Wind power installations are growing rapidly throughout the world due to environmental concerns associated with electric power generation from conventional generating units. Wind power is highly variable and its uncertainty creates considerable difficulties in system operation. Reliable operation of an electric power system with significant wind power requires quantifying the uncertainty associated with wind power and assessing the capacity value of wind power that will be available in the operating lead time. This thesis presents probabilistic techniques that utilize time series models and a conditional probability approach to quantify the uncertainty associated with wind power in a short future time, such as one or two hours. The presented models are applied to evaluate the risk of committing electric power from a wind farm to a power system. The impacts of initial wind conditions, rising and falling wind trends, and different operating lead times are also assessed using the developed methods. An appropriate model for day-ahead wind power commitment is also presented. Wind power commitment for the short future time is commonly made equal to, or a certain percentage, of the wind power available at the present time. The risk in meeting the commitment made in this way is different at various operating conditions, and unknown to the operator. A simplified risk based method has been developed in this thesis to assist the operator in making wind power commitments at a consistent level of risk that is acceptable to the system. This thesis presents a methodology to integrate the developed short-term wind models with the conventional power generation models to evaluate the overall operational reliability of a wind integrated power system. The area risk concept has been extended to incorporate wind power, evaluate the unit commitment risk and the well- being indices of a power system for a specified operating lead time. The method presented in this thesis will assist the operator to determine the generator units and the operating reserve required to integrate wind power and meet the forecast load for a short future time while maintaining an acceptable reliability criterion. System operators also face challenges in load dispatch while integrating wind power since it cannot be dispatched in a conventional sense, and is accepted as and when present in current operational practices. The thesis presents a method to evaluate the response risk and determine the unit schedule while satisfying a specified response risk criterion incorporating wind power. Energy storage is regarded as an effective resource for mitigating the uncertainty of wind power. New methods to incorporate energy storage with wind models, and with wind-integrated power system models to evaluate the wind power commitment risk and unit commitment risk are presented in this thesis. The developed methods and the research findings should prove useful in evaluating the operating risks to wind farm operators and system operators in wind integrated power systems.

Doctor of Philosophy / Electrical and Computer Engineering / Ruth D. Miller / Optimizing renewable distributed generation in distribution systems has gained popularity with changes in federal energy policies. Various studies have been reported in this regard and most of the studies are based on optimum wind and/or solar generation planning in distribution system using various optimization techniques such as analytical, numerical, and heuristic. However, characteristics such as high energy density, relatively lower footprint of land, availability, and local reactive power compensation ability, have gained increased popularity for optimizing distributed wind generation (DWG) in distribution systems. This research investigated optimum distributed generation planning (ODGP) using two primary optimization techniques: analytical and heuristic. In first part of the research, an analytical optimization method called “Combined Electrical Topology (CET)” was proposed in order to minimize the impact of intentional structural changes in distribution system topology, in distributed generation/ DWG placement. Even though it is still rare, DWG could be maximized to supply base power demand of three-phase unbalanced radial distribution system, combined with distributed battery energy storage systems (BESS). In second part of this research the usage of DWG/BESS as base power generation, and to extend the ability to sustain the system in a power grid failure for a maximum of 1.5 hours was studied. IEEE 37-node, three-phase unbalanced radial distribution system was used as the test system to optimize wind turbines and sodium sulfide (NaS) battery units with respect to network real power losses, system voltage profile, DWG/BESS availability and present value of cost savings. In addition, DWG’s ability to supply local reactive power in distribution system was also investigated. Model results suggested that DWG/NaS could supply base power demand of a threephase unbalanced radial distribution system. In addition, DWG/NaS were able to sustain power demand of a three-phase unbalanced distribution system for 1.5 hours in the event of a power grid failure.

