Quantification method and model for output characteristics of photovoltaic string under near-shade

Abstract

The application relates to the field of photovoltaic system performance evaluation, and discloses a photovoltaic module string output characteristic quantification method and model under near shadow. The method inputs standard test condition electrical parameters of a photovoltaic module, including a short-circuit current, an open-circuit voltage, maximum power point parameters, a temperature coefficient, a cell type and a series-parallel topology structure inside the module, calculates module-level parameters based on a single-diode model, and maps the module-level parameters to cell-level parameters through the topology structure inside the module. In combination with irradiance and temperature under unshaded and shaded conditions, parameters such as photogenerated current and reverse saturation current are dynamically adjusted to calculate cell volt-ampere characteristics. Then, volt-ampere characteristic curves of cells, sub-strings, modules and module strings are integrated step by step to finally obtain voltage-current characteristics of the module string under near shadow. The method is suitable for full-cell modules, half-cell modules and heterojunction modules, and can quickly and accurately quantify the output characteristics of the module string under shading conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic system performance evaluation, in particular to a method and model for quantifying output characteristics of a photovoltaic string under near shadow. BACKGROUND

[0002] The output characteristics of a photovoltaic string have a significant impact on the overall efficiency and power generation performance of a photovoltaic power station. In the design of household photovoltaic power stations and commercial and industrial photovoltaic systems, the arrangement of photovoltaic modules and the connection method of the string directly determine the performance of the system. However, photovoltaic modules are often affected by nearby obstructions during actual operation, such as obstructions caused by surrounding trees, buildings, chimneys, and utility poles. Since these obstructions are relatively close to the photovoltaic modules, they often exhibit localized and time-varying characteristics. This obstruction pattern causes complex changes in the current and voltage characteristics of the photovoltaic modules, increasing the difficulty of quantifying the output characteristics of the photovoltaic system.

[0003] In the prior art, the output characteristics of photovoltaic modules are usually calculated using a single-diode model combined with mathematical modeling methods, but these methods have significant limitations. On the one hand, these methods are complex to calculate, requiring a large number of nested judgments and iterative calculations, resulting in low computational efficiency and difficulty in meeting real-time requirements. On the other hand, traditional methods are mainly designed for full-sheet modules, and cannot be adapted to new module structures such as half-sheet modules and heterojunction modules that have been widely used in recent years. In addition, existing methods lack the ability to dynamically model the obstruction conditions, and there is a lack of high-precision modeling methods for the output characteristics of photovoltaic systems under near shadow, making it difficult to accurately assess the impact of shadow on system efficiency.

[0004] In the field of photovoltaic system design and performance optimization, these defects in the prior art result in inaccurate analysis of the impact of shadow obstructions, making it difficult to achieve ideal results in the optimization of string arrangement and connection methods. Therefore, there is an urgent need for a technical method that can quickly and accurately quantify the output characteristics of photovoltaic strings under near shadow, to adapt to photovoltaic modules of different structures and meet the performance evaluation requirements under complex obstruction conditions. SUMMARY

[0005] To address the deficiencies in the prior art, the present application provides a method and model for quantifying the output characteristics of a photovoltaic string under near shadow, solving the problem of the inability to quickly and accurately quantify the output characteristics of a photovoltaic string under near shadow in the prior art, particularly the lack of adaptability to complex topological structure modules and the lack of dynamic obstruction modeling capability.

[0006] To achieve the above objectives, the present application is implemented by the following technical solution: a method for quantifying the output characteristics of a photovoltaic string under near shadow, comprising the following steps:

[0007] S1, input the electrical parameters of the photovoltaic module under standard test conditions, including short-circuit current, open-circuit voltage, maximum power point current, maximum power point voltage, short-circuit current temperature coefficient, open-circuit voltage temperature coefficient, maximum power temperature coefficient, cell type and module series-parallel topology structure information;

[0008] S2, based on the electrical parameters of the module under standard test conditions, calculate the six parameters of the module using the photovoltaic module volt-ampere characteristic model, including photo-generated current, reverse saturation current, diode factor, series resistance, parallel resistance and short-circuit current temperature coefficient adjustment value;

[0009] S3, according to the internal circuit topology of the photovoltaic module, map the module-level parameters to the cell-level parameters;

[0010] S4, based on the irradiance and photovoltaic cell temperature under unshaded conditions, calculate the volt-ampere characteristic of the cell under unshaded conditions;

[0011] S5, based on the irradiance and photovoltaic cell temperature under near shadow shading conditions, dynamically adjust the volt-ampere characteristic parameters of the cell, and calculate the volt-ampere characteristic of the cell under shading conditions;

[0012] S6, based on the series-parallel circuit topology relationship of the photovoltaic module string, integrate the volt-ampere characteristics of the cell, sub-string and module at each level, and calculate the voltage-current characteristic of the module string.

[0013] Preferably, in step S2, the six parameters of the photovoltaic module are calculated by the CEC6PPVMM model, including: photo-generated current I mod_ph_ref , calculated based on the short-circuit current of the module and the irradiance and temperature under standard test conditions;

[0014] Reverse saturation current I mod_o_ref , calculated according to the open-circuit voltage and temperature of the module;

[0015] Diode factor a mod_ref , calculated by fitting the maximum power point parameters of the module;

[0016] Series resistance R mod_s_ref , fitted and calculated in combination with the electrical parameters of the module;

[0017] Parallel resistance R mod_sh_ref , fitted and calculated in combination with the electrical parameters and working conditions of the module;

[0018] Short-circuit current temperature coefficient adjustment value Ajust mod , calculated according to the short-circuit current temperature coefficient and the working temperature of the module.

