A comparative analysis between two approaches for the simulation of power system electromechanical transients

摘要

Traditionally, due the high effort involved in the simulation of power systems electromechanical transients, this simulations is carried out the so-called phasor model approach. This approach considers de following main simplifications: equal distribution of loads among the phases, representation of elements by lumped and identical parameters in all phases, invariance of this elements with respect to the frequency, representation the sinusoidal quantities by phasors and the representation of the system by its one-line diagram. These assumptions are valid for the bulk power system because utilities do their best to balance the loads at substation level, so the transmissions circuits operate with almost identical power in each of their phases. Recently, however, there has been an expansion in the number of synchronous generators connected directly to distribution feeders. In this context, some of the assumptions in the phasor model approach are no longer valid, mainly with respect to the unbalanced operating conditions. Therefore, a detailed three-phase representation is mandatory for the simulation of electromechanical transients originated from de mentioned connections. For this reason, the main objective of this paper is compare the results of simulations using the two previously mentioned approaches for a synchronous generator connected to a balanced distribution feeder. Once an agreement is reached between these two results, the confidence provided by this agreement will make it possible to proceed using the detailed three-phase model to simulate electromechanical transients under unbalanced conditions.