Adjustable speed induction generators, especially the doubly fed induction generators (DFIG), are becoming increasingly popular due to their various advantages over fixed speed generator systems. A DFIG in a wind turbine has the ability to generate maximum power with varying rotational speed, ability to control active and reactive power by the integration of electronic power converters such as the back-to-back converter, low rotor power rating resulting in low cost converter components, and so on. This study presents an extensive literature survey over past 25 years on the different aspects of DFIG.

Three-phase doubly fed induction generators: an overview

http://jcidras.webs.uvigo.es/publicaciones/2000_EPSR_ThirdOrderModel.pdf

A third order model for the doubly-fed induction machine

A comprehensive review on the grid integration of doubly fed induction generator

Undoubtedly, energy has a significant role in economic growth and technical developments. Renewable energy resources are becoming more important in recent years due to their tremendous contributions to the independence of power generation industry from traditional fossil energy resources. Wind energy has been outstanding among renewable energy resources since continuous harvestable potential on the earth is approximately around 10 6  MW. Concerning the variable nature of wind energy, the variable speed machines, especially doubly fed induction generators (DFIG) are one of the considerations for wind energy conversion systems (WECS). Their implementation in renewable energy conversion systems is dramatically increasing due to their numerous advantages such as low cost and small size, the elimination of external DC source, the ability to produce maximum power under various wind and rotational speeds, the capability of controlling active and reactive power, and the opportunity to employ cheaper and smaller convertors and controllers. This paper is an extensive review of researches in the past 30 years on DFIG. The study starts with describing general perspective on wind energy and commonly used generators in wind conversion. Then it presents more details on DFIGs operational modes, utilizations, their modeling and simulation. It is followed by DFIG control methods and overviews of different employed electrical and mechanical controlling methods. Finally the review on the mutual impact of DFIG on power networks and vice versa, including wind uncertainty, power and frequency stability, power and voltage quality, operation under steady state, dynamic and fault conditions, and protections is given. Based on the review DFIG has advantages in terms of electrical, mechanical, and economic perspectives. It can be concluded that the DFIG has the most promising future for WECSs in power generation to complement the conventional systems.

An overview on doubly fed induction generators′ controls and contributions to wind based electricity generation

This paper is concerned with the low-frequency harmonics which originate from the rotor inverter of a doubly-fed induction generator (DFIG). By including the mechanical speed response, it expands the transformer approach previously taken to analyze the harmonic transfer in the machine. A numerical method is proposed to calculate the stator current sidebands, which can be used to predict the voltage fluctuation at the system busbar. It is shown that the pulsating torque associated with the rotor harmonics can induce speed ripple depending on the inertia, causing a significant change in the stator current spectrum. Experiment and simulation verify the analysis and the proposed calculation method.

/pdf/evaluation-of-the-effects-of-rotor-harmonics-in-a-doubly-fed-1q5rk1nftu.pdf

Z. M. Salameh

Papers

Analysis of the double output induction generator using direct three-phase model. II: Harmonic analysis