An Investigation on Inertial Response of DFIG in Frequency Regulation of an Interconnected Power System

Renewable integration is gaining momentum due to declining fossil fuel resources and environmental concerns all over the world. Widespread integration of renewable catering to global needs poses challenges to system operators for ensuring grid stability. Declining inertia due to inverter-based generation is a concern for stable system operation. Efficient control strategies are essential for the smooth operation of renewable integrated systems. Power generation from wind using a Doubly fed Induction Generator (DFIG) is widespread and is on an increasing trend. Following an imbalance event, frequency declines from the nominal value. The initial rate of deviation and nadir needs to be kept within limits to prevent under-frequency load shedding (UFLS) and blackouts. Power electronic interfaces present in Inverter based resources (IBR) hide the inherent inertia of the rotor from the grid. Inertia in the rotor of DFIG can be tapped using effective control strategies for improving nadir and Rate of Change of Frequency (RoCoF), so as to provide timely deployment of kinetic energy through primary response. Strategies mimicking conventional droop characteristics of governors are being used to provide frequency regulation. Nowadays, robust and adaptive strategies are essential to stabilise inverter-rich grids and to ensure the efficient operation of IBRs. Adaptive droop control and fast frequency response (FFR) strategies for providing frequency support are the theme of discussion in this work. The frequency deviations, rotor speed, control inputs, active current command, and active power output of DFIG with various control strategies are examined on the IEEE 9 bus system to validate the control strategies.