Harmonic current detection system for grid side winding of converter transformer in UHVDC transmission system

摘要

In order to deal with harmonics of converter transformers in UHVDC transmission systems, the first task is to accurately detect the harmonic components. This study constructed a detection system for measuring and analyzing AC side harmonics of converter transformers. This detection system combines the following functions: extraction of AC current signals, conversion from analog signal to digital signal, data transmission via optical fiber, and conversion from time domain to frequency domain based on Fourier transform theory. The detection system is composed of hardware and software, including flexible CT, remote signal high-speed acquisition module, local signal conversion module and data analysis module developed using LabVIEW and MATLAB. The winding current can be precisely collected at the grid side bushing of the converter transformer. The optical fiber connection between the remote signal acquisition and local signal conversion module can effectively prevent electromagnetic interference. This detection system can collect the current signal in real time, and perform the harmonic analysis in time and frequency domain. This paper presented details of the detection system and the harmonic characteristics of the converter transformer at grid side under different operating conditions.