Photovoltaic power station current collection line fault studying, judging and positioning system and method

Abstract

The invention relates to a photovoltaic power station current collection line fault studying, judging and positioning system and method, and relates to the technical field of novel power system relay protection, and the system comprises a plurality of collection lines, each collection line is connected to a low-voltage cable in a boosting box transformer, and the low-voltage cable is connected to a high-voltage cable through a transformer. A power frequency current sensor is arranged at the intersection of the low-voltage cable and each collection line, voltage transformers are arranged on the high-voltage side and the low-voltage side of the transformer, and a broadband current sensor is arranged at the grounding end of a copper shielding layer of the high-voltage cable. The voltage transformer, the power frequency current sensor and the broadband current sensor are respectively connected to the fault studying, judging and positioning device; therefore, the photovoltaic power station current collection line fault can be researched, judged and positioned, the current collection line fault searching and first-aid repair efficiency is improved, the power generation reliability of the photovoltaic power station is enhanced, and the economic loss is reduced.

Description

Technical Field

[0001] The present disclosure relates to the technical field of novel power system relay protection, and in particular to a photovoltaic power station collector line fault analysis and positioning system and method. Background Art

[0002] The photovoltaic power station collection line is a cable line, an overhead line or a mixed overhead cable line, and has a multi-T-type radial line structure. After the photovoltaic string passes through the inverter, 9-11 AC (AC) 800V collection lines are formed. The collection lines pass through the step-up box transformer and are connected in parallel to the AC35kV collection line. The AC35kV collection line is connected to the main grid through the 220kV step-up substation. Therefore, an AC35kV collection line contains multiple parallel step-up box transformers. When the collection line fails, the related relay protection of the 220kV step-up substation often trips, causing the entire fault collection line to be out of power. Due to the complex grid structure of the collection line and the numerous branches of the AC35kV line and AC800V line, the fault is difficult to locate and find, and fault troubleshooting often takes 1-2 weeks. This seriously affects the reliability of photovoltaic power station power generation and causes great economic losses. Summary of the invention

[0003] In order to solve the above technical problems, the present disclosure provides a photovoltaic power station collector line fault analysis and positioning system and method, which are used to improve the efficiency of collector line fault detection and repair, enhance the reliability of photovoltaic power station power generation, and reduce economic losses.

[0004] In the first aspect, the present disclosure provides a photovoltaic power station collector line fault analysis and positioning system, including: multiple collection lines, each of the collection lines includes a one-to-one connected photovoltaic string and a photovoltaic inverter; a step-up box transformer, the step-up box transformer includes a low-voltage cable, a high-voltage cable, a transformer, and a fault analysis and positioning device, the low-voltage cable is connected to the low-voltage side of the transformer, the high-voltage cable is connected to the high-voltage side of the transformer, the high-voltage side of the transformer and the low-voltage side of the transformer are both provided with a voltage transformer, and the voltage transformer is connected to the fault analysis and positioning device through a coaxial cable; each of the collection lines is connected to the low-voltage cable via an industrial frequency current sensor, and the industrial frequency current sensor is connected to the fault analysis and positioning device via a coaxial cable; the copper shielding layer of the high-voltage cable is provided with a grounding terminal, and the grounding terminal includes a broadband current sensor, and the broadband current sensor is connected to the fault analysis and positioning device via a coaxial cable.

[0005] Optionally, the booster transformer includes a first output end and a second output end, the first output end is connected to the next booster transformer, and the second output end is connected to the booster substation or the previous booster transformer; one end of the high-voltage cable is connected to the first output end, and the other end of the high-voltage cable is connected to the second output end.

[0006] Optionally, the grounding terminal includes a first grounding terminal and a second grounding terminal, the first grounding terminal is connected to the high-voltage cable and the first output terminal, and the second grounding terminal is connected to the high-voltage cable and the second output terminal; the broadband current sensor includes a first broadband current sensor and a second broadband current sensor, the first broadband current sensor is located at the first grounding terminal, and the first broadband current sensor is connected to the fault analysis and positioning device via a coaxial cable, the second broadband current sensor is located at the second grounding terminal, and the second broadband current sensor is connected to the fault analysis and positioning device via a coaxial cable.

[0007] Optionally, the fault analysis and positioning device includes an acquisition unit, a signal processing and storage unit, and a central processing unit; the acquisition unit is connected to the signal processing and storage unit, and the signal processing and storage unit is connected to the central processing unit; the acquisition unit is used to collect current signals or voltage signals of the high-voltage cable, the low-voltage cable, and the high-voltage side and low-voltage side of the transformer; the signal processing and storage unit is used to pre-process, pre-calculate and cache the signals collected by the acquisition unit; the central processing unit is used to perform data calculation and processing on the pre-processed and pre-calculated information.

[0008] Optionally, the acquisition unit includes an overvoltage protection module, a signal conditioning module, and an analog-to-digital conversion module connected in sequence; the acquisition unit includes a first acquisition unit and a second acquisition unit, the acquisition end of the first acquisition unit is connected to the voltage transformer on the high-voltage side of the transformer and the broadband current sensor through a coaxial cable, and the acquisition end of the second acquisition unit is connected to the voltage transformer on the low-voltage side of the transformer and the power frequency current sensor through a coaxial cable; the output end of the acquisition unit is connected to the signal processing and storage unit; the acquisition end is connected to the overvoltage protection module, and the output end is connected to the analog-to-digital conversion module.

[0009] Optionally, the fault analysis and positioning device also includes a display unit, an operating unit and a communication unit, wherein the display unit, the operating unit and the communication unit are located in the housing of the device, and the display unit, the operating unit and the central processing unit are connected via optocoupler isolation; the display unit includes an indicator light and a liquid crystal display screen, and the liquid crystal display screen is used to display operation information, fault information, and parameter information of each unit of the photovoltaic power station collection line; the operating unit includes a plurality of buttons; the communication unit includes a remote communication network port and a USB debugging interface, wherein the remote communication network port is connected to a remote master station system for receiving instructions or sending information, and the USB debugging interface is connected to an external computer for updating the program of the device or setting parameters.

[0010] In the second aspect, based on the same inventive concept, the present disclosure provides a photovoltaic power station collector line fault analysis and positioning method, which is applied to the photovoltaic power station collector line fault analysis and positioning system as described in the first aspect, and the method comprises the following steps:

[0011] Step S1: The fault analysis and positioning device is initialized, and the first acquisition unit starts sampling and calculating the power frequency zero-sequence voltage, low-frequency transient zero-sequence current and high-frequency transient traveling wave current on the high-voltage side of the transformer; the second acquisition unit starts sampling and calculating the power frequency zero-sequence voltage, power frequency zero-sequence current and power frequency current of each collection line on the low-voltage side of the transformer;

[0012] Step S2: Compare the power frequency zero-sequence current and the low-frequency transient zero-sequence current to see if they exceed the set value; if any of the currents exceeds the set threshold, proceed to step S3; if neither the power frequency zero-sequence current nor the low-frequency transient zero-sequence current exceeds the threshold, the device is initialized, reset, and re-collected back to step S1;

[0013] Step S3: comparing whether the polarities of the high-frequency transient traveling wave currents on the high-voltage cables are consistent;

[0014] Step S31: If they are consistent, determine whether the power frequency zero-sequence voltage on the low-voltage side of the transformer exceeds the first threshold; if it exceeds, determine that the low-voltage line is faulty;

[0015] Step S32: If they are inconsistent, determine whether the power frequency zero-sequence voltage on the high-voltage side of the transformer exceeds the second threshold; if so, determine that the high-voltage line is faulty.

