Study On The Feasibility Of Widely Usage Of PSSs. In Multi-Machine Power System

As the power grid is growing larger and larger, PSS is widely used in our country to damp electromechanical oscillations. But in a Multi-Machine Power System, would PSS weaken other electromechanical mode's damping while enhancing some electromechanical mode's damping? If that is ture, how much damping the PSS may weaken? These are all key issues in applying PSSs widely. This paper calculates the sensitivities of eigenvalues to the PSS gain (Kpss) and discussed the relations between Kpss and the sum of all system' s eigenvalues, the different influences to the electromechanical mode and non-electromechanical mode by PSS. The main work and contribution are as follows:1. Kpss doesn' t change the sum of the real part of all system' s eigenvalues. When Kpss changes, all eigenvalues' real parts changes, but the sum of the real part of all system' s eigenvalues doesn' t change.2. Caculating the sensitivities of eigenvalues to the PSS gain (Kpss), and the sensitivities of eigenvalue's damping to the Kpss. The influence to the electromechanical mode and non-electromechanical mode of PSS is clarified by using a single-machine infinite bus system and a 3-machine example. Otherwise, this paper analyses the influence to all 11 electromechanical modes of PSSs.in a 12-machine system.3. When PSS are widely used in Multi-Machine power system, PSS would neither weaken other electromechanical modes' damping nor non-electromechanical modes' damping too much while enhancing some electromechanical modes' damping. So PSS can be widely used in Multi-Machine power system.