Pilot protection method, device, medium and equipment for sending-out line of wind power plant

Abstract

The invention discloses a wind power plant sending-out line pilot protection method and device, a medium and equipment, and the method comprises the steps: respectively collecting the current data of a sending-out line at a wind power plant side and a power system side, calculating the current increment and the distribution probability of the current increment, and quantifying the similarity of the current characteristic distribution at two sides through a Bhattacharyya coefficient, thereby achieving the pilot protection of the sending-out line. And if the Bhattacharyya coefficient is smaller than a preset first coefficient threshold value, the protection action is controlled to be executed, so that the fault of the sending-out line can be sensitively found. According to the method, the influence of current and voltage characteristic changes caused by fan control strategy adjustment on the sensitivity of the protection device is effectively dealt with, and the accuracy and robustness of fault identification can be improved under complex electrical conditions. Probability distribution analysis is used for replacing traditional constant value judgment, the risk of misoperation or rejection of operation caused by fluctuation of the working condition of the wind power plant is reduced, and the operation safety of a sending-out line is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of wind farms, and in particular to a method, device, medium and equipment for longitudinal protection of transmission lines of a wind farm. Background Art

[0002] As a typical form of renewable energy generation, the transmission lines of wind farms are responsible for transmitting the electricity generated by wind turbines in wind farms to the power grid. However, due to the particularity of wind power generation, the wind turbine control strategy directly affects the operating characteristics of the transmission lines. The control strategies of wind turbines usually include active power control, reactive power control, frequency response, etc. The adjustment of these strategies will have a significant impact on the current and voltage characteristics of the wind farm transmission lines, especially when the power fluctuations are large and the wind speed changes frequently. This also leads to a decrease in the sensitivity of the protection devices of the transmission lines to fault signals, which may cause malfunction or refusal to operate due to the inability to timely identify the fault type or fault location, thereby affecting the safety of the line. Summary of the invention

[0003] Based on this, it is necessary to provide a longitudinal protection method, device, medium and equipment for the wind farm transmission line to solve the problem that the adjustment of the wind turbine control strategy will have a significant impact on the current and voltage characteristics of the wind farm transmission line, thereby causing the protection device of the transmission line to have a decreased sensitivity to fault signals, which may cause false operation or refusal to operate due to the inability to timely identify the fault type or fault location, thereby affecting the safety of the line.

[0004] A method for longitudinal protection of a wind farm transmission line, the method comprising:

[0005] Acquire multiple first sampled current values ​​of the transmission line on the wind farm side and multiple second sampled current values ​​on the power system side within a preset time window;

[0006] Calculating a plurality of corresponding first current increments according to the plurality of first sampled current values, and calculating a plurality of corresponding second current increments according to the plurality of second sampled current values;

[0007] After negating the plurality of first current increments or negating the plurality of second current increments, respectively calculating the distribution probability of the current increments to obtain the first current increment distribution probability on the wind farm side and the second current increment distribution probability on the power system side;

[0008] calculating a Bhattacharyya coefficient between the first current increment distribution probability and the second current increment distribution probability;

[0009] If the Bhattacharyya coefficient is greater than or equal to the preset first coefficient threshold, the process returns to the step of obtaining multiple first sampled current values ​​of the transmission line on the wind farm side and multiple second sampled current values ​​on the power system side within the preset time window and subsequent steps; if the Bhattacharyya coefficient is less than the preset first coefficient threshold, the process controls the execution of the protection action.

[0010] In one embodiment, the calculation of the corresponding multiple first current increments according to the multiple first sampled current values, and the calculation of the corresponding multiple second current increments according to the multiple second sampled current values ​​are expressed as:

[0011]

[0012] In the above formula, Δi M (t) represents the first current increment at time t; i M (t) represents the first sampling current value at time t; T represents the power frequency current cycle; Δi N (t) represents the second current increment at time t; i N (t) represents the second sampling current value at time t.

