Photovoltaic inverter test system and test method thereof

Abstract

The invention discloses a photovoltaic inverter testing system and a testing method thereof, and relates to the field of photovoltaic inverter testing, and the testing method comprises the following steps: S1, obtaining the I-V curve data of an actual photovoltaic panel under different conditions, and extracting the characteristics of the photovoltaic panel; s2, establishing a physical model, and verifying the consistency accuracy of the output characteristics of the physical model; s3, generating a plurality of virtual I-V curves through the physical model; and S4, the virtual I-V curve is transmitted to an MPPT controller of the inverter, the inverter is started, the MPPT controller carries out maximum power point tracking, and performance testing of the inverter is carried out. According to the invention, a plurality of virtual I-V curves are generated through physical model simulation, the limitation that a photovoltaic simulator can only output a single I-V curve is overcome, and a plurality of independent I-V curves can be simulated at the same time, so that the real output characteristics of the string type photovoltaic panel can be reflected more accurately; therefore, a plurality of MPPT controllers in the inverter can be helped to track the maximum power point of each string, and global optimization is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic inverter testing, and in particular to a photovoltaic inverter testing system and a testing method thereof. Background Art

[0002] In the field of renewable energy, photovoltaic power generation, as a clean and efficient way of energy conversion, is gradually becoming an important part of the global energy structure. As the core equipment of the photovoltaic power generation system, the photovoltaic inverter is responsible for converting the direct current (DC) generated by the photovoltaic panel into alternating current (AC) that can be connected to the power grid or directly used for electrical equipment. In order to improve the power generation efficiency, modern photovoltaic inverters generally adopt a string design, that is, multiple photovoltaic panels are connected in series into a group and connected to the inverter through cables for centralized conversion. At the same time, the inverter is equipped with multiple maximum power point tracking (MPPT) controllers, which can simultaneously track the maximum power points of multiple photovoltaic arrays, thereby optimizing the power generation efficiency of the entire system.

[0003] In the testing process of photovoltaic inverters, existing technologies mainly rely on photovoltaic simulators to simulate the output characteristics of photovoltaic panels. A photovoltaic simulator is an electronic device that can generate a current-voltage (IV) curve similar to that of an actual photovoltaic panel, simulating the output behavior of photovoltaic panels under different light intensity, temperature and other environmental conditions. It provides a controllable and repeatable DC power supply for the inverter, which helps to evaluate the performance of the inverter.

[0004] However, in actual use, since photovoltaic simulators can usually only output one IV curve, it is impossible to simulate multiple independent IV curves at the same time. In order to more accurately simulate the structure of string photovoltaic panels, it is theoretically possible to equip each MPPT channel with an independent photovoltaic simulator. This method not only greatly increases the cost of the test equipment, but also makes the test process more complicated. More connection cables, configuration steps and maintenance costs are required, which reduces the efficiency and feasibility of the test.

[0005] Therefore, it is necessary to improve the deficiencies in the prior art to solve the above problems. Summary of the invention

[0006] The present invention overcomes the deficiencies of the prior art and provides a photovoltaic inverter testing system and a testing method thereof.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a photovoltaic inverter testing method, comprising the following steps:

[0008] S1. Obtaining IV curve data of actual photovoltaic panels under different conditions, and analyzing the IV curve data to extract characteristics of photovoltaic panels under different conditions;

[0009] S2. Based on the characteristics of photovoltaic panels, a physical model for simulating the IV curve of photovoltaic panels is established, and the accuracy of the IV curve generated by the physical model and the actual output characteristics of photovoltaic panels is verified;

[0010] S3, generating multiple virtual IV curves through physical model simulation according to the characteristics of actual photovoltaic panels under different conditions;

[0011] S4, transmitting the generated multiple virtual IV curves to each MPPT controller of the inverter, starting the inverter, and the MPPT controller performs maximum power point tracking according to the received virtual IV curve to perform a performance test of the inverter.

[0012] In a preferred embodiment of the present invention, the step S1 includes the following sub-steps:

[0013] S11. Use a set of actual photovoltaic panels and set different usage conditions, including the light intensity, temperature, partial shading and sudden changes in light intensity.

