CN112115412A - Method and system for determining stability of power system based on frequency shift phasor - Google Patents
Method and system for determining stability of power system based on frequency shift phasor Download PDFInfo
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Abstract
The invention discloses a method and a system for determining the stability of a power system based on frequency shift phasors, and belongs to the technical field of stability analysis of the power system. The method comprises the following steps: determining the relation between the dq impedance and the sequence impedance according to the dq impedance model and the sequence impedance model; acquiring four elements of a time domain sub/super synchronous impedance model, and establishing the time domain sub/super synchronous impedance model according to the four elements; obtaining a phasor domain subsynchronous/supersynchronous impedance model by stepping phasor on the disturbance of the voltage/current; determining the relation among a dq impedance model, a sequence impedance model, a time domain subsynchronous/supersynchronous impedance model and a phasor domain subsynchronous/supersynchronous impedance model; and judging by using a generalized Nyquist criterion to determine the stability of the power system. Compared with the traditional dq domain impedance model and the sequence domain impedance model, the obtained frequency shift phasor-based flexible direct current wide frequency domain impedance model is more suitable for stability analysis of the S2SI phenomenon, is more targeted, and has great engineering practical value.
Description
Technical Field
The present invention relates to the field of power system stability analysis technologies, and in particular, to a method and a system for determining power system stability based on frequency shift phasors.
Background
With the rapid development of flexible direct-current power transmission, the broadband interaction between a fan and an alternating-current power grid becomes more serious, and different types of broadband oscillation phenomena occur, such as sub-synchronous resonance (SSR), sub-synchronous control interaction (SSCI), a large wind farm, and ultra-low frequency oscillation between the flexible direct-current power grid and the alternating-current power grid. SSR has been studied for decades, but in recent years, sub/super-synchronous oscillation (S2 SO) events caused by broadband interaction between the converter and the large ac grid have occurred worldwide, such as 2.5Hz/97.5Hz sub/super-synchronous interaction (S2 SI) events of the south china grid, 1000Hz oscillation events caused by broadband interaction between the flexible dc network and the large ac grid, and so on.
The occurrence mechanism and influencing factors of the S2SI phenomenon are greatly different from the traditional SSR phenomenon, and the academic community and the industrial community carry out a lot of analyses on the electromagnetic stability of the S2SI phenomenon, wherein typical methods comprise a characteristic value analysis method and an impedance analysis method. The eigenvalue analysis method has obvious defects, such as the requirement of knowing the detailed structure of each part of the whole system, and the processing capacity of the method for the black box or gray box problem is insufficient.
Disclosure of Invention
In view of the above problem, the present invention provides a method for determining stability of an electric power system based on frequency shift phasors, including:
acquiring parameters of a power system, establishing a dq impedance model and a sequence impedance model according to the parameters of the power system, and determining the relation between dq impedance and sequence impedance according to the dq impedance model and the sequence impedance model;
establishing an admittance matrix model of subsynchronous/supersynchronous frequency voltage and current according to the parameters of the power system, acquiring four elements of a time domain subsynchronous/supersynchronous impedance model according to the admittance matrix model of the subsynchronous/supersynchronous frequency voltage and current, and establishing the time domain subsynchronous/supersynchronous impedance model according to the four elements;
obtaining a phasor domain subsynchronous/supersynchronous impedance model by stepping phasor on the disturbance of the voltage/current;
determining the relation among a dq impedance model, a sequence impedance model, a time domain subsynchronous/supersynchronous impedance model and a phasor domain subsynchronous/supersynchronous impedance model;
and judging the relation between the dq impedance and the sequence impedance and the relation between a dq impedance model, a sequence impedance model, a time domain subsynchronous/supersynchronous impedance model and a phasor domain subsynchronous/supersynchronous impedance model by using generalized Nyquist data to determine the stability of the power system.
Optionally, the method further includes: after a disturbance at a certain frequency ω on the dq axis, a subsynchronous component is generated at ω - ω 1 and a supersynchronous component is generated at ω + ω 1.
