High-power Wind Turbine Research Articles

Full-size experimental investigations on planetary gear journal bearings in high-power wind turbines

Abstract To satisfy the large-scale and high-power demands of wind turbines, planetary gear journal bearings (PGJBs) have been applied in large wind turbine gearboxes (WTGs), as an alternative to traditional rolling bearings, due to their higher reliability and smaller size. To simulate the actual lubrication behaviors of PGJBs and investigate their hydrodynamic performance, a full-size test rig for PGJBs was built in this paper. A multi-parameter detection system coupled with the ultrasonic testing method was developed. Four ultrasonic piezoelectric elements, eight thermistors, two pressure transducers, and one torque sensor were used to obtain the film thickness, oil temperature, oil pressure, and friction torque data of the test PGJB. The rated condition experiment was conducted to investigate the variation of measured lubrication performance with the operating time. Three-dimensional predictions of oil film pressure, temperature, and thickness were presented to analyze the steady-state lubrication characteristic at the rated condition. Moreover, a series of steady-state experiments were also carried out to simulate the normal operations of the test PGJB at different conditions. And the measured results were verified by the numerical predictions. The influence of rotational speed, input load, oil supply temperature, and oil supply flow on the hydrodynamic performance of the test PGJB were explored.

Multidisciplinary design and optimization of journal bearing for high-power wind turbine speed increaser

With the increasing power of wind turbine generators (WTG), the failure rate of rolling bearings in wind turbines due to insufficient bearing capacity increases with the increase of bearing size. To overcome these challenges, this paper proposes a design optimization method for the rectangular groove elliptical sliding bearing (RGEB) of the WTG output shaft. This method can maximize the radial bearing capacity under the premise of ensuring that the oil film pressure is large, the end leakage and the temperature rise are small. The multidisciplinary design and modeling of RGEB are carried out according to the structure and working conditions of WTG. Based on computational fluid dynamics (CFD), the influence of the number of rectangular dynamic pressure grooves on the bearing performance is analyzed. The kriging model, BP neural network model, and SSA-BP model are constructed for each performance index of RGEB, to establish a high-precision combined surrogate model based on global error criterion. After establishing the optimization equation, the PSO and SQP combined optimization algorithm is used to optimize the optimal structural parameters. The results show that the bearing capacity of the optimized RGEB is 95.9% higher than that of the ordinary elliptical bearing (EB) without increasing the size and quality of the bearing. In addition, the combined surrogate model can effectively replace the expensive finite element model to deal with the WTG sliding-bearing optimization problem.

Dynamic performances of novel misaligned non-uniform distributed tilting-pad bearing

The non-uniform distributed tilting-pad journal bearings (NDTPJB) in large wind turbine main shafting has become an important development trend for high-power wind turbines due to the advantages of improving reliability and reducing maintenance costs. However, studies involving NDTPJB have not been reported under specific conditions such as low speed, wide range variable direction and magnitude of heavy-load in wind turbine. A new transient mixed elastohydrodynamic lubrication (mixed EHL) model for NDTPJB is established, taking into account the misalignment effect of the shaft tilt and the swinging of pads in the circumferential and axial directions, as well as the influence of pivot friction and elastic deformation effects. Based on the mathematical model, the dynamic characteristics and structural parameter effects of NDTPJB are systematically studied under low speed, wide range variable direction and magnitude of heavy-load. The results indicate that the NDTPJB exhibits a more significant sensitivity to the heavy load direction due to the different functional roles of the above distributed pads (ADP) and bottom distributed pads (BDP). The modified mixed EHL model can more accurately evaluate the lubrication performance of NDTPJB, and combine the characteristics in individual pad swing and the overall effect of the pads to comprehensively analyze the dynamic lubrication behavior of NDTPJB. By setting the pivot coefficient to 0.55, reducing the distribution angle of BDP, and increasing the distribution angle of ADP, a better load-carrying capacity can be achieved. The research results have guiding significance for further monitoring and analyzing the experimental performance of NDTPJB, as well as designing and optimizing such bearing structures.

