Driven Doubly Fed Induction Generator Research Articles

Synchronizing Control of Wind Turbine Driven Doubly Fed Induction Generator System With DG in Remote Area Involving Solar PV-Battery Energy Storage

This paper presents a synchronizing control for wind turbine (WT) driven doubly fed induction generator (DFIG) system with DG (Diesel Generator) in a remote area consisting of solar photovoltaic (PV) array and the battery energy storage. The DFIG is operated with two voltage source converters (VSCs) namely VSC on rotor side (VSCR) and VSC on load side (VSCL) by sharing common DC link with a battery. Moreover, the solar PV array is connected to the DC link through a boost converter, which is used to acquire peak power from the PV array. The microgrid is designed with minimum power converters with enhanced reliability and reduced intermittency especially for islands. Moreover, two controls are presented for successful and smooth operation of microgrid. An additional frequency loop is added in the control of VSCR for minimizing the power fluctuations and for smooth connection of DG to DFIG-solar-battery based isolated microgrid with static transfer switch. Moreover, the VSCR control is framed to build the rated voltage at the DFIG stator with control over ON/OFF operation of VSCR. It is also designed to harness the maximum power from wind. The control of VSCL is framed to regulate the DG power to operate it in optimal fuel consumption zone whenever it is synchronized. Simulations are performed at steady and varying wind speeds, varying PV insolation and at unbalanced connected loads. Moreover, a prototype of isolated microgrid is developed in the laboratory and its experimental performance is investigated at different operating scenarios to evidence its robustness.

Operation of Grid-Connected PV-Battery-Wind Driven DFIG Based System

This article presents a photovoltaic (PV)-battery and wind driven doubly fed induction generator (DFIG) based grid-connected system with an improved multifunctional control scheme for grid-side converter (GSC). A three-stage improved reduced-order multiple integrator control is used to maintain the reactive power into the grid as well as it regulates the dc-link voltage across the GSC. The grid side control improves power quality in different abnormal conditions. Moreover, it behaves in such a way that it reduces the rise time, the maximum peak overshoot, as well as the settling time during the transients. The rotor side converter is used to provide the required amount of reactive power using the field-oriented control, for the wind power generator (WPG). A DFIG is used as a WPG. The single-stage PV array and a battery with bidirectional converter are connected to the common dc link of the GSC. The battery helps to extract the maximum wind power in light load conditions. The charging and discharging of the battery depend on the renewable energy generation and load demand. The dynamic behavior is improved by adding a PV feedforward term with the total active load current component. Here, the stator current total harmonic distortion (THD) and grid current THD are maintained as per the IEEE standard. Simulated and test results show the performance of the developed system in different dynamic conditions, such as load unbalancing, changes in PV insolation, and change in speed from the cut-in to cut-out speeds of the wind turbine. Moreover, these results show the battery behavior during different dynamic conditions.

Enhanced control technique for a sensor-less wind driven doubly fed induction generator for energy conversion purpose

The current paper is concerned with introducing a predictive polar flux control (PPFC) scheme for a variable speed wind driven doubly fed induction generator (DFIG) without speed sensor. The operation of the designed PPFC is based on the power angle regulation. The adaptation process is performed through studying the relation between the generator’s torque and the power angle between the stator and rotor flux vectors. A robust observer is designed based on the back-stepping theory to estimate the rotor speed, stator currents, rotor flux and stator and rotor resistances. Furthermore, an effective maximum power point tracking (MPPT) scheme is designed to achieve the optimal wind power exploitation. To recognize the operation of the schemed PPFC, a discursive performance evaluation is performed for the modeled control scheme and the classic predictive torque control (PTC) scheme. The achieved results report that the DFIG’s performance is effectively enhanced with the proposed PPFC in comparison with the PTC technique. The improved dynamics are observed through the ripples reduction and reduced switching frequency. In addition, the designed observer has successfully managed in estimating the specified variables with high precision.

Application of DPC and DPC-GA to the dual-rotor wind turbine system with DFIG

<p>The work presents the dual-rotor wind energy conversion system (DRWECS) with a direct driven doubly-fed induction generator (DFIG). The system consists of a dual-rotor wind turbine (DRWT) with a DFIG, the grid side converter (GSC), and the machine side converter (MSC). To command the MSC, the direct power command (DPC) based on genetic algorithm (GA) and classical pulse width modulation (PWM) has been applied. To achieve the maximum power from the DRWT, the maximum powe point tracking (MPPT) technique has been used. The performed simulation studies confirmed the high performances of the DPC-GA contro method.</p>

Using Adaptive Second Order Sliding Mode to Improve Power Control of a Counter-Rotating Wind Turbine under Grid Disturbances

This work presents a new control strategy for counter-rotating wind turbine (CRWT) driven doubly-fed induction generator (DFIG) under grid disturbances, such as unbalanced network voltage scenarios. The proposed strategy based on the power control used dynamic gains second order sliding mode control (SOSMC). The power control of a DFIG by SOSMC widely based on the super-twisting (ST) algorithm with invariable parameters and sign functions. The proposed control method consists in using dynamic-parameters ST algorithm that ensures a better result than a conventional strategy. The proposed control scheme used 2 sliding surfaces such as reactive and active powers to control them. Also, the sign functions are replaced by saturation (sat) functions in order to minimize the chattering problems. Simulation results depicted in this research article have confirmed the good usefulness and effectiveness of the proposed adaptive super-twisting algorithm of the CRWT system during grid disturbances.

