A new energy line protection method based on voltage reverse wave polarity difference

Abstract

The application discloses a new energy line protection method based on voltage reverse wave polarity difference, which firstly performs phase-mode transformation on collected three-phase voltage signals and current signals, extracts line-mode fault voltage and fault current, and then calculates voltage traveling waves propagating in the reverse direction at the protection installation position. On this basis, the wave head signals of voltage reverse waves on both sides of the line are calibrated by using wavelet transformation mode maximum, the polarity characteristics of the first voltage reverse wave with reverse polarity on both ends of the line are extracted, and the internal and external faults are distinguished according to the polarity relationship of the voltage reverse waves on both ends of the line. The scheme considers that when the near-end fault occurs, the first several traveling waves are difficult to capture or the wave head aliasing problem exists due to the influence of the sampling rate, and then the new energy line protection scheme based on the polarity difference of voltage reverse waves on both ends of the line is proposed. The scheme has simple principle and certain fault tolerance.

Description

Technical Field

[0001] This solution relates to a protection scheme for new energy lines based on the polarity difference of voltage reverse traveling waves, belonging to the field of relay protection for new energy AC lines. Background Technology

[0002] To address the increasingly severe energy crisis, my country's energy structure is shifting from a traditional reliance on fossil fuels to a focus on clean and renewable energy. New energy sources require grid connection via power electronic devices, and as the proportion of new energy sources, such as wind and solar power, gradually increases in the power grid, the current power system exhibits a "high proportion of power electronic devices" characteristic.

[0003] The fault characteristics of renewable energy networks differ significantly from those of traditional power grids under control strategies, specifically exhibiting features such as controlled phase angle amplitude and abundant high-frequency components. Traditional protection schemes, primarily based on power frequency quantities, suffer from decreased sensitivity and even protection failure, posing a significant threat to the safe and stable operation of renewable energy networks with a high proportion of renewable energy. Therefore, it is urgent to research protection schemes suitable for renewable energy lines.

[0004] To address the aforementioned issues, current solutions primarily focus on constructing novel protection schemes based on protection principles. Traveling wave protection utilizes the traveling wave transmitted from the fault point to both ends of the line to construct protection criteria. It offers advantages such as fast response speed and insensitivity to renewable energy network control strategies, effectively meeting the requirements for relay protection speed and reliability in scenarios with a high proportion of renewable energy. Many protection schemes based on traveling waves already exist. Existing technologies, such as CN112886547B, calculate the forward and reverse traveling waves using three-phase voltage and current signals collected from measurement points. This data is then synchronized to the protection device at the opposite end, and the Hausdorff distance between the forward and reverse traveling waves on the local side is calculated using a dataset segmentation method, thereby achieving fault identification. This technical solution requires strict synchronization of data at both ends, resulting in poor response speed. Publication No. CN108365599B first calculates the slope of the first traveling wave of the line-mode current measured by the protection device, and uses the relationship between this slope and the setting value as the starting criterion. Based on this, it calculates the correlation coefficient between the fault sampling data and the data when a fault occurs at the line midpoint, thus achieving fault identification. This technical solution is a single-ended protection, but the protection setting value needs to be obtained through simulation, resulting in low reliability. Publication No. CN102288869A uses the initial reverse polarity directional traveling wave and the arrival time of the first traveling wave to achieve fault location. This scheme utilizes the high singularity of the reverse polarity wavefront, improving the accuracy of single-ended fault location. Publication No. CN105699855A uses the arrival times of each traveling wavefront recorded at both ends of the line to derive a fault location formula unaffected by wave velocity, thereby improving the location accuracy. Publication number CN115184722A analyzes the mathematical logic relationship between the arrival times of the first three traveling waves detected at the protection installation point when a fault occurs at different locations. This allows for the differentiation between faults inside and outside the protection zone based on the comparison of predicted and actual values. Furthermore, existing technologies, such as publication number CN115015687A, transform the transient wavefront abrupt change in the time domain into a distribution of traveling wave energy abrupt changes along the propagation path. By calculating the forward and reverse current traveling waves, a forward and reverse traveling wave abrupt change function is constructed. The product of these two functions is integrated within the observation window to form a ranging function. Fault location is achieved by combining the polarity of the abrupt change point within the ranging function with its distance to the measurement end. CN115097253A decouples the acquired fault voltage traveling wave to obtain a line-mode traveling wave. It calculates the voltage and current at regular intervals to obtain the voltage and current distribution at all points along the entire line and calculates the forward and reverse current traveling waves that combine the time and distance dimensions. Then, it constructs analytical expressions for the current traveling wave mutation detection function in both directions and multiplies them to construct an integral function. The fault location is then determined by the distance from the extreme point of the integral function to the measurement end.CN114113890A analyzes the linear and zero-mode components of the fault traveling wave, obtains the time difference by calibrating the arrival times of the zero-mode and linear mode components using wavelet transform, and determines the zero-mode traveling wave velocity by fitting the relationship curve between the zero-mode wave velocity and the fault distance using deep learning. The fault distance is then obtained based on the modulus transmission time difference ranging principle. However, the zero-mode component only exists in ground faults. CN113253052A considers the weak and difficult-to-detect traveling wave energy in high-impedance ground faults. It effectively decomposes the fault current traveling wave through variational mode decomposition; it uses a multi-resolution morphological gradient transform algorithm to successively transform the weak signal, accumulating and amplifying the abrupt change characteristics of the traveling wave signal to accurately calibrate the arrival time of the initial traveling wave front. Simultaneously, it performs Hilbert transform on the high-frequency components of the fault current signal to determine the frequency of the high-frequency components of the fault current signal that first arrive at the measurement points at both ends of the rectifier and inverter sides, thereby determining the fault current traveling wave velocity and ultimately completing the fault location detection. However, the above technical solutions involve large computational loads and complex principles, making them difficult to apply in engineering practice.

