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During the fault period, a phase angle jump may occur at the stator or the point of common coupling, which will deteriorate the low-voltage ride-through (LVRT) characteristics of a doubly fed induction generator (DFIG). The existing LVRT studies focus on the impact of a voltage drop on DFIGs but often ignore that of a phase angle jump. The time-domain simulation is accurate in describing the response of a DFIG during the LVRT process, but it is time-consuming for a DFIG with the full-order model. In this paper, by using the voltage magnitude and phase angle of the stator or the point of common coupling as the inputs, and the state variables as the outputs, the transfer function of a DFIG is derived to analyze its response and find the LVRT measures against the voltage drop and, especially, the phase angle jump. Firstly, the differential-algebraic equations of the DFIG are linearized to propose their transfer function model. Secondly, considering its high-order characteristic, a model reduction method for the transfer function of the DFIG using the Schur decomposition is proposed, and the analytical expression of the output variables of the DFIG with the phase angle jump is derived by the inverse Laplace transformation to judge the necessity of the LVRT measures. Finally, the simulation results of the DFIG are provided to verify the accuracy of the transfer function model and its reduced-order form and validate the feasibility of the LVRT against the phase angle jump with the proposed models. [ABSTRACT FROM AUTHOR]

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Abstract The importance of resolving stability concerns in weak AC grid‐connected doubly fed induction generator (DFIG) wind energy systems during low‐voltage ride‐through (LVRT) events cannot be ignored, given the increasing popularity of wind power‐based microgrids. Furthermore, the emergence of generation loss and postfault oscillation within a microgrid (MG) due to grid faults has also become a significant concern. The static synchronous compensator (STATCOM) under consideration in this study is tuned using particle swarm optimization (PSO), the artificial hummingbird algorithm (AHA), and a hybrid approach incorporating both PSO and AHA. Faults of both a symmetrical and an asymmetrical nature have occurred on the power grid side. The proposed hybrid PSO‐AHA‐tuned STATCOM strategy aims to improve LVRT, minimize power generation loss during faults, and reduce oscillations after a fault by controlling the flow of reactive power between point of common coupling (PCC) and MG. The MATLAB simulation environment was used to simulate the 16 MW MG test system. The performance of the PSO‐AHA‐tuned STATCOM was assessed by comparing results with those from conventional STATCOM, PSO, and AHA optimizer‐tuned STATCOM in four fault situations. A comparison of the results shows that the proposed strategy performed better than other approaches mentioned in this paper and achieved the desired objectives.

The importance of resolving stability concerns in weak AC grid‐connected doubly fed induction generator (DFIG) wind energy systems during low‐voltage ride‐through (LVRT) events cannot be ignored, given the increasing popularity of wind power‐based microgrids. Furthermore, the emergence of generation loss and postfault oscillation within a microgrid (MG) due to grid faults has also become a significant concern. The static synchronous compensator (STATCOM) under consideration in this study is tuned using particle swarm optimization (PSO), the artificial hummingbird algorithm (AHA), and a hybrid approach incorporating both PSO and AHA. Faults of both a symmetrical and an asymmetrical nature have occurred on the power grid side. The proposed hybrid PSO‐AHA‐tuned STATCOM strategy aims to improve LVRT, minimize power generation loss during faults, and reduce oscillations after a fault by controlling the flow of reactive power between point of common coupling (PCC) and MG. The MATLAB simulation environment was used to simulate the 16 MW MG test system. The performance of the PSO‐AHA‐tuned STATCOM was assessed by comparing results with those from conventional STATCOM, PSO, and AHA optimizer‐tuned STATCOM in four fault situations. A comparison of the results shows that the proposed strategy performed better than other approaches mentioned in this paper and achieved the desired objectives. [ABSTRACT FROM AUTHOR]

