CN119247047B - Island micro-grid group fault judging method and system based on star-ground network fusion - Google Patents
Island micro-grid group fault judging method and system based on star-ground network fusion Download PDFInfo
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Abstract
The application provides a island micro-grid group fault judging method and system based on star network fusion, wherein the island micro-grid group fault judging method comprises the steps of obtaining a first three-phase current of a power grid node i to be judged at the current moment, obtaining a second three-phase current of the power grid node i to be judged at the corresponding moment of the last period, obtaining three-phase current fault components of the power grid node to be judged according to the first three-phase current and the second three-phase current, judging whether the island micro-grid group to be judged corresponding to the power grid node i to be judged is faulty according to the three-phase current fault components, extracting fault characteristics according to the three-phase current fault components if the island micro-grid group to be judged is faulty, constructing a fault coefficient vector according to the fault characteristics, and obtaining a fault line and a fault phase of the island micro-grid group to be judged according to the fault coefficient vector. The position and the reason of the fault in the micro-grid can be quickly obtained, and the fault repair can be quickly and accurately carried out.
Description
Technical Field
The application belongs to the field of power grids, and particularly relates to a island micro-grid group fault judging method and system based on satellite-ground network fusion.
Background
The island contains rich renewable energy sources, various new energy sources such as wind power, photovoltaic and the like are integrated according to local conditions to form a micro-grid, adjacent island micro-grids are interconnected to form an island micro-grid group, and the island micro-grid group is an important way for realizing sustainable high-quality power supply of the ocean island group by cooperative operation and energy mutual utilization among sub-micro-grids so as to improve the power supply reliability and the new energy utilization rate of the system. Compared with a single micro-grid, the micro-grid group has the characteristics that firstly, a plurality of interconnection modes exist among the micro-grids, the network topology is changed frequently, so that the system power flow is changed bidirectionally before the fault and the current circulation paths of the system after the fault are more, and secondly, the micro-grid group has complex fault characteristics and fuzzy fault boundaries inside and outside the region due to the superposition effect of the fault currents output by a plurality of types of micro-sources with different fault response processes. Therefore, the design of an effective micro-grid group protection scheme is a key for ensuring safe and reliable operation of the micro-grid group protection scheme.
Disclosure of Invention
The main purpose of the embodiment of the invention is to provide a island micro-grid group fault judging method and system based on satellite-ground network fusion, which can rapidly acquire the position and reason of a fault in a micro-grid, and is convenient for rapid and accurate fault repair.
In a first aspect, a method for determining a fault of an island micro-grid group fused by a star-network is provided, where the method includes:
Acquiring a first three-phase current of a power grid node i to be judged at the current moment, acquiring a second three-phase current of the power grid node i to be judged at the moment corresponding to the previous period, and acquiring a three-phase current fault component of the power grid node to be judged according to the first three-phase current and the second three-phase current;
judging whether the island micro-grid group to be judged corresponding to the grid node i to be judged is faulty or not according to the three-phase current fault components;
If the judgment is fault, extracting fault characteristics according to the three-phase current fault components;
Constructing a fault coefficient vector according to the fault characteristics;
And acquiring a fault line and a fault phase of the island micro-grid group to be judged according to the fault coefficient vector.
In one possible implementation, the three-phase current fault component is according to the formulaThe acquisition is performed, wherein,For the first three-phase current to be present,For the second three-phase current, N is the nth sampling point, and N c is the number of sampling points in one period.
In another possible implementation manner, the determining, according to the three-phase current fault component, whether the island micro-grid group to be determined corresponding to the grid node i to be determined is faulty or not specifically includes:
and if the three-phase current fault components accord with a preset fault judgment formula, the island micro-grid group to be judged breaks down.
Wherein the fault judgment formula isOr alternativelyOr alternativelyWherein I rat is the rated current. The fault judging formula shows that if the current sampling values of any one phase of the three-phase power in two adjacent power frequency periods are different, the island micro-grid group is judged to have faults.
In another possible implementation manner, if the judging is fault, extracting fault characteristics according to the three-phase current fault component includes:
Filtering high-frequency components of the three-phase current fault components to obtain fundamental frequency components of the three-phase current fault components;
Acquiring a fault line fundamental frequency component from the fundamental frequency component;
filtering low-frequency components of the fault components of the three-phase power to obtain high-frequency components of the fault components of the three-phase current;
acquiring a fault line high-frequency component from the high-frequency component;
and acquiring fault characteristics according to the fundamental frequency component of the fault line and the high-frequency component of the fault line.
In a second aspect, a system for determining a fault of an island micro-grid group fused by a star network is provided, the system comprising:
The acquisition module is used for acquiring a first three-phase current of the current moment of the power grid node i to be judged, acquiring a second three-phase current of the power grid node i to be judged at the moment corresponding to the previous period, and acquiring a three-phase current fault component of the power grid node to be judged according to the first three-phase current and the second three-phase current;
the judging module is used for judging whether the island micro-grid group to be judged corresponding to the grid node i to be judged is faulty or not according to the three-phase current fault components;
the fault feature extraction module is used for extracting fault features according to the three-phase current fault components if the fault is judged to be a fault;
the fault coefficient vector construction module is used for constructing a fault coefficient vector according to the fault characteristics;
And the specific fault acquisition module is used for acquiring fault lines and fault phases of the island micro-grid group to be judged according to the fault coefficient vector.
In one possible implementation, the three-phase current fault component is according to the formulaThe acquisition is performed, wherein,For the first three-phase current to be present,For the second three-phase current, N is the nth sampling point, and N c is the number of sampling points in one period.
In another possible implementation manner, the determining, according to the three-phase current fault component, whether the island micro-grid group to be determined corresponding to the grid node i to be determined is faulty or not specifically includes:
and if the three-phase current fault components accord with a preset fault judgment formula, the island micro-grid group to be judged breaks down.
Wherein the fault judgment formula isOr alternativelyOr alternativelyWherein I rat is the rated current. The fault judging formula shows that if the current sampling values of any one phase of the three-phase power in two adjacent power frequency periods are different, the island micro-grid group is judged to have faults.
