Stator Flux Observer Of Direct Torque Control In Induction Motor

Direct Torque Control is a high-performance AC drive technology following vectorcontrol technology, it uses the stator flux orientation, directly control the flux and torquewithout decoupling current, and its control structure is simple, also have good static, anddynamic performance.In this paper, we introduced the mathematical model of asynchronous motor at first,explained the basic principles of direct torque control, analysis the hexagonal flux trajectorycontrol system and the circular flux trajectory control system control programs in depth;hexagonal flux trajectory control system is suit for high power control applications, and thecircular flux trajectory control system is suit for small and medium-power controlapplications because of low torque ripple and noise.Thesis on the stator flux analysis methods, the traditional method using pure integratorinitial error and vulnerable to the impact of DC offset. To address this problem, we study thefixed threshold method and the improved low-pass filter low-pass filter method observer.Threshold fixed by the low-pass filter method based on the pure integrator low-pass filterand the compensation signal, low-pass filter reduces the stator flux caused by the amplitudeand phase error; improved low Pass filter on this basis, an exchange of signals with lowpass filter and compensation order to further improve the observation accuracy.Finally, the direct torque control system and method of stator flux observer issimulated. In the Simulink environment, the establishment of a hexagonal flux trajectorycontrol system and the circular flux trajectory control system simulation model, comparethe advantages and disadvantages of the two control schemes, consistent with the theoreticalsimulation results. Flux through the detection of different methods of simulation shows thatthe improved low-speed low-pass filter with good performance measurement model, thestator flux observer accuracy, effectively inhibited the stator flux in the initial error and theDC offset, it is Large extent, improved the accuracy of the stator flux observer.