A flexible grounding active power distribution network single-phase grounding fault line selection method and system

Abstract

The application discloses a flexible grounding active power distribution network single-phase grounding fault line selection method and system, which comprises detection and protection starting, when a neutral point is connected with a small resistance R N Before investment, if the fault of the flexible grounding active power distribution network does not disappear, the line selection process is started: i. the neutral point is connected with the small resistance R N ; ii. the small resistance R N is extracted; iii. the zero sequence current of each feeder, the neutral line zero sequence current and the bus zero sequence voltage in one power frequency cycle before and after the small resistance R N is connected; iv. the ratio of the zero sequence admittance of each feeder to the neutral line zero sequence admittance before and after the small resistance R N is connected is calculated; v. the line selection analysis criterion is obtained. The application can accurately select the fault line, the line selection logic is simple, and the transition resistance resistance is strong.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power distribution network protection, in particular to a flexible grounding active power distribution network fault line selection method. BACKGROUND

[0002] The active power distribution network refers to a power distribution network with a large number of distributed power sources and bidirectional power flow. In the case of mixed grounding modes of the distributed power source grid-connected transformer, such as no grounding or grounding through a grid-connected small resistance, when a permanent single-phase grounding fault occurs in the power distribution network, the traditional fault line selection method of the power distribution network cannot be directly applied. Therefore, there is an urgent need in the art for a technical solution to accurately select the fault line to quickly remove the grounding fault, thereby solving the problems presented in the background technology. This technical innovation is crucial for improving power supply reliability and safe operation of the power system. SUMMARY

[0003] In view of the problems existing in the above-mentioned traditional technology, the present application aims to provide a flexible grounding active power distribution network single-phase grounding fault line selection method and system, which realizes the selection strategy for the line fault line containing the distributed power source according to the feeder zero sequence admittance and the neutral line inductive zero sequence admittance.

[0004] The present application realizes the following technical solutions:

[0005] In the first aspect, the present application provides a flexible grounding active power distribution network single-phase grounding fault line selection method, which comprises:

[0006] detecting the neutral line zero sequence current I n , and n if the neutral point zero sequence current I 0set is greater than the starting value I , the protection is started;

[0007] Before the neutral point parallel small resistance R N is put into operation, the flexible grounding active power distribution network fault has not disappeared, and the flexible grounding active power distribution network fault further contains busbar fault, line fault without distributed power source, line fault containing distributed power source, specifically, the line without distributed power source is a type I feeder, the line containing distributed power source and all of which are not grounded is a type II feeder, the line containing distributed power source and all of which are grounded through the grounding small resistance R DG of the distributed power source grid-connected transformer is a type III feeder, and the line in which the distributed power source is not grounded and the distributed power source is grounded through the small resistance R DG is a type IV feeder, and each type of feeder includes the type I feeder, the type II feeder, the type III feeder and the type IV feeder, which are collected at the busbar, and the line selection analysis process is started:

[0008] i. put in the neutral point parallel small resistance R N ;

[0009] ii. Extracting the parallel small resistance R N The zero sequence current of each feeder, the zero sequence current of neutral line and the zero sequence voltage of bus in the one power frequency cycle before and after the input;

[0010] iii. Calculating the parallel small resistance R N The parallel small resistance R is calculated according to the ratio of the zero sequence inductive admittance of neutral line to the zero sequence admittance of each feeder before the input N The ratio of the zero sequence admittance of each feeder to the zero sequence inductive admittance of neutral line before the input, and the parallel small resistance R N The parallel small resistance R is calculated according to the ratio of the zero sequence inductive admittance of neutral line to the zero sequence admittance of each feeder after the input N The ratio of the zero sequence admittance of each feeder to the zero sequence inductive admittance of neutral line after the input;

[0011] iv. The parallel small resistance R N The ratio of the zero sequence admittance of each feeder to the zero sequence inductive admittance of neutral line before and after the input, and the ratio amplitude multiplication coefficient of the zero sequence admittance of each feeder Wherein, Y' i-n Indicates the parallel small resistance R N After the input, the ratio of the zero sequence admittance of each feeder to the zero sequence inductive admittance of neutral line, Y i-n Indicates the parallel small resistance R N Before the input, the ratio of the zero sequence inductive admittance of each feeder to the zero sequence inductive admittance of neutral line;

[0012] v. According to the ratio amplitude multiplication coefficient of the zero sequence admittance of each feeder in the active distribution network as the line selection analysis criterion, k i >1 is the fault line, otherwise is the healthy line.

