CN115224674B - Differential protection method, device and medium for power distribution network with inversion type distributed power supply - Google Patents
Differential protection method, device and medium for power distribution network with inversion type distributed power supply Download PDFInfo
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Classifications
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- 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
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
- H02H3/28—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
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- 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
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
-
- 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
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/40—Arrangements for reducing harmonics
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Abstract
The invention discloses a differential protection method, a differential protection device and a differential protection medium for a power distribution network with an inversion type distributed power supply, wherein a certain T-connection IIDG in a protection section is selected as a harmonic source by adding an additional high-frequency voltage signal, and the method is controlled to inject a high-frequency harmonic current with fixed quantity, fixed time limit and specific frequency as a fault identification signal after a fault. When faults occur in the protection section, the amplitude of the difference between the sum of the high-frequency currents measured at the two ends of the protection section and the high-frequency current measured by the harmonic source IIDG grid-connected point is larger than the high-frequency currents absorbed by other T-connection IIDG, unpredictable loads and line-to-ground capacitance in the same section. Otherwise, when the protection section fails, the high-frequency current difference value is smaller than the high-frequency current absorbed by the T-branch. Therefore, the invention can reliably detect various short-circuit faults and has higher engineering application prospect. The invention can be widely applied to the relay protection field of the power distribution network.
Description
Technical Field
The invention relates to the field of relay protection of power distribution networks, in particular to a differential protection method, device and medium for a power distribution network with an inversion type distributed power supply.
Background
At present, the permeability of an inversion type distributed power supply (IIDG for short) represented by a photovoltaic power supply in a power distribution network is continuously improved. Because of the intermittence of IIDG power generation and the nonlinear relation between the output current and the grid-connected point voltage, the fault current characteristics of the power distribution network are changed, and the traditional current protection setting value without directivity is difficult to set, so that the current protection cannot meet the protection requirement of the power distribution network containing IIDG. The IIDG-containing power distribution network is a multi-source system, the protection is required to have directivity, and along with the development of microcomputer protection application and communication technology, particularly 5G technology, the current differential protection with good selectivity becomes one of main research directions of power distribution network protection.
The existing current differential protection of the power distribution network mainly utilizes the amplitude or phase information of the power frequency current synchronously collected at two ends of a protection section to form an action criterion. However, such methods generally only consider the scenario of IIDG access from the bus, and are essentially similar to the power distribution network current differential method without IIDG. However, as the grid of the power distribution network is increasingly complex, the T-branch represented by IIDG and unpredictable load is increasing, and the current differential protection cannot guarantee correct action due to the auxiliary increasing and drawing effect of the T-branch on current. On the one hand, the T-junction branch current can be acquired in real time by additionally installing a current transformer, but the engineering construction cost can be greatly increased. On the other hand, the T-junction branch current can be estimated in real time through the line power flow, but the protection strategy is possibly invalid due to the fact that the power frequency current output by the IIDG is greatly influenced by a control strategy and an operation mode, and the like.
Disclosure of Invention
In order to solve at least one of the technical problems existing in the prior art to a certain extent, the invention aims to provide a differential protection method, a differential protection device and a differential protection medium for a power distribution network with an inversion type distributed power supply.
The technical scheme adopted by the invention is as follows:
a differential protection method for a power distribution network with an inversion type distributed power supply comprises the following steps:
s1, measuring phase voltage u at a feeder line protection installation position and a harmonic source IIDG grid-connected point a/b/c Zero sequence voltage u 0 And low-pass filtering and sampling are carried out on the measured phase voltage and zero sequence voltage;
s2, judging whether the starting condition is met according to the measured data, and if so, continuing to execute the following steps; if not, returning to the execution step S1;
s3, after a starting criterion is met, controlling a harmonic source IIDG to be switched into an operation mode of injecting additional high-frequency harmonic waves, and simultaneously starting feeder protection;
s4, starting time delay T through spectrum analysis sd Then, extracting time window T from two ends (M end and N end) of feeder line and harmonic source IIDG outlet (P end) 1 Three-phase current inAnd performing frequency spectrum analysis to obtain high-frequency current vectors of all ends +.> And
s5, P end transmits high-frequency current vector to M end and N endAt the same time, the M terminal and the N terminal mutually transmit the high-frequency current vector measured by each terminal>And->
S6, calculating a high-frequency harmonic current differential value delta I m.har According to the differential value delta I of the high-frequency harmonic current m.har Judging whether a tripping condition is met, and if so, sending out a warning or a tripping command; if not, the process returns to the step S1.
