CN110838718B - Power system frequency stability adjusting method and system - Google Patents

Power system frequency stability adjusting method and system Download PDF

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CN110838718B
CN110838718B CN201911106480.9A CN201911106480A CN110838718B CN 110838718 B CN110838718 B CN 110838718B CN 201911106480 A CN201911106480 A CN 201911106480A CN 110838718 B CN110838718 B CN 110838718B
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power system
disturbance
frequency
power
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CN110838718A (en
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唐震
曲莹
刘新元
秦文萍
温日永
赵兴勇
郑惠萍
郝捷
程雪婷
陈丹阳
王玮茹
张颖
张谦
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Taiyuan University of Technology
Electric Power Research Institute of State Grid Shanxi Electric Power Co Ltd
Shanxi University
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Taiyuan University of Technology
Electric Power Research Institute of State Grid Shanxi Electric Power Co Ltd
Shanxi University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks

Abstract

The invention provides a method and a system for adjusting the frequency stability of a power system. The method is based on a node power equation of the power system, adopts a mode of modal decomposition to determine an expression of node frequency disturbance of the power system, further determines the frequency change rate of the nodes under nonlinear disturbance, calculates the sensitivity of the stability of the power system to each node disturbance according to the frequency change rate of the nodes under the nonlinear disturbance, optimally sets a unit which presents larger rotational inertia to the power system at a node with large sensitivity to the system frequency stability, and sets a unit which presents smaller rotational inertia to the power system at a node with small sensitivity to the system frequency stability. That is, with this arrangement, in the case of disturbance, the rate of change of the overall frequency of the system is relatively reduced, which is advantageous for improving the stability of the system in the case where the overall moment of inertia of the system is relatively determined.

Description

Power system frequency stability adjusting method and system
Technical Field
The invention relates to the technical field of power system management, in particular to a method and a system for adjusting frequency stability of a power system.
Background
The high-proportion new energy grid-connected operation becomes an important characteristic of a future power supply structure, the replacement proportion of a synchronization unit with traditional inertia is higher and higher by a new energy unit with low inertia, the inertia-free or weak inertia characteristic and the control mode presented by the synchronization unit become the future development trend of the system, and the control mode and the stable operation of the power grid system are influenced.
The core of the frequency stability of the high-proportion new energy power grid is the instantaneous balance of energy. The inertia is used as a first defense line for inhibiting the frequency fluctuation of the system and becomes an important evaluation index for monitoring the safe and stable operation of the system. The distributed power generation unit does not have the rotational inertia and the damping characteristics of the traditional generator set, and along with the continuous improvement of the proportion of the new energy generator set in the system, the effective rotational inertia in the system is continuously reduced, and necessary voltage and frequency support cannot be provided for the system under the condition of small disturbance, so that the power system is more easily influenced by power fluctuation and system faults.
Aiming at the problems of insufficient inertia and reduced system frequency stability of a high-proportion new energy system, the current research mainly focuses on how to improve the inertia level of the system through the auxiliary control of new energy. Scholars at home and abroad propose control methods such as Virtual Synchronous Generator (VSG) control, direct power control, functional frequency droop control and the like, and frequency control is introduced in a power control link of a new energy unit to increase effective inertia of a system, so that the new energy unit has a system frequency adjusting function. How to efficiently utilize the existing inertia of the system, the level of the inertia of the system is improved only by adding auxiliary control at necessary nodes, and the method has great significance for improving the utilization rate of new energy and the operation economy of a power system. A complex network theory is utilized to evaluate the node inertia sensitivity, and a network topology model of a system and actual operation parameters of a power system are mainly considered. However, the above method does not evaluate nodes sensitive to the rotational inertia from the perspective of system frequency stability, and does not consider the influence of inertia distribution on the system frequency stability.
The frequency control of the virtual synchronous machine can locally enhance the effective inertia of the system in a small range, but is limited by factors such as small rated power of a power converter connected with a power grid, limited energy capable of being transmitted, complex specific working conditions and the like, cannot completely respond to the frequency change of the power grid, and cannot timely and effectively inhibit the frequency change of the system. Therefore, the system still faces the problems of insufficient system inertia and low system stability, and when the system determines permeability and determines topology, how to improve the system stability by changing the distribution of the system inertia becomes a research direction.
Disclosure of Invention
The invention aims to provide a method and a system for adjusting the frequency stability of a power system, so as to improve the stability of the system by changing the distribution of system inertia.
