阅读说明：本技术 基于垂段最小距离拟合的高压送出线距离保护方法及装置 (High-voltage outgoing line distance protection method and device based on vertical section minimum distance fitting ) 是由 潘本仁 李正天 桂小智 熊华强 张妍 周仕豪 于 2021-08-30 设计创作，主要内容包括：本发明公开一种基于垂段最小距离拟合的高压送出线距离保护方法及装置,方法包括在距离保护启动并正确选择故障相后,采用保护端对故障相电压、故障相电流、零序电流进行采样,将采样后的信号进行中位原点矩滤波,随后将滤波后的各组电量代入离散化的线路KVL差分方程,得到多组反映故障点距离保护端的线路电阻和电抗,利用垂段最小距离拟合算法,对上述的多组电抗值与电阻值分别进行计算处理,最终得到一组反映故障点距离保护端的线路电抗与电阻值。实现了不受故障电流中引入的谐波干扰的影响,可精确计算故障点距离保护端的线路阻抗值,并可有效防止坏数据干扰,大幅提升装有双馈风机机组的风电场送出线路的距离保护的动作可靠性。(The invention discloses a high-voltage outgoing line distance protection method and device based on vertical section minimum distance fitting. The method and the device have the advantages that the influence of harmonic interference introduced into fault current is avoided, the line impedance value of a fault point distance protection end can be accurately calculated, bad data interference can be effectively prevented, and the action reliability of distance protection of a wind power plant sending line provided with the double-fed fan unit is greatly improved.)

1. A high-voltage outgoing line distance protection method based on vertical section minimum distance fitting is characterized by comprising the following steps:

s1: after the novel distance protection starting criterion is started, the three-phase voltage of the fault phase is controlled on the basis of correctly selecting the fault phaseThree-phase currentSampling is carried out to obtain a three-phase voltage array of a fault phaseThree-phase current array of sum fault phase，Respectively represent a phase a, a phase b and a phase c;

s2: to three-phase voltage arrayAnd three-phase current arrayFiltering the middle position origin moment to obtain a filtered three-phase voltage arrayThree-phase current array after filteringAnd according to the filtered three-phase current arrayCalculating to obtain a zero sequence current array；

S3: three-phase voltage array based on filteringFiltered three-phase current arrayAnd zero sequence current arrayGround measurement voltage array required for calculating fault point distance protection end measurement impedanceGrounding measurement current arrayInter-phase measurement voltage arrayAnd interphase measuring current array；

S4: discretizing a KVL equation between a fault point and a line at a protection end to obtain a KVL discretization equation, performing minimum vertical section distance fitting on a measuring resistor and a measuring inductor by using a plurality of groups of KVL discretization equations to obtain a measuring resistance value R and a measuring inductance value L of the fault point at the protection end, and then correcting the measuring resistance value R and the measuring inductance value L to obtain a corrected resistance valueAnd correcting the inductance value；

S5: will correct the resistance valueAnd correcting the inductance valueSubstituting the impedance characteristic complex plane to further judge whether the protection is operated.

2. The high-voltage outgoing line distance protection method based on vertical section minimum distance fitting as claimed in claim 1, wherein in S1, the starting criterion of the novel distance protection is:

s101: three-phase voltage array for obtaining fault phase by samplingAnd (3) carrying out 4-layer db3 wavelet packet decomposition, wherein the algorithm formula of the wavelet packet decomposition is as follows:

，

in the formula (I), the compound is shown in the specification,、all are wavelet packet decomposition coefficients,for wavelet packet decomposition scale, taking=4, n is the frequency band,the time domain positions of the points in the signal,、respectively low-pass filter coefficients for wavelet packet decomposition and high-pass filter coefficients for wavelet packet decomposition,is the first in the signalA sample point with a decomposition scale ofWavelet packet decomposition coefficient with frequency band n;

s102: constructing an energy function:，

in the formula (I), the compound is shown in the specification,is the wavelet mean square extreme value of the (n-1) th data point,is the wavelet mean square extreme value of the nth data point,is defined as，Defined as the maximum value of the sequence of values in parentheses;

s103: the voltage drop point, namely the starting point of the novel distance protection, is judged according to the numerical value of the energy function:。

3. the high-voltage outgoing line distance protection method based on vertical segment minimum distance fitting as claimed in claim 1, wherein in S2, a three-phase voltage array is subjected toThe specific steps of carrying out median origin moment filtering processing are as follows:

s201: is selected to have a length ofSliding windows, i.e. selectionIn (1)The data form arrayWherein, in the step (A),，for the total number of elements in the array, the elements in each array are pressedArranged in the order from small to large to obtain a new array；

S202: calculating the median of the new array, wherein the calculation method comprises the following steps:median of the formulaSubstitute primitive arrayOf (2) element(s)；

According to the rule, the array is updated from i =1 to i = n-h-1N-h-1 elements of (A), so that an array is obtained；

S203: according to arraysTaking the length of the sliding window with the length of h to obtain an arrayWherein, in the step (A),calculating an arrayThe specific algorithm of the k-order origin moment is as follows:in the formula (I), wherein,is an array ofTo middleOf a single elementTo the power of, will arrayIs/are as followsMoment of origin of orderReplacing the ith element of array Y；

According to the rule, the array is updated from i =1 to i = n-h-1N-h-1 elements in the array to obtain an arrayThis array of numbersIs the meso positionFinal array after point moment filtering.