[0013] In some embodiments, in the step iii, the parallel small resistance R N The zero sequence inductive admittance of neutral line Y n The calculation method of the zero sequence admittance Y1, Y2, Y3, Y4 of each feeder is as follows:

[0014]

[0015] Wherein, Indicates the zero sequence current of each feeder, Indicates the zero sequence current of neutral line, Indicates the zero sequence voltage of bus, C1, C2, C3, C4 indicates the equivalent ground capacitance of each feeder, C 0∑ Indicates the sum of the equivalent ground capacitance of the system, x1, x2, x3 respectively indicates the number of distributed power sources with grounding through small resistance R DG on the feeder l1, l2, l3, and RDG represents the ground small resistance of the distributed power grid-connected transformer, v represents the arc suppression coil off-tuning compensation degree, j represents the imaginary number, ω represents the angular frequency, L s represents the ground small resistance of the distributed power grid-connected transformer, v represents the arc suppression coil off-tuning compensation degree, j represents the imaginary number, ω represents the angular frequency, L N represents the ground small resistance of the distributed power grid-connected transformer, v represents the arc suppression coil off-tuning compensation degree, j represents the imaginary number, ω represents the angular frequency, L

[0016] In some embodiments, in step iii, the parallel small resistance R N The ratio of the zero sequence admittance of each feeder before investment to the inductive zero sequence admittance of the neutral line Y 1-n , Y 2-n , Y 3-n , Y 4-n The calculation method is as follows:

[0017]

[0018] Wherein, Y n represents the parallel small resistance R N The inductive zero sequence admittance of the neutral line before investment.

[0019] In some embodiments, in step iii, the parallel small resistance R N The inductive zero sequence admittance of the neutral line Y n ′ after investment and the calculation method of the zero sequence admittance Y1′, Y2′, Y3′, Y4′ of each feeder are as follows:

[0020]

[0021] In some embodiments, in step iii, the parallel small resistance R N The ratio of the zero sequence admittance of each feeder to the inductive zero sequence admittance component of the neutral line Y′ 1-n , Y′ 2-n , Y′ 3-n , Y′ 4-n The expression is as follows:

[0022]

[0023] In some embodiments, in step iv, the ratio of the amplitude multiplication coefficient k1, k2, k3, k4 of each feeder zero sequence admittance is as follows:

[0024]

[0025] In the second aspect, the present application realizes a flexible grounding active power distribution network single-phase grounding fault line selection system for implementing the flexible grounding active power distribution network single-phase grounding fault line selection method in any embodiment, which includes a protection starting detection module and a line selection analysis module.

[0026] The protection start-up detection module is used to detect the neutral point zero-sequence current I. n At the neutral point, the zero-sequence current I n Greater than the startup value I 0set In this case, protection is activated;

[0027] The line selection analysis module is used to connect a small resistor R in parallel at the neutral point. N Before the flexible grounding active distribution network was put into operation, the faults had not disappeared. These faults further included bus faults, line faults without distributed generation, and line faults with distributed generation. Specifically, lines without distributed generation were classified as Class I feeders, lines with distributed generation and where none of the distributed generation sources were grounded were classified as Class II feeders, and lines with distributed generation sources and where all distributed generation sources were connected to the distributed generation grid-connected transformer had a grounding resistance R. DG The grounded line is a Class III feeder; the distributed power source is ungrounded and connected to the distributed power source via a small resistor R. DG The line with both grounding and current is a Class IV feeder. All feeders, including Class I, Class II, Class III, and Class IV feeders, converge at the busbar. The line selection analysis process begins here:

[0028] i. Connect a small resistor R in parallel at the neutral point. N ;

[0029] ii. Extract the parallel small resistor R N Zero-sequence current of each feeder, inductive zero-sequence current of the neutral line, and zero-sequence voltage of the busbar within one power frequency cycle before and after commissioning;

