Ruba Akram Amarin

Generator emulation controls for photovoltaic inverters

State-of-the-art inverter controls for grid-tied photovoltaic (PV) systems pose a number of challenges to grid stability if deployed on a large scale. This paper addresses large-scale integration of PV and other distributed generation (DG) into the grid. A new control scheme for grid-tied DG inverters is proposed to embed various load-following functions. This control scheme, dubbed Generator Emulation Controls (GEC), allows DG inverters to perform voltage regulation support, reactive power compensation, and fault ride-through. GEC also allows DG inverters to form scalable inverter-dominated micro-grids. These micro-grids are capable of operating in grid-tied mode or of separating and supporting an islanded load. Dynamic modeling of synchronous generators is presented, and used to guide GEC implementation. Experimental results are presented to demonstrate some of the main features of GEC.∗

The hurricane imaging radiometer - an octave bandwidth synthetic thinned array radiometer

The Hurricane Imaging Radiometer (HIRad) is a new airborne sensor that is currently under development. It is intended to produce wide-swath images of ocean surface wind speed and near surface rain rate in hurricanes conditions. HIRad will extend the scientific capabilities and technologies associated with two previous successful airborne microwave radiometers: the real aperture Stepped Frequency Microwave Radiometer (SFMR) and the synthetic aperture Lightweight Rainfall Radiometer (LRR). Both SFMR and HIRad are required to operate over the full C-Band octave in order to estimate precipitation levels experienced in hurricanes without saturation and to penetrate through the precipitation and estimate surface winds. Operation over an octave bandwidth was easily accomplished by the nadir-pointing horn antenna used by SFMR. However, it represents a major technological challenge for the HIRad design because it is a Fourier synthesis imager. Details of how HIRad meets that challenge are described here.

Hurricane Wind Speed Measurements in Rainy Conditions Using the Airborne Hurricane Imaging Radiometer (HIRAD)

This paper describes a realistic computer simulation of airborne hurricane surveillance using the recently developed microwave remote sensor, the hurricane imaging radiometer (HIRAD). An end-to-end simulation is described of HIRAD wind speed and rain rate measurements during two hurricanes while flying on a high-altitude aircraft. This simulation addresses the particular challenge which is accurate hurricane wind speed measurements in the presence of intense rain rates. The objective of this research is to develop baseline retrieval algorithms and provide a wind speed measurement accuracy assessment for future hurricane flights including the NASA GRIP hurricane field program that was conducted in summer of 2010. Examples of retrieved hurricane wind speed and rain rate images are presented, and comparisons of the retrieved parameters with two different numerical hurricane models data are made. Special emphasis is provided on the wind speed measurement error, and statistical results are presented over a broad range of wind and rain conditions over the full measurement swath (earth incidence angle).

Multi-Frequency Synthetic Thinned Array Antenna for the Hurricane Imaging Radiometer

A C-band four-frequency resonant stacked-patch array antenna is developed for synthetic thinned aperture radiometer measurements of hurricane force wind speeds. This antenna is being integrated into an aircraft instrument referred to as the Hurricane Imaging Radiometer (HIRAD). Details of the antenna design are presented along with antenna performance tests and laboratory measurements using a full-scale prototype array with a subset model of the HIRAD instrument.

Restrictions on the field of view for an undersampled 1-D synthetic thinned aperture radiometry

Traditional radio astronomy formulation of the field of view (FOV) applied to a non-Nyquist spatially sampled synthetic thinned aperture radiometers appear to overestimate the FOV. Utilizing the current design of the Hurricane Imaging Radiometer (HIRad) as a baseline instrument, a simple analytical instrument simulator is developed to investigate the different methods of determining the FOV. Analytically, this value is found to be 70deg. However the usable range seems to extend only to 61deg. The presence of aliased grating lobes is easily seen in the synthesized antenna patterns. Beam efficiency plots with threshold levels can be used to determine the reduced FOV. Error analysis is performed utilizing several sample images of Hurricane Katrina.

A Wide-Swath, Hurricane Imaging Radiometer For Airborne Operational Measurements

In recent years, the contributions of microwave remote sensing to hurricane numerical forecasting have increased significantly, particularly with the Stepped Frequency Microwave Radiometer, SFMR, measurements of wind speed and rain rate. The Hurricane Imaging Radiometer, HIRad, is a new instrument concept that improves on the SFMR by imaging surface wind speed and rain rate over a ± 45 deg. swath. It is compatible with high altitude jet aircraft and unpiloted aerial vehicles, and has potential for space- borne use. This paper provides a brief description of the HIRad concept, the status of the HIRad microstrip patch array technology, and a review of a physically based radiative transfer model developed for HIRad modeling and simulations.

