Improved techniques for hybrid method in fast-transient stability assessment

The theoretical background and the development of new techniques for the implementation of hybrid methods in online fast-transient stability assessment are presented. For evaluation of transient energy margin (TEM) along a trajectory, a transformed transient energy function (TEF) is defined. It is proved that along a postfault trajectory the transformed TEF is conserved. Based on the conservation principle and using techniques such as integration stopping criteria and location of the main potential energy peak, an improved pseudofault method for TEM evaluation is reported. These techniques have been tested on several test power systems with different system models. Results show that the proposed techniques are useful. An example shows the improvement of the techniques over the recently published hybrid method