CN113270875A - Transient power angle instability judging method and system based on local measurement - Google Patents

Transient power angle instability judging method and system based on local measurement Download PDF

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CN113270875A
CN113270875A CN202110565338.1A CN202110565338A CN113270875A CN 113270875 A CN113270875 A CN 113270875A CN 202110565338 A CN202110565338 A CN 202110565338A CN 113270875 A CN113270875 A CN 113270875A
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power
oscillation center
variation
angle
generator
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CN113270875B (en
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赵伟
姜苑
李付强
张晶
潘艳
徐鹏
董烨
刘崇茹
黎晓
李庚银
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North China Electric Power University
North China Grid Co Ltd
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North China Grid Co Ltd
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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
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H02J3/241—The oscillation concerning frequency
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/34—Testing dynamo-electric machines
    • G01R31/343—Testing dynamo-electric machines in operation
    • 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
    • H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
    • H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
    • 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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/48—Controlling the sharing of the in-phase component
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation

Abstract

The invention relates to a transient power angle instability judging method and a transient power angle instability judging system based on local measurement. The invention also considers the power variation generated by the load injection system along with the transient power angle variation of the generator, overcomes the defect that the transient instability of the system can not be timely monitored because the potential energy of the oscillation center branch circuit is only used for representing all potential energy components of the network in the system and the transient energy components of the load branch circuit are ignored, and can reach the inherent potential energy peak value occurrence time of the system earlier than the prior method, so that the transient instability fault of the system can be monitored earlier.

Description

Transient power angle instability judging method and system based on local measurement
Technical Field
The invention relates to the field of generator step-out monitoring, in particular to a transient power angle instability judging method and system based on local measurement.
Background
As the operating point of the power system is closer to the stability limit of the power system, the power system always has the risk of transient power angle instability under large disturbance, so that the loss of synchronism of the generator is monitored in time, an emergency control strategy can be adopted as early as possible, and the system can be recovered to be stable. There have been many researches on the out-of-step monitoring of the generator, including methods based on power angle and rotation speed measurement of the generator, methods based on branch potential energy, and the like.
The method for measuring the power angle and the rotating speed of the generator depends on a large amount of Measurement of the rotating speed of the generator or Measurement of a Phasor Measurement Unit (PMU), and thus the burden of data transmission and the difficulty of online implementation are increased. The method based on branch potential energy does not depend on generator measurement and depends on branch local dynamic measurement, so that the method can be easily used for online monitoring. However, the transient instability criterion based on the branch potential energy ignores the transient energy component of the load branch, and represents all potential energy components of the network in the system by using the potential energy of the oscillation center branch, so that the transient instability of the system cannot be monitored in time.
Therefore, there is a need for a method for monitoring transient instability of a system earlier than the existing branch potential energy-based method.
Disclosure of Invention
The invention aims to provide a transient power angle instability judging method and system based on local measurement and a transient instability fault of the system can be monitored.
In order to achieve the purpose, the invention provides the following scheme:
a transient power angle instability distinguishing method based on local measurement comprises the following steps:
collecting the power flow parameters of each oscillation center branch in the power system;
calculating power variation generated by all the oscillation center branches along with transient power angle variation of the generator according to the load flow parameters of all the oscillation center branches, and taking the power variation as first power variation;
calculating power variation of the load injection system along with transient power angle variation of the generator by using a local measurement method according to the load flow parameters of each oscillation center branch circuit, and taking the power variation as second power variation;
and judging whether the power system is unstable or not by using a transient power angle instability criterion according to the first power variation and the second power variation.
Preferably, the calculating, according to the power flow parameter of each oscillation center branch, a power variation generated by all oscillation center branches along with a transient power angle variation of the generator as a first power variation specifically includes:
according to the power flow parameters of each oscillation center branch, using a formula
Figure BDA00030807694300000210
Calculating the transient power angle change of all oscillation center branches along with the generatorThe generated power variation is used as a first power variation;
wherein, Δ PCIs a first power variation, PCFor the active power flow of all the oscillation center branches,
Figure BDA00030807694300000211
for the steady state value, P, of the active power flow of all oscillation center branchesCcFor all power components, P, of the central branch of oscillation that do not vary with the power angle of the generatorC maxFor all power components of the oscillation center branch that vary with the power angle of the generator,
Figure BDA0003080769430000021
the steady-state values of the equivalent power electromotive forces of the group S and the group A respectively,
Figure BDA0003080769430000022
is the conjugate of the steady state value of the equivalent source emf of group a,
Figure BDA0003080769430000023
is the intermediate variable(s) of the variable,
Figure BDA0003080769430000024
YLGSis S group equivalent admittance, ZSSIs the self-impedance of the S group in the node impedance matrix, GSAThe conductance component of the equivalent admittance of the crosstie,
Figure BDA0003080769430000025
the mutual impedance conjugates of the S and a groups in the nodal impedance matrix,
Figure BDA0003080769430000026
is the conjugate of the group a equivalent admittance,
Figure BDA0003080769430000027
is the conjugate of the equivalent admittance of the crosstie,
Figure BDA0003080769430000028
in a node impedance matrixIs the self-impedance of group A, ZASIs the mutual impedance of group S and group A in the node impedance matrix, YASIs equivalent admittance of a connecting line, delta is equivalent power angle of the power system, and gamma isCIs the power angle variation of the generator,
Figure BDA0003080769430000029
angle () is a phase angle function.
