Chaotic analysis of nonlinear phenomena in electrical drive systems and their control with soft computing methods

ABSTRACT PhD Thesis CHAOTIC ANALYSIS OF NONLINEAR PHENOMENA IN ELECTRICAL DRIVE SYSTEMS AND THEIR CONTROL WITH SOFT COMPUTING METHODS Ahmet Bedri ÖZER Fırat University Graduate School of Natural and Applied Sciences Department of Electrical-Electronics Engineering 2005, Page : 141 Soft computing methods were developed for modelling and controlling systems that are either impossible or hard to be modelled mathematically. Soft computing is constructed from many components. Chaos is one of the components of soft computing. Chaos is irregular and unpredictable behaviors that are seen in nonlinear systems. Electical drive systems have a nonlinear structure. Naturally these drives are suitable for chaotic analysis. In this thesis, chaotic analysis in vector controlled induction motor drive of electrical drive systems was implemented. Vector control methods have two types named Indirect Field Oriented Control (IFOC) and Direct Field Oriented Control (DFOC). The performance of the IFOC drive is sensitive to system's parameter values. Among those parameters the most efficient one is rotor time constant. A change in rotor resistance will effect drive's performance. In this thesis, chaotic analysis of the IFOC drive was implemented. The effect over system performance caused by the error, which is done when rotor resistance was estimated, was also investigated. Mathematical model of speed controlled IFOC drive was obtained. For speed control, PI controller was used. After obtaining the mathematical model, Hopf bifurcation analysis was done by using it. How to choose the parameters of PI controller was showed in order to prevent system from entering into Hopf bifurcation because of the error in the resistance estimation. Performance of the DFOC drives is based on the correct estimation of the stator flux. Most frequently used flux estimation method is voltage model. This model includes open integration. Errors occur when such integrations are implemented by digital signal processor. In XVIthis thesis, chaos analysis of voltage model was done. Chaos in voltage model was observed. Later chaos control with both classical methods and fuzzy logic of soft computing methods were applied to eliminate chaos in system. Success of the developed control approach was presented with experimental results. Keywords : Chaos, Chaos Control, Electrical Drives, Vector Control, Soft Computing XVII