The integration of distributed generations (DGs) into distribution systems (DSs) is increasingly becoming a solution for compensating for isolated local energy systems (ILESs). Additionally, distributed generations ar...The integration of distributed generations (DGs) into distribution systems (DSs) is increasingly becoming a solution for compensating for isolated local energy systems (ILESs). Additionally, distributed generations are used for self-consumption with excess energy injected into centralized grids (CGs). However, the improper sizing of renewable energy systems (RESs) exposes the entire system to power losses. This work presents an optimization of a system consisting of distributed generations. Firstly, PSO algorithms evaluate the size of the entire system on the IEEE bus 14 test standard. Secondly, the size of the system is allocated using improved Particles Swarm Optimization (IPSO). The convergence speed of the objective function enables a conjecture to be made about the robustness of the proposed system. The power and voltage profile on the IEEE 14-bus standard displays a decrease in power losses and an appropriate response to energy demands (EDs), validating the proposed method.展开更多
The dependences of the power loss per cycle on frequency f and amplitude flux density Bm have been investigated for the three main original magnetic states in five sorts of Fe-based nanocrystalline soft magnetic alloy...The dependences of the power loss per cycle on frequency f and amplitude flux density Bm have been investigated for the three main original magnetic states in five sorts of Fe-based nanocrystalline soft magnetic alloys in the ranges of 10 Hz<=f<=1000 Hz and 0.4 T<= Bm <=1.0 T. The total loss P is decomposed into the sum of the hysteresis loss Physt, the classical eddy current loss Pel and the excess loss Pexc. Physt has been found to be proportional to Bm^2 and f. The behavior of Pexc/f vs f being equivalent to P/f vs f clearly exhibits nonlinearity in the range not more than about 120 Hz, whereas the behavior of P/f vs f roughly shows linearity in the range far above 100 Hz and not more than 1000 Hz. In the range up to 1000 Hz, Physt is dominant in the original high permeability state and the state of low residual flux density, whereas Pexc in the state of high residual flux density is dominant in the wider range above about 100 Hz. The framework of the statistical theory of power loss has been used for representing the behavior of Pexc/f vs f. It has been found that the number n of the simultaneously active 'Magnetic Objects' linearly varies as n = n0 + Hexc/H0 as a function of the dynamic field Hexc in the range below about 120 Hz, whereas n approximately follows a law of the form n = n0 + (Hexc/H0)^m with 1 < m < 2 in the range far above 100 Hz and not more than 1000 Hz. The values of the field HO in principle related to the microstructure and the domain structure have been calculated for the three states.展开更多
The aim of this paper is to determine the power losses recorded by a PV generator operating under partial shading conditions. These losses are evaluated through two distinct methods. The first method is based on mathe...The aim of this paper is to determine the power losses recorded by a PV generator operating under partial shading conditions. These losses are evaluated through two distinct methods. The first method is based on mathematical modeling, while the second is based on Simulink’s physical model. The losses recorded are considerable and increase as a function of the increase in the percentage of shading up to a limit value where they become constant in the case where an ideal by-pass diode is connected in parallel with the modules. This limit value is non-existent in the case where the bypass diode is not ideal, which in fact corresponds to the real model. However, it emerges that the power losses are minimized in a PV system comprising bypass diodes, in particular in the case where the partial shading is considerable.展开更多
In this report,we show that hyperspectral high-resolution photoluminescence mapping is a powerful tool for the selection and optimiz1ation of the laser ablation processes used for the patterning interconnections of su...In this report,we show that hyperspectral high-resolution photoluminescence mapping is a powerful tool for the selection and optimiz1ation of the laser ablation processes used for the patterning interconnections of subcells on Cu(Inx,Ga1-x)Se2(CIGS)modules.In this way,we show that in-depth monitoring of material degradation in the vicinity of the ablation region and the identification of the underlying mechanisms can be accomplished.Specifically,by analyzing the standard P1 patterning line ablated before the CIGS deposition,we reveal an anomalous emission-quenching effect that follows the edge of the molybdenum groove underneath.We further rationalize the origins of this effect by comparing the topography of the P1 edge through a scanning electron microscope(SEM)cross-section,where a reduction of the photoemission cannot be explained by a thickness variation.We also investigate the laser-induced damage on P1 patterning lines performed after the deposition of CIGS.We then document,for the first time,the existence of a short-range damaged area,which is independent of the application of an optical aperture on the laser path.Our findings pave the way for a better understanding of P1-induced power losses and introduce new insights into the improvement of current strategies for industry-relevant module interconnection schemes.展开更多
The classical minimization of power losses in transmission lines is dominated by artificial intelligence techniques, which do not guarantee global optimum amidst local minima. Revolutionary and evolutionary techniques...The classical minimization of power losses in transmission lines is dominated by artificial intelligence techniques, which do not guarantee global optimum amidst local minima. Revolutionary and evolutionary techniques are encumbered with sophisticated transformations, which weaken the techniques. Power loss minimization is crucial to the efficient design and operation of power transmission lines. Minimization of losses is one way to meet steady grid supply, especially at peak demand. Thus, this paper has presented a gradient technique to obtain optimal variables and values from the power loss model, which efficiently minimizes power losses by modifying the traditional power loss model that combines Ohm and Corona losses. Optimality tests showed that the unmodified model does not support the minimization of power losses on transmission lines as the Hessian matrix portrayed the maximization of power losses. However, the modified model is consistent with the gradient method of optimization, which yielded optimum variables and values from the power loss model developed in this study. The unmodified (modified) models for Bujagali-Kawanda 220 kV and Masaka West-Mbarara North 132 kV transmission lines in Uganda showed maximum power losses of 0.406 (0.391) and 0.452 (0.446) kW/km/phase respectively. These results indicate that the modified model is superior to the unmodified model in minimizing power losses in the transmission lines and should be implemented for the efficient design and operation of power transmission lines within and outside Uganda for the same transmission voltages.展开更多
The research reported in this paper focuses on non-technical power loss reduction for power distribution systems. Such reduction of costs of energy not served (ENS.COST), is intelligently evaluated and optimized using...The research reported in this paper focuses on non-technical power loss reduction for power distribution systems. Such reduction of costs of energy not served (ENS.COST), is intelligently evaluated and optimized using a firefly algorithm, from where savings of 43.3% on energy not served are achieved.展开更多
