CN115000979A - Resonance analysis method for wind power grid-connected system - Google Patents

Resonance analysis method for wind power grid-connected system Download PDF

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CN115000979A
CN115000979A CN202210699144.5A CN202210699144A CN115000979A CN 115000979 A CN115000979 A CN 115000979A CN 202210699144 A CN202210699144 A CN 202210699144A CN 115000979 A CN115000979 A CN 115000979A
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刘敏
罗永捷
黄鹏
孙丽香
卓谷颖
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Chongqing University
China Electric Power Research Institute Co Ltd CEPRI
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Chongqing University
China Electric Power Research Institute Co Ltd CEPRI
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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
    • 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
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • 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
    • H02J3/381—Dispersed generators
    • 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
    • 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
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics

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Abstract

The invention relates to a resonance analysis method of a wind power grid-connected system, which analyzes the resonance problem of the wind power grid-connected system by establishing a direct-drive fan impedance model and considers the influence rule of a direct-current bus capacitor on the direct-drive fan impedance model under the condition that power disturbance exists on an alternating-current side. In addition, in the process of establishing the direct-drive fan impedance model, the harmonic state space theory is used for carrying out the constant normalization processing on the linear single-phase analytical model, and the harmonic state space method can simultaneously represent a plurality of frequency responses in each variable, so that the direct-drive fan impedance model of the multi-dimensional harmonic transfer function is established, and the influence of direct-current bus capacitance or asymmetric control on the direct-drive fan impedance characteristic can be accurately reflected; the direct-drive fan impedance model is used for analyzing the resonance problem of the wind power grid-connected system, and the accuracy of the resonance analysis of the wind power grid-connected system can be improved due to the fact that the influence mechanism of the direct-current bus capacitance on the frequency coupling characteristic of the system is comprehensively reflected.

Description

Resonance analysis method for wind power grid-connected system
Technical Field
The invention relates to the technical field of power transmission and distribution of a power system, in particular to a resonance analysis method of a wind power grid-connected system.
Background
The total installed capacity of the wind power in China is continuously increased from 2015 to 2020, wherein the installed capacity of the wind power in China is newly increased by 71.67GW in 2020, and the accumulated grid-connected installed capacity reaches 282 GW. The permanent magnet direct-drive fan has the advantages of small transmission loss, high power generation efficiency, adaptability to low wind speed environments and the like, and is widely applied to three types of wind energy resource areas with low wind speed in China.
With the continuous improvement of installed capacity of a wind turbine generator, the resonance problem of the whole wind power grid-connected system is frequent, and the safety and the stability of the whole power system are influenced. The broadband resonance problem of wind power integration is one of the key stability problems faced by a power system, and at present, research is mainly carried out by a time domain state space method and a frequency impedance analysis method. The state space analysis method is an effective tool traditionally used for analyzing the resonance problem of the power system, and generally, the state space analysis method analyzes the resonance problem of the system by solving the characteristic value of the system. However, the detailed system modeling and all control parameters are required for obtaining the characteristic values, but in actual operation, the data are difficult to obtain due to the technical secrecy requirements of manufacturers.
An impedance stability analysis method based on the nyquist criterion has been proven to be a feasible method of analyzing a system, which can effectively determine the stability of an interconnection system by using an impedance ratio between interconnection systems. Compared with the state space analysis method, the impedance stability analysis method has the greatest advantage that the impedance stability analysis method can be realized through engineering tests without acquiring detailed information of system parameters in advance. The MMC impedance model is an important tool for analyzing the stability of a system sent out by a direct-drive wind power plant, and at present, an impedance modeling method for the direct-drive wind power plant can be roughly divided into dq domain impedance modeling and sequence domain impedance modeling. The dq domain impedance modeling method is widely applied to impedance modeling of a traditional two-level converter, but direct measurement through experiments is difficult to achieve due to the fact that no definite physical significance exists, and stability judgment needs to be performed by using a generalized Nyquist stability criterion, so that the stability judgment difficulty is high. Besides, due to the frequency coupling characteristic, errors exist in the conventional sequence domain impedance modeling for decoupling the positive sequence impedance and the negative sequence impedance under certain scenes, and the change of the system impedance characteristic when the direct current bus capacitance is large cannot be reflected. Under the condition that an accurate impedance model cannot be obtained, the resonance analysis result of the wind power grid-connected system is difficult to ensure to be accurate, and further the stability of the whole power system is possibly misjudged, so that economic loss which is difficult to estimate is caused.
