DIRECT POWER CONTROL OF DFIG IN A WIND TURBINE TO IMPROVE DYNAMIC RESPONSE
Objective________________________________________
This paper presents a direct power control (DPC) strategy for a doubly-fed induction generator (DFIG)-based wind energy generation system. The strategy is based on the direct control of stator active and reactive power by selecting appropriate voltage vectors on the rotor side. The proposed direct power control (DPC) method produces a fast and robust power response without the need of complex structure and algorithms. Literature review________________________________________
There are two major classifications amongst wind generation units: fixed speed generation and variable speed generation. The fixed speed generators have a design speed for which they have maximum efficiency whereas for other speeds their efficiency is lower. But variable speed generators have the maximum power tracking capability that extracts maximum available power out of the wind at different speeds thereby resulting in more efficient operation. Also the variable speed generators reduce mechanical stresses on the turbine thus increasing the lifetime of the turbine. It also helps damp out oscillations in torques more efficiently. Thus variable speed generators are more commonly installed Fig.1. Block diagram of DFIG based WECS
Amongst the variable speed generators there are two major kinds, synchronous generators with direct power electronic converters and doubly fed induction generators with rotor side power electronic converters. Both have the above mentioned advantages of variable speed generators but the power electronic ratings of the two machines are different. In a doubly fed induction generator the power electronic converter has a rating of about 30% of the machine rating whereas for the synchronous generator the rating of the power electronic