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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
201

Learning Peaks for Commercial and Industrial Electric Loads

B Hari Kiran Reddy (11824361) 18 December 2021 (has links)
<div>As on 2017, US Energy Information Administration (US EIA) claims that 50 % of the total US energy consumption are contributed by Commercial and Industrial (C&I) end-users.</div><div>Most of the energy consumption by these users is in the form of the electric power. Electric utilities, who usually supply the electric power, tend to care about the power consumption profiles of these users mainly because of the scale of consumption and their significant contribution</div><div>towards the system peak. Predicting and managing the peaks of C&I users is crucial both for the users themselves and for utility companies.</div><div>In this research, we aim to understand and predict the daily peaks of individual C&I users. To empirically understand the statistical characteristics of the peaks, we perform an extensive exploratory data analysis using a real power consumption time series dataset. To accurately predict the peaks, we investigate indirect and direct learning approaches. In the indirect approach, daily peaks are identified after forecasting the entire time series for the day whereas in the direct approach, the daily peaks are directly predicted based on the historical data available for different users during different days of the week. The machine learning models used in this research are based on Simple Linear Regression (SLR), Multiple Linear Regression (MLR), and Artificial Neural Networks (ANN).</div>
202

Improvements to a Bi-directional Flyback DC-DC Converter for Battery System of the DC House Project

Wu, Michael 01 June 2014 (has links)
The DC House project relies primarily on renewable energy sources to provide DC power to the various loads of the house. However, not all renewable sources are capable of providing power at all times of the day. A back-up energy source in the form of a battery storage system must be available to meet the electrical needs of the house. A bi-directional flyback power converter was initially designed to allow a battery to charge from as well as discharge to the 48V bus line of the DC House. The design provided a 35W prototype to demonstrate the converter’s feasibility. Further improvements to increase power output through changes in design as well as improving the control scheme of the bi-directional converter were conducted. Results allowed an increase of output power to 48W with efficiency at 82% for both charging and discharging. The improvements to the control scheme allowed for better management of charging and discharging cycles of the battery.
203

Three-Phase Generation Using Reactive Networks

Davenport, Tattiana Karina Coleman 01 March 2015 (has links)
Household appliances utilize single-phase motors to perform everyday jobs whether it is to run a fan in an air conditioner or the compressor in a refrigerator. With the movement of the world going “green” and trying to make everything more efficient, it is a logical step to start with the items that we use every day. This can be done by replacing single-phase motors with three-phase motors in household appliances. Three-phase motors are 14% more efficient than single-phase motors when running at full load and typically cost less over a large range of sizes [1]. One major downside of incorporating three-phase motors in household appliance is that three-phase power is not readily available in homes. With the motor replacement, a single to three-phase converter is necessary to convert the single-phase wall power into the required three-phase input of the motor. One option is active conversion, which uses switches and introduces different stages that produce power loss [2]. An alternative solution is passive conversion that utilizes the resistances within the motor windings along with additional capacitors and inductors, which in theory are lossless. This study focuses on three different single to three-phase passive converters to run both wye and delta-connected three-phase induction motors, and a possible third winding configuration that utilizes one of the three converters. There will be an emphasis on proving the equivalency of two converters, one proposed by Stuart Marinus and Michel Malengret [11] and the other by Otto Smith [12]. Sensitivity analysis is performed to study the effects of variation of torque and converter component tolerances on the system.
204

Energy Management System Modeling of DC Data Center with Hybrid Energy Sources Using Neural Network

Althomali, Khalid 01 February 2017 (has links)
As data centers continue to grow rapidly, engineers will face the greater challenge in finding ways to minimize the cost of powering data centers while improving their reliability. The continuing growth of renewable energy sources such as photovoltaics (PV) system presents an opportunity to reduce the long-term energy cost of data centers and to enhance reliability when used with utility AC power and energy storage. However, the inter-temporal and the intermittency nature of solar energy makes it necessary for the proper coordination and management of these energy sources. This thesis proposes an energy management system in DC data center using a neural network to coordinate AC power, energy storage, and PV system that constitutes a reliable electrical power distribution to the data center. Software modeling of the DC data center was first developed for the proposed system followed by the construction of a lab-scale model to simulate the proposed system. Five scenarios were tested on the hardware model and the results demonstrate the effectiveness and accuracy of the neural network approach. Results further prove the feasibility in utilizing renewable energy source and energy storage in DC data centers. Analysis and performance of the proposed system will be discussed in this thesis, and future improvement for improved energy system reliability will also be presented.
205

Energy Harvesting from Exercise Machines: Comparative Study of EHFEM Performance with DC-DC Converters and Dissipative Overvoltage Protection Circuit

Kiddoo, Cameron 01 May 2017 (has links)
Energy Harvesting from Exercise Machines (EHFEM) is an ongoing project pursuing alternate forms of sustainable energy for Cal Poly State University. The EHFEM project seeks to acquire user-generated DC power from exercise machines and sell that energy back to the local grid as AC power. The end goal of the EHFEM project aims to integrate a final design with existing elliptical fitness trainers for student and faculty use in Cal Poly’s Recreational Center. This report examines whether including the DC-DC converter in the EHFEM setup produces AC power to the electric grid more efficiently and consistently than an EHFEM system that excludes a DC-DC converter. The project integrates an overvoltage protection circuit, a DC-DC converter, and a DC-AC microinverter with an available elliptical trainer modified to include an energy converting circuit. The initial expectation was that a DC-DC converter would increase, when averaged over time, the overall energy conversion efficiency of the EHFEM system, and provide a stable voltage and current level for the microinverter to convert DC power into AC power. In actuality, while including a DC-DC converter in a test setup allows the EHFEM system to function with less frequent interruptions, this occurs at the cost of lower efficiency. Testing demonstrates the EHFEM project can convert user-generated DC mechanical power into usable AC electrical power. Retrofitting existing equipment with the EHFEM project can reduce Cal Poly’s energy cost.
206

