Torsional Modal Damping of a LCI Driven Geared Moto-Compressor Train: Evaluation, Optimization Criteria and Active Control

LecturesThe torsional modal response of geared compression trains driven by Variable Speed Drive Systems (VSDS) can be heavily affected by electro-mechanical interaction phenomena, both in terms of excitation mechanism and resulting damping contribution. A thorough understanding of these phenomena is essential to optimize the system design of motor-compressor shaft lines, thus avoiding equipment oversizing and minimizing string tests and commissioning time. This paper provides a comprehensive analysis of the key systems and parameters affecting the torsional modal response of a Load Commutated Inverter (LCI) driven motorcompressor, and gives practical guidelines for system design optimization. Besides, when the equipment inherent damping properties are not sufficient to achieve demanding vibration performances, an active control could be required: the real implementation of an active damping control system acting on the VSDS is therefore presented, showing its effectiveness on the torsional behavior of a real string by means of experimental results. Simulations and field test results are herein presented, emphasizing the importance of torsional modal response optimization, considering mechanical aspects and mostly analyzing electrical and control influence introduced using a VSDS. It is worth to highlight that the type of VSDS covered in the paper is the LCI, but the presented system design approach is in principle applicable to any VSDS topology, with specific electrical and control aspects to be considered for each drive