CN114530831A - Pilot protection system and pilot protection method for double-fed fan to access flexible direct current - Google Patents

Pilot protection system and pilot protection method for double-fed fan to access flexible direct current Download PDF

Info

Publication number
CN114530831A
CN114530831A CN202210036366.9A CN202210036366A CN114530831A CN 114530831 A CN114530831 A CN 114530831A CN 202210036366 A CN202210036366 A CN 202210036366A CN 114530831 A CN114530831 A CN 114530831A
Authority
CN
China
Prior art keywords
current
pilot protection
head
double
mmc
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN202210036366.9A
Other languages
Chinese (zh)
Other versions
CN114530831B (en
Inventor
段建东
赵宇航
杨威
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Xian University of Technology
Original Assignee
Xian University of Technology
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Xian University of Technology filed Critical Xian University of Technology
Priority to CN202210036366.9A priority Critical patent/CN114530831B/en
Publication of CN114530831A publication Critical patent/CN114530831A/en
Application granted granted Critical
Publication of CN114530831B publication Critical patent/CN114530831B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H1/00—Details of emergency protective circuit arrangements
    • H02H1/0092—Details of emergency protective circuit arrangements concerning the data processing means, e.g. expert systems, neural networks
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Landscapes

  • Engineering & Computer Science (AREA)
  • Artificial Intelligence (AREA)
  • Evolutionary Computation (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

The invention discloses a pilot protection system and a pilot protection method for accessing a double-fed fan to flexible direct current, which comprises the following steps of 1, respectively enabling currents of a head-end breaker or a tail-end breaker to obtain a waveform of the head-end breaker and a current waveform of the tail-end breaker through a programmable processor a and a programmable processor b; step 2, calculating the energy ratio of each frequency band of the current at two ends by utilizing a wavelet packet, substituting the energy ratio of the first frequency band into a criterion for calculation, performing step 3 if the obtained calculated value is greater than a setting value, and continuing sampling if the obtained calculated value is less than the setting value; step 3, tripping the front-end circuit breaker and the tail-end circuit breaker to break the circuit, and completing the pilot protection of the alternating current output circuit by utilizing the DFIG utilizing the frequency band energy to access the MMC-HVDC system; the method solves the problem that the double-end power electronic power supply which cannot be adapted to the method for protecting the alternating current transmission line of the DFIG access MMC-HVDC system in the prior art.

