A relay protection method and system based on an equivalent time domain model of a protected device

Abstract

The application discloses a kind of based on the equivalent time domain model of protected equipment relay protection method, system, storage medium and computing device, the method is by establishing the time domain equivalent model of the applicable frequency band of protected equipment, collection protected equipment each port voltage, current, the typical characteristic parameter of equivalent model is calculated by time domain algorithm, according to the difference or law of the topography or parameter of protected equipment under normal operation, fault or other working conditions, the line protection, component protection principle and method based on model / parameter identification are constructed.The application is not affected by power characteristics compared with traditional protection, can accurately, quickly identify the fault in the area, outside the area of protected equipment.

Description

Technical Field

[0001] This invention relates to a relay protection method, system, storage medium, and computing device based on an equivalent time-domain model of the protected equipment, belonging to the field of relay protection technology. Background Technology

[0002] Under the "dual carbon" goal, accelerating the replacement of traditional fossil fuel power generation with new energy power generation and building a high proportion of new energy with an increasing share has become the main direction of my country's power system development.

[0003] The widespread application of power electronic equipment in all aspects of the new energy power system, including the power source, grid, and load, results in weak support and low immunity, leading to faster fault propagation and a wider impact. If faults are not isolated in a timely and correct manner, it can cause new energy sources to disconnect from the grid, DC power outages, and other issues, easily triggering a chain reaction. This places higher demands on the reliability, sensitivity, and rapid fault clearing capabilities of relay protection.

[0004] At the same time, the large-scale integration of new energy sources has led to profound changes in the fault characteristics of the power system, exhibiting features such as frequency shift, abrupt changes in equivalent electromotive force, controlled fault current, and high harmonics. This has overturned the traditional relay protection theory based on the characteristics of synchronous machines. Existing protection principles based on phasors are no longer suitable for fault identification using short-circuit current, impedance characteristics, and frequency characteristics. As a result, protection maloperation, failure to operate, and slow operation have gradually appeared in the power grid, threatening the safe operation of the system from "points" to "areas".

[0005] In existing technologies, the paper "Equivalent Magnetic Circuit Model and Inter-turn Protection Method of Energy-Pumping High-Voltage Parallel Reactor" (Power System Technology, Vol. 47, No. 5, May 2023, Zheng Tao et al.) proposes an equivalent modeling method for energy-pulling high-voltage reactors based on magnetic circuit decomposition, based on the analysis of their electromagnetic coupling characteristics. This method simulates the electrical characteristics of the energy-pulling high-voltage reactor under rated operating conditions and external faults by constructing a three-segment equivalent magnetic circuit model. Further research and a new inter-turn protection method for the energy-pulling winding based on the zero-sequence current ratio and phase difference are proposed. This method requires no voltage input and no setting, effectively identifies inter-turn faults in the main reactor winding and the energy-pulling winding, and has high sensitivity. However, this technical solution is still based on phasor calculations and is susceptible to the frequency shift of new energy power sources.

[0006] The paper "Practical Criterion for Line Differential Protection Based on the Berylon Model" (Automation of Electric Power Systems, Vol. 28, No. 23, December 10, 2004, Zheng Yuping et al.) derived the expressions for the differential current of the fault phase and the differential current of the non-fault phase under faults in a three-phase coupled line section. Based on this, a practical criterion based on the Berylon model is proposed. This criterion can fully compensate for transient and steady-state capacitive currents under faults outside the protection zone, and has high sensitivity and strong tolerance for transition resistance under faults within the protection zone. This method effectively eliminates the influence of capacitive current by using a time-domain method based on the line distributed parameters. However, it still uses phasor calculations when forming the differential criterion, which may lead to the loss of fault transient information under the controlled characteristics of power electronic equipment, resulting in a decrease in the sensitivity of the differential protection.

[0007] The paper "UHV Transformer Protection Based on Loop Balance Equations and Magnetizing Inductance" (Proceedings of the CSEE, Vol. 32, No. 1, January 5, 2012, Deng Xiangli et al.) addresses the problem that transformer differential protection based on the harmonic braking principle is greatly affected by harmonics and has an excessively long operating time, making it difficult to meet the protection requirements of UHV transformers. It proposes an UHV transformer protection scheme based on a T-type equivalent circuit. A T-type equivalent circuit model of the transformer is established, which is unaffected by the transformer's operating state, and its parameters can be uniquely determined. A protection scheme based on the transformer's equivalent loop balance equation criterion and equivalent magnetizing inductance criterion is proposed. The paper describes how, through the transformer's T-type equivalent model, the equivalent instantaneous magnetizing inductance is calculated through parameter identification, and the average value of the equivalent instantaneous magnetizing inductance within half a cycle is calculated to identify minor inter-turn faults in the transformer. However, the method proposed in this paper for calculating the average value of the equivalent instantaneous magnetizing inductance within half a cycle can misjudge inter-turn faults when the transformer is under no-load charging, leading to maloperation of the protection, and it cannot be used as protection under various fault conditions.

