Photovoltaic string insulation detection method and device, controller, storage medium and photovoltaic system

Abstract

The invention provides an insulation detection method and device for a photovoltaic string, a controller, a storage medium and a photovoltaic system. The method comprises the following steps: when a preset switch is in a closed state, acquiring a current signal of a second pole output end of each photovoltaic string, and taking the current signal as a first current signal; and for each photovoltaic group string, according to the first current signal of the photovoltaic group string, judging whether the photovoltaic group string has an insulation fault or not. According to the method, extra detection equipment is not needed to detect each photovoltaic string one by one, and whether the photovoltaic string has the insulation fault can be determined only by detecting the change of the first current signal of the first pole output end of the photovoltaic string, so that the string level insulation detection process is greatly simplified, the traditional tedious test process is simplified, and the detection efficiency is improved. And the cascade insulation detection efficiency is obviously improved.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic system technology, and in particular to an insulation detection method, device, controller, storage medium, and photovoltaic system for photovoltaic strings. Background Technology

[0002] Insulation testing of photovoltaic strings is a key step in ensuring the safe and stable operation of photovoltaic systems. It can effectively prevent leakage risks caused by string insulation failure, prevent short circuits and arc discharges caused by insulation degradation, reduce equipment damage such as junction box burnout and cable aging, and extend the service life of photovoltaic systems.

[0003] To detect insulation fault types at the string level in photovoltaic (PV) systems, existing technologies typically involve sequentially testing each PV string with an insulation resistance tester and then identifying the faulty PV string based on the test results. While this method can accurately determine the insulation fault type for each PV string, the testing process is cumbersome and time-consuming, resulting in low efficiency in string-level insulation fault detection. Summary of the Invention

[0004] This invention provides a method, apparatus, controller, storage medium, and photovoltaic system for insulation detection of photovoltaic strings, in order to solve the problem of low efficiency in string-level insulation fault detection in the prior art.

[0005] In a first aspect, embodiments of the present invention provide an insulation detection method for photovoltaic strings, applied to a photovoltaic system; the photovoltaic system includes multiple MPPT modules and a preset switch; each MPPT module includes multiple photovoltaic strings; and multiple photovoltaic strings of the same MPPT module are connected in parallel; the first pole output terminal of each MPPT module is grounded through the preset switch; the first pole output terminal is the positive pole output terminal or the negative pole output terminal of the photovoltaic string; The method includes: When the preset switch is closed, the current signal of the second pole output terminal of each photovoltaic string is acquired and used as the first current signal; the second pole output terminal is another output terminal other than the first pole output terminal. For each photovoltaic string, the first current signal of the photovoltaic string is used to determine whether an insulation fault has occurred.

[0006] Secondly, embodiments of the present invention provide an insulation detection device for photovoltaic strings, applied to a photovoltaic system; the photovoltaic system includes multiple MPPT modules and a preset switch; each MPPT module includes multiple photovoltaic strings; and multiple photovoltaic strings of the same MPPT module are connected in parallel; the first pole output terminal of each MPPT module is grounded through the preset switch; the first pole output terminal is the positive pole output terminal or the negative pole output terminal of the photovoltaic string; The device includes: The current acquisition module is used to acquire the current signal of the second pole output terminal of each photovoltaic string when the preset switch is closed, and use it as the first current signal; the second pole output terminal is another output terminal other than the first pole output terminal. The insulation fault detection module is used to determine whether an insulation fault has occurred in each photovoltaic string based on the first current signal of that photovoltaic string.

[0007] Thirdly, embodiments of the present invention provide a controller, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the insulation detection method for photovoltaic strings as described in any possible implementation of the first aspect above.

[0008] Fourthly, embodiments of the present invention provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the insulation detection method for photovoltaic strings as described in any possible implementation of the first aspect above.

[0009] Fifthly, this embodiment provides a photovoltaic system, which includes: a photovoltaic string and a controller as described in the third aspect above.

