Parallel-Operated Single-Stage Flyback-Type Single-Phase Solar Micro-Inverter

In this paper, a parallel-operated single-stage flyback-type single-phase solar micro-inverter is studied. A discontinuous conduction mode (DCM) flyback converter is a well-known cost-effectiveness solution for distributed low-voltage solar inverter system since the least number of components. However, for high power grid-connected applications, the DCM flyback converter has the following disadvantages, which limit the efficiency of the converter: 1) high switching losses due to hard-switching; 2) the high copper/iron transformer losses due to high flux excursions in the coupled-inductor; 3) high MOSFET Rds(on) conduction losses due to high RMS and peak currents in the design. In this paper, a three-module parallel-operated variable-frequency boundary conduction mode (BCM) quasi-resonant (QR) flyback converter topology with low-voltage turn-on and load-sharing capabilities is presented. A prototype with input power rating of 300W and output power rating of 280W/220Vac is constructed. Experimental results verify the feasibility of the developed micro-inverter which delivers greater energy harvest, higher reliability.