A photovoltaic inverter maximum power evaluation and correction method and system

Abstract

A method and system for assessing and correcting the maximum power of a photovoltaic inverter is described. By collecting and recording photovoltaic operating data in MPPT mode, the photovoltaic array characteristic model is online corrected, enabling accurate assessment of photovoltaic maximum power after the unit switches to active power standby mode. The method includes: calibrating the enabling process, detecting environmental conditions, and recording parameters such as power in MPPT mode to determine whether the original model parameters require correction; obtaining a set of correction parameter solutions, and finding a parameter set that meets error requirements through traversal calculations; determining a unique solution for the correction parameters, and using the statistical method of minimum mean square error to select the parameter closest to the actual power value as the final correction value. This method's relatively high frequency of model correction ensures model accuracy, providing more accurate maximum power point estimates to quickly adapt to environmental changes. It also significantly reduces the cost of manual maintenance at photovoltaic stations and extends the downtime and maintenance cycle of photovoltaic stations.

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] Grid-connected PV inverters introduce active power reserve control, utilizing reserved power to respond to grid frequency changes and provide frequency and inertia support. However, the reliability of this reserved reserve capacity depends on an accurate estimation of the current maximum PV power.

[0003] In the context of desertification, the environment and the turbines themselves are changing rapidly, such as system aging and wind and sand blocking photovoltaic panels. This also requires frequent model calibration to ensure the accuracy of the maximum photovoltaic power estimation. Conventional manual operation and maintenance frequency cannot meet this requirement and may significantly reduce the maintenance period of photovoltaic stations. Summary of the Invention

[0004] To address the deficiencies in the prior art, the present invention aims to modify the existing photovoltaic array model parameters in units operating with precise online active standby. Since only factors such as aging and dust shielding are considered, the maximum power operating point position is usually significantly affected. The MPPT provides the power, voltage, and current at the maximum power point under the current temperature and irradiation conditions to modify the STC standard (irradiation is 1000W / The voltage and current at the maximum power point (MPP) at 25°C (temperature) are calculated. This ensures model accuracy, provides a more accurate MPP estimate, and reduces manual maintenance costs at PV stations.

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

[0006] A first aspect of the present invention provides a photovoltaic inverter maximum power evaluation and correction method, comprising:

[0007] The environmental parameters involved in the original model to be calibrated are detected. When the approximate STC conditions are met, a unit in the PV array is selected to operate in MPPT mode and the measured maximum power under the approximate STC conditions is measured. If the measured maximum power is greater than the theoretical maximum power of the original model under the same conditions, calibration is enabled. The unit is measured several times in MPPT mode and the measurement results are used to establish an environmental condition-measured maximum power sample set.

[0008] Within the estimated deviation value range, the original model parameters are corrected by the deviation value, and the theoretical maximum power value under the approximate STC condition is obtained through cyclic traversal calculation. If the deviation from the measured maximum power under the approximate STC condition is less than a threshold, the corresponding deviation value is retained as the correction parameter solution set;

[0009] The original model parameters corrected by the environmental conditions and correction parameter solution set in the environmental condition-measured maximum power sample set are used to calculate the theoretical maximum power after the correction parameters under each environmental condition. The theoretical maximum power after the correction parameters is compared with the corresponding measured maximum power in the environmental condition-measured maximum power sample set. The closest set of correction parameter solutions is used as the final correction value, and the original model for the maximum power evaluation of the photovoltaic inverter is corrected with the final correction value.

[0010] Preferably, at least one unit in the photovoltaic array device is a switchable unit, and the operating mode includes: active standby mode and MPPT control mode for switching;

[0011] 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 PV inverter maximum power evaluation with the final correction value, it is switched back from the MPPT control mode to the active standby mode.

[0012] Preferably, detecting the environmental parameters involved in the original model to be corrected, and when an approximate STC condition is met, selecting a unit in the photovoltaic array to operate in MPPT mode, and measuring the maximum power measured under the approximate STC condition specifically includes:

[0013] 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 ;

[0014] Detect the environmental parameters involved in 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 greater than , 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.

