CN107342628B - New energy access broadband stability multistage early warning method integrating multi-source information - Google Patents
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Abstract
A new energy access broadband stability multistage early warning method integrating multi-source information. The method comprises the steps of firstly, conducting stationing monitoring on key transformer substations of a regional power grid, new energy power stations and subsynchronous oscillation signals of traditional thermal power generating units, obtaining inter-harmonic current, voltage and power of the wide band of the regional power grid, and torsional oscillation data of the thermal power generating units at 10-90Hz, and dividing different early warning levels according to the characteristics of regional oscillation and the spread range of the inter-harmonic in a system through analysis of the inter-harmonic current, voltage and power data. The method is applied to the sub-synchronous monitoring and early warning master station based on the WAMS, and through the setting of different graded early warning information, operators can conveniently and visually determine the sub-synchronous oscillation condition in the system, so that the response measures can be taken in time, and the safe and stable operation of the system can be guaranteed.
Description
Technical Field
The invention belongs to the field of dynamic monitoring of power systems, and particularly relates to a broadband stability multi-stage early warning method for a comprehensive new energy station, a comprehensive system station, a comprehensive thermal power generating unit and a comprehensive direct-current system.
Background
In recent years, with the rapid development of an extra-high voltage power grid, a large amount of new energy such as wind power, photovoltaic and the like is connected to the grid, the long-distance trans-regional power transmission scale is continuously increased, the electronic characteristics of the power grid are obvious, and the characteristics of the power grid are deeply changed. Various power electronic devices or apparatuses, such as static synchronous compensator (STATCOM), flexible dc transmission converters, are widely used. However, once these new power devices are connected to the power grid to operate, in a specific control mode or operation mode, a continuous sub-synchronous and/or super-synchronous harmonic injection system is easily formed, and the shafting torsional vibration of the nearby unit is excited, so that the interlocking reactions such as tripping and direct current blocking of the thermal power unit are caused, the safe and stable operation of the power grid is endangered, and the power supply quality is influenced.
With the increasingly prominent broadband stability problem of power electronic systems, real-time online broadband monitoring of the systems is very necessary. At present, the broadband stability monitoring and early warning work of a power system is just started, and particularly, no major breakthrough exists in the research aspects of the mechanism and the rule of oscillation generation after new energy is accessed, so that relevant oscillation data and the propagation condition of a power grid in a specific area after new energy is accessed need to be obtained by means of monitoring, effective data support is provided for the research of the oscillation mechanism and the propagation rule, and an operation basis is also provided for the operation of power grid dispatching operators. The oscillation problem caused by new energy conservation is the oscillation problem of participation of multiple elements such as a new energy converter, a system, a thermal power generating unit, a direct current control system and the like, so that a monitoring means with complete network source data is needed, and the monitoring is not limited to a power grid or a power supply point.
On the basis of the comprehensive broadband monitoring information of the new energy station, the system station, the thermal power generating unit and the direct current system, the intrinsic parameters of the thermal power generating unit are synthesized to the important degree of influencing the system safety through the identification of the oscillation circuit and the area, and the effective broadband oscillation management of the regional power grid is formed.
Disclosure of Invention
The invention provides a new energy access broadband stability multistage early warning method integrating multi-source information, which integrates harmonic oscillation warning information on a network side and torsional oscillation inherent characteristics and warning information on a thermal power generating unit side while carrying out broadband online monitoring on a power grid, comprehensively judges and gives a graded early warning signal representing the degree of severity of subsynchronous oscillation of a system, is convenient for an operator to find subsynchronous and supersynchronous oscillation of the power grid in time, and takes corresponding measures according to the early warning grade.
