8th IET International Conference on Power Electronics, Machines and Drives (PEMD 2016)
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- Location: Glasgow, UK
- Conference date: 19-21 April 2016
- ISBN: 978-1-78561-188-9
- Conference number: CP684
- The following topics are dealt with: induction machines; wide band gap devices; energy storage; HVDC converters; HF converter; grid interface converters; DC-DC converters; aerospace systems; solar power systems; photovoltaic power systems; tidal power systems; wave power systems; sensorless machine control; thermal management; electric traction; multilevel converters; wind power; motion control; rail systems; automotive systems; actuators; grid connection; power distribution; converter topology; inverter control; reluctance machines; permanent magnet machines; power semiconductor devices; machine drive control; condition monitoring; insulation aging; power quality; demand side control; aerospace machine; marine applications; electromagnetic compatibility; industrial applications; electric fuel cell; hybrid vehicles; and smart grids.
1 - 20 of 257 items found
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Wide range sensorless speed estimation in wound rotor induction machines by sliding window search of the stator current signal
- Author(s): K. Tshiloz and S. Djurović
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This paper investigates the possibility of utilising the stator current signal spectral content to establish a wide operating speed sensorless estimation scheme in an open-loop controlled wound rotor induction machine (WRIM). A novel sliding window estimation technique is presented that utilises the supply frequency value to extract the bandwidth maximised by the tracked speed depended current spectral component. The proposed estimation technique is assessed in real-time tests on a 7.5 kW constant V/Hz controlled laboratory WRIM system and shown to deliver reliable performance in a wide operating speed range.
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Electromagnetic modelling of high speed induction motors
- Author(s): R. Velazquez and A.C. Smith
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The finite element (FE) modelling method has become the predominant tool in the design of electrical machines due to its ability to deliver accurate and reliable results because of its suitability to model the complex structure of the machine. A multi-layer analytical model however is particularly well suited to the simple rotor constructions used in very high speed induction motors. The multi-layer model is fast and accurate and is a useful design tool for high speed motors. This paper provides a detailed description of the method and its implementation. The paper shows how to adapt the method to operate from a voltage source. The layer model is compared with a conventional 2D FE model and the results for a high motor show very good correlation.
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An Improved Induction Machine Design Procedure for Electric Vehicle Traction
- Author(s): N. Zhao and N. Schofield
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Electric vehicles (EVs) represent one of the most promising technologies for increasing the global energy security and reducing emissions. As one of the most potential candidates for EV traction motor, induction machines (IMs) should be designed to satisfy the traction characteristics rather than the fixed voltage and fixed frequency (FVFF) operation point. In this paper, a new IM modelling method is applied to analyse the machine torque and power characteristics over the whole speed range. Based on the analysis of a conventionally designed FVFF IM, an improved IM design procedure for EV traction is proposed. The design procedure leads to improvements in machine performance with regards to torque and power density and efficiency, especially in field weakening region. Finite-element analysis solutions of the traditional and proposed IM designs are compared.
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Degradation and fatigue of epoxy impregnated traction motors due to thermal and thermal induced mechanical stress - part i: thermal mechanical simulation of single wire due to evenly distributed temperature
- Author(s): Zhe Huang ; A. Reinap ; M. Alaküla
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The focus of this work is to characterize the mechanical stresses and fatigue along the enameled wire due to thermal expansion. The stresses and fatigue is estimated for a single wire and as a function of evenly distributed temperature. The estimation is based on both analytical equations and 3D Finite Element (FE) model. This characterization of mechanical stresses and fatigue is then used to examine the outcome of the accelerated test based on the measured thermal loads on the motorette specimen. The outcome of this work is not only to detect the cause of insulation failure but also provide useful hints for the traction motor designers.
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Multi-physics experimental investigation into stator-housing contact interface
- Author(s): N. Simpson ; R. Wrobel ; J.D. Booker ; P.H. Mellor
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The shrink-fitting of housings on to electrical machine stators is a common, semi-permanent and low-cost method of assembly. As the stator-housing interface lies in the main heat extraction path, an ideal shrink-fit should provide the necessary holding torque, present minimal thermal contact resistance and remain mechanically and thermally stable over the operating temperature range and life of the electrical machine. The optimal design of such a shrink-fit represents a multi-physics problem requiring, among other data, accurate coefficient of friction and thermal contact conductance information. However, these parameters are influenced by many factors including interface pressure, surface preparation and temperature, and are therefore difficult to predict unless experimental methods are adopted. To this end, this paper presents two independent experimental apparatus designed to measure the pressure dependent coefficient of friction and thermal contact conductance between typical housing and electrical steel materials under in-service conditions.
