Modulation Techniques for Multi-Phase Converters and Control Strategies for Multi-Phase Electric Drives

The ever-increasing spread of automation in industry puts the electrical engineer in a central role as a promoter of technological development in a sector such as the use of electricity, which is the basis of all the machinery and productive processes. Moreover the spread of drives for motor control and static converters with structures ever more complex, places the electrical engineer to face new challenges whose solution has as critical elements in the implementation of digital control techniques with the requirements of inexpensiveness and efficiency of the final product. The successfully application of solutions using non-conventional static converters awake an increasing interest in science and industry due to the promising opportunities. However, in the same time, new problems emerge whose solution is still under study and debate in the scientific community During the Ph.D. course several themes have been developed that, while obtaining the recent and growing interest of scientific community, have much space for the development of research activity and for industrial applications. The first area of research is related to the control of three phase induction motors with high dynamic performance and the sensorless control in the high speed range. The management of the operation of induction machine without position or speed sensors awakes interest in the industrial world due to the increased reliability and robustness of this solution combined with a lower cost of production and purchase of this technology compared to the others available in the market. During this dissertation control techniques will be proposed which are able to exploit the total dc link voltage and at the same time capable to exploit the maximum torque capability in whole speed range with good dynamic performance. The proposed solution preserves the simplicity of tuning of the regulators. Furthermore, in order to validate the effectiveness of presented solution, it is assessed in terms of performance and complexity and compared to two other algorithm presented in literature. The feasibility of the proposed algorithm is also tested on induction motor drive fed by a matrix converter. Another important research area is connected to the development of technology for vehicular applications. In this field the dynamic performances and the low power consumption is one of most important goals for an effective algorithm. Towards this direction, a control scheme for induction motor that integrates within a coherent solution some of the features that are commonly required to an electric vehicle drive is presented. The main features of the proposed control scheme are the capability to exploit the maximum torque in the whole speed range, a weak dependence on the motor parameters, a good robustness against the variations of the dc-link voltage and, whenever possible, the maximum efficiency. The second part of this dissertation is dedicated to the multi-phase systems. This technology, in fact, is characterized by a number of issues worthy of investigation that make it competitive with other technologies already on the market. Multiphase systems, allow to redistribute power at a higher number of phases, thus making possible the construction of electronic converters which otherwise would be very difficult to achieve due to the limits of present power electronics. Multiphase drives have an intrinsic reliability given by the possibility that a fault of a phase, caused by the possible failure of a component of the converter, can be solved without inefficiency of the machine or application of a pulsating torque. The control of the magnetic field spatial harmonics in the air-gap with order higher than one allows to reduce torque noise and to obtain high torque density motor and multi-motor applications. In one of the next chapters a control scheme able to increase the motor torque by adding a third harmonic component to the air-gap magnetic field will be presented. Above the base speed the control system reduces the motor flux in such a way to ensure the maximum torque capability. The presented analysis considers the drive constrains and shows how these limits modify the motor performance. The multi-motor applications are described by a well-defined number of multiphase machines, having series connected stator windings, with an opportune permutation of the phases these machines can be independently controlled with a single multi-phase inverter. In this dissertation this solution will be presented and an electric drive consisting of two five-phase PM tubular actuators fed by a single five-phase inverter will be presented. Finally the modulation strategies for a multi-phase inverter will be illustrated. The problem of the space vector modulation of multiphase inverters with an odd number of phases is solved in different way. An algorithmic approach and a look-up table solution will be proposed. The inverter output voltage capability will be investigated, showing that the proposed modulation strategy is able to fully exploit the dc input voltage either in sinusoidal or non-sinusoidal operating conditions. All this aspects are considered in the next chapters. In particular, Chapter 1 summarizes the mathematical model of induction motor. The Chapter 2 is a brief state of art on three-phase inverter. Chapter 3 proposes a stator flux vector control for a three- phase induction machine and compares this solution with two other algorithms presented in literature. Furthermore, in the same chapter, a complete electric drive based on matrix converter is presented. In Chapter 4 a control strategy suitable for electric vehicles is illustrated. Chapter 5 describes the mathematical model of multi-phase induction machines whereas chapter 6 analyzes the multi-phase inverter and its modulation strategies. Chapter 7 discusses the minimization of the power losses in IGBT multi-phase inverters with carrier-based pulse width modulation. In Chapter 8 an extended stator flux vector control for a seven-phase induction motor is presented. Chapter 9 concerns the high torque density applications and in Chapter 10 different fault tolerant control strategies are analyzed. Finally, the last chapter presents a positioning multi-motor drive consisting of two PM tubular five-phase actuators fed by a single five-phase inverter.

