Doubly -Fed Induction Generators for Wind Energy Production.

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.

Une alternative, consiste à exploiter les énergies renouvelables qui offrent la possibilité de produire de l’électricité et surtout dans une moindre dépendance des ressources à condition d’accepter leurs fluctuations naturelles. Ce mémoire présente une étude et commande d'un système éolien basé sur un générateur asynchrone à double alimentation (GADA), pour améliorer les performances de régulation de cette dernière est associée à un contrôle des puissances active et réactive, basée sur une commande à flux statorique orienté selon un repère diphasé.
Dans ce travail, une technique de contrôle non linéaire robuste d'une génératrice asynchrone à double alimentation destiné aux systèmes éoliens a été proposée. L'idée principale dans ce mémoire est de découpler la puissance active et réactive de la GADA avec une grande robustesse en utilisant la stratégie de backstepping. Le principe de cette méthode de contrôle repose sur la fonction de Lyapunov, afin de garantir la stabilité asymptotique globale du système. Enfin, nous présentons quelques résultats de simulation afin de vérifier l'efficacité et la robustesse de la technique de contrôle proposée.

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.

Implementations of mini hydro schemes with conventional hydraulic, electrical equipment's and controllers have proven very expensive and uneconomical. Many developing countries that are in need of rural electrification have encountered economical problem when setting up these mini hydro schemes. To address this problem, alternative options and new designs of these equipment's have been explored by many researchers around the world. The application of these new designs would reduce the overall cost of mini hydro development and would help in making it a cost effective technology. These new designs will also help developing countries to provide electricity to rural areas or remote regions where interconnection of transmission line from the electrical grid is uneconomical. The new designs can also be an enabling factor in boosting up electricity generation using a renewable energy source. This paper provides survey of all these alternative options and new designs in the controller, hydraulic turbine and generators that have been implemented in different countries of the world.

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.

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.

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.

Extraction of maximum energy from wind and transferring it to the grid with high efficiency are challenging problems. To this end, this study proposes a smart pitch controller for a wind turbine-doubly fed induction generator system using a Differential Evolution (DE) based adaptive neural network. The nominal weights for the back-propagation neural network controller are obtained from input-output training data generated by DE optimization method. These weights are then adaptively updated in time domain depending on the variation of the system outputs. The adaptive control strategy has been tested through simulation of complete system dynamics comprising of the turbine-generator system and its various components. It has been observed that the DE based smart pitch controller is able to achieve efficient energy transfer to the grid and at the same time provide a good damping profile. Locally collected wind data was used in the testing phase.

— 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.

In recent years the Doubly-Fed Induction Generator (DFIG) based wind turbine system has gained a lot of popularity due to its various advantages, but it has certain demerits also. The sudden tripping of these generators because of the low voltage during fault conditions, results in poor grid stability. One of the most reliable solutions to this problem is the use of Flexible AC Transmission System (FACTS) devices. They ensure the uninterrupted operation of DFIG system and thus maintain the stability of the system. This paper presents the application of UPFC (Unified Power Flow Controller) and HPFC (Hybrid Power Flow Controller) in the DFIG based wind turbine system in order to provide the dynamic reactive power support at the point of common coupling amid three-phase fault condition. A comparison between the performances of the two devices has also been discussed. The simulation has been done in MATLAB/Simulink platform.

The rapid growth of wind power systems worldwide will likely see the integration of large wind farms with electrical network that are series compensated stable transmission of bulk power. Using Flexible AC Transmission System (FACTS) devices are considered in order to maintain stability and provide the reactive power requirement of the grid and transfer the maximum power extracted from wind turbine to consumers. This paper presents the complete modeling and real-time simulation of wind turbine driven doubly-fed induction generator (DFIG) which feeds ac power to the utility grid. Keywords-DFIG, DC Control Link, UPFC, Wind Energy Conversion System (WEBS), Direct Torque Control Technique (DTC)

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.

