Photovoltaic module ash deposition grade evaluation method

Abstract

The invention relates to the technical field of photovoltaic power generation, in particular to a photovoltaic module ash deposition grade evaluation method, which comprises the following steps: acquiring a real-time measured value of output power of a photovoltaic module; calculating a correction reference value of the output power of the photovoltaic module; calculating the ash deposition percentage of the photovoltaic module; and evaluating the dust deposition grade of the photovoltaic module according to the dust deposition percentage of the photovoltaic module. By means of the evaluation method, the problems that the ash deposition prediction result is unstable and the accuracy rate is not high can be effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power generation, and in particular to a method for evaluating the dust accumulation level of a photovoltaic module. 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 the 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 climatic conditions such as sandstorms and extreme dryness often occur, which greatly increases the dust accumulation on the surface of photovoltaic modules, reduces the conversion efficiency of photovoltaic modules, and has an adverse effect on the efficient operation of the entire photovoltaic power generation system. At present, photovoltaic power stations mostly adopt a regular cleaning strategy for all power generation units, which is inefficient and uneconomical.

[0003] In the prior art, a Chinese invention patent document with a publication number of CN107665382A and a publication date of February 6, 2018 is proposed to solve the above-mentioned technical problems. The technical solution disclosed in the patent document is as follows: a photovoltaic module power grayscale prediction algorithm based on historical power data, comprising the following steps in sequence: step 1, selecting one or more photovoltaic module arrays as monitoring groups in a photovoltaic power station; step 2, setting a monitoring subsystem at the photovoltaic module array of the monitoring group to collect power generation data and dust accumulation data; step 3, establishing a function model based on the power generation data and dust accumulation data, and obtaining a functional relationship between the power generation power data and the dust accumulation data; step 3, monitoring the power generation data and dust accumulation data for a period of time through the monitoring subsystem and collecting data; step 4, establishing a database for comparing the relationship between dust accumulation data and power data; step 5, comparing the power data with the currently obtained power data by consulting and analyzing the comparison database, and obtaining the dust accumulation data corresponding to the power data of the current photovoltaic module array.

[0004] The above technical solution is to obtain the relationship between dust accumulation data and power data, and predict 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, which has high requirements for historical power generation data. In addition, historical power generation data cannot fully reflect the dust accumulation situation, and the function established by it cannot fully and effectively fit the relationship between power data and dust accumulation data, resulting in the possibility that the predicted dust accumulation results may be unstable and have low accuracy. Summary of the invention

[0005] In order 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 achieved by adopting the following technical solutions: A method for evaluating the dust accumulation level of a photovoltaic module comprises the following steps: Calculate the corrected reference value of PV module output power : , in, Indicates the correction factor of the ideal reference value of the photovoltaic module output power, Indicates the correction factor of the historical benchmark value of the photovoltaic module output power, Indicates the historical benchmark value of the PV module output power. Indicates the ideal benchmark value of photovoltaic module output power; Collect real-time measurement values ​​of photovoltaic module output power ; Calculate the dust accumulation percentage of photovoltaic modules : , Evaluate the dust accumulation level of photovoltaic modules according to the percentage of dust accumulation on photovoltaic modules .

[0007] The ideal reference value of the photovoltaic module output power The calculation method is: by calculating the diode model parameters of the photovoltaic module, the ideal reference value of the photovoltaic module output power is obtained: , in, It indicates the maximum power point operating current of the photovoltaic module under the conditions of measured temperature and measured irradiation intensity. It indicates the maximum power point operating voltage of the photovoltaic module under the conditions of measured temperature and measured irradiation intensity. V m It indicates the maximum power point operating voltage of the photovoltaic module working under standard temperature and standard irradiation intensity conditions.

[0008] The photovoltaic module diode model parameters are calculated based on the real-time operating parameters of the photovoltaic module and the factory parameters of the photovoltaic module under standard test conditions.

