Silicon carbide (SiC) MOSFETs tend to become one of the main switching elements in power electronics applications of medium- and high-power density. Usually, SiC MOSFETs are connected in parallel to increase power rating. Unfortunately,... more
Silicon carbide (SiC) MOSFETs tend to become one of the main switching elements in power electronics applications of medium- and high-power density. Usually, SiC MOSFETs are connected in parallel to increase power rating. Unfortunately, unequal current sharing between power devices occurs due to mismatches in the technical parameters between devices and the layout of the power circuit. This current imbalance causes different current stress upon power switches, raising concerns about power system reliability. For over a decade, various methods and techniques have been proposed for balancing the currents between parallel-connected SiC MOSFETs. However, most of these methods cannot be implemented unless the deviation between the technical parameters of semiconductor switches is known. This requirement increases the system cost because screening methods are extremely costly and time-consuming. In addition, most techniques aim at suppressing only the transient current imbalance. In this ...
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The modern era of green transportation based on Industry 4.0 is leading the automotive industry to focus on the electrification of all vehicles. This trend is affected by the massive advantages offered by electric vehicles (EV), such as... more
The modern era of green transportation based on Industry 4.0 is leading the automotive industry to focus on the electrification of all vehicles. This trend is affected by the massive advantages offered by electric vehicles (EV), such as pollution-free, economical and low-maintenance cost operation. The heart of this system is the electric motor powered by lithium-ion batteries; however, due to their many limitations, a hybrid energy storage system (HESS) consisting of batteries and ultracapacitors is currently gaining increased attention. This paper aims to review the distinct motor technologies such as brushless motors, synchronous reluctance and induction motors currently used in EVs. Additionally, through eleven selected criteria, such as regenerative braking efficiency and power density at different load ranges, the motors are classified in terms of their combined ability to operate with a HESS in order to maximize efficiency and sizing. The results show that permanent magnet an...
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The current paper presents an inclusive survey about the AC to DC and DC to DC converters for brushed DC Motor Drives. An essential number of different AC to DC and DC to DC topologies and control techniques, applied on the brushed DC... more
The current paper presents an inclusive survey about the AC to DC and DC to DC converters for brushed DC Motor Drives. An essential number of different AC to DC and DC to DC topologies and control techniques, applied on the brushed DC motor drives are presented. This extensive literature review exposes advantages, disadvantages and limitations besides giving the basic operating principles of various topologies and control techniques.
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The penetration of renewable energy sources and the development of autonomous power systems for the supply of isolated consumers find applications such as covering energy needs in lighthouses, small islands, monasteries, and even isolated... more
The penetration of renewable energy sources and the development of autonomous power systems for the supply of isolated consumers find applications such as covering energy needs in lighthouses, small islands, monasteries, and even isolated special industrial facilities. Power plant cost is a major limitation in the development of these systems. For example, although the electromechanical cost of photovoltaic plants has been significantly reduced in recent years, however the land cost is not considered, which is a significant expenditure. In this paper, the real problem of an autonomous power station design for the supply of the shoreline electrode substation on the Stachtorroi islet of Attica, is taken as the starting point. The electrode substation is part of the Attica-Crete high voltage direct current (HVDC) electrical interconnection project. For the above problem, an overall evaluation algorithm for a photovoltaic (PV) plant is proposed that considers the technical characteristi...
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Due to the growing environmental pollution, methods are being sought to improve this situation. One of the main factors influencing this pollution is passenger vehicles. This paper will analyze a new approach to vehicles with in-wheel... more
Due to the growing environmental pollution, methods are being sought to improve this situation. One of the main factors influencing this pollution is passenger vehicles. This paper will analyze a new approach to vehicles with in-wheel electric motors as well as the steering of all four wheels, which will increase the efficiency of the vehicles and at the same time the driving safety. Driving operation modes of vehicles as well as applications of 4-wheel steering (4WS) with steer-by-wire (SBW) system shall be analyzed. Specially, the steering geometry and the vehicle dynamics equations of this vehicle type will be reported. Finally, the proposed 4WS SBW control system will be presented and simulated with New European Driving cycle (NEDC).
