Electronic Capacitor Realization for Grid-Connected Power Converters

The paper suggests a way of operating a DC-DC converter to directly emulate a large capacitance of a controllable value when a much smaller capacitor is actually utilized. Converters that are operated in this way are referred to as Electronic Capacitors (EC). The proposed system has the potential of replacing in a plug-and-play fashion any real large capacitor (within the control bandwidth). The control algorithm forces the converter terminal voltage to follow capacitance equation as a function of sensed (or estimated) terminal current while simultaneously compensating for conversion losses. The proposed method is verified by emulating bulk DC link capacitance of a commercial power factor correction (PFC) front end. It is shown that steady state performance of the system with electrolytic and electronic capacitors is nearly the same at both DC link and grid sides. On the other hand, transients are handled slightly differently due to dissimilar hold-up abilities of real and electronic capacitors and are therefore subject of future research.