Research Of Improved Asynchronous Motor Vector Control System

With the exhausted resources, energy conservation and environmental protection have been the important development trend of modern society. Asynchronous ac motor has many advantages, such as simple structure, low cost, small inertia, durability, less maintenance, stable performance, and so on. It is massively appliced in industrial, agricultural, defense, and other fields, and the utilization rate now holds about 45 per cent of the total market. But the traditional asynchronous ac motor has shortcomings, such as poor speed regulation control performance, low work precisionand, and poor efficiency, so as to the great waste of electric power. With the rapid development of power electronic technology, micro control technology, and modern control theory, the digital control and advanced control strategy of asynchronous ac motor control system have been greatly developed, greatly enhance the speed performance and efficiency of asynchronous ac motor, and save the electric energy consumption.High performance asynchronous ac motor speed regulation system has become one of main research directions in the high power of power transmission. The current high performance asynchronous ac motor mostly use the vector control scheme, and its core is flux observer and output pulse width modulation technology. The current flux observers have many types, mainly include the current flux observer and voltage model flux observer based on open loop rotor two phase static coordinate, the order reduction closed-loop rotor flux observer based on the closed-loop rotor, Romberg state observer, and so on. The precision of above flux observers is greatly influenced by motor parameters, and the algorithm is complex, so directiy influence the motor speed performance. Most of the output pulse width modulation module now used SPWM modulation mode and space voltage vector SVPWM(space vector pulse width modulation) mode,But it has a low utilization of voltage and numerous harmonic for the SPWM algorithm, as well as the structure of general SVPWM algorithm is complex.Aiming at these problems, an improved flux observer observation algorithm is used in this paper. This algorithm builds a new mathematics model of flux estimation observer, and eliminates the influence of flux observer accuracy from the variation of resistances parameters of stator winding and rotor winding when the motor is in long motion. So it improves the precision of vector control system and the algorithm is simple and easy compared to the conventional flux observer. In the output modulation module, pulse width modulation technology adopts the improved SVPWM algorithm, which through the simple addition, subtraction, logic operations, and looking-up table, can get the basic synthesis vector action time. And then the action time of three-phase synthetic circular flux can be calculated. According to the principle of PWM modulation, it can produce the circular flux pulse. The algorithm structure is simplified.The MATLAB simulations show that the system design is correct, response speed is fast, and control accuracy is high.