A method and system for detecting hot spots in a photovoltaic module

Abstract

The embodiment of the present application provides a kind of photovoltaic module hot spot detection method and system, belong to photovoltaic power generation monitoring technical field.The method comprises: obtaining the operation detection data of the photovoltaic module to be measured;When meeting the preset detection condition, control the photovoltaic module to be measured switches between the first working state and the second working state of different actual current, and synchronously obtains switching detection data;According to the local excess temperature response of the to-be-judged connecting area relative to the isomorphic reference area determined by the thermal image sequence corresponding to the effective switching period;According to the abnormal electrothermal response feature between local excess temperature response and switching detection data, determine whether the to-be-judged connecting area is the interconnection resistance abnormal type potential hot spot area.The present application scheme improves the identification accuracy of interconnection resistance abnormal type potential hot spot by actual current excitation, effective period screening and isomorphic reference comparison, reduces normal interconnection heat misjudgment.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic power generation monitoring technology, and specifically to a method and system for detecting hot spots in photovoltaic modules. Background Technology

[0002] As photovoltaic power plants age, the solder strip connection areas, interconnection solder joint areas, and busbar connection areas in photovoltaic modules are susceptible to thermal cycling, mechanical stress, humid and hot environments, and installation vibrations, leading to decreased contact performance or increased local series losses. These problems typically do not cause immediate module failure in the early stages, as the modules can still generate electricity and are not easily detected directly from conventional voltage and current data during on-site maintenance.

[0003] Current hotspot detection methods largely rely on drones or fixed infrared cameras to collect module surface temperatures, then determine hotspot locations based on temperature thresholds, temperature difference distribution, or image features. However, in outdoor scenarios, module surface temperatures are simultaneously affected by irradiation variations, wind cooling, dust accumulation, glass reflection, and camera angle. Normal solder ribbons and solder joints also generate heat when the operating current changes. For early-stage potential hotspots caused by abnormal interconnect resistance, simply comparing high-temperature areas on the surface can easily lead to missed or misjudged detections. Therefore, there is an urgent need for a detection method that can effectively identify potential hotspots with abnormal interconnect resistance by combining changes in actual module electrical parameters and differences in thermal imaging response. Summary of the Invention

[0004] The purpose of this invention is to provide a method and system for detecting hot spots in photovoltaic modules, so as to at least solve the problem that it is difficult to distinguish between normal interconnect heating and abnormal early thermal response of interconnect resistance in existing hot spot detection, which leads to potential hot spot missed detection or misjudgment.

[0005] To achieve the above objectives, a first aspect of the present invention provides a method for detecting hot spots in photovoltaic modules. The method includes: acquiring operational detection data of the photovoltaic module under test, and determining whether the photovoltaic module under test meets preset detection conditions based on the operational detection data; when the preset detection conditions are met, controlling the photovoltaic module under test to switch between a first operating state and a second operating state with different actual currents, and synchronously acquiring switching detection data; determining an effective switching period based on the switching detection data, and determining the local excess temperature response of the connection region to be judged relative to the isomorphic reference region according to the thermal image sequence corresponding to the effective switching period; and determining whether the connection region to be judged is a potential hot spot region with abnormal interconnect resistance based on the abnormal electrothermal response characteristics between the local excess temperature response and the switching detection data.

[0006] Optionally, the operational testing data includes at least the actual terminal voltage, actual current, and radiation thermography data of the photovoltaic module under test; the preset testing conditions include: the photovoltaic module under test is in a continuous electrical operating range without discontinuous changes; the imaging area of ​​the module in the radiation thermography data completely covers the module under test; and the positioning reference of the connection area remains fixed during the testing process and meets the preset positioning accuracy requirements.

[0007] Optionally, before controlling the photovoltaic module under test to switch between a first operating state and a second operating state corresponding to different actual currents, the method includes: determining the first operating state and the second operating state within the electrical continuous operating interval; limiting the first operating state and the second operating state to be located within the same bypass state interval, so that the switching process between the two does not involve a change in the conduction state of the bypass diode.

[0008] Optionally, the switching detection data includes the actual terminal voltage sequence, the actual current sequence, and the thermal image sequence synchronized with it; when controlling the photovoltaic module under test to switch between the first working state and the second working state, a balance state code composed of the first working state and the second working state is used for cyclic switching until a preset number of effective switching cycles are obtained, or a preset maximum number of switching times or a preset maximum detection time is reached.

