Analysis of disturbance source location of direct drive wind turbine based on energy function

In order to locate the disturbance source quickly and accurately in the wind farm, taking the direct drive wind turbine as an example, using the transient energy method, firstly, the transient energy flow formula is derived according to the mathematical model of each part of the direct drive wind turbine, the energy flow power is obtained by linear fitting, and the position of the disturbance source is judged by the positive and negative energy flow power; then a single machine infinite bus system model with forced oscillation source is built on PSCAD/EMTDC simulation platform for simulation. The results show that the transient energy method can accurately locate the disturbance source of direct drive wind turbine unit.

Enhanced Changeover Detection in Industry 4.0 Environments with Machine Learning

Changeover times are an important element when evaluating the Overall Equipment Effectiveness (OEE) of a production machine. The article presents a machine learning (ML) approach that is based on an external sensor setup to automatically detect changeovers in a shopfloor environment. The door statuses, coolant flow, power consumption, and operator indoor GPS data of a milling machine were used in the ML approach. As ML methods, Decision Trees, Support Vector Machines, (Balanced) Random Forest algorithms, and Neural Networks were chosen, and their performance was compared. The best results were achieved with the Random Forest ML model (97% F1 score, 99.72% AUC score). It was also carried out that model performance is optimal when only a binary classification of a changeover phase and a production phase is considered and less subphases of the changeover process are applied.

Quantifying the Effects of Wave—Current Interactions on Tidal Energy Resource at Sites in the English Channel Using Coupled Numerical Simulations

Numerical modeling of currents and waves is used throughout the marine energy industry for resource assessment. This study compared the output of numerical flow simulations run both as a standalone model and as a two-way coupled wave–current simulation. A regional coupled flow-wave model was established covering the English Channel using the Delft D-Flow 2D model coupled with a SWAN spectral wave model. Outputs were analyzed at three tidal energy sites: Alderney Race, Big Roussel (Guernsey), and PTEC (Isle of Wight). The difference in the power in the tidal flow between coupled and standalone model runs was strongly correlated to the relative direction of the waves and currents. The net difference between the coupled and standalone runs was less than 2.5%. However, when wave and current directions were aligned, the mean flow power was increased by up to 7%, whereas, when the directions were opposed, the mean flow power was reduced by as much as 9.6%. The D-Flow Flexible Mesh model incorporates the effects of waves into the flow calculations in three areas: Stokes drift, forcing by radiation stress gradients, and enhancement of the bed shear stress. Each of these mechanisms is discussed. Forcing from radiation stress gradients is shown to be the dominant mechanism affecting the flow conditions at the sites considered, primarily caused by dissipation of wave energy due to white-capping. Wave action is an important consideration at tidal energy sites. Although the net impact on the flow power was found to be small for the present sites, the effect is site specific and may be significant at sites with large wave exposure or strong asymmetry in the flow conditions and should thus be considered for detailed resource and engineering assessments.

An Efficiency Analysis of 27 Level Single-Phase Asymmetric Inverter without Regeneration

For medium voltage applications, multilevel inverters are used. One of its classic topologies is the Cascaded H-Bridge, which requires isolated DC voltages to work. Depending on the DC voltage ratio used in the Cascaded H-bridge can be classified into symmetric and asymmetric. In comparison between symmetric and asymmetric inverters, the latter can generate an AC output voltage with more output voltage levels. DC voltage ratio most documented are binary and trinary. The last can generate an AC voltage of 3n = 27 levels is obtained, using n = 3 inverters in cascade and NLM modulation, which generates a flow power of the load to the inverters (regeneration). This work analyzes the semiconductor losses (switching and conduction) and the THD of the AC output voltage in function of index modulation, considering a non-regenerative modulation technique for a 27-level single-phase asymmetric inverter. To confirm the theoretical analyzes, simulation and experimental results are shown.

Finite Element Analysis of Flow Field in Drill Bit Design for Gas-Lift Drilling

The hole cleaning issue in gas-lift drilling has been a concern and has not been previously investigated due to the difficulties of experimental studies and analytical modeling. The objective of this study is to deliver an assessment of hole cleaning capacity of drilling fluid in reverse circulation conditions for different bit designs. We use the finite element method (FEM) to target this issue and address a critical question in gas-lift drilling. The result of the theoretical investigation indicates that clean bottom hole can be achieved in gas-lift drilling through optimization of drill bit design to balance fluid energy (cleaning power) between tooth blades. Three drill bit designs were investigated in this study. The flow power balance between blades can be achieved with a 3-orifice bit design and a 2-orifice bit design, but there exist flow stagnation zones between these orifices, which are not desirable for bit tooth and borehole cleaning. The 1-orifice bit design with four cutter blades can eliminate flow stagnation zone and improve flow field to achieve a much better flow power balance between blades and thus bit tooth and borehole cleaning. Therefore, drill bits with one orifice are desirable for reverse circulation gas-drilling. This paper presents a novel technique of using FEM to evaluate bit hydraulics for hole cleaning in reverse drilling conditions. Future laboratory tests are desirable to obtain real data for further validating the model result.