Interpretation of association rules in multi-tier structures

Dealing with the large amount of data resulting from association rule mining is a big challenge. The essential issue is how to provide efficient methods for summarizing and representing meaningful discovered knowledge from databases. This paper presents a new approach called multi-tier granule mining to improve the performance of association rule mining. Rather than using patterns, it uses granules to represent knowledge that is implicitly contained in relational databases. This approach also uses multi-tier structures and association mappings to interpret association rules in terms of granules. Consequently, association rules can be quickly assessed and meaningless association rules can be justified according to these association mappings. The experimental results indicate that the proposed approach is promising

Destinations, disasters and public relations: Stakeholder engagement in multi-phase disaster management

Research about disasters in tourism has emerged in earnest since the 1990s covering insights for preparedness and response. However, recently, authors have called for more systematic and holistic approaches to tourism disaster management research. To address this gap, this study adopted a public relations perspective to refocus attention to relationships and stakeholder expectations of destination communities across multiple phases of disaster management. The authors used a mixed method approach and developed a battery of disaster management attributes by conducting interviews and analyzing industry documents and the extant literature. These attributes formed part of a survey of tourism businesses. Exploratory factor analysis resulted in a two factor solution: - i) business disaster preparedness, and; - ii) destination disaster response and recovery. Findings also show that participants reported a gap between the importance and destination performance of these attributes. In particular, tourism businesses perceived destinations did not adequately engage in disaster preparedness activities, which had implications for disaster response and recovery.

Multi power port converter for hybrid electric vehicles using multi phase bidirectional fly-back topology

For hybrid electric vehicles the batteries and the drive dc-link may be at different voltages. The batteries are at low voltage to obtain higher volumetric efficiencies and the dc-link is at higher voltage to have higher efficiency on the motor side. Therefore a power interface between the batteries and the drive's dc-link is essential. This power interface should handle power flow from battery to motor, motor to battery, external genset to battery and grid to battery. This paper proposes a multi power port topology which is capable of handling multiple power sources and still maintains simplicity and features like obtaining any gain, wide load variations, lower output current ripple and capability of parallel battery energy due to the modular structure. The development and testing of a bi-directional fly-back DC-DC converter for hybrid electric vehicle is described in this paper. Simple hysteresis voltage control is used for DC link voltage regulation. The experimental results are presented to show the working of the proposed converter.

Differential Multi-phase DLL for Reconfigurable Radio Frequency Synthesizer

A multi phase, delay-locked loop (DLL) based frequency synthesizer is designed for harmonic rejection mixing in reconfigurable radios. This frequency synthesizer uses a 1 GHz input reference frequency, and achieves <= 20ns settling time by utilizing a wide loop bandwidth. The circuit has been designed in 0.13-mu m CMOS technology. It is designed for a frequency range of 500 MHz to 3 GHz with stuck/harmonic lock removal assist. Index Terms-stuck lock, harmonic lock, delay-locked loops, multi phase, phase detector, frequency synthesis

A Multi-phase Approach for Improving Information Diffusion in Social Networks

For maximizing influence spread in a social network, given a certain budget on the number of seed nodes, we investigate the effects of selecting and activating the seed nodes in multiple phases. In particular, we formulate an appropriate objective function for two-phase influence maximization under the independent cascade model, investigate its properties, and propose algorithms for determining the seed nodes in the two phases. We also study the problem of determining an optimal budget-split and delay between the two phases.

