Performance Analysis of Unified Doubly-Fed Induction Generator for Wind Power Application

Abstract

Increasing penetration of the large wind farm in the system has forced the power system policy makers to develop new electricity grid codes which are required for the wind power generator to fulfill the same requirements as conventional power plants. This paper introduces a new solution for doubly fed induction generators (DFIG) to stay connected to the grid during abnormal conditions. The main idea is to provide a series connected grid side converter (SGSC) with conventional DFIG scheme. A new control scheme is then described and analyzed, which allows relatively low-energy ratings in the SGSC, thereby significantly lowering the overall system cost. Analysis is carried out to explore the grid code requirements (GCR) during static and dynamic conditions for the performance of the system along with the controller for abnormal conditions. Reactive power support capability of series converter during steady state condition is also demonstrated. A detailed small-signal analysis carried out which provides the insight of oscillatory behavior of DFIG. Extensive simulation and analytical results have demonstrated the enhanced performances resulting from the application of the control scheme and in compliance with the new grid codes.