阅读说明：本技术 一种用于电网谐波分析的输电线路谐波参数估计方法 (Power transmission line harmonic parameter estimation method for power grid harmonic analysis ) 是由 徐群伟 吴俊� 黄弘扬 楼伯良 吕文韬 马智泉 李培 陈�峰 许双婷 王杨 于 2019-09-09 设计创作，主要内容包括：本发明公开了一种用于电网谐波分析的输电线路谐波参数估计方法,包括：对输电线路进行监测得到两端的谐波电压有效值、谐波有功功率和谐波无功功率；基于输电线路分布参数模型,建立输电线路谐波参数与两端的所述谐波电压有效值、所述谐波有功功率和所述谐波无功功率之间的关系式；对每个数据段随机选取多个点数据,利用多点估计得到方程组；通过非线性优化算法求解所述方程组,得到输电线路的谐波参数。利用本发明得到的谐波参数进行更为准确的谐波建模,对做电网谐波潮流计算、状态估计、谐波源定位等具有重要意义。(The invention discloses a power transmission line harmonic parameter estimation method for power grid harmonic analysis, which comprises the following steps: monitoring the power transmission line to obtain a harmonic voltage effective value, harmonic active power and harmonic reactive power at two ends; establishing a relation among a harmonic parameter of the power transmission line, the harmonic voltage effective value at two ends, the harmonic active power and the harmonic reactive power based on a power transmission line distribution parameter model; randomly selecting a plurality of point data for each data segment, and obtaining an equation set by utilizing multipoint estimation; and solving the equation set through a nonlinear optimization algorithm to obtain the harmonic parameters of the power transmission line. The harmonic parameters obtained by the method are utilized to carry out more accurate harmonic modeling, and the method has important significance for power grid harmonic load flow calculation, state estimation, harmonic source positioning and the like.)

1. A power transmission line harmonic parameter estimation method for power grid harmonic analysis is characterized by comprising the following steps:

S100: monitoring the power transmission line to obtain a harmonic voltage effective value, harmonic active power and harmonic reactive power at two ends;

S200: establishing a relation among a harmonic parameter of the power transmission line, the harmonic voltage effective value at two ends, the harmonic active power and the harmonic reactive power based on a power transmission line distribution parameter model;

s300: according to the relational expression, randomly selecting a plurality of point data for each data segment, and obtaining an equation set by utilizing multipoint estimation;

s400: and solving the equation set through a nonlinear optimization algorithm to obtain the harmonic parameters of the power transmission line.

2. The method for estimating harmonic parameters of an electric transmission line for harmonic analysis of an electric network according to claim 1, wherein the step S100: the PQ monitoring device monitors the transmission end and the receiving end of the power transmission line to obtain: harmonic voltage effective value V of transmission end of power transmission line₁Harmonic voltage effective value V of sum receiving end₂Harmonic active power of transmitting endP₁harmonic active power P of receiving end₂harmonic reactive power Q of sending terminal₁Harmonic reactive power Q of receiving end₂。

3. The method for estimating harmonic parameters of power transmission lines for harmonic analysis of power grids of claim 2, wherein the step S200:

the distribution parameters of the transmission line can be calculated from the centralized parameters,

Wherein the content of the first and second substances,

R₀、X₀、G₀、B₀As the lumped parameter, R₀and X₀to concentrate series resistance and reactance, G₀And B₀the method is characterized in that parallel conductance and sodium are concentrated, wherein R and X are equivalent series resistance and reactance, and G and B are equivalent parallel conductance and sodium;

the current through the series impedance is calculated from the transmit and receive data,

the harmonic active power loss of the transmission line caused by the series resistance R and the reactance X is,

(I_L)²R＝((P₁-|V₁|²G/2)+(P₂-|V₂|²G/2))

The harmonic reactive power loss of the transmission line caused by the parallel conductance G and the sodium B is,

(I_L)²X＝((Q₁+|V₁|²G/2)+(Q₂+|V₂|²G/2))。

4. The method for estimating harmonic parameters of power transmission lines for harmonic analysis of power grids of claim 3, wherein the step S300:

randomly selecting a plurality of point data for each data segment, obtaining an equation set by utilizing multipoint estimation,

wherein

Epsilon is the estimation error of the equation, i-1, 2,3, … n represents the ith data point, and n is the total data point.

5. the method for estimating harmonic parameters of power transmission lines for harmonic analysis of power grids of claim 4, wherein the step S400,

The Levenberg-Marquardt method is adopted for solving, the objective function is,

Wherein Z is [ R ]₀；X₀；G₀；B₀]And i is 1,2, … 10, and iteratively solving to obtain the centralized parameters of the power transmission line;

And calculating the distribution parameters of the power transmission line according to the centralized parameters.

6. an electronic device comprising at least one processor, and a memory communicatively coupled to the at least one processor; the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method of any one of claims 1 to 5.

Technical Field

the invention relates to the field of power systems, in particular to a power transmission line harmonic parameter estimation method for power grid harmonic analysis.