[0015] Preferably, if the measured maximum power is greater than the theoretical maximum power of the original model under the same conditions, the calibration enabling specifically includes:

[0016] The electrical quantity in the independent variable of the first maximum power calculation function is regarded as a fixed value, and is substituted into the first maximum power calculation function to obtain the second maximum power calculation function. The environmental parameters of the approximate STC conditions obtained are substituted into the second maximum power calculation function to calculate the theoretical maximum power under the approximate STC conditions of the original model. When the deviation between the measured maximum power under the obtained 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.

[0017] Preferably, within the estimated deviation value interval, correcting the original model parameters with the deviation value, and cyclically calculating to obtain the theoretical maximum power value under the approximate STC condition specifically includes:

[0018] The environmental parameters of the approximate STC condition are regarded as fixed values, substituted into the first maximum power calculation function, and the third maximum power calculation function is constructed;

[0019] Using the third maximum power calculation function, the voltage and current parameters at the maximum power point under the current STC conditions in the original model are cyclically calculated to obtain a new theoretical maximum power set.

[0020] Preferably, the method of using 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:

[0021] Set multiple sets 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 traversal loop dataset All data points The voltage and current at the maximum power point are modified in a cyclical manner, and the original model is then substituted into the third maximum power calculation function to obtain a new theoretical maximum power set.

[0022] Preferably, 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:

[0023] 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 measurement 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 Correction parameter solution set of difference points .

[0024] Preferably, the comparison with the corresponding measured maximum power in the environmental condition-measured maximum power sample set, and the closest set of correction parameter solutions as the final correction value specifically includes:

[0025] The minimum RMSE is used to obtain the correction parameter solution closest to the actual maximum power value, which is expressed as the following formula:

[0026]

[0027] Where:

[0028] is the minimum RMSE;

[0029] is the corresponding correction parameter solution set Middle RMSE calculated for each data point;

[0030] Correction parameter solution set 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;

[0031] is the error threshold;

[0032] Environmental conditions and maximum power data set generated for MPPT measurement under approximate STC conditions The number of data points in .

[0033] Preferably, if all points do not meet the error accuracy requirements at this time, then re-do 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.

[0034] A second aspect of the present invention provides a photovoltaic inverter maximum power evaluation and correction system, which runs the photovoltaic inverter maximum power evaluation and correction method, including:

[0035] The calibration enable module is used to trigger the calibration enable when the environmental parameters meet the approximate STC conditions based on the degree of deviation from the theoretical maximum power of the original model under the same conditions, and continue to perform several measurements in MPPT mode to establish an environmental condition-measured maximum power sample set based on the measurement results;

[0036] A correction value initial screening module is used to loop through all potential correction parameters, calculate the theoretical maximum power value under the approximate STC condition, and take the deviation value corresponding to the measured maximum power under the approximate STC condition that is less than the threshold as the initial screening result to form a correction parameter solution set;

[0037] The correction value optimization module is used to compare the environmental condition-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 photovoltaic inverter maximum power evaluation.

[0038] A third aspect of the present invention provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program, when loaded into the processor, implements the photovoltaic inverter maximum power assessment and correction method.

[0039] A fourth aspect of the present invention provides a computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor, implements the photovoltaic inverter maximum power evaluation and correction method.

[0040] Compared with the prior art, the beneficial effects of the present invention include at least:

[0041] 1. Relatively high-frequency model correction ensures the accuracy of model building and can provide more accurate maximum power point estimates to quickly adapt to environmental changes;

[0042] 2. Greatly reduced the cost of manual maintenance of photovoltaic stations and extended the maintenance cycle of photovoltaic stations. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A flowchart of an embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram of the search for an approximate correction parameter point set involved in the present invention. DETAILED DESCRIPTION

[0045] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0046] like Figure 1 、 2 As shown, embodiment 1 of the present invention provides a photovoltaic inverter maximum power evaluation and correction method, which is applicable to the precise standby online correction model parameters of any grid-type photovoltaic inverter, including the following steps:

[0047] Step 1: Detect the environmental parameters involved in the original model to be calibrated. When the approximate STC condition is met, one unit in the PV array operates in MPPT mode and measures the actual maximum power corresponding to the approximate STC condition. If the deviation between the measured maximum power and the theoretical maximum power of the original model under the same conditions exceeds a threshold, calibration is enabled and the unit continues to perform several measurements in MPPT mode. The measurement results are used to establish an environmental condition-measured maximum power sample set, and step 2 is continued. Otherwise, the process returns to continue monitoring the environmental parameters.

