Adaptive remedial action schemes for transient instability

Remedial action schemes (RAS) are designed to avoid wide spread outages after asevere contingency in the power system. RAS have also been installed to increase theoperational transfer capability (OTC) with the restrictions on the transmission expansionin the power systems. In current practice, these schemes are predetermined based onextensive repeated time domain simulations. This dissertation presents an adaptivemethod for RAS computation. Given a two-area system model and a mode of disturbance(MOD) that the system will separate after a severe fault on the ties, the presented methodseparately calculates differential potential energy (DPE) and residual kinetic energy(RKE) with respect to an intermediary case. A sufficient RAS is determined bycomparing the RKE and the DPE. Because the DPE can be reused for the new unstablecases, the repeated time domain simulation can be avoided in RAS calculation. Thismethod is adaptive to different operating points and fault locations; it is also can changewith different fault clearing times and/or RAS initiation time. This method presents a wayto reduce the time domain simulations in the RAS off-line calculation. This method alsoenables us to establish an adaptive RAS using fast on-line computation.To support the adaptive scheme, a new transient energy calculation method is proposed based on the curve of equivalent power versus equivalent angle (EPEA curve) of the power system, which is derived from the concept of corrected kinetic energy. It is particularly suitable for transient energy calculation in situations with varying mechanical power, such as generation rejection.This dissertation also proposes a concept using the transient instability detection asthe trigger of the adaptive RAS. With Phasor Measurement Units (PMU) measurementsas input, a decision tree technique is applied to detect system transient instability. MODinformation is included in the classifications of the decision trees so that it can be appliedfor the MOD specific RAS. The effects of the time delay and the synchronization of thePMU sampling, which are independent of the occurrence of the system events, areinvestigated. Also studied are the effects of different locations of PMU and differentinput features of the decision trees, such as phasor angle and magnitude, pre-fault transferpower, and discrete system events. IEEE 39-bus and WECC 179-bus systems are used toillustrate and evaluate the proposed methods

Penerapan Metode Critical Trajectory pada Optimasi Peletakan Super Capacitor Energy Storage (SCES) Berbasis Indeks Energi

Kestabilan transien merupakan kemampuan sistem tenaga listrik untuk menjaga sinkronisme pada generator selama gangguan. Oleh karena itu, sistem membutuhkan waktu pemutusan kritis atau Critical Clearing Time (CCT) berdasarkan respons sudut rotor. Pemasangan Super Capacitor Energy Storage (SCES) bertujuan untuk memperbaiki CCT agar gangguan dapat dihilangkan sebelum generator terlepas dari sistem. Saat terjadi gangguan, SCES akan merespons sistem dengan menyerap daya mekanis berlebih dari Critical Generator (CG). Kemudian, optimasi peletakan SCES akan didukung oleh metode Boundary Controlling UEP Shadowing (BCU Shadowing) untuk menentukan CG berdasarkan generator yang memiliki indeks energi terbesar. Pada sistem Anderson dan Fouad 3-generator 9-bus, CG terletak di generator ke-2. Sementara pada sistem IEEE 7-generator 57-bus, CG terletak di generator ke-5. Penelitian ini akan membuktikan adanya peningkatan CCT rata-rata selama 0.01 detik apabila SCES diletakkan pada bus CG. Metode Critical Trajectory (CTrj) adalah metode untuk perhitungan CCT dengan menggunakan kehilangan sinkronisme (modified losing synchronism) sebagai kondisi titik akhir. ============================================================================================================================== Transient stability is the ability of a power system to maintain synchronism of the generators during the disturbance. Therefore, the power system needs the Critical Clearing Time (CCT) refers to the responses of the rotor angle. Installing Super Capacitor Energy Storage (SCES) aims to improve the CCT so it will clear the disturbance before the generator is released from the system. When the disturbance happens, SCES will absorb the excess of mechanical power from the Critical Generator (CG). An optimization of SCES placement supported by the Boundary Controlling UEP Shadowing (BCU Shadowing) to determine CG based on a generator which has the biggest of energy index. On 3-machine 9-bus Anderson and Fouad system, the CG is located at the 2nd generator. While, the CG of IEEE 7-machine 57-bus system is the 5th of the generator. This final project proves the enhancement of average of CCT up to 0.01 second when SCES is placed on the CG bus. Critical Trajectory (CTrj) is a method to calculate the CCT uses modified losing synchronism as its endpoint condition

