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In response to climate change, governments around the world have committed to reducing greenhouse gas emissions, which contribute to global warming, through the energy transition from fossil fuels to renewable energy sources and electrification of transportation. This article outlines the design procedure for the electrification of a railway vehicle used for maintenance services on the rail network. The proposed methodology consists of the design of both an all-electric propulsion system and storage system with the aim of zero emissions when the vehicle is operating in tunnels and to minimise noise during maintenance services in cities. After highlighting the characteristics of the railway vehicle under consideration, a simulation model of the propulsion and generation system was developed in order to calculate the energy consumption of the entire railway system. Finally, experimental tests carried out on the prototype proved the effectiveness of the design procedure adopted and the proposed mathematical model, showing a good matching with the simulated results. [ABSTRACT FROM AUTHOR]

An innovative variable-structure-systems-based approach for online training of neural network (NN) controllers as applied to the speed control of electric drives is presented. The proposed learning algorithm establishes an inner sliding motion in terms of the controller parameters, leading the command error towards zero. The outer sliding motion concerns the controlled electric drive, the state tracking error vector of which is simultaneously forced towards the origin of the phase space. The equivalence between the two sliding motions is demonstrated. In order to evaluate the performance of the proposed control scheme and its practical feasibility in industrial settings, experimental tests have been carried out with electric motor drives. Crucial problems such as adaptability, computational costs, and robustness are discussed. Experimental results illustrate that the proposed NN-based speed controller possesses a remarkable learning capability to control electric drives, virtually without requiring a priori knowledge of the plant dynamics and laborious startup procedures. Index Terms--Adaptive control, electric drives, neural networks (NNs), variable structure systems.

This paper presents some analysis techniques of the space vector of voltages induced in the stator windings after supply disconnection, to detect broken rotor bars in squirrel-cage induction machines. When the motor is disconnected from the supply no currents flow in the stator windings and the voltages measurable at its terminals are due to flux produced by rotor currents. When the rotor is healthy, the voltages measured at motor terminals are almost sinusoidal because of the symmetry of rotor windings. When there are broken rotor bars, the magnetomotive force generated by rotor windings is distorted, and some particular harmonics, contained in the voltages induced in the stator windings, increase their amplitudes. The diagnostic technique is based on monitoring these voltage harmonics and analyzing the space vector of the voltages induced in the stator windings via MUSIC pseudospectrum and short-time MUSIC (STMUSIC) time-frequency pseudorepresentation. The MUSIC algorithm is based on the eigen analysis of the autocorrelation matrix, and permits us to evidence the principal harmonic frequencies of the signal and decrease the noise influence, thus allowing a better detection of the broken rotor bars. The results obtained using MUSIC and STMUSIC algorithm have been compared experimentally with those obtained by fast Fourier transform (FFT) and short-time FFT, respectively, and two different sized induction motors have been tested, to demonstrate the superiority of the former approach. Differently from most of the diagnostic techniques already proposed in the technical literature, the proposed approach is effective regardless of the load condition of the machine, source characteristics, and iron saturation. Index Terms--Asynchronous rotating machines, discrete Fourier transforms, fault diagnosis, MUSIC, spectral analysis, transient analysis.

Several techniques exploiting machines anisotropies have been proposed in literature for sensorless control of synchronous machines. Among them, the direct flux control (DFC) technique allows estimating the electrical rotor position by exploiting the zero‐sequence voltage of the machine. This work aims at analysing the effects of magnetic saturation on the application of the DFC technique to permanent magnet synchronous machines. This effect is present when stator flux is controlled during machine operation, leading to an error in the estimation of the electrical rotor position. Starting from an analytical model of the machine phase inductances, a complete mathematical description of the DFC technique is derived and presented. The proposed mathematical model shows how the estimated electrical rotor position is biased when operating under load conditions. Moreover, the result of the analysis of the DFC technique allows to refine the obtained estimate and to reduce the electrical rotor estimation error. Experimental results on a test motor are provided in order to verify and support the proposed mathematical model and technique. [ABSTRACT FROM AUTHOR]