[0030] iii. Based on the parallel small resistor R N Before commissioning, calculate the zero-sequence admittance of the neutral line and each feeder, and connect the parallel small resistor R. N The ratio of the zero-sequence admittance of each feeder to the zero-sequence admittance of the neutral line before commissioning, and based on the parallel small resistor R N The zero-sequence admittance of the neutral line after commissioning is calculated, along with the zero-sequence admittance of each feeder, and the parallel small resistance R. N The ratio of the zero-sequence admittance of each feeder to the inductive zero-sequence admittance of the neutral line after commissioning;

[0031] iv. Based on the parallel small resistor R obtained in step iii N The ratios of zero-sequence admittance of each feeder to the inductive zero-sequence admittance of the neutral line before and after commissioning are calculated, and the amplitude multiplication factor of the zero-sequence admittance ratio of each feeder is calculated. Among them, Y′ i-n This indicates a small resistor R connected in parallel at the neutral point. N After commissioning, the ratio of the zero-sequence admittance of each feeder to the zero-sequence admittance of the neutral line, Y i-n This indicates a small resistor R connected in parallel at the neutral point. NThe ratio of the zero sequence admittance of each feeder to the inductive zero sequence admittance of the neutral line before input;

[0032] v. According to the zero sequence admittance ratio amplitude multiplication coefficient of each feeder in the active power distribution network as the line selection analysis criterion, k i >1 is a fault line, otherwise is a healthy line.

[0033] In a third aspect, the present application provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the flexible grounding active power distribution network single-phase grounding fault line selection method according to any one of the above embodiments when executing the computer program.

[0034] In a fourth aspect, the present application provides a non-transitory computer readable storage medium having a computer program stored thereon, wherein the computer program is executed by a processor to implement the flexible grounding active power distribution network single-phase grounding fault line selection method according to any one of the above embodiments.

[0035] Compared with the prior art, the present application has the following advantages:

[0036] The flexible grounding active power distribution network single-phase grounding fault line selection method can accurately select the fault line when the power distribution network has a permanent single-phase grounding fault, only needs to simply count the number of distributed power sources with small resistance grounding through the grid in each feeder, has simple line selection logic, and has strong resistance to transition resistance. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 Fig. 10 is a 10kV power distribution network topology structure diagram of an embodiment of the present application;

[0038] Figure 2 Fig. 9 is a flexible grounding active power distribution network single-phase grounding fault line selection method overall flowchart of the present application;

[0039] Figure 3 Fig. 8 is a flexible grounding active power distribution network single-phase grounding fault line selection system module diagram of the present application;

[0040] Figure 4 Fig. 7 is a zero sequence current diagram of each feeder and neutral line when a single-phase metallic grounding fault occurs at f;

[0041] Figure 5 Fig. 6 is a bus zero sequence voltage when a single-phase metallic grounding fault occurs at f. DETAILED DESCRIPTION

[0042] The technical solutions of the present application will be described in detail below in combination with the drawings and specific embodiments.

[0043] To enable those skilled in the art to better understand the present invention, a specific embodiment of the present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly describe the technical solution of the present invention.

[0044] This invention proposes a method for selecting the line of a single-phase grounding fault in a flexible grounded active distribution network. The faults in the flexible grounded active distribution network further include bus faults, line faults without distributed generation, and line faults containing distributed generation. Specifically, lines without distributed generation are classified as Class I feeders; lines containing distributed generation where none of the distributed generation sources are grounded are classified as Class II feeders; and lines containing distributed generation sources where all distributed generation sources are connected to the distributed generation grid-connected transformer have a grounding resistance R. DG The grounded line is a Class III feeder; the distributed power source is ungrounded and connected to the distributed power source via a small resistor R. DG The line that is simultaneously grounded is a Class IV feeder. All types of feeders include Class I, Class II, Class III, and Class IV feeders, which converge at the busbar.

[0045] like Figure 1 In the 10kV distribution network system topology shown in the embodiment of the present invention, there are four feeders: l1, l2, l3, and l4. Feeder l1 is a Class I feeder with no distributed generation. Feeder l2 is a Class II feeder with the neutral point of the distributed generation grid-connected transformer not grounded. Feeder l3 has a distributed generation grid-connected transformer connected to a small resistor R. DG (R DG =10Ω) grounding is a Class III feeder. One of the grid-connected transformers of the distributed power source on feeder l4 is not grounded, and the other grid-connected transformer is connected to a small resistor R. DG The grounding is a Class IV feeder, with L1, L2, L3, and L4 converging at the busbar. The system is designed to experience a permanent metallic single-phase ground fault at t = 0.2s, with a small resistor R connected in parallel at the neutral point. N (R N =10Ω) is put into operation at t=1.2s.

