Insulation resistance detection method, system and equipment of photovoltaic power generation system and medium

Abstract

The invention discloses an insulation resistance detection method, system and device of a photovoltaic power generation system and a medium, and relates to the technical field of insulation resistance detection of the photovoltaic power generation system. The method comprises the steps of obtaining a ground insulation resistance value of the photovoltaic inverter, and determining an insulation fault level according to the ground insulation resistance value of the photovoltaic inverter. And whether MPPT-level insulation impedance detection is carried out is determined according to the insulation fault level. If MPPT-level insulation impedance detection is carried out, the fault type is determined, and the fault type comprises a negative electrode grounding fault or a non-negative electrode grounding fault. And under the condition that the fault type is a non-cathode grounding fault, sequentially disturbing the plurality of MPPT branches, and determining a grounding MPPT branch. And determining the photovoltaic module with the insulation impedance fault in the grounded MPPT branch. According to the invention, fault positioning is carried out according to the sequence from the whole machine to the MPPT branch to the photovoltaic module, and the fault positioning precision is high.

Description

Technical Field

[0001] The present invention relates to the technical field of insulation impedance detection of photovoltaic power generation systems, and in particular to an insulation impedance detection method for photovoltaic power generation systems, an insulation impedance detection system for photovoltaic power generation systems, a computer device, and a readable storage medium. Background Art

[0002] As a major clean energy source, photovoltaic power generation is experiencing rapid growth, and its safe operation is crucial. The quality of a system's insulation performance is directly related to personnel safety, stable equipment operation, and long-term profitability. Photovoltaic power generation systems (especially the DC side) operate in high-voltage DC environments ranging from hundreds to thousands of volts. Components and cables are exposed to harsh outdoor conditions (such as temperature and humidity fluctuations, salt spray, aging, and mechanical damage). This can cause insulation materials to gradually degrade or even break, resulting in a decrease in insulation resistance to ground.

[0003] Once insulation fails, high voltage can leak into the ground through the damaged point (generating "leakage current"), posing multiple life-threatening risks: electric shock is the primary threat, and contact with live casing or grounding can be fatal for maintenance personnel. Sustained leakage current accelerates equipment corrosion, generating localized high temperatures and, in severe cases, uncontrollable electrical fires. Ground faults can also cause core equipment like inverters to shut down, resulting in power generation losses. Unlike AC systems, the DC side of a photovoltaic system has no voltage zero crossing, making fault arcs difficult to extinguish and more dangerous.

[0004] Insulation impedance measures the impedance between photovoltaic modules and their surroundings and is a key indicator for assessing the safety of photovoltaic power generation systems. Good insulation impedance prevents current leakage, thereby reducing the risk of electric shock, equipment damage, and system downtime. Insulation impedance testing can promptly detect insulation degradation and implement appropriate repair measures, thereby ensuring the safe and stable operation of the photovoltaic power generation system. Insulation impedance testing primarily targets key equipment in a photovoltaic power generation system, including photovoltaic modules, DC combiner boxes, DC distribution boards, AC distribution boards, and inverters. The insulation performance of these devices directly impacts the safety and stability of the entire system.

[0005] Current DC system insulation testing devices primarily use active methods (such as AC injection, which measures the response by injecting a specific frequency signal) or passive methods (such as the balanced bridge method). These methods measure and evaluate the insulation impedance of the DC positive and negative busbars to ground in real time or periodically. These methods can only locate the fault within the entire system, not the specific MPPT (Maximum Power Point Tracking) branch or the faulty PV module, resulting in low fault location accuracy. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that the traditional insulation impedance detection method can only locate the entire machine, but cannot locate the specific MPPT or the faulty photovoltaic module, and the fault location accuracy is not high.

[0007] In view of the above-mentioned deficiencies in the existing technology, the following solutions are provided:

[0008] In a first aspect, the present invention provides an insulation impedance detection method for a photovoltaic power generation system, comprising: obtaining the insulation impedance value of a photovoltaic inverter to ground, and determining the insulation fault level based on the insulation impedance value of the photovoltaic inverter to ground. Determining whether to perform MPPT-level insulation impedance detection based on the insulation fault level. If MPPT-level insulation impedance detection is performed, the fault type is determined, which includes a negative ground fault or a non-negative ground fault. If the fault type is a non-negative ground fault, multiple MPPT branches are disturbed in sequence to determine the grounded MPPT branch. Furthermore, the photovoltaic module having an insulation impedance fault in the grounded MPPT branch is determined.

[0009] Optionally, determining the insulation fault level based on the insulation resistance value of the photovoltaic inverter to ground includes: determining the insulation fault level as no insulation fault in response to the insulation resistance value of the photovoltaic inverter to ground being greater than a first preset value; determining the insulation fault level as insulation fault warning in response to the insulation resistance value of the photovoltaic inverter to ground being less than or equal to the first preset value but greater than a second preset value; and determining the insulation fault level as insulation fault occurrence in response to the insulation resistance value of the photovoltaic inverter to ground being less than or equal to the second preset value.

