Precise time-based perturbation calculation method based on virtual perturbation admittance

Abstract

The application discloses a kind of based on accurate time-based disturbance calculation method based on virtual disturbance admittance, it is related to voltage sag monitoring technical field, including the following steps: establishing the virtual disturbance admittance of quantitative characterization voltage sag process;Establish voltage sag monitoring model, at least two monitoring points are provided in each bus of the voltage sag monitoring model, and the monitoring point is configured as POM power quality monitor;When any monitoring point in system monitors voltage temporary delay, all POM power quality monitors in the voltage sag monitoring model are started voltage and current recording wave synchronously, save each N complete 3-phase voltage waveform data and current waveform data before and after voltage sag occurs and the complete voltage and current waveform data of voltage sag process;Select three sets of waveforms at the same time for comparison, obtain sag duration tf;Calculate the virtual disturbance admittance between any two adjacent buses in the voltage sag monitoring model.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of voltage sag monitoring, in particular to a disturbance calculation method based on accurate time synchronization based on virtual disturbance admittance. BACKGROUND

[0002] When a voltage sag occurs at a disturbance point, the voltage at the point drops sharply, and the current rises sharply. The admittance of the node before and after the voltage sag will change significantly. According to Kirchhoff's current law, the current flowing into the voltage sag disturbance node comes entirely from other lines that are electrically connected to the node. To analyze the distribution characteristics of voltage sag intensity and adjacent lines, this paper proposes a new method using disturbance admittance to qualitatively determine the proximity relationship between the voltage sag disturbance center and the line topology.

[0003] When a node (disturbance point) experiences a voltage sag, the voltage sag intensity monitored by another node (monitoring point) is related not only to the intensity of the voltage sag at the disturbance point, but also to the topology of the power grid and the electrical distance between the monitoring node and the fault point. Therefore, the propagation of voltage sag can be regarded as the result of the combined action of voltage sag events and power grid topology.

[0004] That is, when a fault occurs in a circuit, it is usually accompanied by a voltage sag, which is usually accompanied by a sudden change in current. The prior art generally compares the voltage effective value near the fault point to determine the nature of the fault. Based on the current conventional technology, there is a voltage sag recognition index with higher resolution than the voltage effective value, namely the virtual disturbance admittance.

[0005] Based on the above technical needs, a new method using disturbance admittance is needed to analyze the distribution characteristics of voltage sag intensity and adjacent lines to qualitatively determine the proximity relationship between the voltage sag disturbance center and the line topology. SUMMARY

[0006] The purpose of the present application is to provide a disturbance calculation method based on accurate time synchronization based on virtual disturbance admittance, which calculates the disturbance admittance according to the three-phase waveform data before and after the duration of the voltage sag in combination with the network time synchronization when the voltage sag occurs.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a sensitivity analysis method for fault intensity and fault distance based on virtual disturbance admittance, comprising the following steps:

[0008] Establishing a virtual disturbance admittance that quantitatively characterizes the voltage sag process;

[0009] Establishing a voltage sag monitoring model, wherein at least two monitoring points are provided on each bus in the voltage sag monitoring model, and the monitoring points are configured as POM power quality monitors;

[0010] When any monitoring point in the system monitors a voltage sag, all POM power quality monitors in the voltage sag monitoring model start voltage and current recording waveforms synchronously, and save each N complete 3-phase voltage waveform data before and after the voltage sag and current waveform data and complete voltage and current waveform data of the voltage sag process and current waveform data

[0011] Three sets of waveforms at the same time are selected for comparison to obtain the duration of the sag tf

[0012] The virtual disturbance admittance between any two adjacent buses in the voltage sag monitoring model is calculated.

[0013] In an embodiment of the present application, a computer-readable storage medium is also proposed, and the storage medium stores a computer program, wherein the computer program is configured to execute the steps in any of the method embodiments described above when running.

[0014] In an embodiment of the present application, an electronic device is also proposed, comprising a memory and a processor, characterized in that the memory stores a computer program, and the processor is configured to execute the computer program to execute the steps in any of the method embodiments described above.

