Operation Of Wind Turbine Generator Research Articles

A frequency control scheme of a doubly-fed induction generator considering random wind speeds

The low inertia characteristic of the power system is increasingly prominent with the increase of wind power penetration. Therefore, the threat of random wind speeds and sudden frequency events to the frequency stability of a low inertia power system is further enhanced. It is necessary for wind power generators to provide frequency auxiliary service for the power system through appropriate control schemes. To address these issues, a frequency control scheme is proposed for a doubly-fed induction generator (DFIG) to support the frequency stability of the system in this paper, which can play a role in additional-loop-based frequency smooth control (FSC) and dynamic inertial control (DIC) by a smooth switcher. The objective of FSC is to smooth the frequency fluctuation caused by random wind speeds, load fluctuation, etc., while DIC aims at improving the frequency nadir (FN) and simultaneously preventing rotor speed over-deceleration during a large disturbance. In addition, a smooth switcher is proposed to coordinate the advantages of FSC and DIC. Note that the proposed approach can be automatically switched from FSC to DIC, while frequency deviation exceeds the given threshold due to a large disturbance. Finally, simulation results on the IEEE 14-bus system show the advantages of the proposed method in improving frequency stability under real complex situations while ensuring the stable operation of wind turbine generators.

Performance Evaluation of Grid-Connected Wind Turbine Generators

The risk of oscillation of grid-connected wind turbine generators (WTGs) is well known, making it all the more important to understand the characteristics of different WTGs and analyze their performance so that the problems’ causes are identified and resolved. While many studies have evaluated the performance of grid-connected WTGs, most lack clarity and precision in the modeling and simulation techniques used. Moreover, most of the literature focuses on a single mode of operation of WTGs to analyze their performances. Therefore, this paper updates the literature by considering the different operating conditions for WTGs. Using MATLAB/SIMULINK it expands the evaluation to the full range of vulnerabilities of WTGs: from the wind turbine to grid connection. A network representing grid-connected squirrel-cage induction generator (SCIG) and doubly-fed induction generator (DFIG) wind turbines are selected for simulation. The performances of SCIG and DFIG wind turbines are evaluated in terms of their energy generation capacity during constant rated wind speed, variable wind speed, and ability of fault-ride through during dynamic system transient operating conditions. The simulation results show the performance of DFIG is better than SCIG in terms of its energy generation capacity during variable wind speed conditions and active and reactive power control capability during steady-state and transient operating conditions. As a result, DFIG wind turbine is more suitable for large-scale wind power plants connected to weak utility grid applications than SCIG.

Leader-Following Diffusion-Based Reactive Power Coordination and Voltage Control of Offshore Wind Farm

This paper proposed a distributed reactive power coordination and voltage control of offshore wind farm based on the leader-following diffusion algorithm. Designating several wind turbine generators (WTGs) as the leaders to receive the information of voltage at point of common coupling (PCC), the reactive power generations required to minimize the voltage deviation could be computed by these leaders. The required reactive power generations are diffused throughout all WTGs by the diffusion algorithm, resulting in the coordinated operation of WTGs to regulate the PCC voltage. The proposed offshore wind farm controller is based on the hierarchical control strategy, which consists of primary and secondary layers. The primary layer is responsible for the inner current, voltage or power regulations whereas the secondary layer is based on the proposed diffusion algorithm to achieve the coordinated operation among WTGs. The proposed strategy could maintain accurate reactive power sharing among WTGs and regulate the PCC voltage. A comparison study with the conventional consensus-based control is presented to show the effectiveness of the proposed diffusion controller. The comparison results show the better performance of the proposed method in terms of dynamic responses of PCC voltage and reactive power coordination. Simulation scenarios of constant wind speed, variable wind speed, and voltage sag in the utility grid are carried out to evaluate the performance of proposed method. The proposed diffusion control is tested either in a small or large offshore wind farm systems. Effect of communication delay on the performance of proposed diffusion control is also described. An experiment of the small-scale wind farm system is conducted to show the feasibility of proposed diffusion strategy.

