CN109617096B - Method for analyzing broadband disturbance stability of regional power grid based on traversal impedance - Google Patents

Method for analyzing broadband disturbance stability of regional power grid based on traversal impedance Download PDF

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CN109617096B
CN109617096B CN201811606850.0A CN201811606850A CN109617096B CN 109617096 B CN109617096 B CN 109617096B CN 201811606850 A CN201811606850 A CN 201811606850A CN 109617096 B CN109617096 B CN 109617096B
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impedance
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CN109617096A (en
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孙小晶
常富杰
刘志超
时伯年
王莹莹
赵伟华
吴雪黎
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Beijing Sifang Automation Co Ltd
Beijing Sifang Engineering Co Ltd
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Beijing Sifang Engineering Co Ltd
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    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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Abstract

A regional power grid broadband disturbance stability factor analysis method based on traversal impedance includes the steps of detecting three-phase voltage and three-phase current signals of an alternating current bus access line of a transformer substation, calculating oscillation power and impedance under oscillation frequency points, giving stability criteria, establishing an oscillation association factor set for stability judgment by combining with system operation condition characteristic data at oscillation time, and analyzing to obtain an important influence factor set and an unimportant influence factor set of system oscillation. The method can analyze the relevant factors before and after the system oscillates according to disturbance data existing in the power system at any time, so that the main factors influencing the sub/super synchronous oscillation generated by the grid connection of the new energy station are obtained, and the method is suitable for effectively preventing and controlling the wind turbine generator when the sub/super synchronous oscillation is generated by the large-scale grid connection.

Description

Method for analyzing broadband disturbance stability of regional power grid based on traversal impedance
Technical Field
The invention belongs to the field of stability analysis of power systems, and particularly relates to a wide-band multi-oscillation-mode traversal impedance stability analysis method suitable for a large-scale new energy grid-connected power system.
Background
The safe and reliable operation of the power system is important for guaranteeing the social and economic development and the social stability. In recent years, the power system in China is undergoing great change and development, mainly including: the application of a large amount of new energy grid connection and direct current transmission technologies and the like obviously shows the trend of power electronization in the links of transmission, transformation and use of the whole power system, the power grade of the power electronic converter is continuously improved, and the permeability of the power electronic converter on the power supply side, the power transmission network and the load side is higher and higher.
The flexibility and controllability of the power electronic converter can enhance the flexibility of the traditional alternating current power system in adjustment, and the transient stability of an alternating current-direct current hybrid system is improved through a direct current transmission technology in the process of constructing an intelligent power transmission network. Therefore, the application of the power electronic converter makes the power system more controllable, easy to adjust, flexible and intelligent, but these advantages are based on the high-speed control of the power electronic converter, and compared with the traditional power system, the time interval for controlling and adjusting is shorter in the time scale of control, even reaching the millisecond level. Different power electronic controllers are not completely consistent in time control intervals, so that new problems caused by inconsistent control time beats occur, such as a novel subsynchronous oscillation problem occurring in a new energy grid-connected power system.
When the stability of the power system with high power electronic permeability is analyzed, the traditional method for analyzing the stability of the power system can still be adopted, such as a time domain method, a direct method based on a modern differential power system and the like, but when a large number of power electronic elements exist in the system, the saturation nonlinear characteristics in the control link of the system have to be specially considered and processed, and only then, the actual state and the characteristics of the system can be reflected more truly. At present, the modeling of the power electronic system which is necessary for time domain simulation is very complex, the calculated amount is large, the simulation time is long, and the comprehensive simulation of all possible operation conditions of the system is not easy to carry out.
The method comprises the steps of providing a wide frequency domain disturbance stability analysis method of traversal impedance based on real-time monitoring data for a large-scale new energy grid-connected regional power system, wherein basic data come from a monitoring system, conducting impedance traversal on line elements under power grid topology through impedance calculation of actually measured data, combining an operation condition data set when disturbance occurs, conducting statistical analysis on transverse and longitudinal dimensions, and finally obtaining a stability judgment result and a main unstable influence factor set of a line accessed to a power grid.
Disclosure of Invention
The invention aims to provide a method which is suitable for a wide-band multi-oscillation mode of a large-scale new energy grid-connected region power system, can quickly and accurately analyze system stability and factors influencing the system stability in subsynchronous and supersynchronous frequency ranges under different operation working conditions by traversing impedance and analyzing main associated factors, and can be used for realizing and deploying on a regional power grid subsynchronous oscillation monitoring master station.
