System Strength and Inertia Constrained Optimal Generator Dispatch Under High Renewable Penetration

Abstract

System strength and inertia inherently provided by synchronous generators (SGs) empower a power system to ride through voltage and frequency disturbances. The requirements of system strength and inertia were not enforced in the National Electricity Market (NEM) of Australia since SGs dominated the generation fleet in the past. However, the increasing wind and solar generation continuously displaces SGs and consequently reduces system strength and inertia in the NEM. This paper proposes a formulation of system strength and inertia constrained generator dispatch to reassure NEM operational security in light of emerging high renewable penetration. A fault current iterative solver is developed to evaluate system strength, in which the current limitation and voltage control logic of inverter-based generators, and the fault current contribution from VAR compensators are properly modelled in the phasor domain. The system strength contribution factor of an SG is defined to linearize system strength constraint for unit commitment (UC). System and sub-network inertia constraints are also formulated for the UC to limit the rate of change of frequency (RoCoF) in the event of generator/interconnector trip. The proposed generator dispatch formulation can fully meet system strength and inertia requirements in the NEM.