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Showing records 51 to 75 of 155. [First] Page: 1 2 3 4 5 6 7 Last
Power Quality Disturbances Feature Selection and Recognition Using Optimal Multi-Resolution Fast S-Transform and CART Algorithm
Nantian Huang, Hua Peng, Guowei Cai, Jikai Chen
February 5, 2019 (v1)
Keywords: classification and regression tree algorithm, decision tree, feature selection, optimal multi-resolution fast S-transform, power quality disturbances
In order to improve the recognition accuracy and efficiency of power quality disturbances (PQD) in microgrids, a novel PQD feature selection and recognition method based on optimal multi-resolution fast S-transform (OMFST) and classification and regression tree (CART) algorithm is proposed. Firstly, OMFST is carried out according to the frequency domain characteristic of disturbance signal, and 67 features are extracted by time-frequency analysis to construct the original feature set. Subsequently, the optimal feature subset is determined by Gini importance and sorted according to an embedded feature selection method based on the Gini index. Finally, one standard error rule subtree evaluation methods were applied for cost complexity pruning. After pruning, the optimal decision tree (ODT) is obtained for PQD classification. The experiments show that the new method can effectively improve the classification efficiency and accuracy with feature selection step. Simultaneously, the ODT can... [more]
New Requirements of the Voltage/VAR Function for Smart Inverter in Distributed Generation Control
Yun-Su Kim, Gyeong-Hun Kim, Jae-Duck Lee, Changhee Cho
February 5, 2019 (v1)
Keywords: International Electronical Committee 61850, inverter-interfaced distributed generation, smart inverter, Volt/VAR function
International Electronical Committee (IEC) 61850-90-7 is a part of the IEC 61850 series which specifies the advanced functions and object models for power converter based Distributed Energy Resources (DERs). One of its functions, the Voltage/VAR (V/V) control function, is used to enhance the stability and the reliability of the voltage in the distribution system. The conventional V/V function acts mainly for flattening the voltage profile as for a basic grid support function. Currently, other objectives such as the minimization of line loss and the operational costs reduction are coming into the spotlight. In order to attain these objectives, the V/V function and hence the DER units shall actively respond to the change of distribution system conditions. In this paper, the modification of V/V function and new requirements are proposed. To derive new requirements of V/V function, loss minimization is applied to a particle swarm optimization (PSO) algorithm where the condition of voltage... [more]
SoC-Based Output Voltage Control for BESS with a Lithium-Ion Battery in a Stand-Alone DC Microgrid
Seung-Yeong Yu, Hyun-Jun Kim, Jae-Hyuk Kim, Byung-Moon Han
February 5, 2019 (v1)
Keywords: battery energy storage system (BESS), droop control, engine generator (EG), lithium-ion (Li-ion) battery, photovoltaic (PV) panel, stand-alone DC microgrid, state of charge (SoC)
This paper proposes a new DC output voltage control for a battery energy storage system (BESS) with a lithium-ion battery based on the state of charge (SoC). The proposed control scheme was verified through computer simulations for a typical stand-alone DC microgrid, which consists of a BESS, photovoltaic (PV) panel, engine generator (EG), and DC load. A scaled hardware prototype for a stand-alone DC microgrid was set up in the lab, in which the proposed control scheme was loaded in a DSP controller. The experimental results were compared with the simulation results for performance verification. The proposed control scheme provides relatively lower variation of the DC grid voltage than the conventional droop control.
