A protection method and system for extended-time single-ended quantity adapted to a new energy power system

Abstract

The present invention discloses a protection method and system for an extended-time single-terminal quantity adapted to a new energy power system. The sudden changes of the modulus voltage and current of the 1-mode voltage and current are calculated according to the modulus voltage and current of the three-phase voltage and current of the transmission line, the protection is started, and the reverse traveling wave of the 1-mode fault voltage is calculated according to the sudden changes of the 1-mode voltage and current; the arrival time of the second wavefront is extracted within a given time window, and then the data window data from the start time to the arrival time of the second wavefront is extracted. The first traveling waves of voltage and current are extracted based on the data window data, and the fault direction is discriminated by the fault direction criterion; when the fault direction is discriminated as a forward fault, the Levenberg-Marquardt algorithm is used to fit the wavefront of the first fault voltage traveling wave to obtain the wavefront exponential coefficient, and the operating time of the backup protection is calculated according to the wavefront exponential coefficient. A low voltage criterion is determined within the time from the fault start ΔT to the operating time of the backup protection, so as to realize the extended-time single-terminal quantity protection. The sensitivity of the backup protection is improved, and the effectiveness of the method is verified by the simulation results.

Description

Technical Field

[0001] The present invention belongs to the technical field, and particularly relates to a delayed single-ended quantity protection method and system adapted to a new energy power system. Background Art

[0002] The rapid development of new energy power generation has promoted the wide application of power electronic equipment, changing the basic form of the traditional AC power system with electromagnetic induction type power equipment as the core. The backup protection of AC transmission lines mainly includes wide-area protection based on communication and single-ended quantity protection that realizes hierarchical coordination based on fixed time differences. Wide-area backup protection requires the construction of a communication channel, and its reliability is restricted by the communication channel. Moreover, affected by the control of power electronic devices, the topology of the power transmission system is more flexible and changeable, making it difficult to formulate the coordination mechanism and cooperation strategy of wide-area backup protection. Single-ended quantity backup protection realizes the near-backup of this line and the far-backup of adjacent lines through "differential coordination". Affected by the changes in power supply characteristics and operating parameters brought about by the adjustment process of power electronic equipment, it is difficult to carry out protection setting and coordination.

[0003] Therefore, it is urgent to study backup protection technologies that do not require hierarchical setting and have an automatic cooperation function to adapt to the frequently changing operation modes of new energy power systems. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a delayed single-ended quantity protection method and system adapted to a new energy power system for solving the technical problems of complex protection coordination of AC systems with energy access and slow action speed and poor adaptability of traditional backup protection.

[0005] The present invention adopts the following technical solutions:

[0006] A delayed single-ended quantity protection method adapted to a new energy power system. First, calculate the mutation quantities of the 1-mode voltage and current according to the modulus voltage and current of the three-phase voltage and current of the transmission line, and start the protection based on the mutation quantity of the 1-mode voltage; calculate the reverse traveling wave of the 1-mode fault voltage according to the mutation quantities of the 1-mode voltage and current; according to the reverse traveling wave of the 1-mode fault voltage, extract the arrival time of the second wave head within a given time window, and then extract the data window data from the start time to the arrival time of the second wave head. Based on the obtained data window data, extract the first traveling waves of the voltage and current, and judge the fault direction through the fault direction criterion; when the fault direction is judged to be a forward fault, use the Levenberg-Marquardt algorithm to fit the front of the first fault voltage traveling wave to obtain the wave front exponential coefficient, and calculate the backup protection action time T delay , determine the low voltage criterion after the fault starts for ΔT until the backup protection action time T delay to realize the delayed single-ended quantity protection.

[0007] Specifically, it is determined whether to start the protection based on the sudden change of the first-mode voltage, as follows:

[0008]

[0009] Among them, |Δu1(n)| is the absolute value of the sudden change of the voltage at the nth sampling point, and Δu 1set is set to avoid the voltage fluctuation during normal operation.

