Search for: doubly-fed-induction-generator
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    Control of DFIG-Based Wind Generation to Improve Inter-area Oscillation Damping

    , M.Sc. Thesis Sharif University of Technology Goodarzi, Ali (Author) ; Ranjbar, Ali Mohammad (Supervisor)
    Low-frequency oscillation damping in power system is main determinants of the stability of the system. According to increasing of wind farms with high penetration levels in the power system, participation and control of wind farms for increase damping inter area oscillations seems important. In this study a damping controller suggested for Doubly Fed Induction Generator (DFIG). Using this controller and only available local signal as input controller and combination of both active and reactive power modulation, can greatly increase damping inter area oscillations and stability of uncertainty and different working points. Using linear analysis system, identified modes oscillating system and... 

    Improvement of DFIG Under Unbalanced Voltage Condition

    , M.Sc. Thesis Sharif University of Technology Karimi Khouzani, Hadi (Author) ; Parniani, Mostafa (Supervisor)
    In this thesis, performance of doubly fed induction generators in wind turbine, under stator unbalanced voltage condition has been studied. Therefore, beside of presenting related equations and models for DFIG, drawbacks of DFIG performance under unbalanced voltage condition on variables such as electric torque, active and reactive stator power and stator current have been shown. Then, controller have been designed in the way that can eliminate electric torque oscillation, active power oscillation, negative sequences of stator current and rotor current. The controller is designed base on decoupling sequences in synchronous reference and stator voltage orientation method(SVO) that consist of... 

    Direct Torque Control of Doubly-Fed Induction Motor

    , M.Sc. Thesis Sharif University of Technology Moayedi, Ali (Author) ; Kaboli, Shahriyar (Supervisor)
    Conventional induction motors are controlled by stator voltage, so the inverter should pass the full power of the motor. In the doubly-fed rotor wound induction motors, the nominal power of inverter can be reduced. Therefore, these types of machines have been concerned in recent decades and they are able to use as alternative for high power conventional induction machines in the future. Direct torque control is one of the well known methods for controlling the induction motors. Fast torque response and independence of machine parameters (except winding resistance). In this thesis, different sterategies of direct torque control of doubly fed induction motors are presented. In the first... 

    Robust Multivariable Control of Electro-mechanical System in Horizontal Wind Turbines under Off-design Conditions

    , M.Sc. Thesis Sharif University of Technology Faraji Nayeh, Reza (Author) ; Vosughi Vahdat, Bijan (Supervisor) ; Moradi, Hamed (Supervisor)
    Advanced control techniques are required to achieve a cost-effective and reliable use of the wind power generation. The wind turbines are generally controlled based on two control objectives: the turbine protection and the generation of acceptable power for the utility grid. These objectives are achieved if the control inputs are applied based on appropriate control logics. In this work, a nonlinear multivariable model of the wind turbine with a DFIG generator is considered. The rotor speed and the d-axis rotor current (as the control outputs) are controlled via manipulation of the two generator voltages (as the control inputs) in low wind velocity condition. For high wind velocity, the... 

    Reliability Model of Wind Turbine System with BDFG

    , Ph.D. Dissertation Sharif University of Technology Arabian, Hooman (Author) ; Oraee, Hashem (Supervisor) ; Fotuhi Firouzabad, Mahmud (Supervisor)
    Considerable attention has been given in recent years to renewable energy sources due to concerns about dwindling fuel reserves and the potential impact of conventional energy systems on the environment. Wind power is one form of renewable energy resources and also considered as Dispersed Generation (DG). Widespread utilization of wind power imposes many effects on planning and operation of power system. In other side, reliability evaluation and enhancement is an important factor in modern power system planning and operation. So, reliability assessment of wind turbines is of great importance and will receive more attention in the future according to increase of WT utilization. The... 

    Study of HVDC Transmission for Offshore Wind Farms Based on Voltage Source Converters

    , M.Sc. Thesis Sharif University of Technology Safaeian, Reza (Author) ; Parniani, Mostafa (Supervisor)
    In this thesis, DC transmission of offshore wind farms is studied thoroughly. Various system configurations that are introduced in the literatures are discussed and their control scheme for normal conditions and grid faults are studied. Then, the HVDC transmission based on voltage source converter, located between a local offshore ac grid and the onshore ac system is investigated as the most practical choice. The HVDC linke circuit elements are calculated and the control strategies of the offshore and onshore converters are introduced. DFIGs are considered to be the best choice for the offshore wind turbine generators. Then, the system is simulated and the frequency of the offshore grid is... 

    Fault Tolerant AC/DC/AC Converters for Wind Energy Turbine with Doubly-Fed Induction Generator

    , Ph.D. Dissertation Sharif University of Technology Shahbazi, Mahmoud (Author) ; Zolghadri, Mohammad Reza (Supervisor) ; Saadate, Shahrokh (Supervisor)
    AC/DC/AC converters are widely being used in a variety of power applications. Continuity of service of these systems, as well as their reliability and performance are now of the major concerns. Indeed, the failure of the converter can lead to the total or partial loss of the control of the phase currents and can cause serious system malfunction or even shutdown. Thus, uncompensated faults can quickly endanger the system. Therefore, to prevent the spread of the fault to the other system components and to ensure continuity of service, fault tolerant converter topologies associated with quick and effective fault detection and compensation methods must be implemented. In this thesis, the... 

