Decoupled control of active and reactive power for a grid-connected doubly-fed wound rotor induction machine without position sensors

In this paper field-oriented control of a doubly-fed wound rotor induction machine without shaft position sensors is presented. The stator is directly connected to the constant frequency three phase grid and the rotor currents are appropriately controlled to vary the slip power thereby enabling variable speed constant frequency operation. Instead of using dynamic angle controllers for rotor position estimation, a direct method based on simple transformations is proposed. The control algorithms are implemented on a DSP-based hardware platform and tested on a laboratory motor-generator set. Details of the algorithms, implementation, and relevant experimental results are presented.