To maintain a stable electricity supply in interconnected power grids, effective frequency and voltage regulation are required. Interconnected power systems use Automatic Load Frequency Control (ALFC) and Automatic Voltage Regulator (AVR) for this purpose. The integration of renewable sources, such as Doubly Fed Induction Generators (DFIGs), creates challenges for such control loops. This study investigates the impact of using various Frequency-Linked Pricing (FLP)-based operating strategies under Availability-Based Tariff (ABT) on combined ALFC and AVR in a two-area interconnected power system with DFIGs. FLP-based operating strategies under ABT react to frequency changes through price signals, which can act faster compared to traditional AGC methods that rely on communication between control centers. This quicker response helps maintain frequency and voltage during load disturbances. Most of the earlier research focused mostly on using only a single type of FLP-based operating strategy under ABT within the ALFC loop, neglecting the combined ALFC-AVR interaction. This work addresses this gap by evaluating three FLP-based operating strategies under ABT along with the traditional approach for their impact on frequency and voltage under step load disturbance. Simulation studies conducted in MATLAB 2022a demonstrate the effectiveness of the proposed strategies, providing valuable insights for improving frequency and voltage control in modern power systems. The investigation reveals that the strategy that considers the difference between the actual and reference values of the unscheduled interchange (UI) charge and the marginal cost of generation to produce the control command outperforms the other strategies and restores the frequency and voltage to their nominal values.

This paper proposes a Power Harmonic Suppression (Damping) (PHS) based reference current generation scheme, which focuses on simultaneous mitigation of harmonic pulsations in electromagnetic torque, stator real and reactive powers, and DC‐link voltage while retaining sinusoidal stator and grid currents and unity power factor at grid side. The crux of this PHS method lies in its ability to eliminate the harmonic powers developed in the DFIG stator and grid at 100Hz, 200Hz, 300Hz, 400Hz, and 600 Hz owing to second, fifth, and seventh harmonic grid voltages. This is achieved as a result of the elimination of natural fluxes developed in the DFIG air gap due to second, fifth, and seventh harmonic distortions in grid voltage. For this, a single concurrent reference current generation technique is developed for RSC and GSC to mitigate the oscillations of electromagnetic torque, stator real and reactive powers, and ripples in DC‐link voltage. Further, the reference rotor currents (positive, negative, fifth, and seventh sequence) are compared with the actual rotor currents using a PI controller to retain sinusoidal stator and grid currents. The proposed scheme's efficacy is validated with PSCAD/EMTDC simulations and using OPAL‐RT OP4510 real‐time simulator, on a 2.3 kVA DFIG. [ABSTRACT FROM AUTHOR]

The large-scale wind power grid connection will change the power distribution between the original system tide and synchronous machine, and the interaction between wind turbine and synchronous machine affects the system's damping oscillation characteristics. Traditional synchronous generators' extra damping control provides an important means for DFIG to improve system damping characteristics. Different types of PSS have different suppression effects on low-frequency oscillations. In this paper, four types of IEEE PSS models are built in DIGSILENT/PowerFactory to study the suppression effects of DFIG additional different types of PSS on low-frequency oscillations of power systems, and the suppression effect of four types of PSS on system low-frequency oscillation after connecting to the DFIG reactive power control loop is compared and analyzed from two perspectives: eigenvalue and time-domain simulation. The MRAC control principle is used to improve PSS4B, and the total least squares-estimation of signal parameters via rotational invariance technique identification method is used to obtain the system transfer function, and the controller parameters are calculated in real time using the adaptive law based on the gradient approach. Finally, the MRAC–PSS4B is connected to the DFIG rotor-side controller's reactive power control loop, and the improvement effect of the designed MRAC–PSS4B controller on the power system's low-frequency oscillation characteristics under different contact line transmission power is confirmed. [ABSTRACT FROM AUTHOR]

This study discusses performance of the power control strategy for a Wind Turbine/Fuel Cell Hybrid System with a Doubly Fed Induction Generator (DFIG)-Direct Current (DC) link configuration. To overcome high cost and the complex structure of the previous paper, a new DFIG-DC link configuration is proposed that uses a single Voltage Source Inverter (VSI) and a diode rectifier to connect the stator and rotor to the DC-link, respectively. Also, the DFIG-DC system is modeled and a Stator Field-Oriented Control (SFOC) is adopted to control the VSI to extract the maximum power generated by the wind turbine. The model and the control of the DC-DC boost converter used to connect the hydrogen fuel cell to the DC-link are established. To achieve better performance of the proposed DFIG-DC system, the power control strategy has been tested by using the dSpace DS1104 processor board and the experimental results show the performance of the control strategy in terms of parameters regulation under a different scenario. [ABSTRACT FROM AUTHOR]

