Β.Ι Papers in Journals

B.I.1
J.M. Prousalidis, N.D. Hatziargyriou, Α.C. Kladas, " Iron Lamination efficient representation in power transformers", Journal of Materials Processing Technology, 2001 Published by Elsevier Science B.V.Vol. 108, (2001), issue 2, pp. 217-220.
Abstract
The paper presents a methodology enabling the accurate representation of iron losses in magnetic cores for a frequency range up to 10 kHz. The classical subdivision of iron losses into hysteresis and eddy current phenomena has been adopted. Hysteresis losses are calculated by means of a conveniently modified Preisach-Neel model representation while iron losses are taken into account through a Foster II equivalent circuit representation of the lamination. A final equivalent circuit of sufficient accuracy, combining both hysteresis and eddy current losses contributions is proposed. The model validity has been checked using an Epstein experimental set-up.
Key-words: Preisach-Neel model; Foster II equivalent circuit; Eddy current effect.

B.I.2
S. Spagkouros, J. Prousalidis, " Electric Power Quality problems in ship systems: A classification method ", IASME TRANSACTIONS, Issue 3, Volume 1, July 2004, pp. 437-444.
Abstract
This paper presents an introduction to the analysis and classification of voltage dips, due to short circuit faults in a ship electric power system. The method followed is based on extending methods of voltage dip classification in continental grids taking into consideration the particular nature of ship electric power systems. The software package EMTDC/PSCAD is used to simulate a large number of short circuit fault case studies in the power system of a vessel with electric pod propulsion. Based on the results of the simulations two new methods of voltage dip classification are presented.
Key-Words: power Quality, dips, sags, faults.

B.I.3
M. Moschakis, J. Prousalidis, N. Hatziargyriou," Performance Assessment of STC used for Alternative Naval Power Supplying Units ", IASME TRANSACTIONS, Issue 2, Volume 1, April 2004, pp.394-399.
Abstract
Critical loads on shipboard installations require electric power of good quality, i.e. free from voltage interruptions and sags. An effective way to improve the quality of the electric power supplied is to use a Static Transfer Switch (STS). This device can be used to connect an alternate (or backup) source of ac power to the sensitive load when the main (or preferred) source fails. Thus, power quality problems become almost transparent to the critical or sensitive equipment. In this paper, the main parts of a STS, performance characteristics and power system as well as fault parameters that influence them, are discussed. A STS model is presented and its behaviour on various cases is shown.
Key-Words: power quality, power conditioning, sensitive loads, static transfer switch, voltage sags.

Β.Ι.4
J. Prousalidis, " Introducing an Effective Method for Teaching Power Electronics in Marine Electrical Engineering Courses", IASME TRANSACTIONS, Issue 4, Volume 2, October 2005, pp.323-328.
Abstract
This paper presents an introduction of a feasible method for teaching power electronic issues to non-electrical engineering disciplines. The method presented is founded on the switching function techniques, which as it is shown does not require any specific branches of knowledge. On these grounds, the topologies of certain fundamental power electronic devices, are analysed and presented. Furthermore, the ways that this methodology has permitted the introduction of power electronics to School of Naval Architecture and Marine Engineering of NTUA are discussed.
Key-Words: Marine electrical engineering, power electronics, switching functions.

Β.Ι.5
Shozo Sekioka, Maria I. Lorentzou, Maria P. Philippakou, and John M. Prousalidis," Current-Dependent Grounding Resistance Model Based on Energy Balance of Soil Ionization", IEEE Transactions On Power Delivery, Vol. 21, No. 1, January 2006, pp. 194-201.
Abstract
Soil ionization occurs around a grounding electrode when current density in the soil exceeds a critical value and reduces grounding resistance. This paper proposes a current- dependent grounding resistance model considering the soil ionization. The proposed model is derived on the basis of energy balance of the soil ionization. The resistivity of the ionization zone depends on energy stored in the zone. Analytical expressions of the model are proposed to estimate the zone resistivity. The model is verified by comparing it with experimental results.
Key-Words: -Current dependence, energy balance, grounding resistance, hysteresis effect, soil ionization.

Β.Ι.6
J. Prousalidis, E. Styvaktakis, "Introducing a classification method of Voltage dips in ship electric energy systems", "The Journal of Marine Engineering & Technology (Part A11)", IMarEST, London (UK), April 2008, pp 53-62.
Abstract
This paper presents an introduction to the analysis and classification of voltage dips, in a ship electric power system. The method followed covers the variety of dips occurring on shipboard installations in its entity. Thus although it has been primarily developed only for dips due to short circuit faults, it is shown that it can include the cases of sags due to motor starting, transformer energizing inrush or even pulsed loads. This method focuses on emerging and characterising the severeness of the event depending on the consequences on the operating equipment. Therefore, besides an implement of assessing the significance of each situation it can be easily assimilated in system power quality monitoring units, in protection scheme design and evaluation processes or even in event identification tools. Where simulations are required, the software package PSCAD is used to simulate a number of case studies in the power system of actual vessels with electric propulsion.
Key-Words: - Power Quality, dips, sags.

