Modeling and Control of Surge and Rotating Stall in Compressors Dr.ing. thesis

This thesis contains new results in the eld of modeling and control of rotating stall and surge in compressors. A close coupled valve is included in the Moore-Greitzer compression system model and controllers for both surge and rotating stall is derived using backstepping. Disturbances, constant and time varying, are then taken into account, and nonlinear controllers are derived. Stability results are given. Then, passivity is used to derive a simple surge control law for the close coupled valve. This proportional control law is shown to stabilize the system even in the presence of time varying disturbances in mass ow and pressure. A novel model for an axial compression system with non-constant compressor speed is derived by extending the Moore-Greitzer model. Rotating stall and surge is studied in connection with acceleration of the compressor. Finally, a model for a centrifugal compression system with time varying compressor speed is derived. The variable speed compressor characteristic is derived based on energy losses in the compressor components. Active control of surge in connection with varying speed is studied. Semi-global exponential stability of the compression system with both surge and speed control is proven. The main results of this thesis have been presented at international conferences. Parts of the thesis has also been submitted for publication in international journals.