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The Brushless Doubly-fed Induction Generator (BDFIG) has high potential for wind energy systems, especially for offshore applications where minimum maintenance is vital. The machine low voltage ride through (LVRT) capability in the light of current grid code requirements was investigated using a precise dynamic model. This is particularly important for future multi- MW BDFIGs. This paper shows the necessity for improvements of the BDFIG LVRT capability with presenting a comprehensive analytical study during asymmetrical voltage dips. Analytical studies are conducted to extract a more precise equivalent circuit model of the BDFIG used for analyzing machine dynamic behavior under various fault... 

The brushless doubly fed induction generator (BDFIG) has substantial benefits, which make it an attractive alternative as a wind generator. However, it suffers from lower efficiency and larger dimensions in comparison with the doubly fed induction generator. A major part of drawbacks arises from undesirable spatial harmonics of air-gap magnetic field. Calculation of core loss is an important issue in optimal design studies to improve the performance characteristics. The iron loss is higher and has a more complex nature in BDFIGs in contrast with conventional machines. Furthermore, additional losses cannot be ignored due to a high level of spatial harmonics distortion. This paper aims to... 

The brushless doubly fed induction generator (BDFIG) has been proposed as a viable alternative in wind turbines to the commonly used doubly fed induction generator (DFIG). The BDFIG retains the benefits of the DFIG, i.e. variable speed operation with a partially rated converter, but without the use of brush gear and slip rings, thereby conferring enhanced reliability. As low voltage ride-through (LVRT) performance of the DFIG-based wind turbine is well understood, this paper aims to analyze LVRT behavior of the BDFIG-based wind turbine in a similar way. In order to achieve this goal, the equivalence between their two-axis model parameters is investigated. The variation of flux linkages,... 

The brushless doubly-fed induction generator (BDFIG) has substantial benefits, which make it an attractive alternative as a wind turbine generator. The aim of this work is to present a nodal-based magnetic equivalent circuit (MEC) model of the BDFIG which provides performance characteristics and flux density distributions. The model takes into account stator winding distributions, special configuration of rotor bars, slotting effects, teeth saturation, flux fringing and current displacement effects. The real flux tubes are considered for creating an MEC network and calculating its non-linear elements. A method for simplifying the rotor magnetic network has been applied and Gauss elimination... 

This paper proposes effective approach for determining appropriate crowbar resistance value to be able to improve the brushless doubly fed induction generator ride through capability during any asymmetrical voltage dip scenarios. The brushless DFIG has great potential for wind power plants particularly in offshore applications where maintenance is a major concern. Dynamic behavior of the machine is studied using two axis model and a more precise equivalent circuit model is extracted for analyzing machine behavior under fault conditions. Important limits and constraints in the use of crowbar are identified and discussed in detail. It is shown that large crowbar values can lead to considerable... 

In view of its special features, the brushless doubly fed induction generator (BDFIG) shows high potentials to be employed as a variable-speed drive or wind generator. However, the machine suffers from low efficiency and power factor and also high level of noise and vibration due to spatial harmonics. These harmonics arise mainly from rotor winding configuration, slotting effects, and saturation. In this paper, analytical equations are derived for spatial harmonics and their effects on leakage flux, additional loss, noise, and vibration. Using the derived equations and an electromagnetic-thermal model, a simple design procedure is presented, while the design variables are selected based on... 

Brushless doubly fed induction generators (BDFIGs) show commercial promise for wind-power generation due to their lower capital and operational costs and higher reliability as compared with doubly fed induction generators. This paper presents a vector-control scheme for a BDFIG operating as a variable-speed generator. The proposed vector controller is developed on the power-winding stator-flux frame and can be used to control both the speed and the reactive power. The machine model and the control system are developed in MATLAB. The test results show that the proposed controller has good dynamic performance when changes in speed and reactive power are applied. © 2009 IEEE  

Brushless doubly fed induction generator (BDFIG) has substantial benefits, which make it an attractive alternative as a wind turbine generator. However, it suffers from lower efficiency and larger dimensions in comparison to DFIG. Hence, optimizing the BDFIG structure is necessary for enhancing its situation commercially. In previous studies, a simple model has been used in BDFIG design procedure that is insufficiently accurate. Furthermore, magnetic saturation and iron loss are not considered because of difficulties in determination of flux density distributions. The aim of this paper is to establish an accurate yet computationally fast model suitable for BDFIG design studies. The proposed... 

This paper discusses the dynamic behavior of the brushless doubly fed induction generator during the grid faults which lead to a decrease in the generator's terminal voltage. The variation of the fluxes, back EMFs, and currents are analyzed during and after the voltage dip. Furthermore, two alternative approaches are proposed to improve the generator ride-through capability using crowbar and series dynamic resistor circuits. Appropriate values for their resistances are calculated analytically. Finally, the coupled circuit model and the generator's speed and reactive power controllers are simulated to validate the theoretical results and the effectiveness of the proposed solutions. Moreover,... 

The use of brushless doubly-fed induction generator has been recently proposed for wind turbines because of its variable speed operation with fractional size converter without the need to brush and slip ring. This paper introduces a control scheme to improve low voltage ride-through capability of doubly-fed induction generator considering grid code requirements. The proposed control strategy is based on analysis of flux linkages and back electromotive forces and intends to retain the control-winding current below the safety limit (typically 2pu) during severe voltage dips. The time-domain simulations validate effectiveness of the proposed scheme to protect the converter against failure as... 

The use of brushless doubly-fed induction generator has been recently proposed for wind turbines because of its variable speed operation with fractional size converter without the need to brush and slip ring. This paper introduces a control scheme to improve low voltage ride-through capability of doubly-fed induction generator considering grid code requirements. The proposed control strategy is based on analysis of flux linkages and back electromotive forces and intends to retain the control-winding current below the safety limit (typically 2 pu) during severe voltage dips. The time-domain simulations validate effectiveness of the proposed scheme to protect the converter against failure as...