Optimal Multi-Stage Under Frequency Load Shedding Scheme Considering Virtual Inertial Response of Wind Turbines

Abstract

Insufficient primary frequency control during severe disturbances requires the implementation of effective under frequency load shedding (UFLS) measures to prevent system collapse. The integration of non-dispatchable renewable energy sources like wind and solar, which are known for their variability, poses challenges to frequency management due to decreased system inertia. Consequently, there is a need for a comprehensive UFLS relay scheme tailored to renewable energy-integrated systems, aiming to enhance reliability and stability while minimizing unnecessary load shedding during under frequency events caused by unpredictable renewable sources. In this research paper, we present an optimal and robust multi-stage UFLS scheme designed for two operating points: base-load and peak-load. The suggested scheme considers different levels of wind power penetration and incorporates various contingency scenarios. The proposed UFLS scheme assumes that wind turbines are equipped with auxiliary controllers to actively participate in the power system frequency control task. To optimize the scheme, a genetic algorithm (GA) is employed, and the performance is evaluated through simulations using MATLAB and DIgSILENT/PowerFactory link. The results of the study demonstrate that the involvement of wind turbines in the frequency response significantly improves the performance of the UFLS scheme and reduces the total amount of load shedding required. This research provides valuable insights into addressing the challenges posed by renewable energy integration and offers a potential solution to enhance the reliability and stability of power systems in the presence of renewable sources.