Advanced Fault Ride-Through Operation Strategy Based on Model Predictive Control for High Power Wind Turbine

Advanced Fault Ride-Through Operation Strategy Based on Model Predictive Control for High Power Wind Turbine

Numerical and experimental investigations on thermoelastic hydrodynamic performance of planetary gear sliding bearings in wind turbine gearboxes

The application of planetary gear sliding bearings (PGSBs) in large wind turbine gearboxes (WTGs) has become an important development trend for high-power wind turbines due to the advantages of improving power density and reducing failure rates. However, the working characteristics of operating at heavy-load conditions and using helical gears to mesh will induce large deformation, axial misalignment, and non-negligible temperature rise in PGSBs. In this paper, a comprehensive analysis model taking into account the influence of axial misalignment, thermal effects, and thermoelastic deformation was presented for the PGSB in WTGs. A full-size test rig for PGSBs was built and simulation experiments were conducted to verify the model. Both the measured oil temperature and film thickness agreed well with the numerical results. The predictions from the model were compared with the results of the isothermal-EHD and rigid-THD models. The comparison results indicated that the pad deformation and temperature rise had obvious effects on the bearing performance and could not be ignored. The effects of bearing clearance and aspect ratios on thermoelastic hydrodynamic performance were analyzed. The numerical results showed that both a lower clearance ratio and a higher aspect ratio could help to reduce the maximum pressure at the bearing edges.

Analysis of the Influence of Calculation Parameters on the Design of the Gearbox of a High-Power Wind Turbine

As wind turbine power requirements have evolved from the order of kilowatts (kWs) to the order of several megawatts (MWs), wind turbine components have been subjected to more demanding and critical operating conditions. The wind turbine must cope with higher wind loads due to larger blade sizes, which are also time-varying, and, ultimately, higher power levels. One of the challenges in the manufacture of high-power wind turbines lies in the gearbox and consists of achieving ever-greater power density without compromising efficiency, i.e., greater load capacity with lower weight (and production cost) and reduced power losses. Epicyclic geartrains are used to build the gearbox due to various advantages in relation to conventional gear systems, such as higher feasible gear ratios, higher efficiency, compactnesss, and lower weight. In this paper, several epicyclic geartrains with different structures will be analysed to reveal the influence that certain design parameters have on the size and weight of the gearbox components in the selected model and, therefore, of the gearbox itself. For this purpose, the theoretical model of the gearbox will be planned and the influence of the calculation parameters on the gearbox design will be analyzed following ISO 6336. Special emphasis is placed on the influence of the material used; the modulus and tooth width on the size and weight of the gearbox will be observed. Critical stresses are also calculated. The goal is to prepare the theoretical basis for an optimization process subject to geometric, kinematic, and dynamic constraints that will result in a gearbox as compact, energy-dense, and light as possible without compromising the service life of the components.

What changes can solar and wind power bring to the electrification of China compared with coal electricity: From a cost-oriented life cycle impact perspective

For carbon neutralization, coal and oil need to be replaced with electricity, and this project is deeply dependent on the development of clean energy. Therefore, this study compared the environmental performance and cost of different substitution technologies, including coal, solar, and wind power, to provide useful information for the electrification of China. A cost-oriented life cycle assessment method and driving force analysis were conducted. Results showed that the solar and wind power scenarios showed low burdens with 35.3%–39.9% and 22.3%–42.6% of coal power, respectively. The main reason was that solar and wind power reduced CO2, particulates, and mercury emissions as well as coal consumption, which led to an improvement in human health and resources damage. However, the higher freshwater ecotoxicity, which was mainly derived from heavy metal emission in the supply chain, in the solar power scenarios than coal power should receive attention, as well as water depletion caused by solar wafer and metal electrode production. Meanwhile, metal depletion in wind power scenarios cannot be ignored. Adopting monocrystalline silicon and high-power wind turbines was beneficial to clean electrification. The driving factors analysis indicated that in addition to improving those environment-sensitive processes (e.g., wafer, metal, and glass fiber), coordinating clean energy development and electrification; reducing costs, especially by ensuring operational reliability; and expanding investment scale are crucial for ensuring the effectiveness of policies on carbon neutralization.

A Comprehensive Overview of Power Converter Applied in High-Power Wind Turbine: Key Challenges and Potential Solutions

The increasing penetration of offshore wind power generation promotes the revolution of wind turbine toward high power application. The development of high-power wind turbine undoubtedly poses new technical challenges. This paper presents a comprehensive overview for high-power wind energy conversion system (WECS) from key technique aspects including topologies, stability, reliability, and ancillary service capability, and further investigates the key challenges and potential solutions. The various topologies of power converter applied in high-power wind turbine are first reviewed and discussed. The different semiconductor technology, including recent wide bandgap (WBG) devices, and their potential contributions for offshore high-power converters are discussed. Furthermore, the potential stability issues of high-power WECS are investigated and reviewed. Also, the stabilization control strategies are discussed. Further, the reliability issue and enhancement strategies of high-power WECS are discussed, including condition monitoring, active thermal control strategy and fault-tolerant operation method. In addition, the ancillary service capability of high-power WECS including frequency-active power control capability and voltage-reactive power control capability is reviewed. Finally, the future trends and potential solutions are discussed in this paper.

