Coordination of Aggregators for Flexibility Provision: A Conceptual Framework

Current trends in power systems include the increasing presence of renewable intermittent energy resources and important deployment of sensing and control capabilities at the premises of end users. The latter ones become important assets to off-set potential operational problems produced by the former, and can be used to provide additional flexibility resources to be traded in energy and ancillary service markets. This paper presents a conceptual framework to bridge the gap between flexible loads and ancillary service markets by means of aggregators of particular loads, and a coordinator of these aggregators which acts as a Balancing Service Provider. This coordinator communicates with lower level aggregators depending on the balancing service required by the System Operator. In the presented methodology, thermoelectric refrigerators, water booster pressure systems and chargers located at electric vehicle charging stations are aggregated and coordinated to provide balancing services such as frequency containment reserve, frequency restoration reserve and replacement reserves, depending on the capabilities in terms of response time, dynamics and available flexibility. The results show the ability of the coordinator and the lower level control algorithms to provide balancing services for different scenarios of power request, as well as how different loads can be managed to cope with multiple types of ancillary services.