Assessment and Design of Frequency Containment Reserves with HVDC Interconnections

Frequency control is one of the main actions in power system operation, since large frequency deviation from the nominal value can lead to automatic frequency protection triggering to avoid equipment damaging. The three main factors which affect the dynamical response of the frequency include the amount of power imbalance due to a disturbance, available reserves and total inertia of the system. Due to increased integration of renewable energy sources, the total inertia of the system decreases and makes the speed of the response more sensitive to power balance disturbances. This paper assesses the dynamical performance of generators involved in the Frequency Containment Reserves and correlates them with additional Emergency Power Control from High Voltage Direct Current (HVDC) interconnections. The currently used constant power ramp control and a new proposed frequency droop control of HVDC interconnections are investigated for different amounts of inertia in a test system representing the Nordic Power System. The performance of each HVDC control is evaluated with respect to the maximum Instantaneous Frequency Deviation and the amount of power required for provided frequency control actions.