We present a theoretic model to calculate skin depths and eddy-current power losses for a magnetic position sensor. Eddy-current, arised from the operation of an alternating-current excitation, induces secondary curre...We present a theoretic model to calculate skin depths and eddy-current power losses for a magnetic position sensor. Eddy-current, arised from the operation of an alternating-current excitation, induces secondary currents and fields between magnetic material and magnetic position sensor. In this paper, a magnetic position sensor system is simplified to be an outer-winding coil along the axial direction of a low carbon steel bar. The analytical model is derived from basic field and circuit theory considering a linear approximation for a nonlinear permeability. Thus the skin depths and eddy-current power losses from the model in eddy-current modeling techniques at various frequencies of an excited current source can be calculated. The proposed configuration is capable of predicting the skin depths and eddy-current power losses for a magnetic position sensor and has a consistence with experiments.展开更多
In the design of the CAT 3408 engine, the Low Temperature (BT) circuits used to cool the engine lubricating oil and the charge air and the High Temperature (HT) circuits for cooling the cylinder liners, cylinder heads...In the design of the CAT 3408 engine, the Low Temperature (BT) circuits used to cool the engine lubricating oil and the charge air and the High Temperature (HT) circuits for cooling the cylinder liners, cylinder heads and body of turbofans are mainly used to cool the engine, so that it works properly. This work, based on the analysis carried out, to determine the lubrication compliance of the Yacco VX 100 - SAE 15 W-40 oil and that of the Camwater water used in the engine of the Boat Yang 1 by carrying out a series of conventional tests such as that: the density, the viscosity, the viscosity index, the flash point, the density, the sulphate center content, the water content, the total acidity index (TAN), total basic number (TBN) and pour point for the oil case and pH, hardness, sodium chloride content [NaCl], sodium sulphate content [NaSO<sub>4</sub>] for the water case which will be compared to the specified requirements to determine whether compliance is achieved for each of these characteristics. The results of the oil and water samples taken from the engine after use show that the used oil gives a specific gravity of 0.8822, a viscosity (at 40°C) of 92.29 mm<sup>2</sup>/s, a viscosity (at 100°C) of 13.99 mm<sup>2</sup>/s, a viscosity index (VI) of 155.39, a pour point -21°C, a Flash Point (VO) 215°C, a Sulfated ash content of 18%, a density 881.5 kg/m<sup>3</sup>, a total basic number (TBN) of 12.60 mgKOH/g, a Total Acid Index (TAN) of 3.096 mgKOH/g, a Water Content of 1.8 % and the water used gives a pH of 6.00, a hardness of 3.2 french degrees, a sodium chloride content [NaCl] of 0.468 mg/L, and a calcium sulphate content [CaSO<sub>4</sub>] of 2.38345 mg/L. the results of the water content and content of sulfated centers justify the thermal overload and power losses in the marine diesel engine CAT 3408 of the boat Yang 1 because of their values which are not in conformity with the standards.展开更多
This paper presents a method for optimizing a grid-connected photovoltaic system through an LCL filter. An algorithm based on particle swarm optimization (PSO) is used to determine the number of batteries, the number ...This paper presents a method for optimizing a grid-connected photovoltaic system through an LCL filter. An algorithm based on particle swarm optimization (PSO) is used to determine the number of batteries, the number of panels in series and in parallel, as well as to evaluate the joule losses due to cable heating and the switching losses of the multilevel inverters. This system is applied to a village named YAGOUA, located in the far north of Cameroon. The evaluation of the Joule effect and the switching losses as well as the regulation of the voltage level at the point of common coupling (PCC) are carried out in PVsyst and Matlab software, then at IEEE 33 bus. This algorithm reduced the Joule losses to 1.2% and the switching losses to 2.2%. A power of 210.4 MWh is produced, to be injected in the electrical network via an LCL filter. The THD calculation gave a rate of 3.015% in accordance with the 519 standards. Synchronization through the Phase Locked Loop (PLL) is performed. After the power was injected into the grid, the voltage and current remained in phase, showing the power factor correction and the efficiency of the filter. According to NASA meteorological data, the locality of YAGOUA gives the global solar irradiation forecast of 6.8 kW/m2.展开更多
This paper presents a powerful approach to find the optimal size and location of distributed generation units in a distribution system using GA （Genetic Optimization algorithm）. It is proved that GA method is fast a...This paper presents a powerful approach to find the optimal size and location of distributed generation units in a distribution system using GA （Genetic Optimization algorithm）. It is proved that GA method is fast and easy tool to enable the planners to select accurate and the optimum size of generators to improve the system voltage profile in addition to reduce the active and reactive power loss. GA fitness function is introduced including the active power losses, reactive power losses and the cumulative voltage deviation variables with selecting weight of each variable. GA fitness function is subjected to voltage constraints, active and reactive power losses constraints and DG size constraint.展开更多
Increased grid integration of photovoltaic(PV)has aggravated the uncertainty of distribution network operations.For a distribution network with PV,the impact of the PV location on the network power losses and voltage ...Increased grid integration of photovoltaic(PV)has aggravated the uncertainty of distribution network operations.For a distribution network with PV,the impact of the PV location on the network power losses and voltage fluctuations is investigated with analytical derivations reflected by the line impedance.Optimization approaches of the PV location with consideration of two aspects,i.e.,minimum network power losses and minimum voltage fluctuations,are analyzed.A particle swarm optimization(PSO)algorithm is used to synthesize an optimal compromised solution so as to determine the PV location.A 10 kV distribution network with one PV is established on the time-domain simulation environment PSCAD/EMTDC.The simulation results justify the theoretical analysis and indicate that when the active power of the PV is more/less than twice that of the overall loads/end loads,the network power losses and node voltage fluctuations are both minimum when the PV is integrated into the head/tail end of the network.When the active power of the PV is between the above two conditions,nodes t/f can be identified for the integration of the PV between the head/end nodes of the network to achieve the minimum network power losses/voltage fluctuations,respectively.The effectiveness of the proposed optimization approach is verified and can provide a reference for selecting the PV location in the distribution network.展开更多