Β.Ι.7
J. Prousalidis, E. Styvaktakis, I.K. Hatzilau, F. Kanellos, S. Perros, E. Sofras, "Electric power supply quality in ship systems - An overview", International Journal of Ocean Systems Management (IJOSM), Special Issue on Sustainable Sea Transportation: The New Research Agenda on Sustainable Ocean Systems, Inderscience Publishers, Geneve (Switzerland), Vol. 1, No.1, pages 68-82.
Abstract
Power Supply Quality (PSQ) has become an important concern for ship electric systems. Thus, deviations of voltage from nominal values and wave-shapes could cause several malfunctions, interruption or even damages of onboard equipment and systems. Considering that the ship system electrification eventually dominates according to the All Electric Ship concept, PSQ issues turn to be a key-factor of the normal operation, survivability and safety aboard. However, limited research work has been reported (even for more conventional ship types) on the investigation and classification of PSQ phenomena. In this paper a short but coherent description and categorisation of the PSQ phenomena (causes, consequences, characteristic parameters etc) is given and the similarities and differences between terrestrial systems and ship systems in terms of these phenomena are identified. This overview is enriched by cross-references to relevant standards (international and national, military and commercial) applied in shipboard applications. This work was done within a research project on power quality on ships and it is the base of the investigation as it creates the necessary framework for the analysis as well as it stresses issues relevant with standards and regulations and the way they treat power quality phenomena.
Key-Words : Power Supply Quality, Standards, All Electric Ship.

B.I.8
J. Prousalidis, E. Xanthopoulos, C. Voutzoulidis, "On reactive power sharing in ship energy systems with shaft generators", "The Journal of Marine Engineering & Technology (Part A13)", IMarEST, London (UK), February 2009, pp 21-38.
Abstract
This paper deals with well based mathematical formulation of active and reactive load sharing among the synchronized generators of a ship electric energy system. Thus, both the first- and second- stage regulation during load sharing is presented via mathematical equations. The novelty introduced in the paper is on the one hand that the hybrid parallel operation of shaft and conventional generators is covered, while on the other hand, that the analysis results in solving the combined proportionate, i.e. according to the generator rated capacity, load sharing problem of not only active power demands but also of the reactive ones, which is not often faced in most ship plants. Furthermore, the dynamic behavior of machines and their controllers during the load sharing problem is also discussed to some extent via simulations in MATLAB/Simulink environment. The entire analysis which is intended to be also exploited for educational purposes, is enriched by figurative results obtained from an actual ship case study, in which this work assisted to resolve a series of load sharing problems.
Key-Words:- Active power, Reactive power, Load sharing, Shaft generators.

B.I.9
G. J. Tsekouras, I. K. Hatzilau, J. M. Prousalidis, "A new pattern recognition methodology for classification of load profiles for ships electric consumers", "The Journal of Marine Engineering & Technology (Part A14)", IMarEST, London (UK), April 2009, pp 45-54.
Abstract
In this paper a new pattern recognition methodology is presented for the classification of the daily chronological load curves of ship electric consumer (equipment) and the determination of the respective typical load curves of each one of them. It is based on pattern recognition methods, such as k-means, adaptive vector quantization, self-organizing maps, fuzzy k-means and hierarchical clustering, which are theoretically described and properly adapted. The parameters of each clustering method are properly selected by an optimization process, which is separately applied for each one of six adequacy measures: the error function, the mean index adequacy, the clustering dispersion indicator, the similarity matrix indicator, the Davies-Bouldin indicator and the ratio of within cluster sum of squares to between cluster variation. As a study case, this methodology is applied to a set of consumers of Hellenic Navy MEKO type frigates.
Key-Words: - Ship load profiles, clustering algorithms, adaptive vector quantization, fuzzy k-means, k-means, self-organizing maps (SOM), fuzzy k-means, hierarchical clustering, pattern recognition.

B.I.10
J. M. Prousalidis, P.S. Mouzakis, "Analysis of Electric Power Demands of Podded Propulsors", The Journal of Marine Engineering & Technology (Part A14), IMarEST, London (UK), January 2010, pp 3-16.
Abstract
The purpose of this paper is to investigate and analyze from the electric power point of view the operating conditions of pod electric motor drives, mainly in an attempt to explain the high failure rates of the electric components in pod propulsion installations. The analysis is based on simulations, where the pod torque demands are obtained from experimental results recently published in the literature. Thus, the same series of loading scenarios for an entire range of turning azimuth angles of a twin pod configuration are considered. The approach is rather generic as only nameplate data of the motor drives are required, while as the simulations focus on the electric motors, the rest of the ship electric system considered, including generator sets, is represented by a simplified network. Two different sets of simulations are considered, one comprising a synchronous AC motor drive and one with an asynchronous motor of similar rating. In all cases, it is shown that during maneuvering in certain range of azimuth angles significant overloading occurs exceeding the apparent power capacity of the motors.