The use of fast wide-bandgap devices in high-speed electrical drives with steep pulsewidth modulation voltage waveforms is the main cause of increased stress on the electric machine insulation system and consequently, of reduced reliability of the whole system. This represents a major concern in safety-critical applications, such as in the aerospace and electric transportation fields. The novel contribution of this work is to assess the effects of electrical aging on complex insulation systems (i.e., a whole stator winding) by analyzing easily measurable macroscopic quantities. To this purpose, an electrical aging procedure is defined, and the effects produced on three tested motors are presented. Three different analysis methods are adopted with the aim of assessing the damage caused to an ac motor winding by such steep voltage waveforms and hence to evaluate the state of aging of the insulation system. [ABSTRACT FROM AUTHOR]

High-speed electrical drives normally require converters capable of high-frequency operation. For this reason, converters based on SiC mosfets have been spreading in this field. Nevertheless, the problems caused by the high dv/dt imposed by SiC mosfets, like the premature failure of the motor winding insulation and the electromagnetic interference generation, are drawing more and more attention of the experts of this sector. In fact, these issues can deeply affect the system reliability and, hence, can represent a limiting factor for all those applications where the continuity of operation is the highest priority. To avoid the use of SiC mosfets in the most sensitive applications, this paper presents a solution, which consists of a Si-insulated gate bipolar transistor (IGBT)-based inverter fed by a Si-IGBT-based dc/dc converter performing a suitable dc voltage regulation. Therefore, the aim of this paper is to prove that a stable operation of a high-speed drive can be guaranteed through the proposed converter configuration. To prove the effectiveness of the proposed solution, experimental results on a laboratory setup have been presented. [ABSTRACT FROM AUTHOR]

Synchronous reluctance (SyR) machines can constitute a promising alternative to permanent magnet machines for low‐cost applications. The recent literature reports some guidelines for choosing the proper number and position of the rotor flux barriers capable of enhancing the electromagnetic performance in low‐speed applications. However, as the rotational speed increases, the electromagnetic and structural mutual interactions become relevant; therefore, an optimal design requires a proper trade‐off between torque production and stress reduction, which can be difficultly predicted analytically. This work proposes an approach based on optimisation algorithms in order to find 'non‐conventional' geometries able to improve the power density: genetic algorithms coupled to magneto‐static finite elements analysis and structural analytical models, are adopted to co‐design SyR machines with different numbers of stator slots and rotor barriers subjected to the same thermal constraints. This study investigates two design procedures aimed at maximising the output power of SyR machines by increasing the rotational speed. Both procedures allow determining the power limits for a given volume of active parts and a fixed amount of admissible losses; moreover, the second procedure automatically finds also the rotational speed which maximises the output power. [ABSTRACT FROM AUTHOR]

Synchronous reluctance (SyR) machines are a high-efficiency alternative to induction motors for variable-speed applications. To mitigate the well known downside of their lower power factor, permanent-magnet-assisted topologies, in which either rare-earth or ferrite magnets are inserted into the rotor in suitable quantities, are often adopted. The design and optimization procedures for PM-assisted topologies have been thoroughly discussed in the related literature. This paper compares SyR machines assisted with NdFeB and ferrite magnets, focusing on torque overload capability and feasibility of saliency-based position estimation algorithms. Three prototypes were realized and tested. They all have the stator of a commercial induction motor and the same custom-designed SyR rotor laminations. Among the three prototypes, one is a pure SyR motor, and the other two have NdFeB and ferrite magnets, respectively; both are designed to give the same torque at rated current. Results from simulations and experiments are presented comparing the transient overload capability of the three machines, in terms of torque capability and de-magnetization limit. A dynamic thermal model of the machines was developed within this scope. Moreover, the feasibility of saliency-based sensorless methods was investigated and is presented here for the three machines, both at high- and low-current loads. The results of the paper suggest that the ferrite-assisted solution is the best candidate for replacing induction motors in variable-speed applications, for its optimal tradeoff between performance and cost. [ABSTRACT FROM AUTHOR]