4. The high-voltage outgoing line distance protection method based on vertical segment minimum distance fitting as claimed in claim 1, wherein in S3, based on filtered three-phase voltage arrayFiltered three-phase current arrayAnd zero sequence current arrayGround measurement voltage array required for calculating fault point distance protection end measurement impedanceGrounding measurement current arrayInter-phase measurement voltage arrayAnd interphase measuring current arrayThe specific method comprises the following steps:

grounding measurement voltage array: ；

grounding measurement current array:，for the zero sequence compensation coefficient, the calculation formula is，Is the zero sequence impedance of the line per unit length,positive sequence impedance per unit length of line;

and (3) measuring voltage arrays among phases:in the formula (I), wherein,andthe three-phase voltage array of one fault phase after filtering and the three-phase voltage array of the other fault phase after filtering are respectively obtained;

measuring current between phases:in the formula (I), wherein,andthe three-phase current array of one fault phase after filtering and the three-phase current array of the other fault phase after filtering are respectively.

5. The high-voltage sending line distance based on vertical minimum distance fitting of claim 1The protection method is characterized in that in S4, the KVL equation between the fault point and the line at the protection end is as follows:or；

Wherein R is the measured resistance value of the fault point far from the protection end, L is the measured inductance value of the fault point far from the protection end,array for measuring voltage for grounding in case of ground fault，Array for measuring current for grounding in case of ground fault，Array of interphase measuring voltages for the occurrence of an interphase short circuit，Measuring current for phase when phase short circuit occurs。

6. A plumbing-based system as in claim 1The high-voltage outgoing line distance protection method based on minimum distance fitting is characterized in that in S4, a discretization KVL equation between a fault point and a line at a protection end is as follows:or；

Wherein R is the measured resistance value of the fault point far from the protection end, L is the measured inductance value of the fault point far from the protection end,in order to be able to sample the frequency,array for measuring voltage for grounding in case of ground faultTo (1) aA number of sample points are sampled at the time of sampling,array for measuring current for grounding in case of ground faultTo (1) aA number of sample points are sampled at the time of sampling,array of interphase measuring voltages for the occurrence of an interphase short circuitTo (1) aA number of sample points are sampled at the time of sampling,measuring current for phase when phase short circuit occursTo (1) aAnd (4) sampling points.

7. The high-voltage outgoing line distance protection method based on vertical section minimum distance fitting as claimed in claim 4, wherein in S4, performing minimum vertical section distance fitting on the measured resistance and the measured inductance to obtain the measured resistance value R and the measured inductance value L of the fault point distance protection terminal specifically includes the following steps:

s401: transforming the discretized KVL equation intoLet us order，，Then the equation becomes；

Wherein R is the measured resistance value of the fault point distance protection end, and L is the faultThe point is away from the measured inductance value of the protection terminal,to sample the frequency, when a ground fault occurs,measuring voltage arrays for groundingTo (1) aA number of sample points are sampled at the time of sampling,measuring current arrays for groundingTo (1) aSampling points; when a short-circuit occurs between the phases,measuring voltage arrays for phasesTo (1) aA number of sample points are sampled at the time of sampling,measuring current for phasesTo (1) aSampling points;

s402: defining a distance accumulation functionThe distance accumulation function calculates the partial derivatives of R and L respectively, and makes the partial derivatives be 0, that is；

S403: solving the equation set in S402 to obtain R and L values solved by the vertical segment minimum distance fitting algorithm:in the formula (I), wherein,，，，，。

8. the high voltage outgoing line distance protection method based on vertical segment minimum distance fitting of claim 1, wherein in S4, the resistance value is correctedAnd correcting the inductance valueThe expression of (a) is as follows:

，

wherein R is the measured resistance value of the fault point far from the protection end, L is the measured inductance value of the fault point far from the protection end,is at the temperature of the surroundings and is,as the length of the transmission line,for the self-geometric spacing of cylindrical wires, take，In order to be a temperature coefficient of the temperature,is the radius of the wire.