[0008] Improving existing protection principles with corresponding technologies can solve the problem of abnormal protection actions in specific scenarios. However, as the proportion of new energy sources gradually increases, the applicable range of traditional protection principles will gradually shrink until they become unapplicable. It is imperative to invent a new protection principle that is not affected by power supply characteristics. Summary of the Invention

[0009] This invention provides a relay protection method, system, storage medium, and computing device based on an equivalent time-domain model of the protected equipment, which solves the problems disclosed in the background art.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: This invention discloses, in one aspect, a relay protection method based on an equivalent time-domain model of the protected equipment, characterized in that it includes: Step 1: Establish a simplified equivalent time-domain model of the protected equipment within the applicable frequency band, and determine the time-domain model expression of the equivalent time-domain model and the characteristic quantities reflecting the changes in the topology and / or parameters of the protected equipment; Step 2: Obtain the voltage and current of each port of the protected device, select an appropriate sampling rate, retain the time domain information within the applicable frequency band, obtain discrete voltage and current sampling points, and discretize the time domain model expression; Step 3: Determine the time-domain algorithm that reflects the differences or patterns of the equivalent model characteristics of the protected equipment under various operating conditions, and calculate the characteristics through the discretized time-domain model expression; Step 4: Construct practical protection criteria based on the differences or patterns of characteristic quantities under normal operation of the protected equipment and fault conditions inside and outside the protection zone.

[0011] More preferably, In step 1, for distance protection of wind power transmission lines, a simplified equivalent time-domain model of the wind power transmission lines is established as follows: The wind farm and power grid system are abstracted into a voltage source in series with internal impedance; the transmission line adopts a lumped parameter line model, ignores the distributed capacitance of the transmission line, and uses a series resistance and inductance model to represent the equivalent line.

[0012] More preferably, The characteristic quantity reflecting changes in the topology and / or parameters of the protected line is the distance from the fault location to the protection installation point at the beginning of the line. .

[0013] More preferably, Under the simplified equivalent time-domain model of wind power transmission lines, the time-domain model expression is established as follows: For three-phase faults and phase-to-phase faults, the differential equations of the time-domain model expression are: ; For asymmetric faults, the differential equation of the time-domain model expression is: ; in, This represents the instantaneous value of the phase-to-phase voltage during a fault. This represents the instantaneous value of the fault-interphase current. r 1. l 1 represents the resistance and inductance per unit length of the line, respectively. The fault distance is the distance from the fault point to the protection installation point at the beginning of the line. , These are the instantaneous values ​​of the voltage and current of the faulty phase. , These are the resistance zero-sequence compensation system and the inductance zero-sequence compensation coefficient, respectively. It is the zero-sequence current. This is the equivalent fault transition resistance. This is the current flowing through the fault transition resistor.

[0014] More preferably, In step 2, the voltage and current at each port of the protected device are acquired, and discrete voltage and current sampling points are obtained using an appropriate sampling rate. An equivalent model discretization time-domain model expression is then established, specifically including: A sampling frequency higher than 2.4kHz is used to collect the three-phase voltage at the protection installation location. , , Three-phase current , , The sampled values; Based on voltage and current information from a series of continuous sampling points, the voltage-current relationship matrix equation is established by combining the time-domain differential equation with the median difference: ; in, This is a matrix of voltage sample values; The current parameter matrix includes the current sampling sequence, the derivative sequence of the current sampling points using the median difference, and the zero-sequence current sampling sequence; For differential equations including , The coefficient matrix to be determined, including the coefficient matrix.

[0015] More preferably, In step 3, a least squares algorithm with a set calculation window length is used to estimate and solve the time-domain differential equations of the discretized equivalent model to obtain the fault distance. and equivalent transition .

[0016] More preferably, In step 4, for distance protection of wind power transmission lines, based on the fault distance... Equivalent transition resistance Determine the fault distance setting range for distance protection based on the differences or patterns under normal line operation and fault conditions inside and outside the zone. When the fault distance When the fault occurs, it is determined that the fault is within the protection range.

[0017] More preferably, In step 1, for the time-domain differential protection of wind power transmission lines: based on the Berylon model, the wind power transmission line with uniform loss is converted into a lossless transmission line, and the wind power transmission line with uniform loss is cut into two segments of the same length. The resistance parameter elements of each segment are concentrated at both ends of the line; the line distribution parameter equation is determined as the time-domain model expression of the wind power transmission line; the characteristic quantity reflecting the topology or parameter change of the wind power transmission line is the current difference between the current on the m side and the current on the n side. For relay protection based on transformer equivalent magnetizing inductance: establish a transformer T-type equivalent model, use the excitation branch voltage equation as the time-domain model expression of the transformer equivalent time-domain model, and use the magnetizing inductance as a characteristic quantity reflecting the changes in transformer topology or parameters. For relay protection based on the bus equivalent time-domain model: the bus differential admittance equation is calculated using the currents and voltages of each branch connected to the bus and serves as the time-domain model expression for the bus equivalent time-domain model. The characteristic quantity reflecting changes in the bus topology and / or parameters is the bus differential admittance. ; For relay protection based on the equivalent time-domain model of the reactor: calculate the zero-sequence current of the small reactor of the reactor, and use the circuit equation of the reactor three-phase branch reactors connected in parallel and the neutral point small reactor in series as the time-domain expression of the equivalent time-domain model of the reactor, and the characteristic quantity reflecting the change of reactor topology and / or parameters is the inductance value per phase.

[0018] More preferably, In step 2, for the time-domain differential protection of the wind power transmission line: the three-phase voltage and three-phase current at the protection installation points on both sides of the line are collected respectively, and the collected discrete current and voltage at both ends are substituted into the time-domain model expression of the line distributed parameters; For relay protection based on the equivalent excitation inductance of a transformer: the sampling rate collects the instantaneous values ​​of current and voltage on each side of the transformer, samples n+2 sampling points, and lists a set of discretized time-domain differential equations containing n equations; For relay protection based on the bus equivalent time domain model: the instantaneous current value of each branch of the bus and the instantaneous voltage value of the bus are collected at a set sampling rate, and the obtained discrete bus voltage and current sampling values ​​of each branch are substituted into the bus differential admittance equation. For relay protection based on the equivalent time-domain model of the reactor: the instantaneous values ​​of the reactor's head-end voltage, current, and neutral point voltage are collected at a set sampling rate, and the collected discrete values ​​of the reactor's head-end voltage, current, and neutral point voltage are substituted into the time-domain expression of the reactor's equivalent time-domain model.

