Method and apparatus for evaluating power performance of a photovoltaic system

Abstract

The application relates to a kind of evaluation method and device of photovoltaic system power performance, including collecting and recording the historical operation data and real-time operation data of photovoltaic system and corresponding environmental factor measurement data, data is cleaned and standardized, then principal component analysis is carried out, the power generation power ratio of each power generation unit of photovoltaic system at a time is calculated with time Attenuation rate and is converted into annual attenuation rate, the annual attenuation rate of the system is calculated using regression model, the abnormal unit is positioned, the time and reason of abnormality are analyzed, and the power performance attenuation evaluation of photovoltaic system is realized.The beneficial effects of the application are: the power generation performance of the power evaluation system is used, which is independent of weather conditions, and accurate evaluation results can be obtained under any weather conditions;And without converting the environmental conditions of the system to standard test conditions STC, the system power generation power is directly used, and the error caused by conversion can be avoided, and accurate evaluation results can be obtained.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic power generation technology, and more specifically, to a method and apparatus for evaluating the power performance of a photovoltaic system. Background Technology

[0002] With the continuous increase in installed photovoltaic power generation capacity and the ongoing operation of systems, the performance of photovoltaic systems directly affects the economic benefits and safe operation of power plants. Timely and accurate performance evaluation of photovoltaic power generation systems is of great significance for the management, operation and maintenance, and trading of power plants.

[0003] Currently, according to IEC 61724-2 and 3, there are no clearly defined calculation models for Predicted Power and Predicted Energy in the performance-power-energy assessment methods for photovoltaic systems. The specific calculation model to be used needs to be agreed upon by multiple parties. STC It is a widely used power performance evaluation index for photovoltaic systems internationally. It is not affected by the scale of the system and is often used for key nodes such as acceptance and performance evaluation of photovoltaic projects. It can be used for comparison and reference in areas with similar environmental conditions. However, 1) it requires long-term measurement because short-term PR is easily affected by climate change and its accuracy is prone to deviation in cloudy and rainy weather; 2) it needs to be converted to STC conditions, which means that environmental factors need to be converted, and errors will be introduced in the conversion process.

[0004] In addition, other power performance evaluation methods all introduce conditional conversions, such as conversion to NOCT conditional calculations, which will also produce conversion errors, resulting in significant uncertainty in the evaluation results. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and to propose a method and apparatus for evaluating the power performance of a photovoltaic system.

[0006] Firstly, a method for evaluating the power performance of a photovoltaic system is provided, including:

[0007] Step 1: Collect and record historical and real-time operating data of the photovoltaic system, as well as corresponding environmental factor measurement data;

[0008] Step 2: Clean and standardize the data collected in Step 1;

[0009] Step 3: Perform principal component analysis on standardized historical and real-time operational data and corresponding environmental factor measurement data;

[0010] Step 4: Calculate K for each power generation unit of the photovoltaic system. n (t i The decay rate of the value over time is converted to the annual decay rate; Kn (t i ) represents the ratio of power generation of the power generation unit at a certain moment, t i Indicates time;

[0011] Step 5: Use regression models to statistically analyze the annual degradation rate of the system, locate abnormal units, and analyze the time and cause of the abnormality to achieve an assessment of the power performance degradation of the photovoltaic system.

[0012] Preferably, in step 1, the environmental factor measurement data includes: total horizontal irradiance, total irradiance received by the photovoltaic module surface, backsheet temperature during module operation, ambient temperature, ambient humidity, wind speed, wind direction, and atmospheric pressure; the operating data includes the current, voltage, and power values ​​of the photovoltaic module, string, and array.

[0013] As a preferred option, in step 3, after performing principal component analysis on the historical operating data and the corresponding environmental factor measurement data, the data with a contribution rate greater than 90% are stored in the database.

[0014] Preferably, in step 3, real-time operating data is used as system evaluation data, and the actual operating data is transformed according to the principal component analysis method.

[0015] Preferably, in step 4, when K n (t i When )>1, store it in the database and assign the value K. n (t i ) = 1; when 0 ≤ K n (t i When )≤1, according to K n (t i The value is used to calculate the system performance degradation rate.

