Alternative operating modes to reduce the load shedding in the power system of El Hierro Island

Abstract

The activation of the load shedding programs in the six isolated power systems belonging to Canary Archipelago has not been uncommon in last years. These power systems have been increasing the penetration of renewable power generation technologies, which are mainly decoupled from the grid through a power electronic converter and not being able to respond naturally to frequency drops. Common Under Frequency Load Shedding programs are activated when a relevant incident, as the outage of a generation unit, takes place. This work analyses the benefits of alternative control strategies in one of the Canary Islands (El Hierro island) in terms of reducing the need of load shedding activation. These control strategies are the variable speed wind turbines inertial contribution to frequency regulation and the use of Pelton turbines as synchronous condensers. Both strategies do not involve a significant loss in the efficiency or in the available wind energy. Additionally, the participation of variable speed pumps in the frequency regulation, control strategy recently adopted in El Hierro power system, has been included in the analysis. To achieve these objectives, a complete dynamic mathematical model of this power system has been delivered. Representative generation schedules that fulfil several real combinations of wind generation and load were generated and used to carry out the study. The results obtained show the effectiveness of the alternatives control strategies proposed. The amount of load to be shed is reduced or even avoided in many scenarios, but the three alternative control strategies present their own particularities.