[0019] More preferably, In step 3, for the time-domain differential protection of the wind power transmission line: the opposite side of the line... ,t, Substitute the voltage and current values ​​at time t into the time-domain model expression of the line distributed parameters to deduce the calculated values ​​of the three current quantities on this side at time t, and calculate the differential current on this side; For relay protection based on the equivalent magnetizing inductance of a transformer: the magnetizing inductance parameters are calculated using the least squares method. L m ; For relay protection based on the bus equivalent time-domain model: the bus differential admittance is calculated based on the discretized time-domain model expression. ; For relay protection based on the equivalent time-domain model of the reactor: set the integration window length and the least squares calculation window length, and calculate the inductance value of each phase of the reactor through the least squares algorithm.

[0020] More preferably, In step 4, for the time-domain differential protection of wind power transmission lines: by utilizing the difference in waveform similarity between the extra-zone / intra-zone local current extrapolation value and the actual value, protection criteria are constructed. If the criteria are met, the differential protection will operate. For relay protection based on the equivalent magnetizing inductance of a transformer: when the magnetizing inductance is less than the magnetizing inductance setting value for 20ms consecutively. L mset At that time, the transformer protection tripped; For relay protection based on the bus equivalent time-domain model: when the bus differential admittance is greater than the differential admittance threshold value... At that time, the busbar protection activated; For relay protection based on the equivalent time-domain model of the reactor: compare the calculated inductance value of the reactor with the set inductance threshold value. When the inductance value of any phase reactor is less than the set inductance threshold value and this condition is met for 20ms, the reactor protection will activate.

[0021] On the other hand, a relay protection system based on an equivalent time-domain model of the protected equipment, utilizing the aforementioned relay protection method, is disclosed, comprising an equivalent time-domain model construction module, a data acquisition module, a feature quantity calculation module, and a protection criterion construction module; characterized in that: The equivalent time-domain model construction module establishes a simplified equivalent time-domain model of the protected equipment within the applicable frequency band, and determines the time-domain model expression of the equivalent time-domain model and the characteristic quantities reflecting the topology and / or parameter changes of the protected equipment. The data acquisition module acquires the voltage and current at each port of the protected device at a set sampling rate. The feature quantity calculation module discretizes the time-domain model expression based on discrete voltage and current sampling points, and calculates the feature quantity through the discretized time-domain model expression; The protection criterion construction module constructs practical protection criteria based on the differences or patterns of characteristic quantities under normal operation of the protected equipment and fault conditions inside and outside the protection zone.

[0022] The present invention also discloses an electronic device, including a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps according to the relay protection method.

[0023] A computer-readable storage medium having a computer program stored thereon, characterized in that the program is processed to perform the steps of the relay protection method.

[0024] A computer-readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to perform a relay protection method based on an equivalent time-domain model of the protected device.

[0025] A computing device includes one or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include instructions for performing a relay protection method based on an equivalent time-domain model of the protected device.

[0026] The beneficial effects achieved by this invention are as follows: This invention establishes a simplified equivalent mathematical model of the protected equipment, calculates the typical characteristic parameters of the equivalent model using a time-domain algorithm, and constructs a protection principle based on model / parameter identification according to the differences or patterns of the topology or parameters of the protected equipment under normal operation, fault, and other conditions. This is unaffected by power supply characteristics and greatly improves the reliability, sensitivity, and speed of relay protection for high-proportion renewable energy access in new power systems. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the line protection principle based on the equivalent time-domain model of the present invention; Figure 2 This is a schematic diagram of the time-domain distance protection circuit for wind power transmission lines in Embodiment 1 of the present invention; Figure 3 This is a simplified equivalent time-domain model diagram of the wind power transmission line in embodiment 1 of the present invention; Figure 4 This is a diagram showing the ranging results obtained in Embodiment 1 of the present invention; Figure 5 This is a diagram of the equivalent time-domain model of the wind power transmission line time-domain differential protection according to Embodiment 2 of the present invention. Figure 6 This is a diagram showing the action results of the time-domain differential protection for wind power transmission lines obtained in Embodiment 2 of the present invention. Figure 7This is a diagram of the equivalent time-domain model of the transformer in Embodiment 3 of the present invention; Figure 8(a) shows the fault protection action time of zone 3 in Embodiment 3 of the present invention, which is 20ms. Figure 8(b) shows the reliable non-operation diagram of the transformer no-charge protection in Embodiment 3 of the present invention; Figure 8(c) is a sensitive action diagram of the transformer 2% inter-turn fault protection in Embodiment 3 of the present invention; Figure 8(d) shows the reliable non-operation diagram of the external fault protection in Embodiment 3 of the present invention; Figure 9 This is a diagram of the equivalent time-domain model of the relay protection bus based on the bus equivalent time-domain model in Embodiment 4 of the present invention; Figure 10(a) is a reliable operation diagram when the fault ride-through current is large in zone 4 of the present invention; Figure 10(b) is a reliable non-operation diagram for an external fault in Embodiment 4 of the present invention; Figure 11 This is a diagram of the equivalent time-domain model of the relay protection reactor based on the equivalent time-domain model of the reactor in Embodiment 5 of the present invention; Figure 12(a) is a diagram of rapid fault response in zone 5 of the present invention; Figure 12(b) is a reliable non-operation diagram for external faults in Embodiment 5 of the present invention; Figure 12(c) shows that the iron core of Embodiment 5 of the present invention does not malfunction when it is saturated. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0029] A relay protection method based on an equivalent time-domain model of the protected equipment, characterized in that it includes: Step 1: Establish a simplified equivalent time-domain model of the protected equipment within the applicable frequency band, and determine the time-domain model expression of the equivalent time-domain model and the characteristic quantities reflecting the changes in the topology and / or parameters of the protected equipment; Step 2: Obtain the voltage and current of each port of the protected device, select an appropriate sampling rate, retain the time domain information within the applicable frequency band, obtain discrete voltage and current sampling points, and discretize the time domain model expression; Step 3: Determine the time-domain algorithm that reflects the differences or patterns of the equivalent model characteristics of the protected equipment under various operating conditions, and calculate the characteristics through the discretized time-domain model expression; Step 4: Construct practical protection criteria based on the differences or patterns of characteristic quantities under normal operation of the protected equipment and fault conditions inside and outside the protection zone.

