阅读说明：本技术 基于节点端口伏安特性的最优戴维南等值参数计算方法 (Optimal Thevenin equivalent parameter calculation method based on node port volt-ampere characteristics ) 是由 贠志皓 马开刚 于 2019-11-07 设计创作，主要内容包括：本发明公开了基于节点端口伏安特性的最优戴维南等值参数计算方法,为基于节点端口的伏安特性偏差最小来计算最优戴维南等值参数的辨识方法；优化目标为：样本点电流向量通过戴维南等值参数计算出的电压向量与样本点的电压向量偏差最小；通过灵敏度的方法计算节点端口伏安特性上样本点的状态量,并根据样本点生成过程的特点对参数计算过程进行优化,加快计算速度；根据目标函数优化求解得到节点端口的最优戴维南等值参数。能够避免由于电力系统中元件的非线性,其端口表现的伏安特性也是非线性的,所以通过网络线性化求解出的戴维南等值参数描述对外的伏安特性与端口真实特性有一定的偏差。(The invention discloses an optimal Thevenin equivalent parameter calculation method based on volt-ampere characteristics of a node port, which is an identification method for calculating optimal Thevenin equivalent parameters based on minimum volt-ampere characteristic deviation of the node port; the optimization target is as follows: the deviation between the voltage vector calculated by the sample point current vector through the Thevenin equivalent parameters and the voltage vector of the sample point is minimum; calculating the state quantity of a sample point on the volt-ampere characteristic of the node port by a sensitivity method, optimizing a parameter calculation process according to the characteristics of a sample point generation process, and accelerating the calculation speed; and obtaining the optimal Thevenin equivalent parameters of the node port according to the objective function optimization solution. The voltage-current characteristic presented by the port of the element in the power system is also nonlinear, so that the external voltage-current characteristic described by thevenin equivalent parameters solved through network linearization has certain deviation from the real characteristic of the port.)

1. An optimal Thevenin equivalent parameter calculation method based on node port volt-ampere characteristics is characterized by comprising the following steps:

rapidly obtaining node voltage vectors and current vector estimated values of node port volt-ampere characteristic sample points under the current state section by a sensitivity-based method;

the optimization target is as follows: the deviation between the voltage vector calculated by the sample point current vector through the Thevenin equivalent parameters and the voltage vector of the sample point is minimum;

and solving and calculating the real part and the imaginary part of the optimal Thevenin equivalent impedance based on the objective function optimization, thereby obtaining the real part and the imaginary part of the optimal Thevenin equivalent potential.

2. The optimal Thevenin equivalent parameter calculation method based on node port volt-ampere characteristics as claimed in claim 1, wherein the method for measuring the precision of Thevenin equivalent parameters comprises the following steps: and measuring the accuracy of the Thevenin equivalent parameters by keeping the loads of other nodes unchanged, adding fluctuation quantity to the loads at the calculation nodes, and calculating the modulus value of the difference between the node voltage phasor obtained by calculating the Thevenin equivalent parameters and the node voltage phasor obtained by calculating the actual load flow.

3. The optimal Thevenin equivalent parameter calculation method based on node port volt-ampere characteristics as claimed in claim 2, wherein the measurement of the Thevenin equivalent parameter precision specifically comprises: adding random disturbance to a load node i, and setting the load after the load node i is disturbed as S _ikK is 1,2 …, m, and the total number of perturbations is m;

with S _ikThe power of the original node i is replaced to carry out load flow calculation to obtain the standard value of the node voltage phasor

Then the S is mixed _ikEstimation value of node voltage phasor calculated by two-node system with Thevenin equivalent parameter correspondence

And measuring the accuracy of the Thevenin equivalent parameters by the proportion of the phasor difference modulus of the estimated value of the node voltage and the standard value to the modulus of the node voltage phasor standard value.

4. The optimal Thevenin equivalent parameter calculation method based on node port volt-ampere characteristics as claimed in claim 1, wherein the sample point used for calculating the node port volt-ampere characteristic curve has two characteristics: firstly, the variation of other load nodes in the active power delta P of the load node is zero; secondly, only the voltage amplitude and the phase angle variation corresponding to the load node need to be solved.

