Survey on knowledge based methods to assist fault restoration in power distribution networks

Abstract. The motivation behind this paper is the many changes that happen in power distribution networks, theoretical developments, and their consequences on power distribution restoration. The stages of this process are defined with a focus on steps taken after the fault isolation. The final purpose of the operators is defined, as are the rules which must be strictly respected. Power quality issues are stressed. Moreover, recent techniques (metaheuristic and learning methods) are discussed. Heuristic rules also known as expert rules or knowledge based rules used in power restoration are outlined for their supportive role. Finally, a comparison of some selected papers is given. This enables to illustrate how the defined goals and changes in the network are reflected in recent literature. Our conclusion from the study of the state of the art is that there is still a lot of work to be done in developing novel techniques, integrating the goals and inserting the evolving features of power distribution networks

Optimal Allocation Of Distributed Renewable Energy Sources In Power Distribution Networks

In this dissertation study, various methods for optimum allocation of renewable distributed generators (DGs) in both balanced and unbalanced distribution networks have been proposed, developed, and tested. These methods were developed with an objective of maximizing several advantages of DG integration into the current distribution system infrastructure. The first method addressed the optimal sitting and sizing of DGs for minimum distribution power losses and maximum voltage profile improvement of distribution feeders. The proposed method was validated by comparing the results of a balanced distribution system with those reported in the literature. This method was then implemented in a co-simulation environment with Electric Power Research Institute\u27s (EPRI) OpenDSS program to solve a three phase optimal power flow (TOPF) problem for optimal location and sizing of multiple DGs in an unbalanced IEEE-123 node distribution network. The results from this work showed that the better loss reduction can be achieved in less computational time compared to the repeated load flow method. The second and third methods were developed with the goal of maximizing the reliability of distribution networks by optimally sitting and sizing DGs and reclosers in a distribution network. The second method focused on optimal allocation of DGs and reclosers with an objective of improving reliability indices while the third method demonstrated the cost based reliability evaluation. These methods were first verified by comparing the results obtained in a balanced network with those reported in literature and then implemented on a multi-phase unbalanced network. Results indicated that optimizing reclosers and DGs based on the reliability indices increases the total cost incurred by utilities. Likewise, when reclosers and DG were allocated to reduce the total cost, the reliability of the distribution system decreased. The fourth method was developed to reduce the total cost incurred by utilities while integrating DGs in a distribution network. Various significant issues like capital cost, operation and maintenance cost, customer service interruption cost, cost of the power purchased from fossil fuel based power plants, savings due to the reduction in distribution power losses, and savings on pollutant emissions were included in this method. Results indicated that integrating DGs to meet the projected growth in demand provides the maximum return on the investment. Additionally, during this project work an equivalent circuit model of a 1.2 kW PEM fuel cell was also developed and verified using electro impedance spectroscopy. The proposed model behaved similar to the actual fuel cell performance under similar loading conditions. Furthermore, an electrical interface between the geothermal power plant and an electric gird was also developed and simulated. The developed model successfully eliminated major issues that might cause instability in the power grid. Furthermore, a case study on the evaluation of geothermal potential has been presented

Identification and development of microgrids emergency control procedures

Tese de doutoramento. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 200

Modelling and analysis of smart localised energy system for a sustainable future power network