[0010] Optionally, determining whether to perform MPPT-level insulation impedance detection according to the insulation fault level includes: in response to the insulation fault level indicating that an insulation fault has occurred, determining to perform MPPT-level insulation impedance detection.

[0011] Optionally, determining whether a negative pole ground fault or a non-negative pole ground fault has occurred includes: obtaining a voltage relative to ground at the negative pole of the busbar. In response to the voltage relative to ground at the negative pole of the busbar being less than or equal to a third preset value, determining that a negative pole ground fault has occurred. Furthermore, in response to the voltage relative to ground at the negative pole of the busbar being greater than the third preset value, determining that a non-negative pole ground fault has occurred.

[0012] Optionally, sequentially perturbing a plurality of MPPT branches to determine a grounded MPPT branch includes: sequentially perturbing each of the plurality of MPPT branches so that the voltage of the MPPT branch currently being perturbed decreases while the voltages of the other MPPT branches remain unchanged. Furthermore, comparing the voltage to ground of the negative pole of the busbar of each of the plurality of MPPT branches before the perturbation with the voltage to ground of the negative pole of the busbar of each of the plurality of MPPT branches after the perturbation, and determining the grounded MPPT branch from the plurality of MPPT branches based on the comparison results.

[0013] Optionally, the grounded MPPT branch is an MPPT branch among the multiple MPPT branches, wherein the difference between the voltage of the negative pole of the busbar to the ground before the disturbance and the voltage of the negative pole of the busbar to the ground after the disturbance is greater than a fourth preset value.

[0014] Optionally, determining a photovoltaic assembly having an insulation impedance fault in a grounded MPPT branch includes determining a voltage relative to ground of a busbar cathode and an MPPT voltage of the grounded MPPT branch. Furthermore, determining the photovoltaic assembly having an insulation impedance fault based on the voltage relative to ground of the busbar cathode and the MPPT voltage of the grounded MPPT branch.

[0015] Optionally, determining a photovoltaic module experiencing an insulation impedance fault based on the voltage relative to ground of the negative pole of the busbar and the MPPT voltage of the grounded MPPT branch includes: calculating a first percentage; determining the number of photovoltaic modules in the grounded MPPT branch; numbering the plurality of photovoltaic modules in the grounded MPPT branch in increasing order from the negative pole of the photovoltaic string to the positive pole of the photovoltaic string; calculating a first product; obtaining a first number and a second number based on the first product; and obtaining a third number based on the first number. Furthermore, determining a photovoltaic module experiencing an insulation impedance fault among the photovoltaic modules numbered first, second, or third. The first percentage ratio is the percentage data obtained by dividing the voltage relative to ground of the negative pole of the busbar by the MPPT voltage of the grounded MPPT branch. The first product is the product of the number of photovoltaic modules in the grounded MPPT branch and the first percentage. The first number is greater than or equal to the first product and has at most one integer between it and the first product. The second number is less than or equal to the first product and has at most one integer between it and the first product. The third number is equal to the sum of the first number and 1.

[0016] In a second aspect, the present invention provides an insulation impedance detection system for a photovoltaic power generation system, comprising an insulation fault level determination module, an impedance detection determination module, a grounding electrode determination module, an MPPT branch determination module, and a fault point determination module. The insulation fault level determination module is configured to obtain the insulation impedance value of the photovoltaic inverter to the ground, and determine the insulation fault level based on the insulation impedance value of the photovoltaic inverter to the ground. The impedance detection determination module is configured to determine whether to perform MPPT-level insulation impedance detection based on the insulation fault level. The grounding electrode determination module is configured to determine the fault type if MPPT-level insulation impedance detection is performed, and the fault type includes a negative pole grounding fault or a non-negative pole grounding fault. The MPPT branch determination module is configured to, in the case where the fault type is a non-negative pole grounding fault, sequentially disturb multiple MPPT branches to determine the grounded MPPT branch. The fault point determination module is configured to determine the photovoltaic component in the grounded MPPT branch that has an insulation impedance fault.

[0017] In a third aspect, the present invention provides a computer device comprising a memory and a processor, wherein a computer program is stored in the memory. When the processor runs the computer program stored in the memory, the processor executes the above-mentioned insulation impedance detection method for the photovoltaic power generation system.

[0018] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the processor executes the above-mentioned insulation impedance detection method for the photovoltaic power generation system.

