Coordination strategies for distributed resources as frequency containment reserves

Distributed resources are increasingly considered to be potential reserves for frequency control but some of these resources, such as demand response (DR) and battery energy storage systems (BESS), are limited in energy capacity. This may complicate their utilization in a frequency containment process if the power system does not have a proper strategy to coordinate and maintain the system frequency. In this paper, we examine the resources provided by refrigerators and BESS, and argue that with proper frequency coordination the contribution of these resources to frequency containment reserves (FCR) can be improved. Two distinctive cases are compared: one where the power system has an automatic process for frequency restoration and the other where such a process does not exist. In the latter case, the resources need to cope with the long lasting frequency deviations locally. The study is based on the simulation of different control strategies and the frequency measured in the Nordic power system. The results indicate that a proper frequency restoration strategy can enhance the potential of distributed resources as FCR.