[0013] In one embodiment, if the plurality of second current increments are inverted, respectively calculating the distribution probability of the current increments to obtain the first current increment distribution probability on the wind farm side and the second current increment distribution probability on the power system side includes:

[0014] Among the opposite values ​​of the plurality of first current increments and the plurality of second current increments, an interval between a maximum value and a minimum value of the current increment is used as a current increment fluctuation range;

[0015] The current increment fluctuation range is evenly divided into a plurality of sub-intervals, and the proportion of the plurality of first current increments falling in each sub-interval is calculated to obtain the first current increment distribution probability, and the proportion of the opposite values ​​of the plurality of second current increments falling in each sub-interval is calculated to obtain the second current increment distribution probability.

[0016] In one embodiment, it is characterized in that the calculation of the Bhattacharyya coefficient between the first current increment distribution probability and the second current increment distribution probability is expressed as:

[0017]

[0018] In the above formula, B C (P,Q) represents the Bhattacharyya coefficient; X represents the total number of sub-intervals; P(x) represents the proportion of the number of the x-th sub-interval in the first current increment distribution probability; Q(x) represents the proportion of the number of the x-th sub-interval in the second current increment distribution probability.

[0019] In one embodiment, the first coefficient threshold is set as follows:

[0020] B Cact =K BC ·K er ·K mar

[0021] In the above formula, B Cact represents the first coefficient threshold; K BC Indicates the reference value; K er Represents the error reliability coefficient; K mar Represents the margin reliability coefficient.

[0022] In one embodiment, the method further comprises:

[0023] The Pearson correlation coefficient between the first current increment distribution probability and the second current increment distribution probability is calculated and expressed as:

[0024]

[0025] In the above formula, r represents the Pearson correlation coefficient, represents the mean value of the number proportion in the first current increment distribution probability, represents the mean value of the quantity proportion in the second current increment distribution probability;

[0026] If the Pearson correlation coefficient is greater than or equal to the preset second coefficient threshold, the process returns to the step of obtaining multiple first sampled current values ​​of the transmission line on the wind farm side and multiple second sampled current values ​​on the power system side within the preset time window and subsequent steps; if the Pearson correlation coefficient is less than the preset second coefficient threshold, the process controls the execution of the protection action.

[0027] A wind farm transmission line longitudinal protection device, the wind farm transmission line longitudinal protection device comprising:

[0028] A current sampling module, used to obtain a plurality of first sampled current values ​​of the transmission line on the wind farm side and a plurality of second sampled current values ​​on the power system side within a preset time window;

[0029] a current increment calculation module, configured to calculate a plurality of corresponding first current increments according to the plurality of first sampled current values, and to calculate a plurality of corresponding second current increments according to the plurality of second sampled current values;

[0030] a distribution probability calculation module, configured to calculate the distribution probability of the current increments respectively after negating the plurality of first current increments or negating the plurality of second current increments, so as to obtain the first current increment distribution probability on the wind farm side and the second current increment distribution probability on the power system side;

[0031] a Bhattacharyya coefficient calculation module, configured to calculate a Bhattacharyya coefficient between the first current increment distribution probability and the second current increment distribution probability;

[0032] The protection judgment module is used to call the current sampling module if the Bhattacharyya coefficient is greater than or equal to the preset first coefficient threshold, and to control the execution of the protection action if the Bhattacharyya coefficient is less than the preset first coefficient threshold.

[0033] A computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the processor executes the steps of the above-mentioned wind farm transmission line longitudinal protection method.

[0034] A terminal device comprises a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the above-mentioned wind farm transmission line longitudinal protection method.