[0009] Optionally, determining the effective switching period based on the switching detection data includes: determining the actual power change and the actual current square change within the corresponding candidate switching period based on the actual terminal voltage sequence and the actual current sequence; determining whether the power deviation between the first and second operating states within the candidate switching period meets a preset balance condition based on the actual power change, and determining whether the current excitation intensity within the candidate switching period meets a preset excitation condition based on the actual current square change; and determining the candidate switching period as the effective switching period when both the preset balance condition and the preset excitation condition are met.

[0010] Optionally, before determining the actual power change and the actual current square change within the candidate switching period, the method includes: determining the transition interval and the stable holding interval after each state switch based on the current change slope in the actual current sequence and the target operating state current deviation; and determining the actual power change and the actual current square change based on the actual terminal voltage sequence and the actual current sequence within the stable holding interval.

[0011] Optionally, determining the local excess temperature response of the connection region to be judged relative to the isomorphic reference region based on the thermal image sequence corresponding to the effective switching cycle includes: performing spatial registration processing on the thermal image sequence to make the corresponding pixel positions of the thermal images consistent at each time; accurately extracting the temperature time series of the connection region to be judged and the temperature time series of the isomorphic reference region based on the connection region positioning reference; and determining the local excess temperature response of the connection region to be judged relative to the isomorphic reference region based on the temperature time series of the connection region to be judged and the temperature time series of the isomorphic reference region.

[0012] Optionally, the isomorphic reference region is a region that has the same connection structure, the same conductive path, and the same current conduction function as the connection region to be judged; the isomorphic reference region is a corresponding region among the solder strip connection region, interconnect solder joint region, or busbar connection region; the isomorphic reference region and the connection region to be judged are located in the same structural position within the same component, and the difference between their edge distances does not exceed a preset distance threshold.

[0013] Optionally, determining whether the connection region to be judged is a potential hot spot region with abnormal interconnect resistance based on the abnormal electrothermal response characteristics between the local excess temperature response and the switching detection data includes: calculating the temperature difference time-by-time between the temperature time series of the connection region to be judged and the temperature time series of the isomorphic reference region to obtain the excess temperature time series; extracting abnormal electrothermal response characteristics based on the response matching relationship between the excess temperature time series and the actual current square change sequence; and determining whether the connection region to be judged is a potential hot spot region with abnormal interconnect resistance based on the abnormal electrothermal response characteristics.

[0014] A second aspect of the present invention provides a photovoltaic module hot spot detection system, the system comprising: a data acquisition unit for acquiring operational detection data of the photovoltaic module under test, and determining whether the photovoltaic module under test meets preset detection conditions based on the operational detection data; a switching unit for controlling the photovoltaic module under test to switch between a first operating state and a second operating state with different actual currents when the preset detection conditions are met, and synchronously acquiring switching detection data; a response unit for determining an effective switching period based on the switching detection data, and determining the local excess temperature response of the connection area to be judged relative to the isomorphic reference area according to the thermal image sequence corresponding to the effective switching period; and an identification unit for determining whether the connection area to be judged is a potential hot spot area with abnormal interconnect resistance based on the abnormal electrothermal response characteristics between the local excess temperature response and the switching detection data.

[0015] Through the above technical solution, the present invention first uses operational detection data to screen out unsuitable operating conditions such as discontinuous electrical states and unstable thermal imaging fields of view, avoiding forced judgments under invalid field conditions. Then, it uses the actual current difference between the first and second operating states to form an observable electrothermal excitation, and uses synchronously obtained switching detection data to determine the effective switching cycle, ensuring that subsequent judgments are based on the consistency of actual electrical parameters and thermal imaging data. Furthermore, this solution does not directly use high-temperature points on the component surface as hotspot criteria, but rather compares the local excess temperature response of the connection area to be judged relative to the isomorphic reference area, thereby reducing the influence of irradiation, air cooling, overall temperature rise, and normal interconnect structure heating. Therefore, it can more effectively identify potential hotspots caused by abnormal interconnect resistance, reducing the risk of early hotspot missed detection and misjudgment of normal interconnect heating.

