A new energy gathering and delivering system line protection method and system

Abstract

The present application relates to a kind of new energy gathering and sending system line protection method and system, belong to the technical field of power system relay protection, solve the existing wind farm high-frequency transient model inaccuracy, gathering line is difficult to quickly and reliably identify the problem of failure.It includes the following steps: collecting the voltage and current of any one gathering line protection installation place and each wind turbine port after failure, and then obtaining the high-frequency impedance of the gathering line protection installation place and each wind turbine port;Based on the high-frequency impedance of the gathering line protection installation place and each wind turbine port, the high-frequency impedance coefficient of the gathering line protection installation place and each wind turbine port is obtained;Based on the high-frequency impedance coefficient of the gathering line protection installation place and each wind turbine port and fault identification criterion, determine whether the gathering line has internal fault, if so, then start the protection action of the gathering line.

Description

Technical Field

[0001] This invention relates to the field of power system relay protection technology, and in particular to a method and system for protecting lines in a new energy collection and transmission system. Background Technology

[0002] Wind turbines exhibit weak feedback characteristics during faults, and their fault transient properties are complex and difficult to characterize. Rapid adjustments in power electronic device control methods and topologies, as well as rapid changes in the operating structure and control strategies of renewable energy sources, all affect the fault characteristics during line faults, impacting the safe operation of wind farms and increasing the probability of accidents. Therefore, researching line protection schemes suitable for renewable energy integration systems to achieve rapid and reliable fault isolation is of great significance for the safe and stable operation of wind power transmission systems.

[0003] Based on the electrical information used to construct protection criteria, existing wind farm collection line protection schemes can be categorized into line protection based on time-domain electrical information and line protection based on frequency-domain electrical information. The time-domain electrical information-based line protection method constructs protection criteria using model parameter identification or waveform characteristics based on time-domain electrical information collected at the protection installation location. However, due to the weak feedback characteristic of renewable energy sources, traditional protection based on power frequency fault electrical quantities cannot fully meet the relay protection requirements of power systems connected to renewable energy generator sets. The frequency-domain electrical information-based collection line protection method extracts the frequency-domain characteristics of the electrical quantities collected at both ends of the line using Fourier transform, wavelet transform, and other methods to construct protection criteria. This method can be used for relay protection of power systems connected to renewable energy generator sets, but it still suffers from inaccurate high-frequency transient models of wind farms and difficulties in quickly and reliably identifying faults in collection lines. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a method and system for protecting the lines of a new energy collection and transmission system, in order to solve the problem that the existing high-frequency transient model of wind farms is inaccurate and that it is difficult to quickly and reliably identify faults in the collection lines.

[0005] On one hand, embodiments of the present invention provide a line protection method for a new energy collection and transmission system, comprising the following steps:

[0006] After a fault, the voltage and current of any collection line protection installation point and each wind turbine port on it are collected, and then the high-frequency impedance of the collection line protection installation point and each wind turbine port on it is obtained.

[0007] Based on the high-frequency impedance of the installation location of the combined line protection and the ports of each wind turbine on it, the high-frequency impedance coefficient of the installation location of the combined line protection and the ports of each wind turbine on it is obtained.

[0008] Based on the high-frequency impedance coefficients and fault identification criteria of the protection installation point of the collection line and the ports of each wind turbine on it, it is determined whether a fault has occurred in the area of ​​the collection line. If so, the protection action of the collection line is activated.

[0009] Furthermore, the high-frequency impedance coefficients of any i-th collection line protection installation point and each wind turbine port thereon are obtained in the following way:

[0010]

[0011] In the formula, S gij S represents the high-frequency impedance coefficient at the port of the j-th wind turbine on the i-th collection line. mi Z represents the high-frequency impedance coefficient at the end protection installation point of the i-th collection line. gij,h (s) represents the equivalent high-frequency impedance measurement value of the port of the j-th wind turbine on the i-th collection line at the h-th sampling point in the frequency domain; Z i,h (s) represents the equivalent high-frequency impedance measurement value at the h-th sampling point of the end protection installation location of the i-th collecting line in the frequency domain, Z. Tij (s) represents the transformer equivalent impedance of the j-th wind turbine on the i-th collection line in the frequency domain, Z DFIGij (s) represents the equivalent impedance of the j-th wind turbine on the i-th collecting line in the frequency domain, Z i1 (s) represents the line impedance between the first wind turbine and the bus on the i-th collection line in the frequency domain, H represents the total number of sampling points, and n represents the total number of wind turbines on each collection line.

[0012] Furthermore, the equivalent high-frequency impedance measurement Z of the j-th wind turbine port on the i-th collection line in the frequency domain at the h-th sampling point is... gij,h (s) is represented as:

[0013]

[0014] In the formula, U gij,h (s), I gij,h (s) represents the high-frequency voltage and high-frequency current sampled values ​​at the h-th sampling point on the j-th wind turbine port of the i-th collection line in the frequency domain;

[0015] The equivalent high-frequency impedance measurement value Z at the h-th sampling point of the end protection installation location of the i-th collecting line in the frequency domain. i,h (s) is represented as:

[0016]

[0017] In the formula, U i,h (s), I i,h(s) represents the high-frequency voltage and high-frequency current sampled values ​​at the h-th sampling point of the end protection installation location of the i-th collection line in the frequency domain.

[0018] Furthermore, the fault identification criteria include:

[0019]

[0020] In the formula, S gijset S represents the high-frequency impedance threshold value at the port of the j-th wind turbine on the i-th collection line. miset This represents the high-frequency impedance coefficient threshold value at the end protection installation point of the i-th collection line.

[0021] If the high-frequency resistance coefficient S of the i-th collecting line mi And the high-frequency resistivity S of all the fans on it gij If all fault identification criteria are met, the fault is determined to have occurred in the i-th collection line area; otherwise, it is determined to be another fault.

[0022] Furthermore, if the fault is determined to be another type, then

[0023] If the high-frequency resistance coefficient S of the i-th collecting line mi It meets the fault identification criteria, and the high-frequency resistance coefficient S of all its fans is... gij If the fault identification criteria are not met, it is determined that a fault has occurred inside the fan connected to the i-th collection line, and the protection of that collection line will not operate.

[0024] If the high-frequency resistance coefficient S of the i-th collection line mi The fault identification criteria are not met, and the high-frequency resistance coefficient S of all the fans on it is... gij If all fault identification criteria are met, it is determined that a fault has occurred in any of the other collection lines or sending lines except for the i-th one, and the protection of that collection line will not operate.

[0025] Furthermore, if a fault occurs within the aggregation line area, the protection action of that aggregation line will be activated, and the following will be executed:

[0026] Send a circuit breaker signal to the circuit breaker of the collection line.

[0027] Furthermore, the high-frequency impedance threshold value S at the port of the j-th wind turbine on the i-th collection line... gijset The threshold value of the high-frequency impedance coefficient at the end protection installation point of the i-th collection line is set to 50. miset Set it to 30.

