Main and backup protection adaptability analysis method and system for sending-out line of wind power plant

Abstract

The invention discloses a main and backup protection adaptability analysis method and system for a wind power plant sending-out line. The method comprises the steps of inputting line impedance parameters and power supply control parameters when a system breaks down after a wind power plant is connected into the system; fault conditions such as transition resistance, fault distance and network side impedance are set; iteratively calculating a fault electrical quantity; traversing and calculating coefficients needing to be calculated for main and backup protection adaptability analysis according to the calculated fault electrical quantity; and comparing the obtained coefficient with the existing protection criterion to judge whether the conditions that the internal fault does not act and the external fault malfunctions occur or not. The method can quickly and reliably calculate the fault electrical quantity after the system breaks down, has higher efficiency compared with a simulation experiment, and can quickly judge whether protection acts correctly or not.

Description

Background Art

[0002] The converter is the core device of wind power, photovoltaic and other new energy systems connected to the receiving grid via AC or connected to the AC grid via flexible direct current. Compared with traditional synchronous machines, power electronic devices represented by converters have a fast response time to disturbances, and the response has the characteristics of nonlinearity and strong coupling. Power electronic devices have poor ability to withstand fault impacts and show fragility. When a system fails, the short-circuit current provided by the power electronic equipment is much smaller than that of the synchronous machine system, that is, weak feed characteristics. At the same time, for large-scale wind power generation and photovoltaic power generation systems connected to the transmission network, the operating specifications require them to have low voltage ride-through capabilities. When a power system fails, wind power generation and photovoltaic power generation systems need to be used as power sources to provide short-circuit current to the grid according to their regulations. Therefore, the fault characteristics and control strategies of new energy access systems are closely related. Therefore, the fault characteristics of the system containing converters are significantly different from those of traditional synchronous machine power systems.

[0003] On this basis, when new energy is connected to the system, the simulation time is greatly increased due to its complex control process. The use of iterative calculation methods to solve the fault electrical quantities can greatly shorten the time to obtain the fault electrical quantities, and then shorten the coefficients required to calculate the adaptability analysis of the main and backup protection, thereby shortening the time to judge whether the protection is operating correctly. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method and system for adaptive analysis of the main and backup protection of wind farm transmission lines in view of the deficiencies in the above-mentioned prior art, so as to solve the technical problem that the simulation time is greatly increased due to the complex control process of new energy, which leads to an increase in the time for obtaining fault electrical quantities and an increase in the time for judging whether the protection is operating correctly.

[0005] The present invention adopts the following technical solutions: A method for analyzing adaptability of main and backup protection of wind farm transmission lines comprises the following steps: Input the line impedance parameters and power supply control parameters when a system fault occurs after the wind farm is connected to the system; Set the fault conditions and iteratively calculate the fault electrical quantities by combining the line impedance parameters and the power supply control parameters; The coefficients required for adaptability analysis of the main and backup protection are calculated by traversing the obtained fault electrical quantities; The obtained coefficient is compared with the existing protection criteria to determine whether no action is taken for faults within the zone or false action is taken for faults outside the zone.

[0006] Preferably, the fault conditions include transition resistance, fault distance, and grid-side impedance.

[0007] Preferably, the fault electrical quantity is calculated as follows: Determine the current of the converter type power supply of the new energy station as a function of its port voltage, and the port current is determined by the fault ride-through control strategy of the power electronic type power supply. d , q Components on the axis i d , i q , the positive sequence voltage and current are obtained by simultaneous solution, and then the equivalent impedance is calculated; the nonlinear equations obtained are solved by iterative method to obtain the fault electrical quantity.

[0008] Preferably, the positive sequence port current of the power electronic power supply is for:

[0009] in, is the additional impedance, It is the sum of the equivalent positive sequence impedance of the grid side and the equivalent positive sequence impedance of the line from the grid side to the fault point. is the positive sequence port voltage of the power electronic power supply, is the grid-side equivalent potential, It is the sum of the equivalent positive sequence impedance of the line from the source side to the fault point and the equivalent positive sequence impedance of the transformer and collector line on the power supply side.

