Photovoltaic i-v curve testing system, testing method and photovoltaic device

Abstract

The application is suitable for the photovoltaic technical field, and provides a photovoltaic I-V curve testing system, a testing method and photovoltaic equipment.The photovoltaic I-V curve testing system comprises a photovoltaic module, a current collecting device, an inverter, an adjustable load, a detection unit and a control unit.By controlling the inverter to be in an off-grid state during testing, adjusting the inverter to be in a voltage source mode, connecting the adjustable load, adjusting the working voltage of the inverter to vary in the range from 0 to a rated voltage, and obtaining the voltage and current of each photovoltaic module string, the photovoltaic I-V curve under the full voltage can be obtained, and whether the photovoltaic module has a fault or current mismatching problem can be accurately judged according to the photovoltaic curve.Compared with the existing photovoltaic I-V curve testing device, the photovoltaic I-V testing system of the embodiment can test the photovoltaic I-V curve in the full voltage range, so that the operation state of the photovoltaic module can be accurately monitored and fine management can be performed.

Description

Technical Field

[0001] The present invention belongs to the field of photovoltaic technology, and in particular relates to a photovoltaic IV curve testing system, a testing method and photovoltaic equipment. Background Art

[0002] As the installed capacity of photovoltaic power generation systems continues to expand, ensuring their efficient and reliable operation has become a goal pursued by the entire industry. Because photovoltaic systems are installed outdoors and continuously exposed to relatively harsh environments, monitoring their operating status is particularly important. Using the photovoltaic IV curve to determine the operating status of a photovoltaic system is a widely used method.

[0003] In existing photovoltaic systems, string inverters, due to their bipolar conversion structure, have a relatively wide range of IV curve detection. However, due to the DC-DC boost range, they still cannot detect IV curves across the entire voltage range. Centralized and distributed inverters, lacking a DC-DC boost mechanism, further restrict their IV curve detection range, theoretically only able to detect IV curves above the power-on voltage. IV curve detection within these two specific voltage ranges is highly detrimental to system status monitoring and refined management. Summary of the Invention

[0004] The embodiment of the present invention provides a photovoltaic IV curve testing system, which aims to solve the problem that the existing system cannot detect the IV curve within the full voltage range, thereby failing to accurately monitor the operating status of the photovoltaic system and failing to quickly identify current mismatch faults in the photovoltaic system.

[0005] The embodiment of the present invention is implemented as follows: a photovoltaic IV curve test system is provided, which includes: a photovoltaic component, composed of a plurality of photovoltaic strings; a confluence device, connected to the photovoltaic component, for converging a plurality of photovoltaic strings; an inverter, connected to the confluence device; an adjustable load, provided in the inverter, for connecting to the inverter when the inverter is in an off-grid state; a detection unit, provided in the confluence device, connected to each photovoltaic string, for detecting the current and voltage of each photovoltaic string; a control unit, the control unit being connected to the confluence device, the inverter, and the adjustable load The control unit is connected to the inverter and the adjustable load, and the control unit is used to send a control signal to the inverter and the adjustable load during testing; it is used to receive data from the detection unit within the inverter voltage adjustment range of the inverter, and obtain a photovoltaic IV curve within the full voltage range based on the data of the detection unit; the adjustable load is used to connect to the inverter according to the control signal; the inverter is used to control the inverter to be in an off-grid state and adjust the inverter to a voltage source mode according to the control signal; and adjust the inverter voltage of the inverter so that the inverter voltage varies within the range of 0 to the rated voltage.

[0006] Furthermore, it also includes a transformer connected to the inverter, and the low-voltage side of the transformer is connected to the inverter.

[0007] Furthermore, a first switch connected to the low-voltage side of the transformer is provided inside the inverter, which is used to be disconnected when measuring the photovoltaic IV curve to put the inverter in an off-grid state.

[0008] Furthermore, a second switch is provided between the adjustable load and the inverter, for closing when the inverter is in an off-grid state.

[0009] Furthermore, it also includes a power grid connected to the transformer, the high voltage side of the transformer is connected to the power grid, and the power grid is connected to the control unit.

[0010] Furthermore, the inverter is of centralized, distributed or string type.

