CN111244937B - Method for screening serious faults of transient voltage stability of power system - Google Patents
Method for screening serious faults of transient voltage stability of power system Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
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Abstract
The invention relates to a method for screening serious faults of transient voltage stability of a power system, and belongs to the field of transient safety evaluation and control of the power system. Firstly, constructing an expected fault set, performing transient simulation on all faults in the expected fault set to obtain a voltage time sequence track under each fault in the expected fault set, and calculating to obtain a bus node transient voltage stability index of each voltage class of 220kV and above under each fault; according to the index calculation result, acquiring a serious fault set formed by serious faults and establishing a cosine distance matrix of the serious fault set; and (4) acquiring representative faults in each cluster for the serious fault cluster, and finally obtaining a representative fault set. The invention can quickly complete the evaluation of the safety condition of the power system, effectively prevent faults and prevent the large-scale problem of the power system.
Description
Technical Field
The invention belongs to the field of power system transient voltage safety assessment and control, and particularly relates to the field of power system transient voltage stability serious fault screening.
Background
In recent years, with the development of technologies such as high-voltage direct-current transmission and new energy power generation, dynamic reactive power reserves of a power system are increasingly insufficient, and the problem of transient voltage stability caused by faults is particularly prominent. However, since the expected number of faults is large, if the reactive power optimization is directly performed on all the faults, the optimization problem is too large in scale, and the solution is difficult. Therefore, there is a need to reduce the number of failures to be considered in an efficient manner.
The existing fault screening method mainly comprises a time domain simulation method, a transient energy function method, an artificial intelligence method and the like. The time domain simulation method has the defects of high calculation precision, long calculation time consumption, incapability of providing stability margin and the like; the energy function method can provide information such as stability margin and the like, the calculation speed is high, and the critical energy is difficult to obtain; the artificial intelligence method has the advantages that the online calculation time of the trained neural network is short, but the method has the common defects that the selection of characteristic variables is not comprehensive, samples do not cover the whole sample space enough, and the accuracy of screening cannot be guaranteed. Therefore, a more effective fault screening method needs to be researched.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for screening serious transient voltage stability faults of a power system. The invention can rapidly complete the evaluation of the safety condition of the power system, effectively prevent faults and prevent the large-scale problem of the power system.
The invention provides a method for screening serious faults of transient voltage stability of a power system, which is characterized by comprising the following steps of:
(1) constructing an expected fault set, and performing transient simulation on all faults in the expected fault set to obtain a voltage time sequence track under each fault in the expected fault set;
(2) calculating a transient voltage stability index TVSI of each bus node with voltage grade of 220kV or above in the power system under each fault in the expected fault set;
the transient voltage stability index of each bus node is calculated as follows:
TVSI2＝|Vs-V0|×(Ts-Tcut)
wherein, TVSI1A first component representing a bus node transient voltage stability index, v (t) representing the bus node voltage at time t, t0Indicates that V (t) falls to a safety threshold value V for the first timethThe following time, TendIndicates that V (t) is restored to the safety threshold value V for the first timethThe above time;
TVSI2a second component, V, representing a transient voltage stability indicator for the bus node0、VSRespectively representing the initial and steady-state values of the bus node voltage, Tcut、TsRespectively showing the fault clearing time and the time of entering a stable state after the fault; TVSIth1、TVSIth2Respectively representing the first componentAnd a safety threshold of the second component; k is a radical of1、k2The weight coefficient of the first component and the weight coefficient of the second component are respectively;
(3) finding out the maximum value of the TVSI of the bus node under each fault according to the result of the step (2), taking the fault with the maximum value of the TVSI of the bus node larger than 1 in all the faults as a serious fault, and forming all the serious faults into a serious fault set;
wherein S issFltIndicates a critical failure set, SBusBus node set, Bus, representing all 220kV and above voltage classes in an electrical power systemjDenotes SBusThe j-th element of (1), SFltIndicating a set of expected failures, FltiIndicating the ith element in the envisioned failure set,
indicating failure FltiBus node BusjTransient voltage stability indicator of (1);
(4) calculating the absolute value of the difference value of TVSI between every two faults in the serious fault set as the cosine distance between the two faults to form a cosine distance matrix of the serious fault set;
wherein M isdisCosine distance matrix representing the set of critical faults, dijIndicating failure FltiAnd FltjThe cosine distance between them, N represents the number of critical faults,
indicating failure FltiBus node BuskTransient voltage stability index of (1), NBusThe number of bus nodes representing 220kV and above voltage levels in the power system is shown;
(5) according to matrix MdisDetermining a final clustering scheme and a clustering number N by adopting a hierarchical clustering algorithm and an outline coefficient method; the method comprises the following specific steps:
(5-1) calculating a contour coefficient corresponding to each clustering scheme;
wherein, aiRepresenting the average distance from a fault i in any serious fault cluster to other faults in the cluster under the clustering scheme, biRepresents the minimum value, sc, of the mean distance from fault i in any one serious fault cluster to each of the other serious fault clustersiRepresenting the contour coefficient of the fault i, and SC representing the contour coefficient of the clustering scheme;
(5-2) selecting the maximum outline coefficient scheme as the final clustering scheme, and taking the outline coefficient corresponding to the scheme as the final clustering number Nc；
(6) And taking the fault corresponding to the maximum value of the TVSI of the bus node in each serious fault cluster as a representative fault corresponding to the cluster, wherein all the representative faults form a representative fault set, and finishing screening.