[0010] This invention provides a method, apparatus, controller, storage medium, and photovoltaic system for insulation detection of photovoltaic strings. The method acquires the current signal from the second pole output terminal of each photovoltaic string when the preset switch is closed, using this signal as the first current signal. For each photovoltaic string, the method determines whether an insulation fault has occurred based on the first current signal. This method eliminates the need to test each string individually with an insulation resistance tester. Instead, it utilizes the built-in MPPT module of the photovoltaic system and the preset switch to complete signal acquisition without shutting down the photovoltaic system, significantly simplifying the string-level insulation detection process and greatly improving its efficiency. Furthermore, the current signal directly reflects the continuity of the string circuit. An insulation fault will create an abnormal grounding loop, causing a characteristic change in the first current signal. Based on this characteristic change, fault signs can be quickly detected, providing more real-time performance compared to traditional resistance testing. This allows for timely prevention of risks such as leakage, short circuits, and arc discharge caused by insulation faults, extending the lifespan of the photovoltaic system and ensuring its long-term safe and stable operation. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the specific structure of the photovoltaic system provided in the embodiment of the present invention; Figure 2 This is a flowchart illustrating the implementation of the insulation detection method for photovoltaic strings provided in this embodiment of the invention. Figure 3 This is a schematic diagram of the structure of the insulation detection device for photovoltaic strings provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the controller provided in an embodiment of the present invention. Detailed Implementation

[0013] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0014] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described below in conjunction with the accompanying drawings.

[0015] In one embodiment, Figure 1 This embodiment shows a schematic diagram of the specific structure of the photovoltaic system provided, such as... Figure 1 As shown, the photovoltaic system includes multiple MPPT (Maximum Power Point Tracking) modules (MPPT1 to MPPT2) and preset switches K0 (K01 to K0-4); each MPPT module includes multiple photovoltaic strings PV (PV1 to PV4); and multiple photovoltaic strings of the same MPPT module are connected in parallel; the first pole output terminal of each MPPT module is grounded through the preset switch K0; the first pole output terminal is the positive output terminal PV+ or the negative output terminal PV- of the photovoltaic string.

[0016] Specifically, the positive output terminal PV+ of each photovoltaic string within the same MPPT module is connected to the positive output terminal of that MPPT module, and the negative output terminal PV- of each photovoltaic string within the same MPPT module is connected to the negative output terminal of that MPPT module. The positive output terminal of each MPPT module is connected to the positive DC bus of the photovoltaic system, and the negative output terminal of each MPPT module is connected to the negative DC bus of the photovoltaic system. The positive and negative DC buses are used to connect to the input terminals of the photovoltaic converter. The photovoltaic converter can be a photovoltaic inverter or a rectifier.

[0017] Specifically, each photovoltaic string has a diode K2 (K2-1 to K2-2) connected between its positive output terminal PV+ and the positive busbar. The positive terminal of the diode is connected to the positive output terminal PV+ of the corresponding photovoltaic string, and the negative terminal of the diode is connected to the positive busbar.

[0018] In this embodiment, the photovoltaic system further includes a current sensor, a voltage sensor, and a controller. The current sensor is used to collect the current signal at the output terminal of the second electrode and send the current signal to the controller. The voltage sensor is used to detect the voltage value between the positive and negative output terminals of the photovoltaic string and send the voltage value to the controller. The controller can control the on / off state of a preset switch, or it can perform insulation detection of the photovoltaic string based on the aforementioned voltage and current signals.

[0019] See Figure 2 The diagram illustrates the implementation flowchart of the insulation detection method for photovoltaic strings provided in this embodiment of the invention. This method is applied to the controller in a photovoltaic system, and is described in detail below: S101: When the preset switch is closed, the current signal of the second pole output terminal of each photovoltaic string is acquired and used as the first current signal; the second pole output terminal is another output terminal other than the first pole output terminal.

[0020] In this embodiment, during the standby state before grid connection after the photovoltaic converter starts up, the controller controls the preset switch to close, grounding the negative / positive output terminals of the photovoltaic strings. The current sensor detects the current signal at the second output terminal of each photovoltaic string at this time and sends the current signal as the first current signal to the controller.

[0021] S102: For each photovoltaic string, determine whether an insulation fault has occurred in the photovoltaic string based on the first current signal of the photovoltaic string.

[0022] In this embodiment, the first current signal is affected by the photovoltaic module experiencing an insulation fault, causing a change in the current value of the entire photovoltaic string. Specifically, taking the first output terminal as the negative output terminal as an example, when the photovoltaic string does not experience an insulation fault, the negative terminal of the photovoltaic string uses the grounding point as a reference potential. The voltage of the positive terminal of the photovoltaic string to ground is the voltage of the entire string. The DC current generated by the photovoltaic string flows through the positive output terminal PV+ of the photovoltaic string to the subsequent devices, then returns to the negative output terminal, and finally flows into the grounding reference point, forming a complete loop. At this time, the leakage current to ground is extremely small (ideally 0), because there is only normal insulation resistance between the positive terminal and ground.

