Performance Analysis and Improvement of PI-Type Current Controller in Digital Average Current Mode Controlled Three-Phase Six-Switch Boost PFC Rectifier

In this article, the performance of the proportional-integral-type (PI-type) current controller in the digital average current mode (ACM) controlled three-phase six-switch (3ph-6s) boost PFC rectifier is analyzed with the consideration of the effect of the dead time, the time delays, and the dc offsets of the sampled input voltages/currents. Current control model is established to analyze the effect of the time delays and the dead time on the inductor currents. Analysis results show that both the time delays and the dead time lead to the phase shift of the inductor currents. The design principle of the current controller to suppress the negative effects of the time delays and the dead time on the phase of the inductor currents is given, and the PI-type current controller is found to considerably restrain the negative effects of the time delays and the dead time. However, in the traditional ACM control scheme with the PI-type current controller, the dc offsets of the sampled input voltages/currents lead to serious inductor current distortion. The current distortion is discussed, and the average line current control scheme is proposed to eliminate it. The analysis results are verified by simulation and experimental results of a 4-kW prototype.