[0005] Polarity comparison-based traveling wave protection schemes, as a type of traveling wave direction protection, determine the fault direction by the polarity of the initial traveling wave. Existing technologies, such as CN104466922A, calculate the integral value of the fault component line-mode current detected by each outgoing line of the busbar protection unit by collecting the current values ​​of each outgoing line connected to the busbar, and construct a busbar fault identification scheme using the polarity difference of the integral value. CN104655981A extracts fault voltage and current signals, performs cross-sequential differential transformation on the extracted traveling wave signals, and substitutes the transformed voltage and current values ​​into a discriminant to distinguish between forward and reverse faults. CN104198881B utilizes the nonlinear function approximation fitting capability of artificial neural networks, sequentially selecting the initial current traveling wave at the measurement end and the time difference and relative polarity of the subsequent three or more traveling wave fronts relative to the initial traveling wave front as sample attributes of the ANN, training and establishing an ANN fault location model to achieve single-end traveling wave location. The paper, published under license number CN114937978A, first analyzes the reflection and refraction process of traveling waves after a fault occurs at different locations, and then verifies the polarity characteristics of the first four voltage traveling waves. Fault identification within and outside the fault zone is achieved based on the polarity differences of the first four voltage traveling waves. However, this method relies on the accurate acquisition of the first four traveling wavefronts, resulting in low reliability.

[0006] The above scheme relies on the accurate capture of the first traveling wave of the fault. However, when a fault occurs near the end of the area, the fault traveling wave is reflected multiple times between the fault point and the bus. At this time, the time interval between each traveling wave surge is very short. When the sampling rate of the measuring device is insufficient, the sampling point cannot accurately fall at the moment of sudden change of the transient signal. Using the wavelet transform modulus maxima for wavefront calibration may result in the incorrect capture of the wavefront signal. At this time, the above technical scheme fails to make the judgment criteria invalid, making it difficult to distinguish between faults inside and outside the area, and the reliability is not high. Summary of the Invention

[0007] The purpose of this invention is to improve upon the traditional polarity comparison-based protection method and propose a new energy line protection method based on the polarity difference of voltage reverse traveling waves. In the event of a near-end fault, the first few traveling waves reaching the protection installation point are reflected waves from the fault point, sharing the same polarity. Considering the wavefront aliasing phenomenon caused by insufficient sampling rate, the physical meaning of these traveling wave front signals is unclear, and the captured reverse traveling waves undergo multiple reflections, resulting in insignificant abrupt changes in the wavefront signal. Compared to the initial wavefront, the first reverse polarity wavefront exhibits high singularity and significant abrupt changes, providing high identification during detection. Based on this, this invention proposes a new energy line protection scheme constructed using the polarity relationship of the first reverse polarity voltage reverse traveling waves at both ends of the line. This scheme is simple in principle and possesses a certain degree of fault tolerance.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A protection method for new energy lines based on the polarity difference of voltage reverse traveling waves specifically includes the following steps:

[0010] (1) When a fault occurs on the transmission line, the measuring devices at both ends collect the three-phase voltage signal and the three-phase current signal after the fault; the line modulus components of the fault voltage and fault current are extracted by Clarke transform.

