Dynamic Time to Surge Computation for Electric Driven Gas Compressors During Voltage Dips

This paper investigates the influence of voltage dips on large electric driven gas compressors (EDC) considering a typical application in the oil and gas industry. Voltage or power dips are electric disturbances encountered in EDC which are mainly caused by faults in the electrical grid and might last for durations up to 150ms. For gas compression applications, the loss of driver torque often puts the gas compression process at risk of surge conditions, which is a safety critical constraint. The critical nature of the present problem and the fast dynamics involved, pose challenging requirements for the control and safety systems of the gas compressor and the variable-speed drive system. The main focus of the present paper is the dynamic computation of the time to surge using online information of the estimated motor torque and a process model to predict the future behavior of the compression system. The time to surge can then be used for ride-through or shut-down decisions of the complete system, as well as for manipulating safety valves, e.g. the anti-surge valve. The fulfillment of strict real-time requirements and their direct implications on the complexity of the chosen prediction model and the implementation of the algorithm on an embedded system are also addressed in this article. As an industrial case study, the algorithm is applied to a voltage dip situation using high fidelity simulation data of a compression station.