The thesis aims at investigating an active power factor correction circuit. In boost power converter, we ser up average large signal model with Matlab and derive control¡Voutput function for pole assignment of control loop with ac small signal model. In controller, control circuit of conventional active power factor correction and modified PI control circuit are adopted, separately. Through simulation results and experimental responses of hardware circuit show that under variation of load or alternating input voltage, modified PI control circuit has better regulating capacity than that of conventional control circuit .

Analysis and experimental results on a polarization independent electrooptic matched filter (EMF) with a center wavelength of 1.53 μm are reported. The EMF utilizes electrooptic phase-matched TE↔TM conversion in a Ti-diffused waveguide on a LiNbO3 substrate. The operation of the EMF to select an optical frequency channel is controlled by applying independent voltages to interdigital electrode sets cascaded along a single mode waveguide. The device is inherently polarization independent and has the potential for submicrosecond tuning. The number of selectable channels N is related to the number of electrode sets P by the formula / 2 1 N P = + . A matrix analysis is used to determine the TE↔TM conversion efficiency for the case that 8 P = and 5 N = . A driving circuit for the EMF was implemented using a digital-to-analog converter (DAC) array controlled from a personal computer (PC). Transmittance spectra of a filter produced in a LiNbO3 substrate are presented. A raised cosine weighting function applied along the 3.8 cm length of an EMF provides a sidelobe suppression level better than –17 dB with a 1.0 nm 3-dB bandwidth.

This thesis proposes a novel structure to realize the monolithic integra-tion of optical spot-size converter (SSC) and high-speed electroabsorption modulator (EAM). The SSC is based on a scheme of coupled asymmetric waveguide fabricated by tapered undercut waveguide. Using a selectively undercut-etching-active-region (UEAR), the laterally tapered undercut ac-tive waveguide (LTUAWG) can be processed from a wide tapered ridge waveguide using in situ control to avoid submicron photolithography as well as complex processing, such as selective area growth, selective area etching and re-growth. By monolithically integrating EAM and SSC, the EAM waveguide width can be beneficial from scaling down the waveguide size for enhancing the EAM bandwidth, while the optical coupling loss from single mode fiber can still be kept low. In this finished SSC-integrated EAM, a 1-dB misalignment tolerance of ¡Ó2.9£gm (horizontal) and ¡Ó2.2 £gm (vertical) is obtained from SSC side, which is better than the results, ¡Ó1.9£gm (horizontal) and ¡Ó1.6£gm (vertical), from EAM side. The measured far-field angles for SSC and EAM are 6.0 (horizontal) ∗ 9.3 (vertical) and 11 (horizontal) ∗ 20 (vertical) respectively. As low as mode transfer loss of -1.6 dB is obtained in such SSC. All the simulation results are quite fitted with the experiment results, realizing the function of SSC by LTUAWG. The fabricated EAM waveguide width is 2.5 £gm, leading to over 40 GHz of -3-dB electrical-to-optical (EO) response. The high efficient SSC integrated with high-speed EAM suggests that the LTUAWG technique can have potential for applications in high-speed optoelectronic fields.

With rapid progress in microelectronics technology, high-performance Integrated Circuits (ICs) bring huge challenge to design the power supplies. Fast loop response is required to handle the high transient current of devices. Power solution size is demanded to reduce due to the size reduction of integrated circuits. The best way to meet these harsh requirements is to increase switching frequency of power supplies. Along with the benefits of increasing switching frequency, the power supplies will suffer from high switching loss and high gate charge loss as these losses are frequency dependant losses. This thesis investigates the best topology to minimize the switching loss. The Series-Parallel Resonant Converter (SPRC) with current-doubler is mainly analyzed for high frequency low voltage high current application. The advantages and disadvantages of SPRC with current-doubler are presented. A new adaptive synchronous rectifiers timing control scheme is also proposed. The proposed timing control scheme demonstrates it can minimize body diode conduction loss of synchronous rectifiers and therefore improve the efficiency of the converter. This thesis also proposes two families of new resonant gate drive circuits. The circuits recover a portion of gate drive energy that is total lost in conventional gate drive circuit. In addition to reducing gate charge loss, it also reduces the switching losses of the power switches. Detail operation principle, loss analysis and design guideline of the proposed drive circuits are provided. Simulation and experimental results are also presented. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2008-01-29 22:37:09.812

