Novel photovoltaic cell model seven-parameter solving method

Abstract

The invention discloses a novel photovoltaic cell model seven-parameter solving method, which comprises the following steps of: simplifying seven parameters in a double-diode into five parameters according to the portrait diffusion theory to obtain a simplified model; the method comprises the following steps: deriving a solution formula of each unknown parameter under various specific conditions; after a solution formula of each unknown parameter is deduced, the parameters of the simplified model are solved, and an output characteristic curve of the component under the standard test condition is drawn; deriving according to a formula under a standard test condition to obtain a solution formula of each parameter under a real environment condition, solving unknown parameters, and drawing an output characteristic curve of the component under the real environment condition; and finally, carrying out accuracy verification on the novel photovoltaic cell model seven-parameter solving method. According to the method, the problem that all unknown parameters are difficult to solve from form data provided by a component manufacturer in the prior art is solved, and the method has enough accuracy for estimating the output power of the photovoltaic array in different environments.

Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaic power generation, and in particular relates to a novel seven-parameter solution method for a photovoltaic cell model. Background Art

[0002] Power output estimation of commercial solar photovoltaic power plants remains a research area of ​​great interest. This is because accurate estimation of the power output of photovoltaic power plants is crucial for optimizing power generation efficiency, managing grid loads, and ensuring the stability of power supply; the existing technology for accurate estimation of the power output of photovoltaic power plants relies on an accurate physical photovoltaic model, which in turn relies on an accurate solution method for unknown parameters. In the past, although a lot of work has been done, the accuracy and reliability of power estimation still depend on the accuracy of the solar cell parameter values ​​used in the model; in order to verify the accuracy of the new solution method, the research team conducted indoor and outdoor experiments and evaluated the performance of the model under different irradiance and temperature conditions. The estimated solar output power was experimentally verified under real outdoor conditions and achieved high accuracy. The results show that the solar cell model with seven parameters shows the highest accuracy and the smallest root mean square error RMSE; therefore, it is necessary to design a new seven-parameter solution method for photovoltaic cell models to solve the above problems. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a new method for solving the seven parameters of a photovoltaic cell model, so as to solve the problem that the traditional method is too dependent on the parameter values ​​obtained by theoretical derivation or experimental measurement, and these parameter values ​​are easily affected by the actual environmental conditions and are difficult to meet the accurate power output estimation requirements in different scenarios.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: A novel seven-parameter solution method for photovoltaic cell model, including: S1, according to the photovoltaic cell double diode model, it is determined that the research object of the present invention is a seven-parameter model of photovoltaic cells, and the output characteristic equation of the photovoltaic cell double diode equivalent circuit is: ; (1) ; Where I is the output current of the photovoltaic module; V is the output voltage of the photovoltaic module; I ph is the photocurrent of the photovoltaic module; I 01 ,I 02 is the reverse saturation current of the photovoltaic module diode; q is the electron charge; k is the Boltzmann constant; a is the ideal factor of the photovoltaic module diode; R sis the series resistance of the photovoltaic module; R sh is the parallel resistance of the photovoltaic module; T is the Kelvin temperature when the photovoltaic module is working; N s is the number of cells in series in the photovoltaic module; the parameter to be identified is I ph ,I 01 ,I 02 , a1, a2, R s , R sh ; S2, the ideality factor of the double diode of a photovoltaic module is defined based on Shockley diffusion theory a 1=1 and a 2=2, thus obtaining the simplified output characteristic equation of the photovoltaic cell double diode equivalent circuit: ; (2) ; The parameters to be identified are I ph , I 01 , I 02 , R s , R sh ; S3, under standard test conditions, respectively, under short-circuit conditions, open-circuit conditions and maximum power point conditions, substitute known parameters and derive formulas to obtain analytical expressions of unknown parameters in the simplified photovoltaic cell dual-diode model; according to the electrical parameters of the photovoltaic module, solve the unknown parameters of the simplified photovoltaic module dual-diode model, substitute the obtained unknown parameters into the model equation, and draw the output characteristic curve of the module under standard test conditions; S4, based on the derivation of the formula for the unknown parameters in the model formula under the standard test conditions in step S3, the analytical formula for solving the unknown parameters under the actual environmental conditions is extended: according to the electrical parameters of the photovoltaic components, the unknown parameters in the model equation under the actual environmental conditions are solved, and the output characteristic curve of the component under the actual environmental conditions is plotted.