The grid-connected or standalone PV central inverter architecture is comprised of several PV modules which are connected in different ways to form the PV array.The power generation capability of the PV array is primar...The grid-connected or standalone PV central inverter architecture is comprised of several PV modules which are connected in different ways to form the PV array.The power generation capability of the PV array is primarily affected by partial shading conditions(PSC).Due to PSCs,the power output of the PV array is dramatically reduced,and mismatching losses are induced in the PV modules.Based on the extent of these problems,multiple peaks also appear in the power-voltage(P-V)curve,which makes it very difficult to track the global maximum power point(GMPP).The main objective of this research paper is to model and simulate the series(S),series-parallel(SP),bridge-link(BL),honey-comb(HC),total-cross-tied(TCT)and proposed triple-tied(TT)solar PV array configurations under various partial shading scenarios.The performance of all PV configurations is evaluated under a uniform approach,considering eight different shading scenarios.The performance of the considered PV configurations is analyzed in terms of their mismatching power losses,fill factors,efficiency,global maximum power points(GMPPs),local maximum power points(LMPPs),voltages and currents at GMPPs,open circuit voltage and short circuit currents.The above-mentioned PV configurations are modeled and simulated in a Matlab/Simulink environment by considering the KC-200GT module parameters.展开更多
In this paper,we present a detailed procedure to determine the semiconductor losses for both structures of a shunt STATCOM(Static Compensator),STATCOM based on Current Source Inverter(CSI)and STATCOM based on Voltage ...In this paper,we present a detailed procedure to determine the semiconductor losses for both structures of a shunt STATCOM(Static Compensator),STATCOM based on Current Source Inverter(CSI)and STATCOM based on Voltage Source Inverter(VSI),both used for voltage unbalance compensation.As a first step,we study the VSI-based STATCOM and the CSI-based STATCOM used in high speed railway substations.Then we analyze the design and the sizing of the unbalance compensator in order to obtain an unbalance factor that does not exceed the limits imposed by the standards or by the energy provider.Following that,we compare the performances obtained with both structures VSI-STATCOM and CSI-STATCOM,after calculating the semiconductor power losses in the STATCOM converters.Finally,we validate our approach by simulation over real data of unbalance compensation caused by the new high-speed railway in Morocco.We use the tools MATLAB/Simulink/Simpowersys for performing our simulations.展开更多
Purpose:The increase in plug-in electric vehicles(PEVs)is likely to see a noteworthy impact on the distribution system due to high electric power consumption during charging and uncertainty in charging behavior.To add...Purpose:The increase in plug-in electric vehicles(PEVs)is likely to see a noteworthy impact on the distribution system due to high electric power consumption during charging and uncertainty in charging behavior.To address this problem,the present work mainly focuses on optimal integration of distributed generators(DG)into radial distribution systems in the presence of PEV loads with their charging behavior under daily load pattern including load models by considering the daily(24 h)power loss and voltage improvement of the system as objectives for better system performance.Design/methodology/approach:To achieve the desired outcomes,an efficient weighted factor multi-objective function is modeled.Particle Swarm Optimization(PSO)and Butterfly Optimization(BO)algorithms are selected and implemented to minimize the objectives of the system.A repetitive backward-forward sweep-based load flow has been introduced to calculate the daily power loss and bus voltages of the radial distribution system.The simulations are carried out using MATLAB software.Findings:The simulation outcomes reveal that the proposed approach definitely improved the system performance in all aspects.Among PSO and BO,BO is comparatively successful in achieving the desired objectives.Originality/value:The main contribution of this paper is the formulation of the multi-objective function that can address daily active power loss and voltage deviation under 24-h load pattern including grouping of residential,industrial and commercial loads.Introduction of repetitive backward-forward sweep-based load flow and the modeling of PEV load with two different charging scenarios.展开更多
During high-speed rotation,the surface of aeronautic spiral bevel gears will generate significant pressure and viscous forces,which will cause a certain amount of windage power loss and reduce the efficiency of the tr...During high-speed rotation,the surface of aeronautic spiral bevel gears will generate significant pressure and viscous forces,which will cause a certain amount of windage power loss and reduce the efficiency of the transmission system.Based on the computational fluid dynamics,this paper analyzes the windage power loss of a single spiral bevel gear and a spiral bevel gear pair under oil injection lubrication.In addition,the shroud is used to suppress gear windage loss,and the clearance size and opening angle of the designed shroud are optimized.Finally,by comparing and analyzing the experimental results,the following conclusions were obtained:(1)For a single gear,the speed is the most important factor affecting windage loss,followed by the hand of spiral,and rotation direction;(2)For gear pairs,under oil injection lubrication,the input speed has the greatest impact on windage power loss,followed by the influence of oil injection port speed,temperature and oil injection port pressure;(3)Installing a shroud is an effective method to reduce windage power loss;(4)In the pure air phase,the smaller the clearance between the shroud and the gear surface,and the smaller the radial direction between the shroud and the shaft,the better the effect of reducing windage;(5)In the two-phase flow of oil and gas,it is necessary to design oil drainage holes on the shroud to ensure the smooth discharge of lubricating oil and improve the drag reduction effect.展开更多
This study examines various issues arising in three-phase unbalanced power distribution networks(PDNs)using a comprehensive optimization approach.With the integration of renewable energy sources,increasing energy dema...This study examines various issues arising in three-phase unbalanced power distribution networks(PDNs)using a comprehensive optimization approach.With the integration of renewable energy sources,increasing energy demands,and the adoption of smart grid technologies,power systems are undergoing a rapid transformation,making the need for efficient,reliable,and sustainable distribution networks increasingly critical.In this paper,the reconfiguration problem in a 37-bus unbalanced PDN test system is solved using five different popular metaheuristic algorithms.Among these advanced search algorithms,the Bonobo Optimizer(BO)has demonstrated superior performance in handling the complexities of unbalanced power distribution network optimization.The study is structured around four distinct scenarios:(Ⅰ)improving mean voltage profile and minimizing active power loss,(Ⅱ)minimizing Voltage Unbalance Index(VUI)and Current Unbalance Index(CUI),(Ⅲ)optimizing key reliability indices using both Line Oriented Reliability Index(LORI)and Customer Oriented Reliability Index(CORI)approaches,and(Ⅳ)employing multi-objective optimization using the Pareto front technique to simultaneously minimize active power loss,average CUI,and System Average Interruption Duration Index(SAIDI).The study aims to contribute to the development of more efficient,reliable,and sustainable energy systems by addressing voltage profiles,power losses,reduction of imbalance,and the enhancement of reliability together.展开更多
