Amplitude-phase coefficient-based Sagomean new energy base collection system pilot protection method

Abstract

The invention discloses an amplitude-phase coefficient-based Sagolig new energy base collection system pilot protection method, which comprises the following steps of: based on a Sagolig new energy base collection system, obtaining a collection line new energy side setting current and a collection line high-voltage direct current side setting current in a first sampling window so as to obtain an amplitude-phase coefficient setting value, acquiring a new energy side current of the collection line and a high-voltage direct-current side current of the collection line in a second sampling window to calculate an amplitude-phase coefficient; acquiring a pilot protection criterion of the collection system according to the amplitude-phase coefficient and the amplitude-phase coefficient setting value; according to the pilot protection criterion, identifying the fault type of the Sagomean new energy base collection system; and starting protection measures according to the fault type. The amplitude-phase coefficient-based Sagomean new energy base collection system pilot protection method provided by the invention has the advantages of reliable fault identification, full-line quick action when a fault occurs, high transition resistance and noise resistance and wide application range.

Description

Technical Field

[0001] The present invention relates to the technical field of grid-connected protection of new energy power supplies, and in particular to a longitudinal protection method for a Shagohuang new energy base collection system based on amplitude-phase coefficients. Background Art

[0002] The existing Shagohuang New Energy Base transmission system mainly adopts the grid-connected mode of AC collection and UHV DC transmission. In the AC collection outgoing line of the line commutated converter (LCC) where the new energy units are connected to the grid, both sides are power electronic power supplies, and the fault characteristics have undergone fundamental changes, resulting in a decrease in the sensitivity of traditional differential protection, and even refusal to operate. Therefore, it is urgent to study new protection principles applicable to the Shagohuang New Energy Base collection system.

[0003] At present, there are many research results on new protection principles that use the similarity of short-circuit current waveforms in the time domain of the transmission line, but the reliability of this type of protection in the Shagohuang New Energy Base Collection System has not yet been clarified. The measurement of waveform similarity mainly includes similarity measurement methods and distance measurement methods. The more commonly used similarity measurement methods currently include Pearson correlation coefficient and cosine similarity. However, the above two protection principles cannot distinguish faults when the new energy side has weak output or overlaps with permanent faults. The more commonly used distance measurement methods currently include Canberra distance and improved Euclidean distance. However, when a high-resistance fault occurs, the short-circuit current waveforms on both sides are very close, and the distance measurement method will refuse to operate. At the same time, the improved Euclidean distance requires the protection setting value to be re-adjusted in different systems, which is difficult. In summary, it is urgent to study new protection principles applicable to the Shagohuang New Energy Base Collection System. Summary of the invention

[0004] In order to solve the above-mentioned problems in the prior art, the present invention provides a longitudinal protection method for the Shagohuang new energy base collection system based on amplitude-phase coefficient, which has reliable fault identification, fast action of the entire line when a fault occurs, strong resistance to transition resistance and noise, and a wide range of applications.

[0005] In order to achieve the above-mentioned invention object, the present invention provides a longitudinal protection method for the Shagohuang new energy base collection system based on amplitude-phase coefficient, comprising the following steps:

[0006] Based on the Shagohuang new energy base collection system, in a first sampling window, a set current on the new energy side of the collection line and a set current on the high-voltage DC side of the collection line are obtained at a first sampling frequency, and in a second sampling window, a current on the new energy side of the collection line and a current on the high-voltage DC side of the collection line are obtained at a second sampling frequency; the duration of the first sampling window is the same as the duration of the second sampling window, and the first sampling frequency is the same as the second sampling frequency;

[0007] According to the setting current on the new energy side of the collection line and the setting current on the high-voltage DC side of the collection line, the amplitude and phase coefficient setting value of the Shagohuang new energy base collection system is obtained;

[0008] The amplitude-phase coefficient is calculated according to the current on the new energy side of the collection line and the current on the high-voltage DC side of the collection line; the amplitude-phase coefficient is:

