Advances in Rotating Electric Machines

It is difficult to imagine a modern society without rotating electric machines. Their use has been increasing not only in the traditional fields of application but also in more contemporary fields, including renewable energy conversion systems, electric aircraft, aerospace, electric vehicles, unmanned propulsion systems, robotics, etc. This has contributed to advances in the materials, design methodologies, modeling tools, and manufacturing processes of current electric machines, which are characterized by high compactness, low weight, high power density, high torque density, and high reliability. On the other hand, the growing use of electric machines and drives in more critical applications has pushed forward the research in the area of condition monitoring and fault tolerance, leading to the development of more reliable diagnostic techniques and more fault-tolerant machines. This book presents and disseminates the most recent advances related to the theory, design, modeling, application, control, and condition monitoring of all types of rotating electric machines

A Novel Zero-Sequence Current Elimination PWM Scheme for an Open-Winding PMSM With Common DC Bus

This paper introduces a novel pulse width modulation (PWM) scheme for an OW-PMSM driven by dual two-level three-phase inverter with common dc bus which can effectively deal with the inherent zero-sequence current (ZSC) problem. Based on conventional symmetrical unipolar double frequency SPWM scheme with appropriate phase-shift, the common mode voltage (CMV) of two inverters can keep the same and cancel out each other to eliminate the modulated zero sequence voltage (ZSV) disturbance source. In this case, the double frequency effect can be retained to reduce the ac side current ripple and suppress both the corresponding motor vibration and acoustic noise which is advantageous to improve the synthetic performance of motor. The DC bus voltage utilization of the novel PWM scheme is proved to reach the maximum value as same as the conventional modulated ZSV elimination scheme. Meanwhile, a zero-sequence controller is designed to suppress ZSC by further adjusting the two CMVs to counteract other zero-sequence disturbance sources. To verify the analysis, the proposed PWM technique associated with the control method is implemented in an OW-PMSM experimental setup to validate the superiority of proposed method

Critical Aspects of Electric Motor Drive Controllers and Mitigation of Torque Ripple - Review

Electric vehicles (EVs) are playing a vital role in sustainable transportation. It is estimated that by 2030, Battery EVs will become mainstream for passenger car transportation. Even though EVs are gaining interest in sustainable transportation, the future of EV power transmission is facing vital concerns and open research challenges. Considering the case of torque ripple mitigation and improved reliability control techniques in motors, many motor drive control algorithms fail to provide efficient control. To efficiently address this issue, control techniques such as Field Orientation Control (FOC), Direct Torque Control (DTC), Model Predictive Control (MPC), Sliding Mode Control (SMC), and Intelligent Control (IC) techniques are used in the motor drive control algorithms. This literature survey exclusively compares the various advanced control techniques for conventionally used EV motors such as Permanent Magnet Synchronous Motor (PMSM), Brushless Direct Current Motor (BLDC), Switched Reluctance Motor (SRM), and Induction Motors (IM). Furthermore, this paper discusses the EV-motors history, types of EVmotors, EV-motor drives powertrain mathematical modelling, and design procedure of EV-motors. The hardware results have also been compared with different control techniques for BLDC and SRM hub motors. Future direction towards the design of EV by critical selection of motors and their control techniques to minimize the torque ripple and other research opportunities to enhance the performance of EVs are also presented.publishedVersio

EFFICIENCY AND RELIABILITY ENHANCEMENT OF MULTIPHASE SYNCHRONOUS MOTOR DRIVES

Multiphase electric machines are attractive in comparison with three-phase ones due to advantages such as fault-tolerant nature, smaller rating per phase and lower torque ripple. More specifically, the machines with multiple three-phase windings are particularly convenient, because they are suitable for standard off-the-shelf three-phase dc/ac converter modules. For instance, they are becoming a serious option for applications such as electric vehicles and wind turbines. On the other hand, in these applications, operation at low power is often required for long time intervals; hence, improving the efficiency under such conditions is highly desired and could save a significant amount of energy in the long term. This dissertation proposes a method to enhance the efficiency of electric drives based on multiple three-phase windings at light load. The number of active legs is selected depending on the required torque at each instant. To ensure that the overall efficiency is effectively optimized, not only the converter losses, but also the stator copper losses, are taken into account. Experimental results verify the theoretical outcomes. Surface-mounted permanent-magnet synchronous motors (SPMSMs) require a position measurement to ensure a high-performance control. To avoid the cost and maintenance associated to position sensors, sensorless methods are often preferred. The approaches based on high-frequency signal injection are currently a well-established solution to obtain an accurate position estimation in SPMSMs. These techniques can be roughly divided into two groups: those based on sinusoidal or on square-wave high-frequency signals. The main drawback of the former is the limitation on the response speed, due to the presence of several low-pass filters (LPFs). On the other hand, the latter methods are sensitive to deadtime effects, and high-frequency closed-loop current control is required to overcome it. This dissertation proposes to improve the sensorless strategies based on sinusoidal high-frequency injection by simplifying the scheme employed to extract the information about the position error. Namely, two LPFs and several multiplications are removed. Such simplification does not only reduce the computational complexity, but also permits to obtain a faster response to the changes in the angle/speed, and hence, a faster closed-loop control. Experimental results based on a SPMSM prove the enhanced functionality of the proposed method with respect to the previous ones based on high-frequency sinusoidal signal injection

