The diploma thesis deals with comparison of heat loss calculation by CSN 06 0210 and CSN EN 12831. This work contains short introduction to the heat loss calculation, definition of basic terms, detailed analysis of heat loss calculation by both standards, description of exemplar buildings, heat loss calculation and heat requirement for heating of buildings according to particular standards. At the end of the work the comparison and discussion of calculation results is presented.

Hydropower is an efficient renewable energy source able to regulate electrical grid fluctuations. However, many hydropower plants were built decades ago, and now it is the time for a major refurbishment. The turbine's efficiency is essential and needs to be determined before and after refurbishment. To this end, the flow rate needs to be determined. Amongst different discharge measurement methods, the pressure-time method is relatively inexpensive and easy to perform compared to other methods. In this method, the flow rate is estimated by the integration of the measured differential pressure and the pressure loss due to friction between two cross-sections in a conduit during the deceleration of the liquid mass by closing a valve or guide vanes. The pressure-time method's accuracy depends on how accurate the head loss and the integration endpoint are estimated. Furthermore, the pressure-time method has limitations specified in IEC-60041, which make it challenging to apply on low-head turbines due to the short water passages when the flow is developing. The main focus of work is to improve the accuracy of the pressure-time method and extend its validity for low-head turbine conditions. Numerical simulation and experimental study have been acquired. A CFD model is developed to investigate the effects of the endpoint of integration and friction models on the method's accuracy. The effect of different boundary conditions is studied in the CFD model, and the result is validated with available experimental data. Different frictional models used with the pressure-time method are compared with CFD simulation for the developing and developed flows. A new parameter is suggested to improve deviation related to the flow status; developing and developed. Furthermore, a new methodology is presented, where the flow rate is estimated with the pressure-time method function of several endpoints. Then, experimental investigations of the pressure-time method outside IEC-60041 recommendations for conditions similar to low-head hydropower are presented. A laboratory setup is designed and built to test the pressure-time method. The method is applied for cases with shorter length, smaller UxL, pipe with variable cross-section and shorter distance to irregularity than IEC-60041 recommendations. Different assumptions for calculating the pressure loss and dynamic pressure variation are studied. Moreover, the quasi-steady assumption's accuracy on the head loss estimation and the difference in dynamic pressure are compared with constant values for their coefficients. The systematic uncertainty of the pressure-time method is also calculated based on the Monte Carlo Method (MCM).

Moore's Law has been used to describe and predict the blossom of IC industries, so increasing the data density is clearly the ultimate goal of all technological development. If the power density of power electronics converters can be analogized to the data density of IC's, then power density is a critical indicator and inherent driving force to the development of power electronics. Increasing the power density while reducing or keeping the cost would allow power electronics to be used in more applications. One of the design challenges of the high-density power converter design is to have high-density magnetic components which are usually the most bulky parts in a converter. Increasing the switching frequency to shrink the passive component size is the biggest contribution towards increasing power density. However, two factors, losses and parasitics, loom and compromise the effect. Losses of high-frequency magnetic components are complicated due to the eddy current effect in magnetic cores and copper windings. Parasitics of magnetic components, including leakage inductances and winding capacitances, can significantly change converter behavior. Therefore, modeling loss and parasitic mechanism and control them for certain design are major challenges and need to be explored extensively. In this dissertation, the abovementioned issues of high-frequency transformers are explored, particularly in regards to high-power converter applications. Loss calculations accommodating resonant operating waveform and Litz wire windings are explored. Leakage inductance modeling for large-number-of-stand Litz wire windings is proposed. The optimal design procedure based on the models is developed. / Ph. D.

Wind power installations have seen a significant rise all over the world in the past decade. Further significant growth is expected in the future. The UK’s ambitions for offshore wind installations are reflected through Round 1, 2 and 3 projects. It is expected that Round 3 alone will add at least 25 GW of offshore wind generation into the system. Current research knowledge is mostly limited to smaller wind farms, the aim of this research is to improve offline and online modelling techniques for large offshore wind farms. A critical part of offline modelling is the design of the wind farm. Design of large wind farms particularly requires careful consideration as high capital costs are involved. This thesis develops a novel methodology which leads to a cost-effective and reliable design of an offshore wind farm. A new industrial-grade software tool is also developed during this research. The tool enables multiple offshore wind farm design options to be built and tested quickly with minimal effort using a Graphical User Interface (GUI). The GUI is designed to facilitate data input and presentation of the results. This thesis also develops an improved method to estimate a wind farm’s energy yield. Countries with large-scale penetration of wind farms often carry out wind energy curtailments. Prior knowledge of estimated energy curtailments from a wind farm can be advantageous to the wind farm owner. An original method to calculate potential wind energy curtailment is proposed. In order to perform wind energy curtailments a network operator needs to decide which turbines to shut down. This thesis develops a novel method to identify turbines inside a wind farm that should be prioritised for shut down and given priority when scheduling preventive maintenance of the wind farm. Once the wind farm has been built and connected to the network, it operates as part of a power system. Real-time online simulation techniques are gaining popularity among system operators. These techniques allow operators to carry out simulations using short-term forecasted wind conditions. A novel method is proposed to probabilistically estimate the power production of a wind farm in real-time, taking into account variation in wind speed and effects of turbulence inside the wind farm. Furthermore, a new probabilistic aggregation technique is proposed to establish a dynamic equivalent model of a wind farm. It determines the equivalent number and parameters of wind turbines that can be used to simulate the dynamic response of the wind farm throughout the year.