Modeling and Experimental Validation of a Low-Cost Radiation Sensor Based on the Photovoltaic Effect for Building Applications
Ángel Gómez-Moreno, Pedro José Casanova-Peláez, José Manuel Palomar-Carnicero, Fernando Cruz-Peragón
February 5, 2019 (v1)
Keywords: building, irradiance estimation, photovoltaic, solar cells, solar radiation, thermal drift
The energy consumed to cool buildings is very elevated and solar gains represent a high percentage of these cooling loads. To minimize the thermal load it is necessary to control external shading systems. This control requires continuous measurement of solar radiation in different locations of the building. However, for such applications the use of conventional irradiance sensors increases the cost and reduces the profitability of the installation. This paper is focused on the development, modeling, and experimental validation of low cost irradiation sensors based on photovoltaic effect in order to reduce the costs of dynamic external shading devices and to improve the profitability of the system. With this proposal, firstly, small commercial photovoltaic cells have been adapted for use as an irradiation measurement device. Subsequently, quasi-stationary and continuous experimental measurements of these silicon cells, facing south and installed horizontally, have been carried out in Ja... [more]
Simulation of Polygeneration Systems
Francesco Calise, Massimo Dentice D’Accadia
February 5, 2019 (v1)
Keywords: distributed generation, dynamic simulations, Polygeneration, Renewable and Sustainable Energy
This Special Issue aims at collecting the recent studies dealing with polygeneration systems, with a special focus on the possible integration of different technologies into a single system, able to convert one or multiple energy sources into energy services (electricity, heat and cooling) and other useful products (e.g., desalinized water, hydrogen, glycerin, ammonia, etc.). Renewable sources (solar, wind, hydro, biomass and geothermal), as well as fossil fuels, feeding advanced energy systems such as fuel cells and cogeneration systems, are considered. Special attention is paid to control strategies and to the management of the systems in general. Studies including thermoeconomic analyses and system optimizations are presented.
Measurement Research on the Decoupling Effect of Industries’ Carbon Emissions—Based on the Equipment Manufacturing Industry in China
Lu Wan, Zi-Long Wang, Jhony Choon Yeong Ng
February 5, 2019 (v1)
Subject: Energy Policy
Keywords: carbon emission, decoupling effect, economic growth, equipment manufacturing industry
Economic development usually leads to increased energy consumption, which in turn will result in an increase in carbon emissions. To break the relationship between economic development and carbon emissions, scholars have turned their attention to the phenomenon of decoupling. In this paper, we studied the decoupling relationship between carbon emissions and economic growth of the equipment manufacturing industry in China from 2000 to 2014. We adapted the LMDI decomposition method, and we used the Tapio decoupling evaluation model to analyze our data. We found that the decoupling relationship between carbon emissions and economic growth of China’s equipment manufacturing industry is weak, which indicates the industry is experiencing faster economic growth than carbon emission growth. We found the economic output is the factor that has the strongest influence on the industry’s carbon emission, and energy consumption intensity has the strongest relationship with the decoupling of economic... [more]
Biomass Residues to Renewable Energy: A Life Cycle Perspective Applied at a Local Scale
Esmeralda Neri, Daniele Cespi, Leonardo Setti, Erica Gombi, Elena Bernardi, Ivano Vassura, Fabrizio Passarini
February 5, 2019 (v1)
Subject: Biosystems
Keywords: energy efficient city, life cycle assessment (LCA), recovery, small community, thermal energy
Italy, like every country member of the European Union (EU), will have to achieve the objectives required by the Energy Roadmap 2050. The purpose of the study was to evaluate the environmental impacts of residue recovery arising from the management of public and private green feedstocks, activity of the cooperative “Green City” in the Bologna district, and usage in a centralized heating system to produce thermal energy for public buildings. Results, obtained using the ReCipe impact assessment method, are compared with scores achieved by a traditional methane boiler. The study shows some advantages of the biomass-based system in terms of greenhouse gases (GHGs) emissions and consumption of non-renewable fuels, which affect climate change (−41%) and fossil resources depletion (−40%), compared to the use of natural gas (NG). Moreover, scores from network analysis denote the great contribution of feedstock transportation (98% of the cumulative impact). The main reason is attributable to al... [more]
Analysis and Speed Ripple Mitigation of a Space Vector Pulse Width Modulation-Based Permanent Magnet Synchronous Motor with a Particle Swarm Optimization Algorithm
Xing Liu, Jinhua Du, Deliang Liang
February 5, 2019 (v1)
Subject: Optimization
Keywords: harmonic superposition, particle swarm optimization (PSO), speed ripple reduction
A method is proposed for reducing speed ripple of permanent magnet synchronous motors (PMSMs) controlled by space vector pulse width modulation (SVPWM). A flux graph and mathematics are used to analyze the speed ripple characteristics of the PMSM. Analysis indicates that the 6P (P refers to pole pairs of the PMSM) time harmonic of rotor mechanical speed is the main harmonic component in the SVPWM control PMSM system. To reduce PMSM speed ripple, harmonics are superposed on a SVPWM reference signal. A particle swarm optimization (PSO) algorithm is proposed to determine the optimal phase and multiplier coefficient of the superposed harmonics. The results of a Fourier decomposition and an optimized simulation model verified the accuracy of the analysis as well as the effectiveness of the speed ripple reduction methods, respectively.
