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Refereed/Peer-reviewed This article proposes a two-stage optimization algorithm to effectively determine the system configuration at one stage, as well as the capacity of components at the other stage in the middle of the former. This algorithm fits in best with the hybrid systems with more possible types of components. The studied system, in this article, includes diesel generators, wind turbines, photovoltaic arrays, and tidal generators as the power generation components, as well as battery banks and flywheels as the energy storage components. It also includes fuel cells and electrolyzers that either work as batteries or generate electricity in the presence of biomass. When the number of components (decision variables) increases, it becomes difficult to find an optimal solution by the conventional methods. Therefore, in this study, a two-stage multiobjective optimization algorithm is applied to design a cost effective and environmental friendly ac minigrid hybrid power system. In each iteration of the proposed algorithm, first, renewable energy sources and energy storage components are selected to form a hybrid power system along with the diesel generator. Then, the capacities of the components are optimized based on the two objective functions, including levelized cost of electricity and emissions. The optimization model uses real annual data in hourly time intervals for the load, solar insolation, ambient temperature, and wind speed. It is found that the proposed algorithm decreases the susceptibility of the solutions to multiple runs compared with the conventional algorithms and achieves a better optimized power system design.

Refereed/Peer-reviewed This paper proposes two structures of dual-stator permanent-magnet vernier machines (VMs) for high-torque low-speed applications. The proposed structures consist of dual-sided rotor which is sandwiched by inner and outer stators. These topologies include 22 and 46 consequent-pole magnets in the rotor and 24 and 48 stator slots for Design A and Design B, respectively. Design A is an improved structure of dual stator VM and Design B is a novel topology of a dual stator VM that can deliver considerably higher back-EMF and torque than Design A. The only drawback in Design B is lower power factor. The characteristics and performance parameters of the proposed VMs are evaluated using FEA. Sensitivity analysis is used to figure out the optimum dimensions of the magnets. In fact, two combinations of slot/pole number of the vernier machines are investigated as Design A and Design B. The capabilities of the proposed vernier machines are presented in a fair comparison with other VMs namely as consequent pole dual rotor VM (CPDRVM), consequent pole dual stator VM (CPDSVM) and dual stator spoke array VM (DSSAVM). In this regard, the key machine features considered for comparison are back-EMF, torque, torque per magnet volume (TPMV), power factor, loss, and efficiency profiles. The proposed structure (Design B) generates higher torque and TPMV compared to the other studied machines while Design A can achieve a higher power factor.

Refereed/Peer-reviewed In this article, the analysis of induction machines using five separated subdomains including the rotor slot, rotor slot opening, airgap, stator slot opening, and stator slot regions is considered. The Maxwell equations of each region are solved considering the boundary conditions. Uniform distributions of the current density in the rectangular slots of both the rotor and stator are considered to find the energy of the winding and to calculate the machine inductances using the energy equation. The calculated flux density of each subdomain is used to find the flux distribution. The calculated magnetic flux intensities are required to estimate the saturation level of the motor cores and correct the saturation-related values such as the leakage and magnetizing inductances. The machine core losses are calculated based on the Steinmetz equation at the no-load condition. The calculated inductances and resistances are used in the equivalent circuit of the squirrel-cage induction machine (SCIM) for the performance prediction. The results demonstrate the reliability of the saturation model in the prediction of the saturation influence in a wide range of magnetization levels. The accuracy of the proposed model in the prediction of the performance of the SCIM is validated using two-dimensional (2-D) and 3-D finite-element analysis results. A sensitivity analysis with 75 different geometries was conducted to show the capability of the model for the performance prediction of a wide range of induction machines.