A regional power grid broadband disturbance stability analysis method based on traversal impedance is mainly used for judging the stability of a large-scale new energy grid-connected regional power grid, stability criteria are given by detecting three-phase voltage and three-phase current signals of an alternating current bus access line of a transformer substation and calculating oscillation power and impedance under oscillation frequency points, an oscillation association factor set for judging the stability is established by combining with system operation condition characteristic data at the oscillation time, and an important influence factor set and an unimportant influence factor set of system oscillation are obtained through analysis.
A method for analyzing broadband disturbance stability of a regional power grid based on traversal impedance comprises the following steps:
step 1: in the new energy collection station, all line three-phase voltage u connected to the bus is monitored through the monitoring substationai、ubi、uciAnd three-phase current iai、ibi、iciThe direction of an outgoing AC bus is defined as a positive direction, and the corresponding sampling data sequences are uai(k)、ubi(k)、uci(k) And iai(k)、ibi(k)、ici(k) And storing the sampled data, wherein i represents the ith line, k is 0,1, …, n;
step 2: calculating three-phase instantaneous power sequence p by using voltage and current sampling sequencei(k) Then aligning the sequence pi(k) Performing digital filtering, wherein the digital filter is designed as a band-pass filter with a passband frequency range of 5Hz-45Hz to ensure instantaneous power pi(k) 5Hz-45Hz component in signal has no attenuationThe pass is subtracted. Selecting a time window with N sampling points, and acquiring p in the time windowi(k) Is calculated using the maximum value pimaxAnd minimum value piminTo satisfy
Figure BDA0001923740660000021
Then, the oscillation in the subsynchronous/supersynchronous frequency band is considered to exist in the monitoring line, and the crossing of the oscillation power sampling value is calculated to be the power average value
Figure BDA0001923740660000022
Number of times of center line NssoAnd a dominant oscillation frequency point fjThen, the monitoring point sends the oscillation identification and the oscillation frequency information to a monitoring main station;
and 3, step 3: the master station records the instantaneous power p of the monitoring lineiThe number of new energy grid-connected fans is miSVG working mode siSeries compensation circuit input condition OiWind speed viThe information is equal, and an oscillation correlation factor set C is formedi＝[pi,mi,si,Oi,vi]；
And 4, step 4: after the monitoring master station acquires the oscillation identifier sent by the monitoring substation, the sampling data u stored by all the line monitoring substations under the time scale is called according to the time scale information of the oscillation identifierai(k)、ubi(k)、uci(k) And iai(k)、ibi(k)、ici(k) (ii) a And performing band-pass filtering on the monitoring sampling data sequence to obtain oscillation power dominant oscillation frequency fjComplementary subsynchronous oscillation frequencies fsubAnd a super-synchronous oscillation frequency fplusThe following sampling sequence:
Figure BDA0001923740660000031
Figure BDA0001923740660000032
and 5: calculating the current disturbance lineSub-synchronous oscillation frequency fsubAnd a super-synchronous oscillation frequency fplusEquivalent impedance of
Figure BDA0001923740660000033
Then, the subsynchronous oscillation frequency f of other line sets is obtainedsubAnd a super-synchronous oscillation frequency fplusEquivalent impedance of
Figure BDA0001923740660000034
Step 6: impedance information of line i
Figure BDA0001923740660000035
Equivalent impedance information for other sets of lines
Figure BDA0001923740660000036
Adding the oscillation correlation factors into an oscillation correlation factor set, and forming a new set together with the operation condition information when disturbance occurs:
Figure BDA0001923740660000037
and 7: and analyzing the stability of the line i after accessing the system, and judging the stability of the system according to the real part and the imaginary part of the total equivalent impedance after accessing the system.
And step 8: repeating the step 2-7, and establishing an oscillation factor analysis set of all the disturbance lines;
and step 9: and analyzing the generated oscillation factors according to the set formed in the steps, if the access system of the line i has the risk of oscillation and the system is unstable in the primary monitoring process, carrying out unified longitudinal comparison analysis on the oscillation factor analysis set of the line to find sensitive difference points, and regarding the line i, the oscillation factor analysis set of the k-th disturbance process is as follows:
Figure BDA0001923740660000038
then the set of oscillation factor analyses aggregated by the perturbation process is: CC ═ CCi1,CCi2,CCi3,...,CCim]And m is the total number of times of disturbance of the line i, and finally, the main factor of instability of the access system of the line i is determined.