This paper proposes an innovative algorithm-based control model for improving the doubly fed induction generator (DFIG) system’s low-voltage ride-through (LVRT) capabilities. The Mountain Gazelle optimization (MGO) algorithm is combined with an adaptive neuro-fuzzy inference system (ANFIS)-based proportional-integral (PI) regulator, called the MGOANFIS-PI approach. In the proposed method, the data set of an MGO-based PI regulator is used after rectification to train the MGOANFIS controller, so updating the ANFIS technique improves MGO’s searching behavior. The implemented control method ensures LVRT capability on grid-tied wind conversion plants based on DFIG in case of a malfunction or a voltage drop. Multiple metrics relating to LVRT are monitored in the proposed system, comprising current, active, and reactive power and voltages. The objective to be achieved, which is resolved through the cascaded MGOANFIS-based PI scheme, is defined. Based on the collected data, ANFIS performs and anticipates the optimal control signal from converters on the rotor and network sides. The MGOANFIS-PI methodology effectively handles system performance and voltage instability during four fault circumstances. The LVRT functionality of the DFIG system and the power quality are enhanced with the assistance of the proposed methodology. Simulations are carried out using MATLAB/Simulink framework. Two test systems are examined: the IEEE 39 bus and the 9 MW wind power plant (WPP) test systems. The WPP’s ability to withstand grid voltage sags is analyzed as part of an effectiveness assessment. The relevance and efficacy of the proposed MGOANFIS-PI method are evaluated, and proved the better performance of the cascaded MGO-based ANFIS-PI controller when compared to PI controllers optimized by comparing it with other well-known optimization techniques, i.e., Gorilla troop optimizer, particle swarm optimization, and genetic algorithm. In the three-phase IEEE 39 bus system and the 9 MW test scheme, detailed wind power plants could persevere in the face of every fault condition.

This paper presents a comprehensive study on the model predictive control (MPC) of doubly fed induction generators (DFIG) in wind energy conversion systems (WECS); in particular the MPC of the rotor side converter. The general principle of prevalent MPC strategies is discussed to introduce the theoretical framework in the first place. Furthermore, mainstream and high-performance MPC methods of DFIGs have been identified as model predictive current control (MPCC), model predictive torque control (MPTC), and model predictive power control (MPPC). Starting from analyzing dynamic models, these MPC strategies are investigated in terms of operating principles and technical developments. The paper further investigates implementation of MPC strategies in unbalanced grids. Based on the quantitative and qualitative analysis of several case studies, performance of various MPC schemes is compared and their special features are identified. Guidelines for designing MPC strategies of DFIGs in WECS are provided.

Wind attribute analysis is a crucial aspect of meteorological and environmental research, with applications ranging from renewable energy generation to weather forecasting. However, existing models encounter several challenges in accurately and comprehensively characterizing wind positions. In this context, the proposed Incremental Tuned Generative Adversarial Network model (incremental GAN model), based on an unsupervised learning approach, introduces innovative solutions to overcome these challenges and enhance the precision and reliability of wind position analysis. This research aims to enhance the reliability and efficiency of wind energy generation by analyzing wind conditions and providing accurate data for decision-making. It introduces an Incremental GAN that refines parameters based on various factors. This GAN model learns and predicts these parameters over time, improving its performance. It incorporates advanced techniques like a 2-level fused discriminator and self-attention for precise predictions of wind characteristics. The GAN model generates important parameters such as droop gain, which influences generator output in response to load or generation changes, aiding grid stability. It also optimizes the frequency control of different types of generators in the presence of wind farms. The model continuously monitors wind farm conditions, adjusting power injection into the grid as needed for efficient and reliable wind energy utilization.

During the fault period, a phase angle jump may occur at the stator or the point of common coupling, which will deteriorate the low-voltage ride-through (LVRT) characteristics of a doubly fed induction generator (DFIG). The existing LVRT studies focus on the impact of a voltage drop on DFIGs but often ignore that of a phase angle jump. The time-domain simulation is accurate in describing the response of a DFIG during the LVRT process, but it is time-consuming for a DFIG with the full-order model. In this paper, by using the voltage magnitude and phase angle of the stator or the point of common coupling as the inputs, and the state variables as the outputs, the transfer function of a DFIG is derived to analyze its response and find the LVRT measures against the voltage drop and, especially, the phase angle jump. Firstly, the differential-algebraic equations of the DFIG are linearized to propose their transfer function model. Secondly, considering its high-order characteristic, a model reduction method for the transfer function of the DFIG using the Schur decomposition is proposed, and the analytical expression of the output variables of the DFIG with the phase angle jump is derived by the inverse Laplace transformation to judge the necessity of the LVRT measures. Finally, the simulation results of the DFIG are provided to verify the accuracy of the transfer function model and its reduced-order form and validate the feasibility of the LVRT against the phase angle jump with the proposed models.

