Maximum Wind Power Extraction Research Articles

Doubly fed induction generator, with crow-bar system, under micro-interruptions fault

The work presented in this paper focuses on studying the application of doubly fed induction generators in wind energy production under micro-interruption fault. In this context, we set out to improve the performance of a wind turbine either from an energetic efficiency, or from the arrangement with behavioral of grid disturbances. To reach the maximum wind power extraction, wind turbine has to reduce their disconnection. For this reason grid operators impose, by theirs grid connection requirements, to wind turbine producer to support some grid disturbance. This paper deals with the behavior of wind turbine equipped with a Doubly Fed Induction Generator (DFIG) under micro-interruption. A scheme tolerant microinterruption is proposed. A control strategy of the Unified Power Flow Control (UPFC) using PI controller is presented. And finally fuzzy logic controller is illustrated and compared to PI controller.

Two novel approaches to capture the maximum power from variable speed wind turbines using optimal fractional high-order fast terminal sliding mode control

In this paper, two nonlinear control approaches using optimal fractional high-order fast terminal sliding mode (FHOFTSM) control are proposed to maximize the captured wind energy and minimize the mechanical loads in the variable speed wind turbines (VSWTs). The optimal condition of the system which uses the presented approaches is achieved by creating a compromise between maximizing the energy extraction and minimizing the control input. So, the mechanical stress on the drive-train is reduced by minimizing the control input. To achieve this compromise, the behavior of the wind turbine system should be precisely modeled. Fractional calculus theory is an effective method for modeling the VSWT, which provides a more accurate description of the system performance compared with integer-order modeling. Based on the fractional-order modeling of the system, the optimal approach is designed by calculating the error dynamics of the system and defining two types of performance indexes, integer-order and fractional-order performance indexes. Hence, the design procedure of an optimal FHOFTSM control for each performance index requires two-stages process. At first phase, an optimal controller is presented for the system nominal error to minimize the quadratic performance index. Then a switching controller is offered in the second phase that is obtained by defining the fractional high-order sliding manifold and fractional nonsingular fast terminal sliding manifold to overcome the unknown disturbance. Hence, the order of the controllers is smaller than the second order. The optimal strategy is applied to minimize the control input, whereas the FHOFTSM method is used to obtain the maximum wind power extraction, reduce mechanical loads, attenuate the chattering, and achieve fast finite-time convergence. The closed-loop stability of the control system is approved by the fractional Lyapunov direct method and the Mittag-Leffler stability theorem. To illustrate the effectiveness of the proposed approaches, the proposed controllers are compared with some already existing controllers. The performance of controllers is verified through three scenarios, i.e., random variation of wind speed, step change of wind speed, and robustness against parameter uncertainties, in which the simulation results confirm the effectiveness of the proposed controllers.

Maximum power extraction from fractional order doubly fed induction generator based wind turbines using homotopy singular perturbation method

In this paper, a novel control mechanism is presented for the control of variable speed wind turbine (VSWT) with a fractional-order doubly fed induction generator (DFIG) to extract the maximum power in region 2. Firstly, the homotopy singular perturbation method (HSPM) is proposed to simplify the fractional order nonlinear model, to reduce the long memory attribute, and to decrease the mechanical stress. This method is a composition of fractional order singular perturbation method (SPM) and modification of the homotopy perturbation method (HPM). Using this method, the nonlinear fractional order DFIG based VSWT is separated into two lower order subsystems, including nonlinear integer order subsystem and linear fractional order subsystem. Integer order modeling is applied to have the maximum wind power extraction and to increase the trajectory tracking speed, while the fractional order modeling is exerted to reduce the mechanical loads and to ensure better tracking. Then, a sliding mode controller based on HSPM is designed and applied to the original fractional order nonlinear system. Stability of the original system is evaluated by investigating the Lyapunov stability theorem for each subsystem. The controller performance designed based on HSPM is compared to the designed controller performance for fractional order nonlinear system decomposed using fractional order SPM, integer order nonlinear system decomposed by SPM, and integer order nonlinear system without simplification. The simulation results affirm the effectiveness of the controller design based on the proposed method.