[0009]

[0010] In the formula, F φ is the phase-amplitude coefficient of φ, φ is the phase of the three-phase electricity, φ is respectively taken as phase A, phase B, and phase C of the three-phase electricity, x φk is the kth current sampling value of the φ phase on the new energy side of the collection line, y φk The k-th current sampling value of the φ-phase on the high-voltage DC side of the collection line is inverted, k is the sampling point number in the second sampling window, and n is the total number of sampling points in the second sampling window;

[0011] Obtaining a criterion for longitudinal protection of a collection system according to the amplitude-phase coefficient and the amplitude-phase coefficient setting value;

[0012] Identify the fault type of the Shagohuang new energy base collection system according to the longitudinal protection criterion;

[0013] Initiate protective measures based on the type of fault described.

[0014] Furthermore, the longitudinal protection criterion of the collection system is:

[0015] F φ <F φset ;

[0016] In the formula, F φset is the setting value of the φ phase amplitude coefficient.

[0017] Furthermore, the step of obtaining the amplitude-phase coefficient setting value is:

[0018] Obtain the set current on the new energy side of the collection line, and obtain the set current on the high-voltage DC side of the collection line;

[0019] Substitute the set current on the new energy side of the collection line and the set current on the high-voltage DC side of the collection line into Formula 1; Formula 1 is:

[0020] F φset =λF φ ' set , 0.88≤λ≤0.98;

[0021]

[0022] In the formula, F φset is the setting value of the φ phase amplitude coefficient, λ is the total margin coefficient, F φ ' set is the amplitude-phase coefficient value of the setting current, I 1φi is the i-th set current of the φ-phase on the new energy side of the collection line, I 2φi is the i-th set current of the φ-phase on the high-voltage DC side of the collection line, i is the sampling point number in the first sampling window, and m is the total number of sampling points in the first sampling window;

[0023] Solve the formula 1 to obtain the amplitude-phase coefficient setting value.

[0024] Furthermore, the set current on the new energy side of the collection line is:

[0025]

[0026] In the formula, I 1φ The φ phase setting current on the new energy side of the collection line, I m is the current amplitude, ω is the power frequency angular frequency, t is the sampling time, is the initial phase angle of φ phase current, and θ1 is the phase angle error.

[0027] Furthermore, the set current on the high-voltage DC side of the collection line is:

[0028]

[0029] In the formula, I 2φ The φ phase setting current on the new energy side of the collection line, I m is the current amplitude, ω is the power frequency angular frequency, t is the sampling time, is the initial phase angle of φ phase current, and ε is the amplitude error.

[0030] Furthermore, the phase angle error has a value range of: -16°≤θ1≤16°.

[0031] Furthermore, the amplitude error has a value range of: ε≤10%.

[0032] Furthermore, the duration of the first sampling window is 10 ms to 20 ms.

[0033] Further, if the longitudinal protection criterion of the collection system is not established, it is determined that the φ phase of the collection system of the Shagohuang new energy base has no fault;

[0034] If the longitudinal protection criterion of the collection system is established, it is determined that the φ phase of the collection system of the Shagohuang New Energy Base is faulty.

[0035] Furthermore, the enabling protection measures include:

[0036] If a single-phase fault occurs, the faulty phase will be disconnected and the non-faulty phase will operate normally;

[0037] If a two-phase or three-phase fault occurs, the three phases are disconnected.

