Single-Phase High-gain Bidirectional DC/AC Converter Based on High Step-up/step-down DC/DC Converter and Dual-input DC/AC Converter

A new system structure of two-stage high-gain bidirectional DC/AC converter is presented for energy storage applications. Varies kinds of high step-up/step-down DC/DC converters and single-phase/three-phase dual-input DC/AC converter is applicable in the structure. A specific topology of single-phase high-gain bidirectional DC/AC converter is analyzed in detail. Two power interfacing ports, i.e. a low voltage battery, AC grid, and two DC-buses, i.e. an intermediate DC-bus, a high voltage DC-bus, are provided by the presented converter. A low input voltage is converted by a three-port high step-up/step-down DC/DC converter which integrates a non-isolated buck/boost converter and a DC transformer. The intermediate bus is employed as a new voltage level for the dual-input DC/AC converter, so part of input power can be transmitted directly to AC grid without being processed by the DC transformer. The size of AC filter inductor is also reduced due to multilevel characteristic of dual-input DC/AC converter. Topology and operation principles of the high-gain bidirectional DC/AC converter are analyzed. An experimental 1-kW prototype is built and tested to verify the effectiveness and advantages of the presented converter.