[0014] S12. Record the IV curve data of the actual photovoltaic panel under different conditions; including the open circuit voltage, short circuit current, maximum power point voltage, maximum power point current, maximum power, light intensity and temperature involved;

[0015] S13. Perform impact analysis on the recorded IV curve data under different conditions to extract the characteristics of the photovoltaic panel under different conditions.

[0016] In a preferred embodiment of the present invention, in the step S13, the analysis of the influence of light intensity includes: the influence of light intensity on photogenerated current; the analysis of the influence of temperature includes: the influence of temperature on reverse saturation current and open circuit voltage; the analysis of the influence of partial shading includes: the influence of partial shading on photogenerated current; the analysis of the influence of sudden illumination change includes: the influence of sudden illumination change on the dynamic change of IV curve and the rapid change of maximum power point.

[0017] In a preferred embodiment of the present invention, the adjustment of the effect of light intensity on photocurrent is: Among them, I ph is the photocurrent, I ph,0 is the photocurrent under standard test conditions; G is the current light intensity; G STC is the light intensity under standard test conditions.

[0018] In a preferred embodiment of the present invention, the adjustment of the effect of temperature on the reverse saturation current is: Among them, I s (T STC ) is the reverse saturation current under standard test conditions; T is the current temperature; T STCis the temperature under standard test conditions; E g is the band gap energy of the photovoltaic material; k is the Boltzmann constant;

[0019] Adjustment of the effect of temperature on open circuit voltage: Voc(T)=Voc(T STC )-α(TT STC ); where Voc(T STC ) is the open circuit voltage under standard test conditions; T is the current temperature; T STC is the temperature under standard test conditions; α is the temperature coefficient of open circuit voltage.

[0020] In a preferred embodiment of the present invention, the adjustment of the effect of partial shielding on the photocurrent is: ph =I ph,0 ×P; where I ph,0 is the photocurrent under standard test conditions; P is the shading ratio, 0 means complete shading, and 1 means no shading.

[0021] In a preferred embodiment of the present invention, the evaluation of the dynamic response capability of the IV curve to the sudden change of illumination comprises the following steps:

[0022] A1. Set the initial light intensity G 1 , generate the corresponding IV curve;

[0023] A2. At a certain time point t0, the light intensity is suddenly changed from G 1 Change to the new light intensity G 2 ;

[0024] A3. According to the light intensity G 2 , recalculate the photocurrent I ph , and generate a new IV curve;

[0025] A4. During the change of light intensity, simulate the dynamic process of sudden change of light intensity and gradually adjust the photocurrent I ph , generate a series of IV curves of intermediate states;

[0026] The response speed evaluation of the sudden change of illumination to the rapid change of the maximum power point comprises the following steps:

[0027] B1. Before the sudden change of light intensity, record the maximum power point voltage V of the inverter. mp and current I mp ;

[0028] B2. According to the simulation steps of the dynamic response of the IV curve to the sudden change of illumination, a sudden change of illumination is introduced to generate the IV curve after the sudden change;

[0029] B3. After the sudden change of light intensity, record the maximum power point voltage V of the inverter. mp and current I mp ;

[0030] B4. The time from the sudden change of light intensity to the time when the inverter finds the new maximum power point again is the response time of the inverter.

[0031] In a preferred embodiment of the present invention, the step S2 includes the following sub-steps:

[0032] S21. Based on the characteristics of photovoltaic panels, a physical model capable of simulating the IV characteristics of photovoltaic panels is established;

[0033] S22, using the IV curve data recorded in step S12, inputting into a physical model to simulate and generate an IV curve;

[0034] S23, comparing the IV curve generated by the physical model simulation with the actually measured IV curve, calculating the error between the simulation value and the actual value, and ensuring that the error is within 5%.

[0035] In a preferred embodiment of the present invention, in the step S21, the physical model is: Where, I is the output current; I ph is the photocurrent, which depends on the light intensity; I s is the reverse saturation current, which depends on temperature; V is the output voltage; R s is the series resistance; R p is the parallel resistance; n is the diode ideality factor; N s is the number of battery cells connected in series; V T is the thermal voltage.

[0036] The present invention provides a testing system for a photovoltaic inverter testing method, comprising:

[0037] Data collection module, used to obtain IV curve data of actual photovoltaic panels under different conditions;

[0038] The characteristic extraction module is used to extract the characteristics of the photovoltaic panel based on the IV curve data under different conditions;

[0039] Physical model, used to simulate and generate IV curve of photovoltaic panels;

[0040] The data transmission module is used to transmit the simulated IV curve to the MPPT controller of the inverter.