In order to achieve the purpose, the invention provides the following scheme:
a method of regulating frequency stability of an electrical power system, the method comprising the steps of:
establishing a node power equation of the power system to be regulated;
determining an expression of node frequency disturbance of the power system by adopting a mode of modal decomposition based on the node power equation;
determining the frequency change rate of each node under nonlinear disturbance by adopting a straight line fitting mode according to the expression of the node disturbance;
calculating the sensitivity of the stability of the power system to the disturbance of each node according to the frequency change rate of each node under the nonlinear disturbance;
the method comprises the steps that a set which shows larger rotary inertia to a power system is arranged at a node with larger sensitivity, and a set which shows smaller rotary inertia to the power system is arranged at a node with smaller sensitivity.
Optionally, the establishing a node power equation of the power system to be adjusted specifically includes:
establishing a node power equation of the power system to be mediated as follows:
Figure BDA0002271469050000021
wherein, PiActive power output for node i, J is node moment of inertia of the power system, D is node damping of the power system, thetaiAnd thetajPhase angles of node i and node j, respectively, t represents time, KijIs the transmission line power capacity, K, between nodes i and jij＝V2/(ωLij)AijV is the node voltage of the power system, LijFor transmission line inductance between nodes i and j, AijIs the value of the element at (i, j) in the adjacency matrix a of the power system.
Optionally, the determining an expression of the node frequency disturbance of the power system by using a modal decomposition method based on the node power equation specifically includes:
in separate order node power equations
Figure BDA0002271469050000022
D/J is equal to gamma, and the obtained small disturbance coupling dynamic model of the power system is as follows:
Figure BDA0002271469050000023
wherein, δ θiAnd δ θjPhase angle disturbances at node i and node j, respectively, ω is the node frequency of the power system,
Figure BDA0002271469050000031
and
Figure BDA0002271469050000032
respectively representing initial phase angles of a node i and a node j;
Figure BDA0002271469050000033
for node i initial active output, δ PiThe active fluctuation at the node i is shown, and gamma represents the ratio of node damping to node rotational inertia of the power system;
coupling the small disturbance into a dynamic model
Figure BDA0002271469050000034
Obtaining a relational expression between phase angle disturbance and active fluctuation of a node i and node topology as follows:
Figure BDA0002271469050000035
wherein, BijA value representing an element at (i, j) in a node topology matrix of the power system;
performing modal decomposition on the relational expression to obtain an expression of node frequency disturbance
Figure BDA0002271469050000036
Wherein, the node frequency disturbance of the delta omega table is lambdaαCharacteristic value u of node topology matrix corresponding to modality alphaαkRepresenting the eigenvector, deltaP, at the perturbation node k in the node topology matrix corresponding to the mode alpha0Indicating electricityNodal active power deviation of the force system.
Optionally, the determining, according to the expression of the node disturbance, the frequency change rate of each node under the nonlinear disturbance by using a straight line fitting manner specifically includes:
applying two times of nonlinear disturbance to nodes i of the power system at time intervals delta t respectively;
respectively determining two node frequency disturbances of a node i according to the expression of the node frequency disturbance;
according to the two node frequency disturbances, a straight line fitting mode is adopted to establish a fitting straight line of the node frequency disturbance of the node i relative to time; and setting the slope of the fitted straight line as the frequency change rate r of the node ii(t)：
Figure BDA0002271469050000037
In the formula uαiFeature vector, δ P, at disturbance node i in node topology matrix corresponding to mode α0The active power deviation of nodes of the power system is shown, delta t is a time interval, and t represents time.
Optionally, the calculating, according to the frequency change rate of each node under the nonlinear disturbance, the sensitivity of the stability of the power system to the disturbance of each node specifically includes:
applying a non-linear perturbation to node i using the formula
Figure BDA0002271469050000041
Calculating the sum of the node frequency change rates of all nodes except the node i in the power system as the sensitivity of the stability of the power system to the disturbance of the node i, wherein N represents the number of nodes in the power system, ZiRepresenting the sensitivity of the stability of the power system to disturbances at node i, rk(k Δ t) represents the rate of change of frequency of the perturbation of node i at node k.
A power system frequency stability conditioning system, the conditioning system comprising:
the node power equation establishing module is used for establishing a node power equation of the power system to be regulated;
the node frequency disturbance expression determining module is used for determining an expression of the node frequency disturbance of the power system by adopting a mode decomposition mode based on the node power equation;
the frequency change rate determining module of the nodes under the nonlinear disturbance is used for determining the frequency change rate of each node under the nonlinear disturbance by adopting a straight line fitting mode according to the expression of the node disturbance;
the disturbance sensitivity calculation module is used for calculating the sensitivity of the stability of the power system to the disturbance of each node according to the frequency change rate of each node under the nonlinear disturbance;
and the adjusting module is used for arranging the set which shows larger rotary inertia to the power system at a node with larger sensitivity and arranging the set which shows smaller rotary inertia to the power system at a node with smaller sensitivity.
