Adaptive concept of controlled islanding in power systems for wide-area out-of-step prediction of synchronous generators based on adaptive tripping index

Here, based on wide-area measurement systems (WAMS), an adaptive tripping index (TI) is proposed for online prediction of tripping signals with respect to wide-area out-of-step (WAOOS) protection of synchronous generators. The proposed TI included two different equations consisting of a straight line for unstable inter-area oscillations and a sinusoidal line for WAOOS transient instability. For online identification of coherent generators with respect to inter-area oscillations, based on evaluating the correlation coefficients between generator behaviours, an index is proposed from which the global tripping signals (GTS) are calculated. The GTS consist of the rate of change of inter-area rotor angle oscillation between two oscillating areas in the centre of inertia frame. Actually, the proposed scheme is an adaptive and online index from which the critical inter-area angle is adjusted individually by evaluating GTS at each sampling time gathered from the WAMS data. The proposed strategy is implemented on an IEEE 39-bus test system and its performance is investigated by simulating typical scenarios during time-domain simulations. The results show the effectiveness of the proposed scheme for fast prediction of WAOOS protection in real-time environment.