Fuzzy logic based MPPT controller for a small wind turbine system

This paper describes the design of a maximum power point tracking (MPPT) strategy for a variable speed, small scale, wind turbine systems based on a fuzzy logic controller (FLC). The FLC has as input variables the change in mechanical power (ΔP_m), the change in rotor speed (Δω), and the sign of ΔP_m/Δω. The change of reference generator current (ΔI^*) is the output variable. For small power applications, when the turbine inertia is relatively small, and the wind speed changes continuously, it is important to consider the transients in order to develop an accurate theoretical model and to attain optimal operation. Therefore, the mechanical power (P_m) is composed of the generator mechanical (input) power (P_g) plus the dynamic power, resulting in the dynamic power versus rotating speed curve. The controller is able to track the maximum power point for changing wind conditions, and is robust with respect to turbine parameter changes. The FLC is described, analyzed and validated by digital simulations.