In the step 2, the band-pass filter with the passband frequency range of 5Hz-45Hz is designed to extract the oscillation power signals in the subsynchronous and supersynchronous frequency ranges in the three-phase instantaneous power, so that on one hand, the oscillation power signals of 5Hz-45Hz are ensured to pass through without attenuation; on the other hand, the output response of the band-pass filter is prevented from being judged as system oscillation by mistake due to sudden change of the power frequency quantity. Therefore, in the oscillation discrimination process, the data window of N points is divided into M sub-windows with equal length on average and then discriminated, taking the ith line as an example, the specific processing process of the oscillation discrimination is as follows:
intercepting data p with the number of sampling points of N from an oscillation power signal sequence filtered by a 5-45Hz filteri(k) K is 0,1, …, N-1; the data window to be analyzed of N points is equally divided into M sub-windows, and the length of each sub-window is
Figure BDA0001923740660000039
The oscillating power data sequence in the divided ith sub-window is as follows:
Figure BDA0001923740660000041
respectively solving maximum value p of data in M sub-windowsij_maxAnd minimum value pij_minWherein i represents the ith line, and j represents the jth sub-window;
Figure BDA0001923740660000042
Figure BDA0001923740660000043
obtaining the maximum value p for calculation in the N point data window of the ith lineimaxAnd the minimum value p for calculationimin(ii) a Reuse of
Figure BDA0001923740660000044
And judging, if so, judging that the line power has oscillation, otherwise, judging that the power oscillation does not exist, wherein:
Figure BDA0001923740660000045
Figure BDA0001923740660000046
th is a preset power oscillation discrimination threshold.
Sequentially judging the data of all the oscillation power sampling points in the filtered N point data window of the ith line, and using the data of all the oscillation power sampling points to calculate the power of the ith line
Figure BDA0001923740660000047
Counting the total times N of the sampling point passing through the central line as the central linessoCorresponding to the dominant oscillation frequency point of the power oscillation
Figure BDA0001923740660000048
Wherein f issampTo monitor the sampling frequency of the point device.
In the step 4, after the monitoring master station acquires the oscillation identifier sent by the monitoring substation, the sampling data u stored by all the substations on the time scale is summoned according to the time scale information of the oscillation identifierai(k)、ubi(k)、uci(k) And iai(k)、ibi(k)、ici(k) (ii) a And performing band-pass filtering on the monitoring sampling data sequence, wherein the specific processing process is as follows:
obtaining a dominant oscillation frequency f at an oscillation powerjThe complementary subsynchronous oscillation frequency fsubAnd a super-synchronous oscillation frequency fplus；
fsub＝50-fj；
fplus＝50+fj；
Through a process of fsubAnd fplusThe band-pass filter obtains a sub-and super-synchronous frequency voltage and current sampling sequence after filtering:
Figure BDA0001923740660000051
Figure BDA0001923740660000052
in the step 5, the current line and other lines which are monitored to be disturbed are respectively subjected to equivalent impedance calculation to obtain the subsynchronous oscillation frequency fsubAnd a super-synchronous oscillation frequency fplusThe following three-phase equivalent impedances:
Figure BDA0001923740660000053
other lines that do not contain the line but have a direct electrical connection to it are three-phase equivalent phase impedances:
Figure BDA0001923740660000054
wherein:
Figure BDA0001923740660000055
Figure BDA0001923740660000056
the three phase equivalent impedance of line A, B, C is then averaged to the average impedance of the line:
Figure BDA0001923740660000057
Figure BDA0001923740660000058
the three-phase equivalent impedances of the other lines A, B, C are averaged to the average impedance of the other lines:
Figure BDA0001923740660000059
Figure BDA00019237406600000510
in the step 7, the stability of the accessed system is judged according to the characteristics of the real part and the imaginary part of the total equivalent impedance after the line i is accessed, and the specific process of the judgment is as follows:
calculating the subsynchronous oscillation frequency f after the access of the line isubAnd a super-synchronous oscillation frequency fplusThe following total equivalent impedance:
Figure BDA0001923740660000061
Figure BDA0001923740660000062
and judging that the system is unstable if any one of the following conditions is met, otherwise, the line is considered to have disturbance after being accessed, but the system is stable and cannot generate oscillation.