[0010] Preferably, , and Z f The values ​​are:

[0011] in, is the equivalent positive sequence impedance of the power supply side transformer and collector line, is the equivalent positive sequence impedance of the line from the source side to the fault point, is the grid-side equivalent positive-sequence impedance, is the equivalent positive sequence impedance of the line from the grid to the fault point, is the excess resistance, is the equivalent negative sequence impedance of the line from the grid to the fault point, is the grid-side equivalent negative-sequence impedance, is the equivalent zero-sequence impedance of the power supply side transformer and collector line, is the equivalent zero-sequence impedance of the line from the source side to the fault point, is the equivalent zero-sequence impedance of the line from the grid to the fault point, is the grid-side equivalent zero-sequence impedance.

[0012] Preferably, the port current is d , q Components on the axis id , i q as follows:

[0013] in, and The upper and lower boundary values ​​of voltage index in the dynamic reactive power regulation stage; is the per unit value of the voltage reference value; I N is the current rating, K is the reactive current proportionality coefficient; i qlim , I max is the limit value of reactive current and total current; P The active power output in normal state.

[0014] Preferably, the coefficients required for traversing and calculating the adaptability analysis of the primary and backup protection are specifically: For the distance protection of three-phase system, the three-phase measurement impedance and phase-to-phase impedance are calculated to distinguish the fault, and then the additional impedance coefficient is calculated according to the judgment results. K R .

[0015] Preferably, the current proportionality factor K I as follows:

[0016] in, Measure the φ phase current of the wind power side busbar, Measure the φ phase current for the grid-side bus.

[0017] Preferably, the additional impedance coefficient under AG fault is K R for:

[0018] Additional impedance coefficient under BCG fault K R for:

[0019] Additional impedance coefficient under BC fault K R for:

[0020] Additional impedance coefficient under three-phase fault K R for:

[0021] in, n Represents the electrical quantity measured at the grid-side busbar. Measure the A-phase current of the wind power side busbar. Measure the A-phase current for the grid-side busbar. is the zero-sequence compensation coefficient, Measure zero-sequence current for the wind power side busbar, Measure the B-phase current of the wind power side busbar. Measure the B-phase current for the grid-side busbar. Measure the C-phase current of the wind power side busbar. Measure the C phase current for the grid-side busbar, Measure the φ phase current of the wind power side busbar, Measure the φ phase current for the grid-side bus.

[0022] In a second aspect, an embodiment of the present invention provides a wind farm transmission line primary and backup protection adaptability analysis system, including: Parameter module, inputting line impedance parameters and power supply control parameters when a system fault occurs after the wind farm is connected to the system; Condition module, which sets fault conditions and iteratively calculates fault electrical quantities by combining line impedance parameters and power supply control parameters; A calculation module, which traverses and calculates the coefficients required for the adaptability analysis of the main and backup protections based on the obtained fault electrical quantities; The judgment module compares the obtained coefficient with the existing protection judgment criteria to determine whether no action is taken for an in-zone fault or false action is taken for an out-of-zone fault.

[0023] In a third aspect, a computer device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for adaptability analysis of main and backup protection of wind farm transmission lines when executing the computer program.

[0024] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, including a computer program, which, when executed by a processor, implements the steps of the above-mentioned method for adaptability analysis of primary and backup protection of wind farm transmission lines.

[0025] In a fifth aspect, a chip comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for adaptability analysis of main and backup protection of wind farm transmission lines when executing the computer program.

[0026] In a sixth aspect, an embodiment of the present invention provides an electronic device, including a computer program, which, when executed by the electronic device, implements the steps of the above-mentioned method for adaptability analysis of primary and backup protection of wind farm transmission lines.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects: A method for analyzing the adaptability of main and backup protection of wind farm transmission lines. After the line impedance parameters and power supply control parameters when a system fault occurs after the wind farm is connected to the system are input, the fault electrical quantity can be calculated by setting the fault condition, and the corresponding fault electrical quantity can be calculated according to different fault conditions. Then, the parameters required for the adaptability analysis of the main and backup protection are calculated, and then compared with the existing protection criteria, which can save a lot of time required for simulation experiments.

