Method and system for evaluating and correcting maximum power of photovoltaic inverter

Abstract

According to the photovoltaic inverter maximum power evaluation correction method and system, photovoltaic operation data are collected and recorded through a unit in an MPPT mode, a photovoltaic array characteristic model is corrected on line, and the photovoltaic maximum power can be accurately evaluated after the unit is switched to an active power standby mode. The method comprises the following steps: a calibration enabling link: detecting environmental conditions, recording parameters such as power in an MPPT mode, and judging whether original model parameters need to be corrected or not; obtaining a correction parameter solution set, and finding a parameter set meeting error requirements through traversal calculation; and determining a unique solution of a correction parameter, and selecting a parameter closest to an actual power value as a final correction value by using a minimum mean square error statistical method. According to the method, the accuracy of model modeling is ensured by relatively high-frequency model correction, a more accurate maximum power point estimation value can be given to quickly adapt to environmental changes, the manual maintenance cost of the photovoltaic station is greatly reduced, and the shutdown maintenance period of the photovoltaic station is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy grid connection, and more specifically, relates to a method and system for evaluating and correcting the maximum power of a photovoltaic inverter. Background Art

[0002] Photovoltaic grid-connected inverters provide frequency and inertia support for the power grid by introducing active power reserve control and using the reserved power to respond to the power grid frequency change. However, the reliability of the reserved reserve capacity depends on the accurate estimation of the current maximum power of the photovoltaic.

[0003] In the context of deserts, gobi, and wastelands, the changes in the environment and the unit itself are relatively rapid. For example, system aging, sand and dust blocking the photovoltaic panels, etc. This also requires more frequent calibration of the model to ensure the accuracy of the estimation of the maximum power of the photovoltaic. The general manual operation and maintenance frequency cannot meet this requirement, and it may significantly reduce the shutdown maintenance cycle of the photovoltaic power station. Summary of the Invention

[0004] To solve the deficiencies in the prior art, the object of the present invention is to correct the existing photovoltaic array model parameters in the unit that operates precisely and online with active power reserve. Since only considering factors such as aging and dust shielding, it usually has a greater impact on the position of the maximum power operating point. By using MPPT to give the power, voltage, and current at the maximum power point under the existing temperature and irradiance conditions, the voltage and current at the maximum power point in the preset STC standard (irradiance is 1000W / , temperature is 25°C) in the model are corrected. This not only ensures the accuracy of the model modeling and can give a more accurate maximum power point estimation value, but also reduces the manual maintenance cost of the photovoltaic power station.

[0005] The present invention adopts the following technical solutions.

[0006] The first aspect of the present invention provides a method for evaluating and correcting the maximum power of a photovoltaic inverter, including: Detect the environmental parameters involved in the original model to be corrected. When the approximate STC condition is met, select a unit in the photovoltaic array to operate in the MPPT mode, measure the measured maximum power under the approximate STC condition. If the measured maximum power is greater than the theoretical maximum power of the original model under the same conditions, the calibration enablement takes effect, and this unit continues to perform several measurements in the MPPT mode to establish an environmental condition - measured maximum power sample set; Within the estimated deviation value range, correct the original model parameters with the deviation value, and cyclically traverse to calculate the theoretical maximum power value under the approximate STC condition. If the deviation from the measured maximum power under the approximate STC condition is less than the threshold, retain the corresponding deviation value as the calibration parameter solution set; Using the environmental conditions in the environmental condition - measured maximum power sample set and the original model parameters corrected by the solution set of correction parameters, calculate the theoretical maximum power after the correction parameters under each environmental condition, compare it with the corresponding measured maximum power in the environmental condition - measured maximum power sample set, and the set of correction parameter solutions that is closest is the final correction value, and correct the original model for evaluating the maximum power of the photovoltaic inverter with this final correction value.

[0007] Preferably, at least one unit in the photovoltaic array device is a switchable unit, and the operating modes include: switching between the active power reserve mode and the MPPT control mode; When the approximate STC condition is met, select a switchable unit in the photovoltaic array to switch from the active power reserve mode to the MPPT control mode. After correcting the original model for evaluating the maximum power of the photovoltaic inverter with this final correction value, switch back from the MPPT control mode to the active power reserve mode.

