MODELING AND SIMULATION OF MULTI PULSE CONVERTER SYSTEM FOR HARMONIC REDUCTION WITH NON-LINEAR LOAD

Abstract

Often power electronic converters generate harmonics in power system which affects the system adversely different manner such as increased rms current which results in heating, resonance in current with connected transformer, interference with communication lines, equipments operating on zero crossing detection etc. Such unwanted harmonics should be avoided while conversion of power from AC-DC, to sustain ideal conditions in power systems. The present work deals with harmonic reduction using multipulse converter. The multi-pulse converter, uses a modular architecture, where each power module comprises of a three-phase bridge and specially designed transformer for shifting of phase . The primary windings of the transformers are wound in star and fed by a power source, while the secondary windings of the transformers are connected to individual power converters with relevant phase shifts to realize the desired ouput. By selecting appropriate phase shifts between the primary and secondary sides of the transformers and synchronously switching the three-phase bridges at specified phase relations, low order harmonics can be eliminated in pairs. Thus a very high power quality current waveform can be synthesized even with low switching frequencies of the converters or with thyristor converters.