CN114142457A - Impedance analysis-based power system frequency oscillation suppression method and system - Google Patents
Impedance analysis-based power system frequency oscillation suppression method and system Download PDFInfo
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Abstract
The disclosure belongs to the technical field of power electronics, and provides a method and a system for suppressing frequency oscillation of a power system based on impedance analysis, wherein the method comprises the following steps: obtaining harmonic equivalent impedance of the power equipment, and constructing small signal impedance models of frequency domains under different coordinate systems; obtaining a polymerization impedance model based on the topological analysis of the power system and the constructed small signal impedance model; and judging whether zero-crossing points exist on the matrix determinant equivalent curve of the polymerization impedance model, and analyzing the frequency oscillation mode of the power system. According to the method, the frequency domain impedance model of the power system is established by adopting an impedance analysis method, the stability of the power system is analyzed based on the impedance stability criterion, and the stability and the reliability of the operation of the power system are improved.
Description
Technical Field
The disclosure belongs to the technical field of power systems, and particularly relates to a power system frequency oscillation suppression method and system based on impedance analysis.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
An electric power system alternating current power grid is an electric energy system which is forced to work at a power frequency, when the frequency oscillation of the electric power system is researched, the parasitic reciprocating energy exchange of machinery, electromagnetism or mechanical and electromagnetic coupling is generally carried out outside the power frequency, and the energy exchange can cause stability or electric energy quality problems and endanger the safe and stable operation of the electric power system.
In recent years, the oscillation phenomenon of a power system with participation of power electronic equipment of different frequency bands is monitored all over the world, the oscillation frequency range is 2 Hz-2 kHz, and the wide-band oscillation has obvious wide-band characteristics, and the common characteristics of the oscillations are as follows:
1) the oscillation mechanism relates to the interaction coupling effect among a multi-power electronic converter, a generator set and an alternating current and direct current power grid, and the oscillation mechanism is essentially different from the traditional low-frequency oscillation and subsynchronous resonance/oscillation which are mainly caused by shafting dynamic and rotating set inertia;
2) the oscillation frequency is 2 Hz-2 kHz, the broadband characteristic is obvious, the frequency bands comprise electric oscillation and mechanical torsional oscillation, and the risk of inducing resonance exists;
3) the power electronic converter has strong nonlinear characteristics and weak overload capacity, and a control signal can be limited, so that oscillation is always started from small-signal negative damping divergence and ended from nonlinear continuous oscillation;
4) the characteristics of oscillation frequency, damping and the like are influenced by external factors such as a power electronic converter, a generator set, a power grid, even wind and light, and the like, and the characteristics of complicated influencing factors and large-range time variation are realized.
Disclosure of Invention
In order to solve the problems, the invention provides a method and a system for suppressing frequency oscillation of a power system based on impedance analysis.
According to some embodiments, a first aspect of the present disclosure provides a method for suppressing frequency oscillation of a power system based on impedance analysis, which adopts the following technical solutions:
a power system frequency oscillation suppression method based on impedance analysis comprises the following steps:
obtaining harmonic equivalent impedance of the power equipment, and constructing small signal impedance models of frequency domains under different coordinate systems;
obtaining a polymerization impedance model based on the topological analysis of the power system and the constructed small signal impedance model;
and judging whether zero-crossing points exist on the matrix determinant equivalent curve of the polymerization impedance model, and analyzing the frequency oscillation mode of the power system.
As a further technical limitation, the specific process of obtaining the harmonic equivalent impedance of the power equipment is as follows: measuring power frequency input voltage of the power equipment; adding small-amplitude harmonic voltage disturbance to the measured power frequency input voltage, and calculating to obtain a harmonic current component of the output current of the power equipment; and obtaining the harmonic equivalent impedance of the power equipment according to the harmonic voltage and the harmonic current.
Further, the harmonic equivalent impedance of the power equipment comprises a positive sequence harmonic equivalent impedance of the power equipment and a negative sequence harmonic equivalent impedance of the power equipment, which are mutually decoupled.
As a further technical limitation, the small-signal impedance models of the frequency domains in the different coordinate systems include frequency-domain impedance modeling in a stationary abc coordinate system and frequency-domain impedance modeling in a synchronously rotating dq coordinate system.