[0011] (2) Calculate the voltage traveling wave propagating in the opposite direction at the protection installation point using the line mode fault voltage and line mode fault current;

[0012] (3) The modulus maxima of the wavelet transform are used to calibrate each wavefront of the voltage reverse traveling wave. The modulus maxima corresponding to the first wavefront with the opposite polarity to the initial traveling wave calibrated at both ends of the line are W, respectively. M (n i ) and W N (n j ), n i With n j These represent the i-th and j-th sampling points, respectively.

[0013] (4) Based on the difference in polarity of the reverse traveling wave of the first reverse polarity at both ends of the line, the faults inside and outside the line can be distinguished.

[0014] Preferably, since the three-phase voltage and three-phase current signals acquired in step 1 exhibit coupling, it is necessary to first transform the off-diagonal elements of the parameter matrix to zero through phase-mode transformation, thereby achieving three-phase decoupling. The Clarke transform modulus calculation is simple, and the α-mode component under the Clarke transform can cover all single-phase grounding faults; therefore, this scheme adopts the Clarke transform, specifically as follows:

[0015]

[0016]

[0017] In the above formula, Ua, Ub, and Uc are the collected three-phase voltages, and Ia, Ib, and Ic are the collected three-phase currents; U α U β U0 represents the line-mode voltage and the zero-mode voltage, respectively, and I α ,I β I0 represents the line-mode current and the zero-mode current, respectively. This scheme selects the α-mode as the line-mode component.

[0018] Preferably, in step (2), the line-mode fault current and line-mode fault voltage at any point on the line can be obtained according to the line's wave equation:

[0019]

[0020] The positive direction of traveling wave propagation is defined as the direction from the busbar to the line, where u + u - These represent the forward traveling wave propagating in the specified forward and reverse directions, and the reverse traveling wave propagating in the opposite direction to the specified forward direction, respectively. Δu and Δi represent the fault voltage and fault current, respectively, x represents the line length, v is the traveling wave velocity, and z... c This represents the surge impedance of the line. The fault current and voltage at any point on the line are both superpositions of traveling and reverse waves. Therefore, the traveling and reverse voltage waves can be extracted using the line-mode components of the fault voltage and current.

[0021]

[0022] Since the reflected wave from the back busbar is equivalent to a traveling wave to the protection device, this scheme uses the reverse traveling wave as the research object to eliminate the influence of the back busbar reflected wave on the subsequent protection scheme.

[0023] Preferably, in step (3), the wavefront signal of the traveling wave is calibrated using the modulus maxima of the wavelet transform. The definition of the modulus maxima of the wavelet transform is:

[0024] For any given positive integer ε, when |nn i When |<ε is satisfied, for any n ≠ n iThere will always be If it is established, then For the maximum value of the wavelet transform modulus, n i Let j be the sampling point corresponding to the modulus maxima, and j be the wavelet transform decomposition level. This invention uses the db3 wavelet with a decomposition level of 6. The modulus maxima of the wavelet transform correspond one-to-one with the signal's abrupt change points. Therefore, the modulus maxima can accurately pinpoint the wavefront of the fault traveling wave, while the direction of the abrupt change in the modulus maxima represents the polarity of the traveling wave.

[0025] Preferably, step (4) uses the difference in polarity of the first reverse-polarity voltage traveling waves at both ends of the line to distinguish between internal and external faults. Traditional polarity comparison protection schemes rely on the polarity relationship of the initial traveling waves, but they have reliability issues. Specifically, when a near-end fault occurs within the line, the fault traveling wave is rapidly reflected between the fault point and the bus. Since the reflected wave at the fault point and the initial traveling wave have the same polarity, when the sampling rate is insufficient, there may be wavefront aliasing between the initial traveling wave and the reflected wave at the fault point. In this case, the initial traveling wave cannot be accurately captured, and the traditional protection criterion fails. To solve the above problem, it is necessary to introduce the subsequent wavefront signal detected by the measuring device. When there is a near-end fault, the first few traveling waves that reach the protection installation point are all reflected waves from the fault point with the same polarity. Considering the wavefront aliasing caused by insufficient sampling rate, the physical meaning of these traveling wave wavefront signals is not clear, and the captured reverse traveling wave undergoes multiple reflections, resulting in no significant change in the wavefront signal. Compared to the initial wavefront polarity, the first reverse polarity wavefront waveform exhibits significant differences and strong singularity, making it easy to identify and effectively detect. Analysis reveals that the first reflected wave from the opposite busbar has the opposite polarity to the initial traveling wave, and this wavefront signal undergoes only one reflection process, resulting in a significant abrupt change. Therefore, this proposal suggests a polarity comparison-based protection scheme based on the first reverse polarity reverse traveling wave.

