An Integrated Multilevel Bridge Tapped Resonant Bidirectional AC to DC Converter

Conventionally, an AC to DC isolated converter follows a two-stage design approach, wherein the first stage is a hard switched power factor correction (PFC) converter followed by a soft switched resonant converter stage. In existing single stage two level converter topologies, the two stages are merged resulting in 25% fewer devices. All the switches in these topologies are soft switched leading to a higher switching frequency of operation. However, the voltage stress on the devices are high. Also, this two level topology is not suitable for medium voltage AC applications. Moreover, this single stage converter is an unidirectional with power flow from AC to DC side. The existing multilevel topologies for medium voltage applications have a hard switched PFC stage followed by a soft switched resonant stage. In order to overcome aforementioned shortcomings, this paper presents a novel isolated bidirectional multilevel bridge tapped resonant (MBTR) AC to DC converter. It is based on a multilevel diode clamped topology where PFC stage and resonant stage are merged into single stage with 25% reduction in device count. The switches in the proposed converter are soft switched facilitating higher switching frequency of operation. A new modulation technique is proposed for generating gating pulses for the switches. The preliminary simulation results of the proposed MBTR converter are provided.