Capability of DFIGs to Provide Reactive Power Support and Low Voltage Ride Through in Hybrid Wind Farms with FSIGs

Abstract

This thesis examines the low voltage event performance of hybrid wind farms containing both economical Fixed Speed Induction Generators (FSIGs) and the increasingly popular but more costly Doubly-Fed Induction Generators (DFIGs). Of particular interest is the ability of DFIGs, through manipulation of the converter control, to supply reactive power support to the point of common coupling, and low voltage ride through (LVRT) capability to the farm as a whole. The study employs a recently proposed vector-based current control scheme in the DFIGs for fast transient response. After constructing detailed models of the DFIG machine and this control scheme in the PSCAD power systems simulation software package, several scenarios are simulated and examined in an effort to observe the practical limits of the DFIGs reactive support capabilities. Specifically, the maximum ratio of FSIGs to DFIGs is investigated, as well as how DFIG rotor current limits and FSIG over-speed relays affect these ratios. The motivation of this work is the reduction in total cost of a hybrid wind farm.