[0005] Furthermore, the electrical parameters of the photovoltaic module are the electrical parameters on the nameplate of the photovoltaic module provided by the module manufacturer.

[0006] Preferably, in step S3, under the short-circuit condition, the open-circuit condition and the maximum power point condition, substituting relevant known parameters to derive the formula includes: S301, under open circuit conditions, the PV module output voltage V is equal to the open circuit voltage V oc , the photovoltaic module output current I=0, substitute it into the formula in step S2 to get the photovoltaic module photocurrentI ph The expression is: ; (3) S302, under short-circuit conditions, the PV module output voltage V = 0, and the PV module output current I is equal to the short-circuit current I sc ; Set constraints: The open circuit voltage is determined by the internal chemical reaction of the photovoltaic cell and has nothing to do with the external circuit. The open circuit voltage represents the maximum available voltage between the two poles of the photovoltaic cell, so the product of the short-circuit current and the series resistance is much smaller than the open circuit voltage, that is: , ; Substitute the above constraints and the formula of step S301 into the formula of step S2 to obtain the short-circuit current I sc Similarly, at the maximum power point, the PV module output voltage V is equal to the maximum power point voltage V m , the PV module output current I is equal to the maximum power point current I m , Substitute the above constraints and the formula of step S301 into the formula of step S2 to obtain the maximum power point current I m The calculation formula of Solve the calculation formulas of short-circuit current and maximum power point current to obtain the reverse saturation current I 01 and I 02 The calculation formula is: ; (4) ; (5) ; ; in, I sc is the short-circuit current of the PV module, V oc is the open circuit voltage of the photovoltaic module, I m is the maximum power point current of the photovoltaic module, V m is the maximum power point voltage of the photovoltaic module; S303, under standard test conditions and at the maximum power point in the PV curve: ; Reflected on the IV curve, the formula of step S2 is differentiated with respect to the voltage to verify that at the maximum power point: ; Under short-circuit conditions, substituteV =0, I = I sc ,get: ; in ,Right now: ; Then, substitute formulas (4) and (5) into and In the expression, we get the following formula: ; (6) ; (7) ; ; R s and R sh are the two unknown quantities in the nonlinear equations (6) and (7). By solving the nonlinear equations, we can obtain R s and R sh Two unknown parameters; S304, the stability of the circuit is related to the change of resistance under different conditions, and appropriate initial values ​​are set for the series resistance and the parallel resistance; first R s The initial value of is set to 0 and substituted into formulas (4) and (5) In the expression of R sh The initial value of R sh The initial value of is expressed as follows: ; (8) ； ； ； Final R s and R sh Through equation (8) R sh and R s = 0 is determined as the initial value of equations (6) and (7);I ph , I 01 , I 02 The value of R s and R sh The final values ​​of are determined in equations (2) to (4) respectively; S305, according to the form data provided by the photovoltaic module manufacturer, solve the values ​​of each unknown parameter under standard test conditions, substitute the values ​​of each unknown parameter into the output characteristic equation of the photovoltaic cell double diode equivalent circuit, and draw the output characteristic curve of the module under standard test conditions.

