Abstract: _In the introductory part of the paper, the reasons for voltage regulation in the distribution network are explained, which is necessary for the purpose of ensuring, on average, equal amounts of voltage for network users as close as possible to the nominal value. Then the entire electric power system is described, what it consists of and how it is divided, all the way to the end users, i.e. consumers.

In the third chapter, the need for voltage regulation is described more precisely and some general methods of voltage regulation of the distribution network are given.

After presenting the general methods of voltage regulation, the fourth chapter explains in more detail the methods of passive and active regulation, such as automatic regulation of the HV or MV bus of the main substation, voltage compensation, voltage regulation using active sources in the network, optimization algorithm.

In the last part of the work, the optimization of the voltage conditions and the position of the transformer switches was carried out using mathematical programming. The optimization was performed on a modified IEEE 33-bus model extended with distributed sources. After the analyzes carried out, we can notice an improvement in voltage conditions along the entire network._

Abstract: The paper presents a tool for calculating the profitability of investment in small photovoltaic power plants. At the beginning of the paper, the basic goals of European countries regarding consumption from renewable energy sources are presented. Then the basic parts of the photovoltaic system (photovoltaic cell, photovoltaic module, inverter and meter) are described and the methods of connecting solar power plants to the power grid are described too. This is followed by a section in which incentives and laws are presented for the purpose of encouraging ever-increasing production from renewable energy sources, including solar energy. Then, the procedure for calculating solar radiation (Liu-Jordan, Klein method) is described, which is later used in the cost-effectiveness calculation tool. The last chapter presents the basic economic parameters used in solar power plant profitability analyzes (discounting, internal rate of return method, present value method, future value method,…). Also a tool (excel document) for calculating the profitability of investments in solar power plants are presented, which was applied at several locations in Croatia. The calculation results are tabulated and commented on for each location.

Abstract: THE IMAPCT OF ELECTRIC VEHICLE CHARGING STATION CONNECTION ON THE ELECTRICAL NETWORK AND THE POSSIBILITY OF IMPROVING NETWORK CONDITIONS THROUGH OPTIMAL CHARGING

Abstract: Electricity generation through distributed sources is increasingly used in the power system. Some benefits of this method of production are: production of electricity with less environmental pollution, lower price of electricity (thus higher economic profitability), higher quality of delivered electricity, potentially reduced investment in the electricity system. In this paper, we examine the pros and cons of integrating a distributed energy source into the electricity grid. In the second chapter, we talked about renewable electricity producers. In the third chapter, we dealt with the impact of renewable energy sources on the power system as well as the impacts on short circuits and losses in the network. The fourth chapter deals with the connection of the distributed system to the electricity network. An overview of the conditions and rules for connection and optimization of the connected distributed source is given. In the fifth chapter we talk about the challenges and solutions in production through distributed sources. Also, the principle of parallel and island operation of the source and the prevention of the negative effect of the distributed source on the electricity system are explained. In the sixth chapter, we made an analysis of a part of the power system to whose busbars we connected two wind power plants and two photovoltaic power plants. We have processed two cases: when the listed distributed sources are switched off, and when they work with their maximum power, and we have shown the impact of these sources on voltage conditions and labor losses in the network

Abstract: In this paper, theoretical bases on the Sun, its motion and solar radiation are given. The procedure of analytical calculation of solar radiation for a specific location and also for determining the optimal angle of inclination of photovoltaic modules at a specific location is also described. A detailed analysis of the geographical parameters of a particular location gave us the necessary knowledge about the dependence of the geographical position of the location and the associated solar radiation. Using the software PVsyst, the operation of the photovoltaic power plant was simulated and the calculation of the annual production for different angles of the photovoltaic module was performed. The analysis of the results of production simulations explains the influence of the angle of inclination of photovoltaic modules on the production curve and on the total amount of production of a solar power plant. Using the available tool, the optimal angle of inclination of the module was also calculated. Also, to investigate the impact of using the Sun tracking system, production simulations were conducted with their use. It has been concluded that Sun tracking systems are a relatively new technology that will develop and in some parts of the Earth they are very likely to find future use.

Abstract: The distribution network is part of a constantly evolving system. The increase in consumption and connection of new consumers requires network topology redefinition and requires the construction of new substations and distribution network power lines. In most European countries, distribution networks by its topology, is radial. For purposes of network planning, a non-automatic and automatic approach can be used. This thesis defines an automatic approach for distribution network expansion planning, so for this purpose, an optimization model was first mathematically defined, and then implemented in Python. Before the practical part, the criteria considered in the process of network expansion planning as well as the possibilities of its integration in the optimization models are presented.

Abstract: This paper analyzes the cost-effectiveness of building a small hydropower. The term small hydropower is considered to be all hydropowers with a capacity of 1-10 MW. The first part of the paper describes the parts of the hydropower plant in two groups: civil works and electromechanical parts. Civil work includes structural parts such as dams, devices to raise the water level, spillways, intake structures and penstock. A more complex group of small hydro parts includes a turbine and a generator. By choosing the right turbine, the cost-effectiveness of small hydro is higher. Small hydro-turbines can achieve efficiency up to 90%. The type of small hydro is selected depending on the terrain on which it is built, and they can be: run-of-river schemes, site configurations, schemes with the powerhouse at the base of a dam, schemes integrated with an irrigation canal. The final design solution of the small hydro is obtained as a result of a complex and interactive process, where, taking into account the impact on the environment, different technological possibilities are always compared, also taking into account the cost side of the project. The paper develops software for the analysis of annual electricity production from hydropower and cost-effectiveness analysis based on substrates defined by RETScreen software. Hydrological data are usually defined by a flow duration curve, which is assumed to represent conditions during the average hydrological year. Production from small hydropower in the mentioned model was determined on the basis of data on available, designed and residual flow, and on the basis of load, gross head and efficiencies/losses. Turbine efficiency can be entered manually if data are known or approximate expressions are used depending on the type of turbine and its basic parameters. Power available as a fuction of flow, capacity factor, total delivered energy, estimation of plant capacity - are calculated by given model equations, while the power duration curve is defined from the flow duration curve.

