Achieving Reduced Sizing for Shunt Active Power Filters: A Design Leveraging Load Impedance Analysis and Conservative Power Theory

The growing integration of power electronics in industrial systems has led to the widespread adoption of variable frequency drives, most of which are powered by 6-pulse diode bridge rectifiers combined with large DC-link capacitors. While this configuration ensures a stable voltage supply for IGBT-based motor drives, it also behaves as a non-linear voltage-source load that injects substantial harmonic distortion into the grid. Conventional mitigation strategies often involve shunt active power filters (SAPFs), but when improperly dimensioned, these filters can end up requiring power ratings nearly as large as the load itself—rendering them impractical for many applications. This paper introduces a streamlined design approach aimed at minimizing the size and rating of SAPFs and associated passive elements for typical rectifier-capacitor-fed induction motor systems. A key part of this approach is the use of one-cycle power components, based on Conservative Power Theory (CPT), both in the filter design and its control. The effectiveness of the proposed strategy is demonstrated through comprehensive PLECS simulations and real-time hardware-in-the-loop experiments. The results demonstrate the effectiveness of the proposed approach. By selecting a load impedance value of 4.5%, which is lower than the 6% commonly recommended in the literature, good performance is achieved in terms of low harmonic distortion and reduced current ripple in the grid current.