A Supervisory Control Algorithm of Hybrid Electric Vehicle Based on Adaptive Equivalent Consumption Minimization Strategy with Fuzzy PI
Fengqi Zhang, Haiou Liu, Yuhui Hu, Junqiang Xi
February 5, 2019 (v1)
Keywords: equivalent consumption minimization strategy, equivalent factor, fuzzy proportional plus integral (PI), hybrid electric vehicle
This paper presents a new energy management system based on equivalent consumption minimization strategy (ECMS) for hybrid electric vehicles. The aim is to enhance fuel economy and impose state of charge (SoC) charge-sustainability. First, the relationship between the equivalent factor (EF) of ECMS and the co-state of pontryagin’s minimum principle (PMP) is derived. Second, a new method of implementing the adaptation law using fuzzy proportional plus integral (PI) controller is developed to adjust EF for ECMS in real-time. This adaptation law is more robust than one with constant EF due to the variation of EF as well as driving cycle. Finally, simulations for two driving cycles using ECMS are conducted as opposed to the commonly used rule-based (RB) control strategy, indicating that the proposed adaptation law can provide a promising blend in terms of fuel economy and charge-sustainability. The results confirm that ECMS with Fuzzy PI adaptation law is more robust than ECMS with constan... [more]
Combustion and Emission Characteristics According to the Fuel Injection Ratio of an Ultra-Lean LPG Direct Injection Engine
Cheolwoong Park, Taeyoung Kim, Gyubaek Cho, Janghee Lee
February 5, 2019 (v1)
Subject: Other
Keywords: brake thermal efficiency, combustion stability, emissions, liquefied petroleum gas (LPG) direct injection, spray-guided type combustion system, ultra-lean combustion
The effect of the fuel injection ratio on the combustion and emission characteristics of stratified lean mixture combustion was investigated for a spray-guided liquefied petroleum gas (LPG) direct injection engine. Inter-injection spark-ignition combustion—a specially designed combustion strategy for LPG fuel derived from a two-staged injection—was employed to maximize the improvement in thermal efficiency when combustion stability is secured. When changing the fuel injection ratio, the optimum spark advance and fuel injection timings were experimentally determined to maximize the thermal efficiency based on sweeping timings. The optimum fuel injection ratio with the highest thermal efficiency (42.76%) and stable operation was 60%/40%, with the optimization of the spark advance and fuel injection timing, because of the locally rich mixture region in the recirculation zone. NOx emissions were at their highest level with a fuel injection ratio of 60%/40% because of the high combustion te... [more]
Minimization of Cogging Force in Fractional-Slot Permanent Magnet Linear Motors with Double-Layer Concentrated Windings
Qian Wang, Bo Zhao, Jibin Zou, Yong Li
February 5, 2019 (v1)
Subject: Other
Keywords: cogging force, concentrated winding, linear motor, permanent magnet motor
Permanent magnet linear motors (PMLMs) with double-layer concentrated windings generally show significant cogging forces due to the introduction of auxiliary teeth for eliminating the end-effect induced phase unbalance, even when the fractional-slot technology is applied. This paper presents a novel approach to reduce the cogging force by adjusting the armature core dimensions in fractional-slot PMLMs with double-layer concentrated windings, together with magnet skewing. It is shown that the proposed technique is capable of reducing the cogging force of the motor in an effective way, with the peak value minimized to less than 0.4% of the rated thrust force in the case study. Such a technique can also be applicable to other linear motors with appropriate changes.