[0028] On the other hand, embodiments of the present invention provide a line protection system for a new energy collection and transmission system, comprising:

[0029] The data acquisition module is used to collect the voltage and current of any collection line protection installation point and each wind turbine port after a fault, and then obtain the high-frequency impedance of the collection line protection installation point and each wind turbine port.

[0030] The high-frequency impedance coefficient calculation module is used to obtain the high-frequency impedance coefficient of the installation point of the collection line protection and the ports of each wind turbine on it based on the high-frequency impedance of the installation point of the collection line protection and the ports of each wind turbine on it.

[0031] The fault identification and protection action module is used to determine whether an intra-area fault has occurred in the collection line based on the high-frequency impedance coefficient of the protection installation point of the collection line and the ports of each wind turbine on it and the fault identification criteria. If so, the protection action of the collection line is activated.

[0032] Furthermore, the high-frequency impedance coefficient calculation module obtains the high-frequency impedance coefficient of any i-th collection line protection installation point and the ports of each wind turbine on it in the following manner:

[0033]

[0034] In the formula, S gij S represents the high-frequency impedance coefficient at the port of the j-th wind turbine on the i-th collection line. mi Z represents the high-frequency impedance coefficient at the end protection installation point of the i-th collection line. gij,h (s) represents the equivalent high-frequency impedance measurement value of the port of the j-th wind turbine on the i-th collection line at the h-th sampling point in the frequency domain; Z i,h (s) represents the equivalent high-frequency impedance measurement value at the h-th sampling point of the end protection installation location of the i-th collecting line in the frequency domain, Z. Tij (s) represents the transformer equivalent impedance of the j-th wind turbine on the i-th collection line in the frequency domain, Z DFIGij (s) represents the equivalent impedance of the j-th wind turbine on the i-th collecting line in the frequency domain, Z i1 (s) represents the line impedance between the first wind turbine and the bus on the i-th collection line in the frequency domain, H represents the total number of sampling points, and n represents the total number of wind turbines on each collection line.

[0035] Furthermore, the equivalent high-frequency impedance measurement Z of the j-th wind turbine port on the i-th collection line in the frequency domain at the h-th sampling point is... gij,h (s) is represented as:

[0036]

[0037] In the formula, U gij,h (s), I gij,h (s) represents the high-frequency voltage and high-frequency current sampled values ​​at the h-th sampling point on the j-th wind turbine port of the i-th collection line in the frequency domain;

[0038] The equivalent high-frequency impedance measurement value Z at the h-th sampling point of the end protection installation location of the i-th collecting line in the frequency domain. i,h (s) is represented as:

[0039]

[0040] In the formula, U i,h (s), I i,h (s) represents the high-frequency voltage and high-frequency current sampled values ​​at the h-th sampling point of the end protection installation location of the i-th collection line in the frequency domain.

[0041] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0042] This invention provides a method and system for protecting lines in a new energy collection and transmission system. By acquiring the high-frequency impedance of the collection line and each wind turbine port on it, the corresponding high-frequency impedance coefficient is obtained. Then, based on the established fault identification criteria, it is determined whether any collection line has an intra-zone fault, achieving accurate identification of intra-zone and intra-zone faults. It also has high sensitivity to high-resistance faults occurring at the end of the line. When the dual-end protection devices exchange information, they transmit logical quantity information rather than electrical quantity information, which reduces the requirements for communication devices. Furthermore, it is not affected by the fault location and wind turbine control strategy, and can accurately identify intra-zone faults, which is more in line with engineering practice.

[0043] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0044] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0045] Figure 1 This is a flowchart illustrating a method for protecting the lines of a new energy collection and transmission system according to Embodiment 1 of the present invention.

[0046] Figure 2 This is the wiring diagram of a doubly fed wind farm provided in Embodiment 1 of the present invention;

[0047] Figure 3 This is the equivalent model of the doubly fed wind turbine provided in Embodiment 1 of the present invention;

[0048] Figure 4This is the wind field equivalent model provided in Embodiment 1 of the present invention;

[0049] Figure 5 This is the wind field model for an intra-regional fault provided in Embodiment 1 of the present invention;

[0050] Figure 6 This is the wind field model for a fault in the receiving-end AC system provided in Embodiment 1 of the present invention;

[0051] Figure 7 This is a wind field model for other collecting lines that fail, as provided in Embodiment 1 of the present invention.

[0052] Figure 8 This is the wind field model provided in Embodiment 1 of the present invention when a fault occurs on the low-pressure side of the wind turbine box transformer;

[0053] Figure 9(a) shows the S-type fault in phase A under different transition resistances in the area provided by Embodiment 3 of the present invention. m1 ;

[0054] Figure 9(b) shows the S-phase fault in phase A under different transition resistances in the area provided by Embodiment 3 of the present invention. g12 ;

[0055] Figure 9(c) shows the S-type fault in the region when there is a phase-to-phase fault with different transition resistances BC provided in Embodiment 3 of the present invention. m1 ;

[0056] Figure 9(d) shows the S-type fault in the region when there is a two-phase fault with different transition resistances BC provided in Embodiment 3 of the present invention. g12 ;

[0057] Figure 10(a) shows the S-phase faults occurring at different locations within the area when a single-phase ground fault of phase A occurs, as provided in Embodiment 3 of the present invention. m1 ;

[0058] Figure 10(b) shows the S-phase faults occurring at different locations within the area when a single-phase ground fault of phase A occurs, as provided in Embodiment 3 of the present invention. g12 ;

[0059] Figure 10(c) shows the S-type faults when two-phase ground faults (BC and PB) occur at different locations within the area, as provided in Embodiment 3 of the present invention. m1 ;

[0060] Figure 10(d) shows the S-axis of a two-phase ground fault (BC) occurring at different locations within the area, as provided in Embodiment 3 of the present invention. g12 ;

[0061] Figure 11(a) shows the S-shaped fault when a three-phase ground fault occurs at 50% of the transmission line according to Embodiment 3 of the present invention. m1 ;

[0062] Figure 11(b) shows the S-shaped fault when a three-phase ground fault occurs at 50% of the output line according to Embodiment 3 of the present invention. g12 ;

[0063] Figure 12(a) shows the S-phase fault when a single-phase ground fault of phase A occurs on the low-voltage side of the wind turbine transformer according to Embodiment 3 of the present invention. m1 ;

[0064] Figure 12(b) shows the S-phase fault when a single-phase ground fault of phase A occurs on the low-voltage side of the wind turbine transformer according to Embodiment 3 of the present invention. g12 . Detailed Implementation

[0065] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0066] Example 1

[0067] A specific embodiment of the present invention discloses a line protection method for a new energy collection and transmission system, such as... Figure 1 As shown, it includes the following steps:

[0068] S1. Collect the voltage and current at the installation point of any collection line protection after the fault and the ports of each wind turbine on it, and then obtain the high-frequency impedance of the installation point of the collection line protection and the ports of each wind turbine on it.