Stability criterion under subsynchronous frequency:
Figure BDA0001923740660000063
or
Figure BDA0001923740660000064
Stability criterion under super-synchronous frequency:
Figure BDA0001923740660000065
or
Figure BDA0001923740660000066
In view of conservation, xi can be 2p.u, which is more appropriate, wherein Real represents the Real part of impedance, and Image represents the imaginary part of impedance;
in step 9, the main process of determining the unstable factors of the line access system is as follows:
to CC ═ CCi1,CCi2,CCi3,...,CCim]Classifying the sets according to stable and unstable access to form sets CC __ s and CC _ ins respectively;
handle CCikElements in the set A are respectively compared with a disturbance set CC _ s under the condition of stable access in the CC, and elements with obvious differences are combined and written into a set A to form an important influence factor combination set;
handle CCikRespectively comparing the elements in the set B with a disturbance set CC _ ins under the condition of unstable access in the CC, and writing the elements with obvious differences into a set B to form an unimportant influence factor set;
removing elements contained in the set B from the set A formed by the influence element combination to form a new influence element combination C;
the set C is the unstable factor and the relevant combination of the access system of the line i.
The invention has the beneficial effects that: by calculating the impedance of a regional power grid in a multi-oscillation mode within a subsynchronous frequency range and a supersynchronous frequency range, the stability of the system is judged, and factors influencing the stability of the system are analyzed in detail by combining with operation conditions, so that the operation mode is adjusted in a targeted manner, effective prevention and control are further performed when subsynchronous/supersynchronous oscillation is generated by large-scale new energy grid connection, and the safe and stable operation of the system is guaranteed.
Drawings
FIG. 1 is a flow chart of a broadband stability discrimination method based on traversal impedance;
FIG. 2 is a schematic diagram of an oscillation analysis data window design;
FIG. 3 is a schematic diagram illustrating the judgment of system stability after line access;
FIG. 4 is a schematic diagram of the analysis of the oscillation-affecting factor.
Detailed Description
The following describes in detail a specific implementation of the present invention with reference to the drawings.
The flow of the method for analyzing the broadband disturbance stability of the regional power grid based on the traversal impedance is shown in fig. 1, and the specific implementation process is described below by taking an algorithm implementation mode in a sub-synchronous oscillation monitoring protection device as an example, wherein the algorithm implementation comprises the following steps:
step 1: at a sampling frequency fsampCollecting three-phase voltage u of all lines connected with alternating current bus of new energy collection stationai、ubi、uciAnd three-phase current iai、ibi、iciThe direction of an outgoing AC bus is defined as a positive direction, and the corresponding sampling data sequences are uai(k)、ubi(k)、uci(k) And iai(k)、ibi(k)、ici(k) And storing the sampled data, wherein i represents the ith line, k is 0,1, …, n; in the embodiment, the subsynchronous oscillation monitoring and protecting device is used for monitoring the three-phase voltage and the three-phase current of the circuit by fsampSampling is carried out at a sampling frequency of 1200Hz, and the case that disturbance occurs in a monitored new energy grid-connected access line is taken as an example, the voltage level of the access line is 220kV, the rated primary value of current is 1000A, the line current is 500A, 35.3Hz oscillation components exist in the instantaneous power of the line, 14.7Hz and 85.3Hz oscillation components exist in corresponding phase current, the amplitude is 20A, 14.7Hz and 85.3Hz oscillation components also exist in phase voltage, and the amplitude is 2000V;
and 2, step: using a voltage-current sampling sequencerCalculating three-phase instantaneous power sequence pi(k) Then aligning the sequence pi(k) Performing digital filtering, wherein the digital filter is designed as a band-pass filter with a passband frequency range of 5Hz-45Hz, and ensures instantaneous power pi(k) The 5Hz-45Hz component of the signal passes unattenuated. Taking the ith line as an example, the specific implementation process is as follows:
in the oscillation judging process, dividing a 1024-point data window of the oscillation power signal obtained by sampling and filtering into 8 sub-windows with equal length on average, and then judging, wherein the length of each sub-window is 128 points, and the oscillation power data sequence in the divided ith sub-window is as follows:
pij(kk)，j＝0,1，…,7；kk＝0,1，…,127；
the segmentation and design of the corresponding oscillation analysis data window is shown in fig. 2. And respectively solving the maximum value and the minimum value of the data of the 8 sub-windows. The results were as follows:
pij_max＝[516,524,522,523,519,518,521,517]，j＝0,1，…,7；
pij_min＝[478,483,479,476,477,482,484,481]，j＝0,1，…,7；
averaging the maximum of the 8 sub-windows yields the maximum for calculation:
Figure BDA0001923740660000081
averaging the minimum values of the 8 sub-windows to obtain a minimum value for calculation:
Figure BDA0001923740660000082
and taking Th as 1% of the rated current of the line as a threshold value for judging whether oscillation occurs, comparing half of the difference between the maximum value and the minimum value of the oscillation power signal with Th, and if the difference is greater than Th, determining that disturbance occurs, and if the difference is less than Th, determining that no obvious disturbance occurs in the data window. Through the above-mentioned calculation, the method,
Figure BDA0001923740660000083
the current line is considered to have subsynchronous oscillations.