[0016] Optionally, the step S31 is specifically as follows: step S311: if the power frequency zero-sequence voltage on the low-voltage side of the transformer is less than a first threshold, the fault analysis and positioning device is initialized, reset and re-collected back to step S1; step S312: if the power frequency zero-sequence voltage on the low-voltage side of the transformer is greater than or equal to the first threshold, the low-voltage line fault is determined, and further detection and determination are made as to whether the power frequency current of each collection line exceeds a third threshold.

[0017] Optionally, the step S312 is specifically as follows: if the power frequency currents of each collection line are less than a third threshold value, it is determined that the external line on the low voltage side is disturbed, the fault analysis and positioning device is initialized, and the data is reset and re-collected to return to step S1; if there is a power frequency current greater than or equal to the third threshold value in each collection line, a fault line is selected to determine that the collection line with a power frequency current greater than the third threshold value has a fault; the fault analysis and positioning device sends a collection line fault alarm signal; the fault analysis and positioning device is initialized, and the data is reset and re-collected to return to step S1.

[0018] Optionally, the step S32 is specifically as follows: if the power frequency zero-sequence voltage on the high-voltage side of the transformer is less than a second threshold value, it is judged that an external power grid disturbance occurs on the high-voltage side, the fault analysis and positioning device is initialized, reset, and re-collected to return to step S1; if the power frequency zero-sequence voltage on the high-voltage side of the transformer is greater than or equal to the second threshold value, it is judged that a high-voltage line fault occurs, the fault section is located according to the line topology, the double-end traveling wave ranging is started, the fault point is accurately located, and the fault analysis and positioning device sends a high-voltage line fault alarm signal; the fault analysis and positioning device is initialized, reset, and re-collected to return to step S1.

[0019] Compared with the prior art, the technical solution provided by the embodiments of the present disclosure has the following advantages:

[0020] By collecting the power frequency voltage characteristic quantity, low frequency current characteristic quantity and high frequency transient traveling wave current characteristic quantity of AC35kV collector line in real time, and collecting the power frequency current and power frequency voltage characteristic quantity of each AC800V collection line in real time, it is possible to comprehensively judge whether the collector line has a fault, quickly determine the line voltage section where the fault occurs, and quickly locate the exact location of the AC35kV collector line fault. For AC800V collection line fault, the faulty line can be quickly identified. It can effectively solve the problem of difficult judgment and location of collector line faults, improve the efficiency of collector line fault finding and repair, enhance the reliability of photovoltaic power station power generation, and reduce economic losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0023] Figure 1 The figure shows a connection diagram of a photovoltaic power station collector line fault analysis and positioning system provided by an embodiment of the present disclosure;

[0024] Figure 2 The figure shows a schematic diagram of the appearance of a fault analysis and location device provided by an embodiment of the present disclosure;

[0025] Figure 3 The figure shows a schematic diagram of the connection of internal modules of a fault analysis and positioning device provided by an embodiment of the present disclosure;

[0026] Figure 4The figure shows a flow chart of a photovoltaic power station collector line fault analysis and positioning method provided by an embodiment of the present disclosure. DETAILED DESCRIPTION

[0027] In order to more clearly understand the above-mentioned objectives, features and advantages of the present disclosure, the scheme of the present disclosure will be further described below. It should be noted that the embodiments of the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0028] In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but the present disclosure may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present disclosure, rather than all of the embodiments.

[0029] Figure 1 FIG. 1 is a connection diagram of a photovoltaic power station collector line fault analysis and positioning system provided by an embodiment of the present disclosure. Figure 2 The figure shows the appearance of a fault analysis and location device provided by the embodiment of the present disclosure; please refer to Figure 1 and Figure 2 The present disclosure provides a photovoltaic power station collector line fault analysis and positioning system 100, including: multiple collection lines 0, each collection line 0 includes a photovoltaic string 6 and a photovoltaic inverter 5 connected in a one-to-one correspondence; a step-up box transformer 1, the step-up box transformer 1 includes a low-voltage cable 4, a high-voltage cable 2, a transformer 3, and a fault analysis and positioning device 7, the low-voltage cable 4 is connected to the low-voltage side of the transformer 3, and the high-voltage cable 2 is connected to the high-voltage side of the transformer 3, which can be specifically connected through a high-voltage switch 03, and the high-voltage side of the transformer 3 and the low-voltage side of the transformer 3 are both provided with a voltage transformer 01, and the voltage transformer 01 is connected to the fault analysis and positioning device 7 through a coaxial cable 10; each collection line 0 is connected to the low-voltage cable 4 through an industrial frequency current sensor 9, and the industrial frequency current sensor 9 is connected to the fault analysis and positioning device 7 through a coaxial cable 10; the copper shielding layer of the high-voltage cable 2 is provided with a grounding terminal 20, and the grounding terminal 20 includes a broadband current sensor 8, and the broadband current sensor 8 is connected to the fault analysis and positioning device 7 through a coaxial cable 10.

[0030] Specifically, in an optional embodiment provided by the present disclosure, the low-voltage cable 4 is an AC800V line, including a three-core 800V cable, for transmitting AC800V electric energy; the high-voltage cable 2 is an AC35kV line, including a three-core 35kV cable, for transmitting AC35kV electric energy. The step-up transformer 1 can step up the AC800V electric energy into AC35kV electric energy for transmission. The step-up transformer 1 includes a high-voltage switch 03, a transformer 3, a low-voltage switch 04, a measuring and protecting device 05, and the like. The high-voltage switch 03 is located on the high-voltage side of the transformer 3, and the low-voltage switch 04 is located on the low-voltage side of the transformer 3. The measuring and protecting device 05 is used to protect the transformer 3 from overload and short-circuit damage, and to ensure the safe and stable operation of the transformer 3.

[0031] Transformer 3 can boost AC800V electric energy into AC35kV electric energy. Optionally, transformer 3 can adopt a three-phase double-winding oil-immersed transformer with a capacity of 2000-3200kVA and a rated transformation ratio of 36.5±2*2.5% / 0.8kV. Transformer 3 can provide high-voltage side and low-voltage side power frequency voltage measurement signals for fault analysis and positioning device 7 through voltage transformer 01 at the same time.

