| With the advancement of modern industrial technology and the development of power electronics, the control performance of induction motor variable frequency drive technology is improved greatly.Because of its good performance, it is applied widely in industrial control field. But now most of the variable frequency drive system applied in control field has a lot of disadvantages, such as high harmonic pollution with input current and energy irreversibility. Based on PWM rectifier technology, the dual-PWM induction motor variable frequency drive system is designed in this paper. Its advantages include the network side with unit power factor control, low harmonic pollution and bidirectional power auto-transmit .Firstly, the basic structure and operation principle of the dual-PWM induction motor variable frequency drive system are studied in this paper. According to its structural characteristics,this paper divides the system into the PWM rectifier and the PWM inverter. The control method of voltage directional vector control in the PWM rectifier side and the rotor flux-oriented vector control in the inverter side is developed in the dual-PWM induction motor variable frequency drive system.Secondly, this paper researches on the key technology of the system——three-phase voltage source PWM rectifier (VSR). The three-phase VSR mathematical model based on the switching function is provided in the three-phase static coordinate and two-phase rotating coordinate. The operation principle of the three-phase VSR is studied. The three-phase PWM rectifier is controlled by network voltage-oriented vector control strategy. On this basis, this paper designs a double close-loop of three-phase voltage source PWM rectifier.Thirdly, the vector control strategy based on rotor flux-oriented is introduced into dual-PWM induction motor variable frequency drive system. Base on the math-model of induction motor, this paper establishes the rotor flux observer and designs the double closed-loop system with the flux and torque as the inner-loop and the speed as the outer-loop.Finally, based on the theoretical analysis, the simulation researches on the steady-state performance and dynamic characteristics of the dual-PWM induction motor variable frequency drive system. Using the TMS320LF2407A digital signal process as the control unit, the experiment system is achieved. The experimental results prove the correctness and practicability of the dual-PWM variable frequency drive system designed by this paper. |
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