Transient Stability Analysis of Ocean Wave Energy Fed to a Power Grid Using a SSSC

This paper proposes the design of a closed-loop vector control structure based on Recurrent Functional Link based Elman Neural Network (RFLENN) for a Static Synchronous Series Compensator (SSSC), linking to a Seashore Wave Energy System (SWES) driven Doubly-Fed Induction Generator (DFIG) is connected. A RFLENN controller for a SSSC in order to reduce the power fluctuations, voltage support and damping for a hybrid power system. The proposed RFLENN is a functional link-based recurrent Elman Neural Network. Analysis of the performance of the proposed controller shows that it can achieve better damping characteristics. The internal power fluctuations to the power system can effectively stabilize the network under unstable conditions. This paper presents a closed-loop vector control structure based on RFLENN for a grid-connected SWES driven DFIG. This paper presents the transient stability improvement and power-flow control results of a DFIG-based SWES connected to a SSSC connected in series with one of two parallel transmission lines.

A Single Input Variable FLC for DFIG-Based WPGS in Standalone Mode

This paper proposes a novel single input variable fuzzy logic controller (FLC) strategy for a wind turbine driven doubly fed induction generator (DFIG) with a battery energy storage in autonomous mode. The proposed control scheme has multi-functionalities such as harmonic elimination, compensation of unbalanced load currents, and extraction of maximum power from the wind. The control of rotor side converter and load side converter is based on the field-oriented approach. The proposed single input variable FLC-based control has good dynamic response as compared to conventional control algorithms. The tip speed ratio-based maximum power point tracking technique is used to extract maximum power from the wind. The simulation of DFIG-based wind power generation system is carried out under various conditions, such as constant wind speed, variable wind speeds, and load currents unbalancing, using Simpower Systems toolbox of MATLAB. The DFIG stator voltages and currents are found balanced and sinusoidal by maintaining constant frequency and voltage at PCC. Finally, a prototype of DFIG-based wind energy system is developed in the laboratory to verify the performance of the proposed control scheme at variable wind speeds and linear, nonlinear loads. The total harmonic distortions of the DFIG stator voltages and currents are obtained within the limits of the IEEE 519 standard.

Modelling and estimation of gear train backlash present in wind turbine driven DFIG system

The backlash, which is always present in the gears of drive-trains to enable smooth operation, may increase with time due to the wear and tear during mechanical power transmission. Accurate knowledge of the amount of backlash non-linearity is required in such systems for monitoring control applications as well as developing maintenance strategies. In this study, the modelling and online estimation of the backlash existing in the gear train of wind turbine driven doubly fed induction generator (DFIG) systems is presented. The estimation has been performed using the unscented Kalman filter considering the backlash as a parameter and augmenting it as a state into the dynamics. Local measurements of the DFIG system have been used to estimate the backlash. The performance and efficacy of the method have been investigated in different scenarios viz. system parameters, noise levels of the measurements and operating points of the DFIG system. The estimation has also been performed in an environment of the time-varying wind, modelled by Van der Hoven's spectral model. The estimation has been enabled by the bad-data detection and examined in the presence of unknown mechanical parameters of the shaft.

A Complete Modeling and Control for Wind Turbine Based of a Doubly Fed Induction Generator using Direct Power Control

<span lang="EN-US">The paper presents the complete modeling and control strategy of variable speed wind turbine system (WTS) driven doubly fed induction generators (DFIG). A back-to-back converter is employed for the power conversion exchanged between DFIG and grid. The wind turbine is operated at the maximum power point tracking (MPPT) mode its maximum efficiency. Direct power control (DPC) based on selecting of the appropriate rotor voltage vectors and the errors of the active and reactive power, the control strategy of rotor side converter combines the technique of MPPT and direct power control. In the control system of the grid side converter the direct power control has been used to maintain a constant DC-Link voltage, and the reactive power is set to 0. Simulations results using MATLAB/SIMULINK are presented and discussed on a 1.5MW DFIG wind generation system demonstrate the effectiveness of the proposed control.</span>

Implementation, Comparison and Application of an Average Simulation Model of a Wind Turbine Driven Doubly Fed Induction Generator

Wind turbine driven doubly-fed induction generators (DFIGs) are widely used in the wind power industry. With the increasing penetration of wind farms, analysis of their effect on power systems has become a critical requirement. This paper presents the modeling of wind turbine driven DFIGs using the conventional vector controls in a detailed model of a DFIG that represents power electronics (PE) converters with device level models and proposes an average model eliminating the PE converters. The PSCAD/EMTDC™ (4.6) electromagnetic transient simulation software is used to develop the detailed and the proposing average model of a DFIG. The comparison of the two models reveals that the designed average DFIG model is adequate for simulating and analyzing most of the transient conditions.