Description

Pilot protection system and pilot protection method for double-fed fan to access flexible direct current
Technical Field
The invention belongs to the technical field of flexible direct current power grid relays, and relates to a pilot protection system for accessing a double-fed fan to flexible direct current and a pilot protection method of the system.
Background
The new energy in the provinces of the central part and the north part of China mainly adopts a centralized development mode, and the direct current system has the advantages of large transmission capacity, long transmission distance, low line loss, narrow transmission corridor and the like, and simultaneously has no problems of reactive power balance, frequency stability, system synchronization and the like of an alternating current system, so that the direct current system is very suitable for large-scale resource development and trans-regional power transmission. Compared with the conventional Direct-Current transmission, the MMC-HVDC (Modular multilevel converter-High Voltage Direct Current) has the advantages of flexible active power and reactive power control, easy formation of a Direct-Current power grid, black start capability and no commutation failure risk, so that the MMC-HVDC is more suitable for the access of new energy sources such as wind power and the like. But the new energy and the MMC-HVDC also bring challenges to the traditional relay protection.
With the scale expansion of wind power centralized access to MMC-HVDC, the relay protection of the power grid faces unprecedented challenges [1 and 2], a relay protection device acts according to fault characteristics, and the fault characteristics of the power grid depend on the power supply and the topological structure of the network. The method is characterized in that pilot protection is adopted for a line between wind power and a large system, the traditional pilot protection theory is established and developed on the basis that power supplies at two ends of a protected line are synchronous generators, in the fault transient process, the synchronous generators are not considered to have any parameter change, on the premise that the parameter change is avoided, fault characteristic analysis of a power grid is carried out, and a series of corresponding relay protection schemes are provided. The wind power generator set and the MMC-HVDC are essentially a nonlinear control system [3] containing power electronic devices, and compared with the traditional synchronous generator, the transient characteristics of the wind power generator set and the MMC-HVDC system in the fault transient process are completely different from the transient characteristics of the synchronous generator. Therefore, for an alternating current transmission line with wind power accessed to MMC-HVDC, the fault characteristics of the alternating current transmission line are obviously different from those of a traditional power grid. Therefore, the wind power access to MMC-HVDC brings great challenges to the traditional relay protection scheme in the aspects of reliability and sensitivity.
At present, research aiming at alternating current protection of a wind power access MMC-HVDC system mainly focuses on an MMC-HVDC grid-connected end. Relatively, line protection studies for power electronic power supplies on both sides are not yet mature. Therefore, a new pilot protection scheme is necessary to be provided on the premise of researching wind power and MMC-HVDC transient characteristics and traditional relay protection adaptability.
Disclosure of Invention
The invention aims to provide a pilot protection system for connecting a double-fed fan into a flexible direct current. The method solves the problem that the protection method for the wind power access MMC-HVDC transmission line in the prior art cannot adapt to a double-end power electronic power supply network.
The invention also aims to provide a pilot protection method for the double-fed fan to be connected into the pilot protection system of the flexible direct current.
The first technical scheme adopted by the invention is as follows: the double-fed fan inserts flexible direct current's pilot protection system, and specific circuit structure is as follows: the system comprises a power supply, an A bus and a B bus, wherein the A bus is connected with the B bus through a line, the B bus is connected with an MMC-HVDC system through a step-up transformer, and the A bus is connected with the power supply through a step-down transformer;
