Parallel arc fault detection and arc extinguishing system and method for photovoltaic power generation

Abstract

The invention discloses a parallel arc fault detection and arc extinguishing system and method for photovoltaic power generation, and belongs to the technical field of photovoltaic power generation, the parallel arc fault detection and arc extinguishing system comprises a differential current sensor, a plurality of diodes, a plurality of thyristors and an arc extinguishing circuit, each diode is connected to a corresponding photovoltaic serial anode, and the cathodes of the diodes are connected to a DC bus anode; the anodes of the thyristors are correspondingly connected with the anodes of the series, the cathodes are jointly connected to the input end of the arc extinguishing circuit, the differential current sensor monitors the system state in real time by measuring the difference value of the total current of the anodes and the cathodes of all the series, and the output end of the arc extinguishing circuit is connected with the cathode of the direct-current bus and used for absorbing fault energy. The system is simple in overall structure and rapid in response, can accurately position a fault photovoltaic serial and implement selective arc extinguishing, and maintains normal power generation of a photovoltaic power generation system to the maximum extent while guaranteeing safety.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic power generation technology, and specifically to a parallel arc fault detection and arc extinguishing system and method for photovoltaic power generation. Background Technology

[0002] A photovoltaic (PV) power generation system connects multiple PV modules in series to form a PV string, and then connects these strings in parallel to a combiner box to collect electrical energy and transmit it to an inverter for grid connection. During system operation, strong environmental factors such as insulation aging, moisture contamination, or mechanical damage can cause unexpected conductive paths to form between conductors at different potentials, resulting in parallel arcing faults. Parallel arcing faults exhibit relatively small current and voltage variations, inconsistent high-frequency components, and irregular, non-periodic fault current characteristics. These faults generate continuous electric sparks and high temperatures, posing a significant risk of electrical fires. Therefore, reliable and rapid detection and elimination of parallel arcing faults are crucial for ensuring the safe and stable operation of PV power plants.

[0003] In existing photovoltaic system arc protection technologies, a common and fundamental method is to use a detection scheme based on current amplitude thresholds. This scheme typically involves installing current sensors on the DC bus of the combiner box or on each branch to continuously monitor the current value. However, this method has certain problems:

[0004] Parallel arc fault current may be superimposed on the normal photovoltaic output current, and its absolute value change may not be obvious. Relying solely on a simple comparison of current amplitude thresholds can easily lead to the underreporting of small but dangerous early arcs due to overly high threshold settings, or the misjudgment of normal operating fluctuations as faults due to overly low threshold settings, resulting in frequent malfunctions and insufficient detection sensitivity and reliability. Secondly, there is a lack of fault location capability. After detecting an anomaly, the output of the entire combiner box needs to be directly cut off, causing all normally operating photovoltaic strings to stop generating electricity. It is impossible to identify which specific string has failed, which is not conducive to rapid troubleshooting and maintenance, and also causes unnecessary power generation loss. On the other hand, if detection units are deployed in each photovoltaic string branch to improve accuracy, it will significantly increase the hardware complexity and cost of the system, which is not conducive to the application of large-scale photovoltaic arrays.

[0005] In addition, with the development of artificial intelligence technology, some data analysis methods based on deep learning have emerged to improve the accuracy of detection and judgment. However, the complex models limit their direct deployment in combiner box hardware. In terms of circuit structure, some studies have used the current control capabilities of various DC / DC converters to achieve fault detection. However, the circuit complexity and control difficulty are also high. The above-mentioned traditional methods are not only limited in terms of complexity and real-time performance, but most of them are designed for series arc faults and cannot quickly deal with parallel arc faults. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a parallel arc fault detection and extinguishing system and method for photovoltaic power generation. The overall structure is simple and the response is rapid. It can accurately locate the faulty photovoltaic string and implement selective arc extinguishing, ensuring safety while maximizing the normal power generation of the photovoltaic power generation system.