Background

with more and more nonlinear loads accessed to a power grid, the problem of harmonic pollution of the power grid becomes more and more serious, so that harmonic analysis on the system, including harmonic load flow calculation, harmonic state estimation, harmonic source positioning and the like, is significant, and harmonic modeling on each element of the system and harmonic parameter estimation are the premise of harmonic analysis. In recent years, fundamental wave parameter identification technology of a power transmission line is mature, but related research on harmonic parameter estimation is less.

The traditional harmonic parameter estimation of the power transmission line is based on the premise assumption that the impedance and the admittance value of the line in unit length are not changed, the harmonic resistance is consistent with the fundamental wave, the harmonic reactance is h times of the fundamental wave reactance, and the parallel conductance of the line is ignored. However, due to the conductor skin effect and the frequency response of the earth loop impedance, the unit impedance of the transmission line actually changes with the frequency, and in the simulation example, the resistance and reactance value per unit length of the transmission line change with the frequency as shown in fig. 2. Therefore, when the harmonic frequency increases, the precondition assumption of the conventional method is not satisfied, and the estimation error of the harmonic parameter becomes larger.

On the other hand, the harmonic parameters of the power transmission line can be accurately calculated by using a Carson formula and a Bessel function, but the calculation process is complex, and the accurate structural parameters of the power transmission line, including the sectional area and height of a conductor, the direct current resistance and the like, need to be known.

disclosure of Invention

In order to solve the problem that the existing power transmission line harmonic parameter estimation method neglects the frequency response of unit impedance, so that parameter estimation is inaccurate, the power transmission line harmonic parameter estimation method for power grid harmonic analysis is provided, and the power transmission line harmonic parameter can be estimated accurately.

A power transmission line harmonic parameter estimation method for power grid harmonic analysis comprises the following steps:

S100: monitoring the power transmission line to obtain a harmonic voltage effective value, harmonic active power and harmonic reactive power at two ends;

S200: establishing a relation among a harmonic parameter of the power transmission line, the harmonic voltage effective value at two ends, the harmonic active power and the harmonic reactive power based on a power transmission line distribution parameter model;

S300: according to the relational expression, randomly selecting a plurality of point data for each data segment, and obtaining an equation set by utilizing multipoint estimation;

s400: and solving the equation set through a nonlinear optimization algorithm to obtain the harmonic parameters of the power transmission line.

preferably, the step S100: the PQ monitoring device monitors the transmission end and the receiving end of the power transmission line to obtain: harmonic voltage effective value V of transmission end of power transmission line₁Harmonic voltage effective value V of sum receiving end₂Harmonic active power P of sending end₁Harmonic active power P of receiving end₂Harmonic reactive power Q of sending terminal₁harmonic reactive power Q of receiving end₂。

preferably, the step S200:

The distribution parameters of the transmission line can be calculated from the centralized parameters,

Wherein the content of the first and second substances,

R₀、X₀、G₀、B₀As the lumped parameter, R₀And X₀To concentrate series resistance and reactance, G₀and B₀The method is characterized in that parallel conductance and sodium are concentrated, wherein R and X are equivalent series resistance and reactance, and G and B are equivalent parallel conductance and sodium;

The current through the series impedance is calculated from the transmit and receive data,

the harmonic active power loss of the transmission line caused by the series resistance R and the reactance X is,

(I_L)²R＝((P₁-|V₁|²G/2)+(P₂-|V₂|²G/2))

the harmonic reactive power loss of the transmission line caused by the parallel conductance G and the sodium B is,

(I_L)²X＝((Q₁+|V₁|²G/2)+(Q₂+|V₂|²G/2))。

Preferably, the step S300:

randomly selecting a plurality of point data for each data segment, obtaining an equation set by utilizing multipoint estimation,

Wherein

Epsilon is the estimation error of the equation, i-1, 2,3, … n represents the ith data point, and n is the total data point.

preferably, in the step S400,

the Levenberg-Marquardt method is adopted for solving, the objective function is,

Wherein Z is [ R ]₀；X₀；G₀；B₀]And i is 1,2, … 10, and iteratively solving to obtain the centralized parameters of the power transmission line;

And calculating the distribution parameters of the power transmission line according to the centralized parameters.

according to another aspect of the present invention, there is provided an electronic device comprising at least one processor, and a memory communicatively coupled to the at least one processor; the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method of any one of the above.

Compared with the prior art, the invention has the beneficial effects that:

1. The frequency response of unit resistance and reactance of the power transmission line is calculated, and harmonic parameters of the power transmission line can be accurately estimated;

2. The parallel conductance of the power transmission line is calculated, and when the power transmission line has corona loss, compared with the traditional method, the parameter estimation error is smaller;

3. The harmonic parameter estimation process only needs the effective value of harmonic voltage and the harmonic active and reactive power values at two ends of the line, data can be obtained from the electric energy quality monitoring device, the calculation is simple and convenient, and the engineering practicability is realized.

The harmonic parameters obtained by the method are utilized to carry out more accurate harmonic modeling, and the method has important significance for power grid harmonic load flow calculation, state estimation, harmonic source positioning and the like.

