Analysis and mitigation of SSCI when integrating wind power to series compensated lines

Abstract

As more power electronics are introduced into the power system, its stability is impacted, e.g., through undesired interactions. One such interaction is called sub-synchronous control interaction (SSCI), an example being an interaction between a DFIG wind farm and a series compensated line. In this paper, two methods are used to assess the risk of SSCI: the reactance crossover method, and the Nyquist criterion. The analysis is performed on three case studies: one system based on the IEEE First Benchmark System, and the other system is modelled as a typical Swedish transmission system with two different degrees of series compensation. Both methods predict SSCI in all three case studies, with the Nyquist criterion being able to predict the oscillation frequency more accurately. To mitigate the sub-synchronous oscillations, a PV farm is implemented and placed in parallel to the wind farm. The performed simulations show that it is able to damp the oscillations successfully in all case studies.