[0041] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0042] (1) The present invention provides a photovoltaic inverter test system and a test method thereof. Based on the IV curve characteristics of an actual single photovoltaic panel under different conditions, combined with a single IV curve output by a photovoltaic simulator, multiple virtual IV curves are generated by using a physical model simulation, thereby overcoming the limitation that the photovoltaic simulator can only output a single IV curve. Multiple independent IV curves can be simulated simultaneously, thereby being able to more accurately reflect the actual output characteristics of string photovoltaic panels, thereby helping multiple MPPT controllers in the inverter to track the maximum power point of each string separately and achieve global optimization.

[0043] (2) In the present invention, by using the actual measured IV curve data for verification when establishing the physical model, it is ensured that the IV curve generated by the physical model is consistent with the actual photovoltaic panel output characteristics, thereby improving the accuracy of the test and making the test results closer to the actual operating conditions, thereby helping to discover potential problems of the inverter under complex lighting and temperature conditions, and providing a reliable basis for optimizing the performance of the inverter.

[0044] (3) In the present invention, a virtual IV curve is generated by simulating a physical model, thereby avoiding the need to equip each MPPT controller with an independent photovoltaic simulator. This not only significantly reduces the cost of the test equipment, reduces the connection cables, configuration steps and maintenance costs, but also simplifies the test process and improves the efficiency and feasibility of the test. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0046] Figure 1 is a flow chart of a photovoltaic inverter testing method according to a preferred embodiment of the present invention;

[0047] Figure 2 It is a structural diagram of a photovoltaic inverter test system according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0048] 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.

[0049] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0050] Application Overview:

[0051] For string photovoltaic panels, that is, when the inverter is equipped with multiple MPPT controllers, the existing photovoltaic inverter test method has obvious limitations when simulating the structure of string photovoltaic panels, specifically:

[0052] 1. Since photovoltaic simulators can usually only output one IV curve, they cannot simulate multiple independent IV curves at the same time. However, in actual string photovoltaic systems, each photovoltaic panel or each group of photovoltaic panels may exhibit different IV characteristics under complex light and temperature conditions. The multiple MPPT controllers of the inverter need to track the maximum power point (MPP) of each string separately to achieve global optimization. Therefore, a single IV curve cannot accurately reflect the true output characteristics of string photovoltaic panels.

[0053] 2. In the existing test method, since the photovoltaic simulator can only output one IV curve, all MPPT controllers of the inverter will share this curve. As a result, the MPPT controllers cannot independently optimize the working point according to the IV characteristics of each string, thus affecting the accuracy of the test results. In fact, each MPPT controller should be able to work independently according to the IV characteristics of its corresponding string to achieve the best power generation efficiency.

[0054] In view of the obvious limitations of the photovoltaic inverter test method in the prior art when simulating the structure of string photovoltaic panels, the concept of the present invention is based on the IV curve characteristics of an actual single photovoltaic panel under different conditions, combined with a single IV curve output by a photovoltaic simulator, to generate multiple virtual IV curves to simulate the behavior of multiple strings.

[0055] like Figure 1 As shown, a photovoltaic inverter testing method includes the following steps:

[0056] S1. Obtaining IV curve data of actual photovoltaic panels under different conditions, and analyzing the IV curve data to extract characteristics of photovoltaic panels under different conditions;

[0057] S2. Based on the characteristics of photovoltaic panels, a physical model for simulating the IV curve of photovoltaic panels is established, and the accuracy of the IV curve generated by the physical model and the actual output characteristics of photovoltaic panels is verified;

[0058] S3, generating multiple virtual IV curves through physical model simulation according to the characteristics of actual photovoltaic panels under different conditions;

[0059] S4, transmitting the generated multiple virtual IV curves to each MPPT controller of the inverter, starting the inverter, and the MPPT controller performs maximum power point tracking according to the received virtual IV curve to perform a performance test of the inverter.

