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This paper concerns the force density optimization for medium-stroke reluctance actuators applied in antivibration applications. The force density in a conventional E-core reluctance actuator is limited for medium strokes by the nonlinear force–displacement characteristic. In this paper, different tooth topologies are analyzed to maximize the force density along the stroke using the finite-element analysis. Teeth parameters are tuned in each topology to analyze the influences on the force density over a stroke of $\pm$12.5 mm. An analytic thermal model is used to estimate the surface temperature and is verified with finite-element simulations. The optimal topology is validated by experiments on a prototype. [ABSTRACT FROM AUTHOR]

A fast finite element (FE) based method for the calculation of eddy current losses in the stator windings of randomly wound electric machines is presented in this paper. The method is particularly suitable for implementation in large-scale design optimization algorithms where a qualitative characterization of such losses at higher speeds is most beneficial for identification of the design solutions that exhibit the lowest overall losses including the ac losses in the stator windings. Unlike the common practice of assuming a constant slot fill factor $s_f$ for all the design variations, the maximum $s_f$ in the developed method is determined based on the individual slot structure/dimensions and strand wire specifications. Furthermore, in lieu of detailed modeling of the conductor strands in the initial FE model, which significantly adds to the complexity of the problem, an alternative rectangular coil modeling subject to a subsequent flux mapping technique for determination of the impinging flux on each individual strand is pursued. Rather than pursuing the precise estimation of ac conductor losses, the research focus of this paper is placed on the development of a computationally efficient technique for the derivation of strand eddy current losses applicable in design optimization, especially where both the electromagnetic and thermal machine behavior are accounted for. A fractional-slot concentrated winding permanent magnet synchronous machine is used for the purpose of this study due to the higher slot leakage flux and slot opening fringing flux of such machines, which are the major contributors to strand eddy current losses in the windings. The analysis is supplemented with an investigation on the influence of the electrical loading on ac winding loss effects for this machine design, a subject that has received less attention in the literature. Experimental ac loss measurements on a 12-slot 10-pole stator assembly will be discussed to verify the existing trends in the simulation results. [ABSTRACT FROM AUTHOR]

With the wind power energy largely interconnected with power grid, it is necessary to develop a robust dynamic equivalent model of the wind farm for the system stability analysis and control. In this paper, a detailed wind farm model with doubly fed induction generators is established according to Western Electricity Coordinating Council benchmark test system. Then, the parameters identification process based on aggregation technique consisting of a hybrid algorithm combined improved-particle swarm optimization with improved-genetic algorithm is proposed for dynamic equivalent model development by using the measurement data from phasor measurement unit at the point of interconnection. Additionally, the robustness of the developed equivalent model is analyzed. The simulation results of the benchmark test system and IEEE-9 bus system demonstrate the effectiveness and robustness of the proposed equivalent modeling and identification methodology. [ABSTRACT FROM AUTHOR]

One of the next challenges for modular multilevel converters (MMCs) is how to the size the critical components to their limits with reduced design margins, while at the same time fulfilling the reliability target. To do it confidently, better thermal modeling with quantitative uncertainty analysis is necessary to support the decision-making during the product design stage. Regarding the conversion of long-term mission profiles into thermal profiles for reliability evaluation, this paper proposes a computationally efficient thermal modeling method for insulated-gate bipolar transistor modules in MMCs. The proposed method considers the impact of the inherent thermal unbalance and has minimum computation with quantitative error analysis. Finally, both simulations and experiments have verified the theoretical results. [ABSTRACT FROM AUTHOR]

Electrically excited synchronous machines have shown potential to be an alternative to permanent magnet synchronous machines in electromobility and wind power applications. High-frequency wireless power transferring technology enables a compact design of brushless exciters for the machine. In this paper, a dynamic model of high-frequency brushless exciters is proposed for the purposes of operating condition monitoring and excitation control. The modeling is done by using arithmetic and differential equations as well as considering different operation modes of the system. The operation modes are defined based on the physical behaviors of the excitation circuit. Experiments are performed to verify the model with variations of different circuit parameters. Furthermore, parameter sensitivity study, component parameter selection, and loss analysis are conducted to demonstrate the effectiveness of the model. The model is therefore proposed as an effective tool to assist the design and optimization of the brushless excitation system. [ABSTRACT FROM AUTHOR]

Electrical system dynamic modeling of associated components such as generators, turbines and other drivers, excitation systems, governors, and rotating loads requires countless engineering man-hours to determine the models' necessary parameters. Therefore, any reduction or simplification of the component dynamic models that can be performed, while assuring statistically equivalent analyses results, will reduce man-hours and modeling process duration. This paper addresses generator excitation system models, which include complex Laplace transfer functions typically provided in IEEE Std 421.5-2005, along with their simplification and parameter reduction by utilizing a novel sensitivity analysis method; the method yields a simplified IEEE model. It further addresses the process for digitizing hard copy trace recorder plots of power plant field test data. This paper then addresses the tuning process for obtaining optimized exciter model parameters. Finally, the original and simplified exciter models are used to perform system dynamic analysis on a stand-alone 6.9-kV microgrid with five large sequentially started induction motors powered from a 7-MW diesel generator with an IEEE type AC5A excitation system. The results of the two dynamic analyses validate the entire process by comparison with the sequential motor start test results. [ABSTRACT FROM PUBLISHER]