As a further technical limitation, the impedance stability criterion adopts the nyquist criterion method based on impedance.
As a further technical limitation, in order to quickly and efficiently locate the oscillation mode of the power system, the small-signal impedance model of the power system is collected into a collective impedance model through collective operation, and the collective impedance model is analyzed by using frequency domain stability.
As a further technical limitation, whether a zero-type zero-crossing point exists on a matrix determinant equivalent curve of the aggregate impedance model is judged, if so, an oscillation mode with the frequency being the zero-crossing point frequency exists in the power system, whether the product of the equivalent impedance at the zero-type zero-crossing point and the equivalent resistance is positive or negative is judged, if the product is the regular power system frequency oscillation mode, the power system frequency oscillation mode is unstable, and if the product is negative, the power system frequency oscillation mode is stable.
According to some embodiments, a second aspect of the present disclosure provides a power system frequency oscillation suppression system based on impedance analysis, which adopts the following technical solutions:
an impedance analysis based power system frequency oscillation suppression system comprising:
the modeling module is configured to obtain harmonic equivalent impedance of the power equipment and construct small signal impedance models of frequency domains under different coordinate systems;
an analysis module configured to obtain an aggregated impedance model based on a topology analysis of the power system and the constructed small-signal impedance model; and judging whether zero-crossing points exist on the matrix determinant equivalent curve of the polymerization impedance model, and analyzing the frequency oscillation mode of the power system.
According to some embodiments, a third aspect of the present disclosure provides a computer-readable storage medium, which adopts the following technical solutions:
a computer readable storage medium, having stored thereon a program which, when executed by a processor, implements the steps in the method for suppressing frequency oscillations of a power system based on impedance analysis according to the first aspect of the present disclosure.
According to some embodiments, a fourth aspect of the present disclosure provides an electronic device, which adopts the following technical solutions:
an electronic device comprising a memory, a processor and a program stored on the memory and executable on the processor, the processor implementing the steps in the method for suppressing frequency oscillations of a power system based on impedance analysis according to the first aspect of the present disclosure when executing the program.
Compared with the prior art, the beneficial effect of this disclosure is:
according to the method, the frequency domain impedance model of the power system is established by adopting an impedance analysis method, the stability of the power system is analyzed based on the impedance stability criterion, the traditional problems of grid-connected consumption and economic operation limitation of the power system caused by frequency suppression based on generator tripping protection, system operation mode change and grid structure enhancement are solved, the comprehensive analysis of the stability of the power system is realized, and the stability and reliability of the operation of the power system are improved.
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The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure.
Fig. 1 is a flowchart of a method for suppressing frequency oscillation of a power system based on impedance analysis in a first embodiment of the disclosure;
fig. 2 is a block diagram of a power system frequency oscillation suppression system based on impedance analysis in the second embodiment of the present disclosure.
Detailed Description
The present disclosure is further described with reference to the following drawings and examples.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The embodiments and features of the embodiments in the present disclosure may be combined with each other without conflict.
Example one
The first embodiment of the disclosure introduces a power system frequency oscillation suppression method based on impedance analysis.
A method for suppressing frequency oscillation of a power system based on impedance analysis as shown in fig. 1 includes the following steps:
obtaining harmonic equivalent impedance of the power equipment, and constructing small signal impedance models of frequency domains under different coordinate systems;
obtaining a polymerization impedance model based on the topological analysis of the power system and the constructed small signal impedance model;
and judging whether zero-crossing points exist on the matrix determinant equivalent curve of the polymerization impedance model, and analyzing the frequency oscillation mode of the power system.
As one or more embodiments, in the frequency domain, the external characteristics exhibited by a power plant when it is subjected to small disturbances near the steady-state operating point can be characterized by impedance, and thus, the impedance model is essentially a small-signal model.
The impedance model of the power system is substantially a transfer function of a port input voltage of the power equipment to a port input current after the power system is linearized with a small signal. The power equipment is connected to the power grid by taking the inverter as an interface, and the inverter has the characteristic of strong nonlinearity. Therefore, the key of modeling the small-signal impedance of the power equipment is to linearize the nonlinear part in the inverter control link. Frequency domain impedance modeling of power equipment is mainly based on two coordinate systems, namely a stationary abc coordinate system and a synchronously rotating dq coordinate system. According to different linearization ideas, the small signal impedance modeling method of the power generation equipment of the power system mainly comprises two methods: frequency domain impedance modeling in a stationary abc coordinate system and frequency domain impedance modeling in a rotating dq coordinate system.