[0007] The technical solution of the present invention is as follows: In a first aspect of the present invention, a parallel arc fault detection and arc extinguishing system for photovoltaic power generation is provided, including a differential current sensor, multiple diodes, multiple thyristors, and an arc extinguishing circuit; The plurality of diodes correspond to the plurality of photovoltaic strings respectively, the anode of each diode is connected to the positive terminal of the corresponding photovoltaic string, and the cathodes of all diodes are connected to the positive terminal bus of the DC bus. The plurality of thyristors correspond to the plurality of photovoltaic strings respectively, the anode of each thyristor is connected to the positive electrode of the corresponding photovoltaic string, and the cathodes of all thyristors are connected to the input terminal of the arc extinguishing circuit. The differential current sensor is used to measure the differential current between the total positive current and the total negative current of all photovoltaic strings. The output terminal of the arc extinguishing circuit is connected to the negative bus of the DC bus to absorb energy when a fault current is received.

[0008] In some embodiments of the present invention, the differential current sensor, multiple diodes, multiple thyristors and arc extinguishing circuit are all disposed in the combiner box, and the DC bus is used to connect to the photovoltaic inverter.

[0009] In some embodiments of the present invention, the arc extinguishing circuit includes a switching device and an inductor connected in series, and a freewheeling circuit connected in parallel between the connection point of the switching device and the inductor and the positive terminal of the DC bus, wherein the input terminal of the arc extinguishing circuit is connected to the input terminal of the switching device.

[0010] In some embodiments of the present invention, the freewheeling circuit is composed of a freewheeling diode and a resistor connected in parallel; the switching device is an insulated gate bipolar transistor or a metal-oxide-semiconductor field-effect transistor.

[0011] In some embodiments of the present invention, a controller is further included, wherein the input terminal of the controller is connected to the output terminal of the differential current sensor, a plurality of first control output terminals of the controller are respectively connected to the control electrode of each of the thyristors, and a second control output terminal of the controller is connected to the control terminal of the switching device in the arc extinguishing circuit.

[0012] In a second aspect of the invention, a method for detecting and extinguishing parallel arc faults in photovoltaic power generation is provided, employing the above-described system, comprising: The differential current measured by the differential current sensor is acquired in real time; When the absolute value of the differential current exceeds the set threshold, the system is determined to have a parallel arc fault and the current fault current value is recorded. The thyristors corresponding to each photovoltaic string are turned on sequentially, and the switching devices in the arc extinguishing circuit are turned on simultaneously each time a thyristor is turned on. Based on the change in differential current relative to the fault current value after a specific thyristor is turned on, it is determined whether the photovoltaic string corresponding to the thyristor is a fault source. If the fault source is identified, the thyristor and switching device are kept in the on state to perform arc extinguishing; if the fault source is not identified, the switching device is turned off and the process switches to the next photovoltaic string.

[0013] In some embodiments of the present invention, determining whether the photovoltaic string corresponding to the thyristor is a fault source specifically means: if the differential current drops to near zero after the thyristor is turned on, then the photovoltaic string is determined to be a fault source.

[0014] In some embodiments of the present invention, during the process of sequentially turning on the thyristors corresponding to each photovoltaic string for judgment, if a certain string is determined to be not a fault source, then after the switching device of the arc extinguishing circuit is turned off, the thyristor is turned off accordingly, and the corresponding photovoltaic string resumes power supply to the DC bus through the diode.

[0015] In some embodiments of the present invention, after locating the fault source and performing arc extinguishing, alarm information containing the faulty photovoltaic string identifier is generated and uploaded.

[0016] In some embodiments of the present invention, when the absolute value of the differential current does not exceed a set threshold, all thyristors and switching devices in the arc-extinguishing circuit remain in the off state.

