CN107017620B - Method for obtaining voltage static stability region tangent plane of alternating current-direct current system containing wind power plant - Google Patents
Method for obtaining voltage static stability region tangent plane of alternating current-direct current system containing wind power plant Download PDFInfo
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- H—ELECTRICITY
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Abstract
The invention discloses a method for solving a tangent plane of a voltage static stable domain of an alternating current-direct current system containing a wind power plant, which relates to the field of power systems. And obtaining a voltage static stability region tangent plane containing the wind power plant alternating current and direct current system by obtaining a voltage collapse node. The method can provide a new idea for the later calculation of the static security domain of the electric power system, provides a basis for the calculation of the security domain of the electric power system which is more consistent with the actual wind power injection, and provides important reference for the safe and stable operation of the electric power system for the electric power dispatching personnel.
Description
Technical Field
The invention belongs to the field of safe and stable operation of a power system, and relates to a tangent plane calculation method of a static voltage stability domain of the power system including a wind power plant and direct current control.
Background
With the demand of people for new energy development, wind power is regarded as a clean renewable energy. The continuous rising of the total capacity of the wind power in the current power system also continuously follows the use of the wind power. The influence of multiple uncertainties of wind power output on a power grid is increasingly obvious, and the influence of the wind power output on the static safety of the power grid is considered, so that the method is very important for maintaining the safety and stability of a power system and improving the utilization rate of wind power.
The wind power generation is a special power generation form different from conventional power generation, has the characteristics different from the traditional power generation form, along with the deepening of encouraging policies of renewable energy development and the environmental protection pressure in the world, the wind power generation is gradually industrialized and scaled, the influence of wind power characteristics on a power grid is more obvious, the large-scale wind power generation has influenced various aspects such as the safety, the stability, the electric energy quality, the coordinated dispatching and the like of a local power grid, even has caused some serious negative influences, and the certain degree becomes an obstacle for restricting the large-scale wind power generation development.
In the face of the world wind power industry and the Chinese wind power industry which are briskly rising, the key technical problem of large-scale wind power grid-connected operation is urgently needed to be solved, especially the influence on the voltage stability of a power grid after the wind power plant is connected with the grid has very important significance for improving the voltage quality of the power grid, ensuring the safety, reliability and economic operation of a system, providing a technical basis for the planning design, the policy making of wind power development and the production operation of the wind power plant, and having important practical value and theoretical significance.
In order to better combine the characteristics of the power system with the concept of developing clean renewable energy, the characteristics of the static security domain of the power system containing wind power active random fuzzy injection are researched, and the research on the characteristics of the voltage collapse point of the power system containing wind power random fuzzy injection is necessary. The method can be used as an important reference for dispatching personnel to fully utilize wind power resources and ensure the operation safety of the system, and has important significance for gradually improving the utilization rate of the wind power of the system.
Disclosure of Invention
The influence of the system safety and stability domain of the wind turbine generator connected into the power system needs to be researched aiming at the hidden danger of the system safety and stability operation caused by the uncertainty of the output of the large-scale wind turbine generator connected into the power system. The conventional view considers that the static security domain of the power system is determined based on the fixed system output mode, and obviously cannot be applied to the real-time uncertain situation of wind power output. According to the method, under the condition that random fuzzy uncertain output of wind power is considered, a tangent plane of a static voltage stability region of an alternating-current power system and a direct-current power system containing a wind power plant is obtained, the distribution condition of the boundary of the stability region can be approximately described by using the tangent plane of the stability region, a model containing reference power flow of the power system of the wind power plant containing DFIG is improved, and approximate fitting of the tangent plane of the static voltage stability region of the power system of the wind power plant containing DFIG.
In order to achieve the purpose, the invention adopts the following technical scheme:
1. a method for solving a tangent plane of a voltage static stability region of an alternating current and direct current system containing a wind power plant is characterized by comprising the following steps:
(1) considering the randomness of wind power access, constructing a parameter-containing power flow equation of the power system;
(2) adding a direct current control mode;
(3) modeling of a static voltage stability domain tangent plane of a wind power plant power system.
2. And (4) considering the randomness of wind power access, and constructing a parameter-containing power flow equation of the power system. Firstly, modeling is carried out on power randomly output by a wind power plant, and then the random power is substituted into an alternating current and direct current continuous power flow equation, so that the load margin expectation and the voltage level expectation of a critical point are solved.