Preferably, the calculating, according to the power flow parameter of each oscillation center branch, a power variation generated by the load injection system along with a transient power angle variation of the generator by using a local measurement method, as a second power variation, specifically includes:
according to the power flow parameter of each oscillation center branch, using the formula alpha as PL2 max/PC maxCalculating a first parameter; wherein alpha is a first parameter, PL2 maxIs the combined power of the power system, PC maxThe power components of all the oscillation center branches are changed along with the power angle of the generator;
using local measurement, using formulas
Figure BDA0003080769430000031
And
Figure BDA0003080769430000032
calculating the derivative of the active power flow of all the oscillation center branches to the power angle of the generator; wherein the content of the first and second substances,
Figure BDA0003080769430000033
the derivative of the active power flow of all the oscillation center branches to the power angle of the generator is shown, sigma is the phase angle difference of the voltages at two ends of the oscillation center branches in a steady state,
Figure BDA0003080769430000034
the derivative of the active power flow of all the oscillation center branches to the phase angle difference of the voltages at two ends of the oscillation center branches in a steady state,
Figure BDA0003080769430000035
for change of phase angle difference of branchThe ratio of the ratio to the center of inertia, beta is the average value of phase angles at two ends of the oscillation center branch, and beta is (beta)1+β2)/2，β1And beta2The voltage values are per unit values of the amplitude values when the phase angle of the branch is swung open to 180 degrees at two ends of the oscillation center branch;
according to the power flow parameters of each oscillation center branch, using a formula
Figure BDA0003080769430000036
Calculating the derivative of the steady-state values of the active power flows of all the oscillation center branches to the power angle of the generator; wherein the content of the first and second substances,
Figure BDA0003080769430000037
the derivative of the steady-state values of the active power flows of all the oscillation center branches to the power angle of the generator is obtained;
according to the first parameter, the derivatives of the active power flows of all the oscillation center branches to the power angle of the generator and the steady-state values of the active power flows of all the oscillation center branches to the power angle of the generator, a formula is utilized
Figure BDA0003080769430000038
Calculating power variation generated by the load injection system along with transient power angle variation of the generator as second power variation; wherein, Δ PL2Is the second power variation.
Preferably, the transient power angle instability criterion includes:
Figure BDA0003080769430000039
wherein the content of the first and second substances,
Figure BDA00030807694300000311
is the phase angle difference, sigma, of the voltage at two ends of the kth oscillation center branch in steady statek(t) is the phase angle difference of the voltages at two ends of the kth oscillation center branch at the time t, sigmaminAnd C is the total number of the oscillation center branches in the load injection system.
Preferably, the transient power angle instability criterion further includes:
Figure BDA00030807694300000310
wherein, min (σ)k) And max (σ)k) Local minimum and maximum of phase angle difference of voltage at two ends of kth oscillation center branch, omegaminIs a phase angle difference threshold, σkIs the phase angle difference of the voltage at two ends of the kth oscillation center branch.
A transient power angle instability discrimination system based on local metrology, the system comprising:
the power flow parameter acquisition module is used for acquiring power flow parameters of each oscillation center branch in the power system;
the first power variation calculation module is used for calculating power variations generated by all the oscillation center branches along with transient power angle variations of the generator according to the load flow parameters of all the oscillation center branches and taking the power variations as first power variations;
the second power variation calculation module is used for calculating power variation of the load injection system generated along with transient power angle variation of the generator by using a local measurement method according to the load flow parameters of each oscillation center branch circuit, and the power variation is used as second power variation;
and the power system instability judgment module is used for judging whether the power system is unstable or not by using a transient power angle instability criterion according to the first power variable quantity and the second power variable quantity.
Preferably, the first power variation calculating module specifically includes:
a first power variation calculation submodule for calculating the power flow parameter of each oscillation center branch according to the formula
Figure BDA00030807694300000410
Calculating power variation generated by all oscillation center branches along with transient power angle variation of the generator as first power variation;
wherein, Δ PCIs a first power variation, PCFor the active power flow of all the oscillation center branches,
Figure BDA00030807694300000411
for the steady state value, P, of the active power flow of all oscillation center branchesCcFor all power components, P, of the central branch of oscillation that do not vary with the power angle of the generatorC maxFor all power components of the oscillation center branch that vary with the power angle of the generator,
Figure BDA0003080769430000041
the steady-state values of the equivalent power electromotive forces of the group S and the group A respectively,
Figure BDA0003080769430000042
is the conjugate of the steady state value of the equivalent source emf of group a,
Figure BDA0003080769430000043
is the intermediate variable(s) of the variable,
Figure BDA0003080769430000044
YLGSis S group equivalent admittance, ZSSIs the self-impedance of the S group in the node impedance matrix, GSAThe conductance component of the equivalent admittance of the crosstie,
Figure BDA0003080769430000045
the mutual impedance conjugates of the S and a groups in the nodal impedance matrix,
Figure BDA0003080769430000046
is the conjugate of the group a equivalent admittance,
Figure BDA0003080769430000047
is the conjugate of the equivalent admittance of the crosstie,
Figure BDA0003080769430000048
is the self-impedance conjugate of group A in the node impedance matrix, ZASFor the S group in the node impedance matrix andmutual impedance of group A, YASIs equivalent admittance of a connecting line, delta is equivalent power angle of the power system, and gamma isCIs the power angle variation of the generator,
Figure BDA0003080769430000049
angle () is a phase angle function.
