Abstract
This paper describes an index for judging the severity of transient events of power systems in simulation. The proposed transient stability index, known as the area‐based COI‐referred rotor angle index, is developed by considering the fact that a large‐sized power system is divided into several areas according to the coherency of generators in a particular area. It can be assumed that an equivalent single large machine can represent all the generators in that area. Thus, the assessment of rotor angles for all generators can be simplified by only assessing the index of areas in a power system. The effectiveness of the proposed index in assessing the stability of power systems and its ability in pinpointing the weakest area in the power system is analyzed. Furthermore, this paper developed an emergency control scheme known as the combined UFLS and generator tripping in order to stabilize the system when unstable faults occurred in a power system. The proposed index is used to identify the generator to be tripped when the developed emergency control scheme operates. The performance of the proposed index and the combined UFLS and generator tripping scheme are evaluated on the IEEE 39‐bus test system.
Highlights
Methods normally employed to calculate TSI are by using time domain simulation 1, direct 2–4, and hybrid methods 5–8
Time domain simulation method is used in this work to assess the transient stability of the power system because it is the most reliable, mature and accurate method compared to other method
A new TSI called area-based COI-referred rotor angle index is developed for assessing transient stability of large power systems
Summary
Methods normally employed to calculate TSI are by using time domain simulation 1 , direct 2–4 , and hybrid methods 5–8. A type of hybrid method known as the marginally unstable injection method 9 uses a reduced TEF and a feedback mechanism to provide a more accurate and consistent TSI Another hybrid method which incorporates the extended equal area criterion method into the time domain simulation has been used to obtain the TSI for classifying whether a power system is stable or unstable 6. The single machine equivalent method which is a hybrid method is used for fast computation of TSI and identification of critical machines 7 Another TSI known as the integral square generator angle index has been developed to measure the severity of transient disturbances and used as part of transient stability control 5
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