Prognostic Condition Monitoring for Wind Turbine Drivetrains via Generator Current Analysis

Maintenance costs account for a significant portion of the total cost of electricity generated by wind turbines.Currently in the wind power industry,maintenance is mainly performed on regular schedules or when significant damage occurs in a wind turbine making it inoperable,instead of being determined by the actual condition of the wind turbine.Among the total maintenance costs,approximately 25%~35%is related to regularly scheduled preventive maintenance and 65%~75%to unscheduled corrective maintenance.To reduce the failure rate and level and maintenance costs and improve the availability,reliability,safety,and lifespans of wind turbines,it is desirable to perform condition-based predictive maintenance for wind turbines,which will require a high-fidelity online prognostic condition monitoring system(CMS)for fault diagnosis and prognosis and remaining useful life(RUL)prediction of wind turbines.Most of the existing wind turbine CMSs are based on vibration monitoring and have no or limited capability in fault prognosis and RUL prediction.Compared to vibration monitoring,the prognostic condition monitoring techniques based on generator current signal analysis proposed recently have significant advantages in terms of cost,hardware complexity,implementation,and reliability.This paper discusses the principles and challenges of using generator current signals for prognostic condition monitoring of wind turbine drivetrains and presents an overview of recent advancements in this area.

Effects of Flexibility and Suspension Configuration of Main Shaft on Dynamic Characteristics of Wind Turbine Drivetrain

The current research of wind turbine drivetrain is mainly concentrated in dynamic characteristics of gearbox with a specific suspension of main shaft, such as one-point and two-point suspension. However, little attention is paid to the e ects of these suspension configurations on the dynamic responses of wind turbine gearbox. This paper investigates the influences of suspension configurations of main shaft on the dynamic characteristics of drivetrain. For evaluating the dynamic behaviors of drivetrain with multi-stage transmission system more realistically, a dynamic modeling approach of drivetrain is proposed based on Timoshenko beam theory and Lagrange's equation. Considering the flexibility and di erent suspension configurations of main shaft, time-varying mesh sti ness excitation, time-varying transmission error excitation and gravity excitation, etc., a three-dimensional dynamic model of drivetrain is developed, and the dynamic responses of drivetrain are investigated. Results show that with the one-point suspension of main shaft, the resonance frequencies in gearbox, especially at the low-speed stage, obviously shift to the higher frequency range compared to the gearbox without main shaft, but this trend could be inversed by increasing main shaft length. Meanwhile, the loads in main shaft, main shaft bearing and carrier bearing are greatly sensitive to the main shaft length. Hence, the load sharing is further disrupted by main shaft, but this e ect could be alleviated by larger load torque. Comparing to the one-point suspension of main shaft, there occurs the obvious load reduction at the low-speed stage with two-point suspension of main shaft. However, those advantages greatly depend on the distance between two main bearings, and come at the expense of increased load in upwind main shaft unit and the corresponding main bearing. Finally, a wind field test is conducted to verify the proposed drivetrain model. This study develops a numerical model of drivetrain which is able to evaluate the e ects of di erent suspension configurations of main shaft on gearbox.

Modeling and Analyzing Dynamic Response for An Offshore Bottom-Fixed Wind Turbine with Individual Pitch Control

The asymmetric or periodically varying blade loads resulted by wind shear become more significant as the blade length is increased to capture more wind power.Additionally,compared with the onshore wind turbines,their offshore counterparts are subjected to additional wave loadings in addition to wind loadings within their lifetime.Therefore,vibration control and fatigue load mitigation are crucial for safe operation of large-scale offshore wind turbines.In view of this,a multi-body model of an offshore bottom-fixed wind turbine including a detailed drivetrain is established in this paper.Then,an individual pitch controller(IPC)is designed using disturbance accommodating control.State feedback is used to add damping in flexible modes of concern,and a state estimator is designed to predict unmeasured signals.Continued,a coupled aero-hydro-servo-elastic model is constructed.Based on this coupled model,the load reduction effect of IPC and the dynamic responses of the drivetrain are investigated.The results showed that the designed IPC can effectively reduce the structural loads of the wind turbine while stabilizing the turbine power out-put.Moreover,it is found that the drivetrain dynamic responses are improved under IPC.

