Inversion control system and control method of photovoltaic grid-connected inverter

Abstract

The invention discloses an inversion control system and method for a photovoltaic grid-connected inverter, and relates to the technical field of inverter control, and the method comprises the following steps: setting a power test experiment, and carrying out the voltage-power test of a photovoltaic array; performing maximum power point tracking on the photovoltaic array based on a voltage-power test result; converting the direct current into alternating current based on the power grid frequency and the power grid phase of photovoltaic grid connection; performing anomaly detection on photovoltaic grid connection in real time, and adjusting the alternating current output by the inverter or directly stopping outputting when the photovoltaic grid connection is abnormal; the method is used for solving the problem that errors occur in calculation of the maximum power of the photovoltaic array due to the fact that analysis of the maximum power point of the photovoltaic array is not accurate enough in an existing inverter control technology.

Description

Technical Field

[0001] The present invention relates to the technical field of inverter control, and in particular to an inverter control system and a control method of a photovoltaic grid-connected inverter. Background Art

[0002] Inverter control technology refers to the technology used to control the operation and output of the inverter. The inverter is an electronic device that converts direct current into alternating current. It is commonly found in solar photovoltaic systems, wind power generation systems, electric vehicles and other fields. The main purpose of inverter control technology is to ensure that the inverter can stably and efficiently convert direct current into alternating current, and adjust the output voltage, frequency and waveform as needed.

[0003] Existing inverter control technologies usually require maximum power point tracking of photovoltaic devices. When analyzing the maximum power point, a single photovoltaic device is usually used for evaluation. In photovoltaic power generation, photovoltaic devices usually appear in groups to form an array. Evaluation through a single device will lead to large errors in the maximum power point tracking results, and an accurate characteristic curve cannot be obtained when the maximum power of the photovoltaic array is tracked. For example, in a patent application with publication number CN105958808A, a photovoltaic grid-connected inverter control method is disclosed. This solution directly obtains the maximum power point of the inverter DC side, and the DC side is the photovoltaic array. The existing maximum power tracking calculation for the photovoltaic array is not mature enough, and usually a single device analysis result is used as the overall analysis result. The maximum power tracking result is prone to large deviations. The existing inverter control technology also has the problem of inaccurate analysis of the maximum power point of the photovoltaic array, which leads to errors in the maximum power calculation of the photovoltaic array. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the prior art to at least a certain extent, by setting an irradiation power test group and a temperature power test group, configuring a test environment, and then testing the irradiation change curve and the temperature change curve of a single solar panel in a photovoltaic array, and then analyzing the voltage-power characteristic curve of the photovoltaic array based on the irradiation change curve and the temperature change curve, and extracting the maximum power point and the open-circuit voltage based on the voltage-power characteristic curve, setting the optimal operating voltage based on the maximum power point and the open-circuit voltage, and then converting direct current into alternating current based on the grid frequency and grid phase of the photovoltaic grid, and finally performing real-time abnormality detection on the photovoltaic grid, adjusting the alternating current output by the inverter or directly stopping the output when an abnormality occurs in the photovoltaic grid, so as to solve the problem that the existing inverter control technology still has the problem that the analysis of the maximum power point of the photovoltaic array is not accurate enough, resulting in errors in the maximum power calculation of the photovoltaic array.

[0005] To achieve the above objectives, in a first aspect, the present application provides an inverter control method for a photovoltaic grid-connected inverter, comprising the following steps: Set up a power test experiment to perform voltage-power test on the photovoltaic array; Perform maximum power point tracking on the photovoltaic array based on the results of voltage-power test; Based on the grid frequency and grid phase of the photovoltaic grid, direct current is converted into alternating current; Real-time abnormal detection of photovoltaic grid-connected power is carried out, and when abnormality occurs in photovoltaic grid-connected power, the AC power output of the inverter is adjusted or the output is directly stopped.

[0006] Furthermore, a power test experiment is set up to perform voltage-power test on the photovoltaic array, including the following sub-steps: Set up irradiation power test groups and temperature power test groups, and configure the test environment; Test the irradiation variation curve and temperature variation curve of a single solar panel in a photovoltaic array.

[0007] Furthermore, setting the irradiation power test group and the temperature power test group, and configuring the test environment includes the following sub-steps: Set the first experimental number of irradiation power test groups and the first experimental number of temperature power test groups, number the irradiation power test groups, and use the symbol RG n Indicates, where n∈Z+ and 1≤n≤N1, Z+ is a positive integer, n is the serial number of RG, where N1 is the first experiment number; the temperature power test groups are numbered and the symbol TG n express; The individual solar panels in the photovoltaic array are numbered using the symbol SP m It is represented by, where m∈Z+ and m is the serial number of SP, and the maximum value of m is the number of single-section solar panels in the photovoltaic array; Set the initial irradiance, expressed as RI, and the initial working temperature, expressed as WT; Set all test temperatures of the irradiated power test group to WT, RG n The test irradiance of the temperature power test group is set to RI, RG n The test temperature is set to n×WT.