1. Frequency domain impedance modeling under static abc coordinate system
In a static abc coordinate system, three-phase voltage and three-phase current of power equipment change in a sine rule along with time, belong to time-varying signals, and cannot provide a steady-state operation point. In order to solve the problem, a Sunji professor team of the Etherler institute of technology introduces a harmonic linearization technology into impedance modeling of the power equipment, the technology needs to add harmonic voltage disturbance with small amplitude to power frequency input voltage of an equipment port, obtain a harmonic current component in equipment output current through theoretical derivation, and further obtain harmonic equivalent impedance of the power equipment.
In the time domain, the power plant input a-phase voltage containing both positive and negative sequence harmonic disturbances may be represented as:
wherein, V1/Vp/VnRespectively representing fundamental wave/positive sequence harmonic/negative sequence harmonic voltage amplitudes; omega1/ωp/ωnΩ represents the fundamental/sequence harmonic/negative sequence harmonic angular frequency, respectively; f. of1/fp/fnRespectively representing fundamental/positive sequence harmonic/negative sequence harmonic frequencies;
respectively, the positive sequence harmonic/negative sequence harmonic initial phase.
In the frequency domain, equation (1) can be expressed in phasor form:
wherein the content of the first and second substances,
respectively representing fundamental/positive/negative sequence harmonicsWave voltage phasor.
Through derivation, the specific structure and control strategy of the target power equipment are combined, and the output A-phase current phasor of the equipment can be obtained, and can be expressed as follows:
wherein the content of the first and second substances,
respectively representing fundamental wave/positive sequence harmonic/negative sequence harmonic current phasors;
indicating the fundamental/positive sequence harmonic/negative sequence harmonic current phases, respectively.
The positive sequence impedance of a power plant is defined as the ratio of the positive sequence harmonic voltage phasor to the positive sequence harmonic current phasor, and the negative sequence impedance is defined as the ratio of the negative sequence harmonic voltage phasor to the negative sequence harmonic current phasor, as follows:
wherein Z ispRepresents a positive sequence impedance of the power device; znRepresenting the negative sequence impedance of the power plant.
Generally, the positive and negative sequence impedances of the power device are decoupled. The impedance modeling process ignores the coupling between the positive sequence impedance model and the negative sequence impedance model of the power equipment, and the positive sequence impedance model and the negative sequence impedance model of the power equipment are respectively established, namely the positive sequence impedance model and the negative sequence impedance model are decoupled. However, subsequent studies have shown that when phase-locked loop (PLL) dynamics are considered, the coupling between the positive and negative sequence impedance models of the power equipment containing the power electronic controller is enhanced and cannot be simply ignored.
The strong coupling between the positive and negative sequence harmonic signals of the current transformer cannot be ignored in the modeling analysis.
When considering the coupling between positive and negative sequence components, a two-dimensional matrix is required to characterize the impedance characteristics of the device. And similarly, deriving a positive-negative sequence coupling impedance matrix model of the static abc coordinate by adopting a harmonic linearization method:
wherein Z ispp(s)/Zpn(s)/Znp(s)/Znn(s) represents an element in the impedance matrix, s represents a Laplace variable; zpp(s) represents the relationship between positive sequence voltage and positive sequence current; zpn(s) represents the relationship between positive sequence voltage and negative sequence current; znp(s) represents the relationship between negative sequence voltage and positive sequence current; znn(s) represents the relationship between negative sequence voltage and negative sequence current.
2. Frequency domain impedance modeling under rotating dq coordinate system
For a three-phase ac system, there is no steady state operating point for the system variables in the stationary abc coordinate system. By transforming the system variables from the stationary abc coordinate system to the synchronously rotating dq coordinate system through park transformation, a three-phase alternating current system can be changed into two coupled direct current systems. At this time, a conventional linearization method can be adopted to establish an impedance matrix model of the device under the rotating dq coordinate system.
