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F. Figure, 1 -Ajouts mondiaux annuels de capacité d'énergie renouvelable, par technologie et total, pp.2012-2018

. Le, Mode est le terme technique designant un modèle d'oscillation particulier (voir l'explication détaillée dans la section F.1.4). Les non-linéarités du système et les interactions modales sont affectées par les conditions de fonctionnement du système

, Uneétude antérieure de l'interaction modale non linéaire dans un système HVDC/AC avec modulation DC a indiqué qu'une interaction modale fortement non linéaire peut résulter des charges AC et DC trèsélevés avec des modulations de puissance DC bien réglées [5].Étant donné que les REs injectent de l'énergie dans le réseau via des convertisseurs PE, entraînant un manque d'inertie et un couple de synchronisation dans le réseau, la deconnexion des générateurs synchrones augmenterait l'effet de non-linéarité [10] affectant ainsi la stabilité de l'angle du rotor. En plus, les convertisseurs PE pourraient former une capacité virtuelle, Le transport d'une grande quantité d'énergie sur de longues distances est très courantes de nos jours en raison des connexions inter-zones (par exemple Ecosse-Angleterre) et de la croissance des sources REs

, en plus de contribuerà la non-linéarité, les REs et les PEs qui les accompagnent introduisent de nouveaux modes d'oscillation sur le reseau en raison du déplacement des machines synchrones. Il aété noté dans [12] que ces nouveaux modes d'oscillation sont très sensibles aux variations des paramètres de contrôle et peuvent rendre le système plus imprévisible et difficileà surveiller ouà contrôler. Les manifestations de ces défis abondent dans les systèmes d'alimentation pratiques avec une intégration RE significative. Par exemple, le 19 février 2011, des oscillations inter-zones au sein du réseauélectrique de l'Europe continentale (CE) se sont produites. Des oscillations similaires se sont reproduites le 24 février, p.25, 2011.

, Il n'y avait aucun indice clair sur la cause de l'oscillation au départ. Les calculs modaux dans [16] ont révélé plus tard que deux modes se superposaientà 0,25 Hz avec la participation de la Turquie, Hz et a duré 15 minutes (voir Figure F.2)

, Le mode inter-zone implique des machines dans une zone se balançant contre des machines dans d'autres zones. Il a généralement une fréquence propre inférieure dans la

. Cependant, CCBG) dans le réseau, les caractéristiques ci-dessus peuvent ne pas toujour? etre de véritables signatures de modesélectromécaniques. Cela est dû au fait que les CCBG conduisentà de nouveaux modes d'oscillation bas semblables aux modesélectromécaniques d'oscillation inter-zones, vol.12

, Ce phénomène pose un problème pour identifier clairement les modesélectromécaniques réels. De nouvelles méthodes sont en cours de développement pour résoudre ce problème, vol.26

, L'analyse des grands systèmes doit nécessairement se concentrer sur les modes critiques d'importance

, L'étude du comportement de ces modes est connue sous le nom d'analyse modale. L'outil le plus courant pour l'analyse modale est l'analyse de stabilité du petit signal (SSA) qui fournit de nombreuses informations concernant ces oscillations. Comme SSA n'explique que le comportement linéaire

, Le mode non linéaire est utilisé pour décrire l'extension d'un mode linéaire au régime non linéaire. Il s'agit donc d'une extension de la propriété invariance d'un mode linéaire au régime non linéaire. Physiquement, c'est le rendu de couplages modaux non linéaires, d'une manière qui, si un mouvement particulier n'est initié que sur un mode particulier; aucuneénergie n'est donnée aux autres, de sorte que le mouvement ne reste que sur ce mode. L'interaction modale est essentielle et peut soit stabiliser, soit déstabiliser le système. Lorsque l'interaction modale non linéaire se produit, la dynamique devient difficileà expliquer avec LMA. L'analyse modale qui prend en compte les interactions non linéaires des modes est connue sous le nom de NLMA. Une illustration simple des interactions modales non linéaires peutêtre montrée en simulant le système (F.1) avec des conditions initiales plusélevées (c'est-à-dire des déplacements plus importants de x 1 , x 2 ). L'effet des non-linéarités ne sera plus négligeable et l'oscillation sera composée des combinaisons linéaires (naturelles) et significatives des modes linéaires. Ceci est illustré dans la figure F.5. Il ressort clairement de la figure F.5a que le mode 1 est dominant. Au moins, la réponse ressembleà celle de la figure F.4a. Cependant, la conclusion que le mode linéaire est suffisant pour comprendre le comportement de ce système peutêtre trompeuse. La FFT de la figure F.5b révèle clairement la présence significative d'autres fréquences, dans ce cas, en raison de distorsions non linéaires des modes naturels, F.1.5 Interactions Modales et Modes Non Linéaires Lorsque le systèmeélectrique est contraint, la dynamique n'est pas complètement décrite par les modes naturels. En plus des modes naturels, la dynamique peutêtre affectée par certaines combinaisons d'ordre supérieur des modes naturels. L'effet de ces combinaisons d'ordre supérieur est appelé interaction modale non linéaire. L'interaction modale non linéaire donne naissanceà "d'autres modes, p.36

, 36 = 2 × mode1), dont l'amplitude estélevée. Il existeégalement une fréquence de 1,08 Hz (c'est-à-dire 0,36 +0, 36 + 0, 36 = 3 × mode 1), +0

. D'une-certaine-manière, Un terme commun habituellement utilisé pour décrire ces nouvelles fréquences est harmoniques non linéaires, car ce sont des multiples des modes fondamentaux. Cependant, comme nous le verrons dans les chapitres suivants, ces nouvelles fréquences ne sont pas nécessairement des multiples d'un mode fondamental mais peuvent provenir de combinaisons de modes différents