CN-122026370-A - Method, system, equipment and medium for analyzing harmonic resonance mode of offshore wind power system

CN122026370ACN 122026370 ACN122026370 ACN 122026370ACN-122026370-A

Abstract

The invention belongs to the technical field of power systems, and discloses a method, a system, equipment and a medium for analyzing harmonic resonance modes of an offshore wind power system, wherein the method comprises the steps of constructing a small signal mathematical model of a direct-drive fan based on constant power control, and refining the equivalent admittance of the direct-drive fan; the method comprises the steps of establishing a model of the offshore wind power system, converting the model into admittance parameters under a two-phase rotating coordinate system, establishing a node admittance matrix of the offshore wind power system, establishing a node voltage equation of the offshore wind power system, carrying out eigenvalue decomposition on the node admittance matrix in the node voltage equation of the offshore wind power system, determining eigenvalues and corresponding modal impedances under each frequency based on frequency ranges and step sizes, and positioning resonance points and key modes according to the eigenvalues and the modal impedances so as to realize harmonic resonance modal analysis of the offshore wind power system. The method can perform modal analysis under the dq coordinate system, and can realize harmonic resonance analysis and key node identification of the wind power system.

Inventors

WU CHUANJIAN
CI WENBIN
YANG BO
LI MING
HUANG ZHENNING
ZHANG BOYI
QIN JIAFENG
LIANG ZHENGTANG
ZHANG YAN
WANG HUAJIA
ZHANG QINGQING
LI FUCUN
CAO WENJUN
YU DANWEN
WANG QINGYU
SU YONGZHI

Assignees

国网山东省电力公司电力科学研究院
国家电网有限公司

Dates

Publication Date: 20260512
Application Date: 20251211

Claims (16)