[0046] definition A small resistor R is connected in parallel at the neutral point. N The ratio of the zero-sequence admittance of each feeder i to the zero-sequence admittance of the neutral line before commissioning; A small resistor R is connected in parallel at the neutral point. N The ratio of the zero-sequence admittance of each feeder i to the inductive zero-sequence admittance component of the neutral line after commissioning. Y′ is the multiplier of the zero-sequence admittance ratio of each feeder; where Y′ i-n This indicates a small resistor R connected in parallel at the neutral point. N After commissioning, the ratio of the zero-sequence admittance to ground of each feeder relative to the neutral line, Yi-n This indicates a small resistor R connected in parallel at the neutral point. N Before commissioning, the ratio of zero-sequence admittance to ground of each feeder relative to the neutral line is given. i represents the feeder number, and i = 1, 2, 3, 4, and n refers to the neutral line of the system.

[0047] like Figure 2 As shown, this invention provides a flexible grounding active distribution network single-phase grounding fault location method, the specific implementation process of which is as follows:

[0048] Step 1: Detect the neutral point zero-sequence current I n Greater than the startup value I 0set When the protection is activated, if the small resistor R... N Before (10Ω) is connected, the neutral point zero-sequence current I n If the fault disappears and the system returns to normal, the line selection process ends; otherwise, continue to step 2.

[0049] Step 2: After determining that it is a permanent ground fault, connect a small parallel resistor R. N Simultaneously, the parallel small resistance R is sampled. N Zero-sequence current I of each feeder during the power frequency cycle prior to commissioning i0 (i represents the feeder type, i = 1, 2, 3, 4), the neutral zero-sequence current I0 and the bus zero-sequence voltage U0 are calculated, and the zero-sequence admittance to ground of the neutral line and each feeder is obtained from these, as expressed below:

[0050]

[0051] Among them, C i C represents the equivalent capacitance to ground of the i-th feeder. 0∑ R represents the sum of the system's equivalent capacitance to ground. x1, x2, and x3 represent the number of distributed power sources connected to ground via a small grid-connected resistor on feeders l1, l2, and l3, respectively. DG This represents the grounding resistance of the distributed power generation grid-connected transformer. This represents the detuning compensation degree of the arc suppression coil, typically ranging from -10% to -5%, indicating that the system is in an overcompensated state. j represents the imaginary number, ω represents the angular frequency, and L... s In the flexible grounding method, R N Parallel arc suppression coils.

[0052] Step 3: According to the formula Calculate the parallel small resistance R N The ratio Y of the zero-sequence admittance of each feeder to the zero-sequence admittance of the neutral line before commissioning 1-n Y 2-n Y 3-n Y 4-n The expression is as follows:

[0053]

[0054] Step 4: Parallel small resistance R N After that, the fast Fourier algorithm is used to obtain each outgoing line zero sequence current of a power frequency cycle after a delay of 0.05s Neutral line zero sequence current And bus zero sequence voltage Thus, the parallel small resistance R N After being put in, the zero sequence ground admittance of the neutral line and each feeder is expressed as follows:

[0055]

[0056] Step 5: According to the formula Calculate the parallel small resistance R N The ratio of the zero sequence admittance of each feeder to the inductive zero sequence admittance component of the neutral line after being put in:

[0057]

[0058] Step 6: According to the parallel small resistance R N The ratio of the zero sequence admittance of each feeder to the inductive zero sequence admittance component of the neutral line before and after being put in is used to calculate the amplitude multiplication coefficient of the zero sequence admittance ratio of each feeder

[0059]

[0060] According to the zero sequence admittance ratio amplitude multiplication coefficient of the type I feeder, type II feeder, type III feeder and type IV feeder in the active distribution network as the line selection analysis criterion,

[0061] k i > 1 is the fault line, otherwise it is a healthy line.

