Investigation of SSO characteristics in grid-connected PMSGs system

In recent years, a new type SSO issue, which has occurred in direct-drive permanent magnetic synchronous generators (PMSGs) based wind farm, brings a new challenge to the stability of the power system. In this paper, the SSO issue in grid-connected PMSGs system is studied by the eigenvalue analysis. The linearised state-space model of this system is built firstly. The impacts on the SSO characteristics from short-circuit ratio (SCR), impedance-frequency characteristic, resonant frequency of AC network and control parameters of PMSGs are observed by the root loci analysis. After that, electromagnetic transient simulation is carried out to verify the eigenvalue analysis. Meanwhile, the participation factors of SSO mode are calculated to analyse the subsynchronous control interaction (SSCI) between AC network and PMSG. The result shows that there is a SSO mode which is greatly influenced by AC network and DC capacitor, grid side converter (GSC) control of PMSG. The characteristics of AC network will affect the SSCI between AC network and PMSG.