Optionally, the node power equation establishing module specifically includes:
the node power equation establishing submodule is used for establishing a node power equation of the power system to be mediated as follows:
Figure BDA0002271469050000042
wherein, PiActive power output for node i, J is node moment of inertia of the power system, D is node damping of the power system, thetaiAnd thetajPhase angles of node i and node j, respectively, t represents time, KijIs the transmission line power capacity, K, between nodes i and jij＝V2/(ωLij)AijV is the node voltage of the power system, LijFor transmission line inductance between nodes i and j, AijIs the value of the element at (i, j) in the adjacency matrix a of the power system.
Optionally, the module for determining an expression of node frequency disturbance specifically includes:
a small disturbance coupling dynamic model acquisition submodule for respectively ordering in the node power equation
Figure BDA0002271469050000043
D/J is equal to gamma, and the obtained small disturbance coupling dynamic model of the power system is as follows:
Figure BDA0002271469050000051
wherein, δ θiAnd δ θjPhase angle disturbances at node i and node j, respectively, ω is the node frequency of the power system,
Figure BDA0002271469050000052
and
Figure BDA0002271469050000053
respectively representing initial phase angles of a node i and a node j;
Figure BDA0002271469050000054
for node i initial active output, δ PiThe active fluctuation at the node i is shown, and gamma represents the ratio of node damping to node rotational inertia of the power system;
a relational expression obtaining submodule for enabling the small disturbance to be coupled in the dynamic model
Figure BDA0002271469050000055
Obtaining a relational expression between phase angle disturbance and active fluctuation of a node i and node topology as follows:
Figure BDA0002271469050000056
wherein, BijA value representing an element at (i, j) in a node topology matrix of the power system;
an expression determining submodule of the node frequency disturbance, which is used for carrying out modal decomposition on the relational expression to obtain the node frequency disturbanceDynamic expression
Figure BDA0002271469050000057
Wherein, the node frequency disturbance of the delta omega table is lambdaαCharacteristic value u of node topology matrix corresponding to modality alphaαkRepresenting the eigenvector, deltaP, at the perturbation node k in the node topology matrix corresponding to the mode alpha0Representing the active deviation of the nodes of the power system.
Optionally, the module for determining a frequency change rate of the node under the nonlinear disturbance specifically includes:
the disturbance application submodule is used for respectively applying two times of nonlinear disturbance to a node i of the power system at a time interval delta t;
the node frequency disturbance calculation submodule is used for respectively determining two node frequency disturbances of a node i according to the expression of the node frequency disturbance;
the straight line fitting submodule is used for establishing a fitting straight line of the node frequency disturbance of the node i relative to time in a straight line fitting mode according to the two node frequency disturbances; and setting the slope of the fitted straight line as the frequency change rate r of the node ii(t)：
Figure BDA0002271469050000058
In the formula uαiFeature vector, δ P, at disturbance node i in node topology matrix corresponding to mode α0The active power deviation of nodes of the power system is shown, delta t is a time interval, and t represents time.
Optionally, the disturbance sensitivity calculation module specifically includes:
a disturbance sensitivity calculation submodule for applying nonlinear disturbance to the node i by using a formula
Figure BDA0002271469050000061
Calculating the sum of the node frequency change rates of all nodes except the node i in the power system as the electricity to electricitySensitivity of the stability of the force system to disturbance at node i, where N denotes the number of nodes in the power system, ZiRepresenting the sensitivity of the stability of the power system to disturbances at node i, rk(k Δ t) represents the rate of change of frequency of the perturbation of node i at node k.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention provides a method and a system for adjusting the frequency stability of a power system. The method is based on a node power equation of the power system, adopts a mode of modal decomposition to determine an expression of node frequency disturbance of the power system, further determines the frequency change rate of the nodes under nonlinear disturbance, calculates the sensitivity of the stability of the power system to each node disturbance according to the frequency change rate of the nodes under the nonlinear disturbance, optimally sets a unit which presents larger rotational inertia to the power system at a node with large sensitivity to the system frequency stability, and sets a unit which presents smaller rotational inertia to the power system at a node with small sensitivity to the system frequency stability. That is, with this arrangement, in the case of disturbance, the rate of change of the overall frequency of the system is relatively reduced, which is advantageous for improving the stability of the system in the case where the overall moment of inertia of the system is relatively determined.
