A MRAS Observer for Sensorless Operation of Grid-Connected BDFRG Wind Turbines

A novel rotor speed and position observer for sensor-less vector control of a brushlesss doubly fed reluctance generator (BDFRG) is put forward in this paper. Implementing such an estimation technique would eliminate the need for a shaft encoder, improving so the reliability and reducing the maintenance costs in wind power applications, off-shore in particular. The proposed model reference adaptive system (MRAS) observer retrieves the rotor speed information by driving the errors between the measured secondary currents and their speed dependent estimates to zero. Unlike the documented MRAS schemes for the BDFRG, the estimated currents are accurately derived from the grid voltage and current measurements, which has ensured a more robust performance and higher observer precision. The realistic simulation studies have showcased the prospective controller stability and insensitivity to the machine parameter mismatches across the whole speed range under variable loading conditions of the BDFRG typical for horizontal-axis wind turbines.