Design and Analysis of a Three-Port Bidirectional DC--DC Converter With Low-Voltage Stress and Flexible Power Flow Control for DC Microgrid Applications

Abstract

Nonisolated bidirectional DC–DC converters (BDCs) are widely used for power flow management in energy storage systems, DC microgrids (DC-MGs), and electric vehicles (EVs); however, many existing topologies suffer from limited voltage gain, narrow duty-cycle range, high component count, bulky structure, and high-voltage stress on power devices. To overcome these limitations, this article proposes a nonisolated three-port high-gain BDC for the integration of renewable energy sources (RESs), energy storage units (ESUs), and DC-MGs. The proposed converter supports multiple power flow paths, including battery-to-DC-MG, photovoltaics (PVs)-to-DC-MG, and DC-MG-to-battery operation. It operates in boost mode for power transfer from Port-A to Port-B and in buck mode for reverse power flow. A wide voltage conversion ratio with reduced voltage stress across most switches is achieved, improving efficiency and reliability. A 200-W SiC MOSFET-based prototype was developed and experimentally validated. The converter achieves a peak efficiency of 96% and exhibits stable operation under both open-loop and closed-loop control. Moreover, operation in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) demonstrates the flexibility and robustness of the proposed topology across a wide operating range.