This thesis analyzes the design and performance of a photovoltaic (PV) emulator. With increasing interest in renewable energies, large amounts of money and effort are being put into research and development for photovoltaic systems. The larger interest in PV systems has increased demand for appropriate equipment with which to test PV systems. A photovoltaic emulator is a power supply with similar current and voltage characteristics as a PV panel. This work uses an existing power supply which is manipulated via Labview to emulate a photovoltaic panel. The emulator calculates a current-voltage (I-V) curve based on the user specified parameters of panel model, irradiance and temperature. When a load change occurs, the power supply changes its current and voltage to track the calculated I-V curve, so as to mimic a solar panel. Over 250 different solar panels at varying irradiances and temperatures are able to be accurately emulated. A PV emulator provides a controlled environment that is not affected by external factors such as temperature and weather. This allows repeatable conditions on which to test PV equipment, such as inverters, and provides a controlled environment to test an overall PV system.

Due to increasing changes in the power industry, Cal Poly San Luis Obispo's electrical engineering department introduced a set of initiatives to adequately equip students with the skills and knowledge to interact with new technologies. Specifically, the department proposed a microgrid and power systems protection and automation laboratory to strengthen students' knowledge of microprocessor-based relays. This paper outlines a microgrid laboratory system that fulfills the initiative's goal and proposes a collection of laboratory experiments for inclusion in a new laboratory course at Cal Poly. The experiments provide students with practical experience using Schweitzer Engineering Laboratory (SEL) relays and teach fundamental concepts in semi-automated generator synchronization and power system data acquisition. The microgrid laboratory system utilizes SEL relays and a centralized SEL controller to automate frequency regulation through load shedding, power factor correction, generator and utility synchronization, and relay protection group switching.

Accurate short-term electricity price forecasts are essential to all electricity market participants. Generation companies adopt price forecasts to hedge generation shortage risks; load serving entities use price forecasts to purchase energy with low cost; and trading companies utilize price forecasts to arbitrage between markets. Currently, researches on point forecast mainly focus on exploring periodic patterns of electricity price in time domain. However, frequency domain enables us to identify more information within price data to facilitate forecast. Besides, price spike forecast has not been fully studied in the existing works. Therefore, we propose a short-term electricity price forecast framework that analyzes price data in frequency domain and consider price spike predictions. First, the variational mode decomposition is adopted to decompose price data into multiple band-limited modes. Then, the extended discrete Fourier transform is used to transform the decomposed price mode into frequency domain and perform normal price forecasts. In addition, we utilize the enhanced structure preserving oversampling and synthetic minority oversampling technique to oversample price spike cases to improve price spike forecast accuracy. In addition to point forecasts, market participants also need probabilistic forecasts to quantify prediction uncertainties. However, there are several shortcomings within current researches. Although wide prediction intervals satisfy reliability requirement, the over-width intervals incur market participants to derive conservative decisions. Besides, although electricity price data follow heteroscedasticity distribution, to reduce computation burden, many researchers assume that price data follow normal distribution. Therefore, to handle the above-mentioned deficiencies, we propose an optimal prediction interval method. 1) By considering both reliability and sharpness, we ensure the prediction interval has a narrow width without sacrificing reliability. 2) To avoid distribution assumptions, we utilize the quantile regression to estimate the bounds of prediction intervals. 3) Exploiting the versatile abilities, the extreme learning machine method is adopted to forecast prediction intervals. The effectiveness of proposed point and probabilistic forecast methods are justified by using actual price data from various electricity markets. Comparing with the predictions derived from other researches, numerical results show that our methods could provide accurate and stable forecast results under different market situations.

Transformer is one of the most reliable components in an electric power system, however its failure has huge opportunity costs for an electric utility. In this work, we detect transformer electrical faults promptly and accurately classify the fault types using voltage/current data from Phasor Measurement Units. Our work can also eliminate uncertainties which are inherent in traditional transformer fault diagnostic techniques like dissolved gas analysis. In this thesis, first, possible causes of transformer failures are discussed, and four common transformer electrical faults are identified. Second, a comprehensive simulation model for electrical faults is developed. Third, fast and efficient abrupt change detection algorithms are applied for fault event detection. Finally, selected supervised machine learning classifiers are trained to classify type of transformer electrical faults. Our proposed work can be used with alarms and relays to notify system operators and remove the faults, as well as for post-mortem analysis of transformer failures.

Battery-powered trends in consumer electronics, transportation, and renewable energy sectors increase demands on DC/DC converter technology. Higher switching frequency and efficiency reduces solution size and cost, while increasing power capabilities. Still, switching noise remains the primary drawback associated with any DC/DC converter. Reducing a converter’s input ripple helps prevent switching noise from spreading to other systems on a shared DC power bus. This thesis covers the analysis, simulation, and implementation of a recently-proposed boost converter topology, alongside an equivalent standard boost converter, operating in steady-state, continuous conduction mode. A Matlab-based simulation predicts each converter’s input ripple performance using a state-space model. The converters’ hardware implementation minimizes component and layout differences to create an equivalent comparison. The simulation and hardware measurements demonstrate a 40% input current ripple reduction using the modified topology. Replacing standard boost converters with the modified topology minimizes the switching noise conducted through a system’s DC power network.