[0035] The present invention provides a longitudinal protection method, device, medium and equipment for a wind farm transmission line. The method collects the current data of the transmission line on the wind farm side and the power system side respectively, calculates the current increment and its distribution probability, and quantifies the similarity of the current characteristic distribution on both sides through the Bhattacharyya coefficient. If the Bhattacharyya coefficient is less than the preset first coefficient threshold, the protection action is controlled to be executed, so that the faults in the transmission line can be sensitively detected. The present invention effectively responds to the influence of the changes in current and voltage characteristics caused by the adjustment of the wind turbine control strategy on the sensitivity of the protection device, and can improve the accuracy and robustness of fault identification under complex electrical conditions. By replacing the traditional fixed value judgment with probability distribution analysis, the risk of false operation or refusal to operate caused by fluctuations in wind farm operating conditions is reduced, and the safe operation of the transmission line is guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] in:

[0038] Figure 1 It is a flow chart of the longitudinal protection method of the wind farm transmission line;

[0039] Figure 2 It is the π-type equivalent circuit of the sending line;

[0040] Figure 3 Schematic diagram for dividing the current increment;

[0041] Figure 4 is the current increment proportion histogram;

[0042] Figure 5 It is a schematic diagram of the current increment on both sides of the line when an out-of-zone fault occurs on the line;

[0043] Figure 6 It is a schematic diagram of the current increment on both sides of the line when a fault occurs in the line area;

[0044] Figure 7 It is a schematic diagram of the phase difference of the current increment on both sides;

[0045] Figure 8 It is a schematic diagram of the calculated value of the Bc coefficient under the maximum phase difference;

[0046] Fig. 9 This is a schematic diagram of the structure of the longitudinal protection device for the outgoing line of the wind farm;

[0047] Fig.10 This is a structural block diagram of the terminal equipment. DETAILED DESCRIPTION

[0048] 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 only 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.

[0049] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0050] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0051] like Figure 1 As shown, Figure 1 The figure is a flow chart of a method for longitudinal protection of a wind farm transmission line in one embodiment. The steps provided by the method for longitudinal protection of a wind farm transmission line in this embodiment include:

[0052] S101, obtaining a plurality of first sampled current values ​​of a transmission line on a wind farm side and a plurality of second sampled current values ​​on a power system side within a preset time window.

[0053] The time window refers to a continuous time range selected during the current sampling and calculation process, which can be a power frequency cycle (20ms) or half a power frequency cycle (10ms). Figure 2 As shown, Figure 2 It is a π-type equivalent circuit of the transmission line. The transmission line is the line that transmits the electric energy generated by the wind turbines in the wind farm to the power grid, which is generally a high-voltage transmission line.

[0054] Specifically, we can install independent current sampling devices on the wind farm side and the power system side. The sampling device performs synchronous high-frequency sampling on the current on both sides of the transmission line, for example, collecting the current value within a time window at a frequency of 10kHz to obtain multiple first sampled current values ​​i on the wind farm side. M (t), and a plurality of second sampling current values ​​i on the power system side N (t).

[0055] S102, calculating a plurality of corresponding first current increments according to a plurality of first sampled current values, and calculating a plurality of corresponding second current increments according to a plurality of second sampled current values.

[0056] Among them, the current increment refers to the difference between the sampled current value at a certain moment and the sampled current value at the previous fixed time interval, which is used to reflect the changing trend of the current and the dynamic change characteristics of the amplitude. The fixed time interval can be set based on actual needs, for example, it can be one power frequency cycle (20ms) or half a power frequency cycle (10ms).

[0057] Optionally, in this embodiment, a plurality of first current increments corresponding to the plurality of first sampled current values ​​are calculated, and a plurality of second current increments corresponding to the plurality of second sampled current values ​​are calculated, which is expressed as:

[0058]

[0059] In the above formula, Δi M (t) represents the first current increment at time t; i M (t) represents the first sampling current value at time t; T represents the power frequency current cycle, 20ms; Δi N (t) represents the second current increment at time t; i N (t) represents the second sampling current value at time t.

[0060] By calculating the current increment in the above manner, the fluctuation characteristics of the current on both sides of the line can be intuitively reflected, providing highly sensitive input data for subsequent further fault judgment.

[0061] S103, after negating the plurality of first current increments or the plurality of second current increments, respectively calculating the distribution probability of the current increments to obtain the first current increment distribution probability on the wind farm side and the second current increment distribution probability on the power system side.