[0010] Furthermore, the sudden changes of the first-mode voltage and current are specifically:

[0011]

[0012] Among them, u1(n) and i1(n) represent the first-mode voltage and current at the nth sampling point, N represents the number of sampling points corresponding to one cycle of the power frequency, and Δu1(n) and Δi1(n) are the sudden changes of the first-mode voltage and current at the nth sampling point.

[0013] Specifically, the backward traveling wave of the first-mode fault voltage Δu b1 is:

[0014] Δu b1 = 0.5(Δu1 - Z c1 Δi1)

[0015] Among them, Δu1 and Δi1 represent the sudden changes of the first-mode voltage and current; Z c1 is the first-mode wave impedance of the line.

[0016] Specifically, the fault direction criterion is specifically:

[0017]

[0018] Among them, Δu 1k and Δi 1k are respectively the kth sampling points of the first-mode voltage and current fault components, N w is the number of sampling points within the data window, and F T is the fault direction criterion.

[0019] Furthermore, if no second wavefront arrival is detected within the entire data window, the entire data window data is extracted.

[0020] Specifically, the low voltage criterion is specifically:

[0021] u 1RMS < k rel u 1N

[0022] Among them, u 1RMS is the effective value of the first-mode voltage, and k relis the reliability coefficient, u 1N is the effective value of the 1-mode voltage during normal operation.

[0023] Furthermore, the operation time T of the backup protection delay is specifically:

[0024]

[0025] where p is the coefficient of the exponential term obtained by fitting, ΔT mainly considers the time delay of the backup protection for proximal faults and the data window length required for calculating the low-voltage criterion, and k T is the coefficient of the mapping from the exponential coefficient to the protection time delay.

[0026] Even further, the coefficient p of the exponential term obtained according to the formula to be fitted is specifically:

[0027] u(t) = C1sin(ω0t + θ) + C2e -pt

[0028] where u(t) is the fitting function of the front wave of the fault voltage traveling wave, C1 is the amplitude of the sine term of the fitting function, C2 is the amplitude of the decaying exponential term, ω0 is the power frequency angular frequency, and θ is the phase angle of the sine term of the fitting function.

[0029] In a second aspect, an extended-time single-terminal quantity protection system adapted to a new energy power system according to an embodiment of the present invention includes:

[0030] A mutation quantity module that calculates the mutation quantities of the 1-mode voltage and current according to the modulus voltages and currents of the three-phase voltages and currents of the transmission line, and starts the protection based on the mutation quantity of the 1-mode voltage;

[0031] A calculation module that calculates the backward traveling wave of the 1-mode fault voltage according to the mutation quantities of the 1-mode voltage and current;

[0032] A discrimination module that extracts the arrival time of the second wavefront within a given time window according to the backward traveling wave of the 1-mode fault voltage, then extracts the data window data from the start time to the arrival time of the second wavefront, extracts the first traveling waves of the voltage and current based on the obtained data window data, and discriminates the fault direction through a fault direction criterion;

[0033] A protection module that, when the fault direction is discriminated as a forward fault, uses the Levenberg-Marquardt algorithm to fit the front wave of the first fault voltage traveling wave to obtain the front wave exponential coefficient, and calculates the operation time T of the backup protection according to the front wave exponential coefficient delay , determines the low-voltage criterion after the fault starts for ΔT until the operation time T of the backup protection delay to implement extended-time single-terminal quantity protection.

[0034] Compared with the prior art, the present invention has at least the following beneficial effects:

[0035] A time-delay single-ended quantity protection method adapted to a new energy power system calculates the reverse traveling wave of the fault voltage by using the voltage and current measured at the protection installation location after a fault. Secondly, the LM algorithm is used to fit the wavefront of the fault traveling wave to obtain the exponential coefficient. Then, the action time delay of the backup protection is calculated by using the fitted exponential coefficient. Finally, it is judged whether the voltage recovers within the calculated time delay to determine whether the backup protection acts.

