Shunt Active dc Filter to Reduce the dc-Link Ripple Current Caused by Power Converters to Improve the Lifetime of Aluminium Electrolytic Capacitors

Electrolytic capacitors are commonly used as a dc-link in power electronics circuits and especially in renewable energy system applications. However, their life expectancy and reliability can be severely affected by the ripple current causing increased thermal stresses. Further, the switching of power electronics and the presence of harmonic components can increase the ripple current that may shorten the lifetime of the electrolytic capacitors. This paper proposes the use of a shunt active dc filter to regulate the dc capacitor current to a near-constant value and hence mitigate the events that can reduce the capacitor life expectancy. The proposed filter reduces the ripple in the capacitor dc current irrespective of the frequency spectrum of the ripple. The design and the operation principles of the proposed filter are presented and discussed. The results from the simulation and experimental studies demonstrate the effectiveness of the proposed technique