[0011] An embodiment of the present invention further provides a photovoltaic IV curve testing method, which includes the following steps:

[0012] Controlling the inverter to be in an off-grid state, adjusting the inverter to a voltage source mode, and connecting an adjustable load to the inverter;

[0013] Adjust the inverter operating voltage so that it varies between 0 and rated voltage;

[0014] Obtain the voltage and current of each PV string when the inverter operating voltage varies from 0 to the rated voltage;

[0015] The photovoltaic IV curve is obtained according to the voltage and current of each photovoltaic string.

[0016] Furthermore, controlling the inverter to be in an off-grid state and accessing an adjustable load includes:

[0017] When the inverter is in an off-grid state, obtaining the opening voltage of the photovoltaic module;

[0018] The adjustable load is adjusted to adapt to the opening voltage.

[0019] Furthermore, after the step of obtaining a photovoltaic curve according to the voltage and current of each photovoltaic string, the step further includes:

[0020] Analyze the photovoltaic curve to determine whether the photovoltaic module has a fault.

[0021] An embodiment of the present invention further provides a photovoltaic device, comprising the above-mentioned photovoltaic IV curve testing system and a processor, wherein the processor can run the above-mentioned photovoltaic IV curve testing method.

[0022] The photovoltaic IV curve testing system of the embodiment of the present invention includes: a photovoltaic component, which is composed of a plurality of photovoltaic strings; a confluence device, which is connected to the photovoltaic component and is used to converge the plurality of photovoltaic strings; an inverter, which is connected to the confluence device; an adjustable load, which is provided in the inverter and is used to connect to the inverter when the inverter is in an off-grid state; a detection unit, which is provided in the confluence device and is connected to each photovoltaic string and is used to detect the current and voltage of each photovoltaic string; a control unit, which is connected to the confluence device, the inverter, the adjustable load and the detection unit, and is used to send a control signal to the inverter and the adjustable load during testing; the control unit is used to receive data from the detection unit within the inverter voltage adjustment range of the inverter, and obtain a photovoltaic IV curve within the full voltage range based on the data from the detection unit; the adjustable load is used to connect to the inverter according to the control signal; the inverter is used to control the inverter to be in an off-grid state according to the control signal and adjust the inverter to a voltage source mode; the inverter voltage is adjusted so that the inverter voltage is between 0 The test system of the present invention connects an adjustable load to the inverter when it is off-grid, then adjusts the inverter's operating voltage so that it fluctuates between 0 and the rated voltage. The system then obtains the voltage and current of each photovoltaic string to obtain a photovoltaic IV curve at full voltage. This photovoltaic IV curve can accurately determine whether a photovoltaic module has a fault or current mismatch. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 2 is a schematic structural diagram of a photovoltaic IV curve test system according to an embodiment of the present invention;

[0024] Figure 2 2. This is a schematic diagram of the corresponding relationship between the test points of the photovoltaic IV curve according to an embodiment of the present invention;

[0025] Figure 3 is a schematic diagram of a photovoltaic IV curve of a photovoltaic string according to an embodiment of the present invention;

[0026] Figure 4 Schematic diagram of photovoltaic IV curves of multiple photovoltaic strings according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] In the present invention, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," "fixed," and the like should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances. The term "and / or" as used herein includes any and all combinations of one or more of the relevant listed items.

[0029] The present invention provides a photovoltaic IV curve testing system. When the inverter is off-grid, it is set to voltage source mode and connected to an adjustable load. The inverter's operating voltage is then adjusted to fluctuate between 0 and the rated voltage. The voltage and current of each photovoltaic string are then measured when the inverter voltage fluctuates between 0 and the rated voltage. This yields a photovoltaic IV curve at full voltage. This photovoltaic IV curve accurately determines whether a photovoltaic module has faults or current mismatches. This testing system enables precise monitoring of the operating status of photovoltaic modules and enables refined management.

[0030] Example 1

[0031] like Figure 1 As shown, this embodiment provides a photovoltaic IV curve test system, which includes: a photovoltaic module, consisting of a plurality of photovoltaic strings; a confluence device, connected to the photovoltaic module, for converging the plurality of photovoltaic strings; an inverter, connected to the confluence device; an adjustable load, provided in the inverter, for connecting to the inverter when the inverter is in an off-grid state; a detection unit, provided in the confluence device, connected to each photovoltaic string, for detecting the current and voltage of each photovoltaic string; a control unit, connected to the confluence device, the inverter, the adjustable load and the detection unit The control unit is used to send a control signal to the inverter and the adjustable load during testing; it is used to receive data from the detection unit within the inverter voltage adjustment range of the inverter, and obtain a photovoltaic IV curve within the full voltage range based on the data from the detection unit; the adjustable load is used to connect to the inverter according to the control signal; the inverter is used to control the inverter to be in an off-grid state and adjust the inverter to a voltage source mode according to the control signal; and the inverter voltage of the inverter is adjusted so that the inverter voltage varies within the range of 0 to the rated voltage.

