The control objectives for a variable-speed wind turbine normally include limiting the captured wind power in the full-load regime and maximizing the harvested wind power in the partial-load regime. In this chapter, an adaptive controller for maximum power point tracking (MPPT) of a small variable-speed wind energy conversion system (WECS) is presented. The proposed control scheme has a generic structure and can be applied for different generator types. The simulation results show that the designed adaptive controller has good tracking performance, even with unmodeled dynamics and in the presence of parameter uncertainties and unknown disturbances.
According to the speed control criterion, WECSs can be classified into two types: fixed speed and variable speed. Since the rotor speed can be regulated within a large range, variable-speed wind turbines have a higher aerodynamic efficiency and are more widely used . Generally, the control system of a variable-speed WECS consists of three main sub-controllers: for pitch control, generator control and power transfer control, as illustrated in Figure 7.1.