A photovoltaic system grounding transformer fault determination and protection method

Abstract

The present application relates to the technical field of transformer fault determination, and discloses a method for determining and protecting a grounding transformer fault in a photovoltaic system. The method comprises: obtaining system operation data through an IEC61850 standard acquisition terminal, judging the fault direction based on zero-sequence current and voltage phase comparison, determining the fault location in combination with the branch characteristic quantity difference and phase relationship, and accurately cutting off the fault branch after safety verification to avoid the problem of mis-cutting. The present application can realize the precise positioning and selective cutting of grounding transformer faults in photovoltaic systems, avoiding the problem of mis-cutting caused by grid-side faults.

Description

Technical Field

[0001] The present application relates to the field of transformer fault determination, and in particular to a photovoltaic system grounding transformer fault determination and protection method. Background Art

[0002] In the existing photovoltaic system, the configuration of grounding transformer is indispensable. The grounding transformer uses an artificially manufactured neutral point grounding resistor or arc suppression coil, and its grounding resistance is generally controlled within a few ohms. When a ground fault occurs in the system, it presents high impedance to positive and negative sequence currents and low impedance to zero sequence currents, so that the grounding protection can operate reliably. In the current photovoltaic system, the communication method based on the IEC61850 standard is generally adopted. This standard adopts an object-oriented information model, abstracts the functions and attributes of the equipment into objects, supports the seamless connection between traditional power equipment and new photovoltaic systems, and provides a wealth of security features, including access control, data encryption, identity authentication and other functions.

[0003] However, there are some technical defects in the existing photovoltaic system grounding transformer protection: first, the grounding transformer protection device does not have the function of detecting and determining the fault point, resulting in the grounding transformer protection also being activated when a single-phase grounding fault occurs in the line outside the photovoltaic power station, cutting off the photovoltaic power station; secondly, when a single-phase grounding fault occurs on the grid side, it will cause the grounding transformer protection of the photovoltaic power station to be activated, cutting off the photovoltaic power station from the grid, causing a loss of power generation. In this case, although the photovoltaic power station has no fault, it is forced to be cut off due to the grid fault; in addition, in the photovoltaic energy storage system, many devices and components do not have the IEC61850 standard functions, which seriously limits the flexible expansion and upgrade capabilities of the system. Summary of the invention

[0004] The present application provides a photovoltaic system grounding transformer fault determination and protection method, which is used to accurately locate and selectively remove grounding transformer faults in photovoltaic systems, thereby avoiding the problem of erroneous removal due to grid-side faults.

[0005] In a first aspect, the present application provides a photovoltaic system grounding transformer fault determination and protection method, the photovoltaic system grounding transformer fault determination and protection method comprising: The zero-sequence current data of the grounding transformer, the current and voltage data of the feeder line, and the operation data of the photovoltaic branch in the photovoltaic system are sampled and acquired through the acquisition terminal based on the IEC61850 standard, and the sampled data are transmitted to the station control system via the sampled value stream and digital quantity message to obtain a synchronous sampling data set; According to the zero-sequence current data and the zero-sequence voltage data in the synchronous sampling data set, a zero-sequence direction criterion result is obtained through phase comparison operation; According to the zero-sequence direction criterion result, the fault type is divided into regions, and the division result is transmitted to the dispatching system through the communication channel to obtain the initial judgment result of the internal and external faults; For internal faults, the fault location operation is performed by using the relationship between the fault branch current and the grounding transformer voltage and combining the multi-branch current comparison formula to obtain the fault branch characteristic quantity; Based on the fault branch characteristic quantity, the difference of each branch characteristic quantity is calculated, and the fault branch is determined in combination with the phase relationship between the voltage and the current, and a removal instruction data packet is generated; The removal instruction data packet is encrypted, authority verified and identity authenticated, and the verified removal instruction is sent to the fault branch circuit breaker to complete the accurate removal of the fault branch.

[0006] In the technical solution provided by the present application, the zero-sequence current data of the grounding transformer, the current and voltage data of the feeder line, and the operation data of the photovoltaic branch in the photovoltaic system are sampled and acquired through an acquisition terminal based on the IEC61850 standard, and transmitted to the station control system via the sampled value stream and the digital message, thereby realizing the real-time and accurate acquisition of the system operation data; the zero-sequence current data and the zero-sequence voltage data in the synchronous sampling data set are phase-compared to accurately determine the fault direction; the fault type is regionalized according to the zero-sequence direction judgment result, and the division result is transmitted to the dispatching system through the communication channel to effectively distinguish between internal and external faults; for internal faults, the relationship between the fault branch current and the grounding transformer voltage is used, and the fault location operation is performed in combination with the multi-branch current comparison formula, thereby realizing the accurate positioning of the fault position; the difference of the characteristic quantities of each branch is calculated based on the characteristic quantity of the fault branch, and the fault branch is judged in combination with the phase relationship between the voltage and the current, thereby ensuring the accuracy of the fault branch judgment; the removal instruction data packet is encrypted, the authority is verified, and the identity is authenticated through a three-layer security protection mechanism, thereby ensuring the safe and reliable execution of the control instruction. The entire solution achieves accurate judgment and selective removal of grounding faults in the photovoltaic system, avoids the problem of mis-removal due to external faults, and reduces unnecessary power generation losses. At the same time, the standard IEC61850 communication protocol is adopted to make the system have good compatibility and scalability, which is convenient for later function upgrades and system expansion. The multi-level data processing and safety protection mechanism in the solution ensures the reliability of fault judgment and processing, and improves the operating stability and power generation efficiency of the photovoltaic system. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0008] Figure 1 A schematic diagram of an embodiment of a method for determining and protecting a grounding transformer fault in a photovoltaic system according to an embodiment of the present application; Figure 2 It is another schematic diagram of the photovoltaic system grounding transformer fault determination and protection method in the embodiment of the present application; Figure 3 Schematic diagram of a photovoltaic system in an embodiment of the present application. DETAILED DESCRIPTION

[0009] The embodiment of the present application provides a method for determining and protecting a grounding transformer fault in a photovoltaic system. The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments described here can be implemented in an order other than that illustrated or described here. In addition, the terms "including" or "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0010] For ease of understanding, the specific process of the embodiment of the present application is described below. Figure 1 , an embodiment of a photovoltaic system grounding transformer fault determination and protection method in the embodiment of the present application includes: Step S101: sampling and acquiring the zero-sequence current data of the grounding transformer, the current and voltage data of the feeder line, and the operation data of the photovoltaic branch in the photovoltaic system through a collection terminal based on the IEC61850 standard, and transmitting the sampled data to the station control system via a sampled value stream and a digital quantity message to obtain a synchronous sampled data set; Step S102, obtaining a zero-sequence direction criterion result by performing phase comparison operation based on the zero-sequence current data and the zero-sequence voltage data in the synchronous sampling data set; Step S103, performing regional division processing on the fault type according to the zero-sequence direction criterion result, transmitting the division result to the dispatching system through the communication channel, and obtaining the preliminary judgment result of the internal and external faults; Step S104: For internal faults, a fault location operation is performed by using the relationship between the fault branch current and the grounding transformer voltage in combination with a multi-branch current comparison formula to obtain a fault branch characteristic value; Step S105, based on the characteristic quantity of the faulty branch, the difference of the characteristic quantity of each branch is calculated, and the faulty branch is determined in combination with the phase relationship between the voltage and the current, and a removal instruction data packet is generated; Step S106: encrypt, verify authority and authenticate identity of the removal instruction data packet, and send the verified removal instruction to the faulty branch circuit breaker to complete accurate removal of the faulty branch.

