Electromagnetic Compatibility of High-Voltage Frequency Converters with Power Plant Networks

Abstract

It is emphasized that distortion of the rectified voltage waveform is the most essential factor specifying the electromagnetic compatibility (EMC) of the frequency converters with power plants networks. The EMC issue is noted to be most relevant while applying variable frequency electric drives at the power plants. There was a challenge to calculate the voltage non-sinusoidality ratio. The paper provides calculation charts enabling forecasting its value at network connection of six- and equivalent twelve-phase rectifiers and various relations between the inductance of the matching transformer (input reactor) and equivalent one of the power supply system. It considers means providing EMC of the powerful frequency converters with the network. As main measures it is sustainable to change the structure of the power supply system, improve the frequency converter circuits, increase the pulse number of the rectifier and use rectifiers with the pulse-width modulation. The most important factor specifying EMC of the frequency converters and electric drive motors is distortion of current and voltage waveform. The paper mentions that optimum values may be achieved due to the application of the frequency converters having self-excited inverters with GTO or SGCT thyristors and pulse-width modulation. It analyses peculiarities of the rectifiers with self-excited voltage inverters. Based on results of experimental studies, we may conclude that it is preferable to use electric drives with eighteen-pulse rectifier featuring pulse-width modulation.