Doubly -Fed Induction Generators for Wind Energy Production.

The development of fault detection methods in wind turbine (WT), especially for single fault detection, is continuously increasing. However, the rapid growth of fault detection in WT leads to another challenge where multiple faults can occur. The single fault detection method in WT is no longer reliable, especially when multiple faults occur simultaneously. Therefore, multiple faults detection in doubly-fed induction generators (DFIG) WT was proposed using an artificial neural networks (ANN) model. These multiple faults include internal and external stator faults happening simultaneously. Internal stator faults cover inter-turn short circuit faults and open circuit faults, while external stator faults cover loss of excitation and external short circuit faults. The performance of the developed multiple faults detection model was measured using accuracy and the root mean square error (RMSE) value. The results show that the developed model performs well with high accuracy and a low RMSE value. Thus, the developed model can accurately detect the coexistence of multiple faults in DFIG WT.

An overview of Hydropower application to the waste water (Sewage) is described here. Firstly the waste water treated in Sewage Treatment plant. It includes physical, chemical and biological contaminants. Its objective is to produce an environmentally. Here the solid waste (treated sludge) suitable for disposal of reuse (usually for fertilizers) and treated water used for generating electricity by a small Hydro power plant. Treated water of sewage at a high pressure or flowing with a high velocity can be used to run turbine or water wheel coupled to Generator and therefore of electrical power is becoming more and more popular as it is reliable and requires least maintenance and care. Output power has been estimated for available different head and flow rate of the waste water. Various types of the turbine-generator sets for different available head have also suggested for reliable operation of the developed this plant. The main advantage of this power plant is an independent power pl...

This paper gives the solution for enhancement of transient stability of smart grid connected squirrel cage induction generators. In most of the wind power plant induction generator is popular because it has low cost and low maintenance. Fault occurs in power system leads to over speed of rotor, consequently the over speed of rotor introduced transients in power system after clearing fault. If the transients are withstanding for more time in the system, the system will have difficult to stable the transients. So, for this paper deals with the transients stability enhancement of smart grid connected squirrel cage induction generator by using plugging mode operation and stable the transients after clearing the fault. Simulation results show that the proposed method can be effective in enhancing the transient stability. Since in this method, there is no need for accessory equipment, the proposed method is more attractive from the economic point of view.

La modulation de largeur d'impulsions (PWM) p.4 Le contrôle vectoriel de tension : contrôle E/F p.5 Le contrôle vectoriel de flux pour moteur asynchrone p.10 Les diagrammes d'essais p.13 Applications Choix des lois de commande Un certain nombre de mots clés sont répertoriés dans la figure 01. Ces mots clés sont rassemblés en 2 groupes qui sont relatifs à 2 techniques distinctes.

L’objectif principal de ce travail est de continuer et améliorer la recherche dans le cadre de production par l’énergie éolienne et d’évaluer les performances de l’aérogénérateur à base de la machine asynchrone double étoile connectée au réseau électrique et l’étude de l’interaction de ce générateur avec le réseau de distribution.

Modelling electric machines is crucial for analysing their behaviour and designing controllers. It is of the utmost importance to make use of a consistent equivalent circuit of the Doubly Fed Induction Machine (DFIM) that is applicable to a variety of operating modes. This is because it helps in the calculation of the machine's steady-state performance, converter ratings and controller set-points. Traditional models of doubly fed induction machines employ the steady-state equivalent circuit of a wound-rotor induction machine with all rotor parameters referred to the stator through a frequency conversion. The present study investigates the validity of the traditional steady-state circuit model by taking into account the sequence change in rotor voltages and currents at super-synchronous speeds. The validity of phasor diagrams constructed using the traditional circuit is assessed, with particular focus on super-synchronous operation in both motoring and generating modes. It has been demonstrated that the existing model is applicable to all rotor speeds (whether sub-synchronous or super-synchronous). However, caution should be exercised when utilising expressions of rotor reactive power that involve dynamic dq and steady-state phasor models. Therefore, modified expressions are developed for rotor reactive power that are applicable regardless of the operating speed. The accuracy of the proposed method for different operating modes is confirmed by comprehensive simulation results developed with Matlab® Simulink. An investigation is also conducted into the sensitivity of rotor reactive power direction to parameter changes, and it is shown that machine parameter changes have a negligible effect on rotor reactive power direction.

The article proposes a nonlinear optimal control approach for the UAV and suspended load system. The dynamic model of the UAV and payload system undergoes approximate linearization with the use of Taylor series expansion around a temporary operating point which recomputed at each iteration of the control method. For the approximately linearized model an H-infinity feedback controller is designed. The linearization procedure relies on the computation of the Jacobian matrices of the state-space model of the system. The proposed control method stands for the solution of the optimal control problem for the nonlinear and multivariable dynamics of the UAV and payload system, under model uncertainties and external perturbations. For the computation of the controller’s feedback gains an algebraic Riccati equation is solved at each time-step of the control method. The new nonlinear optimal control approach achieves fast and accurate tracking for all state variables of the UAV and payload sys...

