Nowadays power systems are facing a high and spreading penetration of Renewable Energy Sources (RES), leading to new problems in terms of grid handling and control. Moreover, in the Italian network, Wind Power Plants and Photovoltaic ones have been traditionally asked to operate at unity power factor, sharpening reactive capability problems. In the described context, this work of thesis presents a preliminary study on RES currently available and future contributions to grid handling with a particular focus on voltage related problems. Three main tools: the Optimal Reactive Power Flow (ORPF), the sensitivity analysis up to the second order and an innovative Short-Circuit calculation accounting for inverter contributions are considered and applied to a short-term forecast of the Sicilian network. In fact, in that region, the combination of grid weakness, low load and remarkable RES production makes the voltage regulation harder to be performed with traditional generators and, at the same time, allows testing the effect of innovative RES control solutions. More in detail, an ORPF procedure is firstly used to estimate the transmission cost reduction as well as the improvement in terms of voltage profile and post-contingency violated limits if reactive power control was extended to HV RES. Then, the influence of innovative Fault Ride Through controls on the network strength (measured by use of the short-circuit power) is analyzed in view of a future grid code extension. Finally, 1st and 2nd order voltage sensitivities to the reactive power injections are performed, tested, and combined with the information contained in short circuit powers, becoming a helpful tool to solve future voltage problems by mean of var compensators or RES reactive capability exploitation.
La consistente penetrazione delle fonti rinnovabili (FER) nei moderni sistemi di trasmissione ha introdotto nuove problematiche in termini di gestione e controllo degli stessi. Tale situazione risulta aggravata in reti deboli ma contraddistinte da un’alta produzione da FER come nel caso del Meridione italiano. Questo lavoro di tesi vuole analizzare gli effetti di un esercizio delle fonti rinnovabili alternativo alla tradizionale produzione a cosfi unitario, con particolare attenzione alle problematiche legate alla regolazione di tensione. A tal fine vengono utilizzati tre strumenti: gli studi di Optimal Reactive Power Flow (ORPF), le sensitivities delle tensioni rispetto alle iniezioni reattive sia di primo che di secondo ordine e un innovativo calcolo di cortocircuito in grado di considerare il singolare comportamento degli inverter in presenza di guasto. I benefici effetti della regolazione di reattivo mediante FER in termini sia di minori costi di trasmissione sia di una maggiore sicurezza sono inizialmente ottenuti mediante ORPF. Dopodiché, l’analisi delle potenze di corto-circuito permette di stimare l’influenza di varie strategie di Fault Ride Through (FRT) sulla solidità della sistema, in vista una futura estensione del codice di rete. Infine, il calcolo e la validazione delle sensitivities di primo e secondo ordine forniscono uno strumento d’analisi alternativo al tradizionale power-flow con cui sarà possibile effettuare accurati studi di sicurezza nonché valutare l’eventuale installazione sistemi di compensazione reattiva a fronte di future problematiche di tensione . Come rete test per le simulazioni è stata scelta la Sicilia in quanto la concomitanza di basso carico, debolezza della rete ed elevata produzione da rinnovabile hanno fatto emergere più volte problematiche di esercizio, rendendola uno scenario ideale per l’implementazione e la verifica di sistemi innovativi di gestione delle FER.
Preliminary study on voltage regulation in presence of high RES penetration
POLINELLI, DARIO
2012/2013
Abstract
Nowadays power systems are facing a high and spreading penetration of Renewable Energy Sources (RES), leading to new problems in terms of grid handling and control. Moreover, in the Italian network, Wind Power Plants and Photovoltaic ones have been traditionally asked to operate at unity power factor, sharpening reactive capability problems. In the described context, this work of thesis presents a preliminary study on RES currently available and future contributions to grid handling with a particular focus on voltage related problems. Three main tools: the Optimal Reactive Power Flow (ORPF), the sensitivity analysis up to the second order and an innovative Short-Circuit calculation accounting for inverter contributions are considered and applied to a short-term forecast of the Sicilian network. In fact, in that region, the combination of grid weakness, low load and remarkable RES production makes the voltage regulation harder to be performed with traditional generators and, at the same time, allows testing the effect of innovative RES control solutions. More in detail, an ORPF procedure is firstly used to estimate the transmission cost reduction as well as the improvement in terms of voltage profile and post-contingency violated limits if reactive power control was extended to HV RES. Then, the influence of innovative Fault Ride Through controls on the network strength (measured by use of the short-circuit power) is analyzed in view of a future grid code extension. Finally, 1st and 2nd order voltage sensitivities to the reactive power injections are performed, tested, and combined with the information contained in short circuit powers, becoming a helpful tool to solve future voltage problems by mean of var compensators or RES reactive capability exploitation.| File | Dimensione | Formato | |
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2013_12_Polinelli.pdf
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https://hdl.handle.net/10589/88583