Doubly Fed Induction Generator Based Wind Energy Conversion Research Articles

Comparative Study and Dynamic Performance Analysis of DFIG based Wind Energy Conversion System

This paper presents a novel control strategy for wind energy conversion system for improving the dynamic stability of the system. In off-grid applications, the load voltage and frequency should be managed in steady-state and transient circumstances. For rural areas with unpredictable wind and load circumstances, electricity quality and control are crucial tasks. In order to improve power quality, dynamic stability and power management in direct drive standalone wind energy systems, this research provides a coordinated proportional resonant (PR) controller. Under different operating situations, such as variable wind with step increases and decreases in wind velocity, balanced and unbalanced load conditions, the dynamic performance of a doubly-fed induction generator (DFIG) is evaluated. In order to meet the load requirement, the suggested PR control technique with battery energy controller also provides efficient power balancing between the wind and battery sources. A fair performance comparison is made between the proposed control strategy and conventional vector control strategy by using the MATLAB/SIMULINK platform under varying wind and load circumstances. The proposed control approach shown better dynamic stability, improving the power quality of the system and better synchronization.

AFIS based Advanced Power Control Scheme for Grid-Connected DFIG-Driven WECS

In wind energy conversion system, extraction of optimum power and efficient operation are two major challenges. In grid connected mode, a doubly fed induction generator (DFIG) control unit is designed to operate at optimum speed to deliver maximum output power in the grid while the voltage, frequency and harmonic regulations need to be fulfilled. Vector control associated with proportional-integral (PI) controllers has been widely applied in wind farms for reliable power regulation of DFIG. As DFIG based wind energy conversion system (WECS) experiences strong nonlinearity and uncertainties originated from the aerodynamics of the wind turbine and magnetic saturation of the generator, different adaptive and nonlinear control schemes have been proposed to resolve the problems associated with fixed-gain PI controllers.

Enhanced Control of DFIG Based Wind Energy Conversion System Under Unbalanced Grid Voltages Using Mixed Generalized Integrator

The operation of a wind energy conversion system based on a doubly fed induction generator (DFIG) is found to be extremely sensitive to unbalanced grid voltages. In this context, this article presents an enhanced control strategy for a DFIG operating under unbalanced grid voltages, using a mixed generalized integrator (MGI). The MGI is a hybrid form of the second and third-order generalized integrators and is employed for positive and negative sequence calculation. The MGI-based enhanced control strategy utilizes the hysteresis band control of rotor currents and grid currents, to generate switching sequences for rotor side converter and grid side converter, respectively. In addition to superior dynamic tracking of reference currents, this scheme eliminates the need for implementation and careful tuning of eight distinct proportional-integral inner current regulators, as is the case with conventional control strategy for the DFIG operating at unbalanced grid voltages. Furthermore, MGI improves the grid synchronization in DFIG system amidst the presence of dc offset and unbalance in the supply voltages. The overall coordinated control strategy is designed to realize seven separate control objectives, and its effectiveness is verified through simulation and experimental results.

Improved Backstepping Control of a DFIG based Wind Energy Conversion System using Ant Lion Optimizer Algorithm

In this paper, an improved Backstepping control based on a recent optimization method called Ant Lion Optimizer (ALO) algorithm for a Doubly Fed Induction Generator (DFIG) driven by a wind turbine is designed and presented. ALO algorithm is applied for obtaining optimum Backstepping control (BCS) parameters that are able to make the drive more robust with a faster dynamic response, higher accuracy and steady performance. The fitness function of the ALO algorithm to be minimized is designed using some indexes criterion like Integral Time Absolute Error (ITAE) and Integral Time Square Error (ITSE). Simulation tests are carried out in MATLAB/Simulink environment to validate the effectiveness of the proposed BCS-ALO and compared to the conventional BCS control. The results prove that the objectives of this paper were accomplished in terms of robustness, better dynamic efficiency, reduced harmonic distortion, minimization of stator powers ripples and performing well in solving the problem of uncertainty of the model parameter.

A new optimal model predictive control scheme for a wind energy conversion system

AbstractThe correct management of power exchange between the doubly‐Fed induction generator (DFIG) and the grid depends on the effective optimal operation of the DFIG based wind energy conversion system (WECS). A modified optimal model predictive controller (MPC) architecture for WECS is proposed in this paper. The proposed scheme is carried out in two stages, as follows: (a) Using the MPC model and the tracking factor, an optimal control law is created, and (b) the aforementioned optimized issue is addressed using the linear matrix inequality (LMI) approach. Some improvements were made to the conventional LMI‐based MPC technique to lower the high computational complexity. To perform active and reactive power control in DFIG, the proposed approach is applied on the rotor‐side converter (RSC) control. The control law is divided into two sections. The first section deals with rotor current, while the second section deals with the RSC switching states. The LMI is used in the second portion of the control law to find the best switching state solution. The proposed method was created using the MATLAB/SIMULINK environment and tested in a 1hP DFIG‐WECS setup. By comparing the obtained results to conventional LMI‐PI, MPC‐based WECS, the effectiveness of the obtained results is verified. Variable wind speed conditions are used to vary all the results. Integral absolute error, integral time absolute error, and Integral square error measurements are used to compare the tracking performance index of all methods.

