A novel concept of unidirectional bridgeless combined boost-buck converter for EV battery chargers

This paper presents a novel concept of unidirectional bridgeless combined boost-buck converter for electric vehicles (EVs) battery chargers. The proposed converter is composed by two power stages: an ac-dc front-end converter used to interface the power grid and the dc-link, and a dc-dc back-end converter used to interface the dc-link and the batteries. The ac-dc converter is a bridgeless boost-type converter and the dc-dc converter is an interleaved buck-type converter. The proposed converter operates with sinusoidal grid current and unitary power factor for all operating power levels. Along the paper is described in detail the proposed converter for EV battery chargers: the circuit topology, the different stages describing the principle of operation, the power control theory, and the current control strategy, for both converters. Along the paper are presented several simulation results for a maximum power of 3.5 kW.

Bidirectional battery charger with grid-to-vehicle, vehicle-to-grid and vehicle-to-home technologies

This paper presents the development of na on-board bidirectional battery charger for Electric Vehicles (EVs) targeting Grid-to-Vehicle (G2V), Vehicle-to-Grid (V2G), and Vehicle-to-Home (V2H) technologies. During the G2V operation mode the batteries are charged from the power grid with sinusoidal current and unitary power factor. During the V2G operation mode the energy stored in the batteries can be delivered back to the power grid contributing to the power system stability. In the V2H operation mode the energy stored in the batteries can be used to supply home loads during power outages, or to supply loads in places without connection to the power grid. Along the paper the hardware topology of the bidirectional battery charger is presented and the control algorithms are explained. Some considerations about the sizing of the AC side passive filter are taken into account in order to improve the performance in the three operation modes. The adopted topology and control algorithms are accessed through computer simulations and validated by experimental results achieved with a developed laboratory prototype operating in the different scenarios.

Desenvolvimento de um filtro ativo paralelo monofásico compacto e didático utilizando MOSFETs

Dissertação de mestrado integrado em Engenharia Eletrónica Industrial e Computadores

Electromagnetic Design of a Solid Steel Rotor Motor for Demanding Operation Environments

The solid-rotor induction motor provides a mechanically and thermally reliable solution for demanding environments where other rotor solutions are prohibited or questionable. Solid rotors, which are manufactured of single pieces of ferromagnetic material, are commonly used in motors in which the rotationspeeds exceed substantially the conventional speeds of laminated rotors with squirrel-cage. During the operation of a solid-rotor electrical machine, the rotor core forms a conductor for both the magnetic flux and the electrical current. This causes an increase in the rotor resistance and rotor leakage inductance, which essentially decreases the power factor and the efficiency of the machine. The electromagnetic problems related to the solid-rotor induction motor are mostly associated with the low performance of the rotor. Therefore, the main emphasis in this thesis is put on the solid steel rotor designs. The rotor designs studied in thisthesis are based on the fact that the rotor construction should be extremely robust and reliable to withstand the high mechanical stresses caused by the rotational velocity of the rotor. In addition, the demanding operation environment sets requirements for the applied materials because of the high temperatures and oxidizing acids, which may be present in the cooling fluid. Therefore, the solid rotors analyzed in this thesis are made of a single piece of ferromagnetic material without any additional parts, such as copper end-rings or a squirrel-cage. A pure solid rotor construction is rigid and able to keep its balance over a large speed range. It also may tolerate other environmental stresses such as corroding substances or abrasive particles. In this thesis, the main target is to improve the performance of an induction motor equipped with a solid steel rotor by traditional methods: by axial slitting of the rotor, by selecting a proper rotor core material and by coating the rotor with a high-resistive stainless ferromagnetic material. In the solid steel rotor calculation, the rotor end-effects have a significant effect on the rotor characteristics. Thus, the emphasis is also put on the comparison of different rotor endfactors. In addition, a corrective slip-dependent end-factor is proposed. The rotor designs covered in this thesis are the smooth solid rotor, the axially slitted solid rotor and the slitted rotor having a uniform ferromagnetic coating cylinder. The thesis aims at design rules for multi-megawatt machines. Typically, mega-watt-size solidrotor machines find their applications mainly in the field of electric-motor-gas-compression systems, in steam-turbine applications, and in various types of largepower pump applications, where high operational speeds are required. In this thesis, a 120 kW, 10 000 rpm solid-rotor induction motor is usedas a small-scale model for such megawatt-range solid-rotor machines. The performance of the 120 kW solid-rotor induction motors is determined by experimental measurements and finite element calculations.

