CN114465280A - Dynamic equivalent modeling method for new energy grid-connected system - Google Patents

Dynamic equivalent modeling method for new energy grid-connected system Download PDF

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CN114465280A
CN114465280A CN202210314670.5A CN202210314670A CN114465280A CN 114465280 A CN114465280 A CN 114465280A CN 202210314670 A CN202210314670 A CN 202210314670A CN 114465280 A CN114465280 A CN 114465280A
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fitting
new energy
energy grid
current
admittance
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冯双
崔昊
雷家兴
汤奕
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Southeast 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
    • H02J3/381—Dispersed generators
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
    • G06F17/10—Complex mathematical operations
    • G06F17/16—Matrix or vector computation, e.g. matrix-matrix or matrix-vector multiplication, matrix factorization
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • 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
    • 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
    • H02J2300/40—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation wherein a plurality of decentralised, dispersed or local energy generation technologies are operated simultaneously

Abstract

The invention discloses a dynamic equivalent modeling method for a new energy grid-connected system, and relates to the technical field of power systems. The method comprises the following steps: under different operation modes, measuring the input admittance of the new energy grid-connected system, and acquiring the steady-state current value of the PCC point; fitting the transfer function and each order coefficient of the transfer function to the measurement admittance in sequence by using a transfer function identification method and a function fitting method; on the basis, calculating the equivalent admittance and the small signal component of the system according to the dynamic characteristics of the phase-locked loop; meanwhile, fitting the steady-state current of the PCC points by adopting a function fitting method; and finally, superposing the fitted steady-state component and the small signal component to obtain the reference output of the controlled current source in the equivalent model, thereby realizing the dynamic equivalent modeling of the new energy grid-connected system under the variable working condition. The method can perform time domain simulation under the condition of keeping frequency domain consistency, does not depend on specific structural parameters of an original system, accelerates the time domain simulation speed of the system, and is also suitable for the stability analysis research of broadband oscillation.

Description

Dynamic equivalent modeling method for new energy grid-connected system
Technical Field
The invention relates to the technical field of power systems, in particular to a dynamic equivalent modeling method for a new energy grid-connected system.
Background
As a renewable energy source with low cost, abundant reserves and high utilization rate, wind power becomes a new energy power generation technology with the largest installed capacity increase in recent years, and has been developed and utilized on a large scale in the global scope. However, in recent years, broadband oscillation events in a wind power grid-connected system often occur, and the propagation path and the induction mechanism of the oscillation are not clear yet, so that the broadband oscillation events are important factors threatening the safe and stable operation of a new energy power system. In order to research the broadband oscillation problem, a wind power grid-connected system model needs to be constructed for theoretical analysis and simulation operation, and because the actual wind power system has a large scale and a high order, a dimension disaster problem is caused by detailed modeling of each device, an equivalent model is usually adopted for dynamic characteristic research of the wind power grid-connected system.
The aggregation method is a common dynamic equivalent modeling method for the new energy grid-connected system, and reduces the number of target units by equating the wind generation units in the whole new energy grid-connected system to a single unit or a plurality of units so as to simplify modeling analysis. However, in the method verification of the existing relevant documents related to the polymerization method, most of the existing relevant documents only pay attention to the consistency of the output active power and the output reactive power of the new energy grid-connected system before and after equivalence on time domain response, and whether the multi-scale dynamic interaction characteristics of the large-scale wind power grid-connected system can be represented by using the modeling method or not is difficult to guarantee for effective analysis of broadband oscillation.
Disclosure of Invention
The invention aims to provide a dynamic equivalent modeling method of a new energy grid-connected system, the method equates the new energy grid-connected system into a current source obtained by superposing a steady-state component and a small signal component, input admittance matrixes of the new energy grid-connected system under different operation modes are obtained by adopting an admittance measuring method based on a dq coordinate system, transfer function fitting is carried out on the measured admittance under each operation mode by utilizing a transfer function identification method, the relation between each order coefficient of the admittance transfer function and the operation point of the new energy grid-connected system is obtained based on a function fitting method, and the equivalent admittance matrix of the original system is further calculated based on the dynamic response characteristic of a phase-locked loop. Meanwhile, acquiring the steady-state current of the PCC points and fitting the relation between the PCC points and the operating points of the new energy grid-connected system under different operating modes of the new energy grid-connected system. And then, acquiring the PCC point voltage under the three-phase static coordinate system to perform dq coordinate transformation, and respectively subtracting corresponding voltage steady-state components to obtain corresponding voltage small signal components. Further, a current small signal component under the dq control coordinate system is calculated based on the equivalent admittance of the new energy grid-connected system, and the current component under the dq control coordinate system can be obtained after the fitted current steady-state components are superposed. And finally, converting the current component from the dq control coordinate system to a three-phase static coordinate system, outputting the current component as a reference value of an equivalent model controlled current source, realizing dynamic equivalent modeling of the new energy grid-connected system under a variable working condition, and providing a foundation for stability analysis and simulation operation of broadband oscillation.