[0007] Preferably, in step S4, solving each unknown parameter in the model equation under the actual environmental conditions includes: S401, since the ideal factor a of photovoltaic cells is affected by the continuously changing outdoor solar radiation and temperature conditions, all unknown parameters must be given analytical expressions under real external conditions. On the basis of obtaining the analytical expressions of each unknown parameter under standard test conditions, the derivation formulas of the unknown parameters under real conditions are obtained as follows: ; (9) ; (10) ; (11) ; (12) ; (13) ; (14) In the formula, the change of ideal factor with temperature is ignored, that is, a = a STC , a 1= a 1,STC , a 2= a 2,STC , where the band gap energy E g Defined as: E g = E g,STC (1-0.0002677( T - T STC )); G is the solar radiation under actual conditions, GSTC is the solar radiation under standard test conditions, T is the temperature of the photovoltaic module under actual conditions, T STC is the temperature of the PV module under standard test conditions; S402, according to the form data provided by the photovoltaic module manufacturer, solve the values ​​of various unknown parameters under realistic environmental conditions, substitute the values ​​of various unknown parameters into the output characteristic equation of the photovoltaic cell double diode equivalent circuit, and draw the output characteristic curve of the module under realistic conditions.

[0008] The beneficial effects of the present invention are as follows: 1. The present invention proposes an effective online prediction method, which solves the problem that conventional offline prediction methods cannot predict photovoltaic power data all the time, can adapt to the needs of various scenarios, and improves the prediction accuracy of photovoltaic power generation.

[0009] 2. The present invention obtains accurate analytical expressions of the seven parameters by accurately solving the seven unknown parameters of the model. By comparing the estimated values ​​of the power parameters of the proposed model with the data provided by the actual manufacturer and with the data obtained by actual measurements under different weather conditions in the real environment, it can obtain an accuracy that is better than other models. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a principle schematic diagram of a photovoltaic cell double diode model of the present invention; Figure 2 A flow chart of the overall analysis method for power estimation of a photovoltaic cell model according to the present invention; Figure 3 A flowchart of the process of solving the unknown parameters in the model proposed in the present invention; Figure 4 This is a comparison diagram of the IV curve obtained by seven-parameter calculation using the proposed model and the measured IV curve. DETAILED DESCRIPTION

[0011] Embodiment 1: like Figure 1 As shown, a novel seven-parameter solution method for photovoltaic cell model includes: S1, according to the photovoltaic cell double diode model, it is determined that the research object of the present invention is a seven-parameter model of photovoltaic cells, and the output characteristic equation of the photovoltaic cell double diode equivalent circuit is: ; (1) ; Where I is the output current of the photovoltaic module; V is the output voltage of the photovoltaic module; I ph is the photocurrent of the photovoltaic module; I 01 ,I02 is the reverse saturation current of the photovoltaic module diode; q is the electron charge; k is the Boltzmann constant; a is the ideal factor of the photovoltaic module diode; R s is the series resistance of the photovoltaic module; R sh is the parallel resistance of the photovoltaic module; T is the Kelvin temperature when the photovoltaic module is working; N s is the number of cells in series in the photovoltaic module; the parameter to be identified is I ph ,I 01 ,I 02 , a1, a2, R s , R sh ; S2, the ideality factor of the double diode of a photovoltaic module is defined based on Shockley diffusion theory a 1=1 and a 2=2, thus obtaining the simplified output characteristic equation of the photovoltaic cell double diode equivalent circuit: ; (2) ; The parameters to be identified are I ph , I 01 , I 02 , R s , R sh ; S3, under standard test conditions, respectively, under short-circuit conditions, open-circuit conditions and maximum power point conditions, substitute known parameters and derive formulas to obtain analytical expressions of unknown parameters in the simplified photovoltaic cell dual-diode model; according to the electrical parameters of the photovoltaic module, solve the unknown parameters of the simplified photovoltaic module dual-diode model, substitute the obtained unknown parameters into the model equation, and draw the output characteristic curve of the module under standard test conditions; S4, based on the derivation of the formula for the unknown parameters in the model formula under the standard test conditions in step S3, the analytical formula for solving the unknown parameters under the actual environmental conditions is extended: according to the electrical parameters of the photovoltaic components, the unknown parameters in the model equation under the actual environmental conditions are solved, and the output characteristic curve of the component under the actual environmental conditions is plotted.

