CN111641229B - Wind power generation system output monitoring method and system based on extended harmonic domain model - Google Patents

Wind power generation system output monitoring method and system based on extended harmonic domain model Download PDF

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CN111641229B
CN111641229B CN202010548069.3A CN202010548069A CN111641229B CN 111641229 B CN111641229 B CN 111641229B CN 202010548069 A CN202010548069 A CN 202010548069A CN 111641229 B CN111641229 B CN 111641229B
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CN111641229A (en
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孙媛媛
许庆燊
李亚辉
王庆岩
路彤
庄静茹
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Shandong University
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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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • 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
    • 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]
    • 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy
    • 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
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/76—Power conversion electric or electronic aspects
    • 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 disclosure provides a wind power generation system output monitoring method and system based on an extended harmonic domain model, wherein a dynamic model comprises the following steps: and respectively establishing a double-fed asynchronous generator dynamic model based on an extended harmonic domain, a converter grid-side system dynamic model based on the extended harmonic domain and a converter direct-current bus dynamic model based on the extended harmonic domain aiming at the wind driven generator, the grid-side system of the back-to-back converter and the direct-current bus. Meanwhile, the harmonic content generated by the switching functions on two sides of the converter is considered in an extended harmonic domain model of a network side system and a direct current bus. The three submodels of the generator, the grid-side system of the back-to-back converter and the direct-current bus are combined into a harmonic state space equation, an extended harmonic domain model of the doubly-fed wind power generation system is obtained, dynamic tracking of the current of the stator and the rotor of the generator is achieved, changes of fundamental frequency current can be accurately represented, harmonic current characteristics of a high-frequency-multiplication stator can be analyzed, and the purposes of monitoring and accurate evaluation are achieved.

Description

Wind power generation system output monitoring method and system based on extended harmonic domain model
Technical Field
The disclosure relates to the technical field of wind power generation, in particular to a wind power generation system output monitoring method and system based on an extended harmonic domain model.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
In order to relieve the energy crisis and reduce the environmental pollution, the renewable energy power generation rises rapidly. Wind power is used as the third power supply in China, and a Doubly-Fed Induction Generator (DFIG) is the mainstream machine type in a grid-connected fan. The wind speed change has the characteristics of randomness and intermittence, so that the electric energy output is unstable, and therefore a large number of power electronic devices are required to be connected to control the output electric energy to meet the grid-connected standard during grid connection of wind power generation. The application of the power electronic device introduces uncertain harmonic current of high frequency and wide frequency domain, when the voltage and current of the stator of the generator contain harmonic components, the stator can output active power and reactive power to generate pulsation, complex problems of oscillation, instantaneous harmonic interaction, voltage flicker and the like of a fan and a power grid are easily induced, and the fan is split in serious conditions to influence the safe and stable operation of the power grid. The method comprises the steps of establishing an accurate dynamic model of the doubly-fed wind turbine, analyzing the transient change process in the dynamic model, obtaining the change condition of the continuous time domain of the harmonic current of the motor and possible transient unsafe behaviors, providing a theoretical basis for further researching the harmonic interaction between the doubly-fed wind turbine and the power grid, and providing a model basis for subsequently designing a filter and improving a control strategy.
Scholars at home and abroad have certain research on establishing a dynamic model of a doubly-fed wind power generation system, and the harmonic characteristics of a wind turbine grid-connected point are analyzed, so that harmonic changes under different output and wind conditions are quantized by mainly applying a time domain simulation method, and a harmonic spectrum of the wind turbine grid-connected point is given. For a doubly-fed wind generator, the selection of the generator model affects the accuracy of the stator current calculation. However, the model accuracy is restricted by the complex system structure and control strategy of the doubly-fed wind power generation system, most dynamic models simplify the wind turbine to different degrees, and the average value model of the wind turbine is established based on the simplified back-to-back converter. The inventor finds that simplifying the back-to-back converter and neglecting the switch modulation process can cause the accuracy of the model analysis harmonic wave to be reduced, and meanwhile, the transient process of the fan operation and the control thereof can be deviated. Meanwhile, the existing average model is generally applied to a continuous time-invariant system and does not meet the requirement of tracking the dynamic change of each variable in the system. On the other hand, the existing general average model of the fan converts the fundamental frequency component into direct current quantity under a dq coordinate system through dq coordinate conversion, but other steady-state harmonics cannot be considered through single dq conversion, and the calculation quantity of the general average model applied to the analysis of harmonic characteristics is large.
Disclosure of Invention
The invention provides a wind power generation system output monitoring method and system based on an extended harmonic domain model for solving the problems, wherein the extended harmonic domain model considers state space models of each subharmonic of stator voltage, stator current, rotor voltage and rotor current of a doubly-fed asynchronous generator, is not only suitable for representing harmonic dynamics under a transient condition, but also can be used for analyzing harmonic characteristics of generator stator output current under a steady state condition, and achieves the purposes of monitoring and accurate evaluation.