Combating the increasing effect of climate change and averting future energy crisis resulting partly due to our continued dependence on conventional energy sources requires exploring aggressively more sustainable means of generating and utilising energy. Currently, most developed countries are transitioning slowly from a fossil fuel dominated energy system to a sustainable and renewable energy based system. However, for the results of these transitions to be impactful and reduce the global temperature rise to the expected 1.5oC, the approach must be wholistic and encompassing. Although there are a lot of ongoing research in the areas of renewable energy integration into the grid, however, there seems to be a dearth of such studies in some specific aspect of the power system application. Consequently, this thesis models and performs several analyses on a smart localised energy system with the aim of decarbonising some aspects of the future power network. The study investigated the dynamics of residential power demand in Nigeria and modelled the residential energy consumption profile. An excel-based algorithm was developed and applied to the developed model. The results of the residential energy consumption was based on the appliance energy end use methodology. This was used to develop a load profile indicative of a typical urban residential energy demand in Nigeria and employed to predict the effects of residential loads on the power system. Following the frequent use of diesel generators by municipal councils to power street lighting, several case studies demonstrating how to optimise street lighting energy consumption and improve energy efficiency were carried out using simple economic analysis indices such as Life Cycle Cost (LCC), Annualized Life Cycle Cost (ALCC), Net Present Cost (NPC), Cost of Energy (COE), and Return on Investment (ROI). The solar photovoltaic (SPV) system had the lowest LCC and ALCC, thus making it the most economically viable option. The response of the power system to Distributed Energy Resources (DERs) integration was also investigated. Data from a real low voltage (LV) distribution network in Nigeria was obtained and used in modelling the network using PSCAD/EMTDC software package. Different impact studies considering addition of distributed generation sources and increase in the load were performed. Volt-VAr optimisation (VVO) was performed to enable the inverter-based PV systems participate actively in voltage regulation by the provision of flexible reactive power support. A net total of 1.359 MVAr and 1.301 MVAr respectively are utilised from the inverter to regulate voltage within the acceptable limits, hence reducing the substation reactive power by 19.8% and 18.9% respectively during the controlled case study. Also, the total active power loss did reduce from 0.437 MW to 0.172 MW while the deviation of consumer voltages from the nominal system voltage was reduced by 33.4% during the controlled case studies. Overall, the VVO did enhance power quality and reliability by improving the feeder voltage profile and reducing the active power losses in the network. Lastly, to decarbonise some operation of the power system and improve the system resilience, DERs integrated black start restoration (BSR) strategy was implemented. The formulated BSR problem was implemented as a dynamic optimisation problem and the simulation was performed on the Nigerian 330 kV 48-bus system. The mixed-integer linear programming (MILP) technique was adopted and modelled to suit the nature of the BSR method developed. The black start power restoration sequence and the development of a viable restoration strategy were actualised. The simulation of the MILP model was achieved in MATLAB® using the IBM CPLEXTM solver. For the Nigerian 330 kV 48-bus system analysed, it was observed that most loads were optimally restored before the 30th time step for a black start operation. Both the experimental and numerical methodology were adopted in the validation of energy storage system (ESS) adopted for the proposed BSR simulated study. The optimal battery power availability for participating in restoration was reached in less than 50 minutes, with ESS optimally contributing to power restoration achieving 4.3% & 18.1% for Kaduna and Jos respectively

Genetic Algorithms Applications to Power System Security Schemes

This thesis details the approaches which aim to automatically optimize power system security schemes. In this research, power system security scheme includes two main plans. The first plan, which is called the defence plan scheme, is about preventing cascading blackouts while the second plan, which is called the restoration plan, is about rebuilding the power system in case of failure of the first plan. Practically, the defence plan includes under-frequency load shedding and under-frequency islanding schemes. These two schemes are always considered the last stage of the defensive actions against any severe incident. It is recognized that it is not easy for any power system’s operational planner to obtain the minimum amount of load shedding or the best power system islanding formation. In the case of defence plan failure, which is always possible, a full or partial system collapse may occur. In this situation, the power system operator is urgently required to promptly restore the system. This is not an easy task, since the operator must not violate many power system security constraints. In this research, genetic algorithms and expert systems are employed, as optimization methods, to identify the best amount of load shedding and island formation for the defence plan and the shortest path to rebuild the power system for the restoration plan. In the process of designing the power system security scheme, the majority of the electromechanical power system security constraints are considered. It is well known that power system optimization problems often have a huge solution space. In this regard, many successful techniques have been used to reduce the size of the solution spaces associated with the optimization of the power system security schemes in this work. The Libyan power system is used as an industrial case study to validate the practicality of the research approaches. The results clearly show that the new methods that have been researched in this PhD work have shown great success. Using the Libyan power system, the optimized defence plan has been compared to the current defence plan. The results of this comparison have shown that the optimized defence plan outperforms the current one. Regarding the optimized restoration plan, the results present the fact that the Libyan power system can be restored in reasonable time.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Smart grid: service restoration in distribution power systems

