Dimitrina Koeva - Academia.edu (original) (raw)

Papers by Dimitrina Koeva

Research paper thumbnail of Integrating Hydrogen Production Capacity in the Energy Transition: Energy Efficiency and Challenges

Research paper thumbnail of High Penetration of Renewable Energy Sources and Power Market Formation for Countries in Energy Transition: Assessment via Price Analysis and Energy Forecasting

Research paper thumbnail of Influence of the Mechanical Equipment on the Drive Behavior of an Electric Vehicle

Research paper thumbnail of Automated System for Control, Monitoring and Diagnostics of Windmill

Research paper thumbnail of Electromechanical model and operating modes of high-voltage induction motor electric drive — Part II: Power losses

The influence of the power supply in the operating modes of the induction electric drives is effe... more The influence of the power supply in the operating modes of the induction electric drives is effected by the occurrence of voltage deflection in some cases. This is directly related to load of the shaft of an induction motor in driving different production mechanisms and reliable operation of the electric drive as a whole. Paper deals with evaluation of the combined expression of the voltage deflection and the value of the torque of inertia on the power losses in a powerful electric drive for a pump unit. Simulation is performed on high-voltage induction motor using the proposed model.

Research paper thumbnail of Statistical approach and multiplicative models for electric vehicles charging behaviour patterns

IOP conference series, 2022

Since the charging processes of electric vehicles are stochastic and time-dependent, the paper vi... more Since the charging processes of electric vehicles are stochastic and time-dependent, the paper views an approach based on a statistical analysis of real data on electricity consumption at charging station connection points. Other types of data (geographical, public sites, distance between individual charging stations, etc.) are also taken into account when making the analysis. Multiplicative models are the most suitable for studying and forecasting time series with pronounced cyclicity and seasonality. Their application allows us to consider the correlation of the load in the consuming nodes with regional features, climatic factors and seasonality. The method and approach discussed in this paper make possible the processing of a large amount of data and the detection of load cyclicity in the load schedule of electricity facilities. The results of the model will identify the requested charging power in a developing charging infrastructure.

Research paper thumbnail of Comparative analysis of energy indicators based on engineering model-oriented design of traction motors

Journal of physics, Sep 1, 2022

Paper deals with a comparative analysis of energy and mass-size indicators of virtual prototypes ... more Paper deals with a comparative analysis of energy and mass-size indicators of virtual prototypes of two traction electric motors, with a view to their application to electric transportation vehicles. For this purpose, specialized software is used, allowing electromagnetic, structural and thermal optimization according to certain criteria. In conclusion, the results of the comparative analysis are summarized.

Research paper thumbnail of Energy and Resource Efficiency of a Biomass Power Plant: Useful Solutions

The main focus of this article is to consider the challenges regarding the construction and commi... more The main focus of this article is to consider the challenges regarding the construction and commissioning of a biomass power plant for combined heat and power generation, built on the territory of a livestock enterprise. One part of the generated renewable energy covers the company's own needs, and the rest is redirected to the electricity supply network. The solution of the technical and technological problems related to the specifics of anaerobic decomposition of biomass requires a specific approach.

Research paper thumbnail of Energy Efficient Solution for Pump System

2022 International Conference on Communications, Information, Electronic and Energy Systems (CIEES)

Research paper thumbnail of Current Status, Features and Operation of Electric Machines in a Public Building – Elevator-Drive Induction Motors and Power Transformer

2022 International Conference on Communications, Information, Electronic and Energy Systems (CIEES)

Research paper thumbnail of Heat energy consumption forecast analysis: model-oriented multi-objective approach

Journal of Physics: Conference Series

Forecasting the expected quantity of heat energy consumption by multiple residential buildings ca... more Forecasting the expected quantity of heat energy consumption by multiple residential buildings can be a time consuming task, if done manually. The energy consumption in a building can be represented as a data parameter that changes over a period of time. For forecasting purposes autoregressive models are most often used to analyse time series data. One solution of the problem is to perform a hyperparameter optimization and derive the best results according to a selected metric. However, the grid search approach is often a time-consuming and resource-intensive task requiring additional human interaction for the final assessment of the most suitable parameters. The purpose of this study is to explore the possibility of developing a fully automated software algorithm that will provide sufficient parameters for the prediction of heat energy using the seasonal autoregressive integrated moving average with exogenous variables model (SARIMAX).