B.I.11
J. Prousalidis, "On investigating the influence of Zero sequence impedance in ship ungrounded electric networks", The Journal of Marine Engineering & Technology (Part A14), IMarEST, London (UK), September 2010, pp 3-16.
Abstract
In shipboard installations ungrounded earthing is particularly selected, as it provides continuous power supply even in case of single-phase earth faults, which can not be accomplished by low resistance earthing in the neutral point of wye-connected generator or transformer windings. However, the electric network is actually earthed via the high impedance capacitances of all the equipment installed onboard. Therefore, as it has already been discussed in the literature, the “ungrounded” earthing type of shipboard installations has to be treated as grounded via capacitive elements. This paper aims to show, for the first time, an analytical description of statements given in previous publications, i.e. that in all analyses performed, it is the entire zero sequence (homopolar) impedance that has to be taken into account. This homopolar impedance includes, among others, leakage capacitances of the entire electrical installation. Therefore, an investigation of the influence of the zero sequence impedance is performed in representative case studies, all referring to unbalanced operating conditions. Within this frame, analytical expressions of voltages and currents with respect to zero sequence impedance are yielded. Moreover, the significant adverse effects of leakage capacitances on the occasion of an actual ship earthing network, are highlighted.

Β.II Papers in International Conferences

B.II.1 J.M. Prousalidis, N.D. Hatziargyriou, B.C. Papadias, " On studying Ship Electric Propulsion Motor Driving Schemes", Proceedings of 4th International Conference on Electromagnetic Transients, IPST '01, Rio de Janeiro (Brazil), June 24-28, 2001, pp. 87-93.
Abstract
In this paper, an effort is made to identify the problems encountered during studying and modeling ship electric propulsion schemes. It is shown that where no existing models are available in programs like ATP/EMTP, new ones can be developed, with the new ones being able to co-operate with the rest of the computer package. In this way, several phenomena can be studied like those related to power quality on shipboard.
Key-Words: ship propulsion, electric motors, converters, motor drives, power quality, EMTP.

B.II.2
S. Sekioka, M. Lorentzou, M.P. Philippakou, J. Prousalidis, " A current Dependent Grounding Resistance Model based on an Energy Balance in Ionization Zone " Proceedings of 4th International Conference on Electromagnetic Transients, IPST '01, Rio de Janeiro (Brazil), June 24-28, 2001, pp. 343-349.
Abstract
Soil ionization occurs around a grounding electrode when current density in the soil exceeds a critical value. The grounding resistance for lightning currents is decreased due to the soil ionization. This paper proposes a new current-dependent grounding resistance model of a rod electrode considering the soil ionization. The proposed model is derived from energy balance in the soil ionization zone. The resistivity of the ionization zone is dependent on energy stored in the zone. The proposed model can treat the soil ionization as well as deionization.
Key-Words: Soil Ionization, Soil Deionization, Grounding Resistance, Current Dependency, Energy Balance, Arc Model.

B.II.3
J. Prousalidis, S. Perros, I.K.Hatzilau, N. Hatziargyriou, " Practical solutions of numerical noise problems at simulation of switching transients to ship electric power systems ", Proceedings of 3rd WSEAS Symposium on Mathematical Methods and Computational Techniques in Electrical Engineerings (MMACTEE 2001), 30-31 December 2001, Vouliagmeni (Greece), Paper No 563, pp. 5631-5636.
Abstract
Simulation of switching transients in electric energy systems requires accurate modeling of most of the components involved. The problems are studied via dedicated computer programs like the well-known EMTP which provide the extra option to synthesize associated user-defined models. In this paper, this capability of EMTP is exploited so that a representative ship electric propulsion scheme is modeled while the interest is focused on the elimination of numerical noise problems emerged during the simulations.
Key-Words: Power Systems Transients, EMTP, Numerical Analysis, Numerical Noise.

B.II.4
J.M. Prousalidis, " Simulation tools for ship electric power and control system studies ", Proceedings of 6th International Naval Exhibition and Conference (INEC2002), Glascow (UK), 23-24 April 2002, pp. 263-275.
Abstract
A problem emerging even at the ship design stage is the usage of proper simulation tools to study the response of the main and auxiliary systems under steady- and transient- state conditions. Moreover, nowadays that the concept of an integrated electric power system in conjunction with an associate monitoring/managing system has started being realized, an equivalent simulation tool is sought, too, especially referring to electric power system which tends to become the most significant system on shipboard. This contribution moves towards answering affirmatively the evident question of marine engineers whether there is a single computer program capable of accurately dealing with all power and control problems encountered on shipboard.
Key-Words: -simulation tools, MATLAB, PSCAD, marine electrical engineering.

