CN110504707B - Method and device for evaluating voltage transient stability level of multi-direct-current feed-in power grid - Google Patents
Method and device for evaluating voltage transient stability level of multi-direct-current feed-in power grid Download PDFInfo
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Abstract
The invention discloses a method for evaluating voltage transient stability of a multi-direct-current feed-in power grid, which comprises the following steps of: counting fault types of a multi-direct-current feed-in power grid according to historical data, and calculating corresponding fault weight values; after a fault is recorded, voltage change curves of all direct current inversion side alternating current buses in the multi-direct current feed-in power grid are recorded; calculating the running power weight value of each direct current line; determining a low voltage threshold value of a direct current inversion side alternating current bus corresponding to each direct current line; and calculating an index for measuring the voltage transient stability level of the multi-direct-current feed-in power grid according to the total number of fault types of the multi-direct-current feed-in power grid, the fault weight value corresponding to each fault type and the voltage change curve. The invention discloses a method for evaluating the voltage transient stability level of a multi-direct-current feed-in power grid, which can be used for measuring the voltage transient stability level of the multi-direct-current feed-in power grid by combining various fault types. The invention also discloses an evaluation device and a storage medium for the voltage transient stability level of the multi-direct-current feed-in power grid.
Description
Technical Field
The invention relates to the technical field of multi-direct-current feed-in power grids, in particular to a method and a device for evaluating voltage transient stability of a multi-direct-current feed-in power grid.
Background
With the implementation of the strategy of 'western and east power transmission' in China, a plurality of power grids and regions in China form a multi-loop direct-current feed-in alternating-current and direct-current hybrid power transmission system. With the increase of the direct current quantity of the planned feed-in receiving end power grid, the problem of voltage stability caused by mutual influence of alternating current and direct current is more prominent. Engineering practice shows that after a fault of a multi-direct-current feed-in power grid occurs, voltage sag caused by the fault may cause multi-circuit direct-current commutation failure, and when the fault is serious, multi-circuit direct-current blocking may be caused. The transient voltage stability problem presents a serious challenge to the safe and stable operation of a multi-dc feed power grid. Therefore, the research on the index capable of measuring the voltage transient stability level of the multi-direct-current feed-in power grid has important significance in quantitatively evaluating the fault resistance capability of the multi-direct-current feed-in power grid.
The problem of phase commutation failure of direct current is the most typical problem in the voltage transient process of a multi-direct-current-fed power grid, and is also a decisive factor for measuring the voltage transient stability level of the multi-direct-current-fed power grid. In the prior art, a commonly used method for judging the direct-current commutation failure is mainly an arc-quenching angle judgment method, and the method judges whether the commutation failure occurs in a system by comparing the difference between the arc-quenching angle of a converter and the minimum arc-quenching angle causing the commutation failure.
The inventor finds that the following technical problems exist in the prior art in the process of implementing the invention:
in a practical system, the converter extinction angle and the minimum extinction angle causing commutation failure are time-varying; in particular, the minimum extinction angle causing commutation failure can be determined only by a large number of calculations, and is difficult to be applied to evaluating an actual system; in addition, for a multi-direct-current feed-in power grid, whether the system has phase change failure or not can not be simply judged according to the voltage drop condition of a certain transformer substation after a single fault.
Disclosure of Invention
The embodiment of the invention provides a method for evaluating the voltage transient stability level of a multi-direct-current feed-in power grid, which can be used for measuring the voltage transient stability level of the multi-direct-current feed-in power grid by combining various fault types.
The embodiment of the invention provides a method for evaluating voltage transient stability of a multi-direct-current feed-in power grid, which comprises the following steps:
counting fault types of a multi-direct-current feed-in power grid according to historical data, and calculating fault weight values corresponding to the fault types;
recording voltage change curves of all direct current inversion side alternating current buses in the multi-direct current feed-in power grid after the multi-direct current feed-in power grid fails;
calculating an operating power weight value of each direct current line in the multi-direct current feed-in power grid;
determining a low voltage threshold value of a direct current inversion side alternating current bus corresponding to each direct current line; the low voltage threshold of the alternating current bus at the direct current inversion side is a voltage value when the corresponding direct current line fails to change the phase;
calculating an index for measuring the voltage transient stability level of the multi-direct-current feed-in power grid according to the total number of fault types of the multi-direct-current feed-in power grid, fault weight values corresponding to the fault types and a voltage change curve;
and obtaining the voltage transient stability level of the multi-direct-current feed-in power grid according to the index for measuring the voltage transient stability level of the multi-direct-current feed-in power grid.
