Doubly Fed Induction Generator Research Articles

Differentiator-Based Output Feedback MPPT Controller for DFIG Wind Energy Conversion Systems with Minimal System Information

This paper introduces a novel differentiator-based maximum power point tracking (MPPT) controller for a wind energy conversion system (WECS) equipped with a doubly fed induction generator (DFIG). Building upon our previous algorithms, the proposed controller reduces the need for detailed system information and displays enhanced robustness against parameter variations and disturbances. The innovation lies in the elimination of the need for explicit functional forms or specific parameter values in the system’s dynamics, relying solely on relative degrees and control directions. Utilizing a higher-order switching differentiator (HOSD), this paper outlines a method for overestimating the time derivatives of system outputs, thereby simplifying both the controller design and stability analysis. Compared to existing solutions, the proposed method requires minimal information, offers simpler control law structures, and follows a systematic design approach with fewer design constants. Simulation results demonstrate the efficacy of the proposed controller in both tracking maximum power and regulating reactive power to zero, suggesting a more efficient and simplified approach to MPPT control in WECS.

Comparative Study of Robust RSC Control of Doubly Fed Induction Generator Based Wind Turbine under Grid Frequency and Voltage Variations

The configuration of a grid-connected doubly fed induction generator (DFIG) for wind energy generation systems consists of direct coupling of the generator stator windings with the grid and partial coupling of the rotor through power converters. This structure makes the system sensitive to the fault grid. Thus, robust control techniques are required to deal with the undesirable transient sequences in the network. In this paper, two robust controllers have integrated to regulate the stator active and reactive power of DFIG based wind turbine. Then, they have been tested and compared to verify their performances when abnormal grid networks have occurred. Firstly, we used high order sliding mode (HOSM) based Super Twisting, which keeps the same conventional sliding mode performances, such as fast dynamic response and redundancy to the extern disturbances, with a simple design and chattering reduction. Secondly, we implement the backstepping control approach which is known for its robustness in transient sequences. A number of simulations have carried out to evaluate the ride-through performance of both control strategies in case of low grid voltage dips and grid frequency variations.

Crowbar Protection Scheme for Fault Ride Through in a Doubly-fed Induction Generator

This study focusses on using a crowbar protection scheme to overcome the symmetrical voltage dips in a doubly fed induction generator (DFIG). The crowbar protection scheme is integrated into the wind energy conversion system of the DFIG. The implementation of this scheme provides automated fault ride-through during sudden transients which may otherwise lead to over current faults. The increased use of renewable sources for electricity generation leads to a reduction in pollution which directly benefits the environment. Sustained usage of renewable resources will be beneficial for the environment.

Reactive Power Management at PCC with DFIG Based Wind Energy System

Reduction in availability of conventional energy sources and their scarcity in the future has led to the research on adoption of renewable energy sources for electricity generation. Wind is recognized as the prominent renewable energy source for electricity generation. Due to the erratic pattern of wind, variable speed generators such as doubly fed induction generator (DFIG) are preferred over fixed speed wind generators which use synchronous generators. Due to the increase in contribution of electricity generation through renewable energy sources, power quality of the system is deteriorating. In the present paper, a new economical and tangible scheme of DFIG is proposed to compensate for the reactive power at PCC, thus improving the power quality of the grid. The effectiveness of the scheme in compensating for the reactive power is evaluated using MATLAB / Simulink environment.

A High Robust Optimal Nonlinear Control with MPPT Speed for Wind Energy Conversion System (WECS) Based on Doubly Fed Induction Generator (DFIG)

As part of efforts to improve wind energy production using a doubly fed induction generator (DFIG), this paper presents modeling with power maximization through control of speed (MPPT) and control of stator active and reactive power for doubly fed induction generator. The quality of the generated energy and the performance of wind energy conversion systems (WECS) based on DFIG are affected by uncertainties and external disturbances. Therefore, the system requires high-performance control under the nonlinearity influence and the applied external disturbances. This work provides a new contribution and approach that combines nonlinear control (Backstepping) and optimal control (LQR). Backstepping control has been applied to give a good performance using nonlinear strategy and stability condition, but its main drawback is that it is relatively robust for sudden changes in wind speed or any external disturbances as well as it is sensitive against the uncertainties, which may lead to a chattering and an instability as well as overshoot or undershoot. To overcome the problems mentioned above the optimal control (LQR) has been applied to address this drawback in nonlinear control. Furthermore, it, the hybrid approach of Backstepping and LQR control resulting a robust control under the hardest scenarios during the wind system operating as well as provides a good performance in terms of chattering, stability and other performance characteristics which help to produce a high-quality energy. Overall, integrating LQR control with Backstepping can lead to a more powerful, flexible, and efficient control system with improved performance and reduced computational complexity.