Efficiency maps (EffMs) illustrate the maximum efficiencies of electric machines over a range of torque-speed operating points. This paper reviews the available techniques for efficiency map calculation and gives a general understanding of EffM modelling and interpretation for traction motors. It shows the accuracy versus calculation effort trade-off for different methods. The process of efficiency map calculation for sample induction motor and permanent magnet synchronous machines is explained. Calculation of EffMs using commercial software is also covered. Finally, possible future research opportunities in this field are suggested. Refereed/Peer-reviewed

The bond-graph (BG) enables to model multi-physics systems in the energy domains. This paper shows that BG models are an alternative, more intuitive and simpler to interpret, graphical tool as compared to existing dynamic models for performance prediction of the line-start permanent-magnet synchronous motors (LSPMSMs). It includes electrical, magnetic, and mechanical energy domains where the stator windings, rotor bars, and permanent magnets are the main components of the model. The dynamical equations of the proposed BG are extracted and solved using the MATLAB ordinary differential equation solver for a sample LSPMSM. The dynamics of the studied LSPMSM is investigated under two operating conditions (1) a healthy motor and (2) a motor with broken rotor bars. The simulation results are compared with the finite-element analysis (FEA) as the most accurate method to simulate the electric motor behaviour. It is shown that the proposed BG model accurately predicts the performance parameters of the motor such as current, torque, and speed under various operating conditions. In addition to the modelling validation, the transient behavior of the LSPMSM are discussed to describe the possible reasons for its behaviour during transient and steady-state operating conditions.

Line-start permanent-magnet synchronous motors (LSPMSMs) have poorer starting performance than induction motors. Optimization focusing only on transient performance improvement of the LSPMSM may degrade steady-state performance, and vice versa. In fact, an optimization focusing on maximizing starting torque may reduce efficiency by up to approximately 7% and optimizing efficiency may cause degradation in starting torque by 5%. Hence, simultaneous steady-state and transient performance optimization of a 4-kW LSPMSM under a multi-objective function is examined in this study. Efficiency maximization and starting torque maximization are nominated as objective functions. Two different optimization approaches, a gradient-based algorithm and gradient-free algorithm, are employed to optimize the LSPMSM. Sequential nonlinear programming is used as the gradient-based algorithm in this study, and the gradient-free algorithm used is the genetic algorithm (GA). A comparative study of the algorithms’ performance is presented. To provide an inclusive comparison of both algorithms’ performance, a similar optimization study is implemented for a baseline induction motor. The results demonstrate that the multi-objective optimization improves steady-state and start-up performance of both motors. Results indicate that both algorithms converge reliably to almost the same optimum (objective) value. Depending on the nature of the optimization problem, number of design variables, and degree of convergence, the genetic algorithm requires many more evaluations than the gradient-based algorithm. Accordingly, optimization time required by the GA is more than the gradient-based algorithm under similar conditions. Refereed/Peer-reviewed

Refereed/Peer-reviewed This article presents the optimization of axial-flux induction motors (AFIMs) for the electric vehicles application by solving the Maxwell's equations inside five subdomains. It allows a detailed modelling and accurate steady-state performance prediction of the AFIMs in a short time (under 1 sec). The analytical model is verified against 2D finite-element analysis. Different design options of the AFIM are considered and then optimized based on the proposed analytical model with the aim of minimizing the motor's volume and satisfy a set of predefined performance parameters for operation in a nominal point and also over a driving cycle. For operation in a nominal point, three power levels and for the driving cycle based operation, three driving cycles are considered. In each operation state, maximum torque per ampere (MTPA) constraint is enforced by changing the number of winding turns per slots. Alternatively, similar optimizations are performed without MTPA constraint by considering the number of winding turns as a variable. It is observed that motor design based on the driving cycle benefits from a lower volume while it is feasible for all the operating conditions. Enforcing the MTPA in design leads to a wider torque-speed operating range and simpler control in the expense of additional volume.

This article investigates the accuracy of the estimation of efficiency maps for permanent magnet (PM) machines using the stator resistance, d - and q -axis flux-linkages versus the corresponding axis current and the iron loss versus the speed characteristic. The ultimate goal is to apply this approach to the experimental measurements, but this article performs initial investigation using only the finite-element (FE) data. Detailed FE data for 50-kW surface PM (SPM) and interior PM (IPM) machines are used to determine the “actual” or exact efficiency map and, hence, the accuracy of using approximations. This article examines the effect on the torque–speed capability curve when ignoring cross-saturation effects. It also examines the modeling of the variation of iron losses as a function of load in the constant torque and power regions. A novel approach based on scaling the no-load (NL) losses as a function of load is proposed and shown to give promising results. FE results from two other machines are also provided, which show good correspondence. Refereed/Peer-reviewed