[0069] Specifically, current and voltage are collected using the current transformer at the end of the line protection installation point, and then high-frequency voltage and current are extracted using existing technologies. Based on the extracted high-frequency voltage and current, the high-frequency impedance of the line protection installation point and the ports of each wind turbine on it is obtained. The high-frequency frequency when extracting high-frequency voltage and high-frequency current is set according to actual needs.

[0070] S2. Based on the high-frequency impedance of the installation point of the collection line protection and the ports of each wind turbine on it, the high-frequency impedance coefficient of the installation point of the collection line protection and the ports of each wind turbine on it is obtained.

[0071] During implementation, in step S2, the high-frequency impedance coefficients of any i-th collection line protection installation point and each wind turbine port thereon are obtained in the following way:

[0072]

[0073] In the formula, S gij S represents the high-frequency impedance coefficient at the port of the j-th wind turbine on the i-th collection line. mi Z represents the high-frequency impedance coefficient at the end protection installation point of the i-th collection line. gij,h(s) represents the equivalent high-frequency impedance measurement value of the port of the j-th wind turbine on the i-th collection line at the h-th sampling point in the frequency domain; Z i,h (s) represents the equivalent high-frequency impedance measurement value at the h-th sampling point of the end protection installation location of the i-th collecting line in the frequency domain, Z. Tij (s) represents the transformer equivalent impedance of the j-th wind turbine on the i-th collection line in the frequency domain, Z DFIGij (s) represents the equivalent impedance of the j-th wind turbine on the i-th collecting line in the frequency domain, Z i1 (s) represents the line impedance between the first wind turbine and the bus on the i-th collection line in the frequency domain, H represents the total number of sampling points, and n represents the total number of wind turbines on each collection line.

[0074] Specifically, the equivalent high-frequency impedance measurement Z of the j-th wind turbine port on the i-th collection line in the frequency domain at the h-th sampling point. gij,h (s) is represented as:

[0075]

[0076] In the formula, U gij,h (s), I gij,h (s) represents the high-frequency voltage and high-frequency current sampled values ​​at the h-th sampling point on the j-th wind turbine port of the i-th collection line in the frequency domain;

[0077] The equivalent high-frequency impedance measurement value Z at the h-th sampling point of the end protection installation location of the i-th collecting line in the frequency domain. i,h (s) is represented as:

[0078]

[0079] In the formula, U i,h (s), I i,h (s) represents the high-frequency voltage and high-frequency current sampled values ​​at the h-th sampling point of the end protection installation location of the i-th collection line in the frequency domain.

[0080] S3. Based on the high-frequency impedance coefficient and fault identification criteria of the protection installation point of the collection line and the ports of each wind turbine on it, determine whether a fault has occurred in the area of ​​the collection line. If so, start the protection action of the collection line.

[0081] In implementation, step S3 includes the following fault identification criteria:

[0082]

[0083] In the formula, S gijset S represents the high-frequency impedance threshold value at the port of the j-th wind turbine on the i-th collection line. misetThis represents the high-frequency impedance coefficient threshold value at the end protection installation point of the i-th collection line.

[0084] If the high-frequency resistance coefficient S of the i-th collecting line mi The high-frequency resistivity S of all the fans and above gij If all fault identification criteria are met, the fault is determined to have occurred in the i-th collection line area; otherwise, it is determined to be another fault.

[0085] Preferably, if the fault is determined to be another type, then

[0086] If the high-frequency resistance coefficient S of the i-th collecting line mi The fault identification criteria are met, and the high-frequency resistivity S of all the fans is satisfied. gij If the fault identification criteria are not met, it is determined that a fault has occurred inside the fan connected to the i-th collection line, and the protection of that collection line will not operate.

[0087] If the high-frequency resistance coefficient S of the i-th collecting line mi The fault identification criteria are not met, and the high-frequency resistivity S of all the fans is not satisfied. gij If all fault identification criteria are met, it is determined that a fault has occurred in any of the other collection lines or sending lines except for the i-th one, and the protection of that collection line will not operate.

[0088] In practice, if a fault occurs within the collection line area, the protection action of that collection line will be activated, and the following will be executed:

[0089] Send a circuit breaker signal to the circuit breaker of the collection line.

[0090] Preferably, the high-frequency impedance coefficient threshold value S at the port of the j-th wind turbine on the i-th collecting line is... gijset The threshold value of the high-frequency impedance coefficient at the end protection installation point of the i-th collection line is set to 50. miset Set it to 30.

[0091] To facilitate a better understanding of the formation process of the solution in this embodiment by those skilled in the art, the following will be used as an example. Figure 2 Taking the doubly fed wind farm wiring diagram shown as an example, the working principle of a new energy collection and transmission system line protection method provided in this embodiment is explained as follows:

[0092] like Figure 2 As shown, a doubly-fed induction generator (DFIG) wind farm comprises m collection lines, which are connected in parallel. Each collection line is connected to n doubly-fed induction generators operating in parallel. Protection devices are installed at the ports of each collection line. ij Let i represent the j-th doubly-fed induction generator (DFIG) on the i-th collection line of the wind farm, where i = 1, ..., m, j = 1, ..., n. iCB is the current supplied by the i-th collecting line to the point of common connection (PCC) of the wind farm, i.e., the total feed current of the i-th collecting line. i The circuit breaker installed on the i-th collection line; the doubly fed fan and the box-type transformer are connected in a one-machine-one-transformer manner;

[0093] To obtain a detailed expression for the short-circuit current in a wind farm, it is first necessary to derive the relationship between the short-circuit current and the port voltage of a single wind turbine when a short-circuit fault occurs.

[0094] The voltage and flux linkage equations for a single DFIG unit in the wind farm in the dq coordinate system are as follows:

[0095]

[0096]

[0097] Where ω=ω1-ω r .

[0098] In the formula, ω1 represents the synchronous angular velocity, and ω represents the sum of the synchronous angular velocity ω1 and the rotor angular velocity ω. r The difference; L m L s L r These represent the equivalent magnetizing inductance, stator inductance, and rotor inductance, respectively. sd u sq Let d and q components, u, represent the stator voltage of the doubly-fed generator, respectively. rd u rq Let i represent the d and q components of the rotor voltage of the doubly-fed generator, respectively. sd i sq Let i represent the d and q components of the stator current of the doubly-fed generator, respectively. rd i rq Let d and q represent the rotor current components of the doubly-fed generator, respectively, and ψ sd ψ sq Let d and q be the stator flux linkages of the doubly-fed generator, respectively, and ψ be the d and q components. rd ψ rq Represent the d and q components of the rotor flux linkage of the doubly-fed generator, respectively, and R s R represents the stator-side resistance. r This indicates the rotor-side resistance.

