A MODIFIED STRUCTURE OF HYBRID ACTIVE DC FILTER IN HVDC SYSTEM

Characteristic harmonics that are 12th, 24th, 36th and 48th orders of the main AC frequency of 50 Hz or 60 Hz, may give rise to interference in adjacent telephone lines, distortion of the AC voltages and currents, disturbance in control and monitoring equipments, enhancement of transmission losses and electromagnetic pollution. AC or harmonic component of DC transmission line current, which is superimposed on its DC component, contains mentioned harmonics. Hence, cancellation of harmonic component of DC transmission line current in HVDC transmission system is very important problem. Removing the harmonic component of DC transmission line current is carried out by Hybrid Active DC Filter (HADF). In this paper, a modified configuration of HADF is proposed and has the ability that by proper designing of its passive elements, the nominal voltage-current (nominal power) of HADF active part is adjustable. Theoretical analyses and simulation results prove and validate the accuracy of aforementioned claims.