CN111049158B - Method and system for determining broadband oscillation stability of power system based on spectrum radius - Google Patents

Abstract

The invention discloses a method and a system for determining broadband oscillation stability of a power system based on spectrum radius, and belongs to the technical field of power system modeling. The method comprises the following steps: acquiring open-loop frequency characteristics of a power system of the doubly-fed wind turbine under the condition of open-loop operation; determining the open-loop frequency characteristic of the doubly-fed fan under the open-loop operation condition; determining an equivalent open-loop process equation of the electric power system of the doubly-fed wind turbine in a closed-loop operation state according to the open-loop frequency characteristic of the doubly-fed wind turbine in the open-loop operation state; determining a spectrum radius function matrix of the electric power system of the doubly-fed wind turbine in a closed-loop operation state according to an equivalent open-loop process equation; determining matrix elements of the spectrum radius function matrix, and generating a spectrum radius function curve according to the spectrum radius matrix elements; and judging the stability of the broadband oscillation of the electric power system of the doubly-fed fan in the closed-loop operation state according to the spectrum radius function curve characteristic. The method can be directly applied to an on-line analysis platform of the power system, and has important engineering application value.

Description

Method and system for determining broadband oscillation stability of power system based on spectral radius

technical field

The present invention relates to the technical field of power system modeling, and more particularly, to a method and system for determining the stability of power system broadband oscillation based on spectral radius.

Background technique

New energy power generation represented by wind power and photovoltaic power generation has been widely used in the power system on a large scale. With the continuous increase in the proportion of power electronic power sources such as new energy units, the problem of broadband oscillation caused by the complex interaction of power electronic equipment, traditional equipment and network has become increasingly prominent. The study of the broadband oscillation analysis method of the grid-connected DFIG has important theoretical significance and practical value for effectively solving the existing oscillation problem and ensuring the safe and stable operation of the power system with a high proportion of new energy.

At present, there have been a lot of studies on the identification methods of broadband oscillation stability of the grid-connected DFIGs, mainly including mode analysis method and impedance analysis method. However, most of the current analysis methods are relatively complex and lack intuition. It is of great theoretical and practical value to study an effective and intuitive method for judging broadband oscillation stability of DFIGs connected to the grid. Therefore, in order to realize the intuitive and effective discrimination of the broadband oscillation of new energy sources, an intuitive and graphical method for discriminating the stability of broadband oscillation of new energy sources is required.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention proposes a method for determining the stability of the broadband oscillation of a power system based on the spectral radius, including:

Taking the power system connected to the DFIG as the target object, the open-loop frequency characteristics of the power system under the open-loop operation of the DFIG are obtained;

According to the open-loop frequency characteristics of the power system, determine the open-loop frequency characteristics of the DFIG under open-loop operation;

According to the open-loop frequency characteristics of the DFIG in the open-loop operation, the equivalent open-loop process equation of the power system under the closed-loop operation of the DFIG is determined;

According to the equivalent open-loop process equation, the spectral radius function matrix of the power system under the closed-loop operation of the DFIG is determined;

Determine the matrix elements of the spectral radius function matrix, and generate the spectral radius function curve according to the spectral radius matrix elements;

According to the curve characteristics of the spectral radius function, the stability of the broadband oscillation of the power system in the closed-loop operation state of the doubly-fed fan is judged.

Optionally, the equivalent open-loop process equation of the power system in the closed-loop operating state of the DFIG is:

Satisfy:

Among them, ΔU is the voltage vector of the common connection point between the power system and the wind turbine, and ΔI is the current vector of the common connection point between the power system and the wind turbine;

i=1 or 2, j=1 or 2;

ΔU ₁ and ΔI ₁ are the components of the voltage vector ΔU and the current vector ΔI on the d-axis, respectively, and ΔU ₂ and ΔI ₂ are the components of the voltage vector ΔU and the current vector ΔI on the q-axis, respectively;

g _ij is the element of the i-th row and the j-th column in G _sys ;

为去除G_sys中g_ij后的第i行向量；

is the i-th row vector after removing g _ij in G _sys ;

表示去除双馈风机开环运行状态下双馈风机的等效开环频率特性 G_w第j行和第i列后所得的矩阵；

represents the matrix obtained after removing the equivalent open-loop frequency characteristic Gw of the DFIG in the open-loop operating state of the _DFIG in the jth row and the ith column;

I is a unit matrix of predetermined dimensions;

为去除双馈风机开环运行状态下电力系统的等效开环频率特性G_sys第i行和第j列后所得的矩阵；

is the matrix obtained by removing the ith row and the jth column of the equivalent open-loop frequency characteristic G _sys of the power system in the open-loop operating state of the DFIG;

为去除G_sys中g_ij后的第j列向量；

is the jth column vector after removing g _ij in G _sys ;

G _sys is the equivalent open-loop frequency characteristic matrix of the power system under the open-loop operating state of the DFIG.

