Stability improvement of simultaneous AC-DC power transmission system

This paper presents the concept of simultaneous ac-dc power transmission system with newly designed self adaptive Voltage Dependent control (VDCOL) procedure. Long ac transmission lines cannot be loaded to their thermal limits due to instability occurs in the power system. It is difficult to load long 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 and the conductors are allowed to carry usual ac along with dc superimposed on it. This thesis with newly designed controller gives us the feasibility of composite ac-dc power transmission line to get the advantages of parallel ac-dc transmission in order to transient stability and dynamic stability and dampen out oscillations. Simulation has been carried out during 1-phase and 3-phase fault in MATLAB software package (Simulink) to prove system stability enhancement.