Impact assessment of virtual synchronous generator on the electromechanical dynamics of type 4 wind turbine generators

The de-loaded operation of wind turbine generators (WTGs) with inertial and frequency control considerably affects the dynamics and stability of variable speed wind turbines. In this context, this work proposes a comprehensive assessment of the simultaneous impact of virtual synchronous generator and frequency controllers on the electromechanical dynamics of type 4 WTGs. The proposed power balance formulation and the performed analysis, which are the main contributions of this work, provide insight into the simultaneous impact of the inertial and frequency control on the dynamics of the wind generation unit and system frequency. The assessment has been performed by means of an analytical formulation for the power balance in the WTG, characteristic curves of the wind turbine, and non-linear time-domain simulations of two test systems. The analyses have shown that the speed and torque deviation magnitudes of the wind turbine, as well as the amount of kinetic energy released by the wind turbine, depend on the wind turbine operating point. The study has also shown that the de-loaded operation considerably increases the inertial response capability of WTGs. The integrated inertial and frequency control approach has resulted in well-behaved electromechanical dynamics for the WTG.

Power Smoothing of a Variable-Speed Wind Turbine Generator in Association With the Rotor-Speed-Dependent Gain

This paper proposes a power-smoothing scheme for a variable-speed wind turbine generator (WTG) that can smooth out the WTG's fluctuating power caused by varying wind speeds, and thereby keep the system frequency within a narrow range. The proposed scheme employs an additional loop based on the system frequency deviation that operates in conjunction with the maximum power point tracking (MPPT) control loop. Unlike the conventional, fixed-gain scheme, its control gain is modified with the rotor speed. In the proposed scheme, the control gain is determined by considering the ratio of the output of the additional loop to that of the MPPT loop. To improve the contribution of the scheme toward maintaining the frequency while ensuring the stable operation of WTGs, in the low rotor speed region, the ratio is set to be proportional to the rotor speed; in the high rotor speed region, the ratio remains constant. The performance of the proposed scheme is investigated under varying wind conditions for the IEEE 14-bus system. The simulation results demonstrate that the scheme successfully operates regardless of the output power fluctuation of a WTG by adjusting the gain with the rotor speed, and thereby improves the frequency-regulating capability of a WTG.

High-Resolution LES of Terrain-Induced Turbulence around Wind Turbine Generators by Using Turbulent Inflow Boundary Conditions

We have developed an LES (Large-Eddy Simulation) code called RIAM-COMPACT (Research Institute for Applied Mechanics, Kyushu University, Computational Prediction of Airflow over Complex Terrain). The analysis do-main of this numerical model extends from several meters to several kilometers. The model is able to predict airflow over complex terrain with high accuracy and is also now able to estimate the annual power output of wind turbine generators with the use of field observation data. In the present study, a numerical simulation of turbulent airflow over an existing wind farm was performed using RIAM-COMPACT and high-resolution elevation data. Based on the simulation results, suitable and unsuitable locations for the operation of WTGs (Wind Turbine Generators) were identified. The latter location was subject to the influence of turbulence induced by small topographical variations just upwind of the WTG location.

Reasons for wind turbine generator failures: a multi-criteria approach for sustainable power production

Power generation quantity from wind sector is increasing at much faster rate day by day in the scenario of power systems, which obviously needs reliable operation. Therefore, accurate monitoring and error diagnosis are almost mandatory. This paper aims to identify important errors that affect the performance and can easily detect the faults of wind turbine generators (WTGs). Wind turbines are subjected to different sort of failures; thus, before starting to identify various kinds of errors, it is necessary to identify what kind of failures can be found in the real world which causes healthy operation of WTGs. Out of different errors, error that is caused by the operation of gearbox could stop or reduce the generation of power from WTGs for a long time. Recently, several condition monitoring and fault diagnosis techniques have been introduced in order to minimize downtime and maintenance cost while increasing energy availability and life time service of the wind farms. Different types of sensors have been used for long time in wind turbine fault diagnosis or monitoring systems to collect data of the generator health. Many researchers analyzed wind turbine failures using different software. The present study uses different approaches and prepares a multi-criteria decision-making framework using analytic hierarchy process (AHP). The analysis of the data under AHP frame work revealed overspeed guard/turbine out of control error got the top most impediment to the healthy operation of WTGs, and high brake temperature fits in the fifth position among the five different error groups considered.