This paper discusses the equivalent circuit of doubly fed induction machine in relevance to reactive power flow from the rotor. In particular, consistency of the traditional circuit model at super-synchronous speed is studied. It is proven that, while the existing model is valid for all rotor speeds, care is necessary when expressing rotor reactive power using the steady-state phasor and the dynamic dq models. Detailed simulation results of the DFIM under different operating modes are presented to validate the proposed method.

We present an analysis of rotor voltage influence on the characteristics of a wound rotor induction motor, the speed of which is regulated by double feeding. Stator windings of the motor are fed from the power system, while the feeding for the rotor ones is provided by a cycloconverter. Expressions for all characteristic variables are derived on the basis of a mathematical model defined for particular operating conditions. Rotor voltage regulation laws, which ensure optimal motor operation according to predetermined criteria and apply to the entire regulated speed range, are defined from the obtained expressions.

Ce travail présente une étude comparative de la commande de l’aérogénérateur asynchrone à double alimentation (GADA) associée aux différentes techniques de commande et de réglage. Dans la première partie de la thèse, pour assurer une commande robuste de la (GADA), améliorer la qualité d’énergie et rendre le système insensible aux perturbations, le principe de la commande découplée consiste à l’appliquer dans la chaîne de conversion d’énergie éolienne connectée directement au réseau, avec l’exploitation de la commande (MPPT). Les résultats des différentes simulations effectuées, sont analysés pour prouver les bonnes performances de ce type de commande. La deuxième partie de cette thèse, porte sur l’application de la commande directe du couple (DTC) classique dans notre système de conversion d’énergie. Cependant, cette stratégie présente des inconvénients importants. D’autre part, la fréquence de commutation est non-maîtrisable ainsi que les ondulations au niveau du flux et du couple ...

The work carried out in this project concerns the modeling and the power control of a wind power system based on a double-fed asynchronous generator (DFIG) driven by its rotor-side converter CCM in order to maximize the efficiency of this system and reduce the mechanical stress. In the first part, the situation of the wind energy and the conversion systems used (types of generators, the most used configurations, etc.) were presented, then the wind chain was modeled and adopted from the theoretical study. In the third and fourth part, an indirect vector control strategy for the control of current and power of the DFIG will be presented and developed. In addition to the problem of optimizing the production of the system and the limitation of mechanical stress, it was also sought to reduce the harmonic rate of the currents by using active filtering by the DFIG itself.

Doubly fed Induction Generators (DFIGs) are quite common in wind energy conversion systems because of their variable speed nature and the lower rating of converters. Magnetic flux saturation in the DFIG significantly affect its behavior during transient conditions such as voltage sag, sudden change in input power and short circuit. The effect of including saturation in the DFIG modeling is significant in determining the transient performance of the generator after a disturbance. To include magnetic saturation in DFIG model, an accurate representation of the magnetization characteristics is inevitable. This paper presents a qualitative modeling for magnetization characteristics of doubly fed induction generator using neuro-fuzzy systems. Neuro-fuzzy systems with one hidden layer of Gaussian nodes are capable of approximating continuous functions with arbitrary precision. The results obtained are compared with magnetization characteristics obtained using discrete fourier transform, po...

The hydroelectric plants flow rate always varies with time due to the speed rotation of turbines which affect the amplitude and frequency of electrical energy generated.  Hydro plants are being utilized for the purpose of peaking as well as base load, pumped storage and spinning reserve power operation etc. Especially in a system consisting of large industries, where frequency and voltage fluctuations are required to be kept minimum, their stability determines the quality of power. For efficient use of plant, complex control techniques are employed in the station automation and these involve the turbine governor in control features for which a flexible governor design is essential. MATLAB 2007 Software was used to carry out simulations analysis to develop fuzzy logic controller for hydropower Generator speed regulation with aims of stabilizing output power supply in order to increase the water flows rate through the hydropower penstock. The result of the research shows the hydropowe...

The present paper studies the DFIG (Doubly-Fed Induction Generator) variable speed wind turbines voltage recovery capability after external short-circuit fault removal. After external short-circuit fault, the transient stability of wind power system relies upon fault conditions and network parameters. If fault conditions are severe, the protection devices in the rotor circuit will be triggered which involves that the generator rotor is short-circuited and the rotor side converter is deactivated. In this situation, to recover the voltage at the wind turbine terminal and restore the wind turbine normal operation, after the fault removal, effective measures should be performed. Simulations are performed using the Matlab&Simulink environment.

