Pregled različitih tehnologija upravljanja naprednim mrežama za povećanje fleksibilnosti elektroenergetskih sustava i omogućavanje masovne integracije obnovljivih izvora energije

Over the last 15 years, major changes have taken place in the electricity sector. A significant increase in the share of renewable energy sources (RES) with variable generation, followed by the decommissioning of conventional power plants based on fossil fuels, has dramatically changed the way of the power system (EPS) operation. During this time, there has been inadequate and untimely investment in the transmission infrastructure. This occurred partly due to the lack of funding, and partly due to the climate change and the rising environmental awareness, as well as the influence of green activists making it difficult to obtain permits to build electrical grid facilities. Additionally, electricity consumption is steadily increasing due to population growth in the undeveloped and developing countries, and due to the rising living standard in the developed countries. Therefore, global electricity consumption is expected to triple by 2050. To meet the new demands, Transmission System Operators (TSOs) are deploying advanced transmission technologies based on a comprehensive application of information and communication solutions. These technologies increase the capacity, efficiency, and reliability of both the existing and new elements of the transmission system. These solutions applied vary from system to system and depend on many influencing factors. The application of these advanced technologies is particularly important for congestion management, as the power system operates closer and closer to stability limits, increasing the risk of collapse. The paper describes the technologies that transform the existing network into smart grids, primarily from the point of view of increasing the capacity of the existing infrastructure through different smart grid investments.U posljednjih 15 godina u elektroenergetskom sektoru dogodile su se velike promjene. Značajno povećanje udjela obnovljivih izvora energije (OIE) s varijabilnom proizvodnjom, praćeno gašenjem konvencionalnih elektrana na fosilna goriva, dramatično je promijenilo način rada elektroenergetskog sustava (EES). Tijekom tog vremena bilo je neodgovarajućih i nepravovremenih ulaganja u prijenosnu infrastrukturu. To se dogodilo dijelom zbog nedostatka financijskih sredstava, a dijelom zbog klimatskih promjena i porasta ekološke svijesti, kao i utjecaja zelenih aktivista koji su otežali dobivanje dozvola za izgradnju energetskih objekata. Osim toga, potrošnja električne energije u stalnom je porastu zbog rasta stanovništva u nerazvijenim zemljama i zemljama u razvoju te zbog povećanja životnog standarda u razvijenim zemljama. Stoga se očekuje da će se globalna potrošnja električne energije utrostručiti do 2050. Kako bi zadovoljili nove zahtjeve, operatori prijenosnih sustava (TSO) uvode napredne tehnologije prijenosa temeljene na sveobuhvatnoj primjeni informacijskih i komunikacijskih rješenja. Ove tehnologije povećavaju kapacitet, učinkovitost i pouzdanost postojećih i novih elemenata prijenosnog sustava. Ova primijenjena rješenja razlikuju se od sustava do sustava i ovise o mnogim utjecajnim čimbenicima. Primjena ovih naprednih tehnologija posebno je važna za upravljanje zagušenjima jer elektroenergetski sustav radi sve bliže i bliže granicama stabilnosti, povećavajući rizik od njegovog sloma. U radu su opisane tehnologije koje transformiraju postojeću mrežu u napredne elektroenergetske mreže, prvenstveno sa stajališta povećanja kapaciteta postojeće infrastrukture kroz različite investicije u napredne tehnologije

DEPARTMENT OF ENERGY AND POWER SYSTEMS – 80 YEARS OF SUCCESS IN SCIENCE, TEACHING AND COOPERATION WITH INDUSTRY

The Department of Energy and Power Systems of the Faculty of Electrical Engineering and Computing, University of Zagreb was founded in 1934 and celebrated its 80th anniversary in 2014. In its long history, many well-known experts, members of the Department, have left their mark on the power engineering activity in Croatia. The Department has been studying and creating improvements in the fields of production, transmission, distribution and final use of electricity, renewable energy sources, advanced power grids, electricity management problems, electricity trading and markets problems and usage of other forms of energy. Throughout the years, the Department has become the leading institution in the field of electrical power engineering in the region, maintaining long-term cooperation with the industry sector and has been recognized for scientific activity since the time of professor Požar and his establishment principles of the Zagreb School of Energy. Determined to remain a respectable research institution, the Department undertakes scientific research at the highest international levels through which valuable international cooperation with many research institutions around the world has been established