Electromagnetic design and performance analysis of coreless superconducting machine

With the development of offshore wind power generation, there is an urgent demand for high-power wind turbines. Superconducting machines with high power density and efficiency are one of the solutions for wind turbines of 10 MW and above. This paper summarizes the existing superconducting synchronous generators in several structural forms and features, and considers that the coreless machine can avoid the impact of core oversaturation on the power density increase of the machine, which is the development direction of the superconducting machine. In this paper, the structural topology of a coreless superconducting machine is established and the similarities and differences between its structure and that of a conventional one are analyzed. Since the conventional magnetic circuit method is no longer applicable, a designing model based on the analytical method is established for the designing of coreless machines, which considers the effects of slotless armature, the superconducting excitation winding thickness and the nonlinearity of the ferromagnetic material. Based on this method, the magnetic field distribution is solved and verified with the finite element method. Further, the effect of the superconducting excitation winding opening angle on the magnetic field in the air gap of the machine is investigated, and the machine structure is optimized based on this. The steady-state and transient performance analysis of the machine is carried out to illustrate the operating characteristics of the coreless superconducting machine. The design method and analysis results of this paper can provide a reference for building higher power density coreless superconducting wind turbines.

Wind resource assessment and influence of atmospheric stability on wind farm design using Computational Fluid Dynamics in the Andes Mountains, Ecuador

In recent years, research has revealed that hydropower designs in Ecuador have not adequately considered sensitivity to climate change. In addition, variations in rainfall patterns cause a drought from July to October. Therefore, it would decrease the flow of the rivers that feed the dams for hydroelectric generation, which would result in a significant reduction of its generating capacity.To prevent this inconvenience from occurring, it is necessary to promote the use of wind energy to diversify the Ecuadorian energy matrix. This matrix is made up of 70% hydropower and 0.26% wind power. Moreover, the Ecuadorian Andes has significant untapped wind potential due to their complex topography. Currently, there are no detailed studies on wind potential or wind energy prediction in the Andes. As a result, wind resource characterization is necessary. In order to address the challenges mentioned above, promote wind energy development, assess wind potential, and diminish the need for thermal generators. This article describes a methodology for wind resource characterization over complex terrain using measured data from two meteorological towers installed in the mountainous zone of study and wind characteristics modeling through the Ansys Computational Fluid Dynamics (CFD) software for the positioning of 11 Goldwind 70/1500 kW wind turbines to optimize the Annual Energy Production (AEP) of a hypothetical wind farm.The study’s main findings indicate that the wind passing between two volcanoes has a high wind potential. This potential is dependent on meteorological variables, orography, and the accelerating effect of wind speed. These favorable conditions make it possible to install a wind farm in this area with 11 high-power wind turbines. Furthermore, the most suitable turbulence model for wind farm design using Ansys Fluent CFD is the K-epsilon which can model with high precision the profile of wind characteristics over a simulated mountain under the influence of atmospheric stability on the state of the air mass to assist in the decision-making process when selecting the best wind farm locations over complex terrain in the Ecuadorian Andes.

Fibre volume fraction screening of pultruded carbon fibre reinforced polymer panels based on analysis of anisotropic ultrasonic sound velocity

Composites have become the material of choice in a wide range of manufacturing applications. Whilst ultrasound inspection is a well-established non-destructive testing (NDT) technique, the application to composite imaging presents significant challenges stemming from the inherent anisotropy of the material. The fibre-volume fraction (FVF) of a composite plays a key role in determining the final strength and stiffness of a part as well as influencing the ultrasonic bulk velocity.In this work, a novel FVF determination technique, based on the angular dependence of the sound velocity with respect to the composite fibre direction, is presented. This method is introduced and validated by inspection of pultruded carbon fibre reinforced polymer (CFRP) panels commonly used in the manufacture of high-power wind turbine blades. Full matrix capture (FMC) data acquired from a phased array (PA) ultrasonic probe is used to generate calibration data for samples ranging in FVF from 60.5% to 69.9%. Sample velocity, as a function of propagation angle, is used to estimate the FVF of samples and ensure they fall within the desired range. Experimental results show values of 61.1, 66.1 and 68.3%, comparing favourably to the known values of 60.5, 66.3 and 69.9% respectively.The work offers significant potential in terms of factory implementation of NDT procedures to ensure final parts satisfy standards and certification by ensuring any FVF inconsistencies are identified as early in the manufacturing process as possible.