[0032] In this embodiment, the detection units are current sensors and voltage sensors connected to each photovoltaic string to measure the voltage and current of each photovoltaic string. The test system includes multiple busbars; multiple photovoltaic strings are combined in a busbar, and each inverter corresponds to multiple busbars.

[0033] During photovoltaic power generation, the inverter is grid-connected only when the voltage of the PV modules reaches the inverter's minimum startup voltage. Therefore, the full-voltage photovoltaic IV curve of the PV modules cannot be detected in this grid-connected state. During testing, the photovoltaic IV curve testing system of the present invention controls the inverter to be in an off-grid state, switching from current source mode to voltage source mode.

[0034] Specifically, when the inverter is off-grid, the PV panel's opening voltage is obtained. At this time, the inverter has no adjustable load connected. The opening voltage is the maximum voltage of the PV panel. The adjustable load is adjusted to match the opening voltage based on the obtained PV panel's opening voltage, and then connected to the inverter to ensure that the inverter's inverter voltage remains within the range of 0 to the rated voltage.

[0035] Furthermore, the test system further includes a transformer T1 connected to the inverter, and a low-voltage side of the transformer T1 is connected to the inverter.

[0036] In this embodiment, the inverter is equipped with a first switch Q1 connected to the low-voltage side of transformer T1. This switch is disconnected during the measurement of the photovoltaic IV curve, placing the inverter in an off-grid state. After the test is complete, the first switch Q1 is closed, placing the inverter in a grid-connected state.

[0037] Furthermore, a second switch Q2 is provided between the adjustable load and the inverter, for closing when the inverter is in an off-grid state.

[0038] In this embodiment, when testing the photovoltaic IV curve, the second switch Q2 is closed, connecting the adjustable load to the inverter. Before connecting the inverter, the load to be connected must be determined. The adjustable load connected to the inverter is adjusted based on the opening voltage of the photovoltaic module.

[0039] Specifically, the adjustable load is an adjustable electronic load. When the inverter is off-grid, the second switch Q2 is closed, and the opening voltage of the photovoltaic module is obtained at this time. The opening voltage at this time is the maximum opening voltage of the photovoltaic module. The control unit calculates the optimal load based on the maximum opening voltage. The adjustable electronic load includes a first control module, which receives a control signal from the control unit. The first control module adjusts the adjustable electronic load to the optimal load position according to the control signal, and then closes the second switch Q2 to connect the adjusted optimal load to the inverter. The above-mentioned optimal load ensures that the inverter voltage of the inverter can be adjusted to 0 volts. If the load is less than the calculated optimal load, the adjustment range of the inverter voltage will not reach 0. This affects the adjustment range of the inverter voltage, and further affects the range of the opening voltage of the photovoltaic module, so that the photovoltaic IV curve within the full voltage range cannot be obtained.

[0040] Furthermore, the test system also includes a power grid connected to the transformer T1 , the high voltage side of the transformer T1 is connected to the power grid, and the power grid is connected to the control unit.

[0041] In this embodiment, the second control module at the grid end is connected to the control unit. The second control module obtains the photovoltaic IV curve obtained by the control unit, and monitors the operating status of the photovoltaic component according to the photovoltaic IV curve, and further determines whether there is an abnormality in the photovoltaic component or whether there is a current mismatch.

[0042] In another embodiment, the control unit can be located at the grid end, and the detection unit can be connected to the grid end to transmit detection data to the control unit located at the grid end. Specifically, the control unit can be located at the grid end, and both the busbar assembly and the inverter can be connected to the grid end. A test signal is sent by the control unit at the grid end, which controls the first switch Q1 to open and the second switch Q2 to close, thereby controlling the inverter to adjust the inverter voltage so that it varies between 0 and the rated voltage, thereby obtaining a photovoltaic IV curve over the full voltage range.

