Nosturin tehonsyöttö rinnankytketyillä verkkovaihtosuuntaajilla

Taajuusmuuttajaohjatuissa nosturikäytöissä taakkaa laskettaessa syntyvä energia on muutettava lämmöksi jarruvastuksissa tai syötettävä takaisin sähköverkkoon esimerkiksi verkkovaihtosuuntaajalla. Verkkovaihtosuuntaajaa on tyypillisesti käytetty suurissa satamanostureissa, joiden tehontarve on yli 1000 kW. Työssä tutkitaan useista yhteiseen välipiiriin rinnankytketyistä nimellisteholtaan 250 kW:n verkkovaihtosuuntaajista koostuvan verkkoonjarrutuslaitteiston soveltuvuutta nosturikäyttöön. Lisäksi johdetaan yhtälöt verkkoonjarrutuslaitteiston virran laskemiseksi, kun nosturin mekaaniset arvot tunnetaan. Viidestä erityyppisestä nosturista esitellään esimerkkitoteutus rinnankytketyillä verkkovaihtosuuntaajilla. Aiemmin vastusjarruttavina toteutettujen nostureiden kustannuksia verrataan verkkovaihtosuuntaajilla toteutettuihin ratkaisuihin. Esimerkkinostureista esitetään nosturin työsykliin perustuva arvio verkkoonjarrutuksen tuomasta energian säästöstä. Tehtyjen mittausten perusteella käytetty menetelmä verkkovaihtosuuntaajien rinnan kytkemiseksi osoittautui nosturikäytössä toimivaksi. Kustannuslaskelmien perusteella verkkovaihtosuuntaajalla toteutetusta nosturista tulee materiaalikustannuksiltaan vastusjarruttavaa kalliimpi, vaikka paljon tilaa vievät vastuskaapit voidaankin jättää pois.

Verkkovaihtosuuntaajan vektorisäädön toteutus FPGA-piirillä

Verkkovaihtosuuntaajalla pystytään muuntamaan tasajännite vaihtojännitteeksi ja päinvastoin. Verkkovaihtosuuntaajan toiminta perustuu tehokytkinten ohjaukseen ja sopivan modulointimenetelmän käyttöön. Vektorisäädössä vaihtosuuntaajanvirrat ja jännitteet esitetään kompleksitasossa, jolloin virta- ja jännitekomponentit voidaan esittää vektoreina. Vektorisäädössä verkkovaihtosuuntaajan ohjaustoteutetaan laskemalla kompleksitasossa vektoreille arvot, jotka tuottavat vaihtosuuntaajan lähtöön halutun vektorin. Koska FPGA-piirit mahdollistavat nopean rinnakkaisen laskennan, soveltuvat ne hyvin vektorisäädön toteuttamiseen. FPGA-piirien rakenteesta johtuen on säätöjärjestelmän suunnittelussa huomioitava kiinteän pilkun lukujen riittävä bittileveys ja järjestelmän diskretointiaika. Työssä suunnitellaan verkkovaihtosuuntaajan vektorisäätö ja tutkitaan bittileveyden vaikutusta säädön toteuttamiseen FPGA-piirillä. Bittileveyden tarkasteluun esitetään käytettäväksi tilastollisia menetelmiä. Työssä tarkastellaan kiinteän pilkun järjestelmän ja liukulukujärjestelmän erosuureen tilastollisia tunnusmerkkejä sekä histogrammia. Tarkasteluissa huomattiin, että maksimivirhe itsessään ei tarjoa riittävästi tietoa erosuureen jakautumisesta. Näin ollen maksimivirhe ei ole kaikissa tilanteissa sovelias menetelmä riittävän bittitarkkuuden määrittämiseen. Työssä esitetään riittävän bittitarkkuuden määrittelemiseen käytettäväksi otossuureista otosvarianssia, keskipoikkeamaa ja vaihteluväliä.

D-luokan audiovahvistimen modulointimenetelmien vertailu ja valinta

Tässä työssä esitellään kaksi D-luokan audiovahvistimissa käytettyä modulointimenetelmää ja vertaillaan niiden välisiä ominaisuuksia. Esitellyt menetelmät ovat pulssinleveysmodulaatio sekä sigma-deltamodulaatio. Lisäksi työssä esitellään signaalin käsittelyssä muodostuvan kohinan ja särön syntyä ja menetelmiä niiden välttämiseksi. Menetelmien ominaisuuksien vertailuun muodostetaan simulointimallit Simulink-ohjelmalla. Simulointitulosten perusteella valitaan käytettävä modulointimenetelmä audiovahvistinsovellukseen huomioon ottaen asetetut vaatimukset ja tavoitteet. Lopuksi valitun modulointimenetelmän suunnittelun pääkohtiin kiinnitetään huomiota.