[0011] It is understandable that the execution subject of the present application may be a photovoltaic system grounding transformer fault determination and protection system, or a terminal or a server, which is not specifically limited here. The present application embodiment is described by taking a server as the execution subject as an example.

[0012] Specifically, basic data collection is performed. The IEC61850 standard collection terminals are deployed at key nodes of the photovoltaic system, including the grounding transformer, the feeder line position, and each photovoltaic branch. The collection terminal continuously samples the zero-sequence current data of the grounding transformer at a sampling frequency of 4800 times per second, and transmits the sampled data through the sampled value stream (SV) after digital conversion; at the same time, the collection terminal arranged at the feeder line collects the current and voltage data, and the sampling frequency is synchronized with the zero-sequence current sampling, and is transmitted through the GOOSE message; the operation data of each photovoltaic branch is sampled by the local collection terminal and transmitted through the SV channel. All sampled data carry unified timestamp information, and are time-sequence aligned after being transmitted to the station control system to form a synchronous sampling data set. For the collected synchronous sampling data set, focus on zero-sequence current data and zero-sequence voltage data. The fundamental components of these two sets of data are extracted by Fourier transform to obtain their amplitude and phase information. The zero-sequence current phase angle is subtracted from the zero-sequence voltage phase angle to obtain the phase difference. This phase difference is the key basis for judging the fault direction. When the phase difference is within the range of plus or minus 90 degrees, it indicates that the fault point is within the protection range. If the phase difference exceeds this range, it indicates that the fault point is outside the system. Such phase comparison calculation forms the zero-sequence direction judgment result.

[0013] Based on the zero-sequence direction judgment result, the fault type is divided into regions. When the judgment result shows that the fault is inside the system, the fault type is marked as an internal fault; when the judgment result shows that the fault is outside the system, the fault type is marked as an external fault. This division result needs to be transmitted to the dispatching system through the communication channel to generate the initial judgment results of internal and external faults. The communication process adopts the message format of the IEC61850 standard to ensure the accuracy and real-time performance of data transmission. For situations judged as internal faults, more accurate positioning is required. By analyzing the relationship between the fault branch current and the grounding transformer voltage, a fault location operation is used. The current value and grounding transformer voltage value of each branch are recorded, and then the current compensation principle is used to calculate the compensated fault branch current value. The compensated current value is compared with the superposition value of other branch currents, and the degree of difference is reflected in the fault branch characteristic quantity.

[0014] After obtaining the characteristic quantity of the faulty branch, the characteristic quantity difference between each branch is calculated. The characteristic quantity of each branch is calculated by difference with other branches, and the voltage and current phase relationship of each branch is combined. The characteristic quantity difference of the normal branch is close to zero, and the voltage and current phases are basically in the same direction; the faulty branch shows obvious characteristic quantity differences, and there is a significant deviation in the voltage and current phases. Based on these criteria, a resection instruction data packet containing the faulty branch information is generated. The resection instruction data packet is hierarchically encrypted and divided into two parts: control information and parameter information. The control information is processed by asymmetric encryption, and the parameter information is processed by symmetric encryption. The encrypted data is added with a header identifier, including a control type tag, timestamp information, source identification code, priority tag, and protocol version number. These identified ciphertext data are then subject to permission verification and identity authentication. Only instructions that pass all verifications can be sent to the faulty branch circuit breaker to perform the resection operation.

[0015] In the data processing process, each link has strict data correlation. The phase comparison of zero-sequence current data and zero-sequence voltage data directly determines the division of the fault area, which in turn affects the processing range of fault location. In the fault location process, the comparison between the compensated current value and the actual measured value reveals the fault location, and the calculation of the characteristic value difference further confirms the specific fault branch. Each data processing step is based on the previous step, forming a data processing chain.

[0016] It should be noted that if Figure 2 FIG. 1 is another schematic diagram of a method for determining and protecting a grounding transformer fault in a photovoltaic system according to an embodiment of the present application. Figure 2The multi-layer control structure based on the IEC61850 standard is shown in the figure, in which the main controller 61850 is the top-level control unit, connected to the lower-level control unit through a communication link; the grounding transformer controller 61850 and the PCSINV controller 61850 monitor the grounding transformer and the energy storage converter respectively, and the two are connected in parallel to the main control unit for data aggregation; the four branch controllers 61850 correspond to different photovoltaic branches, responsible for real-time monitoring and protection control of their respective branches, and also maintain data interaction with the main controller 61850 through communication links; the main control unit serves as a data aggregation point, receiving data information from the grounding transformer controller and the PCS INV controller, and passing the processing results to the corresponding control unit. The IEC61850 standard communication protocol is adopted to realize the unified collection, transmission and processing of data, providing a reliable control basis for accurate fault determination and timely removal.

[0017] like Figure 3 , which is a schematic diagram of a photovoltaic system in an embodiment of the present application, Figure 3 The core electrical structure of the photovoltaic system is shown, in which the transformer is connected to the feeder line DL0 through the DLx line. A grounding transformer is set at the feeder line. The grounding transformer is equipped with a grounding resistor R and an inductor L for system grounding protection. The feeder line is connected to branches 1 to 4 through circuit breakers to form a complete distribution network structure. The part in the dotted box in the figure constitutes the core grounding protection unit of the system. The grounding fault protection of the system is realized through the reasonably configured grounding transformer and its auxiliary equipment. The connection relationship between the transformer, grounding transformer, feeder line and each branch clearly shows the path of power transmission in the system, and also reflects the possible propagation path when a fault occurs.

[0018] In the embodiment of the present application, the zero-sequence current data of the grounding transformer, the current and voltage data of the feeder line, and the operation data of the photovoltaic branch in the photovoltaic system are sampled and acquired through an acquisition terminal based on the IEC61850 standard, and transmitted to the station control system via the sampled value stream and the digital message, thereby realizing real-time and accurate acquisition of the system operation data; the phase comparison operation is performed on the zero-sequence current data and the zero-sequence voltage data in the synchronous sampling data set to accurately determine the fault direction; the fault type is regionalized according to the zero-sequence direction judgment result, and the division result is transmitted to the dispatching system through the communication channel to effectively distinguish internal and external faults; for internal faults, the relationship between the fault branch current and the grounding transformer voltage is used, and the fault location operation is performed in combination with the multi-branch current comparison formula, thereby realizing accurate positioning of the fault position; the difference of the characteristic quantities of each branch is calculated based on the characteristic quantity of the fault branch, and the fault branch is judged in combination with the phase relationship between the voltage and the current, thereby ensuring the accuracy of the fault branch judgment; the removal instruction data packet is encrypted, the authority is verified, and the identity is authenticated through a three-layer security protection mechanism, thereby ensuring the safe and reliable execution of the control instruction. The entire solution achieves accurate judgment and selective removal of grounding faults in the photovoltaic system, avoids the problem of mis-removal due to external faults, and reduces unnecessary power generation losses. At the same time, the standard IEC61850 communication protocol is adopted to make the system have good compatibility and scalability, which is convenient for later function upgrades and system expansion. The multi-level data processing and safety protection mechanism in the solution ensures the reliability of fault judgment and processing, and improves the operating stability and power generation efficiency of the photovoltaic system.