[0032] The photovoltaic inverter 5 is used to invert a DC 380V-1000V current into an AC 800V current. Optionally, the photovoltaic inverter 5 includes 6 MPPTs (Maximum Power Point Tracking).

[0033] Optionally, the photovoltaic string 6 is composed of 28 photovoltaic modules, which can convert solar energy into electrical energy.

[0034] The fault analysis and positioning device 7 can collect the power frequency zero sequence voltage on the high voltage side of the transformer 3, the low frequency transient zero sequence current and the high frequency transient traveling wave current on the high voltage cable 2 in real time, and at the same time, collect the power frequency zero sequence voltage on the low voltage side of the transformer 3, the power frequency current and the power frequency zero sequence current of each collection line 0 in the low voltage cable 4 in real time, and comprehensively judge whether the collection line has a fault. After a fault occurs, the fault is accurately located and the line is selected.

[0035] The broadband current sensor 8 includes a low-frequency current sensor and a high-frequency current sensor. Optionally, the broadband current sensor 8 is installed on the copper shielding layer grounding wire of the high-voltage cable 2 in a snap-on form, and collects the low-frequency transient zero-sequence current and high-frequency transient traveling wave current signals of the AC35KV line in real time, and transmits the current signal to the fault analysis and positioning device 7 through the coaxial cable 10. The sampling bandwidth of the broadband current sensor 8 is: 25khz-25Mhz, wherein the sampling bandwidth of the low-frequency current sensor is 1hz-12khz, and the sampling bandwidth of the high-frequency current sensor is 25khz-25Mhz, the signal input range is: 0A-600A (peak-to-peak value), the signal output range is: 3-5V, and the accuracy is 1%.

[0036] A plurality of power frequency current sensors 9 are mounted on the low voltage cable 4 in a snap-on manner, and the power frequency current and power frequency zero sequence current signals of each collecting line 0 are collected in real time, and the current signals are transmitted to the fault analysis and positioning device 7 through the coaxial cable 10. The sampling bandwidth of the power frequency current sensor 9 is: 1 Hz-1 khz, the signal input range is: 0A-1000A (peak-to-peak value), the signal output range is: 3-5V, and the accuracy is 1%.

[0037] The coaxial cable 10 is used to transmit the current signals collected by the broadband current sensor 8 and the industrial frequency current sensor 9 to the fault analysis and locating device 7, and is also used to transmit the voltage signals collected by the voltage transformer 01 on the high-voltage side and the low-voltage side of the transformer 3 to the fault analysis and locating device 7. Optionally, the coaxial cable 10 is a coaxial shielded twisted pair cable.

[0038] In this way, by arranging a current sensor, a voltage transformer, and a fault analysis and positioning device 7 in the step-up transformer 1, the power frequency zero-sequence voltage on the high-voltage side of the transformer 3, the low-frequency transient zero-sequence current and the high-frequency transient traveling wave current on the high-voltage cable 2 can be collected in real time. At the same time, the power frequency zero-sequence voltage on the low-voltage side of the transformer 3, the power frequency zero-sequence current and the power frequency current of each collecting line 0 in the low-voltage cable 4 can be collected in real time, and a comprehensive analysis can be made as to whether a fault has occurred in the collector line, and a preliminary judgment can be made as to whether the fault has occurred in the high-voltage cable 2 or the low-voltage cable 4, thereby improving the efficiency of fault detection and emergency repair of the collector line of the photovoltaic power station and enhancing the reliability of power generation in the photovoltaic power station.

[0039] Please continue to refer to Figure 1 and Figure 2 In an optional embodiment provided in the present disclosure, the boost box transformer 1 includes a first output terminal 11 and a second output terminal 12, the first output terminal 11 is connected to the next boost box transformer, and the second output terminal 12 is connected to the boost substation or the previous boost box transformer;

[0040] One end of the high-voltage cable 2 is connected to the first output end 11 , and the other end of the high-voltage cable 2 is connected to the second output end 12 .

[0041] Specifically, after the photovoltaic string 6 passes through the photovoltaic inverter 5, 11 collection lines 0 are formed, and the collection lines 0 pass through the boost box transformer 1 and are connected in parallel to the high-voltage cable 2 in the boost box transformer 1. One end of the high-voltage cable 2 is connected to the first output end 11 of the boost box transformer 1, and the other end of the high-voltage cable 2 is connected to the second output end 12 of the boost box transformer 1. The first output end 11 of the boost box transformer 1 is connected to the next boost box transformer, and the second output end 12 of the boost box transformer 1 is connected to the boost substation or the previous boost box transformer. Optionally, when the boost box transformer 1 is the first boost box transformer connected to the boost substation, the second output end 12 of the boost box transformer 1 is connected to the boost substation, the first output end 11 of the boost box transformer 1 is connected to the next boost box transformer, the second output end of the next boost box transformer is connected to the first boost box transformer 1, and the first output end of the next boost box transformer is connected to another box transformer... and connected to other boost box transformers in this way. Optionally, the first output terminal 11 of the booster transformer 1 is connected to the next booster transformer, the second output terminal 12 of the booster transformer 1 is connected to the previous booster transformer, ... and in this way, it is connected to other booster transformers, and the second output terminal of the last booster transformer is connected to the booster substation, that is, an AC35KV line includes multiple booster transformers 1 in parallel, and the AC35KV line is connected to the main grid through the 220kV booster substation. In this way, multiple booster transformers 1 can be collected through the AC35KV line, and then connected to the main grid through the booster substation to transmit electricity to the main grid.

[0042] Please continue to refer to Figure 1 and Figure 2 In an optional embodiment provided in the present disclosure, the high-voltage cable 2 includes a copper shielding layer, a grounding terminal 20 is provided on the copper shielding layer, the grounding terminal 20 includes a first grounding terminal 21 and a second grounding terminal 22, the first grounding terminal 21 is connected to the copper shielding layer of the high-voltage cable 2 and the first output terminal 11, and the second grounding terminal 22 is connected to the copper shielding layer of the high-voltage cable 2 and the second output terminal 12;

[0043] The broadband current sensor 8 includes a first broadband current sensor 81 and a second broadband current sensor 82. The first broadband current sensor 81 is located at the first grounding terminal 21, and is connected to the fault analysis and positioning device 7 via a coaxial cable 10. The second broadband current sensor 82 is located at the second grounding terminal 22, and is connected to the fault analysis and positioning device 7 via a coaxial cable 10.

