Characteristic study for integration of fixed and variable speed wind turbines into transmission grid

Abstract

Wind energy is emerging as an increasing viable source of energy. Many of the newly developed wind power plants are expected to come from offshore, which usually requires the integration of an offshore wind power plant into the grid through a long transmission cable. This paper studies the characteristics of a wind energy conversion system (WECS) when it is integrated to the grid in typical offshore applications using either fixed-speed induction generator (IG) or variable-speed doubly-fed induction generator (DFIG) wind turbines. Steady-state models in d-q reference frame are developed for single wind turbine, a simplified wind farm, and an integrated WECS and grid system. Stator voltage oriented frame is utilized to investigate DFIG-based WECS characteristics under different d-q control conditions. Parallel and series compensations, normally used to improve WECS performance, are simulated and investigated. Comparisons are made for WECSs using fixed-speed IGs and variable-speed DFIGs.