[0028] Furthermore, by setting different fault conditions, it is possible to obtain how the parameters required for the adaptability analysis of the main and backup protection are distributed and changed under different fault conditions, so as to better analyze the adaptability problem of the protection and make the method universal.

[0029] Furthermore, the additional impedance coefficient under different fault conditions can be calculated by calculating the fault electrical quantity. K R and current proportionality factor K I .

[0030] Furthermore, the additional impedance coefficient under different fault conditions can be obtained by traversing and calculating the coefficients required for the adaptability analysis of the main backup protection. K R and current proportionality factor K I The distribution of protection actions can be better analyzed.

[0031] It can be understood that the beneficial effects of the second to sixth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0032] In summary, the method of the present invention can achieve iterative calculation to obtain the fault electrical quantity when a system fault occurs after the new energy is connected, and then obtain the coefficients required for the adaptability analysis of the main and backup protections, and quickly determine whether the protection can operate correctly.

[0033] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The following is a typical power electronic power grid access system diagram, where (a) is a non-fault circuit diagram and (b) is a fault circuit diagram; Figure 2 It is a schematic diagram of the process of the present invention; Figure 3 The composite sequence network diagram of wind power access system faults, where (a) is the simplified fault network diagram, (b) is the composite sequence network diagram of AG faults, (c) is the composite sequence network diagram of BCG faults, and (d) is the composite sequence network diagram of BC faults; Figure 4 For different fault conditions K I and θ mn Value diagram, where (a) is different fault distances K I , (b) for different fault distances θ mn , (c) is different transition resistance K I , (d) is different transition resistance θ mn , (e) is different grid side impedance K I , (f) is different grid side impedance θ mn ; Figure 5 is the additional impedance coefficient under different fault conditions K R Figure 2, where (a) is the distance between different faults. K R , (b) for different transition resistances K R , (c) is different grid side impedance K R ; Figure 6 Transmission line circuit diagrams under various fault types, where (a) is AG fault, (b) is BCG fault, (c) is BC fault, and (d) is three-phase fault; Figure 7 A schematic diagram of a computer device provided by an embodiment of the present invention; Figure 8 The block diagram of a chip provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0037] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0038] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0039] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0040] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0041] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0042] The present invention provides a method for analyzing the adaptability of main and backup protections of a wind farm transmission line, which includes inputting line impedance parameters and power supply control parameters when a system fault occurs after the wind farm is connected to the system; setting fault conditions such as transition resistance, fault distance, and grid-side impedance; iteratively calculating fault electrical quantities; traversing and calculating coefficients required for the adaptability analysis of the main and backup protections based on the calculated fault electrical quantities; judging whether a situation in which no action is taken due to an in-zone fault or a false action is taken due to an out-of-zone fault, based on comparison of the obtained coefficients with existing protection criteria; and being able to quickly and reliably calculate the fault electrical quantities after a system fault occurs, having higher efficiency than simulation experiments, and being able to more quickly judge whether the protection is correctly acting.

[0043] See also Figure 2 The present invention provides a method for analyzing the adaptability of the main and backup protection of a wind farm transmission line, which further obtains the corresponding coefficient of the demand by calculating the fault electrical quantity after a fault occurs in a new energy access system, and then determines whether the protection is operating correctly; it includes the following steps: S1, input line impedance parameters and power supply control parameters when a system fault occurs after the wind farm is connected to the system; S2, set the fault conditions such as transition resistance, fault distance, grid side impedance, etc.; S3, iteratively calculating the fault electrical quantity based on the results obtained in step S1 and step S2; The fault electrical quantity is calculated as follows: (1) in, , and Z f The values ​​are: (2) The current of the converter-type power supply of the new energy station is a function of its terminal voltage: (3) in, u d is the port voltage d The axial component, in the case of voltage orientation, is the port voltage amplitude; δ is the phase angle of the port voltage relative to the reference point; i d , i q The port current is d , q Components on the axis.