Further, the method also comprises the step of setting an initial value, which comprises the following steps:
giving an initial value to a constant voltage value u of phase voltage loss abc.set Zero sequence voltage overvoltage definite value u 0.set ；
Giving an initial value to the amplitude control parameter u of the high-frequency harmonic signal m.har Time window of spectrum analysis T 1 Time delay T for spectrum analysis start sd Injection time length T of high-frequency harmonic signal d ；
Giving an initial value to an action setting value delta I act 。
Further, the motion setting value Δi act The expression of (2) is:
wherein K is re Is a reliable coefficient;and->The high-frequency harmonic current vectors are M, N and P end respectively, and are obtained through spectrum analysis during the setting test; k (K) er Is a transmission error of the current transformer; k (K) st Is the same type coefficient of the transformer; k (K) np Is an aperiodic component coefficient.
Further, the starting condition in step S2 is judged as follows:
wherein, |u a/b/c And (n) |, u0 (n) are three-phase voltage and zero-sequence voltage at the installation position of the feeder protection and the grid-connected point of the harmonic source IIDG respectively obtained by n-th measurement.
Further, the high frequency harmonic current differential value DeltaI m.har The calculation mode of (2) is as follows:
. Further, the trip condition in step S6 is judged as follows:
ΔI m.har >ΔI act
wherein DeltaI act Setting a value for a preset action.
The invention adopts another technical scheme that:
a differential protection device for a distribution network including an inversion type distributed power supply, comprising:
at least one processor;
at least one memory for storing at least one program;
the at least one program, when executed by the at least one processor, causes the at least one processor to implement the method described above.
The invention adopts another technical scheme that:
a computer readable storage medium, in which a processor executable program is stored, which when executed by a processor is adapted to carry out the method as described above.
The beneficial effects of the invention are as follows: the invention can reliably detect various short-circuit faults, has strong transitional resistance tolerance, can effectively reduce the interference of load and the T-junction of the inversion type distributed power supply on the protection performance, and has higher engineering application prospect.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description is made with reference to the accompanying drawings of the embodiments of the present invention or the related technical solutions in the prior art, and it should be understood that the drawings in the following description are only for convenience and clarity of describing some embodiments in the technical solutions of the present invention, and other drawings may be obtained according to these drawings without the need of inventive labor for those skilled in the art.
FIG. 1 is a schematic diagram of a fault scenario of a power distribution network including an inversion type distributed power supply in an embodiment of the invention;
FIG. 2 is a schematic diagram of a control method for injecting high frequency harmonics into an inverter type distributed power supply according to an embodiment of the present invention;
FIG. 3 is a diagram of a high frequency harmonic current path in a single phase earth fault of a power distribution network including an inverter type distributed power source in an embodiment of the present invention;
fig. 4 is a flowchart of a current differential protection method for a power distribution network with an inverter type distributed power supply based on high-frequency harmonic injection in an embodiment of the invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the invention. The step numbers in the following embodiments are set for convenience of illustration only, and the order between the steps is not limited in any way, and the execution order of the steps in the embodiments may be adaptively adjusted according to the understanding of those skilled in the art.
In the description of the present invention, it should be understood that references to orientation descriptions such as upper, lower, front, rear, left, right, etc. are based on the orientation or positional relationship shown in the drawings, are merely for convenience of description of the present invention and to simplify the description, and do not indicate or imply that the apparatus or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present invention.
In the description of the present invention, a number means one or more, a number means two or more, and greater than, less than, exceeding, etc. are understood to not include the present number, and above, below, within, etc. are understood to include the present number. The description of the first and second is for the purpose of distinguishing between technical features only and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.
In the description of the present invention, unless explicitly defined otherwise, terms such as arrangement, installation, connection, etc. should be construed broadly and the specific meaning of the terms in the present invention can be reasonably determined by a person skilled in the art in combination with the specific contents of the technical scheme.
