Koleva, Radmila
Preferred name
Koleva, Radmila
Official Name
Koleva, Radmila
22 results
Now showing 1 - 10 of 22
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Item type:Publication, Energy flexibility scenarios for North Macedonia(International Association for Hydro-Environment Engineering and Research (IAHR), 2022); ; ; The Paris Agreement signed in 2015, unites nearly 200 countries on the goal of limiting global warming and lowering carbon emissions. The goal of lowering carbon emissions can mainly be achieved by lowering fossil fuels within the energy sector since their use in electricity generation is a significant contributor to greenhouse gas emissions. This is why European countries, as well as North Macedonia, are planning to reduce the amount of climate-damaging fossil-fueled power plants, but to cover electricity demand, the share of renewable energies (in North Macedonia mostly wind and solar energy, here addressed as intermittent renewable energy sources - IRES) within their power systems must be increased. Changing power systems and including higher shares of IRES will increase imbalances and thus the need for flexibility (refers to means able to balance electricity supply and demand). Imbalances have always occurred in power systems, resulting from various reasons, and power systems are able to react with flexibility. Considered options, categorized into four kinds of flexibility (dispatchable generation, demand side management, increased interconnection, and energy storage), all offer possibilities to balance the systems by different approaches. Although all providing individual advantages, hydropower, especially pumped storage hydropower, was identified in this paper to be a very flexible, diverse option and a technology capable of meeting flexibility challenges set by the increase of IRES. The need for flexibility in the hydropower production could be improved using variable-speed turbines instead of multiple start-stops depending on the grid demand. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Isolating Interface for Water Quality Sensors Based on Flying Capacitor Principle(IEEE, 2025-06-10); ; In a water quality monitoring project several sensors have electrical contact to each other due to water conductivity. Galvanic isolation is required to avoid electrical interference, which is established in this work by flying capacitor principle. Simultaneously this also provides channel multiplexing for use of a single analog-to-digital converter (ADC). By nature of the circuit, it is the task to measure a decaying voltage caused by capacitor discharge. An error analysis of this situation is given. Furthermore, the usage of an industrial ADC with finite input resistance, built-in lowpass filter, and serial communication with uncertain time behaviour results in additional measurement errors. A method is proposed how to get a measurement under this conditions with acceptable and predictable errors. Finally the analysis is verified with simulation and laboratory measurements. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Measurement of water quality parameters using the spectrophotometry method(University of Niš, Faculty of Mechanical Engineering, Niš, 2024-10); ; ; ; Koleva, MagdalenaHaving quality drinking water is a leading factor in maintaining public health, environmental protection, and the promotion of sustainable development in industrial and agricultural needs. Measurement and analysis of chemical parameters in drinking water are crucial for ensuring the safety and quality of water for public health. This research was conducted using the spectrophotometry method including a UVVIS DR 6000 HACH Lange spectrophotometer with a wavelength range of 190 to 1100 nm and a highspeed temperature thermostat HT 200 S. Chemical parameters that are measured in this research are chlorides, nitrates, nitrites, potassium, phosphates, and ammonium. All of them are measured on a different wavelength. Samples were taken from three measuring points, all of which are used as drinking water sources and irrigation in the nearby villages. One measuring point is a thermal spring and the other two springs from the foot of a mountain. The water from all three water sources is considerable drinking water. One sample is taken from Vardar River and its water is considered as non-drinking. The results of all measured parameters will be represented through a table and bar graphic chart. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, IoT System for Real-Time Water Quality Measurement and Data Visualization(IEEE, 2023-06-06); ; ; - Some of the metrics are blocked by yourconsent settings
Item type:Publication, INTEGRATION OF LEAN PRINCIPLES AND AUTOMATION FOR DIGITAL TRANSFORMATION IN MANUFACTURING(University Ss. Cyril and Methodius in Skopje, 2025-12-29); ; ; ; <jats:p>Introducing automation in manufacturing can lead to increasing efficiency in the assembly process, reducing Lean production waste, and enhancing operator ergonomics. The purpose of combining automation and Lean is to bridge the gap between digital transformation and human-centric automation, ensuring technological evolution together with the operator's well-being while driving industrial optimization, innovation, and efficiency. According to the review, synergy is required; however, challenges remain in effectively aligning automation with Lean principles. This paper aims to analyze the possibilities for integrating automation and Lean management according to literature, exploring similarities and the implementation practices to achieve sustainable and competitive manufacturing.</jats:p> - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Neuro-PID Controller Application for Hydro Power Plant Control(IEEE, 2022-06-07); ; ; - Some of the metrics are blocked by yourconsent settings