In another possible implementation manner, if the judging is fault, extracting fault characteristics according to the three-phase current fault component includes:
Filtering high-frequency components of the three-phase current fault components to obtain fundamental frequency components of the three-phase current fault components;
Acquiring a fault line fundamental frequency component from the fundamental frequency component;
filtering low-frequency components of the fault components of the three-phase power to obtain high-frequency components of the fault components of the three-phase current;
acquiring a fault line high-frequency component from the high-frequency component;
and acquiring fault characteristics according to the fundamental frequency component of the fault line and the high-frequency component of the fault line.
In a third aspect, an electronic device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, where the processor implements a method for determining a fault of an island micro-grid group with a star-to-ground network integration as provided in the first aspect when executing the program.
In a fourth aspect, a non-transitory computer readable storage medium is provided, on which a computer program is stored, which when executed by a processor implements a method for determining a fault of an island micro-grid group with a star-to-ground network fusion as provided in the first aspect.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings that are required to be used in the description of the embodiments of the present application will be briefly described below.
Fig. 1 is a schematic structural diagram of a island micro-grid group system fused by a star network according to an embodiment of the present invention;
Fig. 2 is a flowchart of a method for determining a fault of an island micro-grid group by using a star-network fusion according to an embodiment of the present invention;
FIG. 3a is a schematic diagram of a fault component current at a fault time according to an embodiment of the present invention;
FIG. 3b is a schematic diagram of a fault component current at a non-fault time according to an embodiment of the present invention;
Fig. 3c is a schematic diagram of a current peak extraction result of a fault component current at a fault moment according to an embodiment of the present invention;
Fig. 3d is a schematic diagram of a current peak extraction result of a fault component current at a non-fault time according to an embodiment of the present invention;
fig. 4a is a schematic diagram of a high-frequency current flowing from a node on one side of a fault line according to an embodiment of the present invention;
Fig. 4b is a schematic diagram of a high frequency current flowing from a node on the other side in a fault line according to an embodiment of the present invention;
Fig. 4c is a schematic diagram of a processing result of a first-order accumulation generating operator of a high-frequency current flowing from a node at one side in a fault line according to an embodiment of the present invention;
Fig. 4d is a schematic diagram of a processing result of a first-order accumulation generating operator of a high-frequency current flowing from a node at the other side in a fault line according to an embodiment of the present invention;
fig. 5 is a block diagram of a system for determining a fault of an island micro-grid group by using a star-network fusion according to an embodiment of the present invention;
fig. 6 is a schematic diagram of an entity structure of an electronic device according to the present invention.
Detailed Description
Embodiments of the present application 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 modules or modules 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 application.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless expressly stated otherwise, as understood by those skilled in the art. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, modules, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, modules, components, and/or groups thereof. It will be understood that when a module is referred to as being "connected" or "coupled" to another module, it can be directly connected or coupled to the other module or intervening modules may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or wirelessly coupled. The term "and/or" as used herein includes all or any module and all combination of one or more of the associated listed items.
In order to make the objects, technical solutions and advantages of the present application more apparent, the implementation of the present application will be described in further detail with reference to the accompanying drawings.
The following describes the technical scheme of the present application and the technical scheme of the present application such as solving the above technical problems in detail with specific embodiments. The following embodiments may be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments. Embodiments of the present application will be described below with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of a island micro-grid group system with a star-network fusion according to an embodiment of the present invention.
Fig. 2 is a flowchart of a method for determining a fault of an island micro-grid group fused by a star network according to an embodiment of the present invention, where the method includes:
step S201, a first three-phase current of a current moment of a power grid node i to be judged is obtained, a second three-phase current of the power grid node i to be judged at a moment corresponding to the previous period is obtained, and a three-phase current fault component of the power grid node to be judged is obtained according to the first three-phase current and the second three-phase current;
Step S202, judging whether the island micro-grid group to be judged corresponding to the grid node i to be judged is faulty or not according to the three-phase current fault components;
Step S203, if the judgment is a fault, extracting fault characteristics according to the three-phase current fault components;
Step S204, constructing a fault coefficient vector according to the fault characteristics;
And step S205, obtaining a fault line and a fault phase of the island micro-grid group to be judged according to the fault coefficient vector.
In an embodiment of the invention, the island micro-grid group comprises a physical layer, an information layer and a space layer. Ext> theext> microext> -ext> gridext> groupext> consistsext> ofext> threeext> microext> -ext> gridsext> ofext> MGext> -ext> Aext>,ext> MGext> -ext> Bext> andext> MGext> -ext> Cext>,ext> whichext> areext> interconnectedext> throughext> submarineext> cablesext>,ext> theext> interconnectionext> stateext> isext> controlledext> byext> anext> interconnectionext> switchext>,ext> andext> theext> MGext> -ext> Aext> andext> theext> MGext> -ext> Bext> areext> sixext> -ext> busext> gridext> typeext> systemsext> andext> consistext> ofext> photovoltaicext>,ext> energyext> storageext>,ext> anext> interfaceext> transformerext>,ext> aext> powerext> networkext> andext> aext> loadext>.ext> MG-C is a four busbar radiant system including a blower, an interface transformer, a power network, and a load. Ext> MGext> -ext> Bext> isext> aext> resourceext> -ext> richext> microgridext>,ext> MGext> -ext> Aext>,ext> MGext> -ext> Cext> isext> aext> highext> -ext> proportionext> loadext> -ext> typeext> microgridext>,ext> andext> MGext> -ext> Bext> normallyext> providesext> energyext> supportext> forext> MGext> -ext> Aext> andext> MGext> -ext> Cext>.ext> In addition, a node connected with three or more lines in the system is called a backbone node, and a feeder line with backbone nodes at both ends is called a main feeder line, otherwise, a branch feeder line.
The information layer comprises a data acquisition system, a time synchronization system, a communication system and a central protection unit.
