CN115224674A - Differential protection method, device and medium for power distribution network containing inverter type distributed power supply - Google Patents
Differential protection method, device and medium for power distribution network containing inverter type distributed power supply Download PDFInfo
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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
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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
- 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 inverter type distributed power supply. When a fault occurs in the protection section, the amplitude of the difference value between the sum of the high-frequency currents measured at the two ends of the protection section and the high-frequency current measured at the harmonic source IIDG grid-connected point is larger than the high-frequency current absorbed by other T-connected IIDGs, unpredictable loads and line-to-ground capacitors in the same section. On the contrary, when a fault occurs outside the protection zone, the high-frequency current difference is smaller than the high-frequency current absorbed by the T-branch. Therefore, the invention can reliably detect various types of short-circuit faults and has a higher engineering application prospect. The invention can be widely applied to the field of relay protection 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, a differential protection device and a differential protection medium for a power distribution network with an inverter type distributed power source.
Background
At present, the permeability of inverter type distributed generation (IIDG for short) represented by photovoltaic power supplies in a power distribution network is continuously improved. Due to the intermittent nature of IIDG power generation, the nonlinear relation between the output current and the grid-connected point voltage and the like, the fault current characteristics of the power distribution network are changed, the traditional current protection setting value without directivity is difficult to set, and the current protection cannot meet the protection requirement of the power distribution network containing the IIDG. The distribution network containing the IIDG is a multi-source system, the requirement protection has directionality, and along with the application of microcomputer protection and the development of communication technology, especially 5G technology, current differential protection with good selectivity becomes one of the main research directions for distribution network protection.
The existing current differential protection of the power distribution network mainly utilizes the amplitude value or phase information of power frequency current synchronously acquired at two ends of a protection section to form an action criterion. However, such methods typically only consider scenarios where the IIDG is accessed from the bus, essentially similar to the current differential method of the distribution network without the IIDG. However, as the network frame of the distribution network becomes more complex, the number of T-branch represented by IIDG and unpredictable load increases, and the current differential protection cannot guarantee correct action due to the boosting and drawing effects of the T-branch on the current. On one hand, the T-connection branch current can be acquired in real time by additionally arranging the current transformer, but the engineering construction cost can be greatly increased. On the other hand, the T-connection 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 the control strategy and the operation mode and the like, and the power flow estimation error is large.
Disclosure of Invention
In order to solve at least one of the technical problems 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 inverter-type distributed power supply.
The technical scheme adopted by the invention is as follows:
a differential protection method for a power distribution network containing an inverter type distributed power supply comprises the following steps:
s1, measuring phase voltage u at a feeder protection installation position and a harmonic source IIDG grid-connected point a/b/c Zero sequence voltage u 0 Low-pass filtering and sampling the measured phase voltage and zero sequence voltage;
s2, judging whether a starting condition is met or not according to the measured data, and if so, continuing to execute the following steps; if not, returning to execute the step S1;
s3, when the starting criterion is met, controlling the harmonic source IIDG to be switched into an operation mode of injecting extra high-frequency harmonics, and simultaneously starting feeder protection;
s4, starting time delay T through frequency spectrum analysis sd Then, extracting time windows T from two ends (M end and N end) of the feeder line and the outlet (P end) of the harmonic source IIDG 1 Internal three-phase current
And carrying out spectrum analysis to obtain high-frequency current vectors of each end
And
s5, transmitting high-frequency current vectors from the P end to the M end and the N end
Simultaneously, the M terminal and the N terminal mutually transmit high-frequency current vectors measured by each terminal
And
s6, calculating a high-frequency harmonic current differential value delta I m.har According to the high-frequency harmonic current differential value DeltaI m.har Determine whether or notIf the tripping condition is met, giving out a warning or tripping command; if not, the step S1 is executed again.
Further, the method also comprises a step of setting an initial value, comprising the following steps:
giving an initial value to the phase voltage loss constant value u abc.set And zero sequence voltage overvoltage constant value u 0.set ；
Giving initial value to amplitude control parameter u of high-frequency harmonic signal m.har Time window of spectral analysis T 1 Time delay for start of spectral analysis T sd High frequency harmonic signal injection duration T d ；
Assigning initial value to action setting value delta I act 。
Further, the action setting value delta I act The expression of (a) is:
in the formula, K re Is a reliability factor;
and
respectively obtaining high-frequency harmonic current vectors of the M end, the N end and the P end through spectrum analysis during a setting test period; k er The transmission error of the current transformer is adopted; k st The same type coefficient of the mutual inductor; k np Are non-periodic component coefficients.