Sequentially comparing all the oscillation power sampling point data in the filtered 1024 point data window of the ith line with the data of the sampling points of the first line
Figure BDA0001923740660000084
Comparing and counting the total times N of the sampling points crossing the average power 500Asso17, corresponding to the dominant oscillation frequency point of the power oscillation
Figure BDA0001923740660000085
Wherein f issamp1200Hz is the sampling frequency of the watchpoint device. And transmitting the voltage and current real-time sampling data acquired by the subsynchronous oscillation monitoring control device and the oscillation frequency and oscillation time information obtained by calculation to a subsynchronous oscillation monitoring master station.
And step 3: in the embodiment, the wind power plant is connected to the power grid as an example, five main risk factors which may affect the subsynchronous oscillation are listed, such as line load, the number of grid-connected fans, a reactive compensation control mode, a series compensation switching-in and switching-out condition of a transmission line and a wind speed condition at a disturbance moment. Integrating the operating condition information to form an oscillation associated factor set Ci＝[pi,mi,si,Oi,vi]；
And 4, step 4: after the monitoring master station acquires the oscillation identifier sent by the monitoring substation, the sampling data u stored by all the substations under the time scale is called according to the time scale information of the oscillation identifierai(k)、ubi(k)、uci(k) And iai(k)、ibi(k)、ici(k) (ii) a And performing band-pass filtering on the monitoring sampling data sequence, wherein the specific implementation process is as follows:
(1) according to the power oscillation frequency 35.3Hz obtained by analyzing the oscillation power signal in the step II, the oscillation frequency in the line current is calculated according to the principle of complementation about 50 Hz:
fsub＝50-35.3＝14.7Hz，
fplus＝50+35.3＝85.3Hz。
(2) designing band-pass filters with 14.7Hz and 85.3Hz as central frequencies and band-stop filters respectively connected with 50Hz in series, and filtering to obtain the filtered sequence of voltage and current signals under subsynchronous oscillation frequency and supersynchronous oscillation frequency:
Figure BDA0001923740660000091
Figure BDA0001923740660000092
and 5: the impedance under the subsynchronous frequency of 14.7Hz and the supersynchronous frequency of 85.3Hz is calculated, and the specific calculation method comprises the following steps: firstly, solving a voltage current amplitude value under the corresponding frequency by using a Fourier transform method, and dividing to obtain a modulus value of an impedance vector under the corresponding frequency; and calculating the phase lag of the current signal and the voltage signal under the corresponding frequency to obtain the angle value of the impedance vector. And finally, converting the amplitude angle expression of the impedance vector into a complex form expressed by a real part and an imaginary part.
