Investigation of single-stage flyback inverter under different operating modes

This paper presents a basic review and comparison of single stage flyback inverters (FI) used in photovoltaic (PV) energy conversion systems. Efficient and reliable transfer of raw and fluctuating dc power from PV panels to ac loads has been the centre of focus for the past couple of decades. Due to the low voltage/power output of a single PV panel, using series-parallel configuration of PV panels along with a central inverter has been a standard solution. However, because of some safety and technical issues particularly in residential applications, the use of small dc-ac converters customized and installed on a single PV panel, also known as ac module, has become recently very popular. Although such a converter is low power, it must be very sophisticated and must have all the features of PV energy conversion systems. Among various single and multi-stage configurations proposed for such scheme, flyback inverters have a very simple structure and low component count. From the input current point of view, a FI can operate either in discontinuous conduction mode (DCM), continuous conduction mode (CCM) or boundary between them (BCM). In this regards, this paper is aimed to present a comparative look at different operating modes of a FI. The basic structure of the system along with different operating modes is described. The improvements made on this structure are explained. A comparison is presented on various aspects of these inverters under different operating modes.