This study considers the design of surface-mounted permanent magnet electrical machines for high-speed applications and proposes a methodology to determine the maximum achievable power density. Power density is usually improved by increasing rotational speed. At high speed, a mechanical retaining system for the rotor magnets must be considered. As the speed increases, the thickness of the retaining sleeve becomes larger, reducing torque capability. There will be an optimal speed at which the output power will be maximised. Both structural and electromagnetic design must be considered simultaneously to properly address this design problem. To simplify the design procedure, static finite-element simulations are used for the electromagnetic analysis and analytical formulae are employed for retaining sleeve sizing. The procedure is aided by multi-objective optimisation algorithms. A case study based on the specification of an aeronautical actuator is presented. The performances that can be obtained using different iron cores, high-grade silicon steel, and cobalt iron steel are compared. Finally, results obtained from transient finite-element electromagnetic and structural analysis are presented to validate the feasibility of the proposed procedure. [ABSTRACT FROM AUTHOR]

This paper deals with the design of fuzzy logic-based controllers (FLBC) for dc and ac electric drives. Industrial drives employ the cascaded PI control with a subordinated current control loop to make sure that the current does not exceed the admissible value and improve dynamic performances. The nonlinear FLBC characteristics permit one to achieve the performances of the cascaded control using only one control loop. This is feasible by a suitable choice of the scaling factors together with the rules of the fuzzy controller. The Authors propose a minimum number of rules and the criteria, based on physical considerations, to determine the input and output gains instead of using the trial and error procedure. The designed FLBC is able to control the speed of a dc drive as well as the rotor speed and flux of a vector-controlled induction motor drive. Computer simulations show the effectiveness of the new fuzzy-controller design method. The reduced number of rules and membership functions and the application flexibility together with the possible implementation on low cost [micro]Ps let us think the proposed tuning criteria will be widely adopted. Index Terms--DC motors, electrical drives, fuzzy logic, induction motors.

In this paper, the use of conical induction machines is proposed for an in-wheel traction application. Such machines offer a rotational movement combined with a translational motion of the rotor. The horizontal movement is essential when active engagement and disengagement of the motor from the wheel without any extra mechanical component is required. This paper first investigates the basic concepts of how the conical machine functions and then proposes a mission strategy for a relevant traction application. A detailed description of the full scheme is given. In order to achieve the required performance, an innovative control method for both degrees of freedom of the machine (i.e., torque production and axial movement) is proposed and validated against a small-scale demonstrator of the whole system. [ABSTRACT FROM PUBLISHER]

This paper considers the electromagnetic and structural co-design of superficial permanent magnet synchronous machines for high-speed applications, with the aid of a Pareto optimization procedure. The aim of this work is to present a design procedure for the afore-mentioned machines that relies on the combined used of optimization algorithms and finite element analysis. The proposed approach allows easy analysis of the results and a lowering of the computational burden. The proposed design method is presented through a practical example starting from the specifications of an aeronautical actuator. The design procedure is based on static finite element simulations for electromagnetic analysis and on analytical formulas for structural design. The final results are validated through detailed transient finite element analysis to verify both electromagnetic and structural performance. The step-by-step presentation of the proposed design methodology allows the reader to easily adapt it to different specifications. Finally, a comparison between a distributed-winding (24 slots) and a concentrated-winding (6 slots) machine is presented demonstrating the advantages of the former winding arrangement for high-speed applications. [ABSTRACT FROM AUTHOR]

This paper presents an efficiency comparison of two converters designed for driving high-speed AC machines. In such applications, an inverter based on Si- IGBTs is not a viable solution since the switching losses became too high and physical limits of such devices do not match the required elevated switching frequencies. The use of SiC devices allows higher switching frequencies and reduced losses but issues mainly related to quickened motor insulation aging arise because of high dv/dt values. In this work a topology, made up of a Si IGBT inverter fed by a SiC MOSFET DC-DC converter, is benchmarked over an inverter based on SiC MOSFETs in terms of efficiency. The advantage of the first solution is to reduce the switching frequency and the dv/dt values without reducing the control frequency. Therefore, the major result is to lower the stress on the motor winding insulation. To assess and compare the efficiency performances of the two schemes, simulation and experimental tests have been carried out. Results show the feasibility of the proposed solution. [ABSTRACT FROM AUTHOR]

