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

Preliminary power train design for a state-of-the-art electric vehicle

Power train designs which can be implemented within the current state-of-the-art were identified by means of a review of existing electric vehicles and suitable off-the-shelf components. The affect of various motor/transmission combinations on vehicle range over the SAE J227a schedule D cycle was evaluated. The selected, state-of-the-art power train employs a dc series wound motor, SCR controller, variable speed transmission, regenerative braking, drum brakes and radial ply tires. Vehicle range over the SAE cycle can be extended by approximately 20% by the further development of separately excited, shunt wound DC motors and electrical controllers. Approaches which could improve overall power train efficiency, such as AC motor systems, are identified. However, future emphasis should remain on batteries, tires and lightweight structures if substantial range improvements are to be achieved

On-line Condition Monitoring, Fault Detection and Diagnosis in Electrical Machines and Power Electronic Converters

The objective of this PhD research is to develop robust, and non-intrusive condition monitoring methods for induction motors fed by closed-loop inverters. The flexible energy forms synthesized by these connected power electronic converters greatly enhance the performance and expand the operating region of induction motors. They also significantly alter the fault behavior of these electric machines and complicate the fault detection and protection. The current state of the art in condition monitoring of power-converter-fed electric machines is underdeveloped as compared to the maturing condition monitoring techniques for grid-connected electric machines. This dissertation first investigates the stator turn-to-turn fault modelling for induction motors (IM) fed by a grid directly. A novel and more meaningful model of the motor itself was developed and a comprehensive study of the closed-loop inverter drives was conducted. A direct torque control (DTC) method was selected for controlling IM’s electromagnetic torque and stator flux-linkage amplitude in industrial applications. Additionally, a new driver based on DTC rules, predictive control theory and fuzzy logic inference system for the IM was developed. This novel controller improves the performance of the torque control on the IM as it reduces most of the disadvantages of the classical and predictive DTC drivers. An analytical investigation of the impacts of the stator inter-turn short-circuit of the machine in the controller and its reaction was performed. This research sets a based knowledge and clear foundations of the events happening inside the IM and internally in the DTC when the machine is damaged by a turn fault in the stator. This dissertation also develops a technique for the health monitoring of the induction machine under stator turn failure. The developed technique was based on the monitoring of the off-diagonal term of the sequence component impedance matrix. Its advantages are that it is independent of the IM parameters, it is immune to the sensors’ errors, it requires a small learning stage, compared with NN, and it is not intrusive, robust and online. The research developed in this dissertation represents a significant advance that can be utilized in fault detection and condition monitoring in industrial applications, transportation electrification as well as the utilization of renewable energy microgrids. To conclude, this PhD research focuses on the development of condition monitoring techniques, modelling, and insightful analyses of a specific type of electric machine system. The fundamental ideas behind the proposed condition monitoring technique, model and analysis are quite universal and appeals to a much wider variety of electric machines connected to power electronic converters or drivers. To sum up, this PhD research has a broad beneficial impact on a wide spectrum of power-converter-fed electric machines and is thus of practical importance

Current based condition monitoring of electromechanical systems. Model-free drive system current monitoring: faults detection and diagnosis through statistical features extraction and support vector machines classification.

A non-invasive, on-line method for detection of mechanical (rotor, bearings eccentricity) and stator winding faults in a 3-phase induction motors from observation of motor line current supply input. The main aim is to avoid the consequence of unexpected failure of critical equipment which results in extended process shutdown, costly machinery repair, and health and safety problems. This thesis looks into the possibility of utilizing machine learning techniques in the field of condition monitoring of electromechanical systems. Induction motors are chosen as an example for such application. Electrical motors play a vital role in our everyday life. Induction motors are kept in operation through monitoring its condition in a continuous manner in order to minimise their off times. The author proposes a model free sensor-less monitoring system, where the only monitored signal is the input to the induction motor. The thesis considers different methods available in literature for condition monitoring of induction motors and adopts a simple solution that is based on monitoring of the motor current. The method proposed use the feature extraction and Support Vector Machines (SVM) to set the limits for healthy and faulty data based on the statistical methods. After an extensive overview of the related literature and studies, the motor which is the virtual sensor in the drive system is analysed by considering its construction and principle of operation. The mathematical model of the motor is used for analysing the system. This is followed by laboratory testing of healthy motors and comparing their output signals with those of the same motors after being intentionally failed, concluding with the development of a full monitoring system. Finally, a monitoring system is proposed that can detect the presence of a fault in the monitored machine and diagnose the fault type and severityMinistry of Higher Education, Libya; Switchgear & Instruments Ltd

Design of a novel axial-flux induction machine for traction applications.

