Fast direction protection method and system based on time domain parameters in natural response stage

Abstract

The invention discloses a rapid direction protection method and system based on time domain parameters in a natural response stage, and belongs to the technical field of relay protection, and the method comprises the steps: collecting the three-phase voltage and current of a system line, and starting protection after detecting a system fault; obtaining fault components of the phase voltage and the phase current of the line in the time window of the natural response stage after the fault, and carrying out low-frequency filtering; performing line-mode transformation on the fault components of the filtered phase voltage and phase current to obtain 1-mode voltage and current fault components; constructing a time-frequency resistance-inductance model of 1-mode voltage and current fault components; and calculating the positive resistance sensing model conformity in the natural response stage, judging a fault type based on the positive resistance sensing model conformity, and executing a protection action according to the fault type. According to the invention, rapid and reliable fault direction discrimination and protection action are carried out by using the 1-mode fault component, the discrimination time of fault protection action response is shortened, and ultra-rapid, high-reliability and high-robustness fault direction discrimination and rapid direction protection are realized.

Description

Technical Field

[0001] This invention belongs to the field of relay protection technology, specifically relating to a fast directional protection method and system based on time-domain parameters of the natural response stage. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Currently, the development and utilization of renewable energy and various green energy sources are receiving increasing attention. Large-scale development of renewable energy, represented by solar energy, has become an inevitable choice for human society to achieve long-term sustainable development. The integration of distributed power sources into the distribution system will inevitably change the topology of the distribution network and may become a multi-terminal power supply system. With the grid connection of distributed power sources, the power system is significantly impacted, and the traditional grid-load relationship is gradually shifting from "source follows load" to "source interacts with load," bringing a series of technical challenges to system operation.

[0004] The integration of distributed generation (DG) sources will have both a boosting and draining effect on short-circuit currents. The boosting current from DG sources leads to an increase in fault current, posing a risk of over-tripping of protection devices upstream of the fault point. The draining effect reduces protection sensitivity, potentially causing overcurrent protection to fail to operate. Simultaneously, reverse current from faults on adjacent lines may also cause overcurrent protection to malfunction. For power directional components, the integration of DG sources into the grid will alter the fault characteristics of the grid to some extent. The output current may be capacitive or inductive, thus affecting the speed and accuracy of traditional directional components. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a fast direction protection method and system based on time-domain parameters of the natural response stage. By using the 1-mode fault component of the natural response stage to quickly identify the fault direction and execute the corresponding protection action, it achieves ultra-fast, highly reliable, and robust fault direction identification and fast direction protection.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: On one hand, the technical solution of the present invention provides a fast direction protection method based on time-domain parameters of the natural response stage, including: The system collects three-phase voltage and current data of the system lines and activates protection after detecting a system fault. The fault components of the line phase voltage and phase current within the time window of the natural response stage after the fault are obtained and low-frequency filtered. The fault components of the filtered phase voltage and phase current are converted from line mode to obtain the fault components of the voltage and current in mode 1. Construct a time-frequency impedance-inductance model for the fault components of mode 1 voltage and current; Calculate the positive resistance inductance model compliance degree during the natural response phase, determine the fault type based on the positive resistance inductance model compliance degree, and execute protection actions according to the fault type.

[0007] In at least one embodiment, obtaining the fault components of the line phase voltage and phase current during the natural response phase specifically involves: obtaining the line phase voltage and phase current within the time window of the natural response phase after a system fault, calculating the fault components of the phase voltage and phase current, and representing them as follows: ; In the formula, and The first phase voltage and phase current represent the... One sampling point, This indicates the number of sampling points corresponding to the natural response phase. and The first phase voltage and phase current fault quantities One sampling point, These are the sampling points.

[0008] In at least one embodiment, the fault components of the obtained phase voltage and phase current are filtered to obtain waveforms with frequencies of 300 Hz and below.

[0009] In at least one embodiment, the fault component of the filtered phase voltage is subjected to line-mode conversion, specifically as follows: ; The fault component of the filtered phase current is subjected to line-mode conversion, specifically as follows: ; In the formula and The voltage and current under the modulus after the linear-to-modulus transformation are given, where ;when At the same time, the voltage fault component and the current fault component of the first mode are obtained.