[0019] In a specific embodiment, the process of executing step S101 may specifically include the following steps: (1) Sampling and acquiring the zero-sequence current data of the grounding transformer at the grounding transformer through an acquisition terminal in accordance with the IEC61850 standard, and converting the zero-sequence current data of the grounding transformer into a sampled value stream; (2) The IEC61850 standard data collection terminal collects the current and voltage data of the feeder line at the feeder line and transmits it via digital message; (3) The photovoltaic branch operation data is sampled regularly through the IEC61850 standard acquisition terminal, and the photovoltaic branch operation data is converted into a sample value stream; (4) Transmit the zero-sequence current data of the grounding transformer and the current and voltage data of the feeder line in the sampled value stream to the station control system through the IEC61850 standard protocol; (5) Transmitting PV branch operation data to the station control system via digital messages; (6) Perform timing calibration and synchronization processing on the grounding transformer zero-sequence current data, feeder line current and voltage data, and photovoltaic branch operation data received by the station control system to obtain a synchronous sampling data set.

[0020] Specifically, the IEC61850 standard acquisition terminal arranges a current transformer at the grounding transformer to sample the zero-sequence current. During the sampling process, the sampling frequency is set to 4800 times per second, and the sampled value is converted into a digital quantity after 16-bit AD conversion. These digital data are encapsulated in data frames, and information such as timestamp information, sampling sequence number, quality bit flag, etc. are added to convert them into a standard sampled value stream format. Each data frame in the sampled value stream contains data from 32 sampling points and is transmitted via Ethernet multicast. The IEC61850 standard acquisition terminal installed at the feeder line collects current and voltage signals. The acquisition terminal obtains the original analog signal through the current transformer and the voltage transformer, and also uses a sampling frequency of 4800Hz for digital conversion. The converted data is encapsulated in the GOOSE message format, including data identification, status information, time information, etc. The GOOSE message is transmitted using a publish / subscribe mechanism, supporting point-to-point and point-to-multipoint data transmission methods.

[0021] The collection of PV branch operation data involves multiple measuring points. Each PV branch is equipped with an IEC61850 standard acquisition terminal to collect branch current, voltage, power and other operating parameters. The acquisition terminal performs regular sampling according to the preset sampling period (usually 20ms), and the sampled data is converted into a sampled value stream after digital processing. The data frame structure of the sampled value stream is the same as the format of the zero-sequence current data of the grounding transformer, which is convenient for unified processing. The data in the sampled value stream format (including the zero-sequence current data of the grounding transformer and the current and voltage data of the feeder line) is transmitted to the station control system through the IEC61850 standard protocol. The transmission process uses VLAN technology to divide the virtual network to ensure the transmission priority of the sampled value stream data. After the data arrives at the station control system, a CRC check is performed to verify the data integrity. The data that passes the check is temporarily stored in the buffer according to the timestamp information, waiting for subsequent processing.

[0022] In the process of transmitting the operation data of the photovoltaic branch to the station control system through digital messages, the TCP / IP protocol stack is used for data transmission. The digital message contains information such as data identification, data value, quality factor, time tag, etc. After receiving the digital message, the station control system parses the message content, extracts the valid data information, and stores it in the corresponding data buffer according to the timestamp information. The station control system performs timing calibration and synchronization processing on all received data. According to the timestamp information, the data from different sources are sorted according to the sampling time. Then the continuity of the data time stamp is checked. If the time stamp jumps or is missing, the data compensation mechanism is started. The compensation mechanism calculates the value of the missing data point by linear interpolation method. The data after timing calibration is then synchronized, and the data at the same time is organized together to form a synchronous sampling data set.

[0023] For example, when a single-phase grounding fault occurs in a branch of the photovoltaic system, the acquisition terminal at the grounding transformer detects a sudden change in zero-sequence current. The acquisition terminal collects data from 96 sampling points within one cycle (20ms), and the data of each sampling point is converted into a 16-bit digital quantity through AD conversion. These digital quantities are encapsulated into a sampled value stream data frame together with information such as timestamp and sampling sequence number. At the same time, the acquisition terminal at the feeder line is also collecting current and voltage data. The sampling frequency is synchronized with the zero-sequence current sampling, and the data is transmitted through GOOSE messages. The acquisition terminals of each photovoltaic branch continuously collect operating data and record the changes in branch status before and after the fault occurs. After all data are transmitted to the station control system, timing calibration is performed. Through the timestamp information, it is found that due to network transmission delay, there are slight differences in the arrival time of some data. The station control system reorders these data according to the sampling time, and for data points with a delay of more than 50 microseconds, the data is compensated by linear interpolation. The final synchronous sampling data set contains the system operation status information before and after the fault occurs.

[0024] In a specific embodiment, the process of executing step S102 may specifically include the following steps: (1) Extract zero-sequence current data and zero-sequence voltage data from the synchronous sampling data set; (2) Perform Fourier transform on zero-sequence current data to obtain fundamental wave amplitude and phase angle information; (3) Perform Fourier analysis on the zero-sequence voltage data to obtain fundamental wave amplitude and phase angle information; (4) Subtract the phase angle information of the zero-sequence current data from the phase angle information of the zero-sequence voltage data to obtain a phase comparison value; (5) Judging the phase ratio value and the preset angle interval to obtain the initial judgment data of the zero-sequence direction; (6) Perform a comprehensive analysis based on the relationship between the initial zero-sequence direction judgment data and the fault characteristics to generate the zero-sequence direction judgment result.

[0025] Specifically, when extracting zero-sequence current data and zero-sequence voltage data from a synchronous sampling data set, the data frame is filtered according to the identification bit, and the zero-sequence current sampling point data and the zero-sequence voltage sampling point data are extracted into independent data buffers respectively. Each data buffer contains data of one power frequency cycle, that is, the values ​​of 96 sampling points. The extracted zero-sequence current data is Fourier transformed, and the data is preprocessed according to the requirements of discrete Fourier transform. The data of the 96 sampling points are windowed, and the Hanning window function is used to reduce spectrum leakage. After Fourier transform, the spectrum data of the zero-sequence current is obtained, and the amplitude and phase angle information of the fundamental component are extracted from it. The fundamental component corresponds to the frequency point of the power frequency of 50Hz, the amplitude represents the magnitude of the zero-sequence current, and the phase angle represents the angle offset of the zero-sequence current relative to the reference phase.

[0026] Fourier analysis is also performed on the zero-sequence voltage data, using the same processing flow. The time domain data is converted to the frequency domain through discrete Fourier transform to extract the information of the fundamental component. The fundamental frequency is also 50Hz, and the analysis results include the fundamental amplitude and phase angle information of the zero-sequence voltage.

[0027] The phase comparison calculation process uses the following formula: in: is the phase ratio logarithm; is the zero-sequence current fundamental phase angle correction coefficient; is the fundamental phase angle of zero-sequence current; is the zero-sequence voltage fundamental phase correction coefficient; is the phase angle of the zero-sequence voltage fundamental wave; To compensate the angle.

