DFIG-based Wind Turbine Research Articles

A novel modeling and emergency control method of transient energy of DFIG-based wind turbine under grid fault

The anti-interference ability of the power system continues to decline with the increase of wind power penetration. Due to the limitation of the reduction of the synchronous generators proportion and the response speed, the emergency power controllability of the power system with large-scale wind power is insufficient, and the stability problems of the power system continue to highlight under the grid fault. At the same time, wind turbines can hardly provide emergency support for the power system due to the maximum power point tracking mode. Therefore, the transient energy of doubly fed induction generator based wind turbine (DFWT) during the grid fault is depicted, which is accumulated by the imbalance between the input mechanical power and output electromagnetic power. And a new idea of utilizing the fault transient energy of DFWT to provide emergency power support for the power system is proposed in this paper. Firstly, the expression of stator short-circuit current of DFWT in the crowbar input and reactive power support stage is derived. The dynamic model of the rotor speed of DFWT is established further, and the calculation method of fault transient energy of DFWT is proposed. Next, in order to maximize the utilization of the transient energy, the calculation method of control duration time and control reference value is proposed, and the transient energy emergency control (TEEC) method of DFWT is proposed. The case studies and experimental results show that the TEEC method can not only provide stable power support for the power system, but also alleviate the short-term power impulse of DFWT after the grid fault removal, and accelerate the recovery of the rotor speed of DFWT, which is conducive to the safe and stable operation of DFWT and the power system.

Event-Triggered Robust Optimized Scheme with Impulse Control for DFIG Based Wind Turbine

Event-Triggered Robust Optimized Scheme with Impulse Control for DFIG Based Wind Turbine

Speed control of a DFIG-based wind turbine using a new generation of ADRC

ABSTRACT 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.

Energy Management Strategies and Control of a Hybrid Grid-Connected Renewable Energy System with Three Modes Controlled DFIG based Wind Turbine

This paper deals with three novel Energy Management Strategies (EMS) for a Grid-Connected Hybrid Renewable Energy System (GCHRES) that utilizes a photovoltaic solar generator (PVG) and three modes controlled Wind Turbine system based on DFIG, along with a storage system based on battery. The CCP serves as the connection point between the Utility Grid (UG) and a residential AC load, primarily powered by the Renewable Energy Sources (RES). The UG acts as a backup source, and to limit the subscription power exceeding, the battery is designed to perform the peak shaving. Given the high vulnerability of batteries, the primary goal of all proposed EMSs is to maintain a continuous power supply while also protecting the battery from overcharging and deep discharge. Additionally, these EMSs are designed to lower the monthly energy bill for UG customers. The specific features of these EMSs vary depending on the metering types. And to maintain balance within the system, All components powers are controlled. The performances of the GCHRES were evaluated using simulation in MATLAB/SIMULINK environment. Results concerning the continuous ability to meet demand, stability of the system, tracking of references, and also wind turbine system control are discussed in this article. Keywords—Control and regulation, DFIG, Energy Management Strategies, Grid-Connected, Peak shaving, Photovoltaic,Pitch control, Renewable Energy, Wind Turbine

Virtual inertia coordination control strategy of DFIG-based wind turbine for improved grid frequency response ability

The capability of the inertia response of the Double fed induction generator (DFIG) is mainly achieved at the cost of its economic benefits. As such, this study proposes a coordinated control strategy with frequency modulated inertia layered optimization while considering the inertia response of DFIG direct current (DC) side capacitor. According to the disturbance size of the system, the inertia control task is dynamically assigned to the DFIG DC capacitor and speed inertia control module to reduce the startup times of speed control and improve the operation economy. On this basis, we propose a dynamic recovery of DC capacitor voltage based on State of charge (SOC) self-recovery to solve the problem of voltage clamping after the inertia response of DFIG DC capacitor at its stable operating boundary and thus cannot participate in subsequent inertia control. Aiming at the frequency secondary disturbance caused by DFIG speed recovery, a variable coefficient droop control method based on logistic regression function is proposed to realize the dynamic ordered recovery of DFIG speed. Simulation results show that, compared with the traditional synchronous control with the simulation time sequence of 280 s, the proposed timing optimization coordinated control strategy reduces the rotor start times by 12 times, and the wind energy capture increases by 3.6%.

