Multi-core shield power cable frequency change multi-conductor transmission line model building method

Abstract

A multi-core shield power cable frequency change multi-conductor transmission line model building method comprises the following steps: measuring a common mode impedance and a differential mode impedance of a multi-core shield power cable; building an equivalent circuit model of the common mode impedance and differential mode impedance; indirectly deriving multi-core shield power cable multi-conductor transmission line frequency change unit length electric parameters; respectively reversing resistance, inductance, capacitance and conductance rational function approximation by polynomial in a pole-residual mode, wherein the system in a stable system; respectively processing when the stable system is connected with a passive network and an active network, thus realizing passivation of elements in a unit length frequency change electric parameter wideband equivalent circuit. The method considers structural asymmetry influences on electric parameter frequency change features in the multi-conductor transmission line model, can effectively isolate surrounding electromagnetic interferences from affecting the impedance measuring result, thus improving the measuring precision; the method is suitable for the frequency change multi-conductor transmission line model building process of the power cable, a communication cable and a split cable models with a simple structure.

Description

technical field [0001] The invention relates to power cable broadband modeling, in particular to a method for establishing a multi-core shielded power cable frequency-variable multi-conductor transmission line model. Background technique [0002] According to the CISPR.22 standard of the International Special Committee on Radio Interference, the frequency range of conducted electromagnetic interference is 150kHz to 30MHz. In this frequency range, in the motor variable frequency drive system, the size of the power cable connecting the input and output of the inverter is generally "electrically large" compared to the minimum wavelength of conducted electromagnetic interference. In order to establish its model accurately, the multi-conductor transmission line distributed parameter model should be adopted. [0003] The structure of power cables is usually complex and presents a certain asymmetry; in addition to power lines and ground wires, there are often temperature control l...

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Problems solved by technology

The analytical solution can accurately deal with the cable model with a simple structure, and it is easy to consider the influence of the skin effect on the frequency-varying resistance, but it is difficult to consider the frequency-varying characteristics of electrical parameters; the numerical method is convenient for calculating the cable with a complex structure, and it is easy to consider the skin effect and the proximity effect, but for shielded cables with braided shielding and twisted windings, the modeling is more complicated, and the frequency-varying characteristics of the electrical parameters of the material are often difficult to consider; and the experimental measurement method is accurate for obtaining the frequency-varying electrical parameters of the transmission line. , fast, direct and other advantages, but the measurement results are also easily affected by the accuracy of the impedance analyzer and the surrounding electromagnetic interference

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