[0038] The beneficial effects of the present invention are:

[0039] 1. When a fault occurs in the collection line area, the protection can quickly and reliably identify the fault and realize rapid action of the entire line;

[0040] 2. The present invention has a strong ability to resist transition resistance and noise;

[0041] 3. The present invention is not affected by the capacity and operation mode of the new energy station, and can still reliably identify the fault when the new energy station has weak output or overlaps with a permanent fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic diagram of the process of the present invention;

[0043] Figure 2 This is the topological diagram of the Shagohuang new energy base collection system of the present invention;

[0044] Figure 3 The figure is a calculation value diagram of the amplitude-phase coefficient of the setting current considering the 16° phase angle error and the 10% amplitude error of the present invention;

[0045] Figure 4 Schematic diagram of amplitude-phase coefficient when different faults occur at the midpoint of the collecting line in an embodiment of the present invention: (a) is a single-phase short circuit grounding fault, (b) is a two-phase short circuit fault, (c) is a two-phase short circuit grounding fault, and (d) is a three-phase short circuit fault;

[0046] Figure 5 The performance of different protection methods when a phase A high-resistance grounding fault occurs at the midpoint K3 of the collecting line: (a) is the cosine similarity protection method, (b) is the Canberra distance protection method, (c) is the improved Euclidean distance protection method, and (d) is the Shagohuang new energy base collecting system longitudinal protection method based on amplitude-phase coefficient. DETAILED DESCRIPTION

[0047] In order to clearly illustrate the technical features of this solution, this solution is described below through a specific implementation method.

[0048] Aiming at the Shagohuang New Energy Base collection system, the fault characteristics of new energy power supply and high voltage direct current transmission are analyzed.

[0049] The analytical formula for the fault current of new energy power supply is:

[0050]

[0051]

[0052]

[0053] In the formula, i φ The fault current provided by the φ-phase new energy source, is the reference value of the d-axis current, is the reference value of q-axis current, is the initial phase angle of the φ phase current, ω is the PLL angular frequency, ω d is the damped oscillation frequency, ω n is the natural oscillation angular frequency, ξ is the damping ratio, i d0 is the d-axis current reference value before the fault, β is the damping angle;

[0054] It can be seen from the analytical formula of the fault current of the new energy power supply that, considering the response time of the phase-locked loop, the short-circuit current frequency may deviate from the power frequency. Limited by the current-carrying capacity of the converter, the fault current of the new energy power supply presents the fault characteristics of limited amplitude and frequency deviation.

[0055] The analytical formula of the current of high-voltage direct current transmission DC fed into the AC system is:

[0056] I rec =(k D A Di +k Y A Ym )∫U nr dt+(k D B Di +k Y B Ym )i d ;

[0057] In the formula, I rec is the current fed into the AC system, k D is the transformation ratio of the D-bridge converter transformer, k Y is the transformation ratio of the Y-bridge converter transformer, A Di , A Ym , B Di , B Ym are the conduction coefficients of the converter bridge arms, U nr is the three-phase voltage of the commutation bus, i d is direct current;

[0058] From the current analytical formula of the HVDC transmission DC feeding into the AC system, it can be seen that when a fault occurs, if the commutation failure of the converter valve is not considered, due to the low-voltage current limiting control strategy, the fault current provided by the HVDC transmission converter presents a power frequency fault characteristic with limited amplitude. If a commutation failure occurs, the power frequency current characteristic of the HVDC transmission feed equivalent is distorted, and the fault current of the HVDC transmission presents a fault characteristic with limited amplitude and severe distortion;

[0059] From the above analysis, it can be seen that there is a difference in the waveform of the fault current on the renewable energy side of the collection line and the fault current on the high-voltage DC side of the collection line: the fault current on the renewable energy side of the collection line presents a fault characteristic of limited amplitude and frequency shift, while the fault current on the high-voltage DC side of the collection line presents a power frequency fault characteristic of limited amplitude or a fault characteristic of limited amplitude and severe distortion.

