An Improved Control Strategy of Three-Phase PWM Rectifiers Under Input Voltage Distortions and DC-Offset Measurement Errors

This paper proposes an enhanced current control strategy to reject the impact of dc-offset measurement error and the distortion in the supply voltage on the dc output voltage and the input current performance of three-phase pulsewidth modulation rectifiers. The proposed current controller designed in the synchronous reference frame is developed with a proportional integral (PI) and two vector PI (VPI) controllers. The PI controller regulates the fundamental current to follow its reference generated from outer dc-link voltage control, meanwhile two VPI controllers tuned at the fundamental grid frequency (ωs) and 6ωsare employed to eliminate the dc and harmonic components in the input current. Compared with the standard resonant controllers, the proposed VPI controller offers some advantages such as simpler and straightforward tuning process for controller gains and more robust control system against control delay time and frequency variations. Thanks to the effectiveness of the VPI controllers, the dc output voltage is controlled at a stable manner without any ac ripple, and the three-phase input currents are controlled to be balanced, sinusoidal, and extremely low dc component despite the presence of the dc-offset measurement error and distorted supply voltage conditions. Various experimental tests are provided to verify the effectiveness of the proposed control algorithm.