Optimal Modeled Six-Phase Space Vector Pulse Width Modulation Method for Stator Voltage Harmonic Suppression

Dual Y shift 30 six-phase motors are expected to be extensively applied in high-power yet energy-effective fields, and a harmonic-suppressing control strategy plays a vital role in extending their prominent features of low losses and ultra-quiet operation. Aiming at the suppression of harmonic voltages, this paper proposes a six-phase space vector pulse width modulation method based on an optimization model, namely OM-SVPWM. First, four adjacent large vectors are employed in each of 12 sectors on a fundamental sub-plane. Second, the optimization model is constructed to intelligently determine activation durations of the four vectors, where its objective function aims to minimize the synthesis result on a harmonic sub-plane, and its constraint condition is that the synthesis result on the fundamental sub-plane satisfies a reference vector. Finally, to meet the real-time requirement, optimum solutions are obtained by using general central path following algorithm (GCPFA). Simulation and experiment results prove that, the OM-SVPWM performs around 37% better than a state-of-the-art competitive SVPWM in terms of harmonics suppression, which promise the proposed OM-SVPWM conforms to the energy-effective direction in actual engineering applications.Peer reviewe

Advances in dual-three-phase permanent magnet synchronous machines and control techniques

Multiphase electrical machines are advantageous for many industrial applications that require a high power rating, smooth torque, power/torque sharing capability, and fault-tolerant capability, compared with conventional single three-phase electrical machines. Consequently, a significant number of studies of multiphase machines has been published in recent years. This paper presents an overview of the recent advances in multiphase permanent magnet synchronous machines (PMSMs) and drive control techniques, with a focus on dual-three-phase PMSMs. It includes an extensive overview of the machine topologies, as well as their modelling methods, pulse-width-modulation techniques, field-oriented control, direct torque control, model predictive control, sensorless control, and fault-tolerant control, together with the newest control strategies for suppressing current harmonics and torque ripples, as well as carrier phase shift techniques, all with worked examples

Dual-Segment Three-Phase PMSM With Dual Inverters for Leakage Current and Common-Mode EMI Reduction

In a motor drive system, the inverter working in discrete and impulse states generates a common-mode voltage (CMV) at the terminal of the stator winding neutral point. The high-frequency CMV can induce a leakage current and a common-mode (CM) electromagnetic interference (EMI), which are potential threats to personal safety and system stability. The conventional single three-phase inverter is found to be powerless in eliminating the CMV, while the two paralleled inverters can effectively eliminate the CMV theoretically, but the three coupled inductors (CIs) should be added to the motor drive system which reduces the power density and efficiency of the system. A novel method, which associates a specially designed dual-segment three-phase motor with the CMV elimination modulation algorithm, can be utilized to cancel the extra CIs without degrading the function of the leakage current and the CM EMI suppression. The design of the dual-segment three-phase permanent magnet synchronous machine is introduced, with identical back electromotive forces for two groups of windings but with little magnetic coupling between them. Simulation and experimental results are provided to verify the validity of the proposed method in CM-related reduction and CI cancellation. Compared with the zero-CM pulsewidth modulation for paralleled inverters proposed in a previous work, the proposed dual-segment three-phase motor drive can achieve a better power density by removing the CIs

Special Power Electronics Converters and Machine Drives with Wide Band-Gap Devices