Preferably, the second power variation calculating module specifically includes:
a first parameter calculation submodule for calculating a power flow parameter of each oscillation center branch by using a formula of alpha to PL2 max/PC maxCalculating a first parameter; wherein alpha is a first parameter, PL2 maxIs the combined power of the power system, PC maxThe power components of all the oscillation center branches are changed along with the power angle of the generator;
a first derivative calculation submodule for using the method of local measurement using the formula
Figure BDA0003080769430000051
And
Figure BDA0003080769430000052
calculating the derivative of the active power flow of all the oscillation center branches to the power angle of the generator; wherein the content of the first and second substances,
Figure BDA0003080769430000053
the derivative of the active power flow of all the oscillation center branches to the power angle of the generator is shown, sigma is the phase angle difference of the voltages at two ends of the oscillation center branches in a steady state,
Figure BDA0003080769430000054
the derivative of the active power flow of all the oscillation center branches to the phase angle difference of the voltages at two ends of the oscillation center branches in a steady state,
Figure BDA0003080769430000055
the ratio of the phase angle difference change rate of the branch to the inertia center, beta is the average value of the phase angles at two ends of the oscillation center branch, and beta is (beta)1+β2)/2，β1And beta2Are respectively asThe voltage at two ends of the oscillation center branch has per unit value of amplitude when the phase angle of the branch is swung to 180 degrees;
a second derivative calculation submodule for utilizing a formula according to the load flow parameters of each oscillation center branch
Figure BDA0003080769430000056
Calculating the derivative of the steady-state values of the active power flows of all the oscillation center branches to the power angle of the generator; wherein the content of the first and second substances,
Figure BDA0003080769430000057
the derivative of the steady-state values of the active power flows of all the oscillation center branches to the power angle of the generator is obtained;
a second power variation calculation submodule, configured to calculate a derivative of the power angle of the generator according to the first parameter, the derivatives of the active power flows of all the oscillation center branches to the power angle of the generator, and the steady-state values of the active power flows of all the oscillation center branches, using a formula
Figure BDA0003080769430000058
Calculating power variation generated by the load injection system along with transient power angle variation of the generator as second power variation; wherein, Δ PL2Is the second power variation.
Preferably, the transient power angle instability criterion includes:
Figure BDA0003080769430000059
wherein the content of the first and second substances,
Figure BDA00030807694300000510
is the phase angle difference, sigma, of the voltage at two ends of the kth oscillation center branch in steady statek(t) is the phase angle difference of the voltages at two ends of the kth oscillation center branch at the time t, sigmaminAnd C is the total number of the oscillation center branches in the load injection system.
Preferably, the transient power angle instability criterion further includes:
Figure BDA0003080769430000061
wherein, min (σ)k) And max (σ)k) Local minimum and maximum of phase angle difference of voltage at two ends of kth oscillation center branch, omegaminIs a phase angle difference threshold, σkIs the phase angle difference of the voltage at two ends of the kth oscillation center branch.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention provides a transient power angle instability judging method based on local measurement, which is characterized in that power variation generated by all oscillation center branches along with transient power angle change of a generator is calculated according to a load flow parameter of each oscillation center branch, the power variation generated by a load injection system along with the transient power angle change of the generator is calculated according to the load flow parameter of each oscillation center branch by using the local measurement method, and whether a power system is unstable or not is judged by combining the power variation of the two parts and using a transient power angle instability criterion. The invention not only considers the power variation generated by the oscillation center branch circuit along with the transient power angle variation of the generator, but also considers the power variation generated by the load injection system along with the transient power angle variation of the generator, overcomes the defect that the transient instability of the system can not be monitored in time due to the fact that the potential energy of the oscillation center branch circuit is only used for representing all potential energy components of a network in the system and the transient energy components of the load branch circuit are ignored, and can reach the inherent potential energy peak value occurrence time of the system earlier than the existing method, so that the transient instability fault of the system can be monitored earlier.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
Fig. 1 is a flowchart of a transient power angle instability determination method based on local measurement according to the present invention;
FIG. 2 is a diagram of a model of a loaded dual-machine system according to the present invention;
fig. 3 is a block diagram of an IEEE39 node system according to an embodiment of the present invention;
FIG. 4 is a graph of node voltage amplitude provided by an embodiment of the present invention;
FIG. 5 is a d σ/d δ graph of the oscillation center branch provided by an embodiment of the present invention; FIG. 5(a) is a graph of d σ/d δ for oscillation center branches 1-2, and FIG. 5(b) is a graph of d σ/d δ for oscillation center branches 8-9;
FIG. 6 is a power diagram of a system according to an embodiment of the present invention;
fig. 7 is a schematic diagram of a voltage phase angle difference between two ends of a network line according to an embodiment of the present invention;
fig. 8 is a schematic diagram of two oscillation center branches that do not satisfy and satisfy a startup condition of a destabilization criterion according to an embodiment of the present invention; fig. 8(a) is a schematic diagram of two oscillation center branches not meeting the instability criterion starting condition, and fig. 8(b) is a schematic diagram of two oscillation center branches meeting the instability criterion starting condition.
FIG. 9 is a schematic diagram of determining whether the transient state of the system is stable under the condition of FIG. 8(a) according to an embodiment of the present invention;
FIG. 10 is a schematic diagram of determining whether the transient state of the system is stable under the condition of FIG. 8(b) according to an embodiment of the present invention;
fig. 11 is a graph of a power angle when the system is unstable according to an embodiment of the present invention;
FIG. 12 is a time difference diagram of the original determination method and the determination method of the present invention in determining instability according to the embodiment of the present invention;
fig. 13 is a difference diagram of the power angle difference between the inertia centers of two clusters and the phase angle difference between two ends of the oscillation center branch when the original determination method and the determination method of the present invention monitor the system instability, which is provided by the embodiment of the present invention; fig. 13(a) is a difference diagram of the power angle difference between the inertia centers of two machine groups when the original discrimination method and the discrimination method of the present invention monitor the system instability, and fig. 13(b) is a difference diagram of the phase angle difference between the two ends of the oscillation center branch of the two machine groups when the original discrimination method and the discrimination method of the present invention monitor the system instability.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a transient power angle instability judging method and system based on local measurement and a transient instability fault of the system can be monitored.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
The invention provides a transient power angle instability judging method based on local measurement, as shown in figure 1, the method comprises the following steps:
s101, collecting a power flow parameter of each oscillation center branch in a power system; the power flow parameters comprise: composite power of the power system, network connection parameters (admittance … …), etc.
