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GaN micro-disk resonator arrays were fabricated and measured within the Restrahalen band of GaN. Far-IR spectroscopy shows evidence for localized surface phonon polariton resonances, results which are confirmed by finite-element models of the fabricated structures.
Traditional impurity doping schemes are difficult for extreme-gap semiconductors, such as high Al content AlGaN alloys due to the large activation energies for donors and acceptors. Polarization-induced (or Pi-) doping, since its first demonstration [1], is being gradually implemented as an attractive alternative for effective p-type doping in large-bandgap nitride semiconductors both for power electronics,...
One of the factors hindering the large scale integration of wind power is the post contingency congestion of a network due to limited availability of network capacity and auxiliary constraints. Under such conditions, the network operators can potentially request a curtailment of wind farm output if the remedial strategies fail. The paper investigates this problem in detail and proposes a mathematical...
GaN/AlN structures are utilized to achieve deep-UV emission. By reducing thickenss of GaN QW to 1 ML, 224nm emission is achieved. A further shift to 219 nm is gettable as GaN islands are introduced.
Using wind power forecasts to optimize scheduling of reserves is an active area of research. However, the rating of transmission lines often places a limit on how much wind power can be used and hence reserve scheduling needs to be higher to account for this. Dynamic line ratings have been used to show that rated capacity of a transmission line is quite conservative compared the actual maximum capacity...
Optimising the power flow in a system has been a challenge for decades. Due to the complexities that are introduced by new technologies, this problem is evolving. Lately, the effect of integrating wind turbines into the system has been taken into account when solving optimal power flow. However, transmission system constraints are usually modeled as fixed constraints using deterministic methods. Deterministic...
The penetration of wind power is increasing rapidly in electricity grids around the world. Many governments have set specific targets on the amount of electricity to be produced by wind energy. Due to the intermittent nature of wind, one of the biggest challenges remaining is accurate and robust forecasting of wind power output. Most research so far has focused on predicting wind speeds only. This...
Teaching techniques and contents at institutes of higher learning must be a dynamic and seamless experience. While new concepts and technologies do not find their way into textbooks long after the research is matured and/or commercialized, Professors at Universities are in unique position to bring them into classroom much earlier benefiting from their sponsored research. This is why perhaps high ranked...
Generation of electricity using diesel is costly for a small remote isolated system. At a remote location electricity generation from renewable energy such as wind can help to reduce the overall operating costs by reducing the fuel costs. Siting of wind turbines connected to the diesel in a remote location effects wind penetration and power quality. In this paper we study how the location of a wind...
The optimal voltage restoration and loss minimization in distribution system using genetic algorithms (GAs) is presented. The optimization is carried out by scheduling load tap changer (LTC) and shunt capacitors to simultaneously improve the voltage and minimize the energy loss. Two GAs are developed to determine the load interval division and the optimal schedule of the controllable devices, respectively...
This paper investigates the impact of synchronous generator's damper windings on small-signal stability and dynamic behavior of power systems in the presence of time and space harmonics. A Distorted Single Machine Infinite Bus (DSMIB) system is used for the analysis. A nonlinear model of the synchronous generator (SG) in the Harmonic Domain (HD) is used to include space harmonics. The nonlinear effects...
In an attempt to re-regulate the distribution segment of an electric power system, public utility commissions (PUCs) are increasingly adopting a reward/penalty framework in order to guarantee acceptable electric supply reliability. A distribution utility's historical reliability performance records provide the basis for creating practical performance based ratemaking (PBR) mechanisms at the corporate...
Highly biodegradable and renewable seed-based oils can be an alternative source of dielectric fluids to replace the non-friendly mineral oil-based dielectric fluids. However, the high moisture content of vegetable oils is not suitable for a viable dielectric fluid formulation for safe, economic and trouble free operation of power and distribution transformers. The reduction of the moisture level of...
Furans concentration presence in aged-transformer oil has been one of the key indicators of the solid dielectric deterioration. They are the by-products from the cellulose degradation of insulation paper caused by heat, oxidation and electrical stress. Nowadays, furans concentration is measured by high-performance liquid chromatography (HPLC) or gas chromatography-mass spectrometry (GC/MS) based on...
In the past, electric utilities were continuously adding more facilities to their systems in order to satisfy the growing customer energy requirements based on a set of deterministic criteria that guide transmission planning. The traditional planning guidelines were based on planner's experience and intuition without a formal and consistent framework for their development. In most cases, using the...
There is a remarkable correlation between quality management and safety through design philosophy. In general, a more reliable plant is a safer plant. Equipment in modes of operation not anticipated by the designer can create significant risks. There is a large difference between the predicted performance of systems and those observed in practice including the management of deviations, constraints...
Theoretical and experimental analyses are used to investigate the effects of harmonics on the operation of overcurrent relays. Two analytical approaches based on relay characteristics provided by the manufacturer and simulations using PSCAD software package are used to estimate tripping times under non-sinusoidal operating conditions. The tests were conducted such that the order and the magnitude...
Three-phase power flow for unbalance distribution system is carried out using forward- backward propagation technique. The equivalent injection current method is employed to represent the loads and shunt admittances. The algorithm starts with mapping the distribution network to determine the forward and backward propagation paths. The backward propagation is used to calculate branch currents using...
Power flow calculation is normally carried out for fundamental frequency. Due to the extensive use of nonlinear loads, harmonic frequencies are present and need to be also considered. Unfortunately, unavoidable complexity and heavy computation burden are often encountered by involving nonlinear loads into the calculation. Multiple nonlinear loads typically employed in the real system will further...
The major objective of a safety audit is to determine the effectiveness of the company's safety and loss prevention measures. Identifying potential electrical hazards to prevent or minimize loss of life and property is perceived seriously by the utilities world wide. Safety audit is a methodical approach to evaluate potential hazards enabling suggestions for improvement. It is an important tool for...
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