CN114336685A - Oscillation mode identification method for wind power transmission system through MMC-HVDC - Google Patents
Oscillation mode identification method for wind power transmission system through MMC-HVDC Download PDFInfo
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Abstract
The invention relates to an oscillation mode identification method and system for a wind power transmission system through MMC-HVDC. The method comprises the following steps: establishing mathematical models of all parts of a system for sending wind power out through MMC-HVDC and connecting to obtain an integrated mathematical model of the system; carrying out linearization processing on the integrated mathematical model to obtain a system small interference model; extracting a characteristic matrix in the small interference model for analysis, obtaining all the modes and corresponding state parameters of the system, carrying out normalization processing, and locking main participation links under the corresponding modes according to the state parameters with the highest correlation degree, thereby positioning an oscillation source and determining an oscillation mode; the oscillation mode includes wind farm internal, wind farm control system, MMC internal, MMC control system and interaction. The method covers all possible modes of the system by establishing a detailed mathematical model of the wind turbine generator and the MMC converter station, and effectively identifies and classifies the oscillation mode of the wind power transmitted out of the system through the MMC-HVDC.
Description
Technical Field
The invention relates to the technical field of power transmission and distribution, in particular to an oscillation mode identification method for a system for sending wind power out through MMC-HVDC.
Background
In order to solve the problems of global climate change, environmental pollution, fossil energy depletion and the like, energy structure transformation is actively promoted in various countries, and renewable energy power generation represented by wind power is an important component of a future power system. In recent years, Chinese wind power is rapidly developed, and the installed proportion of the wind power is continuously increased. Among various modes of wind power transmission, flexible direct current transmission is widely applied to the aspect of large-scale wind power transmission due to the advantages of economy, capability of providing alternating voltage and frequency support for a weak power grid or a passive system and the like. The modular multilevel converter based high voltage direct current (MMC-HVDC) has many advantages, such as low harmonic content, no commutation failure, active and reactive decoupling control, and is the mainstream topological structure of the current flexible direct current transmission system.
Multiple oscillation phenomena occur in existing wind power sending projects which are built at home and abroad and put into operation, including a Hami wind power plant, a Hebei Staphylou wind power plant, a south Virginian flexible and straight project and a south Australia multi-end flexible and straight project in China, and subsynchronous oscillation phenomena of different degrees occur, so that corresponding economic losses, such as tripping of a thermal power generating unit, damage of a crowbar circuit of a fan, system shutdown and the like, are caused. Therefore, the method has great significance for identifying and classifying the oscillation modes of the wind power plant through the MMC-HVDC sending-out system.
Recent research shows that the oscillation phenomenon easily occurs when a wind power plant is connected with a high series compensation line, a weak alternating current power grid and other power electronic equipment. MMC-HVDC has the problem of multi-band oscillation, wherein the middle-low frequency band oscillation has a direct relation with a circulating current suppression controller, inner and outer ring control parameters of a main controller, particularly the bandwidth of a phase-locked loop, and the high frequency band oscillation is related with the link delay of the controller. In summary, the wind power has oscillation problem through the MMC-HVDC transmission system, so it is necessary to provide a suitable oscillation mode identification method to identify the oscillation mode of the wind power through the MMC-HVDC transmission system.
Disclosure of Invention
The invention aims to provide an oscillation mode identification method of a system for sending wind power out through MMC-HVDC, so as to effectively identify and classify the oscillation mode of the system.
In order to achieve the purpose, the invention provides the following scheme:
an oscillation mode identification method for wind power through an MMC-HVDC sending system comprises the following steps:
establishing a mathematical model of each part of a wind power sending system through MMC-HVDC;
connecting the wind power through mathematical models of all parts of the MMC-HVDC sending-out system to obtain an integrated mathematical model of the wind power through the MMC-HVDC sending-out system;
carrying out linearization processing on the integrated mathematical model to obtain a small interference model of the wind power transmitted out of the MMC-HVDC system;
extracting a characteristic matrix in the small interference model for analysis to obtain all the modes and corresponding state parameters of the wind power transmitted out of the system through MMC-HVDC;
normalizing each state parameter, and locking a main participation link under a corresponding mode according to the state parameter with the highest correlation degree;
positioning an oscillation source and determining an oscillation mode according to the main participation link; the oscillation modes comprise a wind power plant internal oscillation mode, a wind power plant control system oscillation mode, an MMC internal oscillation mode, an MMC control system oscillation mode and an interaction oscillation mode.