Optionally, determining the stability of the power system includes:
determining a dq impedance matrix, a sequence impedance matrix, a time domain subsynchronous/supersynchronous impedance matrix and a phasor domain subsynchronous/supersynchronous impedance matrix of the power system according to a generalized Nyquist criterion;
and determining characteristic values of the dq impedance matrix, the sequence impedance matrix, the time domain subsynchronous/supersynchronous impedance matrix and the phasor domain subsynchronous/supersynchronous impedance matrix according to the dq impedance matrix, the sequence impedance matrix, the time domain subsynchronous/supersynchronous impedance matrix and the phasor domain subsynchronous/supersynchronous impedance matrix, and judging the stability of the power system according to the characteristic values.
Optionally, if the characteristic locus of the eigenvalue of the dq matrix surrounds the preset point, the power system is unstable, and if the characteristic locus does not surround the preset point, the power system is stable.
The invention also provides a system for determining the stability of the power system based on the frequency shift phasor, which comprises the following steps:
the first modeling module is used for acquiring parameters of the power system, establishing a dq impedance model and a sequence impedance model according to the parameters of the power system, and determining the relation between the dq impedance and the sequence impedance according to the dq impedance model and the sequence impedance model;
the second modeling module is used for establishing an admittance matrix model of subsynchronous/supersynchronous frequency voltage and current according to the parameters of the power system, acquiring four elements of a time domain subsynchronous/supersynchronous impedance model according to the admittance matrix model of the subsynchronous/supersynchronous frequency voltage and current, and establishing the time domain subsynchronous/supersynchronous impedance model according to the four elements;
the third modeling module is used for acquiring a phasor domain secondary/super-synchronous impedance model by shifting the step phasor to the disturbance of the voltage/current;
the analysis module is used for determining the relation among the dq impedance model, the sequence impedance model, the time domain subsynchronous/supersynchronous impedance model and the phasor domain subsynchronous/supersynchronous impedance model;
and the stability determining module is used for judging the relation between the dq impedance and the sequence impedance and the relation between the dq impedance model, the sequence impedance model, the time domain subsynchronous/supersynchronous impedance model and the phasor domain subsynchronous/supersynchronous impedance model by using a generalized Nyquist criterion to determine the stability of the power system.
Optionally, the first modeling module is further configured to: after a disturbance at a certain frequency ω on the dq axis, a subsynchronous component is generated at ω - ω 1 and a supersynchronous component is generated at ω + ω 1.
Optionally, determining the stability of the power system includes:
determining a dq impedance matrix, a sequence impedance matrix, a time domain subsynchronous/supersynchronous impedance matrix and a phasor domain subsynchronous/supersynchronous impedance matrix of the power system according to a generalized Nyquist criterion;
and determining characteristic values of the dq impedance matrix, the sequence impedance matrix, the time domain subsynchronous/supersynchronous impedance matrix and the phasor domain subsynchronous/supersynchronous impedance matrix according to the dq impedance matrix, the sequence impedance matrix, the time domain subsynchronous/supersynchronous impedance matrix and the phasor domain subsynchronous/supersynchronous impedance matrix, and judging the stability of the power system according to the characteristic values.
Optionally, if the characteristic locus of the eigenvalue of the dq matrix surrounds the preset point, the power system is unstable, and if the characteristic locus does not surround the preset point, the power system is stable.
Aiming at the sub-supersynchronous interaction phenomenon of the power system, a time domain sub-supersynchronous impedance model and a phasor domain sub-supersynchronous impedance model based on the frequency shift phasor are established to carry out stability analysis on the system, the simulation result obtained by analysis is highly consistent with the actual test result, and compared with the traditional dq domain impedance model and the sequence domain impedance model, the flexible direct current wide frequency domain impedance model based on the frequency shift phasor obtained by the invention is more suitable for the stability analysis of the S2SI phenomenon, is more targeted and has great engineering practical value.
Drawings
FIG. 1 is a flow chart of a method for determining power system stability based on frequency shift phasors in accordance with the present invention;
FIG. 2 is a model diagram of a method for determining power system stability based on frequency shift phasors in accordance with the present invention;
FIG. 3 is a comparison graph of sequence domain impedance and dq domain impedance results for a method of determining power system stability based on frequency shift phasors in accordance with the present invention;
FIG. 4 is a method S for determining the stability of an electric power system based on frequency shift phasors according to the present invention2SIM and SF-S2Comparing the simulation and measurement results of the SIM impedance model;
fig. 5 is a block diagram of a system for determining power system stability based on frequency-shifted phasors in accordance with the present invention.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the invention and to fully convey the scope of the invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
The invention provides a method for determining the stability of a power system based on frequency shift phasors, which comprises the following steps of:
after a disturbance at a certain frequency ω on the dq axis, a subsynchronous component is generated at ω - ω 1 and a supersynchronous component is generated at ω + ω 1.
