Dissertationen zum Thema „STANDALONE APPLICATIONS“

The proton exchange membrane fuel cell (PEMFC) is a promising technology that can be manufactured in South Africa because of the platinum catalyst required. South Africa is rich in platinum and, therefore, the PEMFC system can be cost-effectively produced. In residential stationary applications of the PEMFC a power conditioning system is required to convert the de voltage output of the PEMFC to ac voltage. Therefore, the focus of this thesis is to analyse, simulate and design a power electronic dc-ac converter. The power electronic dc-ac converter is based on a transformerless single stage power conversion scheme, which has better weight, volume and efficiency than the commonly used two stage power conversion schemes. The selected topology is the boost inverter that consists of two identical boost converters for boosting and inversion of the PEMFC de voltage. Moreover, it achieves reliable operation under nonlinear loads, sudden load changes and inrush current, using a double loop control strategy. Initially, the double loop control strategy was introduced with proportional integral (Pl) controllers. Recently, with the widespread use of proportional resonant PR controllers, the PI controllers were replaced with PR controllers to achieve zero steady state error for the ac components of the reference. However, during the implementation of the PR controllers on the boost inverter, a significant de offset in the output voltage of the boost inverter was observed, which was due to the mismatch of the boost converters' parameters. The de voltage affects pulsating torque AC machines, accuracy in domestic watt-meter and safety of residual current protection. Furthermore, the output voltages of the boost converters showed a clipping effect, which was caused by the dead time of the switching devices used in the boost converters. An integral term was added to the PR controller to form the controller here called the proportional integral resonant (PIR) controller. This controller achieved satisfactory results of de and ac voltage reference following capability and maintains the same advantages of the PI controllers. However, the efficiency was not high due to the high resistance of the inductor used in the boost inverter system.

The scaling down of transistor sizes has imposed significant challenges in today's technology. Memories such as eDRAM, are experiencing poor retention time because of challenges such as reference voltage variation, high transistor leakage, and low cell capacitance. It can be seen that we must consider not only the first order effects, but also the second order effects to ensure we keep up with current technology trends such as Moore's law. In this thesis we explore various circuit level techniques on level shifters in order to achieve better retention time. With our research, we have addressed important design challenges and propose techniques that can be utilized in current and emerging technologies. Level shifters (LS) are crucial components in low-power design where the die is segregated in multiple voltage domains. LS are used at the voltage domain interfaces to mitigate sneak path current. A less-known but very important application of LS is in high voltage drivers for designs where voltage boosting is needed for performance and functionality. We first study LS in eDRAM where LS is employed in the wordline path. Our investigation reveals that leakage power of LS can pose a serious threat by lowering the wordline voltage and subsequently affecting the speed and retention time of the eDRAM. It can also be noted that the delay of the LS under worse case process corners can cause significant functional discrepancies. We propose low-power pulsed-LS with supply gating to circumvent these issues. Our analysis indicate that pulsed-LS design can improve the worst case speed from 2.7%-43%. We extended this concept to design generic self-collapsible LSs that can be used for other applications such as voltage interfaces. The self-collapsed design in both applications improved the worst case speed from 6%-24% and 89% in some cases.

This Ph.D. thesis aims at investigating the effect of state feedback cross‐coupling decoupling of the capacitor voltage on the dynamics performance of Voltage Source Inverters for standalone microgrids/Uninterruptible Power Supply systems. Computation and PWM delays are the main factors which limit the achievable bandwidth of current regulators in digital implementations. In particular, the performance of state feedback decoupling is degraded because of these delays. Two decoupling techniques aimed at improving the transient response of voltage and current regulators are investigated, named nonideal and ideal capacitor voltage decoupling respectively. In particular, the latter solution consists in leading the capacitor voltage on the state feedback decoupling path in order to compensate for system delays. Practical implementation issues are discussed with reference to both the decoupling techniques. Moreover, different resonant regulators structures for the inner current loop are analysed and compared to investigate which is the most suitable for standalone microgrid applications. A design methodology for the voltage loop, which considers the closed loop transfer functions developed for the inner current loop, is also provided. Proportional resonant voltage controllers tuned at specific harmonic frequencies are designed according to the Nyquist criterion taking into account application requirements. For this purpose, a mathematical expression based on root locus analysis is proposed to find the minimum value of the resonant gain at the fundamental frequency. The exact model of the output LC filter of a three‐phase inverter is derived in the z‐domain. The devised formulation allows the comparison of two techniques based on a lead compensator and Smith predictor structure. These solutions permit the bandwidth of the current regulator to be widened while still achieving good dynamic performance. As a consequence, the voltage regulator can be designed for a wide bandwidth and even mitigates odd harmonics arising with unbalance loads supply. Discrete‐time domain implementation issues of an anti‐wind up scheme are discussed as well, highlighting the limitations of some discretization methods. Experimental tests performed in accordance to Uninterruptible Power Supply standards verify the theoretical analysis.