Abstract: In the first part of this master thesis basic parts of photovoltaic power plant are described (photovoltaic modules, substations, inverters, prefabricated structures and AC and DC cable distribution) and characteristics of large PV power plants. Through the second part of this work, concept of real large PV plant is defined in few variants and calculation of production and losses are performed. Topology of PV power plant is defined in two basic variants. In the first variant central inverters/substations are positioned in the center of PV modules which are connected on that inverter. In the second variant, central inverters/substations are positioned on the edge of main internal roads as well as on the edge of related group of PV modules. For each variants PV plant topology is defined for the slope of PV modules 15o, 20o and 25o, using Virtuosolar software. Using the PVSyst software net production and losses are calculated for all variants. Analysis of investment costs for the infrastructure, DC and MV AC cables and discounted costs of energy losses in DC cables is performed. It is shown that variant with „central“ positioned inverters/substations is significantly better from economic perspective.

Abstract: The quality of a certain distribution network, which is primarily measured by the reliability of electricity supply, is significantly influenced by the shape of the network, the method of grounding the neutral point, the types of faults and disturbances, and the selected relay protection. This paper describes the protection mechanisms of distribution transformers and MV distribution networks with regard to different types of faults and different types of grounding of the neutral points of the feeder transformers.

Abstract: This paper describes the short circuit calculation method in matrix form. In the first part of the paper, the types of short circuits were theoretically explained and expressions were obtained for short circuit currents and voltages after the failure, assuming that the voltage before the failure was 1 p.u. When calculating, it is important to know the impedance values ​​of the circuit elements due to the formation of the node impedance matrix. We have broken down the currents and voltages into their symmetrical components and thus made the calculation easier. In the second part of the work, for the analysis of short-circuit currents, we used Matlab in which we entered data, formed the node impedance matrix and calculated short-circuit currents using theoretically obtained expressions. Finally, on the example of the electrical network, a comparison was made of the obtained results for currents through the branches and voltages on the busbars, obtained with the help of Matlab, with the results obtained with the help of Powercad. From the attached tables, we can see that there are no excessive deviations in the results.

Abstract: The wind farm construction project is a multi-year complex project, during which all interested parties are exposed to numerous risks. Risk analysis is necessary in order for the investor and the project manager to better predict and avoid potential problems and costs during the project’s lifetime. Through the first part of the work, the theoretical foundations of wind energy, wind speed, and factors that influence wind speed are given. Below are described the basic parts and performances of wind farms, the way they are connected to the grid, as well as the cost structure of the wind farm project, the basic indicators of the economic profitability of the project and incentive measures for renewable energy sources, among which the most important change is the system of stimulating production from the system of guaranteed tariffs to the system of market premiums . In the project assignment, a financial analysis of the wind farm construction project was made according to the future model of stimulating production with a system of premiums. The basic risks in the wind farm construction project are listed, and a model for calculating the profitability of the wind farm was created on a specific example through various simulations in Visual Basic and Microsoft Excel, in which a risk analysis was carried out, as well as an analysis of the project’s sensitivity to changes in key parameters.

Abstract: The task of this diploma thesis is to carry out an analysis of the economic profitability of building a solar power plant on a selected test example with regard to the current methods of incentives that have been applied in Croatia and the new incentive proposal under the new Law on Renewable Energy Sources and High-Efficiency Cogeneration, and their comparison. In the introductory part, an overview of the development of solar energy in the EU and the Republic of Croatia is given, as well as the directions for the development of this sector in the future. Basic parts, characteristics of operation and production of solar power plants and methods of their connection to the power grid are described. The chronology of state incentives for the FN system of the Republic of Croatia is given, the tariff system for the production of electricity from RES and cogeneration is described, as well as the new law on RES and K. Models of incentives and self-sufficiency are described with examples from other EU countries, as well as the possibilities of obtaining investment incentives. Next, the basic economic parameters used in cost-effectiveness analyzes are described. An Excel model was created for the analysis of annual electricity production according to data on insolation for the Split location, as well as a model for analysis of consumption according to the available consumption data from HEP ODS. The income budget was made in two variants, according to the old and new law, and investment costs and maintenance costs are the same for both cases. The analysis of the economic profitability of building a solar power plant is explained in detail for both cases and accompanied by an example from an excel model. From the analyzes carried out, the conclusion is that the old model of the Law on the Tariff System, which was adopted in 2007, worked in the hands of producers, where it was possible to quickly return the invested capital and make a significant profit, but in the long term, the incentive prices were unrealistic. By changing the law in 2016, following the model of other European countries, a model was created in which there is no direct sale of energy to the grid, but a kind of compensation is carried out, where after settling own consumption, only surpluses are sold to the grid at specially defined market prices. This model is more realistic in the long run, and the analysis showed that it is also profitable for the investor, only with less profit than the previous model. In the future, when we expect a lower price of equipment and an increase in the retail price of electricity, the profitability parameters will be better, and this model will satisfy both manufacturers and suppliers.