1. The method for analyzing the harmonic resonance mode of the offshore wind power system is characterized by comprising the following steps of: Based on the direct-driven fan structure, constructing a small-signal mathematical model of the direct-driven fan based on constant power control, and refining the equivalent admittance of the direct-driven fan according to the small-signal mathematical model of the direct-driven fan; constructing an offshore wind power system model according to the equivalent admittance of the direct-driven fan, converting three-phase static coordinate system parameters of all elements in the offshore wind power system model into admittance parameters under a two-phase rotating coordinate system, and constructing a node admittance matrix of the offshore wind power system; According to the actual operation characteristics of the offshore wind power system, determining a frequency range and a step length, constructing a node voltage equation of the offshore wind power system, and decomposing characteristic values of a node admittance matrix in the node voltage equation of the offshore wind power system; Based on the frequency range and the step length, determining the characteristic value and the corresponding modal impedance under each frequency, and positioning the resonance point and the key mode according to the characteristic value and the modal impedance so as to realize harmonic resonance modal analysis of the offshore wind power system.
2. The method for analyzing harmonic resonance modes of an offshore wind power system according to claim 1, wherein the direct-driven fan structure is used for constructing a small-signal mathematical model of the direct-driven fan based on constant power control, and extracting the equivalent admittance of the direct-driven fan according to the small-signal mathematical model of the direct-driven fan comprises: Based on the dynamic characteristics of a phase-locked loop in a direct-drive fan structure controlled by constant power, determining a transformation relation between a working point variable in an actual synchronous reference system and a working point variable in a control reference domain; Under a control coordinate system, establishing a state equation of the dq axis component of the modulation voltage of the direct-driven fan, and carrying out small disturbance analysis to obtain the state equation of the dq axis component of the modulation voltage of the direct-driven fan after the small disturbance analysis; according to the transformation relation, converting a state equation of the dq axis component of the direct-driven fan modulation voltage after the small disturbance analysis under the control coordinate system into a synchronous coordinate system, and simplifying the state equation to obtain the state equation of the dq axis component of the direct-driven fan modulation voltage under the synchronous coordinate system; And constructing a relationship between the fan output voltage and the current according to the relationship between the state equation of the dq axis component of the direct-drive fan modulation voltage under the simultaneous synchronous coordinate system and the relationship between the power circuit under the synchronous coordinate system, and extracting the equivalent admittance of the direct-drive fan according to the relationship between the fan output voltage and the current.
3. The method for analyzing harmonic resonance modes of an offshore wind power system according to claim 2, wherein the direct-driven fan structure based on constant power control is composed of a power circuit and a control system, wherein the control system is composed of a power outer ring, a current inner ring and a phase-locked loop, and the phase-locked loop is a phase-locked loop based on a synchronous coordinate system.
4. The method of analyzing harmonic resonance modes of an offshore wind power system according to claim 2, wherein the expression of the transformation relationship between the operating point variable in the actual synchronous reference system and the operating point variable in the control reference system is: In the formula, The d-axis components of the parameters under the control coordinate system and the synchronous coordinate system are respectively, G PLL (s) is a phase-locked loop PI regulator, s is complex frequency, V td0 is a terminal voltage d-axis steady-state value, For small disturbance value of the q-axis of the lower voltage of the synchronous coordinate system, The disturbance component of the q-axis component in the control coordinate system and the synchronous coordinate system, Is a stable value of d and q axis components in a synchronous coordinate system.
5. The method for analyzing harmonic resonance modes of an offshore wind system according to claim 2, wherein the expression of the state equation of the dq-axis component of the modulation voltage of the direct-driven fan after the small disturbance analysis is: In the formula, The disturbance components of the reference values of the d and q axis components of the modulation voltage under the control coordinate system are respectively, G c (s) is a current loop PI regulator, Respectively small disturbance components of reference values of d and q axis components of the power grid inductance L 1 under a control coordinate system, The disturbance values of d and q axis components of the power grid inductance L 1 under the control coordinate system are respectively.
6. The method for analyzing harmonic resonance modes of an offshore wind system according to claim 4, wherein the expression of the state equation of the dq-axis component of the modulation voltage of the direct-drive fan in the synchronous coordinate system is: In the formula, Respectively small disturbance values of d and q axis components of the modulation voltage under the synchronous coordinate system, wherein kk 1 、kk 2 、kk 3 、kk 4 、kk p 、kk q is six loop characteristic coefficients, Respectively the disturbance values of the output voltage of the fan system under the synchronous coordinate system, The disturbance values of the output current of the fan system under the synchronous coordinate system are respectively represented by G de , the delay link, h θ1 、h θ2 , the two angle coupling coefficients and U od0 , and the steady state value of the output voltage of the fan system are respectively represented by h θ1 、h θ2 .
7. The method for analyzing harmonic resonance modes of an offshore wind power system according to claim 6, wherein the relation between the output voltage and the current of the fan is expressed as follows: Where H 1 、H 2 、H 3 、H 4 is four current port characteristic coefficients, and D 1 、D 2 、D 3 、D 4 is four voltage port characteristic coefficients, respectively.