Modular multilevel converter (MMC) is believed the most competitive solution for high-voltage direct current (HVDC) transmission using voltage source converters. Circulating current suppressing strategies based on proportional resonant (PR) controllers are widely used in MMC. This kind of strategies can effectively eliminate all the circulating current components in MMC-HVDC. Unfortunately, it can result in dc-line voltage ripples under unbalanced grid conditions, and thus, deteriorates system performance and stability. Moreover, its existing control model may not exactly reveal the inherent characteristic of MMC, and consequently blocks the further understanding and application. To solve these two problems, first, this paper builds a new and effective control model for this strategy. Second, based on the new model, this paper studies the relationship between circulating current reference value and submodule capacitor voltage, modulation index, and arm current to correct and improve the current understanding of this control strategy. Finally, three improved strategies based on PR controllers are proposed. These improved control strategies can eliminate both circulating current and dc-line voltage ripples, which greatly enhance the fault ride-through capability of MMC-HVDC without adding extra control cost or the number of controllers. [ABSTRACT FROM AUTHOR]

Increased photovoltaic installations in densely built-up areas give rise to non-uniform irradiation causing partial shading. Non-uniform irradiation further leads to non-uniform temperature, leading to a reduction in output and the formation of deteriorating hotspots. A detailed model involving subcell level behavior is pivotal in understanding the impact of partial shading. In this paper, such a model is developed that analyzes the output of photovoltaic (PV) modules under different translucent and opaque shades while incorporating the diffused light effects. This model further includes the temperature variation of the module and also captures the bypass diode characteristics. The proposed model is experimentally validated for horizontal, vertical, slant, and patch shading patterns with varying shading intensities. This subcell model is shown to perform better than four existing methods of partial shading output prediction. It improves the output open-circuit voltage and short-circuit current prediction accuracy by more than 10% when compared with the average irradiance-based modeling approach, which is the best among the existing methods. Overall, an output prediction accuracy of more than 93% is achieved for opaque shading and more than 95% for translucent shading. As this paper provides the output of PV modules under partial shading, it finds direct application in partial shading detection, prevention of hotspots, and global maximum power point tracking, thereby enhancing their life and efficiency. [ABSTRACT FROM AUTHOR]

In this paper, the pulsewidth modulation switch method was used to investigate the effect of the transformer leakage inductance on the small-signal model in isolated full-bridge converter. A galvanic isolated hard-switching full-bridge converter that operates in constant-current mode is analyzed, confirming that leakage inductance significantly affects the small-signal model, and the influence of leakage inductance can be equivalent to a resistance in series with the converter's output LC filter just as that in phase-shifted full-bridge converter. However, the same leakage inductance in these both converters will lead to different equivalent resistance due to different operating principles. Results of the modified model, simulations, and the experiments are compared to verify the correctness of the model. Moreover, this paper also shows that the Norton equivalent circuit of the charger operates in constant current mode, which can be used to estimate the dynamic behavior of the system. [ABSTRACT FROM AUTHOR]

This paper proposes the novel scalable saturated model of synchronous permanent magnet machines, which combines ultrafast scaling laws with a saturated flux-linkage and loss model. The scalable model is used for the fast and accurate calculation of efficiency/loss maps and can also be used for drive cycle analysis including the calculation of energy consumption. It is verified by comparison with an existing state-of-the-art efficiency map and drive cycle analysis software. Additionally, an experimental verification of a saturated flux-linkage and loss model is presented. The additional possible usage of the scalable model is to find the optimal size of a scaled machine in order to meet the drive cycle performance and requirements of a traction motor. [ABSTRACT FROM AUTHOR]

Due to the short end windings of nonoverlap winding permanent-magnet (PM) machines, the end-winding inductance component is generally ignored in the design. In most cases, the end-flux fringing effects in PMs are also not taken into account. It is shown in this paper that these end effects have a significant influence on the performance parameters of the machine. In this paper, several nonoverlap winding PM machines are considered with respect to the effects of end-winding inductance and PM end-flux fringing. A number of calculation methods for the per-phase end-winding inductance of the machines are compared. A new simple analytical calculation method is proposed, which is shown to give a relatively good prediction of the end-winding inductance compared with 3-D finite-element (FE) results. It is proposed in this paper that the PM strength should be reduced by a certain fringing factor to take the end-flux fringing effects into account in the 2-D FE analysis. Practical measurements are also presented to validate the FE calculations and to give an indication on the effects that are caused by the end-winding inductance and the PM end-flux fringing. [ABSTRACT FROM AUTHOR]

The introduction of communication systems to power system controllers has brought in another layer of complexity in their design and operation. In this paper, a plug-in hybrid electric vehicle charging facility is studied. A linearized model of the facility is built, including both the dc/dc and dc/ac converters of the distributed energy resources. In addition, a control strategy that includes both local and networked loops is proposed to monitor and control the dc bus voltage of a local energy storage unit. This dc bus voltage is crucial to the self-sustaining capabilities of the system. A review of challenges and opportunities in networked control systems is presented, and the impacts of communication factors to the charging facility stability are analyzed. Finally, a real-time simulation platform which combines both electrical and communication networks is presented to validate the small-signal model, control strategy, and stability analysis including the communication effects. [ABSTRACT FROM PUBLISHER]