[0062] As shown in Figure 3 Fig. 1 is a flexible grounding active distribution network single-phase grounding fault line selection method according to the above embodiment of the present application.

[0063] Flexible grounding active distribution network single-phase grounding fault line selection system. The line selection system comprises a protection starting detection module and a line selection analysis module;

[0064] The protection starting detection module is used to detect the neutral point zero sequence current I n If the neutral point zero sequence current I n is greater than the starting value I 0set , the protection starts;

[0065] The line selection analysis module is used to when the neutral point parallel small resistance R NFlexible grounding active power distribution network fault before the input does not disappear, the flexible grounding active power distribution network fault further includes bus fault, line fault without distributed power supply, line fault with distributed power supply, specifically, the line without distributed power supply is the first type of feeder, the line with distributed power supply and the distributed power supply is not grounded is the second type of feeder, the line with distributed power supply and the distributed power supply is grounded through the grounding small resistance R DG The line with grounding is the third type of feeder, the distributed power supply is not grounded and the distributed power supply is grounded through the small resistance R DG The line with grounding at the same time is the fourth type of feeder, each type of feeder includes the first type of feeder, the second type of feeder, the third type of feeder and the fourth type of feeder, which are collected at the bus, and the line selection analysis process is started:

[0066] i. Input neutral point parallel small resistance R N ;

[0067] ii. Extract parallel small resistance R N The zero sequence current of each feeder, the neutral line zero sequence current and the bus zero sequence voltage in one power frequency cycle before / after the input;

[0068] iii. Calculate the parallel small resistance R N According to the zero sequence admittance of the neutral line and each feeder before the input N The ratio of the zero sequence admittance of each feeder to the neutral line before the input, and according to the parallel small resistance R N The zero sequence admittance of the neutral line and each feeder after the input N The ratio of the zero sequence admittance of each feeder to the neutral line after the input;

[0069] iv. According to the parallel small resistance R N Input before and after the input, the zero sequence admittance ratio of each feeder to the neutral line, calculate the zero sequence admittance ratio amplitude multiplication coefficient of each feeder Wherein, Y′ i-n Indicates the neutral point parallel small resistance R N After the input, the ratio of the zero sequence admittance of each feeder to the neutral line, Y i-n Indicates the neutral point parallel small resistance R N Before the input, the ratio of the zero sequence admittance of each feeder to the neutral line;

[0070] v. According to the zero sequence admittance ratio amplitude multiplication coefficient of each feeder in the active power distribution network as the line selection analysis criterion, k i > 1 is the fault line, otherwise it is a healthy line.

[0071] Combined with the topological structure as shown in Figure 1 The specific embodiments of the line selection method are described as follows:

[0072] Assumption: since the zero sequence admittance ratio amplitude multiplication factor of the feeder l1, l2, l3 is not more than 1, it is determined that the feeder l1, l2, l3 is a healthy line;

[0073] And, analyze the feeder l4:

[0074] Given R N = R DG = 10Ω, then

[0075]

[0076] Since the maximum ground capacitance current of a single line of the 10kV power distribution system is not more than 50A, the ground capacitance current of the system is generally not more than 200A. Therefore, ωC l4 ≤ 2.9mS, ωC 0Σ ≤ 11.6mS, -vωC 0Σ ≤ 1.16mS. The neutral point grounding resistance R N is 10Ω commonly used in engineering practice, then ω(C l4 -C 0Σ ) ≤ 4.06mS. And according to the premise condition, k4 and rounding. Therefore:

[0077]

[0078] Obviously, in the active power distribution network, the number of DGs (x1+x2+x3≥0) in each feeder l1, l2, l3 except the fault line under the small resistance grounding mode affects the value of k4, which also means that it affects the line selection criterion. For example:

[0079]

[0080] In this example, x1=x2=0, x3=1, k4≥1.99, that is, the zero sequence admittance ratio amplitude multiplication factor of the feeder l4 exceeds 1, which meets the line selection criterion, and the feeder l4 is determined as the fault line.

[0081] In addition, based on the similar inventive concept, the embodiment of the present application also provides an electronic device, which comprises a memory, a processor and a computer program stored in the memory and executable on the processor, and the processor implements the above method when executing the computer program.