    Supervisory Model-based Predictive Control for Voltage Regulation of a Grid-Connected Wind Farm

    , M.Sc. Thesis Sharif University of Technology Sabzi, Hadi (Author) ; Sadati, Nasser (Supervisor)
    Concerns about fossil fuels and the consequent effects of burning such fuels on the environment have drawn attention of different countries around the world to the development of renewable energy systems, and it has encouraged researchers to focus on expanding the methods of using different sources of renewable energy. One of the most important renewable energies is wind energy, which is generated by wind turbines. A cluster of wind turbines forms a wind farm. Wind turbines can be equipped with a supervisory control system that sends the data measured by the sensors to the operator. Design of supervisory control algorithm for a wind farm requires a model of the wind farm system. The task of... 

    Analysis and Improvement of Dynamic Performance and Fault Ride-Through Capability of Wind Turbines Based on Doubly-Fed Induction Generators

    , Ph.D. Dissertation Sharif University of Technology Rahimi Kelishadi, Mohsen (Author) ; Parniani, Mostafa (Supervisor)
    Variable speed wind turbines (VSWTs) provide the capability of wide speed operation and independent control of active and reactive power. In contrast to the fixed speed WTs, they have higher efficiency, power quality and controllability. VSWTs are mainly divided in two categories: WTs based on doubly fed induction generator (DFIG) and WTs based on full converter with permanent magnet synchronous generator.
    At now, among the different alternatives to obtain VSWTs, DFIGs are the most commonly used. This is because the voltage source converter (VSC) in DFIG has to handle a fraction of the total power under steady state conditions, and thus the size and cost of the converter is reduced.... 

    Optimum Control of DFIG Based Wind Turbine under Grid Voltage’s Abnormal Conditions

    , M.Sc. Thesis Sharif University of Technology Khazaeli Moghaddam, Farid (Author) ; Oraee Mirzamani, Hashem (Supervisor)
    In this project, the main purpose is attaining the optimum controller for DFIG under permanent voltage unbalances. To achieve this purpose, firstly, the wind turbines’ control strategies, and main control subsystems including DFIG’s controller, Pitch control system, as well as Yaw’s control system are reviewed. The efficient control algorithms to achieve the control purposes for these three subsystems are introduced. To continue, it is focused on generator’s controller, and the different methods besides their performance are discussed. In order to improve DFIG’s controller performance under permanent grid voltage’s unbalance condition, at first, the problems of operating during such a... 

    Analysis and Improvement of Dynamic Behavior of Brushless Doubly-Fed Induction Generator in Wind Turbines

    , M.Sc. Thesis Sharif University of Technology Tohidi, Sajjad (Author) ; Oraee Mirzamani, Hashem (Supervisor) ; Zolghadri, Mohammad Reza (Supervisor)
    Recently, the brushless doubly fed induction generator (BDFIG) has been proposed to be used in wind turbines due to variable speed operation with fractionally size power electronic converter and without brushes and slip rings. In this thesis, for the first time, LVRT capability of BDFIG has been assessed regarding the grid codes and several approaches have been suggested for improving it. Firstly, the steady-state performance of the BDFIG in different operating modes has been investigated and required tests have been performed. In addition, a new operating mode named as "double cascade mode" has been introduced. The fault-on performance of BDFIG has also been studied by means of torque-speed... 

    Power System Load Frequency Control in the Presence of Wind Turbines

    , M.Sc. Thesis Sharif University of Technology Ashoori Zadeh, Alireza (Author) ; Ranjbar, Ali Mohammad (Supervisor)
    This study presents the application of the doubly fed induction generator (DFIG) to reduce the frequency deviation and improve frequency of a power system. This has been done by proposing a wind turbine model and a new fuzzy controller. The fuzzy controller has been suggested to change the speed of the wind turbine rotor and modify the impacts of wind speed fluctuations on the output power. The fuzzy controller parameters are optimized using the genetic algorithm (GA) to achieve the appropriate transient response. A smart controller is combined with fuzzy controller to optimize the usage of wind turbine’s kinetic energy. Furthermore, the DFIG with the proposed controller participates in the... 

    Optimal robust first-order frequency controller design for DFIG-based wind farm utilising 16-plant theorem

    , Article IET Renewable Power Generation ; Volume 12, Issue 3 , 2018 , Pages 298-310 ; 17521416 (ISSN) Toulabi, M. R ; Salehi Dobakhshari, A ; Ranjbar, A. M ; Sharif University of Technology
    Institution of Engineering and Technology  2018
    With increasing the share of wind farms in generation profile, their contribution to frequency regulation has become crucial. This study presents an optimal robust first-order frequency controller in the wind farms, which collectively emulates the inertial response as well as governor droop of synchronous generators. To account for various uncertainties associated with system inertia, damping, and doubly-fed induction generator (DFIG)-based wind turbine's parameters, the robustness of controller is verified through the 16-plant theorem. An analytic method based on the small-signal model of the system is utilised to determine the stability region of the first-order controller. To evaluate the... 