Many companies want a lot of functionality over the web. Is it possible to achieve the same functionality on the web compared to an ordinary windows application? Our work aims towards evaluating which one of the solutions that is the best. Many customers wants a standalone application rich of functionality and demands to have the same functionality on the web. Is it always possible to achieve the costumer’s requirements on a web based solution or do you have to settle with an implementation of a standalone application? There are some factors that the answer depends on: performance, security, usability and implementation. The application that will be tested is developed in .Net and is a maintenance application for Business Intelligence (BI). We will have a short introduction to the Business Intelligence field to make you understand the purpose of the application.

Occasionally, a part of the budget of a city, company or other entity has to be allocated among its parts in the form of subsidies or other contributions. The main objective of such an entity is to find such a set of criteria and such a set of their relative weights that estimate the expected cost best. The objective of a sub-entity is subsidy maximization by influencing the criteria and their weights. From this reason, the best budget splitting is a relative term. From the mathematical point of view, such a problem belongs to mathematical optimization or mathematical programming. In this thesis, five quantitative methods are presented. Two of them set the weights without the participation of decision makers. The first allocation method is based on multiple-criteria decision-making and the second one on data envelopment analysis. Together with them, a different mathematical model with maximum and minimum weights for the set of criteria is presented. Two its modifications are discussed too. As the only one presented multi-criteria mathematical model is based on maximization of the relative and absolute profit simultaneously. The aim of this work is to study the known mathematical models for subsidy allocation problem, to invent new ones, to choose suitable ones and subsequently to implement the suitable ones into a standalone GUI application created in the Matlab environment. The presented application proposes several allocation possibilities according to different selected models using mathematical functions taken from Matlab. This user-friendly application is executable on common computers and can be used at the Magistrate of the City of Prague as a support tool in voting decision. Moreover, this application can be extended to new methods or program functions. The selected quantitative methods are used for the budget allocation problem among the city districts for real data of the City of Prague. Experimental results are discussed.

Saab is a large swedish company providing a multitude of different products and services. This also means that Saab has to provide support and customer service for said products. Currently this is handled online in Support Portals, where customers and partners can access product information as well as an issue management system called SIRS. In the current situation the system is tailored for a desktop experience, and the workflow is therefore limited in terms of mobility. This project aims to allow the users to be more mobile by investigating the possibility of developing a mobile application for usage with SIRS. During the project a proof of concept of such an application has been developed. The implementation relies largely on using currently available api:s and when necessary porting some code from server to client side. By using various UX-related methods during the development of the application it is expected that the application is user friendly and fits the target audience. When looking at the result of the work, it is indeed possible to integrate a standalone mobile application with SIRS. The application also has usability which is comparable to the current system. However, some limitations were found that required rewriting the existing system to provide necessary data to client side applications like the one developed in this project. To conclude, the application is a proof of concept that shows what can be done without modifying the current system. Some of the major things that has to be modified before taking the application to production, such as stability concerns and testing, is also presented as results of the project.

