Analysis of integrated magnetics for input series output series DC-DC converter

Multi-module isolated converters (MMICs) find extensive applications in various DC-DC applications owing to their exceptional features of galvanic isolation, bidirectional power flow, high-power density, and enhanced efficiency. However, voltage and current sharing among the converter modules are the most significant issues in MMICs. This paper proposes multiport integrated-magnetics transformers (MpIMTs) which address the input-output DC-link voltage imbalances within an ISOS converter. The proposed transformers ensure the input voltage sharing (IVS) and output voltage sharing (OVS) through balancing windings within their structures, thus substitutes the complicated active control scheme with the balancing winding. Besides, the input side and output side modules are decoupled from each other; thus, the impact of parameters variation and intermodule energy transfer during a transient of one side does not reflect to the other side. These properties are achieved by proposing a custom-designed core and an off the shelf available U-core assembled MpIMTs. The magnetic and electrical equivalent circuit along with the design criteria of the balancing winding are also presented. Furthermore, the paper includes the comparative analysis of the proposed transformers which reveals that while the U-core MpIMT offers simplified construction, it comes at the expense of slightly reduced efficiency compared with the custom-designed MpIMT. Finally, the proposed U-core MpIMT is validated through a laboratory prototype. The proposed multiport integrated-magnetics transformers (MpIMTs) address the input-output DC-link voltage imbalance issue within a DC-DC ISOS converter. The proposed transformers ensure the input voltage sharing (IVS) and output voltage sharing (OVS) through balancing windings, thus substitutes the complicated active control scheme with the balancing winding. image