Research On Short-Circuits Fault Of Novel Converter Transformer And Its Filter System

With the rapid development of our country's electric network, HVDC transmission system plays an important role in nationwide transmission network. Converter transformer is a very important technical equipment in HVDC. Relative to traditional converter transformer, novel converter transformer have some advantages like the self-coupling,compensation function and harmonic suppression. Research on current calculations of short-circuits fault of novel converter transformer and its filter system (Novel System in short), is the foundation for protection study and the setting calculation of the relay protection of Novel System.This paper makes numbers of studies includes the following:This paper introduces prospect and application of HVDC in china and analyses the necessity of research on current calculations of short-circuits fault of Novel System.This paper introduces the configuration of Novel System and its principle work; and analyses the self-coupling,compensation function and harmonic suppression of Novel System.A systematic analysis method based on multi-winding transformer theory combining the magnetomotive balance, Kirchhoff's law and the voltage, current equations of loop circuit is proposed, and operational characteristics equations of novel system under two conditions of switching on the filer branch at the valve side and switching-off it are established.Current calculation under the short-circuits fault of novel converter transformer under the two conditions with and without filter system are established based on the mathematical models of novel converter transformer and the characteristic of novel system.At last, a computer simulation model from the building DC transmission system exploitation platform based on the designed parameters is established; through comparing the computer simulation results with the current calculation ones, which shows that the current calculation under the short-circuits fault of novel converter transformer is correct.