INTRODUCTION

This special issue of the Journal of Energy is dedicated to the establishment of today the Department for Energy and Power Systems (ZVNE), University of Zagreb Faculty of Electrical Engineering and Computing in 1934. in that time the High Voltage Department as part of the Technical Faculty. For this reason, the history of the Department for Energy and Power Systems is presented in the introductory article, while the other articles are part of a broad scientific and professional work of the employees of the Department and some of the articles were created in wide cooperation with experts from the companies, that graduated from the Department. Journal of Energy special issue: present 17 papers selected for publication in Journal of Energy after having undergone the peer review process. We would like to thank the authors for their contributions and the reviewers who dedicated their valuable time in selecting and reviewing these papers. We hope this special issue will provide you valuable information of some achievements at Department of Energy and Power Systems, Faculty of Electrical Engineering and Computing. Short introduction of scientific and expert work of the Department for Energy and Power Systems (ZVNE): Besides educational energy related programmes for undergraduate, graduate and postgraduate students, DEPARTMENT OF ENERGY AND POWER SYSTEMS has been actively involved for many years in many scientific and expert studies. Studies on scientific projects include collaboration with industry, national institutions, electric utilities, and many foreign universities. The Department has developed valuable international cooperation with many research institutions around the world, either directly or through inter-university cooperation. The Department is the leading institution in the field of electrical power engineering in the region, it has a long lasting cooperation with the economic sector, and it is recognized for its scientific activities and a large number of published scientific papers in globally relevant journals, as well as numerous national and international scientific projects. Main Department areas of activities are: a) Power Engineering and Power Technologies, b) Energy, Environment, Energy Management and c) Nuclear Power Engineering In Power Systems Engineering the research is focused to development of both fundamental knowledge and applications of electrical power engineering. The research is generally directed to increasing the availability and the reliability of a power system with an emphasis on the adjustment to the open market environment. Specific goals include: improving models and methodologies for power system analysis, operation and control; development, production and application of models and methodologies for power systems planning, maintenance and development; application of soft-computing (artificial intelligence, meta-heuristics, etc.), information technologies (web-oriented technologies, geographic information systems, enterprise IT solutions, etc.) and operational research in improving processes of planning, development, exploitation and control of power systems; investigation on applications for coordinated control of power system devices and exploring the power system stability, security and economic operation; integration of intelligent devices and agents in energy management systems and distribution management systems equipment and software; advanced modelling of dynamics, disturbances and transient phenomena in transmission and distribution networks (in particular regarding distributed generation); advances in fault detection, restoration and outage management. The researches also cover high voltage engineering. At time of global changes in the energy sector, with emphasis on sustainable development, significant efforts are devoted to liberalization efforts, facilities revitalization, improved legislation and adoption of new standards. In area of Power Technologies, Energy and Environment, Energy Management the main framework for the research are: sustainable electricity generation on a liberalized market, modelling ETS and electricity market; energy security and climate change; power system optimization with emission trading; rational use of energy and energy savings; energy management in industry and buildings; energy conservation and energy auditing in industry and buildings. General objective of the research is to develop methodologies for quantitative assessment of the environmental impact of applicable energy technologies (electric power producing plants and their technology chains), as a base for estimating optimal long-term development strategy of the Croatian power system. Research work includes new strategies of energy sector and power system development; preparing medium and long-term electricity generation expansion plan for power system; comparison of energy, economic and environmental characteristics of different options for electric power generation; studies for rational use of energy and energy savings, assuming a centralized structure of the electricity market. Research work also includes renewable energy sources and its role in power sector, as well as electricity production considering cap on CO2 emissions. Research covers development of new models for power system generation optimization and planning under uncertainties on the open electricity market. The goal of that research is to create analytical and software tools which will enable a successful transition to liberalized electricity market and ensure healthy and efficient power system operation in compliance with environmental requirements. In the Nuclear Energy Field research cover nuclear physics reactor theory, nuclear power plants. fuel cycles and reactors materials and general objective of the research is to develop methodologies for reliable assessment of nuclear power plants operational safety. In the nuclear energy field the specific analysis cover calculations of transients and consequences of potential accidents in NPP Krško. In the field of safety analyses of nuclear power plants the research activities are oriented to the mathematical modelling of nuclear power plant systems and components