[0036] Furthermore, by setting the protection startup criterion, the calculation of the protection method in the normal operation state is avoided, and the risk of protection misoperation is reduced.

[0037] Furthermore, by calculating the sudden change quantity through the modal voltage and current, the influence of the slow change of the power frequency quantity caused by factors such as slow load change in the normal working state can be eliminated, and the reliability of the method is improved.

[0038] Furthermore, by calculating the reverse traveling wave of the fault voltage through the sudden change quantity of the voltage and current under the mode, the influence of the reflected wave generated due to the discontinuous wave impedance at the line boundary is eliminated.

[0039] Furthermore, by using the fault direction criterion to distinguish reverse faults, the interference of out-of-zone faults in the reverse direction to the protection method is excluded.

[0040] Furthermore, by detecting whether there is a second reflected wave arriving within the data window, an adaptive data window is realized, and the influence on the extraction of the wavefront exponential coefficient after the arrival of the second traveling wave head is eliminated.

[0041] Furthermore, by using the steady-state voltage criterion to judge whether a fault occurs, the reliability of the protection is improved.

[0042] Furthermore, by calculating the action time of the backup protection, the automatic coordination of the upper and lower level protections of the line is realized, and the difficulty of the backup protection coordination is reduced.

[0043] Furthermore, by calculating the wavefront exponential coefficient to reflect the fault distance, the decoupling of the fault distance and the fault severity information is realized, which provides a basis for calculating the action time of the backup protection.

[0044] It can be understood that the beneficial effects of the second aspect above can be referred to the relevant descriptions in the first aspect above, and will not be elaborated here.

[0045] In summary, the present invention realizes the decoupling of the fault distance and the fault severity information by calculating the wavefront exponential coefficient of the fault traveling wave, and constructs the inverse time characteristic of the time-delay protection by using the characteristic that the wavefront exponential coefficient reflects the fault distance. And the steady-state voltage information is used to confirm the fault, so as to realize a backup protection method that can be automatically coordinated. This method does not depend on the power supply characteristics and has high reliability and the ability to withstand transition resistance.

[0046] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0047] Figure 1 It is a schematic flowchart of the present invention;

[0048] Figure 2 It is a simulation model of a wind farm connected to an AC system;

[0049] Figure 3 They are protection action delays for different faults at different positions. Specific Embodiments

[0050] The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0051] In the description of the present invention, it should be understood that the terms "including" and "comprising" indicate the presence of the 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 their combinations.

[0052] It should also be understood that the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms.

[0053] It should be further understood that the term " / and / " used in the specification of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the related listed items, and includes these combinations. For example, A and / or B can represent three cases: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the preceding and following related objects.

[0054] It should be understood that although the terms first, second, third, etc. may be used in the embodiments of the present invention to describe preset ranges, etc., these preset ranges should not be limited to these terms. These terms are only used to distinguish the 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.

[0055] Depending on the context, as used herein, the word "if" can be interpreted as "when" or "while" or "in response to determining" or "in response to detecting". Similarly, depending on the context, the phrase "if determined" or "if detecting (stated condition or event)" can be interpreted as "when determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)".

[0056] Various structural schematic diagrams according to the disclosed embodiments of the present invention are shown in the drawings. These figures are not drawn to scale, where for the purpose of clear expression, some details are enlarged and some details may be omitted. The shapes of various regions and layers shown in the figures, and their relative sizes and positional relationships are merely exemplary, and in practice, there may be deviations due to manufacturing tolerances or technical limitations, and those skilled in the art can design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0057] The present invention provides a time-delayed single-ended quantity protection method adapted to a new energy power system, constructs an inverse time characteristic by using the distribution law of fault transient characteristics in the network, and uses the steady-state voltage characteristic to determine whether the fault has disappeared, realizing a backup protection technology that does not require step-by-step setting and has an automatic coordination function. Specifically, an inverse time characteristic is constructed by using the fault traveling wave front exponential coefficient, and whether the fault has disappeared is determined by using the degree of steady-state voltage drop, and finally a backup protection method of "transient sorting and steady-state confirmation" is realized.

