CN113054655B - Receiving-end power grid strength evaluation method for high-proportion direct current high-proportion new energy - Google Patents

Receiving-end power grid strength evaluation method for high-proportion direct current high-proportion new energy Download PDF

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CN113054655B
CN113054655B CN202110047025.7A CN202110047025A CN113054655B CN 113054655 B CN113054655 B CN 113054655B CN 202110047025 A CN202110047025 A CN 202110047025A CN 113054655 B CN113054655 B CN 113054655B
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CN113054655A (en
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沈广进
韩家辉
郭强
张健
覃琴
张立波
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Zhejiang University ZJU
China Electric Power Research Institute Co Ltd CEPRI
State Grid Tianjin Electric Power Co Ltd
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China Electric Power Research Institute Co Ltd CEPRI
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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Abstract

The invention belongs to the technical field of power systems, and particularly relates to a receiving-end power grid strength evaluation method for high-proportion direct current high-proportion new energy, which comprises the steps of establishing a linearization model of a photovoltaic port by an impedance modeling method, analyzing a sensitivity matrix of a minimum module characteristic value of an alternating current network Jacobian matrix to matrix elements, and obtaining a conclusion that the static stability of a system can be improved when a photovoltaic power station is accessed; the method comprises the steps of obtaining a photovoltaic-free system reduced-order Jacobian matrix by utilizing elementary row-column transformation and Schur transformation, carrying out modal decomposition on a system characteristic equation to obtain a plurality of equivalent single-feed systems, calculating a minimum characteristic root of the system Jacobian matrix and a corresponding characteristic vector thereof, calculating to obtain a critical generalized short-circuit ratio of the system Jacobian matrix, regarding the system after photovoltaic access as perturbation without the photovoltaic feed-in system based on a modal perturbation theory, and correcting the original critical generalized short-circuit ratio to obtain the generalized critical generalized short-circuit ratio of the multi-feed-in direct current system with the large photovoltaic power station.

Description

Method for evaluating strength of receiving-end power grid of high-proportion direct-current high-proportion new energy
Technical Field
The invention belongs to the technical field of power systems, and particularly relates to a receiving-end power grid strength evaluation method for high-proportion direct current high-proportion new energy.
Background
Because the energy and load distribution of China shows that hydroelectric resources are concentrated in southwest regions, wind, light and thermal power resources are concentrated in northwest regions, and the load center is concentrated in the middle-east and eastern coastal regions, the characteristic of high reverse distribution is realized, and the construction of a long-distance, large-capacity and trans-regional power transmission channel is particularly urgent. In recent years, with the rapid development and operation of a power grid commutation high-voltage direct-current transmission technology, a direct-current multi-feed system with multiple direct-current drop points concentrated on the same alternating-current receiving-end power grid is formed in power grids in China, Sanhua and south.
During the thirteen-five period, along with the high-speed development of the wind power/photovoltaic power generation scale and the direct current external power receiving scale in the receiving-end power grid, the east China power grid is developed into a high-proportion direct current high-proportion new energy system which takes high-proportion new energy and high-proportion power electronic equipment as main characteristics. By the end of 2019, wind power, photovoltaic and local power plants in east China are installed in excess of 6000 million kilowatts. Meanwhile, after multiple extra-high voltage direct currents are fed in a centralized manner, the east China power grid is developed into a large receiving-end power grid, the new stage of alternating-current and direct-current extra-high voltage series-parallel operation is started comprehensively, the operation characteristics of the power grid are changed deeply, and the characteristics of strong direct current and weak alternating current are further displayed. The high-ratio new energy power generation replacing a synchronous machine and multi-loop high-capacity direct current centralized feeding is one of outstanding problems in future power grid development, and the existing main problems are whether a high-ratio direct current high-ratio new energy system can provide strong voltage support and how to optimize the operation mode to ensure safe and stable operation of a receiving-end power grid.
