A novel suppression method for input current distortion of the Vienna rectifier under unbalanced grid conditions

Abstract

The Vienna rectifier is an excellent Power Factor Correction (PFC) AC–DC converter which has low Total Harmonic Distortion (THD) of input current, resistance to high-voltage, and high efficiency. Based on the structural characteristics of Vienna rectifier under the unbalanced grid conditions, considering the influence of grid voltage negative sequence component, the reference modulation wave of Vienna rectifier will lead or lag the input current, and the input current will be distorted which affects the power quality of Vienna rectifier. In this paper, a novel modulation waves clamping method by modifying the current command of the rectifier is proposed to eliminate the input current distortion under unbalanced grid conditions. By analyzing the distortion mechanism of the input current for a Vienna rectifier in unbalanced grid, the drawback of the conventional modulation waves clamping method for suppressing the input current distortion is illustrated, which shows that the method is ineffective in certain non-ideal grid conditions. Moreover, the proposed method modifies the current command, which realizes adjusting the clamping interval for modulation waves. So signs of the reference modulation wave and the input current are avoided to be inconsistent, and the input current distortion is suppressed. Besides, the quality of the input current is improved effectively. Finally, experimental results show that the proposed method can suppress the input current distortion obviously under the unbalanced grid conditions. Compared with conventional modulation wave clamping method, the THD value of the input current for a Vienna rectifier is reduced effectively (below 2%) with the proposed method.