Doubly -Fed Induction Generators for Wind Energy Production.

The fast development of wind power generation brings new requirements for wind turbine integration into the network. After clearance of an external short-circuit fault, grid-connected wind turbines should restore their normal operation without power loss caused by disconnections. During the fault by flowing the high current for a several micro seconds transient operations are very crucial for high power insulated-gate bipolar transistor modules. Therefore, the ability for doubly fed induction generator (DFIG) variable speed wind turbine power converters to withstand abnormal conditions is strictly imperative in order to achieve its lifetime specifications and also fulfil the grid codes. In this paper presents a new control scheme for DFIG wind turbine having parallel interleaved converters (PIC) configuration and a series dynamic braking resistor (SDBR) connected at its stator side. Interleaving the wind turbine converters in parallel configuration could help to increase the current capability, while the SDBR helps in post fault recovery of the wind turbine and also used for used to improve the FRT of large wind farms composed of induction generators. The shorter duration of operation of the SDBR gives a better response of the DFIG system during a grid fault. The coordinated control analysis of the scheme was implemented in power system computer aided design and electromagnetic transient including DC simulation environment for a severe three-phase to ground fault. A better performance of the wind turbine variables were achieved using the proposed control scheme of the PIC and SDBR because the space vector modulation of the PIC results in maximum value of the change in common mode voltage, leading to improved switched output voltage of the voltage source converter leg. Simulation results were obtained compared with the conventional DC chopper and crowbar rotor circuit protection scheme for the wind turbine and also demonstrate that in uncritical post-fault situations the control schemes are able to restore the wind turbine's normal operation without disconnections.

A brushless doubly fed machine is equipped with two decoupled windings on its stator, known as the power winding and the control winding. The power winding reactive power can be controlled by voltage amplitude fed by the machine-side converter to the control winding, affecting both the converter size and machine efficiency. This paper investigates different proposed scenarios for optimal reactive power flow targeted to minimize the converter cost and maximize the machine efficiency. Previously, the grid-side converter has not been used for reactive power compensation. However, in the present paper it is shown how the grid-side converter can be effectively used to reduce the converter cost by controlling the flow of reactive power. The optimal power winding reactive powers for minimizing the converter cost and for maximizing the output power are not the same. Then the priority of minimizing converter cost over maximizing machine output power has been justified.

Cooperative level control (CLC) Machine level control (MLC) Grid side converter (GSC) Rotor side converter (RSC) Multi agent system (MAS) Synchronous generator (SG) a b s t r a c t Microgrids and smart grids are the future of the conventional grids. It will be an immense need to integrate the Distributed Generators (DGs) with smart grids and microgrids. DGs are mostly the solar energy, wind energy and small hydel power. These DGs has several advantages as high penetration of power will reduce the power loss, reduce the voltage drop and maintain the terminal voltage. These DGs are difficult to integrate with the microgrids in islanded mode as these causes severe fluctuation which disturbs the supply-demand balance. Renewable generators (RGs) working in MPPT mode cause high fluctuations when the RGs are working on islanded mode and generating more power than demand. Therefore, a control system is required to manage this issue and to maintain the balance of the system. Sub-gradient based distributed coordination technique is utilized for the control of renewable generators in which the supply-demand balance is maintained by coordinating the system with the utilization level. Simulation results will exhibit the operation of the controlled microgrid, its integrated DGs and will prove the efficiency and the effectiveness of the proposed methodology.

— In this paper, phasor measurements taken from stator and rotor terminals are used for dynamic state estimation of a doubly fed induction generator (DFIG) assuming a reduced order model (3 rd order) with unknown mechanical input torque. The proposed estimator provides the advantage that the converter and associated controller dynamics as well as turbine and drive train need not be modelled. In addition the reduced order model reduces the computational complexity of state estimator significantly in comparison to previously reported DFIG models (15 th order). Also this modeling of DFIG provides an additional benefit of minimal knowledge of system parameters i.e. only induction generator parameters are required to be known. Dynamic State Estimation has been performed using Extended Kalman Filter with Unknown Inputs (EKF-UI). Performance of proposed estimator has been demonstrated on a benchmark IEEE network modified by augmenting a wind farm consisting of multiple DFIG.

This paper presents the emulation of an isolated wind energy conversion system, which is composed by a doubly-fed induction generator, a back-to-back converter connected to its rotor, a LC filter to minimize the harmonic pollution in the generated voltage and an isolated three-phase load. In first instance, the test bench is described and its operational capabilities are introduced. Afterwards, the control system design is presented. Next, some associated experimental results are shown as well. A special mention must be made to an experimental study which considers the possibility of using the self-excitation of the doubly fed induction generator to achieve the black-start of the isolated wind energy conversion system.

