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Your search keyword '"Polycarpou, Alexis"' showing total 40 results
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40 results on '"Polycarpou, Alexis"'

1. Photovoltaic grid-forming control strategy investigation using hardware-in-the-loop experiments

Author

Bhattacharya, Somesh, Charalambous, Chrysanthos, Banjac, Anja, Miletic, Zoran, Strasser, Thomas, Azzopardi, Brian, Papadimitriou, Christina, Efthymiou, Venizelos, and Polycarpou, Alexis

Subjects
Electrical Engineering and Systems Science - Systems and Control
Abstract

The frequency stability of a power system is of paramount importance, as a fast frequency swings in the system can lead to oscillatory instability, and thereby blackouts. A grid-connected microgrid, that can operate in the islanded mode can also possess such deteriorating effect due to the higher share of converter-based sources. In this paper, a coordinated frequency control within a distribution network is discussed, with a higher share of Photovoltaics (PV). The main objective of this paper is to test the grid-forming capabilities of PVs, without the requirement of an energy storage in the network. The tests were carried out with the help of the Typhoon Hardware-in-the-loop (HIL) platform using a real Cypriot network feeder. The real-time results confirm the efficacy of the PV as a grid-forming inverter, provided it has sufficient input (irradiance) to provide for the loads within the system of interest. The grid-forming PV also possesses the capability of reconnection with the utility grid through a synchronizer switch that requires minimal communication, makes the overall control independent of any other power source, subject to certain irradiance and loading conditions., Comment: 13th Mediterranean Conference on Power Generation, Transmission, Distribution and Energy Conversion (MEDPOWER 2022)

Published
2023
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7. EAC power distribution line cable monitoring using state-of-the-art distributed sensing instruments

Author

Ioannou, Andreas A., primary, Argyrou, Maria, additional, Kouzoupou, Charalambos, additional, Kalli, Kyriacos, additional, Marchesini, Pierpaolo, additional, Mondanos, Michael, additional, Karaulanov, Rumen, additional, Stavrou, Andreas, additional, Dionysiou, Antreas, additional, Agathocleous, Michalis, additional, Stavrakis, Efstathios, additional, Nicolaou, Nicolas, additional, Polycarpou, Alexis, additional, and Komodromos, Michael, additional

Published
2023
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13. Hybrid Energy System Analysis for a Swimming Pool Complex using HOMER Pro

Author

Farkas Timea, Unguresan Paula, Cretu Mihaela, Stet Denisa, Czumbil Levente, Ceclan Andrei, Muresan Claudia, Polycarpou Alexis, and Micu Dan Doru

Subjects
hybrid energy system, HOMER Pro, renewable energy I
Abstract

—The paper investigates hybrid energy systems that could be applied in case of a swimming pool complex in order to reduce exploitation costs and increase renewable energy usage. The presented approach starts with the assessment of the chosen building at the level of energy consumption, and utility costs, along with two proposed system configurations: one proposed by the RE-COGNITION innovation project, and one proposed by the authors based on the market solutions. The mentioned cases represent two hybrid energy systems using conventional sources, renewable energy, and highly efficient cogeneration units. The two proposed system configurations are simulated using the HOMER Pro program which allows a wide analysis along with techno-economic indicators of the different scenarios. Results and comparisons are presented to highlight the feasibility of the two proposed cases.

Published
2022
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15. EXTENDED ANALYSIS OF DATA CLEANING FOR ELECTRICAL ENERGY CONSUMPTION DATA OF PUBLIC BUILDINGS

Author

Jurj Dacian, Polycarpou Alexis, Czumbil Levente, Berciu Alexandru George, Lancranjan Mircea, Barar Denisa, and Micu Dan Doru

Subjects
The 12th Mediterranean Conference on Power Generation, Transmission, Distribution and Energy Conversion
Abstract

In the past years both companies and academics communities pulled their efforts in generating input that consist in new abstractions, interfaces, approaches for scalability and crowdsourcing techniques. Quantitative and qualitative methods were created with the scope of error reduction and were covered in multiple surveys and overviews in order to cope with outlier detection. The aim of tis paper is to provide an outlier analysis over the consumption data of twelve public buildings from the Technical University of Cluj-Napoca, collected during an EU 2020 Horizon project.