Optionally, the matrix elements of the spectral radius function matrix are determined according to the following formula:

in,

The parameter ρ _ij (s) characterizes the broadband oscillation frequency domain characteristics of the system;

i=1 or 2, j=1 or 2, ΔU ₁ and ΔI ₁ are the components of the voltage vector ΔU and the current vector ΔI on the d-axis, respectively, ΔU ₂ and ΔI ₂ are the voltage vector ΔU and the current vector ΔI on the q-axis, respectively weight;

g _ij is the element of the i-th row and the j-th column in G _sys ;

为去除G_sys中g_ij后的第i行向量；

is the i-th row vector after removing g _ij in G _sys ;

表示去除双馈风机开环运行状态下双馈风机的等效开环频率特性 G_w第j行和第i列后所得的矩阵；

represents the matrix obtained after removing the equivalent open-loop frequency characteristic Gw of the DFIG in the open-loop operating state of the _DFIG in the jth row and the ith column;

I is a unit matrix of predetermined dimensions;

为去除双馈风机开环运行状态下电力系统的等效开环频率特性G_sys第i行和第j列后所得的矩阵；

is the matrix obtained by removing the ith row and the jth column of the equivalent open-loop frequency characteristic G _sys of the power system in the open-loop operating state of the DFIG;

为去除G_sys中g_ij后的第j列向量；

is the jth column vector after removing g _ij in G _sys ;

G _sys is the equivalent open-loop frequency characteristic matrix of the AC system under the open-loop operating state of the DFIG;

g _wji (s) is the equivalent open-loop frequency characteristic of the doubly-fed fan in the open-loop operating state of the doubly-fed fan in the j-th row and the i-th column element of G _w , where s is a complex variable parameter, indicating that the element is a function of s;

ρ is the spectral radius function.

Optionally, the stability of the broadband oscillation of the power system in the closed-loop operation state of the doubly-fed fan is judged according to the characteristics of the spectral radius function curve, specifically:

The characteristic value of the spectral radius function curve is determined according to the spectral radius function curve. If the characteristic value of the spectral radius function curve is greater than 1, it is determined that the power system broadband oscillation is in an unstable state under the closed-loop operation state of the DFIG.

The present invention also proposes a system for determining the broadband oscillation stability of the power system based on the spectral radius, including:

The first parameter acquisition module takes the power system connected to the DFIG as the target object, and acquires the open-loop frequency characteristics of the power system under the open-loop operation of the DFIG;

The second parameter acquisition module determines the open-loop frequency characteristics of the doubly-fed wind turbine under open-loop operation according to the open-loop frequency characteristics of the power system;

The equivalent module determines the equivalent open-loop process equation of the power system under the closed-loop operation of the DFIG according to the open-loop frequency characteristics of the DFIG in the open-loop operation;

The calculation module, according to the equivalent open-loop process equation, determines the spectral radius function matrix of the power system under the closed-loop operating state of the DFIG;

The drawing module determines the matrix elements of the spectral radius function matrix, and generates the spectral radius function curve according to the spectral radius matrix elements;

The judgment module judges the stability of the broadband oscillation of the power system under the closed-loop operation state of the DFIG according to the characteristic of the spectral radius function curve.

