Intentional power system islanding under cascading outages using energy function method

In this study, the 'where to island' issue under the transient stability constraints is addressed. Without considering the transient stability, the islanding strategy may fail to stop the propagation of harmful dynamics throughout the network. This study promotes the current available controlled islanding model to handle the transient stability criteria, which is the most important issue during network splitting. Based on the wide area measurements, a two-stage transient stability constrained network splitting model is developed using a proper transient energy function. In the first stage, the conventional intentional splitting problem is formulated as a mixed-integer linear programming (MILP) optimisation model with considering operational, coherency and linear AC load flow constraints. The boundary of each island is determined using an optimisation model to achieve the minimum total power imbalance. To assess the transient stability, the network splitting plan obtained from the first stage is then evaluated in the second stage using a transient energy function. In the second stage, to satisfy the transient stability constraint of the critical island, a linear constraint is constructed and added to the MILP formulation of the first stage. In the second stage, the saddle or control unstable equilibrium points are determined using an optimisation model.