Optionally, the establishing a mathematical model of each part of the wind power output system through MMC-HVDC specifically includes:
dividing the wind power into a wind power generator set, an MMC converter station and a connecting circuit through an MMC-HVDC sending-out system, respectively modeling each part independently, and establishing a mathematical model of each part of the wind power sending-out system through the MMC-HVDC
Wherein X is the state variable of the DC power transmission system, U is the input variable,
is the first derivative of the state variable, f () is the first derivative of the state variable
A functional relationship with the state variable X and the input variable U; y is the output variable and Y () is the functional relationship between the output variable Y and the state variable X and the input variable U.
Optionally, the connecting the mathematical models of the parts of the MMC-HVDC transmission system of the wind power to obtain the integrated mathematical model of the parts of the MMC-HVDC transmission system of the wind power specifically includes:
and converting the electrical quantities of the wind turbine generator and the MMC converter station to the same coordinate system by adopting an interface conversion formula, and connecting the mathematical models of the wind power transmission system through MMC-HVDC transmission systems to obtain an integrated mathematical model of the wind power transmission system through MMC-HVDC transmission systems.
Optionally, the performing linearization on the integrated mathematical model to obtain a small interference model of the wind power transmitted through the MMC-HVDC transmission system specifically includes:
for the integrated mathematical modelCarrying out linearization processing to obtain a small interference model of the wind power output system through MMC-HVDC
Where A is the feature matrix, B is the input matrix, C is the output matrix, and D is the feedforward matrix.
Optionally, the extracting the feature matrix in the small interference model for analysis to obtain all the modes and corresponding state parameters of the wind power transmitted out of the system through the MMC-HVDC system specifically includes:
extracting a characteristic matrix A in the small interference model for analysis, solving a characteristic value of the characteristic matrix A to obtain characteristic roots, wherein each group of characteristic roots represents a mode, and each mode corresponds to a state parameter; the state quantities comprise the state variables.
An oscillation mode identification system for wind power transmitted by an MMC-HVDC system comprises:
the mathematical model establishing module is used for establishing a mathematical model of each part of the wind power output system through the MMC-HVDC;
the mathematical model connecting module is used for connecting the mathematical models of all parts of the wind power output system through the MMC-HVDC to obtain an integrated mathematical model of the wind power output system through the MMC-HVDC;
the model linearization processing module is used for carrying out linearization processing on the integrated mathematical model to obtain a small interference model of the wind power transmitted out of the MMC-HVDC system;
the model characteristic matrix analysis module is used for extracting a characteristic matrix in the small interference model for analysis to obtain all the modes and corresponding state parameters of the wind power transmitted out of the system through the MMC-HVDC;
the state parameter normalization processing module is used for performing normalization processing on each state parameter and locking main participation links under corresponding modes according to the state parameter with the highest correlation degree;
the oscillation positioning and oscillation mode identification module is used for positioning an oscillation source and determining an oscillation mode according to the main participation link; the oscillation modes comprise a wind power plant internal oscillation mode, a wind power plant control system oscillation mode, an MMC internal oscillation mode, an MMC control system oscillation mode and an interaction oscillation mode.
Optionally, the mathematical model building module specifically includes:
a mathematical model establishing unit for dividing the wind power into a wind power set, an MMC converter station and a connecting circuit through an MMC-HVDC sending-out system, respectively modeling each part separately, and establishing a mathematical model of each part of the wind power sending-out system through the MMC-HVDC
Wherein X is the state variable of the DC power transmission system, U is the input variable,
is the first derivative of the state variable, f () is the first derivative of the state variable
A functional relationship with the state variable X and the input variable U; y is the output variable and Y () is the functional relationship between the output variable Y and the state variable X and the input variable U.
Optionally, the mathematical model connection module specifically includes:
and the mathematical model connecting unit is used for converting the electrical quantities of the wind turbine generator and the MMC converter station to the same coordinate system by adopting an interface conversion formula, and connecting the mathematical models of the wind turbine generator and the MMC-HVDC sending-out system to obtain an integrated mathematical model of the wind turbine generator and the MMC-HVDC sending-out system.