The invention has the characteristics and beneficial effects that:
1. the method adopts the parallel computing technology to realize the transient simulation of a plurality of expected faults simultaneously, and the simulation time is reduced as much as possible on the premise of ensuring the computing precision.
2. The method of the invention obtains the transient voltage stability margin information of each fault by calculating the transient voltage stability index of each node under each fault.
3. The method of the invention combines the clustering algorithm to further screen the serious fault set to obtain a representative fault set, thereby obviously reducing the number of serious faults to be considered.
Detailed Description
The invention provides a method for screening serious faults of transient voltage stability of a power system, which is further described in detail in the following by combining specific embodiments.
The invention provides a method for screening serious faults of transient voltage stability of a power system, which adopts a parallel computing technology to simultaneously carry out transient simulation on a plurality of faults, calculates a voltage stability index according to a simulation result and preliminarily screens a serious fault set according to the voltage stability index, then clusters the serious faults by adopting a hierarchical clustering algorithm, and finally selects a plurality of faults from each type of faults to form a typical representative fault set. The method comprises the following steps:
(1) selecting a plurality of faults to form an expected fault set (the number of the faults in the expected fault set has no special requirement); and calling a PSASP transient simulation program by using MATLAB programming, and simultaneously performing transient simulation calculation on all faults in the expected fault set through a parallel calculation function of the MATLAB to obtain a voltage time sequence track under each fault in the expected fault set.
(2) Calculating a transient voltage stability index TVSI of each bus node with voltage grade of 220kV or above in the power system under each fault in the expected fault set;
the transient voltage stability index of each bus node is calculated as follows:
TVSI2＝|Vs-V0|×(Ts-Tcut)
wherein, TVSI1The first component representing the bus node transient voltage stability indicator,
v (t) represents the bus node voltage at time t, t0Indicates that V (t) falls to a safety threshold value V for the first timethThe following time, TendIndicates that V (t) is restored to the safety threshold value V for the first timethAbove time (wherein the safety threshold V isthPer unit value 0.8).
TVSI2A second component, V, representing a transient voltage stability indicator for the bus node0、VSRespectively representing the initial and steady-state values of the bus node voltage, Tcut、TsRespectively, indicating the time of fault removal and the time of entering steady state after the fault. TVSIth1、TVSIth2Respectively representing a safety threshold of the first component and a safety threshold of the second component (all the safety thresholds take per unit values of 0.8);
the transient voltage stability index TVSI of each bus node is TVSI of two components of the bus node1And TVSI2Weighted sum of (a), k1、k2The weight coefficients are respectively corresponding (0.5 is respectively taken).
(3) According to the result of the step (2), finding out the maximum value of the TVSI of the bus node under each fault for measuring the transient voltage stability degree of the fault, taking the fault with the maximum value of the TVSI of the bus node larger than 1 in all the faults as a serious fault, and forming a serious fault set by all the serious faults: (ii) a
Wherein S issFltIndicates a critical failure set, SBusAnd BusjBus node set respectively representing all voltage classes of 220kV and above in power grid force system and jth element, S in bus node setFltAnd FltiRespectively representing the anticipated failure set and the ith element in the anticipated failure set,
indicating failure FltiBusjThe transient voltage stability index of (1).
(4) Calculating the absolute value of the difference value of TVSI between every two faults in the serious fault set as the cosine distance between the two faults to form a cosine distance matrix of the serious fault set;
wherein M isdisCosine distance matrix representing the set of critical faults, dijIndicating failure FltiAnd FltjThe cosine distance between them, N represents the number of critical faults,
indicating failure FltiBus node BuskTransient voltage stability index of (1), NBusThe number of bus nodes representing 220kV and above voltage levels in the power system is shown;
(5) according to matrix MdisClustering serious faults by adopting a hierarchical clustering algorithm, determining the number of clusters by adopting a contour coefficient, taking a maximum contour coefficient scheme as a final clustering scheme, and taking a contour coefficient corresponding to the scheme as a final clustering number Nc(ii) a The method comprises the following specific steps:
(5-1) calculating a contour coefficient corresponding to each clustering scheme;
wherein, aiRepresenting the average distance from a fault i in any serious fault cluster to other faults in the cluster under the clustering scheme, biRepresents the minimum value, sc, of the mean distance from fault i in any one serious fault cluster to each of the other serious fault clustersiAnd the contour coefficient of the fault i is shown, the SC is shown as the contour coefficient of the clustering scheme, and N is the number of serious faults.