[0009] The specific calculation method of the photovoltaic module diode model parameters is: , Where T represents the measured temperature of the photovoltaic module, Indicates the temperature of the photovoltaic module under standard test conditions. It represents the difference between the actual temperature of the photovoltaic module and the temperature of the photovoltaic module under standard test conditions. S represents the actual irradiation intensity. Indicates the radiation intensity under standard test conditions, Indicates the difference between the measured irradiance and the irradiance intensity under standard test conditions. Indicates the operating current of the maximum power point of the photovoltaic module under standard test conditions. a Indicates the short-circuit current temperature coefficient of photovoltaic modules under standard test conditions. It indicates the maximum power point operating current of the photovoltaic module under the conditions of measured temperature and measured irradiation intensity. b It indicates the open circuit voltage temperature coefficient of photovoltaic modules under standard test conditions. Indicates the maximum power temperature coefficient under standard test conditions, e represents the base of natural logarithm, It indicates the maximum power point operating voltage of the photovoltaic module under the conditions of measured temperature and measured irradiation intensity. V m It indicates the maximum power point operating voltage of the photovoltaic module working under standard temperature and standard irradiation intensity conditions.

[0010] When calculating the diode model parameters of the photovoltaic module, the real-time operating parameters of the photovoltaic module and the factory parameters of the photovoltaic module are also preprocessed; the preprocessing specifically includes: removing abnormal values ​​of weather monitor parameters in the real-time operating parameters of the photovoltaic module and the factory parameters of the photovoltaic module, and filling in the missing values ​​of the parameters based on linear interpolation; extracting the solar irradiance greater than 800w / m 2 , data with component temperature greater than 20°C; linearly normalize the real-time operating parameters of the PV modules and the factory parameters of the PV modules, and calculate the average and / or weighted average of the normalized data.

[0011] The method for calculating the historical reference value of the photovoltaic module output power is as follows: establishing a photovoltaic module historical operating parameter database, searching for working conditions that are similar to the real-time operating parameters of the photovoltaic module in the photovoltaic module historical operating parameter database according to the real-time operating parameters of the photovoltaic module, and calculating the historical reference value of the photovoltaic module output power.

[0012] The method for calculating the historical reference value of the output power of the photovoltaic module specifically includes: searching for a matching operating condition similar to the real-time operating parameters of the photovoltaic module in the historical operating parameter database according to the real-time operating parameters of the photovoltaic module, wherein the error of the search matching does not exceed a preset threshold; extracting the DC output current and DC output voltage of the photovoltaic module from the searched similar operating conditions; calculating 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. .

[0013] The method for establishing the photovoltaic component historical operation parameter database comprises: collecting operation data within one year of the initial operation of the photovoltaic power station, and performing data preprocessing on the operation data to form the photovoltaic component historical operation parameter database.

[0014] Evaluate the dust accumulation level of photovoltaic modules based on the percentage of dust accumulation on photovoltaic modules Specifically refers to: .

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention analyzes multiple factors that affect dust accumulation, such as power generation, irradiance, temperature and other data, combines massive historical data with the photovoltaic module power generation model, and calculates the corrected reference value of photovoltaic module output power. , which can effectively overcome the shortcomings of existing technologies and has the advantages of strong model generalization ability, low data requirements and high accuracy.

[0016] 2. The method for calculating the photovoltaic module diode model parameters in the present invention can improve the calculation efficiency while meeting the engineering accuracy and meet the real-time requirements in actual engineering applications.

[0017] 3. In the present invention, the extracted solar irradiance is greater than 800w / m 2 The data can better assess the degree of dust accumulation of components.

[0018] 4. By linearly normalizing the real-time operating parameters of photovoltaic modules, the influence of various data parameters on dust accumulation can be unified to avoid data deviation caused by inconsistent units. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, wherein: Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0020] Example 1 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: Step S1. Collect real-time measurement values ​​of photovoltaic module output power , calculate the corrected reference value of the PV module output power The two actions of data collection and data calculation can be performed simultaneously or one after the other. The calculation method is: , in, Indicates the correction factor of the ideal reference value of the photovoltaic module output power, Indicates the correction factor of the historical benchmark value of the photovoltaic module output power, Indicates the historical benchmark value of the PV module output power. Indicates the ideal benchmark value of PV module output power.

[0021] Step S2. Calculate the dust accumulation percentage of photovoltaic modules :

[0022] Step S3. Evaluate the dust accumulation level of the photovoltaic module according to the dust accumulation percentage of the photovoltaic module .

[0023] Example 2 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: Step S1. Calculate the corrected reference value of the photovoltaic module output power : , in, Indicates the correction factor of the ideal reference value of the photovoltaic module output power, Indicates the correction factor of the historical benchmark value of the photovoltaic module output power, Indicates the historical benchmark value of the PV module output power. Indicates the ideal benchmark value of PV module output power.

