Critical clearing time of doubly fed induction generator

A detailed model of grid-connected doubly-fed induction generator (DFIG) suitable for fault analysis is presented. 5^th order model of wound rotor induction machine together with a two-mass model of the mechanical drive-train is employed to investigate transient voltage stability of integrated wind turbine. Converter system is represented in such a way to contain adequate model of the rotor- and stator-side converters as well as the DC-link components. PWM converters, respective controllers and the switching schemes are represented in the same reference frame as the machine to realize a combined machine-converter model. Applying a balanced three-phase network fault to the simulated system, case studies are conducted to determine the value of the critical clearing time (CCT) for the DFIG as well as the fixed-speed induction generator (FSIG). Further investigations are also made to evaluate the impact of the shaft system parameters on the CCT of a grid- connected FSIG and DFIG.