Power electronic converters play a key role in power generation, storage, and consumption. The major portion of power losses in the converters is dissipated in the semiconductor switching devices. In recent years, new power semiconductors based on wide band-gap (WBG) devices have been increasingly developed and employed in terms of promising merits including the lower on-state resistance, lower turn-on/off energy, higher capable switching frequency, higher temperature tolerance than conventional Si devices. However, WBG devices also brought new challenges including lower fault tolerance, higher system cost, gate driver challenges, and high dv/dt and resulting increased bearing current in electric machines. This work first proposed a hybrid Si IGBTs + SiC MOSFETs five-level transistor clamped H-bridge (TCHB) inverter which required significantly fewer number of semiconductor switches and fewer isolated DC sources than the conventional cascaded H-bridge inverter. As a result, system cost was largely reduced considering the high price of WBG devices in the present market. The semiconductor switches operated at carrier frequency were configured as Silicon Carbide (SiC) devices to improve the inverter efficiency, while the switches operated at fundamental output frequency (i.e., grid frequency) were constituted by Silicon (Si) IGBT devices. Different modulation strategies and control methods were developed and compared. In other words, this proposed SiC+Si hybrid TCHB inverter provided a solution to ride through a load short-circuit fault. Another special power electronic, multiport converter, was designed for EV charging station integrated with PV power generation and battery energy storage system. The control scheme for different charging modes was carefully developed to improve stabilization including power gap balancing, peak shaving, and valley filling, and voltage sag compensation. As a result, the influence on the power grid was reduced due to the matching between daily charging demand and adequate daytime PV generation. For special machine drives, such as slotless and coreless machines with low inductance, low core losses, typical drive implementations using conventional silicon-based devices are performance limited and also produce large current and torque ripples. In this research, WBG devices were employed to increase inverter switching frequency, reduce current ripple, reduce filter size, and as a result reduce drive system cost. Two inverter drive configurations were proposed and implemented with WBG devices in order to mitigate such issues for 2-phase very low inductance machines. Two inverter topologies, i.e., a dual H-bridge inverter with maximum redundancy and survivability and a 3-leg inverter for reduced cost, were considered. Simulation and experimental results validated the drive configurations in this dissertation. An integrated AC/AC converter was developed for 2-phase motor drives. Additionally, the proposed integrated AC/AC converter was systematically compared with commonly used topologies including AC/DC/AC converter and matrix converters, in terms of the output voltage/current capability, total harmonics distortion (THD), and system cost. Furthermore, closed-loop speed controllers were developed for the three topologies, and the maximum operating range and output phase currents were investigated. The proposed integrated AC/AC converter with a single-phase input and a 2-phase output reduced the switch count to six and resulting in minimized system cost and size for low power applications. In contrast, AC/DC/AC pulse width modulation (PWM) converters contained twelve active power semiconductor switches and a common DC link. Furthermore, a modulation scheme and filters for the proposed converter were developed and modeled in detail. For the significantly increased bearing current caused by the transition from Si devices to WBG devices, advanced modeling and analysis approach was proposed by using coupled field-circuit electromagnetic finite element analysis (FEA) to model bearing voltage and current in electric machines, which took into account the influence of distributed winding conductors and frequency-dependent winding RL parameters. Possible bearing current issues in axial-flux machines, and possibilities of computation time reduction, were also discussed. Two experimental validation approaches were proposed: the time-domain analysis approach to accurately capture the time transient, the stationary testing approach to measure bearing capacitance without complex control development or loading condition limitations. In addition, two types of motors were employed for experimental validation: an inside-out N-type PMSM was used for rotating testing and stationary testing, and an N-type BLDC was used for stationary testing. Possible solutions for the increased CMV and bearing currents caused by the implementation of WGB devices were discussed and developed in simulation validation, including multi-carrier SPWM modulation and H-8 converter topology

Analysis of the Harmonic Performance of Power Converters and Electrical Drives

Power converters have progressively become the most efficient and attractive solution in recent decades in many industrial sectors, ranging from electric mobility, aerospace applications to attain better electric aircraft concepts, vast renewable energy resource integration in the transmission and distribution grid, the design of smart and efficient energy management systems, the usage of energy storage systems, and the achievement of smart grid paradigm development, among others.In order to achieve efficient solutions in this wide energy scenario, over the past few decades, considerable attention has been paid by the academia and industry in order to develop new methods to achieve power systems with maximum harmonic performance aiming for two main targets. On the one hand, the high-performance harmonic performance of power systems would lead to improvements in their power density, size and weight. This becomes critical in applications such as aerospace or electric mobility, where the power converters are on-board systems. On the other hand, current standards are becoming more and more strict in order to reduce the EMI and EMC noise, as well as meeting minimum power quality requirements (i.e., grid code standards for grid-tied power systems)