Numerical polynomial homotopy continuation method to locate all the power flow solutions

The manuscript addresses the problem of finding all solutions of power flow equations or other similar non-linear system of algebraic equations. This problem arises naturally in a number of power systems contexts, most importantly the direct methods for transient stability analysis and voltage stability assessment. Here, the authors introduce a novel form of homotopy continuation method called the numerical polynomial homotopy continuation method that is mathematically guaranteed to find all the solutions without ever encountering a bifurcation. Since finding real solutions is much more challenging, first the authors embed the real form of power flow equation in complex space, and then track the generally unphysical solutions with complex values of real and imaginary parts of the voltages. The solutions converge to physical real form in the end of the homotopy. The so-called gamma-trick mathematically rigorously ensures that all the paths are well-behaved along the paths, so unlike other continuation approaches, no special handling of bifurcations is necessary. The method is embarrassingly parallelisable. The authors demonstrate the technique performance by solving several test cases up to the 14 buses. Finally, they discuss possible strategies for scaling the method to large size systems, and propose several applications for security assessments

Phenotypic and Functional Genomics Analyses of Salmonella for Food Safety Applications

Non-typhoidal Salmonella species have been major foodborne zoonotic pathogens causing serious problems in public health and food industry for several decades. Numerous Salmonella species have frequently been associated with different food commodities mainly poultry meat, eggs, and their products. This dissertation begins with a literature reviews discussing many aspects of Salmonella generally; and subsequently focused on two serotypes, Salmonella Enteritidis and S. Typhimurium as they are at the top of all other serovars responsible for most illness cases and outbreaks. In addition, some Salmonella strains have exhibited their ability to tolerate and survive many food processing treatments. We can divide this dissertation into two major sections. The first section is focused on S. Enteritidis. Since this serovar is the most foodborne routinely isolated from eggs and its products, we aimed to compare the ability of some strains in invading ovarian follicles of laying hens as a route of contaminating eggs (Chapter 2). As an important step in identifying gene function using high-throughput screening, we developed a mutant library of S. Enteritidis strain selected from the previous chapter using transposon mutagenesis (Chapter 3). This library will be a source for numerous future research projects to identify essential genes for survival and virulence in S. Enteritidis serving as potential targets to develop advance technology in controlling Salmonella. In the second section, mutants of S. Typhimurium were utilized to better understand its ability to grow in temperatures associated with human and poultry body temperatures in comparison to their wild type strain through phenotype microarray screening. In addition, we tested the same mutants in surviving some heat treatments practically applied in food processing systems (Chapter 4). In the last part (Chapter 5), a mutant library of S. Typhimurium was screened using Tn-seq technique to identify conditionally essential genes for surviving cold temperature on chicken carcass. All chapters of this dissertation including Literature Reviews (Chapter 1) have been written in journal formats to which they have been published or in preparation to be submitted

Salmonella

This Special Issue “Applications of Stable Isotopes and Tritium in Hydrology” addresses the current state-of-the-art applications of stable isotopes and tritium in studies of hydrological process and the whole water cycle. The six scientific papers belonging to this SI show a wide variety of isotope applications in various studies performed locally or regionally, but the conclusions obtained may be valid worldwide. Precipitation, groundwater, and surface waters belong to classical water bodies, while evapotranspiration, effects of farming, and drip water in karst caves seldom present applications of water isotopes