[0008] Furthermore, testing the irradiation variation curve and temperature variation curve of a single solar panel in a photovoltaic array includes the following sub-steps: With the test voltage as the X-axis and the test power as the Y-axis, two plane rectangular coordinate systems are established, which are named as the irradiation characteristic diagram and the temperature characteristic diagram respectively; The irradiation power test group is tested, and the test voltage is gradually increased from zero. The curve of the test power of a single solar panel changing with the test voltage is updated in real time in the irradiation characteristic diagram, which is named the irradiation change curve. n SP m , the obtained irradiance variation curve is marked as LR(n,m), where LR(n,m) represents RG n Medium SP m Temperature variation curve; The temperature power test is grouped and the test voltage is gradually increased from zero. The curve of the test power of a single solar panel changing with the test voltage is updated in real time in the temperature characteristic diagram. This curve is named the temperature change curve. n SP m , the obtained temperature change curve is marked as LT(n,m), LT(n,m) represents TG n Medium SP m Temperature variation curve.

[0009] Furthermore, performing maximum power point tracking on the photovoltaic array based on the result of the voltage-power test includes the following sub-steps: Analyze the voltage-power characteristic curve of the photovoltaic array based on the irradiation change curve and the temperature change curve; The maximum power point and the open circuit voltage are extracted based on the voltage-power characteristic curve, and the optimal operating voltage is set based on the maximum power point and the open circuit voltage.

[0010] Furthermore, analyzing the voltage-power characteristic curve of the photovoltaic array based on the irradiation variation curve and the temperature variation curve includes the following sub-steps: Starting from n=1, calculate the average value of the Y axis when X in LR(n,m) is equal to any value, and obtain a series of continuous coordinate points. Connect the coordinate points with a smooth curve to obtain the nth irradiation characteristic curve, add n+1 and repeat the analysis until n=N1, and obtain N1 nth irradiation characteristic curves; Starting from n=1, calculate the average value of the Y axis when X is equal to any value in LT(n,m), and obtain a series of continuous coordinate points. Connect the coordinate points with a smooth curve to obtain the nth temperature characteristic curve. Repeat the analysis until n=N1, and obtain N1 nth temperature characteristic curves. The nth radiation characteristic curve and the nth temperature characteristic curve are collectively referred to as initial characteristic curves. The initial characteristic curves are numbered and denoted by the symbol C i It means, where i∈Z+ and i is the serial number of L, and the maximum value of i is 2×N1; C i At this time, it is an irregular curve. For any Ci , for C i To reduce the size of C i Reduce the first reduction factor and get D i , at this time D i Visually presented as a regular curve, D i Extract and obtain i The corresponding regular curve is marked as E i , E i Enlarge the first reduction factor and get F i ; F i The thickness of the curve is marked as H i , increase F i H i , so that F i Covered in C i When applied, it can completely cover C i , at this time F i H i Once it is reduced, it cannot completely cover C i ; Reduce F i H i , let H i With C i The thickness and width are consistent, and the obtained smooth curve is marked as the voltage-power characteristic curve. i After analysis, 2×N1 voltage-power characteristic curves are obtained; Again, a plane rectangular coordinate system is established with the test voltage as the X-axis and the test power as the Y-axis, and is named the voltage-power characteristic diagram. All voltage-power characteristic curves are entered into the voltage-power characteristic diagram.

[0011] Further, extracting the maximum power point and the open circuit voltage based on the voltage-power characteristic curve, and setting the optimal operating voltage based on the maximum power point and the open circuit voltage includes the following sub-steps: The voltage-power characteristic curve is numbered and the symbol L is used i express; Get L i The value of X corresponding to the maximum Y is named the i-th maximum power point and is expressed as PM i , and obtain L i When Y is equal to 0, the value of X is named as the i-th open circuit voltage, expressed as KV i ; Calculate PM i / KV i , mark the calculation result as high-efficiency voltage ratio, calculate the average value of the high-efficiency voltage ratio, and name it as the optimal voltage ratio; The open circuit voltage of the photovoltaic array is monitored in real time, and the optimal operating voltage is obtained by multiplying the open circuit voltage with the optimal voltage ratio.

[0012] Furthermore, based on the grid frequency and grid phase of the photovoltaic grid, converting the direct current into the alternating current includes the following sub-steps: Obtain the grid frequency and grid phase of the photovoltaic grid; The direct current generated by the photovoltaic array is converted into alternating current through an inverter, and the frequency and phase of the alternating current are respectively equal to the grid frequency and the grid phase.

[0013] Furthermore, performing abnormal detection on photovoltaic grid connection in real time and adjusting the AC power output by the inverter or directly stopping the output when abnormal photovoltaic grid connection occurs includes the following sub-steps: Real-time monitoring of the grid frequency and grid phase of the photovoltaic grid-connected system. When the grid frequency and grid phase change, timely adjust the frequency and phase of the AC power output by the inverter; The photovoltaic grid is subjected to overvoltage and undervoltage detection, frequency anomaly detection, current anomaly detection and power anomaly detection. If an abnormality is found in any detection, the current conversion of the inverter is stopped.

[0014] In a second aspect, the present application provides an inverter control system for a photovoltaic grid-connected inverter, including a photovoltaic array test module, a maximum power tracking module, a current conversion module, and a grid-connected monitoring module; the photovoltaic array test module, the current conversion module, and the grid-connected monitoring module are respectively data-connected with the maximum power tracking module; The photovoltaic array test module is used to set up a power test experiment and perform a voltage-power test on the photovoltaic array; The maximum power tracking module is used to track the maximum power point of the photovoltaic array based on the result of the voltage-power test; The current conversion module is used to convert direct current into alternating current based on the grid frequency and grid phase of the photovoltaic grid-connected system; The grid-connected monitoring module is used to detect abnormalities in photovoltaic grid-connected power in real time, and to adjust the AC power output by the inverter or directly stop the output when abnormalities occur in photovoltaic grid-connected power.