Scope & Topics Aerospace Engineering: An International Journal (AEROIJ) is a quarterly open access peer-reviewed journal that publishes articles which contribute new results in all areas of the Aerospace Engineering and related fields. The journal focuses on all technical and practical aspects of Aerospace Engineering Research, plications and Implementation techniques. The goal of this journal is to bring together researchers and practitioners from academia and industry to focus on understanding advances in Aerospace Engineering and establishing new collaborations in these areas. Authors are solicited to contribute to the journal by submitting articles that illustrate research results, projects, surveying works and industrial experiences that describe significant advances in the areas of Aerospace Engineering. Topics of interest include, but are not limited to the following. Topics of interest include, but are not limited to, the following

This paper presents a performance investigation of power optimization by using a Proportional-Integral (PI) controller in a doubly-fed induction generator (DFIG). A detailed, dynamic model of a DFIG based on variable speed systems is presented in the dq-synchronous reference frame. Along with different controller types, a PI controller is chosen. Moreover, besides active and reactive power control, constraints and power optimization are discussed. Matlab software was used for simulation.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6190559

In this paper, Discrete wavelet transform available in Wavelet toolbox, MATLAB/SIMULNIK has been used to analyze harmonics presented in DFIG. The wavelet toolbox is successfully used to calculate the energy levels presented in the harmonics of the voltage and current waveforms generated in the DFIG. A technique to find out the THD independent of FFT is implemented in MATLAB and the THD for all the phases in both the current and voltage waveforms are computed and tabulated in the simulation results. It is observed from the case study that the discrete wavelet transform is an effective tool to detect and quantify the harmonics present in the DFIG. The simulation results in each phase are presented in the simulation results. The results of the proposed approach has been compared with theoretical result and FFT and it is found from the results that the proposed approach provides better results.

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.

In recent years, renewable energy has become one of the most important and promising sources of energy generation, which demands additional transmission capacity and better means of maintaining system reliability. The evolution of technology related to wind systems industry leaded to the development of a generation of variable speed wind turbines that present many advantages compared to the fixed speed wind turbines. Doubly fed induction generators (DFIG) are widely used in wind energy generation systems.

Electric energy generated by wind power plants is the fastest developing and most promising renewable energy source in Europe. Due to the advantages of power electronics wind energy conversion systems equipped with doubly fed induction generators for variable speed wind turbines are one of the most efficient configurations for wind energy conversion. The mathematical model and the simulation programs for such machines to be presented in the paper can help the understanding in this field and can be of real interest for all specialists involved in wind energy exploitation.

Background: Doubly fed induction generator (DFIG) due to its merits, finds its application in large grid connected power systems. DFIG is typically represented by its equivalent circuit parameter by stator and rotor winding resistance, reactance and mutual reactance. During steady state and fault conditions, functioning is important as it impacts on grid performance Materials and Methods: In this paper, the equivalent circuit parameters of DFIG are predicted by using deep neural network with ‘Neural Designer’ [1] and Keras (an open-source Python library). ‘Sequential Network-architecture’ is available on Keras and ‘order selection’ and ‘growing neurons’ algorithms on Neural Designer. Results: The required data set is built for DFIG machine ratings in the range of 1MW to 3 MW. The variables of databank are the DFIG interface parameters and equivalent circuit parameters. The interface parameters are rotor voltage, rotor current, reactive power capability, maximum fault current capacity, maximum transient torque and equivalent circuit parameters (resistance and reactance of stator and rotor and mutual reactance). The predicted results are compared with desired values. The error data is analysed using scatterplots, correlation data and histograms. The predicted parameters i.e. magnetizing reactance, stator winding leakage reactance and rotor resistance are in close agreement. However in case of stator winding resistance and rotor winding leakage reactance, the difference between predicted and desired values are considerable. The model performance is further improved by modifying the model architecture and increasing the data bank size. Conclusion: It is possible to predict DFIG equivalent circuit parameters from system associated parameters by suitable neural network.