Abstract: Distributed production plays an increasingly important role in reducing losses in the network, reducing electricity prices, achieving environmental and economic benefits, reducing investment in production capacity and postponing the upgrade of the transmission and distribution system. This paper deals with the advantages and disadvantages of the growing number of distributed sources. In the introductory part, a broader view of the issues related to the integration of distributed sources is given, and the standard technical conditions that must be met by each power plant when connecting to the distribution network are described. In the third chapter, the effects of connecting distributed sources to the power grid are discussed. An overview of the connection’s influence on voltage conditions, short-circuit currents, power flows, losses and the quality of electricity is given. In the practical part of the work, the situation in the network was analyzed before and after the connection of distributed sources. The analysis includes the impact of the connection of photovoltaic power plants on voltage conditions and losses of working energy in the network for different degrees of penetration of FN power plants into the network.

Abstract: The paper describes the basic guidelines for the design of TS 10(20)/0, 4 kV, taking into account the specifics related to the design of typical urban, prefab suburban, or pole substations. The basic dispositions and characteristics of MV and LV facilities, the method of protecting the element and the method of grounding the substation are described. The method of sizing equipment in distribution substations is described. On the concrete example of a typical city substation with one dry transformer of 1MVA power, the plant elements were selected and dimensioned. The TS 10(20)/0, 4 kV solution includes an MV plant with two water lines and one transformer field in the “ring main unit” design with SF6 gas. The LV plant is equipped with 12 LV outlets.

Abstract: This paper describes the general problems of the integration of renewable energy sources into the power system, with an emphasis on the distribution network, both its planning and the influence of distributed sources on its operation. The paper describes the methods of determining the optimal power and connection point of the distributed source in the distribution network based on the sensitivity factors of the change in losses in the network, the method of the golden ratio, the method based on the assessment of the change in power losses in the network based on incidence matrices. The described methods were implemented in the form of a software package and were tested on radial distribution networks. The paper presents the obtained results, which include the optimal locations and power of distributed sources, and provides a comparison of the obtained results for the different methods described in the paper.

Abstract: This paper describes an algorithm that, by combining heuristic methods and a genetic algorithm, enables optimal reconfiguration of medium-voltage distribution networks while satisfying all operating constraints and maintaining the radial structure. The proposed algorithm introduces a number of improvements compared to previous similar achievements, which enables it to be applied to real distribution networks. With the algorithm, it is possible to achieve two goal functions, minimization of total losses of active power or equalization of load in the network. The algorithm was tested on standard test networks where it was shown that the complexity of the network does not affect the efficiency of the algorithm. In addition to standard test networks, the algorithm was also tested on a real medium-voltage distribution network, and the calculation results show the quality and accuracy of the obtained results. The algorithm leaves enough room for the introduction of further modifications in order to achieve better efficiency.

Abstract: Calculation of power flows is one of the basic calculations used in stationary plant analysis and planning of the power system (EES). Unlike transmission networks, distribution networks in regular operation are fed radially, which enables a simpler and faster calculation of power flows. The goal of this paper is to create a computer program for calculating power flows in radial distribution networks based on the backward-forward algorithm. It is also necessary to explain and computer-implement algorithms for topological sorting and detection of loops in networks. The developed computer program will be applied to typical distribution networks and the results will be compared with commercially available programs for this type of analysis.

Abstract: The paper describes the basic parts, characteristics of operation and production of solar power plants and the method of connecting them to the power grid. The basic structure of the costs of building a solar power plant is stated, and a model for analyzing the economic profitability of the construction is created. The basic economic parameters used in the analysis of the profitability of the project are defined. On the selected test example (location Split and Zagreb), based on the created model, an analysis of the economic profitability of the construction was carried out with regard to the currently valid purchase prices of electricity and currently valid equipment costs.

Abstract: The paper describes the basic properties of electric power in an alternating current system. The main consumers of reactive power are listed, especially transformers in distribution networks and asynchronous motors used in industry. Furthermore, various types of compensating devices, their technical and economic advantages are listed, and a special part of the work refers to the most used capacitor batteries. Finally, detailed calculations of typical compensation claims are added.

Abstract: By integrating electrical energy storage equipment into consumer facilities, greater flexibility is achieved in terms of powering the consumer, and it enables the consumer to control the download of electricity from the power system in accordance with current market prices. In addition, positive effects are also achieved from the aspect of the electric power system, since such consumers can participate in the provision of auxiliary services in the system if they receive an incentive for it. The paper explains the technology and ways of storing electricity, and the storage costs of individual technologies are listed. In addition, a computer program was developed that enables the calculation of the optimal way of powering an industrial consumer that has devices for the production (diesel aggregate or photovoltaic power plant) and storage (batteries) of electricity within its facility. Based on the known technical data on consumer equipment, that is, data on electricity consumption and the prices of the appropriate tariff model for a certain period, the profitability of different consumer power supply strategies was examined.

Abstract: Through the first part of the paper, the theoretical foundations of reactive power are given and the basic problems of integrating capacitor batteries into the system are highlighted. The advantages and disadvantages of using capacitor batteries and the techno-economic benefits of compensation are explained. Before the practical part, an overview of the advantages and problems of using genetic algorithms is given. After the aforementioned theoretical considerations, the parameterization calculation of the genetic algorithm was performed, where various influences of the parameters on the quality of the solution and the speed of convergence can be seen. Then, the calculation of the installation of capacitor batteries in the network was performed using a genetic algorithm using a standard example of a network with 69 buses, and the results of power flows and voltage conditions before and after the installation of capacitor batteries in the network were compared.