8. The method for analyzing harmonic resonance modes of an offshore wind system according to claim 1, wherein the steps of constructing an offshore wind system model according to the equivalent admittance of the direct-driven fan, converting three-phase stationary coordinate system parameters of all elements in the offshore wind system model into admittance parameters under a two-phase rotating coordinate system, and constructing a node admittance matrix of the offshore wind system comprise: Based on a pi-type circuit of the direct-driven fan, constructing an offshore wind power system model by combining a core node of the offshore wind power system and the equivalent admittance of the direct-driven fan; According to a coordinate transformation rule based on a trigonometric function, converting parameters of a three-phase static coordinate system of all elements in the offshore wind power system model into admittance parameters under a two-phase rotating coordinate system; According to admittance parameters under the two-phase rotation coordinate system, a node admittance matrix of the offshore wind power system based on the two-phase rotation coordinate system is constructed, and the electrical connection relation among the nodes is defined.
9. The method for analyzing harmonic resonance modes of an offshore wind power system according to claim 1, wherein the expression of a node voltage equation of the offshore wind power system is: where Deltav i is the small disturbance component of the voltage at the ith node, For elements of the ith row and jth column in the inverse matrix of the node admittance matrix, Δi j is a jth node injection current small disturbance component, Y -1 and V, I are a small disturbance harmonic impedance matrix of the network, node small disturbance positive and negative sequence voltage and node small disturbance positive and negative sequence current respectively, and x is the number of nodes.
10. The method for analyzing harmonic resonance modes of the offshore wind power system according to claim 1, wherein the left eigenvector matrix and the right eigenvector matrix are obtained after eigenvalue decomposition is carried out on a node admittance matrix in a node voltage equation of the offshore wind power system.
11. The method of claim 1, wherein locating the resonance point and the key mode according to the eigenvalue and the modal impedance comprises: When the characteristic value approaches zero at a certain frequency, the corresponding modal impedance is increased sharply, the frequency is taken as a resonance point, the key mode of harmonic resonance corresponding to the minimum characteristic value is identified, and the left and right characteristic vectors of the key mode are taken as key characteristic vectors.
12. An offshore wind power system harmonic resonance modal analysis system, comprising: the direct-drive fan model construction module is used for constructing a small-signal mathematical model of the direct-drive fan based on constant power control based on the direct-drive fan structure, and extracting the equivalent admittance of the direct-drive fan according to the small-signal mathematical model of the direct-drive fan; The system comprises an offshore wind power system model construction module, a node admittance matrix and a node admittance matrix, wherein the offshore wind power system model construction module is used for constructing an offshore wind power system model according to the equivalent admittance of a direct-driven fan, converting three-phase static coordinate system parameters of all elements in the offshore wind power system model into admittance parameters under a two-phase rotating coordinate system; The node voltage equation construction module is used for determining a frequency range and a step length according to the actual operation characteristics of the offshore wind power system, constructing a node voltage equation of the offshore wind power system, and carrying out eigenvalue decomposition on a node admittance matrix in the node voltage equation of the offshore wind power system; The harmonic resonance modal analysis module is used for determining characteristic values and corresponding modal impedances at each frequency based on the frequency range and the step length, and positioning resonance points and key modes according to the characteristic values and the modal impedances so as to realize harmonic resonance modal analysis of the offshore wind power system.
13. The offshore wind power system harmonic resonance modal analysis system according to claim 12, wherein the direct-driven fan model construction module is used for constructing a small-signal mathematical model of the direct-driven fan based on the direct-driven fan structure and converting the state equation of the dq-axis component of the direct-driven fan modulation voltage under the control coordinate system to a synchronous coordinate system according to the conversion relation and simplifying the processing to obtain the state equation of the dq-axis component of the direct-driven fan modulation voltage under the synchronous coordinate system when the equivalent admittance of the direct-driven fan is extracted according to the small-signal mathematical model of the direct-driven fan based on the direct-driven fan structure, establishing a state equation of the dq-axis component of the direct-driven fan modulation voltage under the control coordinate system, performing small-disturbance analysis to obtain the state equation of the dq-axis component of the direct-driven fan modulation voltage under the control coordinate system, and constructing the state equation of the dq-axis component of the direct-driven fan modulation voltage under the synchronous coordinate system according to the conversion relation and the equivalent equation of the direct-driven fan output voltage under the synchronous coordinate system, and the output equation of the direct-driven fan and the equivalent circuit under the synchronous coordinate system.
14. The system for analyzing harmonic resonance modes of the offshore wind power system according to claim 12, wherein the offshore wind power system model building module is used for building an offshore wind power system model according to the equivalent admittance of a direct-driven fan, converting three-phase static coordinate system parameters of all elements in the offshore wind power system model into admittance parameters under a two-phase rotating coordinate system, building a node admittance matrix of the offshore wind power system according to the admittance parameters under the two-phase rotating coordinate system, and defining the electrical connection relation between nodes, wherein the direct-driven fan is used for building the offshore wind power system model by combining a core node of the offshore wind power system and the equivalent admittance of the direct-driven fan on the basis of a pi-type circuit, and the three-phase static coordinate system parameters of all elements in the offshore wind power system model are converted into admittance parameters under the two-phase rotating coordinate system according to coordinate transformation rules based on trigonometric functions.
15. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor implements the steps of the method of any one of claims 1 to 11 when the computer program is executed.
16. A computer readable storage medium, on which a computer program is stored, characterized in that the computer program, when being executed by a processor, implements the steps of the method of any of claims 1 to 11.