(1) Subsynchronous impedance calculation results:
Figure BDA0001923740660000093
Figure BDA0001923740660000094
Figure BDA0001923740660000095
(2) the calculation result of the super-synchronous impedance is as follows:
Figure BDA0001923740660000096
Figure BDA0001923740660000097
Figure BDA0001923740660000098
three-phase equivalent phase impedance of other lines not including the line but having direct electrical connection with the line:
Figure BDA0001923740660000099
(3) the current disturbance line A, B, C three-phase impedance is averaged to get:
Figure BDA00019237406600000910
Figure BDA0001923740660000101
(4) the three phase impedances of the other line set A, B, C are averaged to yield:
Figure BDA0001923740660000102
Figure BDA0001923740660000103
step 6: integrating to the oscillation associated factor set C formed in step 3i＝[pi,mi,si,Oi,vi]Is then expanded into
Figure BDA0001923740660000104
And 7: and judging the system stability after the line access. Taking the determination of the line access stability at the sub-synchronous frequency of the ith line as an example, as shown in fig. 3:
(1) before the line i is accessed, the total equivalent impedance under the subsynchronous frequency of the system is
Figure BDA0001923740660000105
The equivalent impedance at the sub-synchronous frequency of line i is:
Figure BDA0001923740660000106
after the line i is connected, the total equivalent impedance under the subsynchronous frequency of the system is as follows:
Figure BDA0001923740660000107
(2) xi in the embodiment is 2p.u according to the specific power grid condition. At this time, the following relational expression is established,
Figure BDA0001923740660000108
Figure BDA0001923740660000109
because the real part of the impedance under the subsynchronous frequency of the accessed system is negative and the imaginary part is smaller than xi, the circuit i is judged to be unstable after being accessed, subsynchronous oscillation is caused after being accessed, and the subsynchronous oscillation monitoring and protecting device can cut off the circuit i by the action of a subsynchronous oscillation impedance element, so that the network topology structure of the system and the subsynchronous frequency impedance characteristic of the whole system are changed, and the expansion of the oscillation is prevented from damaging the unit and the safety of the system.
And 8: and (5) performing stability analysis and calculation after access on other lines with disturbance according to the steps 2-7, wherein the method is the same as the stability analysis and calculation of the line i.
And step 9: after receiving the corresponding oscillation identification event, the subsynchronous oscillation monitoring master station extracts the operation condition data in the SCADA database at the moment of the disturbance except for traversing impedance scanning and stability analysis by using the real-time data of each line, associates the operation condition data with the oscillation event, establishes a line disturbance record data table, and then analyzes the transverse and longitudinal influence factors, wherein the specific process for analyzing the influence factors for stable access of the ith line is shown in fig. 4.
(1) To CC ═ CCi1,CCi2,CCi3,...,CCim]And (4) judging the access stability of the line i according to the method in the step (7) by the historical disturbance record data in the set, classifying according to the stability judgment result and the stability after access and the instability after access to form a set CC __ s (a set of stable disturbance records after access in the CC) and a set CC _ ins (a set of unstable disturbance records after access in the CC) respectively, wherein the set CC in the embodiment is a total set of historical disturbance impedance data and influence factors of the ith line.
(2) Oscillating the kth oscillation CC formed in step 6ikThe elements in the set A are respectively compared with a disturbance set CC _ s in the CC under the condition of stable access, and the elements with obvious differences are combined and written into a set A to form an important influence factor combination set:
a is equal to { new energy grid-connected fan number, line transmission power, SVG working mode };
(3) handle CCikThe elements in the set B are respectively compared with a disturbance set CC _ ins under the condition of unstable access in the CC, and the elements with obvious differences are written into a set B to form an unimportant influence factor set:
b is { line transmission power, series compensation device input condition };
(4) removing elements contained in a set B from a set A formed by the combination of the influence elements to form a new influence element combination C, namely C-A-B-the number of new energy grid-connected fans, SVG working mode };
(5) the set C is the instability factor and the relevant combination of the access system of the line i.