B.II.5
S. Sekioka, M. Lorentzou, M.P. Philippakou, J. Prousalidis, " A current Dependent Grounding Resistance Model based on an Energy Balance in Ionization Zone (II) ", Proceedings of International Conference on Grounding and Earthing and 3rd Brazilian Workshop on Atmospheric Electricity, November 4-7, 2002, Rio de Janeiro (Brazil), pp. 195-198.
Abstract
The authors proposed a current-dependent grounding resistance model for high impulse currents based on an energy balance of soil ionization. This paper proposes approximate and general expressions of the proposed model, and the determination of constants of the model. Then, this paper investigates accuracy of the approximate expression by comparing with the general expression. The proposed model takes current dependence and hysteresis effect into account.
Key-Words: - grounding resistance, soil ionization.

B.II.6
I.Κ. Ηatzilau, Α. Magoulas, S. Perros, D. Kavoulakos, E. Sakiotis, E. Christofis, F. Martinos, J. Prousalidis , "Harmonic power quality on naval ship electric systems ( overview of standards - field measurements on HN "meko" class frigates ) ", Proceedings of Mediterranean Power Conference and Exhibition (MedPower 2002), Athens (Greece), 5-7 November 2002.
Abstract
The main objective of this paper is a discussion on the power quality problems encountered on naval vessels with respect to the harmonic distortion limits imposed by relevant standards, namely IEEE-519 which refers to all electric systems and STANAG-1008 which is dedicated to warships. A brief discussion is also made on the causes, consequences and remedies of harmonic distortion in the electrical plants, while measurements conducted onboard HN MEKO class frigates are presented. The evaluation of the measurements indicates that it can not be easily argued if the STANAG-1008 as well as IEEE-519 current restrictions are violated or not, while the voltage distortion remains within the imposed limits.
Key-Words: Naval vessel, power quality, harmonic distortion, STANAG 1008, IEEE-519.

B.II.7
J. Prousalidis, I.K. Hatzilau, Cdr S. Perros, " Harmonic electric power quality concepts for the electrified ships (AES) ", Proceedings of International Conference on All Electric Ship (AES 2003), Edinburg (UK), 13-14 February 2003.
Abstract
The problem of harmonic power quality, which has increased lately on the continental grids is expected to deteriorate on shipboard installations, too, after the advent of electric propulsion and other All Electric Ship (AES) schemes where the harmonic pollutant power electronic devices dominate. This work aims at offering a comparative analysis on power quality standards either dedicated for ships or general purpose ones, underlining the importance of these standards, as well as giving some hints for possible further improvement of them.
Key-Words: -Harmonic distortion, power quality, All Electric Ship.

B.II.8
Lt Cdr. I.K. Gyparis, I.K. Hatzilau, J. Prousalidis, Cdr S. Perros, Lt Cdr. A. Dalakos, " Perspectives of enhanced survivability on AES ", Proceedings of International Conference on All Electric Ship (AES 2003), Edinburg (UK), 13-14 February 2003.
Abstract
The development and acquisition of highly survivable warships is of paramount importance, especially with the current trends for cutting down defence budgets. High survivability is an important 'power multiplier' allowing a Navy to keep the number of its fleet units down to a minimum, since each one of them will be a compact low vulnerability unit that will give the best out of a naval battle. All Electric Ship (AES) features comprising Integrated Full Electric Propulsion (IFEP) as well as effectively controlled and completely electrified auxiliaries are expected to be the future key-factor for the desired survivability enhancement. In this paper an effort is made to identify and examine the critical and hence most vulnerable elements of the propulsion and electric power systems of ships as outlined by the AES-concept. Furthermore, the difficulties encountered for a quantitative assessment of a survivability index of a warship are highlighted, while an attempt is made for a qualitative survivability comparison between conventional and AES systems. Thus, the characteristic features of AES systems, namely novel ship designs, electric power distribution architectures, electric power generation schemes, modern storage means and integrated highly automated management systems, all promising great survivability improvements, are overviewed. On the other hand, certain considerations that may cancel out some of the AES theoretic perspective advantages are also stated.
Key-Words: -survivability, All Electric Ship.

B.II.9
S.A. Gertsos, J.M. Prousalidis, C.A. Frangopoulos, " Electric Propulsion: From Infancy To Adolesence ", Proceedings of 8th International Marine Design Conference, 5-8 May 2003, Athens Greece, pp. 529- 540.
Abstract
Electric propulsion on shipboard is an alternative with well-proven advantages and high potentials, and nowadays it can be found on many types of ships as it is considered an alternative option for many projects. In this paper, a technical description of a typical electric power plant is made, while the most significant characteristics and advantages of electric propulsion are highlighted. Moreover, an effort is made to quantify these features from the economic point of view while the results of two comparative studies of Diesel-electric propulsion (with or without pods) with Diesel-conventional machinery are presented.
Key-Words: -electric propulsion, diesel electric propulsion.

