To address the problem of uneven pre-welding assembly gaps widely existing in the laser welding process of complex thin-walled aviation components, adaptive laser welding experiments were conducted on 1.2 mm thick TC4 titanium alloy plates with unequal gaps. A three-dimensional transient thermal-fluid coupling model of the welding process was established to analyze the influence of different welding gaps on the dynamic behavior of the molten pool. The results indicate that to balance welding quality with the linearly increasing weld gap, the laser energy density shows a gradually decreasing trend while matching the corresponding laser spot radius. As the welding gap increases, and the laser energy density decreases, the surface tension and recoil pressure acting on the inner wall of the keyhole decrease significantly, making it difficult to maintain the high-temperature and high-speed Marangoni circulation required for a long conical molten pool. The fluid velocity at the keyhole tip decreases markedly, and the keyhole shape transforms from a long conical shape to a flat gyroscope-like shape, which fails to exert a strong impact on the molten pool bottom. Consequently, the vortex at the molten pool bottom disappears, and the weld profile transitions from an X-shape at the initial section to a Y-shape at the final section.
Polyvinyl chloride (PVC) recycling poses significant engineering challenges and opportunities, particularly regarding material integrity, energy efficiency, and integration into circular manufacturing systems. This systematic review evaluates recent advancements in mechanical innovations, tooling strategies, and intelligent technologies reshaping PVC recycling. An emphasis is placed on machinery-driven solutions—including high-efficiency shredders, granulators, extrusion moulders, and advanced sorting systems employing hyperspectral imaging and robotics. This review further explores chemical recycling technologies, such as pyrolysis, gasification, and supercritical fluid extraction, for managing contamination and additive removal. The integration of Industry 4.0 technologies, notably digital twins and artificial intelligence, is highlighted for its role in predictive maintenance, real-time quality assurance, and process optimisation. A combined PRISMA approach and ontological mapping are applied to classify technological pathways and lifecycle optimisation strategies. Critical engineering constraints—including thermal degradation, additive leaching, and feedstock heterogeneity—are examined alongside emerging innovations, like additive manufacturing and microwave-assisted depolymerisation, offering scalable, low-emission solutions. Regulatory instruments, such as REACH and Extended Producer Responsibility (EPR), are analysed for their influence on machinery compliance and design standards. Drawing from sustainable manufacturing frameworks, this study also promotes energy efficiency, eco-designs, and modular integration in recycling systems. This paper concludes by proposing a digitally optimized, machinery-integrated recycling model aligned with circular economy principles to support the development of future-ready PVC reprocessing infrastructures. This review serves as a comprehensive resource for researchers, practitioners, and policymakers, advancing sustainable polymer recycling.
Recent advancements in virtual reality (VR) technology have enabled the creation of immersive learning environments that provide engineering students with hands-on, interactive experiences. This paper presents a novel framework for virtual laboratory environments (VLEs) focused on embodied learning, specifically designed to teach concepts related to mechanical and materials engineering. Utilizing the principles of embodiment and congruency, these VR modules offer students the opportunity to engage physically with virtual specimens and machinery, thereby enhancing their understanding of complex topics through sensory immersion and kinesthetic interaction. Our framework employs an event-driven, directed-graph-based architecture developed with Unity 3D and C#, ensuring modularity and scalability. Students interact with the VR environment by performing tasks such as selecting and testing materials, which trigger various visual and haptic events to simulate real-world laboratory conditions. A pre-/post-test evaluation method was used to assess the educational effectiveness of these VR modules. Results demonstrated significant improvements in student comprehension and retention, with notable increases in test scores compared to traditional non-embodied VR methods. The implementation of these VLEs in a university setting highlighted their potential to democratize access to high-cost laboratory experiences, making engineering education more accessible and effective. By fostering a deeper connection between cognitive processes and physical actions, our VR framework not only enhances learning outcomes but also provides a template for future developments in VR-based education. Our study suggests that immersive VR environments can significantly improve the learning experience for engineering students.