Research paper thumbnail of Comparative analysis of energy indicators based on engineering model-oriented design of traction motors

Journal of Physics: Conference Series

Paper deals with a comparative analysis of energy and mass-size indicators of virtual prototypes ... more Paper deals with a comparative analysis of energy and mass-size indicators of virtual prototypes of two traction electric motors, with a view to their application to electric transportation vehicles. For this purpose, specialized software is used, allowing electromagnetic, structural and thermal optimization according to certain criteria. In conclusion, the results of the comparative analysis are summarized.

Research paper thumbnail of Vector Control of Pump Unit Electric Drive with Medium Voltage Induction Motor

2020 12th Electrical Engineering Faculty Conference (BulEF)

When operating powerful pump units with medium voltage induction motors, the possible mechanical ... more When operating powerful pump units with medium voltage induction motors, the possible mechanical shocks during start-up and load ripple must be taken into accountAny abrupt change in torque on the motor side, or on the load side, leads to mechanical loads and fatigue in the shafts. Sudden changes in torque can lead to hydraulic shocks in the piping system. This is one of the factors, together with the thermal overload, preferably of soft-start methods, by using a soft-start or a frequency converter. The latter provides an additional advantage - it can cover changes in load resistances during operation and also allows you to quickly go through any resonant frequencies at start-up and avoid operation at these frequenciesThe need for speed control is obvious when the technological process itself requires it. In circulating centrifugal pump units in systems with low static head, the reduction of the speed, respectively the flow, leads to a reduction of the energy consumptionThe greater the static head in the system, the smaller the savings, but still there. Therefore, when the technological process allows to reduce the productivity by frequency control, a large energy savings can be implemented. Additional savings are achieved by increasing the life of the equipmentPaper deals with energy savings by vector control of a medium voltage induction motor driving a centrifugal pump unit.

Research paper thumbnail of Charging Stations for Electric Vehicles – Technical Features and Trends

Machines. Technologies. Materials., 2019

Research paper thumbnail of Retrofit of an electric motor driving a shuttleless weaving grapple machine

Research paper thumbnail of Енергоефективна Техніка Та Технології В Житлово-Комунальному Господарстві Applying of Building Management System for Control of Electricity Consumption

Environmental problems on the planet, global warming and limited energy resources led to extreme ... more Environmental problems on the planet, global warming and limited energy resources led to extreme topicality of the problems associated with overspending of electricity and the use of automatic control to save electricity and improve the parameters of individual systems. Continuous improvement of the automated control systems has been expressed in the search for new models, algorithms and mechanisms for adequate control of all systems of a building. The paper deals with modeling of processes related to increasing the efficiency of operation of automatically controlled lighting system of the school building.

Research paper thumbnail of Comparative analysis of some brushless motors based on catalog data

Analele Universităţii "Eftimie Murgu" Reşiţa: Fascicola I, Inginerie, 2005

Brushless motors (polyphased AC induction, synchronous and brushless DC motors) have no alternati... more Brushless motors (polyphased AC induction, synchronous and brushless DC motors) have no alternatives in modern electric drives. They possess highly efficient and very wide range of speeds. The objective of this paper is to represent some relation between the basic parameters and magnitudes of electrical machines. This allows to be made a comparative analysis and a choice of motor concerning each particular case based not only on catalogue data or price for sale.

Research paper thumbnail of Statistical approach and multiplicative models for electric vehicles charging behaviour patterns

IOP Conference Series: Materials Science and Engineering, 2022

Since the charging processes of electric vehicles are stochastic and time-dependent, the paper vi... more Since the charging processes of electric vehicles are stochastic and time-dependent, the paper views an approach based on a statistical analysis of real data on electricity consumption at charging station connection points. Other types of data (geographical, public sites, distance between individual charging stations, etc.) are also taken into account when making the analysis. Multiplicative models are the most suitable for studying and forecasting time series with pronounced cyclicity and seasonality. Their application allows us to consider the correlation of the load in the consuming nodes with regional features, climatic factors and seasonality. The method and approach discussed in this paper make possible the processing of a large amount of data and the detection of load cyclicity in the load schedule of electricity facilities. The results of the model will identify the requested charging power in a developing charging infrastructure.

