Wind power plant pilot protection method, system and equipment based on complex domain cosine coefficient, medium and product
By using a longitudinal protection method based on complex domain cosine coefficients and constructing a virtual power differential protection criterion using Tellegen's theorem, adaptive adjustments are made to cope with CT saturation. This solves the performance degradation problem of traditional longitudinal protection under high-resistance faults and CT saturation, and achieves fast and reliable fault identification and protection.
Patent Information
- Application Number
- CN202511218057.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-28
- Publication Date
- 2025-11-25
AI Technical Summary
Traditional longitudinal protection systems exhibit significant performance degradation under complex operating conditions such as high-resistance faults in wind farms and current transformer saturation, making it difficult to effectively identify fault types.
A longitudinal protection method for wind farms based on complex domain cosine coefficients is adopted. By extracting fault characteristics, a virtual power differential protection criterion is constructed using Tellegen's theorem. The complex domain cosine coefficients are adaptively adjusted, and the CT saturation characteristics are considered to modify the protection criterion to identify external and internal faults.
It improves the identification capability of wind farm longitudinal protection under high-resistance faults and CT saturation conditions, ensuring the reliability and speed of protection, and enhancing the transient stability and operational safety of the new energy power system.
Smart Images
Figure CN121011968A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of longitudinal protection of wind farms, and in particular to a method, system, equipment, medium and product for longitudinal protection of wind farms based on complex domain cosine coefficients. Background Technology
[0002] With the rapid development of new energy power systems, double-fed induction generators (DFIGs) have been widely used in onshore wind farms due to their excellent performance and cost advantages. However, the fault characteristics of DFIGs are affected by the converter control strategy, resulting in significant differences in the amplitude and phase characteristics of their fault currents compared to synchronous generators. Traditional longitudinal protection systems experience significant performance degradation under complex operating conditions such as high-resistance faults and current transformer (CT) saturation. Summary of the Invention
[0003] The purpose of this application is to provide a method, system, equipment, medium and product for longitudinal protection of wind farms based on complex domain cosine coefficients, so as to solve the problem that the performance of traditional longitudinal protection is significantly reduced under complex operating conditions such as high resistance faults and CT saturation.
[0004] To achieve the above objectives, this application provides the following solution:
[0005] Firstly, this application provides a method for longitudinal protection of wind farms based on complex domain cosine coefficients, including:
[0006] Extract fault characteristics from the wind farm's transmission lines;
[0007] Based on Tellergen's theorem, complex domain cosine coefficients are introduced, and a virtual power differential protection criterion is constructed according to the fault characteristics.
[0008] Considering the CT saturation characteristics, the complex domain cosine coefficients are adaptively adjusted.
[0009] The virtual power differential protection criterion is corrected by using the adjusted complex domain cosine coefficients, and the corrected virtual power differential protection criterion is determined.
[0010] The fault type is determined based on the revised virtual power differential protection criterion; the fault type includes external faults and internal faults.
[0011] The longitudinal protection scheme for the wind farm is determined based on the fault type; the longitudinal protection scheme for the wind farm includes protection reset and sending trip signals.
[0012] Secondly, this application provides a wind farm longitudinal protection system based on complex domain cosine coefficients, comprising:
[0013] The fault feature extraction module is used to extract fault features of wind farm transmission lines.
[0014] The virtual power differential protection criterion construction module is used to construct virtual power differential protection criteria based on Tellegen's theorem, by introducing complex domain cosine coefficients, and according to the fault characteristics.
[0015] An adaptive adjustment module is used to adaptively adjust the complex domain cosine coefficients, taking into account CT saturation characteristics.
[0016] The correction module is used to correct the virtual power differential protection criterion using the adjusted complex domain cosine coefficients, and to determine the corrected virtual power differential protection criterion.
[0017] The fault type determination module is used to determine the fault type based on the modified virtual power differential protection criterion; the fault type includes external faults and internal faults.
[0018] The wind farm longitudinal protection scheme determination module is used to determine the wind farm longitudinal protection scheme according to the fault type; the wind farm longitudinal protection scheme includes protection reset and sending trip signal.
[0019] Thirdly, this application provides a computer device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the above-described wind farm longitudinal protection method based on complex domain cosine coefficients.
[0020] Fourthly, this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described wind farm longitudinal protection method based on complex domain cosine coefficients.
[0021] Fifthly, this application provides a computer program product, including a computer program that, when executed by a processor, implements the above-described wind farm longitudinal protection method based on complex domain cosine coefficients.