Adaptive Dual-layer Sliding Mode Control for Wind Turbines with Estimated Wind Speed

Under the circumstance of inaccurate and intermittent wind speed measurement, maximum power capture control of wind turbines is still a hot and challenging topic in wind power generation field. This paper aims at improving wind turbines’ power production via an adaptive dual-layer sliding mode controller, with the help of estimated rotor effective wind speed. First, a novel effective wind speed estimation algorithm is proposed based on broad learning system (BLS), the training of which is completed by using data collected from the supervisory control and data acquisition (SCADA) system. Further, the trained BLS can deliver the estimated wind speed in an online manner to determine the optimal generator power command for maximum wind power extraction. In addition, a low-pass filter is designed to smooth the output, which is beneficial for drive train systems’ mechanical loads. Thereafter, a sliding mode control theory based maximum power point tracking (MPPT) controller is developed. To compensate for the uncertainties and mitigate the chattering phenomena, dual-layer adaptation laws are designed for the sliding mode controller. Finally, the effectiveness of the proposed control scheme is validated and demonstrated by the FAST (Fatigue, Aerodynamics, Structures, and Turbulence) tool.

Intelligent Maximum Power Tracking Control For a Wind Energy System Based on Magnetic Gear Generator

This paper studies maximum wind power extraction from magnetic gear generator using an artificial neural network for the wind energy system. High speed can be reached with this representation either with magnetic gear generator, under low wind conditions often found inland, or without mechanical gear. In order to track maximum power, the artificial neural network controller adjusts the outer rotor speed, and thus, inner rotor speed. The proposed system is supported by simulation results.

Maximum power extraction from a wind turbine using second-order fast terminal sliding mode control

The maximum wind power extraction and reduction of mechanical stresses in the operating region of below rated wind speed (region 2) are two major issues in wind power. To overcome both issues, two nonlinear control strategies using a second-order sliding mode control (SOSMC) are proposed seeking a better performance. The proposed controllers have been developed to neutralize the effects of parametric uncertainties, unmodeled dynamics, and external disturbances. In the first strategy, a proportional integral derivative (PID) sliding surface is used while in the second strategy a combination of nonlinear terminal sliding surface with PID sliding surface is used to design of the second order fast terminal sliding mode control (SOFTSMC). PID sliding surface is applied to ensure the better tracking, to achieve a zero steady-state error, to reduce the mechanical loads and to attenuate the chattering phenomenon whereas nonlinear terminal sliding surface is applied to have maximum wind power extraction and to establish fast finite-time convergence by applying a small control input. The Lyapunov stability theorem is conducted to show closed loop stability. The results are compared to some existing control laws and their performance evaluation are presented in Table. 1. The results of Table. 1 confirm the effectiveness of the proposed controllers.

Maximum Power Generation Control of a Hybrid Wind Turbine Transmission System Based on H∞ Loop-Shaping Approach

This paper presents the design, modeling, and optimal power generation control of a large hybrid wind turbine transmission system that seamlessly integrates planetary/parallel gear sets with a hydraulic transmission to improve the turbine's reliability and efficiency. The hybrid wind turbine has power splitting flows including both mechanical and hydraulic power transmissions. The turbine transmission ratio can be controlled to continuously vary for the maximum wind power extraction and grid integration. Dynamics of the hybrid wind turbine is modeled as an incremental disturbed state space model based on the dynamic equations of each mechanical/hydraulic element. To achieve good tracking and robustness performance, an optimal H∞ loop-shaping pressure controller is designed, which accurately tracks the optimal load pressure in the hydraulic transmission for maximizing wind power generations. The validations of the proposed hybrid wind turbine and the H∞ loop-shaping pressure controller are performed based on a detailed aero-hydro-servo-elastic hybrid type wind turbine simulation platform with both mechanical geared transmission and hydraulic transmission, which is adapted from the National Renewable Energy Laboratory 5 MW monopile wind turbine model within fatigue, aerodynamics, structures, and turbulence code. The validation results demonstrate that the hybrid wind turbine achieves better performance in both the maximum wind power extraction and power quality than the hydrostatic wind turbine. In addition, the proposed H∞ loop-shaping pressure controller has better tracking performance than the traditional proportional integral controller.