Stochastic Distribution Controller for Wind Turbines with Doubly Fed Induction Generator

The major purpose of this work is to design the controllers for controlling thevariable speed, variable pitch wind turbine (WT) with doubly fed inductiongenerator (DFIG). Vector control strategy is adopted for controlling theDFIG active and reactive power. Generator torque is control to provide theregulated real power with minimum fluctuation. The fixed gain proportional-integral (PI) controller designed to the converter of rotor side and gridside has limited operating range and inherent overshoot. Gain schedulingPI controller is designed to minimize the overshoot and fluctuation existsin proportional-integral controller. Since DFIG based wind energy conver-sion system (WECS) works in uncertain wind speed, stochastic distributioncontrol (SDC) method is proposed to control the probability distributionfunction (PDF) of DFIG based WECS. It copes with nonlinearities in theWECS and contiguous variations at operating point and provides satisfactoryperformance for the whole operating region. It improves the performancetogether with power quality of generated electric power thereby maximizing the lifespan of installation and ensures secure and acceptable operation of theDFIG based WECS.

Nine Switch Back To Back Converter- Design and Simulation for Wind Turbines Based on Doubly Fed Induction Generator

A conventional power system diverges from a Wind Energy Conversion System (WECS). The power output from a wind turbine system varies as the wind varies. Thus, management, design and analysis of WECS become difficult. Various approaches are available theoretically to cram the behavior of WECS. This paper, uses MATLAB simulink model of DFIG based WECS to study steady state characteristics. The analysis is performed to inspect the characteristics of wind and Doubly Fed Induction Generator model. For efficient generation of electricity, it is necessary to operate the wind turbine at variable speed. This is achieved by the Power Electronic Converters. Many designs of converters are available, depending on the aspects of economy, configuration and application. Now-a-days attention of the researchers is diverted towards the Doubly Fed Induction Generator (DFIG). The paper signifies the design, simulation and analysis of back-to-back converters for DFIG based Wind Energy Conversion System WECS. A 9- switch Back to Back converter is designed, simulated in the paper and the results are compared with traditional AC-DC-AC converter. The functioning of the converter is simulated by means of MATLAB/SIMULINK. Results of the simulation illustrate the improved DC link voltage, when compared to that of the conventional converter.

Performance Investigation of Grid-Connected DFIG using Integrated Shunt Active Filtering Capabilities

This paper presents the modified grid side converter control (GSC) technique which enable the GSC to work as a shunt active filter to mitigate the grid current harmonics produced by the nonlinear load, as well as to transfer power from the grid to the rotor of doubly fed induction generator (DFIG) or vice versa. The main contribution of this proposed technique is an addition of a shunt active filter with space vector pulse width modulation (SVPWM) controller in GSC control itself in order to achieve a better grid current %THD profile, and simultaneously to control active power for variable wind speed. The reactive power supply to the DFIG and extraction of maximum power is achieved using RSC. The comparison of the modified GSC control technique using hysteresis current control (HCC), and SVPWM controller used to mitigate the harmonics is presented with different wind speeds. The proposed modified GSC control technique is simulated for grid-connected 2.6 MW DFIG based wind energy conversion system (WECS) in MATLAB Simulink environment.

Sensor fault-tolerant control of DFIG based wind energy conversion systems

This paper proposes a fault-tolerant control (FTC) strategy for a doubly-fed induction generator (DFIG) based wind energy conversion system (WECS) with sensor faults. The DFIG system is decomposed into stator, rotor, grid current models, and the sensor fault observer (SFO) is presented to provide accurate estimations of sensor fault components in the presence of model uncertainties. Based on the independent current dynamics of DFIG system, three SFOs are designed in parallel to respectively estimate the stator, rotor, and grid current senor fault signals. During the occurrence of faults, the fault estimations derived from current observers are adopted to compensate the faulty signals, thereby achieving the system reconfiguration of DFIG without requiring any fault diagnosis schemes. Simulation studies are undertaken on a grid-connected WECS under the conditions of stepped and random wind speeds, and single and multiple current sensor faults. Simulation and experimental results reveal that the FTC-controlled DFIG system is resilient from the sensor faults and maintains continuous stable operation.