[0044] Specifically, a first grounding terminal 21 is provided between the high-voltage cable 2 and the first output terminal 11 of the step-up transformer 1, and the first grounding terminal 21 includes a first broadband current sensor 81, which is installed in the form of a snap on the copper shielding layer grounding wire of the high-voltage cable 2, and the first broadband current sensor 81 is connected to the fault analysis and positioning device 7 via a coaxial cable 10; a second grounding terminal 22 is provided between the high-voltage cable 2 and the second output terminal 12 of the step-up transformer 1, and the second grounding terminal 22 includes a second broadband current sensor 82, which is installed in the form of a snap on the copper shielding layer grounding wire of the high-voltage cable 2, and the second broadband current sensor 82 is connected to the fault analysis and positioning device 7 via a coaxial cable 10. Device 7; the fault analysis and positioning device 7 is used to collect low-frequency transient zero-sequence current and high-frequency transient traveling wave current signals on the high-voltage cable 2. The low-frequency transient zero-sequence current is used to determine whether a ground fault occurs. The fault analysis and positioning device 7 can also determine whether a high-voltage line fault occurs by comparing the polarity of the high-frequency transient traveling wave current signals at both ends of the high-voltage cable 2. In this way, by respectively arranging broadband current sensors 8 at both ends of the copper shielding layer of the high-voltage cable 2 of the booster transformer 1, it is possible to determine whether a ground fault occurs based on the collected low-frequency transient zero-sequence current, and it is possible to determine whether a high-voltage line fault occurs based on the polarity of the collected high-frequency transient traveling wave current signal. The fault of the collector line can be accurately located, thereby improving the efficiency of fault finding.

[0045] Figure 3 FIG. 1 is a schematic diagram showing the connection of the internal modules of a fault analysis and positioning device provided by an embodiment of the present disclosure. Please refer to FIG. Figures 1 to 3 In an optional embodiment provided by the present disclosure, the fault analysis and positioning device 7 includes a collection unit 10, a signal processing and storage unit 25, and a central processing unit 30; the collection unit 10 is connected to the signal processing and storage unit 25, and the signal processing and storage unit 25 is connected to the central processing unit 30; the collection unit 10 is used to collect current signals or voltage signals on the high-voltage cable 2, the low-voltage cable 4, and the high-voltage side and the low-voltage side of the transformer 3; the signal processing and storage unit 25 is used to pre-process, pre-calculate and cache the signals collected by the collection unit 10; the central processing unit 30 is used to perform data calculation and processing on the pre-processed and pre-calculated information.

[0046] Specifically, the fault analysis and positioning device 7 includes a terminal 77, a broadband current sensor 8, an industrial frequency current sensor 9, a high-voltage side voltage transformer 01 of the transformer 3, and a low-voltage side voltage transformer 01 are connected to the terminal 77 through a coaxial cable 10, and the acquisition unit 10 collects low-frequency transient zero-sequence current signals, high-frequency transient traveling wave current signals, industrial frequency current signals, industrial frequency zero-sequence current signals, and industrial frequency zero-sequence voltage signals through the terminal 77.

[0047] The signal processing and storage unit 25 includes an FPGA (Field Programmable Gate Array), which is used to pre-process and pre-calculate data. It has a 32-channel digital sampling interface inside, which performs data pre-processing and logic pre-calculation on the received digital signal. Optionally, the FPGA model is XC7Z020, which consists of 6 parts: a programmable input and output unit, a programmable logic unit, a clock management, an embedded block RAM (Random Access Memory), an embedded bottom functional unit, and an embedded dedicated hardware module. The FPGA can be used repeatedly without a special programmer, and has the advantages of radiation resistance, high and low temperature resistance, low power consumption, and high speed. It integrates commonly used RAM, clock management, and DSP (Digital Signal Process) functions. The high-precision clock in the synchronous clock encoding module 23 inside the FPGA generates a time signal with an accuracy of ns level and transmits it to the FPGA for accurate calibration of the trigger moment, and allows the recorded and stored waveforms to have accurate time stamps. The time signal input is in 1PPS (1Pluse Per Second, one pulse per second) mode. The synchronization signal receiving circuit directly receives the 1PPS pulse from the GPS synchronization clock. The SRAM1-4 inside the FPGA is a static random access memory, which caches the collected and calculated low-frequency transient zero-sequence current signal, high-frequency transient traveling wave current signal, power frequency zero-sequence current signal, power frequency current signal, and power frequency zero-sequence voltage signal of the collector line and the collection line 0.

[0048] The signal processing and storage unit 25 sends the pre-processing and pre-calculation information to the central processing unit 30 through an internal CAN (Controller Area Network) bus interface, and the central processing unit 30 further performs data calculation and processing.

[0049] Optionally, the MCU (Microcontroller Unit) model used by the central processing unit 30 is a DSC (Digital signal controller) chip of STM32f407VG. The chip has abundant internal resources, large storage capacity and low price. At the same time, the ARM chip has a wireless communication interface and an Ethernet communication interface, and can also generate PWM (Pulse-Width Modulation) waves, and can quickly process and output analog quantities, image information, control signals, alarm signals, etc.

[0050] In this way, by setting up a fault analysis and positioning device 7 including a collection unit 10, a signal processing and storage unit 25, and a central processing unit 30, the collected current and voltage signals can be converted into digital signals and then cached or further processed, which is convenient for comprehensive analysis of the photovoltaic power station collection line and improves the efficiency of fault finding.

[0051] Please continue to refer to Figures 1 to 3 In an optional embodiment provided by the present disclosure, the acquisition unit 10 includes an overvoltage protection module 13, a signal conditioning module 14, and an analog-to-digital conversion module 15 connected in sequence; the acquisition unit 10 includes a first acquisition unit 11 and a second acquisition unit 12, the acquisition end of the first acquisition unit 11 is connected to the voltage transformer 01 and the broadband current sensor 8 on the high-voltage side of the transformer 3 through a coaxial cable 10, and the acquisition end of the second acquisition unit 12 is connected to the voltage transformer 01 and the power frequency current sensor 9 on the low-voltage side of the transformer 3 through a coaxial cable 10; the output end of the acquisition unit 10 is connected to the signal processing and storage unit 25; the acquisition end is connected to the overvoltage protection module 13, and the output end is connected to the analog-to-digital conversion module 15, optionally, the acquisition end includes a wiring terminal 77, and the wiring terminal 77 is used to obtain a voltage signal or a current signal through the coaxial cable 10.

[0052] Specifically, the acquisition unit 10 includes an overvoltage protection module 13, a signal conditioning module 14, and an analog-to-digital conversion module 15. The analog-to-digital conversion module 15 includes a low-speed analog-to-digital converter 16 and a high-speed analog-to-digital converter 17. The low-frequency current sensor, the power frequency current sensor 9, and the voltage transformer 01 in the broadband current sensor 8 transmit the collected low-frequency transient zero-sequence current, power frequency zero-sequence current, power frequency current, and power frequency zero-sequence voltage signals to the low-speed analog-to-digital converter 16 through the overvoltage protection module 13 and the signal conditioning module 14, and the low-speed analog-to-digital converter 16 converts them into digital signals and transmits them to the signal processing and storage unit 25. The high-frequency current sensor in the broadband current sensor 8 transmits the collected high-frequency transient traveling wave current signal through the overvoltage protection module 13 and the signal conditioning module 14 to the high-speed analog-to-digital converter 17, and the high-speed analog-to-digital converter 17 converts the high-frequency transient traveling wave current signal into a digital signal and transmits it to the signal processing and storage unit 25.

