Ultra wideband communication link

Ultra-wideband communication (UWB) has been a topic of extensive research in recent years especially for its short-range communication and indoor applications. The preliminary objective of the project was to develop a description and understanding of the basic components of the communication link at microwave frequencies in order to achieve the primary objective of establishing a communication setup at a bandwidth of 2.5 GHz for testing Ultra Wideband (UWB) antennas. This was achieved with the aid of commercially available optical system which was modified for the purpose. Beginning with the generation of baseband narrow pulses with energy spanning over a broad frequency range, through multiplexing of different parallel channels carrying these pulses into a single stream, to finally capturing the received signal to understand the effect of the communication link formed; all provided basis for identifying the issues and possible solutions to establishing a reliable communication link at UWB frequency

Design and Control of Power Converters for High Power-Quality Interface with Utility and Aviation Grids

Power electronics as a subject integrating power devices, electric and electronic circuits, control, and thermal and mechanic design, requires not only knowledge and engineering insight for each subarea, but also understanding of interface issues when incorporating these different areas into high performance converter design.Addressing these fundamental questions, the dissertation studies design and control issues in three types of power converters applied in low-frequency high-power transmission, medium-frequency converter emulated grid, and high-frequency high-density aviation grid, respectively, with the focus on discovering, understanding, and mitigating interface issues to improve power quality and converter performance, and to reduce the noise emission.For hybrid ac/dc power transmission,• Analyze the interface transformer saturation issue between ac and dc power flow under line unbalances.• Proposed both passive transformer design and active hybrid-line-impedance-conditioner to suppress this issue.For transmission line emulator,• Propose general transmission line emulation schemes with extension capability.• Analyze and actively suppress the effects of sensing/sampling bias and PWM ripple on emulation considering interfaced grid impedance.• Analyze the stability issue caused by interaction of the emulator and its interfaced impedance. A criterion that determines the stability and impedance boundary of the emulator is proposed.For aircraft battery charger,• Investigate architectures for dual-input and dual-output battery charger, and a three-level integrated topology using GaN devices is proposed to achieve high density.• Identify and analyze the mechanisms and impacts of high switching frequency, di/dt, dv/dt on sensing and power quality control; mitigate solutions are proposed.• Model and compensate the distortion due to charging transition of device junction capacitances in three-level converters.• Find the previously overlooked device junction capacitance of the nonactive devices in three-level converters, and analyze the impacts on switching loss, device stress, and current distortion. A loss calculation method is proposed using the data from the conventional double pulse tester.• Establish fundamental knowledge on performance degradation of EMI filters. The impacts and mechanisms of both inductive and capacitive coupling on different filter structures are understood. Characterization methodology including measuring, modeling, and prediction of filter insertion loss is proposed. Mitigation solutions are proposed to reduce inter-component coupling and self-parasitics

OPTICAL TRANSCEIVER INTERFACE FOR DATA TRANSMISSION OVER OPTICAL LINK

This final year Project Part 2 is designed for all fmal year students and it is compulsory to be taken. It is designed such so that all the final year students will be trained to produce practical solutions besides having a hands on feel before leaving to the industry. This report presents the intention of creating an optical transceiver interface for data transmission over an optical link. The project is targeted to be completed by the end of the course that is by developing the modulator I demodulator which converts the electrical data from PC to optical data as well as retrieve the optical data back to electrical data before it can be read by the other client PC at the receiving end. These days, the utilization of data via the optical transceiver is very limited and in the recent years, news about communication networks technology always seems to involve some pronouncement on the urgent need for more bandwidth. Thus this is part of creating a device to overcome all these problems. This project covers two parts that is research and design. Fourteen weeks have been allocated to complete the design of this project. The project has been researched about and certain components have been purchased to complete it. Besides that, this project also allows us to design on our own and implement as we want it to be

Power Converters in Power Electronics

In recent years, power converters have played an important role in power electronics technology for different applications, such as renewable energy systems, electric vehicles, pulsed power generation, and biomedical sciences. Power converters, in the realm of power electronics, are becoming essential for generating electrical power energy in various ways. This Special Issue focuses on the development of novel power converter topologies in power electronics. The topics of interest include, but are not limited to: Z-source converters; multilevel power converter topologies; switched-capacitor-based power converters; power converters for battery management systems; power converters in wireless power transfer techniques; the reliability of power conversion systems; and modulation techniques for advanced power converters

