Papers by Vasilis Kleftakis
The main problem of energy supply in the developing counties is that a very large portion of thei... more The main problem of energy supply in the developing counties is that a very large portion of their rural population still does not have access to a secure supply of electricity. DC microgrids seems an attractive solution due to lower capital, operation, engineering and maintenance costs. Many developing countries have shown interest in the development of such systems in order to improve the quality of their inhabitants’ life, together with the development of the local economies (creation of new jobs) through the creation of local energy communities. This paper reviews the conditions under which DC microgrids provide an attractive option for local energy communities in the developing world. It also reviews the best practices of DC local energy communities in developing countries and highlights relevant issues, e.g. regulatory framework, standardization, protection, secure supply etc. that have to be faced, in order to establish DC microgrids in rural areas
Currently HEDNO undergoes an upgrade of its Supervisory Control and Data Acquisition (SCADA) syst... more Currently HEDNO undergoes an upgrade of its Supervisory Control and Data Acquisition (SCADA) systems. As part of this, the Information and Communication Technology (ICT) infrastructure of the organization will undergo a respective change towards data harmonization and smooth interoperation between the heterogeneous ICT systems it consists of. This work presents the current state of the most important of HEDNO ICT systems, in an attempt to point out the diversity and complexity of the ICT infrastructure of such a large organization, and, then, it proposes the implementation of the Enterprise Service Bus (ESB) approach as a means to achieve the desired integration, interoperability and data harmonization between the various ICT systems of HEDNO.
Improving existing methods for stable and more accurate Power Hardware-in-the-Loop experiments
2017 IEEE 26th International Symposium on Industrial Electronics (ISIE)
This paper deals with stability and accuracy issues that occur in Power Hardware-in-the-Loop expe... more This paper deals with stability and accuracy issues that occur in Power Hardware-in-the-Loop experiments (PHIL). Firstly, based on the Bode stability criterion, an analytical investigation of the stability margins of a PHIL simulation without using approximations for the time delay is presented. Then, the proposed analysis is used for the extension of existing methods, which results in the accurate and justified choice of their parameters and, thus, the improvement of the accuracy and stability in PHIL experiments. Finally, the calculated parameters of the feedback filter method are compared with the real parameters derived from the execution of PHIL experiments.
Energies
The role of flexible alternating current transmission systems (FACTSs) in the provision of grid s... more The role of flexible alternating current transmission systems (FACTSs) in the provision of grid services is becoming increasingly important, due to the massive integration of intermittent renewable energy sources, energy storage systems, and the decommissioning of thermal plants. A comprehensive literature review of grid services offered by FACTS is performed, focusing on the different grid services that they can provide, such as power flow control, reactive power control, voltage control, power quality improvement, harmonic mitigation, improvement of transient stability, and damping of inter-area and intra-area oscillations. These grid services need to be realistically and economically validated in suitable testing environments. A review of relevant standards, guides, and the literature is performed, which covers the entire range from functional specification and factory testing up to the field testing of FACTS. Advanced industry practices, such as controller hardware in the loop (...
Optimal control of reversible substations and wayside storage devices for voltage stabilization and energy savings in metro railway networks
IEEE Transactions on Transportation Electrification
Towards the modernisation of the supervisory control and data acquisition systems of the Hellenic electricity distribution network operator: considerations and steps forward
CIRED - Open Access Proceedings Journal
Power-Hardware-in-the-loop simulation of a D-STATCOM equipped MV network interfaced to an actual PV inverter
IEEE PES ISGT Europe 2013, 2013
ABSTRACT Power-Hardware-in-the-Loop (PHIL) simulation is a promising method for studying the inte... more ABSTRACT Power-Hardware-in-the-Loop (PHIL) simulation is a promising method for studying the interaction of various complex components in current and future electricity grids. This paper firstly examines the applicability of PHIL simulation to Fault- Ride-Through tests. A test setup is implemented with a hardware PV inverter as the Hardware Under Test (HUT). Furthermore, the PHIL method is employed for testing and validating the capability of a D-STATCOM to compensate voltage dips. An average model of a D-STATCOM is developed in the RTDS® and its influence on the operation of the hardware PV inverter is investigated.