Design Optimization and Model Predictive Control of a Standalone Hybrid Renewable Energy System: A Case Study on a Small Residential Load in Pakistan

Renewable energy sources (RESs) offer a promising prospect for covering the fundamental needs of electricity for remote and isolated regions. To serve the customers with high power quality and reliability, design optimization methodology and a possible power management strategy (PMS) for wind-diesel-battery-converter hybrid renewable energy system (HRES) is proposed in this paper. The analysis is applied to a real case study of a standalone residential load located in a remote rural area in Pakistan. Firstly, optimal component sizing is investigated according to actual meteorological and load profile data. Different hybrid configurations are modeled, analyzed, and compared in terms of their technical, economic and environmental metrics with the aid of HOMER® software. The main objective is to determine the most feasible and cost-effective solution with least life-cycle cost, keeping in view the impact of carbon emissions. Secondly, a suitable PMS based on the state of charge (SOC) of the battery is proposed and implemented in MATLAB/Simulink® software for the designed HRES. The PMS is targeted to maintain load balance and extract maximum wind power while keeping the battery SOC within the safe range. Model predictive control (MPC) approach is applied to improve the output voltage profile and reduce the total harmonic distortion (THD). The boost converter is used for maximum power extraction from the wind. The DC-DC buck-boost battery controller is utilized to stabilize the DC bus voltage. The design optimization results show that the hybridization of wind, battery, and converter presents optimal configuration plan with minimum values of total net present cost (14,846 $) and cost of energy (0.309 $/kWh), which means 76.7% reduction in both total system cost and energy cost and 100% saving in harmful emissions when compared to the base case using diesel generator. The proposed system is able to support hundred percent of the load demand with excess energy of 30.1%. Performance analysis of PMS under variable load and fluctuating wind power generation is tested, and promising results with efficient load voltage profile is observed. Further, THD is reduced significantly to 0.26% as compared to 2.62% when the conventional PI controller is used. The output of this work is expected to open a new horizon for researchers, system planners for efficient design and utilization of HRES to curb drastic increase in load demand for urban as well as rural areas.

Maximum power extraction under different vector-control schemes and grid-synchronization strategy of a wind-driven Brushless Doubly-Fed Reluctance Generator

This paper proposes an advanced strategy to synchronize the wind-driven Brushless Doubly-Fed Reluctance Generator (BDFRG) to the grid-side terminals. The proposed strategy depends mainly upon determining the electrical angle of the grid voltage, θv and using the same transformation matrix of both the power winding and grid sides to ensure that the generated power-winding voltage has the same phase-sequence of the grid-side voltage. On the other hand, the paper proposes a vector-control (power-winding flux orientation) technique for maximum wind-power extraction under two schemes summarized as; unity power-factor operation and minimum converter-current. Moreover, a soft-starting method is suggested to avoid the employed converter over-current. The first control scheme is achieved by adjusting the command power-winding reactive power at zero for a unity power-factor operation. However, the second scheme depends on setting the command d-axis control-winding current at zero to maximize the ratio of the generator electromagnetic-torque per the converter current. This enables the system to get a certain command torque under minimum converter current. A sample of the obtained simulation and experimental results is presented to check the effectiveness of the proposed control strategies.

Sensored and sensorless scalar-control strategy of a wind-driven BDFRG for maximum wind-power extraction

This paper presents a scalar volt per hertz (V/f) control technique for maximum power tracking of a grid-connected wind-driven brushless doubly fed reluctance generator (BDFRG). The proposed generator has two stator windings namely; power winding, directly connected to the grid and control winding, connected to the grid through a bi-directional converter. In order to enhance the performance of the proposed scalar-control strategy, a soft starting method is suggested to avoid the over-current of the bi-directional converter. Moreover, the capability of generator speed estimation for sensorless control is also studied. The capability of the proposed scalar-control technique is validated using a sample of simulation results. In addition, the presented simulation results ensure the effectiveness of the proposed control strategy for maximum wind-power extraction under wind-speed variations. Furthermore, the results show that the estimated generator speed is in a good accordance with the actual generator speed which supports sensorless control capability.

A comparative study of vector-control strategies for maximum wind-power extraction of a grid-connected wind-driven brushless doubly-fed reluctance generator

This paper proposes a vector-control technique of a grid-connected wind-driven Brushless Doubly Fed Reluctance Generator (BDFRG) for maximum wind-power extraction under three strategies, summarised as unity power-factor operation, minimum converter current and minimum copper losses. The adopted generator has two stator windings namely; power winding, directly connected to the grid, and control winding, connected to the grid through a bi-directional converter. In addition, a soft starting method is suggested to avoid the employed converter over-current. The first control strategy can be achieved by adjusting the command power-winding reactive power at zero for a unity power-factor operation. However, the second strategy depends on setting the command d-axis control-winding current at zero to maximise the ratio of the generator electromagnetic-torque per the converter current. This enables the system to get a certain command torque under minimum converter current. On the other hand, the third strategy can be realised by determining the control-winding current angle at which the BDFRG can operate with minimum copper losses. A sample of the obtained simulation results is presented to check the effectiveness of the proposed control strategies.