[0016] Preferably, in step 4, different power generation units K in the system at the same time point are compared. n (t i The annual attenuation rate of the system power performance was statistically determined using regression analysis.

[0017] Preferably, step 5 includes:

[0018] Step 5.1: Identify and locate inefficient or faulty power generation units;

[0019] Step 5.2, K of inefficient or faulty power generation units at different time periods n (t i Regression analysis of annual decay rate changes;

[0020] Step 5.3: Locate the time point of attenuation rate change and attribute the cause of the system attenuation rate change.

[0021] In a second aspect, a photovoltaic system power performance evaluation apparatus is provided, for performing the photovoltaic system power performance evaluation method described in any one of the first aspects, comprising:

[0022] The data storage unit is used to collect and record historical and real-time operating data of the photovoltaic system, as well as corresponding environmental factor measurement data.

[0023] The data cleaning unit is used to clean and standardize the data collected by the data storage unit.

[0024] Principal component analysis unit is used to perform principal component analysis on standardized historical and real-time operating data and corresponding environmental factor measurement data.

[0025] The performance monitoring unit is used to calculate K for each power generation unit of the photovoltaic system. n (t i The decay rate of the value over time is converted to an annual decay rate;

[0026] The power performance analysis unit is used to statistically analyze the annual degradation rate of the system using regression models, locate abnormal units, analyze the time and cause of abnormalities, and realize real-time monitoring of the power performance of the photovoltaic system.

[0027] Thirdly, a computer storage medium is provided, wherein a computer program is stored therein; when the computer program is run on a computer, the computer executes the evaluation method for the power performance of the photovoltaic system described in any of the first aspects.

[0028] The beneficial effects of this invention are:

[0029] 1. This invention does not utilize power generation parameters, but directly uses power parameters to evaluate the power performance of the system, and can evaluate the short-term performance of the system.

[0030] 2. The present invention utilizes the power generation performance of the power assessment system, which is independent of weather conditions and can obtain relatively accurate assessment results under any weather conditions.

[0031] 3. This invention does not require converting the system's environmental conditions (radiation, component operating temperature) to standard test conditions (STC). It directly utilizes the system's power generation, avoiding errors caused by conversion and obtaining more accurate evaluation results. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a method for real-time monitoring of abnormal power performance in a photovoltaic system.

[0033] Figure 2 A flowchart of a method for real-time monitoring of abnormal power performance in a photovoltaic system;

[0034] Figure 3 This is a schematic diagram of a real-time power performance monitoring device for a photovoltaic system.

[0035] Figure 4 This is a schematic diagram illustrating the annual power performance degradation rate of a photovoltaic system after probability distribution analysis and 0 iterations.

[0036] Figure 5 This is a schematic diagram illustrating the annual power performance degradation rate of a photovoltaic system after probability distribution analysis and one iteration.

[0037] Figure 6 This is a schematic diagram illustrating the annual power performance degradation rate of a photovoltaic system after probability distribution analysis and two iterations.

[0038] Figure 7 This is a schematic diagram illustrating the annual power performance degradation rate of a photovoltaic system after probability distribution analysis and three iterations. Detailed Implementation

[0039] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0040] Example 1:

[0041] like Figure 1 and Figure 2 As shown, this application provides a method for evaluating the power performance of a photovoltaic system, including:

[0042] Step 1: Collect and record the historical and real-time operating data of the photovoltaic system, as well as the corresponding environmental factor measurement data.

[0043] After the system is put into operation, it is necessary to collect and record as much environmental factor measurement data and system power generation data as possible. For example, record at least 6 months of historical operating data and on-site operating data to be evaluated. In addition, environmental factor measurement data includes: total horizontal irradiance, total irradiance received by the photovoltaic module surface, backsheet temperature of the module during operation, ambient temperature, ambient humidity, wind speed, wind direction, and atmospheric pressure; operating data includes the current, voltage, and power values ​​of photovoltaic modules, strings, and arrays (input and output terminals of inverters, input and output terminals of transformer substations, input and output terminals of combiner boxes, etc.).