The Modular Multilevel Converter (MMC) is one of the most commonly used active converters in the high-/medium-voltage sector due to its many advantages such as high scalability, high efficiency, modularity and low harmonic contents. However, in low-voltage and high-current applications, classical MMC designs are not very economical. Recently there has been interest in a new design of modular multilevel converter with interleaved submodules (ISM-MMC) capable of using lower cost, lower current switches. The aim of this study is to compare several different design configurations for a given ISM-MMC topology including classical MMC and to give the best design approach taking into account the efficiency and energy density of the system. The power loss of ISM-MMC influence the final efficiency. The loss studied in this thesis mainly consists of conduction losses and switching losses in the semiconductor devices and inductor losses. An analytical calculation method is summarized and validated by the simulation result. The simulation result is carried out in PLECS model with different system components. Power density is determined by the output power and the converter dimension. The volume of semiconductor devices and passive components determine the general dimension of the converter. This thesis discusses the selection of semiconductor devices, inductor and capacitor in the system, with semiconductor devices constraining interleaved leg current and submodule voltage, inductor constraining output current ripple and capacitor constraining capacitor voltage fluctuation. After the specific components are designed, their dimensions are evaluated, and thus the power density of different configurations can be compared. / Den modulära multinivåomvandlaren (modular multilevel converter, MMC) är en av de mest använda aktiva omvandlarna inom hög-/mellanspänningssektorn på grund av dess många fördelar som hög skalbarhet, hög verkningsgrad, modularitet och lågt övertonsinnehåll. Men i lågspännings- och högströmsapplikationer är konventionella MMC-konstruktioner inte särskilt ekonomiska. Nyligen har det funnits intresse för en ny design av modulär flernivåomvandlare med interfolierade submoduler (ISM-MMC) som kan uppnå lägre kostnad, och använda mindre halvledarelement. Syftet med denna studie är att jämföra flera olika designkonfigurationer för en given ISM-MMC-topologi inklusive konventionell MMC och att ge den bästa designmetoden med hänsyn till systemets verkningsgrad och energitäthet. Effektförlusten för ISM-MMC påverkar den slutliga verkningsgraden. Förluster som studeras i denna avhandling består huvudsakligen av ledningsförluster och kopplingsförluster i halvledarenheterna och induktorförluster. En analytisk beräkningsmetod sammanfattas och valideras av simuleringsresultatet. Simuleringsresultatet utförs men en PLECS-modell med olika systemkomponenter. Effekttätheten bestäms av uteffekten och omvandlardimensionen. Volymen av halvledarenheter och passiva komponenter bestämmer omvandlarens allmänna dimension. Denna avhandling diskuterar valet av halvledarenheter, induktor och kondensator i systemet, med halvledarenheter som begränsar interfolierad benström och submodulspänning, induktor som begränsar utströmsrippel och kondensatorbegränsande kondensatorspänningsfluktuationer. Efter att de specifika komponenterna har valts utvärderas deras storlek, och därmed kan effekttätheten för olika konfigurationer jämföras.