[0015] Compared with the prior art, the present application has the following beneficial effects: according to the three-phase waveform data before and after the occurrence of the sag, in combination with the network time synchronization, it is determined whether it is the same voltage sag event, and the disturbance admittance is accurately calculated. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The method step flowchart of the present application

[0017] Figure 2 The waveform diagram of three-phase voltage u abc when a three-phase symmetrical fault occurs in the distribution network in the embodiment of the present application

[0018] Figure 3 The waveform diagram of three-phase current i abc when a three-phase symmetrical fault occurs in the distribution network in the embodiment of the present application

[0019] Figure 4 The voltage and current waveform diagram of example A phase at the corresponding sag starting time in the embodiment of the present application DETAILED DESCRIPTION

[0020] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0021] As shown in the drawings, Figure 1 In an embodiment, a sensitivity analysis method based on virtual disturbance admittance of fault strength and fault distance includes the following steps:

[0022] A virtual disturbance admittance is established to quantitatively characterize the process of voltage sag.

[0023] A voltage sag monitoring model is established, and at least two monitoring points are provided on each bus in the voltage sag monitoring model, and the monitoring points are configured as POM (Power quality monitoring) power quality monitors.

[0024] When any monitoring point in the system monitors voltage sag, all POM power quality monitors in the voltage sag monitoring model synchronously start voltage and current recording, save N complete 3-phase voltage waveform data and current waveform data before and after voltage sag, and complete voltage and current waveform data of the voltage sag process.

[0025] Three sets of waveforms at the same time are selected for comparison to obtain the duration of the sag tf.

[0026] The virtual disturbance admittance between any two adjacent buses in the voltage sag monitoring model is calculated.

[0027] It should be noted that the essence of voltage sag can be regarded as that in a very short time, the admittance of a node in the power grid rapidly increases, a large amount of current flows into the node, and further causes the voltage of the node to drop sharply. The relative electrical distance of the monitoring point of the voltage sag refers to the electrical distance sorting of multiple PQM from the disturbance center for the same voltage sag disturbance source.

[0028] Among them, three sets of waveforms at the same time are selected for comparison, which specifically refers to comparing and analyzing the three voltage waveforms before, during and after each sag for each monitoring point, taking the effective value dropping below 0.9P.U. as the starting time, and taking the effective value recovering to more than 0.9P.U. as the ending time.

[0029] In an optional implementation, three sets of waveforms at the same time are selected for comparison to obtain the voltage sag duration tf; wherein, when the error of the voltage sag duration tf recorded by each monitoring point is within a very small preset range, and it is determined whether the network time synchronization records are consistent, it is determined that the waveform data of each monitoring point belongs to the same voltage sag event.

[0030] It should be noted that the minimum range of error is a system setting value, which can be set by the user according to application requirements. In this embodiment, it is set to 10µs. This data is not used to limit its range.

[0031] The following examples illustrate this:

[0032] like Figure 2 , Figure 3 As shown, 1(a) and 1(b) represent the three-phase voltage u of a 10kV distribution network when a three-phase symmetrical fault occurs in 0.1s. abc and current i abc The waveform. To accurately describe the disturbance process before and after the transient, this paper proposes a disturbance calculation method based on precise time synchronization. To clearly describe the calculation process, take... Figure 1 The waveforms before and after the voltage dip are explained. Taking phase A as an example, the voltage and current waveforms at the start of the voltage dip are as follows: Figure 4 As shown, it is denoted as f1(t).

[0033] The voltage sag initiation time ts is determined, the sampling frequency of the voltage sag monitoring model is set to fs, and the grid frequency is f. That is, within one cycle, the monitoring device records fs / f points, and the time interval between each point is 1 / fs seconds. The positive zero-crossing point of the corresponding phase voltage of the recorded cycle is taken as the time stamp 0. From this time, the discrete points of the sampled waveform are numbered one by one, and the corresponding sampling point number is Ns. The waveform record of the initial stage of the sag is h1(n). The ideal waveform h0(n) is constructed to obtain the disturbance data h2(n).

[0034]

[0035] h2(n)=h1(n)-h0(n) (2)

[0036] The disturbance ΔU of the three-phase voltage and three-phase current is obtained from the disturbance data. abc and ΔI abc Calculate the effective values ​​of each phase voltage and current before and after time ts. and The disturbance value corresponding to the three-phase admittance is calculated using the following formula.