In order to achieve the purpose, the following technical scheme is adopted in the disclosure:
one or more embodiments provide a wind power generation system output monitoring method based on an extended harmonic domain model, comprising the following steps:
respectively establishing time domain models aiming at a wind driven generator, a network side system of a converter and a direct current bus;
respectively acquiring electrical parameter data of a wind driven generator, a network side system of a converter and a direct current bus;
aiming at the established time domain model, respectively establishing an extended harmonic domain model aiming at a wind driven generator, a network side system of a converter and a direct current bus according to the obtained electrical parameter data through vector transformation and frequency domain normalization;
and integrating the established extended harmonic domain model, taking the terminal voltage of a motor stator as input, outputting the terminal voltage of the motor stator as each subharmonic component of the current of the motor stator, the current of a rotor, the current of a network side and the voltage of a direct current bus in a converter to obtain an integral extended harmonic domain dynamic model of the double-fed asynchronous wind driven generator, and monitoring the output state of the wind power generation system by using the model.
One or more embodiments provide an extended harmonic domain model based wind power system output monitoring system, comprising:
a time domain model building module: the system comprises a wind driven generator, a converter, a network side system and a direct current bus, wherein the network side system and the direct current bus are configured to establish a time domain model respectively aiming at the wind driven generator and the converter;
a data acquisition module: the system comprises a wind driven generator, a converter, a network side system and a direct current bus, wherein the system is configured to obtain electrical parameter data of the wind driven generator, the network side system of the converter and the direct current bus respectively;
an extended harmonic domain model building module: the system is configured to establish an extended harmonic domain model for the wind driven generator, a grid side system of the converter and the direct current bus respectively according to the obtained electrical parameter data through vector transformation and frequency domain normalization aiming at the established time domain model;
an integration monitoring module: the method comprises the steps that an extended harmonic domain model which is configured and used for being integrated and established is used, the end voltage of a motor stator is used as input, the output is the harmonic components of the motor stator current, the rotor current, the network side current and the direct current bus voltage in a converter, the integral extended harmonic domain dynamic model of the double-fed asynchronous wind driven generator is obtained, and the model is used for monitoring the output state of a wind power generation system.
An electronic device comprising a memory and a processor and computer instructions stored on the memory and executed on the processor, the computer instructions when executed by the processor performing the steps of the method of claim.
A computer readable storage medium storing computer instructions which, when executed by a processor, perform the steps of the above method.
Compared with the prior art, the beneficial effect of this disclosure is:
the method establishes the extended harmonic domain model after the frequency domain normalization of the doubly-fed wind power generation system, is suitable for representing the harmonic dynamics under the transient condition, and can be used for analyzing the harmonic characteristics of the internal variables of the whole power generation system under the steady-state condition, thereby achieving the purposes of monitoring and accurate evaluation.
The method provided by the disclosure breaks through the limitation that the existing general average model of the fan calculates single steady-state harmonic through dq coordinate transformation, the provided extended harmonic domain model contains a plurality of frequency components of state variables, input quantity and output quantity in a state space, the fundamental frequency and multiple frequency response of each variable can be simultaneously expressed, the analyzed harmonic frequency can be randomly selected, and the harmonic frequency can be used as a modeling frame of a double-fed wind power generation system to greatly reduce the harmonic calculation workload.
Drawings
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 do not constitute a limitation thereof.
FIG. 1 is a flow chart of a method according to example 1 of the present disclosure;
fig. 2 is a dq equivalent circuit model diagram of a doubly-fed asynchronous generator in a synchronous rotating coordinate system according to embodiment 1 of the present disclosure;
fig. 3 is a simplified model diagram of a grid-side system and a dc bus of a back-to-back converter provided in embodiment 1 of the present disclosure;
fig. 4 is a generator stator current spectrum comparison graph of a harmonic steady-state analysis result (EHD model) and an electromagnetic transient model (EMT model) simulation result under constant wind speed provided by embodiment 1 of the present disclosure;
fig. 5 is a comparison graph of the overall extended harmonic domain dynamic model, the electromagnetic transient model and the average model of the doubly-fed asynchronous wind turbine generator according to embodiment 1 of the present disclosure, in which the voltage of the dc bus changes at a changing wind speed;
fig. 6 is a comparison graph of the stator fundamental frequency current of the overall extended harmonic domain dynamic model, the electromagnetic transient model and the average model of the doubly-fed asynchronous wind turbine according to embodiment 1 of the present disclosure under varying wind speeds;
fig. 7 is a comparison graph of the harmonic current spectrum of the generator stator corresponding to a certain time point under a variable wind speed of the overall extended harmonic domain dynamic model and the electromagnetic transient model of the doubly-fed asynchronous wind turbine according to embodiment 1 of the present disclosure;
fig. 8 is a dynamic change process of stator harmonic currents of 38 th, 42 th, 79 th, and 81 th times of the doubly-fed asynchronous wind turbine generator according to the overall extended harmonic domain dynamic model of the doubly-fed asynchronous wind turbine generator in embodiment 1 of the disclosure.