(1) In the data acquisition system, the basic components are a voltage transformer (PT) and a Current Transformer (CT). In one aspect, the micro-source local control and the micro-grid cluster secondary control collect inverter port voltage and output current for system voltage and frequency regulation. On the other hand, the current amounts of the main feeder and the branch feeder accessing the backbone node are collected by a local intelligent protection device (IED), the required fault characteristics are extracted, and transmitted to a central protection unit for fault detection and localization.
(2) In the time synchronization system, a basic component is a Global Positioning System (GPS) time service module, which is responsible for receiving satellite navigation signals and providing a uniform time-frequency reference for the whole system. Each microgrid is equipped with a set of GPS time synchronization systems, and the data acquisition devices and IEDs acquire time references via Precision Time Protocol (PTP) protocol or Network Time Protocol (NTP) protocol.
(3) The communication system includes a ground network (e.g., private power network, 5G, etc.) and a low-orbit satellite network that complement each other to ensure uninterrupted transmission of power data inside and between the micro-grids. In particular, power failures are often accompanied by communication interruptions due to the coupling of the power transmission of the interconnected submarine cable to the fiber optic communication package. At this time, the low-orbit satellite communication replaces the ground network, and supports the operation control and decision of the micro-grid group.
(4) And each micro-grid is internally provided with a central protection unit, relevant electrical data and control commands of the local IED are collected, functions of fault feature extraction, fault section identification and the like are realized, and protection results are sent to the local IED for fault isolation and maintenance.
The spatial layer is composed of global satellite navigation systems (GNSS) and low-orbit satellite networks. The GNSS is responsible for providing nanosecond or microsecond time references for the data acquisition system and the communication system, and acquiring high-availability electrical data with minimum time synchronization errors and fast data transmission. The low-orbit satellite communication has the advantages of wide coverage, low time delay, high bandwidth, low cost and the like. Starlink can provide global communication services of up 10Mbps and down 100Mbps, the minimum delay is about 20ms, and the method is a good supplement to the ground network. In addition, compared with a medium-high orbit satellite, the low orbit satellite has low signal attenuation and high transmission rate, can be used as a space-based enhanced relay of a GNSS, combines satellite-borne data with a ground observation base station, and improves positioning, navigation and time service accuracy. Thus, high-medium low orbit satellite cooperation can provide accurate time-frequency reference for remote island micro-grid clusters.
The three-phase current fault components are according to the formulaThe acquisition is performed, wherein,For the first three-phase current to be present,For the second three-phase current, N is the nth sampling point, and N c is the number of sampling points in one period.
Judging whether the island micro-grid group to be judged corresponding to the grid node i to be judged is faulty or not according to the three-phase current fault components, specifically:
and if the three-phase current fault components accord with a preset fault judgment formula, the island micro-grid group to be judged breaks down.
Wherein the fault judgment formula isOr alternativelyOr alternativelyWherein I rat is the rated current. The fault judging formula shows that if the current sampling values of any one phase of the three-phase power in two adjacent power frequency periods are different, the island micro-grid group is judged to have faults.
And if the judgment is fault, extracting fault characteristics according to the three-phase current fault components, wherein the fault characteristics comprise:
Filtering high-frequency components of the three-phase current fault components to obtain fundamental frequency components of the three-phase current fault components;
Acquiring a fault line fundamental frequency component from the fundamental frequency component;
filtering low-frequency components of the fault components of the three-phase power to obtain high-frequency components of the fault components of the three-phase current;
acquiring a fault line high-frequency component from the high-frequency component;
and acquiring fault characteristics according to the fundamental frequency component of the fault line and the high-frequency component of the fault line.
In this embodiment, to reflect the direction characteristics of the fundamental frequency current, a low-pass filter is used to filter the high-frequency component to obtain the fundamental frequency component of the three-phase current fault component, and then an opening operator and a closing operator of a mathematical morphology algorithm are used to extract the first peak value of the fundamental frequency current fault component, where the calculation formula isWherein, the method comprises the steps of, wherein,As a positive peak value,For negative Peak NEGAITIVE PEAK, peak ij,a(n)、Peakij,b(n)、Peakij,c (n) represents the Peak value of the three-phase fundamental frequency current fault component, g (M) (0<m. Ltoreq.M) is a structural element. The sum ∈II is an opening operator and a closing operator respectively, noise can be eliminated, pulse is smoothed, positive peak values and negative peak values of current waveforms are obtained through cutting, and therefore the first positive peak value moment T ij,a、Tij,b、Tij,c of three-phase fundamental frequency current fault components is obtained.
Fig. 3a is a schematic current diagram of a fault component current at a fault time provided by an embodiment of the present invention, fig. 3b is a schematic current diagram of a fault component current at a non-fault time provided by an embodiment of the present invention, fig. 3c is a schematic current peak extraction result of a fault component current at a fault time provided by an embodiment of the present invention, and fig. 3d is a schematic current peak extraction result of a fault component current at a non-fault time provided by an embodiment of the present invention. Since a short circuit fault may cause a current amplitude and phase jump, the mathematical morphology algorithm may also detect a peak shape, herein called a false peak, at the moment of the fault, in order to avoid false peak misleading, provision is made to take the first time value of the positive peak time sequence with a time interval of more than 10ms as the first positive peak moment. The power frequency fault component current of the fault line can be seenT ij is less than 5ms, instead of the power frequency fault component current of the fault lineT ij is approximately 10ms.
To reflect the directional characteristics of the high-frequency current, a high-pass filter is used for filtering the low-frequency component to obtain the high-frequency component of the three-phase current、、. Because the high-frequency component is easily influenced by background noise, fault resistance and fault initial angle, the high-frequency component is amplified by adopting a first-order Accumulation Generation Operator (AGO), and the calculation formula is as follows,、、Respectively is、、Is a first order cumulative generator of (a).
Separately calculate、、The slope k zcs,a、kzcs,b、kzcs,c of the first zero crossing. Definition of the definition、、Signed sum S ij,a、Sij,b、Sij,c, calculated asD w1 is the calculated data window length.