This paper aims to examine what the differences is between the three application types, native, hybrid and web. The main focus will be placed on the web app and investigate whether it could be an alternative to native and hybrid app. To explain what a web app has the capacity to do, a web app is created in wordpress. Web development is moving forward, which is obviously positive. The problem may be, however, for companies that come from a completely different industry and who wish to develop a new web solution for their company. A native app can be a very expensive investment and it is far from all companies that can pay this. This study wants to find out if a web app, could be an alternative to the native app. Furthermore, the report will examine what the possibilities are for a web app and what existing web apps there is today. Furthermore, a simple price comparison between the different app types to be made.
Den här rapporten syftar till att undersöka vad skillnaden är mellan de tre applikationstyperna, native, hybrid och webb. Störst fokus kommer att placeras på webb appen och undersöka om denna skulle kunna vara ett alternativ till native och hybrid appen. För att redogöra vad en webb app har kapacitet att göra kommer en webb app att skapas i wordpress. Webbutvecklingen går framåt vilket självklart är positivt. Problemet som kan bli är dock för företag som kommer från en helt annan bransch och som önskar ta fram en ny webb-lösning för sitt företag. En native app kan vara en väldigt dyr investering och det är långt ifrån alla företag som kan betala detta. Denna undersökning vill reda ut om en webb app kan var ett alternativ till native appen. Vidare kommer rapporten undersöka vad det finns för möjligheter för en webb app och vad det finns för webb appar idag. Dessutom kommer en enklare prisjämförelse mellan de olika apptyperna att göras.

This thesis work aimed to develop solar Photovoltaic (PV) powered smart street post. The post was set to serve on highways for wild animals’ detection and warn vehicles of possible crossings. The main aim was to design reliable standalone PV system via PVSyst software and experimenting four different PV technologies including a bifacial module under. Another aim was to select and develop the hardware and software terms of the smart street pot. Radar sensor and analog to digital (A/D) data acquisition (DAQ) card were set to be used for the motion detection. RF wireless communication module was used for communicating with nearby posts to send data and trigger warning light emitting diodes (LED) sign. A Raspberry Pi microcontroller was programmed to control the operation of the street post through processing the signal from radar sensor and communicating with nearby posts. The PV system design included generation of street post’s daily profile, sizing and selection of the components of the system including the module, battery, charge controller and power stage circuit. The later was designed to provide suitable voltage level and interface for the loads connected. PVSyst model was built and set to be located in Ulm, Germany. The design parameters were set, and different set of orientations were tested for each module. The simulation results showed bifacial module delivered a reliable PV system in case of south and south-east orientation and achieved better performance in other orientations in comparison to the other PV modules implemented. Due to limitations in PVSyst software the results provided had an overall uncertainty of 5%. The microcontroller was able to process the data from the radar sensor and DAQ card and perform fast Fourier transform (FFT). However, further processing of motion detection was complex to be included in the thesis work. The radar sensor and DAQ card provided signals with uncertainty of ± 3.4 mV. The RF wireless communication module transmitted signal over various ranges up to 150 m with time delay of 500 ms.

