High-performance three-phase three-wire high-power active front-end

A high-performance three-phase active front-end (AFE) for high-power applications is presented. It can successfully manage the well known trade-off between high power handling and high switching frequency, with regard to utility side effects. The proposed system is made-up by two parallel-connected two-level three-phase AC-DC boost converters with common DC-link capacitor. A high-power AC-DC boost converter which behaves as unitary displacement power factor (DPF) AC-DC rectifier. It works at low switching frequency and so it is able to control only the fundamental components of the line currents to be aligned with the positive sequence of the node voltages. Adding a low-power high-frequency boost converter working as an active parallel compensator (APC), the overall system also allows a low THD factor at the point of common coupling (PCC). An efficient digital control algorithm is proposed for both the converters, using an innovative PLL strategy.