[0022] According to the specific embodiments provided in this application, this application has the following technical effects:
[0023] This application extracts fault characteristics from wind farm transmission lines and, based on Tellegen's theorem, introduces complex domain cosine coefficients to construct a virtual power differential protection criterion. Since the model significantly outperforms fault conditions during normal operation, a smaller restraint value is adjusted during criterion construction, reducing the threshold construction and making it adaptable to high-resistance faults. Therefore, this criterion itself has good identification capability for high-resistance faults. Simultaneously, considering CT saturation characteristics, the complex domain cosine coefficients are adaptively adjusted, and the adjusted coefficients are used to correct the virtual power differential protection criterion. This corrected criterion addresses the impact of CT saturation, enabling longitudinal protection of the wind farm and resolving the issues of high-resistance faults and CT saturation. This improves the performance of wind farm longitudinal protection under complex conditions such as high-resistance faults and CT saturation. Attached Figure Description
[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0025] Figure 1 A schematic diagram of the process flow for a wind farm longitudinal protection method based on complex domain cosine coefficients, provided as an embodiment of this application;
[0026] Figure 2 This is a schematic diagram of the equivalent circuit of WFTL provided in an embodiment of this application;
[0027] Figure 3 A schematic diagram of an equivalent circuit for an external fault provided in an embodiment of this application;
[0028] Figure 4 This is a schematic diagram of an internal fault equivalent circuit provided in an embodiment of this application;
[0029] Figure 5 This is a schematic diagram of the unsaturated primary and secondary currents of a CT provided in one embodiment of this application;
[0030] Figure 6 This is a schematic diagram of the primary and secondary currents after CT saturation provided in an embodiment of this application;
[0031] Figure 7 This is a schematic diagram of the complex plane action boundary provided in an embodiment of this application;
[0032] Figure 8 This is a schematic diagram of a longitudinal protection method for a doubly fed wind farm provided in an embodiment of this application. Detailed Implementation
[0033] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0034] To make the objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0035] like Figure 1 As shown, this application provides a wind farm longitudinal protection method based on complex domain cosine coefficients, including:
[0036] S1: Extract fault characteristics of the wind farm's transmission lines.
[0037] S2: Based on Tellegen's theorem, a complex domain cosine coefficient is introduced, and a virtual power differential protection criterion is constructed according to the fault characteristics.
[0038] S3: Considering the CT saturation characteristics, the complex domain cosine coefficients are adaptively adjusted.
[0039] S4: The virtual power differential protection criterion is corrected by using the adjusted complex domain cosine coefficients to determine the corrected virtual power differential protection criterion.
[0040] S5: Determine the fault type based on the modified virtual power differential protection criterion; the fault type includes external faults and internal faults.
[0041] S6: Determine the longitudinal protection scheme for the wind farm based on the fault type; the longitudinal protection scheme for the wind farm includes protection reset and sending trip signals.
[0042] In practical applications, Tellegen's theorem can be expressed as follows: In any circuit that satisfies Kirchhoff's laws, for two lumped-parameter circuits with the same number of branches, if they have the same topology but are composed of different branch elements, and the branch currents and node voltages are chosen as reference directions, then the following relationship is satisfied:
[0043]
[0044] Among them, (u k i k ), These represent the node voltage and branch current in two different circuits, respectively, with k being the symbol for different voltage and current parameters.
[0045] Equations (1) and (2) are also known as the quasi-power theorem, which reveal that the sum of the power absorbed by all branches in any circuit is always equal to zero, and can reflect the balance between dissipated energy and stored energy in the circuit.
[0046] Because wind farm transmission lines are relatively long, distributed parameter models are typically used for high-frequency, long-distance wind farm transmission lines (WFTL). Therefore, a WFTL can be equivalent to the superposition of multiple Π-type equivalent lumped circuits, forming a multi-node system with distributed capacitance, such as... Figure 2 As shown.
[0047] Figure 2 In a fault-dependent circuit, the electrical information of the equivalent circuit may change after a fault, but the circuit topology remains unchanged. Since Tellegen's theorem's universality depends only on topological relationships and does not restrict component characteristics, it is applicable to the analysis and verification of various lumped-parameter circuits, including linear / nonlinear, time-varying / time-invariant circuits. Therefore, Tellegen's theorem can be applied to fault identification for WFTLs before and after a fault.