Drivetrain system of an ultracapacitor electric bus

This paper proposed a design of the drivetmin system of an electric bus with ultraeapacitor （UC） as the only on-board power source. The system includes three main parts, namely, UC bank, motor and the converter, vehicle management unit （VMU）. Analyses results in detail on the funetional design and ex-periments on work bench of each part were also presented, which validated the reliability of the system. Furthermore, driving results in field of the bus verified the feasibility of the design of the drivetrain sys-tem. The bus has very good dynamic performanees and shows a promising applieations prospeet in the short and medium route buses system.

Physics-based data analysis for wind turbine condition monitoring

This article presents methodologies for improving wind turbine condition monitoring using physics-based data analysis techniques.The unique operating conditions of the wind turbine drivetrain are described,and the complex kinematics of the gearbox is analyzed in detail.The pros and cons of the current wind turbine condition monitoring system(CMS)are evaluated.To improve the wind turbine CMS capability,it is suggested to use linear models with unsteady excitations,instead of using nonlinear and nonstationary process models,when dealing the wind turbine dynamics response model.An analysis is undertaken of the damage excitation mechanisms cause for various components in a gearbox,especially for those associated with lower-speed shafts.Physics(mechanics)-based data analysis methods are presented for different component damage excitation mechanisms.Validation results,using the wind farm and manufacturing floor data,are reported.

Objective Rating of the Launch Behavior of Conventional,Hybrid and Electric Vehicles

The calibration of conventional,hybrid and electric drivetrains is an important process during the development phase of any vehicle.Therefore,to optimize the comfort and dynamic behavior(known as driveability),many test drives are performed by experienced drivers during different driving maneuvers,e.g.,launch,re-launch or gear shift.However,the process can be kept more consistent and independent of human-based deviations by using objective ratings.This study first introduces an objective rating system developed for the launch behavior of conventional vehicles with automatic transmission,dual-clutch transmission,and alternative drivetrains.Then,the launch behavior,namely comfort and dynamic quality,is compared between two conventional vehicles,a plug-in hybrid electric vehicle and a battery electric vehicle.Results show the benefits of pure electric drivetrains due to the lack of launch and shifting elements,as well as the usage of a highly dynamic electric motor.While the plug-in hybrid achieves a 10%higher overall rating compared to the baseline conventional vehicle,the pure electric vehicle even achieves a 21%higher overall rating.The results also highlight the optimization potential of battery electric vehicles regarding their comfort and dynamic characteristics.The transitions and the gradient of the acceleration build-up have a major influence on the launch quality.

A portable wind turbine condition monitoring system and its field applications

This article introduces a portable wind turbine condition monitoring system(CMS)and its applications in wind turbine drivetrain damage detection.The portable CMS based on vibration detection and analysis has a long application history in conventional rotating machineries,but it is not widely used in wind turbines.There are several reasons why it is not used,including the labor-and knowledge-intensive requirements for test setup and result interpretation.There are also reasons specific to wind turbines,such as the structural diversity of drivetrains,the uncertainty of operational conditions,and the complexity of the damage mechanism of different parts that make the conventional vibration-based CMS inefficient and not cost-effective.All these factors affect the wide application of the portable system.The portable wind turbine CMS discussed in this article is integrated using advanced vibration measurement and analysis methodology.Fault detection for the acquired acceleration response and high-speed shaft speed signal is carried out by a suite of data analysis techniques specifically designed for a wind turbine gearbox.Using these techniques,damage detection accuracy for all the components inside a gearbox is improved significantly,especially for those related to medium-and low-speed shafts.The new data processing techniques also are briefly described with the developed methodologies verified by three wind turbines with typical low-speed shaft-related component damages.These damage assessments include the low-and medium-speed planetary stage ring gear,the low-speed planetary stage planet gear and damage to the main bearing.