[0012] Furthermore, the electrical parameters of the photovoltaic module are the electrical parameters on the nameplate of the photovoltaic module provided by the module manufacturer.

[0013] Preferably, in step S3, under the short-circuit condition, the open-circuit condition and the maximum power point condition, substituting relevant known parameters to derive the formula includes: S301, under open circuit conditions, the PV module output voltage V is equal to the open circuit voltage V oc , the photovoltaic module output current I=0, substitute it into the formula in step S2 to get the photovoltaic module photocurrent I ph The expression is: ; (3) S302, under short-circuit conditions, the PV module output voltage V = 0, and the PV module output current I is equal to the short-circuit current I sc ; Set constraints: The open circuit voltage is determined by the internal chemical reaction of the photovoltaic cell and has nothing to do with the external circuit. The open circuit voltage represents the maximum available voltage between the two poles of the photovoltaic cell, so the product of the short-circuit current and the series resistance is much smaller than the open circuit voltage, that is: , ; Substitute the above constraints and the formula of step S301 into the formula of step S2 to obtain the short-circuit current I sc Similarly, at the maximum power point, the PV module output voltage V is equal to the maximum power point voltage V m , the PV module output current I is equal to the maximum power point current I m , Substitute the above constraints and the formula of step S301 into the formula of step S2 to obtain the maximum power point current I m The calculation formula of Solve the calculation formulas of short-circuit current and maximum power point current to obtain the reverse saturation current I 01 and I 02 The calculation formula is: ; (4) ; (5) ; ; in, I sc is the short-circuit current of the PV module, V oc is the open circuit voltage of the photovoltaic module, I m is the maximum power point current of the photovoltaic module, V m is the maximum power point voltage of the photovoltaic module; S303, under standard test conditions and at the maximum power point in the PV curve: ; Reflected on the IV curve, the formula of step S2 is differentiated with respect to the voltage to verify that at the maximum power point: ; Under short-circuit conditions, substitute V =0, I = I sc ,get: ; in ,Right now: ; Then, substitute formulas (4) and (5) into and In the expression, we get the following formula: ; (6) ; (7) ; ; R s and R sh are the two unknown quantities in the nonlinear equations (6) and (7). By solving the nonlinear equations, we can obtain R s and R sh Two unknown parameters; S304, the stability of the circuit is related to the change of resistance under different conditions, and appropriate initial values ​​are set for the series resistance and the parallel resistance; first R s The initial value of is set to 0 and substituted into formulas (4) and (5) In the expression of R sh The initial value of R sh The initial value of is expressed as follows: ; (8) ； ； ； Final R s and R shThrough equation (8) R sh and R s = 0 is determined as the initial value of equations (6) and (7); I ph , I 01 , I 02 The value of R s and R sh The final values ​​of are determined in equations (2) to (4) respectively; S305, according to the form data provided by the photovoltaic module manufacturer, solve the values ​​of each unknown parameter under standard test conditions, substitute the values ​​of each unknown parameter into the output characteristic equation of the photovoltaic cell double diode equivalent circuit, and draw the output characteristic curve of the module under standard test conditions.