[0060] If differential protection is used, there may be a risk of refusal to operate; specifically:

[0061] The protection action criterion of differential protection is:

[0062]

[0063] In the formula, is the differential current, is the braking current, where To collect the current at the protection installation point on the new energy side of the line, To collect the current at the protection installation point on the high-voltage DC side of the line, and The same name, K rel is the ratio braking coefficient, the typical value is 0.5~0.8, I op0 is the starting value;

[0064] Assume that the current amplitude ratio k on both sides of the collection line is the current amplitude on the high-voltage DC side of the collection line / the current amplitude on the new energy side of the collection line, and the absolute value of the phase angle difference on both sides of the collection line is θ. The differential current and the restraining current are obtained and substituted into the protection action criterion of the differential protection. The action boundary of the differential protection can be solved as follows:

[0065]

[0066] Take the ratio braking coefficient K rel is 0.8. From the differential protection action boundary, it can be seen that when the current phase angle difference on both sides is less than 102.7°, the differential protection can be reliably operated. When the current phase angle difference on both sides exceeds 102.7°, the ratio of the differential current to the braking current may be less than the ratio braking coefficient. At this time, the differential protection faces the risk of refusal to operate. For example:

[0067] For three-phase short circuit faults, when a three-phase short circuit fault occurs in the collection line, the fault sequence network diagram can be decoupled into two sub-networks. Since when a three-phase short circuit fault occurs, only positive sequence current is provided on both sides of the collection line, i.e., the high-voltage DC side of the collection line and the new energy side of the collection line. Without considering the phase-locked loop error, the same-phase fault currents on both sides of the collection line tend to be in the same phase. Therefore, when a three-phase short circuit fault occurs, the phase angle difference will not exceed 102.7°, and the differential protection can operate reliably.

[0068] For asymmetric grounding faults, when an asymmetric short-circuit grounding fault occurs, the fault current amplitude on the new energy side of the collection line is limited, the fault current is mainly zero-sequence current, and the zero-sequence currents on both sides of the collection line are in phase, which reduces the phase angle difference of the fault phase currents on both sides of the collection line. Without considering high-resistance faults, when an asymmetric short-circuit grounding fault occurs, the phase angle difference of the fault phase currents on both sides of the collection line will not exceed 102.7°, and the differential protection will not fail to operate.

[0069] For two-phase short-circuit faults, since the converter on the new energy side of the collection line adopts a control strategy to suppress negative sequence current, after the fault occurs, only the high-voltage DC side of the collection line provides a negative sequence path. Taking the BC phase short-circuit fault as an example, the currents on both sides of the collection line are expressed using sequence components and converted into positive and negative sequence currents on the high-voltage DC side of the collection line, which can be expressed as:

[0070]

[0071]

[0072]

[0073] In the formula, To collect the A-phase current on the new energy side of the line, To collect the A-phase current on the high-voltage DC side of the line, To collect the positive sequence current on the high voltage DC side of the line, To collect the negative sequence current on the high voltage DC side of the line, is the phase B current on the new energy side of the collected line, j is an imaginary unit, To collect the B-phase current on the high-voltage DC side of the line, To collect the C-phase current on the new energy side of the line, To collect the C-phase current on the high-voltage DC side of the line.

[0074] Since the positive-sequence and negative-sequence equivalent impedances are equal on the high-voltage DC side of the collection line, when a two-phase interphase fault occurs, the positive-sequence and negative-sequence current amplitudes on the system side are almost equal. and therefore and The phase angle difference is almost equal, and the phase angle difference of phase B is 60°, and the phase angle difference of phase C is 120°. According to the differential protection action boundary, when a phase-to-phase short circuit fault occurs, the B phase differential protection can be reliably operated, and the C phase differential protection may fail to operate.

[0075] See also Figure 1 The present invention provides a longitudinal protection method for a Shagohuang new energy base collection system based on amplitude-phase coefficient, comprising the following steps:

[0076] Based on the Shagohuang new energy base collection system, in the first sampling window, the set current on the new energy side of the collection line and the set current on the high-voltage DC side of the collection line are obtained at the first sampling frequency, and in the second sampling window, the new energy side current of the collection line and the high-voltage DC side current of the collection line are obtained at the second sampling frequency; the duration of the first sampling window is the same as the duration of the second sampling window, and the first sampling frequency is the same as the second sampling frequency; preferably, the duration of the first sampling window and the duration of the second sampling window are 10ms to 20ms respectively, and the first sampling frequency and the second sampling frequency are both 1kHz;