Refereed/Peer-reviewed This paper proposes an optimization model to address the generator preventive maintenance scheduling (GPMS) in large power systems with high penetration of renewable energy resources (RERs). The dynamic programming (DP) technique is modified to reduce the required computational effort. A step for system inertia calculation and a constraint of minimum system inertia requirement are integrated into the GPMS model to address the inertia reduction issue linked with the proliferation of RERs in power networks. This study also considers the energy reserve requirement of the power system. The efficacy of the developed model is evaluated based on the operational data of an actual large power system including 41GW of conventional generators (400 units), and 14GW of wind and solar photovoltaics (PVs). The proposed algorithm is validated against the original DP method and the GPMS technique currently used by the Vietnamese system operator (SO). It is shown that the proposed simplified DP, while being much faster than the full DP, still guarantees an optimal solution as good as the full DP's solution. The proposed method outperforms the technique currently used by the Vietnamese SO, generating significant improvements in the system capacity reserve profile and reliability indexes with less adjustment effort required. The proposed algorithm is validated against the original DP method and the GPMS technique currently used by the Vietnamese system operator (SO). It is shown that the proposed simplified DP, while being much faster than the full DP, still guarantees an optimal solution as good as the full DP's solution. The proposed method outperforms the technique currently used by the Vietnamese SO, generating significant improvements in the system capacity reserve profile and reliability indexes with less adjustment effort required.

Commercialization of electric vehicles (EVs) and light electric vehicles (LEVs) play a major role in reduction of greenhouse gases and environmental pollution. In this paper, the main reasons for popularity of the LEVs are explained based on the statistics available in literature. The propulsion system of the LEVs (including the electric motor, transmission system, battery package, and inverter) aims to offer high efficiency over a wide range of torque-speed operating points. Hence, the optimal design and performance improvement of such vehicles have attracted attention in literature. The investigated drivetrain systems in various LEVs are reviewed in this paper to highlight their advantages and disadvantages. The popular electric motors used in the LEVs are discussed and their characteristics are emphasized. The available research gaps in this field are highlighted at the end of the paper to provide a guide for the new researchers in this field.

Refereed/Peer-reviewed Electrical motors are one of the key building blocks in power systems and an important load type in industry and residential buildings. The concept of axial-flux induction machines (AFIM) is drawing particular attention since it shows performance characteristics that are superior to the conventional radial flux induction machine (RFIM). This paper gives a state-of-the-art overview of AFIMs in the aspects of its history, construction, design, modelling, simulation, analysis, features, electromagnetics, and manufacturing. Especially, the review focus is given on the design, performance analysis, and features. Moreover, comparative studies among different induction machines are provided. Research gaps and possible trends are identified and discussed in this paper.

Refereed/Peer-reviewed Electric motors are one of the key building blocks of electric vehicles (EVs). The electric motor is drawing particular attention due to the variety of topologies that can be chosen as candidates for EV applications. Through the proper motor type selection and design, the performance of EVs can be enhanced, such as efficiency and stability. This paper presents a state-of-the-art overview of alternative electric motors for EV applications. Firstly, the classification and performance of alternative electric motors is described. Then, research gaps and possible future trends are introduced and identified in this review paper.

This paper presents a class of high step-up impedance source inverters. The proposed topologies utilize an optimized coupled transformer with unique structure to reach high voltage boost capability with small turns ratio. In other words, high voltage boost ability is gained by decreasing the turns ratio to 1 which leads to lower cost and volume. The absorbing circuits are exploited to clamp dc-link voltage to reduce the effect of the leakage inductance. So, huge spikes across the inverter bridge are removed effectively. Input inductor and input dc-source are connected in series. It results in continuous input current with low start-up inrush current which is appropriate for renewable energy sources such as fuel cell and photovoltaic (PV). In addition, high output voltage is obtained with small shoot-through (ST) duty ratio and high modulation ratio which causes semiconductor voltage stress reduction and better quality of the output voltage. The simulation results confirm the operation of the introduced inverters. The paper also extracts the mathematical equations of the proposed inverter Refereed/Peer-reviewed

