Nowadays islanding has become a big issue with the increasing use of distributed generators in power system. In order to effectively detect islanding after DG disconnects from main source, author first studied two passive islanding methods in this thesis: THD&VU method and wavelet-transform method. Compared with other passive methods, each of them has small non-detection zone, but both of them are based on the threshold limit, which is very hard to set. What’s more, when these two methods were applied to practical signals distorted with noise, they performed worse than anticipated. Thus, a new composite intelligent based method is presented in this thesis to solve the drawbacks above. The proposed method first uses wavelet-transform to detect the occurrence of events (including islanding and non-islanding) due to its sensitivity of sudden change. Then this approach utilizes artificial neural network (ANN) to classify islanding and non-islanding events. In this process, three features based on THD&VU are extracted as the input of ANN classifier. The performance of proposed method was tested on two typical distribution networks. The obtained results of two cases indicated the developed method can effectively detect islanding with low misclassification.

Recently, more and more disputations about how demand response should be compensated have arisen. Moreover, the court is about to rehear the Order 745. It probably will have significant impact on the whole working system used to be built for demand response before. Nowadays, some power companies and utilities think that they will endure profits leakage while demand response resources still are compensated. In this research, knowledge of demand response, local marginal price, Order 745 and other related concept will be explained in detail in case of misunderstanding. Associated with all these knowledge, a possible compensation method will be proposed. It combines many existing compensation methods. It mainly can be divided into three parts, i.e., high load period, off-peak period and low load period. The demand response resources will be compensated appropriately through these three periods. The compensation method endeavors to be just and reasonable.

In this dissertation, an all-fiber-based single frequency nanosecond pulsed laser system at ~ 1918.4 nm in master-oscillator-power-amplifier (MOPA) configuration is present. The nanosecond pulse seed is achieved by directly modulating a continuous wave (CW) single frequency fiber laser using a fast electro-optical modulator (EOM) driven by an arbitrary waveform generator (AWG). One piece of single mode, large core, polarization-maintaining (PM) highly thulium-doped (Tm-doped) germanate glass fiber (LC-TGF) is used to boost the pulse power and pulse energy of these modulated pulses in the final power amplifier. This laser system can work in both high power and high energy regime: in high power regime, to the best of our knowledge, the highest average power 16 W and peak power 78.1 kW are achieved for single frequency transform-limited ~2.0 ns pulses at 500 kHz and 100 kHz repetition rate, respectively: In high energy regime, nearly 1 mJ and half mJ pulse energy is obtained for ~15 ns pulses at 1 kHz repetition rate and 5 kHz repetition rate, respectively. Theoretical modeling of the large-core highly Tm-doped germanate glass double-cladding fiber amplifier (LC-TG-DC-FA) is also present for 2&mum nanosecond pulse amplification. A good agreement between the theoretical and experimental results is achieved. The model can simulate the evolution of pump power, signal energy, pulse shape and the amplified stimulated emission (ASE) in the amplifier. It can also be utilized to investigate the dependence of the stored energy in the LC-TGF on the pump power, seed energy and repetition rate, which can be used to design and optimize the LC-TG-DC-FA to achieve higher pulse energy and average power. Two channel of high energy nanosecond pulses (at 1918.4 nm and 1938 nm) are utilized to generate THz wave in a quasi-phase-matched (QPM) gallium arsenide (GaAs) based on difference frequency generation. THz wave with ~ 5.4μW average power and ~18 mW peak power has been achieved. Besides, one model is built to simulate a singly resonated THz parametric oscillator. The threshold, the dependence of output THz energy on pump energy has been investigated through this model. One pump enhanced THz parametric oscillator has been proposed. The enhancement factor of the nanosecond pulses in a bow-tie ring cavity has been calculated for different pulse duration, cavity length and the transmission of the coupler. And the laser resonances in the ring cavity have been observed by using a piezo to periodically adjust the cavity length. We also build an all-fiber thulium-doped wavelength tunable mode-locked laser operating near 2&mum. Reliable self-starting mode locking over a large tuning range (>50 nm) using fiber taper based carbon nanotube (FTCNT) saturable absorber (SA) is observed. Spectral tuning is achieved by stretching another fiber taper. To the best of our knowledge, this is the first demonstration of an all-fiber wavelength tunable mode-locked laser near 2&mum.