[0060] It should be noted that the present invention is based on the IV curve characteristics of an actual single photovoltaic panel under different conditions, combined with a single IV curve output by a photovoltaic simulator, and utilizes a physical model to simulate and generate multiple virtual IV curves, thereby overcoming the limitation that the photovoltaic simulator can only output a single IV curve. It can simulate multiple independent IV curves at the same time, and thus can more accurately reflect the true output characteristics of string photovoltaic panels, thereby helping multiple MPPT controllers in the inverter to track the maximum power point of each string separately to achieve global optimization.

[0061] In some specific embodiments, the step of S1 includes the following sub-steps:

[0062] S11. Use a set of actual photovoltaic panels and set different usage conditions, including the light intensity, temperature, partial shading and sudden changes in light intensity.

[0063] S12. Record the IV curve data of the actual photovoltaic panel under different conditions; including the open circuit voltage, short circuit current, maximum power point voltage, maximum power point current, maximum power, light intensity and temperature involved;

[0064] S13. Perform impact analysis on the recorded IV curve data under different conditions to extract the characteristics of the photovoltaic panel under different conditions.

[0065] In this embodiment, in step S11, the setting of light intensity includes standard test conditions (STC, 1000W / m2), low light (500W / m2), and high light (1200W / m2); the setting of temperature includes standard temperature (25°C), high temperature (50°C), and low temperature (-10°C); the setting of partial shading partially blocks some photovoltaic panels in a group to simulate partial shading, such as blocking 50% or 75% of the area; the setting of sudden light change, such as suddenly reducing the light intensity from 1000W / m2 to 300W / m2, is used to simulate cloud shading.

[0066] In this embodiment, in step S12, IV curve data is recorded by a power quality analyzer and a power analyzer; open circuit voltage: represents the voltage of the photovoltaic panel when there is no load; short circuit current: represents the current of the photovoltaic panel when there is a short circuit; maximum power point voltage: represents the voltage when the output power of the photovoltaic panel is maximum; maximum power point current: represents the current when the output power of the photovoltaic panel is maximum; maximum power: represents the maximum output power of the photovoltaic panel; light intensity: represents the light intensity recorded for each test; temperature: represents the temperature recorded for each test.

[0067] In this embodiment, in step S13, the analysis of the influence of light intensity includes: the influence of light intensity on photogenerated current; the analysis of the influence of temperature includes: the influence of temperature on reverse saturation current and open circuit voltage; the analysis of the influence of partial shading includes: the influence of partial shading on photogenerated current; the analysis of the influence of sudden changes in illumination includes: the influence of sudden changes in illumination on the dynamic changes of IV curves and the rapid changes of maximum power points.

[0068] Furthermore, the photocurrent depends on the light intensity. The photocurrent is linearly related to the light intensity. The adjustment of the effect of light intensity on the photocurrent is: Among them, I ph is the photocurrent, I ph,0 is the photocurrent under standard test conditions (STC, 1000W / m2); G is the current light intensity; G STC is the light intensity under standard test conditions.

[0069] It should be noted that, since the influence of light intensity on the open circuit voltage Voc is small and can be ignored, the open circuit voltage Voc can remain unchanged when the light intensity changes.

[0070] Furthermore, as the temperature increases, the reverse saturation current will increase significantly. The adjustment of the effect of temperature on the reverse saturation current is: in,

[0071] I s (T STC ) is the reverse saturation current under standard test conditions (STC, 25°C); T is the current temperature (in K, i.e., absolute temperature); T STC is the temperature under standard test conditions (25°C, i.e. 298.15K); E g is the band gap energy of the photovoltaic material (typically 1.1 eV for silicon photovoltaic panels); k is the Boltzmann constant;

[0072] As the temperature increases, the open circuit voltage will drop significantly. The adjustment of the temperature effect on the open circuit voltage is:

[0073] Voc(T)=Voc(T STC)-α(TT STC ); where Voc(T STC ) is the open circuit voltage under standard test conditions (STC, 25°C); T is the current temperature (in K, i.e., absolute temperature); T STC is the temperature under standard test conditions (25°C, i.e. 298.15K); α is the temperature coefficient of open circuit voltage (usually 2mV / °C for silicon photovoltaic panels).

[0074] Furthermore, partial shading will cause some areas of the photovoltaic panel to be unable to receive light, reducing the overall photocurrent. The adjustment of the effect of partial shading on the photocurrent is: I ph =I ph,0 ×P; where I ph,0 is the photocurrent under standard test conditions (STC, 1000W / m2); P is the shading ratio, 0 means complete shading, 1 means no shading at all, for example, 0.5 means 50% of the area is shaded.

