Simple and Effective Control System for Active AC Ripple Filtering Circuits

In systems where dc and ac subsystems are interacting, dc capacitors are used to balance (filter or decouple) the ac power pulsations. The required capacitance often poses a limitation in terms of physical footprint, cost, and/or reliability. Active ripple filtering circuits are widely studied in the literature for reducing the size of the capacitor needed by using power electronic switches, passive circuit components, and a control system. The passive circuit components include a substantially smaller dc capacitor at a reasonably higher or lower voltage, and an inductor for filtering the switching ripples. The control systems presented in the literature for such systems are complex and need multiple sensors and are hardly plug-and-play and universal. This paper proposes a simple yet effective control system which uses only one voltage sensor. The circuit accurately emulates a large capacitor within a wide frequency bandwidth in a plug-and-play manner. The paper explains the details of the proposed control system and presents simulation and experimental results to illustrate its properties.