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

Design and Application of Electrical Machines

Electrical machines are one of the most important components of the industrial world. They are at the heart of the new industrial revolution, brought forth by the development of electromobility and renewable energy systems. Electric motors must meet the most stringent requirements of reliability, availability, and high efficiency in order, among other things, to match the useful lifetime of power electronics in complex system applications and compete in the market under ever-increasing pressure to deliver the highest performance criteria. Today, thanks to the application of highly efficient numerical algorithms running on high-performance computers, it is possible to design electric machines and very complex drive systems faster and at a lower cost. At the same time, progress in the field of material science and technology enables the development of increasingly complex motor designs and topologies. The purpose of this Special Issue is to contribute to this development of electric machines. The publication of this collection of scientific articles, dedicated to the topic of electric machine design and application, contributes to the dissemination of the above information among professionals dealing with electrical machines

Fault tolerant vector control of five-phase permanent magnet motors

Equipped with appropriate control strategies, permanent magnet (PM) machines are becoming one of the most flexible types of actuators for many industrial applications. Among different types of PM machines, five-phase BLDC machines are very interesting in fault tolerant applications of PM drives. Torque improvement in five-phase BLDC machines can be accomplished by optimizing their mechanical structure or by enhancing their controlling methods. New current controllers are proposed in this thesis to improve the quality of generated torque under normal operations of five-phase BLDC machines. Proposed current controllers are based on combination of predictive deadbeat controlling strategy and Extended Kalman Filter estimation. These controllers will be the basis for accurate faulty operation of the motor. Operation of five-phase BLDC machines under faulty conditions has also been considered in this study. To improve the generated torque under faulty conditions, both amplitude and phase angle of fundamental and third current harmonics are globally optimized for the remaining healthy phases. Under faulty conditions, appropriate reference currents of a five-phase BLDC machine have oscillating dynamics both in phase and rotating reference frames. As a result, the implemented current controllers under these conditions should be robust and fast. Predictive deadbeat controllers are also proposed for faulty conditions of five-phase BLDC machines. Fault tolerant five-phase BLDC machines are very interesting in automotive applications such as electrical vehicles and more electric aircraft. In addition, these devices are gaining more importance in other fields such as power generation in wind turbines. In all of these applications, the efficiency of PM machine is of most importance. The efficiency of a typical five-phase BLDC machine is evaluated in this thesis for normal and different faulty conditions. Experimental evaluations are always conducted to verify the theoretical developments. These developments include proposed controlling methods, optimized reference currents, and simulated efficiency of five-phase BLDC machine under different operational conditions

Design and Control of Axial Flux Permanent Magnet Coreless Machines with Special Windings

Permanent magnet synchronous machines (PMSMs), particularly those of the axial flux type, are being researched and developed for various applications such as HVAC systems, aviation propulsion, and electric vehicles. The coreless (air-cored) stator axial flux permanent magnet (AFPM) machine topology offers notable advantages over conventional designs by eliminating magnetic cores and their associated losses. These advantages include potentially higher efficiency, zero cogging torque, and reduced audible noise and vibration. Eliminating the magnetic core also allows for more effective cooling systems, as coolants can be in direct contact with the stator windings, potentially improving power density and specific torque. The absence of a magnetic core presents an opportunity to incorporate special windings, including printed circuit board (PCB) coils, in coreless AFPM machines. This work proposes a systematic multi-step design procedure for highly efficient PCB stator coreless AFPM machines with minimal eddy and circulating current losses. PCB stators have gained popularity due to their reliable and highly repeatable fabrication process, high modularity, and lightweight nature. In this type of machine, the copper conductors are directly exposed to airgap flux density fluctuations, which can lead to considerable losses due to eddy currents. Additionally, in these machines with a wide magnetic airgap, parallel conductors experience different induced voltages, resulting in circulating current losses. Designers face challenges in mitigating these stator winding losses, which are a primary source of loss in coreless machines. The significant flexibility in PCB coil shape designs and their interconnections provides an excellent opportunity to enhance the efficiency of coreless machines through optimized stator coil designs. The proposed design procedure includes initial sizing, optimization of the machine envelope design using an evolutionary algorithm and computationally efficient 3D finite element analysis (FEA) models, and detailed design of a PCB stator layout to minimize eddy and circulating current losses. Several open-circuit loss mitigation techniques, including a novel layer transposition method, are proposed in this dissertation based on analytical equations and 3D FEA, while considering PCB manufacturing limitations and standards. Experimental results indicate significantly reduced eddy current losses and virtually zero circulating currents, achieving ultra-high efficiency of 96% under rated conditions. To leverage the full potential of coreless axial flux PM machines, a high-performance control system tailored to this type of machine, considering their intrinsic features, is proposed. This dissertation introduces a fault-tolerant control system for both threephase and two-phase configurations. Initially, the performance and fault tolerance of a two-phase variant of a coreless AFPM machine are compared with its three-phase counterpart, indicating that both configurations have comparable specific power and efficiency, while the two-phase variant features a high level of fault tolerance due to electrically and magnetically isolated phases. This dissertation proposes a dual-mode controller for coreless AFPM machines with independent phase modules across a wide range of speeds. Coreless AFPM machines exhibit ultra-low phase inductance due to a wide effective airgap. This low phase inductance can lead to high current ripple, resulting in additional power losses and limiting the flux-weakening capability. The proposed approach includes a combination of sine-wave field-oriented control (FOC) and square-wave control schemes to address these control challenges. The computational burden of the square-wave control mode is considerably lower than that of conventional FOC and eliminates the need for high-precision encoders, facilitating ultra-high speeds and improving reliability. The square-wave control mode also extends the machine’s speed range while fully utilizing the DC-link voltage. Inverters based on wide bandgap devices are used in the drive system, enabling high switching frequencies and significantly reducing current ripple due to low phase inductance and its negative impacts in inverter-fed coreless AFPM machines. Several approaches to improve the fault tolerance of the motor-drive system are introduced in this dissertation. These include a modular design for coreless AFPM machines with PCB stators, which provides electric and magnetic insulation, and encoderless operation with a flux observer-based sensorless control. The performance of the prototype machine, with both two-phase and three-phase configurations operating in different control modes and under normal and post-fault conditions, is experimentally investigated