This paper proposes a robust protection technology to enhance the grid-connected capability of the doubly fed induction generator (DFIG) based on wind turbines (WTs) under low voltage ride through (LVRT) conditions. The proposed method to control the rotor side converter (RSC) and grid side converter (GSC) uses proportional–integral (PI) controllers. The protection devices are the static compensator (STATCOM), crowbar, series dynamic resistor (SDR), and DC-chopper, with the proposed method to control STATCOM using proportional–integral (PI) controllers and the proposed method to control the rest of the protection devices based on the allowable threshold values of rotor current and DC-link voltage. The protection coordination strategy between them is proposed to avoid the disconnection between the rotor circuit and grid, maintain the DC-link at constant voltage, enhance the dynamic response of WT, and improve the voltage response at the point of common coupling (PCC) of WT. The DFIG-WT of 2 MW-575 V connecting to the 34-bus IEEE network is carried out to verify the effectiveness of the proposed method under the conditions of symmetrical and asymmetrical faults, and the LVRT requirements of the Spanish grid code are considered. The obtained simulation results using the PSCAD/EMTDC software show that the rotor current, DC-link voltage, voltage PCC, and power oscillation damping are significantly improved compared to not using it or applying the conventional method based on passivity theory. Therefore, the LVRT capability of the proposed DFIG-WT system is significantly enhanced, and it has enough ability to continue to provide electrical energy to the power network. [ABSTRACT FROM AUTHOR]

Grid code requirements must be provided in the grid-connected operation of Doubly fed induction generator (DFIG)-based wind turbines. For this, many methods have been developed in DFIG-based wind turbines. Low voltage ride through (LVRT) capability is one of the most effective methods to meet the grid code requirement in DFIG. LVRT is the principal method used to decrease voltage dips and overcurrents caused by various symmetrical and asymmetrical faults. One of the efficient and economical methods of providing LVRT capability is Stator resistive hardware model (SRHM). This study developed the SRHM to remove oscillation that may occur during symmetrical and asymmetrical faults. In addition, stator–rotor electromotive force models in DFIG were enhanced with the aim of increasing simulation study performance, calculation, and stability in the system during various faults. In both symmetrical and asymmetrical fault operations, the results indicated that the proposed SRHM and stator-rotor electromotive force models provided dynamic stability of the system and eliminated oscillations. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin University of Science & Technology is the property of Journal of Harbin University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summary: The effects of the wind farm on the low‐frequency oscillations of interconnected power systems have become a significant problem with extensive apprehension. These low‐frequency oscillations are undesirable, malfunctioning and resulting in system instability. This paper studies the influence of various factors on stability, with varying wind penetration, a different combination of controllers, wind farm (WF) integration and replacement of synchronous generators. To enhance the stability, it is integrated and analyzed significance of the controller by considering the power oscillation damper for WF, power system stabilizer for synchronous generators and supplementary controller of flexible AC transmission system devices for the system. The rotor speed deviation is considered an objective function with various constraints for particle swarm optimization to provide the controller's optimized value and combination. The small‐signal and transient stability problems were examined using eigenvalue analysis and time‐domain simulation. The state‐space formulation is derived for eigenvalue analysis for small signal stability assessment with system variables. The nonlinear dynamic simulation results for transient stability analysis are obtained using a three‐phase fault. From stability analysis, coordinated controllers intensify the capability of SGs and WF under extreme disturbances. The effectiveness and robustness of the proposed approaches have been verified using the IEEE‐9 bus test system. All the analysis and simulations are performed using real time digital simulation (RTDS) with interfacing between MATLAB/SIMULINK‐2018a software and RT‐LAB (an OP5600 RT‐LAB). [ABSTRACT FROM AUTHOR]

Due to renewable generation increment in power systems and the complexity of control and protection of them, the evaluation of transient stability is necessary. This paper aims at analyzing the impact of wind power generation on the transient stability of power systems. To this end, doubly fed induction generator (DFIG) converters were first investigated in a closed-loop control mode. More detailed controls were used for the rotor side converter. Controls of the DC link converter on the network side were assumed to be ideal. Then, through using Gershgorin's theory, a new approach to adjust converter control parameters was presented. The simulation results in different operating modes confirmed the capability of this method in adjusting the converter's control parameters. Also, by using performed simulations, the effect of increasing wind power production penetration and the changes of reactive power compensation by DFIG on the transient stability of power system were investigated. Finally, the effect of power system strength and DFIG parameters change, in the presence of DFIGbased wind power generation, on transient stability was analyzed. The simulation results showed that an increase in wind power generation initially led to an improvement and finally to the weakening of the transient stability of the system. In fact, this paper provides a professional and valuable perspective towards the investors and operators of the power systems with wind power generation from the viewpoint of transient stability. [ABSTRACT FROM AUTHOR]

