Study And Realization Of AC Drive System Based On Multirate And Fuzzy Control

Vector control is a high performance motor control method, which makes AC motor obtain the similar control results as DC motor by decoupling and controlling the stator current via the coordinate transformation. However, the rotor flux estimators in traditional vector control system can't achieve the accurate observation within the full speed and directly deteriorate the control performance for parameter variations and other factors. The system can't be always in the best state with the traditional PI controller since the PI parameters are fixed in the whole process. To improve the quality of control performance in AC drive system, the multirate control theory and fuzzy control theory are respectively introduced into rotor flux estimator and traditional PI controller.The principle of vector control, multirate control and fuzzy control are studied deeply. A new rotor flux estimator based on multirate control theory and the discrete state space model of asynchronous motor is derived. A new fuzzy PI controller is designed according to fuzzy control theory. And the simulation models of traditional vector control, multirate control, fuzzy PI control and Multirate-Fuzzy PI control are built in the Matlab/Simulink. After comparing and analyzing the simulation results, the correctness, feasibility and superiority of the two control algorithms are theoretically verified.The experiments of traditional vector control, multirate control and fuzzy PI control had been done in the platform of AC drive system, which captured the experimental waveforms by using the Lab VIEW monitoring software and analyzed the last two experimental waveforms with the former in detail. Experimental results show that the rotor flux estimator based on multirate control theory can observe the rotor flux accurately and improve the system performance. And the system can achieve better dynamic response performance and robustness with the fuzzy PI controller than the traditional PI controller. Therefore, the two control algorithms are feasible and practical in practical applications.