Further, the starting condition in step S2 is determined as follows:
wherein, | u a/b/c And (n) and u0 (n) are three-phase voltage and zero-sequence voltage of a feeder protection installation position and a harmonic source IIDG grid-connected point obtained by nth measurement respectively.
Further, the high frequency harmonicsWave current differential value delta I m.har The calculation method of (c) is as follows:
. Further, the trip condition in step S6 is determined as follows:
ΔI m.har >ΔI act
wherein, delta I act Is a preset action setting value.
The other technical scheme adopted by the invention is as follows:
a differential protection device for a power distribution network containing an inverter type distributed power supply comprises:
at least one processor;
at least one memory for storing at least one program;
when executed by the at least one processor, cause the at least one processor to implement the method described above.
The other technical scheme adopted by the invention is as follows:
a computer readable storage medium in which a processor executable program is stored, which when executed by a processor is for performing the method as described above.
The invention has the beneficial effects that: the invention can reliably detect various types of short-circuit faults, has stronger transition resistance tolerance capability, can effectively reduce the interference of loads and the T-connection of the inverter 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 on the drawings of the embodiments of the present invention or the related technical solutions in the prior art, 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 it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic diagram of a fault scene of a power distribution network with an inverter-type distributed power supply in an embodiment of the invention;
FIG. 2 is a schematic diagram illustrating a control manner of injecting high-frequency harmonics into the inverter-type distributed power supply according to an embodiment of the present invention;
FIG. 3 is a high-frequency harmonic current path diagram under a single-phase earth fault of a distribution network with an inverter type distributed power supply in the embodiment of the invention;
fig. 4 is a flowchart of a current differential protection method for a power distribution network including an inverter type distributed power supply based on high-frequency harmonic injection in the embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention. The step numbers in the following embodiments are provided only for convenience of illustration, the order between the steps is not limited at all, and the execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.
In the description of the present invention, it should be understood that the orientation or positional relationship referred to in the description of the orientation, such as upper, lower, front, rear, left, right, etc., is based on the orientation or positional relationship shown in the drawings only for the convenience of description of the present invention and simplification of the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.
In the description of the present invention, a plurality of means is one or more, a plurality of means is two or more, and greater than, less than, more than, etc. are understood as excluding the essential numbers, and greater than, less than, etc. are understood as including the essential numbers. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood 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 otherwise specifically limited, terms such as set, installation, connection and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention by combining the specific contents of the technical solutions.
Because the high-frequency harmonic current output by the IIDG in normal operation is very small, the method can select a certain T-connection IIDG in a protection section as a harmonic source by adding an extra high-frequency voltage signal in an SPWM modulation wave, and control the T-connection IIDG to inject quantitative, fixed time limit and high-frequency harmonic current with specific frequency as a fault identification signal after the fault. At this time, when a fault occurs 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 greater than the high-frequency current absorbed by other T-connected IIDG, unpredictable loads and line-to-ground capacitors in the same section. On the contrary, when a fault occurs outside the protection zone, the high-frequency current difference is smaller than the high-frequency current absorbed by the T-branch. Therefore, the method focuses on the difference of flow paths of high-frequency current generated inside and outside a region when a fault occurs, and provides the current differential protection method for the distribution network containing the inverter type distributed power supply based on high-frequency harmonic injection. The method can reliably detect various types of short-circuit faults, has strong transition resistance tolerance capability, can effectively reduce the interference of loads and the T-connection of the inverter distributed power supply on the protection performance, and has a high engineering application prospect.
As shown in fig. 4, this embodiment provides a method for current differential protection of a distribution network including an inverter type distributed power supply based on high-frequency harmonic injection, including the following steps:
s101, giving an initial value to a phase voltage-loss fixed value u abc.set And zero sequence voltage overvoltage constant value u 0.set The protection device is used for starting the protection devices (M and N ends) at two ends of the feeder line and the high-frequency harmonic injection (P end) of the IIDG.