3MW 풍력발전기 진동상태감시 및 진단시스템 프레임워크

This paper aims at making a dedicated vibration monitoring and diagnosis framework for 3MW WTG(wind turbine generator). Within the scope of the research, vibration data of WTG drive train are used and WTG operating conditions are involved for dividing the vibration data class which included transient and steady state vibration signals. We separate two health detections which are CHD(continuous health detection) and EHD(event health detection). CHD has function of early detection and continuous monitoring. EHD makes the use of finding vibration values of fault components effectively by spectrum matrix subsystem. We proposed framework and showed application for 3MW WTG in a practical point of view.

Enhancement in Primary Frequency Contribution using Dynamic Deloading of Wind Turbines

This paper presents a fuzzy logic based scheme to enhance the primary frequency contribution of grid connected variable speed wind turbine generators (WTGs). Deloading of WTGs from its maximum power point generates reserve margin which can be used to stabilize the power system during frequency deviations. In this paper, deloading power of WTG is adjusted continuously which increases the output power from deloaded WTG. Combination of dynamic deloading and variable droop operation of WTGs gives best performance in terms of reduction in frequency excursion and increase in output power of deloaded WTG. Extensive MATLAB results are presented by considering different cases.

Research on Wind Turbine Generator Dynamic Reliability Test System Based on Feature Recognition

Wind power resource development is increasingly becoming the focus of the current research and development in various countries' relevant scientific institutions. To make sure the secure and reliable operation of wind turbine generator, the study develops the wind turbine generator dynamic reliability test system. When the fault of gearbox and spindle occurs, their features of vibration signals are special. According to the feature recognition technology, the application of time and frequency domain model identification method has practical significance to the test system. Based on Bayesian network fault diagnosis method, the vibration feature recognition system of wind turbine generator is constructed. Finally, the paper uses GPRS technology to realize the wireless transmission of operation information. The wind turbine generator dynamic reliability test system is built based on GPRS technology to realize automatic control and remote intelligent monitoring and to ensure the safe and stable operation of wind farms.

DSM Considered Probabilistic Reliability Evaluation and an Information System for Power Systems Including Wind Turbine Generators

This paper proposes a methodology for evaluating the probabilistic reliability, considering demand side management (DSM) and Web based on a daily interval reliability information system for a grid constrained composite power system including wind turbine generators(WTG). The proposed model can consider capacity limitations and transmission line unavailabilities and the operation of WTG modeled by multi-states. The importance of renewable energy sources is growing at a rapid rate due to environmental concerns. A web based online daily time interval reliability integrated information system (WORRIS) is applied using the methodology proposed in this paper. This paper describes the architecture of the WORRIS Version 7.0 system.

Improvement of dynamic performance of doubly fed induction generator-based wind turbine power system under an unbalanced grid voltage condition

With the current increase in wind power penetration into the energy market, control and operation of wind turbine generators becomes a major research topic. Wind turbine based on doubly fed induction generator (DFIG), which is sensitive to grid disturbances, is widely used. Under an unbalanced grid voltage condition, oscillations of the DFIG's electromagnetic torque and instantaneous stator powers strongly affect the dynamic performance of the DFIG. In this study, a new configuration based on vector proportional'integral (VPI) controller is proposed to eliminate such oscillations. This new configuration is employed in the rotor side converter (RSC) of the DFIG. With the proposed VPI control strategy, decomposition of sequential components and mathematical complexity are reduced. Compared with the conventional field-oriented control based on the standard single PI controller, the VPI controller can successfully eliminate torque and stator power oscillations. The effectiveness of the proposed control strategy is validated through simulation results obtained on a 1.5'MW DFIG-based wind turbine system model built in MATLAB/Simulink.