[0028] The phase comparison value is compared with the preset angle range for judgment. The preset angle range is usually set to plus or minus 90 degrees. When the phase comparison value falls within this range, it means that the fault point is within the protection range. The comparison result is recorded as the zero-sequence direction preliminary judgment data, including the direction flag and reliability index. When generating the final zero-sequence direction judgment result, the relationship between the zero-sequence direction preliminary judgment data and the fault characteristics is comprehensively analyzed. Fault characteristics include multiple parameters such as zero-sequence current amplitude, zero-sequence voltage amplitude, phase difference stability, etc. These parameters are weighted and calculated according to the predetermined weights to obtain the final direction judgment result.

[0029] For example, when a single-phase grounding fault occurs in a photovoltaic power station, the sampling data shows that the amplitude of the zero-sequence current fundamental wave suddenly increases, and the zero-sequence voltage also changes significantly. Through Fourier analysis, the fundamental phase angle of the zero-sequence current is extracted to be 45 degrees, and the fundamental phase angle of the zero-sequence voltage is -30 degrees. Considering the influence of the transformer angle error and line parameters, the correction coefficient is introduced for compensation. The phase comparison calculation results show that the compensated phase difference is 75 degrees, which falls within the preset judgment range of plus or minus 90 degrees. Combined with the characteristics that the zero-sequence current amplitude is greater than the starting set value, the zero-sequence voltage amplitude exceeds the minimum threshold value, and the phase difference remains stable for multiple consecutive cycles, it is finally determined that the fault point is within the protection range. This judgment process fully considers the logical association between various data to ensure the accuracy of the judgment result.

[0030] In a specific embodiment, the process of executing step S103 may specifically include the following steps: (1) Construct the fault type characteristic matrix according to the zero-sequence direction criterion results; (2) The fault type feature matrix is ​​identified by the phase difference threshold to distinguish internal fault data from external fault data; (3) Performing regional division processing based on internal fault data and external fault data to generate division results; (4) Encapsulate the division results according to the IEC61850 communication protocol to generate standard data messages; (5) Transmitting standard data messages to the dispatching system through the communication channel; (6) The dispatching system parses and judges the standard data message to obtain the initial judgment results of internal and external faults.

[0031] Specifically, a fault type characteristic matrix is ​​constructed based on the zero-sequence direction judgment result. The rows of the matrix represent different fault characteristic parameters, including zero-sequence current amplitude, zero-sequence voltage amplitude, phase difference value, fault duration, etc. The columns of the matrix represent the sampled values ​​of these parameters at different time points. Each matrix element carries timestamp information, which is convenient for tracking the fault development process. The phase difference threshold judgment process analyzes the phase information in the fault type characteristic matrix. In the case of internal faults, the phase difference between zero-sequence current and zero-sequence voltage is usually within the range of plus or minus 90 degrees, while the phase difference of external faults exceeds this range. The phase difference data at each time point is compared with the preset threshold, and the comparison results within multiple consecutive cycles are recorded. If the phase difference of multiple consecutive cycles falls within the judgment range, the corresponding data is marked as internal fault data; otherwise, it is marked as external fault data.

[0032] The regional division processing is based on the marked internal fault data and external fault data. The spatial distribution characteristics of the data marked as internal faults are further analyzed, and the fault area is accurately divided according to the location information of each measurement point. At the same time, the relative position relationship between the fault point and the protection device is considered to generate a division result containing the fault area range, fault characteristic parameters, time information and other contents. When the division result is encapsulated according to the IEC61850 communication protocol, a standard data frame format is constructed. The data frame header contains information such as the source address, destination address, priority, etc., and the data segment contains fault area information, fault type, timestamp and other contents. All data are encoded according to the requirements of the communication protocol, and the checksum and frame tail mark are added to finally form a standard data message.

[0033] The process of transmitting standard data messages to the dispatching system through the communication channel adopts the TCP / IP protocol. The data message is divided into multiple data packets, each of which contains sequence number information to ensure that it can be correctly reassembled at the receiving end. The CRC check mechanism is used during the transmission process to detect whether the data is erroneous or lost. If a data packet error or loss is found, the corresponding data packet is requested to be retransmitted. After receiving the standard data message, the dispatching system performs a message integrity check. After the check is passed, the message content is parsed according to the data frame format to extract data such as fault area information, fault type, and time information. The parsed data is compared with the preset judgment rules, and the location, type, severity and other factors of the fault are comprehensively considered to finally obtain the initial judgment results of internal and external faults.

[0034] For example, when a ground fault occurs in a certain area of ​​the photovoltaic system, the zero-sequence direction criterion result is used to construct a fault type feature matrix. The matrix records the data of multiple consecutive cycles after the fault occurs, including the sudden increase of zero-sequence current from 5A to 50A, the increase of zero-sequence voltage from 0.1kV to 1.2kV, and the phase difference gradually stabilized from the initial unstable state to 75 degrees. The phase difference threshold judgment process found that the phase difference value was within the range of plus or minus 90 degrees for 5 cycles, so the relevant data was marked as internal fault data. Based on these data, the area is divided, and considering the relative position of the fault point and the protection device, as well as the propagation direction of the zero-sequence current, the fault location is determined to be on the collector circuit inside the photovoltaic station. This information is organized into a data frame in a standard format, which contains information such as the time, location, and type of the fault. The data frame is encoded according to the IEC61850 protocol and converted into a standard data message. During the transmission of the message to the dispatching system through the communication channel, CRC verification is performed throughout the process to ensure the integrity of the data. After parsing the message, the dispatching system found that the fault location was within the protection range, the fault characteristics were obvious, and the duration exceeded 100ms. Based on this information, it was determined to be an internal fault.

[0035] In a specific embodiment, the process of executing step S104 may specifically include the following steps: (1) Record the amplitude and phase information of the fault branch current and ground transformer voltage during internal faults; (2) Multiply the fault branch current by the system inherent parameters to obtain the branch impedance relationship value; (3) Divide the ground transformer voltage by the branch impedance relationship value to obtain the compensated current value; (4) Subtract the superposition value of other branch currents from the compensated current value to form a current difference sequence; (5) Construct fault location data based on the relationship between the current difference sequence and the grounding transformer voltage; (6) The fault location data is subjected to branch current comparison operation to obtain the fault branch characteristic quantity.

[0036] Specifically, the data acquisition equipment records the current of the fault branch and the voltage information of the grounding transformer during the internal fault, including the two key parameters of amplitude and phase. The sampling frequency of current and voltage is 4800Hz, and 96 points are collected in each power frequency cycle to ensure sufficient data accuracy. These raw data are Fourier transformed to obtain the amplitude and phase information of the fundamental component, laying the foundation for subsequent fault location calculations.

[0037] The relationship between the fault branch current and the grounding transformer voltage can be expressed as: in: Indicates the fault branch current; Indicates grounding voltage; Indicates the intrinsic parameters of the system.

[0038] Multiply the fault branch current by the system inherent parameters to obtain the branch impedance relationship value: in: Indicates the branch impedance relationship value; Indicates the fault branch current amplitude; Indicates the inherent resistance of the system; Indicates the phase angle.

[0039] The compensated current value is obtained by dividing the grounding transformer voltage by the branch impedance relationship value: in: Indicates the current after compensation; Indicates the compensation coefficient.

[0040] The current difference sequence is formed by subtracting the superposition value of other branch currents from the compensated current value: in: represents the current difference sequence; represents the current amplitude of the nth branch; Indicates the phase angle of the nth branch; N indicates the total number of branches, The fault location data is constructed based on the relationship between the current difference sequence and the grounding transformer voltage, using the vector operation method: in: Indicates fault location data; represents the conjugate complex number of the ground transformer voltage; Represents the weighting coefficient.