[0048] Preferably but not limitedly, step 1 specifically includes:

[0049] Step 1.1: Obtain the photovoltaic array model to be calibrated as the original model, and establish a first maximum power calculation function including environmental parameters and electrical quantities as independent variables.

[0050] Specifically, a photovoltaic array model to be corrected is obtained as the original model, and 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 present invention aims to automatically correct the voltage and current at the maximum power point under the preset STC conditions so that the photovoltaic array model can provide a more accurate maximum power point estimate and reduce the cost of manual maintenance of photovoltaic stations. For example, but not limited to, the photovoltaic array model is expressed as the following formula (3):

[0051] (3)

[0052] Where:

[0053] 、 and are the PV array output current, voltage and power respectively;

[0054] is the number of parallel cells in the array;

[0055] to is an intermediate variable, which is expressed as follows:

[0056] (4)

[0057] Where:

[0058] 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;

[0059] 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;

[0060] is the number of series-connected cells in the array;

[0061] is the equivalent series resistance;

[0062] 、 are ambient temperature and irradiance, respectively;

[0063] 、 are the irradiation intensity and temperature correction coefficient of photovoltaic cells under STC conditions, respectively.

[0064] According to the photovoltaic array model to be corrected, the first maximum power calculation function is obtained The expression is the output power of the photovoltaic array The function of environmental parameters and electrical quantities is expressed as the following formula (5):

[0065] (5)

[0066] Where:

[0067] is the first maximum power calculation function; specifically, 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 .

[0068] It can be understood that the output power of the photovoltaic array Affected by ambient temperature , irradiation intensity , the voltage at the maximum power point under the current STC conditions , current and PV array output voltage Influence.

[0069] Step 1.2: Detect the environmental parameters in the independent variables of the first maximum power calculation function. When the approximate STC condition is met, select one unit in the photovoltaic array to switch from the active standby mode to the MPPT control mode.

[0070] Specifically, the first maximum power calculation function is measured The environmental parameters in the independent variables are compared with the STC conditions. If the difference with the STC conditions is less than the threshold, the current environmental conditions are determined to be approximate STC conditions, and step 1.3 is continued. If the difference with the STC conditions is not less than the threshold, the current environmental conditions are determined not to have reached the approximate STC conditions, and step 1.2 is repeated until the current environmental conditions are determined to be approximate STC conditions, and then step 1.3 is continued. Preferably, but not restrictively, the criterion for approximate STC conditions is expressed as follows:

[0071] (6)

[0072] Where:

[0073] It is the irradiance intensity when measuring in the current MPPT mode;

[0074] The temperature measured in the current MPPT mode;

[0075] is the irradiation intensity under STC conditions;

[0076] is the temperature under STC conditions.

[0077] Further preferably but not restrictively, when the approximate STC conditions are met, one unit in the photovoltaic array is selected to enter MPPT operation, and the remaining units continue to operate normally in active standby mode. As one of the outstanding substantive features of the present invention, the switchable units in the photovoltaic array equipment operate normally in active standby mode most of the time, and can switch between active standby mode and MPPT mode for a small part of the time. When parameter correction is performed, the switchable unit switches from active standby to MPPT mode operation, and records the current maximum power point related data information. After the data collection is completed, it switches back to active standby mode for normal operation. In this way, the following correction method steps can be performed without reducing the external frequency and voltage responses as much as possible. Finally, the corresponding correction parameters are obtained after the test is completed by the switchable unit, and the corrected parameters are then transmitted to all units.