[0016] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart of the steps of a photovoltaic module hot spot detection method provided by one embodiment of the present invention; Figure 2 This is a schematic diagram of the photovoltaic module hot spot detection arrangement provided in one embodiment of the present invention; Figure 3 This is a schematic diagram of the working state switching and stable maintenance range provided by one embodiment of the present invention; Figure 4 This is a schematic diagram of the local excess temperature response delay provided by one embodiment of the present invention; Figure 5 This is a thermal image comparison between a potential hotspot area and a normal area provided by one embodiment of the present invention. Figure 6 This is a system structure diagram of a photovoltaic module hot spot detection system provided in one embodiment of the present invention. Detailed Implementation

[0018] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0019] like Figure 1 As shown, embodiments of the present invention provide a method for detecting hot spots in photovoltaic modules, the method comprising: Step S10: Obtain the operation and testing data of the photovoltaic module under test, and determine whether the photovoltaic module under test meets the preset testing conditions based on the operation and testing data.

[0020] Specifically, the operational testing data includes at least the actual terminal voltage, actual current, and radiation thermography data of the photovoltaic module under test; the preset testing conditions include: the photovoltaic module under test is in a continuous electrical operating range without discontinuous changes; the imaging area of ​​the module in the radiation thermography data completely covers the module under test; and the positioning reference of the connection area remains fixed during the testing process and meets the preset positioning accuracy requirements.

[0021] In this embodiment of the invention, operational detection data is used to determine whether the photovoltaic module under test possesses the basic conditions for subsequent current switching and thermal imaging response analysis. The operational detection data can be obtained jointly by a module-level power optimizer, a string monitoring unit, a temporarily connected controllable detection device, and a radiation thermography camera, and is not limited to a single acquisition device. The actual terminal voltage and actual current are preferably electrical parameters flowing through the photovoltaic module under test itself; in string-level detection scenarios, it is also necessary to ensure that these electrical parameters can reflect the actual operating status of the detection branch where the photovoltaic module under test is located.

[0022] In specific judgments, the presence of step abrupt changes, intermittent zero drops, abnormal fluctuations, or significant hysteresis in the actual terminal voltage and current within a preset observation time is used to determine whether the photovoltaic module under test is in a continuous electrical operating range without discontinuous changes. This continuous electrical operating range is primarily used to exclude sudden changes in electrical parameters caused by bypass diode state transitions, loose contact terminals, sampling interruptions, or rapid cloud cover, thus avoiding the subsequent misinterpretation of temperature changes under unstable operating conditions as abnormal interconnect resistance responses.

[0023] Simultaneously, the imaging area and connection area positioning references of the component are identified based on the radiation thermography thermal imaging data. The component imaging area needs to completely cover the component under test, and should at least cover the solder strip connection area, interconnect solder joint area, or busbar connection area that needs to be determined later. The connection area positioning reference can be the component frame, cell boundary, main bus line, busbar outline, or pre-calibrated component pattern features. If there is occlusion, truncation, severe reflection, excessive viewing angle change, or connection area positioning reference drift exceeding the preset positioning accuracy in the thermal image, it is determined that the preset detection conditions are not met. For cases where the preset detection conditions are not met, the current hot spot detection can be stopped, or the camera position, detection period, or electrical parameter sampling status can be readjusted before re-entering step S10.

[0024] Step S20: When the preset detection conditions are met, control the photovoltaic module under test to switch between a first working state and a second working state with different actual currents, and simultaneously obtain the switching detection data.

[0025] Specifically, before controlling the photovoltaic module under test to switch between a first operating state and a second operating state corresponding to different actual currents, the method includes: determining the first operating state and the second operating state within the electrical continuous operating interval; limiting the first operating state and the second operating state to be located within the same bypass state interval, so that the switching process between the two does not involve a change in the conduction state of the bypass diode.

[0026] Furthermore, the switching detection data includes the actual terminal voltage sequence, the actual current sequence, and the thermal image sequence synchronized with it in time; when controlling the photovoltaic module under test to switch between the first working state and the second working state, the balanced state code composed of the first working state and the second working state is used for cyclic switching until a preset number of effective switching cycles are obtained, or a preset maximum number of switching times or a preset maximum detection time is reached.

[0027] In this embodiment of the invention, both the first and second operating states need to be determined within the electrically continuous operating range confirmed in step S10. The actual currents corresponding to the two states are different, enabling the subsequent formation of a thermal response related to current changes. The first and second operating states can be implemented through a component-level optimizer, a controllable DC / DC detection device, or a string detection interface with corresponding adjustment capabilities, and are not limited to any particular control device. It should be noted that the first and second operating states are not arbitrary two voltage or power points, but rather should avoid the range where the bypass diode's conduction state changes. If the bypass diode turns on or off between the two states, the internal current path and heating location of the component will change abruptly, and the subsequent thermal image response will no longer primarily reflect abnormal interconnect resistance. Therefore, such states are not considered effective switching states in this embodiment.