Acquiring parameters of a power system, establishing a dq impedance model and a sequence impedance model according to the parameters of the power system, and determining the relation between dq impedance and sequence impedance according to the dq impedance model and the sequence impedance model;
establishing an admittance matrix model of subsynchronous/supersynchronous frequency voltage and current according to the parameters of the power system, acquiring four elements of a time domain subsynchronous/supersynchronous impedance model according to the admittance matrix model of the subsynchronous/supersynchronous frequency voltage and current, and establishing the time domain subsynchronous/supersynchronous impedance model according to the four elements;
obtaining a phasor domain subsynchronous/supersynchronous impedance model by stepping phasor on the disturbance of the voltage/current;
determining the relation among a dq impedance model, a sequence impedance model, a time domain subsynchronous/supersynchronous impedance model and a phasor domain subsynchronous/supersynchronous impedance model;
and judging the relation between the dq impedance and the sequence impedance and the relation between a dq impedance model, a sequence impedance model, a time domain subsynchronous/supersynchronous impedance model and a phasor domain subsynchronous/supersynchronous impedance model by using generalized Nyquist data to determine the stability of the power system.
Determining power system stability, comprising:
determining a dq impedance matrix, a sequence impedance matrix, a time domain subsynchronous/supersynchronous impedance matrix and a phasor domain subsynchronous/supersynchronous impedance matrix of the power system according to a generalized Nyquist criterion;
and determining characteristic values of the dq impedance matrix, the sequence impedance matrix, the time domain subsynchronous/supersynchronous impedance matrix and the phasor domain subsynchronous/supersynchronous impedance matrix according to the dq impedance matrix, the sequence impedance matrix, the time domain subsynchronous/supersynchronous impedance matrix and the phasor domain subsynchronous/supersynchronous impedance matrix, and judging the stability of the power system according to the characteristic values.
If the characteristic locus of the characteristic value of the dq matrix surrounds the preset point, the power system is unstable, and if the characteristic locus does not surround the preset point, the power system is stable.
The invention is further illustrated by the following examples:
1) establishing the relation between the dq impedance and the sequence impedance:
the perturbation at a certain frequency ω on the dq axis will be at ω - ω1To study the coupling frequency in dq/sequence domain, a model of dq or sequence domain impedance, i.e. Y, needs to be defineddq(s) and Ypn(s)。
1-1) establishing a dq impedance model:
suppose that the grid voltage U appears with an amplitude of delta U and a frequency of s + j omega1Can be expressed as a rotation vector in the α β coordinate system as follows:
wherein, ω is1Representing power frequency angular frequency, wherein s-j omega represents the difference value between the disturbance frequency and the power frequency, and theta 0 represents an initial phase;
by means of twiddle factors
Transforming equation (1) into dq coordinate system, the time-varying vector of the disturbance voltage can be expressed as:
the voltage and current in the dq domain satisfy the following dq impedance relationship:
wherein, Delta Ud(s),ΔUq(s),ΔId(s) and Δ Iq(s) respectively representing a disturbance voltage and a current phasor corresponding to the frequency s;
1-2) establishing a sequence impedance model:
according to step 1-1), in combination with the following formula:
can derive equivalent expression
Wherein:
it can be seen that in the dq coordinate system, there is a coupling relationship between the vector of the voltage current disturbance and the conjugate vector thereof, and there will be a positive-negative sequence coupling phenomenon in the α β coordinate system or the abc coordinate system, and at this time, a sequence impedance (i.e. pn impedance) matrix can be obtained
Wherein, s ═ j ω represents the angular frequency difference of the disturbance quantity relative to the power frequency;
1-3) obtaining the relation between dq impedance and sequence impedance:
the dq-domain and sequence-domain impedance models obtained according to the steps 1-1) and 1-2), namely Ydq(s) and Ypn(s) satisfying the following relationship:
wherein:
the relation between the dq impedance and the sequence impedance is established, and a foundation is laid for subsequent derivation.
