Ac Induction Motor Speed Sensorless Vector Control Method And Its Application In Electric Vehicles

As a rule, the accurate flux orientation that decide whether or not the electric vehicle can realize steady output of high torque in lower speed range and steady start and run with load, is the core of the sensorless vector control for electric vehicle induction machine drive system. However, out of question, the exact flux observation is the key to the realization of the accurate flux orientation. Based on the full order observer, this paper presents a new flux observation method applied to the induction motor, which mainly includes the following parts: 1. Based on the analyses of the relationship between the flux observation of the full order observer and that of the voltage model / the current model, a new conclusion can be made. That is, the pole point setting of the full order observer can makes the observation value closer to that of current model in the motor's low speed range, as well as closer to that of voltage model in the motor's high speed range. 2. Based on the analyses of the relationship between the voltage error / the current error and the flux observation error of the full order observer, this paper presents a novel pole point setting method with the condition of the definite motor speed. The mathematic analyses and the computer simulations both verify that such method can reduce the influence of voltage error / current error, which is very important to the precision improvement of the flux observation. Otherwise, the analyses of the influence of parameter error to the flux observation of the full order observer, as well as computer simulation, both show that such method also can reduce the influence of stator resistance error and leak inductance error to the steady error of flux observation in the motor's very low speed range. 3. When the motor speed is unknown, based on the analysis of the dynamic performance of MRAS flux observer and steady error of flux observation, this paper make a such conclusion, which also validated by simulations. That is, the improvements in the dynamic performance of flux observation and speed control are inconsistent with the reducing of speed error and steady error of flux observation. As a matter of fact, the precise flux observation, preferable to the unnecessary pole point setting, is more important to the induction motor control applied in electric vehicle.