9. A high-voltage outgoing line distance protection device based on vertical section minimum distance fitting is characterized by comprising:

the sampling module is configured to carry out three-phase voltage comparison on the fault phase on the basis of correctly selecting the fault phase after the novel distance protection starting criterion is startedThree-phase currentSampling is carried out to obtain a three-phase voltage array of a fault phaseThree-phase current array of sum fault phase，Respectively represent a phase a, a phase b and a phase c;

a filter module configured to apply a three-phase voltage arrayAnd three-phase current arrayFiltering the middle position origin moment to obtain a filtered three-phase voltage arrayThree-phase current array after filteringAnd according to the filtered three-phase current arrayCalculating to obtain a zero sequence current array；

A calculation module configured to be based on the filtered three-phase voltage arrayFiltered three-phase powerStream arrayAnd zero sequence current arrayGround measurement voltage array required for calculating fault point distance protection end measurement impedanceGrounding measurement current arrayInter-phase measurement voltage arrayAnd interphase measuring current array；

The fitting module is configured to discretize a KVL equation between the fault point and the line at the protection end to obtain a KVL discretization equation, fit the measurement resistor and the measurement inductor with the minimum vertical section distance by using a plurality of groups of KVL discretization equations to obtain a measurement resistance value R and a measurement inductance value L of the fault point at the protection end, and then correct the measurement resistance value R and the measurement inductance value L to obtain a corrected resistance valueAnd correcting the inductance value；

A determination module configured to correct the resistance valueAnd correcting the inductance valueSubstituting the impedance characteristic complex plane to further judge whether the protection is operated.

10. An electronic device, comprising: at least one processor, and a memory communicatively coupled to the at least one processor, wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method of any of claims 1 to 8.

Technical Field

The invention belongs to the technical field of power grid relay protection, and particularly relates to a high-voltage outgoing line distance protection method and device based on vertical section minimum distance fitting.

Background

Since the 21 st century, the Chinese economy has been rapidly developed, the fossil fuel is greatly consumed, and the problems of environmental pollution and energy shortage are increasingly highlighted. On the seventh fifteen united nations congress, on day 22 of 9 and 2020, the government of China proposed: china will improve the autonomous contribution of the country, adopt more powerful policies and measures, strive for the carbon dioxide emission to reach the peak value 2030 years ago, strive for the carbon neutralization 2060 years ago. "to achieve the goal of carbon neutralization as early as possible, reducing the use of fossil fuels is critical. Wind power is used as clean renewable energy, the available energy is more than ten times of that of water power, and the wind power is an ideal energy for replacing traditional fossil fuels, so in recent years, the total installed capacity of wind power in China is rapidly increased.

Compared with other fans, the double-fed fan (DFIG) has the characteristics of variable-speed constant-frequency operation and high power generation efficiency, so that the DFIG is widely applied. However, when a sending line of a wind power plant with a double-fed fan has a short-circuit fault, the double-fed fan provides an alternating current component with a short-circuit current frequency of 35-65 Hz due to the frequency deviation characteristic of the double-fed fan, and the frequency in the range is too close to the power frequency and is difficult to filter, so that great influence is generated on the traditional line distance protection based on the power frequency fourier algorithm, the impedance of a fault point distance protection end is difficult to accurately calculate due to the influence of harmonic waves in the traditional distance protection, and then the rejection or misoperation is caused, and the protection performance is greatly reduced.

Disclosure of Invention

The invention provides a high-voltage outgoing line distance protection method and device based on vertical section minimum distance fitting, which are used for at least solving one of the technical problems that when a transmission line of a wind power plant provided with a double-fed air generator (DFIG) unit is short-circuited, short-circuit current contains 35-65 Hz alternating-current components which are difficult to filter, and the traditional distance protection based on a power frequency Fourier algorithm cannot accurately calculate short-circuit impedance to cause protection rejection or misoperation.

In a first aspect, the present invention provides a high voltage outgoing line distance protection method based on vertical segment minimum distance fitting, including: s1: after the novel distance protection starting criterion is started, the three-phase voltage of the fault phase is controlled on the basis of correctly selecting the fault phaseThree-phase currentSampling is carried out to obtain a three-phase voltage array of a fault phaseThree-phase current array of sum fault phase，Respectively represent a phase a, a phase b and a phase c; s2: to three-phase voltage arrayAnd three-phase current arrayFiltering the middle position origin moment to obtain a filtered three-phase voltage arrayThree-phase current array after filteringAnd according to the filtered three-phase current arrayCalculating to obtain a zero sequence current array(ii) a S3: three-phase voltage array based on filteringFiltered three-phase current arrayAnd zero sequence current arrayGround measurement voltage array required for calculating fault point distance protection end measurement impedanceGrounding measurement current arrayInter-phase measurement voltage arrayAnd interphase measuring current array(ii) a S4: between fault point and line at protection endDiscretizing the KVL equation to obtain a KVL discretization equation, fitting the minimum vertical section distance between the measuring resistor and the measuring inductor by using a plurality of groups of KVL discretization equations to obtain a measuring resistance value R and a measuring inductance value L of a fault point distance protection end, and correcting the measuring resistance value R and the measuring inductance value L to obtain a corrected resistance valueAnd correcting the inductance value(ii) a S5: will correct the resistance valueAnd correcting the inductance valueSubstituting the impedance characteristic complex plane to further judge whether the protection is operated.