Therefore, how to consider the dynamic state of the direct-current bus capacitor and comprehensively reflect the influence mechanism of the direct-current bus capacitor on the frequency coupling characteristic of the system becomes a problem to be solved urgently when the resonance analysis of the wind power grid-connected system is carried out at present.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a resonance analysis method of a wind power grid-connected system, which can consider the dynamic state of a direct current bus capacitor and comprehensively reflect the influence mechanism of the direct current bus capacitor on the frequency coupling characteristic of the system.
In order to solve the technical problems, the invention adopts the following technical scheme:
a resonance analysis method of a wind power grid-connected system comprises the following steps:
step S1, acquiring a simplified dynamic model of the direct-drive wind turbine generator based on the dynamic characteristics of the direct-drive wind turbine generator in the wind power system;
step S2, obtaining a direct-drive fan electrical analysis model considering direct-drive bus capacitance dynamics based on a direct-drive wind turbine generator simplified dynamic model and kirchhoff law;
step S3, injecting small disturbance of alternating voltage at the alternating current side, and linearizing the direct-drive fan electrical analysis model to obtain a linearized single-phase analysis model;
s4, carrying out normalization processing on the linearized single-phase analytical model by using a harmonic state space theory, and constructing a direct-drive fan harmonic matrix model;
step S5, establishing a small signal model of a control link based on the mathematical relation between control variables in the power grid system, and converting the small signal model into a matrix form;
step S6, acquiring a direct-drive fan impedance model based on consideration of direct-current bus capacitance dynamic based on physical definition of impedance and a direct-drive fan harmonic matrix model;
and step S7, analyzing the resonance problem of the wind power grid-connected system according to the direct-drive fan impedance model obtained in the step S6.
Preferably, in S1, the direct-drive wind turbine simplified dynamic model is a grid-connected inverter model in which a dc current source is connected in parallel to a dc bus capacitor while electromagnetic and electromechanical dynamic behaviors of the generator and the machine-side converter are ignored.
Preferably, in S2, the direct-drive fan electrical analysis model is:
Figure BDA0003703285640000021
wherein, L is AC filter inductance, C is DC bus capacitance, i gj For j phase current on the current side of the phase current, u, flowing through the filter inductor gj Is j cross-current side grid voltage, m j Is a j-phase modulation signal, u, of a network-side converter dc Is a DC bus voltage i dc J represents a variable and j is a phase a, b, c, a, b and c respectively represent a phase a, a phase b and a phase c.
Preferably, in S3, assuming that a small disturbance of ac voltage is injected at the ac side of the direct-drive fan, a small-signal linearization method is applied and a three-phase balance system symmetry characteristic is combined to obtain a linearized single-phase analytic model of the direct-drive fan;
Figure BDA0003703285640000022
wherein, L is the AC filter inductance, Δ i g Small disturbance of alternating current, Δ u g Is a.c.Small voltage perturbation, Δ m small perturbation of the modulation signal, Δ u dc Is small disturbance of DC bus, C is DC bus capacitance, Δ i dc Is the small signal component of the DC load current, M is the steady state value of the modulation signal, i g Is the steady-state value of the alternating current, and t is the time.
