Project: Rock Island HVDC Clean Line

Service: LCC HVDC, Renewables

Client: Mid-continent Independent System Operator (MISO)

Country: USA

Year: 2013-2014


The Rock Island HVDC Clean Line is a merchant-owned 500 mile 3700 MW two-terminal HVDC transmission line in the USA that is planned to deliver approximately 3500 MW of wind generation in northwest Iowa to an inverter in Illinois. TGS Study services:

  • Custom PSSE Transient Stability HVDC Model Development
  • System Impact Studies — performed using PSS/E
    • Power flow
    • Transient stability
    • Generator delta P screening
  • SSTI screening analysis


One of these challenges with this project was the weakness of the HVDC connection at the rectifier to the AC system. There were ~4000 MW of wind generators connected to a 3800 MW HVDC rectifier, with a very weak connection to the AC system. Numerical stability of the wind generator models in the weak system, combined with a detailed transient stability HVDC model was a challenge that we overcame and learned from.