[0078] Step 1.3: Save the environmental parameters of the approximate STC condition and the corresponding measured maximum power.

[0079] Specifically, the irradiance intensity when measuring the current MPPT control mode and temperature The irradiance intensity and temperature are saved to the storage medium as approximate STC conditions; and the power at the actual maximum power point obtained by the MPPT control measurement under the approximate STC conditions is saved to the storage medium; Save to storage media.

[0080] Step 1.4: Treat the electrical quantities in the independent variables 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 environmental parameters of the approximate STC conditions obtained in step 1.2 into the second maximum power calculation function, and calculate the theoretical maximum power under the approximate STC conditions of the original model.

[0081] Specifically, the current ambient temperature and irradiation intensity As the environmental parameter, the voltage at the maximum power point under the current STC condition is , current and the maximum output voltage of the photovoltaic array Substitute the electrical quantity into the first maximum power calculation function , the theoretical maximum power value of the photovoltaic array under current conditions can be calculated , which is expressed as the following formula (8):

[0082] (8)

[0083] Where:

[0084] is the theoretical maximum power value under current conditions,

[0085] is the current temperature,

[0086] is the current irradiance intensity,

[0087] is the voltage at the maximum power point under the current STC conditions;

[0088] is the current at the maximum power point under the current STC condition;

[0089] is the maximum output voltage of the photovoltaic array.

[0090] It is worth noting that the output power of the photovoltaic array and the output voltage of the photovoltaic array in the first maximum power calculation function 𝑓 are As a preferred embodiment of the present invention, the maximum output voltage of the photovoltaic array at the ideal maximum power point under the current conditions is directly set to , and the maximum output voltage of the photovoltaic array Each set of environmental parameters corresponds to a maximum output voltage for the PV array, depending on the environmental conditions. However, analytically determining the maximum output voltage of a PV array is complex, so a loop is typically used to find the point at which the function reaches its maximum. Similarly, as long as the environmental parameters remain constant, the maximum output voltage of the PV array is also fixed. Therefore, after entering the parameter calibration phase using the corresponding environmental parameters, it can be roughly assumed that the maximum operating point information remains unchanged. However, this is not the focus of the present invention and can be easily obtained through looping, so it will not be explained in detail here. Those skilled in the art can use any known method to obtain the maximum output voltage of a PV array.

[0091] In the short time after parameter calibration, it is approximately considered that the voltage at the maximum power operating point under STC conditions is The current value does not change, so it is considered as the first maximum power calculation function Therefore, the voltage at the maximum power point under the STC conditions given when the photovoltaic array equipment leaves the factory is , current Substitute into the first maximum power calculation function , construct the second maximum power calculation function , which is expressed as the following formula (9):

[0092] (9)

[0093] Where:

[0094] is the theoretical maximum power value under the current conditions calculated using the second maximum power calculation function;

[0095] is the second maximum power calculation function.

[0096] The irradiance intensity of the current approximate STC condition obtained in step 1.2 is and ambient temperature Substitute into the second maximum power calculation function After that, the theoretical maximum power value under the current approximate STC condition is calculated and expressed as the theoretical calculation result of the original model in the following formula (10):

[0097] (10)

[0098] Where:

[0099] is the theoretical calculation result of the original model, that is, the current radiation intensity and ambient temperature As an approximate STC condition, the theoretical maximum power is calculated using the original model to be corrected.

[0100] Step 1.5: When the deviation between the measured maximum power under the approximate STC conditions obtained in step 1.3 and the theoretical maximum power under the approximate STC conditions of the original model obtained in step 1.4 exceeds the threshold, the correction is enabled and the current unit continues to operate in the MPPT control mode. During this period, environmental parameters and measured power are collected to establish an environmental condition-measured maximum power sample set.

[0101] Specifically, the theoretical maximum power calculated from the original model obtained in step 1.4 is The maximum power measured in MPPT mode obtained in step 1.3 If the comparison exceeds the first allowable maximum deviation value serving 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 perform certain corrections on the voltage and current at the maximum power point under the STC conditions in the original model. The correction is enabled and step 2 is continued. Otherwise, it indicates that the parameters in the original model are still applicable to the current maximum power estimation, the correction is not enabled and the process returns to step 1.2 to continue monitoring the environmental conditions.

