DFIG WT electromechanical transient behaviour influenced by PLL: Modelling and analysis

With increasing wind power penetrations, WTGs shoulder a higher responsibility. Traditional WTG control and modelling is generally designed assuming that the external grid is strong enough. However, in the case of weak grid in which power variations between synchronous generators (SG) and DFIG are more intense, more appropriate DFIG model needs to be built for electromechanical transient stability analysis of power system. Phase-locked loop (PLL) is typically employed in modern megawatt WTGs and tracks the WT´s terminal voltage phase change, so as to provide reference frame for active/reactive power control. Thus power output of DFIG as well as other power source in the system subjects to PLL´s dynamic responses. This work establishes a DFIG-based WT´s electromechanical transient model considering the dynamic influence of PLL, and analyses its dynamic response which influences WTG electromechanical transient behaviour and system stability.