Virtual inertia control strategy of doubly-fed induction generator with additional inertia and damping torque

Abstract

Doubly-fed induction generator (DFIG) with dual Pulse-Width Modulation (PWM) converter cannot maintain the active power balance or voltage stability of the power grid self-synchronously because of lacking mechanical inertia and mechanical damping. The virtual synchronous generator (VSG) technology can help solve this problem through simulating the mechanical equation and electromagnetic equation of synchronous generator to control the grid-connected converter. However, under the common first-order virtual inertia link used in the VSG control scheme, while DFIG providing active power support, there exists second frequency dip and the rotor speed recovers slowly, which is not conducive for DFIG to provide continuous and effective virtual inertia support. In order to overcome the drawbacks as well as avoid second frequency dip, this paper puts forward a virtual inertia control strategy of DFIG with additional inertia and damping torque. The additional torque is achieved by proportional-derivative (PD) controller with rotor slip as an input signal. Simulation results on DIgSILENT/powerfactory platform show that the proposed control strategy is effective to reduce frequency deviation and recover the rotor speed faster without second frequency dip phenomenon.