For a certain power device, firstly, a nonlinear dynamic equation model under a dq coordinate system of the power device needs to be established, and the power device is linearized into a small-signal state space model at a steady-state operating point. Assuming that the control vector of the small signal model is the terminal voltage udq＝[ud,uq]TAnd the output vector is the terminal current idq＝[id,iq]TThen the small signal state space model of the device can be represented as:
wherein, Δ Xdq/Δudq/ΔidqRespectively representing state/control/output vector increments; a. thedq、Bdq、Cdq、DdqRespectively, represent a matrix of coefficients.
Laplace transformation is carried out on the above formula, and then the relation between the terminal voltage and the current of the equipment is deduced in an s domain:
wherein Z isEE-dq(s)＝[Zdd(s),Zdq(s)；Zqd(s),Zqq(s)]Representing the impedance matrix model of the power equipment in its own dq coordinate system.
Conversion between dq-coordinate impedance model and abc-coordinate impedance model
Due to the influence of the phase-locked loop, the frequency is f when rotating the dq coordinate systemdq(assume f)dq>f1) Is transformed into a stationary abc coordinate system by inverse park transformation, two frequency signals are generated, respectively, with frequency fp＝fdq+f1Of the positive sequence harmonic signal and a frequency of fp＝fdq-f1The negative sequence harmonic signal of (2), namely the coupling of the positive sequence frequency signal and the negative sequence frequency signal; frequency f when rotating dq coordinate systemdq(assume 0<fdq<f1) Will also produce signals of two frequencies, respectively f, when transformed to the stationary abc coordinate system via inverse park transformationp＝fdq+f1Of the positive sequence harmonic signal (super-synchronous frequency signal) and having a frequency fp＝f1-fdqI.e. coupling between the sub/super synchronous frequency signals occurs.
From the foregoing analysis, the power equipment can be represented by a 2 × 2 order impedance matrix model in the rotating dq coordinate system, and can also be represented by a 2 × 2 order positive-negative sequence coupled impedance model in the stationary abc coordinate system.The two impedance models describe the impedance characteristics of the same physical system, and the difference is only that the adopted coordinate systems are different, so that the two impedance models can be mutually converted theoretically. Using the impedance matrix model Z in dq coordinate system in formula (8)EE-dq(s) is expressed in the form of a complex phasor:
wherein the content of the first and second substances,
and is
To represent
The conjugate phasor of (a); z+，dq(s) and Z-，dq(s) represents the equivalent complex transfer function.
Based on the transformation between the stationary abc coordinates and the rotating dq coordinates, the dq coordinate impedance matrix ZEE-dq(s) and static abc coordinates positive and negative sequence coupling impedance matrix ZEE-pnThe conversion relationship between(s) is:
as one or more embodiments, when the Nyquist criterion method based on impedance is adopted, the target system needs to be divided into a power subsystem and a load subsystem in advance, impedance models of the two subsystems are respectively established, and then whether a Nyquist trajectory of a ratio of impedances of the two subsystems contains a point of (-1, j0) is analyzed through the Nyquist criterion to evaluate the stability of the system. However, this method is difficult to apply to a complex power grid, and it can provide only qualitative analysis results, not quantitative damping information. For a source system with a relatively simple topology, analysis can still be developed using the Nyquist criterion.
Specifically, all the power equipment are subjected to impedance identification to obtain an impedance model under a static abc coordinate system, and then series-parallel connection operation is directly carried out according to system topology to carry out interconnection, so that a polymerization impedance model of the system is obtained.
In fact, the power system is a high-order dynamic system, and the interaction between various types of power equipment contained in the system will result in a plurality of oscillation modes, and some of the oscillation modes may have weak damping instability under certain system operation conditions, so as to cause the system to oscillate. The established impedance network model should contain all oscillation modes in the target system as much as possible, and in order to quickly and efficiently locate the concerned system oscillation mode, the impedance network model of the system needs to be collected into a polymerization impedance model through polymerization operation, and then research is carried out by adopting a frequency domain stability analysis technology. Generally, an impedance network model of a system can be integrated into a single high-order aggregate impedance along a certain oscillation path. However, a practical system often has a plurality of different oscillation paths, and if the system is appreciably controllable, the aggregate impedance obtained along any oscillation path will contain all of the oscillation modes of the system. That is, when the impedance aggregation operation is performed along the oscillation path, there is no case where the local series/parallel resonance causes the pole-zero cancellation inside the system. At this time, only one oscillation path needs to be identified, so that the impedance network model of the system can be integrated into the aggregate impedance, and then all system modes can be analyzed. However, when this condition is not satisfied, i.e. there is a local series/parallel resonance inside the system, the aggregate impedance obtained along a certain oscillation path can only reflect those considerable oscillation modes of the system. If the concerned oscillation mode is just not appreciable, another oscillation path needs to be selected for impedance aggregation.