The invention adopts the following technical scheme:
a new energy access broadband stability multistage early warning method integrating multi-source information is characterized by comprising the following steps:
(1) determining the distribution range of monitoring points according to the structure of the regional power grid network frame, wherein the distributed monitoring points comprise: the system comprises lines between a new energy collection station and each new energy power plant, a new energy collection station outlet line, a system hub transformer substation inlet line and outlet line, a local power grid internal fire motor set and a direct current system rectification side converter transformer inlet line;
(2) the method comprises the steps that broadband frequency spectrum calculation of each monitoring line with frequency resolution of at least 0.5Hz is achieved through a PMU (monitoring unit) of each monitoring point, and the calculation comprises each frequency component phasor and frequency;
(3) identifying an oscillation line, traversing according to the frequency of an oscillation signal monitored by each monitoring point, and acquiring each line and stations at two ends of the line which are related under the same oscillation mode;
(4) identifying an oscillation area, identifying the oscillation area according to the relevance of the stations at two ends of the line, identifying different oscillation areas, and judging which of four oscillation areas is oscillation between different new energy power plants, oscillation between the new energy power plants and an alternating current system, oscillation between the new energy power plants and a thermal power generating unit and oscillation between the new energy power plants and a direct current system;
(5) setting different alarm fixed values and time fixed values according to different oscillation areas to generate early warning information of different levels;
(6) and prompting an operator to operate according to the early warning level according to the regional site name, the line name and the early warning level, and informing the new energy site to adjust the operation mode or directly cutting off the new energy site to send out the line.
The invention further comprises the following preferred embodiments:
in the step (1), the layout of the monitoring points realizes hierarchical arrangement, and comprises the following steps:
the new energy collection station monitors a new energy line, monitors a line of each new energy power plant accessed to the new energy collection station and a line of each new energy power plant accessed to an alternating current system after collection, and monitoring data comprise three-phase voltage and three-phase current;
monitoring incoming lines and outgoing lines of a system hub transformer substation, wherein each line of the incoming lines and each line of the outgoing lines accessed into the system hub transformer substation are monitored, and monitoring data comprise three-phase voltage and three-phase current;
monitoring a thermal power generating unit in a regional power grid, and monitoring inherent parameters of the thermal power generating unit, namely inherent frequency parameters of an inherent shafting of the thermal power generating unit in a subsynchronous frequency range;
and monitoring three-phase voltage and three-phase current of a direct current system rectification side converter transformer incoming line.
Uniformly numbering all lines to be monitored, uniformly defining line start and terminal end points according to site IDs, wherein the site IDs are unique in a regional power grid, and forming the following line data set:
{[1,S1_ID,T1_ID],[2,S2_ID,T2_ID],...,[n,Sn_ID,Tn_ID]},
wherein n is the total line number;
Snthe _IDis a line starting end station mark;
TnID is the line termination site identification.
In the step (2), the distributed PMU monitoring devices of the monitoring points realize the function of frequency spectrum calculation based on the original sampling signals of the corresponding lines, the monitoring frequency range of the PMU monitoring devices is 10-90Hz, the length of a data window is selected for at least 2s, the frequency resolution is less than or equal to 0.5Hz, and a broadband oscillation characteristic information set in the range of 10-90Hz of each line is formed through the frequency spectrum calculation of the PMU monitoring devices of the monitoring points:
{[fssoi1,Umssoi1,Imssoi1],[fssoi2,Umssoi2,Imssoi2],...,[fssoip,Umssoip,Imssoip]}
wherein: f. ofssoipThe p oscillation frequency value of the ith line is analyzed by the frequency spectrum;
In the step (3), the following is further included:
3.1 setting the oscillation Current I for each monitoring lineTRiAnd oscillating voltage threshold UTRiWhen the phase voltage amplitude of a certain frequency point in a monitoring line is greater than or equal to the oscillation voltage threshold UTRiOr the phase current amplitude value of a certain frequency point existing in the detection circuit is greater than or equal to the oscillation current ITRiI.e. by
Umssoix≥UTRiOr Imssoix≥ITRiThen the existence frequency in the detection line is considered as fssoixOscillating of (3);
i is the line number, which indicates the ith line, UmssoixRepresents the phase voltage amplitude of the x frequency point of the ith line, ImssoixThe phase current amplitude of the x-th frequency point of the ith line is represented, x represents the x-th oscillation frequency, and x is more than or equal to 1 and less than or equal to p;
3.2 the phase voltage amplitude and the phase current amplitude of each frequency point of all the monitoring lines are judged according to 3.1, the lines and the frequencies meeting the oscillation condition are selected, an oscillation line set which oscillates under each oscillation frequency is formed, and the generation frequency fssoixThe line set of oscillations is:
{[i,Si_ID,Ti_ID,fssoix],[j,Sj_ID,Tj_ID,fssoix],...,[m,Sm_ID,Tm_ID,fssoix]}
wherein f isssoixRepresenting the x-th oscillation frequency value of the ith line, wherein x is more than or equal to 1 and less than or equal to p;
i, j, …, m being all oscillation frequencies fssoixThe line number of (1).