Optimal active and reactive power control of wind turbine driven DFIG using TLBO algorithm and artificial neural networks

This paper investigates the optimal active and reactive power control capabilities for typical wind turbine (WT) driven doubly fed induction generator (DFIG). The main objective is to determine the optimal rotor voltage to extract certain active and reactive power from the DFIG over wide ranges of wind speed. Teaching learning-based optimisation (TLBO) algorithm is a new heuristic optimisation technique, used to obtain the optimum rotor voltages to achieve reference active and reactive powers overall operating points. Artificial neural network (ANN) controller is used as an adaptive controller to predict the value of rotor voltage for all operating points. The ideal power curve of a 2 MW wind turbine has been estimated to design the active power controller. The stator reactive power control capability with the range of ±1.6 MVAR is developed. With the proposed control strategy, the DFIG-based wind farm provides maximum power point tracking (MPPT), fully active and reactive powers control. For all operated wind speeds, the adaptive proposed controller develops useful network support compared to the conventional DFIG-based wind farm. The proposed system is developed in MATLAB/Simulink environment.

Robust Control for Power Sharing in Microgrids With Low-Inertia Wind and PV Generators

This paper presents a robust control design scheme for a multidistributed energy resource (DER) microgrid for power sharing in both interconnected and islanded modes. The scheme is proposed for micgrogrids consisting of photovoltaic (PV) units and wind turbine driven doubly fed induction generators (DFIGs). A battery is integrated with each of the wind and solar DER units. The control scheme has two levels: 1)one centralized multi-inputmulti-output robust controller for regulating the set reference active and reactive powers and 2)local real and reactive power droop controllers, one on each DER unit. The robust control scheme utilizes multivariable ${H_\infty}$ control to design controllers that are robust to the changes in the network and system nonlinearities. The effectiveness of the proposed controller is demonstrated through large-disturbance simulations, with complete nonlinear models, on a test microgrid. It is found that the power sharing controllers provide excellent performance against large disturbances and load variations during islanding transients and interconnected operation.

A stator voltage switching strategy for efficient low speed operation of DFIG using fractional rated converters

This paper presents a scheme for extending low speed operation of a wind driven Doubly Fed Induction Generator (DFIG) with limited rating converters (30%). In this scheme, a low voltage is applied to the stator at rotor speeds below the normal range (0.7 p.u.) while the nominal voltage is applied when the rotor speed is above this range. The switch-over to a lower stator voltage below a threshold speed facilitates to maintain the operational efficiency with the same fractional rated converters. Simulations results of a typical 250 kW DFIG in Matlab/Simulink environment reveal that, a lower stator voltage increases the generator efficiency at lower speeds without exceeding (limited) rating of the rotor side power converter. Typically the speed range is extended by 20% when reduction in voltage is 42%. With a 250 kW generator the energy harvested over one year is increased by 61.1 MWh with the proposed scheme. The scheme is simple, economical and can be implemented through speed sensor and contactors. Experiments on a laboratory test set up demonstrate the efficacy of the proposition.

PIR Regulator Using DTC for DFIG during Unbalanced Grid Voltage Conditions

This paper presents a PIR regulator using direct torque control strategy of grid connected wind turbine driven doubly fed induction generators (DFIGs) when the grid voltage is unbalanced. Under the unbalanced grid voltage condition, the stator voltage and current quality is strongly affected due to the negative and distorted components. It will be reducing the performance of other normal loads connected to the DFIG. That control scheme consisting of indirect matrix converter using DTC. To verify the value of the proposed control strategy, simulation results with 500 MVA DFIG topology are presented and discussed in the paper. Finally,the simulation studies are carried out on a 500 MVA wind-turbine driven DFIG system under unbalanced grid voltage conditions. All the results are validated by using PSCAD simulation.

