Frequency, Voltage and Current Dynamics During Load Rejection and Sudden Load Connection in Island Operation of a Local Power System

U okviru rada modeliran je agregat sa sustavom uzbude i sustavom turbinske regulacije, spojen preko blok transformatora na sustav koji se sastoji od petnaest (15) čvorišta. Na gotovom modelu sustava provedene su dinamičke simulacije korištenjem programskog paketa PSS/E verzije V34, specijaliziranog za analize i proračune u elektroenergetskom sustavu. Analizirana je mogućnost stabilnog otočnog rada agregata sa stajališta naponske i frekvencijske stabilnosti. Promatran je dinamički odziv agregata na skokovite promjene opterećenja u pozitivnom (udarno terećenje) i negativnom (udarno rasterećenje) smjeru. Simulirani su različiti scenariji s obzirom na polazno stacionarno stanje sustava i korišteni model opterećenja (sa stajališta naponske i frekvencijske ovisnosti). Pokazano je je da promatrani agregat ima sposobnost stabilnog otočnog rada ako su zadovoljeni određeni uvjeti u sustavu.In this paper a generation unit together with the excitation system and the prime mover, connected through a step up transformer to the fifteen (15) bus power system, was modelled. Using a prepared model of the system dynamic simulations were performed using the PSS/E programming package, a specialized tool for power system analysis and calculations. The possibility of a stable island operation of the given unit was analyzed with respect to voltage and frequency stability. Dynamic response of the given unit during sudden load increase (load connection) and sudden negative load decrease (load rejection) was observed. Various scenarios were simulated based on the initial steady state of the system and using different load models (with respect to voltage and frequency dependency). The capability of a stable island operation of the given unit under specified system conditions was demonstrated