A Modular Interline Power Flow Controller for Meshed Multi-Terminal DC Grids

In the meshed multi-terminal direct current (MTDC) grids, it is not possible to independently regulate all line currents via terminal controllers. To address this issue, the dc power flow controllers (DCPFCs) are introduced. However, most power flow controllers previously proposed have a small current regulation range. This paper proposes a modular interline power flow controller (IDCPFC) topology with a wide current adjustment range. It can be easily expanded into a multi-port IDCPFC due to its modularity and scalability. The current adjustment range of the proposed IDCPFC can be improved due to the modular structure and optimized control method. Meanwhile, the topology, operation principle and control strategy of the proposed topology are explained in this paper. The comparison with DCPFC topologies previously proposed demonstrates the advantages of wider adjustment range, lower cost and higher efficiency. Simulations performed in PSCAD/EMTDC and experiments based on a down-scaled prototype are completed. Simulation and experiment results validate the operation principle, control strategy and theoretical analysis results.