In this paper the new effective approaches for detecting and mitigating the important cyber-attacks occurred in an AC microgrid (ACMG) renewable energy, including false data injection attack (FDIA), hijack attack (HjA) and denial of service (DoS) are proposed. These methods are applied in the inner loops of the current control in the rotor side converter (RSC) of the doubly fed induction generators (DFIGs) with the marine current turbines (MCTs). The goal is to enhance the power management and consequently, the energy management system against cyber-attacks in the weak grid connected and standalone operation modes. The proposed method is based on correcting and smoothing the reference voltage profiles in the d and q axes sending to the pulse width modulation (PWM) commands of the RSC by occurring the attacks in a multi machine ACMG test system simulated via MATLAB. The obtained results in various scenarios verified the performance of the presented method to contribute for cyber security in ACMGs.

Doubly fed induction generator (DFIG) are vulnerable to unbalanced voltage and harmonic distortion, which will lead to the heating problem of stator/rotor windings and the damage of gearbox. This paper establishes the transient modeling of the DFIG under composite unbalanced voltage and harmonic distortion condition, and elaborates the dynamic response of DFIG from the perspectives of rotor voltage, active power and reactive power under voltage harmonics and unbalance. It also presents an improved control strategy for a dynamic voltage restorer (DVR) to accurately track the specific voltage harmonics, with targeted consideration of constraining unbalanced voltage and fifth- and seventh-order voltage harmonics. The extractions of each voltage signals are presented in this paper via multiple notch filter (MNF), which has a good low-pass characteristic and an excellent performance in trapping the specific AC signals. The presented notch-filter-based algorithm has the advantages of simper control structure and faster response speed, and is more accurate in harmonic extraction. A 1.5-MW DFIG has been employed to establish the object of protection in simulation analysis to verify the validity of the proposed control strategy. The results show that the proposed control strategy is effective which is consistent with the theoretical model, and the oscillations of each crucial parameter can be well-suppressed.

Abstract Recently, renewable resources such as wind, hydro, and tidal have experienced a rapid development. Electricity production, based on wind, has been concentrated on a large scale. Additionally, a doubly fed induction generator has been used in wind farms on a large scale. This machine is influenced by the multiple transient states that are happening in the grid. Many researchers studied the effect of voltage-dip on DFIG performance; none of them studied the effect of voltage-dip sharing with wind-speed changing for both sub- and hyper-synchronous modes. In this paper, DFIG behavior is investigated under a transient state which is represented by 3-phase voltage-dip, in both operation modes (sub-synchronous & hyper-synchronous) with various values of the wind speed. Based on MATLAB Simulink, the various DFIG parameters are extracted to determine the relation between voltage-dip, variable wind speed, and DFIG performance. Results show that the parameters that are affected were rotor-current, rotor-voltage, and DC-Link voltage, while stator-current and stator-flux are not affected. It is also shown that DC-Link voltage values are smaller in the hyper-synchronous mode compared with sub-synchronous one.

Wind curtailment and inadequate grid-connected frequency regulation capability are the main obstacles preventing wind power from becoming more permeable. The electric hydrogen production system can tackle the wind curtailment issue by converting electrical energy into hydrogen energy under normal operating circumstances. It can be applied as a load-reducing method during frequency regulation to help the system restore the power balance. First, this study proposes the concept of a hybrid plant station that combines the production of hydrogen and wind energy. This plant station will be referred to as a hybrid station with centralized hydrogen production and distributed energy storage. By mimicking the synchronous generator's frequency control features, the primary frequency regulation mechanism of a hybrid plant station is examined. Secondly, due to the frequency regulation requirements of the power grid's full-time domain hybrid power station, this paper proposes a hybrid plant station control strategy based on the EEMD variable parameter control algorithm. In frequency regulation power, the electric hydrogen production device load reduction responds to the low-frequency component, and the supercapacitor responds to the high-frequency component. The impact of the dynamic characteristics of alkaline electrolyzers on the frequency regulation effect is analyzed in this article, along with a comparison of the matching of various energy storage devices and electrolyzers in power grid frequency regulation. Finally, the feasibility and soundness of the proposed control strategy are confirmed by creating a simulation model representing a hybrid plant station involved in primary frequency management under various operational scenarios. [ABSTRACT FROM AUTHOR]