[0102] Preferably, but not restrictively, the correction enabling criterion is expressed as follows:

[0103] (11)

[0104] Where:

[0105] is the theoretical calculation result of the original model;

[0106] The maximum power measured in MPPT mode;

[0107] is the first allowable maximum deviation value.

[0108] After the correction is enabled, the current unit continues to operate in MPPT mode and records Different temperatures , irradiation Operating power under parameters etc. data, , forming an environmental condition-measured maximum power sample set and saving the data to the storage medium, which is expressed as the following formula (7):

[0109] (7)

[0110] Where:

[0111] Represents the environmental conditions formed by MPPT measurement under approximate STC conditions - the measured maximum power sample set;

[0112] Environmental conditions - measured maximum power sample set The number of data points in .

[0113] Step 2: Within the estimated deviation value range, use the deviation value to correct the original model parameters, and traverse the calculation to obtain the theoretical maximum power value under the approximate STC condition. 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.

[0114] Preferably but not limitatively, step 2 specifically includes:

[0115] Step 2.1: Treat the environmental parameters approximating the STC condition as fixed values and substitute them into the first maximum power calculation function , construct the third maximum power calculation function .

[0116] Specifically, in step 1, it is known that there is a large deviation in the voltage and current parameters at the maximum power point under the current STC conditions in the original model. In order to understand the theoretical calculation impact of this large deviation, it is necessary to reduce the interference of other factors and change the first maximum power calculation function The irradiation intensity under the approximate STC conditions and ambient temperature Considered as a fixed value, the third maximum power calculation function is constructed , which is expressed as the following formula (12):

[0117] (12)

[0118] Where:

[0119] is the theoretical maximum power value under the current conditions calculated using the third maximum power calculation function;

[0120] is the third maximum power calculation function.

[0121] Step 2.2: Use the third maximum power calculation function , the voltage at the maximum power point under the current STC conditions in the original model , current These two parameters are cyclically calculated to obtain a new theoretical maximum power set.

[0122] 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 to establish a modified traversal cycle data set, which is expressed as the following formula (13):

[0123] (13)

[0124] Where:

[0125] To correct the traversal loop dataset;

[0126] To modify the loop data set The data points in is the voltage at the maximum power point Correction value, is the current at the maximum power point Correction value;

[0127] The lower limit of the voltage deviation at the maximum power point With upper limit The number of correction values between The lower limit of the current deviation at the maximum power point With upper limit Correct the number of values between them; it is understandable that the correction traverses the loop data set The number of data points in indivual.

[0128] Will fix the loop through the dataset Data points Substitute the third maximum power calculation function in a loop traversal manner , calculate and obtain a new theoretical maximum power set, which is expressed as the following formulas (14) and (15):

[0129] (14)

[0130] (15)

[0131] Where:

[0132] The voltage correction value at the maximum power point is , the current correction value is Theoretical maximum power under the condition;

[0133] for the reason A new theoretical maximum power set.

[0134] Step 2.3: Combine the new theoretical maximum power concentration data points obtained by step 2.2 with the current maximum power point power measured by MPPT control. After comparison, if the deviation is smaller than the second allowable maximum deviation value serving as a threshold, the corresponding floating deviation is retained, and all retained floating deviations form a correction parameter solution set.

[0135] Specifically, 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 measurement 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 the difference points is obtained and saved in the storage medium, which is expressed as the following formula (16):

[0136] (16)

[0137] Where:

[0138] is the calibration parameter solution set,

[0139] is the second maximum allowable deviation value.

[0140] Correction parameter solution set The number of data points in .

[0141] Step 3: Using the environmental conditions of the environmental conditions-measured maximum power sample set established in step 1 and the original model parameters corrected by the correction parameter solution set in step 2, calculate the theoretical maximum power after the correction parameters under the environmental conditions. The set of correction parameter solutions that is closest to the corresponding measured maximum power in the environmental conditions-measured maximum power sample set is the final correction value, and the original model for the maximum power evaluation of the photovoltaic inverter is corrected with the final correction value.