[0019] The insulation impedance detection method, system, device and medium of a photovoltaic power generation system provided by the present invention determine, based on the insulation impedance value of the photovoltaic inverter to ground, whether the insulation fault level is a whole-machine-level insulation fault or an MPPT-level insulation fault. If it is an MPPT-level insulation fault, the fault type is further determined to be a negative-pole grounding fault or a non-negative-pole grounding fault. This achieves fault location in the order from the whole machine to the MPPT branch to the photovoltaic module, with high fault location accuracy. Compared with whole-machine-level insulation fault detection, this improves the insulation impedance detection efficiency of a multi-channel photovoltaic power generation system and can reduce the workload of subsequent fault troubleshooting. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart of a method for detecting insulation impedance of a photovoltaic power generation system according to an embodiment of the present invention;

[0021] Figure 2 This is a circuit diagram of insulation impedance detection of a photovoltaic power generation system according to an embodiment of the present invention;

[0022] Figure 3 This is another insulation impedance detection circuit diagram of a photovoltaic power generation system according to an embodiment of the present invention;

[0023] Figure 4 This is a flow chart of another method for detecting insulation impedance of a photovoltaic power generation system according to an embodiment of the present invention;

[0024] Figure 5 This is a flow chart of another method for detecting insulation impedance of a photovoltaic power generation system according to an embodiment of the present invention;

[0025] Figure 6 This is a circuit diagram of an insulation impedance detection circuit of another photovoltaic power generation system in an embodiment of the present invention;

[0026] Figure 7 This is a flow chart of another method for detecting insulation impedance of a photovoltaic power generation system according to an embodiment of the present invention;

[0027] Figure 8 This is a circuit diagram of insulation impedance detection of another photovoltaic power generation system in an embodiment of the present invention;

[0028] Figure 9 This is a flow chart of another method for detecting insulation impedance of a photovoltaic power generation system according to an embodiment of the present invention;

[0029] Figure 10 This is a flow chart of another method for detecting insulation impedance of a photovoltaic power generation system according to an embodiment of the present invention;

[0030] Figure 11 This is a flow chart of another method for detecting insulation impedance of a photovoltaic power generation system according to an embodiment of the present invention;

[0031] Figure 12 This is a circuit diagram of insulation impedance detection of another photovoltaic power generation system in an embodiment of the present invention;

[0032] Figure 13 This is an architecture diagram of an insulation impedance detection system for a photovoltaic power generation system according to an embodiment of the present invention;

[0033] Figure 14 This is a structural diagram of a computer device in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0035] It should be understood that the specific embodiments and drawings described herein are only used to explain the present invention rather than to limit the present invention.

[0036] It is understood that, in the absence of conflict, the various embodiments of the present invention and the various features in the embodiments may be combined with each other.

[0037] It can be understood that, for the convenience of description, the drawings of the present invention only show parts related to the present invention, while parts unrelated to the present invention are not shown in the drawings.

[0038] It can be understood that each unit and module involved in the embodiments of the present invention may correspond to only one physical structure, or may be composed of multiple physical structures, or multiple units and modules may be integrated into one physical structure.

[0039] It will be understood that, without conflict, the functions and steps marked in the flowcharts and block diagrams of the present invention may occur in an order different from that marked in the drawings.

[0040] It is understood that the flowcharts and block diagrams of the present invention illustrate the possible architectures, functions, and operations of the systems, devices, equipment, and methods according to various embodiments of the present invention. Each box in the flowchart or block diagram may represent a unit, module, program segment, or code, which contains executable instructions for implementing the specified functions. Moreover, each box or combination of boxes in the block diagram and flowchart may be implemented using a hardware-based system that implements the specified functions, or may be implemented using a combination of hardware and computer instructions.

[0041] It can be understood that the units and modules involved in the embodiments of the present invention can be implemented by software or hardware. For example, the units and modules can be located in a processor.

[0042] Typically, a photovoltaic power generation system is equipped with multiple MPPT branches, each containing multiple photovoltaic (PV) modules. Multiple MPPT branches are typically connected in parallel. This means each MPPT branch operates independently and does not affect each other. Parallel connection makes the system more flexible and reliable. If an MPPT branch fails, the other branches can still function normally, ensuring continuous system operation. Multiple MPPT branches are typically connected to different input ports of the inverter. The inverter can monitor and control each MPPT branch separately to ensure that they always operate near their maximum power point. For example, a string inverter typically has multiple MPPT channels (i.e., branches), each of which can independently track the maximum power point of one or more photovoltaic module strings (or PV strings). This design allows string inverters to better adapt to complex lighting conditions and module layouts, improving the overall power generation efficiency and stability of the system.

[0043] The embodiment of the present invention provides a method for detecting insulation impedance of a photovoltaic power generation system. Figure 1 As shown, the method includes steps 101 to 105.

[0044] Step 101: Obtain the insulation resistance value of the photovoltaic inverter to ground, and determine the insulation fault level according to the insulation resistance value of the photovoltaic inverter to ground.