[0023] When an insulation fault occurs in a photovoltaic (PV) module within a PV string, a fault occurs somewhere within the string where the positive terminal is directly (or with low impedance) connected to a grounding component (such as a metal frame or support). Since the first output terminal of the PV system is already grounded, this fault point effectively creates a low-impedance short-circuit path between the positive terminal of the faulty PV module and ground (i.e., the reference point for the negative terminal). At this time, the current generated by the faulty PV string no longer flows to subsequent stages but preferentially flows directly to the ground through the fault point and back to the common grounding point. Because other healthy PV strings are connected in parallel with the faulty PV string, the positive voltage of the healthy PV strings is much higher than that of the faulty PV string. Therefore, the current generated by the healthy strings not only flows to the inverter but also flows in reverse through the parallel positive bus to the positive terminal of the faulty PV string, causing the current signal at the positive output terminal of the faulty PV string to decrease or reverse.

[0024] When the first output terminal is positive, the second output terminal is negative. When an insulation fault occurs in a photovoltaic (PV) module within a PV string, since the positive terminal of the PV system is already grounded, this fault point effectively creates a low-impedance short-circuit path between the positive terminal of the faulty PV module and ground. At this time, the current generated by the faulty string preferentially flows directly to the ground through the fault point and returns to the common grounding point, causing a decrease in the voltage between the positive and negative terminals of the faulty PV string, with the negative terminal voltage increasing relative to normal conditions. Since other normal PV strings are connected in parallel with the faulty PV string, the negative terminal voltage of the healthy PV strings is lower than that of the faulty PV string. Therefore, the current from the faulty PV string will flow through its negative output terminal to other healthy PV strings, causing the current signal at the negative output terminal of the faulty PV string to increase or reverse.

[0025] Based on this, this embodiment can determine whether an insulation fault has occurred in a photovoltaic string by observing the changes in the current signal at the second pole output terminal of each photovoltaic string.

[0026] As can be seen from the above embodiments, the insulation testing method for photovoltaic strings provided in this embodiment no longer requires testing each string individually with an insulation resistance tester. Instead, it relies on the MPPT module and preset switch integrated into the photovoltaic system to complete signal acquisition without shutting down the photovoltaic system, thereby significantly simplifying the string-level insulation testing process and significantly improving the string-level insulation testing efficiency. Furthermore, since the photovoltaic strings within the same MPPT module are connected in parallel, closing the preset switch allows for the simultaneous acquisition of the second-pole current signals of multiple strings, enabling parallel detection of the insulation impedance of multiple photovoltaic strings. This significantly shortens the testing time and is particularly suitable for large-scale photovoltaic power plants containing a large number of photovoltaic strings, effectively improving the efficiency of string-level insulation fault detection. Simultaneously, the testing process does not require system shutdown, reducing energy waste caused by frequent power-on and power-off cycles. On the other hand, the current signal can directly reflect the conduction state of the string circuit. Once an insulation fault occurs, an abnormal grounding circuit will be formed, causing the first current signal to show characteristic changes. Based on the characteristic changes of this signal, fault signs can be quickly captured. Compared with traditional resistance testing, it is more real-time and can promptly block the risks of leakage, short circuit, and arc discharge caused by insulation faults, extend the service life of the photovoltaic system, and ensure the long-term safe and stable operation of the system.

[0027] In one possible implementation, the specific implementation process of S102 includes: S201: Determine whether the signal flow direction of the first current signal is consistent with the preset signal flow direction; wherein, the preset signal flow direction is the signal flow direction of the first current signal when the photovoltaic string does not experience an insulation fault; S202: If the signal flow direction of the first current signal of the photovoltaic string is opposite to the preset signal flow direction, then it is determined that the photovoltaic string has an insulation fault.

[0028] In this embodiment, the preset signal flow direction is the signal flow direction of the first current signal when the photovoltaic string has not experienced any faults. When the signal flow direction of the first current signal of the photovoltaic string is opposite to the preset signal flow direction, it is determined that the photovoltaic string has experienced an insulation fault; if the signal flow direction of the first current signal of the photovoltaic string is the same as the preset signal flow direction, it is determined that the photovoltaic string has not experienced an insulation fault.