Various Control Strategies Performance Assessment of the DFIG wind turbine connected to a DC grid

AbstractThis paper deals with the integration and control of the doubly fed induction generator‐based wind turbine (DFIG‐WT) in a DC grid. In this way, the stator of the DFIG‐WT is integrated with the DC grid via an uncontrolled diode‐bridge rectifier as well as a buck converter to provide a flexible connection path. In addition, the rotor of the DFIG‐WT exchanges power with the DC grid through a rotor‐side converter (RSC). By considering the DFIG‐WT system topology, three control strategies based on the stator flux‐oriented vector control are developed for the RSC and buck converter. The control schemes consist of the outer and the inner control loops with the proportional–integral (PI) controllers. Additionally, the stability of control strategies and their dependence on the generator parameters are evaluated and compared using modal analysis and numerical simulations in the MATLAB/SIMULINK environment. Finally, a real‐time hardware‐in‐the‐loop emulation‐based OPAL‐RT 5600 is accomplished to assess the performance of the superior control method from a practical perspective.

Flexible Frequency Response Strategy with Smooth Rotor Speed Recovery of a DFIG-Based Wind Turbine

Grid frequency must be regulated in its nominal range to guarantee the stable operation of an electric power grid. Excessive grid frequency excursions result in load shedding, grid frequency instability, or even synchronous generator damage. With the growing wind penetration, there is an increasing issue about the reduction in inertia response. This paper addresses a self-adaptive inertial control strategy for improving the frequency nadir and smoothly regaining the rotor speed to the initial working condition without causing a second frequency drop (SFD). The first objective is achieved by determining the incremental power considering the maximum rate of change of frequency; the secondary goal is realized by smoothly decreasing the power reference based on the decreasing function. Simulation results verify that the proposed control strategy not only boosts the frequency nadir but also guarantees the smooth rotor speed recovery with a negligible SFD.

Enhancement of LVRT Capability in DFIG-Based Wind Turbines with STATCOM and Supercapacitor

Overvoltage and overcurrent resulting from various faults cause instability in Doubly Fed Induction Generator (DFIG)-based wind turbines connected to a grid. The grid code requirement must be met during faults to minimize the effect of these problems. Low Voltage Ride Through (LVRT) capability is used to meet the grid code requirement. It is important to use coordinate control for transient states in LVRT capability. This study aimed to improve the stator dynamics for ease of calculation and the rotor dynamic model by damping oscillations caused by balanced and unbalanced faults on the grid side. For this, electromotive force (emf) models were developed for stator and rotor dynamic modeling. Furthermore, for the coordinate control of the DFIG, models were developed for a lookup-table-based supercapacitor and a decoupled Static Synchronous Compensator (STATCOM). Using these models, analyses of three-phase and two-phase faults were conducted. Following different balanced and unbalanced faults within the grid, the system was stabilized in a short time, and the oscillations occurring during the faults were quickly damped using the LVRT models developed in this study.

Transfer learning accelerating complex parameters optimizations based on quantum-inspired parallel multi-layer Monte Carlo algorithm: Theory, application, implementation