Fractional-order neural control of a DFIG supplied by a two-level PWM inverter for dual-rotor wind turbine system

Energy ripples are among the common problems in renewable energies as a result of using less efficient strategies. In this work, a new technique is suggested to control a doubly-fed induction generator (DFIG) using the pulse width modulation (PWM). The new technique is based on the combination of neural networks and fractional-order control to minimize the reactive and active power ripples of the DFIG-based variable speed dual-rotor wind turbine system. The suggested fractional-order neural control (FONC) with the PWM is a simple, robust and a high-performance strategy. Simulation is performed using Matlab software to validate the effectiveness of the designed control of 1.5 MW DFIG and the obtained results are compared with the traditional direct power control (DPC) in different working conditions. In addition, the comparison between the suggested control and the DPC is performed in the cases of changing or not changing the device parameters in terms of ripple ratio, dynamic response, steady-state error, current quality, and overshoot of active and reactive power of the DFIG. As compared to the DPC, the proposed FONC technique improves the active and reactive power ripples by 65.71% and 84.74%, respectively. Also, improves the overshoot of the active and reactive power by 71.33% and 91.72%, respectively. The simulation results demonstrate the high performance and robustness of the FONC technique for the parametric variations of the DFIG-based variable speed dual-rotor wind turbine system compared to the DPC control.

Performance Analysis of 9, 11, 13, and 15 – Level Back-to-Back Connected Modular Multilevel Converters fed Doubly Fed Induction Machine

In this paper, back-to-back Modular Multilevel Converters are used to feed the Doubly Fed Induction Machine. The MMC with 9, 11, 13, and 15 – Level output voltages are generated and fed to the DFIM and the performance of the DFIM is analyzed, when the machine is working as Doubly Fed Induction Generator (DFIG) and when the machine is working as Doubly Fed Induction Motor. The performance of the DFIG is analyzed in terms of power factor at Grid Side Converter (GSC) for different levels of operation of MMC. The results show that the power factor is maintained near to unity power factor at grid side. The performance of the Doubly Fed Induction Motor is analyzed in terms of variation of the load torque being applied to motor. The results show that there is clear variation of the speed for two different load conditions. The work is carried out by using Typhoon HIL Real-Time Simulation platform, i.e., both Software and Hardware.

Comparative Study of Control Methods for a 2MW Doubly-Fed Induction Generator Wind Turbine

This paper presents a comparative study of two control methods for a 2MW Doubly-Fed Induction Generator Wind Turbine (DFIG-WT) using MATLAB Simulink. The Proportional-Integral-Derivative (PID) and Model Predictive Control (MPC) control methods were implemented and evaluated in terms of their ability to track reference signals, disturbances tolerance and stabilize the system under uncertain wind conditions. The performance of the control methods was assessed using a high-fidelity WT model that incorporates the dynamics of the wind turbine, the wind speed, and the control system. The results show that the MPC control method outperform the PID control method in terms of tracking accuracy and disturbance tolerance.

Limits of reactive power compensation of a doubly fed induction generator based wind turbine system

The doubly fed induction generator (DFIG) systems feature a significant amount of free power capacity that may be used for reactive power adjustment when they are put into practical use. This change, which is occasionally overlooked, is a significant one. Using DFIG systems for wind turbines (WT), this paper explored strategies for reducing and using reactive power. In order to investigate the power characteristic and how it is regulated in DFIG systems, a mathematical model for the steady-state performance of DFIG WT has been developed and presented. Here is a detailed derivation of the limiting range of DFIG's reactive power capacity as well as the physical constraints on reactive power output. The distribution of the DFIG WT at a distribution network's end is demonstrated by a simulation example. Within this simulation, reactive power management strategy, load fluctuation, and the change in wind speed are all taken into consideration. Due to the possibility of a rise in the voltage at the access point, can concluded that both acceptable and efficient to use DFIG WT's reactive power capabilities as an additional continuous reactive power source for effectiveness.