The new version of the safety and stability guide rule of the power system requires that new energy and direct current scale need to be matched with the strength of the power grid, but the power grid strength quantification is lack of a mature analysis method and an effective calculation tool so far. Therefore, a practical characterization method for the power grid strength needs to be researched to determine boundary conditions, threshold values and analysis flows, so that the safety and stability level of the power grid is improved.
Disclosure of Invention
The invention aims to provide a method for evaluating the strength of a receiving-end power grid of high-proportion direct current and high-proportion new energy, which overcomes the defects of the prior art, and can accurately judge the strength and stability margin of the receiving-end power grid of high-proportion direct current and high-proportion new energy by using a modal perturbation theory.
In order to solve the problems, the technical scheme adopted by the invention is as follows:
a receiving-end power grid strength evaluation method for high-proportion direct current high-proportion new energy specifically comprises the following steps:
establishing a linearization model of a photovoltaic port by an impedance modeling method, and analyzing a sensitivity matrix of a minimum module characteristic value of an alternating current network Jacobian matrix to matrix elements to obtain a photovoltaic power station access which can improve the static stability of the system;
step two, not considering photovoltaic power station access, calculating to obtain a system Jacobian matrix without photovoltaic feed-in based on an alternating current network Jacobian matrix and a direct current Jacobian matrix, and compressing nodes of an alternating current system by utilizing the elementary row-column transformation and Schur transformation of the matrix to obtain a reduced-order Jacobian matrix of the system;
thirdly, calculating to obtain a minimum characteristic root of a system extended Jacobian matrix and a characteristic vector corresponding to the minimum characteristic root according to a plurality of equivalent single-feed systems obtained by performing modal decomposition on a system characteristic equation based on a singular boundary condition of a system reduced Jacobian matrix, and obtaining a critical generalized short-circuit ratio CgSCR under a rated operation condition;
step four, after the photovoltaic power station is accessed, calculating to obtain a system Jacobian matrix added into the photovoltaic power station based on an alternating current network Jacobian matrix, a direct current Jacobian matrix and a photovoltaic Jacobian matrix, compressing the system Jacobian matrix added into the photovoltaic power station through elementary row-column transformation and Schur transformation to obtain a reduced-order Jacobian matrix of the system added into the photovoltaic power station, and calculating a boundary condition when the system achieves the critical static voltage stability;
and step five, calculating perturbation quantity of the photovoltaic power station to a system characteristic equation after the photovoltaic power station is accessed according to a modal perturbation theory, and calculating a system generalized short-circuit ratio and a critical generalized short-circuit ratio CgSCR' of the photovoltaic power station after the photovoltaic power station is accessed according to the perturbation quantity.
Further, in the first step, the sensitivity matrix of the ac network jacobian matrix minimum mode eigenvalue to the matrix elements is expressed as follows:
Figure GDA0003603192350000031
the elements of the matrix are the minimum mode eigenvalues lambda 1 Sensitivity to a position element in the matrix; the symbols of two diagonal elements of the matrix are positive, and the symbols of two off-diagonal elements are negative.
Further, the expression of the reduced-order jacobian matrix of the system in the second step is as follows:
Figure GDA0003603192350000032
wherein the compressed admittance matrix B red The expression is as follows:
Figure GDA0003603192350000033
in the above formula B ij Representing the corresponding elements in the admittance matrix.
Further, the formula for calculating the system characteristic equation in step three is expressed as follows:
Figure GDA0003603192350000034
in the above formula, J eq0 Extending the jacobian matrix for the system, expressed as
J eq0 ＝-diag -1 (P Ni )B red
T i (·)＝2c i K(c i )+2ωB ci /(ρ i P Ni )；ρ i ＝P i /(P Ni U i 2 )；
Wherein, P Ni Rated capacity per DC return; k (c) i ) Is expressed as
Figure GDA0003603192350000035
Wherein gamma is an arc extinguishing angle, X is a phase-change reactance, and K is the transformation ratio of the inverter-side transformer.