[0082] In addition, based on the similar inventive concept, the embodiment of the present application also provides a non-transitory computer readable storage medium having a computer program stored thereon, and the computer program is executed by a processor to implement the above method.

[0083] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the flow Figure 1 The flow or flows and / or blocks Figure 1 The flow or flows and / or blocks

[0084] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flow Figure 1 The flow or flows and / or blocks Figure 1 The flow or flows and / or blocks

[0085] Modifications and variations can be made to the disclosed implementations without departing from the scope of the application. Any modifications, improvements, and variations that are based on the teachings of the application are to be considered within the scope of the application.

Claims

1. A flexible grounded active distribution network single-phase ground fault line selection method, characterized in that, The line selection method comprises: detecting the neutral line zero sequence current I n , if the neutral line zero sequence current I n is greater than a start value I 0set , the protection is started; When the neutral point is connected in parallel with a small resistance R N Before the flexible grounding active power distribution network fault disappears, the flexible grounding active power distribution network fault further includes bus fault, line fault without distributed power supply, line fault with distributed power supply, specifically, the line without distributed power supply is a type I feeder, the line with distributed power supply and the distributed power supply not grounded is a type II feeder, the line with distributed power supply and the distributed power supply grounded through a grounding small resistance R of a distributed power supply grid-connected transformer DG The line grounded is a type III feeder, the distributed power supply is not grounded and the distributed power supply is grounded through a small resistance R DG The line with the grounded distributed power supply simultaneously existing is a type IV feeder, and each type of feeder includes the type I feeder, the type II feeder, the type III feeder and the type IV feeder, which are collected at the bus, and a line selection analysis process is started: i. The neutral point is connected with a small resistance R N ; ii. Extract parallel small resistance R N The zero sequence current of each feeder, the zero sequence current of neutral line and the zero sequence voltage of bus in one power frequency cycle before / after input iii. Parallel small resistance R according to N The ratio of the zero sequence admittance of each feeder before the neutral line is put into operation to the zero sequence admittance of the neutral line, and the parallel small resistance R according to N The ratio of the zero sequence admittance of each feeder before the neutral line is put into operation to the zero sequence admittance of the neutral line, and the parallel small resistance R according to N The ratio of the zero sequence admittance of each feeder after the neutral line is put into operation to the zero sequence admittance of the neutral line, and the parallel small resistance R according to N The ratio of the zero sequence admittance of each feeder after the neutral line is put into operation to the zero sequence admittance of the neutral line, and the parallel small resistance R according to iv. parallel small resistance R obtained according to step iii N The ratio of the zero sequence admittance of each feeder to the inductive zero sequence admittance of the neutral line before and after the investment, and the amplitude multiplication coefficient of the zero sequence admittance ratio of each feeder , wherein, The parallel small resistance R of the neutral point is represented by N The ratio of the zero sequence admittance of each feeder to the inductive zero sequence admittance of the neutral line after the investment, The parallel small resistance R of the neutral point is represented by N The ratio of the zero sequence admittance of each feeder to the inductive zero sequence admittance of the neutral line before the investment; v. According to the zero sequence admittance ratio amplitude multiplication coefficient of each feeder in the active distribution network as the line selection analysis criterion, is a fault line, otherwise it is a healthy line.

2. The single-phase-to-ground fault line selection method for a flexible grounded active distribution network according to claim 1, wherein, In step iii, the small parallel resistance R N Pre-injection neutral inductive zero sequence admittance With each feeder zero sequence admittance , , , The calculation method is as follows: ; wherein, , , , represents the zero sequence current of each feeder, represents the neutral line zero sequence current, represents the bus zero sequence voltage, C1, C2, C3, C4 represent the equivalent ground capacitance of each feeder, C 0∑ represents the sum of the equivalent ground capacitance of the system, , , respectively represent the number of distributed power sources containing ground through small resistance R DG on the feeder l1, l2, l3, DG represents the ground small resistance of the distributed power grid-connected transformer, represents the arc suppression coil detuning compensation degree, represents an imaginary number, represents an angular frequency, represents the arc suppression coil in parallel with R N in the flexible grounding mode.

3. The single-phase-to-ground fault line selection method for a flexible grounded active distribution network according to claim 2, wherein, In step iii, the small parallel resistance R N The ratio of the zero sequence admittance of each feeder to the inductive zero sequence admittance of the neutral line before being put into operation 、 、 、 The calculation method is as follows: ; wherein, represents a small parallel resistance R N Pre-injection neutral inductive zero sequence admittance.