As an improvement of the above scheme, the calculating a fault weight value corresponding to each fault type specifically includes:
setting the ith fault occurrence frequency of the multi-direct-current feed-in power grid to be niThen its corresponding weighted value λiAs shown in the following equation:
where M is the total number of fault types.
As an improvement of the above scheme, the calculating an operating power weight value of each dc line in the multiple dc feed-in power grid specifically includes:
let ujCalculating the value of the operating power weighted value of the jth direct current line by the following formulaj：
Wherein N is the total number of the direct current lines.
As an improvement of the above scheme, the method further comprises the following steps:
determining key substations and key lines that cause the multi-DC feed-in grid to fail.
As an improvement of the above scheme, the calculating a level index for measuring voltage sag stability of the multiple direct current feed-in power grid specifically includes:
calculating the voltage transient stability level index of the multi-direct current feed-in power grid through the following formula:
in the formula IUAs an indication of the level of stability of the voltage transient, λiThe fault type is a weighted value corresponding to the ith fault type, M is the total number of the fault types, and the sum of the weighted values corresponding to the fault types is 1; k is the serial number of the faulted transformer substations and lines, and L is the total number of the faulted transformer substations and lines; mu.sjThe operation power weight value of the jth direct current line is obtained, and N is the total number of the direct current lines; vj,threA low voltage threshold value of a direct current inversion side alternating current bus corresponding to the jth direct current line is set; u shapei,j,k(t) is the kth substationOr after the ith fault occurs in the line, the voltage value of the alternating current bus at the inversion side of the jth direct current line at the time t; t is t0For the voltage after fault to be lower than Vj,threAt a time of Δ t of Ui,j,k(t) is less than Vj,threThe duration of (c).
Correspondingly, an embodiment of the present invention provides an apparatus for evaluating voltage sag stability of a multiple-dc-fed power grid, including:
the fault type counting unit is used for counting fault types generated by the multi-direct-current feed-in power grid according to historical data and calculating fault weight values corresponding to the fault types;
the voltage change acquisition unit is used for recording voltage change curves of all direct current inversion side alternating current buses in the multi-direct current feed-in power grid after the multi-direct current feed-in power grid fails;
the operating power calculating unit is used for calculating an operating power weight value of each direct current line in the multi-direct current feed-in power grid;
the low voltage threshold determining unit is used for determining a low voltage threshold of a direct current inversion side alternating current bus corresponding to each direct current line; the low voltage threshold of the alternating current bus at the direct current inversion side is a voltage value when the corresponding direct current line fails to change the phase;
the index calculation unit is used for calculating an index for measuring the voltage transient stability level of the multi-direct-current feed-in power grid according to the total number of fault types of the multi-direct-current feed-in power grid, fault weight values corresponding to the fault types and a voltage change curve;
and the stable water balance quantity unit is used for obtaining the voltage transient stability level of the multi-direct-current feed-in power grid according to the index for measuring the voltage transient stability level of the multi-direct-current feed-in power grid.
Correspondingly, a third embodiment of the present invention provides an apparatus for evaluating voltage sag stability of a multiple-dc-fed power grid, including: the evaluation method comprises a processor, a memory and a computer program stored in the memory and configured to be executed by the processor, wherein the processor executes the computer program to realize the evaluation method of the voltage transient stability level of the multi-direct-current feed-in power grid according to the first embodiment of the invention.
Correspondingly, the fourth embodiment of the present invention provides a computer-readable storage medium, where the computer-readable storage medium includes a stored computer program, and when the computer program runs, the apparatus where the computer-readable storage medium is located is controlled to execute the method for evaluating voltage sag stability levels of a multiple direct-current feed-in power grid according to the first embodiment of the present invention.
