PQ versus EMC problems at a static excitation system in a power group

This paper presents measurements comprising both power quality and EMC fields for a static excitation system composed of a transformer and controlled rectifier bridge in a power system generator group. The replacement of the old auxiliary excitation generator eliminates the disadvantage of using electrical machines with the mass in motion inertia and wear over time, but with the price of facing two important problems: the line voltage notching due to thyristor commutation and also the line current distorting. FFT decomposition of the currents and voltages waveforms allows the obtaining of their harmonic spectrum in the range [0...2] kHz (PQ domain) and respectively [2...9] kHz (EMC domain). Theoretical aspects of line notching and some solutions for compensation strategies and their limitations are discussed.