[0041] For example, during the operation of a photovoltaic power station, a ground fault occurs in a branch. The current of the branch is recorded to suddenly increase from the normal value, and an obvious zero-sequence voltage is detected at the grounding transformer. Fourier analysis is performed on these data to obtain the fundamental amplitude and phase information of the fault branch current, as well as the fundamental amplitude and phase information of the grounding transformer voltage. The fault branch current is multiplied by the pre-calibrated system inherent parameters to obtain the branch impedance relationship value. This process takes into account the influence of line impedance and grounding resistance. Then the grounding transformer voltage is divided by the branch impedance relationship value to obtain the compensated current value. The compensation process eliminates the influence of line parameters and grounding methods on fault judgment.

[0042] The compensated current value is compared with the current of other normally operating branches. Since the characteristics of the faulty branch are significantly different from those of the normal branch, the characteristics of the faulty branch can be accurately reflected by calculating the current difference sequence. This characteristic not only contains amplitude information, but also phase information, providing a comprehensive basis for fault location. The fault location data is compared with the branch current to determine the specific faulty branch. The comparison process comprehensively considers multiple parameters such as current amplitude, phase angle, impedance characteristics, etc., to ensure the accuracy of fault location.

[0043] In a specific embodiment, the process of executing step S105 may specifically include the following steps: (1) Perform a difference operation on the characteristic quantity of the faulty branch and the characteristic quantity of the non-faulty branch to obtain the difference of the characteristic quantity of each branch; (2) Compare the difference between the characteristic quantities of each branch with the set threshold, and mark the branch with a non-zero difference as a fault branch to be determined; (3) Obtain phase deviation data by calculating the voltage and current phase angle difference of the fault branch to be determined; (4) The phase deviation data is judged as out-of-tolerance, and the branches that exceed the set angle range are judged as fault branches; (5) Based on the fault branch determination result, construct instruction information including the fault branch number and removal timing; (6) Encapsulate the command information according to the IEC61850 message format to generate a removal command data packet.

[0044] Specifically, a characteristic quantity difference operation is performed, and the obtained characteristic quantity of the fault branch is calculated by difference with the characteristic quantity of each other branch. This process extracts the characteristic quantity data of each branch, including parameters such as current amplitude, phase angle, impedance characteristics, and then obtains the characteristic quantity difference between each branch through vector subtraction operation. The difference calculation process takes into account the differences in the two dimensions of amplitude and phase to ensure that the operating status differences of each branch can be fully reflected. The hierarchical threshold method is used to compare and judge the difference of the characteristic quantity of each branch, and the calculated difference is compared with the pre-set judgment threshold. The setting of the threshold is based on a large amount of statistical analysis of fault data, taking into account the normal operation fluctuation range and fault characteristic differences. When the characteristic quantity difference of a branch exceeds the set threshold, the branch is marked as a fault branch to be determined. This marking process not only records the branch number, but also contains information on the degree of difference exceeding the limit.

[0045] For the lines marked as fault branches to be determined, an in-depth analysis of the voltage and current phase angle difference is performed. This analysis process extracts the phase information of voltage and current from the original sampled data, and obtains the accurate phase angle difference through complex operations. The influence of factors such as sampling delay and transformer angle difference is considered in the phase difference calculation process, and the accuracy of the calculation result is ensured by the compensation algorithm. The out-of-tolerance judgment of phase deviation data adopts a multiple judgment method. Set a reference angle range, and the phase difference during normal operation should fall within this range. When the calculated phase deviation exceeds the set range, the duration and change trend of the deviation are further analyzed. Only when the phase deviation continues to exceed the limit and presents typical fault characteristics, the branch is judged as a definite fault branch.

[0046] When constructing the removal instruction information based on the fault branch judgment result, multiple factors need to be considered. Generate a unique identification code based on the number of the fault branch, and then determine the removal priority based on the severity of the fault. The arrangement of the removal sequence needs to consider the system stability requirements, and multiple removal actions are sorted according to the predetermined time interval. The final instruction information contains complete information such as branch identification, operation type, and execution sequence. Encapsulating the instruction information in accordance with the IEC61850 message format is a key step. Construct the basic framework of the message, including the message header, data area, and check area. The message header contains information such as the source address, destination address, priority, etc. The data area is filled with instruction information in the prescribed format, and a CRC check code is added to ensure data integrity. The structure of the entire data packet strictly follows the IEC61850 standard requirements to ensure that the receiving end can correctly parse and execute instructions.

[0047] For example: During the operation of a photovoltaic power station, a suspicious branch was found through the calculation of the fault characteristic quantity in the early stage. The characteristic quantity of this branch (including parameters such as current amplitude, phase angle, impedance characteristics, etc.) is calculated by difference with the characteristic quantity of other normally operating branches. The calculation results show that the difference of the characteristic quantity of this branch is obviously beyond the normal fluctuation range, so it is marked as a fault branch to be determined. Further analysis of the voltage and current phase relationship of this branch shows that the phase angle difference shows obvious abnormal characteristics. During normal operation, the phase difference between voltage and current should be kept within a stable range, but the phase difference of this branch has shifted significantly, and this shift persists. After multiple cycles of data analysis, it was confirmed that a ground fault did occur in this branch.

[0048] Based on this judgment result, a removal instruction containing the branch number is generated. The instruction not only contains the unique identification of the branch, but also contains the specific requirements and execution sequence of the removal operation. This information is converted into the standard IEC61850 message format to form a removal instruction data packet. Each field in the data packet is strictly encoded in accordance with the requirements of the communication protocol to ensure that the instruction can be executed accurately.

[0049] In a specific embodiment, the process of executing step S106 may specifically include the following steps: (1) Performing layered encryption processing on the resection instruction data packet to generate an encrypted data stream; (2) Compare the encrypted data stream with the operation permission table to generate permission verification results; (3) Verify the operator's identity information through the authority verification result to obtain identity authentication data; (4) Generate an operation control code based on the identity authentication data, and combine the operation control code with the encrypted data stream to form a security control instruction; (5) Encapsulate the safety control instructions through the IEC61850 communication protocol to obtain the verified removal instructions; (6) Send a verified removal instruction to the faulty branch circuit breaker to complete the precise removal of the faulty branch.

[0050] Specifically, the resection instruction data packet is encrypted in layers, and the data packet is divided into a control layer and a parameter layer. The control layer contains core instruction information such as operation type and execution timing, and is encrypted using the asymmetric encryption algorithm RSA; the parameter layer contains specific operation parameters and data, and is processed using the symmetric encryption algorithm AES. The two layers of encrypted data are combined together in a specific format to form an encrypted data stream. When the encrypted data stream is compared with the operation permission table, a hierarchical verification mechanism is adopted. The operation type identifier in the encrypted data stream is extracted, and the corresponding permission requirements are found in the operation permission table. The operation permission table is divided into different permission levels according to the operation level, and each level has corresponding verification rules. By matching the operation type with the permission rule, a permission verification result containing information such as permission level, verification requirements, and timeliness is generated.