Guglielmo D’Amico, Giovanni Masala, Filippo Petroni
Abstract In this paper, we propose some new measures of wind power variability based on reliability indexes. The measures are computed for continuous-time Markov models of wind power generation and for different wind parks. This allows us to compare the differences in the measurement of the variability of wind power due to the different geographical positions of the wind plants. The results have direct practical relevance and utility in the real-world wind energy sector, as they contribute to a more in-depth understanding of the variability risk of wind power generation plants.
Renewable energy sources, Environmental engineering
Spurred by the global pandemic, research in health monitoring has pivoted towards the development of smart garments, enabling long-term tracking of individuals’ cardiovascular health by continuously monitoring the electrocardiogram (ECG) and detecting any abnormality in the signal morphology. Many types of dry electrodes have been proposed as alternatives to gold standard Ag/AgCl wet electrodes, and they have been integrated into clothes capable of acquiring only a limited number of the different ECG traces. This limitation severely diminishes the diagnostic utility of the collected ECG data and obstructs the garment’s potential for clinical-level evaluation. Here, we demonstrate a special ECG upper armband with a glove component which houses graphene-textile electrodes, where a fully mobile, exploring electrode located at the index finger enables the user to strategically position the electrode on-demand to desired body areas and measure the different ECG traces that are bipolar limb and unipolar chest leads. Based on measurements with and without employing the well-known Wilson Central Terminal (WCT) arrangement, the correlation ratio of unipolar ECG chest leads acquired with the graphene textile-based armband and Ag/AgCl electrodes both in “WCT-less” configuration reach up to %99.65; and up to %99.54 when Ag/AgCl electrodes are utilized “with WCT” while the graphene-based armband in “WCT-less” configuration. To the authors’ best knowledge, this study reports the first multilead on-demand “touch-and-measure” ECG recording from a fully wearable textile garment. Moreover, owing to the human-centered armband design, we achieved a more than three-fold reduction in electrode count from 10 in clinical ECG practice down to 3.
The usage of cheap crude H2 in proton-exchange membrane fuel cells (PEMFCs) is still unrealistic to date, due to the suffering of the current Pt based nano-catalysts from impurities such as CO in anode. Recently, synergistic active sites between single atom (SA) and nanoparticle (NP) have been found to be promising for overcoming the poisoning problem. However, lengthening the nanoparticle-single atom (SA–NP) interface, i.e., constructing high density synergistic active sites, remains highly challenging. Herein, we present a new strategy based on molecular fusion strategy to create abundant SA–NP interfaces, with high density SA–NP interfaces created on a two dimensional nitrogen doped carbon nanosheets (Ir-SACs&NPs/NC). Owing to the abundance of SA–NP interface sites, the catalyst was empowered with a high tolerance towards up to 1000 ppm CO in H2 feed. These findings provide guidelines for the design and construction of active and anti-poisoning catalysts for PEMFC anode.
Syed Zahir Hussain Shah, Assad Ayub, Umair Khan
et al.
Studying the combination of convection and chemical processes in blood flow can have significant applications like understanding physiological processes, drug delivery, biomedical devices, and cardiovascular diseases, and implications for various fields can lead to developing new treatments, devices, and models. This research paper investigates the combined effect of convection, heterogeneous-homogeneous chemical processes, and shear rate on the flow behavior of a ternary hybrid Carreau bio-nanofluid passing through a stenosed artery. The ternary hybrid Carreau bio-nanofluid consists of three different types of nanoparticles dispersed in a Carreau fluid model, miming the non-Newtonian behavior of blood. This assumed study generates a system of PDEs that are processed with similarity transformation and converted into ODEs. Furthermore, these ODEs are solved with bvp4c. The results show that the convection, heterogeneous-homogeneous chemical processes, and shear rate significantly impact the bio-nano fluid’s flow behavior and the stenosed artery’s heat transfer characteristics.