Preferably, in S4, the periodic time-varying signal in the linearized single-phase analytic model is converted into a time-invariant signal by using a harmonic state space theory, and any one periodic time-varying variable x (t) in the linearized single-phase analytic model of the direct-drive fan is converted into:
x＝[… x -n … x 0 … x n …] T ；
where x represents the formed column vector of the variable x (t) after the harmonic state space transformation, x 0 A direct current component of x (t), x n Is the Fourier coefficient of n times of harmonic wave, and n is the harmonic wave times;
the small signal component Δ x (t) of any variable in the linearized single-phase analytic model is converted into the small signal component Δ x (t) through HHS:
Δx＝[… x p-n … x p … x p+n …] T
where Δ x represents the column vector formed by the small signal components Δ x (t) after the harmonic state space transformation, x p For the disturbance frequency corresponding to the Fourier coefficient, x p-n Is a Fourier coefficient with harmonic frequency of p-n, p is the frequency corresponding to the small signal disturbance component injected, n is the harmonic frequency, x p+n Are fourier coefficients with harmonic frequencies p + n.
Preferably, in S4, the product of the small signal component Δ x (t) and the steady-state component a (t) is subjected to harmonic state space change as follows:
Figure BDA0003703285640000031
wherein A is Topritz matrix of a (t), a 0 For a steady-state parameter DC component, a ±1 Representing a steady state parameter a pair of conjugate fundamental frequency Fourier coefficients, a ±2 Representing a steady state parameter to a conjugate twoFrequency multiplication Fourier coefficient, x p-1 Is a Fourier coefficient of frequency p-, x p Is a Fourier coefficient with frequency p +1, x p+1 Are Fourier coefficients with frequency p + 1.
Preferably, in S4, the direct-drive fan harmonic matrix model is:
Figure BDA0003703285640000032
where Δ s is a matrix of differential operators, Δ i g Column vector, Delauu, formed by alternating current after spatial transformation in harmonic state g Is a column vector formed by alternating voltage after harmonic state space transformation, and is a column vector formed by modulation signal after harmonic state space transformation, U dc The value is a steady state value of the direct current voltage, and M is a time-invariant coefficient matrix of the modulation signal; Δ u dc Is a column vector, delta i, formed by the DC bus voltage after the space transformation of harmonic state dc Is a column vector I formed by the space transformation of the harmonic state of the direct current bus current g A time-invariant coefficient matrix of the alternating current;
Figure BDA0003703285640000041
wherein, Delta I p+n 、ΔI p-n Respectively at a frequency f p +nf 1 、f p -nf 1 The amplitude of the small disturbance of the alternating current; alpha is alpha p+n 、α p-n Respectively at a frequency f p +nf 1 、f p -nf 1 The phase angle of the ac current minor disturbance; delta U p+n 、ΔU p-n Respectively at a frequency f p +nf 1 、f p -nf 1 The amplitude of the small disturbance of the alternating voltage current; theta p+n 、θ p-n Respectively at a frequency f p +nf 1 、f p -nf 1 The phase angle of the small disturbance of the alternating voltage of (1); Δ M p+n 、ΔM p-n Respectively at a frequency f p +nf 1 、f p -nf 1 Modulation ofThe amplitude of the small signal disturbance; beta is a p+n 、β p-n Respectively at a frequency f p +nf 1 、f p -nf 1 The phase angle of the small perturbation of the modulated signal of (3); delta U dc The amplitude of the small disturbance of the direct current voltage; delta I dc The amplitude of the small disturbance of the direct current is obtained.
Preferably, in S5, the matrix form of the small-signal model of the control element is:
Figure BDA0003703285640000042
G u ＝-T d- G i G udc ；
G i ＝T d- (G i T d+ +K d T q+ )+T q- (G i T q+ -K d T d+ )；
wherein, Δ m is a column vector formed after the modulation signal is subjected to harmonic state space transformation; g u Representing the transfer function matrix, G, of the current control loop i Representing the current control loop transfer function matrix, T d- Expressed as d-axis dq inverse transform transfer matrix, G udc Representing a transfer function matrix between the DC voltage loop and the modulation signal; t is d+ Expressed as d-axis dq forward transform transfer matrix, K d Representing a matrix of decoupling coefficients, T q+ Denoted as q-axis dq forward transform transfer matrix, T q- Denoted as the q-axis dq inverse transform transfer matrix.
