DC-DC CONVERTER FOR THERMOELECTRIC SYSTEM

V diplomskem delu so predstavljeni termoelektrični elementi, njihova zgradba in osnovno fizikalno ozadje delovanja. Opisana je zgradba laboratorijskega sistema za preizkušanje termoelektričnih elementov. Za slednjega so predstavljeni merilni rezultati in karakteristika. Vključen je tudi opis pretvorniškega sistema, natančneje pretvornika navzgor. Glede na izmerjeno karakteristiko sistema je bila zasnovana osnovna regulacija pretvornika. Na podlagi rezultatov je bilo potrjeno delovanje pretvornika in regulacije na takšnem sistemu. Predstavljene so tudi osnovne ugotovitve in zaključki o delovanju sistema za preizkušanje termoelektričnih elementov.Thermoelectric elements, their construction and basic physical background of operation are presented in the thesis. The work describes the design of a laboratory prototype for thermoelectric element testing, measurements and characteristics of the system. Also included is a basic description of the converter system, specifically boost converter. A basic control algorithm was designed, with respect to the measurements and characteristics of the system. Operation of the boost converter and the control algorithm was confirmed, based on the output measurements. Also included are the basic findings and conclusions regarding the operation of the laboratory prototype for thermoelectric element testing

Optimization, modelling and control of a switched capacitor boost converter

Namen magistrskega dela je modifikacija pretvornika navzgor s preklopnimi kondenzatorji z namenom povečanja izkoristka. Uporaba pretvornika je mišljena v sistemih pridobivanja energije s termoelektričnimi elementi. Predstavljen je model in simulacije modificiranega pretvornika, podana je tudi primerjava med osnovnim in modificiranim vezjem. Predstavljene so ugotovitve in problemi pri delovanju modificiranega pretvornika navzgor s preklopnimi kondenzatorji. Predstavljeno je odprto-zančno delovanje pretvornika, ter izmerjene statične karakteristike pri različnih bremenskih upornostih. Implementirana je kaskadna regulacija brez linearizacijskih algoritmov, zaradi kompleksnosti in računske zahtevnosti le-teh.The purpose of this master thesis is to improve the efficiency of the switched-capacitor boost converter. The converter is intended to be used in an energy harvesting system that uses thermoelectric generators. Mathematical model and simulations of the converter, along with the comparison between the basic and modified circuit are presented in this thesis. The findings and problems in the operation of the modified switched-capacitor boost converter are also presented. The operation of the converter, as well as the measured static characteristics are presented. A cascade control algorithm is implemented, although without the linearization algorithms due to the complexity and microcontroller performance requirements of these algorithms

Control of a Modified Switched-Capacitor Boost Converter

Switched-capacitor converters and their alternatives have been shown to provide high efficiency with high power densities on smaller volumes, and can thereby be a suitable choice for energy harvesting. This paper proposes a hybrid power architecture based on a switched-capacitor topology and a boost converter that can be used for such purposes. A switching capacitor circuit can achieve any voltage ratio, allowing a boost converter to increase the input voltage to higher voltage levels. The first stage is unregulated with high-efficiency voltage conversion. The boost stage provides a regulated voltage output on such a converter. Rather than cascading two converters, their operation is integrated for the output voltage regulation. One major problem of switched-capacitor converters is output voltage regulation, which is solved by the interconnection of the power stages. The simplicity and robustness of the solution provide the possibility to achieve higher voltage ratios than cascading boost converters and provide higher efficiency. The converter’s size and cost can be improved with the integration of switching capacitors in DC-DC converter structures. A converter prototype has been designed, modelled, and built for the input voltage level of 2 V and power level of 5 W

Switched-Capacitor Boost Converter for Low Power Energy Harvesting Applications

The paper presents a Switched-Capacitor Boost DC-DC Converter (SC-BC) which can be used in energy harvesting applications using thermoelectric generators (TEGs) with low output voltage, low power and a significant internal resistance. It consists of a switching capacitor circuit, where MOSFETs are used as switches, and a boost stage. The converter is a modification of a previously presented scheme in which diodes are used in the switched capacitor stage. A higher voltage gain and an increased efficiency can thus be achieved. The model of the converter was developed considering the internal resistance of the TEG and boost stage inductor. A comparison with the diode based converter is shown, with consideration of the TEG internal resistance. Calculation is presented of the main passive components. A control algorithm is also proposed and evaluated. It is based on a linearization approach, and designed for output voltage and inductor current control. The operation of both converter and control are verified with the simulation and experimental results