Prilikom rešavanja problema obnavljanja pogona distributivnih sistema u postojećoj literaturi su uglavnom upotrebljavane ili modifikovane već poznate metode rešavanja problema iz drugih oblasti elektroenergetike. U radu je prezentovan pregled i opis postojećih načina rešavanja obnavljanja pogona U ovoj disertaciji je razvijen i verifikovan novi način rešavanja problema obnavljanja pogona. U disertaciji se razmatra problem obnavljanja pogona distributivnih sistema i u svetlu aktuelnih i globalnih napora kojim bi se postojeće elektroenergetske mreže transformisale u inteligentne elektroenergetske mreže. Iako postoji određeni broj konvencionalnih metoda i načina rešavanja obnavljanja pogona u distributivnim sistemima ipak novi koncept inteligentnih mreža zahteva usavršavanje postojećih kao i pronalaženje novih načina rešavanja ovog problema. Efikasno rešavanje obnavljanja pogona distributivnih sistema se u predloženoj temi ostvaruje pomoću algoritma koji je zasnovan na Primovom algoritmu, odnosno njegovoj modifikaciji. Primov algoritam, uključujući navedenu modifikaciju, je matematički detaljno opisan a zatim je primenljivost modifikovanog algoritma na rešavanje obnavljanja pogona distributivnih sistema sveobuhvatno analizirana. Iz toga proističe novi način rešavanja obnavljanja pogona distributivnih sistema koji se efikasno uklapa u širi koncept inteligentne mreže. Novi način rešavanja obnavljanja pogona je sastavni deo kompletno razvijenog algoritmom koji uključuje i proračune tokova snaga, rasterećenje preopterećenih elemenata prilikom rešavanja obnavljanja pogona kao i generisanje potrebnih prekidačkih akcija. Na kraju je razvijeni algoritam testiran na modelu složene distributivne mreže...Methods and approaches for the solving of the service restoration problem in the existing literature are based on well known methods that are also used for the solving of other problems in electrical power systems. Review of the methods and approaches is presented in this dissertation. New approach for the solving of the service restoration in distribution systems is developed and verified in this dissertation. The relation between the service restoration problem and transformation of conventional electrical power networks into smart grid are addressed in the dissertation. Although there is a number of known methodologies and approaches for solving the service restoration of the distribution power systems, an improvement of existing methodologies and approaches or research for new ones in order to accommodate the smart grid requirements are required. An effective service restoration approach proposed in the dissertation is based on modified Prim’s algorithm. Prim’s algorithm including its modification is mathematically described in details followed by comprehensive analysis of the modified Prim’s algorithm implementation to the solving of the service restoration. The new approach for the solving of the service restoration problem in distribution networks that can be incorporated into smart grid concept is derived from the analysis. Proposed new approach for the solving of the service restoration problem is incorporated in the developed algorithm. The algorithm also contains other typical distribution power system analysis tools such as load flow, load transfer from elements that are overloaded during the service restoration calculations, and the filtering of the required switching actions. The developed algorithm is tested on the complex model of the distribution network..

Optimización multiobjetivo aplicada a la ubicación y dimensionamiento de generación distribuida renovable en sistemas de distribución, considerando aspectos ambientales y sociales

La ubicación óptima de generación distribuida es un problema de gran importancia en la planificación de sistemas eléctricos y un reto importante en la expansión del uso de energías renovables en el ámbito de los sistemas de distribución de energía eléctrica. Sin embargo, la gran dificultad en la solución de este problema y las limitaciones del mismo al considerar el entorno social y ambiental, reducen la capacidad de los planificadores de este tipo de sistemas de proporcionar soluciones más integrales, constituyéndose en un importante reto para la comunidad científica. Es por ello, que el presente trabajo aborda la inclusión de variables sociales y ambientales en la modelación matemática del problema objeto de estudio y el diseño y prueba de algoritmos que ofrezcan soluciones de alta calidad, todo ello con el fin de dotar a los planificadores de sistemas de distribución de metodologías y herramientas que les permitan obtener soluciones de mejor calidad y más integrales al considerar entornos más complejos. Consecuencia de lo anterior el presente trabajo propone dos modelaciones matemáticas del problema objeto de estudio las cuales consideran aspectos como las pérdidas comerciales y el impacto visual. Además de ello, también se proponen tres algoritmos metaheurísticos que brindan soluciones de buena calidad para las modelaciones propuestas. Todo lo anterior con el fin de mejorar las herramientas de los planificadores de sistemas de distribución eléctrica y de tal manera facilitar el uso de las energías renovables para tal fin.DoctoradoDoctor en Ingeniería Industria