[0053] Optionally, the overvoltage protection module 13 uses a 12V / 5A voltage-stabilized power supply, and the voltage-stabilized range of the overvoltage protection module 13 is 12V. The overvoltage protection module 13 includes a voltage-stabilizing part and an overvoltage protection part. The voltage-stabilizing part is composed of a 7805 three-terminal voltage regulator and a current-expanding transistor, and the potential of the adjustment end is raised by a voltage-stabilizing diode and a light-emitting diode in series. The overvoltage protection part uses a thyristor short-circuit power supply to force the fuse to blow quickly to protect the safety of the subsequent circuit, and the blowing time is 1 to 3 microseconds.

[0054] Optionally, the signal conditioning module 14 may convert the voltage signal of ±3-5V passing through the overvoltage protection module 13 into a current signal of ±2-3mA.

[0055] Optionally, the analog-to-digital converter model used in the analog-to-digital conversion module 15 is AD9252, and the analog-to-digital conversion module 15 includes 8-channel high-speed and 8-channel low-speed, 14-bit, 50M SPS (Sample Per Second, the number of samples per second) and 2k analog-to-digital converters (ADCs). The module is powered by a single 1.8V power supply and has a built-in on-chip sample-and-hold circuit, which has the advantages of low price, low power consumption, small size and ease of use. It uses a 64-pin LFCSP package that complies with the RoHS standard and is rated for an industrial temperature range of -40°C to +85°C.

[0056] The acquisition unit 10 includes a first acquisition unit 11 and a second acquisition unit 12. In an optional embodiment provided in the present disclosure, the first acquisition unit 11 is an AC35KV line analog quantity acquisition unit, and the second acquisition unit 12 is an AC800V line analog quantity acquisition unit. The AC35KV line analog quantity acquisition unit is connected to 1 power frequency zero-sequence voltage signal, 2 low-frequency transient zero-sequence current signals, and 2 high-frequency transient traveling wave current signals, that is, 1 power frequency zero-sequence voltage signal collected by the voltage transformer 01 on the high-voltage side of the transformer 3, 1 low-frequency transient zero-sequence current signal collected by the low-frequency current sensor in the first broadband current sensor 81, 1 low-frequency transient zero-sequence current signal collected by the low-frequency current sensor in the second broadband current sensor 82, 1 high-frequency transient traveling wave current signal collected by the high-frequency current sensor in the first broadband current sensor 81, and 1 high-frequency transient traveling wave current signal collected by the high-frequency current sensor in the second broadband current sensor 82. The AC800V line analog quantity acquisition unit is connected to 11 power frequency current signals and 1 power frequency voltage signal, that is, the power frequency current sensor 9 in the 11-way collection line 0 collects the power frequency current signal and the power frequency transient zero-sequence current signal, and the voltage transformer 01 on the low-voltage side of the 1-way transformer 3 collects the power frequency zero-sequence voltage signal.

[0057] In this way, the current and voltage signals on the high-voltage cable 2 and the low-voltage cable 4 can be collected respectively by the first collection unit 11 and the second collection unit 12, and the collected signals can be processed and converted into digital signals by the overvoltage protection module 13, the signal conditioning module 14, and the analog-to-digital conversion module 15 in the collection unit 10, so as to facilitate further processing by the signal processing and storage unit 25.

[0058] Please continue to refer to Figures 1 to 3In an optional embodiment provided by the present disclosure, the fault analysis and positioning device 7 also includes a display unit 40, an operation unit 50 and a communication unit 60. The display unit 40, the operation unit 50 and the communication unit 60 are located in the housing 71 of the fault analysis and positioning device 7. The display unit 40 and the operation unit 50 are respectively connected to the central processing unit 30 through the optical coupling isolation 51; the display unit 40 includes an indicator light 74 and a liquid crystal display screen 72, and the liquid crystal display screen 72 is used to display the operation information, fault information, and parameter information of each unit of the photovoltaic power station collection line; the operation unit 50 includes a plurality of operation buttons 73; the communication unit 60 includes a remote communication network port and a USB debugging interface 75. The remote communication network port is connected to the remote master station system for receiving instructions or sending information, and the USB debugging interface 75 is connected to an external computer for updating the program of the fault analysis and positioning device 7 or setting parameters.

[0059] Specifically, the fault analysis and positioning device 7 includes a main body shell 71. Optionally, the shell 71 can be made of stainless steel with a protection grade of IP54. The present disclosure does not specifically limit the material of the shell 71, which shall be based on actual needs.

[0060] The display unit 40 includes a liquid crystal display screen 72, which is located in the housing of the fault analysis and positioning device 7 and is used to display a human-computer interaction interface, including equipment information display, fault information display, line operation information display, etc. The display unit 40 also includes an indicator light 74, and the present disclosure does not specifically limit the type of the indicator light 74. Optionally, the indicator light 74 may include a status indicator light, a power indicator light, a communication indicator light, a fault indicator light, an operation indicator light, a self-test indicator light, etc.

[0061] The operating unit 50 includes operating buttons 73 , which are located in the housing 71 of the fault analysis and positioning device 7 . The operating buttons 73 include multiple operating buttons 73 such as “up, down, left, right, cancel, and confirm”.

[0062] The communication unit 60 includes a USB debugging interface 75, which is located in the housing 71 of the fault analysis and locating device 7. The USB debugging interface 75 is used to connect to an external computer to update the program or set fixed value parameters for the fault analysis and locating device 7.

[0063] The communication unit 60 also includes a SIM card slot 76 for accommodating a wireless 4G communication card.

[0064] The communication unit 60 also includes a remote communication network port, which is optionally an RJ45 network port connected to the remote master station system 100, sends information to the remote master station system, and receives various instructions from the master station system 100. RS232 and RS485 interfaces are local communication connection interfaces with other intelligent devices.

[0065] The communication unit 60 also includes a terminal 77, which is used to connect to the broadband current sensor 8, the power frequency current sensor 9, the high-voltage side voltage transformer 01 of the transformer 3, and the low-voltage side voltage transformer 01 through the coaxial cable 10. The present disclosure does not specifically limit the number of the terminal 77, which can be set according to actual conditions.

[0066] Optionally, the optocoupler isolator 51 is of model TLP112, which ensures the stability and anti-interference of the input and output state quantities and analog signals.

[0067] In this way, by setting up a fault analysis and positioning device 7 including a display unit 40, an operating unit 50 and a communication unit 60, the fault analysis and positioning device 7 can be connected to an external system, various sensors, etc. It can also be used to display line information, making the line information and fault information more intuitive, shortening the fault finding time of maintenance personnel, and improving the efficiency of emergency repairs.

