A Three-Port Input-Series and Output-Parallel DC-DC Converter with Distributed Control for Medium-Voltage DC Distribution System

In the medium-voltage DC distribution system, the ISOP DC-DC converters with DAB constituent modules are widely adopted for its advantages in high input voltage and large output current applications. However, when medium-voltage DC side is a unipolar or a pseudo-bipolar system, two ISOP converters are needed with the number of DAB modules doubled, which increases the cost and complexity while the reliability reducing. Therefore, in this paper, an ISOP DC-DC converter was proposed, consisting of modified isolated three-port bidirectional DC-DC modules, in which only half of the modules, half of the high-frequency transformers and two-thirds of the passive components are used to achieve the conversion from the unipolar or pseudo-bipolar input to the true-bipolar output. Meanwhile, the improved three-port sub-module retains the advantages of the DAB. In addition, this paper proposes an optimized distributed control scheme, which improves the modularity, flexibility, and reliability of the system without supervisory controller and communication. The topologies of the consistent modules and the overall system, and the corresponding distributed control scheme, are described in this paper. Finally, the simulation results are provided to illustrate the feasibility of the proposed topologies and distributed control scheme.