[0058] Please refer to Figure 1 , a time-delayed single-ended quantity protection method adapted to a new energy power system of the present invention, comprising the following steps:

[0059] S1. Use a traveling wave voltage sensor to collect the a, b, and c phase voltages and currents of the transmission line, and perform phase-mode transformation on the a, b, and c phase voltages and currents of the transmission line;

[0060] The phase-mode transformation is specifically:

[0061]

[0062] where u m and i m are the voltages and currents under the modulus after phase-mode transformation, where m = 0, 1, 2, and are the phase voltages, where T is the phase-mode transformation matrix, as shown in the following formula:

[0063]

[0064] S2. Calculate the mutation of the first-mode voltage u1 and determine whether the protection is activated;

[0065] The calculation method of the voltage mutation is shown in the following formula.

[0066]

[0067] Wherein, u1(n) and i1(n) represent the nth sampling points of the first-mode voltage and current, N represents the number of sampling points corresponding to one cycle of the power frequency, and Δu1(n) and Δi1(n) are the nth sampling points of the mutations of the first-mode voltage and current.

[0068] Judge whether the protection is activated through the following formula. If the following formula is satisfied, the protection is activated.

[0069]

[0070] Wherein, |Δu1(n)| is the absolute value of the nth sampling point of the voltage mutation, and the setting of Δu 1set can be carried out by avoiding the voltage fluctuation during normal operation.

[0071] S3. After it is determined in step S2 that the protection is activated, calculate the voltage backward traveling wave according to the mutations of the modal voltage and current;

[0072] The specific value of the first-mode fault voltage backward traveling wave is:

[0073] Δu b1 = 0.5(Δu1 - Z c1 Δi1) (5)

[0074] Wherein, Δu1 and Δi1 represent the mutations of the first-mode voltage and current; Z c1 is the first-mode wave impedance of the line, and Δu b1 is the first-mode fault voltage backward traveling wave.

[0075] S4. Use the wavelet modulus maximum algorithm to extract the arrival time of the second traveling wave head within a given time window. After obtaining the arrival time of the second wave head, extract the data window data from the start time to the arrival time of the second wave head. If the arrival of the second wave head is not detected within the entire data window, extract the data of the entire data window. Based on the data window data, extract the first traveling waves of the voltage and current, and then judge the fault direction through the fault direction criterion;

[0076] The specific fault direction criterion is:

[0077]

[0078] Wherein, Δu 1k , Δi 1k are respectively the kth sampling points of the fault components of the first-mode voltage and current, and N wis the number of sampling points within the data window, F T is the fault direction criterion.

[0079] When the fault direction criterion discriminates a positive - direction fault, perform the calculation in step S5.

[0080] S5. Use the Levenberg - Marquardt algorithm to fit the front of the first fault voltage traveling wave to obtain the wavefront exponential coefficient, calculate the backup protection operation time. After the fault starts for ΔT, calculate the obtained delay T delay to calculate whether the low - voltage criterion holds within it.

[0081] The formula to be fitted is specifically:

[0082] u(t) = C1 sin(ω0t + θ)+C2e -pt (7)

[0083] where u(t) is the fitting function of the front of the fault voltage traveling wave, C1 is the amplitude of the sine term of the fitting function, C2 is the amplitude of the decaying exponential term, ω0 is the power - frequency angular frequency, θ is the phase angle of the sine term of the fitting function, and p is the fitting exponential coefficient.

[0084] The backup protection operation delay T delay is:

[0085]

[0086] where p is the coefficient of the exponential term obtained by fitting, ΔT mainly considers the delay of the backup protection for proximal faults and the data window length required for calculating the low - voltage criterion. In the present invention, ΔT is taken as 0.15 s, k T is the coefficient of the mapping from the exponential coefficient to the protection delay, and its setting is carried out according to the delay required to be satisfied by the shortest line in the system, that is, when a fault occurs at the end of the shortest line, the wavefront exponential coefficient is p set , and the set delay is T1, specifically as follows:

[0087]

[0088] Based on the above formula, solve for k T to obtain the delay functions of different protections.