[0030] Example 1: See appendix Figure 1 This invention provides a time-domain distance protection method for wind power transmission lines, the research object of which is as follows: Figure 2 As shown, it includes the following steps: Step 1: For distance protection of wind power transmission lines, first establish a simplified equivalent mathematical model of the wind power transmission line (e.g., Figure 3 The wind farm and its large system are abstracted as a voltage source in series with internal impedance, corresponding to EM, ZM, EN, and ZN. For transmission lines, a lumped-parameter line model is used: the distributed capacitance of the transmission line is ignored, and an equivalent circuit is represented by a series resistor and inductor model. Let the fault point be F, and the fault transition resistance be R. F The fault current is i F Ultimately, the result is as follows Figure 3 The mathematical model is shown. Wherein, r 1. l 1 represents the resistance and inductance per unit length of the line, respectively. R 1. L 1 represents the equivalent resistance and inductance of the faulty section of the line, respectively.

[0031] Under this equivalent model, for three-phase faults and phase-to-phase faults, the transition resistance at the fault point can be ignored, and the following relationship holds: (1) In the above formula and These represent the instantaneous values ​​of the fault phase-to-phase voltage and phase-to-phase current, respectively.

[0032] For asymmetrical faults, taking a single-phase-to-ground fault in phase A as an example, the following relationship holds: (2) In the above formula u mA ( t ), i mA ( t These are the instantaneous values ​​of phase A voltage and current, respectively. im F ( t () represents the zero-sequence current of phase A. K r =( r 0- r 1) / 3 r 1 represents the zero-sequence resistance compensation coefficient. K l =(l 0- l 1) / 3 l 1 represents the zero-sequence compensation coefficient for inductance. r 0, l 0 represents the zero-sequence resistance and inductance per unit length of the line, respectively.

[0033] For uniform transmission lines, the impedance per unit length of the line can be considered a constant. Therefore, the fault location x can be selected as a characteristic quantity that reflects the change in the topology or parameters of the protected equipment to simplify the calculation. Combining equations (1) and (2), the following time-domain differential equation is obtained: (3) (4) In the above formula u mA ( t ), i mA ( t These are the instantaneous values ​​of phase A voltage and current, respectively. i 0( t () represents the zero-sequence current of phase A. K r =( r 0- r 1) / 3 r 1 represents the zero-sequence resistance compensation coefficient. K l =( l 0- l 1) / 3 l 1 represents the zero-sequence compensation coefficient for inductance. r 0, l 0 represents the zero-sequence resistance and inductance per unit length of the line, respectively.

[0034] For symmetric faults, there is only one unknown, x, which is obviously easy to solve. For asymmetric faults, we have... x , i F、 R F For the three unknowns, a solution can be obtained after a certain degree of equivalence. Step 2: Obtain the voltage and current at each port of the protected equipment, use an appropriate sampling rate to obtain discrete voltage and current sampling points, and establish a set of time-domain differential equations for the discretization of the equivalent model; A sampling rate that is too low will cause the loss of high-frequency components containing fault information during the transient process, which will affect the accuracy and convergence speed of subsequent calculations. However, a sampling rate that is too high is easily affected by high-frequency background noise and will also significantly increase the amount of computation. Considering all these factors, a sampling rate of 2.4kHz is adopted.

[0035] Collect electrical quantities at the protection installation location, including sampled values ​​of three-phase voltage and three-phase current, specifically: , , , , , .

[0036] Taking a single-phase ground fault in phase A as an example, for single-ended protection, it is impossible to accurately determine the current flowing through the transition resistor. i F ( t However, under certain conditions, it is approximated that the phase of the zero-sequence current is close to that of the zero-sequence current, thus having i F = i m0 / C F , C F To protect the zero-sequence shunt coefficient at the installation location, the lumped-parameter time-domain model expression for asymmetric faults can be transformed as follows: (5) In the formula, x is the distance from the fault point to the protection installation location. = R F / C F This is the equivalent transition resistance. and These are the positive-sequence resistance and positive-sequence inductance per unit length of the line, respectively. Zero-order compensation coefficient The real part, The imaginary part of the zero-sequence compensation coefficient, the zero-sequence current .