Masters Degree. University of KwaZulu-Natal, Durban.Induction motors are an important element in the industrial world; they are used in many applications, such as electric fans, elevators, pumps, conveyor belts, compressors and now even traction motors. Electric motors consume about 70 % of all industrial power consumption. Induction machines are also the source of the power generation such as in wind turbines. In recent years, the increase in price and supply-chain issues of rare earth magnets, which are currently an important material in brushless permanent machines, which are the most popular vehicular drive motor, has led to a focus on non-permanent magnet machine replacements, such as the induction machine. The induction machine is still undergoing design development and being used in an increasing number of applications. They can be used in fixed speed (grid-connected) or variable speed (variable-frequency inverter-connected) depending on the application. Loss reduction, weight, size, as well as minimizing the cost of raw materials for manufacturing, are some of the issues in design improvement. In view of this, it is important to develop innovative methods for producing electrical machines that will reduce losses and minimizing cost of production. The aim of this research work is to develop an appropriate analytical design procedure for designing an axial-flux induction machine and to evaluate the performance of the designed machine under various conditions. The machine must be robust and cheaper. ANSYS Maxwell software is used for 3D finite element modelling and simulation of the proposed axial-flux induction machine AFIM). For fast calculation, a simple sizing exercise is done using a pre-defined stator core. Then a radial-flux machine representation is developed in Siemens SPEED motor design software for fast assessment. The electromagnetic motor model is further tested to take into account the variations in rotor design. A proof-of-concept prototype was constructed for initial validation that the machine works and this design was modelled. The result of the simulation and the measurements from the laboratory design prove the possibility of the proposed AFIM for use in automotive application. Further design was carried out to improve the prototype using more substantial windings and a longer rotor. This design was tested with ANSYS Maxwell and SPEED. The designed machine offers a cost effective solution for future drive systems in automotive applications

Traction axial flux motor-generator for hybrid electric bus application

Tato dizertační práce se zabývá návrhem původního motor-generátoru s axiálním tokem a buzením permanetními magnety, zkonstruovaným specificky pro hybridní elektrický autobus. Návrhové zadání pro tento stroj přineslo požadavky, které vedly k této unikátní topologii tak, aby byl dosažen výkon, účinnost a rozměry stroje. Tato partikulární topologie motor-generátoru s axiálním tokem je výsledkem literární rešerše, kterou následoval výběr koncepce stroje s představeným návrhem jako výsledkem těchto procesů. Přístup k návrhu stroje s axiálním tokem sledoval „multi-fyzikální“ koncepci, která pracuje s návrhem elektromagnetickým, tepelným, mechanickým, včetně návrhu řízení, v jedné iteraci. Tím je v konečném návrhu zajištěna rovnováha mezi těmito inženýrskými disciplínami. Pro samotný návrh stroje byla vyvinuta sada výpočtových a analytických nástrojů, které byly podloženy metodou konečných prvků tak, aby samotný návrh stroje byl přesnější a spolehlivější. Modelování somtného elektrického stroje a celého pohonu poskytlo představu o výkonnosti a účinnosti celého subsytému v rozmanitých operačních podmínkách. Rovněž poukázal na optimizační potenciál pro návrh řízení subsystému ve smyslu maximalizace účinnosti celého pohonu. Bylo postaveno několik prototypů tohoto stroje, které prošly intensivním testováním jak na úrovni sybsytému, tak systému. Samotné výsledky testů jsou diskutovány a porovnány s analytickými výpočty parametrů stroje. Poznatky získané z prvního prototypu stroje pak sloužily k představení možností, jak zjednodušit výrobu a montáž stroje v příští generaci. Tato práce zaznamenává jednotlivé kroky během všech fází vývoje elektrického stroje s axiálním tokem, počínaje výběrem konceptu stroje, konče sumarizací zkušeností získaných z první generace prototypu tohoto stroje.This thesis deals with a design of a novel Axial-Flux Permanent Magnet Motor-Generator for a hybrid electric bus application. Thus, the design specification represents a set of requirements, which leads toward a concept of a unique topology meeting performance, efficiency and dimensional targets. The particular topology of the Axial-Flux Permanent Magnet Motor-Generator discussed in this work is an outcome of deep literature survey, followed by the concept selection stage with the layout of the machine as an outcome of this processes. The design approach behind this so-called Spoke Axial-Flux Machine follows an idea of multiphysics iterations, including electromagnetic, thermal, mechanical and controls design. Such a process behind the eventually proposed design ensured a right balance in between all of these engineering disciplines. A set of bespoke design and analysis tools was developed for that reason, and was backed up by extensive use of Finite-Element Analysis and Computational Fluid Dynamics. Therefore, the actual machine design gained higher level of confidence and fidelity. Modelling of the machine and its drive provided understanding of performance and efficiency of the whole subsystem at various operational conditions. Moreover, it has illustrated an optimization potential for the controls design, so that efficiency of the machine and power electronics might be maximized. Several prototypes of this machine have been built and passed through extensive testing both on the subsystem and system level. Actual test results are discussed, and compared to analytical predictions in terms of the machine's parameters. As a lesson learned from the first prototype of this machine, a set of redesign proposals aiming for simplification of manufacturing and assembly processes, are introduced. This work records steps behind all phases of development of the Axial Flux Machine from a basic idea as an outcome of concept selection stage, up to testing and wrap-up of experience gained from the first generation of the machine.