[0015] Beneficial effects of the present invention: The present invention sets an irradiation power test group and a temperature power test group, configures a test environment, and then tests the irradiation change curve and the temperature change curve of a single solar panel in a photovoltaic array, and then analyzes the voltage-power characteristic curve of the photovoltaic array based on the irradiation change curve and the temperature change curve, and extracts the maximum power point and the open-circuit voltage based on the voltage-power characteristic curve, and sets the optimal operating voltage based on the maximum power point and the open-circuit voltage. The advantage is that this embodiment tracks the maximum power point of the photovoltaic array as a whole, and in the analysis process, eliminates the floating of the characteristic curve obtained when the maximum power of the photovoltaic array as a whole is tracked, and obtains an accurate voltage-power characteristic curve of the photovoltaic array, thereby analyzing and obtaining an accurate maximum power point, thereby improving the accuracy and efficiency of inverter control; The present invention converts direct current into alternating current based on the grid frequency and grid phase of the photovoltaic grid, and finally performs abnormality detection on the photovoltaic grid in real time, and adjusts the alternating current output by the inverter or directly stops the output when an abnormality occurs in the photovoltaic grid. The advantage is that the frequency and phase of the alternating current output by the inverter are always ensured to be consistent with the frequency and phase of the photovoltaic grid, and the connection between the inverter and the photovoltaic grid can be cut off when an abnormality occurs in the photovoltaic grid, thereby ensuring that the inverter will not be damaged or that the continuous output of the inverter will increase the abnormality degree of the photovoltaic grid, thereby improving the safety and effectiveness of the inverter control. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a functional block diagram of the system of the present invention; Figure 2 is a schematic diagram of the irradiation variation curve of the present invention; Figure 3 is a schematic diagram of multiple irradiation variation curves of the present invention; Figure 4 It is a schematic diagram of the temperature variation curve of the present invention; Figure 5 It is a schematic diagram of the first irradiation characteristic curve of the present invention; Figure 6 is a schematic diagram of F1 of the present invention; Figure 7 is a schematic diagram of the final F1 of the present invention; Figure 8 It is a schematic diagram of placing C1 and F1 into the same coordinate system of the present invention; Fig. 9 is a schematic diagram of the widened F1 of the present invention; Fig.10 is a voltage-power characteristic diagram of the present invention; Fig.11 The figure is a flow chart of the steps of the method of the present invention. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Example 1, please refer to Figure 1 As shown, the present application provides an inverter control system for a photovoltaic grid-connected inverter, including a photovoltaic array test module, a maximum power tracking module, a current conversion module, and a grid-connected monitoring module; the photovoltaic array test module, the current conversion module, and the grid-connected monitoring module are respectively connected to the maximum power tracking module data; The photovoltaic array test module is used to set up a power test experiment and perform voltage-power test on the photovoltaic array; the photovoltaic array test module includes a test environment setting unit and an irradiation temperature test unit; The test environment setting unit is used to set the irradiation power test group and the temperature power test group, and configure the test environment; The test environment setting unit is configured with a test environment setting strategy, which includes: Set the first experimental number of irradiation power test groups and the first experimental number of temperature power test groups, number the irradiation power test groups, and use the symbol RG n Indicates, where n∈Z+ and 1≤n≤N1, Z+ is a positive integer, n is the serial number of RG, where N1 is the first experiment number; the temperature power test groups are numbered and the symbol TG n express; The individual solar panels in the photovoltaic array are numbered using the symbol SP m It is represented by, where m∈Z+ and m is the serial number of SP, and the maximum value of m is the number of single-section solar panels in the photovoltaic array; In practical applications, the first experimental number is only used to set the number of groups and has no practical significance. It is only necessary to ensure that the value is not less than 3. In this embodiment, the first experimental number N1 is set to 3, that is, 3 groups of irradiation power test groups and 3 groups of temperature power test groups are set, namely RG1 to RG3 and TG1 to TG3, 1≤n≤3, there are 4100 single-section solar panels in the photovoltaic array, and SP1 to SP 4100, 1≤m≤4100; the existing maximum power tracking usually only performs maximum power tracking on one single solar panel, and uses the result as the maximum power point of the photovoltaic array as a whole. Although the materials and production processes of the single solar panels in the photovoltaic array are exactly the same, there are still certain minor differences in the actual production process. At the same time, the installation positions of different single solar panels are different, which will also lead to different maximum power points. Under the combined effect of the two, using the maximum power point of a single solar panel as the maximum power point of the photovoltaic array as a whole will cause the photovoltaic array to fail to reach the actual maximum power point and the deviation is large; Set the initial irradiance, expressed as RI, and the initial working temperature, expressed as WT; Set all test temperatures of the irradiated power test group to WT, RG n The test irradiance of the temperature power test group is set to RI, RG n The test temperature is set to n×WT; In practical applications, the initial irradiance and initial operating temperature are used to measure the change in the operating power of a single solar panel when the irradiance and operating temperature gradually increase. There is no specific requirement for the value, and it is only necessary to ensure that N1×WT and N1×RI do not exceed the maximum values ​​of the operating temperature and irradiance in practical applications. In this embodiment, the initial irradiance RI is set to 400W / ㎡, and the initial operating temperature WT is set to 20℃, so that the test irradiances of RG1 to RG3 are 400W / ㎡, 800W / ㎡ and 1200W / ㎡, respectively, and the test temperatures of RI1 to RI3 are 20℃, 40℃ and 60℃, respectively. The irradiation temperature test unit is used to test the irradiation change curve and temperature change curve of a single solar panel in a photovoltaic array; The irradiation temperature test unit is equipped with a irradiation temperature test strategy, which includes: See also Figures 2 to 4 As shown, two plane rectangular coordinate systems are established with the test voltage as the X-axis and the test power as the Y-axis, which are named as the irradiation characteristic diagram and the temperature characteristic diagram respectively; The irradiation power test group is tested, and the test voltage is gradually increased from zero. The curve of the test power of a single solar panel changing with the test voltage is updated in real time in the irradiation characteristic diagram, which is named the irradiation change curve. n SP m , the obtained irradiance variation curve is marked as LR(n,m), where LR(n,m) represents RG n Medium SP m Temperature variation curve; The temperature power test is grouped and the test voltage is gradually increased from zero. The curve of the test power of a single solar panel changing with the test voltage is updated in real time in the temperature characteristic diagram. This curve is named the temperature change curve. n SP m , the obtained temperature change curve is marked as LT(n,m), LT(n,m) represents TG n Medium SP m Temperature variation curve; In practical applications, the three irradiance change curves LR(1,1), LR(2,1) and LR(3,1) are used as examples to show the general trend of the irradiance change curves under different n values. Figure 2 As shown, the irradiance variation curves are LR(1,1), LR(2,1) and LR(3,1) from bottom to top. Figure 3 Multiple irradiation change curves for different n=1 are shown to demonstrate the diversity and volatility of irradiation change curves due to the differences in single-section solar panels; the three temperature change curves LT(1,1), LT(2,1) and LT(3,1) are used as examples to demonstrate the general trend of the temperature change curves for different n values, such as Figure 4 As shown in the figure, the temperature change curves from right to left are LT(1,1), LT(2,1) and LT(3,1). Since the temperature change curve and the irradiation change curve will fluctuate within a certain range based on the difference of n, Figure 3 Similarly, multiple temperature change curves of the temperature change curve are no longer shown in this embodiment.