[0099] Considering the time scale of the control loop, the outer loop control can be ignored during the fault transient process, and the given reference value is continuously output. Only the doubly-fed induction generator (DFIG) current loop control loop is considered:

[0100]

[0101] in,

[0102]

[0103] In the formula, These represent the d-axis and q-axis reference values ​​of the rotor voltage of the doubly-fed generator, respectively. rdref i rqref These represent the d-axis and q-axis reference values ​​of the rotor current, respectively, and k p k i These represent the proportional coefficient and integral coefficient on the rotor side of the doubly-fed generator, respectively.

[0104] By combining equations (12) to (15), we can obtain the relationship between the port voltage and the short-circuit current when a single wind turbine experiences a short-circuit fault:

[0105]

[0106] in,

[0107] α1=L r +R r τ s +k p τ s

[0108] α2=R r +k i τ s +k p

[0109]

[0110]

[0111]

[0112]

[0113] In the formula, U sd U sq Representing the d-axis and q-axis components of the fan port voltage, respectively, i s0d i s0q Represent the d-axis and q-axis components of the grid-side current caused by the voltage drop at the wind turbine port, respectively. ss1d i ss1q Let i represent the d-axis and q-axis components of the first grid-side current caused by grid-side converter control, respectively. sr1d i sr1q These represent the d-axis and q-axis components of the first grid-side current caused by rotor-side converter control, respectively; i ss2d i ss2q Let d and q axis components of the second grid-side current caused by grid-side converter control be represented respectively, in the time domain as a function of time constant τ'. s Attenuation; iss3d i ss3q Let d and q axis components of the third grid-side current caused by grid-side converter control be represented respectively, in the time domain as a function of time constant τ. r 'attenuation; i sr2d i sr2q Let L represent the d-axis and q-axis components of the second grid-side current caused by the rotor-side converter control, respectively, in the time domain as a function of the time constant L. r τ' s / α1 decay; i sr3d i sr3q i sr3d Let L represent the d-axis and q-axis components of the third grid-side current caused by the rotor-side converter control, respectively, in the time domain as a function of the time constant L. r τ' s / α2 decay.

[0114] In equation (16), each short-circuit current fault component is expressed as follows:

[0115]

[0116]

[0117]

[0118]

[0119]

[0120]

[0121]

[0122]

[0123]

[0124]

[0125]

[0126]

[0127] in,

[0128] α3=(R r +k p )ω1τ s +ωL r (1-σ)

[0129]

[0130] In the formula, k represents the voltage drop degree, u s0 This indicates the voltage at the wind turbine's port before the fault.

[0131] When a power grid fault occurs, the voltage phase angle will change abruptly. At this time, the PLL control system cannot perfectly track the power grid phase angle, meaning the output reference value will deviate from the actual power grid phase angle. Considering the dynamic error of the phase-locked loop (PLL), i.e., using the actual PLL output phase angle instead of the synchronization speed when calculating the short-circuit current, as shown in the following equation:

[0132]

[0133] In the formula, k pll-p k pll-i These represent the proportional coefficient and integral coefficient of the phase-locked loop control element, respectively.

[0134] By combining equations (16) and (18) and applying the Parker transformation, we can obtain the relationship between fault current and port voltage in the abc three-phase coordinate system.

[0135] I g (s)=U g (s) / Z g +I μ (s) (19)

[0136] In the formula, I g U represents the feed current of the doubly fed wind turbine. g Z represents the port voltage of the doubly fed wind turbine. g I represents the equivalent impedance of a doubly-fed wind turbine. μ This represents the equivalent current inside the doubly fed fan caused by the control loop during a fault, and its value is independent of the port voltage.

[0137] As shown in equation (19), a doubly fed wind turbine can be equivalently represented as a current source connected in parallel with an impedance. Therefore, the equivalent model of a single doubly fed wind turbine is as follows: Figure 3 As shown.

[0138] Combination Figure 2 and Figure 3 This allows us to obtain a model of the doubly fed wind field, such as... Figure 4 As shown. Figure 4 middle, I gij U gij I μij Z Tij Z DFIGij Z represents the feed current, port voltage, equivalent current source, transformer equivalent impedance, and equivalent impedance of the j-th doubly-fed wind turbine on the i-th collecting line, respectively; T Z represents the impedance value of the main transformer in the wind farm. S This is the equivalent impedance of the AC system.

[0139] Based on equations (5) and (19), and s=jω f Substitute and extract the high-frequency ω f By using coefficients of the same degree, the equivalent impedance expression for a single doubly-fed wind turbine can be obtained as follows:

[0140]

[0141] In the formula, c7, c6, c5, c4, c3, c2, c1, c0, d6, d5, d4, d3, d2, d1, and d0 are constants calculated based on the parameters of each component on the wind farm side of the transmission line, and c7, c6, and d6 are all greater than zero.

[0142] From equation (20), the inductance expression for a single doubly fed wind turbine is:

[0143]

[0144] Besides considering the impact of the doubly-fed induction generator (DFIG) impedance characteristics, it is also necessary to ensure a sufficiently large high-frequency component to facilitate fault detection both inside and outside the fault zone. Given that the transient high-frequency component under fault conditions is much larger than that under normal operation, the selected high-frequency component should also have a sufficiently large value during normal operation. The DFIG converter is based on pulse-width modulation (PWM) control, and its harmonic frequency is 6kHz. w ±1(k w =1,2,...) harmonics, combined with equation (21), the frequency band ω when the rectifier side impedance is inductive and capacitive can be obtained. DFIGL ω DFIGC They are respectively:

[0145]

[0146]

[0147] In the formula, ω 3.1 ω 3.2 ω 3.3 ω 3.4 for Nonnegative solutions; ω 4.1 ω 4.2 ω 4.3 for The nonnegative solution.

[0148] Comparing equations (22) and (23), it can be seen that, compared to the capacitive frequency band, the frequency range when the fault transient impedance of a doubly fed wind turbine is inductive is wider, containing a larger frequency band (angular frequency of 6kHz). wThe frequency band of ±1)*100πrad / s overlaps more with the inductive frequency band. To avoid problems such as changes in the system's equivalent impedance properties or excessively small high-frequency component amplitudes due to changes in system control parameters, this embodiment extracts appropriate high-frequency components and uses a fault component network composed of inductive impedance to construct the protection principle. The analysis process is as follows:

[0149] (1) When a fault occurs in the collection line within the area.

[0150] Taking the protection device at the first converging line as an example, when a fault occurs in the line between the j-th wind turbine and the (j+1)-th wind turbine of the first converging line, the high-frequency model of the wind farm is as follows: Figure 5 As shown. Figure 5 In the middle, R f k is the transition resistance at the fault location. f I represents the percentage of the fault location. s It feeds current to the AC system.

[0151] according to Figure 5 It can be seen that the voltage and current measured at the installation point of the first collection line protection satisfy the following relationship:

[0152]

[0153] In the formula, U PCC U is the voltage value at point PCC. s This refers to the AC system voltage value.