Abstract: This paper provides an insight into power flows in a system with included variable energy sources, in this case wind farms. In the first chapter, the basic facts about wind, how it is created, how much wind energy is and how it is calculated, are presented, then the wind distribution density functions are given. Basic things about wind turbines, their types and parts of individual wind turbines are explained. It is shown how the wind affects the production of wind turbines and how wind farms affect EES. In the second chapter, the importance of power flows in the EES is presented and the main principles of calculating power flows using deterministic and probabilistic methods (point estimate method, method of cumulants, Monte Carlo method) are explained. In the third chapter, an insight into the probabilistic Monte Carlo method is given. The methods of generating the input variables of the method are given and the method of calculation is explained. Chapter number four is the practical part of this work, where the calculation of power flows using the Monte Carlo method for the case without wind farms in the system, as well as cases with connected wind farms for different levels of correlation, was made on the 24-IEE bus model.

Abstract: Renewable sources increase the self-sustainability of the electric power system in the event of a possible energy crisis in the production of electricity, which today is dependent on the supply of coal, gas and oil. In addition to the mentioned problems, when connecting distributed sources to the distributed network, there is a significant change in the technical properties of the distribution network and the appearance of problems that were not characteristic of these voltage levels until then. One of such problems is the occurrence of high voltages and overloads in distribution networks with high shares of distributed sources. In such conditions, the current methods of leading and managing the distribution network are no longer sufficient. In this paper, the impact of the connection of wind power plants and photovoltaic power plants on the operating conditions in the distribution network was investigated. The paper also proposed a model for optimal coordination of the production of working and idle power from distributed sources, which ensures normal operating conditions even with high shares of distributed sources in relation to local consumption.

Abstract: This thesis consists of seven chapters, which will be briefly described below. The first chapter is an introduction, through which a brief description of working with goals is given. Through the second chapter of the paper, the theoretical foundations of wind energy are given and the basic problems of wind energy integration into the system, its utilization and wind speed distribution described by Weibull and Rayleigh probability distributions are highlighted. In the third part, modern versions of wind turbines as well as their parts (tower, rotor, gearbox, brakes, generator) and power regulation of wind turbines are described. In the fourth chapter, an overview of the connection of the wind power plant to the power grid is given, as well as the topology of the internal MV network, a medium-voltage plant is also described with examples of distribution cabinets and a presentation of the switching apparatus used in the MV plant. Along with the medium-voltage plant, a description of the types of medium-voltage cables used for connection and their characteristics is given. The fifth chapter gives examples and a description of three different methods of calculating annual electricity losses. energy (annual simulation of power flows on an hourly basis, discretization of the production duration curve, approximate calculation). The sixth chapter refers to a brief description of the data of the wind turbine that was taken as an example in this thesis, a detailed description of two variants of the internal VE network (spatial representation of wind farms and cable network outlets) that were considered in the analysis. After the aforementioned theoretical considerations, a computer simulation of the calculation of annual electricity losses was performed. of energy and comparison of used methods, calculation of investment costs, costs of electricity losses. energy and selecting the most favorable variant using the cost difference method.

Abstract: This paper describes the basic parts, operation and production characteristics of wind power plants and their connection to the power grid. The basic structure of the costs of the construction of wind farms is stated, and a model for the analysis of the economic profitability of the construction of a wind farm is developed. The basic economic parameters used in the analysis of the profitability of the project are defined. On the chosen test example of the wind power plant, an analysis of the economic profitability of the construction was carried out with regard to the currently valid purchase prices of electricity and the current level of costs. A sensitivity analysis and a risk analysis (based on Monte Carlo simulation) were performed with regard to the selected input parameters of the model.

Abstract: In the introduction, the need for optimization of reactive power is described in a few sentences and a description of the work is given. In the second chapter, what is reactive power is briefly explained and the hierarchical levels of reactive power management and the economic aspects of reactive power management are briefly described. In the third chapter, a general description of devices used for voltage regulation and optimization of reactive power in the network is given. The fourth chapter concerns methods of optimal engagement of reactive power. The mathematical formulation of the classical approach to reactive power optimization is given, as well as the general model of reactive power optimization using evolutionary algorithms. The methods of optimal engagement of reactive power are briefly described. The fifth chapter describes the particle swarm method and the application of the particle swarm method for reactive power optimization. The sixth chapter presents the practical part. The network is described, which is taken as an example of reactive power optimization using the particle swarm method, and the basic technical characteristics of the network and devices used for reactive power optimization are given. The second part of the sixth chapter consists of various calculation variants characterized by different input settings of the particle swarm method.

Abstract: Power system simulation using computers is becoming more and more important in design, management and education. Various calculations are required for this, such as power flows, state estimation, random event analyses, security analyses, transmission stability analyses, etc. In this paper, the theoretical bases for the calculation of alternating power flows in electric power networks are defined. Algorithms based on the Gauss-Seidel method, the Newton-Raphson method, and the algorithm of fast separated power flows, or their combination, were specially developed. Within the Matlab software package, the aforementioned algorithms for the calculation of alternating power flows are implemented. For given power networks, the calculation of alternating power flows was performed using developed algorithms. On the basis of the conducted analyses, the advantages and disadvantages of each method were indicated.

Abstract: Due to the strong development of wind power and lack of investment in the development and revitalization of the transmission network, there is a need for a methodology that will enable the identification of maximum wind power plant integration capabilities into existing transmission network without the need for additional investment in network development, and without significant disruption of relations in the electricity market. The methodology proposed in this thesis is based on a one-year simulation of power system operation with wind power plants on an hourly time basis. Simulation represents a complex optimization problem that is solved by iteratively solving a series of simple subproblems. In the first subproblem, the order of conventional power plants commitment is determined as well as power distribution on deployed units in the system, based on incremental costs of their production, for each hour of the studied time frame. In the second subproblem, the boundary limit on individual wind power plant installed capacity scheduled for connection to a pre-defined network node is determined, taking into account the limitations of the transmission system under normal and N-1 operating conditions, while considering given ( maximum planned) capacities of wind power plants on each location. In order to eliminate a large number of redundant linear constraints in the second-level subproblem enabling its solution, a reduction scheme based on a quick convex hull algorithm is implemented. In addition, since simultaneous wind speed (wind power) data at different locations are often unavailable or not sufficiently long, methods based on vector autoregression and Markov chains that can generate realistic simultaneous time series of wind speed (wind power) data are developed.

