Single-Stage Grid-Connected Forward Inverter in Continuous Conduction Mode

This paper presents a new forward inverter topology for low power applications. The proposed converter is a voltage fed inverter, which makes it suitable for renewable source integration and has current source type output, which matches with grid-connected applications. This solution combines forward based topology in continuous conduction mode, providing MPPT capability and unity power factor in a single-stage converter. These features are obtained with a slow input voltage control and a fast output current control, in a cascaded control-loop. The forward transformer provides isolation and voltage gain in a small volume, hence, the structure can be applied as a step-up inverter. Principles of operation, static analysis, transfer functions, power and control design are developed in the paper. In order to verify the theoretical analysis, simulation results using PSIM are shown, considering a 500 W structure, with 72 V of input voltage and 220 V of grid voltage. The results show that the proposed topology has high output power factor, low current distortion, with the possibility of being applied in any renewable power source ranging from 300 W up to 1 kW.