Research Of Restraint Of Chaotic Oscillations In Power System Based On Improved Time Delayed Feedback Control Strategy

Power system is a typical system with high degree of complexity and strong nonlinear.With the development of society and economy, electricity consumption is increasing andpeople propose higher requirements about stability of the system day by day. But, whenpower system is suffered from the external disturbance, chaotic oscillations may be generated.If the chaotic oscillations lasted too long, power system would be collapsed. This thesisanalyzes the researches of the chaotic oscillations on power system at home and abroad, andmakes a deep analysis on chaotic oscillations of power system. Two improved time deayedfeedback controllers are used to restrain the chaotic oscillations of power system. The maincontents are as follows:(1) Analysis of chaotic characteristic on power system. In order to suppress the chaoticoscillations of power system better, the condition of generated chaotic oscillations of systemmust be analyzed. Melnikov method is used to calculate and analyze the system, so the chaosthreshold is got. But Melnikov method simply proves chaotic oscillations of the system fromthe necessary conditions. Poincare section method, power spectral density method and themaximum Lyapunov exponent are used to analyze the system from sufficient conditions, thusdetermine that the chaotic oscillations are generated from the necessary conditions andsufficient conditions.(2) Design of extended time delayed feedback controller. Owning to the special nature ofthe form of chaotic oscillations, the general controllers can not work effectively. The outputand the delay of the output are used in time delayed feedback control (TDFC), and phasespace reconstruction is not needed, so the design of the controller is greatly simplified.Owning to the small control zone and the weak robustness of the TDFC, extended timedelayed feedback control (ETDFC) is used. Because of the preodic oscillations of thecontrolled system, a preodic oscillation controller is used, and makes the system wrok steadily.If power system is disturbed by noise, the threshold of chaotic oscillations is lower bycalculation. The simulation results prove that the designed ETDFC with immunity in somedegree.(3) Design of fuzzy time delayed feedback controller. Due to the weak robustness toselect feedback gain of TDFC, a fuzzy controller is adopted to replace the gain. In order toimprove steady-state accuracy of the fuzzy controller, integral part is added. A selector isdesigned to increase the respones speed. Chaotic quantum-behaved particle swarmoptimization (CQPSO) algorithm is proposed to optimize parameters of the controller, thisoptimization method has a faster control speed by comparing simulation results. If the system is perturbed by noise, the stability of the controller is deteriorated. The immunity is enhancedby low-pass filter.Both theoretical analysis and simulation studies show that ETDFC and fuzzy timedelayed feedback control method can realize the suppression of the chaotic oscillationseffectively. The former has better stability, and the latter has better quickness. The controllercan be selected by different situations and requirements. In order to expand the scope ofapplication of the controller, low-pass filter can be used to improve the system’s immunity.