[0029] In one possible implementation, another step in S102 includes: When the preset switch is open, the current signal at the second pole output terminal of the photovoltaic string is acquired and used as the second current signal; If the second current signal of the same photovoltaic string flows in the opposite direction to the first current signal, then the photovoltaic string is determined to have an insulation fault.

[0030] The above embodiments compare the flow direction of a first current signal with the flow direction of a preset signal (or a second current signal monitored in real time) for each photovoltaic string. If the two are reversed, an insulation fault is determined to have occurred in that string. This judgment logic is simple and efficient, requiring no complex steps such as comparing the magnitude of current signals. Execution only requires basic logic judgment of flow direction comparison, resulting in low computing power requirements and fast response speed. Fault determination for a single photovoltaic string can be completed in a short time, significantly shortening the fault diagnosis cycle. From an operation and maintenance application perspective, the explicit logic of reverse flow indicating a fault lowers the technical threshold for operation and maintenance personnel, allowing for quick location of faulty strings without the need for additional parameter analysis, thus reducing the workload and time costs of operation and maintenance.

[0031] In one possible implementation, prior to S102, the method provided in this embodiment further includes: When the preset switch is in the off state, the voltage between the positive and negative output terminals of each MPPT module is obtained and used as the first voltage; When the preset switch is closed, the voltage between the positive and negative output terminals of each MPPT module is acquired and used as the second voltage. Accordingly, the specific implementation process of S102 includes: Based on the first current signal of the photovoltaic string and the relationship between the first and second voltages of the MPPT module where the photovoltaic string is located, it is determined whether the photovoltaic string has an insulation fault.

[0032] In this embodiment, when no insulation fault occurs in the photovoltaic string, the voltage between the positive and negative output terminals of each MPPT module can be detected. This output voltage is typically the sum of the voltages of each photovoltaic module in a single photovoltaic string.

[0033] When an insulation fault occurs in a photovoltaic (PV) module within a PV string, a fault occurs where the positive terminal is directly (or with low impedance) connected to a grounding component (such as a metal frame or bracket). Since the first output terminal of the PV system is grounded, this fault point effectively creates a low-impedance short-circuit path between the positive terminal of the faulty PV module and ground (i.e., the reference point of the negative terminal). At this time, the voltage of the faulty PV string decreases, while the voltage of other PV strings within the same MPPT module is higher, resulting in reverse voltage flow into the faulty PV string and causing a decrease in the overall voltage of the MPPT module. Based on this principle, this embodiment can collect the first voltage of the MPPT module when the preset switch is open and the second voltage when the preset switch is closed, comparing the magnitudes of the first and second voltages to determine if an insulation fault has occurred in the MPPT module. If an insulation fault is detected in the PV string, and the MPPT module containing that PV string also detects an insulation fault, then the PV string is ultimately determined to have an insulation fault.

[0034] The above method can improve the accuracy of insulation testing by redundancy in the insulation testing at the MPPT level and the photovoltaic string level.

[0035] As can be seen from the above embodiments, this embodiment can comprehensively determine whether an insulation fault has occurred based on two conditions: abnormal current and voltage change, by comparing the magnitude change of the terminal voltage value of the MPPT module in the open and closed states of the preset switch. This dual verification mechanism can improve the accuracy of insulation detection, effectively filter out abnormal signals caused by instantaneous errors of a single sensor, electromagnetic interference or other non-insulation fault factors, significantly reduce the false alarm rate of the system, and make the diagnostic results more reliable.

[0036] In one possible implementation, further steps of S102 include: If the signal flow direction of the first current signal of the photovoltaic string is opposite to the preset signal flow direction, and the second voltage of the MPPT module corresponding to the photovoltaic string is less than the first voltage, then the photovoltaic string is determined to have an insulation fault.

[0037] In this embodiment, when there is a photovoltaic string with an insulation fault in the same MPPT module, other photovoltaic strings connected in parallel will backfeed voltage to the faulty photovoltaic string, causing the overall voltage of the MPPT module to decrease. Therefore, the second voltage of the MPPT module will be less than the first voltage. Based on this, it can be determined that there is a photovoltaic string with an insulation fault in the MPPT module. Combined with the signal flow direction of the first current signal of each photovoltaic string in the MPPT module, it can be comprehensively determined whether the photovoltaic string has an insulation fault.