[0014] Preferably, in step S4, solving each unknown parameter in the model equation under the actual environmental conditions includes: S401, since the ideal factor a of photovoltaic cells is affected by the continuously changing outdoor solar radiation and temperature conditions, all unknown parameters must be given analytical expressions under real external conditions. On the basis of obtaining the analytical expressions of each unknown parameter under standard test conditions, the derivation formulas of the unknown parameters under real conditions are obtained as follows: ; (9) ; (10) ; (11) ; (12) ; (13) ; (14) In the formula, the change of ideal factor with temperature is ignored, that is, a = a STC , a 1= a 1,STC , a 2= a 2,STC , where the band gap energy E g Defined as: E g = E g,STC (1-0.0002677(T - T STC )); G is the solar radiation under actual conditions, G STC is the solar radiation under standard test conditions, T is the temperature of the photovoltaic module under actual conditions, T STC is the temperature of the PV module under standard test conditions; S402, according to the form data provided by the photovoltaic module manufacturer, solve the values ​​of various unknown parameters under realistic environmental conditions, substitute the values ​​of various unknown parameters into the output characteristic equation of the photovoltaic cell double diode equivalent circuit, and draw the output characteristic curve of the module under realistic conditions.

[0015] Embodiment 2: This embodiment provides a specific method for extracting IV characteristics of photovoltaic modules. The novel photovoltaic cell model seven-parameter analysis method of this embodiment is based on the double diode model of photovoltaic cells. The double diode model is to add another parallel diode to the single diode model to consider the composite loss of the space depletion region, and add a parallel resistor R sh and series resistance R s The solution accuracy is relatively high; the specific steps are: like Figure 2 As shown, step 1: the output characteristic equation of the photovoltaic cell double diode equivalent circuit of the present invention is as follows: (1) in, I Output current for photovoltaic modules; V Output voltage for photovoltaic modules; I ph is the photocurrent of the photovoltaic module; I 01 , I 02 is the reverse saturation current of the photovoltaic module diode; q is the electron charge; k is the Boltzmann constant; a is the ideal factor of the PV module diode; R s is the series resistance of the photovoltaic module; R sh is the parallel resistance of the photovoltaic module; T The Kelvin temperature when the photovoltaic module is working; N s is the number of cells in series in the photovoltaic module. The parameter to be identified is Iph , I 01 , I 02 , a 1. a 2. R s , R sh ; like Figure 3 As shown, step 2: based on standard test conditions, respectively, under short-circuit conditions, open-circuit conditions and maximum power point conditions, substitute the relevant known parameters and derive the formulas to further obtain the analytical solutions of the unknown parameters in the seven-parameter model; Step 2-1: According to Shockley diffusion theory, the ideal factor a 1. a 2 is defined as 1 and 2, and the output characteristic equation of the simplified photovoltaic cell double diode equivalent circuit is as follows; ; (2) The parameters to be identified are I ph , I 01 , I 02 , R s , R sh ; Step 2-2: Under open circuit conditions, the PV module output voltage V = V oc (open circuit voltage), PV module output current I =0, substitute into formula (2), and get the photovoltaic current I ph The expression is: ; (3) Step 2-3: Under short-circuit conditions, the PV module output voltage V =0, PV panel output current I = I sc (short-circuit current), since the open-circuit voltage is determined by the internal chemical reaction of the photovoltaic cell and has nothing to do with the external circuit, the open-circuit voltage represents the maximum available voltage between the two poles of the photovoltaic cell. Therefore, even if the product of the short-circuit current and the series resistance is much smaller than the open-circuit voltage, that is, , , Substituting the above conditions and formula (3) into formula (1), we can get the short-circuit current I scSimilarly, at the maximum power point, V = V m , I = I m , Substituting the above conditions and formula (3) into formula (1), we can get the maximum power point current I m The calculation formula of the short-circuit current and the maximum power point current are then solved to obtain the reverse saturation current. I 01 and I 02 The calculation formulas are: ; (4) ; (5) in , , I sc is the short-circuit current of the PV module, V oc is the open circuit voltage of the photovoltaic module, I m is the maximum power point current of the photovoltaic module, V m is the maximum power point voltage of the photovoltaic module; Step 2-4: Under standard test conditions and at the maximum power point in the PV curve, , which is reflected in the IV curve. , by differentiating formula (1) with respect to voltage, it can be verified that at the maximum power point In addition, under short-circuit conditions, substituting the PV module output voltage V =0, output current I = I sc ,get ,in ,Right now , then substitute formulas (4) and (5) into and In the expression, we get the following formula: ; (6) ; (7) in: ; ; R s andR sh are the two unknown quantities of the nonlinear equations (6) and (7). By solving the nonlinear equations, the two unknown parameters can be obtained at the same time. Since the stability of the circuit is related to the change of resistance under different conditions, it is necessary to set appropriate initial values ​​for the series resistance and the parallel resistance; Step 2-5: First R s The initial value of is set to 0, and is substituted into formulas (5) and (6) , you can get R sh The initial value of , after some mathematical modifications, R sh The initial value of can be expressed as follows: ; (8) in: ; ; ; Final R s and R sh We can use equation (7) R sh and R s = 0 is determined as the initial value of equations (5) and (6). I ph , I 01 , I 02 The value of R s and R sh The final values ​​of are determined in equations (2)-(4) respectively.

