Active Compressor Surge Control System Using Piston Actuation Theory, Design, and Experiments

Abstract

This thesis presents a novel active compressor surge control system using piston actuation, and this system is called the piston-actuated active surge control system (PAASCS). This work addresses the development of PAASCS from the beginning to the experimental results, including system modeling, control design, system improvement, piston prototyping, laboratory test setup, system implementation, and experimental tests. The thesis is presented as a collection of papers, including seven conference papers and a journal paper. The work began by developing a PAASCS model that is a modification of the Greitzer compressor model by including the effect of piston dynamics on the compression system. The resulting model was used in control design. Two control methods were initially applied in the control design. Applying the backstepping method proved that the closed-loop system was globally asymptotically stable (GAS), but the state feedback control law was too complicated and not practical to implement. Applying a linear control method to the linearized model resulted in a simple state feedback control law, but it only achieves locally asymptotic stability (Uddin and Gravdahl, 2011a). The PAASCS performance was evaluated through simulations. Two problems were identified, and the solutions to these problems were presented. 1) The piston was drifting during the surge stabilization. The piston drift was solved by introducing integral control action to the PAASCS controller (Uddin and Gravdahl, 2011b). 2) There are possibilities for the piston to fail during the surge stabilization. Piston failures due to jamming and saturation were discussed. The simulation results showed that a piston failure results in a deep surge when the compressor operates in the stabilized surge area. A solution was presented by introducing a backup system that uses another surge control system. Two studies were performed that presented a blow-off system as a backup system for PAASCS (Uddin and Gravdahl, 2012a) and a surge avoidance system as a backup system for PAASCS (Uddin and Gravdahl, 2012c). A novel approach to model a compression system from an energy flow perspective using bond graphs was presented. A compression system is modelled using bond graph. Energy flows among the components in the compression system are described in a bond graph model of the compression system. Two basic surge solutions were identified through analysing the bond graph model, and named the upstream energy injection and the downstream energy dissipation. The PAASCS is classified as downstream energy dissipation (Uddin and Gravdahl, 2012b, 2015). Two novel state feedback control laws named the -control and the -control derived using Lyapunov based control method are presented for the upstream energy injection and the downstream energy dissipation, respectively. Both control laws guarantee that the closed-loop system is GAS (Uddin and Gravdahl, 2016a). A laboratory-scale compressor test rig was constructed to experimentally examine the PAASCS. The PAASCS was applying the -control. The control algorithm was implemented in a Simulink model and embedded in a dSpace system to construct a hardware-in-loop simulation of compressor surge stabilization. The experimental test results demonstrated that the PAASCS is able to stabilize surge and prove the concept of PAASCS (Uddin and Gravdahl, 2016b).