Power System Stability Enhancement by Simultaneous AC-DC Power Transmission

Abstract

It is difficult to load long extra high voltage (EHV) ac lines to their thermal limits as a sufficient margin is kept against transient instability. With the model proposed in this thesis, it will be possible to load these lines close to their thermal limits. The transmission lines are allowed to carry usual ac along with dc superimposed on it.
The added dc power flow does not cause any instability. This thesis gives us the feasibility of converting a double circuit ac line into composite ac–dc power transmission line to get the advantages of parallel ac–dc transmission in order to improve stability and dampen out oscillations.
The advantage of parallel ac-dc transmission for improvement of transient stability and dynamic stability and dampout oscillations has been established. Simulation has been carried out in MATLAB software package (Simulink Model). The results show the stability of power system both for natural response and response under faulty conditions.