A two-stage soft-switching photovoltaic grid-connected inverter based on pulse DC voltage link

This paper introduces a two-stage soft-switching photovoltaic grid-connected inverter based on pulse DC voltage link. It is composed by a dc-dc pulse converter and a dc pulse-AC inverter. The MPPT (maximum power point tracking) operation is applied for the front stage. A small capacitor is used for the DC link, of which the voltage is discharged to zero in every switching cycle. Accordingly, a high-frequency pulse DC voltage is generated by the resonance of the line inductance and the small DC capacitor. And it is supplied as the input of the latter H-bridge stage. A tri-state DPM (Discrete Pulse Modulation) current hysteresis tracking control strategy is proposed for the latter stage. All of the active switches are running at soft-switching state. Simulation results are given to prove the feasibility of the proposed soft-switching photovoltaic grid-connected inverter and its soft-switching operation characteristics.