Design strategies using rotor, stator and magnet disposition for flux weakening in PM motors with wide operating speed range

LAUREA MAGISTRALERequisiti ambientali e normativi hanno portato ad accresciute esigenze di efcienza in applicazioni industriali, con stringenti specifche normative (cfr IEC 60034-30), che i Motori a Induzione (IM) difcilmente riescono a soddisfare. Grazie alla disponibilità e al minor costo dei magneti permanenti in terre rare (NdFeB o SmCo) e al miglioramento nel progetto e nel controllo dei Motori Sincroni a MP (PMSM), questi ultimi vengono impiegati per applicazioni nelle quali fnora erano impiegati motori IM, come ad esempio la trazione, le turbine eoliche, le applicazioni aerospaziali, etc. L’obiettivo di questo lavoro di tesi é la descrizione, l’analisi e il confronto tra diverse topologie di macchina a MP, impiegate in applicazioni ad estesa zona di funzionamento con indebolimento di campo, in un’ampia intervallo di velocità. Sono descritti diversi tipi di PMSM e vengono analizzati i relativi aspetti di progettazione, riguardo a varie problematiche di funzionamento, quali perdite per correnti parassite nel rotore, perdite nel ferro di statore, parziale smagnetizzazione irreversibile dei MP, coppia di cogging e ondulazione di coppia a carico: nella tesi sono analizzate le soluzioni a tali problemi, basati su opportune modifche di progetto del rotore, dell’avvolgimento statore e dei MP.Environmental and regulatory requirements has lead to improved efciency demands in industrial application, IEC 60034−30 standard demands very stringent requirements, which induction motors are hard pressed to satisfy. With easier and cheaper access to rare earth (NdFebB or SmCo) magnets and improved Permanent Magnet Synchronous machine(PMSM) design and control technologies, PMSM are being employed for applications feld, hitherto occupied by IMs, such as traction, wind turbines, aerospace, etc. The objective of this thesis work is to introduce, analyze and compare different design topologies employed in PM machines for flux weakening operation at wide operating speed range. Different PMSM are described and the design topologies employed in each are analyzed with respect to their effect in issues involved with PMSM operations such as rotor eddy current loss, stator iron loss, partial permanent demagnetization, cogging and torque ripples, and the solutions for them with the help of modifcation in rotor, stator winding and magnet design has been presented in this thesis

A Novel Design Optimization of a Fault-Tolerant AC Permanent Magnet Machine-Drive System

In this dissertation, fault-tolerant capabilities of permanent magnet (PM) machines were investigated. The 12-slot 10-pole PM machines with V-type and spoke-type PM layouts were selected as candidate topologies for fault-tolerant PM machine design optimization problems. The combination of 12-slot and 10-pole configuration for PM machines requires a fractional-slot concentrated winding (FSCW) layout, which can lead to especially significant PM losses in such machines. Thus, a hybrid method to compute the PM losses was investigated, which combines computationally efficient finite-element analysis (CE-FEA) with a new analytical formulation for PM eddy-current loss computation in sine-wave current regulated synchronous PM machines. These algorithms were applied to two FSCW PM machines with different circumferential and axial PM block segmentation arrangements. The accuracy of this method was validated by results from 2D and 3D time-stepping FEA. The CE-FEA approach has the capabilities of calculating torque profiles, induced voltage waveforms, d and q-axes inductances, torque angle for maximum torque per ampere load condition, and stator core losses. The implementation techniques for such a method are presented. A combined design optimization method employing design of experiments (DOE) and differential evolution (DE) algorithms was developed. The DOE approaches were used to perform a sensitivity study from which significant independent design variables were selected for the DE design optimization procedure. Two optimization objectives are concurrently considered for minimizing material cost and power losses. The optimization results enabled the systematic comparison of four PM motor topologies: two different V-shape, flat bar-type and spoke-type, respectively. A study of the relative merits of each topology was determined. An automated design optimization method using the CE-FEA and DE algorithms was utilized in the case study of a 12-slot 10-pole PM machine with V-type PM layout. An engineering decision process based on the Pareto-optimal front for two objectives, material cost and losses, is presented together with discussions on the tradeoffs between cost and performance. One optimal design was finally selected and prototyped. A set of experimental tests, including open circuit tests at various speeds and on-load tests under various load and speed conditions, were performed successfully, which validated the findings of this work

