HVDC links between North Africa and Europe: Impacts and benefits on the dynamic performance of the European system

This document is the Accepted Manuscript version of the following article: Mokhtar Benasla, Tayeb Allaoui, Mostefa Brahami, Mouloud Denai, and Vijay K. Sood, ‘HVDC links between North Africa and Europe: Impacts and benefits on the dynamic performance of the European system’, Renewable and Sustainable Energy Reviews, November 2017. Under embargo. Embargo end date: 20 November 2018. The published version is available online at doi: DOI: https://doi.org/10.1016/j.rser.2017.10.075. Published by Elsevier Ltd. This manuscript version is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.In the last decade, there have been several initiatives for the deployment of cross-Mediterranean HVDC (High Voltage Direct Current) links to enable the transmission of electrical power from renewable energy sources between North Africa and Europe. These initiatives were mainly driven by the potential economic, environmental and technical benefits of these HVDC interconnections. In previous studies on these projects, some technical aspects of critical importance have not been addressed or studied in sufficient detail. One of these key aspects relates to the impact and possible benefit of these HVDC links on the dynamic performance of the European system which is the major focus of this paper. Several issues relating to the dynamic performance of the system are addressed here. Based on the experience gained from existing AC/DC projects around the world, this paper shows that the HVDC links between North Africa and Europe can greatly improve the dynamic performance of the European system especially in the southern regions. In addition, some challenges on the operation and control of these HVDC links are highlighted and solutions to overcome these challenges are proposed. This review paper, therefore, serves as a preliminary study for further detailed investigation of specific impacts or benefits of these interconnections on the overall performance of the European system.Peer reviewe

Upravljanje vjetroagregatom otporno na me.uzavojske kvarove statorskog namota generatora

Faults of wind turbine generator electromechanical parts are common and very expensive. This paper introduces a generator fault-tolerant control scheme for variable-speed variable-pitch wind turbines that can be applied regardless to the AC generator used. The focus is on generator stator isolation inter-turn fault that can be diagnosed and characterised before triggering the safety device. An extension of the conventional wind turbine control structure is proposed that prevents the fault propagation while power delivery under fault is deteriorated as less as possible compared to healthy machine conditions. Fault-induced and inherent asymmetries of the generator are estimated and respected by the field-oriented control of the generator to eliminate torque oscillations. An approach for asymmetry detection based on an unscented Kalman filter is proposed. Presented fault-tolerant control strategy is developed taking into account its modular implementation and installation in available control systems of existing wind turbines to extend their exploitable life span and increase energy production. Simulation results for the case of a megawatt class wind turbine are presented.Kvarovi elektromehaničkih dijelova generatora vjetroagregata česti su i izrazito skupi. U ovom radu predstavljen je koncept na kvarove otpornog upravljanja generatorom vjetroagregata s promjenjivom brzinom vrtnje i zakretom lopatica primjenjiv bez obzira na tip korištenog izmjeničnog generatora. Naglasak je stavljen na oštećenje izolacije unutar namota jedne faze statora generatora koje se može dijagnosticirati i okarakterizirati prije aktiviranja sustava zaštite. Predložena je nadogradnja postojećeg sustava upravljanja vjetroagregatom koja sprječava širenje kvara i pritom postiže čim manje smanjenje proizvodnje električne energije u odnosu na normalan režim rada. Tako.er je prikazano vektorsko upravljanje generatorom koje uzima u obzir nesimetrije generatora, kako one nastale uslijed djelovanja kvara, tako i one inherentne. U radu je prikazan pristup za otkrivanje nesimetrija generatora zasnovan na nederivacijskom Kalmanovu filtru. Predstavljena strategija upravljanja razvijena je uvažavajući mogućnost modularnog nadovezivanja na postojeće algoritme upravljanja već postavljenih vjetroagregata s ciljem produženja njihova životnog vijeka i povećanja proizvodnje energije. Dani su simulacijski rezultati za slučaj vjetroagregata iz megavatne klase