A new control strategy for small wind farm with capabilities of supplying required reactive power and transient stability improvement

This paper presents a new control strategy for a small scale wind farm which is composed of both fixed and variable speed wind turbine generator systems. Fixed speed wind generators (FSWGs) are largely dependent on reactive power, so they require large reactive power when a short circuit fault occurs in the power system. Otherwise the FSWGs become unstable and have to be disconnected from the power system. In this paper, a new wind farm topology is considered, where series connected fixed speed WTGs are installed with variable speed wind turbine (VSWT) driven by doubly fed induction generators (DFIGs). A new direct power control (DPC) strategy based on discrete space vector modulation (DSVM) technique is applied for DFIG-based wind turbine system. No extra power or current control loops are required, simplifying the system design and improving transient performance. Simulation results clearly show that the proposed topology is a cost effective solution and simplified system design to minimize voltage fluctuation of both fixed and variable speed WTGs as well as to improve the transient stability of the wind farm.