The purpose of the invention can be realized by the following technical scheme:
a dynamic equivalent modeling method for a new energy grid-connected system is characterized in that the new energy grid-connected system is equivalent to a three-phase controlled current source, and the equivalent modeling method comprises the following steps:
step S1, under different operation modes of the new energy grid-connected system, adopting an admittance measuring method based on the dq coordinate system to obtain an input admittance matrix of the new energy grid-connected system
Figure BDA0003568658740000021
Figure BDA0003568658740000022
Wherein k and i respectively represent the kth operation mode and the ith measurement frequency;
and S2, under each operation mode of the new energy grid-connected system, utilizing a transfer function identification method to carry out identification on all the measurement frequencies obtained in the step S1
Figure BDA0003568658740000023
Fitting a transfer function to obtain
Figure BDA0003568658740000024
Figure BDA0003568658740000025
Step S3 taking out in step S2
Figure BDA0003568658740000031
Obtaining the relation between each coefficient and the new energy grid-connected system operating point by using the function fitting method for each order coefficient of each admittance of the matrix to obtain the final admittance transfer function fitting result of the new energy grid-connected system
Figure BDA0003568658740000032
And
Figure BDA0003568658740000033
step S4, based on the dynamic response characteristic of the phase-locked loop, comparing with the step S3
Figure BDA0003568658740000034
Figure BDA0003568658740000035
And
Figure BDA0003568658740000036
compensating to obtain an equivalent admittance matrix Y of the new energy grid-connected systemEq；
Step S5, collecting the component I of the steady-state current of the PCC point in the dq coordinate system of the alternating current system under different operation modes of the new energy grid-connected systemgd、Igq；
Step S6, utilizing a function fitting method to the steady-state current component I in the step S5gd、IgqFitting the relation between the current and the new energy grid-connected system operating point to obtain a fitted steady-state current component
Figure BDA0003568658740000037
And
Figure BDA0003568658740000038
step S7, collecting the voltage u of the PCC point under the three-phase static coordinate systempa、upb、upcAnd carrying out dq coordinate transformation to obtain corresponding components under a dq control coordinate system
Figure BDA0003568658740000039
And
Figure BDA00035686587400000310
Figure BDA00035686587400000311
wherein θ is the phase angle provided by the phase locked loop;
step S8 utilizing the result of step S7
Figure BDA00035686587400000312
And
Figure BDA00035686587400000313
respectively subtracting the steady-state component U of the voltage of the PCC points under the dq coordinate system of the infinite power gridpdAnd UpqTo obtain corresponding voltage small signal component
Figure BDA00035686587400000314
And
Figure BDA00035686587400000315
namely:
Figure BDA00035686587400000316
step S9 according to the voltage small signal component in step S8 and the equivalent admittance matrix Y in step S4EqCalculating the current small signal component under the dq control coordinate system
Figure BDA00035686587400000317
And
Figure BDA00035686587400000318
Figure BDA00035686587400000319
step S10 Current Small Signal component at step S9
Figure BDA00035686587400000320
And
Figure BDA00035686587400000321
on the basis, the current steady-state components obtained by fitting in the step S5 are respectively superposed
Figure BDA0003568658740000041
And
Figure BDA0003568658740000042
obtaining current components under dq control coordinate system
Figure BDA0003568658740000043
And
Figure BDA0003568658740000044
Figure BDA0003568658740000045
step S11, current is applied based on the phase angle theta provided by the phase-locked loop
Figure BDA0003568658740000046
And
Figure BDA0003568658740000047
the dq control coordinate system is transformed into a three-phase static coordinate system to obtain iga、igbAnd igcAnd as a reference value of a three-phase controlled current source of the new energy grid-connected system equivalent model:
Figure BDA0003568658740000048
further, in the kth operation mode in step S1, the admittance measurement method based on the dq coordinate system at the ith measurement frequency is:
step S11: in a simulation model, given a system phase angle, keeping the q-axis current disturbance to be 0, and applying a frequency f to the d-axis currentiThe sine disturbance signal is converted into three-phase current disturbance by coordinate transformation;
step S12: injecting the three-phase current disturbance in the step S11 into a PCC point through a controlled current source, and collecting the voltage and current of the PCC point to perform dq coordinate transformation;
step S13: separating the frequency f by using a parameter identification algorithmiVoltage and current of, get
Figure BDA0003568658740000049
Figure BDA00035686587400000410
And
Figure BDA00035686587400000411
step S14: giving a system phase angle in a simulation model, keeping d-axis current disturbance as 0, applying a sine disturbance signal with a specific frequency to q-axis current, and converting the sine disturbance signal into three-phase current disturbance by using abc coordinate transformation;
step S15: repeating the process from step S12 to step S13 to obtain
Figure BDA00035686587400000412
And
Figure BDA00035686587400000413
Figure BDA00035686587400000414
step S16: utilizing step S13 and step S15The frequency f is calculated from the voltage current valueiAdmittance matrix of dq coordinate system under
Figure BDA0003568658740000051
Figure BDA0003568658740000052
Further, the transfer function fitting process in step S2 is:
step S21: taking out all frequency points in the measurement frequency range and corresponding dq coordinate system measurement admittances, and respectively using the frequency points and the corresponding dq coordinate system measurement admittances as frequency and response inputs of a transfer function identification algorithm;
step S22: setting the number of zero poles of the fitting transfer function, and obtaining the fitting admittance transfer function by using a transfer function identification algorithm:
Figure BDA0003568658740000053
in the formula, y(s) represents
Figure BDA0003568658740000054
Or
Figure BDA0003568658740000055
Or
Figure BDA0003568658740000056
Or
Figure BDA0003568658740000057
bm、bm-1、bm-2、…、b1、b0，an、an-1、an-2、…、a1、a0Are all real constants; m and n are respectively the number of zero and pole of the set fitting transfer function;
step S23: and adjusting the number of fitted zero poles, and taking the transfer function with the fitting degree larger than a set value as the transfer function of the final dq coordinate system measurement admittance.
Further, the step of fitting the functions of the coefficients of the orders of the admittance transfer function with respect to the operating point in step S3 includes:
step S31: taking out the characteristic parameters of each operating point and the coefficient of the specific order of the measured admittance numerator or denominator under each operating point;
step S32: setting the times of the respective variables by taking the characteristic parameters as independent variables and the coefficients of admittance specific orders as dependent variables, and inputting a function fitting algorithm to perform relationship fitting among the variables;
step S33: and adjusting the times of the respective variables, and taking a fitting function with the lowest times of the independent variables in the result with the fitting degree larger than the set value as a final result.
Further, the new energy grid-connected system equivalent admittance matrix Y in the step S4EqThe calculation method comprises the following steps:
Figure BDA0003568658740000061
in the formula, Gpll(s) is a transfer function of the phase locked loop control system;
further, the steady-state current component I in the step S6gd、IgqThe function fitting method of (1) is as follows:
step S61: extracting the characteristic parameters of each operating point and the PCC point steady-state current component I under each operating point in the step S4gd、Igq；
Step S62: taking the characteristic parameter as an independent variable, IgdOr IgqSetting the fitting times of the variables for the dependent variables, and inputting a function fitting algorithm to fit the relationship between the variables;
step S63: and adjusting the fitting times of the respective variables, and describing the relationship between the current steady-state component of the PCC points and the operating points by taking the fitting function with the lowest times of the independent variables in the result that the fitting degree is greater than the set value.