[0044] i d , i q Determined by the fault ride-through control strategy of the power electronic power supply: (4) in, and The upper and lower boundary values ​​of the voltage index in the dynamic reactive power regulation stage are generally 0.9 and 0.2; is the per unit value of the voltage reference value, generally , that is, 0.9; I N is the current rating, K is the reactive current proportional coefficient, usually 2; i qlim , I max For the limit of reactive current and total current, generally ; P The active power output in normal state. In the case of asymmetric voltage drop, the positive sequence d , q The shaft current is still calculated according to the above formula, and the negative sequence current is generally controlled to 0.

[0045] The positive sequence voltage and current can be obtained by solving them simultaneously, and then the equivalent impedance can be calculated. The obtained equation is actually a nonlinear equation, which can be solved by iterative method.

[0046] First given The initial value of Secondly, Substituting into equations (1) and (4) we can obtain and , ; Then , Substituting into formula (3) we can get ; Final calculation - If the value is not 0, Perform iterative calculation until - The value is 0, that is, the fault electrical quantity is calculated .

[0047] S4, traversing the fault electrical quantity calculated in step S3 to calculate the coefficients required for the adaptability analysis of the main and backup protections; For differential protection, define the current proportionality factor K I as follows: (5) The typical action criteria of common phase-comparison current differential protection are as follows: (6) in, θ mn To measure the current phase difference at both ends of the line, φ b To protect the locking angle.

[0048] Protective locking angle φ b The values ​​are: (7) For the distance protection of the three-phase system, the three-phase measurement impedance and the phase-to-phase impedance are calculated separately. The fault phase impedance will reflect the fault distance, while the non-fault phase impedance will not. Based on this, the fault is judged. The calculation formula of the protection measurement impedance is: (8) in, , To measure impedance for single phase and phase to phase, , For single-phase and phase-to-phase voltage measurements, , For single-phase and phase-to-phase current measurement, is the zero-sequence compensation coefficient, , is the zero-sequence and positive-sequence impedance per unit length of the transmission line.

[0049] Without loss of generality, the analysis is performed using AG, BCG, BC and three-phase fault conditions. Figure 6 The transmission line circuit diagram under four fault types is shown; subscript n Represents the electrical quantity measured at the grid-side busbar.

[0050] Additional impedance coefficient under AG fault K R for: (9) Additional impedance coefficient under BCG fault K R for: (10) Additional impedance coefficient under BC fault K R for: (11) Additional impedance coefficient under three-phase fault K R for: (12) It can be concluded that in the case of metallic faults, the distance impedance is theoretically unaffected. When there is transition resistance, the effect of transition resistance on the measured impedance is directly related to the current at both ends, and specific calculation is required. Note that the measured impedance has the form of transition resistance multiplied by a coefficient plus the actual line impedance. It is useful to define the additional impedance coefficient K R , then all measured impedances are written as in the form of,. K R The angle actually determines the angle of the additional impedance.

[0051] The fault electrical quantity obtained by calculation Get the φ phase current measured by the busbar on the wind power side , the grid-side bus measures the φ phase current ; Calculate the current proportionality factor K I , measure the current phase difference at both ends of the line θ mn and additional impedance coefficient under different fault conditions K R .

[0052] See also Figure 3 , Figure 3 (a) is a simplified fault network diagram. Figure 3 (b) is the composite sequence network diagram of AG fault. Figure 3 (c) is the BCG fault composite sequence network diagram, Figure 3 (d) is the composite sequence network diagram of BC fault.

[0053] S5. Compare the coefficient calculated in step S4 with the existing protection criteria to determine whether no action is taken for an in-zone fault or erroneous action is taken for an out-of-zone fault.

[0054] See also Figure 4 , for the A-phase current during AG fault and three-phase fault, and the B-phase current during BCG fault and BC fault, K I All above 1, θ mn All are within (−90°, +90°), the protection can be operated reliably with a large margin; however, for the C phase current during BCG fault and BC fault, K I Maybe below 1, θ mn It is also close to the boundary of the action range, with a smaller margin, a greater possibility of protection refusal to operate, and a lower sensitivity; therefore, for the C phase current, the protection needs to set a smaller braking coefficient K res and locking angle φ b, improve protection sensitivity.