In this paper, two designs of interior permanent-magnet synchronous machine (IPMSM) for sensorless drive with absolute rotor position estimation capability are proposed. A conventional IPMSM design proposed for the same purpose had a demerit that for the absolute position estimation, the rotor should initially stroke for 100 degrees in the worst case. Using the proposed IPMSMs featuring asymmetric winding and asymmetric rotor geometry, the initial stroke of the rotor can be reduced to 30 degrees. Moreover, basic characteristics of the motor such as torque ripples and harmonics of electromotive force (EMF) are conspicuously improved. The proposed designs are evaluated by rigorous finite-element analyses and experimental tests. An analytical model of the proposed motors considering their asymmetric structures is also developed and provided in this paper. [ABSTRACT FROM AUTHOR]

Electrical incidents occur globally, providing valuable opportunities for practical-knowledge-based learning and improvements. The underlying root causes of an incident are not always apparent, and an incident investigation method or a loss causation model is required to analyze the facts gathered from an incident. It is important that an incident investigation is effectively executed in order to add value. An ineffective investigation may lead to recurrent incidents and the wastage of resources. Investigators performing an incident investigation can be biased and subjective. Incident investigation methods can be also subjective. Adequately resolving root causes is another subjective area. In order to mitigate subjectivity and biases, various models such as the cause and effect diagram, the five whys method, the sequential cause analysis technique, the management oversight and risk tree, effects and causal factor charting, change analysis, barrier analysis, and casual factor analysis are examined. This aims to improve knowledge on the application of a technique and to establish a review method to determine the effectiveness of an incident investigation process. The review method consists of the development of survey-type questions that can be applied to industry, and this serves as the aim of this research paper. [ABSTRACT FROM PUBLISHER]

This paper presents a semicircular tubular linear machine model, which is called a circular shaft motor (CSM), with trapezoidal magnets. For a conventional CSM system, the stator is difficult to construct as designed, and the thrust characteristics are not high enough. The proposed CSM model includes trapezoidal magnets that are magnetized in the axial direction. This structure can facilitate the construction of the stator and decrease the thrust ripple. In addition, the magnetic flux characteristics are shown as new results of a CSM. Magnetic field is related to thrust characteristics closely. By investigating magnetic distribution characteristics, it is shown that the proposed model can improve magnetic field characteristics. In this paper, the structure of the proposed CSM model is described. The improvement in the thrust characteristics is verified by magnetic field analysis. The thrust characteristics of the proposed CSM system are verified in a thrust characteristics test. The magnetic flux characteristics of the proposed CSM system are compared with those of a conventional CSM system to evaluate the thrust characteristics. [ABSTRACT FROM PUBLISHER]

The purpose of this paper is to compare two optimization approaches, used for the research of optimal configurations of electrical machines. The first one uses a single multiphysical model, called “reference model,” directly used by a classical optimization routine. The second approach proposes the use of a second surrogate model in association with the previous reference model. This second configuration corresponds to the space mapping (SM) methodology. In both cases, models involved are multiphysical descriptions of the main phenomena occurring in electrical machines. They consider electrical, magnetic, thermal, and mechanical aspects. They use different modeling techniques (analytical relations, lumped parameter networks, and finite-element analyses), depending on the physics to be described. Appropriate coupling strategies between these different submodels are chosen to get the best results in the framework of the SM methods. This paper evaluates both approaches by a comparison of the corresponding computation costs, evaluated by the number of evaluations of the fine (reference) model. The paper shows that SM-like methods allow faster optimization processes and require a smaller number of evaluations (of the reference model) and lead to similar final machine designs. The use and the comparison of these two approaches is illustrated through the optimal sizing of an automotive electrical machine. [ABSTRACT FROM AUTHOR]

Storage is being proposed to solve many issues on the electric power grid, especially those issues related to renewable generation such as wind and solar generation. Some North American state and provincial regulators are requiring large amounts of storage to be installed to support anticipated needs of the power grid. Much of that new storage is expected to be connected to distribution feeders. Distribution planners lack tools and methods to assess storage impact on distribution system capacity, reliability, and power quality. Planners are accustomed to static power flow calculations, but accurate analysis of storage requires sequential-time simulation. This paper describes modeling storage for various types of simulations on distribution systems for different time frames typically involved. The basic impact on capacity and voltage regulation can generally be evaluated in simulations with 15-min to 1-h intervals. Evaluations of smoothing of renewable generation variations may require simulations with time step sizes of 1 min or less. Evaluations of such things as frequency control of microgrids and performance during transient disturbances will require dynamics analysis in intervals ranging from seconds down to microseconds. This paper is a summary of recent Electric Power Research Institute research in modeling energy storage for planning studies. [ABSTRACT FROM PUBLISHER]

This paper presents the stability analysis of dc distributed power systems with multiple converter-controlled loads. The load converters are tightly controlled, behaving as constant power loads with low-damped $LC\;$ filters. The dynamic behavior of the system in high frequency range is often not studied with the classical tools based on conventional averaging techniques. However, dc power systems with the reduced size filter, and consequently, the high resonant frequency, are widely used in transportation applications. In this paper, the stability analysis of the system is established based on a discrete-time model of the system, taking into account the switching frequency and intrinsic nonlinearities of the system model. The impacts of the filter parameters and interactions among the constant power loads are investigated with the proposed discrete-time method. Moreover, an active stabilizer is developed and included in the dynamic model of the system, in order to extend the stability margin. The theoretical observations are then validated experimentally on a laboratory hardware prototype. [ABSTRACT FROM AUTHOR]

