A sensorless control method for variable-speed small wind turbines

This paper describes an integrated sensorless control method for small variable-speed, fixed-pitch wind turbines with direct-drive permanent magnet synchronous generator (PMSG), which covers both partial- and full-load operation modes. In partial-load regime, the control system aims to maximize the wind energy conversion by keeping the wind turbine on its optimal power-speed characteristic, while in the full-load regime, when the generator reaches the rated power, the control acts over the rotor speed to create the condition of aerodynamic stall, and thus the output power is substantially reduced. Two PI controllers act on the generator speed and output power by measuring only two DC electrical quantities, i.e. voltage and current. The simulations accomplished with a reduced model and the experiments on a 2.2 kW laboratory test bench assess the effectiveness of the proposed control system. The results emphasize the performance of the proposed solution while also showing its limitations.