Optionally, the equivalent open-loop process equation of the power system in the closed-loop operating state of the DFIG is:

Satisfy:

ΔU=[ΔU ₁ ΔU ₂ ] ^T

ΔI=[ΔI ₁ ΔI ₂ ] ^T

为去除双馈风机开环运行状态下电力系统的等效开环频率特性G_sys第i行和第j列后所得的矩阵，

表示去除双馈风机开环运行状态下双馈风机的等效开环频率特性G_w第i行和第j列后所得的矩阵，

为去除G_sys中g_ij后的第i行向量和

为去除G_sys中g_ij后的第j列向量。Among them, ΔU is the voltage vector of the PCC point connected between the power system and the wind turbine, ΔI is the current vector of the PCC point connected between the power system and the wind turbine,

is the matrix obtained after removing the equivalent open-loop frequency characteristic G _sys of the power system in the open-loop operating state of the DFIG in the i-th row and the j-th column,

represents the matrix obtained by removing the equivalent open-loop frequency characteristics Gw of the DFIG in the open-loop operating state of the DFIG in the i- _th row and the j-th column,

is the ith row vector sum after removing g _ij in G _sys

is the jth column vector after removing g _ij in G _sys .

Optionally, the matrix elements of the spectral radius function matrix are determined according to the following formula:

in,

The parameter ρ _ij (s) characterizes the broadband oscillation frequency domain characteristics of the system;

i=1 or 2, j=1 or 2, ΔU ₁ and ΔI ₁ are the components of the voltage vector ΔU and the current vector ΔI on the d-axis, respectively, ΔU ₂ and ΔI ₂ are the voltage vector ΔU and the current vector ΔI on the q-axis, respectively weight;

g _ij is the element of the i-th row and the j-th column in G _sys ;

为去除G_sys中g_ij后的第i行向量；

is the i-th row vector after removing g _ij in G _sys ;

表示去除双馈风机开环运行状态下双馈风机的等效开环频率特性 G_w第j行和第i列后所得的矩阵；

represents the matrix obtained after removing the equivalent open-loop frequency characteristic Gw of the DFIG in the open-loop operating state of the _DFIG in the jth row and the ith column;

I is a unit matrix of predetermined dimensions;

为去除双馈风机开环运行状态下电力系统的等效开环频率特性G_sys第i行和第j列后所得的矩阵；

is the matrix obtained by removing the ith row and the jth column of the equivalent open-loop frequency characteristic G _sys of the power system in the open-loop operating state of the DFIG;

为去除G_sys中g_ij后的第j列向量；

is the jth column vector after removing g _ij in G _sys ;

G _sys is the equivalent open-loop frequency characteristic matrix of the AC system under the open-loop operating state of the DFIG;

g _wji (s) is the equivalent open-loop frequency characteristic of the doubly-fed fan in the open-loop operating state of the doubly-fed fan in the j-th row and the i-th column element of G _w , where s is a complex variable parameter, indicating that the element is a function of s;

ρ is the spectral radius function.

Optionally, the stability of the broadband oscillation of the power system in the closed-loop operation state of the doubly-fed fan is judged according to the characteristics of the spectral radius function curve, specifically:

The characteristic value of the spectral radius function curve is determined according to the spectral radius function curve. If the characteristic value of the spectral radius function curve is greater than 1, it is determined that the power system broadband oscillation is in an unstable state under the closed-loop operation state of the DFIG.

The invention is more intuitive and clear for the determination of the broadband oscillation stability of the doubly-fed wind power grid-connected, and is more in line with the needs of power system monitoring. The invention can be directly applied to the power system online analysis platform and has important engineering application value.

Description of drawings

1 is a flowchart of a method for determining broadband oscillation stability of a power system based on spectral radius according to the present invention;

FIG. 2 is a flowchart of an embodiment of a method for determining the stability of broadband oscillation of a power system based on a spectral radius according to the present invention;

3 is a two-machine system model diagram of an embodiment of a method for determining broadband oscillation stability of a power system based on spectral radius according to the present invention;

4 is a spectral radius matrix frequency response curve of a method for determining broadband oscillation stability of a power system based on spectral radius according to the present invention;

5 is a time-domain simulation waveform diagram of the stator voltage and current of a fan in a method for determining the stability of a power system broadband oscillation based on the spectral radius of the present invention;

FIG. 6 is a structural diagram of a system for determining the stability of broadband oscillation of a power system based on the spectral radius of the present invention.

Detailed ways

Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for the purpose of this thorough and complete disclosure invention, and fully convey the scope of the invention to those skilled in the art. The terms used in the exemplary embodiments shown in the drawings are not intended to limit the invention. In the drawings, the same elements/elements are given the same reference numerals.

