Fault-tolerant Control For Pmsm Drive Based Hybrid Rotor Speed Estimate Method

The permanent magnet synchronous motors are widely used in various fields of life. Position sensors are often used to orient the rotor field and calculate speed in drive control system based on vector control. However, position sensor failure caused by installation, environment and other factors can lead to serious consequences such as system close down. Position sensor fault tolerant control to handle the fault is required in some applications. Therefore, the study of position sensor fault-tolerant control for permanent magnet synchronous motor drive system is of great significance.In the field of research on fault-tolerant control for position sensor failure, software fault-tolerance method such as sensorless control algorithm is the current hot topic. To deal with the position sensor open circuit fault and the code track fault, on the basis of the vector control of permanent magnet synchronous motors, this thesis focus on the rotor position estimation algorithm, the code track fault tolerance method based on the amplitude-limiting filter and the open circuit fault tolerant method based on posterior probability. Specific research contents of this thesis are as follows:1. The mathematical model of permanent magnet synchronous motor is analyzed, vector control algorithm is studied and different types of position sensor faults’ impact on the system is analyzed with simulations.2. The model reference adaptive method and high frequency injection method are used to estimate rotor speed, but the problem is that it can not maintain a high estimation accuracy in full speed range, so, This paper combines these two methods. The model reference adaptive method is work in high speed range, the high frequency injection method is work in low speed range. It shows the nice accurate in full speed range.3. When the open circuit fault occured in position sensor, the feedback speed position sensor switch from the value of sensor collected to estimated will bring oscillation to system. This paper studied a kind of posterior probability method for open circuit fault, and proposes a method which base on Maximum Likelihood Voting to calculate the prior probability. The simulation and experiment show that this method can effectively restrain the system oscillation when the open circuit fault is happened in position sensor.4. When the code track fault occured in position sensor, the amplitude-limiting filter is used in this paper to eliminate the fluctuations caused by code track fault. Then, this paper proposes a method of calculating the biggest amplitude-limiting cycle for designing a comprehensive fault-tolerant control strategy. In the end, the simulation and experiment prove that the comprehensive fault-tolerant control strategy is working well in detecting and tolerance position sensor fault.The simulation and the permanent magnet synchronous motor experiment prove that the comprehensive fault-tolerant control strategy not only can detected open circuit fault and code track fault in position sensor Correctly, but also can inhibit the fluctuations caused by code track fault and allow the system continue normal operation and smooth transition after the open circuit fault.