[0142] Preferably but not limiting, step 3 specifically includes:

[0143] Step 3.1: Correct the parameters in the original model using the correction parameter solution set, substitute them into the first maximum power calculation function, and calculate the theoretical maximum power corresponding to each correction parameter solution.

[0144] Specifically, using the correction parameter solution set For each data point, the voltage and current at the maximum power point under the STC conditions given at the factory are corrected, and the environmental conditions formed by the MPPT control measurement under the approximate STC conditions - the measured maximum power sample set The environmental parameters in the first maximum power calculation function are used together The independent variable is used to calculate the corresponding theoretical maximum power, which is expressed as the following formula (17):

[0145] (17)

[0146] Where:

[0147] Correction parameter solution set 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;

[0148] Environmental conditions for MPPT control measurement under approximate STC conditions - measured maximum power sample set Middle The temperature and irradiance of each data point.

[0149] 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 average of the two corresponding correction parameter solutions is the final correction value. Use this final correction value to correct the original model and complete the maximum power assessment and correction of the PV inverter.

[0150] Specifically, the correction parameter solution set Provides the voltage at the maximum power point under the STC conditions given when the photovoltaic array equipment leaves the factory. , current of A correction is performed in which the optimal solution, i.e. the correct correction point, is obtained.

[0151] The optimization steps include: using the theoretical maximum power Environmental conditions formed by MPPT measurement under approximate STC conditions - Maximum power sample set Actual power samples in Compare and find the correction parameter solution closest to the actual power as the correct correction point .

[0152] After finding the minimum error point, the voltage at the maximum power point under the STC given by the factory is and current Add separately 、 , which is the final correction value.

[0153] Preferably, but not limited to, (1) RMSE (Root Mean Square Error) statistics are used as a reference; (2) the correction parameter solution closest to the actual maximum power value is obtained by using the minimum RMSE, which is expressed as the following formula (18):

[0154] (18)

[0155] Where:

[0156] is the minimum RMSE;

[0157] is the corresponding correction parameter solution set Middle RMSE calculated for each data point;

[0158] is the error threshold;

[0159] Environmental conditions and maximum power data set generated for MPPT measurement under approximate STC conditions The number of data points in .

[0160] The point with the minimum root mean square error obtained, and the root mean square error is less than the error threshold , which can be considered the correct calibration point. After testing the switchable units, the corresponding calibration parameters are obtained and then transmitted to all units to complete the maximum power evaluation and calibration of the photovoltaic inverter.

[0161] If all points do not meet the error accuracy requirements at this time, then repeat After the MPPT data is measured and stored in the storage medium, the contents of step 3 are executed again until the minimum error point retrieval is completed.

[0162] It can be understood that the first maximum power calculation function , the second maximum power calculation function and the third maximum power calculation function The terms "first, second, and third" are used to distinguish the three functions, not to distinguish the magnitude of the power.

[0163] Embodiment 2 of the present invention provides a photovoltaic inverter maximum power evaluation system, which runs the photovoltaic inverter maximum power evaluation method described in embodiment 1, including:

[0164] The calibration enable module is used to trigger the calibration enable when the environmental parameters meet the approximate STC conditions based on the degree of deviation from the theoretical maximum power of the original model under the same conditions, and continue to perform several measurements in MPPT mode to establish an environmental condition-measured maximum power sample set based on the measurement results;

[0165] A correction value initial screening module is used to loop through all potential correction parameters, calculate the theoretical maximum power value under the approximate STC condition, and take the deviation value corresponding to the measured maximum power under the approximate STC condition that is less than the threshold as the initial screening result to form a correction parameter solution set;

[0166] The correction value optimization module is used to compare the environmental condition-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 photovoltaic inverter maximum power evaluation.

[0167] Embodiment 3 of the present invention provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is loaded into the processor, the method for evaluating the maximum power of a photovoltaic inverter according to embodiment 1 is implemented.