Research paper thumbnail of Evaluation of Electric Power Losses of an Induction Motor Driving a Compact Electric Vehicle at Change of Parameters and Loads

2019 Electric Vehicles International Conference (EV), 2019

Nowadays, the search for ways to increase the efficiency of electric vehicles is particularly rel... more Nowadays, the search for ways to increase the efficiency of electric vehicles is particularly relevant. However, ultimately, the purpose of electric mobility is, besides ecology, to be as cheap as possible. As with conventional cars, the cost is directly related to power. Everything in an electric car is subject to maximum energy savings. A condition for the development of electric vehicles is the use of suitably designed electric motors as a driving component of the electromechanical system. At present, in electric vehicles induction motors are mainly used for better efficiency and due to their known advantages. The motor, subject of research, is suitable for fast and easy vehicle conversions by replacing the engine of many compact front wheel drive vehicles. Paper deals with evaluation of the combined influence of changing the equivalent circuit parameters and the total moment of inertia on the electric power losses in a compact electric car drive in the dynamic modes arisen. Simulations have been performed using an appropriate mathematical model of electromechanical system. Results in tabular and graphical form have been obtained. Relevant conclusions have been made. Except for analysis, the developed model can also be used to finding a solution of the opposite task - development of electric motors and control systems with parameters, guaranteeing ongoing processes at user-defined requirements.

Research paper thumbnail of Analysys of the Performance of Small Wind Turbines Darrieus and Options for Their Integration in Buildings

Contemporary Materials, 2015

Given the environmental and energy saving effect of the use of small wind turbines in urban envir... more Given the environmental and energy saving effect of the use of small wind turbines in urban environments, scientists, architects, manufacturers, investors and government institutions have joined forces for more extensive studies. The paper deals with research work of the optimized design of Darrieus turbine with 1 kW rated power in a particular climate. For purposes of the study a universal algorithm implemented with code in C++ has been developed. Thus it is possible to determine the turbine power developed and its efficiency in climate change factors air temperature, speed and intensity of the wind. The monitoring data cover a period of six months (a total of 18 533 measurements) for specific climatic region.

Research paper thumbnail of Integrating Hydrogen Production Capacity in the Energy Transition: Energy Efficiency and Challenges

Research paper thumbnail of High Penetration of Renewable Energy Sources and Power Market Formation for Countries in Energy Transition: Assessment via Price Analysis and Energy Forecasting

Research paper thumbnail of Influence of the Mechanical Equipment on the Drive Behavior of an Electric Vehicle

Research paper thumbnail of Automated System for Control, Monitoring and Diagnostics of Windmill

Research paper thumbnail of Electromechanical model and operating modes of high-voltage induction motor electric drive — Part II: Power losses

The influence of the power supply in the operating modes of the induction electric drives is effe... more The influence of the power supply in the operating modes of the induction electric drives is effected by the occurrence of voltage deflection in some cases. This is directly related to load of the shaft of an induction motor in driving different production mechanisms and reliable operation of the electric drive as a whole. Paper deals with evaluation of the combined expression of the voltage deflection and the value of the torque of inertia on the power losses in a powerful electric drive for a pump unit. Simulation is performed on high-voltage induction motor using the proposed model.

Research paper thumbnail of Statistical approach and multiplicative models for electric vehicles charging behaviour patterns

IOP conference series, 2022

Since the charging processes of electric vehicles are stochastic and time-dependent, the paper vi... more Since the charging processes of electric vehicles are stochastic and time-dependent, the paper views an approach based on a statistical analysis of real data on electricity consumption at charging station connection points. Other types of data (geographical, public sites, distance between individual charging stations, etc.) are also taken into account when making the analysis. Multiplicative models are the most suitable for studying and forecasting time series with pronounced cyclicity and seasonality. Their application allows us to consider the correlation of the load in the consuming nodes with regional features, climatic factors and seasonality. The method and approach discussed in this paper make possible the processing of a large amount of data and the detection of load cyclicity in the load schedule of electricity facilities. The results of the model will identify the requested charging power in a developing charging infrastructure.

