A high frequency isolated current-fed bidirectional DC/AC converter for grid-tied energy storage system

In applications of modern power distribution with distributed energy resources, grid-tied energy storage systems (ESS) will be increasingly incorporated. Energy storage devices (ESD) such as lithium-ion battery or super-capacitor cells however have low DC terminal voltages. It is essential to develop a bidirectional DC/AC converter to interface ESS based on low voltage cells to the higher voltage grid without using high number of cells in series. In this paper a bidirectional current-fed converter with high frequency transformer isolation is proposed. In this proposed topology, a current source inverter (CSI) is used to interface to the grid. A DC/DC converter with High frequency(HF) transformer is used to feed the current to CSI. Low voltage and high voltage side of DC/DC converter can be either Push-Pull or Full-Bridge. The proposed topology has the advantage of reduced component count and simple control strategy. Simulation and hardware results have shown that the proposed circuit can work in charging and discharging of the ESS and the control strategy is effective.