[0008] Preferably, detecting the environmental parameters involved in the original model to be corrected, when the approximate STC condition is met, selecting a unit in the photovoltaic array to operate in the MPPT mode, and measuring and obtaining the measured maximum power under the approximate STC condition specifically includes: Obtain the photovoltaic array module to be corrected as the original model, and establish a first maximum power calculation function including environmental parameters and electrical quantities as independent variables; the environmental parameters include: temperature and irradiance intensity ; the electrical quantities include: the voltage at the maximum power point under the current STC condition 、current and the output voltage of the photovoltaic array ; Detect the environmental parameters involved in the independent variables of the first maximum power calculation function, and if the deviation from the irradiance intensity 、temperature under the STC condition is less than the set ratio of the irradiance intensity 、temperature under the STC condition, then the approximate STC condition is met, the unit switches from the active power reserve mode to the MPPT control mode, and save the environmental parameters and the corresponding measured maximum power under this approximate STC condition.

[0009] Preferably, when the measured maximum power is greater than the theoretical maximum power of the original model under the same conditions, the calibration enabling takes effect specifically includes: Regard the electrical quantities in the independent variable of the first maximum power calculation function as fixed values, substitute them into the first maximum power calculation function to obtain the second maximum power calculation function, substitute the obtained environmental parameters under the approximate STC conditions into the second maximum power calculation function, and calculate the theoretical maximum power of the original model under the approximate STC conditions; when the deviation between the measured maximum power under the obtained approximate STC conditions and the calculated theoretical maximum power of the original model under the approximate STC conditions exceeds the threshold, the correction enable takes effect.

[0010] Preferably, within the estimated deviation value range, correcting the original model parameters with the deviation value, and the loop traversal calculation to obtain the theoretical maximum power value under the approximate STC conditions specifically includes: Regard the environmental parameters under the approximate STC conditions as fixed values, substitute them into the first maximum power calculation function, and construct the third maximum power calculation function; Use the third maximum power calculation function to perform loop traversal calculations on the voltage and current parameters at the maximum power point under the current STC conditions in the original model to obtain a new set of theoretical maximum powers.

[0011] Preferably, the use of the third maximum power calculation function to perform loop traversal calculations on the voltage and current parameters at the maximum power point under the current STC conditions in the original model to obtain a new set of theoretical maximum powers specifically includes: Set multiple groups of deviation values between the upper and lower limits of the voltage and current deviation values at the maximum power point to establish a correction traversal loop data set , with the correction traversal loop data set All data points of In a loop traversal manner, correct the voltage and current at the maximum power point, then substitute the original model into the third maximum power calculation function to calculate and obtain a new set of theoretical maximum powers.

[0012] Preferably, if the theoretical maximum power value has a deviation less than the threshold from the measured maximum power under the approximate STC conditions, retain the corresponding deviation value as the correction parameter solution set specifically includes: Modify the voltage at the maximum power point to be , and the current correction value is In the case of the theoretical maximum power Compare with the power at the actual maximum power point measured by MPPT control under the approximate STC conditions , if it is less than the second allowable maximum deviation value , take the corresponding voltage correction value and current correction value as a data point in the correction parameter solution set, and finally form a correction parameter solution set containing Differential points .

[0013] Preferably, comparing with the corresponding measured maximum power in the environmental condition - measured maximum power sample set, the set of calibration parameter solutions that is closest is taken as the final correction value, which specifically includes: Using the minimum RMSE to obtain the calibration parameter solution that is on average closest to the actual maximum power value, which is expressed by the following formula:

[0014] In the formula: is the minimum RMSE; is the set of corresponding calibration parameter solutions in which the th data point is calculated for the RMSE; is the set of calibration parameter solutions in which the th data point corrects the voltage and current at the maximum power point under STC conditions given at the factory. After correction, the theoretical maximum power under the temperature and irradiance intensity conditions; is the error threshold; is the environmental condition - maximum power data set formed by MPPT measurement under approximate STC conditions in which the number of data points.

[0015] Preferably, if all points do not meet the error accuracy requirements at this time, then re - perform times of MPPT mode data measurement and store them in the storage medium, and then execute again to obtain the calibration parameter solution that is on average closest to the actual maximum power value using the minimum RMSE until the retrieval of the minimum error point is completed.

[0016] The second aspect of the present invention provides a maximum power evaluation and calibration system for a photovoltaic inverter, which runs the maximum power evaluation and calibration method of a photovoltaic inverter, including: A calibration enable module, which is used to trigger the calibration enable to take effect based on the deviation degree of the theoretical maximum power of the original model under the same conditions when the environmental parameters meet the approximate STC conditions, and continue to perform several measurements in the MPPT mode to establish an environmental condition - measured maximum power sample set; A correction value preliminary screening module, which is used to loop through all potential calibration parameters, calculate the theoretical maximum power value under approximate STC conditions, and take the deviation value corresponding to the measured maximum power deviation less than the threshold under the approximate STC conditions as the preliminary screening result to form a set of calibration parameter solutions; A correction value optimization module is used to compare the environmental condition - measured maximum power sample set with the corresponding measured maximum power, and obtain a set of calibration parameter solutions that are closest by statistical means as the final correction value, and correct the original model for the maximum power evaluation of the photovoltaic inverter with the final correction value.