[0028] After determining the first and second operating states, the photovoltaic module under test is controlled to switch between the two, and switching detection data is collected synchronously. The switching detection data includes the actual terminal voltage sequence, the actual current sequence, and a thermal image sequence synchronized with the actual terminal voltage sequence and the actual current sequence. This synchronization can be achieved through a unified timestamp, a trigger signal, or clock calibration of the acquisition device, as long as the relationship between the thermal image frame and the electrical parameters at the corresponding time can be determined.

[0029] In one implementation, the switching process employs a balanced state encoding consisting of a first operating state and a second operating state, such as a sequential encoding of the first operating state, the second operating state, the second operating state, and the first operating state. The balanced state encoding can be executed cyclically, with each completed encoding sequence serving as a candidate switching cycle. The goal is to obtain a preset number of effective switching cycles through cyclic switching; if the number of switching cycles reaches a preset maximum number of switching cycles, or the detection time reaches a preset maximum detection time, the current switching process is stopped. The preset number, the preset maximum number of switching cycles, and the preset maximum detection time can be preset based on component specifications, camera frame rate, on-site air cooling conditions, and safety requirements.

[0030] In one specific implementation, the photovoltaic module under test is connected to a module-level power optimizer, and a radiation thermography camera is fixed directly in front of the module. First, under the current irradiance conditions, it is confirmed that the voltage and current changes at the module terminals are continuous, and that the bypass diodes do not exhibit any changes in conduction state. Then, within this continuous operating range, a first operating state and a second operating state are selected. The first operating state can be a relatively high current state, and the second operating state can be a relatively low current state. The current difference between the two needs to be sufficient to form a recognizable electrothermal response in the thermal imaging sequence, but should not cause the module voltage and current to exceed the equipment's allowable range.

[0031] During switching, the controller executes a balance state encoding in the order of first operating state, second operating state, second operating state, and first operating state. Each operating state can be held for a certain number of seconds, the holding time of which can be preset according to the infrared camera frame rate, component package thermal inertia, and on-site wind speed. For example, the first operating state is held for 5 seconds before switching to the second operating state, the second operating state is held for two consecutive 5-second intervals, and then the controller switches back to the first operating state for 5 seconds. Throughout the process, the controller continuously records the actual terminal voltage and actual current of the component, and the radiation thermography camera synchronously acquires thermal image frames. After completing one round of the above sequential encoding, this process can be considered as a candidate switching cycle. If this candidate switching cycle is subsequently determined to be a valid switching cycle, thermal image response analysis is initiated; if the validity requirement is not met, the next round of balance state encoding continues until a preset number of valid switching cycles are obtained, or the maximum number of switching cycles or the maximum detection time is reached.

[0032] In another implementation, a thermal image sequence of a preset duration is continuously acquired under the current operating state, and the temperature change trend of the connection area to be judged and the corresponding isomorphic reference area is extracted. The ambient temperature drift rate and the overall component temperature rise rate are determined based on the temperature change trend. When the ambient temperature drift rate or the overall component temperature rise rate exceeds the corresponding threshold, subsequent state switching is temporarily suspended, and monitoring continues until the temperature change enters a stable range. When both the ambient temperature drift rate and the overall component temperature rise rate meet the requirements, the switch between the first and second operating states is executed. By adding a thermal stability pre-detection process, the impact of rapid cloud cover, gust cooling, and the overall component temperature rise process on subsequent local excess temperature response analysis can be reduced, allowing the subsequently obtained thermal image response to better reflect the electrothermal change characteristics of the connection area itself.

[0033] Step S30: Determine the effective switching period based on the switching detection data, and determine the local excess temperature response of the connection region to be judged relative to the isomorphic reference region according to the thermal imaging sequence corresponding to the effective switching period.

[0034] Specifically, determining the effective switching period based on the switching detection data includes: determining the actual power change and the actual current square change within the corresponding candidate switching period based on the actual terminal voltage sequence and the actual current sequence; determining whether the power deviation between the first and second operating states within the candidate switching period meets a preset balance condition based on the actual power change, and determining whether the current excitation intensity within the candidate switching period meets a preset excitation condition based on the actual current square change; and determining the candidate switching period as the effective switching period when both the preset balance condition and the preset excitation condition are met.