[0154] At this time, the voltage and current measured at the protection installation point of the first collecting line meet the following requirements:

[0155]

[0156] In the formula, U1(s) and I1(s) represent the voltage and current measured at the installation point of the first collecting line protection in the frequency domain.

[0157] As can be seen from the above, when the first collection line experiences an in-zone fault, the equivalent high-frequency impedance calculated based on the measured value at its protection installation location satisfies equation (25).

[0158] For the (j+1)th to the nth wind turbines on the first collecting line, their port voltages and short-circuit currents satisfy the following relationship:

[0159]

[0160] In the formula, Z 1(j+1) This represents the line impedance between the (j+1)th wind turbine and the jth wind turbine on the first collection line.

[0161] For the first to j wind turbines on the first collection line, their port voltages and short-circuit currents satisfy the following relationship:

[0162]

[0163] From equation (27), it can be seen that when a fault occurs within the area of ​​the first collection line, the port voltage and short-circuit current of the first to nth wind turbines on the first collection line all satisfy:

[0164]

[0165] In the formula, v = 1, ..., n.

[0166] As can be seen from the above, when the first collection line experiences an in-zone fault, the equivalent high-frequency impedance calculated based on the measured values ​​of each wind turbine port on it all satisfies equation (28).

[0167] Based on the same derivation process, when a fault occurs within the zone on the i-th collecting line, the equivalent high-frequency impedance calculated from the measured value at the protection installation location of that collecting line satisfies the following formula:

[0168]

[0169] When a fault occurs in the area on the i-th collection line, the equivalent high-frequency impedance calculated based on the measured values ​​at the ports of each wind turbine on that collection line satisfies the following formula:

[0170]

[0171] (2) When the transmission line or AC system malfunctions.

[0172] When a fault occurs in the wind farm's transmission line or receiving-end AC system, the wind farm's high-frequency model structure is as follows: Figure 6 As shown.

[0173] Depend on Figure 6 It can be seen that the voltage and current measured at the installation point of the first collection line protection satisfy the following relationship:

[0174]

[0175] At this point, we have:

[0176]

[0177] As can be seen from the above, when the wind farm's transmission line or receiving AC system fails, the equivalent high-frequency impedance calculated based on the measured values ​​at its protection installation location does not satisfy equation (29).

[0178] For the first to nth wind turbines on the first collecting line, their port voltages and short-circuit currents (via transformer) satisfy the following relationship:

[0179]

[0180] As can be seen from equation (33), when the wind farm's transmission line or receiving-end AC system fails, the port voltage and short-circuit current of the first to nth wind turbines on the first collection line all satisfy the following:

[0181]

[0182] As can be seen from the above, when the wind farm's transmission line fails, the equivalent high-frequency impedance calculated based on the measured values ​​of each wind turbine port satisfies equation (30).

[0183] Based on the same derivation process, it can be seen that when the wind farm's transmission line or receiving-end AC system fails, the equivalent high-frequency impedance calculated from the measured value at the protection installation point of any collection line does not satisfy equation (29), while the equivalent high-frequency impedance calculated from the measured values ​​at each wind turbine port satisfies equation (30).

[0184] (3) When a fault occurs on other collection lines

[0185] When a fault occurs on other collection lines of the wind farm, the high-frequency model structure of the wind farm is as follows: Figure 7 As shown.

[0186] Depend on Figure 7 It can be seen that the voltage and current measured at the installation point of the first collection line protection satisfy the following relationship:

[0187]

[0188] At this point, we have:

[0189]

[0190] As can be seen from the above, when other collecting lines in the wind farm fail, the equivalent high-frequency impedance calculated based on the measured value at the end of the first collecting line does not satisfy equation (29).

[0191] For the first to the nth wind turbines on the fault collection line, their port voltages and short-circuit currents satisfy the following relationship:

[0192]

[0193] From equation (37), it can be seen that when other collection lines fail, for the first to the nth wind turbines on the first collection line, their port voltage and short-circuit current all satisfy:

[0194]

[0195] As can be seen from the above, when other collection lines fail, the equivalent high-frequency impedance calculated based on the measured values ​​of each fan port on the first collection line satisfies equation (30).

[0196] Based on the same derivation process, it can be seen that when any one of the collection lines fails, the equivalent high-frequency impedance calculated from the measured value at the protection installation point of any collection line other than that collection line does not satisfy equation (29), while the equivalent high-frequency impedance calculated from the measured value at each wind turbine port satisfies equation (30).

[0197] (4) When a fault occurs on the low-voltage side of the fan box of the collection line.

[0198] When the j-th wind turbine on the first collection line of the wind farm fails, the high-frequency model structure of the wind farm is as follows: Figure 8 As shown.

[0199] Depend on Figure 8 It can be seen that the voltage and current measured at the installation point of the first collection line protection satisfy the following relationship:

[0200]

[0201] At this point, we have:

[0202]

[0203] As can be seen from the above, when the wind turbine on the first collection line fails, the equivalent high-frequency impedance calculated based on the measured value at the end of the first collection line does not satisfy equation (29).

[0204] For the j-th fan that has a fault on the collection line, its port voltage and short-circuit current satisfy the following relationship:

[0205]

[0206] From equation (41), it can be seen that when a fan on the collection line fails, the port voltage and short-circuit current of the failed fan satisfy the following:

[0207]

[0208] As can be seen from the above, when a fan on the collection line fails, the equivalent high-frequency impedance calculated based on the measured value at the port of the failed fan does not satisfy equation (30).

[0209] Based on the same derivation process, it can be seen that when a fan on the i-th collection line fails, the equivalent high-frequency impedance calculated from the measured value at the end of the collection line does not satisfy equation (29), and the equivalent high-frequency impedance calculated from the measured value at each fan port does not satisfy equation (30).

[0210] Based on the above analysis, when a fault occurs in any of the collection lines, the equivalent high-frequency impedance measured at its protection installation point differs significantly from the calculated value of equation (32), while the equivalent high-frequency impedance measured at each fan port differs less significantly from the calculated value of equation (34). When a fault occurs in the back-side system of the collection line protection device, the equivalent high-frequency impedance measured at the protection installation point of any collection line differs less significantly from the calculated value of equation (32), while the equivalent high-frequency impedance measured at each fan port differs less significantly from the calculated value of equation (34). When a fault occurs in a fan within this collection line, the equivalent high-frequency impedance measured at the protection installation point differs less significantly from the calculated value of equation (32), while the equivalent high-frequency impedance measured at each fan port differs significantly from the calculated value of equation (34).

