Control Of Wind Energy System Research Articles

Systemic optimal control of wind energy system regulating conjointly generator speed and battery recharging current

In this paper is presented an optimal control technology of wind energy system recovering energy in a battery energy accumulator. This control technology makes it possible to regulate the speed of the electric generator at its optimum value, to avoid any over-speed problems leading to strong increases in current in the electrical components of the wind turbine, and subsequently to its destruction. This control technology also makes it possible to maintain the induced electromotive forces in phase with the phase’s currents of the generator to have an additive electromagnetic torque, and in this way the recovered energy will be optimal. This control technology is based on two conversions, one is an Alternative-Continuous conversion performed by an AC-DC converter with IGBTs, and the other is a DC-DC conversion performed by a booster chopper to regulate the voltage of recharges batteries at its nominal value.

Enhanced Control of Wind Energy Conversion System Based on DFIG Using Adaptive Super Twisting Controllers

In the control of Wind Energy System (WES), the most serious disturbances to occur are the variations of wind speed which can affect the quality and continuity of the generated power. In this research paper, an enhanced control strategy is proposed for a wind turbine (WT) system equipped with a Doubly Fed Induction Generator (DFIG) connected to the grid network. The proposed strategy design is based on an amended formula of the Super Twisting Control with adaptive gains that can be implemented to the cascaded system scheme comprising the speed and power control loops. This method is effective in reducing and smoothing the control effort by developing a simple formulation of sliding gain despite disturbance regarding variation on the parameters, and the random nature of wind speed. By comparison with the conventional Super Twisting Control, simulation results are given to illustrate the improvements of the use of adaptive Super Twisting Control based controllers in a WES Control.

Reactive Power Compensation in a Hybrid Renewable Energy System through Fuzzy Based Boost Converter

The reactive power compensation is essential during hybrid grid connected system, because the overall power factor of the power systems is reduced due to DC energy fed to the grid using electronic energy inverters. Increased load on the grid due to poor power factor triggers losses in the grid. The main objective of the work related to control the Reactive Power flow in grid connected Hybrid Renewable Energy System (PV-wind-battery). The objectives of the work were achieved by satisfying the load demand, injecting the reactive power from hybrid sources to the grid. First, the proposed technique with fuzzy based boost converter is implemented. It reduced power conversion stages, decreases the losses compared to existing Hybrid Grid-connected systems. The most significant result of the work is the conclusion that the fuzzy based boost converter should increase the Maximum power from solar PV Panel, The speed control of wind energy system is control by speed controller-fuzzy rule, and it created with low speed to high speed. The significance of the obtained results is that the used methodology allowed maximum energy utilized by hybrid renewable energy system to grid. The reactive power is maintained at zero level in order to ensure the unity power factor operation. But rather significantly enhances the small voltage fluctuation in the grid. In addition, to reduces the current total harmonic distortion to 1.9 %, which is good lower than the requirement for network operation. The proposed method is verified using MATLAB/Simulink. The simulation results were supported experimentally.

Methodology for optimal design and control of wind energy system based on simplifying assumptions

The study presented in this paper concerns the development of a new methodology for design and controlling a wind energy generation chain. This methodology is based on combined Analytical-Finite Element-Experimental method. This type of converter chosen is an AC-DC inverter with IGBTs to improve the robustness of the power chain structure. It offers a reduction of the cost of the power chain and the improvement of the performances of the global studied system, as the control at power factor equal to unity and providing an electromagnetic torque which is added to the useful torque in order to extract the maximal energy. The control algorithms permit to regulate Le charging voltage and current in their rated values considered as optimal battery charging voltage and current. The global model of the power chain is implemented under the Matlab-Sumilink simulation environment for performance and efficiency analysis.