Adaptive Electronic Quizzing Method for Introductory Electrical Circuit Course

The interactive technical electronic book, TechEBook, currently under development at the University of Central Florida, provides a useful tool for engineers and scientists through unique features compared to the most used traditional electrical circuit textbooks available in the market. TechEBook has comprised the two worlds of classical circuit books and an interactive operating platform such as laptops and desktops utilizing Java Virtual Machine operator. The TechEBook provides an interactive applets screen that holds many modules, in which each had a specific application in the self learning process. This paper describes one of the interactive techniques in the TechEBook known as, QuizMe, for evaluating the readersâ?? performance and the overall understanding for all subjects at any stage. The QuizMe will be displayed after each section in the TechEBook for the user to evaluate his/her understanding, which introduces the term me-learning, as a comprehensive full experience for self or individualized education. In this paper, a practical example of applying the QuizMe feature is discussed as part of a basic electrical engineering course currently given at the University of Central Florida.

Java based Symbolic Circuit Solver for electrical engineering curriculum

The interactive technical electronic book, TechEBook, currently under development at the University of Central Florida (UCF), introduces a paradigm shift by replacing the traditional electrical engineering course with topic-driven modules that provide a useful tool for engineers and scientists. The TechEBook comprises the two worlds of classical circuit books and interactive operating platforms such as iPads, laptops and desktops. The TechEBook provides an interactive applets screen that holds many modules, each of which has a specific application in the self learning process. This paper describes one of the interactive techniques in the TechEBook known as Symbolic Circuit Solver (SymCirc). The SymCirc develops a versatile symbolic based linear circuit with a switches solver. The solver works by accepting a Netlist and the element that the user wants to find the voltage across or current on, as input parameters. Then it either produces the plot or the time domain expression of the output. Frequency domain plots or Symbolic Transfer Functions are also produced. The solver gets its input from a Web-based GUI circuit drawer developed at UCF. Typical simulation tools that electrical engineers encounter are numerical in nature, that is, when presented with an input circuit they iteratively solve the circuit across a set of small time steps. The result is represented as a data set of output versus time, which can be plotted for further inspection. Such results do not help users understand the ultimate nature of circuits as Linear Time Invariant systems with a finite dimensional basis in the solution space. SymCirc provides all simulation results as time domain expressions composed of the basic functions that exclusively include exponentials, sines, cosines and/or t raised to any power. This paper explains the motivation behind SymCirc, the Graphical User Interface front end and how the solver actually works. The paper also presents some examples and results to better explain the concept.

The Hurricane Imaging Radiometer wide swath simulation and wind speed retrievals

The knowledge of peak winds in hurricanes is critical to classification of hurricane intensity; therefore, there is a strong interest in the operational remote sensing of ocean surface winds for monitoring tropical storms and hurricanes, especially those which threaten landfall. Presently, the airborne Stepped Frequency Microwave Radiometer (SFMR) is the state-of-the-art remote sensor for providing this information in real-time, during hurricane surveillance flights. However, for the future, NASA and NOAA are collaborating in the development of the Hurricane Imaging Radiometer (HIRAD), which is a prototype of the next-generation high-flying airborne instrument for monitoring hurricanes. This paper describes a realistic end-to-end simulation of HIRAD hurricane measurements while flying on an unmanned Global Hawk aircraft. The objective of this research is to develop baseline retrieval algorithms and provide a wind speed measurement accuracy assessment for the upcoming NASA hurricane field program, Genesis and Rapid Intensification Processes (GRIP), to be conducted in 2010.

Impact of Spatial Resolution on Wind Field Derived Estimates of Air Pressure Depression in the Hurricane Eye

Measurements of the near surface horizontal wind field in a hurricane with spatial resolution of order 1-10 km are possible using airborne microwave radiometer imagers. An assessment is made of the information content of the measured winds as a function of the spatial resolution of the imager. An existing algorithm is used which estimates the maximum surface air pressure depression in the hurricane eye from the maximum wind speed. High resolution numerical model wind fields from Hurricane Frances 2004 are convolved with various HIRAD antenna spatial filters to observe the impact of the antenna design on the central pressure depression in the eye that can be deduced from it.