[0045] like Figure 2 and Figure 3 As shown in the whole machine insulation impedance detection circuit, Rx is the impedance of the positive pole of the photovoltaic string (or called PV+) to the ground, Ry is the impedance of the negative pole of the photovoltaic string (or called PV-) to the ground, and R1 and R2 are the equivalent impedances of the detection circuit. Let R = R1 = R2, and record Figure 2 "K1 closed, K2 open" and Figure 3 In the two cases of "K1 open, K2 closed", the voltage U between ground and PV- K1 and U K2 , combined with the bus voltage U bus According to Kirchhoff's current law, we can get formula (1).

[0046]

[0047] In formula (1), the insulation resistance value of the positive pole of all photovoltaic strings is Rx=Rx1 / / Rx2 / / ...Rxn, and the insulation resistance value of the negative pole of all photovoltaic strings is Ry=Ry1 / / Ry2 / / ...Ryn, where n is the number of photovoltaic strings.

[0048] Assume that the insulation resistance of the photovoltaic inverter to the ground is Rxy = Rx / / Ry, that is, the parallel value of Rx and Ry. Formula (2) can be calculated from formula (1).

[0049]

[0050] According to formula (2), the insulation resistance value of the photovoltaic inverter to ground can be calculated.

[0051] In some embodiments, in step 101, the method for determining the insulation fault level based on the insulation resistance value of the photovoltaic inverter to ground includes: determining the insulation fault level as no insulation fault in response to the insulation resistance value of the photovoltaic inverter to ground being greater than a first preset value; determining the insulation fault level as insulation fault warning in response to the insulation resistance value of the photovoltaic inverter to ground being less than or equal to the first preset value but greater than a second preset value; and determining the insulation fault level as insulation fault occurrence in response to the insulation resistance value of the photovoltaic inverter to ground being less than or equal to the second preset value.

[0052] It is understood that both the first preset value and the second preset value are preset, and the first preset value is greater than the second preset value. By setting the first and second preset values, the fault level can be subdivided. If the insulation resistance of the photovoltaic inverter to ground is less than or equal to the first preset value but greater than the second preset value, an alarm message can be issued to alert personnel and determine whether to take preemptive measures to prevent the fault.

[0053] For example, Figure 4 As shown, the first preset value can be a resistance value Rxy_Ref set according to the photovoltaic inverter standard, and the second preset value can be 1kΩ. Rxy_Ref is generally the resistance value obtained by dividing the maximum DC input voltage of the photovoltaic system by 30mA. For example, if the photovoltaic system has a DC side of 1500V and the maximum DC input voltage of the photovoltaic system is 1500V, the first preset value Rxy_Ref can be set to 50kΩ.

[0054] Step 102: Determine whether to perform MPPT-level insulation impedance detection according to the insulation fault level.

[0055] In some embodiments, the implementation method of step 102 includes: in response to the insulation fault level being an insulation fault, determining to perform an MPPT-level insulation impedance test.

[0056] It can be understood that the insulation fault level is an insulation fault, which means that the insulation impedance value of the photovoltaic inverter to ground is less than or equal to the second preset value. At this time, MPPT-level insulation impedance detection is required to determine the specific fault point.

[0057] Step 103: If the MPPT level insulation impedance test is performed, the fault type is determined.

[0058] In step 103 , the fault type includes a negative pole grounding fault or a non-negative pole grounding fault.

[0059] In some embodiments, as Figure 5 As shown, in step 103 , the method for determining whether a positive pole grounding fault or a negative pole grounding fault occurs includes steps 501 to 503 .

[0060] Step 501: Obtain the voltage of the negative electrode of the busbar to ground.

[0061] Step 502: In response to the voltage of the negative electrode of the busbar to ground being less than or equal to a third preset value, it is determined that a negative electrode grounding fault has occurred.

[0062] Step 503: In response to the voltage of the negative electrode of the busbar to ground being greater than a third preset value, it is determined that a non-negative electrode grounding fault has occurred.

[0063] Exemplarily, the third preset value may be 60V.

[0064] It can be understood that the inverter mainly samples the topology of multiple MPPTs with a common negative pole. Therefore, if the negative pole is grounded, it is impossible to identify which MPPT is grounded, and only the negative pole can be located. If the negative pole is not grounded, the voltage of BUS- to ground is greater than 60V; if the negative pole is grounded, the voltage of BUS- to ground is less than or equal to 60V, such as Figure 6 shown.

[0065] Step 104 : perturb multiple MPPT branches in sequence to determine the grounded MPPT branch.

[0066] In some embodiments, as Figure 7 As shown, the implementation method of step 104 includes steps 701 to 702.

[0067] Step 701: disturb each MPPT branch in a plurality of MPPT branches in turn, so that the voltage of the MPPT branch currently disturbed in the plurality of MPPT branches decreases, while the voltages of the other MPPT branches in the plurality of MPPT branches remain unchanged.