Fig. 4a is a schematic diagram of a high-frequency current flowing out of a node on one side of a fault line provided by an embodiment of the present invention, fig. 4b is a schematic diagram of a high-frequency current flowing out of a node on the other side of the fault line provided by an embodiment of the present invention, fig. 4c is a schematic diagram of a processing result of a first-order accumulation generating operator of a high-frequency current flowing out of a node on one side of the fault line provided by an embodiment of the present invention, and fig. 4d is a schematic diagram of a processing result of a first-order accumulation generating operator of a high-frequency current flowing out of a node on the other side of the fault line provided by an embodiment of the present invention. First-order AGO treated compared to the original high-frequency current、、Exhibits smoother, more regular waveform morphology, and faulty and non-faulty lines、、The direction and magnitude differences of (c) are more pronounced.
On a time scale, the voltage sag at the fault point at the fault moment can introduce abrupt changes in current amplitude and phase. After detecting that the system fails, the inversion type micro source can start fault ride-through control to perform fault current limiting and reactive power supporting, and the current phase can be suddenly changed again. To characterize the current amplitude and phase jumps caused by the fault point voltage dip and the micro-source fault ride through control response, the current is reconstructed using fourier-taylor transforms. The difference between the measured current and the reconstructed current is used to quantify the degree of abrupt change in current before and after the fault.
First, the discrete Fourier expansion of the measured current i ij,a(n)、iij,b(n)、iij,c (n) isT s is the sampling period, omega 0 is the power frequency angular frequency,、、Is thatFourier coefficients of phase currents.
Since the measured current is normally a stable fundamental frequency signal, the definition signal of the reconstructed current is also set as the fundamental frequency signal. When the calculated data window length is Dw2, the above formula is expressed asThe least square method can be used to calculate the Fourier coefficient matrix、、The three-phase current reconstruction value can be obtained through the Fourier coefficient matrix。
Finally, calculating the sum of the actual values and the difference values of the reconstruction values of all the line currents connected with the node i to obtain a three-phase current transient monitoring value TM ij,a、TMij,b、TMij,c of the node i, wherein the corresponding formula is as followsG is the number of nodes adjacent to node i,、、The reconstructed values of i ij,a(n)、iij,b(n)、iij,c (n), respectively.
And collecting fault characteristic data of all node IEDs in the micro-grid through ground network or satellite communication, and collecting fault characteristic data of far-end node IEDs on adjacent micro-grid interconnection lines. The data transmitted between the IED i of node i and the central protection unit mainly includes the first positive peak time of the power frequency current fault component, the signed cumulative value of all line current high frequency components connected to node i, and the transient monitoring value of all line currents connected to node i. Since the delay required for the occurrence of the fault signature, calculation and transmission of the ground network is less than about 60ms, when the central protection unit does not receive the fault data of the IED i within 60ms after the fault, the ground communication between the IED i and the central protection unit is considered to be invalid, and at this time, the satellite communication is switched to perform the fault data transmission.
For the construction of the fault coefficient vector, it is specifically:
Three-phase current direction abrupt matrix construction if there is no cable connection between node i and node j, the direction abrupt characteristic of the fundamental frequency current fault components of line ij is D BF_ija、DBF_ijb、DBF_ijc all being 0. If there is a cable connection between node i and node j, and when the absolute value |T ij,a-Tji,a | of the difference between the first positive peak moments of the phase A fundamental frequency current fault components at both ends of the line is less than 5ms, the direction abrupt change feature D BF_ija of the phase A fundamental frequency current fault components on the line ij is equal to 1, otherwise, all are 0, and the fundamental frequency current fault component direction abrupt change feature matrix D BF,a、DBF,b、DBF,c of the micro-grid system can be obtained in summary, the formula is
N A is the node number of the micro-grid system.
Likewise, if there is no cable connection between node i and node j, the high frequency current direction abrupt change of line ij is characterized by D HF_ija、DHF_ijb、DHF_ijc being 0. If there is cable connection between node i and node j, taking phase A as an example, when the signed accumulated value of phase A high-frequency current at two ends of the line satisfies the formulaWhen the direction abrupt characteristic D HF_ija of the A-phase high-frequency current on the line ij is equal to 1, otherwise, the directions of the high-frequency current are all 0, and D HF_ijb、DHF_ijc can be obtained by the same method. To sum up, the abrupt change in direction characteristic matrix D HF,a、DHF,b、DHF,c of the high-frequency current of the micro-grid system can be obtained.
According to the formulaAndThe three-phase current direction mutation matrix of the micro-grid system can be obtained as。
Three-phase current transient monitoring vector construction, namely based on the formula, obtaining three-phase current transient monitoring vector as follows。
Based on the direction mutation matrix and the transient monitoring vector, constructing a fault coefficient vector fusing the space-time characteristic information as follows,Representation ofPhase failure coefficient vector.
Further, by the formulaAnd carrying out mean value normalization processing on the fault coefficient vector.
The obtaining the fault line and the fault phase of the island micro-grid group to be judged according to the fault coefficient vector comprises the following steps:
In the normalized fault coefficient vector, when the fault coefficient AndWhen both are greater than 0, the line ij is a fault line,The phase is a fault phase and sends a single-phase trip signal to the protection devices IED i and IED j at the two end nodes of the line to isolate the fault line from the fault phase, otherwise the line ij is a non-fault line, andThe phase is a non-fault phase and is protected from action.
In the embodiment of the invention, a first three-phase current of a current moment of a power grid node i to be judged is obtained, a second three-phase current of the power grid node i to be judged at a moment corresponding to the last period is obtained, three-phase current fault components of the power grid node to be judged are obtained according to the first three-phase current and the second three-phase current, whether a island micro-grid group to be judged corresponding to the power grid node i to be judged is faulty or not is judged according to the three-phase current fault components, if the island micro-grid group to be judged is faulty, fault characteristics are extracted according to the three-phase current fault components, a fault coefficient vector is constructed according to the fault characteristics, and fault lines and fault phases of the island micro-grid group to be judged are obtained according to the fault coefficient vector. The position and the reason of the fault in the micro-grid can be quickly obtained, and the fault repair can be quickly and accurately carried out.