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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 flowchart of a method for adjusting frequency stability of an electrical power system according to the present invention;
fig. 2 is a schematic structural diagram of a power system frequency stability adjustment system provided in 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 a method and a system for adjusting the frequency stability of a power system, so as to improve the stability of the system by changing the distribution of system inertia.
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.
The existing method for estimating the disturbed condition of the system through the node phase angle and frequency offset and the overall phase angle and frequency offset of the system is limited by the measuring mode and the measuring error of the phase angle and the frequency during the disturbance of the node in the practical engineering, so the evaluation is feasible theoretically, a large amount of data is required to be collected and processed in the practical application, and the essential relation of the disturbance, the phase angle and the frequency offset cannot be reflected. Therefore, the method utilizes the known system topology information and is based on modal decomposition to evaluate the influence of the rotational inertia distribution on the frequency stability of the power system.
As shown in fig. 1, the present invention provides a method for adjusting the frequency stability of a power system, wherein the method comprises the following steps:
before establishing a node power equation, system topology information, such as an adjacency matrix A describing a relationship between nodes in a power system, is first obtainedijTime constant H of node inertiaiNode nominal active power P0Initial phase angle of node
Figure BDA0002271469050000071
Calculating node inertia J and damping D through the formula (1) and the formula (2);
Figure BDA0002271469050000072
Figure BDA0002271469050000073
where ω is the system rated angular velocity and ε is the damping correlation coefficient ε reported at 0.8-2, where ε is set to 1.5
Step 101, establishing a node power equation of the power system to be regulated.
Step 101, establishing a node power equation of the power system to be regulated specifically includes:
establishing a node power equation of the power system to be mediated as follows:
Figure BDA0002271469050000074
wherein, PiActive power output for node i, J is node moment of inertia of the power system, D is node damping of the power system, thetaiAnd thetajPhase angles of node i and node j, respectively, t represents time, KijIs the transmission line power capacity, K, between nodes i and jij＝V2/(ωLij)AijV is the node voltage of the power system, LijFor transmission line inductance between nodes i and j, AijIs the value of the element at (i, j) in the adjacency matrix a of the power system.
And 102, determining an expression of node frequency disturbance of the power system by adopting a mode decomposition mode based on the node power equation.
102, determining an expression of the node frequency disturbance of the power system by adopting a modal decomposition mode based on the node power equation, specifically including:
in separate order node power equations
Figure BDA0002271469050000081
D/J is equal to gamma, and the obtained small disturbance coupling dynamic model of the power system is as follows:
Figure BDA0002271469050000082
wherein, δ θiAnd δ θjPhase angle disturbances at node i and node j, respectively, ω is the node frequency of the power system,
Figure BDA0002271469050000083
and
Figure BDA0002271469050000084
respectively representing initial phase angles of a node i and a node j;
Figure BDA0002271469050000085
for node i initial active output, δ PiThe active fluctuation at the node i is shown, and gamma represents the ratio of node damping to node rotational inertia of the power system;
coupling the small disturbance into a dynamic model
Figure BDA0002271469050000086
Obtaining a relational expression between phase angle disturbance and active fluctuation of a node i and node topology as follows:
Figure BDA0002271469050000087
wherein, BijA value representing an element at (i, j) in a node topology matrix of the power system; the elements in the node topology matrix of the present invention can be calculated by the following method:
Figure BDA0002271469050000088
wherein, bijAnd bikRespectively, the admittance between node i and node j and between node i and node k.
Performing modal decomposition on the relational expression to obtain an expression of node frequency disturbance
Figure BDA0002271469050000089
Wherein, the node frequency disturbance of the delta omega table is lambdaαCharacteristic value u of node topology matrix corresponding to modality alphaαkRepresenting the eigenvector, deltaP, at the perturbation node k in the node topology matrix corresponding to the mode alpha0Representing the active deviation of the nodes of the power system.
The specific steps of modal decomposition are as follows:
Figure BDA00022714690500000810
modal decomposition delta theta (t) to sigma is carried out on node disturbance phase angleαkα(t)uα,δPi(t)＝∑αδP0uαkSubstituting the above formula, the following formula can be obtained:
Figure BDA0002271469050000091
in the formula, λαCharacteristic value, u, for mode alphaαiAnd uαkThe corresponding eigenvectors at node i and perturbation node k are respectively.
