The hierarchical voltage control to face uncertainties given by market structures Titolo in italiano: Il controllo gerarchico di tensione in presenza delle incertezze derivanti dal mercato Autori: M.Pozzi (CESI) A.Berizzi, M.Merlo, F.Tortello (Politecnico di Milano) P.Marannino (Università di Pavia) Pubblicazione: International Journal of Power and Energy Systems Abstract: This paper deals with the exploitation of the advantages of a coordinated voltage control to face uncertainties in the operation of power systems. Due to the electricity market, power systems are operated closer and closer to loadability limits. Unbundling of modern systems is a challenge for the development of an integrated system for voltage and reactive power control. In the past, the system operators had the complete control to operate for the best the system (i.e., real power dispatch, voltage coordination and optimization, etc.); nowadays, the market defines the real power dispatch and the unit commitment and a change of that schedule is acceptable only for security reasons. Security is actually the main responsibility of ISOs that usually can make use of a less efficient set of control actions than in the past. The voltage control is a function whose market is not always well settled, while it is very important for the power security. In Italy, the previous vertically integrated utility, ENEL, studied and partially implemented a hierarchical voltage control (HVC) system. This paper shows how the HVC and a centralized grid voltage control and the related improvement of the operation security, are of interest for all the market participants: it should be therefore implemented as a part of the ancillary services market, mainly concerning voltage quality and security. The paper demonstrates that the presence of such a control structure is still useful in a market environment to improve the security of the operation against perturbation that are more likely to occur in presence of the electricity market. PUBBLICATO A5026184 (PAD – 699072)