A Novel Structure Preserving Energy Function for Direct Stability Evaluation of Power Systems with Known Modes of Instability

ABSTRACT A new structure preserving energy function (SPEF) incorporating mode of instability is presented alongwith application for direct transient stability evaluation of power systems. It is assumed that a fault at the terminals of a generator splits the system into two groups, each group having one or more machines in it and that the machines within a group swing together. The kinetic energy term of the proposed energy function depends on the relative velocity of these two groups and accurately estimates the component of the energy responsible for system separation. Structure preserving model of the system is used and the loads are modelled as arbitrary functions of respective bus voltage. The application to direct stability analysis is provided with the help of a 7-machine and a 10-machine system examples.