Loss-model based interleave technique to improve the efficiency of micro-inverter

Micro-inverters convert direct current (DC) from a single solar panel to alternating current (AC). They have several advantages over conventional string inverters like higher maximum power point tracking (MPPT) efficiency, easier installation and longer lifetime. Interleave technique could be used in micro-inverter to reduce the power devices' conduction loss at full load, enlarge the power capacity and reduce the input/output current ripple. However, if the PV modules' output power decreases, the efficiency of the interleaved micro-inverter will drop sharply due to the increasing switching loss. Besides, the variation of PV modules' voltage and grid voltage will make the maximum efficiency point fluctuated. Therefore, a power loss model which is a function of the input/output voltage and the output power is proposed in this paper to optimize the efficiency of the interleaved micro-inverter at various input/output conditions. A 200W prototype was setup to verify the loss-model and the control strategies.

The nomenclature related to the analysis of the loss-model of the micro-inverter in this paper is listed here.