[0068] Step 702: Compare the voltage to ground of the negative pole of the busbar before each MPPT branch in the multiple MPPT branches is disturbed with the voltage to ground of the negative pole of the busbar after each MPPT branch in the multiple MPPT branches is disturbed, and determine the grounded MPPT branch from the multiple MPPT branches based on the comparison result.

[0069] In some embodiments, in step 702, the grounded MPPT branch is an MPPT branch among the multiple MPPT branches, wherein the difference between the voltage of the negative pole of the busbar to ground before the disturbance and the voltage of the negative pole of the busbar to ground after the disturbance is greater than a fourth preset value.

[0070] It can be understood that the voltage of the negative pole of the bus (or BUS-) to the ground is related to the MPPT voltage of the grounded circuit. Therefore, by disturbing the MPPT branches in sequence (BOOST duty cycle), when the grounded MPPT is disturbed, the voltage of BUS- to the ground will change with the change of the input voltage of the grounded MPPT; when the non-grounded MPPT is disturbed, the voltage of BUS- to the ground remains unchanged.

[0071] like Figure 8 As shown, taking the grounding of MPPT1 in two MPPT branches (each MPPT branch includes two photovoltaic modules) as an example, the voltage of BUS- to ground before the disturbance is recorded as The MPPT1 of the ground circuit is disturbed (the duty cycle of BOOST1 is controlled) to reduce the voltage of MPPT1 and keep the voltage of MPPT2 unchanged. The voltage of BUS- to ground after the disturbance is recorded as Then the change before and after the disturbance ΔUbus-PE1 Greater than 0V, as shown in formula (3).

[0072]

[0073] The ungrounded branch MPPT2 is disturbed (the duty cycle of BOOST2 is controlled) to reduce the voltage of MPPT2 and keep the voltage of MPPT1 unchanged. The voltage of BUS- to ground after the disturbance is recorded as The change before and after the disturbance ΔU bus-PE2 Close to 0V, as shown in formula (4).

[0074]

[0075] That is to say, when the grounded MPPT is disturbed (BOOST open-loop duty cycle), the voltage of BUS- to ground will change with the change of the input voltage of the grounded MPPT, and the MPPT is considered to be grounded; when the non-grounded MPPT is disturbed, the voltage of BUS- to ground remains unchanged, so it can be used to determine which MPPT is grounded.

[0076] Exemplarily, the fourth preset value may be 5V.

[0077] Step 105: Determine the photovoltaic module with insulation impedance fault in the grounded MPPT branch.

[0078] In some embodiments, as Figure 9 As shown, the implementation method of step 105 includes steps 901 to 902.

[0079] Step 901: Determine the voltage of the negative electrode of the busbar to ground and the MPPT voltage of the grounded MPPT branch.

[0080] Step 902: Determine the photovoltaic module with the insulation impedance fault based on the voltage of the negative pole of the busbar to ground and the MPPT voltage of the grounded MPPT branch.

[0081] It is understandable that after detecting an MPPT ground fault, further detection is performed on the suspected fault location to determine the grounding location. The grounding location is related to the voltage of the busbar negative pole to ground and the MPPT voltage of the grounded MPPT branch.

[0082] In some embodiments, as Figure 10 and Figure 11 As shown, the implementation method of step 902 includes steps 1001 to 1007.

[0083] Step 1001: Calculate a first percentage.

[0084] In step 1001, the first percentage is the percentage data of the voltage of the negative pole of the busbar to ground divided by the MPPT voltage of the grounded MPPT branch.

[0085] It can be understood that both the ground voltage of the bus negative pole and the MPPT voltage of the grounded MPPT branch can be sampled, and the ground voltage of the bus negative pole is divided by the MPPT voltage of the grounded MPPT branch to obtain a quotient, and the first percentage can be obtained based on this quotient.

[0086] Step 1002: Determine the number of photovoltaic modules in the grounded MPPT branch.

[0087] It is understandable that a MPPT circuit may include multiple photovoltaic modules. For example, the number of photovoltaic modules in the grounded MPPT branch is recorded as N.

[0088] Step 1003: Number the plurality of photovoltaic modules in the grounded MPPT branch in increasing order from the negative pole position of the photovoltaic string to the positive pole position of the photovoltaic string.

[0089] For example, the positive and negative poles of the photovoltaic string are respectively connected to the PV+ and PV- terminals of the inverter, and the multiple photovoltaic components in the grounded MPPT branch can be numbered in increasing order (for example, from 1 to N) in the direction from the PV- position of the inverter to the PV+ position of the inverter.

[0090] Step 1004: Calculate the first product.

[0091] In step 1004 , the first product is the product of the number of photovoltaic modules in the grounded MPPT branch and the first percentage.

[0092] Step 1005: Obtain a first number and a second number according to the first product.

[0093] In step 1005, the first number is greater than or equal to the first product and there is at most one integer between the first number and the first product. The second number is less than or equal to the first product and there is at most one integer between the first number and the first product.

