Broadband Impedance Modeling and Sub/Super-synchronous Oscillation Analysis of Steam Turbine Generator

Abstract

Impedance-based modeling and analysis method is currently one of the effective tools to analyze and solve the problem of renewable energy grid-connected broadband oscillation. Centralized development of long-distance transmission is an important form of renewable energy development and utilization in China. Among the power generation equipment in the renewable energy base, the impedance model of wind and solar power generation equipment has been built perfectly, but the current broadband impedance model of the steam turbine generator has some simplification, failing to completely reflect the broadband impedance characteristics of the steam turbine generator. Based on the frequency-domain small-signal modeling method, a broadband impedance model of the steam turbine generator containing the prime mover, speed governor, exciter system, shaft system, and synchronous generator was established. A simulation model of a steam turbine generator was built in Matlab/Simulink, and the correctness of the proposed model was verified by frequency sweeping. The influence of different links on the impedance was analyzed. Finally, the effectiveness of the proposed model in the analysis of the sub/super-synchronous oscillation problem was verified by studying a steam turbine generator connected to the grid via a series compensation device.

Keywords

• impedance modeling
• steam turbine generator
• sub-synchronous oscillation
• shaft system modeling
• series compensation