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.

Abstrak Sistem kelistrikan Sulselrabar adalah sistem terinterkoneksi dari bagian Sulawesi selatan, tenggara, dan barat. Sistem ini didominasi oleh pembangkit termal dan hanya ada beberapa pembangkit hidro. Pembangkit termal ini tentunya menggunakan bahan bakar dari fosil yang merupakan sumber energi tak terbarukan yang akan berdampak pada biaya operasional yang mahal dan emisi lingkungan. Energi listrik dengan menggunakan sumber energi yang dapat diperbaharui menjadi satu-satunya solusi cerdas untuk hal ini. Pemerintah dalam programnya untuk membebaskan Indonesia dari emisi membangun kembali pembangkit listrik tenaga bayu (PLTB) di Kabupaten Sidrap Sulawesi Selatan dan PLTB Jeneponto. Tenaga angin yang digunakan PLTB memiliki kecepatan yang tidak selamanya konstan. Kemungkinan terjadinya fluktuasi kecepatan angin sangat tidak bisa dielakkan dan tidak boleh diremehkan. Hal tersebut tentunya akan mempengaruhi kestabilan sistem pada saat kedua PLTB tersebut masuk ke sistem interkoneksi. Penelitian ini dibuat untuk mengatasi permasalahan tersebut dengan merancang sistem kendali menggunakan fuzzy logic controller (FLC) untuk mempertahankan kestabilan sistem. Hasil penelitian menunjukkan bahwa FLC ini mampu mengontrol dampak perubahan kecepatan angin terhadap output PLTB dan pembangkit listrik tenaga termal (PLTT). Hasil pengontrolan FLC ketika kecepatan angin berada pada level sangat rendah 0-0.8 m/s maka output PLTB juga berada pada level sangat rendah 0 kW dan output PLTT berada pada level sangat tinggi 56.000 kW, namun sebaliknya ketika kecepatan angin berada pada level sangat tinggi 8.3-8.4 m/s maka output PLTB juga berada pada level sangat tinggi 2500 kW dan sebaliknya output PLTT berada pada level sangat rendah 5000 kW. Abstract Sulselrabar electrical system is an interconnected system of parts of south, southeast, and west Sulawesi. The system is dominated by thermal plants and there are only a few hydro plants. These thermal plants certainly use fossil fuels that are a non-renewable energy source that will impact on operating costs and environmental emissions. Electrical energy by using renewable energy sources is the only smart solution for this problem. The Government in its program to free Indonesia from the emission is rebuilding wind power plants (WPP) in Sidrap dan Jeneponto District of South Sulawesi. Wind power used WPP has a speed that is not always constant. The possibility of wind speed fluctuations is not anavoidable and should not be underestimated. This will certainly affect the stability of the system when both WPPs join the interconnected system. This research was made to overcome these problems by designing a control system using fuzzy logic controller (FLC) to maintain system stability. The results showed that the FLC is able to control the impact of changes in wind speed on the output of WPP and termal power plants (TPP). FLC results when wind speed is at a very low level (0-0.8 m/s) then the output of the WPP is also at a very low level (0 kW) and the TPP output is at a very high level (56.000 kW), but vice versa when wind speed is at very high level 8.3-8.4 m/s then the output of the WPP is also at a very high level (2500 kW) and vice versa the TPP output is at a very low level (5.000 kW).

There are two topologies for slotted double-sided axial flux permanent magnet generator (AFPG). Choosing an AFPG with high power density is an important parameter in applications. Hence, power density Evaluation between double-sided AFPM generators topologies is necessary. In this paper, the sizing equations of axial flux slotted one-stator-two-rotor (TORUS) and two-stator-one-rotor (AFIR) type PM generators is presented and comparison of the TORUS and AFIR topologies in terms of power density is illustrated. Finally a high power double-sided AFPG is introduced in the paper.

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.

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.