Further, the input signal of the phase-locked loop control system in step S7 is in a three-phase stationary coordinate systemVoltage u of PCC pointpa、upb、upc
The invention has the beneficial effects that:
the dynamic equivalent modeling method of the new energy grid-connected system based on variable working condition admittance fitting is used as a time domain simulation method only based on system measurement data, does not depend on specific structural parameters of an original system, does not need to solve a differential algebraic equation set reflecting the dynamic characteristics of an electric power system, and accelerates the time domain simulation speed of the system; meanwhile, the method takes the consistency of the admittance curves of the new energy grid-connected system before and after equivalence as a target, so that the frequency domain consistency closely related to the broadband oscillation stability is also ensured, and the correctness of the equivalence model of the new energy grid-connected system for time domain stability analysis is ensured.
Drawings
The invention will be further described with reference to the accompanying drawings.
FIG. 1 is a flow chart of the present invention;
fig. 2 is a comparison graph of measured admittance curves before and after equivalence of a new energy grid-connected system in the first embodiment of the present invention;
fig. 3 is a comparison graph of dynamic characteristic curves before and after equivalence of a new energy grid-connected system in the first embodiment of the present invention;
fig. 4 is a comparison graph of measured admittance curves before and after equivalence of the new energy grid-connected system in the second embodiment of the present invention;
fig. 5 is a comparison graph of dynamic characteristic curves before and after equivalence of the new energy grid-connected system in the second embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the embodiment, a new energy grid-connected system model with a single direct-drive fan connected to an infinite power grid is adopted, and dynamic equivalent modeling of a wind power plant is performed based on a PCC (point of stability) steady-state current and a wind power plant input admittance obtained by function fitting, as shown in FIG. 1. The equivalent model of the wind power plant is a current source obtained by superposing a steady-state component and a small signal component, and the specific equivalent process comprises the following steps:
step S1, under different operation modes of the wind power plant, adopting an admittance measuring method based on the dq coordinate system to obtain an input admittance matrix of the wind power plant
Figure BDA0003568658740000071
Figure BDA0003568658740000072
Wherein k and i respectively represent the kth operation mode and the ith measurement frequency. The specific steps of measuring the input admittance of the wind power plant are as follows:
step S11: in a simulation model, given a system phase angle, keeping the q-axis current disturbance to be 0, and applying a frequency f to the d-axis currentiConverting the sine disturbance signal into three-phase current disturbance by using abc coordinate transformation;
step S12: injecting the three-phase current disturbance in the step S11 into a PCC point through a controlled current source, and collecting the voltage and current of the PCC point to perform dq coordinate transformation;
step S13: separating the frequency f by using a parameter identification algorithmiVoltage and current of, get
Figure BDA0003568658740000073
Figure BDA0003568658740000074
And
Figure BDA0003568658740000075
step S14: giving a system phase angle in a simulation model, keeping d-axis current disturbance as 0, applying a sine disturbance signal with a specific frequency to q-axis current, and converting the sine disturbance signal into three-phase current disturbance by using abc coordinate transformation;
step S15: repeating the process from step S12 to step S13 to obtain
Figure BDA0003568658740000081
And
Figure BDA0003568658740000082
(i)；
step S16: the frequency f is calculated by using the voltage current values in step S13 and step S15iAdmittance matrix of dq coordinate system under
Figure BDA0003568658740000083
Figure BDA0003568658740000084
Step S2, under each operation mode of the wind power plant, the transfer function identification method is used for all the measurement frequencies obtained in the step S1
Figure BDA0003568658740000085
Fitting a transfer function to obtain
Figure BDA0003568658740000086
Figure BDA0003568658740000087
The method comprises the following specific steps:
step S21: taking out all frequency points in the measurement frequency range and corresponding dq coordinate system measurement admittances, and respectively using the frequency points and the corresponding dq coordinate system measurement admittances as frequency and response input of a system identification tool box in Matlab software;
step S22: the number of the zero poles of the fitting transfer function is set, a transfer function fitting module in a system identification toolbox is utilized, and the admittance transfer function is fitted:
Figure BDA0003568658740000088
in the formula, y(s) represents
Figure BDA0003568658740000089
Or
Figure BDA00035686587400000810
Or
Figure BDA00035686587400000811
Or
Figure BDA00035686587400000812
bm、bm-1、bm-2、…、b1、b0，an、an-1、an-2、…、a1、a0Are all real constants; m and n are respectively the number of zero and pole of the set fitting transfer function;
step S23: and calculating the fitting degree of the transfer function according to the tfeSt function, adjusting the number of zero poles of the fitting, and taking the transfer function with the fitting degree of more than 95% as the transfer function of the final dq coordinate system measurement admittance.
