Tasasähköverkon modulaarisen vaihtosuuntaajan rakenne- ja kustannusanalyysi

Diplomityössä tarkastellaan tapausta, jossa tasasähköverkon vaihtosuuntaaja toteutetaan kolmella yksivaiheisella suuntaajalla yhden kolmivaiheisen sijaan. Modulaarinen rakenne mahdollistaa sen, että osa vaiheista voitaisiin sammuttaa kun kuormitus on erittäin pientä eikä kuorma ole kolmivaiheista. Galvaaninen erotus oletetaan tehtävän erottavalla DC-DC -konvertterilla, joka mahdollistaa samalla vaihtosuuntaajan DC-syöttöjännitteen muuttamisen. Työssä tutkitaan, mitkä tekijät vaikuttavat DC-syöttöjännitteen valintaan sekä tehdään valinta kyseisen jännitteen arvolle. Valittua jännitetasoa käytetään vaihtosuuntaajan suunnittelemiseen. Vaihtosuuntaajan rakennetta tarkastellaan vaihtosuuntaussillan kytkinkomponenttien sekä lähtöjännitteen suotimen osalta. Yksivaiheiselle moduulille määritetään optimaalinen teholuokka investointi- ja käyttökustannusten kannalta. Tarkastelu pitää sisällään erilaisten transistoritekniikkojen, kytkentätaajuuksien sekä kahden suodintyypin vaikutuksen kustannustehokkuuteen.

Kaksifaasijäähdytysjärjestelmään liittyvien pumppujen vertailu ja kehittäminen sarjatuotannon tarpeisiin

Tehoelektroniikalta vaaditaan nykyään parempaa suorituskykyä entistä pienemmässä tilassa. Tämä luo haasteen riittävälle jäähdytykselle. Eräs ratkaisu on käyttää kaksifaasijäähdytystä, jolla aikaansaadaan tehokas lämmönsiirto komponenttien pinnalta. Lämmönsiirtonesteinä voidaan käyttää kylmäaineita tai muita alhaisessa lämpötilassa kiehuvia nesteitä. Tällaisille nesteille on tyypillistä alhainen höyrynpaine sekä matala viskositeetti. Nämä ominaisuudet tuovat haasteita nesteen pumppaukseen. Tässä työssä tarkastellaan R-134A:ta sekä Novec 7000:ta, perehdytään niiden fysikaalisiin ominaisuuksiin sekä materiaaliyhteensopivuuksiin ja näiden tietojen pohjalta etsitään sopivaa pumpputyyppiä kaksifaasijäähdytysjärjestelmään. Tehoelektroniikan jäähdytysjärjestelmän pumpun on oltava edullinen muuhun järjestelmään nähden. Tyypillinen kiertopumppu nestejäähdytysjärjestelmässä on pieni keskipakopumppu. Alhaisen kiehumispisteen vuoksi kavitointiriski kasvaa ja tämä voi vahingoittaa pumppua. Myös matala viskositeetti tuo haasteita vuotoherkkyyden kasvamisen myötä, joten mekaanisilla aksiaalitiivisteillä varustetut pumput eivät ole pitkäikäisiä. Kylmäainejärjestelmiin tarkoitetut pumput ovat arvokkaita, eikä näin ollen sovellu edullisiin jäähdytysjärjestelmiin. Tässä työssä käydään läpi erilaisia pumpputyyppejä, jotka voisivat soveltua pitkäikäiseen pumppaukseen ilman huoltotöitä. Näiden tietojen perusteella kehitetään edullista ja pitkäikäistä pumppua pieniin kaksifaasijäähdytysjärjestelmiin nesteiden fysikaaliset ominaisuudet huomioon ottaen. Kehitetyn pumpun ominaisuuksia ja kustannuksia vertaillaan kaupallisiin ratkaisuihin ottaen huomioon sarjavalmistus. Itse valmistettuna pienelle sisäryntöiselle hammaspyöräpumpulle jää hintaa alle kymmenesosa markkinoilta löytyviin kylmäaineille soveltuviin pumppuun.