MAXIMUM POWER TRACKING OF A GRID-CONNECTED WIND-DRIVEN BRUSHLESS DOUBLY-FED RELUCTANCE GENERATOR USING SCALAR CONTROL

This paper presents a scalar volt per hertz (v/f) control technique for maximum power tracking of a grid-connected wind-driven Brushless Doubly-Fed Reluctance Generator (BDFRG). The proposed generator has two stator windings namely; power winding, directly connected to the grid, and control winding, connected to the grid through a bi-directional converter. The presented control technique is based on the abc-axis and dq-axis dynamic model of BDFRG. A detailed abc-axis and dq-axis dynamic model, by which the dynamic behaviour of the BDFRG can be successfully predicted under different operating conditions, is presented. In addition, a soft starting method is suggested to avoid the over-current of the bi-directional converter. The presented simulation results ensure the effectiveness of the proposed control strategy for maximum wind-power extraction under wind-speed variations.

Analysis and synthesis of sliding mode control for large scale variable speed wind turbine for power optimization

The problem of designing a nonlinear feedback control scheme for variable speed wind turbines, without wind speed measurements, in below rated wind conditions was addressed. The objective is to operate the wind turbines in order to have maximum wind power extraction while also the mechanical loads are reduced. Two control strategies were proposed seeking a better performance. The first strategy uses a tracking controller that ensures the optimal angular velocity for the rotor. The second strategy uses a Maximum Power Point Tracking (MPPT) algorithm while a non-homogeneous quasi-continuous high-order sliding mode controller is applied to ensure the power tracking. Two algorithms were developed to solve the tracking control problem for the first strategy. The first one is a sliding mode output feedback torque controller combined with a wind speed estimator. The second algorithm is a quasi-continuous high-order sliding mode controller to ensure the speed tracking. The proposed controllers are compared with existing control strategies and their performance is validated using a FAST model based on the Controls Advanced Research Turbine (CART). The controllers show a good performance in terms of energy extraction and load reduction.

SoC Feedback Control for Wind and ESS Hybrid Power System Frequency Regulation

With increased penetration of wind generation, the traditional control scheme of the wind turbine (WT), which is designed for maximum wind power extraction, is no longer suitable to meet emerging grid requirements for wind farms to participate in frequency regulation. The control scheme of the WT with respect to grid frequency regulation is proposed in many studies, such as those on pitch control. Also, energy storage technologies have drawn much attention in recent years because, as technology matures and costs decrease, they present themselves as a potential solution for the challenge brought about by the uncertainty of renewable energy generation with regard to power system stability. A power system consisting of a high penetration of wind generation and energy storage systems (ESS) is investigated in this paper for the regulation of grid frequency. A new strategy called state of charge (SoC) feedback control is proposed, and the performance of the grid frequency deviation response and the SoC of the battery are presented. The model of the power system studied in this paper is established on the MATLAB/SIMULINK platform.

Combined optimization of a wind farm and a well field for wind-enabled groundwater production

Energy requirements constitute a significant cost in groundwater production and can also add to a large carbon footprint when fossil fuels are used for power. Wind-enabled water production is advantageous as it minimizes air pollution impacts associated with groundwater production and relies on a renewable resource. Also, as groundwater extraction represents a deferrable load (i.e., it can be carried out when energy demands within an area are low), it provides a convenient way to overcome the intermittency issue associated with wind power production. Multiple turbine wind farms are needed to generate large quantities of power needed for large-scale groundwater production. Turbines must be optimally located in these farms to ensure proper propagation of kinetic energy throughout the system. By the same token, well placement must reconcile the competing objectives of minimizing interferences between production wells while ensuring the drawdowns at the property boundary are within acceptable limits. A combined simulation–optimization based model is developed in this study to optimize the combined wind energy and water production systems. The wind farm layout optimization model is solved using a re-sampling strategy, while the well field configuration is obtained using the simulated annealing technique. The utility of the developed model is to study wind-enabled water production in San Patricio County, TX. Sensitivity analysis indicated that identifying optimal placement of turbines is vital to extract maximum wind power. The variability of the wind speeds has a critical impact on the amount of water that can be produced. Innovative technologies such as variable flow pumping devices and aquifer storage recovery must be used to smooth out wind variability. While total groundwater extraction is less sensitive to uncertainty in hydrogeological parameters, improper estimation of aquifer transmissivity and storage characteristics can affect the feasibility of wind-driven groundwater production.

