the photovoltaic module. 。

[0025] The method for establishing the historical operation parameter database of the photovoltaic module includes: collecting the operation data within one year at the initial stage of the operation of the photovoltaic power station, and performing data preprocessing on it to form the historical operation parameter database of the photovoltaic module.

[0026] Evaluate the dust accumulation level of the photovoltaic module according to the dust accumulation percentage of the photovoltaic module Specifically refers to:

[0027] 。

[0028] Compared with the prior art, the beneficial effects of the present invention are shown in:

[0029] 1. By analyzing multiple factors affecting the dust accumulation result, such as data such as power generation power, irradiance, and temperature, the present invention combines a large amount of historical data with the photovoltaic module generator mechanism model to calculate the corrected reference value of the output power of the photovoltaic module , which can effectively overcome the disadvantages of the prior art, and has advantages such as strong model generalization ability, low data requirements, and high accuracy.

[0030] 2. The calculation method of the diode model parameters of the photovoltaic module in the present invention can improve the calculation efficiency under the condition of meeting the engineering accuracy and meet the real-time requirements in actual engineering applications.

[0031] 3. In the present invention, extracting data with a solar irradiance greater than 800 w / m 2 can better evaluate the dust accumulation degree of the module.

[0032] 4. By performing linear normalization on the real-time operation parameters of the photovoltaic module, the influence of each data parameter on dust accumulation can be unified, and data deviation caused by inconsistent units can be avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The following will further describe the present invention in detail in conjunction with the drawings in the specification and specific embodiments, where:

[0034] Figure 1 is the flow diagram of the present invention. SPECIFIC EMBODIMENTS

[0035] Example 1

[0036] As a basic embodiment of the present invention, the present invention includes a method for evaluating the dust accumulation level of a photovoltaic module, comprising the following steps:

[0037] Step S1. Collect the real-time measurement value of the output power of the photovoltaic module , and calculate the corrected reference value of the output power of the photovoltaic module . These two actions of data collection and data calculation can be carried out simultaneously or one after the other. Among them, the calculation method of the corrected reference value of the output power of the photovoltaic module is:

[0038] ,

[0039] wherein, represents the correction factor of the ideal reference value of the output power of the photovoltaic module, represents the correction factor of the historical reference value of the output power of the photovoltaic module, represents the historical reference value of the output power of the photovoltaic module, represents the ideal reference value of the output power of the photovoltaic module.

[0040] Step S2. Calculate the dust accumulation percentage of the photovoltaic module :

[0041]

[0042] Step S3. Evaluate the dust accumulation level of the photovoltaic module according to the dust accumulation percentage of the photovoltaic module .

[0043] Embodiment 2

[0044] As a preferred embodiment of the present invention, the present invention includes a method for evaluating the dust accumulation level of a photovoltaic module, comprising the following steps:

[0045] Step S1. Calculate the corrected reference value of the output power of the photovoltaic module :

[0046] ,

[0047] wherein, represents the correction factor of the ideal reference value of the output power of the photovoltaic module, represents the correction factor of the historical reference value of the output power of the photovoltaic module, represents the historical reference value of the output power of the photovoltaic module, represents the ideal reference value of the output power of the photovoltaic module.

[0048] Among them, the ideal reference value of the output power of the photovoltaic module The calculation method is as follows: By calculating the diode model parameters of the photovoltaic module, the ideal reference value of the output power of the photovoltaic module is obtained:

[0049] ,

[0050] Among them, represents the maximum power point operating current of the photovoltaic module under the measured temperature and measured irradiance intensity conditions, represents the maximum power point operating voltage of the photovoltaic module under the measured temperature and measured irradiance intensity conditions.

[0051] Specifically, the calculation method of the diode model parameters of the photovoltaic module can be implemented by adopting the technical solution proposed in "Research on the Identification of Internal Parameters and Output Characteristics of Photovoltaic Modules" proposed by Yang Hongchao, Cheng Ruofa, Lü Caiyan, and Wang Xuewei in the first issue of Application of Electronic Technique in 2018, that is, by iteratively solving the basic diode model of the photovoltaic module to achieve parameter optimization and solution.

[0052] Step S2. Collect the real-time measured value of the output power of the photovoltaic module .

[0053] Step S3. Calculate the dust accumulation percentage of the photovoltaic module :

[0054] .

[0055] Step S4. Evaluate the dust accumulation level of the photovoltaic module according to the dust accumulation percentage of the photovoltaic module :

[0056] .