In modern power system, the energy conversion includes a large number of the energy processors, and demands high quality, small, lightweight, reliable and efficient power procedures. The existing linear power regulators can only handle low power levels and demonstrate a low efficiency in the power processing. Pulse-width modulated (PWM) converters demonstrate high turn on and turn off losses, and increase in the electromagnetic interference (EMI). Resonant power conversion becomes more suitable in the renewable energy and energy harvesting applications. Since the resonant conversion requires operating in high frequency, the electrical components such as transformers, filter inductors and capacitors become much smaller and lighter. This can result in reducing size and cost. In addition, use of soft switching technique in the resonant conversion reduced the switching losses and EMI level. In this research project, a DC/DC resonant converter has been designed and modelled in PSCAD/EMTDC. The functionality of DC/DC resonant converter is validated in a hardware implementation of the small scale DC system.

In modern power system, the energy conversion includes a large number of the energy processors, and demands high quality, small, lightweight, reliable and efficient power procedures. The existing linear power regulators can only handle low power levels and demonstrate a low efficiency in the power processing. Pulse-width modulated (PWM) converters demonstrate high turn on and turn off losses, and increase in the electromagnetic interference (EMI). Resonant power conversion becomes more suitable in the renewable energy and energy harvesting applications. Since the resonant conversion requires operating in high frequency, the electrical components such as transformers, filter inductors and capacitors become much smaller and lighter. This can result in reducing size and cost. In addition, use of soft switching technique in the resonant conversion reduced the switching losses and EMI level. In this research project, a DC/DC resonant converter has been designed and modelled in PSCAD/EMTDC. The functionality of DC/DC resonant converter is validated in a hardware implementation of the small scale DC system.

abstract: Synchronous buck converters have become the obvious choice of design for high efficiency voltage down-conversion applications and find wide scale usage in today's IC industry. The use of digital control in synchronous buck converters is becoming increasingly popular because of its associated advantages over traditional analog counterparts in terms of design flexibility, reduced use of off-chip components, and better programmability to enable advanced controls. They also demonstrate better immunity to noise, enhances tolerance to the process, voltage and temperature (PVT) variations, low chip area and as a result low cost. It enables processing in digital domain requiring a need of analog-digital interfacing circuit viz. Analog to Digital Converter (ADC) and Digital to Analog Converter (DAC). A Digital to Pulse Width Modulator (DPWM) acts as time domain DAC required in the control loop to modulate the ON time of the Power-MOSFETs. The accuracy and efficiency of the DPWM creates the upper limit to the steady state voltage ripple of the DC - DC converter and efficiency in low load conditions. This thesis discusses the prevalent architectures for DPWM in switched mode DC - DC converters. The design of a Hybrid DPWM is presented. The DPWM is 9-bit accurate and is targeted for a Synchronous Buck Converter with a switching frequency of 1.0 MHz. The design supports low power mode(s) for the buck converter in the Pulse Frequency Modulation (PFM) mode as well as other fail-safe features. The design implementation is digital centric making it robust across PVT variations and portable to lower technology nodes. Key target of the design is to reduce design time. The design is tested across large Process (+/- 3σ), Voltage (1.8V +/- 10%) and Temperature (-55.0 °C to 125 °C) and is in the process of tape-out. / Dissertation/Thesis / M.S. Electrical Engineering 2013

In recent years, the loads needing electrical power in military aircraft and civil jet keep increasing, this put huge pressure on the electrical power system (EPS). As EPS becomes more powerful and complex, its reliability and maintenance becomes difficult problems to designers, manufacturers and customers. To improve the mission reliability and reduce life cycle cost, the EPS needs health management. This thesis developed a set of generic health management methods for the EPS, which can monitor system status; diagnose faults/failures in component level correctly and predict impending faults/failures exactly and predict remaining useful life of critical components precisely. The writer compared a few diagnostic and prognostic approaches in detail, and then found suitable ones for EPS. Then the major components and key parameters needed to be monitored are obtained, after function hazard analysis and failure modes effects analysis of EPS. A diagnostic process is applied to EPS using Dynamic Case-based Reasoning approach, whilst hybrid prognostic methods are suggested to the system. After that, Diagnostic, Prognostic and Health Management architecture of EPS is built up in system level based on diagnostic and prognostic process. Finally, qualitative evaluations of DPHM explain given. This research is an extension of group design project (GDP) work, the GDP report is arranged in the Appendix A.