[0094] Step 1006: Obtain a third number according to the first number.

[0095] In step 1006 , the third number is equal to the sum of the first number and 1.

[0096] Step 1007: Determine a photovoltaic assembly having an insulation impedance fault among the photovoltaic assemblies numbered first, second, or third.

[0097] For example, Figure 12As shown, the positive and negative poles of the PV string are connected to the PV+ and PV- terminals of the inverter, respectively. The PV- position of the inverter corresponds to 0%, and the PV+ position of the inverter corresponds to 100%. The grounding position is the BUS- to-ground voltage divided by the MPPT voltage of the corresponding circuit (MPPT voltage and BUS- to-ground voltage are obtained by inverter sampling). The fault location is the total number of PV modules in the PV string multiplied by the grounding position percentage.

[0098] For example, assuming there are 32 modules and the percentage of short-circuit locations is 83.5%, the first product is 26.72. The first number is 27, the second number is 26, and the third number is 28. Therefore, the fault location could be the 26th, 27th, or 28th PV module. With the first-numbered PV module (e.g., the 27th PV module) as the most likely fault location, the inverter detection accuracy is ±1 PV module.

[0099] Some embodiments of the present invention provide a method for detecting the insulation impedance of a photovoltaic power generation system. The method determines whether the insulation fault level is a whole-machine-level insulation fault or an MPPT-level insulation fault based on the insulation impedance value of the photovoltaic inverter to ground. If it is an MPPT-level insulation fault, the fault type is further determined to be a negative-pole grounding fault or a non-negative-pole grounding fault. This method achieves fault location in a sequence from the whole machine to the MPPT branch to the photovoltaic module, with high accuracy. Compared with whole-machine-level insulation fault detection, the method improves the efficiency of insulation impedance detection for multi-channel photovoltaic power generation systems and can reduce the workload of subsequent troubleshooting. Some embodiments of the present invention provide a method for detecting the insulation impedance of a photovoltaic power generation system. The method locates the insulation fault branch through voltage disturbance. Compared with methods such as adjusting the DC bus impedance to ground, this method can avoid the problem of false fault alarms caused by low insulation impedance in environments such as high temperatures. The detection logic is simple, the method is reliable, and compared with methods such as manually intervening in light intensity or photovoltaic-side input to solve the insulation impedance equation, it saves manpower and is highly practical. Furthermore, some embodiments of the present invention provide an insulation impedance detection method for a photovoltaic power generation system, which reduces the use of components, lowers the risk of detection failure due to component failure, enhances detection reliability, saves system costs, and has high engineering application value.

[0100] Some embodiments of the present invention provide an insulation impedance detection system for a photovoltaic power generation system, such as Figure 13 As shown, the insulation impedance detection system 1300 of the photovoltaic power generation system includes an insulation fault level determination module 1301 , an impedance detection determination module 1302 , a grounding electrode determination module 1303 , an MPPT branch determination module 1304 and a fault point determination module 1305 .

[0101] The insulation fault level determination module 1301 is configured to: obtain the insulation impedance value of the photovoltaic inverter to the ground, and determine the insulation fault level according to the insulation impedance value of the photovoltaic inverter to the ground.

[0102] In some embodiments, the insulation fault level determination module 1301 is configured to: determine the insulation fault level as no insulation fault in response to the insulation impedance value of the photovoltaic inverter to ground being greater than a first preset value; determine the insulation fault level as insulation fault warning in response to the insulation impedance value of the photovoltaic inverter to ground being less than or equal to the first preset value but greater than a second preset value; and determine the insulation fault level as insulation fault occurrence in response to the insulation impedance value of the photovoltaic inverter to ground being less than or equal to the second preset value.

[0103] The impedance detection determination module 1302 is configured to determine whether to perform MPPT-level insulation impedance detection according to the insulation fault level.

[0104] In some embodiments, the impedance detection determination module 1302 is configured to: in response to the insulation fault level being an insulation fault, determine to perform an MPPT-level insulation impedance detection.

[0105] The grounding electrode determination module 1303 is configured to: if the MPPT level insulation impedance detection is performed, determine the fault type, which includes a negative pole grounding fault or a non-negative pole grounding fault.

[0106] In some embodiments, the grounding electrode determination module 1303 is configured to: obtain the voltage of the negative pole of the busbar to ground; determine that a negative pole grounding fault has occurred in response to the voltage of the negative pole of the busbar to ground being less than or equal to a third preset value; and determine that a non-negative pole grounding fault has occurred in response to the voltage of the negative pole of the busbar to ground being greater than the third preset value.

[0107] The MPPT branch determination module 1304 is configured to, in response to a non-negative grounding fault, sequentially disturb multiple MPPT branches to determine a grounded MPPT branch.

