Communication-Less Reactive Power Control of Grid-Forming Wind Turbines Connected to Cascaded LCC-DR HVDC System

To achieve long-distance transmission of onshore wind power, different high-voltage direct-current (HVDC) technologies have been proposed, including the line-commutated converter (LCC), the modular multilevel converter (MMC), and the cascaded LCC-MMC converter. However, there is still room for improvement in existing topologies. This paper proposes a cascaded LCC-DR HVDC transmission system and the corresponding communication-less reactive power control (CLRPC) for the grid-forming wind turbines, ensuring operational reliability with good economic efficiency. Firstly, the topology and control strategies of the cascaded LCC-DR HVDC transmission system are introduced. Then, the operation principle and threshold design of CLRPC are analyzed. Finally, the feasibility of the proposed structure and control strategies under various operation scenarios are verified in PSCAD/EMTDC.