    An input-to-state stability approach to inertial frequency response analysis of doubly-fed induction generator-based wind turbines

    , Article IEEE Transactions on Energy Conversion ; Volume 32, Issue 4 , 2017 , Pages 1418-1431 ; 08858969 (ISSN) Toulabi, M ; Bahrami, S ; Ranjbar, A. M ; Sharif University of Technology
    Due to the proliferation of wind turbines in power networks, participation of doubly-fed induction generator (DFIG)-based wind turbines in the frequency regulation task is attracting more attention during recent decades. It is a challenge to design an effective DFIG's auxiliary frequency controller, since back-to-back converters used in DFIG make the possibility of large deviations in current and speed of rotor during frequency support period. Hence, it is necessary to use exact expression of DFIG's output power in the frequency-related studies. This paper addresses this challenge by developing a nonlinear dynamic model for the DFIG's output power integrated into the dynamic model of power... 

    Application of bang-bang controller to emulate primary frequency response in DFIGs

    , Article IEEE Systems Journal ; Volume 14, Issue 2 , 2020 , Pages 2615-2623 Toulabi, M ; Ashouri Zadeh, A ; Kazari, H ; Ranjbar, A. M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    This article proposes a bang-bang auxiliary frequency control scheme for doubly-fed induction generator (DFIG)-based wind turbines. It results in the DFIGs emulate the primary frequency control of conventional units and, thus, increases the power system frequency stability. Indeed, the suggested hysteresis controller causes to deliver the maximum extractable kinetic energy of DFIGs to the grid and consequently further enhance the power system frequency. This is accomplished using different frequency deviation indices, which determine the size of power mismatch and lead to an appropriate frequency response by the DFIGs. The operational constraints of the DFIGs are taken into account in the... 

    Low voltage ride-through of DFIG and brushless DFIG: Similarities and differences

    , Article Electric Power Systems Research ; Vol. 110 , May , 2014 , p. 64-72 ; ISSN: 03787796 Tohidi, S ; Tavner, P ; McMahon, R ; Oraee, H ; Zolghadri, M. R ; Shao, S ; Abdi, E ; Sharif University of Technology
    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,... 

    Analysis and enhancement of low-voltage ride-through capability of brushless doubly fed induction generator

    , Article IEEE Transactions on Industrial Electronics ; Volume 60, Issue 3 , March , 2013 , Pages 1146-1155 ; 02780046 (ISSN) Tohidi, S ; Oraee, H ; Zolghadri, M. R ; Shao, S ; Tavner, P ; Sharif University of Technology
    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,... 

    Dynamic modeling of a wind turbine with brushless doubly fed induction generator

    , Article 2012 3rd Power Electronics and Drive Systems Technology, PEDSTC 2012, 15 February 2012 through 16 February 2012 ; February , 2012 , Pages 490-494 ; 9781467301114 (ISBN) Tohidi, S ; Zolghadri, M. R ; Oraee, H ; Oraee, A ; Sharif University of Technology
    Brushless Doubly Fed Induction Generator (BDFIG) has been recently proposed to be used in variable speed wind turbines. This paper intends to investigate the influence of certain model simplifications to obtain a reduced-order model of a wind turbine with BDFIG suitable for transient studies. To achieve this goal, small signal analysis is performed for a recently manufactured 250 kVA BDFIG to obtain system modes and their participation factors. Identifying highly damped modes, influences of neglecting dynamics of their participated states are studied through time-domain simulation in MATLAB/Simulink  

    Influence of different series dynamic resistors on low-voltage ride-through of brushless doubly fed induction generator

    , Article Electric Power Components and Systems ; Volume 43, Issue 8-10 , 2015 , Pages 995-1005 ; 15325008 (ISSN) Tohidi, S ; Oraee, H ; Zolghadri, M. R ; Tavner, P. J ; Sharif University of Technology
    Taylor and Francis Inc  2015
    The brushless doubly fed induction generator has been proposed for use in wind turbines as a more reliable alternative to the more commonly used doubly fed induction generator. To realize the commercial promises of the brushless doubly fed induction generator in this role, it must meet the existing grid connection codes, particularly with respect to low-voltage ride-through. In this article, the application of series dynamic resistors is proposed to enhance brushless doubly fed induction generator low-voltage ride-through capability, and the required analysis is provided. Three locations for series dynamic resistors are suggested in the brushless doubly fed induction generator circuit and... 

    A control scheme to enhance low voltage ride-through of brushless doubly-fed induction generators

    , Article Wind Energy ; November , 2015 ; 10954244 (ISSN) Tohidi, S ; Oraee, H ; Zolghadri, M. R ; Rahimi, M ; Sharif University of Technology
    John Wiley and Sons Ltd  2015
    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...