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Method for computing harmonic impedance of system based on maximum likelihood estimation theory

A technique of maximum likelihood estimation and harmonic impedance, applied in the direction of measuring resistance/reactance/impedance, measuring devices, instruments, etc., can solve the uncontrollable error of harmonic impedance estimation, and the linear relationship between independent variables and dependent variables cannot be obtained Guarantee etc.

Inactive Publication Date: 2013-03-27
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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Problems solved by technology

The disadvantage of using the real number field for regression analysis is that the error of harmonic impedance estimation is uncontrollable. The root cause is that the real and imaginary parts of the voltage and current phasors are calculated separately in the process of regression analysis, resulting in two results. : On the one hand, the parameters being regressed in the regression equation are variables rather than constants; on the other hand, the linear relationship between the independent variable and the dependent variable in the regression equation is not guaranteed

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  • Method for computing harmonic impedance of system based on maximum likelihood estimation theory
  • Method for computing harmonic impedance of system based on maximum likelihood estimation theory
  • Method for computing harmonic impedance of system based on maximum likelihood estimation theory

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Embodiment Construction

[0065] The preferred embodiments will be described in detail below in conjunction with the accompanying drawings. It should be emphasized that the following description is only exemplary and not intended to limit the scope of the invention and its application.

[0066] figure 2 It is an IEEE14 node standard test system based on a system harmonic impedance calculation method based on the maximum likelihood estimation theory provided by the present invention. The test system consists of 2 generators, 3 synchronous condensers, 14 buses, 15 transmission lines and 3 transformers.

[0067] Select bus 11 as the concerned bus, HL1, HL2 and L3 are the three loads connected to the bus, and select the harmonic source HL1 as figure 1 For the user D shown, HL2 is the rest of the nonlinear load on the load side, and L3 is the linear load. At the same time, the busbar 13 is connected to the harmonic source load HS. Taking the 5th harmonic as an example, calculate the equivalent of the oth...

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Abstract

The invention discloses a method for computing harmonic impedance of a system based on maximum likelihood estimation theory. The method is characterized by comprising the following steps: collecting bus voltage instantaneous value of common coupling point and current instantaneous value of user access system, and establishing a relation between harmonic voltage phasor and harmonic current phasor; on the basis of defining a complex covariance, deriving to obtain a probability density function of unary complex normal distribution so as to obtain a maximum likelihood estimation function; establishing the maximum likelihood estimation theory of complex field estimated by the harmonic impedance of system; utilizing an extreme value theory to solve the maximum likelihood estimation function so as to obtain the estimated value of harmonic impedance of the system finally. The method has the beneficial effects that the method for computing harmonic impedance of the system based on maximum likelihood estimation theory is capable of relatively accurately computing equivalent harmonic impedance of the system and has important meanings for further solving the problem of harmonic pollution and improving the management level of electric energy quality.

Description

technical field [0001] The invention belongs to the design field of harmonic impedance calculation methods, in particular to a system harmonic impedance calculation method based on the maximum likelihood estimation theory. Background technique [0002] On the basis of traditional energy sources and UHV AC / DC transmission network, a large number of non-linear load equipment is connected to the grid, resulting in serious power system harmonic problems. Harmonic management and harmonic control are two main contents of harmonic problems in power system. In terms of harmonic management, the current harmonic management system based on national standards has caused harmonic source users to lack the initiative of harmonic control. Quantitatively determining the responsibility for harmonic source pollution is the key to solving this problem. In terms of harmonic control, installing filters is a major method of harmonic control, and filters must be designed before they are installed....

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Application Information

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IPC IPC(8): G01R27/02G01R27/08
Inventor 华回春贾秀芳曹东升赵成勇
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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