Due to the low-frequency oscillation (LFO) between traction network and electric multiple units (EMUs) of high-speed railway, many traction blockades occur in different EMU depots. Aiming at this problem, the mathematical model and small-signal analysis model of EMUs-traction network cascade system (ETNCS) are built in this paper. The system stability mainly affected by the electrical coupling between source and load module is analyzed and discussed in detail. Considering the autotransformer leakage reactance, traction network impedance, and distributed capacitance, the output source module resistance of ETNCS is calculated based on the generalized symmetrical component method. Using the generalized Nyquist criterion and Bode diagram, the ETNCS's stability is analyzed and the quantitative indicators of system impedance matching are given. Then, the simulation model of full ETNCS is built in this paper, which can reproduce the LFO phenomenon. In addition, the theoretical analysis results and the feasibility of inhibition for LFO are verified based on MATLAB/simulink simulation. Finally, the LFO signal modal analysis is implemented by using Prony and estimating signal parameters via rotational invariance techniques (ESPRIT) methods. The conclusions show that the proposed stability and modal analysis methods could be used not only to analyze the LFO more clearly, but also to provide the technical reference for the stable operation of EMUs. [ABSTRACT FROM PUBLISHER]

This paper presents a comprehensive solution that allows a wirelessly connected electric vehicle (EV) to be autonomously charged and discharged, during long-term parking and/or transient stops. A bilayer power flow controller for bidirectional wireless power transfer system (BWPTS) in EVs applications is proposed. The proposed controller can manage the power flow between the EV and surrounding infrastructures, such as utility grid, home micro-grid, building micro-grid, road, or another vehicle. It consists of two control layers; the first is responsible for communicating with the surrounding infrastructures and gathering information from the vehicle operator, charging station, utility grid, and battery management system. These data are analyzed to generate the reference power signal with information about the mode of operation (charge, discharge, or abstain) and rate. The second layer receives the reference signal and predicts the control parameters for the resonant converters (on both the vehicle and grid sides) to track the desired power. The proposed algorithm is adaptively estimating the mutual inductance to consider the misalignments in the system, based on a new simple real-time mutual estimation algorithm using a single voltage measurement from the vehicle side. The second control layer is designed based on an accurate analytical model for the BWPTS's power flow. For verification purposes, a prototype for BWPTS was built and driven by the proposed controller, which was implemented using a field-programmable gate array integrated circuit. Also, a vehicle-level simulation was performed to validate the operation of the proposed controller in quasi-dynamic wireless charging at traffic signals. The proposed controller shows fast and stable response during both the transient and steady-state operation in comparison with the conventional proportional-integral controller. [ABSTRACT FROM AUTHOR]

This paper proposes a unified approach based on modal control theory to design damping controllers of a thyristor-controlled series capacitor (TCSC) for stabilizing the inherent common-mode torsional interactions occurred in a series-capacitor compensated power system. The studied power system includes two nonidentical turbine-generator sets connected to an infinite bus through a common series-capacitor compensated transmission line. The employed TCSC is properly connected in parallel with a part of the series-capacitor bank of the compensated transmission line. The damping controllers of the TCSC employ the speed deviations of both turbine-generator sets as input signals to stabilize unstable torsional modes of the studied system by increasing the damping of these modes. Both frequency-domain approach based on eigenvalue analysis and time-domain scheme based on nonlinear-model simulations under different disturbance conditions are systematically performed. It can be concluded from the simulated results that the employed TCSC joined with the damping controllers designed by using modal control theory can effectively stabilize the common-mode torsional oscillations of the studied series-capacitor compensated system. [ABSTRACT FROM AUTHOR]

With the emergence of dense power due to the use of relatively low-voltage infrastructures, which are becoming more common in distribution networks, the risks related to low-voltage arc flash are drawing more attention. Arc voltage, as the critical factor in arc flash mitigation, is strongly related to the determination of insulation distance and re-striking voltage level. However, while much attention has focused on the need for hazards calculation and the selection of appropriate personal protective equipment, the physical characteristics of arc has received relatively little attention. Although some related researches have been carried out in high-voltage arc faults with long gaps, the medium–low arc faults, which have more dynamic nature, is rarely to be investigated. To comprehensively analyze the voltage characteristics of medium–low-voltage arc fault in short gaps, this paper discussed the mathematical approach for arc voltage modeling. To achieve the reliable model parameters, the magnetohydrodynamic simulation method is explored as the amendment for mathematical model. Moreover, in order to have an easy application for on-site practice, a concisely alternative model for arc voltage gradient calculation is developed. The fitting result shows the model has a good ability to accurately estimate the voltage gradient of medium–low-voltage short arc. [ABSTRACT FROM AUTHOR]

A semicircular linear motor that realizes a motion along circumference of the circle has been developed. To settle the optimal design of this motor by mathematical analysis, the theoretical equation of motor performance has to be clarified. In this paper, the mathematical modeling of semicircular linear motor is carried out from the viewpoint of Lorentz force and magnetic flux density derived by vector potential. By comparing calculated, analyzed, and measured magnetic flux density and thrust force, the validity of derived mathematical model is confirmed. In addition, the cause of difference among three results is also discussed. [ABSTRACT FROM AUTHOR]

