Investigation of Torque-Angle Characteristics of Synchronous Generators for Transient Stability Analysis Using Equal Area Criterion

Equal area criterion (EAC) has an equivalent concept to Lyapunov's energy function method and has been widely used for analyzing the transient behavior of synchronous generators (SGs) in power systems. This paper investigates various torque-angle characteristics of SGs that can be utilized along with the EAC approach for transient stability analysis (TSA). In addition to the two well-known transient characteristics that have been commonly used in the literature, a new transient torque-angle characteristic for SGs is introduced which uses transient reactance values in both
$d$
and
$q$
axes. Then, the error of EAC method in the calculation of critical clearing angle (CCA) and critical clearing time (CCT) is determined with different torque-angle characteristics for SGs, using computer simulations of a single-machine infinite-bus (SMIB) system. The calculated CCA and CCT values are compared and the accuracy of the subject characteristics for TSA are discussed.