Le travail présenté dans cette thèse est une contribution au dimensionnement et à la commande d’un générateur de type Cascade de Machines Asynchrones à Double Alimentation. Le modèle de la machine pour les simulations est basé sur une représentation modulaire qui découle du modèle de Park de deux machines asynchrones doublement alimentées distinctes, en respectant deux systèmes de référence. Le modèle dynamique est ensuite étendu pour décrire la machine dans un repère unifié. Cette représentation est cruciale pour le dimensionnement de la machine et la synthèse de la commande. Le domaine de fonctionnement de la cascade en régime permanent est exploré. Une méthode analytique générique est proposée pour établir les plages de puissances active-réactive. Les courbes limites sont définies par rapport aux grandeurs nominales de la machine. L’étude prend en compte l’effet de saturation du circuit magnétique. Il est prouvé que la capacité en puissance de la machine est déterminée par les valeurs maximales des courants statoriques et peut être soumise à plusieurs limitations. L’approche analytique est testée et validée par des mesures expérimentales. Deux cas sont considérés pour la commande de la cascade : un générateur raccordé au réseau et un générateur autonome. Pour la connexion au réseau l’application visée est les éoliennes de grande puissance. Une nouvelle méthode pour l’extraction de la puissance maximale d’une éolienne à vitesse variable est proposée. Le système est contrôlé dans le but de fournir une puissance maximale quasi-constante indépendamment des fluctuations du vent. En plus de l’optimisation de la puissance, le facteur de puissance est également ajusté selon les normes de raccordement standard imposées par les services système, et les limites de fonctionnement de l’unité intégrée. Une commande vectorielle sans capteur de tension, basée sur une orientation suivant un flux virtuel, est appliquée pour la régulation découplée des puissances active et réactive. Pour le fonctionnement en mode isolé, l’application visée est la génération électrique pour système avionique embarqué. Deux réseaux de distribution sont traités : réseau AC à fréquence fixe et réseau DC. Dans les deux cas, la commande est élaborée dans le but de maintenir une tension de sortie constante. Le fonctionnement de la cascade alimentant une charge triphasée déséquilibrée est également étudié. Des schémas de contrôle servant à la compensation du déséquilibre des tensions statoriques sont développés. Deux méthodes de compensation sont proposées : l’une basée sur le principe de deux repères tournants et l’autre sur un correcteur répétitif. Les approches présentées sont validées par simulation avec Matlab/Simulink et par expérimentation
This thesis is a contribution to the power sizing and the control of a Cascaded Doubly Fed Induction Generator (CDFIG). The machine model for simulation is based on a modular representation, derived from the Park model of two distinct Doubly Fed Induction Machines expressed in their own reference frames. The dynamic model of the cascaded machine is then extended to be described in a unified reference frame. This representation is convenient for the sizing of the machine and for the design of the controller. The steady state power operating margins of the cascaded machine are investigated. A generic analytic method is suggested to derive the active-reactive power domain. The limit curves are defined in terms of the rated quantities of the machine. The study takes into account the magnetic circuit saturation effect. It is proven that the power capability of the machine is determined by the stator current maximum values and is subject to several limitations. The analytical approach is tested and validated by experimental measurements. The CDFIG is controlled in grid-connected and standalone operation modes. In grid-connected application, the attention is paid to high power wind generation systems. A new maximum power tracking of a variable speed wind turbine is suggested. The generating plant is carried to provide a quasi-constant maximum power regardless wind fluctuations. In addition to active power optimization the power factor is adjusted according to the grid code requirements and the operating domain of the integrated unit. A virtual flux oriented vector control is applied for the decoupled regulation of active and reactive powers, leading to grid voltage sensorless operation. In standalone operating mode, the study treats in particular the embedded aircraft power system generation. Two distribution networks are considered: constant frequency AC network and DC network. In both cases, the control aims to maintain a constant output voltage. The operation of the CDFIG supplying unbalanced three-phase load is further explored. Control schemes to cope with unbalanced stator voltage conditions are developed. Two compensation methods are elaborated: the first dealing with dual rotating frames and the second is based on repetitive controller. Simulations with Matlab/Simulink software and experiments validate the control approaches

碩士
國立成功大學
化學工程學系
104
Integration of more than one renewable energy source for power generation is a research issue that has attracted considerable attention in recent years. Although the photovoltaic (PV) cell, the wind turbine (WT) and the fuel cell (FC) are all viable alternatives to the traditional steam and gas turbines, each is hampered by its own shortcomings. The PV cell alone is clearly not suitable for practical applications because of the intermittent nature of solar irradiation, while the power output of a WT unit is often unstable due to uncertain and uncontrollable weather conditions. The FC unit is fast to respond to demand changes but can be quite expensive. Finally, note that complementing a single power-generating unit with a large enough battery may not be an ideal solution either. This is due to the high investment cost of battery and its questionable durability in the long term. Thus, it is reasonable to expect that a properly configured hybrid system can provide uninterrupted off-grid power to meet the demand of a given community at any time. The goal of this study is to develop a systematic design methodology for configuring flexible hybrid power systems in standalone applications. For actual operation in a realistic environment, such a process must be fully operable despite random fluctuations in energy supplies and power demands. The authors therefore proposed a simulation based optimization strategy to compute two alternative measures, i.e., the dynamic and temporal flexibility indices, for quantitatively evaluating any given design. In order to demonstrate the usefulness of these criteria, the authors synthesized a large number of photovoltaic-fuel cell-wind turbine (PVFCWT) systems for the Annan Campus of National Cheng Kung University in Tainan, Taiwan, and then identified the best design(s) according to their costs and flexibility measures. In addition, the authors also developed a MATLAB/Simulink simulation code to validate these design decisions.