[0017] A third aspect of the present invention provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the computer program is loaded into the processor, the photovoltaic inverter maximum power evaluation and correction method described above is implemented.

[0018] A fourth aspect of the present invention provides a computer-readable storage medium. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the photovoltaic inverter maximum power evaluation and correction method described above is implemented.

[0019] Compared with the prior art, the beneficial effects of the present invention at least include: 1. The relatively high-frequency model correction ensures the accuracy of model modeling, can give a more accurate maximum power point estimation value, and can quickly adapt to environmental changes; 2. Greatly reduces the cost of manual maintenance of the photovoltaic power station and extends the shutdown maintenance cycle of the photovoltaic power station. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a flowchart of an embodiment related to the present invention; Figure 2 is a schematic diagram of searching for an approximate calibration parameter point set related to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the spirit of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

[0022] As Figure 1 、 2 shown, Embodiment 1 of the present invention provides a photovoltaic inverter maximum power evaluation and correction method, which is applicable to accurately preparing and online correcting model parameters of any grid-forming photovoltaic inverter, and includes the following steps: Step 1: Detect the environmental parameters involved in the original model to be corrected. When the approximate STC condition is met, one unit in the photovoltaic array operates in the MPPT mode, and the measured maximum power corresponding to the approximate STC condition is obtained. If the deviation between the measured maximum power and the theoretical maximum power of the original model under the same conditions exceeds the threshold, the calibration enablement takes effect, and this unit continues to perform several measurements in the MPPT mode. An environmental condition - measured maximum power sample set is established based on the measurement results, and Step 2 is continued; otherwise, return to continue monitoring the environmental parameters.

[0023] Preferably but not limited to, Step 1 specifically includes: Step 1.1: Obtain the photovoltaic array model to be corrected as the original model, and establish a first maximum power calculation function that includes environmental parameters and electrical quantities as independent variables.

[0024] Specifically, obtain the photovoltaic array model to be corrected as the original model. The variables used in the photovoltaic array model include the voltage and current at the maximum power point under the preset STC conditions. It can be understood that the purpose of the present invention is to make the photovoltaic array model give a more accurate maximum power point estimate value and reduce the manual maintenance cost of the photovoltaic power station by automatically correcting the voltage and current at the maximum power point under the preset STC conditions. For example but not limited to, the photovoltaic array model is expressed by the following formula (3): (3) In the formula: 、 and are the output current, voltage, and power of the photovoltaic array respectively; is the number of parallel cells in the array; to are intermediate variables, expressed by the following formula (4): (4) In the formula: is the short - circuit current of a single photovoltaic cell, is the current at the maximum power point of a single photovoltaic cell under the current STC conditions; is the open - circuit voltage of a single photovoltaic cell, is the voltage at the maximum power point of a single photovoltaic cell under the current STC conditions; is the number of series cells in the array; is the equivalent series resistance; 、 are the ambient temperature and the irradiation intensity, respectively; and are the irradiation intensity and temperature correction coefficients of the photovoltaic cell under STC conditions, respectively.

[0025] According to the photovoltaic array model to be corrected, obtain the first maximum power calculation function expression, which is a function of the output power of the photovoltaic array with respect to environmental parameters and electrical quantities, and is expressed by the following formula (5): (5) In the formula: is the first maximum power calculation function; specifically, the environmental parameters include: temperature and irradiation intensity ; the electrical quantities include: the voltage , current at the maximum power point under the current STC conditions, and the output voltage of the photovoltaic array.

[0026] It can be understood that the output power of the photovoltaic array is affected by the ambient temperature , irradiation intensity , the voltage , current at the maximum power point under the current STC conditions, and the output voltage of the photovoltaic array.

[0027] Step 1.2: Detect the environmental parameters in the independent variables of the first maximum power calculation function. When the approximate STC conditions are met, select one unit in the photovoltaic array to switch from the active standby mode to the MPPT control mode.