Preferably, in S6, the direct-drive wind turbine impedance model based on consideration of the dc bus capacitance dynamics is:
Figure BDA0003703285640000043
wherein Z is ac Direct-drive wind turbine generator alternating-current side impedance model with direct-current bus capacitance dynamic consideration, G iac Is a transfer function matrix between the current control loop and the modulation signal.
Compared with the prior art, the invention has the following beneficial effects:
1. according to the direct-drive fan impedance model established by the invention, the influence rule of the direct-drive fan impedance model by the direct-current bus capacitor under the condition that power disturbance exists on the alternating-current side is considered. The direct-drive fan impedance model is used for analyzing the resonance problem of the wind power grid-connected system, and the influence mechanism of the direct-current bus capacitance on the frequency coupling characteristic of the system is comprehensively reflected due to the fact that the direct-current bus capacitance dynamic state is considered, so that the accuracy of the resonance analysis of the wind power grid-connected system can be improved.
2. In the process of establishing the direct-drive fan impedance model, the invention uses the harmonic state space theory to carry out the normalization processing on the linear single-phase analytical model, and the harmonic state space method can simultaneously represent a plurality of frequency responses in each variable, so as to establish the direct-drive fan impedance model of the multi-dimensional harmonic transfer function, and can accurately reflect the influence of the direct-current bus capacitance or asymmetric control on the impedance characteristic of the direct-drive fan.
3. The method solves the problems of complex impedance modeling process, low accuracy and the like of the direct-drive wind power plant considering the capacitance characteristic of the direct-current bus, and has higher practical value for analyzing the resonance problem of the wind power grid-connected system.
Drawings
For purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made in detail to the present invention as illustrated in the accompanying drawings, in which:
FIG. 1 is a flow chart of an embodiment of the present invention;
FIG. 2 is an electrical schematic diagram of a complete direct-drive wind turbine generator set in the embodiment;
fig. 3 is a circuit diagram of a simplified direct-drive wind turbine generator in an embodiment.
Detailed Description
The following is further detailed by the specific embodiments:
examples
As shown in fig. 1, the embodiment discloses a resonance analysis method for a wind power integration system. For convenience of description, in the power grid system of the present embodiment, a complete electrical structure of the direct-drive wind turbine is shown in fig. 2, and the direct-drive wind turbine includes a wind turbine, a permanent magnet synchronous generator, and a back-to-back voltage source converter (including a machine side converter and a grid side converter). The generator is directly coupled with the wind turbine and transmits the energy generated by the wind turbine to the power grid through the back-to-back voltage source type converter.
The method comprises the following steps:
and step S1, acquiring a simplified dynamic model of the direct-drive wind turbine generator based on the dynamic characteristics of the direct-drive wind turbine generator in the power grid system. Specifically, the electromagnetic and electromechanical dynamic behaviors of the generator and the machine side converter are ignored, the wind turbine, the permanent magnet synchronous generator and the machine side converter are equivalent to be current sources, the current sources are connected in parallel with the direct current bus capacitor, and finally the simplified direct-drive wind turbine model shown in the figure 3 is formed together with the network side converter, so that the corresponding simplified dynamic model of the direct-drive wind turbine is obtained.
And step S2, obtaining a direct-drive fan electric analysis model considering direct-drive bus capacitance dynamics based on the direct-drive wind turbine generator simplified dynamic model and kirchhoff law.
Figure BDA0003703285640000061
Wherein, L is AC filter inductance, C is DC bus capacitance, i gj For j-phase current, u, across the filter inductor gj Is j cross-current side grid voltage, m j Is a j-phase modulation signal, u, of a network-side converter dc Is a DC bus voltage i dc J represents a phase change amount, and j is a phase change amount, b, c, and a, b, and c represent a phase a, a phase b, and a phase c, respectively.