Unless otherwise defined, terms (including scientific and technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is to be understood that terms defined in commonly used dictionaries should be construed as having meanings consistent with the context in the related art, and should not be construed as idealized or overly formal meanings.

The present invention proposes a method for determining broadband oscillation stability of a power system based on spectral radius, as shown in Figure 1, including:

Taking the power system connected to the DFIG as the target object, the open-loop frequency characteristics of the power system under the open-loop operation of the DFIG are obtained;

According to the open-loop frequency characteristics of the power system, determine the open-loop frequency characteristics of the DFIG under open-loop operation;

According to the open-loop frequency characteristics of the DFIG in the open-loop operation, the equivalent open-loop process equation of the power system under the closed-loop operation of the DFIG is determined;

The equivalent open-loop process equation of the power system under the closed-loop operation of the DFIG is:

Satisfy:

Among them, ΔU is the voltage vector of the common connection point between the power system and the wind turbine, and ΔI is the current vector of the common connection point between the power system and the wind turbine;

i=1 or 2, j=1 or 2;

ΔU ₁ and ΔI ₁ are the components of the voltage vector ΔU and the current vector ΔI on the d-axis, respectively, and ΔU ₂ and ΔI ₂ are the components of the voltage vector ΔU and the current vector ΔI on the q-axis, respectively;

g _ij is the element of the i-th row and the j-th column in G _sys ;

为去除G_sys中g_ij后的第i行向量；

is the i-th row vector after removing g _ij in G _sys ;

表示去除双馈风机开环运行状态下双馈风机的等效开环频率特性 G_w第j行和第i列后所得的矩阵；

represents the matrix obtained after removing the equivalent open-loop frequency characteristic Gw of the DFIG in the open-loop operating state of the _DFIG in the jth row and the ith column;

I is a unit matrix of predetermined dimensions;

为去除双馈风机开环运行状态下电力系统的等效开环频率特性G_sys第i行和第j列后所得的矩阵；

is the matrix obtained by removing the ith row and the jth column of the equivalent open-loop frequency characteristic G _sys of the power system in the open-loop operating state of the DFIG;

为去除G_sys中g_ij后的第j列向量；

is the jth column vector after removing g _ij in G _sys ;

G _sys is the equivalent open-loop frequency characteristic matrix of the power system under the open-loop operating state of the DFIG.

According to the equivalent open-loop process equation, the spectral radius function matrix of the power system under the closed-loop operation of the DFIG is determined;

Determine the matrix elements of the spectral radius function matrix, and generate the spectral radius function curve according to the spectral radius matrix elements;

Determine the matrix elements of the spectral radius function matrix according to the following formula:

in,

The parameter ρ _ij (s) characterizes the broadband oscillation frequency domain characteristics of the system;

i=1 or 2, j=1 or 2, ΔU ₁ and ΔI ₁ are the components of the voltage vector ΔU and the current vector ΔI on the d-axis, respectively, ΔU ₂ and ΔI ₂ are the voltage vector ΔU and the current vector ΔI on the q-axis, respectively weight;

g _ij is the element of the i-th row and the j-th column in G _sys ;

为去除G_sys中g_ij后的第i行向量；

is the i-th row vector after removing g _ij in G _sys ;

表示去除双馈风机开环运行状态下双馈风机的等效开环频率特性 G_w第j行和第i列后所得的矩阵；

represents the matrix obtained after removing the equivalent open-loop frequency characteristic Gw of the DFIG in the open-loop operating state of the _DFIG in the jth row and the ith column;

I is a unit matrix of predetermined dimensions;

为去除双馈风机开环运行状态下电力系统的等效开环频率特性G_sys第i行和第j列后所得的矩阵；

is the matrix obtained by removing the ith row and the jth column of the equivalent open-loop frequency characteristic G _sys of the power system in the open-loop operating state of the DFIG;

为去除G_sys中g_ij后的第j列向量；

is the jth column vector after removing g _ij in G _sys ;

G _sys is the equivalent open-loop frequency characteristic matrix of the AC system under the open-loop operating state of the DFIG;

g _wji (s) is the equivalent open-loop frequency characteristic of the doubly-fed fan in the open-loop operating state of the doubly-fed fan in the j-th row and the i-th column element of G _w , where s is a complex variable parameter, indicating that the element is a function of s;

ρ is the spectral radius function.

