The reliability and stability of the Matrix Converter has improved during the last years due to the enhanced control algorithms. The traditional direct transfer function control mode has been replaced by more complex – digitally implemented control methodologies. These methodologies allow for real time calculation of the optimal switching interval of each individual switch of the matrix converter. These new switching algorithms allow optimal performances, ensuring sinusoidal outputs at any desired power factor. This paper will first revise the underlying theory of matrix converters, then review the various control limitations and finally review the current control algorithms.

The present work describes the development of a control scheme for boost-type switch-mode rectifiers. While controllers for this circuit commonly use a shunt resistor or a magnetic field sensor to measure the instantaneous input or inductor current, here the inductor current is computed from the measured inductor voltage. This calculation requires knowledge of the physical properties of the inductor, most importantly its inductance, which are prone to change with operating conditions of the converter and throughout the lifetime of the inductor. The parameters of the inductor model are estimated during normal converter operation, and the inductor model is adapted accordingly. Simulation and experimental results confirm the effectiveness of the devised scheme in reducing the distortion of the input current. / Graduate / 0544 / aengel@uvic.ca

The present work describes the development of a control scheme for boost-type switch-mode rectifiers. While controllers for this circuit commonly use a shunt resistor or a magnetic field sensor to measure the instantaneous input or inductor current, here the inductor current is computed from the measured inductor voltage. This calculation requires knowledge of the physical properties of the inductor, most importantly its inductance, which are prone to change with operating conditions of the converter and throughout the lifetime of the inductor. The parameters of the inductor model are estimated during normal converter operation, and the inductor model is adapted accordingly. Simulation and experimental results confirm the effectiveness of the devised scheme in reducing the distortion of the input current. / Graduate / 0544 / aengel@uvic.ca

This research project is to investigate the control of the wave power device, known as the 'Manchester Bobber' (MB), and to optimise the output by tuning its drive-train parameters. The work starts with building a numerical model and developing a control strategy. The work sequentially progressed to obtain the experimental results from a physical model in order to make a comparison with the numerical results.An assessment of three different control strategies is made. These are reactive control, latching control, and two methods of torque control based on either time-averaged velocity or a pre-defined static characteristic. It is found that reactive control and latching control are not feasibly applicable to the MB wave energy device due to the configuration of the device. It is also found that the historical data approach is able to reduce the problem of high rate of change of electromagnetic torque but with a subdued output performance. A method based on a static characteristic, similar to the approach used to control wind turbines, is shown to significantly enhance the power output performance although this imposes a high rate of change of electromagnetic torque.The findings of the numerical simulation are supported by experimental measurements obtained in the wave tank. The parameters used in the numerical model (i.e. hydrodynamic damping co-efficient, added mass co-efficient and Froude-Krylov force co-efficient) are calibrated by comparing with the experimental measurements.Two drive-train parameters, the number of generator poles and flywheel inertia, are optimised in order to both maximise output power and minimise rate of change of electromagnetic torque. The proportional gain and integral time constant of the PI controller are tuned to further reduce the maximum rate of change of electromagnetic torque, so that the device is protected from the high mechanical stress. It is found that the annual energy production from the device at a range of locations is found to be almost linear with the annual average significant wave height of each site.

The aim of this thesis is to design a step-up DC/AC converter, an inverter from 12 V to 120 Vrms, with a sinus output signal. The converter should deliver a continuous performance of 300 W and a double peak power output of 600 W. The supposed usage of this inverter would be as a back-up power source for the circulatory pump of the central heating in the case of power outage. The inverter is consisting of a T-type power section.

Wide bandgap devices are the future of this dynamically changing technological world. Considering Gallium Nitride (GaN) and Silicon Carbide (SiC), GaN has exceptional characteristics that will likely allow it to proliferate greatly in the area of low-and-mid-power power electronic converters. One of the current challenges in this context to completely utilize GaN are the reliability issues, especially false turn-on events, which is a main focus of this thesis. False turn-on due to its momentary short circuit capability deteriorates the converter performance. Furthermore, simple and accurate modeling of GaN device losses is critical to help electronic designers optimize converter designs. This thesis focuses on three contributions to help reduce false turn-on events and improve GaN modeling efforts. First, this work uniquely investigates the optimal pulse-width-modulation (PWM) scheme to balance efficiency and false turn-on. The experimental results lead to a recommendation to use a larger negative bias than is currently recommended by device manufacturers. Secondly, the work proposes a new simplified switching loss model with high accuracy that can be used with different gate drive circuits (including negative gate bias voltages) to make it more useful for power electronics design engineers as a tool. And thirdly, since the main contributor to false turn-on events are the parasitic inductances in the switch and on the PCB, this work proposes a new parasitic inductance measurement methodology which can be implemented using only simple laboratory instruments. / Thesis / Doctor of Engineering (DEng) / Wide bandgap devices are the future of this dynamically changing technological world. Considering Gallium Nitride (GaN) and Silicon Carbide (SiC), GaN has exceptional characteristics that will likely allow it to proliferate greatly in the area of low-and-mid-power power electronic converters. One of the current challenges in this context to completely utilize GaN are the reliability issues, especially false turn-on events, which is a main focus of this thesis. False turn-on due to its momentary short circuit capability deteriorates the converter performance. Furthermore, simple and accurate modeling of GaN device losses is critical to help electronic designers optimize converter designs. This thesis focuses on three contributions to help reduce false turn-on events and improve GaN modeling efforts. First, this work uniquely investigates the optimal pulse-width-modulation (PWM) scheme to balance efficiency and false turn-on. The experimental results lead to a recommendation to use a larger negative bias than is currently recommended by device manufacturers. Secondly, the work proposes a new simplified switching loss model with high accuracy that can be used with different gate drive circuits (including negative gate bias voltages) to make it more useful for power electronics design engineers as a tool. And thirdly, since the main contributor to false turn-on events are the parasitic inductances in the switch and on the PCB, this work proposes a new parasitic inductance measurement methodology which can be implemented using only simple laboratory instruments.