Power conversion for a modular lightweight direct-drive wind turbine generator

A power conversion system for a modular lightweight direct-drive wind turbine generator has been proposed, based on a modular cascaded multilevel voltage-source inverter. Each module of the inverter is connected to two generator coils, which eliminates the problem of DC-link voltage balancing found in multilevel inverters with a large number of levels.The slotless design of the generator, and modular inverter, means that a high output voltage can be achieved from the inverter, while using standard components in the modules. Analysis of the high voltage issues shows that isolating the modules to a high voltage is easily possible, but insulating the generator coils could result in a signicant increase in the airgap size, reducing the generator effciency. A boost rectier input to the modules was calculated to have the highest electrical effciency of all the rectier systems tested, as well as the highest annual power extraction, while having a competitive cost. A rectier control system, based on estimating the generator EMF from the coil current and drawing a sinusoidal current in phase with the EMF, was developed. The control system can mitigate the problem of airgap eccentricity, likely to be present in a lightweight generator. A laboratory test rig was developed, based on two 2.5kW generators, with 12 coils each. A single phase of the inverter, with 12 power modules, was implemented, with each module featuring it's own microcontroller. The system is able to produce a good quality AC voltage waveform, and is able to tolerate the fault of a single module during operation. A decentralised inverter control system was developed, based on all modules estimating the grid voltage position and synchronising their estimates. Distributed output current limiting was also implemented, and the system is capable of riding through grid faults

Efficiency enhancements to a linear AC voltage regulator: Multi-transformer and multi-winding designs

Utility companies are expected to distribute electricity that conforms with international or national standards related to RMS voltage fluctuations. However, RMS voltage variations sometimes exceed acceptable limits and this demands consumer-end voltage regulators. Commercial AC regulators such as (i) servo-driven variacs, (ii) ferro-resonant, (iii) transformer tap changers, (iv) solid-state types, have their own advantages and limitations. Common issues include (a) slow response time, (b) low efficiency and flattened-output waveform, (c) tap dancing and related switching issues, (d) harmonics and RFI/EMI at the output, respectively. The linear RMS AC voltage regulator is a patented technique developed in the late 1980s to address most of the above issues. It is a solid-state, single-phase system that employs a line-frequency transformer with its primary connected in series with an AC-operable variable impedance based on power transistors. The secondary winding is placed in series with the varying AC input, so that the induced secondary voltage acts as a correction signal to maintain the output at the desired value. A feedback circuit varies the effective impedance of the transistor-array, thus, manipulate the induced secondary voltage to regulate the output. This is a linear technique that allows seamless transition between boost to buck mode. However, this comes at the cost of lower efficiency at high AC input, particularly when line voltage goes beyond the nominal value. Commercial partner, Thor Technologies, Australia, wanted the team to modify their servo-driven AC regulator (PS-10), based on our technique with efficiency in the range of 90-95% and the response time improved by about 10 times. During development of a commercial prototype, the author implemented two potential solutions: (i) multi-transformer and (ii) multi-winding transformer based techniques to overcome the reduced efficiency during buck-mode operation, an issue inherent to the basic linear AC technique. Thesis was aimed at improving the power stage of the linear technique while maintaining the already developed analog control loop with true RMS regulation capability. thesis presents two alternative transformer solutions to reach efficiencies in the range of $90-95\%$ on a laboratory prototype of 500VA. Experimental results were validated by constructing a theoretical model for the two transformer configurations, supported by an equivalent circuit analysis using MATLAB and LTSpice software

Modelling, simulation and control of photovoltaic converter systems

The thesis follows the development of an advanced solar photovoltaic power conversion system from first principles. It is divided into five parts. The first section shows the development of a circuit-based simulation model of a photovoltaic (PV) cell within the 'SABER' simulator environment. Although simulation models for photovoltaic cells are available these are usually application specific, mathematically intensive and not suited to the development of power electronics. The model derived within the thesis is a circuit-based model that makes use of a series of current/voltage data sets taken from an actual cell in order to define the relationships between the cell double-exponential model parameters and the environmental parameters of temperature and irradiance. Resulting expressions define a 'black box' model, and the power electronics designer may simply specify values of temperature and irradiance to the model, and the simulated electrical connections to the cell provide the appropriate I/V characteristic. The second section deals with the development of a simulation model of an advanced PVaware DC-DC converter system. This differs from the conventional in that by using an embedded maximum power tracking system within a conventional linear feedback control arrangement it addresses the problem of loads which may not require the level of power available at the maximum power point, but is also able to drive loads which consistently require a maximum power feed such as a grid-coupled inverter. The third section details a low-power implementation of the above system in hardware. This shows the viability of the new, fast embedded maximum power tracking system and also the advantages of the system in terms of speed and response time over conventional systems. The fourth section builds upon the simulation model developed in the second section by adding an inverter allowing AC loads (including a utility) to be driven. The complete system is simulated and a set of results obtained showing that the system is a usable one. The final section describes the construction and analysis of a complete system in hardware (c. 500W) and identifies the suitability of the system to appropriate applications

Measurements, Models, Systems and Design

531 s.