Comparison of Degradation on Aluminum Reflectors for Solar Collectors due to Outdoor Exposure and Accelerated Aging
Johannes Wette, Florian Sutter, Aránzazu Fernández-García, Stefan Ziegler, Reinhard Dasbach
February 5, 2019 (v1)
Keywords: accelerated aging, aluminum solar reflector, concentrated solar power, corrosion, degradation, durability
Reflectors for concentrated solar thermal technologies need to withstand 20 or even 30 years of outdoor exposure without significant loss of solar specular reflectance. In order to test the durability of innovative reflectors within a shorter period of time, an accelerated aging methodology is required. The problem with accelerated testing is that poor correlation between laboratory and field test results has been achieved in the past. This is mainly because unrealistic degradation mechanisms are accelerated in the weathering chambers. In order to define a realistic testing procedure, a high number of accelerated aging tests have been performed on differently coated aluminum reflectors. The degradation mechanisms of the accelerated tests have been classified and systematically compared to samples that have been exposed at nine different exposure sites outdoors. Besides the standardized aging tests, innovative aging procedures have been developed in such way that the agreement to the de... [more]
Comparing Apples to Apples: Why the Net Energy Analysis Community Needs to Adopt the Life-Cycle Analysis Framework
David J. Murphy, Michael Carbajales-Dale, Devin Moeller
February 5, 2019 (v1)
Subject: Energy Policy
Keywords: energy return on investment (EROI), Energy Return Ratios (ERRs), function unit, ISO, life cycle assessment (LCA), net energy
How do we know which energy technologies or resources are worth pursuing and which aren’t? One way to answer that question is to compare the energy return of a certain technology—i.e., how much energy is remaining after accounting for the amount of energy expended in the production and delivery process. Such energy return ratios (the most famous of which is energy return on investment (EROI)) fall within the field of net energy analysis (NEA), and provide an easy way to determine which technology is “better”; i.e., higher Energy Return Ratios (ERRs) are, certeris paribus, better than lower ERRs. Although useful as a broad measure of energy profitability, comparisons can also be misleading, particularly if the units being compared are different. For example, the energy content of electricity produced from a photovoltaic cell is different than the energy content of coal at the mine-mouth, yet these are often compared directly within the literature. These types of inconsistencies are comm... [more]
Definition and Experimental Validation of a Simplified Model for a Microgrid Thermal Network and its Integration into Energy Management Systems
Andrea Bonfiglio, Massimo Brignone, Federico Delfino, Alessandro Nilberto, Renato Procopio
February 5, 2019 (v1)
Keywords: energy management, optimization algorithm, parameter identification, smart grids, thermal network
The present paper aims at defining a simplified but effective model of a thermal network that links the thermal power generation with the resulting temperature time profile in a heated or refrigerated environment. For this purpose, an equivalent electric circuit is proposed together with an experimental procedure to evaluate its input parameters. The paper also highlights the simplicity of implementation of the proposed model into a microgrid Energy Management System. This allows the optimal operation of the thermal network to be achieved on the basis of available data (desired temperature profile) instead of a less realistic basis (such as the desired thermal power profile). The validation of the proposed model is performed on the Savona Campus Smart Polygeneration Microgrid (SPM) with the following steps: (i) identification of the parameters involved in the equivalent circuit (performed by minimizing the difference between the temperature profile, as calculated with the proposed mode... [more]
A Procedure to Perform Multi-Objective Optimization for Sustainable Design of Buildings
Cristina Brunelli, Francesco Castellani, Alberto Garinei, Lorenzo Biondi, Marcello Marconi
February 5, 2019 (v1)
Subject: Optimization
Keywords: multi-objective optimization, sustainable buildings, uncertainty analysis