[0017] One or more technical solutions of the present invention have the following beneficial effects: In the detection process, a differential current sensor is used to monitor the total positive and negative current difference of all photovoltaic strings, directly capturing the current imbalance characteristics caused by parallel arc leakage. This detection method is extremely sensitive to minute changes in leakage current, effectively overcoming the problem of missed or false alarms caused by the insignificant change in the absolute value of fault current in traditional methods, and significantly improving the reliability and sensitivity of detection. The system is equipped with diodes and thyristors connected in parallel for each photovoltaic string. During normal power generation, the current only flows through the diodes. When the differential current sensor detects a fault, the controller can sequentially trigger each thyristor to conduct, forming a trial bypass in conjunction with the arc extinguishing circuit. By observing whether the differential current quickly returns to balance after a specific thyristor conducts, the specific photovoltaic string where the arc fault occurred can be accurately located, achieving rapid fault location and ensuring that only the faulty string is isolated and processed. The inductor is used to absorb and suppress the fault current energy, the switching devices achieve rapid on / off control, and the freewheeling circuit ensures the safe release of energy during the turn-off process, thereby effectively and safely extinguishing the arc.

[0018] The entire system boasts a streamlined structure, requiring only a single differential current sensor and a shared arc-extinguishing circuit to protect any number of parallel photovoltaic strings. Its low hardware cost and ease of expansion make it ideal for large-scale photovoltaic power plant applications. Furthermore, since all protection branches are inactive during normal operation, arc extinguishing is only initiated on strings identified as faulty, thus minimizing the impact on the overall continuity of photovoltaic power generation and achieving a balance between safety protection and power generation efficiency. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the working principle of the combiner box in the photovoltaic power generation system provided in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the series arc fault principle provided in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the parallel arc fault principle provided in Embodiment 1 of the present invention; Figure 4 This is a topology diagram of the parallel arc detection and arc extinguishing circuit provided in Embodiment 1 of the present invention; Figure 5 This is a flowchart of the parallel arc detection and extinguishing algorithm provided in Embodiment 1 of the present invention; Figure 6 This is a schematic diagram illustrating the working principle of the photovoltaic power generation system under normal operation as provided in Embodiment 1 of the present invention; Figure 7 This is a schematic diagram illustrating the working principle of the photovoltaic string 2 in the photovoltaic power generation system provided in Embodiment 1 of the present invention when a parallel arc fault occurs. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Example 1 In a typical embodiment of the present invention, such as Figures 1 to 7As shown, a parallel arc fault detection and arc extinguishing system for photovoltaic power generation is proposed, including a differential current sensor, multiple diodes, multiple thyristors, and an arc extinguishing circuit; Multiple diodes correspond to multiple photovoltaic strings, with the anode of each diode connected to the positive terminal of the corresponding photovoltaic string, and the cathodes of all diodes connected to the positive terminal bus of the DC bus. Multiple thyristors correspond to multiple photovoltaic strings, with the anode of each thyristor connected to the positive terminal of the corresponding photovoltaic string, and the cathodes of all thyristors connected to the input terminal of the arc extinguishing circuit. The differential current sensor is used to measure the differential current between the total positive current and the total negative current of all photovoltaic strings; The output of the arc extinguishing circuit is connected to the negative bus of the DC bus to absorb energy when a fault current is received.

[0022] By introducing a differential current sensor to monitor the total positive and negative current difference across all photovoltaic strings, the fundamental characteristic of current imbalance caused by parallel arcing is grasped, making the physical principle of fault detection clear and direct. Secondly, the system configures a diode path and a thyristor bypass in parallel for each photovoltaic string. The diodes ensure unidirectional current convergence during normal power generation, while the thyristors provide a controlled discharge path for potential fault currents. This separation of power generation and protection paths ensures that the system remains completely unaffected when there are no faults, preserving power generation efficiency. Finally, a shared arc-extinguishing circuit is set up as the energy absorption terminal, meaning that regardless of which string experiences a fault, it can be guided to the same processing unit for arc extinguishing, greatly simplifying the system structure and reducing hardware complexity and cost.