Maximum biological samples have some electrical property, which gave us a new dimension in the field of biomedical engineering. Now-a-days measurement of impedance by applying an electrical voltage/current, has a broader application for analyzing different biological samples. Most of the devices used for the measurement of bio-impedance are bulky and much costlier. This approach will help us to design a portable, standalone, multi frequency (10Hz – 10kHz) bio-impedance monitoring device with acceptable accuracy and resolution for in-vitro studies of biological cells and tissue.

In the recent years, increase in consumption of energy, instability of crude oil price and global climate change has forced researchers to focus more on renewable energy sources.Though there are different renewable energy sources available (such as photovoltaic and wind energy), they have some major limitations. The potential techniques which can provide renewable energy are fuel cell technology which is better than other renewable sources of energy. Solid oxide fuel cell (SOFC) is more efficient, environmental friendly renewable energy source. This dissertation focuses on load/grid connected fuel cell power system (FCPS) which can be used as a backup power source for household and commercial units. This backup power source will be efficient and will provide energy at an affordable per unit cost. Load/grid connected fuel cell power system mainly comprises of a fuel cell module, DCDC converter and DC-AC inverter. This thesis primarily focuses on solid oxide fuel cell (SOFC) modelling, digital control of DC-DC converter and DC-AC inverter. Extensive simulation results are validated by experimental results. Dynamic mathematical model of SOFC is developed to find out output voltage, efficiency, over potential loss and power density of fuel cell stack. The output voltage of fuel cell is fed to a DC-DC converter to step up the output voltage. Conventional Proportional-Integral (PI) controller and FPGA based PI controller is implemented and experimentally validated. The output voltage of DC-DC converter is fed to DC-AC inverter. Different pulse width modulation-voltage source inverter (PWM-VSI) control strategy (such as Hysteresis Current Controller (HCC), Adaptive-HCC, Fuzzy-HCC, Adaptive Fuzzy-HCC, Triangular Carrier Current Controller (TCCC) and Triangular Periodical Current Controller (TPCC)) for DC-AC inverter are investigated and validated through extensive simulations using MATLAB/SIMULINK. This work also focuses on number of fuel cells required for application in real time and remedy strategies when one or few fuel cells are malfunctioning. When the required numbers of fuel cells are not available, DC-DC converter is used to step up the output voltage of fuel cell. When there is a malfunction in fuel cell or shortage of hydrogen then a battery is used to provide backup power.

This master thesis deals with the design, programming, implementation and presentation of on-line business applications for IBM's On-Line Transaction Processing (OLTP) system called Customer Information Control System (CICS). According to the book “Designing and Programming CICS Applications” ([HOR00]) published by John Horswill we explain two out of many feasible procedures to present the functionality of CICS resp. CICS business applications.

abstract: While the implementation of both mild hybrid and start-stop technology is widespread as a factory option in newer vehicles, the adaptation of hybrid technology to older or unequipped vehicles has not been fully realized. As such, a straight forward hybrid conversion system that is easily adapted to different vehicles regardless of drivetrain configuration, has been developed and applied to a test vehicle for less than $2,000. System performance was recorded both before and after hybridization using real world drive cycle tracking charts. The vehicle established a fuel economy baseline of 22.93 mpg, and achieved 26.58 mpg after the conversion. This corresponds to a 15.92% increase in fuel economy. Accounting for initial system costs and annual fuel saving, this corresponds to a 6-year payback period. Based on these results, it can be concluded that an inexpensive aftermarket hybrid system is both feasible and effective at improving fuel economy.
Dissertation/Thesis
M.S.Tech Engineering 2012