Fig. 5 is a block diagram of a system for determining a fault of an island micro-grid group by using a star-network fusion according to an embodiment of the present invention, where the system includes:
The obtaining module 501 is configured to obtain a first three-phase current of a current moment of a to-be-determined power grid node i, obtain a second three-phase current of the to-be-determined power grid node i at a moment corresponding to a previous period, and obtain a three-phase current fault component of the to-be-determined power grid node according to the first three-phase current and the second three-phase current;
the judging module 502 is configured to judge whether the island micro-grid group to be judged corresponding to the grid node i to be judged is faulty according to the three-phase current fault component;
A fault feature extraction module 503, configured to extract a fault feature according to the three-phase current fault component if the determination is a fault;
A fault coefficient vector construction module 504, configured to construct a fault coefficient vector according to the fault characteristics;
And the specific fault acquisition module 505 is configured to acquire a fault line and a fault phase of the island micro-grid group to be determined according to the fault coefficient vector.
In an embodiment of the invention, the island micro-grid group comprises a physical layer, an information layer and a space layer. Ext> theext> microext> -ext> gridext> groupext> consistsext> ofext> threeext> microext> -ext> gridsext> ofext> MGext> -ext> Aext>,ext> MGext> -ext> Bext> andext> MGext> -ext> Cext>,ext> whichext> areext> interconnectedext> throughext> submarineext> cablesext>,ext> theext> interconnectionext> stateext> isext> controlledext> byext> anext> interconnectionext> switchext>,ext> andext> theext> MGext> -ext> Aext> andext> theext> MGext> -ext> Bext> areext> sixext> -ext> busext> gridext> typeext> systemsext> andext> consistext> ofext> photovoltaicext>,ext> energyext> storageext>,ext> anext> interfaceext> transformerext>,ext> aext> powerext> networkext> andext> aext> loadext>.ext> MG-C is a four busbar radiant system including a blower, an interface transformer, a power network, and a load. Ext> MGext> -ext> Bext> isext> aext> resourceext> -ext> richext> microgridext>,ext> MGext> -ext> Aext>,ext> MGext> -ext> Cext> isext> aext> highext> -ext> proportionext> loadext> -ext> typeext> microgridext>,ext> andext> MGext> -ext> Bext> normallyext> providesext> energyext> supportext> forext> MGext> -ext> Aext> andext> MGext> -ext> Cext>.ext> In addition, a node connected with three or more lines in the system is called a backbone node, and a feeder line with backbone nodes at both ends is called a main feeder line, otherwise, a branch feeder line.
The information layer comprises a data acquisition system, a time synchronization system, a communication system and a central protection unit.
(1) In the data acquisition system, the basic components are a voltage transformer (PT) and a Current Transformer (CT). In one aspect, the micro-source local control and the micro-grid cluster secondary control collect inverter port voltage and output current for system voltage and frequency regulation. On the other hand, the current amounts of the main feeder line and the branch feeder line of the access backbone node are collected by the local IED, the required fault characteristics are extracted, and the extracted fault characteristics are transmitted to the central protection unit for fault detection and positioning.
(2) In the time synchronization system, a basic component is a GPS time service module which is responsible for receiving satellite navigation signals and providing a uniform time-frequency reference for the whole system. Each microgrid is equipped with a set of GPS time synchronization systems, and the data acquisition devices and IEDs acquire time references via Precision Time Protocol (PTP) protocol or Network Time Protocol (NTP) protocol.
(3) The communication system includes a ground network (e.g., private power network, 5G, etc.) and a low-orbit satellite network that complement each other to ensure uninterrupted transmission of power data inside and between the micro-grids. In particular, power failures are often accompanied by communication interruptions due to the coupling of the power transmission of the interconnected submarine cable to the fiber optic communication package. At this time, the low-orbit satellite communication replaces the ground network, and supports the operation control and decision of the micro-grid group.
(4) And each micro-grid is internally provided with a central protection unit, relevant electrical data and control commands of the local IED are collected, functions of fault feature extraction, fault section identification and the like are realized, and protection results are sent to the local IED for fault isolation and maintenance.
The spatial layer is composed of global satellite navigation systems (GNSS) and low-orbit satellite networks. The GNSS is responsible for providing nanosecond or microsecond time references for the data acquisition system and the communication system, and acquiring high-availability electrical data with minimum time synchronization errors and fast data transmission. The low-orbit satellite communication has the advantages of wide coverage, low time delay, high bandwidth, low cost and the like. Starlink can provide global communication services of up 10Mbps and down 100Mbps, the minimum delay is about 20ms, and the method is a good supplement to the ground network. In addition, compared with a medium-high orbit satellite, the low orbit satellite has low signal attenuation and high transmission rate, can be used as a space-based enhanced relay of a GNSS, combines satellite-borne data with a ground observation base station, and improves positioning, navigation and time service accuracy. Thus, high-medium low orbit satellite cooperation can provide accurate time-frequency reference for remote island micro-grid clusters.
The three-phase current fault components are according to the formulaThe acquisition is performed, wherein,For the first three-phase current to be present,For the second three-phase current, N is the nth sampling point, and N c is the number of sampling points in one period.
Judging whether the island micro-grid group to be judged corresponding to the grid node i to be judged is faulty or not according to the three-phase current fault components, specifically:
and if the three-phase current fault components accord with a preset fault judgment formula, the island micro-grid group to be judged breaks down.
Wherein the fault judgment formula isOr alternativelyOr alternativelyWherein I rat is the rated current. The fault judging formula shows that if the current sampling values of any one phase of the three-phase power in two adjacent power frequency periods are different, the island micro-grid group is judged to have faults.
And if the judgment is fault, extracting fault characteristics according to the three-phase current fault components, wherein the fault characteristics comprise:
Filtering high-frequency components of the three-phase current fault components to obtain fundamental frequency components of the three-phase current fault components;
Acquiring a fault line fundamental frequency component from the fundamental frequency component;
filtering low-frequency components of the fault components of the three-phase power to obtain high-frequency components of the fault components of the three-phase current;
acquiring a fault line high-frequency component from the high-frequency component;
and acquiring fault characteristics according to the fundamental frequency component of the fault line and the high-frequency component of the fault line.