[0035] Further, before determining the actual power change and the actual square change of current within the candidate switching cycle, the method includes: determining the transition interval and the stable holding interval after each state switch based on the current change slope in the actual current sequence and the target operating state current deviation; and determining the actual power change and the actual square change of current based on the actual terminal voltage sequence and the actual current sequence within the stable holding interval.

[0036] In this embodiment of the invention, determining the local excess temperature response of the connection region to be judged relative to the isomorphic reference region based on the thermal image sequence corresponding to the effective switching cycle includes: performing spatial registration processing on the thermal image sequence to make the corresponding pixel positions of the thermal images consistent at each time point; accurately extracting the temperature time series of the connection region to be judged and the temperature time series of the isomorphic reference region based on the connection region positioning reference; and determining the local excess temperature response of the connection region to be judged relative to the isomorphic reference region based on the temperature time series of the connection region to be judged and the temperature time series of the isomorphic reference region.

[0037] Specifically, the isomorphic reference region is a region that has the same connection structure, the same conductive path, and the same current conduction function as the connection region to be judged; the isomorphic reference region is a corresponding region among the solder strip connection region, interconnect solder joint region, or busbar connection region; the isomorphic reference region and the connection region to be judged are located in the same structural position within the same component, and the difference between their edge distances does not exceed a preset distance threshold.

[0038] In this embodiment of the invention, since the switching between the first operating state and the second operating state requires the controller response, DC side electrical parameter adjustment and the component's own electrical transition process, this embodiment does not directly use all the sampled data within the complete candidate switching period, but first distinguishes the transition interval and the stable holding interval within the candidate switching period.

[0039] Specifically, let the candidate switching period be the first The actual terminal voltage at each sampling time is The actual current is Sampling time is The corresponding actual power Represented as: ; in, For the first The actual power at each sampling moment. For the sampling data after each state transition, the transition range and the stable holding range can be determined based on the actual current change slope and the target operating state current deviation. For example, when Greater than the preset slope threshold, or the actual current When the deviation from the current of the current in the current target operating state is greater than a preset deviation threshold, the interval in which that moment occurs is designated as a transition interval; when both the current change slope and the deviation from the current in the target operating state meet the requirements, the corresponding interval is designated as a stable holding interval. The target operating state current can be a set current value of the first operating state or the second operating state, or it can be the average actual current value within the previous stable holding interval in the corresponding operating state.

[0040] After obtaining the stable holding interval, the average power corresponding to the first and second operating states within the candidate switching cycle is determined based on the actual terminal voltage and current sequences within the stable holding interval. , and the square of the average current , The average power is maintained within the stable range. Statistical analysis shows that the square of the average current is maintained within the stable interval. Statistical results were obtained. To determine whether the overall power background under two operating states is comparable, state-dependent power imbalance can be calculated. : ; in, This refers to state-dependent power imbalance. To prevent the default value of a small quantity with a denominator of zero. When When the power imbalance threshold is less than or equal to the preset power imbalance threshold, it indicates that the overall output power difference between the first and second operating states is within an acceptable range, and subsequent thermal image changes are not easily dominated by the overall power difference between the two states.

[0041] Simultaneously, the actual current square excitation quantity is determined based on the average current square. : ; in, This is the square of the actual current excitation. The preset excitation threshold is greater than zero. When... When the current is greater than or equal to the preset excitation threshold, it indicates that a sufficient square-current change has been formed within the candidate switching cycle. The preset power imbalance threshold and the preset excitation threshold can be set jointly to ensure that the candidate switching cycle simultaneously meets the requirements of comparable overall power background and sufficient local square-current excitation. Satisfying the preset balance conditions and When the preset excitation conditions are met, the candidate switching period is determined as the valid switching period.

[0042] After determining the effective switching period, the local excess temperature response is further determined based on the thermal image sequence corresponding to the effective switching period. To avoid the influence of minute camera displacement, bracket vibration, or component edge positioning errors on regional temperature extraction, spatial registration processing needs to be performed on the thermal image sequence first. Spatial registration can be based on the component frame, cell boundary, main bus line, busbar outline, or pre-calibrated connection area positioning reference, so that the connection area to be judged and the isomorphic reference area in the thermal image at each time point maintain a corresponding relationship.