In a second aspect, the present invention provides a high voltage outgoing line distance protection device based on vertical minimum distance fitting, including: the sampling module is configured to carry out three-phase voltage comparison on the fault phase on the basis of correctly selecting the fault phase after the novel distance protection starting criterion is startedThree-phase currentSampling is carried out to obtain a three-phase voltage array of a fault phaseThree-phase current array of sum fault phase，Respectively represent a phase, b phase and c phase(ii) a A filter module configured to apply a three-phase voltage arrayAnd three-phase current arrayFiltering the middle position origin moment to obtain a filtered three-phase voltage arrayThree-phase current array after filteringAnd according to the filtered three-phase current arrayCalculating to obtain a zero sequence current array(ii) a A calculation module configured to be based on the filtered three-phase voltage arrayFiltered three-phase current arrayAnd zero sequence current arrayGround measurement voltage array required for calculating fault point distance protection end measurement impedanceGrounding measurement current arrayInter-phase measurement voltage arrayAnd interphase measuring current array(ii) a The fitting module is configured to discretize a KVL equation between the fault point and the line at the protection end to obtain a KVL discretization equation, fit the measurement resistor and the measurement inductor with the minimum vertical section distance by using a plurality of groups of KVL discretization equations to obtain a measurement resistance value R and a measurement inductance value L of the fault point at the protection end, and then correct the measurement resistance value R and the measurement inductance value L to obtain a corrected resistance valueAnd correcting the inductance value(ii) a A determination module configured to correct the resistance valueAnd correcting the inductance valueSubstituting the impedance characteristic complex plane to further judge whether the protection is operated.

In a third aspect, an electronic device is provided, comprising: the device comprises at least one processor and a memory which is connected with the at least one processor in a communication mode, wherein the memory stores instructions which can be executed by the at least one processor, and the instructions are executed by the at least one processor so as to enable the at least one processor to execute the steps of the high-voltage outgoing line distance protection method based on vertical section minimum distance fitting according to any embodiment of the invention.

In a fourth aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, where the computer program comprises program instructions, which, when executed by a computer, cause the computer to perform the steps of the high voltage outgoing line distance protection method based on vertical segment minimum distance fitting according to any of the embodiments of the present invention.

The high-voltage outgoing line distance protection method and device based on the vertical section minimum distance fitting have the advantages that after the distance protection is started and the fault phase is correctly selected, sampling fault phase voltage, fault phase current and zero sequence current by adopting a protection terminal, filtering the sampled signals by using a middle-position origin moment, substituting each group of filtered electric quantity into a discretized line KVL differential equation to obtain a plurality of groups of line resistances and reactances reflecting the distance between the fault point and the protection terminal, and utilizing a vertical section minimum distance fitting algorithm, the reactance values and the resistance values are respectively calculated and processed to finally obtain a group of line reactance and resistance values reflecting the distance protection end of the fault point, thereby realizing no influence of harmonic interference introduced in the fault current, the method can accurately calculate the line impedance value of the fault point distance protection end, effectively prevent bad data interference and greatly improve the action reliability of distance protection of the wind power plant sending line provided with the double-fed fan unit.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

Fig. 1 is a flowchart of a high-voltage outgoing line distance protection method based on vertical minimum distance fitting according to an embodiment of the present invention;

fig. 2 is a topological diagram of a simulation model built on a PSCAD/EMTDC simulation platform according to an embodiment of the present invention;

FIG. 3 is a graph illustrating the determination of whether a start criterion is enabled according to an energy function according to an embodiment of the present invention;

FIG. 4 is a graph of measured impedance over a time window for an in-zone fault, according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of an impedance vector in the complex plane of the impedance characteristics for an in-zone fault according to an embodiment of the present invention;

FIG. 6 is a graph of measured impedance over a time window for an out-of-range fault, according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of the impedance vectors in the complex plane of the impedance characteristics for an out-of-band fault according to an embodiment of the present invention;

fig. 8 is a block diagram of a high-voltage outgoing line distance protection device based on vertical minimum distance fitting according to an embodiment of the present invention;

fig. 9 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, a flow chart of a high voltage outgoing line distance protection method based on vertical minimum distance fitting according to the present application is shown.

As shown in fig. 1, the high-voltage outgoing line distance protection method based on the vertical minimum distance fitting includes the following steps:

s1: after the novel distance protection starting criterion is started, the three-phase voltage of the fault phase is controlled on the basis of correctly selecting the fault phaseThree-phase currentSampling is carried out to obtain a three-phase voltage array of a fault phaseThree-phase current array of sum fault phase，Respectively, a phase, b phase and c phase.

