An impedance frequency response approach for analyzing interactions in ac-dc systems
Notice bibliographique
Résumé
This thesis presents an integrated technique for screening the interaction level between the ac side system and dc side converters. The system resonances in the sub-synchronous and super-synchronous frequency range are identified and stability determined. This approach applies the Generalized Nyquist stability Criterion (GNC) assuming that the frequency dependent impedance responses are available. The frequency responses of the subsystems are obtained using two different techniques. One is an analytical state variable analysis requiring the mathematical model of the system elements; and the other is a simulation-based frequency scanning approach which does not rely on detailed knowledge of the internal system. These two techniques can be applied in different situations. The state variable analysis is useful when a small signal model is derivable, e.g., for the HVdc converter system, and the frequency scanning method is useful if only ‘black boxed’ models are available. For stability analysis, the systems are represented in the dq0 domain which gets rid of the coupling between frequencies. The frequency scanning is conducted on two Electromagnetic Transients (EMT) simulation platforms, the off-line PSCAD/EMTDC and the real-time RTDS. PSCAD/EMTDC uses a highly-accurate bi-valued resistor model for the switches and its scanned impedance response matches the analytically derived result very well. The RTDS uses a more approximate technique that allows high speed simulation. The impedance scans from RTDS also agree with the analytical results showing that the scanning technique is also a mechanism for validating various new models. An important contribution of this research is the development of an improved small signal analytical model of the Line Commutated Converter (LCC). Traditional studies neglected the transient dynamics of the commutation inductor and modeled it as the reactance of fundamental frequency. The model realized here assumes an infinite series-connected 6- pulse converters and regards the 12-pulse converter as one of its sampled versions. With this treatment, the waveforms of the currents and voltages are ripple-free, and the measured angles, i.e., the overlap angle and the extinction angle become continuous. This model is validated by comparing the analytical converter response with the one obtained from the frequency scanning. Moreover, this LCC model is interfaced with an arbitrary external system, where the system stability is determined using GNC. Based on the impedance responses, the ac-dc system is represented as a closed-loop system, in which the dc side impedance is the forward gain and the ac side admittance is the feedback, or vice versa. The GNC is applied on the closed-loop system and a new index “Harmonic Stability Margin” is proposed to indicate how much a gain or other parameter can be scaled so that the system reaches the boundary of instability. As the index can parameterize the ac-dc interaction level, HSM is then used in several case systems to study the Sub-Synchronous Control Interaction (SSCI), the impact of detailed modeling of remote side converter, as well as the multi-infeed system study. All the results are validated by EMT simulations.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,001 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».