The method for evaluating the voltage transient stability level of the multi-direct-current feed-in power grid provided by the embodiment of the invention has the following beneficial effects:
the voltage transient stability level of the multi-direct-current feed-in power grid can be comprehensively and integrally measured based on multiple fault types and combined with the weight values of the fault types in historical data; fault types appearing in all historical data can be selected, typical or common fault types can be selected selectively, and targeted evaluation can be carried out; by determining key substations and key lines, voltage monitoring after faults is performed in a targeted manner, and voltage change curves of all direct-current inversion side alternating-current buses in the power grid after the faults of the key substations and the key lines are extracted; and finally, measuring the voltage transient stability level of the multi-direct-current feed-in power grid according to the voltage transient stability level index of the multi-direct-current feed-in power grid, and obtaining a comprehensive, accurate and targeted evaluation result.
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Fig. 1 is a schematic flowchart of a method for evaluating a voltage sag stability level of a multiple direct current fed-in power grid according to an embodiment of the present invention.
Fig. 2 is a schematic calculation diagram of a method for evaluating voltage sag stability of a multiple direct current fed-in power grid according to an embodiment of the present invention.
Fig. 3 is a schematic structural diagram of an apparatus for evaluating voltage sag stability of a multiple dc feed-in power grid according to a second embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, a schematic flow chart of a method for evaluating a voltage sag stability level of a multiple direct current fed-in power grid according to an embodiment of the present invention includes:
s101, counting fault types of a multi-direct-current feed-in power grid according to historical data, and calculating a fault weight value corresponding to each fault type;
s102, recording voltage change curves of all direct current inversion side alternating current buses in the multi-direct current feed-in power grid after the multi-direct current feed-in power grid fails;
s103, calculating the running power weight value of each direct current line in the multi-direct current feed-in power grid;
s104, determining a low voltage threshold value of a direct current inversion side alternating current bus corresponding to each direct current line; the low voltage threshold of the alternating current bus at the direct current inversion side is a voltage value when the corresponding direct current line fails to change the phase;
s105, calculating an index for measuring the voltage transient stability level of the multi-direct-current feed-in power grid according to the total number of fault types of the multi-direct-current feed-in power grid, fault weight values corresponding to the fault types and a voltage change curve;
and S106, obtaining the voltage transient stability level of the multi-direct-current feed-in power grid according to the index for measuring the voltage transient stability level of the multi-direct-current feed-in power grid.
Preferably, in the method for evaluating the voltage sag stability level of the multiple dc-fed power grid according to the first embodiment of the present invention, the fault types occurring in the multiple dc-fed power grid are counted according to historical data, where the fault types may be all fault types or typical fault types in the multiple dc-fed power grid. Typical fault types include single-circuit single-phase, interphase, three-phase short-circuit faults, single-tower and multi-circuit simultaneous/sequential faults, bus single-phase or multi-phase grounding/short-circuit faults, and the like.
Further, the calculating a fault weight value corresponding to each fault type specifically includes:
setting the ith fault occurrence frequency of the multi-direct-current feed-in power grid to be niThen its corresponding weighted value λiAs shown in the following equation:
where M is the total number of fault types.
Further, the calculating the operating power weight value of each dc line in the multiple dc feed-in power grid specifically includes:
let ujCalculating the value of the operating power weighted value of the jth direct current line by the following formulaj：
Wherein N is the total number of the direct current lines. Namely, the running power before the jth direct current line fault is divided by the total power of the multiple direct current feed-in power grids fed before all direct current line faults.
Further, the method also comprises the following steps:
determining key substations and key lines that cause the multi-DC feed-in grid to fail.
Preferably, the substation and the line are key elements of the transmission load of the power grid, and when the line or the substation fails, the voltage of the power grid can be reduced. However, different types of faults occur in different lines or substations, and the influence degree of the faults on the grid voltage is different. Therefore, a certain number of multi-direct current feed-in power grid key substations can be screened out according to a certain rule (for example, according to scheduling operation experience or a complex network key node determination method); or screening out a certain number of multi-direct current feed-in power grid key lines according to a certain rule (for example, according to scheduling operation experience or a complex network key line determination method).
Preferably, for step S102, recording voltage variation curves of all dc inverter side ac buses in the multi-dc feed-in power grid after the multi-dc feed-in power grid fails, which may include:
recording voltage variation curves of alternating current buses of all direct current inversion sides along with time after various typical faults occur on a key transformer substation; and recording the voltage change curves of the alternating current buses of all the direct current inversion sides along with time after various typical faults occur on the key line.