Morgongåva is an urban centre in Sweden, with several challenges in the electrical power grid. In order to use the power grid more efficiently, this report investigates potentials of installing a battery energy storage system (BESS). Focus lies on finding economic and technical benefits of reducing power peaks, which occur during high demand hours when transmitting energy is more expensive. This method is referred to as peak shaving. Further, economic calculations if installing a BESS are based on electricity pricing data. Calculations regarding technical benefits are based on net power demand data. Further, the study shows that the usage of the grid, which was measured with the load factor, would increase and thus allow installation of more power sources and connecting more load to the grid. The load factor was estimated to increase by an average of 2.12 percent each month in 2019. In one year, the economic profit was estimated to be 91,000 kr. The conclusion is that there are economic profits for Sala-Heby Energi of installing a BESS, but more importantly a BESS has technical consequences in the power grid. Where technical benefits are important in order to reach the goals of Agenda 2030 but also to obtain a more reliable grid for the customers. A sensitivity analysis shows that the model is robust. Thus, the conclusion is that Sala-Heby Energi and the local electricity grid in Morgongåva would benefit from installing a BESS.

Magíster en Ciencias de la Ingeniería, Mención Eléctrica. Ingeniero Civil Eléctrico / La creciente penetración de energías de carácter variable en los últimos años permite prever que los sistemas eléctricos de potencia requerirán la incorporación de nuevas tecnologías que flexibilicen su operación. Entre estas tecnologías, una de las más importantes son los sistemas de almacenamiento basados en baterías (BESS) los que han demostrado tener la capacidad de entregar un amplio abanico de servicios a los SEP. En particular, en la bibliografía se menciona que los BESS tienen capacidad de aportar a la estabilidad transitoria de ángulo de los SEP, pero pocos trabajos profundizan en esto. Más aún, la incorporación de BESS en el sistema abre el problema de localizarlos óptimamente, lo que ha sido abordado principalmente desde perspectivas de operación económica, reducción de pérdidas o regulación de tensión. En este trabajo se estudia como la interacción de los BESS con los sistemas eléctricos permite mejorar su desempeño dinámico en términos de estabilidad transitoria. Comprendido esto, se diseña una metodología de localización óptima de módulos BESS, considerando criterios de estabilidad transitoria. El estudio demuestra que el intercambio de potencia de los BESS permite elevar la capacidad de transferencia de potencia activa de las máquinas del sistema durante una perturbación. Esto reduce la aceleración de los ángulos de rotor durante y después de la contingencia, aumentando la capacidad del sistema de mantener una operación estable. Se estudia además que este aporte del BESS se puede ver manifestado en el criterio de las áreas iguales, que determina el margen de estabilidad del sistema como la diferencia entre el área desacelerante y el área acelerante. Este margen de estabilidad para sistemas de varias máquinas se puede determinar según el equivalente SIME del sistema (single machine equivalent) el cual condensa la dinámica de los ángulos de todas las máquinas en la dinámica de una máquina equivalente. Por otra parte, el problema de localización óptima es un problema discreto, combinatorial, no lineal, por lo que se utilizan algoritmos genéticos (GA) para explorar el espacio de soluciones factibles. Si bien los GA no garantizan la obtención de optimalidad global, se ha demostrado que tienen una notable capacidad para encontrar soluciones cercanas al óptimo en tiempos de computo reducidos. Para evaluar el desempeño dinámico de una distribución de BESS, el algoritmo evalúa el margen de estabilidad del equivalente SIME del sistema. La metodología se implementa en el IEEE 39 bus system, modificado para representar un escenario de alta penetración renovable. La metodología permite la obtención de una distribución de módulos BESS que mejora el desempeño transitorio del sistema, focalizando el aporte de los BESS en torno a aquellas contingencias con peores desempeños dinámicos. Se comprueba además la capacidad del GA de encontrar buenas soluciones en tiempos de cómputos razonables, requiriendo la exploración de una ínfima porción del espacio de soluciones factibles para encontrar una buena distribución. Se verifica también la pertinencia del margen de estabilidad del equivalente SIME como una buena medida del desempeño dinámico del sistema.