In step (4), the process flow of identifying the oscillation region is as follows:
4.1 from fssoixLine set oscillating at an oscillation frequency
{[i,Si_ID,Ti_ID,fssoix],[j,Sj_ID,Tj_ID,fssoix],...,[m,Sm_ID,Tm_ID,fssoix]Selecting a new energy line set { [ i1, S { [ I1, S ]i1_ID,Ti1_ID,fssoix],[j1,Sj1_ID,Tj1_ID,fssoix],...,[m1,Sm1_ID,Tm1_ID,fssoix]Wherein, i1, j1, …, m1 ∈ [ i, j, …, m]For all oscillation frequencies fssoixThe new energy source oscillation circuit number in the circuit is a circuit of a new energy source power plant accessing a new energy source collection station and a circuit of a regional power grid after collection;
4.2 from the oscillation frequency fssoixStarting from each new energy oscillation line i1, j1, … and m1, all oscillation frequencies of the regional power grid are fssoixI.e. the set [ i, j, …, m ] of oscillating circuits]Finding the relevance of each line so as to determine an oscillatory propagation path line set;
4.3 the set of propagation path lines of the oscillation determined by 4.2 is analyzed:
if the set only contains new energy lines, the oscillation is considered to exist between different new energy power plants;
if the set only contains the new energy source line and other lines, the oscillation between the new energy source power plant and the alternating current system is considered to exist;
if the set only comprises a new energy source line, an alternating current system line and a line connected with the thermal power generating unit, the oscillation between the new energy source power plant and the thermal power generating unit is considered to exist;
and if the set only comprises a new energy source line, an alternating current system line and a direct current converter station incoming line, the direct current system and the new energy source are considered to have oscillation.
In 4.2, the method of forming the propagation path set is as follows:
4.2.1, firstly defining the line to be compared as CP, CP ∈ [ i1, j1, …, m1], taking CP as i1, recording CP1 in the propagation path set, and recording CP1 as i1 to form a set a as [ CP1 ];
4.2.2, searching all the lines CP11, CP12.. No. CP1k which have common end points with the end points at the two ends of the second CP line except the set a in the [ i, j, …, m ] set, and recording CP11, CP12.. No. CP1k into the set a to form a new propagation path line set a [ CP1, CP11, CP12,. No. CP1k ];
4.2.3 assigning values to the CP to be compared according to the sequence of the lines in the set A, repeating the step 4.2.2, recording the line addition with the common end point into the set A, thereby forming a new propagation path line set A with the added associated lines until no line with the common end point of the CP to be compared exists;
4.2.4 sequentially making CP j1, …, and m1, and forming corresponding propagation path line sets B, C, …, and F in a manner of 4.2.2 and 4.2.3, respectively;
4.2.5 merging identical ones of the sets of propagation path lines obtained in steps 4.2.3 and 4.2.4, thereby determining a set of oscillating propagation path lines.
In the step (5), three levels of early warning matrixes are formed according to the oscillation area identified in the step (4), the first level of early warning is the highest and indicates that the oscillation is the most serious, and the second level of early warning is the lowest and only needs attention; the early warning matrix is shown in the following table:
the level design of the early warning follows the following principles:
the oscillation early warning level between the new energy power plants is the lowest, and is set as three-level early warning;
the level of the thermal power unit oscillation early warning is prepared according to two levels:
when the oscillation exists between the thermal power plant unit and the new energy power plant, the alternating current system or the direct current system, and the difference value between the oscillation frequency of the alternating current system and the natural frequency of the thermal power plant unit is within 0.5Hz, namely: l fsso-f1Less than or equal to 0.5Hz or | fsso-f2Less than or equal to 0.5Hz … or fsso-fnIf the absolute value is less than or equal to 0.5Hz, the oscillation is considered to be serious, the torsional vibration fatigue damage problem of the thermal power generating unit can be caused, the early warning level is the first level, wherein fssoFrequency of subsynchronous oscillations, f, for AC systems1，f2，…,fnThe natural frequency of the thermal power generating unit;
when oscillation exists between the thermal power plant unit and the new energy power plant, the alternating current system or the direct current system, and the oscillation frequency of the alternating current system and the natural frequency parameter of the thermal power plant unit are beyond 0.5Hz, the oscillation is not the most serious, the torsional vibration fatigue damage problem of the thermal power plant unit cannot be caused, and the early warning level is the second level;
when oscillation occurs between the direct current system and the alternating current system, the thermal power plant unit or the new energy power plant, the early warning level is the highest level and is set as the first level.