According to the curve characteristics of the spectral radius function, the stability of the broadband oscillation of the power system in the closed-loop operation state of the DFIG is judged, specifically:

The characteristic value of the spectral radius function curve is determined according to the spectral radius function curve. If the characteristic value of the spectral radius function curve is greater than 1, it is determined that the power system broadband oscillation is in an unstable state under the closed-loop operation state of the DFIG.

The present invention takes the example shown in FIG. 2 as an example to further describe the present invention in detail;

Use the electromagnetic transient software platform to build the simulation system shown in FIG. 3, adjust the working state of the system, and use the method provided by the present invention to judge the stability of the system model shown in FIG. 3 under the current working state;

According to the actual operating characteristics, the open-loop state space expression of the power system model under the DFIG open-loop operating state can be described as:

Among them, ΔX _sys is all state variables of the remaining subsystems after removing all fans, A _sys is the state matrix, B _sys is the output matrix, C _sys and D _sys are the output matrix and the direct transmission matrix, respectively, ΔU, ΔI are the dq coordinates The voltage and current vectors of the PCC point connected to the power system and the wind turbine under the system satisfy:

ΔU=[ΔU ₁ ΔU ₂ ] ^T

ΔI=[ΔI ₁ ΔI ₂ ] ^T

According to formula (1), under the condition of DFIG open-loop operation, the open-loop frequency characteristic model of the power system under the condition of grid-connected open-loop operation of DFIG is:

Step 2: According to the actual operating characteristics, the frequency characteristic model of the DFIG in the power system under the condition of grid-connected open-loop operation is:

where ΔU represents the DFIG port voltage vector in the dq coordinate system, which is the input vector; ΔI is the DFIG port current vector in the dq coordinate system, which is the output vector; A _w is the state matrix; B _w is the output matrix; C _w , D _w respectively are the output matrix and the direct transmission matrix; ΔX _w is the state variable of DFIG.

According to equation (4), the open-loop frequency characteristic function of DFIG shown in Fig. 2 is:

The equivalent open-loop frequency characteristic model of the power system under the grid-connected closed-loop operating state of the DFIG grid-connected DFIG is:

表示去除G_sys第i行和第j列后所得的矩阵，

表示去除G_w第i 行和第j列后所得的矩阵，

和

分别表示去除G_sys中g_ij后的第i行向量和第j列向量。in,

represents the matrix obtained by removing the ith row and jth column of G _sys ,

represents the matrix obtained by removing the i- _th row and the j-th column of Gw,

and

respectively represent the i-th row vector and the j-th column vector after removing g _ij in G _sys .

According to formula (6), the spectral radius model of the power system under the grid-connected closed-loop operating state of the DFIG is determined:

According to the spectral radius matrix of the DFIG grid-connected closed-loop system calculated by formula (7), the frequency response curve of the spectral radius of the closed-loop system under the current working state is drawn as shown in Figure 3.

From the characteristics of the spectral radius curve, it can be seen that the frequency response curve of the spectral radius matrix elements of the closed-loop system crosses the straight line representing the critical warning line for system stability in Figure 4. According to the characteristics of the spectral radius matrix frequency response curve, it is judged whether the system is in the current working state. stable. In order to verify the analysis conclusion of the stability discrimination method, the time domain simulation is carried out on the system under the current working state, and the DFIG stator voltage and current waveforms of the system are obtained as shown in Figure 5.

The present invention also proposes a system 200 for determining broadband oscillation stability of a power system based on spectral radius, as shown in FIG. 6 , including:

The first parameter acquisition module 201 takes the power system connected to the DFIG as the target object, and acquires the open-loop frequency characteristics of the power system under the open-loop operation of the DFIG;

The second parameter obtaining module 202 determines the open-loop frequency characteristic of the doubly-fed wind turbine under the open-loop operation condition according to the open-loop frequency characteristic of the power system;

The equivalent module 203 determines the equivalent open-loop process equation of the power system of the DFIG in the closed-loop operation state according to the open-loop frequency characteristic of the DFIG in the open-loop operation state;

The calculation module 204, according to the equivalent open-loop process equation, determines the spectral radius function matrix of the power system under the closed-loop operation state of the doubly-fed wind turbine;