Abstract: structure of small hydroelectric power plants, planned technical characteristics of MHP Peruća, hydrological and energy basis and possible production of MHP Peruća, profitability of construction of MHP Peruća

Abstract: This thesis analyzes the data sets from charging stations from different locations, some of them are public, i.e. availabe to everyone to use, while some of them are busnesslike, i.o. available only to employees. The distribution by arrival time, by required energy and distribution by idle and charging time were analyzed, all with the aim of finding the utilization rates of charging stations.

Abstract: This paper deals with primary types and classifications of energy storage systems. Even though there are various advanced solutions to this question this paper will firstly examine the most frequently used ones. In addition to descriptions of present-day systems the visual representation of them i salso shown. Since every system of storage has its own benefits and flaws it is necessary to elaborately analyze the systems in order to propose the appropriate one. Furthermore, this paper deals with the influence of the energy storage systems on the power grid in ways of its voltage and frequency stability in order to find out how to have more favorable conditions of the grid in relation to such systems. Ultimately the analysis of profitability and costs of energy storage system infrastructure is shown.

Abstract: The final paper describes the basic parts of solar power plants (SP), the method of connection to the power grid, the basic structure of the costs of building solar power plants, and the possibilities of modeling and analyzing the cost-effectiveness of investments in the SAM NREL program package. The basic parts describe the photovoltaic cell, photovoltaic module and DC-AC inverter. This final paper also describes the basic economic parameters used for profitability analysis and the basic cost structure of solar power plant construction. An analysis of the profitability of the investment in the program package SAM NREL was also presented, which offers us the possibility of modeling the system and, with the input of certain parameters, to obtain output data that will give the calculation of the invested and obtained money with the project profitability.

Abstract: _The first part of the final paper describes the idea and operation of the device for recording the current-voltage characteristic. At the beginning of the work, the principle of operation and the very idea of the device are described. The following sections describe its implementation in practice and the development of the device through the first generation of IVS1 until the final minimized and practically realized IVS2.

In the second part of the final paper, the operation of the photovoltaic cell/module is described. The important characteristic points when performing measurements and drawing the current-voltage curve are explained. The influencce of incident angle of light on the photovoltaic module and its connection with the power given by the photovoltaic module, are also described.

The third part of the final paper describes the operation of IVS2, the necessary components for the practical design of the device. The manual generation of current and voltage characteristics, the basics of IVS1 operation and the advantages of improved IVS2 compared to the previous version are described.

The fourth part describes the practical implementation of IVS2. In this final paper we made a version of the device for recording the characteristics of the photovoltaic module with the help of a printed board and an electromagnetic relay.

In the fifth part, measurements were performed and shown using the device. The characteristics for different lighting conditions were recorded and attached. The measurement conditions are described ,and the components used are listed._

Abstract: This paper describes the possibilities of using the sun and solar radiation to obtain electricity and what types of technology are used for this. Ways of battery storage of electricity with emphasis on lithium-ion systems are described, and then the possibilities of the SAM software package for modeling solar power plants and battery warehouses are described. Then, a model of a solar power plant and a battery warehouse was made in it, and data on electricity production, financial profitability and cash flow for such a project were presented.

Abstract: This final thesis describes the principle of electric chargers for electric vehicles. The types, charging modes and the costs of the charging stations are described. It also describes in detail how to charge the batteries of an electric vehicle, through the network in combination with renewable energy sources. The types of modules and chargers, their advantages and disadvantages, are also described. At the end of the paper, the advantages, and disadvantages of switching from diesel and gasoline engines to electric motors are listed as well as and the general impact of the connection of electric vehicles to the electricity network

Abstract: The purpose of this paper was to formulate and optimize a sustainable and cost-effective micro grid solution based on a solar photovoltaic grid and a diesel generator for the supply of electricity to populated areas that do not have access to electricity and remote areas away from the main grid. The production of electricity from renewable energy sources is subsidized, which has led to greater application in distribution networks. Island photovoltaic systems have found their place in performing two important functions: providing power in areas without access to the public electricity grid and ensuring uninterruptible power supply in networked systems. Such systems are mostly installed in areas of Africa, Asia and South America where the public electricity network is poorly developed. Designing an island photovoltaic system requires a good knowledge of photovoltaic technology, power electronics and the climatic specifics of the location itself. The main problem in optimizing island photovoltaic systems in our geographical area is the very large differences in irradiation between the winter and summer months. This makes the whole project more expensive because much more investment is needed in photovoltaic modules, which are the most expensive part of the system. Experience and analysis so far show that it is still best to use a hybrid photovoltaic system or a combination of photovoltaic modules and diesel generators because we get complete independence of the system, optimal use of diesel generators, batteries and reduce the total initial investment. The program used to optimize this system has changes in load and power consumption per hour, which gives it great precision for calculating data, and more accurate optimization.

Abstract: In this thesis, in the first part we discussed about different charger topologies for electrical vehicle. We describe three levels of chargers and compare them. Also, we mention SAE charge standard and battery technology which is most important part of electric vehicles and charge stations which have built-in batteries. In second part of this final paper we describe and compare impact of connecting large charging stations on the electrical grid with device for smart charge and without it. At the end of this final paper we talk about ancillary services to the electrical grid provided by large charging stations.