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Purpose The purpose of this paper is to optimally operate a Smart Microgrid which is interconnected to the main grid so as to minimize expenditures associated with CO2 emissions. Microgrids could come into play to aid the network through... more
Purpose The purpose of this paper is to optimally operate a Smart Microgrid which is interconnected to the main grid so as to minimize expenditures associated with CO2 emissions. Microgrids could come into play to aid the network through CO2 emission reduction while increasing their efficiency through local generation. For this purpose, a Smart Microgrid incorporating Distributed Energy Resources (DER), especially Renewable Energy Sources (RES), is operated optimally while keeping the CO2 emissions in check in order to minimize the financial burden from emissions stemming from the carbon tax. Since the network is assumed to be interconnected with the main grid, there is a consideration of the expected emissions associated with the imported energy. Design/methodology/approach An economic/environmental dispatch problem is mathematically formulated using an objective function and the constraints that it is subject to. The methodology is applied on a typical 17-bus test distribution net...
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The derivation of the characteristic measurements of a photovoltaic cell using computer modeling analysis is discussed. The simulation of the variables and parameters is obtained through an analysis of the equivalent electrical circuit.... more
The derivation of the characteristic measurements of a photovoltaic cell using computer modeling analysis is discussed. The simulation of the variables and parameters is obtained through an analysis of the equivalent electrical circuit. The computer simulation program (TREE) is able to compute, among other parameters, the light current, the short circuit current, the open circuit voltage, and the efficiency of
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ABSTRACT In this paper a research work and its preliminary results exploring the possibility of saving energy in existing dc drive systems in Greece are presented. The purpose of this research is to develop a new motor drive system and... more
ABSTRACT In this paper a research work and its preliminary results exploring the possibility of saving energy in existing dc drive systems in Greece are presented. The purpose of this research is to develop a new motor drive system and its respective control technique to upgrade existing dc drive systems in order to save power and at the same time effectively control their speed and torque characteristics. In addition, the new high voltage low loss semiconductor switches relying on silicon carbide (SiC) are studied, and compared to the existing silicon (Si) semiconductor switches. Furthermore, the possibility of applying H∞ or/and fuzzy logic theory to optimize the control of the dc drive system and the application of a reduced losses dc converter will be considered.
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... "Improvement in Performance of a Passive Pitch Wind Turbine with Variable Speed Operation". Proc. EUEC'94. Thessaloniki. Greece. ... "Power Conversion for the Connection to the Medium-Voltage Grid of a Variable... more
... "Improvement in Performance of a Passive Pitch Wind Turbine with Variable Speed Operation". Proc. EUEC'94. Thessaloniki. Greece. ... "Power Conversion for the Connection to the Medium-Voltage Grid of a Variable Speed Wind Generator". Prof. EUEC'93. Lubeck-Travemunde. ...
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The maintenance experience gained from the solar assisted air conditioning installations (SAC) available in Greece is the primary objective of this study. Today there are six SAC installations in Greece. The majority of the SAC... more
The maintenance experience gained from the solar assisted air conditioning installations (SAC) available in Greece is the primary objective of this study. Today there are six SAC installations in Greece. The majority of the SAC installations (4 systems) are operating by means of thermally driven chillers and flat plate collectors. Three systems were developed for commercial applications. Regarding the commercial applications, their operation begun in 1999 and therefore allowed the authors to draw important data regarding the maintenance activities that took place in the past and make recommendations for their future operation. The “SARANTIS” SAC installation is the “oldest” and one of the two largest in Europe. Additionally holds today a valid maintenance contract. This contract was meticulously examined by the authors regarding its implementation, since 1999, its weak points and its improvements during these years. Furthermore, the maintenance activities that took place in the two ...
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Abstract—The aim of this paper is to present and analyze a series of Power Quality (PQ) field measurements that took place in different sites of the Greek electric grid, such as a nutrition industry, a photovoltaic park with nominal power... more
Abstract—The aim of this paper is to present and analyze a series of Power Quality (PQ) field measurements that took place in different sites of the Greek electric grid, such as a nutrition industry, a photovoltaic park with nominal power of 100kW, a Waste Water Treatment Plant (WWTP), a food industry, a Town hall and in several buildings of two educational institutes. PQ monitoring seems to be very important in Greece due to the fact that there are still no legislative rules covering this issue neither from the users’ nor from the grid administrator’s side. The results of these measurements are used in a research project which aims to create a PQ evaluation model using fuzzy sets methodology in order to calculate a total PQ index of a specific point. In this paper an analysis of these measurements is presented. PQ disturbances are recorded according to EN 50160, while a comparison with PQ limits of EU countries is introduced.