[0048] For faults outside the zone (i.e., external faults), the equivalent circuit is as follows: Figure 3 As shown, the topology of the protected area remains unchanged when an external fault occurs. Based on equations (1) and (2), the Tellergen theorem relationship of the protected area can be derived as follows:
[0049]
[0050] The current and voltage before the fault are marked with the superscript "p", while the current and voltage after the fault are marked with the superscript "f". These represent the voltage and current before the fault on the system side and the wind farm side, respectively. These represent the voltage and current after a fault on the system side and the wind farm side, respectively.
[0051] When the elements in equations (3) and (4) are expressed in phasor form, the equivalent circuit of WFTL satisfies:
[0052]
[0053] Among them, Z j Let j be the impedance of branch j, and the subscript j indicates the electrical quantity of the intermediate equivalent branch.
[0054] Based on equations (3) and (4), we can obtain:
[0055]
[0056] For internal faults, the equivalent circuit is as follows: Figure 4As shown, before the fault occurs, the protected region contains a virtual fault branch, and the current in this branch is zero before the fault occurs. Therefore, the equivalent circuit before and after the fault can be considered to have the same circuit topology. The Tellegen's theorem relationship for the protected region is as follows:
[0057]
[0058] in, The voltage and current of the virtual faulted branch before and after the fault are respectively simulated.
[0059] When the elements in equations (7) and (8) are expressed in phasor form, subtracting the two equations yields:
[0060]
[0061] According to equations (6) and (9), there is a significant difference in the virtual power on both sides of the line before and after the fault. This can be used as a standard to distinguish between internal faults and external faults, and at the same time, it provides a solution for high-resistance faults.
[0062] It should be noted that unpredictable loads are generally not considered in WFTL. The distributed capacitance of the line is also taken into account when equivalent node 1 and equivalent node b are infinitely close to bus W and bus S, respectively.
[0063] Fault characteristics under CT saturation: In actual power systems, when the fault current is large, the CT will exhibit saturation. The relationship between the primary current and the secondary current can be expressed as:
[0064]
[0065] in, These are the primary current, secondary current, and magnetizing current, respectively.
[0066] Under normal conditions, the excitation current in a CT is much smaller than the primary current and can be ignored. Therefore, the relationship between the primary and secondary currents is almost linear. However, when the CT core saturates, the excitation current increases significantly, while the increase in the secondary current is much smaller than that of the primary current. The relationship between the primary and secondary currents is no longer linear, and therefore the waveform of the secondary current will be distorted. The relationship between the secondary and primary currents after CT saturation is as follows: Figures 5-6 As shown.
[0067] like Figures 5-6As shown, when the CT enters saturation, the amplitude of the secondary current increases, while the phase difference between it and the primary current decreases. Therefore, compared to the ideal secondary current, the actual secondary current will exhibit phase lead and reduced amplitude. If the protection system cannot adaptively adjust, performance degradation will occur.
[0068] In an exemplary embodiment, S2 specifically includes:
[0069] S21: Based on Tellegen's theorem, determine the virtual power of the system side and the virtual power of the wind farm side according to the voltage and current before the fault on the system side and the wind farm side and the voltage and current after the fault on the system side and the wind farm side.
[0070] S22: Introduce complex domain cosine coefficients and construct virtual power differential protection criteria based on the virtual power on the system side and the virtual power on the wind farm side.
[0071] In an exemplary embodiment, the fault characteristics of WFTL are extracted according to equations (6) and (9), and the improved longitudinal protection standard (i.e., virtual power differential protection criterion) can be expressed as follows:
[0072] S op >k T S res (11)
[0073]
[0074] Among them, S op ,S res These are the operating power and braking power, respectively. According to equations (11)-(13), it can be noted that the protection judgment criterion is the form of power differential protection. Therefore, the concept of virtual power is introduced to... and These are defined as virtual power on the system side and the wind farm side, respectively.
[0075] In an exemplary embodiment, S3 specifically includes:
[0076] S31: Considering the saturation characteristics of CT, when CT enters a saturation state, construct a critical boundary circle;
[0077] S32: Based on the critical boundary circle, the relationship between the parameters of the critical boundary circle is determined by the law of cosines; the parameters of the critical boundary circle include the distance between the center of the circle and the origin, and the radius.
[0078] S33: Determine the critical factor of the complex domain based on the relationship between the parameters of the critical boundary circle;
[0079] S34: Adaptively adjust the complex domain cosine coefficients according to the complex domain critical factor.