Usually,rural areas can be electrified via three-phase distribution transformers with relatively large capacities.In such areas,low voltage lines are used for long distances,which cause power losses and voltage drop f...Usually,rural areas can be electrified via three-phase distribution transformers with relatively large capacities.In such areas,low voltage lines are used for long distances,which cause power losses and voltage drop for different types of consumers.Reducing losses and improving voltage profiles in rural distribution networks are significant challenges for electricity distribution companies.However different solutions were proposed in the literature to overcome these challenges,most of them face difficulties when applied in the conventional distribution network.To address the above issues,an applicable solution is proposed in this paper by installing a number of small-capacity distribution transformers instead of every single large-capacity transformer in rural areas.The proposed approach is implemented in the branch network of Al-Hoqool village,which belongs to the Nineveh distribution network.The network has been inspected on-site,drawn,and analyzed using the electrical systems analysis program(ETAP).The analysis showed that using the single-phase pole-mounted transformers can improve the voltage in the network’s end by 29%and enhance the voltage profile for all consumers.The analysis has also demonstrated that the modification can reduce the total power losses by 78%compared to the existing network.Concerning the economic aspect,the payback period for the proposed network is assigned to be 20 months.展开更多
The reduction of energy consumption is an increasingly important topic of the railway system.Energy-efficient train control(EETC)is one solution,which refers to mathematically computing when to accelerate,which cruisi...The reduction of energy consumption is an increasingly important topic of the railway system.Energy-efficient train control(EETC)is one solution,which refers to mathematically computing when to accelerate,which cruising speed to hold,how long one should coast over a suitable space,and when to brake.Most approaches in literature and industry greatly simplify a lot of nonlinear effects,such that they ignore mostly the losses due to energy conversion in traction components and auxiliaries.To fill this research gap,a series of increasingly detailed nonlinear losses is described and modelled.We categorize an increasing detail in this representation as four levels.We study the impact of those levels of detail on the energy optimal speed trajectory.To do this,a standard approach based on dynamic programming is used,given constraints on total travel time.This evaluation of multiple test cases highlights the influence of the dynamic losses and the power consumption of auxiliary components on railway trajectories,also compared to multiple benchmarks.The results show how the losses can make up 50%of the total energy consumption for an exemplary trip.Ignoring them would though result in consistent but limited errors in the optimal trajectory.Overall,more complex trajectories can result in less energy consumption when including the complexity of nonlinear losses than when a simpler model is considered.Those effects are stronger when the trajectory includes many acceleration and braking phases.展开更多
The paper reports quality analysis and evaluation at 6 - 10/0.4 kV low-voltage distribution grids in Uzbekistan. Power quality frequently does not correspond to the rated value which is largely due to unbalanced phase...The paper reports quality analysis and evaluation at 6 - 10/0.4 kV low-voltage distribution grids in Uzbekistan. Power quality frequently does not correspond to the rated value which is largely due to unbalanced phase loading in grids and which also results in increased power loss. The study of the asymmetrical operating modes of the rural distribution networks of 0.4 kV was conducted in three steps: measurement, calculations and analysis of relevant data;providing practical guidelines and finally, implementing instruments to normalize grid operation. Measuring was conducted using certified instrumentation analyzer “MALIKA” designed by authors. The study and analysis of additional power losses as the function of indicators of asymmetrical features of voltage and current in operating 0.4 kV grids reveals that, quality of electric power at grids under investigation, merely does not meet the requirements of the Interstate Standard.展开更多
This paper describes the principles of operation and the physical model of an advanced AC-DC converter generator （with the electronic converter acting as an AC-DC rectifier with reverse-conducting MOSFETs （metal-oxi...This paper describes the principles of operation and the physical model of an advanced AC-DC converter generator （with the electronic converter acting as an AC-DC rectifier with reverse-conducting MOSFETs （metal-oxide semiconductor field-effect transistors） as fast-electronic switches with a relatively low ON-state voltage drop） for HSVs. An AC-DC converter, when seen as an AC-DC rectifier, can be used in many fields, e.g., for multi-functional AC-DC/DC-AC convener generator^starter and conventional DC-AC convener motors and AC-DC converter generators or generator sets, welding machines, etc. The paper also describes a novel AC-DC convener, with reverse-conducting transistors and without the use of optoelectronic separation （which does not require a separate power supply）, which may be easily realized in IC （integrated-circuit） technology. Computer simulation allows for waveform evaluation for timing analysis of all components of the AC-DC-converter＇s physical model, both during normal operation as well as in some states of emergency. The paper also presents the results of bench experimental studies where the MOSFETs were used as fast-electronic switches with a relatively low ON-state voltage drop. For experimental studies, a novel AC-DC converter has been put together on the Mitsubishi FM600TU-3A module. The AC-DC converter with reverse-conducting transistors in a double-way connection has a lot of advantages compared to the conventional AC-DC convener acting as a diode rectifier, such as higher energy efficiency and greater reliability resulting from the lower temperature of electronic switches.展开更多
文摘The integration of distributed generations (DGs) into distribution systems (DSs) is increasingly becoming a solution for compensating for isolated local energy systems (ILESs). Additionally, distributed generations are used for self-consumption with excess energy injected into centralized grids (CGs). However, the improper sizing of renewable energy systems (RESs) exposes the entire system to power losses. This work presents an optimization of a system consisting of distributed generations. Firstly, PSO algorithms evaluate the size of the entire system on the IEEE bus 14 test standard. Secondly, the size of the system is allocated using improved Particles Swarm Optimization (IPSO). The convergence speed of the objective function enables a conjecture to be made about the robustness of the proposed system. The power and voltage profile on the IEEE 14-bus standard displays a decrease in power losses and an appropriate response to energy demands (EDs), validating the proposed method.