[0068] Figure 4 The figure is a flow chart of a photovoltaic power station collector line fault analysis and location method provided by the embodiment of the present disclosure. Figures 1 to 4 The present disclosure provides a photovoltaic power station collector line fault analysis and positioning method, which is applied in the photovoltaic power station collector line fault analysis and positioning system 100 as above, and the method includes the following steps:

[0069] Step S1: the fault analysis and positioning device 7 is initialized, the first acquisition unit 11 starts the sampling and calculation of the power frequency zero-sequence voltage, low-frequency transient zero-sequence current and high-frequency transient traveling wave current on the high-voltage side of the transformer 3; the second acquisition unit 12 starts the sampling and calculation of the power frequency zero-sequence voltage, power frequency zero-sequence current and power frequency current of each collection line 0 on the low-voltage side of the transformer 3;

[0070] Step S2: Compare the power frequency zero-sequence current and the low-frequency transient zero-sequence current to see if they exceed the set value; if any of the currents exceeds the set threshold, proceed to step S3; if neither the power frequency zero-sequence current nor the low-frequency transient zero-sequence current exceeds the threshold, the fault analysis and positioning device 7 is initialized, reset, and re-collected to return to step S1;

[0071] Step S3: comparing whether the polarities of the high-frequency transient traveling wave currents on the high-voltage cable 2 are consistent;

[0072] Step S31: If they are consistent, determine whether the power frequency zero-sequence voltage on the low-voltage side of transformer 3 exceeds the first threshold; if it exceeds, determine that the low-voltage line is faulty;

[0073] Step S32: If they are inconsistent, determine whether the power frequency zero-sequence voltage on the high-voltage side of the transformer 3 exceeds the second threshold; if so, determine that the high-voltage line is faulty.

[0074] In an optional embodiment provided by the present disclosure, optionally, the first acquisition unit 11 is used to collect the power frequency zero-sequence voltage, low-frequency transient zero-sequence current and high-frequency transient traveling wave current of the AC35KV line, wherein the power frequency zero-sequence voltage on the high-voltage side of the transformer 3 is sampled and calculated by the voltage transformer 01 on the high-voltage side of the transformer 3, and the low-frequency transient zero-sequence current and high-frequency transient traveling wave current are sampled and calculated by the broadband current sensor 8 on the grounding terminal 20 of the high-voltage cable 2. The second acquisition unit 12 is used to collect the power frequency zero-sequence voltage, power frequency zero-sequence current and power frequency current of each collection line 0 of the AC800V line, wherein the power frequency zero-sequence voltage on the low-voltage side of the transformer 3 is sampled and calculated by the voltage transformer 01 on the low-voltage side of the transformer 3, and the power frequency zero-sequence current and power frequency current are sampled and calculated by the power frequency current sensor 9 on each collection line 0.

[0075] In step S2, based on the different collector lines and operating conditions of each photovoltaic power station, the set values ​​of the power frequency zero-sequence current and the low-frequency transient zero-sequence current are also different. The present disclosure does not specifically limit the numerical value of the set value, and it can be set according to the actual situation. Optionally, the set value can be the maximum short-circuit current. When any current in the power frequency zero-sequence current and the low-frequency transient zero-sequence current exceeds the set value, it is judged that a short-circuit fault occurs in the corresponding line, and step S3 is required to further compare whether the polarity of the high-frequency transient traveling wave current on the high-voltage cable 2 of each booster box transformer 1 is consistent. If neither exceeds the set value, return to step S1 to re-sample and calculate each current and voltage signal.

[0076] In step S3, compare whether the polarity of the high-frequency transient traveling wave current on the high-voltage cable 2 is consistent; further, in step S31, if the polarity of the high-frequency transient traveling wave current collected on the high-voltage cable 2 in each step-up box transformer 1 is consistent (i.e. the same), it means that a short circuit is detected in the photovoltaic power station collector line in step S2, but the AC35KV line is normal, which means that the short circuit occurs in the AC800V line, and it is necessary to further determine whether the power frequency zero-sequence voltage on the low-voltage side of the transformer 3 exceeds the first threshold. If it does not exceed, return to step S1 to re-collect the current and voltage signals. If it exceeds, it can be determined that the AC800V line is faulty and further fault line selection is required. Optionally, the first threshold is set to 50V. The present disclosure does not specifically limit the value of the first threshold, and it can be set according to actual conditions.

[0077] In step S32, when any current in step S2 exceeds the set value, the photovoltaic power station collection line fails, and step S3 needs to be performed to further compare whether the polarity of the high-frequency transient traveling wave current on the high-voltage cable 2 is consistent. If the polarity of the high-frequency transient traveling wave current collected by each step-up transformer 1 is opposite (i.e. inconsistent), it is necessary to determine whether the high-voltage side (AC35kV) industrial frequency zero-sequence voltage exceeds the threshold. If it does not exceed, it indicates that the external power grid on the high-voltage side is disturbed. If it exceeds, it indicates that the AC35KV line has a fault and the fault point needs to be located.

[0078] Optionally, the second threshold is set to 50V. The present disclosure does not specifically limit the value of the second threshold, which can be set according to actual conditions.

[0079] In this way, through multi-level comparison and analysis, the fault analysis and positioning of the photovoltaic power station collection line can be realized. By comparing the current or voltage signal with the set threshold, the fault location can be accurately determined, which can improve the efficiency of fault detection and emergency repair.

[0080] Please continue to refer to Figures 1 to 4 In an optional embodiment provided in the present disclosure, step S31 is specifically as follows: step S311: if the power frequency zero-sequence voltage on the low-voltage side of the transformer 3 is less than the first threshold, the fault analysis and positioning device 7 is initialized, reset and re-collected back to step S1; step S312: if the power frequency zero-sequence voltage on the low-voltage side of the transformer 3 is greater than or equal to the first threshold, it is determined that the low-voltage line is faulty, and further detection and determination are made as to whether the power frequency current of each collection line 0 exceeds the third threshold.

[0081] Specifically, when any current in step S2 exceeds the set value, it indicates that the photovoltaic power station collection line has a fault, and step S3 needs to be performed to further compare whether the polarity of the high-frequency transient traveling wave current on the high-voltage cable 2 is consistent. If the polarity of the high-frequency transient traveling wave current collected on the high-voltage cable 2 in each step-up transformer 1 is consistent (i.e. the same), it means that the AC35KV line has not failed, and it is necessary to further determine whether the industrial frequency zero-sequence voltage on the low-voltage side of the transformer 3 exceeds the first threshold.

[0082] In step S311, when the industrial frequency zero-sequence voltage on the low-voltage side of transformer 3 is less than the first threshold, it indicates that there is no fault in the AC800V line, and the fault analysis and positioning device 7 is initialized, and returns to step S1, resets, and re-collects the current and voltage signals of each line.