For an electric power system with a relatively simple network topology, the impedance network model of the system can be directly aggregated into an aggregated impedance through an impedance aggregation operation (i.e. series-parallel connection, Y/Δ transformation or impedance matrix transformation) along a predetermined oscillation path if the impedance matrix models of N electric power devices are connected in series-parallel connection, the total impedance matrix model can be obtained through the following series-parallel connection operation:
ZSer＝Z1+Z2+...+ZN (11)
ZPar＝Z1||Z2||...||ZN＝inv[inv(Z1)+inv(Z2)+...+inv(ZN)] (12)
wherein Z isSer/ZParRepresenting a total impedance matrix model after series connection/parallel connection; | represents parallel operation; inv () represents the inversion operation of the matrix.
By using the formula (11) and the formula (12), a Y/Δ transformation algorithm based on the impedance matrix model can be conveniently obtained.
For a reasonably controllable system, the stability of the system depends on the closed loop characteristic (or system pole) ZT(s) aggregate impedance, which can be viewed as an impedance network model, and ZT-pn(s) may be viewed as an aggregate impedance matrix of the coupled impedance network model. Wherein the determinant D of the impedance matrix is aggregatedZ(s) can be expressed as:
DZ(s)＝Z11(s)Z22(s)-Z12(s)Z21(s) (13)
wherein D isZ(s) is a polynomial for s; z11(s)，Z22(s)，Z12(s)，Z21(s)) represents the collective impedance matrix ZT-pnFour elements in(s).
One-dimensional polymerization impedance ZT(s) is a polynomial on s, and as can be seen from equation (13), the poly-impedance matrix determinant DZ(s) is also a polynomial on s, both of which can be used for system stability analysis. Thus, determinant D in the aggregate impedance matrix in subsequent analysisZ(s) are described as examples. Theoretically, by calculating determinant DZThe zero point of(s) allows accurate calculation of the damping and frequency of the oscillation mode of interest in the target system. However, practical power systems have a large-scale, high-dimensional nature, often containing thousands of individual types of power equipment. Therefore, the aggregate impedance matrix model of the system will also have a very high order, and it is even difficult to write its analytical expressions. For such higher order systems, by direct couplingSolving equation DZIt is often difficult to calculate the system zero (corresponding to the system characteristic value) at 0(s). In practice, D is usually only available as a function of frequency ωZ(s) numerical solutions of the real and imaginary parts, i.e. the impedance frequency characteristics of the determinant of the aggregated impedance matrix. In the following analysis, the polymerization impedance matrix determinant DZReal part of(s) RD＝Re{DZ(j ω) } is called the equivalent resistance, and the imaginary part XD＝Im{DZ(j ω) } is called equivalent reactance.
Theoretically, the impedance matrix determinant D is aggregatedZThe conjugate zero and conjugate pole of(s) will produce zero crossings on their equivalent reactance-frequency characteristic and equivalent resistance-frequency characteristic. In other words, there are two types of zero-crossing points on the frequency characteristic curve, namely, zero-based zero-crossing point (ZZP) and pole-based zero-crossing point (PZP). It is noted that only zero-type zero-crossings (corresponding to system characteristic values) are relevant for the stability of the system. Therefore, it is first necessary to identify which zero crossings are ZZPs and which are PZPs. By judging the frequency omega at the zero crossing pointrThe slope of the equivalent resistance or reactance curve of the system can realize the identification of the zero crossing point type, and the slope of the resistance or reactance curve can be expressed as:
wherein k isDR(ωr) Representing the frequency omega of the equivalent resistance curve at the zero crossing pointrThe slope of (d); k is a radical ofDX(ωr) Representing the frequency omega of the equivalent reactance curve at the zero crossingrThe slope of (d).
If k at some zero crossingDR(ωr) Or kDX(ωr) Is relatively small, the zero crossing is a ZZP. If at a zero crossingkDR(ωr) Or kDX(ωr) Is a value close to infinity and the zero crossing is a PZP.