基金National Amorphous and Nanocrystalline Alloy Engineering Researeh Cease
文摘The dependences of the power loss per cycle on frequency f and amplitude flux density Bm have been investigated for the three main original magnetic states in five sorts of Fe-based nanocrystalline soft magnetic alloys in the ranges of 10 Hz<=f<=1000 Hz and 0.4 T<= Bm <=1.0 T. The total loss P is decomposed into the sum of the hysteresis loss Physt, the classical eddy current loss Pel and the excess loss Pexc. Physt has been found to be proportional to Bm^2 and f. The behavior of Pexc/f vs f being equivalent to P/f vs f clearly exhibits nonlinearity in the range not more than about 120 Hz, whereas the behavior of P/f vs f roughly shows linearity in the range far above 100 Hz and not more than 1000 Hz. In the range up to 1000 Hz, Physt is dominant in the original high permeability state and the state of low residual flux density, whereas Pexc in the state of high residual flux density is dominant in the wider range above about 100 Hz. The framework of the statistical theory of power loss has been used for representing the behavior of Pexc/f vs f. It has been found that the number n of the simultaneously active 'Magnetic Objects' linearly varies as n = n0 + Hexc/H0 as a function of the dynamic field Hexc in the range below about 120 Hz, whereas n approximately follows a law of the form n = n0 + (Hexc/H0)^m with 1 < m < 2 in the range far above 100 Hz and not more than 1000 Hz. The values of the field HO in principle related to the microstructure and the domain structure have been calculated for the three states.
文摘The aim of this paper is to determine the power losses recorded by a PV generator operating under partial shading conditions. These losses are evaluated through two distinct methods. The first method is based on mathematical modeling, while the second is based on Simulink’s physical model. The losses recorded are considerable and increase as a function of the increase in the percentage of shading up to a limit value where they become constant in the case where an ideal by-pass diode is connected in parallel with the modules. This limit value is non-existent in the case where the bypass diode is not ideal, which in fact corresponds to the real model. However, it emerges that the power losses are minimized in a PV system comprising bypass diodes, in particular in the case where the partial shading is considerable.
基金the DFG research training group GRK 1896 at Erlangen University and from the Joint Project Helmholtz-Institute Erlangen-Nürnberg(HI-ERN)for Renewable Energy Production under Project DBF01253,respectivelyfinancial support through the“Aufbruch Bayern”initiative of the state of Bavaria(EnCN and Solar Factory of the Future)and the“Solar Factory of the Future”with the Energy Campus Nürnberg(EnCN).
文摘In this report,we show that hyperspectral high-resolution photoluminescence mapping is a powerful tool for the selection and optimiz1ation of the laser ablation processes used for the patterning interconnections of subcells on Cu(Inx,Ga1-x)Se2(CIGS)modules.In this way,we show that in-depth monitoring of material degradation in the vicinity of the ablation region and the identification of the underlying mechanisms can be accomplished.Specifically,by analyzing the standard P1 patterning line ablated before the CIGS deposition,we reveal an anomalous emission-quenching effect that follows the edge of the molybdenum groove underneath.We further rationalize the origins of this effect by comparing the topography of the P1 edge through a scanning electron microscope(SEM)cross-section,where a reduction of the photoemission cannot be explained by a thickness variation.We also investigate the laser-induced damage on P1 patterning lines performed after the deposition of CIGS.We then document,for the first time,the existence of a short-range damaged area,which is independent of the application of an optical aperture on the laser path.Our findings pave the way for a better understanding of P1-induced power losses and introduce new insights into the improvement of current strategies for industry-relevant module interconnection schemes.