Step S3 taking out in step S2
Figure BDA0003568658740000091
Obtaining the relation between each coefficient and the wind power plant operating point by using a function fitting method according to each order coefficient of each admittance of the matrix, and the specific steps are as follows:
step S31: the given values of wind speed v (k) and q-axis current of each operating point are taken out
Figure BDA0003568658740000092
And coefficients measuring a particular order of admittance numerator or denominator, e.g. b, at each operating pointm(k) Where K is 1,2, …, K, representing the kth respective operating point;
step S32: wind speeds v (k) and
Figure BDA0003568658740000093
admittance of coefficients of a certain order b as independent variablem(k) Setting the times of the variables as dependent variables, and inputting the times into a fit function in Matlab software to perform binary function fitting;
step S33: using goodness of fit R2And (4) calculating the fitting degree, adjusting the times of the variables, and taking the fitting function with the lowest times of the independent variables in the result with the fitting degree larger than 95% as a final result. Wherein R is2The calculation formula of (2) is as follows:
Figure BDA0003568658740000094
in the formula, XiIs an actual value; x is the number ofiIs a fitting value;
Figure BDA0003568658740000095
is XiAverage value of (a).
Step S4, based on the dynamic response characteristic of the phase-locked loop, comparing with the step S3
Figure BDA0003568658740000096
Y* Re_qd(s) and
Figure BDA0003568658740000097
compensating to obtain an equivalent admittance matrix Y of the new energy grid-connected systemEqWherein Y isEqThe calculation method comprises the following steps:
Figure BDA0003568658740000098
in the formula, Gpll(s) is a transfer function of the phase-locked loop control system, and the transfer function of the phase-locked loop used in the embodiment is as follows:
Figure BDA0003568658740000099
wherein k ispAnd kiProportional and integral coefficients of the phase locked loop, respectively.
Step S5, collecting the component I of the steady-state current of the PCC point in the dq coordinate system of the alternating current system under different operation modes of the wind power plantgd、Igq。
Step S6, utilizing a function fitting method to the steady-state current component I in the step S5gd、IgqFitting the relation between the wind power plant operation points to obtain a fitting steady-state current component
Figure BDA0003568658740000101
And
Figure BDA0003568658740000102
wherein the steady-state current component Igd、IgqThe function fitting method of (1) is as follows:
step S61: taking out the given values of the wind speed v and q axis currents of each operating point
Figure BDA0003568658740000103
And the steady-state current component I of the PCC points at each operating point in the step S4gd、Igq；
Step S62: at wind speeds v and
Figure BDA0003568658740000104
is an independent variable, IgdOr IgqFor the dependent variable, set the wind speeds v and
Figure BDA0003568658740000105
the maximum fitting times are input into a fit function in Matlab software to carry out steady-state component IgdAnd IgqFitting a binary function of;
step S63: using goodness of fit R2Calculating the degree of fitting, adjusting the fitting times of respective variables, and describing the relationship between the stable-state current component of the PCC points and the operating points by taking the fitting function with the lowest times of independent variables in the result with the degree of fitting more than 95 percent, thereby obtaining the fitting stable-state current component
Figure BDA0003568658740000106
And
Figure BDA0003568658740000107
step S7, collecting the voltage u of the PCC point under the three-phase static coordinate systempa、upb、upcAnd carrying out dq coordinate transformation to obtain corresponding components under a dq control coordinate system
Figure BDA0003568658740000108
And
Figure BDA0003568658740000109
Figure BDA00035686587400001010
in the formula, theta is a phase angle provided by the phase-locked loop, and an input signal of the phase-locked loop is a voltage u of a PCC point under a three-phase static coordinate systempa、upb、upc。
Step S8 utilizing the result of step S6
Figure BDA00035686587400001011
And
Figure BDA00035686587400001012
respectively subtracting the steady-state component U of the voltage of the PCC points under the dq coordinate system of the infinite power gridpdAnd UpqTo obtain corresponding voltage small signal component
Figure BDA00035686587400001013
And
Figure BDA00035686587400001014
namely:
Figure BDA00035686587400001015
step S9 according to the stepsThe voltage small signal component in step S7 is calculated as the current small signal component in the dq control coordinate system
Figure BDA00035686587400001016
And
Figure BDA00035686587400001017
Figure BDA0003568658740000111
step S10 Current Small Signal component at step S8
Figure BDA0003568658740000112
And
Figure BDA0003568658740000113
on the basis, the current steady-state components obtained by fitting in the step S5 are respectively superposed
Figure BDA0003568658740000114
And
Figure BDA0003568658740000115
obtaining current components under dq control coordinate system
Figure BDA0003568658740000116
And
Figure BDA0003568658740000117
Figure BDA0003568658740000118
step S11, current is applied based on the phase angle theta provided by the phase-locked loop
Figure BDA0003568658740000119
And
Figure BDA00035686587400001110
converting the dq control coordinate system into a three-phase static abc coordinate system to obtain iga、igbAnd igcAnd as a reference value of a three-phase controlled current source of the wind power plant equivalent model:
Figure BDA00035686587400001111
the method is further illustrated with reference to the results of the specific examples below. Simulation System based on this embodiment, YqdIs always 0, so Y is not considered in the examplesqdThe associated fit is equivalent.
