A low-voltage ride-through capability enhancement scheme of doubly fed induction generator based wind plant considering grid faults

Abstract

This paper presents an improved low-voltage ride-through (LVRT) capability scheme of a grid connected doubly fed induction generator (DFIG) during any type of grid fault. In this context, an effective switching strategy based on computation of rotor current components has been suggested for the proposed passive protection circuits of a rotor side converter (RSC). Simultaneously, the RSC will control the fundamental rotor current within its available capacity for providing reactive power to the faulty grid. The proposed passive protection circuits comprise both stator and rotor side series resistor based passive compensators. The stator passive compensator will only be operated at starting and ending instant of fault to restrict rotor inrush current regardless of the type of fault. On the other hand, the rotor passive compensator is conditionally activated at the time of unbalanced fault to keep the overall rotor current under control. During both types of fault, RSC performs dual functions as partially scaled active compensator cum fractional reactive power generation controlling element. Thus, coordinated operation of passive compensator(s) and RSC will improve the LVRT ability of DFIG based wind power plants under any fault scenario. Various simulations are performed on 1.5 MW DFIG to show the advantage of this proposed control strategy.