[0043] After registration is completed, the temperature time series of the region to be determined is extracted based on the location reference of the connected region. And extract the reference temperature time series corresponding to the isomorphic reference region. When there is only one isomorphic reference region, It can be the temperature time series of the isomorphic reference region; when there are multiple isomorphic reference regions... The reference temperature can be the median or mean of multiple isomorphic reference regions at the same time. The isomorphic reference region is a region that has the same connection structure, the same conductive path, and the same current conduction function as the region to be judged, such as the solder strip connection area, interconnect solder joint area, or busbar connection area at the corresponding structural position within the same component, and the difference in edge distance between the isomorphic reference region and the region to be judged does not exceed a preset distance threshold.

[0044] The local excess temperature response of the region to be judged relative to the isomorphic reference region can be expressed as: ; in, For the region to be connected at time... Local excess temperature response, The temperature time series of the region to be connected is shown. This is a reference temperature time series corresponding to the isomorphic reference region. Through the above processing, subsequent steps can compare the local temperature response of the connection region to be judged among similar connection structures, rather than directly judging based on the absolute high temperature point on the component surface.

[0045] In another implementation, temperature time series of multiple candidate isomorphic reference regions are extracted within the effective switching cycle, and the response consistency among each candidate isomorphic reference region is calculated. If a candidate isomorphic reference region exhibits a persistently high temperature relative to other candidate isomorphic reference regions, a significant shift in response phase, or an abnormally strong correlation with the square change of the actual current, then this candidate isomorphic reference region is marked as a suspected abnormal reference region and removed from the isomorphic reference set. Subsequently, a reference temperature time series is constructed using the temperature time series of the remaining isomorphic reference regions. This method avoids using connection regions with slight interconnection anomalies as normal reference regions, reducing the impact of the isomorphic reference region's own anomalies on the calculation of local excess temperature response.

[0046] Step S40: Based on the abnormal electrothermal response characteristics between the local excess temperature response and the switching detection data, determine whether the connection area to be judged is a potential hot spot area with abnormal interconnect resistance.

[0047] Specifically, the temperature difference is calculated moment by moment based on the temperature time series of the connection region to be judged and the temperature time series of the isomorphic reference region to obtain the excess temperature time series; abnormal electrothermal response features are extracted based on the response matching relationship between the excess temperature time series and the actual current square change series; and the abnormal electrothermal response features are used to determine whether the connection region to be judged is a potential hot spot region with abnormal interconnect resistance.

[0048] In this embodiment of the invention, abnormal electrothermal response characteristics are used to determine whether the local excess temperature change in the connection region to be determined corresponds to the actual square change of the current during the switching process. Specifically, after obtaining the local excess temperature response of the connection region to be determined relative to the isomorphic reference region in step S30, the local excess temperature response can be used as an excess temperature time series. Simultaneously, the actual current squared change sequence is obtained based on the actual current sequence in the switching detection data. The actual current square variation sequence is used to characterize the electrothermal excitation formed between the first and second operating states.

[0049] Considering the thermal conduction hysteresis between the module glass, encapsulation film, solar cells, and solder ribbons, the excess temperature time series does not need to be perfectly synchronized with the actual current square change series at the same moment. It can be adjusted according to a preset thermal response delay range. and Response matching is performed to extract abnormal electrothermal response features. These abnormal electrothermal response features may include at least one of the following: excess temperature response amplitude, correlation with the square change of actual current, response delay time, and recurrence patterns in multiple effective switching cycles.

[0050] For example, when the first operating state corresponds to a higher actual current, if the excessive temperature response of the connection region to be judged continues to increase after a reasonable thermal delay, and this response is significantly higher than the response of the isomorphic reference region in multiple effective switching cycles, then the connection region to be judged can be identified as a potential hotspot region with abnormal interconnect resistance. If the excessive temperature response does not have a stable correspondence with the square change of the actual current, or only occurs occasionally in a single cycle, then the connection region to be judged will not be identified as a potential hotspot region with abnormal interconnect resistance.

[0051] Example: according to Figure 2 The testing setup shown is used for on-site testing of the photovoltaic module under test. The photovoltaic module is operating under natural sunlight. A module-level power optimizer or an equivalent controllable detection module is connected above the module. An infrared camera is fixed to one side of the front of the module to continuously acquire radiation thermography images during the testing process. Before testing, the actual terminal voltage, actual current, and initial thermal image of the photovoltaic module under test are collected to confirm that the imaging area of ​​the module is complete and that the connection area to be judged can be stably located in the thermal image. Figure 2 The dashed box can be used as a positioning reference for the connection area, which is then used to lock the connection area to be judged and the isomorphic reference area.