To treat the stochastic wind nature, it is required to attain all available power from the wind energy conversion system (WECS). Therefore, several maximum power point tracking (MPPT) techniques are utilized. Among them, hill-climbing search (HCS) techniques are widely implemented owing to their various features. Regarding current HCS techniques, the rotor speed is mainly perturbed using predefined constants or objective functions, which makes the selection of step sizes a multifaceted task. These limitations are directly reflected in the overall dynamic WECS performance such as tracking speed, power fluctuations, and system efficiency. To deal with the challenges of the existing HCS techniques, this paper proposes a new adaptive HCS (AD-HCS) technique with self-adjustable step size using model reference adaptive control (MRAC) based on the PID controller. Firstly, the mechanical power fluctuations are detected, then the MRAC continuously optimizes the PID gains so as to generate an...

This paper reviews the current research works on the end suction centrifugal pump coupled with induction generator running in turbine mode for microhydro application. The information can be used by practicing engineers, researchers, and plant managers to understand the potential of pump running as turbine. Review on experimental and simulation works was carried out encompassing end suction single stage low specific speed which is less than 10 kW. This is followed by review of their efficiency improvement through modifications. The results show that centrifugal pump can operate in turbine modes without any modification on mechanical components. However, to achieve the best efficiency point (BEP), it requires higher flow rate and head than pumping rating. Efficiency improvement is viable through geometric modification to improve hydraulic characteristic. The studies also show that pump as turbine (PAT) can be directly coupled with modified induction motor as generator by adding capaci...

in the most remote areas, diesel generator is the main power source. For these regions, the price of grid extension would be prohibitive and the additional cost of the fuel supply increases dramatically with isolation that gives the advantage to renewable energy such as wind and hydro plants. In this context, the contribution envisaged with this memory for the power and control of a double-fed asynchronous machine and the effect it may bring its application in a chain of dedicated energy conversion for isolated site. The study selected structure. Modeling the double-fed asynchronous machine has been presented, and we have proposed a vector control strategy based on the principle of the stator flux orientation, the results of the simulation model in MATLAB / environment Simulank shows that control permits adjustment of the voltage and the stator frequency at constant values despite external stresses due to the variation of load and driving speed.

In this paper, an experimental study of a Wind Energy Conversion System (WECS) is performed. A test bench with a power of 1.5 kW is setup. The system consists of a Doubly-Fed Induction Generator (DFIG) and a wind emulator based on a DC motor associated with a Maximum Power Point Tracking (MPPT) control. The proposed emulator is driven by a four quadrants DC/DC converter to produce a real wind turbine behavior. The aim of this work is to improve the DIFG performances by using the fuzzy logic-based intelligent controller. This control technic is designed to monitor the stator reactive and active powers. This can be achieved by the DFIG rotor side converter (RSC) using the field-oriented control. The experimental setup uses a dSPACE DS1104 device, MATLAB/Simulink software and a ControlDesk interface. The paper shows that, the desired amount of active and reactive powers has been independently controlled and the implementation is successfully verified the effectiveness of the proposed c...

Induction motors (IM) that are driven using the conventional direct torque control algorithm (DTC) suffer from vital drawbacks which are high ripples in the torque and flux. These ripples result due to the use of a look-up table and hysteresis comparators which causes variable switching frequency. Moreover, the use of a traditional two-level inverter leads to the production of low-quality voltage and current. The work presented in this paper proposed a modified control system to overcome these drawbacks. The proposed control system is based on the use of the space vector modulation-based DTC algorithm (DTC-SVM) for driving three-phase IM via a three-level T-Type inverter. The conventional DTC-SVM algorithm has been modified to match the work of the proposed inverter. The modification process was based on the mapping of the standard DTC-SVM algorithm in the space vector of the three-level inverter. The conventional and the modified control systems are implemented using MATLAB/Simulin...

To treat the stochastic wind nature, it is required to attain all available power from the wind energy conversion system (WECS). Therefore, several maximum power point tracking (MPPT) techniques are utilized. Among them, hill-climbing search (HCS) techniques are widely implemented owing to their various features. Regarding current HCS techniques, the rotor speed is mainly perturbed using predefined constants or objective functions, which makes the selection of step sizes a multifaceted task. These limitations are directly reflected in the overall dynamic WECS performance such as tracking speed, power fluctuations, and system efficiency. To deal with the challenges of the existing HCS techniques, this paper proposes a new adaptive HCS (AD-HCS) technique with self-adjustable step size using model reference adaptive control (MRAC) based on the PID controller. Firstly, the mechanical power fluctuations are detected, then the MRAC continuously optimizes the PID gains so as to generate an...