[0026] Beneficial effects

[0027] The present invention adopts the above technical solution and has the following technical advantages: 1. This solution considers the failure of the traditional polarity comparison scheme caused by wavefront aliasing, and has a certain fault tolerance capability. 2. The new solution uses polarity characteristics to identify faults, without the need for complex threshold tuning and dual-end signal synchronization, has a wide range of applications, and is easy to implement in engineering. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 Schematic diagram of grid connection for new energy power plants

[0030] Figure 2 Peterson equivalent circuit diagram of the traveling wave fault component of the voltage at bus M;

[0031] Figure 3 The Peterson equivalent circuit diagram for the traveling wave fault component of the voltage at the fault point;

[0032] Figure 4 Peterson equivalent circuit diagram of the traveling wave fault component of the voltage at bus N;

[0033] Figure 5 This is a diagram showing the reflection and refraction process of the voltage traveling wave mode component during a near-end fault within the region.

[0034] Figure 6 This diagram illustrates the reflection and refraction process of the voltage traveling wave mode component during a near-end fault outside the fault zone.

[0035] Figure 7 The present invention provides a flowchart of a new energy line protection scheme based on the polarity difference of voltage reverse traveling waves.

[0036] Figure 8 The reverse traveling wave of the voltage on the M side during a fault within the zone and its wavelet transform modulus maxima.

[0037] Figure 9 The inverse traveling wave of the N-side voltage and its wavelet transform modulus maxima during a fault within the zone;

[0038] Figure 10 The reverse traveling wave of the voltage on the M side and its wavelet transform modulus maxima during an external fault.

[0039] Figure 11 This represents the reverse traveling wave of the N-side voltage and its wavelet transform modulus maxima during an external fault. Detailed Implementation

[0040] The specific structure and method embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The detailed exemplary embodiments disclosed below are merely for the purpose of describing exemplary embodiments; however, the present invention is not limited to the specific exemplary embodiments disclosed, but can cover all modifications, equivalents, and substitutions falling within the scope of this disclosure.

[0041] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] A protection method for new energy lines based on the polarity difference of voltage reverse traveling waves includes the following steps:

[0043] Step 1: When a fault occurs on the transmission line, the measuring devices at both ends collect the three-phase voltage signal and the three-phase current signal after the fault, respectively; and use Clark transform to extract the line modulus components of the fault voltage and fault current.

[0044]

[0045]

[0046] Step 2: Calculate the reverse voltage wave propagating in the opposite direction at the protection installation point using the line-mode voltage and line-mode current.

[0047] The positive direction of traveling wave propagation is defined as the direction from the busbar to the line, where u + u - These represent the forward traveling wave propagating in the specified forward and reverse directions, and the reverse traveling wave propagating in the opposite direction to the specified forward direction, respectively. Δu and Δi represent the fault voltage and fault current, respectively, x represents the line length, v is the traveling wave velocity, and z... c This represents the surge impedance of the line. The fault current and voltage at any point on the line are both superpositions of traveling and reverse waves. Therefore, the traveling and reverse voltage waves can be extracted using the line-mode components of the fault voltage and current.

[0048]

[0049] Step 3: Use wavelet transform modulus maxima to calibrate each wavefront of the voltage reverse traveling wave, where the modulus maxima corresponding to the first reverse polarity wavefront calibrated at both ends of the line are W... M (n i ) and W N (n j ).

[0050] Figure 1 This is a schematic diagram of a new energy power station connected to the grid. Multiple power generation units within the power station transmit electricity to the main transformer via a collecting bus, and then connect to the external system via high-voltage line MN. The research object of this invention is line MN. After a ground fault occurs on the transmission line, according to the superposition principle, a negative voltage source is superimposed at the fault point. This voltage source transmits energy to both ends in the form of a wave. The traveling wave will be reflected when it encounters a discontinuity in wave impedance (at the bus and the fault point).

