Adaptation virtual inertia control strategy of DFIG and assessment of equivalent virtual inertia time constant of connected power system

Abstract

As the mechanical parts of doubly fed induction generator (DFIG) are decoupled from electrical part, the total equivalent rotary inertia of power system are decreased with growing continuously of wind power penetration, which will bring pressure to frequency stability of system. On the basis of analysing operation and control characteristics of DFIG, the equivalent virtual inertia time constant of DFIG, wind farms based on DFIG, and connected power system was calculated. A virtual inertia control strategy of DFIG using rotor current direct control based on equivalent virtual inertia time constant was proposed. The proposed virtual inertia control strategy of DFIG includes traditional control function module, status assessment module, and additional virtual inertia control module. The time domain simulation was carried out on the basis of theoretical analysis, the simulation results show that the proposed virtual inertia control strategy of DFIG can provide efficacious frequency support to the power grid at all kinds of operating conditions, and the frequency stability of power system with large-scale wind power was improved.