Optionally, the model linearization processing module specifically includes:
the model linearization processing unit is used for carrying out linearization processing on the integrated mathematical model to obtain a small interference model of the wind power transmitted out from the MMC-HVDC system
Wherein A is a feature matrix and B isThe input matrix, C the output matrix, and D the feedforward matrix.
Optionally, the model feature matrix analysis module specifically includes:
the model characteristic matrix analysis unit is used for extracting a characteristic matrix A in the small interference model for analysis, solving a characteristic value of the characteristic matrix A to obtain characteristic roots, wherein each group of characteristic roots represents a mode, and each mode corresponds to a state parameter; the state quantities comprise the state variables.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention provides an oscillation mode identification method and system for wind power transmitted out of a system through MMC-HVDC, wherein the method comprises the following steps: establishing a mathematical model of each part of a wind power sending system through MMC-HVDC; connecting the wind power through mathematical models of all parts of the MMC-HVDC sending-out system to obtain an integrated mathematical model of the wind power through the MMC-HVDC sending-out system; carrying out linearization processing on the integrated mathematical model to obtain a small interference model of the wind power transmitted out of the MMC-HVDC system; extracting a characteristic matrix in the small interference model for analysis to obtain all the modes and corresponding state parameters of the wind power transmitted out of the system through MMC-HVDC; normalizing each state parameter, and locking a main participation link under a corresponding mode according to the state parameter with the highest correlation degree; positioning an oscillation source and determining an oscillation mode according to the main participation link; the oscillation modes comprise a wind power plant internal oscillation mode, a wind power plant control system oscillation mode, an MMC internal oscillation mode, an MMC control system oscillation mode and an interaction oscillation mode. The method covers all possible modes of the system by establishing a detailed mathematical model of the wind turbine generator and the MMC converter station, effectively identifies and classifies the oscillation mode of the wind power transmitted out of the system through the MMC-HVDC, and the identification result can provide reference for system stability analysis.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a flow chart of an oscillation mode identification method of a wind power transmission system through MMC-HVDC according to the present invention;
FIG. 2 is a schematic diagram of the method for identifying the oscillation mode of wind power transmitted through MMC-HVDC transmission system according to the present invention;
FIG. 3 is a schematic diagram illustrating a transformation of a wind farm and an MMC rotating coordinate system according to an embodiment of the present invention;
FIG. 4 is a structural diagram of an oscillation mode identification system of a wind power transmission system through MMC-HVDC according to 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.
The invention aims to provide an oscillation mode identification method of a system for sending wind power out through MMC-HVDC, so as to effectively identify and classify the oscillation mode of the system.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Fig. 1 is a flow chart of an oscillation mode identification method of a system for sending wind power out through MMC-HVDC, and fig. 2 is a schematic principle diagram of the oscillation mode identification method of the system for sending wind power out through MMC-HVDC. Referring to fig. 1 and 2, the method for identifying the oscillation mode of the wind power transmission system through the MMC-HVDC system according to the present invention includes:
step 101: and establishing a mathematical model of each part of the wind power output system through MMC-HVDC.
The invention divides wind power into a wind power generator set, an MMC converter station and a connecting circuit through an MMC-HVDC sending-out system (hereinafter referred to as the system for short), and models each part independently. Firstly, considering the detailed structure of the wind turbine generator and the internal harmonic characteristics of the MMC, determining a state variable and an input variable, respectively establishing a state space equation of the wind turbine generator, the MMC converter station and a connecting circuit, and obtaining a mathematical model of each part, wherein the mathematical model is shown as the following formula (1):
the steps of establishing the state space model in the three parts of the system are the same, and the formula (1) is a general expression of the state space equation. Wherein X is a state variable of the direct current transmission system; u is an input variable; y is an output variable;
for the first derivative of the state variable, f () represents the first derivative of the state variable as a function of the state variable and the input variable, and y () represents the output variable as a function of the state variable and the input variable.
Therefore, the step 101 of establishing a mathematical model of each part of the wind power transmission system through the MMC-HVDC transmission specifically includes:
dividing the wind power into a wind power generator set, an MMC converter station and a connecting circuit through an MMC-HVDC sending-out system, respectively modeling each part independently, and establishing a mathematical model of each part of the wind power sending-out system through the MMC-HVDC
Wherein X is the state variable of the DC power transmission system, U is the input variable,
is the first derivative of the state variable, f () is the first derivative of the state variable
A functional relationship with the state variable X and the input variable U; y is the output variable and Y () is the functional relationship between the output variable Y and the state variable X and the input variable U.