Neue elektrische Antriebskonzepte ermöglichen es, eine hohe Funktionalität in einem eingeschränkten Bauraum unterzubringen. Damit steigt auch in der Landwirtschaft das Interesse an elektrischen Antrieben. Die Projektgruppe Elektrische Maschinen und Antriebe der HTW Dresden beteiligt sich mit der TU Dresden an einem Projekt, bei dem beginnend mit der elektrisch angetriebenen Dreschtrommel umfassend an einem Mähdrescher untersucht wird, wie diese Antriebe in einzelne Funktionselemente integriert werden können. Neben der Auslegung der Antriebe werden Verfahren erarbeitet, die Verluste im Motor mit hoher Genauigkeit zu berechnen. So können in Zukunft passgenaue Kühlkonzepte für diese Antriebstechnik entwickelt werden. Anforderungen gerade im Bereich der Elektromobilität fordern den Blick für neue Materialien, deren elektromagnetisches und thermisches Verhalten werden in ihrem Einfluss auf die Erwärmung untersucht. Analytische und kombinierte Berechnungsmethoden in 2D-FEM gestatten die vereinfachte Rechnung unter Berücksichtigung von Grundwelle und entstehenden Harmonischen zu qualifizieren. Verlustberechnungen aus der transienten FEM-Rechnung ermöglichen diese Verbesserung. Die Methode wird am Beispiel der elektrischen Dreschtrommel mit den berechneten Verlustverteilungen beschrieben. Neue Methoden der 3D-FEM, wie sie die Software Ansys bietet, werden für die Nutzung von Einflüssen der Wirbelstromeffekte und in Auswertung für die Segmentierung von Permanentmagneten dargestellt. Die exemplarisch gewonnenen Erkenntnisse liefern einen Beitrag für weitere Schneidwerksantriebe am Mähdrescher, aber auch darüber hinaus in Projekten mit Herstellern elektrischer Maschinen. / New concepts for electrical drives make it possible to put a high functionality into a restricted structural form. Thereby the interest in electrical drives increases also in the farming. The project team Electrical machines and drives of the HTW Dresden participates together with the TU Dresden in a project, where starting with the electrically driven threshing cylinder is comprehensively examined at a combine harvester, how these drives can be integrated into single function elements. Besides the dimensioning of the drives are developed methods to calculate losses in the engine with high precision. So custom-fit cooling concepts can be developed for this drive technology in future. Requirements just in the area of the electric mobility call looking for new materials, whose electromagnetic and thermic behavior are examined in her influence on the warming. Analytical and combined computation methods in 2D-FEM allow the simplified calculation under consideration of the fundamental wave and the arising harmonic ones. Loss calculations by means of the transient FEM calculation make possible this improvement. The method is described at the example of the electrical threshing cylinder with the calculated loss distributions. New methods of the 3D-FEM, as the software of Ansys offers, are presented for the use of influences of the eddy current effects and in evaluation for the segmentation of permanent magnets. The exemplarily got knowledge provides a contribution for further cut header drives at the combine but also furthermore in projects together with manufacturers of electrical machines.

Neue elektrische Antriebskonzepte ermöglichen es, eine hohe Funktionalität in einem eingeschränkten Bauraum unterzubringen. Damit steigt auch in der Landwirtschaft das Interesse an elektrischen Antrieben. Die Projektgruppe Elektrische Maschinen und Antriebe der HTW Dresden beteiligt sich mit der TU Dresden an einem Projekt, bei dem beginnend mit der elektrisch angetriebenen Dreschtrommel umfassend an einem Mähdrescher untersucht wird, wie diese Antriebe in einzelne Funktionselemente integriert werden können. Neben der Auslegung der Antriebe werden Verfahren erarbeitet, die Verluste im Motor mit hoher Genauigkeit zu berechnen. So können in Zukunft passgenaue Kühlkonzepte für diese Antriebstechnik entwickelt werden. Anforderungen gerade im Bereich der Elektromobilität fordern den Blick für neue Materialien, deren elektromagnetisches und thermisches Verhalten werden in ihrem Einfluss auf die Erwärmung untersucht. Analytische und kombinierte Berechnungsmethoden in 2D-FEM gestatten die vereinfachte Rechnung unter Berücksichtigung von Grundwelle und entstehenden Harmonischen zu qualifizieren. Verlustberechnungen aus der transienten FEM-Rechnung ermöglichen diese Verbesserung. Die Methode wird am Beispiel der elektrischen Dreschtrommel mit den berechneten Verlustverteilungen beschrieben. Neue Methoden der 3D-FEM, wie sie die Software Ansys bietet, werden für die Nutzung von Einflüssen der Wirbelstromeffekte und in Auswertung für die Segmentierung von Permanentmagneten dargestellt. Die exemplarisch gewonnenen Erkenntnisse liefern einen Beitrag für weitere Schneidwerksantriebe am Mähdrescher, aber auch darüber hinaus in Projekten mit Herstellern elektrischer Maschinen. / New concepts for electrical drives make it possible to put a high functionality into a restricted structural form. Thereby the interest in electrical drives increases also in the farming. The project team Electrical machines and drives of the HTW Dresden participates together with the TU Dresden in a project, where starting with the electrically driven threshing cylinder is comprehensively examined at a combine harvester, how these drives can be integrated into single function elements. Besides the dimensioning of the drives are developed methods to calculate losses in the engine with high precision. So custom-fit cooling concepts can be developed for this drive technology in future. Requirements just in the area of the electric mobility call looking for new materials, whose electromagnetic and thermic behavior are examined in her influence on the warming. Analytical and combined computation methods in 2D-FEM allow the simplified calculation under consideration of the fundamental wave and the arising harmonic ones. Loss calculations by means of the transient FEM calculation make possible this improvement. The method is described at the example of the electrical threshing cylinder with the calculated loss distributions. New methods of the 3D-FEM, as the software of Ansys offers, are presented for the use of influences of the eddy current effects and in evaluation for the segmentation of permanent magnets. The exemplarily got knowledge provides a contribution for further cut header drives at the combine but also furthermore in projects together with manufacturers of electrical machines.