The above formula is subjected to laplace transform to obtain the following formula.
Figure BDA0002271469050000092
The above formula is subjected to inverse Laplace transform to obtain kαThe time domain expression of (2) is shown as follows.
Figure BDA0002271469050000093
From the view point of modal decomposition, the active power deviation delta P generated at the disturbance point k is considered0Then, the frequency deviation δ ω corresponding to the node i is represented by the following formula, and the node frequency response is taken as the eigenvector { u } of the laplacian matrix corresponding to the system topologyαAnd a characteristic value λαThe frequency spectrum and coefficients.
Figure BDA0002271469050000094
In the above formula, the ratio of the damping D to the moment of inertia J
Figure BDA0002271469050000095
Thus, the above formula can be equivalent to the following formula
Figure BDA0002271469050000096
And 103, determining the frequency change rate of each node under the nonlinear disturbance by adopting a straight line fitting mode according to the expression of the node disturbance.
103, determining the frequency change rate of each node under the nonlinear disturbance by adopting a straight line fitting mode according to the expression of the node disturbance specifically comprises:
applying two times of nonlinear disturbance to nodes i of the power system at time intervals delta t respectively;
respectively determining two node frequency disturbances of a node i according to the expression of the node frequency disturbance;
according to the two node frequency disturbances, a straight line fitting mode is adopted to establish a fitting straight line of the node frequency disturbance of the node i relative to time; and setting the slope of the fitted straight line as the frequency change rate r of the node ii(t)：
Figure BDA0002271469050000101
In the formula uαiFeature vector, δ P, at disturbance node i in node topology matrix corresponding to mode α0Indicating electricityThe active power deviation of the nodes of the force system, Δ t, is the time interval, and t represents the time.
And 104, calculating the sensitivity of the stability of the power system to the disturbance of each node according to the frequency change rate of each node under the nonlinear disturbance.
Step 104, calculating the sensitivity of the stability of the power system to the disturbance of each node according to the frequency change rate of each node under the nonlinear disturbance specifically includes:
applying a non-linear perturbation to node i using the formula
Figure BDA0002271469050000102
Calculating the sum of the node frequency change rates of all nodes except the node i in the power system as the sensitivity of the stability of the power system to the disturbance of the node i, wherein N represents the number of nodes in the power system, ZiRepresenting the sensitivity of the stability of the power system to disturbances at node i, rk(k Δ t) represents the rate of change of frequency of the perturbation of node i at node k.
And 105, arranging the set presenting larger rotary inertia to the power system at a node with larger sensitivity, and arranging the set presenting smaller rotary inertia to the power system at a node with smaller sensitivity.
Setting disturbance at each node in sequence except for the balance node, determining a monitoring time interval, wherein t represents time delta t equal to 0.5s, and pressing the formula for a time domain
Figure BDA0002271469050000103
And calculating the sum of absolute values of the frequency change rates. And sequencing all the nodes in sequence from small to large according to the magnitude of the sum of the absolute values of the frequency change rates of other nodes caused by the node disturbance, namely sequencing the magnitude of the influence of the rotational inertia distribution on the frequency stability of the power system.
Under the sequencing, the set which shows larger rotational inertia to the system is arranged at the node which has larger influence on the frequency stability of the system, and the set which shows smaller rotational inertia to the system is arranged at the node which has smaller influence on the frequency stability of the system. That is, with this arrangement, in the case of disturbance, the rate of change of the overall frequency of the system is relatively reduced, which is advantageous for improving the stability of the system in the case where the overall moment of inertia of the system is relatively determined.
As shown in fig. 2, the present invention further provides a power system frequency stability adjusting system, which includes:
a node power equation establishing module 201, configured to establish a node power equation of the power system to be adjusted;
the node power equation establishing module 201 specifically includes:
the node power equation establishing submodule is used for establishing a node power equation of the power system to be mediated as follows:
Figure BDA0002271469050000111
wherein, PiActive power output for node i, J is node moment of inertia of the power system, D is node damping of the power system, thetaiAnd thetajPhase angles of node i and node j, respectively, t represents time, KijIs the transmission line power capacity, K, between nodes i and jij＝V2/(ωLij)AijV is the node voltage of the power system, LijFor transmission line inductance between nodes i and j, AijIs the value of the element at (i, j) in the adjacency matrix a of the power system.