Objectives: Bone tissue grinding is one of the common and basic applications in orthopedic surgery clinics. The grinding process is energy-intensive and generates a lot of grinding heat. The accumulation of this heat may cause thermal damage to biological tissues. This paper presents experimental research to investigate the bone-grinding heat and the cooling method. Methods: The combined influence of nozzle position and feed direction on the cooling effect of bone grinding under cryogenic spray cooling conditions is experimentally investigated. A bone grinding platform with three-dimensional motion, as well as a cryogenic spray generation device, is designed and constructed. A spherical diamond grinding head with a diameter of 4 mm and a grit size of #150 is utilized. Fresh bovine cortical bone is used as the processing sample. The temperature at the nozzle outlet is 13 ℃, and the flow rate valve regulates the coolant flow rate to 400 mL/h. A three-dimensional force transducer (DJSW-40, China) is connected to a data acquisition system, which captures the forces applied to the bone sample along the X, Y, and Z directions at a frequency of 100 Hz. Simultaneously, a 0.1 mm diameter type K thermocouple (Omega Inc., TT-K-36) is embedded inside the bone sample to measure the grinding temperature in real-time. Three different nozzle arrangements were designed: above, in front of, and to the side of the abrasive tool, with the nozzles 10 mm away from the spray surface. Six sets of experiments (3×2) were designed using three nozzle orientations and two feeding directions. Each set of experiments was repeated three times to study the cooling effect of the spray under the combined influence of nozzle orientation and feed direction. Results: (1) During bone grinding, the abrasive tool is subjected to three orthogonal directional forces, namely FX (the tangential grinding force used for removing material), FY (the axial grinding force, representing the resistance of the abrasive tool during its feed), and FZ (the normal grinding force, which serves as the support force of the workpiece on the abrasive tool). For forward feed, the average values of the individual forces are: FX = 0.37 N, FY = -0.72 N, FZ = 1.38 N. For backward feed, FX = 0.46 N, FY = 0.78 N, FZ = 1.67 N. Since the grinding tool remains in the same rotational direction, the tangential force FX is consistently positive. For forward/backward feed, the axial force FY is in the -Y and +Y directions respectively, thus the sign of the FY value changes. When feeding forward/backward, the tangential force (FX) is 0.37 N and 0.46 N, respectively, which are relatively similar to each other, in accordance with the grinding theory. The power consumed for grinding is approximately 1.6 W and 1.9 W for forward and backward feed, respectively. (2) The nerve tissue is more heat-sensitive than bone tissue. Taking the human body's 37 ℃ as the base temperature, the threshold for the occurrence of thermal injury is 43 ℃, so the temperature rise threshold for thermal injury of nerve tissue is 6 ℃. In our experiment, the maximum temperature rise of bone under low-temperature spray cooling was lower than 4 ℃, indicating that the cooling method is effective. The effect of the nozzle arrangement was investigated under a fixed forward or backward feeding direction. When the abrasive tool is fed forward, the cooling of the thermocouple under the front nozzle is obvious. This is because, in addition to the contact arc area between the abrasive tool and the bone sample, a portion of the coolant from the front nozzle is sprayed onto the bone sample surface, resulting in a pre-cooling effect within the bone. When the abrasive tool is fed backward, the grinding temperature is lowest when the nozzle is placed above. For the different nozzle orientations, the side nozzles are in a perpendicular plane to the feed direction (Y-direction) of the grinding tool, so the feed direction has the least influence on the grinding temperature. The upper and front nozzles are in the same plane as the feed direction of the abrasive tool, so the influence of the feed direction is more significant. Conclusions: (1) The average tangential grinding force is 0.42 N, axial grinding force is 0.75 N, normal grinding force is 1.53 N, and the average power consumed by grinding is approximately 1.75 W when bone grinding is performed at a depth of 0.5 mm using a spherical diamond abrasive tool with a diameter of 4 mm. (2) Under the cooling effect of the cryogenic spray, the maximum temperature rise of grinding is less than 4 ℃, which can effectively prevent the occurrence of thermal damage in biological tissues. The temperatures of the two thermocouples in the same set of experiments were more consistent when the nozzle was placed above or side, while there was a significant difference in the temperatures of the two thermocouples when the nozzle was placed in front. This indicates that the cooling effect is more uniform when the nozzle is placed above and to the side. (3) The coupling of the nozzle arrangement and the feeding mode has a greater impact on the grinding temperature. When the nozzle is placed on top, it is favorable to backward feeding; when the nozzle is placed in front, it is conducive to forward feeding; and when the nozzle is placed on the side, there is no significant difference in the temperature between forward and backward feeding.