B.II.10
J.M. Prousalidis, "Application of Space- vector theory to multi-phase multi-winding AC machines ", 7th WSEAS International Multi-conference on Circuits, Systems, Communications and Computers, Corfu (Greece), 2003, Paper No 457-201.
Abstract
Sophisticated control techniques of AC motors have been extensively evolved via the space-vector theory, the mathematical presentation of which is often presented only for 3-phase arrangements, i.e. the typical application field of AC motors. However, in certain cases, such as ship electric propulsion motors, novel schemes have been introduced, including multi-phase / multi-winding arrangements. This contribution aims at extending the space-vector theory and its liaison with the well-known dqo (Park) transformation to these multi-phase machines.
Key-Words: space-vector, dq transformation, multi-phase AC machines.

B.II.11
J. Prousalidis, I.K. Hatzilau, Cdr S. Perros, P. Buchanan, D. Muthumuni, " Introducing a COTS simulation tool for ship electric power quality studies", Proceedings of International Naval Exhibition and Conference, Amsterdam (The Netherlands), 16-18 March 2004, Vol. II, pp. 23-34.
Abstract
This paper primarily makes the effort to investigate if a computer program originally developed for numerical simulations of phenomena occurring in continental electric power grids can be exploited as a Commercial Off The Shelf (COTS) implement for analysis of power quality case studies occurring in shipboard installations. However, besides a theoretical argumentation the selected computer program is used for the simulation of representative power quality phenomena occurring in ship electric power systems, while where necessary the effect of certain critical parameters is investigated, too. On this occasion, as the case studies especially in warships with extended electrification involve problems emerging from the integration of modern devices without authenticated circuit modeling, novel circuit models proposed or improved by the authors are presented and validated.
Key-Words: -COTS technology, simulation tools, PSCAD, All Electric Ship.

B.II.12
G. Diamantis, J. Prousalidis, " Simulation of a DTC Ship Propulsion Scheme", Proceedings of International Conference on Power Electric Machine and Drives (PEMD2004), 31 march - 2 april 2004, Edinburg (2004).
Abstract
In this paper an effort is made to represent the behaviour of a ship propulsion system comprising a Permanent Magnet Synchronous Motor (PMSM) driven by a 6-pulse driving system using the Direct Torque Control (DTC) control technique. The DTC technique cited is emulated via MATLAB's Simulink toolbox while all study cases are performed successfully in MATLAB's Power System Blockset environment.
Key-Words: - Direct Torque Control (DTC), ship electric propulsion, MATLAB, Permanent Magnet Synchronous Motor (PMSM).

B.II.13
S. Cofinas, I.K. Hatzilau, J.M. Prousalidis, S. Perros, "Commutatorless series motor without damping circuits and a diode placed in d-axis", Proceedings of International Conference on Electric Machines (ICEM2004), September 2004, Lodz -Poland (2004).
Abstract
An appealing motor drive operating as a DC series machine, is presented. Both experimental and simulated results agree that this variable speed drive is very promising and has to be investigated further as it is fairly simple comprising rather conventional and non-expensive equipment while its operation combines both fairly good power quality, high performance indices and simple control schemes.
Key-Words: - commutatorless series AC motor drive.

B.II.14
S. Cofinas, J.M. Prousalidis, I.K. Hatzilau, "Introducing a DC Commutatorless series motor ", Proceedings of International Symposium on Ship Propulsion and Railway Traction Systems (SPRTS2004), 4-6 October 2004, Bologna - Italy 2004.
Abstract
An appealing motor drive operating as a DC series machine, is presented. Both experimental and simulated results agree that this variable speed drive is very promising and has to be investigated further as it is fairly simple comprising rather conventional and non-expensive equipment while its operation combines both fairly good power quality, high performance indices and simple control schemes.
Key-Words: - commutatorless series DC motor drive.

B.II.15
J. Prousalidis, I.K. Hatzilau, P. Michalopoulos, I. Pavlou, D. Muthumuni, "Studying ship electric energy systems with shaft generator ", Proceedings of International Symposium on Electric Ship Technologies (ESTS05), Philadelphia - USA (25-27 July 2005).
Abstract
This contribution aims at a twofold target. On one hand to make an in-depth discussion on the shaft systems installed onboard highlighting their advantages and disadvantages focusing on that they can possibly be a hybrid alternative to "Full Electric Propulsion" concept. On the other hand, make an investigation of the conditions of the ship electric network operation at different modes of operation of the shaft generator system.
Key-Words: - shaft generators, power electronics, simulations.

