A digital control strategy for three-phase PWM converter to suppress output voltage ripple under unbalanced input voltages

Three-phase pulse width modulation (PWM) converter has been widely used in motor drive field, data center system and grid-connected power generation system for the advantages of operating at unit power factor and bidirectional power transmission. However, under the input voltages unbalance condition, the dc output of PWM rectifier will have a large second-order voltage ripple with conventional control strategy, which can deteriorate the performance of dc side, leading to odd input currents harmonics and reduce efficiency. To solve the above problems, especially the second order voltage ripple, a digital control strategy for three-phase PWM rectifier is proposed in this letter. Compared with the existed control strategies, the proposed control strategy does not need to extract positive and negative sequence components of input voltages, so that there is no phase locked loop and complex calculation. The correctness and effectiveness of the proposed control strategy are verified by simulation results and experimental results.