Direct power control of DFIGs based wind energy generation systems under distorted grid voltage conditions

This paper presents an improved direct power control (DPC) strategy of a wind turbine driven doubly fed induction generators (DFIGs) connected to distorted grid voltage conditions. A coordinate control strategy of the grid side converter (GSC) and rotor side converter (RSC) of the DFIG is designed to improve the overall scheme performance. The RSC is controlled based on a DPC principle to eliminate the electromagnetic torque and stator reactive power oscillations. The total active and reactive power oscillations are compensated by the GSC control to achieve constant active and reactive powers from the overall DFIG system. A current control scheme consisting of a proportional integral controller and a resonant compensator tuned at six the grid frequency is proposed to provide accurate control of the GSC current. The proposed control scheme removes rotor current regulators and the decomposition process of the rotor and GSC currents. In addition, the proposed scheme preserves the advantages of the classical DPC. The feasibility of the proposed DPC scheme is validated by simulation studies on a 1.5MW wind power generation system under harmonically distorted grid voltage conditions. The performance of the proposed and conventional DPC schemes is compared under the same operating conditions. The proposed scheme results show significant improvements in the scheme performance.

Discrete sliding mode control strategy for direct real and reactive power regulation of wind driven DFIG

This paper investigates a discrete sliding mode control (DSMC) strategy for direct real and reactive power regulation for wind driven doubly fed induction generator (DFIG). The real and reactive power errors are eliminated by directly calculating the rotor control voltages through DSMC. In the stator stationary reference frame, direct real and reactive power control strategy is implemented. Therefore, it does not require the angular information of the stator and rotor currents or voltages. It does not involve any extra current loops which results into simple design. The use of constant converter switching frequency via space vector pulse width modulation eases the AC harmonic filter design and improves the power quality. The use of fast and flexible discrete controller makes the system competent with modern digital world. Detailed simulations have been carried out to validate the method. The simulation results reveal that the real and reactive power references are followed smoothly even in the presence of speed perturbations and performance of the system is robust against parameter variations and system disturbances.

Electrical machines and power‐electronic systems for high‐power wind energy generation applications

Purpose – Power‐electronic systems have been playing a significant role in the integration of large‐scale wind turbines into power systems due to the fact that during the past three decades power‐electronic technology has experienced a dramatic evolution. This second part of the paper aims to focus on a comprehensive survey of power converters and their associated control systems for high‐power wind energy generation applications.Design/methodology/approach – Advanced control strategies, i.e. field‐oriented vector control and direct power control, are initially reviewed for wind‐turbine driven doubly fed induction generator (DFIG) systems. Various topologies of power converters, comprising back‐to‐back (BTB) connected two‐ and multi‐level voltage source converters (VSCs), BTB current source converters (CSCs) and matrix converters, are identified for high‐power wind‐turbine driven PMSG systems, with their respective features and challenges outlined. Finally, several control issues, viz., basic control targ...

Fault Ride-Through Enhancement of DFIG-Based Wind Generation Considering Unbalanced and Distorted Conditions

A control strategy is proposed to enhance the operation, under network disturbances, of a wind turbine driven doubly fed induction generator (DFIG). The scheme allows us to overcome low voltages, imbalances, and harmonic distortions at the point of common coupling. The control law is designed using a feedback linearization approach plus resonant filters; this law directly controls the DFIG stator powers from the rotor voltages, unlike the most used nested two-loop approaches. An accurate control of the active and reactive powers delivered to the grid permits us to fulfill severe grid code requirements and to improve the fault ride-through capability. Under unbalanced conditions, the reference currents of both grid- and rotor-side converters are coordinately chosen to simultaneously eliminate the double-frequency pulsations in the total active power and electromagnetic torque. Several tests and disturbances to provide a realistic assessment and validation have been performed, showing the adequacy of the proposed controller. Comparisons with other control approaches with different objectives are also presented to illustrate the advantages regarding elimination of the double-frequency ripples and harmonic rejection capability.

Doubly-Fed Induction Generator Wind Turbine Model for Fault Ride-Through Investigation

The paper presents an investigation into the behavior of a grid-connected, wind turbine driven Doubly-Fed Induction Generator (DFIG) during Grid faults which are represented by a voltage dip on all three phases of the voltage supply. Stator-voltage- oriented vector control is used to decouple the active and reactive power generated by the machine. The dynamic DFIG model is used to simulate the behaviour of the wind turbine generator during both normal and fault conditions. Simulation and experiment results are shown in a very good agreement. Further the model can be used to investigate Fault ride-through performance of the DFIG.

Modelling and control of a variable speed wind turbine driving doubly fed induction generator using three-level PWM converter

The aim of this researcher is to develop a complete wind central model driven doubly fed induction generator (DFIG) which feeds an AC power grid. For that, two-pulse width modulated (PWM) voltage converters are connected back to back between the rotor terminals of DFIG and the utility grid via a common DC link, in there, our contribution will appear in the utilisation of three levels voltage inverters in order to ameliorate the energy quality. The simulation was carried out on a 2 MW wind-turbine driven DFIG system and the developed unified model validity and the proposed control strategies feasibility are all confirmed by the simulated results.