Further, in the third step, after modal decomposition is performed on the characteristic equation, the characteristic equation is equivalent to a plurality of single-feed systems, and is expressed as follows:
Figure GDA0003603192350000041
wherein λ is 0i Is J eq0 Corresponding to the short circuit ratio of each equivalent single feed.
Further, solving the equivalent single feed-in system in the third step to obtain a critical generalized short-circuit ratio CgSCR under a rated operation condition:
Figure GDA0003603192350000042
further, the reduced Jacobian matrix of the system incorporating the photovoltaic station in step four is represented as follows:
Figure GDA0003603192350000043
wherein, the first and the second end of the pipe are connected with each other,
Figure GDA0003603192350000044
in the above formula, | A | is a determinant of a lower right corner matrix after elementary row-column transformation, and the expression is as follows:
Figure GDA0003603192350000045
further, the perturbation of the system characteristic equation taking into account the photovoltaic feed in step four is expressed by the following formula:
Figure GDA0003603192350000046
further, the critical generalized short-circuit ratio CgSCR' calculation formula in step four adopts the following formula:
Figure GDA0003603192350000051
wherein W -1 And W represents the minimum feature root λ 01 Corresponding left and right feature vectors.
Compared with the prior art, the invention has the following beneficial effects:
the method can promote the practicability of the generalized short-circuit ratio index in the high-proportion direct-current high-proportion new energy receiving end power grid, and can guide the actual high-proportion direct-current high-proportion new energy receiving end power grid to be scheduled and operated by utilizing the index. The method is applied to the voltage support strength evaluation of the high-proportion direct-current high-proportion new energy receiving end power grid in multiple operation modes, the voltage support strength of the high-proportion direct-current high-proportion new energy receiving end power grid in the multiple operation modes is quantized by using the change rule of the generalized short circuit ratio index threshold in different actual operation modes, and the voltage support strength of the high-proportion direct-current high-proportion new energy receiving end power grid can be accurately evaluated.
Drawings
FIG. 1 is a flow chart illustrating a specific calculation method according to the present invention.
Fig. 2 is a model diagram of a multi-feed system including photovoltaic devices according to the present invention.
Fig. 3 is a standard dc model proposed in 1991 by CIGRE dc working group adopted in the present invention.
Fig. 4 is a minimum mode characteristic value change curve of a system jacobian matrix under different photovoltaic capacities in simulation verification according to an embodiment of the present invention.
Fig. 5 is a variation curve of the critical generalized short-circuit ratio of the system under different photovoltaic capacities in the simulation verification according to the embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A receiving-end power grid strength evaluation method for high-proportion direct current high-proportion new energy specifically comprises the following steps:
establishing a linearization model of a photovoltaic port by an impedance modeling method, and analyzing a sensitivity matrix of a minimum module characteristic value of an alternating current network Jacobian matrix to matrix elements to obtain a photovoltaic power station access which can improve the static stability of the system;
step two, regardless of photovoltaic power station access, adding the Jacobian matrix of the alternating current network and the Jacobian matrix of the direct current network, calculating to obtain a Jacobian matrix of the system without photovoltaic feed-in, and compressing nodes of the alternating current system by utilizing elementary row-column transformation and Schur transformation of the matrix to obtain a reduced-order Jacobian matrix of the system;
thirdly, calculating to obtain a minimum characteristic root of a system extended Jacobian matrix and a characteristic vector corresponding to the minimum characteristic root according to a plurality of equivalent single-feed systems obtained by performing modal decomposition on a system characteristic equation based on a singular boundary condition of a system reduced Jacobian matrix, and obtaining a critical generalized short-circuit ratio CgSCR under a rated operation condition;
step four, after the photovoltaic power station is considered to be accessed, adding the alternating current network Jacobian matrix, the direct current Jacobian matrix and the photovoltaic Jacobian matrix, calculating to obtain a system Jacobian matrix added into the photovoltaic power station, compressing the system Jacobian matrix added into the photovoltaic power station through elementary row-column transformation and Schur transformation to obtain a reduced-order Jacobian matrix of the system added into the photovoltaic power station, and calculating a boundary condition when the system achieves the critical static voltage stability;
and step five, calculating perturbation quantity of the photovoltaic power station to a system characteristic equation after the photovoltaic power station is accessed according to a modal perturbation theory, and calculating a system generalized short-circuit ratio and a critical generalized short-circuit ratio CgSCR' of the photovoltaic power station after the photovoltaic power station is accessed according to the perturbation quantity.
