Hybrid intelligent adjusting method of torque hysteresis width in DTC (Direct Torque Control) system

Abstract

The invention discloses a hybrid intelligent adjusting method of torque hysteresis width in a DTC (Direct Torque Control) system. According to the hybrid intelligent adjusting method, with speed change and stator current change as input signals and increment of the torque hysteresis width as an output signal, a dynamic and adjustable torque hysteresis width value is obtained on the basis of determining a torque hysteresis width basic value, and the torque hysteresis width value changes along with the change of the control process; and the hybrid intelligent adjusting method has stronger adaptability and overcomes the defect that the torque hysteresis width is set into a fixed value in the conventional technology. The hybrid intelligent adjusting method disclosed by the invention has the beneficial effects that: the harmonic content in current is weakened, minimum values of flux linkage and torque pulse of an induction motor are obtained, and noise and vibration of the induction motor are reduced; the problems of high torque pulse and existence of speed steady-state error and periodic pulse of the rotating speed, of the induction motor under the low-speed operation condition, are solved; and the induction motor can obtain a smooth and effective driving performance. Therefore, the hybrid intelligent adjusting method is a fuzzy-neural-network hybrid intelligent control mode with high performance.

Description

technical field [0001] The invention relates to a control technology of an induction motor, in particular to a hybrid intelligent adjustment method of a torque hysteresis loop width in a DTC system. Background technique [0002] The main advantages of DTC control (direct torque control) of induction motors are: fast dynamic torque response and certain robustness to changes in rotor parameters; Especially noticeable at low speeds. [0003] In fact, under the action of the switch voltage vector, when the stator flux deviation reaches the upper or lower limit of the hysteresis comparator, although there is a new switch vector suddenly added, the stator flux vector will not change direction and amplitude immediately, Instead, it needs to continue to increase or decrease; in this case, the stator flux linkage and electromagnetic torque may rush out of the deviation range, and an "overshoot" phenomenon occurs, causing a large pulsation. [0004] The torque ripple will direct...

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Problems solved by technology

[0004] The torque ripple will directly affect the speed characteristics of the transmission system: the DC component of the torque ripple will affect the steady-state error of the system, and will also lead to the extension of the time to reach the steady state, both at high and low speeds; The AC component of the pulsation will cause the pulsation of the speed, especially at low speed. When running at low speed, the stator flux rotates slowly, and the frequency of the AC component of the torque pulsation is low, which will cause the periodicity of the speed at low speed. Therefore, the speed error is superimposed on the basis of the steady-state error and the periodic speed pulsation is superimposed. Especially serious, when running at low speed, the small torque pulsation will cause a large relative speed error, even as high as 100 %, such a speed effect is the main reason for the low-speed performance degradation of the DTC system

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