INTRODUCTION

This special issue of the Journal of Energy is dedicated to the establishment of today the Department for Energy and Power Systems (ZVNE), University of Zagreb Faculty of Electrical Engineering and Computing in 1934. in that time the High Voltage Department as part of the Technical Faculty. For this reason, the history of the Department for Energy and Power Systems is presented in the introductory article, while the other articles are part of a broad scientific and professional work of the employees of the Department and some of the articles were created in wide cooperation with experts from the companies, that graduated from the Department. Journal of Energy special issue: present 17 papers selected for publication in Journal of Energy after having undergone the peer review process. We would like to thank the authors for their contributions and the reviewers who dedicated their valuable time in selecting and reviewing these papers. We hope this special issue will provide you valuable information of some achievements at Department of Energy and Power Systems, Faculty of Electrical Engineering and Computing. Short introduction of scientific and expert work of the Department for Energy and Power Systems (ZVNE): Besides educational energy related programmes for undergraduate, graduate and postgraduate students, DEPARTMENT OF ENERGY AND POWER SYSTEMS has been actively involved for many years in many scientific and expert studies. Studies on scientific projects include collaboration with industry, national institutions, electric utilities, and many foreign universities. The Department has developed valuable international cooperation with many research institutions around the world, either directly or through inter-university cooperation. The Department is the leading institution in the field of electrical power engineering in the region, it has a long lasting cooperation with the economic sector, and it is recognized for its scientific activities and a large number of published scientific papers in globally relevant journals, as well as numerous national and international scientific projects. Main Department areas of activities are: a) Power Engineering and Power Technologies, b) Energy, Environment, Energy Management and c) Nuclear Power Engineering In Power Systems Engineering the research is focused to development of both fundamental knowledge and applications of electrical power engineering. The research is generally directed to increasing the availability and the reliability of a power system with an emphasis on the adjustment to the open market environment. Specific goals include: improving models and methodologies for power system analysis, operation and control; development, production and application of models and methodologies for power systems planning, maintenance and development; application of soft-computing (artificial intelligence, meta-heuristics, etc.), information technologies (web-oriented technologies, geographic information systems, enterprise IT solutions, etc.) and operational research in improving processes of planning, development, exploitation and control of power systems; investigation on applications for coordinated control of power system devices and exploring the power system stability, security and economic operation; integration of intelligent devices and agents in energy management systems and distribution management systems equipment and software; advanced modelling of dynamics, disturbances and transient phenomena in transmission and distribution networks (in particular regarding distributed generation); advances in fault detection, restoration and outage management. The researches also cover high voltage engineering. At time of global changes in the energy sector, with emphasis on sustainable development, significant efforts are devoted to liberalization efforts, facilities revitalization, improved legislation and adoption of new standards. In area of Power Technologies, Energy and Environment, Energy Management the main framework for the research are: sustainable electricity generation on a liberalized market, modelling ETS and electricity market; energy security and climate change; power system optimization with emission trading; rational use of energy and energy savings; energy management in industry and buildings; energy conservation and energy auditing in industry and buildings. General objective of the research is to develop methodologies for quantitative assessment of the environmental impact of applicable energy technologies (electric power producing plants and their technology chains), as a base for estimating optimal long-term development strategy of the Croatian power system. Research work includes new strategies of energy sector and power system development; preparing medium and long-term electricity generation expansion plan for power system; comparison of energy, economic and environmental characteristics of different options for electric power generation; studies for rational use of energy and energy savings, assuming a centralized structure of the electricity market. Research work also includes renewable energy sources and its role in power sector, as well as electricity production considering cap on CO2 emissions. Research covers development of new models for power system generation optimization and planning under uncertainties on the open electricity market. The goal of that research is to create analytical and software tools which will enable a successful transition to liberalized electricity market and ensure healthy and efficient power system operation in compliance with environmental requirements. In the Nuclear Energy Field research cover nuclear physics reactor theory, nuclear power plants. fuel cycles and reactors materials and general objective of the research is to develop methodologies for reliable assessment of nuclear power plants operational safety. In the nuclear energy field the specific analysis cover calculations of transients and consequences of potential accidents in NPP Krško. In the field of safety analyses of nuclear power plants the research activities are oriented to the mathematical modelling of nuclear power plant systems and components