a head-end circuit breaker and a head-end voltage current transformer for detecting the voltage and current values of the head-end circuit breaker are arranged at an outlet of the A bus, the head-end circuit breaker is connected with an action controller a, and the head-end voltage current transformer and the action controller a are both connected with a programmable processor a; and a tail end circuit breaker and a tail end voltage current transformer for detecting the voltage current value at the tail end circuit breaker are arranged at an outlet of the bus B, wherein the tail end circuit breaker is connected with an action controller B, and the tail end voltage current transformer and the action controller B are both connected with a programmable processor B.
The power supply is a double-fed wind driven generator.
The second technical scheme adopted by the invention is as follows: the pilot protection method for accessing the double-fed fan to the flexible direct current pilot protection system is implemented according to the following steps:
step 1, respectively acquiring current values of a head-end circuit breaker and a tail-end circuit breaker on a line through a head-end voltage current transformer and a tail-end voltage current transformer (10), inputting the measured current value into a programmable processor a through the head-end voltage current transformer, and inputting the measured current value into a programmable processor b through the tail-end voltage current transformer;
step 2, calculating the frequency band energy ratio of the current at two ends by using the waveform of the head-end circuit breaker and the current of the tail-end circuit breaker obtained in the step 1, if the difference value M of the calculated first frequency band energy ratio is greater than a setting value, the circuit breaker acts, the head-end circuit breaker and the tail-end circuit breaker trip out to break a circuit, and if the calculated M is less than the setting value, sampling is continued; and completing the pilot protection of the MMC-HVDC transmission line.
The invention is also characterized in that:
step 1 is specifically carried out as follows: and simulating different types of faults of an MMC-HVDC transmission line through a PSCAD simulation experiment, and importing half-period fault current data into a matlab program.
Step 2, specifically implementing the following steps: solving the energy ratio of each frequency band component of the current data of the head-end circuit breaker and the current data of the tail-end circuit breaker under different faults obtained in the step 1, if the energy ratio of the first frequency band obtained is smaller than a setting value, continuing sampling, and if the energy ratio of the first frequency band obtained is larger than the setting value, performing the step 3, wherein the calculation method of the energy ratio of the frequency band components comprises the following steps:
the method for calculating the frequency band energy ratio in the step 2 comprises the following steps:
selecting Meyer wavelet decomposition according to characteristics and requirements of sampling current, and defining Meyer wavelet as function
Figure BDA0003468514080000031
By dual-scale differential equations
Figure BDA0003468514080000041
Where w (t) is an orthogonal scale function, { hk}k∈ZAnd { gk}k∈ZIs a pair of conjugate orthogonal filter coefficients, t is the time scale;
production function set { wn,j,k(t):＝2-j/2wn(2-j-k), n ∈ Z, j ∈ Z, k ∈ Z } is said to pertain to
Figure BDA0003468514080000046
Z represents an integer set;
for the current sampling signal i (t) in step 1, it is discrete positiveThe cross-wavelet packet transform is defined as i (t) at the orthogonal wavelet packet basis { w }n,j,k(t)}n∈Z,j∈Z,k∈ZI.e.:
Figure BDA0003468514080000042
wherein, { ps(n,j,k)}k∈ZIs i (t) in the orthogonal wavelet packet space
Figure BDA0003468514080000043
A sequence of wavelet packet transform coefficients;
orthogonal wavelet packet space Uj nThe energy distribution E (j, n) of the current signal i (t) in the time-frequency localization space is defined as follows:
Figure BDA0003468514080000044
wherein the wavelet packet transform coefficient psThe discrete numerical calculation of (n, j, k) adopts a recursion algorithm of formula (1), and the energy of the first frequency band is the ratio D of the energy distribution of the first wavelet packet transform coefficient in the whole energy distribution as follows:
Figure BDA0003468514080000045
in conclusion, by taking the traditional current differential protection as a reference, a pilot protection criterion of the line between the DFIG and the MMC-HVDC is constructed:
(DMMC+DDFIG)-(DMMC-DDFIG)≥Dop0 (5)
wherein D isMMCRepresenting the first frequency band component, D, in the MMC short-circuit currentDFIGRepresents the first frequency band component in the short-circuit current of the DFIG; dop0Is a setting value.
The setting value in step 2 is 0.2.
