A Transformerless Bidirectional DC-DC Converter based on Power Units with Unipolar and Bipolar structure for MVDC Interconnection

摘要

In this paper, a novel bidirectional DC-DC converter based on series-connected power units (BPUC) for unipolar and bipolar MVDC interconnection is proposed. Compared with traditional grid-connecting converters, the proposed converter has a transformerless structure to reduce size, cost, and power loss, being more suitable for MVDC systems emphasizing on efficiency, small volume, and low cost. In addition, the proposed converter can be applied as both a unipolar and a bipolar converter in MVDC networks, which greatly extends its scope of application and improves its transmission efficiency. Its control system can realized precise power interaction between DC grids. Simulations of the 4-level unipolar BPUC and bipolar BPUC were implemented, and a 1 kW experimental implementation of the 4-level unipolar BPUC was developed to verify the converter effectiveness.