This paper introduces a new single-phase ac-ac converter according to an impedance network. The introduced topology retains the excellences of the conventional non-isolated single-phase ac-ac Z-source converter (ZSC), including buck- boost ability and capability of reversing and maintaining of the phase angle. The suggested converter hires coupled inductors to control output voltage by adjusting its turns ratio along with duty ratio. By utilizing unique shape of coupled inductors, the introduced converter can acquire high voltage boost capability by reducing turns ratio which leads to cost and size reduction. Unlike the single-phase ac gamma source converter, the input current in the introduced converter is continuous. As a result, it does not suffer from non-sinusoidal high THD input current. The voltage and current spikes across the switches are removed by a safe commutation strategy. The introduced converter can be exploited as a dynamic voltage restorer for voltage sag and voltage swell compensating. Simulation results in MATLAB are supplied to survey the converter's operation. Refereed/Peer-reviewed

This paper presents the design process, detailed analysis, and a comparative study on the advantages of axial-flux induction machines (AFIM). A radial-flux induction machine (RFIM) is also studied as benchmark motor. Both motors are designed with six poles, 36 stator slots, and 32 rotor bars. Finite-element analysis is used to predict the performance of the two motors under both transient and steady state conditions. A complete comparative study along with the simulation results are reported. It is found that the studied AFIM has higher efficiency and power density. Refereed/Peer-reviewed

This paper presents an improved analytical model for axial-flux induction motors (AFIMs) based on solving the magnetic vector potential equations. The advantage of the proposed approach is its fast simulation time (fractions of a second against minutes/hours in FEA) while maintaining over 95 % accuracy compared to FEA that makes it suitable for an optimization purpose. This method applies a uniform distribution of the current density in the rectangular shaped rotor/stator slots. The equivalent circuit parameters of the studied AFIMs are extracted using the magnetic energy analysis. The proposed model allows the saturation effect in calculation of the motor performance parameters (power factor and efficiency). The accuracy of analytical model is validated using FEA results. A comprehensive design optimization is presented to show its capability for an optimization purpose. The objective functions in this study are maximum efficiency, maximum power factor, maximum efficiency times power factor, minimum mass, minimum price, maximum efficiency over slip, and maximum power factor over slip. The proposed analytical model can be easily used for AFIMs with different number of poles and phases. Refereed/Peer-reviewed

Refereed/Peer-reviewed Subdomain technique is a computationally efficient approach with an acceptable accuracy for performance evaluation of the electric machines. This paper develops the subdomain model of three types of permanent magnet (PM) machines including surface-mounted PM (SPM), Inset PM, and consequent pole PM (CPPM) machines. The performance parameters of the studied machines are extracted via subdomain technique and validated by 2D finite-element analysis (FEA). The airgap flux density is calculated using the vector potentials obtained from the subdomain model. The flux density of the iron parts, that is required to find the core losses, are found using the magnetic vector potentials in the iron parts. The developed model is then employed for optimal design of various wind generators. The optimization is executed through two different scenarios. Firstly, the machines are optimized for maximization of the generator efficiency for a single operating point. In the second scenario, the optimization is done over annual wind regime of an area to maximize the annual energy efficiency. The airgap length, magnet dimensions, stack length, and the rotor and stator diameters are the variables of the optimization problem. The optimal designs are compared to show the advantageous and disadvantageous of the considered machines for the wind generator application.

This paper presents an explicit comparison of the three-phase line-start permanent-magnet synchronous (LSPM) motor with the squirrel-cage induction motor (IM). It investigates the effect of number of rotor bars on the performance of the motors by considering two alternative options including 32 and 45 rotor bars. Finite-element analysis is utilized for design and performance prediction of the studied motors. Both steady-state and dynamic responses of the motors under no-load, constant load, fan load, and step load are investigated. The simulation results confirm that the LSPM motor with 32 rotor bars can remain stable at constant speed when operating in overloaded and variable voltage conditions. The LSPM motor has advantages of high efficiency and high power factor while IM has superior dynamic performance Refereed/Peer-reviewed

Refereed/Peer-reviewed This paper presents the comparative study of two induction machines (IMs). It investigates the conversion of an existing three-phase IM to five-phase IMs and explores the effect of phase number on the performance parameters. The two studied machines in this work have the same number of winding turns per phase and similar rotor but modified stator.2D finite-element analysis and MATLAB are used to extract the performance parameters of the machine. The performance comparison of the machines consists of inductance, resistance, current, torque, power factor, and efficiency. It is found that the five-phase IM is more efficient than three-phase IM considering the same physical characteristics. This study aims to provide useful understanding on the effect of the number of phases on performance of IMs.