The specific implementation mode is as follows:
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. It should be noted that, in the case of no conflict, the embodiments and features in the embodiments in the present disclosure may be combined with each other. The embodiments will be described in detail below with reference to the accompanying drawings.
Example 1
In the technical solution disclosed in one or more embodiments, as shown in fig. 1, a method for monitoring the output of a wind power generation system based on an extended harmonic domain model includes the following steps:
s1, respectively establishing a time domain model for the wind driven generator, a network side system of the converter and the direct current bus;
s2, respectively acquiring electrical parameter data of the wind driven generator, a network side system of the converter and the direct current bus;
s3, aiming at the established time domain model, respectively establishing an extended harmonic domain model aiming at a wind driven generator, a network side system of a converter and a direct current bus according to the obtained electrical parameter data through vector transformation and frequency domain normalization;
and S4, integrating the established extended harmonic domain model, taking the terminal voltage of the motor stator as input, outputting the terminal voltage as each subharmonic component of the stator current, the rotor current, the network side current and the direct current bus voltage in the converter to obtain an integral extended harmonic domain dynamic model of the doubly-fed asynchronous wind driven generator, and monitoring the output state of the wind power generation system by using the model. According to the model, the wind power generation system can be effectively monitored and accurately evaluated.
The extended harmonic domain model after the frequency domain normalization of the doubly-fed wind power generation system is established by adopting the frequency domain normalization, is suitable for representing harmonic dynamics under the transient condition and analyzing harmonic characteristics of internal variables of the whole power generation system under the steady-state condition, and can achieve the purposes of effective monitoring and accurate evaluation on the wind power generation system through the model of the embodiment.
1) The method for establishing the double-fed asynchronous generator dynamic model based on the extended harmonic domain for the wind driven generator can be as follows:
s101, describing stator voltage, stator current, rotor voltage and rotor current by adopting space vectors for the doubly-fed asynchronous generator. According to a dq equivalent circuit model of the doubly-fed asynchronous generator, a state space equation of the doubly-fed asynchronous generator is established by taking stator dq axis current and rotor dq axis current as state quantities and taking stator dq axis voltage and rotor dq axis voltage as input quantities;
s102, obtaining an extended harmonic domain dynamic model of the doubly-fed asynchronous generator by adopting a frequency domain normalization method according to a state space equation and an extended harmonic domain core equation of the doubly-fed asynchronous generator;
s103, obtaining electrical parameter data of the wind driven generator, determining coefficients of a harmonic state space model of the doubly-fed asynchronous generator, and establishing a final harmonic state space model of the doubly-fed asynchronous generator.
Wherein, optionally, the frequency domain normalizing method specifically comprises: a differential term of the state quantity is newly added on the left side of the original state space; each state quantity and input quantity are decomposed into harmonic space vectors through bilateral Fourier; establishing a column vector of Fourier coefficients containing each subharmonic of a harmonic space vector, and correspondingly taking the column vector as a state quantity and an input quantity; and adjusting the coefficient matrix of the original state space according to the dimension changes of the state quantity and the input quantity.
The extended harmonic domain dynamic model of the doubly-fed asynchronous generator established in this embodiment is a state space model considering each harmonic of the stator voltage, the stator current, the rotor voltage and the rotor current of the doubly-fed asynchronous generator in a dq coordinate system, and is suitable for representing the harmonic dynamics under the transient condition, and also can be used for analyzing the harmonic characteristics of the generator stator output current under the steady-state condition, so as to achieve the purposes of monitoring and accurate evaluation.
In S101, the stator voltage, the stator current, the rotor voltage and the rotor current of the doubly-fed asynchronous generator are described by space vectors respectively
Figure BDA0002541467000000071
Optionally, a dq equivalent circuit model of the doubly-fed asynchronous generator of this embodiment may be as shown in fig. 2, where the equivalent circuit model includes a generator stator resistance RsAnd generator rotor resistance RrGenerator stator inductance LsRotor inductance LrAnd an excitation inductance LmThree inductances through the stator leakage inductance LσsRotor leakage inductance LσrAnd realizing association, and satisfying the following formula:
Figure BDA0002541467000000081
in fig. 2, the components for the d-axis and q-axis are represented by equivalent circuits, respectively, where vdsAnd vqsAre respectively stator voltages
Figure BDA0002541467000000082
The d-axis and q-axis components of (1); i.e. idsAnd iqsAre respectively stator currents
Figure BDA0002541467000000083
D-axis and q-axis components of (1); v. ofdrAnd vqrAre respectively rotor voltage
Figure BDA0002541467000000084
D-axis and q-axis components of (1); i.e. idrAnd iqrAre respectively rotor currents
Figure BDA0002541467000000085
D-axis and q-axis components.
The method comprises the following steps of establishing a state space equation of the doubly-fed asynchronous generator by taking stator dq axis current and rotor dq axis current as state quantities and stator dq axis voltage and rotor dq axis voltage as input quantities, wherein the state space equation can be specifically as follows:
Figure BDA0002541467000000086
in the formula, ωmIs the electrical angular frequency, omega, of the generator rotorsIs the angular frequency of the stator of the generator,
Figure BDA0002541467000000088
is omegasToeplitz matrix form (Toeplitz-type matrix).