[0019] Preferably, in the step S3, the step of mapping the six parameters of the photovoltaic module into the cell-level parameters based on the component-based circuit topology comprises:

[0020] Conversion of the photo-generated current:

[0021]

[0022] where I cell_ph_ref is the photo-generated current of the cell, I mod_ph_ref is the photo-generated current of the module, and N is the number of series-connected cells in the module;

[0023] Conversion of the reverse saturation current:

[0024]

[0025] where I cell_o_ref is the reverse saturation current of the cell, I mod_o_ref is the reverse saturation current of the module;

[0026] Conversion of the diode factor:

[0027]

[0028] where a cell_ref is the diode factor of the cell, a mod_ref is the diode factor of the module, M1 is the number of cells per sub-string, and M2 is the number of parent strings per module;

[0029] Conversion of the series resistance:

[0030]

[0031] where R cell_s_ref is the series resistance of the cell, and R mod_s_ref is the series resistance of the module;

[0032] Conversion of the parallel resistance:

[0033]

[0034] where R cell_sh_ref is the parallel resistance of the cell, and R mod_sh_ref is the parallel resistance of the module;

[0035] Conversion of the short-circuit current temperature coefficient adjustment value:

[0036] Ajust cell = Ajust mod

[0037] where Ajust cellAjust is the short-circuit current temperature coefficient adjustment value of the battery piece mod Ajust is the short-circuit current temperature coefficient adjustment value of the module.

[0038] Preferably, in the step S4, the step of calculating the voltage-current characteristic of the battery piece under the unshaded condition based on the irradiance and the photovoltaic cell temperature under the unshaded condition comprises:

[0039] The working conditions of the photovoltaic module under the unshaded condition are input, including the irradiance G unshaded and the photovoltaic cell temperature T unshaded ; the battery piece level parameters obtained in the step S3 are used to adjust the parameters from the standard test condition to the unshaded working condition, and the dynamic parameters of the battery piece are calculated;

[0040] The voltage-current characteristic curve of the battery piece under the unshaded condition is calculated using the single diode model, and is solved point by point according to the following formula:

[0041]

[0042] Wherein, I is the output current of the battery piece, V is the output voltage of the battery piece, R s is the series resistance of the battery piece, R sh is the parallel resistance of the battery piece, and a is the diode factor of the battery piece;

[0043] The voltage of the battery piece is set to be equally spaced between 0 and its open circuit voltage V oc , and the output current corresponding to each voltage point is calculated using the single diode model to obtain the voltage-current characteristic curve of the battery piece under the unshaded condition.

[0044] Preferably, in the step S5, the step of calculating the voltage-current characteristic of the battery piece under the shaded condition based on the irradiance and the photovoltaic cell temperature under the near shadow shading condition comprises:

[0045] The working conditions of the photovoltaic module under the near shadow shading condition are input, including the irradiance G unshaded and the photovoltaic cell temperature T unshaded after shading;

[0046] The battery piece level parameters obtained in the step S3 are used to adjust the parameters from the standard test condition to the shaded working condition, and the dynamic parameters of the battery piece are calculated;

[0047] The voltage-current characteristic curve of the battery piece under the unshaded condition is calculated using the single diode model;

[0048] The voltage of the battery piece is set to be equally spaced between 0 and its open circuit voltage V ocan equal interval of points between the two, using a single diode model to calculate the corresponding output current at each voltage point, to obtain the voltage-current characteristic curve of the battery piece under the shading condition.

[0049] Preferably, the equal interval of points is set according to the calculation resources and time limit.

[0050] Preferably, in the step S6, based on the series-parallel circuit topology relationship of the photovoltaic string, the voltage-current characteristics of the battery piece, the sub-string and the component are integrated step by step, and the step of calculating the voltage-current characteristics of the string includes:

[0051] According to the voltage-current characteristic curve of the battery piece under the unshading condition calculated in step 4 and the voltage-current characteristic curve of the battery piece under the shading condition calculated in step 5, and combining the shadow distribution information of the photovoltaic component, the voltage matrix V cell and the current matrix I cell of the battery piece are initialized.

[0052] According to the series connection relationship of the battery piece in the sub-string, the voltage matrix and the current matrix of the sub-string are calculated by using the voltage-current characteristic law of the series circuit.

[0053] According to the parallel connection relationship of the sub-string in the parent string, the voltage matrix and the current matrix of the parent string are calculated by using the voltage-current characteristic law of the parallel circuit.

[0054] According to the series connection relationship of the parent string in the component, the voltage matrix and the current matrix of the component are calculated by using the voltage-current characteristic law of the series circuit.

[0055] According to the series connection relationship of the component in the string, the voltage matrix and the current matrix of the string are calculated by using the voltage-current characteristic law of the series circuit.

[0056] The voltage matrix and the current matrix of the string under the near shadow shading condition are output, and the voltage-current characteristic curve thereof is drawn, for evaluating the output characteristics of the string under the current condition.

[0057] The application also provides a photovoltaic string output characteristic quantification model under the near shadow, comprising:

[0058] A parameter initialization module is used to input the electrical parameters and the component topology structure of the photovoltaic component under the standard test condition.

[0059] A parameter conversion module is used to convert the component-level parameters into the battery piece-level parameters.

[0060] A voltage-current characteristic calculation module is used to calculate the voltage-current characteristics of the battery piece under the unshading and shading conditions.

[0061] An output characteristic integration module is used to integrate the voltage-current characteristics of the battery piece, the sub-string and the component based on the series-parallel law of the photovoltaic string, to generate the voltage-current characteristic curve of the string.

[0062] The application further provides a computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the method as described above when executing the computer program.

[0063] The application further provides a storage medium having a computer program stored thereon, wherein the computer program is executable on a processor to implement the method as described above.

[0064] The application provides a method and model for quantifying output characteristics of photovoltaic module strings under near shadow.

[0065] 1. The application supports full-piece modules, half-piece modules and heterojunction modules (HJT) with complex topologies by introducing the topology of internal circuits of the modules. Through dynamic parameter adjustment and voltage-current characteristic modeling, it can adapt to different module types and connection modes, has good universality, and meets the diversified photovoltaic application requirements.