5. An optimal Thevenin equivalent parameter calculation system based on node port volt-ampere characteristics is characterized by comprising the following steps:

a sample point acquisition module for rapidly acquiring node voltage vectors and current vector estimated values of node port volt-ampere characteristic sample points under the current state section by a sensitivity-based method;

an optimization target module, wherein the optimization target is as follows: the deviation between the voltage vector calculated by the sample point current vector through the Thevenin equivalent parameters and the voltage vector of the sample point is minimum;

and the solving module is used for solving and calculating the real part and the imaginary part of the optimal Thevenin equivalent impedance based on the objective function optimization, so that the real part and the imaginary part of the optimal Thevenin equivalent potential are obtained.

6. The optimal Thevenin equivalent parameter calculation system based on node port volt-ampere characteristics as claimed in claim 5, wherein the method for measuring the precision of Thevenin equivalent parameters comprises the following steps: and measuring the accuracy of the Thevenin equivalent parameters by keeping the loads of other nodes unchanged, adding fluctuation quantity to the loads at the calculation nodes, and calculating the modulus value of the difference between the node voltage phasor obtained by calculating the Thevenin equivalent parameters and the node voltage phasor obtained by calculating the actual load flow.

7. The optimal Thevenin equivalent parameter calculation system based on node port volt-ampere characteristics as claimed in claim 6, wherein the measurement of the Thevenin equivalent parameter precision is as follows: adding random disturbance to a load node i, and setting the load after the load node i is disturbed as S _ikK is 1,2 …, m, and the total number of perturbations is m;

with S _ikThe power of the original node i is replaced to carry out load flow calculation to obtain the standard value of the node voltage phasor

Then the S is mixed _ikEstimation value of node voltage phasor calculated by two-node system with Thevenin equivalent parameter correspondence

And measuring the accuracy of the Thevenin equivalent parameters by the proportion of the phasor difference modulus of the estimated value of the node voltage and the standard value to the modulus of the node voltage phasor standard value.

8. A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor when executing the program performs the steps of:

rapidly obtaining node voltage vectors and current vector estimated values of node port volt-ampere characteristic sample points under the current state section by a sensitivity-based method;

the optimization target is as follows: the deviation between the voltage vector calculated by the sample point current vector through the Thevenin equivalent parameters and the voltage vector of the sample point is minimum;

and solving and calculating the real part and the imaginary part of the optimal Thevenin equivalent impedance based on the objective function optimization, thereby obtaining the real part and the imaginary part of the optimal Thevenin equivalent potential.

9. A computer-readable storage medium, on which a computer program is stored, which program, when executed by a processor, carries out the steps of:

rapidly obtaining node voltage vectors and current vector estimated values of node port volt-ampere characteristic sample points under the current state section by a sensitivity-based method;

the optimization target is as follows: the deviation between the voltage vector calculated by the sample point current vector through the Thevenin equivalent parameters and the voltage vector of the sample point is minimum;

and solving and calculating the real part and the imaginary part of the optimal Thevenin equivalent impedance based on the objective function optimization, thereby obtaining the real part and the imaginary part of the optimal Thevenin equivalent potential.

Technical Field

The invention belongs to the field of electricity, and particularly relates to an optimal Thevenin equivalent parameter calculation method based on node port volt-ampere characteristics.

Background

The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.

With the expansion of the scale of the interconnected power grid and the implementation of the power market, the operation point of the power grid is closer to the static voltage stability limit point. Due to the large-scale access of clean energy, the operation modes of the power system are more complex and diversified, and therefore the requirement for online static voltage stability monitoring is increasingly urgent. The method based on Thevenin equivalent parameter identification in the existing online static voltage stability assessment method is widely applied because of clear concept, simple structure and high calculation speed.

Static voltage stability on-line evaluation requires rapid and accurate acquisition of thevenin equivalent parameters of a node. The current equivalent parameter calculation methods mainly have two types. One is a local measurement-based method, network frame parameters are not needed, pure data drive is achieved, and calculation is simple and fast.