Because the high-frequency harmonic current output by the IIDG during normal operation is very small, the method can select a certain T-joint IIDG in the protection section as a harmonic source in a mode of adding an additional high-frequency voltage signal into the SPWM modulation wave, and control the high-frequency harmonic current which is injected into a fixed quantity, fixed time limit and specific frequency after a fault to serve as a fault identification signal. At this time, when a fault occurs in the protection section, the magnitude of the difference between the sum of the high-frequency currents measured at the two ends of the protection section and the high-frequency current measured by the harmonic source IIDG parallel point is larger than the high-frequency currents absorbed by other T-connection IIDG, unpredictable load and line-to-ground capacitance in the same section. Otherwise, when the protection section fails, the high-frequency current difference value is smaller than the high-frequency current absorbed by the T-branch. Accordingly, the current differential protection method for the power distribution network with the inverter type distributed power supply based on high-frequency harmonic injection is provided by focusing the flow path difference of high-frequency current in and out of a region where faults occur. The method can reliably detect various short-circuit faults, has strong transitional resistance tolerance, can effectively reduce the interference of load and the T-junction of the inversion type distributed power supply on the protection performance, and has higher engineering application prospect.
As shown in fig. 4, the present embodiment provides a current differential protection method for a power distribution network including an inversion type distributed power supply based on high-frequency harmonic injection, which includes the following steps:
s101, giving an initial value to a phase voltage loss constant value u abc.set Zero sequence voltage overvoltage definite value u 0.set And the protection device (M, N end) is used for starting the high-frequency harmonic injection (P end) of the IIDG at the two ends of the feeder line.
In normal operation, the phase voltage approaches the nominal value and the zero sequence voltage is almost zero. When a grid fails in phase or in ground, a fault phenomenon of phase voltage drop or zero sequence voltage rise usually occurs. By utilizing the characteristics, sampling values of phase voltage and zero sequence voltage are selected to construct a starting criterion of feed line protection and IIDG harmonic injection. To ensure a certain margin, the phase voltage is out of voltage by a constant value u abc.set Setting according to 90% of rated voltage, overvoltage fixed value u of zero sequence voltage 0.set The tuning is carried out within the range of 5-100V (which is larger than zero sequence voltage caused by three-phase unbalance of the system in normal operation). The fixed value can be flexibly adjusted according to the transition resistance and sensitivity requirements of the net rack in actual operation.
S102, giving an initial value to a high-frequency harmonic signal amplitude control parameter u m.har Time window of spectrum analysis T 1 Time delay T for spectrum analysis start sd High frequency harmonic signal injectionDuration T d 。
Wherein, the amplitude control parameter u of the high-frequency harmonic signal m.har The magnitude of the current is related to the reference value of the control parameter of the inverter, the rated installed capacity of the power supply, the times of specific high-frequency harmonic waves and other factors, and directly influences the amplitude i of the specific high-frequency harmonic wave current output by IIDG m.har . To avoid the problem of damage to the device caused by excessive harmonic wave, the method also needs to be applied to the circuit m.har I under parameters m.har The verification is carried out, so that the requirement of the metering precision of the current transformer is met, meanwhile, the requirement of the IEEE standard on the deformation rate of the waveform of the output current of the inverter cannot be obviously exceeded, namely, the IIDG is allowed to inject proper excessive high-frequency harmonic current for fault identification in a short time after the fault.
Spectral analysis time window T 1 : because the high-frequency harmonic current content is obviously smaller than the power frequency current, if the power frequency component is filtered by adopting a high-pass or band-pass filtering mode, higher performance requirements are put forward on the filter, and engineering economy is not enough. Therefore, in order to analyze the spectral characteristics of specific high-frequency harmonics, the time window for collecting current information is set to 1-2 power frequency cycles (20-40 ms).
Spectral analysis start time delay T sd : in the fault transient stage, the distributed power supply switching control strategy has the phenomenon of unstable output of short-time high-frequency harmonic current. To reduce this phenomenon, a start delay is required for spectrum analysis, and the delay is according to the time required for stabilizing the current output of the harmonic source DG after a three-phase metallic short-circuit fault occurs at the upstream outlet of the protection section, and is usually 20 to 30ms to ensure reliability.
High-frequency harmonic signal injection duration T d : in order to avoid the damage to the service life of the device caused by long-time harmonic injection, the IIDG adopts a mode of automatically stopping the injection at the harmonic timing, and the M, N end is not required to send an additional control signal to the harmonic source IIDG, so that the injection time length T of the harmonic signal is long d Should be longer than the time period required for the fail-safe action within the zone.