In normal operation, the phase voltage approaches the rated value and the zero sequence voltage is almostIs zero. When a phase or ground fault occurs in a power grid, a fault phenomenon that phase voltage is reduced or zero sequence voltage is increased usually occurs. By utilizing the characteristics, sampling values of phase voltage and zero sequence voltage are selected to construct a starting criterion of feeder protection and IIDG harmonic injection. To ensure a certain margin, the phase voltage is no-voltage constant u abc.set Setting according to 90% of rated voltage, and determining the overvoltage constant value u of zero-sequence voltage 0.set Setting is carried out within the range of 5-100V (greater than zero sequence voltage caused by three-phase unbalance of a system during normal operation). The fixed value can be flexibly adjusted according to the requirements of the anti-transition resistance capability and the sensitivity of the net rack in actual operation.
S102, assigning initial values to amplitude control parameters u of high-frequency harmonic signals m.har Time window of spectral analysis T 1 Time delay for start of spectral analysis T sd High frequency harmonic signal injection duration 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 factors such as the reference value of the control parameter of the inverter, the rated installed capacity of the power supply, the number of times of the specific high-frequency harmonic wave and the like, and directly influences the amplitude i of the specific high-frequency harmonic wave current output by the IIDG m.har . In order to avoid the problem of device damage caused by excessive harmonic, u is also required to be paired m.har I under the parameter m.har And (4) checking, namely, the requirement of the metering precision of the current transformer is met, and the requirement can not obviously exceed the specification of the IEEE standard on the waveform distortion rate of the output current of the inverter, namely, the IIDG is allowed to inject a proper excessive high-frequency harmonic current for fault identification in a short time after the fault.
Time window T for spectral analysis 1 : because the content of the high-frequency harmonic current is obviously less 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 on the filter, and the engineering economy is not enough. Therefore, in order to analyze the spectral characteristics of a specific high-frequency harmonic, the time window for collecting current information is set to 1 to 2 power frequency cycles (20 to 40 ms).
Spectral analysis start-up delay T sd : in the fault transient state stage, short-time high-frequency harmonic current output exists in the distributed power supply switching control strategyAnd (4) instability phenomenon. In order to weaken the phenomenon, a starting time delay needs to be set for frequency spectrum analysis, the time required by the harmonic source DG current output to be stable after the three-phase metallic short circuit fault occurs at the upstream outlet of the protection section is delayed, and 20-30 ms can be generally adopted to ensure the reliability.
High frequency harmonic signal injection duration T d : in order to avoid damage to the service life of the device due to harmonic wavelength time injection, the IIDG adopts a mode of automatically stopping injection at a harmonic timing mode without sending additional control signals to the harmonic source IIDG from the M end and the N end, and the injection time length T of the harmonic signal d Should be greater than the time required for in-zone failsafe action.
S103, assigning an initial value to the action setting value delta I act 。
Setting value delta I of high-frequency harmonic current differential protection act It is necessary to consider the absorption action of elements such as unpredictable load, capacitance to ground, and T-junction IIDG in the same section as the harmonic generation source IIDG on the high-frequency harmonic current. When a new IIDG or a new distribution transformer is accessed in the T type of the protection section, the harmonic source IIDG is controlled to send a short-time high-frequency harmonic signal, and according to the flow from the step S105 to the step S108, the delta I act This can be found from the following equation (assuming the system is in minimum operation mode, the unpredictable load is calculated as maximum active power):
in the formula: k is re For reliable coefficient, 1.3-1.5 can be taken;
and
respectively obtaining high-frequency harmonic current vectors of the M end, the N end and the P end through spectrum analysis during a setting test period; k is er The transmission error of the current transformer is adopted; k st The same type coefficient of the mutual inductor; k np Are non-periodic component coefficients.
S104, measuring feeder protection installation positions and harmonic sourcesPhase voltage u at IIDG grid-connected point a/b/c Zero sequence voltage u 0 And low pass filtered and sampled.
S105, judging whether the starting condition is met:
wherein, | u a/b/c (n)|、u 0 (n) respectively obtaining three-phase voltage and zero-sequence voltage at a feeder protection installation position and a harmonic source IIDG grid-connected point by nth measurement;
a. if yes, continuing the following process;
b. if not, return to step S104.
