Research On Identification Methods Of Rotor Resistance And Flux Linkage For Asynchronous Motor

The research of speed sensorless vector control system is a trend in recent years. The core problem is how to accurately obtain the motor parameter information, such as rotor inductance and rotor resistance, excitation inductance, electronic resistance and rotor time constant, etc. Generally motors brand can show some parameters, such as the rated power, rated voltage and rated current. But motor parameters can change according to environmental factors while in operation, which directly affects the accuracy of the field oriented vector control. Therefore, in this paper the discussion on identification methods of rotor resistance and flux linkage for asynchronous motor is very important theoretically and practically.Firstly, the vector control principle of asynchronous motor is analyzed in this paper. The analysis on electromagnetic torque and rotor flux linkage can show that the rotor time constant directly affect the accuracy of the magnetic field orientation. The influence on the motor static performance and dynamic performance by the change of rotor time constant is analyzed, which provides a theoretical basis for the study of rotor resistance and flux linkage identification.Asynchronous motor parameter identification can be divided into two types: off-line identification and online identification. The offline identification based on locked-rotor experiment and no-load experiment has less accuracy than online identification and is easy to be disturbed by power frequency interference signal and high order harmonic. The commonly used filter can only filter out part of some interference, which leads to low identification precision of parameters. Therefore, a new method composed of compound digital filter and recursive least square method is put forward to identify asynchronous motor rotor resistance. The S-function in MATLAB programming is used to simulate. The simulation results show that the design of the compound digital filter with least squares parameter identification can effectively improve the precision of parameter identification and performance of vector control system.In order to improve the accuracy of the vector control system of asynchronous motor, the pros and cons of rotor flux identification methods based on voltage model and current model are disscussed. In order to overcome the shortcomings of both methods, an adaptive flux identification method based on fuzzy PI control model is presented. The simulation results show that the rotor flux can get good identification accuracy at both low and high speed condition.Based on the aboved theoretical research, a hardware experiment platform is established. The PCB control board, adopting DSP TMS3202812 as a controller chip, is drawed. From the analyzation and comparion of experimental results, the feasibility of the design algorithm and the good dynamic performance of identification are verified.