[0028] Specifically, measure the environmental parameters in the independent variables of the first maximum power calculation function , and compare them with the STC conditions. If the difference from the STC conditions is less than the threshold, it is determined that the current environmental conditions are approximate STC conditions, and step 1.3 is continued; if the difference from the STC conditions is not less than the threshold, it is determined that the current environmental conditions do not reach the approximate STC conditions, and step 1.2 is repeated until it is determined that the current environmental conditions are approximate STC conditions, and then step 1.3 is continued. Preferably but not restrictively, the criterion for the approximate STC conditions is expressed by the following formula (6): (6) In the formula: is the irradiation intensity measured in the current MPPT mode; is the temperature during the current MPPT mode measurement; is the irradiance under STC conditions; is the temperature under STC conditions.

[0029] Further preferably but not restrictively, when approximately STC conditions are met, one unit in the photovoltaic array is selected to enter MPPT operation, and the remaining units still operate normally in the active standby mode. As one of the prominent substantive features of the present invention, most of the time, the switchable units in the photovoltaic array equipment operate normally in the active standby mode, and in a small part of the time, they can switch between the active standby mode and the MPPT mode. When parameter correction is performed, the switchable unit switches from active standby to MPPT mode operation and records the relevant data information of the current maximum power point. After the data collection is completed, it switches back to the active standby mode and operates normally. Thus, the following correction method steps can be carried out while minimizing the reduction of the external frequency and voltage response as much as possible. Finally, the corresponding correction parameters are obtained through tests on the switchable units, and then the corrected parameters are transmitted to all units.

[0030] Step 1.3: Save the environmental parameters of the approximate STC conditions and the corresponding measured maximum power.

[0031] Specifically, the irradiance during the current MPPT control mode measurement and the temperature are saved as the irradiance and temperature under approximate STC conditions to the storage medium; and the power at the actual maximum power point obtained by MPPT control measurement under the approximate STC conditions is saved to the storage medium.

[0032] Step 1.4: Regard the electrical quantities in the independent variable of the first maximum power calculation function as fixed values, substitute them into the first maximum power calculation function to obtain the second maximum power calculation function, and substitute the environmental parameters of the approximate STC conditions obtained in Step 1.2 into the second maximum power calculation function to calculate the theoretical maximum power under the approximate STC conditions of the original model.

[0033] Specifically, the current ambient temperature and the irradiance are used as environmental parameters, and the voltage , current at the maximum power point under the current STC conditions, and the maximum output voltage of the photovoltaic array are used as electrical quantities and substituted into the first maximum power calculation function , and the theoretical maximum power value of the photovoltaic array under the current conditions can be calculated, which is expressed by the following formula (8): (8) Wherein: is the theoretical maximum power value under the current conditions, is the current temperature, is the current irradiance intensity, is the voltage at the maximum power point under the current STC conditions; is the current at the maximum power point under the current STC conditions; is the maximum output voltage of the photovoltaic array.

[0034] It should be noted that in the first maximum power calculation function 𝑓, the output power of the photovoltaic array is related to the output voltage of the photovoltaic array. As a preference of the present invention, it is directly set to the maximum output voltage of the photovoltaic array at the ideal power maximum point under the current conditions, while the maximum output voltage of the photovoltaic array is related to the environmental conditions and changes with the environmental conditions. For each set of environmental parameters, there is a corresponding maximum output voltage of the photovoltaic array. However, it is very complicated to solve the maximum output voltage of the photovoltaic array by an analytical method. Therefore, generally, a loop traversal method is used to find the point that can maximize the function. Similarly, as long as the environmental parameters are fixed, the maximum output voltage of the photovoltaic array is also fixed. Therefore, after using the corresponding environmental parameters to enter the parameter correction link, it can be approximately considered that the maximum operating point information remains unchanged. However, this is not the focus of the present invention and can be simply obtained by traversal. Therefore, no detailed description is given here. Those skilled in the art can obtain the maximum output voltage of the photovoltaic array using any known method.

[0035] Within a short period of time after parameter correction, it is approximately considered that the voltage and current value at the maximum power operating point under STC conditions do not change. Therefore, they are regarded as fixed values in the first maximum power calculation function . Thus, substituting the voltage and current at the maximum power point under STC conditions given when the photovoltaic array device leaves the factory into the first maximum power calculation function , a second maximum power calculation function is constructed and expressed by the following formula (9): (9) Wherein: is the theoretical maximum power value under the current conditions calculated using the second maximum power calculation function; is the second maximum power calculation function.

[0036] Substitute the irradiance intensity of the current approximate STC condition obtained in Step 1.2 and the ambient temperature into the second maximum power calculation function After that, calculate the theoretical maximum power value under the current approximate STC condition, which is used as the theoretical calculation result of the original model, and is expressed by the following formula (10): (10) In the formula: is the theoretical calculation result of the original model, that is, the current irradiance intensity and the ambient temperature As the approximate STC condition, it is the theoretical maximum power obtained by calculating with the original model to be corrected.