[0108] In some embodiments, the MPPT branch determination module 1304 is configured to sequentially perturb each of the multiple MPPT branches such that the voltage of the MPPT branch currently being perturbed among the multiple MPPT branches decreases, while the voltages of the other MPPT branches among the multiple MPPT branches remain unchanged. Furthermore, the module 1304 is configured to compare the voltage to ground of the negative pole of the busbar before each of the multiple MPPT branches is perturbed with the voltage to ground of the negative pole of the busbar after each of the multiple MPPT branches is perturbed, and determine a grounded MPPT branch from the multiple MPPT branches based on the comparison results.

[0109] In some embodiments, the grounded MPPT branch is an MPPT branch among multiple MPPT branches, wherein the difference between the voltage of the negative pole of the busbar to the ground before the disturbance and the voltage of the negative pole of the busbar to the ground after the disturbance is greater than a fourth preset value.

[0110] The fault point determination module 1305 is configured to determine a photovoltaic assembly having an insulation impedance fault in a grounded MPPT branch.

[0111] In some embodiments, the fault point determination module 1305 is configured to determine the voltage of the negative pole of the busbar to ground and the MPPT voltage of the grounded MPPT branch, and to determine the photovoltaic module having the insulation impedance fault based on the voltage of the negative pole of the busbar to ground and the MPPT voltage of the grounded MPPT branch.

[0112] In some embodiments, the fault point determination module 1305 is configured to: calculate a first percentage; determine the number of photovoltaic modules in the grounded MPPT branch; number the plurality of photovoltaic modules in the grounded MPPT branch in increasing order from the negative pole position of the photovoltaic string to the positive pole position of the photovoltaic string; calculate a first product; obtain a first number and a second number based on the first product; obtain a third number based on the first number; and determine the photovoltaic module with an insulation impedance fault among the photovoltaic modules numbered first, second, or third. The first percentage ratio is the percentage data of the voltage to ground of the negative pole of the busbar divided by the MPPT voltage of the grounded MPPT branch. The first product is the product of the number of photovoltaic modules in the grounded MPPT branch and the first percentage. The first number is greater than or equal to the first product and there is at most one integer between the first number and the first product. The second number is less than or equal to the first product and there is at most one integer between the first number and the first product. The third number is equal to the sum of the first number and 1.

[0113] The specific scheme and beneficial effects of the insulation impedance detection system of a photovoltaic power generation system provided by an embodiment of the present invention can refer to the relevant description of the insulation impedance detection method of a photovoltaic power generation system provided by an embodiment of the present invention, and will not be repeated here.

[0114] Some embodiments of the present invention provide a computer device, such as Figure 14 As shown, the computer device 1400 includes a memory 1401 and a processor 1402. The memory 1401 stores a computer program. When the processor 1402 runs the computer program stored in the memory 1401, the processor 1402 executes the above-mentioned insulation impedance detection method of the photovoltaic power generation system.

[0115] The specific solutions and beneficial effects of a computer device provided by some embodiments of the present invention can be referred to the relevant description of an insulation impedance detection cloud platform for a photovoltaic power generation system provided by some embodiments of the present invention, and will not be repeated here.

[0116] Some embodiments of the present invention provide a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the processor executes the above-mentioned insulation impedance detection method for a photovoltaic power generation system.

[0117] The specific solutions and beneficial effects of a computer-readable storage medium provided by some embodiments of the present invention can be referred to the relevant description of an insulation impedance detection cloud platform for a photovoltaic power generation system provided by some embodiments of the present invention, and will not be repeated here.

[0118] It will be understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present invention, and the present invention is not limited thereto. Those skilled in the art will appreciate that various modifications and improvements can be made without departing from the spirit and substance of the present invention, and such modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for detecting insulation impedance of a photovoltaic power generation system, characterized in that: include: Obtaining an insulation resistance value of the photovoltaic inverter to ground, and determining an insulation fault level according to the insulation resistance value of the photovoltaic inverter to ground; Determining whether to perform MPPT level insulation impedance detection according to the insulation fault level; If the MPPT level insulation impedance test is performed, the fault type is determined, and the fault type includes a negative pole grounding fault or a non-negative pole grounding fault; When the fault type is a non-negative ground fault, multiple MPPT branches are disturbed in sequence to determine the grounded MPPT branch; as well as A photovoltaic module having an insulation impedance fault in the grounded MPPT branch is determined.

2. The method for detecting insulation impedance of a photovoltaic power generation system according to claim 1, wherein: Determining the insulation fault level according to the insulation resistance value of the photovoltaic inverter to ground includes: In response to the insulation resistance value of the photovoltaic inverter to ground being greater than a first preset value, determining that the insulation fault level is no insulation fault; In response to the insulation resistance value of the photovoltaic inverter to ground being less than or equal to the first preset value but greater than a second preset value, determining that the insulation fault level is an insulation fault alarm; and In response to the insulation resistance value of the photovoltaic inverter to ground being less than or equal to the second preset value, it is determined that the insulation fault level is an insulation fault.

