New boundary mode sinusoidal input current control of the VIENNA rectifier

In hard switching boost-type or buck-type three-phase power factor corrected rectifier systems the turn-on losses in continuous conduction mode (CCM) are usually higher than the turn-off losses. This is mainly caused by the reverse recovery effect of the freewheeling diode. The reverse recovery related turn-on losses however may be eliminated if the converter is operated in boundary conduction mode (BCM), i.e. at the boundary of discontinuous conduction mode (DCM) and CCM. This paper shows that the Vienna Rectifier (VR) can be operated in BCM with zero current turn-on and that the reverse recovery current of the freewheeling diodes can be used to achieve partial zero voltage switching (ZVS). The principle of three-phase, three-level BCM control is described using space vectors, the effect of the variable switching frequency on the design of the input filter is investigated in detail and dimensioning criteria for the filter elements as well as the semiconductors are given. A current slope detector circuit using auxiliary windings on the input boost inductors is proposed for turning on the switches at minimum voltage. Further, a method to compensate the delay caused by the freewheeling diode reverse recovery time and an efficient implementation of the modulation with FPGAs using a quadratic counter is proposed. The proposed control scheme is finally experimentally verified on a hardware prototype.