A dual coupled inductors-based high step-up/step-down bidirectional dc-dc converter for energy storage system
A non-isolated dual coupled inductors-based bidirectional DC-DC converter is analyzed in this paper for high step-up/step-down applications. The topology is derived by integrating a staked dual-active half-bridge converter (DAHB) into a switched-inductor buck-boost BDC. With the secondary windings of two coupled inductors in series connection, high voltage gain and reduced switch voltage stresses can be obtained. Hence, reduced turns-ratio of two coupled inductors and low-voltage rated MOSFETs can be used to realize high efficiency conversion. The coupled inductors can operate not only as a switched-inductor of two buck-boost BDCs, but also as two transformers of the equivalent DAHB converter. What's more, with PWM plus phase shift (PPS) control scheme, soft-switching of all the active switches can be realized. Operational principles, the steady-state analysis and characteristics of the analyzed BDC are discussed in detail. Experiments of a 40–60V/400V 1kW prototype have been carried out to verify the feasibility and effectiveness of the analyzed converter.