The drawing module 205 determines the matrix elements of the spectral radius function matrix, and generates a spectral radius function curve according to the spectral radius matrix elements;

The following formula determines the matrix elements of the spectral radius function matrix:

in,

The parameter ρ _ij (s) characterizes the broadband oscillation frequency domain characteristics of the system;

i=1 or 2, j=1 or 2, ΔU ₁ and ΔI ₁ are the components of the voltage vector ΔU and the current vector ΔI on the d-axis, respectively, ΔU ₂ and ΔI ₂ are the voltage vector ΔU and the current vector ΔI on the q-axis, respectively weight;

g _ij is the element of the i-th row and the j-th column in G _sys ;

为去除G_sys中g_ij后的第i行向量；

is the i-th row vector after removing g _ij in G _sys ;

表示去除双馈风机开环运行状态下双馈风机的等效开环频率特性 G_w第j行和第i列后所得的矩阵；

represents the matrix obtained after removing the equivalent open-loop frequency characteristic Gw of the DFIG in the open-loop operating state of the _DFIG in the jth row and the ith column;

I is a unit matrix of predetermined dimensions;

为去除双馈风机开环运行状态下电力系统的等效开环频率特性G_sys第i行和第j列后所得的矩阵；

is the matrix obtained by removing the ith row and the jth column of the equivalent open-loop frequency characteristic G _sys of the power system in the open-loop operating state of the DFIG;

为去除G_sys中g_ij后的第j列向量；

is the jth column vector after removing g _ij in G _sys ;

G _sys is the equivalent open-loop frequency characteristic matrix of the AC system under the open-loop operating state of the DFIG;

g _wji (s) is the equivalent open-loop frequency characteristic of the doubly-fed fan in the open-loop operating state of the doubly-fed fan in the j-th row and the i-th column element of G _w , where s is a complex variable parameter, indicating that the element is a function of s;

ρ is the spectral radius function.

The determination module 206 determines the stability of the broadband oscillation of the power system under the closed-loop operation state of the doubly-fed wind turbine according to the characteristic of the spectral radius function curve.

The equivalent open-loop process equation of the power system under the closed-loop operation of the DFIG is:

Satisfy:

ΔU=[ΔU ₁ ΔU ₂ ] ^T

ΔI=[ΔI ₁ ΔI ₂ ] ^T

Among them, ΔU is the voltage vector of the common connection point between the power system and the wind turbine, and ΔI is the current vector of the common connection point between the power system and the wind turbine;

i=1 or 2, j=1 or 2;

ΔU ₁ and ΔI ₁ are the components of the voltage vector ΔU and the current vector ΔI on the d-axis, respectively, and ΔU ₂ and ΔI ₂ are the components of the voltage vector ΔU and the current vector ΔI on the q-axis, respectively;

g _ij is the element of the i-th row and the j-th column in G _sys ;

为去除G_sys中g_ij后的第i行向量；

is the i-th row vector after removing g _ij in G _sys ;

表示去除双馈风机开环运行状态下双馈风机的等效开环频率特性 G_w第j行和第i列后所得的矩阵；

represents the matrix obtained after removing the equivalent open-loop frequency characteristic Gw of the DFIG in the open-loop operating state of the _DFIG in the jth row and the ith column;

I is a unit matrix of predetermined dimensions;

为去除双馈风机开环运行状态下电力系统的等效开环频率特性G_sys第i行和第j列后所得的矩阵；

is the matrix obtained by removing the ith row and the jth column of the equivalent open-loop frequency characteristic G _sys of the power system in the open-loop operating state of the DFIG;

为去除G_sys中g_ij后的第j列向量；

is the jth column vector after removing g _ij in G _sys ;

G _sys is the equivalent open-loop frequency characteristic matrix of the power system under the open-loop operating state of the DFIG.

According to the curve characteristics of the spectral radius function, the stability of the broadband oscillation of the power system in the closed-loop operation state of the DFIG is judged, specifically:

The characteristic value of the spectral radius function curve is determined according to the spectral radius function curve. If the characteristic value of the spectral radius function curve is greater than 1, it is determined that the power system broadband oscillation is in an unstable state under the closed-loop operation state of the DFIG.

