Method for accurately measuring harmonic voltage of capacitive voltage transformer based on interpolation method

Abstract

The invention provides a method for accurately measuring the harmonic voltage of a capacitive voltage transformer based on an interpolation method. The method comprises using a curve fitting method tooffline obtain mathematical interpolation calculation equations under different parameter combination conditions; and inputting the nameplate parameters (actual parameters) of a specific CVT device into a harmonic correction device by means of man-machine dialogue, and using the mathematical interpolation calculation equations to obtain the network transfer function of any parameter under a normal temperature condition, that is, to obtain the amplitude-frequency curve and phase-frequency curve of CVT under normal temperature for the specific parameter; then by using the CVT operating ambienttemperature measured by a temperature sensor and the calculation of the equivalent circuit parameter offset caused by a temperature change obtained under an offline condition, obtaining correction curves of the amplitude-frequency curve and the phase-frequency curve of the CVT with temperature changes to achieve accurate correction measurement of the harmonic content of the CVT.

Description

technical field [0001] The present invention relates to the field of power system measurement methods, and more specifically, to a method for accurately measuring harmonic voltages of capacitive voltage transformers based on interpolation methods. Background technique [0002] Capacitor Voltage Transformer (CVT—Capacitor Voltage Transformer) has gained more and more applications in power system because of its unique advantages. However, due to the particularity of its working principle, the national standard GB / T14549-1993 "Power Quality Harmonics in Public Power Grids" clearly stipulates that CVT cannot be used for harmonic measurement, and with the increasing nonlinear load, the harmonic voltage Measurement has become an essential requirement in the power industry to ensure stable operation, and the development of the situation has led to the need for accurate measurement of harmonic voltage. [0003] In the prior art, there is a harmonic measurement error correction devi...

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Problems solved by technology

This method does not affect the structural parameters (namely: the high-voltage capacitor C 1 , medium voltage capacitor C 2 and partial pressure ratio k parameter) caused by the change of transmission characteristics (such as figure 1 and figure 2 As shown), the operability of the actual processing is less considered, and the influence of stray capacitance is not considered sufficiently; and, theoretical analysis and computer simulation research show that the characteristics of CVT equivalent circuit element parameters changing with temperature Although the influence on the transfer characteristics of the fundamental wave is small, it has a great influence on the transmission and change of the harmonic signal. The harmonic measurement correction method that does not consider the influence of temperature will cause a large additional error in temperature clothing in actual specific applications. image 3 After considering the factors of component parameters changing with temperature, the change of sensing ratio and phase difference of some harmonics is given. It can be seen that temperature has a great influence on the measurement accuracy of CVT harmonic voltage. The higher the harmonic order, The more serious the impact is, therefore, in the research on the accurate measurement method of CVT harmonic voltage, the influence of temperature on the measurement results must be considered

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