The falling cost of batteries, along with an increasing need to cut emissions, has spurred significant interest in the electrification of vehicles. In addition, as semiconductor devices have evolved, the research for electric vehicles with higher battery voltage has increased. The traction inverter is an important part of the electric power train and can account for a substantial portion of the drive train’s losses. This thesis therefore models, simulates, and studies the losses for a convectional Two-Level (2L) inverter and a Three-Level T-Type (3LT) inverter utilizing Silicon Carbide (SiC) MOSFETs and compares the two inverter topologies in terms of efficiency. The rated power of the inverters is 120 kW at a DC voltage of 800 V. The theoretical basis of SiC MOSFET and its reverse conduction, operation of 2L and 3LT inverter topologies, and Space Vector Pulse Width Modulation (SVPWM) technique are introduced in the initial part of the thesis. To estimate switching and conduction losses, Simulink is used to model and simulate an electric drive system. These estimated losses are then utilized to develop efficiency maps for both topologies over the complete speed-torque range. Based on the efficiency comparison, the 3LT topology outperforms the 2L topology for any requested torque in the medium to the high-speed range, which is typical of highway driving. In the low-speed, high-torque region, which is typical of city driving, the 2L topology is superior. The efficiency of each topology is affected by switching frequency, device junction temperature, and DC-link voltage. However, the comparison reveals that the maximum average difference in efficiency is 0.35%, with the 3LT topology being superior. Finally, the efficiency differences between the two inverter topologies are minimal. As a result, it may be concluded that the two topologies perform similarly. Thus, it can be inferred that comparing the efficiency of the two topologies should not be the sole criterion for selecting which topology should be used for the electric drive. / Den sjunkande kostnaden för batterier, tillsammans med ett ökande behov av att minska utsläppen, har lett till ett stort intresse för elektrifiering av fordon. Dessutom, har utvecklingen av halvledare lett till en ökning inom forskningen av elfordon med högre batterispänning. Traktionsomriktaren är en viktig del av den elektriska drivlinan och kan stå för en stor del av de totala förlusterna i drivlinan. I denna rapport modelleras, simuleras och studeras därför förlusterna i en konventionell omriktare med två nivåer (2L) och en T-typ omriktare med tre nivåer (3LT). Båda topologierna använder kiselkarbid (SiC) MOSFETs i jämförelsen av resultaten med avseende på verkningsgrad. Inverterarnas nominella effekt är 120 kW vid en likspänning på 800 V. Den teoretiska grunden för SiC MOSFET och hur de fungerar, hur 2L- och 3LT-inverterstopologierna fungerar samt tekniken för Space Vector Pulse Width Modulation (SVPWM) presenteras i rapporten. För att uppskatta switch- och ledningsförluster används Simulink för att modellera och simulera det elektriska drivsystemet. De uppskattade förlusterna används sedan för att utveckla verkningsgradskartor för de båda topologierna över hela det operativa området. Baserat på verkningsgradsjämförelsen mellan topologierna så presterar 3LT-topologin bättre än 2L-topologin i driftspunkter i medelhöga till höga hastigheter, vilket är typiskt för motorvägskörning. Vid låga hastigheter med högt vridmoment, vilket är typiskt för stadskörning, är 2L-topologin bättre. Verkningsgraden för de båda topologierna påverkas av switchfrekvensen, halvledarens temperatur samt DC-länkspänning. Jämförelsen visar dock att den största genomsnittliga skillnaden i verkningsgrad mellan de två topologierna är 0,35%, där 3LT-topologin är bättre. Sammanfattningsvis så är skillnaderna i verkningsgrad mellan de två topologierna minimala, vilket innebär att de båda topologierna har liknande prestanda med avseende på verkningsgrad. Man bör därför inte bara ha verkningsgrad som det enda kriteriet vid val av topologi för elektriska drivlinor.