Comparison of voltage and flux modulation schemes of StatComs regarding transformer saturation during fault recovery

A transformer might be driven into saturation by faults in the connected system. In a transmission system with a Static synchronous Compensator and transformers connected at the point of common coupling, different modulation schemes utilized by the voltage source converter influence the transformer saturation in different ways. This paper compares the saturation effect during fault recovery when two alternative modulation schemes are utilized: voltage modulation and flux modulation. The comparison shows that utilization of flux modulation scheme tends to soften the saturation problem during fault recovery. However, this is achieved at a higher converter transient peak current. Index Terms--Converters, fault recovery, pulse width modulated power converters, StatCom, static synchronous compensator, transformer saturation, transformers, voltage source converter (VSC).