文摘The classical minimization of power losses in transmission lines is dominated by artificial intelligence techniques, which do not guarantee global optimum amidst local minima. Revolutionary and evolutionary techniques are encumbered with sophisticated transformations, which weaken the techniques. Power loss minimization is crucial to the efficient design and operation of power transmission lines. Minimization of losses is one way to meet steady grid supply, especially at peak demand. Thus, this paper has presented a gradient technique to obtain optimal variables and values from the power loss model, which efficiently minimizes power losses by modifying the traditional power loss model that combines Ohm and Corona losses. Optimality tests showed that the unmodified model does not support the minimization of power losses on transmission lines as the Hessian matrix portrayed the maximization of power losses. However, the modified model is consistent with the gradient method of optimization, which yielded optimum variables and values from the power loss model developed in this study. The unmodified (modified) models for Bujagali-Kawanda 220 kV and Masaka West-Mbarara North 132 kV transmission lines in Uganda showed maximum power losses of 0.406 (0.391) and 0.452 (0.446) kW/km/phase respectively. These results indicate that the modified model is superior to the unmodified model in minimizing power losses in the transmission lines and should be implemented for the efficient design and operation of power transmission lines within and outside Uganda for the same transmission voltages.
文摘The research reported in this paper focuses on non-technical power loss reduction for power distribution systems. Such reduction of costs of energy not served (ENS.COST), is intelligently evaluated and optimized using a firefly algorithm, from where savings of 43.3% on energy not served are achieved.
文摘We present a theoretic model to calculate skin depths and eddy-current power losses for a magnetic position sensor. Eddy-current, arised from the operation of an alternating-current excitation, induces secondary currents and fields between magnetic material and magnetic position sensor. In this paper, a magnetic position sensor system is simplified to be an outer-winding coil along the axial direction of a low carbon steel bar. The analytical model is derived from basic field and circuit theory considering a linear approximation for a nonlinear permeability. Thus the skin depths and eddy-current power losses from the model in eddy-current modeling techniques at various frequencies of an excited current source can be calculated. The proposed configuration is capable of predicting the skin depths and eddy-current power losses for a magnetic position sensor and has a consistence with experiments.
文摘In the design of the CAT 3408 engine, the Low Temperature (BT) circuits used to cool the engine lubricating oil and the charge air and the High Temperature (HT) circuits for cooling the cylinder liners, cylinder heads and body of turbofans are mainly used to cool the engine, so that it works properly. This work, based on the analysis carried out, to determine the lubrication compliance of the Yacco VX 100 - SAE 15 W-40 oil and that of the Camwater water used in the engine of the Boat Yang 1 by carrying out a series of conventional tests such as that: the density, the viscosity, the viscosity index, the flash point, the density, the sulphate center content, the water content, the total acidity index (TAN), total basic number (TBN) and pour point for the oil case and pH, hardness, sodium chloride content [NaCl], sodium sulphate content [NaSO<sub>4</sub>] for the water case which will be compared to the specified requirements to determine whether compliance is achieved for each of these characteristics. The results of the oil and water samples taken from the engine after use show that the used oil gives a specific gravity of 0.8822, a viscosity (at 40°C) of 92.29 mm<sup>2</sup>/s, a viscosity (at 100°C) of 13.99 mm<sup>2</sup>/s, a viscosity index (VI) of 155.39, a pour point -21°C, a Flash Point (VO) 215°C, a Sulfated ash content of 18%, a density 881.5 kg/m<sup>3</sup>, a total basic number (TBN) of 12.60 mgKOH/g, a Total Acid Index (TAN) of 3.096 mgKOH/g, a Water Content of 1.8 % and the water used gives a pH of 6.00, a hardness of 3.2 french degrees, a sodium chloride content [NaCl] of 0.468 mg/L, and a calcium sulphate content [CaSO<sub>4</sub>] of 2.38345 mg/L. the results of the water content and content of sulfated centers justify the thermal overload and power losses in the marine diesel engine CAT 3408 of the boat Yang 1 because of their values which are not in conformity with the standards.
文摘This paper presents a method for optimizing a grid-connected photovoltaic system through an LCL filter. An algorithm based on particle swarm optimization (PSO) is used to determine the number of batteries, the number of panels in series and in parallel, as well as to evaluate the joule losses due to cable heating and the switching losses of the multilevel inverters. This system is applied to a village named YAGOUA, located in the far north of Cameroon. The evaluation of the Joule effect and the switching losses as well as the regulation of the voltage level at the point of common coupling (PCC) are carried out in PVsyst and Matlab software, then at IEEE 33 bus. This algorithm reduced the Joule losses to 1.2% and the switching losses to 2.2%. A power of 210.4 MWh is produced, to be injected in the electrical network via an LCL filter. The THD calculation gave a rate of 3.015% in accordance with the 519 standards. Synchronization through the Phase Locked Loop (PLL) is performed. After the power was injected into the grid, the voltage and current remained in phase, showing the power factor correction and the efficiency of the filter. According to NASA meteorological data, the locality of YAGOUA gives the global solar irradiation forecast of 6.8 kW/m2.
文摘This paper presents a powerful approach to find the optimal size and location of distributed generation units in a distribution system using GA （Genetic Optimization algorithm）. It is proved that GA method is fast and easy tool to enable the planners to select accurate and the optimum size of generators to improve the system voltage profile in addition to reduce the active and reactive power loss. GA fitness function is introduced including the active power losses, reactive power losses and the cumulative voltage deviation variables with selecting weight of each variable. GA fitness function is subjected to voltage constraints, active and reactive power losses constraints and DG size constraint.
基金This work was supported by National Natural Science Foundation of China under Grant 51807091Natural Science Foundation of Jiangsu Province BK20180478+1 种基金the China Postdoctoral Science Foundation under Grant 2019M661846,EPSRC under Grant EP/N032888/1the International Science and Technology Collaborative Project of Policy Guidance Plan of Jiangsu Province under Grant BZ2018026。
文摘Increased grid integration of photovoltaic(PV)has aggravated the uncertainty of distribution network operations.For a distribution network with PV,the impact of the PV location on the network power losses and voltage fluctuations is investigated with analytical derivations reflected by the line impedance.Optimization approaches of the PV location with consideration of two aspects,i.e.,minimum network power losses and minimum voltage fluctuations,are analyzed.A particle swarm optimization(PSO)algorithm is used to synthesize an optimal compromised solution so as to determine the PV location.A 10 kV distribution network with one PV is established on the time-domain simulation environment PSCAD/EMTDC.The simulation results justify the theoretical analysis and indicate that when the active power of the PV is more/less than twice that of the overall loads/end loads,the network power losses and node voltage fluctuations are both minimum when the PV is integrated into the head/tail end of the network.When the active power of the PV is between the above two conditions,nodes t/f can be identified for the integration of the PV between the head/end nodes of the network to achieve the minimum network power losses/voltage fluctuations,respectively.The effectiveness of the proposed optimization approach is verified and can provide a reference for selecting the PV location in the distribution network.
