Energy management accordingto to load conditions for lithium battery system fed by photovoltaic panels in the microgrids

For centuries, most of the electrical energy obtained from fossil fuels. Today, energy is a strategic value and became a phenomenon that shows the level of development of countries. However, the pollution problem that the fossil fuels cause and the amount of carbon emission associated with the fossil fuels reached such a dangerous extent would damage the balance of the world. This condition forced the governments to find new energy sources. To achieve the target of reducing carbon emissions, future electricity generation will progress with diminishing reliance on fossil fuels, growing use of renewable energy sources and with a greater interest for the environment. Renewable energy resources offered as the alternative sources to fossil fuels, which are currently increasing in popularity. However, a large part of the world's energy still supplied from the fossil fuels. The most commonly used systems from renewable energy sources are solar and wind derived systems. As these renewable energy sources have an environmentally friendly and sustainable structure, their usage rate is increasing. On the other hand, although they are environmentally friendly and useful they have a nature-dependent characteristic. Besides, most of the renewable energy sources are intermittent in their nature, which presents a challenge in energy generation and load balance maintenance to ensure power network stability and reliability. One of the most important problems in adding renewable energy sources to electric power systems is that the energy generated from these sources is often unstable and variable depending on the climatic conditions. Electricity can be generated from solar energy, when the sun shines very well. The energy production values are constantly changing according to the climatic conditions (solar brightness). When the sun is brightest, the photovoltaic systems produce electrical energy in a stable manner, while the electricity production lessens in cloudy condition and eventually the electricity production stops in the evening. The electricity productions from the wind energy systems are also dependent on the environmental conditions such as the speed of the wind. The unstable and intermittent nature of renewable energy sources poses significant problems for the continuity of energy production. For this reason, the energy generated from renewable energy sources are not synchronize with the general energy demand. Therefore, the energy storage systems are necessary when the users do not demand the energy and the amount of peak energy generated from the renewable energy sources is large. When it comes to renewable energy source, hydroelectric power sources come first. However, hydroelectric power plants are only being able to apply on the places where natural structures let through. Studies about the important renewable energy sources such as wind and solar power have accelerated recently. The discontinuous power characteristics of renewable energy sources reveal various quality and reliability problems for the electric supply system. In an attempt to overcome these problems and increase the rate of making use of renewable energy sources, energy storage solutions come to the scene first. The use of energy storage applications with the use of microgrids provides quality power to the loads. While energy storage technologies do not represent energy sources, they provide valuable benefits to improve stability, power quality and reliability of supply. Battery technologies have improved significantly in order to meet the challenges of practical electric vehicles and utility applications. The power network faces great challenges in transmission and distribution to meet demand with unpredictable daily and seasonal variations. Electrical energy storage recognized as underpinning technologies to have great potential whereby energy is stored in a certain state according to the technology used and converted to electrical energy when needed. If renewable energy systems used in conjunction with storage units, the generated energy will be stored to ensure the continuity of energy for users. There are various energy storage alternatives. Particularly, batteries are among the indispensable ones as storage unit with the development of technology. The use of ultracapacitors in applications as a further energy storage unit is becoming widespread. Along with the difference between energy demand and energy production is in increasing trend, the central power stations producing quality power need to use energy storage technology. In this thesis, first the energy storage techniques are introduced. Batteries, compressed water storage, compressed air energy storage, flywheel energy storage, superconducting magnetic energy storage and supercapacity energy storage are some of the important energy storage methods. Solar and wind energy systems can be integrated with above energy storage technologies to form hybrid systems. Today, power systems are focused on local systems closer to load centers. Energy storage systems are mainly used for three purposes; energy stabilization, capacity to meet the load demand and distribution of power. Energy stabilization allows the distributed generation to operate at a constant output with the aid of energy storage systems, even if the load changes often. The distributed generation unit can serve a load with capacity even at very high peaks. Since the distributed generation unit does not respond quickly to load changes, problems of power quality can be further increased. However, if the energy storage unit is connected in parallel to the load, the energy storage unit may meet this need for any sudden change in energy demand. When the need is low, it can be charged by the distributed generation unit and distributed generation runs continuously with the same output. The capacity to meet the required capacity of the energy storage unit is such that the distributed generation unit is energized in the proper amount when not in operation. The distribution of the power allows the distributed generation owners to operate in advance regardless of the power that the distributed generation unit is generating at that moment. Energy sources such as photovoltaic cell and wind energy depend on solar radiation and wind. However, when combined with an energy storage system and a non-distributable system, it becomes a distributable system. In this thesis, smart grid and energy storage systems are mentioned first. History and detailed information about solar energy has been given from renewable energy sources and batteries have been preferred as a storage system. The technical information is shared with the history of the batteries. In this thesis, a battery system is selected as an effective energy storage method to increase the performance of the photovoltaic system. In this context, different energy storage systems classified for different purposes for comparative state analysis of the battery system have also been examined. In the introduction of the thesis, the overall energy system in Turkey is examined and then the smart grid systems were introduced. Fossil fuels and renewable energy systems are described comparatively and the advantages and disadvantages of these energy systems are discussed. The integration of energy storage units fed by renewable energy sources in intelligent networks has been defined and studied in detail. In this context, the history of solar energy, how to obtain energy from the sun and solar energy potential in Turkey have been described. The main objective of the thesis is to model microgrid in Matlab Simulink environment having a solar panel supported by a battery system as an energy storage unit. In different loads, network connection and island mode network design is done. Charge and discharge conditions of the battery, the status of the solar panel at different periods, and the simulation results of power and voltage drop are interpreted. As a result, the operating system of the network was simulated using the Matlab Simulink program and the results were analyzed in the numerical application section.