Research On Speed Sensorless Vector Control System Of Induction Motor

The induction motor variable frequency speed regulation system has been widely used in variable speed drive field after years of development. In it’s many control methods, the performance of vector control is the best one and most widely used method. Yet for vector control system, speed sensor’s installation and maintenance are its biggest trouble. So speed sensorless vector control becomes hot research. To enlarge speed range of vector control system in constant power state, weak magnetic speeding becomes another important research subject. Based on thorough analysis induction motor vector control theory, a speed sensorless control theory and weak magnetic speeding theory, this paper completed simulation and system experiment of speed sensorless vector control and weak magnetic regional vector control. The main content of the complete as follows:On the basis of thorough analysis vector control theory, this paper improved and optimized speed sensorless vector control procedures existing in laboratory,The experimental results of a110kW motor show that the system has good start, stop, adjusting speed, disturbances etc dynamic and static performance. In speed sensorless vector control, a deep research has been done based on reactive power model reference adaptive speed identification principle.The experimental results show that this method has problem of start-up estimate convergence speed slow, poor effect in low speed identification and unstable generation state.The paper analysis the cause about unstable speed estimate method using sensorless vector control system speed identification error transfer function, this cause is according with the experiment results.In order to improve low speed performance of the speed sensorless vector control system and solve the unstable problem of the system in generation state, this paper researched a method based on the improved model reference adaptive speed estimation. The experimental results show that, compared with the method of the reactive power model reference adaptive speed identification, this method can stably operate on start-up, low speed and power generation braking states, the speed changes according to the linear rule during the reversing and braking process, and the system can stably run in1Hz, the system runs through the zero frequency points when reversing. The system received the good speed identification and system control effects.In Weak magnetic speeding, the traditional"" weak magnetic method, with torque current compensation""weak magnetic method and the best current distribution method were been further studied and compared. The simulation results show that the best current distribution method can still run under the identification and system control effects.In Weak magnetic speeding, the traditional "" weak magnetic method, with torque current compensation""weak magnetic method and the best current distribution method were been further studied and compared. The simulation results show that the best current distribution method can still run under the condition of constant power operation in speed to reach2.3times rated speed and the system stability. So it is the best weak magnetic control method. Limited by experiment equipment, experimental results that nearby1.5times the rated speed show that these three methods have basic similar performance.Referenced the weakening field method of the speed sensor vector control system,the field weakening method of best current distribution was realized in the speed sensorless vector control system,the experiment results show that,the weakening field method of the speed sensorless vector control system has a certain performance of speed adjustment.Speed sensorless vector control and weak magnetic speeding experiment have been completed based on a TMS320LF2407A AC speed regulation experiment platform in the laboratory. Experimental platform and software programming were also briefly introduced in this paper.