A comparison between bond graphs switching modelling techniques implemented on a boost dc-dc converter

A Bond Graph is a graphical modelling technique that allows the representation of energy flow between the components of a system. When used to model power electronic systems, it is necessary to incorporate bond graph elements to represent a switch. In this paper, three different methods of modelling switching devices are compared and contrasted: the Modulated Transformer with a binary modulation ratio (MTF), the ideal switch element, and the Switched Power Junction (SPJ) method. These three methods are used to model a dc-dc Boost converter and then run simulations in MATLAB/SIMULINK. To provide a reference to compare results, the converter is also simulated using PSPICE. Both quantitative and qualitative comparisons are made to determine the suitability of each of the three Bond Graph switch models in specific power electronics applications

A 2kW interleaved ZCS-FM boost rectifier digitally controlled by FPGA device

This paper presents a 2kW single-phase high power factor boost rectifier with four cells in interleave connection, operating in critical conduction mode, and employing a soft-switching technique, controlled by Field Programmable Gate Array (FPGA). The soft-switching technique Is based on zero-current-switching (ZCS) cells, providing ZC (zero-current) turn-on and ZCZV (zero-current-zero-voltage) turn-off for the active switches, and ZV (zero-voltage) turn-on and ZC (zero-current) turn-off for the boost diodes. The disadvantages related 'to reverse recovery effects of boost diodes operated in continuous conduction mode (additional losses, and electromagnetic interference (EMI) problems) are minimized, due to the operation in critical conduction mode. In addition, due to the Interleaving technique, the rectifer's features include the reduction in the input current ripple, the reduction in the output voltage ripple, the use of low stress devices, low volume for the EMI input filter, high input power factor (PF), and low total harmonic distortion (THD) In the input current, in compliance with the TEC61000-3-2 standards. The digital controller has been developed using a hardware description language (VHDL) and implemented using a XC2S200E-SpartanII-E/Xilinx FPGA device, performing a true critical conduction operation mode for four interleaved cells, and a closed-loop to provide the output voltage regulation, like as a pre-regulator rectifier. Experimental results are presented for a 2kW implemented prototype with four interleaved cells, 400V nominal output voltage and 220V(rms) nominal input voltage, in order to verify the feasibility and performance of the proposed digital control through the use of a FPGA device.

Fluorescent lamp model based on equivalent resistances, considering the effects of dimming operation

This paper presents a new methodology for the determination of fluorescent lamp models based on equivalent resistances. One important feature of the proposed methodology is concerned with the inclusion of the filaments into the model, considering the effects of dimming operation on the equivalent resistances. The classical Series-Resonant Parallel-Loaded Half-Bridge inverter is used as the power stage of the ballast. Moreover, the variation of the inverter's switching frequency is the dimming technique assumed for the analyses. Results obtained with a F32T8 lamp indicate that the accuracy of the model is very satisfactory. Thus, the lamp models obtained with the proposed methodology have the potential to serve as an important tool for ballast designers, considering the necessity for evaluating the lamp/ballast compatibility, according to issues concerned to the operating conditions of the electrodes' filaments.

Mnltiloop Controller and Reference Generator for a Dynamic Voltage Restorer Implementation

This paper deals with the design and analysis of a Dynamic Voltage Restorer output voltage control. Such control is based on a multiloop strategy, with an inner current PID regulator and an outer P+Resonant voltage controller. The inner regulator is applied on the output inductor current. It will be also demonstrated how the load current behavior may influence in the DVR output voltage, which. justifies the need for the resonant controller. Additionally, it will be discussed the application of a modified algorithm for the identification of the DVR voltage references, which is based on a previously presented positive sequence detector. Since the studied three-phase DVR is assumed to be based on three identical H-bridge converters, all the analysis and design procedures were realized by means of single-phase equivalent circuits. The discussions and conclusions are supported by theoretical calculations, nonlinear simulations and some experimental results.

Multiloop controller and reference generator for a dynamic voltage restorer implementation

This paper deals with the design and analysis of a Dynamic Voltage Restorer output voltage control. Such control is based on a multiloop strategy, with an inner current PID regulator and an outer P+Resonant voltage controller. The inner regulator is applied on the output inductor current. It will be also demonstrated how the load current behavior may influence in the DVR output voltage, which justifies the need for the resonant controller. Additionally, it will be discussed the application of a modified algorithm for the identification of the DVR voltage references, which is based on a previously presented positive sequence detector. Since the studied three-phase DVR is assumed to be based on three identical H-bridge converters, all the analysis and design procedures were realized by means of single-phase equivalent circuits. The discussions and conclusions are supported by theoretical calculations, nonlinear simulations and some experimental results. ©2008 IEEE.

