Design aspects of upgradation from 6 pulse to 12 pulse operation of NHVDC project

In India, the first HVDC project was a back to back link between the Northern grid and the Western grid at Vindhyachal. This project was commissioned by an external agency. The Government of India approved a proposal for an experimental HVDC line project to give Indian planners, manufacturers and utilities an opportunity to absorb the technology. This project was to be designed and commissioned with cooperation of a number of Indian agencies. Stage-I of this National HVDC (NHVDC) project was successfully commissioned in October 1990, and has since been operating quite satisfactorily. In continuation of that effort, the Government of India has since approved stage-II of the NHVDC project. In stage-II the focus is on modernisation and project engineering. The major change in stage-II are the modernisation of the controls. Upgrade details and the care being taken to have minimum disturbance to the existing setup, is discussed in this paper. The operational requirements, system solutions and control system aspects which have been considered and are being implemented for this project are also covered.