With the increase of the train speed, the pantograph-catenary (PC) detachment becomes more frequent, which results in more serious PC detachment arc. In order to analyze the influence of PC detachment arc on the train system, several arc models are established. However, these models do not consider the actual PC detachment process. In this paper, an extended black-box model of PC arc is proposed, which considers the dynamic detachment process of PC based on the PC dynamics. First, the Habedank arc model is presented and the relationship of the PC detachment distance with the arc voltage and arc dissipated power is established. Next, the dynamic detachment trajectory is obtained from the dynamic simulation of the PC structure model. Then, by introducing the dynamic PC detachment trajectory model into the arc model, the dynamic arc model is built. Finally, the performance of the arc current and arc voltage is analyzed and the effectiveness of the dynamic arc model is verified. [ABSTRACT FROM AUTHOR]

This paper presents a methodology of the battery modeling based on experimental tests results. As a main contribution, authors conducted an analysis of the main constraints and effects of each parameter of the batteries model on its behavior and lifetime. This can help to improve the accuracy of the model. Due to its capability to model the recovery effect and the rate-capacity one, the kinetic battery model serves as the basis of the study. Results of experimental tests are used to realize the analysis and to define the suitable methodology of batteries parameters identification. These last can serve for prediction and estimation of the battery lifetime according to the actual operating conditions, particularly in microgrid and distributed systems. [ABSTRACT FROM AUTHOR]

This paper presents the effects of installing variable current-limit reactors (CLRs) and adjusting load tap changers (LTCs) on the performance of a commercial wind farm in Taiwan using computer simulations. The companion paper (Part I) demonstrates the field-measured results, simulation model, and simulation results of the studied Jang-Bin wind farm with 23 2-MW doubly fed induction generator-type wind turbine generators connected to the utility system through a 23/161-kV 60-MVA step-up main transformer (MT) from six feeders. Six CLRs, which were originally designed to limit short-circuit currents under faulted conditions, are connected in series with the six feeders. The LTCs of the MT are used to adjust/regulate the secondary-side voltage at the 23-kV bus. Some simulated steady-state and transient results of the studied wind farm with variable values of the proposed CLRs and LTCs are analyzed and compared. [ABSTRACT FROM PUBLISHER]

Series-dc collection and transmission is suggested to be competitive for remote offshore wind farms. However, severe overcurrent, overvoltage, and other impacts that arise from faults cause challenges on system protection, which have not been fully studied yet. In this paper, simplified equivalent circuits are developed for fault analysis, based on which analytical models for fault transients are derived. The expressions can be used for stress estimation, as well as provide insight in understanding the mechanism of fault propagation. A cost-effective protection scheme characterized by a breakerless design is proposed. Parameter selection for stress mitigation is also discussed. Simulation results verify that the proposed fault protection and stress mitigation design is effective for such a series-dc system. [ABSTRACT FROM AUTHOR]

This paper investigates the modeling methods for the structural design optimization of permanent magnet synchronous linear motors (PMSLMs), which are applied to linear motion machines. First, an initial PMSLM model is established by finite element analysis (FEA), and the data space is obtained for subsequent rapid regression modeling. Second, a powerful regression machine learning method, that is, distance-weighted K-nearest neighbor algorithm (DW-KNNA), is introduced to establish a calculation model by grasping the nonlinear relationships between input structural parameters and output motor performances. Model comparison experiments among analytical method, response surface method, K-nearest neighbor algorithm, and DW-KNNA demonstrate the superiority of the DW-KNNA. Finally, the differential evolution algorithm is used to determine the best combination of structural parameters and performances. The FEA and prototype motor experiments proved the validity and advantages of the proposed method. [ABSTRACT FROM AUTHOR]

While the use of foil windings in transformers and air core inductors is not uncommon, their use in electric machines is just emerging. Although prototype realizations have been reported in the literature, a definitive analysis of their thermal performance is necessary to evaluate their potential for broad applications. This paper is devoted to presenting a comprehensive model for evaluating their thermal performance including loss modeling and temperature rise prediction in realistic designs. An overview of foil windings in electric machines and their advantages in improved fill factor is presented, along with experimental results that compare the ac losses and temperature distribution under identical steady-state operating conditions with a prototype round conductor coil and foil conductor coil. A lumped parameter thermal model that predicts the heat transfer behavior of the foil conductor coil is presented along with supporting experimental results. [ABSTRACT FROM AUTHOR]

In this paper, an integrated model for acoustic evaluation of electric vehicles is introduced. The paper focuses on the force excitation part of the model. The analysis is performed for permanent magnet synchronous machines. The excitation forces are placed on the stator teeth and calculated for a structure dynamic model of the power train. A model for the acoustic emission is adapted, and finally, the psychoacoustical behavior is characterized at the position of the driver of the e-car. An approach for the design of the rotor pole topology is introduced to ensure a beneficial acoustic behavior under consideration of air gap flux density and related force densities on the stator teeth. The calculation is performed using finite-element analysis simulation, but also analytical design methods are considered. Objective of this comparison is a very short computation time and, therefore, an efficient simulation process. The model is validated by measurements on test benches. [ABSTRACT FROM PUBLISHER]