[0043] It is understandable that, in other embodiments, the control unit may be provided at the inverter end, and the detection unit directly transmits the detection data to the inverter.

[0044] Furthermore, the inverter includes an inverter bridge, control logic and a filter circuit. The control logic includes a controller, which is connected to the control unit and is used to control the inverter to adjust the inverter voltage.

[0045] In this embodiment, the control unit can be integrated into the controller of the inverter, and in the off-grid state, adjust the inverter to the voltage source mode, adjust the adjustable load, and connect it to the inverter; control the inverter to adjust the inverter voltage so that the inverter voltage varies within the range of 0 to the rated voltage; receive data from the detection unit within the inverter voltage adjustment range, and obtain the photovoltaic IV curve within the full voltage range based on the data of the detection unit.

[0046] Furthermore, the control unit and the detection unit are connected via an RS485 communication interface or via an optical fiber.

[0047] In this embodiment, the control unit and the detection unit are connected via an RS485 communication interface located on the converging device and the inverter. In other embodiments, they can also be connected via optical fiber, which is not specifically limited in this embodiment.

[0048] Reference Figure 2 In this embodiment, the rated voltage of the inverter voltage is U0, the maximum power of the adjustable load is P0, and the opening voltage of the photovoltaic string is V CS During the inverter voltage change process, the lowest value of the inverter voltage is 0.01% U0, which is infinitely close to 0. It can be determined that the lowest value of the inverter voltage adjustment range is 0. At this time, the photovoltaic string current reaches the maximum value of I CS The inverter voltage adjustment range can be determined from 0 to U0, and the specific adjustment ratio can be set as needed. For example, it can be increased in 1% increments until U0 is reached. Alternatively, it can be increased in 0.01% increments until U0 is reached. Testing is performed based on the rate of change of the adjusted voltage to obtain the voltage and current of each PV string.

[0049] Specifically, during the inverter voltage adjustment process from low to high, the initial minimum value is 0.01% U0, making it infinitely close to 0, while the current of the photovoltaic string is the maximum I CS When the load is fixed, the load current decreases as the inverter voltage increases. When the solar irradiance is stable, the voltage of the photovoltaic string will increase as the inverter voltage increases, while the current of the photovoltaic string will gradually decrease. When the inverter voltage rises to the rated voltage U0, and the working voltage of the photovoltaic string also reaches the maximum opening voltage V CS At this time, the IV curve point test of the full voltage range is completed.

[0050] It can be understood that in this embodiment, the change trend of the inverter voltage can be adjusted from the highest value to the lowest value. In the process of adjusting the inverter voltage from high to low, the highest value is U0, at which time the opening voltage of the photovoltaic string is the maximum V CS, at this time the current of the photovoltaic string is 0. When the load is fixed, the load current increases as the inverter voltage decreases. When the solar irradiance is stable, the voltage of the photovoltaic string will decrease as the inverter voltage decreases, and the current of the photovoltaic string will gradually increase. When the inverter voltage drops to 0.01% U0, the inverter voltage is infinitely close to 0, and the current of the photovoltaic string reaches its maximum value of I CS At this time, the IV curve point test of the full voltage range is completed. At this time, the relationship between the voltage and current corresponding to the test point is as follows Figure 2 shown.

[0051] Reference Figure 3 and Figure 4 In this embodiment, according to Figure 2 The corresponding relationship diagram can be used to draw a schematic diagram of the photovoltaic IV curve. The photovoltaic IV curve corresponding to each photovoltaic string is as follows Figure 3 The photovoltaic IV curves of multiple photovoltaic strings can also be obtained, such as Figure 4 shown.

[0052] Reference Figure 4 In actual use, the photovoltaic IV curve is affected by the opening voltage, irradiance, temperature, temperature or actual internal damage. Figure 4 Curves a and b in the figure represent normal operation, each with a single knee bend. Curve c, however, has multiple knee bends, indicating that curve c is abnormal. This indicates that the PV string corresponding to curve c is abnormal.

[0053] Generally, slight deviations in the open-circuit voltage and short-circuit current of a PV module are affected by factors such as irradiance and temperature. However, excessively low open-circuit voltage and short-circuit current, as seen in the D curve, or the C curve with multiple knee bends, indicate a PV module problem. Therefore, analyzing the PV IV curve can help diagnose PV string anomalies and their causes.