[0038] As can be seen from the above embodiments, this embodiment clarifies the specific judgment criteria for current and voltage. Only when the signal flow direction of the first current signal is opposite to the preset signal flow direction, and the second voltage of the MPPT module corresponding to the photovoltaic string is less than the first voltage, can it be determined as an insulation fault, significantly improving the consistency of the detection method. Secondly, the superposition of dual conditions improves the accuracy of insulation fault judgment, effectively isolating the influence of single-point faults. Occasional errors of the current sensor will not trigger false alarms when the voltage parameters are normal; conversely, brief voltage fluctuations will not lead to misjudgment when the current direction is normal, ensuring that the system only determines that an insulation fault has occurred when both the current and voltage parameters point to the same fault conclusion.

[0039] In one possible implementation, the first pole output terminal is a negative pole output terminal; the preset signal flow direction is from inside to outside; the specific implementation process of S202 includes: If the signal flow direction of the first current signal of the photovoltaic string is opposite to the flow direction from the inside to the outside, then it is determined that the photovoltaic string has an insulation fault.

[0040] In this embodiment, when the first output terminal is the negative output terminal, the second output terminal is the positive output terminal. That is, the negative output terminal of the photovoltaic string is grounded, and the current signal at its positive output terminal is detected. When the photovoltaic string does not experience an insulation fault, the current signal at its positive output terminal flows from the inside of the photovoltaic string to the outside. When the photovoltaic string experiences a fault, due to backflow from other photovoltaic strings, the current signal at the positive output terminal of the photovoltaic string flows from the outside to the inside. Therefore, the direction of the first current signal's flow can be used to determine whether the photovoltaic string has experienced an insulation fault.

[0041] As can be seen from the above embodiments, this embodiment, targeting the negative grounding architecture of a photovoltaic system, clearly defines the preset signal flow direction from the inside out, ensuring that the current signal acquisition and judgment benchmark perfectly matches the current flow pattern of the negative grounding system, significantly improving the accuracy of insulation fault detection under this architecture. Secondly, the clearly defined preset signal flow direction from the inside out provides clear guidance for system installation and commissioning, eliminating the need for repeated testing and adjustments, enabling rapid location of faulty strings, timely circuit disconnection, and prevention of heat accumulation and equipment damage.

[0042] In one possible implementation, the first pole output terminal is a positive pole output terminal; the preset signal flow direction is from the outside to the inside; the specific implementation process of S202 includes: If the signal flow direction of the first current signal of the photovoltaic string is opposite to the flow direction from the outside to the inside, then it is determined that the photovoltaic string has an insulation fault.

[0043] In this embodiment, when the first output terminal is the positive output terminal, the second output terminal is the negative output terminal. That is, the positive output terminal of the photovoltaic string is grounded, and the current signal at its negative output terminal is detected. When the photovoltaic string does not experience an insulation fault, the current signal at its negative output terminal flows from the outside to the inside of the photovoltaic string. When the photovoltaic string experiences a fault, since its positive output terminal is grounded, the voltage value (negative value) at the negative output terminal will increase due to short circuits in some components. Since the negative output terminal is connected to the negative terminals of other photovoltaic strings, and the negative voltage of other normal photovoltaic strings is lower than that of this photovoltaic string, the voltage of the photovoltaic string with the insulation fault will flow back through its negative output terminal to other photovoltaic strings in the same MPPT module, causing the current signal at the negative output terminal of this photovoltaic string to reverse. Therefore, whether the photovoltaic string has experienced an insulation fault can be determined based on the signal flow direction of the first current signal.

[0044] As can be seen from the above embodiments, this embodiment, for the positive grounding architecture of a photovoltaic system, clearly defines the preset signal flow direction from the outside to the inside, ensuring that the current signal acquisition and judgment benchmark fully matches the current flow pattern of the positive grounding system, significantly improving the accuracy of insulation fault detection under this architecture. Secondly, the clearly defined preset signal flow direction from the outside to the inside provides clear guidance for system installation and commissioning, eliminating the need for repeated testing and adjustments, enabling rapid location of faulty strings, timely circuit disconnection, and prevention of heat accumulation and equipment damage.

[0045] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0046] The following are device embodiments of the present invention. For details not described in detail, please refer to the corresponding method embodiments described above.