This thesis presents a new type of solar simulator and new measurement methods that allow for fast power rating of photovoltaic devices and for fast performance measurements for energy rating and energy yield predictions indoors under controlled, and more realistically simulated outdoor conditions. A novel indoor measurement system for photovoltaic device characterisation based on light emitting diodes (LEDs) as the light sources is described. The solar simulator is capable of reproducing spectral changes seen in natural sunlight, with its intricacies of variable air mass and weather conditions, to a better match than previously possible. Furthermore, it allows measurements under varying light intensity and device temperature. The prototype LED-based solar simulator developed is characterised and its measurement quality is analysed. The system achieves a class BAA solar simulator classification with a class B spectral match, class A light intensity uniformity and a class A temporal stability. It is the first system of its kind that meets the standards of a solar simulator in spectral match to the standard sunlight spectrum and in terms of minimum light intensity. An uncertainty analysis shows that calibration uncertainty for crystalline silicon solar cells is 5% in maximum power with a 95.45% level of confidence. Recommendations for further versions of the solar simulator are given and show potential of reducing this uncertainty down to 2.9% across all measurement spectra (1.8% with a primary calibrated reference cell). A new method for automated power-rating of single- and multi-junction devices is developed. The method uses a unique spectral response measurement and fitting method. It eliminates the need of external measurement equipment for determining spectral response. A simulated characterisation of an amorphous silicon single- and double-junction solar cell show accuracy of better than 0.5% in maximum power. First measurements on the LED-based solar simulator show a measurement error of 4.5% in maximum power, which is due to a lack of measurement feedback of spectral output and measurement irradiance. The first three-dimensional performance matrix for use in photovoltaic energy rating is reported, utilising the LED-based solar simulator. Device characteristics are measured indoors under varying irradiance, temperature and spectrum. A measurement method is detailed and utilised on a crystalline and amorphous silicon solar cell. It allows for the first time a direct investigation of spectral effects on photovoltaic devices under controlled conditions. Results show that amorphous silicon devices are very sensitive to changes in spectrum. Thus, spectral effects should not be neglected in energy yield predictions for such devices.

Compared with conventional measurements from supervisory control and data acquisition (SCADA) system, phasor measurement units (PMUs) provide time-synchronized and direct measurements of phasors. The availability of synchronized phasor measurements can significantly improve power system protection and analysis. This dissertation is specifically committed to using synchronized measurements for estimation of fault locations in transmission systems. Transmission lines are prone to various short-circuit faults. Accurate fault location is critical for rapid power recovery. Chapter 2 proposes a new fault location method based on sparse wide area measurements. One distinguishing feature of this method is its applicability to both transposed and untransposed transmission lines. In addition, the method is developed based on sparse-wide area measurement that may be taken far away from the faulted line. Shunt capacitances of transmission lines are also fully considered by the algorithm. Moreover, when synchronized measurements from multiple buses are available, an optimal estimator can be used to make the most use of measurements, and to detect and identify potential bad measurements. Most of the existing fault location literatures discuss common shunt faults, including single line-to-ground faults, line-to-line faults, line-to-line-to-ground faults, and three-phase faults. However, in addition to common shunt faults, some complex faults may also occur in power systems. Among these complex faults, evolving fault and inter-circuit fault are two typical examples. Chapter 3 extends the method developed in Chapter 2 to deal with evolving faults. The proposed wide-area fault location methods are immune to fault type evolution, and are applicable to both transposed and untransposed lines. Chapter 4 discusses location of inter-circuit faults. Inter-circuit fault is a type of simultaneous fault, and it is the most common simultaneous fault type. Inter-circuit faults between each circuit in a double-circuit line is the most common inter-circuit fault. A fault location method for inter-circuit faults on double-circuit lines are developed and evaluated in Chapter 4. Chapter 5 puts forward a fault location algorithm, which does not require line parameters information, for series-compensated transmission lines. Two-end synchronized voltage and current measurements are utilized. The proposed method is independent of source impedance and fully considers shunt capacitances of transmission lines.

Differential protection is the unit protection system which is applied to protect a particular unit of power systems. Unit is known as zone in protection terminology which is equivalent to simple electrical node. In recent time, low impedance current differential protection schemes based on percentage restrained characteristics are widely used in power systems to protect busbar systems. The main application issue of these schemes is mis-operation due to current transformer (CT) saturation during close-in external faults. Researchers have suggested various solution of this problem; however, individually they are not sufficient to puzzle out all mis-operational scenarios. This thesis presents a new bus differential algorithm by defining alternative partial operating current characteristics of a differential protection zone and investigating its performance for all practical bus faults. Mathematical model of partial operating current and operating principle of the proposed bus differential relay are described in details. A CT saturation detection algorithm which includes fast and late CT saturation detection techniques is incorporated in relay design to increase the sensitivity of partial operating current based internal-external fault discriminator for high impedance internal faults. Performance of the proposed relay is validated by an extensive test considering all possible fault scenarios.