[0057] Embodiment 3

[0058] As another preferred embodiment of the present invention, the present invention includes a method for evaluating the dust accumulation level of a photovoltaic module, including the following steps:

[0059] Step S1. Collect the real-time measured value of the output power of the photovoltaic module .

[0060] Step S2. Calculate the corrected reference value of the output power of the photovoltaic module :

[0061] ,

[0062] Among them, represents the correction factor of the ideal reference value of the output power of the photovoltaic module, represents the correction factor of the historical reference value of the output power of the photovoltaic module, represents the historical reference value of the output power of the photovoltaic module, Represents the ideal reference value of the output power of the photovoltaic module.

[0063] Among them, the calculation method of the historical reference value of the output power of the photovoltaic module specifically includes: establishing a database of historical operation parameters of the photovoltaic module, and according to the real-time operation parameters of the photovoltaic module, searching in the historical operation parameter database for working conditions similar to the real-time operation parameters of the photovoltaic module, and the search matching error does not exceed a preset threshold. Extract the DC output current and DC output voltage of the photovoltaic module from the similar working conditions found; calculate the product of the DC output current and the DC output voltage of the photovoltaic module, which is the historical reference value of the output power of the photovoltaic module .

[0064] Among them, the method for establishing the database of historical operation parameters of the photovoltaic module includes: collecting the operation data within one year at the initial stage of the operation of the photovoltaic power station, and performing data preprocessing on it to form a database of historical operation parameters of the photovoltaic module.

[0065] Step S3. Calculate the dust accumulation percentage of the photovoltaic module :

[0066] .

[0067] Step S4. Evaluate the dust accumulation level of the photovoltaic module according to the dust accumulation percentage of the photovoltaic module .

[0068] Embodiment 4

[0069] As the best implementation mode of the present invention, referring to the attached Figure 1 of the specification, the present invention includes a method for evaluating the dust accumulation level of a photovoltaic module, including the following steps:

[0070] Collect the real-time measured value of the output power of the photovoltaic module .

[0071] Calculate the corrected reference value of the output power of the photovoltaic module . Specifically, it includes the following steps:

[0072] Step S 11 . Data collection. The data collection includes collecting the factory parameters of the photovoltaic module, collecting the real-time operation parameters of the photovoltaic module, and collecting the historical operation parameters of the photovoltaic module. The photovoltaic module includes a weather monitor, a photovoltaic device, a photovoltaic inverter, and a photovoltaic busbar box. Specifically, the factory parameters of the photovoltaic module under standard test conditions can be collected, the real-time operation parameters of the weather monitor, the photovoltaic device, the photovoltaic inverter, and the photovoltaic busbar box can be collected, and the historical operation parameters within one year at the initial stage of the operation of the photovoltaic power station can be collected, and data preprocessing is performed respectively. The standard test conditions refer to: the solar irradiance is , the module temperature is 。

[0073] The real-time operating parameters of the photovoltaic device should at least include: DC output current, DC output voltage, and device temperature. The real-time operating data of the photovoltaic inverter should at least include: DC-side power, AC-side power, and daily cumulative power generation. The real-time operating parameters of the photovoltaic busbar box should at least include: total incoming voltage and total incoming current. The real-time operating parameters of the weather monitor should at least include: solar irradiance, instantaneous wind speed, instantaneous wind direction, peak sunshine hours, instantaneous rainfall, daily cumulative inclined total radiation, and instantaneous ambient temperature.

[0074] The factory parameters of the photovoltaic module should at least include: the theoretical maximum output power, the operating voltage at the maximum power point, the operating current at the maximum power point, the maximum power temperature coefficient, the short-circuit current temperature coefficient, the open-circuit voltage temperature coefficient, and the module power attenuation coefficient.

[0075] Among them, the preprocessing specifically includes: removing the abnormal values of the weather monitor parameters such as solar irradiance and ambient temperature, and filling in the missing parameter values based on linear interpolation; extracting the data with solar irradiance greater than 800 w / m 2 and module temperature greater than 20 °C; linearly normalizing the factory parameters of the photovoltaic module, the real-time operating parameters of the photovoltaic module, and the historical operating parameters of the photovoltaic module respectively, and calculating the average value and / or weighted average value of the normalized data.