[0051] The result of the permission verification is used to verify the identity of the operator, and the verification process includes multiple dimensions. Verify the basic identity information of the operator, including work number, rank, department, etc.; then check the validity period and scope of use of the operation authority; and conduct a comprehensive assessment in combination with environmental factors such as operation time and location. These verification information are integrated into identity authentication data, which records the authentication process and results. Generating operation control codes based on identity authentication data involves multiple steps. Extract key fields from the identity authentication data, including authentication results, timestamps, operation levels, etc. This information is processed by a specific algorithm to generate a unique operation control code. The operation control code is combined with the previous encrypted data stream, and information such as timestamps and serial numbers are added to form a security control instruction.

[0052] When encapsulating the safety control instructions according to the IEC61850 communication protocol, the standard format must be strictly followed. Construct the message header and fill in the source address, destination address, priority and other fields. Then put the safety control instructions into the message body according to the specified format, and add the necessary control fields and verification information. The encapsulated data forms a verified removal instruction, which contains safety verification information. When sending the verified removal instruction to the fault branch circuit breaker, a reliable communication mechanism is used. Confirm the status of the communication link, and then send the instruction according to the predetermined communication protocol. The response mechanism is used during the sending process, requiring the receiving end to return confirmation information. Only when the correct confirmation information is received, the instruction is considered to have been sent successfully and the fault branch is accurately removed.

[0053] For example, when a photovoltaic power station needs to cut off a branch with a ground fault, the cutting instruction data packet containing information such as the fault branch number, cutting operation type, and execution sequence is encrypted. The control information is encrypted using the RSA algorithm, and the operation parameters are encrypted using the AES algorithm to form a double-layer encrypted data stream. This encrypted data stream is verified by authority, and the system finds that the cutting operation is a high-level operation and requires authority above the level of the duty supervisor. The authority verification process not only checks the operator's job level, but also verifies whether the current time is within his or her duty time. After the verification is passed, identity authentication data containing information such as the operator's employee number, job level, and operation time is generated. Based on this authentication information, a special operation control code is generated. The control code contains information such as operation time, authorization level, and validity period, and is combined with the encrypted instruction data. This combined safety control instruction is converted into a standard IEC61850 message format, and various control fields required by the communication protocol are added. The cutting instruction is sent to the circuit breaker of the faulty branch through the communication network. The sending process uses a three-way handshake mechanism to ensure that the instruction is accurately received and executed.

[0054] In a specific embodiment, the process of performing the hierarchical encryption processing step on the resection instruction data packet may specifically include the following steps: (1) Divide the excision instruction data packet into control information and parameter information according to the information type; (2) Perform the first layer of encryption on the control information using an asymmetric encryption algorithm to obtain the ciphertext of the control information; (3) Perform a second layer of encryption on the parameter information using a symmetric encryption algorithm to obtain the ciphertext of the parameter information; (4) Fusing the control information ciphertext and the parameter information ciphertext to form an encrypted data block; (5) Convert the encrypted data block into a data format according to the IEC61850 communication protocol; (6) Encapsulate the converted data through the data stream protocol to generate an encrypted data stream.

[0055] Specifically, the resection instruction data packets are divided into types. The control information contains core instruction information such as the operation command type, execution sequence, and operation identification; the parameter information contains specific operation parameters, such as the fault branch number, resection time window, operation priority, and other data. This information division method facilitates the subsequent use of different encryption strategies. The asymmetric encryption algorithm RSA is used to encrypt the control information. This step generates a pair of public and private keys. The public key is used for data encryption, and the private key is kept by the receiving end for decryption. The encryption process divides the control information into blocks of fixed length, and each block is encrypted by the public key to finally generate the control information ciphertext. Asymmetric encryption ensures the security of the control instructions.

[0056] The encryption of parameter information adopts the symmetric encryption algorithm AES, and selects a 128-bit key length. The encryption process fills the parameter information so that its length meets the grouping requirements, and then divides the data into several data blocks according to the grouping size. Each data block is encrypted by AES in turn to obtain the parameter information ciphertext. Symmetric encryption has high processing efficiency while ensuring security. The ciphertext fusion process adopts a specific data organization method. A header identifier is added before the control information ciphertext to mark the data type and length information. Then a header identifier is also added before the parameter information ciphertext. The two sets of ciphertexts with identifiers are combined in a predetermined format to form a unified encrypted data block. The data block also contains check information to verify data integrity.

[0057] When the encrypted data block is converted to the IEC61850 communication protocol format, the standard data frame structure needs to be followed. Construct the frame header and fill in the source address, destination address, priority and other fields. Then put the encrypted data block into the data area and add the necessary control fields. Calculate and add the CRC checksum to ensure the reliability of data transmission. When the data stream protocol is used for final encapsulation, the streaming mechanism is adopted. The converted data is divided into multiple data packets according to the transmission requirements, and sequence number information is added to each data packet. Then add flow control information according to the requirements of the data stream protocol, including packet sequence number, timestamp, transmission priority, etc. Finally, an encrypted data stream is formed and ready for network transmission.

[0058] For example, when a branch with a ground fault needs to be removed, the removal instruction data packet contains the operation command "removal instruction", execution priority "urgent", fault branch number "PV-L3", removal time window "100ms" and other information. This information is divided into two categories: control information and parameter information. The control information contains the operation command and execution priority, and the parameter information contains the branch number and time window. The control information is encrypted with RSA and a 2048-bit key length is used to ensure the security of the instruction. The encrypted control information ciphertext length increases significantly, but it ensures that it will not be tampered with during data transmission. The parameter information is encrypted using the AES algorithm and the ECB mode is used to ensure the confidentiality of the operation parameters.

[0059] When the two sets of ciphertexts are merged, the type identifiers of "CTL" and "PRM" and their respective length information are added. The merged data block has a clear structure, which is convenient for the receiving end to parse correctly. After the data block is converted to the IEC61850 format, various control fields required by the communication protocol are added to form a standard communication frame format. Through data stream protocol encapsulation, information such as stream sequence number and timestamp are added to generate an encrypted data stream and prepare for subsequent data transmission.

[0060] In a specific embodiment, the process of performing the step of data fusion on the control information ciphertext and the parameter information ciphertext may specifically include the following steps: (1) Add a header identifier to the control information ciphertext to generate an identified control ciphertext; (2) The parameter information ciphertext is segmented according to the data length to obtain segmented parameter ciphertext; (3) Add check bit information to the segmented parameter ciphertext to generate checksum parameter ciphertext; (4) Align the identification control ciphertext and the verification parameter ciphertext in time sequence; (5) Sequentially number the aligned ciphertext data to form a serialized ciphertext; (6) Pack the serialized ciphertext according to the IEC61850 data format requirements to form an encrypted data block.

[0061] Specifically, when adding a header identifier to the control information ciphertext, a standardized header identifier structure needs to be constructed. Add the data type identifier "CTL" to indicate that this is control information, and then add the timestamp information to record the exact time when the ciphertext was generated. Then add a priority identifier to indicate the processing priority level of the control information. Add version number information to mark the protocol version of the ciphertext. These identification information are combined at the front end of the ciphertext in a fixed format to generate an identified control ciphertext. The segmentation processing of the parameter information ciphertext adopts a fixed-length segmentation method. Set the standard segment length to 256 bytes, and divide the parameter information ciphertext according to this length. For a segment that is less than the standard length, a padding method is used. Each segment is added with a segment number and length information to facilitate subsequent reorganization. The ciphertext processed in this way is divided into multiple data segments of equal size to form a segmented parameter ciphertext.

