This thesis introduces a new photovoltaic (PV) system architecture employing low voltage parallel-connected PV panels interfaced to a high voltage regulated DC bus of a three-phase grid-tied inverter. The concept provides several improvements over existing technologies in terms of cost, safety, reliability, and modularity. A novel resonant mode DC-DC boost converter topology is proposed to enable the PV modules to deliver power to the fixed DC bus. The topology offers high step-up capabilities and a nearly constant efficiency over a wide operating range. A reduced sensor maximum power point tracking (MPPT) controller is developed for the converter to maximize energy harvesting of the PV panels. The reduced sensor algorithm can be generally applied to the class of converters employing pulse frequency modulation control. A ZigBee wireless communication system is implemented to provide advanced control, monitoring and protection features. A testbench for a low cost 500 $W$ smart microconverter is designed and implemented, demonstrating the viability of the system architecture.

This diploma thesis is focused on complete construction of lab source which is controlled and powered by USB in personal computer. Different types of possible solutions are mentioned and finally one of them has been picked up as a best choice, which is developed in the rest of this thesis. Besides hardware construction there is also shown creation of main program for PIC18F14K50 microcontroller and main application that provides controlling of USB source via personal computer.

Introduction: Chronic diseases can be prevented and improved by regular physical activity and reduced sedentary time. An adequate leg strength and leg function in treatment and prevention of these disease is something to strive for. To the Lifestyle Reception at Karlskoga Hospital are patients with mild to moderate mental illness referred where a new method Self-measurement tests of leg strength is used, containing 30 seconds chair-stand test, squat, heel rise and maximal step-up test, aiming to simple training and indicating an objective measure of leg strength. Objective: To describe the group of patients referred to the Lifestyle Reception and investigate change of leg strength/leg function using Self-measurement tests, self-rated health and self-rated physical function following 12 weeks of intervention. Methods: A clinical intervention study of 29 patients referred to the Lifestyle Reception at Karlskoga Hospital between Nov 2017 and March 2018. They participated in an intervention consisting of group training twice a week for 12 weeks. A sign-in and a sign-out interview was carried out where data (tests and a questionnaire) of the study was collected. Result: 29 patients (24 women / 5 men) participated. The mean age was 39 years and the mean BMI was 31 (corresponding to obesity). All patients were on sick leave to some extent. The theoretical individual maximal step-up height (% -tMSH) improved from 65% to 75% (p <0.001). The patients could on average do 5.5 more 30s-chair-stand-test (p <0.001) and the proportion who managed to do squats without support increased from 57% to 90%. Significant improvements were seen for the self-rated health (p <0.001) and also for the HAD scale (anxiety p = 0.012; depression p = 0.04). However, the improvement of the self-rated physical function was not significant. Conclusion: Significant improvements in all four self-tests of leg strength / leg function could be measured after the intervention as well as a significant improvement of self-rated health. Self-measurement test of leg strength is considered to be a simple and useful test method in clinical practice.

The proliferation of distributed energy resources (DER)s has prompted interest in the expansion of DC power systems. The technological limitations that hinder the expansion of DC power systems are the absence of DC circuit breakers and high step-up/high step-down DC converters for interconnecting DC systems. This thesis presents a transformerless high step-up DC-DC converter intended for use as an interconnect between DC systems. The converter is required to operate at medium to high voltage (>1kV) and provide high voltage gain (>5). This work details the steady state operation and dynamic model of the proposed converter. The component ratings are identified and converter design limitations are investigated. A 100V:1kV/4kW prototype is produced to verify the analytic steady state model and measure efficiency. An experimental efficiency of 90% was achieved at a step-up ratio of 1:10, however efficiency at low power is limited due to the need to circulate power.

The proliferation of distributed energy resources (DER)s has prompted interest in the expansion of DC power systems. The technological limitations that hinder the expansion of DC power systems are the absence of DC circuit breakers and high step-up/high step-down DC converters for interconnecting DC systems. This thesis presents a transformerless high step-up DC-DC converter intended for use as an interconnect between DC systems. The converter is required to operate at medium to high voltage (>1kV) and provide high voltage gain (>5). This work details the steady state operation and dynamic model of the proposed converter. The component ratings are identified and converter design limitations are investigated. A 100V:1kV/4kW prototype is produced to verify the analytic steady state model and measure efficiency. An experimental efficiency of 90% was achieved at a step-up ratio of 1:10, however efficiency at low power is limited due to the need to circulate power.

In this thesis suggest the involvement of appropriate driver for mobile phone travel charger. The work is a treatise on the available accumulators, which can be used as a source for the proposed power converter.