[0062] When the line in the section operates normally, ideally the currents on both sides are sinusoidal waves with equal amplitude and opposite directions. The increment form is also the same, which should also be sinusoidal waves with equal amplitude and opposite directions, satisfying formula (2):

[0063] Δi M =-Δi N (2)

[0064] Negation means to reverse the sign of each element in a numerical sequence. For example, if a current increment is positive, it will be negative after negation; if it is negative, it will be positive after negation. From the principle of the above formula (2), it can be seen that the purpose of negation here is to facilitate the comparison of the current change characteristics on the wind farm side and the power system side, so as to achieve data consistency judgment.

[0065] The distribution probability refers to the probability distribution of the current increment occurring in different increment intervals within a period of time, which can be expressed in the form of a probability histogram or a distribution function. The distribution probability calculated in this step is used for the consistency judgment of the current change on both sides in the subsequent steps.

[0066] Optionally, if multiple second current increments are inverted, calculating the distribution probability of the current increments respectively in S103 to obtain the first current increment distribution probability on the wind farm side and the second current increment distribution probability on the power system side specifically includes the following steps:

[0067] A1. Among the opposite values ​​of the plurality of first current increments and the plurality of second current increments, the interval between the maximum value and the minimum value of the current increment is used as the current increment fluctuation range.

[0068] A2. Evenly divide the current increment fluctuation range into multiple sub-intervals, and calculate the proportion of the number of multiple first current increments falling in each sub-interval to obtain the first current increment distribution probability, and calculate the proportion of the number of opposite values ​​of multiple second current increments falling in each sub-interval to obtain the second current increment distribution probability.

[0069] That is, among the opposite values ​​of the first current increments and the second current increments, if the fluctuation range is [Δi min , Δi max ], recorded as Δi, in order to calculate the distribution histogram and distribution probability, the fluctuation range Δi is evenly divided into k sub-intervals, and the length of each sub-interval is The first subinterval ranges from The second subinterval is By analogy, the last subinterval is Find the current increment Δi respectively M and Δi N The number of current increments falling in each sub-interval is divided by the total number of current increment samples in the time window to obtain its proportion in the corresponding interval, that is, the probability distribution. Furthermore, if the interval number is used as the horizontal axis and the current increment proportion is used as the vertical axis, the current increment probability distribution histogram can be obtained, that is, the corresponding probability distribution functions P(x) and Q(x).

[0070] For example, assuming that the current increment Δi on both sides M , Δi N It is known that the data window length is 4ms, and the interval division is as follows Figure 3 As shown, let k = 10, the maximum value is 0.9986kA corresponding to the current increment on the M side, and the minimum value is 0, then the fluctuation range is [0, 0.9986], and the width of each sub-interval is 0.09986. By dividing the number of current increments in each interval by the total number of samples, we can get its proportion in each interval, as shown in Figure 4 As shown, the discrete distribution functions P(x) and Q(x) can be obtained through the distribution histogram, and their proportions in each interval are shown in Table 1 below:

[0071]

[0072] Table 1

[0073] S104, calculating the Bhattacharyya coefficient between the first current increment distribution probability and the second current increment distribution probability.

[0074] Among them, the Bhattacharyya coefficient is an indicator used to measure the similarity between two probability distributions. By calculating the Bhattacharyya coefficient, it is possible to quickly and quantitatively determine whether the distribution of current increments on the wind farm side and the power system side is consistent, which helps to accurately identify the fault area.

[0075] Optionally, a Bhattacharyya coefficient between the first current increment distribution probability and the second current increment distribution probability is calculated and expressed as:

[0076]

[0077] And calculate the Bhattacharyya distance D between two discrete probability distributions P(x) and Q(x) B Defined as:

[0078] D B (P,Q)=-ln(B C (P,Q)) (4)

[0079] In the above formula, DB(P,Q) represents the Bhattacharyya distance; B C (P,Q) represents the Bhattacharyya coefficient; X represents the total number of sub-intervals; P(x) represents the proportion of the number of the x-th sub-interval in the first current increment distribution probability; Q(x) represents the proportion of the number of the x-th sub-interval in the second current increment distribution probability.

