Grid-Interfaced DFIG-Based Variable Speed Wind Energy Conversion System With Power Smoothening

This paper deals with the analysis, design, and control of grid-interfaced doubly fed induction generator (DFIG) based variable speed wind energy conversion system (WECS) for power smoothening with maximum power point tracking (MPPT) capability. This DFIG uses rotor position computation algorithm for the sensorless control through rotor position estimation. Power fluctuations due to the unpredictable nature of the wind are eliminated by introducing battery energy storage system (BESS) in the dc link between two back-to-back connected voltage source converters. The design of BESS is presented for feeding regulated power to the grid irrespective of the wind speeds. The control algorithm of the grid-side converter is modified for feeding regulated power to the grid. Rotor-side converter is controlled for achieving MPPT and unity power factor operation at the stator terminals. A prototype of the proposed DFIG-based wind energy conversion system is developed using a digital signal processor (DSP-dSPACE DS1103). This developed DFIG is tested extensively at different wind speeds and also presented some of the steady-state test results. Dynamic performance of this DFIG is also demonstrated for the variable wind speed operation.