S103, giving an initial value to an action setting value delta I act 。
Setting value delta I of high-frequency harmonic current differential protection act Consideration of being in the presence of harmonic emission source IIDGUnpredictable load, capacitance to ground, and absorption of high-frequency harmonic current by elements such as T-connection IIDG in the same section. Whenever a new IIDG or distribution transformer is accessed in the T-type of the protection section, the control harmonic source IIDG sends a short-time high-frequency harmonic signal once, and the process from step S105 to step S108 is carried out, wherein DeltaI is controlled act The following equation can be used (assuming the system is in minimum mode of operation, unpredictable load is calculated as maximum active power):
wherein: k (K) re 1.3 to 1.5 of the reliability coefficient can be taken;and->The high-frequency harmonic current vectors are M, N and P end respectively, and are obtained through spectrum analysis during the setting test; k (K) er Is a transmission error of the current transformer; k (K) st Is the same type coefficient of the transformer; k (K) np Is an aperiodic component coefficient.
S104, measuring phase voltage u at feeder line protection installation position and harmonic source IIDG grid-connected point position a/b/c Zero sequence voltage u 0 And low pass filtered and sampled.
S105, judging whether a starting condition is met:
wherein, |u a/b/c (n)|、u 0 (n) respectively obtaining three-phase voltage and zero-sequence voltage at the installation position of the feeder line protection and the point of the harmonic source IIDG parallel connection for the nth measurement;
a. if yes, continuing the following flow;
b. if not, return to step S104.
S106, when the starting criterion is met, the control harmonic source IIDG is immediately switched to an operation mode of injecting additional high-frequency harmonic. As an alternative embodiment, the control may be performed using a control manner as shown in fig. 2.
S107, performing spectrum analysis to start time delay T sd Then, the protection at two ends of the feeder line (M, N end) and the extraction of the time window T at the outlet of the harmonic source IIDG (P end) are started 1 Three-phase current inPerforming spectral analysis to obtain high-frequency current vector +.> And->
S108.P terminal transmits high-frequency current vector to M terminal and N terminalAt the same time, the M terminal and the N terminal mutually transmit the high-frequency current vector measured by each terminal>And->The transmission process needs to keep data synchronization.
S109, calculating a high-frequency harmonic current differential value delta I m.har ：
S110, judging whether the condition is satisfied: ΔI m.har >ΔI act ；
a. If so, issuing a warning or trip command;
b. if not, return to step S104.
The above method is explained in detail below in connection with specific engineering examples.
Taking a single feeder line of a 10kV power distribution network with T-connection IIDG as an example, the method is shown in figure 1. The power frequency equivalent impedance Zs of the upper system power supply is j0.2356 omega, the feeder line is mainly divided into three sections (SM, MN and NT), and the power frequency impedance parameter of the line is 0.165+j0.365 omega/km. The MN segment has 3T-connected IIDG (photovoltaic power) and 1T-connected load (b-point access). IIDG rated installed capacity and grid connection point numbers are 1MVA (a), 2MVA (P) and 1MVA (c) respectively. Four permanent fault points f are respectively set 1-4 Faults all occurred at 0.1s. The length of each section of line is shown in table 1, and the load position and the capacity size are shown in table 2.
The IIDG operates normally under constant power control (assuming that only active power is output), and under low voltage ride through control requirements after failure. And selecting a T-connection IIDG with larger capacity and P-terminal connection as a harmonic source, and injecting additional high-frequency harmonic current into the power grid in a fixed time period after the fault for identifying a fault section.
Table 1 feeder length of each segment of distribution network
Table 2 distribution network load location and capacity thereof
The simulation adopts a 2-order Butterworth low-pass filter to carry out low-pass filtering treatment on three-phase voltage and zero-sequence voltage sampling values required by starting, and the cut-off frequency is set to be 1000Hz. The data sampling frequency is 10kHz, and the reliability coefficient is K re 1.5, the current transformer transmission error K er 10% of the transformer model coefficient K st Taking 0.5, non-periodic component coefficient K np Taking 1. Action setting value Δi act 0.70 is obtained after measurement and calculationA。
Other parameter settings are as follows: u (u) abc.set =5.196 kV (effective value); u (u) 0.set =10v; let u output 10 th harmonic assuming harmonic source IIDG m.bar =5, then the harmonic phase current effective value is about 6.2A (thd≡5%); t (T) 1 ＝20ms；T sd ＝30ms；T d ＝60ms。
Referring to FIG. 3, tables 3-6 give four failure points f 1 -f 4 Simulation results of short circuit faults (considering different fault types and different transition resistances) occur. Three-phase high-frequency current differential value in meterThe action condition of the line MN can be known, and the protection method can accurately identify the fault section (in or out of the area) and the fault phase, and has stronger transitional resistance tolerance. Wherein, fig. 3 (a) is a high-frequency harmonic current path diagram under an intra-zone single-phase earth fault, and fig. 3 (b) is a high-frequency harmonic current path diagram under an out-of-zone single-phase earth fault.
