Interleaved Modular Multi-Level Multi-Line DC Power Flow Controller: Phasor-Domain Modelling and Analyses of Operation

The Multi-line DC Power Flow Controller (MDCPFC) is a promising candidate to increase the control degrees of freedom of power flows in meshed DC grids. To boost the voltage rating and operation range of MDCPFCs, an interleaved modular multi-level MDCPFC (IM³DCPFC) is proposed in this paper. Phasor-domain modelling and analyses are conducted to accurately unveil its operation principles. Firstly, the circuit topology of the proposed IM³DCPFC and its key electrical quantities are elaborated on. Secondly, through phasor-domain modelling, the internal energy exchange mechanism underlying the proposed IM³DCPFC is clarified. Furthermore, a hierarchical steady-state model is developed to precisely calculate its operation point. Besides, a tailored control scheme for the proposed IM³DCPFC is designed. Finally, simulations verify the effectiveness of the proposed topology.