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

Claim 15:
16. 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 first LCC converter unit coupled between a first node and a second node, a second LCC converter unit coupled between the second node and a third node, a third LCC converter unit coupled between the third node and a fourth node, and a fourth LCC converter unit coupled between the fourth node and a fifth node, a first LCC transformer coupled between an AC network and the first LCC converter unit, a second LCC transformer coupled between the AC network and the second LCC converter unit, a third LCC transformer coupled between the AC network and the third LCC converter unit, and a fourth LCC transformer coupled between the AC network and the fourth LCC converter unit, a first bypass breaker coupled between the first node and the third node, and a second bypass breaker coupled between the third node and the fifth node, the method comprising:
replacing the first LCC converter unit with a first VSC converter unit and coupling the first VSC converter unit to the first LCC transformer, the first node, and the second node;
replacing the second LCC converter unit with a second VSC converter unit and coupling the second VSC converter unit to the second LCC transformer, the second node, and the third node;
replacing the third LCC converter unit with a third VSC converter unit and coupling the third VSC converter unit to the third LCC transformer, the third node, and the fourth node;
replacing the fourth LCC converter unit with a fourth VSC converter unit and coupling the fourth VSC converter unit to the fourth LCC transformer, the fourth node, and the fifth node;
coupling a third bypass breaker between the first node and the second node;
coupling a fourth bypass breaker between the second node and the third node;
coupling a fifth bypass breaker between the third node and the fourth node;
coupling a sixth bypass breaker between the fourth node and the fifth node; and
adjusting tap changers of the first, second, third, and fourth LCC transformers to lower an output voltage of these LCC transformers.