Abstract: The task of this final paper is to conduct a cost-effectiveness analysis of the construction of a solar power plant on a selected example, taking into account the new Act on Renewable Energy Sources and High-efficiency Cogeneration. The first part describes the technical potential of solar energy required for the operation of photovoltaic systems and the occurrence of the photovoltaic effect that is the basis for the production of solar energy. Then, photovoltaic systems are described, from the history of solar cells, through their types to the way they can be connected to the electricity grid, and an overview of technologies on which the future of solar energy use should be based is given. The second part analyzes the economic profitability of building a solar power plant using a model made in Excel that takes into account the insolation of the location, the possibility of tilting the module, the characteristics of the module and household electricity consumption to ensure maximum return on investment.

Abstract: The aim of this work is to explain the optimal voltage regulation in the distribution network through the theoretical and practical part. The introduction lists the four main units of the power system and its main task as well as the two basic types of distribution networks. The second chapter lists the basic equations for the voltage drop along the circuit and the ways in which the voltage drop along the circuit can be reduced. The third chapter describes the voltage drop allocation, the principle of the load flow model and the problems and voltage reduction including the solution of these problems. The fourth chapter describes the principle of operation of the regulator as well as three types of compensation: line-drop compensation, load-center and voltage-spread compensation. Chapters five and six describe the methods for parallel operation of regulators, bus regulation settings and line loss and voltage drop relationships. In the practical part of the work, the optimal voltage regulation is shown using the DIgSILENT PowerFactory program, and the voltage profiles before and after the optimization are compared.

Abstract: One of the most important parts in the electric power system is the distribution system as it connects transmission networks with their end users – customers. Due to constant technological and industrial development there has been a significant increase in electricity demand. Therefore, the distribution systems have become more complex which requires frequent improvements in the reliability of distribution systems. Some of the main distribution system problems include: the minimization of total losses in the distribution network, equalization of voltage profiles along MV terminals, equalization of load per terminals and increasing reliability of power supply. To minimize these problems it is essential to plan the structure of the distribution network. There have been developed various reconfiguration methods aiming to reduce overall system losses, equalize voltage profiles, load, and increase reliability. Distribution system reconfiguration consists of changing the distribution network topology in order to find the most optimal topology. This paper covers optimization methods, the proposed model of SN 10 kV network for the real area processed with DigSilent Powerfactory software package and complete analysis of power flows, voltage conditions, loads and power reliability for the existing network switching condition. By using the DM topology optimization module, the optimal network switching condition was determined regarding a certain target function. The obtained results are presented and thoroughly analyzed.

Abstract: In this thesis, small hydropower plants are described as a plant in which the potential energy of water is converted into the kinetic energy of its flow, then into the mechanical energy of rotation of the turbine shaft and finally into electrical energy in a synchronous generator. The second chapter describes the properties and characteristics of the hydropower plant, while the third chapter describes the components of the hydropower plant. A small hydropower plant consists of all plants and buildings from water supply and drainage, plants for the production of electricity and transformation to a level suitable for the final consumer. The fourth chapter describes the method of calculating the hydro potential and determining the possible production of electricity from a small hydropower plant. While the sixth and seventh chapters explain the economic viability of SHPPs and the consequences of SHPP connection to the distribution network in the context of power flows, loads, voltage quality, re-establishment of drive after failure, parallel drive with distribution network, power reliability and frequency change in the network. In the final, eighth chapter, testing and simulation of conformity of production modules is explained.

Abstract: The introductory part explains which electrical properties are contained in electric power lines. Also, the advantage of overhead in relation to underground lines was explained, as well the most commonly used types of conductors in transmission lines. The third chapter describes the resistance, and its change with increasing temperature. The fourth and fifth chapters describe the inductance and capacity of power lines, and their calculation in relation to types of line, the number of bundle conductors, and whether the line is transposed or not. The method of mean geometric distances used to calculate capacitance and inductance is also described. At the end of the work, typical examples are shown for 110-kV, 220-kV, and 440-kV lines used in Republic of Croatia, and their solutions in the Matlab.

Abstract: The main objective of this document was to realize the system a practical model of the system for active monitoring the position of light based on the Arduino platform, and to continuously monitor its work. Multiple photovoltaic panels can be connected to the selected controller, but all tests and measurements have been performed on a single panel. This document describes in detail all the electronic components that were required to create the model. The communication between the computer and the controller of the photovoltaic panel is described. An application has been created that allows the user to manually and automatically control the photovoltaic panel. It also describes the processing of an analog signal that needed to be averaged to allow the controller to control the rotation angle correctly.

Abstract: The introductory section explains the reasons for the need for voltage regulation in the distribution network so that all consumers have a fairly equal amount of voltage of the nominal amount. The second chapter describes the voltage regulation procedures in general, we touched on the back-up power supply of adjacent MN networks to provide additional protection in the event of a power failure of a substation. Also in the second chapter we have seen some basic voltage regulation schemes of main substations. After introducing the general voltage control modes in Chapter 3, the control modes are explained in more detail, such as automatic control of the main substation HV or LV bus, voltage compensation, and some analyzes of voltage regulation using additional reactive power injection from the HV network to the MN network. In the practical part, the data were analyzed after applying the method of changing the transformer switch. In addition to the above method, the method of simultaneous use of the Booster transformer and the method of changing the transformer switches were used. Both methods proved to be positive and led to an improvement in voltage conditions, as can be seen from the graphical representations. Although both methods are effective, by installing Booster transformers we achieve better voltage opportunities on terminals that have longer lengths and more consumers.