Step 102: and connecting the wind power through mathematical models of all parts of the MMC-HVDC sending-out system to obtain an integrated mathematical model of the wind power through the MMC-HVDC sending-out system.
And establishing model interfaces of all parts, connecting all parts to obtain an integrated mathematical model, and performing linearization processing to obtain a system small interference model.
The process of establishing the model interface of each part is as follows:
and establishing different rotating coordinate systems determined by the wind power plant and the MMC phase-locked loop, wherein the coordinate conversion relation is shown in figure 3. In FIG. 3,. omega.pRepresenting the angular frequency, omega, of the phase-locked loop of a wind farm side converter1Representing the MMC phase-locked loop rotation angular frequency. dq is a coordinate system rotated at a constant angular frequency, with the index m (i.e. d)mqmCoordinate system) at an angular frequency ω1A rotating coordinate system with a phase angle theta1(θ1＝ω1t), t represents time; subscript w (i.e. d)wqwCoordinate system) at an angular frequency ωpA rotating coordinate system with a phase angle θ p (θ p ═ ω [)pt)。θp-θ1Is the phase angle difference of the two rotating coordinate systems. i.e. isOutputting three-phase current i for wind farmsj(j ═ a, b, c) a spatially synthesized vector in the complex plane; i.e. isThe dq axis component under the coordinate system of the wind farm is isd,isq，isThe dq axis component under the coordinate system of the MMC converter station is Isd,Isq。
The specific interface conversion formula is shown in the following formula (2):
wherein X represents an MMC side variable and X represents a wind farm side variable. x is the number ofsd、xsqRepresenting dq-axis components of a wind farm side variable x, e.g. isd、isq。Xsd、XsqRepresenting dq-axis components of MMC-side variable X, e.g. Isd、Isq。
And (3) converting the electrical quantities of the wind power plant and the MMC converter station to the same coordinate system according to an interface conversion formula shown in the formula (2), so as to connect the mathematical models and obtain an integrated mathematical model of the whole system. The connection of the mathematical models means that the electrical quantities of the wind power plant and the MMC converter station are converted to the same coordinate system, and the process is essentially to convert state variables on a connection line so as to connect all parts.
Therefore, the step 102 of connecting the mathematical models of the parts of the MMC-HVDC transmission system of the wind power to obtain the integrated mathematical model of the parts of the MMC-HVDC transmission system of the wind power specifically includes:
and converting the electrical quantities of the wind turbine generator and the MMC converter station to the same coordinate system by adopting an interface conversion formula, and connecting the mathematical models of the wind power transmission system through MMC-HVDC transmission systems to obtain an integrated mathematical model of the wind power transmission system through MMC-HVDC transmission systems.
Step 103: and carrying out linearization processing on the integrated mathematical model to obtain a small interference model of the wind power transmitted out of the MMC-HVDC system.
The integrated mathematical model is subjected to linearization processing to obtain a small interference model of the system, which is specifically shown in the following formula (3):
where A is the feature matrix, B is the input matrix, C is the output matrix, and D is the feedforward matrix. The expression form of the integrated mathematical model after linearization is shown as formula (3).
Therefore, the step 103 of performing linearization processing on the integrated mathematical model to obtain a small interference model of the wind power transmitted through the MMC-HVDC transmission system specifically includes:
for the integrated mathematical modelLine linearization processing is carried out to obtain a small interference model of the wind power output system through MMC-HVDC
Where A is the feature matrix, B is the input matrix, C is the output matrix, and D is the feedforward matrix.
Step 104: and extracting a characteristic matrix in the small interference model for analysis to obtain all the modes and corresponding state parameters of the wind power transmitted out of the system through MMC-HVDC.
Based on the small interference model (3) in step 103, a stability characterization matrix a is extracted and analyzed to obtain all states of the system and oscillation characteristic information corresponding to the states. The stability characterization matrix A can represent the stability of the system, the state of the system can be obtained by analyzing the matrix A, the state of the system refers to characteristic roots obtained by solving characteristic values of the characteristic matrix A, and each group of characteristic roots represents a mode and contains oscillation characteristic information such as damping ratio, oscillation frequency and the like. Each state parameter corresponding to each modality refers to all parameters of the system, including system parameters and state variables. The system parameters comprise fan, MMC main circuit parameters, connecting circuit parameters and the like.