In step 102, the extended harmonic domain core equation may specifically be:
Figure BDA0002541467000000087
Y＝CX+EU
and substituting the state space equation obtained in the step S101 into an extended harmonic domain core equation to realize frequency domain normalization.
Decomposing each state quantity and input quantity into harmonic space vectors through bilateral Fourier, and expressing the structure of each variable as a column vector
Figure BDA0002541467000000091
The vector contains the fourier coefficients of each harmonic. And the coefficient matrix of the original state space is adjusted along with the dimension of the state quantity and the input quantity. Obtaining a harmonic state space model of the doubly-fed asynchronous generator in the synchronous rotating coordinate system, and expressing the harmonic state space model as follows:
Figure BDA0002541467000000095
Figure BDA0002541467000000092
Figure BDA0002541467000000093
wherein D is composed of 4 differential matrices D0＝diag{-jhω0 … -jω0 0 -jω0 … jhω0Formed in diagonal lines, ω0Is the electrical angular velocity of the generator stator, which is a constant value, in units rad/s; i is an identity matrix with the order of (2 h)max+1)，hmaxIs the number of times each variable contains a harmonic;
Figure BDA0002541467000000094
is the electrical angular frequency omega of the generator rotormIn the form of a Toplitz matrix, the elements of which are determined by Fourier coefficients of the electrical angular frequency of the rotor for each harmonic.
In step S2, the electrical parameter data of the wind turbine to be acquired includes: resistance, inductance and leakage inductance of wind driven generator, the resistance including stator resistance RSAnd rotor resistance RrThe inductor comprises a generator stator inductor LsRotor inductance LrAnd an excitation inductance LmThe leakage inductance includes stator leakage inductance LσsAnd rotor leakage inductance Lσr。
And determining the coefficient of the harmonic state space model of the doubly-fed asynchronous generator according to the obtained electrical parameter data of the wind driven generator, so as to establish the harmonic state space model of the doubly-fed asynchronous generator.
2) The method for establishing the converter grid-side dynamic model based on the extended harmonic domain for the back-to-back converter grid-side system can be as follows:
in this embodiment, a two-level topology back-to-back converter is used for explanation, and fig. 3 is a simplified model diagram of a grid-side system and a dc bus of the back-to-back converter provided in the embodiment of the present disclosure. And the direct current side capacitor is assumed to be large enough, so that the independent control of a machine side system and a grid side system can be realized, and the grid side system comprises a grid side converter, a grid side filter and a power grid system.
Step 201, respectively establishing a network side converter model according to the equivalent circuit model of the network side system and the ideal bidirectional switch function, wherein the network side converter is connected to a three-phase inductive filter model of the power grid. And carrying out vector transformation on three-phase variables in the two sub-models, and integrating the three-phase variables into a dynamic mathematical model described by a network side system in a synchronous rotating coordinate system in a state space equation form.
Step 202, converting a state space equation of the network side system into an extended harmonic domain, wherein the frequency domain regularization method specifically comprises the following steps: adding a differential term of the state quantity on the left side of the original state space equation; each state quantity and input quantity are decomposed into harmonic space vectors through bilateral Fourier, the structure is expressed as a column vector, and Fourier coefficients of each subharmonic are contained in the vector; and the coefficient matrix of the original state space is correspondingly adjusted along with the dimensionality of the state quantity and the input quantity.
Taking the output current of the power grid as a state quantity, decomposing each state quantity and input quantity in a state space equation of a grid-side system into harmonic space vectors by adopting bilateral Fourier decomposition according to an extended harmonic source core equation, and obtaining a harmonic state space model of a back-to-back converter grid-side system, namely obtaining a converter grid-side system dynamic model of an extended harmonic domain, wherein the harmonic space vectors are obtained by adopting the following steps:
Figure BDA0002541467000000111
in the formula, RgIs the resistance of the filter, LgIs the inductance of the filter;
Figure BDA0002541467000000112
is the Toplitz matrix of the generator stator angular velocity; ideal bidirectional switching function
Figure BDA0002541467000000113
And
Figure BDA0002541467000000114
respectively showing the switching states of three-phase upper and lower bridge arms of the grid-side converter A, B, C; d is composed of 4 differential matrixes D0＝diag{-jhω0 … -jω0 0 -jω0 … jhω0-is composed in diagonal form; i is an identity matrix with the order of (2 h)max+1)；
Figure BDA0002541467000000115
And
Figure BDA0002541467000000116
the amplitudes are equal, the phases are opposite, and the amplitudes represent the voltages to the ground of two capacitors on the direct current bus respectively; vdsAnd VqsRespectively corresponding to the grid voltage (stator voltage)
Figure BDA0002541467000000117
The d-axis and q-axis components of (a); i isdgAnd IqgRespectively corresponding to the components of a d axis and a q axis of the current input into the power grid by the grid-side converter; c3/2Is a transformation matrix for transforming variables of an abc three-phase coordinate system into a dq coordinate system, and is expressed as:
Figure BDA0002541467000000118
in the formula, thetasIndicating the stator electrical angular position.