Documents "K.Vu, M.M.Begovic, D.Novosel and M.M.Saha", "Use of localization to estimate voltage-stability flag", "Proceedings of the 20th International Conference on Power Industry computers Applications, Columbus, OH, USA,1997, pp.318-323.doi: 10.1109/PICA.1997.599420" first proposed a method for estimating Thevenin equivalence parameters based on local measurements and applied the Thevenin equivalence method to static voltage stabilization analysis. On the basis of the documents, a large number of methods for identifying thevenin equivalent parameters based on local measurement are proposed, such as a method for estimating thevenin parameters in a z-V space, a method for optimizing and searching thevenin equivalent parameters based on an extended PV curve, and the like. The above algorithms all assume that thevenin equivalent parameters in the time window of the measured data remain unchanged, but this assumption does not conform to the actual operating conditions of the power system. In view of the above, the davinan equivalent parameter identification method based on local area measurement is continuously improved. The literature, "leerifu, successes to, scalding, davinan equivalence tracking parameter drift problem research [ J ]. Chinese electro-mechanical engineering, 2005(20): 1-5" analyzes the essential cause of parameter drift, and proposes a method for screening candidate sampling points to inhibit parameter drift.

The literature, "Zhaojinli, mytilus," analysis of voltage instability index working condition based on local phasor measurement [ J ]. electric power system automation, 2006(24):1-4+10, "analyzes the reason for calculating the parameter drift of equivalent parameters by using a curve fitting method, and provides the correct working condition and validity criterion of the voltage instability prediction index.

The voltage stability online monitoring method is characterized in that a voltage stability online monitoring model based on a PMU and an improved Davinan equivalent model is proposed on the basis of qualitative analysis of circuit theories in documents of Liuming pine, Zenbergine, Yao, Sunwandun, Wuwen, and the power system automation 2009,33(10):6-10.

Further improvement is made on the basis of the documents, and methods such as a Thevenin equivalent parameter tracking algorithm based on full differentiation, an iterative optimization solution based on trajectory sensitivity Thevenin equivalent parameters and the like are provided, so that the error of parameter identification is further reduced. From a review of the above documents, it can be seen that Thevenin equivalent parameters based on local measurement have improved the accuracy of identification much on the basis of the original model. However, when the system has line tripping, capacitor switching, generator reactive power out-of-limit and other situations, the limitation of parameter time variation and drift still remains the problem that the local area measurement method cannot completely overcome. The randomness and the fluctuation of the system operation mode caused by the access of large-scale clean energy sources make the limitation more prominent.

The second type is based on a wide area measurement method, and node Thevenin equivalent parameters are obtained by single-state section data. The method can overcome the limitation of time variation and drift of the parameters, and the identification of the parameters is more accurate than that of a local area measurement method. Documents "Y.Wang et al", "Voltage Stability Monitoring Based on the Concept of Coupled Single-Port Circuit", "in IEEE Transactions on Power Systems, vol.26, No.4, pp.2154-2163, and Nov.2011.doi: 10.1109/TPWRS.2011.2154366" propose the Concept of coupling Single port, realize the identification of Thevenin equivalent parameters Based on Single-state section data, and the parameter identification precision is greatly improved compared with the local measurement method. The document ' Davinan, Yijun, Houjunxian, Sun China east, Shaoyao, Linweifang ' Thevenin equivalent parameter tracking calculation method [ J ] based on time domain simulation, China electro-mechanical engineering, 2010,30(34):63-68 ' proposes a Thevenin equivalent parameter calculation method based on time domain simulation, wherein the load in a network is equivalent to impedance under the current section to correct a node admittance matrix of the system, and an open-circuit voltage is calculated by adopting a compensation method. The document shows that the method takes account of the wide-area Thevenin equivalent parameter online calculation method for the reactive power out-of-limit of the generator [ J ] the power system automation, 2016,40(11):53-60+67 ], the load in the network is equivalent to impedance to correct the node admittance matrix of the system, and then the Thevenin equivalent potential of each node is solved according to a node voltage equation. The problem of quantitative calculation of load node Thevenin equivalent parameters when the reactive power of the generator exceeds the limit is solved. The two documents differ in that a method of compensating the current source and a method of disconnecting the branch impedance are respectively adopted when the open-circuit voltage is obtained. However, when solving thevenin equivalent parameters of different nodes, the two documents need to solve a linear equation for many times, and the calculation time is slow, so that the online identification of the parameters cannot be met.

