This thesis proposes two novel algorithms to analyze whether the power system loses synchronism subsequent to credible contingencies. The two algorithms are based on the concept of Lyapunov exponents (LEs) and the Prony analysis respectively. The concept of LEs is a theoretically sound technique to study the system stability of nonlinear dynamic systems. The LEs measure the exponential rates of divergence or convergence of trajectories in the state space. Considering the higher computational burden associated with the convergence of the true LEs, a modified algorithm is proposed to study the transient stability of the post-fault power system. It is shown that the finite-time LEs calculated by the modified algorithm accurately predicts the said stability. If the power system is transient stable, the rotor angle trajectories of the post-fault system exponentially decay with time. The damping ratios of the dominant oscillatory modes present in these power swings provide the indication on the oscillatory stability. The improved Prony algorithm presented in the thesis can be used to identify the oscillatory stability of the power system subsequent to a contingency. It is shown that that these new algorithms can be used in two applications in power systems, online dynamic security assessment and online oscillations monitoring. The proposed algorithm for rotor angle security assessment first uses the LEs-based algorithm to identify the transient stability. The stable cases are then processed by the improved Prony algorithm. The proposed online oscillations monitoring algorithm uses an event-detection logic and a parallel filter bank before applying the improved Prony algorithm on the measured response to extract the dominant oscillatory modes and to determine their frequencies and damping ratios. The suitability of the two algorithms for the aforementioned applications is investigated using different case studies. It is shown that the computational burdens of the two algorithms are acceptable for the online applications. Furthermore, the oscillations monitoring algorithm, extracts only the dominant modes present in the input signal, extracts both low-frequency inter-area modes and sub-synchronous modes, and performs well under noisy conditions. These features make it more appropriate for wide-area monitoring of power system oscillations using synchronized measurements. / February 2016

Electric power is a basic requirement for present day life and its various economic sectors. To satisfy the ever-increasing needs for electricity, the number of generating units, transmission lines and distribution systems is rising steadily. In addition, electric power systems are among the most complex industrial systems of the modern age. Beside complexity, the generation of electric power is a main source of gaseous emissions and pollutants. The planning and operation of electric power systems must be done in a way that the load demand is met reliably, cost-effectively and in an environmentally responsible manner. Practitioners strive to achieve these goals for successful planning and operations utilizing various optimization tools. It is clear that the objectives to be satisfied are mostly conflicting. In particular, minimizing the fuel cost and the gaseous emissions are two conflicting and non-commensurate objectives. Therefore, multi-objective optimization techniques are employed to obtain trade-off relationships between these incompatible objective functions in order to help decision makers take proper decisions. In this thesis, two main power system operation problems are addressed. These are the economic load dispatch (ED) and the short-term hydro-thermal generation scheduling (STHTS). They are treated first as single-objective optimization problems then they are tackled as multi-objective ones considering the environmental aspects. These problems, single and multi-objective, are nonlinear non-convex constrained optimization problems with high-dimensional search spaces. This makes them a real challenge for any optimization technique. To obtain the optimal or close to optimal solutions, a modified bacterial foraging algorithm is proposed, developed and successfully applied. The bacterial foraging algorithm is a metaheuristic non-calculus-based optimization technique. The proposed algorithm is validated using diverse benchmark optimization examples before implementing it to solve the problems of this thesis. Various practical constraints are considered in the different cases of each problem. These include transmission losses, valve-point effects for both the ED and the STHTS problems and water availability and reservoir configurations for the STHTS problem. In all cases the optimal or near-optimal solution is obtained. For the multi-objective optimization cases, the Pareto optimal solution set that shows the trade-off relationship between the conflicting objectives is successfully captured.

Generation and transmission investment planning in deregulated markets faces new challenges particularly as deregulation has introduced more uncertainty to the planning problem. Tradi- tional planning techniques and processes cannot be applied to the deregulated planning problem as generation investments are profit driven and competitive. Transmission investments must facilitate generation access rather than servicing generation choices. The new investment plan- ning environment requires the development of new planning techniques and processes that can remain flexible as uncertainty within the system is revealed. The optimisation technique of Stochastic Dual Dynamic Programming (SDDP) has been success- fully used to optimise continuous stochastic dynamic planning problems such as hydrothermal scheduling. SDDP is extended in this thesis to optimise the stochastic, dynamic, mixed integer power system investment planning problem. The extensions to SDDP allow for optimisation of large integer variables that represent generation and transmission investment options while still utilising the computational benefits of SDDP. The thesis also details the development of a math- ematical representation of a general power system investment planning problem and applies it to a case study involving investment in New Zealand’s HVDC link. The HVDC link optimisation problem is successfully solved using the extended SDDP algorithm and the output data of the optimisation can be used to better understand risk associated with capital investment in power systems. The extended SDDP algorithm offers a new planning and optimisation technique for deregulated power systems that provides a flexible optimal solution and informs the planner about investment risk associated with uncertainty in the power system.