For simplicity of illustration, the description will be made using the loaded two-machine system model shown in FIG. 2, where Y isLSAnd YLARepresenting the equivalent conductance of the load. y isLGS、yLGA、ySARespectively, the equivalent admittance, P, of the S group, A group and the connecting lineLS、PLARespectively the equivalent load active power, I, of the group S and the group ALS、ILAMeans the current, V, injected into the power system by the equivalent loads of group S and group A, respectivelyLS、VLABus voltages, E, respectively for group S and group AGSThe equivalent power source electromotive force, | E, of the S groupGSI is the modulus, delta, of the electromotive forceSGenerators being the phase angle of the electromotive force, i.e. the S groupA power angle; eGARefers to the equivalent power source electromotive force, | E, of group AGAI is the modulus, delta, of the electromotive forceAThe phase angle of the electromotive force is the generator power angle of the group a.
S102, calculating a power variation of all oscillation center branches generated along with a transient power angle variation of the generator according to the power flow parameter of each oscillation center branch, as a first power variation, specifically including:
according to the power flow parameters of each oscillation center branch, using a formula
Figure BDA00030807694300000810
Calculating power variation generated by all oscillation center branches along with transient power angle variation of the generator as first power variation;
wherein, Δ PCIs a first power variation, PCFor the active power flow of all the oscillation center branches,
Figure BDA00030807694300000811
for the steady state value, P, of the active power flow of all oscillation center branchesCcFor all power components, P, of the central branch of oscillation that do not vary with the power angle of the generatorC maxFor all power components of the oscillation center branch that vary with the power angle of the generator,
Figure BDA0003080769430000081
the steady-state values of the equivalent power electromotive forces of the group S and the group A respectively,
Figure BDA0003080769430000082
is the conjugate of the steady state value of the equivalent source emf of group a,
Figure BDA0003080769430000083
is the intermediate variable(s) of the variable,
Figure BDA0003080769430000084
YLGSis S group equivalent admittance, ZSSIs the self-impedance of the S group in the node impedance matrix, GSAAs a tie line, etcThe conductance component of the effective admittance is,
Figure BDA0003080769430000085
the mutual impedance conjugates of the S and a groups in the nodal impedance matrix,
Figure BDA0003080769430000086
is the conjugate of the group a equivalent admittance,
Figure BDA0003080769430000087
is the conjugate of the equivalent admittance of the crosstie,
Figure BDA0003080769430000088
is the self-impedance conjugate of group A in the node impedance matrix, ZASIs the mutual impedance of group S and group A in the node impedance matrix, YASIs equivalent admittance of a connecting line, delta is equivalent power angle of the power system, and gamma isCIs the power angle variation of the generator,
Figure BDA0003080769430000089
angle () is a phase angle function.
S103, calculating a power variation generated by the load injection system along with a transient power angle variation of the generator by using a local measurement method according to the power flow parameter of each oscillation center branch, as a second power variation, specifically including:
according to the power flow parameter of each oscillation center branch, using the formula alpha as PL2 max/PC maxCalculating a first parameter; wherein alpha is a first parameter, PL2 maxIs the combined power of the power system, PC maxThe power components of all the oscillation center branches are changed along with the power angle of the generator;
using local measurement, using formulas
Figure BDA0003080769430000091
And
Figure BDA0003080769430000092
calculating active power flow of all oscillation center branches to generate electricityA derivative of the power angle; wherein the content of the first and second substances,
Figure BDA0003080769430000093
the derivative of the active power flow of all the oscillation center branches to the power angle of the generator is shown, sigma is the phase angle difference of the voltages at two ends of the oscillation center branches in a steady state,
Figure BDA0003080769430000094
the derivative of the active power flow of all the oscillation center branches to the phase angle difference of the voltages at two ends of the oscillation center branches in a steady state,
Figure BDA0003080769430000095
the ratio of the phase angle difference change rate of the branch to the inertia center, beta is the average value of the phase angles at two ends of the oscillation center branch, and beta is (beta)1+β2)/2，β1And beta2The voltage values are per unit values of the amplitude values when the phase angle of the branch is swung open to 180 degrees at two ends of the oscillation center branch;
according to the power flow parameters of each oscillation center branch, using a formula
Figure BDA0003080769430000096
Calculating the derivative of the steady-state values of the active power flows of all the oscillation center branches to the power angle of the generator; wherein the content of the first and second substances,
Figure BDA0003080769430000097
the derivative of the steady-state values of the active power flows of all the oscillation center branches to the power angle of the generator is obtained;
according to the first parameter, the derivatives of the active power flows of all the oscillation center branches to the power angle of the generator and the steady-state values of the active power flows of all the oscillation center branches to the power angle of the generator, a formula is utilized
Figure BDA0003080769430000098
Calculating power variation generated by the load injection system along with transient power angle variation of the generator as second power variation; wherein, Δ PL2Is the second power variation.
The load injection system comprises: the loads of the oscillation center branches and the buses where the nodes are located, and the like.
And S104, judging whether the power system is unstable or not by using a transient power angle instability criterion according to the first power variation and the second power variation.
The transient power angle instability criterion comprises the following steps:
Figure BDA0003080769430000101
wherein the content of the first and second substances,
Figure BDA0003080769430000102
is the phase angle difference, sigma, of the voltage at two ends of the kth oscillation center branch in steady statek(t) is the phase angle difference of the voltages at two ends of the kth oscillation center branch at the time t, sigmaminAnd C is the total number of the oscillation center branches in the load injection system.
σminTaking 10 °, its effect is two: 1) the misjudgment of power fluctuation caused by oscillation is prevented; 2) and the misjudgment when the power angle swings back to the state before the fault under the condition of transient stability is prevented.
In order to prevent erroneous judgment when the power angle swings to the maximum position and then swings back, the following conditions are supplemented on the basis of the instability judgment conditions:
Figure BDA0003080769430000103
wherein, min (σ)k) And max (σ)k) Local minimum and maximum of phase angle difference of voltage at two ends of kth oscillation center branch, omegaminIs a phase angle difference threshold, σkIs the phase angle difference of the voltage at two ends of the kth oscillation center branch.