[0080] It can be seen from formula (3) and formula (4) that the Bhattacharyya distance D B is non-negative if and only if B C =1, that is, when the two probability distributions are exactly the same, the Bhattacharyya distance is 0, and in other cases they are greater than zero and can be infinite. In theory, both can reflect the consistency of the probability distributions, but due to the Bhattacharyya distance D B The range of values ​​is too large, and it will be difficult to set the protection setting value when applied in the field of relay protection. Therefore, this embodiment considers using the Bartlett coefficient B C When the discrete distribution functions P(x) and Q(x) are known, the Bhattacharyya coefficient can be calculated for the data in Table 1 according to formula (3). The result is 0.9928, which is very close to B C The maximum value of Figure 3 and Figure 4 In the example, the Bhattacharyya coefficient reflects that the two sets of data are highly consistent.

[0081] S105, determining whether the Bhattacharyya coefficient is greater than or equal to a preset first coefficient threshold. If the Bhattacharyya coefficient is greater than or equal to the preset first coefficient threshold, returning to S101 and subsequent steps, if the Bhattacharyya coefficient is less than the preset first coefficient threshold, executing S106, controlling the execution of the protection action.

[0082] When the line is not faulty, when calculating the Barthel coefficient of the current increment on both sides, the current increment on the opposite side is reversed, and the current increment waveforms on both sides should completely overlap. However, due to the influence of factors such as line distributed capacitance and mutual inductance, there are slight differences in the current increments on both sides, making B C ≈1.

[0083] When an out-of-zone fault occurs in the line, the current flowing in the line is of a through-type nature, the current increment changes in opposite trends, and the amplitudes are approximately equal, such as Figure 5 As shown, Figure 5 As shown in the waveform of the fault current increment outside the wind farm side area after 1s, the following formula should be satisfied:

[0084] Δi M ≈-Δi N (5)

[0085] Similarly, (when calculating the Barthel coefficient, the current increment on one side is reversed) at this time, the current increments on both sides of the line basically coincide. According to the Barthel coefficient calculation method, the calculated value at this time should be B C ≈1.

[0086] like Figure 6 As shown, Figure 6 1s is the fault boundary of the line. When a fault occurs in the line, the currents on both sides of the line flow into the fault point in a positive direction. After the fault, the currents on both sides change in the same direction. However, due to the weak feedback characteristics of the wind farm, the amplitudes of the two are very different. Figure 4 The current increment waveform after 1 second is shown in the figure. By calculating the Barthel coefficient, the Barthel coefficient will quickly move away from the upper limit of 1.

[0087] In summary, when the line is operating normally or an out-of-area fault occurs, B C The calculated value is close to 1, which does not satisfy the following formula (5), and no protection action is required. At this time, the process returns to S101 and subsequent steps. C The calculated value is much less than 1. C If the coefficient satisfies the following formula (5), it can be determined as a fault within the line area, and S106 needs to be executed to control the protection device to perform the protection action. The formula (5) is expressed as:

[0088] B C Cact (5)

[0089] Among them, B Cact Represents the first coefficient threshold.

[0090] ​It can be seen that it is particularly important to set the first coefficient threshold reasonably. In the process of calculating the current increment, it is necessary to know the current sampling data at both ends, which places high demands on the current sensors on both sides. In the actual operating system, the current sensor will have a maximum amplitude error of 10% and a maximum phase angle error of 7° when sampling. In addition, the longitudinal protection has relatively strict requirements on the data transmission time on both sides. The ping-pong timing method is often used for data communication, and its data communication time difference is about 0.5ms, which is equivalent to a current angle deviation of 9° at both ends. Considering that the ground capacitance, current transformer, and data transmission will cause the deviation of the current phase angle, in the most unfavorable case, the total deviation angle is about 23.4°. Figure 7 As shown, the corresponding Bhattacharyya coefficient is calculated as Figure 8 , the first coefficient threshold is set to 0.9182. At the same time, the maximum deviation of the amplitudes generated by the primary and secondary currents of the current transformer is 10%. Considering the maximum deviation, the first coefficient threshold is modified to 0.8328.