[0075] It should be noted that, since the influence of partial shielding on the open circuit voltage Voc is small and can be ignored, the open circuit voltage Voc can remain unchanged in the case of partial shielding.

[0076] Furthermore, in the case of sudden changes in light intensity, the output characteristics of the photovoltaic panel will change instantaneously. The MPPT controller of the inverter needs to respond quickly to find a new maximum power point. The evaluation of the dynamic response capability of the IV curve to sudden changes in light intensity includes the following steps:

[0077] A1. Set the initial light intensity G 1 , generate the corresponding IV curve;

[0078] A2. At a certain time point t0, the light intensity is suddenly changed from G 1 Change to the new light intensity G 2 ;

[0079] A3. According to the light intensity G 2 , recalculate the photocurrent I ph , and generate a new IV curve;

[0080] A4. During the change of light intensity, simulate the dynamic process of sudden change of light intensity and gradually adjust the photocurrent I ph , generating a series of intermediate state IV curves.

[0081] It should be noted that, in step A4, the IV curve in the intermediate state is realized by interpolation method to ensure that the change of the IV curve is continuous.

[0082] Interpolation example:

[0083] Assume that the light intensity is 1000W / m 2 Decrease linearly to 300W / m in 1 second 2 , 1 second can be divided into multiple time steps (for example, 10 steps), each step corresponds to an intermediate light intensity G i ; For each intermediate light intensity G i , calculate the corresponding photocurrent I ph,i , and input the physical model to generate the corresponding IV curve; the IV curve in the intermediate state is transmitted to the inverter to simulate the dynamic process of sudden change in illumination.

[0084] Sudden changes in illumination will cause the maximum power point to move rapidly. The MPPT controller of the inverter needs to quickly track the new maximum power point. The response speed evaluation of sudden changes in illumination to the rapid change of the maximum power point includes the following steps:

[0085] B1. Before the sudden change of light intensity, record the maximum power point voltage V of the inverter. mp and current I mp ;

[0086] B2. According to the simulation steps of the dynamic response of the IV curve to the sudden change of illumination, a sudden change of illumination is introduced to generate the IV curve after the sudden change;

[0087] B3. After the sudden change of light intensity, record the maximum power point voltage V of the inverter. mp and current I mp ;

[0088] B4. The time from the sudden change of light intensity to the time when the inverter finds the new maximum power point again is the response time of the inverter.

[0089] In some specific embodiments, the step of S2 includes the following sub-steps:

[0090] S21. Based on the characteristics of photovoltaic panels, a physical model capable of simulating the IV characteristics of photovoltaic panels is established;

[0091] S22, using the IV curve data recorded in step S12, inputting into the physical model to simulate and generate an IV curve;

[0092] S23, comparing the IV curve generated by the physical model simulation with the actually measured IV curve, calculating the error between the simulation value and the actual value, and ensuring that the error is within 5%.

[0093] It should be noted that the present invention uses actual measured IV curve data for verification when establishing the physical model, thereby ensuring that the IV curve generated by the physical model is consistent with the actual photovoltaic panel output characteristics, thereby improving the accuracy of the test and making the test results closer to the actual operating conditions, thereby helping to discover potential problems of the inverter under complex lighting and temperature conditions, and providing a reliable basis for optimizing the performance of the inverter.

[0094] In this embodiment, in step S21, the physical model is:

[0095] Where, I is the output current; I ph is the photocurrent, which depends on the light intensity; I s is the reverse saturation current, which depends on temperature; V is the output voltage; R s is the series resistance; R p is the parallel resistance; n is the diode ideality factor; N s is the number of battery cells connected in series; V T is the thermal voltage.

[0096] It should be noted that the thermal voltage Where k is the Boltzmann constant; T is the absolute temperature; and q is the electron charge.