[0077] According to the setting current on the new energy side of the collection line and the setting current on the high voltage DC side of the collection line, the amplitude and phase coefficient setting value of the collection system of the Shagohuang new energy base is obtained;

[0078] The amplitude-phase coefficient is calculated based on the current on the new energy side of the collection line and the current on the high-voltage DC side of the collection line; the amplitude-phase coefficient is:

[0079]

[0080] In the formula, F φ is the phase-amplitude coefficient of φ, φ is the phase of the three-phase electricity, φ is respectively taken as phase A, phase B, and phase C of the three-phase electricity, x φk is the kth current sampling value of the φ phase on the new energy side of the collection line, y φk The k-th current sampling value of the φ-phase on the high-voltage DC side of the collection line is inverted, k is the sampling point number in the second sampling window, and n is the total number of sampling points in the second sampling window;

[0081] Get the amplitude and phase coefficient setting value;

[0082] Obtain the longitudinal protection criterion of the collection system according to the amplitude-phase coefficient and the amplitude-phase coefficient setting value;

[0083] Identify the fault type of the Shagohuang New Energy Base collection system based on the longitudinal protection criteria;

[0084] Enable protection measures based on the fault type.

[0085] When an intra-area fault occurs in the collecting line, the short-circuit current waveforms on both sides of the collecting line are very different, and the amplitude-phase coefficient is much less than 1; when operating normally or an out-of-area fault occurs, the short-circuit current waveforms on both sides are opposite. After inversion processing, the current waveforms on both sides of the collecting line are basically the same, and the amplitude-phase coefficient is close to 1; when the new energy side of the collecting line has weak output, the current sampling value on the new energy side of the collecting line is 0, and the amplitude-phase coefficient is 0.

[0086] It can be seen that the amplitude-phase coefficient can reliably identify faults inside and outside the area and is suitable for the scenario of weak output on the renewable energy side of the collection line.

[0087] The criteria for the longitudinal protection of the collection system are:

[0088] F φ <F φset ;

[0089] In the formula, F φset is the setting value of the φ phase amplitude coefficient.

[0090] The steps to obtain the amplitude and phase coefficient setting value are:

[0091] Obtain the set current on the new energy side of the collection line, and obtain the set current on the high-voltage DC side of the collection line;

[0092] Substitute the setting current on the new energy side of the collection line and the setting current on the high-voltage DC side of the collection line into Formula 1; Formula 1 is:

[0093] F φset =λF φ ' set , 0.88≤λ≤0.98;

[0094]

[0095] In the formula, F φset is the setting value of the φ phase amplitude coefficient, λ is the total margin coefficient, F φ ' set is the amplitude-phase coefficient value of the setting current, I 1φi is the i-th set current of the φ-phase on the new energy side of the collection line, I 2φi is the i-th set current of the φ-phase on the high-voltage DC side of the collection line, i is the sampling point number in the first sampling window, and m is the total number of sampling points in the first sampling window; since the duration of the first sampling window is the same as that of the second sampling window and the first sampling frequency is the same as that of the second sampling frequency, m=n;

[0096] Solve formula 1 to obtain the setting value of the amplitude and phase coefficient.

[0097] The set current on the new energy side of the collection line is:

[0098]

[0099] The set current on the high-voltage DC side of the collection line is:

[0100]

[0101] In the formula, I 1φ The φ phase setting current on the new energy side of the collection line, I 2φ The φ phase setting current on the new energy side of the collection line, I m is the current amplitude, ω is the power frequency angular frequency, t is the sampling time, is the initial phase angle of the φ phase current, θ1 is the phase angle error, and ε is the amplitude error.

[0102] Data synchronization and CT transmission may cause errors in amplitude and phase coefficients during normal operation or out-of-zone faults. Therefore, the amplitude error ε and phase angle error θ1 need to be considered when setting the protection setting. Preferably, the phase angle error range is: -16°≤θ1≤16°, and the amplitude error range is: ε≤10%.

