Distributed power flow control using cascaded multilevel isolated bidirectional DC–DC converter with multi‐phase shift modulation

This study proposes a cascaded multilevel isolated bidirectional DC–DC converter (CMIBDC) suitable for large capacity energy storage applications. Compared to conventional IBDC, the proposed converter has higher power-handling capacity distributed among multiple cascaded HV and LV bridges. The HV bridges are cascaded through a high-frequency transformer with a common DC bus. On the other hand, the LV bridges are directly cascaded with isolated DC storage batteries. Effectively, the CMIBDC requires only a single DC input to store the energy in multiple battery units. A multi-phase shift (MPS) modulation scheme has been introduced which provide wide range of power flow control. The MPS modulation shapes the high-frequency link AC current with low THD thus reducing high-frequency losses. Detailed operating waveforms of the proposed CMIBDC converter in different modes are presented. The performance of the proposed converter and modulation scheme has been demonstrated through PSCAD/EMTDC simulation and validated experimentally using Spartan 3AN FPGA processor-controlled CMIBDC.