As the demand for energy in AI-driven data centers continues to rise, there is an urgent need for innovative solutions to enhance the efficiency and power density of isolated three-phase AC/DC converters. In this context, the Integrated-Active-Filter Rectifier (IAFR) emerges as a promising solution due to its low complexity and high efficiency, achieved through the low switching frequency of all power semiconductors except for an injection leg needed to shape the three-phase sinusoidal input currents. However, the IAFR's performance limits concerning efficiency and power density, as well as its behaviour under unbalanced grid conditions, are still unclear. This paper presents a detailed analysis of the IAFR operation and introduces a Triangular-Current-Mode (TCM) operation for the injection leg, ensuring Zero-VoltageSwitching (ZVS) across the entire grid cycle. Additionally, a control strategy for the IAFR is proposed to ensure sinusoidal input currents and minimize power fluctuations under unbalanced grid conditions. The proposed control and modulation strategies are verified through simulations, while a multi-objective Pareto optimization is employed to determine the performance limits of the IAFR when paired with an isolated downstream DC/DC converter stage required for galvanic isolation and output voltage regulation.
Ultra-Efficient Three-Phase Integrated-Active-Filter Isolated Rectifier for AI Data Center Applications
Sbabo P.
;Biadene D.;Mattavelli P.;
2025
Abstract
As the demand for energy in AI-driven data centers continues to rise, there is an urgent need for innovative solutions to enhance the efficiency and power density of isolated three-phase AC/DC converters. In this context, the Integrated-Active-Filter Rectifier (IAFR) emerges as a promising solution due to its low complexity and high efficiency, achieved through the low switching frequency of all power semiconductors except for an injection leg needed to shape the three-phase sinusoidal input currents. However, the IAFR's performance limits concerning efficiency and power density, as well as its behaviour under unbalanced grid conditions, are still unclear. This paper presents a detailed analysis of the IAFR operation and introduces a Triangular-Current-Mode (TCM) operation for the injection leg, ensuring Zero-VoltageSwitching (ZVS) across the entire grid cycle. Additionally, a control strategy for the IAFR is proposed to ensure sinusoidal input currents and minimize power fluctuations under unbalanced grid conditions. The proposed control and modulation strategies are verified through simulations, while a multi-objective Pareto optimization is employed to determine the performance limits of the IAFR when paired with an isolated downstream DC/DC converter stage required for galvanic isolation and output voltage regulation.
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