Preferably, in step S104, when the voltage of the ac bus on the dc inversion side drops below the threshold, the dc will have a phase change failure, but the low voltage thresholds of different dc are different.
When the voltage on the alternating current side of the direct current inversion side commutation bus falls to a certain percentage of the voltage value before the fault after the fault of the multi-direct current feed-in power grid, the direct current commutation failure is considered to occur, and the criterion is the engineering practical criterion of the direct current commutation failure. Therefore, according to the common knowledge of the skilled person, the ac bus low voltage threshold value at which the commutation failure of each dc of the multi-dc feed network starts to occur can be determined.
Further, the calculating and measuring a level index for stabilizing voltage transient of the multi-dc feed-in power grid specifically includes:
calculating the voltage transient stability level index of the multi-direct current feed-in power grid through the following formula:
in the formula IUAs an indication of the level of stability of the voltage transient, λiThe fault type is a weighted value corresponding to the ith fault type, M is the total number of the fault types, and the sum of the weighted values corresponding to the fault types is 1; k is the serial number of the faulted transformer substations and lines, and L is the total number of the faulted transformer substations and lines; mu.sjThe operation power weight value of the jth direct current line is obtained, and N is the total number of the direct current lines; vj,threIs the jth DC lineA low voltage threshold value of an alternating current bus of the direct current inversion side corresponding to the circuit is set; u shapei,j,k(t) the voltage value of the alternating current bus at the inversion side of the jth direct current line at the time of t after the ith fault occurs in the kth transformer substation or line; t is t0For the voltage after fault to be lower than Vj,threAt a time of Δ t of Ui,j,k(t) is less than Vj,threThe duration of (c).
Preferably, referring to fig. 2, a schematic diagram of a calculation of a method for evaluating a voltage sag stability level of a multiple direct current feed-in power grid according to an embodiment of the present invention is shown. Integral term
Showing the area, particularly if the voltage value of the alternating current bus on the inverting side of the j direct current line is always higher than V after the ith faultj,threIf Δ t is 0.
In a specific implementation, the method for evaluating the voltage sag stability level of the multi-dc-fed power grid specifically comprises the following steps:
searching historical data, and solving the most typical five types of faults and corresponding fault weight values of the power grid of Guangdong province in the last five years as shown in the following table 1:
TABLE 1 most typical five types of faults and weights in the last five years for the Guangdong electric network
| Serial number | Type of failure | Weighted value |
| 1 | Single-circuit line single-phase grounding | 0.8933 |
| 2 | Interphase short circuit of single-circuit line | 0.0501 |
| 3 | Three-phase short circuit of single-circuit line | 0.0265 |
| 4 | Double circuit line sequential fault on same tower | 0.0177 |
| 5 | Single-phase permanent fault single-phase switch refusing action of bus | 0.0124 |
The first ten key substations/lines of the Guangdong province power grid determined by an organization according to the scheduling operation experience are shown in tables 2 and 3.
TABLE 2 Guangdong province ten key substations before the grid
| Serial number | Name of transformer station |
| 1 | 500kV capital station |
| 2 | 500kV slave station |
| 3 | 500kV ear of grain east station |
| 4 | 500kV city increasing station |
| 5 | 500kV compass station |
| 6 | 500kV modern station |
| 7 | 500kV transverse draining station |
| 8 | 500kV Baoan station |
| 9 | 500kV cis-De station |
| 10 | 500kV water country station |
TABLE 3 Guangdong province electric network ten key lines
| Serial number | Line name |
| 1 | 500kV Huadu-Slave line |
| 2 | 500kV Slave-Boruo line |
| 3 | 500kV ear east-transverse draining line |
| 4 | 500kV city-increasing-water town line |
| 5 | 500kV Dongguan-Huizhou line |
| 6 | 500kV compass-suburb line |
| 7 | 500kV redbud-modern line |
| 8 | 500kV cis-de-Guannan line |
| 9 | 500kV Yangjiang-skive city line |
| 10 | 500kV Dongpo-Huadu line |
The multi-direct-current feed-in power grid of Guangdong province has eight direct-current feed-in circuits, namely a cattle direct current, a general direct current, a Chu ear direct current, a Xingan direct current, a Tianguan direct current, a GaoZhao direct current, a Sanguan direct current and a Yunnan northwest direct current, and the corresponding eight direct-current inversion stations are a west direct current, a Qiao county, a Tuonan, a suburb, a Zhaoqing, a goose city and an east station.
