The effects of voltage collapse problems in the reliability evaluation of composite systems

This paper describes an approach to calculate voltage collapse related bulk reliability indices as well as their impact on the adequacy reliability indices of power systems. In this approach, the adequacy analysis of each selected system state is carried out in two steps. In the first, the minimum load shedding to restore system solvability is computed, neglecting operational constraints such as bus voltage levels and circuit power flows. In the second, the additional minimum load curtailment to alleviate any operating limit violations is calculated. In each step, optimal power flow is solved by a direct interior point algorithm, and related reliability indices are evaluated. The proposed methodology can be used in both enumeration and Monte Carlo methods. Case studies with a practical 11-bus network (the Brazilian Reduced Mato Grosso system) and with a 1600-bus network derived from the Brazilian South/Southeast/Central West system are presented and discussed.