The invention has the beneficial effects that: the pilot protection method for the pilot protection system with the double-fed fan accessed to the flexible direct current solves the problem that the protection method for the DFIG accessed to the MMC-HVDC system sending-out line in the prior art cannot adapt to a double-end power electronic power supply; the frequency band energy ratio of the current at the two ends of the protected line is calculated by adopting a wavelet packet algorithm, so that the intra-area fault or the extra-area fault is realized, and the reliability of protection is improved.
Drawings
FIG. 1 is a circuit diagram of a pilot protection system for connecting a double-fed fan to a flexible direct current according to the invention;
FIG. 2 is a flow chart of a pilot protection method of the pilot protection system for accessing a double-fed fan to a flexible direct current according to the invention;
FIG. 3 is a schematic diagram of calculating current band energy by wavelet packet decomposition in a pilot protection method of a pilot protection system for accessing a double-fed fan to a flexible direct current according to the present invention;
FIG. 4 is a schematic diagram of calculating current band energy through wavelet packet decomposition at DFIG short-circuit current according to the pilot protection method of the pilot protection system for accessing the double-fed fan to the flexible direct current;
FIG. 5 shows that various frequency band energies are generated by decomposing a wavelet packet at an MMC short-circuit current according to the pilot protection method of the pilot protection system for accessing a double-fed fan to a flexible direct current;
fig. 6(a) - (d) are line graphs of the pilot protection method of the double-fed fan switched-in flexible direct current pilot protection system according to the invention, which are calculated results of protection setting values under different fault types.
In the figure, 1 is a power supply, 2 is a step-down transformer, 3 is an A bus, 4 is a head-end breaker, 5 is a line, 6 is a mutual inductor a, 7 is a programmable processor a, 8 is an action controller a, 9 is an end breaker, 10 is a mutual inductor B, 11 is a programmable processor B, 12 is an action controller B, 13 is a B bus, 14 is a transformer, and 15 is an MMC-HVDC system.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
The pilot protection system for accessing the double-fed fan to the flexible direct current is described by taking the following circuit as an example: as shown in fig. 1, the system comprises a power supply 1, an a bus 3 and a B bus 13, wherein the a bus 3 is connected with the B bus 13 through a line 5, the B bus 13 is connected with an MMC-HVDC system 15 through a step-up transformer 14, and the a bus 3 is connected with the power supply 1 through a step-down transformer 2;
a head-end circuit breaker 4 and a head-end voltage current transformer 6 for detecting the voltage and current values of the head-end circuit breaker are arranged at an outlet of the A bus 3, the head-end circuit breaker 4 is connected with an action controller a8, and the head-end voltage current transformer 6 and the action controller a8 are both connected with a programmable processor a 7; at the outlet of the B bus 13, a terminal breaker 9 and a terminal voltage current transformer 10 for detecting the voltage current value at the terminal breaker are arranged, wherein the terminal breaker 9 is connected with the action controller B12, and the terminal voltage current transformer 10 and the action controller B12 are both connected with the programmable processor B11.
The power supply 1 is a doubly-fed wind generator.
The pilot protection method for the pilot protection system for accessing the double-fed fan to the flexible direct current is implemented according to the following steps as shown in fig. 2:
step 1, current values of a head-end breaker 4 and a tail-end breaker 9 on an AB line are respectively acquired through a transformer a6 and a transformer b10, the transformer a6 inputs the measured current values into a programmable processor a7, and the transformer b10 inputs the measured current values into a programmable processor b 11;
step 1 is specifically carried out as follows: the method comprises the steps of simulating that different types of faults occur in a line which is connected with an MMC-HVDC system through a PSCAD simulation experiment, and importing obtained fault current data into a matlab program.
Step 2, calculating the frequency band energy ratio of the current at two ends by using the waveform of the head circuit breaker 4 obtained in the step 1 and the current of the tail circuit breaker 9, substituting the calculated first frequency band energy ratio into a constructed protection criterion, if the calculated first frequency band energy ratio is greater than a setting value, actuating the circuit breaker to cut off a line, and if the calculated value is less than the setting value, continuing sampling;
