Study the Robustness Active Filter for a Three-Phase Power Rectifier Considering Line Frequency and Load Variations


Power electronic converters (e.g. AC-DC and DC-AC) produce harmonics which distorting the waveforms of voltage and current. Many research works have examined various techniques to mitigate harmonics at operating conditions (i.e. at a fixed line frequency and a specific load) such as: (i) passive filters, (ii) Current-injection converters, (iii) active filters and (iv) hybrid filters. Active filters are widely used with three-phase bridge rectifiers due to their excellent features for reducing harmonics using power switches instead of passive components that minimize the efficiency of the system. This paper investigates the robustness and the dynamic performance of active filters under the variation of line frequency and DC load. In case of using active filters, it is observed that total harmonic distortion (THD) of voltage and current waveforms is kept at IEEE Standard limits(i.e. less than 5%) under the variation of line frequency . Whilst the performance of passive filters is highly affected by the variations of line frequency and THD of voltage and current waveforms is always greater than 5% except at designed frequency, i.e. 50 Hz. Moreover the load is changed from full-load to half-load, it is observed that the dynamic response of active filters is faster than passive filters for canceling harmonics. It is worth noting that the hysteresis-current-control method is utilized for adjusting the control pulses of active filters due to its rapid dynamic responsem. Simulation results present the highest values of THD of line currents in cases: without any filters , passive filters and active filters are 24.36%, 80.79% and 3.03%, respectively.