[0054] Furthermore, the inverter includes but is not limited to a centralized inverter, a distributed inverter, and a string inverter. The photovoltaic IV curve test system of this embodiment is applicable to various types of inverters and can test photovoltaic IV curves of various inverter types.

[0055] Furthermore, the voltage of the photovoltaic module includes photovoltaic systems of various voltage levels, for example: photovoltaic systems applicable to 1000V, 1500V, 2000V, 3000V and higher voltage levels.

[0056] The photovoltaic IV test system of this embodiment is suitable for photovoltaic modules of large, medium and small voltage levels, and can test the photovoltaic IV curves of photovoltaic modules of various voltage levels. Therefore, the operating status of photovoltaic modules of various voltage levels can be monitored and finely managed.

[0057] The photovoltaic IV curve testing system of this embodiment operates by controlling the inverter in an off-grid state during testing, adjusting the inverter to voltage source mode, connecting an adjustable load, and then adjusting the inverter's operating voltage to vary between 0 and the rated voltage. The system then obtains the voltage and current of each photovoltaic string as the inverter voltage varies between 0 and the rated voltage, thereby generating a photovoltaic IV curve at full voltage. This photovoltaic curve can accurately determine whether a photovoltaic module has faults or current mismatches. Compared to existing photovoltaic IV curves, the photovoltaic IV test system of this embodiment can test photovoltaic IV curves across the full voltage range, enabling precise monitoring and refined management of the operating status of photovoltaic modules.

[0058] Example 2

[0059] This embodiment provides a method for testing a photovoltaic IV curve, which includes the following steps:

[0060] Control the inverter to be in an off-grid state, adjust the inverter to the voltage source mode, and connect the adjustable load to the inverter;

[0061] Adjust the inverter operating voltage so that it varies between 0 and rated voltage;

[0062] Obtain the voltage and current of each PV string when the inverter operating voltage varies from 0 to the rated voltage;

[0063] The photovoltaic IV curve is obtained according to the voltage and current of each photovoltaic string.

[0064] In this embodiment, after receiving the test signal, the control unit opens the first switch Q1 between the inverter and transformer T1, controlling the inverter to be in an off-grid state and switching the inverter from current source mode to voltage source mode. The control unit then closes the switch between the adjustable load and the inverter, connecting the adjustable load to the inverter to adjust the inverter's inverter voltage so that the inverter voltage can vary between 0 and the rated voltage. The control unit then receives the voltage and current of each PV module string when the inverter voltage varies between 0 and the rated voltage, and generates a photovoltaic curve based on the voltage and current of each PV string.

[0065] Furthermore, controlling the inverter to be in an off-grid state and connecting to an adjustable load also includes:

[0066] When the inverter is in off-grid state, obtain the opening voltage of the photovoltaic module;

[0067] Adjust the adjustable load to match the opening voltage.

[0068] In this embodiment, the PV panel's opening voltage is obtained when the inverter is off-grid. At this time, the inverter is not connected to an adjustable load. The opening voltage at this time is the maximum voltage of the PV panel. The adjustable load is adjusted based on the obtained PV panel's opening voltage to match the opening voltage, and then connected to the inverter to ensure that the inverter's inverter voltage can be adjusted within the range of 0 to the rated voltage. If the load is too low, the minimum value of the inverter voltage will not reach 0, and the PV curve within the full voltage range cannot be obtained.

[0069] In this embodiment, the rated voltage of the inverter voltage is U0, the maximum power of the adjustable load is P0, and the opening voltage of the photovoltaic string is V CS During the inverter voltage change process, the minimum value of the inverter voltage is 0.01% U0, which is infinitely close to 0. It can be determined that the minimum value of the inverter voltage adjustment range is 0. At this time, the photovoltaic string current reaches the maximum value of I CS The inverter voltage can be adjusted from 0 to U0, and the specific adjustment ratio can be set as needed. For example, it can be increased in 1% increments until it reaches U0. Alternatively, it can be increased in 0.01% increments until it reaches U0. The voltage and current of each PV string are determined based on the rate of change of the inverter voltage.