The node frequency disturbance expression determining module 202 is configured to determine, based on the node power equation, an expression of node frequency disturbance of the power system in a mode of modal decomposition;
the expression determining module 202 for node frequency disturbance specifically includes:
a small disturbance coupling dynamic model acquisition submodule for respectively ordering in the node power equation
Figure BDA0002271469050000112
D/J is equal to gamma, and the obtained small disturbance coupling dynamic model of the power system is as follows:
Figure BDA0002271469050000113
wherein, δ θiAnd δ θjPhase angle disturbances at node i and node j, respectively, ω is the node frequency of the power system,
Figure BDA0002271469050000114
and
Figure BDA0002271469050000115
respectively representing initial phase angles of a node i and a node j;
Figure BDA0002271469050000116
for node i initial active output, δ PiThe active fluctuation at the node i is shown, and gamma represents the ratio of node damping to node rotational inertia of the power system;
a relational expression obtaining submodule for enabling the small disturbance to be coupled in the dynamic model
Figure BDA0002271469050000117
Obtaining a relational expression between phase angle disturbance and active fluctuation of a node i and node topology as follows:
Figure BDA0002271469050000118
wherein, BijA value representing an element at (i, j) in a node topology matrix of the power system;
an expression determining submodule of the node frequency disturbance, which is used for carrying out modal decomposition on the relational expression to obtain an expression of the node frequency disturbance
Figure BDA0002271469050000121
Wherein, the node frequency disturbance of the delta omega table is lambdaαCharacteristic value u of node topology matrix corresponding to modality alphaαkAt disturbing node k in a node topology matrix representing the correspondence of mode alphaFeature vector, δ P0Representing the active deviation of the nodes of the power system.
And the frequency change rate determining module 203 of the nodes under the nonlinear disturbance is used for determining the frequency change rate of each node under the nonlinear disturbance by adopting a straight line fitting mode according to the expression of the node disturbance.
The frequency change rate determining module 203 of the node under the nonlinear disturbance specifically includes:
the disturbance application submodule is used for respectively applying two times of nonlinear disturbance to a node i of the power system at a time interval delta t;
the node frequency disturbance calculation submodule is used for respectively determining two node frequency disturbances of a node i according to the expression of the node frequency disturbance;
the straight line fitting submodule is used for establishing a fitting straight line of the node frequency disturbance of the node i relative to time in a straight line fitting mode according to the two node frequency disturbances; and setting the slope of the fitted straight line as the frequency change rate r of the node ii(t)：
Figure BDA0002271469050000122
In the formula uαiFeature vector, δ P, at disturbance node i in node topology matrix corresponding to mode α0The active power deviation of nodes of the power system is shown, delta t is a time interval, and t represents time.
And the disturbance sensitivity calculation module 204 is configured to calculate, according to the frequency change rate of each node under the nonlinear disturbance, a sensitivity of the stability of the power system to the disturbance of each node.
The disturbance sensitivity calculation module 204 specifically includes:
a disturbance sensitivity calculation submodule for applying nonlinear disturbance to the node i by using a formula
Figure BDA0002271469050000123
Computing all sections in the power system except for node iThe sum of the node frequency rate of change of the points, as a sensitivity to disturbance of the node i to the stability of the power system, where N represents the number of nodes in the power system, ZiRepresenting the sensitivity of the stability of the power system to disturbances at node i, rk(k Δ t) represents the rate of change of frequency of the perturbation of node i at node k.
And the adjusting module 205 is configured to set the group of machines with larger rotational inertia to the power system at the node with larger sensitivity, and set the group of machines with smaller rotational inertia to the power system at the node with smaller sensitivity.
The invention provides a method and a system for adjusting the frequency stability of a power system. The method is based on a node power equation of the power system, adopts a mode of modal decomposition to determine an expression of node frequency disturbance of the power system, further determines the frequency change rate of the nodes under nonlinear disturbance, calculates the sensitivity of the stability of the power system to each node disturbance according to the frequency change rate of the nodes under the nonlinear disturbance, optimally sets a unit which presents larger rotational inertia to the power system at a node with large sensitivity to the system frequency stability, and sets a unit which presents smaller rotational inertia to the power system at a node with small sensitivity to the system frequency stability. That is, with this arrangement, in the case of disturbance, the rate of change of the overall frequency of the system is relatively reduced, which is advantageous for improving the stability of the system in the case where the overall moment of inertia of the system is relatively determined.
The equivalent embodiments in the present specification are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts between the equivalent embodiments can be 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 principle and the implementation manner of the present invention are explained by applying specific examples, the above description of the embodiments is only used to help understanding the method of the present invention and the core idea thereof, the described embodiments are only a part of the embodiments of the present invention, not all embodiments, and all other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the protection scope of the present invention.