[0037]

[0038] k = a, b, c; h = u, i

[0039]

[0040] k=a, b, c; h=u, i

[0041]

[0042]

[0043]

[0044] wherein, are the three-phase voltages before and at the beginning of the voltage sag, respectively, are the three-phase currents before and at the beginning of the voltage sag, respectively, Δu abc , Δi abc , Δy abc are the three-phase voltage, current and admittance disturbances at the moment of the voltage sag, respectively.

[0045] For each voltage sag monitoring device m, the item with the largest absolute value in its Δy abcm vector is taken as the disturbance admittance of the monitoring point, denoted as y m .

[0046]

[0047] For any voltage sag event, whether the source of the voltage sag is located on the power supply side, the grid side or the load side, the disturbance admittance value of the fault point is the largest, and the disturbance admittance shows a decreasing distribution trend from the fault center to the power supply end, the grid side and the load side, and this distribution characteristic is not affected by the power flow, distributed voltage and ring network topology.

[0048] According to still another aspect of the embodiments of the present application, an electronic device based on a precise time-based disturbance calculation method based on virtual disturbance admittance is also provided, which can be but is not limited to be applied in a server. The processor is configured to execute the steps in any of the method embodiments by a computer program.

[0049] Optionally, in the present embodiment, the processor can be configured to execute the following steps by a computer program:

[0050] S1, a virtual disturbance admittance quantitatively characterizing the process of voltage sag is established;

[0051] S2, a voltage sag monitoring model is established, at least two monitoring points are provided on each bus in the voltage sag monitoring model, and the monitoring points are configured as POM power quality monitors;

[0052] S3, when any monitoring point in the system monitors the voltage delay, all POM power quality monitors in the voltage delay monitoring model start voltage and current recording wave synchronously, save N complete 3-phase voltage waveform data and current waveform data before and after the voltage delay, and complete voltage and current waveform data during the voltage delay process;

[0053] S4, select three sets of waveforms at the same time for comparison to obtain the duration of the voltage delay tf;

[0054] S5, calculate the virtual disturbance admittance between any two adjacent buses in the voltage delay monitoring model.

[0055] Embodiments of the present application also provide a computer-readable storage medium, which stores a computer program, wherein the computer program is configured to execute the steps in any of the method embodiments described above when running.

[0056] Optionally, in the present embodiment, the storage medium described above can be configured to store a computer program for executing the following steps:

[0057] S1, establish a virtual disturbance admittance for quantitatively characterizing the voltage delay process;

[0058] S2, establish a voltage delay monitoring model, at least two monitoring points are provided on each bus in the voltage delay monitoring model, and the monitoring points are configured as POM power quality monitors;

[0059] S3, when any monitoring point in the system monitors the voltage delay, all POM power quality monitors in the voltage delay monitoring model start voltage and current recording wave synchronously, save N complete 3-phase voltage waveform data and current waveform data before and after the voltage delay, and complete voltage and current waveform data during the voltage delay process;

[0060] S4, select three sets of waveforms at the same time for comparison to obtain the duration of the voltage delay tf;

[0061] S5, calculate the virtual disturbance admittance between any two adjacent buses in the voltage delay monitoring model.

[0062] Optionally, in the present embodiment, those skilled in the art can understand that all or part of the steps in the various methods of the above embodiments can be completed by instructing the hardware related to the terminal device through a program, and the program can be stored in a computer-readable storage medium, and the storage medium can include a flash disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, etc.

[0063] The above application embodiment serial numbers are only for description, and do not represent the advantages and disadvantages of the embodiments.

[0064] The integrated units in the above embodiments, if realized in the form of software function units and sold or used as independent products, can be stored in the above computer-readable storage medium. Based on such understanding, the technical solutions of the present application essentially or the parts that make contributions to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a plurality of instructions for causing one or more computer devices (which can be personal computers, servers or network devices, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application.

[0065] In the above embodiments of the present application, the description of each embodiment has its own focus, and the parts not described in detail in a certain embodiment can be referred to the relevant description of other embodiments.