[0055] See also Figure 5 The default fault location is the midpoint of the line, the transition resistance is 10 Ω, and the full length of the line, 0~100 Ω transition resistance, and 1~10 times the grid-side impedance are traversed to calculate K R The value of K R It is presented in the form of a complex plane diagram.

[0056] from Figure 5 It can be seen that for AG faults and BCG faults, K R Near the positive real axis, it is slightly biased towards the fourth quadrant, indicating that the additional impedance is mainly resistive with a little capacitance; for BC faults, the additional impedance is mainly capacitive; for three-phase faults, both resistance and capacitance are large. In addition, the BC fault and three-phase fault K R It is obviously larger than that of AG fault and BCG fault, which indicates that the transition resistance of BC fault and three-phase fault has a greater impact on the protection.

[0057] In summary, the additional impedance is mainly in the form of resistance and capacitance, which, when reflected in the measurement impedance of the distance protection, will cause the measurement impedance to shift to the lower right.

[0058] It will be appreciated by those skilled in the art that various aspects of the present invention may be implemented as systems, methods or program products. Therefore, various aspects of the present invention may be specifically implemented in the following forms, namely: complete hardware implementation, complete software implementation (including firmware, microcode, etc.), or a combination of hardware and software implementations, which may be collectively referred to herein as "circuits", "modules" or "platforms".

[0059] In another embodiment of the present invention, a wind farm transmission line main backup protection adaptability analysis system is provided. The system can be used to implement the above-mentioned wind farm transmission line main backup protection adaptability analysis method. Specifically, the wind farm transmission line main backup protection adaptability analysis system includes a parameter module, a condition module, a calculation module and a judgment module.

[0060] Among them, the parameter module inputs the line impedance parameters and power supply control parameters when a system fault occurs after the wind farm is connected to the system; Condition module, which sets fault conditions and iteratively calculates fault electrical quantities by combining line impedance parameters and power supply control parameters; A calculation module, which traverses and calculates the coefficients required for the adaptability analysis of the main and backup protections based on the obtained fault electrical quantities; The judgment module compares the obtained coefficient with the existing protection judgment criteria to determine whether no action is taken for an in-zone fault or false action is taken for an out-of-zone fault.

[0061] In another embodiment of the present invention, a terminal device is provided, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used for the operation of the main backup protection adaptability analysis method of the wind farm transmission line, including: Input the line impedance parameters and power supply control parameters when a system fault occurs after the wind farm is connected to the system; set the fault conditions, and iteratively calculate the fault electrical quantities by combining the line impedance parameters and power supply control parameters; traverse and calculate the coefficients required for the adaptability analysis of the main and backup protections based on the obtained fault electrical quantities; compare the obtained coefficients with the existing protection criteria to determine whether no action occurs for an in-zone fault or false action occurs for an out-of-zone fault.

[0062] See also Figure 7 , the terminal device is a computer device, and the computer device 60 of this embodiment includes: a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. When the computer program 63 is executed by the processor 61, the method for analyzing the adaptability of the main backup protection of the wind farm transmission line in the embodiment is implemented. To avoid repetition, it is not described one by one here. Alternatively, when the computer program 63 is executed by the processor 61, the functions of each model / unit in the adaptability analysis system for the main backup protection of the wind farm transmission line in the embodiment are implemented. To avoid repetition, it is not described one by one here.

[0063] The computer device 60 may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The computer device 60 may include, but is not limited to, a processor 61 and a memory 62. Those skilled in the art will appreciate that Figure 7This is only an example of the computer device 60 and does not constitute a limitation of the computer device 60. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the computer device may also include input and output devices, network access devices, buses, etc.

[0064] The processor 61 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0065] The memory 62 may be an internal storage unit of the computer device 60, such as a hard disk or memory of the computer device 60. The memory 62 may also be an external storage device of the computer device 60, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc., equipped on the computer device 60.

[0066] Furthermore, the memory 62 may include both an internal storage unit of the computer device 60 and an external storage device. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 may also be used to temporarily store data that has been output or is to be output.