The doubly fed induction generator (DFIG)-based wind energy conversion system (WECS) has seen rapid growth all over the world, resulting in a growing access of this source of energy into electrical grids. The low-voltage ride-through (LVRT) capability of the DFIG-based wind turbine must be improved to make it stay connected to the grid during the occurrence of grid faults. Because of its vulnerability to grid disruptions, careful arrangements must be made to the DFIG to keep it connected with the grid. Hence, this paper presents a modified control technique with crowbar protection for improving the LVRT of the WECS. This proposed scheme can be sufficient to meet the LVRT requirements as demanded by grid codes. The fault ride-through capability of the rotor side convertor (RSC) and grid side converter (GSC) is regulated in accordance with grid code requirements. During grid faults, the proposed scheme enhances device recovery by providing reactive power support through the GSC and the stator. The dynamic performance of the proposed scheme is investigated under symmetrical grid disturbances. The operation of the proposed system has been simulated in a MATLAB/Simulink environment for a 2.6 MW-grid-connected DFIG system. [ABSTRACT FROM AUTHOR]

This paper represents a new generation of adaptive disturbance rejection control (ADRC) which is more robust against disturbances than conventional ADRC. The non-derivability of the fal function employed in the traditional ADRC has negative impacts on its operation, so alternate functions will be used which are derivable at all segments. In this regard, odd hyperbolic and trigonometric functions were employed. The performance of the proposed structure was investigated to control the doubly fed induction generator (DFIG) speed. To enhance the efficiency of the suggested ADRC, fractional-order calculations and fuzzy logic were utilized simultaneously. The results in MATLAB platform indicate that: 1) With constant wind speed and changing reference speed, using new fal functions in fuzzy fractional-order ADRC (FFOADRC) has improved the performance compared to the PI regulator and FFOADRC with default fal function. 2) During wind speed variations and using new fal functions, the DFIG speed reaches the final steady amount as over damping, while this condition is critical damping when using FFOADRC with default fal function. 3) During network voltage reduction, using new FFOADRCs leads to fewer oscillations in the stator flux, DC-bus voltage, and DFIG speed, which shows their better performance than PI regulator and traditional ADRC. [ABSTRACT FROM AUTHOR]

This paper proposes a novel method for reference current generation based on Power Oscillation Damping for the reliable operation and control of Doubly Fed Induction Generator (DFIG) under distorted grid voltage conditions. The dominant harmonic components in grid voltage such as 5th and 7th harmonic voltages lead to braking and forward torques thus causing speed oscillations and mechanical vibrations. Further, the stator active and reactive power have oscillations at 200 Hz, 300 Hz, 400 Hz and 600 Hz leading to unreliable operation of the DFIG and a possible instability of the grid. In this study, an improved method of generating the modified current references to eliminate the undesirable effect of fifth and seventh harmonics apart from the unbalance in grid voltage on DFIG performance. Here, the RSC is equipped to minimize the harmonic contents in electromagnetic torque and stator active and reactive power through a single target of damping the power oscillations, by forcing the pulsating terms of reactive and active powers to zero while maintaining decoupled steady state power flow control. The GSC focuses on mitigating the DC link voltage fluctuations while facilitating a unity power factor operation at the grid. The new reference currents for RSC and GSC are obtained by adding the fifth and seventh harmonic compensating currents to the steady state current references to meet the target. The proposed scheme is validated using PSCAD/EMTDC simulations on a 3 hp DFIG. [ABSTRACT FROM AUTHOR]