Let λ be1,2＝α0±jω0Is determinant DZA pair of conjugate zeros in(s) that correspond to a zero crossing on the system equivalent resistance and/or reactance curve. Extensive analysis has shown that there are mainly two cases:
case 1: the conjugate zero point corresponds to a ZZP on the equivalent reactance curve;
case 2: there is no ZZP on the equivalent reactance curve corresponding to the conjugate zero, but there is one corresponding ZZP on the equivalent resistance curve.
Assuming conjugate zero λ1,2＝α0±jω0Corresponding system equivalent reactance curve XDA ZZP on, and identifies the zero crossing frequency as omegar. At this time, the following conclusions are made:
1) if the real part of the zero point is numerically much smaller than the imaginary part of the zero point, i.e. | α0|<<|ω0L (this condition holds true for weakly damped oscillation modes of interest), the identified zero crossing frequency ωrFrequency omega approximately equal to the conjugate zero0I.e. omegar≈ω0。
2) If at zero crossing frequency ωrThe slope of the equivalent reactance curve of the system is larger than 0, namely kDX(ωr)>0, equivalent resistance R at the frequencyD(ωr) Symbol of (a) and-alpha0The same; conversely, the equivalent resistance RD(ωr) Symbol of (a) and-alpha0The same is true.
Based on these conclusions, the criteria for evaluating the stability of the system oscillation mode can be summarized as follows: if the impedance matrix determinant D is aggregatedZ(s) an equivalent reactance curve with a frequency ωrZZP of (1), then the target system exists at a frequency of ωrBy analysing the equivalent resistance R at ZZPD(ωr) And equivalent reactance slope kDX(ωr) The positive and negative of the product can determine the stability of the oscillation mode. If R isD(ωr)·kDX(ωr)>0, stable open-open oscillation mode; conversely, the oscillation mode is unstable.
If there is no corresponding conjugate zero λ on the equivalent reactance curve1,2＝α0±jω0And a corresponding zero-crossing point exists on the equivalent resistance curve, and the frequency of the zero-crossing point is omegar. At this time, the following conclusions are made:
1) if | α0|<<|ω0L (consistent with previous assumptions), the identified zero crossing frequency ωrFrequency omega approximately equal to the conjugate zero0I.e. omegar≈ω0。
2) If at zero crossing frequency ωrThe slope of the equivalent resistance curve of the system is greater than 0, namely kDX(ωr)>0, equivalent reactance X at this frequencyD(ωr) Symbol of (a) and0the same; conversely, the equivalent reactance XD(ωr) Symbol of (a) and-alpha0The same is true.
In this case, the stability criterion can be summarized as: if the impedance matrix determinant D is aggregatedZ(s) a frequency ω exists on the equivalent resistance curverZZP of (1), then a frequency of ω exists in the systemrBy analysing the equivalent reactance X at ZZPD(ωr) And equivalent resistance slope kDX(ωr) The positive and negative of the product can determine the stability of the oscillation mode. If X isD(ωr)·kDX(ωr)>0, indicating unstable oscillation mode; otherwise, the oscillation mode is stable.
Example two
The second embodiment of the disclosure introduces a power system frequency oscillation suppression system based on impedance analysis.
An impedance analysis based power system frequency oscillation suppression system as shown in fig. 2 comprises:
the modeling module is configured to obtain harmonic equivalent impedance of the power equipment and construct small signal impedance models of frequency domains under different coordinate systems;
an analysis module configured to obtain an aggregated impedance model based on a topology analysis of the power system and the constructed small-signal impedance model; and judging whether zero-crossing points exist on the matrix determinant equivalent curve of the polymerization impedance model, and analyzing the frequency oscillation mode of the power system.
The detailed steps are the same as those of the method for suppressing frequency oscillation of the power system based on impedance analysis provided in the first embodiment, and are not described herein again.
EXAMPLE III
The third embodiment of the disclosure provides a computer-readable storage medium.
A computer readable storage medium, on which a program is stored, which when executed by a processor implements the steps in the method for suppressing frequency oscillation of a power system based on impedance analysis according to the first embodiment of the present disclosure.