[0037] Step 1.5: When the deviation between the measured maximum power under the approximate STC condition obtained in Step 1.3 and the theoretical maximum power under the approximate STC condition of the original model calculated in Step 1.4 exceeds the threshold, the correction enable takes effect, and the current unit continues to operate in the MPPT control mode. During this period, the environmental parameters and the measured power are collected to establish an environmental condition - measured maximum power sample set.

[0038] Specifically, compare the theoretical maximum power calculated by the original model obtained in Step 1.4 with the maximum power measured in the MPPT mode obtained in Step 1.3 If it exceeds the first allowable maximum deviation value as the threshold, it indicates that the parameters in the original model have changed and are no longer applicable to the current maximum power estimation. It is necessary to correct the voltage and current at the maximum power point under the STC condition in the original model. The correction enable takes effect, and continue to execute Step 2; otherwise, it indicates that the parameters in the original model are still applicable to the current maximum power estimation, the correction enable does not take effect, and return to Step 1.2 to continue monitoring the environmental conditions.

[0039] Preferably but not limitedly, the correction enable criterion is expressed by the following formula (11): (11) In the formula: is the theoretical calculation result of the original model; is the maximum power measured in the MPPT mode; is the first allowable maximum deviation value.

[0040] After the correction enabling takes effect, the current unit continues to operate in the MPPT mode, and record times of different temperatures and irradiance under the operating power and other data, , form an environmental condition - measured maximum power sample set and save the data to the storage medium, which is expressed by the following formula (7): (7) In the formula: represents the environmental condition - measured maximum power sample set formed by MPPT measurement under approximate STC conditions; is the environmental condition - measured maximum power sample set the number of data points in.

[0041] Step 2: Within the estimated deviation value range, correct the original model parameters with the deviation value, and loop through the calculation to obtain the theoretical maximum power value under approximate STC conditions. If the deviation from the measured maximum power obtained in Step 1 is less than the threshold, retain the corresponding deviation value as the correction parameter solution set.

[0042] Preferably but not limited to, Step 2 specifically includes: Step 2.1: Regard the environmental parameters under approximate STC conditions as fixed values and substitute them into the first maximum power calculation function , and construct the third maximum power calculation function .

[0043] Specifically, in Step 1, it is already known that there are large deviations in the voltage and current parameters at the maximum power point under the current STC conditions in the original model. To know the theoretical calculation impact caused by this large deviation, it is necessary to reduce the interference of other factors. The irradiance intensity under approximate STC conditions in the first maximum power calculation function and the environmental temperature are regarded as fixed values, and the third maximum power calculation function is constructed, which is expressed by the following formula (12): (12) In the formula: is the theoretical maximum power value under the current conditions calculated using the third maximum power calculation function; is the third maximum power calculation function.

[0044] Step 2.2: Use the third maximum power calculation function , the voltage at the maximum power point under the current STC condition in the original model , current These two parameters are calculated by cyclic traversal to obtain a new set of theoretical maximum powers.

[0045] Specifically, multiple sets of deviation values are set between the upper and lower limits of the voltage and current deviation values at the maximum power point, and a modified traversal loop data set is established, which is expressed by the following formula (13): (13) In the formula: is the modified traversal loop data set; is the data point in the modified traversal loop data set , is the th correction value of the voltage at the maximum power point, is the th correction value of the current at the maximum power point; is the lower limit of the voltage deviation value at the maximum power point and the upper limit between the number of correction values, is the lower limit of the current deviation value at the maximum power point and the upper limit between the number of correction values; it can be understood that the number of data points in the modified traversal loop data set is ones.

[0046] Substitute the data points of the modified traversal loop data set into the third maximum power calculation function in a cyclic traversal manner , and calculate to obtain a new set of theoretical maximum powers, which are expressed by the following formulas (14), (15): (14) (15) In the formula: is the theoretical maximum power when the voltage correction value at the maximum power point is and the current correction value is ; is composed of a new set of theoretical maximum powers.

[0047] Step 2.3: Compare each data point in the newly obtained theoretical maximum power calculated through traversal in Step 2.2 with the power at the current maximum power point measured by MPPT control. If the deviation is less than the second allowable maximum deviation value used as the threshold, retain the corresponding floating deviation, and all the retained floating deviations form a solution set of correction parameters.

[0048] Specifically, when the voltage correction value at the maximum power point is and the current correction value is for the theoretical maximum power compare it with the power at the actual maximum power point obtained by MPPT control measurement under approximate STC conditions If it is less than the second allowable maximum deviation value , take the corresponding voltage correction value and current correction value as a data point in the solution set of correction parameters, and finally form a solution set of correction parameters containing differential points, and save it in the storage medium, which is represented by the following formula (16): (16) In the formula: is the solution set of correction parameters, is the second allowable maximum deviation value.