[0097] In some specific embodiments, in step S3, the photocurrent I under different light intensities G ph , obtained by analyzing the influence of light intensity in step S13, and the obtained photocurrent I ph Input the physical model to generate the IV curve under the corresponding light intensity;

[0098] Reverse saturation current I at different temperatures T s (T) and open circuit voltage Voc ( T ) , obtained by analyzing the influence of temperature in step S13, the reverse saturation current I s (T) and open circuit voltage Voc ( T ) Input the physical model respectively to generate IV curve at corresponding temperature;

[0099] Photocurrent I under different partial shading ratios P ph , obtained by analyzing the influence of partial shading in step S13, and the obtained photocurrent I ph Input the physical model and generate the IV curve under the corresponding occlusion ratio;

[0100] The IV curve of the intermediate state under the sudden change of illumination is obtained by analyzing the influence of the sudden change of illumination on the dynamic change of the IV curve in step S13.

[0101] It should be noted that the present invention generates a virtual IV curve through physical model simulation, avoiding the need to equip each MPPT controller with an independent photovoltaic simulator. It not only significantly reduces the cost of test equipment, reduces connection cables, configuration steps and maintenance costs, but also simplifies the test process and improves the efficiency and feasibility of the test.

[0102] In some specific embodiments, the step of S4 includes the following sub-steps:

[0103] S41. According to the requirements of the inverter, the baud rate and data format parameters of the communication protocol are set, and the generated virtual IV curve is transmitted to the corresponding MPPT controller of the inverter through the communication interface;

[0104] S42, starting the inverter, and the MPPT controller performs maximum power point tracking according to the received virtual IV curve, and monitors the input voltage, current and output power of the inverter in real time;

[0105] S43. Record the input voltage, current and output power of the inverter in real time, and ensure that the recorded data includes the MPPT performance indicators under different light and temperature conditions.

[0106] In this embodiment, in step S42, the input voltage, current and output power of the inverter are monitored by a power quality analyzer and a power analyzer.

[0107] In this embodiment, in step S43, the MPPT performance indicators include: MPPT efficiency, which is used to measure the maximum power point tracking accuracy of the inverter under different lighting and temperature conditions; response speed, which is used to measure the time required for the inverter to recover from a non-optimal operating point to the maximum power point when the light changes suddenly; recovery time, which is used to measure the time required for the inverter to find the maximum power point again after partial shading is released.

[0108] like Figure 2 As shown, a testing system for a photovoltaic inverter testing method includes:

[0109] Data collection module, used to obtain IV curve data of actual photovoltaic panels under different conditions;

[0110] The characteristic extraction module is used to extract the characteristics of the photovoltaic panel based on the IV curve data under different conditions;

[0111] Physical model, used to simulate and generate IV curve of photovoltaic panels;

[0112] The data transmission module is used to transmit the simulated IV curve to the MPPT controller of the inverter.

[0113] It should be noted that the photovoltaic inverter testing system can implement the steps in the photovoltaic inverter testing method in the above embodiment and can achieve the same technical effects. Please refer to the description in the above embodiment and no detailed description will be given here.

[0114] The above is based on the ideal embodiment of the present invention. Through the above description, it is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is limited by the attached claims rather than the above description, and it is intended to include all changes within the meaning and scope of the equivalent elements of the claims. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0115] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A photovoltaic inverter testing method, characterized in that: The following steps are involved: S1. Obtaining IV curve data of actual photovoltaic panels under different conditions, and analyzing the IV curve data to extract characteristics of photovoltaic panels under different conditions; S2. Based on the characteristics of photovoltaic panels, a physical model for simulating the IV curve of photovoltaic panels is established, and the accuracy of the IV curve generated by the physical model and the actual output characteristics of photovoltaic panels is verified; S3, generating multiple virtual IV curves through physical model simulation according to the characteristics of actual photovoltaic panels under different conditions; S4, transmitting the generated multiple virtual IV curves to each MPPT controller of the inverter, starting the inverter, and the MPPT controller performs maximum power point tracking according to the received virtual IV curve to perform a performance test of the inverter.

2. A photovoltaic inverter testing method according to claim 1, characterized in that: The step S1 includes the following sub-steps: S11. Use a set of actual photovoltaic panels and set different usage conditions, including the light intensity, temperature, partial shading and sudden changes in light intensity. S12. Record the IV curve data of the actual photovoltaic panel under different conditions; including the open circuit voltage, short circuit current, maximum power point voltage, maximum power point current, maximum power, light intensity and temperature involved; S13. Perform impact analysis on the recorded IV curve data under different conditions to extract the characteristics of the photovoltaic panel under different conditions.