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According to Directive 2009/28/EC on the promotion of the use of energy from renewable sources, for Greece the target of RES penetration into gross final energy consumption in 2020 is set at 18%. The contribution of RES to energy... more
According to Directive 2009/28/EC on the promotion of the use of energy from renewable sources, for Greece the target of RES penetration into gross final energy consumption in 2020 is set at 18%. The contribution of RES to energy consumption in Greece during the period 2006-2016 showed a significant increase. More specifically, the total contribution of RES as a share of gross final energy consumption in the year 2016 was 15.2%, more than doubling the relative share corresponding to RES in 2006. Similarly, the share of electricity from RES to gross electricity consumption in the year 2016 stood at 23.8%. In the National Energy and Climate Plan (NECP) prepared and submitted to the European Commission in January 2019 on the basis of Regulation EU) 2018/1999 on the governance of the Energy Union and Climate Action and Directive (EU) 2018/2001 on the promotion of the use of energy from renewable sources, a target for the RES share in the gross final energy consumption in 2030 is set at 31%and respectively a target for the RES share in the gross final electricity consumption is set at 55%. More specifically, to achieve the above target in the electricity sector, it is estimated that more than 9GW of variable wind and photovoltaic (PV) plants must be installed. To reach such high levels of such RES penetration into the gross final electricity consumption, energy storage needs arise. For several decades, Pumped Hydro Energy Storage (PHES) is the most widespread international format for large-scale storage of electricity. This paper attempts to provide an overview of the status and prospects of PHES in Greece. It also tries to identify obstacles in installing and operating PHES in Greece using experience from other countries.
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Abstract Power grids face a new and important challenge: the oncoming mass penetration of plug-in Electrical Vehicles (EVs). Nevertheless, the architectures of transmission and distribution grids are still focused on traditional design... more
Abstract Power grids face a new and important challenge: the oncoming mass penetration of plug-in Electrical Vehicles (EVs). Nevertheless, the architectures of transmission and distribution grids are still focused on traditional design and operational rules. Consequently, it is necessary to predict the adequate solutions for the problems which are going to rise to the electrical and production grids as well as the effect on their commercial operation as a result of the gradual integration of EVs into the network. For example major congestion problems may appear in already heavily loaded grids as well as voltage profile problems mainly in radial networks, particularly if the peak load periods coincide with EV charging periods. In this paper the impacts of penetration of EVs on selected buses of a Distribution Network are assessed. The analysis takes into account driving profiles of EV owners, type of vehicle (battery capacity, energy consumption), travelling distance, road conditions etc, and approximates the hourly allocation of the energy requirements under various EV charging strategies. A steady state analysis toolbox is used to their impact to its operation.
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Abstract Nowadays, the connections of Renewable Energy Sources to Distribution Networks are increasing in large number. In order to assess the performance of Distribution Network under normal operating conditions Probabilistic Load Flow... more
Abstract Nowadays, the connections of Renewable Energy Sources to Distribution Networks are increasing in large number. In order to assess the performance of Distribution Network under normal operating conditions Probabilistic Load Flow analysis is necessary in order to take into consideration the stochastic behavior of Load Demands and Renewable Energy Sources (for example the Photovoltaics Generation Units). Generally, Deterministic Load Flow calculations are typically needed to assess the allowed Distributed Generation penetration level for a given network in order to ensure, for example, that Voltage limits are not exceeded. The present paper deals with the Probabilistic Load Flow using Monte Carlo techniques. The developed program allows probabilistic predictions of Voltages profiles at all buses or nodes of a Distribution Networks. A practical case is also discussed to show the application of the study in order to assess the maximum Photovoltaic power penetration that can be installed into a Distribution Network without violating Voltage Constraints.