Non-isolated high-gain three-port converter for hybrid storage systems

This work proposes a non-isolated power electronic topology to interface two distinct electrical energy storage units to a DC link, resulting in a Hybrid Storage System. The proposed solution, called Series-Parallel Connection, allows for interfacing these three ports in a simple, compact and reliable approach, based on the standard configuration of the H-bridge converter. The main advantage is that one of the storage units can be of much smaller voltage ratings than the other two, avoiding the use of multilevel or galvanic-isolated power stages. The resulting structure is compared against the most significant transformerless alternatives based on the H-bridge converter, stating their advantages and drawbacks. An analysis of the switching and conduction losses in the power switches of the proposed solution is carried out in order to state the design constraints at which this solution presents improved efficiency versus the alternatives. A final set of experiments in a 10 kW built prototype demonstrates the feasibility and states the benefits as well as the main limitations of the proposed scheme.