Very low voltage, high current output requirement have necessitated improvements in power supply's density and efficiency. Existing power conversion techniques cannot meet very stringent size and efficiency requirements. By applying the proposed magnetic integration procedure, new integrated magnetic circuits featuring low loss, simple structure, and ripple cancellation technique are then developed to overcome the limitations of prior art. Both cores and windings are integrated. Consequently, the power loss and the size of the integrated magnetic device are greatly reduced. Detailed analysis and design considerations of the proposed circuits are presented. As a result of applying the proposed technique, very high density, high efficiency, low voltage, high current power modules were developed. A typical example features an isolated 3.3V/30A power module with a power density of 130W/in3 and an efficiency of 90% at 500 KHz switching frequency. / Ph. D.

Photovoltaic (PV) systems are renewable, DC sources which provide non-linear output power with respect to PV panel operating voltage or current. The majority of PV sources yield poor conversion efficiencies between available solar radiation and electrical output. Additionally, they are expensive compared to other conventional power sources. Power electronic converters are capable of harvesting the most energy from these resources due to their configurability and high-efficiency. These converters form a power conditioning stage which allows for numerous control methods and energy management options. Traditional systems group PV sources into arrays in order to increase operating voltage and power to levels where it is practical to connect them to the utility grid. Grid-tied PV has the potential to increase the acceptance of PV energy by reducing end-user complexity — there are no batteries to manage and additional wiring can be kept to a minimum. However, these arrays of PV panels have significant drawbacks when they are subjected to non-ideal conditions. If a single panel is shaded, or covered in some way, then it will have greatly reduced output current. As a result, any other panel which is connected in series with the affected panel is also subject to the same output current reduction. This series grouping of panels may then indirectly affect other series-sets of panels which are connected in parallel to it by tricking the power electronics unit into operating at a point which is not the true maximum-power-point (MPP). By connecting a single PV panel to a single DC-DC converter, these array-effects can be avoided. Reliability and power output of the whole system should increase at the expense of additional hardware. The outputs of several PV-connected DC-DC converters can be connected either in series or in parallel. If they are connected in parallel, the converters must be able to boost the PV panel voltage up to a level greater than the desired utility-grid voltage. This thesis focuses on the design and control of a high-boost-ratio DC-DC converter suitable for use in a parallel-connected, grid-tied PV system. It demonstrates the feasibility of boost-ratios of up to 10 times while still achieving high efficiency. The design avoids the use of electrolytic capacitors in favor of smaller ceramic capacitors and a few large film-capacitors. A simplified model is proposed which is still suitable for use in the design of high-bandwidth control loops. Testing is done with a PV source showing preliminary results with a maximum-power-point-tracker (MPPT) which achieves very good steady-state performance. / Master of Science

The objective of this thesis is to design a multilevel converter circuit for driving slotless tubular linear generators (STLG) on retrieving renewable energy application. With the changing speeds and reciprocating directions of the movers, the electric energy generated from the STLG will exhibit large fluctuations and is hard to be used directly. Based on machine modeling and mover reference frame projection, a converter circuit and a data acquisition (DAQ)-based drive control scheme have been developed. From the experimental results, the control scheme implemented on the converter circuit can provide acceptable multilevel dc outputs at various operating modes.

This thesis presents the design of a step-up DC-DC converter with on-chip coupled inductors. Circuit theory of DC-DC converters in general is presented, after which a mathematical model of a step up converter is developed. A circuit implementation optimized from results of the mathematical model follows. For a completely integrated step-up converter, the inductor size is reduced by increasing the frequency of operation and using a circuit topology that employs coupled inductors. Spiral inductors are also studied to achieve maximum quality factor and inductance. A fast PWM control system is used to regulate the high-frequency converter. The fabrication was done in standard TSMC 0.18-$\mu$m digital CMOS process for four circuits, including one with a conventional topology and the others with a coupled inductor topology with varying inductor geometries. Measurement results from a fabricated prototype have been presented, demonstrating the functionality of the four circuits with coupled inductors on the fabricated chip and the improvement of the coupled solution over the conventional design. It is demonstrated that the circuits with coupled inductors have a significant improvement in performance based on conversion ratio and efficiency. Finally, the design process is evaluated and recommendations are made for future work. Furthermore, a new self-oscillating and robust control system is proposed that enables simpler and more efficient regulation for high-frequency converters such as one developed for this thesis.