Technical and economic aspects of ancillary services markets in the electric power industry: an international comparison

We present a comparative analysis of technical and economic aspects of ancillary services on the markets of England and Wales, Nordic Countries, California, Argentina, Australia and Spain, comparing the services of voltage control, frequency regulation and system restoration. All the analyzed markets rely on the existence of an administrator of ancillary services, function that leads to the figure of the system operator. Among the services analyzed, the mandatory nature of voltage control and primary frequency regulation stands out, being both the ancillary services with the higher market price and the shortest period of time requirements. In general, the recognized costs of the services correspond to investments operation, maintenance, and opportunity costs. In the provision of these ancillary services, there are no clear preferences for a particular resource allocation mechanism, where mandatory provision, auctions, competitive offers and different time length bilateral contracts are combined.