DER supporting the grid simulationS by means of Power-Hardware-in-the-Loop
Power hardware-in-the-loop technique applied to a LV network for integrating a supercapacitor with an average model of STATCOM
2013 IEEE International Workshop on Inteligent Energy Systems (IWIES), 2013
ABSTRACT This paper investigates the effects on voltage stability of a converter based STATCOM in... more ABSTRACT This paper investigates the effects on voltage stability of a converter based STATCOM integrated with a Supercapacitor into a low voltage (LV) distribution network. An Average Model of a STATCOM was simulated, where the IGBT Voltage-Source Converter was represented by equivalent controlled voltage sources. The STATCOM was modeled in the Real Time Digital Simulator’s (RTDS®) dedicated software RSCAD. Subsequently, Power Hardware- in- the -Loop (PHIL) tests were executed with an impedance load as Hardware under Test (HuT) in order to validate the system’s performance. Simulations and PHIL experimental results are outlined to demonstrate the STATCOM’s contribution on nodal voltage regulation, whereas the integration and control of an energy storage system (ESS) such as a Supercapacitor is further discussed throughout this paper.
Seamless transition between interconnected and islanded operation of DC Microgrids
IEEE Transactions on Smart Grid
Μελέτη προσομοίωσης Power Hardware In The Loop και διερεύνηση ανύψωσης της τάσης εξαιτίας της διείσδυσης φωτοβολταϊκών στη Χαμηλή Τάση
Η προσομοίωση σε πραγματικό χρόνο παρέχει τη δυνατότητα σύνδεσης πραγματικών συσκευών ισχύος με η... more Η προσομοίωση σε πραγματικό χρόνο παρέχει τη δυνατότητα σύνδεσης πραγματικών συσκευών ισχύος με ηλεκτρικά δίκτυα που προσομοιώνονται σε κατάλληλο εξοπλισμό. Αυτή η τεχνική συνδυάζει πλεονεκτήματα της προσομοίωσης (ευελιξία) και των εργαστηριακών δοκιμών (ακρίβεια) και ονομάζεται Power Hardware in Loop (PHIL). Στόχος της εργασίας είναι η εξέταση και η υλοποίηση ενός τέτοιου πειράματος με το εργαστηριακό μικροδίκτυο του ΕΜΠ*, και συγκεκριμένα με τον αντιστροφέα φωτοβολταϊκών, σε ρόλο δοκιμίου. Αρχικά μελετώνται ζητήματα ευστάθειας της PHIL προσομοίωσης. Παρουσιάζεται η τοπολογία στο κύκλωμα ενός διαιρέτη τάσης και λαμβάνονται αποτελέσματα που αφορούν την ευστάθεια της προσομοίωσης. Γίνεται αναφορά στη σημασία της τοπολογίας «σύνδεσης» του προσομοιωμένου συστήματος και του δοκιμίου. Έπειτα, περιγράφεται θεωρητικά το φαινόμενο της ανύψωσης τάσης σε δίκτυα Χαμηλή Τάσης εξαιτίας της υψηλής διείσδυσης Φωτοβολταϊκών. Εφαρμόζεται η PHIL προσομοίωση σε δίκτυο Χαμηλής Τάσης αγροτικής περιοχής ...
Στόχος της εργασίας είναι η εξέταση και η αντιμετώπιση του φαινομένου ανύψωσης τάσης λόγω της σύν... more Στόχος της εργασίας είναι η εξέταση και η αντιμετώπιση του φαινομένου ανύψωσης τάσης λόγω της σύνδεσης φωτοβολταϊκών (Φ/Β) μονάδων παραγωγής στη Χαμηλή Τάση (ΧΤ). Γίνεται διερεύνηση του φαινομένου, και παρουσιάζονται οι συνήθεις μέθοδοι αντιμετώπισής του, ενώ δίνεται έμφαση στη μέθοδο της περικοπής ενεργού ισχύος, καθώς και στη μέθοδο ρύθμισης της αέργου ισχύος. Παρουσιάζεται η θεωρία της ανάλυσης ευαισθησίας τάσης ως προς την ενεργό και άεργο ισχύ στους κόμβους του δικτύου. Πραγματοποιούνται προσομοιώσεις στο Matlab/Simulink, όπου χρησιμοποιούνται οι προτεινόμενοι ελεγκτές για την αντιμετώπιση του φαινομένου σε δίκτυο ΧΤ αγροτικής περιοχής. Γίνεται μοντελοποίηση ενός Φ/Β συστήματος, και εισάγονται χρονοσειρές παραγωγής Φ/Β και οικιακού φορτίου στο δίκτυο ΧΤ. Καταγράφεται το προφίλ της τάσης και της ενεργού και αέργου ισχύος στους κόμβους, για διάφορα σενάρια χρήσης των ελεγκτών. Τέλος, μοντελοποιείται το δίκτυο ΧΤ, και εκτελούνται προσομοιώσεις στον εξομοιωτή πραγματικού χρόνου RTD...