[0089] The low - voltage criterion is specifically:

[0090] u 1RMS <k rel u 1N (10)

[0091] where u 1RMS is the effective value of the 1 - mode voltage, k rel is the reliability coefficient, which is taken as 0.9 in the present invention, u 1Nis the effective value of the 1-mode voltage during normal operation.

[0092] In another embodiment of the present invention, a time-delayed single-ended quantity protection system adapted to a new energy power system is provided. This system can be used to implement the time-delayed single-ended quantity protection method adapted to the new energy power system. Specifically, the time-delayed single-ended quantity protection system adapted to the new energy power system includes a mutation quantity module, a calculation module, a discrimination module, and a protection module.

[0093] Among them, the mutation quantity module calculates the mutation quantities of the 1-mode voltage and current according to the modulus voltages and currents of the three-phase voltages and currents of the transmission line, and starts the protection based on the mutation quantity of the 1-mode voltage;

[0094] The calculation module calculates the 1-mode fault voltage backward traveling wave according to the mutation quantities of the 1-mode voltage and current;

[0095] The discrimination module extracts the arrival time of the second traveling wave head within a given time window according to the 1-mode fault voltage backward traveling wave, then extracts the data window data from the start time to the arrival time of the second wave head, extracts the first traveling waves of the voltage and current based on the obtained data window data, and discriminates the fault direction through the fault direction criterion;

[0096] The protection module, when the fault direction is discriminated as a forward fault, uses the Levenberg-Marquardt algorithm to fit the front of the first fault voltage traveling wave to obtain the front exponential coefficient, and calculates the backup protection action time T according to the front exponential coefficient delay , determines the low voltage criterion after the fault starts ΔT until the backup protection action time T delay to implement the time-delayed single-ended quantity protection.

[0097] To make the objectives, 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 some, but not all, of the embodiments of the present invention. Usually, the components described and shown in the drawings here can 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 present invention, but merely represents the selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0098] To verify the correctness of the protection method proposed by the present invention, a simulation is built in PSCAD as Figure 2The shown simulation model of a wind farm connected to an AC system. The wind turbines are direct-drive turbines, which are connected to the AC system through a back-to-back VSC and a step-up transformer T2. Among them, the machine-side VSC adopts a constant active power and AC voltage control strategy on the wind turbine side, and the grid-side VSC adopts a constant DC voltage and reactive power control strategy. The transmission lines all adopt frequency-variable parameter models. The parameters of the simulation system are shown in Table 1.

[0099] Table 1 Parameters of the simulation model

[0100]

[0101] In Figure 2 the fault f1 occurs on the line segment PM, the fault f2 occurs on the line segment MN, and the fault f3 occurs on the line segment NQ. Taking the protection K P , K M and K N as an example for verification. Figure 2 Among the three-level lines of the shown system, the line L MN has the shortest length. Therefore, the delay function of the protection K M is used as the unified delay function expression of the protections K P , K M and K N .

[0102] It can be seen from the delay calculation function that the delay function T M of the protection K Mdelay is as follows:

[0103]

[0104] Assume that when a three-phase metallic short-circuit fault occurs 50 km away from the bus N on the line L M , the delay of the protection K M is 0.40 s. At this time, the wavefront index coefficient p measured by the protection K 5 is 3.0×10 T = 0.75×10 5 . The delay characteristics of the protections K P , K M and K N are as follows:

[0105]

[0106] When a three-phase metallic short-circuit fault occurs 50 km away from the bus N on the line L NQ , the backup protection delays at the protections K P , K M and K N are: 0.64 s, 0.43 s and 0.25 s respectively. It can be seen that the coordination relationship is automatically satisfied in terms of time.