[pt] O crescimento constante da demanda de energia elétrica está tornando necessário o aproveitamento, cada vez maior, dos potenciais hidroelétricos existentes em diversos pontos do País. O grande porte de algumas das futuras usinas hidroelétricas bem como o seu afastamento dos principais centros de consumo, tornará necessária a construção de extensa linha de transmissão em extra alta tensão. As características elétricas destas linhas, especialmente quando se usa compensação série, introduzem muitos problemas que tornam difícil ou em alguns casos impossível, a aplicação de esquemas convencionais de proteção por relés. O sistema de transmissão de Itaipu, atualmente em fase de projeto e que deverá entrar em funcionamento na década de 1980 na região sudeste do País, prevê a transmissão de cerca de 10.000 MW através de uma de aproximadamente 900 KM, numa faixa de tensão de 750 a 800kV. O presente trabalho, utilizando como exemplo um estudo preliminar das características elétricas deste sistema, analisa especificamente os problemas relacionados com a proteção de linhas dotadas de compensação série e apresenta ferramentas computacionais para a análise detalhada do comportamento de sistemas compensados em condições de curto-circuito bem como para a avaliação do desempenho de diversos esquemas de proteção. / [en] The Constant growth of the demand for electrical energy in Brazil is leading to an increased use of the country’s vast hydro potencial. The great size of the hydroelectric plants being planned for the near future, as well as their distance from the main load centers, will make it necessary to transmit vast amounts of power over long EHV lines. The electrical characteristics of some of these lines, specially those using series capacitores. Make it difficult, and in some cases impossible, to apply conventional protection schemes. This paper, using as an example a preliminary study of the above mentioned system, analyses specifically the problems related to the protection of series compensated transmission lines and describes two series computer programs suitable for circuit for short circuit studies and the evaluation of various protection schemes.

The inherent difficulty in designing high voltage power supplies is often compounded by demands of high reliability, high performance, and safe functionality. A proposed high step-up ratio DC-DC converter meets the exacting requirements of applications such as uninterruptible power systems, radar, and pulsed power systems. The proposed DC-DC converter topology combines a multi-phase buck input stage with a novel self-tracking zero-voltage-switching (ZVS) resonant output stage. Traditionally, the inclusion of multiple power processing stages within a power supply topology severely degrades the overall converter efficiency. Due to the inherent high efficiency per stage, however, this effect is minimized. The self-tracking switching scheme ensures that ZVS occurs across the full range of load variation. Furthermore, the switching scheme allows significantly increased flexibility in component tolerances compared to traditional resonant converter designs. The converter also demonstrates indefinite short-circuit protection and true ZVS during transient processes. Computer simulation and hardware analysis verify the efficacy of the topology as a rugged and efficient converter.

In this thesis, a proof of concept for a current-source DC-DC converter for powering sensors used in an underwater communications system is presented. The proposed converter steps down an input current of 0.9 A to 0.625 A, while maintaining an output voltage of 24 V and output power of 15 W. The complete steady-state analysis and design of the proposed converter in its single-stage form is also explained in detail. Performance evaluation of the proposed converter was carried out using LTspice. Results of the simulation demonstrate that the design was able to produce average output current of 0.639 A at maximum output power of 15.292 W while maintaining 24.39 V regulated output voltage. The overall efficiency of the converter was determined to be 88.73% and the output voltage ripple was calculated to be 0.4%, meeting the original specifications of the design.

The growing popularity of photovoltaic (PV) generation systems leads to an increase in the number of residential and commercial grid-tied PV systems that interconnect to the distribution circuit. This affects the characteristics of the distribution circuit; for example, the assumption that the voltage profile of a radial line decreases down-stream becomes invalid because of the addition of the PV system on the line. This poses new challenges when setting the parameters of voltage regulating devices. Add to that the fact that PV systems are intermittent, especially on cloudy days, which make the line even more difficult to regulate, and the number of switching occurrences of the regulating devices increases, thus accelerating wear-and-tear to the utility’s equipment. The objective of this thesis is to develop an index which qualitatively indicates the impact of PV system(s) on operation, efficiency, reliability, and lifetime of voltage regulation equipment. Tests on the proposed index will be performed on several cases including circuits containing state-of-the art methods that integrate PV systems with minimum impact to utility equipment. Investigation of methods to further mitigate equipment wear by selecting the best interconnect point on the circuit will also be conducted to test the proposed index. The development and validation of the proposed index will entail power system modeling and simulation of distributed generation using PSCAD. The proposed index resulted from this study will provide a useful tool to allow utility companies pick the optimum locations for distributed generation to minimize their negative impact on the distribution lines as well as to determine the need for extra mitigation equipment.

As the ‘green’ energy movement continues to gain momentum, photovoltaic generation is becoming an increasingly popular source for new power generation. The primary focus of this paper is to demonstrate the benefits of close-to real-time cloud sensing for Photovoltaic generation. In order to benefit from this close-to real-time data, a source of cloud cover information is necessary. This paper looks into the potential of point insolation sensors to determine overhead cloud coverage. A look into design considerations and economic challenges of implementing such a monitoring system is included. The benefits of cloud location sensing are examined using computer simulations to target important time-scales and options available to plant operators. Finally, the economics of advanced forecasting options will be examined in order to determine the benefit to plant operators.