Oskars Krievs

Design of efficient current fed DC/DC converter for fuel cell applications

In order to use hydrogen fuel cells in domestic applications either as main power supply or backup source, their low DC output voltage has to be matched to the level and frequency of the utility grid AC voltage. Such power converter systems usually consist of a DC-DC converter and a DC-AC inverter. A double inductor step-up push-pull converter is investigated in this paper, presenting simulation and experimental results. The prototype of the investigated converter is elaborated for 1200 W power to match the rated power of the proton exchange membrane (PEM) fuel cell located in hydrogen fuel cell research laboratory.

Practically oriented e-learning workshop for knowledge improvement in engineering education computer control of electrical technology

Creation of good knowledge is based on practical exercise combined with theory learning. Studies in electrical engineering require many different laboratory exercises, traditionally carried out within the premises of university, where students can practice only several hours per week or even less. Such limited possibilities stipulate longer course durations and reduce knowledge creation quality. Possibility to gain some practical skills before carrying out laboratory assignments in real laboratory can become an essential part of the studies., facilitating much deeper understanding of the subject. For this reason a web-based e-Learning distance workshop in electrical engineering is elaborated and discussed in this paper. It is planned to cover courses in electrical drives, power electronics, LED lightning and automatic control.

Micro-grid for on-site wind-and-hydrogen powered generation

Abstract The authors propose a micro-grid for autonomous wind-and-hydrogen power generation thus replacing such traditional fossil-fuelled equipment as domestic diesel generators, gas micro-turbines, etc. In the proposed microgrid the excess of electrical energy from a wind turbine is spent on electrolytic production of hydrogen which is then stored under low-pressure in absorbing composite material. The electrolyser has a non-traditional feeding unit and electrode coatings. The proposed DC/DC conversion topologies for different micro-grid nodes are shown to be well-designed. The prototypes elaborated for the converters and hydrogen storage media were tested and have demonstrated a good performance. Kopsavilkums Rakstā piedāvātā mikrotīkla izpēte ir veikta ar mērķi izstrādāt autonomu, uz vēja un ūdeņraža enerģiju balstītu elektroapgādes sistēmu, kas varētu aizvietot tradicionālās fosilā kurināmā sistēmas, piemēram, mājsaimniecību dīzeļa ģeneratorus, gāzes mikroturbīnas u.c. Mikrotīkla elektroapgādes sistēmā vēja agregāta saražotā elektroenerģija tiek pārveidota atbilstoši standarta maiņsprieguma elektroapgādes parametriem un piegādāta slodzei. Pārpalikusī enerģija tiek pārveidota un uzkrāta ūdeņraža formā, izmantojot elektrolīzes iekārtu un kompozītmateriālu uzkrājēju. Ja pieejamā vēja enerģija nenosedz slodzes enerģijas patēriņu, elektroenerģijas padeves funkciju ar atbilstoša energoelektronikas pārveidotāja palīdzību pārņem ūdeņraža degvielas elements. Ja, savukārt, slodzei nav nepieciešama enerģija, no vēja saražoto enerģiju izmanto elektrolīzes iekārta un tā tiek uzkrāta ūdeņraža formā, atbilstoši uzkrājēja ietilpībai. Piedāvātajā mikrotīklā ir izmantota elektrolīzes iekārta ar netradicionāliem elektrodu pārklājumiem un barošanas bloku, kā arī zemspiediena kompozītmateriālu ūdeņraža uzkrājējs. Galvenie mikrotīkla elektriskās enerģijas pārveidošanas mezgli ir realizēti uz energoefektīvu energoelektronikas pārveidotāju bāzes. Ir izveidoti atsevišķo piedāvātās elektroapgādes sistēmas iekārtu prototipi un veiktas to eksperimantālās pārbaudes, gan atsevišķi, gan darbam kopējā sistēmā.