The invention has the following beneficial technical effects:
the broadband stability multi-stage early warning method integrating the multi-source information can be realized by modifying the existing power system wide area monitoring system, so that effective early warning on the problem of the next synchronous oscillation after new energy is accessed is realized, and powerful technical support is provided for operators to deal with the oscillation.
Drawings
FIG. 1 is a flow diagram of a new energy access broadband stability multi-stage early warning method integrating multi-source information according to the present invention;
FIG. 2 is a schematic view of the layout of monitoring points according to the present invention;
FIG. 3 is a flow chart of step 3 oscillation line identification according to the present invention;
fig. 4 is a schematic diagram of a three-level setting of the oscillation warning according to the present invention.
Detailed Description
The following describes in detail a specific implementation of the present invention with reference to the drawings. The early warning method provided by the invention is already applied to practical engineering, and the subsynchronous oscillation monitoring and early warning of a mixed bundling and delivering system containing new energy and thermal power is realized. The monitoring and early warning processing flow for subsynchronous oscillation of the invention is shown in fig. 1.
Step 1: determining the distribution range of monitoring points according to the structure of the regional power grid network frame, wherein the distributed monitoring points must comprise: the new energy collecting station comprises lines between the new energy collecting station and each new energy power plant, a new energy collecting station outlet line, a system hub transformer substation inlet line and outlet line, a local power grid internal fire motor set and a direct current system rectification side converter transformer inlet line, as shown in fig. 2:
(1) the new energy collection station monitors a new energy line, each new energy power plant is monitored to be connected with a line of the new energy collection station and a line of an alternating current system after collection, and monitoring data comprise three-phase voltage and three-phase current. In actual engineering, the number of incoming lines of each new energy collection station is generally 6-9, the types of new energy access are different, and a photovoltaic power station is provided with wind power, so that three-phase voltage and three-phase current of the incoming lines of the collection station need to be monitored, and outgoing lines are also monitored.
And monitoring three-phase voltage and three-phase current of a direct current system rectification side converter transformer incoming line.
(2) Monitoring incoming lines and outgoing lines of a system hub transformer substation, monitoring each incoming line and each outgoing line of the system hub transformer substation, and monitoring data comprises three-phase voltage uai、ubi、uciThree-phase current iai、ibi、iciFor evaluating the impact on the regional grid system;
(3) the natural parameters of the thermal power generating unit refer to natural frequency parameters of a natural shafting of the unit in a subsynchronous frequency range, and the frequencies of the thermal power generating unit mainly comprise 16Hz, 26Hz, 30Hz, 21.3Hz, 19.2Hz and 12.1Hz in the example;
(4) direct current system rectification side converter transformer incoming line main monitoring line three-phase voltage uai、ubi、uciAnd three-phase current iai、ibi、iciAnd the method is used for evaluating the oscillation condition between the new energy source and the direct current system.
Finally, all lines to be monitored are numbered uniformly, the line start and the terminal end are defined uniformly according to site IDs, the site IDs are unique in a regional power grid, and the following line data sets are formed:
{[1,nod_1,nod_8],[2,nod_2,nod_9],...,[n,nod_m,nod_n]},
wherein n is a line number;
nod _ m is a line starting end station mark;
nod _ n is the line termination site identity.
Step 2: the wide-band frequency spectrum calculation of each monitoring line with the frequency resolution of at least 0.5Hz is realized through a PMU (monitoring unit) of each monitoring point, and the wide-band frequency spectrum calculation comprises each frequency component phasor and frequency.