[0010] In at least one embodiment, the time-frequency impedance model is expressed as: ; In the formula, This represents the mode 1 voltage fault component. Indicates the fault component of the mode 1 current; This indicates the resistance parameter; when a positive fault occurs, This includes the resistive portion protecting the back-side line impedance and the resistive portion protecting the system impedance. In the event of a reverse fault, This includes the resistance and transition resistance of the line impedance from the installation point to the fault point. This indicates the inductance parameter; when a positive fault occurs, To protect the inductance of the back-side line impedance and the system impedance, when a reverse fault occurs, Inductance to protect the impedance of the line from the installation point to the fault point.

[0011] In at least one embodiment, the conformity of the positive resistance-inductance model is represented by a correlation coefficient, specifically: ; In the formula, The moment of failure; For the natural response phase time window; It is the derivative of the current.

[0012] In at least one embodiment, if the positive resistance-inductance model conformity in the natural response phase is less than zero, a positive direction fault is determined to have occurred; otherwise, a negative direction fault is determined to have occurred. If a fault occurs in the positive direction, the fault component direction element of module 1 will operate reliably, triggering a trip signal and tripping the protection; if a fault occurs in the reverse direction, the protection will be blocked.

[0013] On the other hand, the technical solution of the present invention also provides a fast direction protection system based on time-domain parameters of the natural response stage, including: The fault detection module is configured to: collect the three-phase voltage and current of the system lines, and activate protection after detecting a system fault; The fault component acquisition module is configured to acquire the fault components of the line phase voltage and phase current within the time window of the natural response stage after the fault and perform low-frequency filtering. The line-mode conversion module is configured to perform line-mode conversion on the fault components of the filtered phase voltage and phase current to obtain the fault components of the voltage and current in mode 1. The model building module is configured to: build a time-frequency impedance-inductance model with 1-mode voltage and current fault components; The fault protection module is configured to: calculate the conformity of the positive resistance inductance model during the natural response phase, determine the fault type based on the conformity of the positive resistance inductance model, and execute protection actions according to the fault type.

[0014] The beneficial effects of the above-described technical solution of the present invention are as follows: The fast directional protection method based on time-domain parameters of the natural response stage of this invention aims to quickly determine the fault direction using the 1-mode fault component. By focusing on the voltage and current fault quantities in the very early 2ms natural response time window of the fault occurrence, and utilizing the characteristic that the photovoltaic is equivalent to a constant current source during this stage, it is immune to photovoltaic output characteristic interference. By effectively extracting the characteristic quantities of the fault direction through low-frequency filtering, the feature extraction is optimized, the anti-noise capability is enhanced, and thus the accuracy of the direction judgment is improved. Based on the positive and negative signs of the conformity between the time-frequency impedance model and the positive impedance model as the fault direction criterion, the complex frequency domain analysis is avoided, the calculation is simpler and more efficient, and the fault direction can be quickly and reliably determined and the corresponding protection action response is performed. This greatly shortens the judgment time of the fault protection action response and realizes ultra-fast, highly reliable, and robust fault direction determination and fast directional protection. Attached Figure Description

[0015] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0016] Figure 1 This is a schematic diagram of the fast direction protection method based on time-domain parameters of the natural response stage disclosed in Embodiment 1 of the present invention; Figure 2 This is a schematic flowchart of the fast direction protection method based on time-domain parameters of the natural response stage disclosed in Embodiment 1 of the present invention; Figure 3 This is a simulation diagram of the 10kV distribution network model disclosed in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the simulation results of the method disclosed in Embodiment 1 of the present invention under a three-phase short-circuit fault in F1; wherein, (a) is the simulation result when the distributed power source penetration rate is 50%, (b) is the simulation result when the distributed power source penetration rate is 100%, and (c) is the simulation result when the distributed power source penetration rate is 140%. Figure 5 This is a schematic diagram of the simulation results of the method disclosed in Embodiment 1 of the present invention under a three-phase short-circuit fault in F2; wherein, (a) is the simulation result when the distributed power source penetration rate is 50%, (b) is the simulation result when the distributed power source penetration rate is 100%, and (c) is the simulation result when the distributed power source penetration rate is 140%. Figure 6 This is a schematic diagram of the simulation results of the method disclosed in Embodiment 1 of the present invention under a two-phase short-circuit fault in F1; wherein, (a) is the simulation result when the distributed power source penetration rate is 50%, (b) is the simulation result when the distributed power source penetration rate is 100%, and (c) is the simulation result when the distributed power source penetration rate is 140%. Figure 7This is a schematic diagram of the simulation results of the method disclosed in Embodiment 1 of the present invention under a two-phase short-circuit fault in F2; wherein, (a) is the simulation result when the distributed power source penetration rate is 50%, (b) is the simulation result when the distributed power source penetration rate is 100%, and (c) is the simulation result when the distributed power source penetration rate is 140%. Detailed Implementation