ωminOnly a small value is required, and the value range is more than 0 and less than 1, and preferably 0.5 degrees.
The method carries out compensation according to the derivative of the oscillation center branch power, and can reach the inherent potential energy peak value occurrence time of the system earlier than the existing method after compensation, so that the instability of the system is monitored earlier than the existing method based on branch potential energy. The instability fault can be accurately detected,
the accuracy of the local measurement information is analyzed by taking an IEEE39 node system as an embodiment, and the structure of the IEEE39 node system is shown in FIG. 3.
In fig. 3, reference numerals 1-39 denote 39 nodes, reference numeral r-r denotes 10 generators, C1-C2Two cut sets under two examples are shown, in which the system is respectively from C1And C2Where the tear is two coherent (coherent means that all generator power angles vary equally in each region) regions.
Fig. 4 is a graph of the node voltage amplitude across two oscillation center branches (branch 1-2 and branch 8-9). The voltage amplitude of the node 1 is at least 0.432(pu) in the power angle swing process, and the point voltage amplitude of the node 2 is at least 0.470 in the power angle swing process, so that the beta of the branch 1-21And beta20.432 and 0.470, respectively, thus beta1-2Calculated value was 0.451; the beta values of nodes 8 and 9 are also determined in the same way, beta8＝0.293，β9Equal to 0.482, thus beta8-9The calculated value was 0.3875. Fig. 5 is a d σ/d δ curve of the two oscillation center branches, and fig. 5(a) corresponds to 1-2 branches and fig. 5(b) corresponds to 8-9 branches.
The accurate value curve in fig. 5 is obtained by simulating the power angle curve of the generator, calculating the power angle inertia center change rate of the two clusters, and finally obtaining the ratio of the branch phase angle difference change rate to the inertia center. The estimated value curve is calculated according to the set beta parameter by the following formula:
Figure BDA0003080769430000111
the calculation result shows that the method can accurately estimate d sigma/d delta through local measurement, and further estimate dPC/dδ。
The transient power angle instability judging method based on branch potential energy can accurately judge the stability after the influence of the load potential energy on the relative kinetic energy of the generator is improved by utilizing the oscillation center power derivative to compensate, and can accurately distinguish the instability situation from the stability situation even if the transient power angle instability judging method is near the critical generator tripping time.
The stability identification accuracy of the method is analyzed by taking an IEEE39 node as a case. A three-phase transient short-circuit fault occurs at node 24 when the fault duration is 0.117s (denoted as t)f0.117), the system experiences transient power angle instability. The power angle of the system is shown in fig. 6, and the voltage angle difference between the two ends of the network line is shown in fig. 7. When t isfAt 0.116, the system transient is stable, so the critical ablation time is between 0.116 and 0.117.
When the voltage phase angle difference of the two end nodes of all the oscillation center branches is small (deviation is less than 10 degrees compared with a steady state value), the instability judgment method is not started, because the system is stable at the moment. When the voltage angle difference at the two ends of the oscillation center branch circuit is monitored to reach a local extreme value, the instability judging method is not started, because the power angle of the system swings back at the moment, and the instability judging method is started until the phase angle difference at the two ends of all the oscillation center branch circuits deviates from the extreme value by 0.5 degrees.
The dashed and solid lines in fig. 8 indicate that the branch fails to meet and satisfies the instability criterion startup condition, respectively. For the reasons described above, the solid line in fig. 8(a) is divided into 4 segments, and the instability criterion in fig. 8(b) is initiated after 0.26 seconds.
Fig. 9 depicts how to determine whether the system is transient stable in the case of fig. 8 (a). Delta PC+ΔPL2The (approximation) and the 0 value have no intersection, so the instability criterion is not satisfied, and the system stability is judged correctly. Wherein Δ PC+ΔPL2The (approximate) is divided into 3 parts corresponding to the first 3 solid lines in fig. 8 (a). Delta PC+ΔPL2(estimatd) denotes Δ PC+ΔPL2Estimated value of, VPE2And the relative potential energy of the group S and the group A in the double-machine instability mode is shown.
Fig. 10 depicts how to determine whether the system is transient stable in the case of fig. 8 (b). In the lower graph Δ PC+ΔPL2The (approximate) value crosses 0 at point B, corresponding toAnd the instability criterion monitors the moment when the instability criterion of the system occurs. Therefore, the method for judging the instability of the computer can correctly distinguish the stable examples from the unstable examples.
The transient power angle instability judging method based on local measurement considers the influence of potential energy corresponding to load power change on transient stability monitoring, overcomes the defect that the transient power angle instability judging method based on branch potential energy has delay in judging time when the influence of the load potential energy on the relative kinetic energy of the generator is considered, compensates the influence of the load potential energy on the relative kinetic energy of the generator by using the oscillation center power derivative, and can judge the transient power angle instability earlier than the existing method based on the branch potential energy.
The rapidity of the method is analyzed by taking an IEEE39 node as a case. Point a in fig. 10 corresponds to the NRP point in fig. 11, and point C corresponds to a point at which the following instability criterion (the original transient instability discrimination method based on branch potential energy) holds.
Figure BDA0003080769430000121
In FIG. 11,. DELTA.Ploss2Representing the equivalent power loss, Δ P, inside the coherent networkClossRepresenting the equivalent power loss, Δ P, between two coherent networksC+ΔPL2+ΔPloss2+ΔPClossRepresenting the active component, δ, contributing to the network potential0Representing the steady state operating point, δ, of the equivalent systems-δAThe power angle difference between the group S and the group a, i.e., the power angle of the equivalent system, is shown.
The judging method of the invention advances the system transient instability judgment from the time corresponding to the point C in the graph 10 to the time corresponding to the point B, and is slightly later than the point A.
The temporal difference in discrimination instability between the original discrimination method and the improved method of the present invention is compared in fig. 12.