Development of a comprehensive energy model to simulate the energy efficiency of a battery electric vehicle to allow for prototype design optimisation and validation.

Masters Degree in mechanical Engineering. University of KwaZulu-Natal, Durban.This dissertation describes the development of an energy model of a battery electric vehicle (BEV) to assist designers in evaluating the impact of overall energy efficiency on vehicle performance. Energy efficiency is a crucial metric for BEVs as it defines the driving range of the vehicle and optimises the limited amount of energy available from the on-board battery pack, typically the most expensive component of the vehicle. Energy modelling also provides other useful information to the designer, such as the range of the vehicle according to legislative drive cycles and the maximum torque required from the motor. An accurate, fast and efficient model is therefore required to simulate BEVs in the early stages of design and for prototype validation. An extensive investigation into BEV modelling and the mechanisms of energy losses within BEVs was conducted. Existing literature was studied to characterise the effect of operating conditions on the efficiency of each mechanism, as well as investigating existing modelling techniques used to simulate each energy loss. A complete vehicle model was built by considering multiple domain modelling methods and the flow of energy between components in both mechanical and electrical domains. Simscape™, a MathWorks MATLAB™ tool, was used to build a physics based, forward facing model comprising a combination of custom coded blocks representing the flow of energy from the battery pack to the wheels. The acceleration and speed response of the vehicle was determined over a selected drive cycle, based on vehicle parameters. The model is applicable to normal driving conditions where the power of the motor does not exceed its continuous rating. The model relies on datasheet or non-proprietary parameters. These parameters can be changed depending on the architecture of the BEV and the exact components used, providing model flexibility. The primary model input is a drive cycle and the primary model output is range as well as the dynamic response of other metrics such as battery voltage and motor torque. The energy loss mechanisms are then assessed qualitatively and quantitatively to allow vehicle designers to determine effective strategies to increase the overall energy efficiency of the vehicle. The Mamba BEV, a small, high-power, commercially viable electric vehicle with a 21 kWh lithium-ion battery was simulated using the developed model. As the author was involved in the design and development of the vehicle, required vehicle parameters were easily obtained from manufacturers. The range of the vehicle was determined using the World-Harmonised Light Duty Vehicles Test Procedure and provided an estimated range of 285.3 km for the standard cycle and 420.8 km for the city cycle

Konttilukin sähköisen voimalinjan optimointi

This thesis concentrates on improving the energy efficiency of a straddle carrier by optimizing the electrical powertrain. Mobile working machines have significantly varying power demands in operation. Average demand is considerably lower than the maximum power requirements. This results in the machine operating far from its optimum efficiency range significant amount of its operating hours. This work cycle power level variation is vastly different from road vehicle power demands and optimization scenarios. Diesel powered working machine efficiency can be significantly improved with electric hybridization. The study is beneficial to both direct electric driven and hybrid systems. Main focus is the optimizing the motor and generator with the analysed load cycles. Comprehensive measurement data sets of vehicle use in real port operations are used as a base for the load analysis. In conjunction with the load models several mechanical and electrical simulation models were created. These component models were used to estimate changes that different motor and generator combinations would have on the overall efficiency. For this the efficiency maps for electrical machines are determined analytically in the whole torque–rotational speed plane based on the electrical machine parameters. Electrical machine losses and torque generation were studied in depth to find appropriate future development paths for the electrical powertrain of a straddle carrier. Additionally the payback time for the most feasible improvements were estimated. The thesis provides a case example of dimensioning and improving electrical powertrain of a working machine