Adaptive Step Size Based Hill-Climb Search Algorithm for MPPT Control of DFIG-WECS With Reduced Power Fluctuation and Improved Tracking Performance

One of the major challenges in harnessing wind energy is to extract maximum power from intermittent generation of wind farms as wind power generation strongly depends on wind speed variation. Among different maximum power point tracking (MPPT) algorithms, traditionally, hill climb search (HCS) method is widely used because of its simple implementation and turbine parameter-independence. However, the conventional HCS algorithm has some drawbacks such as power fluctuation and speed-efficiency tradeoff. Similarly constant tip-speed ratio (TSR) MPPT control method requires precise knowledge of optimal TSR of the turbine. Therefore, in this paper a new adaptive step size based HCS controller is proposed to mitigate the deficiencies of other techniques by incorporating wind speed measurement. The function-based adaptive control scheme evaluates the step size by the variation of the wind speed and extracted power range. The proposed variable step size based HCS-MPPT system is simulated at variable wind speed. A prototype system is also built with a low-power doubly-fed induction generator (DFIG). It is found from the results that the proposed controller reduces the steady-state power fluctuation of the DFIG based wind energy conversion system significantly compared to the conventional HCS-MPPT controller and constant TSR based MPPT controller at variable wind speeds.

Controller design for doubly fed induction generator using particle swarm optimization technique

This manuscript describes the controller design for doubly fed induction generator (DFIG) driven by a variable speed wind turbine using particle swarm optimization technique. The mathematical model of the DFIG, its power converters, and their controllers have illustrated in this paper appropriately. The lower order simple illustration of DFIG have been used for PID controller design using numerical differentiation of Simulink model. The controller design for DFIG based WECS using PSO technique and its fitness functions are described in detail. The responses of the DFIG system regarding terminal voltage, current, active-reactive power and DC-Link voltage along with generator speed have slightly improved with PSO based controller. Finally, the obtained output is equated with a standard technique for performance improvement of the DFIG based wind energy conversion system.

Adaptive terminal sliding mode power control of DFIG based wind energy conversion system for stability enhancement

Summary A novel adaptive terminal sliding mode instantaneous active and reactive power control for both the rotor-side as well as grid-side converters of the doubly fed induction generator (DFIG) based wind power extraction system is proposed in this paper using the abc frame of reference. This approach is independent of unmodeled dynamics of the phase-locked loops that reduces the nonlinearities in computing the control objective. The adaptive nature of the terminal sliding mode controller design offers a better and enhanced transient response as compared with some of the conventional methods for a wide range of disturbances such as switching faults, reference tracking and wind speed variation for both the sub-synchronous and synchronous modes of operation of the doubly fed induction generator subjected to lower and higher wind speeds. Moreover, a maximum power point tracking algorithm has been incorporated to compute the reference power of the stator of the DFIG, which is utilized in designing the control system for the rotor-side converter. Further extensive computer simulations have been carried out with the DFIG operating in a single machine or multimachine environment to validate the effectiveness of the proposed control. Also the robustness and stability of the proposed adaptive terminal sliding mode control is verified using the MATLAB/SIMULINK based DFIG model. Copyright © 2015 John Wiley & Sons, Ltd.

Fast adaptive finite-time terminal sliding mode power control for the rotor side converter of the DFIG based wind energy conversion system

Abstract A novel control strategy for doubly fed induction generator (DFIG) based wind energy conversion system (WECS) is proposed in this paper. The detailed dynamic model of the DFIG based WECS connected to the infinite bus is also presented in the paper, in terms of the d – q reference frame. In order to overcome the chattering phenomenon and the saturation of control input signals as accounted for the well-known sliding mode control strategy, a non-linear sliding surface based fast and adaptive terminal sliding mode control strategy is implemented. Moreover the proposed control strategy involves DFIG active and reactive power as its input instead of currents, which has been implemented in most of the available literatures. The proposed control strategy precision, reliability and robustness is successfully validated in MATLAB environment (both mathematical model in MATLAB/EDITOR environment as well as the MATLAB/SIMULINK environment), in terms of its superior dynamic transient response (for the model parameters) subjected to a diverse and tough situations for lower and higher wind speeds, as well as their random variations, as illustrated in the paper.

Analysis, calculation and reduction of shaft voltage in induction generators

This paper presents analysis of shaft voltage in different configurations of a Doubly Fed Induction Generator (DFIG) and an Induction Generator (IG) with a back-to-back inverter in wind turbine applications. Detailed high frequency model of the proposed systems have been developed based on existing capacitive couplings in IG & DFIG structures and common mode voltage sources. In this research work, several arrangements of DFIG based wind energy conversion systems are investigated on shaft voltage calculation and its mitigation techniques. Placements of an LC line filter in different locations and its effects on shaft voltage elimination are studied with mathematical analysis and simulations.

Investigation of Shaft Voltage in Wind Turbine Systems with Induction Generators

This paper presents the analysis of shaft voltage in different configurations of a doubly fed induction generator (DFIG) and an induction generator (IG) with a back-to-back inverter in wind turbine applications. Detailed high frequency model of the proposed systems have been developed based on existing capacitive couplings in IG & DFIG structures and common mode voltage sources. In this research work, several arrangements of DFIG based wind energy conversion systems (WES) are investigated in case of shaft voltage calculation and its mitigation techniques. Placements of an LC line filter in different locations and its effects on shaft voltage elimination are studied via Mathematical analysis and simulations. A pulse width modulation (PWM) technique and a back-to-back inverter with a bidirectional buck converter have been presented to eliminate the shaft voltage in a DFIG wind turbine.