[0067] See also Figure 8 , the terminal device is a chip, and the chip 600 of this embodiment includes a processor 622, which may be one or more, and a memory 632 for storing a computer program executable by the processor 622. The computer program stored in the memory 632 may include one or more modules, each corresponding to a set of instructions. In addition, the processor 622 may be configured to execute the computer program to execute the above-mentioned wind farm transmission line main backup protection adaptability analysis method.

[0068] In addition, the chip 600 may further include a power supply component 626 and a communication component 650, wherein the power supply component 626 may be configured to perform power management of the chip 600, and the communication component 650 may be configured to implement communication, for example, wired or wireless communication, of the chip 600. In addition, the chip 600 may further include an input / output interface 658. The chip 600 may operate based on an operating system stored in the memory 632.

[0069] In another embodiment of the present invention, the present invention also provides a storage medium, specifically a computer-readable storage medium, which is a memory device in a terminal device for storing programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and the extended storage medium supported by the terminal device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs. It should be noted that the computer-readable storage medium here can be a high-speed RAM memory, or a non-volatile memory (Non-VolatileMemory), such as at least one disk memory.

[0070] The processor may load and execute one or more instructions stored in a computer-readable storage medium to implement the corresponding steps of the method for adaptability analysis of primary and backup protection of wind farm transmission lines in the above embodiment; the processor may load and execute the following steps: Input the line impedance parameters and power supply control parameters when a system fault occurs after the wind farm is connected to the system; set the fault conditions, and iteratively calculate the fault electrical quantities by combining the line impedance parameters and power supply control parameters; traverse and calculate the coefficients required for the adaptability analysis of the main and backup protections based on the obtained fault electrical quantities; compare the obtained coefficients with the existing protection criteria to determine whether no action occurs for an in-zone fault or false action occurs for an out-of-zone fault.

[0071] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0072] Experimental verification In order to verify the correctness of the protection method proposed in the present invention, Figure 1 The typical power electronic power grid access system shown in the figure is iteratively calculated in MATLAB, and the model line parameters are derived from the artificial short-circuit test data of the 330 kV Jianfan line of the Northwest Power Grid.

[0073] For current differential protection, m and n It is the busbar on the wind farm side and the grid side of the transmission line. , Measure the current and voltage of the wind power side busbar. , Measure the current and voltage of the grid-side busbar. , is the port current and port voltage of the power electronic power supply, is the equivalent impedance of the transformer and collector line on the power supply side, , is the current and voltage at the measuring point. Z GT is the grid-side equivalent impedance, is the grid side equivalent potential. Z Sk and Z Gk are the equivalent impedances of the lines from the source side and the grid side to the fault point respectively. R f is the transition resistance, is the fault point voltage.

[0074] For differential protection, define the current proportionality factor K I as follows: (13) The typical action criteria of common phase-comparison current differential protection are as follows: (14) in, θ mn To measure the current phase difference at both ends of the line, φ b To protect the locking angle.

[0075] Protective locking angle φ b The general value is: (15) The default fault location is the midpoint of the line, the transition resistance is 10 Ω, and the entire length of the line, 0~100 Ω transition resistance, and 1~10 times the grid-side impedance are traversed to calculate the fault phase. K I and θ mn , the results are as follows Figure 4 When a three-phase fault occurs, the situation of phase BC is similar to that of phase A, so only phase A is shown as a representative.

[0076] The larger the grid-side impedance is, the smaller the fault current provided by the grid-side power supply is, and the weaker the grid strength is. Figure 4 (e) and (f) represent the quantitative relationship between grid strength and protection action performance.

[0077] See also Figure 4 , for the A-phase current during AG fault and three-phase fault, and the B-phase current during BCG fault and BC fault, K I All above 1, θ mn All are within (−90°, +90°), the protection can be operated reliably with a large margin. However, for the C phase current during BCG fault and BC fault, K I Maybe below 1, θ mn It is also close to the boundary of the action range, with a smaller margin, a greater possibility of protection refusal to operate, and a lower sensitivity. Therefore, for the C phase current, the protection needs to set a smaller braking coefficient K res and locking angle φ b , improve protection sensitivity.