the method for specifically calculating the frequency band energy ratio in the step 2 comprises the following steps:
in wavelet packet analysis, a scale function orthogonalized by a standard
Figure BDA0003468514080000071
By dual-scale differential equations
Figure BDA0003468514080000072
Production function set { wn,j,k(t):＝2-j/2wn(2-j-k), n ∈ Z, j ∈ Z, k ∈ Z } is said to pertain to
Figure BDA0003468514080000073
Of orthogonal wavelet packet of, wherein
Figure BDA0003468514080000074
hkFor the orthogonal low-pass real coefficient filter corresponding to ω (t) { hk}k∈ZAnd { gk}k∈ZIs a pair of conjugate quadrature filter coefficients derived from s (t), Z being an integer set; the definition of the orthogonal wavelet packet transform is given below.
For observed signal s (t) e L2(R) discrete orthogonal wavelet packet transform is defined as i (t) on an orthogonal wavelet packet basis { w }n,j,k(t)}n∈Z,j∈Z,k∈ZI.e.:
Figure BDA0003468514080000075
wherein, { ps(n,j,k)}k∈ZIs i (t) in the orthogonal wavelet packet space
Figure BDA0003468514080000076
The wavelet packet transform coefficient sequence.
The biggest characteristics of wavelet packet analysis are: the signal frequency band can be divided in multiple layers, a more precise analysis method is provided for the signal, and meanwhile, the corresponding frequency band can be adaptively selected to be matched with the signal spectrum according to the characteristics of the analyzed signal. The completeness and orthogonality of the wavelet packet space enable the information quantity to be complete and all components to be reserved after the signal s (t) is subjected to wavelet packet transformation, and conditions are provided for analyzing signal characteristics, particularly energy distribution characteristics.
At any decomposition level j of the wavelet packet, different orthogonal wavelet packet spaces
Figure BDA0003468514080000081
All of which are different time-frequency resolution spaces, all of which are orthogonal wavelet packet spaces
Figure BDA0003468514080000082
Can completely cover the whole frequency bandwidth of the signal s (t). According to the time-frequency resolution technology of wavelet packet analysis for signals, the orthogonal wavelet packet transformation on any decomposition level j can adaptively project the signal frequency spectrum component to the orthogonal wavelet packet space of the corresponding frequency band, and the information component of the signal is complete, so that the projection component of each orthogonal wavelet packet space of the original signal s (t) on each decomposition level represents the time-frequency local information of the signal s (t) on the corresponding time-frequency resolution space. If the energy of signal distribution in each orthogonal wavelet packet space at a decomposition level is calculated, the energy can be calculated according to the wavelet packet space
Figure BDA0003468514080000083
The sequential arrangement of the frequency indices n constitutes the feature vector of the original signal s (t).
For a given orthogonal wavelet packet space
Figure BDA0003468514080000084
The energy distribution E (j, n) of the original signal s (t) in the time-frequency localization space is defined as follows:
E(j,n)＝∑[ps(n,j,k)]2 (3)
wherein the wavelet packet transform coefficient psThe discrete numerical calculation of (n, j, k) uses the recursion algorithm of equation (2).
The first frequency band energy is the ratio of the energy distribution of the first wavelet packet transform coefficient in the whole energy distribution, namely:
Figure BDA0003468514080000085
the setting value in the step 2 is 0.2. If the calculated value is larger than 0.2, the head-end circuit breaker 4 and the tail-end circuit breaker 9 trip out to break the circuit, and the pilot protection of the alternating current output circuit of the MMC-HVDC system by using the DFIG of the frequency band energy is completed.
The value-taking principle of the protection criterion and the setting value is as follows:
when the double-fed wind driven generator works in a steady state, the current waveforms at two ends of the AB line are approximately consistent, the frequencies of the currents are power frequencies, and after a fault occurs, the short-circuit current of the double-fed wind driven generator can contain attenuated direct-current components due to the influence of an asynchronous motor, so that i1Contains a certain DC component, pair i1The energy of the wavelet band is calculated, and the first band of the wavelet band accounts for a certain proportion of the whole energy. For the MMC-HVDC system, after a fault occurs, the controller of the MMC responds quickly, and usually a certain dc component exists in the period of time 3-4ms before the controller responds, but after the controller responds, the