Research paper thumbnail of Comparative analysis of energy indicators based on engineering model-oriented design of traction motors

Journal of physics, Sep 1, 2022

Paper deals with a comparative analysis of energy and mass-size indicators of virtual prototypes ... more Paper deals with a comparative analysis of energy and mass-size indicators of virtual prototypes of two traction electric motors, with a view to their application to electric transportation vehicles. For this purpose, specialized software is used, allowing electromagnetic, structural and thermal optimization according to certain criteria. In conclusion, the results of the comparative analysis are summarized.

Research paper thumbnail of Energy and Resource Efficiency of a Biomass Power Plant: Useful Solutions

The main focus of this article is to consider the challenges regarding the construction and commi... more The main focus of this article is to consider the challenges regarding the construction and commissioning of a biomass power plant for combined heat and power generation, built on the territory of a livestock enterprise. One part of the generated renewable energy covers the company's own needs, and the rest is redirected to the electricity supply network. The solution of the technical and technological problems related to the specifics of anaerobic decomposition of biomass requires a specific approach.

Research paper thumbnail of Energy Efficient Solution for Pump System

2022 International Conference on Communications, Information, Electronic and Energy Systems (CIEES)

Research paper thumbnail of Current Status, Features and Operation of Electric Machines in a Public Building – Elevator-Drive Induction Motors and Power Transformer

2022 International Conference on Communications, Information, Electronic and Energy Systems (CIEES)

Research paper thumbnail of Heat energy consumption forecast analysis: model-oriented multi-objective approach

Journal of Physics: Conference Series

Forecasting the expected quantity of heat energy consumption by multiple residential buildings ca... more Forecasting the expected quantity of heat energy consumption by multiple residential buildings can be a time consuming task, if done manually. The energy consumption in a building can be represented as a data parameter that changes over a period of time. For forecasting purposes autoregressive models are most often used to analyse time series data. One solution of the problem is to perform a hyperparameter optimization and derive the best results according to a selected metric. However, the grid search approach is often a time-consuming and resource-intensive task requiring additional human interaction for the final assessment of the most suitable parameters. The purpose of this study is to explore the possibility of developing a fully automated software algorithm that will provide sufficient parameters for the prediction of heat energy using the seasonal autoregressive integrated moving average with exogenous variables model (SARIMAX).

Research paper thumbnail of Comparative analysis of energy indicators based on engineering model-oriented design of traction motors

Journal of Physics: Conference Series

Paper deals with a comparative analysis of energy and mass-size indicators of virtual prototypes ... more Paper deals with a comparative analysis of energy and mass-size indicators of virtual prototypes of two traction electric motors, with a view to their application to electric transportation vehicles. For this purpose, specialized software is used, allowing electromagnetic, structural and thermal optimization according to certain criteria. In conclusion, the results of the comparative analysis are summarized.

Research paper thumbnail of Vector Control of Pump Unit Electric Drive with Medium Voltage Induction Motor

2020 12th Electrical Engineering Faculty Conference (BulEF)

When operating powerful pump units with medium voltage induction motors, the possible mechanical ... more When operating powerful pump units with medium voltage induction motors, the possible mechanical shocks during start-up and load ripple must be taken into accountAny abrupt change in torque on the motor side, or on the load side, leads to mechanical loads and fatigue in the shafts. Sudden changes in torque can lead to hydraulic shocks in the piping system. This is one of the factors, together with the thermal overload, preferably of soft-start methods, by using a soft-start or a frequency converter. The latter provides an additional advantage - it can cover changes in load resistances during operation and also allows you to quickly go through any resonant frequencies at start-up and avoid operation at these frequenciesThe need for speed control is obvious when the technological process itself requires it. In circulating centrifugal pump units in systems with low static head, the reduction of the speed, respectively the flow, leads to a reduction of the energy consumptionThe greater the static head in the system, the smaller the savings, but still there. Therefore, when the technological process allows to reduce the productivity by frequency control, a large energy savings can be implemented. Additional savings are achieved by increasing the life of the equipmentPaper deals with energy savings by vector control of a medium voltage induction motor driving a centrifugal pump unit.

