Expandable Three-Port DC-DC Converter with Notable Properties and Without Effective Limitations Suitable for Off-Grid Applications

A new expandable, non-isolated, high step-up threeport DC-DC converter (TPC), with two inputs and one output, which includes a bidirectional port for charging and discharging energy storage, is presented in this paper. The proposed TPC is compatible with expanding the number of inputs and becoming a multi-input converter (MIC). Also, it has a high voltage gain, an appropriate number of components, low voltage stress on the semiconductors, and low input current ripple. In addition, the paper includes new kinds of comparison criteria to assess multiinput converters from various perspectives, such as performance limitations and quality. The design of the converter incorporates beneficial characteristics, such as continuous input current and a common ground between the energy sources and the load. It also has the capability to operate in battery-alone mode and under unbalanced conditions, accommodating different powers and voltage levels of the input sources. Moreover, the employed switching strategy enables effective control over the input current of the sources as well as the output voltage. Various operating modes and steady-state analysis have been discussed to validate the advantages of the proposed TPC. Finally, a 300W laboratory prototype is designed to verify the performance of the proposed TPC under sudden changes and during mode transitions.