[0107] When faults of different types and with different transition resistances occur at different fault locations, the protection delays are as shown in the following figure. It can be seen that when faults occur at different fault locations, the protection delays obtained according to the backup protection operation time calculation method proposed by the present invention automatically satisfy the coordination relationship. Protection K P 、K M and K N successively constitute the backup protection for adjacent lines.

[0108] Figure 3 The descriptions of different fault locations in ,

[0108] , and Figure 3 are shown in Table 2.

[0109] Table 2 Description of Fault Locations

[0110]

[0111] In summary, a time-delay single-ended quantity protection method and system for adapting to a new energy power system according to the present invention can calculate the backup protection operation time based on the wavefront index coefficient, simplifies the coordination strategy and setting calculation difficulty of the backup protection, and is not affected by the fault time, fault type, and transition resistance. It is applicable to different new energy and power electronic equipment access scenarios, improves the sensitivity of the backup protection, and the simulation results verify the effectiveness of the method.

[0112] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the above-mentioned division of each functional unit and module is used as an example. In actual applications, the above functions can be allocated to different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the above-described functions. Each functional unit and module in the embodiment can be integrated into a processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit. In addition, the specific names of each functional unit and module are only for the convenience of mutual distinction and do not limit the protection scope of the present application. The specific working processes of the units and modules in the above system can refer to the corresponding processes in the foregoing method embodiments and will not be described herein again.

[0113] In the above embodiments, the descriptions of each embodiment have their own emphases. For the parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0114] Those of ordinary skill in the art will realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods for each specific application to implement the described functions, but such implementation should not be considered to exceed the scope of the present invention.

[0115] In the embodiments provided by the present invention, it should be understood that the disclosed device / terminal and method can be implemented in other ways. For example, the device / terminal embodiments described above are merely illustrative. For example, the division of the modules or units is only a logical function division. In actual implementation, there may be other division methods. For example, 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 displayed or discussed coupling or direct coupling or communication connection between each other can be through some interfaces, and the indirect coupling or communication connection of the device or unit can be in an electrical, mechanical or other form.

[0116] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they can be located in one place, or can be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0117] In addition, the functional units in each embodiment of the present invention can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units.

[0118] When 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, to implement all or part of the processes in the above-described embodiment methods of the present invention, it can also be completed by a computer program instructing relevant hardware. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above-described various method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file, or some intermediate form, etc. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disc, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the content included 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, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0119] This application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, and the combination of 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 the processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing device to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing device generate a device for implementing the specified function in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0120] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device, and the instruction device implements the specified function in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0121] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, so that a series of operation steps are executed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions for implementing the steps of the process Figure 1 in one process or a plurality of processes and / or boxes Figure 1 or steps for implementing the functions specified in one box or a plurality of boxes.

[0122] The above is only to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A protection method for extended time - segment single - end quantity adapted to a new - energy power system, characterized in that, Calculate the sudden changes of the modulus voltage and current of the 1-mode voltage and current based on the three-phase voltage and current of the transmission line, and start the protection according to the sudden change of the 1-mode voltage; calculate the reverse traveling wave of the 1-mode fault voltage according to the sudden changes of the 1-mode voltage and current; according to the reverse traveling wave of the 1-mode fault voltage, extract the arrival time of the second wave head within a given time window, and then extract the data window data from the start time to the arrival time of the second wave head. Extract the first traveling waves of voltage and current based on the obtained data window data, and judge the fault direction through the fault direction criterion; when the fault direction is judged to be a forward fault, use the Levenberg-Marquardt algorithm to fit the front of the first fault voltage traveling wave to obtain the wave front exponential coefficient, and calculate the backup protection action time T according to the wave front exponential coefficient delay , determine the low voltage criterion after the fault starts ΔT and before the backup protection action time T delay to implement the time-delay single-ended quantity protection.