Optionally, the time-domain switching function of the network-side converter
Figure BDA0002541467000000119
And
Figure BDA00025414670000001110
obtaining a switching function S in an extended harmonic domain by bilateral Fourier decompositionx: obtaining the angular frequency of the stator and the Fourier coefficient of each harmonic corresponding to the switching function, and determining the switching function S under the extended harmonic domainxThe element (b); switching function SxDetermined by the switching modulation method, the signal is expressed in a Toeplitz matrix form in the extended harmonic domain, and is expressed as:
Figure BDA0002541467000000121
the embodiment represents the harmonic content generated in the switching process in the extended harmonic domain model in the form of the Toeplitz matrix, and simultaneously considers the characteristics of the switching modulation method.
The method specifically considers the switching process of the power electronic device, the switching function can be easily embodied in an equation after Fourier decomposition, and the method is more suitable for reflecting the dynamic response inside a fan and tracking the dynamic process of stator harmonic current.
3) The method for establishing the converter direct-current bus dynamic model based on the extended harmonic domain for the back-to-back converter direct-current bus can be as follows:
for a two-level topology back-to-back converter, a dc bus connects a rotor-side converter and a grid-side converter, and the current flow of each branch is as shown in fig. 3.
S301, obtaining the direct current input and direct current output relation of the direct current bus according to the current direction of each branch in the two-level topology back-to-back converter and the ideal bidirectional switching function. And acquiring the capacitance parameter of the direct current bus, and establishing a dynamic mathematical model of the direct current bus. And then converting the rotor variable into a stator coordinate system through inverse rotation transformation, carrying out vector transformation on the three-phase variable, and establishing a state space equation of a direct current bus in a synchronous rotation coordinate system.
S302, adding a differential term of the state quantity on the left side of the original state space equation according to the core equation of the extended harmonic source; performing bilateral Fourier decomposition on each state quantity and input quantity in a state space equation of the direct current bus to obtain a harmonic wave state space model of the direct current bus of the back-to-back converter, namely obtaining a converter direct current bus dynamic model of an extended harmonic wave domain, wherein the harmonic wave state space model is expressed as follows:
Figure BDA0002541467000000131
in the formula (I), the compound is shown in the specification,
Figure BDA0002541467000000132
and
Figure BDA0002541467000000133
the amplitudes are equal, the phases are opposite, and the amplitudes represent the voltages to the ground of two capacitors on the direct current bus respectively; c1、C2The direct current bus is provided with the same capacitance to ground; ideal bidirectional switching function
Figure BDA0002541467000000134
Figure BDA0002541467000000135
Respectively showing the switching states of three-phase upper and lower bridge arms of the grid-side converter A, B, C; ideal bidirectional switching function
Figure BDA0002541467000000136
Respectively showing the switching states of the three-phase upper and lower arms of rotor-side converter A, B, C; i isdgAnd IqgRespectively corresponding to the components of a d axis and a q axis of the current input into the power grid by the grid-side converter; i isdrAnd IqrComponents of d-axis and q-axis of the current input to the rotor-side converter corresponding to the rotor, respectively; c3/2Is a transformation matrix for transforming variables of an abc three-phase coordinate system into a dq coordinate system, and a superscript-1 represents an inverse matrix.
Wherein M is-1Is the inverse of the rotation transformation matrix, which is specifically represented as:
Figure BDA0002541467000000137
wherein, thetamThe rotor electrical angular position.
Time domain switching function of rotor side converter
Figure BDA0002541467000000138
And time domain switching function of the network side converter
Figure BDA0002541467000000141
Obtaining a switching function S by bilateral Fourier decompositionxIn this stepSwitching function S under extended harmonic domainxAnd the switching function S in step S202xSame, switching function SxConverter direct current bus dynamic model as extended harmonic domain
Figure BDA0002541467000000142
Figure BDA0002541467000000143
Values are provided.
In step 4), integrating the models obtained in steps 1) to 3) to obtain a dynamic model of the doubly-fed wind power generation system, wherein the specific integration method can be as follows:
due to xdAnd xqThere is a phase difference of 90 DEG, and the relation between the two can be expressed as xq＝ExdWherein, in the step (A),
Figure BDA0002541467000000144
then when simplifying the model, only x can be extracteddAre variables.