And S106, controlling the harmonic source IIDG to be immediately switched into an operation mode of injecting extra high-frequency harmonics after the starting criterion is met. As an alternative embodiment, the control may be performed in the manner shown in fig. 2.
S107, starting time delay T through spectrum analysis sd Then, the protection at the two ends of the feeder (M and N ends) and the extraction of a time window T at the outlet (P end) of the harmonic source IIDG are started 1 Internal three-phase current
Carrying out frequency spectrum analysis to obtain high-frequency current vectors of each end
And
s108.P end transmits high-frequency current vector to M end and N end
Simultaneously, the M terminal and the N terminal mutually transmit high-frequency current vectors measured by each terminal
And
the transmission process needs to keep the data synchronous.
S109, calculating a high-frequency harmonic current differential value delta I m.har ：
S110, judging whether the conditions are met: delta I m.har >ΔI act ；
a. If yes, issuing a warning or trip command;
b. if not, return to step S104.
The above process is explained in detail below with reference to specific engineering examples.
A single feeder of a 10kV distribution network with T-connection IIDG is taken as an example, and is shown in figure 1. The power frequency equivalent impedance Zs of the power supply of the superior system 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. In the MN segment, there are 3T-connected IIDGs (photovoltaic power sources) and 1T-connected loads (b-point access). The IIDG rated installed capacity and its grid-connected point numbers are 1MVA (a), 2MVA (P) and 1MVA (c), respectively. Four permanent fault points f are respectively set 1-4 The faults all occur at 0.1s. The lengths of the lines are shown in Table 1, and the load positions and the capacity sizes thereof are shown in Table 2.
The IIDG follows constant power control (assuming that only active power is output) in normal operation, and follows the requirement of low voltage ride through control after a fault. And selecting a T-connection IIDG with a P end connected and a large capacity as a harmonic source, and injecting extra high-frequency harmonic current into the power grid in a fixed time period after the fault for identifying the fault section.
TABLE 1 length of each section of feeder line of distribution network
TABLE 2 distribution network load location and capacity
The simulation adopts a 2-order Butterworth low-pass filter to carry out low-pass filtering processing on three-phase voltage and zero-sequence voltage sampling values required by starting, and the cutoff frequency is set to be 1000Hz. The data sampling frequency is 10kHz, and the reliability coefficient is K re 1.5 is taken, and the transmission error K of the current transformer er Taking 10 percent of the isomorphic coefficient K of the transformer st Taking a coefficient K of 0.5, non-periodic component np 1 is taken. Setting value delta I act After measurement and calculation, 0.70A is taken.
Other parameter settings are as follows: u. of abc.set =5.196kV (effective value); u. of 0.set =10V; suppose that the harmonic source IIDG outputs 10 harmonics, let u m.bar =5, the harmonic phase current effective value is about 6.2A (THD ≈ 5%); t is a unit of 1 ＝20ms；T sd ＝30ms；T d ＝60ms。
Referring to FIG. 3, tables 3-6 show four points of failure f 1 -f 4 Where a simulation result of a short-circuit fault (taking into account different fault types and different transition resistances) occurred. Three-phase high-frequency current differential value in the table
And the action condition of the line MN can be known, the protection method can not only correctly identify a fault section (inside or outside a zone) and a fault phase, but also has stronger transient resistance tolerance capability. Fig. 3 (a) is a high-frequency harmonic current path diagram under the intra-zone single-phase ground fault, and fig. 3 (b) is a high-frequency harmonic current path diagram under the out-of-zone single-phase ground fault.
TABLE 3 at f 1 Test results of faults with different fault types and different transition resistances
TABLE 4 at f 2 Test results of faults with different fault types and different transition resistances
TABLE 5 at f 3 Test results of faults with different fault types and different transition resistances
TABLE 6 at f 4 Test results of faults with different fault types and different transition resistances
Table 7 shows f 2 When different types of short-circuit faults occur (the transition resistance is fixed to be 20 omega), under the condition that harmonic sources have different power reference values (simulating DG normal operation modes under different external environments), three-phase high-frequency current differential values
And the behavior of the line MN. Therefore, the influence of the external environment and the running state of the harmonic source IIDG on the algorithm is small, and the algorithm can still accurately identify the fault section and the fault phase. It should be noted that the harmonic source IIDG needs to be configured to maintain the dc voltage stable when the external environment (e.g., lighting conditions) is not able to maintain the dc voltage stableAnd the energy storage device maintains the voltage of the direct current side.
