A STATCOM controller provides voltage support by absorbing or generating reactive power at the point of coupling without the need of large external reactor or capacitor banks. Additionally damping controller is added into the STATCOM for enhancing the power system oscillation stability.

The thesis deals with the design of STATCOM controllers. Investigations have been carried out considering single machine infinite bus system and STATCOM is connected at midpoint of the transmission line. The main objective is to regulate midpoint voltage and damp out the power system oscillations by STATCOM controllers. The controller parameters are optimized using linear dynamic models of the system (known as modified Heffron-Phillips model).

A detailed model of the STATCOM has been developed to study dynamic responses of the system under Simulink/Matlab environment. Models of both power circuit and control circuit have been implemented. Investigations are carried out considering two alternative control strategies.

Investigations have also been carried out to examine whether the STATCOM based damping controllers designed using linear models assist in improving transient stability of the system. The dynamic interaction of PSS and STATCOM based damping controller has been investigated.