The Research On Speed Sensorless Vector Controlled Induction Motor Drives

A close-loop control of rotor speed is necessary in high performance AC drive systems. However, the installation of speed sensors will bring some disadvantages to the drive systems such as increased hardware complexity, reduced reliability, limited working environment and higher cost. Therefore, the developing work of speed-sensorless drive system becomes a popular research aspect in AC drive field. An induction motor speed-sensorless vector control system with a speed estimation scheme based on the PI close-loop control theory is designed in this thesis, while deep and comprehensive researches on the proposed system are carried out too.First, a general review and simple analysis of some AC drive control methods and speed-sensorless control schemes are given in this thesis. Then, mathematic models of induction motor are introduced. The performances and parameter sensitivities of several rotor flux observation methods are discussed and an improved voltage-current model rotor flux observer is chosen. A speed estimation method based on PI algorithm is introduced and an indirect flux orientation vector controlled (IFOC) AC drive system is hereby designed. Furthermore, a single-neuron PID controller is added to the system to improve the dynamic speed estimation effect, a dead-time compensation method is also added to the system in order to improve both its steady performance and low-speed running performance. Finally, both Matlab simulations and real experiments based on a DSP controlled AC drive hardware platform are implemented.Primary simulation and experiment results show that the proposed system is stable, feasible and is suitable for practical applications.