In the field of ocean wave energy converters (WECs), active areas of research are on a priori or in situ methods for power production estimates and on control system design. Linear potential flow theory modelling techniques often underpin these studies; however, such models rely upon small wave and body motion amplitude assumptions and therefore cannot be applied to all wave conditions. Nonlinear extensions can be applied to the fluid loads upon the structure to extend the range of wave conditions for which these models can provide accurate predictions. However, careful consideration of the thresholds of wave height and periods to which these models can be applied is still required. Experimental modelling in wave tank facilities can be used for this purpose by comparing experimental observations to numerical predictions using the experimental wave field as an input. This study establishes a recommended time domain numerical modeling approach for power production assessments of oscillating wave surge converters (OWSCs), a class of WEC designed to operate in shallow and intermediate water depths. Three candidate models were developed based on nonlinear numerical modelling techniques in literature, each with varying levels of complexity. Numerical predictions provided by each model were found to be very similar for small wave amplitudes, but divergence between the models was observed as wave height increased. Experimental data collected with a scale model OWSC for a variety of wave conditions was used to evaluate the accuracy of the candidate models. These experiments were conducted in a small-scale wave flume at the University of Victoria. A challenge with this experimental work was managing wave reflections from the boundaries of the tank, which were significant and impacted the dynamics of the scale model OWSC. To resolve this challenge, a modified reflection algorithm based upon the Mansard and Funke method was created to identify the incident and reflected wave amplitudes while the OWSC model is in the tank. Both incident and reflected wave amplitudes are then input to the candidate models to compare numerical predictions with experimental observations. The candidate models agreed reasonably well with the experimental data, and demonstrated the utility of the modified wave reflection algorithm for future experiments. However, the maximum wave height generated in the wave tank was found to be limited by the stroke length of the wavemaker. As a result, no significant divergence of the candidate model predictions from the experimental data could be observed for the limited range of wave conditions, and therefore a recommended model could not be selected based solely on the experimental/numerical model comparisons. Preliminary assessments of the annual power production (APP) for the OWSC were obtained for a potential deployment site on the west coast of Vancouver Island. Optimal power take-off (PTO) settings for the candidate models were identified using a least-squares optimization to maximize power production for a given set of wave conditions. The power production of the OWSC at full scale was then simulated for each bin of a wave histogram representing one year of sea states at the deployment site. Of the three candidate models, APP estimates were only obtained for Model 1, which has the lowest computational requirements, and Model 3, which implements the most accurate algorithm for computing the fluid loads upon the OWSC device. Model 2 was not considered as it provides neither advantages of Models 1 and 3. The APP estimates from Models 1 and 3 were 337 and 361 MWh per year. For future power production assessments, Model 3 is recommended due to its more accurate model of the fluid loads upon the OWSC. However, if the high computational requirements of Model 3 are problematic, then Model 1 can be used to obtain a slightly conservative estimate of APP with a much lower computational effort. / Graduate

This diploma thesis deals with design and comparison of selected DC/DC converters, where the better of them is practically realized. The first part of the diploma thesis is focused on the general analysis of DC/DC power converters. The following part is theoretical analysis focused on the first selected topology – step-up converter. The second analysed topology is forward converter with full bridge on the primary side. The theoretical analysis also includes a description of synchronous rectifier, the differences between hard and soft switching, and the types of secondary rectifiers. Another part specializes in the detailed calculation of main components of selected converters and their subsequent power dimensioning. Both designed topologies are compared according to the required aspects. The selected better topology is supplemented by the design of control circuits and an auxiliary power supply. Practical realization of converter and commissioning follows. The diploma thesis ends with verification measurements on the realized converter and their subsequent analysis.