[0017] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0018] As described in the background section, the purpose of this invention is to overcome the shortcomings of the prior art and provide a fast direction protection method and system based on time-domain parameters of the natural response stage. By using the 1-mode fault component of the natural response stage to quickly identify the fault direction and execute corresponding protection actions, it achieves ultra-fast, highly reliable, and robust fault direction identification and fast direction protection.

[0019] Example 1 Considering that distributed photovoltaic (PV) power sources can be modeled as a constant current during the natural response phase, the directional element for the fault component during the natural response phase can be unaffected by the PV. However, in scenarios where PV is connected, the protection of the back-side system during a forward fault mainly involves the parallel connection of the upstream distributed power source impedance and the system impedance. Since the system impedance is relatively small, it primarily exhibits the characteristics of system impedance. Therefore, the directional element for the 1-mode fault component operates reliably during a forward fault and protects the impedance of the upstream system during a reverse fault. Based on this, in a typical embodiment of the present invention, such as... Figure 1 and Figure 2 As shown, this embodiment discloses a fast direction protection method based on time-domain parameters of the natural response stage, including the following steps: S100. Collects the three-phase voltage and current of the system lines, and activates protection after detecting a system fault; S200. Obtain the fault components of the line phase voltage and phase current within the time window of the natural response stage after the fault and perform low-frequency filtering; S300. Perform line-mode conversion on the fault components of the filtered phase voltage and phase current to obtain the mode-1 voltage and current fault components; S400. Construct a time-frequency impedance-inductance model for the fault components of the first-mode voltage and current; S500. Calculate the positive resistance inductance model compliance degree during the natural response stage, determine the fault type based on the positive resistance inductance model compliance degree, and execute protection actions according to the fault type.

[0020] The fast direction protection method based on time-domain parameters of the natural response stage described above will be explained in detail below with reference to specific implementation methods.

[0021] S100. Collects the three-phase voltage and current of the system lines, and activates protection after detecting a system fault.

[0022] In this step, by collecting the three-phase voltage and current of the system lines, and referring to the low-voltage ride-through strategy of inverter-type distributed power sources, protection is activated when the power frequency voltage drop exceeds 10% and lasts for more than 3ms. The protection activation criterion can be expressed as: (1); In the formula, This represents the collected circuit power frequency voltage; Indicates the rated voltage of the power frequency line; Indicates duration.

[0023] S200. Obtain the fault components of the line phase voltage and phase current within the time window of the natural response stage after the fault and perform low-frequency filtering.

[0024] Considering that the natural response phase lasts for the first 1-2 cycles after a system fault, during this stage, the system has not yet reached steady state, and the transient components of the fault current / voltage (such as DC offset and aperiodic components) are significant. At this time, the distributed photovoltaic system can be equivalent to a constant current source model, and its output current characteristics (capacitive / inductive) have a relatively small dominant influence on the transient components during this phase. This allows direction discrimination based on the characteristics of this phase to effectively avoid interference from the distributed photovoltaic output characteristics (capacitive / inductive current) on traditional directional elements, solving the problem of potential malfunction or failure of traditional directional elements. Therefore, in this step, the waveform of the natural response phase time window after the fault is collected to avoid the delay in inverter control response, thereby ensuring the rapidity of direction judgment and protection action response. In this step, data within the minimum natural response phase time window of 2ms is used for discrimination.