In this embodiment, the starting criterion of the novel distance protection is as follows:

s101: three-phase voltage array for obtaining fault phase by samplingAnd (3) carrying out 4-layer db3 wavelet packet decomposition, wherein the algorithm formula of the wavelet packet decomposition is as follows:

（1）

in the formula (1), the reaction mixture is,、all are wavelet packet decomposition coefficients,for wavelet packet decomposition scale, taking=4, n is the frequency band,the time domain positions of the points in the signal,、low pass filter coefficients for wavelet packet decomposition and wavelet packet decomposition, respectivelyThe high-pass filter coefficients are used to,a wavelet packet decomposition coefficient with the decomposition scale of j-1 and the frequency band of n is the kth sampling point in the signal;

s102: constructing an energy function: （2）

in the formula (2), the reaction mixture is,is the wavelet mean square extreme value of the (n-1) th data point,the mean square extreme value of the wavelet of the nth data point is taken as the mean square extreme value of the wavelet;

is composed of（3）

In the formula (3), the reaction mixture is,defined as the maximum value of the sequence of values in parentheses;

s103: the voltage drop point, namely the starting point of the novel distance protection, is judged according to the numerical value of the energy function: （4）

s2: to three-phase voltage arrayAnd three-phase current arrayFiltering the middle position origin momentObtaining the filtered three-phase voltage arrayThree-phase current array after filteringAnd according to the filtered three-phase current arrayCalculating to obtain a zero sequence current array。

In this embodiment, the sampled three-phase voltage array isAnd three-phase current arrayAnd (3) carrying out median origin moment filtering treatment, which comprises the following specific steps:

s201: is selected to have a length ofSliding windows, i.e. selectionIn (1)The data form arrayWherein, in the step (A),，is in an arrayThe total number of elements, the elements in each array are arranged from small to big to obtain a new array；

S202: calculating the median of the new array, wherein the calculation method comprises the following steps: （5）

the median in the formula (5)Substitute primitive arrayOf (2) element(s)(ii) a According to the rule, the array is updated from i =1 to i = n-h-1N-h-1 elements of (A), so that an array is obtained；

S203: according to arraysTaking the length of the sliding window with the length of h to obtain an arrayWherein, in the step (A),calculating an arrayThe specific algorithm of the k-order origin moment is as follows: （6）

in the formula (6), the reaction mixture is,is an array ofTo middleOf a single elementTo the power of, will arrayIs/are as followsMoment of origin of orderReplacing the ith element of array Y；

According to the rule, the array is updated from i =1 to i = n-h-1N-h-1 elements in the array to obtain an arrayThis array of numbersNamely the final array after the median origin moment filtering.

The three-phase current filtering process is the same as the process, and is not repeated, and the finally obtained filtered three-phase current array is。

S3: three-phase voltage array based on filteringFiltered three-phase current arrayAnd zero sequence current arrayGround measurement voltage array required for calculating fault point distance protection end measurement impedanceGrounding measurement current arrayInter-phase measurement voltage arrayAnd interphase measuring current array。

In the embodiment, the three-phase voltage array after filtering is based onFiltered three-phase current arrayAnd zero sequence current arrayGround measurement voltage array required for calculating fault point distance protection end measurement impedanceGrounding measurement current arrayInter-phase measurement voltage arrayAnd interphase measuring current arrayThe specific method comprises the following steps:

（7）

in the formula (7), the reaction mixture is,、、respectively the filtered currents after the A phase sampling, the B phase sampling and the C phase sampling,andrespectively a three-phase voltage array of a certain fault phase after filtering and a three-phase voltage array of another fault phase after filtering,andrespectively a three-phase current array of a certain fault phase after filtering and a three-phase current array of another fault phase after filtering,is a zero sequence compensation coefficientThe calculation formula of (2) is as follows:

（8）

in the formula (8), the reaction mixture is,is the zero sequence impedance of the line per unit length,positive sequence impedance per unit length of lineIs the zero sequence impedance of the line per unit length,is the positive sequence impedance per unit length of the line.