And step S3, injecting small disturbance of alternating voltage at the alternating current side, and linearizing the direct-drive fan electrical analysis model to obtain a linearized single-phase analysis model. In specific implementation, a direct-drive fan linearization single-phase analytical model is obtained by assuming that small disturbance of alternating voltage is injected at the alternating current side of the direct-drive fan and applying a small-signal linearization method and combining the symmetrical characteristics of a three-phase balance system;
Figure BDA0003703285640000062
wherein L is the AC filter inductance, Δ i g Small disturbance of alternating current, Δ u g For small disturbances of the AC voltage,. DELTA.m for small disturbances of the modulated signal,. DELTA.u dc Is small disturbance of DC bus, C is capacitance of DC bus, Δ i dc Is the small signal component of the DC load current, M is the steady state value of the modulation signal, i g Is the steady-state value of the alternating current, and t is the time.
And S4, performing normalization processing on the linearized single-phase analytical model by using a harmonic state space theory, and constructing a direct-drive fan harmonic matrix model. In specific implementation, a harmonic state space theory is utilized to convert a periodic time-varying signal in the linearized single-phase analysis model into a time-invariant signal, and any one periodic time-varying variable x (t) in the linearized single-phase analysis model of the direct-drive fan is converted into the time-varying variable x (t) through HHS:
x＝[… x -n … x 0 … x n …] T (3)
wherein x represents the formed column vector of variable x (t) after harmonic state space transformation, x 0 Is a direct current component of x (t), x n Is the Fourier coefficient of n times of harmonic wave, and n is the harmonic wave times;
the small signal component Δ x (t) of any variable in the linearized single-phase analytic model is converted into the small signal component Δ x (t) through HHS:
Δx＝[… x p-n … x p … x p+n …] T (4)
where Δ x represents the column vector formed by the small signal components Δ x (t) after the harmonic state space transformation, x p For disturbance frequencies corresponding to Fourier coefficients, x p-n Is a Fourier coefficient with harmonic frequency of p-n, p is the frequency corresponding to the small signal disturbance component injected, n is the harmonic frequency, x p+n Are fourier coefficients with harmonic frequencies p + n.
The product of the small signal component Δ x (t) and the steady-state component a (t) is harmonically state-spatially changed to:
Figure BDA0003703285640000071
wherein A is Topritz matrix of a (t), a 0 For a steady-state parameter, DC component, a ±1 Representing a steady state parameter a pair of conjugate fundamental frequency Fourier coefficients, a ±2 Representing a steady state parameter a pair of conjugated frequency-doubled Fourier coefficients, x p-1 Is a Fourier coefficient of frequency p-, x p Is a Fourier coefficient with frequency p +1, x p+1 Are Fourier coefficients with frequency p + 1.
The obtained direct-drive fan harmonic matrix model by combining the formulas (2), (3), (4) and (5) is as follows:
Figure BDA0003703285640000072
where Δ s is a matrix of differential operators, Δ i g Column vector, Δ u, formed by alternating current after spatial transformation of the harmonic state g Is a column vector formed by alternating voltage after harmonic state space transformation, and is a column vector formed by modulation signal after harmonic state space transformation, U dc The value is a steady state value of the direct current voltage, and M is a time-invariant coefficient matrix of the modulation signal; Δ u dc Is a column vector, delta i, formed by the DC bus voltage after the space transformation of harmonic state dc Is a column vector I formed by the space transformation of the harmonic state of the direct current bus current g Is a time-invariant coefficient matrix of alternating current. The specific expression of the vector is as follows:
Figure BDA0003703285640000073
wherein, Delta I p+n 、ΔI p-n Respectively at a frequency f p +nf 1 、f p -nf 1 The amplitude of the small disturbance of the alternating current; alpha (alpha) ("alpha") p+n 、α p-n Respectively at a frequency f p +nf 1 、f p -nf 1 Small disturbance of alternating currentThe phase angle of (d); delta U p+n 、ΔU p-n Respectively at a frequency f p +nf 1 、f p -nf 1 The amplitude of the small disturbance of the alternating voltage current; theta.theta. p+n 、θ p-n Respectively at a frequency f p +nf 1 、f p -nf 1 The phase angle of the small disturbance of the alternating voltage of (1); Δ M p+n 、ΔM p-n Respectively at a frequency f p +nf 1 、f p -nf 1 The amplitude of the small perturbation of the modulation signal; beta is a p+n 、β p-n Respectively at a frequency f p +nf 1 、f p -nf 1 The phase angle of the small perturbation of the modulated signal of (1); delta U dc The amplitude of the small disturbance of the direct current voltage is obtained; delta I dc The amplitude of the small dc disturbance.