[0080] In an exemplary embodiment, when an internal fault occurs, the current transformer (CT) in the wind farm typically does not saturate due to current limiting control. However, fault current from the system side may cause the CT on that side to saturate. Therefore, when the CT is saturated, the virtual power on the system side can be expressed as:
[0081]
[0082] in, This is the system-side virtual power when CT is saturated. It is the virtual power on the system side.
[0083] Substituting equation (14) into equation (11), the protection criterion can be expressed as follows:
[0084]
[0085] Where a+bi represents a complex number, a is the real part, b is the imaginary part, and i is the imaginary unit, used to represent the deviation between the actual value and the ideal value.
[0086] definition and The relationship is as follows:
[0087]
[0088] Where x is the real part, y is the imaginary part, and i is the imaginary unit.
[0089] Substituting equation (16) into equation (15), we get the following equation:
[0090] |(x+a)+j(y+b)|>k T |x+yi| (17)
[0091] By taking the amplitude values on both sides of equation (17), we can obtain:
[0092]
[0093] When the current transformer (CT) enters saturation, the nonlinear characteristics of the core material cause the rise time of the secondary current to become slower. This phenomenon results in a phase lag between the secondary current and the primary current. Therefore, a > 0 and b < 0.
[0094] When CT is severely saturated, a approaches 0, while b is less than 1. Based on this, setting a = 0 and b = 1, the expression for the critical boundary is constructed as follows:
[0095]
[0096] According to equation (19), the parameters of the critical boundary circle are:
[0097]
[0098] Where d is the distance between the center of the circle and the origin, and r is the radius.
[0099] When CT enters saturation, the action boundary circle is as follows: Figure 7 As shown, Where λ is the power coefficient. This represents the virtual power on the wind farm side. For system-side virtual power, Let y1 be the virtual power phase difference between the two sides of the line, y1 be the imaginary part of the fault point, and x1 be the real part of the fault point.
[0100] The area outside the circle is the operating zone, and the area inside the circle is the braking zone. When the CT is not saturated, the boundary circle is located in the second quadrant of the complex plane, and the fault point is usually located in the first and fourth quadrants. However, when the CT enters saturation, the boundary circle will move towards the fourth quadrant. Considering the fluctuations in current and voltage in the transient time domain, the fault point is more likely to fall into the braking zone, thus increasing the risk of protection failure.
[0101] In the actual saturation state of CT, the center of the boundary circle is located in the third quadrant, and its radius is smaller than that of the critical boundary circle. For example... Figure 7 As shown, by using the law of cosines, the relationship between r and d can be expressed as:
[0102]
[0103] Substituting the critical boundary circle parameters into equation (21), we get:
[0104]
[0105] In equation (22), the discriminant of the root is:
[0106]
[0107] By analyzing equation (22), the solution equation can be obtained as follows:
[0108]
[0109] Where, k c As the critical factor in the complex domain, when k is obtained c Then, the braking coefficient of the protection can be expressed as:
[0110]
[0111] Where γ is the amplitude factor, and These are the rated currents on the system side and the wind farm side, respectively. 4.7 is a constant factor that takes into account the system level and wind farm capacity, and can be adjusted according to the actual system.
[0112] Under external fault conditions, and near, and These are the fault current amplitudes on the system side and the wind farm side after the fault, respectively, where γ < 4.7. Therefore, equation (26) can avoid CT saturation caused by faults outside the zone, which could lead to k T The problem of malfunction caused by insufficient modulation.
[0113] like Figure 8 As shown, it consists of two parts: the first part is data processing, and the second part is fault identification. First, the current amplitude difference ΔI is calculated, which is the difference between the current at the current moment and the sample current measured in the previous cycle. If ΔI is greater than 0.2 times the rated current amplitude (0.2I...), then... N I N If the line rated current is used, then the preceding data is acquired and the fault detection process is executed: the virtual power and amplitude factor on both sides of the line are calculated respectively. If γ > 4.7, then k is started. c If γ≤4.7, then lock k c After obtaining k T If the measured data on both sides of the transmission line satisfy equation (11), then a trip signal is sent; otherwise, the protection is reset.
[0114] In practical applications, the specific steps for the longitudinal protection method of doubly-fed wind farms are as follows:
[0115] Step 1: Use Tellegen's theorem to extract fault features on both sides of the transmission line.