Independent power flow control of multiple energy sources using a single electric machine

In this thesis, an independent power flow control of different energy sources connected to a single electric machine with a multitude of three-phase winding sets has been investigated. These machines are highly suitable for high power and critical applications. Additionally, these machines utilise the well-established three-phase power electronics technologies. The interest towards electrification of the transportation systems makes having multiple energy source a viable solution in the near future. Independent power flow control will enable the integration of hybrid energy storage systems on electrical vehicles such that the regenerative power can be directed to a super-capacitor while the cruising power is consumed from a battery bank. Nevertheless, this technique can be envisaged for different applications, from wind turbines to microgrids. In order to make all of this possible, the current amplitude of each winding set needs to be controlled first. Therefore, the control of the individual winding set’s currents’ amplitude and direction for multiple three-phase machines is the main subject of this thesis. The developed control schemes are based on vector space decomposition (VSD) rather than multi-stator (MS) approach. The former approach has a unique harmonic mapping and a single flux and torque producing subspace. Primarily in the thesis, current sharing strategy has been developed for both symmetrical and asymmetrical multiple three-phase machines with a common mode of operation for all the winding sets (motoring or generation). The strategy is based on the correlation of the xi-yi currents of the VSD and the αi-βi currents of the MS approach. These links enable the control of the current amplitude of the winding sets separately while maintaining the same torque and speed. The correlations between these modelling approaches combine good features of both modelling methods, the ability of the MS approach to control each winding set individually, and the VSD feature to perform the control in a completely decoupled subspace. Afterwards, the same strategy is employed to change the power flow direction as well as the amplitude of the multiple three-phase winding sets currents such that concurrent motoring and generation mode of operation is established. Two novel power sharing schemes have been proposed and analysed in this thesis. Both are based on VSD. The first scheme is sharing the flux and torque producing currents equally, while the second one is controlling the power by the torque producing current while preserving the same flux producing current. The transferred power efficiency has been improved significantly using the second approach. The same power sharing technique has been applied to an unorthodox type of machine – a twelve-phase machine implemented as a six-phase machine with double winding (hence, consisting of two six-phase sub-machines). The proposed power sharing scheme here is using a hybrid control approach combining two vector control schemes, based on MS and VSD. The control based on MS is controlling the power transfer from one six-phase sub-machine to the other one, while the control based on VSD, and with auxiliary current control, is sharing and directing power to a specific three-phase winding set within each sub-machine. Last but not least, two novel regenerative test methods have been proposed for multiple three-phase machines. The first approach is based on utilising a modified power sharing control strategy to operate the machine with iv rated current while maintaining the speed and circulating the power among the winding sets. The approach can be implemented differently based on the number of winding sets. With an even number of neutral points, half of the winding sets will be in motoring while the other half are in generation mode. However, when there is an odd number of winding sets, one of the winding sets will be in no-load mode of operation. The second approach is implementing the motoring and generation of the winding sets using a unique y-current component of the VSD. This method is only applicable to multiple three-phase machines with an even number of neutral points. The regenerative test can be applied to induction and synchronous machines equally but with a completely different outcome. For synchronous machines, the test can be used for efficiency evaluation and temperature rise test while for the induction machines the test can provide a straightforward experimental approach to segregate constant losses (core and mechanical losses) from load dependent losses (copper losses). All the proposed control methods have been validated by simulation and experimentally, except for the double winding machine where experiments were not done

Lightweight High-Efficiency Power Train Propulsion with Axial- Flux Machines for Electric or Hybrid Vehicles

The aim of this chapter is to present a new type of powertrain with dimensions and low weight, for vehicles with reduced carbon emissions, which have an axial synchronous machine with one stator and two rotor, with static converter that is simple and inexpensive, a broadcast transmission system using an electric differential, with the control of the two rotors so that they can operate as motor/generator, at the same rotational direction or in opposite directions, at the same speed value, at slightly different speeds or at much different speeds by using an original dual vector control with operating on dual frequency. This is a major concern of hybrid and electric vehicle manufacturers. Expected results: a lighter power train with 20% and an increase in 5% of electric drive efficiency, low inertia rotor at high speed, a compact electric drive system with high torque and simple control, intelligent energy management system with a new vision of technological and innovation development, and equal importance of environment protection. The electrical machines for hybrid (HEV) or electric (EV) drives include a variety of different topologies. According to outcomes of literature survey, induction machines alongside synchronous machines take the major place in HEV or EV power trains