Orust Kretsloppsakademi is a nonprofit organisation, with a goal of annually generate the same amount of electrical energy that is consumed. Orust is an island on the west coast of Sweden, north of Gothenburg. The population of 15 000 reaches 40 000 during summer, due to the large amount of vacationer. The total electricity demand is 174 GWh a year with a maximum power need of 32 MW. This report presents an analysis for the plausibility of their plan and from a power system stability perspective, the effects on the electrical grid. The conclusion is that the restraints for development of power generation from wind, solar and wave generation, are the power systems capability to transfer power, primarily in the transformers of the grid. Various actions, such as constraints of power output at certain times, and clever location of generation facilities, reduces the utilisation rate of the line segments. In order to substantially decrease the utilisation rate of the line segments, the actions need to be combined. Executed simulations showed that Orust needs to be provided with reactive power, even if Orust is self-sufficient of active power, through its connection to the Swedish power system. The need for reactive power decreased when the feeding transformer allowed a reduced voltage in the regional network. Additionally, generation of reactive power could further increase the possibility for Orust to become self-sufficient on electricity generation.

There are presently worldwide targets for decreasing anthropogenic greenhouse gases (GHGs) emissions owing to global climate change concerns. Here in the United Kingdom, the government has committed to reduce its GHGs emissions by at least 80% by 2050 relative to 1990 levels. In order to achieve the ambitious 2050 targets and minimise cumulative emissions along the way, modern power systems are facing a series of great challenges. These challenges include extensive utilisation of renewable generation, diverse demand--side participation in power system operation and planning, as well as considerable application of emerging smart devices and appliances. All of these challenges will significantly increase the complexity of future power systems in terms of both operation and design. Regardless, the primary objective of power systems remains the same. That is the system must supply all the customers (responsive ones and non-responsive ones) with electricity as economically as possible and with an adequate level of continuity and quality. With the widespread utilisation of smart meters and appliances as well as the large-scale installation of different storage technologies, the services that demand response (DR) and electrical energy storage (EES) resources can provide will cover a wide range of ancillary services. More importantly, the grid-scale penetration of DR and EES resources is able to provide energy management and capacity support services, which can be considered as the alternative to generation resources. In this light, considerable amount of research has been done focusing on engaging particular types of electricity users with different kinds of incentives and/or tariff schemes, so that the economic benefits to both utilities and customers are optimised. However, no general framework for systematic assessment of the contribution to power system adequacy of supply from potential grid-scale penetration of DR and EES resources is available up till now, particularly taking specific consideration of DR's flexibility and payback characteristics as well as EES's operational parameters. The research work in this thesis therefore emphasises exclusively on the potential of grid-scale DR and EES resources to serve as alternative resources to electricity generation within the context of power system adequacy of supply. More specifically, based on literature survey of existing studies in similar topics, this thesis has made some substantial contributions and innovations, such as developing novel models of these emerging demand-side resources, implementing a systematic adequacy of supply assessment with new aspect to measure the level of adequacy of supply (new indices), proposing a novel and comprehensive framework for evaluation of the capacity credit of DR and EES, and analysing the economic value based on power system fundamental long--term costs of interruption and supply. Ultimately, this thesis has established a comprehensive framework for assessment of the contribution of DR and EES to power system adequacy of supply. Additionally, the numerical studies carried out in this thesis have enabled the inference of general adequacy of supply implications in terms of deploying DR and EES resources to provide capacity support to power systems.