[0044] Step 2: Clean and standardize the data collected in Step 1.

[0045] Data cleaning refers to filtering and removing abnormal data based on the physical meaning of the collected data. After data cleaning, each power generation data point and its corresponding environmental factor data are recorded, such as the inverter output power P. inv (t0,GHI,POA,T PV V wind (RH...). Then, the recorded data is standardized, making the power generation data independent of its unit and normalized.

[0046] Step 3: Perform principal component analysis on the standardized historical and real-time operating data and the corresponding environmental factor measurement data.

[0047] In step 3, principal component analysis is performed on the standardized environmental factor data to establish, for example, P... 0,inv (t0,A,B,C…), when the contribution rate of environmental factors A, B, C, etc. after principal component analysis is higher than 90%, the environmental factors after principal component analysis are considered to be effective for the system to be analyzed and are stored in the database.

[0048] In addition, real-time operational data was selected as system evaluation data, and the actual operational data was transformed using principal component analysis. For example, the irradiance range of the inclined surface was selected as 600-1200 W / m. 2 Real-time power generation operation data is used as performance evaluation data. After collecting and storing the actual operation data of the system to be evaluated, the data is cleaned, standardized, and then environmental factors (t0, A, B, C…) are used to evaluate the actual operation data, such as P. 0,inv,act (t i ,GHI,POA,T PV V wind, RH…) is converted to obtain P 0,inv,act (t i (A, B, C…).

[0049] Step 4: Calculate K for each power generation unit of the photovoltaic system. n (t i The decay rate of the value over time is converted to the annual decay rate; K n (t i () represents the power generation ratio of a power generation unit under similar environmental conditions.

[0050] K n (t i The formula for calculating ) is: When K n (t i When )>1, store it in the database and assign the value K. n (t i ) = 1; when 0 ≤ K n (t iWhen )≤1, according to K n (t i The value is used to calculate the system performance degradation rate.

[0051] In step 4, different power generation units K in the system at the same time point are compared. n (t i The annual attenuation rate of the system power performance was statistically determined using regression analysis.

[0052] Step 5: Use regression models to statistically analyze the annual attenuation rate of the system, locate abnormal units, and analyze the time and cause of the abnormality to achieve real-time monitoring of the power performance of the photovoltaic system.

[0053] In step 5, piecewise regression analysis is performed on the annual decay rate, which exhibits significant variations, to pinpoint the time points of change in the decay rate and attribute the causes of these changes. Specifically, for different sub-units K in the system at the same time point... n (t i The annual degradation rate of the system power performance is calculated using Theil-Sen regression analysis, or the annual degradation rate of the K value for the sub-unit is calculated. n (t i Probability distribution analysis of the annual decay rate, such as Figures 4-7 As shown, using the iterative outlier detection method, sub-cells that are still below the expected value by 2 times the standard deviation after 4 iterations will be judged as inefficient or faulty cells. Figures 4-7 In this context, μ represents the expected value / mean of the distribution, and σ represents the standard deviation of the distribution. Furthermore, the K values ​​of a system at different time periods are calculated. n (t i The annual decay rate is calculated using regression algorithms such as OLS, resulting in R0. 2 For annual decay rates below 0.5, segmented regression analysis was performed to pinpoint the time points of decay rate changes and attribute the causes of these changes in the system decay rate.

[0054] Example 2:

[0055] A device for evaluating the power performance of a photovoltaic system, such as Figure 3 As shown, it includes:

[0056] The data storage unit is used to collect and record historical and real-time operating data of the photovoltaic system, as well as corresponding environmental factor measurement data.

[0057] The data cleaning unit is used to clean and standardize the data collected by the data storage unit.

[0058] The principal component analysis unit is used to perform principal component analysis on standardized historical and real-time operating data and corresponding environmental factor measurement data; after performing principal component analysis on the data, the data with a contribution rate greater than 90% are stored in the data storage unit.