[0083] In step S312, when the power frequency zero-sequence voltage on the low-voltage side of transformer 3 is greater than or equal to the first threshold, it is determined that the AC800V line has a fault, and it is necessary to perform fault line selection on collection line 0.

[0084] In this way, by comparing the power frequency zero-sequence voltage on the low-voltage side of the transformer 3 with the first threshold, it is possible to determine whether a fault has occurred in the AC800V line based on the consistency of the polarity of the high-frequency transient traveling wave current on the high-voltage cable 2, thereby shortening the scope of fault detection and improving the efficiency of fault finding.

[0085] Please continue to refer to Figures 1 to 4 In an optional embodiment provided by the present disclosure, step S312 is specifically as follows: if the power frequency currents of each collecting line 0 are all less than the third threshold value, it is determined that the external line on the low-voltage side is disturbed, the fault analysis and positioning device 7 is initialized, reset and re-collected to return to step S1; if there is a power frequency current greater than the third threshold value in each collecting line 0, a fault line is selected, and it is determined that the collecting line 0 with a power frequency current greater than or equal to the third threshold value has a fault; the fault analysis and positioning device 7 sends a fault alarm signal for the collecting line 0; the fault analysis and positioning device 7 is initialized, reset and re-collected to return to step S1.

[0086] Specifically, in step S312, when the power frequency zero sequence voltage on the low voltage side of the transformer 3 is greater than or equal to the first threshold, it is determined that the AC800V line has a fault, and it is necessary to determine the fault type and perform fault line selection, that is, it is necessary to detect the power frequency current sensor 9 corresponding to each collection line 0 in the AC800V line to determine whether the power frequency current of each collection line 0 exceeds the third threshold. Optionally, the third threshold is set to 60A, which is only an example here. The present disclosure does not specifically limit the value of the third threshold, and it can be set with reference to the actual situation.

[0087] When the power frequency current is less than the third threshold value 60A, it is determined that there is a disturbance in the external line on the low voltage side, and the fault analysis and positioning device 7 is initialized, reset, and re-collected to return to step 1.

[0088] When the power frequency current is greater than or equal to the third threshold value 60A, the fault line is selected to determine that the collection line 0 with a power frequency current greater than or equal to 60A is faulty. The fault analysis and positioning device 7 sends an AC800V line fault alarm signal, the fault analysis and positioning device 7 is initialized, reset, and re-collected back to step S1.

[0089] In this way, on the basis of the consistent polarity of the high-frequency transient traveling wave current on the high-voltage cable 2, by comparing the power frequency current with the third threshold, the fault line can be selected for the line whose collecting line 0 in the AC800V line is greater than the third threshold, the fault can be accurately located, the fault scope can be reduced, and the efficiency of fault finding and emergency repair can be improved.

[0090] Please continue to refer to Figures 1 to 4In an optional embodiment provided by the present disclosure, step S32 is specifically as follows: if the power frequency zero-sequence voltage on the high-voltage side of the transformer 3 is less than the second threshold value, it is judged that the external power grid on the high-voltage side is disturbed, the fault analysis and positioning device 7 is initialized, reset and re-collected to return to step S1; if the power frequency zero-sequence voltage on the high-voltage side of the transformer 3 is greater than or equal to the second threshold value, it is judged that a high-voltage line fault occurs, the fault section is located according to the line topology structure, the double-end traveling wave ranging is started, the fault point is accurately located, and the fault analysis and positioning device 7 sends a high-voltage line fault alarm signal; the fault analysis and positioning device 7 is initialized, reset and re-collected to return to step S1.

[0091] Specifically, based on the consistency judgment of the high-frequency transient traveling wave current of the high-voltage cable 2 in each step-up transformer 1 in step S3, if the polarity of the high-frequency transient traveling wave current is inconsistent, it is necessary to further judge whether the power frequency zero-sequence voltage on the high-voltage side of the transformer 3 exceeds the second threshold.

[0092] When the power frequency zero-sequence voltage on the high-voltage side of the transformer 3 is less than the second threshold, it is determined that there is a disturbance in the external power grid on the high-voltage side, and the fault analysis and positioning device 7 is initialized, reset, and re-collected to return to step S1.

[0093] When the power frequency zero-sequence voltage is greater than or equal to the second threshold, it is determined that a fault has occurred in the AC35kV line. The fault section is located according to the line topology structure, and the fault location is between two step-up transformers 1 with opposite polarities. At the same time, the double-end traveling wave ranging is started to accurately locate the fault point. Optionally, other methods can be selected to locate the fault, and the present disclosure does not make specific limitations on this. The fault analysis and positioning device 7 sends out an AC35kV line fault alarm signal. Optionally, the indicator light 74 may send out a flashing signal, or the LCD display 72 may pop up an alarm message, etc. The present disclosure does not make specific limitations on the fault alarm method. The fault analysis and positioning device 7 is initialized, reset, and re-collected back to step 1.

[0094] In this way, on the basis of the inconsistent polarity of the high-frequency transient traveling wave current, by comparing the power frequency zero-sequence voltage on the high-voltage side of transformer 3 with the second threshold, it is judged whether a fault has occurred in the AC35kV line, and the fault point is accurately located through the topological structure and double-end traveling wave ranging, thus shortening the scope of fault investigation and improving the efficiency of fault finding.

[0095] In summary, the present disclosure provides a photovoltaic power station collector line fault analysis and positioning system and method, which collects the power frequency zero-sequence voltage, low-frequency transient zero-sequence current and high-frequency transient traveling wave current of the high-voltage cable in the photovoltaic power station collector line in real time, and at the same time, collects the power frequency zero-sequence current, power frequency current and power frequency zero-sequence voltage of each low-voltage cable collection line in real time, and comprehensively judges whether the collector line has a fault, whether the fault occurs on the high-voltage cable or the low-voltage cable collection line. If the fault occurs on the high-voltage cable collection line, the high-voltage cable collector line is accurately located at the same time. If the fault occurs on the low-voltage cable collection line, the collection line is selected for fault at the same time. The system and method effectively solve the problem that collector line faults are difficult to analyze and locate, and can improve the efficiency of collector line fault finding and repair, enhance the reliability of photovoltaic power station power generation, and reduce economic losses.

[0096] The above description is only a specific embodiment of the present disclosure, so that those skilled in the art can understand or implement the present disclosure. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to the embodiments described herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A photovoltaic power station collector line fault analysis and positioning system, characterized in that: include: A plurality of collecting lines, each of which includes photovoltaic strings and photovoltaic inverters connected in a one-to-one correspondence; A step-up transformer, the step-up transformer comprising a low-voltage cable, a high-voltage cable, a transformer, and a fault analysis and positioning device, the low-voltage cable is connected to the low-voltage side of the transformer, the high-voltage cable is connected to the high-voltage side of the transformer, the high-voltage side of the transformer and the low-voltage side of the transformer are both provided with a voltage transformer, and the voltage transformer is connected to the fault analysis and positioning device via a coaxial cable; Each of the collecting lines is connected to the low-voltage cable via an industrial frequency current sensor, and the industrial frequency current sensor is connected to the fault analysis and positioning device via a coaxial cable; The copper shielding layer of the high-voltage cable is provided with a grounding terminal, and the grounding terminal includes a broadband current sensor, and the broadband current sensor is connected to the fault analysis and positioning device via a coaxial cable.

