Research On DC Bus Voltage Sensorless Vector Control Of Three-phase Induction Motor

Compared with DC motors, AC motors have a lot of advantages such as low operation and maintenance costs, high production efficiency, easy programming. Among them, Asynchronous motor with simple structure, convenience and reliable operation in all aspects of industry are given a wide range of applications. Vector control is considered to be the most widely used control method in high-performance control occasions of induction motor. This control method can make the dynamic performance of induction motor comparable to DC motors. No matter what kind of AC motors and control methods are used, stability and monitoring of the DC bus voltage is an important factor in the system to get good control performance. In practical applications, the study of the DC bus voltage sensor failure is also less. Especially study of the sensor failure based on the motor control system is lacking. For this reason, this thesis focuses on the DC bus voltage sensor malfunction of induction motor vector control system in-depth analysis and research.The key to DC bus voltage sensorless vector control is an accurate estimate of the DC bus voltage on the basis of the parameters that can be measured directly. After analysis and studies of various types of calculation method, the DC bus voltage adaptive observer is designed based on the Model Reference Adaptive Control Method. Taking into account the actual rotor resistance will change while the motor is running, then the adaptive observer is designed based on the DC bus voltage and rotor resistance identification simultaneously. For both cases, Modeling and simulation of the asynchronous motor vector control system without DC bus voltage sensor is realized, and the theory was validated from the simulation results.Dissertation research is divided into the following areas:(1) After reviewing the relevant literature, the estimation method on sensorless systems is classified and summarized, and the advantages and disadvantages of various types of sensorless control schemes of AC motor are concluded. Combined with induction motor mathematical model and the characteristics of the vector control, this thesis proposes observation of DC bus voltage using model reference adaptive system(MRAS) method.(2) The asynchronous motors mathematical model under a three-phase in stationary coordinate system A-B-C, two-phase stationary coordinate α-β, synchronous rotating coordinate system M-T is introduced and established. The main motor control strategies are introduced, especially a more detailed description for vector control principle and the principle of SVPWM control method. The model of asynchronous motor SVPWM vector control based on motor mathematical model on M-T synchronous rotating coordinate system is established. It does the preparatory work for observer studies.(3) Details of the working principle and the mathematical model of the rectifier are introduced. The voltage oriented control which is selected in the paper is described in detail, and the voltage oriented control-field oriented control(VOC-FOC) system is modeled and simulated at the same time.(4) The principles of MRAS are described. The DC bus voltage and rotor resistance adaptation law in two different situations is derived using this method in detail. DC bus voltage sensorless vector control system model for induction motor is built in MATLAB/Simulink environment for simulation. Simulation results show that the DC bus voltage and rotor resistance can better follow the given value, and have a good anti-jamming capability. It also proved the feasibility and validity of the method.