2) Establishing a time domain sub/super synchronous impedance model:
2-1) establishing an admittance matrix model of subsynchronous/supersynchronous frequency voltage and current
To study the subsynchronous/supersynchronous interaction, the relationship between voltage and current at subsynchronous/supersynchronous frequencies was modeled as a 2 x 2 admittance matrix:
wherein, Ysub,sup(S) is defined as the subsynchronous/supersynchronous interaction (S)2SI) frequency coupling model (S)2SIM) of the model, Y11(s) reflects a voltage disturbance U1(s) response to Current I1(s); y is12(s) reflects voltage disturbances
In response to current I1(s); y is21(s) reflects a voltage disturbance U1(s) response to Current
The influence of (a); y is22(s) reflects voltage disturbances
Response to current
The influence of (c).
Thus, S2The size ratio of off-diagonal elements to diagonal elements of the SI frequency coupling model can reflect the degree of frequency coupling;
2-2) obtaining four elements of a time domain sub/super synchronous impedance model:
from the definition of the self-impedance of the positive sequence component, it can be known that:
wherein, Ip(s+jω1)，Up(s+jω1) Respectively corresponding to frequency of omega + omega1Positive sequence current and voltage disturbances.
From this, the Y of the time domain sub/super-synchronous impedance model11The(s) element can be obtained by positive sequence impedance frequency shift, namely:
similarly, according to the definition of positive and negative sequence impedance, it can be known
Other elements of the time-domain sub/super-synchronous impedance model can thus be derived:
2-3) establishing a time domain subsynchronous/supersynchronous impedance model expression
According to step 2-1) and step 2-2), by aligning the impedance model Ypn(s) to obtain a time domain subsynchronous/supersynchronous impedance model;
3) establishing a phasor domain subsynchronous/supersynchronous impedance model:
the subsynchronous/supersynchronous impedance model can be obtained by frequency-shifting phasors from voltage/current disturbance;
3-1) A typical signal with frequency ω can be modeled in the form of a phase shift:
where s ═ j ω.
Representing the frequency-shifted phasor of S (S, t).
The signal can be regarded as a signal obtained by shifting the frequency bandwidth of the S (S, t) signal by 50Hz to the right;
3-2) time-domain perturbation and e-jθThe product of (d) may represent the form of the frequency shift:
where s ═ j ω denotes the frequency of the subsynchronous component. θ ═ j ω1,ω1＝2πf1100 pi rad/s. As indicated above, the phasors are frequency shifted
Can be defined as that Δ U (s, t)/Δ I (s, t) is shifted left by 50 Hz.
3-3) according to the concept of frequency-shift phasors, the elements of the S2SIM can be derived in the form of frequency-shift phasors as:
3-4) finally, sub/super-synchronous impedance model (SF-S) based on frequency-shifted phasors2SIM)
The following can be obtained from a frequency-shift phasor-based sequence impedance model:
wherein the content of the first and second substances,
4) stability analysis was performed using the Generalized Nyquist Criterion (GNC):
from step 1 to step 3, the relationship of dq impedance, sequence impedance, time domain subsynchronous/supersynchronous impedance and phasor domain subsynchronous/supersynchronous impedance models is obtained, as shown in fig. 2;
to analyze the subsynchronous/supersynchronous interactions (S)2SI) phenomenon, and evaluating electromagnetic stability of different influencing factors, such as parameters of PLL, controller, and thyristor of ac power grid, by using Generalized Nyquist Criterion (GNC).
4-1) according to the definition of GNC, the Ldq(s) matrix of the system can be obtained:
wherein R isgrid,LgridThe resistance and the inductance of the alternating current network Thevenin respectively correspond to the alternating current network. It should be noted that if L isdqNeither of the two characteristic traces of(s) encompasses the point (-1, j0), the system is considered stable, otherwise the system will be unstable.
