| The pulse width modulated rectifiers is capable of: unity power factor, sinusoidal current waveform, and steady dc voltage compared to the conventional diode- and thyristor- rectifiers. However, under the unbalanced voltage source, the PWM rectifiers performances were deterated by the appearance of second harmonic component in dc current, which caused by the negative sequence of the voltage source. A scheme to cancel the second harmonic current and to improve the performances of the PWM rectifier under unbalanced voltage source is presented.This paper analyzed the conventional rectifiers, presented the principles of the three-phase voltage-sourced PWM rectifiers, constructed the regular three-phase and the roltate coordinate models. According to the demmand of the control system, constructed the duty cycle models of the PWM rectifiers. It presented the control schemes of the current, the control schemes under balanced and unbalanced, the space vector modulation and the selection of the inductor of the input side. The simulation of the PWM rectifier under balanced input voltage in MATLAB verified the direct current control schemes.The dual current control scheme was verified under unbalanced input voltage, which canceled the second harmonic current significantly. The rules of the selection of the inductor was verified in the simulations. The paper presented the basic hardwares of the PWM rectifiers. The experimental result verified the validity of the proposed control schemes. |
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