Large Scale Numerical Simulations For Multi-Phase Fluid Dynamics With Moving Interfaces

This short communication presents our recent studies to implement numerical simulations for multi-phase flows on top-ranked supercomputer systems with distributed memory architecture. The numerical model is designed so as to make full use of the capacity of the hardware. Satisfactory scalability in terms of both the parallel speed-up rate and the size of the problem has been obtained on two high rank systems with massively parallel processors, the Earth Simulator (Earth simulator research center, Yokohama Kanagawa, Japan) and the TSUBAME (Tokyo Institute of Technology, Tokyo, Japan) supercomputers.

Development of realistic liquid equations of state for multi-phase CFD modelling

Several equations of state (EOS) have been incorporated into a novel algorithm to solve a system of multi-phase equations in which all phases are assumed to be compressible to varying degrees. The EOSs are used to both supply functional relationships to couple the conservative variables to the primitive variables and to calculate accurately thermodynamic quantities of interest, such as the speed of sound. Each EOS has a defined balance of accuracy, robustness and computational speed; selection of an appropriate EOS is generally problem-dependent. This work employs an AUSM+-up method for accurate discretisation of the convective flux terms with modified low-Mach number dissipation for added robustness of the solver. In this paper we show a newly-developed time-marching formulation for temporal discretisation of the governing equations with incorporated time-dependent source terms, as well as considering the system of eigenvalues that render the governing equations hyperbolic.

Development of accurate, robust liquid equations of state for multi-phase CFD simulations with a modified AUSM+-up scheme

Eight equations of state (EOS) have been evaluated for the simulation of compressible liquid water properties, based on empirical correlations, the principle of corresponding states and thermodynamic relations. The IAPWS-IF97 EOS for water was employed as the reference case. These EOSs were coupled to a modified AUSM+-up convective flux solver to determine flow profiles for three test cases of differing flow conditions. The impact of the non-viscous interaction term discretisation scheme, interfacial pressure method and selection of low-Mach number diffusion were also compared. It was shown that a consistent discretisation scheme using the AUSM+-up solver for both the convective flux and the non-viscous interfacial term demonstrated both robustness and accuracy whilst facilitating a computationally cheaper solution than discretisation of the interfacial term independently by a central scheme. The simple empirical correlations gave excellent results in comparison to the reference IAPWS-IF97 EOS and were recommended for developmental work involving water as a cheaper and more accurate EOS than the more commonly used stiffened-gas model. The correlations based on the principles of corresponding-states and the modified Peng-Robinson cubic EOS also demonstrated a high degree of accuracy, which is promising for future work with generic fluids. Further work will encompass extension of the solver to multiple dimensions and to account for other source terms such as surface tension, along with the incorporation of phase changes. © 2013.

Oscillatory magneto-conductance in quantum waveguides with lateral multi-barrier structures

The magneto-transport properties of a narrow quantum waveguide with lateral multibarrier modulation are investigated theoretically. It is found that the magnetoconductance as a function of Fermi energy or magnetic field exhibits square-wave-like oscillations. In the presence of magnetic field, the edge states are formed near each barrier and the boundaries. Therefore, the number of edge states increases with the number of lateral barriers, leading to the increase of the propagating modes. On the other hand, owing to the tunneling effect a pair of edge states around the barrier region with opposite moving directions may be coupled and formed a circulating localized state, leading to the quenching of the related propagating states. The resulting dispersion relation exhibits oscillation structures superimposed on the bulk Landau levels. These novel conductance characteristics may provide potential applications to the fabrication of new quantum devices.