[0025] Specifically, the phase voltage and phase current of the line within a 2ms time window after a system fault are obtained, and the fault components of the phase voltage and phase current are calculated and expressed as follows: (2); In the formula, and The first phase voltage and phase current represent the... One sampling point, This represents the number of sampling points corresponding to the natural response phase (2ms). and The first phase voltage and phase current fault quantities One sampling point, Indicates the sampling point.

[0026] Considering that noise and interference in the distribution network are concentrated in the high-frequency band, while the main characteristics of fault components are generally concentrated in the low-frequency band, this step involves low-frequency filtering of the obtained fault component voltage and current to obtain waveforms at frequencies of 300Hz and below. This effectively extracts the characteristic quantities of the fault direction, thereby improving the accuracy of direction determination. As an optional implementation method, a Butterworth second-order filter can be used for low-frequency filtering, with the transfer function expressed as: (3); In the formula, Represents the Laplace transform operator; This indicates the upper limit of the filter bandwidth, i.e., the cutoff frequency. It determines the position of the filter response on the frequency axis and is the frequency boundary at which the filter begins to apply significant attenuation to the signal.

[0027] This transfer function is characterized by a flat amplitude-frequency response in the low-frequency range, which minimizes distortion of fault components. This is achieved by adjusting the cutoff frequency. The frequency is limited to 300Hz ± 5%, thus obtaining waveforms with frequencies of 300Hz and below.

[0028] S300. Perform line-mode conversion on the fault components of the filtered phase voltage and phase current to obtain the fault components of the 1-mode voltage and current.

[0029] In this step, the phase voltage fault components and phase current fault components obtained after low-frequency filtering are subjected to linear-mode transformation to obtain the voltage fault components and current fault components in the modulus after line-mode transformation. Specifically, the fault components of the filtered phase voltage are subjected to line-mode transformation, calculated as follows: (4); The fault component of the filtered phase current is converted to a line-mode model, and the calculation method is as follows: (5); In the formula and These are the voltage fault components and current fault components under the modulus after the line-mode transformation, where... ;when At that time, the fault component of the modulus voltage was obtained. and 1-mode current fault component .

[0030] S400. Construct a time-frequency impedance-inductance model for the fault components of the first-order voltage and current.

[0031] When a positive fault occurs in the system, the modulus voltage fault component and current fault components satisfy: (6); At this time, the resistance parameters It mainly includes the resistive part protecting the back-side line impedance and the resistive part of the system impedance, as well as inductance parameters. It mainly includes inductors that protect the impedance of the back-side lines and inductors that protect the system impedance.

[0032] When a reverse fault occurs in the system, the 1-mode voltage fault component and current fault components satisfy: (7); At this time, the resistance parameters This mainly includes the resistance and transition resistance of the line impedance from the protection installation point to the fault point, and inductance parameters. This mainly includes the inductance of the line impedance from the installation point to the fault point.

[0033] Based on this, the time-frequency impedance-inductance model for the fault components of mode 1 voltage and current is constructed as follows: (8); The resistance parameters are obtained by inverse calculation using the model matrix. and inductance parameters If a positive fault occurs, the voltage fault component and current fault component of mode 1 satisfy the negative resistance-inductance model; if a reverse fault occurs, the voltage fault component and current fault component of mode 1 satisfy the positive resistance-inductance model.

[0034] S500. Calculate the positive resistance inductance model compliance degree during the natural response stage, determine the fault type based on the positive resistance inductance model compliance degree, and execute protection actions according to the fault type.

[0035] In this step, the correlation coefficient is used to define the conformity of the positive resistance-inductance model, also known as the correlation coefficient of the natural response stage, which is specifically expressed as follows: (9); In the formula, The moment of failure; The time window is selected as 2ms in this embodiment; Indicates sampling point Voltage at the point; Sampling points The derivative of the current at that point.

[0036] Based on the time-frequency resistance-inductance model analysis constructed using S400, the type of fault can be determined in this step by judging the sign of the positive resistance-inductance model conformity. If the positive resistance-inductance model conformity... If the positive resistance-inductance model conforms to the condition, then a positive direction fault is determined. If the fault occurs, a reverse fault is determined. By using the waveform of the fault component, the waveform will change before and after a fault occurs. At this time, the voltage and current waveforms are collected, and the correlation coefficient (i.e., the positive resistance-inductance model fit) can be calculated. By judging the sign of the correlation coefficient, the direction of the fault can be correctly determined.