This paper is concerned with the use of conical induction machines. Such machines are extremely valuable when apart from the rotational torque output; an axial translation of the rotor is also required. The inherent attraction between the stator and rotor of any machine combined with the geometry of a conical machine will provide the required axial movement. However, when applied to aerospace applications, where reliability is very important, then full monitoring of the axial position is required. In this paper, an innovative approach aimed at monitoring and controlling the axial translation of a conical induction machine is proposed and investigated. In order to increase the system reliability and also decrease component count as demanded by the application, the methodology is a sensor-less technique based on an innovative variant of the high-frequency injection approach. In this paper, the technique has been fully investigated and experimentally validated on a purposely built instrumented test-rig. [ABSTRACT FROM PUBLISHER]

High-speed regimes allow an increase in the power density of electrical drives, which is a necessary characteristic in aeronautical applications. In such a context, together with the typical nonlinearities of low-speed drives, i.e., core saturation, phenomena related to high fundamental to sampling frequency ratios appear increasingly significant. This paper applies methodologies based on modern robust control to high-speed synchronous reluctance machines. The proposed method is based on a reformulation of the motor model as a linear parameter varying system. This allows transforming the current controller design in a multivariable optimization problem, which is solved with efficient numeric tools. The mathematical formulation of a robust digital controller directly designed in the discrete time domain is proposed. The controller performance are experimentally compared to of its counterpart designed in the continuous-time domain, and subsequently, discretized, as proposed in a previous work by the same authors, to have agreement a more standard decoupled current control using proportional-integral regulators. Results demonstrate the effectiveness of the proposed controller structure in current regulation, especially at high-speed regimes. [ABSTRACT FROM PUBLISHER]

This paper describes the design procedure followed to realize a high-speed synchronous reluctance machine for aeronautical application. The attention is mainly focused on the rotor design that is the most critical part of any synchronous reluctance machine; in particular for high-speed applications. After a preliminary optimization of the rotor geometry, a multiphysical design that considered mechanical, thermal, and electromagnetic properties was developed. The main steps of the design procedure together with an extensive analysis of the final design are presented here. Two prototypes have been realized using different rotor lamination materials in order to validate the design procedure. [ABSTRACT FROM PUBLISHER]

In modern electrical drives, all regulators are implemented in discrete-time domain. The design of the current controller in the continuous time and its following discretization is a common and effective procedure as long as the ratio between the fundamental frequency and the sampling frequency remains sufficiently small. If this condition is violated, the performance of the closed-loop system becomes increasingly poor or even unstable. Literature has proposed some effective strategies to design the controllers directly in the discrete-time domain, but these methods can be applied only to nonsalient machines. However, saliency is another major cause of loss of performance when not properly considered. This paper focuses on the extension of the discrete-time design rules to salient machines. Simulation and experimental results demonstrate the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Proximity losses are one of the main drawbacks in electrical machines with high rotational speed and electrical frequency. The reduction of proximity losses is usually pursued by adopting thin wires, which are twisted in the case of parallel connection. Twisting is a very effective solution for reducing proximity losses, but it also worsens the slot filling factor, heat dissipation, and dc resistance. This paper proposes an optimal twisting criterion that allows the minimization of the ac Joule losses due to parasitic circulating currents and reduces the number of twists and the length of the coils. The criterion applies to machines having tooth-wound coils and is validated by finite-element analysis and experimental results. [ABSTRACT FROM PUBLISHER]

The automated design of synchronous reluctance (SyR) motors based on multiobjective genetic optimization and finite-element analysis is considered in this paper. Three types of barrier shapes are considered, all described by an effective limited set of input variables. The three solutions are investigated to establish which of the geometries can give the best torque output and also which one represents the best compromise between output performance and computational time. The analysis presented in this paper shows that SyR motors designed automatically can give a good performance and can be designed in a reasonable time, and it is also shown that not all design degrees of freedom are useful in terms of motor performance. Two prototypes of automatically designed machines have been fabricated and experimentally compared with a third prototype designed according to state-of-the-art design principles. [ABSTRACT FROM PUBLISHER]

