IOS analysis of electric power equipment based on integral-integral estimate and application examples

ISS(Input-to-State Stability) theory judges the stability of a system according to the stabilities of its interconnected subsystems, especially suitable for the stability analysis of an independent power system with variable topology, and to acquire the ISS/IOS(Input-to-Output Stability) property of equipment and make it less conservative is the prerequisites of its application. The definition of ISS represented as the L_∞ norm and its equivalence, the integral-integral estimate, are introduced. Because of the inverse time character of relaying protection devices, the integral-integral estimate is applied to analyze the ISS/IOS property of electric power equipment and the applicable range is used as reference to deal with the nonunique equilibrium point during topology change. It is proposed to estimate the ISS property of subsystem by simulation. Two equivalent methods are applied to estimate the ISS properties of generator and motor subsystems with PSCAD simulation software and results show the proposed integral-integral estimate is more suitable for the IOS analysis of electric power equipments.