Lesnicar and Marquardt introduced a modular multilevel converter (MMC) topology back in 2003. Although this topology has received a great deal of attention in recent years by both the research community and industry, hitherto no steady-state model has been developed which accurately captured all the relevant power losses while being computationally light. Hence, the aim of this paper is to introduce a fast MMC loss model which captures the key sources of power losses in steady-state operation. The proposed model was compared to a loss model developed by Marquardt. Both models presented similar results under the same assumptions. However, the proposed model captures the switching losses more realistically and considers the temperature of operation of the electronics, as well as the losses of the inductors and cooling system, in the overall efficiency of the MMC. To validate these new additions, the proposed steady-state model was compared to a dynamic model. Once again, the proposed model was able to capture the different sources of power losses. Nonetheless, results demonstrated that the balancing strategy greatly influences the efficiency of the MMC. Therefore, information regarding the envisioned control strategy is necessary to accurately calculate the efficiency curve of the MMC. [ABSTRACT FROM AUTHOR]

Axial structures of the hysteresis motors, similar to the other axial types of electrical machines, have some outstanding characteristics with regard to radial structures, such as higher torque-to-weight ratio, excellent efficiency, adjustable airgap, and balanced rotor–stator attractive forces. Since the accurate measurement of the hysteresis machine characteristics by prototyping and testing is expensive and time consuming, in this paper, the finite-element analysis is adopted for the prediction and analysis of an axial flux hysteresis motor. The analysis is conducted based on the elliptical approximation of the hysteresis loop. Since the elliptical approximation is not able to model the saturation of the hysteresis loop, an iteration-based method is proposed to overcome this problem and increase the analysis accuracy. Finally, in order to investigate the proposed model accuracy, the device is prototyped, whose experimental results agree well with those extracted from the analytical model. [ABSTRACT FROM AUTHOR]

This paper deals with the design of a synchronous reluctance motor suited for hybrid electric vehicles. The focus is mainly on rotor design: the angles of the flux barrier ends are chosen with the aim of reducing the torque ripple due to the slot harmonics. A comparison among different rotor arrangements (one, two, and three flux barriers per pole) is presented. Furthermore, an improvement in terms of low ripple and high average torque is given owing to the “Machaon” configuration. The current vector control method is used to maximize the torque according to the voltage and current constraints, taking into account the saturation effects. The impact of the electrical design on the mechanical characteristics of the rotor (natural frequencies) is discussed as well. At last, the predicted mechanical characteristics of the reluctance motor are presented: torque versus speed behavior, power losses, and power factor. The efficiency map of the machine is also reported in the whole operating region. [ABSTRACT FROM PUBLISHER]

The accuracy of a microbalance is highly dependent on the level of floor vibrations. One strategy to reduce floor vibrations is a magnetic vibration isolator. Magnetic vibration isolators have the possibility to obtain a zero-stiffness region, which is beneficial for attenuating vibrations. In this paper, a 3-D analytical magnetic surface charge model is used to calculate the spring characteristics of a cone-shaped magnetic vibration isolator for different angles. [ABSTRACT FROM AUTHOR]

In this paper, the economic analysis of a real-time power flow control algorithm for charging a large-scale plug-in electric vehicles (PEVs) network is proposed. Such a system is in an urban area power system with optimized renewable energy resources in South Florida. In this model, the PEVs charging rates are controlled by a central aggregator through wireless communication. To limit the impact of the PEVs' charging to the utility grid, while optimizing the scheduling of vehicle-to-grid (V2G) frequency regulation services, a V2G intelligent power flow management algorithm based on fuzzy logic control was developed. The smart charging system will improve the power system stability and robustness while bringing benefits to the utility ac grid, the PEVs network, and its customers. An economic analysis model was built with the consideration of the battery degradation and capital cost. The proposed smart charging algorithm was tested with a 50 000 PEVs network model. The simulation results show the effectiveness and economic value of the proposed model. [ABSTRACT FROM AUTHOR]

With the aid of finite-element and analytical methods, this paper investigates the influence of static/rotating eccentricities on the cogging torque of permanent-magnet machines having various pole/slot number combinations (2p/Ns), including fractional-slot topologies, such as 2p = Ns\pm 1, 2p = Ns\pm\break 2, and 2p/Ns = 8/12, as well as an integer-slot machine 2p/Ns = 4/12. It is found that the influence of eccentricity reduces significantly with the number of structure cyclic symmetry, which is equal to the greatest common divisor of slot and pole numbers. Hence, the eccentricity shows the largest influence in machines having 2p = Ns\pm 1, small influence in machines having 2p = Ns\pm 2, and the smallest influence in the other machines. The static and rotating eccentricities result in cogging torque components multiples of $(2p)$th and (N_{s})th orders, respectively. Both static and rotating eccentricities produce similar cogging torque magnitude. The experimental results validate the FE and analytical investigation. [ABSTRACT FROM PUBLISHER]

