Method for determining the ageing of a photovoltaic module

Abstract

The application provides a kind of photovoltaic module aging determination method, based on obtaining the I_V characteristic curve of all components in multiple days and multiple times, the average fill factor is calculated, and whether aging and belonging to what degree of aging is determined according to the average fill factor, and the suspected aging component list is included, and the aging component is finally determined after multiple measurement cycles.The application considers that the component aging is a relatively slow process, and the voltage, current, power and other data of the component are greatly affected by temperature, light and other environmental factors, so multiple cycles, multiple days and time periods are measured to avoid the randomness of data as much as possible.The combined judgment of the fill factor and the decay rate of the component effectively locates the aging component and preliminarily determines the aging degree, ensuring the long-term and stable operation of the photovoltaic power generation system.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic module testing technology, and in particular to a method for determining the aging condition of photovoltaic modules. Background Technology

[0002] The key to the long-term effective operation of a photovoltaic power station for 25 years lies in the photovoltaic modules themselves. The modules are the core of a photovoltaic power station, and their power generation efficiency is a major focus of attention. Module power generation efficiency is its inherent power generation capacity, and it is interdependent with timely monitoring and maintenance, ultimately determining the key to power generation and revenue. Given a fixed set of modules, low power generation efficiency can be caused by two main reasons: first, module malfunction leading to severe mismatch; and second, normal or abnormal aging and degradation of the modules. For the former, many specialized instruments are already available for identification. For the latter, the aging process is extremely slow, with high-quality modules degrading even more slowly. However, abnormal aging caused by environmental or destructive factors cannot be ruled out. Therefore, effective identification methods are needed to alert power station staff and prevent further losses. Summary of the Invention

[0003] In many distributed generation systems, to ensure safe system operation and improve component power generation efficiency, fast shutdown devices are equipped on the components to quickly shut them down in case of failure. Alternatively, power optimizers and micro-inverters with I / V scanning capabilities are used to monitor component operating status in real time and ensure they operate at their optimal points. The presence of I / V characteristic curves on the components helps determine if they are aging. Using the fill factor in electrical parameters to aid in determining component aging and its degree is highly reliable and effective. The fill factor is a fundamental indicator of component quality; a higher fill factor is better. Generally, a normal component fill factor is between 0.7 and 0.75.

[0004] The purpose of this invention is to provide a method for determining the aging of photovoltaic modules. Based on obtaining the I-V characteristic curves of all modules over multiple days and at multiple times, the average fill factor is calculated accordingly. The average fill factor is used to determine whether the modules are aging and to what extent they are aging. The modules are then included in a list of suspected aging modules. After multiple measurement cycles, the aging modules are finally identified.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for determining the aging of photovoltaic modules includes the following steps:

[0007] S1. Obtain the I_V characteristic curves for N pv components over D days in the current testing period, at time T each day; S2. Based on the fill factor calculation formula, one I_V characteristic curve corresponds to one fill factor. Calculate the fill factor FF for all components. d_t_iEach component has a D-row, T-column information matrix regarding the fill factor; S3, process the D-row, T-column fill factor information matrix of each component according to the rules, and calculate the unique average fill factor FF for each component. avg_i S4. Determine the aging of components. If all components are within the aging threshold range, they are considered to be suspected of aging and proceed to the next step S5. Otherwise, the subsequent aging degree determination of the component is directly terminated. S5. Perform the determination of light, medium and heavy aging degree of components in sequence. After all components are determined, a list of "suspected aging components" is formed. S6. Perform steps S1 to S5 in multiple test cycles. After N test cycles, a list of "aged components" is finally formed.

[0008] The beneficial effects of this invention are as follows:

[0009] The aging determination method of the present invention analyzes whether the component is aging based on the characteristics of the component's I-V characteristic curve under multiple test cycles, and finally determines the aging component and the degree of aging. This method can reliably locate aging components, serve as an alert, and prevent the continuous reduction of power generation efficiency.

[0010] The method proposed in this invention has good adaptability and strong identification ability, and is of great practical significance for improving the safety and reliability of photovoltaic systems and promoting the realization of intelligent operation and maintenance technology for power plants. Attached Figure Description

[0011] Figure 1 This is a flowchart illustrating the aging determination of photovoltaic modules according to an embodiment of the present invention;

[0012] Figure 2 This is a schematic diagram of the P-V characteristic curve of an aging photovoltaic module according to an embodiment of the present invention;

[0013] Figure 3 This is a schematic diagram of the I-V characteristic curves of an aging photovoltaic module according to an embodiment of the present invention; Detailed Implementation