[0024] Among them, the ideal reference value of the photovoltaic module output power The calculation method is: by calculating the diode model parameters of the photovoltaic module, the ideal reference value of the photovoltaic module output power is obtained: , in, It indicates the maximum power point operating current of the photovoltaic module under the conditions of measured temperature and measured irradiation intensity. It indicates the maximum power point operating voltage of the photovoltaic module under the conditions of measured temperature and measured radiation intensity.

[0025] Specifically, the calculation method of the diode model parameters of the photovoltaic module can be implemented by adopting the technical solution proposed by Yang Hongchao, Cheng Ruofa, Lv Caiyan, and Wang Xuewei in the "Research on Internal Parameter Identification and Output Characteristics of Photovoltaic Modules" in the first issue of "Electronic Technology Applications" in 2018, that is, by iteratively solving the basic diode model of the photovoltaic module to achieve parameter optimization solution.

[0026] Step S2. Collect real-time measurement values ​​of photovoltaic module output power .

[0027] Step S3. Calculate the dust accumulation percentage of photovoltaic modules : .

[0028] Step S4. Evaluate the dust accumulation level of the photovoltaic module according to the dust accumulation percentage of the photovoltaic module : .

[0029] Example 3 As another 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: Step S1. Collect real-time measurement values ​​of photovoltaic module output power .

[0030] Step S2. Calculate the corrected reference value of the photovoltaic module output power : , in, Indicates the correction factor of the ideal reference value of the photovoltaic module output power, Indicates the correction factor of the historical benchmark value of the photovoltaic module output power, Indicates the historical benchmark value of the PV module output power. Indicates the ideal benchmark value of PV module output power.

[0031] The method for calculating the historical reference value of the output power of the photovoltaic module specifically includes: establishing a database of historical operating parameters of the photovoltaic module, searching the database for operating conditions that are similar to the real-time operating parameters of the photovoltaic module according to the real-time operating parameters of the photovoltaic module, and the error of the search match does not exceed a preset threshold. 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 output power of the photovoltaic module. .

[0032] The method for establishing the photovoltaic component historical operating parameter database includes: collecting operating data within one year of the initial operation of the photovoltaic power station, and performing data preprocessing on the data to form a photovoltaic component historical operating parameter database.

[0033] Step S3. Calculate the dust accumulation percentage of photovoltaic modules : .

[0034] Step S4. Evaluate the dust accumulation level of the photovoltaic module according to the dust accumulation percentage of the photovoltaic module .

[0035] Example 4 As the best embodiment of the present invention, refer to the attached specification Figure 1The present invention includes a method for evaluating the dust accumulation level of a photovoltaic module, comprising the following steps: Collect real-time measurement values ​​of photovoltaic module output power .

[0036] Calculate the corrected reference value of PV module output power The specific steps include: Step S 11 . Data collection. The data collection includes collecting the factory parameters of photovoltaic modules, collecting the real-time operating parameters of photovoltaic modules, and collecting the historical operating parameters of photovoltaic modules. The photovoltaic modules include weather monitors, photovoltaic equipment, photovoltaic inverters, and photovoltaic combiner boxes. Specifically, the factory parameters of photovoltaic modules under standard test conditions, the real-time operating parameters of weather monitors, photovoltaic equipment, photovoltaic inverters, and photovoltaic combiner boxes, and the historical operating parameters of the photovoltaic power station within one year of initial operation can be collected, and data preprocessing can be performed separately. The standard test conditions refer to: the solar irradiance is , component temperature is .

[0037] The real-time operating parameters of the photovoltaic equipment should at least include: DC output current, DC output voltage and equipment 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 combiner box should at least include: total input voltage and total input 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 tilt total radiation and instantaneous ambient temperature.

[0038] The factory parameters of photovoltaic modules should at least include: theoretical maximum output power, maximum power point operating voltage, maximum power point operating current, maximum power temperature coefficient, short-circuit current temperature coefficient, open-circuit voltage temperature coefficient and module power attenuation coefficient.

[0039] The preprocessing specifically includes: removing abnormal values ​​of weather monitoring instrument parameters such as solar irradiance and ambient temperature, and filling in missing parameter values ​​based on linear interpolation; extracting solar irradiance greater than 800w / m 2 , data with component temperature greater than 20°C; linearly normalize the factory parameters of PV modules, real-time operating parameters of PV modules and historical operating parameters of PV modules, and calculate the average and / or weighted average of the normalized data.

[0040] Step S 12 . Calculate the historical benchmark value of PV module output power And the ideal benchmark value of photovoltaic module output power .