Since the current Phasor Monitoring Units (PMUs) have become widely used in systems. On a PMU device, an FFT algorithm of a long data window is carried out on sampling data with the sampling rate of 1200Hz, 4096 points are adopted for calculation in order to realize higher frequency analysis precision, the frequency resolution can reach 0.29Hz, and only frequency point amplitude and frequency information between 10 Hz and 90Hz are reserved in the calculation result. In the present example, the lines 3,4,5,6,9,13,15 all find an oscillating signal with an oscillating frequency of 25Hz and only oscillations with a frequency of 25Hz are present, the lines 3,4,5,6 are lines with a voltage class of 110kV, 9 is a line with a voltage class of 220kV, 13,15 are lines with a voltage class of 500kV, forming oscillation information in which the lines oscillate: { [25Hz,400V,15A ] }, { [25Hz,390V,20A ] }, { [25Hz,220V,21A ] }, { [25Hz,220V,23A ] }, { [25Hz,416V,15A ] }, { [25Hz,800V,12A ] }, { [25Hz,860V,16A ] }
And step 3: and identifying the oscillation circuit, traversing according to the frequency of the oscillation signal monitored by each monitoring point, and acquiring each line and the stations at two ends of the line which are related under the same oscillation mode.
(1) Firstly, setting threshold I for oscillation current and voltage of monitoring circuitTRiAnd UTRiIn general, the threshold value is designed in consideration of the identification accuracy of the device and the risk of oscillation according to the oscillation occurring in the field, and in the implementation process, ITRiAnd UTRiAre set to be 0.5% of rated current and rated voltage of the line, in the example, the rated phase current of the line with the voltage level of 110kV is 2000A, the rated phase current of the line with the voltage level of 220kV is 1500A, and the rated phase current of the line with the voltage level of 500kV is 2000A. Therefore, the threshold values of the voltage and current of the lines 3,4,5,6,9,13, and 15 are: 317.55V/10A, 317.55V/10A, 317.55V/10A, 317.55V/10A, 635.1V/7.5A, 1443V/10A. the 25Hz voltage or current amplitude calculated by the lines 3,4,5,6,9,13,15 exceeds 0.5% of the rated voltage or current of the line, and 25Hz oscillation can be considered to exist in the line;
(2) taking the line in fig. 2 as an example, if lines 3,4,5,6,9,13,15 all find an oscillating signal with an oscillating frequency of 25Hz, a set of lines of system 25Hz oscillation is established:
wherein:
and 4, step 4: the oscillation areas are identified, the oscillation areas are identified according to the relevance of the stations at two ends of the line, different oscillation areas are identified, and it is determined which of four oscillation areas, namely oscillation between different new energy power plants, oscillation between the new energy power plants and an alternating current system, oscillation between the new energy power plants and a thermal power generating unit and oscillation between the new energy power plants and a direct current system is, as shown in fig. 3:
4.1 select the new energy line set { [3, nod _3, nod _9], [4, nod _4, nod _9], [5, nod _5, nod _10], [6, nod _6, nod _10] }from the line set oscillating at 25Hz oscillation frequency
4.2 starting from each new energy source oscillation line with an oscillation frequency of 25Hz, namely, the line number of 3,4,5 and 6, respectively, finding the relevance of each line in all oscillation line sets with the oscillation frequency of 25Hz of the regional power grid, namely, the set [3,4,5,6,9,13 and 15], so as to determine the propagation path line set of the oscillation, wherein the method for forming the propagation path set comprises the following steps:
1) firstly, defining the number of a line to be compared as CP, CP ∈ [3,4,5,6], taking CP as 3, recording CP1 in a propagation path set, and taking CP1 as 3 to form a set A as [3 ];
2) searching all lines except the set A and having common end points with the end points of the two ends of the 3 rd line in the set [3,4,5,6,9,13,15], wherein the line numbers are 4 and 9, and recording the line numbers 4 and 9 into the set A to form a new set A which is [3,4,9 ];
3) sequentially assigning values to the CP according to the sequence of the lines in the set A, repeating the step 2), recording the lines with common end points into the set A in an increasing mode, thereby forming a new set A until no lines with common end points with the CP lines exist, and forming A as [3,4,9, 13,15 ];
4) let CP be 4,5,6 in sequence, compare procedure and 2)3) the same, forming sets B, C, …,
B＝[4，3，9，13，15]；C＝[5，6]；D＝[6，5]
5) merging A, B, C, …, identical sets in the sets, because A and B sets contain the same line number and can be merged, and C and D contain the same line number and can be merged, thus forming two oscillation propagation path sets:
A’＝[3，4，9，13，15],B’＝[5，6]。
4.3 analyzing the recorded line number sets A ', B', … respectively,
the oscillation propagation path comprises a new energy station, an alternating current system station, a thermal power generating unit line and a direct current converter station, and the propagation range is relatively far; if the set only contains new energy lines, the oscillation is considered to exist between different new energy power plants;
and B' ═ 5,6], the oscillation propagation path only comprises the new energy station, and the propagation range is small although the oscillation with the same frequency is also adopted.