Modular Double-Cascade Converter

Medium-voltage motor drives extend the power rating of AC motor drives in industrial applications. Multilevel converters are gaining an ever-stronger foothold in this field. This doctoral dissertation introduces a new topology to the family of modular multilevel converters: the modular double-cascade converter. The modularity of the converter is enabled by the application of multiwinding mediumfrequency isolation transformers. Owing to the innovative transformer link, the converter presents many advantageous properties at a concept level: modularity, high input and output power quality, small footprint, and wide variety of applications, among others. Further, the research demonstrates that the transformer link also plays a key role in the disadvantages of the topology. An extensive simulation study on the new converter is performed. The focus of the simulation study is on the development of control algorithms and the feasibility of the topology. In particular, the circuit and control concepts used in the grid interface, the coupling configurations of the load inverter, and the transformer link operation are thoroughly investigated. Experimental results provide proof-of-concept results on the operation principle of the converter. This work concludes a research collaboration project on multilevel converters between LUT and Vacon Plc. The project was active from 2009 until 2014.

A CMOS/SOI single-input PWM discriminator for low-voltage body-implanted applications

A CMOS/SOI circuit to decode Pulse-Width Modulation (PWM) signals is presented as part of a body-implanted neurostimulator for visual prosthesis. Since encoded data is the sole input to the circuit, the decoding technique is based on a novel double-integration concept and does not require low-pass filtering. Non-overlapping control phases are internally derived from the incoming pulses and a fast-settling comparator ensures good discrimination accuracy in the megahertz range. The circuit was integrated on a 2 mum single-metal thin-film CMOS/SOI fabrication process and has an effective area of 2 mm(2). Measured resolution of encoding parameter a is better than 10% at 6 MHz and V-DD = 3.3 V. Idle-mode consumption is 340 LW. Pulses of frequencies up to 15 MHz and alpha = 10% can be discriminated for 2.3 V less than or equal to V-DD less than or equal to 3.3 V. Such an excellent immunity to V-DD deviations meets a design specification with respect to inherent coupling losses on transmitting data and power by means of a transcutaneous link.

Single-phase high power factor hybrid rectifier suitable for high-power applications

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

New family of zero-current-switching PWM converter

A new family of dc-to-dc pulse-width-modulated (PWM) converters is presented. These converters feature soft-commutation at zero-current (ZC) in the active switches. The new ZCS-PWM Boost and new ZCS-PWM Zeta converters, both based on the new ZCS-PWM soft-commutation cell proposed, are used as examples to illustrate the operation of the new family of converters.

Novos conversores retificadores Sepic ZCS-PWM, operando como abaixadores de tensao, com elevados rendimento e fator de potencia - um estudo comparativo

A comparative evaluation regarding a new zero-current-switching (ZCS) pulse width modulated (PWM) Sepic rectifier, operating in voltage step-down mode, employing two different techniques, in order to obtain high power factor and reduced total harmonic distortion (THD) at the input current, is presented. The methods are those in continuous-current mode operation, known as peak current mode control with slope compensation, and average-current mode control. The principle of operation, the theoretical analysis, a design example and the main experimental results are presented for both proposed control techniques.

Novel high-power-factor isolated electronic ballast for multiple tubular fluorescent lamps

This paper presents a novel isolated electronic ballast for multiple fluorescent lamps, featuring high power-factor, and high efficiency. Two stages compose this new electronic ballast, namely, a new voltage step-down isolated Sepic rectifier, and a classical resonant Half-Bridge inverter. The new isolated Sepic rectifier is obtained from a Zero-Current-Switching (ZCS) Pulse-Width-Modulated (PWM) soft-commutation cell. The average-current control technique is used in this preregulator stage in order to provide low phase displacement and low Total-Harmonic-Distortion (THD) at input current, resulting in high power-factor, and attending properly IEC 61000-3-2 standards. The resonant Half-Bridge inverter performs Zero-Voltage-Switching (ZVS), providing conditions for the obtaining of overall high efficiency. It is developed a design example for the new isolated electronic ballast rated at 200W output power, 220Vrms input voltage, 115Vdc dc link voltage, with rectifier and inverter stages operating at 50kHz. Finally, experimental results are presented in order to verify the developed analysis. The THD at input current is equal to 5.25%, for an input voltage THD equal to 1.63%, and the measured overall efficiency is about 88.25%, at rated load.