4. The single-phase-to-ground fault line selection method for a flexible grounded active distribution network according to claim 3, wherein, In step iii, the small parallel resistance R N The post-injection neutral inductive zero sequence admittance The zero sequence admittance of each feeder 、 、 、 The calculation method is as follows: 。 5. The single-phase-to-ground fault line selection method for a flexible grounded active distribution network according to claim 4, wherein, In step iii, the small parallel resistance R N The ratio of the zero sequence admittance of each feeder to the inductive zero sequence admittance component of the neutral line after energization 、 、 、 The expression is as follows: 。 6. The single-phase-to-ground fault line selection method for a flexible grounded active distribution network according to claim 5, wherein, In the step iv, the zero sequence admittance of each feeder is multiplied by the amplitude multiplication factor , , , The expression of the amplitude multiplication factor is as follows: 。 7. A flexible grounded active power distribution network single-phase-to-ground fault line selection system for implementing the method of any one of claims 1 to 6, characterized in that, The line selection system comprises a protection start detection module and a line selection analysis module; The protection starting detection module is configured to detect the neutral line zero sequence current I n In the case where the neutral line zero sequence current I n is greater than the starting value I 0set , the protection starts. The line selection analysis module is configured to, when the neutral point is connected in parallel with a small resistance R N If the flexible grounding active power distribution network fault does not disappear before being input, the flexible grounding active power distribution network fault further includes a bus fault, a line fault without a distributed power supply, a line fault with a distributed power supply, specifically, the line without a distributed power supply is a type I feeder, the line with a distributed power supply and the distributed power supply not grounded is a type II feeder, the line with a distributed power supply and the distributed power supply grounded through a grounding small resistance R of a distributed power supply grid-connected transformer DG The line grounded is a type III feeder, the distributed power supply is not grounded, and the distributed power supply is grounded through a small resistance R DG The line with the grounded distributed power supply simultaneously exists is a type IV feeder, and the various feeders include the type I feeder, the type II feeder, the type III feeder, and the type IV feeder, are collected at a bus, and a line selection analysis process is started: i. The neutral point is connected with a small resistance R N ; ii. Extract parallel small resistance R N The zero sequence current of each feeder, the zero sequence current of neutral line and the zero sequence voltage of bus in one power frequency cycle before / after input iii. Parallel small resistance R according to N The ratio of the zero sequence admittance of each feeder before the neutral line is put into operation to the zero sequence admittance of the neutral line, and the parallel small resistance R according to N The ratio of the zero sequence admittance of each feeder before the neutral line is put into operation to the zero sequence admittance of the neutral line, and the parallel small resistance R according to N The ratio of the zero sequence admittance of each feeder after the neutral line is put into operation to the zero sequence admittance of the neutral line, and the parallel small resistance R according to N The ratio of the zero sequence admittance of each feeder after the neutral line is put into operation to the zero sequence admittance of the neutral line. iv. parallel small resistance R obtained according to step iii N The ratio of the zero sequence admittance of each feeder to the inductive zero sequence admittance of the neutral line before and after the investment, and the amplitude multiplication coefficient of the zero sequence admittance ratio of each feeder wherein, indicates the parallel small resistance R of the neutral point N The ratio of the zero sequence admittance of each feeder to the inductive zero sequence admittance of the neutral line after the investment, indicates the parallel small resistance R of the neutral point N The ratio of the zero sequence admittance of each feeder to the inductive zero sequence admittance of the neutral line before the investment; v. According to the zero sequence admittance ratio amplitude multiplication coefficient of each feeder in the active distribution network as the line selection analysis criterion, is a fault line, otherwise it is a healthy line.

8. An electronic device, comprising: Comprise: The memory, the processor and the computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to realize the single-phase ground fault line selection method of the flexible grounding active power distribution network according to any one of claims 1-6.

9. A non-transitory computer-readable storage medium, comprising: The computer program is stored on the memory and executable on the processor, wherein the processor executes the computer program to realize the single-phase ground fault line selection method of the flexible grounding active power distribution network according to any one of claims 1-6.

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