And 5: setting different alarm fixed values and time fixed values according to different oscillation areas to generate early warning information of different levels;
as shown in fig. 4, the first-level alarm constant value 12A, the time constant value 5 s; a second-level alarm fixed value 15A and a time fixed value 15 s;
a third level alarm constant value 20A and a time constant value 20 s.
The oscillation areas are determined according to the following table:
the propagation path A' is [3,4,9, 13,15], and comprises a new energy field station, an alternating current system station, a thermal power generating unit and a direct current system, although the oscillation frequency is 25Hz, the natural frequency parameters of the thermal power generating unit of the power grid in the whole area have larger difference and are all larger than or equal to 1Hz, because the converter station of the direct current system comprises, the influence is caused on the direct current system, and therefore the early warning level is 1 level;
the propagation path B' is [5, 6] only contains new energy stations, that is, oscillation occurs between new energy stations, which has no influence on the system, and therefore, the early warning level is 3.
For the propagation path a' [3,4,9, 13,15], the scheduling operator needs to isolate the lines 3,4 in time, so as to ensure that the system is not affected; and for the propagation path B' [5, 6], the scheduling operator continues to observe, and does not perform the operation of cutting the line.
(6) And prompting an operator to operate according to the early warning level according to the regional site name, the line name and the early warning level, and informing the new energy site to adjust the operation mode or directly cutting off the new energy site to send out the line.
The foregoing is a detailed description of embodiments of the invention, and although specific embodiments have been described above, it will be apparent that various changes and modifications may be made without departing from the scope of the disclosure as defined in the following claims.
Claims (9)
1. A new energy access broadband stability multistage early warning method integrating multi-source information is characterized by comprising the following steps:
(1) determining the distribution range of monitoring points according to the structure of the regional power grid network frame, wherein the distributed monitoring points comprise: the system comprises lines between a new energy collection station and each new energy power plant, a new energy collection station outlet line, a system hub transformer substation inlet line and outlet line, a local power grid internal fire motor set and a direct current system rectification side converter transformer inlet line;
(2) the method comprises the steps that broadband frequency spectrum calculation of each monitoring line with frequency resolution of at least 0.5Hz is achieved through a PMU (monitoring unit) of each monitoring point, and the calculation comprises each frequency component phasor and frequency;
(3) identifying an oscillation line, traversing according to the frequency of an oscillation signal monitored by each monitoring point, and acquiring each line and stations at two ends of the line which are related under the same oscillation mode;
(4) identifying an oscillation area, identifying the oscillation area according to the relevance of the stations at two ends of the line, identifying different oscillation areas, and judging which of four oscillation areas is oscillation between different new energy power plants, oscillation between the new energy power plants and an alternating current system, oscillation between the new energy power plants and a thermal power generating unit and oscillation between the new energy power plants and a direct current system;
(5) setting different alarm fixed values and time fixed values according to different oscillation areas to generate early warning information of different levels;
(6) and prompting an operator to operate according to the early warning level according to the regional site name, the line name and the early warning level, and informing the new energy site to adjust the operation mode or directly cutting off the new energy site to send out the line.
2. The new energy access broadband stability multistage early warning method integrating multisource information as claimed in claim 1, wherein the method comprises the following steps:
in the step (1), the layout of the monitoring points realizes hierarchical arrangement, and comprises the following steps:
the new energy collection station monitors a new energy line, monitors a line of each new energy power plant accessed to the new energy collection station and a line of each new energy power plant accessed to an alternating current system after collection, and monitoring data comprise three-phase voltage and three-phase current;
monitoring incoming lines and outgoing lines of a system hub transformer substation, wherein each line of the incoming lines and each line of the outgoing lines accessed into the system hub transformer substation are monitored, and monitoring data comprise three-phase voltage and three-phase current;
monitoring a thermal power generating unit in a regional power grid, and monitoring inherent parameters of the thermal power generating unit, namely inherent frequency parameters of an inherent shafting of the thermal power generating unit in a subsynchronous frequency range;
and monitoring three-phase voltage and three-phase current of a direct current system rectification side converter transformer incoming line.
