Design of High Power Converter with SiC MOSFETs

Tato diplomová práce se zabývá návrhem výkonového měniče založeného na topologii typu synchronní buck. Měnič je zkonstruován s využitím MOSFET tranzistorů na bázi silikon karbidu. Tato práce se věnuje analýze měniče s cílem navrhnout a realizovat řídící jednotku umožňující jak zpětnovazební regulaci měniče, tak řízení v otevřené smyčce. Za tímto účelem je odvozen analytický model měniče coby dynamického systému, který je použit pro návrh a simulaci řízení. Kontrolní jednotka je implementována s využitím 32 bitového mikrořadiče založeného na architektuře ARM. V této práci je poskytnut popis a použití klíčových periférií mikrořadiče pro realizaci řízení. Na závěr jsou shrnuty výsledky měření dynamického chování výkonových tranzistorů při provozu měniče. Pozornost je především věnována měření proudu tekoucího jedním tranzistorem s využitím běžného rezistoru pro snímání proudu a kompenzaci frekvenční charakteristiky rezistoru.This master degree thesis is concerned with the design of high power converter. The converter is based on synchronous buck topology and is realized using silicon carbide MOSFET transistors. This work deals with an analysis of such type of converter to design and realize a control unit providing feedback control of the converter. Therefore, a dynamic model of the converter is derived using a conventional technique of averaged state space modeling. The derived model is used for controller design and closed-loop control simulation. The control unit is implemented using a 32-bit ARM-based microcontroller. Hence, an insight into the microcontroller key peripherals is provided as well as a brief overview of the firmware architecture. This work concludes by a brief investigation of switching waveforms of SiC MOSFETs acquired during the converter operation. Attention is called to a transistor current measurement with a low-cost current sensing resistor and its frequency characteristic compensation

Methyl 5′-(2-hy­droxy­phen­yl)-4′,5′,6′,7′-tetra­hydro­spiro­[2H-1-benzopyran-2,7′-1,2,4-triazolo[1,5-a]pyrimidine]-3-carboxyl­ate

There are two crystallographically independent mol­ecules in the asymmetric unit of the title compound, C21H18N4O4. The substituted benzopyran portion of one of the independent mol­ecules exhibits disorder [occupancy 0.5248 (18):0.4752 (18)], which was modelled by using two sets of atomic positions and restraints on the chemically equivalent bond lengths and angles. The central, partially saturated pyrimidine rings of both independent mol­ecules were found to assume unsymmetrical half-chair conformations. The hy­droxy­phenyl substituent occupies an equatorial position in both mol­ecules, and is rotated by 55.6 (1)° from the mean plane of the pyrimidine ring in one independent mol­ecule, and by 53.4 (1)° in the other. In the crystal, there are two types of inter­molecular hydrogen bond present: reciprocal N—H⋯N inter­actions join the two crystallographically independent mol­ecules into a dimer and O—H⋯N inter­actions link the dimers into sheets in the ab plane

4-[(5R*,10bR*)-2-Methyl-1,10b-dihydro­pyrazolo[1,5-c][1,3]benzoxazin-5-yl]benzoic acid

In the title compound, C18H16N2O3, a potential inhibitor of the cyclo­oxygenase-2 isoenzyme, the pyrazoline ring exists in a flattened envelope conformation with one C atom deviating by 0.463 Å from the mean plane of the remaining four atoms. The puckering of the central oxazine ring is more severe, with one N atom and one C atom displaced by 0.235 (6) and 0.370 (2) Å, respectively, on opposite sides of the mean plane defined by the other four atoms; the conformation is that of a half-chair. As a result, the mol­ecule as a whole is not planar. The carboxyl group is involved in an inter­molecular O—H⋯N hydrogen bond, which links the mol­ecules into centrosymmetric dimers

rac-2-Methyl-3,4,5,6-tetra­hydro-2H-2,6-methano-1,3-benzoxazocin-4-one

The title compound, C12H13NO2, represents a conformationally restricted 2-pyridone analogue of 1,4-dihydro­pyridine-type calcium antagonists and was selected for a crystal structure determination in order to explore some aspects of drug-receptor inter­action. In the mol­ecule, two stereogenic centres are of opposite chirality, whereas a racemate occurs in the crystal. It was found that the formally aminic N atom of the heterocycle is essentially sp 2-hybridized with the lone-pair electrons partially delocalized through conjugation with the adjacent carbonyl bond. As a result, the central pyridone ring assumes an unsymmetrical half-chair conformation. The critical 4-phenyl ring is fixed in a pseudo-axial and perpendicular orientation [dihedral angle 85.8 (1)°] with respect to the pyridone ring via an oxygen bridge. In the crystal a pair of centrosymmetric N—H⋯O hydrogen bonds connect mol­ecules of opposite chirality into a dimer. The dimers are packed by hydrophobic van der Waals inter­actions

