An Immittance-Network-based Multiport ZVS Bidirectional Converter with Power Decoupling Capability

This article investigates an immittance-network-based multiport zero-voltage-switching (ZVS) bidirectional converter with power decoupling capability. It has a highly modularized design, bidirectional and decoupled power control for each energy port, high efficiency and easy realization of ZVS, and good compatibility with different types of energy subsystems, which make it a promising topology for renewable energy systems. By connecting the independent current sources to a voltage bus or independent voltage sources to a current bus, the power flow between each energy port is decoupled and can be easily controlled. A current-bus-based multiport converter is discussed thoroughly, including its power control principle, modulation strategy, and ZVS realization. It is shown that the power flow directions of energy ports, as well as the high-order harmonics generated in the resonant tank, have great effects on the ZVS realization at different ports. A modified enhanced-phase-shift modulation by inserting an additional phase shift is proposed to alleviate the negative effects of high-order harmonics generated from energy ports with different power directions without introducing excessive reactive current. A minimum phase shift is derived under the worst-case scenario so that ZVS is ensured at all ports under all power flow conditions. Finally, a 1 kW, 96 V/72 V/300 V prototype is implemented to verify all theoretical analysis. ZVS is ensured under different operation modes and the system efficiency is above 91% over the full load range.