[0103] Preferably, the phase angle error θ1 is 16°, the amplitude error ε is 10%, the duration of the first sampling window is 10ms, and when the initial time is 0-20ms and the initial phase angle is 0-180°, the amplitude-phase coefficient value F of the set current is obtained. φ ' set is 0.917384, taking into account the margin of 0.95, and considering that other factors may affect the calculation of the amplitude-phase coefficient, a certain margin is also left, so the total margin coefficient λ takes a value of 0.92~0.93, and the amplitude-phase coefficient setting value F can be obtained φset is 0.85, that is, the criterion for the longitudinal protection of the collection system is:

[0104] F φ <0.85;

[0105] By comparing the calculated values ​​of the amplitude-phase coefficients of each phase on both sides of the collecting line with the set values ​​of the amplitude-phase coefficients, the fault type can be identified and the corresponding protection measures can be enabled, as follows:

[0106] If the longitudinal protection criterion of the collection system is not established, it is determined that there is no fault in the φ phase of the collection system of the Shagohuang New Energy Base;

[0107] If the longitudinal protection criteria of the collection system are established, it is determined that the φ phase of the collection system of the Shagohuang New Energy Base is faulty.

[0108] Enabling protection measures includes:

[0109] If a single-phase fault occurs, the faulty phase will be disconnected and the non-faulty phase will operate normally;

[0110] If a two-phase or three-phase fault occurs, the three phases are disconnected.

[0111] Figure 2 This is the topology diagram of the Shagohuang New Energy Base collection system. The new energy stations in the figure are photovoltaic stations and permanent magnet wind farms. Taking the permanent magnet wind farm as an example, the capacities are set to 400MW, 500MW, and 500MW respectively. The collection line voltage level is 220kV, the line length is 40km, the positive and negative sequence impedances are both (0.075+j0.335)Ω / km, and the zero sequence impedance is (0.285+j0.825)Ω / km. The rated capacity of the main transformer is 500MVA, the transformation ratio is 220kV / 35kV, and the short-circuit impedance is 6%. According to Figure 2 The topological structure and the above parameters are used to build a Shagohuang new energy base aggregation system model in a real-time digital simulator (RTDS) and a universal protection platform to verify the effect of the protection method proposed in the present invention.

[0112] The fault line is set as the 220kV collecting line of the 500MW permanent magnet wind farm, and 5 fault points are set, namely the external outlet of the new energy side of the collecting line, 10km, 20km, 30km away from the new energy side of the collecting line in the area, and the external outlet of the high-voltage DC side of the collecting line, respectively denoted as K1, K2, K3, K4 and K5. The fault types are set as A-phase short circuit to ground, BC two-phase short circuit, BC two-phase short circuit to ground and ABC three-phase short circuit, respectively denoted as AG, BC, BCG, ABC.

[0113] Figure 3 The figure shows the calculated value of the amplitude-phase coefficient of the setting current considering the 16° phase angle error and the 10% amplitude error. It can be seen that the difference between the maximum and minimum values ​​of the amplitude-phase coefficient of the setting current calculated is only 10 -15 , indicating that the value of the amplitude-phase coefficient of the setting current is not affected by the initial calculation time and initial phase angle, and has extremely strong reliability. The amplitude-phase coefficient of the setting current at this time is selected to obtain the amplitude-phase coefficient setting value and realize protection.

[0114] Figure 4 The figure is a schematic diagram of the amplitude-phase coefficient when a fault occurs at the midpoint of the collection line. It can be seen from the figure that when a fault occurs in the collection line, the calculated value of the amplitude-phase coefficient of the fault phase is less than the protection setting value of 0.85 within 5ms, and the protection is reliably operated. The calculated value of the amplitude-phase coefficient of the non-fault phase is always higher than the protection setting value, and the protection is reliable and does not operate.