Effect of substitution of chromium for nickel on structure and electrochemical characteristic of Ti0.26Zr0.07V0.24Mn0.1Ni0.33 multi-phase hydrogen storage alloy

Ti-Zr-V-Mn-Ni-based multi-component alloys demonstrate high discharge capacity in KOH electrolyte. However, the drastic decrease in their discharge capacities makes them unsuitable for use as negative electrode material in the Ni/MH battery. In present work, Ni is partially replaced by Cr in the Ti-Zr-V-Mn-Ni-based alloys to improve their cycle life. The effects of Cr substitution on microstructures and the electrochemical characteristics of the alloys are investigated. It is found that Cr substitution is very effective to improve the cyclic durability of the alloys although the discharge capacity decreases with changing x from 0.05 to 0.20. Some kinetic performances have been also investigated using electrochemical impedance spectroscopy (EIS) and potentiostatic discharge technique.

Synthesis and Luminescence Properties of Sheaflike TbPO4 Hierarchical Architectures with Different phase Structures

Sheaflike terbium phosphate hydrate hierarchical architectures composed of filamentary nanorods have been fabricated by a hydrothermal method. The X-ray diffraction patterns and thermogravimetric/differential thermal analysis investigations reveal that the obtained terbium phosphate hydrate has a structural formula of TbPO4 center dot H2O, which can be readily indexed to the hexagonal phase GdPO4 center dot nH(2)O in JCPDS file 39-0232. The evolution of the morphology of the products has been investigated in detail. It is found that the addition of CTAB and Na2H2L (disodium ethylenediamine tetraacetate) plays an important role in controlling the final morphology of the products. A possible formation mechanism of the sheaflike architectures was proposed according to the experimental results and analysis. In addition, the phase structure of the product changes to monoclinic phase when it is annealed at 750 degrees C for 2 h in N-2-H-2 atmosphere. Tetragonal chase TbPO4 can be obtained when annealed temperature increases to 1150 degrees C.

Phase identification in a series of liquid crystalline TPP polyethers and copolyethers having highly ordered mesophase structures. 7. Phase structures in a series of copolyethers containing odd and even numbers of methylene units of different compositions

A series of liquid crystalline copolyethers have been synthesized from 1-(4-hydroxy-4'-biphenyl)-2-(4-hydroxyphenyl)propane with 1,7-dibromoheptane and 1,12-dibromododecene [coTPPs(7/12)], which represents copolyethers containing both odd and even numbers of methylene units. The molar ratio of odd to even methylene units in this series ranges from 1/9 to 9/1. The coTPPs(7/12) exhibit multiple phase transitions during cooling and heating in differential scanning calorimetry experiments. For all these thermal transitions, a small undercooling and superheating dependence is observed upon cooling and heating at different rates. Three types of phase behaviors can be classified in coTPPs(7/12) on the basis of the structural analyses by wide-angle X-ray diffraction on powder and fiber samples and by electron diffraction experiments in transmission electron microscopy. At room temperature, highly ordered smectic and smectic crystal (SC) phases are identified in coTPPs(7/12: 1/9 and 2/8), which is similar to the homopolymer TPP(m = 12). The coTPPs(7/12: 3/7, 4/6, and 5/5) possess a hexagonal columnar (Phi(H)) phase in which the molecular and columnar axes are parallel to the fiber direction and perpendicular to the hexagonal lateral packing. The coTPPs(7/12: 6/4, 7/3, and 8/2) possess a tilted hexagonal columnar (Phi(TH)) phase with a single tilt angle which increases with the increasing composition of the seven-numbered methylene units. However, in coTPP(7/12: 9/1), a Phi(TH) phase with multiple tilt angles is found. Upon heating, phase structures in most coTPPs(7/12) involving the columnar phases enter directly into the nematic (N) phase, while the coTPP(7/12: 1/9) exhibits a highly ordered smectic F (S-F) phase before it reaches the N phase. One exception is found in coTPP(7/12: 2/8), wherein the transformation from the S-F to Phi(H) occurs prior to the N phase. Combining the copolymer phase behaviors observed with the corresponding homopolymers TPP(n = 7) and TPP(m = 12), a phase diagram describing transition temperatures with respect to the composition can be constructed.