A proposed flicker mitigation scheme of DFIG in weak distribution networks

Abstract

Abstract Wind power is intermittent and fluctuating renewable source that irritates system performance during normal operation. Besides, wind speed changes caused by tower shadow and wind shear effects which known as 3p oscillations increase the level of active power variations and impede wind power expansion. Several power quality concerns such as voltage constancy and flicker emissions manifested owing to lower short circuit ratios and grid impedance angle at the wind turbine point of connection. This article presents a combined active and reactive power mitigation approach for a doubly-fed induction generator DFIG in order to reduce output power pulsations, minimize voltage perturbations so as to alleviate flicker emissions for weak distribution networks. The principal premise of the proposed scheme relies on varying the wind generator speed in order to store the 3p oscillations in the wind turbine WT shaft inertia. Furthermore, an optimal grid impedance angle that cancels voltage fluctuations and hence attains further reduction of flicker is obtained. A detailed system model is built in MATLAB/SIMULINK to explore the system performance for a range of wind speed changes. The obtained results reveal the significance of the proposed methodology to allay flicker emissions of DFIG operated in weak distribution networks and to comply with grid code regulations.