Enhanced Excitation Converter With Parallel/Series DC-Link Based on TAB for DFIG to Improve the LVRT Capability Under Severe Grid Faults

The low-voltage ride-through (LVRT) capability of the doubly-fed induction generator (DFIG) based on the conventional excitation converter is insufficient under severe grid faults. The reason is that the dynamic rotor electromotive forces (EMF) will far exceed the dc-link voltage. To solve this issue, this letter proposes an enhanced excitation converter with parallel/series dc-link based on the triple active bridge (TAB) for DFIG. The dc-link of the enhanced excitation converter consists of the TAB and switching circuit, replacing the capacitive-type dc-link. Based on this topology, the dc-link voltage can increase instantaneously during severe grid faults to resist rotor EMF and improve the LVRT capability of DFIG. Compared with existing LVRT schemes, the enhanced excitation converter enables DFIG to achieve LVRT and inject the reactive current requirements of the grid code into the grid under severe grid faults. Finally, experiments verified the effectiveness of the proposed enhanced excitation converter and its control strategy.

An optimum design and economic feasibility analysis of wind farms in Kuwait using different wind generation technologies

Kuwait plans to produce 15 % of its electricity from renewable resources by 2030. This paper aims at designing a 300-MW wind farm in six different sites in Kuwait. The study uses the measured wind data at Kuwait International Airport to predict the wind profile (speed and power density) at the selected sites. To validate the work, two different types of wind generation technologies are used in the design. The first type is Full-Converter Wind Turbine Generators (FCWTGs), and the second type is Doubly Fed Induction Generators (DFIGs). The designed wind farms are simulated using the Wind Atlas Analysis and Application Program (WAsP®) to estimate the Annual Energy Production (AEP) for each type of wind farms in each selected site. The location of every wind turbine in each wind farm (both types) for every selected site is accurately determined while considering needed spacing between rows and columns of turbines. The wake effect for downstream wind turbines is considered and estimated in the design. A comparison between the different wind farms in the six sites using the DIFGs and the FCWTGs generators is carried out. The economic feasibility of the designed wind farms is studied using the estimated Annual Energy Production (AEP) in each one of the designed wind farms.

AMCC-Based Power Management Scheme With Full Ancillary Services Support for a Wind–Solar Renewable Power Generation System

This paper introduces a power management scheme (PMS) for an integrated wind-solar renewable power generation system (RPGS). The PMS takes advantage of time of use electricity pricing mechanism to manage the net power exchange between the grid and the RPGS. A battery energy storage (BES) is utilized for enabling the system price arbitrage functionality. Meanwhile, the system control is performed through a novel application of the adaptive kernel width maximum correntropy criterion (AMCC) strategy. Apart from utilizing the electricity price volatility to maximize returns, the RPGS is also equipped to offer ancillary services support to the utility grid in the form of, (i) grid reactive current injection considering system constraints and (ii) grid power quality conditioning through local compensation of load reactive power, harmonics and unbalance. Moreover, for reduced system losses and minimized ripples in the grid currents amidst variations in grid voltages, a self-adjustable DC voltage reference technique is accommodated in the control strategy. An RPGS, employing a solar photovoltaic array and a doubly-fed induction generator for wind power generation, is utilized to experimentally demonstrate the effective operation of the overall control strategy.