[0115] In order to verify the performance of the longitudinal protection method of the Shagohuang new energy base collection system based on the amplitude-phase coefficient, a hardware-in-the-loop dynamic model experimental platform was built. According to the actual topological structure and parameters of the Kubuqi large base station, a hardware-in-the-loop dynamic model experimental platform was built in RTDS. Figure 2The Shagohuang New Energy Base collection system shown in the figure. When verifying the proposed protection performance, taking the permanent magnet wind farm as an example, the capacity is set to 400MW, 500MW, and 500MW respectively, the collection line voltage level is 220kV, and the line length is 40km. Figure 2 The situations of different types of faults occurring at different fault locations in the simulation experiment platform were simulated in the hardware-in-the-loop dynamic simulation experiment platform, and all simulation results are given in Tables 1 to 4. Table 1 shows the action performance of the proposed protection under different fault scenarios, where all coefficients are calculated values ​​of amplitude and phase coefficients; Table 2 shows the calculated values ​​of amplitude and phase coefficients under different transition resistances; Table 3 shows the calculated values ​​of amplitude and phase coefficients under different noise scenarios; Table 4 shows the calculated values ​​of amplitude and phase coefficients under different capacity new energy stations.

[0116] Table 1 Action performance of simulation experiments under different fault scenarios

[0117]

[0118]

[0119] Table 2 Calculated values ​​of amplitude-phase coefficient under different transition resistances

[0120]

[0121] Table 3 Calculated values ​​of amplitude-phase coefficients under different noise scenarios

[0122]

[0123]

[0124] Table 4 Calculated values ​​of amplitude-phase coefficients for new energy stations with different capacities

[0125]

[0126] The simulation results show that the protection proposed in the present invention can reliably identify various internal and external faults. In various fault scenarios, when an internal fault occurs, the fault phase amplitude coefficient is less than the protection setting value, and the protection can operate reliably. In different transition resistance scenarios, different noise scenarios and different station capacities, the proposed protection can reliably identify faults.

[0127] In order to further verify the performance of the protection principle proposed in the present invention, the protection method proposed in the present invention is compared with the longitudinal protection principle based on the cosine similarity protection method, the Canberra distance protection method and the improved Euclidean distance protection method. Figure 5 The operating performance of the above three similarity methods and the proposed protection is given when a phase A high-resistance grounding fault occurs at the midpoint K3 of the collecting line.

[0128] Depend on Figure 5 It can be seen that when a high-resistance fault occurs, the fault phase current amplitudes on both sides of the line are relatively small, and the phase angle difference is close to 180°. The above three similarity measurement methods all fail to operate, while the proposed protection principle can still reliably identify the fault when a high-resistance fault occurs, and has a higher sensitivity. The simulation results verify that the protection proposed in the present invention has a strong ability to withstand high-resistance faults compared to other similarity methods.

[0129] The system embodiment described above is merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art may understand and implement it without creative work.

[0130] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0131] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A longitudinal protection method for the Shagohuang new energy base collection system based on amplitude-phase coefficient, characterized in that: The following steps are involved: Based on the Shagohuang new energy base collection system, in a first sampling window, a set current on the new energy side of the collection line and a set current on the high-voltage DC side of the collection line are obtained at a first sampling frequency, and in a second sampling window, a current on the new energy side of the collection line and a current on the high-voltage DC side of the collection line are obtained at a second sampling frequency; the duration of the first sampling window is the same as the duration of the second sampling window, and the first sampling frequency is the same as the second sampling frequency; According to the setting current on the new energy side of the collection line and the setting current on the high-voltage DC side of the collection line, the amplitude and phase coefficient setting value of the Shagohuang new energy base collection system is obtained; The amplitude-phase coefficient is calculated according to the current on the new energy side of the collection line and the current on the high-voltage DC side of the collection line; the amplitude-phase coefficient is: In the formula, F φ is the phase-amplitude coefficient of φ, φ is the phase of the three-phase electricity, φ is respectively taken as phase A, phase B, and phase C of the three-phase electricity, x φk is the kth current sampling value of the φ phase on the new energy side of the collection line, y φk The k-th current sampling value of the φ-phase on the high-voltage DC side of the collection line is inverted, k is the sampling point number in the second sampling window, and n is the total number of sampling points in the second sampling window; Obtaining a criterion for longitudinal protection of a collection system according to the amplitude-phase coefficient and the amplitude-phase coefficient setting value; Identify the fault type of the Shagohuang new energy base collection system according to the longitudinal protection criterion; Initiate protective measures based on the type of fault described.

