Arc Fault Detection in DC Photovoltaic Systems

Arc faults have always been a concern for electrical systems as they can cause fires, personnel shock hazard, and system failure. In photovoltaic (PV) systems, a large number of electrical connectors and long wire runs are expected. Combined with the high DC voltage, deterioration of the wire insulation due to aging or other circumstances such as rodent bites and abrasion due to chaffing with trees, building walls, or conduit during installation can cause electric arcs to occur. These dc arcs may result in shock hazards, fires, and system failures or faults in the PV systems. NEC 2011 includes a requirement for new rooftop arrays to include UL1699B listed arc fault current interrupters (AFCI). NEC 2014 expands this requirement to include ground-mounted arrays as well. Existing commercialized techniques that rely on pattern recognition in the time domain, or frequency domain analysis using a Fourier Transform do not work well because the signal to noise ratio is low, and the arc signal is not periodic. Instead, wavelet transform provides a time-frequency approach to analyzing target signals with multiple resolutions. In this work, a technique for arc fault detection photovoltaic systems by using discrete wavelet transform (DWT) for feature extraction and support vector machines for decision making is proposed. The frequency characteristics of electric arcs in the PV systems are first studied. The fundamental feasibility of applying wavelet theory to detect arc fault and arc flash in solar PV power systems is then examined both in simulation using synthetic waveforms generated in MATLAB / Simulink and experimentally using arc waveforms measured from actual dc PV systems with/without operating inverters. In the later chapter, a supervised learning method for arcing/non-arcing event classification using support vector machines (SVMs) is introduced. SVMs are believed to be one of the best “off-the-shelf” supervised learning algorithms. The main concept behind SVM is to create a hyperplane with a maximum margin between the two adjacent classes which helps bound the generalization error of the classification model. Different combinations of mother wavelets, decomposition levels, and kernel functions are examined in this work. Some of the strategies have shown very promising results

Engineering aperiodic spiral order for photonic-plasmonic device applications

Thesis (Ph.D.)--Boston UniversityDeterministic arrays of metal (i.e., Au) nanoparticles and dielectric nanopillars (i.e., Si and SiN) arranged in aperiodic spiral geometries (Vogel's spirals) are proposed as a novel platform for engineering enhanced photonic-plasmonic coupling and increased light-matter interaction over broad frequency and angular spectra for planar optical devices. Vogel's spirals lack both translational and orientational symmetry in real space, while displaying continuous circular symmetry (i.e., rotational symmetry of infinite order) in reciprocal Fourier space. The novel regime of "circular multiple light scattering" in finite-size deterministic structures will be investigated. The distinctive geometrical structure of Vogel spirals will be studied by a multifractal analysis, Fourier-Bessel decomposition, and Delaunay tessellation methods, leading to spiral structure optimization for novel localized optical states with broadband fluctuations in their photonic mode density. Experimentally, a number of designed passive and active spiral structures will be fabricated and characterized using dark-field optical spectroscopy, ellipsometry, and Fourier space imaging. Polarization-insensitive planar omnidirectional diffraction will be demonstrated and engineered over a large and controllable range of frequencies. Device applications to enhanced LEDs, novel lasers, and thin-film solar cells with enhanced absorption will be specifically targeted. Additionally, using Vogel spirals we investigate the direct (i.e. free space) generation of optical vortices, with well-defined and controllable values of orbital angular momentum, paving the way to the engineering and control of novel types of phase discontinuities (i.e., phase dislocation loops) in compact, chip-scale optical devices. Finally, we report on the design, modeling, and experimental demonstration of array-enhanced nanoantennas for polarization-controlled multispectral nanofocusing, nanoantennas for resonant near-field optical concentration of radiation to individual nanowires, and aperiodic double resonance surface enhanced Raman scattering substrates

Performance evaluation of a quantum-well infrared photodetector in patch-antenna architecture

Nel presente lavoro di tesi si dimostra il miglioramento delle perfomances di un detector basato su pozzi quantici (QWIP-Quantum Well Infrared Photo detector)(n-type GaAs/AlGaAs) nel range infrarosso (λ ≈8.6µm), processato in un array di nano-antenne a doppio metallo. I Quantum Well detectors generano fotocorrente attivando transizioni intersottobanda nel supereticolo di pozzi quantici. Le prestazioni di questi detectors sono deteriorate dal rumore associato alla corrente di dark, proporzionale all’area del detector e dipendente esponenzialemente dalla temperatura. In questo lavoro, si dimostra che le antenne patches agiscono da micro-cavitá che confinano il campo elettrico incidente in uno strato di semiconduttore con dimensioni minori della lunghezza d’onda, evitano la regola di selezione intersottobanda e raccolgono fotoni da un’area maggiore delle dimensioni fisiche del dispositivo stesso, riducendo la corrente di dark senza diminuire la fotocorrente. Il miglioramento delle prestazioni del detector é espresso in termini di area di collezione Acoll e di focusing factor, l’aumento di campo locale. Queste quantitá sono state estratte da spettri di riflettivitá presi tramite spettroscopia infrarosso a Trasformata di Fourier (FTIR) a 300K. Caratteristiche tensione-corrente sono state misurate in condizioni dark e di background (300K) da 4K a 300K, e paragonate ad un dispositivo con la stessa regione attiva ma processato con una faccetta a 45 °. Da queste curve la temperatura di BLIP (Background Infrared Limited Performance) è stata ricavata. Misure di fotocorrente in funzione del bias sono state prese tramite tecnica con amplificatore lock-in. Le figure di merito responsivitá e detectivity sono state estratte dalle misure di fotocorrente, dopo la calibrazione della potenza radiativa incidente. Queste misure mostrano un miglioramento di 10K nelle performaneces rispetto al dispositivo mesa, dimostrando un’elevata sensibilitá fino a temperatura ambiente

