Bifurcation Analysis And Chaotic Control In Induction Motor Drives

Bifurcation phenomenon in induction motor drives, together with theories and methods for chaotic control and its applications to induction motor drives are studied in this dissertation.Firstly, Modeling and simulation techniques of induction motor are introduced. State equations based on reference frame transformation theory are employed as mathematical model to induction motor operating under different control strategies for the further research work.Secondly, Bifurcations in induction motor and drives are concerned with. Stability of induction motor is analyzed with Lyapunov stability theory and center manifold theorem. It is shown that saddle-node bifurcation happens in induction motor when there is not enough input power to drive load. The result is useful in motion analysis of vertical traction such as elevator and crane that should avoid the occurrence of operation fault. Moreover, bifurcation in indirect field oriented control (IFOC) of induction motor drive is also analyzed. In IFOC system, with poor PI speed controller setting, oscillations may occur due to the existence of Hopf bifurcation provided the motor rotor resistance is not exactly estimated. Conditions for the emergence of Hopf bifurcation are derived and, guidelines for proper PI speed controller setting are proposed to improve stability and reliability of IFOC.Thirdly, recent research has shown that chaotic oscillation could actually promote oscillating efficiency, save energy and reduce noise. Induction motor is widely used in driving oscillating machines. Thus, how to make it chaotic or how to obtain anti-control of chaos in it is a significant work. In this dissertation, anti-control of chaos in an induction motor is realized by a feedback control to IFOC. The chaotic drive's characteristics are measured by Lyapunov exponents, Lyapunov dimensions and power spectra of time series. The study, which our researches are preceding, lays the foundation for oscillating engineering applications.Fourthly, two new PWM schemes: chaos-based SPWM and chaos-based SVPWM are brought forward. There are cluster harmonics around the multiples of switching frequency in conventional SPWM and SVPWM output waves owing to their fixed switching frequencies. Chaos-based PWM strategies utilize a chaotic changing switching frequency to spread the harmonics continuously to a wideband area so that...