Materials of engineering and construction. Mechanics of materials, Mechanical engineering and machinery
Objectives: Femtosecond laser technology has become the primary method for micropore processing due to its high precision and low energy consumption. However, during the process, it is easy to cause microcracks and burrs in the micropores. Additionally, due to the small size, low structural stability and weak wear resistance of the micropores, conventional methods are ineffective in polishing them. To address the challenge of polishing femtosecond laser-processed micropores, the abrasive water jet polishing method is employed. This method leverages the stable removal function and strong adaptability of the abrasive water jet to improve the quality of femtosecond laser-processed micropores. Methods: Computational fluid dynamics (CFD) simulations of the abrasive water jet micropore polishing process under different process parameters were carried out by using Fluent software. A finite element model of abrasive water jet polishing for femtosecond laser-processed micropores was established under various working conditions. The flow field distribution, the erosion rate and the wall shear force under different parameters were analyzed. Corresponding experiments were conducted for each variable discussed in the Fluent simulation, and the variation patterns of micropore inner wall roughness were summarized. Subsequently, optimization experiments were conducted on the three factors, namely jet target distance, jet pressure and abrasive particle size, using the response surface method. The mean square error of shear force on the inner wall of the hole was taken as the response value Y, and the response surface equation was established. The optimal polishing parameter combination was obtained through the response surface equation and experimentally verified. Results: A jet impact angle of 90° is suitable for polishing the inner wall of the micropore, as wall erosion is uniform and the shear force distribution is concentrated at this angle. At a target distance of 4.2 to 6.0 mm, the jet on the end face enters the deceleration stage, and the jet velocity decreases as the target distance increases. The shear force increases with increasing jet pressure. When the jet pressure is 0.80 MPa, the shear force is the smallest, concentrated in the range of 1 500 to 3 500 Pa. At a jet pressure of 1.50 MPa, the shear force is the largest, concentrated in the range of 3 500 to 5 500 Pa. When jet pressure increases from 0.80 to 1.50 MPa, the shear force on the inner wall of the hole increases more than twice. The effects of abrasive particle size and jet pressure on wall shear force are similar. When the abrasive particle size is 1.0 μm, the shear force is the smallest, concentrated in the range of 1 000 to 2 500 Pa. At an abrasive particle size of 30.0 μm, the shear force reaches its maximum, concentrated between 3 000 and 5 500 Pa. Corresponding tests are carried out for each variable discussed in the simulation, and the minimum roughness Ra of the inner wall of the micropore was 0.386 μm. The optimal process parameter combination obtained through response surface analysis is as follows: jet impact angle of 90°, jet target distance of 3.5 mm, jet pressure of 1.10 MPa, and abrasive particle size of 15.0 μm. Under the optimal parameter combination, with an abrasive mass fraction of 5% and a polishing time of 5.0 minutes, the surface roughness Ra of the polished micropore inner wall surface was reduced to 0.354 µm, which is better than the minimum roughness of 0.386 µm observed in the simulation. Polishing efficiency is improved by about 3%, and the quality of the micropore inner wall surface is further enhanced. Conclusions: When the impact angle is constant, the shear force on the inner wall of the hole increases with increasing jet pressure and abrasive particle size. It increases first and then decreases with the increase in jet target distance, with jet pressure having the greatest influence on the wall shear force. Different structural segments of the jet can be applied to different working conditions due to different properties. Additionally, the simulation and experimental results are in good agreement, and the improvement in roughness is significant. This indicates that abrasive water jet polishing significantly enhances the quality of micropore walls, and the data model for response surface prediction has high accuracy.