[0016] Step 2-6: After obtaining the analytical expressions of the seven unknown parameters of the photovoltaic cell double diode model, substitute the nameplate electrical parameter values ​​provided by the photovoltaic module manufacturer to obtain the seven unknown parameters of the photovoltaic cell double diode model under standard test conditions: photovoltaic module photocurrent I ph =1.277A, reverse saturation current of photovoltaic module I 01 =1.469A, I 02 =4.842A, series resistance of photovoltaic module R s=1.274Ω, parallel resistance of photovoltaic modules R sh =1421.58Ω, ideal factor of photovoltaic cell a 1=1, a 2=2; Step 2-7: Then, under the condition of obtaining the seven unknown parameters of the double diode model, estimate the parameters of each form of the photovoltaic module to obtain the short-circuit current of the photovoltaic module. I sc =1.276A, open circuit voltage of photovoltaic module V oc =23.165V, maximum power point current of photovoltaic module I m =1.1859A, maximum power point voltage of photovoltaic module V m =18.76V, maximum power point power of photovoltaic module P m =22.249W.

[0017] Step 2-8: Compare the estimated values ​​of each parameter in step 2-7 with the parameter values ​​in the data sheet provided by the manufacturer and calculate the relative errors. The relative errors of each parameter of the dual diode seven-parameter model are shown in Table 1 below: Table 1: Relative error of each parameter of the double diode seven-parameter model;

[0018] It can be seen from Table 1 that the relative errors between the unknown parameters and the nameplate electrical parameter values ​​are all within the error range, which verifies the accuracy of the seven-parameter solution method for the new photovoltaic cell model proposed in the present invention.

[0019] Step 3: According to the present invention, the formula of the unknown parameters in the model formula is derived under standard test conditions, and the analytical formulas for solving the unknown parameters under realistic environmental conditions are further generalized. The derivation formulas of the unknown parameters under realistic conditions are: ; (9) ; (10) ; (11) ; (12) ; (13) ; (14) In the formula, the change of ideal factor with temperature can be ignored, that is, a = a STC ,a 1= a 1,STC , a 2= a 2,STC , where the band gap energy E g Defined as: E g = E g,STC (1-0.0002677( T - T STC )), G is the solar radiation under actual conditions, G STC is the solar radiation under standard test conditions, T is the temperature of the photovoltaic module under actual conditions, T STC is the temperature of the PV module under standard test conditions.

[0020] Step 3-1: By substituting the form data provided by the manufacturer, the double diode model of the photovoltaic cell under realistic conditions can be obtained, such as Figure 4 As shown, between 200~1000W / m 2 Within the irradiance range and at a stable module temperature of 25°C, the IV and PV curves of the seven-parameter model are compared with the IV and PV curves in the data sheet provided by the factory. The results show that the new seven-parameter solution method for the photovoltaic cell model proposed in the present invention has higher accuracy and usability than other solution methods.