In this paper, an analytical model in the $dq$ reference frame is developed to recognize the steady state of the self-excited reluctance generator considering no-load and resistive load conditions. A fast method to estimate the minimum capacitance requirement is proposed. Experiments have been carried out to verify the analytical results. After that, attention is paid to the capability of self-excitation in the reluctance generator with different residual magnetisms in the rotor. Different levels of residual rotor magnetism are achieved by different magnetizing dc currents. An indicative value of phase current is defined to determine the self-excitation and the required minimum residual rotor magnetism for self-excitation in the reluctance generator connected with different capacitances is discussed. At last, the capability of self-excitation in the reluctance generator by connecting charged capacitors is investigated. [ABSTRACT FROM AUTHOR]

In this paper, the authors introduce a semianalytical model for the analysis and the design of a permanent magnet (PM) tubular linear generator intended for electrical energy generation from sea waves. The translator of the analyzed machine is constituted by axially magnetized ferrite PMs with alternating polarity and soft magnetic pole pieces in between; a two-pole, double-layer, three-phase winding is located in the slots of the stator. The presented model, based on the use of the Carter coefficient and of the Fourier transform in the direction of the motion, is able to take into account the end effects due to the finite length of the stator. The presence of slots and teeth is subsequently considered by some postprocessing calculation carried on the results of the semianalytical model. Comparison with a finite element analysis and measurements taken on a prototype has been performed to validate the presented model. The model can be easily extended to other translator typologies, e.g., to air core translator with Halbach array of NdFeB PMs. [ABSTRACT FROM AUTHOR]

This paper presents a novel distributed approach to achieve both bounded voltage and accurate reactive power sharing regulation in ac microgrid. The coupling/trade-off effects between bus voltages and reactive power sharing regulation are first analyzed in detail to provide a guideline for coordinated control design. Furthermore, a containment and consensus-based distributed coordination controller is proposed, by which the bus voltage magnitudes can be bounded within a reasonable range, instead of only controlling average voltage value. Furthermore, the accurate reactive power sharing between distributed generators can be achieved simultaneously. Then, a detailed small-signal model is developed to analyze the stability of the system and the sensitivity of different parameters. Experimental results are presented and compared, where the controller performance, robust performance under communication failure, and plug-and-play operation are successfully verified. [ABSTRACT FROM PUBLISHER]

This paper presents a novel reactive-power minimization method under the three-level modulated phase-shift control to improve the efficiency for a wide operation condition. First, in order to unify all operation modes, a mathematic model of the dual-active-bridge converter with the three-level modulated phase-shift control by a harmonic analysis method is obtained. Then, the detailed analysis of the odd-order harmonic components of the active and reactive powers varied with the multiple control dimensions is presented. The soft-switching boundaries with respect to the voltage ratio and unified active power are specified. On this basis, a novel optimal three-level phase-shift (OPS) control strategy for minimizing reactive power is proposed. Experimental results of reactive power and operation efficiency among the proposed OPS method, and other methods are compared to verify the effectiveness of the OPS algorithm. [ABSTRACT FROM PUBLISHER]

Electric vehicle (EV) can act as an energy consuming device or a distributed energy resource in the concepts known as vehicle-to-grid (V2G) and grid-to-vehicle (G2V). The bidirectional wireless power interface is a successful choice for this application, since it provides automatic, reliable, and safe operation. Therefore, this paper presents modeling and assessment analysis for the steady-state performance of bidirectional inductive wireless power transfer system (BIWPTS) in EV implementations. The analysis is presented for the three main compensation configurations: LC-series, LC-parallel, and LCL-topology. Moreover, the steady-state equivalent circuit-based mathematical models for all topologies are developed. These models were used to precisely determine the system response during V2G and G2V operations based on Fourier series. The study presents evident criteria to pick among the different BIWPTS structures in the diverse applications. The proposed analyses were verified both in simulation and experiment. The results demonstrate the ability of the proposed models to provide accurate estimation for BIWPTS performance under various operating and control conditions. Also, the evaluation analysis shows that LCL-topology is more appropriate for the bidirectional operation due to the simple design and control requirements, and being less sensitive to the misalignment. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach in the modeling of efficiency maps for electrical machines. It is based on using the sum of terms in the form of kmnTmωn to represent the variation of the stator and rotor copper, iron, and magnet losses with torque and speed. The effect of each term on the shape of the efficiency map is explored. Analysis is performed on the calculated efficiency and loss maps of an induction, an interior permanent magnet, and a surface permanent magnet machine to demonstrate the validity of the approach. [ABSTRACT FROM AUTHOR]

Despite a strong nonlinear behavior and a complex design, the interior permanent-magnet (IPM) machine is proposed as a good candidate among the PM machines owing to its interesting peculiarities, i.e., higher torque in flux-weakening operation, higher fault tolerance, and ability to adopt low-cost PMs. A second trend in designing PM machines concerns the adoption of fractional-slot (FS) nonoverlapped coil windings, which reduce the end winding length and consequently the Joule losses and the cost. Therefore, the adoption of an IPM machine with an FS winding aims to combine both advantages: high torque and efficiency in a wide operating region. However, the combination of an anisotropic rotor and an FS winding stator causes some problems. The interaction between the magnetomotive force harmonics due to the stator current and the rotor anisotropy causes a very high torque ripple. This paper illustrates a procedure in designing an IPM motor with the FS winding exhibiting a low torque ripple. The design strategy is based on two consecutive steps: at first, the winding is optimized by taking a multilayer structure, and then, the rotor geometry is optimized by adopting a nonsymmetric structure. As an example, a 12-slot 10-pole IPM machine is considered, achieving a torque ripple lower than 1.5% at full load. [ABSTRACT FROM PUBLISHER]