[0051] according to Figure 2 From the Peterson equivalent circuit of the traveling wave at bus M, the expressions for the refractive index and reflection index at the bus and their ranges are as follows:

[0052]

[0053]

[0054] In the formula: α M β M Let C represent the refraction coefficient and reflection coefficient of the voltage traveling wave at bus M, respectively. M Let Z be the stray capacitance of bus M; assume that bus M has n outgoing lines (n≥2), and the surge impedance of each bus is Z. C1 Z T Z represents the equivalent wave impedance of the main transformer. CM This represents the equivalent impedance of the busbar M to ground capacitance.

[0055] pass Figure 3 From the Peterson equivalent circuit of the line-mode traveling wave at the fault point, it can be seen that, during a ground fault, the expressions for the refractive index and reflection index at the fault point, and their ranges, are as follows:

[0056]

[0057]

[0058] In the formula: Z f =Z C1 / / R f =(Z C1 ·R f ) / (Z C1 +R f );α f β f R represents the refraction coefficient and reflection coefficient of the voltage traveling wave at the fault point, respectively; f The transition resistance indicates the fault point.

[0059] according to Figure 4 From the Peterson equivalent circuit of the traveling wave at bus N shown, the expressions for the refractive index and reflection index at the bus and their ranges are as follows:

[0060]

[0061]

[0062] In the formula: n is the number of outgoing lines on bus N (n≥2); α N β N Z represents the refraction coefficient and reflection coefficient of the voltage traveling wave at bus N, respectively; C1 Indicates the line-mode impedance of the line; C N The stray capacitance at bus M; Z CN This represents the equivalent impedance of the bus N-to-ground capacitance.

[0063] As can be seen from the above analysis, the reflection coefficient of the fault traveling wave at the busbar and the fault point is less than 0 and the refraction coefficient is greater than 0.

[0064] Figure 5 This diagram illustrates the reflection and refraction process of the traveling wave during a fault in section (0, 1 / 3) of the fault zone. If wavefront aliasing is disregarded, the first reverse traveling wave detected by the measuring device at end M, with the opposite polarity to the initial traveling wave, is a first reflection from the opposite bus N. The first reverse traveling wave detected by the measuring device at end N, with the opposite polarity to the initial traveling wave, is a first reflection from the opposite bus M; they share the same polarity. When a near-end fault occurs, the fault traveling wave rapidly reflects and refractions between the fault point and the bus. Since the reflected wave at the fault point and the initial traveling wave have the same polarity, wavefront aliasing may occur between the initial traveling wave and the reflected wave at the fault point when the sampling rate is insufficient. In this case, the initial traveling wave cannot be accurately captured. During a near-end fault, the first few reverse traveling waves detected by the measuring device are of the same polarity, but after multiple reflections, the wavefront signal abruptly changes in the captured reverse traveling wave. Considering the potential wavefront aliasing problem, its physical meaning is also unclear. Therefore, the protection scheme based on the difference in the polarity of the first wavefront is not highly reliable. Compared with the initial wavefront polarity, the first reverse polarity wavefront has high singularity and obvious abrupt change, and has high recognition during the detection process. Therefore, this scheme proposes to use the first reverse traveling voltage wave with the opposite polarity to the initial traveling wave detected by the M-end measuring device as the research object.

[0065] Figure 6 This is a diagram showing the reflection and refraction process of the traveling wave during a fault in the (0, 1 / 3) section outside the fault zone. At this time, the first reverse traveling wave detected by the measuring device at end M, which has the opposite polarity to the initial traveling wave, is a first reflected wave from bus O. The first reverse traveling wave detected by the measuring device at end N, which has the opposite polarity to the initial traveling wave, is a first reflected wave from the opposite bus M. They have opposite polarities.

[0066] Step 4: Differentiate between internal and external faults based on the polarity difference of the first reverse-polarity voltage traveling wave measured at both ends of the line. The polarity corresponding to the first reverse-polarity voltage traveling wave measured at both ends is expressed as M1 = sgn(W M (n i M2 = sgn(W) N (n j If M1M2 = 1, then it is an internal fault; if M1M2 = -1, then it is an external fault.

[0067] Example 1:

[0068] exist Figure 1 In the new energy network topology diagram shown, the line MN is 200km long. A single-phase ground fault occurs 40km from the M end inside the line, and the sampling frequency is 200kHz. Figure 8 , 9 The simulation diagram of the voltage inverse traveling wave and its wavelet transform modulus maxima are given. From the simulation results, we know that: M1 = sgn(W M(n4))=-1,M2=sgn(W N (n2))=-1, at this time M1M2=1, which is determined to be a fault within the area.