[0049] is the solution set of correction parameters is the number of data points in it.

[0050] Step 3: Using the environmental conditions in the environmental condition - measured maximum power sample set established in Step 1 and the original model parameters corrected by the solution set of correction parameters in Step 2, calculate the theoretical maximum power after the correction parameters under this environmental condition. The set of correction parameter solutions closest to the corresponding measured maximum power in the environmental condition - measured maximum power sample set is the final correction value, and use this final correction value to correct the original model for evaluating the maximum power of the PV inverter.

[0051] Preferably but not restrictively, Step 3 specifically includes: Step 3.1: Correct the parameters in the original model with the solution set of correction parameters, and substitute them into the first maximum power calculation function to calculate the theoretical maximum power corresponding to each solution of the correction parameters.

[0052] Specifically, use each data point in the solution set of correction parameters to respectively correct the voltage and current at the maximum power point under STC conditions given at the time of factory, and form the environmental condition - measured maximum power sample set with the MPPT control measurement under approximate STC conditions The environmental parameters in are used as the independent variables of the first maximum power calculation function to calculate the corresponding theoretical maximum power, which is expressed by the following formula (17): (17) In the formula: is the solution set of correction parameters The th data point corrects the voltage at the maximum power point under STC conditions given at the factory , current After that, the theoretical maximum power under the conditions of temperature and irradiation intensity ; is the environmental condition - measured maximum power sample set formed by MPPT control measurement under approximate STC conditions The th data point in the temperature and irradiation intensity.

[0053] Step 3.2: Use statistical methods to compare the theoretical maximum power corresponding to each correction parameter solution with the measured maximum power under the same environmental conditions. The correction parameter solution with the closest average of the two is the final correction value. Use this final correction value to correct the original model to complete the maximum power evaluation and correction of the photovoltaic inverter.

[0054] Specifically, the solution set of correction parameters provides corrections to the voltage , current at the maximum power point under STC conditions given for the photovoltaic array device at the factory Find the optimal solution, that is, the correct correction point.

[0055] The optimization steps include: using the theoretical maximum power and the environmental condition - maximum power sample set formed by MPPT measurement under approximate STC conditions The actual power sample in is compared, and the correction parameter solution closest to the actual power is the correct correction point .

[0056] After finding the point with the minimum error, the voltage and current at the maximum power point under STC given at the factory are respectively added with , to obtain the final correction value.

[0057] Preferably but not limitedly, (1) the RMSE (Root Mean Square Error) statistic is used as a reference: (2) the calibration parameter solution that is on average closest to the actual maximum power value is obtained using the minimum RMSE, which is represented by the following formula (18): (18)

[0058] In the formula: is the minimum RMSE; is the corresponding calibration parameter solution set in the th data point calculated RMSE; is the error threshold; is the environmental condition - maximum power data set formed by MPPT measurement under approximate STC conditions the number of data points in.

[0059] The point with the obtained minimum root mean square error, and satisfying that the root mean square error is less than the error threshold , can be considered as the correct calibration point. After performing tests through the switchable unit to obtain the corresponding calibration parameters, the calibrated parameters are then transmitted to all units to complete the calibration of the maximum power evaluation of the photovoltaic inverter.

[0060] If all points do not meet the error accuracy requirements at this time, then re - perform times of MPPT data measurement and store it in the storage medium, and then execute the content in step 3 again until the retrieval of the minimum error point is completed.

[0061] It can be understood that the "first, second, and third" used in the description of the first maximum power calculation function , the second maximum power calculation function and the third maximum power calculation function are used to distinguish the three functions, rather than to distinguish the magnitudes of the powers.

[0062] Embodiment 2 of the present invention provides a maximum power evaluation system for a photovoltaic inverter, which operates a maximum power evaluation method for a photovoltaic inverter as described in Embodiment 1, including: A calibration enable module, which is used to trigger the calibration enable to take effect based on the degree of deviation of the theoretical maximum power of the original model under the same conditions when the environmental parameters meet the approximate STC conditions, and continue to perform a number of measurements in the MPPT mode, and establish an environmental condition - measured maximum power sample set based on the measurement results; The correction value preliminary screening module is used to loop through all potential correction parameters, calculate the theoretical maximum power value under the approximate STC condition, and use the deviation value corresponding to the deviation between the measured maximum power under the approximate STC condition and the threshold as the preliminary screening result to form a correction parameter solution set; The correction value optimization module is used to compare the environmental condition - measured maximum power sample set with the corresponding measured maximum power, and obtain a set of correction parameter solutions that are closest by statistical means as the final correction value, and correct the original model for evaluating the maximum power of the photovoltaic inverter with the final correction value.