The method judges the system instability at least 0.24s in advance. Fig. 13 compares the difference between the power angle difference of the inertia centers of two clusters and the phase angle difference between the two ends of the oscillation center branch when the original discrimination method and the method herein monitor the system instability. The method can monitor the transient instability of the system under the conditions of a smaller power angle swing-out angle and a smaller branch swing-out angle, and the transient instability can be monitored only when the power angle of the generator and the branch swing-out angle are close to 180 degrees in the original method.
Simulation finds that the transient power angle instability judging method based on branch potential energy can accurately judge the stability after the influence of the oscillation center power derivative compensation load potential energy on the relative kinetic energy of the generator is improved, and the method can accurately distinguish instability situations from stable situations even if the transient power angle instability judging method is near the critical generator tripping time.
The transient power angle instability judging method based on local measurement considers the influence of potential energy corresponding to load power change on transient stability monitoring, overcomes the defect that the transient power angle instability judging method based on branch potential energy has delay in judging time when the influence of the load potential energy on the relative kinetic energy of the generator is considered, compensates the influence of the load potential energy on the relative kinetic energy of the generator by using the oscillation center power derivative, and can judge the transient power angle instability earlier than the existing method based on the branch potential energy.
The invention also provides a transient power angle instability distinguishing system based on local measurement, which comprises:
the power flow parameter acquisition module is used for acquiring power flow parameters of each oscillation center branch in the power system;
the first power variation calculation module is used for calculating power variations generated by all the oscillation center branches along with transient power angle variations of the generator according to the load flow parameters of all the oscillation center branches and taking the power variations as first power variations;
the second power variation calculation module is used for calculating power variation of the load injection system generated along with transient power angle variation of the generator by using a local measurement method according to the load flow parameters of each oscillation center branch circuit, and the power variation is used as second power variation;
and the power system instability judgment module is used for judging whether the power system is unstable or not by using the transient power angle instability criterion according to the first power variable quantity and the second power variable quantity.
The first power variation calculating module specifically includes:
a first power variation calculation submodule for calculating the power flow parameter of each oscillation center branch according to the formula
Figure BDA0003080769430000131
Calculating power variation generated by all oscillation center branches along with transient power angle variation of the generator as first power variation;
wherein, Δ PCIs a first power variation, PCFor the active power flow of all the oscillation center branches,
Figure BDA0003080769430000133
for the steady state value, P, of the active power flow of all oscillation center branchesCcFor all power components, P, of the central branch of oscillation that do not vary with the power angle of the generatorC maxFor all power components of the oscillation center branch that vary with the power angle of the generator,
Figure BDA0003080769430000132
the steady-state values of the equivalent power electromotive forces of the group S and the group A respectively,
Figure BDA0003080769430000141
is the conjugate of the steady state value of the equivalent source emf of group a,
Figure BDA0003080769430000142
is the intermediate variable(s) of the variable,
Figure BDA0003080769430000143
YLGSis S group equivalent admittance, ZSSIs the self-impedance of the S group in the node impedance matrix, GSAThe conductance component of the equivalent admittance of the crosstie,
Figure BDA0003080769430000144
mutual impedance of S group and A group in node impedance matrixThe yoke is provided with a plurality of yokes,
Figure BDA0003080769430000145
is the conjugate of the group a equivalent admittance,
Figure BDA0003080769430000146
is the conjugate of the equivalent admittance of the crosstie,
Figure BDA0003080769430000147
is the self-impedance conjugate of group A in the node impedance matrix, ZASIs the mutual impedance of group S and group A in the node impedance matrix, YASIs equivalent admittance of a connecting line, delta is equivalent power angle of the power system, and gamma isCIs the power angle variation of the generator,
Figure BDA0003080769430000148
angle () is a phase angle function.
The second power variation calculating module specifically includes:
a first parameter calculation submodule for calculating a power flow parameter of each oscillation center branch by using a formula of alpha to PL2 max/PC maxCalculating a first parameter; wherein alpha is a first parameter, PL2 maxIs the combined power of the power system, PC maxThe power components of all the oscillation center branches are changed along with the power angle of the generator;
a first derivative calculation submodule for using the method of local measurement using the formula
Figure BDA0003080769430000149
And
Figure BDA00030807694300001410
calculating the derivative of the active power flow of all the oscillation center branches to the power angle of the generator; wherein the content of the first and second substances,
Figure BDA00030807694300001411
the derivative of the active power flow of all the oscillation center branches to the power angle of the generator is shown, sigma is the phase angle difference of the voltages at two ends of the oscillation center branches in a steady state,
Figure BDA00030807694300001412
the derivative of the active power flow of all the oscillation center branches to the phase angle difference of the voltages at two ends of the oscillation center branches in a steady state,
Figure BDA00030807694300001413
the ratio of the phase angle difference change rate of the branch to the inertia center, beta is the average value of the phase angles at two ends of the oscillation center branch, and beta is (beta)1+β2)/2，β1And beta2The voltage values are per unit values of the amplitude values when the phase angle of the branch is swung open to 180 degrees at two ends of the oscillation center branch;
a second derivative calculation submodule for utilizing a formula according to the load flow parameters of each oscillation center branch
Figure BDA00030807694300001414
Calculating the derivative of the steady-state values of the active power flows of all the oscillation center branches to the power angle of the generator; wherein the content of the first and second substances,
Figure BDA00030807694300001415
the derivative of the steady-state values of the active power flows of all the oscillation center branches to the power angle of the generator is obtained;
a second power variation calculation submodule, configured to calculate a derivative of the power angle of the generator according to the first parameter, the derivatives of the active power flows of all the oscillation center branches to the power angle of the generator, and the steady-state values of the active power flows of all the oscillation center branches, using a formula
Figure BDA00030807694300001416
Calculating power variation generated by the load injection system along with transient power angle variation of the generator as second power variation; wherein, Δ PL2Is the second power variation.
