Multiwinding Coupled-Inductor and LC Series Resonant Voltage Balancer for MVDC Integration of Distributed Photovoltaic Energy

The integration of distributed photovoltaics (PVs) into medium-voltage dc (MVDC) system using input-independent output series (IIOS) multiport dc-dc converter has gained more attention due to its superior voltage boosting capability. However, the output voltage unbalance caused by the mismatched input PV power has emerged as a critical issue. Thus, voltage balancer (VB) based on multiwinding coupled-inductor (MWCI) and LC branch is proposed in this article to solve this problem. Semi-dual-active half-bridges (DAHBs) serve as submodules (SMs) for linking PV panels with MVDC bus; by pairwise grouping all SMs, voltage balancing within and between groups is achieved by LC series resonant VB (LCSRVB) and MWCI, respectively. Besides, all switching devices achieve zero-voltage switching-on (ZVS-on). Thus, the topology is characterized by its high efficiency and low cost, making it suitable for using in PV power MVDC collection system. The circuit operation principle, power transfer mechanism, parameter design, and performance comparison are discussed in detail. Finally, both the simulations and down-scale experimental results with six SMs are showcased to confirm the practicality of the proposed system.