[0211] Therefore, in this embodiment, fault identification of the collection line is performed by measuring the high-frequency impedance coefficients at the end protection installation point of any collection line and at each wind turbine port, as shown below:

[0212]

[0213] In the formula, S gij S represents the high-frequency impedance coefficient at the port of the j-th wind turbine on the i-th collection line. mi Z represents the high-frequency impedance coefficient at the end protection installation point of the i-th collection line. gij,h (s) represents the equivalent high-frequency impedance measurement value of the port of the j-th wind turbine on the i-th collection line at the h-th sampling point in the frequency domain; Z i,h (s) represents the equivalent high-frequency impedance measurement value at the h-th sampling point of the end protection installation location of the i-th collecting line in the frequency domain, Z. Tij (s) represents the transformer equivalent impedance of the j-th wind turbine on the i-th collection line in the frequency domain, Z DFIGij (s) represents the equivalent impedance of the j-th wind turbine on the i-th collecting line in the frequency domain, Z i1 (s) represents the line impedance between the first wind turbine and the bus on the i-th collection line in the frequency domain, H represents the total number of sampling points, and n represents the total number of wind turbines on each collection line.

[0214] Specifically, the equivalent high-frequency impedance measurement Z of the j-th wind turbine port on the i-th collection line in the frequency domain at the h-th sampling point. gij,h (s) is represented as:

[0215]

[0216] In the formula, U gij,h (s), I gij,h (s) represents the high-frequency voltage and high-frequency current sampled values ​​at the h-th sampling point on the j-th wind turbine port of the i-th collection line in the frequency domain;

[0217] The equivalent high-frequency impedance measurement value Z at the h-th sampling point of the end protection installation location of the i-th collecting line in the frequency domain. i,h (s) is represented as:

[0218]

[0219] In the formula, U i,h (s), I i,h (s) represents the high-frequency voltage and high-frequency current sampled values ​​at the h-th sampling point of the end protection installation location of the i-th collection line in the frequency domain.

[0220] In summary, the fault identification criteria can be constructed as follows:

[0221]

[0222] In the formula, S gijset S represents the high-frequency impedance threshold value at the port of the j-th wind turbine on the i-th collection line. miset This represents the high-frequency impedance coefficient threshold value at the end protection installation point of the i-th collection line.

[0223] If the high-frequency resistance coefficient S of the i-th collecting line mi And the high-frequency resistivity S of all the fans on it gij If all fault identification criteria are met, the fault is determined to have occurred in the area of ​​the i-th collection line; otherwise, it is determined to be another fault.

[0224] Preferably, if the fault is determined to be another type, then

[0225] If the high-frequency resistance coefficient S of the i-th collecting line mi It meets the fault identification criteria, and the high-frequency resistance coefficient S of all its fans is... gij If the fault identification criteria are not met, it is determined that a fault has occurred inside the fan connected to the i-th collection line, and the protection of that collection line will not operate.

[0226] If the high-frequency resistance coefficient S of the i-th collecting line mi The fault identification criteria are not met, and the high-frequency resistance coefficient S of all the fans on it is... gij If all fault identification criteria are met, it is determined that a fault has occurred in any of the other collection lines or sending lines except for the i-th one, and the protection of that collection line will not operate.

[0227] In practice, if a fault occurs within the collection line area, the protection action of that collection line will be activated, and the following will be executed:

[0228] Send a circuit breaker signal to the circuit breaker of the collection line.

[0229] Preferably, in this embodiment, considering the influence of factors such as measurement errors, the high-frequency impedance coefficient threshold value S at the port of the j-th wind turbine on the i-th collection line is... gijset The threshold value of the high-frequency impedance coefficient at the end protection installation point of the i-th collection line is set to 50. miset Set it to 30.

[0230] Understandably, this embodiment analyzes the wind farm topology under different fault locations based on the high-frequency fault model of doubly-fed induction generator (DFIG) wind turbines, establishes a high-frequency equivalent model of wind farm faults, and accurately characterizes the transient characteristics of multi-unit grid connection in DFIG wind farms. Furthermore, based on the differences in network structure under different fault scenarios, a protection criterion based on high-frequency impedance coefficient is constructed, enabling accurate fault identification within any convergence line area.

[0231] Compared with existing technologies, this embodiment provides a line protection method for a new energy collection and transmission system. By acquiring the high-frequency impedance of the collection line and each wind turbine port on it, the corresponding high-frequency impedance coefficient is obtained. Then, based on the established fault identification criteria, it is determined whether any collection line has an intra-zone fault, achieving accurate identification of intra-zone and intra-zone faults. It also has high sensitivity to high-resistance faults occurring at the end of the line. When the dual-end protection devices exchange information, they transmit logical quantity information rather than electrical quantity information, which reduces the requirements for communication devices. Furthermore, it is not affected by the fault location and wind turbine control strategy, and can accurately identify intra-zone faults, which is more in line with engineering practice.

[0232] Example 2

[0233] A specific embodiment of the present invention discloses a line protection system for a new energy collection and transmission system, comprising:

[0234] The data acquisition module is used to collect the voltage and current of any collection line protection installation point and each wind turbine port after a fault, and then obtain the high-frequency impedance of the collection line protection installation point and each wind turbine port.

[0235] The high-frequency impedance coefficient calculation module is used to obtain the high-frequency impedance coefficient of the installation point of the collection line protection and the ports of each wind turbine on it based on the high-frequency impedance of the installation point of the collection line protection and the ports of each wind turbine on it.

[0236] The fault identification and protection action module is used to determine whether a fault has occurred in the collection line based on the high-frequency impedance coefficient of the collection line protection installation point and the ports of each wind turbine on it and the fault identification criteria. If so, the protection action of the collection line is activated.

[0237] In practice, the high-frequency impedance coefficient calculation module obtains the high-frequency impedance coefficient of any i-th collection line protection installation point and the ports of each wind turbine on it in the following way:

[0238]

[0239] In the formula, S gij S represents the high-frequency impedance coefficient at the port of the j-th wind turbine on the i-th collection line. mi Z represents the high-frequency impedance coefficient at the end protection installation point of the i-th collection line. gij,h (s) represents the equivalent high-frequency impedance measurement value of the port of the j-th wind turbine on the i-th collection line at the h-th sampling point in the frequency domain; Z i,h (s) represents the equivalent high-frequency impedance measurement value at the h-th sampling point of the end protection installation location of the i-th collecting line in the frequency domain, Z. Tij (s) represents the transformer equivalent impedance of the j-th wind turbine on the i-th collection line in the frequency domain, Z DFIGij (s) represents the equivalent impedance of the j-th wind turbine on the i-th collecting line in the frequency domain, Z i1 (s) represents the line impedance between the first wind turbine and the bus on the i-th collection line in the frequency domain, H represents the total number of sampling points, and n represents the total number of wind turbines on each collection line.

