Patent ID: 11894684
Assignee: HITACHI ENERGY LTD
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H  Y | IPC H

Claim 11:
12. A method of upgrading a line-commutated converter (LCC) high-voltage direct current (HVDC) system to a voltage source converter (VSC) HVDC system, the LCC HVDC system comprising a plurality of LCC transformers, a plurality of LCC units, and a plurality of bypass breakers, the plurality of LCC transformers include tap changers, the method comprising:
disconnecting the LCC units from the LCC transformers;
removing the LCC units;
replacing the removed LCC units with a plurality of VSC units;
coupling the VSC units in series with each other;
coupling the VSC units to the plurality of LCC transformers, so that the VSC HVDC system comprises the plurality of VSC units coupled in series, and each LCC transformer respectively coupled to a single converter unit of only the VSC type; and
adjusting the tap changers of the LCC transformers to lower an output voltage of the LCC transformers.