The above is only one embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims (6)

1. A method for analyzing broadband disturbance stability of a regional power grid based on traversal impedance comprises the following steps:
step 1: in the new energy collection station, all line three-phase voltage u connected to the bus is monitored through the monitoring substationai、ubi、uciAnd three-phase current iai、ibi、iciThe direction of an outgoing AC bus is defined as a positive direction, and the corresponding sampling data sequences are uai(k)、ubi(k)、uci(k) And iai(k)、ibi(k)、ici(k) And storing the sampled data, wherein i represents the ith line, k is 0,1, …, n;
step 2: calculating three-phase instantaneous power sequence p by using voltage and current sampling sequencei(k) Then for sequence pi(k) Perform digital filtering
The digital filter is designed as a band-pass filter with a passband frequency range of 5Hz-45Hz to ensure instantaneous power pi(k) 5Hz-45Hz components in the signal pass through without attenuation; selecting a time window with N sampling points, and acquiring p in the time windowi(k) Is calculated by the maximum value pimaxAnd a minimum value piminTo satisfy
Figure FDA0003573981810000011
Then, the oscillation in the subsynchronous/supersynchronous frequency band is considered to exist in the monitoring line, and the crossing of the oscillation power sampling value is calculated to be the power average value
Figure FDA0003573981810000012
Number of times of center line NssoAnd a dominant oscillation frequency point fjThen, the monitoring point sends the oscillation identification and the oscillation frequency information to a monitoring master station;
and step 3: the master station records the instantaneous power p of the monitoring lineiThe number m of new energy grid-connected fansiSVG working mode siSeries compensation circuit input condition OiAnd wind speed conditions viForming a set of oscillation-related factors Ci＝[pi,mi,si,Oi,vi]；
And 4, step 4: after the monitoring master station acquires the oscillation identifier sent by the monitoring substation, the sampling data u stored by all the line monitoring substations under the time scale is called according to the time scale information of the oscillation identifierai(k)、ubi(k)、uci(k) And iai(k)、ibi(k)、ici(k) (ii) a And to the sampled data uai(k)、ubi(k)、uci(k) And iai(k)、ibi(k)、ici(k) Band-pass filtering is carried out to obtain the oscillation frequency f dominated by the oscillation powerjThe complementary subsynchronous oscillation frequency fsubAnd a super-synchronous oscillation frequency fplusThe following sampling sequence:
Figure FDA0003573981810000013
Figure FDA0003573981810000014
and 5: obtaining the subsynchronous oscillation frequency f of the current disturbance linesubAnd a super-synchronous oscillation frequency fplusEquivalent impedance of
Figure FDA0003573981810000015
Then, the subsynchronous oscillation frequency f of other line sets is obtainedsubAnd a super-synchronous oscillation frequency fplusEquivalent impedance of
Figure FDA0003573981810000016
And 6: information about the impedance of a line i
Figure FDA0003573981810000021
Equivalent impedance information for other sets of lines
Figure FDA0003573981810000022
Adding the oscillation correlation factors into an oscillation correlation factor set, and forming a new set together with the operation condition information when disturbance occurs:
Figure FDA0003573981810000023
and 7: analyzing the stability of the line i after being accessed into the system, and judging the stability of the system according to the real part and the imaginary part of the total equivalent impedance after being accessed into the system;
and 8: repeating the step 2 to the step 7, and establishing an oscillation factor analysis set of all the disturbed lines;
and step 9: and analyzing the generated oscillation factors according to the set formed in the steps, if the access system of the line i has the risk of oscillation and the system is unstable in the primary monitoring process, carrying out unified longitudinal comparison analysis on the oscillation factor analysis set of the line to find sensitive difference points, and regarding the line i, the oscillation factor analysis set of the k-th disturbance process is as follows:
Figure FDA0003573981810000024
then the set of oscillation factor analyses aggregated by the perturbation process is: CC ═ CCi1,CCi2,CCi3,...,CCim]And m is the total number of times of disturbance of the line i, and finally the main factor of instability of the access system of the line i is determined.
2. The method for analyzing the broadband disturbance stability of the regional power grid based on the traversal impedance as claimed in claim 1, wherein: in the step 2, the data window of N points is divided into M sub-windows of equal length in the oscillation discrimination process, and then the discrimination is performed, and the specific processing process of the oscillation discrimination is as follows:
intercepting data p with the number of sampling points N from an oscillation power signal sequence filtered by a 5-45Hz filteri(k) K is 0,1, …, N-1; the data window to be analyzed of N points is equally divided into M sub-windows, and the length of each sub-window is
Figure FDA0003573981810000025
The oscillating power data sequence in the divided ith sub-window is as follows:
Figure FDA0003573981810000026
respectively solving the maximum value p of the data in the M sub-windowsij_maxAnd a minimum value pij_minWherein i represents the ith line, and j represents the jth sub-window;
Figure FDA0003573981810000027
Figure FDA0003573981810000028
obtaining the maximum value p for calculation in the N point data window of the ith lineimaxAnd the minimum value p for calculationimin(ii) a Reuse of
Figure FDA0003573981810000029
And judging, if so, judging that the line power has oscillation, otherwise, judging that no power oscillation exists, wherein:
Figure FDA0003573981810000031
Figure FDA0003573981810000032
th is a preset power oscillation judging threshold value, and 1% of the rated current of the circuit is taken;
sequentially judging the data of all the oscillation power sampling points in the N point data window after the filtration of the ith line, and using the data of all the oscillation power sampling points
Figure FDA0003573981810000033
Counting the total times N of the sampling points passing through the central line as the central linessoCorresponding to the dominant oscillation frequency point of the power oscillation
Figure FDA0003573981810000034
Wherein f issampTo monitor the sampling frequency of the point device.