[0021] Step 3-2: Further, under the condition of fixed irradiance, the temperature changes from 25 to 75°C, and the obtained photovoltaic cell double diode model under realistic conditions is used to draw IV and PV curves to check the accuracy of the novel photovoltaic cell seven-parameter solution method proposed in the present invention at different temperatures, such as Figure 4 The verification results show that under fixed irradiance and different temperatures, all curves obtained by the new solution method proposed in the present invention show better matching with the manufacturer's curves and are closer to reality.

[0022] Step 3-3: Further utilize the parameter values ​​calculated by the seven-parameter solution method of the new photovoltaic cell model proposed in the present invention, use the dual diode model to estimate the maximum power, and obtain an estimated maximum power value of 245.2513Wp. Compare the maximum power estimated by the model established by the new calculation method proposed in the present invention with the actual power, and calculate the relative error between the two to be 0.0096. It is found that the model established by the new seven-parameter solution method proposed in the present invention has a very high accuracy in estimating the maximum power.

[0023] Step 3-4: Finally, under different weather conditions, an experimental platform is built on the ground at a specific location to collect solar radiation and temperature data. Then the experimental results are compared with the prediction results of the proposed model. The experimental study shows that the power value predicted by the proposed model is very close to the true value, and the accuracy of the seven-parameter model parameters is little affected by radiation changes. Then use formula (15) to calculate the root mean square error (RMSE) and determine the overall best model among all models: ; (15) The root mean square error calculation of all the developed models showed that the seven-parameter model had the highest accuracy, with an RMSE value of 0.02. Therefore, the seven-parameter solar cell model developed in this embodiment can be used for parameter identification and accurate power prediction anywhere in the world.

Claims

1. A novel seven-parameter solution method for photovoltaic cell model, characterized in that: include: S1, according to the photovoltaic cell double diode model, it is determined that the research object of the present invention is a seven-parameter model of photovoltaic cells, and the output characteristic equation of the photovoltaic cell double diode equivalent circuit is: ；（1） ； Where I is the output current of the photovoltaic module; V is the output voltage of the photovoltaic module; I ph is the photocurrent of the photovoltaic module; I 01 ,I 02 is the reverse saturation current of the photovoltaic module diode; q is the electron charge; k is the Boltzmann constant; a is the ideal factor of the photovoltaic module diode; R s is the series resistance of the photovoltaic module; R sh is the parallel resistance of the photovoltaic module; T is the Kelvin temperature when the photovoltaic module is working; N s is the number of cells in series in the photovoltaic module; the parameter to be identified is I ph ,I 01 ,I 02 、a1、a2、R s , R sh ; S2, the ideality factor of the double diode of a photovoltaic module is defined based on Shockley diffusion theory a 1=1 and a 2=2, thus obtaining the simplified output characteristic equation of the photovoltaic cell double diode equivalent circuit: ；（2） ； The parameters to be identified are I ph , I 01 , I 02 , R s , R sh ; S3, under standard test conditions, respectively, under short-circuit conditions, open-circuit conditions and maximum power point conditions, substitute known parameters and derive formulas to obtain analytical expressions of unknown parameters in the simplified photovoltaic cell dual-diode model; according to the electrical parameters of the photovoltaic module, solve the unknown parameters of the simplified photovoltaic module dual-diode model, substitute the obtained unknown parameters into the model equation, and draw the output characteristic curve of the module under standard test conditions; S4, based on the derivation of the formula for the unknown parameters in the model formula under the standard test conditions in step S3, the analytical formula for solving the unknown parameters under the actual environmental conditions is extended: according to the electrical parameters of the photovoltaic components, the unknown parameters in the model equation under the actual environmental conditions are solved, and the output characteristic curve of the component under the actual environmental conditions is plotted.