[0041] Among them, the ideal reference value of the photovoltaic module output power The calculation methods include: Step S 121. The pre-processed real-time operating parameters of the photovoltaic modules and the factory parameters of the photovoltaic modules under standard test conditions are used as input to calculate the diode model parameters of the photovoltaic modules: , Where T represents the measured temperature of the photovoltaic module, Indicates the temperature of the photovoltaic module under standard test conditions. It represents the difference between the actual temperature of the photovoltaic module and the temperature of the photovoltaic module under standard test conditions. S represents the actual irradiation intensity. Indicates the radiation intensity under standard test conditions, Indicates the difference between the measured irradiance and the irradiance intensity under standard test conditions. Indicates the operating current of the maximum power point of the photovoltaic module under standard test conditions. a Indicates the short-circuit current temperature coefficient of photovoltaic modules under standard test conditions. It indicates the maximum power point operating current of the photovoltaic module under the conditions of measured temperature and measured irradiation intensity. b It indicates the open circuit voltage temperature coefficient of photovoltaic modules under standard test conditions. It represents the maximum power temperature coefficient under standard test conditions, e represents the base of natural logarithm, It indicates the maximum power point operating voltage of the photovoltaic module under the conditions of measured temperature and measured irradiation intensity. V m It indicates the maximum power point operating voltage of the photovoltaic module working under standard temperature and standard irradiation intensity conditions.

[0042] Step S 122. Get the ideal benchmark value of PV module output power: , in, It indicates the maximum power point operating current of the photovoltaic module under the conditions of measured temperature and measured irradiation intensity. It indicates the maximum power point operating voltage of the photovoltaic module under the conditions of measured temperature and measured radiation intensity.

[0043] Among them, the historical benchmark value of photovoltaic module output power The calculation method is as follows: establish a database of historical operating parameters of photovoltaic modules, search for working conditions that match the real-time operating parameters in the database of historical operating parameters of photovoltaic modules, and calculate the historical reference value of photovoltaic module output power. The working conditions should at least include: solar irradiance, module temperature, instantaneous ambient temperature, instantaneous wind direction, peak sunshine hours, instantaneous rainfall, daily cumulative tilt 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, combiner box total input voltage, combiner box total input current.

[0044] More specifically, according to the real-time operating parameters of the photovoltaic module, the operating conditions that are similar to the real-time operating parameters of the photovoltaic module are searched in the historical operating parameter database, and the error of the search match does not exceed the preset threshold. In this embodiment, the preset threshold can be 5%. More specifically: the historical operating parameters in the historical operating parameter database of the photovoltaic module and the real-time operating parameters of the photovoltaic module are normalized to eliminate the calculation error caused by the inconsistency of the units of each parameter under a unified scale. Then, the Mahalanobis distance is used 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 judged that the historical operating parameters match the real-time operating parameters of the photovoltaic module, otherwise they do not match and are discarded.

[0045] Extract the DC output current and DC output voltage of the photovoltaic module from the searched similar working conditions. Calculate the product of the DC output current and DC output voltage of the photovoltaic module, which is the historical benchmark value of the photovoltaic module output power. .

[0046] Step S 13 . Using the historical reference value and ideal reference value of the PV module output power as input, calculate the corrected reference value of the PV module output power: , in, Indicates the correction factor of the ideal reference value of the photovoltaic module output power, Indicates the correction factor of the historical benchmark value of the photovoltaic module output power, Indicates the historical benchmark value of the PV module output power. It indicates the ideal reference value of the output power of the photovoltaic module. The correction factor can be obtained by testing after multiple tests.

[0047] Calculate the dust accumulation percentage of photovoltaic modules : .

[0048] Evaluate the dust accumulation level of photovoltaic modules according to the percentage of dust accumulation on photovoltaic modules : .

[0049] In summary, after reading the present invention document, ordinary technicians in this field can make various other corresponding transformation schemes based on the technical scheme and technical concept of the present invention without creative mental labor, which all fall within the scope of protection of the present invention.

Claims

1. A method for evaluating the dust accumulation level of photovoltaic modules, characterized by: The following steps are involved: Calculate the corrected reference value of PV module output power : ， in, Indicates the correction factor of the ideal reference value of the photovoltaic module output power, Indicates the correction factor of the historical benchmark value of the photovoltaic module output power, Indicates the historical benchmark value of the PV module output power. Indicates the ideal benchmark value of photovoltaic module output power; Collect real-time measurement values ​​of photovoltaic module output power ; Calculate the percentage of dust accumulation on photovoltaic modules : ， Evaluate the dust accumulation level of photovoltaic modules according to the percentage of dust accumulation on photovoltaic modules .