Abstract: This paper begins by generally describing hydro power plants and their parts, as well as mentioning the biggest hydro power plants in the world. This is followed by a description of small hydro power plants, their construction and the two types of small hydro developments. In addition, we look at some of the formulas required for calculation that takes place at the end of the paper. Before the very calculation, we have a detailed description of every type of turbine we used, as well as tables of formulas for flow and efficiency of each turbine. Using the mentioned tables and calculating these formulas, we obtained an efficiency curve for each turbine. Furthermore, the terms for total production of energy on a daily, monthly and yearly basis are written down. By calculating the terms at the very end of the paper, we obtained the tables for total production. These are substantiated with corresponding diagram of production of energy on a monthly basis.

Abstract: This work presents smart lighting and describes its parts and the benefits of installing it. After that, a light-technical calculation was made for one office where smart lighting is planned to be installed. The practical equipment testing was carried out in the laboratory conditions of the company “LEDeno Doba d.o.o.” All equipment that will be installed later is tested in the laboratory. The paper also describes communicate for DALI devices used for smart lighting systems. Three control modes are described: manual, automatic and using smart devices. After the connection, in practical part selected equipment was tested with some external signals and interference and the test results showed that the equipment was of high quality and the system worked without problems.

Abstract: The introductory part of this work describes the basic principles of wind energy conversion as well as electricity production from wind turbines. It contains a list and overview of internal and external parts of wind turbines. In addition to this different ways of connecting wind power plant to the electricity grid are described in addition to technical conditions which must be satisfied. Detail technical data related to the wind turbines; transformers and medium voltage cables used in the internal cable network is described for wind power plant „Krš - Pađene“.The cable routes and characteristic cross sections of cable ducts which lead to wind turbine substations and main supply substation are given. Depending on the number of connected wind turbines per feeder; the length of the feeder and the cable type; the calculation of the current sizing of the cables is described. For defined internal cable network detail power flow calculation is conducted using MATPOWER software package. The calculation uses the input data related to cable lines; transformers and buses electric parameters and produces results related to power flows; power cable line loading level; voltage increase and active power losses in the internal cable network.

Abstract: The theoretical part of this final paper describes distribution networks, their characteristics and specificities. Special emphasis is placed on low-voltage distribution networks, which, in addition to phase conductors, also have a neutral conductor, and earth as a return conductor. In this paper, the Backward-Forward algorithm was used for calculating the power flows of the low-voltage network, which is based on Kirchhoff’s laws and the calculation of voltage drops on all busbars of the network. This algorithm is convenient to use because it converges even in cases of large R/X ratios that are characteristic of distribution networks. In the experimental part, this algorithm was implemented in the Python program package. The BF algorithm was used to calculate the power flows of the radial distribution network of 9 buses and a network of 906 buses. It is shown that the developed algorithm is a powerful tool with which we can calculate the power flows of an arbitrary distribution network. To verify the accuracy, the results were compared with the OpenDSS software package and the accuracy was confirmed numerically using a very low percentage error of the order of 0.0001%.

Abstract: In the first chapter, an overview of the structure of the distribution system, its components, and the role of the distribution system in the larger picture of the power system is given. Then, in the following text, terms related to the quality of electricity, factors that provide insight into the quality of delivered energy and reliability of delivery are explained. Basic modeling of system components and their behavior as they age are also explained. Before the elaboration of some more complex analyzes and simulations of system behavior, the basic terms related to these simulations and analyzes are explained in order to enable a clear understanding, and the frameworks and principles of modern methods and analysis of distribution systems are given.

Abstract: This paper describes microgrids with a large proportion of renewable sources, and electric vehicles as consumers and sources of electricity. The aim of the work was to analyze the influence of electric vehicles on the operating conditions of the microgrid. In order to carry out such an analysis, basic knowledge about the principle of operation of microgrids, renewable energy sources and electric vehicles is required, which is covered in the first part of the paper. After this knowledge was adopted, a microgrid model was designed in the MATLAB software package, in which all the previously mentioned elements essential for a properly conducted analysis were used. By simulating the operation of the microgrid without, and then with the influence of the V2G regime, different results of electricity production and consumption in the microgrid were obtained. By observing the frequency deviations in both cases, the conclusion was reached that the use of the V2G regime must be carried out within certain limits of the integration of electric vehicles in order to achieve the best possible regulation of the operating conditions of the network.

Abstract: This paper describes the use of Arduino microcontrollers, stepper motors and photoresistors, which are connected with the help of software into a functional unit for monitoring light sources. The task was realized in several ways with the help of a PC with a graphical interface in automatic mode, manual mode, and in fully autonomous mode. The model is assembled into a functional unit that can be applied to static and moving objects.

Abstract: In order to produce electricity from the energy of solar radiation, it is necessary to know certain parameters, the basic of which is the global solar irradiance on the horizontal surface. In order to achieve greater electricity production, solar panels are placed at a certain angle or actively follow the movement of the Sun. Calculations of the expected irradiance on solar panels depend on the model used to transform the measured global irradiance values ​​for the horizontal surface to the values ​​for the tilt of the panels. In this paper, the irradiance calculation of the panel under variable inclination was performed using the initial measured values ​​of the global solar irradiance on the horizontal surface. The first part of the paper describes basic terms related to the Sun and solar radiation, the geometric relationship between the Earth and the Sun, the influence of the atmosphere on radiation, and the components of solar radiation (direct, scattered, reflected). The second part of the paper describes the calculation of solar radiation and the application of that calculation for the city of Split. The Liu-Jordan model for south-facing surfaces was chosen for the calculation, and this model was extended by Klein to arbitrary surface orientation.