Materials of engineering and construction. Mechanics of materials, Mechanical engineering and machinery
Abstract The presence of periodic impulses in vibration signals is a typical symptom of localized faults of rotating machinery. It is of great significance to study how to effectively extract the periodic impulses in vibration signals for realizing the fault diagnosis of rotating machinery. Variational mode decomposition (VMD) provides a feasible tool for non-stationary signal analysis. However, the reasonable selection of algorithm parameters and under- or over-decomposition problem in VMD hinder its application in engineering signals processing to some extent. Therefore, a new periodic impulses extraction method based on improved adaptive VMD and adaptive sparse code shrinkage denoising is proposed for the fault diagnosis of rotating machinery. The method can adaptively determine the mode number and the penalty factor depending on different signals. Meanwhile, the decomposition results are clustered and combined by using the spectrum overlap coefficient and kurtosis index to eliminate the over decomposition phenomenon and realize the effective extraction of the periodic impulses. The adaptive sparse code shrinkage algorithm is developed to denoise the mode component containing the periodic impulses, further highlighting the impulses and improving the accuracy of fault identification. Simulation data and real data acquired from rolling bearing and gearbox are adopted to verify the effectiveness and superiority of the proposed method compared with other methods.
Optimization design of machinery is usually a multi-objective one inevitably. At present, the popular mechanical optimization design is limited by the intrinsic shortcomings of the previous multi-objective optimization methods, which leads to the difficulty of non-comprehensive and nonsystematic optimal solutions in the viewpoint of probability theory. In the linear weighting “additive” method, there is inherent problems of normalization and introduction of subjective factors, and the final results depend on the normalization method to a great extent; the Pareto solution set is a “set” instead of an exact solution. In this paper, the probability—based multi-objective optimization, discretization with uniform design and sequential optimization are combined to establish a new approach of multi-objective optimization mechanical design based on probability theory; the probabilistic multi-objective optimization is used to transform the multi-objective optimization problem into single-objective optimization one from the perspective of probability theory; the discretization by means of uniform design provides an effective sampling to simplify the mathematical processing, which is especially important for dealing with multi-objective optimization problems with continuous objective functions; the sequential optimization algorithm is used to conduct the successive deep optimization. Furthermore, the implementation steps are illustrated with two examples. The results show that the approach can not only give excellent optimization results, but also provide a relatively simple processing.
The HMCVT (Hydro-mechanical Continuously Variable Transmission) can realize continuously variable speed in a large range and transmit high power through power diving, and thus, it is widely applied in agricultural machineries, such as tractors. The engineering technology requirements of precision agriculture and intelligent agriculture have put forward higher requests for the research and development of HMCVT. In order to further improve the performance of HMCVT in the design stage and match the service characteristics of agricultural tractors in the whole life cycle, this paper proposes a new HMCVT optimization design method which mainly consists of 5 steps. The proposed method takes the regular and continuous transmission ratio variation, matching the working requirements in the whole life cycle of agricultural tractors and transmission efficiency maximization as comprehensive objectives. The improved genetic algorithm (I-GA) is applied. The HMCVT efficiency characteristic model combines the characteristic efficiency model of the hydraulic system, which has been verified, and the theoretical calculation model based on the engaging power method. By analyzing the statistical data of the tractor speed operating frequency in the whole life cycle, the proposed method is used to determine the weight of each hydro-mechanical power dividing stage (i.e., HM stage) service time. In the design process, the HMCVT efficiency is integrated with the displacement ratio so as to realize the evaluation of the maximum efficiency in the whole life cycle of the tractor. Research results show that the proposed method can improve HMCVT performance significantly, and the mean error between speed regulating characteristics and expected value in design is 1.04% or so. The HMCVT service efficiency in the whole life cycle of the tractor has been improved by 19.93%. The research in the paper offers a valuable reference for getting the law of HMCVT characteristics and performance improvement design of tractors.