[0052] After the testing conditions are met, the photovoltaic module under test is controlled to switch between two operating states with different actual currents. The specific switching process is as follows: Figure 3As shown, state 1 corresponds to a higher current state, and state 2 corresponds to a lower current state. Because the actual current does not immediately stabilize after the controller issues a switching command, Figure 3 The system divides the short period after each switch into a transition interval, and the portion of the current that remains relatively stable after the transition interval into a stable holding interval. When subsequently determining the power change and the square of the current change, the actual terminal voltage and actual current within the stable holding interval are used first to avoid mistaking the control response transient process as an effective excitation.

[0053] After completing several candidate switching cycles, the effective switching cycle is selected based on the actual power change and the square of the actual current change. For the thermal imaging sequence corresponding to the effective switching cycle, the local excess temperature response is further extracted. This response is as follows: Figure 4 As shown, after the square of the actual current changes, the local excess temperature in the connection area to be judged will not change immediately and synchronously, but will exhibit a certain thermal response delay, gradually increasing and then gradually decreasing. This delay is mainly related to the thermal conduction of the module glass, solar cells, encapsulation layer, and connection structure. Therefore, this embodiment does not require the temperature response to be completely synchronized with the current change during the judgment, but focuses on the matching relationship between the two within a reasonable delay range.

[0054] based on Figure 5 The thermal imaging results output the detection conclusion. If the connection area to be judged exhibits a stable local excess temperature response relative to the isomorphic reference area, and this response repeats in multiple effective switching cycles, then the area can be identified as a potential hotspot area with abnormal interconnect resistance. Figure 5 As shown in (a) above. If the corresponding connection region does not exhibit a significant excess temperature response, or if there is no stable matching relationship between the response and the actual square change of current, it is determined to be a normal region, such as... Figure 5 As shown in (b) in the figure. Thus, this embodiment does not simply determine the hot spot based on the highest temperature position in the thermal image, but rather combines actual current excitation, effective period screening, and comparison of isomorphic regions to complete the judgment.

[0055] like Figure 6As shown, this invention provides a photovoltaic module hot spot detection system. The system includes: a data acquisition unit for acquiring operational detection data of the photovoltaic module under test and determining whether the photovoltaic module under test meets preset detection conditions based on the operational detection data; a switching unit for controlling the photovoltaic module under test to switch between a first operating state and a second operating state with different actual currents when the preset detection conditions are met, and synchronously acquiring switching detection data; a response unit for determining an effective switching period based on the switching detection data and determining the local excess temperature response of the connection area to be judged relative to the isomorphic reference area according to the thermal image sequence corresponding to the effective switching period; and an identification unit for determining whether the connection area to be judged is a potential hot spot area with abnormal interconnect resistance based on the abnormal electrothermal response characteristics between the local excess temperature response and the switching detection data.

[0056] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a microcontroller, chip, or processor to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0057] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details described above. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not further describe the various possible combinations.

[0058] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the embodiments of the present invention, they should also be regarded as the content disclosed by the embodiments of the present invention.

Claims

1. A method for detecting hot spots in photovoltaic modules, characterized in that, The method includes: The system acquires operational testing data of the photovoltaic module under test and determines whether the photovoltaic module under test meets the preset testing conditions based on the operational testing data. When the preset detection conditions are met, the photovoltaic module under test is controlled to switch between a first working state and a second working state with different actual currents, and the switching detection data is obtained synchronously. The effective switching period is determined based on the switching detection data, and the local excess temperature response of the connection region to be judged relative to the isomorphic reference region is determined according to the thermal imaging sequence corresponding to the effective switching period. Based on the abnormal electrothermal response characteristics between the local excess temperature response and the switching detection data, it is determined whether the connection area to be judged is a potential hot spot area with abnormal interconnect resistance.

2. The photovoltaic module hot spot detection method according to claim 1, characterized in that, The operational detection data includes at least the actual terminal voltage, actual current, and radiation thermography data of the photovoltaic module under test. The preset detection conditions include: The photovoltaic module under test is in a continuous electrical operating range without discontinuous changes; The component imaging area in the radiation thermography data completely covers the component under test; The positioning reference of the connecting area remains fixed during the detection process and meets the preset positioning accuracy requirements.