The detailed steps are the same as those of the method for suppressing frequency oscillation of the power system based on impedance analysis provided in the first embodiment, and are not described herein again.
Example four
The fourth embodiment of the disclosure provides an electronic device.
An electronic device includes a memory, a processor, and a program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the method for suppressing frequency oscillation of a power system based on impedance analysis according to the first embodiment of the present disclosure.
The detailed steps are the same as those of the method for suppressing frequency oscillation of the power system based on impedance analysis provided in the first embodiment, and are not described herein again.
The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure, and various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.
Claims (10)
1. A power system frequency oscillation suppression method based on impedance analysis is characterized by comprising the following steps:
obtaining harmonic equivalent impedance of the power equipment, and constructing small signal impedance models of frequency domains under different coordinate systems;
obtaining a polymerization impedance model based on the topological analysis of the power system and the constructed small signal impedance model;
and judging whether zero-crossing points exist on the matrix determinant equivalent curve of the polymerization impedance model, and analyzing the frequency oscillation mode of the power system.
2. The method for suppressing the frequency oscillation of the power system based on the impedance analysis as claimed in claim 1, wherein the specific process for obtaining the harmonic equivalent impedance of the power equipment is as follows: measuring power frequency input voltage of the power equipment; adding small-amplitude harmonic voltage disturbance to the measured power frequency input voltage, and calculating to obtain a harmonic current component of the output current of the power equipment; and obtaining the harmonic equivalent impedance of the power equipment according to the harmonic voltage and the harmonic current.
3. The method for suppressing frequency oscillation of an electric power system based on impedance analysis as claimed in claim 2, wherein the harmonic equivalent impedance of the electric power equipment comprises a positive sequence harmonic equivalent impedance of the electric power equipment and a negative sequence harmonic equivalent impedance of the electric power equipment, which are decoupled from each other.
4. The method for suppressing frequency oscillation of a power system based on impedance analysis as claimed in claim 1, wherein the small signal impedance models of the frequency domains in different coordinate systems comprise frequency domain impedance modeling in a stationary abc coordinate system and frequency domain impedance modeling in a synchronously rotating dq coordinate system.
5. A method for suppressing frequency oscillations in an electrical power system based on impedance analysis, as set forth in claim 1, characterized in that said impedance stability criterion is based on the impedance-based nyquist criterion method.
6. The method for suppressing the frequency oscillation of the power system based on the impedance analysis as claimed in claim 1, wherein for fast and efficient positioning of the oscillation mode of the power system, the impedance model of the power system for small signals is collected as an aggregate impedance model through aggregation operation, and the aggregate impedance model is analyzed by using the frequency domain stability.
7. The method for suppressing frequency oscillation of an electric power system based on impedance analysis as claimed in claim 1, wherein it is determined whether a zero-crossing point exists on a matrix determinant equivalent curve of the aggregate impedance model, if so, it is determined that an oscillation mode with a frequency of the zero-crossing point exists in the electric power system, and it is determined whether a product of an equivalent impedance at the zero-crossing point and an equivalent resistance is positive or negative, if the product is a regular oscillation mode of the electric power system, the oscillation mode is unstable, and if the product is negative, the oscillation mode is stable.
8. An impedance analysis-based power system frequency oscillation suppression system, comprising:
the modeling module is configured to obtain harmonic equivalent impedance of the power equipment and construct small signal impedance models of frequency domains under different coordinate systems;
an analysis module configured to obtain an aggregated impedance model based on a topology analysis of the power system and the constructed small-signal impedance model; and judging whether zero-crossing points exist on the matrix determinant equivalent curve of the polymerization impedance model, and analyzing the frequency oscillation mode of the power system.
9. A computer readable storage medium, having a program stored thereon, where the program, when executed by a processor, is adapted to carry out the steps of the method for suppressing frequency oscillations of a power system based on impedance analysis of any of claims 1 to 7.
10. An electronic device comprising a memory, a processor and a program stored on the memory and executable on the processor, wherein the processor implements the steps of the method for suppressing frequency oscillations of a power system based on impedance analysis as claimed in any one of claims 1 to 7 when executing said program.
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| CN116505520B (en) * | 2023-06-26 | 2023-11-07 | 国网江西省电力有限公司电力科学研究院 | Oscillation suppression method and system for photovoltaic grid-connected power generation system |
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