Abstract
This paper presents a new operational strategy for a large-scale wind farm (WF) which is composed of both fixed speed wind turbines with squirrel cage induction generators (FSWT-SCIGs) and variable speed wind turbines with permanent magnet synchronous generators (VSWT-PMSGs) or VSWT with doubly fed induction generators (VSWT-DFIGs). SCIGs suffer greatly from meeting the requirements of low voltage ride-through (LVRT). On the other hand, PMSG and DFIG have sufficient LVRT capability and can also control active and reactive power delivered to the grid independently. But PMSG and DFIG are expensive due to its full or partial power rating AC/DC/AC converter. Therefore, combined installation of SCIG with PMSG or DFIG could be an effective solution. A suitable fuzzy logic controller (FLC) is proposed in the cascaded controller of grid side converter (GSC) of PMSG and rotor side converter (RSC) of DFIG to perform effective reactive power injection to the grid and improve the LVRT capability during transient period of WF which is mainly composed of SCIG. Simulation results clearly show that both PMSG and DFIG could stabilize larger rating of SCIG in a WF, but DFIG is more superior as it is inexpensive compared to PMSG.
