High-efficiency grid-connected photovoltaic module integrated converter system

This paper presents a high-efficiency grid-connected photovoltaic (PV) module integrated converter (MIC) system. The proposed PV MIC system consists of a high step-up dc-dc converter and a single-phase full-bridge dc-ac inverter. A flyback dc-dc converter with a high step-up ratio is proposed to convert the low PV module voltage into a high dc-link voltage. The full-bridge inverter performs the maximum power point tracking (MPPT) function, supplying the electrical power to the grid. To reduce the PV ripple current variation introduced by the inverter, a PV power decoupling control is introduced. To produce a smooth transition to the maximum power point, an improved sensorless MPPT control is suggested. To supply the electrical power to the grid with unity power-factor, a simple current controller is also presented. The proposed step-up dc-dc converter achieves an efficiency of 97 % at 260 W output power to generated 350V output voltage for 36 V PV module voltage. The overall system including the dc-dc converter and the full-bridge inverter achieves an efficiency of 94.5 % with ripple current less than 3 % of the rated input current.