Optimized selection method of voltage vectors for direct torque control of asynchronous motor

Abstract

The invention discloses an optimized selection method of the voltage vectors for direct torque control of an asynchronous motor on the basis of limited switching state of an inverter. The optimized selection method comprises the following steps: S1, setting acting time t1 of each voltage vector inputted by the asynchronous motor to be a highest switching-frequency allowed value; S2, raising an optimized evaluation index by the action mechanism of the voltage vector to the variation of flux linkage and the torque of the motor and computer simulation; S3, at the fixed time of each sampling period, calculating the increment of torque T1 and the flux linkage generated by action of 7 voltage vectors by an optimized vector calculation method, and selecting one optimized voltage vector to act on the inverter according to the obtained evaluation index; S4, constructing a rapid prototyping experiment system of direct torque control by utilizing a DSP microprocessor and an IGBT module, and carrying out calculation on vector decomposition and electromagnetic torque on the flux linkage of the motor so as to realize production line type calculation, reduce the calculation amount of a controller, increase the switching frequency of the inverter, and further improve the real-time performance of the system. The optimized selection method disclosed by the invention has the beneficial effect that the dynamic performance of the system can be greatly improved according to the optimization control principle.

Description

technical field [0001] The invention relates to the technical field of asynchronous motors, in particular to an optimal selection method of a direct torque control voltage vector of an asynchronous motor. Background technique [0002] Direct torque control of asynchronous motor is an AC speed regulation method with high static and dynamic performance. Its torque response can be limited to within one beat without overshoot. The core research content of direct torque control is the suppression of low-speed torque ripple. Foreign Julius Luukko and others proposed an improved flux linkage estimation model. They obtained the correction value of the stator flux linkage through the filter from the estimated stator flux linkage and the measured stator current, and then obtained the stator flux linkage Accurate estimation; Murat Barut et al. proposed a rotor resistance estimation algorithm based on the extended Kalman filter algorithm, thereby improving the accuracy of speed estima...

AI Technical Summary

Problems solved by technology

There are three problems caused by this. First, the switching frequency of the switching device is not fully utilized; second, the subdivision or insertion vector action time calculated according to the aforementioned algorithms may be shorter than the switching period of the switching device, which is limited by the minimum switching time. , the actual calculated voltage vector does not work; the third is the complexity of the algorithm, and the real-time performance is affected

[0004] At present, there are mainly two methods for selecting the voltage vector in the prior art: one is direct torque self-control (DSC), which analyzes the mathematical model and static and dynamic characteristics of the motor in the stator reference coordinate system. The torque is directly controlled as the controlled quantity, and the emphasis is on the direct control effect of the torque. The control method is to compare the torque detection value with the torque given value through the torque two-point regulator for hysteresis comparison, and the torque The torque fluctuation is limited within a certain tolerance range, and its disadvantage is that the control effect of torque direct self-control does not depend on whether the mathematical model of the motor can be simplified, but on the actual situation of the torque. It is used to control the amount of flux linkage, but the comprehensive control is centered on the torque. When the speed decreases, the voltage drop of the electronic resistance cannot be ignored, otherwise, the deviation between the flux linkage angle, amplitude and the real value will increase; other The second is that the basic idea of ​​the approximate circular flux linkage DTC is to control the instantaneous input voltage of the motor under the condition of accurately observing the spatial position and size of the stator flux linkage, keeping its amplitude basically constant, and accurately calculating the load torque. The instantaneous rotation speed of the stator flux of the motor is used to change the instantaneous slip of the rotor to achieve the purpose of directly controlling the output of the motor. Accurate observation, which in turn affects the control effect of flux linkage and torque, and reduces the low-speed control performance of the DTC system. The traditional switch selection table of the DTC system and the inherent defects of the hysteresis controller itself will cause serious torque ripple. The speed observation effect of the speed sensor or speed observer becomes worse, which causes the performance of the system to decline

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