New Converter Solution With a Compact Modular Multilevel Structure Suitable for High-Power Medium-Voltage Wind Turbines

Modern wind turbines with increasing power levels are continuously emerging. These power levels are reaching a point where excessively high currents are obtained if the traditional low-voltage wind-turbine structure is adopted. High currents lead to excessively high losses and the need for bulky and heavy conductors to carry them. A medium-voltage structure should be a more competitive alternative to be adopted in high-power wind turbines. In this article, a new converter solution with a modular multilevel structure suitable for driving modern/future high-power medium-voltage wind turbines is proposed. This converter topology has desirable features common to modular multilevel converters, such as the improved reliability at high voltage levels, and the possibility to synthesize high-power-quality staircase-shape voltages, which leads to low requirements for harmonic and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${dv}/{dt}$</tex-math></inline-formula> filters. Furthermore, the proposed converter presents reduced capacitance and inductance requirements compared with other well-established modular multilevel converter topologies, which should result in a lighter and more compact solution. The proposed solution could potentially allow for the reduction of the overall costs of the supporting structure required to withstand the weight of the wind turbine. Simulation and experimental results are presented in this article to validate the proposed topology.

A Review of Fault Diagnosis, Status Prediction, and Evaluation Technology for Wind Turbines

With the rapid development and increasing energy production capacity of high-power wind turbines, a corresponding increase in maintenance requirements has been observed. Reducing the failure rate of wind turbines is a critical objective, alongside decreasing affiliated operation and maintenance costs. This review focuses on the status monitoring, fault diagnosis, fault prediction, and status evaluation of wind turbines. The early fault diagnosis of wind turbines is explored with regard to existing condition monitoring technology. Moreover, the current mathematics-based fault diagnosis and smart fault diagnosis technologies are further explored. Through comprehensive investigation, this paper summarizes the research status of wind turbine fault prediction and complete machine status evaluation, conclusively presenting relevant research points and trends in the fault diagnosis, fault prediction, and status assessment of high-power wind turbines.

Electrical Generators for Large Wind Turbine: Trends and Challenges

This paper presents an overview of the emerging trends in the development of electrical generators for large wind turbines. To describe the developments in the design of electrical generators, it is necessary to look at the conversion system as a whole, and then, the structural and mechanical performances of the drive train need to be considered. Many drive train configurations have been proposed for large wind turbines; they should ensure high reliability, long availability and reduced maintainability. Although most installed wind turbines are geared, directly driven wind turbines with permanent magnet generators have attracted growing interest in the last few years, which has been in parallel to the continuous increase of the per unit turbine power. The aim of this work is to present the recent commercial designs of electrical generators in large wind turbines. Both the strengths and weaknesses of the existing systems are discussed. The most emerging technologies in high-power, low-speed electrical generators are investigated. Furthermore, a comparative analysis of different electrical generator concepts is performed, and the generators are assessed upon a list of criteria such as the mass, cost, and mass-to-torque ratio. Within the framework of these criteria, it may help to determine whether the electrical generator is technically feasible and economically viable for high-power wind turbines. Finally, this review could help to determine suitable generators for use in large and ultra-large wind energy systems.

Transformerless Grid Connected Control of Wind Turbine Based on H-MMC

A high-power wind turbine has low rotational speed and a relatively low terminal voltage level. Thus, the wind energy conversion system (WECS) is commonly connected to the grid by an isolated boost transformer, which increases costs and room greatly. In this article, the hexagonal modular multilevel converter (H-MMC) is applied so that the high-power wind turbine can be directly connected to the medium-voltage ac grid. It has the advantages of transformerless grid connection and low ripples of capacitor voltages. As the bridge arm voltage of H-MMC contains both the low-frequency component induced by a wind turbine and the power frequency component induced by the grid, the voltage ripples of submodules (SMs) are reduced. Due to the large differences in the voltage level between the wind turbine and the grid, the low-amplitude-modulation voltage of the wind turbine side is easily obliterated by the high-amplitude-modulation voltage of the grid side, which will cause distortion of the bridge arm current. Therefore, auxiliary SMs with variable reference voltage are adopted to improve the tracking accuracy. The MATLAB/Simulink simulation and the RT-LAB hardware-in-the-loop experimental results verify the feasibility of the proposed topology and the effectiveness of the control strategy.