With Power System being restructured in the vision of Smart Grid, it is important now more than ever to find suitable locations to place Distributed Generators (DG). Distributed generators, which may be renewable, are not limited to specific locations as in the case of conventional generators. Several papers have been published that make suggestions on where the optimal location of DG should be in a system. Objectives ranging from loss minimization to total cost minimization have been the factor for such studies. In this study, a new method is introduced that hopes to improve a current system in three ways by maximizing load, minimizing the locational marginal price and improving line contingency scenarios. The proposed methodology is simulated using MATPOWER’s Optimal Power Flow on the IEEE 14 bus test system.

Current transformer saturation will cause the secondary current distortion. When saturation occurs, the secondary current will not be linearly proportional to the primary current, which may lead to maloperation of protection devices. This thesis researches and tests two detecting methods: Fast Fourier Transform (FFT) and Wavelet Transform based methods. Comparing these two methods, FFT has a better performance in steady state saturation, and Wavelet Transform can determine singularity to provide the moment of distortion. The Jiles-Atherton (J-A) theory of ferromagnetic hysteresis is one approach used in electromagnetics transient modeling. With decades of development, the J-A model has evolved into different versions. The author summarizes the different models and implements J-A model in both MATLAB and Simulink.

Fiber amplifiers with high power and high pulse energy are strongly in demand for both scientific research and industrial applications. Ytterbium-doped fiber has been an outstanding choice for its broad-gain bandwidth and excellent power conversion efficiencies. In this dissertation, we introduced a compact high power high pulsed energy laser system with chirally coupled core (3C) Yb-doped fibers as the gain media. Traditional standard fibers and photonic crystal fibers are not suitable for compact high power high pulse energy laser systems because of poor higher order modes (HOMs) management and complicated air-hole structure. Newly invented 3C silica fibers solve these problems. A helical side-core around the Yb-doped central core extracts the HOMs from the central core. By adjusting this chirally structure, the core of the 3C fiber can be enlarged and the transverse mode of the fiber can be single mode at certain wavelengths. To simulate the amplification process with high power high pulse energy better, a new modeling method based on a combination of the rate equations and the nonlinear Schrödinger equations is invented. The gain was calculated from rate equations and the pulse evolution was analyzed using nonlinear Schrödinger equation. The simulation provided a good guidance for building compact high power high pulse energy laser systems. To achieve high power and high pulse energy, the system is designed as a two-stage structure. The laser

While global, national, and regional efforts to address climate and energy challenges remain essential, local governments and community groups are playing an increasingly stronger and vital role. As an active state in energy system policy, planning and innovation, Vermont offers a testing ground for research into energy governance at the local level. A baseline understanding of the energy planning and energy organizing activities initiated at the local level can support efforts to foster a transition to a sustainable energy system in Vermont. Following an inductive, applied and participatory approach, and grounded in the fields of sustainability transitions, energy planning, and community energy, this research project identifies conditions for change, including opportunities and challenges, within Vermont energy system decision-making and governance at the local level. The following questions are posed: What are the main opportunities and challenges for sustainable energy development at the town level? How are towns approaching energy planning? What are the triggers that will facilitate a faster transition to alternative energy systems, energy efficiency initiatives, and localized approaches? In an effort to answer these questions two studies were conducted: 1) an analysis of municipal energy plans, and 2) a survey of local energy actors. Study 1 examined Vermont energy planning at the state and local level through a review and comparison of 40 municipal plan energy chapters with the state 2011 Comprehensive Energy Plan. On average, municipal plans mentioned just over half of the 24 high-level strategies identified in the Comprehensive Energy Plan. Areas of strong and weak agreement were examined. Increased state and regional interaction with municipal energy planners would support more holistic and coordinated energy planning. The study concludes that while municipalities are keenly aware of the importance of education and partnerships, stronger policy mechanisms and financial stimulus are essential if Vermont hopes to increase strategic energy planning alignment and spur whole-scale energy system change. Study 2 examined local energy actors to assess their ability to develop and sustain energy action on the local level. A survey of 120 municipalities collected statewide baseline data covering the structures, processes, and activities of local energy actors. The analysis examined the role that various forms of capacity play in local energy activity. The results show that towns with higher incomes are more likely to have local energy actors and towns with higher populations have higher aggregate energy activity levels. Structurally, energy actors that had both an energy coordinator and an energy committee were more active, and municipal committees were more active than independent committees. Access to a budget and volunteer engagement were both associated with higher activity levels. The network of local energy actors in Vermont consists of committed and knowledgeable volunteers. Yet, the capacity of these local energy actors to implement sustainable energy change is limited due to resource constraints of time and money. In most cases, the scope of municipal energy planning strategy is modest. Prioritization of strategy and action at the central and local levels, along with increased interaction and coordination, is necessary to increase the regional compatibility and pace of energy system transformation.