3. The new energy access broadband stability multistage early warning method integrating multisource information as claimed in claim 2, wherein the method comprises the following steps:
uniformly numbering all lines to be monitored, uniformly defining line start and terminal end points according to site IDs, wherein the site IDs are unique in a regional power grid, and forming the following line data set:
{[1,S1_ID,T1_ID],[2,S2_ID,T2_ID],...,[n,Sn_ID,Tn_ID]},
wherein n is the total line number;
Snthe _IDis a line starting end station mark;
TnID is the line termination site identification.
4. The new energy access broadband stability multistage early warning method integrating multisource information as claimed in claim 1, wherein the method comprises the following steps:
in the step (2), the distributed PMU monitoring devices of the monitoring points realize the function of frequency spectrum calculation based on the original sampling signals of the corresponding lines, the monitoring frequency range of the PMU monitoring devices is 10-90Hz, the length of a data window is selected for at least 2s, the frequency resolution is less than or equal to 0.5Hz, and a broadband oscillation characteristic information set in the range of 10-90Hz of each line is formed through the frequency spectrum calculation of the PMU monitoring devices of the monitoring points:
{[fssoi1,Umssoi1,Imssoi1],[fssoi2,Umssoi2,Imssoi2],...,[fssoip,Umssoip,Imssoip]}
wherein: f. ofssoipThe p oscillation frequency value of the ith line is analyzed by the frequency spectrum;
Umssoipthe phase voltage amplitude of the p-th oscillation frequency of the ith line is analyzed by the frequency spectrum;
Imssoipand the phase current amplitude of the p-th oscillation frequency of the ith line is analyzed by the frequency spectrum.
5. The new energy access broadband stability multistage early warning method integrating multisource information as claimed in claim 1, wherein the method comprises the following steps:
in the step (3), the following is further included:
3.1 setting the oscillation Current I for each monitoring lineTRiAnd oscillating voltage threshold UTRiWhen the phase voltage amplitude of a certain frequency point in a monitoring line is greater than or equal to the oscillation voltage threshold UTRiOr the phase current amplitude value of a certain frequency point existing in the monitoring line is greater than or equal to the oscillation current ITRiI.e. by
Umssoix≥UTRiOr Imssoix≥ITRiThen the existence frequency in the monitoring line is considered as fssoixOscillating of (3);
i is the line number, which indicates the ith line, UmssoixRepresents the phase voltage amplitude of the x frequency point of the ith line, ImssoixThe phase current amplitude of the x-th frequency point of the ith line is represented, x represents the x-th oscillation frequency, and x is more than or equal to 1 and less than or equal to p;
3.2 the phase voltage amplitude and the phase current amplitude of each frequency point of all the monitoring lines are judged according to 3.1, the lines and the frequencies meeting the oscillation condition are selected, an oscillation line set which oscillates under each oscillation frequency is formed, and the generation frequency fssoixThe line set of oscillations is:
{[i,Si_ID,Ti_ID,fssoix],[j,Sj_ID,Tj_ID,fssoix],...,[m,Sm_ID,Tm_ID,fssoix]}
wherein f isssoixRepresenting the x-th oscillation frequency value of the ith line, wherein x is more than or equal to 1 and less than or equal to p;
i, j, …, m being all oscillation frequencies fssoixThe line number of (1).