Analysis of electromagnetic performance of differential multi-stage coaxial magnetic gears with large gear ratio and high torque density applied to high-power wind turbines

Magnetic gear is a non-contact transmission mechanism, which overcomes the drawback of mechanical gear transmission. Although the series multi-stage magnetic gear can provide a large gear ratio compared to the single-stage magnetic gear, the lower torque density of the series multi-stage magnetic gear limits its use in high-power wind turbines. According to the magnetic gear field modulation mechanism and the differential transmission method, a differential multi-stage coaxial magnetic gear transmission device is proposed, which can achieve transmission with a large gear ratio and large torque density. Based on the differential multi-stage coaxial magnetic gear structure and its working principle, the finite element method is used to simulate the electromagnetic performance of the multi-stage coaxial magnetic gear. Futhermore, the electromagnetic performance of the two stages of the proposed magnetic gear are compared. The results show that there is a significant difference between the the electromagnetic performance of the first stage and that of the second stage. The torque ripple of the first stage is more dramatic than that of the second stage. The torque ripple amplietude of the inner rotor of the first stage is 5.08‰ larger than that of the second stage. The torque ripple amplietude of the outer rotor of the first stage is 4.591‰ larger than that of the second stage.

Design and optimization of permanent magnet synchronous generator dedicated to direct-drive, high power wind turbine

This paper presents analysis, design, and optimization of a high-power permanent-magnet synchronous generator (PMSG). This generator is introduced in a large-scale wind turbine which can be used in a big wind farm. This generator is used in gearless configuration. The work focuses on the geometric sizing and the finite element analysis (FEA) of the PMSG. FEA is a good choice for analyzing problems over complicated domains. The flux, the electromotive force, the cogging torque, and the torque are calculated using analytical equations. Then, these parameters are obtained using finite element method (FEM) in the software FEMM and the compared with analytical results in order to validate our study. The second part presents the formulation of the optimization problem, including the optimization space, constraints, and objectives. The genetic algorithm (GA) is adopted in this design optimization in order to minimize the generator cost.

Measurement and Analysis of Infrasound Signals Generated by Operation of High-Power Wind Turbines

The development of wind energy and the increasing number of installed wind turbines make it necessary to assess them in terms of the nuisance of the emitted infrasound noise generated by such devices. The article presents the results of measurements and analyses of infrasound emitted during the operation of wind turbines installed in various locations in Poland. Comparative analysis of noise levels in the infrasound and audible range has shown that acoustic energy is mainly in the low and infrasound frequency range, and the measured levels depend significantly on the weighting curves used. On the basis of the results, it was confirmed that the sound pressure level of infrasound signals emitted by the operation of high-power wind turbines, regardless of wind velocity, weather conditions, design solutions of turbines, operating time, rated capacity, does not exceed the criteria specified in the applicable legislation dealing with the assessment of infrasound noise on the working environment.

Structure Design and Experimental Study of Pin-Cycloidal Planetary Reducer for the Pitch of High-Power Wind Turbine

In recent years, with the development of manufacturing technology and production capacity, wind power industry has been developed rapidly.A new type of pin-cycloidal planetary reducer was proposed in this studyfor the actuator of the pitch of high-power wind turbines. Based on the transformation mechanism method, the transmission efficiency of the reducer was calculated by analyzing the pin-cycloidal meshing efficiency, bearing efficiency, and output mechanism efficiency. Prototype testing were combined to systematically and deeply study the design theory of the reducer for the pitch of high-power wind turbines. Finally, a new design was proposed for a reliable two-stage pin-cycloidal planetary reducer with a strong bearing capacity and multi-tooth meshing on the hard gear surface that can be applied to the pitch system of high-power wind turbines.

A Local Perspective on Wind Energy Potential in Six Reference Sites on the Western Coast of the Black Sea Considering Five Different Types of Wind Turbines

This paper aims to evaluate the energy potential of six sites located in the Black Sea, all of them near the Romanian shore. To conduct this study, a climate scenario was chosen which considers that the emissions of carbon dioxide will increase until 2040 when they reach a peak, decreasing afterward. This scenario is also known as RCP 4.5. The wind dynamics is considered for two periods of time. The first is for the near future with a duration of 30 years from 2021 to 2050, the second period is for the far-distant future with a span of 30 years from 2071 to 2100. In this study, parameters such as minimum, maximum, mean wind speed, interpolated at 90 m height were analyzed to create an overview of the wind quality in these areas, followed by an analysis of the power density parameters such as seasonal and monthly wind power. In the end, the annual electricity production and capacity factor were analyzed using five high-power wind turbines, ranging from 6 to 9.5 MW. For the purpose of this paper, the data on the wind speed at 10 m height in the RCP 4.5 scenario was obtained from the database provided by the Swedish Meteorology and Hydrology Institute (SMHI).