Sequential frequency regulation strategy for DFIG and battery energy storage system considering artificial deadbands

To address the issues of the mechanical stress of doubly-fed induction generator (DFIG) and the service life of energy storage systems (ESSs) resulting from excessively and frequently participate in grid frequency regulation (GFR), this paper suggests a sequential GFR of the DFIG and ESS considering the artificial dead-bands. Firstly, the system frequency deviation expression is derived considering the dead-band to analyze the influences of the dead-bands on the grid frequency dynamics. Secondly, based on the artificial dead-bands, the GFR process is divided into three zones: the GFR zone of DFIG, the transaction zone of DFIG and ESS, and the GFR zone of ESS. To avoid the large mechanical stress of the wind turbines and shallow charging and discharging phenomenon of the ESS, the DFIG provides GFR function to mitigate the system frequency fluctuations, while ESS provides frequency regulation function to arrest the grid frequency variation taking into account the condition of state-of-charge constraints for severe frequency disturbances. Finally, simulations are conducted to verify the effectiveness of the proposed strategy under varying wind speed conditions combined with large disturbance. The results show that the proposed sequential GFR can maintain the frequency support while reducing the negative effects of mechanical fatigue of the DFIG and service life of ESS.

Application and Comparison of a Modified Protection Scheme Utilizing a Proportional–Integral Controller with a Conventional Design to Enhance Doubly Fed Induction Generator Wind Farm Operations during a Balanced Voltage Dip

The doubly fed induction generator (DFIG) is vulnerable to grid faults due to its direct stator connection, causing issues like excess stator current during voltage dips. Consequently, sensitive inverters suffer from increased currents, and the DC-link capacitor undergoes overcharging. This document examines two protection strategies employing a proportional–integral (PI) controller to manage the transient rotor current and mitigate DC-link overcharging, thereby optimizing DFIG behavior during network faults. One option combines a classic crowbar circuit with a DC-chopper, while the other is a modified protection scheme (MPS) that includes an impedance with passive elements and a crowbar. The impedance forms a resistance Rp parallel with an inductance Lp. Both configurations, situated between the rotor coils and the rotor-side converter (RSC), augment the capacity for low-voltage ride-through (LVRT). MATLAB/SIMULINK simulations of the two schemes demonstrate successful rotor current reduction at 2.9 kA and 3.4 kA, and DC-link tension reduction below and at 1.4 KV. In addition, the conventional crowbar and MPS configurations efficiently restrict the RSC current to levels below 0.21 kA and 2.94 kA, while absorbing up to 2.52 kA and 1.52 kA, respectively. The key difference lies in the fact that fine-tuning the parameters in the MPS design prevents rotor disconnection when faced with a balanced fault. This enhancement enhances machine performance and enables full stator power control via the RSC.

A new integral-synergetic controller for direct reactive and active powers control of a dual-rotor wind system

This paper proposes a new integral-synergetic controller for direct reactive and active powers control (DARPC) for a grid-connected doubly-fed induction generators (DFIGs) in dual-rotor wind power generation applications. The proposed DARPC strategy employs integral-synergetic control (ISC) to regulate the reactive and active powers of the DFIG-based variable speed dual-rotor wind turbine systems. The proposed ISC technique is the contribution of this work, where this strategy is a development of synergetic control and simplicity and robustness are the most prominent features. The main advantages of the proposed ISC-DARPC technique are ease of implement, good dynamic response, simple structure, and constant switching frequency operation. The Matlab software is used to validate the design of the ISC-DARPC technique, and the obtained results are compared with traditional DARPC. In addition, the ISC-DARPC technique is able to fully minimize ripples in both torque and active power during grid voltage imbalance or parametric changes on the DFIG.

Small signal stability and dynamic performance investigation on multi-machines power system including DFIG wind farm

<p>The boundless potential of wind power in augmenting global energy production is a promising prospect. The efficient design and cost-effectiveness of doubly fed induction generator (DFIG) wind systems make them an optimistic solution for incorporating wind power on a massive scale. However, integrating these systems into power grids poses several challenges, including power system stability. This study examines the small signal stability and dynamic performance of a modified Western System Coordinating Council (WSCC) 9-bus system including a DFIG wind farm using load flow analysis, and both electromechanical oscillations and eigenvalue analysis. Three case studies were conducted based on the DFIG location and power increment.The simulation is carried out with the aid of the power system analysis toolbox (PSAT) that operates within the MATLAB environment. The study’s findings suggest that the perturbation and location of the DFIG relative to the system’s load have a minimal influence on the overall system’s stability and efficiency. However, when considering damping ratio, power angle, and rotor speed deviations, generators 1 and 2 with the perturbed DFIG installed on bus 8 are the most sensitive units to instability. Hence, larger perturbations and different DFIG’s location influence on power systems necessitates further analysis.</p>

