Abstract: As variable frequency alternating current (AC) power system grids are presently being applied to the new type of more electric aircraft (MEA), traditional active filters cannot satisfy the requirement of wide frequency variation. Therefore there arises the need for an aeronautic power active filter suitable for wide frequency input. In this article, a novel series hybrid active power filter (SHAPF) for variable frequency AC power systems is introduced which works with fundamental current compensation, and attains better harmonic suppression effect for various input frequencies. The variable frequency harmonic suppression principle is discussed, and the detailed design of the process control system is provided, including the design of a dual digital signal processing (DSP) based controller platform and the point-by-point dynamic detection algorithms of the fundamental current. Finally, experiments are carried out to verify the proposed system. The input current waveforms and harmonic analysis are compared before and after the power filter is added. The input current total harmonic distortion (THD) with power filter changes from 174.00% to 4.80%, and a good filter effect is displayed. The filter experiments are also performed in conditions of 360 Hz, 400 Hz and 720 Hz input frequencies, and good control performance of the system in the wide range is verified, which can meet the power factor correction requirements under the conditions of aviation variable frequency input.

Key words: active power filter, variable frequency, fundament current detection, digital signal processing, dynamic detection