Research on direct torque control of surface-mount permanent magnet synchronous motor
DTC has the advantages of simple control structure, rapid torque dynamic response, less dependence on motor parameters, and good robustness to motor parameter changes. It is widely used in asynchronous motors and permanent magnet synchronous motors, and plays a huge role in industrial production such as household appliances, automobile industry, and electric locomotive traction.
The direct torque control (DTC) method uses the space vector analysis method to analyze the mathematical model of the AC motor directly in the stator stationary coordinate system, constructs an algorithm model of the torque and flux linkage, calculates and controls the torque of the AC motor, and uses the hysteresis loop. The controller (Bang-Bang control) generates a PWM signal, and directly controls the switching state of the inverter through the switch table to obtain high dynamic performance of the torque.
The basic principle is to make full use of the switching characteristics of the voltage-type inverter. By continuously switching the voltage state, the stator flux linkage trajectory approaches the circle, and the slip frequency is changed by the insertion of the zero voltage vector to control the torque of the motor and The rate of change is such that the flux linkage and torque of the AC motor change rapidly as required.
The motor starts very fast, the actual speed can change rapidly and there is no overshoot. When the given speed changes greatly, it can track quickly, indicating that the direct torque control does have excellent dynamic and static performance. In addition to the process of establishing the magnetic field at startup, the running track of the stator flux linkage remains approximately circular during static and dynamic processes, and the amplitude of the flux linkage does not fluctuate significantly, effectively reducing the ripple of the flux linkage when the motor parameters change. After the load torque is applied, the dynamic response of the electromagnetic torque is faster and the fluctuation is not large, which improves the steady state performance of the AC speed control system.