[0070] Specifically, during the inverter voltage adjustment process from low to high, the initial minimum value is 0.01% U0, making it infinitely close to 0, while the current of the photovoltaic string is the maximum I CS When the load is fixed, the load current decreases as the inverter voltage increases. When the solar irradiance is stable, the voltage of the photovoltaic string will increase as the inverter voltage increases, while the current of the photovoltaic string will gradually decrease. When the inverter voltage rises to the rated voltage U0, and the working voltage of the photovoltaic string also reaches the maximum opening voltage V CS At this time, the IV curve point test of the full voltage range is completed.

[0071] It can be understood that in this embodiment, the change trend of the inverter voltage can be adjusted from the highest value to the lowest value. In the process of adjusting the inverter voltage from high to low, the highest value is U0, at which time the opening voltage of the photovoltaic string is the maximum V CS , at this time the current of the photovoltaic string is 0. When the load is fixed, the load current increases as the inverter voltage decreases. When the solar irradiance is stable, the voltage of the photovoltaic string will decrease as the inverter voltage decreases, and the current of the photovoltaic string will gradually increase. When the inverter voltage drops to 0.01% U0, the inverter voltage is infinitely close to 0, and the current of the photovoltaic string reaches its maximum value of ICS At this time, the IV curve point test of the full voltage range is completed. At this time, the relationship between the voltage and current corresponding to the test point is as follows Figure 2 shown.

[0072] Reference Figure 3 and Figure 4 In this embodiment, according to Figure 2 The corresponding relationship diagram can be used to draw a schematic diagram of the photovoltaic IV curve. The photovoltaic IV curve corresponding to each photovoltaic string is as follows Figure 3 As shown. The photovoltaic IV curve of multiple photovoltaic strings can also be obtained as shown Figure 4 shown.

[0073] Furthermore, after the step of obtaining a photovoltaic curve according to the voltage and current of each photovoltaic string, the following steps are further included:

[0074] Analyze the photovoltaic curve to determine whether there is a fault in the photovoltaic module.

[0075] Reference Figure 4 In actual use, the photovoltaic IV curve is affected by the opening voltage, irradiance, temperature, temperature or actual internal damage. Figure 4 Curves a and b in the figure represent normal operation, each with a single knee bend. Curve c, however, has multiple knee bends, indicating that curve c is abnormal. This indicates that the PV string corresponding to curve c is abnormal.

[0076] Generally, slight deviations in the open-circuit voltage and short-circuit current of a PV module are affected by factors such as irradiance and temperature. However, excessively low open-circuit voltage and short-circuit current, as seen in the D curve, or the C curve with multiple knee bends, indicate a PV module problem. Therefore, analyzing the PV IV curve can help diagnose PV string anomalies and their causes.

[0077] Furthermore, after the step of obtaining the photovoltaic IV curve according to the voltage and current of each photovoltaic string, the method further includes:

[0078] After the test is completed, the inverter is controlled to be in the grid-connected state, and the controller is adjusted to the current source mode to make the photovoltaic system work normally.

[0079] In this embodiment, after the test is completed, if the working state of the photovoltaic assembly is normal, the first switch Q1 between the inverter and the transformer T1 is closed, and the adjustable load is disconnected, so that the photovoltaic system can operate normally.

[0080] If any abnormality is found after analysis, the problematic PV strings need to be inspected or replaced.

[0081] The photovoltaic IV curve testing method of this embodiment includes: controlling the inverter to be in an off-grid state, adjusting the inverter to voltage source mode, connecting an adjustable load, then adjusting the inverter's operating voltage so that it varies between 0 and the rated voltage, and then obtaining the voltage and current of each photovoltaic string when the inverter voltage varies between 0 and the rated voltage, thereby obtaining a photovoltaic IV curve under full voltage. Based on this photovoltaic curve, it is possible to accurately determine whether the photovoltaic module has problems such as faults or current mismatch. Compared to existing photovoltaic IV curves, the photovoltaic IV test system of this embodiment can test photovoltaic IV curves across the full voltage range, thereby accurately monitoring the operating status of photovoltaic modules and performing refined management.

[0082] Example 3

[0083] This embodiment further provides a photovoltaic device, which includes the above-mentioned test system and a processor, wherein the processor can execute the steps of the above-mentioned photovoltaic IV curve test method. The photovoltaic IV curve test method is as described above and will not be described in detail in this embodiment.