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Analytical Field Calculation of Doubly Fed Induction Generator with Core Saturation Considered
- Author(s): Z. Zhang ; C.L. Xia ; Y. Yan ; H.M. Wang
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In this paper, an analytical field calculation model is developed for Doubly Fed Induction Generator (DFIG). The field calculation region is divided into five solution subdomains, i.e. rotor slot, rotor slot opening, air-gap, stator slot opening and stator slot. The vector potential in each subdomain can be obtained by solving the governing function with the variable separation method and employing the boundary conditions between of adjacent interface. Furthermore, to improve the correctness of the analytical field calculation model in condition of saturation, a modification method using equivalent air-gap permeability is proposed. The equivalent air-gap permeability is calculated by the magnetic equivalent circuit (MEC) method. Based on the developed analytical field calculation model, the air-gap flux density can be obtained and flux linkage, back-electromotive force (EMF) can also be further calculated. The accuracy of analytical field calculation model results is validated by the finite element analysis (FEA) method.
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Design optimisation of high performance fractional-slot distributed winding PM Synchronous machines for In-wheel application in Electric Vehicles
- Author(s): S. Bandyopadhyay ; M. van der Geest ; H. Polinder
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In general, PM machines with conventional integer slot distributed winding (ISDW) schemes exhibit significant cogging torque resulting in high torque ripple which makes them unsuitable for EV applications which require low torque pulsations. This paper presents detailed analysis of the performance of PM Synchronous motor (PMSM) with fractional slot distributed winding (FSDW) scheme which shows significant reduction in torque ripple compared ISDW PM machines. Effect of the fractional slot winding distribution on electromagnetic torque pulsations has been analysed using Finite element (FE) computation technique. For a fair quantitative comparison between the above machine types, a flexible optimisation approach is proposed in this paper which generates Pareto fronts of the individual machine types.
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Modelling the mechanical and thermal properties of compressed stator windings
- Author(s): M.C. Kulan ; N.J. Baker ; J.D. Widmer ; S.M. Lambert
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This paper discusses coil pressing through which stator windings are compressed at high pressures to enhance the slot fill factor of electrical machines. Deterioration of insulation in compressed windings is investigated by performing quasistatic explicit dynamics finite element simulations. The results obtained from the proposed method are further investigated experimentally to validate the durability of the compressed coils. It is shown that stator windings can be compressed to a certain degree without observing material failure. In order to demonstrate the thermal advantages of densely packed stator windings, both steady state thermal finite element analysis (FEA) simulations and semi-analytical methods have also been studied. A good agreement between analytical and FEA simulations is obtained. It is noted that steady state thermal finite element modeling could be used to predict effective thermal conductivity of stator windings for different slot fill factors.
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A Unified Framework for Computationally Efficient Power Converter Design Optimisation
- Author(s): I.D. Laird ; J. Scoltock ; A.J. Forsyth ; X. Yuan
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Within the field of power converter design, the use of optimisation techniques is a popular method to ensure that the best possible design is achieved for a given objective, e.g. weight or volume reduction. However, there is currently a lack of efficient unified frameworks for optimising the system level design of converters in terms of the device, heatsink and passive component selection. This paper presents an efficient unified design optimisation framework that can be applied to a wide range of power converter design problems. The main advantage of the proposed framework is that it produces optimal solutions with great computational efficiency. The proposed framework was validated by applying to SiC-based converter design problems, achieving power densities of 8.32 kW/kg for a 50-kW DC-DC converter, and 3.50 kW/L for a 5-kW 3-phase DC-AC converter.
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Design considerations for 600 V GaN cascode based half-bridge converter systems for utility based applications
- Author(s): N. Hari ; T. Logan ; R. McMahon
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Gallium Nitride (GaN) devices are evolving in the market with 600 V devices getting commercialised and industry keen to zero in on a high-volume application to drive the market. This paper is thus aimed at evaluating the stability issues of GaN cascode based half-bridges, that is widely used in utility based applications which is foreseen by the authors, as a potential application for GaN. In this work, thorough investigation of the influence of parasitics on cascode based half-bridges is performed by detailed theoretical analysis, Pspice simulations and design rules are framed. Based on these findings, two different gate drives are designed and demonstrated for a hard-switching 1 kW, 100 KHz GaN half bridge converter to validate the analysis. The novelty of this paper lies in providing an analytical treatment to the design issues caused due to the instability in GaN cascode based half-bridge circuits.