Aiming at the problem document,' Liangchen, Liudawei, coking army, Mashiying, Octopus, Thevenin equivalent parameters added based on an accelerating branch are calculated on line [ J ]. the power grid technology, 2017,41(09):2972 and 2978.

For a linear network, the two-node system corresponding to the Thevenin equivalent parameter and the original system show completely the same linear volt-ampere characteristics, and theoretically, the two-node system and the original system can be equivalently replaced. For an actual power system, a node port externally shows nonlinear volt-ampere characteristics, and the nonlinear volt-ampere characteristics of the node port are approximated by the Thevenin equivalent which is essentially the linear volt-ampere characteristics formed by combining the equivalent potential and the equivalent impedance of a node with the voltage and current under the current section. In the existing literature, nonlinear part linearization processing in a power network is performed by observing a node port to a system side, so that the network is changed into a linear network under a current state section, and the volt-ampere characteristic of the node port is expressed as linearity. The document "y.wang et al", "voltage stability Monitoring Based on the Concept of Coupled Single-Port Circuit", "ieee Transactions on Power Systems, vol.26, No.4, pp.2154-2163", and No. 2011.doi:10.1109/tpwrs.2011.2154366 "deduces the volt-ampere characteristic expression of the node Port, and under the assumption that the load of each node of the system increases in proportion and the voltage amplitude proportion is approximately unchanged, the volt-ampere characteristic relation of the node Port can be obtained to be a linear relation. But in actual operation the power of the individual nodes cannot fluctuate exactly to scale. Therefore, the node port voltage-current characteristic obtained by the existing document has a certain deviation from the actual node port voltage-current characteristic.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides an optimal Thevenin equivalent parameter calculation method based on the node port volt-ampere characteristic.

In order to achieve the above object, one or more embodiments of the present invention provide the following technical solutions:

an optimal Thevenin equivalent parameter calculation method based on node port volt-ampere characteristics comprises the following steps:

rapidly obtaining node voltage vectors and current vector estimated values of node port volt-ampere characteristic sample points under the current state section by a sensitivity-based method;

the optimization target is as follows: the deviation between the voltage vector calculated by the sample point current vector through the Thevenin equivalent parameters and the voltage vector of the sample point is minimum;

and solving and calculating the real part and the imaginary part of the optimal Thevenin equivalent impedance based on the objective function optimization, thereby obtaining the real part and the imaginary part of the optimal Thevenin equivalent potential.

The further technical scheme is a method for measuring the precision of thevenin equivalent parameters, which comprises the following steps: and measuring the accuracy of the Thevenin equivalent parameters by keeping the loads of other nodes unchanged, adding fluctuation quantity to the loads at the calculation nodes, and calculating the modulus value of the difference between the node voltage phasor obtained by calculating the Thevenin equivalent parameters and the node voltage phasor obtained by calculating the actual load flow.

Further techniqueThe technical scheme is used for measuring the precision of thevenin equivalent parameters, and specifically comprises the following steps: adding random disturbance to a load node i, and setting the load after the load node i is disturbed as S _ikK is 1,2 …, m, and the total number of perturbations is m;

with S _ikThe power of the original node i is replaced to carry out load flow calculation to obtain the standard value of the node voltage phasor

Then the S is mixed _ikEstimation value of node voltage phasor calculated by two-node system with Thevenin equivalent parameter correspondence

And measuring the accuracy of the Thevenin equivalent parameters by the proportion of the phasor difference modulus of the estimated value of the node voltage and the standard value to the modulus of the node voltage phasor standard value.

The further technical scheme is used for calculating the sample points on the node port volt-ampere characteristic curve and has two characteristics: firstly, the variation of other load nodes in the active power delta P of the load node is zero; secondly, only the voltage amplitude and the phase angle variation corresponding to the load node need to be solved.

An optimal Thevenin equivalent parameter calculation system based on node port volt-ampere characteristics comprises:

a sample point acquisition module for rapidly acquiring node voltage vectors and current vector estimated values of node port volt-ampere characteristic sample points under the current state section by a sensitivity-based method;

an optimization target module, wherein the optimization target is as follows: the deviation between the voltage vector calculated by the sample point current vector through the Thevenin equivalent parameters and the voltage vector of the sample point is minimum;

and the solving module is used for solving and calculating the real part and the imaginary part of the optimal Thevenin equivalent impedance based on the objective function optimization, so that the real part and the imaginary part of the optimal Thevenin equivalent potential are obtained.