[0091] From the above analysis, we can see that the first coefficient threshold B Cact The setting value of cannot be set to the ideal upper limit value 1. Errors will occur in actual operation. Setting it to the ideal situation may cause the protection to malfunction. The above error factors should be considered. We introduce the reliability coefficient and consider a certain safety margin. The setting method of the first coefficient threshold is:

[0092]

[0093] In the above formula, B Cact represents the first coefficient threshold; K BC Indicates the reference value, which can be 1; K er It represents the error reliability coefficient, which is mainly affected by the line capacitance, CT error and signal transmission delay, and can be taken as 0.8; K mar represents the margin reliability coefficient, which can be taken as 0.95; in summary, the first coefficient threshold B can be calculated Cact It is 0.76.

[0094] The above-mentioned wind farm transmission line longitudinal protection method collects the current data of the transmission line on the wind farm side and the power system side respectively, calculates the current increment and its distribution probability, and quantifies the similarity of the current characteristic distribution on both sides through the Bhattacharyya coefficient. If the Bhattacharyya coefficient is less than the preset first coefficient threshold, the protection action is controlled to be executed, so that the fault of the transmission line can be sensitively discovered. The advantages of the present invention are:

[0095] (1) It is not affected by factors such as wind farm control strategies, and the current increment feature is significantly different. This feature can be used to construct a protection system that can adapt to wind farms with variable control strategies.

[0096] (2) The current increment consistency judgment has low requirements for system communication, does not require a high sampling frequency and a long time window, and can quickly and accurately identify a fault within about 5ms after the fault occurs at a 4kHz sampling frequency and a 10ms time window. It has high flexibility and meets engineering application conditions. It has been verified that the protection has good characteristics in terms of resistance to transition resistance, data transmission delay, and white noise interference.

[0097] (3) The unique advantage of the Bhattacharyya coefficient is that it uses probability to measure consistency. Unlike common algorithms, it can still calculate the protection criteria even when the sampling data is lost, thus avoiding problems such as false protection operation or refusal to operate caused by data loss during current transformer or line transmission, and has high reliability.

[0098] Furthermore, in a specific embodiment, the following steps may be performed: calculating the Pearson correlation coefficient between the first current increment distribution probability and the second current increment distribution probability, expressed as:

[0099]

[0100] In the above formula, r represents the Pearson correlation coefficient, represents the mean value of the number proportion in the first current increment distribution probability, represents the mean value of the quantity proportion in the second current increment distribution probability;

[0101] If the Pearson correlation coefficient is greater than or equal to the preset second coefficient threshold, the process returns to execute S101 and subsequent steps. If the Pearson correlation coefficient is less than the preset second coefficient threshold, the process executes S106 to control the execution of the protection action.

[0102] It can be understood that this specific embodiment is linked with the Bhattacharyya coefficient to provide a dual basis for judgment, which can further improve the reliability of the protection action.

[0103] In one embodiment, Fig. 9 As shown, a wind farm transmission line longitudinal protection device is proposed, the device comprising:

[0104] The current sampling module 901 is used to obtain a plurality of first sampled current values ​​of the transmission line on the wind farm side and a plurality of second sampled current values ​​on the power system side within a preset time window;

[0105] A current increment calculation module 902, configured to calculate a plurality of corresponding first current increments according to a plurality of first sampled current values, and to calculate a plurality of corresponding second current increments according to a plurality of second sampled current values;

[0106] A distribution probability calculation module 903 is used to calculate the distribution probability of the current increments after negating the multiple first current increments or the multiple second current increments, so as to obtain the first current increment distribution probability on the wind farm side and the second current increment distribution probability on the power system side;

[0107] A Bhattacharyya coefficient calculation module 904, configured to calculate a Bhattacharyya coefficient between a first current increment distribution probability and a second current increment distribution probability;

[0108] The protection judgment module 905 is used to call the current sampling module 901 if the Bhattacharyya coefficient is greater than or equal to the preset first coefficient threshold, and to control the execution of the protection action if the Bhattacharyya coefficient is less than the preset first coefficient threshold.