In a balanced system, the DC bus in a back-to-back converter is satisfied
Figure BDA0002541467000000145
DC bus voltage
Figure BDA0002541467000000146
Integrating the obtained dynamic model of the doubly-fed asynchronous generator based on the extended harmonic domain, the dynamic model of the grid-side system of the back-to-back converter and the dynamic model of the direct-current bus, so that the model is input as the voltage of a motor stator terminal, and is output as the current of the motor stator, the current of a rotor, the current of the grid side and each subharmonic component of the voltage of the direct-current bus in the converter, and the dynamic model of the integrally extended harmonic domain of the doubly-fed asynchronous wind-driven generator is obtained, and is specifically represented as follows:
Figure BDA0002541467000000147
wherein, each element expression in the coefficient matrix is respectively expressed as:
Figure BDA0002541467000000148
Figure BDA0002541467000000151
Figure BDA0002541467000000152
Figure BDA0002541467000000153
Figure BDA0002541467000000154
Figure BDA0002541467000000155
Figure BDA0002541467000000156
Figure BDA0002541467000000157
to illustrate the effects of the present example, a simulation experiment was performed:
the harmonic characteristics of the doubly-fed wind power generation system under the steady-state and transient conditions are analyzed by the embodiment. Fig. 4 shows a comparison between the harmonic steady-state analysis result (EHD model) and the electromagnetic transient model (EMT model) simulation result in the present embodiment at a constant wind speed, and the analytic value and the simulation value have better consistency.
FIG. 5 shows a comparison of the voltage variation of the direct current bus in the embodiment with an electromagnetic transient model and an average model under a varying wind speed, and the embodiment can track the dynamic response of the voltage variation of the direct current bus in the wind power system in time; FIG. 6 shows a comparison between the present embodiment and electromagnetic transient model, average model under varying wind speed, the present embodiment can reflect the phenomenon of impulse instability of the current; FIG. 7 is a graph comparing the harmonic current spectrum of the stator of the generator corresponding to a certain time point under a changing wind speed according to the present embodiment and the electromagnetic transient model; fig. 8 shows the dynamic variation process of stator harmonic current of 38 times, 42 times, 79 times and 81 times of generator under the condition of changing wind speed in the embodiment. Therefore, the mathematical model for definitely considering the switching process in the algorithm of the embodiment is more suitable for reflecting the dynamic response in the fan and tracking the dynamic process of the harmonic current of the stator, has higher accuracy in both a steady state and a transient state, can accurately reflect the impact jump of each subharmonic and feeds back the quality condition of electric energy in time.
Example 2
The embodiment provides a wind power generation system output monitoring system based on an extended harmonic domain model, which includes:
a time domain model building module: the system comprises a wind driven generator, a converter, a network side system and a direct current bus, wherein the network side system and the direct current bus are configured to establish a time domain model respectively aiming at the wind driven generator and the converter;
a data acquisition module: the system is configured to respectively acquire electrical parameter data of a wind driven generator, a network side system of a converter and a direct current bus;
an extended harmonic domain model building module: the system is configured to establish an extended harmonic domain model for the wind driven generator, a grid side system of the converter and the direct current bus respectively according to the obtained electrical parameter data through vector transformation and frequency domain normalization aiming at the established time domain model;
an integration monitoring module: the method comprises the steps that an extended harmonic domain model which is configured and used for being integrated and established is used, the end voltage of a motor stator is used as input, the output is the harmonic components of the motor stator current, the rotor current, the network side current and the direct current bus voltage in a converter, the integral extended harmonic domain dynamic model of the double-fed asynchronous wind driven generator is obtained, and the model is used for monitoring the output state of a wind power generation system.
Example 3
The present embodiment provides an electronic device comprising a memory and a processor, and computer instructions stored on the memory and executed on the processor, wherein the computer instructions, when executed by the processor, perform the steps of the method of embodiment 1.
Example 4
The present embodiment provides a computer readable storage medium for storing computer instructions which, when executed by a processor, perform the steps of the method of embodiment 1.
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.
Although the present disclosure has been described with reference to specific embodiments, it should be understood that the scope of the present disclosure is not limited thereto, and those skilled in the art will appreciate that various modifications and changes can be made without departing from the spirit and scope of the present disclosure.

