Advanced Digital Controller for Improving Input Current Quality of Integrated Active Virtual Ground-Bridgeless PFC

The paper presents a new digital control scheme for active virtual ground-bridgeless PFC (AVG-BPFC) which is able to obtain an optimized solution between the system efficiency and electromagnetic interference performance in the PFC stage. However, a resonant characteristic is generating from the input LCL filter structure of the converter. In addition, there is a phase difference between two inductor currents which also leads the controller design in the AVG-BPFC to become challenging, especially on the system stability and the current quality. Thus, a triple loop control's architecture together with an integrated state machine is proposed as the control methodology of the AVG-BPFC. Under the simple control structure in the digital platform, a stable system is achieved together with a precise grid current tracking function. Such control scheme was implemented digitally on a 1.5 kW prototype. In the paper, theoretical models of the whole system were analysed and the system performance was successfully verified in both steady state and transient state conditions. The experimental results show a good agreement with the theoretical knowledge.