This paper deals with an improved analytical model of synchronous reluctance (REL) machine considering rotor eccentricity. This model considers the magnetic saturation in the iron parts of both the stator and the rotor. This saturation results from the actual B–H characteristic of the iron. In addition, the slotting effect is considered in the analytical model. The unbalanced magnetic force (UMF) on the rotor is accurately estimated. Furthermore, the impact on the estimated UMF due to the slotting effect and the magnetic saturation is studied. Both static and dynamic eccentricity cases are considered. As an example, a four-pole 36-slot REL motor with three flux-barriers per rotor pole is considered. Experimental measurements confirm the results achieved by means of both finite-element analysis and the improved analytical model. [ABSTRACT FROM AUTHOR]

Despite transverse-flux machines (TFMs) being intrinsically three-dimensional, it is still possible to analyze them using relatively simple analytical models. This paper aims to provide an insight into the behavior of TFMs using a compact equation, which relates torque to the electric and magnetic loadings of the machine and a flux factor. The flux factor is also used to estimate the flux linkage and therefore the power factor of this kind of machine. It is shown that the low power factor of TFMs is not only due to leakage, but also due to the nature of the electromagnetic interaction that takes place. The TFM developed at the University of Southampton is used as the basis of a case study to illustrate the tradeoff between torque density and power factor, and to provide some design guidelines. The analytical results are verified using finite elements analysis and experimental data. [ABSTRACT FROM AUTHOR]

This paper examines the performance of a three-phase interior permanent-magnet generator used in a portable ac generator when directly driving isolated single-phase (1-ph) ac loads. The performance of the generator was compared under three alternative connections: 1) 1-ph star; 2) 1-ph delta; and 3) a proposed “open delta” connection. The voltage regulation, total harmonic distortion, and efficiency as three main performance criteria of the portable generators were examined using analytical calculation, finite element simulation, and experimental measurements. [ABSTRACT FROM PUBLISHER]

Electrical engineers rely on analytical models to design industrial induction motors for different customer-driven applications. These models are fundamental and do not normally consider additional core losses due to stamping or welding or the impact of being inverter fed. To overcome the resulting gap between analytical results and measured data, these equivalent circuit models are traditionally adapted by correction factors. This paper presents a methodology allowing the parameterization of such an analytical model based on inverter-fed load and no-load measurements carried out for several frequencies. The results show a fair agreement over a wide range of operating points, which is acceptable for daily regular industrial applications. [ABSTRACT FROM AUTHOR]

In high-speed aircraft, an altitude adjustment system is an important auxiliary part that needs rapid power support. In this paper, an ultrahigh-speed generator is described. However, the ultrahigh-speed generator's safe operation and smooth power supply to the load can be threatened by mismatch between the open-loop generator and fickle load conditions. In this study, a power converter with a paralleled energy-matching link was developed, which can broaden the safe operation zone and ensure the generator's safe operation as well as the load's smooth power supply under relatively light-load conditions. This power converter can also ensure the power supply voltage under relatively heavy-load conditions. The validity of the proposed power converter was verified by experiments. [ABSTRACT FROM AUTHOR]

The increasing number of renewable energy sources in the distribution grid is becoming a major issue for utility companies since grid-connected converters are operating at different operating points due to the probabilistic characteristics of the renewable energy. Usually, the harmonics and impedance from other renewable energy sources are not taken carefully into account in the installation and design of the systems. It can bring an unknown harmonic instability into a multiple power-sourced system and makes the analysis difficult due to the complexity of the grid network. This paper proposes a new model of a single-phase grid-connected renewable energy source by using the harmonic state-space modeling approach, which can identify such problems. The model can be extended to a multiple connected converter analysis. The modeling results show the harmonic impedance matrixes, which represent the harmonic coupling characteristic, as well as different dynamic characteristics. The theoretical modeling and analysis are verified by simulations, as well as experimental results. [ABSTRACT FROM PUBLISHER]

This paper develops a modeling method for robust stability analysis of nonlinear electrical power systems over a range of operating points and under parameter uncertainties. Standard methods can guarantee stability under nominal conditions, but do not take into account any uncertainties of the model. In this study, stability is assessed by using structured singular value (SSV) analysis, also known as $\mu$ analysis. This method provides a measure of stability robustness of linear systems against all considered sources of structured uncertainties. The aim of this study is to apply the SSV method for robust small-signal analysis of nonlinear systems over a range of operating points and parameter variations. To that end, a modeling methodology is developed to represent any such system with an equivalent linear model that contains all system variability, in addition to being suitable for $\mu$ analysis. The method employs symbolic linearization around an arbitrary operating point. Furthermore, in order to reduce conservativeness in the stability assessment of the nonlinear system, the approach takes into account dependences of operating points on parameter variations. The methodology is verified through $\mu$ analysis of the equivalent linear model of a 4-kW permanent magnet machine drive, which successfully predicts the destabilizing torque over a range of different operating points and under parameter variations. Further, the predictions from $\mu$ analysis are validated against experimental results. [ABSTRACT FROM PUBLISHER]