magnitude and phase of the output voltage of the converter change immediately, so that the inner loop current tracks the reference value of the MMC-HVDC system, and the fault current does not contain the dc component, so that the content of the energy of the first frequency band in the whole energy is very small. As shown in fig. 3, if a fault occurs outside the AB line region, the currents at both ends are steady-state currents, which do not contain attenuated dc components, and the energy ratios of the first frequency bands are consistent. As shown in fig. 4 and 5, when a fault occurs, the schematic diagram of calculating the current band energy by wavelet packet decomposition of the short-circuit current at the DFIG side and the schematic diagram of calculating the current band energy by wavelet packet decomposition of the short-circuit current at the MMC side in the pilot protection method of the pilot protection system that the doubly-fed wind turbine is connected to the flexible direct current are respectively shown
Based on this feature, it can be derived: in normal operation/out-of-range fault, i1And i2The energy ratio of the first frequency band is basically identical, the difference between the first frequency band and the first frequency band is basically equal to 0, and when a fault occurs in a region, i2And i1First frequency band energy ofThe ratio is very different when the low frequency energy ratio between them is a number significantly larger than 0. Using this difference, it is possible to identify whether the failure occurs inside or outside the zone.
In summary, a pilot protection criterion for the line between the DFIG and the MMC-HVDC system can be constructed:
in summary, the pilot protection criterion of the line between the DFIG and the flexible direct current system can be constructed by taking the traditional current differential protection as reference:
(DMMC+DDFIG)-(DMMC-DDFIG)≥Dop0 (5)
wherein DMMCRepresenting the content of the first frequency band component, D, in the MMC short-circuit currentDFIGRepresenting the content of the first frequency band component in the DFIG short-circuit current. Dop0A threshold value, D, which takes into account that the maximum transmission error of the current sensor is 10% and leaves a certain marginop0Take 0.2.
Verifying different fault types and fault positions
The specific process is as follows:
(1) the fault occurring at different positions on the line can also affect the magnitude of the short-circuit current and further affect the calculation of the frequency band energy. Therefore, multiple sets of simulation are carried out at different positions in the protected line, and the fault types are three-phase short circuit, two-phase short circuit grounding and single-phase short circuit. The simulation results are shown in table 1.
TABLE 1
Figure BDA0003468514080000101
Figure BDA0003468514080000111
From table 1 it can be seen that anywhere along the full length of the line, no matter which fault occurs, the protection action value is greater than 0.2 a short time after the fault occurs, i.e. the proposed protection scheme can act reliably and quickly. However, in the test results, it was found that the different positions where the faults occurred affect the protection operation values, and the closer the fault position is to the system side (about 10% of the entire line length), the lower the protection operation values are, and the reliability is not affected, but the sensitivity is lowered. Therefore, the subsequent simulation verification is performed under the most extreme condition of the fault occurrence position, and the performance of the protection scheme is verified.
(2) At a distance of 10%, a three-phase short, an AB two-phase ground short and an AB inter-phase short, respectively, were set, and also a single-phase ground, and the performance of the proposed protection scheme was tested in extreme cases, with the results shown in fig. 6(a) - (d). As can be seen from fig. 6(a) - (d), the protection can still act reliably and quickly when various types of faults occur at the head end of the line.
The pilot protection method for the alternating current transmission line of the DFIG access MMC-HVDC system utilizes pilot protection in a double-power-supply mode, has simple and quick calculation process, and utilizes a wavelet packet algorithm to calculate the current frequency band energy at two ends of a protected line so as to judge whether the fault is in an area or outside the area, thereby improving the reliability of protection. The problem that the protection method for AC output of a DFIG access MMC-HVDC system in the prior art cannot adapt to the characteristics of power electronic power supplies at two ends is solved, and the practicability is high; and the fault identification and removal are facilitated.