[0168] Embodiment 4 of the present invention provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the method for evaluating the maximum power of a photovoltaic inverter according to embodiment 1 is implemented.

[0169] After the detailed introduction of the above embodiments, those skilled in the art can clearly understand that the photovoltaic inverter maximum power assessment and correction method provided by the present invention is a real-time online and fully automatically executable photovoltaic array model accuracy modification method, which does not require downtime for maintenance and can update photovoltaic model parameters online in the background, so that the inverter can accurately assess the maximum photovoltaic power in active standby mode and accurately reserve standby capacity.

[0170] More specifically, the significant improvements brought by the present invention to the existing technology include at least: 1. Relatively high-frequency model correction ensures the accuracy of model modeling, and can provide more accurate maximum power point estimates to quickly adapt to environmental changes; 2. It greatly reduces the cost of manual maintenance of photovoltaic stations and extends the shutdown maintenance cycle of photovoltaic stations.

[0171] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A photovoltaic inverter maximum power evaluation and correction method, characterized in that: include: The environmental parameters involved in the original model to be calibrated are detected. When the approximate STC conditions are met, a unit in the PV array is selected to operate in MPPT mode and the measured maximum power under the approximate STC conditions is measured. If the measured maximum power is greater than the theoretical maximum power of the original model under the same conditions, calibration is enabled. The unit is measured several times in MPPT mode and the measurement results are used to establish an environmental condition-measured maximum power sample set. Within the estimated deviation value range, the original model parameters are corrected by the deviation value, and the theoretical maximum power value under the approximate STC condition is obtained through cyclic traversal calculation. If the deviation from the measured maximum power under the approximate STC condition is less than a threshold, the corresponding deviation value is retained as the correction parameter solution set; The original model parameters corrected by the environmental conditions and correction parameter solution set in the environmental condition-measured maximum power sample set are used to calculate the theoretical maximum power after the correction parameters under each environmental condition. The theoretical maximum power after the correction parameters is compared with the corresponding measured maximum power in the environmental condition-measured maximum power sample set. The closest set of correction parameter solutions is used as the final correction value, and the original model for 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 operating modes include: active standby mode and MPPT control mode; 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 PV inverter maximum power evaluation 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, and when an approximate STC condition is met, selecting a unit in the photovoltaic array to operate in the MPPT mode, and measuring the maximum power actually measured 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 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 greater than , 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, and the obtained environmental parameters of the approximate STC condition are substituted into the second maximum power calculation function to calculate the theoretical maximum power under the approximate STC condition of the original model; 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 function takes effect.

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 by using the deviation value within the estimated deviation value range and cyclically calculating to obtain the theoretical maximum power value under the approximate STC condition specifically includes: The environmental parameters of the approximate STC condition are regarded as fixed values, substituted into the first maximum power calculation function, and the third maximum power calculation function is constructed; Using the third maximum power calculation function, the voltage and current parameters at the maximum power point under the current STC conditions in the original model are cyclically calculated 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 method of using 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 sets 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 traversal loop dataset All data points The voltage and current at the maximum power point are modified in a cyclical manner, and then the original model is substituted into the third maximum power calculation function to obtain 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 measurement 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 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 closest to the actual maximum power value, which is expressed as the following formula: Where: is the minimum RMSE; is the corresponding correction parameter solution set Middle RMSE calculated for each data point; P max_j for k Different temperatures T m_j , irradiation S Lx_j Operating power under parameters, j =1,2,…, k ; Correction parameter solution set 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 and maximum power data set generated for MPPT measurement under approximate STC conditions 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, then repeat 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 when the environmental parameters meet the approximate STC conditions based on the degree of deviation from the theoretical maximum power of the original model under the same conditions, and continue to perform several measurements in 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 the theoretical maximum power value under the approximate STC condition, and take the deviation value corresponding to the measured maximum power under the approximate STC condition that is 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 condition-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 photovoltaic inverter maximum power evaluation.

11. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: 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.

Images