Details:

Project: Plains & Eastern HVDC Clean Line

Service: LCC HVDC, Renewables

Client: Clean Line Energy Partners

Country: USA

Year: 2013 & currently providing on-going support

Overview:

The Plains & Eastern HVDC Clean Line is a merchant-owned 700 mile 4300 MW three-terminal LCC HVDC transmission line in the USA that is planned to deliver approximately 4300 MW of wind generation in Oklahoma to a 500 MW tap in Arkansas and to a 3500 MW main inverter in Tennessee.

TGS study services:

  • AC Network Reduction— performed using PSS/E
  • Custom PSCAD HVDC Model & Reduced AC system Model Development
  • Custom PSSE Transient Stability HVDC Model Development
  • System Impact Studies — performed using PSS/E
    • Power flow
    • Short circuit
    • Transient stability
  • Detailed Electromagnetic Transient Studies — performed using PSCAD
  • Harmonic Impedance Scans — at each of the HVDC terminals
  • Sub-Synchronous Torsional Interaction (SSTI) Studies

TGS Owner’s Engineer services:

  • Development of the Technical Specification for the HVDC converters
  • On-going technical support during the design phase of the project

TGS Power Quality services:

  • Performed background harmonic measurements for the potential converter locations

Challenges:

One of these challenges with this project was the weakness of the HVDC connection at the rectifier to the AC system. There were ~4500 MW of wind generators connected to a 4300 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. Additionally, the small tap at Arkansas presented a technical challenge to which several possible solutions were presented, including a monopolar tap (instead of bipole), as well as DC controller tuning.