Investigation of PWM current mode controllers for UPF three phase - Rectifier with split DC bus based on the Scott transformer

In this paper, the unity power factor isolated three phase rectifier based on the Scott transformer is analyzed. This topology presents a Scott transformer for galvanic isolation and uses instantaneous current control. The various current control schemes like PI control, Hysteresis control and One cycle control are tested. The use of the Scott transformer makes a split dc-bus voltage possible and the rectifier operates with unity power factor. The proposed approach draws sinusoidal input current at unity power factor and has output voltage regulation capability. Using only two active switches, the rectifier is able to generate symmetrical currents in the line and a balanced split dc-bus output voltage, which is necessary in several applications. The control technique is independent for each boost that integrates the rectifier. Therefore, it makes possible with two single-phase boosts to obtain a unity power factor three-phase rectifier. This rectifier is particularly attractive when galvanic isolation and minimum number of active switches is required. Pulse width modulation and instantaneous average current control are used. There are two voltage controls that regulate the output voltage and the split dc-bus voltage. Complete simulation results under closed loop operation are presented.