Claims (7)

1. The wind power generation system output monitoring method based on the extended harmonic domain model is characterized by comprising the following steps of:
respectively establishing time domain models aiming at a wind driven generator, a network side system of a converter and a direct current bus;
respectively acquiring electrical parameter data of a wind driven generator, a network side system of a converter and a direct current bus;
aiming at the established time domain model, respectively establishing an extended harmonic domain model aiming at a wind driven generator, a network side system of a converter and a direct current bus according to the obtained electrical parameter data through vector transformation and frequency domain normalization;
the method for establishing the doubly-fed asynchronous generator dynamic model based on the extended harmonic domain for the wind driven generator comprises the following steps:
according to a dq equivalent circuit model of the doubly-fed asynchronous generator, a state space equation of the doubly-fed asynchronous generator is established by taking stator current and rotor current as state quantities and taking stator voltage and rotor voltage as input quantities, and the method specifically comprises the following steps:
Figure FDF0000016945170000011
in the formula, omegamIs the electrical angular frequency, omega, of the generator rotorsIs the angular frequency of the stator of the generator,
Figure FDF0000016945170000012
is omegasOf Toplitz matrix form idsAnd iqsAre respectively stator currents
Figure FDF0000016945170000021
D-axis and q-axis components of (1); i.e. idrAnd iqrAre respectively rotor currents
Figure FDF0000016945170000022
D-axis and q-axis components of (1); rsIs the generator stator resistance, RrIs the generator rotor resistance, Ls、Lr、LmThe inductance of the stator, the inductance of the rotor and the excitation inductance of the generator are respectively; v. ofdsAnd vqsAre respectively stator voltages
Figure FDF0000016945170000023
The d-axis and q-axis components of (a); v. ofdrAnd vqrAre respectively rotor voltage
Figure FDF0000016945170000024
D-axis and q-axis components of (1);
obtaining an extended harmonic domain dynamic model of the doubly-fed asynchronous generator by adopting a frequency domain normalization method according to a state space equation and an extended harmonic domain core equation of the doubly-fed asynchronous generator;
acquiring electrical parameter data of the wind driven generator, determining coefficients of a harmonic state space model of the doubly-fed asynchronous generator, and establishing a final harmonic state space model of the doubly-fed asynchronous generator;
the method for establishing the converter grid-side dynamic model based on the extended harmonic domain for the back-to-back converter grid-side system comprises the following steps:
establishing a grid-side converter model and a three-phase inductive filter model of the grid-side converter connected to the power grid according to the equivalent circuit model of the grid-side system and the ideal bidirectional switch function;
carrying out vector transformation on three-phase variables in the network side converter model and the three-phase inductive filter model, and then integrating the three-phase variables into a dynamic mathematical model described by a network side system in a synchronous rotating coordinate system in a state space equation form;
converting a state space equation of the network side system into an extended harmonic domain by adopting a frequency domain constant method;
the method for establishing the converter direct-current bus dynamic model based on the extended harmonic domain for the direct-current bus comprises the following steps:
obtaining the relation between the direct current input and the direct current output of the direct current bus according to an ideal bidirectional switching function and a two-level topology back-to-back converter; acquiring capacitance parameters of the direct current bus, and establishing a dynamic mathematical model of the direct current bus; converting the rotor variable into a stator coordinate system through inverse rotation transformation, performing vector transformation on the three-phase variable, and establishing a state space equation of a direct current bus in a synchronous rotation coordinate system;
taking the direct-current bus capacitor voltage as a state quantity, and adding a differential term of the state quantity on the left side of an original state space equation according to an extended harmonic source core equation; performing bilateral Fourier decomposition on each state quantity and input quantity in a state space equation of the direct current bus to obtain a harmonic wave state space model of the direct current bus of the back-to-back converter, namely obtaining a converter direct current bus dynamic model of an extended harmonic wave domain, wherein the harmonic wave state space model is expressed as follows:
Figure FDF0000016945170000031
in the formula (I), the compound is shown in the specification,
Figure FDF0000016945170000032
and
Figure FDF0000016945170000033
the amplitudes are equal, the phases are opposite, and the amplitudes represent the voltages to the ground of two capacitors on the direct current bus respectively; c1、C2The direct current bus is provided with the same capacitance to ground; ideal bidirectional switching function
Figure FDF0000016945170000034
Figure FDF0000016945170000035
Respectively showing the switching states of three-phase upper and lower bridge arms of the grid-side converter A, B, C; ideal bidirectional switching function
Figure FDF0000016945170000036
Respectively showing the switching states of the three-phase upper and lower arms of rotor-side converter A, B, C; i isdgAnd IqgRespectively corresponding to the components of a d axis and a q axis of the current input into the power grid by the grid-side converter; i isdrAnd IqrComponents of d-axis and q-axis of the current input to the rotor-side converter corresponding to the rotor, respectively; c3/2Converting variables of an abc three-phase coordinate system into a transformation matrix of a dq coordinate system, and superscript-1 represents an inverse matrix; m-1Is the inverse of the rotation transformation matrix;
and integrating the established extended harmonic domain model, taking the terminal voltage of a motor stator as input, and outputting the terminal voltage of the motor stator, the rotor current, the network side current and each subharmonic component of the direct current bus voltage in the converter to obtain an integral extended harmonic domain dynamic model of the doubly-fed asynchronous wind driven generator, which is specifically expressed as follows:
Figure FDF0000016945170000037
wherein, each element expression in the coefficient matrix is respectively expressed as:
Figure FDF0000016945170000041
Figure FDF0000016945170000042
Figure FDF0000016945170000043
Figure FDF0000016945170000044
Figure FDF0000016945170000045
Figure FDF0000016945170000046
Figure FDF0000016945170000047
Figure FDF0000016945170000051
and monitoring the output state of the wind power generation system by using the integral extended harmonic domain dynamic model.
2. The method according to claim 1, wherein the method comprises the following steps: the method for frequency domain stationary normalization comprises the following steps of obtaining a dynamic model of an extended harmonic domain of a doubly-fed asynchronous generator, specifically: a differential term of the state quantity is newly added on the left side of the original state space; each state quantity and input quantity are decomposed into harmonic space vectors through bilateral Fourier; establishing a column vector of Fourier coefficients containing each subharmonic of a harmonic space vector, and correspondingly taking the column vector as a state quantity and an input quantity; and adjusting the coefficient matrix of the original state space according to the dimension changes of the state quantity and the input quantity.