As will be appreciated by those skilled in the art, the embodiments of the present application may be provided as a method, a system, or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It will be understood that each flow and/or block in the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to the processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing device to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing device produce Means for implementing the functions specified in a flow or flow of a flowchart and/or a block or blocks of a block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions The apparatus implements the functions specified in the flow or flows of the flowcharts and/or the block or blocks of the block diagrams.

These computer program instructions can also be loaded on a computer or other programmable data processing device to cause a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process such that The instructions provide steps for implementing the functions specified in the flow or blocks of the flowcharts and/or the block or blocks of the block diagrams.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be Modifications or equivalent replacements are made to the specific embodiments of the present invention, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (8)

1. A method for determining broadband oscillation stability of a power system based on a spectral radius, the method comprising: Taking the power system connected to the DFIG as the target object, the open-loop frequency characteristics of the power system under the open-loop operation of the DFIG are obtained; According to the open-loop frequency characteristics of the power system, determine the open-loop frequency characteristics of the DFIG under open-loop operation; According to the open-loop frequency characteristics of the DFIG in the open-loop operation, the equivalent open-loop process equation of the power system under the closed-loop operation of the DFIG is determined; According to the equivalent open-loop process equation, the spectral radius function matrix of the power system under the closed-loop operation of the DFIG is determined; Determine the matrix elements of the spectral radius function matrix, and generate the spectral radius function curve according to the spectral radius matrix elements; According to the characteristic of the spectral radius function curve, the stability of the broadband oscillation of the power system under the closed-loop operation state of the DFIG is judged. 2. The method according to claim 1, wherein the equivalent open-loop process equation of the power system of the DFIG in a closed-loop operating state is:

Satisfy:

Among them, ΔU is the voltage vector of the common connection point between the power system and the wind turbine, and ΔI is the current vector of the common connection point between the power system and the wind turbine; i=1 or 2, j=1 or 2; ΔU ₁ and ΔI ₁ are the components of the voltage vector ΔU and the current vector ΔI on the d-axis, respectively, and ΔU ₂ and ΔI ₂ are the components of the voltage vector ΔU and the current vector ΔI on the q-axis, respectively; g _ij is the element of the i-th row and the j-th column in G _sys ;

is the i-th row vector after removing g _ij in G _sys ;

represents the matrix obtained after removing the equivalent open-loop frequency characteristic Gw of the DFIG in the open-loop operating state of the _DFIG in the jth row and the ith column; I is a unit matrix of predetermined dimensions;

is the matrix obtained by removing the ith row and the jth column of the equivalent open-loop frequency characteristic G _sys of the power system in the open-loop operating state of the DFIG;

is the jth column vector after removing g _ij in G _sys ; G _sys is the equivalent open-loop frequency characteristic matrix of the power system under the open-loop operating state of the DFIG. 3. The method according to claim 1, the matrix elements of the spectral radius function matrix are determined according to the following formula:

in, The parameter ρ _ij (s) characterizes the broadband oscillation frequency domain characteristics of the system; i=1 or 2, j=1 or 2, ΔU ₁ and ΔI ₁ are the components of the voltage vector ΔU and the current vector ΔI on the d-axis, respectively, ΔU ₂ and ΔI ₂ are the voltage vector ΔU and the current vector ΔI on the q-axis, respectively weight; g _ij is the element of the i-th row and the j-th column in G _sys ;

is the i-th row vector after removing g _ij in G _sys ;

represents the matrix obtained after removing the equivalent open-loop frequency characteristic Gw of the DFIG in the open-loop operating state of the _DFIG in the jth row and the ith column; I is a unit matrix of predetermined dimensions;

is the matrix obtained by removing the ith row and the jth column of the equivalent open-loop frequency characteristic G _sys of the power system in the open-loop operating state of the DFIG;