(5-2) after calculating the corresponding outline coefficients of all the clustering schemes, selecting the maximum outline coefficient scheme as the final clustering scheme, and taking the outline coefficient corresponding to the scheme as the final clustering number Nc。
(6) Taking the fault corresponding to the maximum value of TVSI in each serious fault cluster as a representative fault corresponding to the cluster, forming a representative fault set by all representative faults, and finishing screening;
the specific method comprises the following steps: take out class a serious faults one by one
Each fault Flt iniFinding out the maximum value in TVSI corresponding to all bus nodes under the fault action
Compare all under the cluster of serious faults
Size, finding the maximum value
Then
Corresponding failure FltpNamely, the representative fault of the a-th serious fault is marked as psFlta. Finally, the representative faults in each serious fault cluster form a representative fault set SpsFltAnd finishing the screening.
Claims (1)
1. A method for screening serious faults of transient voltage stability of a power system is characterized by comprising the following steps:
(1) constructing an expected fault set, and performing transient simulation on all faults in the expected fault set to obtain a voltage time sequence track under each fault in the expected fault set;
(2) calculating a transient voltage stability index TVSI of each bus node with voltage grade of 220kV or above in the power system under each fault in the expected fault set;
the transient voltage stability index of each bus node is calculated as follows:
TVSI2＝|Vs-V0|×(Ts-Tcut)
wherein, TVSI1A first component representing a bus node transient voltage stability index, v (t) representing the bus node voltage at time t, t0Indicates that V (t) falls to a safety threshold value V for the first timethThe following time, TendIndicates that V (t) is restored to the safety threshold value V for the first timethThe above time;
TVSI2a second component, V, representing a transient voltage stability indicator for the bus node0、VSRespectively representing the initial and steady-state values of the bus node voltage, Tcut、TsRespectively showing the fault clearing time and the time of entering a stable state after the fault; TVSIth1、TVSIth2Respectively representing a safety threshold of the first component and a safety threshold of the second component; k is a radical of1、k2The weight coefficient of the first component and the weight coefficient of the second component are respectively;
(3) finding out the maximum value of the TVSI of the bus node under each fault according to the result of the step (2), taking the fault with the maximum value of the TVSI of the bus node larger than 1 in all the faults as a serious fault, and forming all the serious faults into a serious fault set;
wherein S issFltIndicates a critical failure set, SBusBus node set, Bus, representing all 220kV and above voltage classes in an electrical power systemjDenotes SBusThe j-th element of (1), SFltIndicating a set of expected failures, FltiIndicating the ith element in the envisioned failure set,
indicating failure FltiBus node BusjTransient voltage stability indicator of (1);
(4) calculating the absolute value of the difference value of TVSI between every two faults in the serious fault set as the cosine distance between the two faults to form a cosine distance matrix of the serious fault set;
wherein M isdisCosine distance matrix representing the set of critical faults, dijIndicating failure FltiAnd FltjThe cosine distance between them, N represents the number of critical faults,
indicating failure FltiBus node BuskTransient voltage stability index of (1), NBusThe number of bus nodes representing 220kV and above voltage levels in the power system is shown;
(5) according to matrix MdisDetermining a final clustering scheme and a clustering number N by adopting a hierarchical clustering algorithm and an outline coefficient method; the method comprises the following specific steps:
(5-1) calculating a contour coefficient corresponding to each clustering scheme;
wherein, aiRepresenting the average distance from a fault i in any serious fault cluster to other faults in the cluster under the clustering scheme, biRepresents the minimum value, sc, of the mean distance from fault i in any one serious fault cluster to each of the other serious fault clustersiRepresenting the contour coefficient of the fault i, and SC representing the contour coefficient of the clustering scheme;
(5-2) selecting the maximum outline coefficient scheme as the final clustering scheme, and taking the outline coefficient corresponding to the scheme as the final clustering number Nc；
(6) And taking the fault corresponding to the maximum value of the TVSI of the bus node in each serious fault cluster as a representative fault corresponding to the cluster, wherein all the representative faults form a representative fault set, and finishing screening.
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