Harmonic mitigation improvement with a new parallel topology for shunt active power filters

This paper describes the control and parallel operation of two Active Power Filters. The filters are coupled in a combined topology in which one filter is connected in a feedback loop and the other is in a feedforward loop for harmonic compensation. Thus, both active power filters bring their own characteristic advantages i.e. the feedback filter improves the steady-state performance of the harmonic mitigation and the feedforward filter improves the stability and the dynamics. Another characteristic of the proposed topology is the cooperation of both filters either as load-sharing or frequency-sharing. The evaluation of the proposed topology concludes that this approach is very practical for achieving both low and high order harmonic compensation and stable grid operation. This is supported by measurement results on a 15 kVA laboratory setup, indicating a reduction in Total Harmonic Current Distortion from existing 30 % to less than 2 % in an adjustable speed drive application.