Research On Surge Control Of Active Magnetic Bearing Suspended Centrifugal Compressor

Surge is a kind of unstable state that happens on fluid machineries like compressors and blowers when the flow rate decreases to a limit value,whicn could cause serious damage to the equipment.This research presented a method for active surge control using active magnetic thrust bearing(AMTB)as actuator to change the impeller tip clearance to suppress surge.The method could enlarges the operation of the compresor.The following research works have been done.First,the compressor Greitzer model was built and the influence equation of tip clearance on the compressor pressure rise was established.The linear analysis of the influence equation was carried out and the linearization error was within?1%.In order to facilitate the controller design,the compressor system model was linearized.According to the pole distribution,the surge occurs when the throttle opening is less than 15%.Then,the PID surge controller based on mass flow feedback was designed,and the stability of the control strategy was verified by the Lyapunov stability.PID surge control effect was simulated and analyzed under different throttle openings.Finally,to research the influence of magnetic thrust bearing system model on surge control,a mathematical model of the system was established and added to the surge control simulation.The results showed that the combined simulation of PID surge controller and magnetic thrust bearing system model had the ideal effects on the surge control.Then,considering the changeable axial load of compressor during operation,V-Gap metric method was introduced to design a robust controller to improve its robustness and stability.Firstly,magnetic thrust bearing system was modeled based on the experiments.Then,the parameter uncertainty in the actual modeling process was analyzed based on V-Gap metric method.The influence of the perturbations on system was analyzed.Finally,the H_?controller design method was proposed with the stability requirement of the generalized stability margin.The results showed that the anti-interference and position tracking performance of system were improved.Under the same excitation signal,the amplitude of H_?robust controller designed based on V-Gap metric reduced by25%,the phase difference was lower,and under the same disturbance,the adjusting time was reduced by about 25%.Finally,in order to verify the surge control strategy of changing tip clearance by magnetic thrust bearing,a maglev centrifugal compressor surge control platform based on dSPACE was built.The joint simulation of compressor surge model and magnetic thrust bearing system was carried out.Firstly,the position tracking and stability performances of magnetic thrust bearing system under H_?control were analyzed.To research the compressor surge control platform,under two conditions of throttle opening,the influence of speed,compressor system disturbance and magnetic thrust bearing system disturbance on the control performance of surge control was researched and compared with PID control.The results showed that the control performance of the whole surge control system under H_?robust control is better than PID control.