Sensorless variable speed operation of doubly-fed reluctance wind generators

An improved and more robust flux vector orientated control scheme for an emerging doubly-fed reluctance generator without a shaft angular position or velocity sensor has been proposed, computer-simulated, and experimentally verified. Whilst retaining the cost and other advantages of using a fractional power electronics converter rating, this promising medium-speed brushless machine technology has been viewed by research and industrial communities as an appealing economical solution for the compromised reliability and high maintenance requirements associated with the presence of slip rings, brushes, and the failures prone three-stage gearbox of conventional wound rotor doubly-fed induction generators, traditionally deployed for commercial wind turbines. The comprehensive comparative simulation and test results obtained have been shown to agree very well undoubtedly demonstrating the good overall performance of the sensorless controller. A precise speed reference tracking with smooth, intrinsically decoupled real and reactive power responses of the grid-connected winding has been achieved for the typical variable loading profiles and narrow speed ranges (e.g. around 2:1 or so) of a laboratory emulated wind turbine.