Transient Stability Improvement of Two Machine System using Fuzzy Controlled STATCOM

Today Transmission & Distribution network of power systems are very stressed due to growing demand of better quality of power at lower cost. As a result transmission networks are operating on high transmission levels. Transient stability, damping oscillations etc are the major operating problems that power engineers are confronting during transmitting power at high levels.Transient Stability indicates the capability of the power system to maintain synchronism when subjected to a severe transient disturbances such as fault on heavily loaded lines, loss of a large load etc [1].Generator excitation controller with only excitation control can improve transient stability for minor faults but it is not sufficient to maintain stability of system for large faults occur near to generator terminals [2].Researchers worked on other solution and found that Flexible ac transmission systems (FACTS) is one of the most prominent solution that can improve stability by changing electrical characteristics of Power system [3],[4]. A static synchronous compensator is one of the FACTS device operated on principle of reactive power compensation can use to improve the transient stability of the system by increasing (decreasing) the power transfer capability when the machine angle increases (decreases) [5]. Static synchronous compensator’s three modes i.e. capacitive mode, inductive mode and no load mode regulates voltage in transmission system. When Converter a.c. output voltage (Vc) > transmission system voltage (Vs), STATCOM considered to be in Capacitive mode and when Vs > Vc, STATCOM considered to be in inductive mode and in No-Load mode Vs=Vc, no reactive power exchange takes place [6]. STATCOM mainly