[0019] The maximum power tracking module is used to track the maximum power point of the photovoltaic array based on the results of the voltage-power test; the maximum power tracking module includes a characteristic curve analysis unit and a maximum power extraction unit; The characteristic curve analysis unit is used to analyze the voltage-power characteristic curve of the photovoltaic array based on the irradiation variation curve and the temperature variation curve; The characteristic curve analysis unit is configured with a characteristic curve analysis strategy, which includes: See also Figure 5 As shown, starting from n=1, the average value of the Y axis when X in LR(n,m) is equal to any value is calculated to obtain a series of continuous coordinate points, and the coordinate points are connected by a smooth curve to obtain the nth irradiation characteristic curve, and n+1 is repeated until n=N1, and N1 nth irradiation characteristic curves are obtained; Starting from n=1, calculate the average value of the Y axis when X is equal to any value in LT(n,m), and obtain a series of continuous coordinate points. Connect the coordinate points with a smooth curve to obtain the nth temperature characteristic curve. Repeat the analysis until n=N1, and obtain N1 nth temperature characteristic curves. In practical applications, Figure 3 For example, when n=1, any value on the X axis is taken, for example, X is 20, then find the value of Y in all LR(1,m) where X is equal to 20 and calculate the average value. The average value of Y when X=20 is 65, that is, the coordinate point is (20,65). Analyze each value of X to obtain a series of continuous coordinate points, and connect them with a smooth curve to obtain Figure 5 , Figure 5 The first characteristic curve of irradiation obtained when n=1 is shown, Figure 5 As shown, the first irradiation characteristic curve is an irregular floating curve rather than a smooth curve, which will cause errors in the extraction of the maximum power point. The same is true for the nth temperature characteristic curve, so they need to be converged to make them smooth; the analysis process of the nth temperature characteristic curve is the same as the analysis process of the first irradiation characteristic curve, so this embodiment will not be explained in detail; The nth radiation characteristic curve and the nth temperature characteristic curve are collectively referred to as initial characteristic curves. The initial characteristic curves are numbered and denoted by the symbol C i It means, where i∈Z+ and i is the serial number of L, and the maximum value of i is 2×N1; See also Figure 6 to Figure 7 As shown, C i At this time, it is an irregular curve. For any C i , for C i To reduce the size of C i Reduce the first reduction factor and get D i , at this time D i Visually presented as a regular curve, D i Extract and obtain i The corresponding regular curve is marked as E i , E i Enlarge the first reduction factor and get F i ; In practical applications, Figure 5 For example, the first characteristic curve of irradiation is processed. The first characteristic curve of irradiation is marked with C1. There is no fixed value for the first reduction factor. It only needs to ensure that the extracted D i It can be a smooth curve, and then it can be enlarged according to the corresponding first reduction factor. For C1, the first reduction factor is set to 20 times to get D1, D1 is extracted to get E1 and enlarged 20 times to get F1. Figure 6 As shown, Figure 6 Although F1 still has some floating, it has been significantly improved compared with C1. At this time, we can repeat the process of shrinking, extracting and enlarging again to get Figure 7 , Figure 7 The smooth curve in is F1 obtained after processing C1. In this embodiment, there are 6 initial characteristic curves, and their analysis process is the same as that of C1, so they will not be described in detail in this embodiment. See also Figures 8 to 9 As shown, F i The thickness of the curve is marked as H i , increase F i H i , so that F i Covered in C i When applied, it can completely cover C i , at this time F i H i Once it is reduced, it cannot completely cover C i ; Reduce F i H i , let H i With C i The thickness and width are consistent, and the obtained smooth curve is marked as the voltage-power characteristic curve. i After analysis, 2×N1 voltage-power characteristic curves are obtained; See also Fig.10 As shown, a plane rectangular coordinate system is established again with the test voltage as the X-axis and the test power as the Y-axis, named as the voltage-power characteristic diagram, and all voltage-power characteristic curves are entered into the voltage-power characteristic diagram; In practical applications, increasing H i When it is not F i The same width is added to both sides at the same time. In this embodiment, C1 and F1 are taken as examples. C1 and F1 are placed in the same coordinate system to obtain Figure 8 ,against Figure 8 , the side of F1 facing the X-axis is called the lower side, and the side of F1 facing the non-X-axis is called the upper side. First, widen the upper side. Each widening will produce a new overlap with C1. When no new overlap occurs after widening the upper side, stop widening and perform the same treatment on the lower side. Fig. 9 The widened F1 shown in the figure is Fig. 9The upper and lower sides of F1 in the embodiment are shrunk at the same time. For example, in this embodiment, the thickness width of C1 is 0.05 mm, and H1 of F1 is widened to 2.11 mm, wherein the upper side is widened by 1 mm, and the lower side is widened by 1.06 mm. When F1 is shrunk, the width of the upper and lower sides is reduced by (2.11-0.05) / 2=1.03 mm at the same time, and the voltage-power characteristic curve corresponding to C1 is obtained. For all C i After analysis, 6 voltage-power characteristic curves are obtained, and the voltage-power characteristic diagram is constructed as shown in Fig.10 As shown; Fig.10 The curve in Figure 2 and Figure 3 This is because they follow the same law of change, but the values ​​have changed. Fig.10 The maximum power point in Figure 2 as well as Figure 3 The maximum power point is more accurate; The maximum power extraction unit is used to extract the maximum power point and the open circuit voltage based on the voltage-power characteristic curve, and set the optimal operating voltage based on the maximum power point and the open circuit voltage; The maximum power extraction unit is configured with a maximum power extraction strategy, which includes: The voltage-power characteristic curve is numbered and the symbol L is used i express; Get L i The value of X corresponding to the maximum Y is named the i-th maximum power point and is expressed as PM i , and obtain L i When Y is equal to 0, the value of X is named as the i-th open circuit voltage, expressed as KV i ; Calculate PM i / KV i , mark the calculation result as high-efficiency voltage ratio, calculate the average value of the high-efficiency voltage ratio, and name it as the optimal voltage ratio; Monitor the open circuit voltage of the photovoltaic array in real time, multiply the open circuit voltage by the optimal voltage ratio to obtain the optimal operating voltage; In practical applications, Fig.10There are 6 maximum power points, and PM1 to PM6 are 28.8, 30.9, 31, 32.2, 33.1 and 33.1 respectively. The corresponding KV1 to KV6 are 35.5, 38, 38.5, 39.7, 40.6 and 40.6 respectively. The high-efficiency voltage ratios when i=1 to 6 are calculated to be 0.8113, 0.8132, 0.8052, 0.8111, 0.8153 and 0.8153 respectively. The calculation results retain four decimal places. The average value is calculated to obtain the optimal voltage ratio of 0.81. The calculation results retain two decimal places. The open-circuit voltage of the photovoltaic array is monitored in real time. The open-circuit voltage is multiplied by 0.81 to obtain the optimal working voltage and set the working voltage of the photovoltaic array to the optimal working voltage. At this time, the working power of the photovoltaic array reaches the best.