When dealing with sustainable design concepts in new construction or in retrofitting existing buildings, it is useful to define both economic and environmental performance indicators, in order to select the optimal technical solutions. In most of the cases, the definition of the optimal strategy is not trivial because it is necessary to solve a multi-objective problem with a high number of the variables subjected to nonlinear constraints. In this study, a powerful multi-objective optimization genetic algorithm, NSGAII (Non-dominated Sorting Genetic Algorithm-II), is used to derive the Pareto optimal solutions, which can illustrate the whole trade-off relationship between objectives. A method is then proposed, to introduce uncertainty evaluation in the optimization procedure. A new university building is taken as a case study to demonstrate how each step of the optimization process should be performed. The results achieved turn out to be reliable and show the suitableness of this proced... [more]
A Principal Component Analysis in Switchgrass Chemical Composition
Mario Aboytes-Ojeda, Krystel K. Castillo-Villar, Tun-hsiang E. Yu, Christopher N. Boyer, Burton C. English, James A. Larson, Lindsey M. Kline, Nicole Labbé
February 5, 2019 (v1)
Subject: Biosystems
Keywords: bioenergy, lignocellulosic biomass, principal component analysis, statistical hypothesis, switchgrass
In recent years, bioenergy has become a promising renewable energy source that can potentially reduce the greenhouse emissions and generate economic growth in rural areas. Gaining understanding and controlling biomass chemical composition contributes to an efficient biofuel generation. This paper presents a principal component analysis (PCA) that shows the influence and relevance of selected controllable factors over the chemical composition of switchgrass and, therefore, in the generation of biofuels. The study introduces the following factors: (1) storage days; (2) particle size; (3) wrap type; and (4) weight of the bale. Results show that all the aforementioned factors have an influence in the chemical composition. The number of days that bales have been stored was the most significant factor regarding changes in chemical components due to its effect over principal components 1 and 2 (PC1 and PC2, approximately 80% of the total variance). The storage days are followed by the particl... [more]
Experimental Optimization of Passive Cooling of a Heat Source Array Flush-Mounted on a Vertical Plate
Antoine Baudoin, Didier Saury, Bo Zhu, Cecilia Boström
February 5, 2019 (v1)
Subject: Other
Keywords: discrete heat sources, natural convection, Optimization, source array
Heat sources, such as power electronics for offshore power, could be cooled passively—mainly by conduction and natural convection. The obvious advantage of this strategy is its high reliability. However, it must be implemented in an efficient manner (i.e., the area needs to be kept low to limit the construction costs). In this study, the placement of multiple heat sources mounted on a vertical plate was studied experimentally for optimization purposes. We chose a regular distribution, as this is likely to be the preferred choice in the construction process. We found that optimal spacing can be determined for a targeted source density by tuning the vertical and horizontal spacing between the heat sources. The optimal aspect ratio was estimated to be around two.
Solar Resource for Urban Communities in the Baja California Peninsula, Mexico
Alberto-Jesús Perea-Moreno, Quetzalcoatl Hernandez-Escobedo
January 31, 2019 (v1)
Keywords: assessment, Baja California Peninsula, geographic information system (GIS), solar irradiation, urban communities
Several studies have determined that Mexico has great renewable energy potential, and one of its most abundant resources is solar energy, a source that could be exploited to provide development opportunities to its population, however it is necessary to calculate the amount of this source available. The aim of this study was to assess solar irradiance at urban communities in the Baja California Peninsula. For this purpose data recorded every 10 min during 6 years (2010⁻2015) by the Automatic Meteorological Stations (AMSs) and Synoptic Automatic Meteorological Stations (SAMSs) of the National Meteorological System of Mexico (NMS) were analyzed. Satellite data from the Surface and Meteorology Energy System (SMSE) were also used, and a linear regression was performed to compare the measured and satellite data. The highest R-square value found was 0.97 and the lowest was 0.82. Daily patterns show that Cabo San Lucas had the highest average solar irradiation/day, with 1000 W/m². Considering... [more]
Thermal Cracking of Jatropha Oil with Hydrogen to Produce Bio-Fuel Oil
Yi-Yu Wang, Chia-Chi Chang, Ching-Yuan Chang, Yi-Hung Chen, Je-Lueng Shie, Min-Hao Yuan, Yen-Hau Chen, Li-Xuan Huang, Cesar Augusto Andrade-Tacca, Do Van Manh, Min-Yi Tsai, Michael Huang
January 31, 2019 (v1)
Subject: Biosystems
Keywords: bio-fuel oil, cracking, hydrogenation, jatropha oil (JO)
