Speed Estimation Methods Of Sensorless Vector Control Of Induction Motor

In recent years, the induction motor rotor field oriented control has brought essential advances in AC variable speed drive system.Speed sensorless induction motor drive promotes the simplicity and robustness further. The study target of this paper has been sensorless vector control system of induction motors. The most important assignment of this study is the estimation methods of motor speed.Research result in these years for sensorless control of induction motors has been summarized; development of technology of power electronics and controller is also introduced . The basic principle of the rotor field oriented vector control is brought out, including coordinate transform formula and dynamic formula of induction motor.The basic stucture of Model Reference Adaptive System(MRAS) and Popov theory is introduced, then speed sensorless vector control system based on MRAS is formed and simulated. Simulation results show the MRAS-based field orientedcontrol system has good static and dynamic performance.Because of the multiplication terms of state variables, the induction motor model is still the non-linear state equations. To estimate the state variables of motor model and gain the rotor flux and velocity signals, the method of extended kalman filter is used to estimate them. The simulation of the method gets satisfied results.Artificial neural networks have mighty learning ability. After being properly trained, the multiplayer networks are capable of approximating any nonlinear functions with any precision. Therefore it has become a powerful tool in nonlinear system identification field. Research is made into the multiplayer feedforward networks, and a method is proposed to estimate the speed of induction motors using the multiplayer feedforward networks. In the multiplayer feedforward networks, speed is taken as a weight and is estimated by the on-line BP algorithm. Simulation studies is made into the field oriented control systems based on multiplayer feedforward networks. It can be seen that the convergence speed and approximate extent is better than the former methods.On the study system using TMS320F240 as the controller, Software programs for speed sensorless vector control are designed, estimation of the rotor speed and Space Vector Pulse Width Modulation(SVPWM) algorithm is carried out, establishing the found of experiment of the whole drive system.