A Practical Framework for Investigating the SSTI between HVDC and Nearby Generators

This research investigates the sub-synchronous torsional interaction (SSTI) between multiple generator units and a line-commutated converter (LCC) HVDC system. We provide a method for estimating electrical damping in SSTI analysis. The proposed method of applying filters can reduce the burden of data storage capacity with time-consuming simulations. This method simultaneously calculates electrical damping when the test system is simulated in the EMT program. In Korea, LCC HVDC has been installed in the BukDangjin area and operated as a monopole with multiple generators. The SSTI study is conducted by modeling the equivalent grid of BukDangjin area. By varying the DC power reference and the number of in-service generator units, the grid could worsen to evoke the torsional interaction. This paper analyzes the SSTI for multiple generator units with a nearby LCC HVDC to confirm the tendency of change in electrical damping by generator units and DC power reference.