College of Engineering

Theses and dissertations submitted to the College of Engineering

Items in this Collection

The integration of wind energy conversion system (WECS) to existing diesel generator system is an immediate step for developing a highly sustainable practical system that offers minimal pollution. It was already established that maximizing extracted power from the wind reduces the amount of energy needed from the diesel generator. However, integrating WECS tends to increase the variability of operation of the diesel system due to the intermittent nature of the wind. In addition, low load operation times also increase making the diesel engine operate inefficiently for a longer hours.

In this study, a hybrid wind-diesel system is devised so that simultaneous optimal power extraction from wind and fuel source can be obtained. A maximum power point tracker was designed to extract power from the wind turbine optimally and the diesel engine was made to operate at variable speed for least fuel consumption. A comparison is made between the performance of a conventional fixed speed diesel engine hybrid system and the devised system.

Distribution system engineers can optimize distribution system reliability through the optimal placement of reclosers, fuse-blow fuses, fuse-save fuses, switches, and tie lines. Currently, there is no objective function formulation that is explicitly expressed as a function of the locations of these devices. This situation presents a barrier to the application of mathematical methods for reliability optimization.

This thesis presents such a formulation: a binary System Average Interruption Duration Index (SAIDI) formulation explicitly expressed as a function of the placement of reclosers, fuse-blow fuses, fuse-save fuses, switches, and tie lines in a radially operated distribution system. This formulation can be used (1) for predictive reliability assessment as an alternative assessment methodology and (2) for reliability optimization as an objective function that is compatible with deterministic, heuristic, and stochastic optimization approaches. This formulation can be easily modified to model the Average System Interruption Duration Index (ASIDI) and the Expected Energy Not Supplied (EENS).

We were able to validate this formulation using published results and an established predictive reliability assessment method. Furthermore, we demonstrated that this formulation can be used in finding the global optimal SAIDI of distribution systems.

The Tidal In-Stream Energy (TISE) industry is growing at a relatively fast pace. Crucial and augmentative to TISE’s development is the existence of an appropriate ecosystem of methodologies, tools, and protocols for assessment and planning of resources, technology / devices, environment, economics, installations, social impact, and policy. Current TISE evaluation rarely combine site suitability, resource assessment, and technology / device matching; and hardly can any of these tools be described as rapid, labelled as integrated nor deemed as flexible.

This work develops, studies, and proposes: (1) a simpler TISE metric for resource estimation, (2) a novel Tidal Resource Investigation, Device and Energy Tool (TRIDEnT), and (3) a method for assessing multiple sites and multiple devices using adapted power development planning criteria. Validation and benchmarking of the proposed metric and developed tool against in-situ measurement and selected methods / tools (EPRI, STEM, ESRU, GeorgiaTech) for resource assessment are done. Energy density maps are generated via TRIDEnT and are presented for four sites in the Philippines, namely: Matnog-San Bernardino Strait, Verde Island Passage, Cebu-Santander Strait, and Davao Samal-Talicud Channel.

Case studies for TRIDEnT featuring its key capabilities, such as resource analysis, device performance assessment, site-device suitability scoring scheme for 4 sites and 8 TISE conversion (TISEC) devices, and decision support mechanism (using depth constraints, and factoring in of power demand), are demonstrated. The TISE potential of selected sites in the Philippines is quantified for the first time. Selected TISEC devices are nominated, matched, and ranked (in order of suitability) as candidate tidal power plant installations: RTT2000, HS1000, Open-Center for Matnog-San Bernardino Strait, RTT2000, Open-Center, GCK Gorlov Verde Island Passage, and RTT2000, Gen5, HS1000 for Davao Samal-Talicud Channel.

Five key contributions for the field of TISE evaluation are presented in this work, namely: (1) a macro-level resource assessment using an energy potential metric based on tide-height differences at the boundaries of a channel of interest; a MatlabTM-based integrated, rapid evaluation tool (2) with multiple site resource analysis (equipped with velocity histograms, frequency-intensity-direction diagrams, time- series plots, and energy density maps) capability, (3) multiple device (featuring a flexible database with parameters of interest) performance assessment capability, (4) a combined multi-site, multi-device suitability scoring scheme, and (5) a decision support system for use in pre-development / feasibility studies.

The conformity of microstrip antennas has interested so many because of its ability to function normally whether it remains flat or transformed geometrically to the shape of the surface on which they are mounted upon. An obvious benefit is the increase in their inconspicuousness. At the same time their performances have been known to change. Recently these changes have been studied to realize any potential for positively exploiting them to achieve various design goals. This thesis is an intensive study of the behavior of conformal microstrip antennas when adapted to circular and elliptical curvatures on either of the two (2) geometric planes of an antenna. A scheme is employed to deal with the potential ambiguity of having to mention different antenna dimensions and curvature dimensions when trying to generalize results. Two (2) terms are been used to make simpler the vast amount of results: ‘circumferential coverage’ instead of simply ‘curvature radius’ (that is rather specific in influence to a specific antenna dimension), and ‘eccentricities’ instead of ‘semi-axes’ (for describing different elliptical curvatures). A total of eight (8) different antennas and antenna arrays operating at different frequency bands (902 – 928MHz, 2.400 – 2.484GHz, and 5.725 – 5.850GHz) are studied. The chosen frequency bands are to realize functional antenna models with very different dimensions. The thesis then provides information on the effects of curvature on the different performance parameters of the different antennas including the resonant frequency, return loss, impedance bandwidth, directivity, radiation and overall efficiency, beam-width, and side-lobe level. All of the works therein have been conducted in CST Microwave Studio.

The Interleaved Two Switch Forward Topology is widely used in DC-DC power converters. The limitation to its operation is its duty cycle. This imposes limits on transformer and output choke design. A Three Switch Forward Topology is able to operate at higher duty cycle which can overcome these limitations. An Interleaved Three Switch Forward Converter was compared to an Interleaved Two Switch Forwared Converter. Both having the same devices and output choke but with the different transformer design to allow different operating duty cycles. Comparison was done on ripple characteristics, voltage stresses, efficiency and duty cycle characteristics. Results show that ripple for both input and output was lower for the new topology (US Patent No. 6707690, Issued March 2004). Measured output voltage ripple is 28.4mV lower and input voltage ripple is 15.32V lower for this topology. Voltage stresses on the switches are the same and the diode voltage stresses are subject to the difference in the transformer. Moreover, efficiency was also measured to be 1.2% higher at half-load. The drawback of the new topology is added parts count and a possible increase in EMI.