The automatic design of synchronous reluctance (SyR) machines is considered in this paper by means of finite-element analysis and multiobjective optimization algorithms (MOOAs). The research focuses on the design of the rotor geometry, which is the key aspect of the SyR machine design. In particular, the performance of three popular MOOAs is analyzed and compared in terms of quality of the final design and computational time. A procedure to minimize the computational burden of the optimized design process is introduced and applied to a three-layer and a five layer rotor. Two prototypes experimentally demonstrate the feasibility of the design procedure. [ABSTRACT FROM AUTHOR]

The insulation system's dielectric of the electric motor is very often subjected to severe electrical stress generated by the high d v / d t seen at the machine's terminals. The electrical stress and high reflected wave transient overvoltage are even more evident in case of high-speed machines fed by high-frequency (HF) converters featuring very fast wide-bandgap devices. They are promoting the occurrence of partial discharges and consequently accelerate ageing. As this is serious issue and the main cause of the drive failure, it is important to analyse and characterise the surges at the motor terminals. Several HF models of motors have been proposed in the literature for this purpose. This article presents a survey on HF motor models, which is crucial in understanding and studying the most critical parameter identification and overvoltage mitigation techniques. Moreover, it offers a comparison of the models' main features as well as a comparison with the experimental voltage waveform at motor terminals. A general overview of the partial discharge (PD) phenomenon is also provided, as it is favoured by HF operation and together with HF motor modelling provides key insights to the insulation ageing issue. In particular, an analysis of the effects of PWM waveform affecting insulation is given, as well as useful methods for developing strategies for the inspection and maintenance of winding insulation. [ABSTRACT FROM AUTHOR]

This paper proposes a scheme for precise position control of a mechatronic servo system based on linear synchronous motors. The control is based on gain-scheduled proportional integral derivatives (PIDs) (known as NPID in related literature) and adaptive approximation of uncertainties. NPID and adaptive approximation are combined in a constructive way to inherit advantages and overcome limitations of the single methods. In particular, NPID is used to stabilize the nominal plant, and its gains are scheduled so as to minimize the effects of friction and other uncertainties. Adaptive approximation is used to compensate further effects of nonlinearities and obtain a better overall tracking accuracy. A report on an extensive experimental investigation is provided to illustrate the practical advantages of the proposed scheme. [ABSTRACT FROM PUBLISHER]

The sensorless position control of permanent-magnet motors is successfully implemented by superimposing a high-frequency voltage signal on the voltage reference or adding a high-frequency current signal to the current reference. The former approach is usually preferred because of its simplicity, although the latter one may allow better performance. This paper presents a new algorithm for the sensorless control of low-saliency permanent-magnet synchronous motors based on high-frequency sinusoidal current signal injection into the d-axis. Different from the related literature, the position information is derived by analyzing the measured high-frequency currents. The amplitude of the d-axis voltage reference is also exploited to improve performance. A proportional–integral (PI) controller plus a resonant term (PI-RES) is adopted to ensure the accurate tracking of both the dc and high-frequency components of the d-axis current reference. The main advantages of the proposed approach are the increased accuracy and sensitivity with respect to the approach based on voltage injection, the insensitiveness to inverter nonlinearities that are compensated by the current regulation loop, the actual control on the injected current value, and the practical absence of acoustic noise. Experiments on a linear tubular permanent-magnet synchronous motor prototype have been carried out to verify the aforementioned advantages. This paper also presents a discussion of the parameters of the PI-RES. [ABSTRACT FROM AUTHOR]

Phase-locked loop (PLL) algorithms are commonly used to track sinusoidal components in currents and voltage signals in three-phase power systems. Despite the simplicity of those algorithms, problems arise when signals have variable frequency or amplitude, or are polluted with harmonic content and measurement noise, as can be found in aircraft ac power systems where the fundamental frequency can vary in the range 360–900 Hz. To improve the quality of phase and frequency estimates in such power systems, a novel PLL scheme based on a real-time implementation of the discrete Fourier transform (DFT) is presented in this paper. The DFT algorithm calculates the amplitudes of three consecutive components in the frequency domain. These components are used to determine an error signal which is minimized by a proportional–integral loop filter in order to estimate the fundamental frequency. The integral of the estimated frequency is the estimated phase of the fundamental component, and this is fed back to the DFT algorithm. The proposed algorithm can therefore be considered to be a PLL in which phase detection is performed via a DFT-based algorithm. A comparison has been made of the performances of a standard PLL and the proposed DFT-PLL using computer simulations and through experiments. [ABSTRACT FROM AUTHOR]