Claims (8)

1. A method for adjusting the frequency stability of a power system is characterized by comprising the following steps:
establishing a node power equation of the power system to be regulated;
determining an expression of node frequency disturbance of the power system by adopting a mode of modal decomposition based on the node power equation; the method specifically comprises the following steps: in separate order node power equations
Figure FDA0002847166470000011
Pi＝Pi 0+δPiD/J is equal to gamma, and the obtained small disturbance coupling dynamic model of the power system is as follows:
Figure FDA0002847166470000012
wherein, δ θiAnd δ θjPhase angle disturbances at node i and node j, respectively, ω is the node frequency of the power system,
Figure FDA0002847166470000013
and
Figure FDA0002847166470000014
respectively representing initial phase angles of a node i and a node j; pi 0For node i initial active output, δ PiFor active fluctuation at a node i, gamma represents the ratio of node damping to node rotational inertia of the power system, PiActive power output for node i, thetaiIs the phase angle of the node i, J is the node moment of inertia of the power system, D is the node damping of the power system, KijIs the transmission line power capacity between nodes i and j; coupling the small disturbance into a dynamic model
Figure FDA0002847166470000015
Obtaining a relational expression between phase angle disturbance and active fluctuation of a node i and node topology as follows:
Figure FDA0002847166470000016
wherein, BijA value representing an element at (i, j) in a node topology matrix of the power system; carrying out modal decomposition on the relational expression to obtain an expression of node frequency disturbance:
Figure FDA0002847166470000017
wherein, the node frequency disturbance of the delta omega table is lambdaαCharacteristic value u of node topology matrix corresponding to modality alphaαkRepresenting the eigenvector, deltaP, at the perturbation node k in the node topology matrix corresponding to the mode alpha0Representing node active deviations of the power system;
determining the frequency change rate of each node under nonlinear disturbance by adopting a straight line fitting mode according to the expression of the node frequency disturbance;
calculating the sensitivity of the stability of the power system to the disturbance of each node according to the frequency change rate of each node under the nonlinear disturbance;
the method comprises the steps that a set which shows larger rotary inertia to a power system is arranged at a node with larger sensitivity, and a set which shows smaller rotary inertia to the power system is arranged at a node with smaller sensitivity.
2. The method according to claim 1, wherein the establishing a node power equation of the power system to be regulated specifically includes:
establishing a node power equation of the power system to be mediated as follows:
Figure FDA0002847166470000021
wherein, PiActive power output for node i, J is the power trainThe rotational inertia of the system node, D is the node damping of the power system, thetaiAnd thetajPhase angles of node i and node j, respectively, t represents time, KijIs the transmission line power capacity, K, between nodes i and jij＝V2/(ωLij)AijV is the node voltage of the power system, LijFor transmission line inductance between nodes i and j, AijIs the value of the element at (i, j) in the adjacency matrix a of the power system.
3. The method for adjusting the frequency stability of the power system according to claim 2, wherein the determining the frequency change rate of each node under the nonlinear disturbance by adopting a straight line fitting manner according to the expression of the node frequency disturbance specifically comprises:
applying two times of nonlinear disturbance to nodes i of the power system at time intervals delta t respectively;
respectively determining two node frequency disturbances of a node i according to the expression of the node frequency disturbance;
according to the two node frequency disturbances, a straight line fitting mode is adopted to establish a fitting straight line of the node frequency disturbance of the node i relative to time; and setting the slope of the fitted straight line as the frequency change rate r of the node ii(t)：
Figure FDA0002847166470000022
In the formula uαiFeature vector, δ P, at disturbance node i in node topology matrix corresponding to mode α0The active power deviation of nodes of the power system is shown, delta t is a time interval, and t represents time.
4. The method according to claim 3, wherein the calculating the sensitivity of the stability of the power system to the disturbance of each node according to the frequency change rate of each node under the nonlinear disturbance specifically comprises:
applying a non-linear perturbation to node i using the formula
Figure FDA0002847166470000023
Calculating the sum of the node frequency change rates of all nodes except the node i in the power system as the sensitivity of the stability of the power system to the disturbance of the node i, wherein N represents the number of nodes in the power system, ZiRepresenting the sensitivity of the stability of the power system to disturbances at node i, rk(k Δ t) represents the rate of change of frequency of the perturbation of node i at node k.
