Stability Study of the Portugese Transmission Network with a High Share of Renewable Energies

Actually, the electric energy has a high importance in all activities, namely, the economic activity and on its development. Sectors of activity like, communications, transports, illumination and many others industrial processes are sustained. With the increase of the global energy needs, and considering the Kyoto´s protocol, the importance of green power as been increased. Based in that scenario, it´s easy to understand the appearance of new low capacity producers, which should satisfy certain operation parameters to be connected to the network. Connections of small electric energy producers lead to some problems related with the voltage stability on transport and distribution systems, being crucial the satisfaction of several parameters with the objective to guarantee the electric system stability. In this article, the state of the art for the stability problems in power systems is made, being specially analyzed the Portuguese case. It´s also analyzed lower producers response on voltage collapse and the parameters that they should satisfy in those situations.