[0020] The current conversion module is used to convert direct current into alternating current based on the grid frequency and grid phase of the photovoltaic grid; The current conversion module is configured with a current conversion strategy, which includes: Obtain the grid frequency and grid phase of the photovoltaic grid; The DC power generated by the photovoltaic array is converted into AC power through an inverter, and the frequency and phase of the AC power are equal to the grid frequency and grid phase respectively; In actual applications, the inverter converts DC power into AC power using existing conversion technology, ensuring that the frequency and phase are consistent with the frequency and phase of the photovoltaic grid.

[0021] The grid-connected monitoring module is used to detect abnormalities in photovoltaic grid-connected power in real time. When abnormalities occur in photovoltaic grid-connected power, the AC power output by the inverter is adjusted or the output is directly stopped. The grid-connected monitoring module is configured with a grid-connected monitoring strategy, which includes: Real-time monitoring of the grid frequency and grid phase of the photovoltaic grid-connected system. When the grid frequency and grid phase change, timely adjust the frequency and phase of the AC power output by the inverter; Perform overvoltage and undervoltage detection, frequency anomaly detection, current anomaly detection, and power anomaly detection on photovoltaic grid-connected power. If an abnormality is found in any detection, the inverter's current conversion is stopped. In practical applications, since the frequency and phase of the AC power converted by the inverter need to be consistent with the grid-connected frequency and grid-connected phase of the photovoltaic grid, it is necessary to monitor it in real time so as to adjust the AC power output by the inverter in time to prevent abnormalities during grid connection; for overvoltage and undervoltage detection, frequency anomaly detection, current anomaly detection and power anomaly detection of the photovoltaic grid, existing detection technologies can be used to disconnect the connection with the photovoltaic grid in time to prevent the photovoltaic array from being implicated when an abnormality occurs in the photovoltaic grid.