[0066] 2. The application can accurately model the influence of near shadow on the output characteristics of photovoltaic modules, combine the irradiance and temperature under shading conditions, and realize accurate quantification of the voltage-current characteristics of modules and strings by adjusting parameters such as photo-generated current and reverse saturation current, thereby significantly improving the accuracy of analysis of the influence of shadow shading.

[0067] 3. The application uses the series-parallel law of the circuit to simplify the multi-level judgment process, integrates the voltage-current characteristics of the battery piece, sub-string, module and string by stages, reduces the calculation complexity and redundant judgment logic, and improves the calculation efficiency, thereby providing technical support for real-time performance evaluation and engineering application.

[0068] 4. The application accurately reflects the output characteristics of photovoltaic modules and strings under different light conditions by calculating the voltage-current characteristics under unshaded and shaded conditions respectively. This dual-mode modeling capability is not only suitable for normal working conditions, but also suitable for complex photovoltaic power station scene analysis, such as local shading and dynamic changes in shading.

[0069] 5. The voltage-current characteristic curve and string output characteristics generated by the application can be directly used for performance analysis, design optimization and power generation prediction of photovoltaic systems, helping engineers to optimize module arrangement and system connection mode, improve the overall power generation efficiency of photovoltaic systems, and reduce the influence of shadow shading on the system. BRIEF DESCRIPTION OF DRAWINGS

[0070] Figure 1 Figure 1 is a schematic diagram of the method of the application;

[0071] Figure 2 Figure 2 is another schematic diagram of the method of the application; and

[0072] Figure 3 A schematic diagram of a model structure of the present application;

[0073] Figure 4 A schematic diagram of a computer device structure of the present application.

[0074] Wherein, 100, parameter initialization module; 200, parameter conversion module; 300, volt-ampere characteristic calculation module; 400, output characteristic integration module; 40, computer device; 41, processor; 42, memory; 43, storage medium. DETAILED DESCRIPTION

[0075] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the specification of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0076] Please refer to the drawings in the specification of the present application Figure 1 - the drawings in the specification of the present application Figure 2 The present application provides a method for quantifying output characteristics of a photovoltaic string under near shadow, aiming to quickly and accurately quantify the output characteristics of the photovoltaic string under shadow condition.

[0077] The method of the present application starts from the standard test condition (STC) parameters of the photovoltaic module, maps the parameters of the module and the cell, combines the volt-ampere characteristic calculation under unshaded and shaded conditions, and gradually integrates the output characteristics by using the series-parallel circuit law. The present application is suitable for various photovoltaic module structures (such as full-sheet module, half-sheet module, heterojunction module, etc.), and can provide accurate output performance quantization analysis at the string level. The steps of the method of the present application will be described in detail below.

[0078] As shown in the figure, the method for quantifying output characteristics of a photovoltaic string under near shadow includes the following steps: Figure 1 S1, input the electrical parameters of the photovoltaic module under standard test conditions;

[0079] S2, based on the electrical parameters of the module under standard test conditions, calculate the parameters of the module by using the volt-ampere characteristic model of the photovoltaic module;

[0080] S3, according to the internal circuit topology structure of the photovoltaic module, map the module-level parameters to the cell-level parameters;

[0081] S4, based on the irradiance and the temperature of the photovoltaic cell under unshaded condition, calculate the volt-ampere characteristic of the cell under unshaded condition;

[0082] S5, based on the irradiance and the temperature of the photovoltaic cell under shaded condition, calculate the volt-ampere characteristic of the cell under shaded condition;

[0083] S5, dynamically adjusting the volt-ampere characteristic parameters of the cell based on the irradiance and the temperature of the photovoltaic cell under the condition of the nearby shadow shielding, and calculating the volt-ampere characteristic of the cell under the condition of the shielding;

[0084] S6, based on the series-parallel circuit topology relationship of the photovoltaic string, integrating the volt-ampere characteristics of the cell, the sub-string and the component in stages, and calculating the voltage-current characteristic of the string.

[0085] For step S1, the present application is based on the electrical parameters of the photovoltaic module under the standard test condition (STC, Standard Test Condition), including the short-circuit current, the open-circuit voltage, the maximum power point current, the maximum power point voltage, the short-circuit current temperature coefficient, the open-circuit voltage temperature coefficient, the maximum power temperature coefficient, the cell type and the series-parallel topology structure information inside the module. It should be noted that these parameters can be directly obtained from the product specification of the photovoltaic module, which provides basic data for subsequent calculation of the present application.

[0086] 1. Short-circuit current (I sc ) and open-circuit voltage (V oc ):

[0087] The short-circuit current is the maximum current when the output end of the photovoltaic module is short-circuited, and the unit is ampere (A). The open-circuit voltage is the maximum voltage when the output end of the photovoltaic module is open-circuited, and the unit is volt (V). These parameters are usually provided under the rated condition of the photovoltaic module, and are the most important basic performance indicators of the photovoltaic module.

[0088] 2. Maximum power point current (I mp ) and maximum power point voltage (V mp ):

[0089] The maximum power point current is the working current of the photovoltaic module under the maximum power output state, and the unit is ampere (A). The maximum power point voltage is the working voltage under the maximum power output state, and the unit is volt (V). These two parameters are used to describe the maximum power output characteristics of the photovoltaic module.

[0090] 3. Temperature coefficient related parameters:

[0091] Short-circuit current temperature coefficient (α_I sc ): unit: % / ℃, indicating the percentage change rate of the short-circuit current with temperature change;

[0092] Open-circuit voltage temperature coefficient (β_V oc ): unit: % / ℃, indicating the percentage change rate of the open-circuit voltage with temperature change;

[0093] Maximum power temperature coefficient (γ_P mp ): unit: % / ℃, indicating the percentage change rate of the maximum power with temperature change.