[0063] Embodiment 3 of the present invention provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the computer program is loaded into the processor, it implements a method for evaluating the maximum power of a photovoltaic inverter according to Embodiment 1.

[0064] Embodiment 4 of the present invention provides a computer-readable storage medium. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, it implements a method for evaluating the maximum power of a photovoltaic inverter according to Embodiment 1.

[0065] After the detailed introduction of the above embodiments, those skilled in the art can clearly know that the method for evaluating and correcting the maximum power of a photovoltaic inverter provided by the present invention is a real-time online and fully automatic photovoltaic array model accuracy modification method, which does not require shutdown maintenance, can update the photovoltaic model parameters online in the background, and enables the inverter to accurately evaluate the photovoltaic maximum power in the active standby mode and accurately reserve the standby capacity.

[0066] More specifically, the significant improvements brought by the present invention to the prior art at least include: 1. The relatively high-frequency model correction ensures the accuracy of model modeling, can give a more accurate maximum power point estimation value to quickly adapt to environmental changes; 2. Greatly reduces the cost of manual maintenance of photovoltaic power stations and extends the shutdown maintenance cycle of photovoltaic power stations.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: still can modify the specific implementation manners of the present invention or make equivalent replacements, and any modification or equivalent replacement without departing from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A photovoltaic inverter maximum power evaluation and correction method, characterized in that: include: Detect the environmental parameters involved in the original model to be corrected. When the approximate STC conditions are met, select a unit in the photovoltaic array to operate in MPPT mode, and measure the actual maximum power of the approximate STC conditions. If the actual maximum power is greater than the theoretical maximum power of the original model under the same conditions, the calibration is enabled, and the unit continues to be measured in MPPT mode for several times, and the environmental conditions-actual maximum power sample set is established based on the measurement results. Within the estimated deviation value interval, the original model parameters are corrected with the deviation value, and the theoretical maximum power value under the approximate STC condition is obtained by cyclic traversal calculation. If the deviation from the measured maximum power under the approximate STC condition is less than a threshold value, the corresponding deviation value is retained as a correction parameter solution set; The original model parameters corrected by the environmental conditions and correction parameter solution set in the environmental conditions-measured maximum power sample set are used to calculate the theoretical maximum power after the corrected parameters under each environmental condition, and compared with the corresponding measured maximum power in the environmental conditions-measured maximum power sample set. The closest set of correction parameter solutions is used as the final correction value, and the original model of the maximum power evaluation of the photovoltaic inverter is corrected with the final correction value.

2. A photovoltaic inverter maximum power evaluation and correction method according to claim 1, characterized in that: include: At least one unit in the photovoltaic array equipment is a switchable unit, and the operation mode includes: active standby mode and MPPT control mode for switching; When the approximate STC condition is met, a switchable unit in the PV array is selected to switch from the active standby mode to the MPPT control mode. After correcting the original model of the maximum power evaluation of the PV inverter with the final correction value, it is switched back from the MPPT control mode to the active standby mode.

3. A photovoltaic inverter maximum power evaluation and correction method according to claim 1 or 2, characterized in that: include: The detecting of the environmental parameters involved in the original model to be corrected, when the approximate STC condition is met, selecting a unit in the photovoltaic array to operate in the MPPT mode, and measuring the actual maximum power under the approximate STC condition specifically includes: The photovoltaic array model to be corrected is obtained as the original model, and the first maximum power calculation function including environmental parameters and electrical quantities as independent variables is established; the environmental parameters include: temperature and irradiation intensity ;Electrical quantities include: voltage at maximum power point under current STC conditions , Current and PV array output voltage ; Detect the environmental parameters involved in the independent variable of the first maximum power calculation function and the irradiation intensity under STC conditions ,temperature If the deviation is less than the irradiation intensity under STC conditions ,temperature If the set ratio is met, the approximate STC condition is met, the unit switches from the active standby mode to the MPPT control mode, and saves the environmental parameters of the approximate STC condition and the corresponding measured maximum power.