S4: discretizing a KVL equation between a fault point and a line at a protection end to obtain a KVL discretization equation, performing minimum vertical section distance fitting on a measuring resistor and a measuring inductor by using a plurality of groups of KVL discretization equations to obtain a measuring resistance value R and a measuring inductance value L of the fault point at the protection end, and then correcting the measuring resistance value R and the measuring inductance value L to obtain a corrected resistance valueAnd correcting the inductance value。

In this embodiment, the KVL equation between the fault point and the line at the protection end is:

(9) or

Wherein R is the measured resistance value of the fault point far from the protection end, L is the measured inductance value of the fault point far from the protection end,array for measuring voltage for grounding in case of ground fault，Array for measuring current for grounding in case of ground fault，Array of interphase measuring voltages for the occurrence of an interphase short circuit，Measuring current for phase when phase short circuit occurs；

The discretization KVL equation between the fault point and the line at the protection end is as follows:

(10) or

Wherein R is the measured resistance value of the fault point far from the protection end, L is the measured inductance value of the fault point far from the protection end,in order to be able to sample the frequency,array for measuring voltage for grounding in case of ground faultTo (1) aA number of sample points are sampled at the time of sampling,array for measuring current for grounding in case of ground faultTo (1) aA number of sample points are sampled at the time of sampling,array of interphase measuring voltages for the occurrence of an interphase short circuitTo (1) aA number of sample points are sampled at the time of sampling,measuring current for phase when phase short circuit occursTo (1) aSampling points;

and performing vertical section minimum distance fitting solving on the obtained discretization differential equation and the obtained electric quantity arrays to obtain a measured resistance value R and a measured inductance value L of the fault point distance protection end, wherein the specific method is as follows:

s401: performing equivalent transformation on the formula (10) to obtain a formula (11);

（11）

order to，，Then the equation becomes equation (12);

（12）

s402: defining a distance accumulation function as shown in formula (13);

（13）

the function is expressed as all discrete points to a fitted straight lineThe sum of squares of the vertical distances is solved R, L to minimize the sum of squares of the distances, i.e., to complete a R, L minimum distance fit for the vertical segment.

Distance accumulationThe function calculates the partial derivatives for R and L respectively, and makes the partial derivatives to be 0, namely （14）

Solving the formula (14) to obtain the R and L values obtained by the vertical minimum distance fitting algorithm, as shown in the formula (15):

（15）

in the formula (15), the reaction mixture is,，，，，。 （16）

s5: will correct the resistance valueAnd correcting the inductance valueSubstituting the impedance characteristic complex plane to further judge whether the protection is operated.

In this embodiment, since parameters such as resistance and inductance are related to factors such as the line length, the line radius, and the ambient temperature, the calculated R, L fitting value needs to be further modified, and the modified expression is:

（17）

in the formula (17), the compound represented by the formula (I),in order to correct the resistance value, the resistance value is corrected,for correcting the inductance value, R is the measured resistance value of the fault point away from the protection end, L is the measured inductance value of the fault point away from the protection end,is at the temperature of the surroundings and is,as the length of the transmission line,for the self-geometric spacing of cylindrical wires, take，In order to be a temperature coefficient of the temperature,is the radius of the wire;

converting the corrected inductance value into a line reactance value, wherein the conversion formula is as follows:

（18）

line reactance value to be calculatedSubstituting into the conventional impedance characteristic plane, if the impedance vector is in the impedance characteristic plane, determining that the impedance vector is in the forward regionAnd when a fault occurs, the protection acts, otherwise, the protection does not act.

To sum up, in the method of this embodiment, after the distance protection is started and the fault phase is correctly selected, the protection terminal is used to sample the fault phase voltage, the fault phase current and the zero sequence current, the sampled signals are subjected to middle-position origin moment filtering, then each group of filtered electric quantity is substituted into the discretization line KVL differential equation to obtain a plurality of groups of line resistances and reactances reflecting the fault point and the distance protection terminal, and a vertical minimum distance fitting algorithm is used, the reactance values and the resistance values are respectively calculated and processed to finally obtain a group of line reactance and resistance values reflecting the distance protection end of the fault point, thereby realizing no influence of harmonic interference introduced in the fault current, the method can accurately calculate the line impedance value of the fault point distance protection end, effectively prevent bad data interference and greatly improve the action reliability of distance protection of the wind power plant sending line provided with the double-fed fan unit.

Please refer to fig. 2, which shows a topological diagram of a simulation model built on a PSCAD/EMTDC simulation platform according to the present application.

As shown in fig. 2, the specific parameters of the model are as follows: the equivalent DFIG wind power unit is formed by equivalent 60 DFIG wind power units of 1.5 MW, the line length is 150 km, and the positive sequence impedance isZero sequence impedance ofZero sequence compensation coefficient K =1.9999, sampling frequencyAt 2.4 kHz, the sliding sampling window is h =20 data points, i.e. 1 ms. And the adaptability of the novel distance protection is analyzed by combining two scenes of the intra-area metal ground fault and the outer-area metal ground fault.

The first embodiment is as follows: at time 1 s, phase a metallic ground fault was present in the zone (10%, 15 km).