Therefore, the step 104 of extracting the feature matrix in the small interference model for analysis to obtain all the modes and corresponding state parameters of the wind power transmitted out of the system through the MMC-HVDC system specifically includes:
extracting a characteristic matrix A in the small interference model for analysis, solving a characteristic value of the characteristic matrix A to obtain characteristic roots, wherein each group of characteristic roots represents a mode, and each mode corresponds to a state parameter; the state quantities comprise the state variables.
Step 105: and carrying out normalization processing on each state parameter, and locking main participation links under corresponding modes according to the state parameter with the highest correlation degree.
And (3) carrying out normalization processing on each state parameter, and locking main participation links (namely an electric quantity, an electric element or a certain molecular system and the like) in the mode according to the parameter with the highest degree of correlation. Each state parameter refers to all parameters of the system, including system parameters and state variables. There are many methods for determining the degree of participation (correlation), such as sensitivity analysis, which are not unique, and this belongs to basic knowledge in the field of power system stability research, and is not described herein again. The state parameter with the highest degree of correlation can be obtained, and the related control link or system structure can be positioned, namely the main participation link in the mode is locked. The main participation links in each mode can provide basis for positioning the oscillation source.
Step 106: and positioning an oscillation source and determining an oscillation mode according to the main participation link.
The oscillation mode is divided into 5 types of the interior of a wind power plant, the control system of the wind power plant, the interior of an MMC, the control system of the MMC and interaction through a main participation link to position an oscillation source. The main participation links are different, the corresponding main participation variables are also different, the participation variables are from a wind power plant and an MMC, and the generation source (namely the oscillation source) of the oscillation can be known to be a subsystem by judging which part the participation variables belong to, so that the corresponding oscillation mode is further determined. For example, the main participating variable obtained through analysis is a wind power plant side phase-locked loop control parameter, and then the oscillating wind power plant side is related to a wind power plant control link and belongs to an oscillating mode of a wind power plant control system.
The method can effectively identify the oscillation mode of the wind power transmitted out of the system through the MMC-HVDC through the step 101 and the step 106, and the identification result can provide reliable reference for the stability analysis of the subsequent system.
The invention provides an oscillation mode identification method of a system for sending wind power out through MMC-HVDC, which comprises the steps of dividing the system into a wind power generator set, an MMC converter station and a connecting circuit, and respectively carrying out independent modeling on each part; establishing an interface, connecting all parts to obtain an integrated mathematical model, and performing linearization processing to obtain a system small interference model; extracting a stability characterization matrix A, and analyzing the stability characterization matrix A to obtain all states of the system and corresponding oscillation characteristic information thereof; normalizing each state parameter, and locking main participation links (namely, an electric quantity, an electric element or a certain molecular system and the like) in the mode according to the parameter with the highest degree of correlation; the oscillation mode is divided into 5 types of the interior of a wind power plant, the control system of the wind power plant, the interior of an MMC, the control system of the MMC and interaction through a main participation link to position an oscillation source. The method covers all possible modes of the system by establishing a detailed mathematical model of the wind turbine generator and the MMC converter station, effectively identifies the oscillation mode of the wind power transmitted out of the system through the MMC-HVDC, and the identification result can provide reference for system stability analysis.
Based on the method for identifying the oscillation mode of the wind power output system through the MMC-HVDC provided by the invention, the invention also provides an identification system for identifying the oscillation mode of the wind power output system through the MMC-HVDC, and referring to fig. 4, the system comprises:
the mathematical model establishing module 401 is used for establishing a mathematical model of each part of the wind power output system through the MMC-HVDC;
the mathematical model connecting module 402 is used for connecting mathematical models of all parts of the MMC-HVDC sending-out system of the wind power to obtain an integrated mathematical model of the MMC-HVDC sending-out system of the wind power;
the model linearization processing module 403 is configured to perform linearization processing on the integrated mathematical model to obtain a small interference model of the wind power passing through the MMC-HVDC transmission system;
a model feature matrix analysis module 404, configured to extract a feature matrix in the small interference model for analysis, so as to obtain all modes and corresponding state parameters of the wind power transmitted from the MMC-HVDC transmission system;
a state parameter normalization processing module 405, configured to perform normalization processing on each state parameter, and lock a main participation link in a corresponding mode according to a state parameter with the highest correlation;
an oscillation positioning and oscillation mode identification module 406, configured to position an oscillation source and determine an oscillation mode according to the main participation link; the oscillation modes comprise a wind power plant internal oscillation mode, a wind power plant control system oscillation mode, an MMC internal oscillation mode, an MMC control system oscillation mode and an interaction oscillation mode.