This paper optimally determines the configuration of the system, as well as each component capacity, in order to design a cost-effective and environment-friendly AC mini-grid hybrid power system for a remote area in South Australia. To this purpose, a modified Multi-Objective Particle Swarm Optimization (MOPSO) algorithm is applied. In each iteration of the modified proposed MOPSO, first, renewable power sources, including photovoltaic arrays and wind turbines along with energy storage components, are selected to form a hybrid power system along with the diesel generator. Then, the capacities of the components are optimized based on two objective functions, including Levelized Cost of Energy (LCOE) and CO2 emission, by analyzing the system using real data in hourly time-step for the load, solar insolation, ambient temperature, and wind speed over a 20-year timespan. Afterward, positions for system configuration and component capacities are updated according to the objective functions. Refereed/Peer-reviewed

Robustness, low cost and high torque density are the main characteristics of switched reluctance machines (SRM) that have made them promising for a variety of applications. In this paper a small diameter, long stack length (small aspect ratio) 6kW SRM is designed. In the first step, the dimensions of the studied SRM are derived based on conventional sizing equations. The significance of the rotor and stator pole arcs and also the effective torque zone as a constraint of the design are discussed. A finite-element study is carried out to validate the analytical model of the proposed SRM. The performance of the machine is comprehensively studied in different operating speeds. Simulation results demonstrate the capability of the machine for operation over a wide speed range.pa Refereed/Peer-reviewed

This paper presents the design and analysis of a novel axial-flux synchronous reluctance motor (AFSynRM). A magnetic equivalent circuit (MEC) model for the proposed axial-flux machine is derived. The feasibility of fabrication is discussed. Finite-element analysis is applied to predict the performance of the proposed motor design. This paper provides a baseline study by comparing the performance of the proposed AFSynRM design with a similar rating radial-flux motor. The motors are designed to have similar volume and both have three rotor barriers. The operating parameters are obtained through static and dynamic FEA. The power, torque, power factor and efficiency of the motors are studied. The saturation and flux distribution in the motor structures are investigated. Refereed/Peer-reviewed

This paper proposes a dual rotor halbach array permanent magnet vernier machine (DRHAVM). Proposed vernier machine demonstrate high power factor with high torque density at low speed which is promising for low speed transportation applications. Proposed permanent magnet vernier machine structure omits necessity of gearbox and directly convert energy to low speed rotation. A comprehensive FEA of proposed DRHAVM including sensitivity analysis, back-EMF, torque density, torque per magnet volume, power factor, core loss, copper loss and efficiency are performed. Additionally, a detailed comparison is conducted between proposed DRHAVM and other types of Vernier machines in the literature. Results display that proposed halbach array vernier machine structure can achieve an appropriate power factor (0.84) and generate higher torque (2850 Nm) at speed rotation of 30 rpm. Refereed/Peer-reviewed

This paper presents a novel dual-stator linear-vernier permanent-magnet (DSLVPM) machine. The proposed machine utilizes consequent-pole permanent magnets (PMs) rather than the adjacent topology of conventional linear-vernier permanent-magnet (LVPM) machines. The proposed structure of DSLPMV is analyzed and compared against the conventional topology of the LVPM machine. 2D finite-element analysis is utilized to evaluate the electromagnetic aspects and performance parameters of the machines at no-load and full-load conditions. To assess the machines with different PM volume usage, indices such as thrust force per magnet volume (FPMV) and back-EMF per magnet volume are introduced. Simulation results display a better performance of the proposed linear vernier machine in comparison with the typical machine due to the optimized usage of magnets in the consequent-pole configuration.