Abstract: As part of the final work, it is necessary to create a cheap and efficient circuit for measuring the frequency of the power system using the Raspberry PI platform. The corresponding program should convert the measured values ​​from the sensor into corresponding physical values ​​with eventual calibration. Computer support should enable the choice of different averaging intervals of the measured quantity. In addition, the developed solution should ensure periodic reading of the frequency along with the time stamp of the reading with the possibility of sending data to a “cloud” service that enables free storage and downloading of chronological measurement data. To examine the precision of various designs of circuits and algorithms for frequency measurement in relation to the available reference measurements.

Abstract: In this paper, the scope of functions related to the automation of distribution networks is defined. The paper explains the reasons for the introduction of new remote control systems, defines distribution network control models, and defines the basic characteristics of modern remote control systems. Below we have described the Distribution Network Management System (DMS). The main functions are explained in more detail, which include, among other things: consumption management, Q/U voltage regulation, calculation of electricity consumption and billing in accordance with current market prices, management of distributed power plants and elements for storing electricity, locating faults in the network, maintaining the quality of electricity , network reconfiguration and power restoration…

Abstract: Through the first part of the paper, primitive network matrices, incidence matrices, and the method of their formation are theoretically defined. In the second part of the paper, the procedures for forming the impedance and admittance matrix of the node are listed and processed. In the last part of the work, expressions for the calculation of currents through the branches and node voltages in the event of a three-pole short circuit were derived. Finally, on the example of the electrical network, a comparison was made of the results obtained for currents through the branches and voltages on the busbars, obtained with the help of a program developed in the MATLAB environment, with the results obtained with the help of the TOKSwin program package.

Abstract: The problem of optimal economic involvement of power plants in traditional systems boils down to satisfying consumption in the system by producing electricity from available power plants while minimizing the costs of their operation. When forming the plan of operation of the power plants, it is necessary to take into account the limitations of the production units that affect the possibility of placing energy at a regulated moment in time. In addition to covering consumption in the system, it is also necessary to take into account losses in the transmission of electricity to end consumers. In this paper, the theoretical basis for the calculation of the optimal engagement of power plants will be given, and a computer program will be developed that will enable the calculation of the optimal engagement of power plants in a system of realistic dimensions. Using specific examples, the developed computer program will be implemented and its characteristics will be described.

Abstract: The paper describes the basic elements, types, method of execution and characteristics of distribution transformers. In addition to the main parts of the transformer, other additional parts of the transformer that may exist in certain versions are described. Ways to protect transformers from internal and external faults are also explained. The characteristic ways of grounding the constellation of medium voltage networks and the advantages and disadvantages of each design are described.

Abstract: The paper describes the physical basis of water power utilization, the basic parts, the method of execution and the types of hydroelectric power plants. The method of calculating the hydro potential and determining the possible production of electricity from the hydro power plant is described, along with the previous calculation of all losses or the total utility of the hydro power plant, based on which the type, number and power of the hydro unit is selected.

Abstract: The first part describes the historical development of the electricity market, which has been followed by electrical companies since the eighties of the twentieth century. For years, the electric power sector was a vertically integrated monopoly in state/private ownership, which, as a model of the organization of the electricity market, proved ineffective due to the unrealistic price of electricity. This, along with technological progress in the production and transmission of electricity, imposed the need for reform, i.e. liberalization of the electricity market. The only competitive market results in positive effects for all participants in market competition. This prompted a series of reforms throughout the world. Restructuring, regulation and privatization of the electric power sector took place. The reasons for the restructuring are also listed. Over time, the basic models of the organization of the electricity market are formed. We distinguish between three basic models, the model of vertically and horizontally integrated monopoly, the model of one customer and the market model that can be organized as a wholesale market and retail. The second part describes the main participants in the electricity market, as well as their roles and responsibilities. In the third part, the ways of determining the price of electricity in market conditions are briefly described. Price formation is a complex process that requires reaching a compromise between different interests and expectations. Finally, in the last chapter, an overview of the electricity market in the Republic of Croatia was made. Development of the electricity market. of energy is a continuous process that adapts to technical, economic and liberalization requirements.

Abstract: In the introductory part of the paper, the problem of today’s energy and energy sources is briefly explained, and how more and more countries are turning to the production of electricity from alternative sources. In the second part, the physics of wind formation, its movement in the atmosphere, the influence of height and the surface of the earth on wind intensity and parameters for the assessment of wind potential are discussed. Different heights, as well as the surface itself, greatly affect the movement of the wind, and it is very important to place the wind farm in the right place. Also, there are certain parameters that should be taken into account and which are very important for the creation of wind farms in a certain location. In the third part of the paper, wind turbines, different forms of land-based wind turbines, components and materials used in making wind turbines, and the type of generator and mechanical connection with the turbine are covered. There are many forms of wind turbines that have been developed over the past as well as different materials, and research is still ongoing for even better refinement. In the fourth part, the aerodynamic conversion of wind on wind turbine blades is explained, what is the maximum utilization of wind energy, and how we use the blades and the angle of attack of the wind to regulate the workforce. Furthermore, how are buoyancy and drag forces created and why are these two forces one of the most important forces in wind turbines. The fifth chapter discusses the current state of wind energy in Europe and Croatia and what are the predictions for the future in that sector.

Abstract: The paper describes the materials used for the construction of transformers, and the types and consequences of the resulting losses. It is also explained how losses can be minimized during construction. Loss calculations were made for three characteristic transformer drives: •sine balanced •sine unbalanced •non-sine balanced system. Within the program package “MATLAB” an algorithm was developed and implemented for the optimization of the substation drive in order to minimize the losses of working energy while avoiding frequent switching operations at the substation level. Based on historical consumption data at the substation level and electrical parameters of the transformer, the schedule of optimal switching states was determined.