[0094] For example, these temperature coefficients are key parameters for adjusting the electrical characteristics of the photovoltaic module with respect to the ambient temperature, which will be dynamically adjusted in the subsequent steps to the volt-ampere characteristics of the cell.

[0095] 4. Cell type:

[0096] The type of cell used in the photovoltaic module (cell type ) needs to be input, such as mono-Si or poly-Si, and HJT type. These different types of photovoltaic modules have different characteristics due to the material properties, which will be reflected in the subsequent single-diode model parameters.

[0097] 5. Series-parallel topology of the module, number of cells in the module (cells in_series ):

[0098] A photovoltaic module is usually composed of multiple cells, and its internal circuit can be in series, parallel, or a combination of the two. For example:

[0099] In some embodiments, the number of cells in a standard photovoltaic module is 60, and the connection mode is completely in series;

[0100] In another possible implementation, a half-module is composed of two groups of 60 cells, each group is in series, and finally connected in parallel to form a module;

[0101] For HJT modules, there can be more complex sub-string structures, each with different series-parallel connection relationships.

[0102] It can be understood that this topology information has an important influence on the mapping of module parameters to cell parameters, and needs to be input completely in this step.

[0103] It should be noted that the input parameter data is the core input information in the calculation model of the present application, and the subsequent module-level six-parameter calculation, parameter mapping to the cell level, and volt-ampere characteristic modeling all directly depend on these basic data.

[0104] In one possible implementation, parameters such as short-circuit current and open-circuit voltage are input statically and do not change with environmental conditions, while temperature coefficient-related parameters are used to correct the electrical performance of the module when the ambient temperature is dynamically adjusted in the subsequent steps. The internal topology information of the module will be used to define the distribution rules of the parameters, such as the number of sub-strings, which determines how the photo-generated current and voltage parameters are mapped to the cell level.

[0105] For step S2, in this embodiment, based on the electrical parameters of the photovoltaic module under standard test conditions (STC), the six key parameters of the photovoltaic module are calculated using the photovoltaic module volt-ampere characteristic model (CEC6PPVMM), including the photo-generated current, the reverse saturation current, the diode factor, the series resistance, the parallel resistance, and the short-circuit current temperature coefficient adjustment value.

[0106] It should be noted that the six parameters of the photovoltaic module are the core parameters for describing the volt-ampere characteristic curve of the photovoltaic module, and accurate calculation of these parameters provides a reliable basis for subsequent parameter mapping from the module to the cell and volt-ampere characteristic calculation.

[0107] As an option, the six parameters of the photovoltaic module can be calculated from the standard test condition parameters of the photovoltaic module. Specifically, the standard test condition is usually defined as irradiance G STC = 1000 W / m 2 and T STC = 25℃. In this embodiment, these parameters will be used to calculate the six parameters of the module.

[0108] In one possible implementation, the photo-generated current I mod_ph_ref is the photo-generated current that the module can generate under standard test conditions, and the calculation formula is as follows:

[0109]

[0110] wherein:

[0111] I sc is the short-circuit current of the module (unit: A), which has been input in step S1;

[0112] is the short-circuit current temperature coefficient (unit: % / ℃), which is used to correct the influence of temperature change on the photo-generated current;

[0113] T STC is the operating temperature of the module, and the default value under standard test conditions is 25℃.

[0114] It should be noted that the above formula takes into account the influence of the temperature of the module on the photo-generated current, and the accuracy of the calculation result is ensured through adjustment of the temperature coefficient.

[0115] The reverse saturation current I mod_o_ref is a key parameter for describing the dark current characteristics of the module, and the calculation formula is as follows:

[0116]

[0117] wherein:

[0118] q is the electronic charge constant, and the value is 1.602×10 -19 C.

[0119] V oc is the open-circuit voltage of the module (unit: V), which has been input in step S1 ;

[0120] n is a diode factor, usually a dimensionless constant between 1 and 2, related to the material properties of the module;

[0121] k is the Boltzmann constant, taking the value 1.38 x 10 -23 J / K;

[0122] T STC is the absolute temperature of the module, calculated as 298 K (i.e. 25 °C converted to absolute temperature).

[0123] In particular, the reverse saturation current reflects the leakage current characteristics of the module under no light conditions, and is an important parameter for describing the nonlinear voltage-current characteristics of the module.

[0124] In one possible implementation, the diode factor a mod_ref is an important parameter representing the nonlinear characteristics of the PN junction inside the module, and its value is usually obtained by experimental fitting or data table lookup. It should be noted that the diode factor directly affects the output characteristics of the single-diode model, and its value range is usually between 1 and 2.

[0125] The series resistance R mod_s_ref represents the resistance value of the internal series elements (such as wires, internal contact resistance of the battery sheet) of the module, and is usually obtained by fitting the slope of the voltage-current characteristic curve of the module, with units of Ω. As an option, it can be obtained by experimental measurement or table lookup.

[0126] The parallel resistance R mod_sh_ref represents the leakage characteristics of the internal parallel branch of the module, with units of Ω. The parallel resistance usually has a significant impact on the open-circuit voltage and the bending degree of the voltage-current characteristic curve of the module, and its value is usually large, which can be obtained by experimental fitting.

[0127] The short-circuit current temperature coefficient adjustment value Ajust mod is obtained by correcting the input temperature coefficient a sc , and is mainly used for subsequent dynamic adjustment of the influence of temperature conditions on the voltage-current characteristics of the module.

[0128] For example, if the input parameters of the photovoltaic module are as follows:

[0129] I sc = 9.5 A

[0130] V oc = 39.8 V

[0131]

[0132] T STC = 25℃

[0133] Then the calculation is obtained:

[0134] I mod_ph_ref = 9.5A (since the temperature is the standard value, no correction term)

[0135]

[0136] It should be noted that in actual calculation, the diode factor a mod_ref , the calculation or table lookup of series resistance R mod_s_ref and parallel resistance R mod_sh_ref need to be combined with the experimental data of the photovoltaic module.