Description

Method, system, equipment and medium for analyzing harmonic resonance mode of offshore wind power system Technical Field The invention relates to the technical field of power systems, in particular to a method, a system, equipment and a medium for analyzing harmonic resonance modes of an offshore wind power system. Background The data show that large-scale new energy is connected into a power grid through an inverter in the offshore wind power flexible direct current end system. The resonance phenomenon of the AC transmission system caused by the complex uncertainty of offshore wind power is increasingly serious. Harmonic resonance is one of the important causes of degradation in the power quality of an electrical power system. A large number of capacitive and inductive elements exist in the system, parameters are matched with each other under specific frequency to form a low-resistance loop, and characteristic harmonic current is amplified to form resonance. Harmonic resonance easily causes the consequences of damage, loss increase and the like of power equipment, and seriously affects the safe and reliable operation of a power system. Therefore, analysis of resonance in power systems has become one of the hot spots of research today. In order to comprehensively consider the influence of various elements on the harmonic resonance of the sea-wind system, a modal analysis method is applied to the harmonic resonance analysis of the sea-wind system, and the fact that the node admittance matrix tends to be singular is found to be the real reason for the occurrence of the parallel harmonic resonance phenomenon, and the analysis on the harmonic resonance can be converted into the analysis on the key mode of the harmonic resonance. The modal analysis method can identify the potential harmonic resonance frequency of the system, effectively evaluate the resonance observability of each node, and has wide theoretical and engineering application in the fields of complex system resonance analysis, resonance monitoring point optimal configuration and the like. However, most of the conventional modal analysis methods are analyzed under an abc coordinate system, so that the modal analysis methods are difficult to apply to converters with complex control structures such as PQ control and sagging control, and further difficult to perform harmonic resonance analysis on specific scenes of a wind power system composed of various power electronic converters. At present, the modal analysis method for the converter system is mostly carried out under the traditional abc three-phase static coordinate system. The method has the advantages of intuitionistic and easy understanding when being applied to a single-phase converter or a three-phase system with a simple structure. However, with the development of new energy technologies such as offshore wind power, the electric power system increasingly presents the characteristic of high-proportion power electronic equipment access, the system structure and the control strategy become more complex, the limitation of the traditional abc coordinate system analysis method is also more remarkable, and the main defects are that: 1) The model is complex, the analysis difficulty is high, and under the abc coordinate system, the state variables (such as voltage and current) of the system are sinusoidal time variables. Small signal modeling and analysis of such time-varying systems can result in complex mathematical models that contain time-varying parameters. The application of modern control theory methods such as eigenvalue analysis becomes extremely difficult, the calculated amount is huge, and the deep dynamic characteristics of the system are difficult to reveal. 2) The control system of the modern converter, particularly the high-power converter used for the offshore wind power system, is designed under the dq synchronous rotation coordinate system mostly. The dq control strategy can transform the ac traffic to dc traffic, thereby realizing decoupling control of the active power and the reactive power, which is one of the core advantages thereof. If a current transformer controlled by dq is subjected to modal analysis under an abc coordinate system, complex coordinate transformation and model transformation are required, which not only increases the difficulty of analysis, but also is easy to introduce errors in the transformation process, and even the dynamic behavior of the controller cannot be accurately incorporated into the system model. In particular, when a plurality of converters are operated in parallel and the control strategies are mutually influenced, the analysis in the abc coordinate system is hardly performed. 3) The root cause of resonance is difficult to identify, the modal analysis is performed under an abc coordinate system due to the complexity of model and control coupling, the source of a specific resonance mode is difficult to identify clearly, and the influence of diff