First, sampling a phase electricity4 layers of wavelet packet transformation are performed, and an energy function is calculated by the formula (1) and the formula (4). As can be seen from fig. 3, near the time of 1 s, the threshold of the energy function is higher than 0.2, which satisfies the starting criterion condition, and the novel distance protection scheme is started. Then sampling the A-phase voltage and the three-phase current of the fault phase, filtering the middle-position origin moment, and calculating to obtain a ground measurement voltage array required by calculating and measuring impedanceOr measuring voltage array between phasesGrounding measurement current arrayOr measuring current array between phasesAnd zero sequence current array. Then, the calculated data is substituted into the formula (7) and the formula (15) to obtain the measured resistance value R and the measured inductance value L, the measured resistance value R and the measured inductance value L are corrected by the formula (17), and finally, the inductance value is corrected by the formula (18)Conversion to line reactance valueTo obtain=2.3 Ω，=5.87 Ω, impedance Z =6.3 Ω, and corrected resistance valueAnd line reactance valueThe impedance calculated by the traditional distance protection algorithm oscillates around a true value due to the frequency deviation of the short-circuit current, the oscillation triggers the locking of distance protection oscillation, and the protection is unreliable, while the impedance calculated by the novel distance protection algorithm provided by the invention is not influenced by the frequency deviation, is rapidly stable within 3 ms, and protects a correct outlet, as can be seen from the illustration of the drawing and fig. 4. Will correct the resistance valueAnd line reactance valueSubstituting into the complex plane of impedance characteristics as shown in fig. 5. As can be seen from fig. 5, the impedance vector is within the impedance characteristic circle, protecting proper action.

Example two: at time 1 s, phase a metallic ground fault out of zone (90%, 135 km).

Similar to the procedure in example one, the calculated corrected resistance=21.438 Ω，=50.6499 Ω, impedance Z =55.0149 Ω, and correction resistanceAnd line reactance valueAs shown in the drawing description FIG. 6, it can be seen from the drawing description FIG. 6 that the impedance calculated by the conventional distance protection algorithm oscillates around the true value due to the frequency shift of the short-circuit current, and the oscillation will causeThe distance protection oscillation is locked, so that the protection is unreliable, and the impedance calculated by the novel distance protection algorithm provided by the invention is not influenced by frequency deviation, is rapidly stable within 3 ms, and protects a correct outlet. The resistance Rr and the reactance Xr are substituted into the impedance characteristic complex plane as shown in fig. 7. As can be seen from fig. 7, the impedance vector is outside the impedance characteristic circle, protecting the impedance.

In conclusion, when the novel distance protection scheme for solving the impedance of the fault point distance protection end based on the vertical section minimum distance fitting algorithm is applied to the sending-out line of the wind power plant with the double-fed fan unit, compared with the traditional distance protection scheme, the novel distance protection scheme is not influenced by the short-circuit current frequency deviation characteristic of the double-fed fan unit, the distance between the fault point and the protection end can be accurately reflected, in addition, the measured impedance can be rapidly stabilized within 3 ms, the oscillation locking is prevented, and therefore the correct outlet of protection is guaranteed.

Referring to fig. 8, a block diagram of a high voltage outgoing line distance protection device based on vertical minimum distance fitting according to the present application is shown.

As shown in fig. 8, the high voltage outgoing line distance protection apparatus 600 includes a sampling module 610, a filtering module 620, a calculating module 630, a fitting module 640, and a determining module 650.

Wherein, the sampling module 610 is configured to start the novel distance protection starting criterion and then carry out three-phase voltage comparison on the fault phase on the basis of correctly selecting the fault phaseThree-phase currentSampling is carried out to obtain a three-phase voltage array of a fault phaseThree-phase current array of sum fault phase，Respectively represent a phase a, a phase b and a phase c; a filtering module 620 configured to apply a three-phase voltage arrayAnd three-phase current arrayFiltering the middle position origin moment to obtain a filtered three-phase voltage arrayThree-phase current array after filteringAnd according to the filtered three-phase current arrayCalculating to obtain a zero sequence current array(ii) a A calculation module 630 configured to filter based three-phase voltage arrayFiltered three-phase current arrayAnd zero sequence current arrayGround measurement voltage array required for calculating fault point distance protection end measurement impedanceGrounding measurement current arrayInter-phase measurement voltage arrayAnd interphase measuring current array(ii) a The fitting module 640 is configured to discretize a KVL equation between the fault point and the line at the protection end, so that a KVL discretization equation is obtained, perform minimum vertical distance fitting on the measurement resistor and the measurement inductor by using multiple groups of KVL discretization equations, obtain a measurement resistance value R and a measurement inductance value L of the fault point and the protection end, and then correct the measurement resistance value R and the measurement inductance value L so that a corrected resistance value is obtainedAnd correcting the inductance value(ii) a A determination module 650 configured to correct the resistance valueAnd correcting the inductance valueSubstituting the impedance characteristic complex plane to further judge whether the protection is operated.