[0014] To make the technical problems, technical solutions, and advantages of the embodiments of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0015] This invention provides a method for determining the aging of photovoltaic modules. Based on the implementation of a module-level power optimizer and a micro-inverter, the I-V characteristic curves of the modules can be acquired at any time over multiple days. The average fill factor is calculated, and this value is used to determine the degree of aging of the modules, forming a list of suspected aging modules. After multiple test cycles, the final aging modules are identified. The fault detection method of this invention includes the following steps: S1, acquiring the I-V characteristic curves of N pv modules over D days in the current test cycle, at time T each day; S2, calculating the fill factor FF for all modules according to the formula for calculating the fill factor, where one I-V characteristic curve corresponds to one fill factor. d_t_i Each component has a D-row, T-column information matrix regarding the fill factor; S3, process the D-row, T-column fill factor information matrix of each component according to the rules, and calculate the unique average fill factor FF for each component. avg_i S4. Determine the aging of components. If all components are within the aging threshold range, they are considered to be suspected of aging and proceed to the next step S5. Otherwise, the subsequent aging degree determination of the component is directly terminated. S5. Perform the determination of light, medium and heavy aging degree of components in sequence. After all components are determined, a list of "suspected aging components" is formed. S6. Perform steps S1 to S5 in multiple test cycles. After N test cycles, a list of "aged components" is finally formed.

[0016] To ensure the rationality of the data, the fill factor obtained from multiple calculations was filtered and averaged, which mitigated the data deviation caused by environmental factors such as temperature and light to a certain extent.

[0017] Considering the slow process of normal component aging, the average fill factor of the same component over multiple test cycles is combined with the "suspected aged components" list formed after a single test cycle to finally determine whether the component is an aged component and to what extent it is aged.

[0018] To ensure that there are no misjudgments of aging or other faults, a reasonable threshold is set for the component fill factor. For components with excessively low fill factors, their power is reduced too much, and other component fault judgments should be performed instead of aging judgments.

[0019] If the average fill factor of a component is higher than or equal to Thr_FF, it indicates that the component is currently in good health, and the subsequent aging determination of the component will end directly. If all components are in good health, there is no need to form an aging component list.

[0020] In some embodiments, a method for determining the aging of a photovoltaic module includes the following steps:

[0021] S1. Under the current testing period, obtain the I_V characteristic curves of each component sequentially for D consecutive days, with T fixed moments each day, where D∈[3,10] and T∈[5,10].

[0022] S2. Calculate the fill factor FF of the component based on the I_V characteristic curve of the component on day d (d∈[1,Npv]) (t∈[1,T]) (idx) (idx∈[1,Npv]). d_t_i , where is the total number of Npv components, in I sc U oc These represent the short-circuit current and open-circuit voltage of the components under standard conditions, respectively, until the fill factor of Npv components is calculated.

[0023] S3. Process the D×T matrix Array_FF of Npv components according to certain rules to obtain the unique average fill factor FF of the component. avg_i ;

[0024] S4. Determining whether a component enters the aging process: Determine the status of each of the Npv components. If the average fill factor of the idx-th component is FF... avg_i ≥Thr_FF or FF avg_i If Thr_l < FF, the component aging process ends directly; if Thr_l ≤ FF, the aging process ends directly. avg_i If the value is less than or equal to Thr_FF, then the component will be subject to S5 aging determination, where Thr_FF is the fill factor threshold and Thr_l is the severe aging determination threshold.

[0025] S5. Determination of aging level: For components entering S5, the aging level is determined based on their average fill factor FF. avg_i The size of the component determines its aging level as mild, moderate, or severe, and the component index idx is recorded in the "suspected aging component" list.

[0026] S6. Multi-cycle testing: For the next N test cycles, where N >= 4, steps S1 to S5 are executed. After N test cycles, the components in the suspected aging component list with different degrees of aging are counted. If the number of times the idx-th component appears in the suspected aging component list is greater than the counting threshold Thr_count, Then move component idx to the list of aged components.

[0027] In a preferred embodiment, in step S1, since the component already has a micro-inverter and a power optimizer, the I_V curve can be obtained, and the fault type of the component can be determined simply and intuitively based on the model method. An I_V scan is performed at time t (t∈[1,T]) on day d (d∈[1,D]) to obtain the characteristic curve of the component output at the current time.

[0028] In a preferred embodiment, in step S2, based on the I_V characteristic curve of day d (d∈[1,Npv]) at time t (t∈[1,T]) on day d (d∈[1,D]), the quality status FF of component idx at time t on day d is obtained using the fill factor calculation formula. d_t_i Where idx is the unique index of the photovoltaic module, and the fill factor is calculated using the following formula: I d_t_i_max U d_t_i_max These represent the current and voltage values ​​corresponding to the point of maximum output power on the I_V characteristic curve of component idx at time t on day d, respectively. Generally, I... sc U oc The current and voltage of the photovoltaic modules are known after they have undergone rigorous environmental testing by the photovoltaic module manufacturing company according to strict standards before leaving the factory.

