Research on Sub-synchronous Oscillation Characteristics between PMSG-based Wind Farms and Weak AC Grids Based on Prony Method

To investigate the new type of sub-synchronous oscillation (SSO) incidents in permanent magnet synchronous generators (PMSG) based wind farm in Xinjiang grids, this paper establishes an equivalent grid model based on practical Xinjiang grids data in PSCAD/EMTDC. To avoid the complexity and limitations of eigenvalue analysis, the Prony method is adopted to obtain system damping information. Then, taking one of those wind farms as a research case, the impacts of main factors on SSO characteristics are discussed in detail. The analysis of results reveal that improper operating conditions would weak the sub-synchronous damping and stimulate SSO in wind farm. Additionaly, a possible safe operation range of one PMSG-based wind farm through extensive simulations is presented in this research work. To further extend the solution of exsiting problems, an additional mitigation strategy based on static synchronous series compensator (SSSC) is introduced to compensate the sub-synchronous voltage and thus to suppress the SSO.