Primary reserve ancillary service is the available generation capacity of the units that can be provided to the system upon the request of the primary frequency regulation. Isolated power systems and interconnected power systems exhibit different features. Isolated systems are much smaller than interconnected systems. In addition, they cannot count on the support of the neighbour systems. That is, the size and the lack of external support of isolated systems make that primary reserve service is of key importance for system stability when a unit trip disturbance occurs. Provision of primary reserve service in an isolated power system may have a significant impact on the economic operation of such systems since its provision may require not only generators operating below their optimal operating points but also the connection of units that otherwise could not be needed. Provision of primary reserve with Energy Storage Systems (EESs) could be an economic alternative to scheduling spare generation capacity in the on-line units. Although pumped storage power plants have been the only practical solutions for massive storage, current developments of battery energy storage systems may make possible providing primary reserve service with them in isolated systems. Endesa is leading a research project on testing the state of the art of battery energy storage systems in two power systems of the Canary Islands. Several applications are being investigated. This paper details a model of the economic operation of Spanish isolated systems. It is used to determine the savings of providing the primary reserve requirements by EES. Two power systems of different size and with different generation technologies (Gran Canaria and La Gomera) are considered. Sensitivity studies with respect to the size of the energy storage systems are reported.
Keywords: Energy storage systems, primary reserve, isolated power systems.
Cigré 2012 Session 44, Paris, France, 27-31 August 2012
Published: August 2012.