An Effective Control Strategy for Pitch control of Wind Energy System Connected with Grid

Recently the main concern all over the world is carbon emission reduction and due to this renewable energy sources are the main point of attraction for the power generation. Especially wind energy into the electrical power grid is extensively increased, the influence of the wind turbine system on the voltage stability and frequency becomes more and more significant. Wind turbine rotor has different types of loads and these loads results in fatigue and vibration in blades. These loads and losses can overcome by using a good pitch controller. As we know that energy extracted is limited according to Betz law but with the help of good pitch angle controllers it is possible to get desired output in certain conditions. A maximum performance can be obtain by designing a good pitch angle controller. A system with wind turbine generator system connected with grid is designed and simulated in Matlab software with the PID control system and the results are evaluated and by analysing these results some future analysis can be planned.

New design and comparative study via two techniques for wind energy conversion system

Introduction. With the advancements in the variable speed direct drive design and control of wind energy systems, the efficiency and energy capture of these systems is also increasing. As such, numerous linear controllers have also been developed, in literature, for MPPT which use the linear characteristics of the wind turbine system. The major limitation in all of those linear controllers is that they use the linearized model and they cannot deal with the nonlinear dynamics of a system. However, real systems exhibit nonlinear dynamics and a nonlinear controller is required to handle such nonlinearities in real-world systems. The novelty of the proposed work consists in the development of a robust nonlinear controller to ensure maximum power point tracking by handling nonlinearities of a system and making it robust against changing environmental conditions. Purpose. In the beginning, sliding mode control has been considered as one of the most powerful control techniques, this is due to the simplicity of its implementation and robustness compared to uncertainties of the system and external disturbances. Unfortunately, this type of controller suffers from a major disadvantage, that is, the phenomenon of chattering. Methods. So in this paper and in order to eliminate this phenomenon, a novel non-linear control algorithm based on a synergetic controller is proposed. The objective of this control is to maximize the power extraction of a variable speed wind energy conversion system compared to sliding mode control by eliminating the phenomenon of chattering and have a good power quality by fixing the power coefficient at its maximum value and the Tip Speed Ratio maintained at its optimum value. Results. The performance of the proposed nonlinear controllers has been validated in MATLAB/Simulink environment. The simulation results show the effectiveness of the proposed scheme, suppression of the chattering phenomenon and robustness of the proposed controller compared to the sliding mode control law.

Output power control of wind energy system by tip speed ratio control using fractional PIβDα controller

Various non-linear systems are well designed using a non-integer order mathematical model based differential and integral components. The fractional-order concept provides an effective method for turning the technology robust in various industry applications. This paper presents a fractional proportional-integral-derivative (FPID) controller and its benefits in variable speed wind turbine (WT) application. The FPID controller improves the operational environment of WT from the initiation of two more tuning parameters i.e., the fractional-order integral and derivative gains. These gains are well-tuned using the manual tuning method. For analysis of the effectiveness of the FPID controller, a comparison has been carried out between FPID and conventional PID controllers. The overshoot, rise time and settling time in various parameter responses like rotor speed, electromagnetic torque, and load power are considered for comparison of effectiveness of both the controllers. Performance indexes are also calculated and compared for both the controllers.

Improved wind system using non-linear power control

<p>This article, present a new contribution to the control of wind energy systems, a robust nonlinear control of active and reactive power with the use of the Backstepping and Sliding Mode Control approach based on a doubly fed Induction Generator power (DFIG-Generator) in order to reduce the response time of the wind system. In the first step, a control strategy of the MPPT for the extraction of the maximum power of the turbine generator is presented. Subsequently, the Backstepping control technique followed by the sliding mode applied to the wind systems will be presented. These two types of control system rely on the stability of the system using the LYAPUNOV technique. Simulation results show performance in terms of set point tracking, stability and robustness versus wind speed variation. </p>

Super-capacitor-based inverter control of wind energy system connected to weak grid

ABSTRACTThis paper proposed an inverter control scheme for wind energy system under weak grid conditions. Wind-based hybrid energy system (HES) is often having the issue of poor transients and slow dynamic response due to the unpredictable nature of the wind speed and inertia of the generator who cannot respond the changes instantly. The proposed control scheme is designed to improve the transients and dynamic responses of the wind energy system. The control scheme introduces super-capacitor (SC) fast charging/discharging characteristics in the inverter control using a bidirectional buck–boost converter to improve the transients and the frequency response of the system. The inverter control scheme under the weak grid conditions is designed and analysed. The proposed control can be applied in the marine electrical system where wind system is installed in the marine to reduce fuel consumption and improve electric power quality. Wind-based HES is modelled and simulated in the MATLAB to demonstrate the effectiveness of the proposed control scheme under different conditions. The results are presented and compared to the conventional control scheme to justify the improvement in the power quality and the frequency response of the system.

