The invention provides a compound type high-
voltage direct current transmission system which comprises at least one
rectifier station, a contravariant
station and an aerial
electric power transmission line. The
rectifier station and the contravariant station both comprise positive electrodes and negative electrodes, a
thyristor current converter is adopted in the
rectifier station, a positive
electrode and a negative
electrode of the
thyristor current converter both comprise at least one twelve-impulse
thyristor current converter, a
voltage source current converter which has
direct current fault
processing capacity is adopted in the contravariant station, and a positive
electrode and a negative electrode of
voltage source current converter both comprise at least one multi-level current converter with two series-wound modules. Connection points of the positive electrodes and negative electrodes of each station are connected with a grounding electrode or a local network according to
operation mode, a double electrode ground return wire or a single ground return wire or a
single electrode metal return wire, of the
direct current transmission system. By means of the compound type high-voltage direct current
transmission system, a commutation failure of the contravariant station in the direct current transmission
system is avoided,
operation mode is flexible, reliability is high, and project cost is reduced. Besides, the advantages of the thyristor current converter and the
voltage source current converter are integrated, and thus the compound type high-voltage direct current transmission
system has direct current side fault
processing capacity.