3. The photovoltaic module hot spot detection method according to claim 2, characterized in that, Before controlling the photovoltaic module under test to switch between a first operating state and a second operating state corresponding to different actual currents, the method includes: Within the electrical continuous operating range, the first operating state and the second operating state are determined; The first operating state and the second operating state are limited to the same bypass state interval, so that the switching process between the two does not involve a change in the conduction state of the bypass diode.

4. The photovoltaic module hot spot detection method according to claim 1, characterized in that, The switching detection data includes the actual terminal voltage sequence, the actual current sequence, and the thermal image sequence synchronized with them in time. When controlling the photovoltaic module under test to switch between the first working state and the second working state, a balanced state code composed of the first working state and the second working state is used for cyclic switching until a preset number of effective switching cycles are obtained, or a preset maximum number of switching times or a preset maximum detection time is reached.

5. The photovoltaic module hot spot detection method according to claim 4, characterized in that, Determining the effective handover period based on the handover detection data includes: The actual power change and the actual current square change within the corresponding candidate switching period are determined based on the actual terminal voltage sequence and the actual current sequence. Based on the actual power change, it is determined whether the power deviation between the first and second operating states within the candidate switching cycle meets the preset balance condition, and based on the actual square change of current, it is determined whether the current excitation intensity within the candidate switching cycle meets the preset excitation condition. When both the preset balance condition and the preset excitation condition are satisfied, the candidate switching period is determined as the effective switching period.

6. The photovoltaic module hot spot detection method according to claim 5, characterized in that, Before determining the actual power change and the actual square change of current within the candidate switching cycle, the method includes: Based on the current change slope in the actual current sequence and the current deviation of the target operating state, determine the transition interval and stable holding interval after each state switch; The actual power change and the actual current square change are determined based on the actual terminal voltage sequence and the actual current sequence within the stable holding interval.

7. The photovoltaic module hot spot detection method according to claim 1, characterized in that, Determine the local excess temperature response of the connection region to be judged relative to the isomorphic reference region based on the thermal imaging sequence corresponding to the effective switching cycle, including: Spatial registration processing is performed on the thermal image sequence to ensure that the corresponding pixel positions of the thermal images are consistent at each time step. Accurately extract the temperature time series of the connection region to be judged and the temperature time series of the isomorphic reference region based on the location benchmark of the connection region. The local excess temperature response of the region to be judged relative to the isomorphic reference region is determined based on the temperature time series of the region to be judged and the temperature time series of the isomorphic reference region.

8. The photovoltaic module hot spot detection method according to claim 7, characterized in that, The isomorphic reference region is a region that has the same connection structure, the same conductive path, and the same current conduction function as the connection region to be judged. The isomorphic reference region is the corresponding region among the solder strip connection region, interconnect solder joint region, or busbar connection region; The isomorphic reference region and the connection region to be judged are located in the same structural position within the same component, and the difference between their edge distances does not exceed a preset distance threshold.

9. The photovoltaic module hot spot detection method according to claim 7, characterized in that, Based on the abnormal electrothermal response characteristics between the local excess temperature response and the switching detection data, it is determined whether the connection region to be judged is a potential hotspot region with abnormal interconnect resistance, including: The temperature difference is calculated moment by moment between the temperature time series of the region to be judged and the temperature time series of the isomorphic reference region to obtain the excess temperature time series. Abnormal electrothermal response features are extracted based on the response matching relationship between the excess temperature time series and the actual current square change series. Based on the abnormal electrothermal response characteristics, it is determined whether the connection area to be judged is a potential hot spot area with abnormal interconnect resistance.

10. A photovoltaic module hot spot detection system, characterized in that, The system includes: The acquisition unit is used to acquire the operation and testing data of the photovoltaic module under test, and to determine whether the photovoltaic module under test meets the preset testing conditions based on the operation and testing data. The switching unit is used to control the photovoltaic module under test to switch between a first operating state and a second operating state with different actual currents when the preset detection conditions are met, and to simultaneously obtain switching detection data. The response unit is used to determine the effective switching period based on the switching detection data, and to determine the local excess temperature response of the connection area to be judged relative to the isomorphic reference area according to the thermal image sequence corresponding to the effective switching period. The identification unit is used to determine whether the connection area to be judged is a potential hot spot area with abnormal interconnect resistance based on the abnormal electrothermal response characteristics between the local excess temperature response and the switching detection data.

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