[0076] Step S 12 . Calculate the historical reference value of the photovoltaic module output power and the ideal reference value of the photovoltaic module output power 。

[0077] Among them, the calculation method of the ideal reference value of the photovoltaic module output power includes:

[0078] Step S 121. Taking the preprocessed real-time operating parameters of the photovoltaic module and the factory parameters of the photovoltaic module under standard test conditions as inputs, calculate the diode model parameters of the photovoltaic module:

[0079] ,

[0080] Among them, T represents the measured temperature of the photovoltaic module, represents the temperature of the photovoltaic module under standard test conditions, represents the difference between the measured temperature of the photovoltaic module and the temperature of the photovoltaic module under standard test conditions, S represents the measured irradiance intensity, represents the irradiance intensity under standard test conditions, represents the difference between the measured irradiance and the irradiance intensity under standard test conditions, Represents the working current at the maximum power point of a photovoltaic module under standard test conditions, a Represents the temperature coefficient of the short - circuit current of a photovoltaic module under standard test conditions, Represents the working current at the maximum power point when the photovoltaic module operates under the measured temperature and measured irradiance intensity conditions, b Represents the temperature coefficient of the open - circuit voltage of a photovoltaic module under standard test conditions, Represents the temperature coefficient at the maximum power under standard test conditions, where e is the base of the natural logarithm, Represents the working voltage at the maximum power point when the photovoltaic module operates under the measured temperature and measured irradiance intensity conditions, V m Represents the working voltage at the maximum power point when the photovoltaic module operates under standard temperature and standard irradiance intensity conditions.

[0081] Step S 122. Obtain the ideal reference value of the output power of the photovoltaic module:

[0082] ,

[0083] where, Represents the working current at the maximum power point when the photovoltaic module operates under the measured temperature and measured irradiance intensity conditions, Represents the working voltage at the maximum power point when the photovoltaic module operates under the measured temperature and measured irradiance intensity conditions.

[0084] where, the historical reference value of the output power of the photovoltaic module is calculated as follows: Establish a historical operation parameter database of the photovoltaic module, search for and match the working conditions similar to the real - time operation parameters in the historical operation parameter database of the photovoltaic module, and calculate the historical reference value of the output power of the photovoltaic module. The working conditions should at least include: solar irradiance, module temperature, instantaneous ambient temperature, instantaneous wind direction, peak sunshine hours, instantaneous rainfall, daily cumulative inclined total radiation, instantaneous wind speed, module DC output current, module DC output voltage, inverter DC - side power, inverter AC - side power, inverter daily cumulative power generation, busbar box total incoming voltage, busbar box total incoming current.

[0085] More specifically, according to the real-time operating parameters of the photovoltaic module, search for operating conditions in the historical operating parameter database that match the real-time operating parameters of the photovoltaic module, and the search matching error does not exceed a preset threshold. In this embodiment, the preset threshold can be 5%. More specifically: normalize the historical operating parameters in the historical operating parameter database of the photovoltaic module and the real-time operating parameters of the photovoltaic module to eliminate the calculation error caused by inconsistent parameter units under the unified scale. Then, use the Mahalanobis distance to calculate the matching error between the historical operating parameters and the real-time operating parameters of the photovoltaic module. If the error is less than 5%, it is determined that the historical operating parameters match the real-time operating parameters of the photovoltaic module, otherwise they do not match and are discarded.

[0086] Extract the DC output current and DC output voltage of the photovoltaic module from the searched similar operating conditions. Calculate the product of the DC output current and DC output voltage of the photovoltaic module, which is the historical reference value of the photovoltaic module output power. .

[0087] Step S 13 . Taking the historical reference value of the photovoltaic module output power and the ideal reference value as inputs, calculate the corrected reference value of the photovoltaic module output power:

[0088] ,

[0089] Among them, represents the correction factor of the ideal reference value of the photovoltaic module output power, represents the correction factor of the historical reference value of the photovoltaic module output power, represents the historical reference value of the photovoltaic module output power, represents the ideal reference value of the photovoltaic module output power. Among them, the correction factor can be obtained through multiple tests.

[0090] Calculate the dust accumulation percentage of the photovoltaic module :

[0091] .

[0092] Evaluate the dust accumulation level of the photovoltaic module according to the dust accumulation percentage of the photovoltaic module :

[0093] .

[0094] In summary, after reading the present invention document, various other corresponding transformation schemes made by those of ordinary skill in the art without creative mental labor according to the technical solutions and technical concepts of the present invention all fall within the scope protected by the present invention.