Simulasi Homogenitas Pencampuran Air Limbah Pabrik Kelapa Sawit dan Pengaruhnya Terhadap Pengolahan Awal di Kolam Ekualisasi Pilot Plant Biogas Sei Pagar

ABSTRACTPalm oil mill effluent (POME) produced from palm oil mills is classified as waste that can pollute the environment and needs severe treatment because it still contains high BOD and COD. POME has the potential to be further processed to produce biogas products through the anaerobic digestion process. Anaerobic process of biogas production from Palm Oil Mill Effluent (POME) waste is a fermentation process which quite a long time. So it is necessary to have a POME pretreatment process for preparation before being fed into the biodigester reactor. It is aimed at considering optimum conditioning, good homogeneity, and preparing for the formation of gas products. One of the POME pretreatment steps was carried out in an equalization tank to be homogenized before entering the reactor. However, when passing the equalization process, there are indications of sedimentation or separation between liquid waste and dissolved solids. Thus, an attempt was made to carry out a stirring system so that homogeneity would occur with the agitator. Therefore, the POME conditions in all parts of the pond could be relatively similar. The stirring is one of the factors that influence microbial life. In this research, a stirrer design simulation will be conducted to determine the effectiveness of the stirrer and homogeneity of POME in equalization pond. Design is adjusted to the actual POME parameters according to results of the analysis carried out related to POME physical properties such as temperature, density, viscosity, pH, and flow rate. Conditions analyzed in the simulation are agitator speed, the direction of fluid flow, power consumption, and homogeneity of mixing.Keywords: agitator, mixing, equalization tank, homogeneity, POMEABSTRAKLimbah cair pabrik kelapa sawit (POME) yang dihasilkan dari pabrik pengolahan sawit tergolong limbah yang dapat mencemari lingkungan dan perlu penanganan serius, karena masih mengandung BOD dan COD tinggi. POME sangat berpotensi untuk diolah lebih lanjut untuk menghasilkan produk biogas melalui proses penguraian anaerob. Proses pengolahan air limbah pabrik minyak sawit menjadi biogas merupakan proses fermentasi anaerobik yang memerlukan waktu yang lama. Oleh karena itu, perlu adanya proses pengolahan awal POME untuk penyiapan sebelum diumpankan ke dalam reaktor biodigester untuk pengkondisian yang optimum, homogenitas yang baik, dan persiapan pembentukan produk gas. Salah satu pengolahan awal POME dilakukan di kolam ekualisasi untuk proses homogenisasi air limbah sebelum masuk ke dalam reaktor. Selama melewati kolam ekualisasi, ada indikasi terjadi pengendapan atau pemisahan antara limbah cair dengan padatan terlarut. Untuk itu, muncul upaya untuk melakukan sistem pengadukan agar tercapai kondisi homogen dengan menggunakan pengaduk agar kondisi POME di seluruh bagian kolam relatif sama. Adapun pengadukan merupakan salah satu faktor yang berpengaruh pada kehidupan mikroba. Pada penelitian ini akan dilakukan simulasi desain pengaduk yang untuk mengetahui efektivitas pengaduk dan homogenitas POME di dalam kolam equalisasi. Desain disesuaikan dengan parameter POME sesuai hasil analisis yang dilakukan terkait properti fisik POME seperti temperatur, densitas, viskositas, pH, dan laju alir. Kondisi yang dianalisis dalam simulasi adalah kecepatan putaran pengaduk, arah aliran fluida, konsumsi daya dan homogenitas pencampuran.Kata kunci: pengaduk, pencampuran, kolam ekualisasi, homogenitas, POME

Turbulence in the Sun is suppressed on large scales and confined to equatorial regions

Convection in the Sun’s outer envelope generates turbulence and drives differential rotation, meridional circulation, and the global magnetic cycle. We develop a greater understanding of these processes by contrasting observations with simulations of global convection. These comparisons also enhance our comprehension of the physics of distant Sun-like stars. Here, we infer toroidal flow power as a function of wave number, frequency, and depth in the solar interior through helioseismic analyses of space-based observations. The inferred flows grow with spatial wave number and temporal frequency and are confined to low latitudes, supporting the argument that rotation induces systematic differences between the poles and equator. In contrast, the simulations used here show the opposite trends—power diminishing with increasing wave number and frequency while flow amplitudes become weakest at low latitudes. These differences highlight gaps in our understanding of solar convection and point to challenges ahead.