TABLE 7 area of the harmonic source IIDG in different operating states (f) 2 ) Failure test result (transition resistance =20 Ω)
Table 8 shows f 2 When different types of short-circuit faults occur (the transition resistance is fixed to be 20 omega), under different powers of T-connection loads connected to the point b, three-phase high-frequency current differential values
And the behavior of the line MN. It can be seen that, after the maximum T-connection load has been considered in the fixed value to perform harmonic shunting, the influence of the fluctuation (not exceeding the normal fluctuation of the transformer capacity) of the T-connection load on the algorithm is small, and the algorithm can still accurately identify the fault section and the fault phase.
TABLE 8 Intra-zone at different T-connection load capacities (f) 2 ) Failure test result (transition resistance =20 Ω)
In summary, compared with the prior art, the embodiment has the following advantages and beneficial effects: the method can reliably detect various types of short-circuit faults, has strong transition resistance tolerance capability, can effectively reduce the interference of loads and the T-connection pair protection performance of the inverter type distributed power supply, and has a high engineering application prospect.
This embodiment still provides a contain contravariant distributed power source distribution network differential protection device, includes:
at least one processor;
at least one memory for storing at least one program;
when executed by the at least one processor, cause the at least one processor to implement the method of 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 high-frequency harmonic injection, can execute any combination of the implementation steps of the method embodiment, and has corresponding functions and beneficial effects of the method.
Embodiments of the present application also disclose a computer program product or computer program comprising computer instructions stored in a computer readable storage medium. The computer instructions may be read by a processor of a computer device from a computer-readable storage medium, and executed by the processor to cause the computer device to perform the method illustrated in fig. 4.
The embodiment also provides a storage medium, which stores an instruction or a program capable of executing the inverter-type distributed power distribution network current differential protection method based on high-frequency harmonic injection, and when the instruction or the program is run, the method can be executed by any combination of the method embodiments, and has corresponding functions and beneficial effects of the method.
In 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 flow charts 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 larger operations are performed independently.
Furthermore, although the present invention is described in the context of functional modules, it should be understood that, unless otherwise stated to the contrary, 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 a separate physical device or software module. It will also be appreciated that a detailed discussion of the actual implementation of each module is not necessary for an understanding of the present invention. Rather, the actual implementation of the various functional modules in the apparatus disclosed herein will be understood within the ordinary skill of an engineer given the nature, function, and interrelationships of the modules. Accordingly, those of ordinary skill in the art will be able to practice 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 of and not intended to limit the scope of the invention, which is defined by the appended claims and their full scope of equivalents.
The functions may be stored in a computer-readable storage medium if they are implemented in the form of software functional units and sold or used as separate products. Based on such understanding, the technical solution of the present invention or a part thereof which substantially contributes to the prior art may be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute 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), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The logic and/or steps represented in the flowcharts or otherwise described herein, e.g., an ordered listing of executable instructions that can be considered to implement 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). Further, the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can 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 should be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, 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, any one or combination of the following technologies, which are well known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.
In the foregoing description of the specification, reference to the description of "one embodiment/example," "another embodiment/example," or "certain embodiments/examples," etc., 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 embodiment or example. 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: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (8)
1. A differential protection method for a power distribution network containing an inverter type distributed power supply is characterized by comprising the following steps:
s1, measuring phase voltage u at a feeder 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 a starting condition is met or not according to the measured data, and if so, continuing to execute the following steps; if not, returning to execute the step S1;
s3, when the starting criterion is met, controlling the harmonic source IIDG to be switched into an operation mode of injecting extra high-frequency harmonics, and simultaneously starting feeder protection;
s4, passing spectrumAnalyzing the startup delay T sd Then, extracting time windows T from two ends (M end and N end) of the feeder line and the outlet (P end) of the harmonic source IIDG 1 Internal three-phase current
And carrying out frequency spectrum analysis to obtain high-frequency current vectors of each end
And
s5, transmitting high-frequency current vectors from the P end to the M end and the N end
Simultaneously, 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 high-frequency harmonic current differential value DeltaI m.har Judging whether a tripping condition is met, and if the condition is met, giving out a warning or a tripping command; if not, the step S1 is executed in a returning way.
