Control of a doubly fed induction machine in a wind energy conversion system

Abstract

This paper presents research done on the closed-loop control of the Doubly Fed Induction Machine (DFIM) applied to a Wind Energy Conversion System (WECS). Basic generator configurations used in wind energy systems, mainly fixed-speed and adjustable speed generators are discussed. A suitable Stator Flux Oriented (SFO) control topology for the DFIM is shown with which it is possible to control the stator active and reactive power. The control system designed was implemented on an experimental rig which emulates the behaviour of a practical WECS. A brief overview of sensorless algorithms is also presented; these algorithms are used to provide rotor speed/position estimates in the absence of a speed sensor. Practical results in both sensored and sensorless operation are shown including measurements for rotor currents, stator active/reactive power and rotor speed/position estimates.