3. The method for analyzing the broadband disturbance stability of the regional power grid based on the traversal impedance as claimed in claim 1, wherein: in the step 4, after the monitoring master station acquires the oscillation identifier sent by the monitoring substation, the sampling data u stored by all the substations under the time scale is called according to the time scale information of the oscillation identifierai(k)、ubi(k)、uci(k) And iai(k)、ibi(k)、ici(k) (ii) a And to the sampled data uai(k)、ubi(k)、uci(k) And iai(k)、ibi(k)、ici(k) Performing band-pass filtering, wherein the specific processing process is as follows:
obtaining a dominant oscillation frequency f at an oscillation powerjComplementary subsynchronous oscillation frequencies fsubAnd a super-synchronous oscillation frequency fplus；
fsub＝50-fj；
fplus＝50+fj；
Through a processWith fsubAnd fplusThe band-pass filter obtains a sub-and super-synchronous frequency voltage and current sampling sequence after filtering:
Figure FDA0003573981810000035
Figure FDA0003573981810000036
4. the method for analyzing the broadband disturbance stability of the regional power grid based on the traversal impedance as claimed in claim 1, wherein: in the step 5, the current line and other lines which are monitored to be disturbed are respectively subjected to equivalent impedance calculation to obtain the subsynchronous oscillation frequency fsubAnd a super-synchronous oscillation frequency fplusThree-phase equivalent impedance:
Figure FDA0003573981810000037
other lines that do not contain the line but have a direct electrical connection to it are three-phase equivalent phase impedances:
Figure FDA0003573981810000041
wherein:
Figure FDA0003573981810000042
Figure FDA0003573981810000043
the three phase equivalent impedances of line A, B, C are then averaged to the average impedance of the line:
Figure FDA0003573981810000044
Figure FDA0003573981810000045
the three-phase equivalent impedances of the other lines A, B, C are averaged to the average impedance of the other lines:
Figure FDA0003573981810000046
Figure FDA0003573981810000047
5. the method for analyzing the broadband disturbance stability of the regional power grid based on the traversal impedance as claimed in claim 1, wherein: in the step 7, the stability of the accessed system is judged according to the characteristics of the real part and the imaginary part of the total equivalent impedance after the line i is accessed, and the specific process of the judgment is as follows:
calculating the subsynchronous oscillation frequency f after the line i is accessedsubAnd a super-synchronous oscillation frequency fplusThe following total equivalent impedance:
Figure FDA0003573981810000048
Figure FDA0003573981810000049
wherein Z isifsubAnd
Figure FDA00035739818100000410
respectively representing the average impedance of the line at the subsynchronous oscillation frequency and the supersynchronous oscillation frequency,
Figure FDA00035739818100000411
and
Figure FDA00035739818100000412
respectively representing the average impedance of other lines under the subsynchronous oscillation frequency and the supersynchronous oscillation frequency;
judging whether the system is considered to have oscillation risk and be unstable if any one of the following conditions is met, otherwise, judging that the line has disturbance after being accessed but is stable and cannot generate oscillation,
and (3) stability criterion under the subsynchronous frequency:
Figure FDA0003573981810000051
stability criterion under super-synchronous frequency:
Figure FDA0003573981810000052
where ξ is the per-unit value of the impedance of the system at rated power, ξ takes 2 p.u., where Real represents the Real part of the impedance and Image represents the imaginary part of the impedance.
6. The method for analyzing the broadband disturbance stability of the regional power grid based on the traversal impedance as claimed in claim 1, wherein: in the step 9, the main process of determining the unstable factors of the line access system is as follows:
to CC ═ CCi1,CCi2,CCi3,...,CCim]Classifying the sets according to stability and instability after access to respectively form a set CC __ s and a set CC _ ins;
handle CCikWherein each of the elements is represented by formula (I) and (II)C, accessing a disturbance set CC _ s under a stable condition for comparison, and writing element combinations with obvious differences into a set A to form an important influence factor combination set;
handle CCikRespectively comparing the elements in the set B with a disturbance set CC _ ins under the condition of unstable access in the CC, and writing the elements with obvious differences into a set B to form an unimportant influence factor set;
removing elements contained in the set B from the set A formed by the influence element combination to form a new influence element combination C;
the set C is the unstable factor and the relevant combination of the access system of the line i.
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