The system identifies the oscillation mode of the wind power through the MMC-HVDC sending-out system, positions the oscillation source, and can divide the oscillation mode into 5 types of wind power plant interior, wind power plant control system, MMC interior, MMC control system and interaction.
The mathematical model building module 401 specifically includes:
a mathematical model establishing unit for dividing the wind power into a wind power set, an MMC converter station and a connecting circuit through an MMC-HVDC sending-out system, respectively modeling each part separately, and establishing a mathematical model of each part of the wind power sending-out system through the MMC-HVDC
Wherein X is the state variable of the DC power transmission system, U is the input variable,
is the first derivative of the state variable, f () is the first derivative of the state variable
A functional relationship with the state variable X and the input variable U; y is the output variable and Y () is the functional relationship between the output variable Y and the state variable X and the input variable U.
The mathematical model connection module 402 specifically includes:
and the mathematical model connecting unit is used for converting the electrical quantities of the wind turbine generator and the MMC converter station to the same coordinate system by adopting an interface conversion formula, and connecting the mathematical models of the wind turbine generator and the MMC-HVDC sending-out system to obtain an integrated mathematical model of the wind turbine generator and the MMC-HVDC sending-out system.
The model linearization processing module 403 specifically includes:
the model linearization processing unit is used for carrying out linearization processing on the integrated mathematical model to obtain a small interference model of the wind power transmitted out from the MMC-HVDC system
Wherein A is a feature matrix and B isThe input matrix, C the output matrix, and D the feedforward matrix.
The model feature matrix analysis module 404 specifically includes:
the model characteristic matrix analysis unit is used for extracting a characteristic matrix A in the small interference model for analysis, solving a characteristic value of the characteristic matrix A to obtain characteristic roots, wherein each group of characteristic roots represents a mode, and each mode corresponds to a state parameter; the state quantities comprise the state variables.
The invention provides an oscillation mode identification method and system for sending wind power out of a system through MMC-HVDC, which provide a basis for a parameter adjustment method for system stability analysis and oscillation inhibition by classifying system oscillation modes, including an internal oscillation mode of a wind power plant, an oscillation mode of a wind power plant control system, an internal oscillation mode of an MMC, an oscillation mode of an MMC control system and an interaction oscillation mode.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (10)
1. An oscillation mode identification method for wind power through an MMC-HVDC sending system is characterized by comprising the following steps:
establishing a mathematical model of each part of a wind power sending system through MMC-HVDC;
connecting the wind power through mathematical models of all parts of the MMC-HVDC sending-out system to obtain an integrated mathematical model of the wind power through the MMC-HVDC sending-out system;
carrying out linearization processing on the integrated mathematical model to obtain a small interference model of the wind power transmitted out of the MMC-HVDC system;
extracting a characteristic matrix in the small interference model for analysis to obtain all the modes and corresponding state parameters of the wind power transmitted out of the system through MMC-HVDC;
normalizing each state parameter, and locking a main participation link under a corresponding mode according to the state parameter with the highest correlation degree;
positioning an oscillation source and determining an oscillation mode according to the main participation link; the oscillation modes comprise a wind power plant internal oscillation mode, a wind power plant control system oscillation mode, an MMC internal oscillation mode, an MMC control system oscillation mode and an interaction oscillation mode.
2. The method according to claim 1, wherein the establishing of the mathematical model of each part of the wind power output system through MMC-HVDC specifically comprises:
dividing the wind power into a wind power generator set, an MMC converter station and a connecting circuit through an MMC-HVDC sending-out system, respectively modeling each part independently, and establishing a mathematical model of each part of the wind power sending-out system through the MMC-HVDC
Wherein X is the state variable of the DC power transmission system, U is the input variable,
is the first derivative of the state variable, f () is the first derivative of the state variable
A functional relationship with the state variable X and the input variable U; y is the output variable and Y () is the functional relationship between the output variable Y and the state variable X and the input variable U.