[0022] Example 2, please refer to Fig.11 As shown, the present application provides an inverter control method for a photovoltaic grid-connected inverter, comprising the following steps: Step S1, setting a power test experiment to perform a voltage-power test on the photovoltaic array; Step S1 includes the following sub-steps: Step S101, setting a radiation power test group and a temperature power test group, and configuring a test environment; Step S101 includes the following sub-steps: Step S1011, setting a first experimental number of irradiation power test groups and a first experimental number of temperature power test groups, numbering the irradiation power test groups, and using symbols RG n Indicates, where n∈Z+ and 1≤n≤N1, Z+ is a positive integer, n is the serial number of RG, where N1 is the first experiment number; the temperature power test groups are numbered and the symbol TG n express; Step S1012: numbering the individual solar panels in the photovoltaic array, using symbols SP m It is represented by, where m∈Z+ and m is the serial number of SP, and the maximum value of m is the number of single-section solar panels in the photovoltaic array; Step S1013, setting the initial irradiance, expressed as RI, and setting the initial working temperature, expressed as WT; Step S1014, setting all test temperatures of the irradiated power test group to WT, RG n The test irradiance of the temperature power test group is set to RI, RG n The test temperature is set to n×WT; Step S102, testing the irradiation change curve and temperature change curve of a single solar panel in the photovoltaic array; Step S102 includes the following sub-steps: Step S1021, establishing two plane rectangular coordinate systems with the test voltage as the X-axis and the test power as the Y-axis, and naming them as the irradiation characteristic diagram and the temperature characteristic diagram respectively; Step S1022, test the irradiation power test group, gradually increase the test voltage from zero, and update the curve of the test power of a single solar panel as the test voltage changes in real time in the irradiation characteristic diagram, named irradiation change curve, for RG n SP m , the obtained irradiance variation curve is marked as LR(n,m), where LR(n,m) represents RG n Medium SP m Temperature variation curve; Step S1023, test the temperature power test group, gradually increase the test voltage from zero, and update the curve of the test power of a single solar panel as the test voltage changes in real time in the temperature characteristic diagram, named the temperature change curve, for TG n SP m , the obtained temperature change curve is marked as LT(n,m), LT(n,m) represents TG n Medium SP m Temperature variation curve; Step S2, performing maximum power point tracking on the photovoltaic array based on the result of the voltage-power test; Step S2 includes the following sub-steps: Step S201, analyzing the voltage-power characteristic curve of the photovoltaic array based on the irradiation change curve and the temperature change curve; Step S201 includes the following sub-steps: Step S2011, starting from n=1, calculate the average value of the Y axis when X in LR(n,m) is equal to any value, obtain a series of continuous coordinate points, connect the coordinate points by a smooth curve to obtain the nth irradiation characteristic curve, add n+1 and repeat the analysis until n=N1, and obtain N1 nth irradiation characteristic curves; Step S2012, starting from n=1, calculate the average value of the Y axis when X is equal to any value in LT(n,m), obtain a series of continuous coordinate points, connect the coordinate points by a smooth curve to obtain the nth temperature characteristic curve, add n+1 and repeat the analysis until n=N1, and obtain N1 nth temperature characteristic curves; Step S2013: The radiation nth characteristic curve and the temperature nth characteristic curve are collectively referred to as initial characteristic curves, and the initial characteristic curves are numbered, and the initial characteristic curves are represented by symbols C i It means, where i∈Z+ and i is the serial number of L, and the maximum value of i is 2×N1; Step S2014, C i At this time, it is an irregular curve. For any C i , for C i To reduce the size of C i Reduce the first reduction factor and get D i , at this time D i Visually presented as a regular curve, D i Extract and obtain i The corresponding regular curve is marked as E i , E i Enlarge the first reduction factor and get F i ; Step S2015: F i The thickness of the curve is marked as Hi , increase F i H i , so that F i Covered in C i When applied, it can completely cover C i , at this time F i H i Once it is reduced, it cannot completely cover C i ; Step S2016, reduce F i H i , let H i With C i The thickness and width are consistent, and the obtained smooth curve is marked as the voltage-power characteristic curve. i After analysis, 2×N1 voltage-power characteristic curves are obtained; Step S2017, again establish a plane rectangular coordinate system with the test voltage as the X-axis and the test power as the Y-axis, named as the voltage-power characteristic diagram, and enter all voltage-power characteristic curves into the voltage-power characteristic diagram; Step S202, extracting the maximum power point and the open circuit voltage based on the voltage-power characteristic curve, and setting the optimal operating voltage based on the maximum power point and the open circuit voltage; Step S202 includes the following sub-steps: Step S2021, numbering the voltage-power characteristic curves, using the symbol L i express; Step S2022, obtain L i The value of X corresponding to the maximum Y is named the i-th maximum power point and is expressed as PM i , and obtain L i When Y is equal to 0, the value of X is named as the i-th open circuit voltage, expressed as KV i ; Step S2023, calculate PM i / KV i , mark the calculation result as high-efficiency voltage ratio, calculate the average value of the high-efficiency voltage ratio, and name it as the optimal voltage ratio; Step S2024, monitoring the open circuit voltage of the photovoltaic array in real time, and multiplying the open circuit voltage by the optimal voltage ratio to obtain the optimal operating voltage; Step S3, based on the grid frequency and grid phase of the photovoltaic grid, converting the direct current into alternating current; step S3 includes the following sub-steps: Step S301, obtaining the grid frequency and grid phase of the photovoltaic grid-connected system; Step S302, converting the direct current generated by the photovoltaic array into alternating current through an inverter, wherein the frequency and phase of the alternating current are respectively equal to the grid frequency and the grid phase; Step S4, performing real-time abnormality detection on the photovoltaic grid connection, and adjusting the AC power output by the inverter or directly stopping the output when an abnormality occurs in the photovoltaic grid connection; Step S4 includes the following sub-steps: Step S401, real-time monitoring of the grid frequency and grid phase of the photovoltaic grid-connected system, and timely regulating the frequency and phase of the AC power output by the inverter when the grid frequency and grid phase change; Step S402, overvoltage and undervoltage detection, frequency anomaly detection, current anomaly detection and power anomaly detection are performed on the photovoltaic grid-connected system. When an abnormality is found in any detection, the current conversion of the inverter is stopped.