A photonic bandgap resonator to facilitate GHz frequency conductivity experiments in pulsed magnetic fields

We describe instrumentation designed to perform millimeter-wave conductivity measurements in pulsed high magnetic fields at low temperatures. The main component of this system is an entirely non-metallic microwave resonator. The resonator utilizes periodic dielectric arrays (photonic bandgap structures) to confine the radiation, such that the resonant modes have a high Q-factor, and the system possesses sufficient sensitivity to measure small samples within the duration of a magnet pulse. As well as measuring the sample conductivity to probe orbital physics in metallic systems, this technique can detect the sample permittivity and permeability allowing measurement of spin physics in insulating systems. We demonstrate the system performance in pulsed magnetic fields with both electron paramagnetic resonance experiments and conductivity measurements of correlated electron systems.Comment: Submitted to the Review of Scientific instrument

Modelling, Monitoring, Control and Optimization for Complex Industrial Processes

This reprint includes 22 research papers and an editorial, collected from the Special Issue "Modelling, Monitoring, Control and Optimization for Complex Industrial Processes", highlighting recent research advances and emerging research directions in complex industrial processes. This reprint aims to promote the research field and benefit the readers from both academic communities and industrial sectors

Microwave Package Design for Superconducting Quantum Processors

Solid-state qubits with transition frequencies in the microwave regime, such as superconducting qubits, are at the forefront of quantum information processing. However, high-fidelity, simultaneous control of superconducting qubits at even a moderate scale remains a challenge, partly due to the complexities of packaging these devices. Here, we present an approach to microwave package design focusing on material choices, signal line engineering, and spurious mode suppression. We describe design guidelines validated using simulations and measurements used to develop a 24-port microwave package. Analyzing the qubit environment reveals no spurious modes up to 11GHz. The material and geometric design choices enable the package to support qubits with lifetimes exceeding 350 {\mu}s. The microwave package design guidelines presented here address many issues relevant for near-term quantum processors.Comment: 15 pages, 9 figure

PRINCIPLES FOR NEW OPTICAL TECHNIQUES IN MEDICAL DIAGNOSTICS FOR mHEALTH APPLICATIONS

Medical diagnostics is a critical element of effective medical treatment. However, many modern and emerging diagnostic technologies are not affordable or compatible with the needs and conditions found in low-income and middle-income countries and regions. Resource-poor areas require low-cost, robust, easy-to-use, and portable diagnostics devices compatible with telemedicine (i.e. mHealth) that can be adapted to meet diverse medical needs. Many suitable devices will need to be based on optical technologies, which are used for many types of biological analyses. This dissertation describes the fabrication and detection principles for several low-cost optical technologies for mHealth applications including: (1) a webcam based multi-wavelength fluorescence plate reader, (2) a lens-free optical detector used for the detection of Botulinum A neurotoxin activity, (3) a low cost micro-array reader that allows the performance of typical fluorescence based assays demonstrated for the detection of the toxin staphylococcal enterotoxin (SEB), and (4) a wide-field flow cytometer for high throughput detection of fluorescently labeled rare cells. This dissertation discusses how these technologies can be harnessed using readily available consumer electronics components such as webcams, cell phones, CCD cameras, LEDs, and laser diodes. There are challenges in developing devices with sufficient sensitivity and specificity, and approaches are presented to overcoming these challenges to create optical detectors that can serve as low cost medical diagnostics in resource-poor settings for mHealth

Interim Design Report

The International Design Study for the Neutrino Factory (the IDS-NF) was established by the community at the ninth "International Workshop on Neutrino Factories, super-beams, and beta- beams" which was held in Okayama in August 2007. The IDS-NF mandate is to deliver the Reference Design Report (RDR) for the facility on the timescale of 2012/13. In addition, the mandate for the study [3] requires an Interim Design Report to be delivered midway through the project as a step on the way to the RDR. This document, the IDR, has two functions: it marks the point in the IDS-NF at which the emphasis turns to the engineering studies required to deliver the RDR and it documents baseline concepts for the accelerator complex, the neutrino detectors, and the instrumentation systems. The IDS-NF is, in essence, a site-independent study. Example sites, CERN, FNAL, and RAL, have been identified to allow site-specific issues to be addressed in the cost analysis that will be presented in the RDR. The choice of example sites should not be interpreted as implying a preferred choice of site for the facility