Performing time domain simulation analysis on each fault by using PSD-BPA time domain simulation analysis software: under a certain operation mode, when the single-phase permanent fault single-phase switch operation rejection fault of the bus occurs on each of the ten key substations shown in the table 2, the voltage change curves of the eight direct-current inversion side alternating-current buses along with time are recorded; when single-circuit single-phase grounding, single-circuit interphase short circuit, single-circuit three-phase short circuit and double-circuit line sequential faults of the same tower parallel connection occur on the ten key circuits described in the table 3 above, the voltage change curves of the eight direct current inversion side alternating current buses along with time are recorded.
The operating power and corresponding operating power weight values of each dc line before the fault are shown in table 4.
TABLE 4 DC-LINE OPERATING POWER AND RELATED WEIGHT VALUES BETWEEN PRE FAULT
According to engineering experience, the low voltage threshold (per unit of the voltage value before the fault is taken as a reference value) of the ac bus at which the commutation failure starts to occur for each dc is shown in table 5 below.
TABLE 5 AC BUS LOW VOLTAGE THRESHOLD FOR THE PHASE CHANGE FAILURE AT THE START OF THE PHASE CHANGE OF THE LINE
| Serial number | DC line name | Low voltage threshold |
| 1 | DC of cow | 0.91p.u. |
| 2 | General DC | 0.88p.u. |
| 3 | DC of Chu ear | 0.90p.u. |
| 4 | Xingan DC | 0.91p.u. |
| 5 | Tianguang DC | 0.89p.u. |
| 6 | High DC | 0.88p.u. |
| 7 | Three wide direct current | 0.89p.u. |
| 8 | Yunnan northwest direct current | 0.90p.u. |
According to the formula
Calculating voltage transient change stability level index I for measuring multiple direct currents fed into power grid in Guangdong under the operation modeU0.986. The larger this value, the weaker the voltage sag stability level, and the network is fault-tolerantThe weaker the capacity.
The method, the device and the storage medium for evaluating the voltage transient stability level of the multi-direct-current feed-in power grid provided by the embodiment of the invention have the following beneficial effects:
the voltage transient stability level of the multi-direct-current feed-in power grid can be comprehensively and integrally measured based on multiple fault types and combined with the weight values of the fault types in historical data; fault types appearing in all historical data can be selected, typical or common fault types can be selected selectively, and targeted evaluation can be carried out; by determining key substations and key lines, voltage monitoring after faults is performed in a targeted manner, and voltage change curves of all direct-current inversion side alternating-current buses in the power grid after the faults of the key substations and the key lines are extracted; and finally, measuring the voltage transient stability level of the multi-direct-current feed-in power grid according to the voltage transient stability level index of the multi-direct-current feed-in power grid, and obtaining a comprehensive, accurate and targeted evaluation result.
Referring to fig. 3, a schematic structural diagram of an apparatus for evaluating a voltage sag stability level of a multiple direct-current fed-in power grid according to a second embodiment of the present invention includes:
the fault type counting unit 201 is used for counting fault types generated by multiple direct current feed-in power grids according to historical data and calculating fault weight values corresponding to the fault types;
the voltage change acquisition unit 202 is configured to record voltage change curves of all dc inverter side ac buses in the multi-dc feed-in power grid after the multi-dc feed-in power grid fails;
the operating power calculating unit 203 is configured to calculate an operating power weight value of each dc line in the multiple dc feed-in power grid;
a low voltage threshold determining unit 204, configured to determine a low voltage threshold of the dc-inverter-side ac bus corresponding to each dc line; the low voltage threshold of the alternating current bus at the direct current inversion side is a voltage value when the corresponding direct current line fails to change the phase;
the index calculation unit 205 is configured to calculate an index for measuring a voltage transient stability level of the multiple dc feed-in power grid according to the total number of fault types occurring in the multiple dc feed-in power grid, a fault weight value corresponding to each fault type, and a voltage change curve;
and the stable water balance amount unit 206 is configured to obtain the multiple direct-current feed-in power grid voltage transient stability level according to the index for measuring the multiple direct-current feed-in power grid voltage transient stability level.