In the first step, the sensitivity matrix of the AC network Jacobian matrix minimum modulus eigenvalue to the matrix element is expressed as the following form:
Figure GDA0003603192350000061
the elements of the matrix are the minimum mode eigenvalues lambda 1 Sensitivity to a position element in the matrix; the symbols of two diagonal elements of the matrix are positive, and the symbols of two off-diagonal elements are negative.
The expression of the reduced-order Jacobian matrix of the system in the second step is as follows:
Figure GDA0003603192350000071
wherein the compressed admittance matrix B red The expression is as follows:
Figure GDA0003603192350000072
in the above formula B ij Representing the corresponding elements in the admittance matrix.
The calculation formula of the system characteristic equation in the third step is expressed as follows:
Figure GDA0003603192350000073
in the above formula, J eq0 The jacobian matrix is expanded for the system, and the expression is
J eq0 ＝-diag -1 (P Ni )B red
T i (·)＝2c i K(c i )+2ωB ci /(ρ i P Ni )；ρ i ＝P i /(P Ni U i 2 )；
Wherein, P Ni Rated capacity per DC return, K (c) i ) Is expressed as
Figure GDA0003603192350000074
Wherein gamma is an arc extinguishing angle, X is a phase-change reactance, and K is the transformation ratio of the inverter-side transformer.
In the third step, after modal decomposition is carried out on the characteristic equation, the characteristic equation is equivalent to a plurality of single-feed systems, and the characteristic equation is expressed as the following form:
Figure GDA0003603192350000075
wherein λ is 0i Is J eq0 Corresponding to the short circuit ratio of each equivalent single feed.
Solving the equivalent single feed-in system in the third step to obtain a critical generalized short-circuit ratio CgSCR under a rated operation condition:
Figure GDA0003603192350000081
the reduced Jacobian matrix of the system incorporating the photovoltaic station in step four is represented as follows:
Figure GDA0003603192350000082
wherein the content of the first and second substances,
Figure GDA0003603192350000083
in the above formula, | A | is a determinant of a lower right corner matrix after elementary row-column transformation, and the expression is as follows:
Figure GDA0003603192350000084
in the fourth step, the perturbation of the system characteristic equation of the photovoltaic feed is considered and is expressed by the following formula:
Figure GDA0003603192350000085
the formula for calculating the critical generalized short-circuit ratio CgSCR' in the fourth step adopts the following formula:
Figure GDA0003603192350000086
wherein W -1 And W represents the minimum feature root λ 01 Corresponding left and right feature vectors.
The specific implementation result is as follows:
the three-feed system shown in fig. 1 is built in Matlab software, and the specifically used dc systems all adopt a standard model proposed by CIGRE dc working group in 1991, and a specific model thereof is shown in fig. 2. The variables have the following symbolic meanings: p d1 、P d2 、Q d1 、Q d2 Injecting active power and reactive power of a receiving end alternating current system into the two loops of direct current respectively; p pv 、Q pv Active power and reactive power output by the photovoltaic converter; i is 1 、I 2 、I 3 The currents are respectively output by the two-circuit direct current converter and the photovoltaic converter; p ac1 、P ac2 、P ac3 、Q ac1 、Q ac2 、Q ac3 Respectively an active power and a reactive power transmitted to a receiving end alternating current system;
Figure GDA0003603192350000091
the voltage amplitude and the phase angle of the equivalent voltage sources of the three equivalent alternating current systems are respectively; b is c1 、B c1 Parameters of the reactive power compensation device which are connected in parallel on the bus 1 and the bus 2 are respectively; z 11 ∠θ 1 、Z 22 ∠θ 2 、Z 33 ∠θ 3 Are respectively provided withThe amplitude and phase angle of equivalent impedance of three equivalent alternating current systems; z 12 ∠θ 12 、Z 23 ∠θ 23 、Z 13 ∠θ 13 Respectively, the magnitude and magnitude of the tie-line impedance. The control parameter T of each dc system is set to 1.5. The three-feed system network parameters are shown in table 1.
