Vector control variable frequency speed regulation refers to the stator currents Ia, Ib, Ic of the asynchronous motor in the three-phase coordinate system, through the three-phase-two-phase transformation, equivalent to the alternating current Ia1Ib1 in the two-phase stationary coordinate system, and then press Rotor field oriented rotation transformation, equivalent to DC current Im1, It1 in synchronous rotating coordinate system (Im1 is equivalent to the excitation current of DC motor; It1 is equivalent to armature current proportional to torque), and then imitating the control of DC motor The method obtains the control quantity of the DC motor, and realizes the control of the asynchronous motor through the inverse transformation of the corresponding coordinates.
Vector control is a method of field oriented control of a motor:
Taking the vector control of asynchronous motor as an example: it first obtains some flux linkage equations through the equivalent circuit of the motor, including stator flux linkage, air gap flux linkage and rotor flux linkage, wherein the gas flux linkage is connected to the stator and rotor. The general induction motor rotor current is not easy to measure, so it is transited by the breath to turn it into the stator current.
Then, there are some coordinate transformations, first through the 3/2 transformation, into a static dq coordinate, and then through the unit vector generated by the previous flux equation to obtain the torque current component and field current similar to the DC machine in the rotating coordinates. The component, thus achieving decoupling control, speeds up the response of the system.
Finally, after 2/3 conversion, three-phase AC is generated to control the motor, so that good performance is obtained. Comprehensive above: Vector control is nothing more than four knowledge: equivalent circuit, flux equation, torque equation, coordinate transformation (including stationary and rotating)
V/F controlVF control belongs to open-loop control. No matter how the load is disturbed, it is unaffected and outputs a fixed value. Therefore, at some time, it is more stable and less susceptible to external environmental interference. However, it is precisely because it is essentially open-loop control, so its control accuracy is relatively low, and it is impossible to achieve unbiased control like vector control.
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