Claims (6)

1. The pilot protection system for accessing the double-fed fan to the flexible direct current is characterized in that a specific circuit structure is as follows: the system comprises a power supply (1), an A bus (3) and a B bus (13), wherein the A bus (3) is connected with the B bus (13) through a line (5), the B bus (13) is connected with an MMC-HVDC system (15) through a step-up transformer (14), and the A bus (3) is connected with the power supply (1) through a step-down transformer (2);
a head-end circuit breaker (4) and a head-end voltage current transformer (6) for detecting the voltage and current values of the head-end circuit breaker are arranged at an outlet of the A bus (3), the head-end circuit breaker (4) is connected with an action controller a (8), and the head-end voltage current transformer (6) and the action controller a (8) are both connected with a programmable processor a (7); and a tail end breaker (9) and a tail end voltage current transformer (10) for detecting the voltage current value at the tail end breaker are arranged at an outlet of the B bus (13), wherein the tail end breaker (9) is connected with an action controller B (12), and the tail end voltage current transformer (10) and the action controller B (12) are both connected with a programmable processor B (11).
2. The double-fed wind turbine flexible direct current connection pilot protection system according to claim 1, wherein the power supply (1) is a double-fed wind driven generator.
3. The pilot protection method for the pilot protection system of the double-fed fan access flexible direct current according to any one of claims 1 to 2, characterized by comprising the following steps:
step 1, respectively acquiring current values of a head-end circuit breaker (4) and a tail-end circuit breaker (9) on a line (5) through a head-end voltage current transformer (6) and a tail-end voltage current transformer (10), inputting the measured current values into a programmable processor a (7) through the head-end voltage current transformer (6), and inputting the measured current values into a programmable processor b (11) through the tail-end voltage current transformer (10);
and 2, calculating the frequency band energy ratio of the currents at two ends by using the waveform of the head-end circuit breaker and the current of the tail-end circuit breaker obtained in the step 1, if the difference value M of the calculated first frequency band energy ratio is greater than a setting value, actuating the circuit breaker, tripping the head-end circuit breaker and the tail-end circuit breaker to break a circuit, and if the calculated M is less than the setting value, continuing sampling.
4. The pilot protection method for the double-fed fan to access the pilot protection system of the flexible direct current according to claim 3, wherein the step 1 is implemented specifically as follows: and simulating different types of faults of the power distribution network through a PSCAD simulation experiment, and importing the obtained fault current data into an MATLAB program.
5. The pilot protection method of the pilot protection system for the double-fed fan to access the flexible direct current according to claim 3, wherein the frequency band energy ratio calculation method in the step 2 is as follows:
selecting Meyer wavelet decomposition according to characteristics and requirements of sampling current, and defining Meyer wavelet as function
Figure FDA0003468514070000021
By dual-scale differential equations
Figure FDA0003468514070000022
Where w (t) is an orthogonal scale function, { hk}k∈ZAnd { gk}k∈ZIs a pair of conjugate orthogonal filter coefficients, t is the time scale;
production function set { wn,j,k(t):＝2-j/2wn(2-j-k), n ∈ Z, j ∈ Z, k ∈ Z } is said to pertain to
Figure FDA0003468514070000025
Z represents an integer set;
for the current sampling signal i (t) in step 1, the discrete orthogonal wavelet packet transform is defined as i (t) in the orthogonal wavelet packet basis { w } { (t)n,j,k(t)}n∈Z,j∈Z,k∈ZI.e.:
Figure FDA0003468514070000023
wherein, { ps(n,j,k)}k∈ZIs i (t) in the orthogonal wavelet packet space
Figure FDA0003468514070000024
A sequence of wavelet packet transform coefficients;
then orthogonal wavelet packet space
Figure FDA0003468514070000031
The energy distribution E (j, n) of the current signal i (t) in the time-frequency localization space is defined as follows:
Figure FDA0003468514070000032
wherein the wavelet packet transform coefficient psThe discrete numerical calculation of (n, j, k) adopts a recursion algorithm of formula (1), and the energy of the first frequency band is the ratio D of the energy distribution of the first wavelet packet transform coefficient in the whole energy distribution as follows:
Figure FDA0003468514070000033
in conclusion, by taking the traditional current differential protection as a reference, a pilot protection criterion of the line between the DFIG and the MMC-HVDC is constructed:
(DMMC+DDFIG)-(DMMC-DDFIG)≥Dop0 (5)
wherein D isMMCRepresenting the first frequency band component, D, in the MMC short-circuit currentDFIGRepresents the first frequency band component in the DFIG short-circuit current; dop0Is a setting value.
6. The pilot protection method of the pilot protection system for accessing the double-fed fan to the flexible direct current according to claim 5, wherein the setting value D in the step 2op0Is 0.2.
CN202210036366.9A 2022-01-13 2022-01-13 Pilot protection system and pilot protection method for flexible direct current connected to double-fed fan Active CN114530831B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202210036366.9A CN114530831B (en) 2022-01-13 2022-01-13 Pilot protection system and pilot protection method for flexible direct current connected to double-fed fan

