Low voltage ride through of wind energy systems
This chapter titled, "Low Voltage Ride Through of Wind Energy Systems" focuses on the importance of low voltage ride through (LVRT) of wind turbines. The investigation of some selected grid codes has revealed that LVRT has different requirements in different grid codes. The results of the investigation have found that higher penetration of wind energy in grid results in stricter LVRT requirements. On the other hand, increasing the wind energy penetration in grid is an ongoing process; so it will be mandatory to increase the LVRT performance of existing wind turbines as well as newly installed units. This chapter has presented some key power circuit topology based and control strategy based LVRT improvement methods. While power circuit topology based strategies are usually more efficient than control strategy based methods, they need extra power electronic-based electrical circuits which might be expensive or bulky and they may affect the normal operation of wind turbines, too. This chapter has also discussed the problems of resynchronization of wind turbines. It is shown that without sufficient LVRT capability, wind turbines would be disconnected from grid during faults and resynchronization of them would be a time-consuming process which may impose large transients to the grid. A resynchronization scheme for automatic reconnection of wind turbines has been presented and validated through simulation.