The sensorless position control of permanent-magnet (PM) synchronous motors can be successfully implemented by superimposing a high-frequency voltage signal on the control voltage. In this paper, the position estimation is obtained by means of a high-frequency sinusoidal voltage signal injected along the estimated d-axis. Several methods proposed in the literature obtain the position estimation by tracking the zero condition of the high-frequency q current component. We propose a new approach that also exploits the d-axis high-frequency current component and allows working with injected voltage signal of reduced amplitude, thus reducing noise and additional losses. The main contribution of this paper relies in the compensation of the motor end effects due to the finite length of the tubular motor armature. These effects must be taken into account in the motor modeling because they cause an error in the position estimation that varies with the motor position. The modeling of the phenomenon and a proper compensation technique are proposed in this paper. Last, a simplified integral-type controller is used to estimate motor position instead of the commonly adopted proportional–integral controller plus integrator, and this requires a low-effort design. Experiments on a linear tubular PM synchronous-motor prototype are presented to validate the theoretical analysis and evidence the feasibility of the proposed sensorless technique. [ABSTRACT FROM AUTHOR]

This paper proposes the compact differential evolution (cDE) algorithm. cDE, like other compact evolutionary algorithms, does not process a population of solutions but its statistic description which evolves similarly to all the evolutionary algorithms. In addition, cDE employs the mutation and crossover typical of differential evolution (DE) thus reproducing its search logic. Unlike other compact evolutionary algorithms, in cDE, the survivor selection scheme of DE can be straightforwardly encoded. One important feature of the proposed cDE algorithm is the capability of efficiently performing an optimization process despite a limited memory requirement. This fact makes the cDE algorithm suitable for hardware contexts characterized by small computational power such as micro-controllers and commercial robots. In addition, due to its nature cDE uses an implicit randomization of the offspring generation which corrects and improves the DE search logic. An extensive numerical setup has been implemented in order to prove the viability of cDE and test its performance with respect to other modern compact evolutionary algorithms and state-of-the-art population-based DE algorithms. Test results show that cDE outperforms on a regular basis its corresponding population-based DE variant. Experiments have been repeated for four different mutation schemes. In addition cDE outperforms other modern compact algorithms and displays a competitive performance with respect to state-of-the-art population-based algorithms employing a DE logic. Finally, the cDE is applied to a challenging experimental case study regarding the on-line training of a nonlinear neural-network-based controller for a precise positioning system subject to changes of payload. The main peculiarity of this control application is that the control software is not implemented into a computer connected to the control system but directly on the micro-controller. Both numerical results on the test functions and experimental results on the real-world problem are very promising and allow us to think that cDE and future developments can be an efficient option for optimization in hardware environments characterized by limited memory. [ABSTRACT FROM PUBLISHER]

Recent research on compact genetic algorithms (cGAs) has proposed a number of evolutionary search methods with reduced memory requirements. In cGAs, the evolution of populations is emulated by processing a probability vector with specific update rules. This paper considers the implementation of cGAs in microcontroller-based control platforms. In particular, to overcome some problems related to the binary encoding schemes adopted in most cGAs, this paper also proposes a new variant based on a real-valued solution coding. The presented variant achieves final solutions of the same quality as those found by binary cGAs, with a significantly reduced computational cost. The potential of the proposed approach is assessed by means of an extensive comparative study, which includes numerical results on benchmark functions, simulated and experimental microcon-troller design problems. [ABSTRACT FROM AUTHOR]

The article focuses on the design of a fuzzy logic-based navigation algorithm for autonomous robots. Its main goal is to allow autonomous units, equipped with relatively low-cost sensors and actuators, to perform complex tasks in uncertain or unknown environments. In addition, its technologies have a wide range of potential application fields including the exploration of inaccessible or hazardous environment, industrial automation, and biomedicine.