Table 3 at f 1 Test results of faults of different fault types and different transition resistances
Table 4 at f 2 Test results of faults of different fault types and different transition resistances
Table 5 at f 3 Test results of faults of different fault types and different transition resistances
Table 6 at f 4 Test results of faults of different fault types and different transition resistances
Table 7 gives f 2 When different types of short-circuit faults occur (the transition resistance is fixed to be 20Ω), under different power reference values of the harmonic source (simulating DG normal operation modes under different external environments), three-phase high-frequency current differential valuesAnd the behavior of the line MN. Therefore, the external environment and the running state of the harmonic source IIDG have small influence on the algorithm, and the algorithm can still accurately identify the fault section and the fault phase. It should be noted that when the external environment (such as illumination condition) cannot maintain the stable dc voltage, the harmonic source IIDG needs to configure an energy storage device capable of maintaining the dc side voltage.
TABLE 7 within regions of different operating states of harmonic source IIDG (f 2 ) Fault test result (transition resistance=20Ω)
Table 8 gives f 2 When different types of short-circuit faults occur (the transition resistance is fixed to be 20Ω), under the different powers of the T-junction load connected at the point b, three-phase high-frequency current differential valueAnd the behavior of the line MN. Therefore, when the maximum T-junction load has a harmonic shunting effect in consideration of the fixed value, the fluctuation of the T-junction load (not exceeding the normal fluctuation of the capacity of the transformer) has less influence on the algorithm, and the algorithm can still accurately identify the fault section and the fault phase.
TABLE 8 within zones (f) at different T-connect loading capacities 2 ) Fault test result (transition resistance=20Ω)
In summary, compared with the prior art, the embodiment has the following advantages and beneficial effects: the current differential protection method for the power distribution network with the inverter type distributed power supply based on the high-frequency harmonic injection can reliably detect various short-circuit faults, has strong transitional resistance, can effectively reduce the interference of load and the T-junction of the inverter type distributed power supply on the protection performance, and has a high engineering application prospect.
The embodiment also provides a differential protection device of a power distribution network with an inversion type distributed power supply, which comprises:
at least one processor;
at least one memory for storing at least one program;
the at least one program, when executed by the at least one processor, causes the at least one processor to implement the method as shown in fig. 4.
The differential protection device for the power distribution network with the inverter type distributed power supply can execute the current differential protection method for the power distribution network with the inverter type distributed power supply based on the high-frequency harmonic injection, can execute any combination implementation steps of the method embodiments, and has corresponding functions and beneficial effects.
The present application also discloses a computer program product or a computer program comprising computer instructions stored in a computer readable storage medium. The computer instructions may be read from a computer-readable storage medium by a processor of a computer device, and executed by the processor, to cause the computer device to perform the method shown in fig. 4.
The embodiment also provides a storage medium which stores instructions or programs capable of executing the inversion type distributed power distribution network current differential protection method based on the high-frequency harmonic injection, and when the instructions or programs are operated, any combination implementation steps of the method embodiments can be executed, so that the method has corresponding functions and beneficial effects.
In some alternative embodiments, the functions/acts noted in the block diagrams may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Furthermore, the embodiments presented and described in the flowcharts of the present invention are provided by way of example in order to provide a more thorough understanding of the technology. The disclosed methods are not limited to the operations and logic flows presented herein. Alternative embodiments are contemplated in which the order of various operations is changed, and in which sub-operations described as part of a larger operation are performed independently.
Furthermore, while the invention is described in the context of functional modules, it should be appreciated that, unless otherwise indicated, one or more of the described functions and/or features may be integrated in a single physical device and/or software module or one or more functions and/or features may be implemented in separate physical devices or software modules. It will also be appreciated that a detailed discussion of the actual implementation of each module is not necessary to an understanding of the present invention. Rather, the actual implementation of the various functional modules in the apparatus disclosed herein will be apparent to those skilled in the art from consideration of their attributes, functions and internal relationships. Accordingly, one of ordinary skill in the art can implement the invention as set forth in the claims without undue experimentation. It is also to be understood that the specific concepts disclosed are merely illustrative and are not intended to be limiting upon the scope of the invention, which is to be defined in the appended claims and their full scope of equivalents.
