Research on Natural Voltage and Current-Sharing Characteristics of Input Series Combined DC Converters

The input-series output-parallel connection and the input-series output-series connections of a DC/DC converter are mainly used in the high-voltage fields. After the combination, the voltage and power levels of each module in the system can be reduced. At the same time, the problem of difficult device selection owing to excessive voltage can be solved. To maintain the average operation between modules, the most widely used voltage sharing method is the common duty-ratio control. This study, investigated the natural voltage sharing and current-sharing characteristics of common duty-ratio control for different types of topologies when connecting ISOP and ISOS. A method is proposed to determine the characteristics of natural voltage equalization based on the topological steady-state voltage—current relationship. The most widely used buck, boost, and buck-boost derivation duty-ratio control topologies and the bidirectional operating frequency control resonant topologies, LLC, and CLLC, are investigated in this study. By calculating whether different topologies have a steady-state natural voltage-sharing operating point, the natural voltage-equalization and current-equalization characteristics are determined, and the corresponding conclusions are provided by simulating results.