Analysis and simulation of active surge control in centrifugal compressor based on multiple model controllers
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Analysis and simulation of active surge control in centrifugal compressor based on multiple model controllers Niki Molana1 · Pooya Khodaparast2 · Alireza Fatehi3
· Seyed Mehrdad Hosseini3
Received: 8 April 2020 / Revised: 20 August 2020 / Accepted: 30 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Compressor operating point may change based on plant requirements and can cause sudden variations in compressor dynamics if beyond the surge line. Active surge control of a centrifugal compressor is developed using drive torque in both stable and unstable regions based on multiple model controllers to extend an operating region over the surge line together with proper control on the operating point. In this work, the compressor dynamic model in the whole operating region is used to simulate instabilities beyond the surge line. The model is based on a reverse technique to determine the compressor pressure ratio and compressor torque with limited data available from the manufacturer. After designing stable controllers on both sides of the surge line, multiple model controllers with two different switching criteria are implemented to achieve desired operating points in each region. The first criterion is based on the surge line equation, while the second one relies on flow variation of the linearized model in each area compared to the real system signals. Results show that the stated criteria are qualified supervisors to select operating regions and cause the system to switch between them correctly. Furthermore, we investigate the impact of uncertainties, such as ambient temperature variation and performance curve bias on the model. Simulation results demonstrate that by observing the flow variation instead of using expensive sensors, and in the presence of noise as well as uncertainties, the system is stable beyond the surge line and can track the desired operating point in both regions successfully. Keywords Centrifugal compressor · Active surge · Multiple model controllers · Drive torque · State observer
List of symbols A Through flow area (m2 ) a Speed of sound ( ms ) C p Specific heat capacity at constant pressure ( kgJK ) H
J Compressor head ( kg )
Hp I Kt kf L m
J Polytropic head ( kg ) Momentum of inertia (kg m2 ) Throttle flow capacity coefficient ( √kg ) Pa·s Fluid friction loss (–) Compressor duct length (m) Mass flow ( kg s )
B
Alireza Fatehi [email protected]
1
APAC Research Group, Department of Mechatronics, K.N. Toosi University of Technology, Tehran, Iran
2
Department of Energy and Mineral Engineering, Pennsylvania State University, State College, USA
3
APAC Research Group, Faculty of Electrical Engineering, K.N. Toosi University of Technology, Tehran, Iran
mt p P R r T t u V yc α β γ p ηp λ ρ σ τ ψ ω
Mass flow through the throttle valve ( kg s ) Pressure (kPa) Power ( Js ) Universal gas constant ( kgJK ) Impeller radius (m) Temperature (◦ K) Time (s) System input vector (−) Volume (m3 ) Measurable output vector (−) Zero incidence loss (−) Rotor’s backwards
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