Accurate measurement method of capacitor voltage transformer harmonic voltage based on interpolation method

Abstract

A method for accurately measuring the harmonic voltage of a capacitor voltage transformer (CVT) by means of interpolation. In the method, by means of curve fitting, a mathematical interpolation calculation equation under the condition of different parameter combinations is obtained in an off-line state, then, for a specific CVT device, a nameplate parameter (an actual parameter) thereof is input to a harmonic correction device by means of man-machine dialogue, and a network transfer function for an arbitrary parameter at room temperature is obtained by means of the mathematical interpolation calculation equation, i.e., obtaining an amplitude-frequency curve and a phase-frequency curve of the CVT for a specific parameter at room temperature; then, according to the operation environment temperature of the CVT measured by a temperature sensor, correction curves of the amplitude-frequency curve and phase-frequency curve of the CVT which change with temperature is obtained by means of offline calculation of the equivalent circuit parameter offset caused by a temperature change. Thus, accurate correction measurement of the harmonic content of the CVT is achieved.

Description

technical field [0001] The 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 an interpolation method. Background technique [0002] Capacitive 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 / T 14549-1993 "Power Quality Harmonics in Public Grids" clearly stipulates that CVT cannot be used for harmonic measurement, and with the increasing nonlinear load, the harmonic voltage The measurement of harmonic voltage has become a requirement necessary for 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 c...

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Problems solved by technology

The structural parameters (namely: high-voltage capacitance C 1 , medium voltage capacitor C 2 and partial pressure ratio k parameter) caused by the difference in transmission characteristics change (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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