[0029] In a preferred embodiment, in step S3, any idx-th component has a D-row, T-column data array Array_FF containing fill factor information, which stores the fill factor FF of that component at time t (t ∈ [1, T]) on day d (d ∈ [1, D]). d_t_i The unique fill factor FF of the component is obtained by processing the D rows and T columns matrix according to certain rules. avg_i .

[0030] In a preferred embodiment, in step S4, based on the component's unique average fill factor FF... avg_i To determine if aging has occurred, when the average fill factor FF... avg_i ≥Thr_FF indicates that the component quality is good and there is no aging. When FF avg_i <Thr_l indicates a significant decrease in component output power. In such cases, the determination of the aging level should be terminated immediately, regardless of whether the component has malfunctioned. Otherwise, the component can proceed to the determination of the aging level.

[0031] In a preferred embodiment, in step S5, the average fill factor FF of the idx-th component is... avg_i Combining the mild aging threshold Thr_s = Thr_FF - diff1, the moderate aging threshold Thr_m = Thr_FF - diff2, and the severe aging threshold Thr_l = Thr_FF - diff3, the aging degree of the component is determined, where diff1 = 0.05, diff2 = 0.1, and diff3 = 0.15, representing the differences between the mild, moderate, and severe aging thresholds and the fill factor threshold, respectively. The component index idx is recorded in the suspected aging component list, and the component is classified according to its aging degree. When FF... avg_i ∈[Thr_s,Thr_FF), the component is considered to be slightly aged, FFavg_i ∈[Thr_m,Thr_s), the component is identified as moderately aged, FF avg_i The component is identified as severely aged if it is ∈[Thr_l,Thr_m).

[0032] In a preferred embodiment, in step S6, N test cycles are performed, with steps S1 to S5 executed in each cycle. In the Nth cycle, the number of times component idx appears in the suspected aging component list is greater than or equal to the threshold Thr_count is also counted. Only then can the component index idx be moved into the "Aging Components" list and distinguished according to the degree of aging. Among them, if a component exists in more than one degree of aging in multiple test cycles, it will be classified as the more severely aged category.

[0033] In step S1, the environment at time T on day D should be as sunny and the temperature as possible. The T times each day should be as consistent as possible to minimize the measurement error caused by differences in the external environment.

[0034] Furthermore, the data processing in step S3, which follows certain rules, could be as follows: For each component, remove the daily max(FF) d_t_i ) and min(FF d_t_i ), then for the remaining FF of t-2 d_t_i Calculate the mean, where max() and min() find the maximum and minimum values, respectively. The mean FF can be obtained daily by calculating t-2 fill factors. avg_d_i Finally, the D fill factors FF for D days. avg_d_i The mean value is then calculated to obtain the average fill factor FF of the i-th component. avg_i Second: For each component, over a total of D days, the D×T fill factor matrix Array_FF is processed. The maximum and minimum values ​​are removed, and the average of the remaining D×T-2 fill factors is calculated to obtain the average fill factor FF of the idx-th component. avg_i "Data processing according to certain rules" can be extended to other methods, not limited to the two mentioned above. The operation of removing excessively large and small values ​​and averaging the fill factor obtained by the component within a test cycle is to avoid the randomness of test data and test errors caused by environmental factors. Any other methods that can mitigate such errors are also acceptable.

[0035] Furthermore, in step S6, generally, N ≥ 4. The longer the photovoltaic modules operate, the more data is available. N is variable, meaning that the more Array_FF data collected from previous test cycles, the more reliable the statistics. One test cycle can be six months, one year, or even two years. Since photovoltaic module aging is a slow process, especially when weather changes bring variations in sunlight and temperature, it can cause significant power loss, leading to misjudgments by the diagnostic system. Therefore, each test cycle generates a list of suspected aging modules. After multiple test cycles, it can be determined whether the modules are indeed aging and to what extent.

[0036] The background section of this invention may include background information about the problems or environment in which the invention is being developed, and is not necessarily a description of prior art. Therefore, the content included in the background section does not constitute an admission of prior art by the applicant.