Correspondingly, the third embodiment of the present invention provides an apparatus for evaluating a voltage sag stability level of a multiple direct-current feeding grid, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, where the processor executes the computer program to implement the method for evaluating a voltage sag stability level of a multiple direct-current feeding grid according to the first embodiment of the present invention. The device for evaluating the voltage transient stability level of the multi-direct-current feed-in power grid can be computing equipment such as a desktop computer, a notebook computer, a palm computer and a cloud server. The device for evaluating the voltage sag stability level of the multi-direct current feed-in power grid can comprise, but is not limited to, a processor and a memory.
Correspondingly, the fourth embodiment of the present invention provides a computer-readable storage medium, where the computer-readable storage medium includes a stored computer program, and when the computer program runs, the apparatus where the computer-readable storage medium is located is controlled to execute the method for evaluating the voltage sag stability level of the multiple direct-current feed-in power grid according to the first embodiment of the present invention.
The Processor may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic device, discrete hardware component, or the like. The general-purpose processor may be a microprocessor or the processor may be any conventional processor or the like, the processor is a control center of the evaluation device of the voltage sag stability level of the multiple direct current feeding network, and various interfaces and lines are used to connect various parts of the evaluation device of the voltage sag stability level of the entire multiple direct current feeding network.
The memory can be used for storing the computer program and/or the module, and the processor realizes various functions of the evaluation device of the voltage transient stability level of the multi-direct-current feed power grid by running or executing the computer program and/or the module stored in the memory and calling the data stored in the memory. The memory may mainly include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required by at least one function (such as a sound playing function, an image playing function, etc.), and the like; the storage data area may store data (such as audio data, a phonebook, etc.) created according to the use of the cellular phone, and the like. In addition, the memory may include high speed random access memory, and may also include non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), at least one magnetic disk storage device, a Flash memory device, or other volatile solid state storage device.
Wherein, the modules/units integrated by the device for evaluating the voltage sag stability level of the multi-direct current feed-in power grid can be stored in a computer readable storage medium if the modules/units are realized in the form of software functional units and sold or used as independent products. Based on such understanding, all or part of the flow of the method according to the embodiments of the present invention may also be implemented by a computer program, which may be stored in a computer-readable storage medium, and when the computer program is executed by a processor, the steps of the method embodiments may be implemented. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, usb disk, removable hard disk, magnetic disk, optical disk, computer Memory, Read-Only Memory (ROM), Random Access Memory (RAM), electrical carrier wave signals, telecommunications signals, software distribution medium, and the like.
It should be noted that the above-described device embodiments are merely illustrative, where the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. In addition, in the drawings of the embodiment of the apparatus provided by the present invention, the connection relationship between the modules indicates that there is a communication connection between them, and may be specifically implemented as one or more communication buses or signal lines. One of ordinary skill in the art can understand and implement it without inventive effort.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Claims (7)
1. A method for evaluating voltage transient stability of a multi-direct current feed-in power grid is characterized by comprising the following steps:
counting fault types of a multi-direct-current feed-in power grid according to historical data, and calculating fault weight values corresponding to the fault types;
recording voltage change curves of all direct current inversion side alternating current buses in the multi-direct current feed-in power grid after the multi-direct current feed-in power grid fails;
calculating an operating power weight value of each direct current line in the multi-direct current feed-in power grid;
determining a low voltage threshold value of a direct current inversion side alternating current bus corresponding to each direct current line; the low voltage threshold of the alternating current bus at the direct current inversion side is a voltage value when the corresponding direct current line fails to change the phase;
calculating an index for measuring the voltage transient stability level of the multi-direct-current feed-in power grid according to the total number of fault types of the multi-direct-current feed-in power grid, fault weight values corresponding to the fault types and a voltage change curve;
obtaining the voltage transient stability level of the multi-direct-current feed-in power grid according to the index for measuring the voltage transient stability level of the multi-direct-current feed-in power grid;
the index for calculating and measuring voltage transient stability level of the multi-direct-current feed-in power grid specifically comprises the following steps:
calculating the voltage transient stability level index of the multi-direct current feed-in power grid through the following formula:
in the formula (I), the compound is shown in the specification,I U is an index of the voltage transient stability level,λ i is as followsiThe weight value corresponding to the type of the fault,Mthe sum of the weighted values corresponding to the fault types is 1;kfor the number of the faulty substation and line,Lis the total number of faulty substations and lines;μ j is as followsjThe operating power weight value of the dc link,Nis the total number of DC lines;V j,thre is as followsjA low voltage threshold value of a direct current inversion side alternating current bus corresponding to the direct current line;U i,j,k (t) Is as followskGeneration of individual substation or lineiAfter the occurrence of the seed failure,ttime of dayjThe voltage value of an alternating current bus at the inversion side of the strip direct current line;t 0for voltage after fault to be lower thanV j,thre Δ (d) is detectedtIs composed ofU i,j,k (t) Is lower thanV j,thre The duration of (c).