Converter-flux-based current control of voltage source PWM rectifiers - analysis and implementation

Pulsewidth-modulated (PWM) rectifier technology is increasingly used in industrial applications like variable-speed motor drives, since it offers several desired features such as sinusoidal input currents, controllable power factor, bidirectional power flow and high quality DC output voltage. To achieve these features,however, an effective control system with fast and accurate current and DC voltage responses is required. From various control strategies proposed to meet these control objectives, in most cases the commonly known principle of the synchronous-frame current vector control along with some space-vector PWM scheme have been applied. Recently, however, new control approaches analogous to the well-established direct torque control (DTC) method for electrical machines have also emerged to implement a high-performance PWM rectifier. In this thesis the concepts of classical synchronous-frame current control and DTC-based PWM rectifier control are combined and a new converter-flux-based current control (CFCC) scheme is introduced. To achieve sufficient dynamic performance and to ensure a stable operation, the proposed control system is thoroughly analysed and simple rules for the controller design are suggested. Special attention is paid to the estimationof the converter flux, which is the key element of converter-flux-based control. Discrete-time implementation is also discussed. Line-voltage-sensorless reactive reactive power control methods for the L- and LCL-type line filters are presented. For the L-filter an open-loop control law for the d-axis current referenceis proposed. In the case of the LCL-filter the combined open-loop control and feedback control is proposed. The influence of the erroneous filter parameter estimates on the accuracy of the developed control schemes is also discussed. A newzero vector selection rule for suppressing the zero-sequence current in parallel-connected PWM rectifiers is proposed. With this method a truly standalone and independent control of the converter units is allowed and traditional transformer isolation and synchronised-control-based solutions are avoided. The implementation requires only one additional current sensor. The proposed schemes are evaluated by the simulations and laboratory experiments. A satisfactory performance and good agreement between the theory and practice are demonstrated.

Permanent magnet synchronous motor for industrial inverter applications - analysis and design

During the latest few years the need for new motor types has grown, since both high efficiency and an accurate dynamic performance are demanded in industrial applications. For this reason, new effective control systems such as direct torque control (DTC) have been developed. Permanent magnet synchronous motors (PMSM) are well suitable for new adjustable speed AC inverter drives, because their efficiency and power factor are not depending on the pole pair number and speed to the same extent as it is the case in induction motors. Therefore, an induction motor (IM) with a mechanical gearbox can often be replaced with a direct PM motor drive. Space as well as costs will be saved, because the efficiency increases and the cost of maintenance decreases as well. This thesis deals with design criterion, analytical calculation and analysis of the permanent magnet synchronous motor for both sinusoidal air-gap flux density and rectangular air-gapflux density. It is examined how the air-gap flux, flux densities, inductances and torque can be estimated analytically for salient pole and non-salient pole motors. It has been sought by means of analytical calculations for the ultimate construction for machines rotating at relative low 300 rpm to 600 rpm speeds, which are suitable speeds e.g. in Pulp&Paper industry. The calculations are verified by using Finite Element calculations and by measuring of prototype motor. The prototype motor is a 45 kW, 600 rpm PMSM with buried V-magnets, which is a very appropriate construction for high torque motors with a high performance. With the purposebuilt prototype machine it is possible not only to verify the analytical calculations but also to show whether the 600 rpm PMSM can replace the 1500 rpm IM with a gear. It can also be tested if the outer dimensions of the PMSM may be the same as for the IM and if the PMSM in this case can produce a 2.5 fold torque, in consequence of which it may be possible to achieve the same power. The thesis also considers the question how to design a permanent magnet synchronous motor for relatively low speed applications that require a high motor torqueand efficiency as well as bearable costs of permanent magnet materials. It is shown how a selection of different parameters affects the motor properties. Key words: Permanent magnet synchronous motor, PMSM, surface magnets, buried magnets

A comparative performance study of four-pole induction motors and synchronous reluctance motors in variable speed drives

Design aspects of the Transversally Laminated Anisotropic (TLA) Synchronous Reluctance Motor (SynRM) are studied and the machine performance analysis compared to the Induction Motor (IM) is done. The SynRM rotor structure is designed and manufactured for a30 kW, four-pole, three-phase squirrel cage induction motor stator. Both the IMand SynRM were supplied by a sensorless Direct Torque Controlled (DTC) variablespeed drive. Attention is also paid to the estimation of the power range where the SynRM may compete successfully with a same size induction motor. A technicalloss reduction comparison between the IM and SynRM in variable speed drives is done. The Finite Element Method (FEM) is used to analyse the number, location and width of flux barriers used in a multiple segment rotor. It is sought for a high saliency ratio and a high torque of the motor. It is given a comparison between different FEM calculations to analyse SynRM performance. The possibility to take into account the effect of iron losses with FEM is studied. Comparison between the calculated and measured values shows that the design methods are reliable. A new application of the IEEE 112 measurement method is developed and used especially for determination of stray load losses in laboratory measurements. The study shows that, with some special measures, the efficiency of the TLA SynRM is equivalent to that of a high efficiency IM. The power factor of the SynRM at rated load is smaller than that of the IM. However, at lower partial load this difference decreases and this, probably, brings that the SynRM gets a better power factor in comparison with the IM. The big rotor inductance ratio of the SynRM allows a good estimating of the rotor position. This appears to be very advantageous for the designing of the rotor position sensor-less motor drive. In using the FEM designed multi-layer transversally laminated rotor with damper windings it is possible to design a directly network driven motor without degrading the motorefficiency or power factor compared to the performance of the IM.