[0069] Example 2:

[0070] exist Figure 1 In the new energy network topology diagram shown, line NO is 100km long, and a single-phase ground fault occurs 30km from end M inside the line. The sampling frequency is 200kHz. Figure 10 , 11 Simulation diagrams of the reverse traveling wave voltages at terminals M and N, and their wavelet transform modulus maxima, are given. From the simulation results, we know that: M1 = sgn(W M (n3))=-1,M2=sgn(W N (n3))=1, at this time M1M2=-1, which is determined to be an external fault.

[0071] This invention provides a protection scheme for new energy lines based on the polarity difference of voltage reverse traveling waves. The scheme first performs phase-mode transformation on the acquired three-phase voltage and current signals to extract the line-mode fault voltage and fault current, and then calculates the voltage traveling wave propagating in the opposite direction at the protection installation point. Based on this, the wavefront signals of the voltage reverse traveling waves on both sides of the line are calibrated using wavelet transform modulus maxima, and the polarity characteristics of the first reverse polarity voltage reverse traveling wave at both ends of the line are extracted. This invention considers the wavefront aliasing phenomenon that occurs when the sampling rate is insufficient. Analysis shows that compared with the initial wavefront, the first reverse polarity wavefront has high singularity and obvious abrupt change, exhibiting high recognition during detection. Based on this, this invention proposes a protection scheme for new energy lines constructed using the polarity relationship of the first reverse polarity voltage reverse traveling waves at both ends of the line. This scheme is simple in principle, requires no complex threshold tuning or dual-end signal synchronization, has a wide range of applications, and is easy to implement in engineering.

[0072] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection claimed by this invention is defined by the appended claims and their equivalents.

Claims

1. A protection method for new energy lines based on the polarity difference of voltage reverse traveling waves, characterized by: Includes the following steps: Step 1: When a fault occurs on the transmission line, the measuring devices at both ends collect the three-phase voltage signal and the three-phase current signal after the fault, and use Clarke transform to extract the line-mode components of the fault voltage and fault current. Step 2: Calculate the voltage traveling wave propagating in the reverse direction at the protection installation point using the line-mode fault voltage and line-mode fault current; Step 3: Use wavelet transform modulus maxima to calibrate each wavefront of the voltage reverse traveling wave. The modulus maxima corresponding to the first wavefront with the opposite polarity to the initial traveling wave, calibrated at both ends of the line, are respectively... and , and These represent the i-th and j-th sampling points, respectively. Step 4: Differentiate between internal and external faults based on the polarity difference of the first reverse-polarity voltage traveling wave at both ends of the line; In step 2, the line-mode fault current and line-mode fault voltage at any point on the line are obtained according to the line's fluctuation equation: ； The positive direction of traveling wave propagation is defined as from the busbar to the line, where... , These represent the forward traveling wave propagating in the defined positive direction and the reverse traveling wave propagating in the opposite direction to the defined positive direction, respectively. and These represent the fault voltage and fault current, respectively. Indicates the length of the line. For traveling wave speed, Indicates the wave impedance of the line; The transient current and voltage at any point on the line are both superpositions of traveling waves and reverse traveling waves. The traveling waves and reverse traveling waves of the voltage can be extracted using the line-mode components of the fault voltage and current. ； In step 3, the wavefront signal of the traveling wave is calibrated using the modulus maxima of wavelet transform; the modulus maxima of wavelet transform correspond one-to-one with the abrupt change points of the signal. In step 4, the polarities corresponding to the first reverse polarity voltage traveling wave measured at both ends are respectively represented as: ; As a sign function, it is defined that when the wavelet transform modulus maxima W(n) is negative, When the wavelet transform modulus maxima W(n) are positive, ;like If so, it is a fault within the zone; if If so, it indicates an out-of-area fault.

2. The new energy line protection method based on voltage reverse traveling wave polarity difference according to claim 1, characterized in that: The three-phase voltage and current signals acquired in step 1 are coupled to each other. First, the off-diagonal elements of the parameter matrix need to be reduced to zero through Clarke transformation to achieve three-phase decoupling. Line-mode voltage traveling wave is used as the research object.

3. A non-volatile storage medium, characterized in that, The non-volatile storage medium includes a stored program, wherein the program, when executed, controls the device where the non-volatile storage medium is located to perform the method described in any one of claims 1 to 2.

4. An electronic device, characterized in that, It includes a processor and a memory; the memory stores computer-readable instructions, and the processor is configured to execute the computer-readable instructions, wherein the computer-readable instructions, when executed, perform the method according to any one of claims 1 to 2.

Images