HT-PLL-Based Seamless Transition Strategy for DFIG With Power Quality Enhancement Through Fractional-Order Adaptive Filter

Abstract

The seamless operational mode transition of doubly-fed induction generator (DFIG) driven by wind turbine (WT) is focused here. Moreover, remote geographical allocation of wind farm installations demand power quality (PQ) improvement feature, where the WT becomes a significant contributor to the grid stability. This paper presents a real-time implementation of seamless transition of DFIG based WT with the grid. The seamless transition process is aided by accurate phase angle estimates from a half-tangent (HT) phase locked loop (PLL) technique, which is an improved version of synchronous-reference-frame (SRF) based PLL. The phase detector of SRF-PLL is aided with HT function, which improves the accuracy at steady-state and has faster dynamics under large frequency excursions. For PQ enhancement, an adaptive filter based current control approach is suggested for grid-side converter during grid-feeding operation. The adaptive filter is based on fractional-order gradient-descent total least mean p-norm algorithm. The benefit of this algorithm compared to its parent total least square methods, is its ability to repress impulse noises in the eccentricities of the signal, showing better convergence rate. The proposed control approaches are tested and compared with popular methods in simulation, and an experimental setup validates the satisfactory operation by subjecting through dynamic conditions and load unbalances.