28 Small Scale Wind Energy Conversion Systems Mostafa Abarzadeh, Hossein Madadi Kojabadi 1 and Liuchen Chang 2 1 Sahand University of Technology 2 University of New Brunswick 1 Iran 2 Canada 1. Introduction Electricity generation using wind energy has been well recognized as environmentally friendly, socially beneficial, and economically competitive for many applications. Because of crucial fossil energy resources shortage and environmental issues the wind energy is very important resource for electricity production. Small wind turbines, photovoltaic systems, full cells and pump as turbines (PAT) in small scale are main resources for distributed generation systems. Meanwhile, for remote areas wind energy beside photovoltaic system can combine as a hybrid system to provide necessary electric power of users. This system should be designed in such a way that the load demand of remote areas be provided with maximum reliability. Usually Direct coupled axial flux permanent magnet synchronous generator (AFPMSG), self-excited induction generator with gear box and permanent magnet synchronous generator(PMSG) with gear box can be used to connect to small wind turbine. In the past few years, there have been many studies on small scale wind energy conversion systems. Authors of (Jia Yaoqin et al., 2002), (Nobutoshi Mutoh et al., 2006), (T.Tafticht et al., 2006), (Ch.Patsios et al., 2008) and (M.G.Molina et al., 2008) presented maximum power point tracking(MPPT) methods for small scale wind turbines. (Etienne Audierne et al., 2009), (M.G.Molina et al., 2008), (Boubekeur Boukhezzar et al., 2005), (Md.Arifujjaman et al., 2005) and (Jan T.Bialasiewicz, 2003) described small scale wind turbine furling system and modeled small scale wind turbines. In this chapter we reviewed the working principles, over speed, output power control and MPPT control methods of small scale wind energy conversion system. 2. Wind turbine characteristics The kinetic energy of the air stream available for the wind turbine given by 2 1 2 a E vV ρ = (1) where a ρ is air density, v is the volume of air available to the wind turbine rotor and V is the velocity of wind stream in / m s . The air parcel interacting with the rotor per second has a cross-sectional area equal to that of the rotor ( 2 ( ) T A m ) and thickness equal to the wind velocity ( ( /) Vm s ). Hence power of air stream available for wind turbine given by www.intechopen.com