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New optimum modulation of three-phase ZVS triangular current mode GaN inverter ensuring limited switching frequency variation
- Author(s): M. Kaufmann ; A. Tüysüz ; J.W. Kolar
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In three-phase pulse width modulation inverters with an LC output filter, switching losses can be reduced by increasing the current ripple in the inductor until a current zero crossing occurs between the two switching instances of a bridge leg. A disadvantage of this triangular current mode (TCM) operation is the varying switching frequency. This paper presents new modulation methods where the current ripple amplitude is adjusted and a common-mode voltage is introduced in order to limit the switching frequency variation. Moreover, the possibility of increasing the efficiency and minimizing the filter volume are investigated. Numerical optimization results are presented for a 2.5 kW inverter with 400 V DC link voltage as a case study.
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Extended Soft-switching Operation of the Dual Interleaved Boost Converter
- Author(s): M.R. Ahmed ; R. Todd ; A.J. Forsyth
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The use of soft-switching techniques, interleaved topologies and silicon carbide (SiC) MOSFETs can improve the efficiency and power-density of high-power, high-voltage DC-DC converters for electric vehicle and aircraft applications. In this paper, to extend the operating range of the Snubber Assisted Zero Voltage and Zero Current Transition (SAZZ) dual-interleaved boost converter beyond its inherent soft-switching limit of D=0.5, a resonant pulse transformer is proposed instead of the resonant inductor to enable soft-switching over the full duty ratio range. The 2:1 turns ratio of the transformer ensures full discharge of the snubber capacitor at all duty ratio values to facilitate zero voltage zero current switching (ZVZCS) at turn on of the main switching devices. The effectiveness of the topology has been confirmed by SPICE simulation and demonstrated by a multi-kW SiC MOSFET based SAZZ converter.
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Investigating enhancement mode gallium nitride power FETs in high voltage, high frequency soft switching converters
- Author(s): Y. Nour ; A. Knott ; I.H.H. Jørgensen
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An increased attention has been detected to develop smaller and lighter high voltage power converters in the range of 50V to 400V domain. The main applications for these converters are mainly focused for Power over Ethernet (PoE), LED lighting and AC adapters. This work will discuss a study of using enhancement mode gallium nitride switches to form a 50V quasi-square-wave zero-voltage-switching buck converter running at 2-6 MHz under full load. The designed converter achieved 83% efficiency converting 50V input voltage to 12.2V at 9W load.
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A threshold logic control strategy for parallel light hybrid electric vehicle implementation
- Author(s): D. Da Ru ; M. Morandin ; S. Bolognani ; M. Castiello
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This paper presents the development and the implementation of a logic threshold control strategy for light hybrid vehicle with parallel architecture. The aim of the control logic is to maximize the efficiency of the thermal engine during its operation. To verify its effectiveness, the logic has been first simulated and then implemented on the test bench.
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Single-stage battery charger based on a LLC resonant converter: a concept study
- Author(s): L. Keuck ; B. Strothmann ; R. Hermelingmeier ; N. Fröhleke ; J. Böcker
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It has been a common practice to charge batteries with pure a DC current. Thus, chargers require a large electrolytic capacitor bank to suppress the low frequency components from entering into the battery. However, according to recent studies a pure DC charging current is not a mandatory requirement for high battery-lifetime and efficiency. This allows to omit the bulky and fast-aging electrolytic capacitors and its input PFC-rectifier. This paper presents the concept of a single-stage battery charger based on a LLC resonant converter. Component stresses are reduced by utilizing a minimized input voltage range. The LLC resonant tank is designed using an improved time-domain-analysis which considers major losses. This facilitates a higher degree of accuracy in determining the range and the modes of operation, which in turn helps in developing an optimized design. An experimental lab prototype achieves a peak efficiency of 97.0 % and a calculated PFC-efficiency of 96.6 %.