This paper presents an optimisation study of an 8-pole, 3-phase, 1kW line-start permanent magnet synchronous motor (LSPMSM) designed based on a benchmark induction motor (IM). The initial IM (IM0) is designed using a machine sizing technique and then the initial LSPMSM (L0) is designed based on some modifications in the rotor of the IM0. The finite element method (FEM) is employed to analyze the motor’s performance. The initial LSPMSM (L0) operates with higher efficiency and power factor compared with the IM0. L0 efficiency is categorized in the IE4 efficiency standard class while IM0 efficiency is in the IE3 class. Then, IM0 and L0 are individually optimised based on a FEM optimisation technique using genetic algorithm (GA) to improve their transient and steady-state performance through maximizing the starting torque and the efficiency as two optimisation objectives, respectively. The optimised LSPMSM (L1) has better performance in terms of the starting torque (transient representative) and the efficiency (steady state representative) in comparison to other L0. The results indicate that, it is not necessarily true that a LSPMSM designed based on an optimised IM has better performance than a LSPMSM design based on a non-optimised IM (in this case L0). Refereed/Peer-reviewed

A line-start permanent magnet synchronous motor (LSPMSM) is designed based on modifying the rotor of a 4kW commercial induction motor (IM). The designed LSPMSM provides a higher output power, efficiency and power factor as well as lower maximum operating temperature than the IM. Finite-element electromagnetic and thermal analyses are used to compare thermal behavior of the motors and verify the accuracy of the assumed temperature rise. Refereed/Peer-reviewed

This paper presents an analytical method to design an optimum Line-Start Permanent-Magnet Synchronous Motor (LSPMSM). An initial LSPMSM (L0) is designed by combining an induction motor (IM0) and an interior permanent magnet (IPM0) motor. The IM0 and IPM0 are designed analytically from sizing equations. The optimum LSPMSM is developed from IM cage optimization for starting torque and permanent magnet (PM) optimization of the IPM for efficiency. By combining the rotors of the optimised IM and IPM, an optimum hybrid rotor is obtained for the LSPMSM. The optimized motor has better performance in the transient and steady state compared to L0. The proposed optimisation method based on a mathematical model is implemented using a genetic algorithm (GA). An optimization case study is implemented using both the proposed mathematical method and FEM. The optimization results indicate that the optimum design found using the proposed mathematical method is obtained more rapidly and has comparable performance to that found using FEM optimization.

In this paper, the magnetic vector potential (MVP) equations are solved for a 5.5-kW radial-flux induction machine (RFIM) in five subdomains. The proposed modeling technique considers a uniform distribution of the current density in the rectangular slots of both rotor and stator. The RFIM is represented using a 2D model in the cylindrical coordinate system. The magnetic flux distribution in each region which is used to calculate the core losses and the machine inductances for the steady state analysis of the machine. T-equivalent circuit (T-EC) is considered to study the machine performance parameters. The rotor and stator resistances are calculated based on the geometry of the machine. The results demonstrate the accuracy of the model in prediction of the airgap flux density. The comparison of the machine performance parameters with the 2D FEA results demonstrate the reliability of the analytical model in the prediction of the machine behavior at the rated condition. Refereed/Peer-reviewed

Notice of Violation of IEEE Publication Principles "Performance Improvement of a Line-Start Permanent-Magnet Synchronous Motor" by Solmaz Kahourzade, Amin Mahmoudi and Wooi Ping Hew, in the IEEE Transactions on Industrial Electronics After careful and considered review of the content of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE's Publication Principles. This paper was submitted with significant similarity to ideas and applications presented in the thesis listed below. The paper includes a reference to the thesis, but there was no clear delineation between their work and previous work presented in the thesis. Two of the authors, Solmaz Kahourzade and Amin Mahmoudi were found to be responsible for the misconduct. "Line Start Permanent Magnet Motors," by Arash Hassanpour Isfahani, in Ph.D dissertation, Department of Electrical Engineering, Tehran University, Iran, 2011. This paper presents the design and performance analysis of a line-start permanent-magnet synchronous motor to overcome the efficiency and power factor deficiencies of induction motors. Proper start-up and synchronization are considered. An optimization algorithm is applied to improve the rotor bar resistance for the smooth line start of the motor. Dynamic d-q modeling and finite element analysis are performed to predict the transient and steady-state performances of the motor. Based on the presented optimized design, a 3-phase, 4-pole, 2 kW line-start permanent-magnet synchronous motor is fabricated and tested. Simulation and experimental results validate the improved performance of the proposed optimized motor.