[0047] Figure 3 A schematic diagram of the insulation detection device for photovoltaic strings provided in an embodiment of the present invention is shown. For ease of explanation, only the parts related to the embodiment of the present invention are shown, and are described in detail below: like Figure 3 As shown, the insulation testing device 100 for photovoltaic strings includes: The current acquisition module 110 is used to acquire the current signal of the second pole output terminal of each photovoltaic string when the preset switch is closed, and use it as the first current signal; the second pole output terminal is another output terminal other than the first pole output terminal. The insulation fault detection module 120 is used to determine whether an insulation fault has occurred in each photovoltaic string based on the first current signal of that photovoltaic string.

[0048] In one possible implementation, the insulation fault detection module 120 includes: The signal flow direction determination unit is used to determine whether the signal flow direction of the first current signal is consistent with the preset signal flow direction; wherein, the preset signal flow direction is the signal flow direction of the first current signal when the photovoltaic string does not experience an insulation fault; An insulation fault determination unit is used to determine that an insulation fault has occurred in the photovoltaic string if the signal flow direction of the first current signal of the photovoltaic string is opposite to the preset signal flow direction.

[0049] In one possible implementation, the insulation detection device 100 for the photovoltaic string further includes a voltage acquisition module for: When the preset switch is in the off state, the voltage between the positive and negative output terminals of each MPPT module is obtained and used as the first voltage; When the preset switch is closed, the voltage between the positive and negative output terminals of each MPPT module is acquired and used as the second voltage. Accordingly, the insulation fault detection module is specifically used for: Based on the first current signal of the photovoltaic string and the relationship between the first and second voltages of the MPPT module where the photovoltaic string is located, it is determined whether the photovoltaic string has an insulation fault.

[0050] In one possible implementation, the insulation fault detection module is further used for: If the signal flow direction of the first current signal of the photovoltaic string is opposite to the preset signal flow direction, and the second voltage of the MPPT module corresponding to the photovoltaic string is less than the first voltage, then the photovoltaic string is determined to have an insulation fault.

[0051] In one possible implementation, the first pole output terminal is a negative pole output terminal; the preset signal flow direction is from inside to outside; the insulation fault judgment unit is specifically used for: If the signal flow direction of the first current signal of the photovoltaic string is opposite to the flow direction from the inside to the outside, then it is determined that the photovoltaic string has an insulation fault.

[0052] In one possible implementation, the first pole output terminal is a positive pole output terminal; the preset signal flow direction is from the outside to the inside; the insulation fault judgment unit is specifically used for: If the signal flow direction of the first current signal of the photovoltaic string is opposite to the flow direction from the outside to the inside, then it is determined that the photovoltaic string has an insulation fault.

[0053] Figure 4 This is a schematic diagram of the controller provided in an embodiment of the present invention. Figure 4As shown, the controller 4 in this embodiment includes a processor 40, a memory 41, and a computer program 42 stored in the memory 41 and executable on the processor 40. When the processor 40 executes the computer program 42, it implements the steps in the insulation detection method embodiments of the various photovoltaic strings described above, for example... Figure 2 Steps S101 to S102 are shown. Alternatively, when the processor 40 executes the computer program 42, it implements the functions of each module / unit in the above-described device embodiments.

[0054] For example, the computer program 42 may be divided into one or more modules / units, which are stored in the memory 41 and executed by the processor 40 to complete the present invention. The one or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program 42 in the controller 4.

[0055] The controller 4 can be a computing device such as a desktop computer, laptop, handheld computer, or cloud server. The controller 4 may include, but is not limited to, a processor 40 and a memory 41. Those skilled in the art will understand that... Figure 4 This is merely an example of controller 4 and does not constitute a limitation on controller 4. It may include more or fewer components than shown, or combine certain components, or different components. For example, the controller may also include input / output devices, network access devices, buses, etc.

[0056] The processor 40 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0057] The memory 41 can be an internal storage unit of the controller 4, such as a hard disk or memory of the controller 4. The memory 41 can also be an external storage device of the controller 4, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the controller 4. Furthermore, the memory 41 can include both internal storage units and external storage devices of the controller 4. The memory 41 is used to store the computer program and other programs and data required by the controller. The memory 41 can also be used to temporarily store data that has been output or will be output.