[0037] Furthermore, the response protection action is executed according to the determined fault type. If a positive fault occurs, the directional element of the 1st mode fault component operates reliably, triggering a trip signal and tripping the protection. If a reverse fault occurs, the protection is blocked, and the directional element of the 1st mode fault component protects the impedance of the upstream system.

[0038] The fast directional protection method based on time-domain parameters of the natural response stage proposed in this embodiment aims to quickly determine the fault direction using the 1-mode fault component. By focusing on the voltage and current fault quantities in the very early 2ms natural response time window of the fault occurrence, and utilizing the characteristic that the photovoltaic is equivalent to a constant current source during this stage, it is immune to photovoltaic output characteristic interference. The characteristic quantities of the fault direction are effectively extracted through low-frequency filtering, optimizing feature extraction, enhancing noise resistance, and thus improving the accuracy of direction judgment. The fault direction criterion is based on the positive and negative signs of the conformity between the time-frequency impedance model and the positive impedance model, avoiding complex frequency domain analysis, making the calculation simpler and more efficient. It can quickly and reliably determine the fault direction and perform corresponding protection actions, greatly shortening the judgment time of the fault protection action response, and realizing ultra-fast, highly reliable, and robust fault direction judgment and fast directional protection.

[0039] To verify the correctness of fault direction discrimination in the fast directional protection method based on time-domain parameters of the natural response stage proposed in this embodiment, this embodiment takes a 10kV distribution network as an example and establishes a simulation platform on the SIMULINK platform as follows: Figure 3The diagram shows a 10kV distribution network model. The power supply side transformer capacity is 40MVA, and the short-circuit voltage is [not specified]. The positive sequence impedance per unit length of the line is (0.13 + j0.35)Ω / km. Line I (feeder 1) is 3km long, and the connection point PCC1 of IIDER1 is 1km from the outlet of line II (feeder II). The load LD1 at the end of this line has a capacity of 5MVA and a power factor of 0.9. Line II (feeder II) is 6km long and is divided into two sections by the sectionalizing circuit breaker QF4. The rated capacities of loads LD2 and LD3 are [not specified]. The capacities are 2MVA and 2.5MVA, with a load power factor of 0.9, and a constant power model is adopted. The IIDER2 grid connection point PCC2 is 1.5km away from the line outlet, and the IIDER3 grid connection point PCC3 is 3.5km away from the line outlet. The branch point B21 is 2.5km away from the line outlet. When the penetration rate of the synchronous motor power supply DER1 and the inverter distributed power supply IIDER2 and IIDER3 in the system is 100%, their capacities are 5MVA, 2.25MVA and 1.8MVA, respectively.

[0040] The phase-to-phase short circuit fault point can be set at Figure 3 Points F1-F2 in the circuit. In line II, fault point F1 is set 1km from the busbar, and fault point F2 is set at the outlet of branch line B21. Two-phase and three-phase short-circuit faults are simulated at these different fault points after 0.5s of system operation, with a transition resistance of 0.1Ω. Directional current protection devices are installed at the outlet circuit breakers QF1 and QF3, the sectionalizing circuit breaker QF4, and the branch circuit breaker QF5 to protect circuits 1, 3, 4, and 5, respectively. The above directional element discrimination and processing procedures are performed, and the simulation results are as follows: Figures 4 to 7 As shown.

[0041] Fault point F1 is set 1 km away from the busbar in line II. When the system runs for 0.5 seconds, a three-phase short-circuit fault occurs with a transition resistance of 0.1Ω. The forward fault at this time is set as QF3. According to this method, the correlation coefficients measured by the current protection devices in each direction under different penetration rates of distributed power sources are as follows: Figure 4 As shown, it can be seen that, under different permeability, the measurement point with a correlation coefficient less than zero is QF3. Therefore, the measurement point QF3 should be determined to be a positive fault, which is consistent with the set fault result.

[0042] Fault point F2 is set at the outlet of branch line B21 in line II. When the system runs for 0.5 seconds, a three-phase short-circuit fault occurs with a transition resistance of 0.1Ω. At this time, the forward faults are set as QF3 and QF5. According to this method, the correlation coefficients measured by the current protection devices in each direction under different penetration rates of distributed power sources are as follows: Figure 5As shown, it can be seen that the measurement points with a correlation coefficient less than zero under different permeability are QF3 and QF5. Therefore, it is determined that measurement points QF3 and QF5 should be positive faults, which is consistent with the set fault results.

