(SAIEE Publications., 2013) Chetty, Leon.; Ijumba, Nelson Mutatina.
Line Current Commutated (LCC) HVDC systems consists of uncertain plants. These
uncertainties are result of changes/disturbances in the ac networks or in the LCC HVDC system itself.
Further uncertainties can be introduced due to simplified system modelling techniques. Quantitative
Feedback Theory is a frequency-domain technique that utilises the Nichols chart to achieve a robust
design over a specified region of uncertainty. The Quantitative Feedback Theory design philosophy
was applied to design the LCC HVDC control system parameters. The stable start-up and step
responses of the LCC HVDC system, for varying ac system conditions, conclusively validate the
Quantitative Feedback Theory design method of the LCC HVDC control system parameters.
