No description available.

No description available.

SaskPower has two separate systems, namely the North and the South systems. The South system contains SaskPower major generation and system load. The North system load is located relatively far from its generation (200 to 300 km). The North system is considered, therefore, to be electrically weaker than the South system. Recently there has been an interest in connecting the two systems to improve the security, stability and reliability of the integrated system. Grid interconnections, however, especially between weak and strong systems, often result in the arising of low-frequency oscillations between the newly connected areas. These oscillations that are termed “inter-area oscillations” exhibit, generally poor damping and can severely restrict system operations by requiring the curtailment of electric power transfers level as an operational measure. There are two options for SaskPower North and South systems interconnection, namely HVAC and HVDC interconnections (tie-lines). This thesis reports the results of digital time-domain simulation studies that are carried out to investigate the dynamic performance of a proposed 260 km, ± 110 kV, 50 MW Voltage-Sourced Converter HVDC tie-line that would connect SaskPower North and South systems. The potential problems that might arise due to such an interconnection, namely power flow control and low-frequency oscillations are studied and quantified and a proposed feasible solution is presented. In this context, the effectiveness of the HVDC and a Power Oscillations Damping (POD) controller in damping power system oscillations in the tie-line is investigated. Time-domain simulations are conducted on the benchmark model using the ElectroMagnetic Transients program (EMTP-RV). The results of the investigations have demonstrated that the presented HVDC link and its POD controller are effective in mitigating the low-frequency oscillations between the North and South systems at different system contingencies and operating conditions.

Under some conditions in real world, precise parameters and/or initial values of dynamic systems are hard to be determined. Fuzzy Differential Equation (FDE) is a powerful tool to model dynamical systems with the uncertainty of impreciseness. This thesis presents the first numerical solution for Fuzzy Differential Equations with multiple fuzzy parameters and initial Values (FDEPIV) problems. Previous approaches for solving the FDEs only focused on FDEs with single fuzzy condition. In this thesis, we applied the proper fuzzy arithmetic on Runge-Kutta method for solving the FDEPIV problems with multiple fuzzy parameters and initial conditions. Furthermore, comparing with directly applying the extension principle in solving FDEPIV, the complexity of the proposed method is much lower, and parallelization of the proposed algorithm is feasible. Numerical examples of the FDEPIV problems are presented to demonstrate the effectiveness of the proposed method.

Studien avser att ur ett ledningsperspektiv undersöka vilka faktorer som påverkar privata företag samt hur företagen arbetar för att vara flexibla och skapar förhållningssätt i relation till dessa. Vidare vill vi jämföra det empiriska materialet med det teoretiska resonemang som producerats i den vetenskapliga arenan för att bidra med insikter som kan utveckla forskning inom området. Det empiriska resultatet bygger på åtta kvalitativa intervjuer med representanter från HR-funktionen i företag inom privat sektor. Både resultat och vetenskaplig genomgång har visat på variationer av såväl påverkan som förhållningssätt. Företagens val av förhållningssätt eller strategi har gjorts med bakgrund av varierande orsaker och har lett till olika effekter beroende på verksamhetsspecifika förutsättningar. Detta medför svårigheter avseende definitionen av vad som påverkar, hur det påverkar samt hur företag bör förhålla sig. Vissa strategier visade sig fungera bra i en typ av verksamhet medan samma typ av strategi inte påstods vara möjlig i andra. Sammanfattningsvis kan vi konstatera att företagens möjlighet att förhålla sig till förändrade förutsättningar utgör deras överlevnads förmåga. Vidare har det visat sig att detta omfattar både företagets flexibilitet och dess förmåga att minska flexibilitetsbehovet.

This thesis presents a new general purpose power system simulation technique based on dynamic phasors and conventional power system simulation methods. The method developed in this work converts time-domain circuits to equivalent dynamic phasor representations. These dynamic phasor equivalents are then simulated using nodal analysis and numerical integrator substitution. Simple linear circuit models are presented first in order to demonstrate that the new method is capable of accurately simulating small systems. The method developed in this work is then expanded to include control systems, power electronic converters, and synchronous machines. Visual comparisons with simulation results obtained using time-domain electromagnetic transient simulators demonstrate that the new dynamic phasor-based technique is capable of accurately simulating power system components.

No description available.

No description available.

No description available.

Finding, understanding, and fixing bugs in software systems is challenging. Dynamic binary translation (DBT) systems provide a powerful facility for building program analysis and debugging tools. However, DBT abstractions are too low-level and provide limited contextual information to instrumentation tools, making it hard to implement such tools. In this theis, we introduce behavioral watchpoints, a new software-based watchpoint framework that simplifies the implementation of DBT-based program analysis and debugging tools. Behavioral watchpoints have two key features: 1) they provide contextual information at the instruction level which are directly available with watchpoints and 2) they enable specializing instruction-level instrumentation with individual data structures. We describe three applications that were easily developed using our watchpoint framework: detecting buffer overflows, detecting read-before-write and memory freeing bugs and detecting memory leaks. We implemented behavioral watchpoints using Granary, a DBT framework for instrumenting operating system kernels. We evaluated the overheads of watchpoints for analyzing and debugging operating system kernel modules and show that these overheads are reasonable.