Control of a three-phase AC/DC VIENNA converter based on the sliding mode loss-free resistor approach

The three-phase VIENNA rectifier supplying a regulated DC bus in a micro-grid architecture is controlled in this study by means of a sliding-mode regulation loop, which imposes a loss-free resistor (LFR) behaviour in each phase for power factor correction. Assuming equal parameters per phase and that the intermediate node between the output capacitors of the DC link is the neutral point of the AC generator, the rectifier can then be modelled as a tetra-port LFR with three decoupled resistive input ports and one output port characterised by a power source representing the input power absorbed by the rectifier. After demonstrating that the resulting sliding dynamics are globally stable, the control is analogically executed, this only requiring an analogue multiplier, several operational amplifiers and some auxiliary digitally implemented logic circuitry. Experimental results for different power levels and frequencies supplied by a low-power wind generator are in perfect agreement with the theoretical predictions.