Damping of the low-frequency oscillations of the generator: dynamic interactions and the effectiveness of the controllers

Dynamic interactions among various controllers used for stabilising a synchronous generator are investigated. The effectiveness of a power system stabiliser (PSS) connected to the exciter and/or governor in damping electromechanical oscillations of an isolated synchronous generator is examined. The interaction(s) among power system stabiliser(s) connected to the exciter and/or the governor loop, automatic voltage regulator, governor and multi-stage double-reheat turbine and dynamic load are considered. It is shown that depending on the type and number of controllers used and dynamics modelled, interactions can result in unstable operation of the system for a range of operating conditions. It is also shown that the power system stabiliser connected to the governor loop provides better damping of low-frequency oscillations and better robustness of the generator to a change in operating conditions than the PSS connected to the exciter loop.