[0116] Step 2: Construct virtual power based on Tellegen's criterion and Based on this, a protection criterion is constructed: if γ > 4.7, then the cosine coefficient k is activated. c If γ≤4.7, then the locking cosine coefficient k c Finally, k is calculated. T .
[0117] Step 3: Based on the fault and Sure Then we obtain the discriminant Δ.
[0118] This application uses complex domain cosine coefficients to modify the virtual power differential protection criterion. If the protection satisfies equation (11), it is determined to be an in-zone fault. If it does not satisfy equation (11), it is determined to be a non-fault or an out-of-zone fault, and the protection is reset, thus ensuring the reliability of the protection.
[0119] This application effectively addresses the protection challenges of transmission lines from doubly-fed induction generator (DFIG) wind farms under complex conditions such as high-resistance faults and current transformer (CT) saturation. First, the scheme possesses high-resistance fault tolerance capability, able to withstand transition resistances up to 300Ω, solving the problem of insufficient sensitivity in traditional longitudinal protection under high-resistance faults and ensuring reliable operation under complex conditions such as high-resistance grounding faults. Second, the scheme exhibits CT saturation adaptability, ensuring reliable operation even under severe CT saturation. By introducing a complex domain cosine coefficient and adaptively adjusting the protection criterion, the impact of CT saturation on virtual power is effectively addressed, avoiding the potential for false tripping or failure to trip under CT saturation conditions in traditional protection systems. Furthermore, the scheme possesses rapid fault identification capability. Under metallic faults, the protection can quickly identify the fault within 10ms; under high-resistance faults, the protection can complete fault identification within 15ms, significantly improving the speed and accuracy of fault detection and ensuring rapid system recovery after a fault occurs. Finally, the scheme achieves high sensitivity and high reliability through Tellegen's theorem and virtual power differential protection. The application of Tellegen's theorem enables more accurate fault feature extraction, while the introduction of the virtual power differential protection criterion effectively solves the protection challenges of DFIG transmission lines under current limitations, distributed capacitance current, and the influence of DFIG control strategies. In summary, the solution designed in this patent not only withstands high-resistance faults and adapts to CT saturation, but also features rapid fault identification, high sensitivity, and high reliability, significantly improving the transient stability and operational safety of new energy power systems.
[0120] This application also provides a wind farm longitudinal protection system based on complex domain cosine coefficients, including:
[0121] The fault feature extraction module is used to extract fault features of wind farm transmission lines.
[0122] The virtual power differential protection criterion construction module is used to construct a virtual power differential protection criterion based on Tellegen's theorem, by introducing complex domain cosine coefficients, and according to the fault characteristics.
[0123] An adaptive adjustment module is used to adaptively adjust the complex domain cosine coefficients, taking into account CT saturation characteristics.
[0124] The correction module is used to correct the virtual power differential protection criterion using the adjusted complex domain cosine coefficients, and to determine the corrected virtual power differential protection criterion.
[0125] The fault type determination module is used to determine the fault type based on the modified virtual power differential protection criterion; the fault type includes external faults and internal faults.
[0126] The wind farm longitudinal protection scheme determination module is used to determine the wind farm longitudinal protection scheme according to the fault type; the wind farm longitudinal protection scheme includes protection reset and sending trip signal.
[0127] In an exemplary embodiment, a computer device is provided, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps in the above-described method embodiments. The computer device can be a server or a terminal. The computer device includes a processor, a memory, an input / output interface (I / O), and a communication interface. The processor, memory, and I / O interface are connected via a system bus, and the communication interface is connected to the system bus via the I / O interface. The processor of the computer device provides computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The database of the computer device stores data to be processed. The I / O interface of the computer device is used for exchanging information between the processor and external devices. The communication interface of the computer device is used for communicating with external terminals via a network connection. When the computer program is executed by the processor, it implements a wind farm longitudinal protection method based on complex domain cosine coefficients.
[0128] In one exemplary embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above-described method embodiments.
[0129] In one exemplary embodiment, a computer-readable storage medium is provided storing a computer program that, when executed by a processor, implements the steps in the above-described method embodiments.
[0130] In one exemplary embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps in the above-described method embodiments.
[0131] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.
[0132] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by hardware related to computer program instructions. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM).
[0133] The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.
[0134] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0135] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.