abstract: An important operating aspect of all transmission systems is power system stability and satisfactory dynamic performance. The integration of renewable resources in general, and photovoltaic resources in particular into the grid has created new engineering issues. A particularly problematic operating scenario occurs when conventional generation is operated at a low level but photovoltaic solar generation is at a high level. Significant solar photovoltaic penetration as a renewable resource is becoming a reality in some electric power systems. In this thesis, special attention is given to photovoltaic generation in an actual electric power system: increased solar penetration has resulted in significant strides towards meeting renewable portfolio standards. The impact of solar generation integration on power system dynamics is studied and evaluated. This thesis presents the impact of high solar penetration resulting in potentially problematic low system damping operating conditions. This is the case because the power system damping provided by conventional generation may be insufficient due to reduced system inertia and change in power flow patterns affecting synchronizing and damping capability in the AC system. This typically occurs because conventional generators are rescheduled or shut down to allow for the increased solar production. This problematic case may occur at any time of the year but during the springtime months of March-May, when the system load is low and the ambient temperature is relatively low, there is the potential that over voltages may occur in the high voltage transmission system. Also, reduced damping in system response to disturbances may occur. An actual case study is considered in which real operating system data are used. Solutions to low damping cases are discussed and a solution based on the retuning of a conventional power system stabilizer is given in the thesis. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2015

abstract: This research develops decision support mechanisms for power system operation and planning practices. Contemporary industry practices rely on deterministic approaches to approximate system conditions and handle growing uncertainties from renewable resources. The primary purpose of this research is to identify soft spots of the contemporary industry practices and propose innovative algorithms, methodologies, and tools to improve economics and reliability in power systems. First, this dissertation focuses on transmission thermal constraint relaxation practices. Most system operators employ constraint relaxation practices, which allow certain constraints to be relaxed for penalty prices, in their market models. A proper selection of penalty prices is imperative due to the influence that penalty prices have on generation scheduling and market settlements. However, penalty prices are primarily decided today based on stakeholder negotiations or system operator’s judgments. There is little to no methodology or engineered approach around the determination of these penalty prices. This work proposes new methods that determine the penalty prices for thermal constraint relaxations based on the impact overloading can have on the residual life of the line. This study evaluates the effectiveness of the proposed methods in the short-term operational planning and long-term transmission expansion planning studies. The second part of this dissertation investigates an advanced methodology to handle uncertainties associated with high penetration of renewable resources, which poses new challenges to power system reliability and calls attention to include stochastic modeling within resource scheduling applications. However, the inclusion of stochastic modeling within mathematical programs has been a challenge due to computational complexities. Moreover, market design issues due to the stochastic market environment make it more challenging. Given the importance of reliable and affordable electric power, such a challenge to advance existing deterministic resource scheduling applications is critical. This ongoing and joint research attempts to overcome these hurdles by developing a stochastic look-ahead commitment tool, which is a stand-alone advisory tool. This dissertation contributes to the derivation of a mathematical formulation for the extensive form two-stage stochastic programming model, the utilization of Progressive Hedging decomposition algorithm, and the initial implementation of the Progressive Hedging subproblem along with various heuristic strategies to enhance the computational performance. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2017

Thesis (DTech (Electrical Engineering))--Cape Peninsula University of Technology, 2010. / Static state estimation is a mathematical procedure in which physical measurements from sub-stations and physical model are combined in an optimal way. That is, the measurements obtained from the sub-stations are used with the physical model and the states of the power system are selected or calculated such that the states match the measurements in some best way. The states of a power system are the bus voltage magnitude and voltage angle of each bus of the system. Static state estimation is an increasingly common part of electrical power utility energy management systems (EMS). It plays a critical part in a day-to-day operation of a power system utility. The system measurements obtained from static estimation are used for realtime operations like optimal power flow calculations and contingency analysis. Proper system operations with regards to avoidance of insecure conditions includes situational awareness, therefore, the static estimator plays an important role in power system security. A further motivation: in increasingly electrical power deregulation, more economic operations mean savings for customers and electrical power provider alike. Economic benefit might be realized if system operators have a more accurate situational awareness of the system through improved power system state estimator. The objective of the study was to develop method, algorithm and MATLAB program for solution of power system state estimation using parallel processing techniques. In achieving the objective, the study has concentrated on development of an approximate Tanzanian power system network model comprising of 30 buses and used as a case study; decomposing the bus admittance matrix of the model into 3 interconnected sub-systems; development of mathematical model for real and reactive power injections, real and reactive power flows in the transmission lines and tie-lines connecting the sub-systems; development of measurement data model for voltage magnitude, real and reactive power injections, real and reactive power flows; formulating of a constrained weighted least absolute value state estimation problem; development of decomposition-coordination method and algorithm; and formulating algorithm and MATLAB program for solving the constrained state estimation problem using parallel processing technique.

CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / Neste trabalho foi desenvolvido o estudo e as aplicaÃÃes das condiÃÃes de estabilidade na operaÃÃo do sistema elÃtrico de potÃncia incorporado em um simulador interativo de usinas termelÃtricas de ciclo combinado, que permita melhorar os processos de treinamento e, consequentemente, o nÃvel de qualidade dos futuros operadores e mantenedores de usinas termelÃtricas, bem como manter atualizados os atuais operadores. Um pequeno conjunto de definiÃÃes e conceitos das Ãreas de âestabilidade, confiabilidade e anÃlise de desempenho de sistemas de potÃnciaâ à apresentado com o objetivo de distinguir a operaÃÃo no sistema de potÃncia. O simulador contempla a modelagem matemÃtica de 3 e 6 ordem das partes fÃsicas e elÃtricas da mÃquina sÃncrona, a modelagem de seus controladores projetados como compensador dinÃmico e mÃtodos numÃricos para a resoluÃÃo da equaÃÃo diferenciais. O cÃlculo dos parÃmetros à realizado atravÃs de um programa desenvolvido com a ferramenta computacional MATLAB e comparados aos implementados em uma UTCC. As simulaÃÃes e validaÃÃo de variaÃÃes dos modelos sÃo realizadas com os programas ANATEM - CEPEL para analisar a eficiÃncia do sistema projetado e avaliar a melhoria do desempenho dinÃmico do sistema. / This work was developed the study and application of conditions of stability in the operation of power system embedded in an interactive simulation of combined cycle power plants that will improve the training processes and therefore the quality of the future operators and maintainers of thermoelectric plants and keep up the current operators. A small set of definitions and concepts in the areas of "stability, reliability and performance analysis of power systems" is presented in order to distinguish the operation in the power system. The simulation includes the modeling of the 6th order of the parts of the physical and electrical synchronous machine, the modeling of its Controlled designed as dynamic and rewarding numerical methods for solving differential equation. The calculation of the parameters is accomplished through a program developed with MATLAB software tool and compared to those implemented at the plant. The simulations and validation of variations of the model are performed with the programs ANATEM - CEPEL to analyze the efficiency of the system designed to evaluate and improve the dynamic performance of the system.

Government of Sri Lanka has policy target to achieve 100% electrification by end of year 2012. Grid-based electrification is possible up to maximum 95% of the population in Sri Lanka. Balance 5% of the electrification has to be mainly depending on off-grid technologies such as solar PV, wind, biomass and micro hydro.   Use of renewable based off-grid technologies is limited by the seasonal variation of the resource. This barrier could be overcome by coupling renewable based power generation technologies with a diesel generation thereby forming a hybrid power system. Given the comparatively higher investment cost, a hybrid power plant needs to be carefully designed and optimized to generate electricity at competitive prices.   There are some Isolated Islands located in the Jaffna Peninsula (Northern part of Sri Lanka) called Eluvaithivu, Analaithivu, Nainathivu and Delft Islands. These islands are far away from mainland. At present diesel generators are supplying electricity to these islands for limited hours. Electrification rate of these islands are very low due to the Grid limitations. Also cost of electricity generation is very high due to the high diesel price.   The main objective of the present study is “Selection of optimized mix of renewable based power generation technologies to form a mini-grid and to supply reliable, cost effective electricity supply to the people living in Eluvaithivu Island’ and thereby support the 100% electrification target by Govt. of Sri Lanka in 2012.   Data collection, survey has been conducted in the Eluvaithivu Island to find out the status of present system, priority needs, resource data and load data to propose suitable power system for this Island. An extensive analyse was conducted using HOMER software model and the result is presented in the report. Optimum design emerges as a wind-diesel hybrid power system having wind turbines generator, diesel generators, battery bank, converter and a hybrid controller.   The result revealed that the economic viability of the project, in the form of a community owned wind-diesel hybrid power system operated on cost-recovery basis is not feasible. But it is an attractive option for CEB to reduce its long term losses on diesel fuel. In other words, if CEB implement this project, it would be an ideal win-win situation where both the CEB and the island community are benefited.