Research On Bifurcation Essence Of Losing Stability For Speed Sensorless Indirect Field Oriented Induction Motor System

For bringing out the essence of nonlinear phenomenon caused by the estimation error of rotor time constant or some special load torque in speed sensorless induction motor (IM) drive system with indirect field oriented control (IFOC), the mathematical model and SIMULINK model of IM drive system with IFOC are set up. An effective criterion of Hopf bifurcation and saddle-node bifurcation is provided and achieved for IM drive system with IFOC, according to the criterion, the bifurcation surfaces are shown to indicate parameters'influences on system stability, research results are not only validate the correctness of theoretical analysis, but also instruct us to quench these bifurcations'occurrence and improve system stability by proper setting of PI controller or avoiding system's operating in some special load torque. Then, a time-delayed feedback controller is designed and numerical results validate that Hopf bifurcation can be suppressed effectively. Finally, the sliding-mode control scheme is introduced, according to the design of sliding-mode flux/speed observer and sliding-mode controller and the build of SIMULINK model, the indirect field oriented IM system without speed sensor is achieved by computer simulation.