Step S5, establishing a small signal model of a control link based on the mathematical relation between control variables in the power grid system, and converting the small signal model into a matrix form; the matrix form of the small signal model of the control link is as follows:
Figure BDA0003703285640000081
G u ＝-T d- G i G udc (8)
G i ＝T d- (G i T d+ +K d T q+ )+T q- (G i T q+ -K d T d+ ) (9)
wherein, Δ m is a column vector formed after the modulation signal is subjected to harmonic state space transformation; g u Representing the transfer function matrix, G, of the current control loop i Representing the current control loop transfer function matrix, T d- Expressed as d-axis dq inverse transform transfer matrix, G udc Representing a transfer function matrix between the DC voltage loop and the modulation signal; t is d+ Denoted as d-axis dq forward transform transfer matrix, K d Representing a matrix of decoupling coefficients, T q+ Denoted as q-axis dq forward transform transfer matrix, T q- Denoted as the q-axis dq inverse transform transfer matrix.
Step S6, obtaining a direct-drive fan impedance model based on consideration of direct-current bus capacitance dynamic based on physical definition of impedance and a direct-drive fan harmonic matrix model:
Figure BDA0003703285640000082
wherein Z is ac Direct-drive wind turbine generator alternating-current side impedance model taking direct-current bus capacitance dynamic into consideration, G iac Is a transfer function matrix between the current control loop and the modulation signal.
And step S7, analyzing the resonance problem of the wind power grid-connected system according to the direct-drive fan impedance model obtained in the step S6.
According to the direct-drive fan impedance model established by the invention, the influence rule of the direct-drive fan impedance model by the direct-current bus capacitor under the condition that power disturbance exists on the alternating-current side is considered. Besides, in the process of establishing the direct-drive fan impedance model, the linear single-phase analytical model is subjected to the normalizing treatment by using the harmonic state space theory, and the harmonic state space method can simultaneously represent a plurality of frequency responses in each variable, so that the direct-drive fan impedance model of the multi-dimensional harmonic transfer function is established, and the influence of direct-current bus capacitance or asymmetric control on the direct-drive fan impedance characteristic can be accurately reflected. The direct-drive fan impedance model is used for analyzing the resonance problem of the wind power grid-connected system, and the influence mechanism of the direct-current bus capacitance on the frequency coupling characteristic of the system is comprehensively reflected due to the consideration of the direct-current bus capacitance dynamic state, so that the accuracy of the resonance analysis of the wind power grid-connected system can be improved.
In conclusion, the method solves the problems of complex impedance modeling process, low accuracy and the like of the direct-drive wind power plant considering the capacitance characteristic of the direct-current bus, and has higher practical value for analyzing the resonance problem of the wind power grid-connected system.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the technical solutions, and those skilled in the art should understand that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all that should be covered by the claims of the present invention.

Claims (9)

1. A resonance analysis method of a wind power grid-connected system is characterized by comprising the following steps:
step S1, acquiring a simplified dynamic model of the direct-drive wind turbine generator based on the dynamic characteristics of the direct-drive wind turbine generator in the wind power system;
step S2, obtaining a direct-drive fan electrical analysis model considering direct-drive bus capacitance dynamics based on a direct-drive wind turbine generator simplified dynamic model and kirchhoff law;
step S3, injecting small disturbance of alternating voltage at the alternating current side, and linearizing the direct-drive fan electrical analysis model to obtain a linearized single-phase analysis model;
s4, carrying out normalization processing on the linearized single-phase analytical model by using a harmonic state space theory, and constructing a direct-drive fan harmonic matrix model;
step S5, establishing a small signal model of a control link based on the mathematical relation between control variables in the power grid system, and converting the small signal model into a matrix form;
step S6, acquiring a direct-drive fan impedance model based on consideration of direct-current bus capacitance dynamics based on physical definition of impedance and a direct-drive fan harmonic matrix model;
and step S7, analyzing the resonance problem of the wind power grid-connected system according to the direct-drive fan impedance model obtained in the step S6.
