Tuning and Optimization of Compressor Controls Using Dynamic Simulation

Compressor systems are critical and integral part of an LNG plant for safe, productive and cost effective operations. Robust control design and strategies are essential for stable operation and for protection of machines during abnormal operations. With advancements in dynamic modeling and its use in designing, testing and troubleshooting of plant operations it is important to apply it in designing and testing of control strategies of compressor systems.

In this paper we present and discuss a case study based on a high fidelity dynamic simulation model integrated with CCC emulator for centrifugal compressors. Integration of dynamic model with CCC controls eliminates emulated controllers in the model and brings the actual controller functionality. The integrated dynamic model augments the capability and accuracy of results in dynamic simulations.

Placement of SCL is done by balancing two different objectives – placed to the right of Surge Line for better controllability and as close to Surge Line as possible for production. Location of the SCL is usually determined at site during startup.  Purpose of this work is to demonstrate how to achieve this at the EPC phase of the project using dynamic simulation model.

A high fidelity dynamic model gives a good representation of the plant leading to pre-determination of Surge Control Line (SCL), adequacy of SCL for compressor control, pre-tuning of the compressor controllers, check the adequacy of the limit controls.  

Opportunity of compressor control tuning at site is less due to risk and complication of compressor surge.  Therefore the final controls are usually sub-optimal.  Main benefit of performing this activity at EPC stage of the project is to achieve optimal compressor control with minimal compressor surge tests at site during startup.