Traditional methods of removing snow and ice from pavements using chemicals are combined with mechanical removal that involves a lot of manpower, advanced machinery, chemicals that are harmful to the environment, and damage to pavements. Furthermore, annually, large quantities of ceramic materials become waste due to their fragile nature during processing, transport, and installation, and their accumulation in the nature has brought about environmental and health-related concerns. Therefore, the study aims to investigate the effect of using waste ceramic as a replacement for fine aggregate in roller compacted concrete (RCC) and the application of carbon fiber to improve the mechanical properties and electrical conductivity of RCC. To achieve this goal, several tests such as compressive strength, indirect tensile strength, electrical resistance, chloride ion penetration, specific gravity, and skid resistance tests were carried out on the fabricated samples before and after freeze-thaw cycling exposure. The experimental results illustrated that replacing waste ceramics with fine-grained aggregate increased the compressive strength and tensile strength of RCC. Furthermore, carbon fiber increased tensile strength but had no noticeable influence on compressive strength. Freeze-thaw conditioning led to a reduction in the compressive and tensile strength regardless of the aggregate type and carbon fiber utilization. In the samples containing waste ceramic aggregate, the electrical conductivity was reduced, and by adding carbon fiber, its electrical conductivity was increased. Exposure to freeze-thaw cycling resulted in an increase in electrical resistance and the passing charge. Waste ceramic incorporation created a similar mixture in terms of skid resistance, while in contrast, the carbon fiber slightly reduced the skid resistance. In addition, freeze-thaw conditioning resulted in an increase in the skid resistance. Besides, in this study, kernelized support vector regression (KSVR) and radial bias function (RBF) neural network models were proposed to estimate the indirect tensile strength (ITS) and compressive strength (CS) values. The results showed that both models have high performance in estimating these values, but RBF was a more efficient model.
A field experiment was conducted to determine the effect of the locally manufactured agricultural machine on some performance indicators of the mechanical unit and some physical soil properties in a silty clay loamy soil texture in one of the fields of the College of Agricultural Engineering Sciences / University of Baghdad/Al-Jadriya for the spring season of 2023. The experiment used a tractor type (MF-650), and the study included one factor, the plowing depths, with three levels: 15, 20, and 25 cm. The study examined some performance indicators of the mechanical unit, including: pulling force, fuel consumption, slippage percentage, soil bulk density, soil moisture content, total soil porosity, germination percentage, number of dropped seeds, and the percentage of broken or damaged dropped seeds. The experimental design used was a randomized complete block design (RCBD) with three replications, and the least significant difference (LSD) test was used at a significance level of 0.05 to compare the means of the variables. The results indicated that increasing the plowing depth from 15 to 20 and then to 25 cm led to a significant increase in the percentage of slippage, which increased from 4.37% to 7.37% and then to 14.33%, respectively. The pulling force also increased from 5.33 to 9.67 and then to 14.44 kilonewtons, respectively. The fuel consumption increased from 43.32 to 56.84 and then to 66.67 liters per hectare, respectively. The bulk density of the soil increased from 1.06 to 1.08 and then to 1.15 micrograms per cubic meter, respectively. There was an increase in soil moisture content from 14.11 to 15.19 and then to 16.63%, respectively. There was no significant effect of plowing depth on the percentage of germination, the number of dropped seeds, and the percentage of broken seeds.
: Under the background of “double first class” and “new engineering” construction, the construction of mechanical laboratories in colleges and universities is facing major changes. Higher requirements and standards for laboratory safety management are put forward for the increase of teaching and scientific research tasks, the expansion of laboratory scale, the increase of laboratory equipment and the change of laboratory environmental conditions. Based on the characteristics of the construction of university mechanical laboratories under new situation, this paper analyses the problems and challenges in the safety management of university mechanical laboratories at present. The aspects of strengthening safety concept, improving management system, introducing laboratory information management system and establishing virtual simulation experiment are considered. A new idea and system for the safety management of university machinery laboratories are proposed in this paper, which can provide some reference for the construction and safety management of relevant university machinery laboratories.
