Hybrid direct current transmission system

A hybrid direct current transmission system. The hybrid direct current transmission system is of a bipolar structure, comprising a positive convertor transformer (T1) and a positive converter (LCC), as well as a negative convertor transformer (T2) and a negative converter (MMC). In the bipolar structure, the converter on one pole is an MMC converter consisting of an MMC sub-module, and the other pole is an LCC converter system consisting of at least one LCC. The hybrid direct current transmission system has features of the mature technology and low costs of the LCC-HVDC, and also has advantages of no commutation failure, flexible control, and strong extension performance of the VSC-HVDC.