2. The method according to claim 1, wherein the calculating a fault weight value corresponding to each fault type specifically includes:
setting the multiple direct current feed-in power gridiThe number of seed faults occurring isn i Then its corresponding weighted valueλ i As shown in the following equation:
in the formula (I), the compound is shown in the specification,Mis the total number of fault types.
3. The method according to claim 2, wherein the calculating the operating power weight value of each dc line in the multiple dc-fed power grid specifically comprises:
is provided withμ j Is as followsjThe running power weight value of the DC line is calculated by the following formulaμ j ：
In the formula (I), the compound is shown in the specification,Nis the total number of said dc lines.
4. The method for evaluating voltage sag stability level of a multi-fed dc power grid according to claim 3, further comprising:
determining key substations and key lines that cause the multi-DC feed-in grid to fail.
5. An apparatus for evaluating voltage sag stability levels of a multiple dc feed-in grid, comprising:
the fault type counting unit is used for counting fault types generated by the multi-direct-current feed-in power grid according to historical data and calculating fault weight values corresponding to the fault types;
the voltage change acquisition unit is used for recording voltage change curves of all direct current inversion side alternating current buses in the multi-direct current feed-in power grid after the multi-direct current feed-in power grid fails;
the operating power calculating unit is used for calculating an operating power weight value of each direct current line in the multi-direct current feed-in power grid;
the low voltage threshold determining unit is used for determining a low voltage threshold of a direct current inversion side alternating current bus corresponding to each direct current line; the low voltage threshold of the alternating current bus at the direct current inversion side is a voltage value when the corresponding direct current line fails to change the phase;
the index calculation unit is used for calculating an index for measuring the voltage transient stability level of the multi-direct-current feed-in power grid according to the total number of fault types of the multi-direct-current feed-in power grid, fault weight values corresponding to the fault types and a voltage change curve;
the stable water balance unit is used for obtaining the voltage transient stability level of the multi-direct-current feed-in power grid according to the index for measuring the voltage transient stability level of the multi-direct-current feed-in power grid;
the index for calculating and measuring voltage transient stability level of the multi-direct-current feed-in power grid specifically comprises the following steps:
calculating the voltage transient stability level index of the multi-direct current feed-in power grid through the following formula:
in the formula (I), the compound is shown in the specification,I U is an index of the voltage transient stability level,λ i is as followsiThe weight value corresponding to the type of the fault,Mthe sum of the weighted values corresponding to the fault types is 1;kfor the number of the faulty substation and line,Lis the total number of faulty substations and lines;μ j is as followsjOperating power authority of DC lineThe weight value of the weight is set to be,Nis the total number of DC lines;V j,thre is as followsjA low voltage threshold value of a direct current inversion side alternating current bus corresponding to the direct current line;U i,j,k (t) Is as followskGeneration of individual substation or lineiAfter the occurrence of the seed failure,ttime of dayjThe voltage value of an alternating current bus at the inversion side of the strip direct current line;t 0for voltage after fault to be lower thanV j,thre Δ (d) is detectedtIs composed ofU i,j,k (t) Is lower thanV j,thre The duration of (c).
6. An apparatus for evaluating voltage sag stability levels of a multi-dc-fed power grid, comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, the processor implementing a method for evaluating voltage sag stability levels of a multi-dc-fed power grid as claimed in any one of claims 1 to 4 when executing the computer program.
7. A computer-readable storage medium, comprising a stored computer program, wherein when the computer program is executed, the computer-readable storage medium controls a device to execute the method for evaluating voltage sag stability levels of a multiple-dc-fed power grid according to any one of claims 1 to 4.
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