3. The method according to claim 2, wherein the connecting the mathematical models of the parts of the MMC-HVDC delivery system of the wind power to obtain the integrated mathematical model of the parts of the MMC-HVDC delivery system of the wind power comprises:
and converting the electrical quantities of the wind turbine generator and the MMC converter station to the same coordinate system by adopting an interface conversion formula, and connecting the mathematical models of the wind power transmission system through MMC-HVDC transmission systems to obtain an integrated mathematical model of the wind power transmission system through MMC-HVDC transmission systems.
4. The method according to claim 3, wherein the linearizing the integrated mathematical model to obtain a small interference model of the wind power transmitted through the MMC-HVDC transmission system specifically comprises:
carrying out linearization treatment on the integrated mathematical model to obtain a small interference model of the wind power through an MMC-HVDC sending-out system
Where A is the feature matrix, B is the input matrix, C is the output matrix, and D is the feedforward matrix.
5. The method according to claim 4, wherein the extracting of the feature matrix in the small interference model for analysis to obtain all the modes and corresponding state parameters of the wind power transmitted from the MMC-HVDC transmission system specifically comprises:
extracting a characteristic matrix A in the small interference model for analysis, solving a characteristic value of the characteristic matrix A to obtain characteristic roots, wherein each group of characteristic roots represents a mode, and each mode corresponds to a state parameter; the state quantities comprise the state variables.
6. An oscillation mode identification system for wind power through an MMC-HVDC transmission system is characterized by comprising:
the mathematical model establishing module is used for establishing a mathematical model of each part of the wind power output system through the MMC-HVDC;
the mathematical model connecting module is used for connecting the mathematical models of all parts of the wind power output system through the MMC-HVDC to obtain an integrated mathematical model of the wind power output system through the MMC-HVDC;
the model linearization processing module is used for carrying out linearization processing on the integrated mathematical model to obtain a small interference model of the wind power transmitted out of the MMC-HVDC system;
the model characteristic matrix analysis module is used for extracting a characteristic matrix in the small interference model for analysis to obtain all the modes and corresponding state parameters of the wind power transmitted out of the system through the MMC-HVDC;
the state parameter normalization processing module is used for performing normalization processing on each state parameter and locking main participation links under corresponding modes according to the state parameter with the highest correlation degree;
the oscillation positioning and oscillation mode identification module is used for positioning an oscillation source and determining an oscillation mode according to the main participation link; the oscillation modes comprise a wind power plant internal oscillation mode, a wind power plant control system oscillation mode, an MMC internal oscillation mode, an MMC control system oscillation mode and an interaction oscillation mode.
7. The system of claim 6, wherein the mathematical model building module specifically comprises:
a mathematical model establishing unit for dividing the wind power into a wind power set, an MMC converter station and a connecting circuit through an MMC-HVDC sending-out system, respectively modeling each part separately, and establishing a mathematical model of each part of the wind power sending-out system through the MMC-HVDC
Wherein X is the state variable of the DC power transmission system, U is the input variable,
is the first derivative of the state variable, f () is the first derivative of the state variable
A functional relationship with the state variable X and the input variable U; y is the output variable and Y () is the functional relationship between the output variable Y and the state variable X and the input variable U.
8. The system according to claim 7, wherein the mathematical model connection module specifically comprises:
and the mathematical model connecting unit is used for converting the electrical quantities of the wind turbine generator and the MMC converter station to the same coordinate system by adopting an interface conversion formula, and connecting the mathematical models of the wind turbine generator and the MMC-HVDC sending-out system to obtain an integrated mathematical model of the wind turbine generator and the MMC-HVDC sending-out system.
9. The system of claim 8, wherein the model linearization processing module specifically comprises:
the model linearization processing unit is used for carrying out linearization processing on the integrated mathematical model to obtain a small interference model of the wind power transmitted out from the MMC-HVDC system
Where A is the feature matrix, B is the input matrix, C is the output matrix, and D is the feedforward matrix.
10. The system of claim 9, wherein the model feature matrix analysis module specifically comprises:
the model characteristic matrix analysis unit is used for extracting a characteristic matrix A in the small interference model for analysis, solving a characteristic value of the characteristic matrix A to obtain characteristic roots, wherein each group of characteristic roots represents a mode, and each mode corresponds to a state parameter; the state quantities comprise the state variables.
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