[0137] In one possible implementation, the calculation of the six parameters can be realized by programming, for example, using software such as Python or MATLAB, by inputting the STC parameters of the module, automatically generating the calculation results, and providing data support for subsequent steps.

[0138] For step S3, this step describes in detail the method of mapping the module-level parameters calculated in step S2 to cell-level parameters for the internal circuit topology of the photovoltaic module. It should be noted that the photovoltaic module is composed of multiple cells, and its internal connection is usually in series, parallel or a combination of the two. Therefore, this embodiment realizes the conversion of photovoltaic module parameters to cell parameters through the internal circuit topology of the module, providing a basis for subsequent calculation of cell volt-ampere characteristics.

[0139] As an option, the parameter mapping of the photovoltaic module is based on the circuit topology of the module. Specifically, the module-level parameters include photo-generated current, reverse saturation current, diode factor, series resistance and parallel resistance, which are converted to cell-level parameters through series-parallel connection rules. The number of cells in the module, the number of sub-strings and the connection mode between sub-strings determine the specific rules of parameter distribution.

[0140] In one possible implementation, the circuit topology of the module is determined by the input number of cells N, the number of sub-strings M1, and the number of module parent strings M2. Wherein:

[0141] N is the number of cells in series in each module;

[0142] M1 is the number of cells in each sub-string;

[0143] M2 is the number of parent strings in each module.

[0144] It should be noted that the internal topology of the photovoltaic module may vary depending on the type of module. For example:

[0145] In some embodiments, the full module is generally composed of 60 or 72 cells in series;

[0146] In another possible implementation, the half module is composed of two parallel sub-strings, each of which contains a series structure of 60 cells.

[0147] For a heterojunction (HJT) module, it can contain multiple parent strings, each of which is composed of multiple sub-strings in series.

[0148] According to the above topology, the specific calculation formula of the module-level parameter distribution to the cell-level is as follows:

[0149] The distribution formula of the photo-generated current I cell_ph_ref is:

[0150]

[0151] Where I mod_ph_ref is the module-level photo-generated current, which is the value calculated in step S2. It can be understood that the photo-generated current is directly related to the series relationship inside the module, so the photo-generated current is evenly distributed according to the number of cells.

[0152] The distribution formula of the reverse saturation current I cell_o_ref is:

[0153]

[0154] Where I mod_o_ref is the module-level reverse saturation current, which is the value calculated in step S2. It should be noted that the reverse saturation current reflects the leakage current characteristics of each cell, so it is also evenly distributed according to the number of cells.

[0155] The distribution formula of the diode factor a cell_ref is:

[0156]

[0157] Where a mod_ref is the module-level diode factor, which is the value calculated in step S2; M1 is the number of cells in each sub-string, and M2 is the number of parent strings of each module. It can be understood that the diode factor is decomposed to the cell level through the series-parallel topology structure, and its value directly affects the nonlinear characteristics of the single-diode model.

[0158] The distribution formula of the series resistance R cell_s_ref is:

[0159]

[0160] where R mod_s_ref is the component-level series resistance, which is the value calculated in step S2. It should be noted that the series resistance reflects the internal wire and contact resistance between the cells, and therefore needs to be scaled and distributed according to the topological relationship.

[0161] The distribution formula of the parallel resistance R cell_sh_ref is:

[0162]

[0163] where R mod_sh_ref is the component-level parallel resistance, which is the value calculated in step S2. It should be noted that the parallel resistance reflects the characteristics of the internal leakage channel of the component, and its value is scaled and distributed through the series-parallel relationship inside the component.

[0164] It should be noted that the above formula is applicable to various component types, including full-cell components, half-cell components, and photovoltaic components with complex topological structures. Those skilled in the art can adapt different circuit topologies by adjusting parameters N, M1, and M2 to achieve accurate mapping of component parameters to cell parameters.

[0165] For step S4, in this embodiment, the voltage-current characteristic of the cell under the unshaded condition is calculated based on the irradiance and the photovoltaic cell temperature under the unshaded condition. The goal of this step is to calculate the voltage-current (I-V) characteristic curve of each cell using a single diode model, providing a basis for subsequent calculation of the output characteristics of sub-strings, components, and strings.

[0166] It should be noted that the voltage-current characteristic of the cell under the unshaded condition is the ideal state of the component performance, mainly affected by irradiance and temperature. This step combines the input environmental parameters and the cell-level parameters calculated in step S3 to establish a single diode equation and solve it point by point.

[0167] As an option, the input conditions of this step include the irradiance G unshaded (unit: W / m 2 ) and the photovoltaic cell temperature T unshaded (unit: °C) under unshaded conditions. These conditions are usually obtained by real-time monitoring equipment of the photovoltaic power station or experimental settings of the test scenario.

[0168] Specifically, irradiance is the main factor affecting the output current of the cell, while temperature has a significant impact on the open-circuit voltage of the cell and the shape of the voltage-current characteristic curve. In this embodiment, by inputting these two environmental parameters, the voltage-current characteristic of the cell can be dynamically adjusted to adapt to different working conditions.

[0169] In one possible implementation, the voltage-current characteristic of the cell is calculated using the cell-level five parameters Icell_ph_ref 、I cell_o_ref 、a cell_ref 、R cell_s_ref 、R cell_sh_ref and the environmental parameters, the dynamic parameters under the unshading condition are calculated:

[0170] The calculation formula of the photo-generated current I ph is as follows:

[0171]

[0172] Wherein:

[0173] I cell_ph_ref is the reference value of the photo-generated current at the cell level, which is calculated by step S3;

[0174] G unshaded is the irradiance under the unshading condition, with the unit of W / m 2 ;

[0175] The 1000 in the denominator is the irradiance under the standard test condition, with the unit of W / m 2 .