In this paper, we describe an evolutionary design procedure for discrete-time anti-windup controller for electrical drives. Using a genetic algorithm devised to test and compare controllers of different orders, we search for the discrete anti-windup controller achieving the optimal compromise of weighted cost and performance indices. The search is performed online, on the physical hardware, by continuously downloading and testing new solutions on a microprocessor running the control algorithms in real time. The controller obtained through genetic search significantly outperforms alternative schemes obtained with conventional design techniques. [ABSTRACT FROM AUTHOR]

Permanent magnet machines with segmented stator cores are affected by additional harmonic components of the cogging torque which cannot be minimized by conventional methods adopted for one-piece stator machines. In this study, a novel approach is proposed to minimize the cogging torque of such machines. This approach is based on the design of multiple independent shapes of the tooth tips through a topological optimization. Theoretical studies define a design formula that allows to choose the number of independent shapes to be designed, based on the number of stator core segments. Moreover, a computationally-efficient heuristic approach based on genetic algorithms and artificial neural network-based surrogate models solves the topological optimization and finds the optimal tooth tips shapes. Simulation studies with the finite element method validates the design formula and the effectiveness of the proposed method in suppressing the additional harmonic components. Moreover, a comparison with a conventional heuristic approach based on a genetic algorithm directly coupled to finite element analysis assesses the superiority of the proposed approach. Finally, a sensitivity analysis on assembling and manufacturing tolerances proves the robustness of the proposed design method. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the guest editors discuss various reports within the issue on topics including design of power converters, design of electrical filters and machines, and electronic control.

This paper proposes a new variable structure control scheme for a variable-speed, fixed-pitch ducted wind turbine, equipped with an annular, brushless permanent-magnet synchronous generator, considering a back-to-back power converter topology. The purpose of this control scheme is to maximise the aerodynamic power over the entire wind speed range, considering the mechanical safety limits of the ducted wind turbine. The ideal power characteristics are achieved with the design of control laws aimed at performing the maximum power point tracking control in the low wind speeds region, and the constant speed, power, and torque control in the high wind speed region. The designed control laws utilize a Luenberger observer for the estimation of the aerodynamic torque and a shallow neural network for wind speed estimation. The effectiveness of the proposed method was verified through tests in a laboratory setup. Moreover, a comparison with other solutions from the literature allowed us to better evaluate the performances achieved and to highlight the originality of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Widespread dissemination of electric mobility is highly dependent on the power converters, storage systems and renewable energy sources. The efficiency and reliability, combined with the emerging and innovative technologies, are crucial when speaking of power converters. In this paper the interleaved dc–dc topology has been considered for EV charging, due to its improved reliability. The efficiency comparison of the SiC-MOSFET and Si-IGBT-based converters has been done on wide range of switching frequency and output inductances. The interleaved converters were considered with the optimal switching parameters resulting from the analysis done on a detailed parasitic circuit model, ensuring minimum losses and maintaining the safe operating area. The analysis included the comparison of different inductors, and for the selected ones the complete system efficiency and cost were conducted. The results indicate the benefits when SiC-MOSFETs are applied to the interleaved dc–dc topology for wide ranges of output inductances and switching frequencies, and most importantly, they offer lower total volume but also total cost. The realistic and dynamic models of power devices obtained from the manufacturer's experimental tests have been considered in both LTspice and PLECS simulation tools. [ABSTRACT FROM AUTHOR]

In the field of sensorless control of permanent magnet synchronous motors (PMSMs), different techniques based on machine anisotropies have been studied and implemented successfully. Nevertheless, most proposed approaches extract the rotor position information from the measured machine currents, that, when applied to low-power machines, might require high-bandwidth current sensors. An interesting alternative is given by sensorless techniques that exploit the star-point voltage of PMSMs, such as the direct flux control technique. This work aims at analyzing the conditions of applicability of such technique by considering a more thorough description of the machine inductance matrix. After a comprehensive mathematical description of the technique and characterization of the machine anisotropy information that is extracted from the star-point voltage, simulation as well as experimental results conducted on a test machine are presented and discussed in order to validate the proposed theory. [ABSTRACT FROM AUTHOR]