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. Refereed/Peer-reviewed

This paper proposes several methods to compare the overload performance of different types of synchronous machines for electric traction applications. An ideal model to predict the performance of the motor at high overload condition is introduced. In the simplified analytical saturation model, the saturation flux linkage is a parameter. This allows the performance prediction as a function of three normalized parameters: magnet flux linkage, unsaturated inductance and saliency ratio.The other main part of the work concerns the machines analysis using the finite element approach. Models with different levels of accuracy and generality show the possibility of reducing the number of simulations in the d- and q-axis currents plane to obtain the full performance prediction. Machines with different level of cross saturation are considered to test the proposed models.Simulation results of the studied approaches are compared with the prediction obtained from the full machine mapping using finite element analysis, in which a large number of evenly spaced points in the (id,iq) plane are analyzed to derive the working characteristics. Refereed/Peer-reviewed

This paper proposes a two-stage data-driven methodology in condition monitoring (CM) of wind turbines (WTs). In the first stage, a fast and powerful network, namely a parallel generative adversarial network (PGAN) is proposed to resolve the problem of limited available information by generating artificial data. In the second stage, a robust deep network is designed based on a one-module Gabor filter oriented convolutional neural network and reformulation of a new loss function, namely robust deep Gabor network (RDGN). The experimental dataset of 3MW wind turbines in Ireland is used to verify the effectiveness of the proposed method and demonstrate the superiority of the proposed two-stage method in comparison with several state-of-the-art methods in terms of accuracy and reliability Refereed/Peer-reviewed

This paper presents the comparative study of two permanent-magnet synchronous machines (PMSMs). It investigates the design of two different motors with different pole numbers and explores the pole effect on the performance of parameters. Considered machines in this study are 4-pole and 40-pole SPMMs with same magnet volume on the rotor. Using sizing equations, physical dimensions of the motor are identified, and performance parameter of the motor are extracted via 2D finite-element-analysis. The performance comparison of the machines includes the flux distribution across the geometry, airgap flux density, flux linkage, cogging torque, torque, and motor losses. This comparative study aims to serve useful understanding on the effect of the number of poles on performance of PMSMs for electrical vehicle applications. Refereed/Peer-reviewed

This paper presents design optimization of axialflux induction motors (AFIMs) for electric vehicles. The approach is based on an analytical resolution of the Maxwell's equations inside a set of subdomains. The analytical method is verified against 2D finite-element analysis. It allows detailed modelling and accurate steady-state performance prediction of AFIMs in a very short time (under 1sec), making possible evaluation of numerous design for the optimization. The optimization effortlessly simulates and predict the performance of various AFIM designs based on driving cycles and vehicle limitations. An optimization based on driving cycle of electric vehicles is studied through considering a driving cycle and designing minimum-mass AFIMs capable of fulfilling it. It is observed that driving-cycle based motor designs benefit from mass reduction and ensures the feasibility of all operating conditions Refereed/Peer-reviewed

Measuring the efficiency map of an electric machine is a complex and time-consuming process. This paper examines means for estimating the efficiency map of PM machines using a reduced number of tests. It uses a modified saturation model which gives good results even in the presence of high cross-saturation. It also models the iron loss variation with load and speed using curve fitting in the constant torque and power regions based on a limited number of load points. Both the flux-linkage and iron loss methods are applicable to finite element (FE) simulation and have the capability of being generalized to other electrical machine types. The results are verified both with FE simulation and experimental tests. Refereed/Peer-reviewed

Step-up DC-DC converters play a determinative role in traction vehicles by providing the required DC- link voltage for traction drives supplied by battery packages or fuel cells. Bi-directional converters are preferred to be used in the construction of battery-based traction drives to charge batteries when drivetrains system work in the generation mode. However, due to the fact that fuel-cells cannot be charged electrically, the bi-directional structure is not required for fuel cell-based traction drives. The proposed step up converter benefits from the resonance between its elements to provide the soft- switching condition for the converter switches. The resonance assists to transmit high power from input and to output while there is no high-frequency transformer or coupled inductor in the converter topology. In brief, the generated resonance not only leads to a high power density converter but also result in a soft-switching which means higher efficiency in comparison to previously introduced high-step up converters working in hard switching condition. So, the proposed high-efficiency high power density high step-up (HHH) converter could be employed as a reliable DC-DC converter for traction vehicles supplied by fuel cells. Refereed/Peer-reviewed