[0037] x and The two unknown parameters can be solved by solving the equation. For discrete sampled data, the median difference is used instead of the differential, and equation (5) based on the line resistance-inductance model can be written as: (6) Equation (6) based on the line resistance-inductance model can be written as: (7) In the above formula, k is the sampling point number, and Δt is the sampling interval. Using the voltage and current information continuously collected by the protection device, a series of equations such as (6) or (7) can be obtained, which can be rearranged into a matrix form: (8) Among them, matrix U , β ,I These are the voltage information matrix, the coefficient matrix to be determined, and the current information matrix, respectively.

[0038] Step 3: Determine the time-domain algorithm and calculation window length that can reflect the differences or patterns of the characteristic parameters of the equivalent model of the protected equipment under various operating conditions, and calculate the characteristic parameters through a discretized set of time-domain differential equations; Short window length calculation can quickly obtain calculation results, but the convergence is poor; long window length calculation can obtain more stable calculation results, but the calculation delay is long, affecting the protection action speed. Considering both the speed and convergence of solving equation (8), the least squares algorithm with a calculation window length of 5ms is adopted, specifically: Let the number of sampling points within the unit data window be n. For equation (8), , (9) , For equation (8),

[0039] (10)

[0040] In the above formula, p(k) is the current sampling sequence used for calculation, p d (k) is the differential sequence of current sampling points used for calculation, and p0(k) is the zero-sequence current sampling sequence used for calculation:

[0041] (11)

[0042] Based on the sampling sequence with a certain redundancy data window, the least squares approach is used to estimate and solve the equation system (4) to obtain the fault location x and the equivalent transition resistance. .

[0043] Step 4: Construct protection principles and engineering application criteria based on the differences or patterns of characteristic parameters under operating conditions such as normal operation of the protected equipment and faults inside and outside the protection zone; Assume the distance protection setting is X. set When x <X set The fault is considered to occur within the protection range, thus meeting the protection operation conditions.

[0044] by Figure 2Taking the line shown as an example, the line is 100km long, the protection setting value is 70% of the line length, and an AN-to-ground fault occurs at 50km. The ranging result obtained using the above method is as follows. Figure 4 As shown, the distance is 49.9 km. This meets the protection activation conditions, and the distance protection is activated.

[0045] Example 2: This invention provides a time-domain differential protection method for wind power transmission lines, the research object of which is as follows: Figure 2 As shown, it includes the following steps: Step 1: Construct a simplified equivalent model of the wind power transmission line within the applicable frequency band. Based on the Berylon model, convert the uniformly lossy wind power transmission line into a lossless transmission line. Divide the uniformly lossy wind power transmission line into two segments of equal length, with the resistance parameters of each segment concentrated at both ends of the line. s is the total line length, r is the resistance per unit length, c is the capacitance per unit length, l is the inductance per unit length, and the characteristic impedance is... Total line resistance The characteristic quantity reflecting changes in the topology or parameters of wind power transmission lines is the current difference between the current on the m-side and the current on the n-side.

[0046] Build as Figure 5 The time-domain model expression for the line distributed parameters is shown below: (12) in: (13) (14) (15) In the formula: , For traveling wave transmission speed, Here it is defined as the delay factor, satisfying... .

[0047] Step 2: Collect the three-phase voltage and three-phase current at the protection installation points on both sides of the line, specifically including the voltage on side m. , , m-side current , , n-side voltage , , n-side current , , The sampling rate was 1.2kHz. The collected discrete currents and voltages at both ends were then substituted into the time-domain model expression of the line distributed parameters.

[0048] Step 3: Determine the time-domain algorithm that reflects the differences or patterns of the equivalent model characteristics of the protected equipment under various operating conditions, and calculate the characteristics through the discretized time-domain model expression; Line n side ,t, By substituting the voltage and current values ​​at time t into the wave equation of the Berylon model, the calculated values ​​of the three current quantities on the m-side at time t are derived. , , By combining the current sampling value on side m at time t, the differential current on side m is calculated. , , .

[0049] m side of the line ,t, By substituting the voltage and current values ​​at time t into the wave equation of the Berylon model, the calculated values ​​of the three current quantities on the n-side at time t are derived. , , By combining the current sampling value on side n at time t, the differential current on side n is calculated. , , .

[0050] When the system is operating normally or an external fault occurs, since the fault does not damage the line model, the current extrapolation value on the m side is... It should be consistent with the true value of the current on the m side. The waveforms almost overlap. When a fault occurs within the system, the current projection value on the m side is affected by the damage to the line Berylon model caused by the faulty branch. It should be consistent with the true value of the current on the m side. The waveforms show significant differences.

[0051] Step 4: Construct protection principles and practical engineering criteria based on the differences or patterns of characteristic quantities under normal operation of the protected equipment and fault conditions inside and outside the protection zone.

[0052] In Example 2, faults are identified based on differential current.

[0053] The current from side n, calculated using the Berylon model, propagates along the entire line to side m. Comparing this with the actual measured current on side m reveals differences in waveform similarity under different fault types. Utilizing the difference in waveform similarity between the extrapolated and actual current values ​​on side m (outside / inside the fault zone), a protection criterion can be constructed: when... At that time, the differential protection meets the operating conditions.

[0054] by Figure 2Taking a phase-A ground fault at point K3 in the line section shown as an example, the differential current of phase-A calculated by the above method meets the operating conditions, while phases B and C do not. Figure 6 The protection option is to trip phase A.

[0055] Example 3: A relay protection method based on the equivalent magnetizing inductance of a transformer includes the following steps: Step 1: Establish a T-type equivalent model of the transformer, such as... Figure 7 As shown, the excitation branch voltage equation is used as the time-domain model expression of the transformer's equivalent time-domain model, and the excitation inductance is used as a characteristic quantity reflecting changes in the transformer's topology or parameters.