Important considerations of a photovoltaic (PV) source are achieving a high voltage and drawing currents with very little ripple component from it. Furthermore, the output from such a source is variable depending on irradiation and temperature. In this research, literature review of prior methods employed to boost the output voltage of a PV source is examined and their limitations identified. This research then proposes a multi-phase tapped-coupled inductor boost DC-DC converter that can achieve high voltage boost ratios, without adversely compromising performance, to be used as an interface to a PV source. The proposed converter achieves minimal current and voltage ripple both at the input and output. The suitability of the proposed converter topology for variable input voltage and variable power operation is demonstrated in this dissertation. The proposed converter is also shown to have good performance at high power levels, making it very suitable for high power applications. Detailed analysis of the proposed converter is done. Advantages of the proposed converter are explained analytically and confirmed through simulations and experimentally. Regulation of the converter output voltage is also explained and implemented using a digital controller. The simulation and experimental results confirm that the proposed converter is suitable for high power as well as variable power, variable voltage applications where high voltage boost ratios are required. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Electrical, Electronic and Computer Engineering / Unrestricted

Deaf and Hard of Hearing (D/HH) students often do not graduate with their same age peers, continue on to college, have satisfying social and emotional relationships, or achieve gainful employment as adults due to their delays in language and communication skills (Antia, Stinson, & Gaustad, 2002; Siegel, 2002a). The purpose of this study is to determine and align the Kern County Superintendent of School's Deaf Education Program with the research-based elements of a quality D/HH program and to explore the instructional program of "Step Up to Writing" as a viable curricular tool for improving English and language skills for the D/HH population in the Kern County Superintendent of Schools' Deaf Education Program. The statistical evidence generated by the t -Test: Two Sample Assuming Unequal Variances, supported "Step Up to Writing" as an option for language skills development and curricular changes within the KCSOS Deaf Education Program. The continued collection of data through a longitudinal study of fourth- through eighth-grade D/HH students in the KCSOS Deaf program will develop certainty of these findings.

The energy produced by the flow of water is known as hydropower. It is an easily accessible and available source of energy in large quantity in the form of, rivers, lakes, streams and runoffs around the world. Hydropower is dependent upon hydrological cycle hence; this beneficial characteristic of hydropower makes it a renewable source of energy. Hydropower is free from poisonous emission; therefore, it is considered as a safer and pollution free source of energy. It is usually used to develop electricity from generators. These generators are connected to the hydro turbines by means of shaft. The electricity produced from hydropower is stable and steady because of its higher capacity, thus it can be a suitable source to work as base-load and used to balance the power fluctuations caused by varying loads. The hydropower can also be accommodated with different sources such as solar and wind system. This way of power sharing needs quick regulation as the deviation in the power grid changes rapidly. To fulfil this power demand with higher stability prompted to the development of modern turbines with more efficient, reliable and robust design.   To achieve the above target, it is of prime importance to improve efficiency of hydro turbine. Nevertheless, many methods are in practice for improvement for efficiency of the turbine; though one of the prime elements which influence the turbine efficiency is surface roughness. The effect of surface roughness differs for different turbine components like stay vanes, guide vanes, runner, draft tube and spiral casing.   The main purpose of this thesis is to examine the effect of surface roughness for hydro turbine step-up efficiency. It is based on reduced scale model to prototype conversion method. For this purpose, IEC_62097 has provided an excel sheet as an attachment for calculation. There has been always a need to perform model test, since performing test on the prototype itself is very accurate, and calculations too, do not yield reliable results. Therefore, the model to prototype conversion method is considered a better solution.   A sensitivity analysis is conducted on a Kaplan turbine situated at the Granfors power station located along the Skellefteå river about 30 km from the city of Skellefteå. The results obtained after applying the latest step-up expressions are described and presented. These outcomes have shown significant positive impact on the hydro turbine efficiency improvement, which are presented in graphs.   The most significant variations of step-up efficiency against surface roughness were observed in the runner part of the turbine. This specific characteristic makes it evident that more focus and test should be conducted on this part to improve efficiency.

Mikronät är ett självförsörjande elnät och används bland annat då elektriskaprodukter kräver en AC-spänning men inte har tillgång till huvudnätet. Målet idetta projekt är att dimensionera och analysera de olika delarna som ett mikronätbestår av, för att sedan konstruera och testa ifall den uppfyller kraven utifrånvissa specifikationer.Metoderna som används för att dimensionera och analysera mikronätet bestårfrämst av beräkningar och simuleringar samt konstruktion av enstaka kretsar.Mikronätet består av en AC-drive, ett lågpassfilter och trefastransformator.Mikronätet konstrueras med en varierbar frekvens mellan 45 och 65 Hz, samtomvandling av 540 VDC till 400 VAC.