This paper presents the design and analysis of an axial-flux permanent-magnet synchronous motor with a novel line-starting capability using an induction cage. This machine can be used as a higher-efficiency substitute for the induction motors. It also offers higher efficiency and lower cost compared to conventional radial-flux line-start permanent-magnet motors. This paper is a baseline study which compares the performance of the proposed design with a similar rating radial-flux motor. Both 2D and 3D finite-element analysis are used to predict the performance of the two motors under transient and steady-state conditions. A double-stator single-rotor line-start AFPM motors is also studied to increase the output power. Refereed/Peer-reviewed

In this paper, two-dimensional (2D) analytical model is proposed for axial-flux induction motor (AFIMs) based on the solution of magnetic vector potential equations, which also considers the saturation's effect on the performance of the machine. The model is developed from the quasi- magneto-static Maxwell's equations, which are analytically solved. It considers a uniform distribution of current density in the rectangular shaped rotor/stator slots. By computing the magnetic energy of the machine, this method obtains the inductances and uses them to assess the design performance parameters. The accuracy of the 2-D analytical solutions is verified against those obtained from the finite element method (FEM). The suggested model is generic and applicable to AFIMs with any number of poles and phases. A case study on optimization axial-flux induction motor is presented to evaluate the performance of the proposed model. The proposed method can replace the FEM in designing and optimization of the AFIMs. Refereed/Peer-reviewed

This paper examines correction of the finite-element (FE) calculated efficiency maps based on simple experimental tests. The error between calculated and measured efficiency maps significantly affects the energy consumption in variable-speed applications like electric vehicles. The flux-linkage correction requires the measured saturation flux-linkage obtained from stationary testing and the iron loss correction requires open-circuit or no-load test results. These tests need minimum effort and equipment and in the case of open-circuit tests, no inverter is required.This paper also provides a detailed loss analysis by using fitting functions in the form of T m ω n for the losses in the constant torque region and in the form of P m ω n for the losses in the constant power region for both FE and measured results. The results indicated that superposition of the speed dependent coefficients obtained from the no-load test and coefficients obtained from the FE calculation provides a good estimation of the measured loss. Comparing the original FE and modified losses provides loss scaling factors for the iron losses. Refereed/Peer-reviewed

Amorphous magnetic materials (AMMs) have been used in low-frequency power transformer applications for more than two decades but not commercially utilized in high-frequency rotating electrical machines despite their low iron losses, which is an order of magnitude lower than conventional silicon iron. This was primarily due to the lack of a suitable handling method and an economical cutting technique. This paper reports a novel brushless synchronous permanent magnet rotating electrical machine that combines the benefits of the previous machine topologies while offering higher torque (due to the larger air-gap surface area compared with the flat axial-field machine) and ease of manufacturing from AMM material, which is suitable for a range of high-efficiency, high-power density, and high-speed machine applications. This paper provides the details and the performance characteristics of this novel tapered-field AMM machine as a generator at high speeds using a bonded rotor magnet topology. Refereed/Peer-reviewed

This paper investigates the accuracy of the estimation of efficiency maps for permanent magnet (PM) machines using the pmb{d}-pmb{q} equivalent circuit model and limited experimental data. The study is based on the detailed finite-element results for 50-kW surface and interior PM machines. It discusses the variation of the flux-linkages and losses with pmb{I-{d}} and pmb{I-{q}}. It examines the effect of modeling the flux-linkage characteristics using saturating and linear models and modelling the non-copper losses using the open-circuit and short-circuit losses. The effect of these approximations on the output torque versus speed capability curve and efficiency contours are shown. Guidelines are proposed for fast and reasonably accurate calculation of efficiency maps.versus speed capability curve and efficiency contours are shown. Guidelines are proposed for fast and reasonably accurate calculation of efficiency maps. Refereed/Peer-reviewed