3. A photovoltaic inverter testing method according to claim 2, characterized in that: In the step S13, the analysis of the impact of light intensity includes: the impact of light intensity on photogenerated current; the analysis of the impact of temperature includes: the impact of temperature on reverse saturation current and open circuit voltage; the analysis of the impact of partial shading includes: the impact of partial shading on photogenerated current; the analysis of the impact of sudden changes in illumination includes: the impact of sudden changes in illumination on the dynamic changes of IV curves and the rapid changes of maximum power points.

4. A photovoltaic inverter testing method according to claim 3, characterized in that: Adjustment of the effect of light intensity on photogenerated current: Among them, I ph is the photocurrent, I ph,0 is the photocurrent under standard test conditions; G is the current light intensity; G STC is the light intensity under standard test conditions.

5. A photovoltaic inverter testing method according to claim 3, characterized in that: Adjustment of the effect of temperature on reverse saturation current: Among them, I s (T STC ) is the reverse saturation current under standard test conditions; T is the current temperature; T STC is the temperature under standard test conditions; E g is the band gap energy of the photovoltaic material; k is the Boltzmann constant; Adjustment of the effect of temperature on open circuit voltage: Voc(T)=Voc(T STC )-α(TT STC ); where Voc(T STC ) is the open circuit voltage under standard test conditions; T is the current temperature; T STC is the temperature under standard test conditions; α is the temperature coefficient of open circuit voltage.

6. A photovoltaic inverter testing method according to claim 3, characterized in that: Adjustment of the effect of partial shading on photocurrent: I ph =I ph,0 ×P; where I ph,0 is the photocurrent under standard test conditions; P is the shading ratio, 0 means complete shading, and 1 means no shading.

7. A photovoltaic inverter testing method according to claim 3, characterized in that: The evaluation of the dynamic response capability of the IV curve to the sudden change of illumination comprises the following steps: A1, set the initial light intensity G1 and generate the corresponding IV curve; A2, at a certain time point t0, suddenly change the light intensity from G1 to the new light intensity G2; A3. Recalculate the photocurrent I according to the light intensity G2 ph , and generate a new IV curve; A4. During the change of light intensity, simulate the dynamic process of sudden change of light intensity and gradually adjust the photocurrent I ph , generate a series of intermediate state IV curves; The response speed evaluation of the sudden change of illumination to the rapid change of the maximum power point comprises the following steps: B1. Before the sudden change of light intensity, record the maximum power point voltage V of the inverter. mp and current I mp ; B2. According to the simulation steps of the dynamic response of the IV curve to the sudden change of illumination, a sudden change of illumination is introduced to generate the IV curve after the sudden change; B3. After the sudden change of light intensity, record the maximum power point voltage V of the inverter. mp and current I mp ; B4. The time from the sudden change of light intensity to the time when the inverter finds the new maximum power point again is the response time of the inverter.

8. A photovoltaic inverter testing method according to claim 2, characterized in that: The step S2 includes the following sub-steps: S21. Based on the characteristics of photovoltaic panels, a physical model capable of simulating the IV characteristics of photovoltaic panels is established; S22, using the IV curve data recorded in step S12, inputting into a physical model to simulate and generate an IV curve; S23, comparing the IV curve generated by the physical model simulation with the actually measured IV curve, calculating the error between the simulation value and the actual value, and ensuring that the error is within 5%.

9. A photovoltaic inverter testing method according to claim 8, characterized in that: In the step S21, the physical model is: Where, I is the output current; I ph is the photocurrent, which depends on the light intensity; I s is the reverse saturation current, which depends on temperature; V is the output voltage; R s is the series resistance; R p is the parallel resistance; n is the diode ideality factor; N s is the number of battery cells connected in series; V T is the thermal voltage.

10. A test system for a photovoltaic inverter test method according to any one of claims 1 to 9, characterized in that: include: Data collection module, used to obtain IV curve data of actual photovoltaic panels under different conditions; The characteristic extraction module is used to extract the characteristics of the photovoltaic panel based on the IV curve data under different conditions; Physical model, used to simulate and generate IV curve of photovoltaic panels; The data transmission module is used to transmit the simulated IV curve to the MPPT controller of the inverter.

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