Voltage stability constrained load curtailment procedure to evaluate power system reliability measures

This paper reports a method to evaluate composite power system reliability indices incorporating the voltage stability margin criteria. To compute the load curtailment evaluation, an optimal power flow (OPF) computation algorithm, considering the steady state voltage stability margin constraint is developed. A steady state voltage stability indicator is first discussed for its applicability as a suitable indicator for representing stability margin from the collapse point. The load curtailment formulation is then evolved and described in the OPF´s objective function. A criterion based on the voltage stability indicator is then incorporated as an additional constraint into the OPF. A numerical example has been used to illustrate the effect of the algorithm on the composite system reliability evaluation. The expected energy not served (EENS) and down time is computed, both analytically and by the Monte Carlo Simulation.