[0062] When adding check bit information to the segmented parameter ciphertext, a multiple check mechanism is used. The CRC check value is calculated for each segment to verify the integrity of the individual segment. Then the cumulative check value of all segments is calculated to verify the correctness of the overall data. These check information are added to the end of each segment to form the check parameter ciphertext. The timing alignment of the identification control ciphertext and the check parameter ciphertext needs to consider the processing order of the data. The two ciphertexts are sorted according to the generation time based on the timestamp information. Then a synchronization mark is inserted in the data stream to ensure that the two ciphertexts can be correctly paired. The alignment process must also ensure the timing of data processing to avoid misordering.

[0063] When the aligned ciphertext data is marked with sequential numbers, an increasing serial number mechanism is used. Each data block is assigned a unique serial number starting from 0, and the serial number information is included in the header of the data block. At the same time, the total number of data blocks is recorded to facilitate the receiving end to determine the data integrity. The data processed in this way forms a serialized ciphertext. Packing is performed in accordance with the IEC61850 data format requirements. Construct a standard data frame structure, including a frame header, a data area, and a frame tail. Fill the source address, destination address, priority and other information in the frame header. The serialized ciphertext is placed in the data area, and the necessary control fields are added according to the protocol requirements. Calculate and add the frame check sequence to form an encrypted data block.

[0064] For example, when processing a removal instruction for a photovoltaic branch, a header identifier is added to the control information ciphertext. The header contains the "CTL_CMD" type identifier, the "20240117_153022" timestamp, the "P1" priority identifier, and the "V2.1" version number. These identifiers help the receiving end to correctly identify and process the data. The original length of the parameter information ciphertext is 789 bytes, which is segmented by 256 bytes to obtain 4 segments: 3 complete segments and 1 incomplete segment of 83 bytes. A segment is padded to the standard length. Sequence number and length information are added to each segment to facilitate subsequent reorganization.

[0065] The checksum is calculated for these segments, and each segment obtains a 32-bit CRC checksum. At the same time, a global checksum covering all segments is calculated. These checksum information are added to the end of the corresponding segment to ensure the accuracy of data transmission.

[0066] During the timing alignment process, the identified control ciphertext is placed at the top of the data stream, and then the parameter ciphertext segments with checksum information are arranged in sequence. The synchronization mark "SYN_FLAG" is inserted between the control ciphertext and the parameter ciphertext to ensure the correct pairing of the data. The entire data stream is assigned a continuous sequence number, starting from "SEQ_0000". This unique sequence number is included in the header of each data block. These data with sequence numbers are assembled according to the format requirements of IEC61850 to form encrypted data blocks, ready for subsequent transmission processing.

[0067] In a specific embodiment, the process of performing the step of adding a header identifier to the control information ciphertext may specifically include the following steps: (1) Classify and mark the control information ciphertext according to different control types to obtain typed ciphertext; (2) Add timestamp information to the typed ciphertext to generate time-series ciphertext; (3) Add the source identification code to the time-series ciphertext to form the source identification ciphertext; (4) Add a priority tag to the source identification ciphertext to obtain a priority ciphertext; (5) Add the protocol version number to the priority ciphertext to form a versioned ciphertext; (6) Assemble the versioned ciphertext according to the header format specification to generate the identified control ciphertext.

[0068] Specifically, the identification processing of control information ciphertext involves multiple layers of data marking. The control information ciphertext is classified and marked by type, and the control information is divided into different categories according to the functional type. The fault removal control mark is "FLT_CUT", the device operation mark is "DEV_OPR", and the parameter setting mark is "PRM_SET". These type identifiers are added as prefixes to the corresponding control ciphertext to form typed ciphertext.

[0069] The timestamp information is added in a time format accurate to milliseconds. The timestamp contains year, month, day, hour, minute, second, and millisecond information, and is constructed in the format of "YYYYMMDD_HHmmss_msec". This timestamp information is added to the header of the typed ciphertext and separated from the type identifier with a specific separator to generate a timed ciphertext. This format of timestamp facilitates subsequent time series analysis and processing.

[0070] The addition of source identification code is used to mark the place and device where the control instruction is issued. The source identification contains three parts: device type code "DEV", device number "NO" and location information "LOC". These information are combined in a fixed format, such as "DEV001_NO123_LOC456", and added to the timed ciphertext to form the source identification ciphertext. The source identification ensures the traceability of the control instruction. The addition of priority tag is based on the urgency of the control instruction. Four priority levels are set: emergency cut-off type is marked as "P0", fault handling type is marked as "P1", normal operation type is marked as "P2", and parameter setting type is marked as "P3". The corresponding priority tag is added to the source identification ciphertext to obtain the priority ciphertext. The addition of protocol version number is used to identify the version information of the communication protocol. The version number adopts the format of major version number and minor version number, such as "V2.1". The major version number indicates the major update of the protocol, and the minor version number indicates a minor modification. The version number information is added to the priority ciphertext to form the versioned ciphertext. The version number information helps the receiving end to correctly parse the data format.

[0071] When the final assembly is performed according to the header format specification, all identification information is arranged in a fixed order and format. It is the control type identifier, then the timestamp, followed by the source identifier, then the priority tag, and the protocol version number. Each field is separated by a specific separator to ensure the clarity of the data structure. The final identified control ciphertext has a header identification structure.

[0072] For example, when a branch in a photovoltaic system needs to be fault-cut, the relevant control ciphertext is marked as the fault-cut type "FLT_CUT". Assuming that this control instruction is generated at 15:30:22:789 on January 17, 2024, the timestamp "20240117_153022_789" is added. The instruction comes from the master control device of photovoltaic zone 3, and the source identification "DEV003_NO001_LOC301" is added. Since it is a fault-cutting operation, it is set to the highest priority "P0". The instruction uses the latest communication protocol and adds the version number "V2.1". Finally, these identification information are assembled in a standardized format to form an identified control ciphertext for subsequent data transmission and processing. This multi-layer identification structure ensures the traceability and processing accuracy of control instructions.

[0073] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A photovoltaic system grounding transformer fault determination and protection method, characterized in that: The photovoltaic system grounding transformer fault determination and protection method comprises: The zero-sequence current data of the grounding transformer, the current and voltage data of the feeder line, and the operation data of the photovoltaic branch in the photovoltaic system are sampled and acquired through the acquisition terminal based on the IEC61850 standard, and the sampled data are transmitted to the station control system via the sampled value stream and digital quantity message to obtain a synchronous sampling data set; According to the zero-sequence current data and the zero-sequence voltage data in the synchronous sampling data set, a zero-sequence direction criterion result is obtained through phase comparison operation; According to the zero-sequence direction criterion result, the fault type is divided into regions, and the division result is transmitted to the dispatching system through the communication channel to obtain the initial judgment result of the internal and external faults; For internal faults, the fault location operation is performed by using the relationship between the fault branch current and the grounding transformer voltage and combining the multi-branch current comparison formula to obtain the fault branch characteristic quantity; Based on the fault branch characteristic quantity, the difference of each branch characteristic quantity is calculated, and the fault branch is determined in combination with the phase relationship between the voltage and the current, and a removal instruction data packet is generated; The removal instruction data packet is encrypted, authority verified and identity authenticated, and the verified removal instruction is sent to the fault branch circuit breaker to complete the accurate removal of the fault branch.

