Voltage stability assessment with inclusion of hard limits

The work presents new methodologies in order to represent, with more accuracy, the hard limits of voltage regulators in modal analysis. These hard limits are treated in the linearisation process by Taylor and power series and hyperbolic functions. The procedures required to adapt a conventional load flow in order to include a more realistic behaviour of generators in the determination of initial conditions are described. A methodology is presented which considers the dependence of generator reactive power limits on the operating conditions. Such procedures aim at a more realistic analysis of the power system especially at high loadings. Results are presented for a power system which validate the proposed methodologies