In high-performance AC speed control systems,advanced control strategies have important significance and impact on improving the performance of asynchronous motor drives.Compared to vector control,the direct torque control structure is simple and easy to implement,has fast torque response and good dynamic performance,and is widely used in the industry as an evolving motor control technology.In the asynchronous motor control system,speed measurement is indispensable,but the speed sensor has the disadvantages of reduced reliability,poor robustness and high cost.Therefore,researching high-precision speed sensorless technology has important theoretical significance and application value.In addition,for a wide range of applications,a wide range of speed control is applied,and the torque demand is large.However,as the speed increases,the flux linkage decreases,and there is a problem that the torque capacity is reduced because the stator reference flux chain is highly selected.Affect the output torque capacity to a certain extent.Therefore,it is of great significance to study the direct torque control system with high torque output capability.To solve these problems,firstly,to achieve high-precision speed sensorless technology,the model reference adaptive system(MRAS)speed identification algorithm is improved in this paper,and a fuzzy PI model reference adaptive regulator is proposed.Through simulation,it is proved that the algorithm can improve the speed oscillation and overshoot in speed sensorless systems.Simulations show that the variable stator flux linkage influences the actual output speed of the motor based on speed sensor,and the mathematical relationship between the stator flux linkage and the speed identification error is determined by the least-squares curve fitting,and an error correction link is established for the speed.The identification module is improved to improve the overall system speed identification accuracy.Secondly,in order to achieve direct torque control with high torque capability,an overmodulation strategy is proposed in this paper.The torque dynamic response in the constant torque and constant power regions is analyzed and simulated for a wide range of motor speed regulation processes.verification.In particular,when the motor enters the constant power speed regulation area,the problem of degrading the motor drive capability due to a sudden torque drop is improved,and a smooth switching of the magnetic flux path is achieved.This control method has a fast torque response during motor acceleration.In the field weakening zone,it not only expands the constant torque range,but also automatically weakens the flux linkage to the optimal value,thereby accelerating the system speed response.Finally,the two improved algorithms are applied to the asynchronous motor direct torque control system to realize the speed sensorless wide range speed regulation effect with high torque performance. |