This study used thermal cracking with hydrogen (HTC) to produce bio-fuel oil (BFO) from jatropha oil (JO) and to improve its quality. We conducted HTC with different hydrogen pressures (PH2; 0⁻2.07 MPa or 0⁻300 psig), retention times (tr; 40⁻780 min), and set temperatures (TC; 623⁻683 K). By applying HTC, the oil molecules can be hydrogenated and broken down into smaller molecules. The acid value (AV), iodine value, kinematic viscosity (KV), density, and heating value (HV) of the BFO produced were measured and compared with the prevailing standards for oil to assess its suitability as a substitute for fossil fuels or biofuels. The results indicate that an increase in PH2 tends to increase the AV and KV while decreasing the HV of the BFO. The BFO yield (YBFO) increases with PH2 and tr. The above properties decrease with increasing TC. Upon HTC at 0.69 MPa (100 psig) H₂ pressure, 60 min time, and 683 K temperature, the YBFO was found to be 86 wt%. The resulting BFO possesses simulated di... [more]
Numerical Investigation of Wind Conditions for Roof-Mounted Wind Turbines: Effects of Wind Direction and Horizontal Aspect Ratio of a High-Rise Cuboid Building
Takaaki Kono, Tetsuya Kogaki, Takahiro Kiwata
January 31, 2019 (v1)
Keywords: horizontal aspect ratio, large-eddy simulation (LES), roof-top, small wind turbine (SWT), wind condition, wind direction
From the viewpoint of installing small wind turbines (SWTs) on rooftops, this study investigated the effects of wind direction and horizontal aspect ratio (HAR = width/length) of a high-rise cuboid building on wind conditions above the roof by conducting large eddy simulations (LESs). The LES results confirmed that as HAR decreases (i.e., as the building width decreases), the variation in wind velocity over the roof tends to decrease. This tendency is more prominent as the angle between the wind direction and the normal vector of the building’s leeward face with longer roof edge increases. Moreover, at windward corners of the roof, wind conditions are generally favorable at relatively low heights. In contrast, at the midpoint of the roof's windward edge, wind conditions are generally not favorable at relatively low heights. At leeward representative locations of the roof, the bottoms of the height range of favorable wind conditions are typically higher than those at the windward repres... [more]
Multi-Objective Distribution Network Expansion Incorporating Electric Vehicle Charging Stations
Yue Xiang, Wei Yang, Junyong Liu, Furong Li
January 31, 2019 (v1)
Keywords: charging station, distribution network expansion planning, multi-objectives, multi-stage search strategy, traffic flow
The paper develops a multi-objective planning framework for distribution network expansion with electric vehicle charging stations. Charging loads are modeled in the first place, and then integrated into the optimal distribution network expansion planning. The formulation is extended from the single objective of the economic cost minimization into three objectives with the additional maximization of the charging station utilization, and maximization of the reliability level. Compared with the existing models, it captures the interactive impacts between charging infrastructures planning and distribution network planning from the aspects of economy, utilization, and reliability. A multi-stage search strategy is designed to solve the multi-objective problem. The models and the strategy are demonstrated by the test case. The results show that the proposed planning framework can make a trade-off among the three objectives, and offer a perspective to effectively integrate the network constra... [more]
Promise and Challenges of High-Voltage SiC Bipolar Power Devices
Tsunenobu Kimoto, Kyosuke Yamada, Hiroki Niwa, Jun Suda
January 31, 2019 (v1)
Keywords: (merged pin-Schottky) diodes, carrier lifetime, conductivity modulation, power device, silicon carbide
Although various silicon carbide (SiC) power devices with very high blocking voltages over 10 kV have been demonstrated, basic issues associated with the device operation are still not well understood. In this paper, the promise and limitations of high-voltage SiC bipolar devices are presented, taking account of the injection-level dependence of carrier lifetimes. It is shown that the major limitation of SiC bipolar devices originates from band-to-band recombination, which becomes significant at a high-injection level. A trial of unipolar/bipolar hybrid operation to reduce power loss is introduced, and an 11 kV SiC hybrid (merged pin-Schottky) diodes is experimentally demonstrated. The fabricated diodes with an epitaxial anode exhibit much better forward characteristics than diodes with an implanted anode. The temperature dependence of forward characteristics is discussed.