TABLE 1 three feed-in system network parameters
Figure GDA0003603192350000092
FIG. 3 shows the specific parameters of the standard model proposed by CIGRE DC working group in 1991.
It can be seen from fig. 4 that the minimum mode eigenvalue after the dc system is connected is 0.15, and compared with the jacobian matrix of the original ac system, the minimum mode eigenvalue is obviously close to the origin, which indicates that the system is close to the critical static voltage and stable. After the photovoltaic power station is added, the minimum module characteristic value of the Jacobian matrix of the system becomes farther away from the original point, and the minimum module characteristic value is gradually far away from the original point along with the increase of the capacity of the photovoltaic power station. This is consistent with the analysis conclusion in chapter ii, which indicates that the access of the photovoltaic power station can enhance the intensity of the receiving-end ac power grid.
It can be seen from fig. 5 that the value of the critical generalized short-circuit ratio of the dc system without photovoltaic is 2 for a given dc system and ac network parameters. After the photovoltaic power station is connected, the critical generalized short-circuit ratio of the system is reduced, and along with the increase of the capacity of the photovoltaic power station, the critical generalized short-circuit ratio of the system shows a monotonous decreasing trend. The photovoltaic power station is connected to the photovoltaic power station, so that the static voltage stability of the system can be effectively improved, the stability margin of the system is increased, the voltage support strength of the multi-feed-in direct-current receiving-end alternating-current power grid is equivalently improved, and the improvement effect is more obvious along with the improvement of the proportion of the connected photovoltaic new energy.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Claims (9)

1. A receiving-end power grid strength evaluation method for high-proportion direct current high-proportion new energy is characterized by comprising the following steps of: the method specifically comprises the following steps:
establishing a linearization model of a photovoltaic port by an impedance modeling method, and analyzing a sensitivity matrix of a minimum module characteristic value of an alternating current network Jacobian matrix to matrix elements to obtain a photovoltaic power station access which can improve the static stability of the system;
step two, not considering photovoltaic power station access, calculating to obtain a system Jacobian matrix without photovoltaic feed-in based on an alternating current network Jacobian matrix and a direct current Jacobian matrix, and compressing nodes of an alternating current system by utilizing the elementary row-column transformation and Schur transformation of the matrix to obtain a reduced-order Jacobian matrix of the system;
thirdly, calculating to obtain a minimum characteristic root of a system expansion Jacobian matrix and a corresponding characteristic vector thereof based on singular boundary conditions of a system reduced Jacobian matrix and according to a plurality of equivalent single feed systems obtained after modal decomposition is carried out on a system characteristic equation, and obtaining a critical generalized short-circuit ratio CgSCR under a rated operation condition;
step four, after the photovoltaic power station is accessed, calculating to obtain a system Jacobian matrix added into the photovoltaic power station based on an alternating current network Jacobian matrix, a direct current Jacobian matrix and a photovoltaic Jacobian matrix, compressing the system Jacobian matrix added into the photovoltaic power station through elementary row-column transformation and Schur transformation to obtain a reduced-order Jacobian matrix of the system added into the photovoltaic power station, and calculating a boundary condition when the system reaches the critical static voltage stability;
and step five, calculating perturbation quantity of the photovoltaic power station to a system characteristic equation after the photovoltaic power station is accessed according to a modal perturbation theory, and calculating to obtain a system generalized short-circuit ratio and a critical generalized short-circuit ratio CgSCR' after the photovoltaic power station is accessed according to the perturbation quantity.