In this embodiment, to reflect the direction characteristics of the fundamental frequency current, a low-pass filter is used to filter the high-frequency component to obtain the fundamental frequency component of the three-phase current fault component, and then an opening operator and a closing operator of a mathematical morphology algorithm are used to extract the first peak value of the fundamental frequency current fault component, where the calculation formula isWherein, the method comprises the steps of, wherein,As a positive peak value,For negative Peak NEGAITIVE PEAK, peak ij,a(n)、Peakij,b(n)、Peakij,c (n) represents the Peak value of the three-phase fundamental frequency current fault component, g (M) (0<m. Ltoreq.M) is a structural element. The sum ∈II is an opening operator and a closing operator respectively, noise can be eliminated, pulse is smoothed, positive peak values and negative peak values of current waveforms are obtained through cutting, and therefore the first positive peak value moment T ij,a、Tij,b、Tij,c of three-phase fundamental frequency current fault components is obtained.
Since a short circuit fault may cause a current amplitude and phase jump, the mathematical morphology algorithm may also detect a peak shape, herein called a false peak, at the moment of the fault, in order to avoid false peak misleading, provision is made to take the first time value of the positive peak time sequence with a time interval of more than 10ms as the first positive peak moment. The power frequency fault component current of the fault line can be seenT ij is less than 5ms, instead of the power frequency fault component current of the fault lineT ij is approximately 10ms.
To reflect the directional characteristics of the high-frequency current, a high-pass filter is used for filtering the low-frequency component to obtain the high-frequency component of the three-phase current、、. Because the high-frequency component is easily influenced by background noise, fault resistance and fault initial angle, the high-frequency component is amplified by adopting a first-order Accumulation Generation Operator (AGO), and the calculation formula is as follows,、、Respectively is、、Is a first order cumulative generator of (a).
Separately calculate、、The slope k zcs,a、kzcs,b、kzcs,c of the first zero crossing. Definition of the definition、、Signed sum S ij,a、Sij,b、Sij,c, calculated asD w1 is the calculated data window length.
The high frequency current flowing out of the nodes at two sides of the fault line and the first-order AGO processing junction can be seen, compared with the original high frequency current, the first-order AGO processing junction、、Exhibits smoother, more regular waveform morphology, and faulty and non-faulty lines、、The direction and magnitude differences of (c) are more pronounced.
On a time scale, the voltage sag at the fault point at the fault moment can introduce abrupt changes in current amplitude and phase. After detecting that the system fails, the inversion type micro source can start fault ride-through control to perform fault current limiting and reactive power supporting, and the current phase can be suddenly changed again. To characterize the current amplitude and phase jumps caused by the fault point voltage dip and the micro-source fault ride through control response, the current is reconstructed using fourier-taylor transforms. The difference between the measured current and the reconstructed current is used to quantify the degree of abrupt change in current before and after the fault.
First, the discrete Fourier expansion of the measured current i ij,a(n)、iij,b(n)、iij,c (n) isT s is the sampling period, omega 0 is the power frequency angular frequency,、、Is thatFourier coefficients of phase currents.
Since the measured current is normally a stable fundamental frequency signal, the definition signal of the reconstructed current is also set as the fundamental frequency signal. When the calculated data window length is Dw2, the above formula is expressed asThe least square method can be used to calculate the Fourier coefficient matrix、、The three-phase current reconstruction value can be obtained through the Fourier coefficient matrix。
Finally, calculating the sum of the actual values and the difference values of the reconstruction values of all the line currents connected with the node i to obtain a three-phase current transient monitoring value TM ij,a、TMij,b、TMij,c of the node i, wherein the corresponding formula is as followsG is the number of nodes adjacent to node i,、、The reconstructed values of i ij,a(n)、iij,b(n)、iij,c (n), respectively.
And collecting fault characteristic data of all node IEDs in the micro-grid through ground network or satellite communication, and collecting fault characteristic data of far-end node IEDs on adjacent micro-grid interconnection lines. The data transmitted between the IED i of node i and the central protection unit mainly includes the first positive peak time of the power frequency current fault component, the signed cumulative value of all line current high frequency components connected to node i, and the transient monitoring value of all line currents connected to node i. Since the delay required for the occurrence of the fault signature, calculation and transmission of the ground network is less than about 60ms, when the central protection unit does not receive the fault data of the IED i within 60ms after the fault, the ground communication between the IED i and the central protection unit is considered to be invalid, and at this time, the satellite communication is switched to perform the fault data transmission.
For the construction of the fault coefficient vector, it is specifically:
Three-phase current direction abrupt matrix construction if there is no cable connection between node i and node j, the direction abrupt characteristic of the fundamental frequency current fault components of line ij is D BF_ija、DBF_ijb、DBF_ijc all being 0. If there is a cable connection between node i and node j, and when the absolute value |T ij,a-Tji,a | of the difference between the first positive peak moments of the phase A fundamental frequency current fault components at both ends of the line is less than 5ms, the direction abrupt change feature D BF_ija of the phase A fundamental frequency current fault components on the line ij is equal to 1, otherwise, all are 0, and the fundamental frequency current fault component direction abrupt change feature matrix D BF,a、DBF,b、DBF,c of the micro-grid system can be obtained in summary, the formula is NA is the number of nodes of the micro-grid system.
Likewise, if there is no cable connection between node i and node j, the high frequency current direction abrupt change of line ij is characterized by D HF_ija、DHF_ijb、DHF_ijc being 0. If there is cable connection between node i and node j, taking phase A as an example, when the signed accumulated value of phase A high-frequency current at two ends of the line satisfies the formulaWhen the direction abrupt characteristic D HF_ija of the A-phase high-frequency current on the line ij is equal to 1, otherwise, the directions of the high-frequency current are all 0, and D HF_ijb、DHF_ijc can be obtained by the same method. To sum up, the abrupt change in direction characteristic matrix D HF,a、DHF,b、DHF,c of the high-frequency current of the micro-grid system can be obtained.