Published
2020

16. Multicell Power Supplies for Improved Energy Efficiency in the Information and Communications Technology Infrastructures

Author

Chrysostomou, Michael, Christofides, Nicholas, Ioannou, Stelios, Polycarpou, Alexis, Chrysostomou, Michael, Christofides, Nicholas, Ioannou, Stelios, and Polycarpou, Alexis

Abstract

The rapid growth of the Information and Communications Technology (ICT) sector requires additional infrastructure, such as more micro-datacenters and telecom stations, to support the higher internet speeds and low latency requirements of 5G networks. The increased power requirements of the new ICT technologies necessitate the proposal of new power supplies, in an attempt to support the increase in energy demand and running costs. This work provides an in-depth theoretical analysis on the losses of the individual stages of commercially available PSU and proposes a new multicell PSU, the buck PFC converter, which offers a higher overall efficiency at varying load levels. The theoretical results are verified using simulation results, via a PSIM Thermal Module, and using experimental data. The results indicate that multicell structures can improve the overall PSU efficiency by 1.2% at 50% rated power and more than 2.1% at full power. Finally, taking into consideration the economic implications of this study, it is shown that the proposed multicell structure may increase the PSU costs by 10.78%, but the payback period is in the order of just 3.3 years.

Published
2021

31. Performance evaluation and benchmarking of PLL algorithms for grid‐connected RES applications.

Author

Ali, Zunaib, Christofides, Nicholas, Saleem, Komal, Polycarpou, Alexis, and Mehran, Kamyar

Abstract

The phase‐locked loop (PLL) is the main controller element for the fast and accurate synchronisation and operation of grid‐connected renewable energy systems (RESs). It is used to extract the grid voltage information such as the phase angle, the frequency and amplitude. Subsequently, this information is used in the control system of the grid‐side converter of the RES. The performance of the PLL is critical under abnormal grid conditions such as in the event of balanced and/or unbalanced faults, frequency and phase variations, the presence of harmonics, interharmonics and DC offset. This study sets out with a benchmarking study of the four latest state‐of‐the‐art PLLs. The PLLs compared are the decoupled dual synchronous reference frame PLL, the decoupling network designed in αβ‐frame PLL, the enhanced pre‐filtering moving average filter type‐2 PLL and the harmonic–interharmonic DC‐offset PLL. The PLLs are analysed and compared based on their performance, their dynamic response and their computational complexity. The benchmarking concludes with a PLL selection guide depending on the application and other system constraints. Experiments and simulation results are presented to compare and analyse the performance of the selected PLLs. [ABSTRACT FROM AUTHOR]

Published
2020
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33. Application of a line constant impedance magnitude method for the investigation of the accuracy of a mathematical voltage index

Author

Polycarpou Alexis and Zaos Theodoros

Subjects
Engineering, Index (economics), Control theory, business.industry, Voltage sag, Line (geometry), Electronic engineering, Range (statistics), Magnitude (mathematics), Voltage source, business, Induction motor, Voltage
Abstract

A developed voltage sag index based on power flow equations is presented and investigated in this paper. The index supervises the power quality of a system, through predicting voltage sags caused by an increase in reactive demand due to induction motor starting. The accuracy of the index is investigated for a range of distribution X/R ratio values and various motor loading levels through simulation. The constant impedance magnitude technique is introduced, and applied in order to validate the mathematical index. Results demonstrate the effectiveness and applicability of the proposed index under the investigated load and line impedance variation conditions. (4 pages)

Published
2010
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34. A new tool for computational analysis and design of electrical installations

Author

Pakkos Michalis and Polycarpou Alexis

Subjects
Engineering, BS 7671, Software, business.industry, Electrical installation, Systems engineering, Mechanical engineering, Software design, Electrical wiring, Computational analysis, business, Software package
Abstract

This paper presents findings of an investigation regarding the implementation of laws and regulations in electrical installation design software. The investigation examined existing software following the BS 7671 (British standard for electrical wiring regulations). The investigation also looked at specific differences of the implementation of BS 7671 between United Kingdom and Cyprus. The findings of the investigation lead to the design of a new software package which utilizes the advantages of the existing software packages and avoid their disadvantages. The new software was named ORKAT. (5 pages)

Published
2010
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