[0176] It should be noted that the formula adjusts the photo-generated current through the proportional relationship of the irradiance, which reflects the output characteristics of the cell under different light intensities.

[0177] The calculation formula of the reverse saturation current I o is as follows:

[0178]

[0179] Wherein:

[0180] I cell_o_ref is the reference value of the reverse saturation current at the cell level, which is calculated by step S3;

[0181] E g is the band gap energy of the photovoltaic material (unit: eV), which is usually 1.12 eV for single crystal silicon;

[0182] k is the Boltzmann constant;

[0183] T unshaded is the temperature of the cell, with the unit of Celsius, which needs to be converted into Kelvin temperature (T+273);

[0184] 298 is the absolute temperature under the standard test condition.

[0185] It can be understood that the reverse saturation current increases exponentially with the increase of the temperature, which affects the nonlinear part of the volt-ampere characteristic curve.

[0186] The series resistance Rs parallel resistance R sh The value of the diode factor a is kept consistent with the value calculated in step S3 in this embodiment, and does not change with environmental conditions.

[0187] In one possible implementation, the above-described dynamically adjusted parameters are used to calculate the volt-ampere characteristic curve of the battery piece under the unshaded condition based on a single diode model, and the specific equation is as follows:

[0188]

[0189] wherein:

[0190] I is the output current of the battery piece, in amperes (A);

[0191] V is the output voltage of the battery piece, in volts (V);

[0192] R s is the series resistance, in ohms (Ω);

[0193] R sh is the parallel resistance, in ohms (Ω);

[0194] a is the diode factor, without unit.

[0195] As an option, when calculating the volt-ampere characteristic curve of the battery piece, the voltage V is set to take equal-interval points between 0 and the open-circuit voltage V oc For example, in some embodiments, the number of points is 200; in another possible implementation, the number of points can be adjusted to 100 or 300 according to the computing resources. By substituting the single diode equation point by point, the corresponding current I is solved, thereby generating the voltage-current pair of the battery piece.

[0196] Through the calculation of this step, the volt-ampere characteristic curve of the battery piece under the unshaded condition can be completely generated, providing a basis for subsequent sub-string, component, and string characteristic calculations.

[0197] For step S5, in this embodiment, based on the irradiance and photovoltaic cell temperature under the near shadow shading condition, the volt-ampere characteristic parameters of the battery piece are dynamically adjusted, and the volt-ampere characteristic curve of the battery piece under the shading condition is calculated. This step aims to accurately reflect the output characteristics of the battery piece under partial shading by adjusting the photo-generated current, reverse saturation current, and other parameters, and generate the corresponding voltage-current (I-V) characteristic curve.

[0198] It should be noted that due to the shading condition of the photovoltaic module, the cell may be subjected to local irradiance attenuation or uneven illumination. In this embodiment, the five parameters (photo-generated current, reverse saturation current, series resistance, parallel resistance and diode factor) of the single-diode model are dynamically adjusted to achieve accurate modeling of the voltage-current characteristics of the cell under shading conditions.

[0199] As an option, the input conditions of this step include the irradiance G under the shading condition unshaded and the temperature T of the photovoltaic cell unshaded . These conditions are usually obtained through the monitoring system of the photovoltaic power station or experimental data in the simulated scene.

[0200] In a possible implementation, the dynamic parameters under the shading condition are calculated using the cell-level five parameters I cell_ph_ref , I cell_o_ref , a cell_ref , R cell_s_ref , R cell_sh_ref and the environmental parameters calculated in step S3. Specifically, the calculation steps and formulas are the same as those in the aforementioned step S4.

[0201] For step S6, in this embodiment, based on the series-parallel circuit topology relationship of the photovoltaic string, the voltage-current characteristics of the cell, sub-string and module are integrated step by step, and finally the voltage-current (I-V) characteristics of the string are calculated. The core of this step is to synthesize the voltage-current characteristic curves of the cell, sub-string, module and string from bottom to top step by step through the series and parallel rules, so as to accurately reflect the output characteristics of the string under given conditions.

[0202] It should be noted that the output characteristics of the photovoltaic string are synthesized by the voltage-current characteristics of its internal components (cell, sub-string, module). Therefore, this embodiment realizes the integration and calculation of the voltage-current characteristics step by step through the basic rules of circuit characteristics (series circuit voltage addition, current same; parallel circuit current addition, voltage same).

[0203] As an option, the input conditions of this step include the voltage-current characteristic curves of the cell under unshaded and shaded conditions calculated in the aforementioned steps S4 and S5, and the topology structure information of the module and string, such as the number of cells in each sub-string, the number of sub-strings in each module and the number of modules in each string.

[0204] Specifically, the step-by-step integration of the voltage-current characteristics includes the following parts:

[0205] In a possible implementation, first, based on the series relationship of the cell, the voltage-current characteristics of the sub-string are calculated. Specifically, the cells in the sub-string are connected in series, and the current remains unchanged, and the voltage is the sum of the voltages of all the cells.

[0206] It should be noted that the output voltage and current of the battery piece are calculated by steps S4 and S5, so in this embodiment, the voltage of the sub-string can be directly accumulated according to the number of battery pieces of the sub-string, thereby generating the volt-ampere characteristic curve of the sub-string.

[0207] After the volt-ampere characteristic of the sub-string is calculated, the volt-ampere characteristic of the parent string is integrated according to the parallel relationship of the parent string. Specifically, the sub-strings in the parent string are connected in parallel, the voltage remains unchanged, and the current is the sum of the currents of all sub-strings.

[0208] It can be understood that the volt-ampere characteristic of the parent string reflects the total output characteristic after the parallel connection of the sub-strings. By keeping the voltage the same and accumulating the current, the voltage-current characteristic of the parent string can be accurately calculated.