Claims

1. A method for evaluating the dust accumulation level of a photovoltaic module, characterized in that: Including the following steps: Calculate the corrected reference value of the output power of the photovoltaic module : ， Among them, represents the correction factor of the ideal reference value of the output power of the photovoltaic module, represents the correction factor of the historical reference value of the output power of the photovoltaic module, represents the historical reference value of the output power of the photovoltaic module; represents the ideal reference value of the output power of the photovoltaic module, which is obtained based on the diode model of the photovoltaic module; Among them, the calculation method of the historical reference value of the output power of the photovoltaic module is as follows: establish a historical operation parameter database of the photovoltaic module, and according to the real-time operation parameters of the photovoltaic module, search and match the working conditions similar to the real-time operation parameters of the photovoltaic module in the historical operation parameter database of the photovoltaic module, and calculate the historical reference value of the output power of the photovoltaic module; Collect real-time measured values of the output power of the photovoltaic module ; Calculate the real-time dust accumulation percentage of photovoltaic modules : ， Evaluate the dust accumulation level of photovoltaic modules according to the dust accumulation percentage of photovoltaic modules .

2. The method for evaluating the dust accumulation level of a photovoltaic module according to claim 1, wherein: The ideal reference value of the output power of the photovoltaic module The calculation method is as follows: By calculating the diode model parameters of the photovoltaic module, the ideal reference value of the output power of the photovoltaic module is obtained: ， Among them, represents the maximum power point operating current of the photovoltaic module under the conditions of the measured temperature and the measured irradiance intensity, represents the maximum power point operating voltage of the photovoltaic module under the conditions of the measured temperature and the measured irradiance intensity.

3. The method for evaluating the dust accumulation level of a photovoltaic module according to claim 2, wherein: The diode model parameters of the photovoltaic module are calculated based on the real-time operation parameters of the photovoltaic module and the factory parameters of the photovoltaic module under standard test conditions.

4. The method for evaluating the dust accumulation level of a photovoltaic module according to claim 3, wherein: The specific calculation method of the diode model parameters of the photovoltaic module is as follows: ， ， ， ， Where, T represents the measured temperature of the photovoltaic module, represents the temperature of the photovoltaic module under standard test conditions, represents the difference between the measured temperature of the photovoltaic module and the temperature of the photovoltaic module under standard test conditions, S represents the measured irradiance intensity, represents the irradiance intensity under standard test conditions, represents the difference between the measured irradiance intensity and the irradiance intensity under standard test conditions, represents the operating current at the maximum power point of the photovoltaic module under standard test conditions, a represents the temperature coefficient of the short-circuit current of the photovoltaic module under standard test conditions, represents the operating current at the maximum power point when the photovoltaic module operates under the measured temperature and measured irradiance intensity conditions, b represents the temperature coefficient of the open-circuit voltage of the photovoltaic module under standard test conditions, represents the maximum power temperature coefficient under standard test conditions, e represents the base of the natural logarithm, represents the operating voltage at the maximum power point when the photovoltaic module operates under the measured temperature and measured irradiance intensity conditions, V m represents the operating voltage at the maximum power point when the photovoltaic module operates under standard temperature and standard irradiance intensity conditions.

5. The method for evaluating the dust accumulation level of a photovoltaic module according to claim 4, wherein: When calculating the diode model parameters of a photovoltaic module, it also includes preprocessing the real-time operating parameters and the factory parameters of the photovoltaic module; the specific preprocessing includes: respectively removing the outliers of the weather monitor parameters in the real-time operating parameters and the factory parameters of the photovoltaic module, and filling in the missing parameter values based on linear interpolation; extracting the data with solar irradiance greater than 800 w / m 2 , and the module temperature greater than 20 °C; respectively performing linear normalization on the real-time operating parameters and the factory parameters of the photovoltaic module, and calculating the average value and / or weighted average value of the normalized data.

6. The method for evaluating the dust accumulation level of a photovoltaic module according to claim 1, wherein: The calculation method of the historical reference value of the output power of the photovoltaic module specifically includes: according to the real-time operation parameters of the photovoltaic module, search and match the working conditions similar to the real-time operation parameters of the photovoltaic module in the historical operation parameter database, and the search and match error does not exceed the preset threshold; extract the DC output current and DC output voltage of the photovoltaic module from the similar working conditions found; calculate the product of the DC output current and the DC output voltage of the photovoltaic module, which is the historical reference value of the output power of the photovoltaic module 。 7. The method for evaluating the dust accumulation level of a photovoltaic module according to claim 1, characterized in that: The establishment method of the historical operation parameter database of the photovoltaic module includes: collecting the operation data within one year at the initial stage of the operation of the photovoltaic power station, and performing data preprocessing on it to form a historical operation parameter database of the photovoltaic module.

8. A method for evaluating the dust accumulation level of a photovoltaic module according to claim 1, characterized in that: Evaluate the dust accumulation level of a photovoltaic module based on the dust accumulation percentage of the photovoltaic module Specifically refers to: 。

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