A two-stage grid-connected single-phase micro-inverter with long lifetime, continuous input current and fewer number of switches

Abstract

This paper proposes a grid-connected single-phase MI1 with a rated power of 300 W and an appropriate control strategy for PV2 systems. The proposed MI is designed based on a two-stage topology. The first stage consists of a SEPIC DC-DC converter with high voltage gain, while the second stage includes a full-bridge DC-AC converter. The high voltage gain is obtained in the first stage of the proposed MI by adjusting the coupled inductor conversion ratio at the low duty cycle ratio of the switch. The advantages of the proposed MI are the use of fewer components to provide suitable output voltage level for connection to a single-phase network, continuous input current, limited voltage stress on the switch, long operational lifetime, and high reliability. Lower input current ripple and the presence of film capacitors in the power decoupling circuit increase the lifetime and reliability of the proposed MI. The continuous input current in the proposed MI helps to the MPPT3 in PV panel with an efficiency of %99. The operating principles of the proposed MI are analyzed under different conditions. The results of design and simulation confirm the advantages and proper performance of the proposed MI.