The transient power angle instability criterion comprises the following steps:
Figure BDA0003080769430000151
wherein the content of the first and second substances,
Figure BDA0003080769430000152
is the phase angle difference, sigma, of the voltage at two ends of the kth oscillation center branch in steady statek(t) is the phase angle difference of the voltages at two ends of the kth oscillation center branch at the time t, sigmaminAnd C is the total number of the oscillation center branches in the load injection system.
The transient power angle instability criterion further comprises:
Figure BDA0003080769430000153
wherein, min (σ)k) And max (σ)k) Local minimum and maximum of phase angle difference of voltage at two ends of kth oscillation center branch, omegaminIs a phase angle difference threshold, σkIs the phase angle difference of the voltage at two ends of the kth oscillation center branch.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.

Claims (10)

1. A transient power angle instability distinguishing method based on local measurement is characterized by comprising the following steps:
collecting the power flow parameters of each oscillation center branch in the power system;
calculating power variation generated by all the oscillation center branches along with transient power angle variation of the generator according to the load flow parameters of all the oscillation center branches, and taking the power variation as first power variation;
calculating power variation of the load injection system along with transient power angle variation of the generator by using a local measurement method according to the load flow parameters of each oscillation center branch circuit, and taking the power variation as second power variation;
and judging whether the power system is unstable or not by using a transient power angle instability criterion according to the first power variation and the second power variation.
2. The method according to claim 1, wherein the calculating power variation of all the oscillation center branches generated along with the transient power angle variation of the generator according to the power flow parameter of each oscillation center branch as a first power variation specifically includes:
according to the power flow parameters of each oscillation center branch, using a formula
Figure FDA0003080769420000011
Calculating power variation generated by all oscillation center branches along with transient power angle variation of the generator as first power variation;
wherein, Δ PCIs a first power variation, PCFor the active power flow of all the oscillation center branches,
Figure FDA00030807694200000112
for the steady state value, P, of the active power flow of all oscillation center branchesCcFor all power components, P, of the central branch of oscillation that do not vary with the power angle of the generatorCmaxFor all power components of the oscillation center branch that vary with the power angle of the generator,
Figure FDA0003080769420000012
Figure FDA0003080769420000013
the steady-state values of the equivalent power electromotive forces of the group S and the group A respectively,
Figure FDA0003080769420000014
is the conjugate of the steady state value of the equivalent source emf of group a,
Figure FDA0003080769420000015
is the intermediate variable(s) of the variable,
Figure FDA0003080769420000016
YLGSis S group equivalent admittance, ZSSIs the self-impedance of the S group in the node impedance matrix, GSAThe conductance component of the equivalent admittance of the crosstie,
Figure FDA0003080769420000017
the mutual impedance conjugates of the S and a groups in the nodal impedance matrix,
Figure FDA0003080769420000018
is the conjugate of the group a equivalent admittance,
Figure FDA0003080769420000019
is the conjugate of the equivalent admittance of the crosstie,
Figure FDA00030807694200000110
is the self-impedance conjugate of group A in the node impedance matrix, ZASIs the mutual impedance of group S and group A in the node impedance matrix, YASIs equivalent admittance of a connecting line, delta is equivalent power angle of the power system, and gamma isCIs the power angle variation of the generator,
Figure FDA00030807694200000111
angle () is a phase angle function.
3. The method according to claim 2, wherein the calculating a power variation generated by the load injection system along with the transient power angle variation of the generator as a second power variation by using a local measurement method according to the power flow parameter of each oscillation center branch specifically comprises:
according to the power flow parameter of each oscillation center branch, using the formula alpha as PL2max/PCmaxCalculating a first parameter; wherein alpha is a first parameter, PL2maxIs the composite power of the power system;
using local measurement, using formulas
Figure FDA0003080769420000021
Calculating the derivative of the active power flow of all the oscillation center branches to the power angle of the generator; wherein the content of the first and second substances,
Figure FDA0003080769420000022
the derivative of the active power flow of all the oscillation center branches to the power angle of the generator is shown, sigma is the phase angle difference of the voltages at two ends of the oscillation center branches in a steady state,
Figure FDA0003080769420000023
the derivative of the active power flow of all the oscillation center branches to the phase angle difference of the voltages at two ends of the oscillation center branches in a steady state,
Figure FDA0003080769420000024
the ratio of the phase angle difference change rate of the branch to the inertia center, beta is the average value of the phase angles at two ends of the oscillation center branch, and beta is (beta)1+β2)/2，β1And beta2The voltage values are per unit values of the amplitude values when the phase angle of the branch is swung open to 180 degrees at two ends of the oscillation center branch;
according to the power flow parameters of each oscillation center branch, using a formula
Figure FDA0003080769420000025
Calculating the derivative of the steady-state values of the active power flows of all the oscillation center branches to the power angle of the generator; wherein the content of the first and second substances,
Figure FDA0003080769420000026
the derivative of the steady-state values of the active power flows of all the oscillation center branches to the power angle of the generator is obtained;
according to the first parameter, the derivatives of the active power flows of all the oscillation center branches to the power angle of the generator and the steady-state values of the active power flows of all the oscillation center branches to the power angle of the generator, a formula is utilized
Figure FDA0003080769420000027
Calculating power variation generated by the load injection system along with transient power angle variation of the generator as second power variation; wherein, Δ PL2Is the second power variation.
4. The method of claim 3, wherein the criterion of transient power angle instability comprises:
Figure FDA0003080769420000028
wherein the content of the first and second substances,
Figure FDA0003080769420000029
is the phase angle difference, sigma, of the voltage at two ends of the kth oscillation center branch in steady statek(t) is the phase angle difference of the voltages at two ends of the kth oscillation center branch at the time t, sigmaminAnd C is the total number of the oscillation center branches in the load injection system.