[0078] For the distance protection of the three-phase system, the three-phase measurement impedance and the phase-to-phase impedance are calculated separately. The fault phase impedance will reflect the fault distance, while the non-fault phase impedance will not. Based on this, the fault is judged. The calculation formula of the protection measurement impedance is: (16) in, , Measuring impedance for single phase and phase to phase, , For single-phase and phase-to-phase voltage measurements, , For single-phase and phase-to-phase current measurement, is the zero-sequence compensation coefficient, , is the zero-sequence and positive-sequence impedance per unit length of the transmission line.

[0079] Without loss of generality, the analysis is performed using AG, BCG, BC and three-phase fault conditions. Figure 6 The transmission line circuit diagram under four fault types is shown. n Represents the electrical quantity measured at the grid-side busbar. , and Meaning and Figure 1 Consistent.

[0080] The measured impedance of phase A under AG fault is: (17) The measured impedance of phase B under BCG fault is: (18) The measured impedance between BC phases under BC fault is: (19) Three-phase fault ϕ The phase measurement impedance is: (20) It can be concluded that in the case of metallic faults, the distance impedance is theoretically unaffected. When there is transition resistance, the effect of transition resistance on the measured impedance is directly related to the current at both ends, and specific calculation is required. Note that the measured impedance has the form of transition resistance multiplied by a coefficient plus the actual line impedance. It is useful to define the additional impedance coefficient K R , then all measured impedances can be written as form. K R The angle actually determines the angle of the additional impedance.

[0081] The default fault location is the midpoint of the line, the transition resistance is 10 Ω, and the full length of the line, 0-100 Ω transition resistance, and 1-10 times the grid-side impedance are traversed to calculate. K R The value of Figure 5 ;by K R It is presented in the form of a complex plane diagram.

[0082] analyze Figure 5 It can be seen that for AG fault and BCG fault, K R Near the positive real axis, it is slightly biased towards the fourth quadrant, indicating that the additional impedance is mainly resistive with a slight capacitance. For BC faults, the additional impedance is mainly capacitive. For three-phase faults, both resistance and capacitance are large.

[0083] In addition, BC fault and three-phase fault K R It is obviously larger than AG fault and BCG fault, indicating that the transition resistance of BC fault and three-phase fault has a greater impact on protection. In summary, the additional impedance is mainly resistance and capacitance, which is reflected in the measurement impedance of distance protection, causing the measurement impedance to shift to the lower right.

[0084] In summary, the present invention provides a method and system for analyzing the adaptability of the main and backup protections of a wind farm transmission line, which can quickly and reliably calculate the fault electrical quantities after a system fault occurs. Compared with simulation experiments, it has higher efficiency and can more quickly determine whether the protection is operating correctly.

[0085] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0086] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0087] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in the present invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0088] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0089] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0090] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0091] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0092] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices, and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0093] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0094] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0095] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for analyzing the adaptability of main and backup protection of wind farm transmission lines, characterized in that: The following steps are involved: Input the line impedance parameters and power supply control parameters when a system fault occurs after the wind farm is connected to the system; Set the fault conditions and iteratively calculate the fault electrical quantities by combining the line impedance parameters and the power supply control parameters; The coefficients required for adaptability analysis of the main and backup protection are calculated by traversing the obtained fault electrical quantities; The obtained coefficient is compared with the existing protection criteria to determine whether no action is taken for faults within the zone or false action is taken for faults outside the zone.

2. The method for analyzing the adaptability of the main and backup protection of the wind farm transmission line according to claim 1 is characterized in that: Fault conditions include transition resistance, fault distance, and grid-side impedance.

3. The method for analyzing the adaptability of the main and backup protection of the wind farm transmission line according to claim 1 is characterized in that: The fault electrical quantity is calculated as follows: Determine the current of the converter type power supply of the new energy station as a function of its port voltage, and the port current is determined by the fault ride-through control strategy of the power electronic type power supply. d , q Components on the axis i d , i q , the positive sequence voltage and current are obtained by simultaneous solution, and then the equivalent impedance is calculated; the nonlinear equations obtained are solved by iterative method to obtain the fault electrical quantity.