Induction motor versus permanent magnet synchronous motor in motion control applications: a comparative study

High dynamic performance of an electric motor is a fundamental prerequisite in motion control applications, also known as servo drives. Recent developments in the field of microprocessors and power electronics have enabled faster and faster movements with an electric motor. In such a dynamically demanding application, the dimensioning of the motor differs substantially from the industrial motor design, where feasible characteristics of the motor are for example high efficiency, a high power factor, and a low price. In motion control instead, such characteristics as high overloading capability, high-speed operation, high torque density and low inertia are required. The thesis investigates how the dimensioning of a high-performance servomotor differs from the dimensioning of industrial motors. The two most common servomotor types are examined; an induction motor and apermanent magnet synchronous motor. The suitability of these two motor types indynamically demanding servo applications is assessed, and the design aspects that optimize the servo characteristics of the motors are analyzed. Operating characteristics of a high performance motor are studied, and some methods for improvements are suggested. The main focus is on the induction machine, which is frequently compared to the permanent magnet synchronous motor. A 4 kW prototype induction motor was designed and manufactured for the verification of the simulation results in the laboratory conditions. Also a dynamic simulation model for estimating the thermal behaviour of the induction motor in servo applications was constructed. The accuracy of the model was improved by coupling it with the electromagnetic motor model in order to take into account the variations in the motor electromagnetic characteristics due to the temperature rise.

Teholähdesuunnittelu

Työssä vertaillaan massatuotannon näkökulmasta eri tehoalueille sopivia teholähteen toteuttamisvaihtoehtoja. Lisäksi esitellään standardien asettamia vaatimuksia teholähteille. Työssä käsitellään teholähdesuunnittelun eri osa-alueita ja niihin sopivien simulointityökalujen hyödyntämismahdollisuuksia suunnitteluprosessin osana. Simulointituloksia ja teoreettisia laskelmia vertaillaan prototyypistä suoritettuihin mittauksiin.

Tehokerroinkorjatun hakkuriteholähteen toteutusvaihtoehdot

Hyötysuhteen merkitys tehoelektroniikan järjestelmissä kasvaa jatkuvasti kun käytössä olevien järjestelmien määrä lisääntyy ja toisaalta energian hinta kallistuu. Hyötysuhteen lisäksi verkkovirran käyrämuotovaatimukset asettavat omat haasteensa sähköverkkoon liitettävien tehoelektroniikkajärjestelmien suunnittelulle. Tässä työssä tutkitaan häviöiden syntyyn vaikuttavia tekijöitä hakkuriteholähteissä ja pyritään löytämään keinoja hyötysuhteen parantamiseksi. Työssä analysoidaan 300 W – 2 kW tehoalueelle soveltuvat, tehokerroinkorjattujen AC/DC-hakkuriteholähteiden topologiavaihtoehdot ja arvioidaan niiden soveltuvuutta tavanomaisen boost-topologian korvaajaksi. Tarkastelussa otetaan huomioon kustannukset, toimivuus sekä saavutettu hyötysuhteen parantuminen verrattuna perinteisellä topologialla toteutettuun teholähteeseen. Tarkasteltavat topologiat valitaan kirjallisuustutkimuksen perusteella. Valittujen topologioiden häviöt ja hyötysuhde selvitetään analyyttisin menetelmin sekä simuloimalla. Käytännön testausta varten suunnitellaan ja rakennetaan prototyyppi valitusta topologiasta.

Tehokerrointa korjaava skalaariohjaus puoliohjatussa ja kuusikytkintasasuuntaajassa

Verkon harmonisvirtoja rajoittavien standardien tiukentuessa joudutaan etenkin suuritehoisissa tehoelektronisissa laitteissa siirtymään aktiivisiin transistoriohjattuihin tasasuuntaajiin, jotka korjaavat tehokerrointa ja siten pienentävät verkkoon kytkeytyviä häiriövirtoja. Tässä diplomityössä esitellään yleisimpien kolmivaiheisten tasasuuntaajatopologioiden eroja ja vertaillaan puoliohjatun kolmikytkintopologian ja kuusikytkintopologian suorituskykyä tehokertoimen ja harmonissärön osalta, 16 kilowatin teholuokan taajuusmuuttajassa. Tasasuuntaajille tehtiin skalaariohjaukseen perustuva simulointimalli. Työn tavoitteena esitellään simulointitulokset harmonistason sekä tehokertoimen osalta. Työ liittyy Lappeenrannan teknillisen yliopiston sovelletun elektroniikan laboratorion ja Vacon Oyj:n yhteiseen hankkeeseen.

