Abstract
Unbalanced supply voltages can be fully compensated in boost type power converters with active front end if sufficient energy storage is provided by the DC-link capacitor. In converters that have no energy storage, for example in a matrix converter, the maximum voltage transfer ratio will be limited if one or more input lines is at a reduced voltage. Control techniques to compensate the effect of unbalanced voltage supply for matrix converters allow for a limited output voltage and power capabilities, which depends on the level of unbalance. This paper proposes the utilization of the clamp capacitor, which is normally needed to protect a Direct Power Converter (DPC), to extend the operating range of a Two-Stage DPC during unbalanced supply conditions preserving its theoretic maximum voltage transfer ratio capability. A new topology based on a hybrid approach, consisting of an H-bridge inverter inserted into the intermediary link, which is also able to preserve the output voltage capability under unbalanced supply conditions, is proposed. Both solutions are validated through simulations.