[0209] In one possible implementation, after the volt-ampere characteristic of the parent string is calculated, the volt-ampere characteristic of the module is integrated according to the series relationship of the parent strings in the module. Specifically, the parent strings in the module are connected in series, the current remains unchanged, and the voltage is the sum of the voltages of all parent strings.

[0210] It should be noted that the volt-ampere characteristic of the module directly reflects the series characteristic of the internal parent strings. By accumulating the voltages of the parent strings and keeping the current the same, the volt-ampere characteristic of the module can be accurately calculated.

[0211] After the volt-ampere characteristic of the module is calculated, the volt-ampere characteristic of the group string is integrated according to the series relationship of the modules in the group string. Specifically, the modules in the group string are connected in series, the current remains unchanged, and the voltage is the sum of the voltages of all modules.

[0212] Through the above step-by-step integration calculation, the volt-ampere characteristic curve of the group string is finally obtained. For example, if the group string contains 4 modules, each module contains 2 parent strings, each parent string contains 3 sub-strings, and each sub-string contains 60 battery pieces, the volt-ampere characteristic of the group string can be synthesized step by step by the above formula.

[0213] It can be understood that the integration calculation of this step fully considers the series-parallel topology structure of the photovoltaic group string, and accurately reflects the output characteristic of the group string under the unshaded and shaded conditions by step-by-step accumulation of voltage or current.

[0214] In general, the present application inputs the standard test condition parameters of a photovoltaic module and its internal circuit topology, combines a single diode model to dynamically calculate the voltage-current characteristics of the module and the cell, especially for the near shadow blocking condition, adjusts key parameters such as the photo-generated current and the reverse saturation current, and generates the voltage-current characteristic curve of the cell. By using the series-parallel circuit law, the voltage-current characteristics of the cell, the sub-string, the module and the string are integrated from bottom to top, and finally the voltage-current characteristic curve of the string is obtained. The present application is suitable for various photovoltaic module structures, can quickly and accurately quantify the output characteristics of the string under the blocking condition, and provides important technical support for photovoltaic system design optimization, power generation performance evaluation and shadow influence analysis.

[0215] The photovoltaic string output characteristic quantification model under the near shadow described below can be mutually corresponding with the photovoltaic string output characteristic quantification method under the near shadow described above.

[0216] Please refer to the accompanying drawings Figure 3 The present application also provides a photovoltaic string output characteristic quantification model under the near shadow, comprising:

[0217] The parameter initialization module 100 is used for inputting the electrical parameters under the standard test condition of the photovoltaic module and the module topology structure;

[0218] The parameter conversion module 200 is used for converting the module level parameters into the cell level parameters;

[0219] The voltage-current characteristic calculation module 300 is used for calculating the voltage-current characteristics of the cell under the unblocked and blocked conditions;

[0220] The output characteristic integration module 400 is used for integrating the voltage-current characteristics of the cell, the sub-string and the module based on the series-parallel law of the photovoltaic string, and generating the voltage-current characteristic curve of the string.

[0221] The model of the present embodiment can be used to execute the above method embodiments, and the principles and technical effects are similar, which will not be repeated here.

[0222] Please refer to the accompanying drawings Figure 4 The present application also provides a computer device 40, comprising a processor 41 and a memory 42, wherein the memory 42 stores a computer program executable by the processor 41, and the computer program is executed by the processor 41 to perform the above method.

[0223] The present application also provides a storage medium 43, wherein the storage medium 43 stores a computer program, and the computer program is executed by the processor 41 to perform the above method.

[0224] The storage medium 43 can be implemented by any type of volatile or nonvolatile storage devices or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read-Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk or optical disk.

[0225] While the embodiments of the application have been illustrated and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and alterations can be made therein without departing from the spirit and scope of the application, which is defined by the appended claims and their equivalents.

Claims

1. A method for quantifying the output characteristics of a photovoltaic string under near- shade conditions, the method comprising: The method comprises the following steps: S1, input the electrical parameters of the photovoltaic module under standard test conditions, including short-circuit current, open-circuit voltage, maximum power point current, maximum power point voltage, short-circuit current temperature coefficient, open-circuit voltage temperature coefficient, maximum power temperature coefficient, cell type and module series-parallel topology structure information; S2, based on the electrical parameters of the module under standard test conditions, the parameters of the photovoltaic module are calculated by using the photovoltaic module volt-ampere characteristic model, including photogenerated current, reverse saturation current, diode factor, series resistance, parallel resistance and short-circuit current temperature coefficient adjustment value; S3, according to the internal circuit topology structure of the photovoltaic module, the module-level parameters are mapped to the cell-level parameters; S4, based on the irradiance and photovoltaic cell temperature under the unshaded condition, the volt-ampere characteristic of the cell under the unshaded condition is calculated; S5, based on the irradiance and photovoltaic cell temperature under the near shadow shading condition, the volt-ampere characteristic parameters of the cell are dynamically adjusted, and the volt-ampere characteristic of the cell under the shading condition is calculated; S6, based on the series-parallel circuit topology relationship of the photovoltaic module string, the volt-ampere characteristics of the cell, the sub-string and the module are integrated level by level, and the voltage-current characteristic of the module string is calculated.

2. The near-shade photovoltaic string output characteristic quantification method according to claim 1, characterized in that, In the step S2, the parameters of the photovoltaic module are calculated by the CEC6PPVMM model, including: Photogenerated current I mod_ph_ref calculated based on the short-circuit current of the component and the irradiance, temperature under standard test conditions; Reverse saturation current I mod_o_ref calculated from the open circuit voltage of the assembly and the temperature; Diode factor a mod_ref By fitting the maximum power point parameters of the assembly; Series resistance R mod_s_ref , the electrical parameters of the assembly are fitted. Parallel resistor R mod_sh_ref , fitting calculation combined with electrical parameters and working conditions of the assembly; Short circuit current temperature coefficient adjustment value Ajust mod , calculated from the short circuit current temperature coefficient and the component operating temperature.