3. The method according to claim 1, wherein the method comprises the following steps: for the wind driven generator, the electrical parameter data of the wind driven generator required to be acquired comprises: the wind driven generator comprises a resistor, an inductor and a leakage inductor, wherein the resistor comprises a stator resistor and a rotor resistor, the inductor comprises a generator stator inductor, a rotor inductor and an excitation inductor, and the leakage inductor comprises a stator leakage inductor and a rotor leakage inductor.
4. The method according to claim 1, wherein the method comprises the following steps: a method for converting a state space equation of a network side system into an extended harmonic domain by adopting a frequency domain constancy method specifically comprises the following steps:
adding a differential term of the state quantity on the left side of the original state space equation;
each state quantity and input quantity are decomposed into harmonic space vectors through bilateral Fourier, and the vectors contain Fourier coefficients of each harmonic; the method comprises the following steps that a time domain switching function of a network side converter is subjected to bilateral Fourier decomposition to obtain a switching function expressed in a Toeplitz matrix form in an extended harmonic domain;
the coefficient matrix of the original state space is adjusted correspondingly according to the dimension of the state quantity and the input quantity.
5. An output monitoring system for the wind power generation system output monitoring method based on the extended harmonic domain model according to any one of claims 1 to 4, comprising:
a time domain model building module: the system comprises a wind driven generator, a converter, a network side system and a direct current bus, wherein the network side system and the direct current bus are configured to establish a time domain model respectively aiming at the wind driven generator and the converter;
a data acquisition module: the system comprises a wind driven generator, a converter, a network side system and a direct current bus, wherein the system is configured to obtain electrical parameter data of the wind driven generator, the network side system of the converter and the direct current bus respectively;
an extended harmonic domain model building module: the system is configured to establish an extended harmonic domain model for the wind driven generator, a grid side system of the converter and the direct current bus respectively according to the obtained electrical parameter data through vector transformation and frequency domain normalization aiming at the established time domain model;
an integration monitoring module: the method comprises the steps that an extended harmonic domain model which is configured and used for being integrated and established is used, the end voltage of a motor stator is used as input, the output is the harmonic components of the motor stator current, the rotor current, the network side current and the direct current bus voltage in a converter, the integral extended harmonic domain dynamic model of the double-fed asynchronous wind driven generator is obtained, and the model is used for monitoring the output state of a wind power generation system.
6. An electronic device comprising a memory and a processor and computer instructions stored on the memory and executable on the processor, the computer instructions when executed by the processor performing the steps of the method of any of claims 1 to 4.
7. A computer-readable storage medium storing computer instructions which, when executed by a processor, perform the steps of the method of any one of claims 1 to 4.
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101949774A (en) * 2010-08-30 2011-01-19 杨彦利 Method for monitoring remote real-time state of wind generating multi-set
WO2011060130A1 (en) * 2009-11-12 2011-05-19 Paul Reed Smith Guitars Limited Partnership Domain identification and separation for precision measurement of waveforms
CN106026175A (en) * 2016-07-08 2016-10-12 电子科技大学 Time domain matrix modeling method for a full-order doubly-fed wind power generation system
CN108923463A (en) * 2018-07-27 2018-11-30 湖南大学 Consider the frequency coupling modeling method of the single-phase LCL type gird-connected inverter of phaselocked loop
CN110676874A (en) * 2019-10-09 2020-01-10 西安热工研究院有限公司 Direct-drive fan subsynchronous oscillation electrical quantity analysis method considering frequency coupling effect

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108508320B (en) * 2018-03-28 2019-11-26 山东大学 Arc grounding fault identification method based on harmonic energy and wave distortion feature
CN109061302A (en) * 2018-08-30 2018-12-21 内蒙古工业大学 A kind of wind power generator incorporated in power network group harmonic measure system converted based on EEMD and Hilbert

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011060130A1 (en) * 2009-11-12 2011-05-19 Paul Reed Smith Guitars Limited Partnership Domain identification and separation for precision measurement of waveforms
CN101949774A (en) * 2010-08-30 2011-01-19 杨彦利 Method for monitoring remote real-time state of wind generating multi-set
CN106026175A (en) * 2016-07-08 2016-10-12 电子科技大学 Time domain matrix modeling method for a full-order doubly-fed wind power generation system
CN108923463A (en) * 2018-07-27 2018-11-30 湖南大学 Consider the frequency coupling modeling method of the single-phase LCL type gird-connected inverter of phaselocked loop
CN110676874A (en) * 2019-10-09 2020-01-10 西安热工研究院有限公司 Direct-drive fan subsynchronous oscillation electrical quantity analysis method considering frequency coupling effect

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Extended Harmonic Domain Model of a Wind Turbine Generator for Harmonic Transient Analysis;Uriel Vargas、Abner Ramirez;《IEEE TRANSACTIONS ON POWER DELIVERY》;20160630;第31卷(第3期);第1360-1368页 *

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