Razvoj studija elektroenergetike na Sveučilištu u Zagrebu

Zavod za visoki napon i energetiku Fakulteta elektrotehnike i raču­ narstva u Zagrebu osnovan je 1934. godine, a u 2019. godini proslavio je 85 godina postojanja. U svojoj dugogodišnjoj povijesti iznjedrio je mnoge po­ znate stručnjake koji su ostavili neizbrisiv trag u elektroprivrednoj djelatno­ sti. Na zavodu se izučavaju i unapređuju područja proizvodnje, prijenosa, razdiobe i uporabe električne energije, obnovljivi izvori energije, napredne elektroenergetske mreže, problemi gospodarenja i trgovanja električnom energijom te područje nuklearnog inženjerstva. Zavod je vodeća institucija iz područja elektroenergetike u široj regiji, ima dugotrajnu suradnju s gospo­ darstvom, a prepoznatljiv je po znanstvenoj djelatnosti. Na zavodu se provo­ de istraživanja u skladu s najvišim međunarodnim standardima što je rezulti­ ralo s velikim brojem objavljenih radova u svjetski relevantnim časopisima, mnogobrojnim znanstvenim projektima te suradnjom s mnogim poznatim in­ stitucijama i sveučilištima

GENERATION SCHEDULING IN POWER SYSTEMS WITH HIGH PENETRATION OF RENEWABLE ENERGY

Share of renewable energy sources increased rapidly over last two decades primary as wind and solar power plants. Their increase was driven by governmental subsidies and priority access and dispatch regarding conventional units. Wind and solar power plants are inflexible sources because their generation depends on exterior, weather conditions and they cannot be controlled as conventional units. This paper will define term power system flexibility and provide an insight into flexibility of conventional and modern power systems. Detailed mathematical model of power system and all its components has been created and explained. Modeling has been executed as mixed integer linear program using Fico Xpress optimization suite. Using those models, flexibility analyses of power systems with different renewable energy sources share has been conducted

SHORT-TERM POWER SYSTEM HOURLY LOAD FORECASTING USING ARTIFICIAL NEURAL NETWORKS

Artificial neural networks (ANN) have been used for many application in various sectors. The learning property of an ANN algorithm in solving both linear and non-linear problems can be utilized and applied to different forecasting problems. In the power system operation load forecasting plays a key role in the process of operation and planning. This paper present the development of an ANN based short-term hourly load forecasting model applied to a real data from MIBEL – Iberian power market test case. The historical data for 2012 and 2013 ware used for a Multilayer Feed Forward ANN trained by Levenberg-Marquardt algorithm. The forecasted next day 24 hourly peak loads and hourly consumptions are generated based on the stationary output of the ANN with a performance measured by Mean Squared Error (MSE) and MAPE (Mean Absolute Percentage Error). The results have shown good alignment with the actual power system data and have shown proposed method is robust in forecasting future (short-term) hourly loads/consumptions for the daily operational planning

NONLINEAR MATHEMATICAL MODEL OF HYDROELECTRIC POWER PLANT

Mathematical and simulation models enable hydroelectric power unit dynamic behavior analysis using computers. In this paper, nonlinear mathematical models of all elements in hydroelectrical power plant are detailed described. Basic elements of hydroelectric power unit are water supply tunnel, surge tank, penstock, water turbine and synchronous generator. If we want more credible simulations models and calculation results, we have to use nonlinear differential equations. Using these nonlinear differential equations, a simulation model was developed for Zakucac HPP

NONLINEAR MATHEMATICAL MODEL OF HYDROELECTRIC POWER PLANT

Mathematical and simulation models enable hydroelectric power unit dynamic behavior analysis using computers. In this paper, nonlinear mathematical models of all elements in hydroelectrical power plant are detailed described. Basic elements of hydroelectric power unit are water supply tunnel, surge tank, penstock, water turbine and synchronous generator. If we want more credible simulations models and calculation results, we have to use nonlinear differential equations. Using these nonlinear differential equations, a simulation model was developed for Zakucac HPP

Overload Mitigation SIPS Based on DC Model Optimization and PMU Technology

System integrity protection schemes (SIPS) supported by phasor measurement unit (PMU) technology are based on the concept of collecting information from remote stations, sending the information to a central concentrator that executes a decision-making algorithm and initiates specialized actions to prevent the spread of system disturbance. This paper gives application of overload mitigation SIPS. Described protection scheme is based on a mixed integer linear programming (MILP) optimization of the DC power flow model whose objective is to maximize total load on the observed part of the network. Inaccuracy of the used DC model and the actual state is replaced by using the PMU technology. In this way, the influence of reactive power that is ignored in the DC model power flow model calculation is replaced in real-time with real synchronized measurements. Described SIPS is tested on IEEE 14 busbar test system. Conducted simulations indicate that developed optimization algorithm can mitigate potential element overloads with extremely high accuracy by using load shedding methods. Example on real part of Croatian power transmission network is given at the end of paper. This specific analysis demonstrates benefits of using SIPS based on synchro phasors in real world