3. The near-shade photovoltaic string output characteristic quantification method according to claim 1, characterized in that, In the step S3, based on the circuit topology structure of the module, the conversion of the six parameters of the photovoltaic module to the cell-level parameters includes: where I cell_ph_ref is the photo-generated current of the battery piece, I mod_ph_ref is the photo-generated current of the assembly, and N is the number of series-connected battery pieces in the assembly. Conversion of the photogenerated current: wherein I cell_o_ref is the reverse saturation current of the cell, I mod_o_ref is the reverse saturation current of the assembly; Conversion of the reverse saturation current: Wherein, a cell_ref is a diode factor of the battery piece, a mod_ref is a diode factor of the assembly, M1 is the number of battery pieces of each substring, and M2 is the number of parent strings of each assembly; Conversion of the diode factor: wherein R cell_s_ref is the series resistance of the battery sheet, R mod_s_ref is the series resistance of the assembly; Conversion of the series resistance: wherein R cell_sh_ref is the parallel resistance of the battery piece, R mod_sh_ref is the parallel resistance of the assembly; Conversion of the parallel resistance: Ajust cell = Ajust mod Ajust cell is the short-circuit current temperature coefficient adjustment value of the battery piece, Ajust mod is the short-circuit current temperature coefficient adjustment value of the assembly.

4. The near-shade photovoltaic string output characteristic quantification method according to claim 1, characterized in that, Conversion of the short-circuit current temperature coefficient adjustment value: Input the working conditions of the photovoltaic module under unshading condition, including irradiance G unshaded , and photovoltaic cell temperature T unshaded ; adjust the parameters from the standard test conditions to the unshading working conditions according to the cell-level parameters obtained in step S3, and calculate the dynamic parameters of the cell; In the step S4, based on the irradiance and photovoltaic cell temperature under the unshaded condition, the volt-ampere characteristic of the cell under the unshaded condition is calculated, and the step includes: where I is the output current of the battery piece, V is the output voltage of the battery piece, R s is the series resistance of the battery piece, R sh is the parallel resistance of the battery piece, a is the diode factor of the battery piece, I ph is the photo-generated current, I o is the reverse saturation current; The voltage of the battery piece is set from 0 to its open circuit voltage V oc The voltage of the battery piece is set from 0 to its open circuit voltage V The voltage of the battery piece is set from 0 to its open circuit voltage V 5. The method of quantifying the output characteristics of a near-shaded photovoltaic string of claim 4, wherein, The volt-ampere characteristic curve of the cell under the unshaded condition is calculated by using the single diode model, and is solved point by point according to the following formula: Input the working conditions of the photovoltaic module under the condition of near shadow blocking, including the irradiance G after blocking unshaded and the temperature T of the photovoltaic cell unshaded ; In the step S5, based on the irradiance and photovoltaic cell temperature under the near shadow shading condition, the volt-ampere characteristic parameters of the cell are dynamically adjusted, and the volt-ampere characteristic of the cell under the shading condition is calculated, and the step includes: The dynamic parameters of the cell are calculated by adjusting the parameters from the standard test condition to the shading working condition according to the cell-level parameters obtained in the step S3; The voltage of the battery piece is set from 0 to its open circuit voltage V oc The voltage-current characteristic curve of the battery piece under the shading condition is obtained by calculating the corresponding output current at each voltage point using a single diode model.

6. The method of quantifying the output characteristics of a near-shaded photovoltaic string of claim 5, wherein, The volt-ampere characteristic curve of the cell under the unshaded condition is calculated by using the single diode model; 7. The method of quantifying the output characteristics of a near-shaded photovoltaic string of claim 1, wherein, The equal-interval value point number is set according to the calculation resource and time limit. In the step S6, based on the series-parallel circuit topology relationship of the photovoltaic module string, the volt-ampere characteristics of the cell, the sub-string and the module are integrated level by level, and the voltage-current characteristic of the module string is calculated, and the step includes: According to the volt-ampere characteristic curve of the cell under the unshaded condition calculated in the step 4 and the volt-ampere characteristic curve of the cell under the shading condition calculated in the step 5, the shadow distribution information of the photovoltaic module is combined to initialize the cell voltage matrix and the current matrix; According to the series connection relationship of the cell in the sub-string, the volt-ampere characteristic law of the series circuit is used to calculate the voltage matrix and the current matrix of the sub-string; According to the parallel connection relationship of the sub-string in the parent string, the volt-ampere characteristic law of the parallel circuit is used to calculate the voltage matrix and the current matrix of the parent string; According to the series connection relationship of the parent string in the component, the voltage matrix and the current matrix of the component are calculated by using the voltage-current characteristic law of the series circuit; According to the series connection relationship of the component in the string, the voltage matrix and the current matrix of the string are calculated by using the voltage-current characteristic law of the series circuit; The voltage matrix and the current matrix of the string under the condition of near shadow blocking are output, and the voltage-current characteristic curve is drawn, so as to evaluate the output characteristics of the string under the current condition.

8. A model for quantifying the output characteristics of a photovoltaic string under near- shade, for performing the method for quantifying the output characteristics of a photovoltaic string under near-shade according to any one of claims 1 to 7, characterized in that, It comprises: A parameter initialization module for inputting the electrical parameters of the photovoltaic component under the standard test condition and the component topology structure; A parameter conversion module for converting the component-level parameters into cell-level parameters; A voltage-current characteristic calculation module for calculating the voltage-current characteristics of the cell under unblocked and blocked conditions; An output characteristic integration module for integrating the voltage-current characteristics of the cell, the sub-string and the component based on the series-parallel connection law of the photovoltaic string, and generating the voltage-current characteristic curve of the string.

9. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the computer program to implement the method of any one of claims 1-7.

10. A storage medium having stored thereon a computer program, characterized in that The computer program is executed by the processor to implement the method of any one of claims 1-7.

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