2. The time-delay single-ended quantity protection method adapted to a new energy power system according to claim 1, wherein Judge whether to start the protection based on the sudden change of the modulus 1 voltage as follows: Among them, |Δu1(n)| is the absolute value of the nth sampling point of the voltage mutation amount, and the setting of Δu 1set is set to avoid voltage fluctuations during normal operation.

3. The over-time single-ended quantity protection method adapted to a new energy power system according to claim 2, wherein The sudden changes of the modulus 1 voltage and current are specifically: Among them, u1(n) and i1(n) represent the nth sampling points of the modulus 1 voltage and current, N represents the number of sampling points corresponding to one cycle of the power frequency, and Δu1(n) and Δi1(n) are the nth sampling points of the sudden changes of the modulus 1 voltage and current.

4. The extended-time single-ended quantity protection method adapted to a new energy power system according to claim 1, wherein, 1-mode fault voltage backward traveling wave Δu b1 is as follows: Δu b1 = 0.5(Δu1 - Z c1 Δi1) Among them, Δu1 and Δi1 represent the sudden changes in voltage and current of Mode 1; Z c1 is the wave impedance of Mode 1 of the line.

5. The extended-time single-ended quantity protection method adapted to a new energy power system according to claim 1, wherein The fault direction criterion is specifically: where, Δu 1k , Δi 1k are respectively the k-th sampling points of the voltage and current fault components of one module, N w is the number of sampling points within the data window, and F T is the fault direction criterion.

6. The extended-time single-ended quantity protection method adapted to a new energy power system according to claim 5, characterized in that If no second wavefront arrival is detected within the entire data window, extract the data of the entire data window.

7. The over-time single-ended quantity protection method adapted to a new energy power system according to claim 1, wherein The low voltage criterion is specifically: u 1RMS <k rel u 1N Among them, u 1RMS is the effective value of the 1-mode voltage, k rel is the reliability coefficient, and u 1N is the effective value of the 1-mode voltage during normal operation.

8. The over-time single-ended quantity protection method adapted to the new energy power system according to claim 7, characterized in that Backup protection operation time T delay Specifically: Among them, p is the coefficient of the exponential term obtained by fitting. ΔT mainly considers the time delay of the backup protection for proximal faults and the data window length required for calculating the low-voltage criterion, and k T is the coefficient of the mapping from the exponential coefficient to the protection time delay.

9. The method for protecting a single-ended quantity in an extended time period adapted to a new energy power system according to claim 8, wherein The exponential term coefficient p obtained according to the formula to be fitted is specifically: u(t) = C1sin(ω0t + θ) + C2e -pt Among them, u(t) is the fitting function of the front of the fault voltage traveling wave, C1 is the amplitude of the sine term of the fitting function, C2 is the amplitude of the attenuation exponential term, ω0 is the power frequency angular frequency, and θ is the phase angle of the sine term of the fitting function.

10. A single-ended quantity protection system for an extended time period adapted to a new energy power system, characterized in that, Include: A sudden change amount module that calculates the sudden changes of the modulus 1 voltage and current according to the modulus voltages and currents of the three-phase voltages and currents of the transmission line, and starts the protection based on the sudden change amount of the modulus 1 voltage; A calculation module that calculates the backward traveling wave of the modulus 1 fault voltage according to the sudden changes of the modulus 1 voltage and current; A discrimination module that, according to the backward traveling wave of the modulus 1 fault voltage, extracts the arrival time of the second wavefront within a given time window, then extracts the data window data from the start time to the arrival time of the second wavefront, extracts the first traveling waves of the voltage and current based on the obtained data window data, and discriminates the fault direction through the fault direction criterion; Protection module: when the fault direction is judged as a positive-direction fault, the Levenberg-Marquardt algorithm is used to fit the front of the first fault voltage traveling wave to obtain the front exponential coefficient, and the backup protection operation time T is calculated according to the front exponential coefficient. delay , within the time period from the fault start ΔT to the backup protection operation time T delay , a low-voltage criterion is determined to implement the time-delay single-ended quantity protection.

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