[0023] The differential current sensor, multiple diodes, multiple thyristors, and arc extinguishing circuit are all housed in the combiner box, and the DC bus is used to connect to the photovoltaic inverter.

[0024] The combiner box itself is the central node for current collection in the photovoltaic array. It integrates differential current sensors, diodes, thyristors, and arc-extinguishing circuits, making the system a standardized, self-contained functional module that can be manufactured, installed, and maintained. This integrated design simplifies the wiring of photovoltaic power plants, reduces external connection points and potential faults, and improves the overall reliability of the system. For new power plants, it can be used as a standard configuration for high-performance combiner boxes; for the renovation and upgrading of existing power plants, only the combiner box needs to be replaced or added, making implementation very convenient and quick, greatly enhancing its practicality.

[0025] The arc extinguishing circuit includes a switching device and an inductor connected in series, and a freewheeling circuit connected in parallel between the connection point of the switching device and the inductor and the positive terminal of the DC bus. The input terminal of the arc extinguishing circuit is connected to the input terminal of the switching device.

[0026] Understandably, an inductor is an inertial element in a circuit, its characteristic being to impede sudden changes in current. When a fault current flows through the inductor after the switching device is turned on, the inductor attempts to maintain a constant current, thereby absorbing and storing arc energy. This directly suppresses drastic changes in the fault current, creating conditions for extinguishing the arc. The switching device acts as a gate in the arc-extinguishing circuit; its rapid and controllable switching capability allows the system to precisely start and stop the arc-extinguishing process. The freewheeling circuit provides a safe release path for the energy stored in the inductor when the switching device is turned off, preventing high-voltage spikes caused by sudden current changes from damaging the switching device or other components, thus ensuring the safety and durability of the arc-extinguishing circuit itself.

[0027] The freewheeling circuit consists of a freewheeling diode and a resistor connected in parallel; the switching device is an insulated gate bipolar transistor or a metal-oxide-semiconductor field-effect transistor.

[0028] A freewheeling diode and a resistor connected in parallel form a freewheeling circuit. The diode provides the main freewheeling path for the inductor current, while the parallel resistor dissipates some energy, helping the system dampen oscillations and stabilize more quickly, thus optimizing the energy dissipation process. The switching devices are limited to insulated-gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs). Using these devices results in extremely fast response speeds for the arc-extinguishing circuit, enabling rapid fault intervention. Furthermore, these devices have low drive power, are easy to control, and readily integrate with digital controllers, laying the hardware foundation for high-precision, automated intelligent control of the entire system.

[0029] It also includes a controller, whose input terminal is connected to the output terminal of the differential current sensor, whose multiple first control output terminals are respectively connected to the control electrode of each thyristor, and whose second control output terminal is connected to the control terminal of the switching device in the arc extinguishing circuit.

[0030] With this configuration, the controller can continuously monitor subtle changes in the differential current and use algorithms for judgment. Compared to simple hardware comparison, it has higher anti-interference capabilities and judgment accuracy, realizing intelligent detection. Secondly, the controller can automatically execute subsequent fault cascade screening sequences and precisely control the on / off timing of each thyristor and arc-extinguishing switch. The entire detection, location, and arc-extinguishing process requires no manual intervention, with rapid and reliable response, achieving process automation. Furthermore, the controller can record fault data, generate alarm information, and even communicate with the power plant monitoring system, greatly enriching the system's management and maintenance functions, making it an advanced device integrating protection, diagnosis, and management, and expanding the system's functional potential.

[0031] In a second aspect of the invention, a method for detecting and extinguishing parallel arc faults in photovoltaic power generation is provided, employing the above-described system, comprising: Real-time acquisition of differential current measured by differential current sensor; When the absolute value of the differential current exceeds the set threshold, the system is determined to have a parallel arc fault and the current fault current value is recorded. The thyristors corresponding to each photovoltaic string are turned on sequentially, and the switching devices in the arc extinguishing circuit are turned on synchronously each time a thyristor is turned on. Based on the change of differential current relative to fault current after a specific thyristor is turned on, determine whether the photovoltaic string corresponding to that thyristor is a fault source. If the fault source is identified, the thyristor and switching device are kept in the on state to perform arc extinguishing; if the fault source is not identified, the switching device is turned off and the process switches to the next photovoltaic string.