The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
Logic and/or steps represented in the flowcharts or otherwise described herein, e.g., a ordered listing of executable instructions for implementing logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). In addition, the computer readable medium may even be paper or other suitable medium on which the program is printed, as the program may be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory.
It is to be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above-described embodiments, the various steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, may be implemented using any one or combination of the following techniques, as is well known in the art: discrete logic circuits having logic gates for implementing logic functions on data signals, application specific integrated circuits having suitable combinational logic gates, programmable Gate Arrays (PGAs), field Programmable Gate Arrays (FPGAs), and the like.
In the foregoing description of the present specification, reference has been made to the terms "one embodiment/example", "another embodiment/example", "certain embodiments/examples", and the like, means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the invention, the scope of which is defined by the claims and their equivalents.
While the preferred embodiment of the present invention has been described in detail, the present invention is not limited to the above embodiments, and various equivalent modifications and substitutions can be made by those skilled in the art without departing from the spirit of the present invention, and these equivalent modifications and substitutions are intended to be included in the scope of the present invention as defined in the appended claims.
Claims (6)
1. The differential protection method for the power distribution network with the inversion type distributed power supply is characterized by comprising the following steps of:
s1, measuring phase voltage u at a feeder line protection installation position and a harmonic source IIDG grid-connected point a/b/c Zero sequence voltage u 0 Sampling the measured phase voltage and zero sequence voltage;
s2, judging whether the starting condition is met according to the measured data, and if so, continuing to execute the following steps;
if not, returning to the execution step S1;
s3, after a starting criterion is met, controlling a harmonic source IIDG to be switched into an operation mode of injecting additional high-frequency harmonic waves, and simultaneously starting feeder protection;
s4, starting time delay T through spectrum analysis sd Then, extracting time window T from M end, N end and P end of harmonic source IIDG outlet of feeder line 1 Three-phase current inAnd performing frequency spectrum analysis to obtain high-frequency current vectors of all ends +.>And->
S5, P end transmits high-frequency current vector to M end and N endAt the same time, the M terminal and the N terminal mutually transmit the high-frequency current vector measured by each terminal>And->
S6, calculating a high-frequency harmonic current differential value delta I m.har According to the differential value delta I of the high-frequency harmonic current m.har Judging whether a tripping condition is met, and if so, sending out a warning or a tripping command; if not, returning to the execution step S1;
the method also comprises the following steps:
giving an initial value to an action setting value delta I act ；
The action setting value delta I act The expression of (2) is:
wherein K is re Is a reliable coefficient;and->The high-frequency harmonic current vectors are M, N and P end respectively, and are obtained through spectrum analysis during the setting test; k (K) er Is a transmission error of the current transformer; k (K) st Is the same type coefficient of the transformer; k (K) np As non-periodic component coefficients
The high-frequency harmonic current differential value delta I m.har The calculation mode of (2) is as follows:
2. the differential protection method for a power distribution network with an inverter type distributed power source according to claim 1, further comprising the step of setting an initial value, comprising:
giving an initial value to a constant voltage value u of phase voltage loss abc.set Zero sequence voltage overvoltage definite value u 0.set ；
Giving an initial value to the amplitude control parameter u of the high-frequency harmonic signal m.har Time window of spectrum analysis T 1 Time delay T for spectrum analysis start sd Injection time length T of high-frequency harmonic signal d 。
3. The differential protection method for a power distribution network with an inverter type distributed power supply according to claim 2, wherein the starting condition in step S2 is determined as follows:
wherein, |u a/b/c (n)|、u 0 And (n) respectively obtaining three-phase voltage and zero-sequence voltage at the installation position of the feeder line protection and the grid-connected point of the harmonic source IIDG for the nth measurement.
4. The differential protection method for a power distribution network with an inverter type distributed power supply according to claim 1, wherein the trip condition in step S6 is determined as follows:
ΔI m.har >ΔI act
wherein DeltaI act Setting a value for a preset action.
5. The utility model provides a contain differential protection device of contravariant formula distributed power supply distribution network which characterized in that includes:
at least one processor;
at least one memory for storing at least one program;
the at least one program, when executed by the at least one processor, causes the at least one processor to implement the method of any one of claims 1-4.
6. A computer readable storage medium, in which a processor executable program is stored, characterized in that the processor executable program is for performing the method according to any of claims 1-4 when being executed by a processor.
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