Topologies and control of low-frequency alternating current for offshore wind farms based on modular multilevel matrix converter

As a new alternative to power transmission, low-frequency alternating current (LFAC) transmission system has a bright future for offshore wind power transmission. As a core equipment for LFAC system, modularised multi-level matrix converter (M3C) is a direct electric energy conversion device, which can achieve bi-directional power flow and provide any value of the power factor. In this study, the application of LFAC transmission system based on M3C (M3C-LFAC) for offshore wind farms is studied. For the characteristics of LFAC transmission system for offshore wind power, four types of LFAC offshore wind power grid-connected topological structure are proposed, and related control strategies are designed. By use of PSCAD/EMTDC to verify the feasibility of the proposed schemes, the advantages of the proposed topologies are verified through different working conditions.