[0240] Specifically, the equivalent high-frequency impedance measurement Z of the j-th wind turbine port on the i-th collection line in the frequency domain at the h-th sampling point. gij,h (s) is represented as:

[0241]

[0242] In the formula, U gij,h (s), I gij,h (s) represents the high-frequency voltage and high-frequency current sampled values ​​at the h-th sampling point on the j-th wind turbine port of the i-th collection line in the frequency domain;

[0243] The equivalent high-frequency impedance measurement value Z at the h-th sampling point of the end protection installation location of the i-th collecting line in the frequency domain. i,h (s) is represented as:

[0244]

[0245] In the formula, U i,h (s), I i,h(s) represents the high-frequency voltage and high-frequency current sampled values ​​at the h-th sampling point of the end protection installation location of the i-th collection line in the frequency domain.

[0246] The specific implementation process of this invention can be found in the above method embodiments, and will not be repeated here.

[0247] Since this embodiment is based on the same principle as the above method embodiments, this system also has the corresponding technical effects of the above method embodiments.

[0248] Example 3

[0249] To verify the correctness of Embodiments 1 and 2 of the present invention, this embodiment conducts experimental verification of the solutions in the above embodiments. The system structure diagram used in this embodiment is as follows. Figure 2 As shown in Table 1, the main parameters of the wind field are as follows. This method selects the high-frequency components of voltage and current at 1150Hz, requiring a sampling rate of 10kHz.

[0250] Table 1 Main System Parameters

[0251]

[0252] Scenario 1 in this implementation is as follows: Taking the first collection line in the wind farm as an example, A-phase grounding fault, BC two-phase fault, and ABC three-phase grounding fault are set at 50% of the area of ​​the first collection line in the wind farm, with a transition resistance of 0 to 300Ω.

[0253] In the above fault scenarios, by extracting the high-frequency voltage and current measured at the protection installation point at the end of the collection line, and substituting the high-frequency current measured at each wind turbine port into the formula, the S value at the protection installation point under each fault condition can be obtained. m1 S g1v (In this embodiment, the second wind turbine on the first collecting line is taken as an example, namely S) g12 ),like Figures 9(a)-9(d) As shown.

[0254] Depend on Figures 9(a)-9(d) It can be seen that regardless of the type of failure, S m1 All are greater than the threshold value, S g12 All values ​​are less than the threshold value, indicating a fault in the convergence line within the area. As shown in Figures 9(a) and 9(b), when a phase A ground fault occurs, S... m1 It reaches its minimum value of 66.70 Ω at t = 9.8 ms and a transition resistance of 0 Ω; S g12 The transition resistance reaches its maximum value of 12.44 at t = 6.2 ms with a resistance of 225 Ω. As can be seen from Figures 9(c) and 9(d), when a phase-to-phase fault occurs between phases BC, S... m1It reaches its minimum value of 189.86 Ω at t = 9.5 ms and a transition resistance of 0 Ω; S g12 The transition resistance reaches its maximum value of 12.78 at t = 1.5 ms with a transition resistance of 300 Ω. It can be deduced that S... m1 The minimum value of S is greater than the threshold value. g1v The maximum values ​​are all less than the threshold value, satisfying S m1 >S m1set ,,S g1v g1vset Therefore, all of the above types of faults can be identified as faults within the area.

[0255] As can be seen from the above analysis, the method proposed in Example 1 can accurately identify the occurrence of faults in the area when faults occur in the collection line through different transition resistances, and has a strong ability to withstand high transition resistances.

[0256] Scenario 2 in this implementation involves setting up phase A ground fault and phase B / C two-phase ground fault at different locations within the first collection line area, with a transition resistance of 150Ω. The high-frequency impedance coefficient S measured at the protection installation point and each wind turbine port (taking the second wind turbine as an example) under this fault condition is... m1 S g1v ,like Figures 10(a)-10(d) As shown.

[0257] Depend on Figures 10(a)-10(d) It can be seen that under different fault types, S m1 All are greater than the threshold value, S g1v All are less than the threshold value. As can be seen from Figures 10(a) and 10(b), when a phase A ground fault occurs, S... m1 The minimum value of 79.20 is obtained when the fault occurs at t = 0.1 ms and 75% of the line is faulty; S g12 The maximum value of 11.97 is obtained when the fault occurs at t = 6.2 ms and 50% of the line is faulty. As can be seen from Figures 10(c) and 10(d), when a two-phase-to-ground fault (BC) occurs, S... m1 The minimum value of 73.4096 was obtained at t = 9.9 ms, when the fault occurred at 75% of the line. g12 At t = 1.2 ms, the fault occurs at 25% of the line, reaching its maximum value of 11.36. It can be deduced that S... m1 The minimum value of S is greater than the threshold value. g1v The maximum values ​​are all less than the threshold value, satisfying S m1 >S m1set S g1v g1vset Therefore, all of the above types of faults can be identified as faults within the area.

[0258] ​​The above analysis shows that this method can accurately identify faults within the area when faults are collected at different locations on the line, and it still has high sensitivity when the fault is at the end of the line.

[0259] Scenario 3 in this implementation is as follows: A three-phase ground fault occurs at 50% of the wind farm's transmission line, and the transition resistance varies from 0 to 300Ω. The high-frequency impedance coefficient S measured at the protection installation point and each wind turbine port (taking the second wind turbine as an example) under this fault condition is... m1 S g1v ,like Figures 11(a)-11(b) As shown.

[0260] As can be seen from Figures 11(a) and 11(b), when the outgoing line is faulty, S m1 and S g1v All are less than the threshold value. When a three-phase ground fault occurs on the transmitting line, S m1 It reaches its maximum value of 12.15 at t = 6.0 ms and a transition resistance of 75 Ω; S g12 The transition resistance reaches its maximum value of 14.18 at t = 9.7 ms and a value of 75 Ω. Therefore, S... m1 The maximum values ​​of all values ​​are less than the threshold value, S g1v The maximum values ​​are all less than the threshold value, which does not satisfy S. m1 >S m1set S g1v g1vset Therefore, all of the above types of faults can be identified as other faults, and the combined line protection will not operate.

[0261] Scenario 4 in this implementation is as follows: A single-phase ground fault (phase A) occurs on the line between the second wind turbine and the transformer substation on the first collection line, with the transition resistance varying from 0 to 300Ω. The high-frequency impedance coefficient S measured at the protection installation point and each wind turbine port (taking the second wind turbine as an example) under this fault condition is... m1 S g1v ,like Figures 12(a)-12(b) As shown.

[0262] Depend on Figures 12(a)-12(b) It can be seen that when the outgoing line fails, S m1 and S g1v All are greater than the threshold value. When a single-phase ground fault of phase A occurs in the line between the wind turbine and the transformer substation, S m1 It reaches its minimum value of 191.82 at t = 0.1 ms and a transition resistance of 150 Ω; S g12 It reaches its minimum value of 90.29 at t = 0.1 ms and a transition resistance of 300 Ω. Therefore, S... m1 The minimum value of S is greater than the threshold value. g1v The minimum value is greater than the threshold value, which does not satisfy S. m1 >S​m1set S g1v g1vset Therefore, all of the above types of faults can be identified as other faults, and the combined line protection will not operate.

