Impact of Wind Farms in Power Systems

Beyond any doubt, we can consider century 21st as the one devoted to renewable energy. According to the International Energy Agency (IEA) (IEA, 2009) renewable sources shall provide about 35% of the European Union’s (EU) electricity by 2020, and within this context, wind energy is set to contribute the most nearly 35% of all the power coming from renewable sources. This evolution is based on sustainability scenarios, like the BLUE one (IEA, 2008) related to the reduction of greenhouse emissions. However, the appropriate integration of such renewable energy into power system grids still presents major challenges to Power Systems Operators (PSO) and planners. Nowadays wind energy has widely proved to be one of the most competitive and efficient renewable energy sources and, as a result, its use is indeed continuously increasing. As an example, in June 2010 total installed wind energy capacity around the world was 175,000 MW. Incorporation of wind energy units into distribution networks not only modifies power flows but also, in some situations could also result in under or over-voltage on specific points of the network (Jenkins, 2000), as well as could increase the cases of power quality problems and produce any type of alterations regarding voltage stability (Abdullah et al., 2010, Baghaee et al., 2009). The process of high wind energy penetration requires the impact analysis of this new technology in power systems. In these terms, some countries have developed grid codes in order to establish the requirements of wind farms (WF) into power networks. Moreover, power network planning with high wind energy penetration requires the definition of several factors, such as: the best technology to be used, the optimal number of units to be connected and the optimal size to be chosen. Currently a connected variable speed wind turbine to power systems by means of power electronics has the ability to supply reactive power to power systems. This capability allows wind turbines to participate in ancillary services as synchronous generators (Bhattacharya & Zhong, 2001), however, there are little works focusing on the participation of variable speed wind turbines in reactive power ancillary services (Amaris & Alonso, 2011; Bhattacharya & Zhong, 2001). In this chapter, a review of wind farms impact on power networks and on Grid codes requirements are analyzed. An optimal allocation of wind farms has been selected in order to maximize the system loadability as well as to reduce active any power losses of the whole network by using an optimization algorithm where reactive power capability of Double Fed Inductor Generator (DFIG) is already included in the formulation. Finally, conclusions and future researches are shown.