Details:

Project: CREZ Series Capacitors

Service: SSR

Client: Alstom Grid

Country: USA

Year: 2011

Overview:

TGS performed a comprehensive sub-synchronous interaction (SSI) analysis to assist a leading manufacturer in their bid to provide series capacitors for the CREZ project. The series capacitors were located in an area containing a large number of wind farms. TGS evaluated the risk of sub-synchronous interactions between the wind farms and the series capacitors, and proposed a novel network based sub-synchronous interaction mitigation method.

TGS Study services:

  • Sub-synchronous interaction analysis
    • Large number of wind farms and series capacitor combinations to analyze
    • Frequency scans for screening
    • Detailed analysis using dynamic phasor based small signal analysis
    • Electromagnetic transient simulations to validate and consolidate the findings
  • Sub-synchronous interaction mitigation
    • A network based SSI mitigation method using SVCs
    • SSI damping controller tuning
    • Electromagnetic transient simulations to validate and consolidate the findings
  • Custom PSCAD Model Development
    • Generic SVC model
    • Generic Wind Turbine Generator models

Challenges:

The main challenge in this project was the large number of wind farms and the large number of series capacitor locations that needed to be studied. TGS’s dynamic phasor based small signal stability program TGSSR was used to systematically identify the problematic locations and contingencies in a very short time. Another challenge in this project was to propose an SSI mitigation method without by-passing the series capacitors, tripping the wind farms or modifying the wind farm controllers. This was achieved by strategically placing an SSI damping controller equipped SVC. The Eigen properties provided by TGSSR were used to select the best location for the SVC, the best input signals for the damping controller, and tune the damping controller.