5. The method as claimed in claim 4, wherein the criterion of transient power angle instability further comprises:
Figure FDA0003080769420000031
wherein, min (σ)k) And max (σ)k) Local minimum and maximum of phase angle difference of voltage at two ends of kth oscillation center branch, omegaminIs a phase angle difference threshold, σkIs the phase angle difference of the voltage at two ends of the kth oscillation center branch.
6. A transient power angle instability discrimination system based on local measurement, the system comprising:
the power flow parameter acquisition module is used for acquiring power flow parameters of each oscillation center branch in the power system;
the first power variation calculation module is used for calculating power variations generated by all the oscillation center branches along with transient power angle variations of the generator according to the load flow parameters of all the oscillation center branches and taking the power variations as first power variations;
the second power variation calculation module is used for calculating power variation of the load injection system generated along with transient power angle variation of the generator by using a local measurement method according to the load flow parameters of each oscillation center branch circuit, and the power variation is used as second power variation;
and the power system instability judgment module is used for judging whether the power system is unstable or not by using a transient power angle instability criterion according to the first power variable quantity and the second power variable quantity.
7. The system according to claim 6, wherein the first power variation calculating module specifically includes:
a first power variation calculation submodule for calculating the power flow parameter of each oscillation center branch according to the formula
Figure FDA0003080769420000032
Calculating the transient power angles of all oscillation center branches along with the generatorChanging the generated power variation as a first power variation;
wherein, Δ PCIs a first power variation, PCFor the active power flow of all the oscillation center branches,
Figure FDA0003080769420000033
for the steady state value, P, of the active power flow of all oscillation center branchesCcFor all power components, P, of the central branch of oscillation that do not vary with the power angle of the generatorCmaxFor all power components of the oscillation center branch that vary with the power angle of the generator,
Figure FDA0003080769420000041
Figure FDA0003080769420000042
the steady-state values of the equivalent power electromotive forces of the group S and the group A respectively,
Figure FDA0003080769420000043
is the conjugate of the steady state value of the equivalent source emf of group a,
Figure FDA0003080769420000044
is the intermediate variable(s) of the variable,
Figure FDA0003080769420000045
YLGSis S group equivalent admittance, ZSSIs the self-impedance of the S group in the node impedance matrix, GSAThe conductance component of the equivalent admittance of the crosstie,
Figure FDA0003080769420000046
the mutual impedance conjugates of the S and a groups in the nodal impedance matrix,
Figure FDA0003080769420000047
is the conjugate of the group a equivalent admittance,
Figure FDA0003080769420000048
is the conjugate of the equivalent admittance of the crosstie,
Figure FDA0003080769420000049
is the self-impedance conjugate of group A in the node impedance matrix, ZASIs the mutual impedance of group S and group A in the node impedance matrix, YASIs equivalent admittance of a connecting line, delta is equivalent power angle of the power system, and gamma isCIs the power angle variation of the generator,
Figure FDA00030807694200000410
angle () is a phase angle function.
8. The system according to claim 6, wherein the second power variation calculating module specifically includes:
a first parameter calculation submodule for calculating a power flow parameter of each oscillation center branch by using a formula of alpha to PL2max/PCmaxCalculating a first parameter; wherein alpha is a first parameter, PL2maxIs the combined power of the power system, PCmaxThe power components of all the oscillation center branches are changed along with the power angle of the generator;
a first derivative calculation submodule for using the method of local measurement using the formula
Figure FDA00030807694200000411
And
Figure FDA00030807694200000412
calculating the derivative of the active power flow of all the oscillation center branches to the power angle of the generator; wherein the content of the first and second substances,
Figure FDA00030807694200000413
the derivative of the active power flow of all the oscillation center branches to the power angle of the generator is shown, sigma is the phase angle difference of the voltages at two ends of the oscillation center branches in a steady state,
Figure FDA00030807694200000414
the derivative of the active power flow of all the oscillation center branches to the phase angle difference of the voltages at two ends of the oscillation center branches in a steady state,
Figure FDA00030807694200000415
the ratio of the phase angle difference change rate of the branch to the inertia center, beta is the average value of the phase angles at two ends of the oscillation center branch, and beta is (beta)1+β2)/2，β1And beta2The voltage values are per unit values of the amplitude values when the phase angle of the branch is swung open to 180 degrees at two ends of the oscillation center branch;
a second derivative calculation submodule for utilizing a formula according to the load flow parameters of each oscillation center branch
Figure FDA00030807694200000416
Calculating the derivative of the steady-state values of the active power flows of all the oscillation center branches to the power angle of the generator; wherein the content of the first and second substances,
Figure FDA00030807694200000417
the derivative of the steady-state values of the active power flows of all the oscillation center branches to the power angle of the generator is obtained;
a second power variation calculation submodule, configured to calculate a derivative of the power angle of the generator according to the first parameter, the derivatives of the active power flows of all the oscillation center branches to the power angle of the generator, and the steady-state values of the active power flows of all the oscillation center branches, using a formula
Figure FDA0003080769420000051
Calculating power variation generated by the load injection system along with transient power angle variation of the generator as second power variation; wherein, Δ PL2Is the second power variation.
9. The system of claim 8, wherein the transient power angle instability criterion comprises:
Figure FDA0003080769420000052
wherein the content of the first and second substances,
Figure FDA0003080769420000053
is the phase angle difference, sigma, of the voltage at two ends of the kth oscillation center branch in steady statek(t) is the phase angle difference of the voltages at two ends of the kth oscillation center branch at the time t, sigmaminAnd C is the total number of the oscillation center branches in the load injection system.
10. The system of claim 9, wherein the criterion for transient power angle instability further comprises:
Figure FDA0003080769420000054
wherein, min (σ)k) And max (σ)k) Local minimum and maximum of phase angle difference of voltage at two ends of kth oscillation center branch, omegaminIs a phase angle difference threshold, σkIs the phase angle difference of the voltage at two ends of the kth oscillation center branch.
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