Brushless doubly fed iuduction machine has recently attracted attention in variable speed generators and motor drives. In order to have a high performance control, a precise dynamic model is required. This paper aims at introducing a model of brushless doubly fed induction machine taking core loss into account. The details of model derivation are outlined and the torque relation is expressed in the general reference frame. The model is then used for simulation of the dynamic performance of the machine. The error introduced by neglecting core loss effect is also shown.

fed wind generation system is presented in this article. Nonlinear as well as linearized dynamic models of the wind system pitch controller and the doubly fed induction generator
including the drive train are developed. A PI controller is
employed to generate the appropriate pitch angle for varying
wind speed conditions. An adaptive artificial neural network
(ANN) is trained to produce PI gain settings for various
wind speed conditions. The training data, on the other hand,
was generated through differential evolution (DE). Simulation
studies show that the DE based adaptive ANN can generate
the appropriate control to deliver the wind power to the
generator efficiently with minimum transients. The data used
was collected from the wind generator located at the King
Fahd University beach front.

In this report, work done to develop generator model using MATLAB (Matrix laboratory) environment is explained. The main aim of the project was to develop an excellent Doubly fed induction generator model. The model can be used to understand, simulate and analyze transients load. The simulation of the model under different grid condition and articulation of the resonant excitation would be possible. This report also contains the technology of generator systems in wind energy conversion systems which are already in use and some of the new concepts and their technical features. The new generator technologies could generate invariable wind power and does not depends on the changes happen in the velocity of the wind. It has huge application across the globe and especially at the remote areas of the world.

This paper deals with a complete 1.5 MW Horizontal Axis Wind Turbine (HAWT) design using a novel Maximum Power Point Tracking (MPPT) algorithm based on real time machine testing and a low cost network communication system. It also includes a blade design study and simulation for a maximum efficiency and a high control strategy for maximum energy production with a minimum harmonic distortion for the generated current. The parameters studied are varied: electrical characteristics, static and aerodynamic, blade geometric profiles, and the influence of wind speed. The wind turbine uses a doubly fed induction generator « DFIG » controlled by a Pulse Width Modulation (PWM) strategy for 27 levels Cascaded three H-Bridge voltage source inverter. It will allow us to control the rotor voltage in magnitude and phase angle more easily & with high efficiency. This wind turbine was used on a 15MW wind farm. The study was conducted through several simulation software (Matlab, Catia, and Solid works). The whole control strategy, design principle and simulation results are shown & discussed. KEYWORDS Doubly Fed Induction Generator – Wind Turbine Design – Cascaded H-Bridge Inverter – Pulse Width Modulation.

In this paper, the performance of single-tone Radio over Fiber (RoF) system has been analyzed by employing different duobinary modulation formats. This single-tone RoF system has been modeled and analyzed using OptiSystem (14.0) software. To evaluate the transmission performance of RoF system, various performance metrics such as Q-factor, BER, and Eye Height are considered. Simulation results indicate that duobinary Hyperbolic-Secant pulse generator format with Single Drive Mach-Zehnder modulator provides better Q-factor and minimum BER as compared to existing modulation format in RoF system.

A smart pitch control strategy for a variable speed doubly fed wind generation system is presented in this article. Non-linear as well as linearized dynamic models of the wind system pitch
controller and the doubly fed induction generator including the drive train are developed. A PI controller is employed to generate the appropriate pitch angle for varying wind speed conditions. An artificial neural network (ANN) is trained to produce PI gain settings for various wind speed conditions. The training data, on the other hand, was generated through differential evolution intelligent technique (DEIT). Simulation studies show that the DEIT based ANN can generate the
appropriate control to deliver the wind power to the generator efficiently with minimum transients. The data used was collected from the wind generator located at the King Fahd University beach front.

El estudio eléctrico de un aerogenerador superconductor para bajas velocidades de viento, se

puede desglosar en dos etapas: diseño eléctrico y construcción. Para desarrollar el diseño eléctrico del

aerogenerador, es necesario comprender ciertos conceptos de estos; la parte eléctrica principal del

aerogenerador es el rotor y el estator el cual es el generador de una FEM y por el otro lado los materiales

necesarios para su construcción tomando en cuenta las condiciones de operación de las máquinas eléctricas

superconductoras. En el presente trabajo, se mencionan los componentes principales de una maquina

eléctricas y los materiales necesarios para la construcción de prototipos que nos sirvan como referencia para

poder innovar en un futuro en otros aerogeneradores superconductores.