[0056] in, , , , These represent the voltage and current on the primary and secondary sides of the transformer, respectively. It is the magnetizing current. , , , These are the leakage resistance and leakage inductance of the primary and secondary sides of the transformer, respectively. and These are the excitation resistor and excitation inductance of the excitation branch, respectively.

[0057] The time-domain model expression of the transformer equivalent model is the excitation branch voltage equation: (16) Step 2: Collect the instantaneous current and voltage values ​​on each side of the transformer at a sampling rate of 2kHz, sample n+2 sampling points, and list a set of discretized time-domain differential equations containing n equations.

[0058] (17) in, , is the sampling interval, and n is the least squares window length.

[0059] Step 3: Calculate the excitation inductance parameters using the least squares method. L m .

[0060] The transformer magnetizing inductance Lm is calculated as follows: (18) (19) (20) (twenty one) Where A is a matrix composed of current sampling values ​​from each side, X is the excitation resistance and excitation inductance of the excitation branch to be identified, and B is a matrix composed of voltage sampling values ​​from each side.

[0061] Step 4: The transformer's magnetizing inductance is relatively large during normal operation or external faults, and relatively small during internal faults. When the core is saturated, it fluctuates periodically between high and low values, as shown in Figures 8(a)-8(d). Figure 8(a) shows the operation time of the internal fault protection (20ms), Figure 8(b) shows the reliable non-operation of the transformer no-charge protection, Figure 8(c) shows the sensitive operation of the 2% inter-turn fault protection, and Figure 8(d) shows the reliable non-operation of the external fault protection. Therefore, when the magnetizing inductance is continuously less than the set value for 20ms... L mset If the transformer protection activates, the transformer protection will activate; otherwise, return to step 2.

[0062] Example 4: A relay protection method based on a bus equivalent time-domain model includes the following steps: Step 1, establish the equivalent time-domain model of the bus, such as Figure 9 As shown, the bus differential admittance equation is calculated using the currents and voltages of each branch connected to the bus, serving as the time-domain model expression for the bus's equivalent time-domain model. The characteristic quantity reflecting changes in the bus topology and / or parameters is the bus differential admittance. In the appendix Figure 9 In, i1~i n Let be the instantaneous current value of bus branch 1~n, and u be the instantaneous voltage value of the bus.

[0063] Step 2: Acquire the instantaneous current values ​​and instantaneous voltage values ​​of each branch of the bus at a sampling rate of 2kHz. Collect m sampling points continuously.

[0064] Step 3: Substitute the obtained discrete bus voltage and branch current sample values ​​into the bus differential admittance equation: (twenty two) in, For the instantaneous differential current of the busbar, The instantaneous voltage of the busbar. for The first sampling point in the nth sampling point One sampling point, This is the differential admittance of the busbar.

[0065] Among them, the bus instantaneous differential current The following formula is used to calculate: (twenty three) in, For the first The branch road in the first The instantaneous current sampled value at each sampling point. For connection with busbar The first of the branch roads A side road.

[0066] Step 4, when the bus differential admittance is greater than the differential admittance threshold value If the fault current is large within the area shown in Figure 10(a) or Figure 10(b), the busbar protection will operate reliably. Otherwise, it will return to step 2, as shown in Figure 10(a) and Figure 10(b). In Figure 10(a), the fault crossing current is large within the area, and the fault current outside the area shown in Figure 10(b) will not operate reliably. This is the threshold value for the differential admittance that is being tuned.

[0067] Example 5: A relay protection method based on an equivalent time-domain model of a reactor includes the following steps: Step 1, establish the equivalent time-domain model of the reactor, such as Figure 11 As shown. The zero-sequence current of the small reactor is calculated, using the circuit equation of the reactor's three-phase branch reactors connected in parallel and the neutral point small reactor in series as the time-domain expression of the reactor's equivalent time-domain model. The characteristic quantity reflecting the changes in the reactor's topology and / or parameters is the inductance value per phase.

[0068] exist Figure 11 in,u a u b u c i is the voltage at the start of the reactor. a i b i c i is the current at the beginning of the reactor. la i lb i lc U is the current at the end of the reactor, and u0 is the neutral point voltage of the reactor.

[0069] Step 2: Acquire the instantaneous values ​​of the reactor's starting-end voltage, current, and neutral-point voltage at a sampling rate of 2kHz. Collect m sampling points continuously.

[0070] Calculate the zero-sequence current of the small reactance of the reactor.

[0071]

[0072] Wherein, 3i0 is the instantaneous value of the zero-sequence current generated by the reactor at the end, which is the instantaneous value of the zero-sequence current of the small reactor.

[0073] The collected discrete values ​​of the reactor's start-up voltage, current, and neutral point voltage are substituted into the time-domain expression of the reactor's equivalent time-domain model. Step 3: Set the integration window length and the least squares calculation window length, and calculate the inductance value of each phase of the reactor using the least squares algorithm. The following formula uses phase A as an example: (twenty four) Where N is the integration window length, m is the least squares calculation window length, ΔT is the sampling interval, which is the reciprocal of the sampling frequency and is 1 / 2000, k is the k-th point in the least squares calculation with window length m, n is the n-th point in the integration calculation with integration window length N, L0 is the neutral point reactance value, and L a This is the inductance value of phase A.

[0074] The calculation of the inductance values ​​for phase B and phase C is similar.