Description of the drawings:

FIG. 1 is a schematic flow chart of the present invention.

Fig. 2 is a schematic diagram of the frequency response of the impedance per unit length of the transmission line.

fig. 3 is a schematic diagram of a transmission line lumped parameter model.

Fig. 4 is a schematic diagram of a distribution parameter model of the power transmission line.

fig. 5 is a schematic of 3 rd harmonic voltage, real and reactive power values in example 1.

Fig. 6 is a schematic diagram of calculation errors of example 1.

Fig. 7 is a schematic structural diagram of an electronic device according to an embodiment of the invention.

Detailed Description

the present invention will be described in further detail with reference to test examples and specific embodiments. It should be understood that the scope of the above-described subject matter is not limited to the following examples, and any techniques implemented based on the disclosure of the present invention are within the scope of the present invention.

As shown in fig. 1, a method for estimating harmonic parameters of a power transmission line for power grid harmonic analysis includes:

s100: monitoring the power transmission line to obtain harmonic voltage, harmonic active power and harmonic reactive power at two ends;

the step S100: the PQ monitoring device monitors the transmission end and the receiving end of the power transmission line to obtain: harmonic voltage effective value V of transmission end of power transmission line₁Harmonic voltage effective value V of sum receiving end₂Harmonic active power P of sending end₁and receiveHarmonic active power P of terminal₂Harmonic reactive power Q of sending terminal₁Harmonic reactive power Q of receiving end₂。

s200: establishing a relation among a harmonic parameter of the power transmission line and the harmonic voltage, the harmonic active power and the harmonic reactive power at two ends based on a power transmission line distribution parameter model;

the lumped parameter model of the transmission line is shown in FIG. 3, where R₀and X₀To concentrate series resistance and reactance, G₀and B₀To concentrate parallel conductance and sodium. With the increase of the harmonic frequency and the increase of the harmonic wavelength, the ratio of the length of the transmission line to the wavelength of the electromagnetic wave is reduced, and the harmonic voltage and the current along the transmission line have volatility, so that the harmonic analysis of the transmission line needs to adopt a distributed parameter model, and the model is shown in fig. 4. Wherein, R and X are equivalent series resistance and reactance, G and B are equivalent parallel conductance and sodium, V₁And V₂amplitude of the voltage at the sending and receiving ends, P, respectively₁And P₂Harmonic active power, Q, of the transmitting and receiving ends, respectively₁And Q₂The harmonic active power of the sending end and the receiving end respectively. The distribution parameters of the transmission line can be calculated from the centralized parameters,

wherein the content of the first and second substances,

R₀、X₀、G₀、B₀As the lumped parameter, R₀and X₀To concentrate series resistance and reactance, G₀And B₀In order to concentrate parallel conductance and sodium, wherein R and X are equivalent series resistance and reactance, and G and B are equivalent parallel conductance and sodium.

The current through the series impedance is calculated from the transmit and receive data,

The harmonic active power loss of the transmission line caused by the series resistance R and the reactance X is,

(I_L)²R＝((P₁-|V₁|²G/2)+(P₂-|V₂|²G/2))

The harmonic reactive power loss of the transmission line caused by the parallel conductance G and the sodium B is,

(I_L)²X＝((Q₁+|V₁|²G/2)+(Q₂+|V₂|²G/2))

At this time, the unknown R, X, G, B is greater than the number of equations and cannot be directly solved. To solve this problem, the present invention proposes a multi-point method, i.e., step S300.

S300: randomly selecting a plurality of point data for each data segment, and obtaining an equation set by utilizing multipoint estimation;

Randomly selecting a plurality of point data for each data segment (such as 10min), obtaining an equation set by utilizing multipoint estimation,

Wherein

epsilon is the estimation error of the equation, i is 1,2,3, … n represents the ith data point, n is the total data point, and the equation set contains 4 unknowns R in total₀、X₀、G₀、B₀。

Therefore, when n is greater than or equal to 2, the number of equations is greater than or equal to the number of unknowns, and a nonlinear optimization algorithm is used for solving, namely step S400.

S400: and solving the equation set through a nonlinear optimization algorithm to obtain the harmonic parameters of the power transmission line.

the Levenberg-Marquardt method is adopted for solving, the objective function is,

wherein Z is [ R ]₀；X₀；G₀；B₀]and i is 1,2, … 10, and iteratively solving to obtain the centralized parameters of the power transmission line;

and calculating the distribution parameters of the power transmission line according to the centralized parameters.

According to the method, the frequency response of unit resistance and reactance of the power transmission line is calculated, and harmonic parameters of the power transmission line can be accurately estimated; the parallel conductance of the power transmission line is calculated, and when the power transmission line has corona loss, compared with the traditional method, the parameter estimation error is smaller; the harmonic parameter estimation process only needs the effective value of harmonic voltage and the harmonic active and reactive power values at two ends of the line, data can be obtained from the electric energy quality monitoring device, the calculation is simple and convenient, and the engineering practicability is realized.