[0032] By sequentially connecting each photovoltaic string to the arc-extinguishing circuit and observing the changes in differential current, the system's topology is utilized to locate the fault. If the differential current disappears after connecting a certain string, it proves that the fault path has been successfully diverted by that bypass, thus pinpointing the fault source; if there is no change, that string is ruled out. This closed-loop process of probing, observing, and judging ensures the accuracy of fault string identification. Ultimately, continuous arc-extinguishing is performed only on the strings confirmed as fault sources, while power supply to other normal strings is restored after a brief detection window, maximizing the overall continuity of photovoltaic system power generation.

[0033] To determine whether the photovoltaic string corresponding to the thyristor is a fault source, specifically: if the differential current drops to near zero after the thyristor is turned on, then the photovoltaic string is determined to be a fault source.

[0034] Understandably, when the bypass thyristor of the fault series is turned on, the current that was originally leaking through the arc is transferred to the low-resistance arc-extinguishing branch, causing the current between the positive and negative buses to return to balance. The theoretical value of the differential current should approach zero. This setting ensures the real-time performance and reliability of fault diagnosis and avoids delays or misjudgments that may be caused by using complex algorithms.

[0035] During the process of sequentially turning on the thyristors corresponding to each photovoltaic string for judgment, if a certain string is determined to be not a fault source, then after the switching device of the arc extinguishing circuit is turned off, the thyristor is turned off, and the corresponding photovoltaic string resumes power supply to the DC bus through the diode.

[0036] During the screening process, once a series circuit is detected and confirmed to be normal, the switching devices of the arc-extinguishing circuit will be immediately turned off. Since the thyristor is a semi-controlled device, it will automatically turn off after the main circuit current drops to zero. At this time, the current path of the normal series circuit will automatically and seamlessly switch back to the original diode path, continuing to deliver power to the DC bus. The entire process is automatic and fast, ensuring that the power outage time of the series circuit is only a very short detection time (usually in the millisecond range), with a negligible impact on the total power generation of the system. This achieves the goal of isolating only the fault and minimizing the impact of protection actions on power generation.

[0037] After locating the fault source and performing arc extinguishing, an alarm message containing the identifier of the faulty photovoltaic string is generated and uploaded.

[0038] After successful arc extinguishing, alarm information containing fault string identifiers is automatically generated and uploaded, enabling power plant operation and maintenance personnel to know the precise location of the fault immediately without having to conduct tedious line-by-line troubleshooting on-site. This greatly shortens fault response and repair time, improves the maintainability and operational reliability of the power plant, and at the same time, the accumulated fault data helps to analyze the weak links of the power plant, provides a basis for preventive maintenance, improves the long-term operational safety of the power plant, and reduces operating costs.

[0039] When the absolute value of the differential current does not exceed the set threshold, all thyristors and switching devices in the arc extinguishing circuit remain in the off state.

[0040] When the differential current does not exceed the threshold, i.e., when the system determines that there is no risk of parallel arcing, all thyristors and arc-extinguishing switching devices remain off. At this time, the entire arc-extinguishing circuit is equivalent to being completely disconnected from the main system, and each photovoltaic string supplies power to the bus only through diodes. This ensures that under most normal operating conditions, the system does not consume any additional energy, introduce any additional losses, or have any impact on power quality. It achieves the function of timely intervention in case of faults and complete invisibility in normal conditions, fundamentally solving the problem of adding protection devices affecting power generation efficiency.