3. And a direct current control mode is added, the static stability of the system voltage is still influenced by the power transmission limit of the alternating current transmission system, and the PV curve and the critical operating point of the system can be accurately solved by adopting continuous power flow.
4. Firstly, a voltage collapse point (namely an SNB point) is obtained through continuous power flow, and then a voltage static stability domain tangent plane containing a wind power plant alternating current and direct current system is obtained.
Drawings
FIG. 1 is a PV characteristic curve of an AC/DC system;
fig. 2 is a direct current transmission line.
Detailed Description
The invention comprises the following steps:
1. considering the randomness of wind power access, a parameter-containing power flow equation of a power system is constructed
The AC/DC power system containing the wind power plant comprises a parameter load flow equation set:
in the formula: pi0、Qi0Respectively representing active power and reactive power initially injected by a node i; pWi、QWiThe active power and the reactive power sent by the wind power plant are respectively represented, and the value is zero when the node is not connected with the wind turbine generator; viAnd theta respectively represents the node voltage and the phase angle of i;
is the power factor angle of each load; alpha is alphaiRepresenting the output increasing direction of each generator; beta is aiIndicating the direction of power increase for each load. Lambda is a load change parameter of the system; n is the sum of the number of PV nodes and PQ nodes, and M is the sum of the number of PQ nodes; 1,2, Nc，NcThe number of the current converters; vdk，IdkRespectively DC voltage and DC current, V when the node is not connected with DC linedk，IdkAre all zero;
is the converter power factor angle; thetakThe inverter control angle.
2. Considering the randomness of wind power access, a parameter-containing power flow equation of a power system is constructed
(1) Basic equation of a direct current system converter:
Δd1k＝Vdk-kTkVN+k cosθdk+XckIdk＝0 (2)
in the formula, Xck is equivalent reactance of the converter; kTk is the transformation ratio of the converter transformer; k gamma is the commutation coefficient and is generally 0.995.
(2) Direct current network equation:
in the formula: gdkj is the dc network admittance.
(3) Converter control equation:
the control of the current converters needs to be determined, and each current converter needs to determine two control variables corresponding to an equation set consisting of two equations in the following 5 equation equations:
3. continuous power flow to obtain voltage collapse point
When a tangent plane containing a stable domain of a wind power plant alternating current-direct current power system is calculated, firstly, a voltage collapse point (namely an SNB point) is obtained through continuous power flow, and a linear approximation equation of a stable domain boundary at the SNB point can be obtained by linearizing a formula F (x, alpha, beta, Pw, C1ds, C2ds, lambda) to be 0:
Fx|*Δx+Fα|*Δα+Fβ|*Δβ+FW|*ΔPW+FC1d|*ΔC1d+
FC2d|*ΔC2d+Fλ|*Δλ＝0 (7)
in the formula*Indicating that the corresponding coefficient comes from the SNB point of the system stability domain boundary, i.e. the point satisfies equation (3.1); fx|*The Jacobian matrix of the system at the SNB point AC/DC power system; fα|*，Fβ|*，Fλ|*，FC1d|*，FC2d|*Respectively, the partial derivatives of the power flow equation to the subscripts thereof at the SNB points. Left-multiplying the 3.2 formula by FxAnd substituting the formula 3.1 into the left eigenvector omega corresponding to the zero eigenvalue to obtain the tangent plane equation of the stable domain boundary at the point SNB as follows:
ωFW|*ΔPW+ωFα|*Δα+ωFβ|*Δβ+ωFC1d|*ΔC1d+
ωFC2d|*ΔC2d+ωFλ|*Δλ＝0 (8)
(8) formula (la) may also be expressed as:
in the formula:
in order to make the system static voltage stability domain tangent plane expressed by the equation (9) in the power injection space and the direct current control value space, according to the relationship between α, β and λ and the output and load size of the generator, the following is performed:
substitution of formula (11) for formula (9) eliminates α, β and λ, yielding:
the formula (12) can be linearized at a given SNB point:
2. static voltage stability region tangent plane of alternating current and direct current power system containing wind power plant
The equation (13) is simplified to obtain, and the power injection space tangent plane equation is:
aPG+bPL+mC1d+nC2d+zPW+Y＝0 (14)
wherein a, b, m, n and z are row vectors, Y is a real number, and the value is shown in formula (15):
(15) where e is the same unit row vector as the number of K α columns. Equation (14) is an expression of a static voltage stability domain tangent plane containing the wind farm alternating current and direct current power system in a power injection space and a direct current control value space.
