Variable frequency adaptive selective compensation for active power filters

This paper investigates an adaptive current controller for active power filters for aeronautic applications, which compensate selected load current harmonics. The attention is focused on the load current harmonic compensation when the fundamental frequency varies over a wide range (typically between 400 Hz and 800 Hz) and the harmonics produced by distorting loads (such as the 5^th and the 7^th) are above the achievable current loop bandwidth. Compared to previously reported resonant controllers, this paper proposes an adaptive leading angle compensation in the resonant filter, which - by compensating the variable process delay -is potentially able to guarantee the theoretical current control stability when the selected frequency is up to the Nyquist frequency. However, the presence of intermodulation, i.e. distortion introduced due to the compensation of frequencies approaching the Nyquist limit, introduces an additional distortion, which limits the maximum compensation frequency. Experimental results are also presented.