The relevance of research is caused by the development and active introduction of new technologies in the sphere of the processing industry and, in this connection, an increase of interest from the state and experts to questions of legal regulation of this process. The scientific article aims to reveal legal features of the turn of Kazakhstan factories producing various machinery and equipment of agrotechnical nature to digital and intellectual tools, through which the essence of production of agricultural mechanical factories of the Republic of Kazakhstan, the whole branch of agricultural engineering, can be radically changed. The article uses the method of empirical and comparative legal analysis of the national legislation of the Republic of Kazakhstan, international agreements in the relevant areas of mechanical engineering, works of Kazakhstan, and foreign authors on the subject. The results of the article are presented recommendations on the need to adopt several new Kazakhstan laws, new international agreements, and conventions on the problems of digitalisation and intellectualisation of agricultural engineering plants.
This editorial discusses the importance of Advanced Fluid Machinery in the sustainable development of energy. Fluid machinery is crucial in many engineering applications, including aerospace, civil, mechanical, and chemical engineering. This Special Issue, entitled “Optimization and Flow Characteristics in Advanced Fluid Machinery”, features several research articles exploring flow characteristics and optimization in fluid mechanics. The authors present innovative ideas, methodologies, and techniques to advance the field of fluid mechanics. The papers cover a wide range of topics, including computational fluid dynamics (CFD), turbulence modeling, heat transfer, multiphase flow, and fluid–structure interactions. The articles featured in this Special Issue also investigate the relevant hydrodynamic attributes of turbomachinery, high-pressure jets, marine propulsion systems, and internal combustion engines to a considerable extent, significantly expanding the scope of research within the Special Issue.
Grid-forming (GFM) control based high-voltage DC (HVDC) systems and renewable energy sources (RESs) provide support for enhancing the stability of power systems. However, the interaction and coordination of frequency support between the GFM-based modular multilevel converter based HVDC (MMC-HVDC) and grid-following (GFL) based RESs or GFM-based RESs have not been fully investigated, which are examined in this study. First, the detailed AC- and DC-side impedances of GFM-based MMC-HVDC are analyzed. The impedance characteristics of GFL- and GFM-based wind turbines are next analyzed. Then, the influences of GFL- and GFM-based wind farms (WFs) on the DC- and AC-side stabilities of WF-integrated MMC-HVDC systems are compared and evaluated. The results show that the GFM-based wind turbine performs better than the GFL-based wind turbine. Accordingly, to support a receiving-end AC system, the corresponding frequency supporting strategies are proposed based on the GFM control for WF-integrated MMC-HVDC systems. The GFM-based WF outperforms the GFL-based WF in terms of stability and response time. Simulations in PSCAD/EMTDC demonstrate the DC- and AC-side stability issues and seamless grid support from the RESs, i.e., WFs, to the receiving-end AC system.
Production of electric energy or power. Powerplants. Central stations, Renewable energy sources
Intelligent fault diagnosis is of great significance to guarantee the safe operation of mechanical equipment. However, the widely used diagnosis models rely on sufficient independent and homogeneously distributed monitoring data to train the model. In practice, the available data of mechanical equipment faults are insufficient and the data distribution varies greatly under different working conditions, which leads to the low accuracy of the trained diagnostic model and restricts it, making it difficult to apply to other working conditions. To address these problems, a novel fault diagnosis method combining a generative adversarial network and transfer learning is proposed in this paper. Dummy samples with similar fault characteristics to the actual engineering monitoring data are generated by the generative adversarial network to expand the dataset. The transfer fault characteristics of monitoring data under different working conditions are extracted by a deep residual network. Domain-adapted regular term constraints are formulated to the training process of the deep residual network to form a deep transfer fault diagnosis model. The bearing fault data are used as the original dataset to validate the effectiveness of the proposed method. The experimental results show that the proposed method can reduce the influence of insufficient original monitoring data and enable the migration of fault diagnosis knowledge under different working conditions.