It should be understood that the modules recited in fig. 8 correspond to various steps in the method described with reference to fig. 1. Thus, the operations and features described above for the method and the corresponding technical effects are also applicable to the modules in fig. 8, and are not described again here.

In other embodiments, an embodiment of the present invention further provides a computer-readable storage medium, where computer-executable instructions are stored, and the computer-executable instructions may execute the high-voltage outgoing line distance protection method based on vertical minimum distance fitting in any of the above method embodiments;

as one embodiment, the computer-readable storage medium of the present invention stores computer-executable instructions configured to:

after the novel distance protection starting criterion is started, the three-phase voltage of the fault phase is controlled on the basis of correctly selecting the fault phaseThree-phase currentSampling is carried out to obtain a three-phase voltage array of a fault phaseThree-phase current array of sum fault phase，Respectively represent a phase a, a phase b and a phase c;

to three-phase voltage arrayAnd three-phase current arrayFiltering the middle position origin moment to obtain a filtered three-phase voltage arrayThree-phase current array after filteringAnd according to the filtered three-phase current arrayCalculating to obtain a zero sequence current array；

Three-phase voltage array based on filteringFiltered three-phase current arrayAnd zero sequence current arrayGround measurement voltage array required for calculating fault point distance protection end measurement impedanceGrounding measurement current arrayInter-phase measurement voltage arrayAnd interphase measuring current array；

Discretizing a KVL equation between a fault point and a line at a protection end to obtain a KVL discretization equation, performing minimum vertical section distance fitting on a measuring resistor and a measuring inductor by using a plurality of groups of KVL discretization equations to obtain a measuring resistance value R and a measuring inductance value L of the fault point at the protection end, and then correcting the measuring resistance value R and the measuring inductance value L to obtain a corrected resistance valueAnd correcting the inductance value；

Will correct the resistance valueAnd correcting the inductance valueSubstituting the new impedance characteristic to judge whether the protection is operated.

The computer-readable storage medium may include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function; the storage data area may store data created according to the use of the high voltage transmission line distance protection device, and the like. Further, the computer-readable storage medium may include high speed random access memory, and may also include memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some embodiments, the computer readable storage medium optionally includes a memory remotely located from the processor, and these remote memories may be connected to the high voltage feeder distance protection device over a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.

Fig. 9 is a schematic structural diagram of an electronic device according to an embodiment of the present invention, and as shown in fig. 9, the electronic device includes: a processor 710 and a memory 720. The electronic device may further include: an input device 730 and an output device 740. The processor 710, the memory 720, the input device 730, and the output device 740 may be connected by a bus or other means, such as the bus connection in fig. 9. The memory 720 is a computer-readable storage medium as described above. The processor 710 executes the nonvolatile software program, instructions and modules stored in the memory 720, so as to execute various functional applications and data processing of the server, that is, implement the high-voltage outgoing line distance protection method based on vertical minimum distance fitting of the above method embodiment. The input device 730 may receive input numeric or character information and generate key signal inputs related to user settings and function control of the high voltage transmission line distance protection device. The output device 740 may include a display device such as a display screen.

The electronic device can execute the method provided by the embodiment of the invention, and has the corresponding functional modules and beneficial effects of the execution method. For technical details that are not described in detail in this embodiment, reference may be made to the method provided by the embodiment of the present invention.

As an embodiment, the electronic device is applied to a high-voltage outgoing line distance protection device for a client, and includes: at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor to cause the at least one processor to:

after the novel distance protection starting criterion is started, the three-phase voltage of the fault phase is controlled on the basis of correctly selecting the fault phaseThree-phase currentSampling is carried out to obtain a three-phase voltage array of a fault phaseThree-phase current array of sum fault phase，Respectively represent a phase a, a phase b and a phase c;

to three-phase voltage arrayAnd three-phase current arrayFiltering the middle position origin moment to obtain a filtered three-phase voltage arrayThree-phase current array after filteringAnd according to the filtered three-phase current arrayCalculating to obtain a zero sequence current array；

Three-phase voltage array based on filteringFiltered three-phase current arrayAnd zero sequence current arrayGround measurement voltage array required for calculating fault point distance protection end measurement impedanceGrounding measurement current arrayInter-phase measurement voltage arrayAnd interphase measuring current array；

Discretizing a KVL equation between the fault point and the line at the protection end to obtain a KVL discretization equation, and fitting the minimum vertical distance between the measured resistance and the measured inductance by using a plurality of groups of KVL discretization equations to obtain the fault pointMeasuring resistance R and inductance L of the protective end at the barrier point distance, and then correcting the resistance R and the inductance L to correct the resistanceAnd correcting the inductance value；

Will correct the resistance valueAnd correcting the inductance valueSubstituting the new impedance characteristic to judge whether the protection is operated.

Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium, such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods of the various embodiments or some parts of the embodiments.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.