Control strategy for combined operation of fixed speed and variable speed wind turbines connected to grid

This paper presents control strategies for combined operation of fixed speed and direct drive variable speed wind turbines connected to the grid. The system consists of a direct drive permanent magnet synchronous generator (PMSG) and a directly connected self-excited induction generator (SEIG). The wind energy system together with its controllers is implemented in Matlab/SimPowerSystem. Since SEIGs do not perform voltage regulation and absorb reactive power from the grid as they are the source of voltage fluctuations. During the faults, it is essential to determine the possible impacts on system stability when wind penetration increases. A static synchronous compensator (STATCOM) is used to enhance the system performance during loss of generation, voltage sag, voltage swell, load change and faults. The simulation results show that the STATCOM improves the transient voltage stability and therefore, helps the system to remain in service during disturbances.