Digital controller for hybrid filter in HVDC based on approximate inverse system

Abstract

In order to eliminate the characteristic harmonics in high voltage direct current (HVDC) transmission systems and to simplify the analog controller structure, this paper proposes a new digital controller by adopting an approximate inverse system control strategy according to the frequency response characteristic of the hybrid power filter. The proposed digital controller is implemented with a TMS320C32 DSP, including a series of parallel digital band-pass filters, phase shifters and amplifiers. The results of both simulations based on PSCAD and experiments on a 30 kVA HVDC system prove that the proposed digital control system is stable and efficient for eliminating the harmonics.