[0059] The performance monitoring unit is used to calculate K for each power generation unit of the photovoltaic system. n (t i The decay rate of the value over time is converted to an annual decay rate;

[0060] The power performance analysis unit is used to statistically analyze the annual degradation rate of the system using regression models, locate abnormal units, analyze the time and cause of abnormalities, and realize real-time monitoring of the power performance of the photovoltaic system.

[0061] In summary, this invention provides a method and apparatus for evaluating the power performance of a photovoltaic system. It considers the initial power generation performance of the photovoltaic system as its initial performance and calculates the ratio K between the real-time power and the initial power at a certain moment under the same environmental conditions. n (t i ), calculate K n (t i The annual degradation rate of the photovoltaic system and regression analysis are performed to achieve real-time power performance evaluation of the photovoltaic system and each power generation unit.

Claims

1. A method for evaluating the power performance of a photovoltaic system, characterized in that, include: Step 1: Collect and record historical and real-time operating data of the photovoltaic system, as well as corresponding environmental factor measurement data; Step 2: Clean and standardize the data collected in Step 1; Step 3: Perform principal component analysis on standardized historical and real-time operational data and corresponding environmental factor measurement data; in Step 3, real-time operational data is used as system evaluation data, and the actual operational data is transformed according to the principal component analysis method; Step 4: Calculate the power generation units of the photovoltaic system The decay rate of the value over time is converted to the annual decay rate; The ratio of power generation of the power generation unit at a certain moment. Indicates the time; in step 4, when When the value is greater than 1, store it in the database and assign a value. =1; when 0≤ When ≤1, according to Calculate the system performance degradation rate; in step 4, compare the different power generation units in the system at the same time point. The annual degradation rate of the value was statistically determined using regression analysis to calculate the annual degradation rate of the system power performance. Step 5: Utilize regression models to statistically analyze the annual degradation rate of the system, locate abnormal units, and analyze the timing and causes of anomalies to achieve an assessment of the photovoltaic system's power performance degradation. Step 5 includes: Step 5.1: Identify and locate inefficient or faulty power generation units; Step 5.2, inefficient or faulty power generation units at different time periods Regression analysis of annual decay rate changes; Step 5.3: Locate the time point of attenuation rate change and attribute the cause of the system attenuation rate change.

2. The method for evaluating the power performance of a photovoltaic system according to claim 1, characterized in that, In step 1, the environmental factor measurement data includes: total horizontal irradiance, total irradiance received by the photovoltaic module surface, backsheet temperature during module operation, ambient temperature, ambient humidity, wind speed, wind direction, and atmospheric pressure; the operating data includes the current, voltage, and power values ​​of the photovoltaic module, string, and array.

3. The method for evaluating the power performance of a photovoltaic system according to claim 1, characterized in that, In step 3, after performing principal component analysis on the historical operating data and the corresponding environmental factor measurement data, the data with a contribution rate greater than 90% are stored in the database.

4. A device for evaluating the power performance of a photovoltaic system, characterized in that, A method for evaluating the power performance of a photovoltaic system according to any one of claims 1 to 3, comprising: The data storage unit is used to collect and record historical and real-time operating data of the photovoltaic system, as well as corresponding environmental factor measurement data. The data cleaning unit is used to clean and standardize the data collected by the data storage unit. Principal component analysis unit is used to perform principal component analysis on standardized historical and real-time operating data and corresponding environmental factor measurement data. The performance monitoring unit is used to calculate the power generation of each unit in the photovoltaic system. The decay rate of the value over time is converted to the annual decay rate; This represents the ratio of power generation capacity of the power generation unit under similar environmental conditions. The power performance analysis unit is used to statistically analyze the annual degradation rate of the system using regression models, locate abnormal units, analyze the time and cause of abnormalities, and realize real-time monitoring of the power performance of the photovoltaic system.

5. A computer storage medium, characterized in that, The computer storage medium stores a computer program; when the computer program is run on the computer, it causes the computer to execute the evaluation method for the power performance of the photovoltaic system according to any one of claims 1 to 3.

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