The purpose of this study is to analyse how a battery energy storage system (BESS) can support the frequency and voltage stability for an islanded microgrid containing a hydropower plant. Two different microgrids, both situated in Sweden, are evaluated. Modelling and dynamic simulations are conducted in the PowerFactory tool. The result shows that both the frequency and the voltage control can be improved with the BESS. However, with the allowed limit of ± 1 Hz, not all simulated scenarios including a BESS meets the requirement. A large difference between the BESS and generator capacity might be a possible cause for this. By dividing the larger loads so that smaller loads are attained, the frequency deviation might be reduced. Furthermore, by adjusting the systems PID-parameters according to the island mode operation, faster regulation can be attained. The system operates according to the Master slave control strategy, with the hydropower being the master unit with voltage control and the BESS being a slave unit with PQ control. The ability to operate an islanded microgrid can ensure the supply of electricity to inhabitants and vital functions in society. By utilizing a BESS for increasing electric stability, emission of CO2 is indirectly mitigated. As cost for BESS are expected to decrease rapidly, they will be accessible for utilization all over the world.

No description available.

In deregulated electricity markets, profit driven electricity retailers compete to supply cheap reliable electricity to electricity consumers, and the electricity consumers have free will to switch between the electricity retailers. The need to maximize the profits of the electricity retailers while minimizing the electricity costs of the electricity consumers has therefore seen a drastic increase in the research of electricity markets. One of the factors that affect the profits of the electricity retailers and the energy cost of the consumers in electricity retail markets is the supply and demand. During high-supply and low-demand periods, the excess electricity if not managed, is wasted. During low-supply high-demand periods, the deficit supply can lead to electricity blackouts or costly electricity because of the volatile electricity wholesale spot market prices. Research studies have shown that electricity retailers can achieve significant profits and reduced electricity costs for their electricity consumers by minimizing the excess electricity and deficit electricity. Existing studies developed load forecasting models that aimed to match electricity supply and electricity demand. These models reached excellent accuracy levels, however due to the high volatility character of load demand and the rise of new electricity consumers, load forecasting alone is unable to mitigate excess and deficit electricity. In other studies, researchers proposed charging the electricity consumers’ batteries with excess electricity during high-supply low-demand periods and supplying their deficit electricity during low-supply high-demand periods. Electricity consumers’ incorporating batteries resulted in minimized excess and deficit electricity, in turn, maximizing the profits for the electricity retailers and minimizing the electricity costs for the electricity consumers. However, the batteries are consumer centric and only provide battery energy for the battery-owned consumer. Electricity consumers without battery energy during low-supply highdemand periods have electricity blackouts or require costly electricity from the electricity wholesale spot market. The peer-to-peer (P2P) energy sharing framework which allows electricity consumers to share their energy resources with one another is a viable solution to allow electricity consumers to share their battery energy. P2P energy sharing is a hot topic in research because of its potential to maximize the electricity retailers’ profits and minimize the electricity consumers’ electricity costs. Due to the increased profits for the electricity retailer and reduced electricity costs for the electricity consumers from implementing battery charging and P2P energy sharing, this dissertation proposes a day-ahead electricity retail market structure in which the electricity retailer supplies consumers’ batteries with excess electricity during high-supply low-demand periods, and during low-supply highdemand periods the electricity retailer discharges the consumers’ batteries to supply their deficit supply or supply their peers’ deficit supply. The electricity retailer aims to maximize its profits and minimize the electricity cost of the electricity consumers in its electricity retail market, by minimizing the excess and deficit electricity. The problem is formulated as a non-linear optimization model and solved using game theory. This dissertation compares the profits of the electricity retailer and electricity costs of the consumers that charge their batteries with excess electricity, discharge their batteries and purchase electricity from their peers to supply their deficit supply, with consumers that only charge their batteries with excess electricity but do not share their battery energy with their peers, consumers that only purchase electricity from their peers to supply their deficit supply but do not employ a battery, and consumers that neither employ a battery nor purchase electricity from their peers to supply their deficit supply. The results show that the consumers that charge their batteries with excess electricity, discharge their batteries and purchase electricity from their peers to supply their deficit supply achieved the lowest electricity cost and highest profits for the electricity retailer. / Dissertation (MEng)--University of Pretoria, 2020. / Electrical, Electronic and Computer Engineering / MEng / Unrestricted

The rising use of fossil fuels and the resulting rise in environmental harm have fueled the advancement of automobiles that are fuel-efficient. A severe existential challenge facing the planet earth has given rise to hybrid electric vehicles (HEVs), which have developed from their incipient stage and are shown promise as a solution. Additionally, when needed to produce peaking power, batteries' efficiency is reduced. Instead, supercapacitors have smaller energy storage capacity but can withstand peaking power. Designing a clever method to manage the energy balance between a supercapacitor and a battery is the main goal of this research. Different topologies are used to study the battery-supercapacitor energy storage system in great detail. Nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons (HC), and other harmful gases are less released when a battery-supercapacitor energy storage system is integrated. Additionally, it can lower the load on the battery, extending its life and improving its performance in HEVs.