A MPPT Strategy for Wind Power PMSG System with Full Power Converter

The direct-drive permanent-magnet synchronous generator (PMSG) system with full power converter can achieve wind maximum power point tracking (MPPT) in wide range variation of wind-speed. In this paper an operating characteristic of PMSG is investigated, a MPPT strategy based on hill climbing method for PMSG are present. Simulation and experimental results show that the controllers can extract maximum wind power in good dynamic performance.

Dynamic model of wind energy conversion systems with PMSG-based variable-speed wind turbines for power system studies

In order to study the impact of a wind farm on the dynamics of the power system, a significant issue is to develop appropriate equivalent models that allow characterizing the dynamics of all individual wind turbine generators (WTGs) composing the park. In this sense, with the advance of power electronics, direct-driven permanent magnet synchronous generators (PMSGs) have drawn increased interest to wind turbine manufacturers due to their advantages over other variable-speed WTGs. These include the possibility of multi-pole design with a gearless construction that offers slow speed operation and reduced maintenance since no brushes are used, elimination of the excitation system, full controllability for maximum wind power extraction and grid interface, and easiness in accomplishing fault-ride through and grid support. In this way, this paper presents a comprehensive dynamic equivalent model of a wind farm with direct-driven PMSG wind turbines using full-scale converters and its control scheme. The proposed simplified modelling is developed using the state-space averaging technique and is implemented in the MATLAB/Simulink environment. The dynamic performance of the wind farm and its impact on the power system operation is evaluated using the phasor simulation method.

Research on Modeling and Control Methods of Variable-Speed Variable-Pitch Wind Turbine Generators

In view of the high-order, nonlinear, strong coupling, multivariable and time varying character of wind energy conversion system, the fuzzy-logic control strategy is introduced in this paper. First, this thesis analyzes and establishes the mechanism model for each component element of the megawatt class variable-speed variable-pitch wind turbines as well as the wind speed model. Second, for the goal of maximum wind power extraction under rated wind and peak power output maintaining above rated speed wind, PID controllers as well as fuzzy-logic controllers are designed respectively by different wind velocity condition. The simulation results demonstrate that no matter for the following up performance or the anti-interference capability, the fuzzy controllers which are devised in the paper have a better control effect than PID controllers. The fuzzy controllers can reduce system’s overshoot and regulation time more effectively, offset the negative impacts of nonlinearity, and they have better robustness too.

Model Predictive Control for Direct-Drive Wind Power Generation Systems

Permanent magnet synchronous generator (PMSG) are commonly used in direct-drive wind power generation systems, which produce high efficiency, high reliability and low cost in wind power generation. This paper presents a new and simple control scheme using predictive control, which is used in PMSGs and grid-connected inverters. The controller uses the models of PMSGs and grid-connected inverters to predict on each sampling interval. A cost function defines the desired behavior of the system. The switching state that minimizes the cost function is selected and applied during the next sampling interval. At any wind speed within the operating range, the PMSG rotor speed can optimally controlled to extract maximum wind power. The simulated results show that the proposed control scheme can provide the direct-drive wind power generation system with the maximum efficiency and high dynamic performance.

Estimating maximum global land surface wind power extractability and associated climatic consequences

Abstract. The availability of wind power for renewable energy extraction is ultimately limited by how much kinetic energy is generated by natural processes within the Earth system and by fundamental limits of how much of the wind power can be extracted. Here we use these considerations to provide a maximum estimate of wind power availability over land. We use several different methods. First, we outline the processes associated with wind power generation and extraction with a simple power transfer hierarchy based on the assumption that available wind power will not geographically vary with increased extraction for an estimate of 68 TW. Second, we set up a simple momentum balance model to estimate maximum extractability which we then apply to reanalysis climate data, yielding an estimate of 21 TW. Third, we perform general circulation model simulations in which we extract different amounts of momentum from the atmospheric boundary layer to obtain a maximum estimate of how much power can be extracted, yielding 18–34 TW. These three methods consistently yield maximum estimates in the range of 18–68 TW and are notably less than recent estimates that claim abundant wind power availability. Furthermore, we show with the general circulation model simulations that some climatic effects at maximum wind power extraction are similar in magnitude to those associated with a doubling of atmospheric CO2. We conclude that in order to understand fundamental limits to renewable energy resources, as well as the impacts of their utilization, it is imperative to use a "top-down" thermodynamic Earth system perspective, rather than the more common "bottom-up" engineering approach.