2. The resonance analysis method of the wind power integration system according to claim 1, characterized in that: in the S1, the direct-drive fan simplified dynamic model is a grid-connected inverter model with a direct current source and a direct current bus capacitor connected in parallel, wherein electromagnetic and electromechanical dynamic behaviors of the generator and the machine side converter are ignored.
3. The resonance analysis method of the wind power integration system according to claim 2, characterized in that: in S2, the direct-drive fan electrical analysis model is:
Figure FDA0003703285630000011
wherein, L is AC filter inductance, C is DC bus capacitance, i gj For j-phase current, u, across the filter inductor gj Is j cross-current side grid voltage, m j Is a j-phase modulation signal, u, of a network-side converter dc Is a DC bus voltage i dc J represents a variable, and j represents a phase a, a phase b, a phase c, a phase b, and a phase c, respectively.
4. The resonance analysis method of the wind power integration system according to claim 3, characterized in that: in S3, assuming that small disturbance of alternating voltage is injected at the alternating current side of the direct-drive fan, a small-signal linearization method is applied and the symmetrical characteristic of a three-phase balance system is combined to obtain a linearized single-phase analytic model of the direct-drive fan;
Figure FDA0003703285630000012
wherein, L is the AC filter inductance, Δ i g Small disturbance of alternating current, Δ u g For small disturbances of the AC voltage,. DELTA.m for small disturbances of the modulated signal,. DELTA.u dc Is small disturbance of DC bus, C is DC bus capacitance, Δ i dc Is the small signal component of the DC load current, M is the steady state value of the modulation signal, i g Is the steady-state value of the alternating current, and t is the time.
5. The wind power integration system resonance analysis method according to claim 4, characterized in that: in the step S4, a harmonic state space theory is used to convert a periodic time-varying signal in the linearized single-phase analytic model into a time-invariant signal, and any periodic time-varying variable x (t) in the linearized single-phase analytic model of the direct-drive fan is converted into a time-varying variable x (t) after HHS:
x＝[…x -n …x 0 …x n …] T ；
wherein x represents the formed column vector of variable x (t) after harmonic state space transformation, x 0 A direct current component of x (t), x n Is Fourier coefficient of n harmonic, n is harmonic frequency;
the small signal component Δ x (t) of any variable in the linearized single-phase analytic model is converted into the small signal component Δ x (t) through HHS:
Δx＝[…x p-n …x p …x p+n …] T
where Δ x represents the column vector formed by the small signal components Δ x (t) after the harmonic state space transformation, x p For disturbance frequencies corresponding to Fourier coefficients, x p-n Is a Fourier coefficient with harmonic frequency of p-n, p is the frequency corresponding to the small signal disturbance component injected, n is the harmonic frequency, x p+n Are fourier coefficients with harmonic frequencies p + n.
6. The resonance analysis method of the wind power integration system according to claim 5, characterized in that: at S4, the product of the small signal component Δ x (t) and the steady-state component a (t) is subjected to harmonic state space change to:
Figure FDA0003703285630000021
wherein A is a Topritz matrix of a (t), a 0 For a steady-state parameter DC component, a +1 Representing a steady state parameter a pair of conjugate fundamental frequency Fourier coefficients, a +2 A pair of conjugate frequency-doubled Fourier coefficients, x, representing steady-state parameters p-1 Is a Fourier coefficient of frequency p-, x p Is a Fourier coefficient with frequency p +1, x p+1 Are Fourier coefficients with frequency p + 1.