[0043] Fault point F1 is set 1 km away from the busbar in line II. When the system runs for 0.5 seconds, a two-phase short-circuit fault occurs with a transition resistance of 0.1Ω. The forward fault at this time is set as QF3. According to this method, the correlation coefficients measured by the current protection devices in each direction under different penetration rates of distributed power sources are as follows: Figure 6 As shown, it can be seen that, under different permeability, the measurement point with a correlation coefficient less than zero is QF3. Therefore, the measurement point QF3 should be determined to be a positive fault, which is consistent with the set fault result.

[0044] Fault point F2 is set at the outlet of branch line B21 in line II. When the system runs for 0.5 seconds, a two-phase short circuit fault occurs with a transition resistance of 0.1Ω. At this time, the forward faults are set as QF3 and QF5. According to this method, the correlation coefficients measured by the current protection devices in each direction under different penetration rates of distributed power sources are as follows: Figure 7 As shown, the measurement points with correlation coefficients less than zero are QF3 and QF5. Therefore, it is determined that measurement points QF3 and QF5 should be positive direction faults, which is consistent with the set fault results.

[0045] The comprehensive simulation results show that, under different fault types and distributed power supply penetration rates, when the fault at the measuring point is in the forward direction, the correlation coefficient is less than zero; when the fault at the measuring point is in the reverse direction, the correlation coefficient is greater than zero. Both methods can correctly reflect the fault direction, thus verifying the accuracy of the proposed method.

[0046] Example 2 In a typical embodiment of the present invention, this embodiment discloses a fast direction protection system based on time-domain parameters of the natural response stage, comprising: The fault detection module is configured to: collect the three-phase voltage and current of the system lines, and activate protection after detecting a system fault; The fault component acquisition module is configured to acquire the fault components of the line phase voltage and phase current within the time window of the natural response stage after the fault and perform low-frequency filtering. The line-mode conversion module is configured to perform line-mode conversion on the fault components of the filtered phase voltage and phase current to obtain the fault components of the voltage and current in mode 1. The model building module is configured to: build a time-frequency impedance-inductance model with 1-mode voltage and current fault components; The fault protection module is configured to: calculate the conformity of the positive resistance inductance model during the natural response phase, determine the fault type based on the conformity of the positive resistance inductance model, and execute protection actions according to the fault type.

[0047] Example 3 In a typical embodiment of the present invention, this embodiment provides a computer-readable storage medium storing a computer program thereon. When executed by a processor, the program implements the steps in the fast direction protection method based on time-domain parameters of the natural response phase as described in Embodiment 1. These steps include: S100. Collects the three-phase voltage and current of the system lines, and activates protection after detecting a system fault; S200. Obtain the fault components of the line phase voltage and phase current within the time window of the natural response stage after the fault and perform low-frequency filtering; S300. Perform line-mode conversion on the fault components of the filtered phase voltage and phase current to obtain the mode-1 voltage and current fault components; S400. Construct a time-frequency impedance-inductance model for the fault components of the first-mode voltage and current; S500. Calculate the positive resistance inductance model compliance degree during the natural response stage, determine the fault type based on the positive resistance inductance model compliance degree, and execute protection actions according to the fault type.

[0048] Example 4 In a typical embodiment of the present invention, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in the fast direction protection method based on time-domain parameters of the natural response phase as described in Embodiment 1. These steps include: S100. Collects the three-phase voltage and current of the system lines, and activates protection after detecting a system fault; S200. Obtain the fault components of the line phase voltage and phase current within the time window of the natural response stage after the fault and perform low-frequency filtering; S300. Perform line-mode conversion on the fault components of the filtered phase voltage and phase current to obtain the mode-1 voltage and current fault components; S400. Construct a time-frequency impedance-inductance model for the fault components of the first-mode voltage and current; S500. Calculate the positive resistance inductance model compliance degree during the natural response stage, determine the fault type based on the positive resistance inductance model compliance degree, and execute protection actions according to the fault type.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fast directional protection method based on time domain parameters of natural response phase, characterized in that, The method comprises the following steps: A system line three-phase voltage and current are collected, and protection is started after a system fault is detected; Fault components of the line phase voltage and phase current in a time window of a natural response stage after the fault are obtained and low-frequency filtering is performed; Line-mode transformation is performed on the filtered fault components of the phase voltage and phase current to obtain 1-mode voltage and current fault components; A time-frequency inductive model of the 1-mode voltage and current fault components is constructed; A positive inductive model coincidence degree of the natural response stage is calculated, a fault type is judged based on the positive inductive model coincidence degree, and a protection action is performed according to the fault type.