Teholähteet led-valaistuksessa ja sopivan valinta kotitalouskäyttöön

Led-valaisun kehitys on mahdollistanut sen käytön kodin yleisvalaistuksessa. Työssä tutkitaan eri led-valaisuun soveltuvia teholähteitä, joista valitaan teknisiltä ominaisuuksiltaan sopivin kodin yleiskäyttöön. Tutkittavia teholähteitä ovat lineaariset ja hakkuriteholähteet. Teholähteiden ominaisuuksista tarkastellaan hyötysuhteita ja tehokertoimia, joista molempien perusteella sopivin teholähdetyyppi valitaan.

Automation Concept for Electrically Excited LV Synchronous Motor: Implementation into AC500 Programmable Logic Environment

This bachelor’s thesis is a part of the research project realized in the summer 2011 in Lappeenranta University of Technology. The goal of the project was to develop an automation concept for controlling the electrically excited synchronous motor. Thesis concentrates on the implementation of the automation concept into the ABB’s AC500 programmable logic enviroment. The automation program was developed as a state machine with the ABB’s PS501 Control Builder software. For controlling the automation program is developed a fieldbus control and with CodeSys Visualization Tool a local control with control panel. The fieldbus control is done to correspond the ABB drives communication profile and the local control is implemented with a function block which feeds right control words into the statemachine. A field current control of the synchronous motor is realized as a method presented in doctoral thesis of Olli Pyrhönen (Pyrhönen 1998). The Method combines stator flux and torque based openloop control and power factor based feedback control.

Sähkön laadun tutkimus hypermarketin pysäköintihallin valaistustekniikkamuutoksessa

Talotekniikan alalla valaistusmuutoksissa LED-valaistus on nykypäivää. Valaistuksen käyttöominaisuudet ja hyödyt tekevät siitä perustellun valinnan myös suurissa kohteissa. Näistä laajemmista valaistuksen muutoksista ja niiden vaikutuksista sähkön laatuun ei ole yleisesti mittaustietoa. Tämä tutkimus perustui sähkön laadun käytännön mittauksiin valaistusmuutoksessa, jossa elohopeahöyrylampuilla toteutettu valaistus vaihdettiin LED-valaistukseen hypermarketin pysäköintihallissa. Valaistusjärjestelmän muutoksen vaikutusta sähkön laatuun tutkittiin vertailemalla mittaustuloksia vanhan ja uuden järjestelmän välillä. Tutkimuksen tarkoituksena oli osoittaa miten LED-valaistukseen siirtyminen vaikuttaa sähkön laatuun valitussa tutkimuskohteessa. Tutkimuksessa tuotettu tieto on hyödynnettävissä vastaavissa kohteissa LED-valaistukseen siirryttäessä sekä valaistuksen käyttöönoton suunnittelussa ja toteuttamisessa. Tutkimuksen tuloksia voidaan hyödyntää myös kustannusten arvioimisessa valaistavan tilan sähkönkulutuksen osalta. Tutkimus toteutettiin käyttämällä triangulaatiomenetelmää eli teemahaastattelulla, kirjallisuuskatsauksella ja käytännön mittauksilla. Näiden menetelmien tulokset tukivat tutkimukselle asetettuja hypoteeseja. Valitulla tutkimusmenetelmällä saatiin selville, että LED-valaistukseen siirtymisellä ei ollut heikentäviä vaikutuksia sähkön laatuun tutkitun kohteen valaistusjärjestelmässä. Toisaalta positiivisina vaikutuksina huomioitiin muun muassa merkittävä energian säästö, virran harmonisten häiriöiden väheneminen sekä kokonaistehokertoimen parantuminen.

Co3M2S2 (M ¼ Sn, In) shandites as tellurium-free thermoelectrics

Chemical substitution in Co3Sn2-xInxS2 (0 # x # 2) enables tuning of the Fermi level within narrow bands of Co d-states. This results in a compositionally induced double metal–semiconductor–metal transition and manipulation of the thermoelectric power factor. The maximum power factor (14 mW cm-1 K-2) is found for x ¼ 0.85, which corresponds to ZT z 0.2 at 300 K.