5. A power system frequency stability conditioning system, the conditioning system comprising:
the node power equation establishing module is used for establishing a node power equation of the power system to be regulated;
the node frequency disturbance expression determining module is used for determining an expression of the node frequency disturbance of the power system by adopting a mode decomposition mode based on the node power equation; the expression determining module for node frequency disturbance specifically includes:
a small disturbance coupling dynamic model acquisition submodule for respectively ordering in the node power equation
Figure FDA0002847166470000031
Pi＝Pi 0+δPiD/J is equal to gamma, and the obtained small disturbance coupling dynamic model of the power system is as follows:
Figure FDA0002847166470000032
wherein, δ θiAnd δ θjPhase angle disturbances at node i and node j, respectively, ω is the node frequency of the power system,
Figure FDA0002847166470000033
and
Figure FDA0002847166470000034
respectively representing initial phase angles of a node i and a node j; pi 0For node i initial active output, δ PiThe active fluctuation at the node i is shown, and gamma represents the ratio of node damping to node rotational inertia of the power system; piActive power output for node i, thetaiIs the phase angle of the node i, J is the node moment of inertia of the power system, D is the node damping of the power system, KijIs the transmission line power capacity between nodes i and j; a relational expression obtaining submodule for enabling the small disturbance to be coupled in the dynamic model
Figure FDA0002847166470000035
Obtaining a relational expression between phase angle disturbance and active fluctuation of a node i and node topology as follows:
Figure FDA0002847166470000036
wherein, BijA value representing an element at (i, j) in a node topology matrix of the power system; an expression determining submodule of the node frequency disturbance, which is used for carrying out modal decomposition on the relational expression to obtain an expression of the node frequency disturbance
Figure FDA0002847166470000037
Wherein, the node frequency disturbance of the delta omega table is lambdaαCharacteristic value u of node topology matrix corresponding to modality alphaαkRepresenting the eigenvector, deltaP, at the perturbation node k in the node topology matrix corresponding to the mode alpha0Representing node active deviations of the power system;
the frequency change rate determining module of the nodes under the nonlinear disturbance is used for determining the frequency change rate of each node under the nonlinear disturbance by adopting a straight line fitting mode according to the expression of the node frequency disturbance;
the disturbance sensitivity calculation module is used for calculating the sensitivity of the stability of the power system to the disturbance of each node according to the frequency change rate of each node under the nonlinear disturbance;
and the adjusting module is used for arranging the set which shows larger rotary inertia to the power system at a node with larger sensitivity and arranging the set which shows smaller rotary inertia to the power system at a node with smaller sensitivity.
6. The system according to claim 5, wherein the node power equation establishing module specifically includes:
the node power equation establishing submodule is used for establishing a node power equation of the power system to be mediated as follows:
Figure FDA0002847166470000041
wherein, PiActive power output for node i, J is node moment of inertia of the power system, D is node damping of the power system, thetaiAnd thetajPhase angles of node i and node j, respectively, t represents time, KijIs the transmission line power capacity, K, between nodes i and jij＝V2/(ωLij)AijV is the node voltage of the power system, LijFor transmission line inductance between nodes i and j, AijIs the value of the element at (i, j) in the adjacency matrix a of the power system.
7. The system for adjusting frequency stability of an electric power system according to claim 6, wherein the module for determining the frequency change rate of the node under the nonlinear disturbance specifically comprises:
the disturbance application submodule is used for respectively applying two times of nonlinear disturbance to a node i of the power system at a time interval delta t;
the node frequency disturbance calculation submodule is used for respectively determining two node frequency disturbances of a node i according to the expression of the node frequency disturbance;
the straight line fitting submodule is used for establishing a fitting straight line of the node frequency disturbance of the node i relative to time in a straight line fitting mode according to the two node frequency disturbances; and combining the aboveThe slope of the fitted line is set as the frequency change rate r of the node ii(t)：
Figure FDA0002847166470000042
In the formula uαiFeature vector, δ P, at disturbance node i in node topology matrix corresponding to mode α0The active power deviation of nodes of the power system is shown, delta t is a time interval, and t represents time.
8. The system for adjusting frequency stability of an electric power system according to claim 7, wherein the disturbance sensitivity calculation module specifically includes:
a disturbance sensitivity calculation submodule for applying nonlinear disturbance to the node i by using a formula
Figure FDA0002847166470000051
Calculating the sum of the node frequency change rates of all nodes except the node i in the power system as the sensitivity of the stability of the power system to the disturbance of the node i, wherein N represents the number of nodes in the power system, ZiRepresenting the sensitivity of the stability of the power system to disturbances at node i, rk(k Δ t) represents the rate of change of frequency of the perturbation of node i at node k.
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