(5R*,11R*)-5-Methyl-1,2-dihydro-5,11-methano-5H,11H-1,3-thia­zolo[2,3-d][1,3,5]benzoxadiazo­cine

The title compound, C13H14N2OS, crystallizes as a racemate in a non-chiral space group. It represents a conformationally restricted analogue of so-called Biginelli compounds known to exhibit multiple pharmacological activities and was selected for a single-crystal X-ray analysis in order to probe the chemical and spatial requirements of some kinds of activity. It was found that the state of hybridization of the formally aminic nitro­gen of the heterocycle is between sp 2 and sp 3 with the lone-pair electrons partially delocalized through conjugation with the sulfur atom rather than the double bond of the pyrimidine nucleus. As a result, the thia­zolo ring adopts a flat-envelope conformation and the puckering of the central pyrimidine ring is close to a half-chair. The critical phenyl ring is fixed in a pseudo-axial and perpendicular [dihedral angle 84.6 (1)°] orientation with respect to the pyrimidine ring via an oxygen bridge

2-Methyl-1,10b-dihydro-5H-pyrazolo[1,5-c][1,3]benzoxazin-5-one

In the title compound, C11H10N2O2, a potential inhibitor of the cyclo­oxygenase-2 isoenzyme, the pyrazoline ring exists in a flat-envelope conformation while the puckering of the central oxazine ring is more severe. As a result, the mol­ecule as a whole is non-planar. The formal sp 3 pyrazoline N atom is sp 2 hybridized, with the lone-pair electrons delocalized through conjugation with the carbonyl group rather than the double bond of the pyrazoline ring

Ethyl 6-ethoxy­carbonyl­methyl-4-(2-hydroxy­phen­yl)-2-oxo-1,2,3,4-tetra­hydro­pyrimidine-5-carboxyl­ate

The title compound, C17H20N2O6, belongs to the monastrol-type of anti­cancer agents and was selected for crystal structure determination in order to confirm its mol­ecular structure and explore some aspects of its structure–activity relationships. The central tetra­hydro­pyrimidine ring has a flat-envelope conformation. The 4-hydroxy­phenyl group occupies a pseudo-axial position and is inclined at an angle of 87.7 (2)° to the mean plane of the heterocyclic ring. Of the two ethyl ester groups, one (in the 5-position) is in a coplanar and the other (in the 6-position) is in a perpendicular orientation with respect to the heterocyclic plane. There is a three-dimensional hydrogen-bonding network in which all hydrogen-bond donors and acceptors are involved

The 2018 European heatwave led to stem dehydration but not to consistent growth reductions in forests

Publisher Copyright: © 2022, The Author(s).Heatwaves exert disproportionately strong and sometimes irreversible impacts on forest ecosystems. These impacts remain poorly understood at the tree and species level and across large spatial scales. Here, we investigate the effects of the record-breaking 2018 European heatwave on tree growth and tree water status using a collection of high-temporal resolution dendrometer data from 21 species across 53 sites. Relative to the two preceding years, annual stem growth was not consistently reduced by the 2018 heatwave but stems experienced twice the temporary shrinkage due to depletion of water reserves. Conifer species were less capable of rehydrating overnight than broadleaves across gradients of soil and atmospheric drought, suggesting less resilience toward transient stress. In particular, Norway spruce and Scots pine experienced extensive stem dehydration. Our high-resolution dendrometer network was suitable to disentangle the effects of a severe heatwave on tree growth and desiccation at large-spatial scales in situ, and provided insights on which species may be more vulnerable to climate extremes.Peer reviewe

A Novel Approach to Evaluate the Effect of Neighboring Trees and the Orientation of Tree Social Area on Stem Radial Increment of Norway Spruce Trees

Tree growth depends on many factors such as microsite conditions, vitality, and variations in climate and genetics. It is generally accepted that higher growth indicates both an economic benefit and better vitality of any tree. Here we use a modified approach of evaluating tree social area to study mutual tree competition based on the orientation and shape of trees social area. The investigation was performed in nine Norway spruce stands in the Czech Republic. The objective of this study performed from 2008 to 2012 was to quantify relative tree radial increments with respect to the lowest and highest competition found in specific sectors of tree social area (AS). Specific groups of trees (tree classes) were evaluated according to their classes (dominant, co-dominant and sub-dominant) and their composition status in ninety-degree sectors of AS using established classifying rules. The results showed that a spatially-available area (AA) is an inappropriate parameter for predicting tree growth, whereas AS provided robust explanatory power to predict relative radial growth. Tree size was observed as an important indicator of relative radial increments. A significantly positive correlation was found for a radial increment of sub-dominant trees with the lowest competition from western directions; whereas a negative correlation was observed when the lowest competition was observed from eastern directions. For dominant trees, there was an evident growth reaction only when more than 50% of the AS was oriented towards one of the cardinal points. Individual differences in the orientation of tree AS may be important parameters with regard to competition and its spatial variability within an area surrounding a particular tree and deserve more detailed attention in tree growth models and practice