is the jth column vector after removing g _ij in G _sys ; G _sys is the equivalent open-loop frequency characteristic matrix of the AC system under the open-loop operating state of the DFIG; _{g wji} (s) is the equivalent open-loop frequency characteristic of the doubly-fed fan in the open-loop operating state of the doubly-fed fan, Gw, the jth row, the ith column element, where s is a complex variable parameter, indicating that the element is a function of s; ρ is the spectral radius function. 4. The method according to claim 1, wherein the characteristic of the spectral radius function curve determines the stability of the power system broadband oscillation of the doubly-fed fan in a closed-loop operating state, specifically: The characteristic value of the spectral radius function curve is determined according to the spectral radius function curve. If the characteristic value of the spectral radius function curve is greater than 1, it is determined that the power system broadband oscillation is in an unstable state under the closed-loop operation state of the DFIG. 5. A system for determining broadband oscillation stability of a power system based on a spectral radius, the system comprising: The first parameter acquisition module takes the power system connected to the DFIG as the target object, and acquires the open-loop frequency characteristics of the power system under the open-loop operation of the DFIG; The second parameter acquisition module determines the open-loop frequency characteristics of the doubly-fed wind turbine under open-loop operation according to the open-loop frequency characteristics of the power system; The equivalent module determines the equivalent open-loop process equation of the power system under the closed-loop operation of the DFIG according to the open-loop frequency characteristics of the DFIG in the open-loop operation; The calculation module, according to the equivalent open-loop process equation, determines the spectral radius function matrix of the power system under the closed-loop operating state of the DFIG; The drawing module determines the matrix elements of the spectral radius function matrix, and generates the spectral radius function curve according to the spectral radius matrix elements; The judgment module judges the stability of the broadband oscillation of the power system under the closed-loop operation state of the DFIG according to the characteristic of the spectral radius function curve. 6. The system according to claim 5, wherein the equivalent open-loop process equation of the power system under the closed-loop operating state of the DFIG is:

Satisfy:

Among them, ΔU is the voltage vector of the common connection point between the power system and the wind turbine, and ΔI is the current vector of the common connection point between the power system and the wind turbine; i=1 or 2, j=1 or 2; ΔU ₁ and ΔI ₁ are the components of the voltage vector ΔU and the current vector ΔI on the d-axis, respectively, and ΔU ₂ and ΔI ₂ are the components of the voltage vector ΔU and the current vector ΔI on the q-axis, respectively; g _ij is the element of the i-th row and the j-th column in G _sys ;

is the i-th row vector after removing g _ij in G _sys ;

represents the matrix obtained after removing the equivalent open-loop frequency characteristic Gw of the DFIG in the open-loop operating state of the _DFIG in the jth row and the ith column; I is a unit matrix of predetermined dimensions;

is the matrix obtained by removing the ith row and the jth column of the equivalent open-loop frequency characteristic G _sys of the power system in the open-loop operating state of the DFIG;

is the jth column vector after removing g _ij in G _sys ; G _sys is the equivalent open-loop frequency characteristic matrix of the power system under the open-loop operating state of the DFIG. 7. The system of claim 5, the matrix elements of the spectral radius function matrix are determined according to the following formula:

in, The parameter ρ _ij (s) characterizes the broadband oscillation frequency domain characteristics of the system; i=1 or 2, j=1 or 2, ΔU ₁ and ΔI ₁ are the components of the voltage vector ΔU and the current vector ΔI on the d-axis, respectively, ΔU ₂ and ΔI ₂ are the voltage vector ΔU and the current vector ΔI on the q-axis, respectively weight; g _ij is the element of the i-th row and the j-th column in G _sys ;

is the i-th row vector after removing g _ij in G _sys ;

represents the matrix obtained after removing the equivalent open-loop frequency characteristic Gw of the DFIG in the open-loop operating state of the _DFIG in the jth row and the ith column; I is a unit matrix of predetermined dimensions;

is the matrix obtained by removing the ith row and the jth column of the equivalent open-loop frequency characteristic G _sys of the power system in the open-loop operating state of the DFIG;

is the jth column vector after removing g _ij in G _sys ; G _sys is the equivalent open-loop frequency characteristic matrix of the AC system under the open-loop operating state of the DFIG; _{g wji} (s) is the equivalent open-loop frequency characteristic of the doubly-fed fan in the open-loop operating state of the doubly-fed fan, Gw, the jth row, the ith column element, where s is a complex variable parameter, indicating that the element is a function of _s ; ρ is the spectral radius function. 8. The system according to claim 5, wherein the characteristic of the spectral radius function curve determines the stability of the power system broadband oscillation of the doubly-fed fan in a closed-loop operating state, specifically: The characteristic value of the spectral radius function curve is determined according to the spectral radius function curve. If the characteristic value of the spectral radius function curve is greater than 1, it is determined that the power system broadband oscillation is in an unstable state under the closed-loop operation state of the DFIG.

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