2. According to claim 1, a novel photovoltaic cell model seven-parameter solution method is characterized in that: In step S3, under the short-circuit condition, the open-circuit condition and the maximum power point condition, the formula is derived by substituting relevant known parameters: S301, under open circuit conditions, the PV module output voltage V is equal to the open circuit voltage V oc , the photovoltaic module output current I=0, substitute it into the formula in step S2 to get the photovoltaic module photocurrent I ph The expression is: ；（3） S302, under short-circuit conditions, the PV module output voltage V = 0, and the PV module output current I is equal to the short-circuit current I sc ; Set constraints: The open circuit voltage is determined by the internal chemical reaction of the photovoltaic cell and has nothing to do with the external circuit. The open circuit voltage represents the maximum available voltage between the two poles of the photovoltaic cell, so the product of the short-circuit current and the series resistance is much smaller than the open circuit voltage, that is: ， ； Substitute the above constraints and the formula of step S301 into the formula of step S2 to obtain the short-circuit current I sc Similarly, at the maximum power point, the PV module output voltage V is equal to the maximum power point voltage V m , the PV module output current I is equal to the maximum power point current I m , Substitute the above constraints and the formula of step S301 into the formula of step S2 to obtain the maximum power point current I m The calculation formula of Solve the calculation formulas of short-circuit current and maximum power point current to obtain the reverse saturation current I 01 and I 02 The calculation formula is: ；（4） ；（5） ； ； in, I sc is the short-circuit current of the PV module, V oc is the open circuit voltage of the photovoltaic module, I m is the maximum power point current of the photovoltaic module, V m is the maximum power point voltage of the photovoltaic module; S303, under standard test conditions and at the maximum power point in the PV curve: ； Reflected on the IV curve, the formula of step S2 is differentiated with respect to the voltage to verify that at the maximum power point: ； Under short-circuit conditions, substitute V =0, I = I sc ,get: ； in ,Right now: ； Then, substitute formulas (4) and (5) into and In the expression, we get the following formula: ；（6） ；（7） ； ； R s and R sh are the two unknown quantities in the nonlinear equations (6) and (7). By solving the nonlinear equations, we can obtain R s and R sh Two unknown parameters; S304, the stability of the circuit is related to the change of resistance under different conditions, and appropriate initial values ​​are set for the series resistance and the parallel resistance; first R s The initial value of is set to 0 and substituted into formulas (4) and (5) In the expression of R sh The initial value of R sh The initial value of is expressed as follows: ；（8） ； ； ； Final R s and R sh Through equation (8) R sh and R s = 0 is determined as the initial value of equations (6) and (7); I ph , I 01 , I 02 The value of R s and R sh The final values ​​of are determined in equations (2) to (4) respectively; S305, according to the form data provided by the photovoltaic module manufacturer, solve the values ​​of each unknown parameter under standard test conditions, substitute the values ​​of each unknown parameter into the output characteristic equation of the photovoltaic cell double diode equivalent circuit, and draw the output characteristic curve of the module under standard test conditions.

3. The seven-parameter solution method of a novel photovoltaic cell model according to claim 1 is characterized in that: In step S4, solving the unknown parameters in the model equation under the actual environmental conditions includes: S401, on the basis of obtaining the analytical expressions of the unknown parameters under the standard test conditions, the derivation formulas of the unknown parameters under the actual conditions are obtained as follows: ；（9） ；（10） ；（11） ；（12） ；（13） ；（14） Where a=a STC , a1=a 1,STC , a2=a 2,STC , where the band gap energy E g Defined as: E g = E g,STC (1-0.0002677( T - T STC ))； G is the solar radiation under actual conditions, G STC is the solar radiation under standard test conditions, T is the temperature of the photovoltaic module under actual conditions, T STC is the temperature of the PV module under standard test conditions; S402, according to the form data provided by the photovoltaic module manufacturer, solve the values ​​of various unknown parameters under realistic environmental conditions, substitute the values ​​of various unknown parameters into the output characteristic equation of the photovoltaic cell double diode equivalent circuit, and draw the output characteristic curve of the module under realistic conditions.

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