Item type:Publication, An Overview of Machine Learning Techniques Used in Real-Time Water Quality Index Measurement(IEEE, 2025-06-10); ; Water quality index (WQI) has been a universally recognized metric that quantifies water quality, calculated traditionally through analysis of physicochemical characteristics as well as using empirical methods. These conventional approaches can be time-intensive, costly, and may not effectively capture complex relationships among variables. The implementation of machine learning (ML) techniques for more efficient and accurate WQI measurement is the main focus of this paper. Models like Random Forest, Gradient Boosting and so on, required historical data in order to predict WQI dynamically, introducing automation and improving response times. Unique innovations, such as ecological data and hybrid systems, that put together ML and rule-based systems, would improve the accuracy and future development. Results gathered from various experimental data, have demonstrated that ML-based prototypes outperform traditional methods in predictive adaptability, laying foundations for real-time water monitoring solutions. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, 14. Energy Flexibility Scenarios for North Macedonia(IAHR, 2022-06-22); ; ; The Paris Agreement signed in 2015, unites nearly 200 countries on the goal of limiting global warming and lowering carbon emissions. The goal of lowering carbon emissions can mainly be achieved by lowering fossil fuels within the energy sector since their use in electricity generation is a significant contributor to greenhouse gas emissions. This is why European countries, as well as North Macedonia, are planning to reduce the amount of climate-damaging fossil-fueled power plants, but to cover electricity demand, the share of renewable energies (in North Macedonia mostly wind and solar energy, here addressed as intermittent renewable energy sources - IRES) within their power systems must be increased. Changing power systems and including higher shares of IRES will increase imbalances and thus the need for flexibility (refers to means able to balance electricity supply and demand). Imbalances have always occurred in power systems, resulting from various reasons, and power systems are able to react with flexibility. Considered options, categorized into four kinds of flexibility (dispatchable generation, demand side management, increased interconnection, and energy storage), all offer possibilities to balance the systems by different approaches. Although all providing individual advantages, hydropower, especially pumped storage hydropower, was identified in this paper to be a very flexible, diverse option and a technology capable of meeting flexibility challenges set by the increase of IRES. The need for flexibility in the hydropower production could be improved using variable-speed turbines instead of multiple start-stops depending on the grid demand. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Toward a Sustainable Energy Future: Scenario-Based Analysis for North Macedonia(2025-08-25); In this paper, three alternative scenarios are examined and presented for the possibilities of North Macedonia’s transitioning energy sector toward renewable energy sources. Various combinations of photovoltaics, wind turbines, cogeneration plants, and hydropower plants are taken into consideration for analysing the technical, and environmental aspects. The results represent a comparison of CO₂ emissions, stability of the power grid, and energy imports and exports. According to the represented results, the scenarios with a dominant share of photovoltaics significantly reduce CO₂ emissions, while scenarios with increased involvement of wind turbines have a significant impact on export potential. Hydropower is a crucial factor for energy flexibility and stability. Also, cogeneration plants have an important role in grid balancing and import dependency reduction. The results indicate that the proper investments distribution is essential for a sustainable energy transition. Čebren, as a future planned project provide a baseline for better optimization of the energy system. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Kalman Filter Based Detection of FDIA on a Hybrid Nonlinear Hydro-power Plant Control System Model(IEEE, 2022-06-07); ; ; Rath, GerhardCyber-Physical Systems (CPSs) are becoming more relevant, and ever more present in today's world. The integration of cyber/computer systems with the physical world gives improvements on various efficiency and reliability parameters, as well as convenience. Unfortunately, by their very nature CPSs come with various risks and complications that come from the integration of the cyber and physical worlds. One of these risks are cyber and physical attacks on CPSs. Research across various disciplines on these attacks is growing each passing day. In this paper we simulate the possible effects of False Data Injection Attacks (FDIAs) on a hybrid nonlinear model of a hydropower plant (HPP), and then we implement a classical control engineering method - Kalman filtering, as a detection system for these attacks. It is proven that a Kalman filter designed on a linearized continuous system model is a successful detection method in various attack scenarios on the nonlinear hybrid system model.
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