[0058] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0059] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0060] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0061] In the embodiments provided by this invention, it should be understood that the disclosed devices / controllers and methods can be implemented in other ways. For example, the device / controller embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0062] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0063] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0064] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the insulation detection method embodiments for each photovoltaic string described above. The computer program includes computer program code, which can be in the form of source code, object code, executable file, or some intermediate form. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0065] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for insulation testing of photovoltaic strings, characterized in that, This technology is applied to photovoltaic systems. The photovoltaic system includes multiple MPPT modules and a preset switch. Each MPPT module includes multiple photovoltaic strings. The multiple photovoltaic strings of the same MPPT module are connected in parallel. The first pole output terminal of each MPPT module is grounded through the preset switch. The first output terminal is either the positive or negative output terminal of the photovoltaic string; The method includes: When the preset switch is closed, the current signal of the second pole output terminal of each photovoltaic string is acquired and used as the first current signal; the second pole output terminal is another output terminal other than the first pole output terminal. For each photovoltaic string, the first current signal of the photovoltaic string is used to determine whether an insulation fault has occurred.

2. The insulation testing method for photovoltaic strings according to claim 1, characterized in that, The step of determining whether an insulation fault has occurred in each photovoltaic string based on the first current signal of that photovoltaic string includes: Determine whether the signal flow direction of the first current signal is consistent with the preset signal flow direction; wherein, the preset signal flow direction is the signal flow direction of the first current signal when the photovoltaic string does not experience an insulation fault; If the signal flow direction of the first current signal of the photovoltaic string is opposite to the preset signal flow direction, then it is determined that the photovoltaic string has an insulation fault.

3. The insulation testing method for photovoltaic strings according to claim 1, characterized in that, Before determining whether an insulation fault has occurred in the photovoltaic string based on the first current signal of the photovoltaic string, the method further includes: When the preset switch is in the off state, the voltage between the positive and negative output terminals of each MPPT module is obtained and used as the first voltage; When the preset switch is closed, the voltage between the positive and negative output terminals of each MPPT module is acquired and used as the second voltage. Accordingly, determining whether an insulation fault has occurred in the photovoltaic string based on the first current signal of the photovoltaic string includes: Based on the first current signal of the photovoltaic string and the relationship between the first and second voltages of the MPPT module where the photovoltaic string is located, it is determined whether the photovoltaic string has an insulation fault.

4. The insulation testing method for photovoltaic strings according to claim 3, characterized in that, The step of determining whether an insulation fault has occurred in the photovoltaic string based on the first current signal of the photovoltaic string and the relationship between the first voltage and the second voltage of the MPPT module containing the photovoltaic string includes: If the signal flow direction of the first current signal of the photovoltaic string is opposite to the preset signal flow direction, and the second voltage of the MPPT module corresponding to the photovoltaic string is less than the first voltage, then the photovoltaic string is determined to have an insulation fault.

5. The insulation testing method for photovoltaic strings according to claim 2, characterized in that, The first output terminal is the negative output terminal; the preset signal flow direction is from inside to outside; if the signal flow direction of the first current signal of the photovoltaic string is opposite to the preset signal flow direction, then it is determined that the photovoltaic string has an insulation fault, including: If the signal flow direction of the first current signal of the photovoltaic string is opposite to the flow direction from the inside to the outside, then it is determined that the photovoltaic string has an insulation fault.

6. The insulation testing method for photovoltaic strings according to claim 2, characterized in that, The first output terminal is a positive output terminal; the preset signal flow direction is from the outside to the inside; if the signal flow direction of the first current signal of the photovoltaic string is opposite to the preset signal flow direction, then it is determined that the photovoltaic string has an insulation fault, including: If the signal flow direction of the first current signal of the photovoltaic string is opposite to the flow direction from the outside to the inside, then it is determined that the photovoltaic string has an insulation fault.

7. An insulation testing device for a photovoltaic string, characterized in that, This technology is applied to photovoltaic systems. The photovoltaic system includes multiple MPPT modules and a preset switch. Each MPPT module includes multiple photovoltaic strings. The multiple photovoltaic strings of the same MPPT module are connected in parallel. The first pole output terminal of each MPPT module is grounded through the preset switch. The first output terminal is either the positive or negative output terminal of the photovoltaic string; The device includes: The current acquisition module is used to acquire the current signal of the second pole output terminal of each photovoltaic string when the preset switch is closed, and use it as the first current signal; the second pole output terminal is another output terminal other than the first pole output terminal; The insulation fault detection module is used to determine whether an insulation fault has occurred in each photovoltaic string based on the first current signal of that photovoltaic string.

8. A controller comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the insulation detection method for photovoltaic strings as described in any one of claims 1 to 6.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the insulation detection method for photovoltaic strings as described in any one of claims 1 to 6.

10. A photovoltaic system, characterized in that, It includes photovoltaic strings and the controller as described in claim 8.

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