[0023] Embodiment 3, the present application provides an electronic device, which may include: a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other through the communication bus. The memory stores computer-readable instructions, and the processor can call the instructions in the memory. When the computer-readable instructions are executed by the processor, the steps in the inverter control method of a photovoltaic grid-connected inverter are executed to achieve the following functions: setting a power test experiment, performing a voltage-power test on the photovoltaic array; performing maximum power point tracking on the photovoltaic array based on the results of the voltage-power test; converting direct current into alternating current based on the grid frequency and grid phase of the photovoltaic grid; performing real-time abnormal detection on the photovoltaic grid, and adjusting the alternating current output by the inverter or directly stopping the output when an abnormality occurs in the photovoltaic grid.

[0024] In addition, the logic instructions in the above-mentioned memory can be implemented in the form of software functional units and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on this understanding, the technical solution of the present application can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0025] Embodiment 4, the present application also provides a computer-readable storage medium, the present application provides a storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps in the inverter control method of the above photovoltaic grid-connected inverter are executed to achieve the following functions: setting a power test experiment to perform a voltage-power test on the photovoltaic array; tracking the maximum power point of the photovoltaic array based on the results of the voltage-power test; converting direct current into alternating current based on the grid frequency and grid phase of the photovoltaic grid; performing real-time abnormality detection on the photovoltaic grid, and adjusting the alternating current output of the inverter or directly stopping the output when an abnormality occurs in the photovoltaic grid.

[0026] Through the description of the above implementation methods, the embodiments of the present invention can be provided as methods, systems or computer program products. Based on such an understanding, the above technical solutions can be essentially or partly contributed to the prior art in the form of software products, which can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., and include several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0027] In the embodiments provided in the present application, it should be understood that the disclosed system or method can be implemented in other ways. The embodiments described above are merely schematic. For example, the division of modules or units is only a logical function division. There may be other division methods in actual implementation. For example, multiple modules or units can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, and the indirect coupling or communication connection of systems, modules and units can be electrical, mechanical or other forms.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An inverter control method for a photovoltaic grid-connected inverter, characterized in that: The steps include: Set up a power test experiment to perform voltage-power test on the photovoltaic array; Perform maximum power point tracking on the photovoltaic array based on the results of voltage-power test; Based on the grid frequency and grid phase of the photovoltaic grid, direct current is converted into alternating current; Real-time abnormal detection of photovoltaic grid-connected power is carried out, and when abnormality occurs in photovoltaic grid-connected power, the AC power output of the inverter is adjusted or the output is directly stopped.

2. The inverter control method of a photovoltaic grid-connected inverter according to claim 1, characterized in that: Setting up a power test experiment and performing a voltage-power test on a photovoltaic array includes the following sub-steps: Set up irradiation power test groups and temperature power test groups, and configure the test environment; Test the irradiation variation curve and temperature variation curve of a single solar panel in a photovoltaic array.

3. The inverter control method of a photovoltaic grid-connected inverter according to claim 2, characterized in that: Set up the irradiance power test group and the temperature power test group. Configuring the test environment includes the following sub-steps: Set the first experimental number of irradiation power test groups and the first experimental number of temperature power test groups, number the irradiation power test groups, and use the symbol RG n Indicates, where n∈Z+ and 1≤n≤N1, Z+ is a positive integer, n is the serial number of RG, where N1 is the first experiment number; the temperature power test groups are numbered and the symbol TG n express; The individual solar panels in the photovoltaic array are numbered using the symbol SP m It is represented by, where m∈Z+ and m is the serial number of SP, and the maximum value of m is the number of single-section solar panels in the photovoltaic array; Set the initial irradiance, expressed as RI, and the initial working temperature, expressed as WT; Set all test temperatures of the irradiated power test group to WT, RG n The test irradiance of the temperature power test group is set to RI, RG n The test temperature is set to n×WT.

4. The inverter control method of a photovoltaic grid-connected inverter according to claim 3, characterized in that: Testing the irradiation change curve and temperature change curve of a single solar panel in a photovoltaic array includes the following sub-steps: With the test voltage as the X-axis and the test power as the Y-axis, two plane rectangular coordinate systems are established, which are named as the irradiation characteristic diagram and the temperature characteristic diagram respectively; The irradiation power test group is tested, and the test voltage is gradually increased from zero. The curve of the test power of a single solar panel changing with the test voltage is updated in real time in the irradiation characteristic diagram, which is named the irradiation change curve. n SP m , the obtained irradiance variation curve is marked as LR(n,m), where LR(n,m) represents RG n Medium SP m Temperature variation curve; The temperature power test is grouped and the test voltage is gradually increased from zero. The curve of the test power of a single solar panel changing with the test voltage is updated in real time in the temperature characteristic diagram. This curve is named the temperature change curve. n SP m , the obtained temperature change curve is marked as LT(n,m), LT(n,m) represents TG n Medium SP m Temperature variation curve.

