Impact of an Unsymmetrical Fault on the Controller of the DFIG Wind Farm

Abstract

Objectives: DFIG-based wind farms are predominant in their performance when compared to other types of generators. In the field study, due to transient events, converters at the machine side and grid side are affected. To protect the converters from an abnormal operation, overcurrent protective relays have to be designed and incorporated. Unsymmetrical fault analysis are help in the design of protective devise and speed sensors. Methods: DFIG-based wind systems are developed using the DIgSILENT power factory software and EMT simulations are executed during the unsymmetrical faults applied near the Machine Side Converter (MSC) and Grid Side Converter(GSC). Findings: During the simulation studies, various parameters are transient time, maximum current, steady-state, and voltage drop identified near the MSC and GSC. The short circuit parameters are attenuated during the unsymmetrical faults and the rotor maximum current increases by 2 to 3 times the rated current per unit, 40% to 50% voltage dip, and the current reach the steady state value after 1.213 sec during the fault. The parameters are affected more when a fault occurs near the GSC when compared to a fault near MSC. Novelty: These research findings will contribute to a better understanding and improvement of sensor sensitivity, as well as the development of control mechanisms, and protection tactics in designing more accurate and appropriate for DFIG-WT. Keywords: DoublyFed Induction Generator; Machine Side Controller; Grid Side Controller; Unsymmetrical Fault; Sensor