According to the formulaAndThe three-phase current direction mutation matrix of the micro-grid system can be obtained as。
Three-phase current transient monitoring vector construction, namely based on the formula, obtaining three-phase current transient monitoring vector as follows。
Based on the direction mutation matrix and the transient monitoring vector, constructing a fault coefficient vector fusing the space-time characteristic information as follows,Representation ofPhase failure coefficient vector.
Further, by the formulaAnd carrying out mean value normalization processing on the fault coefficient vector.
The obtaining the fault line and the fault phase of the island micro-grid group to be judged according to the fault coefficient vector comprises the following steps:
In the normalized fault coefficient vector, when the fault coefficient AndWhen both are greater than 0, the line ij is a fault line,The phase is a fault phase and sends a single-phase trip signal to the protection devices IED i and IED j at the two end nodes of the line to isolate the fault line from the fault phase, otherwise the line ij is a non-fault line, andThe phase is a non-fault phase and is protected from action.
In the embodiment of the invention, a first three-phase current of a current moment of a power grid node i to be judged is obtained, a second three-phase current of the power grid node i to be judged at a moment corresponding to the last period is obtained, three-phase current fault components of the power grid node to be judged are obtained according to the first three-phase current and the second three-phase current, whether a island micro-grid group to be judged corresponding to the power grid node i to be judged is faulty or not is judged according to the three-phase current fault components, if the island micro-grid group to be judged is faulty, fault characteristics are extracted according to the three-phase current fault components, a fault coefficient vector is constructed according to the fault characteristics, and fault lines and fault phases of the island micro-grid group to be judged are obtained according to the fault coefficient vector. The position and the reason of the fault in the micro-grid can be quickly obtained, and the fault repair can be quickly and accurately carried out.
Fig. 6 illustrates a physical schematic diagram of an electronic device, which may include a processor (processor) 601, a communication interface (Communications Interface) 602, a memory (memory) 603, and a communication bus 604, where the processor, the communication interface, and the memory communicate with each other via the communication bus, as shown in fig. 6. The method comprises the steps of obtaining a first three-phase current of a current moment of a power grid node i to be judged, obtaining a second three-phase current of the power grid node i to be judged at a moment corresponding to a previous period, obtaining three-phase current fault components of the power grid node to be judged according to the first three-phase current and the second three-phase current, judging whether the island micro-grid group to be judged corresponding to the power grid node i to be judged is faulty according to the three-phase current fault components, extracting fault characteristics according to the three-phase current fault components if the island micro-grid group to be judged is faulty, constructing a fault coefficient vector according to the fault characteristics, and obtaining fault lines and fault phases of the island micro-grid group to be judged according to the fault coefficient vector.
Further, the logic instructions in the memory described above may be implemented in the form of software functional units and stored in a computer-readable storage medium when sold or used as a stand-alone product. 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. The 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, an optical disk, or other various media capable of storing program codes.
On the other hand, the embodiment of the invention also provides a computer program product, which comprises a computer program stored on a non-transitory computer readable storage medium, wherein the computer program comprises program instructions, when the program instructions are executed by a computer, the computer can execute the island micro grid group fault judging method of the star network fusion provided by the above method embodiments, the method comprises the steps of obtaining a first three-phase current of a current moment of a grid node i to be judged, obtaining a second three-phase current of the grid node i to be judged at a moment corresponding to the last period, obtaining three-phase current fault components of the grid node to be judged according to the first three-phase current and the second three-phase current, judging whether the island micro grid group to be judged corresponding to the grid node i to be judged is faulty according to the three-phase current fault components, if the island micro grid group to be judged is faulty, extracting fault characteristics according to the three-phase current fault components, constructing fault coefficient vectors according to the fault characteristic, and obtaining fault and fault phase vectors of the island micro grid group to be judged according to the fault coefficient vectors.
In still another aspect, an embodiment of the present invention further provides a non-transitory computer readable storage medium, where a computer program is stored, where the computer program is implemented when executed by a processor to perform the island micro grid group fault determination method for satellite-to-ground network fusion provided in the foregoing embodiments, where the method includes obtaining a first three-phase current of a current moment of a grid node i to be determined, obtaining a second three-phase current of the grid node i to be determined at a moment corresponding to a previous period, obtaining three-phase current fault components of the grid node to be determined according to the first three-phase current and the second three-phase current, determining whether the island micro grid group to be determined corresponding to the grid node i to be determined has a fault according to the three-phase current fault components, if the determining is a fault, extracting a fault feature according to the three-phase current fault components, constructing a fault coefficient vector according to the fault feature, and obtaining a fault line and a fault phase of the island micro grid group to be determined according to the fault coefficient vector.
It should be understood that, although the steps in the flowcharts of the figures are shown in order as indicated by the arrows, these steps are not necessarily performed in order as indicated by the arrows. The steps are not strictly limited in order and may be performed in other orders, unless explicitly stated herein. Moreover, at least some of the steps in the flowcharts of the figures may include a plurality of sub-steps or stages that are not necessarily performed at the same time, but may be performed at different times, the order of their execution not necessarily being sequential, but may be performed in turn or alternately with other steps or at least a portion of the other steps or stages.
While only a partial implementation of the invention has been described, it should be noted that it will be apparent to those skilled in the art that several modifications and adaptations can be made without departing from the principles of the invention, and such modifications and adaptations should and are intended to be comprehended within the scope of the invention.