In doubly-fed induction generator-based wind turbines (DFIG-WTs), the rotor-side controller (RSC) with optimized parameters improves wind energy utilization efficiency. With long optimization times and inadequate exploration and development capabilities, conventional intelligent optimization algorithms are hard to find the controller parameters quickly in the complexity and nonlinearity of DFIG-WTs. A quantum-inspired parallel multi-layer Monte Carlo algorithm accelerated by transfer learning (QPMMCOA-TL) is proposed to shorten the optimization time of parameters and obtain the controller parameters more satisfactorily simultaneously. The QPMMCOA-TL possesses strong optimization capabilities through an accelerated search method based on transfer learning, a diversified population coding way, a parallel multi-layer structure, way of searching in the narrowing feasible region. In the optimization process, the fitness function replaced by trained deep neural networks is transferred to the search process of the QPMMCOA-TL for shorting the optimization time. The QPMMCOA-TL is applied to test two benchmark functions and compared with seven metaheuristic algorithms for completing the validity verification. The optimization time of the QPMMCOA-TL when searching the parameters of the RSC is 1188 s, which is one-tenth or less than other algorithms. Furthermore, the reliability and stability of the optimized controller are comprehensively enhanced.

Optimal Gearbox Ratio to Minimize the Power Converter Ratings in DFIG-Based Type-3 Wind Turbines

Optimal Gearbox Ratio to Minimize the Power Converter Ratings in DFIG-Based Type-3 Wind Turbines

Control of a DFIG based wind turbine using modified Conditional Servo-compensator

This paper presents the control of a wind turbine composed by a doubly fed induction generator (DFIG), which provides power to the main grid through a feeder. The control algorithm is designed following the modified Conditional Servo-Compensator (mCS) theory. This control technique was recently developed to a broad class of nonlinear systems, and this paper brings the first result applied to wind turbines. The mCS theory has several advantages compared to others, as it is a robust nonlinear control scheme. First, it provides rigorous stability analysis, that allows explicit definition of performance and operating conditions. Secondly, it is a robust controller, and only needs lump values and bounds for parameters and dynamics. Finally it is very simple and easy to implement, and does not need heavy computer burden, it is only based on standard local measurements, and represents a promising solution for real applications. The theoretical results are verified by simulations using detailed Simpower models. These simulations show very good results facing a Low Voltage Ride Through scenario, which is one of the most severe tests used for practical applications. The proposed scheme could easily be adapted to the control of other applications based on power converters, as the control of the interconnection of a full wind farm to the main grid, or the control of a terminal in a DC grid.

Experimental Comparison of the Different Switching Techniques applied to Back-to-Back Converter connected to DFIGbased Wind Turbine for Harmonic Analysis

To mitigate the fast-growing demand of electrical energy, the use of renewable energy resources (RES), e.g., solar and wind, can offer an environmentally friendly and sustainable solution. However, the massive penetration of power converters interfaced RESs in electric power systems introduces power quality issues, such as harmonic distortion and voltage variations. Therefore, these issues may lead to serious problems, such as cable and transformers overheating, harmonic overvoltage, and more related to harmonic resonances. This article quantifies the harmonic distortion produced by different switching techniques used in the back-to-back converter of the DFIG. The different switching techniques implemented are: SPWM, THIPWM and SVPWM. Modeling and simulation of the DFIG is carried out using the commercial software MATLABSimulink. The model is validated with an experimental 3 kW DFIG prototype. Finally, the results obtained from the experimental tests corroborate the correct functioning of the proposed model.

Fuzzy Frequency Droop Control of DFIG Wind Turbine Generators Adapted to Continuous Changes in Wind Speeds

Fuzzy Frequency Droop Control of DFIG Wind Turbine Generators Adapted to Continuous Changes in Wind Speeds

Self-adapting PI controller for grid-connected DFIG wind turbines based on recurrent neural network optimization control under unbalanced grid faults