[0075] Step 5: Compare the calculated reactor inductance value with the set inductance threshold value. If the inductance value of any phase reactor is less than the set inductance threshold value and this condition is met for 20ms, the reactor protection will activate. Otherwise, return to step 2. The protection effect is shown in Figures 12(a)-12(c). Figure 12(a) shows the rapid activation diagram for faults within the zone, Figure 12(b) shows the reliable non-activation diagram for faults outside the zone, and Figure 12(c) shows the non-malfunction when the core is saturated.

[0076] Disclosed is a relay protection system based on the equivalent time-domain model of the protected equipment using the relay protection method, comprising an equivalent time-domain model construction module, a data acquisition module, a feature quantity calculation module, and a protection criterion construction module.

[0077] The equivalent time-domain model construction module establishes a simplified equivalent time-domain model of the protected equipment within the applicable frequency band, and determines the time-domain model expression of the equivalent time-domain model and the characteristic quantities reflecting the topology and / or parameter changes of the protected equipment. The data acquisition module acquires the voltage and current at each port of the protected device at a set sampling rate. The feature quantity calculation module discretizes the time-domain model expression based on discrete voltage and current sampling points, and calculates the feature quantity through the discretized time-domain model expression; The protection criterion construction module constructs practical protection criteria based on the differences or patterns of characteristic quantities under normal operation of the protected equipment and fault conditions inside and outside the protection zone.

[0078] A computer-readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to perform a relay protection method based on an equivalent time-domain model of the protected device.

[0079] A computing device includes one or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include instructions for executing a relay protection method based on an equivalent time-domain model of the protected device.

[0080] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0081] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0082] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0083] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0084] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention pending approval.

Claims

1. A relay protection method based on an equivalent time-domain model of the protected equipment, characterized in that, include: Step 1: Establish a simplified equivalent time-domain model of the protected equipment within the applicable frequency band, and determine the time-domain model expression of the equivalent time-domain model and the characteristic quantities reflecting the changes in the topology and / or parameters of the protected equipment; Step 2: Obtain the voltage and current of each port of the protected device, select an appropriate sampling rate, retain the time domain information within the applicable frequency band, obtain discrete voltage and current sampling points, and discretize the time domain model expression; Step 3: Determine the time-domain algorithm that reflects the differences or patterns of the equivalent model characteristics of the protected equipment under various operating conditions, and calculate the characteristics through the discretized time-domain model expression; Step 4: Construct practical protection criteria based on the differences or patterns of characteristic quantities under normal operation of the protected equipment and fault conditions inside and outside the protection zone.

2. The relay protection method based on the equivalent time-domain model of the protected equipment according to claim 1, characterized in that: In step 1, for distance protection of wind power transmission lines, a simplified equivalent time-domain model of the wind power transmission lines is established as follows: The wind farm and power grid system are abstracted into a voltage source in series with internal impedance; the transmission line adopts a lumped parameter line model, ignores the distributed capacitance of the transmission line, and uses a series resistance and inductance model to represent the equivalent line.

3. The relay protection method based on the equivalent time-domain model of the protected equipment according to claim 2, characterized in that: The characteristic quantity reflecting changes in the topology and / or parameters of the protected line is the distance from the fault location to the protection installation point at the beginning of the line. .

4. The relay protection method based on the equivalent time-domain model of the protected equipment according to claim 2 or 3, characterized in that: Under the simplified equivalent time-domain model of wind power transmission lines, the time-domain model expression is established as follows: For three-phase faults and phase-to-phase faults, the differential equations of the time-domain model expression are: ； For asymmetric faults, the differential equation of the time-domain model expression is: ； in, This represents the instantaneous value of the phase-to-phase voltage during a fault. This represents the instantaneous value of the fault-interphase current. r 1. l 1 represents the resistance and inductance per unit length of the line, respectively. The fault distance is the distance from the fault point to the protection installation point at the beginning of the line. , These are the instantaneous values ​​of the voltage and current of the faulty phase. , These are the resistance zero-sequence compensation system and the inductance zero-sequence compensation coefficient, respectively. It is the zero-sequence current. This is the equivalent fault transition resistance. This is the current flowing through the fault transition resistor.

5. The relay protection method based on the equivalent time-domain model of the protected equipment according to claim 4, characterized in that: In step 2, the voltage and current at each port of the protected device are acquired, and discrete voltage and current sampling points are obtained using an appropriate sampling rate. An equivalent model discretization time-domain model expression is then established, specifically including: A sampling frequency higher than 2.4kHz is used to collect the three-phase voltage at the protection installation location. , , Three-phase current , , The sampled values; Based on voltage and current information from a series of continuous sampling points, the voltage-current relationship matrix equation is established by combining the time-domain differential equation with the median difference: ； in, This is a matrix of voltage sample values; The current parameter matrix includes the current sampling sequence, the derivative sequence of the current sampling points using the median difference, and the zero-sequence current sampling sequence; For differential equations including , The coefficient matrix to be determined, including the coefficient matrix.

6. The relay protection method based on the equivalent time-domain model of the protected equipment according to claim 2 or 5, characterized in that: In step 3, a least squares algorithm with a set calculation window length is used to estimate and solve the time-domain differential equations of the discretized equivalent model to obtain the fault distance. and equivalent transition .

7. The relay protection method based on the equivalent time-domain model of the protected equipment according to claim 6, characterized in that: In step 4, for distance protection of wind power transmission lines, based on the fault distance... Equivalent transition resistance Determine the fault distance setting range for distance protection based on the differences or patterns under normal line operation and fault conditions inside and outside the zone. When the fault distance When the fault occurs, it is determined that the fault is within the protection range.

