A two-stage high power density single-phase ac-dc bi-directional PWM converter for renewable energy systems

It is well-known that single-phase ac-dc conversion requires a bulky dc-link capacitor for filtering the ripple power from the grid. Also, in order to interface a dc renewable energy system to a single-phase utility grid, bi-directional power flow control and dc-bus voltage regulation are major concerns. By using an H-bridge in series with a bi-directional SR dc-dc converter, this paper proposes a two-stage topology as a grid-interfaced single-phase PWM converter which reduces the dc-link capacitor value. A bi-directional control system and a design process are also presented for the dc renewable energy system application. This converter can be easily integrated as a compact power module with intrinsic short-circuit protection ability, small converter volume, and the simplification of the system-level design. A 10 kW prototype and experimental results are presented for the verification purpose.