[0041] In this embodiment, the differential current is measured by a differential current sensor. Two current-carrying conductors (such as an outgoing line and a return line) are simultaneously passed through the sensor, and the sensor calculates the difference by comparing the currents flowing through the two conductors. This method is commonly used in single-phase or three-phase power cables for monitoring and protection, particularly for detecting leakage current or unbalanced current. The proposed method measures the differential current through the sensor. i d The physical meaning is N The positive current of a parallel photovoltaic series i pk With negative current i nk The sum is defined as follows:

[0042] When the photovoltaic system is operating normally, the positive current and the negative current have equal amplitudes but opposite directions. i d It should tend towards 0. However, when parallel arcs occur, some current leaks out through parasitic paths, causing current imbalance and leading to... i d ≠0. Based on this, whether an electric arc occurs can be determined by... i d Make a quick judgment.

[0043] Only one differential current sensor needs to be configured inside the combiner box. After all photovoltaic strings are connected to the combiner box, the differential current sensor measures the total differential current of all photovoltaic input and output lines, thus enabling real-time detection of current imbalance in each string. The overall configuration of the proposed parallel arc fault detection and arc extinguishing circuit is as follows: Figure 3 As shown.

[0044] Each photovoltaic string is connected to a corresponding diode ( D 1~ D N The thyristors are connected to the DC bus for outputting power. Additionally, each series is branched by a separate thyristor (SCR1~SCR2). N It is connected to a shared arc-extinguishing circuit. The DC bus is then connected to the photovoltaic inverter, which is ultimately connected to the grid. The proposed structure will not affect the normal power generation operation of the photovoltaic system.

[0045] The arc extinguishing circuit consists of IGBTs ( Q ),inductance( L ),diode( D ), and resistance ( R The inductor is composed of several components. Its essence is to resist changes in current. When an electric arc occurs, the inductor generates an induced electromotive force to resist this change, storing energy in the form of a magnetic field to extinguish the arc. Diodes and resistors are used to provide a freewheeling path for the arc energy absorbed in the inductor when the IGBT is turned off, thereby releasing the energy and preventing damage to the IGBT.

[0046] The proposed parallel arc detection and extinguishing algorithm is as follows: Figure 4 As shown, when the system is operating in generator mode, if the absolute value of the total differential current is | i d |Exceeded the preset safety value i d,min This indicates the presence of leakage current, confirming the existence of a parallel arc fault. The differential current at the time of the fault is recorded as follows: i d,arcTo extinguish the arc, the IGBT is first turned on, followed by the thyristor SCR1 corresponding to the first series. If, after thyristor SCR1 is turned on, i d / i d,arc If the ratio does not converge to zero but remains constant, it indicates that... i d There was no significant change, and no arc was observed in series 1. Therefore, the IGBT should be turned off, and the corresponding thyristor SCR1 should turn off naturally, allowing series 1 to resume normal operation. Subsequently, the second series was checked, and the above detection process was repeated. If the thyristor SCR1 of a certain series k is turned on... k back, i d / i d,arc If the value is close to zero, then the string k is considered faulty. (This is determined via path SCR.) k After the IGBT and inductor L perform arc extinguishing, the differential current... i d When the arc approaches zero, there are no more parallel arcs in the system. This fault information is then transmitted to the higher-level controller to prompt maintenance.

[0047] When a photovoltaic system is operating normally, the photovoltaic string is connected to diodes ( D 1~ D N The energy is transferred to the DC bus for external transmission. At this time, there is no arc fault, and the thyristors and arc-extinguishing circuit do not operate. Taking a parallel arc fault in photovoltaic string 2 as an example, in this case, the thyristor SCR2 and IGBT are turned on, the faulty string 2 is selected, and targeted arc extinguishing is performed, while the remaining strings continue to operate normally, thus ensuring stable system operation.