B.II.16
E.Sofras, J.Prousalidis, " On Performing Short Circuit Studies On Ship Electric Energy Systems ", Proceedings of International Symposium on All Electric Ship 2005 (AES05), Paris - France (2005).
Abstract
This paper initially presents a comparative analysis both qualitative and quantitative of the scope and subject of IEC 61363 and IEC 61909 highlighting points of convergence and divergence between them, while certain critical issues emerged is also underlined. Following the results of the aforementioned standards has been applied at a medium voltage electrical power system of a ship with electrical propulsion. The type of ship is a car / passenger ferry named "ALKYON 2000" which has fully preliminary designed by the school of Naval Architecture and Marine Engineering of National Technical University of Athens. All the results and the differences in percentages between the resultant magnitudes are categorized and presented in tables hereafter.
Key-Words: - Short circuit, faults, and Electric propulsion.

B.II.17
S. Cofinas, J.M. Prousalidis, I.K. Hatzilau, "Introducing a DC supplied Commutatorless series motor drive for naval applications", Proceedings of International Symposium on All Electric Ship 2005 (AES05), Paris - France (2005).
Abstract
This paper deals with a variable speed drive based on a conventional rotor wound induction motor, which has similar characteristics to a DC series machine. More specifically, the motor system considered is a naturally commutated series excited rotor machine where the excitation current is obtained naturally by placing the excitation winding in the dc link. The motor scheme described in this paper is the fourth edition in the evolution of the series naturally commutated variable speed drives, devised by the first author. Thus, a summary is given on past editions along with the introduction of the last proposed scheme.
Key-Words: Series commutatorless motor, natural commutation.

B.II.18
I.K. Hatzilau, J. Prousalidis, E. Styvaktakis, E. Sofras , " Voltage and Current Spikes & Transients - Power Supply Quality aspects for the AES", Proceedings of International Symposium on All Electric Ship 2005 (AES05), Paris - France (2005). Abstract
In this paper a discussion of the sources and effects of Voltage and Current spikes and transients in shore and ship electric power networks and the characterization parameters and methods are presented. Moreover, the paper investigates, discusses and compares the relevant issues dealt by different standards (inter-national and national, military and commercial) applied to shipboard applications, taking into account the standard status of similar continental power systems and the perspective of the AES technology.
Key-Words: Spikes, Transients, Ships, PSQ, AES.

B.II.19
I.K. Hatzilau, J. Prousalidis, E. Styvaktakis, F. Kanellos, S. Perros, E. Sofras , " Electric power supply quality concepts for the All Electric Ship (AES) ", Proceedings of 2006 joined World Maritime Transport Conference - International Naval Exhibition (WMTC2006-INEC2006) London - UK (2006).
Abstract
Power Supply Quality (PSQ) has become an important concern for ship electrical systems. Deviations of voltage from nominal values and wave-shapes could cause several malfunctions, interruption or even damages of onboard equipment and systems. In contrast to the All Electric Ship perspective domination, limited research work has been reported (even for more conventional ship types) on the investigation and classification of PSQ phenomena. The paper aims : To make a short but coherent description and categorisation of the PSQ phenomena (causes, consequences, characteristic parameters etc). To investigate, discuss and compare, both in a qualitative and, where possible, quantitative manner, the relevant issues covered by different standards (international and national, military and commercial) applied in shipboard applications, taking also into account the standard status of similar continental power systems. To lead to conclusions, where possible, on which specific standardized issues appear closer to the current and forthcoming status of ship electric networks and the relevant PSQ problems.
Key-Words : Power Supply Quality, Standards, All Electric Ship.

B.II.20
G. Petropoulos, J. Prousalidis, "Modeling a Fuel Cell Generator set for DC Transient-State studies", Proceedings of International Conference on Electric Machines (ICEM-2006), Chania (Crete), September 2006.
Abstract
In this paper, a Fuel Cell Circuit Model (FCCM) is presented. The model consists of a voltage source in series with a variable resistance controlled by the value of the current produced. Furthermore, in order to find rules and regulations setting operation limits concerning power quality issues in DC networks with Fuel Cells, the results of a survey of appropriate standards is presented. The proposed FCCM is exploited in a series of simulations of representastive case studies of D.C. networks, in the well-known computer program PSCAD of Manitoba HVDC Research Center.
Key-Words : circuit models, fuel cells, standards.

B.II.21
P. Vallianatos, J. Prousalidis, E. Styvaktakis, "On starting-up large power motors rotating high inertia loads in autonomous systems", Proceedings of International Conference on Electric Machines (ICEM-2006), Chania (Crete), September 2006.
Abstract
This paper deals with an efficient motor starting-up technique applied in stand-alone networks. The method is based on appropriate control of the stand-alone generator supplying the power plant via its AVR (AVR soft-starting method) and resembles to the well-known soft starting via power electronic devices. The work presented has been triggered by two different actual case studies encountered, i.e. a fire pump station supplied by a stand-alone generator and a ship auxiliary electric propulsion sub-network supplied by a dedicated generator coupled on the shaft of the main propulsion engine (shaft generator system).
Key-Words:-autonomous systems, motor starting-up, inrush current.