[0109] Fig.10 FIG. 2 shows an internal structure diagram of a terminal device in an embodiment. Fig.10 As shown, the terminal device includes a processor, a memory and a network interface connected via a system bus. The memory includes a non-volatile storage medium and an internal memory. The non-volatile storage medium of the terminal device stores an operating system and may also store a computer program. When the computer program is executed by the processor, the processor may implement a longitudinal protection method for a wind farm transmission line. The internal memory may also store a computer program. When the computer program is executed by the processor, the processor may implement a longitudinal protection method for a wind farm transmission line. Those skilled in the art will understand that Fig.10 The structure shown in the figure is only a block diagram of a partial structure related to the scheme of the present application, and does not constitute a limitation on the terminal device to which the scheme of the present application is applied. The specific terminal device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0110] A computer-readable storage medium stores a computer program, which implements the following steps when executed by a processor: obtaining a plurality of first sampled current values ​​of a transmission line on a wind farm side and a plurality of second sampled current values ​​on a power system side within a preset time window; calculating a plurality of corresponding first current increments according to the plurality of first sampled current values, and calculating a plurality of corresponding second current increments according to the plurality of second sampled current values; negating the plurality of first current increments, or negating the plurality of second current increments, respectively calculating the distribution probability of the current increments to obtain the first current increment distribution probability on the wind farm side and the second current increment distribution probability on the power system side; calculating the Bhattacharyya coefficient between the first current increment distribution probability and the second current increment distribution probability; if the Bhattacharyya coefficient is greater than or equal to a preset first coefficient threshold, returning to the step of obtaining a plurality of first sampled current values ​​of a transmission line on a wind farm side and a plurality of second sampled current values ​​on a power system side within a preset time window and subsequent steps, and if the Bhattacharyya coefficient is less than the preset first coefficient threshold, controlling the execution of a protection action.

[0111] A terminal device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the following steps when executing the computer program: obtaining a plurality of first sampled current values ​​of a transmission line on a wind farm side and a plurality of second sampled current values ​​on a power system side within a preset time window; calculating a plurality of corresponding first current increments according to the plurality of first sampled current values, and calculating a plurality of corresponding second current increments according to the plurality of second sampled current values; after negating the plurality of first current increments or negating the plurality of second current increments, respectively calculating the distribution probability of the current increments to obtain the first current increment distribution probability on the wind farm side and the second current increment distribution probability on the power system side; calculating the Bhattacharyya coefficient between the first current increment distribution probability and the second current increment distribution probability; if the Bhattacharyya coefficient is greater than or equal to a preset first coefficient threshold, returning to execute the step of obtaining a plurality of first sampled current values ​​of a transmission line on a wind farm side and a plurality of second sampled current values ​​on the power system side within the preset time window and subsequent steps, and if the Bhattacharyya coefficient is less than the preset first coefficient threshold, controlling the execution of a protection action.

[0112] It should be noted that the above-mentioned wind farm transmission line longitudinal protection method, device, equipment and computer-readable storage medium belong to a general inventive concept, and the contents of the wind farm transmission line longitudinal protection method, device, equipment and computer-readable storage medium embodiments are applicable to each other.

[0113] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0114] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0115] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for longitudinal protection of wind farm transmission lines, characterized in that: The method comprises: Acquire multiple first sampled current values ​​of the transmission line on the wind farm side and multiple second sampled current values ​​on the power system side within a preset time window; Calculating a plurality of corresponding first current increments according to the plurality of first sampled current values, and calculating a plurality of corresponding second current increments according to the plurality of second sampled current values; After negating the plurality of first current increments or negating the plurality of second current increments, respectively calculating the distribution probability of the current increments to obtain the first current increment distribution probability on the wind farm side and the second current increment distribution probability on the power system side; calculating a Bhattacharyya coefficient between the first current increment distribution probability and the second current increment distribution probability; If the Bhattacharyya coefficient is greater than or equal to the preset first coefficient threshold, the process returns to the step of obtaining multiple first sampled current values ​​of the transmission line on the wind farm side and multiple second sampled current values ​​on the power system side within the preset time window and subsequent steps; if the Bhattacharyya coefficient is less than the preset first coefficient threshold, the process controls the execution of the protection action.