4-2) similar to step 3-1), L can be obtaineddq(s),Lpn(s),Lsub,super(s) and
expression (c):
in step 1, according to (8), Lpn(s) and Ldq(S) are similar in the S-domain, they have the same eigenvalues, and are derived from step 2 and step 3, S2SIM,SF-S2The characteristic value of the SIM and the characteristic value of the sequence impedance model have the following relations:
Ldq(s),Lpn(s),Lsub,super(s) and
corresponding to the same characteristic trace measurement maps as shown in fig. 3 and 4, or the same nyquist diagram, so that the stability of the system can be analyzed according to the GNC method.
The present invention further provides a system 200 for determining stability of an electric power system based on frequency-shifted phasors, as shown in fig. 5, including:
the first modeling module 201 is used for acquiring parameters of the power system, establishing a dq impedance model and a sequence impedance model according to the parameters of the power system, and determining the relationship between dq impedance and sequence impedance according to the dq impedance model and the sequence impedance model;
the second modeling module 202 is used for establishing an admittance matrix model of subsynchronous/supersynchronous frequency voltage and current according to the parameters of the power system, acquiring four elements of a time domain subsynchronous/supersynchronous impedance model according to the admittance matrix model of the subsynchronous/supersynchronous frequency voltage and current, and establishing the time domain subsynchronous/supersynchronous impedance model according to the four elements;
the third modeling module 203 acquires a phasor domain subsynchronous/supersynchronous impedance model by stepping phasor on the disturbance of the voltage/current;
the analysis module 204 determines the relationship among the dq impedance model, the sequence impedance model, the time domain subsynchronous/supersynchronous impedance model and the phasor domain subsynchronous/supersynchronous impedance model;
the stability determination module 205 determines a relationship between the dq impedance and the sequence impedance, and a relationship between the dq impedance model, the sequence impedance model, the time domain sub/super synchronous impedance model, and the phasor domain sub/super synchronous impedance model, by using a generalized nyquist criterion, and determines the stability of the power system.
A first modeling module 201, further configured to: after a disturbance at a certain frequency ω on the dq axis, a subsynchronous component is generated at ω - ω 1 and a supersynchronous component is generated at ω + ω 1.
Determining power system stability, comprising:
determining a dq impedance matrix, a sequence impedance matrix, a time domain subsynchronous/supersynchronous impedance matrix and a phasor domain subsynchronous/supersynchronous impedance matrix of the power system according to a generalized Nyquist criterion;
and determining characteristic values of the dq impedance matrix, the sequence impedance matrix, the time domain subsynchronous/supersynchronous impedance matrix and the phasor domain subsynchronous/supersynchronous impedance matrix according to the dq impedance matrix, the sequence impedance matrix, the time domain subsynchronous/supersynchronous impedance matrix and the phasor domain subsynchronous/supersynchronous impedance matrix, and judging the stability of the power system according to the characteristic values.
If the characteristic locus of the characteristic value of the dq matrix surrounds the preset point, the power system is unstable, and if the characteristic locus does not surround the preset point, the power system is stable.
Aiming at the sub-supersynchronous interaction phenomenon of the power system appearing in recent years, the method establishes a time domain sub/supersynchronous impedance model and a phasor domain sub/supersynchronous impedance model based on frequency shift phasor to carry out stability analysis on the system, the simulation result obtained by analysis is highly consistent with the actual test result, and compared with the traditional dq domain impedance model and the sequence domain impedance model, the flexible direct-current broadband impedance model based on the frequency shift phasor obtained by the method is more suitable for S2The stability analysis of the SI phenomenon is more targeted, and has great engineering practical value.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein. The scheme in the embodiment of the application can be implemented by adopting various computer languages, such as object-oriented programming language Java and transliterated scripting language JavaScript.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While the preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all alterations and modifications as fall within the scope of the application.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to encompass such modifications and variations.