2. The differential protection method for the power distribution network comprising the inverter type distributed power supply according to claim 1, further comprising the step of setting an initial value, comprising the steps of:
giving an initial value to the phase voltage loss constant value u abc.set And zero sequence voltage overvoltage constant value u 0.set ；
Giving initial value to amplitude control parameter u of high-frequency harmonic signal m.har Time window of spectral analysis T 1 Time delay for start of spectral analysis T sd High frequency harmonicWave signal injection duration T d ；
Assigning initial value to action setting value delta I act 。
3. The differential protection method for the distribution network with the inverter type distributed power supplies according to claim 2, wherein the action setting value delta I act The expression of (c) is:
in the formula, K re Is a reliability factor;
and
respectively obtaining high-frequency harmonic current vectors of the M end, the N end and the P end through spectrum analysis during a setting test period; k is er The transmission error of the current transformer is adopted; k st The same type coefficient of the mutual inductor; k np Are non-periodic component coefficients.
4. The differential protection method for the distribution network with the inverter-type distributed power supply according to claim 1, wherein the starting conditions in the step S2 are determined as follows:
wherein, | u a/b/c (n)|、u 0 And (n) respectively obtaining three-phase voltage and zero-sequence voltage at a feeder protection installation position and a harmonic source IIDG grid-connected point by nth measurement.
5. The differential protection method for the distribution network containing the inverter type distributed power supplies according to claim 1, wherein the high-frequency harmonic current differential value Δ I m.har The calculation of (c) is as follows:
6. the differential protection method for the distribution network with the 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, delta I act The preset action setting value is obtained.
7. A power distribution network differential protection device containing an inverter type distributed power supply is characterized by comprising:
at least one processor;
at least one memory for storing at least one program;
when executed by the at least one processor, cause the at least one processor to implement the method of any one of claims 1-6.
8. A computer-readable storage medium, in which a program executable by a processor is stored, wherein the program executable by the processor is adapted to perform the method according to any one of claims 1 to 6 when executed by the processor.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0332318A (en) * | 1989-06-27 | 1991-02-12 | Mitsubishi Electric Corp | Fault diagnostics for input section of differential protective device |
| CN109193586A (en) * | 2018-09-30 | 2019-01-11 | 西安工程大学 | A kind of both-end HVDC transmission line differential relaying algorithm |
| CN111900704A (en) * | 2020-08-04 | 2020-11-06 | 国网山东省电力公司聊城供电公司 | Active power distribution network current differential protection method and device without strict data synchronization |
| CN112653102A (en) * | 2020-11-27 | 2021-04-13 | 山东大学 | Active power distribution network differential protection method and system based on quadrature axis current |
| CN113162003A (en) * | 2021-05-10 | 2021-07-23 | 国网浙江余姚市供电有限公司 | IIDG-containing power distribution network harmonic differential protection method and system based on energy injection |
-
2022
- 2022-07-12 CN CN202210813776.XA patent/CN115224674B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0332318A (en) * | 1989-06-27 | 1991-02-12 | Mitsubishi Electric Corp | Fault diagnostics for input section of differential protective device |
| CN109193586A (en) * | 2018-09-30 | 2019-01-11 | 西安工程大学 | A kind of both-end HVDC transmission line differential relaying algorithm |
| CN111900704A (en) * | 2020-08-04 | 2020-11-06 | 国网山东省电力公司聊城供电公司 | Active power distribution network current differential protection method and device without strict data synchronization |
| CN112653102A (en) * | 2020-11-27 | 2021-04-13 | 山东大学 | Active power distribution network differential protection method and system based on quadrature axis current |
| CN113162003A (en) * | 2021-05-10 | 2021-07-23 | 国网浙江余姚市供电有限公司 | IIDG-containing power distribution network harmonic differential protection method and system based on energy injection |
Non-Patent Citations (1)
| Title |
|---|
| 孙德娟 等: "基于励磁电感计算的双馈风电场送出变差动保护", 电工技术学报, no. 02, 25 January 2020 (2020-01-25), pages 185 * |
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