B.II.22
F. Kanellos, I.K. Hatzilau, J. Prousalidis, E. Styvaktakis, " Simulation of a Shipboard Electrical Network (AES) Comprising Pulsed Loads", International Symposium "Engine as a Weapon II", 5-6 December 2006, London (UK).
Abstract
In the advent of All Electric Ship (AES) and electric warship in particular, several sophisticated and energy demanding electric systems are to be installed aboard including propulsion motors and pulsed loads. The latter require high power for a very short interval and therefore introduce certain severe power quality problems to the ship electric network, especially referring to voltage and frequency modulation. In this paper, an initial attempt is made to study thoroughly these modulation phenomena caused by pulsed loads. Thus, the typical electric network of a warship in the context of the AES is considered, focusing mainly on appropriate modeling and studying the consequences of a pulsed load along with the propulsion motors and the generator set. More specifically, a generating set of two synchronous generators, a large propulsion asynchronous motor, the electrical loads of the system through a MV/LV transformer and a pulsed load. The studied pulsed load is a rail gun which uses the stored energy of a large capacitor. All models are developed by using Matlab toolboxes, namely Power Systems Blockset and Simulink. The developed pulsed load model is fully parametric enabling the analysis of various case studies. Critical factors are investigated, while power quality indices for the assessment of voltage or frequency modulation as referred in the relative standards are calculated. Finally, general conclusions are drawn regarding the problems that will be emerged at the future integration of electrical pulsed loads into warships, the design of their power systems and the energy storage systems in order to ensure operational characteristics imposed by relative standards.
Key-Words : AES, pulsed loads, modulation, power quality, railgun, simulations.

B.II.23
J. Prousalidis, E. Styvaktakis, E. Sofras, I.K. Hatzilau, D. Muthumuni, "Voltage dips in ship systems", Proceedings of 2007 IEEE Electric Ship Technologies Symposium (ESTS07), Anaheim (USA), July 2007.
Abstract
In this paper, voltage dips (an important aspect of power quality) are presented in the context of ship power systems. Voltage dips are analyzed with respect to their origin (fault, motor starting, transformer saturation) considering the characteristics of the on-board installations. Emphasis is given to voltage dips and power quality issues of the All Electric Ship. Related issues are presented and discussed.
Key-Words: power quality, voltage dips(sags), ship power systems.

B.II.24
F. Kanellos, I.K. Hatzilau, J. Prousalidis, "Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints", Proceedings of 2007 All Electric Ship Symposium (AES2007), London (UK), September 2007.
Abstract
The future electric power system of naval warships in the context of the All Electric Ship (AES) will supply energy to sophisticated systems for propulsion, electric guns, electric launchers, high power sensors, navigation etc. Some of the conventional and mainly of the new systems, referred as "pulsed loads", require high power, for short intervals and are the main cause of the power supply quality phenomenon referred as "voltage/frequency modulation". The aforementioned may affect the operation of sensitive several subsystems of the ship such as radarscopes, communication equipment, missile guidance systems, gear systems etc. In NATO standard STANAG 1008 2% and 0,5% limits are set for voltage and frequency modulation, respectively. Furthermore in STANAG 1008 design constraints exist for the reactive and active power of the pulsed load, in order voltage/frequency modulation not exceed the above-mentioned limits. Although STANAG 1008 does not directly apply to AES, but only to Low Voltage systems, it can be used as a discussion reference for standards for the LV sub-networks of AES. The STANAG 1008 design constraints seem to be a method leading to a rather rough estimation of pulsed loads acceptable operational limits. In this paper, an effort is made to examine and validate the STANAG 1008 design constraints, via simulations in Matlab/Simulink, taking into account certain parameters affecting the entire phenomenon such as : periodicity, duty cycle, time-profile and point of connection of the pulsed load, the voltage level and system impedance at the point of connection, the operational characteristics of the generators and their associated frequency and voltage controllers, loading of the generator at the time of pulsed load occurrence etc. A further effort to investigate the voltage and frequency modulation phenomenon in AES electrical power system configuration (HV, electrical propulsion) is made. Finally, general conclusions are derived, as well as directions and methodologies that could be possibly adopted regarding pulsed loads limitation in conjunction with voltage/frequency modulation limits.
Key-Words : ship electric power system, AES, pulsed loads , voltage and frequency modulation, modeling.

B.II.25
I.K. Hatzilau, G.J. Tsekouras, J. Prousalidis, I.K. Gyparis, "On electric load characterization and categorization in ship electric installations", Proceedings of International Naval Exhibition and Conference (INEC2008), London (UK), 1-3 April 2008, pp. 123-135.
Abstract
Each load of a ship's electric network can be characterized by several operating parameters, which are not always readily available or even easily measured. In most cases, the manufacturer provides the so-called nameplate data, which do not at all suffice for the purposes of many studies performed during design and construction or operation and planned maintenance stages. This paper makes the effort to define, analyse and discuss the issues related to the characteristic parameters of onboard electric loads, in an attempt to highlight some fundamental steps for establishing classification criteria, according to which electric loads are grouped into categories. The paper focuses on the discussion of "load demand profile", "load factor" and "priority index" in conjunction to methodologies of studies. Further a two-stage methodology is presented, which can estimate both the typical load curves of each consumer and the consumer clusters together with their respective representative load curves.
Key-Words : ship electric load characterization, load profile, load factor, priority index.