Coordinated Control for Seamless Integration of Wind Energy Conversion System With Small Hydrogenerator Through Modified Notch Filters

This paper deals with the seamless integration of doubly fed induction generator (DFIG) based wind energy conversion system (WECS) with local grid constituted by a permanent magnet based small hydrogenerator (PMHG). The seamless integration is carried out using a solid state static transfer switch (SSSTS). The WECS-PMHG system is operated using a coordinated control strategy based on modified notch filters. The modified notch filters are adopted for the computation of (a) sensorless speed and position of the DFIG rotor, (b) fundamental constituents of unbalanced/nonlinear load current and (c) filtered DFIG stator voltages and phase angle. Moreover, the notch filters are also used for mitigating the effects of unbalance/nonlinearity in load currents on the stator and rotor currents of DFIG as well as PMHG currents. Additionally, the control methodology ensures no power interaction between the WECS and the PMHG during the synchronization process. This enables transient-free WECS and PMHG currents. Further, the coordinated control regulates the amplitude and frequency of system voltages even amidst wide variations in wind speed and load. The DFIG stator and wind currents are injected at unity power factor with the system voltages, while the excitation requirement of the DFIG is met by its machine side converter. The validness of the control is demonstrated experimentally through a developed laboratory-scale test bench.

A Novel Adaptive Model Predictive Control Strategy for DFIG Wind Turbine With Parameter Variations in Complex Power Systems

In this paper, a novel adaptive model predictive control (MPC) strategy is proposed for doubly fed induction generator (DFIG) wind turbine (WT), which is integrated into a complex power system, in order to improve the power output tracking precision and dynamic performance. Considering the existence of parameter variations in DFIG, an adaptive parameter estimation method is firstly designed. By analysis of stability, the convergence of the parameter estimation algorithm is rigorously proved. Furthermore, the parameter estimation algorithm is effectively integrated into MPC to realize real-time optimal control of DFIG with the adaptive model. To achieve the rotor side converter (RSC) design based on adaptive MPC, the DFIG model is linearized. In addition, a virtual output compensation (VOC) strategy is adopted to alleviate the impact of model linearization errors on the MPC, especially the variation of the model parameter. The newly proposed adaptive MPC-based RSC is capable of greatly improving the tracking performance, meanwhile taking into account the realistic constraints under various operation conditions. The simulation results demonstrate the effectiveness and superiority of the proposed control method.

Dual Converter Operating With Floating Capacitors Connecting Open-End Winding Doubly-Fed Induction Generator to the DC Microgrid

This paper presents a novel configuration to connect a three-phase doubly-fed induction generator (DFIG) to the dc microgrid. The proposed topology connects an uncontrolled con- verter and a full-controlled converter in series with the generator stator windings in an open-end winding (OEW) configuration. The full-controlled converter is connected to an independent dc link based on floating capacitors. The paper discusses the converter operating principles, pulse-width modulation (PWM), DFIG power control, and the floating capacitors' voltage reg- ulation. The work compares the proposed and conventional systems regarding current harmonic distortions, torque ripple, and semiconductor losses. Simulations and experiments show steady-state and transient results for a 0.56-kW DFIG operating at the rated power. Finally, it was verified that the proposed topology presents lower power losses and low-distorted voltages and currents over the DFIG stator windings.

Fault tolerant control for DFIG wind turbine controlled by ADRC and optimized by genetic algorithm

This research work deals with the modelling, control and simulation of a wind turbine based on the doubly fed induction generator (DFIG) in the current sensor’s failure event. We present in the first time the model of the wind energy conversion system based on the DFIG and the control by active disturbances rejection control (ADRC) optimized by genetic algorithm. Particular focus is directed towards on a technique for detection, identification, isolation and reconfiguration of current sensor signals after failure. The combination of the two preceding techniques makes it possible to have a fault tolerant control to sensor faults which ensures continuity of service in all circumstances. The robustness of the proposed technique is tested under the MATLAB/Simulink environment.