Cost-Effectiveness Comparison of Coupler Designs of Wireless Power Transfer for Electric Vehicle Dynamic Charging
Weitong Chen, Chunhua Liu, Christopher H.T. Lee, Zhiqiang Shan
January 31, 2019 (v1)
Keywords: cost-effectiveness, dynamic charging, electric vehicle, electromagnetic field analysis, wireless power transfer
This paper presents a cost-effectiveness comparison of coupler designs for wireless power transfer (WPT), meant for electric vehicle (EV) dynamic charging. The design comparison of three common types of couplers is first based on the raw material cost, output power, transfer efficiency, tolerance of horizontal offset, and flux density. Then, the optimal cost-effectiveness combination is selected for EV dynamic charging. The corresponding performances of the proposed charging system are compared and analyzed by both simulation and experimentation. The results verify the validity of the proposed dynamic charging system for EVs.
Basic Characteristics and Design of a Novel Hybrid Magnetic Bearing for Wind Turbines
Yanjun Yu, Weiyu Zhang, Yuxin Sun, Peifeng Xu
January 31, 2019 (v1)
Subject: Other
Keywords: cylindrical rotor, equivalent magnetic circuit method, finite element analysis (FEA), hybrid magnetic bearing (HMB), magnetic suspension force, radial control windings
This paper proposes a five-degree-of-freedom (5-DOF) hybrid magnetic bearing (HMB) for direct-drive wind turbines, which can realize suspension in the 4-DOF radial and 1-DOF axial directions. Only two sets of radial control windings are employed in the proposed HMB because only one set of radial control windings can achieve the 2-DOF suspension in the radial direction. Unlike the traditional active thrust magnetic bearings, this paper uses a cylindrical rotor core without a large thrust disc in the novel HMB. The numbers of the controller, power amplifier and system volume can be reduced in the magnetic suspension system. This paper also presents the structure and basic characteristics of the proposed magnetic bearing. A precision equivalent magnetic circuit analysis of the permanent magnet ring and control magnetic field is conducted in this study, in consideration of the non-uniform distribution of magnetic density. Accordingly, the mathematical models, including the suspension force... [more]
A Novel Flux Focusing Magnetically Geared Machine with Reduced Eddy Current Loss
Jin Liu, Wenxiang Zhao, Jinghua Ji, Guohai Liu, Tao Tao
January 31, 2019 (v1)
Subject: Other
Keywords: back-electromotive force, eddy current loss, finite-element method, magnetic gear, serial-spoke structure, torque
This paper proposes a novel flux focusing magnetically geared (MG) machine for wind power generation, considering the permanent magnets (PMs) eddy current loss and the balance between the pull-out torque of MG machine and the back-electromotive force (EMF)of the PM brushless machine. The PM eddy current loss in the two rotors of the conventional surface-mounted MG machine is calculated and analyzed by using finite-element method. By adopting serial-spoke structure in the inner rotor, a novel rotor structure for a MG machine is proposed to reduce the PM eddy current loss. Moreover, in order to balance the pull-out torque and the back-EMF, several serial-spoke structures and the main design parameters are investigated. Then, a quantitative comparison between the proposed topology and the conventional surface-mounted MG machine is performed. The analysis results indicate that the PM eddy current loss of the proposed MG machine can be significantly reduced and its pull-out torque and back-... [more]
Showing records 51 to 75 of 155. [First] Page: 1 2 3 4 5 6 7 Last