Protection Against Ungrounded Single Phase Open Circuit Faults in 3-Phase Distribution Transformers

Montoya, Higinio Ariel 01 May 2018 (has links)
This thesis explores the impacts and behavior of 3-phase distribution transformers when subject to ungrounded single phase open circuit faults. A simple 3-phase system is modeled using MATLAB Simulink and operation under fault conditions are simulated and studied. Simulation results are confirmed via lab experimentation. Finally, a robust detection and protection method using neutral current injection (as proposed in industry literature) is built and demonstrated. Electric utility operating experience has demonstrated that all too often, loads on 3-phase distribution transformers are not adequately protected against an ungrounded single phase open circuit fault (commonly called “single phasing”). This type of fault is amongst the least understood and hence the least protected against. This is especially true at end of transmission system radial feeds where 3-phase transformers can re-create the opened phase voltage due to a variety of effects including magnetic coupling, voltage loops and loading effects. Operating experience in the nuclear power industry has shown that the results can be catastrophic especially considering the impacts to motor loads. Impacts can result in unavailability of emergency loads, tripping of motor protection circuits or even motor damage and failure.
207

The Modified-Multiphase Boost Converter: Combined Inductors and Capacitors Topology

Eldredge, Zachary L 01 June 2018 (has links)
In this work, a modified boost converter design has been implemented in a multiphase configuration with a condensed topology. The modified aspect of the design has already been proven to drastically reduce input current ripple by about 40% in a single-phase implementation. By placing two modified boost converters in parallel with interleaving main switches (multiphase), the input inductors and modified capacitors of the modified topology can be reduced to just one of each, lowering the number of components, size, and cost. Additionally, multiphase DC/DC converters lower input/output voltage and current ripples while delivering more power compared to single-phase converters. By combining the modified and multiphase benefits, this thesis creates a topology with low ripple and noise while providing high power capability. This thesis covers the analysis, simulation, hardware implementation, and testing of the Modified-Multiphase Boost Converter as well as an equivalent Standard-Multiphase Boost Converter for comparison. Simulation and hardware test results exhibited a 9% input current ripple reduction with the Modified-Multiphase design, presenting a high-power converter with considerable input noise reduction. Keywords: dc/dc, boost, multiphase, interleave, modified, power, ripple
208

Low-Frequency Series Loaded Resonant Inverter Characterization

Medina, Alfredo 01 June 2016 (has links)
Modern power systems require multiple conversions between DC and AC to deliver power from renewable energy sources. Recent growth in DC loads result in increased system costs and reduced efficiency, due to redundant conversions. Advances in DC microgrid systems demonstrate superior performance by reducing conversion stages. The literature reveals practical DC microgrid systems composed of wind and solar power to replace existing fossil fuel technologies for residential consumers. Although higher efficiencies are achieved, some household appliances require AC power; thus, the need for highly efficient DC to AC converters is imperative in establishing DC microgrid systems. Resonant inverter topologies exhibit zero current switching (ZCS); hence, eliminate switching losses leading to higher efficiencies in comparison to hard switched topologies. Resonant inverters suffer severe limitations mainly attributed to a load dependent resonant frequency. Recent advancements in power electronics propose an electronically tunable inductor suited for low frequency applications [24], [25]; as a consequence, frequency stability in resonant inverters is achievable within a limited load range. This thesis characterizes the operational characteristics of a low-frequency series loaded resonant inverter using a manually tunable inductor to achieve frequency stability and determine feasibility of utilization. Simulation and hardware results demonstrate elimination of switching losses via ZCS; however, significant losses are observed in the resonant inductor which compromises overall system efficiency. Additionally, harmonic distortion severely impacts output power quality and limits practical applications.
209

Arc Fault Circuit Interrupter Development for Residential DC Electricity

Aarstad, Cassidy Alan 01 June 2016 (has links)
The following technical report describes the development and testing of an arc fault circuit interrupter (AFCI) for DC circuits operating primarily at 48 volts. We have identified an effective method for determining when arcing is occurring. Our method is primarily based on comparing the frequency spectrum of current flowing through the circuit during an arcing event to a known characteristic spectrum. Once an arc has been identified, our interrupter is capable of responding adequately to eliminate the arc. Hardware tests show the AFCI developed in this thesis responded, in all test cases, within 2 seconds of an arc fault occurrence. Commercialization and adoption of our interrupter will increase the safety of DC circuits operating at 80 volts or less.
210

Design, Simulation, and Hardware Construction of a 600 W Solid State DC Circuit Breaker for the DC House Project

Bukur, Calin Matthew 01 June 2018 (has links)
DC circuit breakers must be able to arrest overcurrent conditions to prevent electrical equipment and wiring from causing building fires or other hazards from occurring. With more DC renewable sourced structures such as Cal Poly’s DC House, an inexpensive and reliable protection system is necessary to ensure safe energy transfer to the loads. One method of protecting a system is preventing excessive amounts of current to be drawn by the load when the surrounding components are rated at a lesser value. DC circuit breakers act as a monitoring system and barely presents an effect on the voltage or power. With most DC circuit breakers on the market being mechanical, the response time to an overload condition is limited to the speed the contacts can disconnect. The examination of response timing and overcurrent limiting is explored in this thesis when using a solid state based DC circuit breaker. The system is designed to handle 600 W, where the operating voltage is 48 V and the maximum allowable current is 12.5 A. The solid state DC circuit breaker has the capability of arresting excessive currents within 30 µs and can be reset through a single pole single throw switch.

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