Active capacitors: Concept and implementation

In this paper, the idea of implementing capacitors with DC/AC power converters (also called inverters) is proposed and demonstrated. Such capacitors are active capacitors. The voltage rating of an active capacitor is determined by the voltage rating of the power semiconductor devices used to build the inverter and the current rating of the capacitor is determined by the current rating of the power semiconductor devices used. The capacitance can be freely set in a very wide range and it is possible to have some special properties, e.g. to reduce harmonic current components. Experimental results are provided to demonstrate the design, implementation and performance of a prototype active capacitor. Active capacitors outperform passive capacitors in terms of tolerance, stability with respect to time and temperature.