[0263] The above analysis shows that when a fault occurs outside the collection line area via a different transition resistance, the protection can accurately identify it as another fault, and the collection line protection will not operate.

[0264] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0265] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.​

Claims

1. A method for line protection in a new energy collection and transmission system, characterized in that, Includes the following steps: After a fault, the voltage and current of any collection line protection installation point and each wind turbine port on it are collected, and then the high-frequency impedance of the collection line protection installation point and each wind turbine port on it is obtained. Based on the high-frequency impedance of the installation point of the collection line protection and the ports of each wind turbine on it, the high-frequency impedance coefficient of the installation point of the collection line protection and the ports of each wind turbine on it is obtained. Based on the high-frequency impedance coefficient and fault identification criteria of the protection installation point of the collection line and the ports of each wind turbine on it, it is determined whether a fault has occurred in the area of ​​the collection line. If so, the protection action of the collection line is activated. Any number can be obtained through the following methods. High-frequency impedance coefficients of the line protection installation point and the ports of each wind turbine on it: ； In the formula, Indicates the first The first convergence line High-frequency impedance coefficient of the typhoon generator port. Indicates the first The high-frequency impedance coefficient at the end protection installation point of the convergence line. In the frequency domain, the first The first convergence line Typhoon port at the The equivalent high-frequency impedance measurement value of each sampling point; In the frequency domain, the first The end protection installation point of the collection line is at the first The equivalent high-frequency impedance measurement value at each sampling point In the frequency domain, the first The first convergence line The transformer equivalent impedance of a typhoon generator In the frequency domain, the first The first convergence line The equivalent impedance of a typhoon generator. In the frequency domain, the first The line impedance between the first wind turbine and the busbar on the collection line. Indicates the total number of sampling points. This indicates the total number of fans on each collection line; The fault identification criteria include: ； In the formula, Indicates the first The first convergence line The high-frequency impedance threshold value of the typhoon turbine port. Indicates the first The threshold value of the high-frequency impedance coefficient at the end protection installation point of the line convergence line; If the first High-frequency resistance coefficient of the line Furthermore, the high-frequency resistivity of all the fans on it If all meet the fault identification criteria, then it is determined to be the fault. If a fault occurs within the collection line area, it is considered an other fault.

2. The method for line protection of a new energy collection and transmission system according to claim 1, characterized in that, The first in the frequency domain The first convergence line The typhoon turbine port is at the Equivalent high-frequency impedance measurement value at each sampling point Represented as; ； In the formula, , In the frequency domain, the first The first convergence line Typhoon port at the High-frequency voltage and high-frequency current sampled values ​​at each sampling point; The first in the frequency domain The end protection installation point of the collection line is at the first Equivalent high-frequency impedance measurement value at each sampling point Represented as: ； In the formula, , In the frequency domain, the first The end protection installation point of the collection line is at the first High-frequency voltage and high-frequency current sampling values ​​at each sampling point.

3. The method for line protection of a new energy collection and transmission system according to claim 2, characterized in that, If it is determined to be another type of fault, then If the first High-frequency resistance coefficient of the line It meets the fault identification criteria, and the high-frequency resistance coefficient of all its fans is... If the unevenness meets the fault identification criterion, then it is determined to be the fault of the first type. A fault occurs inside the fan connected to the collection line, and the protection of the collection line does not activate. If the first High-frequency resistance coefficient of the line The fault identification criteria are not met, and the high-frequency resistance coefficient of all the fans on it is... If all meet the fault identification criteria, then it is determined to be fault except for the first one. If a fault occurs in other collection lines or sending lines outside the designated area, the protection of that collection line will not operate.

4. The method for line protection of a new energy collection and transmission system according to claim 2, characterized in that, If a fault occurs within the collection line area, the protection action of that collection line will be activated, and the following will be executed: Send a circuit breaker signal to the circuit breaker of the collection line.

5. The method for line protection of a new energy collection and transmission system according to claim 2, characterized in that, The first The first convergence line High-frequency impedance threshold value of typhoon turbine port Set to 50, the first Setting the high-frequency impedance coefficient threshold value at the end protection installation point of the line. Set it to 30.

6. A line protection system for a new energy collection and transmission system, characterized in that, include: The data acquisition module is used to collect the voltage and current of any collection line protection installation point and each wind turbine port after a fault, and then obtain the high-frequency impedance of the collection line protection installation point and each wind turbine port. The high-frequency impedance coefficient calculation module is used to obtain the high-frequency impedance coefficient of the installation point of the collection line protection and the ports of each wind turbine on it based on the high-frequency impedance of the installation point of the collection line protection and the ports of each wind turbine on it. The fault identification and protection action module is used to determine whether a fault has occurred in the area of ​​the collection line based on the high-frequency impedance coefficient of the protection installation point of the collection line and the ports of each wind turbine on it and the fault identification criteria. If so, the protection action of the collection line is activated. The high-frequency impedance coefficient calculation module obtains any number of values ​​in the following manner. The high-frequency impedance coefficient of the line protection installation point and the ports of each wind turbine on it: ； In the formula, Indicates the first The first convergence line High-frequency impedance coefficient of the typhoon turbine port. Indicates the first The high-frequency impedance coefficient at the end protection installation point of the convergence line. In the frequency domain, the first The first convergence line Typhoon port at the The equivalent high-frequency impedance measurement value of each sampling point; In the frequency domain, the first The end protection installation point of the collection line is at the first The equivalent high-frequency impedance measurement value at each sampling point In the frequency domain, the first The first convergence line The transformer equivalent impedance of a typhoon generator In the frequency domain, the first The first convergence line The equivalent impedance of a typhoon generator. In the frequency domain, the first The line impedance between the first wind turbine and the busbar on the collection line. Indicates the total number of sampling points. This indicates the total number of fans on each collection line; The fault identification criteria include: ； In the formula, Indicates the first The first convergence line The high-frequency impedance threshold value of the typhoon turbine port. Indicates the first The threshold value of the high-frequency impedance coefficient at the end protection installation point of the line convergence line; If the first High-frequency resistance coefficient of the line Furthermore, the high-frequency resistivity of all the fans on it If all meet the fault identification criteria, then it is determined to be the fault. If a fault occurs within the collection line area, it is considered an other fault.

7. The line protection system for a new energy collection and transmission system according to claim 6, characterized in that, The first in the frequency domain The first convergence line Typhoon port at the Equivalent high-frequency impedance measurement value at each sampling point Represented as; ； In the formula, , In the frequency domain, the first The first convergence line Typhoon port at the High-frequency voltage and high-frequency current sampled values ​​at each sampling point; The first in the frequency domain The end protection installation point of the collection line is at the first Equivalent high-frequency impedance measurement value at each sampling point Represented as: ； In the formula, , In the frequency domain, the first The end protection installation point of the collection line is at the first High-frequency voltage and high-frequency current sampling values ​​at each sampling point.

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