2. The method according to claim 1, characterized in that The corresponding multiple first current increments are calculated according to the multiple first sampled current values, and the corresponding multiple second current increments are calculated according to the multiple second sampled current values, which is expressed as: In the above formula, Δi M (t) represents the first current increment at time t; i M (t) represents the first sampling current value at time t; T represents the power frequency current cycle; Δi N (t) represents the second current increment at time t; i N (t) represents the second sampling current value at time t.

3. The method according to claim 1, characterized in that If the multiple second current increments are inverted, the distribution probabilities of the current increments are calculated respectively to obtain the first current increment distribution probability on the wind farm side and the second current increment distribution probability on the power system side, including: Among the opposite values ​​of the plurality of first current increments and the plurality of second current increments, an interval between a maximum value and a minimum value of the current increment is used as a current increment fluctuation range; The current increment fluctuation range is evenly divided into a plurality of sub-intervals, and the proportion of the plurality of first current increments falling in each sub-interval is calculated to obtain the first current increment distribution probability, and the proportion of the opposite values ​​of the plurality of second current increments falling in each sub-interval is calculated to obtain the second current increment distribution probability.

4. The method according to claim 3, characterized in that The calculation of the Bhattacharyya coefficient between the first current increment distribution probability and the second current increment distribution probability is expressed as: In the above formula, B C (P,Q) represents the Bhattacharyya coefficient; X represents the total number of sub-intervals; P(x) represents the proportion of the number of the x-th sub-interval in the first current increment distribution probability; Q(x) represents the proportion of the number of the x-th sub-interval in the second current increment distribution probability.

5. The method according to claim 4, characterized in that The first coefficient threshold is set as follows: In the above formula, B Cact represents the first coefficient threshold; Indicates the reference value; K er Represents the error reliability coefficient; K mar Represents the margin reliability coefficient.

6. The method according to claim 4, characterized in that The method further comprises: The Pearson correlation coefficient between the first current increment distribution probability and the second current increment distribution probability is calculated and expressed as: In the above formula, r represents the Pearson correlation coefficient, represents the mean value of the quantity proportion in the first current increment distribution probability, represents the mean value of the quantity proportion in the second current increment distribution probability; If the Pearson correlation coefficient is greater than or equal to the preset second coefficient threshold, the process returns to the step of obtaining multiple first sampled current values ​​of the transmission line on the wind farm side and multiple second sampled current values ​​on the power system side within the preset time window and subsequent steps; if the Pearson correlation coefficient is less than the preset second coefficient threshold, the process controls the execution of the protection action.

7. A wind farm transmission line longitudinal protection device, characterized in that: The wind farm transmission line longitudinal protection device comprises: A current sampling module, used to obtain a plurality of first sampled current values ​​of the transmission line on the wind farm side and a plurality of second sampled current values ​​on the power system side within a preset time window; a current increment calculation module, configured to calculate a plurality of corresponding first current increments according to the plurality of first sampled current values, and to calculate a plurality of corresponding second current increments according to the plurality of second sampled current values; a distribution probability calculation module, configured to calculate the distribution probability of the current increments respectively after negating the plurality of first current increments or negating the plurality of second current increments, so as to obtain the first current increment distribution probability on the wind farm side and the second current increment distribution probability on the power system side; a Bhattacharyya coefficient calculation module, configured to calculate a Bhattacharyya coefficient between the first current increment distribution probability and the second current increment distribution probability; The protection judgment module is used to call the current sampling module if the Bhattacharyya coefficient is greater than or equal to the preset first coefficient threshold, and to control the execution of the protection action if the Bhattacharyya coefficient is less than the preset first coefficient threshold.

8. A computer-readable storage medium, characterized in that: A computer program is stored, and when the computer program is executed by a processor, the processor is caused to execute the steps of the method according to any one of claims 1 to 6.

9. A terminal device, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method according to any one of claims 1 to 6.

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