2. The fast directional protection method based on natural response phase time domain parameters as claimed in claim 1, wherein, The fault components of the line phase voltage and phase current in the natural response stage are obtained, specifically as follows: the line phase voltage and phase current in a time window of the natural response stage after the system fault are obtained, the fault components of the phase voltage and phase current are calculated, and are expressed as: ； wherein and denote the first sample points of the phase voltage and the phase current, denote the number of sample points corresponding to the natural response phase, and denote the first sample points of the fault quantities of the phase voltage and the phase current, denote the sample points.

3. The fast directional protection method based on natural response phase time domain parameters as claimed in claim 2, wherein, The obtained fault components of the phase voltage and phase current are filtered to obtain waveforms of 300 Hz and below.

4. The fast directional protection method based on natural response phase time domain parameters as claimed in claim 1, wherein, Line-mode transformation is performed on the filtered fault components of the phase voltage, specifically as follows: ； Line-mode transformation is performed on the filtered fault components of the phase current, specifically as follows: ； wherein and are the voltage and current at the modulus of the line mode transform, where The 1-mode voltage fault component and the 1-mode current fault component are obtained when ​ 5. The fast directional protection method based on natural response phase time domain parameters as claimed in claim 1 wherein, The time-frequency inductive model is expressed as: ； wherein represents the one-mode voltage fault component, represents the one-mode current fault component; represents the resistance parameter when a forward direction fault occurs, includes the resistance of the protection backside line impedance and the resistance of the system impedance when a reverse direction fault occurs, includes the resistance of the protection installation to fault point line impedance and the transition resistance; represents the inductance parameter when a forward direction fault occurs, is the inductance of the protection backside line impedance and the inductance of the system impedance when a reverse direction fault occurs, is the inductance of the protection installation to fault point line impedance.

6. The fast directional protection method based on natural response phase time domain parameters as claimed in claim 1 wherein, The positive inductive model coincidence degree is expressed in terms of a correlation coefficient, specifically as follows: ； In the formula, is the time of failure; is the time window; is the derivative of the current.

7. The fast directional protection method based on natural response phase time domain parameters as claimed in claim 6, wherein, If the positive inductive model coincidence degree of the natural response stage is less than zero, it is determined that a positive direction fault occurs, otherwise, it is determined that a reverse direction fault occurs; If the positive direction fault occurs, a 1-mode fault component direction element reliably acts, a trip signal is triggered, and the protection trips; If the reverse direction fault occurs, the protection is locked.

8. A fast directional protection system based on natural response phase time domain parameters, characterized in that, The method comprises the following steps: A fault detection module is configured to collect a system line three-phase voltage and current, and start protection after a system fault is detected; A fault component acquisition module is configured to obtain fault components of line phase voltage and phase current in a time window of a natural response stage after the fault and perform low-frequency filtering; A line-mode transformation module is configured to perform line-mode transformation on the filtered fault components of the phase voltage and phase current to obtain 1-mode voltage and current fault components; A model construction module is configured to construct a time-frequency inductive model of the 1-mode voltage and current fault components; A fault protection module is configured to calculate a positive inductive model coincidence degree of the natural response stage, judge a fault type based on the positive inductive model coincidence degree, and perform a protection action according to the fault type.

9. A computer readable storage medium having stored thereon a computer program, characterized in that, The program is executed by the processor to implement the steps in the fast direction protection method based on time-domain parameters of a natural response stage in any one of claims 1-7.

10. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the program to implement the steps in the fast direction protection method based on time-domain parameters of a natural response stage in any one of claims 1-7.

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