Due to renewable generation increment in power systems and the complexity of control and protection of them, the evaluation of transient stability is necessary. This paper aims at analyzing the impact of wind power generation on the transient stability of power systems. To this end, doubly fed induction generator (DFIG) converters were first investigated in a closed-loop control mode. More detailed controls were used for the rotor side converter. Controls of the DC link converter on the network side were assumed to be ideal. Then, through using Gershgorin's theory, a new approach to adjust converter control parameters was presented. The simulation results in different operating modes confirmed the capability of this method in adjusting the converter's control parameters. Also, by using performed simulations, the effect of increasing wind power production penetration and the changes of reactive power compensation by DFIG on the transient stability of power system were investigated. Finally, the effect of power system strength and DFIG parameters change, in the presence of DFIGbased wind power generation, on transient stability was analyzed. The simulation results showed that an increase in wind power generation initially led to an improvement and finally to the weakening of the transient stability of the system. In fact, this paper provides a professional and valuable perspective towards the investors and operators of the power systems with wind power generation from the viewpoint of transient stability. [ABSTRACT FROM AUTHOR]

Abstract Emerging sub-synchronous interactions (SSI) in wind-integrated power systems have added intense attention after numerous incidents in the US and China due to the involvement of series compensated transmission lines and power electronics devices. SSI phenomenon occurs when two power system elements exchange energy below the synchronous frequency. SSI phenomenon related to wind power plants is one of the most significant challenges to maintaining stability, while SSI phenomenon in practical wind farms, which has been observed recently, has not yet been described on the source of conventional SSI literature. This paper first explains the traditional development of SSI and its classification as given by the IEEE, and then it proposes a classification of SSI according to the current research status, reviews several mitigation techniques and challenges, and discusses analysis techniques for SSI. The paper also describes the effect of the active damping controllers, control scheme parameters, degree of series compensation, and various techniques used in wind power plants (WPPs). In particular, a supplementary damping controller with converter controllers in Doubly Fed Induction Generator based WPPs is briefly pronounced. This paper provides a realistic viewpoint and a potential outlook for the readers to properly deal with SSI and its mitigation techniques, which can help power engineers for the planning, economical operation, and future expansion of sustainable development.

The current study proposed a robust sensor-less sliding mode second-order based on a super twisting algorithm (STA-SMSO) approach using a new observer Model Reference Adaptive System-Adaptative Neuro-Fuzzy Inference System (MRAS-ANFIS). This model was applied to a doubly fed induction generator (DFIG) wind turbine running under variable wind speed and DFIG fed with a power voltage source without a speed sensor, while the control objective was used to regulate independently, the active and reactive power DFIG stator were decoupled by using the field-oriented control technique. Additionally, this process reduced the cost of the control scheme and the size of DFIG by eliminating the speed sensor (encoder). In order to improve the traditional MRAS, the MRAS-ANFIS observer was proposed to replace the usual PI controller in the adaptation mechanism of MRAS with an Adaptative Neuro-Fuzzy Inference System (ANFIS) controller. The estimation of rotor position was tested and discussed under varying load conditions in low, zero, and high-speed region. The results mentioned that the proposed observer (MRAS-ANFIS) presented an attractive feature, such as guarantees finite time convergence, good response on speed wind variations, high robustness against machine parameter variations, and load variations compared to the conventional MRAS observer and MRAS-Fuzzy. Hence, the estimated rotor speed converged to their actual value has the capacity for estimating position in deferent region (low/zero/high) of speed. [ABSTRACT FROM AUTHOR]

Early detection of faults in wind energy systems can reduce downtime, operating, and maintenance costs while increasing productivity. This paper proposes a method based on the analysis of generator stator current signals to detect faults in a wind turbine gearbox equipped with a doubly fed induction generator (DFIG). A localized parameter model was established to simulate the vibratory response of a two-stage gear system under healthy and faulty conditions. The simulation was performed in the MATLAB/Simulink environment. The results include a detailed analysis of the mechanical part of the gearbox, highlighting mesh stiffness, output speed, and accelerations. Additionally, the electrical part was evaluated based on the current supplied by the doubly fed induction generator. The results were presented in the case of healthy gears and in the presence of faults such as a broken or cracked tooth. Fast Fourier transform (FFT) analysis was employed to detect gear defects in the stator current signal. The presence of a crack or broken tooth in the gearbox induces modulation of the DFIG stator current signals according to the shaft frequencies corresponding to the faulty gear. These findings provide a preliminary basis for the detection and diagnosis of this type of failure. [ABSTRACT FROM AUTHOR]

