Loadability Assessment and Enhancement in Unbalanced Distribution Systems

Voltage stability is a major concern in heavily loaded distribution networks. Careful determination of control parameters for loadability enhancement may maximize the utilization of distribution networks. In applicable studies, most of the approaches optimize real/reactive power losses for the current operating conditions of the distribution network. Although, these types of approaches increase the stability margin, such an increase may not be sufficient. The most important factor in loadability enhancement is representation of future load scenarios in addressing the optimization problem. In this paper a look ahead approach is developed for loadability enhancement of an unbalanced distribution system. The determination of the critical loading point is conventionally done using continuation power flow, which is computationally very demanding, and also complex for implementation in unbalanced distribution networks. Therefore, a new, computationally very efficient voltage stability indicator is developed here for determination of the loadability limit. The proposed methodology is demonstrated on IEEE 4 bus and 25 bus unbalanced distribution systems with different transformer connections.