The Control Strategy And System Realization Of High Performance Variable Frequency Speed Regulation Of Asynchronous Motor

The electric drives are widely used in industry, agriculture, national defense and other fields of social life. At present, about 70 percent of the electric energy in my country is used by electric motors, and more than 80 percent of electric drives are AC drives. Before 1970s, the speed regulation systems of electric drives include about 90 percent of the DC drives and less than 10 percent of the AC drives. Since the torque and flux are independence each other, the torque of DC motor is easily controlled by adjusting armature current when the flux is constant. Thus, both the speed regulation performance and starting and braking performance of DC motors are better than AC motors. After 1970s, the vector control theory is constructed so that the asynchronous motor is equivalent to DC motor. So the speed regulation performance of asynchronous motors is as good as DC motor, further the variable frequency speed regulation is advantage replacing DC motor and become the main development direction of electric drives. The purpose of this dissertation is to study control scheme for high performance variable frequency speed regulation of asynchronous motors. The main works and innovations are generalized as follows:Based on auto-disturbances-rejection controller, the variable frequency speed regulation (VFSR) scheme of the asynchronous motors is proposed. Both the coupled terms and parameters uncertainty of the asynchronous motors model are regarded as inner disturbances of the system. The states are observed and compensated by expanded state observer, and the disadvantage of classic PID controller is overcome by nonlinear framework. Thus the effect of time-varying parameters on decoupling is eliminated. Meantime, the analysis of robust of auto-disturbances-rejection control scheme is addressed. The given simulation results show that the response rate of the proposed control system is increased, the stability of system is improved, and the ability of disturbance rejection is advanced. The proposed controller can achieve good adaptability and robustness. Based on multi-model adaptive control, the variable frequency speed regulation (VFSR) scheme of the asynchronous motors is proposed. For being two operation sections, i.e., constant torque and constant power operation section, and the parameters saltation resulted from the saturation of flux and the effect of trend to skin, the whole character of the asynchronous motor is described by multiple models, then the each controllers corresponding to each model are designed. In practice, the multiple controllers are mapped to the adaptive controllers under different operating models; the satisfied performance of the variable frequency speed regulation (VFSR) of the asynchronous motors is obtained in whole operation range. The proposed adaptive Dahlin control based on neural network can improve the bad stability of the system resulted form the time-delay of switching models. The simulation results indicate that the proposed multi-model adaptive control can achieve high performance control of asynchronous motor in whole operation range and under different operating modes.The LMS algorithm of varying region and varying step and the variable frequency speed regulation (VFSR) scheme of the asynchronous motors are proposed. By using the inverse of the plant as controller in series, the relation between input and output of system become a unit mapping approximately, thus the output of system can track the input of system very well. The parameters uncertainty of the plant and exterior disturbance are regarded as the disturbance, which is eliminated by disturbance rejection method. The whole disturbance between the plant and model drive both the plant and model, farther, this disturbance that is subtracted from the input of plant drives the inverse of the model, and the noise and disturbance of system can be eliminated ultimately. Since the given signal and disturbance are independently controlled, the above two control performance does not need be considered and compromised in the meantime, which is the prominent advantage of adaptive inverse control of the variable frequency speed regulation(VFSR) of the asynchronous motors. The proposed LMS algorithm of varying region and varying step, in which stepμ(K) changes with the error region e(k) change, can achieve three optimization performance indexes, include initial convergence rate, the tracking ability for time-varying system, and the convergence precision. The system of the variable frequency speed regulation (VFSR) of the asynchronous motors can obtain the high identification precision and better real-time ability by the identification of inverse model. The simulation results show that the adaptive inverse control of the variable frequency speed regulation (VFSR) of the asynchronous motors has advantage and validity obviously.