The first embodiment is as follows: wind speed v is 4.5m/s,
Figure BDA00035686587400001112
Wind farm equivalent result comparison under conditions
(1) Comparison of measured admittance curves before and after equivalence of wind power plant
FIG. 2 shows that the wind speed v is 4.5m/s,
Figure BDA00035686587400001113
And comparing the admittance curve of the original system of the wind power plant under the condition with the admittance curve of the equivalent model based on the phase-locked loop. The measured admittance curve of the equivalent system is consistent with the admittance curve of the original system of the wind power plant, and the wind power plant equivalent modeling method provided by the invention can keep the frequency domain consistency before and after equivalence of the wind power plant.
(2) Dynamic characteristic curve comparison before and after equivalence of wind power plant
In the 2 nd second of time domain simulation, adding an impulse disturbance to the PCC point voltage in the system before and after equivalence respectively, and comparing the wind speed v to 4.5m/s,
Figure BDA00035686587400001114
The results of the dynamic characteristics before and after the equivalent of the wind farm in the case are shown in FIG. 3. It can be seen that the dynamic process of the wind power plant before and after equivalence is basically consistent, and the correctness of the method for the dynamic equivalence of the wind power plant is verifiedAnd the method can be used for judging the time domain stability of the wind power system.
(3) Simulation time comparison before and after equivalence of wind power plant
In the comparison test of the dynamic characteristic curves before and after equivalence of the wind power plant in the first embodiment (2), the simulation time of an original system is 7.711023 seconds, the simulation time of an equivalence system is 5.132814 seconds, and the simulation time of the system after equivalence is shortened.
Example two: the wind speed v is 6m/s,
Figure BDA0003568658740000121
Wind farm equivalent result comparison under condition
(1) Comparison of measured admittance curves before and after equivalence of wind power plant
FIG. 4 shows that the wind speed v is 6m/s,
Figure BDA0003568658740000122
And comparing the admittance curve of the original system of the wind power plant under the condition with the admittance curve of the equivalent model based on the phase-locked loop. The measured admittance curve of the equivalent system is consistent with the admittance curve of the original system of the wind power plant, and the wind power plant equivalent modeling method provided by the invention can keep the frequency domain consistency before and after equivalence of the wind power plant.
(2) Dynamic characteristic curve comparison before and after equivalence of wind power plant
In the 2 nd second of time domain simulation, adding a pulse disturbance to the PCC point voltage in the system before and after equivalence respectively, comparing the wind speed v to 6m/s,
Figure BDA0003568658740000123
The results of the dynamic characteristics before and after the equivalent of the wind farm in the case are shown in FIG. 5. As can be seen, the dynamic process of the wind power plant before and after equivalence is basically consistent, the correctness of the method for the dynamic equivalence of the wind power plant is verified, and the method can be used for judging the time domain stability of the wind power system.
(3) Simulation time comparison before and after equivalence of wind power plant
In the comparison test of the dynamic characteristic curves before and after equivalence of the wind power plant in the second embodiment (2), the simulation time of the original system is 7.533677 seconds, the simulation time of the equivalence system is 4.858612 seconds, and the simulation time of the equivalence system is shortened, so that the time domain simulation speed can be improved.
