Extraction and Compensation of Dominate Harmonics in High Power Hybrid Active Power Filters for HVDC Applications

Abstract:- For nonlinear loads beyond 10 MW, the hybrid active power filters are not cost effective due to high bandwidth, high ratting and low efficiency; therefore, the passive filters are typically used for harmonic filtering of high power nonlinear loads. On the other hand, the passive filters compensation characteristics are affected by utility system impedance variations. The HVDC systems that use the highest power nonlinear converters, use the 12- pulse converters in which the 11th and 13th harmonics are the dominate harmonics. In the conventional links, these harmonics are compensated by tuned passive filters. However, the hybrid active power filters that can inject the certain components, don’t need to have high bandwidth and have acceptable efficiency. This paper presents a new control scheme for a shunt hybrid parallel active power filter (HPAF) intended for high power application to meet IEEE 519 recommended harmonic standards. The instantaneous value of those harmonics are extracted separately by abc to dq transformation (SRF) and the active inductor reference voltage which have to be applied to the voltage source inverter of hybrid active power filter, are made by active inductance concept. In addition, it controls the dc voltage of the capacitor in the dc side of HPAF. Finally, the resultant vector, which is obtained from control unit, is applied to produce the gating signals of the HAPF converter by space vector modulation (SVM) method