Sub-Synchronous Torsional Interactions and Start-Up Issues in Oil&Gas Plants: a Real Case Study

This paper provides theoretical determination and experimental validation of the currents interharmonics of a Thyristor Variable Frequency Drive (TVFD) in an Oil&Gas plant. Currents harmonics imply torque harmonics of the turbine generator resulting in Sub-Synchronous Torsional Interactions (SSTIs). This phenomenon can lead to blackouts of the plant or damage of the equipment. An integrated electrical and mechanical simulation model allows to emulate the behavior of the overall Oil&Gas plant at the start-up of the moto-compressor train. During the start-up interharmonics are frequency-variant, hence it represents a condition particularly critical for the turbine generator.