Design and Construction of a Wind Turbine Simulator for Integration to a Microgrid with Renewable Energy Sources

In this paper, a physical wind turbine simulator (WTS) has been designed, constructed, and evaluated in a microgrid environment. The reference turbine is a physical wind turbine (PWT), whose characteristics are obtained through wind tunnel experiments. The main purpose of this WTS is to investigate the integration and coordination control of wind energy systems in a microgrid environment. A comprehensive literature review has been performed, and the lessons learned from existing WTSs have been considered. A vector torque control strategy with an induction motor has been selected for implementation. Due to the feature of independent torque control in a vector mode, superior dynamic behavior, high accuracy at low-wind speed conditions can be achieved. This simulator, therefore, provides flexibility to accommodate a wide range of wind conditions. In addition, the simulator construction and control system design are also included. The steady-state and dynamic characteristics of the WTS correlate well with the considered reference PWT. The performance of WTS has been validated against the reference turbine under realistic wind conditions. Real-time coordination of this WTS with photovoltaic (PV) devices and battery storage within a microgrid has been also investigated.

Sensorless Nonlinear Control of Wind Energy Systems with Doubly Fed Induction Generator

The problem of controlling doubly fed induction generators (DFIG) associated with wind turbines is addressed. The control objective is twofold: maximum power point tracking and reactive power regulation in the DFIG. Unlike previous works, we seek the achievement of this control objective without resorting to physical sensors of mechanical variables (e.g., wind turbine velocity and DFIG rotor speed). Interestingly, wind velocity is also not assumed to be accessible to measurements. The control problem is dealt with using an output feedback controller designed on the basis of the nonlinear state-space representation of the controlled system. The controller is constituted of a high-gain nonlinear state observer and a nonlinear sliding state feedback mode. Using tools from Lyapunov’s stability, it is formally shown that the closed-loop control system, expressed in terms of the state estimation errors and the output-reference tracking errors, enjoys a semi-global practical stability. Accordingly, it is possible to tune the controller design parameters so that it meets its objectives with an arbitrarily high accuracy, whatever the initial conditions are. These theoretical results are confirmed by simulations involving wide range variation of the wind speed.

WIND PARAMETERS ANALYSIS ON FIVE LOCATIONS IN MACEDONIA –- THE SECOND MEASUREMENT CAMPAIGN

The world population growth and the technological development have increased the demands for electricity. Because of the limited deposits of fossil fuel and the negative impact its combustion causes to the envi ronment, the electricity production technologies are orienting towards using the renewable energy sources. From all the renewable energy sources, the most studied one over the last decade is the wind. Wind parameters of interest in electrical study are its speed and direction; once they are measured it is easy to determine other characteristic parame ters such as wind energy density on the specific location. In the manuscript, monthly and seasonal mean wind speeds are presented, alongside the wind energy density for five locations in the Republic of Macedonia, for almost four years of measurements. Key words: monthly mean wind speeds; seasonal mean wind speed; scale parameter; shape parameter; wind energy density REFERENCES: [1] Vladimir Dimcev, Vlatko Stoilkov, Krste Najdenkovski, Živko Kokolanski, Maja Celeska: Establishing wind energy data base in the Republic of Macedonia, Faculty of Electrical Engineering and IT, Skopje, September 2015. [2] Vladimir Dimcev, Vlatko Stoilkov, Krste Najdenkovski, Živko Kokolanski, Maja Celeska: Summary report for the second wind measurement campaign in the Republic of Macedonia, Faculty of Electrical Engineering and IT, Skopje, April 2016. [3] Kiril Demerdžiev: Wind energy potential measurement and data analysis, bachelor thesis, Faculty of Electrical Engineering and IT, Skopje, October 2015. [4] I. Munteanu, A. I. Bratcu, N. A. Cutululis, E. Ceanga: Optimal Control of Wind Energy Systems – Towards a Global Approach, Springer-Verlag, London, 2008. [5] A. N. Celik: A statistical Analysis of Wind Power Density Based on the Weibull and Rayleigh Models at the Southern Region of Turkey, Renewable Energy, 29, (2), 21–33 (2006). [6] Mahyoub H. Al-Buhairi, Ahmed Al-Haydari: Monthly and Seasonal Investigation of Wind Characteristics and Assessment of Wind Energy Potential in Al-Mokha, Yemen, Energy and Power Engineering, 4 (3), 125–131 (2012), doi: 10.4236/epe.2012.43017. [7] Sunday O. Oyedepo, Muyiwa S. Adaramola, Samuel S.Paul: Analysis of wind speed data and wind energy potential in three selected locations in south-east Nigeria, International Journal of Energy and Environmental Engineering, 3 (7), 1–11 (2012) (http://www. journal-ijeee.com/content/3/1/7).

