Sustainability of High-Power Frequency Converters with Active Rectifiers Connected in Parallel with “EAF-SVC” Complex

Abstract

Control systems of active rectifiers are not adapted to asymmetrical voltage dips occurring in the supply mains. 15-30% voltage dips lasting 150–300 ms cause emergency shutdowns of the main electric drives of rolling mills thus resulting in significant economic and process losses. In the previous investigations the research group suggested compensating voltage dips by means of the reactive power reserves of the static var compensator operating in the power supply systems of electric arc furnaces (EAFs). However, there were a number of issues to be investigated, such as the processes taking place in the frequency converter with active rectifiers during asymmetry and voltage fluctuations caused by the EAF operation as well as by the surge voltages during commutations of the SVC filter compensating circuits and by the voltage dips during the furnace transformer switching. The paper describes the investigation of parallel operation of the frequency converter with active rectifiers and the powerful electric steel-making complex «EAF-SVC». As a result of the research work it was found that steady operation of the frequency converter with active rectifiers continues even during disturbances caused by the EAF operation. It was also proved that the frequency converter with active rectifiers is capable of operating during surge voltage caused by switching of high harmonic filters and during voltage dips caused by switching of the furnace transformer.