7. The resonance analysis method of the wind power integration system according to claim 6, characterized in that: in S4, the direct-drive fan harmonic matrix model is as follows:
Figure FDA0003703285630000022
where Δ s is a matrix of differential operators, Δ i g Column vector, Δ u, formed by alternating current after spatial transformation of the harmonic state g Is a column vector formed by alternating voltage after harmonic state space transformation, and is a column vector formed by modulation signal after harmonic state space transformation, U dc The value is a steady state value of the direct current voltage, and M is a time-invariant coefficient matrix of the modulation signal; Δ u dc Is a column vector, delta i, formed by the DC bus voltage after the space transformation of harmonic state dc Is a column vector I formed by the space transformation of the harmonic state of the direct current bus current g A time-invariant coefficient matrix of the alternating current;
Figure FDA0003703285630000031
wherein, Delta I p+n 、ΔI p-n Respectively at a frequency f p +nf 1 、f p -nf 1 The amplitude of the small disturbance of the alternating current; alpha (alpha) ("alpha") p+n 、α p-n Respectively at a frequency f p +nf 1 、f p -nf 1 Phase angle of small disturbance of alternating current of (1); delta U p+n 、ΔU p-n Respectively at a frequency f p +nf 1 、f p -nf 1 The amplitude of the small disturbance of the alternating voltage current; theta p+n 、θ p-n Respectively at a frequency f p +nf 1 、f p -nf 1 The phase angle of the small disturbance of the alternating voltage of (1); Δ M p+n 、ΔM p-n Respectively at a frequency f p +nf 1 、f p -nf 1 The amplitude of the small perturbation of the modulation signal; beta is a p+n 、β p-n Respectively at a frequency f p +nf 1 、f p -nf 1 The phase angle of the small perturbation of the modulated signal of (1); delta U dc The amplitude of the small disturbance of the direct current voltage is obtained; delta I dc The amplitude of the small disturbance of the direct current is obtained.
8. The resonance analysis method of the wind power integration system according to claim 7, characterized in that: in S5, the matrix form of the small signal model of the control link is:
Figure FDA0003703285630000032
G u ＝-T d- G i G udc ；
G i ＝T d- (G i T d+ +K d T q+ )+T q- (G i T q+ -K d T d+ )；
wherein, Δ m is a column vector formed after the modulation signal is subjected to harmonic state space transformation; g u Representing the transfer function matrix, G, of the current control loop i Representing the current control loop transfer function matrix, T d- Expressed as d-axis dq inverse transform transfer matrix, G udc Representing a transfer function matrix between the direct current voltage loop and the modulation signal; t is d+ Expressed as d-axis dq forward transform transfer matrix, K d Representing a matrix of decoupling coefficients, T q+ Denoted as q-axis dq forward transform transfer matrix, T q- Denoted as the q-axis dq inverse transform transfer matrix.
9. The resonance analysis method of the wind power integration system according to claim 8, characterized in that: in S6, the direct-drive fan impedance model based on consideration of the dc bus capacitance dynamics is:
Figure FDA0003703285630000041
wherein Z is ac Direct-drive wind turbine generator alternating-current side impedance model with direct-current bus capacitance dynamic consideration, G iac Is a transfer function matrix between the current control loop and the modulation signal.
CN202210699144.5A 2022-06-20 2022-06-20 Resonance analysis method for wind power grid-connected system Pending CN115000979A (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116094416A (en) * 2023-02-17 2023-05-09 哈尔滨工业大学 Electrolytic capacitor-free permanent magnet synchronous motor harmonic suppression method based on steady-state point adaptation

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116094416A (en) * 2023-02-17 2023-05-09 哈尔滨工业大学 Electrolytic capacitor-free permanent magnet synchronous motor harmonic suppression method based on steady-state point adaptation
CN116094416B (en) * 2023-02-17 2023-08-29 哈尔滨工业大学 Electrolytic capacitor-free permanent magnet synchronous motor harmonic suppression method based on steady-state point adaptation

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