A mechanism study of SSR for multiple DFIG wind generators connected to a series-compensated power system

With the increasing application of series compensation in power systems to transmit power from large wind farms, a new type of subsynchronous resonance (SSR) is emerging as a bottleneck. This paper investigates its mechanism and influential factors by conducting an in-depth analysis on a real SSR event happening on a practical system in North China. The SSR event is reproduced with time-domain simulation. Eigenvalue calculation and circuit analysis reveals that this SSR is a kind of induction generation effect (IGE) with active participation by DFIG controllers. Besides grid parameters, several other factors, including wind speed, number of online wind generators and their grid/rotor-side converter control parameters, affect the damping and thus stability of the SSR Their influence on this DFIG control-participated IGE is examined. Some counter-measures to the problem are also suggested and commented.