PROJECT TITLE :

Analysis of middle frequency resonance in DFIG system considering phase locked loop - 2017

ABSTRACT:

As the wind power technology develops, the doubly fed induction generator (DFIG) primarily based wind power system, when connected to a weak network with massive impedance, might suffer resonances, i.e., subsynchronous resonance or high-frequency resonance when connected to the series- or parallel- weak network. Besides these 2 resonances, a middle frequency resonance (MFR) between two hundred and 800 Hz could seem when the phase-locked loop (PLL) with quick control dynamics is applied. In order to investigate the MFR, the DFIG system impedance considering the PLL is studied based on the vector-oriented control strategy in rotor-facet converter and grid-side converter. On the premise of the established impedance modeling of the DFIG system, it's found that the PLL with fast management dynamics may lead to the prevalence of MFR thanks to a decreasing section margin. The simulation results of each a 7.five kW little-scale DFIG system and a 2 MW giant-scale DFIG system are provided to validate the theoretical analysis of the MFR.