Current-Fed Multiactive Bridge Converter With Inherently Output Voltage Balance for Distributed Photovoltaics MVDC Integration

The input-independent output-series (IIOS) modular multiport dc/dc converter, which has one power conversion stage and high efficiency, is a promising method for distributed photovoltaics (PVs) medium-voltage dc (MVDC) integration. The variable PV input power will lead to the output voltage unbalance. To avoid the power curtailment and device damage caused by the uneven output voltage, a multiwinding transformer (MWT) based current-fed multiactive bridge (CFMAB) with inherently output voltage balance is proposed. The topology consists of current-fed full bridge (CF-FB) on PV side, half bridge (HB) on MVDC grid side, and an MWT which is used to connect the CF-FB and HB. By using external inductors to replace the leakage inductors of MWT and making the external inductance of the windings which connected to the grid side approximately zero, the power flow between the ports is decoupled. Thus, the inherently output voltage balance can be achieved. In addition, the proposed topology has small input current ripple, and all switches can achieve zero-voltage switching (ZVS), which is conducive to the improvement of system efficiency. Finally, the feasibility of the topology is verified by both simulation and experiments.