Modular Multi-Level Multi-Line DC Power Flow Controller for Meshed HVDC Grids Enabled by Decentralized Power Exchange Mechanism

Multi-line DC power flow controller (MDCPFC) has emerged as a promising candidate to increase the control degrees of freedom for power flows in multi-terminal DC grids. Characterized by centralized internal power exchange, traditional MDCPFCs inevitably suffer from high stress across semiconductors and reduced regulation ranges. To address these challenges, an interleaved modular multi-level MDCPFC (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\rm {IM^{3}DCPFC}$</tex-math></inline-formula>) is proposed and a novel decentralized power exchange mechanism is presented in this paper. The proposed topology features high voltage scalability and extended operation range. To fully unleash the power flow control capabilities of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\rm {IM^{3}DCPFC}$</tex-math></inline-formula>, an optimal power exchange scheme is developed via a close-form solution, paving way for complex power flow manipulations in real engineering. Meanwhile, a comprehensive steady-state analysis method is developed against <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\rm {IM^{3}DCPFC}$</tex-math></inline-formula>, offering an accurate and high-efficient solution to the characterization of its steady-state performance. Simulations and in-house hardware experiments validate the operation principles, control scheme and theoretical analyses of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\rm {IM^{3}DCPFC}$</tex-math></inline-formula>.