2. A photovoltaic module dust accumulation level assessment method according to claim 1, characterized in that: The ideal reference value of the photovoltaic module output power The calculation method is: by calculating the diode model parameters of the photovoltaic module, the ideal reference value of the photovoltaic module output power is obtained: ， in, It indicates the maximum power point operating current of the photovoltaic module under the conditions of measured temperature and measured irradiation intensity. It indicates the maximum power point operating voltage of the photovoltaic module under the conditions of measured temperature and measured radiation intensity.

3. A photovoltaic module dust accumulation level assessment method according to claim 2, characterized in that: The photovoltaic module diode model parameters are calculated based on the real-time operating parameters of the photovoltaic module and the factory parameters of the photovoltaic module under standard test conditions.

4. A photovoltaic module dust accumulation level assessment method according to claim 3, characterized in that: The specific calculation method of the photovoltaic module diode model parameters is: ， Where T represents the measured temperature of the photovoltaic module, Indicates the temperature of the photovoltaic module under standard test conditions. It represents the difference between the actual temperature of the photovoltaic module and the temperature of the photovoltaic module under standard test conditions. S represents the actual irradiation intensity. Indicates the radiation intensity under standard test conditions, Indicates the difference between the measured irradiance and the irradiance intensity under standard test conditions. Indicates the operating current of the maximum power point of the photovoltaic module under standard test conditions. a Indicates the short-circuit current temperature coefficient of photovoltaic modules under standard test conditions. It indicates the maximum power point operating current of the photovoltaic module under the conditions of measured temperature and measured irradiation intensity. b It indicates the open circuit voltage temperature coefficient of photovoltaic modules under standard test conditions. Indicates the maximum power temperature coefficient under standard test conditions, e represents the base of natural logarithm, It indicates the maximum power point operating voltage of the photovoltaic module under the conditions of measured temperature and measured irradiation intensity. V m It indicates the maximum power point operating voltage of the photovoltaic module working under standard temperature and standard irradiation intensity conditions.

5. A photovoltaic module dust accumulation level assessment method according to claim 4, characterized in that: When calculating the diode model parameters of the photovoltaic module, the real-time operating parameters of the photovoltaic module and the factory parameters of the photovoltaic module are also preprocessed; the preprocessing specifically includes: removing abnormal values ​​of weather monitor parameters in the real-time operating parameters of the photovoltaic module and the factory parameters of the photovoltaic module, and filling in the missing values ​​of the parameters based on linear interpolation; extracting the solar irradiance greater than 800w / m 2 , data with component temperature greater than 20°C; linearly normalize the real-time operating parameters of the PV modules and the factory parameters of the PV modules, and calculate the average and / or weighted average of the normalized data.

6. A method for evaluating the dust accumulation level of a photovoltaic module according to claim 1 or 5, characterized in that: The method for calculating the historical reference value of the photovoltaic module output power is as follows: establishing a photovoltaic module historical operating parameter database, searching for working conditions that are similar to the real-time operating parameters of the photovoltaic module in the photovoltaic module historical operating parameter database according to the real-time operating parameters of the photovoltaic module, and calculating the historical reference value of the photovoltaic module output power.

7. A method for evaluating the dust accumulation level of a photovoltaic module according to claim 6, characterized in that: The method for calculating the historical reference value of the output power of the photovoltaic module specifically includes: searching for a matching operating condition similar to the real-time operating parameters of the photovoltaic module in the historical operating parameter database according to the real-time operating parameters of the photovoltaic module, wherein the error of the search matching does not exceed a preset threshold; extracting the DC output current and DC output voltage of the photovoltaic module from the searched similar operating conditions; calculating 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. .

8. A photovoltaic module dust accumulation level assessment method according to claim 6, characterized in that: The method for establishing the photovoltaic component historical operation parameter database comprises: collecting operation data within one year of the initial operation of the photovoltaic power station, and performing data preprocessing on the operation data to form the photovoltaic component historical operation parameter database.

9. A photovoltaic module dust accumulation level assessment method according to claim 6, characterized in that: Evaluate the dust accumulation level of photovoltaic modules based on the percentage of dust accumulation on photovoltaic modules Specifically refers to: 。

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