Increasing Light Load Efficiency in Phase-Shifted, Variable Frequency Multiport Series Resonant Converters

Multiport power conversion topologies provide the functionality of more single (and independent) converters but with just one transformer having multiple windings (i.e., ports). In automotive on-board chargers, multiport approach combined symmetrical series resonant circuits, so-called converter (MSRC), enable required galvanic isolated connection from grid-side usually an AC-DC factor correction (PFC) stage) to vehicle’s batteries, i.e., main high-voltage (HV) traction and auxiliary low-voltage (LV), theoretically allowing achieve increased densities enabling a flexible bidirectional) routing among different ports. High efficiency figures are normally specified in considered application field for very wide voltage ratios ports, due variability battery voltages, thus requiring proper optimized control strategies underlying converter. The variation is fact highly affecting MSRC operation, especially light loads at low state-of-charge, high losses can be experienced since zero switching conditions lost. Beside conventional MSRC, where flow set phase-shift between individual full bridges or by changing frequency, this paper proposes novel coordinated approach, including manipulation both additional modulation duty-cycle as function DC-link output PFC stage), aiming introducing zero-voltage interval on bridge voltages. A mathematical description adopted topology reported, also accurate simulation models estimation fair comparison proposed duty-cycle mode strategy. Detailed operation guideline achieving within connected reported. Experimental results validate proposal highlight significant peak average improvements respect standard approaches.