[0084] The photovoltaic device of this embodiment controls the inverter in an off-grid state when testing the photovoltaic IV curve, adjusts the inverter to voltage source mode, connects an adjustable load, and then adjusts the inverter's operating voltage so that it fluctuates between 0 and the rated voltage. The voltage and current of each photovoltaic string are then measured when the inverter voltage fluctuates between 0 and the rated voltage, thereby obtaining a photovoltaic IV curve at full voltage. Based on this photovoltaic curve, the operating status of the photovoltaic module can be monitored and any faults or current mismatches can be determined. Compared to existing photovoltaic devices, the photovoltaic device of this embodiment can monitor the operating status of the photovoltaic module across the entire voltage range and provide refined management of this monitoring.

[0085] The photovoltaic IV curve testing system of the present invention operates by controlling the inverter in an off-grid state during testing, adjusting the inverter to voltage source mode, connecting an adjustable load, and adjusting the inverter's operating voltage to vary between 0 and the rated voltage. The system then obtains the voltage and current of each photovoltaic string as the inverter voltage varies between 0 and the rated voltage, thereby generating a photovoltaic IV curve at all voltages. This photovoltaic curve can accurately determine whether a photovoltaic module has faults or current mismatches. Compared to existing photovoltaic IV curve testing systems, the photovoltaic IV test system of this embodiment can test photovoltaic IV curves across the entire voltage range, enabling precise monitoring and refined management of the operating status of photovoltaic modules.

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A photovoltaic IV curve test system, characterized in that: The photovoltaic IV curve test system includes: Photovoltaic modules, consisting of multiple photovoltaic strings; A confluence device, connected to the photovoltaic assembly, for converging multiple photovoltaic strings; an inverter connected to the merging device; An adjustable load is provided in the inverter and is used to connect to the inverter when the inverter is in an off-grid state; The detection unit is provided in the converging device and is connected to each photovoltaic string to detect the current and voltage of each photovoltaic string; A control unit is connected to the merging device, the inverter, the adjustable load and the detection unit. The control unit is used to send a control signal to the inverter and the adjustable load during testing; is used to receive data from the detection unit within the inverter voltage adjustment range of the inverter, and obtain a photovoltaic IV curve within the full voltage range based on the data from the detection unit; The adjustable load is used to adjust the adjustable load according to the control signal so that the adjustable load is adapted to the opening voltage of the photovoltaic module and connected to the inverter; The inverter is used to control the inverter to be in an off-grid state and adjust the inverter to a voltage source mode according to a control signal; and adjust the inverter voltage of the inverter so that the inverter voltage varies within a range of 0 to a rated voltage.

2. The photovoltaic IV curve test system according to claim 1, characterized in that: It also includes a transformer connected to the inverter, wherein the low-voltage side of the transformer is connected to the inverter.

3. The photovoltaic IV curve test system according to claim 1, characterized in that: The inverter is provided with a first switch connected to the low-voltage side of the transformer, which is used to be disconnected when measuring the photovoltaic IV curve to put the inverter in an off-grid state.

4. The photovoltaic IV curve test system according to claim 1, characterized in that: A second switch is provided between the adjustable load and the inverter, and is configured to be closed when the inverter is in an off-grid state.

5. The photovoltaic IV curve testing system according to claim 1, wherein: It also includes a power grid connected to the transformer, the high voltage side of the transformer is connected to the power grid, and the power grid is connected to the control unit.

6. The photovoltaic IV curve test system according to claim 5, characterized in that: The inverter is of centralized, distributed or string type.

7. A photovoltaic IV curve testing method, characterized in that: The test method comprises the following steps: Controlling the inverter to be in an off-grid state, adjusting the inverter to a voltage source mode, obtaining the opening voltage of the photovoltaic module, adjusting the adjustable load to adapt to the opening voltage, and connecting the adjustable load to the inverter; Adjust the inverter operating voltage so that it varies between 0 and rated voltage; Obtain the voltage and current of each PV string when the inverter operating voltage varies from 0 to the rated voltage; The photovoltaic IV curve is obtained according to the voltage and current of each photovoltaic string.

8. The photovoltaic IV curve testing method according to claim 7, wherein: After the step of obtaining a photovoltaic curve based on the voltage and current of each photovoltaic string, the method further includes: Analyze the photovoltaic curve to determine whether the photovoltaic module has a fault.

9. A photovoltaic device, characterized in that: The test system and processor described in any one of 1 to 6 above are included, and the processor can run the test method described in any one of 7 to 8 above.

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