[0037] The above description provides a further detailed explanation of the present invention in conjunction with specific / preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A method for determining the aging of photovoltaic modules, characterized in that: Includes the following steps: S1. Obtain the total number of tests in the current test period. 1 component, total Every day S2. According to the formula for calculating the fill factor, one I_V characteristic curve corresponds to one fill factor. The fill factor is calculated for all components. Each component has OK Column fill factor information matrix; S3, for each component OK The column fill factor information matrix is ​​processed according to rules, and a unique average fill factor is obtained for each component. S4. Determine the aging of components. If all components are within the aging threshold range, they are considered to be suspected of aging and proceed to the next step S5. Otherwise, the aging degree determination of the component is directly terminated. S5. Perform the determination of light, medium and heavy aging degree of components in sequence. After all components are determined, a list of "suspected aging components" is formed. S6. Perform steps S1 to S5 in multiple test cycles. After N test cycles, a list of "aged components" is finally formed. In step S2, according to the first Each component , No. The first day The I_V characteristic curve is obtained by using the fill factor calculation formula. Component No. Heavenly Time fill factor ,in It is a unique index for photovoltaic modules. The fill factor calculation formula is as follows: , They represent the first Heavenly Time of the first The current and voltage values ​​corresponding to the point of maximum output power on the I-V characteristic curve of the component. These represent the short-circuit current and open-circuit voltage of the component under standard conditions, respectively. The data processing in step S3 according to the rules is selected from at least two of the following processing methods: Method 1: For each component, remove the daily data. and Then for the remaining of Calculate the mean, where max() and min() find the maximum and minimum values, respectively; calculate daily. Each fill factor yields a mean. Finally, for The sky Each mean Then calculate the average to the th The unique average fill factor of each component Method 2: For each component... Within a day Fill factor matrix Remove the maximum and minimum values, then process the remaining values. The average of the n fill factors is obtained to get the nth... The unique average fill factor of each component ; In step S5, the first The unique average fill factor of each component Combined with mild aging threshold , It is the fill factor threshold and the moderate aging threshold. Threshold for judging severe aging To determine the degree of aging of the component, among which , , , representing the difference between the mild, moderate, and severe aging thresholds and the fill factor threshold, respectively; component indexing Record the suspected aging components in the list and classify the aging degree of the components. The components were classified as slightly aged. The components were classified as moderately aged. The components were identified as severely aged. In step S6, the first During each cycle, the components are also counted. The number of times the suspected aging component appears in the list is greater than or equal to the threshold. , Only then will the component index be set. Move the component to the "Aging Components" list and categorize them by aging level. If a component exhibits more than one aging level across multiple test cycles, it will be classified as a more severe aging category. Each test cycle generates a list of suspected aging components. After multiple test cycles, it is determined whether the components are indeed aging and to what extent.

2. The method for determining the aging of photovoltaic modules as described in claim 1, characterized in that: Specifically, the steps include the following: S1. During the current testing period, sequentially acquire the I_V characteristic curves of each component for D consecutive days, with T fixed moments each day. ; S2, according to the first The first component Heavenly The fill factor of the component is calculated once using the I_V characteristic curve. , among which is Total number of components, up to The fill factor for each component has been calculated; S3, sequentially Each component matrix Data processing is performed according to the rules to obtain the unique average fill factor for this component. ; S4. Determine the aging of components. Each component is judged one by one, if the first component... The unique average fill factor of the component or If the aging determination process for that component is terminated directly, then the process ends. Then, the S5 aging level determination is performed on the component, where... This is the threshold for judging severe aging; S5. Determine the degree of aging based on the unique average fill factor of the component. The component is determined by its size and categorized into mild, moderate, and severe aging levels, and then indexed accordingly. Recorded in the "Suspected Aging Components" list; S6 There are 1 test cycle, among which All steps S1 to S5 are executed, after which... After one test cycle, statistical analysis is conducted on components in the suspected aging component list to determine those with varying degrees of aging. If the first cycle is... The number of times a component appears in the list of suspected aging components exceeds the counting threshold. , Then the component Move to the aging component list; In the current testing period, obtain the first... The I_V characteristic curves of each component over multiple days and at multiple times are obtained, and the fill factor of the corresponding day-time-component is calculated based on the I_V characteristic curves. And calculate the unique average fill factor of the component according to the data processing rules. According to the unique average fill factor Determine whether aging has occurred and the degree of aging; record suspected aging components. One test cycle to determine the final aging components.

3. The method for determining the aging of photovoltaic modules as described in claim 1, characterized in that: In step S1, based on the fact that the component already has a micro-inverter and a power optimizer, the I_V characteristic curve is obtained, and the fault type of the component is determined based on the model method; for the first... Each component , No. The first day Perform an I_V scan at any time to obtain the I_V characteristic curve output by the component at the current time.

4. The method for determining the aging of photovoltaic modules as described in claim 1, characterized in that: In step S3, any of the first Each component has one OK A data array containing fill factor information. It stores the component in the first... Heavenly Time fill factor It is through this OK The column matrix is ​​processed according to rules to obtain the unique average fill factor of the component. .

5. The method for determining the aging of photovoltaic modules as described in claim 1, characterized in that: In step S4, based on the component's unique average fill factor To determine if aging has occurred, the unique average fill factor is used. It is determined that there is no aging, when This directly ends the subsequent determination of the degree of aging; Otherwise, the component will be assessed for aging.

6. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by the processor, it implements the method for determining the aging of photovoltaic modules as described in any one of claims 1 to 5.

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