4. A photovoltaic inverter maximum power evaluation and correction method according to claim 3, characterized in that: include: If the measured maximum power is greater than the theoretical maximum power of the original model under the same conditions, the calibration is enabled to take effect, specifically including: The electrical quantity in the independent variable of the first maximum power calculation function is regarded as a fixed value, substituted into the first maximum power calculation function to obtain the second maximum power calculation function, the environmental parameters of the obtained approximate STC conditions are substituted into the second maximum power calculation function, and the theoretical maximum power under the approximate STC conditions of the original model is calculated; When the deviation between the measured maximum power under the approximate STC conditions and the calculated theoretical maximum power under the approximate STC conditions of the original model exceeds a threshold, the correction is enabled.

5. A photovoltaic inverter maximum power evaluation and correction method according to claim 1, characterized in that: include: The method of correcting the original model parameters with the deviation value within the estimated deviation value interval and cyclically calculating to obtain the theoretical maximum power value under the approximate STC condition specifically includes: The environmental parameters of the approximate STC conditions are regarded as fixed values, substituted into the first maximum power calculation function, and the third maximum power calculation function is constructed; The third maximum power calculation function is used to perform cyclic traversal calculations on the two parameters of voltage and current at the maximum power point under the current STC conditions in the original model to obtain a new theoretical maximum power set.

6. A photovoltaic inverter maximum power evaluation and correction method according to claim 5, characterized in that: include: The use of the third maximum power calculation function to cyclically calculate the voltage and current parameters at the maximum power point under the current STC condition in the original model to obtain a new theoretical maximum power set specifically includes: Set multiple groups of deviation values ​​between the upper and lower limits of the voltage and current deviation values ​​at the maximum power point to establish a correction traversal cycle data set , to correct the loop through the data set All data points The voltage and current at the maximum power point are corrected in a cyclical manner, and then the original model is substituted into the third maximum power calculation function to calculate a new theoretical maximum power set.

7. A photovoltaic inverter maximum power evaluation and correction method according to claim 5 or 6, characterized in that: include: If the deviation between the theoretical maximum power value and the measured maximum power under the approximate STC condition is less than a threshold, the corresponding deviation value is retained as a correction parameter solution set, specifically including: The voltage correction value at the maximum power point is , the current correction value is Theoretical maximum power The actual maximum power point power obtained by MPPT control under approximate STC conditions Compare and if it is less than the second maximum allowable deviation value , the corresponding voltage correction value and current correction value are used as a data point in the correction parameter solution, and finally a data point containing The correction parameter solution set of difference points .

8. A photovoltaic inverter maximum power evaluation and correction method according to claim 1, characterized in that: include: The closest set of correction parameter solutions to the corresponding measured maximum power in the environmental condition-measured maximum power sample set as the final correction value specifically include: The minimum RMSE is used to obtain the correction parameter solution that is closest to the actual maximum power value on average, which is expressed as follows: Where: is the minimum RMSE; is the corresponding correction parameter solution set Middle RMSE calculated for each data point; The calibration parameter solution Middle Data points Correct the voltage at the maximum power point under the STC conditions given at the factory , Current After that, at temperature and irradiation intensity Theoretical maximum power under conditions; is the error threshold; Environmental conditions for MPPT measurement under approximate STC conditions - Maximum power data set The number of data points in .

9. A photovoltaic inverter maximum power evaluation and correction method according to claim 8, characterized in that: include: If all points do not meet the error accuracy requirements at this time, repeat the After the MPPT mode data is measured and stored in the storage medium, the minimum RMSE is used again to obtain the correction parameter solution closest to the actual maximum power value average until the minimum error point retrieval is completed.

10. A photovoltaic inverter maximum power evaluation and correction system, running a photovoltaic inverter maximum power evaluation and correction method according to any one of claims 1 to 9, characterized in that: include: The calibration enable module is used to trigger the calibration enable to take effect when the environmental parameters meet the approximate STC conditions based on the degree of deviation of the theoretical maximum power of the original model under the same conditions, and continue to perform several measurements in the MPPT mode to establish an environmental condition-measured maximum power sample set based on the measurement results; A correction value initial screening module is used to loop through all potential correction parameters, calculate and obtain the theoretical maximum power value under the approximate STC condition, and take the deviation value corresponding to the measured maximum power deviation under the approximate STC condition less than the threshold as the initial screening result to form a correction parameter solution set; The correction value optimization module is used to compare the environmental conditions-measured maximum power sample set with the corresponding measured maximum power, obtain the closest set of correction parameter solutions as the final correction value by statistical means, and use the final correction value to correct the original model of the maximum power evaluation of the photovoltaic inverter.

11. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the computer program is loaded into a processor, a photovoltaic inverter maximum power evaluation and correction method according to any one of claims 1 to 9 is implemented.

12. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, a photovoltaic inverter maximum power evaluation and correction method according to any one of claims 1 to 9 is implemented.

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