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A Mixed-Signal Computer Architecture and Its Application to Power System Problems

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A Mixed-Signal Computer Architecture and Its Application to Power System Problems A mixed-signal computer architecture and its application to power system problems THÈSE NO 6613 (2015) PRÉSENTÉE LE 4 SEPTEMBRE 2015 À LA FACULTÉ DES SCIENCES ET TECHNIQUES DE L'INGÉNIEUR GROUPE KAYAL PROGRAMME DOCTORAL EN GÉNIE ÉLECTRIQUE ÉCOLE POLYTECHNIQUE FÉDÉRALE DE LAUSANNE POUR L'OBTENTION DU GRADE DE DOCTEUR ÈS SCIENCES PAR Theodoros KYRIAKIDIS acceptée sur proposition du jury: Dr J.-M. Sallese, président du jury Prof. M. Kayal, Dr S.-R. Cherkaoui, directeurs de thèse Prof. T. Van Cutsem, rapporteur Prof. A. Hatzopoulos, rapporteur Prof. M. Paolone, rapporteur Suisse 2015 >En rq¬ ªn å Lìgoc. — >Iw. a'v 1 To my family. Acknowledgements First of all I would like to thank my supervisors Maher Kayal and Rachid Cherkaoui. They gave me the opportunity to conduct my research “the old way”, in the sense of providing me with suggestions and tips along the way rather constraining me to a fixed target. It is this kind of freedom that allows the investigation of “crazy ideas” and it is due to them that this work has been enabled. I would like to equally thank the professor Thierry Van Cutsem of the University of Liège and his group for their exemplary hospitality during my spell with them in Liège. Particular mention goes to dear friend and colleague Petros Aristidou for all our fruitful discussions and his invaluable help. A big part of what you read in this manuscript is done in collaboration with colleagues of my lab and elsewhere. Sometimes collaboration was so tight that is is really difficult to say who has really contributed what. I would like to specially mention Guillaume Lanz, Denis Sallin and Georgios Lilis. Each one with his deep dedication to his field, and each one always willing to share and help. Apart from the above, there is a number of people that have contributed their bit in the scientific part of this work. It being a discussion over a coffee, a review of a paper, a coding idea, or some useful small-talk over a pint of beer, to you all people, I am grateful. I would also like to thank all the people who have made my days here in Switzerland happy and cheerful: my office-, flat-, and team-mates, and all my amazing Greek and Swiss friends. I would finally like to thank my family, for their constant support and for the happiness they bring to my life. Lausanne, 04 Juin 2015 £. K. i Abstract Radical changes are taking place in the landscape of modern power systems. This massive shift in the way the system is designed and operated has been termed the advent of the “smart grid”. One of its implications is a strong market pull for faster power system analysis computing. This work concerns in particular transient simulation, which is one of the most demanding power system analyses. This refers to the imitation of the operation of the real-world system over time, for time scales that cover the majority of slow electromechanical transient phe- nomena. The general mathematical formulation of the simulation problem includes a set of non-linear differential algebraic equations (DAEs). In the algebraic part of this set, heavy linear algebra computations are included, which are related to the admittance matrix of the topology. These computations are a critical factor to the overall performance of a transient simulator. This work proposes the use of analog electronic computing as a means of exceeding the performance barriers of conventional digital computers for the linear algebra operations. Analog computing is integrated in the frame of a power system transient simulator yielding significant computational performance benefits to the latter. Two hybrid, analog and digital computers are presented. The first prototype has been implemented using reconfigurable hardware. In its core, analog computing is used for linear algebra operations, while pipelined digital resources on a field programmable gate array (FPGA) handle all remaining computations. The properties of the analog hardware are thoroughly examined, with special attention to accuracy and timing. The application of the platform to the transient analysis of power system dynamics showed a speedup of two orders of magnitude against conventional software solutions. The second prototype is proposed as a future conceptual architecture that would overcome the limitations of the already implemented hardware, while retaining its virtues. The design space of this future architecture has been thoroughly explored, with the help of a software emulator. For one possible suggested implementation, speedups of two orders of magnitude against software solvers have been observed for the linear algebra operations. Key words: [Computing]: analog computing, pipeline processing, field