Bridgeless interleaved boost PFC converter with variable duty cycle control

This paper proposes a bridgeless boost interleaved PFC (power factor correction) converter with variable duty cycle control. The application of bridgeless technique causes reduction of conduction losses, while the interleaving technique of converters cells allows division of efforts in semiconductor devices and reduction of weight and volume of the input EMI filter. The use of variable duty cycle control has the functions of regulating the output voltage and eliminating the low order harmonic components that appears in the input current of the common interleaved power factor converters working in Discontinuous Conduction Mode (DCM). The simulation results of the proposed converter presented high power factor and a good transient response in relation to the output voltage regulation in presence of high load variations and supply voltage variations. © 2011 IEEE.

Uma nova metodologia de projeto e controle para o inversor Boost (CSI) monofásico, para o aproveitamento de fontes alternativas e renováveis de energia elétrica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação experimental de um sistema não linear para extração de energia através de vibrações utilizando material piezelétrico

Pós-graduação em Engenharia Mecânica - FEIS

Modeling of piezoelectric energy harvesting considering the dependence of the rectifier circuit

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Partial Discharge Phenomena in Converter and Traction Transformers: Identification and Reliability

After the development of power electronics converters, the number of transformers subjected to non-sinusoidal stresses (including DC) has increased in applications such as HVDC links and traction (electric train power cars). The effects of non-sinusoidal voltages on transformer insulation have been investigated by many researchers, but still now, there are some issues that must be understood. Some of those issues are tackled in this Thesis, studying PD phenomena behavior in Kraft paper, pressboard and mineral oil at different voltage conditions like AC, DC, AC+DC, notched AC and square waveforms. From the point of view of converter transformers, it was found that the combined effect of AC and DC voltages produces higher stresses in the pressboard that those that are present under pure DC voltages. The electrical conductivity of the dielectric systems in DC and AC+DC conditions has demonstrated to be a critical parameter, so, its measurement and analysis was also taken into account during all the experiments. Regarding notched voltages, the RMS reduction caused by notches (depending on firing and overlap angles) seems to increase the PDIV. However, the experimental results show that once PD activity has incepted, the notches increase PD repetition rate and magnitude, producing a higher degradation rate of paper. On the other hand, the reduction of mineral oil stocks, their relatively low flash point as well as environmental issues, are factors that are pushing towards the use of esters as transformer insulating fluids. This PhD Thesis also covers the study of two different esters with the scope to validate their use in traction transformers. Mineral oil was used as benchmark. The complete set of dielectric tests performed in the three fluids, show that esters behave better than mineral oil in practically all the investigated conditions, so, their application in traction transformers is possible and encouraged.

PWM Control of a Buck Converter with an Amorphous Core Coil

Pulse-width modulation is widely used to control electronic converters. One of the most topologies used for high DC voltage/low DC voltage conversion is the Buck converter. It is obtained as a second order system with a LC filter between the switching subsystem and the load. The use of a coil with an amorphous magnetic material core instead of air core lets design converters with smaller size. If high switching frequencies are used for obtaining high quality voltage output, the value of the auto inductance L is reduced throughout the time. Then, robust controllers are needed if the accuracy of the converter response must not be affected by auto inductance and load variations. This paper presents a robust controller for a Buck converter based on a state space feedback control system combined with an additional virtual space variable which minimizes the effects of the inductance and load variations when a not-toohigh switching frequency is applied. The system exhibits a null steady-state average error response for the entire range of parameter variations. Simulation results are presented.

Using the Own Flexibility of a Climbing Robot as a Double Force Sensor

Force sensors are used when interaction tasks are carried out by robots in general, and by climbing robots in particular. If the mechanics and electronics systems are contained inside the own robot, the robot becomes portable without external control. Commercial force sensors cannot be used due to limited space and weight. By selecting the links material with appropriate stiffness and placing strain gauges on the structure, the own robot flexibility can be used such as force sensor. Thus, forces applied on the robot tip can be measured without additional external devices. Only gauges and small internal electronic converters are necessary. This paper illustrates the proposed algorithm to achieve these measurements. Additionally, experimental results are presented.