Impact of distributed synchronous and doubly-fed induction generators on small-signal stability of a distribution network

The increase in the demand for electric energy, the technological developments, and the environmental problems have led to a strong trend for the use of distributed generation (DG) in power systems. This kind of generation presents many advantages over the conventional centralized generation (as for example, low environmental impact and reduction of the transmission losses). However, the distributed generation units (DGUs) may affect the power system dynamics in a meaningful way. In the context of small-signal stability, this work investigates electromechanical oscillations caused by DGUs connected to distribution networks. The carried out study takes into account two kinds of DGUs widely employed nowadays: synchronous generator (SG) and wind energy conversion system based on doubly-fed induction generator (DFIG). The main factors affecting the electromechanical oscillations of DGUs based on SG and DFIG are discussed and evaluated. The possible interactions between SG and DFIG, operating simultaneously in a distribution system, are also evaluated.