[0066] In the several embodiments provided by the present application, it should be understood that the disclosed client can be implemented in other ways. Of course, the above device embodiment is only illustrative, and for example, the division of the units is only a logical function division, and there can be another division manner in actual implementation, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interface, unit or module, and can be electrical or other forms.

[0067] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e., they can be located in one place or distributed on multiple network units. Part or all of the units can be selected to achieve the purpose of the embodiment according to actual needs.

[0068] In addition, each functional unit in the various embodiments of the present application can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The above integrated unit can be realized in the form of hardware or software function unit.

[0069] The above is only the preferred embodiment of the present application, and it should be pointed out that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should be considered as the protection scope of the present application.

Claims

1. A precision time-based perturbation calculation method based on virtual perturbation admittance, characterized in that, The method comprises the following steps: establishing a virtual disturbance admittance for quantitatively characterizing a voltage sag process; establishing a voltage sag monitoring model, at least two monitoring points being arranged at each bus in the voltage sag monitoring model, and the monitoring points being configured as POM power quality monitors; When any monitoring point in the system monitors voltage sag, all POM power quality monitors in the voltage sag monitoring model start voltage and current recording wave synchronously, save each N complete 3-phase voltage waveform data before and after voltage sag and current waveform data and complete voltage and current waveform data of voltage sag process and current waveform data; selecting three sets of waveforms at the same time for comparison to obtain a voltage sag duration tf; calculating a virtual disturbance admittance between any two adjacent buses in the voltage sag monitoring model.

2. The method of claim 1, wherein the method is a precision time-based perturbation calculation method based on virtual perturbation admittance. The three sets of waveforms at the same time are selected for comparison to obtain the voltage sag duration tf; wherein, when the voltage sag duration tf recorded by each monitoring point is within a preset range, and it is judged whether the records of network time are consistent, it is judged that the waveform data of each monitoring point is caused by the same voltage sag event.

3. The method of claim 1, wherein the method is a precision time synchronization based perturbation calculation method based on virtual perturbation admittance. The three sets of waveforms at the same time are selected for comparison to obtain the voltage sag duration tf; further comprising: determining a voltage sag starting time ts, setting a sampling frequency of the voltage sag monitoring model as fs, and a grid frequency as f, that is, within one cycle, the monitoring device records fs / f points, and the time interval between each point is 1 / fs seconds, taking the corresponding phase voltage positive zero point of the recorded cycle as the time mark 0, and numbering the discrete points of the sampled waveforms one by one from the time, and the corresponding sampling point number is Ns, the waveform record of the voltage sag starting stage is h1(n), an ideal waveform h0(n) is constructed, and disturbance data h2(n) is obtained; h2(n) = h1(n) - h0(n) (2) 4. The method of claim 3, wherein the method is a precision time synchronization based perturbation calculation method based on virtual perturbation admittance. The calculating the virtual disturbance admittance between any two adjacent buses in the voltage sag monitoring model comprises: acquiring the disturbance ΔU of three-phase voltage and three-phase current according to the disturbance data abc and ΔI abc , calculating the effective values of each phase voltage and current before and after the time ts and The disturbance value of the corresponding three-phase admittance is calculated by the following formula, wherein the three-phase voltages before and at the beginning of the dip, respectively, the three-phase currents before and at the beginning of the dip, respectively, Δu abc , Δi abc , Δy abc the three-phase voltage, current and admittance disturbances at the instant of the dip, respectively.

5. The method of claim 4, wherein: The calculation of the virtual disturbance admittance between any two adjacent buses in the voltage sag monitoring model; further comprising: for each voltage sag monitoring device m, taking its Δy abcm The item with the maximum absolute value in the vector as the disturbance admittance of the monitoring point, denoted as y m .

6. A computer readable storage medium, characterized in that, The storage medium has a computer program stored therein, wherein the computer program is configured to execute the method in any one of claims 1 to 5 when running. 7.An electronic device comprising a memory and a processor, the electronic device characterized by, The storage medium has a computer program stored therein, wherein the computer program is configured to execute the method in any one of claims 1 to 5 when running.

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