The invention also discloses a computer device, which comprises a memory, a processor and a computer program which is stored on the memory and can run on the processor, and is characterized in that the processor executes the program to realize the following steps:

rapidly obtaining node voltage vectors and current vector estimated values of node port volt-ampere characteristic sample points under the current state section by a sensitivity-based method; (ii) a

The optimization target is as follows: the deviation between the voltage vector calculated by the sample point current vector through the Thevenin equivalent parameters and the voltage vector of the sample point is minimum;

and solving and calculating the real part and the imaginary part of the optimal Thevenin equivalent impedance based on the objective function optimization, thereby obtaining the real part and the imaginary part of the optimal Thevenin equivalent potential.

The invention also discloses a computer readable storage medium having a computer program stored thereon, characterized in that the program, when executed by a processor, implements the steps of:

acquiring a sample point on a current section real volt-ampere characteristic curve of a node port in a power system;

the optimization target is as follows: the deviation between the voltage vector calculated by the sample point current vector through the Thevenin equivalent parameters and the voltage vector of the sample point is minimum;

obtaining node voltage vectors and current vector estimated values of node port volt-ampere characteristic sample points obtained under the current state section based on an optimization target;

and calculating the real part and the imaginary part of the optimal Thevenin equivalent impedance based on the obtained node voltage vector and current vector estimated values, thereby obtaining the real part and the imaginary part of the optimal Thevenin equivalent potential.

The above one or more technical solutions have the following beneficial effects:

the invention provides a method for finding the optimal Thevenin equivalent parameter according to the minimum volt-ampere characteristic expression deviation of a node port in order that a simplified circuit obtained through the node Thevenin equivalent parameter has a port volt-ampere characteristic close to that of an original system circuit. Different from a method for carrying out linear processing on a current power flow section in the prior art, the method for calculating the voltage-current characteristic of the current power flow section of the power flow system rapidly obtains sample points on a real voltage-current characteristic curve of a node port through a sensitivity method, obtains the linear characteristic with the minimum voltage-current characteristic deviation with the actual node port under the current section through a fitting method, obtains the optimal Thevenin equivalent parameter, and finally optimizes a parameter calculation method according to the characteristics of a sample point generation process so as to improve the calculation speed. In order to verify the reasonability of the method, the accuracy of thevenin equivalent parameters is measured by keeping loads of other nodes unchanged, adding fluctuation quantity to the loads at the calculation nodes and calculating the module value of the difference between the node voltage phasor obtained by calculating the thevenin equivalent parameters and the node voltage phasor obtained by calculating the actual load flow, so that the limitation that the voltage amplitude is only compared in the prior art is avoided.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a schematic diagram illustrating fast calculation of node state quantity variation according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of an inversion process of a Jacobian matrix according to an embodiment of the invention;

FIG. 3 is a schematic diagram of errors of Thevenin equivalent parameters of different sampling intervals and sampling quantities of a node system in embodiment 9 of the present invention;

FIG. 4 is a schematic diagram of errors of Thevenin equivalent parameters of different sampling intervals and sampling quantities of a node system in embodiment 39 of the present invention;

FIG. 5 is a schematic diagram of a real voltammetric characteristic curve of a node 29 according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of an imaginary volt-ampere characteristic curve of a node 29 according to an embodiment of the present invention;

FIG. 7 is a diagram illustrating a comparison of the mean values of the relative errors of the nodes according to the embodiment of the present invention.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The embodiments and features of the embodiments of the present invention may be combined with each other without conflict.

The general idea provided by the invention is as follows:

and (3) providing a method for finding the optimal Thevenin equivalent parameter according to the minimum volt-ampere characteristic expression deviation of the node port. Different from the method for linearly processing the current power flow section in the documents, the method disclosed by the invention can be used for quickly obtaining the sample points on the real volt-ampere characteristic curve of the node port by a sensitivity method, obtaining the linear characteristic with the minimum volt-ampere characteristic deviation with the actual node port under the current section by a fitting method, obtaining the optimal Thevenin equivalent parameter, and optimizing the parameter calculation method according to the characteristics of the sample point generation process so as to improve the calculation speed.