• Establish the MPPT with optimal speed ratio combined with hidden layer recurrent neural network (HLRNN) to obtain faster convergence. • Optimize the PI controller gains by using a hidden layer recurrent neural network. • Investigate the active power behavior in the presence of unbalanced grid faults. • Amelioration of the response time of the produced power compared with some other existing neural network schemes. This paper suggests the Hidden Layer Recurrent Neural Network (HLRNN) for controlling a wind power generation system based on a dual-fed induction generator. The generator's stator is connected directly to the electrical grid, while the rotor is linked through bidirectional converters. A PI controller-based Indirect Vector Control (IVC) scheme has been established to pilot the system. The PI regulator allows linear systems to perform well, but when subjected to physical variation conditions, the system's response becomes unstable, making the PI controller insufficient. This paper aims to ensure the PI controller gains self-adaptation regardless of the severity of the circumstances. The effectiveness of the proposed control is demonstrated by taking into account critical conditions such as wind speed changes, generator parameter variations, and asymmetrical faults in the grid. Furthermore, it is confirmed by the enhanced performance and the reduced oscillations during a voltage dip. The simulation results, achieved using MATLAB/Simulink, demonstrate that the response time is reduced to 1.8 (m s), the static error is minimized to 0.16%, and the overshoot is improved to 0.24% when compared to the IVC based on the PI controller and some existing neural network schemes.

Secures and maintains non-linear control of DFIG-wind turbine by implementing the appropriate protection configuration against overcurrent in the rotor circuit under grid fault

One significant disadvantage of the doubly fed induction generator (DFIG) is its high vulnerability to grid faults, which can be attributed to the direct linkage of its stator windings to the electrical network. The electromagnetic pairing of the stator and rotor in the DFIG implies that a voltage dip causing excessive stator current results in high currents in the sensitive back-to-back inverters and an overcharge in the DC-link capacitor. A comparative study of two protection configurations with a sliding mode non-linear control (SMC) for the rotor transient current for the better operation of the DFIG under network faults is presented in this document. One conventional configuration consists of a crowbar with DC-chopper and another is changed by adding to the crowbar an RL series device known as an appropriate protection configuration (APC). Both are placed within the rotor windings and ride-side converter (RSC) to achieve secures and maintains SMC of DFIG. The comparison of the results reached with the MATLAB/ SIMULINK application is evidenced by the success of these two configuration reduce the high rotor current and DC-link voltage. Additionally, the conventional configuration, in conjunction with the APC, diminishes the current RSC to levels below 0.2kA and exactly 2.25kA, while also being capable of absorbing up to 2.52kA and 1.3kA in the event of a grid fault. So the main difference is that with the APC, the decoupling of the RSC to the rotor in the presence of a fault can be averted, thereby assuring the control of all stator power via the RSC converte.

Modified distance protection of transmission lines originating from DFIG-based WPPs by considering the impact of fault-induced rotor frequency and LVRT requirements

This paper focuses on the protection of transmission lines connected to doubly-fed induction generator (DFIG)-based wind power plants (WPPs). DFIG-based wind turbines (WTs), which are connected to the AC grid via reduced-size converters, impose additional challenges on the reliable operation of distance relays due to their distinctive fault current characteristics, converter protective actions, and voltage or reactive control strategy of the converter. In this paper, a modified distance protection scheme is proposed which is able to reliably estimate the fault distance under the aforementioned challenges. The proposed scheme consists of two main components: phasor correction and fault resistance elimination. The phasor correction component eliminates the impedance error due to the fault-induced rotor frequency component of the DFIG short-circuit current. The fault resistance elimination component eliminates the impedance error due to the fault resistance during non-solid faults, which cannot be eliminated by conventional methods as a result of the variable nature of the equivalent impedance of the DFIG-based WTs during faults. Various simulation results are exhibited to validate the effectiveness of the proposed scheme in detecting and identifying all different types of faults on transmission lines emanating from DFIG-based WPPs.