Wide bandgap (WBG) power devices such as silicon carbide (SiC) can viably supply high speed electrical drives, due to their capability to increase efficiency and reduce the size of the power converters. On the other hand, high frequency operation of the SiC devices emphasizes the effect of parasitics, which generates reflected wave transient overvoltage on motor terminals, reducing the life time and the reliability of electric drives. In this paper, a SiC metal-oxide-semiconductor field-effect transistor (MOSFET) based two level (2L) inverter is systematically studied and compared to the performance of Si insulated-gate bipolar transistor (IGBT) based three level (3L) neutral point clamped (NPC) inverter topologies, for high speed AC motor loads, in terms of efficiency, overvoltages, heat sink design, and cost. A fair comparison was introduced for the first time, having the same output voltage capabilities, output current total harmonic distortion (THD), and overvoltages for the three systems. The analysis indicated the convenience of using the SiC MOSFET based 2L inverter for lower output power. In the case of the maximum output power, the heat sink volume was found to be 20% higher for the 2L SiC based inverter when compared to 3L NPC topologies. Simulations were carried out by realistic dynamic models of power switch modules obtained from the manufacturer's experimental tests and verified both in the LTspice and PLECS simulation packages. [ABSTRACT FROM AUTHOR]

Hysteresis motor and clutches have several advantages, such as constant torque from zero to synchronous speed, low torque ripple, and low fabrication cost. Low efficiency and power factor are the main features that have limited the application of this type of electrical machine to few applications. Being a niche argument, little literature has addressed the problem of analytical and finite element (FE) modelling of hysteresis electrical machines. This paper first describes the most important contributions of the literature on the analytical and FE modelling of hysteresis motors and clutches and then proposes a method for the fast computation of its performance. The proposed procedure consists of two steps: first, a magneto-static FE simulation is performed considering the normal magnetization curve of the hysteresis material; then, the average torque is computed by a post-processing analysis. The proposed method is used to analyze a hysteresis clutch and the obtained results are compared with those achieved using a commercial finite element software that implements a vector hysteresis model. [ABSTRACT FROM AUTHOR]

The present research aims to exploit commercially available materials and machines to fabricate multilayer, topologically designed transducers, which can be embedded into mechanical devices, such as soft or rigid grippers. Preliminary tests on the possibility of fabricating 3D-printed transducers using a commercial conductive elastomeric filament, carbon black-filled thermoplastic polyurethane, are presented. The commercial carbon-filled thermoplastic polyurethane (TPU), analyzed in the present paper, has proven to be a candidate material for the production of 3D printed displacement sensors. Some limitations in fabricating the transducers from a 2.85 mm filament were found, and comparisons with 1.75 mm filaments should be conducted. Moreover, further research on the low repeatability at low displacements and the higher performance of the hollow structure, in terms of repeatability, must be carried out. To propose an approach that can very easily be reproduced, only commercial filaments are used. [ABSTRACT FROM AUTHOR]

This work is focused on the design optimization of electrical machines that are used in small-scale direct-drive aerogenerators. A ducted wind turbine, equipped with a diffuser, is considered due to its enhanced power capability with respect to bare turbines. An annular type Permanent Magnet brushless generator is integrated in the turbine structure: the stator coils are placed in the internal part of the diffuser, whereas the permanent magnets are on an external ring connected to the turbine blade tips. Moreover, as regards the stator windings, the Printed Circuit Board (PCB) technology is investigated in order to exploit its advantages with respect to conventional wire coils, such as the increased current density capacity, the reduction of costs, and the enhanced precision and repeatability of the PCBs. An original design procedure is presented together with some scalability rules. An automated tool has been developed in order to aid the electrical machine designer in the first design stages: the tool performs multi-objective optimizations (using the Matlab Genetic Algorithm Toolbox), coupled to fast Finite Element analysis (through the open-source software FEMM) for the evaluation of the electromagnetic torque and field distribution. The proposed procedure is applied to the design of an annular PM generator directly coupled to a small-scale turbine for an urban application. [ABSTRACT FROM AUTHOR]