The fast improvement of wind energy conversion technology with optimization algorithms has recently received a lot of attention. However, their slow convergence speed, huge computational load, and low efficiency are the main drawbacks and to improve these disadvantages, a new adaptive fuzzy logic controller strategy is proposed to enhance the low voltage ride-through of the grid-connected doubly fed induction generator during severe grid faults. The rotor side converter and the grid side converter are controlled using an adaptive fuzzy logic controller topology under cascaded structure to improve the performance. The novel application of the 'generalized variable step-size diffusion continuous mixed p-norm' adaptive filtering algorithm is proposed to modify the calibrating factors of the fuzzy logic controllers at a rapid convergence speed with low normalized misalignment error. The proposed adaptive algorithm-based fuzzy logic controller has a better low voltage ride-through improvement capability than that of using the particle swarm optimization-based proportional-integral controller during severe grid disturbances. The convergence speed of the proposed adaptive filtering algorithm is compared to that of existing algorithms such as least mean fourth, least mean square, and continue mixed p-norm algorithms. In addition, a comparison is also made with different common optimization methods. The field-programmable gate array-based real-time experimental results are presented to validate the proposed adaptive control topology. • A novel application of GVSS-DCMPN based adaptive filtering algorithm is proposed. • The proposed algorithm modifies the calibrating factors on-line of the FLCs. • Proposed algorithm having faster convergence speed with low steady-state error. • The proposed adaptive filtering algorithm improves the LVRT of the DFIG. • The proposed algorithm is validated with another state-of-art algorithms. [ABSTRACT FROM AUTHOR]

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Recently, renewable resources such as wind, hydro, and tidal have experienced a rapid development. Electricity production, based on wind, has been concentrated on a large scale. Additionally, a doubly fed induction generator has been used in wind farms on a large scale. This machine is influenced by the multiple transient states that are happening in the grid. Many researchers studied the effect of voltage-dip on DFIG performance; none of them studied the effect of voltage-dip sharing with wind-speed changing for both sub- and hyper-synchronous modes. In this paper, DFIG behavior is investigated under a transient state which is represented by 3-phase voltage-dip, in both operation modes (sub-synchronous & hyper-synchronous) with various values of the wind speed. Based on MATLAB Simulink, the various DFIG parameters are extracted to determine the relation between voltage-dip, variable wind speed, and DFIG performance. Results show that the parameters that are affected were rotor-current, rotor-voltage, and DC-Link voltage, while stator-current and stator-flux are not affected. It is also shown that DC-Link voltage values are smaller in the hyper-synchronous mode compared with sub-synchronous one. [ABSTRACT FROM AUTHOR]

This article presents an analysis of selected characteristics of the modular multilevel matrix converter (M3C) operating a doubly fed induction generator (DFIG) in a flywheel energy storage system. A detailed analysis of the necessary electrical input and output quantities, as well as the identification of required internal currents and voltages, leads to a newly introduced iterative design process for the converter. This process ultimately provides information on the required number of submodules and demonstrates the overload capability of the converter in reactive power operation. Also, the short-circuit current contribution of the system for this unique configuration of M3C and DFIG is investigated for the first time. Taking into account the unique operating characteristics of the M3C, a loss analysis of the converter and the machine is performed, and a loss-optimized distribution of reactive power between the machine and the converter is proposed. The article is conducted analytically and is validated by experimental results on a small-scale demonstrator.

Cosimulation studies of electric power systems and electric machines have always been a challenge. In order to reduce the simulation time to a reasonable value, lumped-parameter electric machine models are commonly used in electric power system modeling software packages to avoid the heavy computational burden of more accurate modeling methods especially finite-element method (FEM) on the expense of less accuracy. The proposed technique in this article combines the dynamic phasor modeling technique for power system simulations with the FEM to accurately model the doubly fed induction generator while connected to the grid. The utilization of dynamic phasors enables adopting large simulation time steps resulting in a significant reduction in the simulation time compared to the conventional time-domain FEM modeling. The mathematical foundation of the proposed modeling method is presented including the generator's core saturation. Custom-written C++ codes have been developed by the authors to execute the new dynamic phasor FEM algorithm and the conventional time-domain FEM in order to fairly compare their accuracy and numerical performances. As the proposed method combines time and frequency domains, a unique capability of modeling the rotor movement can be achieved. The rotation can be represented by physically incrementing the rotor and airgap mesh as in regular time-domain solvers, by mathematically representing the rotation using the virtual blocked rotor method as in frequency-domain solvers, and the proposed method of combining the two aforementioned approaches. The three methods of modeling rotor rotation are discussed, and their simulation results are compared to give a guide to choose the proper method for the different modeling targets. The results show that the proposed dynamic phasor FEM is capable of producing comparable results to the traditional time-domain solver at a substantially reduced simulation time.