A Practical Digital Implementation of Completely Decentralized Ripple Minimization in Parallel-Connected DC–DC Converters

Abstract

Parallel dc–dc converters are commonplace in applications such as computing power supplies, point of load systems, and dc microgrids. The presence of multiple converters in such systems allows for switch interleaving and ripple cancellation. One class of existing ripple reduction methods depends on central controllers that require communication among the converters. These approaches compromise system scalability and reliability. When it comes to decentralized methods, the state-of-the-art is limited to uniform conditions and cannot handle mismatches in physical parameters and operating points among converters. In this article, we address these shortcomings with fully decentralized controller that robustly drives the pulsewidth modulation carriers of a collection of heterogeneous converters to the phase-shifts that give minimized ripple. More precisely, the proposed controller eliminates the dominant fundamental switching harmonic from the output current and voltage using only local voltage feedback. After outlining a comprehensive analytical model, we experimentally validate our approach on a system of five parallel-connected buck converters under a variety of parametric and operational mismatches. Measurements show ripple reduction of more than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$4\times$</tex-math></inline-formula> in the output voltage and the fundamental switching frequency harmonic is attenuated by more than 30 dB compared to conventional symmetric interleaving.