Validation of Single- and Multiple-Machine Equivalents for Modeling Wind Power Plants

This paper presents an exhaustive simulation study performed to validate the adequacy of the equivalencing method promoted by the National Renewable Energy Laboratory for modeling wind power plants by single- and multiple-machine equivalents. The main simulation results are presented for a number of steady state and transient wind turbine generator operating conditions following various faults and a typical low-voltage ride through. The impact of protection systems such as the crowbar is also taken into account. The aggregation technique has shown to be adequate for load flow, stability, and electromagnetic transient studies with limitations, as presented in the paper.

State criterion of wind turbine generator operation using tower shadow effect (Part 2)

AbstractIn order to obtain wind energy effectively, the pole‐change‐type induction generators are used as the wind turbine generators. Otherwise, the pole‐change‐type induction generator causes the voltage dips at pole changing time. To maintain the power quality, it is important to know the state change of the generator operation. Therefore, the authors have studied a state criterion of generator using the tower shadow effect, which is the active power oscillation caused by a rotation torque drop when the tower and the turbine blade overlap each other.In this paper, an improved identification method of oscillation frequency, which is the criterion of wind turbine generator operation, is proposed. The proposed method is applied to measured data and good results are obtained. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(1): 25–31, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20395

Disturbance rejection by dual pitch control and self-tuning regulator for wind turbine generator parametric uncertainty compensation

Operation of wind turbine generator (WTG) systems in the above-rated region characterised by high wind turbulence intensities invariably induces fatigue stresses on the drive train components. This demands a trade-off between two performance metrics: maximisation of energy harvested from the wind and minimisation of the damage caused by mechanical fatigue. A learning adaptive controller in the form of a self-tuning regulator (STR) for output power levelling and decrementing fatigue loads is presented. The STR incorporates a hybrid controller of a linear quadratic Gaussian (LQG), neurocontroller and a linear parameter estimator (LPE). The main control objective is to regulate the relationship between rotational speed and wind speed by controlling the generator torque and further, the rotational speed. A pitch actuator ensures system operation geared toward maintaining output at rated power. A second-order model and a stochastic wind field model are used to systematically analyse the dynamical relationship between the WTG subsystems. The LQG is used as a basis upon which the performance of the proposed method in the trade-off studies is assessed. Simulation results indicate the proposed control scheme captures the performance and critical reliability loci thereby ensuring the wind turbine operates optimally in mechanically harmless conditions.

タワーシャドウ効果を用いた風力発電機の運転状態判定法（その2）

In order to get wind energy effectively, the pole-change-type induction generators are used as the wind turbine generators. Otherwise, the pole-change-type induction generator causes the voltage dips at pole changing time. To keep the power quality, it is important to know the state change of the generator operation. Therefore, the authors have studied a state criterion of generator using the tower shadow effect, which is the active power oscillation caused by a rotation torque drop when the tower and the turbine blade overlap each other.In this paper, an improved identification method of oscillation frequency, which is the criterion of wind turbine generator operation, is proposed. A proposed method is applied to measured data and shows that it gives the good results.

Response measurements for two building structures excited by noise from a large horizontal axis wind turbine generator

Window and wall acceleration measurements and interior noise measurements ere made for two different building structures during excitation by noise from the WTS-4 horizontal axis wind turbine generator operating in a normal power generation mode. With turbine noise input pulses resulted in acceleration pulses for the wall and window elements of the two tests buildings. Response spectra suggest that natural vibration modes of the structures are excited. Responses of a house trailer were substantially greater than those for a building of sturdier construction. Peak acceleration values correlate well with similar data for houses excited by flyover noise from commercial and military airplanes and helicopters, and sonic booms from supersonic aircraft. Interior noise spectra have peaks at frequencies corresponding to structural vibration modes and room standing waves; and the levels for particular frequencies and locations can be higher than the outside levels.