4. The method for analyzing the adaptability of the main and backup protection of the wind farm transmission line according to claim 3 is characterized in that: Positive sequence port current of power electronic power supply for: in, is the additional impedance, It is the sum of the equivalent positive sequence impedance of the grid side and the equivalent positive sequence impedance of the line from the grid side to the fault point. is the positive sequence port voltage of the power electronic power supply, is the grid-side equivalent potential, It is the sum of the equivalent positive sequence impedance of the line from the source side to the fault point and the equivalent positive sequence impedance of the transformer and collector line on the power supply side.

5. The method for analyzing the adaptability of the main and backup protection of the wind farm transmission line according to claim 4 is characterized in that: , and Z f The values ​​are: in, is the equivalent positive sequence impedance of the power supply side transformer and collector line, is the equivalent positive sequence impedance of the line from the source side to the fault point, is the grid-side equivalent positive sequence impedance, is the equivalent positive sequence impedance of the line from the grid to the fault point, is the excess resistance, is the equivalent negative sequence impedance of the line from the grid to the fault point, is the grid-side equivalent negative-sequence impedance, is the equivalent zero-sequence impedance of the power supply side transformer and collector line, is the equivalent zero-sequence impedance of the line from the source side to the fault point, is the equivalent zero-sequence impedance of the line from the grid to the fault point, is the grid-side equivalent zero-sequence impedance.

6. The method for analyzing the adaptability of the main and backup protection of the wind farm transmission line according to claim 3 is characterized in that: Port current at d , q Components on the axis i d , i q as follows: in, and The upper and lower boundary values ​​of voltage index in the dynamic reactive power regulation stage; is the per unit value of the voltage reference value; I N is the current rating, K is the reactive current proportionality coefficient; i qlim , I max is the limit value of reactive current and total current; P The active power output in normal state.

7. The method for analyzing the adaptability of the main and backup protection of the wind farm transmission line according to claim 1 is characterized in that: The coefficients required for traversal calculation of the adaptability analysis of the main backup protection are as follows: For the distance protection of the three-phase system, the three-phase measurement impedance and the phase-to-phase impedance are calculated respectively to identify the fault, and then the additional impedance coefficient is calculated based on the identification results. K R .

8. The method for analyzing the adaptability of the main and backup protection of the wind farm transmission line according to claim 7 is characterized in that: Current proportionality factor K I as follows: in, Measure the φ phase current of the wind power side busbar, Measure the φ phase current for the grid-side bus.

9. The method for analyzing the adaptability of the main and backup protection of the wind farm transmission line according to claim 7 is characterized in that: Additional impedance coefficient under AG fault K R for: Additional impedance coefficient under BCG fault K R for: Additional impedance coefficient under BC fault K R for: Additional impedance coefficient under three-phase fault K R for: in, n Represents the electrical quantity measured at the grid-side busbar. Measure the A-phase current of the wind power side busbar. Measure the A-phase current for the grid-side busbar. is the zero-sequence compensation coefficient, Measure zero-sequence current for the wind power side busbar, Measure the B-phase current of the wind power side busbar. Measure the B-phase current for the grid-side busbar. Measure the C-phase current of the wind power side busbar. Measure the C phase current for the grid-side busbar, Measure the φ phase current of the wind power side busbar, Measure the φ phase current for the grid-side bus.

10. A wind farm transmission line main and backup protection adaptability analysis system, characterized in that: include: Parameter module, inputting line impedance parameters and power supply control parameters when a system fault occurs after the wind farm is connected to the system; Condition module, which sets fault conditions and iteratively calculates fault electrical quantities by combining line impedance parameters and power supply control parameters; A calculation module, which traverses and calculates the coefficients required for the adaptability analysis of the main and backup protections based on the obtained fault electrical quantities; The judgment module compares the obtained coefficient with the existing protection judgment criteria to determine whether no action is taken for an in-zone fault or false action is taken for an out-of-zone fault.

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