The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modifications made on the basis of the technical scheme according to the technical idea of the present invention fall within the protection scope of the present invention.

Claims (7)

1. A dynamic equivalent modeling method for a new energy grid-connected system is characterized in that the new energy grid-connected system is equivalent to a three-phase controlled current source, and the equivalent modeling method comprises the following steps:
step S1, under different operation modes of the new energy grid-connected system, adopting an admittance measuring method based on the dq coordinate system to obtain an input admittance matrix of the new energy grid-connected system
Figure FDA0003568658730000011
Figure FDA0003568658730000012
Wherein k and i respectively represent the kth operation mode and the ith measurement frequency;
and S2, under each operation mode of the new energy grid-connected system, utilizing a transfer function identification method to carry out identification on all the measurement frequencies obtained in the step S1
Figure FDA0003568658730000013
Fitting a transfer function to obtain
Figure FDA0003568658730000014
Figure FDA0003568658730000015
Step S3 taking out in step S2
Figure FDA0003568658730000016
Obtaining the relation between each coefficient and the new energy grid-connected system operating point by using the function fitting method for each order coefficient of each admittance of the matrix to obtain the final admittance transfer function fitting result of the new energy grid-connected system
Figure FDA0003568658730000017
And
Figure FDA0003568658730000018
step S4, based on the dynamic response characteristic of the phase-locked loop, comparing with the step S3
Figure FDA0003568658730000019
Figure FDA00035686587300000110
And
Figure FDA00035686587300000111
compensating to obtain an equivalent admittance matrix Y of the new energy grid-connected systemEq；
Step S5, collecting component I of PCC point steady state current in dq coordinate system of alternating current system under different operation modes of new energy grid-connected systemgd、Igq；
Step S6, utilizing a function fitting method to the steady-state current component I in the step S5gd、IgqFitting the relation between the current and the new energy grid-connected system operating point to obtain a fitted steady-state current component
Figure FDA00035686587300000112
And
Figure FDA00035686587300000113
step S7, collecting the voltage u of the PCC point under the three-phase static coordinate systempa、upb、upcAnd carrying out dq coordinate transformation to obtain corresponding components under a dq control coordinate system
Figure FDA00035686587300000114
And
Figure FDA00035686587300000115
Figure FDA0003568658730000021
in the formula, theta is a phase angle provided by the phase-locked loop;
step S8 utilizing the result of step S7
Figure FDA0003568658730000022
And
Figure FDA0003568658730000023
respectively subtracting the steady-state component U of the voltage of the PCC points under the dq coordinate system of the infinite power gridpdAnd UpqTo obtain corresponding voltage small signal component
Figure FDA0003568658730000024
And
Figure FDA0003568658730000025
namely:
Figure FDA0003568658730000026
step S9 according to the voltage small signal component in step S8 and the equivalent admittance matrix Y in step S4EqCalculating the current small signal component under the dq control coordinate system
Figure FDA0003568658730000027
And
Figure FDA0003568658730000028
Figure FDA0003568658730000029
step S10 Current Small Signal component at step S9
Figure FDA00035686587300000210
And
Figure FDA00035686587300000211
on the basis, the current steady-state components obtained by fitting in the step S5 are respectively superposed
Figure FDA00035686587300000212
And
Figure FDA00035686587300000213
obtaining current components under dq control coordinate system
Figure FDA00035686587300000214
And
Figure FDA00035686587300000215
Figure FDA00035686587300000216
step S11, current is applied based on the phase angle theta provided by the phase-locked loop
Figure FDA00035686587300000217
And
Figure FDA00035686587300000218
the dq control coordinate system is transformed into a three-phase static coordinate system to obtain iga、igbAnd igcAnd as a reference value of a three-phase controlled current source of the new energy grid-connected system equivalent model:
Figure FDA00035686587300000219
2. the dynamic equivalent modeling method for the new energy grid-connected system according to claim 1, wherein in the kth operation mode in step S1, the admittance measuring method based on the dq coordinate system at the ith measuring frequency is:
step S11: in a simulation model, given a system phase angle, keeping the q-axis current disturbance to be 0, and applying a frequency f to the d-axis currentiThe sine disturbance signal is converted into three-phase current disturbance by coordinate transformation;
step S12: injecting the three-phase current disturbance in the step S11 into a PCC point through a controlled current source, and collecting the voltage and the current of the PCC point to perform dq coordinate transformation;