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A cascaded transformer-based equalisation converter for series connected battery cells
- Author(s): Huaxia Zhan ; Xin Xiang ; S.M. Lambert ; V. Pickert ; Haimeng Wu ; Xiang Lu
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Hybrid electric vehicles (HEVs) and electric vehicles (EVs) have increased in popularity as they use rechargeable battery as energy source instead of petrol, furthermore, help to reduce the release of greenhouse gases. Generally, for applications such as EVs and HEVs, a battery pack may consist of hundreds individual cells batteries in order to meet voltage and energy capacity requirements. However, due to individual chemical characteristics and manufacturing tolerances each cell in a pack will have a slightly different capacity. The capacity of a cell also changes over time as the cell ages. During charging and discharging this leads to unbalanced voltages across the battery pack, and unchecked could result in over-charging/over-discharging for certain cells. This in turn can lead to cell and pack failure or even fire. Therefore, as part of the battery management system a process for voltage equalisation of cells throughout the stack is essential. This paper proposes a new cascaded multi-winding transformer based equalisation circuit topology which, compared to more traditional multi-winding transformerbased topologies is simpler in transformer construction and is therefore far easier to manufacture. The topology concept and operating principals are discussed followed by simulation results for the proposed system. In addition accelerated equalisation speed compared to existing solutions is demonstrated.
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Optimization of a 12V dual-battery system for micro-hybrid vehicles
- Author(s): D. Renner ; F. Achhammer ; P. Jansen ; D. Vergossen ; W. John ; S. Frei
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The lead-acid batteries mainly used for energy storage in conventional vehicles today have to handle both high power applications and charge acceptance. Supporting the lead-acid technology using a small, high power lithium-ion battery connected in parallel yields great benefits. Besides battery properties, the batteries' connection to the power network is crucial for the overall system performance. Given that there is a close interaction between these factors, we present in our study a simulation-based optimization method to obtain the best trade-off between performance, charge acceptance, system size, weight and costs. Vehicle measurements prove the ability to simulate scaling of the battery and wiring harness and help in developing new and optimized vehicle power systems regardless of topology or voltage level.
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Electric Vehicle Battery Parameter Identification and SOC Observability Analysis: NiMH and Li-S Case Studies
- Author(s): A. Fotouhi ; D.J. Auger ; K. Propp ; S. Longo
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In this study, a framework is proposed for battery model identification to be applied in electric vehicle energy storage systems. The main advantage of the proposed approach is having capability to handle different battery chemistries. Two case studies are investigated: nickel-metal hydride (NiMH), which is a mature battery technology, and Lithium-Sulphur (Li-S), a promising next-generation technology. Equivalent circuit battery model parametrisation is performed in both cases using the Prediction-Error Minimization (PEM) algorithm applied to experimental data. The use of identified parameters for battery state-of-charge (SOC) estimation is then discussed. It is demonstrated that the set of parameters needed can change with a different battery chemistry. In the case of NiMH, the battery's open circuit voltage (OCV) is adequate for SOC estimation. However, Li-S battery SOC estimation can be challenging due to the chemistry's unique features and the SOC cannot be estimated from the OCVSOC curve alone because of its flat gradient. An observability analysis demonstrates that Li-S battery SOC is not observable using the common state-space representations in the literature. Finally, the problem's solution is discussed using the proposed framework.
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The star-switched MMC (SSMMC) - a hybrid VSC for HVDC applications
- Author(s): D.L. Woldegiorgis ; J. Outram ; E. Amankwah ; D. Trainer ; J. Clare
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This paper presents a new hybrid VSC topology (the StarSwitched MMC) - suitable for HVDC applications. The basic structure and operating principles of the topology are described. Control strategies that regulate the power exchanged between the VSC, the AC network and the DC network are presented. A modulation strategy ensuring appropriate switching of the individual chain-link submodules and a capacitor voltage balancing algorithm that ensures the capacitor voltages are maintained within the required tolerance are discussed. Results from a simulation model are presented to validate the expected performance of the converter and the proposed control schemes.
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Design and implementation of 30kW 200/900V LCL modular multilevel based DC/DC converter for high power applications
- Author(s): S.M. Fazeli ; A. Aboushady ; K.H. Ahmed ; D. Jovcic
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This paper presents the design, development and testing of a 30kW, 200V/900V modular multilevel converter (MMC) based DC/DC converter prototype. An internal LCL circuit is used to provide voltage stepping and fault tolerance property. The converter comprises two five level MMC based on insulated gate bipolar transistors (IGBTs) and metal oxide semiconductor field effect transistor (MOSFET). Due to low number of levels, selective harmonic elimination modulation (SHE) is used, which determines the switching angles in such a way that third harmonic is minimized whereas the fundamental component is a linear function of the modulation index. In addition, instead of using an expensive control board, three commercial control boards are embedded. This is required to implement the sophisticated DC/DC converter control algorithm. Simulation and experimental results are presented to demonstrate the converter performance in step up and down modes.