2. The photovoltaic system grounding transformer fault determination and protection method according to claim 1 is characterized in that: The grounding transformer zero-sequence current data, feeder line current and voltage data, and photovoltaic branch operation data in the photovoltaic system are sampled and acquired through a collection terminal based on the IEC61850 standard, and the sampled data are transmitted to the station control system via a sampled value stream and a digital quantity message to obtain a synchronous sampled data set, including: Sampling and acquiring the zero-sequence current data of the grounding transformer at the grounding transformer through an acquisition terminal in accordance with the IEC61850 standard, and converting the zero-sequence current data of the grounding transformer into a sample value stream; The IEC61850 standard acquisition terminal acquires the current and voltage data of the feeder line at the feeder line and transmits the data via a digital quantity message; The photovoltaic branch operation data is sampled regularly via the IEC61850 standard acquisition terminal, and the photovoltaic branch operation data is converted into a sample value stream; Transmitting the zero-sequence current data of the grounding transformer and the current and voltage data of the feeder line in the sampled value stream to the station control system through the IEC61850 standard protocol; Transmitting the photovoltaic branch operation data to the station control system via the digital message; The grounding transformer zero-sequence current data, feeder line current and voltage data, and photovoltaic branch operation data received by the station control system are time-sequence calibrated and synchronously processed to obtain a synchronous sampling data set.

3. The photovoltaic system grounding transformer fault determination and protection method according to claim 1, characterized in that: The zero-sequence current data and zero-sequence voltage data in the synchronous sampling data set are subjected to phase comparison operation to obtain a zero-sequence direction criterion result, including: Extracting the zero-sequence current data and the zero-sequence voltage data from the synchronously sampled data set; Performing Fourier transform on the zero-sequence current data to obtain fundamental wave amplitude and phase angle information; Performing Fourier analysis on the zero-sequence voltage data to obtain fundamental wave amplitude and phase angle information; Subtract the phase angle information of the zero-sequence voltage data from the phase angle information of the zero-sequence current data to obtain a phase comparison value; The phase ratio value and the preset angle interval are judged to obtain the initial judgment data of the zero-sequence direction; A comprehensive analysis is performed based on the relationship between the zero-sequence direction preliminary judgment data and the fault characteristics to generate a zero-sequence direction judgment result.

4. The photovoltaic system grounding transformer fault determination and protection method according to claim 1, characterized in that: The fault type is divided into regions according to the zero-sequence direction criterion result, and the division result is transmitted to the dispatching system through the communication channel to obtain the initial judgment result of the internal and external faults, including: Constructing a fault type characteristic matrix according to the zero-sequence direction criterion result; The fault type characteristic matrix is ​​judged by a phase difference threshold to distinguish internal fault data from external fault data; Performing area division processing according to the internal fault data and the external fault data to generate a division result; Encapsulate the division results according to the IEC61850 communication protocol to generate a standard data message; Transmitting the standard data message to the dispatching system through the communication channel; The dispatching system analyzes and determines the standard data message to obtain a preliminary determination result of internal and external faults.

5. The photovoltaic system grounding transformer fault determination and protection method according to claim 1, characterized in that: For the internal fault, the fault location operation is performed by using the relationship between the fault branch current and the grounding transformer voltage in combination with the multi-branch current comparison formula to obtain the fault branch characteristic quantity, including: Recording the amplitude and phase information of the fault branch current and the ground transformer voltage during the internal fault; Multiplying the fault branch current by the system inherent parameter to obtain a branch impedance relationship value; Dividing the grounding transformer voltage by the branch impedance relationship value to obtain a compensated current value; Subtract the superposition value of other branch currents from the compensated current value to form a current difference sequence; Constructing fault location data according to the relationship between the current difference sequence and the grounding transformer voltage; The fault location data is subjected to branch current comparison operation to obtain the fault branch characteristic quantity.

6. The photovoltaic system grounding transformer fault determination and protection method according to claim 1, characterized in that: The method of calculating the difference of the characteristic quantities of each branch based on the characteristic quantity of the fault branch, and determining the fault branch in combination with the phase relationship between the voltage and the current, and generating a removal instruction data packet includes: Performing a difference operation on the characteristic quantity of the faulty branch and the characteristic quantity of the non-faulty branch to obtain the difference of the characteristic quantity of each branch; Compare the difference between the characteristic quantities of each branch with a set threshold, and mark the branch with a non-zero difference as a fault branch to be determined; The phase deviation data is obtained by calculating the voltage and current phase angle difference of the fault branch to be determined; The phase deviation data is judged as out-of-tolerance, and the branch that exceeds the set angle range is judged as a fault branch; Based on the fault branch determination result, construct instruction information including the fault branch number and removal timing; The instruction information is encapsulated according to the IEC61850 message format to generate a removal instruction data packet.

7. The photovoltaic system grounding transformer fault determination and protection method according to claim 1, characterized in that: The encryption processing, authority verification and identity authentication of the removal instruction data packet and sending the verified removal instruction to the fault branch circuit breaker to complete the accurate removal of the fault branch include: Performing layered encryption processing on the excision instruction data packet to generate an encrypted data stream; Compare the encrypted data stream with the operation permission table to generate a permission verification result; The identity information of the operator is verified through the authority verification result to obtain identity authentication data; Generate an operation control code based on the identity authentication data, and combine the operation control code with the encrypted data stream to form a security control instruction; Encapsulating the safety control instruction through the IEC61850 communication protocol to obtain a verified removal instruction; The verified removal instruction is sent to the fault branch circuit breaker to complete the accurate removal of the fault branch.

8. The photovoltaic system grounding transformer fault determination and protection method according to claim 7, characterized in that: The step of performing layered encryption processing on the excision instruction data packet to generate an encrypted data stream includes: Dividing the excision instruction data packet into control information and parameter information according to information type; Performing a first layer encryption on the control information using an asymmetric encryption algorithm to obtain a ciphertext of the control information; Performing a second layer of encryption on the parameter information using a symmetric encryption algorithm to obtain a ciphertext of the parameter information; Performing data fusion on the control information ciphertext and the parameter information ciphertext to form an encrypted data block; Convert the encrypted data block into a data format according to the IEC61850 communication protocol; The converted data is encapsulated through the data stream protocol to generate an encrypted data stream.

9. The photovoltaic system grounding transformer fault determination and protection method according to claim 8, characterized in that: The step of fusing the control information ciphertext and the parameter information ciphertext to form an encrypted data block includes: Adding a header identifier to the control information ciphertext to generate an identified control ciphertext; The parameter information ciphertext is segmented according to the data length to obtain segmented parameter ciphertext; Adding check bit information to the segmented parameter ciphertext to generate a checksum parameter ciphertext; Aligning the identification control ciphertext and the verification parameter ciphertext in time sequence; Sequentially number the aligned ciphertext data to form serialized ciphertext; The serialized ciphertext is packaged according to the IEC61850 data format requirements to form an encrypted data block.

10. The photovoltaic system grounding transformer fault determination and protection method according to claim 9, characterized in that: The step of adding a header identifier to the control information ciphertext to generate an identified control ciphertext includes: Classify and mark the control information ciphertext according to different control types to obtain typed ciphertext; Adding timestamp information to the typed ciphertext to generate time-series ciphertext; Adding a source identification code to the time-series ciphertext to form a source identification ciphertext; Adding a priority mark to the source identification ciphertext to obtain a priority ciphertext; Adding a protocol version number to the priority ciphertext to form a versioned ciphertext; The versioned ciphertext is assembled according to the header format specification to generate the identified control ciphertext.

Images