A dual-frame hybrid vector control of vector modulated VIENNA I rectifier for unity power factor operation under unbalanced mains condition

In this paper, a dual-frame hybrid vector control (DFHVC) of vector-modulated VIENNA I rectifier is proposed. The purpose of this novel vector control system is not only to reduce second-order harmonic pulsation on the dc-side and consequently, to reduce odd-order harmonics on the ac side of VIENNA I rectifier under unbalanced mains, but also to ensure a near unity power factor operation of the rectifier under such circumstances. To serve this purpose, at first, a mathematical model of the VIENNA I rectifier under unbalanced condition is derived. In this model, besides demonstrating the nonlinear nature of the DC-link voltage dynamic, a new set of equations for current reference generation are derived. It is shown mathematically that under unbalanced mains, for the second harmonic pulsation of the output voltage to be eliminated, ripple component of the instantaneous active power at the rectifier pole must be nullified. Based on the derived model, a dual-frame hybrid vector control (DFHVC) scheme, meaning linear vector control of inner dynamic in both positive- and negative- sequence synchronous reference frames (SRFs) and nonlinear vector control of outer dynamic, is designed and employed. Simulation results alongside of experimental results demonstrate the validity of the proposed control scheme with regard to harmonic reduction at both ac and dc sides of the rectifier and near unity power factor operation under unbalanced conditions.