High-power hybrid commutated converter for carbon-neutral power transmission

To achieve carbon neutrality, we must overcome the challenges associated with the long-distance and large-capacity transmission of renewable energy. Direct-current transmission system has advantages in terms of high voltage and high controllability over the alternating-current transmission system. First-generation line-commutated-converter-based high-voltage direct-current systems risk commutation failures that threaten the safety of power grid, whereas second-generation voltage-source-converter systems entail higher carbon emissions, lower robustness, and higher power loss. We propose a next-generation high-power hybrid commutated converter that accesses renewable power, eliminating commutation failures through its hybrid operation modes of forced and recovery-enhanced commutation, with a hybrid device connection topology. We investigate the commutation principles and present the system design. Experimental results from a 120 kV/360 MW prototype demonstrate the efficacy of this high-power converter, which has been deployed in the Lingbao super-high-voltage direct-current project in Henan, China, and Mengxi ultra-high-voltage direct-current project in Inner Mongolia, China.