B.II.26
J. Prousalidis, G. Sfakianos, E. Sofras, "Analyzing Voltage Dips in Ship Electric Energy Systems", Proceedings of Mediterranean Power Conference and Exhibition (MedPower 2008), Thessaloniki (Greece), 3-5 November 2008.
Abstract
In this paper, an analysis of voltage dips in ship electric energy systems is presented. Thus, a coherent overview of the different dip types occurred in such networks is made followed by a classification method developed in a previous work. Moreover, an investigation via simulations is performed on the impact of certain factors like the stray capacitive elements and the dynamic loads, which are not taken into account in conventional studies.
Key-Words: ship electric energy systems, power quality, voltage dips.

B.II.27
J.M. Prousalidis, P. Mouzakis,E. Sofras, D. Muthumuni, O. Nayak , "On Studying the Power Supply Quality problems due to Thruster Start-ups", Proceedings of 2009 IEEE Electric Ship Technologies Symposium (ESTS09), Baltimore (USA), April 2009.
Abstract
The target of this paper is twofold: primarily to highlight the significant effect of certain power supply quality problems on the normal operation of the entire ship grid, namely inrush currents and voltage dips due to manoeuvring thruster motor starting-ups. At a second stage, the paper aims at recommending some amelioration of standardization status. Hence, the authors suggest the exploitation of existing experience on pulsed load standardizing, taking into account the resemblance between the systems. The study is enriched by actual case studies and simulations in PSCAD computer program.
Key-Words: power quality, thruster, pulsed loads.

B.II.28
C. Patsios, Ev. Tsambouris, A. Chaniotis, A. Kladas, and J. Prousalidis: “Coupled Field and Circuit Model Analysis of Permanent Magnet Synchronous Machine for Direct Torque Control Optimization”, Proceedings of 6th Japanese-Mediterranean Workshop on applied electromagnetic engineering for magnetic, superconducting and nano materials, July 27-29, 2009.
Abstract
The pulsating torque of a permanent magnet motor has detrimental effects on the motor operation, resulting in speed perturbation, positioning error, vibration, and noise. Several efforts of countering the torque ripple focus on magnet pole shape optimization procedures while other efforts apply sophisticated modifications of control algorithms. In this paper a coupled field and circuit model of a permanent magnet synchronous machine (PMSM) is introduced in order to reduce the effects of pulsating torque. The model comprises of a 2D finite element model for detailed computation of the machine field distribution coupled with an external equivalent circuit for macroscopic parameter evaluation. Model results are then integrated in a direct torque control algorithm for the minimization of torque ripple in a PM machine prototype.

Β.ΙΙΙ Other publications

B.ΙΙΙ.1
1 Ι.Κ. Hatzilau, J.Μ. Prousalidis, G. Antonopoulos, J.Κ. Gyparis, P. Vallianatos, " Ship Electric Propulsion trends and All Electric Ship ", Symposium of Technical Chamber of Greece on " Electric Vehicle Transportation Current Status and Trends", Athens, 12&13 Jan 2006 (in greek).

B.ΙΙΙ.2
J.Μ. Prousalidis, Ι.Κ. Hatzilau, E. Styvaktakis, F. Kanellos, N. Hatziargyriou, C. Frangopoulos, E. Sofras, " Ship Electric Propulsion and All Electric Ship : Electric Power Supply Quality Problems", Symposium of Technical Chamber of Greece on " Electric Vehicle Transportation Current Status and Trends", Athens, 12&13 Jan 2006 (in greek).

B.ΙΙΙ.3
J.Μ. Prousalidis, Ι.Κ. Hatzilau, E. Styvaktakis, F. Kanellos, N. Hatziargyriou, C. Frangopoulos, E. Sofras, "Investigation Power Supply Quality Phenomena in Ship Electric Energy Systems focusing on Voltage Fluctuation Phenomena " -presentation of research projects within the frame "Pythagoras - ΙΙ" performed by NTUA, 5-8 July 2007, Plomari (Lesvos) (in greek).

Β.ΙΙΙ.4
J. Prousalidis, D. Muthumuni, "Power quality on electric ships", Manitoba HVDC Research Centre, Winnipeg, MB, Pulse - The Manitoba HVDC Research Centre Journal, Summer 2005.

B.ΙΙΙ.5
J. Prousalidis, P. Vallianatos: " The merits of thruster start-up using a shaft generator - A Ready Solution?", Marine Engineering Review (MER) , July - August 2006.