2. The method for evaluating the receiving-end power grid strength of the high-proportion direct-current high-proportion new energy according to claim 1, wherein the method comprises the following steps: in the first step, the sensitivity matrix of the AC network Jacobian matrix minimum modulus eigenvalue to the matrix element is expressed as follows:
Figure FDA0003719438970000021
the elements of the matrix are the minimum mode eigenvalues lambda 1 Sensitivity to a position element in the matrix; the symbols of two diagonal elements of the matrix are positive, and the symbols of two off-diagonal elements are negative.
3. The method for evaluating the receiving-end power grid strength of the high-proportion direct-current high-proportion new energy according to claim 1, wherein the method comprises the following steps: the expression of the reduced-order Jacobian matrix of the system in the second step is as follows:
Figure FDA0003719438970000022
wherein the compressed admittance matrix B red The expression is as follows:
Figure FDA0003719438970000023
in the above formula B ij Representing the corresponding elements in the admittance matrix.
4. The method for evaluating the receiving-end power grid strength of the high-proportion direct-current high-proportion new energy according to claim 1, wherein the method comprises the following steps: the calculation formula of the system characteristic equation in the third step is expressed as follows:
Figure FDA0003719438970000024
in the above formula, J eq0 The jacobian matrix is expanded for the system, and the expression is
J eq0 ＝-diag -1 (P Ni )B red
T i (·)＝2c i K(c i )+2ωB ci /(ρ i P Ni )；ρ i ＝P i /(P Ni U i 2 )；
Wherein, P Ni Rated capacity per dc return; k (c) i ) Is expressed as
Figure FDA0003719438970000031
Wherein gamma is an arc extinguishing angle, X is a commutation reactance, and K is a transformation ratio of the inverter side transformer.
5. The method for evaluating the receiving-end power grid strength of the high-proportion direct-current high-proportion new energy according to claim 4, wherein the method comprises the following steps: in the third step, the multiple equivalent single-feed systems obtained by performing modal decomposition on the system characteristic equation are expressed as follows:
Figure FDA0003719438970000032
wherein λ is 0i Is J eq0 Corresponding to the short circuit ratio of each equivalent single feed.
6. The method for evaluating the receiving-end power grid strength of the high-proportion direct-current high-proportion new energy according to claim 5, characterized by comprising the following steps of: solving the equivalent single feed-in system in the third step to obtain a critical generalized short-circuit ratio CgSCR under a rated operation condition:
Figure FDA0003719438970000033
7. the method for evaluating the receiving-end power grid strength of the high-proportion direct-current high-proportion new energy according to claim 1, characterized by comprising the following steps of: the reduced Jacobian matrix of the system incorporating the photovoltaic power plant described in step four is represented in the form:
Figure FDA0003719438970000034
wherein the content of the first and second substances,
Figure FDA0003719438970000035
Figure FDA0003719438970000041
in the above formula, | A | is a determinant of a lower right corner matrix after elementary row-column transformation, and the expression is as follows:
Figure FDA0003719438970000042
8. the method for evaluating the receiving-end power grid strength of the high-proportion direct-current high-proportion new energy according to claim 7, wherein the method comprises the following steps: and fifthly, calculating the perturbation quantity of the photovoltaic power station to the system characteristic equation after the photovoltaic power station is accessed according to the modal perturbation theory, and adopting the following formula to represent the perturbation quantity:
Figure FDA0003719438970000043
9. the method for evaluating the receiving-end power grid strength of the high-proportion direct-current high-proportion new energy according to claim 8, wherein the method comprises the following steps: the critical generalized short-circuit ratio CgSCR' calculation formula in step four adopts the following formula:
Figure FDA0003719438970000044
wherein W -1 And W represents the minimum feature root λ 01 Corresponding left and right feature vectors.
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