Research paper thumbnail of Charging Stations for Electric Vehicles – Technical Features and Trends

Machines. Technologies. Materials., 2019

Research paper thumbnail of Retrofit of an electric motor driving a shuttleless weaving grapple machine

Research paper thumbnail of Енергоефективна Техніка Та Технології В Житлово-Комунальному Господарстві Applying of Building Management System for Control of Electricity Consumption

Environmental problems on the planet, global warming and limited energy resources led to extreme ... more Environmental problems on the planet, global warming and limited energy resources led to extreme topicality of the problems associated with overspending of electricity and the use of automatic control to save electricity and improve the parameters of individual systems. Continuous improvement of the automated control systems has been expressed in the search for new models, algorithms and mechanisms for adequate control of all systems of a building. The paper deals with modeling of processes related to increasing the efficiency of operation of automatically controlled lighting system of the school building.

Research paper thumbnail of Comparative analysis of some brushless motors based on catalog data

Analele Universităţii "Eftimie Murgu" Reşiţa: Fascicola I, Inginerie, 2005

Brushless motors (polyphased AC induction, synchronous and brushless DC motors) have no alternati... more Brushless motors (polyphased AC induction, synchronous and brushless DC motors) have no alternatives in modern electric drives. They possess highly efficient and very wide range of speeds. The objective of this paper is to represent some relation between the basic parameters and magnitudes of electrical machines. This allows to be made a comparative analysis and a choice of motor concerning each particular case based not only on catalogue data or price for sale.

Research paper thumbnail of Statistical approach and multiplicative models for electric vehicles charging behaviour patterns

IOP Conference Series: Materials Science and Engineering, 2022

Since the charging processes of electric vehicles are stochastic and time-dependent, the paper vi... more Since the charging processes of electric vehicles are stochastic and time-dependent, the paper views an approach based on a statistical analysis of real data on electricity consumption at charging station connection points. Other types of data (geographical, public sites, distance between individual charging stations, etc.) are also taken into account when making the analysis. Multiplicative models are the most suitable for studying and forecasting time series with pronounced cyclicity and seasonality. Their application allows us to consider the correlation of the load in the consuming nodes with regional features, climatic factors and seasonality. The method and approach discussed in this paper make possible the processing of a large amount of data and the detection of load cyclicity in the load schedule of electricity facilities. The results of the model will identify the requested charging power in a developing charging infrastructure.

Research paper thumbnail of Evaluation of Electric Power Losses of an Induction Motor Driving a Compact Electric Vehicle at Change of Parameters and Loads

2019 Electric Vehicles International Conference (EV), 2019

Nowadays, the search for ways to increase the efficiency of electric vehicles is particularly rel... more Nowadays, the search for ways to increase the efficiency of electric vehicles is particularly relevant. However, ultimately, the purpose of electric mobility is, besides ecology, to be as cheap as possible. As with conventional cars, the cost is directly related to power. Everything in an electric car is subject to maximum energy savings. A condition for the development of electric vehicles is the use of suitably designed electric motors as a driving component of the electromechanical system. At present, in electric vehicles induction motors are mainly used for better efficiency and due to their known advantages. The motor, subject of research, is suitable for fast and easy vehicle conversions by replacing the engine of many compact front wheel drive vehicles. Paper deals with evaluation of the combined influence of changing the equivalent circuit parameters and the total moment of inertia on the electric power losses in a compact electric car drive in the dynamic modes arisen. Simulations have been performed using an appropriate mathematical model of electromechanical system. Results in tabular and graphical form have been obtained. Relevant conclusions have been made. Except for analysis, the developed model can also be used to finding a solution of the opposite task - development of electric motors and control systems with parameters, guaranteeing ongoing processes at user-defined requirements.

Research paper thumbnail of Analysys of the Performance of Small Wind Turbines Darrieus and Options for Their Integration in Buildings

Contemporary Materials, 2015

Given the environmental and energy saving effect of the use of small wind turbines in urban envir... more Given the environmental and energy saving effect of the use of small wind turbines in urban environments, scientists, architects, manufacturers, investors and government institutions have joined forces for more extensive studies. The paper deals with research work of the optimized design of Darrieus turbine with 1 kW rated power in a particular climate. For purposes of the study a universal algorithm implemented with code in C++ has been developed. Thus it is possible to determine the turbine power developed and its efficiency in climate change factors air temperature, speed and intensity of the wind. The monitoring data cover a period of six months (a total of 18 533 measurements) for specific climatic region.