6. The new energy access broadband stability multilevel early warning method integrating the multisource information according to claim 5, characterized in that:
in step (4), the process flow of identifying the oscillation region is as follows:
4.1 from fssoixLine set oscillating at an oscillation frequency
{[i,Si_ID,Ti_ID,fssoix],[j,Sj_ID,Tj_ID,fssoix],...,[m,Sm_ID,Tm_ID,fssoix]Select new energy line set
{[i1,Si1_ID,Ti1_ID,fssoix],[j1,Sj1_ID,Tj1_ID,fssoix],...,[m1,Sm1_ID,Tm1_ID,fssoix]}
Wherein, i1, j1, …, m1 ∈ [ i, j, …, m]For all oscillation frequencies fssoixThe new energy source oscillation circuit number in the circuit is a circuit of a new energy source power plant accessing a new energy source collection station and a circuit of a regional power grid after collection;
4.2 from the oscillation frequency fssoixStarting from each new energy oscillation line i1, j1, … and m1, all oscillation frequencies of the regional power grid are fssoixI.e. the set [ i, j, …, m ] of oscillating circuits]Finding the relevance of each line so as to determine an oscillatory propagation path line set;
4.3 the set of propagation path lines of the oscillation determined by 4.2 is analyzed:
if the set only contains new energy lines, the oscillation is considered to exist between different new energy power plants;
if the set only contains the new energy source line and other lines, the oscillation between the new energy source power plant and the alternating current system is considered to exist;
if the set only comprises a new energy source line, an alternating current system line and a line connected with the thermal power generating unit, the oscillation between the new energy source power plant and the thermal power generating unit is considered to exist;
and if the set only comprises a new energy source line, an alternating current system line and a direct current converter station incoming line, the direct current system and the new energy source are considered to have oscillation.
7. The new energy access broadband stability multilevel early warning method integrating the multisource information according to claim 6, characterized in that:
in 4.2, the method of forming the propagation path set is as follows:
4.2.1, firstly defining the line to be compared as CP, CP ∈ [ i1, j1, …, m1], taking CP as i1, recording CP1 in the propagation path set, and recording CP1 as i1 to form a set a as [ CP1 ];
4.2.2, finding all lines CP11, CP12.. jon CP1k which have common end points with the end points at the two ends of the second CP line except the set a in the [ i, j, …, m ] set, and recording CP11, CP12.. jon CP1k into the set a to form a new propagation path line set a [ CP1, CP11, CP12,. jon CP1k ];
4.2.3 assigning values to the CP to be compared according to the sequence of the lines in the set A, repeating the step 4.2.2, recording the line addition with the common end point into the set A, thereby forming a new propagation path line set A with the added associated lines until no line with the common end point of the CP to be compared exists;
4.2.4 sequentially making CP j1, …, and m1, and forming corresponding propagation path line sets B, C, …, and F in a manner of 4.2.2 and 4.2.3, respectively;
4.2.5 merging identical ones of the sets of propagation path lines obtained in steps 4.2.3 and 4.2.4, thereby determining a set of oscillating propagation path lines.
8. The new energy access broadband stability multistage early warning method integrating multisource information as claimed in claim 1, wherein the method comprises the following steps:
in the step (5), three levels of early warning matrixes are formed according to the oscillation area identified in the step (4), the first level of early warning is the highest and indicates that the oscillation is the most serious, and the second level of early warning is the lowest and only needs attention.
9. The new energy access broadband stability multilevel early warning method integrating the multisource information according to claim 8, characterized in that:
the oscillation early warning level between new energy power plants is the lowest, three-level early warning is set, the first level of alarm fixed value is the highest, and the first level of alarm time fixed value is the lowest;
the level of the thermal power unit oscillation early warning is prepared according to two levels:
when the oscillation exists between the thermal power plant unit and the new energy power plant, the alternating current system or the direct current system, and the difference value between the oscillation frequency of the alternating current system and the natural frequency of the thermal power plant unit is within 0.5Hz, namely: l fsso-f1Less than or equal to 0.5Hz or | fsso-f2Less than or equal to 0.5Hz … or fsso-fnIf the absolute value is less than or equal to 0.5Hz, the oscillation is considered to be serious, the torsional vibration fatigue damage problem of the thermal power generating unit can be caused, the early warning level is the first level, wherein fssoFrequency of subsynchronous oscillations, f, for AC systems1，f2，…,fnThe natural frequency of the thermal power generating unit;
when oscillation exists between the thermal power plant unit and the new energy power plant, the alternating current system or the direct current system, and the oscillation frequency of the alternating current system and the natural frequency parameter of the thermal power plant unit are beyond 0.5Hz, the oscillation is not the most serious, the torsional vibration fatigue damage problem of the thermal power plant unit cannot be caused, and the early warning level is the second level;
when oscillation occurs between the direct current system and the alternating current system, the thermal power plant unit or the new energy power plant, the early warning level is the highest level and is set as the first level.
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