The Research And Design Of Sensor-less DTC System

During the recent 20 years, direct torque control (DTC) for induction machine is developed greatly because of its simple system scheme, excellent dynamic and static performances. This technology is based on the following controls thought: By using the method of vector analysis, firstly calculate the motor's parameters of the flux and torque in the stator reference frame, then choose directly the inverter switching mode according to the errors of the torque and flux and the flux position in space, finally realize the high-powered control of the induction machine.A design scheme of the sensor-less DTC system is particularly proposed in this dissertation, and the elaborate recommendations about the design principle, implement process, and simulation of each units of the designed system is also given. This part mainly refers to three aspects:1. The observation of the flux and the identification of the stator resistance. Because flux and stator resistance are two indispensable parameters for the calculation of the rotor speed, the system units which complete the observation of flux and the identification of stator resistance are optimized respectively. A modified integrator with amplitude limitation function is used to achieve the observation of stator flux;it can effectively solve the error accumulation and DC drift problem, and also better the track of the flux. The stator resistance identification unit is designed by using a neural network. Besides providing the stator resistance parameter for the unit of the speed calculation, it can also provide parameter for the unit of the flux observation and improve the precision of the flux;thereby it is of great advantage to the calculation of the speed.2. The identification of rotor-speed. Basing on the accurate observation oridentification of the flux and stator resistance, a very effective open-loop method is adopted to accomplish the identification of rotor-speed, and the speed parameter which is figured out by using this method can be successfully applied to realize the closed-loop control system.3. The design of rotor-speed adjustor. Rotor-speed adjuster is a critical unit in the system to produce the torque control command;the PID parameters will directly influence the torque performance of the system. In order to optimize the design of this unit, fuzzy control technology is adopted. Through controlling the on-line PID parameter, the purpose to improve the system performance is accomplished.Otherwise, the speed sensor-less DTC system's software and hardware based on TMS320LF2407DPS is also introduced fully. The system software is compiled with C and assembly language.Finally, the experimental results of the speed sensor system and speed sensor-less system are compared in the dissertation, and it adequately validates the practicality of the speed sensor-less DTC system scheme.