[0048] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A parallel arc fault detection and arc extinguishing system for photovoltaic power generation, characterized in that, It includes a differential current sensor, multiple diodes, multiple thyristors, and an arc-extinguishing circuit; The plurality of diodes correspond to the plurality of photovoltaic strings respectively, the anode of each diode is connected to the positive terminal of the corresponding photovoltaic string, and the cathodes of all diodes are connected to the positive terminal bus of the DC bus. The plurality of thyristors correspond to the plurality of photovoltaic strings respectively, the anode of each thyristor is connected to the positive electrode of the corresponding photovoltaic string, and the cathodes of all thyristors are connected to the input terminal of the arc extinguishing circuit. The differential current sensor is used to measure the differential current between the total positive current and the total negative current of all photovoltaic strings. The output terminal of the arc extinguishing circuit is connected to the negative bus of the DC bus to absorb energy when a fault current is received.

2. The parallel arc fault detection and arc extinguishing system for photovoltaic power generation as described in claim 1, characterized in that, The differential current sensor, multiple diodes, multiple thyristors, and arc extinguishing circuit are all housed in the combiner box, and the DC bus is used to connect to the photovoltaic inverter.

3. The parallel arc fault detection and arc extinguishing system for photovoltaic power generation as described in claim 1, characterized in that, The arc-extinguishing circuit includes a switching device and an inductor connected in series, and a freewheeling circuit connected in parallel between the connection point of the switching device and the inductor and the positive terminal of the DC bus. The input terminal of the arc-extinguishing circuit is connected to the input terminal of the switching device.

4. The parallel arc fault detection and arc extinguishing system for photovoltaic power generation as described in claim 3, characterized in that, The freewheeling circuit consists of a freewheeling diode and a resistor connected in parallel; the switching device is an insulated gate bipolar transistor or a metal-oxide-semiconductor field-effect transistor.

5. The parallel arc fault detection and arc extinguishing system for photovoltaic power generation as described in claim 1, characterized in that, It also includes a controller, the input of which is connected to the output of the differential current sensor, a plurality of first control outputs of which are respectively connected to the control electrode of each of the thyristors, and a second control output of which is connected to the control terminal of the switching device in the arc extinguishing circuit.

6. A method for detecting and extinguishing parallel arc faults in photovoltaic power generation, employing the system described in any one of claims 1-5, characterized in that, include: The differential current measured by the differential current sensor is acquired in real time; When the absolute value of the differential current exceeds the set threshold, the system is determined to have a parallel arc fault and the current fault current value is recorded. The thyristors corresponding to each photovoltaic string are turned on sequentially, and the switching devices in the arc extinguishing circuit are turned on simultaneously each time a thyristor is turned on. Based on the change in differential current relative to the fault current value after a specific thyristor is turned on, it is determined whether the photovoltaic string corresponding to the thyristor is a fault source. If the fault source is identified, the thyristor and switching device are kept in the on state to perform arc extinguishing; if the fault source is not identified, the switching device is turned off and the process switches to the next photovoltaic string.

7. The method for parallel arc fault detection and arc extinguishing in photovoltaic power generation as described in claim 6, characterized in that, The determination of whether the photovoltaic string corresponding to the thyristor is a fault source is as follows: if the differential current drops to near zero after the thyristor is turned on, then the photovoltaic string is determined to be a fault source.

8. The method for parallel arc fault detection and arc extinguishing in photovoltaic power generation as described in claim 6, characterized in that, During the process of sequentially turning on the thyristors corresponding to each photovoltaic string for judgment, if a certain string is determined to be not a fault source, then after the switching device of the arc extinguishing circuit is turned off, the thyristor is turned off, and the corresponding photovoltaic string resumes power supply to the DC bus through the diode.

9. The method for detecting and extinguishing parallel arc faults in photovoltaic power generation as described in claim 6, characterized in that, After locating the fault source and performing arc extinguishing, an alarm message containing the identifier of the faulty photovoltaic string is generated and uploaded.

10. The method for detecting and extinguishing parallel arc faults in photovoltaic power generation as described in claim 6, characterized in that, When the absolute value of the differential current does not exceed the set threshold, all thyristors and switching devices in the arc extinguishing circuit remain in the off state.

Images