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210036366.9A CN114530831B (en) 2022-01-13 2022-01-13 Pilot protection system and pilot protection method for flexible direct current connected to double-fed fan

Publications (2)

Publication Number Publication Date
CN114530831A true CN114530831A (en) 2022-05-24
CN114530831B CN114530831B (en) 2024-08-27

Family

ID=81620749

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202210036366.9A Active CN114530831B (en) 2022-01-13 2022-01-13 Pilot protection system and pilot protection method for flexible direct current connected to double-fed fan

Country Status (1)

Country Link
CN (1) CN114530831B (en)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104578013A (en) * 2015-01-20 2015-04-29 西安理工大学 Directional protection method for distribution network comprising DFIG based on current frequency difference
CN109245044A (en) * 2018-09-20 2019-01-18 西安理工大学 A kind of power distribution network equivalent sequence impedance longitudinal linkage protection method
CN109507534A (en) * 2018-11-29 2019-03-22 昆明理工大学 One kind being based on the accident analysis of MMC-HVDC overhead transmission line and recognition methods
US10908202B1 (en) * 2020-09-15 2021-02-02 North China Electric Power University High-frequency fault component based distance protection system and method for a transmission line of a renewable energy source system
CN113203916A (en) * 2021-04-21 2021-08-03 国网安徽省电力有限公司电力科学研究院 Inside and outside fault identification method and system of extra-high voltage direct current transmission line based on sym8 wavelet packet transformation

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104578013A (en) * 2015-01-20 2015-04-29 西安理工大学 Directional protection method for distribution network comprising DFIG based on current frequency difference
CN109245044A (en) * 2018-09-20 2019-01-18 西安理工大学 A kind of power distribution network equivalent sequence impedance longitudinal linkage protection method
CN109507534A (en) * 2018-11-29 2019-03-22 昆明理工大学 One kind being based on the accident analysis of MMC-HVDC overhead transmission line and recognition methods
US10908202B1 (en) * 2020-09-15 2021-02-02 North China Electric Power University High-frequency fault component based distance protection system and method for a transmission line of a renewable energy source system
CN113203916A (en) * 2021-04-21 2021-08-03 国网安徽省电力有限公司电力科学研究院 Inside and outside fault identification method and system of extra-high voltage direct current transmission line based on sym8 wavelet packet transformation

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
段建东，等: "基于电流衰减因子的含DFIG配电线路保护方案", 《中国电机工程学报》, vol. 40, no. 6, 20 March 2020 (2020-03-20), pages 1915 - 1921 *

Also Published As

Publication number Publication date
CN114530831B (en) 2024-08-27

Similar Documents

Publication Publication Date Title
EP3460936B1 (en) Pilot protection method for transmission line of new energy station based on current waveform similarity
Han et al. A virtual multi-terminal current differential protection scheme for distribution networks with inverter-interfaced distributed generators
CN109494697B (en) Cosine similarity-based new energy station multi-end pilot protection method
CN100530883C (en) Route selection method for single-phase ground fault of two-phase TA power distribution network
Yang et al. High-frequency fault component-based distance protection for large renewable power plants
CN109449899B (en) Pilot protection method based on spearman grade correlation coefficient
CN110880743B (en) Kendel rank correlation-based pilot protection method for outgoing line of wind power plant
CN107329044A (en) A kind of wire selection method for power distribution network single phase earthing failure based on electric arc transient state component
CN107765139A (en) A kind of resonant earthed system fault line selection method for single-phase-to-ground fault of high-accuracy
CN113437734B (en) Fault protection method and device suitable for wind power plant output line
CN110165644B (en) New energy station pilot protection method based on transient current time-frequency characteristics
CN113054661A (en) New energy station outgoing line pilot protection method based on Kaemphrara distance
Jia et al. Incipient fault identification-based protection for a photovoltaic DC integration system
CN117110783A (en) Fault direction judging method and system based on current waveform distortion characteristics
CN114884032B (en) High-speed protection method suitable for T-connection type outgoing line of new energy station and application thereof
CN115085164B (en) Wind field outbound interactive protection method and system
CN116365486A (en) Differential protection method and system for outgoing line of wind power station
Tripathy et al. A differential protection scheme for tapped transmission line containing UPFC and wind farm
CN110492438A (en) A kind of wind power plant main transformer protection method based on instantaneous frequency difference
CN114530831B (en) Pilot protection system and pilot protection method for flexible direct current connected to double-fed fan
CN115184735A (en) Fault phase selection method, system, equipment and terminal for new energy centralized sending line
Jia et al. Pilot protection based on amplitude comparison for renewable power teed lines
CN114928031A (en) Double-fed wind power alternating current circuit pilot protection system and protection method based on singular entropy
CN114696301A (en) Double-fed wind power plant output line single-phase grounding protection method and system
Liu et al. Fault diagnosis of HVDC transmission system using wavelet energy entropy and the wavelet neural network

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant