The integration of distributed generators (DGs) into the distribution grid has exacerbated voltage unbalance issues leading to greater risks of reducing equipment lifetime, equipment damages, and increased ohmic losses. Most approaches to regulating voltage in distribution systems only focus on voltage magnitude and neglect phasor discrepancies and do little to remedy voltage unbalance. To combat this, a novel Optimal Power Flow (OPF) is designed to help operate these resources in a manner that curtails voltage unbalance using the reactive power compensation capabilities of inverters. The OPF was run for a wide variety of loading conditions on a pair of systems using MATLAB and was shown to improve the voltage profile of the system in addition to minimizing losses in most cases. However, it is noted that the OPF loses exactness in highly stressed conditions and is unable to provide meaningful solutions / Master of Science / With the power grid getting greener and smarter by the day, a slew of new challenges arise to overcome. Distributed sources of energy like solar panels and batteries are being added to the grid right from the household level. While they are desirable for reducing our need for traditional sources of energy, the addition of these resources has been shown to cause issues in the quality of the power grid. This is particularly observed at the low-voltage domestic part of the grid where the resources cause issues with the voltage quality. The distribution grid is unbalanced by nature and adding these resources only amplifies this problem. To help mitigate voltage quality issues grid operators are starting to require voltage regulation capabilities from resources to be connected to the grid and a lot of work has been conducted to find the optimal strategies for operating these resources. However, existing paradigms for these sources only focus on fixing the voltage magnitude part of the power quality and neglect phasor relationships. This thesis aims to bridge this gap by developing a method to determine the optimal operation of these resources by using the voltage regulation capability to address both voltage magnitude and voltage unbalance issues in addition to optimal operation.

Detailed measurements were taken downstream of several modified trailing edge configurations designed to impart streamwise velocity into the flow behind a cascade of GE Rotor B fan blades. These measurements were conducted in the Virginia Tech Low Speed Linear Cascade wind tunnel. The trailing edge configurations tested utilized passive techniques for producing streamwise vorticity, which in turn causes downstream wake diffusion and increased mixing. A more diffuse wake, when it impinges on the downstream stator, will produce lower noise levels as a result of this rotor-stator interaction. Furthermore, increased mixing in the flow will reduce the levels of turbulence kinetic energy observed downstream of the blade trailing edge. Thus, this project seeks to identify which passive techniques of imparting streamwise vorticity are most effective at improving the flow characteristics responsible for some of the noise production in modern jet aircraft. The three trailing edge configurations tested in detail for this project showed significant ability to widen and stretch the downstream wake by utilizing vorticity generation techniques. The TE-8 configuration was the most effective at increasing the wake width downstream of the trailing edge. Additionally, each configuration was able to successfully reduce some of the turbulence kinetic energy levels observed downstream when compared to the baseline blade, the most effective configuration being TE-8. Finally, the momentum thickness of each configuration was measured. When compared to the baseline, the TE-1 configuration showed an increased momentum thickness, TE-8 showed little change, and TE-7 actually showed an improved momentum thickness value. / Master of Science

Master of Science

A variable-speed constant frequency (VSCF) power conversion scheme with a permanent magnet synchronous generator (PMSG) is studied in this dissertation. The scheme consists of a PMSG, diode-rectifier bridge, dc-link filter, controlled converter for conversion to the constant frequency ac utility, and transformer. The various subsystems listed above are modeled for steady-state analysis and the simulation results are experimentally verified. All the relevant performance equations are derived for both the three-phase half-wave (THWI!) and full-wave (TFWI) controlled converter options and the harmonics are computed. / Master of Science

The distinction between the magnetohydrodynamic generator and the conventional wire-wound generator is that the role of the armature in the letter is played by an electrically conducting fluid in the former. This fluid is passed through a transverse electric and magnetic field and between two parallel plate electrodes. The induced electric field in the fluid, which is proportional to the fluid velocity and magnetic flux density, maintains a voltage drop across the electrodes and a current is generated when the electrodes are connected to an external load, closing the circuit. Thus energy is extracted from the fluid and delivered to an external load as electrical power. / Master of Science

This thesis is in an attempt to realistically model a real-time digital generator which interfaces to an analog system simulator and which consists of the synchronous machine and its peripheral controllers such as the exciter and the governor-turbine subsystems. In this work, the exciter, the synchronous machine, the machine dynamics and the governor are modeled in detail while a simplified model of the turbine is used. The synchronous machine, the main component of this simulation, solves the discretized Park's machine equations which include flux derivative tenns and tenns pertaining to the two amortisseur windings. Treatment of saturation effects in the mutual inductances is also discussed. The Park's model is arranged to obtain a field voltage and machine armature cutTent input - machine tenninal voltage output structure, where the armature current and terminal voltage are rotor based quantities (i.e. in d-q domain). In order to interface the Park's machine model to the analog system model, the Park's and inverse Park's transformation are implemented by software modules. The implementation of a prototype model generator using a Motorola 68020 microprocessor and fast computer peripherals is discussed. The results of the digital computer simulation in real-time for the generator model under various operating conditions are presented. / Master of Science

Master of Science

Sustainable energy solutions are aimed to reduce the consumption of fossil fuels by using renewable energy sources and energy efficiency techniques. This thesis presents two new sustainable energy applications in the field of electrical machines.Polyphase induction motors dominate the energy usage spectrum for industrial and commercial applications. The conventional winding structure used in both synchronous and induction machines has a basic unit of the winding with a 60 degree phase belt and a three phase connection either in star or delta. A new winding structure using an innovative Star-Delta Series Connection (SDSC) which has a high winding coefficient and low harmonic content is presented in this thesis. The principle of the SDSC winding is described. The Electro-Magnetic Belt and Electro-Magnetic Space diagram are two important means to be used for optimization of the new winding. Experimental results from two prototypes confirm the theoretical analysis. The efficiency of the new machine at rated load increased by about 3.8% as compared to the standard machine with a conventional winding structure.Wind energy is one of the most attractive renewable energy options. Wind turbines are designed to couple either synchronous or asynchronous generators with various forms of direct or indirect connection with grid or diesel generators. Permanent magnet (PM) generators using high energy Neodymium- Iron-Boron magnets offer advantages such as direct coupling without gear box, absence of excitation winding and slip rings, light weight and smaller size. This thesis presents the design and development of an outer-rotor PM generator suitable for wind energy conversion. The initial electromagnetic design followed by a Finite Element Analysis is presented in detail. A 20 kW prototype machine was built and extensively tested. It was found that the machine could maintain an ++ / efficiency of about 85% for a wide operating range. Equivalent circuit models were developed. The results of the Finite Element analysis matches closely with the experimental and the designed values.

The dynamics of a tether cable for a flying wind generator, employed to generate electricity by utilising the high velocity jet-stream winds in the troposphere, is analysed. A non-linear mathematical model for the study of the dynamics of the cable is described by a partial differential equation, which is solved analytically without damping. For unsteady and damped states, ordinary differential equations are obtained by adopting a discrete analysis approach, which are solved numerically with the aid of MATLAB software. Solutions are found for a range of lumped masses to represent the cable and each solution is verified against a previous case. Likewise, the result for the three masses is checked against the cable using a single lumped mass. The analysis is extended to seven discrete masses. This research highlights the dynamic behaviour of the cable subjected to wind gusts on the rotors and it also represents an appreciable input to the flying wind generator concept. The dynamic behaviour of the cable is critical for a flying electric generator. / Master of Engineering (Hons)

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