基金This work was supported by the Science and Engineering Research Board(SERB),Department of Science and Technology,Government of India under the Grant No:ECR/2017/000316。
文摘The grid-connected or standalone PV central inverter architecture is comprised of several PV modules which are connected in different ways to form the PV array.The power generation capability of the PV array is primarily affected by partial shading conditions(PSC).Due to PSCs,the power output of the PV array is dramatically reduced,and mismatching losses are induced in the PV modules.Based on the extent of these problems,multiple peaks also appear in the power-voltage(P-V)curve,which makes it very difficult to track the global maximum power point(GMPP).The main objective of this research paper is to model and simulate the series(S),series-parallel(SP),bridge-link(BL),honey-comb(HC),total-cross-tied(TCT)and proposed triple-tied(TT)solar PV array configurations under various partial shading scenarios.The performance of all PV configurations is evaluated under a uniform approach,considering eight different shading scenarios.The performance of the considered PV configurations is analyzed in terms of their mismatching power losses,fill factors,efficiency,global maximum power points(GMPPs),local maximum power points(LMPPs),voltages and currents at GMPPs,open circuit voltage and short circuit currents.The above-mentioned PV configurations are modeled and simulated in a Matlab/Simulink environment by considering the KC-200GT module parameters.
基金Received:4 October 2019 Accepted:16 December 2019。
文摘In this paper,we present a detailed procedure to determine the semiconductor losses for both structures of a shunt STATCOM(Static Compensator),STATCOM based on Current Source Inverter(CSI)and STATCOM based on Voltage Source Inverter(VSI),both used for voltage unbalance compensation.As a first step,we study the VSI-based STATCOM and the CSI-based STATCOM used in high speed railway substations.Then we analyze the design and the sizing of the unbalance compensator in order to obtain an unbalance factor that does not exceed the limits imposed by the standards or by the energy provider.Following that,we compare the performances obtained with both structures VSI-STATCOM and CSI-STATCOM,after calculating the semiconductor power losses in the STATCOM converters.Finally,we validate our approach by simulation over real data of unbalance compensation caused by the new high-speed railway in Morocco.We use the tools MATLAB/Simulink/Simpowersys for performing our simulations.
基金Proposal Number:EEQ-2016-000263,Financially supported by Department of Science and Technology(DST),Science and Engineering Research Board(SERB),Govt.of India,New Delhi,India.
文摘Purpose:The increase in plug-in electric vehicles(PEVs)is likely to see a noteworthy impact on the distribution system due to high electric power consumption during charging and uncertainty in charging behavior.To address this problem,the present work mainly focuses on optimal integration of distributed generators(DG)into radial distribution systems in the presence of PEV loads with their charging behavior under daily load pattern including load models by considering the daily(24 h)power loss and voltage improvement of the system as objectives for better system performance.Design/methodology/approach:To achieve the desired outcomes,an efficient weighted factor multi-objective function is modeled.Particle Swarm Optimization(PSO)and Butterfly Optimization(BO)algorithms are selected and implemented to minimize the objectives of the system.A repetitive backward-forward sweep-based load flow has been introduced to calculate the daily power loss and bus voltages of the radial distribution system.The simulations are carried out using MATLAB software.Findings:The simulation outcomes reveal that the proposed approach definitely improved the system performance in all aspects.Among PSO and BO,BO is comparatively successful in achieving the desired objectives.Originality/value:The main contribution of this paper is the formulation of the multi-objective function that can address daily active power loss and voltage deviation under 24-h load pattern including grouping of residential,industrial and commercial loads.Introduction of repetitive backward-forward sweep-based load flow and the modeling of PEV load with two different charging scenarios.
基金Supported by National Natural Science Foundation of China(Grant Nos.51175422,61973011)Shaanxi Provincial Natural Science Basic Research Plan of China(Grant No.2022JM-195)+1 种基金Fundamental Research Funds for the Central Universities of Chinathe Research Start-up Funds of Hangzhou International Innovation Institute of Beihang University(Grant No.2024KQ036)。
文摘During high-speed rotation,the surface of aeronautic spiral bevel gears will generate significant pressure and viscous forces,which will cause a certain amount of windage power loss and reduce the efficiency of the transmission system.Based on the computational fluid dynamics,this paper analyzes the windage power loss of a single spiral bevel gear and a spiral bevel gear pair under oil injection lubrication.In addition,the shroud is used to suppress gear windage loss,and the clearance size and opening angle of the designed shroud are optimized.Finally,by comparing and analyzing the experimental results,the following conclusions were obtained:(1)For a single gear,the speed is the most important factor affecting windage loss,followed by the hand of spiral,and rotation direction;(2)For gear pairs,under oil injection lubrication,the input speed has the greatest impact on windage power loss,followed by the influence of oil injection port speed,temperature and oil injection port pressure;(3)Installing a shroud is an effective method to reduce windage power loss;(4)In the pure air phase,the smaller the clearance between the shroud and the gear surface,and the smaller the radial direction between the shroud and the shaft,the better the effect of reducing windage;(5)In the two-phase flow of oil and gas,it is necessary to design oil drainage holes on the shroud to ensure the smooth discharge of lubricating oil and improve the drag reduction effect.