5. The inverter control method of a photovoltaic grid-connected inverter according to claim 4, characterized in that: Based on the results of the voltage-power test, the maximum power point tracking of the photovoltaic array includes the following sub-steps: Analyze the voltage-power characteristic curve of the photovoltaic array based on the irradiation change curve and the temperature change curve; The maximum power point and the open circuit voltage are extracted based on the voltage-power characteristic curve, and the optimal operating voltage is set based on the maximum power point and the open circuit voltage.

6. The inverter control method of a photovoltaic grid-connected inverter according to claim 5, characterized in that: Analyzing the voltage-power characteristic curve of a photovoltaic array based on the irradiation variation curve and the temperature variation curve includes the following sub-steps: Starting from n=1, calculate the average value of the Y axis when X in LR(n,m) is equal to any value, and obtain a series of continuous coordinate points. Connect the coordinate points with a smooth curve to obtain the nth irradiation characteristic curve, add n+1 and repeat the analysis until n=N1, and obtain N1 nth irradiation characteristic curves; Starting from n=1, calculate the average value of the Y axis when X is equal to any value in LT(n,m), and obtain a series of continuous coordinate points. Connect the coordinate points with a smooth curve to obtain the nth temperature characteristic curve. Repeat the analysis until n=N1, and obtain N1 nth temperature characteristic curves. The nth radiation characteristic curve and the nth temperature characteristic curve are collectively referred to as initial characteristic curves. The initial characteristic curves are numbered and denoted by the symbol C i It means, where i∈Z+ and i is the serial number of L, and the maximum value of i is 2×N1; C i At this time, it is an irregular curve. For any C i , for C i To reduce the size of C i Reduce the first reduction factor and get D i , at this time D i Visually presented as a regular curve, D i Extract and obtain i The corresponding regular curve is marked as E i , E i Enlarge the first reduction factor and get F i ; F i The thickness of the curve is marked as H i , increase F i H i , so that F i Covered in C i When applied, it can completely cover C i , at this time F i H i Once it is reduced, it cannot completely cover C i ; Reduce F i H i , let H i With C i The thickness and width are consistent, and the obtained smooth curve is marked as the voltage-power characteristic curve. i After analysis, 2×N1 voltage-power characteristic curves are obtained; Again, a plane rectangular coordinate system is established with the test voltage as the X-axis and the test power as the Y-axis, and is named the voltage-power characteristic diagram. All voltage-power characteristic curves are entered into the voltage-power characteristic diagram.

7. The inverter control method of a photovoltaic grid-connected inverter according to claim 6, characterized in that: Extracting the maximum power point and the open circuit voltage based on the voltage-power characteristic curve, and setting the optimal operating voltage based on the maximum power point and the open circuit voltage include the following sub-steps: The voltage-power characteristic curve is numbered and the symbol L is used i express; Get L i The value of X corresponding to the maximum Y is named the i-th maximum power point and is expressed as PM i , and obtain L i When Y is equal to 0, the value of X is named as the i-th open circuit voltage, expressed as KV i ; Calculate PM i / KV i , mark the calculation result as high-efficiency voltage ratio, calculate the average value of the high-efficiency voltage ratio, and name it as the optimal voltage ratio; The open circuit voltage of the photovoltaic array is monitored in real time, and the optimal operating voltage is obtained by multiplying the open circuit voltage with the optimal voltage ratio.

8. The inverter control method of a photovoltaic grid-connected inverter according to claim 7, characterized in that: Based on the grid frequency and grid phase of the photovoltaic grid, converting DC power into AC power includes the following sub-steps: Obtain the grid frequency and grid phase of the photovoltaic grid; The direct current generated by the photovoltaic array is converted into alternating current through an inverter, and the frequency and phase of the alternating current are respectively equal to the grid frequency and the grid phase.

9. The inverter control method of a photovoltaic grid-connected inverter according to claim 8, characterized in that: Real-time abnormal detection of photovoltaic grid connection is performed. When abnormal photovoltaic grid connection occurs, the AC power output by the inverter is adjusted or the output is directly stopped, including the following sub-steps: Real-time monitoring of the grid frequency and grid phase of the photovoltaic grid-connected system. When the grid frequency and grid phase change, timely adjust the frequency and phase of the AC power output by the inverter; The photovoltaic grid is subjected to overvoltage and undervoltage detection, frequency anomaly detection, current anomaly detection and power anomaly detection. If an abnormality is found in any detection, the current conversion of the inverter is stopped.

10. An inverter control system for a photovoltaic grid-connected inverter, used to implement an inverter control method for a photovoltaic grid-connected inverter according to any one of claims 1 to 9, characterized in that: It includes a photovoltaic array test module, a maximum power tracking module, a current conversion module and a grid-connected monitoring module; the photovoltaic array test module, the current conversion module and the grid-connected monitoring module are respectively connected to the maximum power tracking module data; The photovoltaic array test module is used to set up a power test experiment and perform a voltage-power test on the photovoltaic array; The maximum power tracking module is used to track the maximum power point of the photovoltaic array based on the result of the voltage-power test; The current conversion module is used to convert direct current into alternating current based on the grid frequency and grid phase of the photovoltaic grid-connected system; The grid-connected monitoring module is used to detect abnormalities in photovoltaic grid-connected power in real time, and to adjust the AC power output by the inverter or directly stop the output when abnormalities occur in photovoltaic grid-connected power.

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