A high efficiency HPF-ZCS-PWM Sepic for electronic ballast with multiple tubular fluorescent lamps

This paper presents a high efficiency Sepic rectifier for an electronic ballast application with multiple fluorescent lamps. The proposed Sepic rectifier is based on a Zero-Current-Switching (ZCS) Pulse-Width-Modulated (PWM) soft-commutation cell. The high power-factor of this structure is obtained using the instantaneous average-current control technique, in order to attend properly IEC61000-3-2 standards. The inverting stage of this new electronic ballast is a classical Zero-Voltage-Switching (ZVS) Half-Bridge inverter. A proper design methodology is developed for this new electronic ballast, and a design example is presented for an application with five fluorescent lamps 40W-T12 (200W output power), 220Vrms input voltage, 130Vdc dc link voltage, with rectifier and inverter stages operating at 50kHz. Experimental results are also presented. The THD at input current is equal to 6.41%, for an input voltage THD equal to 2.14%, and the measured overall efficiency is about 92.8%, at rated load.

3-D Space Vector PWM implementation for Four-Leg Voltage Source Inverter

The Space Vector PWM implementation and operation for a Four-leg Voltage Source Inverter (VSI) is detailed and discussed in this paper. Although less common, four-leg VSIs are a viable solution for situations where neutral connection is necessary, including Active Power Filter applications. This topology presents advantages regarding the VSI DC link and capacitance, which make it useful for high power devices. Theory, implementation and simulations are also discussed in this paper. © 2011 IEEE.

Eletroestimulador funcional de oito canais com malha de realimentação utilizando Controlador Digital

Pós-graduação em Engenharia Elétrica - FEIS

Reatores eletrônicos para sistemas de iluminação com múltiplas lâmpadas tubulares fluorescentes com controle de luminosidade, elevada eficiência e elevado fator de potência

Pós-graduação em Engenharia Elétrica - FEIS

Chaveamento de cargas intermitentes usando sensor de corrente

Due to concerns about rational use of energy, several alternative technologies of power generation appeared, including the conversion of solar energy into electrical energy by photovoltaic panels. In low-income households, the refrigerator represents considerable impact on the electric bill, since it requires constant power given its use in food preservation. It is possible to reduce this share, with the use of an alternative energy source. This work presents a timed switching electronic system, which allows commercial equipment that is not affected by short interruptions in the power supply to use a photovoltaic panel as a source of alternative energy, which usually do not provide energy continuously. Switching is made automatically in case of low incidence of sunlight, and without any form of energy storage. Between each switching, there is a dead time without power supply, therefore preventing the use of synchronizers circuits between the photovoltaic panel and the public power grid. A circuit containing a 80C31 microcontroller is used to control the system’s switching. The photovoltaic panel’s voltage inverter is in H bridge configuration, and is also controlled by the microcontroller through Pulse Width Modulation, which makes use of preprogrammed tables to generate the control signals of the power transistors. Through the use of software simulations, the proposed system was tested, which is capable of supplying intermittent single-phase loads. The simulations indicates that the project developed in this paper can be assembled into a prototype and be tested under real operating conditions, as long as the scaling of components, the characteristics of the photovoltaic panel to be used, and the project involved load are taken into account

A low-power silicon-on-insulator PWM discriminator for biomedical applications

A CMOS/SOI circuit to decode PWM signals is presented as part of a body-implanted neurostimulator for visual prosthesis. Since encoded data is the sole input to the circuit, the decoding technique is based on a double-integration concept and does not require dc filtering. Nonoverlapping control phases are internally derived from the incoming pulses and a fast-settling comparator ensures good discrimination accuracy in the megahertz range. The circuit was integrated on a 2 mu m single-metal SOI fabrication process and has an effective area of 2mm(2) Typically, the measured resolution of encoding parameter a was better than 10% at 6MHz and V-DD=3.3V. Stand-by consumption is around 340 mu W. Pulses with frequencies up to 15MHz and alpha = 10% can be discriminated for V-DD spanning from 2.3V to 3.3V. Such an excellent immunity to V-DD deviations meets a design specification with respect to inherent coupling losses on transmitting data and power by means of a transcutaneous link.