Control of unidirectional three-phase Vienna rectifier as Power Factor Corrector is relatively simple in the Continuous Conduction Mode. However, peculiar issues arise in the transition to Discontinuous Conduction Mode, resulting in lower regulation performance (e.g. higher Total Harmonic Distortion). To solve this problem, open-loop current control techniques have been recently proposed, which strongly rely on the voltage sensing for achieving accurate control of input current. Moreover, the phase of grid voltage needs to be known with high accuracy, for imposing the correct power factor. In this paper, the effects of poor voltage sensing (e.g. when using a low-cost transformer) on the current distortion and on Power Factor are considered. In order to overcome these issues, while keeping the cost low, a phase-shift compensation method is proposed in this paper, which is based on a simple digital filter. Also, the most important parameter of the transformer transfer function is identified by means of a self-commissioning procedure, which requires no additional hardware and can be easily carried out in the field. Selected simulation and experimental results are reported to validate the proposal. It is worth to mention that the proposal may be applied also to other topologies, i.e. virtually to any grid-tied converter.