Sensorless adaptive output feedback control of wind energy systems with PMS generators

This paper addresses the problem of controlling wind energy conversion (WEC) systems involving permanent magnet synchronous generator (PMSG) fed by IGBT-based buck-to-buck rectifier–inverter. The prime control objective is to maximize wind energy extraction which cannot be achieved without letting the wind turbine rotor operate in variable-speed mode. Interestingly, the present study features the achievement of the above energetic goal without resorting to sensors of wind velocity, PMSG speed and load torque. To this end, an adaptive output-feedback control strategy devoid of any mechanical sensor is developed (called sensorless), based on the nonlinear model of the whole controlled system and only using electrical variables measurements. This control strategy involves: (i) a sensorless online reference-speed optimizer designed using the turbine power characteristic to meet the maximum power point tracking (MPPT) requirement; (ii) a nonlinear speed regulator designed by using the backstepping technique; (iii) a sensorless interconnected adaptive state observer providing online estimates of the rotor position as well as speed and load/turbine torque. The proposed output-feedback control strategy is backed by a formal analysis showing that all control objectives are actually achieved. Several simulations show that the control strategy enjoys additional robustness properties.

Wind Energy and Time-Triggered Networks: Power Conversion and Control of Wind Energy Systems (Wu, B. et al; 2011) [Book News

The book discusses all problems related to wind energy, including generators and voltage source converters and current source converters.

Energy-based approach to the output feedback control of wind energy systems

Wind energy systems can be classified into constant speed and variable speed ones. In constant speed schemes, the generator is directly connected to the electric grid. On the other hand, variable speed operation can be accomplished interposing a static converter in the energy flow between the generator and the grid, permitting a high control flexibility. The main control objectives are the maximization of the conversion efficiency and the elimination of torque oscillations propagated through the drive train. It is assumed in this paper that the most flexible part of the system lies on the turbine, constraining the control solutions to generator speed feedback. The control task is addressed from a passivity-based control viewpoint. The drive train dynamics is modelled as a port-controlled Hamiltonian system with dissipation. Then, stabilization of the desired operating point is achieved through energy shaping and damping injection. Depending on the damping matrix assignment, different control solutions are recovered. Finally, a dynamic feedback controller which preserves the system structure is proposed to improve the system performance without measuring the wind velocity.

Sliding mode control of wind energy systems with DOIG-power efficiency and torsional dynamics optimization

Wind turbines with double output induction generators can operate at variable speed permitting conversion efficiency maximization over a wide range of wind velocities. However, random wind fluctuations, wind shear and tower shadow, may excite the oscillation mode of the mechanical system, producing large torque ripple. Consequently, damage to drive train components and power quality problems may occur. In this paper, a sliding mode control is developed which provides a suitable compromise between conversion efficiency and torque oscillation smoothing. The resultant sliding dynamics is completely robust to uncertainties in the electrical variables and parameters. In addition, to prevent windup problems due to saturation, a combined sliding surface that incorporates such limitations is proposed.