A Novel Method for Islanding Detection in DC Networks
IEEE Transactions on Sustainable Energy, 2016
Microgrids in Distribution
Smart Grid Handbook, 2016
Hardware-In-the-Loop Design and Optimal Setting of Adaptive Protection Schemes for Distribution Systems with Distributed Generation
IEEE Transactions on Power Delivery, 2015
Review of Synchronization Algorithms used in Grid-Connected Renewable Agents
This paper presents a review of several synchronization algorithms used in Grid-Connected Renewab... more This paper presents a review of several synchronization algorithms used in Grid-Connected Renewable Agents. Different synchronization algorithm structures will be shown and their advantages and disadvantages will be discussed using MATLAB/SIMULINK tool from The MathWorks, Inc. Some simulations will be shown firstly, and secondly, a Real Time Digital Simulator (RTDS) platform will be used for testing and debugging the Synchronization Algorithms.
Design, development and operation of a PHIL environment for Distributed Energy Resources
IECON 2012 - 38th Annual Conference on IEEE Industrial Electronics Society, 2012
ABSTRACT The challenges in achieving higher integration of Distributed Energy Resources (DER) in ... more ABSTRACT The challenges in achieving higher integration of Distributed Energy Resources (DER) in electricity grids require advances and novel approaches in simulation and testing. An approach that is increasingly gaining interest is Hardware-in-the-Loop (HIL) simulation and especially Power-Hardware-in-the-Loop (PHIL), where power equipment is connected to a simulated system. This paper firstly discusses interfacing issues of PHIL simulation providing a theoretical basis. A detailed description of the design and development phase of a PHIL environment for DER devices is provided. The development of the Power Interface, stability analysis and design of appropriate protection schemes are presented, aiming at assisting the development of other PHIL environments. As a first experiment, a voltage divider circuit is implemented in the PHIL approach. Subsequently, hardware PV panels and a PV inverter are connected at a simulated simple distribution grid and it is demonstrated that the voltage of the common-node follows the variation of the solar irradiation
A novel islanding detection method for microgrids based on variable impedance insertion
Electric Power Systems Research, 2015
ABSTRACT Islanding is the situation in which part of the power grid, consisting of load and distr... more ABSTRACT Islanding is the situation in which part of the power grid, consisting of load and distributed generation (DG) is isolated from the utility grid remaining active, i.e. serving load. The idea of islanding parts of the distribution network in case of faults, in order to increase the consumer quality of service, is the basic notion behind the formation of Microgrids. In the context of Microgrids, it becomes necessary to distinguish between intended islanding e.g. due to maintenance and unintended islanding due to faults at the upstream grid. When the emergency situation ceases, the Microgrid should reconnect seamlessly to the upper grid.
Power-Hardware-in-the-Loop (PHIL) simulation is an advanced tool that can support the higher inte... more Power-Hardware-in-the-Loop (PHIL) simulation is an advanced tool that can support the higher integration of Distributed Energy Resources (DER) to electricity grids. This paper provides an introduction to PHIL simulation and demonstrates its applicability in the domain of DER by presenting representative applications. A description of the facility at NTUA is provided focusing on the Power Interface for PHIL simulation, the laboratory microgrid and the Multi-Agent System. In addition interfacing issues are addressed. A PHIL experiment is performed, where hardware photovoltaic (PV) panels and a PV inverter are connected to a simulated rural distribution network. An irradiation sensor provides input to simulated PVs in order to achieve realistic conditions. Steady-state and dynamic simulations (i.e. solar irradiation drop) are performed, where the voltages of the different buses of the distribution network are monitored. More PHIL experiments with a PV inverter and a voltage divider circuit are presented.
Real-Time Simulation Technique of a Microgrid Model for DER Penetration
EAI Endorsed Transactions on Energy Web, 2014
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Papers by Vasilis Kleftakis