2. The photovoltaic power station collector line fault analysis and positioning system according to claim 1, characterized in that: The boost box transformer comprises a first output end and a second output end, the first output end is connected to the next boost box transformer, and the second output end is connected to the boost substation or the previous boost box transformer; One end of the high-voltage cable is connected to the first output end, and the other end of the high-voltage cable is connected to the second output end.

3. The photovoltaic power station collector line fault analysis and positioning system according to claim 2, characterized in that: The grounding terminal comprises a first grounding terminal and a second grounding terminal, the first grounding terminal is connected to the high-voltage cable and the first output terminal, and the second grounding terminal is connected to the high-voltage cable and the second output terminal; The broadband current sensor includes a first broadband current sensor and a second broadband current sensor. The first broadband current sensor is located at the first ground end and is connected to the fault analysis and positioning device via a coaxial cable. The second broadband current sensor is located at the second ground end and is connected to the fault analysis and positioning device via a coaxial cable.

4. The photovoltaic power station collector line fault analysis and positioning system according to claim 3, characterized in that: The fault analysis and positioning device includes a collection unit, a signal processing and storage unit, and a central processing unit; The acquisition unit is connected to the signal processing and storage unit, and the signal processing and storage unit is connected to the central processing unit; The acquisition unit is used to collect current signals or voltage signals of the high-voltage cable, the low-voltage cable, and the high-voltage side and the low-voltage side of the transformer; The signal processing and storage unit is used to pre-process, pre-calculate and cache the signals collected by the collection unit; The central processing unit is used to perform data calculation and processing on the pre-processed and pre-calculated information.

5. The photovoltaic power station collector line fault analysis and positioning system as claimed in claim 4, characterized in that: The acquisition unit includes an overvoltage protection module, a signal conditioning module, and an analog-to-digital conversion module which are connected in sequence; The acquisition unit includes a first acquisition unit and a second acquisition unit, wherein the acquisition end of the first acquisition unit is connected to the voltage transformer on the high voltage side of the transformer and the broadband current sensor through a coaxial cable, and the acquisition end of the second acquisition unit is connected to the voltage transformer on the low voltage side of the transformer and the power frequency current sensor through a coaxial cable; the output end of the acquisition unit is connected to the signal processing and storage unit; The acquisition end is connected to the overvoltage protection module, and the output end is connected to the analog-to-digital conversion module.

6. The photovoltaic power station collector line fault analysis and positioning system according to claim 4, characterized in that: The fault analysis and positioning device further comprises a display unit, an operation unit and a communication unit, wherein the display unit, the operation unit and the communication unit are located in the housing of the device, and the display unit, the operation unit and the central processing unit are connected via optical coupling isolation; The display unit includes an indicator light and a liquid crystal display screen, and the liquid crystal display screen is used to display the operation information, fault information, and parameter information of each unit of the photovoltaic power station collector line; The operating unit includes a plurality of buttons; The communication unit includes a remote communication network port and a USB debugging interface. The remote communication network port is connected to a remote master station system for receiving instructions or sending information. The USB debugging interface is connected to an external computer for updating the program of the device or setting parameters.

7. A photovoltaic power station collector line fault analysis and positioning method, applied in a photovoltaic power station collector line fault analysis and positioning system as claimed in any one of claims 1 to 6, characterized in that: The method comprises the following steps: Step S1: The fault analysis and positioning device is initialized, and the first acquisition unit starts sampling and calculating the power frequency zero-sequence voltage, low-frequency transient zero-sequence current and high-frequency transient traveling wave current on the high-voltage side of the transformer; the second acquisition unit starts sampling and calculating the power frequency zero-sequence voltage, power frequency zero-sequence current and power frequency current of each collection line on the low-voltage side of the transformer; Step S2: Compare the power frequency zero-sequence current and the low-frequency transient zero-sequence current to see if they exceed the set value; If any of the currents exceeds the set threshold, proceed to step S3; if both the power frequency zero-sequence current and the low-frequency transient zero-sequence current do not exceed the threshold, the device is initialized, reset, and re-collected back to step S1; Step S3: comparing whether the polarities of the high-frequency transient traveling wave currents on the high-voltage cables are consistent; Step S31: If they are consistent, determine whether the power frequency zero-sequence voltage on the low-voltage side of the transformer exceeds the first threshold; If it exceeds, it is judged that the low-voltage line is faulty; Step S32: If not, determine whether the power frequency zero-sequence voltage on the high-voltage side of the transformer exceeds a second threshold; If it exceeds, it is judged that the high-voltage line is faulty.

8. The photovoltaic power station collector line fault analysis and location method according to claim 7, characterized in that: The step S31 is specifically as follows: Step S311: If the power frequency zero-sequence voltage on the low-voltage side of the transformer is less than the first threshold, the fault analysis and positioning device is initialized, reset, and re-collected to return to step S1; Step S312: If the power frequency zero-sequence voltage on the low voltage side of the transformer is greater than or equal to the first threshold, it is determined that the low voltage line is faulty, and further detection and determination are made as to whether the power frequency current of each collection line exceeds a third threshold.

9. The photovoltaic power station collector line fault analysis and location method according to claim 8, characterized in that: The step S312 is specifically as follows: If the power frequency currents of all the collection lines are less than the third threshold, it is determined that the external line on the low voltage side is disturbed, the fault analysis and positioning device is initialized, reset and re-collected to return to step S1; If there is a power frequency current greater than or equal to the third threshold in each collection line, a fault line is selected to determine that the collection line with the power frequency current greater than the third threshold is faulty; The fault analysis and locating device sends out a collection line fault alarm signal; the fault analysis and locating device is initialized, reset, and re-collected back to step S1.

10. The photovoltaic power station collector line fault analysis and location method according to claim 7, characterized in that: The step S32 is specifically as follows: If the power frequency zero-sequence voltage on the high-voltage side of the transformer is less than the second threshold, it is determined that there is a disturbance in the external power grid on the high-voltage side, the fault analysis and positioning device is initialized, reset, and re-collected to return to step S1; If the industrial frequency zero-sequence voltage on the high-voltage side of the transformer is greater than or equal to the second threshold, it is determined that a high-voltage line fault has occurred. The fault section is located according to the line topology structure, and the double-terminal traveling wave ranging is started to accurately locate the fault point. The fault analysis and locating device sends a high-voltage line fault alarm signal; the fault analysis and locating device is initialized, reset, and re-collected to return to step S1.

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