8. The relay protection method based on the equivalent time-domain model of the protected equipment according to claim 1, characterized in that: In step 1, for the time-domain differential protection of wind power transmission lines: based on the Berylon model, the wind power transmission line with uniform loss is converted into a lossless transmission line, and the wind power transmission line with uniform loss is cut into two segments of the same length. The resistance parameter elements of each segment are concentrated at both ends of the line. The equations for the distributed parameters of the line are determined to be time-domain model expressions for wind power transmission lines; The characteristic quantity reflecting the change in the topology or parameters of the wind power transmission line is the current difference between the current on the m side and the current on the n side. For relay protection based on transformer equivalent magnetizing inductance: establish a transformer T-type equivalent model, use the excitation branch voltage equation as the time-domain model expression of the transformer equivalent time-domain model, and use the magnetizing inductance as a characteristic quantity reflecting the changes in transformer topology or parameters. For relay protection based on the bus equivalent time-domain model: the bus differential admittance equation is calculated using the currents and voltages of each branch connected to the bus and serves as the time-domain model expression for the bus equivalent time-domain model. The characteristic quantity reflecting the changes in bus topology and / or parameters is the bus differential admittance. ; For relay protection based on the equivalent time-domain model of the reactor: calculate the zero-sequence current of the small reactor of the reactor, and use the circuit equation of the reactor three-phase branch reactors connected in parallel and the neutral point small reactor in series as the time-domain expression of the equivalent time-domain model of the reactor, and the characteristic quantity reflecting the change of reactor topology and / or parameters is the inductance value per phase.

9. The relay protection method based on the equivalent time-domain model of the protected equipment according to claim 8, characterized in that: In step 2, for the time-domain differential protection of the wind power transmission line: the three-phase voltage and three-phase current at the protection installation points on both sides of the line are collected respectively, and the collected discrete current and voltage at both ends are substituted into the time-domain model expression of the line distributed parameters; For relay protection based on the equivalent excitation inductance of a transformer: the sampling rate collects the instantaneous values ​​of current and voltage on each side of the transformer, samples n+2 sampling points, and lists a set of discretized time-domain differential equations containing n equations; For relay protection based on the bus equivalent time domain model: the instantaneous current value of each branch of the bus and the instantaneous voltage value of the bus are collected at a set sampling rate, and the obtained discrete bus voltage and current sampling values ​​of each branch are substituted into the bus differential admittance equation. For relay protection based on the equivalent time-domain model of the reactor: the instantaneous values ​​of the reactor's head-end voltage, current, and neutral point voltage are collected at a set sampling rate, and the collected discrete values ​​of the reactor's head-end voltage, current, and neutral point voltage are substituted into the time-domain expression of the reactor's equivalent time-domain model.

10. The relay protection method based on the equivalent time-domain model of the protected equipment according to claim 9, characterized in that: In step 3, for the time-domain differential protection of the wind power transmission line: the opposite side of the line... ,t, Substitute the voltage and current values ​​at time t into the time-domain model expression of the line distributed parameters to deduce the calculated values ​​of the three current quantities on this side at time t, and calculate the differential current on this side; For relay protection based on the equivalent magnetizing inductance of a transformer: the magnetizing inductance parameters are calculated using the least squares method. L m ; For relay protection based on the bus equivalent time-domain model: the bus differential admittance is calculated based on the discretized time-domain model expression. ; For relay protection based on the equivalent time-domain model of the reactor: set the integration window length and the least squares calculation window length, and calculate the inductance value of each phase of the reactor through the least squares algorithm.

11. The relay protection method based on the equivalent time-domain model of the protected equipment according to claim 10, characterized in that: In step 4, for the time-domain differential protection of wind power transmission lines: by utilizing the difference in waveform similarity between the extra-zone / intra-zone local current extrapolation value and the actual value, protection criteria are constructed. If the criteria are met, the differential protection will operate. For relay protection based on the equivalent magnetizing inductance of a transformer: when the magnetizing inductance is less than the magnetizing inductance setting value for 20ms consecutively. L mset At that time, the transformer protection tripped; For relay protection based on the bus equivalent time-domain model: when the bus differential admittance is greater than the differential admittance threshold value... At that time, the busbar protection activated; For relay protection based on the equivalent time-domain model of the reactor: compare the calculated inductance value of the reactor with the set inductance threshold value. When the inductance value of any phase reactor is less than the set inductance threshold value and this condition is met for 20ms, the reactor protection will activate.

12. A relay protection system based on an equivalent time-domain model of the protected equipment using the relay protection method according to any one of claims 1-11, comprising an equivalent time-domain model construction module, a data acquisition module, a feature quantity calculation module, and a protection criterion construction module; characterized in that: The equivalent time-domain model construction module establishes a simplified equivalent time-domain model of the protected equipment within the applicable frequency band, and determines the time-domain model expression of the equivalent time-domain model and the characteristic quantities reflecting the topology and / or parameter changes of the protected equipment. The data acquisition module acquires the voltage and current at each port of the protected device at a set sampling rate. The feature quantity calculation module discretizes the time-domain model expression based on discrete voltage and current sampling points, and calculates the feature quantity through the discretized time-domain model expression; The protection criterion construction module constructs practical protection criteria based on the differences or patterns of characteristic quantities under normal operation of the protected equipment and fault conditions inside and outside the protection zone.

13. An electronic device, comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of the relay protection method according to any one of claims 1-11.

14. A computer-readable storage medium having a computer program stored thereon, characterized in that, The procedure is processed to perform the steps of the relay protection method according to any one of claims 1-11.

Images