Claims (8)
1. A method of determining power system stability based on frequency-shifted phasors, the method comprising:
acquiring parameters of a power system, establishing a dq impedance model and a sequence impedance model according to the parameters of the power system, and determining the relation between dq impedance and sequence impedance according to the dq impedance model and the sequence impedance model;
establishing an admittance matrix model of subsynchronous/supersynchronous frequency voltage and current according to the parameters of the power system, acquiring four elements of a time domain subsynchronous/supersynchronous impedance model according to the admittance matrix model of the subsynchronous/supersynchronous frequency voltage and current, and establishing the time domain subsynchronous/supersynchronous impedance model according to the four elements;
obtaining a phasor domain subsynchronous/supersynchronous impedance model by stepping phasor on the disturbance of the voltage/current;
determining the relation among a dq impedance model, a sequence impedance model, a time domain subsynchronous/supersynchronous impedance model and a phasor domain subsynchronous/supersynchronous impedance model;
and judging the relation between the dq impedance and the sequence impedance and the relation between a dq impedance model, a sequence impedance model, a time domain subsynchronous/supersynchronous impedance model and a phasor domain subsynchronous/supersynchronous impedance model by using a generalized Nyquist criterion to determine the stability of the power system.
2. The method of claim 1, further comprising: after a disturbance at a certain frequency ω on the dq axis, a subsynchronous component is generated at ω - ω 1 and a supersynchronous component is generated at ω + ω 1.
3. The method of claim 1, the determining power system stability, comprising:
determining a dq impedance matrix, a sequence impedance matrix, a time domain subsynchronous/supersynchronous impedance matrix and a phasor domain subsynchronous/supersynchronous impedance matrix of the power system according to a generalized Nyquist criterion;
and determining characteristic values of the dq impedance matrix, the sequence impedance matrix, the time domain sub/super synchronous impedance matrix and the phasor domain sub/super synchronous impedance matrix according to the dq impedance matrix, the sequence impedance matrix, the time domain sub/super synchronous impedance matrix and the phasor domain sub/super synchronous impedance matrix, and judging the stability of the power system according to the characteristic values.
4. The method of claim 3, wherein the trajectory of the eigenvalues of the dq matrix is such that the power system is unstable if it encloses a preset point and stable if it does not enclose a preset point.
5. A system for determining power system stability based on frequency-shifted phasors, the system comprising:
the first modeling module is used for acquiring parameters of the power system, establishing a dq impedance model and a sequence impedance model according to the parameters of the power system, and determining the relation between the dq impedance and the sequence impedance according to the dq impedance model and the sequence impedance model;
the second modeling module is used for establishing an admittance matrix model of subsynchronous/supersynchronous frequency voltage and current according to the parameters of the power system, acquiring four elements of a time domain subsynchronous/supersynchronous impedance model according to the admittance matrix model of the subsynchronous/supersynchronous frequency voltage and current, and establishing the time domain subsynchronous/supersynchronous impedance model according to the four elements;
the third modeling module is used for acquiring a phasor domain sub/super-synchronous impedance model by shifting the step phasor to the disturbance of the voltage/current;
the analysis module is used for determining the relation among the dq impedance model, the sequence impedance model, the time domain subsynchronous/supersynchronous impedance model and the phasor domain subsynchronous/supersynchronous impedance model;
and the stability determining module is used for judging the relation between the dq impedance and the sequence impedance and the relation between the dq impedance model, the sequence impedance model, the time domain subsynchronous/supersynchronous impedance model and the phasor domain subsynchronous/supersynchronous impedance model by using a generalized Nyquist criterion to determine the stability of the power system.
6. The system of claim 5, the first modeling module further to: after a disturbance at a certain frequency ω on the dq axis, a subsynchronous component is generated at ω - ω 1 and a supersynchronous component is generated at ω + ω 1.
7. The system of claim 5, the determining power system stability, comprising:
determining a dq impedance matrix, a sequence impedance matrix, a time domain subsynchronous/supersynchronous impedance matrix and a phasor domain subsynchronous/supersynchronous impedance matrix of the power system according to a generalized Nyquist criterion;
and determining characteristic values of the dq impedance matrix, the sequence impedance matrix, the time domain sub/super synchronous impedance matrix and the phasor domain sub/super synchronous impedance matrix according to the dq impedance matrix, the sequence impedance matrix, the time domain sub/super synchronous impedance matrix and the phasor domain sub/super synchronous impedance matrix, and judging the stability of the power system according to the characteristic values.
8. The system of claim 7, wherein the trajectory of the eigenvalues of the dq matrix is such that the power system is unstable if it encloses a preset point and stable if it does not enclose a preset point.
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