The Research On Speed Sensorless Vector Controlled Induction Motor Drives

The AC drives with high performance need speed closed loop control and the speed sensor is necessary. However the sensor is hard to fix and the cost of device is increased obviously. Therefore, Speed sensorless induction motor drives have been widely used for past 20 years. Many domestic and overseas researchers apply themselves to research of sensorless induction motor drives. This paper carried out a deep and comprehensive research work on rotor speed estimation for speed sensorless motor drives from the motor equation. Firstly, some popular methods for speed estimation are introduced and their advantages and disadvantages are analyzed separately. The theory that motor parameters must be identified synchronously if speed estimation comes from the motor equation is recommended. Secondly, a method of speed estimation for speed sensorless induction motor drives based on a model reference adaptive system is proposed in the paper. In this scheme, the motor model is considered as a reference model and an adaptive full-order observer is used as an adjustable model. And the error between estimated stator current and real stator current is regarded as the system error to estimate the rotor speed. The rotor speed is identified by a PI adaptive relation which deduces from the Lyapunov's criterion on condition of the system's stability. The method is given to compensate the stator resistance variation and identify the rotor resistance due to the motor parameters vary with inner temperature of the induction motor. And then, methods of simulate based on MATLAB for speed sensorless vector controlled induction motor drives are discussed thoroughly. The proposed speed adaptive estimation is applied to the indirect field oriented control of an induction motor drive. Both the speed estimation and the error compensation of the stator resistance are simulated respectively. Simulation results indicate that the proposed scheme is feasible and the torque and speed have good performance at low speeds especially. Finally, the algorithm for speed estimation is realized in the experimental system of induction drives based on DSP. The experiment results show that the method for speed estimation has some applied value.