The above embodiments are merely illustrative, and not restrictive, and various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention, and therefore all equivalent technical solutions are intended to be included within the scope of the invention.
Claims (4)
1. The method for solving the tangent plane of the voltage static stability region of the alternating current-direct current system containing the wind power plant is characterized by comprising the following steps of:
(1) considering the randomness of wind power access, constructing a power system parameter-containing power flow equation, firstly modeling power randomly output by a wind power plant, and then substituting the random power into an alternating current and direct current continuous power flow equation to obtain a load margin expectation and a voltage level expectation of a critical point;
(2) adding a direct current control mode, constructing a parameter-containing power flow equation of the power system, adding the direct current control mode, wherein the static stability of the system voltage is still influenced by the power transmission limit of the alternating current power transmission system, and accurately calculating a PV curve and a critical operating point of the system by adopting continuous power flow;
(3) modeling a static voltage stable region tangent plane of a power system of a wind power plant, firstly solving an SNB point through continuous power flow, and then solving the static voltage stable region tangent plane containing the alternating current and direct current system of the wind power plant.
2. The method for obtaining the tangent plane of the voltage static stability region of the wind farm-containing alternating current and direct current system according to claim 1, wherein the step (1) comprises the following steps:
constructing a parameter-containing power flow equation set of an alternating current and direct current power system containing a wind power plant:
in the formula: pi0、Qi0Respectively representing active power and reactive power initially injected by a node i; pWi、QWiRespectively representing active power and reactive power generated by a wind power plant, and P when a node is not connected with a wind turbine generatorWi、QWiIs zero; vi、θiRespectively representing the node voltage and the phase angle of i;
is the power factor angle of each load; alpha is alphaiRepresenting the output increasing direction of each generator; beta is aiRepresenting the power increasing direction of each load; lambda is a load change parameter of the system; n is the sum of the number of PV nodes and PQ nodes, and M is the sum of the number of PQ nodes; 1,2, Nc，NcThe number of the current converters; vdk，IdkRespectively DC voltage and DC current, V when the node is not connected with DC linedk，IdkAre all zero;
is the converter power factor angle; thetakThe inverter control angle.
3. The method for obtaining the tangent plane of the voltage static stability region of the wind farm-containing alternating current and direct current system according to claim 1, wherein the step (2) is characterized in that:
3.1 the fundamental equation of the DC system converter:
Δd1k＝Vdk-kTkVN+kcosθdk+XckIdk＝0
in the formula, XckIs the equivalent reactance of the converter; k is a radical ofTkConverting the ratio of the converter transformer; k is a radical ofγThe value is 0.995 for the commutation coefficient;
3.2 direct current network equation:
in the formula: gdkjAdmittance for a direct current network;
3.3 converter control equation:
4. the method for obtaining the tangent plane of the voltage static stability region of the wind farm-containing alternating current and direct current system according to claim 1, wherein the step (3) is characterized in that:
4.1 Linear approximation equation of the stability domain at SNB Point:
Fx|*Δx+Fα|*Δα+Fβ|*Δβ+FW|*ΔPW+FC1d|*ΔC1d+FC2d|*ΔC2d+Fλ|*Δλ＝0
Fx|*the Jacobian matrix of the system at the SNB point AC/DC power system; fα|*，Fβ|*，Fλ|*，FC1d|*，FC2d|*Respectively representing partial derivatives of the power flow equation to the subscript of the SNB point;
4.2 tangent plane equation of the stability domain boundary at the SNB point:
ωFW|*ΔPW+ωFα|*Δα+ωFβ|*Δβ+ωFC1d|*ΔC1d+ωFC2d|*ΔC2d+ωFλ|*Δλ＝0
in the formula: omega is FxThe left eigenvector corresponding to the zero eigenvalue of (1);
it can also be expressed as:
in the formula:
according to the relationship between the output and the load size of the generator and the output and the load size of the generator, the following steps are carried out:
the tangent plane equation of the steady-state domain boundary at the SNB point can be expressed as:
linearizing the tangent plane equation at the SNB point to obtain a power injection space tangent plane equation:
aPG+bPL+mC1d+nC2d+zPW+Y＝0
in the formula, a, b, m, n and z are row vectors, Y is a real number, and the value is as follows:
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