Investigation on Multi-Physics Modelling of Fault Tolerant Stator Mounted Permanent Magnet Machines

This thesis investigates the stator mounted permanent magnet machines from the point of view of fault tolerant capability. The topologies studied are switched flux (and its derivatives C-Core, E-Core and modular), doubly salient and flux reversal permanent magnet machines. The study focuses on fault mode operation of these machines looking at severe conditions like short-circuit and irreversible demagnetization. The temperature dependence of the permanent magnet properties is taken into account. A complex multi-physics model is developed in order to assess the thermal state evolution of the switched flux machine during both healthy and faulty operation modes. This model couples the electro-mechanical domain with the thermal one, thus being able to consider a large range of operating conditions. It also solves issues such as large computational time and resources while still maintaining the accuracy. Experimental results are also provided for each chapter. A hierarchy in terms of fault tolerant capability is established. A good compromise can be reached between performance and fault tolerant capability. The mechanism of the magnet irreversible demagnetization process is explained based on magnetic circuit configuration. It is also found that the studied topology are extremely resilient against the demagnetizing influence of the short-circuit current and the magnet demagnetization is almost only affected by temperature

Fractional slot concentrated winding PM synchronous motors for transport electrification applications

Moving towards electrification of transport including electric vehicles (EV), more electric aircraft (MEA), and electric ships offers a crucial way in dealing with global carbon emissions and climate change. Electric motors are a key enabling technique in these applications, but their increased use is associated with requirements of extreme power/torque density, excellent fault-tolerance, high efficiency, and good manufacturability. The main goal of this thesis is to study permanent magnet electric machine winding theory to determine the suitable electric machine winding topologies for different applications. Two separate vehicle transport applications are investigated, including an EV traction motor and a novel modular electromechanical actuator (EMA) for MEA. The study of the EV traction motor involves the investigation of methods for reducing the significant stator MMF harmonics in fractional slot concentrated winding (FSCW) electric machines, and the development of novel FSCW topologies while keeping the benefits of easy manufacturing and the non-overlapping characteristic of concentrated windings. The novel FSCW topologies can be extended to multi-phase FSCW motors. A traction motor equipped with a novel 24 slots, 14 poles FSCW topology and interior PM (IPM) rotor is developed for evaluation. The performance under normal and fault conditions is fully explored and validated with simulation and experimental results, which demonstrates the applicability and strong potential of the proposed 24 slots, 14 poles IPM motor in fault-tolerant traction motor applications. The second topic focuses on modular fault-tolerant EMAs for aircraft actuation systems which can meet a diverse range of requirements. The architecture and design considerations of the actuator system are firstly determined considering reliability, fault-tolerance, and weight. The modular EMA scheme consisting of a direct-drive rotary motor and mechanical screw is identified. A dual 3-phase 24 slots, 22 poles FSCW motor with a surface-mounted permanent magnet (SPM) rotor is developed and evaluated in terms of electromagnetics, thermal management, and fault-tolerance. Experimental results of the modular EMA motor prototypes agree well with predicted results. All this confirms the applicability and satisfactory implementation of the modular EMA motor for aircraft actuation system applications

Fault detection of permanent magnet synchronous machines: an overview

These days, as the application of permanent magnet synchronous machines (PMSMs) and drive systems becomes popular, the reliability issue of PMSMs gains more and more attention. To improve the reliability of PMSMs, fault detection is one of the practical techniques that enables the early interference and mitigation of the faults and subsequently reduces the impact of the faults. In this paper, the state-of-the-art fault detection methods of PMSMs are systematically reviewed. Three typical faults, i.e., the inter-turn short-circuit fault, the PM partial demagnetization fault, and the eccentricity fault, are included. The existing methods are firstly classified into signal-, model-, and data-based methods, while the focus of this paper is laid on the signal sources and the signatures utilized in these methods. Based on this perspective, this paper intends to provide a new insight into the inherent commonalities and differences among these detection methods and thus inspire further innovation. Furthermore, comparison is conducted between methods based on different signatures. Finally, some issues in the existing methods are discussed, and future work is highlighted

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