Power system direct stability analysis with nonlinear load models

The author presents a formulation of the transient energy function method with nonlinear loads. It is based on the full network representation, allowing the use of sparse matrix methods for efficient computations of the unstable equilibrium point. Assuming negligible line conductance values, the expression for the potential energy function can be obtained in closed form except for the term associated with real power loads. This term can be approximated numerically using integrals along a linear trajectory in the machine angle space