Heidari - Tarbiat Modarres University Tehran -; Iran
Parsa - Tarbiat Modarres University Tehran -; Iran

Lightly damped or even negative damping oscillatory modes associated with rotor dynamics of synchronous machines are widely experienced in practice. Power system stabilizer are usually used to enhance system stability. In multimachine Power systems, The best to be equipped with stabilizers for the damping of troublesome moeds are not easily identified.In the literature there has been several studies concerning pss allocation in multimachine power systems. This paper makes an overview on some of these methods and presents an effective method in etail.In this method an index so called Mode Input Assignability Index is introduced by which we can determine strongness of thecoupling between oscillatory modes and particular generator. Numerical study on a 13-machine system is done to evaluate the effectiveness of the method.