基金supported by the Scientific and Technological Research Council of Turkey(TUBITAK)under Grant No.124E002(1001-Project).
文摘This study examines various issues arising in three-phase unbalanced power distribution networks(PDNs)using a comprehensive optimization approach.With the integration of renewable energy sources,increasing energy demands,and the adoption of smart grid technologies,power systems are undergoing a rapid transformation,making the need for efficient,reliable,and sustainable distribution networks increasingly critical.In this paper,the reconfiguration problem in a 37-bus unbalanced PDN test system is solved using five different popular metaheuristic algorithms.Among these advanced search algorithms,the Bonobo Optimizer(BO)has demonstrated superior performance in handling the complexities of unbalanced power distribution network optimization.The study is structured around four distinct scenarios:(Ⅰ)improving mean voltage profile and minimizing active power loss,(Ⅱ)minimizing Voltage Unbalance Index(VUI)and Current Unbalance Index(CUI),(Ⅲ)optimizing key reliability indices using both Line Oriented Reliability Index(LORI)and Customer Oriented Reliability Index(CORI)approaches,and(Ⅳ)employing multi-objective optimization using the Pareto front technique to simultaneously minimize active power loss,average CUI,and System Average Interruption Duration Index(SAIDI).The study aims to contribute to the development of more efficient,reliable,and sustainable energy systems by addressing voltage profiles,power losses,reduction of imbalance,and the enhancement of reliability together.
文摘Usually,rural areas can be electrified via three-phase distribution transformers with relatively large capacities.In such areas,low voltage lines are used for long distances,which cause power losses and voltage drop for different types of consumers.Reducing losses and improving voltage profiles in rural distribution networks are significant challenges for electricity distribution companies.However different solutions were proposed in the literature to overcome these challenges,most of them face difficulties when applied in the conventional distribution network.To address the above issues,an applicable solution is proposed in this paper by installing a number of small-capacity distribution transformers instead of every single large-capacity transformer in rural areas.The proposed approach is implemented in the branch network of Al-Hoqool village,which belongs to the Nineveh distribution network.The network has been inspected on-site,drawn,and analyzed using the electrical systems analysis program(ETAP).The analysis showed that using the single-phase pole-mounted transformers can improve the voltage in the network’s end by 29%and enhance the voltage profile for all consumers.The analysis has also demonstrated that the modification can reduce the total power losses by 78%compared to the existing network.Concerning the economic aspect,the payback period for the proposed network is assigned to be 20 months.
基金supported by Swiss Federal Office of Transport,the ETH foundation and via the grant RAILPOWER.
文摘The reduction of energy consumption is an increasingly important topic of the railway system.Energy-efficient train control(EETC)is one solution,which refers to mathematically computing when to accelerate,which cruising speed to hold,how long one should coast over a suitable space,and when to brake.Most approaches in literature and industry greatly simplify a lot of nonlinear effects,such that they ignore mostly the losses due to energy conversion in traction components and auxiliaries.To fill this research gap,a series of increasingly detailed nonlinear losses is described and modelled.We categorize an increasing detail in this representation as four levels.We study the impact of those levels of detail on the energy optimal speed trajectory.To do this,a standard approach based on dynamic programming is used,given constraints on total travel time.This evaluation of multiple test cases highlights the influence of the dynamic losses and the power consumption of auxiliary components on railway trajectories,also compared to multiple benchmarks.The results show how the losses can make up 50%of the total energy consumption for an exemplary trip.Ignoring them would though result in consistent but limited errors in the optimal trajectory.Overall,more complex trajectories can result in less energy consumption when including the complexity of nonlinear losses than when a simpler model is considered.Those effects are stronger when the trajectory includes many acceleration and braking phases.
文摘The paper reports quality analysis and evaluation at 6 - 10/0.4 kV low-voltage distribution grids in Uzbekistan. Power quality frequently does not correspond to the rated value which is largely due to unbalanced phase loading in grids and which also results in increased power loss. The study of the asymmetrical operating modes of the rural distribution networks of 0.4 kV was conducted in three steps: measurement, calculations and analysis of relevant data;providing practical guidelines and finally, implementing instruments to normalize grid operation. Measuring was conducted using certified instrumentation analyzer “MALIKA” designed by authors. The study and analysis of additional power losses as the function of indicators of asymmetrical features of voltage and current in operating 0.4 kV grids reveals that, quality of electric power at grids under investigation, merely does not meet the requirements of the Interstate Standard.
文摘This paper describes the principles of operation and the physical model of an advanced AC-DC converter generator （with the electronic converter acting as an AC-DC rectifier with reverse-conducting MOSFETs （metal-oxide semiconductor field-effect transistors） as fast-electronic switches with a relatively low ON-state voltage drop） for HSVs. An AC-DC converter, when seen as an AC-DC rectifier, can be used in many fields, e.g., for multi-functional AC-DC/DC-AC convener generator^starter and conventional DC-AC convener motors and AC-DC converter generators or generator sets, welding machines, etc. The paper also describes a novel AC-DC convener, with reverse-conducting transistors and without the use of optoelectronic separation （which does not require a separate power supply）, which may be easily realized in IC （integrated-circuit） technology. Computer simulation allows for waveform evaluation for timing analysis of all components of the AC-DC-converter＇s physical model, both during normal operation as well as in some states of emergency. The paper also presents the results of bench experimental studies where the MOSFETs were used as fast-electronic switches with a relatively low ON-state voltage drop. For experimental studies, a novel AC-DC converter has been put together on the Mitsubishi FM600TU-3A module. The AC-DC converter with reverse-conducting transistors in a double-way connection has a lot of advantages compared to the conventional AC-DC convener acting as a diode rectifier, such as higher energy efficiency and greater reliability resulting from the lower temperature of electronic switches.