3. The method for detecting insulation impedance of a photovoltaic power generation system according to claim 2, wherein: The determining whether to perform MPPT-level insulation impedance detection according to the insulation fault level includes: In response to the insulation fault level being an insulation fault, it is determined to perform an MPPT-level insulation impedance detection.

4. The method for detecting insulation impedance of a photovoltaic power generation system according to claim 1, wherein: The determining whether a negative grounding fault or a non-negative grounding fault occurs includes: Get the voltage of the negative pole of the busbar to ground; In response to the voltage of the negative electrode of the busbar to ground being less than or equal to a third preset value, determining that a negative electrode grounding fault has occurred; and In response to the voltage of the negative pole of the busbar to ground being greater than a third preset value, it is determined that a non-negative pole grounding fault has occurred.

5. The method for detecting insulation impedance of a photovoltaic power generation system according to claim 1, wherein: The method of sequentially disturbing a plurality of MPPT branches to determine a grounded MPPT branch includes: Disturbing each of the multiple MPPT branches in sequence, so that the voltage of the MPPT branch currently being disturbed among the multiple MPPT branches decreases, and the voltages of the other MPPT branches among the multiple MPPT branches except the MPPT branch currently being disturbed remain unchanged; and The voltage to ground of the negative pole of the busbar before each of the multiple MPPT branches is disturbed is compared with the voltage to ground of the negative pole of the busbar after each of the multiple MPPT branches is disturbed, and the grounded MPPT branch is determined from the multiple MPPT branches based on the comparison result.

6. The method for detecting insulation impedance of a photovoltaic power generation system according to claim 5, wherein: The grounded MPPT branch is an MPPT branch among the multiple MPPT branches, wherein the difference between the voltage to ground of the negative pole of the busbar before the disturbance and the voltage to ground of the negative pole of the busbar after the disturbance is greater than a fourth preset value.

7. The method for detecting insulation impedance of a photovoltaic power generation system according to claim 1, wherein: The step of determining a photovoltaic assembly having an insulation impedance fault in the grounded MPPT branch includes: Determining the voltage of the busbar negative electrode to ground and the MPPT voltage of the grounded MPPT branch; and The photovoltaic assembly having the insulation impedance fault is determined according to the voltage of the negative pole of the busbar to ground and the MPPT voltage of the grounded MPPT branch.

8. The method for detecting insulation impedance of a photovoltaic power generation system according to claim 7, wherein: The method of determining a photovoltaic assembly having an insulation impedance fault according to the voltage of the negative pole of the busbar to ground and the MPPT voltage of the grounded MPPT branch includes: Calculating a first percentage; the first percentage is a percentage of the voltage of the negative pole of the busbar to ground divided by the MPPT voltage of the grounded MPPT branch; Determining the number of photovoltaic modules in the grounded MPPT branch; The plurality of photovoltaic modules in the grounded MPPT branch are numbered in increasing order from the negative pole position of the photovoltaic string to the positive pole position of the photovoltaic string; Calculating a first product; the first product is the product of the number of photovoltaic modules in the grounded MPPT branch and the first percentage; A first number and a second number are obtained according to the first product, wherein the first number is greater than or equal to the first product and there is at most one integer between the first number and the first product; and the second number is less than or equal to the first product and there is at most one integer between the second number and the first product; Obtain a third number based on the first number; the third number is equal to the sum of the first number and 1; and A photovoltaic component having an insulation impedance fault is determined among the photovoltaic components numbered as the first, the second, or the third.

9. An insulation impedance detection system for a photovoltaic power generation system, characterized in that: include: an insulation fault level determination module, configured to: obtain an insulation impedance value of the photovoltaic inverter to ground, and determine an insulation fault level according to the insulation impedance value of the photovoltaic inverter to ground; The impedance detection determination module is configured to determine whether to perform MPPT level insulation impedance detection according to the insulation fault level; a grounding electrode determination module configured to: if an MPPT-level insulation impedance test is performed, determine a fault type, the fault type including a negative grounding fault or a non-negative grounding fault; The MPPT branch determination module is configured to: when the fault type is a non-negative grounding fault, sequentially disturb multiple MPPT branches to determine the grounded MPPT branch; and The fault point determination module is configured to determine a photovoltaic component having an insulation impedance fault in the grounded MPPT branch.

10. A computer device, characterized in that: The method comprises a memory and a processor, wherein a computer program is stored in the memory, and when the processor runs the computer program stored in the memory, the processor executes the insulation impedance detection method of the photovoltaic power generation system according to any one of claims 1 to 8.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the processor performs the insulation impedance detection method for a photovoltaic power generation system according to any one of claims 1 to 8.

Images