Keywords: passive filters, harmonics, active power filters, hybrid APF, power quality, thyristor controlled reactors, TCR, harmonic frequency, load compensation, self–tuning
Selective harmonic frequency–based non–linear load compensation using hybrid active power filter
This paper presents a hybrid active power filter for harmonics and reactive current compensation while reducing the rating of active power filter. The proposed topology of hybrid active power filter uses the combination of active power filter and a new self–tuned passive filter. The control technique of the proposed system separates the compensation frequency band for active and passive filters. The self–tuned passive filters are tuned to suppress two lower most harmonic components, i.e., fifth and seventh and the active power filter compensates the remaining higher order harmonics. The active power filter control is based on reference current estimation in a–b–c frame. An analytical study of thyristor controlled reactor (TCR)–based self–tuned passive filters is presented to keep the passive filters in the resonant state during deviation of their parameters under the influence of external factors like temperature rise, aging, etc. The firing angle of the TCR is derived as a function of the deviation of passive filter parameters. The proposed hybrid active power filter is also capable to damp out the harmonics propagation due to passive filter resonance. The proposed algorithm is simulated in MATLAB/Simulink environment under various operation conditions to show the effectiveness of the controller.