Fault ride-through capability improvement in a DFIG-based wind turbine using modified ADRC

In this paper, an overview of several strategies for fault ride-through (FRT) capability improvement of a doubly-fed induction generator (DFIG)-based wind turbine is presented. Uncertainties and parameter variations have adverse effects on the performance of these strategies. It is desirable to use a control method that is robust to such disturbances. Auto disturbance rejection control (ADRC) is one of the most common methods for eliminating the effects of disturbances. To improve the performance of the conventional ADRC, a modified ADRC is introduced that is more robust to disturbances and offers better responses. The non-derivability of the fal function used in the conventional ADRC degrades its efficiency, so the modified ADRC uses alternative functions that are derivable at all points, i.e., the odd trigonometric and hyperbolic functions (arcsinh, arctan, and tanh). To improve the efficiency of the proposed ADRC, fuzzy logic and fractional-order functions are used simultaneously. In fuzzy fractional-order ADRC (FFOADRC), all disturbances are evaluated using a nonlinear fractional-order extended state observer (NFESO). The performance of the suggested structure is investigated in MATLAB/Simulink. The simulation results show that during disturbances such as network voltage sag/swell, using the modified ADRCs leads to smaller fluctuations in stator flux amplitude and DC-link voltage, lower variations in DFIG velocity, and lower total harmonic distortion (THD) of the stator current. This demonstrates the superiority over conventional ADRC and a proportional-integral (PI) controller. Also, by changing the crowbar resistance and using the modified ADRCs, the peak values of the waveforms (torque and currents) can be controlled at the moment of fault occurrence with no significant distortion.

Evaluating a Hybrid Circuit Topology for Fault-Ride through in DFIG-Based Wind Turbines

Large-scale wind power integration has raised concerns about the reliability and stability of power systems. The rotor circuit of a doubly fed induction generator (DFIG) is highly vulnerable to unexpected voltage dips, which can cause considerable electromotive force in the circuit. Consequently, the DFIG must fulfil the fault-ride through (FRT) criteria to ensure the system's performance and contribute to voltage regulation during severe grid outages. This paper provides a hybrid solution for DFIG wind turbines with FRT capabilities, using both a modified switch-type fault current limiter (MSFTCL) and a direct current (DC) chopper. The proposed system has the merit of keeping the rotor current and the DC-link voltage within the permissible limits, enhancing the FRT capability of generators. Moreover, the boundness of supply voltage into its reference value ensures dynamic stability during symmetric and asymmetric grid failures. Further, electromagnetic torque variations are significantly reduced during fault events. Finally, the performance validation of the proposed scheme is performed in a simulation setup, and the results are compared with the existing sliding mode control (SMC) and proportional-integral (PI) controller-based approaches. The comparison results show that a hybrid strategy with advanced controllers provides superior performance for all critical parameters.

MPPT Performance and Power Quality Improvement by Using Fractional-Order Adaptive Backstepping Control of a DFIG-Based Wind Turbine with Disturbance and Uncertain Parameters

MPPT Performance and Power Quality Improvement by Using Fractional-Order Adaptive Backstepping Control of a DFIG-Based Wind Turbine with Disturbance and Uncertain Parameters

Design and Analysis of DFIG-STATCOM Coordinated P2P Grid Connected System Using RMSProp

This research work establishes a relationship between STATCOM and DFIG wind turbines in a transmission network for coordinated operation during grid disturbances. A change in wind gust also produces a variable output nonlinearly, thereby making the system unstable. Assuring bus voltage and proper balance of load angle in all the connected generating stations becomes challenging. Therefore, increasing voltage security at all the lines and further enhancing system stability leads to the placement of STATCOM at the proper location in the transmission line. Appropriate coordinated control of STATCOM and DFIG can lead to adequate power flow in the system. This research includes a multi-objective optimization problem for properly tuning the PI- controller. The voltage at the controlled bus, low-frequency oscillating waveforms, and real power available at the bus under pre-fault and post-fault conditions are identified as objective function parameters. To avoid the overgrowth of error inside the search space due to lack of normalization, this method uses the RMSProp algorithm for proper convergence in the state vector. The coordinated control action has been investigated in the different shunt fault conditions. Again, to enhance the system stability, low voltage ride-through capability has been thoroughly verified using Matlab software.