A Sensorless Adaptive Maximum Power Point Extraction Method With Voltage Feedback Control for Small Wind Turbines in Off-Grid Applications

Due to the ever growing global energy demand and pollution levels, clean and renewable alternative energy resources, such as wind, have become indispensable for preserving the planet for future generations. With wind being an unpredictable resource, it is imperative that wind systems extract as much power from the wind as possible while it is available. The conventional maximum power point tracking (MPPT) algorithms that use predetermined mathematical relationships to represent a specific wind system´s power/torque characteristics suffer the drawback of deteriorated efficiency over time whereas the perturb and observe algorithms are susceptible to logical errors when subjected to frequent atmospheric variations. In order to solve the aforementioned drawbacks as well as to reduce the cost of the sensing network required to achieve MPPT, this paper proposes a novel sensorless slope-assisted MPPT algorithm that is able to avoid logical errors attributed to wind fluctuations by detecting and identifying atmospheric changes. Atmospheric changes are detected by a state observer by monitoring the generator output power, the ac/dc rectifier output voltage, and the rate of change of the power-voltage ratio without the need for anemometers and any generator speed sensors. The detailed description of the proposed MPPT control logic will be provided in this paper. The functionality of the proposed control method is verified through the simulation results on a 3-kW system, as well as the experimental results on a proof-of-concept 200-W prototype.