programmable gate arrays, reconfigurable computing, computer accelerator architectures, high performance computing; [Power systems]: power system simulations, power system analysis computing, power system dynamics; [Mathematics]: linear algebra - linear systems, numerical analysis - numerical simulation, numerical linear algebra; iii Résumé Des changements radicaux prennent place dans les systèmes électriques modernes. Ces changements massifs dans la façon dont le système est conçu et exploité correspondent à l’avènement du “smart grid”. L’une des conséquences est le besoin d’outils d’analyse du système plus rapides. Ce travail concerne en particulier une analyse très exigeante, la simulation transitoire. Ceci se rapporte à l’imitation de l’opération du système réel, pour des échelles de temps qui couvrent la majorité des phénomènes transitoires électromécaniques lents. La formulation mathéma- tique générale du problème comprend un ensemble d’équations algébriques différentielles non-linéaires (DAE). Dans la partie algébrique de cet ensemble, de lourds calculs d’algèbre linéaire prennent place, qui sont liés à la matrice d’admittance de la topologie. Ces calculs sont un facteur critique de la performance globale d’un simulateur transitoire. Ce travail propose l’utilisation des calculs analogiques comme un moyen de dépasser les barrières de performance des ordinateurs numériques classiques pour les opérations d’algèbre linéaire. Le calcul analogique est intégré dans le cadre d’un simulateur transitoire et apporte d’importants avantages en termes de performances. Deux ordinateurs hybrides, analogique et numérique, sont présentés. Le premier prototype a été mis en œuvre en utilisant ressources reconfigurables. Dans son cœur, le calcul analogique est utilisé pour des opérations d’algèbre linéaire, tandis que les ressources numériques sur un Field Programmable Gate Array (FPGA) gèrent tous les calculs restants. Les propriétés du matériel analogique sont examinées. Une attention particulière est portée à la précision et au timing. L’application de la plate-forme à l’analyse transitoire de la dynamique du réseau électrique a montré une accélération de deux ordres de grandeur par rapport à des solutions logicielles classiques. Le deuxième prototype est proposé comme une future architecture conceptuelle qui permet- trait de surmonter les limitations du matériel déjà mis en œuvre, tout en conservant ses vertus. L’espace de conception de cette future architecture a été explorée à fond, avec l’aide d’un émulateur en logiciel. Pour une mise en œuvre suggérée, accélérations de deux ordres de grandeur contre logiciels classiques ont été observées pour les opérations d’algèbre linéaire. Mots clefs : [Informatique] : calcul analogique, traitement en pipeline, circuit logique pro- grammable, computing reconfigurable, architectures d’ordinateur de l’accélérateur, calcul haute performance ; [Réseau électrique] : simulations du réseau électrique, informatique v Acknowledgements de l’ analyse du réseau électrique, dynamique du réseau électrique ; [Mathématiques] : al- gèbre linéaire - systèmes linéaires, analyse numérique - simulation numérique, algèbre linéaire numérique ; vi PerÐlhyh Rizikèc allagèc lambnoun q¸ra ston tomèa twn sÔgqronwn susthmtwn hlektrik c e- nèrgeiac (SHE). Aut h metbash ston trìpo me ton opoÐo to sÔsthma sqedizetai kai leitourgeÐtai apokaleÐtai h èleush tou èxupnou diktÔou. 'Ena apì ta epakìlouja thc eÐnai h angkh gia taqÔterouc upologistèc anlushc SHE. Aut h ergasÐa epikentr¸netai se mia idiaÐterh apaithtik anlush, thn prosomoÐwsh SHE. Autì anafèretai sthn pist anaparstash thc leitourgÐac tou sust matoc gia stajerèc qrìnou pou kalÔptoun thn pleionìthta twn hlektromhqanik¸n metabatik¸n fainomènwn sto sÔsthma. H genik majhmatik diatÔpwsh tou probl matoc thc prosomoÐwshc peri- lambnei èna sÔnolo mh grammik¸n diaforik¸n-algebrik¸n exis¸sewn (DAE). Sto algebrikì mèroc autoÔ tou sunìlou perilambnontai polloÐ kai apaithtikoÐ upologi- smoÐ grammik c lgebra. AutoÐ sqetÐzontai me ton pÐnaka agwgimot twn thc topologÐac kai eÐnai krÐsimoi gia thn sunolik apìdosh enìc prosomoiwt metabatik¸n fainomènwn SHE. Se aut thn ergasÐa proteÐnetai h qr sh analogik¸n arqitektonik¸n wc mèso upèrbashc twn periorism¸n twn sumbatik¸n yhfiak¸n upologist¸n ìson afor idiaÐtera touc upo- logismoÔc grammik c lgebrac. Oi analogikoÐ upologismoÐ enswmat¸nontai sthn ro tou prosomoiwt metabatik¸n fainomènwn apofèrontac shmantik wfèlh sthn apìdosh tou. DÔo ubridikoÐ upologistèc parousizontai. O pr¸toc afor èna prwtìtupo to opoÐo èqei kataskeuasteÐ se epanadiamorf¸simo ulikì. Ston pur na tou analogikoÐ upologismoÐ qrhsimopoioÔntai gia thn grammik lgebra, en¸ swlhnomènoi epexergastèc èqoun programmatisteÐ se mia sustoiqÐa epitìpia programmati- zomènwn pul¸n (FPGA) gia touc upìloipouc upologismoÔc. Oi idiìthtec tou analogikoÔ tm matoc exetzontai diexodik, me
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