Current-fed Step-up DC/DC Converter for Fuel Cell Applications with Active Overvoltage Clamping

Current-fed Step-up DC/DC Converter for Fuel Cell Applications with Active Overvoltage Clamping In order to use hydrogen fuel cells in domestic applications either as main power supply or backup source, their low DC output voltage has to be matched to the level and frequency of the utility grid AC voltage. Such power converter systems usually consist of a DC-DC converter and a DC-AC inverter. A double inductor step-up push-pull converter is investigated in this paper, presenting simulation and experimental results for passive and active overvoltage clamping. The prototype of the investigated converter is elaborated for 1200 W power to match the rated power of the proton exchange membrane (PEM) fuel cell located in hydrogen fuel cell research laboratory.

A PLL Scheme for Synchronization with Grid Voltage Phasor in Active Power Filter Systems

A PLL Scheme for Synchronization with Grid Voltage Phasor in Active Power Filter Systems Voltage source inverters connected to the grid in applications such as active power filters require synchronization with the grid voltage. Since in practice the grid voltage can be unbalanced and distorted, but the operation of the whole active filter control system is strongly dependant on precise estimation of grid voltage phase, the fundamental positive sequence phasor of the grid voltage has to be extracted. In this paper a system for smooth estimation of the position of the voltage phasor at the point of common coupling of a parallel active filter system is presented using a sinusoidal signal integrator and a simple software PLL. The performance of the proposed system is verified by simulation and experimental results. The proposed PLL scheme can also be used in other vector oriented control systems.

Design of current source DC/DC converter and inverter for 2kW fuel cell application

In order to use hydrogen fuel cell in domestic applications either as main power supply or backup power source, the low DC output voltage of the fuel cell has to be matched to the voltage level and frequency of the utility grid AC voltage. The interfacing power converter systems usually consist of a DC/DC converter and an inverter. In this paper a detailed simulation study of such interfacing converter system comprising a double inductor push-pull step-up DC/DC converter and a cascaded H-bridge inverter has been carried out and further confirmed with experimental results. The power converter system is designed for interfacing a 2kW proton exchange membrane (PEM) fuel cell.

A double inductor current source DC/DC converter for 2kW fuel cell application

In order to use hydrogen fuel cells in domestic applications either as main power supply or backup source, their low DC output voltage has to be matched to the level and frequency of the utility grid AC voltage. Such power converter systems usually consist of a DC-DC converter and a DC-AC inverter. In this paper a double inductor step-up push-pull converter is investigated, presenting simulation and experimental results of the system. The converter is elaborated for 2kW power to match the rated power of the proton exchange membrane (PEM) fuel cell located in hydrogen fuel cell research laboratory of Riga Technical University.

Design of resonant DC/DC converter for fuel cell application

In order to use hydrogen fuel cells in domestic applications either as main power supply or backup source, their low DC output voltage has to be matched to the level and frequency of the utility grid AC voltage. Such power converter systems usually consist of a DC-DC converter and a DC-AC inverter. The paper focuses on double-stage, grid-connected Fuel Cell conversion systems. The converter is elaborated for 5 kW power to match the rated power of the proton exchange membrane (PEM) fuel cell.

Current-fed DC/DC converter for fuel cell applications

In order to use hydrogen fuel cells in domestic applications either as main power supply or backup source, their low DC output voltage has to be matched to the level and frequency of the utility grid AC voltage. Such power converter systems usually consist of a DC-DC converter and a DC-AC inverter. A double inductor step-up push-pull converter is investigated in this paper, presenting simulation and experimental results. The prototype of the investigated converter is elaborated for 1200 W power to match the rated power of the proton exchange membrane (PEM) fuel cell located in hydrogen fuel cell research laboratory.

Current Fed Step-up DC/DC Converter for Fuel Cell Inverter Applications

Current Fed Step-up DC/DC Converter for Fuel Cell Inverter Applications In order to use hydrogen fuel cells in domestic applications either as main power supply or backup source, their low DC output voltage has to be matched to the level and frequency of the utility grid AC voltage. Such power converter systems usually consist of a DC-DC converter and a DC-AC inverter. Comparison of different current fed step-up DC/DC converters is done in this paper and a double inductor step-up push-pull converter investigated, presenting simulation and experimental results. The converter is elaborated for 1200 W power to match the rated power of the proton exchange membrane (PEM) fuel cell located in hydrogen fuel cell research laboratory of Riga Technical University.