Claims
1. A method for longitudinal protection of wind farms based on complex domain cosine coefficients, characterized in that, include: Extract fault characteristics from the wind farm's transmission lines; Based on Tellergen's theorem, complex domain cosine coefficients are introduced, and a virtual power differential protection criterion is constructed according to the fault characteristics. Considering the CT saturation characteristics, the complex domain cosine coefficients are adaptively adjusted. The virtual power differential protection criterion is corrected by using the adjusted complex domain cosine coefficients, and the corrected virtual power differential protection criterion is determined. The fault type is determined based on the revised virtual power differential protection criterion; the fault type includes external faults and internal faults. Determine the longitudinal protection scheme for the wind farm based on the fault type; The wind farm longitudinal protection scheme includes protection reset and sending trip signals.
2. The wind farm longitudinal protection method based on complex domain cosine coefficients according to claim 1, characterized in that, Based on Tellergen's theorem, a complex domain cosine coefficient is introduced, and a virtual power differential protection criterion is constructed according to the fault characteristics, specifically including: Based on Tellergen's theorem, the virtual power of the system side and the virtual power of the wind farm side are determined according to the voltage and current before the fault on the system side and the wind farm side and the voltage and current after the fault on the system side and the wind farm side. A complex domain cosine coefficient is introduced, and a virtual power differential protection criterion is constructed based on the virtual power on the system side and the virtual power on the wind farm side.
3. The wind farm longitudinal protection method based on complex domain cosine coefficients according to claim 2, characterized in that, The virtual power differential protection criterion is as follows: S op >k T S res Among them, S op For action power, This refers to the virtual power on the system side. This refers to the virtual power on the wind farm side. and These represent the voltage and current before the fault on the system side and the wind farm side, respectively. and These represent the voltage and current after a fault on the system side and the wind farm side, respectively; k T S represents the complex domain cosine coefficients; res For braking power, 4. The wind farm longitudinal protection method based on complex domain cosine coefficients according to claim 1, characterized in that, Considering CT saturation characteristics, the complex domain cosine coefficients are adaptively adjusted, specifically including: Considering the saturation characteristics of CT, a critical boundary circle is constructed when CT enters a saturation state; Based on the critical boundary circle, the relationship between the parameters of the critical boundary circle is determined by the law of cosines; the parameters of the critical boundary circle include the distance between the center of the circle and the origin, and the radius. Determine the critical factor of the complex domain based on the relationship between the parameters of the critical boundary circle; The complex domain cosine coefficients are adaptively adjusted based on the complex domain critical factor.
5. The wind farm longitudinal protection method based on complex domain cosine coefficients according to claim 4, characterized in that, The complex domain cosine coefficient k T for: Where, k c It is the critical factor for the complex domain. λ is the power coefficient. This represents the virtual power on the wind farm side. For system-side virtual power, Let Δ be the virtual power phase difference between the two sides of the line, γ be the discriminant of the root, and γ be the amplitude factor. and These are the rated currents on the system side and the wind farm side, respectively. and These are the fault current amplitudes on the system side and the wind farm side, respectively, after the fault.
6. The wind farm longitudinal protection method based on complex domain cosine coefficients according to claim 1, characterized in that, The revised virtual power differential protection criterion is as follows: Where a+bi represents a complex number, a is the real part, b is the imaginary part, and i is the imaginary unit.
7. A wind farm longitudinal protection system based on complex domain cosine coefficients, characterized in that, include: The fault feature extraction module is used to extract fault features of wind farm transmission lines. The virtual power differential protection criterion construction module is used to construct virtual power differential protection criteria based on Tellegen's theorem, by introducing complex domain cosine coefficients, and according to the fault characteristics. An adaptive adjustment module is used to adaptively adjust the complex domain cosine coefficients, taking into account CT saturation characteristics. The correction module is used to correct the virtual power differential protection criterion using the adjusted complex domain cosine coefficients, and to determine the corrected virtual power differential protection criterion. The fault type determination module is used to determine the fault type based on the modified virtual power differential protection criterion. The fault types include external faults and internal faults; The wind farm longitudinal protection scheme determination module is used to determine the wind farm longitudinal protection scheme based on the fault type. The wind farm longitudinal protection scheme includes protection reset and sending trip signals.
8. A computer device, comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor executes the computer program to implement the wind farm longitudinal protection method based on complex domain cosine coefficients as described in any one of claims 1-6.
9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the wind farm longitudinal protection method based on complex domain cosine coefficients as described in any one of claims 1-6.
10. A computer program product, comprising a computer program, characterized in that, When executed by a processor, the computer program implements the wind farm longitudinal protection method based on complex domain cosine coefficients as described in any one of claims 1-6.