2. The longitudinal protection method of the Shagohuang new energy base collection system based on amplitude-phase coefficient according to claim 1 is characterized in that: The longitudinal protection criterion of the collection system is: F φ <F φset ; In the formula, F φset is the setting value of the φ phase amplitude coefficient.

3. The longitudinal protection method for the Shagohuang new energy base collection system based on amplitude-phase coefficient according to claim 2 is characterized in that: The steps of obtaining the amplitude-phase coefficient setting value are: Substitute the set current on the new energy side of the collection line and the set current on the high-voltage DC side of the collection line into Formula 1; Formula 1 is: F φset =λF φ ' set ,0.88≤λ≤0.98; In the formula, F φset is the setting value of the φ phase amplitude coefficient, λ is the total margin coefficient, F φ ' set is the amplitude-phase coefficient value of the setting current, I 1φi is the i-th set current of the φ-phase on the new energy side of the collection line, I 2φi is the i-th set current of the φ-phase on the high-voltage DC side of the collection line, i is the sampling point number in the first sampling window, and m is the total number of sampling points in the first sampling window; Solve the formula 1 to obtain the amplitude-phase coefficient setting value.

4. The longitudinal protection method for the Shagohuang new energy base collection system based on amplitude-phase coefficient according to claim 3 is characterized in that: The set current on the new energy side of the collection line is: In the formula, I 1φ I is the set current of the φ phase on the new energy side of the collection line, m is the current amplitude, ω is the power frequency angular frequency, t is the sampling time, is the initial phase angle of φ phase current, and θ1 is the phase angle error.

5. The longitudinal protection method for the Shagohuang new energy base collection system based on amplitude-phase coefficient according to claim 3 is characterized in that: The set current on the high-voltage DC side of the collection line is: In the formula, I 2φ I is the set current of the φ phase on the new energy side of the collection line, m is the current amplitude, ω is the power frequency angular frequency, t is the sampling time, is the initial phase angle of φ phase current, and ε is the amplitude error.

6. The longitudinal protection method for the Shagohuang new energy base collection system based on amplitude-phase coefficient according to claim 4 is characterized in that: The phase angle error has a value range of -16°≤θ1≤16°.

7. The longitudinal protection method for the Shagohuang new energy base collection system based on amplitude-phase coefficient according to claim 5 is characterized in that: The amplitude error has a value range of: ε≤10%.

8. The longitudinal protection method for the Shagohuang new energy base collection system based on amplitude-phase coefficient according to claim 1 is characterized in that: The duration of the first sampling window is 10 ms to 20 ms.

9. The longitudinal protection method for the Shagohuang new energy base collection system based on amplitude-phase coefficient according to claim 1 is characterized in that: If the longitudinal protection criterion of the collection system is not established, it is determined that the φ phase of the collection system of the Shagohuang New Energy Base has no fault; If the longitudinal protection criterion of the collection system is established, it is determined that the φ phase of the collection system of the Shagohuang New Energy Base is faulty.

10. The longitudinal protection method for the Shagohuang new energy base collection system based on amplitude-phase coefficient according to any one of claims 1 to 9, characterized in that: The enabling protection measures include: If a single-phase fault occurs, the faulty phase will be disconnected and the non-faulty phase will operate normally; If a two-phase or three-phase fault occurs, the three phases are disconnected.

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