Sub and Super Synchronous Oscillations between Type 4 Wind Turbines and Series Compensated AC Transmission Systems

Project experiences and studies have indicated that Type 3 and Type 4 wind turbines that integrated to compensated grids or weak AC networks are susceptible to sub synchronous oscillations. This paper investigate the sub and super oscillations of type 4 based wind farms integrated to series compensated transmission systems. The state space model of PMSG based wind farms interfaced with compensated AC networks is established first, then modal analysis and participation analysis are conducted to delve into the interactions between type 4 wind turbines and compensated grid. The results show that the sub and super oscillations are caused by interaction between type 4 converters and compensated transmission system on the condition that the compensation level is high enough. A detailed PSCAD/EMTDC model is applied to validate the results.