چكيده به لاتين
In this dissertation, first, trigonometric, polynomial, and hybrid models of rotor angle trajectory based on the reasonable assumptions are presented. Then, as the first approach in designating the optimal data window (DW), by computing the second order derivative of post-fault data, the starting point of the calculation the DW is determined. In the second approach, based on defining the forecast horizon (FH) and DW with incremental length, maximum use of available data will be assumed to predict the stability/instability of generating units. Afterwards, two response-based approaches for online prediction of power system angular instability are presented. The proposed methods utilize bus phase angle data measured by phasor measurement unit at the point of common coupling of power plant transformer to the bulk power grid. Next, three aforementioned models are fitted on the designated DW to predict the angular curve of generating unit. Based on the sign of the first order derivative of predicted curve in specific FH, the angular stability of generating unit is judged. These approaches are testified on the SIME and the WSCC standard test bed under different operation and fault type scenarios. Simulation results confirm that the proposed methods outperform the existing ones in terms of accuracy, speed, and applicability in generator rejection schemes (GRS) to prevent severe power plant outages. Finally, a response-based GRS based on an angular stability prediction logic to initiate the outage of accelerated generating units while saving the rest of generating units from the loss of synchronism is presented. In the developed logic, if at least two models of the three aforementioned models yield the same response about the unit stability status, the trip signal is accordingly fired or blocked. Simulation results demonstrate that beside simplicity, low computational burden, and very short processing time,the proposed combinatorial method outperforms the existing ones working with individual prediction models.