Det finns en ökande efterfrågan på förnybar elproduktion och effektiva lösningar att kombinera med denna. Ett flertal tidigare arbeten har undersökt energilagringssystem (ESS) och dess lönsamhet i olika tillämpningar. Det råder en osäkerhet kring lönsamheten hos ESS för ökad självkonsumtion i Sverige. Detta arbete undersöker lönsamheten hos batterilagringssystem (BESS) som används i syftet att öka självkonsumtionen för aktörer med solceller i den svenska bostadssektorn. En modell konstruerades baserat på Levelized Cost of Storage (LCOS), och indata till modellen varierades för olika scenarier. Resultaten visade att BESS kostnader i dagsläget är för höga, med LCOS mellan 1,68 kr/kWh och 3,56 kr/kWh beroende på aktör och indata. För lönsamhet krävs reduktion av LCOS mellan 55% och 85%. Vidare undersöker arbetet vilka variabler som har störst påverkan på BESS lönsamhet. En känslighetsanalys genomfördes, där CAPEX, antalet battericykler per år, WACC och skattereduktioner vid elhandel identifierades som viktiga variabler. Arbetet visade att det antagligen krävs en kombination av högre elpriser och reducerade investeringskostnader för att motivera en investering i BESS. Utöver ökad självkonsumtion behövs ytterligare värden för att motivera en investering i BESS inom en snar framtid. / There is a growing demand for renewable power generation and efficient solutions to combine with renewables. Previous works have explored energy storage systems (ESS) and their profitability in various applications. There is an uncertainty about the profitability of ESS for increased self-consumption in Sweden. This thesis explores the profitability of battery energy storage systems (BESS) used for increased self-consumption for stakeholders with solar photovoltaics in the Swedish residential sector. A model based on levelized cost of storage (LCOS) was constructed, and varying input values were used for different scenarios. The results showed that the current cost of BESS is too high, with LCOS ranging between 1,68 SEK/kWh and 3,56 SEK/kWh depending on the stakeholder as well as input data. For profitability, a reduction of LCOS between 55% and 85% is needed. Furthermore, this thesis explores which variables have the greatest effect on a BESS’s profitability. A sensitivity analysis was conducted, where CAPEX, the number of battery cycles per year, WACC and tax reductions linked to electricity trading were identified as important variables. This thesis concluded that higher electricity prices in combination with reduced investment costs is needed to justify an investment in BESS. Besides increased self-consumption, other values are needed to justify an investment in a BESS in the near future.

This thesis suggests a new approach to extend the lifetime of Lithium-ion batteries for a Home Energy Storage System equipped with a renewable energy source. The new configuration improves the lifetime of the energy storage device by using the pulsed charge-discharge method. The batteries in this system can be charged either using solar panels when solar energy is available or by the grid power during off-peak hours when the electricity cost is at its lowest rate. In the new configuration, the battery bank is split into two equal sections to employ pulsed charge-discharge method. Interrupting the charge or discharge current provides a relaxation time for the lithium ions to diffuse gradually into the electrodes material of Lithium-ion batteries, this reduces the damage in the microstructure of the electrodes and thus it helps to prolong the battery lifetime. The spilt bank strategy improves the longevity of Lithium-ion batteries while maximizing the solar energy utilization. This strategy leads to reduce the reliance on the grid power which decreases the consumer’s total energy cost as well. To show the usefulness of the new approach, different modes of operation are discussed in details along with simulation results. An experimental setup is also developed to evaluate the effectiveness of the new approach in extending the Lifetime of Lithium-ion batteries. / Thesis / Master of Applied Science (MASc)