Claims (10)
1. A satellite-ground network fused island micro-grid group fault judging method is characterized by comprising the following steps:
Acquiring a first three-phase current of a power grid node i to be judged at the current moment, acquiring a second three-phase current of the power grid node i to be judged at the moment corresponding to the previous period, and acquiring a three-phase current fault component of the power grid node to be judged according to the first three-phase current and the second three-phase current;
judging whether the island micro-grid group to be judged corresponding to the grid node i to be judged is faulty or not according to the three-phase current fault components;
If the judgment is fault, extracting fault characteristics according to the three-phase current fault components;
Constructing a fault coefficient vector according to the fault characteristics, including:
According to the formula The fault coefficient vector is obtained, wherein,A vector of failure coefficients is represented and,Representing a three-phase current direction mutation matrix,Representing three-phase current transient detection vectors, wherein the three-phase current direction mutation matrix is prepared according to a formulaThe acquisition is performed, wherein,N A is the node number of the micro-grid system,Representing between node i and node jThe abrupt change of direction of the phase fundamental frequency current fault component is characterized when between the node i and the node jThe absolute value of the difference between the first positive peak instants of the phase fundamental current fault components Tij,-Tji,When it is <5ms,The value of (1) is equal to 1, the other values are equal to 0,,Representing between node i and node jAbrupt direction characteristic of phase high frequency current fault component, when between node i and node jSigned accumulated value of phase high frequency current satisfies formulaAnd is also provided withAnd sgn (S ij,ϕ)=sgn(Sji,ϕ),The value of (2) is 1, and the other values are 0;
And acquiring a fault line and a fault phase of the island micro-grid group to be judged according to the fault coefficient vector.
2. The method of claim 1, wherein the three-phase current fault component is according to the formulaThe acquisition is performed, wherein,For the first three-phase current to be present,For the second three-phase current, N is the nth sampling point, and N c is the number of sampling points in one period.
3. The method of claim 1, wherein the determining, according to the three-phase current fault component, whether the island micro-grid group to be determined corresponding to the grid node i to be determined is faulty, specifically is:
If the three-phase current fault component accords with a preset fault judgment formula, the island micro-grid group to be judged is in fault;
Wherein the fault judgment formula is Or alternativelyOr alternativelyThe fault judging formula shows that if the current sampling values of any one phase of the three-phase power in two adjacent power frequency periods are different, the island micro-grid group is judged to have faults.
4. The method of claim 1, wherein extracting fault signatures from the three-phase current fault components if the determination is a fault comprises:
Filtering high-frequency components of the three-phase current fault components to obtain fundamental frequency components of the three-phase current fault components;
Acquiring a fault line fundamental frequency component from the fundamental frequency component;
filtering low-frequency components of the fault components of the three-phase power to obtain high-frequency components of the fault components of the three-phase current;
acquiring a fault line high-frequency component from the high-frequency component;
and acquiring fault characteristics according to the fundamental frequency component of the fault line and the high-frequency component of the fault line.
5. A island micro-grid group fault judging system based on star-ground network fusion is characterized by comprising:
The acquisition module is used for acquiring a first three-phase current of the current moment of the power grid node i to be judged, acquiring a second three-phase current of the power grid node i to be judged at the moment corresponding to the previous period, and acquiring a three-phase current fault component of the power grid node to be judged according to the first three-phase current and the second three-phase current;
the judging module is used for judging whether the island micro-grid group to be judged corresponding to the grid node i to be judged is faulty or not according to the three-phase current fault components;
the fault feature extraction module is used for extracting fault features according to the three-phase current fault components if the fault is judged to be a fault;
The fault coefficient vector construction module is used for constructing a fault coefficient vector according to the fault characteristics and comprises the following steps:
According to the formula The fault coefficient vector is obtained, wherein,A vector of failure coefficients is represented and,Representing a three-phase current direction mutation matrix,Representing three-phase current transient detection vectors, wherein the three-phase current direction mutation matrix is prepared according to a formulaThe acquisition is performed, wherein,N A is the node number of the micro-grid system,Representing between node i and node jThe abrupt change of direction of the phase fundamental frequency current fault component is characterized when between the node i and the node jThe absolute value of the difference between the first positive peak instants of the phase fundamental current fault components Tij,-Tji,When it is <5ms,The value of (1) is equal to 1, the other values are equal to 0,,Representing between node i and node jAbrupt direction characteristic of phase high frequency current fault component, when between node i and node jSigned accumulated value of phase high frequency current satisfies formulaAnd is also provided withAnd sgn (S ij,ϕ)=sgn(Sji,ϕ),The value of (2) is 1, and the other values are 0;
And the specific fault acquisition module is used for acquiring fault lines and fault phases of the island micro-grid group to be judged according to the fault coefficient vector.
6. The system of claim 5, wherein the three-phase current fault component is according to the formulaThe acquisition is performed, wherein,For the first three-phase current to be present,For the second three-phase current, N is the nth sampling point, and N c is the number of sampling points in one period.
7. The system of claim 5, wherein the determining whether the island micro-grid group to be determined corresponding to the grid node i to be determined is faulty according to the three-phase current fault component is specifically:
If the three-phase current fault component accords with a preset fault judgment formula, the island micro-grid group to be judged is in fault;
Wherein the fault judgment formula is Or alternativelyOr alternativelyThe fault judging formula shows that if the current sampling values of any one phase of the three-phase power in two adjacent power frequency periods are different, the island micro-grid group is judged to have faults.
8. The system of claim 5, wherein extracting fault signatures from the three-phase current fault components if the determination is a fault comprises:
Filtering high-frequency components of the three-phase current fault components to obtain fundamental frequency components of the three-phase current fault components;
Acquiring a fault line fundamental frequency component from the fundamental frequency component;
filtering low-frequency components of the fault components of the three-phase power to obtain high-frequency components of the fault components of the three-phase current;
acquiring a fault line high-frequency component from the high-frequency component;
and acquiring fault characteristics according to the fundamental frequency component of the fault line and the high-frequency component of the fault line.
9. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements a method for determining a fault in a star-network-fused island micro-grid group according to any one of claims 1-4 when executing the program.
10. A non-transitory computer readable storage medium having stored thereon a computer program, wherein the computer program when executed by a processor implements a star-to-ground network-fused island micro-grid group fault determination method according to any one of claims 1-4.
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| CN115453265A (en) * | 2022-09-14 | 2022-12-09 | 湖南大学 | A Fault Transient Protection Method for Island Microgrid Based on Current Waveform Characteristics of Initial Fault |
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