A study on the nonlinear controller to prevent unstable Hopf bifurcation

A model of a power system with load dynamics is studied by investigating qualitative changes in its behavior as the reactive power demand at a load bus is increased. The load is composed of induction motors in parallel with the constant power and constant impedance load. The response of the system undergoes various bifurcations such as subcritical and supercritical Hopf, period-doubling and saddle-node bifurcations as the load increased. The latter may lead the system to voltage collapse. A nonlinear controller is used to control the subcritical Hopf bifurcation and hence mitigate voltage collapse and is applied to KEPCO (Korean Electric Power Company) system to show its validity.