Nowadays, development of bidirectional DC-DC converters (BDCs) has become an important topic in power electronics. BDCs are capable of reversing the direction of current flow and thereby the power flow between two DC sources while maintaining the voltage polarity of both DC sources. Considering the mentioned points, these converters are widely used in many industry applications. BDCs are key components of the industry equipments with energy storage device (e.g. battery or supercapacitor). In these equipments such as uninterruptible power supplies, fuel cell power systems, hybrid electric/fuel cell vehicles, solar cell power systems and dual voltage automotive systems, BDCs are applied to manage power flow and maintain energy storage devices health. Besides, BDCs can play the role of converting voltage level between an energy storage device and the dc bus and thus, there is flexibility in the choice of energy storage device voltage level. Various BDCs can be divided into the non-isolated BDCs and isolated BDCs. The isolated type is necessary when both sides cannot be grounded simultaneously and high voltage gain is required. In this case, a transformer is needed which adds extra cost and losses. So if high voltage ratio is not needed, non-isolated BDCs are always employed for their simple structure and control scheme. Four basic non-isolated BDCs are derived by combining of basic converters (buck, boost, buck-boost, cuk, sepic and zeta). These converters are buck and boost, buck-boost/buck-boost, sepic/zeta, and cuk/cuk. In order to significantly reduce reactive component size and cost, high frequency operation of BDCs is desirable. However, in a hard-switching converter, as the switching frequency increases, switching losses and electromagnetic interference increase. To resolve this problem, soft-switching converters are employed. In this thesis, basic non isolated bidirectional converters are introduced and soft switching non isolated bidirectional converters are discussed and evaluated. Then, three families of novel soft switching bidirectional converters are introduced. The proposed converters include (I) new family of non isolated ZVT bidirectional converters with coupled inductors, (II) new family of non isolated ZCT bidirectional converters with one auxiliary switch and (III) new family of non isolated bidirectional converters with improved active clamp. In all proposed converter families, the bidirectional buck and boost converter is fully analyzed. Also, the validity of the theoretical analysis is justified by simulation and experimental results for the first and second proposed converter families and simulation results for the third proposed converter family. At the end, conclusions and suggestions are presented. Keywords DC-DC converters, Bidirectional converters, Zero voltage switching, Zero current switching