step S13: separating the frequency f by using a parameter identification algorithmiVoltage and current of, get
Figure FDA0003568658730000031
Figure FDA0003568658730000032
And
Figure FDA0003568658730000033
step S14: giving a system phase angle in a simulation model, keeping d-axis current disturbance as 0, applying a sine disturbance signal with a specific frequency to q-axis current, and converting the sine disturbance signal into three-phase current disturbance by using abc coordinate transformation;
step S15: repeating the process from step S12 to step S13 to obtain
Figure FDA0003568658730000034
And
Figure FDA0003568658730000035
Figure FDA0003568658730000036
step S16: the frequency f is calculated by using the voltage current values in step S13 and step S15iAdmittance matrix of dq coordinate system under
Figure FDA0003568658730000037
Figure FDA0003568658730000038
3. The dynamic equivalent modeling method for the new energy grid-connected system according to claim 1, wherein the transfer function fitting process in the step S2 is as follows:
step S21: taking out all frequency points in the measurement frequency range and corresponding dq coordinate system measurement admittances, and respectively using the frequency points and the corresponding dq coordinate system measurement admittances as frequency and response inputs of a transfer function identification algorithm;
step S22: setting the number of zero poles of the fitting transfer function, and obtaining the fitting admittance transfer function by using a transfer function identification algorithm:
Figure FDA0003568658730000039
in the formula, y(s) represents
Figure FDA0003568658730000041
Or
Figure FDA0003568658730000042
Or
Figure FDA0003568658730000043
Or
Figure FDA0003568658730000044
bm、bm-1、bm-2、…、b1、b0，an、an-1、an-2、…、a1、a0Are all real constants; m and n are respectively the number of zero and pole of the set fitting transfer function;
step S23: and adjusting the number of fitted zero poles, and taking the transfer function with the fitting degree larger than a set value as the transfer function of the final dq coordinate system measurement admittance.
4. The dynamic equivalent modeling method for the new energy grid-connected system according to claim 1, wherein the function fitting step of each order coefficient of the admittance transfer function with respect to the operating point in the step S3 is as follows:
step S31: taking out the characteristic parameters of each operating point and the coefficient of the specific order of the measured admittance numerator or denominator under each operating point;
step S32: setting the times of the respective variables by taking the characteristic parameters as independent variables and the coefficients of admittance specific orders as dependent variables, and inputting a function fitting algorithm to perform relationship fitting among the variables;
step S33: and adjusting the times of the respective variables, and taking a fitting function with the lowest times of the independent variables in the result of which the fitting degree is greater than the set value as a final result.
5. The dynamic equivalent modeling method for the new energy grid-connected system according to claim 1, characterized in that the equivalent admittance matrix Y of the new energy grid-connected system in the step S4EqThe calculation method comprises the following steps:
Figure FDA0003568658730000045
in the formula, Gpll(s) is the transfer function of the phase locked loop control system.
6. The dynamic equivalent modeling method for the new energy grid-connected system according to claim 1, characterized in that in the step S6, the steady-state current component Igd、IgqThe function fitting method of (1) is as follows:
step S61: extracting the characteristic parameters of each operating point and the PCC point steady-state current component I under each operating point in the step S4gd、Igq；
Step S62: taking the characteristic parameter as an independent variable, IgdOr IgqSetting the fitting times of the variables for the dependent variables, and inputting a function fitting algorithm to fit the relationship between the variables;
step S63: and adjusting the fitting times of the respective variables, and describing the relationship between the current steady-state component of the PCC points and the operating points by taking the fitting function with the lowest times of the independent variables in the result that the fitting degree is greater than the set value.
7. The dynamic equivalent modeling method for the new energy grid-connected system according to claim 1, wherein the input signal of the phase-locked loop control system in the step S7 is a voltage u of a PCC point in a three-phase static coordinate systempa、upb、upc。
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Publication number Priority date Publication date Assignee Title
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116467986A (en) * 2023-03-31 2023-07-21 燕山大学 Automatic control principle-based alkaline electrolytic tank dynamic model modeling method
CN116467986B (en) * 2023-03-31 2023-09-19 燕山大学 Automatic control principle-based alkaline electrolytic tank dynamic model modeling method

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